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Anthracotheriidae is a paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, Elomeryx, first appeared during the middle Eocene in Asia. They thrived in Africa and Eurasia, with a few species ultimately entering North America during the Oligocene. They died out in Europe and Africa during the Miocene, possibly due to a combination of climatic changes and competition with other artiodactyls, including pigs and true hippopotamuses. The youngest genus, Merycopotamus, died out in Asia during the late Pliocene, possibly for the same reasons. The family is named after the first genus discovered, Anthracotherium, which means "coal beast", as the first fossils of it were found in Paleogene-aged coal beds in France. Fossil remains of the anthracothere genus were discovered by the Harvard University and Geological Survey of Pakistan joint research project (Y-GSP) in the well-dated middle and late Miocene deposits of the Pothohar Plateau in northern Pakistan.
In life, the average anthracothere would have resembled a skinny hippopotamus with a comparatively small, narrow head and most likely pig-like in general appearance. They had four or five toes on each foot, and broad feet suited to walking on soft mud. They had full sets of about 44 teeth with five semicrescentric cusps on the upper molars, which, in some species, were adapted for digging up the roots of aquatic plants.
Evolutionary relationships
Some skeletal characters of anthracotheres suggest they are related to hippos.
The nature of the sediments in which they are fossilized implies they were amphibious, which supports the view, based on anatomical evidence, that they were ancestors of the hippopotamuses. In many respects, especially the anatomy of the lower jaw, Anthracotherium, as with other members of the family, is allied to the hippopotamus, of which it is probably an ancestral form. However, one study suggests that instead of anthracotheres, another pig-like group of artiodactyls, the palaeochoerids, are the true stem group of Hippopotamidae. | Anthracotheriidae | Wikipedia | 486 | 8686104 | https://en.wikipedia.org/wiki/Anthracotheriidae | Biology and health sciences | Other artiodactyla | Animals |
Recent evidence, gained from comparative gene sequencing, further suggests that hippos are the closest living relatives of whales, so, if anthracotheres are stem hippos, they would also be related to whales in a clade provisionally called Whippomorpha.
However, the earliest known anthracotheres appear in the fossil record in the middle Eocene, well after the archaeocetes had already taken up totally aquatic lifestyles. Although phylogenetic analyses of molecular data on extant animals strongly support the notion that hippopotamids are the closest relatives of cetaceans (whales, dolphins and porpoises), the two groups are unlikely to be closely related when extant and extinct artiodactyls are analyzed. Cetaceans originated about 50 million years ago in the Tethys Sea between India and China, whereas the family Hippopotamidae is only 15 million years old, and the first Asian hippopotamids are only 6 million years old. Yet, analyses of fossil clades have not resolved the issue of cetacean relations.
Another study has offered a suggestion that anthracotheres are part of a clade that also consists of entelodonts (and even Andrewsarchus) and that is a sister clade to other cetancodonts, with Siamotherium as the most basal member of the clade Cetacodontamorpha. | Anthracotheriidae | Wikipedia | 292 | 8686104 | https://en.wikipedia.org/wiki/Anthracotheriidae | Biology and health sciences | Other artiodactyla | Animals |
Hammond's postulate (or alternatively the Hammond–Leffler postulate), is a hypothesis in physical organic chemistry which describes the geometric structure of the transition state in an organic chemical reaction. First proposed by George Hammond in 1955, the postulate states that:
If two states, as, for example, a transition state and an unstable intermediate, occur consecutively during a reaction process and have nearly the same energy content, their interconversion will involve only a small reorganization of the molecular structures.
Therefore, the geometric structure of a state can be predicted by comparing its energy to the species neighboring it along the reaction coordinate. For example, in an exothermic reaction the transition state is closer in energy to the reactants than to the products. Therefore, the transition state will be more geometrically similar to the reactants than to the products. In contrast, however, in an endothermic reaction the transition state is closer in energy to the products than to the reactants. So, according to Hammond’s postulate the structure of the transition state would resemble the products more than the reactants. This type of comparison is especially useful because most transition states cannot be characterized experimentally.
Hammond's postulate also helps to explain and rationalize the Bell–Evans–Polanyi principle. Namely, this principle describes the experimental observation that the rate of a reaction, and therefore its activation energy, is affected by the enthalpy of that reaction. Hammond's postulate explains this observation by describing how varying the enthalpy of a reaction would also change the structure of the transition state. In turn, this change in geometric structure would alter the energy of the transition state, and therefore the activation energy and reaction rate as well.
The postulate has also been used to predict the shape of reaction coordinate diagrams. For example, electrophilic aromatic substitution involves a distinct intermediate and two less well defined states. By measuring the effects of aromatic substituents and applying Hammond's postulate it was concluded that the rate-determining step involves formation of a transition state that should resemble the intermediate complex. | Hammond's postulate | Wikipedia | 427 | 4131678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Physical sciences | Kinetics | Chemistry |
History
During the 1940s and 1950s, chemists had trouble explaining why even slight changes in the reactants caused significant differences in the rate and product distributions of a reaction. In 1955 George Hammond, a young professor at Iowa State University, postulated that transition-state theory could be used to qualitatively explain the observed structure-reactivity relationships. Notably, John E. Leffler of Florida State University proposed a similar idea in 1953. However, Hammond's version has received more attention since its qualitative nature was easier to understand and employ than Leffler's complex mathematical equations. Hammond's postulate is sometimes called the Hammond–Leffler postulate to give credit to both scientists.
Interpreting the postulate
Effectively, the postulate states that the structure of a transition state resembles that of the species nearest to it in free energy. This can be explained with reference to potential energy diagrams:
In case (a), which is an exothermic reaction, the energy of the transition state is closer in energy to that of the reactant than that of the intermediate or the product. Therefore, from the postulate, the structure of the transition state also more closely resembles that of the reactant. In case (b), the energy of the transition state is close to neither the reactant nor the product, making none of them a good structural model for the transition state. Further information would be needed in order to predict the structure or characteristics of the transition state. Case (c) depicts the potential diagram for an endothermic reaction, in which, according to the postulate, the transition state should more closely resemble that of the intermediate or the product.
Another significance of Hammond’s postulate is that it permits us to discuss the structure of the transition state in terms of the reactants, intermediates, or products. In the case where the transition state closely resembles the reactants, the transition state is called “early” while a “late” transition state is the one that closely resembles the intermediate or the product. | Hammond's postulate | Wikipedia | 415 | 4131678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Physical sciences | Kinetics | Chemistry |
An example of the “early” transition state is chlorination. Chlorination favors the products because it is an exothermic reaction, which means that the products are lower in energy than the reactants. When looking at the adjacent diagram (representation of an "early" transition state), one must focus on the transition state, which is not able to be observed during an experiment. To understand what is meant by an “early” transition state, the Hammond postulate represents a curve that shows the kinetics of this reaction. Since the reactants are higher in energy, the transition state appears to be right after the reaction starts.
An example of the “late” transition state is bromination. Bromination favors the reactants because it is an endothermic reaction, which means that the reactants are lower in energy than the products. Since the transition state is hard to observe, the postulate of bromination helps to picture the “late” transition state (see the representation of the "late" transition state). Since the products are higher in energy, the transition state appears to be right before the reaction is complete.
One other useful interpretation of the postulate often found in textbooks of organic chemistry is the following:
Assume that the transition states for reactions involving unstable intermediates can be closely approximated by the intermediates themselves.
This interpretation ignores extremely exothermic and endothermic reactions which are relatively unusual and relates the transition state to the intermediates which are usually the most unstable.
Structure of transition states
SN1 reactions
Hammond's postulate can be used to examine the structure of the transition states of a SN1 reaction. In particular, the dissociation of the leaving group is the first transition state in a SN1 reaction. The stabilities of the carbocations formed by this dissociation are known to follow the trend tertiary > secondary > primary > methyl. | Hammond's postulate | Wikipedia | 393 | 4131678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Physical sciences | Kinetics | Chemistry |
Therefore, since the tertiary carbocation is relatively stable and therefore close in energy to the R-X reactant, then the tertiary transition state will have a structure that is fairly similar to the R-X reactant. In terms of the graph of reaction coordinate versus energy, this is shown by the fact that the tertiary transition state is further to the left than the other transition states. In contrast, the energy of a methyl carbocation is very high, and therefore the structure of the transition state is more similar to the intermediate carbocation than to the R-X reactant. Accordingly, the methyl transition state is very far to the right.
SN2 reactions
Bimolecular nucleophilic substitution (SN2) reactions are concerted reactions where both the nucleophile and substrate are involved in the rate limiting step. Since this reaction is concerted, the reaction occurs in one step, where the bonds are broken, while new bonds are formed. Therefore, to interpret this reaction, it is important to look at the transition state, which resembles the concerted rate limiting step. In the "Depiction of SN2 Reaction" figure, the nucleophile forms a new bond to the carbon, while the halide (L) bond is broken.
E1 reactions
An E1 reaction consists of a unimolecular elimination, where the rate determining step of the mechanism depends on the removal of a single molecular species. This is a two-step mechanism. The more stable the carbocation intermediate is, the faster the reaction will proceed, favoring the products. Stabilization of the carbocation intermediate lowers the activation energy. The reactivity order is (CH3)3C- > (CH3)2CH- > CH3CH2- > CH3-.
Furthermore, studies describe a typical kinetic resolution process that starts out with two enantiomers that are energetically equivalent and, in the end, forms two energy-inequivalent intermediates, referred to as diastereomers. According to Hammond's postulate, the more stable diastereomer is formed faster. | Hammond's postulate | Wikipedia | 437 | 4131678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Physical sciences | Kinetics | Chemistry |
E2 reactions
Elimination, bimolecular reactions are one step, concerted reaction where both base and substrate participate in the rate limiting step. In an E2 mechanism, a base takes a proton near the leaving group, forcing the electrons down to make a double bond, and forcing off the leaving group-all in one concerted step. The rate law depends on the first order concentration of two reactants, making it a 2nd order (bimolecular) elimination reaction. Factors that affect the rate determining step are stereochemistry, leaving groups, and base strength.
A theory, for an E2 reaction, by Joseph Bunnett suggests the lowest pass through the energy barrier between reactants and products is gained by an adjustment between the degrees of Cβ-H and Cα-X rupture at the transition state. The adjustment involves much breaking of the bond more easily broken, and a small amount of breaking of the bond which requires more energy. This conclusion by Bunnett is a contradiction from the Hammond postulate. The Hammond postulate is the opposite of what Bunnett theorized. In the transition state of a bond breaking step it involves little breaking when the bond is easily broken and much breaking when it is difficult to break. Despite these differences, the two postulates are not in conflict since they are concerned with different sorts of processes. Hammond focuses on reaction steps where one bond is made or broken, or the breaking of two or more bonds is done with no time taken occur simultaneously. The E2 theory transition state concerns a process when bond formation or breaking are not simultaneous.
Kinetics and the Bell–Evans–Polanyi principle
Technically, Hammond's postulate only describes the geometric structure of a chemical reaction. However, Hammond's postulate indirectly gives information about the rate, kinetics, and activation energy of reactions. Hence, it gives a theoretical basis for the understanding the Bell–Evans–Polanyi principle, which describes the experimental observation that the enthalpy and rate of a similar reactions were usually correlated.
The relationship between Hammond's postulate and the BEP principle can be understood by considering a SN1 reaction. Although two transition states occur during a SN1 reaction (dissociation of the leaving group and then attack by the nucleophile), the dissociation of the leaving group is almost always the rate-determining step. Hence, the activation energy and therefore rate of the reaction will depend only upon the dissociation step. | Hammond's postulate | Wikipedia | 506 | 4131678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Physical sciences | Kinetics | Chemistry |
First, consider the reaction at secondary and tertiary carbons. As the BEP principle notes, experimentally SN1 reactions at tertiary carbons are faster than at secondary carbons. Therefore, by definition, the transition state for tertiary reactions will be at a lower energy than for secondary reactions. However, the BEP principle cannot justify why the energy is lower.
Using Hammond's postulate, the lower energy of the tertiary transition state means that its structure is relatively closer to its reactants R(tertiary)-X than to the carbocation product when compared to the secondary case. Thus, the tertiary transition state will be more geometrically similar to the R(tertiary)-X reactants than the secondary transition state is to its R(secondary)-X reactants. Hence, if the tertiary transition state is close in structure to the (low energy) reactants, then it will also be lower in energy because structure determines energy. Likewise, if the secondary transition state is more similar to the (high energy) carbocation product, then it will be higher in energy.
Applying the postulate
Hammond's postulate is useful for understanding the relationship between the rate of a reaction and the stability of the products.
While the rate of a reaction depends just on the activation energy (often represented in organic chemistry as ΔG‡ “delta G double dagger”), the final ratios of products in chemical equilibrium depends only on the standard free-energy change ΔG (“delta G”). The ratio of the final products at equilibrium corresponds directly with the stability of those products.
Hammond's postulate connects the rate of a reaction process with the structural features of those states that form part of it, by saying that the molecular reorganizations have to be small in those steps that involve two states that are very close in energy. This gave birth to the structural comparison between the starting materials, products, and the possible "stable intermediates" that led to the understanding that the most stable product is not always the one that is favored in a reaction process. | Hammond's postulate | Wikipedia | 416 | 4131678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Physical sciences | Kinetics | Chemistry |
Explaining seemingly contradictory results
Hammond's postulate is especially important when looking at the rate-limiting step of a reaction. However, one must be cautious when examining a multistep reaction or one with the possibility of rearrangements during an intermediate stage. In some cases, the final products appear in skewed ratios in favor of a more unstable product (called the kinetic product) rather than the more stable product (the thermodynamic product). In this case one must examine the rate-limiting step and the intermediates. Often, the rate-limiting step is the initial formation of an unstable species such as a carbocation. Then, once the carbocation is formed, subsequent rearrangements can occur. In these kinds of reactions, especially when run at lower temperatures, the reactants simply react before the rearrangements necessary to form a more stable intermediate have time to occur. At higher temperatures when microscopic reversal is easier, the more stable thermodynamic product is favored because these intermediates have time to rearrange. Whether run at high or low temperatures, the mixture of the kinetic and thermodynamic products eventually reach the same ratio, one in favor of the more stable thermodynamic product, when given time to equilibrate due to microreversal. | Hammond's postulate | Wikipedia | 272 | 4131678 | https://en.wikipedia.org/wiki/Hammond%27s%20postulate | Physical sciences | Kinetics | Chemistry |
Ultrafast laser spectroscopy is a category of spectroscopic techniques using ultrashort pulse lasers for the study of dynamics on extremely short time scales (attoseconds to nanoseconds). Different methods are used to examine the dynamics of charge carriers, atoms, and molecules. Many different procedures have been developed spanning different time scales and photon energy ranges; some common methods are listed below.
Attosecond-to-picosecond spectroscopy
Dynamics on the femtosecond time scale are in general too fast to be measured electronically. Most measurements are done by employing a sequence of ultrashort light pulses to initiate a process and record its dynamics. The temporal width (duration) of the light pulses has to be on the same scale as the dynamics that are to be measured or even shorter.
Light sources
Titanium-sapphire laser
Ti-sapphire lasers are tunable lasers that emit red and near-infrared light (700 nm- 1100 nm).Ti-sapphire laser oscillators use Ti doped-sapphire crystals as a gain medium and Kerr-lens mode-locking to achieve sub-picosecond light pulses. Typical Ti:sapphire oscillator pulses have nJ energy and repetition rates 70-100 MHz. Chirped pulse amplification through regenerative amplification can be used to attain higher pulse energies. For amplification, laser pulses from the Ti:sapphire oscillator must first be stretched in time to prevent damage to optics, and then are injected into the cavity of another laser where pulses are amplified at a lower repetition rate. Regeneratively amplified pulses can be further amplified in a multi-pass amplifier. Following amplification, the pulses are recompressed to pulse widths similar to the original pulse widths.
Dye laser
A dye laser is a four-level laser that uses an organic dye as the gain medium. Pumped by a laser with a fixed wavelength, due to various dye types you use, different dye lasers can emit beams with different wavelengths. A ring laser design is most often used in a dye laser system. Also, tuning elements, such as a diffraction grating or prism, are usually incorporated in the cavity. This allows only light in a very narrow frequency range to resonate in the cavity and be emitted as laser emission. The wide tunability range, high output power, and pulsed or CW operation make the dye laser particularly useful in many physical & chemical studies. | Ultrafast laser spectroscopy | Wikipedia | 499 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Fiber laser
A fiber laser is usually generated first from a laser diode. The laser diode then couples the light into a fiber where it will be confined. Different wavelengths can be achieved with the use of doped fiber. The pump light from the laser diode will excite a state in the doped fiber which can then drop in energy causing a specific wavelength to be emitted. This wavelength may be different from that of the pump light and more useful for a particular experiment.
X-ray generation
Ultrafast optical pulses can be used to generate x-ray pulses in multiple ways. An optical pulse can excite an electron pulse via the photoelectric effect, and acceleration across a high potential gives the electrons kinetic energy. When the electrons hit a target they generate both characteristic x-rays and bremsstrahlung. A second method is via laser-induced plasma. When very high-intensity laser light is incident on a target, it strips electrons off the target creating a negatively charged plasma cloud. The strong Coulomb force due to the ionized material in the center of the cloud quickly accelerates the electrons back to the nuclei left behind. Upon collision with the nuclei, Bremsstrahlung and characteristic emission x-rays are given off. This method of x-ray generation scatters photons in all directions, but also generates picosecond x-ray pulses.
Conversion and characterization
Pulse characterization
For accurate spectroscopic measurements to be made, several characteristics of the laser pulse need to be known; pulse duration, pulse energy, spectral phase, and spectral shape are among some of these. Information about pulse duration can be determined through autocorrelation measurements, or from cross-correlation with another well-characterized pulse. Methods allowing for complete characterization of pulses include frequency-resolved optical gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). | Ultrafast laser spectroscopy | Wikipedia | 386 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Pulse shaping
Pulse shaping is to modify the pulses from the source in a well-defined manner, including manipulation on pulse’s amplitude, phase, and duration.
To amplify pulse’s intensity, chirped pulse amplification is generally employed, which includes a pulse stretcher, amplifier, and compressor. It will not change the duration or phase of the pulse during the amplification. Pulse compression (shortening of the pulse duration) is achieved by first chirping the pulse in a nonlinear material and broadening the spectrum, with the following compressor for chirp compensation. A fiber compressor is generally used in this case.
Pulse shapers usually refer to optical modulators which apply Fourier transforms to a laser beam. Depending on which property of light is controlled, modulators are called intensity modulators, phase modulators, polarization modulators, spatial light modulators. Depending on the modulation mechanism, optical modulators are divided into Acoustic-optic modulators, Electro-optic modulators, Liquid crystal modulators, etc. Each is dedicated to different applications.
High harmonic generation
High harmonic generation (HHG) is a nonlinear process where intense laser radiation is converted from one fixed frequency to high harmonics of that frequency by ionization and recollision of an electron. It was first observed in 1987 by McPherson et al. who successfully generated harmonic emission up to the 17th order at 248 nm in neon gas.
HHG is seen by focusing an ultra-fast, high-intensity, near-IR pulse into a noble gas at intensities of 1013–1014 W/cm2 and it generates coherent pulses in the XUV to Soft X-ray (100–1 nm) region of the spectrum. It is realizable on a laboratory scale (table-top systems) as opposed to large free electron-laser facilities.
High harmonic generation in atoms is well understood in terms of the three-step model (ionization, propagation, and recombination).
Ionization: The intense laser field modifies the Coulomb potential of the atom, electron tunnels through the barrier and ionize.
Propagation: The free-electron accelerates in the laser field and gains momentum.
Recombination: When the field reverses, the electron is accelerated back toward the ionic parent and releases a photon with very high energy. | Ultrafast laser spectroscopy | Wikipedia | 484 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Frequency conversion techniques
Different spectroscopy experiments require different excitation or probe wavelengths. For this reason, frequency conversion techniques are commonly used to extend the operational spectrum of existing laser light sources.
The most widespread conversion techniques rely on using crystals with second-order non-linearity to perform either parametric amplification or frequency mixing.
Frequency mixing works by superimposing two beams of equal or different wavelengths to generate a signal which is a higher harmonic or the sum frequency of the first two.
Parametric amplification overlaps a weak probe beam with a higher energy pump beam in a non-linear crystal such that the weak beam gets amplified and the remaining energy goes out as a new beam called the idler. This approach has the capability of generating output pulses that are shorter than the input ones. Different schemes of this approach have been implemented. Examples are optical parametric oscillator (OPO), optical parametric amplifier (OPA), non-collinear parametric amplifier (NOPA).
Techniques | Ultrafast laser spectroscopy | Wikipedia | 205 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Ultrafast transient absorption
This method is typical of 'pump-probe' experiments, where a pulsed laser is used to excite the electrons in a material (such as a molecule or semiconducting solid) from their ground states to higher-energy excited states. A probing light source, typically a xenon arc lamp or broadband laser pulse created by supercontinuum generation, is used to obtain an absorption spectrum of the compound at various times following its excitation. As the excited molecules absorb the probe light, they are further excited to even higher states or induced to return to the ground state radiatively through stimulated emission. After passing through the sample, the unabsorbed probe light continues to a photodetector such as an avalanche photodiode array or CMOS camera, and the data is processed to generate an absorption spectrum of the excited state. Since all the molecules or excitation sites in the sample will not undergo the same dynamics simultaneously, this experiment must be carried out many times (where each "experiment" comes from a single pair of pump and probe laser pulse interactions), and the data must be averaged to generate spectra with accurate intensities and peaks. Because photobleaching and other photochemical or photothermal reactions can happen to the samples, this method requires evaluating these effects by measuring the same sample at the same location many times at different pump and probe intensities. Most time the liquid samples are stirred during measurement making relatively long-time kinetics difficult to measure due to flow and diffusion. Unlike time-correlated single photon counting (TCSPC), this technique can be carried out on non-fluorescent samples. It can also be performed on non-transmissive samples in a reflection geometry. | Ultrafast laser spectroscopy | Wikipedia | 353 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Ultrafast transient absorption can use almost any probe light, so long as the probe is of a pertinent wavelength or set of wavelengths. A monochromator and photomultiplier tube in place of the avalanche photodiode array allows observation of a single probe wavelength, and thus allows probing of the decay kinetics of the excited species. The purpose of this setup is to take kinetic measurements of species that are otherwise nonradiative, and specifically it is useful for observing species that have short-lived and non-phosphorescent populations within the triplet manifold as part of their decay path. The pulsed laser in this setup is used both as a primary excitation source, and a clock signal for the ultrafast measurements. Although laborious and time-consuming, the monochromator position may also be shifted to allow absorbance decay profiles to be constructed, ultimately to the same effect as the above method.
The data of UTA measurements usually are reconstructed absorption spectra sequenced over the delay time between the pump and probe. Each spectrum resembles a normal steady-state absorption profile of the sample after the delay time of the excitation with the time resolution convoluted from the pump and probe time resolutions. The excitation wavelength is blinded by the pump laser and cut out. The rest of the spectra usually have a few bands such as ground-state absorption, excited-state absorption, and stimulated emission. Under normal conditions, the angles of the emission are randomly orientated and not detected in the absorption geometry. But in UTA measurement, the stimulated emission resembles the lasing effect, is highly oriented, and is detected. Many times this emission overlaps with the absorption bands and needs to be deconvoluted for quantitative analysis. The relationship and correlation among these bands can be visualized using the classical spectroscopic two-dimensional correlation analysis. | Ultrafast laser spectroscopy | Wikipedia | 380 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Time-resolved photoelectron spectroscopy and two-photon photoelectron spectroscopy
Time-resolved photoelectron spectroscopy and two-photon photoelectron spectroscopy (2PPE) combine a pump-probe scheme with angle-resolved photoemission. A first laser pulse is used to excite a material, a second laser pulse ionizes the system. The kinetic energy of the electrons from this process is then detected, through various methods including energy mapping, time of flight measurements etc. As above, the process is repeated many times, with different time delays between the probe pulse and the pump pulse. This builds up a picture of how the molecule relaxes over time.
A variation of this method looks at the positive ions created in this process and is called time-resolved photo-ion spectroscopy (TRPIS)
Multidimensional spectroscopy
Using the same principles pioneered by 2D-NMR experiments, multidimensional optical or infrared spectroscopy is possible using ultrafast pulses. Different frequencies can probe various dynamic molecular processes to differentiate between inhomogeneous and homogeneous line broadening as well as identify coupling between the measured spectroscopic transitions. If two oscillators are coupled together, be it intramolecular vibrations or intermolecular electronic coupling, the added dimensionality will resolve anharmonic responses not identifiable in linear spectra. A typical 2D pulse sequence consists of an initial pulse to pump the system into a coherent superposition of states, followed by a phase conjugate second pulse that pushes the system into a non-oscillating excited state, and finally, a third pulse that converts back to a coherent state that produces a measurable pulse. A 2D frequency spectrum can then be recorded by plotting the Fourier transform of the delay between the first and second pulses on one axis, and the Fourier transform of the delay between a detection pulse relative to the signal-producing third pulse on the other axis. 2D spectroscopy is an example of a four-wave mixing experiment, and the wavevector of the signal will be the sum of the three incident wavevectors used in the pulse sequence. Multidimensional spectroscopies exist in infrared and visible variants as well as combinations using different wavelength regions. | Ultrafast laser spectroscopy | Wikipedia | 448 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
2D spectroscopy using ultrafast pulses can be combined with complementary experimental methods to characterize the system under study. Photoelectrochemical measurements of photosynthetic complexes have been correlated with ultrafast pulses to stimulate and probe chromophores involved in photosynthesis and to characterize the charge transfer processes in photosynthetic reaction centers. Since charge separation and transfer is the final, biologically relevant process (in contrast to intermediate excitations and relaxations of the chromophores), the combination of photoelectrochemistry and 2D spectroscopy (PEC2DES) can be considered a form of "action spectroscopy".
Ultrafast imaging
Most ultrafast imaging techniques are variations on standard pump-probe experiments. Some commonly used techniques are Electron Diffraction imaging, Kerr Gated Microscopy, imaging with ultrafast electron pulses and terahertz imaging.
This is particularly true in the biomedical community where safe and non-invasive techniques for diagnosis are always of interest. Terahertz imaging has recently been used to identify areas of decay in tooth enamel and image the layers of the skin. Additionally, it has shown to be able to successfully distinguish a region of breast carcinoma from healthy tissue.
Another technique called Serial Time-encoded amplified microscopy has shown to have the capability of even earlier detection of trace amounts of cancer cells in the blood. Other non-biomedical applications include ultrafast imaging around corners or through opaque objects.
Femtosecond up-conversion
Femtosecond up-conversion is a pump-probe technique that uses nonlinear optics to combine the fluorescence signal and probe signal to create a signal with a new frequency via photon upconversion, which is subsequently detected. The probe scans through delay times after the pump excites the sample, generating a plot of intensity over time.
Applications | Ultrafast laser spectroscopy | Wikipedia | 370 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Applications of femtosecond spectroscopy to biochemistry
Ultrafast processes are found throughout biology. Until the advent of femtosecond methods, many of the mechanism of such processes were unknown. Examples of these include the cis-trans photoisomerization of the rhodopsin chromophore retinal, excited state and population dynamics of DNA, and the charge transfer processes in photosynthetic reaction centers Charge transfer dynamics in photosynthetic reaction centers has a direct bearing on man’s ability to develop light harvesting technology, while the excited state dynamics of DNA has implications in diseases such as skin cancer. Advances in femtosecond methods are crucial to the understanding of ultrafast phenomena in nature.
Photodissociation and femtosecond probing
Photodissociation is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule. Any photon with sufficient energy can affect the chemical bonds of a chemical compound, such as visible light, ultraviolet light, x-rays and gamma rays. The technique of probing chemical reactions has been successfully applied to unimolecular dissociations. The possibility of using a femtosecond technique to study bimolecular reactions at the individual collision level is complicated by the difficulties of spatial and temporal synchronization. One way to overcome this problem is through the use of Van der Waals complexes of weakly bound molecular cluster. Femtosecond techniques are not limited to the observation of the chemical reactions, but can even exploited to influence the course of the reaction. This can open new relaxation channels or increase the yield of certain reaction products.
Picosecond-to-nanosecond spectroscopy
Streak camera
Unlike attosecond and femtosecond pulses, the duration of pulses on the nanosecond timescale are slow enough to be measured through electronic means. Streak cameras translate the temporal profile of pulses into that of a spatial profile; that is, photons that arrive on the detector at different times arrive at different locations on the detector. | Ultrafast laser spectroscopy | Wikipedia | 434 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
Time-correlated single photon counting
Time-correlated single photon counting (TCSPC) is used to analyze the relaxation of molecules from an excited state to a lower energy state. Since various molecules in a sample will emit photons at different times following their simultaneous excitation, the decay must be thought of as having a certain rate rather than occurring at a specific time after excitation. The experimental setup is adjusted to detect 1 photon per 100 excitation pulses. In other words, less than one emitted photon is detected per laser pulse, and the process is repeated multiple times to get an average value. It measures the time difference between the excitation pulse and the photon detection, also called the time width (Δt). The fluorescence decay curve is obtained by plotting the measured time on the x-axis and the number of photons detected on the y-axis. However, it is difficult to simultaneously monitor multiple molecules. Instead, individual excitation-relaxation events are recorded and then averaged to generate the curve.
This technique analyzes the time difference between the excitation of the sample molecule and the release of energy as another photon. Repeating this process many times will give a decay profile. Pulsed lasers or LEDs can be used as a source of excitation. Part of the light passes through the sample, the other to the electronics as "sync" signal. The light emitted by the sample molecule is passed through a monochromator to select a specific wavelength. The light then is detected and amplified by a photomultiplier tube (PMT). The emitted light signal as well as reference light signal is processed through a constant fraction discriminator (CFD) which eliminates timing jitter. After passing through the CFD, the reference pulse activates a time-to-amplitude converter (TAC) circuit. The TAC charges a capacitor which will hold the signal until the next electrical pulse. In reverse TAC mode the signal of "sync" stops the TAC. This data is then further processed by an analog-to-digital converter (ADC) and multi-channel analyzer (MCA) to get a data output. To make sure that the decay is not biased to early arriving photons, the photon count rate is kept low (usually less than 1% of excitation rate). | Ultrafast laser spectroscopy | Wikipedia | 482 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
This electrical pulse comes after the second laser pulse excites the molecule to a higher energy state, and a photon is eventually emitted from a single molecule upon returning to its original state. Thus, the longer a molecule takes to emit a photon, the higher the voltage of the resulting pulse. The central concept of this technique is that only a single photon is needed to discharge the capacitor. Thus, this experiment must be repeated many times to gather the full range of delays between excitation and emission of a photon. After each trial, a pre-calibrated computer converts the voltage sent out by the TAC into a time and records the event in a histogram of time since excitation. Since the probability that no molecule will have relaxed decreases with time, a decay curve emerges that can then be analyzed to find out the decay rate of the event.
Three curves are associated with the observed decay intensity in a fluorescence decay experiment: the measured data, the instrument response function (IRF), and the calculated decay. The IRF, which represents the shortest time profile the instrument can detect, serves as a reference for accurately deconvolving the measured data. This allows for a more precise determination of the fluorescence decay time by accounting for the system's inherent response. As the term implies, this curve illustrates the response of the instrument to a sample with zero lifetime. Usually, dilute scattering solutions, such as Ludox (colloidal silica) and titanium dioxide are used to collect the curve. The measured intensity indicates the number of photons detected within a given time interval, while the calculated decay curve, also known as the fitted curve, represents the convolution of the IRF with the impulse response function.
A major complicating factor is that many decay processes involve multiple energy states, and thus multiple rate constants. Though non-linear least squares analysis can usually detect the different rate constants, determining the processes involved is often very difficult and requires the combination of multiple ultra-fast techniques. Even more complicating is the presence of inter-system crossing and other non-radiative processes in a molecule. A limiting factor of this technique is that it is limited to studying energy states that result in fluorescent decay. The technique can also be used to study relaxation of electrons from the conduction band to the valence band in semiconductors. | Ultrafast laser spectroscopy | Wikipedia | 488 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
TCSPC has extensive applications in fluorescence spectroscopy, microscopy (FLIM), and optical tomography. Over the years, this technique has gained significant attention for studying the fluorescence decay of various classes of molecules, including the fluorescence decay of residues in biological systems. The modulation of the fluorescence of the biological sample provides a better understanding of the complex system. TCSPC is widely used to study the intensity decay of Green Fluorescent Proteins (GFP), Chlorophyll aggregates in hexane, single fluorescence amino acid-containing proteins, and dinucleotides (FAD). It is also used to study the bandwidth in semiconductors. | Ultrafast laser spectroscopy | Wikipedia | 138 | 4136723 | https://en.wikipedia.org/wiki/Ultrafast%20laser%20spectroscopy | Physical sciences | Spectroscopy | Chemistry |
A pyeong (abbreviationpy) is a Korean unit of area and floorspace, equal to a square kan or 36square Korean feet. The ping and tsubo are its equivalent Taiwanese and Japanese units, similarly based on a square bu (ja:步) or ken, equivalent to 36square Chinese or Japanese feet.
Current use
Korea
In Korea, the period of Japanese occupation produced a pyeong of or 3.3058m2. It is the standard traditional measure for real estate floorspace, with an average house reckoned as about 25pyeong, a studio apartment as 8–12py, and a garret as 1½py. In South Korea, the unit has been officially banned since 1961 but with little effect prior to the criminalization of its commercial use effective 1 July 2007. Informal use continues, however, including in the form of real estate use of unusual fractions of meters equivalent to unit amounts of pyeong. Real estate listings on major websites such as Daum show measurements in square meters with the pyeong equivalent.
Taiwan
In Taiwan, the Taiwanese ping was introduced in the period of Taiwan under Japanese rule, which remains in fairly common use and is about 3.305m2.
Japan
In Japan, the usual measure of real estate floorspace is the tatami and the tsubo is reckoned as two tatami. The tatami varies by region but the modern standard is usually taken to be the Nagoya tatami of about 1.653m2, producing a tsubo of 3.306m2. It is sometimes reckoned as comprising 10gō.
China
In China, the metrication of traditional units would produce a ping of 4m2, but it is almost unknown, with most real estate floorspace simply reckoned in square meters. The longer length of the Hong Kong foot produces a larger ping of almost 5m2, but it is similarly uncommon. | Pyeong | Wikipedia | 393 | 4137557 | https://en.wikipedia.org/wiki/Pyeong | Physical sciences | Area | Basics and measurement |
Chemical decomposition, or chemical breakdown, is the process or effect of simplifying a single chemical entity (normal molecule, reaction intermediate, etc.) into two or more fragments. Chemical decomposition is usually regarded and defined as the exact opposite of chemical synthesis. In short, the chemical reaction in which two or more products are formed from a single reactant is called a decomposition reaction.
The details of a decomposition process are not always well defined. Nevertheless, some activation energy is generally needed to break the involved bonds and as such, higher temperatures generally accelerates decomposition. The net reaction can be an endothermic process, or in the case of spontaneous decompositions, an exothermic process.
The stability of a chemical compound is eventually limited when exposed to extreme environmental conditions such as heat, radiation, humidity, or the acidity of a solvent. Because of this chemical decomposition is often an undesired chemical reaction. However chemical decomposition can be desired, such as in various waste treatment processes.
For example, this method is employed for several analytical techniques, notably mass spectrometry, traditional gravimetric analysis, and thermogravimetric analysis. Additionally decomposition reactions are used today for a number of other reasons in the production of a wide variety of products. One of these is the explosive breakdown reaction of sodium azide [(NaN3)2] into nitrogen gas (N2) and sodium (Na). It is this process which powers the life-saving airbags present in virtually all of today's automobiles.
Decomposition reactions can be generally classed into three categories; thermal, electrolytic, and photolytic decomposition reactions.
Reaction formula
In the breakdown of a compound into its constituent parts, the generalized reaction for chemical decomposition is:
AB → A + B (AB represents the reactant that begins the reaction, and A and B represent the products of the reaction)
An example is the electrolysis of water to the gases hydrogen and oxygen:
2 H2O() → 2 H2() + O2()
Additional examples
An example of a spontaneous (without addition of an external energy source) decomposition is that of hydrogen peroxide which slowly decomposes into water and oxygen (see video at right):
2 H2O2 → 2 H2O + O2
This reaction is one of the exceptions to the endothermic nature of decomposition reactions. | Chemical decomposition | Wikipedia | 483 | 1533184 | https://en.wikipedia.org/wiki/Chemical%20decomposition | Physical sciences | Other reactions | Chemistry |
Other reactions involving decomposition do require the input of external energy. This energy can be in the form of heat, radiation, electricity, or light. The latter being the reason some chemical compounds, such as many prescription medicines, are kept and stored in dark bottles which reduce or eliminate the possibility of light reaching them and initiating decomposition.
When heated, carbonates will decompose. A notable exception is carbonic acid, (H2CO3). Commonly seen as the "fizz" in carbonated beverages, carbonic acid will spontaneously decompose over time into carbon dioxide and water. The reaction is written as:
H2CO3 → H2O + CO2
Other carbonates will decompose when heated to produce their corresponding metal oxide and carbon dioxide. The following equation is an example, where M represents the given metal:
MCO3 → MO + CO2
A specific example is that involving calcium carbonate:
CaCO3 → CaO + CO2
Metal chlorates also decompose when heated. In this type of decomposition reaction, a metal chloride and oxygen gas are the products. Here, again, M represents the metal:
2 MClO3 → 2 MCl+ 3 O2
A common decomposition of a chlorate is in the reaction of potassium chlorate where oxygen is the product. This can be written as:
2 KClO3 → 2 KCl + 3 O2 | Chemical decomposition | Wikipedia | 284 | 1533184 | https://en.wikipedia.org/wiki/Chemical%20decomposition | Physical sciences | Other reactions | Chemistry |
The needle-gun was a 19th-century military breech-loading rifle, as well as the first breech-loading rifle to use a bolt action to open and close the chamber. It was used as the main infantry weapon of the Prussians in the Wars of German Unification. It was invented in 1836 by the German gunsmith Johann Nikolaus von Dreyse (1787–1867), who had been conducting numerous design experiments since 1824.
The name "ignition needle rifle" () was based on its firing pin, since it passed like a needle through the paper cartridge to strike a percussion cap at the base of the bullet. However, to conceal the revolutionary nature of the design, the rifle entered military service in 1841 as the (). It had a rate of fire of about six rounds per minute.
History
The first types of needle gun made by Johann Nikolaus von Dreyse were muzzle-loading, with a firing pin consisting of a long needle driven by a coiled conchoidal spring that fired the internal percussion cap on the base of the sabot. His adoption of the bolt-action breech-loading principle combined with this igniter system gave the rifle its military potential, as these factors allowed a much faster rate of fire.
After successful testing in 1840, the Prussian king Friedrich Wilhelm IV ordered 60,000 of the new rifles. Dreyse set up the factory in Sömmerda with the help of state loans to ramp up production. It was accepted for service in 1841 as the , but only 45,000 units had been produced by 1848. It was used in combat for the first time during the German revolutions of 1848–49 and proved its combat superiority in street fighting during the May Uprising in Dresden in 1849. Many German states subsequently adopted the weapon. The Sömmerda factory could not meet demand and produced only 30,000 rifles a year. Most of the Prussian infantry in the 1850s were still equipped with the obsolete 1839 Model Potsdam musket, a smoothbore weapon whose range and accuracy was far inferior to the French Minié and Austrian Lorenz rifle. The Prussian Army's low level of funding resulted in just 90 battalions being equipped with the weapon in 1855. Dreyse consented to state manufacture of the rifle to increase production. The Royal Prussian Rifle Factory at the Spandau Arsenal began production in 1853, followed by Danzig, and Erfurt. At first, the Spandau factory produced 12,000 Dreyse needle guns a year, rising to 48,000 in 1867. | Dreyse needle gun | Wikipedia | 509 | 1533521 | https://en.wikipedia.org/wiki/Dreyse%20needle%20gun | Technology | Specific firearms | null |
The British Army evaluated the Dreyse needle gun in 1849–1851. In the British trials, the Dreyse was shown to be capable of six rounds per minute, and to maintain accuracy at . The trials suggested that the Dreyse was "too complicated and delicate" for service use. The French muzzle-loading rifle was judged to be a better weapon, and an improved version was adopted as the Pattern 1851 Minié-type muzzle-loading rifle.
After the Prussian army received a 25% increase in funding and was reformed by Wilhelm I, Albrecht von Roon and Helmuth von Moltke the Elder from 1859 to 1863, the Dreyse needle gun played an important role in the Austro-Prussian victory in the Second Schleswig War against Denmark in 1864. The introduction of cast steel barrels made industrial mass production of the weapon possible in the early 1860s. The new 1862 model and the enhanced M/55 ammunition type expedited the use and widespread adoption of the weapon in the 1860s. The success of German private industry in delivering the necessary amount of armaments for the army marked the definite end of government-owned army workshops. The Prussian Army infantry had 270,000 Dreyse needle guns by the outbreak of the Austro-Prussian War in 1866. The employment of the needle-gun changed military tactics in the 19th century, as a Prussian soldier could fire five (or more) shots, even while lying on the ground, in the time that it took his Austrian muzzle-loading counterpart to reload while standing. Production was ramped up after the war against Austria and when the Franco-Prussian War broke out in 1870, the Prussian Army had 1,150,000 needle guns in its inventory.
In 1867, Romania purchased 20,000 rifles and 11,000 carbines from the Prussian government. These were used to great effect in the Romanian War of Independence.
Sometime in the late 1860s, Japan acquired an unknown number of Model 1862 rifles and bayonets. These were marked with the imperial chrysanthemum stamp. China also acquired Dreyse rifles for the modernisation of their armed forces.
Ammunition and mechanism | Dreyse needle gun | Wikipedia | 430 | 1533521 | https://en.wikipedia.org/wiki/Dreyse%20needle%20gun | Technology | Specific firearms | null |
The cartridge used with this rifle consisted of the paper case, the bullet, the percussion cap and the black powder charge. The 15.4 mm (0.61 in) bullet was shaped like an acorn, with the broader end forming a point and the primer attached to its base. The bullet was held in a paper case known as a sabot, which separated from the bullet as it exited the muzzle. Between this inner lining and the outer case was the powder charge, consisting of 4.8 g (74 grains) of black powder.
The upper end of the paper case is rolled up and tied. Upon release of the trigger, the point of the needle pierces the rear of the cartridge, passes through the powder and hits the primer fixed to the base of the sabot. Thus the burn-front in the black powder charge passes from the front to the rear. This front-to-rear burn pattern minimizes the effect seen in rear-igniting cartridges where a portion of the powder at the front of the charge is wasted, as it is forced down and out of the barrel and burns in the air as muzzle flash. It also ensures that the whole charge burns under the highest possible pressure, theoretically minimising unburnt residues. Consequently, a smaller charge can be used to obtain the same velocity as a rear-ignited charge of the same bullet calibre and weight. It also increases the handling security of the cartridge, since it is virtually impossible to set the primer off accidentally.
There was also a blank cartridge developed for the needle gun. It was shorter and lighter than the live round, since it lacked the projectile, but was otherwise similar in construction and powder load.
Limitations
British trials in 1849–1851 showed that:
The spring that drove the needle was delicate.
When the needle was dirty, the rifle tended to misfire. Colonel Hawker considered that a new needle was required every 12 shots.
When the gun was heated and foul, operating the bolt required much strength.
The barrel tended to wear at the junction with the cylinder.
The escape of gas at the breech got worse as firing continued.
Its effective range was less than that of the Chassepot, against which it was fielded during the Franco-Prussian War. This was mainly because a sizable amount of gas escaped at the breech when the rifle was fired with a paper cartridge. An improved model, giving greater muzzle velocity and increased speed in loading, was introduced later, but it was replaced shortly thereafter by the Mauser Model 1871 rifle. | Dreyse needle gun | Wikipedia | 512 | 1533521 | https://en.wikipedia.org/wiki/Dreyse%20needle%20gun | Technology | Specific firearms | null |
The placement of the primer directly behind the bullet meant the firing needle was enclosed in black powder when the gun was fired, causing stress to the pin, which could break over time and render the rifle useless until it could be replaced. Soldiers were provided with two replacement needles for that purpose. The needle could be easily replaced in under 30 seconds, even in the field. Because the rifle used black powder, residue accumulated at the back of the barrel, making cleaning necessary after about 60–80 shots. This was not a large problem because the individual soldier carried fewer cartridges than that and Dreyse created an "air chamber" by having a protruding needle tube. (The Chassepot also had this, but it was more likely to jam after fewer shots because its chamber had a smaller diameter.) A soldier trained before the Austro-Prussian War of 1866 had to finish field cleaning in less than 10 minutes.
Comparison with contemporary rifles | Dreyse needle gun | Wikipedia | 186 | 1533521 | https://en.wikipedia.org/wiki/Dreyse%20needle%20gun | Technology | Specific firearms | null |
Ammonium sulfate (American English and international scientific usage; ammonium sulphate in British English); (NH4)2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen and 24% sulfur.
Uses
Agriculture
The primary use of ammonium sulfate is as a fertilizer for alkaline soils. In the soil, the ammonium ion is released and forms a small amount of acid, lowering the pH balance of the soil, while contributing essential nitrogen for plant growth. One disadvantage to the use of ammonium sulfate is its low nitrogen content relative to ammonium nitrate, which elevates transportation costs.
It is also used as an agricultural spray adjuvant for water-soluble insecticides, herbicides, and fungicides. There, it functions to bind iron and calcium cations that are present in both well water and plant cells. It is particularly effective as an adjuvant for 2,4-D (amine), glyphosate, and glufosinate herbicides.
Laboratory use
Ammonium sulfate precipitation is a common method for protein purification by precipitation. As the ionic strength of a solution increases, the solubility of proteins in that solution decreases. Being extremely soluble in water, ammonium sulfate can "salt out" (precipitate) proteins from aqueous solutions. Precipitation by ammonium sulfate is a result of a reduction in solubility rather than protein denaturation, thus the precipitated protein can be resolubilized through the use of standard buffers. Ammonium sulfate precipitation provides a convenient and simple means to fractionate complex protein mixtures.
In the analysis of rubber lattices, volatile fatty acids are analyzed by precipitating rubber with a 35% ammonium sulfate solution, which leaves a clear liquid from which volatile fatty acids are regenerated with sulfuric acid and then distilled with steam. Selective precipitation with ammonium sulfate, opposite to the usual precipitation technique which uses acetic acid, does not interfere with the determination of volatile fatty acids.
Food additive
As a food additive, ammonium sulfate is considered generally recognized as safe (GRAS) by the U.S. Food and Drug Administration, and in the European Union it is designated by the E number E517. It is used as an acidity regulator in flours and breads. | Ammonium sulfate | Wikipedia | 497 | 1536137 | https://en.wikipedia.org/wiki/Ammonium%20sulfate | Physical sciences | Salts | null |
Other uses
Ammonium sulfate is a precursor to other ammonium salts, especially ammonium persulfate.
Ammonium sulfate is listed as an ingredient for many United States vaccines per the Centers for Disease Control.
Ammonium sulfate has also been used in flame retardant compositions acting much like diammonium phosphate. As a flame retardant, it increases the combustion temperature of the material, decreases maximum weight loss rates, and causes an increase in the production of residue or char.
Preparation
Ammonium sulfate is made by treating ammonia with sulfuric acid:
A mixture of ammonia gas and water vapor is introduced into a reactor that contains a saturated solution of ammonium sulfate and about 2% to 4% of free sulfuric acid at 60 °C. Concentrated sulfuric acid is added to keep the solution acidic, and to retain its level of free acid. The heat of reaction keeps reactor temperature at 60 °C. Dry, powdered ammonium sulfate may be formed by spraying sulfuric acid into a reaction chamber filled with ammonia gas. The heat of reaction evaporates all water present in the system, forming a powdery salt. Approximately 6,000 million tons were produced in 1981.
Ammonium sulfate also is manufactured from gypsum (CaSO4·2H2O). Finely divided gypsum is added to an ammonium carbonate solution. Calcium carbonate precipitates as a solid, leaving ammonium sulfate in the solution.
Ammonium sulfate occurs naturally as the rare mineral mascagnite in volcanic fumaroles and due to coal fires on some dumps.
Ammonium sulfate is a byproduct in the production of methyl methacrylate.
Properties
Ammonium sulfate becomes ferroelectric at temperatures below –49.5 °C. At room temperature it crystallises in the orthorhombic system, with cell sizes of a = 7.729 Å, b = 10.560 Å, c = 5.951 Å. When chilled into the ferrorelectric state, the symmetry of the crystal changes to space group Pna21.
Reactions
Ammonium sulfate decomposes upon heating above , first forming ammonium bisulfate. Heating at higher temperatures results in decomposition into ammonia, nitrogen, sulfur dioxide, and water. | Ammonium sulfate | Wikipedia | 458 | 1536137 | https://en.wikipedia.org/wiki/Ammonium%20sulfate | Physical sciences | Salts | null |
As a salt of a strong acid (H2SO4) and weak base (NH3), its solution is acidic; the pH of 0.1 M solution is 5.5. In aqueous solution the reactions are those of and ions. For example, addition of barium chloride, precipitates out barium sulfate. The filtrate on evaporation yields ammonium chloride.
Ammonium sulfate forms many double salts (ammonium metal sulfates) when its solution is mixed with equimolar solutions of metal sulfates and the solution is slowly evaporated. With trivalent metal ions, alums such as ferric ammonium sulfate are formed. Double metal sulfates include ammonium cobaltous sulfate, ferrous diammonium sulfate, ammonium nickel sulfate which are known as Tutton's salts and ammonium ceric sulfate. Anhydrous double sulfates of ammonium also occur in the Langbeinites family. The ammonia produced has a pungent smell and is toxic.
Airborne particles of evaporated ammonium sulfate comprise approximately 30% of fine particulate pollution worldwide.
It reacts with additional sulfuric acid to give triammonium hydrogen disulphate,, .
Legislation and control
In November 2009, a ban on ammonium sulfate, ammonium nitrate and calcium ammonium nitrate fertilizers was imposed in the former Malakand Division—comprising the Upper Dir, Lower Dir, Swat, Chitral and Malakand districts of the North West Frontier Province (NWFP) of Pakistan, by the NWFP government, following reports that they were used by militants to make explosives. In January 2010, these substances were also banned in Afghanistan for the same reason. | Ammonium sulfate | Wikipedia | 350 | 1536137 | https://en.wikipedia.org/wiki/Ammonium%20sulfate | Physical sciences | Salts | null |
In modern models of physical cosmology, a dark matter halo is a basic unit of cosmological structure. It is a hypothetical region that has decoupled from cosmic expansion and contains gravitationally bound matter.
A single dark matter halo may contain multiple virialized clumps of dark matter bound together by gravity, known as subhalos.
Modern cosmological models, such as ΛCDM, propose that dark matter halos and subhalos may contain galaxies. The dark matter halo of a galaxy envelops the galactic disc and extends well beyond the edge of the visible galaxy. Thought to consist of dark matter, halos have not been observed directly. Their existence is inferred through observations of their effects on the motions of stars and gas in galaxies and gravitational lensing. Dark matter halos play a key role in current models of galaxy formation and evolution. Theories that attempt to explain the nature of dark matter halos with varying degrees of success include cold dark matter (CDM), warm dark matter, and massive compact halo objects (MACHOs).
Rotation curves as evidence of a dark matter halo
The presence of dark matter (DM) in the halo is inferred from its gravitational effect on a spiral galaxy's rotation curve. Without large amounts of mass throughout the (roughly spherical) halo, the rotational velocity of the galaxy would decrease at large distances from the galactic center, just as the orbital speeds of the outer planets decrease with distance from the Sun. However, observations of spiral galaxies, particularly radio observations of line emission from neutral atomic hydrogen (known, in astronomical parlance, as 21 cm Hydrogen line, H one, and H I line), show that the rotation curve of most spiral galaxies flattens out, meaning that rotational velocities do not decrease with distance from the galactic center. The absence of any visible matter to account for these observations implies either that unobserved (dark) matter, first proposed by Ken Freeman in 1970, exist, or that the theory of motion under gravity (general relativity) is incomplete. Freeman noticed that the expected decline in velocity was not present in NGC 300 nor M33, and considered an undetected mass to explain it. The DM Hypothesis has been reinforced by several studies.
Formation and structure of dark matter halos | Dark matter halo | Wikipedia | 466 | 1539785 | https://en.wikipedia.org/wiki/Dark%20matter%20halo | Physical sciences | Basics_2 | Astronomy |
The formation of dark matter halos is believed to have played a major role in the early formation of galaxies. During initial galactic formation, the temperature of the baryonic matter should have still been much too high for it to form gravitationally self-bound objects, thus requiring the prior formation of dark matter structure to add additional gravitational interactions. The current hypothesis for this is based on cold dark matter (CDM) and its formation into structure early in the universe.
The hypothesis for CDM structure formation begins with density perturbations in the Universe that grow linearly until they reach a critical density, after which they would stop expanding and collapse to form gravitationally bound dark matter halos. The spherical collapse framework analytically models the formation and growth of such halos. These halos would continue to grow in mass (and size), either through accretion of material from their immediate neighborhood, or by merging with other halos. Numerical simulations of CDM structure formation have been found to proceed as follows: A small volume with small perturbations initially expands with the expansion of the Universe. As time proceeds, small-scale perturbations grow and collapse to form small halos. At a later stage, these small halos merge to form a single virialized dark matter halo with an ellipsoidal shape, which reveals some substructure in the form of dark matter sub-halos.
The use of CDM overcomes issues associated with the normal baryonic matter because it removes most of the thermal and radiative pressures that were preventing the collapse of the baryonic matter. The fact that the dark matter is cold compared to the baryonic matter allows the DM to form these initial, gravitationally bound clumps. Once these subhalos formed, their gravitational interaction with baryonic matter is enough to overcome the thermal energy, and allow it to collapse into the first stars and galaxies. Simulations of this early galaxy formation matches the structure observed by galactic surveys as well as observation of the Cosmic Microwave Background.
Density profiles
A commonly used model for galactic dark matter halos is the pseudo-isothermal halo: | Dark matter halo | Wikipedia | 437 | 1539785 | https://en.wikipedia.org/wiki/Dark%20matter%20halo | Physical sciences | Basics_2 | Astronomy |
where denotes the finite central density and the core radius. This provides a good fit to most rotation curve data. However, it cannot be a complete description, as the enclosed mass fails to converge to a finite value as the radius tends to infinity. The isothermal model is, at best, an approximation. Many effects may cause deviations from the profile predicted by this simple model. For example, (i) collapse may never reach an equilibrium state in the outer region of a dark matter halo, (ii) non-radial motion may be important, and (iii) mergers associated with the (hierarchical) formation of a halo may render the spherical-collapse model invalid.
Numerical simulations of structure formation in an expanding universe lead to the empirical NFW (Navarro–Frenk–White) profile:
where is a scale radius, is a characteristic (dimensionless) density, and = is the critical density for closure. The NFW profile is called 'universal' because it works for a large variety of halo masses, spanning four orders of magnitude, from individual galaxies to the halos of galaxy clusters. This profile has a finite gravitational potential even though the integrated mass still diverges logarithmically. It has become conventional to refer to the mass of a halo at a fiducial point that encloses an overdensity 200 times greater than the critical density of the universe, though mathematically the profile extends beyond this notational point. It was later deduced that the density profile depends on the environment, with the NFW appropriate only for isolated halos. NFW halos generally provide a worse description of galaxy data than does the pseudo-isothermal profile, leading to the cuspy halo problem.
Higher resolution computer simulations are better described by the Einasto profile:
where r is the spatial (i.e., not projected) radius. The term is a function of n such that is the density at the radius that defines a volume containing half of the total mass. While the addition of a third parameter provides a slightly improved description of the results from numerical simulations, it is not observationally distinguishable from the 2 parameter NFW halo, and does nothing to alleviate the cuspy halo problem.
Shape | Dark matter halo | Wikipedia | 454 | 1539785 | https://en.wikipedia.org/wiki/Dark%20matter%20halo | Physical sciences | Basics_2 | Astronomy |
The collapse of overdensities in the cosmic density field is generally aspherical. So, there is no reason to expect the resulting halos to be spherical. Even the earliest simulations of structure formation in a CDM universe emphasized that the halos are substantially flattened. Subsequent work has shown that halo equidensity surfaces can be described by ellipsoids characterized by the lengths of their axes.
Because of uncertainties in both the data and the model predictions, it is still unclear whether the halo shapes inferred from observations are consistent with the predictions of ΛCDM cosmology.
Halo substructure
Up until the end of the 1990s, numerical simulations of halo formation revealed little substructure. With increasing computing power and better algorithms, it became possible to use greater numbers of particles and obtain better resolution. Substantial amounts of substructure are now expected. When a small halo merges with a significantly larger halo it becomes a subhalo orbiting within the potential well of its host. As it orbits, it is subjected to strong tidal forces from the host, which cause it to lose mass. In addition the orbit itself evolves as the subhalo is subjected to dynamical friction which causes it to lose energy and angular momentum to the dark matter particles of its host. Whether a subhalo survives as a self-bound entity depends on its mass, density profile, and its orbit.
Angular momentum
As originally pointed out by Hoyle and first demonstrated using numerical simulations by Efstathiou & Jones, asymmetric collapse in an expanding universe produces objects with significant angular momentum.
Numerical simulations have shown that the spin parameter distribution for halos formed by dissipation-less hierarchical clustering is well fit by a log-normal distribution, the median and width of which depend only weakly on halo mass, redshift, and cosmology:
with and . At all halo masses, there is a marked tendency for halos with higher spin to be in denser regions and thus to be more strongly clustered. | Dark matter halo | Wikipedia | 413 | 1539785 | https://en.wikipedia.org/wiki/Dark%20matter%20halo | Physical sciences | Basics_2 | Astronomy |
Milky Way dark matter halo
The visible disk of the Milky Way Galaxy is thought to be embedded in a much larger, roughly spherical halo of dark matter. The dark matter density drops off with distance from the galactic center. It is now believed that about 95% of the galaxy is composed of dark matter, a type of matter that does not seem to interact with the rest of the galaxy's matter and energy in any way except through gravity. The luminous matter makes up approximately solar masses. The dark matter halo is likely to include around to solar masses of dark matter. A 2014 Jeans analysis of stellar motions calculated the dark matter density (at the sun's distance from the galactic centre) = 0.0088 (+0.0024 −0.0018) solar masses/parsec^3. | Dark matter halo | Wikipedia | 164 | 1539785 | https://en.wikipedia.org/wiki/Dark%20matter%20halo | Physical sciences | Basics_2 | Astronomy |
Madtsoiidae is an extinct family of mostly Gondwanan snakes with a fossil record extending from early Cenomanian (Upper Cretaceous) to late Pleistocene strata located in South America, Africa, India, Australia and Southern Europe. Madtsoiidae include very primitive snakes, which like extant boas and pythons would likely dispatch their prey by constriction. Genera include some of the longest snakes known such as Vasuki, measuring at least long, and the Australian Wonambi and Yurlunggur. As a grouping of basal forms the composition and even the validity of Madtsoiidae is in a state of flux as new pertinent finds are described, with more recent evidence suggesting that it is paraphyletic as previously defined.
Although madtsoiids persisted on Australia until the Pleistocene, they largely went extinct elsewhere during the Eocene. However, some species persisted in South America and India through the Oligocene.
Description | Madtsoiidae | Wikipedia | 194 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
Madtsoiidae was first classified as a subfamily of Boidae, Madtsoiinae, in Hoffstetter (1961). Further study and new finds allowed ranking the group as a distinct family in Linnaean systems. With the recent use of cladistics to unravel phylogeny, various analyses have posited Madtsoiidae as a likely clade within Serpentes, or possible paraphyletic stem group outside Serpentes and within a more inclusive Ophidia.
Madtsoiid snakes ranged in size from less than (estimated total length) to over , and are thought to have been constrictors analogous to modern pythons and boas, but with more primitive jaw structures less highly adapted for swallowing large prey. There are specific anatomical features that diagnose members of this family, such as the presence of hypapophyses only in anterior trunk, that the middle and posterior trunk vertebrae possess a moderately or well-developed haemal keel, except for a few near the cloacal region, often with short laterally paired projections on the posterior part of the keel. Also, all trunk and caudal vertebrae have at least a parazygantral foramen, sometimes several of them, located in a more or less distinct fossa that is lateral to each zygantral facet. Additional features are the prezygapophyseal processes' absence while the paracotylar foramina are present and that the diapophyses are relatively wide, exceeding width across prezygapophyses at least in the posterior trunk vertebrae. (Scanlon 2005) | Madtsoiidae | Wikipedia | 332 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
Like most fossil snakes the majority of madtsoiids are known only from isolated vertebrae, but several (Madtsoia bai, M. camposi, Wonambi naracoortensis, Nanowana spp., unnamed Yurlunggur spp., Najash rionegrina) have associated or articulated parts of skeletons. Of the genera listed below, all have been referred to Madtsoiidae in all recent classifications except Najash rionegrina, which is included here based on diagnostic vertebral characters described by Apesteguía and Zaher (2006). These authors didn't include Najash among madtsoiids because they consider that madtsoiids are a paraphyletic assemblage of basal macrostomatans related to Madtsoia bai and consequently, not related to the Cretaceous alethinophidians from southern continents. | Madtsoiidae | Wikipedia | 183 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
Rieppel et al. (2002) classified Wonambi naracoortensis within the extant radiation (crown group) of snakes as Macrostomata incertae sedis, but many of their character state attributions for this species have been criticised or refuted by Scanlon (2005) and the better-preserved skulls of Yurlunggur sp./spp. have numerous characters apparently more plesiomorphic than any macrostomatans (Scanlon, 2006). The partial skull attributed to Najash rionegrina (Apesteguía and Zaher 2006) resembles that of the non-madtsoiid Dinilysia patagonica, and vertebrae support that they are related. The type material of Najash is the only possible madtsoiid specimen retaining evidence of pelvic and hindlimb elements, which are claimed to be more plesiomorphic than other Cretaceous limbed snakes, such as Pachyrhachis, Haasiophis or Eupodophis, in retaining a sacro-iliac contact and well-developed limbs, with a huge and well-defined trochanter. The sacro iliac contact is perhaps misleadingly described by Apesteguía and Zaher as unique possession of a sacrum, whereas it has rarely been questioned that the cloacal vertebrae in snakes are homologous to the sacrals of limbed squamates (i.e. the sacrum is present but has lost contact with the reduced ilia in other taxa). It would be unsurprising if other madtsoiids also possessed hindlimbs as complete as those of Najash.
Several madtsoiid genera have been named using indigenous words for legendary Rainbow Serpents or dragons, including Wonambi (Pitjantjatjara), Yurlunggur (Yolngu) and Nanowana (Ancient Greek nano-, 'dwarf' + Warlpiri Wana) in Australia, and Herensugea (Basque) in Europe. G.G. Simpson (1933) apparently started this trend by compounding Madtsoia from indigenous roots. In this particular case these originated from the Tehuelche language, although the reference made was geographic rather than mythological, the derivation being from that language's terms mad, "valley" and tsoi, "cow" as a rough translation from Spanish name of the type locality, Cañadón Vaca. | Madtsoiidae | Wikipedia | 507 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
A 2022 morphological study found Madtsoiidae to be paraphyletic, with Sanajeh being found to be the most basal member of the Ophidia, whereas the Cenozoic Australian madtsoiids were basal alethinophidians.
Classification | Madtsoiidae | Wikipedia | 56 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
Gigantophis Andrews, 1901
Gigantophis garstini Andrews, 1901 (Andrews, 1906; Hoffstetter, 1961b; Paleogene, Late Eocene; Egypt (Birket Qarun and Qasr el-Sagha Formations), Libya)
Madtsoia Simpson, 1933
Madtsoia bai Simpson, 1933 (Paleogene, Early Eocene Sarmiento Formation; Argentina)
Madtsoia cf. M. bai (Simpson, 1935; Hoffstetter, 1960; Paleogene, Late Paleocene Las Flores Formation; Argentina)
Madtsoia madagascariensis Hoffstetter, 1961a (Piveteau, 1933; Cretaceous, Maastrichtian Maevarano Formation; Madagascar)
Madtsoia aff. madagascariensis (de Broin et al., 1974; Cretaceous, Coniacian or Santonian In Beceten Formation, Niger)
Madtsoia camposi Rage, 1998 (Paleogene, middle Paleocene Itaboraí Formation; Brazil)
Madtsoia pisdurensis Mohabey et al, 2011 (Cretaceous, Maastrichtian Lameta Formation; India)
Wonambi Smith, 1976
Wonambi naracoortensis Smith, 1976 (Scanlon and Lee, 2000; Scanlon, 2005; Neogene, Pliocene to Pleistocene; Australia)
Wonambi barriei Scanlon in Scanlon and Lee, 2000 (Neogene, early Miocene; Australia)
Patagoniophis Albino, 1986
Patagoniophis parvus Albino, 1986 (Cretaceous, Campanian or Maastrichtian Los Alamitos Formation; Argentina)
Patagoniophis australiensis Scanlon, 2005 (Scanlon, 1993; Paleogene, early Eocene; Australia)
Alamitophis Albino, 1986
Alamitophis argentinus Albino, 1986 (Cretaceous, Campanian or Maastrichtian Los Alamitos and La Colonia Formations; Argentina)
Alamitophis elongatus Albino, 1994 (Cretaceous, Campanian or Maastrichtian Allen Formation; Argentina)
Alamitophis tingamarra Scanlon, 2005 (Scanlon, 1993; Paleogene, early Eocene; Australia)
Rionegrophis Albino, 1986
Rionegrophis madtsoioides Albino, 1986 (Cretaceous, Campanian or Maastrichtian Los Alamitos Formation; Argentina)
Yurlunggur Scanlon, 1992 | Madtsoiidae | Wikipedia | 509 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
Yurlunggur camfieldensis Scanlon, 1992 (Neogene, middle Miocene Bullock Creek (Northern Territory); Australia)
Yurlunggur spp. (Scanlon, 2004; 2006; Paleogene-Neogene, Oligocene to Miocene; Australia)
Herensugea Rage, 1996
Herensugea caristiorum Rage, 1996 (Cretaceous, Campanian or Maastrichtian Vitoria Formation; Spain)
Nanowana Scanlon, 1997
Nanowana godthelpi Scanlon, 1997 (Neogene, early-to-middle Miocene Australian Fossil Mammal Sites (Riversleigh); Australia)
Nanowana schrenki Scanlon, 1997 (Neogene, early-to-middle Miocene; Australia)
Sanajeh Wilson et al., 2010
Sanajeh indicus Wilson et al., 2010 (Cretaceous, Maastrichtian Lameta Formation; India)
Menarana Laduke et al., 2010
Menarana nosymena Laduke et al., 2010 (Late Cretaceous, Maastrichtian Maevarano Formation; Madagascar)
Menarana laurasiae Rage, 1996 (Astibia et al., 1990; Cretaceous, Campanian or Maastrichtian; Spain)
Nidophis Vasile et al., 2013
Nidophis insularis Vasile et al., 2013 (Late Cretaceous, Maastrichtian Densus-Ciula Formation; Romania)
Adinophis Pritchard et al., 2014
Adinophis fisaka Pritchard et al., 2014 (Late Cretaceous, Maastrichtian Maevarano Formation; Madagascar)
Platyspondylophis Smith et al., 2016
Platyspondylophis tadkeshwarensis Smith et al., 2016 (Paleogene, Eocene Cambay Shale; India)
Eomadtsoia Gómez et al., 2019
Eomadtsoia ragei Gómez et al., 2019 (Cretaceous, Maastrichtian La Colonia Formation; Argentina)
Powellophis Garberoglio et al., 2022
Powellophis andina Garberoglio et al., 2022 (Paleogene, Paleocene Mealla Formation; Argentina)
Vasuki Datta & Bajpai, 2024
Vasuki indicus Datta & Bajpai, 2024 (Paleogene, Eocene Naredi Formation; India) | Madtsoiidae | Wikipedia | 507 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
Unnamed specimens
Madtsoiidae indet. (Rage, 1987; Paleogene, Paleocene; Morocco)
Madtsoiidae indet. (Werner and Rage, 1994, Rage and Werner 1999; Cretaceous, Cenomanian; Sudan)
?Madtsoiid (Rage and Prasad, 1992; Cretaceous, Maastrichtian; India)
?Madtsoiid (Rage, 1991; Paleogene, early Paleocene Santa Lucía Formation; Bolivia)
?Madtsoiidae indet. cf. Madtsoia sp. (Scanlon, 2005; Paleogene, early Eocene; Australia)
Madtsoiidae indet. (Folie and Codrea, 2005; Cretaceous, Maastrichtian; Romania)
Madtsoiidae nov. (Gomez and Baez, 2006; Cretaceous, late Campanian or early Maastrichtian; Argentina)
Madtsoiidae indet. (Wazir et al., 2022; Late-Oligocene, India)
Phylogeny
According to a cladistic analysis by Scanlon (2006), Wonambi and Yurlunggur as representative genera of Madtsoiidae form a monophyletic assembly. However, as Madtsoia is not included, its grouping in the same family is questionable. | Madtsoiidae | Wikipedia | 266 | 9337873 | https://en.wikipedia.org/wiki/Madtsoiidae | Biology and health sciences | Prehistoric squamates | Animals |
Magnesium citrates are metal-organic compounds formed from citrate and magnesium ions. They are salts. One form is the 1:1 magnesium preparation in salt form with citric acid in a 1:1 ratio (1 magnesium atom per citrate molecule). It contains 11.33% magnesium by weight. Magnesium citrate (sensu lato) is used medicinally as a saline laxative and to empty the bowel before major surgery or a colonoscopy. It is available without a prescription, both as a generic and under various brand names. It is also used in the pill form as a magnesium dietary supplement. As a food additive, magnesium citrate is used to regulate acidity and is known as E number E345.
Structures
The structures of solid magnesium citrates have been characterized by X-ray crystallography. In the 1:1 salt, only one carboxylate of citrate is deprotonated. It has the formula The other form of magnesium citrate has the formula , consisting of the citrate dianion (both carboxylic acids are deprotonated). Thus, it is clear that name "magnesium citrate" is ambiguous and sometimes may refer to other salts such as trimagnesium dicitrate which has a magnesium:citrate ratio of 3:2, or monomagnesium dicitrate with a ratio of 1:2, or a mix of two or three of the salts of magnesium and citric acid.
Mechanism of action
Magnesium citrate works by attracting water through the tissues by a process known as osmosis. Once in the intestine, it can attract enough water into the intestine to induce defecation. The additional water stimulates bowel motility. This means it can also be used to treat rectal and colon problems. Magnesium citrate functions best on an empty stomach, and should always be followed with a full (eight-ounce or 250 ml) glass of water or juice to help counteract water loss and aid in absorption. Magnesium citrate solutions generally produce bowel movement in one-half to three hours. | Magnesium citrate | Wikipedia | 449 | 9339120 | https://en.wikipedia.org/wiki/Magnesium%20citrate | Physical sciences | Citrates | Chemistry |
Use and dosage
The maximum upper tolerance limit (UTL) for magnesium in supplement form for adults is 350 mg of elemental magnesium per day, according to the National Institutes of Health (NIH). In addition, according to the NIH, total dietary requirements for magnesium from all sources (in other words, food and supplements) is 320–420 mg of elemental magnesium per day, though there is no UT for dietary magnesium.
Laxative
Magnesium citrate is used as a laxative agent. It is not recommended for use in children and infants two years of age or less.
Magnesium deficiency treatment
Although less common, as a magnesium supplement the citrate form is sometimes used because it is believed to be more bioavailable than other common pill forms, such as magnesium oxide. But, according to one study, magnesium gluconate was found to be marginally more bioavailable than even magnesium citrate.
Potassium-magnesium citrate, as a supplement in pill form, is useful for the prevention of kidney stones.
Side effects
Magnesium citrate is generally not a harmful substance, but care should be taken by consulting a healthcare professional if any adverse health problems are suspected or experienced. Extreme magnesium overdose can result in serious complications such as slow heartbeat, low blood pressure, nausea, drowsiness, etc. If severe enough, an overdose can even result in coma or death. However, a moderate overdose will be excreted through the kidneys, unless one has serious kidney problems. Rectal bleeding or failure to have a bowel movement after use could be signs of a serious condition. | Magnesium citrate | Wikipedia | 327 | 9339120 | https://en.wikipedia.org/wiki/Magnesium%20citrate | Physical sciences | Citrates | Chemistry |
Energy engineering is a multidisciplinary field of engineering that focuses on optimizing energy systems, developing renewable energy technologies, and improving energy efficiency to meet the world's growing demand for energy in a sustainable manner. It encompasses areas such as energy harvesting and storage, energy conversion, energy materials, energy systems, energy efficiency, energy services, facility management, plant engineering, energy modelling, environmental compliance, As one of the most recent engineering disciplines to emerge, energy engineering plays a critical role in addressing global challenges like climate change, carbon reduction, and the transition from fossil fuels to renewable energy sources and sustainable energy.
Energy engineering is one of the most recent engineering disciplines to emerge. Energy engineering combines knowledge from the fields of physics, math, and chemistry with economic and environmental engineering practices. Energy engineers apply their skills to increase efficiency and further develop renewable sources of energy. The main job of energy engineers is to find the most efficient and sustainable ways to operate buildings and manufacturing processes. Energy engineers audit the use of energy in those processes and suggest ways to improve the systems. This means suggesting advanced lighting, better insulation, more efficient heating and cooling properties of buildings. Although an energy engineer is concerned about obtaining and using energy in the most environmentally friendly ways, their field is not limited to strictly renewable energy like hydro, solar, biomass, or geothermal. Energy engineers are also employed by the fields of oil and natural gas extraction.
Purpose
The primary purpose of energy engineering is to optimize the production and use of energy resources while minimizing energy waste and reducing environmental impact. This discipline is vital for designing systems that consume less energy, meet carbon reduction targets, and improve the energy efficiency of processes in industrial, commercial, and residential sectors. Often applied to building design, heavy consideration is given to HVAC, lighting, refrigeration, to both reduce energy loads and increase efficiency of current systems. Energy engineering is increasingly seen as a major step forward in meeting carbon reduction targets. Since buildings and houses consume over 40% of the United States energy, the services an energy engineer performs are in demand. | Energy engineering | Wikipedia | 421 | 9348093 | https://en.wikipedia.org/wiki/Energy%20engineering | Technology | Disciplines | null |
History
Human civilizations have long relied on the conversion of energy for various purposes, from the use of fire to the development of water wheels, windmills, and, eventually, electricity generation. The formalization of energy engineering began during the industrial revolution and accelerated in the mid-20th century with advancements in electrical power systems, nuclear energy, and renewable energy technologies. The oil crisis of 1973 highlighted the need for increased energy efficiency and energy independence, leading to the establishment of new government programs and industry standards. In addition, the energy crisis of 1979 brought to light the need to get more work out of less energy. The United States government passed several laws to promote increased energy efficiency, such as United States public law 94-413, the Federal Clean Car Incentive Program.
Power engineering
Power engineering, often viewed as a subset of electrical engineering, focuses on the generation, transmission, distribution, and utilization of electrical power. This subfield covers critical infrastructure such as power plants, electric grids, and energy storage systems, ensuring the efficient and reliable delivery of energy across various sectors. Emerging technologies in power engineering include the development of smart grids, microgrids, and advanced energy storage systems like lithium-ion batteries and hydrogen fuel cells, which are central to the future of renewable energy integration.
Leadership in Energy and Environmental Design
Leadership in Energy and Environmental Design (LEED) is a program created by the United States Green Building Council (USGBC) in March 2000. LEED is a program that encourages green building and promotes sustainability in the construction of buildings and the efficiency of the utilities in the buildings.
In 2012 the United States Green Building Council asked the independent firm Booz Allen Hamilton to conduct a study on the effectiveness of LEED program. "This study confirmed that green buildings generate substantial energy savings. From 2000–2008, green construction and renovation generated $1.3 billion in energy savings. Of that $1.3 billion, LEED-certified buildings accounted for $281 million." The study also found the summation of all green construction supported 2.4 million jobs.
Energy efficiency | Energy engineering | Wikipedia | 419 | 9348093 | https://en.wikipedia.org/wiki/Energy%20engineering | Technology | Disciplines | null |
Energy efficiency is seen two ways. The first view is that more work is done from the same amount of energy used. The other perception is that the same amount of work is accomplished with less energy used in the system. Some ways to get more work out of less energy is to "Reduce, Reuse, and Recycle" the materials used in daily life. The advancement of technology has led to other uses of waste. Technology such as waste-to-energy facilities which convert solid wastes through the process of gasification or pyrolysis to liquid fuels to be burned. The Environmental Protection Agency stated that the United States produced 250 million tons of municipal waste in 2010. Of that 250 million tons roughly 54% gets thrown in land fills, 33% is recycled, and 13% goes to energy recovery plants. In European countries who pay more for fuel, such as Denmark where the price of gas neared in 2010, have more fully developed waste-to energy facilities. In 2010 Denmark sent 7% of waste to landfills, 69% was recycled, and 24% was sent to waste-to-energy facilities. There are several other developed Western European countries that also have taken energy engineering into consideration. Germany's "Energiewende", a policy which set the goal by 2050 to meet 80% of electrical needs from renewable energy sources.
Statistics
As of 2023, the median annual salary for energy engineers in the U.S. ranges from $75,000 to $95,000, depending on experience and location. Energy engineers with expertise in renewable energy and energy storage tend to receive higher salaries due to the growing demand for sustainable solutions. The gender distribution in the field remains prominent, with around 80% male engineers, though efforts to increase diversity are underway through scholarships and mentorship programs. The job market for energy engineers is expected to grow rapidly over the next decade, driven by the shift towards clean energy and sustainable solutions to modern climate issues. | Energy engineering | Wikipedia | 397 | 9348093 | https://en.wikipedia.org/wiki/Energy%20engineering | Technology | Disciplines | null |
Education
To become an energy engineer, a bachelor's degree in energy engineering or related fields such as mechanical, electrical, or environmental engineering is typically required. Many universities now offer specialized energy engineering programs with a focus on renewable energy, energy storage, and grid management. Advanced certifications like the Certified Energy Manager (CEM) credential, offered by the Association of Energy Engineers, and graduate programs in sustainable energy systems further improve career plans. Also, several universities across the world have established departments or centers offering energy engineering degrees, to better prepare future engineers for their career. One of those programs is the IEP PEM Certification which is offered at Virginia Tech University.
Emerging Technologies
Emerging technologies in energy engineering are reshaping the way energy is produced, stored, and consumed. Innovations such as next-generation solar panels, modern wind turbine innovations, energy storage systems (such as flow batteries and hydrogen fuel cells), and smart grid technologies are paving the way for a more sustainable energy future. These technologies are critical in reducing reliance on fossil fuels and ensuring the stability of renewable energy systems. Other advances include artificial intelligence and machine learning applications for optimizing energy use in real-time, and carbon capture and storage (CCS) systems to mitigate emissions from existing power plants.
Energy Engineering in Policy and Society
Energy engineers play a key role in shaping energy policies and regulations worldwide. Their expertise is essential in setting standards for energy efficiency, renewable energy integration, and reducing carbon footprints. Global initiatives like the Paris Agreement and the European Green Deal are influencing energy engineering practices, pushing the field toward more sustainable and equitable energy solutions. Additionally, energy engineers are increasingly involved in public and private sector collaborations, working with governments and corporations to design and implement large-scale energy infrastructure projects which would have both societal and political impacts. | Energy engineering | Wikipedia | 364 | 9348093 | https://en.wikipedia.org/wiki/Energy%20engineering | Technology | Disciplines | null |
Perch is a common name for freshwater fish from the genus Perca, which belongs to the family Percidae of the large order Perciformes. The name comes from , meaning the type species of this genus, the European perch (P. fluviatilis).
Many species of freshwater game fish more or less resemble perch, but belong to different genera. In fact, the exclusively saltwater-dwelling red drum (which belong to a different order Acanthuriformes) is often referred to as a "red perch", though by definition perch are freshwater species. Though many fish are referred to as perch as a common name, to be considered a true perch, the fish must be of the family Percidae. | Perch | Wikipedia | 148 | 47325 | https://en.wikipedia.org/wiki/Perch | Biology and health sciences | Acanthomorpha | null |
Species
Most authorities recognize three species within the perch genus:
The European perch (P. fluviatilis) is primarily found in Europe, but a few can also be found in South Africa, and even as far east on the Southern hemisphere as Australia. This species is typically greenish in color with dark vertical bars on its sides with a red or orange coloring in the tips of its fins. The European perch has been successfully introduced in New Zealand and Australia, where it is known as the redfin perch or English perch. In Australia, larger specimens have been bred, but the species rarely grows heavier than .
The Balkhash perch (P. schrenkii) is found in Kazakhstan, (in Lake Balkhash and Lake Alakol), Uzbekistan, and China. It has a dark gray/black color on its dorsal side, but the ventral areas of the fish are a lighter silver or even sometimes green color. The Balkhash perch also displays the vertical bars on its sides, similar to the European and yellow perches. In the latter half of the 20th century, the Balkhash perch was introduced into the basins of the Nuru and Chu rivers. The introduction of these fishes to the Nuru and Chu rivers was successful. Because of this success, the population of Balkhash perch in the Balkhash Lake is rarer now. They are similar in size to the yellow and European perches, weighing around .
The yellow perch (P. flavescens), smaller and paler than the European perch (but otherwise nearly identical), is found in North America. In northern areas, it is sometimes referred to as the lake perch. This species is prized for its food quality and has often been raised in hatcheries and introduced into areas in which it is not native. These fish typically only reach a size of about and .
Anatomy | Perch | Wikipedia | 375 | 47325 | https://en.wikipedia.org/wiki/Perch | Biology and health sciences | Acanthomorpha | null |
External anatomy
Perch have a long and round body shape which allows for fast swimming in the water. True perch have "rough" or ctenoid scales. Perch have paired pectoral and pelvic fins, and two dorsal fins, the first one spiny and the second soft. These two fins can be separate or joined. The head consists of the skull (formed from loosely connected bones), eyes, mouth, operculum, gills, and a pair of nostrils (which has no connection to the oral cavity). They have small brush-like teeth across their jaws and on the roof of their mouth. The gills are located under the operculum on both sides of the head and are used to extract oxygen molecules from water and expel carbon dioxide; the gills have gill rakers inside the mouth.
External anatomy can be used to determine the sex of perch in multiple ways. Perch have two posterior openings located on their abdomen, the anal and urogenital. In males, the shape of the urogenital opening is round and larger than the anal opening. In females, the urogenital opening is often a V- or U-shape which is a similar size to the anal opening. Also, males usually have a more brown-red colored urogenital opening compared to females. | Perch | Wikipedia | 265 | 47325 | https://en.wikipedia.org/wiki/Perch | Biology and health sciences | Acanthomorpha | null |
Internal anatomy
The esophagus is a flexible tube that goes from the mouth to the stomach. The stomach is connected to the intestine via the pyloric sphincter. The intestines of perch consist of the small intestine and large intestine; the intestines have many pyloric caeca and a spiral value, the small intestine consists of a part called the duodenum. The spleen is located after the stomach and before the spiral value. The spleen is connected to the circulatory system, not part of the digestive tract. The liver is composed of three lobes: one small lobe (includes the gall bladder) and two large lobes. Perch have long and narrow kidneys that contain clusters of nephrons which empty into the mesonephric duct. They have a two-chambered heart consisting of four compartments: the sinus venous, one atrium, one ventricle, and conus. Perch have a swim bladder that helps control buoyancy or floating within the water, the swim bladder is only found in bony fish. In perch, the duct connecting the swim bladder to the pharynx is closed so air is unable to pass through from the mouth, these fish are called physoclists. Specifically in perch, the gas bladder can vary from 12% to 25% of oxygen and 1.4% to 2.9% of carbon dioxide gas. Perch reproductive organs include either a pair of testes (sperm-producing) or a pair of ovaries (egg-producing).
Habitats
Perch are classified as carnivores, choosing waters where smaller fish, shellfish, zooplankton, and insect larvae are abundant. The yellow perch can be found in the central parts of the United States in freshwater ponds, lakes, streams, or rivers. These fish can be found in freshwater all over the world, and are known to inhabit the Great Lake region, in particular Lake Erie. These fish inhabit bodies of water where vegetation and debris is readily accessible. In the spring when the perch chooses to spawn, they use vegetation to conceal their eggs from predators. | Perch | Wikipedia | 441 | 47325 | https://en.wikipedia.org/wiki/Perch | Biology and health sciences | Acanthomorpha | null |
Fishing
Perch are a popular sport fish species. They are known to put up a fight, and to be good for eating. They can be caught with a variety of methods, including float fishing, lure fishing, and legering. Fly fishing for perch using patterns that imitate small fry or invertebrates can be successful. The record weight for this fish in Britain is , the Netherlands , and in America . The biggest recorded catch in Sweden is 3.15 kg (6lb 15oz) in 1985.
Perch grow to around and or more, but the most common size caught are around and or less and anything over and is considered a prize catch. | Perch | Wikipedia | 129 | 47325 | https://en.wikipedia.org/wiki/Perch | Biology and health sciences | Acanthomorpha | null |
Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera Oncorhynchus, Salmo and Salvelinus, all of which are members of the subfamily Salmoninae in the family Salmonidae. The word trout is also used for some similar-shaped but non-salmonid fish, such as the spotted seatrout/speckled trout (Cynoscion nebulosus, which is actually a croaker).
Trout are closely related to salmon and have similar migratory life cycles. Most trout are strictly potamodromous, spending their entire lives exclusively in freshwater lakes, rivers and wetlands and migrating upstream to spawn in the shallow gravel beds of smaller headwater creeks. The hatched fry and juvenile trout, known as alevin and parr, will stay upstream growing for years before migrating down to larger waterbodies as maturing adults. There are some anadromous species of trout, such as the steelhead (a coastal subspecies of rainbow trout) and sea trout (the sea-run subspecies of brown trout), that can spend up to three years of their adult lives at sea before returning to freshwater streams for spawning, in the same fashion as a salmon run. Brook trout and three other extant species of North American trout, despite the names, are actually char (or charr), which are salmonids also closely related to trout and salmon.
Trout are classified as oily fish and have been important food fish for humans. As mid-level predators, trout prey upon smaller aquatic animals including crustaceans, insects, worms, baitfish and tadpoles, and themselves in turn are also important staple prey items for many wildlifes including brown bears, otters, raccoons, birds of prey (e.g. sea eagles, ospreys, fish owls), gulls, cormorants and kingfishers, and other large aquatic predators. Discarded remains of trout also provide a source of nutrients for scavengers, detrivores and riparian florae, making trout keystone species across aquatic and terrestrial ecosystems.
Species
The name "trout" is commonly used for many (if not most) species in three of the seven genera in the subfamily Salmoninae: Salmo (Atlantic), Oncorhynchus (Pacific) and Salvelinus (circum-arctic). Fish species referred to as trout include: | Trout | Wikipedia | 496 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Genus Salmo, all extant species except Atlantic salmon
Adriatic trout, Salmo obtusirostris
Brown trout, Salmo trutta
River trout, S. t. morpha fario
Lake trout/Lacustrine trout, S. t. morpha lacustris
Sea trout, S. t. morpha trutta
Flathead trout, Salmo platycephalus
Marble trout, Soca River trout or Soča trout – Salmo marmoratus
Ohrid trout, Salmo letnica, S. balcanicus (extinct), S. lumi, and S. aphelios
Sevan trout, Salmo ischchan | Trout | Wikipedia | 134 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Genus Oncorhynchus, six of the 12 extant species
Apache trout, Oncorhynchus apache
Biwa trout, Oncorhynchus masou rhodurus
Cutthroat trout, Oncorhynchus clarki
Coastal cutthroat trout, O. c. clarki
Crescenti trout, O. c. c. f. crescenti
Alvord cutthroat trout, O. c. alvordensis (extinct)
Bonneville cutthroat trout, O. c. utah
Humboldt cutthroat trout, O. c. humboldtensis
Lahontan cutthroat trout, O. c. henshawi
Whitehorse Basin cutthroat trout
Paiute cutthroat trout, O. c. seleniris
Snake River fine-spotted cutthroat trout, O. c. behnkei
Westslope cutthroat trout, O. c. lewisi
Yellowfin cutthroat trout, O. c. macdonaldi (extinct)
Yellowstone cutthroat trout, O. c. bouvieri
Colorado River cutthroat trout, O. c. pleuriticus
Greenback cutthroat trout, O. c. stomias
Rio Grande cutthroat trout, O. c. virginalis
Gila trout, Oncorhynchus gilae
Rainbow trout, Oncorhynchus mykiss
Kamchatkan rainbow trout, Oncorhynchus mykiss mykiss
Columbia River redband trout, Oncorhynchus mykiss gairdneri
Coastal rainbow trout (steelhead), Oncorhynchus mykiss irideus
Beardslee trout, Oncorhynchus mykiss irideus var. beardsleei
Great Basin redband trout, Oncorhynchus mykiss newberrii
Golden trout, Oncorhynchus mykiss aguabonita
Kern River rainbow trout, Oncorhynchus mykiss aguabonita var. gilberti
Sacramento golden trout, Oncorhynchus mykiss aguabonita var. stonei
Little Kern golden trout, Oncorhynchus mykiss aguabonita var. whitei
Kamloops rainbow trout, Oncorhynchus mykiss kamloops
Baja California rainbow trout, Nelson's trout, or San Pedro Martir trout, Oncorhynchus mykiss nelsoni | Trout | Wikipedia | 511 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Eagle Lake trout, Oncorhynchus mykiss aquilarum
McCloud River redband trout, Oncorhynchus mykiss stonei
Sheepheaven Creek redband trout
Mexican golden trout, Oncorhynchus chrysogaster | Trout | Wikipedia | 54 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Genus Salvelinus, five of the 52 extant species
Brook trout, Salvelinus fontinalis
Aurora trout, S. f. timagamiensis
Bull trout, Salvelinus confluentus
Dolly Varden trout, Salvelinus malma
Lake trout, Salvelinus namaycush
Silver trout, † Salvelinus agassizi (extinct)
Hybrids
Tiger trout, Salmo trutta X Salvelinus fontinalis (infertile)
Speckled Lake (Splake) trout, Salvelinus namaycush X Salvelinus fontinalis (fertile)
Fish from other families
Pseudaphritidae
Genus Pseudaphritis
Sand trout, Pseudaphritis urvillii
Sciaenidae
Genus Cynoscion
Spotted sea-trout, Cynoscion nebulosus
Anatomy
Trout that live in different environments can have dramatically different colorations and patterns. Mostly, these colors and patterns form as camouflage, based on the surroundings, and will change as the fish moves to different habitats. Trout in, or newly returned from the sea, can look very silvery, while the same fish living in a small stream or in an alpine lake could have pronounced markings and more vivid coloration; it is also possible that in some species, this signifies that they are ready to mate. In general, trout that are about to breed have extremely intense coloration and can look like an entirely different fish outside of spawning season. It is virtually impossible to define a particular color pattern as belonging to a specific breed; however, in general, wild fish are claimed to have more vivid colors and patterns.
Trout have fins entirely without spines, and all of them have a small adipose fin along the back, near the tail. The pelvic fins sit well back on the body, on each side of the anus. The swim bladder is connected to the esophagus, allowing for gulping or rapid expulsion of air, a condition known as physostome. Unlike many other physostome fish, trout do not use their bladder as an auxiliary device for oxygen uptake, relying solely on their gills. | Trout | Wikipedia | 434 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
There are many species, and even more populations, that are isolated from each other and morphologically different. However, since many of these distinct populations show no significant genetic differences, what may appear to be a large number of species is considered a much smaller number of distinct species by most ichthyologists. The trout found in the eastern United States are a good example of this. The brook trout, the aurora trout, and the (extinct) silver trout all have physical characteristics and colorations that distinguish them, yet genetic analysis shows that they are one species, Salvelinus fontinalis.
Lake trout (Salvelinus namaycush), like brook trout, belong to the char genus. Lake trout inhabit many of the larger lakes in North America, and live much longer than rainbow trout, which have an average maximum lifespan of seven years. Lake trout can live many decades, and can grow to more than .
Habitat
As salmonids, trout are coldwater fish that are usually found in cool (), clear streams, wetlands and lakes, although many of the species have anadromous populations as well. Juvenile trout are referred to as troutlet, troutling or parr. They are distributed naturally throughout North America, northern Asia and Europe. Several species of trout were introduced to Australia and New Zealand by amateur fishing enthusiasts in the 19th century, effectively displacing and endangering several upland native fish species. The introduced species included brown trout from England and rainbow trout from California. The rainbow trout has a steelhead subspecies, generally accepted as coming from Sonoma Creek. The rainbow trout of New Zealand still show the steelhead tendency to run up rivers in winter to spawn.
In Australia, the rainbow trout was introduced in 1894 from New Zealand and is an extremely popular gamefish in recreational angling.
Despite severely impacting the distribution and abundance of native Australian fish, such as the climbing galaxias, millions of rainbow and other trout species are released annually from government and private hatcheries.
The closest resemblance of seema trout and other trout family can be found in the Himalayan Region of India, Nepal, Bhutan, Pakistan and in Tian Shan mountains of Kyrgyzstan.
Diet | Trout | Wikipedia | 437 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Trout generally feed on other fish, and soft-bodied aquatic invertebrates, such as flies, mayflies, caddisflies, stoneflies, mollusks and dragonflies. In lakes, various species of zooplankton often form a large part of the diet. In general, trout longer than about prey almost exclusively on fish, where they are available. Adult trout will devour smaller fish up to one-third of their length. Trout may feed on shrimp, mealworms, bloodworms, insects, small animal parts, and eel.
Trout who swim the streams love to feed on land animals, aquatic life, and flies. Most of their diet comes from macroinvertebrates, or animals that do not have a backbone like snails, worms, or insects. They also eat flies, and most people who try to use lures to fish trout mimic flies because they are one of trout's most fed on meals. Trout enjoy certain land animals, including insects like grasshoppers. They also eat small animals like mice when they fall in. (Although only large trout have mouths capable of eating mice.) They consume a diet of aquatic life like minnows or crawfish as well. Trout have a diverse diet they follow; they have plenty of different oppositions.
Trout as food
Compared to other salmonids, trout are somewhat more bony, but the flesh is generally considered delicious, and the texture is often indistinguishable from that of salmon. The flavor of the flesh is heavily influenced by the diet of the fish. For example, trout that have been feeding on crustaceans tend to be more flavorful than those feeding primarily on insects and larvae. Because of their popularity, trout are often raised on fish farms and then stocked into heavily fished waters, in an effort to mask the effects of overfishing. Farmed trout are also sold commercially as seafood, although they are not saltwater fish. Trout meat is typically prepared the same way as salmon, often by smoking. | Trout | Wikipedia | 407 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
In Mainland China, farm-raised rainbow trout from Qinghai was officially sanctioned to be labeled and sold domestically as salmon, which caused much controversy regarding food safety and consumer rights violation, as raw fish dishes or yusheng using Atlantic salmon are gaining popularity in southern China. Farmed rainbow trout is much cheaper than the imported Atlantic salmon and the meat are indistinguishable to the untrained eyes, and the news of trout being sold as salmon triggered public scrutiny accusing seafood suppliers of bait-and-switch and unethical business practices. Also, many people believe freshwater trout are more prone to parasites than oceanic salmon (even though both live in freshwater for significant periods of their life cycles) and thus unsafe for raw eating.
Nutritional value
One fillet of trout (about ) contains:
Energy:
Fat (g): 5.22
Carbohydrates (g): 0
Fibers (g): 0
Protein (g): 16.41
Cholesterol (mg): 46
Trout fishing
Trout are very popular freshwater game fish highly prized especially by creek fishermen, because they generally put up a good fight when caught with a hook and line. As trout are predatory fish, lure fishing (which use replica baits called lures to imitate live prey) is the predominant form of sport fishing involving trout, although traditional bait fishing techniques using floats and/or sinkers (particularly with moving live baits such as baitfish, crayfish or aquatic insects) are also successful, especially against stocked trout that are hatchery/farm-raised and thus more accustomed to artificial feeds.
Many species of trout, most noticeably rainbow trout and brown trout, have been widely introduced into waterbodies outside of their native ranges purely for the sake of recreational fishing, and some of these introduced populations have even become invasive in the new habitats.
River fishing
While trout can be caught with a normal rod and reel, fly fishing is a distinctive lure fishing method developed for trout, and now extended to other species. Due to the high proportion of insects and small crustaceans within the trout's diet, small lures made of hand-tied hairs and threads are often used to imitate these aquatic invertebrates that the trout prey upon. These ultralight fly lures cannot be cast adequately by conventional techniques, and a specialized heavy line (i.e. fly line) is needed to launch the lure. | Trout | Wikipedia | 483 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Understanding how moving water shapes the stream channel makes it easier to find trout. In most streams, the current creates a riffle-run-pool pattern that repeats itself over and over. A deep pool may hold a big brown trout, but rainbow trout and smaller brown trout are likely found in runs. Riffles are where fishers will find small trout, called troutlet, during the day and larger trout crowding in during morning and evening feeding periods.
Riffles have a fast current and shallow water. This gives way to a bottom of gravel, rubble or boulder. Riffles are morning and evening feeding areas. Trout usually spawn just above or below riffles, but may spawn right in them.
Runs are deeper than riffles with a moderate current and are found between riffles and pools. The bottom is made up of small gravel or rubble. These hot spots hold trout almost anytime, if there is sufficient cover.
Pools are smoother and look darker than the other areas of the stream. The deep, slow-moving water generally has a bottom of silt, sand, or small gravel. Pools make good midday resting spots for medium to large trout.
It is recommended that when fishing for trout, that the fisher(s) should use line in the 4–8 lb test for streamfish, and stronger line with the same diameter for trout from the sea or from a large lake, such as Lake Michigan. It is also recommended to use a hook size 8–5 for trout of all kind. Trout, especially farm-raised ones, tend to like salmon roes, worms, minnows, cut bait, maize, or marshmallows.
Ice fishing
Fishing for trout under the ice generally occurs in depths of . Because trout are cold water fish, during the winter they move from up-deep to the shallows, replacing the small fish that inhabit the area during the summer. Trout in winter constantly cruise in shallow depths looking for food, usually traveling in groups, although bigger fish may travel alone and in water that's somewhat deeper, around . Rainbow, Brown, and Brook trout are the most common trout species caught through the ice.
Trout fishing records
By information from International Game Fish Association (IGFA), the most outstanding records are: | Trout | Wikipedia | 455 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Brook trout caught by Dr. W. Cook in the Nipigon River, Canada, on July 1, 1916, that weighed
Cutthroat trout caught by John Skimmerhorn in Pyramid Lake located in Nevada, US, on December 1, 1925, that weighed
Bull trout caught by N. Higgins in Lake Pend Oreille located in Idaho, US, on October 27, 1949, that weighed
Golden trout caught by Chas Reed in Cooks Lake located in Wyoming, US, on August 5, 1948, that weighed
Rainbow trout caught by Sean Konrad in Lake Diefenbaker, Canada, on September 5, 2009, that weighed
Lake trout caught by Lloyd Bull in Great Bear Lake, Canada, on August 19, 1995, that weighed
Baits | Trout | Wikipedia | 151 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Declines in native trout populations
Salmonid populations in general have been declining due to numerous factors, including invasive species, hybridization, wildfires, and climate change. Native salmonid fish in the western and southwestern United States are threatened by non-native species that were introduced decades ago. Non-native salmonids were introduced to enrich recreational fishing; however, they quickly started outcompeting and displacing native salmonids upon their arrival. Non-native, invasive species are quick to adapt to their new environment and learn to outcompete any native species, making them a force the native salmon and trout have to reckon with. Not only do the non-native fish drive the native fish to occupy new niches, but they also try to hybridize with them, contaminating the native gene construction. As more hybrids between native and non-native fish are formed, the lineage of the pure fish is continuously being contaminated by other species and soon may no longer represent the sole native species. The Rio Grande cutthroat trout (Oncorhynchus clarki virginalis) are susceptible to hybridization with other salmonids such as rainbow trout (Oncorhynchus mykiss) and yield a new "cutbow" trout, which is a contamination of both lineages’ genes. One solution to this issue is implemented by New Mexico Department of Game and Fish hatcheries: stock only sterile fish in river streams. Hatcheries serve as a reservoir of fish for recreational activities but growing and stocking non-sterile fish would worsen the hybridization issue on a quicker, more magnified time scale. By stocking sterile fish, the native salmonids can't share genes with the non-native hatchery fish, thus, preventing further gene contamination of the native trout in New Mexico. Fire is also a factor in deteriorating Gila trout (Oncorhynchus gilae) populations because of the ash and soot that can enter streams following fires. The ash lowers water quality, making it more difficult for the Gila trout to survive. In some New Mexico streams, the native Gila trout will be evacuated from streams that are threatened by nearby fires and be reintroduced after the threat is resolved. | Trout | Wikipedia | 449 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Climate change is also dwindling native salmonid populations. Global warming continually affects various cold-water fish such as trout, especially as inland waterbodies are more prone to warming than oceans. With an increase of temperature along with changes in spawning river flow, an abundance of trout species are effected negatively. In the past, a mere increase was predicted to eliminate half of the native brook trout in the Southern Appalachian Mountains. Trout generally prefer streams with colder water () to spawn and thrive, but raising water temperatures are altering this ecosystem and further deteriorate native populations. | Trout | Wikipedia | 115 | 47326 | https://en.wikipedia.org/wiki/Trout | Biology and health sciences | Salmoniformes | null |
Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment.
Mackerel species typically have deeply forked tails and vertical "tiger-like" stripes on their backs with an iridescent green-blue quality. Many are restricted in their distribution ranges and live in separate populations or fish stocks based on geography. Some stocks migrate in large schools along the coast to suitable spawning grounds, where they spawn in fairly shallow waters. After spawning they return the way they came in smaller schools to suitable feeding grounds, often near an area of upwelling. From there they may move offshore into deeper waters and spend the winter in relative inactivity. Other stocks migrate across oceans.
Smaller mackerel are forage fish for larger predators, including larger mackerel and Atlantic cod. Flocks of seabirds, whales, dolphins, sharks, and schools of larger fish such as tuna and marlin follow mackerel schools and attack them in sophisticated and cooperative ways. Mackerel flesh is high in omega-3 oils and is intensively harvested by humans. In 2009, over 5 million tons were landed by commercial fishermen. Sport fishermen value the fighting abilities of the king mackerel.
Species
Over 30 different species, principally belonging to the family Scombridae, are commonly referred to as mackerel. The term "mackerel" is derived from Old French and may have originally meant either "marked, spotted" or "pimp, procurer". The latter connection is not altogether clear, but mackerel spawn enthusiastically in shoals near the coast, and medieval ideas on animal procreation were creative.
Scombroid mackerels
About 21 species in the family Scombridae are commonly called mackerel. The type species for the scombroid mackerel is the Atlantic mackerel, Scomber scombrus. Until recently, Atlantic chub mackerel and Indo-Pacific chub mackerel were thought to be subspecies of the same species. In 1999, Collette established, on molecular and morphological considerations, that these are separate species. Mackerel are smaller with shorter lifecycles than their close relatives, the tuna, which are also members of the same family.
Scombrini, the true mackerels | Mackerel | Wikipedia | 501 | 47332 | https://en.wikipedia.org/wiki/Mackerel | Biology and health sciences | Acanthomorpha | null |
The true mackerels belong to the tribe Scombrini. The tribe consists of seven species, each belonging to one of two genera: Scomber or Rastrelliger.
Scomberomorini, the Spanish mackerels
The Spanish mackerels belong to the tribe Scomberomorini, which is the "cousin tribe" of the true mackerels. This tribe consists of 21 species in all—18 of those are classified into the genus Scomberomorus, two into Grammatorcynus, and a single species into the monotypic genus Acanthocybium.
Other mackerel
In addition, a number of species with mackerel-like characteristics in the families Carangidae, Hexagrammidae and Gempylidae are commonly referred to as mackerel. Some confusion had occurred between the Pacific jack mackerel (Trachurus symmetricus) and the heavily harvested Chilean jack mackerel (T. murphyi). These have been thought at times to be the same species, but are now recognised as separate species.
The term "mackerel" is also used as a modifier in the common names of other fish, sometimes indicating the fish has vertical stripes similar to a scombroid mackerel:
Mackerel icefish—Champsocephalus gunnari
Mackerel pike—Cololabis saira
Mackerel scad—Decapterus macarellus
Mackerel shark—several species
Shortfin mako shark—Isurus oxyrinchus
Mackerel tuna—Euthynnus affinis
Mackerel tail goldfish—Carassius auratus
By extension, the term is applied also to other species such as the mackerel tabby cat, and to inanimate objects such as the altocumulus mackerel sky cloud formation.
Characteristics | Mackerel | Wikipedia | 382 | 47332 | https://en.wikipedia.org/wiki/Mackerel | Biology and health sciences | Acanthomorpha | null |
Most mackerel belong to the family Scombridae, which also includes tuna and bonito. Generally, mackerel are much smaller and slimmer than tuna, though in other respects, they share many common characteristics. Their scales, if present at all, are extremely small. Like tuna and bonito, mackerel are voracious feeders, and are swift and manoeuvrable swimmers, able to streamline themselves by retracting their fins into grooves on their bodies. Like other scombroids, their bodies are cylindrical with numerous finlets on the dorsal and ventral sides behind the dorsal and anal fins, but unlike the deep-bodied tuna, they are slim.
The type species for scombroid mackerels is the Atlantic mackerel, Scomber scombrus. These fish are iridescent blue-green above with a silvery underbelly and near-vertical wavy black stripes running along their upper bodies.
The prominent stripes on the back of mackerels seemingly are there to provide camouflage against broken backgrounds. That is not the case, though, because mackerel live in midwater pelagic environments which have no background. However, fish have an optokinetic reflex in their visual systems that can be sensitive to moving stripes. For fish to school efficiently, they need feedback mechanisms that help them align themselves with adjacent fish, and match their speed. The stripes on neighbouring fish provide "schooling marks", which signal changes in relative position.
A layer of thin, reflecting platelets is seen on some of the mackerel stripes. In 1998, E J Denton and D M Rowe argued that these platelets transmit additional information to other fish about how a given fish moves. As the orientation of the fish changes relative to another fish, the amount of light reflected to the second fish by this layer also changes. This sensitivity to orientation gives the mackerel "considerable advantages in being able to react quickly while schooling and feeding."
Mackerel range in size from small forage fish to larger game fish. Coastal mackerel tend to be small. The king mackerel is an example of a larger mackerel. Most fish are cold-blooded, but exceptions exist. Certain species of fish maintain elevated body temperatures. Endothermic bony fishes are all in the suborder Scombroidei and include the butterfly mackerel, a species of primitive mackerel. | Mackerel | Wikipedia | 498 | 47332 | https://en.wikipedia.org/wiki/Mackerel | Biology and health sciences | Acanthomorpha | null |
Mackerel are strong swimmers. Known in the latin family as "punctualis piscis" which translates to "punctual fish." This is due to its punctuality of migration during mating season as it moves from warm to cold waters. Atlantic mackerel can swim at a sustained speed of 0.98 m/sec with a burst speed of 5.5 m/sec, while chub mackerel can swim at a sustained speed of 0.92 m/sec with a burst speed of 2.25 m/sec.
Distribution
Most mackerel species have restricted distribution ranges.
Some mackerel species migrate vertically. Adult snake mackerel conduct a diel vertical migration, staying in deeper water during the day and rising to the surface at night to feed. The young and juveniles also migrate vertically, but in the opposite direction, staying near the surface during the day and moving deeper at night.
Lifecycle
Mackerel are prolific broadcast spawners, and must breed near the surface of the water because the eggs of the females float. Individual females lay between 300,000 and 1,500,000 eggs. Their eggs and larvae are pelagic, that is, they float free in the open sea. The larvae and juvenile mackerel feed on zooplankton. As adults, they have sharp teeth, and hunt small crustaceans such as copepods, forage fish, shrimp, and squid. In turn, they are hunted by larger pelagic animals such as tuna, billfish, sea lions, sharks, and pelicans.
Off Madagascar, spinner sharks follow migrating schools of mackerel. Bryde's whales feed on mackerel when they can find them. They use several feeding methods, including skimming the surface, lunging, and bubble nets.
Fisheries
Chub mackerel, Scomber japonicus, are the most intensively fished scombroid mackerel. They account for about half the total capture production of scombroid mackerels. As a species, they are easily confused with Atlantic mackerel. Chub mackerel migrate long distances in oceans and across the Mediterranean. They can be caught with drift nets and suitable trawls, but are most usually caught with surround nets at night by attracting them with lampara lamps. | Mackerel | Wikipedia | 480 | 47332 | https://en.wikipedia.org/wiki/Mackerel | Biology and health sciences | Acanthomorpha | null |
The remaining catch of scombroid mackerels is divided equally between the Atlantic mackerel and all other scombroid mackerels.
Just these two species (Chub mackerel and Atlantic mackerel) account for about 75% of the total catch of scombroid mackerels.
Chilean jack mackerel are the most commonly fished nonscombroid mackerel, fished as heavily as chub mackerel. The species has been overfished, and its fishery may now be in danger of collapsing.
Smaller mackerel behave like herrings, and are captured in similar ways. Fish species like these, which school near the surface, can be caught efficiently by purse seining. Huge purse-seine vessels use spotter planes to locate the schooling fish. Then they close in using sophisticated sonar to track the shape of the school, which is then encircled with fast auxiliary boats that deploy purse seines as they speed around the school.
Suitably designed trollers can also catch mackerels effectively when they swim near the surface. Trollers typically have several long booms which they lift and drop with "topping lifts". They haul their lines with electric or hydraulic reels. Fish aggregating devices are also used to target mackerel.
Management
The North Sea has been overfished to the point where the ecological balance has become disrupted and many jobs in the fishing industry have been lost.
The Southeast US region spans the Gulf of Mexico, the Caribbean Sea, and the US Southeast Atlantic. Overfishing of king and Spanish mackerel occurred in the 1980s. Regulations were introduced to restrict the size, fishing locations, and bag limits for recreational fishers and commercial fishers. Gillnets were banned in waters off Florida. By 2001, the mackerel stocks had bounced back.
As food
Mackerel is an important food fish that is consumed worldwide. As an oily fish, it is a rich source of omega-3 fatty acids. The flesh of mackerel spoils quickly, especially in the tropics, and can cause scombroid food poisoning. Accordingly, it should be eaten on the day of capture, unless properly refrigerated or cured. | Mackerel | Wikipedia | 451 | 47332 | https://en.wikipedia.org/wiki/Mackerel | Biology and health sciences | Acanthomorpha | null |
Mackerel preservation is not simple. Before the 19th-century development of canning and the widespread availability of refrigeration, salting and smoking were the principal preservation methods available. Historically in England, this fish was not preserved, but was consumed only in its fresh form. However, spoilage was common, leading the authors of The Cambridge Economic History of Europe to remark: "There are more references to stinking mackerel in English literature than to any other fish!" In France, mackerel was traditionally pickled with large amounts of salt, which allowed it to be sold widely across the country.
For many years mackerel was regarded as 'unclean' in the UK and other places due to folklore which suggested that the fish fed on the corpses of dead sailors. A 1976 survey of housewives in Britain undertaken by the White Fish Authority indicated a reluctance to departing from buying the traditional staples of cod, haddock or salmon. Less than 10% of the survey's 1,931 respondents had ever bought mackerel, and only 3% did so regularly. As a result of this trend, many UK fishmongers during the 1970s did not display or even stock mackerel. | Mackerel | Wikipedia | 245 | 47332 | https://en.wikipedia.org/wiki/Mackerel | Biology and health sciences | Acanthomorpha | null |
Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, the Mekong giant catfish from Southeast Asia, the wels catfish of Eurasia, and the piraíba of South America, to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru, Vandellia cirrhosa. Neither the armour-plated types nor the naked types have scales. Despite their name, not all catfish have prominent barbels or "whiskers". Members of the Siluriformes order are defined by features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species, particularly the genus Corydoras, are important in the aquarium hobby. Many catfish are nocturnal, but others (many Auchenipteridae) are crepuscular or diurnal (most Loricariidae or Callichthyidae, for example).
Taxonomy
Molecular evidence suggests that in spite of the great morphological diversity in the order, all catfish form a monophyletic group. Catfish belong to a superorder called the Ostariophysi, which also includes the Cypriniformes (carps and minnows), Characiformes (characins and tetras), Gonorynchiformes (milkfish and beaked salmons) and Gymnotiformes (South American knifefish), a superorder characterized by the Weberian apparatus. Some place Gymnotiformes as a sub-order of Siluriformes; however, this is not as widely accepted. Currently, the Siluriformes are said to be the sister group to the Gymnotiformes, though this has been debated due to more recent molecular evidence. there were about thirty-six extant catfish families, and about 3,093 extant species have been described. This makes the catfish order the second or third most diverse vertebrate order; in fact, one out of every twenty vertebrate species is a catfish. | Catfish | Wikipedia | 483 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Catfish are believed to have a Gondwanan origin primarily centered around South America, as the most basal living catfish groups are known from there. The earliest known definitive members lived in the Americas from the Campanian to Maastrichtian stages of the Late Cretaceous, including the Andinichthyidae, Vorhisia vulpes and possibly Arius. A potential fossil record is known from the earlier Coniacian-Santonian stages in Niger of West Africa, though this has been considered unreliable, and the putative earliest armored catfish known from the fossil record, Afrocascudo, lived during the Cenomanian age of the Late Cretaceous in Morocco of North Africa (Kem Kem Group). The describers of Afrocascudo claimed that the presence of a derived loricariid so early on would indicate the extensive diversification of catfish, or at least loricarioids, prior to the beginning of the Late Cretaceous. As extant loricariids are only known from South America, much of this diversification must have occurred on the supercontinent of West Gondwana prior to its fragmentation into South America and Africa. Britz and colleagues suggested that Afrocascudo instead represents a juvenile obaichthyid lepisosteiform, possibly a junior synonym of Obaichthys. The authors of the original study still stood by their original conclusion based on the absence of important holostean characters, and noted that it could not be a juvenile, since the bones were completely ossified. | Catfish | Wikipedia | 314 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
The taxonomy of catfish is quickly changing. In a 2007 and 2008 paper, Horabagrus, Phreatobius, and Conorhynchos were not classified under any current catfish families. There is disagreement on the family status of certain groups; for example, Nelson (2006) lists Auchenoglanididae and Heteropneustidae as separate families, while the All Catfish Species Inventory (ACSI) includes them under other families. FishBase and the Integrated Taxonomic Information System lists Parakysidae as a separate family, while this group is included under Akysidae by both Nelson (2006) and ACSI. Many sources do not list the recently revised family Anchariidae. The family Horabagridae, including Horabagrus, Pseudeutropius, and Platytropius, is not shown by some authors but presented by others as a true group. Thus, the actual number of families differs between authors. The species count is in constant flux due to taxonomic work as well as description of new species. Between 2003 and 2005, over one hundred species were named, a rate three times faster than that of the past century. In June 2005, researchers named the newest family of catfish, Lacantuniidae, only the third new family of fish distinguished in the last seventy years, the others being the coelacanth in 1938 and the megamouth shark in 1983. The new species in Lacantuniidae, Lacantunia enigmatica, was found in the Lacantun river in the Mexican state of Chiapas. | Catfish | Wikipedia | 321 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
The higher-level phylogeny of Siluriformes has gone through several recent changes, mainly due to molecular phylogenetic studies. While most studies, both morphological and molecular, agree that catfishes are arranged into three main lineages, the relationship among these lineages has been a contentious point in which these studies, performed for example by Rui Diogo, differ. The three main lineages in Siluriformes are the family Diplomystidae, the denticulate catfish suborder Loricarioidei (containing the Neotropical "suckermouth" catfishes), and the suborder Siluroidei, which contains the remaining families of the order. According to morphological data, Diplomystidae is usually considered to be the earliest branching catfish lineage and the sister group to the other two lineages, Loricarioidei and Siluroidei. Molecular evidence usually contrasts with this hypothesis, and shows the suborder Loricarioidei as the earliest branching catfish lineage, and sister to a clade that includes the Diplomystidae and Siluroidei; this phylogeny has been obtained in numerous studies based on genetic data. However, it has been suggested that these molecular results are errors as a result of long branch attraction, incorrectly placing Loricarioidei as the earliest-branching catfish lineage. When a data filtering method was used to reduce lineage rate heterogeneity (the potential source of bias) on their dataset, a final phylogeny was recovered which showed the Diplomystidae are the earliest-branching catfish, followed by Loricarioidei and Siluroidei as sister lineages, providing both morphological and molecular support for Diplomystidae being the earliest branching catfish.
Below is a list of family relationships by different authors. Lacantuniidae is included in the Sullivan scheme based on recent evidence that places it sister to Claroteidae.
Phylogeny
Phylogeny of living Siluriformes based on 2017 and extinct families based on Nelson, Grande & Wilson 2016. | Catfish | Wikipedia | 424 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Unassigned families:
Bachmanniidae†
Scoloplacidae (Loricarioidei)
Akysidae (Sisoroidea)
Amblycipitidae (Sisoroidea)
Anchariidae (Arioidea)
Ariidae (Arioidea)
Amphiliidae (Big African catfishes)
Austroglanididae (Arioidea)
Chacidae (Siluroidei)
Conorhynchos (Pimelodoidea)
Cranoglanididae (Ictaluroidea)
Heteropneustidae (Clarioidea)
Horabagridae (Sisoroidea)
Kryptoglanidae (Siluroidea)
Lacantuniidae (Big African catfishes)
Malapteruridae (Big African catfishes)
Phreatobiidae (Pimelodoidea)
Rita (Sisoroidea)
Schilbeidae (Big African catfishes)
Ecology
Distribution and habitat
Extant catfish species live inland or in coastal waters of every continent except Antarctica. Catfish have inhabited all continents at one time or another. They are most diverse in tropical South America, Asia, and Africa, with one family native to North America and one family in Europe. More than half of all catfish species live in the Americas. They are the only ostariophysans that have entered freshwater habitats in Madagascar, Australia, and New Guinea.
They are found in fresh water/brackish water environments, though most inhabit shallow, running water. Representatives of at least eight families are hypogean (live underground) with three families that are also troglobitic (inhabiting caves). One such species is Phreatobius cisternarum, known to live underground in phreatic habitats. Numerous species from the families Ariidae and Plotosidae, and a few species from among the Aspredinidae and Bagridae, are found in salt water.
In the Southern United States, catfish species may be known by a variety of slang names, such as "mud cat", "polliwogs", or "chuckleheads". These nicknames are not standardized, so one area may call a bullhead catfish by the nickname "chucklehead", while in another state or region, that nickname refers to the blue catfish.
As invasive species | Catfish | Wikipedia | 477 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Representatives of the genus Ictalurus have been introduced into European waters in the hope of obtaining a sporting and food resource, but the European stock of American catfishes has not achieved the dimensions of these fish in their native waters and have only increased the ecological pressure on native European fauna. Walking catfish have also been introduced in the freshwater areas of Florida, with the voracious catfish becoming a major alien pest there. Flathead catfish, Pylodictis olivaris, is also a North American pest on Atlantic slope drainages. Pterygoplichthys species, released by aquarium fishkeepers, have also established feral populations in many warm waters around the world.
Physical characteristics
External anatomy of catfish
Most catfish are bottom feeders. In general, they are negatively buoyant, which means that they usually sink rather than float due to a reduced gas bladder and a heavy, bony head. Catfish have a variety of body shapes, though most have a cylindrical body with a flattened ventrum to allow for benthic feeding.
A flattened head allows for digging through the substrate, as well as perhaps serving as a hydrofoil. Some have a mouth that can expand to a large size and contains no incisiform teeth; catfish generally feed through suction or gulping rather than biting and cutting prey. Some families, though, notably the Loricariidae and Astroblepidae, have a suckermouth that allows them to fasten themselves to objects in fast-moving water. Catfish also have a maxilla reduced to a support for barbels; this means that they are unable to protrude their mouths as other fish such as carp.
Catfish may have up to four pairs of barbels - nasal, maxillary (on each side of mouth), and two pairs of chin barbels, though pairs of barbels may be absent depending on the species. Catfish barbels always occur in pairs. Many larger catfish also have chemoreceptors across their entire bodies, which means they "taste" anything they touch and "smell" any chemicals in the water. "In catfish, gustation plays a primary role in the orientation and location of food". Because their barbels and chemoreception are more important in detecting food, the eyes on catfish are generally small. Like other ostariophysans, they are characterized by the presence of a Weberian apparatus. Their well-developed Weberian apparatus and reduced gas bladder allow for improved hearing and sound production. | Catfish | Wikipedia | 503 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Catfish do not have scales; their bodies are often naked. In some species, their mucus-covered skin is used in cutaneous respiration, where the fish breathes through its skin. In some catfish, the skin is covered in bony plates called scutes; some form of body armor appears in various ways within the order. In loricarioids and in the Asian genus Sisor, the armor is primarily made up of one or more rows of free dermal plates. Similar plates are found in large specimens of Lithodoras. These plates may be supported by vertebral processes, as in scoloplacids and in Sisor, but the processes never fuse to the plates or form any external armor. By contrast, in the subfamily Doumeinae (family Amphiliidae) and in hoplomyzontines (Aspredinidae), the armor is formed solely by expanded vertebral processes that form plates. Finally, the lateral armor of doradids, Sisor, and hoplomyzontines consists of hypertrophied lateral line ossicles with dorsal and ventral lamina.
All catfish other than members of the Malapteruridae (electric catfish), possess a strong, hollow, bony, leading spine-like ray on their dorsal and pectoral fins. As a defense, these spines may be locked into place so that they stick outwards, enabling them to inflict severe wounds. In numerous catfish species, these fin rays can be used to deliver a stinging protein if the fish is irritated; as many as half of all catfish species may be venomous in this fashion, making the Siluriformes overwhelmingly the vertebrate order with the largest number of venomous species. This venom is produced by glandular cells in the epidermal tissue covering the spines. In members of the family Plotosidae and of the genus Heteropneustes, this protein is so strong it may hospitalize humans who receive a sting; in Plotosus lineatus, the stings can be lethal. The dorsal- and pectoral-fin spines are two of the most conspicuous features of siluriforms, and differ from those in other fish groups. Despite the widespread use of the spines for taxonomic and phylogenetic studies the fields have struggled to effectively use the information due to a lack of consistency in the nomenclature, with a general standard for the descriptive anatomy of catfish spines proposed in 2022 to try and resolve this problem. | Catfish | Wikipedia | 509 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Juvenile catfish, like most fish, have relatively large heads, eyes, and posterior median fins in comparison to larger, more mature individuals. These juveniles can be readily placed in their families, particularly those with highly derived fin or body shapes; in some cases, identification of the genus is possible. As far as known for most catfish, features that are often characteristic of species, such as mouth and fin positions, fin shapes, and barbel lengths, show little difference between juveniles and adults. For many species, pigmentation pattern is also similar in juveniles and adults. Thus, juvenile catfish generally resemble and develop smoothly into their adult form without distinct juvenile specializations. Exceptions to this are the ariid catfish, where the young retain yolk sacs late into juvenile stages, and many pimelodids, which may have elongated barbels and fin filaments or coloration patterns.
Sexual dimorphism is reported in about half of all families of catfish. The modification of the anal fin into an intromittent organ (in internal fertilizers) as well as accessory structures of the reproductive apparatus (in both internal and external fertilizers) have been described in species belonging to 11 different families.
Size
Catfish have one of the largest ranges in size within a single order of bony fish. Many catfish have a maximum length of under . Some of the smallest species of the Aspredinidae and Trichomycteridae reach sexual maturity at only .
The wels catfish, Silurus glanis, and the much smaller related Aristotle's catfish, are the only catfish indigenous to Europe; the former ranges throughout Europe, and the latter is restricted to Greece. Mythology and literature record wels catfish of astounding proportions yet are to be proven scientifically. The typical size of the species is about , and fish more than are rare. However, they are known to exceed in length and in weight. In July 2009, a catfish weighing was caught in the River Ebro, Spain, by an 11-year-old British schoolgirl.
In North America, the largest Ictalurus furcatus (blue catfish) caught in the Missouri River on 20 July 2010, weighed . The largest flathead catfish, Pylodictis olivaris, ever caught was in Independence, Kansas, weighing . | Catfish | Wikipedia | 468 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
These records pale in comparison to a Mekong giant catfish caught in northern Thailand on 1 May 2005, and reported to the press almost 2 months later, that weighed . This is the largest giant Mekong catfish caught since Thai officials started keeping records in 1981. Also in Asia, Jeremy Wade caught a goonch following three fatal attacks on humans in the Kali River on the India-Nepal border. Wade was of the opinion that the offending fish must have been significantly larger than this to have taken an 18-year-old boy, as well as a water buffalo.
Piraíba (Brachyplatystoma filamentosum) can grow exceptionally large and are native to the Amazon Basin. They can occasionally grow to , as evidenced by numerous catches. Deaths from being swallowed by these fish have been reported in the region.
Internal anatomy
In many catfish, the "humeral process" is a bony process extending backward from the pectoral girdle immediately above the base of the pectoral fin. It lies beneath the skin, where its outline may be determined by dissecting the skin or probing with a needle.
The retinae of catfish are composed of single cones and large rods. Many catfish have a tapetum lucidum, which may help enhance photon capture and increase low-light sensitivity. Double cones, though present in most teleosts, are absent from catfish.
The anatomical organization of the testis in catfish is variable among the families of catfish, but the majority of them present fringed testis: Ictaluridae, Claridae, Auchenipteridae, Doradidae, Pimelodidae, and Pseudopimelodidae. In the testes of some species of Siluriformes, organs and structures such as a spermatogenic cranial region and a secretory caudal region are observed, in addition to the presence of seminal vesicles in the caudal region. The total number of fringes and their length are different in the caudal and cranial portions between species. Fringes of the caudal region may present tubules, in which the lumen is filled by secretion and spermatozoa. Spermatocysts are formed from cytoplasmic extensions of Sertoli cells; the release of spermatozoa is allowed by breaking of the cyst walls. | Catfish | Wikipedia | 482 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
The occurrence of seminal vesicles, in spite of their interspecific variability in size, gross morphology, and function, has not been related to the mode of fertilization. They are typically paired, multichambered, and connected with the sperm duct, and have been reported to play glandular and storage functions. Seminal vesicle secretion may include steroids and steroid glucuronides, with hormonal and pheromonal functions, but it appears to be primarily constituted of mucoproteins, acid mucopolysaccharides, and phospholipids.
Fish ovaries may be of two types - gymnovarian or cystovarian. In the first type, the oocytes are released directly into the coelomic cavity and then eliminated. In the second type, the oocytes are conveyed to the exterior through the oviduct. Many catfish are cystovarian in type, including Pseudoplatystoma corruscans, P. fasciatum, Lophiosilurus alexandri, and Loricaria lentiginosa.
Communication
Catfish can produce different types of sounds and also have well-developed auditory reception used to discriminate between sounds with different pitches and velocities. They are also able to determine the distance of the sound's origin and from what direction it originated. This is a very important fish communication mechanism, especially during agonistic and distress behaviors. Catfish are able to produce a variety of sounds for communication that can be classified into two groups: drumming sounds and stridulation sounds. The variability in catfish sound signals differs due to a few factors: the mechanism by which the sound is produced, the function of the resulting sound, and physiological differences such as size, sex, and age. To create a drumming sound, catfish use an indirect vibration mechanism using a swimbladder. In these fishes, sonic muscles insert on the ramus Mulleri, also known as the elastic spring. The sonic muscles pull the elastic spring forward and extend the swimbladder. When the muscles relax, the tension in the spring quickly returns the swimbladder to its original position, which produces the sound. | Catfish | Wikipedia | 451 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Catfish also have a sound-generating mechanism in their pectoral fins. Many species in the catfish family possess an enhanced first pectoral fin ray, called the spine, which can be moved by large abductor and adductor muscles. The base of the catfishes' spines has a sequence of ridges, and the spine normally slides within a groove on the fish's pelvic girdle during routine movement; but, pressing the ridges on the spine against the pelvic girdle groove creates a series of short pulses. The movement is analogous to a finger moving down the teeth of a comb, and consequently a series of sharp taps is produced.
Sound-generating mechanisms are often different between the sexes. In some catfish, pectoral fins are longer in males than in females of similar length, and differences in the characteristic of the sounds produced were also observed. Comparison between families of the same order of catfish demonstrated family and species-specific patterns of vocalization, according to a study by Maria Clara Amorim. During courtship behavior in three species of Corydoras catfish, all males actively produced stridulation sounds before egg fertilization, and the species' songs were different in pulse number and sound duration.
Sound production in catfish may also be correlated with fighting and alarm calls. According to a study by Kaatz, sounds for disturbance (e.g. alarm) and agonistic behavior were not significantly different, which suggests distress sounds can be used to sample variation in agonistic sound production. However, in a comparison of a few different species of tropical catfish, some fish put under distress conditions produced a higher intensity of stridulatory sounds than drumming sounds. Differences in the proportion of drumming versus stridulation sounds depend on morphological constraints, such as different sizes of drumming muscles and pectoral spines. Due to these constraints, some fish may not even be able to produce a specific sound. In several different species of catfish, aggressive sound production occurs during cover site defense or during threats from other fish. More specifically, in long-whiskered catfish, drumming sounds are used as a threatening signal and stridulations are used as a defense signal. Kaatz investigated 83 species from 14 families of catfish, and determined that catfish produce more stridulatory sounds in disturbance situations and more swimbladder sounds in intraspecific conflicts.
Economic importance
Aquaculture | Catfish | Wikipedia | 485 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Catfish are easy to farm in warm climates, leading to inexpensive and safe food at local grocers. About 60% of U.S. farm-raised catfish are grown within a 65-mile (100-km) radius of Belzoni, Mississippi. Channel catfish (Ictalurus punctatus) supports a $450 million/yr aquaculture industry. The largest producers are located in the Southern United States, including Mississippi, Alabama, and Arkansas.
Catfish raised in inland tanks or channels are usually considered safe for the environment, since their waste and disease should be contained and not spread to the wild.
In Asia, many catfish species are important as food. Several airbreathing catfish (Clariidae) and shark catfish (Pangasiidae) species are heavily cultured in Africa and Asia. Exports of one particular shark catfish species from Vietnam, Pangasius bocourti, have met with pressures from the U.S. catfish industry. In 2003, The United States Congress passed a law preventing the imported fish from being labeled as catfish. As a result, the Vietnamese exporters of this fish now label their products sold in the U.S. as "basa fish." Trader Joe's has labeled frozen fillets of Vietnamese Pangasius hypophthalmus as "striper."
There is a large and growing ornamental fish trade, with hundreds of species of catfish, such as Corydoras and armored suckermouth catfish (often called plecos), being a popular component of many aquaria. Other catfish commonly found in the aquarium trade are banjo catfish, talking catfish, and long-whiskered catfish.
Catfish as food
Catfish have widely been caught and farmed for food for thousands of years in Africa, Asia, Europe, and North America. Judgments as to the quality and flavor vary, with some food critics considering catfish excellent to eat, while others dismiss them as watery and lacking in flavor. Catfish is high in vitamin D. Farm-raised catfish contains low levels of omega-3 fatty acids and a much higher proportion of omega-6 fatty acids.
In Central Europe, catfish were often viewed as a delicacy to be enjoyed on feast days and holidays. Migrants from Europe and Africa to the United States brought along this tradition, and in the Southern United States, catfish is an extremely popular food. | Catfish | Wikipedia | 476 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
The most commonly eaten species in the United States are the channel catfish and the blue catfish, both of which are common in the wild and increasingly widely farmed. Farm-raised catfish became such a staple of the U.S. diet that President Ronald Reagan proclaimed National Catfish Day on June 25, 1987, to recognize "the value of farm-raised catfish."
Catfish is eaten in a variety of ways. In Europe, it is often cooked in similar ways to carp, but in the United States it is popularly crumbed with cornmeal and fried.
In Indonesia, catfish is usually served fried or grilled in street stalls called warung and eaten with vegetables, sambal (a spicy relish or sauce), and usually nasi uduk (traditional coconut rice). The dish is called or . is the Indonesian word for catfish. The same dish can also be called as (squashed catfish) if the fish is lightly squashed along with sambal with a stone mortar-and-pestle. The or version presents the fish in a separate plate while the mortar is solely for sambal.
In Malaysia, catfish is called ikan keli and is fried with spices or grilled and eaten with tamarind and Thai chili gravy and is also often eaten with steamed rice.
In Bangladesh and the Indian states of Odisha, West Bengal and Assam, catfish (locally known as magur) is eaten as a favored delicacy during the monsoons. In the Indian state of Kerala, the local catfish, known as thedu''' or etta in Malayalam, is also popular.
In Hungary, catfish is often cooked in paprika sauce (Harcsapaprikás) typical of Hungarian cuisine. It is traditionally served with pasta smothered with curd cheese (túrós csusza).
In Myanmar (formally Burma), catfish is usually used in mohinga, a traditional noodle fish soup cooked with lemon grass, ginger, garlic, pepper, banana stem, onions, and other local ingredients. | Catfish | Wikipedia | 416 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
Vietnamese catfish, of the genus Pangasius, cannot be legally marketed as catfish in the United States, and so is referred to as swai or basa. Only fish of the family Ictaluridae may be marketed as catfish in the United States.See Piazza's Seafood World, LLC v. Odom , 448 F. 3d 744 (5th Cir. 2006), citing Kerrilee E. Kobbeman, "Legislative Note, Hook, Line and Sinker: How Congress Swallowed the Domestic Catfish Industry's Narrow Definition of this Ubiquitous Bottomfeeder," 57 ARK. L.REV. 407, 411-18 (2004). In the UK, Vietnamese catfish is sometimes sold as "Vietnamese river cobbler", although more commonly as Basa.
In Nigeria, catfish is often cooked in a variety of stews. It is particularly cooked in a delicacy popularly known as "catfish pepper soup" which is enjoyed throughout the nation.
In Jewish dietary law, known as kashrut, fish must have fins and scales to be kosher. Since catfish lack scales, they are not kosher.
Mythology
In the mythology of the Japanese Shinto religion natural phenomenon are caused by kami. Earthquakes are caused by a giant catfish called Namazu. There are other kami associated with earthquakes. In Kyoto it's usually an eel, but after the 1855 Edo earthquake were printed giving more popularity to the catfish kami that has been known since the 16th century Otsu-e. In one catfish print the divine white horse of Amaterasu is depicted knocking down the earthquake-causing catfish.
Dangers to humans
While the vast majority of catfish are harmless to humans, a few species are known to present some risk. Many catfish species have "stings" (actually non-venomous in most cases) embedded behind their fins; thus precautions must be taken when handling them. Stings by the venomous striped eel catfish have killed people in rare cases.
Catfish fishing records
By information from International Game Fish Association IGFA the most outstanding record:
The biggest flathead catfish caught was by Ken Paulie in the Elk City Reservoir in Kansas, US on 19 May 1998 that weighed | Catfish | Wikipedia | 447 | 47335 | https://en.wikipedia.org/wiki/Catfish | Biology and health sciences | Siluriformes | null |
A fishing rod is a long, thin rod used by anglers to catch fish by manipulating a line ending in a hook (formerly known as an angle, hence the term "angling"). At its most basic form, a fishing rod is a straight rigid stick/pole with a line fastened to one end (as seen in traditional bamboo rod fishing such as Tenkara fishing); however, modern rods are usually more elastic and generally have the line stored in a reel mounted at the rod handle, which is hand-cranked and controls the line retrieval, as well as numerous line-restricting rings (also known as line guides) that distribute bending stress along the rod and help dampening down/prevent line whipping and entanglement. To better entice fish, baits or lures are dressed onto the hook attached to the line, and a bite indicator (e.g. a float) is typically used, some of which (e.g. quiver tip) might be incorporated as part of the rod itself.
Fishing rods act as an extended lever and allow the angler to amplify line movements while luring and pulling the fish. It also enhances casting distance by increasing the launch speed of the terminal tackles (the hook, bait/lure, and other accompanying attachments such as float and sinker/feeder), as a longer swing radius (compared to that of a human arm) corresponds to greater arc speed at the tip under the same angular velocity. The length of fishing rods usually vary between and depending on the style of angling, while the Guinness World Record is .
Traditional fishing rods are made from a single piece of hardwood (such as ash and hickory) or bamboo; while contemporary rods are usually made from alloys (such as aluminium) or more often high-tensile synthetic composites (such as fibreglass or carbon fiber), and may come in multi-piece (joined via ferrules) or telescoping forms that are more portable and storage-friendly. Most fishing rods are tapered towards the tip to reduce the gravitational leverage front of the handle that an angler has to overcome when lifting the rod. Many modern rods are also constructed from hollow blanks to increase the specific strength of the design and reduce the overall weight. | Fishing rod | Wikipedia | 461 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
In contrast with fishing nets and traps, which are usually used in subsistence and commercial fishing, angling with rods is a far less efficient method of catching fish, and is used more often in recreational fishing and competitive casting, which focus less on the yield and more on the experience. Fishing rods also come in many sizes, actions, hardness and configurations depending on whether they are to be used for small, medium or large fish, in fresh or saltwater situations, or the different angling styles. Various types of fishing rods are designed for specific subtypes of angling, for instance: spin fishing rods (both spinning and baitcasting rods) are optimized for frequent, repeated casting, and are usually lighter and have faster action; fly rods are designed to better sling heavy lines and ultralight artificial flies, and are usually much more flexible; surfcasting rods are designed to cast baits or lures out over far distances into the surf zone, and tends to be quite long; ice fishing rods are designed to fish through small drilled holes in ice covered lakes, and usually very short; and trolling rods are designed to drag heavy bait or lures through water while boat fishing, and usually have greater ultimate tensile strength due to the frequently large sizes of the target fish.
History
Fly fishing
The art of fly fishing took a great leap forward after the English Civil War, where a newly found interest in the activity left its mark on the many books and treatises that were written on the subject at the time. The renowned officer in the Parliamentary army, Robert Venables, published in 1662 The Experienced Angler, or Angling improved, being a general discourse of angling, imparting many of the aptest ways and choicest experiments for the taking of most sorts of fish in pond or river. Compleat Angler was written by Izaak Walton in 1653 (although Walton continued to add to it for a quarter of a century) and described the fishing in the Derbyshire Wye. It was a celebration of the art and spirit of fishing in prose and verse; six verses were quoted from John Dennys's earlier work. A second part to the book was added by Walton's friend Charles Cotton. | Fishing rod | Wikipedia | 450 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
The 18th century was mainly an era of consolidation of the techniques developed in the previous century. Running rings began to appear along the fishing rods, which gave anglers greater control over the cast line. The rods themselves were also becoming increasingly sophisticated and specialized for different roles. Jointed rods became common from the middle of the century and bamboo came to be used for the top section of the rod, giving it a much greater strength and flexibility.
The industry also became commercialized – rods and tackle were sold at the haberdashers store. After the Great Fire of London in 1666, artisans moved to Redditch which became a centre of production of fishing related products from the 1730s. Onesimus Ustonson established his trading shop in 1761, and his establishment remained as a market leader for the next century. He received a Royal Warrant from three successive monarchs starting with King George IV.
Technological improvements
The impact of the Industrial Revolution was first felt in the manufacture of fly lines. Instead of anglers twisting their own lines, a laborious and time-consuming process, the new textile spinning machines allowed for a variety of tapered lines to be easily manufactured and marketed.
The material used for the rod itself changed from the heavy woods native to England, to lighter and more elastic varieties imported from abroad, especially from South America and the West Indies. Bamboo rods became the generally favored option from the mid 19th century, and several strips of the material were cut from the cane, milled into shape, and then glued together to form light, strong, hexagonal rods with a solid core that were superior to anything that preceded them.
Other materials used, were Tonkin bamboo Calcutta reed, ash wood, hickory, ironwood, maple, lancewood, or malacca cane. These products were light, tough, and pliable. Rods were generally made in three pieces called a butt, midsection, and tip. The butts were frequently made of maple, with bored bottom; this butt outlasted several tops. Midsections were generally made from ironwood because it was a thicker, strong wood. Tips were generally made from bamboo for its elasticity which could throw the bait further and more accurately. Handles and grips were generally of cork, wood, or wrapped cane. Many different types of glue held these sections together, most commonly Irish glue and bone glue. This was until hilton glue, or cement glue, was introduced because of its waterproof qualities. Even today, Tonkin split-bamboo rods are still popular in fly fishing. | Fishing rod | Wikipedia | 507 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Until the mid 19th century, rods were generally made in England. This changed in 1846 when American Samuel Phillippe introduced an imported fishing rod the first six strips of Calcutta cane made in Bavaria where Phillippe was importing Violins that he passed off as his own hand work. Split-cane rods were later independently produced after Phillippe started to sell the imported rods to a New York retailer and then copied by Americans Charles Orvis, Hiram Leonard and Englishman William Hardy in the 1870s and mass production methods made these rods accessible to the public. Horton Manufacturing Company first introduced an all steel rod in 1913. These rods were heavy and flexible and did not satisfy many customers. The next big occurrence in fishing rods was the introduction of the fiberglass rod in the 1940s and was developed by Robert Gayle and a Mr. Mcguire.
Boron and Graphite rods came around in the 1960s and 1970s when the United States and United Kingdom invested considerable research into developing the new technologies. Hewitt and Howald were the first to come up with a way to lay the fibers into the shape of a fishing rod by wrapping them around a piece of balsa wood. However, by 1977, boron fibre technology had been muscled out by the cheaper material graphite and was no longer competitive in the market.
Rods for travelers were made with nickel-silver metal joints, or ferrules, that could be inserted into one another forming the rod. Some of them were made to be used as a walking cane until needed for sport. Since the 1980s, with the advent of flexible, yet stiff graphite ferrules, travel rod technology has greatly advanced, and multi-piece travel rods that can be transported in a suitcase or backpack constitute a large share of the market.
Modern design
In theory, an ideal rod should gradually taper from butt to tip, be tight in all its joints (if any), and have a smooth, progressive taper, without 'dead spots'. Modern design and fabrication techniques, along with advanced materials such as graphite, boron, magnesium alloy and fiberglass composites as well as stainless steel (see Emmrod) – have allowed rod makers to tailor both the shape and action of fishing rods for greater casting distance, accuracy, and fish-fighting qualities. Today, fishing rods are identified by their weight (meaning the weight of line or lure required to flex a fully loaded rod) and action (describing the speed with which the rod returns to its neutral position). | Fishing rod | Wikipedia | 496 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Generally there are three types of rods used today graphite, fiberglass, and bamboo rods. Bamboo rods are the heaviest of the three, but people still use it for its feel. Fiberglass rods are the heaviest of the new chemically-made material rods. They are mostly popular with the new and young anglers, as well as anglers who cannot afford the generally more expensive graphite rods. They are more commonly found among those anglers that fish in rugged areas such as on rocks or piers where knocking the rod on hard objects is a greater possibility. This may potentially cause breakage, making a fiberglass rod preferable for some anglers due to its higher durability and affordability compared to graphite rods. Today's most popular rod tends to be graphite for its light weight characteristics and its ability to allow for further and more accurate cast. Graphite rods tend to be more sensitive, allowing the user to feel bites from fish easier.
Modern fishing rods retain cork as a common material for grips. Cork is light, durable, and keeps warm. EVA foam and carbon fiber grips are also used. Reel seats are often of graphite-reinforced plastic, aluminium, or wood. Guides are available in steel and titanium with a wide variety of high-tech ceramic and metal alloy inserts replacing the classic agate inserts of earlier rods.
Back- or butt-rests can also be used with modern fishing rods to make it easier to fight large game fish. These are fork-like supports that help keep the rod in position, providing leverage and counteracting tensions caused by a caught fish.
Rod making bench
An old rod-making bench would generally consist of a bench, vice, a drawing knife, a jack, a fore plane, large coarse flat file, sand paper, and several strips of wood about long with different size grooves in them. Newer rod building benches are smaller versions of lathes powered by small motors that turn the rod as thread is applied to secure the guides. The motor is controlled by a foot operated rheostat, similar to that found on a sewing machine. A low rpm motor can be used to apply rod finish, typically a two-part resin, to protect the threads.
Specifications
There are several specifications manufacturers use to delineate rod uses. These include power, action, line weight, lure weight, and number of pieces. | Fishing rod | Wikipedia | 480 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Power value
Also known as "rod weight", the power value of a fishing rod implies its stiffness by vaguely describing the force needed to produce a certain degree of flexure upon the rod, and may be classified as ultra-light (UL), light (L), medium-light (ML), medium (M), medium-heavy (MH), heavy (H), extra-heavy (XH), or other similar combinations. It is often an indicator of what styles of fishing, species of target fish, or size of fish a particular rod may be best suited for. The heavier the power of a rod, the more weight it can lift up easily without snapping. However, stiffer rods are also less sensitive, as light forces (such as vibrations from fish touching the hook) do not transmit well through a stiffer rod, but the bites from larger fish to heavy lures tend not to be hard to detect. Ultra-light rods are suitable for catching baitfish and small panfish, for situations where rod responsiveness is critical, or for casting very light tackles. Heavy/extra-heavy rods are used in deep-sea fishing, surf fishing, or big-game boat fishing.
While manufacturers use various designations for a rod's power value, there is no consensus or industrial standard, hence application of a particular weight tag a manufacturer is somewhat subjective. Any fish can theoretically be caught with any rod, but catching panfish on a heavy rod offers no sport whatsoever, and successfully landing a large fish on an ultralight rod requires supreme rod handling skills but more frequently still ends in broken tackles and a lost fish. It is generally advised to "pick the right tool for the job" and choose rod weights that are best suited to the intended type of fishing. | Fishing rod | Wikipedia | 363 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Action
The action of a fishing rod refers to the speed with which it elastically returns to the neutral (straightened) position after a flexional load is removed (i.e. the "recoil" or "rebound" speed), and is generally described as being "slow", "medium", "fast", or anything in between (e.g. "medium-fast") or beyond (e.g. "extra-fast"). Contrary to how it is often colloquially described, action does not refer to the bending characteristics (shape of the "curve") of the rod — a fast-action rod can as easily have a more evenly progressive bending curve (from tip to butt) as opposed to a more tip-bending curve, although tip-bending rods do inherently tend to have faster action. The action can also be influenced by the length of a rod, the tapering profile, and the blank materials used. Typically a rod that uses a fiberglass composite blank has slower action than one that uses a carbon fiber composite blank.
Action, however, is also often a subjective description of a manufacturer. Very often action is misused to note the bending curve instead of the speed. Some manufacturers list the power value of the rod as its action. A "medium" action bamboo rod may have a faster action than a "fast" fibreglass rod. Action is also subjectively used by anglers, as an angler might compare a given rod as "faster" or "slower" than a different rod.
A rod's action and power may change when load is greater or lesser than the rod's specified casting weight. When the load used greatly exceeds a rod's specifications a rod may break during casting, if the line does not break first. When the load is significantly less than the rod's recommended range the casting distance is significantly reduced, as the rod's action cannot launch the load. It acts like a stiff pole. In fly rods, exceeding weight ratings may warp the blank or have casting difficulties when rods are improperly loaded.
Rods with a fast action combined with a full progressive bending curve allows the fisherman to make longer casts, given that the cast weight and line diameter is correct. When a cast weight exceeds the specifications lightly, a rod becomes slower, slightly reducing the distance. When a cast weight is slightly less than the specified casting weight the distance is slightly reduced as well, as the rod action is only used partially. | Fishing rod | Wikipedia | 499 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Rod sensitivity
A rods blank will determine the amount of sensitivity anglers feel. Fishing rods made of graphite are the most sensitive due to the fact they can transfer vibrations better than rods made of fiberglass. But the rod blank is not the only thing that translates into sensitivity. The rods design will impact how well an angler feels a fish's bite or the bottom of the lake, stream, reservoir, creek, or river. The more sensitivity a rod has the more likely you are to feel the bite and be able to get a good hookset to land the fish.
Bending curvature and tapering
A fishing rod's main function is to bend and deliver a certain resistance or power. While casting, the rod acts as a catapult: by moving the rod shaft forward, the inertia of the mass of the terminal tackles and the distal portion of rod itself will load (bend) the rod tip backwards, and the subsequent forward elastic rebound will sling out the lure/bait. When a hook bite is registered and the fisherman jerks the rod, the bending of the rod will realign the pull along the line and help setting the hook properly. When fighting a fish, the elasticity of the rod not only enables the fisherman to keep the line under tension, but also dampens the shock of the fish struggling and avoid line snapping, which helps to exhaust the fish and enable the fisherman to reel it in. The rod bending also lessens the torque the fisherman has to overcome when fighting the fish by shortening the practical leverage the line is pulling on the rod, as stiffer rods have more distance between the tip and the handle even when bent, which actually translates to less effective force being transmitted due to more mechanical advantage in favor of the fish. In comparison, a deeper bending rod will demand less power from the fisherman, but deliver more fighting power to the fish. In practice, this leverage effect often misleads fisherman. Often it is believed that a hard, stiff rod puts more control and power on the fish to fight, while it is actually the fish who is putting the power on the fisherman. In commercial fishing practice, large fish are often pulled in on the line itself without much effort, which is possible because the absence of the leverage effect. | Fishing rod | Wikipedia | 457 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
A rod can bend in different curves. Traditionally the bending curve is mainly determined by its tapering. In simplified terms, a fast taper will bend a lot more in the tip area and not much in the butt part, and a slow taper will tend to bend too much at the butt and delivers a weak rod. A progressive tapering which loads smooth from top to butt, adding in power the deeper the rod is bent. In practice, the tapers of quality rods often are curved or in steps to achieve the right action and bending curve for the type of fishing a rod is built. In today's practice, different fibres with different properties can be used in a single rod. In this practice, there is no straight relationship anymore between the actual tapering and the bending curve.
The bending curve is not easily described by terms. However, some rod and blank manufacturers try to simplify things towards their customers by describing the bending curve by associating them with their action. The term fast action is used for rods where only the tip is bending, and slow action for rods bending from tip to butt. In practice, this is misleading, as top-quality rods are very often fast-action rods, bending from tip to butt. While the so-called 'fast-action' rods are stiff rods (with absence of any action) which end in a soft or slow tip section. The construction of a progressive bending, fast action rod is more difficult and more expensive to achieve. Common terms to describe the bending curve or properties which influence the bending curve are: progressive taper/loading/curve/bending/..., fast taper, heavy progressive (notes a bending curve close to progressive, tending to become fast-tapered), tip action (also referred to as 'umbrella'-action), broom-action (which refers to the previously mentioned stiff 'fast action'-rods with soft tip). A parabolic action is often used to note a progressive bending curve, in fact this term comes from a series of splitcane fly rods built by Pezon & Michel in France since the late 1930s, which had a progressive bending curve. Sometimes the term parabolic is more specific used to note the specific type of progressive bending curve as was found in the Parabolic series. | Fishing rod | Wikipedia | 466 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
A common way today to describe a rod's bending properties is the Common Cents System, which is "a system of objective and relative measurement for quantifying rod power, action and even this elusive thing ... fishermen like to call feel."
The bending curve determines the way a rod builds up and releases its power. This influences not only the casting and the fish-fighting properties, but also the sensitivity to strikes when fishing lures, the ability to set a hook (which is also related to the mass of the rod), the control over the lure or bait, the way the rod should be handled and how the power is distributed over the rod. On a full progressive rod, the power is distributed most evenly over the whole rod.
Line weight
The line weight of a fishing rod describes the optimal tension along the fishing line the rod is designed to handle, usually expressed in pounds or kilograms. A fishing line's "breaking weight" describes the maximum tensile force that can be exerted before the line breaks apart, while the line weight for a rod describes as the extent of bending force that the rod can support. Fly rod weights are typically expressed as a number from 1 to 12 written as "N"wt (e.g. 6wt), and each weight represents a standard weight in grains for the first of the fly line, established by the American Fishing Tackle Manufacturing Association. For example, the first of a 6wt fly line should weigh between , with the optimal weight being . In casting and spinning rods, designations such as "8-15 lb line weight" are typical.
Lure weight
The lure weight of a fishing rod describes the optimal weight range of terminal tackle (mainly the bait and hook/lure, and any attached float, sinker, swivel and/or heavy leader), usually expressed in ounces or grams, that the rod is designed to handle in order to achieve good casting outcome. Casting lures heavier than the designated weights might result in the rod tip breaking, while lures that are too light might have trouble with casting distance and accuracy. | Fishing rod | Wikipedia | 423 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Number of sections
Rods that are one piece from butt to tip are considered to have the most natural "feel" due to the theoretically uninterrupted transfer of vibrations to the angler's hand, and are preferred by many. However, the difficulty in transporting one-piece rod safely becomes an increasing problem with increasing rod length. Two-piece rods, joined by a ferrule, are very common, and if well engineered (especially with tubular glass or carbon fibre rods), sacrifice very little in the way of natural feel. Some fishermen do feel a difference in sensitivity with two-piece rods, but most do not.
Some rods are joined through a metal "bus". These add mass to the rod which helps in setting the hook and help activating the rod from tip to butt when casting, resulting in a better casting experience. Some anglers experience this kind of fitting as superior to a one piece rod. They are found on specialized hand-built rods. Apart from adding the correct mass, depending on the kind of rod, this fitting also is the strongest known fitting, but also the most expensive one. For that reason they are almost never to be found on commercial fishing rods.
Types
Fishing rods can be constructed out of a vast number of materials. Generally they are made with either fiberglass, graphite, or a new generation composite, also known as carbon fibre. Many times carbon fibre and graphite are used together in the rod making process.
Carbon fibre rods
A carbon fibre rod is not necessarily better than a glass fibre rod; the two fibres have different properties, with their own tradeoffs. Carbon fibre is less flexible (stiffer) than glass fibre and more brittle and prone to breakage when misused, while carbon fibre allows for longer and faster rods. Carbon fibre also allows for a smaller diameter rod that is more sensitive than a glass fibre rod. A carbon fibre rod is also much lighter than a glass fibre rod allowing for longer days of fishing. Each has its purpose in the fishing industry and both improve an anglers chances of being successful when the blanks are used for the right purposes.
Fly rods | Fishing rod | Wikipedia | 431 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Fly rods, thin, flexible fishing rods designed to cast an artificial fly, usually consisting of a hook tied with fur, feathers, foam, or other lightweight material. More modern flies are also tied with synthetic materials. Originally made of yew, green heart, and later split bamboo (Tonkin cane), most modern fly rods are constructed from man-made composite materials, including fibreglass, carbon/graphite, or graphite/boron composites. Split bamboo rods are generally considered the most beautiful, the most "classic", and are also generally the most fragile of the styles, and they require a great deal of care to last well. Instead of a weighted lure, a fly rod uses the weight of the fly line for casting, and lightweight rods are capable of casting the very smallest and lightest fly. Typically, a monofilament segment called a "leader" is tied to the fly line on one end and the fly on the other.
Each rod is sized to the fish being sought, the wind and water conditions and also to a particular weight of line: larger and heavier line sizes will cast heavier, larger flies. Fly rods come in a wide variety of line sizes, from size #000 to #0 rods for the smallest freshwater trout and pan fish up to and including #16 rods for large saltwater game fish. Fly rods tend to have a single, large-diameter line guide (called a stripping guide), with a number of smaller looped guides (aka snake guides) spaced along the rod to help control the movement of the relatively thick fly line. To prevent interference with casting movements, most fly rods usually have little or no butt section (handle) extending below the fishing reel. However, the Spey rod, a fly rod with an elongated rear handle, is often used for fishing either large rivers for salmon and Steelhead or saltwater surf casting, using a two-handed casting technique. | Fishing rod | Wikipedia | 390 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
Fly rods are, in modern manufacture, almost always built out of carbon graphite. The graphite fibres are laid down in increasingly sophisticated patterns to keep the rod from flattening when stressed (usually referred to as hoop strength). The rod tapers from one end to the other and the degree of taper determines how much of the rod flexes when stressed. The larger amount of the rod that flexes the 'slower' the rod. Slower rods are easier to cast, create lighter presentations but create a wider loop on the forward cast that reduces casting distance and is subject to the effects of wind. Furthermore, the process of wrapping graphite fibre sheets to build a rod creates imperfections that result in rod twist during casting. Rod twist is minimized by orienting the rod guides along the side of the rod with the most 'give'. This is done by flexing the rod and feeling for the point of most give or by using computerized rod testing.
Custom rod building is an active hobby among fly fishermen. See Fly rod building. | Fishing rod | Wikipedia | 212 | 47337 | https://en.wikipedia.org/wiki/Fishing%20rod | Technology | Hunting and fishing | null |
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