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Lipophilic bacteria ( fat -loving bacteria ) are bacteria that may proliferate in lipids .
They include lipophilic corynebacteria . [ 1 ]
Cutibacterium acnes is a type of lipophilic bacteria, [ 2 ] releasing fatty acids and worsening comedones in acne .
However, the group of lipophilic bacteria are not pathogenic, i.e. they don't cause food poisoning or food infection [ 3 ]
In terms of evolution , lipophilism can be regarded as fine-tuning the metabolism to lipophilic habitats . Some bacteria do not only accelerate their metabolism using lipids prevailing in their environment , some of them cannot proliferate without external lipid supply. For example, some Corynebacteria, such as Corynebacterium uropygiale , [ 4 ] lost their ability to produce certain fatty acids by themselves. On the one hand, this renders the bacteria vulnerable to environmental changes. On the other hand, energy can be saved as there is no need to put effort into lipid synthesis. [ 4 ]
Most materials in laboratories and health-care centers have small amounts of lipids on their surface, and thus may support the proliferation of lipophilic bacteria. [ 5 ] However, since they are not pathogenic, [ 3 ] this is not a serious threat.
Lipophilic bacteria may also proliferate in diet fat. However, in modern food industry this is very rare [ 3 ] and at worst causes a discoloration of the fat. [ 3 ]
Many lipophilic bacteria are a good source of biosurfactants, hence are used commercially, e.g. Bacillus licheniformis . These kinds of bacteria produce biosurfactants which replace chemically produced surfactants . Biosurfactants are degradable unlike the chemical ones. [ citation needed ] | https://en.wikipedia.org/wiki/Lipophilic_bacteria |
Lipophilic efficiency [ 1 ] ( LiPE ), sometimes referred to as ligand-lipophilicity efficiency ( LLE ) is a parameter used in drug design and drug discovery to evaluate the quality of research compounds, linking potency and lipophilicity in an attempt to estimate druglikeness . [ 2 ] [ 3 ] For a given compound LiPE is defined as the pIC 50 (or pEC 50 ) of interest minus the LogP of the compound.
In practice, calculated values such as cLogP or calculated LogD are often used instead of the measured LogP or LogD. LiPE is used to compare compounds of different potencies (pIC 50 s) and lipophilicities (LogP). High potency (high value of pIC 50 ) is a desirable attribute in drug candidates, as it reduces the risk of non-specific, off-target pharmacology at a given concentration. When associated with low clearance, high potency also allows for low total dose, which lowers the risk of idiosyncratic drug reaction . [ 4 ] [ 5 ]
On the other hand, LogP is an estimate of a compound's overall lipophilicity, a value that influence its behavior in a range of biological processes relevant to a drug discovery, such as solubility, permeability through biological membranes, hepatic clearance , lack of selectivity and non-specific toxicity. [ 6 ] For oral drugs, a LogP value comprised between 2 and 3 is often considered optimal to achieve a compromise between permeability and first-pass clearance.
LiPE allows capturing both values in a single parameter, and empirical evidence suggest that quality drug candidates have a high LiPE (>6); this value corresponds to a compound with a pIC 50 of 8 and a LogP of 2. Plotting LogP against pIC 50 for a range of compounds allows ranking series and individual compounds.
An alternative equation uses the logarithm of the ratio of potency (measured as binding energy) and the partition coefficient to compute a lipophilic ligand efficiency index (LE) with a different scale. [ 7 ]
The following review discusses LipE in the context of other compound efficiency metrics. [ 8 ] | https://en.wikipedia.org/wiki/Lipophilic_efficiency |
Lipophilicity (from Greek λίπος "fat" and φίλος "friendly") is the ability of a chemical compound to dissolve in fats , oils , lipids , and non-polar solvents such as hexane or toluene . Such compounds are called lipophilic (translated as "fat-loving" or "fat-liking" [ 1 ] [ 2 ] ). Such non-polar solvents are themselves lipophilic, and the adage "like dissolves like" generally holds true. Thus lipophilic substances tend to dissolve in other lipophilic substances, whereas hydrophilic ("water-loving") substances tend to dissolve in water and other hydrophilic substances.
Lipophilicity, hydrophobicity, and non-polarity may describe the same tendency towards participation in the London dispersion force , as the terms are often used interchangeably. However, the terms "lipophilic" and " hydrophobic " are not synonymous, as can be seen with silicones and fluorocarbons , which are hydrophobic but not lipophilic. [ citation needed ]
Hydrocarbon -based surfactants are compounds that are amphiphilic (or amphipathic), having a hydrophilic, water interactive "end", referred to as their "head group", and a lipophilic "end", usually a long chain hydrocarbon fragment, referred to as their "tail". They congregate at low energy surfaces, including the air-water interface (lowering surface tension ) and the surfaces of the water-immiscible droplets found in oil/water emulsions (lowering interfacial tension). At these surfaces they naturally orient themselves with their head groups in water and their tails either sticking up and largely out of water (as at the air-water interface) or dissolved in the water-immiscible phase that the water is in contact with (e.g. as the emulsified oil droplet). In both these configurations the head groups strongly interact with water while the tails avoid all contact with water. Surfactant molecules also aggregate in water as micelles with their head groups sticking out and their tails bunched together. Micelles draw oily substances into their hydrophobic cores, explaining the basic action of soaps and detergents used for personal cleanliness and for laundering clothes. Micelles are also biologically important for the transport of fatty substances in the small intestine surface in the first step that leads to the absorption of the components of fats (largely fatty acids and 2-monoglycerides). [ citation needed ]
Cell membranes are bilayer structures principally formed from phospholipids , molecules which have a highly water interactive, ionic phosphate head groups attached to two long alkyl tails. [ citation needed ]
By contrast, fluorosurfactants are not amphiphilic or detergents because fluorocarbons are not lipophilic. [ citation needed ]
Oxybenzone , a common cosmetic ingredient often used in sunscreens, penetrates the skin particularly well because it is not very lipophilic. [ 3 ] Anywhere from 0.4% to 8.7% of oxybenzone can be absorbed after one topical sunscreen application, as measured in urine excretions. [ 4 ] | https://en.wikipedia.org/wiki/Lipophilicity |
Lipophobicity , also sometimes called lipophobia (from the Greek λιποφοβία from λίπος lipos "fat" and φόβος phobos "fear"), is a chemical property of chemical compounds which means " fat rejection", literally "fear of fat". Lipophobic compounds are those not soluble in lipids or other non-polar solvents . From the other point of view, they do not absorb fats.
" Oleophobic " (from the Latin oleum "oil", Greek ελαιοφοβικό eleophobico from έλαιο eleo "oil" and φόβος phobos "fear") refers to the physical property of a molecule that is seemingly repelled from oil . (Strictly speaking, there is no repulsive force involved; it is an absence of attraction.)
The most common lipophobic substance is water .
Fluorocarbons are also lipophobic/oleophobic in addition to being hydrophobic .
A lipophobic coating has been used on the touchscreens of Apple 's iPhones since the 3GS, [ 1 ] their iPads , [ 2 ] Nokia 's N9 and Lumia devices, [ citation needed ] the HTC HD2 [ citation needed ] , the Blackberry DTEK50 , [ 3 ] Hero , and Flyer [ 4 ] and many other phones to repel fingerprint oil, which aids in preventing and cleaning fingerprint marks. Most "oleophobic" coatings used on mobile devices are fluoropolymer -based solids (similar to Teflon , which was used on the HTC Hero [ 5 ] ) and are both lipophobic and hydrophobic. The oleophobic coating beads up the oils left behind a user's fingers, making it easy to clean without smearing and smudging. This helps decrease the feasibility of a successful smudge attack . [ 6 ] In addition to being lipophobic or oleophobic, perfluoropolyether coatings impart exceptional lubricity to touch screens and give them a "slick feel" that eases their use. [ 7 ]
DIY products exist to restore or add an oleophobic coating to devices lacking one. [ 8 ] | https://en.wikipedia.org/wiki/Lipophobicity |
Lipophorin is a lipid -carrying protein of insects, first identified in 1981, [ 1 ] and is the major lipoprotein in the plasma of insects . Lipophorin has been identified in all insect species, in every life stage. Recently, additional nomenclature has been introduced to designate specific lipophorin subspecies that differ in lipid and/or apoprotein content. The concentration of lipophorin subspecies (HDLp and LDLp) changes can be considered to reflect the physiological state of the organism with respect to lipid metabolism . [ 2 ] The versatility of this particle concerning its lipid binding capacity may be unparalleled in nature.
Lipophorins are synthesized in fat body and secreted into hemolymph . In larval Manduca sexta , nascent lipophorin particles were synthesized from fat body cells and they associate with phospholipid to form a nascent Very High Density Lipophorin (VHDLp), which is essentially devoid of diacylglycerol . The VHDLp is then secreted into the hemolymph, where it later interacts with the mid gut to load DAG, which is derived from dietary lipids. [ 3 ] The maturation of lipophorin into circulating High Density Lipophorin (HDLp) results in a density shift from 1.26 to 1.15 g/ml with no change in apoprotein content. The lipophorin contains two structural apolipoproteins , derived from ApoLp-II/I precursor by enzymatic cleavage ( furin ). [ 4 ] Furin is a member of the proprotein convertase family of subtilisin like serine endoproteases that is mainly active in the trans-Golgi network . [ 5 ] The favored consensus substrate sequence for furin, R-X-K/R-R, is present in all precursor sequences characterized to date. [ 6 ] In agreement with the activity of furin, Locusta migratoria ApoLp II/I precursor appears to be cleaved C-terminal of its furin substrate sequence, RQKR, as indicated by the N-terminal sequence of ApoLp I. [ 7 ]
Lipophorins are large, amphipathic complexes composed of proteins and lipids. They are structurally similar to vertebrate lipoproteins, like low-density lipoproteins (LDLp) and high-density lipoproteins (HDLp). The core of a lipophorin particle typically consists of nonpolar lipids, such as diacylglycerols and hydrocarbons , surrounded by a layer of phospholipids, cholesterol , and apolipoproteins .
For HDLp, there is a remarkable abundance of a single lipoprotein particle in the hemolymph of insects. HDLp-reuse discrimination is one of the characteristics that strain it to be a reusable shuttle for the lipids within the target tissue. HDLp is largely a spherical particle about 450-600 kDa and has a density similar to that of a mammalian HDLp (~ 1.12 g/ml). This is usually containing DAG as its predominant lipid in addition to phospholipids, sterols, and hydrocarbons. The lipoprotein generally contains one copy of each of the two non-exchangeable apolipoproteins, viz. apolipophorin I (apoLp-I) and apolipophorin II (apoLp-II; weighing ~ 240 and ~ 80 kDa, respectively), derived from a single common precursor protein by post-translational cleavage. As a novel molecular characterization of the apolipophorin precursor, it has recently been revealed for a few insect species that the protein is arranged with apoLp-II at the N-terminal end and apoLp-I at C-terminal end (thus also termed as apoLp-II/I). At the N-terminus of apoLp-I, followed by the amino acid sequence RQKR, similar to the other apolipophorin precursors known to date, in locust apoLp-II/I (3359 aa residues). Therefore, it is likely that during the proteolytic processing of this precursor protein to generate apoLp-II and apoLp-I, dibasic processing endoproteases of the subtilisin family are involved. [ 4 ]
Lipophorin exists in three subspecies, each serving specialized functions in lipid transport within insects. The primary forms are high-density lipophorin (HDLp) and low-density lipophorin (LDLp). [ 8 ] HDLp acts as the principal circulating lipoprotein, shuttling lipids such as diacylglycerol, phospholipids and sterols throughout the hemolymph. LDLp is derived from HDLp during periods of high lipid transport demand, such as flight or vitellogenesis, as it becomes enriched with diacylglycerol. Additionally, very high-density lipophorin (VHDLp), found in some species, primarily carries hydrocarbons. [ 9 ] These subspecies work together dynamically, adapting to the insect’s metabolic and developmental needs.
Lipophorin is an incredible lipid-transporting protein studied in insects. Lipophorin is an important protein whose lipid metabolism and transfer are critical in general. Lipophorin is the main carrier of different lipids, such as diacylglycerol (DAG), hydrocarbons, phospholipids, and sterols, into insect hemolymph (blood). Invertebrate lipophorin carries these molecules from storage organs such as body fat to energy demanding or structural lipid – dependent tissues in the organism. A unique feature of lipophorin is its storage effectiveness, as it is able to shuttle lipids multiple times without being destroyed in the process. Thus, it is a very useful means of lipid transport over a long period of time.
While flying, diacylglycerol from lipophorin is being carried to the flight muscles, where it gets converted into energy through β-oxidation. Lipophorin is also necessary for cholesterol transport and performs functions similar to HDL in humans, such as membrane synthesis and hormone production. Interaction with such other proteins as lipid transfer particles (LTP) provides lipophorin with dynamic flexibility in transferring and uptake lipids. Combined with the metabolic state of the insect, the idea of adaptability within the lipophorin is further strengthening its versatility and performance level.
During vitellogenesis, lipophorin transports lipids like diacylglycerol (DAG) from the fat body to the ovaries, where they are used for yolk formation in developing oocytes. Acting as a reusable shuttle, it interacts with ovarian receptors to deliver lipids essential for vitellogenin synthesis and lipid-rich yolk deposition. This efficient lipid transport is crucial for oocyte maturation and successful embryogenesis. Lipophorin was present in nurse cells and follicle cells and marginally with perioocyte space in immature ovariole. In the mature ovariole, nurse cell was narcotized and lipophorin appeared in follicular cell. Its illustrate that lipids and proteins gradually accumulated in the developing ovary. But lipophorin was endocytic uptake in immature ovariole, after the maturation uptake halted. [ 10 ]
Lipophorin transports the hydrophobic molecule from origin to destination in time specific manner. All hydrocarbons bound in a lipid binding pocket, most of these sharing the same binding sites for hydrophobic interaction and hydrogen bonding. Overall findings elucidated that lipophorin associated with different hydrocarbons by hydrogen bonds and hydrophobic interactions, and each of the hydrocarbon having various functional roles. [ 11 ] | https://en.wikipedia.org/wiki/Lipophorin |
Lipophosphoglycan ( LPG ) is a class of molecules found on the surface of some eukaryotes , in particular protozoa . Each is made up of two parts, lipid and polysaccharide (also called glycan ). They are bonded by a phosphodiester , hence the name lipo-phospho-glycan. [ 1 ]
One species with extensive lipophosphoglycan coating is Leishmania , a group of single- celled protozoan parasite which cause leishmaniasis in many mammals , including humans . Their coats help modulate their hosts' immunological responses. [ 2 ] LPG-like substances are released into medium by the parasite and are called excreted factor in aggregate. [ 2 ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Lipophosphoglycan |
Lipopolysaccharide ( LPS ), now more commonly known as endotoxin , [ 1 ] is a collective term for components of the outermost membrane of the cell envelope of gram-negative bacteria, such as E. coli and Salmonella [ 2 ] with a common structural architecture. Lipopolysaccharides are large molecules consisting of three parts: an outer core polysaccharide termed the O- antigen , an inner core oligosaccharide and Lipid A (from which toxicity is largely derived), all covalently linked. In current terminology, the term endotoxin is often used synonymously with LPS, although there are a few endotoxins (in the original sense of toxins that are inside the bacterial cell that are released when the cell disintegrates) that are not related to LPS, such as the so-called delta endotoxin proteins produced by Bacillus thuringiensis . [ 3 ]
Lipopolysaccharides can have substantial impacts on human health, primarily through interactions with the immune system. LPS is a potent activator of the immune system and is a pyrogen (agent that causes fever). [ 4 ] In severe cases, LPS can trigger a brisk host response and multiple types of acute organ failure [ 5 ] which can lead to septic shock . [ 6 ] In lower levels and over a longer time period, there is evidence LPS may play an important and harmful role in autoimmunity , obesity , depression , and cellular senescence . [ 7 ] [ 8 ] [ 9 ] [ 10 ]
The toxic activity of LPS was first discovered and termed endotoxin by Richard Friedrich Johannes Pfeiffer . He distinguished between exotoxins , toxins that are released by bacteria into the surrounding environment, and endotoxins, which are toxins "within" the bacterial cell and released only after destruction of the bacterial outer membrane. [ 11 ] Subsequent work showed that release of LPS from Gram negative microbes does not necessarily require the destruction of the bacterial cell wall, but rather, LPS is secreted as part of the normal physiological activity of membrane vesicle trafficking in the form of bacterial outer membrane vesicles (OMVs) , which may also contain other virulence factors and proteins. [ 12 ] [ 2 ]
LPS is a major component of the outer cell membrane of gram-negative bacteria , contributing greatly to the structural integrity of the bacteria and protecting the membrane from certain kinds of chemical attack. LPS is the most abundant antigen on the cell surface of most gram-negative bacteria, contributing up to 80% of the outer membrane of E. coli and Salmonella . [ 2 ] LPS increases the negative charge of the cell membrane and helps stabilize the overall membrane structure. It is of crucial importance to many gram-negative bacteria, which die if the genes coding for it are mutated or removed. However, it appears that LPS is nonessential in at least some gram-negative bacteria, such as Neisseria meningitidis , Moraxella catarrhalis , and Acinetobacter baumannii . [ 13 ] It has also been implicated in non-pathogenic aspects of bacterial ecology, including surface adhesion, bacteriophage sensitivity, and interactions with predators such as amoebae . LPS is also required for the functioning of omptins , a class of bacterial protease. [ 14 ]
LPS are amphipathic and composed of three parts: the O antigen (or O polysaccharide) which is hydrophilic, the core oligosaccharide (also hydrophilic), and Lipid A , the hydrophobic domain.
The repetitive glycan polymer contained within an LPS is referred to as the O antigen , O polysaccharide , or O side-chain of the bacteria. The O antigen is attached to the core oligosaccharide, and comprises the outermost domain of the LPS molecule. The structure and composition of the O chain is highly variable from strain to strain, determining the serological specificity of the parent bacterial strain; [ 15 ] there are over 160 different O antigen structures produced by different E. coli strains. [ 16 ] The presence or absence of O chains determines whether the LPS is considered "rough" or "smooth". Full-length O-chains would render the LPS smooth, whereas the absence or reduction of O-chains would make the LPS rough. [ 17 ] Bacteria with rough LPS usually have more penetrable cell membranes to hydrophobic antibiotics, since a rough LPS is more hydrophobic . [ 18 ] O antigen is exposed on the very outer surface of the bacterial cell, and, as a consequence, is a target for recognition by host antibodies .
The core domain always contains an oligosaccharide component that attaches directly to lipid A and commonly contains sugars such as heptose and 3-Deoxy-D-manno-oct-2-ulosonic acid (also known as KDO, keto-deoxyoctulosonate). [ 19 ] The core oligosaccharide is less variable in its structure and composition, a given core structure being common to large groups of bacteria. [ 15 ] The LPS cores of many bacteria also contain non-carbohydrate components, such as phosphate, amino acids, and ethanolamine substituents.
Lipid A is, in normal circumstances, a phosphorylated glucosamine disaccharide decorated with multiple fatty acids . These hydrophobic fatty acid chains anchor the LPS into the bacterial membrane, and the rest of the LPS projects from the cell surface. The lipid A domain is the most bioactive and responsible for much of the toxicity of Gram-negative bacteria . When bacterial cells are lysed by the immune system , fragments of membrane containing lipid A may be released into the circulation, causing fever, diarrhea, and possible fatal endotoxic septic shock (a form of septic shock ). The Lipid A moiety is a very conserved component of the LPS. [ 20 ] However Lipid A structure varies among bacterial species. Lipid A structure largely defines the degree and nature of the overall host immune activation. [ 21 ]
The "rough form" of LPS has a lower molecular weight due to the absence of the O polysaccharide. In its place is a short oligosaccharide: this form is known as Lipooligosaccharide (LOS), and is a glycolipid found in the outer membrane of some types of Gram-negative bacteria , such as Neisseria spp. and Haemophilus spp. [ 7 ] [ 22 ] LOS plays a central role in maintaining the integrity and functionality of the outer membrane of the Gram negative cell envelope. LOS play an important role in the pathogenesis of certain bacterial infections because they are capable of acting as immunostimulators and immunomodulators. [ 7 ] Furthermore, LOS molecules are responsible for the ability of some bacterial strains to display molecular mimicry and antigenic diversity , aiding in the evasion of host immune defenses and thus contributing to the virulence of these bacterial strains . In the case of Neisseria meningitidis , the lipid A portion of the molecule has a symmetrical structure and the inner core is composed of 3-deoxy-D-manno-2-octulosonic acid (KDO) and heptose (Hep) moieties. The outer core oligosaccharide chain varies depending on the bacterial strain . [ 7 ] [ 22 ]
A highly conserved host enzyme called acyloxyacyl hydrolase (AOAH) may detoxify LPS when it enters, or is produced in, animal tissues. It may also convert LPS in the intestine into an LPS inhibitor. Neutrophils, macrophages and dendritic cells produce this lipase, which inactivates LPS by removing the two secondary acyl chains from lipid A to produce tetraacyl LPS. If mice are given LPS parenterally, those that lack AOAH develop high titers of non-specific antibodies, develop prolonged hepatomegaly, and experience prolonged endotoxin tolerance. LPS inactivation may be required for animals to restore homeostasis after parenteral LPS exposure. [ 23 ] Although mice have many other mechanisms for inhibiting LPS signaling, none is able to prevent these changes in animals that lack AOAH.
Dephosphorylation of LPS by intestinal alkaline phosphatase can reduce the severity of Salmonella tryphimurium and Clostridioides difficile infection restoring normal gut microbiota. [ 24 ] Alkaline phosphatase prevents intestinal inflammation (and
" leaky gut ") from bacteria by dephosphorylating the Lipid A portion of LPS. [ 25 ] [ 26 ] [ 27 ]
The entire process of making LPS starts with a molecule called lipid A-Kdo2, which is first created on the surface of the bacterial cell's inner membrane. Then, additional sugars are added to this molecule on the inner membrane before it's moved to the space between the inner and outer membranes ( periplasmic space ) with the help of a protein called MsbA. The O-antigen, another part of LPS, is made by special enzyme complexes on the inner membrane. It is then moved to the outer membrane through three different systems: one is Wzy-dependent, another relies on ABC transporters, and the third involves a synthase-dependent process. [ 30 ]
Ultimately, LPS is transported to the outer membrane by a membrane-to-membrane bridge of lipolysaccharide transport (Lpt) proteins. [ 29 ] [ 31 ] This transporter is a potential antibiotic target. [ 32 ] [ 33 ]
The human body carries endogenous stores of LPS. [ 34 ] The epithelial surfaces are colonized by a complex microbial flora (including gram-negative bacteria), which outnumber human cells by a factor of 10 to 1. Gram-negative bacterial will shed endotoxins. This host-microbial interaction is a symbiotic relationship which plays a critical role in systemic immunologic homeostasis. When this is disrupted, it can lead to disease such as endotoxemia and endotoxic septic shock.
LPS acts as the prototypical endotoxin because it binds the CD14 / TLR4 / MD2 receptor complex in many cell types, but especially in monocytes , dendritic cells , macrophages and B cells , which promotes the secretion of pro- inflammatory cytokines , nitric oxide , and eicosanoids . [ 35 ] Bruce Beutler was awarded a portion of the 2011 Nobel Prize in Physiology or Medicine for his work demonstrating that TLR4 is the LPS receptor. [ 36 ] [ 37 ]
As part of the cellular stress response , superoxide is one of the major reactive oxygen species induced by LPS in various cell types that express TLR ( toll-like receptor ). [ 38 ] LPS is also an exogenous pyrogen (fever-inducing substance). [ 4 ]
LPS function has been under experimental research for several years due to its role in activating many transcription factors . LPS also produces many types of mediators involved in septic shock . Of mammals, humans are much more sensitive to LPS than other primates, [ 39 ] and other animals as well (e.g., mice). A dose of 1 μg/kg induces shock in humans, but mice will tolerate a dose up to a thousand times higher. [ 40 ] This may relate to differences in the level of circulating natural antibodies between the two species. [ 41 ] [ 42 ] It may also be linked to multiple immune tactics against pathogens, and part of a multi-faceted anti-microbial strategy that has been informed by human behavioral changes over our species' evolution (e.g., meat eating, agricultural practices, and smoking). [ 39 ] Said et al. showed that LPS causes an IL-10 -dependent inhibition of CD4 T-cell expansion and function by up-regulating PD-1 levels on monocytes which leads to IL-10 production by monocytes after binding of PD-1 by PD-L1 . [ 43 ]
Endotoxins are in large part responsible for the dramatic clinical manifestations of infections with pathogenic Gram-negative bacteria, such as Neisseria meningitidis , the pathogens that causes meningococcal disease , including meningococcemia , Waterhouse–Friderichsen syndrome , and meningitis .
Portions of the LPS from several bacterial strains have been shown to be chemically similar to human host cell surface molecules; the ability of some bacteria to present molecules on their surface which are chemically identical or similar to the surface molecules of some types of host cells is termed molecular mimicry . [ 44 ] For example, in Neisseria meningitidis L2,3,5,7,9, the terminal tetrasaccharide portion of the oligosaccharide (lacto-N-neotetraose) is the same tetrasaccharide as that found in paragloboside , a precursor for ABH glycolipid antigens found on human erythrocytes . [ 7 ] In another example, the terminal trisaccharide portion (lactotriaose) of the oligosaccharide from pathogenic Neisseria spp. LOS is also found in lactoneoseries glycosphingolipids from human cells. [ 7 ] Most meningococci from groups B and C, as well as gonococci , have been shown to have this trisaccharide as part of their LOS structure. [ 7 ] The presence of these human cell surface 'mimics' may, in addition to acting as a 'camouflage' from the immune system, play a role in the abolishment of immune tolerance when infecting hosts with certain human leukocyte antigen (HLA) genotypes, such as HLA-B35 . [ 7 ]
LPS can be sensed directly by hematopoietic stem cells (HSCs) through the bonding with TLR4, causing them to proliferate in reaction to a systemic infection. This response activate the TLR4-TRIF-ROS-p38 signaling within the HSCs and through a sustained TLR4 activation can cause a proliferative stress, leading to impair their competitive repopulating ability. [ 45 ] Infection in mice using S. typhimurium showed similar results, validating the experimental model also in vivo .
O-antigens (the outer carbohydrates) are the most variable portion of the LPS molecule, imparting antigenic specificity. In contrast, lipid A is the most conserved part. However, lipid A composition also may vary (e.g., in number and nature of acyl chains even within or between genera). Some of these variations may impart antagonistic properties to these LPS. For example, diphosphoryl lipid A of Rhodobacter sphaeroides (RsDPLA) is a potent antagonist of LPS in human cells, but is an agonist in hamster and equine cells. [ 46 ]
It has been speculated that conical lipid A (e.g., from E. coli ) is more agonistic, while less conical lipid A like that of Porphyromonas gingivalis may activate a different signal ( TLR2 instead of TLR4), and completely cylindrical lipid A like that of Rhodobacter sphaeroides is antagonistic to TLRs. [ 47 ] [ 48 ] In general, LPS gene clusters are highly variable between different strains, subspecies, species of bacterial pathogens of plants and animals. [ 49 ] [ 50 ]
Normal human blood serum contains anti-LOS antibodies that are bactericidal and patients that have infections caused by serotypically distinct strains possess anti-LOS antibodies that differ in their specificity compared with normal serum. [ 51 ] These differences in humoral immune response to different LOS types can be attributed to the structure of the LOS molecule, primarily within the structure of the oligosaccharide portion of the LOS molecule. [ 51 ] In Neisseria gonorrhoeae it has been demonstrated that the antigenicity of LOS molecules can change during an infection due to the ability of these bacteria to synthesize more than one type of LOS, [ 51 ] a characteristic known as phase variation . Additionally, Neisseria gonorrhoeae , as well as Neisseria meningitidis and Haemophilus influenzae , [ 7 ] are capable of further modifying their LOS in vitro , for example through sialylation (modification with sialic acid residues), and as a result are able to increase their resistance to complement -mediated killing [ 51 ] or even down-regulate complement activation [ 7 ] or evade the effects of bactericidal antibodies. [ 7 ] Sialylation may also contribute to hindered neutrophil attachment and phagocytosis by immune system cells as well as a reduced oxidative burst. [ 7 ] Haemophilus somnus , a pathogen of cattle, has also been shown to display LOS phase variation, a characteristic which may help in the evasion of bovine host immune defenses. [ 52 ] Taken together, these observations suggest that variations in bacterial surface molecules such as LOS can help the pathogen evade both the humoral (antibody and complement-mediated) and the cell-mediated (killing by neutrophils, for example) host immune defenses.
Recently, it was shown that in addition to TLR4 mediated pathways, certain members of the family of the transient receptor potential ion channels recognize LPS. [ 53 ] LPS-mediated activation of TRPA1 was shown in mice [ 54 ] and Drosophila melanogaster flies. [ 55 ] At higher concentrations, LPS activates other members of the sensory TRP channel family as well, such as TRPV1 , TRPM3 and to some extent TRPM8 . [ 56 ] LPS is recognized by TRPV4 on epithelial cells. TRPV4 activation by LPS was necessary and sufficient to induce nitric oxide production with a bactericidal effect. [ 57 ]
Lipopolysaccharide is a significant factor that makes bacteria harmful, and it helps categorize them into different groups based on their structure and function. This makes LPS a useful marker for telling apart various Gram-negative bacteria. Swiftly identifying and understanding the types of pathogens involved is crucial for promptly managing and treating infections. Since LPS is the main trigger for the immune response in our cells, it acts as an early signal of an acute infection. Therefore, LPS testing is more specific and meaningful than many other serological tests. [ 58 ]
The current methods for testing LPS are quite sensitive, but many of them struggle to differentiate between different LPS groups. Additionally, the nature of LPS, which has both water-attracting and water-repelling properties (amphiphilic), makes it challenging to develop sensitive and user-friendly tests. [ 58 ]
The typical detection methods rely on identifying the lipid A part of LPS because Lipid A is very similar among different bacterial species and serotypes. LPS testing techniques fall into six categories, and they often overlap: in vivo tests, in vitro tests, modified immunoassays, biological assays, and chemical assays. [ 58 ]
Because the LPS is very difficult to measure in whole blood and because most LPS is bound to proteins and complement, the Endotoxin Activity Assay (EAA™) was developed and cleared by the US FDA in 2003. EAA is a rapid in vitro chemiluminescent immunodiagnostic test. It utilizes a specific monoclonal antibody to measure the endotoxin activity in EDTA whole blood specimens. This assay uses the biological response of the neutrophils in a patient’s blood to an immunological complex of endotoxin and exogenous antibody – the chemiluminescent reaction formed creates an emission of light. The amount of chemiluminescence is proportional to the logarithmic concentration of LPS in the sample and is a measure of the endotoxin activity in the blood. [ 59 ] The assay reacts specifically with the Lipid A moiety of LPS of Gram-negative bacteria and does not cross-react with cell wall constituents of Gram-positive bacteria and other microorganisms.
LPS is a powerful toxin that, when in the body, triggers inflammation by binding to cell receptors. Excessive LPS in the blood, endotoxemia, may cause a highly lethal form of sepsis known as endotoxic septic shock. [ 5 ] This condition includes symptoms that fall along a continuum of pathophysiologic states, starting with a systemic inflammatory response syndrome (SIRS) and ending in multiorgan dysfunction syndrome (MODS) before death. Early symptoms include rapid heart rate, quick breathing, temperature changes, and blood clotting issues, resulting in blood vessels widening and reduced blood volume, leading to cellular dysfunction. [ 58 ]
Recent research indicates that even small LPS exposure is associated with autoimmune diseases and allergies. High levels of LPS in the blood can lead to metabolic syndrome, increasing the risk of conditions like diabetes, heart disease, and liver problems. [ 58 ]
LPS also plays a crucial role in symptoms caused by infections from harmful bacteria, including severe conditions like Waterhouse-Friderichsen syndrome, meningococcemia, and meningitis. Certain bacteria can adapt their LPS to cause long-lasting infections in the respiratory and digestive systems. [ 58 ]
Recent studies have shown that LPS disrupts cell membrane lipids, affecting cholesterol and metabolism, potentially leading to high cholesterol, abnormal blood lipid levels, and non-alcoholic fatty liver disease. In some cases, LPS can interfere with toxin clearance, which may be linked to neurological issues. [ 58 ]
In general the health effects of LPS are due to its abilities as a potent activator and modulator of the immune system, especially its inducement of inflammation. LPS is directly cytoxic and is highly immunostimulatory – as host immune cells recognize LPS, complement are strongly activated. Complement activation and a rising anti-inflammatory response can lead to immune cell dysfunction, immunosuppression, widespread coagulopathy, and serious tissue damage, and can progress to multi-system organ failure and death. [ 39 ]
The presence of endotoxins in the blood is called endotoxemia. High level of endotoxemia can lead to septic shock , [ 60 ] or more specifically endotoxic septic shock, [ 5 ] while lower concentration of endotoxins in the bloodstream is called metabolic endotoxemia. [ 61 ] Endotoxemia is associated with obesity, diet, [ 62 ] cardiovascular diseases, [ 62 ] and diabetes, [ 61 ] while also host genetics might have an effect. [ 63 ]
Moreover, endotoxemia of intestinal origin, especially, at the host-pathogen interface , is considered to be an important factor in the development of alcoholic hepatitis, [ 64 ] which is likely to develop on the basis of the small bowel bacterial overgrowth syndrome and an increased intestinal permeability . [ 65 ]
Lipid A may cause uncontrolled activation of mammalian immune systems with production of inflammatory mediators that may lead to endotoxic septic shock . [ 22 ] [ 5 ] This inflammatory reaction is primarily mediated by Toll-like receptor 4 which is responsible for immune system cell activation. [ 22 ] Damage to the endothelial layer of blood vessels caused by these inflammatory mediators can lead to capillary leak syndrome , dilation of blood vessels and a decrease in cardiac function and can further worsen shock. [ 66 ] LPS is also a potent activator of complemen. [ 66 ] Uncontrolled complement activation may trigger destructive endothelial damage leading to disseminated intravascular coagulation (DIC), or atypical hemolytic uremic syndrome (aHUS) with injury to various organs such as including kidneys and lungs. [ 67 ] The skin can show the effects of vascular damage often coupled with depletion of coagulation factors in the form of petechiae , purpura and ecchymoses . The limbs can also be affected, sometimes with devastating consequences such as the development of gangrene , requiring subsequent amputation . [ 66 ] Loss of function of the adrenal glands can cause adrenal insufficiency and additional hemorrhage into the adrenals causes Waterhouse-Friderichsen syndrome , both of which can be life-threatening.
It has also been reported that gonococcal LOS can cause damage to human fallopian tubes . [ 51 ]
Toraymyxin is a widely used extracorporeal endotoxin removal therapy through direct hemoadsorption (also referred to as hemoperfusion ). It is a polystyrene-derived cartridge with molecules of polymyxin B (PMX-B) covalently bound to mesh fibers contained within it. Polymyxins are cyclic cationic polypeptide antibiotics derived from Bacillus polymyxa with an effective antimicrobial activity against Gram-negative bacteria, but their intravenous clinical use has been limited due to their nephrotoxicity and neurotoxicity side effects. [ 68 ] The extracorporeal use of the Toraymyxin cartridge allows PMX-B to bind lipid A with a very stable interaction with its hydrophobic residues thereby neutralizing endotoxins as the blood is filtered through the extracorporeal circuit inside the cartridge, thus reversing endotoxemia and avoiding its toxic systemic effects. [ 69 ]
The molecular mimicry of some LOS molecules is thought to cause autoimmune-based host responses, such as flareups of multiple sclerosis . [ 7 ] [ 44 ] Other examples of bacterial mimicry of host structures via LOS are found with the bacteria Helicobacter pylori and Campylobacter jejuni , organisms which cause gastrointestinal disease in humans, and Haemophilus ducreyi which causes chancroid . Certain C. jejuni LPS serotypes (attributed to certain tetra- and pentasaccharide moieties of the core oligosaccharide) have also been implicated with Guillain–Barré syndrome and a variant of Guillain–Barré called Miller-Fisher syndrome . [ 7 ]
Epidemiological studies have shown that increased endotoxin load, which can be a result of increased populations of endotoxin-producing bacteria in the intestinal tract, is associated with certain obesity-related patient groups. [ 8 ] [ 70 ] [ 71 ] Other studies have shown that purified endotoxin from Escherichia coli can induce obesity and insulin-resistance when injected into germ-free mouse models . [ 72 ] A more recent study has uncovered a potentially contributing role for Enterobacter cloacae B29 toward obesity and insulin resistance in a human patient. [ 73 ] The presumed mechanism for the association of endotoxin with obesity is that endotoxin induces an inflammation-mediated pathway accounting for the observed obesity and insulin resistance. [ 72 ] Bacterial genera associated with endotoxin-related obesity effects include Escherichia and Enterobacter .
There is experimental and observational evidence that LPS might play a role in depression. Administration of LPS in mice can lead to depressive symptoms, and there seem to be elevated levels of LPS in some people with depression. Inflammation may sometimes play a role in the development of depression, and LPS is pro-inflammatory. [ 9 ]
Inflammation induced by LPS can induce cellular senescence , as has been shown for the lung epithelial cells and microglial cells (the latter leading to neurodegeneration ). [ 10 ]
Lipopolysaccharides are frequent contaminants in plasmid DNA prepared from bacteria or proteins expressed from bacteria, and must be removed from the DNA or protein to avoid contaminating experiments and to avoid toxicity of products manufactured using industrial fermentation . [ 74 ]
Ovalbumin is frequently contaminated with endotoxins. Ovalbumin is one of the extensively studied proteins in animal models and also an established model allergen for airway hyper-responsiveness (AHR). Commercially available ovalbumin that is contaminated with LPS can falsify research results, as it does not accurately reflect the effect of the protein antigen on animal physiology. [ 75 ]
In pharmaceutical production, it is necessary to remove all traces of endotoxin from drug product containers, as even small amounts of endotoxin will cause illness in humans. A depyrogenation oven is used for this purpose. Temperatures in excess of 300 °C are required to fully break down LPS. [ 76 ]
The standard assay for detecting presence of endotoxin is the Limulus Amebocyte Lysate (LAL) assay, utilizing blood from the Horseshoe crab ( Limulus polyphemus ). [ 77 ] Very low levels of LPS can cause coagulation of the limulus lysate due to a powerful amplification through an enzymatic cascade. However, due to the dwindling population of horseshoe crabs, and the fact that there are factors that interfere with the LAL assay, efforts have been made to develop alternative assays, with the most promising ones being ELISA tests using a recombinant version of a protein in the LAL assay, Factor C. [ 78 ] | https://en.wikipedia.org/wiki/Lipopolysaccharide |
A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid (also known as fat ) molecules in water, as in blood plasma or other extracellular fluids . They consist of a triglyceride and cholesterol center, surrounded by a phospholipid outer shell, with the hydrophilic portions oriented outward toward the surrounding water and lipophilic portions oriented inward toward the lipid center. A special kind of protein, called apolipoprotein , is embedded in the outer shell, both stabilising the complex and giving it a functional identity that determines its role.
Plasma lipoprotein particles are commonly divided into five main classes, based on size, lipid composition, and apolipoprotein content. They are, in increasing size order: HDL , LDL , IDL , VLDL and chylomicrons . Subgroups of these plasma particles are primary drivers or modulators of atherosclerosis . [ 1 ]
Many enzymes , transporters , structural proteins, antigens , adhesins , and toxins are sometimes also classified as lipoproteins, since they are formed by lipids and proteins.
Some transmembrane proteolipids , especially those found in bacteria , are referred to as lipoproteins; they are not related to the lipoprotein particles that this article is about. [ 2 ] Such transmembrane proteins are difficult to isolate, as they bind tightly to the lipid membrane, often require lipids to display the proper structure, and can be water-insoluble. Detergents are usually required to isolate transmembrane lipoproteins from their associated biological membranes.
Because fats are insoluble in water, they cannot be transported on their own in extracellular water, including blood plasma. Instead, they are surrounded by a hydrophilic external shell that functions as a transport vehicle. The role of lipoprotein particles is to transport fat molecules, such as triglycerides , phospholipids, and cholesterol within the extracellular water of the body to all the cells and tissues of the body. The proteins included in the external shell of these particles, called apolipoproteins, are synthesized and secreted into the extracellular water by both the small intestine and liver cells. The external shell also contains phospholipids and cholesterol.
All cells use and rely on fats and cholesterol as building blocks to create the multiple membranes that cells use both to control internal water content and internal water-soluble elements and to organize their internal structure and protein enzymatic systems. The outer shell of lipoprotein particles have the hydrophilic groups of phospholipids, cholesterol, and apolipoproteins directed outward. Such characteristics make them soluble in the salt-water-based blood pool. Triglycerides and cholesteryl esters are carried internally, shielded from the water by the outer shell. The kind of apolipoproteins contained in the outer shell determines the functional identity of the lipoprotein particles. The interaction of these apolipoproteins with enzymes in the blood, with each other, or with specific proteins on the surfaces of cells, determines whether triglycerides and cholesterol will be added to or removed from the lipoprotein transport particles.
Characterization in human plasma [ 3 ]
Lipoproteins are complex particles that have a central hydrophobic core of non-polar lipids, primarily cholesteryl esters and triglycerides. This hydrophobic core is surrounded by a hydrophilic membrane consisting of phospholipids, free cholesterol, and apolipoproteins. Plasma lipoproteins, found in blood plasma , are typically divided into five main classes based on size, lipid composition, and apolipoprotein content: HDL , LDL , IDL , VLDL and chylomicrons . [ 4 ]
The handling of lipoprotein particles in the body is referred to as lipoprotein particle metabolism . It is divided into two pathways, exogenous and endogenous , depending in large part on whether the lipoprotein particles in question are composed chiefly of dietary (exogenous) lipids or whether they originated in the liver (endogenous), through de novo synthesis of triglycerides.
The hepatocytes are the main platform for the handling of triglycerides and cholesterol; the liver can also store certain amounts of glycogen and triglycerides. While adipocytes are the main storage cells for triglycerides, they do not produce any lipoproteins.
Bile emulsifies fats contained in the chyme , then pancreatic lipase cleaves triglyceride molecules into two fatty acids and one 2-monoacylglycerol. Enterocytes readily absorb the small molecules from the chymus. Inside of the enterocytes, fatty acids and monoacylglycerides are transformed again into triglycerides. Then these lipids are assembled with apolipoprotein B-48 into nascent chylomicrons . These particles are then secreted into the lacteals in a process that depends heavily on apolipoprotein B-48. As they circulate through the lymphatic vessels , nascent chylomicrons bypass the liver circulation and are drained via the thoracic duct into the bloodstream.
In the blood stream, nascent chylomicron particles interact with HDL particles, resulting in HDL donation of apolipoprotein C-II and apolipoprotein E to the nascent chylomicron. The chylomicron at this stage is then considered mature. Via apolipoprotein C-II, mature chylomicrons activate lipoprotein lipase (LPL), an enzyme on endothelial cells lining the blood vessels. LPL catalyzes the hydrolysis of triglycerides that ultimately releases glycerol and fatty acids from the chylomicrons. Glycerol and fatty acids can then be absorbed in peripheral tissues, especially adipose and muscle , for energy and storage.
The hydrolyzed chylomicrons are now called chylomicron remnants . The chylomicron remnants continue circulating the bloodstream until they interact via apolipoprotein E with chylomicron remnant receptors, found chiefly in the liver. This interaction causes the endocytosis of the chylomicron remnants, which are subsequently hydrolyzed within lysosomes . Lysosomal hydrolysis releases glycerol and fatty acids into the cell, which can be used for energy or stored for later use.
The liver is the central platform for the handling of lipids: it is able to store glycerols and fats in its cells, the hepatocytes . Hepatocytes are also able to create triglycerides via de novo synthesis. They also produce the bile from cholesterol. The intestines are responsible for absorbing cholesterol. They transfer it over into the blood stream.
In the hepatocytes, triglycerides and cholesteryl esters are assembled with apolipoprotein B-100 to form nascent VLDL particles . Nascent VLDL particles are released into the bloodstream via a process that depends upon apolipoprotein B-100.
In the blood stream, nascent VLDL particles bump with HDL particles; as a result, HDL particles donate apolipoprotein C-II and apolipoprotein E to the nascent VLDL particle. Once loaded with apolipoproteins C-II and E, the nascent VLDL particle is considered mature. VLDL particles circulate and encounter LPL expressed on endothelial cells . Apolipoprotein C-II activates LPL, causing hydrolysis of the VLDL particle and the release of glycerol and fatty acids. These products can be absorbed from the blood by peripheral tissues, principally adipose and muscle. The hydrolyzed VLDL particles are now called VLDL remnants or intermediate-density lipoproteins (IDLs). VLDL remnants can circulate and, via an interaction between apolipoprotein E and the remnant receptor, be absorbed by the liver, or they can be further hydrolyzed by hepatic lipase .
Hydrolysis by hepatic lipase releases glycerol and fatty acids, leaving behind IDL remnants , called low-density lipoproteins (LDL), which contain a relatively high cholesterol content [ 5 ] ( see native LDL structure at 37°C on YouTube ). LDL circulates and is absorbed by the liver and peripheral cells. Binding of LDL to its target tissue occurs through an interaction between the LDL receptor and apolipoprotein B-100 on the LDL particle. Absorption occurs through endocytosis , and the internalized LDL particles are hydrolyzed within lysosomes, releasing lipids, chiefly cholesterol.
Plasma lipoproteins may carry oxygen gas. [ 6 ] This property is due to the crystalline hydrophobic structure of lipids, providing a suitable environment for O 2 solubility compared to an aqueous medium. [ 7 ]
Inflammation , a biological system response to stimuli such as the introduction of a pathogen , has an underlying role in numerous systemic biological functions and pathologies. This is a useful response by the immune system when the body is exposed to pathogens, such as bacteria in locations that will prove harmful, but can also have detrimental effects if left unregulated. It has been demonstrated that lipoproteins, specifically HDL, have important roles in the inflammatory process. [ 8 ]
When the body is functioning under normal, stable physiological conditions, HDL has been shown to be beneficial in several ways. [ 8 ] LDL contains apolipoprotein B (apoB), which allows LDL to bind to different tissues, such as the artery wall if the glycocalyx has been damaged by high blood sugar levels . [ 8 ] If oxidised, the LDL can become trapped in the proteoglycans, preventing its removal by HDL cholesterol efflux. [ 8 ] Normal functioning HDL is able to prevent the process of oxidation of LDL and the subsequent inflammatory processes seen after oxidation. [ 8 ]
Lipopolysaccharide , or LPS, is the major pathogenic factor on the cell wall of Gram-negative bacteria . Gram-positive bacteria has a similar component named Lipoteichoic acid , or LTA. HDL has the ability to bind LPS and LTA, creating HDL-LPS complexes to neutralize the harmful effects in the body and clear the LPS from the body. [ 9 ] HDL also has significant roles interacting with cells of the immune system to modulate the availability of cholesterol and modulate the immune response. [ 9 ]
Under certain abnormal physiological conditions such as system infection or sepsis , the major components of HDL become altered, [ 9 ] [ 10 ] The composition and quantity of lipids and apolipoproteins are altered as compared to normal physiological conditions, such as a decrease in HDL cholesterol (HDL-C), phospholipids, apoA-I (a major lipoprotein in HDL that has been shown to have beneficial anti-inflammatory properties), and an increase in Serum amyloid A . [ 9 ] [ 10 ] This altered composition of HDL is commonly referred to as acute-phase HDL in an acute-phase inflammatory response, during which time HDL can lose its ability to inhibit the oxidation of LDL. [ 8 ] In fact, this altered composition of HDL is associated with increased mortality and worse clinical outcomes in patients with sepsis. [ 9 ]
Lipoproteins may be classified as five major groups, listed from larger and lower density to smaller and higher density. Lipoproteins are larger and less dense when the fat to protein ratio is increased. They are classified on the basis of electrophoresis , ultracentrifugation and nuclear magnetic resonance spectroscopy via the Vantera Analyzer . [ 11 ]
For young healthy research subjects, ~70 kg (154 lb), these data represent averages across individuals studied, percentages represent % dry weight:
[ 12 ] [ 13 ] However, these data are not necessarily reliable for any one individual or for the general clinical population.
It is also possible to classify lipoproteins as "alpha" and "beta", according to the classification of proteins in serum protein electrophoresis . This terminology is sometimes used in describing lipid disorders such as abetalipoproteinemia .
Lipoproteins, such as LDL and HDL, can be further subdivided into subspecies isolated through a variety of methods. [ 14 ] [ 15 ] These are subdivided by density or by the protein contents/ proteins they carry. [ 14 ] While the research is currently ongoing, researchers are learning that different subspecies contain different apolipoproteins, proteins, and lipid contents between species which have different physiological roles. [ 14 ] For example, within the HDL lipoprotein subspecies, a large number of proteins are involved in general lipid metabolism. [ 14 ] However, it is being elucidated that HDL subspecies also contain proteins involved in the following functions: homeostasis , fibrinogen , clotting cascade , inflammatory and immune responses, including the complement system , proteolysis inhibitors, acute-phase response proteins, and the LPS-binding protein , heme and iron metabolism, platelet regulation, vitamin binding and general transport. [ 14 ]
High levels of lipoprotein(a) are a significant risk factor for atherosclerotic cardiovascular diseases via mechanisms associated with inflammation and thrombosis . [ 16 ] The links of mechanisms between different lipoprotein isoforms and risk for cardiovascular diseases, lipoprotein synthesis, regulation, and metabolism, and related risks for genetic diseases are under active research, as of 2022. [ 16 ] | https://en.wikipedia.org/wiki/Lipoprotein |
Lipoteichoic acid ( LTA ) is a major constituent of the cell wall of gram-positive bacteria. These organisms have an inner (or cytoplasmic) membrane and, external to it, a thick (up to 80 nanometer ) peptidoglycan layer. The structure of LTA varies between the different species of gram-positive bacteria and may contain long chains of ribitol or glycerol phosphate. LTA is anchored to the cell membrane via a diacylglycerol . [ 1 ] It acts as regulator of autolytic wall enzymes ( muramidases ). It has antigenic properties being able to stimulate specific immune response.
LTA may bind to target cells non-specifically through membrane phospholipids , or specifically to CD14 and to Toll-like receptors . Binding to TLR-2 has shown to induce NF-κB expression(a central transcription factor ), elevating expression of both pro- and anti- apoptotic genes. Its activation also induces mitogen-activated protein kinases (MAPK) activation along with phosphoinositide 3-kinase activation.
LTA's molecular structure has been found to have the strongest hydrophobic bonds of an entire bacteria [ citation needed ] .
Said et al. showed that LTA causes an IL-10 -dependent inhibition of CD4 T-cell expansion and function by up-regulating PD-1 levels on monocytes which leads to IL-10 production by monocytes after binding of PD-1 by PD-L. [ 2 ]
Lipoteichoic acid (LTA) from Gram-positive bacteria exerts different immune effects depending on the bacterial source from which it is isolated. For example, LTA from Enterococcus faecalis is a virulence factor positively correlating to inflammatory damage to teeth during acute infection. [ 3 ] On the other hand, a study reported Lacticaseibacillus rhamnosus GG LTA (LGG-LTA) oral administration reduces UVB-induced immunosuppression and skin tumor development in mice. [ 4 ] In animal studies, specific bacterial LTA has been correlated with induction of arthritis, nephritis, uveitis, encephalomyelitis, meningeal inflammation, and periodontal lesions, and also triggered cascades resulting in septic shock and multiorgan failure. | https://en.wikipedia.org/wiki/Lipoteichoic_acid |
Lipotoxicity is a metabolic syndrome that results from the accumulation of lipid intermediates in non- adipose tissue , leading to cellular dysfunction and death . The tissues normally affected include the kidneys , liver , heart and skeletal muscle . Lipotoxicity is believed to have a role in heart failure , obesity , and diabetes , and is estimated to affect approximately 25% of the adult American population. [ 1 ]
In normal cellular operations, there is a balance between the production of lipids, and their oxidation or transport. In lipotoxic cells, there is an imbalance between the amount of lipids produced and the amount used. Upon entrance of the cell, fatty acids can be converted to different types of lipids for storage. Triacylglycerol consists of three fatty acids bound to a glycerol molecule and is considered the most neutral and harmless type of intracellular lipid storage. Alternatively, fatty acids can be converted to lipid intermediates like diacylglycerol , ceramides and fatty acyl-CoAs. These lipid intermediates can impair cellular function, which is referred to as lipotoxicity. [ 2 ]
Adipocytes , the cells that normally function as lipid store of the body, are well equipped to handle the excess lipids. Yet, too great of an excess will overburden these cells and cause a spillover into non-adipose cells, which do not have the necessary storage space. When the storage capacity of non-adipose cells is exceeded, cellular dysfunction and/or death result. The mechanism by which lipotoxicity causes death and dysfunction is not well understood. The cause of apoptosis and extent of cellular dysfunction is related to the type of cell affected, as well as the type and quantity of excess lipids. [ 3 ] A theory has been put forward by Cambridge researchers relating the development of lipotoxicity to the perturbation of membrane glycerophospholipid/sphingolipid homeostasis and their associated signalling events. [ 4 ]
Currently, there is no universally accepted theory for why certain individuals are afflicted with lipotoxicity. Research is ongoing into a genetic cause, but no individual gene has been named as the causative agent. The causative role of obesity in lipotoxicity is controversial. Some researchers claim that obesity has protective effects against lipotoxicity as it results in extra adipose tissue in which excess lipids can be stored. Others claim obesity is a risk factor for lipotoxicity. Both sides accept that high fat diets put patients at increased risk for lipotoxic cells. Individuals with high numbers of lipotoxic cells usually experience both leptin and insulin resistance . However, no causative mechanism has been found for this correlation. [ 5 ]
Renal lipotoxicity occurs when excess long-chain nonesterified fatty acids are stored in the kidney and proximal tubule cells. It is believed that these fatty acids are delivered to the kidneys via serum albumin . This condition leads to tubulointerstitial inflammation and fibrosis in mild cases, and to kidney failure and death in severe cases. The current accepted treatments for lipotoxicity in renal cells are fibrate therapy and intensive insulin therapy . [ 6 ]
An excess of free fatty acids in liver cells plays a role in Nonalcoholic Fatty Liver Disease (NAFLD). In the liver, it is the type of fatty acid, not the quantity, that determines the extent of the lipotoxic effects. In hepatocytes , the ratio of monounsaturated fatty acids and saturated fatty acids leads to apoptosis and liver damage. There are several potential mechanisms by which the excess fatty acids can cause cell death and damage. They may activate death receptors , stimulate apoptotic pathways, or initiate cellular stress response in the endoplasmic reticulum . These lipotoxic effects have been shown to be prevented by the presence of excess triglycerides within the hepatocytes. [ 7 ]
Lipotoxicity in cardiac tissue is attributed to excess saturated fatty acids. The apoptosis that follows is believed to be caused by unfolded protein response in the endoplasmic reticulum. Researchers are working on treatments that will increase the oxidation of these fatty acids within the heart in order to prevent the lipotoxic effects. [ 8 ]
Lipotoxicity affects the pancreas when excess free fatty acids are found in beta cells , causing their dysfunction and death. The effects of the lipotoxicity is treated with leptin therapy and insulin sensitizers. [ 9 ]
The skeletal muscle accounts for more than 80 percent of the postprandial whole body glucose uptake and therefore plays an important role in glucose homeostasis. Skeletal muscle lipid levels – intramyocellular lipids (IMCL) – correlate negatively with insulin sensitivity in a sedentary population and hence were considered predictive for insulin resistance and causative in obesity-associated insulin resistance. However, endurance athletes also have high IMCL levels despite being highly insulin sensitive, which indicates that not the level of IMCL accumulation per se, but rather the characteristics of this intramyocellular fat determine whether it negatively affects insulin signaling. [ 2 ] Intramyocellular lipids are mainly stored in lipid droplets , the organelles for fat storage. Recent research indicates that creating intramyocellular neutral lipid storage capacity for example by increasing the abundance of lipid droplet coat proteins [ 2 ] [ 10 ] protects against obesity-associated insulin resistance in skeletal muscle.
The methods to prevent and treat lipotoxicity are divided into three main groups.
The first strategy focuses on decreasing the lipid content of non-adipose tissues. This can be accomplished by either increasing the oxidation of the lipids, or increasing their secretion and transport. Current treatments involve extreme weight loss and leptin treatment. [ 11 ]
Another strategy is focusing on diverting excess lipids away from non-adipose tissues, and towards adipose tissues. This is accomplished with thiazolidinediones , a group of medications that activate nuclear receptor proteins responsible for lipid metabolism. [ 12 ]
The final strategy focuses on inhibiting the apoptotic pathways and signaling cascades. This is accomplished by using drugs that inhibit production of specific chemicals required for the pathways to be functional. While this may prove to the most effective protection against cell death, it will also require the most research and development due to the specificity required of the medications. [ 3 ]
Lipoexpediency refers to the beneficial effects of lipids in a cell or a tissue, primarily lipid-mediated signal transmission events, that may occur even in the setting of excess fatty acids . The term was coined as an antonym to lipotoxicity. [ 13 ] | https://en.wikipedia.org/wiki/Lipotoxicity |
Lipotropic compounds are those that help catalyse the breakdown of fat during metabolism in the body. A lipotropic nutrient promotes or encourages the export of fat from the liver . Lipotropics are necessary for maintenance of a healthy liver, and for burning the exported fat for additional energy. Without lipotropics, such as choline and inositol , fats and bile can become trapped in the liver, causing severe problems such as cirrhosis and blocking fat metabolism .
Choline is the major lipotrope in mammals and other known lipotropes are important only insofar as they contribute to the synthesis of choline. [ 1 ] [ full citation needed ] Choline is essential for fat metabolism. Choline functions as a methyl donor and it is required for proper liver function. Though choline can be synthesized from methionine or serine , mammals don't produce a sufficient amount on their own. Liver , eggs , wheat bran , meat , and broccoli are dietary sources of choline.
Inositol exerts lipotropic effects as well. Oranges and cantaloupe are high in inositol. [ citation needed ]
Methionine , an essential amino acid, is a major lipotropic compound in humans. When estrogen levels are high, the body requires more methionine. Estrogens reduce bile flow through the liver and increase bile cholesterol levels. Methionine helps deactivate estrogens. Egg whites are high in methionine.
Methionine levels also affect the amount of sulfur-containing compounds, such as glutathione , in the liver. Glutathione and other sulfur-containing peptides play a critical role in defending against toxic compounds. Supplementation with vitamin C , vitamin D , and NAC can increase glutathione levels. [ citation needed ]
Betaine hydrochloride is a lipotropic and increases gastric acid. [ 2 ] Betaine itself (in a non-hydrochloric form, also known as TMG or Trimethylglycine ) also has a lipotropic effect. [ 3 ] Quinoa is high in betaine. [ citation needed ]
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Lipotropic |
Lipozyme , a registered trademark of Novo Nordisk A/S Corp., is a class of industrial enzymes , specifically: lipases .
Lipozymes can be differentiated by origin - it can be extracted from Mucor miehei , Thermomyces lanuginosus , Candida antarctica , and others. [ 1 ] [ 2 ] For industrial purposes, it can be immobilized on macroporous ion-exchange resins. [ 2 ] Lipases like Lipozyme and Novozyme (reg.trademark by Novozymes ) play a big role in the synthesis of biodiesel . [ 3 ] Lipozyme is also offered as a food supplement clad in capsules. [ 4 ] It comes in different activities , measured e.g. in IUN/g or KLU/g (IUN = Interesterification Unit, K = Kilo, LU = Lipase unit). [ 5 ] | https://en.wikipedia.org/wiki/Lipozyme |
A Lippmann diagram is a graphical plot showing the solidus/solutus equilibrium states for a given binary solid solution ( e.g. , (Ba 1-x Sr x )SO 4 , barite / celestite ) in equilibrium with an aqueous solution containing the two substituting ions: Ba 2+ and Sr 2+ (solid solution – aqueous solution system, or SS-AS). It was proposed in the 1970s by F. Lippmann [ 1 ] to determine excess Gibbs functions. [ 2 ] This diagram summarizes the thermodynamic basis of solid-solution aqueous-solution systems (SS-AS) equilibria and helps to predict the nucleation kinetics for solid solutions crystallizing from an aqueous solution. [ 3 ]
In the diagram, the abscissa (horizontal axis) represents two variables with different scales to represent both the solid phase mole fraction and the aqueous activity fraction. The ordinate (vertical axis) represents the solid phase. [ 4 ]
There are two variants of Lippmann diagrams: [ citation needed ]
This material -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Lippmann_diagram |
A Lippmann electrometer is a device for detecting small rushes of electric current and was invented by Gabriel Lippmann in 1873. [ 1 ] The device consists of a tube which is thick on one end and very thin on the other. The thin end is designed to act as a capillary tube. The tube is half-filled with mercury with a small amount of dilute sulfuric acid above the mercury in the capillary tube. Metal wires are connected at the thick end into the mercury and at the thin end into the sulfuric acid.
When the pulse of electricity arrives it changes the surface tension of the mercury and allows it to leap up a short distance in the capillary tube. This device was used in the first practical ECG machine which was invented by Augustus Desiré Waller .
This article related to medical imaging is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Lippmann_electrometer |
The Lippmann–Schwinger equation (named after Bernard Lippmann and Julian Schwinger [ 1 ] ) is one of the most used equations to describe particle collisions – or, more precisely, scattering – in quantum mechanics . It may be used in scattering of molecules, atoms, neutrons, photons or any other particles and is important mainly in atomic, molecular, and optical physics , nuclear physics and particle physics , but also for seismic scattering problems in geophysics . It relates the scattered wave function with the interaction that produces the scattering (the scattering potential) and therefore allows calculation of the relevant experimental parameters ( scattering amplitude and cross sections ).
The most fundamental equation to describe any quantum phenomenon, including scattering, is the Schrödinger equation . In physical problems, this differential equation must be solved with the input of an additional set of initial and/or boundary conditions for the specific physical system studied. The Lippmann–Schwinger equation is equivalent to the Schrödinger equation plus the typical boundary conditions for scattering problems. In order to embed the boundary conditions, the Lippmann–Schwinger equation must be written as an integral equation . [ 2 ] For scattering problems, the Lippmann–Schwinger equation is often more convenient than the original Schrödinger equation.
The Lippmann–Schwinger equation's general form is (in reality, two equations are shown below, one for the + {\displaystyle +\,} sign and other for the − {\displaystyle -\,} sign): [ 3 ] | ψ ( ± ) ⟩ = | ϕ ⟩ + 1 E − H 0 ± i ϵ V | ψ ( ± ) ⟩ . {\displaystyle |\psi ^{(\pm )}\rangle =|\phi \rangle +{\frac {1}{E-H_{0}\pm i\epsilon }}V|\psi ^{(\pm )}\rangle .\,}
The potential energy V {\displaystyle V} describes the interaction between the two colliding systems. The Hamiltonian H 0 {\displaystyle H_{0}} describes the situation in which the two systems are infinitely far apart and do not interact. Its eigenfunctions are | ϕ ⟩ {\displaystyle |\phi \rangle \,} and its eigenvalues are the energies E {\displaystyle E\,} . Finally, i ϵ {\displaystyle i\epsilon \,} is a mathematical technicality necessary for the calculation of the integrals needed to solve the equation. It is a consequence of causality, ensuring that scattered waves consist only of outgoing waves. This is made rigorous by the limiting absorption principle .
The Lippmann–Schwinger equation is useful in a very large number of situations involving two-body scattering. For three or more colliding bodies it does not work well because of mathematical limitations; Faddeev equations may be used instead. [ 4 ] However, there are approximations that can reduce a many-body problem to a set of two-body problems in a variety of cases. For example, in a collision between electrons and molecules, there may be tens or hundreds of particles involved. But the phenomenon may be reduced to a two-body problem by describing all the molecule constituent particle potentials together with a pseudopotential . [ 5 ] In these cases, the Lippmann–Schwinger equations may be used. Of course, the main motivations of these approaches are also the possibility of doing the calculations with much lower computational efforts.
We will assume that the Hamiltonian may be written as H = H 0 + V {\displaystyle H=H_{0}+V} where H 0 is the free Hamiltonian (or more generally, a Hamiltonian with known eigenvectors). For example, in nonrelativistic quantum mechanics H 0 may be H 0 = p 2 2 m . {\displaystyle H_{0}={\frac {p^{2}}{2m}}.}
Intuitively V is the interaction energy of the system. Let there be an eigenstate of H 0 : H 0 | ϕ ⟩ = E | ϕ ⟩ . {\displaystyle H_{0}|\phi \rangle =E|\phi \rangle .}
Now if we add the interaction V {\displaystyle V} into the mix, the Schrödinger equation reads [ clarification needed ] ( H 0 + V ) | ψ ⟩ = E | ψ ⟩ . {\displaystyle \left(H_{0}+V\right)|\psi \rangle =E|\psi \rangle .}
Now consider the Hellmann–Feynman theorem , which requires the energy eigenvalues of the Hamiltonian to change continuously with continuous changes in the Hamiltonian. Therefore, we wish that | ψ ⟩ → | ϕ ⟩ {\displaystyle |\psi \rangle \to |\phi \rangle } as V → 0 {\displaystyle V\to 0} . A naive solution to this equation would be | ψ ⟩ = | ϕ ⟩ + 1 E − H 0 V | ψ ⟩ . {\displaystyle |\psi \rangle =|\phi \rangle +{\frac {1}{E-H_{0}}}V|\psi \rangle .} where the notation 1/ A denotes the inverse of A . However E − H 0 is singular since E is an eigenvalue of H 0 . As is described below, this singularity is eliminated in two distinct ways by making the denominator slightly complex: | ψ ( ± ) ⟩ = | ϕ ⟩ + 1 E − H 0 ± i ϵ V | ψ ( ± ) ⟩ . {\displaystyle |\psi ^{(\pm )}\rangle =|\phi \rangle +{\frac {1}{E-H_{0}\pm i\epsilon }}V|\psi ^{(\pm )}\rangle .}
By insertion of a complete set of free particle states, | ψ ( ± ) ⟩ = | ϕ ⟩ + ∫ d β | ϕ β ⟩ E − E β ± i ϵ ⟨ ϕ β | V | ψ ( ± ) ⟩ , H 0 | ϕ β ⟩ = E β | ϕ β ⟩ , {\displaystyle |\psi ^{(\pm )}\rangle =|\phi \rangle +\int d\beta {\frac {|\phi _{\beta }\rangle }{E-E_{\beta }\pm i\epsilon }}\langle \phi _{\beta }|V|\psi ^{(\pm )}\rangle ,\quad H_{0}|\phi _{\beta }\rangle =E_{\beta }|\phi _{\beta }\rangle ,}
the Schrödinger equation is turned into an integral equation. The "in" (+) and "out" (−) states are assumed to form bases too, in the distant past and distant future respectively having the appearance of free particle states, but being eigenfunctions of the complete Hamiltonian. Thus endowing them with an index, the equation becomes | ψ α ( ± ) ⟩ = | ϕ α ⟩ + ∫ d β T β α ( ± ) | ϕ β ⟩ E α − E β ± i ϵ , T β α ( ± ) = ⟨ ϕ β | V | ψ α ( ± ) ⟩ . {\displaystyle |\psi _{\alpha }^{(\pm )}\rangle =|\phi _{\alpha }\rangle +\int d\beta {\frac {T_{\beta \alpha }^{(\pm )}|\phi _{\beta }\rangle }{E_{\alpha }-E_{\beta }\pm i\epsilon }},\quad T_{\beta \alpha }^{(\pm )}=\langle \phi _{\beta }|V|\psi _{\alpha }^{(\pm )}\rangle .}
From the mathematical point of view the Lippmann–Schwinger equation in coordinate representation is an integral equation of Fredholm type . It can be solved by discretization . Since it is equivalent to the differential time-independent Schrödinger equation with appropriate boundary conditions, it can also be solved by numerical methods for differential equations. In the case of the spherically symmetric potential V {\displaystyle V} it is usually solved by partial wave analysis . For high energies and/or weak potential it can also be solved perturbatively by means of Born series . The method convenient also in the case of many-body physics, like in description of atomic, nuclear or molecular collisions is the method of R-matrix of Wigner and Eisenbud. Another class of methods is based on separable expansion of the potential or Green's operator like the method of continued fractions of Horáček and Sasakawa. Very important class of methods is based on variational principles, for example the Schwinger-Lanczos method combining the variational principle of Schwinger with Lanczos algorithm .
In the S-matrix formulation of particle physics , which was pioneered by John Archibald Wheeler among others, [ 6 ] all physical processes are modeled according to the following paradigm. [ 7 ]
One begins with a non-interacting multiparticle state in the distant past. Non-interacting does not mean that all of the forces have been turned off, in which case for example protons would fall apart, but rather that there exists an interaction-free Hamiltonian H 0 , for which the bound states have the same energy level spectrum as the actual Hamiltonian H . This initial state is referred to as the in state . Intuitively, it consists of elementary particles or bound states that are sufficiently well separated that their interactions with each other are ignored.
The idea is that whatever physical process one is trying to study may be modeled as a scattering process of these well separated bound states. This process is described by the full Hamiltonian H , but once it's over, all of the new elementary particles and new bound states separate again and one finds a new noninteracting state called the out state . The S-matrix is more symmetric under relativity than the Hamiltonian, because it does not require a choice of time slices to define.
This paradigm allows one to calculate the probabilities of all of the processes that we have observed in 70 years of particle collider experiments with remarkable accuracy. But many interesting physical phenomena do not obviously fit into this paradigm. For example, if one wishes to consider the dynamics inside of a neutron star sometimes one wants to know more than what it will finally decay into. In other words, one may be interested in measurements that are not in the asymptotic future. Sometimes an asymptotic past or future is not even available. For example, it is very possible that there is no past before the Big Bang .
In the 1960s, the S-matrix paradigm was elevated by many physicists to a fundamental law of nature. In S-matrix theory , it was stated that any quantity that one could measure should be found in the S-matrix for some process. This idea was inspired by the physical interpretation that S-matrix techniques could give to Feynman diagrams restricted to the mass-shell , and led to the construction of dual resonance models . But it was very controversial, because it denied the validity of quantum field theory based on local fields and Hamiltonians.
Intuitively, the slightly deformed eigenfunctions ψ ( ± ) {\displaystyle \psi ^{(\pm )}} of the full Hamiltonian H are the in and out states. The ϕ {\displaystyle \phi } are noninteracting states that resemble the in and out states in the infinite past and infinite future.
This intuitive picture is not quite right, because ψ ( ± ) {\displaystyle \psi ^{(\pm )}} is an eigenfunction of the Hamiltonian and so at different times only differs by a phase. Thus, in particular, the physical state does not evolve and so it cannot become noninteracting. This problem is easily circumvented by assembling ψ ( ± ) {\displaystyle \psi ^{(\pm )}} and ϕ {\displaystyle \phi } into wavepackets with some distribution g ( E ) {\displaystyle g(E)} of energies E {\displaystyle E} over a characteristic scale Δ E {\displaystyle \Delta E} . The uncertainty principle now allows the interactions of the asymptotic states to occur over a timescale ℏ / Δ E {\displaystyle \hbar /\Delta E} and in particular it is no longer inconceivable that the interactions may turn off outside of this interval. The following argument suggests that this is indeed the case.
Plugging the Lippmann–Schwinger equations into the definitions ψ g ( ± ) ( t ) = ∫ d E e − i E t g ( E ) ψ ( ± ) {\displaystyle \psi _{g}^{(\pm )}(t)=\int dE\,e^{-iEt}g(E)\psi ^{(\pm )}} and ϕ g ( t ) = ∫ d E e − i E t g ( E ) ϕ {\displaystyle \phi _{g}(t)=\int dE\,e^{-iEt}g(E)\phi } of the wavepackets we see that, at a given time, the difference between the ψ g ( t ) {\displaystyle \psi _{g}(t)} and ϕ g ( t ) {\displaystyle \phi _{g}(t)} wavepackets is given by an integral over the energy E .
This integral may be evaluated by defining the wave function over the complex E plane and closing the E contour using a semicircle on which the wavefunctions vanish. The integral over the closed contour may then be evaluated, using the Cauchy integral theorem , as a sum of the residues at the various poles. We will now argue that the residues of ψ ( ± ) {\displaystyle \psi ^{(\pm )}} approach those of ϕ {\displaystyle \phi } at time t → ∓ ∞ {\displaystyle t\to \mp \infty } and so the corresponding wavepackets are equal at temporal infinity.
In fact, for very positive times t the e − i E t {\displaystyle e^{-iEt}} factor in a Schrödinger picture state forces one to close the contour on the lower half-plane. The pole in the ( ϕ , V ψ ± ) {\displaystyle (\phi ,V\psi ^{\pm })} from the Lippmann–Schwinger equation reflects the time-uncertainty of the interaction, while that in the wavepackets weight function reflects the duration of the interaction. Both of these varieties of poles occur at finite imaginary energies and so are suppressed at very large times. The pole in the energy difference in the denominator is on the upper half-plane in the case of ψ − {\displaystyle \psi ^{-}} , and so does not lie inside the integral contour and does not contribute to the ψ − {\displaystyle \psi ^{-}} integral. The remainder is equal to the ϕ {\displaystyle \phi } wavepacket. Thus, at very late times ψ − = ϕ {\displaystyle \psi ^{-}=\phi } , identifying ψ − {\displaystyle \psi ^{-}} as the asymptotic noninteracting out state.
Similarly one may integrate the wavepacket corresponding to ψ + {\displaystyle \psi ^{+}} at very negative times. In this case the contour needs to be closed over the upper half-plane, which therefore misses the energy pole of ψ + {\displaystyle \psi ^{+}} , which is in the lower half-plane. One then finds that the ψ + {\displaystyle \psi ^{+}} and ϕ {\displaystyle \phi } wavepackets are equal in the asymptotic past, identifying ψ + {\displaystyle \psi ^{+}} as the asymptotic noninteracting in state.
This identification of the ψ {\displaystyle \psi } 's as asymptotic states is the justification for the ± ϵ {\displaystyle \pm \epsilon } in the denominator of the Lippmann–Schwinger equations.
The S -matrix is defined to be the inner product S a b = ( ψ a − , ψ b + ) {\displaystyle S_{ab}=(\psi _{a}^{-},\psi _{b}^{+})} of the a th and b th Heisenberg picture asymptotic states. One may obtain a formula relating the S -matrix to the potential V using the above contour integral strategy, but this time switching the roles of ψ + {\displaystyle \psi ^{+}} and ψ − {\displaystyle \psi ^{-}} . As a result, the contour now does pick up the energy pole. This can be related to the ϕ {\displaystyle \phi } 's if one uses the S-matrix to swap the two ψ {\displaystyle \psi } 's. Identifying the coefficients of the ϕ {\displaystyle \phi } 's on both sides of the equation one finds the desired formula relating S to the potential S a b = δ ( a − b ) − 2 i π δ ( E a − E b ) ( ϕ a , V ψ b + ) . {\displaystyle S_{ab}=\delta (a-b)-2i\pi \delta (E_{a}-E_{b})(\phi _{a},V\psi _{b}^{+}).}
In the Born approximation , corresponding to first order perturbation theory , one replaces this last ψ + {\displaystyle \psi ^{+}} with the corresponding eigenfunction ϕ {\displaystyle \phi } of the free Hamiltonian H 0 , yielding S a b = δ ( a − b ) − 2 i π δ ( E a − E b ) ( ϕ a , V ϕ b ) {\displaystyle S_{ab}=\delta (a-b)-2i\pi \delta (E_{a}-E_{b})(\phi _{a},V\phi _{b})\,} which expresses the S-matrix entirely in terms of V and free Hamiltonian eigenfunctions.
These formulas may in turn be used to calculate the reaction rate of the process b → a {\displaystyle b\to a} , which is equal to | S a b − δ a b | 2 . {\displaystyle |S_{ab}-\delta _{ab}|^{2}.}
With the use of Green's function, the Lippmann–Schwinger equation has counterparts in homogenization theory (e.g. mechanics, conductivity, permittivity). | https://en.wikipedia.org/wiki/Lippmann–Schwinger_equation |
Liquation is a metallurgical method for separating metals from an ore or alloy . The material must be heated until one of the metals starts to melt and drain away from the other and can be collected. This method was largely used to remove lead containing silver from copper , but it can also be used to remove antimony from ore minerals , and refine tin .
The 16th-century process of separating copper and silver using liquation, described by Georg Agricola in his 1556 treatise De re metallica , [ 1 ] remained almost unchanged until the 19th century when it was replaced by cheaper and more efficient processes such as sulphatization and eventually electrolytic methods. [ 2 ]
The first known use of liquation on a large scale was in Germany in the mid-15th century. Metal workers had long known that Central European copper ore was rich in silver, so it was only a matter of time until a method was discovered that could separate the two metals. [ 3 ]
Liquation is first documented in the archives of the municipal foundry in Nuremberg in 1453. Nuremberg was one of Germany's main centres of metal refining and fabrication, and was a leader in metallurgical techniques. Five liquation plants soon sprang up around the city, and within 15 years had spread throughout Germany, Poland and the Italian Alps . [ 3 ]
This is often regarded as the beginning of liquation, but evidence suggests liquation may have existed in smaller-scale use centuries earlier. The sophisticated nature of the 15th century liquation plants with custom-made furnaces would be surprising for a new technology. There was also a far simpler but more labour-intensive version of the method brought to Japan by the Portuguese in 1591; this is possibly the remnants of an earlier European method. [ 4 ]
Agricola discusses various types of copper produced from the liquation process; one of these is caldarium or ‘cauldron copper’ which contains a high level of lead and was used to make medieval cauldrons . Analysis of 13th century cauldrons shows that they are made out of copper with a low level of silver and high levels of lead which would match that produced by liquation. [ 5 ]
Liquation may even have existed as early as the 12th century; in Theophilus’ On Divers Arts he makes a possible reference to liquation. [ 4 ] However, he was not an expert in metallurgy, so his writings may not be accurate, and though there were similar cauldrons in the 12th century, no compositional analysis has been published that supports this theory. [ 5 ]
Against the idea that this process was used significantly before it became widespread in the mid-15th century, is the fact that it had to be done on a large-scale to be financially viable. There is no evidence of large-scale liquation before Nuremberg. Also, efficient liquation requires an extremely skilled practitioner. Anyone with that much skill is unlikely to spend much time on something unprofitable. [ 3 ]
Some suggest liquation existed even earlier. Babylonian texts from Mari mention that ‘mountain copper’ was ‘washed’ to produce ‘washed copper’ and that lead was used with silver to produce ‘washed silver’. Some say this shows liquation was being carried out in the Near East as early as the second millennium BC . Crucially, however, these texts do not specifically mention lead being used with copper to produce silver, as would be expected for liquation. [ 6 ]
Liquation requires that the silver-rich copper first be melted with approximately three times its weight in lead; as silver has a greater affinity with lead, most of the silver would end up within this rather than the copper. [ 7 ] If the copper is assayed and found to contain too little silver for liquation to be financially viable (around 0.31% is the minimum required, [ 2 ] ) it is melted and allowed to settle so that much of the silver sinks towards the bottom. The ‘tops’ are then drawn off and used to produce copper while the silver-rich ‘bottoms’ are used in the liquation process. [ 1 ] The copper-lead alloy created can be tapped off and cast into large plano-convex ingots known as ‘liquation cakes’. As the metals cool and solidify the copper and the silver-containing lead separate as they are immiscible with each other.
The ratio of lead to copper in these cakes is an important factor for the process to work efficiently. Agricola recommended 3 parts copper to 8–12 parts lead. The copper must be assayed to accurately determine how much silver it contains; for copper rich in silver the top end of this ratio was used to make sure the maximum amount of silver possible would end up within the lead. However, there also needs to be enough copper to allow the cakes to keep their shape once most of the lead has drained away; too much copper and it would trap some of the lead within and the process would be very inefficient. [ 1 ]
The size of these cakes remained consistent from when Agricola wrote of them in 1556 to the 19th century when the process became obsolete. They were usually 2 + 1 ⁄ 2 to 3 + 1 ⁄ 2 inches (6.4 to 8.9 cm) thick, about 2 feet (0.61 m) in diameter and weighed from 225 to 375 lb (102 to 170 kg). This consistency is not without reason as the size of the cakes is very important to the smooth running of the liquation process. If the cakes are too small, the product would not be worth the time and costs spent on the process, if they are too large then the copper would begin to melt before the maximum amount of lead has drained away. [ 1 ]
The cakes are heated in a liquation furnace , usually four or five at once, to a temperature above the melting point of lead (327 °C ), but below that of copper (1084 °C), so that the silver-rich lead melts and flows away. [ 5 ] As the melting point of lead is so low a high-temperature furnace is not required and it can be fuelled with wood. [ 7 ] It is important that this takes place in a reducing atmosphere, i.e. one with little oxygen , to avoid the lead oxidising ; the cakes are therefore well covered by charcoal and little air is allowed into the furnace. [ 1 ] It is impossible to stop some of the lead oxidising, however, and this drops down and forms spiky projections known as ‘liquation thorns’ in the channel underneath the hearth. [ 2 ]
The older and relatively simple method of cupellation can then be used to separate the silver from the lead. If the lead is assayed and found not to contain enough silver to make the cupellation process worthwhile it is reused in liquation cakes until it has sufficient silver. [ 1 ]
The ‘exhausted liquation cakes’ which still contain some lead and silver are ‘dried’ in a special furnace which is heated to a higher temperature under oxidising conditions. This is essentially just another stage of liquation and most of the remaining lead is expelled and oxidised to form liquation thorns, though some remains as lead metal. The copper can then be refined to remove other impurities and produce copper metal. [ 1 ]
Waste products can be reused to produce new liquation cakes to try to minimise loss of metals, especially silver. [ 1 ] The waste products are mostly in the form of liquation thorns from the liquation and the drying process but there are also some slags produced.
This process is not 100% efficient. At the Lautenthal, Altenau , and Sankt Andreasberg smelting -works in the Upper Harz between 1857 and 1860 25% of the silver, 25.1% of the lead and 9.3% of the copper was lost. Some of this is lost in slag that is not worth reusing, some is lost by what is termed ‘burning’, and some of the silver is lost to the refined copper. [ 8 ] It is clear therefore that a constant supply of lead was needed to make up for that lost at various stages.
John U. Nef, an expert on Renaissance economics , described liquation as ‘even more important than the invention of the printing press ’ for the development of industry during this period. [ 9 ] It increased production of silver on a massive scale. Between 1460 and 1530, the output of silver increased as much as fivefold in central Europe. [ 10 ] This had a secondary effect of lowering the costs of producing copper at a time when its demand had increased due to the needs of the brassmaking industry, [ 9 ] and the use of copper on ships and roofs. Lead production also received a boost, indeed the lack of lead available held the liquation process back until a large lead-bearing seam was discovered at Tarnowitz in Poland . [ 3 ]
Liquation triggered an increase in mining operations, and a new class of wealthy merchants clamoured to participate. Some of the wealthiest merchants in Europe invested in mining, including the French Royal Banker Jacques Coeur and the powerful Medici family of Florence. However, most of the funds came from merchants in neighbouring towns. For example, the burghers of Nuremberg funded mines in the mountains of Bohemia and the Harz. [ 3 ]
Many new copper and silver mines sprang up. A mine at Jáchymov (Joachimstal) in the Ore Mountains was so successful that a coin called ' tolar ' was created, which led to the term, dollar . [ 3 ] Others of note included Schneeberg , and Annaberg (also in the Ore Mountains), Schwaz , in the valley of the Inn , and at Neusohl in Hungary . The new mining wealth allowed some of the largest mines of previous centuries to reopen, such as the silver-bearing lead and copper mines of Rammelsberg . These old mines had previously been abandoned due to flooding, collapses, lack of technology, or simply a lack of money. Now shafts could be sunk deeper and water more efficiently drained, so miners could work seams once out of reach. [ 9 ]
Liquation-based wealth helped build roads between mining and processing regions, and financed improvements to mining technology. Thus its influence went beyond just increasing silver and copper production. It helped revive the economy of large parts of Europe, and the mining of other metals such as iron and mercury . | https://en.wikipedia.org/wiki/Liquation |
In materials science , liquefaction [ 1 ] is a process that generates a liquid from a solid or a gas [ 2 ] or that generates a non-liquid phase which behaves in accordance with fluid dynamics . [ 3 ] It occurs both naturally and artificially . As an example of the latter, a "major commercial application of liquefaction is the liquefaction of air to allow separation of the constituents, such as oxygen, nitrogen, and the noble gases." [ 4 ] Another is the conversion of solid coal into a liquid form usable as a substitute for liquid fuels. [ 5 ]
In geology , soil liquefaction refers to the process by which water-saturated, unconsolidated sediments are transformed into a substance that acts like a liquid, often in an earthquake. [ 6 ] Soil liquefaction was blamed for building collapses in the city of Palu, Indonesia in October 2018. [ 7 ]
In a related phenomenon, liquefaction of bulk materials in cargo ships may cause a dangerous shift in the load. [ 8 ] [ 9 ]
In physics and chemistry , the phase transitions from solid and [gas to liquid ( melting and condensation , respectively) may be referred to as liquefaction. The melting point (sometimes called liquefaction point) is the temperature and pressure at which a solid becomes a liquid. In commercial and industrial situations, the process of condensing a gas to liquid is sometimes referred to as liquefaction of gases . Coal liquefaction is the production of liquid fuels from coal using a variety of industrial processes.
Liquefaction is also used in commercial and industrial settings to refer to mechanical dissolution of a solid by mixing , grinding or blending with a liquid. In kitchen or laboratory settings, solids may be chopped into smaller parts sometimes in combination with a liquid, for example in food preparation or laboratory use. This may be done with a blender .
In biology , liquefaction often involves organic tissue turning into a more liquid-like state. For example, liquefactive necrosis in pathology , [ 10 ] or liquefaction as a parameter in semen analysis . [ 11 ] | https://en.wikipedia.org/wiki/Liquefaction |
Liquefaction of gases is physical conversion of a gas into a liquid state ( condensation ). The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures, using, for example, turboexpanders .
Liquefaction processes are used for scientific, industrial and commercial purposes. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling; a few, such as carbon dioxide , require pressurization as well. Liquefaction is used for analyzing the fundamental properties of gas molecules (intermolecular forces), or for the storage of gases, for example: LPG , and in refrigeration and air conditioning . There the gas is liquefied in the condenser , where the heat of vaporization is released, and evaporated in the evaporator , where the heat of vaporization is absorbed. Ammonia was the first such refrigerant , and is still in widespread use in industrial refrigeration, but it has largely been replaced by compounds derived from petroleum and halogens in residential and commercial applications.
Liquid oxygen is provided to hospitals for conversion to gas for patients with breathing problems, and liquid nitrogen is used in the medical field for cryosurgery , by inseminators to freeze semen , and by field and lab scientists to preserve samples. Liquefied chlorine is transported for eventual solution in water, after which it is used for water purification, sanitation of industrial waste , sewage and swimming pools, bleaching of pulp and textiles and manufacture of carbon tetrachloride , glycol and numerous other organic compounds as well as phosgene gas.
Liquefaction of helium ( 4 He ) with the precooled Hampson–Linde cycle led to a Nobel Prize for Heike Kamerlingh Onnes in 1913. At ambient pressure the boiling point of liquefied helium is 4.22 K (−268.93 °C). Below 2.17 K liquid 4 He becomes a superfluid ( Nobel Prize 1978, Pyotr Kapitsa ) and shows characteristic properties such as heat conduction through second sound , zero viscosity and the fountain effect among others.
The liquefaction of air is used to obtain nitrogen , oxygen , and argon and other atmospheric noble gases by separating the air components by fractional distillation in a cryogenic air separation unit .
Air is liquefied by the Linde process , in which air is alternately compressed, cooled, and expanded, each expansion results in a considerable reduction in temperature. With the lower temperature the molecules move more slowly and occupy less space, so the air changes phase to become liquid.
Air can also be liquefied by Claude 's process in which the gas is allowed to expand isentropically twice in two chambers. While expanding, the gas has to do work as it is led through an expansion turbine . The gas is not yet liquid, since that would destroy the turbine. [ citation needed ] Commercial air liquefication plants bypass this problem by expanding the air at supercritical pressures. [ 1 ] Final liquefaction takes place by isenthalpic expansion in a thermal expansion valve . | https://en.wikipedia.org/wiki/Liquefaction_of_gases |
Liquefactive necrosis (or colliquative necrosis ) is a type of necrosis which results in a transformation of the tissue into a liquid viscous mass. [ 1 ] Often it is associated with focal bacterial or fungal infections, and can also manifest as one of the symptoms of an internal chemical burn . [ 2 ] In liquefactive necrosis, the affected cell is completely digested by hydrolytic enzymes , resulting in a soft, circumscribed lesion consisting of pus and the fluid remains of necrotic tissue. Dead leukocytes will remain as a creamy yellow pus. [ 1 ] After the removal of cell debris by white blood cells , a fluid filled space is left. It is generally associated with abscess formation and is commonly found in the central nervous system .
Due to excitotoxicity , hypoxic death of cells within the central nervous system can result in liquefactive necrosis. [ 1 ] This is a process in which lysosomes turn tissues into pus as a result of lysosomal release of digestive enzymes. Loss of tissue architecture means that the tissue can be liquefied. This process is not associated with bacterial action or infection. Ultimately, in a living patient most necrotic cells and their contents disappear.
The affected area is soft with liquefied centre containing necrotic debris. Later, a cyst wall is formed.
Microscopically, the cystic space contains necrotic cell debris and macrophages filled with phagocytosed material. The cyst wall is formed by proliferating capillaries , inflammatory cells, and gliosis (proliferating glial cells) in the case of brain and proliferating fibroblasts in the case of abscess cavities.
Brain cells have a large amount of digestive enzymes (hydrolases). These enzymes cause the neural tissue to become soft and liquefy.
Liquefactive necrosis can also occur in the lung, especially in the context of lung abscesses. [ 3 ] [ 4 ]
Liquefactive necrosis can also take place due to certain infections. Neutrophils, fighting off a bacterium, will release hydrolytic enzymes which will also attack the surrounding tissues. | https://en.wikipedia.org/wiki/Liquefactive_necrosis |
Liquefied gas (sometimes referred to as liquid gas ) is a gas that has been turned into a liquid by cooling or compressing it. Examples of liquefied gases include liquid air , liquefied natural gas , and liquefied petroleum gas .
At the Lister Institute of Preventive Medicine , liquid air has been brought into use as an agent in biological research. An inquiry into the intracellular constituents of the typhoid bacillus , initiated under the direction of Doctor Allan Macfadyen , necessitated the separation of the cell-plasma of the organism. The method at first adopted for the disintegration of the bacteria was to mix them with silver-sand and churn the whole up in a closed vessel in which a series of horizontal vanes revolved at a high speed. But certain disadvantages attached to this procedure, and accordingly some means was sought to do away with the sand and triturate the bacilli per se. This was found in liquid air, which, as had long before been shown at the Royal Institution, has the power of reducing materials like grass or the leaves of plants to such a state of brittleness that they can easily be powdered in a mortar. By its aid a complete trituration of the typhoid bacilli has been accomplished at the Jenner Institute , and the same process, already applied with success also to yeast cells and animal cells, is being extended in other directions.
When air is liquefied the oxygen and nitrogen are condensed simultaneously. However, owing to its greater volatility the latter boils off the more quickly of the two, so that the remaining liquid becomes gradually richer and richer in oxygen.
Liquefied natural gas is natural gas that has been liquefied for the purpose of storage or transport. Since transportation of natural gas requires a large network of pipeline that crosses through various terrains and oceans, a huge investment and long term planning are required. Before transport, natural gas is liquefied by pressurization. The liquefied gas is then transported through tankers with special airtight compartments. When the tanks are opened and the liquid exposed to atmospheric pressure, the liquid boils off from the latent heat of the air or its container.
This article incorporates text from a publication now in the public domain : Dewar, James (1911). " Liquid Gases ". In Chisholm, Hugh (ed.). Encyclopædia Britannica . Vol. 16 (11th ed.). Cambridge University Press. pp. 744– 759. | https://en.wikipedia.org/wiki/Liquefied_gas |
Liquefied natural gas ( LNG ) is natural gas (predominantly methane , CH 4 , with some mixture of ethane , C 2 H 6 ) that has been cooled to liquid form for ease and safety of non-pressurized storage or transport. It takes up about 1/600th the volume of natural gas in the gaseous state at standard conditions for temperature and pressure .
LNG is odorless , colorless , non-toxic and non-corrosive . Hazards include flammability after vaporization into a gaseous state, freezing and asphyxia . The liquefaction process involves removal of certain components, such as dust, acid gases , helium , water, and heavy hydrocarbons , which could cause difficulty downstream. The natural gas is then condensed into a liquid at close to atmospheric pressure by cooling it to approximately −162 °C (−260 °F); maximum transport pressure is set at around 25 kPa (4 psi) ( gauge pressure ), which is about 0.25 times atmospheric pressure at sea level.
The gas extracted from underground hydrocarbon deposits contains a varying mix of hydrocarbon components, which usually includes mostly methane (CH 4 ), along with ethane (C 2 H 6 ), propane (C 3 H 8 ) and butane (C 4 H 10 ). Other gases also occur in natural gas, notably CO 2 . These gases have wide-ranging boiling points and also different heating values, allowing different routes to commercialization and also different uses. The acidic components, such as hydrogen sulphide (H 2 S) and carbon dioxide (CO 2 ), together with oil, mud, water, and mercury, are removed from the gas to deliver a clean sweetened stream of gas. Failure to remove much or all of such acidic molecules, mercury, and other impurities could result in damage to equipment. Corrosion of steel pipes and amalgamization of mercury to aluminum within cryogenic heat exchangers could cause expensive damage.
The gas stream is typically separated into the liquefied petroleum fractions (butane and propane), which can be stored in liquid form at relatively low pressure, and the lighter ethane and methane fractions. These lighter fractions of methane and ethane are then liquefied to make up the bulk of LNG that is shipped.
Natural gas was considered during the 20th century to be economically unimportant wherever gas-producing oil or gas fields were distant from gas pipelines or located in offshore locations where pipelines were not viable. In the past, this usually meant that natural gas produced was typically flared , especially since unlike oil, no viable method for natural gas storage or transport existed other than compressed gas pipelines to end users of the same gas. This meant that natural gas markets were historically entirely local, and any production had to be consumed within the local or regional network.
Developments of production processes, cryogenic storage , and transportation created the tools required to commercialize natural gas into a global market which now competes with other fuels. Furthermore, the development of LNG storage also introduced a reliability in networks which was previously thought impossible. Given that storage of other fuels is relatively easily secured using simple tanks, a supply for several months could be kept in storage. With the advent of large-scale cryogenic storage, it became possible to create long term gas storage reserves. These reserves of liquefied gas could be deployed at a moment's notice through regasification processes, and today are the main means for networks to handle local peak shaving requirements. [ 1 ]
The heating value depends on the source of gas that is used and the process that is used to liquefy the gas. The range of heating value can span ±10 to 15 percent. A typical value of the higher heating value of LNG is approximately 50 MJ/kg or 21,500 BTU/lb. [ 2 ] A typical value of the lower heating value of LNG is 45 MJ/kg or 19,350 BTU/lb.
For the purpose of comparison of different fuels, the heating value may be expressed in terms of energy per volume, which is known as the energy density expressed in MJ/litre. The density of LNG is roughly 0.41 kg/litre to 0.5 kg/litre, depending on temperature, pressure, and composition, [ 3 ] compared to water at 1.0 kg/litre. Using the median value of 0.45 kg/litre, the typical energy density values are 22.5 MJ/litre (based on higher heating value) or 20.3 MJ/litre (based on lower heating value).
The volumetric energy density of LNG is approximately 2.4 times that of compressed natural gas (CNG), which makes it economical to transport natural gas by ship in the form of LNG. The energy density of LNG is comparable to propane and ethanol but is only 60 percent that of diesel and 70 percent that of gasoline . [ 4 ]
Experiments on the properties of gases started early in the 17th century. By the middle of the seventeenth century Robert Boyle had derived the inverse relationship between the pressure and the volume of gases. About the same time, Guillaume Amontons started looking into temperature effects on gas. Various gas experiments continued for the next 200 years. During that time there were efforts to liquefy gases. Many new facts about the nature of gases were discovered. For example, early in the nineteenth century Cagniard de la Tour showed there was a temperature above which a gas could not be liquefied. There was a major push in the mid to late nineteenth century to liquefy all gases. A number of scientists including Michael Faraday , James Joule , and William Thomson (Lord Kelvin) did experiments in this area. In 1886 Karol Olszewski liquefied methane, the primary constituent of natural gas. By 1900 all gases had been liquefied except helium , which was liquefied in 1908.
The first large-scale liquefaction of natural gas in the U.S. was in 1918 when the U.S. government liquefied natural gas as a way to extract helium, which is a small component of some natural gas. This helium was intended for use in British dirigibles for World War I . The liquid natural gas (LNG) was not stored, but regasified and immediately put into the gas mains. [ 5 ]
The key patents having to do with natural gas liquefaction date from 1915 and the mid-1930s. In 1915 Godfrey Cabot patented a method for storing liquid gases at very low temperatures. It consisted of a Thermos bottle -type design which included a cold inner tank within an outer tank; the tanks being separated by insulation. In 1937 Lee Twomey received patents for a process for large-scale liquefaction of natural gas. The intention was to store natural gas as a liquid so it could be used for shaving peak energy loads during cold snaps. Because of large volumes it is not practical to store natural gas, as a gas, near atmospheric pressure. However, when liquefied, it can be stored in a volume 1/600th as large. This is a practical way to store it but the gas must be kept at −260 °F (−162 °C).
There are two processes for liquefying natural gas in large quantities. The first is the cascade process, in which the natural gas is cooled by another gas which in turn has been cooled by still another gas, hence named the "cascade" process. There are usually two cascade cycles before the liquid natural gas cycle. The other method is the Linde process , with a variation of the Linde process, called the Claude process, being sometimes used. In this process, the gas is cooled regeneratively by continually passing and expanding it through an orifice until it is cooled to temperatures at which it liquefies. This process was developed by James Joule and William Thomson and is known as the Joule–Thomson effect . Lee Twomey used the cascade process for his patents.
The East Ohio Gas Company built a full-scale commercial LNG plant in Cleveland, Ohio , in 1940 just after a successful pilot plant built by its sister company, Hope Natural Gas Company of West Virginia. This was the first such plant in the world. Originally it had three spheres, approximately 63 feet (19 m) in diameter containing LNG at −260 °F (−162 °C). Each sphere held the equivalent of about 50 million cubic foot (1,400,000 m 3 ) of natural gas. A fourth tank, a cylinder, was added in 1942. It had an equivalent capacity of 100 million cubic foot (2,800,000 m 3 ) of gas. The plant operated successfully for three years. The stored gas was regasified and put into the mains when cold snaps hit and extra capacity was needed. This precluded the denial of gas to some customers during a cold snap.
The Cleveland plant failed on October 20, 1944, when the cylindrical tank ruptured, spilling thousands of gallons of LNG over the plant and nearby neighborhood. The gas evaporated and caught fire, which caused 130 fatalities. [ 6 ] The fire delayed further implementation of LNG facilities for several years. However, over the next 15 years new research on low-temperature alloys, and better insulation materials, set the stage for a revival of the industry. It restarted in 1959 when a U.S. World War II Liberty ship , the Methane Pioneer , converted to carry LNG, made a delivery of LNG from the U.S. Gulf Coast to energy-starved Great Britain. In June 1964, the world's first purpose-built LNG carrier, the Methane Princess , entered service. [ 7 ] Soon after that a large natural gas field was discovered in Algeria. International trade in LNG quickly followed as LNG was shipped to France and Great Britain from the Algerian fields. One more important attribute of LNG had now been exploited. Once natural gas was liquefied it could not only be stored more easily, but it could be transported. Thus energy could now be shipped over the oceans via LNG the same way it was shipped in the form of oil.
The LNG industry in the U.S. restarted in 1965 with the building of a number of new plants, which continued through the 1970s. These plants were not only used for peak-shaving, as in Cleveland, but also for base-load supplies for places that never had natural gas before this. A number of import facilities were built on the East Coast in anticipation of the need to import energy via LNG. However, a recent boom in U.S. natural gas production (2010–2014), enabled by hydraulic fracturing ("fracking"), has many of these import facilities being considered as export facilities. The first U.S. LNG export was completed in early 2016. [ 8 ]
By 2023, the U.S. had become the biggest exporter in the world, and projects already under construction or permitted would double its export capacities by 2027. [ 9 ] The largest exporters were Cheniere Energy Inc., Freeport LNG , and Venture Global LNG Inc. [ 10 ] The U.S. Energy Information Administration reported that the U.S. had exported 4.3 trillion cubic foot (1.2 × 10 11 m 3 ) in 2023. [ 11 ]
The process begins with the pre-treatment of a feedstock of natural gas entering the system to remove impurities such as H 2 S , CO 2 , H 2 O, mercury and higher-chained hydrocarbons . Feedstock gas then enters the liquefaction unit where it is cooled to between −145 °C and −163 °C. [ 12 ] Although the type or number of heating cycles and/or refrigerants used may vary based on the technology, the basic process involves circulating the gas through aluminum tube coils and exposure to a compressed refrigerant. [ 12 ] As the refrigerant is vaporized, the heat transfer causes the gas in the coils to cool. [ 12 ] The LNG is then stored in a specialized double-walled insulated tank at atmospheric pressure ready to be transported to its final destination. [ 12 ]
Most domestic LNG is transported by land via truck/trailer designed for cryogenic temperatures. [ 12 ] Intercontinental LNG transport travels by special tanker ships. LNG transport tanks comprise an internal steel or aluminum compartment and an external carbon or steel compartment with a vacuum system in between to reduce the amount of heat transfer. [ 12 ] Once on site, the LNG must be stored in vacuum insulated or flat bottom storage tanks . [ 12 ] When ready for distribution, the LNG enters a regasification facility where it is pumped into a vaporizer and heated back into gaseous form. [ 12 ] The gas then enters the gas pipeline distribution system and is delivered to the end-user. [ 12 ]
The natural gas fed into the LNG plant will be treated to remove water, hydrogen sulfide , carbon dioxide , benzene and other components that will freeze under the low temperatures needed for storage or be destructive to the liquefaction facility. LNG typically contains more than 90% methane . It also contains small amounts of ethane , propane , butane , some heavier alkanes , and nitrogen. The purification process can be designed to give almost 100% methane . One of the risks of LNG is a rapid phase transition explosion (RPT), which occurs when cold LNG comes into contact with water . [ 13 ]
The most important infrastructure needed for LNG production and transportation is an LNG plant consisting of one or more LNG trains, each of which is an independent unit for gas liquefaction and purification. A typical train consists of a compression area, propane condenser area, and methane and ethane areas.
The largest LNG train in operation is in Qatar, with a total production capacity of 7.8 million tonnes per annum (MTPA). LNG is loaded onto ships and delivered to a regasification terminal, where the LNG is allowed to expand and reconvert into gas. Regasification terminals are usually connected to a storage and pipeline distribution network to distribute natural gas to local distribution companies (LDCs) or independent power plants (IPPs).
Information for the following table is derived in part from publication by the U.S. Energy Information Administration. [ 14 ] See also List of LNG terminals
The LNG industry developed slowly during the second half of the last century because most LNG plants are located in remote areas not served by pipelines, and because of the high costs of treating and transporting LNG. Constructing an LNG plant costs at least $1.5 billion per 1 MTPA capacity, a receiving terminal costs $1 billion per 1 bcf/day throughput capacity and LNG vessels cost $200 million–$300 million.
In the early 2000s, prices for constructing LNG plants, receiving terminals and vessels fell as new technologies emerged and more players invested in liquefaction and regasification. This tended to make LNG more competitive as a means of energy distribution, but increasing material costs and demand for construction contractors have put upward pressure on prices in the last few years.
The standard price for a 125,000 cubic meter LNG vessel built in European and Japanese shipyards used to be US$250 million. When Korean and Chinese shipyards entered the race, increased competition reduced profit margins and improved efficiency—reducing costs by 60 percent. Costs in US dollars also declined due to the devaluation of the currencies of the world's largest shipbuilders: the Japanese yen and Korean won.
Since 2004, the large number of orders increased demand for shipyard slots, raising their price and increasing ship costs. The per-ton construction cost of an LNG liquefaction plant fell steadily from the 1970s through the 1990s. The cost reduced by approximately 35 percent. However, recently the cost of building liquefaction and regasification terminals doubled due to increased cost of materials and a shortage of skilled labor, professional engineers, designers, managers and other white-collar professionals.
Due to natural gas shortage concerns in the northeastern U.S. and surplus natural gas in the rest of the country, many new LNG import and export terminals are being contemplated in the United States. Concerns about the safety of such facilities create controversy in some regions where they are proposed. One such location is in the Long Island Sound between Connecticut and Long Island. Broadwater Energy , an effort of TransCanada Corp. and Shell, wishes to build an LNG import terminal in the sound on the New York side. Local politicians including the Suffolk County Executive raised questions about the terminal. In 2005, New York Senators Chuck Schumer and Hillary Clinton also announced their opposition to the project. [ 25 ] Several import terminal proposals along the coast of Maine were also met with high levels of resistance and questions. On September 13, 2013, the U.S. Department of Energy approved Dominion Cove Point 's application to export up to 770 million cubic foot (22,000,000 m 3 ) per day of LNG to countries that do not have a free trade agreement with the U.S. [ 26 ] In May 2014, the FERC concluded its environmental assessment of the Cove Point LNG project, which found that the proposed natural gas export project could be built and operated safely. [ 27 ] Another LNG terminal is currently proposed for Elba Island , Georgia, US. [ 28 ] Plans for three LNG export terminals in the U.S. Gulf Coast region have also received conditional Federal approval. [ 26 ] [ 29 ] In Canada, an LNG export terminal is under construction near Guysborough , Nova Scotia. [ 30 ]
In the commercial development of an LNG value chain, LNG suppliers first confirm sales to the downstream buyers and then sign long-term contracts (typically 20–25 years) with strict terms and structures for gas pricing. Only when the customers are confirmed and the development of a greenfield project deemed economically feasible, could the sponsors of an LNG project invest in their development and operation. Thus, the LNG liquefaction business has been limited to players with strong financial and political resources. Major international oil companies (IOCs) such as ExxonMobil , Royal Dutch Shell , BP , Chevron , TotalEnergies and national oil companies (NOCs) such as Pertamina and Petronas are active players.
LNG is shipped around the world in specially constructed seagoing vessels . The trade of LNG is completed by signing an SPA (sale and purchase agreement) between a supplier and receiving terminal, and by signing a GSA (gas sale agreement) between a receiving terminal and end-users. [ 31 ] Most of the contract terms used to be DES or ex ship , holding the seller responsible for the transport of the gas. With low shipbuilding costs, and the buyers preferring to ensure reliable and stable supply, however, contracts with FOB terms increased. Under such terms the buyer, who often owns a vessel or signs a long-term charter agreement with independent carriers, is responsible for the transport.
LNG purchasing agreements used to be for a long term with relatively little flexibility both in price and volume. If the annual contract quantity is confirmed, the buyer is obliged to take and pay for the product, or pay for it even if not taken, in what is referred to as the obligation of take-or-pay contract (TOP).
In the mid-1990s, LNG was a buyer's market. At the request of buyers, the SPAs began to adopt some flexibilities on volume and price. The buyers had more upward and downward flexibilities in TOP, and short-term SPAs less than 16 years came into effect. At the same time, alternative destinations for cargo and arbitrage were also allowed. By the turn of the 21st century, the market was again in favor of sellers. However, sellers have become more sophisticated and are now proposing sharing of arbitrage opportunities and moving away from S-curve pricing.
Research from Global Energy Monitor in 2019 warned that up to US$1.3 trillion in new LNG export and import infrastructure currently under development is at significant risk of becoming stranded, as global gas risks becoming oversupplied, particularly if the United States and Canada play a larger role. [ 32 ]
The current surge in unconventional oil and gas in the U.S. has resulted in lower gas prices in the U.S. This has led to discussions in Asia' oil linked gas markets to import gas based on Henry Hub index. [ 33 ] Recent high level conference in Vancouver, the Pacific Energy Summit 2013 Pacific Energy Summit 2013 convened policy makers and experts from Asia and the U.S. to discuss LNG trade relations between these regions.
Receiving terminals exist in about 40 [ 34 ] countries, including Belgium, Chile, China, the Dominican Republic, France, Greece, India, Italy, Japan, Korea, Poland, Spain, Taiwan, the UK, the US, among others. Plans exist for Bahrain, Germany, Ghana, Morocco, Philippines, Vietnam [ 35 ] and others to also construct new receiving ( regasification ) terminals.
Base load (large-scale, >1 MTPA) LNG projects require natural gas reserves, [ 36 ] buyers [ 37 ] and financing. Using proven technology and a proven contractor is extremely important for both investors and buyers. [ 38 ] Gas reserves required: 1 tcf of gas required per Mtpa of LNG over 20 years. [ 36 ]
LNG is most cost efficiently produced in relatively large facilities due to economies of scale , at sites with marine access allowing regular large bulk shipments direct to market. This requires a secure gas supply of sufficient capacity. Ideally, facilities are located close to the gas source, to minimize the cost of intermediate transport infrastructure and gas shrinkage (fuel loss in transport). The high cost of building large LNG facilities makes the progressive development of gas sources to maximize facility utilization essential, and the life extension of existing, financially depreciated LNG facilities cost effective. Particularly when combined with lower sale prices due to large installed capacity and rising construction costs, this makes the economic screening/ justification to develop new, and especially greenfield, LNG facilities challenging, even if these could be more environmentally friendly than existing facilities with all stakeholder concerns satisfied. Due to high financial risk, it is usual to contractually secure gas supply/ concessions and gas sales for extended periods before proceeding to an investment decision.
The primary use of LNG is to simplify transport of natural gas from the source to a destination. On the large scale, this is done when the source and the destination are across an ocean from each other. It can also be used when adequate pipeline capacity is not available. For large-scale transport uses, the LNG is typically regassified at the receiving end and pushed into the local natural gas pipeline infrastructure.
LNG can also be used to meet peak demand when the normal pipeline infrastructure can meet most demand needs, but not the peak demand needs. These plants are typically called LNG Peak Shaving Plants as the purpose is to shave off part of the peak demand from what is required out of the supply pipeline.
LNG can be used to fuel internal combustion engines. LNG is in the early stages of becoming a mainstream fuel for transportation needs. It is being evaluated and tested for over-the-road trucking, [ 39 ] off-road, [ 40 ] marine, and train applications. [ 41 ] There are known problems with the fuel tanks and delivery of gas to the engine, [ 42 ] but despite these concerns the move to LNG as a transportation fuel has begun. LNG competes directly with compressed natural gas as a fuel for natural gas vehicles since the engine is identical. There may be applications where LNG trucks, buses, trains and boats could be cost-effective in order to regularly distribute LNG energy together with general freight and/or passengers to smaller, isolated communities without a local gas source or access to pipelines.
China has been a leader in the use of LNG vehicles [ 43 ] with over 100,000 LNG-powered vehicles on the road as of Sept 2014. [ 44 ]
In the United States the beginnings of a public LNG fueling capability are being put in place. An alternative fuelling centre tracking site shows 84 public truck LNG fuel centres as of Dec 2016. [ 45 ] It is possible for large trucks to make cross country trips such as Los Angeles to Boston and refuel at public refuelling stations every 500 miles (800 km). The 2013 National Trucker's Directory lists approximately 7,000 truckstops, [ 46 ] thus approximately 1% of US truckstops have LNG available.
While as of December 2014 LNG fuel and NGV's were not taken to very quickly within Europe and it was questionable whether LNG will ever become the fuel of choice among fleet operators, [ 47 ] recent trends from 2018 onwards show different prospect. [ 48 ] During the year 2015, the Netherlands introduced LNG-powered trucks in transport sector. [ 49 ] Additionally, the Australian government is planning to develop an LNG highway to utilise the locally produced LNG and replace the imported diesel fuel used by interstate haulage vehicles. [ 50 ]
In the year 2015, India also began transporting LNG using LNG-powered road tankers in Kerala state. [ 51 ] In 2017, Petronet LNG began setting up 20 LNG stations on highways along the Indian west coast that connect Delhi with Thiruvananthapuram covering a total distance of 4,500 km via Mumbai and Bengaluru. [ 52 ] In 2020, India planned to install 24 LNG fuelling stations along the 6,000 km Golden Quadrilateral highways connecting the four metros due to LNG prices decreasing. [ 53 ]
Japan, the world's largest importer of LNG, is set to begin use of LNG as a road transport fuel. [ 54 ]
Engine displacement is an important factor in the power of an internal combustion engine . Thus a 2.0 L engine would typically be more powerful than an 1.8 L engine, but that assumes a similar air–fuel mixture is used.
However, if a smaller engine uses an air–fuel mixture with higher energy density (such as via a turbocharger), then it can produce more power than a larger one burning a less energy-dense air–fuel mixture. For high-power, high-torque engines, a fuel that creates a more energy-dense air–fuel mixture is preferred, because a smaller and simpler engine can produce the same power.
With conventional gasoline and diesel engines the energy density of the air–fuel mixture is limited because the liquid fuels do not mix well in the cylinder. Further, gasoline and diesel fuel have autoignition temperatures and pressures relevant to engine design. An important part of engine design is the interactions of cylinders, compression ratios, and fuel injectors such that pre-ignition is prevented but at the same time as much fuel as possible can be injected, become well mixed, and still have time to complete the combustion process during the power stroke.
Natural gas does not auto-ignite at pressures and temperatures relevant to conventional gasoline and diesel engine design, so it allows more flexibility in design. Methane, the main component of natural gas, has an autoignition temperature of 580 °C (1,076 °F), [ 55 ] whereas gasoline and diesel autoignite at approximately 250 °C (482 °F) and 210 °C (410 °F) respectively.
With a compressed natural gas (CNG) engine, the mixing of the fuel and the air is more effective since gases typically mix well in a short period of time, but at typical CNG pressures the fuel itself is less energy-dense than gasoline or diesel, so the result is a less energy-dense air–fuel mixture. For an engine of a given cylinder displacement, a normally-aspirated CNG-powered engine is typically less powerful than a gasoline or diesel engine of similar displacement. For that reason turbochargers are popular in European CNG cars. [ 56 ] Despite that limitation, the 12-litre Cummins Westport ISX12G engine [ 57 ] is an example of a CNG-capable engine designed to pull tractor–trailer loads up to 80,000 pounds (36,000 kg) showing CNG can be used in many on-road truck applications. The original ISX G engine incorporated a turbocharger to enhance the air–fuel energy density. [ 58 ]
LNG offers a unique advantage over CNG for more demanding high-power applications by eliminating the need for a turbocharger. Because LNG boils at approximately −160 °C (−256 °F), by using a simple heat exchanger a small amount of LNG can be converted to its gaseous form at extremely high pressure with the use of little or no mechanical energy. A properly designed high-power engine can leverage this extremely-high-pressure, energy-dense gaseous fuel source to create a higher-energy-density air–fuel mixture than can be efficiently created with a CNG-powered engine. The result when compared to CNG engines is more overall efficiency in high-power engine applications when high-pressure direct-injection technology is used. The Westport HDMI2 [ 59 ] fuel system is an example of a high-pressure direct-injection system that does not require a turbocharger if paired with an appropriate LNG heat exchanger. The Volvo Trucks 13-litre LNG engine [ 60 ] is another example of an LNG engine leveraging advanced high-pressure technology.
Westport recommends CNG for engines 7 litres or smaller and LNG with direct-injection for engines between 20 and 150 litres. For engines between 7 and 20 litres either option is recommended. See slide 13 from their NGV Bruxelles – Industry Innovation Session presentation. [ 61 ]
High-power engines in the oil drilling, mining, locomotive, and marine fields have been or are being developed. [ 62 ] Paul Blomerus has written a paper [ 63 ] concluding as much as 40 million tonnes per annum of LNG (approximately 26.1 billion gallons/year or 71 million gallons/day) could be required just to meet the global needs of such high-power engines by 2025 to 2030.
As of the end of first quarter of 2015, Prometheus Energy Group Inc claimed to have delivered over 100 million gallons of LNG to the industrial market within the previous four years [ 64 ] and is continuing to add new customers.
LNG bunkering has been established in some ports via truck-to-ship fueling. This type of LNG fueling is straightforward to implement, assuming a supply of LNG is available.
Feeder and short-sea shipping company Unifeeder has been operating the world's first LNG powered container vessel, the Wes Amelie, since late 2017, transiting between the port of Rotterdam and the Baltics on a weekly schedule. [ 65 ] Container shipping company Maersk Group has decided to introduce LNG-powered container ships. [ 66 ] The DEME Group has contracted Wärtsilä to power its new generation 'Antigoon' class dredger with dual fuel (DF) engines. [ 67 ] Crowley Maritime of Jacksonville, Florida , launched two LNG-powered ConRo ships, the Coquí and Taino, in 2018 and 2019, respectively. [ 68 ]
In 2014, Shell ordered a dedicated LNG bunker vessel. [ 69 ] It is planned to go into service in Rotterdam in the summer of 2017 [ 70 ]
The International Convention for the Prevention of Pollution from Ships (MARPOL), adopted by the IMO , has mandated that marine vessels shall not consume fuel (bunker fuel, diesel, etc.) with a sulphur content greater than 0.5% from the year 2020 within international waters and the coastal areas of countries adopting the same regulation. Replacement of high sulphur bunker fuel with sulphur-free LNG is required on a major scale in the marine transport sector, as low sulphur liquid fuels are costlier than LNG. [ 71 ] Japan's is planning to use LNG as bunker fuel by 2020. [ 72 ] [ 73 ]
BHP , one of the largest mining companies in the world, is aiming to commission minerals transport ships powered with LNG by late 2021. [ 74 ]
In January 2021, 175 sea-going LNG-powered ships were in service, with another 200 ships ordered. [ 75 ]
Florida East Coast Railway has 24 GE ES44C4 locomotives adapted to run on LNG fuel. [ 76 ]
The global trade in LNG is growing rapidly from negligible in 1970 to what is expected to be a globally substantial amount by 2020. [ 77 ] As a reference, the 2014 global production of crude oil was 14.6 million cubic metres (92 million barrels) per day [ 78 ] or 54,600 terawatt-hours (186.4 quadrillion British thermal units ) per year.
In 1970, global LNG trade was of 3 billion cubic metres (bcm) (0.11 quads). [ 79 ] In 2011, it was 331 bcm (11.92 quads). [ 79 ] The U.S. started exporting LNG in February 2016. The Black & Veatch Oct 2014 forecast is that by 2020, the U.S. alone will export between 10 and 14 billion cu ft/d (280 and 400 million m 3 /d) or by heating value 3.75 to 5.25 quad (1,100 to 1,540 TWh). [ 80 ] E&Y projects global LNG demand could hit 400 mtpa (19.7 quads) by 2020. [ 81 ] If that occurs, the LNG market will be roughly 10% the size of the global crude oil market, and that does not count the vast majority of natural gas which is delivered via pipeline directly from the well to the consumer.
In 2004, LNG accounted for 7 percent of the world's natural gas demand. [ 82 ] The global trade in LNG, which has increased at a rate of 7.4 percent per year over the decade from 1995 to 2005, is expected to continue to grow substantially. [ 83 ] LNG trade is expected to increase at 6.7 percent per year from 2005 to 2020. [ 83 ]
Until the mid-1990s, LNG demand was heavily concentrated in Northeast Asia: Japan, South Korea and Taiwan . At the same time, Pacific Basin supplies dominated world LNG trade. [ 83 ] The worldwide interest in using natural gas-fired combined cycle generating units for electric power generation, coupled with the inability of North American and North Sea natural gas supplies to meet the growing demand, substantially broadened the regional
markets for LNG. It also brought new Atlantic Basin and Middle East suppliers into the trade. [ 83 ]
By the end of 2017, there were 19 LNG exporting countries and 40 LNG importing countries. The three biggest LNG exporters in 2017 were Qatar (77.5 MT), Australia (55.6 MT) and Malaysia (26.9 MT). The three biggest LNG importers in 2017 were Japan (83.5 MT), China (39 MT) and South Korea (37.8 MT). [ 84 ] LNG trade volumes increased from 142 MT in 2005 to 159 MT in 2006, 165 MT in 2007, 171 MT in 2008, 220 MT in 2010, 237 MT in 2013, 264 MT in 2016 and 290 MT in 2017. [ 84 ] Global LNG production was 246 MT in 2014, [ 85 ] most of which was used in trade between countries. [ 86 ] During the next several years there would be significant increase in volume of LNG Trade. [ 81 ] For example, about 59 MTPA of new LNG supply from six new plants came to market just in 2009, including:
In 2006, Qatar became the world's biggest exporter of LNG. [ 79 ] As of 2012, Qatar is the source of 25 percent of the world's LNG exports. [ 79 ] As of 2017, Qatar was estimated to supply 26.7% of the world's LNG. [ 84 ]
Investments in U.S. export facilities were increasing by 2013, these investments were spurred by increasing shale gas production in the United States and a large price differential between natural gas prices in the U.S. and those in Europe and Asia. Cheniere Energy became the first company in the United States to receive permission and export LNG in 2016. [ 8 ] After a US-EU agreement in 2018, exports from USA to EU increased. [ 87 ] In November 2021, U.S. producer Venture Global LNG signed a twenty-year contract with China's state-owned Sinopec to supply liquefied natural gas. [ 88 ] China's imports of U.S. natural gas will more than double. [ 89 ] U.S. exports of liquefied natural gas to China and other Asian countries surged in 2021 , with Asian buyers willing to pay higher prices than European importers. [ 90 ] This reversed in 2022, when most of US LNG went to Europe. US LNG export contracts are mainly made for 15–20 years. [ 91 ] Exports from the U.S. are likely to reach 13.3 Bcf/d in 2024 due to projects coming online on the Gulf of Mexico. [ 92 ]
In 1964, the UK and France made the first LNG trade, buying gas from Algeria , witnessing a new era of energy.
In 2014, 19 countries exported LNG. [ 79 ]
Compared with the crude oil market, in 2013 the natural gas market was about 72 percent of the crude oil market (measured on a heat equivalent basis), [ 93 ] of which LNG forms a small but rapidly growing part. Much of this growth is driven by the need for clean fuel and some substitution effect due to the high price of oil (primarily in the heating and electricity generation sectors).
Japan, South Korea , Spain, France, Italy and Taiwan import large volumes of LNG due to their shortage of energy. In 2005, Japan imported 58.6 million tons of LNG, representing some 30 percent of the LNG trade around the world that year. Also in 2005, South Korea imported 22.1 million tons, and in 2004 Taiwan imported 6.8 million tons. These three major buyers purchase approximately two-thirds of the world's LNG demand. In addition, Spain imported some 8.2 MTPA in 2006, making it the third largest importer. France also imported similar quantities as Spain. [ citation needed ] Following the Fukushima Daiichi nuclear disaster in March 2011 Japan became a major importer accounting for one third of the total. [ 94 ] European LNG imports fell by 30 percent in 2012, and fell further by 24 percent in 2013, as South American and Asian importers paid more. [ 95 ] European LNG imports increased to new heights in 2019, remained high in 2020 and 2021, and increased even more in 2022. [ 91 ] Main contributors were Qatar, USA, and Russia. [ 96 ]
In 2017, global LNG imports reached 289.8 [ 97 ] million tonnes of LNG. In 2017, 72.9% of global LNG demand was located in Asia. [ 98 ]
Based on the LNG SPAs, LNG is destined for pre-agreed destinations, and diversion of that LNG is not allowed. However, if Seller and Buyer make a mutual agreement, then the diversion of the cargo is permitted — subject to sharing the additional profit created by such a diversion, by paying a penalty fee. [ 91 ] In the European Union and some other jurisdictions, it is not permitted to apply the profit-sharing clause in LNG SPAs.
For an extended period of time, design improvements in liquefaction plants and tankers had the effect of reducing costs.
In the 1980s, the cost of building an LNG liquefaction plant cost $350/tpa (tonne per annum). In the 2000s, it was $200/tpa. In 2012, the costs can go as high as $1,000/tpa, partly due to the increase in the price of steel. [ 79 ]
As recently as 2003, it was common to assume that this was a "learning curve" effect and would continue into the future. But this perception of steadily falling costs for LNG has been dashed in the last several years. [ 83 ]
The construction cost of greenfield LNG projects started to skyrocket from 2004 afterward and has increased from about $400 per ton per year of capacity to $1,000 per ton per year of capacity in 2008.
The main reasons for skyrocketed costs in LNG industry can be described as follows:
Excluding high cost projects the increase of 120% over the period 2002–2012 is more in line with escalation in the upstream oil & gas industry as reported by the UCCI index [ 99 ]
The 2008 financial crisis and the Great Recession led to a general decline in raw material and equipment prices, which somewhat lessened the construction cost of LNG plants. [ 100 ] [ 101 ] However, by 2012 this was more than offset by increasing demand for materials and labor for the LNG market.
Small-scale liquefaction plants are suitable for peakshaving on natural gas pipelines, transportation fuel, or for deliveries of natural gas to remote areas not connected to pipelines. [ 102 ] They typically have a compact size, are fed from a natural gas pipeline, and are located close to the location where the LNG will be used. This proximity decreases transportation and LNG product costs for consumers. [ 103 ] [ 104 ] It also avoids the additional greenhouse gas emissions generated during long transportation.
The small-scale LNG plant also allows localized peakshaving to occur—balancing the availability of natural gas during high and low periods of demand. It also makes it possible for communities without access to natural gas pipelines to install local distribution systems and have them supplied with stored LNG. [ 105 ]
There are three major pricing systems in the current LNG contracts:
The formula for an indexed price is as follows:
CP = BP + β X
The formula has been widely used in Asian LNG SPAs, where base price represents various non-oil factors, but usually a constant determined by negotiation at a level which can prevent LNG prices from falling below a certain level. It thus varies regardless of oil price fluctuation.
Some LNG buyers have already signed contracts for future US-based cargos at prices linked to Henry Hub prices. [ 107 ] Cheniere Energy's LNG export contract pricing consists of a fixed fee (liquefaction tolling fee) plus 115% of Henry Hub per million British thermal units of LNG. [ 108 ] Tolling fees in the Cheniere contracts vary: US$2.25 per million British thermal units ($7.7/MWh) with BG Group signed in 2011; $2.49 per million British thermal units ($8.5/MWh) with Spain's GNF signed in 2012; and $3.00 per million British thermal units ($10.2/MWh) with South Korea's Kogas and Centrica signed in 2013. [ 109 ]
Oil parity is the LNG price that would be equal to that of crude oil on a barrel of oil equivalent (BOE) basis. If the LNG price exceeds the price of crude oil in BOE terms, then the situation is called broken oil parity. A coefficient of 0.1724 results in full oil parity. In most cases the price of LNG is less than the price of crude oil in BOE terms.
In 2009, in several spot cargo deals especially in East Asia, oil parity approached the full oil parity or even exceeded oil parity. [ 110 ] In January 2016, the spot LNG price of $5.461 per million British thermal units ($18.63/MWh) has broken oil parity when the Brent crude price (≤32 US$/bbl) has fallen steeply. [ 111 ] By the end of June 2016, LNG price has fallen by nearly 50% below its oil parity price, making it more economical than more-polluting diesel/gas oil in the transport sector. [ 112 ] LNG briefly touched the oil parity in winter of 2018/2019 [ 113 ] and then rose above it during the recent global energy crisis in mid-2021 [ 114 ] only falling below it in early 2024. [ 115 ]
Most of the LNG trade is governed by long-term contracts. Many formulae include an S-curve , where the price formula is different above and below a certain oil price, to dampen the impact of high oil prices on the buyer, and low oil prices on the seller. When the spot LNG price is cheaper than long term oil price indexed contracts, the most profitable LNG end use is to power mobile engines for replacing costly gasoline and diesel consumption.
In most of the East Asian LNG contracts, price formula is indexed to a basket of crude imported to Japan called the Japan Crude Cocktail (JCC). In Indonesian LNG contracts, price formula is linked to Indonesian Crude Price (ICP).
In continental Europe, the price formula indexation does not follow the same format, and it varies from contract to contract. Brent crude price (B), heavy fuel oil price (HFO), light fuel oil price (LFO), gas oil price (GO), coal price , electricity price and in some cases, consumer and producer price indexes are the indexation elements of price formulas.
Usually there exists a clause allowing parties to trigger the price revision or price reopening in LNG SPAs. In some contracts there are two options for triggering a price revision. regular and special. Regular ones are the dates that will be agreed and defined in the LNG SPAs for the purpose of price review.
LNG quality is one of the most important issues in the LNG business. Any gas which does not conform to the agreed specifications in the sale and purchase agreement is regarded as "off-specification" (off-spec) or "off-quality" gas or LNG. Quality regulations serve three purposes: [ 116 ]
In the case of off-spec gas or LNG the buyer can refuse to accept the gas or LNG and the seller has to pay liquidated damages for the respective off-spec gas volumes.
The quality of gas or LNG is measured at delivery point by using an instrument such as a gas chromatograph.
The most important gas quality concerns involve the sulphur and mercury content and the calorific value. Due to the sensitivity of liquefaction facilities to sulfur and mercury elements, the gas being sent to the liquefaction process shall be accurately refined and tested in order to assure the minimum possible concentration of these two elements before entering the liquefaction plant, hence there is not much concern about them.
However, the main concern is the heating value of gas. Usually natural gas markets can be divided in three markets in terms of heating value: [ 116 ]
There are some methods to modify the heating value of produced LNG to the desired level. For the purpose of increasing the heating value, injecting propane and butane is a solution. For the purpose of decreasing heating value, nitrogen injecting and extracting butane and propane are proven solutions. Blending with gas or LNG can be a solution; however all of these solutions while theoretically viable can be costly and logistically difficult to manage in large scale. Lean LNG price in terms of energy value is lower than the rich LNG price. [ 117 ]
There are several liquefaction processes available for large, baseload LNG plants (in order of prevalence): [ 118 ]
As of January 2016, global nominal LNG liquefaction capacity was 301.5 MTPA (million tonnes per annum), with a further 142 MTPA under construction. [ 120 ]
The majority of these trains use either APCI AP-C3MR or Cascade technology for the liquefaction process. The other processes, used in a small minority of some liquefaction plants, include Shell's DMR (double-mixed refrigerant) technology and the Linde technology.
APCI technology is the most-used liquefaction process in LNG plants: out of 100 liquefaction trains onstream or under-construction, 86 trains with a total capacity of 243 MTPA have been designed based on the APCI process. Phillips' Cascade process is the second most-used, used in 10 trains with a total capacity of 36.16 MTPA. The Shell DMR process has been used in three trains with total capacity of 13.9 MTPA; and, finally, the Linde/Statoil process is used in the Snohvit 4.2 MTPA single train.
Floating liquefied natural gas (FLNG) facilities float above an offshore gas field, and produce, liquefy, store and transfer LNG (and potentially LPG and condensate ) at sea before carriers ship it directly to markets. The first FLNG facility to produce and export LNG was PFLNG1 in 2017, built and operated by Petronas . [ 121 ] [ 122 ]
Modern LNG storage tanks are typically of the full containment type, which has a prestressed concrete outer wall and a high-nickel steel inner tank, with extremely efficient insulation between the walls. Large tanks are low aspect ratio (height to width) and cylindrical in design with a domed steel or concrete roof. Storage pressure in these tanks is very low, less than 10 kilopascals (1.5 psi ). Sometimes more expensive underground tanks are used for storage.
Smaller quantities (say 700 cubic metres (180,000 US gal) and less) may be stored in horizontal or vertical, vacuum-jacketed, pressure vessels. These tanks may be at pressures anywhere from less than 50 to over 1,700 kPa (7.3–246.6 psi).
LNG must be kept cold to remain a liquid, independent of pressure. Despite efficient insulation, there will inevitably be some heat leakage into the LNG, resulting in vaporisation of the LNG. This boil-off gas acts to keep the LNG cold (see " Refrigeration " below). The boil-off gas is typically compressed and exported as natural gas , or it is reliquefied and returned to storage.
LNG is transported in specially designed ships with double hulls protecting the cargo systems from damage or leaks. There are several special leak test methods available to test the integrity of an LNG vessel's membrane cargo tanks. [ 123 ]
The tankers cost around US$200 million each. [ 79 ]
Transportation and supply is an important aspect of the gas business, since natural gas reserves are normally quite distant from consumer markets. Natural gas has far more volume than oil to transport, and most gas is transported by pipelines. There is a natural gas pipeline network in the former Soviet Union , Europe and North America. Natural gas is less dense, even at higher pressures. Natural gas will travel much faster than oil through a high-pressure pipeline, but can transmit only about a fifth of the amount of energy per day due to the lower density. Natural gas is usually liquefied to LNG at the end of the pipeline, before shipping.
Short LNG pipelines for use in moving product from LNG vessels to onshore storage are available. Longer pipelines, which allow vessels to offload LNG at a greater distance from port facilities, are under development. This requires pipe-in-pipe technology due to requirements for keeping the LNG cold. [ 124 ]
LNG is transported using tanker trucks, [ 125 ] railway tanker cars, [ 126 ] and purpose built ships known as LNG carriers . LNG is sometimes taken to cryogenic temperatures to increase the tanker capacity. The first commercial ship-to-ship transfer (STS) transfers were undertaken in February 2007 at the Flotta facility in Scapa Flow [ 127 ] with 132,000 m 3 of LNG being passed between the vessels Excalibur and Excelsior. Transfers have also been carried out by Exmar Shipmanagement , the Belgian gas tanker owner in the Gulf of Mexico , which involved the transfer of LNG from a conventional LNG carrier to an LNG regasification vessel (LNGRV). Before this commercial exercise, LNG had only ever been transferred between ships on a handful of occasions as a necessity following an incident. [ citation needed ] The Society of International Gas Tanker and Terminal Operators ( SIGTTO ) is the responsible body for LNG operators around the world and seeks to disseminate knowledge regarding the safe transport of LNG at sea. [ 128 ]
Besides LNG vessels, LNG is also used in some aircraft .
Liquefied natural gas is used to transport natural gas over long distances, often by sea. In most cases, LNG terminals are purpose-built ports used exclusively to export or import LNG.
The United Kingdom has LNG import facilities for up to 50 billion cubic meters per year. [ 129 ]
The insulation, as efficient as it is, will not keep LNG cold enough by itself. Inevitably, heat leakage will warm and vapourise the LNG. Industry practice is to store LNG as a boiling cryogen . That is, the liquid is stored at its boiling point for the pressure at which it is stored (atmospheric pressure). As the vapour boils off, heat for the phase change cools the remaining liquid. Because the insulation is very efficient, only a relatively small amount of boil-off is necessary to maintain temperature. This phenomenon is also called auto-refrigeration .
Boil-off gas from land based LNG storage tanks is usually compressed and fed to natural gas pipeline networks. Some LNG carriers use boil-off gas for fuel.
Natural gas could be considered the least environmentally harmful fossil fuel because it has the lowest CO 2 emissions per unit of energy and is suitable for use in high efficiency combined cycle power stations. For an equivalent amount of heat, burning natural gas produces about 30 percent less carbon dioxide than burning petroleum and about 45 per cent less than burning coal . [ 130 ] Biomethane is considered roughly CO 2 -neutral and avoids most of the CO 2 -emissions issue. If liquefied (as LBM), it serves the same functions as LNG. [ 131 ]
On a per kilometer transported basis, emissions from LNG are lower than piped natural gas, which is a particular issue in Europe, where significant amounts of gas are piped several thousand kilometers from Russia. However, emissions from natural gas transported as LNG can be higher than those of natural gas produced regionally and piped to the point of combustion, as emissions associated with transport are lower for the latter. [ 132 ]
However, on the West Coast of the United States, where up to three new LNG importation terminals were proposed before the U.S. fracking boom, environmental groups, such as Pacific Environment , Ratepayers for Affordable Clean Energy (RACE), and Rising Tide had moved to oppose them. [ 133 ] They claimed that, while natural gas power plants emit approximately half the carbon dioxide of an equivalent coal power plant, the natural gas combustion required to produce and transport LNG to the plants adds 20 to 40 percent more carbon dioxide than burning natural gas alone. [ 134 ] A 2015 peer-reviewed study evaluated the full end-to-end life cycle of LNG produced in the U.S. and consumed in Europe or Asia. [ 135 ] It concluded that global CO 2 production would be reduced due to the resulting reduction in other fossil fuels burned.
Some scientists and local residents have raised concerns about the potential effect of Poland 's underground LNG storage infrastructure on marine life in the Baltic Sea . [ 136 ] Similar concerns were raised in Croatia . [ 137 ]
Natural gas is a fuel and a combustible substance. To ensure safe and reliable operation, particular measures are taken in the design, construction and operation of LNG facilities. In maritime transport, the regulations for the use of LNG as a marine fuel are set out in the IGF Code . [ 138 ]
In its liquid state, LNG is not explosive and can not ignite. For LNG to burn, it must first vaporize, then mix with air in the proper proportions (the flammable range is 5 percent to 15 percent), and then be ignited. In the case of a leak, LNG vaporizes rapidly, turning into a gas (methane plus trace gases), and mixing with air. If this mixture is within the flammable range , there is risk of ignition, which would create fire and thermal radiation hazards.
Gas venting from vehicles powered by LNG may create a flammability hazard if parked indoors for longer than a week. Additionally, due to its low temperature, refueling an LNG-powered vehicle requires training to avoid the risk of frostbite . [ 139 ] [ 140 ]
LNG tankers have sailed over 100 million miles (160,000,000 km) without a shipboard death or even a major accident. [ 141 ]
Several on-site accidents involving or related to LNG are listed below:
On 8 May 2018, the United States withdrew from the Joint Comprehensive Plan of Action with Iran , reinstating Iran sanctions against their nuclear program. [ 148 ] In response, Iran threatened to close off the Strait of Hormuz to international shipping. [ 149 ] The Strait of Hormuz is a strategic route through which a third of the world's LNG passes from Middle East producers. [ 150 ]
In January 2024, Qatar halted tankers of liquefied natural gas through the strait of Bab-el-Mandeb after US-led airstrikes on Houthi targets in Yemen increased risks in the strait. [ 151 ] The LNG tankers were forced to sail around Africa via the Cape of Good Hope to avoid the war zone. [ 152 ] | https://en.wikipedia.org/wiki/Liquefied_natural_gas |
Liquid–feed flame spray pyrolysis (LF-FSP) is one of the most recent iterations in flame spray pyrolysis (FSP) powder production technology. [ 1 ] [ 2 ] FSP produces metal oxide powders from highly volatile gaseous metal chlorides that are decomposed/oxidized in hydrogen-oxygen flames to form nano-oxide powders . [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ] However, products made from FSP's vapor-phase process are limited to Al- , Ti- , Zr- , and Si- based oxides from their metal chlorides. Thus, interest in producing more complex materials required a new methodology, LF-FSP. [ 14 ] [ 15 ] [ 16 ]
LF-FSP, as invented at the University of Michigan, uses metalloorganic precursors such as metal carboxylates or alkoxides , not metal chlorides. Briefly, alcohol (typically ethanol) solutions containing 1–10 wt % loading of the target ceramic components as precursors are aerosolized with O 2 into a quartz chamber and ignited with methane pilot torches. [ 1 ] [ 17 ] [ 18 ] Initial combustion temperatures run 1500–2000 °C, depending on the processing conditions, generating nanopowder "soot". [ 9 ] [ 12 ] [ 13 ] [ 19 ] Temperatures drop to 300–500 °C over 1.5 m, equivalent to a 1000 °C quench in 100 ms leading to kinetic products and nanopowders that are unaggregated. Production rates can be 200 g/h when using wire-in-tube electrostatic precipitators operating at 10 kV. Typical powders have 15–100 nm average particle sizes (APS) with specific surface areas of 30–100 m 2 /g. LF-FSP technology can be used to produce mixed and single metal oxides easily from low-cost starting materials in a single step without forming harmful byproducts like HCl , which forms when metal chlorides are used as precursors. [ 1 ] [ 12 ] [ 13 ] [ 17 ] [ 18 ] [ 20 ] [ 21 ]
Initially, metalloorganic precursors are dissolved in alcohol, typically ethanol , to a desired ceramic loading. For further explanation on precursors, refer to precursors section below. The mass of final ceramic oxide can be calculated with the ceramic yield and the amount of precursors used. [ 12 ] [ 13 ] The production process, called as "shooting", refers broadly to aerosolizing the dissolved liquid precursor solution and combusting it in the flame. Metal oxides are produced, having final stoichiometries determined by the precursor solution compositions. [ 1 ] [ 17 ] [ 18 ] [ 20 ] [ 21 ]
Production rates depend on the precursor solution's ceramic yield; this can be understood practically as the number of metal atoms injected into the flame per volume of liquid. Additionally, particle collection efficiency is important to minimize waste and loss. The collection efficiency is defined as mass of powder collected over theoretically expected mass. While "shooting", a portion of powder flows into exhaust without being deposited onto the electrostatic precipitators (ESP), and during collection of powder which is done by brushing it off, powder loss occurs which causes deviation of mass of collected powder from theoretically expected value. In laboratory settings, production rates can range from 10 to 300 g/hour, producing uniform, unaggregated nanoparticles with APS between 15 and 100 nm. [ 3 ] [ 7 ] [ 9 ] [ 22 ] Commercially, Nanocerox holds an exclusive license for LF-FSP and can produce 4 kg/hour quantities via the continuous process. [ 23 ] [ 24 ]
Typically, the solvent serves as the fuel; thus cost and solubility issues leads to use of ethanol or other "low cost" alcohols to dissolve the precursors. The oxygen/alcohol aerosol undergoes rapid combustion within milliseconds, oxidizing all the organic components at temperatures up to 2000 °C leaving only metal-oxyanions e.g., (M-O) x in the gas phase. [ 19 ] These oxyanions thereafter nucleate to form clusters and finally sub-100 nm particles, as seen in Figure 1 . [ 7 ] [ 9 ] [ 19 ] [ 25 ]
Combustion of the precursor results in oxidation of ligands / adducts generating vapors that likely consist of gaseous metal ions and oxyanion species, which co-react to nucleate and grow to form clusters of metal oxide bonds. [ 26 ] [ 27 ]
These clusters condense to form nuclei, which subsequently grow by consuming the vapor phase species and bonding with oxygen available in the atmosphere. [ 20 ] In this context, the term cluster refers to the initially generated species that form as a vapor. These clusters coalesce to form nuclei, which later form stable particles.
Once formed, nuclei collide to coalesce or agglomerate where temperature and species dictate the mechanism. Cooling changes the effect of collision from coalescence to agglomeration. LF-FSP's rapid drop in temperature as the particles exit the flame prevents the formation of aggregate. Definition of aggregate and its detrimental effect is discussed in advantages section. Collisions that take place after the temperature drop result in agglomerates, in which particles bond weakly by Van der Waals forces , and they can be separated easily with ultrasonication or ball-milling .
While exceptions exist, most flame-made particles are nano-sized (< 100 nm) and highly crystalline. Also, neither phase separation within each particle nor composition variance among particles is observed, as the entire process is so rapid that atomically mixed particles are formed. [ 1 ] [ 12 ] [ 13 ] Their properties stem from the flame temperature (up to 2000 °C) and high cooling rates (>500 °C/s). Low residence times in the flame (the amount of time metal ions spend in the flame zone) and rapid cooling lead to metastable phase formation and more importantly unaggregated particles, as they do not have the energy to coalesce and neck . [ 7 ] [ 28 ] [ 29 ] The purity of the initial reactants largely drives the final powder's purity. [ 1 ] [ 9 ] Some carbonate species may be present on as-produced powders; however, processing techniques can minimize these impurities in final products. First, the powder is dispersed in a solvent via ultrasonication and left to sit for 8 to 12 hours, which leads to some small fraction of larger particles, mostly carbonates, settling at the bottom. The suspension is separated from the sediment and is dried in an oven before being ground into a powder. [ 1 ] [ 12 ] [ 13 ] Thus, LF-FSP provides a robust, versatile route to single and mixed-metal oxide powders in the 15–100 nm size range with varying phase and morphology from relatively low-cost organic precursors. [ 4 ] [ 9 ] [ 30 ]
A LF-FSP apparatus has five components: aerosol generator with fluid feed and reservoir, cylindrical quartz combustion chamber, Y-shaped quartz tube, four wire-in-cylinder electrostatic precipitators (ESPs) connected in parallel-series, and exhaust piping. [ 1 ]
The precursor, typically a single- or mixed-metal alkoxide , or carboxylate dissolved in ethanol at 1–10 wt% is introduced to the combustion chamber via twin, high-shear fluid (Bernoulli) aerosol generators with oxygen as the atomizing gas. [ 1 ] [ 20 ] [ 31 ] The aerosol generator is composed of a precursor delivery tube oriented perpendicularly to a high-velocity oxygen flow tube. The twin aerosol generators provide high throughput of the precursor solution and stabilize the flame. Two methane pilot torches made of alumina are used to ignite the aerosol. The ensuing combustion results in flame temperatures of 1500–2000 °C, depending on the solvent, precursor loading, and rate of aerosolization . [ 9 ] [ 12 ] [ 25 ] The precursor vaporizes on combustion and subsequently gets converted to nanoparticles in the flame. Temperatures drop to 300–500 °C over a 1.5 m length of the combustion chamber, which is equivalent to a 1000 °C quench in ≤ 100 ms . The process leads to kinetic products and nanopowders that are largely unaggregated. [ 1 ] [ 20 ] [ 25 ] [ 32 ]
The resulting nanopowders are collected by electrophoretic deposition in a parallel-series arrangement of wire-in-aluminum tube electrostatic precipitators (ESPs). A direct current bias of 5–10 kV is applied between the wire and the ESP wall, which induces particle deposition on both the wall and the wire.
Metal alkoxides, carboxylates such as alumatrane [ 17 ] [ 20 ] [ 21 ] [Al(OCH 2 CH 2 ) 3 N], silatrane [ 20 ] Si(OCH 2 CH 2 ) 3 N[OCH 2 CH 2 N(CH 2 CH 2 OH) 2 ], and zirconium propionate [ 33 ] [Zr(O 2 CCH 2 CH 3 ) 2 -(OH) 2 ], are generally used, and they are dissolved in an alcohol solvent such as methanol or ethanol. Solubility of the precursor in alcohol is an important property, which is controlled by the ligands. Too much carbon in the ligand may promote formation of metal carbonate as a secondary minor phase since enormous amounts of CO 2 are generated on combustion which may react with metal oxides. Too little carbon in the ligand will limit the solubility of precursor in alcohol. The process is inexpensive as metal oxides, [ 1 ] hydroxides, [ 20 ] carbonates [ 33 ] or nitrates [ 21 ] can be used as starting points for precursor synthesis. For mixed-metal oxides, one can either synthesize a double-alkoxide which contains two metal elements such as magnesium aluminum double alkoxide [ 20 ] as shown in Table 1 , or simply mix different alkoxide and/or carboxylates in stoichiometric ratios. For example, LF-FSP products of alumatrane and silatrane glycolate dissolved in ethanol at 3:1 molar ratio is mullite (3Al 2 O 3 •2SiO 2 ). [ 20 ] Stoichiometry of nanopowder made through LF-FSP corresponds to that of its precursor.
One way to make a metal alkoxide precursor is through a simple "one-pot" synthesis. Alkoxide precursors of single or mixed metal-oxides are prepared this way. [ 20 ] [ 25 ] In this process, an ethylene glycol suspension of metal oxide or hydroxides with triethanolamine is heated at 200 °C. The reaction proceeds by dissolving the starting materials while concurrently removing byproduct water to form a clear solution. Excluding oxygen, hydrogen, carbon, and nitrogen, the ratio of different metal elements in the alkoxide corresponds to the stoichiometry of the LF-FSP made nanoparticles. Examples of alkoxides that have been used in LF-FSP are shown in Table 1 .
Table 1. Examples of metal alkoxides.
Metal carbonates or nitrates can be reacted with excess carboxylic acid (e.g. propionic acid) in a flask equipped with a still head and an addition funnel. [ 21 ] [ 32 ] [ 33 ] N 2 is sparged into the solution as the solution is heated to 120 °C and maintained until all of byproduct water and appropriate amount of excess carboxylic acid are removed with the aid of N 2 flow. Additional gaseous byproducts CO 2 and (NO) x are produced for metal carbonates and nitrates respectively. Pure carboxylates are typically ground to powder to facilitate dissolution in alcohol. Table 2 provides examples of common metal carboxylates that have been used in LF-FSP.
Table 2. Examples of metal carboxylates.
LF-FSP offers several advantages over other nanopowder production methods. A key problem in nanopowder synthesis is the use of expensive raw materials. These expensive raw materials include metal chloride precursors, which are highly corrosive. Protective construction of equipment is needed when using metal chloride precursors in FSP. In addition, toxic, polluting byproducts need to be disposed. In LF-FSP, organometallic precursors are used which do not pose this problem. Due to the use of non-corrosive precursors, LF-FSP does not require protective equipment and disposal of toxic byproducts. Also, organometallic precursors are low-cost and easy to produce. For instance, silatrane glycolate, a precursor in the production of SiO 2 through LF-FSP, can be synthesized in kilogram quantities in one step from silica. [ 34 ]
Another problem in nanopowder synthesis is the difficulty in controlling the size, size distribution, and agglomeration of particles. Milling , grinding, jet milling, crushing, and micronization are conventionally used for particle size reduction. However, neither the particle size can reach the nanoscale, nor are the shapes uniform. [ 35 ] LF-FSP directly produces nanopowders that are not possible via grinding. [ 22 ] Uniform particle size distributions are obtained using LF-FSP as it is a vapor phase process. For instance, Al 2 O 3 nanopowders produced from LF-FSP have an average particle size (APS) of 20–150 nm with a log-normal particle size distribution . [ 36 ]
Obtaining a final product with high purity and relatively narrow size distribution is much easier compared to alternatives, and such powders do not require additional powder processing which may result in introduction of impurities. Aggregation is another key problem in nanopowder synthesis. Aggregates contain discrete primary particles that are necked. Particle necking refers to particles, which chemically bond together from the diffusion of atoms to the particles' interface in the presence of a driving force, such as heat. Neck formation is shown in Figure 3 . A major disadvantage of vapor-fed FSP is the formation of hard agglomerates in the gas phase. As a result, it leads to difficulties in producing high-quality, bulk materials. [ 37 ] LF-FSP largely avoids this problem by limiting aggregation through rapid quenching. [ 12 ] [ 13 ] [ 38 ]
LF-FSP can be used to produce nanopowders in commercial quantities, while other nano-powder synthesis methods have low production rates. For example, hydrothermal processing of nanoparticles in supercritical water can produce nanopowders at a rate of 10–15 g/h. [ 39 ] Production rates of nanopowders using LF-FSP is significantly greater. For example, Nanocerox can produce nanopowders up to 4 kilogram/hour using LF-FSP. [ 22 ]
Common methods of producing coated nanoparticles are primarily based on solution phase methods and sol-gel processing , which are multi-step processes. These multi-step processes are inefficient in cost, time and homogeneity of the final product. [ 29 ] [ 40 ] Also, the disposal of solvents is costly. These coated nanoparticles include ZrO 2 coated Al 2 O 3 , SiO 2 coated ZrO 2 , and SnO 2 coated ZrO 2 . [ 13 ] However, LF-FSP has the potential to provide simple and efficient routes to coated nanopowder production without aggregation. LF-FSP allows access to core–shell nanoparticles of (ZrO 2 ) 1−x (Al 2 O 3 ) x , which can be produced in a single step. [ 13 ]
LF-FSP can produce a wide variety of nanopowders for multiple applications. Yttrium aluminum garnet or YAG (Y 3 Al 5 O 12 ) doped with rare earth metals (Ce 3+ , Pr 3+ , or Nd 3+ ) can be produced through LF-FSP, which have phosphor and laser applications. YAG doped with rare earth metals, Nd:YAG for example, show electron pump lasing behavior. The small particle size of the rare earth metals provide optical feedback. YAG has been studied because of their high temperature mechanical strength and photonic properties. The development of YAG nanopowders that are easily sintered to full density and transparency have been studied because transparent polycrystalline YAG lasers outperform single crystal YAG lasers. [ 41 ]
Nanopowders produced from LF-FSP can be used for several catalytic applications. If nanocatalysts aggregate, their activity is lower due to the decrease in surface area. LF-FSP allows the production of nanocatalyst with minimal aggregation. It is known that bimetallic and trimetallic catalysts offer improved properties over single metal catalysts. Bimetallic nanocatalysts have been produced via LF-FSP. NiO-Co 3 O 4 , NiO-MoO 3 , and NiO-CuO are used for several types of catalytic reactions. [ 42 ] For example, NiO-Co 3 O 4 nanoparticles are used as catalysts for the production of fuels and chemicals, and the reduction of environmental pollution. CeO 2 /ZrO 2 catalysts have been studied for automotive catalytic converters. [ 36 ] CeO 2 /ZrO 2 catalysts have been added to catalytic systems for the elimination and reduction of the pollutants contained in the exhaust gases of vehicles.
Zirconia toughened alumina composites are composed of Al 2 O 3 and ZrO 2 nanopowders, which are producible via LF-FSP. [ 38 ] Zirconia toughened alumina has been studied for its high toughness and resistance to wear and has biomedical applications. [ 24 ] [ 43 ] It has the potential to produce tougher and harder ceramic surfaces that may be used for ceramic hip implants. The lifetime of such implants depends on the surface quality. [ 44 ] [ 45 ] Zirconia toughened alumina implants offer increased component life and a more cost effective long term solution.
Alpha (α)-alumina produced with an APS of less than 100 nm may be used for manufacturing transparent armor. [ 46 ] Transparent armor provides enhanced protection against severe ballistic and blast threats. [ 47 ] Traditional bullet proof glass cannot stop a .50-caliber armor-piercing round. This clear ceramic α-alumina material can stop a round from an anti-aircraft gun and a .50-caliber gun. In addition, it is half as heavy and thick as bullet-resistant glass. [ 48 ] In the future, this material may be incorporated in a wide range of vehicles including lightly armored trucks to low-flying planes. [ 48 ]
Uniform TiO 2 nanoparticles have been produced using the LF-FSP process, which have potential applications in producing self-cleaning windows, paint, interior furnishings, and aluminum siding. In addition, TiO 2 has been used for self-sterilizing applications in hospitals and bathrooms. [ 49 ] For instance, Optimus Services LLC has incorporated TiO 2 into the tiles used to cover the floor and walls of medical operating rooms. [ 50 ] TiO 2 is currently the leading material for self-cleaning applications due to its high photocatalytic activity, chemical inertness, mechanical properties, and low cost. [ 51 ]
Table 3 lists several potential applications of nanopowders produced from LF-FSP.
Table 3 . Nanopowders produced from LF-FSP and their potential applications.
Nanomaterials synthesis | https://en.wikipedia.org/wiki/Liquid-feed_flame_spray_pyrolysis |
A liquid hydrogen tank car , also called liquid hydrogen tank wagon or liquid hydrogen tanker wagon , is a railroad tank car designed to carry cryogenic liquid hydrogen (LH 2 ). LH 2 tank cars with a capacity of 17,000 pounds (7,711 kg) are used for transcontinental transport. [ 1 ] [ 2 ]
The pressure within the tank is 25 psi (170 kPa ) or lower [ 3 ] [ 4 ] with a temperature below 20.27 K (−423.17 °F or −252.87 °C) and a boil-off rate of 0.3% to 0.6% per day [ 5 ] The tank is double walled like a vacuum flask with multi-layer insulation , with the valves and fittings enclosed in a cabinet at the lower side or end of the car.
Cryogenic liquid tank cars in the US are classified as follows: [ 6 ] | https://en.wikipedia.org/wiki/Liquid-hydrogen_tank_car |
A liquid hydrogen tank-tainer , also known as a liquid hydrogen tank container , is a specialized type of container designed to carry cryogenic liquid hydrogen (LH 2 ) on standard intermodal equipment. [ 1 ] The tank is held within a box-shaped frame the same size and shape as a container.
Liquid hydrogen tanktainers are referenced by their size or volume capacity, generally an ISO 40 ft (12.19 m) container . [ 2 ] | https://en.wikipedia.org/wiki/Liquid-hydrogen_tanktainer |
A liquid-hydrogen trailer is a trailer designed to carry cryogenic liquid hydrogen (LH 2 ) on roads being pulled by a powered vehicle . The largest such vehicles are similar to railroad tanktainers which are also designed to carry liquefied loads. Liquid-hydrogen trailers tend to be large; they are insulated . Some are semi-trailers . [ 1 ]
The U-1 semi-trailer was a liquid-hydrogen trailer designed in the 1950s to carry cryogenic liquid hydrogen (LH 2 ) on roads being pulled by a powered vehicle . It was constructed by the Cambridge Corporation and had a capacity of 26,000 liters (6,900 U.S. gal; 5,700 imp gal) with a hydrogen loss rate of approximately 2 percent per day. The U-1 was a single- axle semi-trailer . The specifications for its successor the U-2, a double axle semi-trailer, were issued on 15 March 1957. [ 2 ]
Liquid hydrogen trailers are referenced by their size or volume capacity. Liquid-hydrogen trailers typically have capacities ranging from 28,400 to 49,200 liters (7,502 to 12,997 U.S. gal; 6,247 to 10,822 imp gal) gross volume. [ 3 ] [ 4 ]
This truck-related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Liquid-hydrogen_trailer |
A liquid-mirror space telescope is a concept for a reflecting space telescope that uses a reflecting liquid such as mercury as its primary reflector. [ 1 ]
There are several designs for such a telescope:
Regardless of the specific configuration, such a telescope would be similar to an Earth-based liquid-mirror telescope . However, instead of relying on Earth's gravity to maintain the necessary parabolic shape of the rotating mercury mirror, it relies on artificial gravity instead.
Other possibilities for inducing a parabolic shape in the reflecting liquid include:
The concept is seen as an enabler of very large optical space telescopes, as a liquid mirror would be much cheaper to construct than a conventional glass mirror of comparable performance.
In April 2022, NASA reported that they would conduct the Fluidic Telescope Experiment (FLUTE) in the ISS , which would be part of the Axiom Mission 1 astronaut Eytan Stibbe 's research portfolio. The research would test liquid lens by using water injected by polymers in microgravity through utilizing buoyancy to even gravitational forces and cause weightlessness , to be later hardened by UV light or temperature in-orbit. [ 2 ] | https://en.wikipedia.org/wiki/Liquid-mirror_space_telescope |
An important parameter in wet scrubbing systems is the rate of liquid flow. It is common in wet scrubber terminology to express the liquid flow as a function of the gas flow rate that is being treated. This is commonly called the liquid-to-gas ratio ( L/G ratio ) and uses the units of gallons per 1,000 actual cubic feet or litres per cubic metre (L/m 3 ).
Expressing the amount of liquid used as a ratio enables systems of different sizes to be readily compared.
For particulate removal, the liquid-to-gas ratio is a function of the mechanical design of the system; while for gas absorption this ratio gives an indication of the difficulty of removing a pollutant . Most wet scrubbers used for particulate control operate with liquid-to-gas ratios in the range of 4 to 20 gallons per 1,000 actual cubic foot (0.5 to 3 litres per actual cubic metre).
Depending on scrubber design, a minimum volume of liquid is required to "wet" the scrubber internals and create sufficient collection targets. After a certain optimum point, adding excess liquid to a particulate wet scrubber does not increase efficiency and in fact, could be counter-productive by causing excessive pressure loss . Liquid-to-gas ratios for gas absorption are often higher, in the range of 20 to 40 gallons per 1,000 actual cubic foot (3 to 6 litres per actual cubic metre).
L/G ratio illustrates a number of points about the choice of wet scrubbers used for gas absorption. For example, because flue-gas desulfurization systems must deal with heavy particulate loadings, open, simple designs (such as venturi , spray chamber and moving bed ) are used.
Also, the liquid-to-gas ratio for the absorption process is higher than for particle removal and gas velocities are kept low to enhance the absorption process.
Solubility is a very important factor affecting the amount of a pollutant that can be absorbed. Solubility governs the amount of liquid required (liquid-to-gas ratio) and the necessary contact time. More soluble gases require less liquid. Also, more soluble gases will be absorbed faster. [ 1 ] | https://en.wikipedia.org/wiki/Liquid-to-gas_ratio |
Liquid 3 (also known as Liquid Trees) is a clean energy photobioreactor project designed to replace the function of trees in heavily polluted urban areas where planting and growing real vegetation is not viable.
The project was designed by the Institute for Multidisciplinary Research at the University of Belgrade . The United Nations Development Programme (UNDP) selected Liquid 3 as an "innovative" solution for "Climate Smart Urban Development," a project produced in partnership with Serbia's Ministry of Environmental Protection and the municipality of Stari Grad . [ 1 ]
The Liquid3 algal photobioreactor is powered by solar panels. The glass tank is embedded into a structure that acts as a bench and is outfitted with other utilities such as charging ports. Similar to other photobioreactors, air is sucked through a pressure pump and fed to the microalgae, with oxygen released as a byproduct. Additionally, the Liquid 3 bioreactor can filter out heavy metal contaminants in the air and contains a temperature regulation system in case external climate conditions become too extreme for the microalgae. [ 2 ] [ 3 ] [ 4 ] The creator of the Liquid 3, Dr. Ivan Spasojevic, was motivated to install it in Belgrade due to the city's struggle with pollution. [ 5 ] | https://en.wikipedia.org/wiki/Liquid3 |
Liquid carbon dioxide is the liquid state of carbon dioxide ( CO 2 ), which cannot occur under atmospheric pressure. It can only exist at a pressure above 5.1 atm (5.2 bar; 75 psi), under 31.1 °C (88.0 °F) (temperature of critical point ) and above −56.6 °C (−69.9 °F) (temperature of triple point ). [ 1 ] Low-temperature carbon dioxide is commercially used in its solid form, commonly known as " dry ice ". Solid CO 2 sublimes at 194.65 K (−78.5 °C; −109.3 °F) at Earth atmospheric pressure — that is, it transitions directly from solid to gas without an intermediate liquid stage. The uses and applications of liquid carbon dioxide include decaffeinating coffee, [ 2 ] extracting virgin olive oil from olive paste, in fire extinguishers , and as a coolant.
Liquid carbon dioxide is a type of liquid which is formed from highly compressed and cooled gaseous carbon dioxide. It does not form under atmospheric conditions. It only exists when the pressure is above 5.1 atm and the temperature is under 31.1 °C (88.0 °F) (temperature of critical point ) and above −56.6 °C (−69.9 °F) (temperature of triple point ). The chemical symbol remains the same as gaseous carbon dioxide ( CO 2 ). [ 3 ] It is transparent and odorless, and its density is 1101 kg/m 3 when the liquid is at full saturation at −37 °C (−35 °F). [ 4 ]
The solubility of water in liquid carbon dioxide is measured in a range of temperatures, ranging from −29 °C (−20 °F) to 22.6 °C (72.7 °F). At this temperature, the pressure is measured in a range from 15 to 60 atmospheres. The solubility turned out to be very low: from 0.02 to 0.10 %. [ 5 ]
Uses of liquid carbon dioxide include the preservation of food, in fire extinguishers, and in commercial food processes. For food preservation , liquid carbon dioxide is used to refrigerate, preserve, store, and soften. In a fire extinguisher, the CO 2 is stored under pressure as a liquid to act as an anti-flammable. [ 3 ] The liquid carbon dioxide not only reduces combustion by displacing oxygen , but also cools the burning surface to avoid further damage. Solvent extraction using compressed liquid CO 2 can be used in industrial processes such as removing caffeine from coffee [ 3 ] or improving the yield of olive oil production. [ 6 ]
Liquid carbon dioxide is being considered as a means of CO 2 transportation for underground or subsea storage purposes. Due to its high density as a liquid, it is much more feasible to ship than as a gas. [ citation needed ]
CO 2 is also used in large-scale air-to-water heat pumps for district heating, replacing less-environmentally-friendly refrigerants. The CO 2 changes phases between liquid and gaseous in the process. [ 7 ]
Other chemical compounds and elements are commonly used for commercial and research purposes in their liquid state: | https://en.wikipedia.org/wiki/Liquid_CO2 |
Liquid air is air that has been cooled to very low temperatures ( cryogenic temperatures ), so that it has condensed into a pale blue mobile liquid. [ 1 ] It is stored in specialized containers, such as vacuum flasks , to insulate it from room temperature . Liquid air can absorb heat rapidly and revert to its gaseous state. It is often used for condensing other substances into liquid and/or solidifying them, and as an industrial source of nitrogen , oxygen , argon , and other inert gases through a process called air separation (industrially referred to as air rectification.).
Liquid air has a density of approximately 870 kg/m 3 (870 g/L ; 0.87 g / cm 3 ). The density of a given air sample varies depending on the composition of that sample (e.g. humidity & CO 2 concentration). Since dry gaseous air contains approximately 78% nitrogen, 21% oxygen, and 1% argon , the density of liquid air at standard composition is calculated by the percentage of the components and their respective liquid densities (see liquid nitrogen and liquid oxygen ). Although air contains trace amounts of carbon dioxide (about 0.03%), carbon dioxide solidifies from the gas phase without passing through the intermediate liquid phase, and hence will not be present in liquid air at pressures less than 5.1 atm (520 kPa ).
The boiling point of air is −194.35 °C (78.80 K ; −317.83 °F ), intermediate between the boiling points of liquid nitrogen and liquid oxygen . However, it can be difficult to keep at a stable temperature as the liquid boils, since the nitrogen will boil off first, leaving the mixture oxygen-rich and changing the boiling point. This may also occur in some circumstances due to the liquid air condensing oxygen out of the atmosphere. [ 2 ] : 36
Liquid air starts to freeze at approximately 60 K (−213.2 °C; −351.7 °F), precipitating nitrogen-rich solid (but with appreciable amount of oxygen in solid solution). Unless the oxygen is previously accommodated in the solid solution, the eutectic freezes at 50 K. [ 3 ]
The constituents of air were once known as "permanent gases", as they could not be liquified solely by compression at room temperature. A compression process will raise the temperature of the gas. This heat is removed by cooling to the ambient temperature in a heat exchanger, and then expanding by venting into a chamber. The expansion causes a lowering of the temperature, and by counter-flow heat exchange of the expanded air, the pressurized air entering the expander is further cooled. With sufficient compression, flow, and heat removal, eventually droplets of liquid air will form, which may then be employed directly for low temperature demonstrations.
The main constituents of air were liquefied for the first time by Polish scientists Karol Olszewski and Zygmunt Wróblewski in 1883.
Devices for the production of liquid air are not commercially available, and not easily fabricated.
The most common process for the preparation of liquid air is the two-column Hampson–Linde cycle using the Joule–Thomson effect . Air is fed at high pressure (>75 atm (7,600 kPa ; 1,100 psi )) into the lower column, in which it is separated into pure nitrogen and oxygen-rich liquid. The rich liquid and some of the nitrogen are fed as reflux into the upper column, which operates at low pressure (<25 atm (2,500 kPa; 370 psi)), where the final separation into pure nitrogen and oxygen occurs. A raw argon product can be removed from the middle of the upper column for further purification. [ 4 ]
Air can also be liquefied by Claude's process , which combines cooling by Joule–Thomson effect , isentropic expansion and regenerative cooling. [ 5 ]
In manufacturing processes, the liquid air product is typically fractionated into its constituent gases in either liquid or gaseous form, as the oxygen is especially useful for fuel gas welding and cutting and for medical use, and the argon is useful as an oxygen-excluding shielding gas in gas tungsten arc welding . Liquid nitrogen is useful in various low-temperature applications, being nonreactive at normal temperatures (unlike oxygen), and boiling at 77 K (−196 °C; −321 °F).
Between 1899 and 1902, the automobile Liquid Air was produced and demonstrated by a joint American/English company, with the claim that they could construct a car that would run a hundred miles on liquid air.
On 2 October 2012, the Institution of Mechanical Engineers said liquid air could be used as a means of storing energy. This was based on a technology that was developed by Peter Dearman, a garage inventor in Hertfordshire , England to power vehicles. [ 6 ] | https://en.wikipedia.org/wiki/Liquid_air |
Liquid bandage is a topical skin treatment for minor wounds which binds to the skin to form a protective polymeric layer that keeps dirt and germs out and moisture in. [ 1 ] It can be directly applied to the wound after removing debris.
For the fast-acting, reactive adhesive that is used to mend deep cuts or surgery wounds, see cyanoacrylates (specifically 2-Octyl cyanoacrylate ).
Liquid bandage is typically a polymer dissolved in a solvent (commonly water or an alcohol), sometimes with an added antiseptic and local anesthetic , although the alcohol in some brands may serve the same purpose. [ 1 ] These products protect the wound by forming a thin film of polymer when the carrier evaporates. [ 1 ] Polymers used may include polyvinylpyrrolidone (water based), ethyl cellulose, pyroxylin / nitrocellulose or poly(methylacrylate-isobutene-monoisopropylmaleate) (alcohol based), and acrylate or siloxane polymers ( hexamethyldisiloxane or isooctane solvent based). [ 1 ]
In addition to their use in replacing conventional bandages in minor cuts and scrapes, they have found use in surgical and veterinary offices. [ 1 ] Liquid bandages are increasingly finding use in the field of combat, where they can be used to rapidly stanch a wound until proper medical attention can be obtained. [ 1 ]
Liquid bandages are suitable for clean cuts that close easily and shallow small wounds, as it will help both sides of the wound to bond and produce a suture -like effect. Due to the drying of liquid wound dressing, it will form a nonelastic film on the wound and cannot absorb tissue fluid . If the wound area is too large, it will actually hinder wound shrinkage and healing.
It's not recommended for use on large wounds, abrasion patches, ulcers, suppuration , burns, sensitive skin areas around the eyes, mucosa , and patients with favism . | https://en.wikipedia.org/wiki/Liquid_bandage |
Liquid carryover [ 1 ] refers to the unintended transport of liquids such as water , hydrocarbon condensates , compressor oil or glycol in a natural gas , hydrogen , carbon dioxide or other industrial gas pipeline or process. [ 2 ] Ideally, only gas enters gas processing. [ 3 ]
Understanding pipeline composition at critical points is crucial to ensure optimal efficiency and safety.
Natural gas processing aims to deliver gas suitable for transmission systems without causing operational issues in downstream pipelines, compressors , or equipment. Ideally, all dry industrial gases remain "dry" during processing. However, due to fluid dynamics complexities, gas and liquid phases may not fully separate, leading to wet gas or two-phase flows . These can occur as mist flow (tiny liquid droplets) or stratified flow (a liquid stream along the pipe wall). These conditions can significantly impact gas processing facilities' operational safety, efficiency, and lifespan.
Liquid carryover is a major concern, responsible for roughly 60% of plant failures in natural gas processing . [ 4 ] Effective phase separation at the beginning of the processing train prevents hydrocarbons and other liquids from entering the gas treatment plant. Improper separation allows liquid carryover to contaminate the desulfurization stage, triggering foaming and fouling, leading to unplanned shutdowns and reduced gas flow. [ 5 ]
As the gas progresses through desulfurization and dehumidification, it comes into contact with significant processing liquids. Amine -based liquids used in desulfurization to remove hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) can carry over if not properly separated, contaminating the dehumidification stage. Dehumidification utilizes a liquid desiccant , such as monoethylene glycol (MEG) or triethylene glycol (TEG), to reduce gas moisture content and meet sales gas specifications. Carryover of glycol into this process can cause issues by blocking heat exchangers or disrupting temperature control. Notably, while glycol is a common component found during pipeline pigging analysis, there's currently no method to directly determine glycol carryover besides process cameras. [ 6 ]
The primary method for extracting natural gas liquids (NGLs) involves reducing gas temperature below its hydrocarbon dew point, separating the liquids. However, achieving temperature reduction through Joule-Thompson pressure reduction creates ideal conditions for sub-micron mist flow formation. This type of wet gas flow is particularly challenging to filter and requires specialized filtration systems. As the gas warms up, the liquids vaporize, saturating the vapor phase with respect to hydrocarbons. This can lead to liquid dropout as mist or stratified flows due to pressure and temperature drops during gas transmission.
Over time, solid and liquid accumulation at low points in the transmission system can lead to corrosion, potentially causing ruptures and failures at compressor stations.
Standards from the American Petroleum Institute (API) 14.1 and the International Organization for Standardization (ISO) EN10715 provide guidance for gas sampling for either laboratory or online analyzers of gas streams. They also offer guidelines for managing high-pressure gases to prevent liquid dropout in the sample system during pressure reduction from line pressure to atmospheric pressure. These standards aim to ensure a representative gas sample reaches the analyzer and prevent liquids from damaging it. However, wet gas or two-phase flows fall outside the scope of these standards, meaning gas analyzers can have significant errors and often miss liquid carryover events. [ 7 ]
Liquid carryover's operational inefficiencies have both immediate and long-term consequences. Foaming, [ 8 ] requiring reduced gas flow and de-foaming chemicals, can occur. As a precaution, gas processing facilities may intentionally limit operational capacities, sacrificing optimal gas throughput. For gas processors, errors in hydrocarbon dew point and BTU determination can lead to lost revenue, pigging costs, and rectification or rebuild costs.
The presence of wet gas and liquid hold-up in pipelines significantly increases the risks of pipeline ruptures [ 9 ] and shortens the lifespan of pipeline assets. To mitigate these risks, operators must increase the frequency of pipeline pigging.
As the gas reaches the power station, the likelihood of contamination rises due to various factors. These include:
Even though some power stations preheat the fuel gas, contamination with compressor oil or glycol (if not properly vaporized) can cause several maintenance issues. These include:
Liquid carryover in incoming natural gas feed lines can also disrupt operations at LNG plants . Molecular sieves, used to dry the gas to extremely low moisture levels, become contaminated and lose efficiency when exposed to liquid hydrocarbons. In some cases, heavy hydrocarbons, believed to be compressor oil, have reached the LNG plant's "cold box," causing pressure differentials and shortening the operational period of the LNG train.
During periods of mixed-phase flow (containing both gas and liquid), removing liquids from the gas sample being analyzed can lead to significant errors in determining the calorific value (BTU) of the gas. This makes it difficult to obtain an accurate picture of the overall fluid stream.
Gas analyzers can only report on the portion of the fluid they are presented with. This means that measurements made at custody transfer points, where gas ownership changes hands, are unreliable when two-phase flow is present. Process camera systems offer the highest level of sensitivity to both mist flow and stratified flow, providing operators with greater certainty about gas quality [ 10 ] and improving the accuracy of BTU or Wobbe Index measurements.
When liquid carryover is not specifically monitored, operators remain unaware of both continuous and occasional liquid events that significantly affect BTU calculations. This leads to inaccurate gas quality measurements.
Process camera systems have observed [ 11 ] that when liquid events occur as stratified flow, debris from the pipe wall (such as iron sulfide and scale) can accumulate on the bottom of the pipe. The high-velocity gas stream above the liquid layer removes lighter liquids, leaving behind a sludge that eventually dries into a stationary material. This material can reduce the pipe diameter.
If this scenario occurs at a custody transfer point, flow computers might use an incorrect pipe diameter in their calculations. Even with a properly calibrated flow meter, small amounts of debris (2-3mm) can cause a significant offset (0.2%) in the measurement. To ensure accurate fiscal measurements, these potential errors must be continuously monitored and factored into the uncertainty budget for all flow meters.
The Sarbanes-Oxley Act mandates that flow uncertainty budgets for fiscal flow measurements account for potential errors. [ 12 ] Unexpected liquids in dry gas systems can substantially increase the uncertainty budget associated with both flow and BTU measurements. | https://en.wikipedia.org/wiki/Liquid_carryover |
The term liquid chalk, or sharkchalk, refers to several different kinds of liquified chalk including liquid-chalk marking pens (with water-soluble ink), liquid-chalk mixtures (for athletic use: rock climbing , weightlifting, gymnastics), and liquid-chalk hobby-craft paints made of cornstarch and food coloring (some with small amounts of flour ). Some forms of "liquid chalk" contain no actual chalk.
Liquid chalk can be a variation of normal chalk (see: magnesium carbonate ) used to improve grip for sports, such as rock climbing , weight lifting , or gymnastics .
Rock climbers use liquid chalk to prevent their hands from sweating. It may be used by climbers in situations where powdered chalk is restricted. It is preferred by some athletes because it remains effective longer and leaves less residue on rocks [ 1 ] and equipment. [ 2 ] Liquid chalk for rock climbers is made from magnesium carbonate .
In other sports, liquid chalk is less beneficial to the athlete, because re-chalking can be done more easily between sets or rounds. However, some gyms require liquid chalk because it leaves less residue on gym equipment. Liquid chalk adheres to the hand better, reducing the need to re-chalk. [ 3 ] [ 4 ]
Some liquid-chalk mixtures for climbing are made with magnesium carbonate , colophony , and ethanol or an alcohol that dissolves the colophony and quickly evaporates from the solution (as isopropyl alcohol or ethanol ). Sometimes, an additive for aroma is included because of the bad smell of spirit. | https://en.wikipedia.org/wiki/Liquid_chalk |
Liquid chromatography–mass spectrometry ( LC–MS ) is an analytical chemistry technique that combines the physical separation capabilities of liquid chromatography (or HPLC ) with the mass analysis capabilities of mass spectrometry (MS). Coupled chromatography – MS systems are popular in chemical analysis because the individual capabilities of each technique are enhanced synergistically. While liquid chromatography separates mixtures with multiple components, mass spectrometry provides spectral information that may help to identify (or confirm the suspected identity of) each separated component. [ 1 ] MS is not only sensitive, but provides selective detection, relieving the need for complete chromatographic separation. [ 2 ] LC–MS is also appropriate for metabolomics because of its good coverage of a wide range of chemicals. [ 3 ] This tandem technique can be used to analyze biochemical, organic, and inorganic compounds commonly found in complex samples of environmental and biological origin. Therefore, LC–MS may be applied in a wide range of sectors including biotechnology , environment monitoring, food processing , and pharmaceutical , agrochemical , and cosmetic industries. [ 4 ] [ 5 ] Since the early 2000s, LC–MS (or more specifically LC– MS/MS ) has also begun to be used in clinical applications. [ 6 ]
In addition to the liquid chromatography and mass spectrometry devices, an LC–MS system contains an interface that efficiently transfers the separated components from the LC column into the MS ion source. [ 5 ] [ 7 ] The interface is necessary because the LC and MS devices are fundamentally incompatible. While the mobile phase in a LC system is a pressurized liquid, the MS analyzers commonly operate under high vacuum. Thus, it is not possible to directly pump the eluate from the LC column into the MS source. Overall, the interface is a mechanically simple part of the LC–MS system that transfers the maximum amount of analyte, removes a significant portion of the mobile phase used in LC and preserves the chemical identity of the chromatography products (chemically inert). As a requirement, the interface should not interfere with the ionizing efficiency and vacuum conditions of the MS system. [ 5 ] Nowadays, most extensively applied LC–MS interfaces are based on atmospheric pressure ionization (API) strategies like electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI). These interfaces became available in the 1990s after a two decade long research and development process. [ 8 ] [ 7 ]
The coupling of chromatography with MS is a well developed chemical analysis strategy dating back from the 1950s. Gas chromatography (GC)–MS was originally introduced in 1952, when A. T. James and A. J. P. Martin were trying to develop tandem separation – mass analysis techniques. [ 9 ] In GC, the analytes are eluted from the separation column as a gas and the connection with electron ionization ( EI ) or chemical ionization ( CI ) ion sources in the MS system was a technically simpler challenge. Because of this, the development of GC-MS systems was faster than LC–MS and such systems were first commercialized in the 1970s. [ 7 ] The development of LC–MS systems took longer than GC-MS and was directly related to the development of proper interfaces. Victor Talrose and his collaborators in Russia started the development of LC–MS in the late 1960s, [ 10 ] [ 11 ] when they first used capillaries to connect an LC column to an EI source. [ 12 ] [ 8 ] A similar strategy was investigated by McLafferty and collaborators in 1973 who coupled the LC column to a CI source, [ 13 ] which allowed a higher liquid flow into the source. This was the first and most obvious way of coupling LC with MS, and was known as the capillary inlet interface. This pioneer interface for LC–MS had the same analysis capabilities of GC-MS and was limited to rather volatile analytes and non-polar compounds with low molecular mass (below 400 Da). In the capillary inlet interface, the evaporation of the mobile phase inside the capillary was one of the main issues. Within the first years of development of LC–MS, on-line and off-line alternatives were proposed as coupling alternatives. In general, off-line coupling involved fraction collection, evaporation of solvent, and transfer of analytes to the MS using probes. Off-line analyte treatment process was time-consuming and there was an inherent risk of sample contamination. Rapidly, it was realized that the analysis of complex mixtures would require the development of a fully automated on-line coupling solution in LC–MS. [ 8 ]
The key to the success and widespread adoption of LC–MS as a routine analytical tool lies in the interface and ion source between the liquid-based LC and the vacuum-base MS. The following interfaces were stepping-stones on the way to the modern atmospheric-pressure ionization interfaces, and are described for historical interest.
The moving-belt interface (MBI) was developed by McFadden et al. in 1977 and commercialized by Finnigan. [ 14 ] This interface consisted of an endless moving belt onto which the LC column effluent was deposited in a band. On the belt, the solvent was evaporated by gently heating and efficiently exhausting the solvent vapours under reduced pressure in two vacuum chambers. After the liquid phase was removed, the belt passed over a heater which flash desorbed the analytes into the MS ion source. One of the significant advantages of the MBI was its compatibility with a wide range of chromatographic conditions. [ 8 ] MBI was successfully used for LC–MS applications between 1978 and 1990 because it allowed coupling of LC to MS devices using EI, CI, and fast-atom bombardment (FAB) ion sources. The most common MS systems connected by MBI interfaces to LC columns were magnetic sector and quadrupole instruments. MBI interfaces for LC–MS allowed MS to be widely applied in the analysis of drugs, pesticides, steroids, alkaloids, and polycyclic aromatic hydrocarbons . This interface is no longer used because of its mechanical complexity and the difficulties associated with belt renewal (or cleaning) as well as its inability to handle very labile biomolecules.
The direct liquid-introduction (DLI) interface was developed in 1980. This interface was intended to solve the problem of evaporation of liquid inside the capillary inlet interface. In DLI, a small portion of the LC flow was forced through a small aperture or diaphragm (typically 10 μm in diameter) to form a liquid jet composed of small droplets that were subsequently dried in a desolvation chamber. [ 11 ] The analytes were ionized using a solvent-assisted chemical ionization source, where the LC solvents acted as reagent gases. To use this interface, it was necessary to split the flow coming out of the LC column because only a small portion of the effluent (10 to 50 μl/min out of 1 ml/min) could be introduced into the source without raising the vacuum pressure of the MS system too high. Alternately, Henion at Cornell University had success with using micro-bore LC methods so that the entire (low) flow of the LC could be used. One of the main operational problems of the DLI interface was the frequent clogging of the diaphragm orifices. The DLI interface was used between 1982 and 1985 for the analysis of pesticides, corticosteroids, metabolites in horse urine, erythromycin, and vitamin B 12 . However, this interface was replaced by the thermospray interface, which removed the flow rate limitations and the issues with the clogging diaphragms. [ 5 ] [ 8 ]
A related device was the particle beam interface (PBI), developed by Willoughby and Browner in 1984. [ 15 ] Particle beam interfaces took over the wide applications of MBI for LC–MS in 1988. [ 8 ] [ 16 ] The PBI operated by using a helium gas nebulizer to spray the eluant into the vacuum, drying the droplets and pumping away the solvent vapour (using a jet separator) while the stream of monodisperse dried particles containing the analyte entered the source. [ 11 ] Drying the droplets outside of the source volume, and using a jet separator to pump away the solvent vapour, allowed the particles to enter and be vapourized in a low-pressure EI source. As with the MBI, the ability to generate library-searchable EI spectra was a distinct advantage for many applications. Commercialized by Hewlett Packard , and later by VG and Extrel, it enjoyed moderate success, but has been largely supplanted by the atmospheric pressure interfaces such as electrospray and APCI which provide a broader range of compound coverage and applications.
The thermospray (TSP) interface was developed in 1980 by Marvin Vestal and co-workers at the University of Houston. [ 17 ] It was commercialized by Vestec and several of the major mass spectrometer manufacturers. The interface resulted from a long-term research project intended to find a LC–MS interface capable of handling high flow rates (1 ml/min) and avoiding the flow split in DLI interfaces. The TSP interface was composed of a heated probe, a desolvation chamber, and an ion focusing skimmer. The LC effluent passed through the heated probe and emerged as a jet of vapor and small droplets flowing into the desolvation chamber at low pressure. Initially operated with a filament or discharge as the source of ions (thereby acting as a CI source for vapourized analyte), it was soon discovered that ions were also observed when the filament or discharge was off. This could be attributed to either direct emission of ions from the liquid droplets as they evaporated in a process related to electrospray ionization or ion evaporation, or to chemical ionization of vapourized analyte molecules from buffer ions (such as ammonium acetate). The fact that multiply-charged ions were observed from some larger analytes suggests that direct analyte ion emission was occurring under at least some conditions. [ 11 ] The interface was able to handle up to 2 ml/min of eluate from the LC column and would efficiently introduce it into the MS vacuum system. TSP was also more suitable for LC–MS applications involving reversed phase liquid chromatography (RT-LC). With time, the mechanical complexity of TSP was simplified, and this interface became popular as the first ideal LC–MS interface for pharmaceutical applications comprising the analysis of drugs , metabolites, conjugates, nucleosides , peptides , natural products , and pesticides . The introduction of TSP marked a significant improvement for LC–MS systems and was the most widely applied interface until the beginning of the 1990s, when it began to be replaced by interfaces involving atmospheric pressure ionization (API). [ 5 ] [ 7 ] [ 16 ]
The first fast atom bombardment ( FAB ) and continuous flow-FAB (CF-FAB) interfaces were developed in 1985 and 1986 respectively. [ 16 ] Both interfaces were similar, but they differed in that the first used a porous frit probe as connecting channel, while CF-FAB used a probe tip. From these, the CF-FAB was more successful as a LC–MS interface and was useful to analyze non-volatile and thermally labile compounds. In these interfaces, the LC effluent passed through the frit or CF-FAB channels to form a uniform liquid film at the tip. There, the liquid was bombarded with ion beams or high energy atoms (fast atoms). For stable operation, the FAB based interfaces were able to handle liquid flow rates of only 1–15 μl and were also restricted to microbore and capillary columns. In order to be used in FAB MS ionization sources, the analytes of interest had to be mixed with a matrix (e.g., glycerol) that could be added before or after the separation in the LC column. FAB based interfaces were extensively used to characterize peptides, but lost applicability with the advent of electrospray based interfaces in 1988. [ 5 ] [ 8 ]
Liquid chromatography is a method of physical separation in which the components of a liquid mixture are distributed between two immiscible phases, i.e., stationary and mobile. The practice of LC can be divided into five categories, i.e., adsorption chromatography , partition chromatography , ion-exchange chromatography , size-exclusion chromatography , and affinity chromatography . Among these, the most widely used variant is the reverse-phase (RP) mode of the partition chromatography technique, which makes use of a nonpolar (hydrophobic) stationary phase and a polar mobile phase. In common applications, the mobile phase is a mixture of water and other polar solvents (e.g., methanol, isopropanol, and acetonitrile), and the stationary matrix is prepared by attaching long-chain alkyl groups (e.g., n-octadecyl or C 18 ) to the external and internal surfaces of irregularly or spherically shaped 5 μm diameter porous silica particles. [ 5 ]
In HPLC, typically 20 μl of the sample of interest are injected into the mobile phase stream delivered by a high pressure pump. The mobile phase containing the analytes permeates through the stationary phase bed in a definite direction. The components of the mixture are separated depending on their chemical affinity with the mobile and stationary phases. The separation occurs after repeated sorption and desorption steps occurring when the liquid interacts with the stationary bed. [ 8 ] The liquid solvent (mobile phase) is delivered under high pressure (up to 400 bar or 5800 psi) into a packed column containing the stationary phase. The high pressure is necessary to achieve a constant flow rate for reproducible chromatography experiments. Depending on the partitioning between the mobile and stationary phases, the components of the sample will flow out of the column at different times. [ 16 ] The column is the most important component of the LC system and is designed to withstand the high pressure of the liquid. Conventional LC columns are 100–300 mm long with outer diameter of 6.4 mm (1/4 inch) and internal diameter of 3.0 – 4.6 mm. For applications involving LC–MS, the length of chromatography columns can be shorter (30–50 mm) with 3–5 μm diameter packing particles. In addition to the conventional model, other LC columns are the narrow bore, microbore, microcapillary, and nano-LC models. These columns have smaller internal diameters, allow for a more efficient separation, and handle liquid flows under 1 ml/min (the conventional flow-rate). [ 8 ] In order to improve separation efficiency and peak resolution, ultra performance liquid chromatography (UHPLC) can be used instead of HPLC. This LC variant uses columns packed with smaller silica particles (~1.7 μm diameter) and requires higher operating pressures in the range of 310000 to 775000 torr (6000 to 15000 psi, 400 to 1034 bar). [ 5 ]
Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio ( m/z) of charged particles (ions). Although there are many different kinds of mass spectrometers, all of them make use of electric or magnetic fields to manipulate the motion of ions produced from an analyte of interest and determine their m/z. [ 18 ] The basic components of a mass spectrometer are the ion source , the mass analyzer , the detector, and the data and vacuum systems. The ion source is where the components of a sample introduced in a MS system are ionized by means of electron beams , photon beams ( UV lights ), laser beams or corona discharge . In the case of electrospray ionization, the ion source moves ions that exist in liquid solution into the gas phase. The ion source converts and fragments the neutral sample molecules into gas-phase ions that are sent to the mass analyzer. While the mass analyzer applies the electric and magnetic fields to sort the ions by their masses, the detector measures and amplifies the ion current to calculate the abundances of each mass-resolved ion. In order to generate a mass spectrum that a human eye can easily recognize, the data system records, processes, stores, and displays data in a computer. [ 5 ]
The mass spectrum can be used to determine the mass of the analytes, their elemental and isotopic composition, or to elucidate the chemical structure of the sample. [ 5 ] MS is an experiment that must take place in gas phase and under vacuum (1.33 * 10 −2 to 1.33 * 10 −6 pascal). Therefore, the development of devices facilitating the transition from samples at higher pressure and in condensed phase (solid or liquid) into a vacuum system has been essential to develop MS as a potent tool for identification and quantification of organic compounds like peptides. [ 19 ] MS is now in very common use in analytical laboratories that study physical, chemical, or biological properties of a great variety of compounds. Among the many different kinds of mass analyzers, the ones that find application in LC–MS systems are the quadrupole , time-of-flight (TOF) , ion traps , and hybrid quadrupole-TOF (QTOF) analyzers. [ 7 ]
The interface between a liquid phase technique (HPLC) with a continuously flowing eluate, and a gas phase technique carried out in a vacuum was difficult for a long time. The advent of electrospray ionization changed this. Currently, the most common LC–MS interfaces are electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo-ionization (APPI). These are newer MS ion sources that facilitate the transition from a high pressure environment (HPLC) to high vacuum conditions needed at the MS analyzer. [ 20 ] [ 7 ] Although these interfaces are described individually, they can also be commercially available as dual ESI/APCI, ESI/APPI, or APCI/APPI ion sources. [ 8 ] Various deposition and drying techniques were used in the past (e.g., moving belts) but the most common of these was the off-line MALDI deposition. [ 21 ] [ 22 ] A new approach still under development called direct-EI LC–MS interface , couples a nano HPLC system and an electron ionization equipped mass spectrometer. [ 23 ] [ 24 ]
ESI interface for LC–MS systems was developed by Fenn and collaborators in 1988. [ 25 ] This ion source/ interface can be used for the analysis of moderately polar and even very polar molecules (e.g., metabolites, xenobiotics, peptides, nucleotides, polysaccharides). The liquid eluate coming out of the LC column is directed into a metal capillary kept at 3 to 5 kV and is nebulized by a high-velocity coaxial flow of gas at the tip of the capillary, creating a fine spray of charged droplets in front of the entrance to the vacuum chamber. To avoid contamination of the vacuum system by buffers and salts, this capillary is usually perpendicularly located at the inlet of the MS system, in some cases with a counter-current of dry nitrogen in front of the entrance through which ions are directed by the electric field. In some sources, rapid droplet evaporation and thus maximum ion emission is achieved by mixing an additional stream of hot gas with the spray plume in front of the vacuum entrance. In other sources, the droplets are drawn through a heated capillary tube as they enter the vacuum, promoting droplet evaporation and ion emission. These methods of increasing droplet evaporation now allow the use of liquid flow rates of 1 - 2 mL/min to be used while still achieving efficient ionisation [ 26 ] and high sensitivity. Thus while the use of 1 – 3 mm microbore columns and lower flow rates of 50 - 200 μl/min was commonly considered necessary for optimum operation, this limitation is no longer as important, and the higher column capacity of larger bore columns can now be advantageously employed with ESI LC–MS systems. Positively and negatively charged ions can be created by switching polarities, and it is possible to acquire alternate positive and negative mode spectra rapidly within the same LC run . While most large molecules (greater than MW 1500–2000) produce multiply charged ions in the ESI source, the majority of smaller molecules produce singly charged ions. [ 7 ]
The development of the APCI interface for LC–MS started with Horning and collaborators in the early 1973. [ 27 ] However, its commercial application was introduced at the beginning of the 1990s after Henion and collaborators improved the LC–APCI–MS interface in 1986. [ 8 ] The APCI ion source/ interface can be used to analyze small, neutral, relatively non-polar, and thermally stable molecules (e.g., steroids, lipids, and fat soluble vitamins). These compounds are not well ionized using ESI. In addition, APCI can also handle mobile phase streams containing buffering agents. The liquid from the LC system is pumped through a capillary and there is also nebulization at the tip, where a corona discharge takes place. First, the ionizing gas surrounding the interface and the mobile phase solvent are subject to chemical ionization at the ion source. Later, these ions react with the analyte and transfer their charge. The sample ions then pass through small orifice skimmers by means of or ion-focusing lenses. Once inside the high vacuum region, the ions are subject to mass analysis. This interface can be operated in positive and negative charge modes and singly-charged ions are mainly produced. [ 7 ] APCI ion source can also handle flow rates between 500 and 2000 μl/min and it can be directly connected to conventional 4.6 mm ID columns. [ 16 ]
The APPI interface for LC–MS was developed simultaneously by Bruins and Syage in 2000. [ 28 ] [ 8 ] APPI is another LC–MS ion source/ interface for the analysis of neutral compounds that cannot be ionized using ESI. [ 7 ] This interface is similar to the APCI ion source, but instead of a corona discharge, the ionization occurs by using photons coming from a discharge lamp. In the direct-APPI mode, singly charged analyte molecular ions are formed by absorption of a photon and ejection of an electron. In the dopant-APPI mode, an easily ionizable compound (Dopant) is added to the mobile phase or the nebulizing gas to promote a reaction of charge-exchange between the dopant molecular ion and the analyte. The ionized sample is later transferred to the mass analyzer at high vacuum as it passes through small orifice skimmers. [ 8 ]
The coupling of MS with LC systems is attractive because liquid chromatography can separate delicate and complex natural mixtures, which chemical composition needs to be well established (e.g., biological fluids, environmental samples, and drugs). Further, LC–MS has applications in volatile explosive residue analysis. [ 29 ] Nowadays, LC–MS has become one of the most widely used chemical analysis techniques because more than 85% of natural chemical compounds are polar and thermally labile and GC-MS cannot process these samples. [ 5 ] As an example, HPLC–MS is regarded as the leading analytical technique for proteomics and pharmaceutical laboratories. [ 7 ] [ 5 ] Other important applications of LC–MS include the analysis of food, pesticides , and plant phenols . [ 8 ]
LC–MS is widely used in the field of bioanalysis and is specially involved in pharmacokinetic studies of pharmaceuticals. Pharmacokinetic studies are needed to determine how quickly a drug will be cleared from the body organs and the hepatic blood flow. MS analyzers are useful in these studies because of their shorter analysis time, and higher sensitivity and specificity compared to UV detectors commonly attached to HPLC systems. One major advantage is the use of tandem MS–MS , where the detector may be programmed to select certain ions to fragment. The measured quantity is the sum of molecule fragments chosen by the operator. As long as there are no interferences or ion suppression in LC–MS , the LC separation can be quite quick. [ 30 ]
LC–MS is used in proteomics as a method to detect and identify the components of a complex mixture. The bottom-up proteomics LC–MS approach generally involves protease digestion and denaturation using trypsin as a protease, urea to denature the tertiary structure, and iodoacetamide to modify the cysteine residues. After digestion, LC–MS is used for peptide mass fingerprinting , or LC–MS/MS ( tandem MS ) is used to derive the sequences of individual peptides. [ 31 ] LC–MS/MS is most commonly used for proteomic analysis of complex samples where peptide masses may overlap even with a high-resolution mass spectrometry. Samples of complex biological (e.g., human serum) may be analyzed in modern LC–MS/MS systems, which can identify over 1000 proteins. However, this high level of protein identification is possible only after separating the sample by means of SDS-PAGE gel or HPLC-SCX. [ 30 ] Recently, LC–MS/MS has been applied to search peptide biomarkers. Examples are the recent discovery and validation of peptide biomarkers for four major bacterial respiratory tract pathogens ( Staphylococcus aureus , Moraxella catarrhalis ; Haemophilus influenzae and Streptococcus pneumoniae ) and the SARS-CoV-2 virus. [ 32 ] [ 33 ]
LC–MS has emerged as one of the most commonly used techniques in global metabolite profiling of biological tissue (e.g., blood plasma, serum, urine). [ 34 ] LC–MS is also used for the analysis of natural products and the profiling of secondary metabolites in plants. [ 35 ] In this regard, MS-based systems are useful to acquire more detailed information about the wide spectrum of compounds from a complex biological samples. LC–nuclear magnetic resonance ( NMR ) is also used in plant metabolomics, but this technique can only detect and quantify the most abundant metabolites. LC–MS has been useful to advance the field of plant metabolomics, which aims to study the plant system at molecular level providing a non-biased characterization of the plant metabolome in response to its environment. [ 36 ] The first application of LC–MS in plant metabolomics was the detection of a wide range of highly polar metabolites, oligosaccharides , amino acids , amino sugars , and sugar nucleotides from Cucurbita maxima phloem tissues. [ 37 ] Another example of LC–MS in plant metabolomics is the efficient separation and identification of glucose , sucrose , raffinose , stachyose , and verbascose from leaf extracts of Arabidopsis thaliana . [ 38 ]
LC–MS is frequently used in drug development because it allows quick molecular weight confirmation and structure identification. These features speed up the process of generating, testing, and validating a discovery starting from a vast array of products with potential application. LC–MS applications for drug development are highly automated methods used for peptide mapping, glycoprotein mapping, lipodomics, natural products dereplication, bioaffinity screening, in vivo drug screening, metabolic stability screening, metabolite identification, impurity identification, quantitative bioanalysis , and quality control. [ 39 ] | https://en.wikipedia.org/wiki/Liquid_chromatography–mass_spectrometry |
The color measurement of a liquid is the evaluation of that liquid 's color properties. [ 1 ] This is usually done through visual means, but can also be done by through automated means. The former provides approximate data , while the latter can provide objective data on the color properties of any given liquid.
Visual color measurement is the conventional and usual form of liquid color measurement. In this case the sample is held up to a series of color standards in order to see which standard the sample most closely resembles. [ 2 ] This measurement is only approximate, but is the less expensive method as the only expense is the set of color standards to which the sample is matched. This is by far the most commonly used method because of this inexpensive nature. [ citation needed ]
Automated color measurement is a newer method of liquid color measurement. In this case the sample is contained in a test tube ; the tube is inserted into the instrument, and the color properties of the liquid read out on a screen. This method can provide objective measurements, but is far more expensive than a set of color standards. This method is used less frequently because of how expensive it is. There is also an automated method which compares a sample to its standard, also providing objective measurement. [ 3 ] | https://en.wikipedia.org/wiki/Liquid_color_measurement |
Liquid crystal ( LC ) is a state of matter whose properties are between those of conventional liquids and those of solid crystals . For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as in a solid. There are many types of LC phases , which can be distinguished by their optical properties (such as textures ). The contrasting textures arise due to molecules within one area of material ("domain") being oriented in the same direction but different areas having different orientations. An LC material may not always be in an LC state of matter (just as water may be ice or water vapour).
Liquid crystals can be divided into three main types: thermotropic , lyotropic , and metallotropic . Thermotropic and lyotropic liquid crystals consist mostly of organic molecules , although a few minerals are also known. Thermotropic LCs exhibit a phase transition into the LC phase as temperature changes. Lyotropic LCs exhibit phase transitions as a function of both temperature and concentration of molecules in a solvent (typically water). Metallotropic LCs are composed of both organic and inorganic molecules; their LC transition additionally depends on the inorganic-organic composition ratio.
Examples of LCs exist both in the natural world and in technological applications. Lyotropic LCs abound in living systems; many proteins and cell membranes are LCs, as well as the tobacco mosaic virus . [ 1 ] LCs in the mineral world include solutions of soap and various related detergents , and some clays . Widespread liquid-crystal displays (LCD) use liquid crystals.
In 1888, Austrian botanical physiologist Friedrich Reinitzer , working at the Karl-Ferdinands-Universität , examined the physico-chemical properties of various derivatives of cholesterol which now belong to the class of materials known as cholesteric liquid crystals . Previously, other researchers had observed distinct color effects when cooling cholesterol derivatives just above the freezing point , but had not associated it with a new phenomenon. Reinitzer perceived that color changes in a derivative cholesteryl benzoate were not the most peculiar feature.
He found that cholesteryl benzoate does not melt in the same manner as other compounds, but has two melting points . At 145.5 °C (293.9 °F) it melts into a cloudy liquid, and at 178.5 °C (353.3 °F) it melts again and the cloudy liquid becomes clear. The phenomenon is reversible. Seeking help from a physicist , on March 14, 1888, he wrote to Otto Lehmann , at that time a Privatdozent in Aachen . They exchanged letters and samples. Lehmann examined the intermediate cloudy fluid, and reported seeing crystallites . Reinitzer's Viennese colleague von Zepharovich also indicated that the intermediate "fluid" was crystalline. The exchange of letters with Lehmann ended on April 24, with many questions unanswered. Reinitzer presented his results, with credits to Lehmann and von Zepharovich, at a meeting of the Vienna Chemical Society on May 3, 1888. [ 2 ]
By that time, Reinitzer had discovered and described three important features of cholesteric liquid crystals (the name coined by Otto Lehmann in 1904): the existence of two melting points, the reflection of circularly polarized light , and the ability to rotate the polarization direction of light.
After his accidental discovery, Reinitzer did not pursue studying liquid crystals further. The research was continued by Lehmann, who realized that he had encountered a new phenomenon and was in a position to investigate it: In his postdoctoral years he had acquired expertise in crystallography and microscopy . Lehmann started a systematic study, first of cholesteryl benzoate, and then of related compounds which exhibited the double-melting phenomenon. He was able to make observations in polarized light , and his microscope was equipped with a hot stage (sample holder equipped with a heater) enabling high temperature observations. The intermediate cloudy phase clearly sustained flow, but other features, particularly the signature under a microscope, convinced Lehmann that he was dealing with a solid. By the end of August 1889 he had published his results in the Zeitschrift für Physikalische Chemie . [ 3 ]
Lehmann's work was continued and significantly expanded by the German chemist Daniel Vorländer , who from the beginning of the 20th century until he retired in 1935, had synthesized most of the liquid crystals known. However, liquid crystals were not popular among scientists and the material remained a pure scientific curiosity for about 80 years. [ 4 ]
After World War II, work on the synthesis of liquid crystals was restarted at university research laboratories in Europe. George William Gray , a prominent researcher of liquid crystals, began investigating these materials in England in the late 1940s. His group synthesized many new materials that exhibited the liquid crystalline state and developed a better understanding of how to design molecules that exhibit the state. His book Molecular Structure and the Properties of Liquid Crystals [ 5 ] became a guidebook on the subject. One of the first U.S. chemists to study liquid crystals was Glenn H. Brown, starting in 1953 at the University of Cincinnati and later at Kent State University . In 1965, he organized the first international conference on liquid crystals, in Kent, Ohio, with about 100 of the world's top liquid crystal scientists in attendance. This conference marked the beginning of a worldwide effort to perform research in this field, which soon led to the development of practical applications for these unique materials. [ 6 ] [ 7 ]
Liquid crystal materials became a focus of research in the development of flat panel electronic displays beginning in 1962 at RCA Laboratories. [ 8 ] When physical chemist Richard Williams applied an electric field to a thin layer of a nematic liquid crystal at 125 °C, he observed the formation of a regular pattern that he called domains (now known as Williams Domains). This led his colleague George H. Heilmeier to perform research on a liquid crystal-based flat panel display to replace the cathode ray vacuum tube used in televisions. But the para-azoxyanisole that Williams and Heilmeier used exhibits the nematic liquid crystal state only above 116 °C, which made it impractical to use in a commercial display product. A material that could be operated at room temperature was clearly needed.
In 1966, Joel E. Goldmacher and Joseph A. Castellano, research chemists in Heilmeier group at RCA, discovered that mixtures made exclusively of nematic compounds that differed only in the number of carbon atoms in the terminal side chains could yield room-temperature nematic liquid crystals. A ternary mixture of Schiff base compounds resulted in a material that had a nematic range of 22–105 °C. [ 9 ] Operation at room temperature enabled the first practical display device to be made. [ 10 ] The team then proceeded to prepare numerous mixtures of nematic compounds many of which had much lower melting points. This technique of mixing nematic compounds to obtain wide operating temperature range eventually became the industry standard and is still used to tailor materials to meet specific applications.
In 1969, Hans Keller succeeded in synthesizing a substance that had a nematic phase at room temperature, N-(4-methoxybenzylidene)-4-butylaniline (MBBA), which is one of the most popular subjects of liquid crystal research. [ 11 ] The next step to commercialization of liquid-crystal displays was the synthesis of further chemically stable substances (cyanobiphenyls) with low melting temperatures by George Gray . [ 12 ] That work with Ken Harrison and the UK MOD ( RRE Malvern ), in 1973, led to design of new materials resulting in rapid adoption of small area LCDs within electronic products.
These molecules are rod-shaped, some created in the laboratory and some appearing spontaneously in nature. Since then, two new types of LC molecules have been synthesized: disc-shaped (by Sivaramakrishna Chandrasekhar in India in 1977) [ 13 ] and cone or bowl shaped (predicted by Lui Lam in China in 1982 and synthesized in Europe in 1985). [ 14 ]
In 1991, when liquid crystal displays were already well established, Pierre-Gilles de Gennes working at the Université Paris-Sud received the Nobel Prize in physics "for discovering that methods developed for studying order phenomena in simple systems can be generalized to more complex forms of matter, in particular to liquid crystals and polymers". [ 15 ]
A large number of chemical compounds are known to exhibit one or several liquid crystalline phases. Despite significant differences in chemical composition, these molecules have some common features in chemical and physical properties. There are three types of thermotropic liquid crystals: discotic, conic (bowlic), and rod-shaped molecules. Discotics are disc-like molecules consisting of a flat core of adjacent aromatic rings, whereas the core in a conic LC is not flat, but is shaped like a rice bowl (a three-dimensional object). [ 16 ] [ 17 ] This allows for two dimensional columnar ordering, for both discotic and conic LCs. Rod-shaped molecules have an elongated, anisotropic geometry which allows for preferential alignment along one spatial direction.
An extended, structurally rigid, highly anisotropic shape seems to be the main criterion for liquid crystalline behavior, and as a result many liquid crystalline materials are based on benzene rings. [ 18 ]
The various liquid-crystal phases (called mesophases together with plastic crystal phases) can be characterized by the type of ordering. One can distinguish positional order (whether molecules are arranged in any sort of ordered lattice) and orientational order (whether molecules are mostly pointing in the same direction). Liquid crystals are characterized by orientational order, but only partial or completely absent positional order. In contrast, materials with positional order but no orientational order are known as plastic crystals . [ 19 ] Most thermotropic LCs will have an isotropic phase at high temperature: heating will eventually drive them into a conventional liquid phase characterized by random and isotropic molecular ordering and fluid -like flow behavior. Under other conditions (for instance, lower temperature), a LC might inhabit one or more phases with significant anisotropic orientational structure and short-range orientational order while still having an ability to flow. [ 20 ] [ 21 ]
The ordering of liquid crystals extends up to the entire domain size, which may be on the order of micrometers, but usually not to the macroscopic scale as often occurs in classical crystalline solids. However some techniques, such as the use of boundaries or an applied electric field , can be used to enforce a single ordered domain in a macroscopic liquid crystal sample. [ 22 ] The orientational ordering in a liquid crystal might extend along only one dimension , with the material being essentially disordered in the other two directions. [ 23 ] [ 24 ]
Thermotropic phases are those that occur in a certain temperature range. If the temperature rise is too high, thermal motion will destroy the delicate cooperative ordering of the LC phase, pushing the material into a conventional isotropic liquid phase. At too low temperature, most LC materials will form a conventional crystal. [ 20 ] [ 21 ] Many thermotropic LCs exhibit a variety of phases as temperature is changed. For instance, a particular type of LC molecule (called a mesogen ) may exhibit various smectic phases followed by the nematic phase and finally the isotropic phase as temperature is increased. An example of a compound displaying thermotropic LC behavior is para-azoxyanisole . [ 25 ]
The simplest liquid crystal phase is the nematic. In a nematic phase, calamitic (rod-like) organic molecules lack a crystalline positional order, but do self-align with their long axes roughly parallel. The molecules are free to flow and their center of mass positions are randomly distributed as in a liquid, but their orientation is constrained to form a long-range directional order. [ 26 ]
The word nematic comes from the Greek νήμα ( Greek : nema ), which means "thread". This term originates from the disclinations : thread-like topological defects observed in nematic phases.
Nematics also exhibit so-called "hedgehog" topological defects . In two dimensions, there are topological defects with topological charges + 1 / 2 and - 1 / 2 . Due to hydrodynamics, the + 1 / 2 defect moves considerably faster than the - 1 / 2 defect. When placed close to each other, the defects attract; upon collision, they annihilate. [ 27 ] [ 28 ]
Most nematic phases are uniaxial: they have one axis (called a directrix) that is longer and preferred, with the other two being equivalent (can be approximated as cylinders or rods). However, some liquid crystals are biaxial nematic , meaning that in addition to orienting their long axis, they also orient along a secondary axis. [ 29 ] Nematic crystals have fluidity similar to that of ordinary (isotropic) liquids but they can be easily aligned by an external magnetic or electric field. Aligned nematics have the optical properties of uniaxial crystals and this makes them extremely useful in liquid-crystal displays (LCD). [ 8 ]
Nematic phases are also known in non-molecular systems: at high magnetic fields, electrons flow in bundles or stripes to create an "electronic nematic" form of matter. [ 30 ] [ 31 ]
The smectic phases, which are found at lower temperatures than the nematic, form well-defined layers that can slide over one another in a manner similar to that of soap. The word "smectic" originates from the Latin word "smecticus", meaning cleaning, or having soap-like properties. [ 32 ] The smectics are thus positionally ordered along one direction. In the Smectic A phase, the molecules are oriented along the layer normal, while in the Smectic C phase they are tilted away from it. These phases are liquid-like within the layers. There are many different smectic phases, all characterized by different types and degrees of positional and orientational order. [ 20 ] [ 21 ] Beyond organic molecules, Smectic ordering has also been reported to occur within colloidal suspensions of 2-D materials or nanosheets. [ 33 ] [ 34 ] One example of smectic LCs is p,p' -dinonylazobenzene . [ 35 ]
The chiral nematic phase exhibits chirality (handedness). This phase is often called the cholesteric phase because it was first observed for cholesterol derivatives. Only chiral molecules can give rise to such a phase. This phase exhibits a twisting of the molecules perpendicular to the director, with the molecular axis parallel to the director. The finite twist angle between adjacent molecules is due to their asymmetric packing, which results in longer-range chiral order. In the smectic C* phase (an asterisk denotes a chiral phase), the molecules have positional ordering in a layered structure (as in the other smectic phases), with the molecules tilted by a finite angle with respect to the layer normal. The chirality induces a finite azimuthal twist from one layer to the next, producing a spiral twisting of the molecular axis along the layer normal, hence they are also called twisted nematics . [ 21 ] [ 23 ] [ 24 ]
The chiral pitch , p, refers to the distance over which the LC molecules undergo a full 360° twist (but note that the structure of the chiral nematic phase repeats itself every half-pitch, since in this phase directors at 0° and ±180° are equivalent). The pitch, p, typically changes when the temperature is altered or when other molecules are added to the LC host (an achiral LC host material will form a chiral phase if doped with a chiral material), allowing the pitch of a given material to be tuned accordingly. In some liquid crystal systems, the pitch is of the same order as the wavelength of visible light . This causes these systems to exhibit unique optical properties, such as Bragg reflection and low-threshold laser emission, [ 36 ] and these properties are exploited in a number of optical applications. [ 4 ] [ 23 ] For the case of Bragg reflection only the lowest-order reflection is allowed if the light is incident along the helical axis, whereas for oblique incidence higher-order reflections become permitted. Cholesteric liquid crystals also exhibit the unique property that they reflect circularly polarized light when it is incident along the helical axis and elliptically polarized if it comes in obliquely. [ 37 ]
Blue phases are liquid crystal phases that appear in the temperature range between a chiral nematic phase and an isotropic liquid phase. Blue phases have a regular three-dimensional cubic structure of defects with lattice periods of several hundred nanometers, and thus they exhibit selective Bragg reflections in the wavelength range of visible light corresponding to the cubic lattice . It was theoretically predicted in 1981 that these phases can possess icosahedral symmetry similar to quasicrystals . [ 39 ] [ 40 ]
Although blue phases are of interest for fast light modulators or tunable photonic crystals , they exist in a very narrow temperature range, usually less than a few kelvins . Recently the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260–326 K) has been demonstrated. [ 41 ] [ 42 ] Blue phases stabilized at room temperature allow electro-optical switching with response times of the order of 10 −4 s. [ 43 ] In May 2008, the first blue phase mode LCD panel had been developed. [ 44 ]
Blue phase crystals, being a periodic cubic structure with a bandgap in the visible wavelength range, can be considered as 3D photonic crystals . Producing ideal blue phase crystals in large volumes is still problematic, since the produced crystals are usually polycrystalline (platelet structure) or the single crystal size is limited (in the micrometer range). Recently, blue phases obtained as ideal 3D photonic crystals in large volumes have been stabilized and produced with different controlled crystal lattice orientations. [ 45 ]
Disk-shaped LC molecules can orient themselves in a layer-like fashion known as the discotic nematic phase. If the disks pack into stacks, the phase is called a discotic columnar . The columns themselves may be organized into rectangular or hexagonal arrays. Chiral discotic phases, similar to the chiral nematic phase, are also known.
Conic LC molecules, like in discotics, can form columnar phases. Other phases, such as nonpolar nematic, polar nematic, stringbean, donut and onion phases, have been predicted. Conic phases, except nonpolar nematic, are polar phases. [ 46 ]
A lyotropic liquid crystal consists of two or more components that exhibit liquid-crystalline properties in certain concentration ranges. In the lyotropic phases, solvent molecules fill the space around the compounds to provide fluidity to the system. [ 47 ] In contrast to thermotropic liquid crystals, these lyotropics have another degree of freedom of concentration that enables them to induce a variety of different phases.
A compound that has two immiscible hydrophilic and hydrophobic parts within the same molecule is called an amphiphilic molecule. Many amphiphilic molecules show lyotropic liquid-crystalline phase sequences depending on the volume balances between the hydrophilic part and hydrophobic part. These structures are formed through the micro-phase segregation of two incompatible components on a nanometer scale. Soap is an everyday example of a lyotropic liquid crystal.
The content of water or other solvent molecules changes the self-assembled structures. At very low amphiphile concentration, the molecules will be dispersed randomly without any ordering. At slightly higher (but still low) concentration, amphiphilic molecules will spontaneously assemble into micelles or vesicles . This is done so as to 'hide' the hydrophobic tail of the amphiphile inside the micelle core, exposing a hydrophilic (water-soluble) surface to aqueous solution. These spherical objects do not order themselves in solution, however. At higher concentration, the assemblies will become ordered. A typical phase is a hexagonal columnar phase, where the amphiphiles form long cylinders (again with a hydrophilic surface) that arrange themselves into a roughly hexagonal lattice. This is called the middle soap phase. At still higher concentration, a lamellar phase (neat soap phase) may form, wherein extended sheets of amphiphiles are separated by thin layers of water. For some systems, a cubic (also called viscous isotropic) phase may exist between the hexagonal and lamellar phases, wherein spheres are formed that create a dense cubic lattice. These spheres may also be connected to one another, forming a bicontinuous cubic phase.
The objects created by amphiphiles are usually spherical (as in the case of micelles), but may also be disc-like (bicelles), rod-like, or biaxial (all three micelle axes are distinct). These anisotropic self-assembled nano-structures can then order themselves in much the same way as thermotropic liquid crystals do, forming large-scale versions of all the thermotropic phases (such as a nematic phase of rod-shaped micelles).
For some systems, at high concentrations, inverse phases are observed. That is, one may generate an inverse hexagonal columnar phase (columns of water encapsulated by amphiphiles) or an inverse micellar phase (a bulk liquid crystal sample with spherical water cavities).
A generic progression of phases, going from low to high amphiphile concentration, is:
Even within the same phases, their self-assembled structures are tunable by the concentration: for example, in lamellar phases, the layer distances increase with the solvent volume. Since lyotropic liquid crystals rely on a subtle balance of intermolecular interactions, it is more difficult to analyze their structures and properties than those of thermotropic liquid crystals.
Similar phases and characteristics can be observed in immiscible diblock copolymers .
Liquid crystal phases can also be based on low-melting inorganic phases like ZnCl 2 that have a structure formed of linked tetrahedra and easily form glasses. The addition of long chain soap-like molecules leads to a series of new phases that show a variety of liquid crystalline behavior both as a function of the inorganic-organic composition ratio and of temperature. This class of materials has been named metallotropic. [ 48 ]
Thermotropic mesophases are detected and characterized by two major methods, the original method was use of thermal optical microscopy, [ 49 ] [ 50 ] in which a small sample of the material was placed between two crossed polarizers; the sample was then heated and cooled. As the isotropic phase would not significantly affect the polarization of the light, it would appear very dark, whereas the crystal and liquid crystal phases will both polarize the light in a uniform way, leading to brightness and color gradients. This method allows for the characterization of the particular phase, as the different phases are defined by their particular order, which must be observed. The second method, differential scanning calorimetry (DSC), [ 49 ] allows for more precise determination of phase transitions and transition enthalpies. In DSC, a small sample is heated in a way that generates a very precise change in temperature with respect to time. During phase transitions, the heat flow required to maintain this heating or cooling rate will change. These changes can be observed and attributed to various phase transitions, such as key liquid crystal transitions.
Lyotropic mesophases are analyzed in a similar fashion, though these experiments are somewhat more complex, as the concentration of mesogen is a key factor. These experiments are run at various concentrations of mesogen in order to analyze that impact.
Lyotropic liquid-crystalline phases are abundant in living systems, the study of which is referred to as lipid polymorphism . Accordingly, lyotropic liquid crystals attract particular attention in the field of biomimetic chemistry. In particular, biological membranes and cell membranes are a form of liquid crystal. Their constituent molecules (e.g. phospholipids ) are perpendicular to the membrane surface, yet the membrane is flexible. [ 51 ] These lipids vary in shape (see page on lipid polymorphism ). The constituent molecules can inter-mingle easily, but tend not to leave the membrane due to the high energy requirement of this process. Lipid molecules can flip from one side of the membrane to the other, this process being catalyzed by flippases and floppases (depending on the direction of movement). These liquid crystal membrane phases can also host important proteins such as receptors freely "floating" inside, or partly outside, the membrane, e.g. CTP:phosphocholine cytidylyltransferase (CCT).
Many other biological structures exhibit liquid-crystal behavior. For instance, the concentrated protein solution that is extruded by a spider to generate silk is, in fact, a liquid crystal phase. The precise ordering of molecules in silk is critical to its renowned strength. DNA and many polypeptides , including actively-driven cytoskeletal filaments, [ 52 ] can also form liquid crystal phases. Monolayers of elongated cells have also been described to exhibit liquid-crystal behavior, and the associated topological defects have been associated with biological consequences, including cell death and extrusion. [ 53 ] Together, these biological applications of liquid crystals form an important part of current academic research.
Examples of liquid crystals can also be found in the mineral world, most of them being lyotropic. The first discovered was vanadium(V) oxide , by Zocher in 1925. [ 54 ] Since then, few others have been discovered and studied in detail. [ 55 ] The existence of a true nematic phase in the case of the smectite clays family was raised by Langmuir in 1938, [ 56 ] but remained an open question for a very long time and was only confirmed recently. [ 57 ] [ 58 ]
With the rapid development of nanosciences, and the synthesis of many new anisotropic nanoparticles , the number of such mineral liquid crystals is increasing quickly, with, for example, carbon nanotubes and graphene. A lamellar phase was even discovered, H 3 Sb 3 P 2 O 14 , which exhibits hyperswelling up to ~250 nm for the interlamellar distance. [ 33 ]
Anisotropy of liquid crystals is a property not observed in other fluids. This anisotropy makes flows of liquid crystals behave more differentially than those of ordinary fluids. For example, injection of a flux of a liquid crystal between two close parallel plates ( viscous fingering ) causes orientation of the molecules to couple with the flow, with the resulting emergence of dendritic patterns. [ 59 ] This anisotropy is also manifested in the interfacial energy ( surface tension ) between different liquid crystal phases. This anisotropy determines the equilibrium shape at the coexistence temperature, and is so strong that usually facets appear. When temperature is changed one of the phases grows, forming different morphologies depending on the temperature change. [ 60 ] Since growth is controlled by heat diffusion, anisotropy in thermal conductivity favors growth in specific directions, which has also an effect on the final shape. [ 61 ]
Microscopic theoretical treatment of fluid phases can become quite complicated, owing to the high material density, meaning that strong interactions, hard-core repulsions, and many-body correlations cannot be ignored. In the case of liquid crystals, anisotropy in all of these interactions further complicates analysis. There are a number of fairly simple theories, however, that can at least predict the general behavior of the phase transitions in liquid crystal systems.
As we already saw above, the nematic liquid crystals are composed of rod-like molecules with the long axes of neighboring molecules aligned approximately to one another. To describe this anisotropic structure, a dimensionless unit vector n called the director , is introduced to represent the direction of preferred orientation of molecules in the neighborhood of any point. Because there is no physical polarity along the director axis, n and -n are fully equivalent. [ 21 ]
The description of liquid crystals involves an analysis of order. A second rank symmetric traceless tensor order parameter, the Q tensor is used to describe the orientational order of the most general biaxial nematic liquid crystal. However, to describe the more common case of uniaxial nematic liquid crystals, a scalar order parameter is sufficient. [ 62 ] To make this quantitative, an orientational order parameter is usually defined based on the average of the second Legendre polynomial :
where θ {\displaystyle \theta } is the angle between the liquid-crystal molecular axis and the local director (which is the 'preferred direction' in a volume element of a liquid crystal sample, also representing its local optical axis ). The brackets denote both a temporal and spatial average. This definition is convenient, since for a completely random and isotropic sample, S = 0, whereas for a perfectly aligned sample S=1. For a typical liquid crystal sample, S is on the order of 0.3 to 0.8, and generally decreases as the temperature is raised. In particular, a sharp drop of the order parameter to 0 is observed when the system undergoes a phase transition from an LC phase into the isotropic phase. [ 63 ] The order parameter can be measured experimentally in a number of ways; for instance, diamagnetism , birefringence , Raman scattering , NMR and EPR can be used to determine S. [ 24 ]
The order of a liquid crystal could also be characterized by using other even Legendre polynomials (all the odd polynomials average to zero since the director can point in either of two antiparallel directions). These higher-order averages are more difficult to measure, but can yield additional information about molecular ordering. [ 20 ]
A positional order parameter is also used to describe the ordering of a liquid crystal. It is characterized by the variation of the density of the center of mass of the liquid crystal molecules along a given vector. In the case of positional variation along the z -axis the density ρ ( z ) {\displaystyle \rho (z)} is often given by:
The complex positional order parameter is defined as ψ ( r ) = ρ 1 ( r ) e i φ ( r ) {\displaystyle \psi (\mathbf {r} )=\rho _{1}(\mathbf {r} )e^{i\varphi (\mathbf {r} )}} and ρ 0 {\displaystyle \rho _{0}} the average density. Typically only the first two terms are kept and higher order terms are ignored since most phases can be described adequately using sinusoidal functions. For a perfect nematic ψ = 0 {\displaystyle \psi =0} and for a smectic phase ψ {\displaystyle \psi } will take on complex values. The complex nature of this order parameter allows for many parallels between nematic to smectic phase transitions and conductor to superconductor transitions. [ 21 ]
A simple model which predicts lyotropic phase transitions is the hard-rod model proposed by Lars Onsager . This theory considers the volume excluded from the center-of-mass of one idealized cylinder as it approaches another. Specifically, if the cylinders are oriented parallel to one another, there is very little volume that is excluded from the center-of-mass of the approaching cylinder (it can come quite close to the other cylinder). If, however, the cylinders are at some angle to one another, then there is a large volume surrounding the cylinder which the approaching cylinder's center-of-mass cannot enter (due to the hard-rod repulsion between the two idealized objects). Thus, this angular arrangement sees a decrease in the net positional entropy of the approaching cylinder (there are fewer states available to it). [ 64 ] [ 65 ]
The fundamental insight here is that, whilst parallel arrangements of anisotropic objects lead to a decrease in orientational entropy, there is an increase in positional entropy. Thus in some case greater positional order will be entropically favorable. This theory thus predicts that a solution of rod-shaped objects will undergo a phase transition, at sufficient concentration, into a nematic phase. Although this model is conceptually helpful, its mathematical formulation makes several assumptions that limit its applicability to real systems. [ 65 ] An extension of Onsager Theory was proposed by Flory to account for non entropic effects.
This statistical theory, proposed by Alfred Saupe and Wilhelm Maier, includes contributions from an attractive intermolecular potential from an induced dipole moment between adjacent rod-like liquid crystal molecules. The anisotropic attraction stabilizes parallel alignment of neighboring molecules, and the theory then considers a mean-field average of the interaction. Solved self-consistently, this theory predicts thermotropic nematic-isotropic phase transitions, consistent with experiment. [ 66 ] [ 67 ] [ 68 ] Maier-Saupe mean field theory is extended to high molecular weight liquid crystals by incorporating the bending stiffness of the molecules and using the method of path integrals in polymer science . [ 69 ]
McMillan's model, proposed by William McMillan, [ 70 ] is an extension of the Maier–Saupe mean field theory used to describe the phase transition of a liquid crystal from a nematic to a smectic A phase. It predicts that the phase transition can be either continuous or discontinuous depending on the strength of the short-range interaction between the molecules. As a result, it allows for a triple critical point where the nematic, isotropic, and smectic A phase meet. Although it predicts the existence of a triple critical point, it does not successfully predict its value. The model utilizes two order parameters that describe the orientational and positional order of the liquid crystal. The first is simply the average of the second Legendre polynomial and the second order parameter is given by:
The values z i , θ i , and d are the position of the molecule, the angle between the molecular axis and director, and the layer spacing. The postulated potential energy of a single molecule is given by:
Here constant α quantifies the strength of the interaction between adjacent molecules. The potential is then used to derive the thermodynamic properties of the system assuming thermal equilibrium. It results in two self-consistency equations that must be solved numerically, the solutions of which are the three stable phases of the liquid crystal. [ 24 ]
In this formalism, a liquid crystal material is treated as a continuum; molecular details are entirely ignored. Rather, this theory considers perturbations to a presumed oriented sample. The distortions of the liquid crystal are commonly described by the Frank free energy density . One can identify three types of distortions that could occur in an oriented sample: (1) twists of the material, where neighboring molecules are forced to be angled with respect to one another, rather than aligned; (2) splay of the material, where bending occurs perpendicular to the director; and (3) bend of the material, where the distortion is parallel to the director and molecular axis. All three of these types of distortions incur an energy penalty. They are distortions that are induced by the boundary conditions at domain walls or the enclosing container. The response of the material can then be decomposed into terms based on the elastic constants corresponding to the three types of distortions. Elastic continuum theory is an effective tool for modeling liquid crystal devices and lipid bilayers. [ 71 ] [ 72 ]
Scientists and engineers are able to use liquid crystals in a variety of applications because external perturbation can cause significant changes in the macroscopic properties of the liquid crystal system. Both electric and magnetic fields can be used to induce these changes. The magnitude of the fields, as well as the speed at which the molecules align are important characteristics industry deals with. Special surface treatments can be used in liquid crystal devices to force specific orientations of the director.
The ability of the director to align along an external field is caused by the electric nature of the molecules. Permanent electric dipoles result when one end of a molecule has a net positive charge while the other end has a net negative charge. When an external electric field is applied to the liquid crystal, the dipole molecules tend to orient themselves along the direction of the field. [ 73 ]
Even if a molecule does not form a permanent dipole, it can still be influenced by an electric field. In some cases, the field produces slight re-arrangement of electrons and protons in molecules such that an induced electric dipole results. While not as strong as permanent dipoles, orientation with the external field still occurs.
The response of any system to an external electrical field is
where E i {\displaystyle E_{i}} , D i {\displaystyle D_{i}} and P i {\displaystyle P_{i}} are the components of the electric field, electric displacement field and polarization density. The electric energy per volume stored in the system is
(summation over the doubly appearing index i {\displaystyle i} ). In nematic liquid crystals, the polarization, and electric displacement both depend linearly on the direction of the electric field. The polarization should be even in the director since liquid crystals are invariants under reflexions of n {\displaystyle n} . The most general form to express D {\displaystyle D} is
(summation over the index j {\displaystyle j} ) with ϵ ⊥ {\displaystyle \epsilon _{\bot }} and ϵ ∥ {\displaystyle \epsilon _{\parallel }} the electric permittivity parallel and perpendicular to the director n {\displaystyle n} . Then density of energy is (ignoring the constant terms that do not contribute to the dynamics of the system) [ 74 ]
(summation over i {\displaystyle i} ). If ϵ ∥ − ϵ ⊥ {\displaystyle \epsilon _{\parallel }-\epsilon _{\bot }} is positive, then the minimum of the energy is achieved when E {\displaystyle E} and n {\displaystyle n} are parallel. This means that the system will favor aligning the liquid crystal with the externally applied electric field. If ϵ ∥ − ϵ ⊥ {\displaystyle \epsilon _{\parallel }-\epsilon _{\bot }} is negative, then the minimum of the energy is achieved when E {\displaystyle E} and n {\displaystyle n} are perpendicular (in nematics the perpendicular orientation is degenerated, making possible the emergence of vortices [ 75 ] ).
The difference Δ ϵ = ϵ ∥ − ϵ ⊥ {\displaystyle \Delta \epsilon =\epsilon _{\parallel }-\epsilon _{\bot }} is called dielectrical anisotropy and is an important parameter in liquid crystal applications. There are both Δ ϵ > 0 {\displaystyle \Delta \epsilon >0} and Δ ϵ < 0 {\displaystyle \Delta \epsilon <0} commercial liquid crystals. 5CB and E7 liquid crystal mixture are two Δ ϵ > 0 {\displaystyle \Delta \epsilon >0} liquid crystals commonly used. MBBA is a common Δ ϵ < 0 {\displaystyle \Delta \epsilon <0} liquid crystal.
The effects of magnetic fields on liquid crystal molecules are analogous to electric fields. Because magnetic fields are generated by moving electric charges, permanent magnetic dipoles are produced by electrons moving about atoms. When a magnetic field is applied, the molecules will tend to align with or against the field. Electromagnetic radiation, e.g. UV-Visible light, can influence light-responsive liquid crystals which mainly carry at least a photo-switchable unit. [ 76 ]
In the absence of an external field, the director of a liquid crystal is free to point in any direction. It is possible, however, to force the director to point in a specific direction by introducing an outside agent to the system. For example, when a thin polymer coating (usually a polyimide) is spread on a glass substrate and rubbed in a single direction with a cloth, it is observed that liquid crystal molecules in contact with that surface align with the rubbing direction. The currently accepted mechanism for this is believed to be an epitaxial growth of the liquid crystal layers on the partially aligned polymer chains in the near surface layers of the polyimide.
Several liquid crystal chemicals also align to a 'command surface' which is in turn aligned by electric field of polarized light. This process is called photoalignment .
The competition between orientation produced by surface anchoring and by electric field effects is often exploited in liquid crystal devices. Consider the case in which liquid crystal molecules are aligned parallel to the surface and an electric field is applied perpendicular to the cell. At first, as the electric field increases in magnitude, no change in alignment occurs. However at a threshold magnitude of electric field, deformation occurs. Deformation occurs where the director changes its orientation from one molecule to the next. The occurrence of such a change from an aligned to a deformed state is called a Fréedericksz transition and can also be produced by the application of a magnetic field of sufficient strength.
The Fréedericksz transition is fundamental to the operation of many liquid crystal displays because the director orientation (and thus the properties) can be controlled easily by the application of a field.
As already described, chiral liquid-crystal molecules usually give rise to chiral mesophases. This means that the molecule must possess some form of asymmetry, usually a stereogenic center. An additional requirement is that the system not be racemic : a mixture of right- and left-handed molecules will cancel the chiral effect. Due to the cooperative nature of liquid crystal ordering, however, a small amount of chiral dopant in an otherwise achiral mesophase is often enough to select out one domain handedness, making the system overall chiral.
Chiral phases usually have a helical twisting of the molecules. If the pitch of this twist is on the order of the wavelength of visible light, then interesting optical interference effects can be observed. The chiral twisting that occurs in chiral LC phases also makes the system respond differently from right- and left-handed circularly polarized light. These materials can thus be used as polarization filters . [ 77 ]
It is possible for chiral LC molecules to produce essentially achiral mesophases. For instance, in certain ranges of concentration and molecular weight , DNA will form an achiral line hexatic phase. An interesting recent observation is of the formation of chiral mesophases from achiral LC molecules. Specifically, bent-core molecules (sometimes called banana liquid crystals) have been shown to form liquid crystal phases that are chiral. [ 78 ] In any particular sample, various domains will have opposite handedness, but within any given domain, strong chiral ordering will be present. The appearance mechanism of this macroscopic chirality is not yet entirely clear. It appears that the molecules stack in layers and orient themselves in a tilted fashion inside the layers. These liquid crystals phases may be ferroelectric or anti-ferroelectric, both of which are of interest for applications. [ 79 ] [ 80 ]
Chirality can also be incorporated into a phase by adding a chiral dopant , which may not form LCs itself. Twisted-nematic or super-twisted nematic mixtures often contain a small amount of such dopants.
Liquid crystals find wide use in liquid crystal displays, which rely on the optical properties of certain liquid crystalline substances in the presence or absence of an electric field . In a typical device, a liquid crystal layer (typically 4 μm thick) sits between two polarizers that are crossed (oriented at 90° to one another). The liquid crystal alignment is chosen so that its relaxed phase is a twisted one (see Twisted nematic field effect ). [ 8 ] This twisted phase reorients light that has passed through the first polarizer, allowing its transmission through the second polarizer (and reflected back to the observer if a reflector is provided). The device thus appears transparent. When an electric field is applied to the LC layer, the long molecular axes tend to align parallel to the electric field thus gradually untwisting in the center of the liquid crystal layer. In this state, the LC molecules do not reorient light, so the light polarized at the first polarizer is absorbed at the second polarizer, and the device loses transparency with increasing voltage. In this way, the electric field can be used to make a pixel switch between transparent or opaque on command. Color LCD systems use the same technique, with color filters used to generate red, green, and blue pixels. [ 8 ] Chiral smectic liquid crystals are used in ferroelectric LCDs which are fast-switching binary light modulators. Similar principles can be used to make other liquid crystal based optical devices. [ 81 ]
Liquid crystal tunable filters are used as electro-optical devices, [ 82 ] [ 83 ] e.g., in hyperspectral imaging .
Thermotropic chiral LCs whose pitch varies strongly with temperature can be used as crude liquid crystal thermometers , since the color of the material will change as the pitch is changed. Liquid crystal color transitions are used on many aquarium and pool thermometers as well as on thermometers for infants or baths. [ 84 ] Other liquid crystal materials change color when stretched or stressed. Thus, liquid crystal sheets are often used in industry to look for hot spots, map heat flow, measure stress distribution patterns, and so on. Liquid crystal in fluid form is used to detect electrically generated hot spots for failure analysis in the semiconductor industry. [ 85 ]
Liquid crystal lenses converge or diverge the incident light by adjusting the refractive index of liquid crystal layer with applied voltage or temperature. Generally, the liquid crystal lenses generate a parabolic refractive index distribution by arranging molecular orientations. Therefore, a plane wave is reshaped into a parabolic wavefront by a liquid crystal lens. The focal length of liquid crystal lenses could be continuously tunable when the external electric field can be properly tuned. Liquid crystal lenses are a kind of adaptive optics . Imaging systems can benefit from focusing correction, image plane adjustment, or changing the range of depth-of-field or depth of focus . The liquid crystal lense is one of the candidates to develop vision correction devices for myopia and presbyopia (e.g., tunable eyeglass and smart contact lenses). [ 86 ] [ 87 ] Being an optical phase modulator , a liquid crystal lens feature space-variant optical path length (i.e., optical path length as the function of its pupil coordinate). In different imaging system, the required function of optical path length varies from one to another. For example, to converge a plane wave into a diffraction limited spot, for a physically-planar liquid crystal structure, the refractive index of liquid crystal layer should be spherical or paraboloidal under paraxial approximation . As for projecting images or sensing objects, it may be expected to have the liquid crystal lens with aspheric distribution of optical path length across its aperture of interest. Liquid crystal lenses with electrically tunable refractive index (by addressing the different magnitude of electric field on liquid crystal layer) have potentials to achieve arbitrary function of optical path length for modulating incoming wavefront; current liquid crystal freeform optical elements were extended from liquid crystal lens with same optical mechanisms. [ 88 ] The applications of liquid crystals lenses includes pico-projectors, prescriptions lenses (eyeglasses or contact lenses), smart phone camera, augmented reality, virtual reality etc.
Liquid crystal lasers use a liquid crystal in the lasing medium as a distributed feedback mechanism instead of external mirrors. Emission at a photonic bandgap created by the periodic dielectric structure of the liquid crystal gives a low-threshold high-output device with stable monochromatic emission. [ 36 ] [ 89 ]
Polymer dispersed liquid crystal (PDLC) sheets and rolls are available as adhesive backed Smart film which can be applied to windows and electrically switched between transparent and opaque to provide privacy.
Many common fluids, such as soapy water , are in fact liquid crystals. Soap forms a variety of LC phases depending on its concentration in water. [ 90 ]
Liquid crystal films have revolutionized the world of technology. Currently they are used in the most diverse devices, such as digital clocks, mobile phones, calculating machines and televisions. The use of liquid crystal films in optical memory devices, with a process similar to the recording and reading of CDs and DVDs may be possible. [ 91 ] [ 92 ]
Liquid crystals are also used as basic technology to imitate quantum computers , using electric fields to manipulate the orientation of the liquid crystal molecules , to store data and to encode a different value for every different degree of misalignment with other molecules. [ 93 ] [ 94 ] | https://en.wikipedia.org/wiki/Liquid_crystal |
Liquid crystal elastomers (LCEs) are slightly crosslinked liquid crystalline polymer networks. These materials combine the entropy elasticity of an elastomer with the self-organization of the liquid crystalline phase. In liquid crystalline elastomers, the mesogens can either be part of the polymer chain (main-chain liquid crystalline elastomers) or are attached via an alkyl spacer (side-chain liquid crystalline elastomers). [ 1 ]
Due to their actuation properties, liquid crystalline elastomers are attractive candidates for the use as artificial muscles or microrobots .
LCE were predicted by Pierre-Gilles de Gennes in 1975 and first synthesized by Heino Finkelmann . [ 2 ]
In the temperature range of the liquid crystalline phase, the mesogen's orientation forces the polymer chains into a stretched conformation. Heating the sample above the clearing temperature destroys this orientation and the polymer backbone can relax into (the more favored) random coil conformation. That can lead to a macroscopic, reversible deformation. Good actuation requires a good alignment of the domains' directors before cross-linking . This can be achieved by: stretching of the prepolymerized sample, [ 3 ] photo-alignment layers, [ 4 ] magnetic or electric fields and microfluidics . [ 5 ] [ 6 ]
Because of their anisotropy , the mechanical response of aligned nematic LCEs varies depending upon the direction of applied stress. When stress is applied along the direction of alignment (parallel to the director , n ^ {\displaystyle {\widehat {n}}} ), the strain responds in a linear fashion, with a slope dictated by the material’s Young’s modulus . This linear stress-strain behavior continues until the material reaches its yield stress, at which point it may neck or strain harden before eventually failing. The shape of the stress-strain curve for LCEs stretched parallel to their aligned direction matches that of most classical rubbers and can be described using treatments such as rubber elasticity .
In contrast, when stress is applied perpendicular to the direction of alignment, the strain behavior exhibits a drastically different response. For an unconstrained LCE, after an initial region where the stress-strain response matches that of classical rubbers, the material exhibits a large plateau where near-constant stress leads to ever-increasing strain. The term “soft elasticity” describes this large plateau region. [ 7 ] After a critical strain is reached in this region, the stress-strain response returns to that of LCEs stretched in a direction parallel to their director.
The theory used to describe soft elasticity first arose to explain experimental observations of the phenomena in unconstrained LCEs that reoriented in the presence of an external electric field. [ 8 ] The theory of soft elasticity states that when an LCE is stretched in a direction perpendicular to its alignment direction, its chains rotate and reorient to align in the direction of applied stress. Assuming that the LCE chains are allowed to freely move in all three dimensions, this reorientation occurs without a change in the elastic free energy of the system. This implies that there is no energy barrier to the rotation of the LCE chains, meaning that zero-stress would be required to fully reorient them.
Experimentally, a small but non-zero stress is required to induce soft elasticity and achieve this chain rotation. This deviation from the theoretical prediction arises due to the fact that real LCEs are not truly free in all three dimensions, and are instead geometrically restricted by neighboring chains. As a result, some small, finite stress is necessary in experimental systems to induce chain reorientation. Once the chain has fully rotated and is aligned parallel to the direction of applied stress, the subsequent stress-strain response is again described by that of rubber elasticity.
Soft elasticity has also been exploited to develop materials with unique and useful properties. By controlling the local liquid crystal alignment in an LCE, films with spatially varying mechanical anisotropy can be fabricated. [ 9 ] When strained, different regions of these chemically homogeneous films stretch to different extents as a result of the relative orientation of the director to the applied stress. This has the effect of localizing deformation to predetermined regions. This predictable deformation is useful because it allows for the design of soft electronic devices that are globally compliant but locally stiff, ensuring important components do not break when the film is deformed.
Upon transitioning from a liquid crystalline phase to an isotropic (orientationally disordered) phase, or vice versa, an LCE sample will spontaneously deform into a different shape. For example, if a nematic LCE transitions to its isotropic state, it will undergo contraction parallel to its director and expansion in the perpendicular plane. Any stimulus that drives the ordered ⇔ disordered phase transition can induce such actuation (or 'activation'). A patterned director field thus allows an LCE sample to morph into a radically different shape upon stimulation, returning to its original shape when the stimulus is removed. Due to its reversibility, large strain, and the potential to prescribe extremely complex shape changes, this shape morphing effect has attracted much interest as a potential tool for creating soft machines such as actuators or robots. As a simple example, consider a thin disk-shaped LCE sheet with a 'concentric-circles' (everywhere azimuthal) in-plane director pattern. Upon heating to the isotropic state, the disk will rise into a cone, which can be used to lift a weight thousands of times the weight of the LCE itself. [ 10 ]
Beside the thermal deformation of a sample, a light-responsive actuation can be obtained for samples by incorporating azobenzenes in the liquid crystalline phase. [ 11 ] The phase transition temperature of an azo -liquid crystalline elastomer can be reduced due to the trans-cis isomerization of the azobenzenes during UV-irradiation and thus the liquid crystalline phase can be destroyed isothermally . For liquid crystalline elastomers with a high azo-concentration, a light-responsive change of the sample's length of up to 40% could be observed. [ 12 ] [ 13 ]
LCE have been examined for use as a light-weight energy absorption material. Tilted slabs of LCE were attached to stiff materials, approximating a honeycomb lattice. Arranged in multiple layers, allowed the material to buckle at different rates on impact, efficiently dissipating energy across the structure. Increasing the number of layers increased absorption capacity. [ 14 ] [ 15 ] | https://en.wikipedia.org/wiki/Liquid_crystalline_elastomer |
The liquid droplet radiator ( LDR ), previously termed liquid droplet stream radiator , is a proposed lightweight radiator for the dissipation of waste heat generated by power plants , propulsion or spacecraft systems in space.
An advanced or future space mission must have a power source or propulsion that will require the rejection of waste heat.
Disposing large quantities of waste heat must be considered in order to realize a large-space structure (LSS) that handle high power such as a nuclear reactor or a space solar power satellite (SPS) .
Such space systems require advanced high-temperature thermal control systems .
Liquid metal heat pipes with conventional radiators are considered ideally suited for such applications. [ 5 ] However, the required radiator surface area is huge, hence, the system mass is very large. The liquid droplet radiator (LDR) has an advantage in terms of the rejected heat power-weight ratio. The results of the studies indicate that for rejection temperatures below approximately 700 K, the LDR system is significantly lighter in weight than the other advanced radiator concepts. A LDR can be seven times lighter than conventional heat pipe radiators of similar size. [ 6 ] The LDR is more resistant to meteorite impacts due to less critical surface or windage, and requires less storage volume.
Therefore, the LDR has attracted attention as an advanced radiator for high-power space systems.
In 1978, John M. Hedgepeth proposed, in "Ultralightweight Structures for Space Power," in Radiation Energy Conversion in Space, Vol. 61 of Progress in Astronautics and Aeronautics, K. W. Billman, ed. (AIAA, New York, 1978), p. 126,
the use of a dust radiator to reduce the radiator weight of solar power satellites. Practical problems of this dust system led to the LDR concept in 1979. [ 1 ] Numerous studies have been made by companies, organizations and universities around the world.
Practical experiments were carried out for example with STS-77 [ 5 ] and at drop shafts in Japan: Japan Microgravity Center (JAMIC) and Microgravity Laboratory of Japan . [ 7 ]
The liquid droplet radiator (LDR) system consists of a droplet generator, a collector, a heat exchanger , a recirculating pump, and a bellows-type pressure regulator ( accumulator ).
While undergoing a reduction in pressure the saturated liquid is sprayed into space as coherent streams of tiny, discrete droplets.
The droplet stream can be a column or a sheet of liquid droplets moving through space from the droplet generator to the collector.
The droplets carry the waste heat generated by a space power system and radiate this waste heat directly to space during their flight by transient radiative heat transfer .
The liquid droplets are collected at a lower temperature, reheated, and pumped to the droplet generator and reused to continue to remove waste heat from the thermodynamic power cycle.
The pressure at which liquid droplets are formed can vary widely in different applications, but it was found that once the droplet flow has been established, substantially lower pressures are needed to maintain the flow of droplet streams. [ 8 ]
Spacecraft waste heat is ultimately rejected to space by radiator surfaces. Radiators can be of different forms, such as spacecraft structural panels, flat-plate radiators mounted to the side of the spacecraft, panels deployed after the spacecraft is on orbit, and droplets.
All radiators reject heat by infrared (IR) radiation from their surfaces. The radiating power depends on the surface's emittance and temperature.
The radiator must reject both the spacecraft waste heat plus any radiant-heat loads from the environment or other spacecraft surfaces. [ 9 ] Most radiators are therefore given surface finishes with high IR emittance ( ε > 0.8) to maximize heat rejection and low solar absorption ( α < 0.2) to limit heat loads from the sun.
High-temperature radiators are preferred for better efficiency and size reduction considerations, however, fluid property and droplet cloud property are additional factors.
Droplet size formation and droplet density govern emission and reabsorption .
A smaller droplet is essential for obtaining effective radiation in the liquid droplet radiator. A droplet with a diameter of 1 μm has been calculated to cool from 500 K to 252 K in two seconds. A dense cloud of the droplet sheet will retard the cooling rate of the droplets because of the reabsorption of the emitted light. [ 10 ]
A single droplet radiates heat as it travels through space and at any time this heat loss is given by: [ 6 ]
q ˙ = ( 4 π a 2 ) σ F T 4 {\displaystyle {\dot {q}}=(4\pi a^{2})\sigma FT^{4}}
where σ {\displaystyle \sigma } is the Stefan–Boltzmann constant , q ˙ {\displaystyle {\dot {q}}} is the droplet heat loss rate to space (joules/second), a {\displaystyle a} is the droplet radius (meters), F {\displaystyle F} is the average gray body view factor for droplet at stream center (less than one), and T {\displaystyle T} is the absolute droplet temperature at any time ( kelvin ).
This equation models the droplet as a gray body with
constant average emissivity. The instantaneous radiation
rate is equal to the rate of energy loss resulting in this
equation: [ 6 ]
( 4 π a 2 ) σ F T 4 = − c ρ 4 π a 3 3 d T d t {\displaystyle (4\pi a^{2})\sigma FT^{4}=-c\rho {\frac {4\pi a^{3}}{3}}{\frac {dT}{dt}}}
where c {\displaystyle c} is the specific heat capacity , ρ {\displaystyle \rho } is the density of droplet (kg/m 3 ), t {\displaystyle t} is the droplet transit time (seconds).
The operating environment is not simply black space, but one with solar radiation and diffuse radiation reflected and emitted from the sun (stars), earth, other objects, and or the spacecraft's own propulsion. It is possible to "orient" the droplet sheet edge towards an external heat source but the sheet area would still be subject to radiation from other sources. Most of the presented solutions of the equation of radiative transfer are practical simplifications by introducing assumptions.
In order to achieve high collection efficiency splashing of the droplet on the collector surface has to be minimized. It was determined that droplet collector with an incidence angle of 35 degrees can prevent a uniform droplet stream with droplet diameter 250 μm and a velocity of 16 m/s from splashing under microgravity condition. [ 7 ] Another solution is to have a liquid film formed on the inner surface of the collector. When the droplet streams are absorbed in this liquid film, no splashes should be formed. A miscapture rate of incoming droplets was required to be less than 10 −6 . The droplet diameter was determined to be less than 300 μm and the droplet speed less than 20 m/s. [ 11 ] If a ferrofluid is used a magnetic focusing means can effectively suppress splashing. [ 8 ]
As the droplet sheet is in free fall a spacecraft performing a maneuver or angular acceleration would lose coolant. Even a magnetically focused LDR has a very limited tolerance of less than 10 −3 g.
A droplet generator has approximately 10 5 – 10 6 holes (orifices) per system with diameters of 50–20 μm. [ 12 ] These orifices are more susceptible to damage than a conventional solid radiator or heat pipe which may affect droplet formation and droplet stream flow direction, potentially causing fluid loss.
Liquids with low vapor pressures are preferred for the working fluids to minimize evaporation loss due to flash evaporation . [ 13 ] Liquids have been found that in the range of 300 to 900 K have a vapor pressure so low that the evaporation loss during the normal lifetime of a space system
(possibly as long as 30 years) will be only a small fraction of the total mass of the radiator. [ 14 ] Operating life of the fluid in the LDR environment is affected by thermal stability , oxidative stability , and resistance to radiation . [ 15 ]
If a liquid metal is used as the coolant, the pumping of the liquid may use an electromagnetic device. The device induces eddy currents in the metal that generate a Lorentz force with their associated magnetic fields. The effect is the pumping of the liquid metal resulting in a simplified design with no moving parts. This is known as MHD pumping. [ 16 ] For example, a simple mixture of mineral oil and iron filings was found to approximate a suitable ferrofluid for several seconds, before separation of the iron filings and oil was observed in the presence of a magnetic field. At droplet sizes of approximately 200 μm , surface tension will hold the two components at accelerations up to about 1 g. [ 8 ]
If an ionic fluid is used as the coolant, the fluid can be used for momentum transfer between spacecraft traveling at different speeds. It may be possible to synthesize the fluid in-situ. For example, BMIM-BF4 ( [C 8 H 15 N 2 ] + BF 4 − ) is 42.5% carbon by mass. Lunar regolith typically contains several compounds with carbon and about 5% of asteroids are carbonaceous chondrites which are rich in carbon as well as metals and water.
It may be possible to mine the moon for carbon and combine it with other elements to produce ionic fluid. Another good source of carbon is Mars ' largest moon, Phobos , which is a captured asteroid believed to be rich in carbon. [ 17 ]
There are two different droplet collection schemes: the centrifugal approach and the linear collection scheme. The linear collector is considered to be simpler, more reliable and lighter. [ 1 ]
Several different LDR configurations have been proposed and evaluated. [ 1 ] [ 18 ]
Rectangular and triangular versions of the LDR have been investigated the most.
The LDR is being studied as a byproduct of a concept using a fluid stream for momentum transfer between an approaching spacecraft and another spacecraft, station or Moon base. This method could reduce spacecraft mass while increasing space flight efficiency. [ 15 ]
A Liquid Sheet Radiator (LRS), adapted for planetary surfaces, is essentially a fountain enclosed in a transparent envelope. The liquid flows down on the inside of this envelope. The liquid sheet radiator concept is exceptionally stable and does not require special machining of the orifice to achieve its performance. [ 19 ] | https://en.wikipedia.org/wiki/Liquid_droplet_radiator |
The liquid entry pressure (LEP) of a hydrophobic membrane is the pressure that must be applied to a dry membrane so that the liquid penetrates inside the membrane. LEP with the application in membrane distillation or pervaporation can be calculated as a first parameter to indicate how wettable a membrane is toward different liquid solutions. [ 1 ]
LEP depends on many parameters, including the membrane maximum pore size, the surface tension of the liquid, the contact angle of the liquid on the membrane surface, and the geometrical structure of the membrane. [ 1 ]
In the simplest form based on the Young–Laplace equation , [ 2 ] the LEP is specified as:
L E P = − ( β γ l cos θ ) / r m a x {\displaystyle \mathrm {LEP} =-(\beta {\gamma }_{\rm {l}}\cos {\theta })/r_{\rm {max}}}
where β {\displaystyle \beta } is a pore geometry coefficient ( β {\displaystyle \beta } = 1 for cylindrical pores and 0 < β {\displaystyle \beta } < 1 for non-cylindrical pores), [ 3 ] γ l {\displaystyle {\gamma }_{\rm {l}}} is the liquid surface tension, θ {\displaystyle \theta } is the contact angle measured on the liquid side, where the liquid-vapor interface meets the membrane surface, and r m a x {\displaystyle r_{\rm {max}}} is the maximum pore size of the membrane.
Membranes with small pore size, narrow pore size distribution, ideal cylindrical pore geometry, low surface energy, high contact angle, and high roughness typically show higher LEP. Rezaei et al. have shown that the presence of a secondary phase such as air on the surface of membrane can markedly increase the LEP of the membrane, especially for less hydrophobic materials. [ 5 ]
As wetting is generally undesirable and represents a failure of the membrane process, design and research focus around avoiding its occurrence (e.g. through operating conditions), [ 6 ] or reversing wetting after it has occurred (e.g. through backwashing or drying out the membrane). [ 7 ] Surface coatings are a key way to improve LEP: [ 8 ] these ideally are uniform, cause very high contact angles , and avoid pore clogging. [ 9 ] | https://en.wikipedia.org/wiki/Liquid_entry_pressure |
Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures . Liquid helium may show superfluidity .
At standard pressure, the chemical element helium exists in a liquid form only at the extremely low temperature of −269 °C (−452.20 °F; 4.15 K). Its boiling point and critical point depend on the isotope of helium present: the common isotope helium-4 or the rare isotope helium-3 . These are the only two stable isotopes of helium. See the table below for the values of these physical quantities. The density of liquid helium-4 at its boiling point and a pressure of one atmosphere (101.3 kilopascals ) is about 125 g/L (0.125 g/ml), or about one-eighth the density of liquid water . [ 1 ]
Helium was first liquefied on July 10, 1908, by the Dutch physicist Heike Kamerlingh Onnes at the University of Leiden in the Netherlands . [ 2 ] At that time, helium-3 was unknown because the mass spectrometer had not yet been invented. In more recent decades, liquid helium has been used as a cryogenic refrigerant (which is used in cryocoolers ), and liquid helium is produced commercially for use in superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), magnetoencephalography (MEG), and experiments in physics , such as low temperature Mössbauer spectroscopy . The Large Hadron Collider contains superconducting magnets that are cooled with 120 tonnes of liquid helium. [ 3 ]
A helium-3 atom is a fermion and at very low temperatures, they form two-atom Cooper pairs which are bosonic and condense into a superfluid . These Cooper pairs are substantially larger than the interatomic separation.
The temperature required to produce liquid helium is low because of the weakness of the attractions between the helium atoms. These interatomic forces in helium are weak to begin with because helium is a noble gas , but the interatomic attractions are reduced even more by the effects of quantum mechanics . These are significant in helium because of its low atomic mass of about four atomic mass units . The zero point energy of liquid helium is less if its atoms are less confined by their neighbors. Hence in liquid helium, its ground state energy can decrease by a naturally occurring increase in its average interatomic distance. However at greater distances, the effects of the interatomic forces in helium are even weaker. [ 4 ]
Because of the very weak interatomic forces in helium, the element remains a liquid at atmospheric pressure all the way from its liquefaction point down to absolute zero . At temperatures below their liquefaction points, both helium-4 and helium-3 undergo transitions to superfluids . (See the table below.) [ 4 ] Liquid helium can be solidified only under very low temperatures and high pressures . [ 5 ]
Liquid helium-4 and the rare helium-3 are not completely miscible . [ 6 ] Below 0.9 kelvin at their saturated vapor pressure , a mixture of the two isotopes undergoes a phase separation into a normal fluid (mostly helium-3) that floats on a denser superfluid consisting mostly of helium-4. [ 7 ] This phase separation happens because the overall mass of liquid helium can reduce its thermodynamic enthalpy by separating.
At extremely low temperatures, the superfluid phase, rich in helium-4, can contain up to 6% helium-3 in solution. This makes the small-scale use of the dilution refrigerator possible, which is capable of reaching temperatures of a few millikelvins . [ 6 ] [ 8 ]
Superfluid helium-4 has substantially different properties from ordinary liquid helium.
In 1908, Kamerlingh-Onnes succeeded in liquifying a small quantity of helium. In 1923, he provided advice to the Canadian physicist John Cunningham McLennan , who was the first to produce quantities of liquid helium almost on demand. [ 9 ]
Important early work on the characteristics of liquid helium was done by the Soviet physicist Lev Landau , later extended by the American physicist Richard Feynman .
In 1961, Vignos and Fairbank reported the existence of a different phase of solid helium-4, designated the gamma-phase. It exists for a narrow range of pressure between 1.45 and 1.78 K. [ 10 ] | https://en.wikipedia.org/wiki/Liquid_helium |
Liquid hydrogen ( H 2 (l) ) is the liquid state of the element hydrogen . Hydrogen is found naturally in the molecular H 2 form. [ 4 ]
To exist as a liquid, H 2 must be cooled below its critical point of 33 K . However, for it to be in a fully liquid state at atmospheric pressure , H 2 needs to be cooled to 20.28 K (−252.87 °C; −423.17 °F). [ 5 ] A common method of obtaining liquid hydrogen involves a compressor resembling a jet engine in both appearance and principle. Liquid hydrogen is typically used as a concentrated form of hydrogen storage . Storing it as liquid takes less space than storing it as a gas at normal temperature and pressure. However, the liquid density is very low compared to other common fuels. Once liquefied, it can be maintained as a liquid for some time in thermally insulated containers. [ 6 ]
There are two spin isomers of hydrogen ; whereas room temperature hydrogen is mostly orthohydrogen, liquid hydrogen consists of 99.79% parahydrogen and 0.21% orthohydrogen. [ 5 ]
Hydrogen requires a theoretical minimum of 3.3 kWh/kg (12 MJ/kg) to liquefy, and 3.9 kWh/kg (14 MJ/kg) including converting the hydrogen to the para isomer, but practically generally takes 10–13 kWh/kg (36–47 MJ/kg) compared to a 33 kWh/kg (119 MJ/kg) heating value of hydrogen. [ 7 ]
In 1885, Zygmunt Florenty Wróblewski published hydrogen's critical temperature as 33 K (−240.2 °C; −400.3 °F); critical pressure, 13.3 standard atmospheres (195 psi); and boiling point, 23 K (−250.2 °C; −418.3 °F).
Hydrogen was liquefied by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask . The first synthesis of the stable isomer form of liquid hydrogen, parahydrogen, was achieved by Paul Harteck and Karl Friedrich Bonhoeffer in 1929.
The two nuclei in a dihydrogen molecule can have two different spin states.
Parahydrogen, in which the two nuclear spins are antiparallel, is more stable than orthohydrogen, in which the two are parallel. At room temperature, gaseous hydrogen is mostly in the ortho isomeric form due to thermal energy, but an ortho-enriched mixture is only metastable when liquified at low temperature. It slowly undergoes an exothermic reaction to become the para isomer, with enough energy released as heat to cause some of the liquid to boil. [ 8 ] To prevent loss of the liquid during long-term storage, it is therefore intentionally converted to the para isomer as part of the production process, typically using a catalyst such as iron(III) oxide , activated carbon , platinized asbestos, rare earth metals, uranium compounds, chromium(III) oxide , or some nickel compounds. [ 8 ]
Liquid hydrogen is a common liquid rocket fuel for rocketry application and is used by NASA and the U.S. Air Force , which operate a large number of liquid hydrogen tanks with an individual capacity up to 3.8 million liters (1 million U.S. gallons). [ 9 ]
In most rocket engines fueled by liquid hydrogen, it first cools the nozzle and other parts before being mixed with the oxidizer, usually liquid oxygen , and burned to produce water with traces of ozone and hydrogen peroxide . Practical H 2 –O 2 rocket engines run fuel-rich so that the exhaust contains some unburned hydrogen. This reduces combustion chamber and nozzle erosion. It also reduces the molecular weight of the exhaust, which can increase specific impulse , despite the incomplete combustion.
Liquid hydrogen can be used as the fuel for an internal combustion engine or fuel cell . Various submarines, including the Type 212 submarine , Type 214 submarine , and others, and concept hydrogen vehicles have been built using this form of hydrogen, such as the DeepC , BMW H2R , and others. Due to its similarity, builders can sometimes modify and share equipment with systems designed for liquefied natural gas (LNG). Liquid hydrogen is being investigated as a zero carbon fuel for aircraft . Because of the lower volumetric energy , the hydrogen volumes needed for combustion are large. Unless direct injection is used, a severe gas-displacement effect also hampers maximum breathing and increases pumping losses.
Liquid hydrogen is also used to cool neutrons to be used in neutron scattering . Since neutrons and hydrogen nuclei have similar masses, kinetic energy exchange per interaction is maximum ( elastic collision ). Finally, superheated liquid hydrogen was used in many bubble chamber experiments.
The first thermonuclear bomb , Ivy Mike , used liquid deuterium , also known as hydrogen-2, for nuclear fusion.
The product of hydrogen combustion in a pure oxygen environment is solely water vapor. However, the high combustion temperatures and present atmospheric nitrogen can result in the breaking of N≡N bonds, forming toxic NOx if no exhaust scrubbing is done. [ 10 ] Since water is often considered harmless to the environment, an engine burning it can be considered "zero emissions". In aviation, however, water vapor emitted in the atmosphere contributes to global warming (to a lesser extent than CO 2 ). [ 11 ] Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel. [ 12 ]
The density of liquid hydrogen is only 70.85 kg/m 3 (at 20 K ), a relative density of just 0.07. Although the specific energy is more than twice that of other fuels, this gives it a remarkably low volumetric energy density , many fold lower.
Liquid hydrogen requires cryogenic storage technology such as special thermally insulated containers and requires special handling common to all cryogenic fuels . This is similar to, but more severe than liquid oxygen . Even with thermally insulated containers it is difficult to keep such a low temperature, and the hydrogen will gradually leak away (typically at a rate of 1% per day [ 12 ] ). It also shares many of the same safety issues as other forms of hydrogen, as well as being cold enough to liquefy, or even solidify atmospheric oxygen, which can be an explosion hazard.
The triple point of hydrogen is at 13.81 K [ 5 ] and 7.042 kPa. [ 13 ]
Due to its cold temperatures, liquid hydrogen is a hazard for cold burns . Hydrogen itself is biologically inert and its only human health hazard as a vapor is displacement of oxygen, resulting in asphyxiation, and its very high flammability and ability to detonate when mixed with air. Because of its flammability, liquid hydrogen should be kept away from heat or flame unless ignition is intended. Unlike ambient-temperature gaseous hydrogen, which is lighter than air, hydrogen recently vaporized from liquid is so cold that it is heavier than air and can form flammable heavier-than-air air–hydrogen mixtures. | https://en.wikipedia.org/wiki/Liquid_hydrogen |
In mass spectrometry , liquid junction interface is an ion source or set-up that couples peripheric devices, such as capillary electrophoresis , to mass spectrometry.
See the IUPAC recommendation [ 1 ] definition as a means of coupling capillary electrophoresis to mass spectrometry in which a liquid reservoir surrounds the separation capillary and transfer capillary to the mass spectrometer. The reservoir provides electrical contact for the capillary electrophoresis.
The term liquid junction interface has also been used by Henry M. Fales and coworkers for ion sources where the analyte is in direct contact with the high voltage supply. [ 2 ] This includes in particular nanospray ion sources where a wire made of stainless steel, gold or other conducting material makes contact with the sample solution inside uncoated spray capillaries. The principle is also applied when a stainless steel union connects a chromatography outlet to a spray capillary. Its use has a number of advantages with respect to simplification of interface or source design, easy handling and cost. Electrolysis effects have to be controlled.
Liquid junction interfaces have been used for on-line desalting in conjunction with mass spectrometry . Thereby, chromatographic material such as C18 phase was directly placed in the flow path coming from a pump or an HPLC device. [ 3 ] In a variation of the method, fine capillaries were densely packed with chromatographic phase to form separation columns and act as electrospray capillaries at the same time. This method is commonly employed in many proteomics laboratories. [ 4 ]
It is of note that experimental designs where the direct application of high voltages to liquids to form aerosols and sprays has been described as early as 1917 [ 5 ] in the context of not ionization, but atomization of liquids. [ 6 ]
Liquid junction potential - the process which occurs when two solutions of different concentrations are in contact with each other | https://en.wikipedia.org/wiki/Liquid_junction_interface |
Liquid junction potential (shortly LJP) occurs when two solutions of electrolytes of different concentrations are in contact with each other. The more concentrated solution will have a tendency to diffuse into the comparatively less concentrated one. The rate of diffusion of each ion will be roughly proportional to its speed in an electric field , or their ion mobility . If the anions diffuse more rapidly than the cations , they will diffuse ahead into the dilute solution, leaving the latter negatively charged and the concentrated solution positively charged. This will result in an electrical double layer of positive and negative charges at the junction of the two solutions. Thus at the point of junction, a potential difference will develop because of the ionic transfer . This potential is called liquid junction potential or diffusion potential which is non-equilibrium potential. The magnitude of the potential depends on the relative speeds of the ions' movement.
The liquid junction potential cannot be measured directly but calculated. The electromotive force (EMF) of a concentration cell with transference includes the liquid junction potential.
The EMF of a concentration cell without transport is:
where a 1 {\displaystyle a_{1}} and a 2 {\displaystyle a_{2}} are activities of HCl in the two solutions, R {\displaystyle R} is the universal gas constant , T {\displaystyle T} is the temperature and F {\displaystyle F} is the Faraday constant .
The EMF of a concentration cell with transport (including the ion transport number ) is:
where a 2 {\displaystyle a_{2}} and a 1 {\displaystyle a_{1}} are activities of HCl solutions of right and left hand electrodes, respectively, and t M {\displaystyle t_{M}} is the transport number of Cl − .
Liquid junction potential is the difference between the two EMFs of the two concentration cells, with and without ionic transport:
The liquid junction potential interferes with the exact measurement of the electromotive force of a chemical cell, so its effect should be minimized as much as possible for accurate measurement. The most common method of eliminating the liquid junction potential is to place a salt bridge consisting of a saturated solution of potassium chloride (KCl) and ammonium nitrate (NH 4 NO 3 ) with lithium acetate (CH 3 COOLi) between the two solutions constituting the junction. When such a bridge is used, the ions in the bridge are present in large excess at the junction and they carry almost the whole of the current across the boundary. The efficiency of KCl/NH 4 NO 3 is connected with the fact that in these salts, the transport numbers [ clarification needed ] of anions and cations are the same. | https://en.wikipedia.org/wiki/Liquid_junction_potential |
Liquid marbles are non-stick droplets (normally aqueous ) wrapped by micro- or nano-metrically scaled hydrophobic , colloidal particles ( Teflon , polyethylene , lycopodium powder , carbon black , etc.); representing a platform for a diversity of chemical and biological applications. [ 1 ] [ 2 ] [ 3 ] Liquid marbles are also found naturally; aphids convert honeydew droplets into marbles. [ 4 ] A variety of non-organic and organic liquids may be converted into liquid marbles. [ 3 ] [ 5 ] [ 6 ] Liquid marbles demonstrate elastic properties and do not coalesce when bounced or pressed lightly. [ 6 ] Liquid marbles demonstrate a potential as micro-reactors, micro-containers for growing micro-organisms and cells , micro-fluidics devices, and have even been used in unconventional computing . [ 5 ] [ 6 ] [ 7 ] Liquid marbles remain stable on solid and liquid surfaces. [ 1 ] [ 8 ] Statics and dynamics of rolling and bouncing of liquid marbles were reported. [ 9 ] [ 10 ] Liquid marbles coated with poly-disperse [ 6 ] and mono-disperse particles have been reported. [ 11 ] Liquid marbles are not hermetically coated by solid particles but connected to the gaseous phase. Kinetics of the evaporation of liquid marbles has been investigated. [ 12 ] [ 13 ] [ 14 ]
Liquid marbles were first reported by P. Aussillous and D. Quere [ 1 ] in 2001, who described a new method to construct portable water droplets in the atmospheric environment with hydrophobic coating on their surface to prevent the contact between water and the solid ground (Figure 1). Liquid marbles provide a new approach to transport liquid mass on the solid surface, which sufficiently transform the inconvenient glass containers into flexible, user-specified hydrophobic coating composed of powders of hydrophobic materials. Since then, the applications of liquid marbles in no-loss mass transport, microfluidics and microreactors have been extensively investigated. [ 15 ] [ 16 ] [ 17 ] [ 18 ] However, liquid marbles only reflect the water behavior at the solid-air interface, while there is no report on the water behavior at the liquid-liquid interface, as a result of the so-called coalescence cascade phenomenon.
When a water droplet is in contact with a water reservoir, it will quickly pinch off from the reservoir and form a smaller daughter droplet, while this daughter droplet will continue to go through a similar contact-pinch off-splitting process until completed coalescence into the reservoir, the combination or summary of these self-similar coalescence processes is called coalescence cascade. [ 19 ] The underlying mechanism of coalescence cascade has been studied in detail but there has been mere attempt to control and make use of it. [ 20 ] [ 21 ] [ 22 ] Until recently, Liu et al. has filled this void by proposing a new method to control coalescence cascade by using nanostructured coating at the liquid-liquid interface, —the interfacial liquid marbles. [ 23 ]
Similar to liquid marbles at the solid-air interface, the interfacial liquid marbles are constructed on the hexane / water interface using water droplets with a surface coating composed of nanoscale materials with special wettability (Figure 2). To realize interfacial water marbles at hexane/water interface, the individual particle size of the surface coating layer should be as small as possible, so that the contact line between the particles and the water reservoir can be minimized; special wettability with mixed hydrophobicity and hydrophilicity is also preferred for the interfacial water marble formation. The interfacial water marble can be fabricated by firstly coating a water droplet with nanomaterials with special wettability, e.g. hybrid carbon nanowires, graphene oxide . Afterwards a secondary coating layer of polyvinylidene fluoride (PVDF) is applied onto the coated water droplet. The doubly-coated water droplet is then cast into the hexane/water mixture and eventually settled at the hexane/water interface to form the interfacial water marble. During this process, the PVDF coating quickly diffused into hexane to balance the hydrophobic interaction between hexane and the water droplet, while the nanomaterials quickly self-assembled into a nanostructured protective layer on the droplet surface through the Marangoni effect .
The interfacial water marble can completely resist coalescence cascade and exist nearly permanently at the hexane/water interface, providing that the hexane phase is not depleted by vaporization . The interfacial water marbles can also realize a series of stimuli-responsive motions by integrating the functional materials into the surface coating layer. Due to their uniqueness in both form and behavior, the interfacial water marbles are speculated to have remarkable applications in microfluidics , microreactors and mass-transport. | https://en.wikipedia.org/wiki/Liquid_marbles |
A liquid metal is a metal or a metal alloy which is liquid at or near room temperature . [ 1 ]
The only stable liquid elemental metal at room temperature is mercury (Hg), which is molten above −38.8 °C (234.3 K, −37.9 °F). Three more stable elemental metals melt just above room temperature: caesium (Cs), which has a melting point of 28.5 °C (83.3 °F); gallium (Ga) (30 °C [86 °F]); and rubidium (Rb) (39 °C [102 °F]). The radioactive metal francium (Fr) is probably liquid close to room temperature as well. Calculations predict that the radioactive metals copernicium (Cn) and flerovium (Fl) should also be liquid at room temperature. [ 2 ]
Alloys can be liquid if they form a eutectic , meaning that the alloy's melting point is lower than any of the alloy's constituent metals. The standard metal for creating liquid alloys used to be mercury , but gallium -based alloys, which are lower both in their vapor pressure at room temperature and toxicity, are being used as a replacement in various applications. [ 3 ] [ 4 ]
Alloy systems that are liquid at room temperature have thermal conductivity far superior to ordinary non-metallic liquids, [ 5 ] allowing liquid metal to efficiently transfer energy from the heat source to the liquid. They also have a higher electrical conductivity that allows the liquid to be pumped more efficiently, by electromagnetic pumps. [ 6 ] This results in the use of these materials for specific heat conducting and/or dissipation applications.
Another advantage of liquid alloy systems is their inherent high densities.
The viscosity of liquid metals can vary greatly depending on the atomic composition of the liquid, especially in the case of alloys. In particular, the temperature dependence of the viscosity of liquid metals may range from the standard Arrhenius law dependence, to a much steeper (non-Arrhenius) dependence such as that given empirically by the Vogel–Fulcher–Tammann equation .
A physical model for the viscosity of liquid metals, which captures this great variability in terms of the underlying interatomic interactions, was also developed. [ 7 ]
The electrical resistance of a liquid metal can be estimated by means of the Ziman formula, which gives the resistance in terms of the static structure factor of the liquid as can be determined by neutron or X-ray scattering measurements.
Once oxides have been removed from the substrate surface, most liquid metals will wet most metallic surfaces. At room temperature, liquid metals are often reactive and soluble to metallic surfaces, though some solid metals are resistant to attack by the common liquid metals. [ 8 ] For example gallium is corrosive to all metals except tungsten and tantalum , which have a high resistance to corrosion, more so than niobium , titanium and molybdenum . [ 9 ]
Similar to indium , gallium and gallium-containing alloys have the ability to wet to many non-metallic surfaces such as glass and quartz . Gently rubbing the alloy into the surface may help induce wetting. However, this observation of "wetting by rubbing into glass surface" has created a widely spread misconception that the gallium-based liquid metals wet glass surfaces, as if the liquid breaks free of the oxide skin and wets the surface. The reality is the opposite: the oxide makes the liquid wet the glass. In more details: as the liquid is rubbed into and spread onto the glass surface, the liquid oxidizes and coats the glass with a thin layer of oxide (solid) residues, on which the liquid metal wets. In other words, what is seen is a gallium-based liquid metal wetting its solid oxide, not glass. Apparently, the above misconception was caused by the super-fast oxidation of the liquid gallium in even a trace amount of oxygen, i.e., nobody observed the true behavior of a liquid gallium on glass, until research at the UCLA debunked the above myth by testing Galinstan , a gallium-based alloy that is liquid at room temperature, in an oxygen-free environment. [ 10 ] Note: These alloys form a thin dull looking oxide skin that is easily dispersed with mild agitation . The oxide-free surfaces are bright and lustrous.
Applications of liquid metals include thermostats , switches , barometers , heat transfer systems, and thermal cooling and heating designs. They can also be used to conduct heat and electricity between non-metallic and metallic surfaces. Due to their free-flowing nature, another potential application is wearable and medical devices, where material deformability is important. [ 4 ] [ 3 ]
Liquid metal is sometimes used as a thermal interface material between coolers and processors because of its high thermal conductivity. The PlayStation 5 video game console uses liquid metal to cool components inside the console. [ 11 ] Liquid metal cooled nuclear reactors also use them.
Liquid metal can sometimes be used for biological applications, i.e., making interconnects that flex without fatigue. As Galinstan is not particularly toxic, wires made from silicone with a core of liquid metal would be ideal for intracardiac pacemakers and neural implants where delicate brain tissue cannot tolerate a conventional solid implant. In fact, a wire constructed of this material can be stretched to 3 or even 5 times its length and still conduct electricity, returning to its original size and shape with no loss. [ 12 ]
Due to their unique combination of high surface tension and fluidic deformability , liquid metals are useful for creating soft actuators . [ 13 ] [ 14 ] [ 15 ] The force-generating mechanisms in liquid metal actuators are typically achieved by modulation of their surface tension. [ 16 ] [ 17 ] [ 18 ] For instance, a liquid metal droplet can be designed to bridge two moving parts (e.g., in robotic systems ) in such a way to generate contraction when the surface tension increases. [ 19 ] The principles of muscle-like contraction in liquid metal actuators have been studied for their potential as a next-generation artificial muscle that offers several liquid-specific advantages over other solid materials. [ 20 ]
Liquid-mirror telescopes can use liquid metals formed into a parabola through a spinning tank to serve as the primary mirror of a reflecting telescope . [ 21 ]
The Spallation Neutron Source employs liquid metals as targets for generating pulsed neutron beams. | https://en.wikipedia.org/wiki/Liquid_metal |
A liquid metal cooled nuclear reactor ( LMR ) is a type of nuclear reactor where the primary coolant is a liquid metal . Liquid metal cooled reactors were first adapted for breeder reactor power generation. They have also been used to power nuclear submarines .
Due to their high thermal conductivity, metal coolants remove heat effectively, enabling high power density . This makes them attractive in situations where size and weight are at a premium, like on ships and submarines. Most water-based reactor designs are highly pressurized to raise the boiling point (thereby improving cooling capabilities), which presents safety and maintenance issues that liquid metal designs lack. Additionally, the high temperature of the liquid metal can be used to drive power conversion cycles with high thermodynamic efficiency. This makes them attractive for improving power output, cost effectiveness, and fuel efficiency in nuclear power plants.
Liquid metals, being electrically highly conductive, can be moved by electromagnetic pumps . [ 1 ] Disadvantages include difficulties associated with inspection and repair of a reactor immersed in opaque molten metal, and depending on the choice of metal, fire hazard risk (for alkali metals ), corrosion and/or production of radioactive activation products may be an issue.
Liquid metal coolant has been applied to both thermal- and fast-neutron reactors .
To date, most fast neutron reactors have been liquid metal cooled and so are called liquid metal cooled fast reactors (LMFRs). When configured as a breeder reactor (e.g. with surrounding material to breed fissile material; i.e. a breeding blanket), such reactors are called liquid metal fast breeder reactors (LMFBRs).
Suitable liquid metal coolants must have a low neutron capture cross section , must not cause excessive corrosion of the structural materials, and must have melting and boiling points that are suitable for the reactor's operating temperature .
Liquid metals generally have high boiling points , reducing the probability that the coolant can boil, which could lead to a loss-of-coolant accident . Low vapor pressure enables operation at near- ambient pressure , further dramatically reducing the probability of an accident. Some designs immerse the entire core and heat exchangers into a pool of coolant, virtually eliminating the risk that inner-loop cooling will be lost.
Clementine was the first liquid metal cooled nuclear reactor and used mercury coolant, thought to be the obvious choice since it is liquid at room temperature. However, because of disadvantages including high toxicity, high vapor pressure even at room temperature, low boiling point producing noxious fumes when heated, relatively low thermal conductivity, [ 2 ] and a high [ 3 ] neutron cross-section , it has fallen out of favor.
Sodium and NaK (a eutectic sodium-potassium alloy) do not corrode steel to any significant degree and are compatible with many nuclear fuels, allowing for a wide choice of structural materials. NaK was used as the coolant in the first breeder reactor prototype, the Experimental Breeder Reactor-1 , in 1951.
Sodium and NaK do, however, ignite spontaneously on contact with air and react violently with water, producing hydrogen gas. This was the case at the Monju Nuclear Power Plant in a 1995 accident and fire. Sodium is also the coolant used in the Russian BN reactor series and the Chinese CFR series in commercial operation today. [ 4 ] [ 5 ] Neutron activation of sodium also causes these liquids to become intensely radioactive during operation, though the half-life is short and therefore their radioactivity does not pose an additional disposal concern.
There are two proposals for a sodium cooled Gen IV LMFR , one based on oxide fuel, the other on the metal-fueled integral fast reactor .
Lead has excellent neutron properties (reflection, low absorption) and is a very potent radiation shield against gamma rays . The high boiling point of lead provides safety advantages as it can cool the reactor efficiently even if it reaches several hundred degrees Celsius above normal operating conditions. However, because lead has a high melting point and a high vapor pressure, it is tricky to refuel and service a lead cooled reactor. The melting point can be lowered by alloying the lead with bismuth , but lead-bismuth eutectic is highly corrosive to most metals [ 6 ] [ 7 ] used for structural materials.
Lead-bismuth eutectic allows operation at lower temperatures while preventing the freezing of the metal coolant in a lower temperature range ( eutectic point : 123.5 °C / 255.3 °F) . [ 6 ] [ 8 ]
Beside its highly corrosive character, [ 6 ] [ 7 ] its main disadvantage is the formation by neutron activation of 209 Bi (and subsequent beta decay ) of 210 Po ( T 1 ⁄ 2 = 138.38 day), a volatile alpha-emitter highly radiotoxic (the highest known radiotoxicity , above that of plutonium ).
Although tin today is not used as a coolant for working reactors because it builds a crust, [ 9 ] it can be a useful additional or replacement coolant at nuclear disasters or loss-of-coolant accidents . [ 10 ]
The Soviet November-class submarine K-27 and all seven Alfa-class submarines used reactors cooled by lead-bismuth eutectic and moderated with beryllium as their propulsion plants. ( VT-1 reactors in K-27 ; BM-40A and OK-550 reactors in others).
The second nuclear submarine, USS Seawolf was the only U.S. submarine to have a sodium-cooled, beryllium - moderated nuclear power plant. It was commissioned in 1957, but it had leaks in its superheaters , which were bypassed. In order to standardize the reactors in the fleet, [ citation needed ] the submarine's sodium-cooled, beryllium-moderated reactor was removed starting in 1958 and replaced with a pressurized water reactor .
Liquid metal cooled reactors were studied by Pratt & Whitney for use in nuclear aircraft as part of the Aircraft Nuclear Propulsion program. [ 11 ]
The Sodium Reactor Experiment was an experimental sodium-cooled graphite -moderated nuclear reactor (A Sodium-Graphite Reactor, or SGR) sited in a section of the Santa Susana Field Laboratory then operated by the Atomics International division of North American Aviation .
In July 1959, the Sodium Reactor Experiment suffered a serious incident involving the partial melting of 13 of 43 fuel elements and a significant release of radioactive gases. [ 12 ] The reactor was repaired and returned to service in September 1960 and ended operation in 1964. The reactor produced a total of 37 GW-h of electricity.
SRE was the prototype for the Hallam Nuclear Power Facility , another sodium-cooled graphite-moderated SGR that operated in Nebraska .
Fermi 1 in Monroe County, Michigan was an experimental, liquid sodium-cooled fast breeder reactor that operated from 1963 to 1972. It suffered a partial nuclear meltdown in 1963 and was decommissioned in 1975.
At Dounreay in Caithness , in the far north of Scotland , the United Kingdom Atomic Energy Authority (UKAEA) operated the Dounreay Fast Reactor (DFR), using NaK as a coolant, from 1959 to 1977, exporting 600 GW-h of electricity to the grid over that period. It was succeeded at the same site by PFR, the Prototype Fast Reactor , which operated from 1974 to 1994 and used liquid sodium as its coolant.
The Soviet BN-600 is sodium cooled. The BN-350 and U.S. EBR-II nuclear power plants were sodium cooled. EBR-I used a liquid metal alloy, NaK , for cooling. NaK is liquid at room temperature. Liquid metal cooling is also used in most fast neutron reactors including fast breeder reactors such as the Integral Fast Reactor .
Many Generation IV reactors studied are liquid metal cooled: | https://en.wikipedia.org/wiki/Liquid_metal_cooled_reactor |
Liquid metal embrittlement (also known as LME and liquid metal induced embrittlement ) is a phenomenon of practical importance, where certain ductile metals experience drastic loss in tensile ductility or undergo brittle fracture when exposed to specific liquid metals. Generally, tensile stress , either externally applied or internally present, is needed to induce embrittlement . Exceptions to this rule have been observed, as in the case of aluminium in the presence of liquid gallium . [ 1 ] This phenomenon has been studied since the beginning of the 20th century. Many of its phenomenological characteristics are known and several mechanisms have been proposed to explain it. [ 2 ] [ 3 ] The practical significance of liquid metal embrittlement is revealed by the observation that several steels experience ductility losses and cracking during hot-dip galvanizing or during subsequent fabrication. [ 4 ] Cracking can occur catastrophically and very high crack growth rates have been measured. [ 5 ]
Similar metal embrittlement effects can be observed even in the solid state, when one of the metals is brought close to its melting point; e.g. cadmium -coated parts operating at high temperature. This phenomenon is known as solid metal embrittlement . [ 6 ]
Liquid metal embrittlement is characterized by the reduction in the threshold stress intensity, true fracture stress or in the strain to fracture when tested in the presence of liquid metals as compared to that obtained in air / vacuum tests. The reduction in fracture strain is generally temperature dependent and a “ductility trough” is observed as the test temperature is decreased. [ 2 ] A ductile-to-brittle transition behaviour is also exhibited by many metal couples. The shape of the elastic region of the stress-strain curve is not altered, but the plastic region may be changed during LME. Very high crack propagation rates, varying from a few centimeters per second to several meters per second are induced in solid metals by the embrittling liquid metals. An incubation period and a slow pre-critical crack propagation stage generally precede the final fracture.
It is believed that there is specificity in the solid-liquid metal combinations experiencing LME. [ 7 ] There should be limited mutual solubilities for the metal couple to cause embrittlement. Excess solubility makes sharp crack propagation difficult, but no solubility condition prevents wetting of the solid surfaces by liquid metal and prevents LME. The presence of an oxide layer on the solid metal surface also prevents good contact between the two metals and stops LME. The chemical compositions of the solid and liquid metals affect the severity of embrittlement. The addition of third elements to the liquid metal may increase or decrease the embrittlement and alter the temperature region over which embrittlement is seen. Metal combinations which form intermetallic compounds do not cause LME. There are a wide variety of LME couples. [ 3 ] Most technologically important are the LME of aluminum and steel alloys.
Alloying of the solid metal alters its LME. Some alloying elements may increase the severity while others may prevent LME. The action of the alloying element is known to be segregation to grain boundaries of the solid metal and alteration of the grain boundary properties. Accordingly, maximum LME is seen in cases where alloy addition elements have saturated the grain boundaries of the solid metal. [ 2 ] The hardness and deformation behaviour of the solid metal affects its susceptibility to LME. Generally, harder metals are more severely embrittled. Grain size greatly influences LME. Solids with larger grains are more severely embrittled and the fracture stress varies inversely with the square root of grain diameter. Also the brittle to ductile transition temperature is increased by increasing grain size.
The interfacial energy between the solid and liquid metals and the grain boundary energy of the solid metal greatly influence LME. These energies depend upon the chemical compositions of the metal couple. [ 2 ]
External parameters like temperature, strain rate, stress and time of exposure to the liquid metal prior to testing affect LME. Temperature produces a ductility trough and a ductile to brittle transition behaviour in the solid metal. The temperature range of the trough as well as the transition temperature are altered by the composition of the liquid and solid metals, the structure of the solid metal and other experimental parameters. The lower limit of the ductility trough generally coincides with the melting point of the liquid metal. The upper limit is strain rate sensitive. Temperature also affects the kinetics of LME.
An increase in strain rate increases the upper limit temperature as well as the crack propagation rate. In most metal couples LME does not occur below a threshold stress level.
Testing typically involves tensile specimens but more sophisticated testing using fracture mechanics specimens is also performed. [ 8 ] [ 9 ] [ 10 ] [ 11 ]
Many theories have been proposed for LME. [ 3 ] The major ones are listed below;
All of these models, with the exception of Robertson, [ 2 ] [ 12 ] utilize the concept of an adsorption-induced surface energy lowering of the solid metal as the central cause of LME. They have succeeded in predicting many of the phenomenological observations. However, quantitative prediction of LME is still elusive.
The most common liquid metal to cause embrittlement is mercury , as it is a common contaminant in the processing of hydrocarbons in petroleum reservoirs . [ 19 ] The embrittling effects of mercury were first recognized by Pliny the Elder circa 78 AD. [ 20 ] Mercury spills present an especially significant danger for airplanes. The aluminium-zinc-magnesium-copper alloy DTD 5050B is especially susceptible. The Al-Cu alloy DTD 5020A is less susceptible. Spilled elemental mercury can be immobilized and made relatively harmless by silver nitrate . [ 21 ]
On 1 January 2004, the Moomba, South Australia , natural gas processing plant operated by Santos suffered a major fire. The gas release that led to the fire was caused by the failure of a heat exchanger (cold box) inlet nozzle in the liquids recovery plant. The failure of the inlet nozzle was due to liquid metal embrittlement of the train B aluminium cold box by elemental mercury. [ 22 ]
Liquid metal embrittlement plays a central role in the novel Killer Instinct by Joseph Finder .
In the film Big Hero 6 , Honey Lemon, voiced by Genesis Rodriguez , uses liquid metal embrittlement in her lab. | https://en.wikipedia.org/wiki/Liquid_metal_embrittlement |
Liquid nitrogen ( LN 2 ) is nitrogen in a liquid state at low temperature . Liquid nitrogen has a boiling point of about −196 °C (−321 °F; 77 K). It is produced industrially by fractional distillation of liquid air . It is a colorless, mobile liquid whose viscosity is about one-tenth that of acetone (i.e. roughly one-thirtieth that of water at room temperature ). Liquid nitrogen is widely used as a coolant .
The diatomic character of the N 2 molecule is retained after liquefaction . The weak van der Waals interaction between the N 2 molecules results in little interatomic attraction. This is the cause of nitrogen's unusually low boiling point . [ 1 ]
The temperature of liquid nitrogen can readily be reduced to its freezing point −210 °C (−346 °F; 63 K) by placing it in a vacuum chamber pumped by a vacuum pump . [ 2 ] Liquid nitrogen's efficiency as a coolant is limited by the fact that it boils immediately on contact with a warmer object, enveloping the object in an insulating layer of nitrogen gas bubbles. This effect, known as the Leidenfrost effect , occurs when any liquid comes in contact with a surface which is significantly hotter than its boiling point. Faster cooling may be obtained by plunging an object into a slush of liquid and solid nitrogen rather than liquid nitrogen alone. [ 2 ]
As a cryogenic fluid that rapidly freezes living tissue, its handling and storage require thermal insulation . It can be stored and transported in vacuum flasks , the temperature being held constant at 77 K by slow boiling of the liquid. Depending on the size and design, the holding time of vacuum flasks ranges from a few hours to a few weeks. The development of pressurised super-insulated vacuum vessels has enabled liquid nitrogen to be stored and transported over longer time periods with losses reduced to 2 percent per day or less. [ 3 ]
Liquid nitrogen is a compact and readily transported source of dry nitrogen gas, as it does not require pressurization. Further, its ability to maintain temperatures far below the freezing point of water, specific heat of 1040 J ⋅kg −1 ⋅K −1 and heat of vaporization of 200 kJ⋅kg −1 makes it extremely useful in a wide range of applications, primarily as an open-cycle refrigerant , including:
The culinary use of liquid nitrogen is mentioned in an 1890 recipe book titled Fancy Ices authored by Agnes Marshall , [ 14 ] but has been employed in more recent times by restaurants in the preparation of frozen desserts, such as ice cream, which can be created within moments at the table because of the speed at which it cools food. [ 14 ] The rapidity of chilling also leads to the formation of smaller ice crystals, which provides the dessert with a smoother texture. [ 14 ] The technique is employed by chef Heston Blumenthal who has used it at his restaurant, The Fat Duck , to create frozen dishes such as egg and bacon ice cream. [ 14 ] [ 15 ] Liquid nitrogen has also become popular in the preparation of cocktails because it can be used to quickly chill glasses or freeze ingredients. [ 16 ] It is also added to drinks to create a smoky effect, which occurs as tiny droplets of the liquid nitrogen come into contact with the surrounding air, condensing the vapour that is naturally present. [ 16 ]
Nitrogen was first liquefied at the Jagiellonian University on 15 April 1883 by Polish physicists Zygmunt Wróblewski and Karol Olszewski . [ 17 ]
Because the liquid-to-gas expansion ratio of nitrogen is 1:694 at 20 °C (68 °F), a tremendous amount of force can be generated if liquid nitrogen is vaporized in an enclosed space. In an incident on January 12, 2006 at Texas A&M University , the pressure-relief devices of a tank of liquid nitrogen were malfunctioning and later sealed. As a result of the subsequent pressure buildup, the tank failed catastrophically. The force of the explosion was sufficient to propel the tank through the ceiling immediately above it, shatter a reinforced concrete beam immediately below it, and blow the walls of the laboratory 0.1–0.2 m off their foundations. [ 18 ] In January 2021, a line carrying liquid nitrogen ruptured at a poultry processing plant in the U.S. state of Georgia, killing six people and injuring 11 others. [ 19 ]
Because of its extremely low temperature, careless handling of liquid nitrogen and any objects cooled by it may result in cold burns . In that case, special gloves should be used while handling. However, a small splash or even pouring down skin will not burn immediately because of the Leidenfrost effect , the evaporating gas thermally insulates to some extent, like touching a hot element very briefly with a wet finger. If the liquid nitrogen manages to pool anywhere, it will burn severely.
As liquid nitrogen evaporates it reduces the oxygen concentration in the air and can act as an asphyxiant , especially in confined spaces . Nitrogen is odorless, colorless, and tasteless and may produce asphyxia without any sensation or prior warning. [ 20 ] [ 21 ] [ 22 ]
Oxygen sensors are sometimes used as a safety precaution when working with liquid nitrogen to alert workers of gas spills into a confined space. [ 23 ]
Vessels containing liquid nitrogen can condense oxygen from air. The liquid in such a vessel becomes increasingly enriched in oxygen (boiling point 90 K; −183 °C; −298 °F) as the nitrogen evaporates, and can cause violent oxidation of organic material. [ 24 ]
Ingestion of liquid nitrogen can cause severe internal damage, due to freezing of the tissues which come in contact with it and to the volume of gaseous nitrogen evolved as the liquid is warmed by body heat. In 1997, a physics student demonstrating the Leidenfrost effect by holding liquid nitrogen in his mouth accidentally swallowed the substance, resulting in near-fatal injuries. This was apparently the first case in medical literature of liquid nitrogen ingestion. [ 25 ] In 2012, a young woman in England had her stomach removed after ingesting a cocktail made with liquid nitrogen. [ 26 ]
Liquid nitrogen is produced commercially from the cryogenic distillation of liquified air or from the liquefaction of pure nitrogen derived from air using pressure swing adsorption . An air compressor is used to compress filtered air to high pressure; the high-pressure gas is cooled back to ambient temperature, and allowed to expand to a low pressure. The expanding air cools greatly (the Joule–Thomson effect ), and oxygen, nitrogen, and argon are separated by further stages of expansion and distillation. Small-scale production of liquid nitrogen is easily achieved using this principle. [ citation needed ] Liquid nitrogen may be produced for direct sale, or as a byproduct of manufacture of liquid oxygen used for industrial processes such as steelmaking . Liquid-air plants producing on the order of tons per day of product started to be built in the 1930s but became very common after the Second World War; a large modern plant may produce 3000 tons/day of liquid air products. [ 27 ] | https://en.wikipedia.org/wiki/Liquid_nitrogen |
Liquid Nitrogen Wash is a process mainly used for the production of ammonia synthesis gas within fertilizer production plants. It is usually the last purification step in the ammonia production process sequence upstream of the actual ammonia production . [ 1 ]
The purpose of the final purification step upstream of the actual ammonia production is to remove all components that are poisonous for the sensitive ammonia synthesis catalyst . [ 2 ] This can be done with the following concepts:
The liquid nitrogen wash has two principle functions: [ 1 ]
The carbon monoxide must be removed completely from the synthesis gas (i.e. syngas ) since it is poisonous for the sensitive ammonia synthesis catalyst . [ 4 ] The components argon and methane are inert gases within the ammonia synthesis loop, but would enrich there and call for a purge gas system with synthesis gas losses or additional expenditures for a purge gas separation unit.
The main sources for the supply of feed gases are partial oxidation processes.
Since the synthesis gas exiting the partial oxidation process consists mainly of carbon monoxide and hydrogen , usually a sulfur tolerant CO shift (i.e. water-gas shift reaction ) is installed in order to convert as much carbon monoxide into hydrogen as possible.
Shifting carbon monoxide and water into hydrogen also produces carbon dioxide , usually this is removed in an acid gas scrubbing process together with other sour gases as e.g. hydrogen sulfide (e.g. in a Rectisol Wash Unit). [ 1 ]
The liquid nitrogen wash consists of
Nitrogen is supplied from outside of the unit to be used for scrubbing as gaseous high pressure nitrogen, supplied by the Air separation Unit that usually also provides the oxygen for the upstream Partial Oxidation . [ 7 ] This gaseous high pressure nitrogen is partially liquefied in the process and is used as washing agent. In a so-called nitrogen wash column, the impurities carbon monoxide, argon and methane are washed out of the synthesis gas by means of this liquid nitrogen. These impurities are dissolved together with a small part of hydrogen and leave the column as the bottom stream. The purified gas leaves the column at the top. The now purified synthesis gas is warmed up and is mixed with the required amount of gaseous high pressure nitrogen in order to achieve the hydrogen to nitrogen ratio of 3 to 1, and can then be routed to the ammonia synthesis . [ 5 ] At operating pressures higher than about 50 bar(a), the refrigeration demand of the liquid nitrogen wash is covered by the Joule–Thomson effect , [ 4 ] and no additional external refrigeration, e.g. by vaporization of liquid nitrogen is required.
The liquid nitrogen wash is especially favorable when combined with the Rectisol Wash Unit. The combination and advantageous interconnections between a Rectisol Wash Unit and a liquid nitrogen wash lead to smaller equipment and better operability. The gas coming from the Rectisol Wash Unit can be sent to the Liquid Nitrogen Wash at low temperature (directly from the methanol absorber without being warmed up). [ 5 ] Since part of the purified gas is reheated in the Rectisol Wash Unit, small fluctuations in flow and temperatures can easily be compensated leading to best operability. To improve the hydrogen recovery, an integrated hydrogen recycle from the liquid nitrogen wash to the Rectisol Wash Unit can be installed, which uses the already existing recycle compressor of the Rectisol Wash Unit to recycle the hydrogen-rich flash gas from the liquid nitrogen wash back into the feed gas of the Rectisol Wash Unit. This leads to extremely high hydrogen recovery rates without any further equipment. | https://en.wikipedia.org/wiki/Liquid_nitrogen_wash |
Regarding biological membranes , the liquid ordered phase is a liquid crystalline phase of a lipid bilayer, and is of significant biological importance. It occurs in many lipid mixtures combining cholesterol with a phospholipid and/or sphingolipids e.g. sphingomyelin . This phase has been related to lipid rafts that may exist in plasma membranes .
The liquid ordered phase can be defined as:
This was first called the liquid ordered phase by Ipsen et al. (1987). However, it has also been called the LG I subgel phase by Huang et al. (1993) and the β phase by Vist and Davis (1990).
This biochemistry article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Liquid_ordered_phase |
Liquid oxygen , sometimes abbreviated as LOX or LOXygen , is a clear cyan liquid form of dioxygen O 2 . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard , [ 1 ] an application which is ongoing.
Liquid oxygen has a clear cyan color and is strongly paramagnetic : it can be suspended between the poles of a powerful horseshoe magnet . [ 2 ] Liquid oxygen has a density of 1.141 kg/L (1.141 g/ml), slightly denser than liquid water, and is cryogenic with a freezing point of 54.36 K (−218.79 °C; −361.82 °F) and a boiling point of 90.19 K (−182.96 °C; −297.33 °F) at 1 bar (14.5 psi). Liquid oxygen has an expansion ratio of 1:861 [ 3 ] [ 4 ] and because of this, it is used in some commercial and military aircraft as a transportable source of breathing oxygen. [ citation needed ]
Because of its cryogenic nature, liquid oxygen can cause the materials it touches to become extremely brittle. Liquid oxygen is also a very powerful oxidizing agent: organic materials will burn rapidly and energetically in liquid oxygen. Further, if soaked in liquid oxygen , some materials such as coal briquettes, carbon black , etc., can detonate unpredictably from sources of ignition such as flames, sparks or impact from light blows. Petrochemicals , including asphalt , often exhibit this behavior. [ 5 ]
The tetraoxygen molecule (O 4 ) was predicted in 1924 by Gilbert N. Lewis , who proposed it to explain why liquid oxygen defied Curie's law . [ 6 ] Modern computer simulations indicate that, although there are no stable O 4 molecules in liquid oxygen, O 2 molecules do tend to associate in pairs with antiparallel spins , forming transient O 4 units. [ 7 ]
Liquid nitrogen has a lower boiling point at −196 °C (77 K) than oxygen's −183 °C (90 K), and vessels containing liquid nitrogen can condense oxygen from air: when most of the nitrogen has evaporated from such a vessel, there is a risk that liquid oxygen remaining can react violently with organic material. Conversely, liquid nitrogen or liquid air can be oxygen-enriched by letting it stand in open air; atmospheric oxygen dissolves in it, while nitrogen evaporates preferentially. [ citation needed ]
The surface tension of liquid oxygen at its normal pressure boiling point is 13.2 dyn/cm (13.2 mN/m). [ 8 ]
In commerce, liquid oxygen is classified as an industrial gas and is widely used for industrial and medical purposes. Liquid oxygen is obtained from the oxygen found naturally in air by fractional distillation in a cryogenic air separation plant . [ citation needed ]
Air forces have long recognized the strategic importance of liquid oxygen, both as an oxidizer and as a supply of gaseous oxygen for breathing in hospitals and high-altitude aircraft flights. In 1985, the USAF started a program of building its own oxygen-generation facilities at all major consumption bases. [ 9 ] [ 10 ]
Liquid oxygen is the most common cryogenic liquid oxidizer propellant for spacecraft rocket applications, usually in combination with liquid hydrogen , kerosene or methane . [ 11 ] [ 12 ]
Liquid oxygen was used in the first liquid fueled rocket . The World War II V-2 missile also used liquid oxygen under the name A-Stoff and Sauerstoff . In the 1950s, during the Cold War both the United States' Redstone and Atlas rockets, and the Soviet R-7 Semyorka used liquid oxygen. Later, in the 1960s and 1970s, the ascent stages of the Apollo Saturn rockets , and the Space Shuttle main engines used liquid oxygen. [ citation needed ]
As of 2025, many active rockets use liquid oxygen: | https://en.wikipedia.org/wiki/Liquid_oxygen |
First demonstrated in 2008, [ 1 ] liquid-phase exfoliation (LPE) is a solution-processing method which is used to convert layered crystals into two-dimensional nanosheets in large quantities. [ 2 ] It is currently one of the pillar methods for producing 2D nanosheets. [ 3 ] According to IDTechEx, the family of exfoliation techniques which are directly or indirectly descended from LPE now make up over 60% of global graphene production capacity. [ 4 ]
This method involves adding powdered layered crystals, for example of graphite, to appropriate solvents and inserting energy, often by ultrasonication , although high-shear mixing [ 5 ] is often commonly used. The addition of energy causes a combination of fragmentation and exfoliation resulting in the removal of small nanosheets from the layered crystals. [ 6 ] In this way graphite can be converted into large quantities of graphene nanosheets. [ 7 ] In general, these nanosheets tend to be a few monolayers thick and of lateral sizes ranging from tens of nanometers to many microns. [ 8 ] These dispersed nanosheets form quasi stable suspensions so long as solvents used have surface energies similar to that of the nanosheets. Dispersed concentrations of order 1 gram per litre can be achieved. In addition to solvents, it is also possible to use molecular stabilizers, for example surfactants or polymers to coat the nanosheets and stabilise them against regaggregation. [ 9 ] This has the advantage that it allows nanosheets to be suspended in water.
Although this method was first applied to exfoliate graphite to yield graphene nanosheets, it has since been used to produce a wide range of 2D materials including molybdenum disulfide , tungsten diselenide , boron nitride , nickel(II) hydroxide , germanium monosulfide , SnP 3 , and black phosphorus . The liquid suspensions produced by liquid phase exfoliation can be used to create a range of functional structures. For example, they can be printed into thin films and networks using standard techniques such as inkjet printing . [ 10 ]
Printed structures have been used in a range of applications in areas included printed electronics, sensors and nanocomposites . Related methods include exfoliation by wet ball milling , homogenization, microfluidization and wet jet milling . [ 11 ] Liquid phase exfoliation is different from other liquid exfoliation methods, for example the production of graphene oxide , because it is much less destructive, leaving minimal defects in the basal planes of the nanosheets. It has recently emerged that LPE can also be used to convert non-layered crystals into quasi-2D nanoplatelets . [ 12 ]
Liquid phase exfoliation was first described in detail in a paper by a research team in Ireland in 2008, [ 14 ] although a very short description of a similar process was published by the Manchester group around the same time. [ 15 ] While other papers had previously described methods to exfoliate layered crystals in liquids, [ 16 ] these papers were the first to describe exfoliation in liquids without any previous ion intercalation or chemical treatment.
LPE involves inserting layered crystals into appropriate stabilizing liquids and then adding energy to remove nanosheets from the layered crystals. A number of different methods have been used to supply energy to the liquid. The earliest and most common is ultrasonication. [ 17 ] In order to scaleup the process, high shear mixing was introduced in 2014. [ 18 ] This method proved extremely useful and inspired a number of other methods of generating shear in the suspension, including wet ball milling, homogenization, microfluidization and wet jet milling. [ 19 ]
The simplest stabilizing liquids are solvents with surface energy close to the layered crystal being exfoliated. In practice, liquids with surface tensions close to 70 mJ/m 2 are used. [ 20 ] In addition aqueous surfactant solutions are often used. [ 21 ] Less common, but useful for certain applications, is using molecular or polymeric additives to stabilise the exfoliated nanosheets. [ 22 ] [ 23 ] [ 24 ]
A very wide range of 2D materials have been produced by LPE. The first material to be exfoliated was graphene in 2008. This was followed in 2011 by the exfoliation of BN, MoS2 and WS2. [ 25 ] Since, the a wide range of 2D materials have been exfoliated including molybdenum diselenide, tungsten diselenide, gallium sulphide, molybdemum trioxide, nickel(II) hydroxide, germanium monosulfide, SnP3, black phosphorus etc. [ 26 ]
Recent work has shown that liquid phase exfoliation can be used to produce 2D-nanoplatelets from non-layered 3D-strongly bonded bulk materials. [ 27 ] This is intuitively unexpected as these 3D-solid bulk crystals consists of strong bonds in all the three-directions. Nevertheless, many non-layered materials such as boron, silicon, germanium, iron disulfide, iron oxide, iron trifluoride, manganese telluride, have been converted to 2D nanoplatelets when sonicated in appropriate solvents. [ 28 ] This raises many open questions on the mechanism of liquid-phase exfoliation process. [ 29 ] For layered materials, the energy required to break inter-plane (perdominately van der Waals) bonds forces is small compared to that required to break in-plane ionic or covalent bonds. Then, the exfoliation procedure results in the formation of 2D-nanosheets. [ 30 ] However, for non-layered 3D-strongly bonded materials, with minimal difference in bonding between different atomic planes, there is no "easily exfoliated" direction and sonication should yield quasi spherical particles. [ 31 ] Nevertheless, near isotropic materials such as silicon have been exfoliated to give high-aspect ratio platelets. [ 32 ] Therefore, developing an understanding of the mechanisms by which non-layered materials are exfoliated will be important, in particular because the application scope of such nonlayered 2D-nanoplatelets is broad, ranging from biomedical applications to energy storage to opto-electronics. [ 33 ] | https://en.wikipedia.org/wiki/Liquid_phase_exfoliation |
Propane ( / ˈ p r oʊ p eɪ n / ) is a three- carbon alkane with the molecular formula C 3 H 8 . It is a gas at standard temperature and pressure , but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is often a constituent of liquefied petroleum gas (LPG), which is commonly used as a fuel in domestic and industrial applications and in low-emissions public transportation; other constituents of LPG may include propylene , butane , butylene , butadiene , and isobutylene . Discovered in 1857 by the French chemist Marcellin Berthelot , it became commercially available in the US by 1911. Propane has lower volumetric energy density than gasoline or coal, but has higher gravimetric energy density than them and burns more cleanly. [ 6 ]
Propane gas has become a popular choice for barbecues and portable stoves because its low −42 °C boiling point makes it vaporise inside pressurised liquid containers (it exists in two phases, vapor above liquid). It retains its ability to vaporise even in cold weather, making it better-suited for outdoor use in cold climates than alternatives with higher boiling points like butane. [ 7 ] LPG powers buses, forklifts, automobiles, outboard boat motors, and ice resurfacing machines , and is used for heat and cooking in recreational vehicles and campers . Propane is becoming popular as a replacement refrigerant (R290) for heatpumps also as it offers greater efficiency than the current refrigerants: R410A / R32, higher temperature heat output and less damage to the atmosphere for escaped gasses—at the expense of high gas flammability. [ 8 ]
Propane was first synthesized by the French chemist Marcellin Berthelot in 1857 during his researches on hydrogenation . Berthelot made propane by heating propylene dibromide (C 3 H 6 Br 2 ) with potassium iodide and water. [ 9 ] [ 10 ] : p. 9, §1.1 [ 11 ] Propane was found dissolved in Pennsylvanian light crude oil by Edmund Ronalds in 1864. [ 12 ] [ 13 ] Walter O. Snelling of the U.S. Bureau of Mines highlighted it as a volatile component in gasoline in 1910, which marked the "birth of the propane industry" in the United States. [ 14 ] The volatility of these lighter hydrocarbons caused them to be known as "wild" because of the high vapor pressures of unrefined gasoline. On March 31, 1912, The New York Times reported on Snelling's work with liquefied gas, saying "a steel bottle will carry enough gas to light an ordinary home for three weeks". [ 15 ]
It was during this time that Snelling — in cooperation with Frank P. Peterson, Chester Kerr, and Arthur Kerr — developed ways to liquefy the LP gases during the refining of gasoline. [ 14 ] Together, they established American Gasol Co., the first commercial marketer of propane. Snelling had produced relatively pure propane by 1911, and on March 25, 1913, his method of processing and producing LP gases was issued patent #1,056,845. [ 14 ] A separate method of producing LP gas through compression was developed by Frank Peterson and its patent was granted on July 2, 1912. [ 16 ]
The 1920s saw increased production of LP gases, with the first year of recorded production totaling 223,000 US gallons (840 m 3 ) in 1922. In 1927, annual marketed LP gas production reached 1 million US gallons (3,800 m 3 ), and by 1935, the annual sales of LP gas had reached 56 million US gallons (210,000 m 3 ). Major industry developments in the 1930s included the introduction of railroad tank car transport, gas odorization, and the construction of local bottle-filling plants. The year 1945 marked the first year that annual LP gas sales reached a billion gallons. By 1947, 62% of all U.S. homes had been equipped with either natural gas or propane for cooking. [ 14 ]
In 1950, 1,000 propane-fueled buses were ordered by the Chicago Transit Authority , and by 1958, sales in the U.S. had reached 7 billion US gallons (26,000,000 m 3 ) annually. In 2004, it was reported to be a growing $8-billion to $10-billion industry with over 15 billion US gallons (57,000,000 m 3 ) of propane being used annually in the U.S. [ 17 ]
During the COVID-19 pandemic , propane shortages were reported in the United States due to increased demand. [ 18 ] [ 19 ] [ 20 ]
The " prop- " root found in "propane" and names of other compounds with three-carbon chains was derived from " propionic acid ", [ 21 ] which in turn was named after the Greek words protos (meaning first) and pion (fat), as it was the "first" member of the series of fatty acids . [ 22 ]
Propane is a colorless, odorless gas. Ethyl mercaptan is added as a safety precaution as an odorizer , [ 23 ] and is commonly called a "rotten egg" smell. [ 24 ] At normal pressure it liquifies below its boiling point at −42 °C and solidifies below its melting point at −187.7 °C. Propane crystallizes in the space group P2 1 /n. [ 25 ] [ 26 ] The low space-filling of 58.5% (at 90 K), due to the bad stacking properties of the molecule, is the reason for the particularly low melting point.
Propane undergoes combustion reactions in a similar fashion to other alkanes . In the presence of excess oxygen, propane burns to form water and carbon dioxide . C 3 H 8 + 5 O 2 ⟶ 3 CO 2 + 4 H 2 O + heat {\displaystyle {\ce {C3H8 + 5 O2 -> 3 CO2 + 4 H2O + heat}}} When insufficient oxygen is present for complete combustion, carbon monoxide , soot ( carbon ), or both, are formed as well: C 3 H 8 + 9 2 O 2 ⟶ 2 CO 2 + CO + 4 H 2 O + heat {\displaystyle {\ce {C3H8 + 9/2 O2 -> 2 CO2 + CO + 4 H2O + heat}}} C 3 H 8 + 2 O 2 ⟶ 3 C + 4 H 2 O + heat {\displaystyle {\ce {C3H8 + 2 O2 -> 3 C + 4 H2O + heat}}} The complete combustion of propane produces about 50 MJ/kg of heat. [ 27 ]
Propane combustion is much cleaner than that of coal or unleaded gasoline. Propane's per-BTU production of CO 2 is almost as low as that of natural gas. [ 28 ] Propane burns hotter than home heating oil or diesel fuel because of the very high hydrogen content. The presence of C–C bonds , plus the multiple bonds of propylene and butylene , produce organic exhausts besides carbon dioxide and water vapor during typical combustion. These bonds also cause propane to burn with a visible flame.
The enthalpy of combustion of propane gas where all products return to standard state, for example where water returns to its liquid state at standard temperature (known as higher heating value ), is (2,219.2 ± 0.5) kJ/mol, or (50.33 ± 0.01) MJ/kg. [ 27 ]
The enthalpy of combustion of propane gas where products do not return to standard state, for example where the hot gases including water vapor exit a chimney, (known as lower heating value ) is −2043.455 kJ/mol. [ 29 ] The lower heat value is the amount of heat available from burning the substance where the combustion products are vented to the atmosphere; for example, the heat from a fireplace when the flue is open.
The density of propane gas at 25 °C (77 °F) is 1.808 kg/m 3 , about 1.5× the density of air at the same temperature. The density of liquid propane at 25 °C (77 °F) is 0.493 g/cm 3 , which is equivalent to 4.11 pounds per U.S. liquid gallon or 493 g/L. Propane expands at 1.5% per 10 °F. Thus, liquid propane has a density of approximately 4.2 pounds per gallon (504 g/L) at 60 °F (15.6 °C). [ 30 ]
As the density of propane changes with temperature, this fact must be considered every time when the application is connected with safety or custody transfer operations. [ 31 ]
Propane is a popular choice for barbecues and portable stoves because the low boiling point of −42 °C (−44 °F) makes it vaporize as soon as it is released from its pressurized container. Therefore, no carburetor or other vaporizing device is required; a simple metering nozzle suffices.
Blends of pure, dry "isopropane" [isobutane/propane mixtures of propane (R-290) and isobutane (R-600a)] can be used as the circulating refrigerant in suitably constructed compressor-based refrigeration. [ 32 ] Compared to fluorocarbons, propane has a negligible ozone depletion potential and very low global warming potential (having a GWP value of 0.072, [ 33 ] 13.9 times lower than the GWP of carbon dioxide) and can serve as a functional replacement for R-12 , R-22 , R-134a , and other chlorofluorocarbon or hydrofluorocarbon refrigerants in conventional stationary refrigeration and air conditioning systems. [ 34 ] Because its global warming effect is far less than current refrigerants, propane was chosen as one of five replacement refrigerants approved by the EPA in 2015, for use in systems specially designed to handle its flammability. [ 35 ]
Such substitution is widely prohibited or discouraged in motor vehicle air conditioning systems, on the grounds that using flammable hydrocarbons in systems originally designed to carry non-flammable refrigerant presents a significant risk of fire or explosion. [ 36 ]
Vendors and advocates of hydrocarbon refrigerants argue against such bans on the grounds that there have been very few such incidents relative to the number of vehicle air conditioning systems filled with hydrocarbons. [ 37 ] [ 38 ]
Propane is also instrumental in providing off-the-grid refrigeration, as the energy source for a gas absorption refrigerator and is commonly used for camping and recreational vehicles.
It has also been proposed to use propane as a refrigerant in heat pumps . [ 39 ]
Since it can be transported easily, it is a popular fuel for home heat and backup electrical generation in sparsely populated areas that do not have natural gas pipelines. In June 2023, Stanford researchers found propane combustion emitted detectable and repeatable levels of benzene that in some homes raised indoor benzene concentrations above well-established health benchmarks. The research also shows that gas and propane fuels appear to be the dominant source of benzene produced by cooking. [ 40 ]
In rural areas of North America, as well as northern Australia, propane is used to heat livestock facilities, in grain dryers, and other heat-producing appliances. When used for heating or grain drying it is usually stored in a large, permanently-placed cylinder which is refilled by a propane-delivery truck. As of 2014 [update] , 6.2 million American households use propane as their primary heating fuel. [ 41 ]
In North America, local delivery trucks with an average cylinder size of 3,000 US gallons (11 m 3 ), fill up large cylinders that are permanently installed on the property, or other service trucks exchange empty cylinders of propane with filled cylinders. Large tractor-trailer trucks, with an average cylinder size of 10,000 US gallons (38 m 3 ), transport propane from the pipeline or refinery to the local bulk plant. The bobtail tank truck is not unique to the North American market, though the practice is not as common elsewhere, and the vehicles are generally called tankers . In many countries, propane is delivered to end-users via small or medium-sized individual cylinders, while empty cylinders are removed for refilling at a central location.
There are also community propane systems, with a central cylinder feeding individual homes. [ 42 ]
In the U.S., over 190,000 on-road vehicles use propane, and over 450,000 forklifts use it for power. It is the third most popular vehicle fuel in the world, [ 43 ] behind gasoline and diesel fuel . In other parts of the world, propane used in vehicles is known as autogas. In 2007, approximately 13 million vehicles worldwide use autogas. [ 43 ]
The advantage of propane in cars is its liquid state at a moderate pressure. This allows fast refill times, affordable fuel cylinder construction, and price ranges typically just over half that of gasoline. Meanwhile, it is noticeably cleaner (both in handling, and in combustion), results in less engine wear (due to carbon deposits) without diluting engine oil (often extending oil-change intervals), and until recently [ when? ] was relatively low-cost in North America. The octane rating of propane is relatively high at 110. In the United States the propane fueling infrastructure is the most developed of all alternative vehicle fuels. Many converted vehicles have provisions for topping off from "barbecue bottles". Purpose-built vehicles are often in commercially owned fleets, and have private fueling facilities. A further saving for propane fuel vehicle operators, especially in fleets, is that theft is much more difficult than with gasoline or diesel fuels.
Propane is also used as fuel for small engines , especially those used indoors or in areas with insufficient fresh air and ventilation to carry away the more toxic exhaust of an engine running on gasoline or diesel fuel. More recently, [ when? ] there have been lawn-care products like string trimmers , lawn mowers and leaf blowers intended for outdoor use, but fueled by propane in order to reduce air pollution . [ 44 ]
Many heavy-duty highway trucks use propane as a boost, where it is added through the turbocharger, to mix with diesel fuel droplets. Propane droplets' very high hydrogen content helps the diesel fuel to burn hotter and therefore more completely. This provides more torque, more horsepower, and a cleaner exhaust for the trucks. It is normal for a 7-liter medium-duty diesel truck engine to increase fuel economy by 20 to 33 percent when a propane boost system is used. It is cheaper because propane is much cheaper than diesel fuel. The longer distance a cross-country trucker can travel on a full load of combined diesel and propane fuel means they can maintain federal hours of work rules with two fewer fuel stops in a cross-country trip. Truckers, tractor pulling competitions, and farmers have been using a propane boost system for over forty years [ when? ] in North America.
The North American standard grade of automotive-use propane is rated HD-5 (Heavy Duty 5%). HD-5 grade has a maximum of 5 percent butane, but propane sold in Europe has a maximum allowable amount of butane of 30 percent, meaning it is not the same fuel as HD-5. The LPG used as auto fuel and cooking gas in Asia and Australia also has very high butane content.
Propylene (also called propene) can be a contaminant of commercial propane. Propane containing too much propene is not suited for most vehicle fuels. HD-5 is a specification that establishes a maximum concentration of 5% propene in propane. Propane and other LP gas specifications are established in ASTM D-1835. [ 46 ] All propane fuels include an odorant , almost always ethanethiol , so that the gas can be smelled easily in case of a leak. Propane as HD-5 was originally intended for use as vehicle fuel. HD-5 is currently being used in all propane applications.
Typically in the United States and Canada, LPG is primarily propane (at least 90%), while the rest is mostly ethane , propylene , butane , and odorants including ethyl mercaptan . [ 47 ] [ 48 ] This is the HD-5 standard, (maximum allowable propylene content, and no more than 5% butanes and ethane) defined by the American Society for Testing and Materials by its Standard 1835 for internal combustion engines. Not all products labeled "LPG" conform to this standard, however. In Mexico, for example, gas labeled "LPG" may consist of 60% propane and 40% butane. "The exact proportion of this combination varies by country, depending on international prices, on the availability of components and, especially, on the climatic conditions that favor LPG with higher butane content in warmer regions and propane in cold areas". [ 49 ]
Propane is bought and stored in a liquid form, LPG. It can easily be stored in a relatively small space.
By comparison, compressed natural gas (CNG) cannot be liquefied by compression at normal temperatures, as these are well above its critical temperature . As a gas, very high pressure is required to store useful quantities. This poses the hazard that, in an accident, just as with any compressed gas cylinder (such as a CO 2 cylinder used for a soda concession) a CNG cylinder may burst with great force, or leak rapidly enough to become a self-propelled missile. Therefore, CNG is much less efficient to store than propane, due to the large cylinder volume required. An alternative means of storing natural gas is as a cryogenic liquid in an insulated container as liquefied natural gas (LNG). This form of storage is at low pressure and is around 3.5 times as efficient as storing it as CNG.
Unlike propane, if a spill occurs, CNG will evaporate and dissipate because it is lighter than air.
Propane is much more commonly used to fuel vehicles than is natural gas, because that equipment costs less. Propane requires just 1,220 kilopascals (177 psi) of pressure to keep it liquid at 37.8 °C (100 °F). [ 50 ]
Propane is a simple asphyxiant . [ 51 ] Unlike natural gas , it is denser than air. It may accumulate in low spaces and near the floor. When abused as an inhalant , it may cause hypoxia (lack of oxygen), pneumonia , cardiac failure or cardiac arrest . [ 52 ] [ 53 ] Propane has low toxicity since it is not readily absorbed and is not biologically active . Commonly stored under pressure at room temperature, propane and its mixtures will flash evaporate at atmospheric pressure and cool well below the freezing point of water. The cold gas, which appears white due to moisture condensing from the air, may cause frostbite.
Propane is denser than air. If a leak in a propane fuel system occurs, the vaporized gas will have a tendency to sink into any enclosed area and thus poses a risk of explosion and fire. The typical scenario is a leaking cylinder stored in a basement; the propane leak drifts across the floor to the pilot light on the furnace or water heater, and results in an explosion or fire. This property makes propane generally unsuitable as a fuel for boats. In 2007, a heavily investigated vapor-related explosion occurred in Ghent, West Virginia, U.S., killing four people and completely destroying the Little General convenience store on Flat Top Road , causing several injuries. [ 54 ] [ 55 ]
Another hazard associated with propane storage and transport is known as a BLEVE or boiling liquid expanding vapor explosion . The Kingman Explosion involved a railroad tank car in Kingman, Arizona, U.S., in 1973 during a propane transfer. The fire and subsequent explosions resulted in twelve fatalities and numerous injuries. [ 56 ]
Propane is produced as a by-product of two other processes, natural gas processing and petroleum refining . The processing of natural gas involves removal of butane , propane, and large amounts of ethane from the raw gas, to prevent condensation of these volatiles in natural gas pipelines. Additionally, oil refineries produce some propane as a by-product of cracking petroleum into gasoline or heating oil.
The supply of propane cannot easily be adjusted to meet increased demand, because of the by-product nature of propane production. About 90% of U.S. propane is domestically produced. [ 41 ] The United States imports about 10% of the propane consumed each year, with about 70% of that coming from Canada via pipeline and rail. The remaining 30% of imported propane comes to the United States from other sources via ocean transport.
After it is separated from the crude oil, North American propane is stored in huge salt caverns . Examples of these are Fort Saskatchewan , Alberta ; Mont Belvieu, Texas ; and Conway, Kansas . These salt caverns [ 57 ] can store 80,000,000 barrels (13,000,000 m 3 ) of propane.
As of October 2013 [update] , the retail cost of propane was approximately $2.37 per gallon, or roughly $25.95 per 1 million BTUs. [ 58 ] This means that filling a 500-gallon propane tank, which is what households that use propane as their main source of energy usually require, cost $948 (80% of 500 gallons or 400 gallons), a 7.5% increase on the 2012–2013 winter season average US price. [ 59 ] However, propane costs per gallon change significantly from one state to another: the Energy Information Administration (EIA) quotes a $2.995 per gallon average on the East Coast for October 2013, [ 60 ] while the figure for the Midwest was $1.860 for the same period. [ 61 ]
As of December 2015 [update] , the propane retail cost was approximately $1.97 per gallon, [ 62 ] which meant filling a 500-gallon propane tank to 80% capacity costed $788, a 16.9% decrease or $160 less from November 2013. Similar regional differences in prices are present with the December 2015 EIA figure for the East Coast at $2.67 per gallon and the Midwest at $1.43 per gallon. [ 62 ]
As of August 2018 [update] , the average US propane retail cost was approximately $2.48 per gallon. The wholesale price of propane in the U.S. always drops in the summer as most homes do not require it for home heating. The wholesale price of propane in the summer of 2018 was between 86 cents to 96 cents per U.S. gallon, based on a truckload or railway car load. The price for home heating was exactly double that price; at 95 cents per gallon wholesale, a home-delivered price was $1.90 per gallon if ordered 500 gallons at a time. Prices in the Midwest are always less than in California. Prices for home delivery always go up near the end of August or the first few days of September when people start ordering their home tanks to be filled. [ 63 ] | https://en.wikipedia.org/wiki/Liquid_propane |
A liquid rheostat or water rheostat [ 1 ] or salt water rheostat is a type of variable resistor .
This may be used as a dummy load or as a starting resistor for large slip ring motors.
In the simplest form it consists of a tank containing brine or other electrolyte solution, in which electrodes are submerged to create an electrical load . The electrodes may be raised or lowered into the liquid to respectively increase or decrease the electrical resistance of the load. To stabilize the load, the mixture must not be allowed to boil.
Modern designs use stainless steel electrodes, and sodium carbonate, or other salts, and do not use the container as one electrode. In some designs the electrodes are fixed and the liquid is raised and lowered by an external cylinder or pump. Motor start systems used for frequent and rapid starts and re-starts, thus a high heat load to the rheostats, may include water circulation to external heat exchangers. In such cases anti-freeze and anti-corrosion additives must be carefully chosen to not change the resistance or support the growth of algae or bacteria.
The salt water rheostat operates at unity power factor and presents a resistance with negligible series inductance compared to a wire wound equivalent, and was widely used by generator assemblers, until 20 years ago, [ as of? ] as a matter of course. They are still sometimes constructed on-site for the commissioning of large diesel generators in remote places, where discarded oil drums and scaffold tubes may form an improvised tank and electrodes.
Typically a traditional liquid rheostat consists of a steel cylinder (the negative ), about 5 feet (1.5 m) in size, standing on insulators, in which was suspended a hollow steel cylinder. This acted as the positive electrode and was supported by a steel rope and insulator from an adjustable pulley. The water pipe connection included an insulated section. The tank contained salt water, but not at the concentration that could be described as “brine”. The whole device was fenced off for safety.
Operation was very simple, as adding more salt, more water or varying the height of the centre electrode would vary the load. [ 2 ] The load proved to be quite stable, varying only slightly as the water heated up, which never came to boil. Power dissipation was about 1 megawatt , at a potential of about 700 volts and current of about 1,500 amperes .
Modern designs use stainless steel electrodes, and sodium carbonate, or other salts, and do not use the container as one electrode.
Systems with frequent starting may include water circulation to external heat exchangers. In such cases anti-freeze and anti-corrosion additives must be carefully chosen to not change the resistance or support the growth of algae or bacteria.
An advantage is silent operation, with none of the fan noise of current resistive grid designs .
Disadvantages include:
Railways commonly used salt water load banks in the 1950s to test the output power of diesel-electric locomotives . [ 3 ] They were subsequently replaced by specially designed resistive load banks . Some early three-phase AC electric locomotives also used liquid rheostats for starting up the motors and balancing load between multiple locomotives. [ 4 ]
Liquid rheostats were sometimes used in large (thousands of kilowatts/horsepower) wound rotor motor drives, to control the rotor circuit resistance and so the speed of the motor. Electrode position could be adjusted with a small electrically operated winch or a pneumatic cylinder. A cooling pump and heat exchanger were provided to allow slip energy to be dissipated into process water or other water system. [ 5 ]
Massive rheostats were once used for dimming theatrical lighting, but solid-state components have taken their place in most high-wattage applications. [ 6 ]
High voltage distribution networks use fixed electrolyte resistors to ground the neutral, to provide a current limiting action, so that the voltage across the ground during fault is kept to a safe level. Unlike a solid resistor, the liquid resistor is self healing in the event of overload. Normally the resistance is set up during commissioning, and then left fixed. [ 7 ]
Modern motor starters [ 8 ] are totally enclosed and the electrode movement is servo motor controlled. Typically a 1 tonne tank will start a 1 megawatt slip ring type motor, but there is considerable variation in start time depending on application.
The fully salt-water load bank dates from an earlier, less regulated and litigious era. To pass current safety legislation, a more enclosed design is required.
They are no more dangerous than electrode heaters , which work on the same principle, but with plain water, or electrical immersion heaters, provided the correct precautions are used. This requires connecting the container to both ground and neutral and breaking all poles with a linked over-current circuit breaker . If in the open, safety barriers are required. | https://en.wikipedia.org/wiki/Liquid_rheostat |
The liquid rope coil effect or liquid rope coiling is a fluid mechanics phenomenon characterized by the steadily rotating helical structure formed when pouring a thin stream of viscous fluid from a sufficient height onto a surface, resulting from a buckling instability in which the initially vertical fluid stream becomes unstable to bending deformation under axial compressive stress . [ 1 ]
The rope can change shape in three ways: stretching, bending, and twisting. Each deformation faces resistance in the form of viscous forces. The rope's shape is influenced by the balance between these forces and the fluid's inertia . Surface tension , usually significant in fluid dynamics, plays only a minor role. [ 2 ] | https://en.wikipedia.org/wiki/Liquid_rope_coil_effect |
Liquid scintillation counting is the measurement of radioactive activity of a sample material which uses the technique of mixing the active material with a liquid scintillator (e.g. zinc sulfide ), and counting the resultant photon emissions . The purpose is to allow more efficient counting due to the intimate contact of the activity with the scintillator . It is generally used for alpha particle or beta particle detection.
Samples are dissolved or suspended in a "cocktail" containing a solvent (historically aromatic organics such as xylene or toluene , but more recently less hazardous solvents are used), typically some form of a surfactant , and "fluors" or scintillators which produce the light measured by the detector. Scintillators can be divided into primary and secondary phosphors , differing in their luminescence properties.
Beta particles emitted from the isotopic sample transfer energy to the solvent molecules: the π cloud of the aromatic ring absorbs the energy of the emitted particle. The energized solvent molecules typically transfer the captured energy back and forth with other solvent molecules until the energy is finally transferred to a primary scintillator. The primary phosphor will emit photons following absorption of the transferred energy. Because that light emission may be at a wavelength that does not allow efficient detection, many cocktails contain secondary phosphors that absorb the fluorescence energy of the primary phosphor and re-emit at a longer wavelength. [ 1 ] Two widely used primary and secondary
fluors are 2,5-diphenyloxazole (PPO) with an emission maximum of 380 nm and 1,4-bis-2-(5-phenyloxazolyl)benzene (POPOP) with an emission maximum of 420 nm. [ 2 ]
The radioactive samples and cocktail are placed in small transparent or translucent (often glass or plastic ) vials that are loaded into an instrument known as a liquid scintillation counter. Newer machines may use 96-well plates with individual filters in each well. Many counters have two photo multiplier tubes connected in a coincidence circuit . The coincidence circuit assures that genuine light pulses, which reach both photomultiplier tubes, are counted, while spurious pulses (due to line noise , for example), which would only affect one of the tubes, are ignored.
Counting efficiencies under ideal conditions range from about 30% for tritium (a low-energy beta emitter) to nearly 100% for phosphorus-32 , a high-energy beta emitter. Some chemical compounds (notably chlorine compounds) and highly colored samples can interfere with the counting process. This interference, known as "quenching", can be overcome through data correction or through careful sample preparation.
High-energy beta emitters, such as phosphorus-32 and yttrium-90 can also be counted in a scintillation counter without the cocktail, instead using an aqueous solution containing no scintillators. This technique, known as Cherenkov counting , relies on Cherenkov radiation being detected directly by the photomultiplier tubes. Cherenkov counting benefits from the use of plastic vials which scatter the emitted light, increasing the potential for light to reach the photomultiplier tube. | https://en.wikipedia.org/wiki/Liquid_scintillation_counting |
Liquid slugging is the phenomenon of liquid entering the cylinder of a reciprocating compressor , a common cause of failure. [ 1 ]
Under normal conditions, the intake and output of a compressor cylinder is entirely vapor or gas, when a liquid accumulates at the suction port liquid slugging can occur. As more of the practically incompressible liquid enters, strain is placed upon the system leading to a variety of failures. [ 2 ]
This physics -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Liquid_slugging |
Liquidmetal and Vitreloy are commercial names of a series of amorphous metal alloys developed by a California Institute of Technology (Caltech) research team and marketed by Liquidmetal Technologies . Liquidmetal alloys combine a number of desirable material features, including high tensile strength , excellent corrosion resistance , very high coefficient of restitution and excellent anti-wearing characteristics, while also being able to be heat-formed in processes similar to thermoplastics . Despite the name, they are not liquid at room temperature. [ 1 ]
Liquidmetal was introduced for commercial applications in 2003. [ 2 ] It is used for, among other things, golf clubs , watches , and covers of cell phones .
The alloy was the result of a research program into amorphous metals carried out at Caltech. It was the first of a series of experimental alloys that could achieve an amorphous structure at relatively slow cooling rates. [ citation needed ] Amorphous metals had been made before, but only in small batches because cooling rates needed to be in the millions of degrees per second. For example, amorphous wires could be fabricated by splat quenching a stream of molten metal on a spinning disk. Because Vitreloy allowed such slow cooling rates, production of larger batch sizes was possible. More recently, a number of additional alloys have been added to the Liquidmetal portfolio. These alloys also retain their amorphous structure after repeated re-heating, allowing them to be used in a wide variety of traditional machining processes.
Liquid metal, created by Dr. Atakan Peker, contain atoms of significantly different sizes. They form a dense mix with low free volume. Unlike crystalline metals, there is no obvious melting point at which viscosity drops suddenly. Vitreloy behaves more like other glasses , in that its viscosity drops gradually with increased temperature. At high temperature, it behaves in a plastic manner, allowing the mechanical properties to be controlled relatively easily during casting. The viscosity prevents the atoms moving enough to form an ordered lattice, so the material retains its amorphous properties even after being heat-formed.
The alloys have relatively low softening temperatures, allowing casting of complex shapes without needing finishing. The material properties immediately after casting are much better than those of conventional metals; usually, cast metals have worse properties than forged or wrought ones. The alloys are also malleable at low temperatures (400 °C or 752 °F for the earliest formulation), and can be molded . The low free volume also results in low shrinkage during cooling. For all of these reasons, Liquidmetal can be formed into complex shapes using processes similar to thermoplastics, [ 3 ] which makes Liquidmetal a potential replacement for many applications where plastics would normally be used. [ citation needed ]
Due to their non-crystalline ( amorphous ) structures, Liquidmetals are harder than alloys of titanium or aluminum of similar composition. The zirconium and titanium based Liquidmetal alloys achieved yield strength of over 1,723 MPa (249,900 psi), nearly twice the strength of conventional crystalline titanium alloys ( Ti-6Al-4V is ~830 MPa (120,000 psi)), and about the strength of high-strength steels and some highly engineered bulk composite materials (see tensile strength for a list of common materials). However, the early casting methods introduced microscopic flaws that were excellent sites for crack propagation which led to Vitreloy being fragile like glass. Although strong, these early batches shattered easily when struck. Newer casting methods, adjustments of the alloy mixtures and other changes have improved this. [ citation needed ]
The lack of grain boundaries in a metallic glass eliminates grain-boundary corrosion—a common problem in high-strength alloys produced by precipitation hardening and sensitized stainless steels. Liquidmetal alloys are therefore generally more corrosion resistant, both due to the mechanical structure as well as the elements used in its alloy. The combination of mechanical hardness, high elasticity and corrosion resistance makes Liquidmetal wear resistant. [ citation needed ]
Although at high temperatures, plastic deformation occurs easily, almost none occurs at room temperature before the onset of catastrophic failure . This limits the material's applicability in reliability-critical applications, as the impending failure is not evident. The material is also susceptible to metal fatigue with crack growth. A two-phase composite structure with amorphous matrix and a ductile dendritic crystalline-phase reinforcement, or a metal matrix composite reinforced with fibers of other material can reduce or eliminate this disadvantage. [ 4 ]
Liquidmetal combines a number of features that are normally not found in any one material. This makes them useful in a wide variety of applications.
One of the first commercial uses of Liquidmetal was in golf clubs made by the company, where the highly elastic metal was used in portions of the club face. [ 5 ] These were highly rated by users, but the product was later dropped, in part because the prototypes shattered after fewer than 40 hits. [ 6 ] Since then, Liquidmetal has appeared in other sports equipment, including the cores of golf balls , skis , baseball and softball bats , and tennis racquets . [ 7 ]
The ability to be cast and molded, combined with high wear resistance, has also led to Liquidmetal being used as a replacement for plastics in some applications. [ 8 ] It has been used on the casing of late-model SanDisk "Cruzer Titanium" USB flash drives as well as their Sansa line of flash -based MP3 player , and casings of some mobile phones , like the luxury Vertu products, and other toughened consumer electronics. [ citation needed ] Liquidmetal was used in the Biolase dental laser Ilase [ 9 ] and the Socketmobile ring bar code scanner. Liquidmetal has also notably been used for making the SIM ejector tool of some iPhone 3Gs made by Apple Inc. , shipped in the US. This was done by Apple as an exercise to test the viability of usage of the metal. [ 10 ] They retain a scratch-free surface longer than competing materials, while still being made in complex shapes. The same qualities lend it to use as protective coatings for industrial machinery, including petroleum drill pipes and power plant boiler tubes . [ citation needed ]
It also replaces titanium in applications ranging from medical instruments and cars to the military and aerospace industry. In military applications, amorphous metals could replace depleted uranium in kinetic energy penetrators . [ 11 ] Plates of Liquidmetal were used in the solar wind ion collector array in the Genesis space probe . [ citation needed ]
A range of zirconium -based alloys have been marketed under this trade name. Some example compositions are listed below, in molar percent: | https://en.wikipedia.org/wiki/Liquidmetal |
While chemically pure materials have a single melting point , chemical mixtures often partially melt at the temperature known as the solidus ( T S or T sol ), and fully melt at the higher liquidus temperature ( T L or T liq ). The solidus is always less than or equal to the liquidus, but they need not coincide. If a gap exists between the solidus and liquidus it is called the freezing range, and within that gap, the substance consists of a mixture of solid and liquid phases (like a slurry ). Such is the case, for example, with the olivine ( forsterite - fayalite ) system, which is common in Earth's mantle . [ 1 ]
In chemistry , materials science , and physics , the liquidus temperature specifies the temperature above which a material is completely liquid, [ 2 ] and the maximum temperature at which crystals can co-exist with the melt in thermodynamic equilibrium . The solidus is the locus of temperatures (a curve on a phase diagram ) below which a given substance is completely solid (crystallized). The solidus temperature specifies the temperature below which a material is completely solid, [ 2 ] and the minimum temperature at which a melt can co-exist with crystals in thermodynamic equilibrium .
Liquidus and solidus are mostly used for impure substances (mixtures) such as glasses , metal alloys , ceramics , rocks , and minerals . Lines of liquidus and solidus appear in the phase diagrams of binary solid solutions , [ 2 ] as well as in eutectic systems away from the invariant point. [ 3 ]
For pure elements or compounds, e.g. pure copper, pure water, etc. the liquidus and solidus are at the same temperature, and the term melting point may be used.
There are also some mixtures which melt at a particular temperature, known as congruent melting . One example is eutectic mixture . In a eutectic system, there is particular mixing ratio where the solidus and liquidus temperatures coincide at a point known as the invariant point. At the invariant point, the mixture undergoes a eutectic reaction where both solids melt at the same temperature. [ 3 ]
There are several models used to predict liquidus and solidus curves for various systems. [ 4 ] [ 5 ] [ 6 ] [ 7 ]
Detailed measurements of solidus and liquidus can be made using techniques such as differential scanning calorimetry and differential thermal analysis . [ 8 ] [ 9 ] [ 10 ] [ 11 ]
For impure substances, e.g. alloys , honey , soft drink , ice cream , etc. the melting point broadens into a melting interval. If the temperature is within the melting interval, one may see "slurries" at equilibrium, i.e. the slurry will neither fully solidify nor melt. This is why new snow of high purity on mountain peaks either melts or stays solid, while dirty snow on the ground in cities tends to become slushy at certain temperatures. Weld melt pools containing high levels of sulfur, either from melted impurities of the base metal or from the welding electrode, typically have very broad melting intervals, which leads to increased risk of hot cracking .
Above the liquidus temperature, the material is homogeneous and liquid at equilibrium. As the system is cooled below the liquidus temperature, more and more crystals will form in the melt if one waits a sufficiently long time, depending on the material. Alternately, homogeneous glasses can be obtained through sufficiently fast cooling, i.e., through kinetic inhibition of the crystallization process.
The crystal phase that crystallizes first on cooling a substance to its liquidus temperature is termed primary crystalline phase or primary phase . The composition range within which the primary phase remains constant is known as primary crystalline phase field .
The liquidus temperature is important in the glass industry because crystallization can cause severe problems during the glass melting and forming processes, and it also may lead to product failure. [ 12 ] | https://en.wikipedia.org/wiki/Liquidus_and_solidus |
A liquid–liquid critical point (or LLCP ) is the endpoint of a liquid–liquid phase transition line (LLPT); it is a critical point where two types of local structures coexist at the exact ratio of unity. This hypothesis was first developed by Peter Poole, Francesco Sciortino , Uli Essmann and H. Eugene Stanley in Boston [ 1 ] to obtain a quantitative understanding of the huge number of anomalies present in water. [ 2 ]
Near a liquid–liquid critical point, there is always a competition between two alternative local structures. For instance, in supercooled water, two types of local structures have been predicted: a low-density local configuration (LD) and a high-density local configuration (HD), so above the critical pressure, the liquid is composed by a majority of HD local structure, while below the critical pressure a higher fraction of LD local configurations is present. The ratio between HD and LD configurations is determined according to the thermodynamic equilibrium of the system, which is often governed by external variables such as pressure and temperature. [ 3 ]
The liquid–liquid critical point theory can be applied to several liquids that possess the tetrahedral symmetry. The study of liquid–liquid critical points is an active research area with hundreds of articles having been published, though only a few of these investigations have been experimental [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] since most modern probing techniques are not fast and/or sensitive enough to study them. | https://en.wikipedia.org/wiki/Liquid–liquid_critical_point |
Liquid–liquid extraction , also known as solvent extraction and partitioning , is a method to separate compounds or metal complexes , based on their relative solubilities in two different immiscible liquids, usually water (polar) and an organic solvent (non-polar). There is a net transfer of one or more species from one liquid into another liquid phase, generally from aqueous to organic. The transfer is driven by chemical potential, i.e. once the transfer is complete, the overall system of chemical components that make up the solutes and the solvents are in a more stable configuration (lower free energy). The solvent that is enriched in solute(s) is called extract. The feed solution that is depleted in solute(s) is called the raffinate . Liquid–liquid extraction is a basic technique in chemical laboratories, where it is performed using a variety of apparatus, from separatory funnels to countercurrent distribution equipment called as mixer settlers . [ not verified in body ] This type of process is commonly performed after a chemical reaction as part of the work-up , often including an acidic work-up.
The term partitioning is commonly used to refer to the underlying chemical and physical processes involved in liquid–liquid extraction , but on another reading may be fully synonymous with it. The term solvent extraction can also refer to the separation of a substance from a mixture by preferentially dissolving that substance in a suitable solvent. In that case, a soluble compound is separated from an insoluble compound or a complex matrix. [ not verified in body ]
From a hydrometallurgical perspective, solvent extraction is exclusively used in separation and purification of uranium and plutonium, zirconium and hafnium, separation of cobalt and nickel, separation and purification of rare earth elements etc., its greatest advantage being its ability to selectively separate out even very similar metals. One obtains high-purity single metal streams on 'stripping' out the metal value from the 'loaded' organic wherein one can precipitate or deposit the metal value. Stripping is the opposite of extraction: Transfer of mass from organic to aqueous phase.
Liquid–liquid extraction is also widely used in the production of fine organic compounds , the processing of perfumes , the production of vegetable oils and biodiesel , and other industries. [ not verified in body ] It is among the most common initial separation techniques, though some difficulties result in extracting out closely related functional groups.
Liquid-Liquid extraction can be substantially accelerated in microfluidic devices, reducing extraction and separation times from minutes/hours to mere seconds compared to conventional extractors. [ 1 ]
Liquid–liquid extraction is possible in non-aqueous systems: In a system consisting of a molten metal in contact with molten salts , metals can be extracted from one phase to the other. This is related to a mercury electrode where a metal can be reduced, the metal will often then dissolve in the mercury to form an amalgam that modifies its electrochemistry greatly. For example, it is possible for sodium cations to be reduced at a mercury cathode to form sodium amalgam , while at an inert electrode (such as platinum) the sodium cations are not reduced. Instead, water is reduced to hydrogen. A detergent or fine solid can be used to stabilize an emulsion , or third phase . [ not verified in body ]
In solvent extraction, a distribution ratio (D) is often quoted as a measure of how well-extracted a species is. The distribution ratio is a measure of the total concentration of a solute in the organic phase divided by its concentration in the aqueous phase . [ 2 ] The partition or distribution coefficient (K d ) is the ration of solute concentration in each layer upon reaching equilibrium. [ 3 ] This distinction between D and K d is important. The partition coefficient is a thermodynamic equilibrium constant and has a fixed value for the solute’s partitioning between the two phases. The distribution ratio’s value, however, changes with solution conditions if the relative amounts of A and B change. If we know the solute’s equilibrium reactions within each phase and between the two phases, we can derive an algebraic relationship between K d and D . The partition coefficient and the distribution ratio are identical if the solute has only one chemical form in each phase; however, if the solute exists in more than one chemical form in either phase, then K d and D usually have different values. [ 2 ] Depending on the system, the distribution ratio can be a function of temperature, the concentration of chemical species in the system, and a large number of other parameters. Note that D is related to the Gibbs Free Energy (Δ G) of the extraction process. [ 4 ]
In solvent extraction, two immiscible liquids are shaken together. The more polar solutes dissolve preferentially in the more polar solvent, and the less polar solutes in the less polar solvent. In this experiment, the nonpolar halogens preferentially dissolve in the non-polar mineral oil. [ 5 ]
The separation factor is one distribution ratio divided by another; it is a measure of the ability of the system to separate two solutes. For instance, if the distribution ratio for nickel (D Ni ) is 10 and the distribution ratio for silver (D Ag ) is 100, then the silver/nickel separation factor (SF Ag/Ni ) is equal to D Ag /D Ni = SF Ag/Ni = 10. [ 6 ]
Success of liquid–liquid extraction is measured through separation factors and decontamination factors. The best way to understand the success of an extraction column is through the liquid–liquid equilibrium (LLE) data set. The data set can then be converted into a curve to determine the steady state partitioning behavior of the solute between the two phases. The y-axis is the concentration of solute in the extract (solvent) phase, and the x-axis is the concentration of the solute in the raffinate phase. From here, one can determine steps for optimization of the process. [ 7 ]
This is commonly used on the small scale in chemical labs. It is normal to use a separating funnel . Processes include DLLME and direct organic extraction. [ 8 ] After equilibration, the extract phase containing the desired solute is separated out for further processing. [ 9 ]
A process used to extract small amounts of organic compounds from water samples. [ 10 ] This process is done by injecting small amounts of an appropriate extraction solvent (C 2 Cl 4 ) and a disperser solvent (acetone) into the aqueous solution. The resulting solution is then centrifuged to separate the organic and aqueous layers. This process is useful in extraction organic compounds such as organochloride and organophsophorus pesticides, as well as substituted benzene compounds from water samples. [ 10 ]
By mixing partially organic soluble samples in organic solvent (toluene, benzene, xylene), the organic soluble compounds will dissolve into the solvent and can be separated using a separatory funnel . This process is valuable in the extraction of proteins and specifically phosphoprotein and phosphopeptide phosphatases. [ 11 ]
Another example of this application is extracting anisole from a mixture of water and 5% acetic acid using ether , then the anisole will enter the organic phase. The two phases would then be separated. [ citation needed ] The acetic acid can then be scrubbed (removed) from the organic phase by shaking the organic extract with sodium bicarbonate . The acetic acid reacts with the sodium bicarbonate to form sodium acetate , carbon dioxide , and water.
Caffeine can also be extracted from coffee beans and tea leaves using a direct organic extraction. The beans or leaves can be soaked in ethyl acetate which favorably dissolves the caffeine, leaving a majority of the coffee or tea flavor remaining in the initial sample. [ 12 ]
These are commonly used in industry for the processing of metals such as the lanthanides ; because the separation factors between the lanthanides are so small many extraction stages are needed. [ 13 ] In the multistage processes, the aqueous raffinate from one extraction unit is fed to the next unit as the aqueous feed, while the organic phase is moved in the opposite direction. Hence, in this way, even if the separation between two metals in each stage is small, the overall system can have a higher decontamination factor.
Multistage countercurrent arrays have been used for the separation of lanthanides. For the design of a good process, the distribution ratio should be not too high (>100) or too low (<0.1) in the extraction portion of the process. It is often the case that the process will have a section for scrubbing unwanted metals from the organic phase, and finally a stripping section to obtain the metal back from the organic phase.
Battery of mixer-settlers counter currently interconnected. Each mixer-settler unit provides a single stage of extraction. A mixer settler consists of a first stage that mixes the phases together followed by a quiescent settling stage that allows the phases to separate by gravity.
A novel settling device, Sudhin BioSettler, can separate an oil-water emulsion continuously at a much faster rate than simple gravity settlers. In this photo, an oil-water emulsion, stirred by an impeller in an external reservoir and pumped continuously into the two bottom side ports of BioSettler, is separated very quickly into a clear organic (mineral oil) layer exiting via the top of BioSettler and an aqueous (coloured with a red food dye) layer being pumped out continuously from the bottom of BioSettler.
In the multistage countercurrent process, multiple mixer settlers are installed with mixing and settling chambers located at alternating ends for each stage (since the outlet of the settling sections feed the inlets of the adjacent stage's mixing sections). Mixer-settlers are used when a process requires longer residence times and when the solutions are easily separated by gravity. They require a large facility footprint, but do not require much headspace, and need limited remote maintenance capability for occasional replacement of mixing motors. (Colven, 1956; Davidson, 1957) [ 14 ]
Centrifugal extractors mix and separate in one unit. Two liquids will be intensively mixed between the spinning rotor and the stationary housing at speeds up to 6000 RPM. This develops great surfaces for an ideal mass transfer from the aqueous phase into the organic phase. At 200–2000 g, both phases will be separated again. Centrifugal extractors minimize the solvent in the process, optimize the product load in the solvent and extract the aqueous phase completely. Counter current and cross current extractions are easily established. [ 15 ]
Some solutes such as noble gases can be extracted from one phase to another without the need for a chemical reaction (see absorption ). This is the simplest type of solvent extraction. When a solvent is extracted, two immiscible liquids are shaken together. The more polar solutes dissolve preferentially in the more polar solvent, and the less polar solutes in the less polar solvent. Some solutes that do not at first sight appear to undergo a reaction during the extraction process do not have distribution ratio that is independent of concentration. A classic example is the extraction of carboxylic acids ( HA ) into nonpolar media such as benzene . Here, it is often the case that the carboxylic acid will form a dimer in the organic layer so the distribution ratio will change as a function of the acid concentration (measured in either phase).
For this case, the extraction constant k is described by k = [ HA organic ] 2 /[ HA aqueous ]
Using solvent extraction it is possible to extract uranium , plutonium , thorium and many rare earth elements from acid solutions in a selective way by using the right choice of organic extracting solvent and diluent. One solvent used for this purpose is the organophosphate tributyl phosphate (TBP). The PUREX process that is commonly used in nuclear reprocessing uses a mixture of tri-n-butyl phosphate and an inert hydrocarbon ( kerosene ), the uranium(VI) are extracted from strong nitric acid and are back-extracted (stripped) using weak nitric acid. An organic soluble uranium complex [UO 2 (TBP) 2 (NO 3 ) 2 ] is formed, then the organic layer bearing the uranium is brought into contact with a dilute nitric acid solution; the equilibrium is shifted away from the organic soluble uranium complex and towards the free TBP and uranyl nitrate in dilute nitric acid. The plutonium(IV) forms a similar complex to the uranium(VI), but it is possible to strip the plutonium in more than one way; a reducing agent that converts the plutonium to the trivalent oxidation state can be added. This oxidation state does not form a stable complex with TBP and nitrate unless the nitrate concentration is very high (circa 10 mol/L nitrate is required in the aqueous phase). Another method is to simply use dilute nitric acid as a stripping agent for the plutonium. This PUREX chemistry is a classic example of a solvation extraction . In this case, D U = k [TBP] 2 [NO 3 − ] 2 .
Another extraction mechanism is known as the ion exchange mechanism. Here, when an ion is transferred from the aqueous phase to the organic phase, another ion is transferred in the other direction to maintain the charge balance. This additional ion is often a hydrogen ion ; for ion exchange mechanisms, the distribution ratio is often a function of pH . An example of an ion exchange extraction would be the extraction of americium by a combination of terpyridine and a carboxylic acid in tert - butyl benzene . In this case
Another example is the extraction of zinc , cadmium , or lead by a di alkyl phosphinic acid (R 2 PO 2 H) into a nonpolar diluent such as an alkane . A non- polar diluent favours the formation of uncharged non-polar metal complexes.
Some extraction systems are able to extract metals by both the solvation and ion exchange mechanisms; an example of such a system is the americium (and lanthanide ) extraction from nitric acid by a combination of 6,6'- bis -(5,6-di pentyl -1,2,4-triazin-3-yl)- 2,2'-bipyridine and 2-bromo hexanoic acid in tert - butyl benzene . At both high- and low-nitric acid concentrations, the metal distribution ratio is higher than it is for an intermediate nitric acid concentration.
It is possible by careful choice of counterion to extract a metal. For instance, if the nitrate concentration is high, it is possible to extract americium as an anionic nitrate complex if the mixture contains a lipophilic quaternary ammonium salt .
An example that is more likely to be encountered by the 'average' chemist is the use of a phase transfer catalyst . This is a charged species that transfers another ion to the organic phase. The ion reacts and then forms another ion, which is then transferred back to the aqueous phase.
For instance, the 31.1 kJ mol −1 is required to transfer an acetate anion into nitrobenzene, [ 16 ] while the energy required to transfer a chloride anion from an aqueous phase to nitrobenzene is 43.8 kJ mol −1 . [ 17 ] Hence, if the aqueous phase in a reaction is a solution of sodium acetate while the organic phase is a nitrobenzene solution of benzyl chloride , then, when a phase transfer catalyst, the acetate anions can be transferred from the aqueous layer where they react with the benzyl chloride to form benzyl acetate and a chloride anion. The chloride anion is then transferred to the aqueous phase. The transfer energies of the anions contribute to that given out by the reaction.
A 43.8 to 31.1 kJ mol −1 = 12.7 kJ mol −1 of additional energy is given out by the reaction when compared with energy if the reaction had been done in nitrobenzene using one equivalent weight of a tetraalkylammonium acetate. [ 18 ]
Polymer–polymer systems. In a Polymer–polymer system, both phases are generated by a dissolved polymer. The heavy phase will generally be a polysaccharide , and the light phase is generally Polyethylene glycol (PEG). Traditionally, the polysaccharide used is dextran . However, dextran is relatively expensive, and research has been exploring using less expensive polysaccharides to generate the heavy phase. If the target compound being separated is a protein or enzyme, it is possible to incorporate a ligand to the target into one of the polymer phases. This improves the target's affinity to that phase, and improves its ability to partition from one phase into the other. This, as well as the absence of solvents or other denaturing agents, makes polymer–polymer extractions an attractive option for purifying proteins. The two phases of a polymer–polymer system often have very similar densities, and very low surface tension between them. Because of this, demixing a polymer–polymer system is often much more difficult than demixing a solvent extraction. Methods to improve the demixing include centrifugation , and application of an electric field .
Polymer–salt systems. Aqueous two-phase systems can also be generated by generating the heavy phase with a concentrated salt solution. The polymer phase used is generally still PEG. Generally, a kosmotropic salt, such as Na 3 PO 4 is used, however PEG–NaCl systems have been documented when the salt concentration is high enough. Since polymer–salt systems demix readily they are easier to use. However, at high salt concentrations, proteins generally either denature, or precipitate from solution. Thus, polymer–salt systems are not as useful for purifying proteins.
Ionic liquids systems. Ionic liquids are ionic compounds with low melting points. While they are not technically aqueous, recent research has experimented with using them in an extraction that does not use organic solvents.
The ability to purify DNA from a sample is important for many modern biotechnology processes. However, samples often contain nucleases that degrade the target DNA before it can be purified. It has been shown that DNA fragments will partition into the light phase of a polymer–salt separation system. If ligands known to bind and deactivate nucleases are incorporated into the polymer phase, the nucleases will then partition into the heavy phase and be deactivated. Thus, this polymer–salt system is a useful tool for purifying DNA from a sample while simultaneously protecting it from nucleases. [ citation needed ]
The PEG–NaCl system has been shown to be effective at partitioning small molecules, such as peptides and nucleic acids. These compounds are often flavorants or odorants. The system could then be used by the food industry to isolate or eliminate particular flavors. Caffeine extraction used to be done using liquid–liquid extraction, specifically direct and indirect liquid–liquid extraction (Swiss Water Method), but has since moved towards super-critical CO 2 as it is cheaper and can be done on a commercial scale. [ 19 ] [ 20 ]
Often there are chemical species present or necessary at one stage of sample processing that will interfere with the analysis. For example, some air monitoring is performed by drawing air through a small glass tube filled with sorbent particles that have been coated with a chemical to stabilize or derivatize the analyte of interest. The coating may be of such a concentration or characteristics that it would damage the instrumentation or interfere with the analysis. If the sample can be extracted from the sorbent using a nonpolar solvent (such as toluene or carbon disulfide), and the coating is polar (such as HBr or phosphoric acid) the dissolved coating will partition into the aqueous phase. Clearly the reverse is true as well, using polar extraction solvent and a nonpolar solvent to partition a nonpolar interferent. A small aliquot of the organic phase (or in the latter case, polar phase) can then be injected into the instrument for analysis.
Amines (analogously to ammonia) have a lone pair of electrons on the nitrogen atom that can form a relatively weak bond to a hydrogen atom. It is therefore the case that under acidic conditions amines are typically protonated, carrying a positive charge and under basic conditions they are typically deprotonated and neutral. Amines of sufficiently low molecular weight are rather polar and can form hydrogen bonds with water and therefore will readily dissolve in aqueous solutions. Deprotonated amines on the other hand, are neutral and have greasy , nonpolar organic substituents, and therefore have a higher affinity for nonpolar inorganic solvents. As such purification steps can be carried out where an aqueous solution of an amine is neutralized with a base such as sodium hydroxide, then shaken in a separatory funnel with a nonpolar solvent that is immiscible with water. The organic phase is then drained off. Subsequent processing can recover the amine by techniques such as recrystallization, evaporation or distillation; subsequent extraction back to a polar phase can be performed by adding HCl and shaking again in a separatory funnel (at which point the ammonium ion could be recovered by adding an insoluble counterion), or in either phase, reactions could be performed as part of a chemical synthesis.
Temperature swing solvent extraction is an experimental technique for the desalination of drinking water. It has been used to remove up to 98.5% of the salt content in water, and is able to process hypersaline brines that cannot be desalinated using reverse osmosis. [ 21 ]
It is important to investigate the rate at which the solute is transferred between the two phases, in some cases by an alteration of the contact time it is possible to alter the selectivity of the extraction. For instance, the extraction of palladium or nickel can be very slow because the rate of ligand exchange at these metal centers is much lower than the rates for iron or silver complexes.
If a complexing agent is present in the aqueous phase then it can lower the distribution ratio. For instance, in the case of iodine being distributed between water and an inert organic solvent such as carbon tetrachloride then the presence of iodide in the aqueous phase can alter the extraction chemistry: instead of D I + 2 {\displaystyle D_{\mathrm {I} ^{+2}}} being a constant it becomes
This is because the iodine reacts with the iodide to form I 3 − . The I 3 − anion is an example of a polyhalide anion that is quite common.
In a typical scenario, an industrial process will use an extraction step in which solutes are transferred from the aqueous phase to the organic phase; this is often followed by a scrubbing stage in which unwanted solutes are removed from the organic phase, then a stripping stage in which the wanted solutes are removed from the organic phase. The organic phase may then be treated to make it ready for use again. [ 22 ] [ 23 ]
After use, the organic phase may be subjected to a cleaning step to remove any degradation products; for instance, in PUREX plants, the used organic phase is washed with sodium carbonate solution to remove any dibutyl hydrogen phosphate or butyl dihydrogen phosphate that might be present.
In order to calculate the phase equilibrium, it is necessary to use a thermodynamic model such as NRTL, UNIQUAC, etc. The corresponding parameters of these models can be obtained from literature (e.g. Dechema Chemistry Data Series, Dortmund Data Bank , etc.) or by a correlation process of experimental data. [ 24 ] [ 25 ] [ 26 ] [ 27 ]
While solvent extraction is often done on a small scale by synthetic lab chemists using a separatory funnel , Craig apparatus or membrane-based techniques, [ 28 ] it is normally done on the industrial scale using machines that bring the two liquid phases into contact with each other. Such machines include centrifugal contactors , Thin Layer Extraction , spray columns , pulsed columns , and mixer-settlers .
The extraction methods for a range of metals include: [ 29 ] [ 30 ]
Ce(IV) can separated from other rare earth (III) ions by using sulfuric acid and HDEHP to produce high-purity cerium oxide. [ 31 ]
The extraction of cobalt from hydrochloric acid using Alamine 336 (tri-octyl/decyl amine) in meta - xylene . [ 32 ] Cobalt can be extracted also using Ionquest 290 or Cyanex 272 { bis -(2,4,4-trimethylpentyl) phosphinic acid} .
Copper can be extracted using hydroxy oximes as extractants, a recent paper describes an extractant that has a good selectivity for copper over cobalt and nickel . [ 33 ]
The rare earth element Gadolinium can be extracted with n- tributyl phosphate and nitric acid to yield over a kilogram of gadolinium oxide. [ 34 ]
The rare earth element Neodymium is extracted by di(2-ethyl-hexyl)phosphoric acid into hexane by an ion exchange mechanism. [ 35 ] Neodymium can also be separated from dysprosium through selective precipitation of dysprosium with Cyanex 272 when the HNO3 concentration was 0.001 mol/L. [ 36 ]
Nickel can be extracted using di(2-ethyl-hexyl)phosphoric acid and tributyl phosphate in a hydrocarbon diluent (Shellsol). [ 37 ]
Dialkyl sulfides, tributyl phosphate and alkyl amines have been used for extracting palladium and platinum. [ 38 ] [ 39 ]
Polonium is produced in reactors from natural 209 Bi , bombarded with neutrons , creating 210 Bi, which then decays to 210 Po via beta-minus decay. The final purification is done pyrochemically with sodium hydroxide at 500 °C. This is then followed by liquid-liquid extraction, with dibutyl Carbitol as the extractant. [ 40 ]
Thorium can be extracted from other rare earths by using sulfuric acid and the extractant, N1923, to produce thorium oxide with 99.5% purity and 99% recovery. [ 31 ]
Zinc and cadmium are both extracted by an ion exchange process, the N,N,N′,N′ -tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) acts as a masking agent for the zinc and an extractant for the cadmium. [ 41 ] In the modified Zincex process, zinc is separated from most divalent ions by solvent extraction. D2EHPA (Di (2) ethyl hexyl phosphoric acid) is used for this. A zinc ion replaces the proton from two D2EHPA molecules. To strip the zinc from the D2EHPA, sulfuric acid is used, at a concentration of above 170g/L (typically 240-265g/L).
Lithium extraction is more popular due to the high demand of lithium-ion batteries . TBP (Tri-butyl phosphate) and FeCl 3 are mostly used to extract lithium from brine (with high Li/Mg ratio). [ 42 ] Alternatively, Cyanex 272 was also used to extract lithium. The mechanism of lithium extraction was found differently from other metals, such as cobalt, due to the weak coordinating bonding between lithium ions and extractants. [ 43 ] | https://en.wikipedia.org/wiki/Liquid–liquid_extraction |
Liquor ( / ˈ l ɪ k ər / LIK -ər , sometimes hard liquor ), spirits , distilled spirits , or spiritous liquor are alcoholic drinks produced by the distillation of grains , fruits , vegetables , or sugar that have already gone through alcoholic fermentation . While the word liquor ordinarily refers to distilled alcoholic spirits rather than drinks produced by fermentation alone, [ 1 ] it can sometimes be used more broadly to refer to any alcoholic beverage (or even non-alcoholic ones produced by distillation or some other practices, such as the brewed liquor of a tea ). [ 2 ]
The distillation process concentrates the alcohol, the resulting condensate has an increased alcohol by volume . [ 3 ] As liquors contain significantly more alcohol ( ethanol ) than other alcoholic drinks, they are considered "harder". In North America , the term hard liquor is sometimes used to distinguish distilled alcoholic drinks from non-distilled ones, whereas the term spirits is more commonly used in the United Kingdom . Some examples of liquors include vodka , rum , gin and tequila . Liquors are often aged in barrels , such as for the production of brandy and whiskey , or are infused with flavorings to form flavored liquors , such as absinthe .
Like other alcoholic drinks, liquor is typically consumed for the psychoactive effects of alcohol. Liquor may be consumed on its own (i.e. " neat "), typically in amounts of around 50 millilitres (1.7 US fluid ounces) per served drink; or frequently mixed with other ingredients to form a cocktail . In an undiluted form, distilled beverages are often slightly sweet and bitter and typically impart a burning mouthfeel with an odor derived from the alcohol and the production and aging processes; the exact flavor varies between different varieties of liquor and the different impurities they impart.
Rapid consumption of a large amount of liquor can cause severe alcohol intoxication or alcohol poisoning , which can be fatal either due to acute biochemical damage to vital organs (e.g. alcoholic hepatitis and pancreatitis ), or due to trauma (e.g. falls or motor vehicle accidents ) caused by alcohol-induced delirium . Consistent consumption of liquor over time correlates with higher mortality and other harmful health effects, even when compared to other alcoholic beverages. [ 4 ] [ 5 ]
The term "spirit" (singular and used without the additional term "drink") refers to liquor that should not contain added sugar [ 6 ] and is usually 35–40% alcohol by volume (ABV). [ 7 ] Fruit brandy , for example, is also known as 'fruit spirit'.
Liquor bottled with added sugar and flavorings, such as Grand Marnier , amaretto , and American schnapps , are known instead as liqueurs . [ 8 ]
Liquor generally has an alcohol concentration higher than 30% when bottled, and before being diluted for bottling, it typically has a concentration over 50%. Beer and wine , which are not distilled, typically have a maximum alcohol content of about 15% ABV, as most yeasts cannot metabolize when the concentration of alcohol is above this level; as a consequence, fermentation ceases at that point.
The origin of liquor and its close relative liquid is the Latin verb liquere , meaning 'to be fluid'. According to the Oxford English Dictionary ( OED ), an early use of the word in the English language, meaning simply "a liquid", can be dated to 1225. The first use documented in the OED defined as "a liquid for drinking" occurred in the 14th century. Its use as a term for "an intoxicating alcoholic drink" appeared in the 16th century.
In accordance with the regulation (EU) 2019/787 of the European Parliament and of the Council of April 17, 2019, [ 9 ] a spirit drink is an alcoholic beverage that has been produced:
Spirit drinks must contain at least 15% ABV (except in the case of egg liqueur such as Advocaat , which must contain a minimum of 14% ABV). [ 9 ] [ 10 ]
Regulation makes a difference between "ethyl alcohol of agricultural origin" and a "distillate of agricultural origin". Distillate of agricultural origin is defined as an alcoholic liquid that is the result of the distillation, after alcoholic fermentation, of agricultural products which does not have the properties of ethyl alcohol and which retain the aroma and taste of the raw materials used. [ 11 ]
Annex 1 to the regulation lists 44 categories of spirit drinks and their legal requirements. [ 12 ]
Some spirit drinks can fall into more than one category. Specific production requirements distinguish one category from another (London gin falls into the Gin category but any gin cannot be considered as London gin).
Spirit drinks that are not produced within the EU, such as tequila or baijiu , are not listed in the 44 categories.
Early evidence of distillation comes from Akkadian tablets dated c. 1200 BC describing perfumery operations, providing textual evidence that an early, primitive form of distillation was known to the Babylonians of ancient Mesopotamia . [ 16 ] Early evidence of distillation also comes from alchemists working in Alexandria , Roman Egypt , in the 1st century. [ 17 ] Distilled water was described in the 2nd century AD by Alexander of Aphrodisias . [ 18 ] Alchemists in Roman Egypt were using a distillation alembic or still device in the 3rd century.
Distillation was known in the ancient Indian subcontinent , evident from baked clay retorts and receivers found at Taxila and Charsadda in Pakistan and Rang Mahal in India dating to the early centuries of the Common Era . [ 19 ] [ 20 ] [ 21 ] Frank Raymond Allchin says these terracotta distill tubes were "made to imitate bamboo". [ 20 ] These " Gandhara stills" were capable of producing only very weak liquor, as there was no efficient means of collecting the vapors at low heat. [ 22 ]
Distillation in China could have begun during the Eastern Han dynasty (1st–2nd centuries), but the distillation of beverages began in the Jin (12th–13th centuries) and Southern Song (10th–13th centuries) dynasties according to archaeological evidence. [ 23 ]
Freeze distillation involves freezing the alcoholic beverage and then removing the ice. The freezing technique had limitations in geography and implementation limiting how widely this method was put to use.
The flammable nature of the exhalations of wine was already known to ancient natural philosophers such as Aristotle (384–322 BCE), Theophrastus ( c. 371 – c. 287 BCE ), and Pliny the Elder (23/24–79 CE). [ 24 ] This did not immediately lead to the isolation of alcohol, however, despite the development of more advanced distillation techniques in second- and third-century Roman Egypt . [ 25 ] An important recognition, first found in one of the writings attributed to Jābir ibn Ḥayyān (ninth century CE), was that by adding salt to boiling wine, which increases the wine's relative volatility , the flammability of the resulting vapors may be enhanced. [ 26 ] The distillation of wine is attested in Arabic works attributed to al-Kindī (c. 801–873 CE) and to al-Fārābī (c. 872–950), and in the 28th book of al-Zahrāwī 's (Latin: Abulcasis, 936–1013) Kitāb al-Taṣrīf (later translated into Latin as Liber servatoris ). [ 27 ] In the twelfth century, recipes for the production of aqua ardens ("burning water", i.e., alcohol) by distilling wine with salt started to appear in a number of Latin works, and by the end of the thirteenth century, it had become a widely known substance among Western European chemists. [ 28 ] Its medicinal properties were studied by Arnald of Villanova (1240–1311 CE) and John of Rupescissa (c. 1310–1366), the latter of whom regarded it as a life-preserving substance able to prevent all diseases (the aqua vitae or "water of life", also called by John the quintessence of wine). [ 29 ]
In China, archaeological evidence indicates that the true distillation of alcohol began during the 12th century Jin or Southern Song dynasties. [ 23 ] A still has been found at an archaeological site in Qinglong, Hebei , dating to the 12th century. [ 23 ]
In India, the true distillation of alcohol was introduced from the Middle East and was in wide use in the Delhi Sultanate by the 14th century. [ 22 ] [ 30 ]
The works of Taddeo Alderotti (1223–1296) describe a method for concentrating alcohol involving repeated fractional distillation through a water-cooled still, by which an alcohol purity of 90% could be obtained. [ 31 ]
In 1437, "burned water" ( brandy ) was mentioned in the records of the County of Katzenelnbogen in Germany. [ 32 ]
It is legal to distill beverage alcohol as a hobby for personal use in some countries, including New Zealand [ 33 ] and the Netherlands. [ note 1 ]
In many others including the United States , it is illegal to distill beverage alcohol without a license, and the licensing process is too arduous for hobbyist-scale production. In some parts of the U.S., it is also illegal to sell a still without a license. Nonetheless, all states allow unlicensed individuals to make their own beer , and some also allow unlicensed individuals to make their own wine (although making beer and wine is also prohibited in some local jurisdictions). [ citation needed ]
Some countries and sub-national jurisdictions limit or prohibit the sale of certain high-percentage alcohol, commonly known as neutral spirit . Due to its flammability (see below) alcoholic beverages with an alcohol content above 70% by volume are not permitted to be transported in aircraft. [ 34 ]
Microdistilling (also known as craft distilling) began to re-emerge as a trend in the United States following the microbrewing and craft beer movement in the last decades of the 20th century.
Liquor that contains 40% ABV (80 US proof ) will catch fire if heated to about 26 °C (79 °F) and if an ignition source is applied to it. This temperature is called its flash point . [ 35 ] The flash point of pure alcohol is 16.6 °C (61.9 °F), less than average room temperature. [ 36 ]
The flammability of liquor is applied in the cooking technique flambé .
The flash points of alcohol concentrations from 10% to 96% by weight are: [ 37 ]
Liquor can be served:
The World Health Organization (WHO) measures and publishes alcohol consumption patterns in different countries. The WHO measures alcohol consumed by persons 15 years of age or older and reports it on the basis of liters of pure alcohol consumed per capita in a given year in a country. [ 41 ]
In Europe, spirits (especially vodka) are more popular in the north and east of the continent.
Distilled spirits contain ethyl alcohol , the same chemical that is present in beer and wine , and as such, spirit consumption has short-term psychological and physiological effects on the user. Different concentrations of alcohol in the human body have different effects on a person. The effects of alcohol depend on the amount an individual has drunk, the percentage of alcohol in the spirits and the timespan over which the consumption took place. [ 42 ]
The short-term effects of alcohol consumption range from a decrease in anxiety and motor skills and euphoria at lower doses to intoxication (drunkenness), to stupor , unconsciousness, anterograde amnesia (memory "blackouts"), and central nervous system depression at higher doses. Cell membranes are highly permeable to alcohol , so once it is in the bloodstream, it can diffuse into nearly every cell in the body. Alcohol can greatly exacerbate sleep problems. During abstinence , residual disruptions in sleep regularity and sleep patterns are the greatest predictors of relapse . [ 42 ]
Drinking more than 1–2 drinks a day increases the risk of heart disease, high blood pressure , atrial fibrillation , and stroke . [ 43 ] The risk is greater in younger people due to binge drinking , which may result in violence or accidents. [ 43 ] About 3.3 million deaths (5.9% of all deaths) are due to alcohol each year. [ 44 ] Unlike wine and perhaps beer, there is no evidence for a J-shaped health effect for the consumption of distilled alcohol. [ 4 ] Long-term use can lead to an alcohol use disorder , an increased risk of developing physical dependence . cardiovascular disease and several types of cancer . [ 42 ]
Alcoholism , also known as "alcohol use disorder", is a broad term for any drinking of alcohol that results in problems. [ 45 ] Alcoholism reduces a person's life expectancy by around ten years [ 46 ] and alcohol use is the third-leading cause of early death in the United States. [ 43 ]
Consumption of alcohol in any quantity can cause cancer . Alcohol causes breast cancer , colorectal cancer , esophageal cancer , liver cancer , and head-and-neck cancers . The more alcohol is consumed, the higher the cancer risk. [ 47 ]
A survey of high school students in Alstahaug, Nordland county, revealed that adolescents consume alcohol at rates above the national average, with home-made liquor being prevalent and easily accessible, highlighting an urgent need for preventive measures. [ 48 ] | https://en.wikipedia.org/wiki/Liquor |
Lisa Michelle Jones (born February 1977) is an American professor of chemistry and biochemistry at the University of California, San Diego (UCSD). [ 1 ] Her research is in structural proteomics, using mass spectrometry (MS) together with fast photochemical oxidation of proteins (FPOP), allowing researchers to study the solvent accessibility of proteins experimentally.
Jones became interested in science as a freshman at high school, where she took part in a national Science Technology Engineering Program. [ 2 ] She earned a BS in biochemistry at Syracuse University in 1999. [ 3 ] Jones completed her PhD at Georgia State University and specialized in structural biology. [ 4 ]
Jones received postdoctoral training in structural virology at the University of Alabama at Birmingham . She was a Pfizer postdoctoral researcher at Washington University in St. Louis working with Michael Gross on MS-based protein footprinting developed by Maleknia and co-workers in the late 1990s. [ 5 ] [ 6 ] [ 2 ] [ 7 ]
After her postdoctoral research, she joined Indiana University , where she became an associate professor. [ 8 ] [ 9 ] She moved to the University of Maryland School of Pharmacy in 2016. [ 10 ] In her research, Jones focusses on structural proteomics , having developed fast photochemical oxidation of proteins (FPOP) which uses an excimer laser for photolysis , which generates hydroxyl radicals. Hydroxyl radicals go on to oxidise the side chains of amino acids and provide solvent accessibility of proteins within a cell. [ 11 ] FPOP can provide information on the sites of ligand binding, protein interaction and protein conformational changes in vivo . More recently, her group has extended the platform with a no-flow platform for high-throughput in-cell measurements. [ 12 ]
In 2019, she received the Biophysical Society 's Junior Faculty Award. [ 13 ]
Jones also works on science outreach and improving representation in the sciences. She is a mentor in the UMD CURE Scholars Program [ 14 ] [ 15 ] and a member of the American Society for Mass Spectrometry Diversity and Outreach Working Group. [ 16 ] Jones is also co-director of the Initiative to Maximize Student Development (IMSD) Meyerhoff Graduate Fellowship Program , a program for increasing representation of minority students in STEM. [ 17 ]
In 2021, Jones was in the news for turning down a faculty position at the University of North Carolina at Chapel Hill in protest of controversy regarding the tenure status of journalist Nikole Hannah-Jones . [ 18 ] [ 19 ] | https://en.wikipedia.org/wiki/Lisa_Jones_(scientist) |
The Lise Meitner Prize for nuclear physics , established in 2000, is awarded every two years by the European Physical Society for outstanding work in the fields of experimental, theoretical or applied nuclear science. It is named after Lise Meitner to honour her fundamental contributions to nuclear physics and her courageous and exemplary life. [ 1 ] Not to be confused with the Gothenburg Lise Meitner Award . | https://en.wikipedia.org/wiki/Lise_Meitner_Prize |
Lisinopril is a medication belonging to the drug class of angiotensin-converting enzyme (ACE) inhibitors and is used to treat hypertension (high blood pressure), heart failure , and heart attacks . [ 7 ] For high blood pressure it is usually a first-line treatment. It is also used to prevent kidney problems in people with diabetes mellitus. [ 7 ] Lisinopril is taken orally (swallowed by mouth). [ 7 ] Full effect may take up to four weeks to occur. [ 7 ]
Common side effects include headache, dizziness, feeling tired, cough, nausea, and rash. [ 7 ] Serious side effects may include low blood pressure , liver problems, hyperkalemia (high blood potassium), and angioedema . [ 7 ] Use is not recommended during the entire duration of pregnancy as it may harm the baby. [ 7 ] Lisinopril works by inhibiting the renin–angiotensin–aldosterone system . [ 7 ]
Lisinopril was patented in 1978 and approved for medical use in the United States in 1987. [ 7 ] [ 10 ] It is available as a generic medication . [ 7 ] In 2022, it was the third most commonly prescribed medication in the United States, with more than 82 million prescriptions. [ 11 ] [ 12 ] It is available in combination with amlodipine (as lisinopril/amlodipine ) and in combination with hydrochlorothiazide (as lisinopril/hydrochlorothiazide ).
Lisinopril is typically used for the treatment of high blood pressure , congestive heart failure , and diabetic nephropathy and after acute myocardial infarction (heart attack). [ 7 ] [ 1 ] Lisinopril is part of the ACE inhibitors drug class. [ 1 ] Lisinopril is indicated for the treatment of hypertension, adjunctive therapy for heart failure, and acute myocardial infarction. [ 1 ]
Lisinopril is contraindicated in people who have a history of angioedema ( hereditary or idiopathic ) or who have diabetes and are taking aliskiren . [ 1 ]
Common side effects include headache, dizziness, feeling tired, cough, nausea, and rash. [ 7 ] Serious side effects may include low blood pressure , liver problems, hyperkalemia , and angioedema . [ 7 ] Use is not recommended during the entire duration of pregnancy as it may harm the baby. [ 7 ]
Animal and human data have revealed evidence of harm to the embryo and teratogenicity associated with ACE inhibitors. [ 1 ]
ACE-inhibitors like lisinopril are considered to be generally safe for people undergoing routine dental care , though the use of lisinopril prior to dental surgery is more controversial, with some dentists recommending discontinuation the morning of the procedure. [ 13 ] People may present to dental care suspicious of an infected tooth, but the swelling around the mouth may be due to lisinopril-induced angioedema, prompting emergency and medical referral. [ 13 ]
Lisinopril is the lysine -analog of enalaprilat , the active metabolite of enalapril. [ 14 ] Unlike other ACE inhibitors, it is not a prodrug , is not metabolized by the liver, and is excreted unchanged in the urine. [ 1 ]
Lisinopril is an ACE inhibitor , meaning it blocks the actions of angiotensin-converting enzyme (ACE) in the renin–angiotensin–aldosterone system (RAAS), preventing angiotensin I from being converted to angiotensin II . Angiotensin II is a potent direct vasoconstrictor and a stimulator of aldosterone release. Reduction in the amount of angiotensin II results in relaxation of the arterioles. Reduction in the amount of angiotensin II also reduces the release of aldosterone from the adrenal cortex, which allows the kidney to excrete sodium along with water into the urine and increases the retention of potassium ions. [ 15 ] Specifically, this process occurs in the peritubular capillaries of the kidneys in response to a change in Starling forces . [ 16 ] The inhibition of the RAAS system causes an overall decrease in blood pressure. [ 15 ]
Following oral administration of lisinopril, peak serum concentrations of lisinopril occur within about seven hours, [ 1 ] [ 15 ] although there was a trend to a small delay in time taken to reach peak serum concentrations in acute myocardial infarction patients. The peak effect of lisinopril is about 6 hours after administration for most people. [ 17 ] [ 18 ] Declining serum concentrations exhibit a prolonged terminal phase, which does not contribute to drug accumulation. This terminal phase probably represents saturable binding to ACE and is not proportional to dose. Lisinopril does not undergo metabolism and the absorbed drug is excreted unchanged entirely in the urine. Based on urinary recovery, the mean extent of absorption of lisinopril is approximately 25% (reduced to 16% in people with New York Heart Association Functional Classification (NYHA) Class II–IV heart failure), with large interpatient variability (6 to 60%) at all doses tested (5 to 80 mg). [ 1 ] [ 15 ] Lisinopril absorption is not affected by the presence of food in the gastrointestinal tract. [ 17 ] [ 19 ] [ 20 ]
Studies in rats indicate that lisinopril crosses the blood-brain barrier poorly. Multiple doses of lisinopril in rats result in little or no accumulation in brain tissue. [ 21 ]
Lisinopril does not bind to proteins in the blood. [ 1 ] [ 15 ] It does not distribute as well in people with NYHA Class II–IV heart failure. [ 1 ] [ 15 ]
Lisinopril leaves the body completely unchanged in the urine. [ 1 ] [ 15 ] The half-life of lisinopril is 12 hours, and is increased in people with kidney problems. [ 1 ] [ 15 ] While the plasma half-life of lisinopril has been estimated between 12 and 13 hours, the elimination half-life is much longer, at around 30 hours. [ 17 ] The full duration of action is between 24 and 30 hours. [ 17 ]
Lisinopril is the only water-soluble member of the ACE inhibitor class and thus has no metabolism by the liver . [ 17 ]
Pure lisinopril powder is white to off-white in color. [ 1 ] Lisinopril is soluble in water (approximately 13 mg/L at room temperature), [ 22 ] less soluble in methanol , and virtually insoluble in ethanol . [ 1 ]
Captopril , the first ACE inhibitor, is a functional and structural analog of a peptide derived from the venom of the jararaca, a Brazilian pit viper ( Bothrops jararaca ). [ 23 ] Enalapril is a derivative, designed by scientists at Merck to overcome the rash and bad taste caused by captopril. [ 24 ] [ 25 ] : 12–13
Enalapril is actually a prodrug ; the active metabolite is enalaprilat . [ 26 ]
The di-acid metabolite of enalapril , enalaprilat , and its lysine analogue lisinopril are potent inhibitors of angiotensin-converting enzyme (ACE); they do not contain sulphydryl groups. Both drugs can be assayed by high-pressure liquid chromatography and by radioimmunoassay and plasma ACE inhibition remains stable under normal storage conditions. It is therefore possible to study their pharmacokinetics as well as their pharmacodynamic effects in humans. Enalaprilat and lisinopril as well as ACE activity have been measured in blood taken during the course of two studies of the effects of these drugs on blood pressure and autonomic responsiveness. [ citation needed ]
Lisinopril is a synthetic peptide derivative of captopril. [ 22 ] Scientists at Merck created lisinopril by systematically altering each structural unit of enalaprilat, substituting various amino acids. Adding lysine at one end of the drug turned out to have strong activity and adequate bioavailability when given orally; analogs of that compound resulted in lisinopril, which takes its name from the discovery of lysine. Merck conducted clinical trials, and the drug was approved for hypertension in 1987 and congestive heart failure in 1993. [ 26 ]
The discovery posed a problem, since sales of enalapril were strong for Merck, and the company did not want to diminish those sales. Merck ended up entering into an agreement with Zeneca under which Zeneca received the right to co-market lisinopril, and Merck received the exclusive rights to an earlier stage aldose reductase inhibitor drug candidate, a potential diabetes treatment. Zeneca's marketing and brand name, "Zestril", turned out to be stronger than Merck's effort. [ 27 ] The drug became a blockbuster for AstraZeneca (formed in 1998), with annual sales in 1999 of $1.2B. [ 28 ]
The US patents expired in 2002. [ 28 ] Since then, lisinopril has been available under many brand names worldwide; it is also available in combination drugs with diuretic hydrochlorothiazide (as lisinopril/hydrochlorothiazide ), and with calcium channel blocker amlodipine (as lisinopril/amlodipine ). [ 5 ]
In July 2016, an oral solution formulation of lisinopril was approved for use in the United States. [ 7 ] [ 29 ] | https://en.wikipedia.org/wiki/Lisinopril |
The Lisp Algebraic Manipulator (also known as LAM ) was created by Ray d'Inverno , who had written Atlas LISP Algebraic Manipulation ( ALAM was designed in 1970). [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] LAM later became the basis for the interactive computer package SHEEP . | https://en.wikipedia.org/wiki/Lisp_Algebraic_Manipulator |
A Lissajous curve / ˈ l ɪ s ə ʒ uː / , also known as Lissajous figure or Bowditch curve / ˈ b aʊ d ɪ tʃ / , is the graph of a system of parametric equations
which describe the superposition of two perpendicular oscillations in x and y directions of different angular frequency ( a and b). The resulting family of curves was investigated by Nathaniel Bowditch in 1815, and later in more detail in 1857 by Jules Antoine Lissajous (for whom it has been named). [ 1 ] [ 2 ] [ 3 ] Such motions may be considered as a particular kind of complex harmonic motion .
The appearance of the figure is sensitive to the ratio a / b . For a ratio of 1, when the frequencies match a=b, the figure is an ellipse , with special cases including circles ( A = B , δ = π / 2 radians ) and lines ( δ = 0 ). A small change to one of the frequencies will mean the x oscillation after one cycle will be slightly out of synchronization with the y motion and so the ellipse will fail to close and trace a curve slightly adjacent during the next orbit showing as a precession of the ellipse. The pattern closes if the frequencies are whole number ratios i.e. a / b is rational .
Another simple Lissajous figure is the parabola ( b / a = 2 , δ = π / 4 ). Again a small shift of one frequency from the ratio 2 will result in the trace not closing but performing multiple loops successively shifted only closing if the ratio is rational as before. A complex dense pattern may form see below.
The visual form of such curves is often suggestive of a three-dimensional knot , and indeed many kinds of knots, including those known as Lissajous knots , project to the plane as Lissajous figures.
Visually, the ratio a / b determines the number of "lobes" of the figure. For example, a ratio of 3 / 1 or 1 / 3 produces a figure with three major lobes (see image). Similarly, a ratio of 5 / 4 produces a figure with five horizontal lobes and four vertical lobes. Rational ratios produce closed (connected) or "still" figures, while irrational ratios produce figures that appear to rotate. The ratio A / B determines the relative width-to-height ratio of the curve. For example, a ratio of 2 / 1 produces a figure that is twice as wide as it is high. Finally, the value of δ determines the apparent "rotation" angle of the figure, viewed as if it were actually a three-dimensional curve. For example, δ = 0 produces x and y components that are exactly in phase, so the resulting figure appears as an apparent three-dimensional figure viewed from straight on (0°). In contrast, any non-zero δ produces a figure that appears to be rotated, either as a left–right or an up–down rotation (depending on the ratio a / b ).
Lissajous figures where a = 1 , b = N ( N is a natural number ) and
are Chebyshev polynomials of the first kind of degree N . This property is exploited to produce a set of points, called Padua points , at which a function may be sampled in order to compute either a bivariate interpolation or quadrature of the function over the domain [−1,1] × [−1,1] .
The relation of some Lissajous curves to Chebyshev polynomials is clearer to understand if the Lissajous curve which generates each of them is expressed using cosine functions rather than sine functions.
The animation shows the curve adaptation with continuously increasing a / b fraction from 0 to 1 in steps of 0.01 ( δ = 0 ).
Below are examples of Lissajous figures with an odd natural number a , an even natural number b , and | a − b | = 1 .
Prior to modern electronic equipment, Lissajous curves could be generated mechanically by means of a harmonograph .
Lissajous curves can also be generated using an oscilloscope (as illustrated). An octopus circuit can be used to demonstrate the waveform images on an oscilloscope. Two phase-shifted sinusoid inputs are applied to the oscilloscope in X-Y mode and the phase relationship between the signals is presented as a Lissajous figure.
In the professional audio world, this method is used for realtime analysis of the phase relationship between the left and right channels of a stereo audio signal. On larger, more sophisticated audio mixing consoles an oscilloscope may be built-in for this purpose.
On an oscilloscope, we suppose x is CH1 and y is CH2, A is the amplitude of CH1 and B is the amplitude of CH2, a is the frequency of CH1 and b is the frequency of CH2, so a / b is the ratio of frequencies of the two channels, and δ is the phase shift of CH1.
A purely mechanical application of a Lissajous curve with a = 1 , b = 2 is in the driving mechanism of the Mars Light type of oscillating beam lamps popular with railroads in the mid-1900s. The beam in some versions traces out a lopsided figure-8 pattern on its side.
When the input to an LTI system is sinusoidal, the output is sinusoidal with the same frequency, but it may have a different amplitude and some phase shift . Using an oscilloscope that can plot one signal against another (as opposed to one signal against time) to plot the output of an LTI system against the input to the LTI system produces an ellipse that is a Lissajous figure for the special case of a = b . The aspect ratio of the resulting ellipse is a function of the phase shift between the input and output, with an aspect ratio of 1 (perfect circle) corresponding to a phase shift of ±90° and an aspect ratio of ∞ (a line) corresponding to a phase shift of 0° or 180°. [ citation needed ]
The figure below summarizes how the Lissajous figure changes over different phase shifts. The phase shifts are all negative so that delay semantics can be used with a causal LTI system (note that −270° is equivalent to +90°). The arrows show the direction of rotation of the Lissajous figure. [ citation needed ]
A Lissajous curve is used in experimental tests to determine if a device may be properly categorized as a memristor . [ citation needed ] It is also used to compare two different electrical signals: a known reference signal and a signal to be tested. [ 4 ] [ 5 ]
Lissajous figures are sometimes used in graphic design as logos . Examples include:
Lissajous curves have been used in the past to graphically represent musical intervals through the use of the Harmonograph , [ 11 ] a device that consists of pendulums oscillating at different frequency ratios. Because different tuning systems employ different frequency ratios to define intervals, these can be compared using Lissajous curves to observe their differences. [ 12 ] Therefore, Lissajous curves have applications in music education by graphically representing differences between intervals and among tuning systems. | https://en.wikipedia.org/wiki/Lissajous_curve |
In orbital mechanics , a Lissajous orbit ( pronounced [li.sa.ʒu] ), named after Jules Antoine Lissajous , is a quasi-periodic orbital trajectory that an object can follow around a Lagrangian point of a three-body system with minimal propulsion. Lyapunov orbits around a Lagrangian point are curved paths that lie entirely in the plane of the two primary bodies. In contrast, Lissajous orbits include components in this plane and perpendicular to it, and follow a Lissajous curve . Halo orbits also include components perpendicular to the plane, but they are periodic, while Lissajous orbits are usually not.
In practice, any orbits around Lagrangian points L 1 , L 2 , or L 3 are dynamically unstable, meaning small departures from equilibrium grow over time. [ 1 ] As a result, spacecraft in these Lagrangian point orbits must use their propulsion systems to perform orbital station-keeping . Although they are not perfectly stable, a modest effort of station keeping keeps a spacecraft in a desired Lissajous orbit for a long time.
In the absence of other influences, orbits about Lagrangian points L 4 and L 5 are dynamically stable so long as the ratio of the masses of the two main objects is greater than about 25. [ 2 ] The natural dynamics keep the spacecraft (or natural celestial body) in the vicinity of the Lagrangian point without use of a propulsion system, even when slightly perturbed from equilibrium. [ 3 ] These orbits can however be destabilized by other nearby massive objects. For example, orbits around the L 4 and L 5 points in the Earth–Moon system can last only a few million years instead of billions because of perturbations by the other planets in the Solar System . [ 4 ]
Several missions have used Lissajous orbits: ACE at Sun–Earth L1, [ 5 ] SOHO at Sun–Earth L1, DSCOVR at Sun–Earth L1, [ 6 ] WMAP at Sun–Earth L2, [ 7 ] and also the Genesis mission collecting solar particles at L1. [ 8 ] On 14 May 2009, the European Space Agency (ESA) launched into space the Herschel and Planck observatories, both of which use Lissajous orbits at Sun–Earth L2. [ 9 ]
ESA's Gaia mission also uses a Lissajous orbit at Sun–Earth L2. [ 10 ]
In 2011, NASA transferred two of its THEMIS spacecraft from Earth orbit to Lunar orbit by way of Earth–Moon L1 and L2 Lissajous orbits. [ 11 ]
In June 2018, Queqiao , the relay satellite for China's Chang'e 4 lunar lander mission, entered orbit around Earth-Moon L2. [ 12 ] [ a ]
In the 2005 science fiction novel Sunstorm by Arthur C. Clarke and Stephen Baxter , a huge shield is constructed in space to protect the Earth from a deadly solar storm. The shield is described to have been in a Lissajous orbit at L 1 . In the story a group of wealthy and powerful people shelter opposite the shield at L 2 so as to be protected from the solar storm by the shield, the Earth and the Moon.
In the 2017 science fiction novel Artemis by Andy Weir , a Lissajous orbit is used as a transfer point for routine travel to and from the Moon. | https://en.wikipedia.org/wiki/Lissajous_orbit |
This article contains a list of libraries that can be used in .NET languages . These languages require .NET Framework , Mono , or .NET , which provide a basis for software development , platform independence, language interoperability and extensive framework libraries. Standard Libraries (including the Base Class Library ) are not included in this article.
Apps created with .NET Framework or .NET run in a software environment known as the Common Language Runtime (CLR), [ 1 ] an application virtual machine that provides services such as security, memory management , and exception handling . The framework includes a large class library called Framework Class Library (FCL).
Thanks to the hosting virtual machine, different languages that are compliant with the .NET Common Language Infrastructure (CLI) can operate on the same kind of data structures. These languages can therefore use the FCL and other .NET libraries that are also written in one of the CLI compliant languages. When the source code of such languages are compiled, the compiler generates platform-independent code in the Common Intermediate Language (CIL, also referred to as bytecode ), which is stored in CLI assemblies . When a .NET app runs, the just-in-time compiler (JIT) turns the CIL code into platform-specific machine code. To improve performance, .NET Framework also comes with the Native Image Generator (NGEN), which performs ahead-of-time compilation to machine code.
This architecture provides language interoperability . Each language can use code written in other languages. Calls from one language to another are exactly the same as would be within a single programming language. If a library is written in one CLI language, it can be used in other CLI languages. Moreover, apps that consist only of pure .NET assemblies, can be transferred to any platform that contains an implementation of CLI and run on that platform. For example, apps written using .NET can run on Windows, macOS , and various versions of Linux .
.NET apps or their libraries, however, may depend on native platform features, e.g. COM . As such, platform independence of .NET apps depends on the ability to transfer necessary native libraries to target platforms. In 2019, the Windows Forms and Windows Presentation Foundation portions of .NET Framework were made open source. [ 2 ]
There are four primary .NET implementations that are actively developed and maintained:
Each implementation of .NET includes the following components:
The .NET Standard is a set of common APIs that are implemented in the Base Class Library of any .NET implementation. The class library of each implementation must implement the .NET Standard, but may also implement additional APIs. Traditionally, .NET apps targeted a certain version of a .NET implementation, e.g. .NET Framework 4.6. [ 5 ] [ 6 ] Starting with the .NET Standard, an app can target a version of the .NET Standard and then it could be used (without recompiling) by any implementation that supports that level of the standard. This enables portability across different .NET implementations.
The following table lists the .NET implementations that adhere to the .NET Standard and the version number at which each implementation became compliant with a given version of .NET Standard. For example, according to this table, .NET Core 3.0 was the first version of .NET Core that adhered to .NET Standard 2.1. This means that any version of .NET Core bigger than 3.0 (e.g. .NET Core 3.1) also adheres to .NET Standard 2.1.
First released in 2002, ASP.NET is an open-source server-side web application framework designed for web development to produce dynamic web pages. It is the successor to Microsoft's Active Server Pages (ASP) technology, built on the Common Language Runtime (CLR).
ASP.NET was completely rewritten in 2016 as a modular web framework, together with other frameworks like Entity Framework . The re-written framework uses the new open-source .NET Compiler Platform (also known by its codename "Roslyn") and is cross platform. The programming models ASP.NET MVC , ASP.NET Web API, and ASP.NET Web Pages (a model using only Razor pages) were merged into a unified MVC 6. [ 10 ]
Blazor is a free and open-source web framework that enables developers to create Single-page Web apps using C# and HTML in ASP.NET Razor pages ("components"). Blazor is part of the ASP.NET Core framework. Blazor Server apps are hosted on a web server, while Blazor WebAssembly apps are downloaded to the client's web browser before running. In addition, a Blazor Hybrid framework is available with server-based and client-based application components.
This is a computer vision and artificial intelligence library. It implements a number of genetic, fuzzy logic and machine learning algorithms with several architectures of artificial neural networks with corresponding training algorithms.
This is a cross-platform open source numerical analysis and data processing library. It consists of algorithm collections written in different programming languages (C++, C#, FreePascal, Delphi, VBA) and has dual licensing – commercial and GPL .
This library aims to provide methods and algorithms for numerical computations in science, engineering and everyday use. Covered topics include special functions, linear algebra, probability models, random numbers, interpolation, integral transforms and more. MIT/X11 license. [ 11 ]
This is a library for advanced scientific computation in the .NET Framework.
This is a high performance, typesafe numerical array set of classes and functions for general math, FFT and linear algebra. The library, developed for .NET/Mono, aims to provide 32- and 64-bit script-like syntax in C#, 2D & 3D plot controls, and efficient memory management. It is released under GPLv3 or commercial license. [ 11 ]
This is a integrated suite of UI controls and class libraries for use in developing test and measurement applications. The analysis class libraries provide various digital signal processing, signal filtering, signal generation, peak detection, and other general mathematical functionality.
This is a numerical component library for the .NET platform developed by CenterSpace Software . It includes signal processing (FFT) classes, a linear algebra (LAPACK & BLAS) framework, and a statistics package. [ 11 ]
This is a low-level C# binding for OpenGL , OpenGL ES and OpenAL . It runs on Windows, Linux, Mac OS X, BSD, Android and iOS. It can be used standalone or integrated into a GUI.
This is a graphical subsystem for rendering user interfaces, developed by Microsoft. It also contains a 3D rendering engine. In addition, interactive 2D content can be overlaid on 3D surfaces natively. [ 12 ] [ 13 ] It only runs on Windows operating systems.
This is a cross-platform game engine developed by Unity Technologies [ 14 ] and used to develop video games for PC , consoles , mobile devices and websites .
This is a computer vision and artificial intelligence library. [ 15 ] [ 16 ] It implements a number of image processing algorithms and filters. It is released under the LGPLv3 and partly GPLv3 license. Majority of the library is written in C# and thus cross-platform. [ citation needed ] Functionality of AForge.NET has been extended by the Accord.NET library. [ 17 ] [ 18 ]
This is another computer vision and artificial intelligence library, available under the Gnu Lesser General Public License , version 2.1. It is mainly written in C#.
These are C# wrappers around the underlying GTK+ and GNOME libraries, written in C and available on Linux, MacOS and Windows. [ 19 ]
This is a Microsoft GUI framework. The original Microsoft implementation runs on Windows operating systems and provides access to Windows User Interface Common Controls by wrapping the Windows API in managed code . [ 20 ] The alternative Mono implementation is open source and cross-platform (it runs on Windows, Linux, Unix and OS X). It is mainly compatible with the original implementation but not completely. The library is written in C# in order to avoid Windows dependence. [ 21 ] At the Microsoft Connect event on December 4, 2018, Microsoft announced releasing of Windows Forms as open source project on GitHub . [ 22 ] It is released under the MIT License . Windows Forms has become available for projects targeting the .NET framework. However, the framework is still available only on Windows platform and the Mono incomplete implementation of WinForms remains the only cross-platform implementation. [ 23 ] [ 24 ]
This is a graphical subsystem for rendering user interfaces in Windows-based applications by Microsoft. It is based on DirectX and employs XAML, an XML-based language, to define and link various interface elements. [ 25 ] WPF applications can be deployed as standalone desktop programs or hosted as an embedded object in a website. [ citation needed ] At the Microsoft Connect event on December 4, 2018, Microsoft announced releasing of WPF as open source project on GitHub . [ 22 ] It is released under the MIT License . Windows Presentation Foundation has become available for projects targeting the .NET framework. However, the system is still available only on Windows platform. [ 23 ] [ 24 ]
This is a set of Microsoft UI controls and features for the Universal Windows Platform (UWP). At the Microsoft Connect event on December 4, 2018, Microsoft announced releasing of WinUI as open source project on GitHub . [ 22 ] WinUI has become available for projects targeting the .NET framework. It is released under the MIT License . However, the library is still available only on Windows platform. [ 23 ] [ 24 ]
This is a cross-platform UI toolkit for development of native user interfaces that can be run on macOS, iOS, Android, and Universal Windows Platform apps. [ 26 ] [ 27 ] [ 19 ]
This is a cross-platform UI toolkit announced in May 2020 that originated as a fork of Xamarin.Forms and that can run on Android, iOS, Linux, macOS, Tizen, and Windows. .NET MAUI will run on .NET 6 and later. [ 28 ] [ 29 ] [ 30 ] The source code is licensed under MIT License and available on GitHub . [ 29 ]
This is an open-source cross-platform UI toolkit for development of user interfaces that can be run on Windows, Linux, macOS, iOS, Android, and WebAssembly. The source code is licensed under MIT License and available on GitHub [ 31 ]
This is an open source unit testing framework for .NET, written in C# and thus cross-platform. It is one of many programs in the xUnit family. Licensed under MIT License .
.NET Framework natively provides utilities for object–relational mapping [ 32 ] through ADO.NET , a part of the .NET stack since version 1.0. In the earlier years of .NET development, a number of third-party object–relational libraries emerged in order to fill some perceived gaps in the framework. [ 33 ] [ 34 ] [ 35 ] As the framework evolved, additional object–relational tools were added, such as the Entity Framework and LINQ to SQL , both introduced in .NET Framework 3.5 . These tools reduced the significance and popularity of third-party object–relational libraries.
This is an open source [ 36 ] object–relational mapping (ORM) framework for ADO.NET . It was a part of .NET Framework , but since Entity framework version 6 it is separated from .NET framework.
NHibernate is an object–relational mapper for the .NET platform.
General:
Numerical libraries:
Data: | https://en.wikipedia.org/wiki/List_of_.NET_libraries_and_frameworks |
This is a list of two-dimensional animation software . | https://en.wikipedia.org/wiki/List_of_2D_animation_software |
The following is a list of 3D animation software that have articles in Wikipedia. | https://en.wikipedia.org/wiki/List_of_3D_animation_software |
This list of 3D graphics software contains software packages related to the development and exploitation of 3D computer graphics . For a comparison, see Comparison of 3D computer graphics software . | https://en.wikipedia.org/wiki/List_of_3D_computer_graphics_software |
3D graphics have become so popular, particularly in video games , that specialized APIs (application programming interfaces) have been created to ease the processes in all stages of computer graphics generation. These APIs have also proved vital to computer graphics hardware manufacturers, as they provide a way for programmers to access the hardware in an abstract way, while still taking advantage of the special hardware of any specific graphics card .
The first 3D graphics framework was probably Core , published by the ACM in 1977.
These APIs for 3D computer graphics are particularly popular:
There are also higher-level 3D scene-graph APIs which provide additional functionality on top of the lower-level rendering API. Such libraries under active development include:
There is more interest in web browser based high-level API for 3D graphics engines. Some are: | https://en.wikipedia.org/wiki/List_of_3D_graphics_libraries |
Following is a list of notable software, computer programs, used to develop a mathematical representation of any three dimensional surface of objects, as 3D computer graphics , also called 3D modeling . | https://en.wikipedia.org/wiki/List_of_3D_modeling_software |
This page provides a list of 3D rendering software , the dedicated engines used for rendering computer-generated imagery . This is not the same as 3D modeling software , which involves the creation of 3D models, for which the software listed below can produce realistically rendered visualisations. Also not included are general-purpose packages which can have their own built-in rendering capabilities; these can be found in the List of 3D computer graphics software and List of 3D animation software . See 3D computer graphics software for more discussion about the distinctions. | https://en.wikipedia.org/wiki/List_of_3D_rendering_software |
The following is a list that contains general information about GPUs and video cards made by AMD , including those made by ATI Technologies before 2006, based on official specifications in table-form.
The headers in the table listed below describe the following:
Due to conventions changing over time, some numerical definitions such as core config, core clock, performance and memory should not be compared one-to-one across generations. The following tables are for reference use only, and do not reflect actual performance.
The following table shows features of AMD / ATI 's GPUs .
@165 Hz
The following table shows the graphics and compute APIs support across ATI/AMD GPU microarchitectures. Note that a branding series might include older generation chips.
1.3 (GCN 4)
[ 23 ] [ 24 ] [ 25 ]
1 Pixel pipelines : Vertex shaders : Texture mapping units : Render output units 2 OpenGL 1.0 (Generic 2D) is provided through software implementations.
1 Pixel pipelines : Vertex shaders : Texture mapping units : Render output units A First number indicates cards with 32 MB of memory. Second number indicates cards with 64 MB of memory. B First number indicates OEM cards. Second number indicates Retail cards.
1 Pixel pipelines : Vertex shaders : Texture mapping units : Render output units
250
250
4.0
64
1 Pixel shaders : Vertex shaders : Texture mapping units : Render output units
1 Pixel shaders : Vertex shaders : Texture mapping units : Render output units
17.28
256
350 (256 MB)
256
22.40
GDDR2
380 [ 35 ]
340 [ 35 ]
1520 [ 35 ]
1520 [ 35 ]
1520 [ 35 ]
380 [ 35 ]
256
21.76 [ 35 ]
256 2 [ 35 ]
1 Pixel shaders : Vertex Shaders : Texture mapping units : Render output units 2 The 256-bit version of the 9800 SE when unlocked to 8-pixel pipelines with third party driver modifications should function close to a full 9800 Pro. [ 37 ]
4
64
1 Pixel shaders : Vertex Shaders : Texture mapping units : Render output units
12.8 system
1 Pixel shaders : Vertex Shaders : Texture mapping units : Render output units
1 Pixel shaders : Vertex shaders : Texture mapping units : Render output units
9.6
GDDR3
128
1 Pixel shaders : Vertex Shaders : Texture mapping units : Render output units
Note that ATI X1000 series cards (e.g. X1900) do not have Vertex Texture Fetch, hence they do not fully comply with the VS 3.0 model. Instead, they offer a feature called "Render to Vertex Buffer (R2VB)" that provides functionality that is an alternative Vertex Texture Fetch.
1 Pixel shaders : Vertex shaders : Texture mapping units : Render output units
1 Unified shaders : Texture mapping units : Render output units 2 The clock frequencies may vary in different usage scenarios, as AMD PowerPlay technology is implemented. The clock frequencies listed here refer to the officially announced clock specifications. 3 The sideport is a dedicated memory bus. It is preferably used for a frame buffer .
PCIe 256
1 Pixel shaders : Vertex shaders : Texture mapping units : Render output units 2 Unified shaders : Texture mapping units : Render output units
1 Unified shaders : Texture mapping units : Render output units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory. 3 The TDP is reference design TDP values from AMD. Different non-reference board designs from vendors may lead to slight variations in actual TDP. 4 All models feature UVD2 and PowerPlay .
1 Unified shaders : Texture mapping units : Render output units 2 The clock frequencies may vary in different usage scenarios, as ATI PowerPlay technology is implemented. The clock frequencies listed here refer to the officially announced clock specifications. 3 The sideport is a dedicated memory bus. It preferably used for frame buffer .
• The Radeon HD 6000 series has a new tesselation engine which is said to double the performance when working with tesselation compared to the previous HD 5000 series.
China Only
28 CU
1073
120.2
34.3
3846
240.4
These GPUs are either integrated into the mainboard or occupy a Mobile PCI Express Module (MXM) .
1 Vertex shaders : Pixel shaders : Texture mapping units : Render output units .
1 Vertex shaders : Pixel shaders : Texture mapping units : Render output units .
1 Vertex shaders : Pixel shaders : Texture mapping units : Render output units .
1 Vertex shaders : Pixel shaders : Texture mapping units : Render output units .
OpenGL 3.3 is possible with latest drivers for all RV6xx.
1 Vertex shaders : Pixel shaders : Texture mapping units : Render output units . 2 Unified Shaderss : Texture mapping units : Render output units
(Watts)
1 Unified Shaders : Texture mapping units : Render output units
1 Unified shaders : Texture mapping units : Render output units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory.
800
1024
12.8
1 Unified shaders : Texture mapping units : Render output units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory.
1 Unified shaders : Texture mapping units : Render output units : Compute units 2 TDP specified for AMD reference designs, includes CPU power consumption. Actual TDP of retail products may vary.
1 Vertex shaders : Pixel shaders : Texture mapping units : Render output units 2 Unified shaders : Texture mapping units : Render output units : Compute Units
1 Vertex shaders : Pixel shaders : Texture mapping unit : Render output units 2 Unified shaders : Texture mapping unit : Render output units
1 Unified shaders : Texture mapping units : Render output units : Compute Units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory 3 Windows 7, 8.1, 10 Support for Fire Pro Cards with Terascale 2 and later by firepro driver 15.301.2601 [ 331 ]
1 Unified shaders : Texture mapping units : Render output units : Compute Units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory. 3 Support for Windows 7, 8.1 for OpenGL 4.4 and OpenCL 2.0, when Hardware is prepared with firepro driver 14.502.1045 [ 336 ]
1 Unified shaders : Texture mapping units : Render output units : Compute Units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory. 3 OpenGL 4.4: support with AMD FirePro driver release 14.301.000 or later, in footnotes of specs [ 346 ]
In 2014, AMD released the D-Series specifically for Mac Pro workstations. [ 347 ]
1 Unified shaders : Texture mapping units : Render output units : compute units
1 Unified shaders : Texture mapping units : Render output units : compute units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory. 3 OpenGL 4.4: support with AMD FirePro driver release 14.301.000 or later, in footnotes of specs [ 346 ]
1 Unified shaders : Texture mapping units : Render output units : compute units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory.
1 Unified shaders : Texture mapping units : Render output units : Compute units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory. 3 OpenGL 4.4: support with AMD FirePro driver release 14.301.000 or later, in footnotes of specs [ 346 ]
2013
1 Unified shaders : Texture mapping units : Render output units : compute units 2 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory.
1 Unified shaders : Texture mapping units : Render output units 2 CU = Compute units 3 The effective data transfer rate of GDDR5 is quadruple its nominal clock, instead of double as it is with other DDR memory.
105 (eDRAM) [ 669 ]
eDRAM (192 parallel pixel processors)
eDRAM (16000 with 4x MSAA)
GPU + eDRAM
FP16: 8,012,800
FP16: 8013
FP16: 24,294,400
(2:1 sparse
(2:1 sparse
FP16: 24294.4
FP16: 20,579,328 (Boost)
FP16: 20579.2 (Boost)
FP16: ~2,048,000/ ~3,276,800 (Boost)
FP16: 2048/ 3276.8 (Boost)
Radeon 740M - Phoenix ( ROG Ally )
FP16: 5,120,000 (Boost) ( dual-issue shader ALUs - Resulting in half of this value.) 5
FP16: 5120 (Boost) ( dual-issue shader ALUs) 5
DirectML
( ROG Ally Extreme )
FP16: 16,590,000 (Boost) ( dual-issue shader ALUs - Resulting in half of this value.) 5
FP16: 16590 (Boost) ( dual-issue shader ALUs) 5
FP16: 66,662,400 (Boost) ( dual-issue shader ALUs - Resulting in half of this value.) 5
(2:1 sparse (Boost)
DDR5
FP16: 33331.2 (Boost)
1 Pixel shaders : Vertex shaders : Texture mapping units : Render output units 2 Unified shaders : Texture mapping units : Render output units 3 Unified shaders : Texture mapping units : Render output units : RT Cores 4 The Latte looks similar to the RV730 used in the Radeon HD4650/4670. [ 682 ] 5 In most cases, especially in games, half of this data can be considered. [ 683 ] | https://en.wikipedia.org/wiki/List_of_AMD_graphics_processing_units |
This is a list of development tools for 32-bit ARM Cortex-M -based microcontrollers , which consists of Cortex-M0, Cortex-M0+, Cortex-M1, Cortex-M3, Cortex-M4, Cortex-M7, Cortex-M23, Cortex-M33, Cortex-M35P, Cortex-M52, Cortex-M55, and Cortex-M85 cores.
IDE, compiler, linker, debugger, flashing (in alphabetical order):
Notes:
JTAG and/or SWD debug interface host adapters (in alphabetical order):
Debugging tools and/or debugging plug-ins (in alphabetical order):
Commonly referred to as RTOS :
The following are free C/C++ libraries: | https://en.wikipedia.org/wiki/List_of_ARM_Cortex-M_development_tools |
This is a comparison of chipsets , manufactured by ATI Technologies .
VIA VT82C686B , ALI M1535D+
Turion 64
Athlon 64 X2, Sempron
ULi M1573
Athlon 64 X2, Sempron
ULi M1573
Turion 64, Athlon 64
ULi M1575
Athlon 64 X2, Sempron
Athlon 64 X2, Sempron | https://en.wikipedia.org/wiki/List_of_ATI_chipsets |
The following is a list of notable software for creating, modifying and deploying Adobe Flash and Adobe Shockwave format.
"Authoring" in computing, is the act of creating a document , especially a multimedia document, hypertext or hypermedia . [ 1 ] [ 2 ] | https://en.wikipedia.org/wiki/List_of_Adobe_Flash_software |
The following is a list of software products by Adobe Inc.
Creative Suite Creative Cloud eLearning Suite
Standalone package
Adobe Experience Cloud ( AEC ) is a collection of integrated online marketing and Web analytics solutions by Adobe Inc. It includes a set of analytics , social , advertising , media optimization , targeting , Web experience management and content management solutions. It includes: [ 3 ]
Adobe Creative Suite ( CS ) was a series of software suites of graphic design , video editing , and web development applications made or acquired by Adobe Systems . It included:
Adobe Creative Cloud is the successor to Creative Suite. It is based on a software as a service model. It includes everything in Creative Suite 6 with the exclusion of Fireworks and Encore , as both applications were discontinued. It also introduced a few new programs, including Muse , Animate , InCopy and Story CC Plus.
Adobe Technical Communication Suite is a collection of applications made by Adobe Systems for technical communicators, help authors, instructional designers, and eLearning and training design professionals. It includes:
Adobe eLearning Suite was a collection of applications made by Adobe Systems for learning professionals, instructional designers, training managers, content developers, and educators.
An Adobe Certified Expert ( ACE ) is a person who has demonstrated proficiency with Adobe Systems software products by passing one or more product-specific proficiency exams set by Adobe. [ 13 ] | https://en.wikipedia.org/wiki/List_of_Adobe_software |
This is a list of notable Ajax frameworks , used for creating web applications with a dynamic link between the client and the server. Some of the frameworks are JavaScript compilers, for generating JavaScript and Ajax that runs in the web browser client; some are pure JavaScript libraries; others are server-side frameworks that typically rely on JavaScript libraries.
JavaScript frameworks are browser-side frameworks very commonly used in Ajax development.
There are hundreds of JavaScript frameworks available. According to latest surveys, [ 1 ] [ 2 ] the most used JavaScript frameworks are:
Other notable frameworks that are more AJAX specific, and not among the list of general purpose frameworks:
These frameworks use Java for server-side Ajax operations:
The following frameworks are available for the Windows .NET platform:
A PHP Ajax framework is able to deal with database, search data, and build pages or parts of page and publish the page or return data to the XMLHttpRequest object.
These frameworks use Python for client-side Ajax operations:
The Ruby on Rails framework used to implement a Domain-specific language named RJS, which can be used to write Ruby code that generates Javascript code. The code generated by RJS was usually loaded using Ajax, e.g. by using Ajax-enabled helper methods Ruby on Rails provides, such as the link_to_remote helper. It was replaced by jQuery as of Rails 3.1 [ 8 ]
Many of the Ruby on Rails Ajax-enabled helper methods used to work by using Prototype to perform an Ajax request in older versions of Rails. In most cases Javascript code is returned by the server to be executed by the browser, unlike the usual case where Ajax is used to retrieve data in XML or JSON format. [ 9 ] | https://en.wikipedia.org/wiki/List_of_Ajax_frameworks |
This is a list of Android launchers , which present the main view of the device and are responsible for starting other apps and hosting live widgets .
[ 48 ]
(API level 21) [ 57 ]
Source available on GitHub. | https://en.wikipedia.org/wiki/List_of_Android_launchers |
This is a list of Apple II applications including utilities and development tools. There is a separate List of Apple II games . | https://en.wikipedia.org/wiki/List_of_Apple_II_application_software |
This is a list of notable bulletin board system (BBS) software packages. [ 1 ] | https://en.wikipedia.org/wiki/List_of_BBS_software |
The following table provides an overview of notable building information modeling (BIM) software. | https://en.wikipedia.org/wiki/List_of_BIM_software |
This is a list of notable Business Process Execution Language (BPEL) and Business Process Model and Notation (BPMN) engines. | https://en.wikipedia.org/wiki/List_of_BPEL_engines |
This is a list of notable Business Process Model and Notation 2.0 (BPMN 2.0) Workflow Management Systems (WfMSs). | https://en.wikipedia.org/wiki/List_of_BPMN_2.0_engines |
The Balkan endemic plants includes a number of unique taxa and ( species , subspecies , variety and forms ) that are widespread in a variety of sizes area and,
including stenoendemics .
The following list of endemic plants on the Balkans includes taxa from Bulgaria , Greece , Albania , Kosovo , North Macedonia , Serbia , Bosnia and Herzegovina , Montenegro , Croatia , Slovenia and the European part of Turkey . The northeast limit of this area is the Sava river valley. The boundary then continues along the Danube . It also includes the Pannonian zone of the Balkans up to southern Romania .
Observed endemics are classified in 163 genera and 52 families . [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] | https://en.wikipedia.org/wiki/List_of_Balkan_endemic_plants |
This is a list of recipients of the Balzan Prize , one of the world's most prestigious academic awards. The International Balzan Prize Foundation awards four annual monetary prizes to people or organizations who have made outstanding achievements in the humanities, natural sciences, culture, and peace on an international level. The Prizes are awarded in four subject areas: "two in literature, the moral sciences and the arts" and "two in the physical, mathematical and natural sciences and medicine." [ 1 ] The special Prize for Humanity, Peace and Fraternity is presented at intervals of every three years or longer. | https://en.wikipedia.org/wiki/List_of_Balzan_Prize_recipients |
In the US, a Basic Trading Area is a geographic region defined originally in the Rand McNally Commercial Atlas and Marketing Guide and used by the FCC where a Personal Communications Service can operate. [ 1 ] It consists of the counties surrounding a city designated as the basic trading center. [ 2 ] | https://en.wikipedia.org/wiki/List_of_Basic_Trading_Areas |
List of cross-platform multi-threading libraries for the C++ programming language . | https://en.wikipedia.org/wiki/List_of_C++_multi-threading_libraries |
In botany, C 4 carbon fixation is one of three known methods of photosynthesis used by plants. C 4 plants increase their photosynthetic efficiency by reducing or suppressing photorespiration , which mainly occurs under low atmospheric CO 2 concentration, high light, high temperature, drought, and salinity. [ 2 ] [ 3 ] There are roughly 8,100 known C 4 species, which belong to at least 61 distinct evolutionary lineages in 19 families (as per APG IV classification [ 4 ] ) of flowering plants . [ 1 ] Among these are important crops such as maize , sorghum and sugarcane , but also weeds and invasive plants . [ 1 ] Although only 3% of flowering plant species use C 4 carbon fixation, they account for 23% of global primary production . [ 5 ] The repeated, convergent C 4 evolution from C 3 ancestors has spurred hopes to bio-engineer the C 4 pathway into C 3 crops such as rice . [ 1 ] [ 5 ]
C 4 photosynthesis probably first evolved 30–35 million years ago in the Oligocene , and further origins occurred since, most of them in the last 15 million years. C 4 plants are mainly found in tropical and warm-temperate regions, predominantly in open grasslands where they are often dominant. While most are graminoids , other growth forms such as forbs , vines, shrubs, and even some trees and aquatic plants are also known among C 4 plants. [ 1 ]
C 4 plants are usually identified by their higher 13 C/ 12 C isotopic ratio compared to C 3 plants or their typical leaf anatomy. [ 5 ] The distribution of C 4 lineages among plants has been determined through phylogenetics and was considered well known as of 2016 [update] . Monocots – mainly grasses ( Poaceae ) and sedges ( Cyperaceae ) – account for around 80% of C 4 species, but they are also found in the eudicots . [ 1 ] Moreover, almost all C 4 plants are herbaceus , with the notable exception of some woody species from the Euphorbia genus, such as the tree Euphorbia olowaluana . [ 6 ] The reason behind C 4 metabolism extreme rarity in trees is debated: hypotheses vary from a possible reduction in photosynthetic quantum yield under dense canopy conditions, coupled with an increased metabolic energy consumption (inherent to C 4 metabolism itself), to less efficient sunflecks utilization. [ 7 ]
The following list presents known C 4 lineages by family, based on the overview by Sage (2016). [ 1 ] They correspond to single species or clades thought to have acquired the C 4 pathway independently. In some lineages that also include C 3 and C 3 –C 4 intermediate species, the C 4 pathway may have evolved more than once. [ 1 ]
The large acanthus family Acanthaceae includes one genus with C 4 species, found in dry habitats from Africa to Asia. [ 10 ]
While many species in the ice plant family Aizoaceae use crassulacean acid metabolism (CAM), one subfamily with drought-tolerant and halophytic plants includes C 4 species: [ 11 ]
The amaranth family Amaranthaceae (including the former goosefoot family Chenopodiaceae) contains around 800 known C 4 species, which belong to 14 distinct lineages in seven subfamilies. This makes Amaranthaceae the family with most C 4 species and lineages among the eudicots. [ 1 ] Suaeda aralocaspica and species of the genus Bienertia use a particular, single-cell type of C 4 carbon fixation. [ 1 ] [ 12 ]
The composite family Asteraceae contains three C 4 lineages, in two different tribes of subfamily Asteroideae . [ 1 ] [ 20 ] They include the model genus Flaveria with closely related C 3 , C 4 , and intermediate species. [ 1 ]
The borage family Boraginaceae contains one widespread C 4 genus, Euploca , which has also been treated as part of a distinct family Heliotropiaceae . [ 24 ]
The Cleomaceae , formerly included in the caper family Capparaceae , contains three C 4 species in genus Cleome . These three species independently acquired the C 4 pathway; the genus also contains numerous C 3 as well as C 3 –C 4 intermediate species. [ 1 ] [ 26 ] [ 27 ]
In the carnation family Caryophyllaceae , the C 4 pathway evolved once, in a clade within the polyphyletic genus Polycarpaea . [ 1 ] [ 28 ]
The sedge family Cyperaceae is second only to the grasses in number of C 4 species. Prominent C 4 sedges include culturally important species such as papyrus ( Cyperus papyrus ) and chufa ( C. esculentus ) but also purple nutsedge ( C. rotundus ), one of the world's major weeds. Eleocharis vivipara uses C 3 carbon fixation in underwater leaves and C 4 carbon fixation in aerial leaves. [ 1 ]
The spurge family Euphorbiaceae contains the largest single C 4 lineage among eudicots. The C 4 spurges are diverse and widespread; they range from weedy herbs to the only known C 4 trees – four species from Hawaii, including Euphorbia olowaluana (up to 10 m) and E. herbstii (up to 8 m). [ 1 ] [ 8 ]
Contains a C 4 genus with a single species.
Includes the only known aquatic C 4 plants. [ 1 ]
The two C 4 species within the same genus have acquired the pathway independently.
The single genus of this family forms one C 4 lineage. CAM photosynthesis is also known. Common purslane ( Portulaca oleracea ) is a major weed but also a vegetable. [ 1 ]
The grass family includes most of the known C 4 species – around 5000. They are only found in subfamilies of the PACMAD clade. Major C 4 crops such as maize , sugarcane , sorghum and pearl millet belong in this family. The only known species with C 3 , C 4 and intermediate variants, Alloteropsis semialata , is a grass. [ 1 ] | https://en.wikipedia.org/wiki/List_of_C4_plants |
This is a list of CAS numbers by chemical formulas and chemical compounds , indexed by formula.The CAS number is a unique number applied to a specific chemical by the Chemical Abstracts Service (CAS). This list complements alternative listings to be found at list of inorganic compounds and glossary of chemical formulae . | https://en.wikipedia.org/wiki/List_of_CAS_numbers_by_chemical_compound |
This is a list of computer-aided technologies (CAx) companies and their software products. Software using computer-aided technologies (CAx) has been produced since the 1970s for a variety of computer platforms . This software may include applications for computer-aided design (CAD), computer-aided engineering (CAE), computer-aided manufacturing (CAM) and product data management (PDM).
The list is far from complete or representative as the CAD business landscape is very dynamic: almost every month new companies appear, old companies go out of business, and companies split and merge. Sometimes some names disappear and reappear again.
Shalin Designs
United States
Germany
Australia
Note: whilst IMSI design continues to market, according to their Facebook page they do not appear to be providing customer support nor have they actively posted since 2019.
Production Milling
Advanced Milling
FreeForm Machining
Production Turning
Advanced Turning
Advanced Wire EDM
Advanced Fabrication
Acquired, orphaned, failed or rebranded.
Developed by companies for their own use. Some are no longer used as the organizations are now using commercial systems. | https://en.wikipedia.org/wiki/List_of_CAx_companies |
Many synthetic cannabinoids were designed by Pfizer in the 1970s and 1980s, and feature an alphanumeric code beginning with the prefix "CP" (after Charles Pfizer ). [ 1 ] Recently, several members of this class of cannabinoids have been discovered in recreational drug products. [ 2 ] [ 3 ] [ 4 ] | https://en.wikipedia.org/wiki/List_of_CP_cannabinoids |
C# is a programming language . The following is a list of software programmed in it: | https://en.wikipedia.org/wiki/List_of_C_Sharp_software |
Chi Epsilon is a national collegiate civil engineering honor society in the United States. [ 1 ] Following are its chapters. [ 1 ] [ 2 ] Chapters are designated by the school at which they are located and a number indicating charter order. | https://en.wikipedia.org/wiki/List_of_Chi_Epsilon_chapters |
As of September 2021 [update] , the International Union for Conservation of Nature (IUCN) has evaluated the conservation status of 15 species within Chromista . [ 1 ] The IUCN has not evaluated any protist species other than those in Phaeophyceae. No Chromista subspecies or subpopulations have been evaluated. No evaluated Chromista species are confirmed to be extinct , but four are tagged as possibly extinct.
As of 2005 [update] the New Zealand Threat Classification System has evaluated 38 species of macroalgae as Threatened and 23 as Data Deficient. [ 2 ] Some of these species are only of concern nationally. [ 2 ]
All are brown algae ( Phaeophyceae ): | https://en.wikipedia.org/wiki/List_of_Chromista_by_conservation_status |
This is a list of old Macintosh software that no longer runs on current Macs. The software might require Mac OS 9 or other versions of the classic Mac OS that doesn't run on Apple 's current Macs . Note that most old programs can still be run using emulators , such as SheepShaver , vMac , or Basilisk II .
For a list of current programs, see List of Mac software . Third-party databases include VersionTracker , MacUpdate and iUseThis . Since a list like this might grow too big and become unmanageable, this list is confined to those programs for which a Wikipedia article exists. | https://en.wikipedia.org/wiki/List_of_Classic_Mac_OS_software |
This is a list of notable CD and DVD copy protection schemes.
For other medias, see List of Copy Protection Schemes . | https://en.wikipedia.org/wiki/List_of_Compact_Disc_and_DVD_copy_protection_schemes |
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