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Countercurrent chromatography CCD was used to separate a wide variety of useful compounds for several decades. Standard column chromatography consists of a solid stationary phase and a liquid mobile phase, while gas chromatography (GC) uses a solid or liquid stationary phase on a solid support and a gaseous mobile phase. By contrast, in liquid-liquid chromatography, both the mobile and stationary phases are liquid. The contrast is, however not as stark as it first appears. In reversed-phase chromatography, for example, the stationary phase can be regarded as a liquid which is immobilized by chemical bonding to a micro-porous silica solid support. In countercurrent chromatography centrifugal or gravitational forces immobilize the stationary liquid layer. By eliminating solid supports, permanent adsorption of the analyte onto the column is avoided, and a high recovery of the analyte can be achieved. The countercurrent chromatography instrument is easily switched between normal phase chromatography and reversed-phase chromatography simply by changing the mobile and stationary phases. With column chromatography, the separation potential is limited by the commercially available stationary phase media and its particular characteristics. Nearly any pair of immiscible solutions can be used in countercurrent chromatography provided that the stationary phase can be successfully retained. Solvent costs are also generally lower than for high-performance liquid chromatography (HPLC) | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography In comparison to column chromatography, flows and total solvent usage can in most countercurrent chromatography separations may be reduced by half and even up to a tenth. Also, the cost of purchasing and disposing of stationary phase media is eliminated. Another advantage of countercurrent chromatography is that experiments conducted in the laboratory can be scaled to industrial volumes. When gas chromatography or HPLC is carried out with large volumes, resolution is lost due to issues with surface-to-volume ratios and flow dynamics; this is avoided when both phases are liquid. The CCC separation process can be thought of as occurring in three stages: mixing, settling, and separation of the two phases (although they often occur continuously). Vigorous mixing of the phases is critical in order to maximize the interfacial area between them and enhance mass transfer. The analyte will distribute between the phases according to its partition coefficient which is also called the distribution coefficient, distribution constant, or partition ratio and is represented by P, K, D, K, or K. The partition coefficient for an analyte in a particular biphasic solvent system is independent of the volume of the instrument, flow rate, stationary phase retention volume ratio and the g-force required to immobilize the stationary phase. The degree of stationary phase retention is a crucial parameter | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography Common factors that influence stationary phase retention are flow rate, solvent composition of the biphasic solvent system, and the g-force. The stationary phase retention is represented by the stationary phase volume retention ratio (Sf) which is the volume of the stationary phase divided by the total volume of the instrument. The settling time is a property of the solvent system and the sample matrix, both of which greatly influence stationary phase retention. To most process chemists, the term "countercurrent" implies two immiscible liquids moving in opposing directions, as typically occurs in large centrifugal extractor units. With the exception of dual flow (see below) CCC, most countercurrent chromatography modes of operation have a stationary phase and a mobile phase. Even in this situation, countercurrent flows occur within the instrument column. Several researchers have proposed renaming both CCC & CPC to liquid-liquid chromatography, but others feel the term "countercurrent" itself is a misnomer. Unlike column chromatography and high-performance liquid chromatography, countercurrent chromatography operators can inject large volumes relative to column volume. Typically 5 to 10% of coil volume can be injected. In some cases this can be increased to as high as 15 to 20% of the coil volume. Typically, most modern commercial CCC and CPC can inject 5 to 40 g per liter capacity | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography The range is so large, even for a specific instrument, let alone all instrument options, as the type of target, matrix and available biphasic solvent vary so much. Approximately 10 g per liter would be a more typical value, that the majority of applications could use as a base value. The countercurrent separation starts with choosing an appropriate biphasic solvent system for the desired separation. A wide array of biphasic solvent mixtures are available to the CCC practitioner including the combination n-hexane (or heptane), ethyl acetate, methanol and water in different proportions. This basic solvent system is sometimes referred to as the HEMWat solvent system. The choice of solvent system may be guided by perusal of the CCC literature. The familiar technique of thin layer chromatography may also be employed to determine an optimal solvent system. The organization of solvent systems into "families" has greatly facilitated the choice of solvent systems as well. A solvent system can be tested with a one-flask partitioning experiment. The measured partition coefficient from the partitioning experiment will indicate the elution behavior of the compound. Typically, it is desirable to choose a solvent system where the target compound(s) have a partition coefficient between 0.25 and 8. Historically, it was thought that no commercial countercurrent chromatograph could cope with the high viscosities of ionic liquids | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography However, modern instruments that can accommodate 30 to 70+ % ionic liquids (and potentially 100% ionic liquid, if both phases are suitably customized ionic liquids) have become available. Ionic liquids can be customized for polar / non-polar organic, achiral and chiral compounds, bio-molecule, and inorganic separations, as ionic liquids can be customized to have extraordinary solvency and specificity. After the biphasic solvent system has been chosen a batch of is formulated and equilibrated in a separatory funnel. This step is called pre-equilibration of the solvent system. The two phases are separated. Then the column is filled with stationary with a pump. Next, the column is set an equilibration conditions, such as the desired rotation speed, and the mobile phase is pumped through the column. The mobile phase displaces the a portion of the stationary phase until column equilibration is achieved and the mobile phase elutes from the column. The sample may be introduced into the column at any time during the column equilibration step or after equilibration has been accomplished. After the volume of eluant surpasses the volume of the mobile phase in the column, the sample components will begin to elute. Compounds with a partition coefficient of unity will elute when one column volume of mobile phase has passed through the column since the time of injection. The compound can then be introduced to another stationary phase to help increase the resolution of results | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography The flow is stopped after the target compound(s) are eluted or the column is extruded by pumping the stationary phase through the column. An example of a major application of countercurrent chromatography is to take an extremely complex matrix such as a plant extract, perform the countercurrent chromatography separation with a carefully selected solvent system, and extrude the column to recover all of the sample. The original complex matrix will have been fractionated into discrete narrow polarity bands, which may then be assayed for chemical composition or bioactivity. Performing one or more countercurrent chromatography separations in conjunction with other chromatographic and non chromatographic techniques has the potential for rapid advances in compositional recognition of extremely complex matrices. Droplet countercurrent chromatography (DCCC) was introduced in 1970 by Tanimura, Pisano, Ito, and Bowman. DCCC uses only gravity to move the mobile phase through the stationary phase which is held in long vertical tubes connected in series. In the descending mode, droplets of the denser mobile phase and sample are allowed to fall through the columns of the lighter stationary phase using only gravity. If a less-dense mobile phase is used it will rise through the stationary phase; this is called ascending mode. The eluent from one column is transferred to another; the more columns that are used, the more theoretical plates can be achieved | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography DCCC enjoyed some success with natural product separations but was largely eclipsed by the rapid development of high-speed countercurrent chromatography. The main limitation of DCCC is that flow rates are low, and poor mixing is achieved for most binary solvent systems. The modern era of CCC began with the development of the planetary centrifuge by Dr. Yoichiro Ito which was first introduced in 1966 as a closed helical tube which was rotated on a "planetary" axis as is turned on a "sun" axis. A flow-through model was subsequently developed and the new technique was called countercurrent chromatography in 1970. The technique was further developed by employing test mixtures of DNP amino acids in a chloroform:glacial acetic acid:0.1 M aqueous hydrochloric acid (2:2:1 v/v) solvent system. Much development was needed to engineer the instrument so that required planetary motion could be sustained while the phases were being pumped through the coil(s). Parameters such as the relative rotation of the two axes (synchronous or non-synchronous), the direction of flow through the coil, and the rotor angles were investigated. By 1982 the technology was sufficiently advanced for the technique to be called "high-speed" countercurrent chromatography (HSCCC). Peter Carmeci initially commercialized the PC Inc. Ito Multilayer Coil Separator/Extractor which utilized a single bobbin (onto which the coil is wound) and a counterbalance, plus a set of "flying leads" which are tubing that connect the bobbins. Dr | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography Walter Conway & others later evolved the bobbin design such that multiple coils, even coils of different tubing sizes, could be placed on the single bobbin. Edward Chou later evolved and commercialized a triple bobbin design as the Pharmatech CCC which had a de-twist mechanism for leads between the three bobbins. The Quattro CCC released in 1993 further evolved the commercially available instruments by utilizing a novel mirror image, twin bobbin design that did not need the de-twist mechanism of the Pharmatech between the multiple bobbins, so could still accommodate multiple bobbins on the same instrument. Hydrodynamic CCC are now available with up to 4 coils per instrument. These coils can be in PTFE, PEEK, PVDF, or stainless steel tubing. The 2, 3 or 4 coils can all be of the same bore to facilitate "2D" CCC (see below). The coils may be connected in series to lengthen the coil and increase the capacity, or the coils may be linked in parallel so that 2, 3, or 4 separations may be done simultaneously. The coils can also be of different sizes, on one instrument, ranging from 1 to 6 mm on one instrument, thus allowing a single instrument to optimize from mg to kilos per day. More recently instrument derivatives have been offered with rotating seals for various hydrodynamic CCC designs, instead of flying leads, either as custom or standard options. The operating principle of CCC equipment requires a column consisting of a tube coiled around a bobbin | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography The bobbin is rotated in a double-axis gyratory motion (a cardioid), which causes a variable g-force to act on the column during each rotation. This motion causes the column to see one partitioning step per revolution and components of the sample separate in the column due to their partitioning coefficient between the two immiscible liquid phases. "High-performance" countercurrent chromatography (HPCCC) works in much the same way as HSCCC. A seven-year R&D process produced HPCCC instruments that generated 240 g's, compared to the 80 g's of the HSCCC machines. This increase in g-force and larger bore of the column has enabled a ten-fold increase in throughput, due to improved mobile phase flow rates and a higher stationary phase retention. is a preparative liquid chromatography technique, however with the advent of the higher-g HPCCC instruments it is now possible to operate instruments with sample loadings as low as a few milligrams, whereas in the past 100s of milligrams had been necessary. Major application areas for this technique include natural product purification and drug development. Hydrostatic CCC or centrifugal partition chromatography (CPC) was invented in the 1980s by the Japanese company Sanki Engineering Ltd, whose president was Kanichi Nunogaki. CPC has been extensively developed in France starting from the late 1990s. In France, they initially optimized the stacked disc concept initiated by Sanki | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography More recently, in France and UK, non-stacked disc CPC configurations have been developed with PTFE, stainless steel or titanium rotors. These have been designed to overcome possible leakages between the stacked discs of the original concept, and to allow steam cleaning for Good manufacturing practice. The volumes ranging from a 100 ml to 12 liters are available in different rotor materials. The 25-liter rotor CPC has a titanium rotor. This technique is sometimes sold under the name "fast" CPC or "high-performance" CPC. The centrifugal partition chromatograph instrument is constituted with a unique rotor which contains the column. This rotor rotates on its central axis (while HSCCC column rotates on its planetary axis and simultaneously rotates eccentrically about another solar axis). With less vibrations and noise, the CPC offers a typical rotation speed range from 500 to 2000 rpm. Contrary to hydrodynamic CCC, the rotation speed is not directly proportional to the retention volume ratio of the stationary phase. Like DCCC, CPC can be operated in either descending or ascending mode, where the direction is relative to the force generated by the rotor rather than gravity. A redesigned CPC column with larger chambers and channels has been named centrifugal partition extraction (CPE). In the CPE design, faster flow rates and increased column loading can be achieved. CPC offers direct scale-up from analytical apparatuses (few milliliters) to industrial apparatuses (several liters) for fast batch-production | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography CPC seems particularly suited to accommodate aqueous two-phase solvent systems. Generally, CPC instruments can retain solvent systems that are not well-retained in a hydrodynamic instrument due to small differences in density between the phases. It has been very helpful for the development of CPC instrumentation to visualize the flow patterns which give rise to the mixing and settling in the CPC chamber with an asynchronous camera and a stroboscope triggered by the CPC rotor. The aforementioned hydrodynamic and hydrostatic instruments may be employed in a variety of ways, or modes of operation, in order to address the particular separation needs of the scientist. Many modes of operation have been devised to take advantage of the strengths and potentialities of the countercurrent chromatography technique. Generally, the following modes may be performed with commercially available instruments. Normal phase elution is achieved by pumping the non-aqueous or phase of a biphasic solvent system through the column as the mobile phase, with a more polar stationary phase being retained in the column. The cause of original nomenclature of is relevant. As original stationary phases of paper chromatography were superseded by more efficient materials such as diatomaceous earths (natural micro-porous silica) and followed by modern silica gel, the thin-layer chromatography stationary phase was polar (hydroxy groups attached to silica) and maximum retention was achieved with non-polar solvents such as n-hexane | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography Progressively more polar eluents were then used to move polar compounds up the plate. Various alkane bonded phases were tried with C18 becoming the most popular. Alkane chains were chemically bonded to the silica, and a reversal of the elution trend occurred. Thus a polar stationary became "normal" phase chromatography, and the non-polar stationary phase chromatography became "reversed" phase chromatography. In reversed-phase (e.g. aqueous mobile phase) elution, the aqueous phase is used as the mobile phase with a less polar stationary phase. In countercurrent chromatography the same solvent system may be used in either normal or reversed phase mode simply by switching the direction of mobile phase flow through the column. The extrusion of stationary phase from the column at the end of a separation experiment by stopping rotation and pumping solvent or gas through the column was used by CCC practitioners before the term EECCC was suggested. In elution-extrusion mode (EECCC), The mobile phase is extruded after a certain point by switching the phase being pumped into the system whilst maintaining rotation. For example, if the separation has been initiated with the aqueous phase as the mobile phase at a certain point the organic phase is pumped through the column which effectively pushes out both phases that are present in the column at the time of switching. The complete sample is eluted in the order of polarity (either normal or reversed) without loss of resolution by diffusion | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography It requires only one column volume of solvent phase and leaves the column full of fresh stationary phase for the subsequent separation. The use of a solvent gradient is very well developed in column chromatography but is less common in CCC. A solvent gradient is produced by increasing (or decreasing) the polarity of the mobile phase during the separation to achieve optimal resolution across a wider range of polarities. For example, a methanol-water mobile phase gradient may be employed using heptane as the stationary phase. This is not possible with all biphasic solvent systems, due to excessive loss of stationary phase created by disruption the equilibrium conditions within the column. Gradients may either be produced in steps, or continuously. In dual-mode, the mobile and stationary phases are reversed part way through the separation experiment. This requires changing the phase being pumped through the column as well as the direction of flow. Dual-mode operation is likely to elute the entire sample from the column but the order of elution is disrupted by switching the phase and direction of flow. Dual-flow, also known as dual, countercurrent chromatography occurs when both phases are flowing in opposite directions inside the column. Instruments are available for dual-flow operation for both Hydrodynamic and hydrostatic CCC. Dual-flow countercurrent chromatography was first described by Yoichiro Ito in 1985 for foam CCC where gas-liquid separations were performed. Liquid–liquid separations soon followed | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography The countercurrent chromatography instrument must be modified so that both ends of the column have both inlet and outlet capabilities. This mode may accommodate continuous or sequential separations with the sample being introduced in the middle of the column or between two bobbins in a hydrodynamic instrument. A technique called intermittent countercurrent extraction (ICcE) is a quasi-continuous method where the flow of the phases is alternated "intermittently" between normal and reversed-phase elution so that the stationary phase also alternates. Recycling chromatography is mode practiced in both HPLC and CCC. In recycling chromatography, the target compounds are reintroduced into the column after they elute. Each pass through the column increases the number of theoretical plates the compounds experience and enhances chromatographic resolution. Direct recycling must be done with an isocratic solvent system. With this mode, the eluant can be selectively re-chromatographed on the same or a different column in order to facilitate the separation. This process of selective recycling has been termed a "heart-cut" and is especially effective in purifying selected target compounds with some sacrificial loss of recovery. The process of re-separating selected fractions from one chromatography experiment with another chromatographic method has long been practiced by scientists. Recycling and sequential chromatography is a streamlined version of this process | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography In CCC, the separation characteristics of the column may be modified simply by changing the composition of the biphasic solvent system. In an conventional CCC experiment the biphasic solvent system is pre-equilibrated before the instrument is filled with the stationary phase and equilibrated with the mobile phase. An ion-exchange mode has been created by modifying both of the phases after pre-equilibration. Generally, an ionic displacer (or eluter) is added to mobile phase and an ionic retainer is added to the stationary phase. For example, the aqueous mobile phase may contain NaI as a displacer and the organic stationary phase may be modified with the quaternary ammonium salt called Aliquat 336 as a retainer. The mode known a pH-zone-refining is a type of ion-exchange mode that utilizes acids and/or bases as solvent modifiers. Typically, the analytes are eluted in an order determined by their pKa values. For example, 6 oxindole alkaloids were isolated from a 4.5g sample of "Gelsemium elegans" stem extract with a biphasic solvent system composed of hexane–ethyl acetate–methanol–water (3:7:1:9, v/v) where 10 mM triethylamine (TEA) was added to the upper organic stationary phase as a retainer and 10 mM hydrochloric acid (HCl) to the aqueous mobile phase as an eluter. Ion-exchange modes such as pH-zone-refining have tremendous potential because high sample loads can be achieved without sacrificing separation power | https://en.wikipedia.org/wiki?curid=30862402 |
Countercurrent chromatography It works best with ionizable compounds such as nitrogen containing alkaloids or carboxylic acid containing fatty acids. and related liquid-liquid separation techniques have been used on both industrial and laboratory scale to purify a wide variety of chemical substances. Separation realizations include proteins, DNA, Cannabidiol (CBD) from "Cannabis Sativa" antibiotics, vitamins, natural products, pharmaceuticals, metal ions, pesticides, enantiomers, polyaromatic hydrocarbons from environmental samples, active enzymes, and carbon nanotubes. is known for its high dynamic range of scalability: milligram to kilogram quantities purified chemical components may be obtained with this technique. It also has the advantage of accommodating chemically complex samples with undissolved particulates. | https://en.wikipedia.org/wiki?curid=30862402 |
Tin(II) chloride (data page) This page provides supplementary chemical data on tin(II) chloride. Phase behavior Liquid properties Gas properties UV-Vis IR NMR MS Structure and properties The handling of this chemical may incur notable safety precautions. It is highly recommend that you seek the Safety Datasheet (SDS) for this chemical from a reliable source and follow its directions: Except where noted otherwise, data relate to standard ambient temperature and pressure. | https://en.wikipedia.org/wiki?curid=30862636 |
Acid attack An Acid Attack, also called acid throwing, vitriol attack, or vitriolage, is a form of violent assault involving the act of throwing acid or a similarly corrosive substance onto the body of another "with the intention to disfigure, maim, torture, or kill". Perpetrators of these attacks throw corrosive liquids at their victims, usually at their faces, burning them, and damaging skin tissue, often exposing and sometimes dissolving the bones. Acid attacks can often lead to permanent blindness. The most common types of acid used in these attacks are sulfuric and nitric acid. Hydrochloric acid is sometimes used, but is much less damaging. Aqueous solutions of strongly alkaline materials, such as caustic soda (sodium hydroxide), are used as well, particularly in areas where strong acids are controlled substances. The long term consequences of these attacks may include blindness, as well as eye burns, with severe permanent scarring of the face and body, along with far-reaching social, psychological, and economic difficulties. Today, acid attacks are reported in many parts of the world, though more commonly in developing countries. Since the 1990s, Bangladesh has been reporting the highest number of attacks and highest incidence rates for women, with 3,512 Bangladeshi people acid attacked between 1999 and 2013, and in India acid attacks are at an all-time high and increasing every year. Although acid attacks occur all over the world, this type of violence is most common in South Asia | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack The UK has one of the highest rates of acid attacks per capita in the world, according to Acid Survivors Trust International (ASTI). In 2016 there were over 601 acid attacks in the UK based on ASTI figures, and 67% of the victims were male, but statistics from ASTI suggest that 80% of victims worldwide are women. Over 1,200 cases were recorded over the past five years. From 2011 to 2016 there were 1,464 crimes involving acid or corrosive substance in London alone. The intention of the attacker is often to humiliate rather than to kill the victim. In Britain such attacks, particularly those against men, are believed to be underreported, and as a result many of them do not show up in official statistics. Some of the most common motivations of perpetrators include: Acid attacks often occur as revenge against a woman who rejects a proposal of marriage or a sexual advance. Gender inequality and women's position in the society, in relation to men, plays a significant role in these types of attacks. Attacks against individuals based on their religious beliefs or social or political activities also occur. These attacks may be targeted against a specific individual, due to their activities, or may be perpetrated against random persons merely because they are part of a social group or community. In Europe, Konstantina Kouneva, currently a member of the European Parliament, had acid thrown on her in 2008, in what was described as "the most severe assault on a trade unionist in Greece for 50 years | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack " Female students have had acid thrown in their faces as a punishment for attending school. Acid attacks due to religious conflicts have been also reported. Both males and females have been victims of acid attacks for refusing to convert to another religion. Conflicts regarding property issues, land disputes, and inheritance have also been reported as motivations of acid attacks. Acid attacks related to conflicts between criminal gangs occur in many places, including the UK, Greece, and Indonesia. According to researchers and activists, countries typically associated with acid assault include Bangladesh, India, Nepal, Cambodia, Vietnam, Laos, China, United Kingdom, Kenya, South Africa, Uganda, Pakistan, and Afghanistan. However, acid attacks have been reported in countries around the world, including: Additionally, anecdotal evidence for acid attacks exists in other regions of the world such as South America, Central and North Africa, the Middle East, and Central Asia. However, South Asian countries maintain the highest incidence of acid attacks. Police in the United Kingdom have noted that many victims are afraid to come forward to report attacks, meaning the true scale of the problem may be unknown. An accurate estimate of the gender ratio of victims and perpetrators is difficult to establish because many acid attacks are not reported or recorded by authorities. According to a 2010 study in "The Lancet", there are "no reliable statistics" on the prevalence of acid attacks in Pakistan | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack A 2007 literature review analyzed 24 studies in 13 countries over the past 40 years, covering 771 cases. According to the London-based charity Acid Survivors Trust International, 80% of acid attacks are on women, and acid assaults are grossly under-estimated. In some regions, assaults perpetrated on female victims by males are often driven by the mentality "If I can't have you, no one shall." In Bangladesh, throwing acid has been labeled as a "gender crime", as there is a dominance of female victims who are assaulted by males, for the reason of refusing to marry, or refusing sexual advances from male perpetrators. In Jamaica, women throwing acid on other women in relation to fights over male partners is a common cause. In the UK, the majority of victims are men, and many of these attacks are related to gang violence. Another factor that puts victims at increased risk for an acid assault is their socioeconomic status, as those living in poverty are more likely to be attacked. , the three nations with the most noted incidence of acid attacks – Bangladesh, India, and Cambodia – were ranked 75th, 101st, and 104th, respectively, out of 136 countries on the Global Gender Gap Index, a scale that measures equality in opportunities between men and women in nations. Such attacks or threats against women who failed to wear hijab, dress "modestly" or otherwise threaten traditional norms have been reported in Afghanistan. In November 2008, extremists subjected girls to acid attacks for attending school | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack High incidence of acid assaults have been reported in some African countries, including Nigeria, Uganda, and South Africa. Unlike occurrences in South Asia, acid attacks in these countries show less gender discrimination. In Uganda, 57% of acid assault victims were female and 43% were male. A study focusing on chemical burns in Nigeria revealed a reversal in findings—60% of the acid attack patients were male while 40% were female. In both nations, younger individuals were more likely to suffer from an acid attack: the average age in the Nigeria study was 20.6 years, while Ugandan analysis shows 59% of survivors were 19–34 years of age. Motivation for acid assault in these African countries is similar to that of Cambodia. Relationship conflicts caused 35% of acid attacks in Uganda in 1985–2011, followed by property conflicts at 8%, and business conflicts at 5%. Disaggregated data was not available in the Nigeria study, but they reported that 71% of acid assaults resulted from an argument with either a jilted lover, family member, or business partner. As with the other nations, researchers believe these statistics to be under-representative of the actual scope and magnitude of acid attacks in African nations. In August 2013, two Jewish women volunteer teachers—Katie Gee and Kirstie Trup from the UK—were injured by an acid attack by men on a moped near Stone Town in Tanzania. A few cases also occurred in Ethiopia and Nigeria | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack There has recently been a surge in high-profile, public acid attacks in Bulgaria and Greece. In Bangladesh, such attacks are relatively common. Bangladesh has the highest reported incidence of acid assault in the world. According to the Acid Survivors Foundation in Bangladesh, the country has reported 3000 acid attack victims since 1999, peaking at 262 victims for the year of 2002. Rates have been steadily decreasing by 15% to 20% since 2002, with the amount of acid attack victims reported at 91 in Bangladesh as recently as 2011. Bangladesh acid attacks shows the most gendered discrimination, with one study citing a male to female victim ratio of 0.15:1 and another reporting that 82% of acid attack survivors in Bangladesh are women. Younger women were especially prone to attack, with a recent study reporting that 60% of acid assault survivors are between the ages of 10 and 19. According to Mridula Bandyopadhyay and Mahmuda Rahman Khan, it is a form of violence primarily targeted at women. They describe it as a relatively recent form of violence, with the earliest record in Bangladesh from 1983. Acid attacks are often referred to as a "crime of passion", fueled by jealousy and revenge. Actual cases though, show that they are usually the result of rage at a woman who rebuffs the advances of a male. For the country of Bangladesh, such passion is often rooted in marriage and relationships | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack One study showed that refusal of marriage proposals accounted for 55% of acid assaults, with abuse from a husband or other family member (18%), property disputes (11%) and refusal of sexual or romantic advances (2%) as other leading causes. Additionally, the use of acid attacks in dowry arguments has been reported in Bangladesh, with 15% of cases studied by the Acid Survivors Foundation citing dowry disputes as the motive. The chemical agents most commonly used to commit these attacks are hydrochloric acid and sulfuric acid. Recent studies on acid attacks in Cambodia found the victims were almost equally likely to be men or women (48.4% men, 51.6% women). As with India, rates of acid attacks in Cambodia have generally increased in the past decades, with a high rate of 40 cases reported for 2000 that started the increasing trend. According to the Cambodian Acid Survivors Charity, 216 acid attacks were reported from 1985 to 2009, with 236 reported victims. Jealousy and hate is the biggest motivator for acid attacks in Cambodia, as 28% of attacks reported those emotions as the cause. Such assaults were not only perpetrated by men—some reports suggest women attack other women occur more frequently than men do. Such incidents usually occur between a husband's wife and mistress to attain power and socioeconomic security | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack A particularly high-profile case of this nature was the attack on Cambodian teenager Tat Marina in 1999, allegedly carried out by the jealous wife of a government official (the incident prompted a rash of copycat crimes that year, raising the number from seven in 1998 to 40 in 1999). One third of the victims are bystanders. In Cambodia, there is only one support center that is aiming to help acid attack survivors. There they can receive medical and legal support. The Mong Kok acid attacks were incidents in 2008, 2009, and 2010 where plastic bottles filled with corrosive liquid (drain cleaner) were thrown onto shoppers on Sai Yeung Choi Street South, Hong Kong, a pedestrian street and popular shopping area. A reward, originally HK$100,000, for information about the perpetrator or perpetrators, was raised to HK$300,000 following the second incident, and cameras were to be installed in the area following the December incident. The third incident occurred the very day the cameras were turned on. The fifth incident happened after Hong Kong government announced its new strategies against the incident. 130 people were injured in these attacks. Acid attacks in India, like Bangladesh, have a gendered aspect to them: analyses of news reports revealed at least 72% of reported attacks included at least one female victim. However, unlike Bangladesh, India's incidence rate of chemical assault has been increasing in the past decade, with a high 27 reported cases in 2010 | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Altogether, from January 2002 to October 2010, 153 cases of acid assault were reported in Indian print media while 174 judicial cases were reported for the year of 2000. The motivation behind acid attacks in India mirrors those in Bangladesh: a study of Indian news reports from January 2002 to October 2010 uncovered that victims’ rejected sex or marriage proposals motivated attacks in 35% of the 110 news stories providing a motive for the attack. Notable cases of acid attacks are Sonali Mukherjee's case of 2003 and Laxmi Agarwal in 2005. Police in India are also known to use acid on individuals, particularly on their eyes, causing blindness to the victims. A well known such case is the Bhagalpur blindings, where police blinded 31 individuals under trial (or convicted criminals, according to some versions) by pouring acid into their eyes. The incident was widely discussed, debated and acutely criticized by several human rights organizations. The Bhagalpur blinding case had made criminal jurisprudence history by becoming the first in which the Indian Supreme Court ordered compensation for violation of basic human rights. According to Afshin Molavi, in the early years of the revolution and following the mandating of the covering of hair by women in Iran, some women were threatened with acid attacks by Islamic vigilantes for failing to wear hijab. Recently, acid assault in Iran has been met with increased sanctions | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack The Sharia "code of qisas", or equivalence justice, required a caught perpetrator of acid violence to pay a fine and may be blinded with acid in both eyes. Under Iranian law, victims or their families can ask a court's permission to enact "qisas" either by taking the perpetrator's life in murder cases or afflicting an equal injury to his or her body. One victim, Ameneh Bahrami, sentenced her attacker to be blinded in 2008. However, as of July 31, 2011, she pardoned her attacker, thereby absolving Majid Movahedi of his crime and halting the retributive justice of Qisas. In October 2014, a series of acid attacks on women occurred in the city of Isfahan, resulting in demonstrations and arrests of journalists who had covered the attacks. The attacks were thought by many Iranians to be the work of conservative Islamist vigilantes, but the Iranian government denies this. In 1983 acid attacks were reported to be carried out by Mujama al-Islamiya against men and woman who spoke out against the Mujama in the Islamic University of Gaza. Additional attacks by Mujama al-Islamiya were reported through 1986. During the First Intifada, Hamas and other Islamist factions conducted an organized intimidation of women to dress "modestly" or wear the hijab. Circulars were distributed specifying proper modest dress and behavior | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Women who did not conform to these expectations, or to "morality expectations" of secular factions, were vulnerable to attacks which included pouring acid on their bodies, rock pelting, threats, and even rape. B'Tselem has also documented additional attacks with acid in specific attacks involving women in a collaboration context. In 2006–07, as part of a wider campaign to enforce Islamist moral conduct, the al-Qaida affiliated "Suyuf al-Haq" (Swords of Righteousness) claimed to have thrown acid on the faces of "immodestly" dressed woman in Gaza as well as engaging in intimidation via threats. Following 2014 Israel–Gaza conflict Amnesty International has claimed that Hamas used acid during interrogations as a torture technique. Hamas denies this claim. In 2016, during a teacher's strike, unknown assailants hurled acid in the face of a striking Palestinian teacher in Hebron. There have also been recorded incidents of acid use against Israelis. In December 2014, a Palestinian hurled acid (concentrated vinegar which contains a high percentage of acetic acid and can cause burns) into a car containing a Jewish family of six and a hitchhiker at a checkpoint between Beitar Illit and Husan in the West Bank, causing serious face injuries to the father and lightly injuring other occupants, including children. In September 2008 a Palestinian woman carried out two separate acid attacks against soldiers at Huwwara checkpoint, blinding one soldier | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Moshe Hirsch was the leader of the anti-Zionist Neturei Karta group in Jerusalem. Hirsch had one glass eye due to an injury sustained when someone threw acid in his face. According to his cousin, journalist Abraham Rabinovich, the incident had no link with Hirsch's political activities but was connected to a real estate dispute. Drug cartels such as the Los Zetas are known to use acid on civilians. For example, In the 2011 San Fernando massacre, Los Zetas members took away children from their mothers, and shot the rest of the civilians in a bus. The women were taken to a warehouse where many other women were held captive. Inside a dark room, the women were reportedly raped and beaten. Screams of the women and of the children being put in acid were also heard. According to "New York Times" reporter Nicholas D. Kristof, acid attacks are at an all-time high in Pakistan. The Pakistani attacks are typically the work of husbands against their wives who have "dishonored them." Statistics compiled by the Human Rights Commission of Pakistan (HRCP) show that 46 acid attacks occurred in Pakistan during 2004 and decreased with only 33 acid assaults reported for 2007. According to a "New York Times" article, in 2011 there were 150 acid attacks in Pakistan, up from 65 in 2010. However, estimates by the Human Rights Watch and the HRCP cite the number of acid attack victims to be as high 40–70 per year. Motivation behind acid assaults range from marriage proposal rejections to religious fundamentalism | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Acid attacks have been dropped by half in 2019 Acid attacks in Pakistan came to international attention after the release of a documentary by Sharmeen Obaid-Chinoy called "Saving Face" (2012). According to Shahnaz Bukhari, the majority of these attacks occur in the summer when acid is used extensively to soak certain seeds to induce germination. Various reasons have been given for such attacks, such as a woman dressing inappropriately or rejecting a proposal of marriage. The first known instance of an acid attack occurred in East Pakistan in 1967. According to the Acid Survivors Foundation, up to 150 attacks occur every year. The foundation reports that the attacks are often the result in an escalation of domestic abuse, and the majority of victims are female. In 2019, the "Acid Survivors Foundation Pakistan (ASFP)" have said that the reported cases of acid attacks on women have dropped by around 50 per cent compared to the last five years. On January 17, 2013, Russian ballet dancer Sergei Filin was attacked with acid by an unknown assailant, who cornered him outside of his home in Moscow. He suffered third-degree burns to his face and neck. While it was initially reported that he was in danger of losing his eyesight, his physicians stated on January 21, 2013 that he would retain eyesight in one eye. Though comprehensive statistics on acid attacks in South America are sparse, a recent study investigating acid assault in Bogota, Colombia, provides some insight for this region | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack According to the article, the first identified survivor of acid violence in Bogota was attacked in 1998. Since then reported cases have been increasing with time. The study also cited the Colombian Forensics Institute, which reported that 56 women complained of aggression by acid in 2010, 46 in 2011, and 16 during the first trimester of 2012. The average age of survivors was about 23 years old, but ranged from 13 to 41 years. The study reported a male:female victim ratio of 1:30 for acid assault in Bogota, Colombia, although recent reports show the ratio is closer to 1:1. Reasons behind these attacks usually stemmed from poor interpersonal relationships and domestic intolerance toward women. Moreover, female victims usually came from low socioeconomic classes and had low education. The authors state that the prevalence of acid attacks in other areas of South America remains unknown due to significant underreporting. On March 27, 2014, a woman named Natalia Ponce de León was assaulted by Jonathan Vega, who threw a liter of sulphuric acid on her face and body. Vega, a former neighbor, was reported to have been "obsessed" with Ponce de León and had been making death threats against her after she turned down his proposal for a relationship. 24% of her body was severely burned as a result of the attack. Ponce de León has undergone 15 reconstruction surgeries on her face and body since the attack | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Three years before the attack took place, Colombia reported one of the highest rates of acid attacks per capita in the world. However, there was not an effective law in place until Ponce de León's campaign took off in the months after her attack. The new law, which is named after her, defines acid attacks as a specific crime and increases maximum sentences to 50 years in jail for convicted offenders. The law also aims to provide victims with better state medical care including reconstructive surgery and psychological therapy. Ponce de León expressed hope that the new law would act as a deterrent against future attacks. In South Asia, acid attacks have been used as a form of revenge for refusal of sexual advances, proposals of marriage and demands for dowry. Scholars Taru Bahl and M.H. Syed say that land/property disputes are another leading cause. On July 31, 2018, Kateryna Handziuk, an anti-corruption activist and political advisor from the southern Ukrainian city of Kherson, was attacked with sulfuric acid outside her home by an unknown attacker. She died of her injuries on November 3, 2018. She was 33 years old. Acid attacks are common in Vietnam although not to the level of countries such as Pakistan and India. An example of an acid attack in Vietnam is the Ho Chi Minh City acid attack where four people were injured. Most of Vietnam's acid attack victims spend their lives isolated and ignored and also blamed for their agony | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack The UK has one of highest rates of acid attacks in the world, according to the police. According to London's Metropolitan Police, 2017 was the worst year for acid attacks in London, with 465 attacks recorded, up from 395 the previous year and 255 in 2015. In 2016, the Metropolitan Police in London recorded 454 attacks involving corrosive fluids in the city, with 261 in the previous year, indicating a rise of 36%. A rise of 30% was also recorded in the UK as a whole. Between 2005-2006 and 2011-2012 the number of assaults involving acid throwing and other corrosive substances tripled in England, official records show. NHS hospital figures record 144 assaults in 2011-2012 involving corrosive substances, which can include petrol, bleach and kerosene. Six years earlier, 56 such episodes were noted. The official records for 2017-2018 now shows 150 patients in the UK admitted to hospital for "Assault by corrosive substance". Acid attacks in London continued to rise in 2017. In July 2017, the BBC's George Mann reported that police statistics showed that: "Assaults involving corrosive substances have more than doubled in England since 2012. The vast majority of cases were in London." According to "Time" magazine, motives included organized crime, revenge, and domestic violence. According to Newham police there is no trend of using acid in hate crimes | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack According to data from London's Metropolitan Police, a demographic breakdown of known suspects in London attacks for the period (2002–2016) showed White Europeans comprising 32% of suspects, African Caribbeans 38% and Asian 6%. Victims for the same period were 45% White Europeans, 25% African Caribbeans and 19% Asian. Of the total population, whites constitute 60%, blacks 13% and Asians 18% as per the 2011 census of London. Known suspects were overwhelmingly male, 77% of known suspects were male and just 2% of suspects female. Four out of five victims in 2016 were male in contrast to other countries where women are most frequently victimized by men. Mark van Dongen chose to undergo euthanasia months after he was attacked by his ex-girlfriend Berlinah Wallace during the early hours of 23 September 2015. He was left paralysed, scarred, had his lower left leg amputated and lost the sight in his left eye, as well as most of the sight in his right eye, following the incident. On April 2017, a man named Arthur Collins, the ex-boyfriend of Ferne McCann, threw acid inside a nightclub across terrified clubbers in east London forcing a mass evacuation of 600 partygoers flooding into the street. 22 people were injured in the attack. Collins was sentenced to 20 years for the attack. Another similar attack is the 2017 Beckton acid attack. Katie Piper was also attacked in 2008 with acid by her ex-boyfriend Daniel Lynch and an accomplice Stefan Sylvestre | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack On 3 October 2017, the UK government announced that sales of acids to under 18s would be banned. In January 2018, CNN reported that acid attacks in London increased six-fold between 2012 and 2017 and that 71% of attackers and 72% of victims were male. In April 2019, a teenage girl, 13, and a woman, 63, were attacked by a man driving a white car, who poured sulfuric acid on them in Thornton Heath, South London. Victor Riesel was a broadcast journalist, specializing in labor issues, who was attacked while leaving Lindy's restaurant in midtown Manhattan in the early morning of 5 April 1956. Riesel was left blind as a result. The attack was motivated by Riesel's reporting on the influence of organized crime on certain corrupt labor unions. In 1959, American attorney Burt Pugach hired a man to throw lye in the face of his ex-girlfriend Linda Riss. Riss suffered blindness and permanent scarring. Pugach served 14 years in prison for the incident. Gabrielle White, a 22-year-old single mother living in Detroit, was attacked on 26 August 2006 by a stranger. She was left with third and fourth degree burns on her face, throat, and arms, leaving her blind and without one ear. She also miscarried her unborn child. A 25-year-old nursing student at Merritt College was the victim of an acid attack. In 2017, a 17-year-old girl was permanently scarred by an acid attack in Dallas. In November 2019, a man in Milwaukee was attacked and sustained multiple burns | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack The most notable effect of an acid attack is the lifelong bodily disfigurement. According to the Acid Survivors Foundation in Pakistan, there is a high survival rate amongst victims of acid attacks. Consequently, the victim is faced with physical challenges, which require long-term surgical treatment, as well as psychological challenges, which require in-depth intervention from psychologists and counselors at each stage of physical recovery. These far-reaching effects on their lives impact their psychological, social and economic viability in communities. The medical effects of acid attacks are extensive. As a majority of acid attacks are aimed at the face, several articles thoroughly reviewed the medical implications for these victims. The severity of the damage depends on the concentration of the acid and the time before the acid is thoroughly washed off with water or neutralized with a neutralizing agent. The acid can rapidly eat away skin, the layer of fat beneath the skin, and in some cases even the underlying bone. Eyelids and lips may be completely destroyed and the nose and ears severely damaged. Though not exhaustive, Acid Survivors Foundation Uganda findings included: In addition to these above-mentioned medical effects, acid attack victims face the possibility of sepsis, kidney failure, skin depigmentation, and even death. A 2015 attack that involved throwing sulfuric acid on a man's face and body while he lay in bed caused him, among other serious injuries, to become paralyzed from the neck down | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Acid assault survivors face many mental health issues upon recovery. One study showed that when compared to published Western norms for psychological well-being, non-Caucasian acid attack victims reported higher levels of anxiety, depression, and scored higher on the Derriford appearance scale, which measures psychological distress due to one's concern for their appearance. Additionally, female victims reported lowered self-esteem according to the Rosenberg scale and increased self-consciousness, both in general and in the social sphere. In addition to medical and psychological effects, many social implications exist for acid survivors, especially women. For example, such attacks usually leave victims handicapped in some way, rendering them dependent on either their spouse or family for everyday activities, such as eating and running errands. These dependencies are increased by the fact that many acid survivors are not able to find suitable work, due to impaired vision and physical handicap. This negatively impacts their economic viability, causing hardships on the families/spouses that care for them. As a result, divorce rates are high, with abandonment by husbands found in 25% of acid assault cases in Uganda (compared to only 3% of wives abandoning their disfigured husbands). Moreover, acid survivors who are single when attacked almost certainly become ostracized from society, effectively ruining marriage prospects | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Some media outlets overwhelmingly avoid reporting acid attack violence, or the description of the attack is laconic or often implies that the act was inevitable or even justified. Treatment for burn victims remains inadequate in many developing nations where incidence is high. Medical underfunding has resulted in very few burn centers available for victims in countries such as Uganda, Bangladesh, and Cambodia. For example, Uganda has one specialized burn center in the entire nation, which opened in 2003; likewise, Cambodia has only one burn facility for victims, and scholars estimate that only 30% of the Bangladeshi community has access to health care. In addition to inadequate medical capabilities, many acid assault victims fail to report to the police due to a lack of trust in the force, a sense of hopelessness due to the attackers' impunity, and a fear of male brutality in dealing with their cases. Most of the female victims suffer more because of police apathy in dealing with cases of harassment as safety issues as victims refused to register a police case despite being attacked thrice before meriting police aid after an acid attack. These problems are exacerbated by a lack of knowledge of how to treat burns: many victims applied oil to the acid, rather than rinsing thoroughly and completely with water for 30 minutes or longer to neutralize the acid. Such home remedies only serve to increase the severity of damage, as they do not counteract the acidity | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Research has prompted many solutions to the increasing incidence of acid attacks in the world. Many countries look to Bangladesh, whose rates of attack have been decreasing, as a model, following their lead in many legislative reforms. However, several reports highlighted the need for an increased, legal role of NGOs to offer rehabilitation support to acid survivors. Additionally, nearly all research stressed the need for stricter regulation of acid sales to combat this social issue. Many non-governmental organizations (NGOs) have been formed in the areas with the highest occurrence of acid attacks to combat such attacks. Bangladesh has its Acid Survivors Foundation, which offers acid victims legal, medical, counseling, and monetary assistance in rebuilding their lives. Similar institutions exist in Uganda, which has its own Acid Survivors Foundation, and in Cambodia which uses the help of Cambodian Acid Survivors Charity. NGOs provide rehabilitation services for survivors while acting as advocates for social reform, hoping to increase support and awareness for acid assault. In Bangladesh, the Acid Survivors Foundation, Nairpokkho, Action Aid, and the Bangladesh Rural Advancement Committee's Community Empowerment & Strengthening Local Institutions Programme assist survivors. The Depilex Smileagain Foundation and The Acid Survivors Foundation in Pakistan operates in Islamabad, offering medical, psychological and rehabilitation support | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack The Acid Survivors Foundation in Uganda operates in Kampala and provides counseling and rehabilitation treatment to victims, as well as their families. The LICADHO, the Association of the Blind in Cambodia, and the Cambodian Acid Survivors Charity assist survivors of acid attacks. The Acid Survivors Foundation India operates from different centres with national headquarters at Kolkata and chapters at Delhi and Mumbai. Acid Survivors Trust International (UK registered charity no. 1079290) provides specialist support to its sister organizations in Africa and Asia. Acid Survivors Trust International is the only international organisation whose sole purpose is to end acid violence. The organisation was founded in 2002 and now works with a network of six Acid Survivors Foundations in Bangladesh, Cambodia, India, Nepal, Pakistan and Uganda that it has helped to form. Acid Survivors Trust International has helped to provide medical expertise and training to partners, raised valuable funds to support survivors of acid attacks and helped change laws. A key role for ASTI is to raise awareness of acid violence to an international audience so that increased pressure can be applied to governments to introduce stricter controls on the sale and purchase of acid. Indian acid attack survivor Shirin Juwaley founded the Palash Foundation to help other survivors with psychosocial rehabilitation | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack She also spearheads research into social norms of beauty and speaks publicly as an advocate for the empowerment of all victims of disfigurement and discrimination. In 2011, the principal of an Indian college refused to have Juwaley speak at her school for fear that Juwaley's story of being attacked by her husband would make students "become scared of marriage". A positive correlation has been observed between acid attacks and ease of acid purchase. Sulfuric, nitric, and hydrochloric acid are most commonly used and are all cheap and readily available in many instances. For example, often acid throwers can purchase a liter of concentrated sulfuric acid at motorbike mechanic shops for about 40 U.S. cents. Nitric acid costs around $1.50 per liter and is available for purchase at gold or jewelry shops, as polishers generally use it to purify gold and metals. Hydrochloric acid is also used for polishing jewelry, as well as for making soy sauce, cosmetics, and traditional medicine/amphetamine drugs. Due to such ease of access, many organizations call for a stricter regulation on the acid economy. Specific actions include required licenses for all acid traders, a ban on concentrated acid in certain areas, and an enhanced system of monitoring for acid sales, such as the need to document all transactions involving acid. However, some scholars have warned that such stringent regulation may result in black market trading of acid, which law enforcements must keep in mind | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Acid has been used in metallurgy and for etching since ancient times. The rhetorical and theatrical term "La Vitrioleuse" was coined in France after a "wave of vitriolage" occurred according to the popular press where, in 1879, 16 cases of vitriol attacks were widely reported as crimes of passion perpetrated predominantly by women against other women. Much was made of the idea that women, no matter how few, had employed such violent means to an end. On October 17, 1915, acid was fatally thrown on Prince Leopold Clement of Saxe-Coburg and Gotha, heir to the House of Koháry, by his distraught mistress, Camilla Rybicka, who then killed herself. Sensationalizing such incidents made for lucrative newspaper sales. The use of acid as a weapon began to rise in many developing nations, specifically those in South Asia. The first recorded acid attacks in South Asia occurred in Bangladesh in 1967, India in 1982, and Cambodia in 1993. Since then, research has witnessed an increase in the quantity and severity of acid attacks in the region. However, this can be traced to significant underreporting in the 1980s and 1990s, along with a general lack of research on this phenomenon during that period. Research shows acid attacks increasing in many developing nations, with the exception of Bangladesh which has observed a decrease in incidence in the past few years. Many countries have begun pushing for legislation addressing acid attacks, and a few have recently employed new laws against this crime | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack Under the Qisas law of Pakistan, the perpetrator may suffer the same fate as the victim, and may be punished by having drops of acid placed in their eyes. This law is not binding and is rarely enforced according to a report in "The New York Times". In Pakistan, the Lower House of Parliament unanimously passed the Acid Control and Acid Crime Prevention Bill on May 10, 2011. As punishment, according to the bill individuals held responsible for acid attacks face harsh fines and life in prison. However, the country with the most specific, effective legislation against acid attacks is Bangladesh, and such legal action has resulted in a steady 20–30% decrease in acid violence for the past few years. In 2013, India introduced an amendment to the Indian Penal Code through the Criminal Law (Amendment) Act, 2013, making acid attacks a specific offence with a punishment of imprisonment not less than 10 years and which can extend to life imprisonment and with fine. India's top court ruled that authorities must regulate the sale of acid. The Supreme Court's ruling on July 16, 2013, came after an incident in which four sisters suffered severe burns after being attacked with acid by two men on a motorbike. Acid which is designed to clean rusted tools is often used in the attacks can be bought across the counter. But the judges said the buyer of such acids should in future have to provide a photo identity card to any retailer when they make a purchase. The retailers must register the name and address of the buyer | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack In 2013, section 326 A of Indian Penal Code was enacted by the Indian Parliament to ensure enhanced punishment for acid throwing. In 2002, Bangladesh introduced the death penalty for acid attacks and laws strictly controlling the sale, use, storage, and international trade of acids. The acids are used in traditional trades carving marble nameplates, conch bangles, goldsmiths, tanneries, and other industries, which have largely failed to comply with the legislation. Salma Ali of the Bangladesh National Women Lawyers' Association derided these laws as ineffective. The names of these laws are the Acid Crime Control Act (ACCA) and the Acid Control Act (ACA), respectively. The ACCA directly impacts the criminal aspect of acid attacks, and allows for the death penalty or a level of punishment corresponding to the area of the body affected. If the attack results in a loss of hearing or sight or damages the victim's face, breasts, or sex organs then the perpetrator faces either the death penalty or life sentencing. If any other part of the body is maimed, then the criminal faces 7–14 years of imprisonment in addition to a fine of US$700. Additionally, throwing or attempting to throw acid without causing any physical or mental harm is punishable by this law and could result in a prison term of 3–7 years along with a US$700 fine. Furthermore, conspirators that aid in such attacks assume the same liability as those actually committing the crime | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack The ACA regulates the sale, usage, and storing of acid in Bangladesh through the creation of the National Acid Control Council (NACC). The law requires that the NACC implement policies regarding the trade, misuse, and disposal of acid, while also undertaking initiatives that raise awareness about the dangers of acid and improve victim treatment and rehabilitation. The ACA calls for district-level committees responsible for enacting local measures that enforce and further regulate acid use in towns and cities. Under the Qisas (eye-for-an-eye) law of Pakistan, the perpetrator could suffer the same fate as the victim, if the victim or the victim's guardian chooses. The perpetrator may be punished by having drops of acid placed in their eyes. Section 336B of Pakistan Penal Code states: "Whoever causes hurt by corrosive substance shall be punished with imprisonment for life or imprisonment of either description which shall not be less than fourteen years and a minimum fine of one million rupees." Additionally, section 299 defines "Qisas" and states: ""Qisas" means punishment by causing similar hurt at the same part of the body of the convict as he has caused to the victim or by causing his death if he has committed qatl-iamd (intentional manslaughter) in exercise of the right of the victim or a Wali (the guardian of the victim) | https://en.wikipedia.org/wiki?curid=30862640 |
Acid attack " After a spate of attacks in London in 2017, the Home Office said it would consider changes in laws and measures regarding sales of acid, as well as changes in prosecution and sentencing guidelines. As of 2017, it is unlawful to carry acid with the intent to cause harm. Attacks are prosecuted as acts of actual bodily harm and grievous bodily harm. Three quarters of police investigations do not end in prosecution, either because the attacker could not be found, or because the victim is unwilling to press charges. According to ASTI, of the 2,078 acid attack crimes recorded for the years 2011–2016 in UK, only 414 of those crimes resulted in charges being brought. Most acid attack crimes happened in London, where over 1,200 cases were recorded over the past five years. From 2011–2016 there were 1,464 crimes involving acid or corrosive substance. Northumbria recorded the second highest with 109 recorded attacks, Cambridgeshire had 69 attacks, Hertfordshire 67, Greater Manchester 57 and Humberside 52. Vitriolage is the deliberate splashing of a person or object with acid, also known as vitriol, in order to deface or kill. A female who engages in such an act is known as a vitrioleuse. There are instances of this act throughout history and in modern times, often in places where honor killings are also common. | https://en.wikipedia.org/wiki?curid=30862640 |
Gold(III) chloride (data page) This page provides supplementary chemical data on gold(III) chloride The handling of this chemical may incur notable safety precautions. It is highly recommend that you seek the Material Safety Datasheet (MSDS) for this chemical from a reliable source such as SIRI, and follow its directions. Except where noted otherwise, data relate to standard ambient temperature and pressure. | https://en.wikipedia.org/wiki?curid=30862646 |
Pre-exponential factor In chemical kinetics, the pre-exponential factor or A factor is the pre-exponential constant in the Arrhenius equation, an empirical relationship between temperature and rate coefficient. It is usually designated by A when determined from experiment, while Z is usually left for collision frequency. The units of the pre-exponential factor A are identical to those of the rate constant and will vary depending on the order of the reaction. For a first-order reaction, it has units of s. For that reason, it is often called frequency factor. According to collision theory, the frequency factor, A, depends on how often molecules collide when all concentrations are 1 mol/L and on whether the molecules are properly oriented when they collide. Values of A for some reactions can be found at Collision theory#Steric factor. According to transition state theory, A can be expressed in terms of the entropy of activation of the reaction. IUPAC Gold Book definition of pre-exponential factor | https://en.wikipedia.org/wiki?curid=30862748 |
Rotating biological contactor A rotating biological contactor or RBC is a biological treatment process used in the treatment of wastewater following primary treatment. The primary treatment process means protection by removal of grit and sand and coarse material through a screening process, followed by a removal process of sediment by settling. The RBC process involves allowing the wastewater to come in contact with a biological medium in order to remove pollutants in the wastewater before discharge of the treated wastewater to the environment, usually a body of water (river, lake or ocean). A rotating biological contactor is a type of secondary (Biological) treatment process. It consists of a series of closely spaced, parallel discs mounted on a rotating shaft which is supported just above the surface of the waste water. Microorganisms grow on the surface of the discs where biological degradation of the wastewater pollutants takes place. The rotating packs of disks (known as the media) are contained in a tank or trough and rotate at between 2 and 5 revolutions per minute. Commonly used plastics for the media are polyethylene, PVC and expanded polystyrene. The shaft is aligned with the flow of wastewater so that the discs rotate at right angles to the flow, with several packs usually combined to make up a treatment train. About 40% of the disc area is immersed in the wastewater. Biological growth is attached to the surface of the disc and forms a slime layer | https://en.wikipedia.org/wiki?curid=30862811 |
Rotating biological contactor The discs contact the wastewater with the atmospheric air for oxidation as it rotates. The rotation helps to slough off excess solids. The disc system can be staged in series to obtain nearly any detention time or degree of removal required. Since the systems are staged, the culture of the later stages can be acclimated to the slowly degraded materials. The discs consist of plastic sheets ranging from 2 to 4 m in diameter and are up to 10 mm thick. Several modules may be arranged in parallel and/or in series to meet the flow and treatment requirements. The discs are submerged in waste water to about 40% of their diameter. Approximately 95% of the surface area is thus alternately submerged in waste water and then exposed to the atmosphere above the liquid. Carbonaceous substrate is removed in the initial stage of RBC. Carbon conversion may be completed in the first stage of a series of modules, with nitrification being completed after the 5th stage. Most design of RBC systems will include a minimum of 4 or 5 modules in series to obtain nitrification of waste water. Biofilms, which are biological growths that become attached to the discs, assimilate the organic materials in the wastewater. Aeration is provided by the rotating action, which exposes the media to the air after contacting them with the wastewater, facilitating the degradation of the pollutants being removed. The degree of wastewater treatment is related to the amount of media surface area and the quality and volume of the inflowing wastewater | https://en.wikipedia.org/wiki?curid=30862811 |
Rotating biological contactor The first RBC was installed in West Germany in 1959, later it was introduced in the United States and Canada. In the United States, rotating biological contactors are used for industries producing wastewaters high in biochemical oxygen demand (BOD) (e.g., petroleum industry and dairy industry). A properly designed RBC produced a very high quality final effluent. However both the organic and hydraulic loading had to be addressed. In the 1980's problems were encountered in the USA prompting the Environmental Agency to commission a number of reports. These reports identified a number of issues and criticized the RBC process. One author suggested that since manufacturers were aware of the problem, the problems would be resolved and suggested that design engineers should specify a long life. However, this was only possible when the manufacturers became aware of the design problems and the stress to ensure a long life and since failures still occurred it was unlikely any design stresses were known. Severn Trent Water Ltd, a large UK Water Company based in the Midlands, employed RBCs as the preferred process for their small works which amount to over 700 sites Consequently, long life was essential to compliance. This issue was successfully addressed by Eric Findlay C Eng when he was employed by Severn Trent Water Ltd in the UK following a period of failure of a number of plants | https://en.wikipedia.org/wiki?curid=30862811 |
Rotating biological contactor As a result, the issue of short life failure became fully understood in the early 1990s when the correct process and hydraulic issues had been identified to produce a high quality nitrified effluent. There are several other papers which address the whole issue of RBCs. Findlay also developed a system for repairing defective RBCs enabling shaft and frame life to be extended up to 30 years based on the Cranfield designed frame. Where additional capacity was required intermediate frames are used maximising minimising the need for duplication Secondary clarifiers following RBCs are identical in design to conventional humus tanks, as used downstream of trickling filters. Sludge is generally removed daily, or pumped automatically to the primary settlement tank for co-settlement. Regular sludge removal reduces the risk of anaerobic conditions from developing within the sludge, with subsequent sludge flotation due to the release of gases. | https://en.wikipedia.org/wiki?curid=30862811 |
Gadolinium gallium garnet Gadolinium Gallium Garnet (GGG, ) is a synthetic crystalline material of the garnet group, with good mechanical, thermal, and optical properties. It is typically colorless. It has a cubic lattice, a density of 7.08 g/cm and its Mohs hardness is variously noted as 6.5 and 7.5. Its crystals are produced with the Czochralski method. During production, various dopants can be added for colour modification. The material is also used in fabrication of various optical components and as a substrate material for magneto–optical films (magnetic bubble memory). It also finds use in jewelry as a diamond simulant. GGG can also be used as a seed substrate for the growth of other garnets such as YIG. | https://en.wikipedia.org/wiki?curid=30862832 |
Aluminium chloride (data page) Supplementary data for aluminium chloride. NIST website Except where noted otherwise, data relate to standard ambient temperature and pressure. | https://en.wikipedia.org/wiki?curid=30862971 |
Temozolomide (TMZ; brand names Temodar and Temodal and Temcad) is an oral chemotherapy drug. It is an alkylating agent used as a treatment of some brain cancers; as a second-line treatment for astrocytoma and a first-line treatment for glioblastoma multiforme. Olaparib in combination with temozolomide demonstrated substantial clinical activity in relapsed small cell lung cancer. is contraindicated in patients with hypersensitivity to it or to the similar drug dacarbazine. The use of temozolomide is not recommended in patients with severe myelosuppression. The most common side effect is bone marrow suppression. The most common non-hematological adverse effects associated with temozolomide are nausea and vomiting, which are either self-limiting or readily controlled with standard antiemetic therapy. These latter effects are usually mild to moderate (grade 1 to 2). The incidence of severe nausea and vomiting is around 4% each. Patients who have pre-existing or a history of severe vomiting may require antiemetic therapy before initiating temozolomide treatment. should be administered in the fasting state, at least one hour before a meal. Antiemetic therapy may be administered before, or following, administration of temozolomide. is genotoxic, teratogenic and fetotoxic and should not be used during pregnancy. Lactating women should discontinue nursing while receiving the drug because of the risk of secretion into breast milk | https://en.wikipedia.org/wiki?curid=30863182 |
Temozolomide One study indicated that women that have taken temozolomide without concomitant fertility preservation measures achieve pregnancy to a lesser rate later in life, but the study was too small to show statistical significance in the hypothesis that temozolomide would confer a risk of female infertility. In male patients, temozolomide can have genotoxic effects. Men are advised not to father a child during or up to six months after treatment and to seek advice on cryoconservation of sperm prior to treatment, because of the possibility of irreversible infertility due to temozolomide therapy. Very rarely temozolomide can cause acute respiratory failure or liver damage. As temozolomide is not metabolized in the liver and has a low affinity to plasma proteins, it is expected to have a low potential for interactions. An analysis of patient data showed no interactions with a range of other drugs; the exception is valproic acid, which slightly slows down temozolomide elimination from the body. Combining the drug with other myelosuppressants may increase the risk of myelosuppression. The therapeutic benefit of temozolomide depends on its ability to alkylate/methylate DNA, which most often occurs at the N-7 or O-6 positions of guanine residues. This methylation damages the DNA and triggers the death of tumor cells | https://en.wikipedia.org/wiki?curid=30863182 |
Temozolomide However, some tumor cells are able to repair this type of DNA damage, and therefore diminish the therapeutic efficacy of temozolomide, by expressing a protein "O"-alkylguanine DNA alkyltransferase (AGT) encoded in humans by the "O"-6-methylguanine-DNA methyltransferase ("MGMT") gene. In some tumors, epigenetic silencing of the "MGMT" gene prevents the synthesis of this enzyme, and as a consequence such tumors are more sensitive to killing by temozolomide. Conversely, the presence of AGT protein in brain tumors predicts poor response to temozolomide and these patients receive little benefit from chemotherapy with temozolomide. is quickly and almost completely absorbed from the gut, and readily penetrates the blood–brain barrier; the concentration in the cerebrospinal fluid is 30% of the concentration in the blood plasma. Intake with food decreases maximal plasma concentrations by 33% and the area under the curve by 9%. Only 15% (10–20%) of the substance are bound to blood plasma proteins. is a prodrug; it is spontaneously hydrolyzed at physiological pH to 3-methyl-(triazen-1-yl)imidazole-4-carboxamide (MTIC). MTIC splits into monomethylhydrazine, probably the active methylating agent, and 5-aminoimidazole-4-carboxamide (AIC). Other metabolites include temozolomide acid and unidentified hydrophilic substances. Plasma half-life is 1.8 hours. The substance and its metabolites are mainly excreted via the urine. is an imidazotetrazine derivative | https://en.wikipedia.org/wiki?curid=30863182 |
Temozolomide It is slightly soluble in water and aqueous acids, and melts at under decomposition. The agent was developed by Malcolm Stevens and his team at Aston University in Birmingham. It has been available in the US since August 1999, and in other countries since the early 2000s. Laboratory studies and clinical trials have started investigating the possibility of increasing the anticancer potency of temozolomide by combining it with other pharmacologic agents. For example, clinical trials have indicated that the addition of chloroquine might be beneficial for the treatment of glioma patients. Laboratory studies found that temozolomide killed brain tumor cells more efficiently when epigallocatechin gallate (EGCG), a component of green tea, was added; however, the efficacy of this effect has not yet been confirmed in brain-tumor patients. Preclinical studies reported in 2010 on investigations into the use of the novel oxygen diffusion-enhancing compound trans sodium crocetinate (TSC) when combined with temozolomide and radiation therapy and a clinical trial was underway . While the above-mentioned approaches have investigated whether the combination of temozolomide with other agents might improve therapeutic outcome, efforts have also started to study whether altering the temozolomide molecule itself can increase its activity. One such approach permanently fused perillyl alcohol, a natural compound with demonstrated therapeutic activity in brain cancer patients, to the temozolomide molecule | https://en.wikipedia.org/wiki?curid=30863182 |
Temozolomide The resultant novel compound, called NEO212 or TMZ-POH, revealed anticancer activity that was significantly greater than that of either of its two parent molecules, temozolomide and perillyl alcohol. Although , NEO212 has not been tested in humans, it has shown superior cancer therapeutic activity in animal models of glioma, melanoma, and brain metastasis of triple-negative breast cancer. Because tumor cells that express the MGMT gene are more resistant to the effects of temozolomide, researchers investigated whether the inclusion of "O"-benzylguanine ("O"-BG), an AGT inhibitor, could overcome this resistance and improve the drug's therapeutic effectiveness. In the laboratory, this combination indeed showed increased temozolomide activity in tumor-cell culture in vitro and in animal models in vivo. However, a recently completed phase-II clinical trial with brain-tumor patients yielded mixed outcomes; while there was some improved therapeutic activity when "O"-BG and temozolomide were given to patients with temozolomide-resistant anaplastic glioma, there seemed to be no significant restoration of temozolomide sensitivity in patients with temozolomide-resistant glioblastoma multiforme. Some efforts focus on engineering hematopoietic stem cells expressing the "MGMT" gene prior to transplanting them into brain-tumor patients. This would allow for the patients to receive stronger doses of temozolomide, since the patient's hematopoietic cells would be resistant to the drug | https://en.wikipedia.org/wiki?curid=30863182 |
Temozolomide High doses of temozolomide in high-grade gliomas have low toxicity, but the results are comparable to the standard doses. | https://en.wikipedia.org/wiki?curid=30863182 |
Akira Ogata In 1912, Ogata graduated from the Faculty of Medicine of the University of Tokyo. In 1919 he received a degree from the Humboldt University of Berlin, where he had performed pharmacological experiments. In 1920, he was appointed assistant professor at the Faculty of Medicine of the University of Tokyo, where he taught until 1948. In 1893, Methamphetamine was first synthesised from ephedrine by Nagayoshi Nagai and in 1919, was the first to synthesise methamphetamine in a crystallized form. Ogata blended the red phosporus and ephedrine, which is derived from an Asian herbal plant, to produce an amphetamine that could be dissolved in water. The procedure involved reduction of ephedrine using iodine and red phosphorus. Ogata's synthesis of methamphetamine replaced much more complicated earlier syntheses, and continues to be used as the basis for modern production and usage of the drug. Particularly, is the method favored in illegal drug production. Amphetamine was synthesized in 1887 by Lazar Edeleanu in Germany. Ogata released this new drug to a British-based pharmaceutical company. It was then introduced as a pill form to treat diseases such as sinus congestion, asthma, and depression. The drug took on a new form in 1934 by the German pharmaceutical company Temmler. A tablet was named ‘Pervitin’. This was marketed in Germany where it was known as Herman-Göring Pill. It became popular among soldiers, Luftwaffe pilots, and even Adolf Hitler | https://en.wikipedia.org/wiki?curid=30864054 |
Akira Ogata The new pill could keep tired pilots more alert and lift the spirits of those in battle. In Japan the drug was used as a workforce pill. It was called ‘Philopon’ which means ‘love of work’. It was given to military personnel as well as government factories. Many pharmaceutical companies in the US patented the methamphetamines under various names, one of which was called Obetrol. They treated extreme obesity as a way to curb the appetite. However, these pills were outlawed in the 70s due to some of the obvious side effects. | https://en.wikipedia.org/wiki?curid=30864054 |
TEMPO (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl, commonly known as TEMPO, is a chemical compound with the formula (CH)(CMe)NO. This heterocyclic compound is a red-orange, sublimable solid. As a stable aminoxyl radical, it has applications in chemistry and biochemistry. is used as a radical marker, as a structural probe for biological systems in conjunction with electron spin resonance spectroscopy, as a reagent in organic synthesis, and as a mediator in controlled radical polymerization. was discovered by Lebedev and Kazarnowskii in 1960. It is prepared by oxidation of 2,2,6,6-tetramethylpiperidine. According to X-ray crystallography, the N-O distance is 1.284 Å and the O is 0.1765 Å out of the CN plane. The stability of this radical can be attributed to the delocalization of the radical to form a 2-center 3-electron N-O bond. The stability is reminiscent of the stability of nitric oxide and nitrogen dioxide. Additional stability is attributed to the steric protection provided by the four methyl groups adjacent to the aminoxyl group. These methyl groups serve as inert substituents, whereas any CH center adjacent to the aminoxyl would be subject to abstraction by the aminoxyl. Regardless of the reasons for the stability of the radical, the O–H bond in the hydrogenated derivative (the hydroxylamine) TEMPO–H is weak. With an O–H bond dissociation energy of about 70 kcal/mol, this bond is about 30% weaker than a typical O–H bond | https://en.wikipedia.org/wiki?curid=30864235 |
TEMPO is employed in organic synthesis as a catalyst for the oxidation of primary alcohols to aldehydes. The actual oxidant is the "N"-oxoammonium salt. In a catalytic cycle with sodium hypochlorite as the stoichiometric oxidant, hypochlorous acid generates the "N"-oxoammonium salt from TEMPO. One typical reaction example is the oxidation of ("S")-(−)-2-methyl-1-butanol to ("S")-(+)-2-methylbutanal: 4-Methoxyphenethyl alcohol is oxidized to the corresponding carboxylic acid in a system of catalytic and sodium hypochlorite and a stoichiometric amount of sodium chlorite. oxidations also exhibit chemoselectivity, being inert towards secondary alcohols, but the reagent will convert aldehydes to carboxylic acids. In cases where secondary oxidizing agents cause side reactions, it is possible to stoichiometrically convert to the oxoammonium salt in a separate step. For example, in the oxidation of geraniol to geranial, 4-acetamido-is first oxidized to the oxoammonium tetrafluoroborate. can also be employed in nitroxide-mediated radical polymerization (NMP), a controlled free radical polymerization technique that allows better control over the final molecular weight distribution. The free radical can be added to the end of a growing polymer chain, creating a "dormant" chain that stops polymerizing. However, the linkage between the polymer chain and is weak, and can be broken upon heating, which then allows the polymerization to continue | https://en.wikipedia.org/wiki?curid=30864235 |
TEMPO Thus, the chemist can control the extent of polymerization and also synthesize narrowly distributed polymer chains. is sufficiently inexpensive for use on a laboratory scale, however at an industrial scale its price is often prohibitive. Structurally related analogues do exist, which are largely based on 4-hydroxy-(TEMPOL). This is produced from acetone and ammonia, via triacetone amine, making it much less expensive. Other alternatives include polymer-supported catalysts, which are economic due to their recyclability. Industrial-scale examples of TEMPO-like compounds include hindered amine light stabilizers and polymerisation inhibitors. | https://en.wikipedia.org/wiki?curid=30864235 |
Jacob Israelachvili Jacob Nissim Israelachvili (19 August 1944 – 20 September 2018) was an Israeli physicist and chemical engineer who was a professor of chemical engineering at the University of California, Santa Barbara (UCSB). He was born in Tel Aviv, Israel and sent to an English boarding school at the age of 7. After completing his secondary education he returned to Israel to carry out his military service before moving back to England to study physics at Cambridge University. He received his Ph.D. in Physics from Christ's College, Cambridge in 1972 and became a Research Fellow at the Biophysics Institute, University of Stockholm and at the Karolinska Institute, Sweden until 1974. He moved to Australia to take a post as fellow in the Research School of Physical Science and the Research School of Biological Sciences at the Institute of Advanced Studies, Australian National University in Canberra from 1974 to 1977. He was then appointed senior fellow in the Department of Applied Mathematics and Department of Neurobiology at the Institute of Advanced Studies, Australian National University in Canberra. He relocated to California to join UCSB in 1986, where he worked till his death on the 20th of September 2018. His research has involved study of molecular and interfacial forces. His work is applicable to a wide range of industrial and fundamental science problems. In particular, he has contributed significantly to the understanding of colloidal dispersions, biological systems, and polymer engineering applications | https://en.wikipedia.org/wiki?curid=30864881 |
Jacob Israelachvili Currently, he is studying interfacial phenomena, the physics of thin films, and fundamental questions in rheology and tribology of surfaces. Israelachvili has developed numerous techniques for the static and dynamic measurement of material and molecular properties of vapors, liquids, and surfaces. In particular, he pioneered a sensitive interfacial force-sensing technique known as the surface forces apparatus (SFA). This instrument involves carefully approaching two surfaces (usually immersed in a solvent, such as water), and measuring the force of attraction and repulsion between them. Using piezoelectric positional movement and optical interferometry for position sensing, this instrument can resolve distances to within 0.1 nanometer, and forces at the 10 N level. This technique is similar to measuring the force of interaction between an atomic force microscope (AFM) and a sample surface, except that the specialized SFA can measure much longer-range forces and is intended for surface-surface interaction measurements (as opposed to tip-surface or molecule-surface measurements). The results of SFA experiments can be used to characterize the nature of intermolecular potentials and other molecular properties. Israelachvili is also well known as the author of the textbook "Intermolecular and Surface Forces," published by Academic Press. This authoritative book describes the fundamental concepts and equations applicable to all intermolecular and interfacial science disciplines | https://en.wikipedia.org/wiki?curid=30864881 |
Jacob Israelachvili Israelachvili was also founder of SurForce, LLC. The company specializes in researching surface force interactions and producing SFA systems. | https://en.wikipedia.org/wiki?curid=30864881 |
Water quality modelling Water quality modeling involves the prediction of water pollution using mathematical simulation techniques. A typical water quality model consists of a collection of formulations representing physical mechanisms that determine position and momentum of pollutants in a water body. Models are available for individual components of the hydrological system such as surface runoff; there also exist basinwide models addressing hydrologic transport and for ocean and estuarine applications. Often finite difference methods are used to analyse these phenomena, and, almost always, large complex computer models are required. Water quality is modeled by one or more of the following formulations: | https://en.wikipedia.org/wiki?curid=30865207 |
Complementarity (molecular biology) In molecular biology, complementarity describes a relationship between two structures each following the lock-and-key principle. In nature complementarity is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary, much like looking in the mirror and seeing the reverse of things. This complementary base pairing allows cells to copy information from one generation to another and even find and repair damage to the information stored in the sequences. The degree of complementarity between two nucleic acid strands may vary, from complete complementarity (each nucleotide is across from its opposite) to no complementarity (each nucleotide is not across from its opposite) and determines the stability of the sequences to be together. Furthermore, various DNA repair functions as well as regulatory functions are based on base pair complementarity. In biotechnology, the principle of base pair complementarity allows the generation of DNA hybrids between RNA and DNA, and opens the door to modern tools such as cDNA libraries. While most complementarity is seen between two separate strings of DNA or RNA, it is also possible for a sequence to have internal complementarity resulting in the sequence binding to itself in a folded configuration | https://en.wikipedia.org/wiki?curid=30865488 |
Complementarity (molecular biology) Complementarity is achieved by distinct interactions between nucleobases: adenine, thymine (uracil in RNA), guanine and cytosine. Adenine and guanine are purines, while thymine, cytosine and uracil are pyrimidines. Purines are larger than pyrimidines. Both types of molecules complement each other and can only base pair with the opposing type of nucleobase. In nucleic acid, nucleobases are held together by hydrogen bonding, which only works efficiently between adenine and thymine and between guanine and cytosine. The base complement A=T shares two hydrogen bonds, while the base pair G≡C has three hydrogen bonds. All other configurations between nucleobases would hinder double helix formation. DNA strands are oriented in opposite directions, they are said to be antiparallel. A complementary strand of DNA or RNA may be constructed based on nucleobase complementarity. Each base pair, A=T vs. G≡C, takes up roughly the same space, thereby enabling a twisted DNA double helix formation without any spatial distortions. Hydrogen bonding between the nucleobases also stabilizes the DNA double helix. Complementarity of DNA strands in a double helix make it possible to use one strand as a template to construct the other. This principle plays an important role in DNA replication, setting the foundation of heredity by explaining how genetic information can be passed down to the next generation. Complementarity is also utilized in DNA transcription, which generates an RNA strand from a DNA template | https://en.wikipedia.org/wiki?curid=30865488 |
Complementarity (molecular biology) DNA repair mechanisms such as proof reading are complementarity based and allow for error correction during DNA replication by removing mismatched nucleobases. Nucleic acids strands may also form hybrids in which single stranded DNA may readily anneal with complementary DNA or RNA. This principle is the basis of commonly performed laboratory techniques such as the polymerase chain reaction, PCR. Two strands of complementary sequence are referred to as sense and anti-sense. The sense strand is, generally, the transcribed sequence of DNA or the RNA that was generated in transcription. While the anti-sense strand is the strand that is complementary to the sense sequence. Self-complementarity refers to the fact that a sequence of DNA or RNA may fold back on itself, creating a double-strand like structure. Depending on how close together the parts of the sequence are that are self-complementary, the strand may form hairpin loops, junctions, bulges or internal loops. RNA is more likely to form these kinds of structures due to base pair binding not seen in DNA, such as guanine binding with uracil. Complementarity can be found between short nucleic acid stretches and a coding region or an transcribed gene, and results in base pairing. These short nucleic acid sequences are commonly found in nature and have regulatory functions such as gene silencing. Antisense transcripts are stretches of non coding mRNA that are complementary to the coding sequence | https://en.wikipedia.org/wiki?curid=30865488 |
Complementarity (molecular biology) Genome wide studies have shown that RNA antisense transcripts occur commonly within nature. They are generally believed to increase the coding potential of the genetic code and add an overall layer of complexity to gene regulation. So far, it is known that 40% of the human genome is transcribed in both directions, underlining the potential significance of reverse transcription. It has been suggested that complementary regions between sense and antisense transcripts would allow generation of double stranded RNA hybrids, which may play an important role in gene regulation. For example, "hypoxia-induced factor 1α mRNA" and "β-secretase mRNA" are transcribed bidirectionally, and it has been shown that the antisense transcript acts as a stabilizer to the sense script. miRNAs, microRNA, are short RNA sequences that are complementary to regions of a transcribed gene and have regulatory functions. Current research indicates that circulating miRNA may be utilized as novel biomarkers, hence show promising evidence to be utilized in disease diagnostics. MiRNAs are formed from longer sequences of RNA that are cut free by a Dicer enzyme from an RNA sequence that is from a regulator gene. These short strands bind to a RISC complex. They match up with sequences in the upstream region of a transcribed gene due to their complementarity to act as a silencer for the gene in three ways. One is by preventing a ribosome from binding and initiating translation. Two is by degrading the mRNA that the complex has bound to | https://en.wikipedia.org/wiki?curid=30865488 |
Complementarity (molecular biology) And three is by providing a new double-stranded RNA (dsRNA) sequence that Dicer can act upon to create more miRNA to find and degrade more copies of the gene. Small interfering RNAs (siRNAs) are similar in function to miRNAs; they come from other sources of RNA, but serve a similar purpose to miRNAs. Given their short length, the rules for complementarity means that they can still be very discriminating in their targets of choice. Given that there are four choices for each base in the strand and a 20bp - 22bp length for a mi/siRNA, that leads to more than possible combinations. Given that the human genome is ~3.1 billion bases in length, this means that each miRNA should only find a match once in the entire human genome by accident. Kissing hairpins are formed when a single strand of nucleic acid complements with itself creating loops of RNA in the form of a hairpin. When two hairpins come into contact with each other "in vivo", the complementary bases of the two strands form up and begin to unwind the hairpins until a double-stranded RNA (dsRNA) complex is formed or the complex unwinds back to two separate strands due to mismatches in the hairpins. The secondary structure of the hairpin prior to kissing allows for a stable structure with a relatively fixed change in energy. The purpose of these structures is a balancing of stability of the hairpin loop vs binding strength with a complementary strand | https://en.wikipedia.org/wiki?curid=30865488 |
Complementarity (molecular biology) Too strong an initial binding to a bad location and the strands will not unwind quickly enough; too weak an initial binding and the strands will never fully form the desired complex. These hairpin structures allow for the exposure of enough bases to provide a strong enough check on the initial binding and a weak enough internal binding to allow the unfolding once a favorable match has been found. Complementarity allows information found in DNA or RNA to be stored in a single strand. The complementing strand can be determined from the template and vice versa as in cDNA libraries. This also allows for analysis, like comparing the sequences of two different species. Shorthands have been developed for writing down sequences when there are mismatches (ambiguity codes) or to speed up how to read the opposite sequence in the complement (ambigrams). A cDNA library is a collection of expressed DNA genes that are seen as a useful reference tool in gene identification and cloning processes. cDNA libraries are constructed from mRNA using RNA-dependent DNA polymerase reverse transcriptase (RT), which transcribes an mRNA template into DNA. Therefore, a cDNA library can only contain inserts that are meant to be transcribed into mRNA. This process relies on the principle of DNA/RNA complementarity. The end product of the libraries is double stranded DNA, which may be inserted into plasmids. Hence, cDNA libraries are a powerful tool in modern research | https://en.wikipedia.org/wiki?curid=30865488 |
Complementarity (molecular biology) When writing sequences for systematic biology it may be necessary to have IUPAC codes that mean "any of the two" or "any of the three". The IUPAC code R (any purine) is complementary to Y (any pyrimidine) and M (amino) to K (keto). W (weak) and S (strong) are usually not swapped but have been swapped in the past by some tools. W and S denote "weak" and "strong", respectively, and indicate a number of the hydrogen bonds that a nucleotide uses to pair with its complementing partner. A partner uses the same number of the bonds to make a complementing pair. An IUPAC code that specifically excludes one of the three nucleotides can be complementary to an IUPAC code that excludes the complementary nucleotide. For instance, V (A, C or G - "not T") can be complementary to B (C, G or T - "not A"). Specific characters may be used to create a suitable (ambigraphic) nucleic acid notation for complementary bases (i.e. guanine = "b", cytosine = "q", adenine = "n", and thymine = "u"), which makes it is possible to complement entire DNA sequences by simply rotating the text "upside down". For instance, with the previous alphabet, (GTCA) would read as (TGAC, reverse complement) if turned upside down. Ambigraphic notations readily visualize complementary nucleic acid stretches such as palindromic sequences. This feature is enhanced when utilizing custom fonts or symbols rather than ordinary ASCII or even Unicode characters. | https://en.wikipedia.org/wiki?curid=30865488 |
Teclu burner The is a laboratory gas burner, a variant of the Bunsen burner, named after the Romanian chemist Nicolae Teclu. It can produce a hotter flame than a Bunsen burner. The lower part of its tube is conical, with a round screw nut below its base. The gap, set by the distance between the nut and the end of the tube, regulates the influx of the air in a way similar to the open slots of the Bunsen burner. The provides better mixing of air and fuel, which is what allows it to achieve higher flame temperatures than the Bunsen burner. | https://en.wikipedia.org/wiki?curid=30868647 |
Surface plasmon polariton Surface plasmon polaritons (SPPs) are electromagnetic waves that travel along a metal–dielectric or metal–air interface, practically in the infrared or visible-frequency. The term "surface plasmon polariton" explains that the wave involves both charge motion in the metal ("surface plasmon") and electromagnetic waves in the air or dielectric ("polariton"). They are a type of surface wave, guided along the interface in much the same way that light can be guided by an optical fiber. SPPs are shorter in wavelength than the incident light (photons). Hence, SPPs can have tighter spatial confinement and higher local field intensity. Perpendicular to the interface, they have subwavelength-scale confinement. An SPP will propagate along the interface until its energy is lost either to absorption in the metal or scattering into other directions (such as into free space). Application of SPPs enables subwavelength optics in microscopy and lithography beyond the diffraction limit. It also enables the first steady-state micro-mechanical measurement of a fundamental property of light itself: the momentum of a photon in a dielectric medium. Other applications are photonic data storage, light generation, and bio-photonics. SPPs can be excited by both electrons and photons. Excitation by electrons is created by firing electrons into the bulk of a metal. As the electrons scatter, energy is transferred into the bulk plasma | https://en.wikipedia.org/wiki?curid=30868906 |
Surface plasmon polariton The component of the scattering vector parallel to the surface results in the formation of a surface plasmon polariton. For a photon to excite an SPP, both must have the same frequency and momentum. However, for a given frequency, a free-space photon has "more" momentum than an SPP because the two have different dispersion relations (see below). This momentum mismatch is the reason that a free-space photon from air cannot couple directly to an SPP. For the same reason, an SPP on a smooth metal surface "cannot" emit energy as a free-space photon into the dielectric (if the dielectric is uniform). This incompatibility is analogous to the lack of transmission that occurs during total internal reflection. Nevertheless, coupling of photons into SPPs can be achieved using a coupling medium such as a prism or grating to match the photon and SPP wave vectors (and thus match their momenta). A prism can be positioned against a thin metal film in the Kretschmann configuration or very close to a metal surface in the Otto configuration (Figure 1). A grating coupler matches the wave vectors by increasing the parallel wave vector component by an amount related to the grating period (Figure 2). This method, while less frequently utilized, is critical to the theoretical understanding of the effect of surface roughness. Moreover, simple isolated surface defects such as a groove, a slit or a corrugation on an otherwise planar surface provides a mechanism by which free-space radiation and SPs can exchange energy and hence couple | https://en.wikipedia.org/wiki?curid=30868906 |
Surface plasmon polariton The properties of an SPP can be derived from Maxwell's equations. We use a coordinate system where the metal–dielectric interface is the formula_1 plane, with the metal at formula_2 and dielectric at formula_3. The electric and magnetic fields as a function of position formula_4 and time "t" are as follows: where A wave of this form satisfies Maxwell's equations "only" on condition that the following equations also hold: and Solving these two equations, the dispersion relation for a wave propagating on the surface is In the free electron model of an electron gas, which neglects attenuation, the metallic dielectric function is where the bulk plasma frequency in SI units is where "n" is the electron density, "e" is the charge of the electron, "m" is the effective mass of the electron and formula_25 is the permittivity of free-space. The dispersion relation is plotted in Figure 3. At low "k", the SPP behaves like a photon, but as "k" increases, the dispersion relation bends over and reaches an asymptotic limit called the "surface plasma frequency". Since the dispersion curve lies to the right of the light line, "ω" = "k"⋅"c", the SPP has a shorter wavelength than free-space radiation such that the out-of-plane component of the SPP wavevector is purely imaginary and exhibits evanescent decay | https://en.wikipedia.org/wiki?curid=30868906 |
Surface plasmon polariton The surface plasma frequency is the asymptote of this curve, and is given by In the case of air, this result simplifies to If we assume that "ε" is real and "ε" > 0, then it must be true that "ε" < 0, a condition which is satisfied in metals. Electromagnetic waves passing through a metal experience damping due to Ohmic losses and electron-core interactions. These effects show up in as an imaginary component of the dielectric function. The dielectric function of a metal is expressed "ε" = "ε"′ + "i"⋅"ε"″ where "ε"′ and "ε"″ are the real and imaginary parts of the dielectric function, respectively. Generally » "ε"″ so the wavenumber can be expressed in terms of its real and imaginary components as The wave vector gives us insight into physically meaningful properties of the electromagnetic wave such as its spatial extent and coupling requirements for wave vector matching. As an SPP propagates along the surface, it loses energy to the metal due to absorption. The intensity of the surface plasmon decays with the square of the electric field, so at a distance "x", the intensity has decreased by a factor of formula_29. The propagation length is defined as the distance for the SPP intensity to decay by a factor of "1/e". This condition is satisfied at a length Likewise, the electric field falls off evanescently perpendicular to the metal surface. At low frequencies, the SPP penetration depth into the metal is commonly approximated using the skin depth formula | https://en.wikipedia.org/wiki?curid=30868906 |
Surface plasmon polariton In the dielectric, the field will fall off far more slowly. The decay lengths in the metal and dielectric medium can be expressed as where formula_32 is the polarization angle and formula_33 is the angle from the "z"-axis in the "xz"-plane. Two important consequences come out of these equations. The first is that if formula_34 (s-polarization), then formula_35 and the scattered light formula_36. Secondly, the scattered light has a measurable profile which is readily correlated to the roughness. This topic is treated in greater detail in reference. | https://en.wikipedia.org/wiki?curid=30868906 |
Plasmonic metamaterial A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength. The properties stem from the unique structure of the metal-dielectric composites, with features smaller than the wavelength of light separated by subwavelength distances. Light hitting such a metamaterial is transformed into surface plasmon polaritons, which are shorter in wavelength than the incident light. Plasmonic materials are metals or metal-like materials that exhibit negative real permittivity. Most common plasmonic materials are gold and silver. However, many other materials show metal-like optical properties in specific wavelength ranges. Various research groups are experimenting with different approaches to make plasmonic materials that exhibit lower losses and tunable optical properties. Plasmonic metamaterials are realizations of materials first proposed by Victor Veselago, a Russian theoretical physicist, in 1967. Also known as left-handed or negative index materials, Veselago theorized that they would exhibit optical properties opposite to those of glass or air | https://en.wikipedia.org/wiki?curid=30869356 |
Plasmonic metamaterial In negative index materials energy is transported in a direction opposite to that of propagating wavefronts, rather than paralleling them, as is the case in positive index materials. Normally, light traveling from, say, air into water bends upon passing through the normal (a plane perpendicular to the surface) and entering the water. In contrast, light reaching a negative index material through air would not cross the normal. Rather, it would bend the opposite way. Negative refraction was first reported for microwave and infrared frequencies. The negative refractive index in the optical range was first demnstrated in 2005 by Shalaev et al. (at the telecom wavelength λ = 1.5 μm) and by Brueck et al. (at λ = 2 μm) at nearly the same time. In 2007, a collaboration between the California Institute of Technology, and the NIST reported narrow band, negative refraction of visible light in two dimensions. To create this response, incident light couples with the undulating, gas-like charges (plasmons) normally on the surface of metals. This photon-plasmon interaction results in SPPs that generate intense, localized optical fields. The waves are confined to the interface between metal and insulator. This narrow channel serves as a transformative guide that, in effect, traps and compresses the wavelength of incoming light to a fraction of its original value. Nanomechanical systems incorporating metamaterials exhibit negative radiation pressure | https://en.wikipedia.org/wiki?curid=30869356 |
Plasmonic metamaterial Light falling on conventional materials, with a positive index of refraction, exerts a positive pressure, meaning that it can push an object away from the light source. In contrast, illuminating negative index metamaterials should generate a negative pressure that pulls an object toward light. Computer simulations predict plasmonic metamaterials with a negative index in three dimensions. Potential fabrication methods include multilayer thin film deposition, focused ion beam milling and self-assembly. PMMs can be made with a gradient index (a material whose refractive index varies progressively across the length or area of the material). One such material involved depositing a thermoplastic, known as a PMMA, on a gold surface via electron beam lithography. Hyperbolic metamaterials behave as a metal when light passes through it in one direction and like a dielectric when light passes in the perpendicular direction, called extreme anisotropy. The material's dispersion relation forms a hyperboloid. The associated wavelength can in principle be infinitely small. Recently, hyperbolic metasurfaces in the visible region has been demonstrated with silver or gold nanostructures by lithographic techniques. The reported hyperbolic devices showed multiple functions for sensing and imaging, e.g., diffraction-free, negative refraction and enhanced plasmon resonance effects, enabled by their unique optical properties | https://en.wikipedia.org/wiki?curid=30869356 |
Plasmonic metamaterial These specific properties are also highly required to fabricate integrated optical meta-circuits for the quantum information applications. The first metamaterials created exhibit anisotropy in their effects on plasmons. I.e., they act only in one direction. More recently, researchers used a novel self-folding technique to create a three-dimensional array of split-ring resonators that exhibits isotropy when rotated in any direction up to an incident angle of 40 degrees. Exposing strips of nickel and gold deposited on a polymer/silicon substrate to air allowed mechanical stresses to curl the strips into rings, forming the resonators. By arranging the strips at different angles to each other, 4-fold symmetry was achieved, which allowed the resonators to produce effects in multiple directions. Negative refraction for visible light was first produced in a sandwich-like construction with thin layers. An insulating sheet of silicon nitride was covered by a film of silver and underlain by another of gold. The critical dimension is the thickness of the layers, which summed to a fraction of the wavelength of blue and green light. By incorporating this metamaterial into integrated optics on an IC chip, negative refraction was demonstrated over blue and green frequencies. The collective result is a relatively significant response to light. Graphene also accommodates surface plasmons, observed via near field infrared optical microscopy techniques and infrared spectroscopy | https://en.wikipedia.org/wiki?curid=30869356 |
Plasmonic metamaterial Potential applications of graphene plasmonics involve terahertz to midinfrared frequencies, in devices such as optical modulators, photodetectors and biosensors. A hyperbolic metamaterial made from titanium nitride (metal) and aluminum scandium nitride (dielectric) have compatible crystal structures and can form a superlattice, a crystal that combines two (or more) materials. The material is compatible with existing CMOS technology (unlike traditional gold and silver), mechanically strong and thermally stable at higher temperatures. The material exhibits higher photonic densities of states than Au or Ag. The material is an efficient light absorber. The material was created using epitaxy inside a vacuum chamber with a technique known as magnetron sputtering. The material featured ultra-thin and ultra-smooth layers with sharp interfaces. Possible applications include a “planar hyperlens” that could make optical microscopes able to see objects as small as DNA, advanced sensors, more efficient solar collectors, nano-resonators, quantum computing and diffraction free focusing and imaging. The material works across a broad spectrum from near-infrared to visible light. Near-infrared is essential for telecommunications and optical communications, and visible light is important for sensors, microscopes and efficient solid-state light sources. One potential application is microscopy beyond the diffraction limit | https://en.wikipedia.org/wiki?curid=30869356 |
Plasmonic metamaterial Gradient index plasmonics were used to produce Luneburg and Eaton lenses that interact with surface plasmon polaritons rather than photons. A theorized superlens could exceed the diffraction limit that prevents standard (positive-index) lenses from resolving objects smaller than one-half of the wavelength of visible light. Such a superlens would capture spatial information that is beyond the view of conventional optical microscopes. Several approaches to building such a microscope have been proposed. The subwavelength domain could be optical switches, modulators, photodetectors and directional light emitters. Other proof-of-concept applications under review involve high sensitivity biological and chemical sensing. They may enable the development of optical sensors that exploit the confinement of surface plasmons within a certain type of Fabry-Perot nano-resonator. This tailored confinement allows efficient detection of specific bindings of target chemical or biological analytes using the spatial overlap between the optical resonator mode and the analyte ligands bound to the resonator cavity sidewalls. Structures are optimized using finite difference time domain electromagnetic simulations, fabricated using a combination of electron beam lithography and electroplating, and tested using both near-field and far-field optical microscopy and spectroscopy. Optical computing replaces electronic signals with light processing devices. In 2014 researchers announced a 200 nanometer, terahertz speed optical switch | https://en.wikipedia.org/wiki?curid=30869356 |
Plasmonic metamaterial The switch is made of a metamaterial consisting of nanoscale particles of vanadium dioxide (), a crystal that switches between an opaque, metallic phase and a transparent, semiconducting phase. The nanoparticles are deposited on a glass substrate and overlain by even smaller gold nanoparticles that act as a plasmonic photocathode. Femtosecond laser pulses free electrons in the gold particles that jump into the and cause a subpicosecond phase change. The device is compatible with current integrated circuit technology, silicon-based chips and high-K dielectrics materials. It operates in the visible and near-infrared region of the spectrum. It generates only 100 femtojoules/bit/operation, allowing the switches to be packed tightly. Gold group metals (Au, Ag and Cu) have been used as direct active materials in photovoltaics and solar cells. The materials act simultaneously as electron and hole donor, and thus can be sandwiched between electron and hole transport layers to make a photovoltaic cell. At present these photovoltaic cells allow powering smart sensors for the Internet of Things (IoT) platform. | https://en.wikipedia.org/wiki?curid=30869356 |
Glazing (window) Glazing, which derives from the Middle English for 'glass', is a part of a wall or window, made of glass. Glazing also describes the work done by a professional "glazier". Glazing is also less commonly used to describe the insertion of ophthalmic lenses into an eyeglass frame. Common types of glazing that are used in architectural applications include clear and tinted float glass, tempered glass, and laminated glass as well as a variety of coated glasses, all of which can be glazed singly or as double, or even triple, glazing units. Ordinary clear glass has a slight green tinge but special colorless glasses are offered by several manufacturers. Glazing can be mounted on the surface of a window sash or door stile, usually made of wood, aluminium or PVC. The glass is fixed into a rabbet (rebate) in the frame in a number of ways including triangular glazing points, putty, etc. Toughened and laminated glass can be glazed by bolting panes directly to a metal framework by bolts passing through drilled holes. Glazing is commonly used in low temperature solar thermal collectors because it helps retain the collected heat. | https://en.wikipedia.org/wiki?curid=30871229 |
Curie's law In a paramagnetic material, the magnetization of the material is (approximately) directly proportional to an applied magnetic field. However, if the material is heated, this proportionality is reduced: for a fixed value of the field, the magnetization is (approximately) inversely proportional to temperature. This fact is encapsulated by Curie's law, after Pierre Curie: where This relation was discovered experimentally (by fitting the results to a correctly guessed model) by Pierre Curie. It only holds for high temperatures, or weak magnetic fields. As the derivations below show, the magnetization saturates in the opposite limit of low temperatures, or strong fields. A simple model of a paramagnet concentrates on the particles which compose it which do not interact with each other. Each particle has a magnetic moment given by formula_6. The energy of a magnetic moment in a magnetic field is given by To simplify the calculation, we are going to work with a 2-state particle: it may either align its magnetic moment with the magnetic field, or against it. So the only possible values of magnetic moment are then formula_8 and formula_9. If so, then such a particle has only two possible energies and When one seeks the magnetization of a paramagnet, one is interested in the likelihood of a particle to align itself with the field | https://en.wikipedia.org/wiki?curid=30872301 |
Curie's law In other words, one seeks the expectation value of the magnetization formula_8: where the probability of a configuration is given by its Boltzmann factor, and the partition function formula_14 provides the necessary normalization for probabilities (so that the sum of all of them is unity.) The partition function of one particle is: Therefore, in this simple case we have: This is magnetization of one particle, the total magnetization of the solid is given by formula_17 where "n" is the number density of magnetic moments. The formula above is known as the Langevin paramagnetic equation. Pierre Curie found an approximation to this law which applies to the relatively high temperatures and low magnetic fields used in his experiments. Let's see what happens to the magnetization as we specialize it to large formula_4 and small formula_19. As temperature increases and magnetic field decreases, the argument of hyperbolic tangent decreases. Another way to say this is this is sometimes called the Curie regime. We also know that if formula_21, then so with a Curie constant given by formula_24. In the regime of low temperatures or high fields, formula_25 tends to a maximum value of formula_26, corresponding to all the particles being completely aligned with the field. Since this calculation doesn't describe the electrons embedded deep within the Fermi surface, forbidden by the Pauli Exclusion principle to flip their spins, it does not exemplify the quantum statistics of the problem at low temperatures | https://en.wikipedia.org/wiki?curid=30872301 |
Curie's law Using the Fermi-Dirac distribution, one will find that at low temperatures formula_25 is linear dependent on the magnetic field, so that the magnetic susceptibility saturates to a constant. When the particles have an arbitrary spin (any number of spin states), the formula is a bit more complicated. At low magnetic fields or high temperature, the spin follows Curie's law, with where formula_29 is the total angular momentum quantum number and formula_30 is the spin's g-factor (such that formula_31 is the magnetic moment). For this more general formula and its derivation (including high field, low temperature) see the article: Brillouin function. As the spin approaches infinity, the formula for the magnetization approaches the classical value derived in the following section. An alternative treatment applies when the paramagnetons are imagined to be classical, freely-rotating magnetic moments. In this case, their position will be determined by their angles in spherical coordinates, and the energy for one of them will be: where formula_33 is the angle between the magnetic moment and the magnetic field (which we take to be pointing in the formula_34 coordinate | https://en.wikipedia.org/wiki?curid=30872301 |
Curie's law ) The corresponding partition function is We see there is no dependence on the formula_36 angle, and also we can change variables to formula_37 to obtain Now, the expected value of the formula_34 component of the magnetization (the other two are seen to be null (due to integration over formula_36), as they should) will be given by To simplify the calculation, we see this can be written as a differentiation of formula_14: (This approach can also be used for the model above, but the calculation was so simple this is not so helpful.) Carrying out the derivation we find where formula_45 is the Langevin function: This function would appear to be singular for small formula_47, but it is not, since the two singular terms cancel each other. In fact, its behavior for small arguments is formula_48, so the Curie limit also applies, but with a Curie constant three times smaller in this case. Similarly, the function saturates at formula_49 for large values of its argument, and the opposite limit is likewise recovered. | https://en.wikipedia.org/wiki?curid=30872301 |
Hypoxia (environmental) Hypoxia refers to low oxygen conditions. Normally, 20.9% of the gas in the atmosphere is oxygen. The partial pressure of oxygen in the atmosphere is 20.9% of the total barometric pressure. In water, oxygen levels are much lower, approximately 7 ppm 0.0007% in good quality water, and fluctuate locally depending on the presence of photosynthetic organisms and relative distance to the surface (if there is more oxygen in the air, it will diffuse across the partial pressure gradient). Atmospheric hypoxia occurs naturally at high altitudes. Total atmospheric pressure decreases as altitude increases, causing a lower partial pressure of oxygen which is defined as hypobaric hypoxia. Oxygen remains at 20.9% of the total gas mixture, differing from hypoxic hypoxia, where the percentage of oxygen in the air (or blood) is decreased. This is common in the sealed burrows of some subterranean animals, such as blesmols. Atmospheric hypoxia is also the basis of altitude training which is a standard part of training for elite athletes. Several companies mimic hypoxia using normobaric artificial atmosphere. Oxygen depletion is a phenomenon that occurs in aquatic environments as dissolved oxygen (DO; molecular oxygen dissolved in the water) becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system | https://en.wikipedia.org/wiki?curid=30872597 |
Hypoxia (environmental) Dissolved oxygen is typically expressed as a percentage of the oxygen that would dissolve in the water at the prevailing temperature and salinity (both of which affect the solubility of oxygen in water; see oxygen saturation and underwater). An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing, or anoxic; a system with low concentration—in the range between 1 and 30% saturation—is called hypoxic or dysoxic. Most fish cannot live below 30% saturation. Hypoxia leads to impaired reproduction of remaining fish via endocrine disruption. A "healthy" aquatic environment should seldom experience less than 80%. The exaerobic zone is found at the boundary of anoxic and hypoxic zones. Hypoxia can occur throughout the water column and also at high altitudes as well as near sediments on the bottom. It usually extends throughout 20-50% of the water column, but depending on the water depth and location of pycnoclines (rapid changes in water density with depth). It can occur in 10-80% of the water column. For example, in a 10-meter water column, it can reach up to 2 meters below the surface. In a 20-meter water column, it can extend up to 8 meters below the surface. Oxygen depletion can result from a number of natural factors, but is most often a concern as a consequence of pollution and eutrophication in which plant nutrients enter a river, lake, or ocean, and phytoplankton blooms are encouraged | https://en.wikipedia.org/wiki?curid=30872597 |
Hypoxia (environmental) While phytoplankton, through photosynthesis, will raise DO saturation during daylight hours, the dense population of a bloom reduces DO saturation during the night by respiration. When phytoplankton cells die, they sink towards the bottom and are decomposed by bacteria, a process that further reduces DO in the water column. If oxygen depletion progresses to hypoxia, fish kills can occur and invertebrates like worms and clams on the bottom may be killed as well. Hypoxia may also occur in the absence of pollutants. In estuaries, for example, because freshwater flowing from a river into the sea is less dense than salt water, stratification in the water column can result. Vertical mixing between the water bodies is therefore reduced, restricting the supply of oxygen from the surface waters to the more saline bottom waters. The oxygen concentration in the bottom layer may then become low enough for hypoxia to occur. Areas particularly prone to this include shallow waters of semi-enclosed water bodies such as the Waddenzee or the Gulf of Mexico, where land run-off is substantial. In these areas a so-called "dead zone" can be created. Low dissolved oxygen conditions are often seasonal, as is the case in Hood Canal and areas of Puget Sound, in Washington State. The World Resources Institute has identified 375 hypoxic coastal zones around the world, concentrated in coastal areas in Western Europe, the Eastern and Southern coasts of the US, and East Asia, particularly in Japan | https://en.wikipedia.org/wiki?curid=30872597 |
Hypoxia (environmental) Scientists have determined that high concentrations of minerals dumped into bodies of water causes significant growth of phytoplankton blooms. As these blooms are broken down by bacteria, such as "Phanerochaete chrysosprium", oxygen is depleted by the enzymes of these organisms. Phytoplankton are mostly made up of lignin and cellulose, which are broken down by enzymes present in organisms such as "P. chrysosprium", known as white-rot"." The breakdown of cellulose does not deplete oxygen concentration in water, but the breakdown of lignin does. This breakdown of lignin includes an oxidative mechanism, and requires the presence of dissolved oxygen to take place by enzymes like ligninperoxidase. Other fungi such as brown-rot, soft-rot, and blue stain fungi also are necessary in lignin transformation. As this oxidation takes place, CO is formed in its place Ligninperoxidase (LiP) serves as the most import enzyme because it is best at breaking down lignin in these organisms. LiP disrupts C-C bonds and C-O bonds within Lignin's three-dimensional structure, causing it to break down. LiP consists of ten alpha helices, two Ca structural ions, as well as a heme group called a tetrapyrrol ring. Oxygen serves an important role in the catalytic cycle of LiP to form a double bond on the Fe ion in the tetrapyrrol ring. Without the presence of diatomic oxygen in the water, this breakdown cannot take place because Ferrin-LiP will not be reduced into Oxyferroheme. Oxygen gas is used to reduce Ferrin-LiP into Oxyferroheme-LiP | https://en.wikipedia.org/wiki?curid=30872597 |
Hypoxia (environmental) Oxyferroheme and veratric alcohol combine to create oxygen radical and Ferri-LiP, which can now be used to degrade lignin. Oxygen radicals cannot be used in the environment, and are harmful in high presence in the environment. Once Ferri-LiP is present in the ligninperoxidase, it can be used to break down lignin molecules by removing one phenylpropane group at a time through either the LRET mechanism or the mediator mechanism. The LRET mechanism (long range electron transfer mechanism) transfers an electron from the tetrapyrrol ring onto a molecule of phenylpropane in a lignin. This electron moves onto a C-C or C-O bond to break one phenylpropane molecule from the lignin, breaking it down by removing one phenylpropane at a time. In the mediator mechanism, LiP enzyme is activated by the addition of hydrogen peroxide to make LiP radical, and a mediator such as veratric alcohol is added and activated creating veratric alcohol radical. Veratric alcohol radical transfers one electron to activate the phenylpropane on lignin, and the electron dismantles a C-C or C-O bond to release one phenylpropane from the lignin. As the size of a lignin molecule increases, the more difficult it is to break these C-C or C-O bonds. Three types of phenyl propane rings include coniferyl alcohol, sinapyl alcohol, and-coumaryl alcohol. LiP has a very low MolDock score, meaning there is little energy required to form this enzyme and stabilize it to carry out reactions. LiP has a MolDock score of -156.03 kcal/mol | https://en.wikipedia.org/wiki?curid=30872597 |
Hypoxia (environmental) This is energetically favorable due to its negative free energy requirements, and therefore this reaction catalyzed by LiP is likely to take place spontaneously. Breakdown of propanol and phenols occur naturally in the environment because they are both water-soluble. The breakdown of phytoplankton in the environment depends on the presence of oxygen, and once oxygen is no longer in the bodies of water, ligninperoxidases cannot continue to break down the lignin. When oxygen is not present in the water, the breakdown of phytoplankton changes from 10.7 days to a total of 160 days for this to take place. The rate of phytoplankton breakdown can be represented using this equation: formula_1 In this equation, G(t) is the amount of particulate organic carbon (POC) overall at a given time, t. G(0) is the concentration of POC before breakdown takes place. k is a rate constant in year-1, and t is time in years. For most POC of phytoplankton, the k is around 12.8 years-1, or about 28 days for nearly 96% of carbon to be broken down in these systems. Whereas for anoxic systems, POC breakdown takes 125 days, over four times longer. It takes approximately 1 mg of Oxygen to break down 1 mg of POC in the environment, and therefore, hypoxia takes place quickly as oxygen is used up quickly to digest POC. About 9% of POC in phytoplankton can be broken down in a single day at 18 °C, therefore it takes about eleven days to completely break down a full phytoplankton | https://en.wikipedia.org/wiki?curid=30872597 |
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