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Microtechnology is technology with features near one micrometre (one millionth of a metre, or 10 metre, or 1μm). It focuses on physical and chemical processes as well as the production or manipulation of structures with one-micrometre magnitude. Around 1970, scientists learned that by arraying large numbers of microsco... | https://en.wikipedia.org/wiki?curid=156428 |
Microtechnology The term MEMS, for Micro Electro Mechanical Systems, was coined in the 1980s to describe new, sophisticated mechanical systems on a chip, such as micro electric motors, resonators, gears, and so on. Today, the term MEMS in practice is used to refer to any microscopic device with a mechanical function, w... | https://en.wikipedia.org/wiki?curid=156428 |
Microtechnology MEMS technology has generated a tremendous amount of excitement, due to the vast range of important applications where MEMS can offer previously unattainable performance and reliability standards. In an age where everything must be smaller, faster, and cheaper, MEMS offers a compelling solution. MEMS ha... | https://en.wikipedia.org/wiki?curid=156428 |
Effective mass (solid-state physics) In solid state physics, a particle's effective mass (often denoted formula_1) is the mass that it "seems" to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band ... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) At the highest energies of the valence band in many semiconductors (Ge, Si, GaAs, ...), and the lowest energies of the conduction band in some semiconductors (GaAs, ...), the band structure can be locally approximated as where is the energy of an electron at wavevector in that band,... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) In such complex materials there is no single definition of "effective mass" but instead multiple definitions, each suited to a particular purpose. The rest of the article describes these effective masses in detail. In some important semiconductors (notably, silicon) the lowest energ... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) However, the averaging method turns out to depend on the purpose: In general the dispersion relation cannot be approximated as parabolic, and in such cases the effective mass should be precisely defined if it is to be used at all. Here a commonly stated definition of effective mass ... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) Since Newton's second law uses the inertial mass (not the gravitational mass), we can identify the inverse of this mass in the equation above as the tensor This tensor expresses the change in group velocity due to a change in crystal momentum. Its inverse, , is known as the effectiv... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) By defining to be the area enclosed by this loop (this area depends on the energy , the direction of the magnetic field, and the on-axis wavevector ), then it can be shown that the cyclotron effective mass depends on the band structure via the derivative of this area in energy: Typi... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) The concept of effective mass is useful to model the temperature dependence of , thereby allowing the above relationship to be used over a range of temperatures. In an idealized three-dimensional material with a parabolic band, the concentration coefficient is given by In semiconduc... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) Traditionally effective masses were measured using cyclotron resonance, a method in which microwave absorption of a semiconductor immersed in a magnetic field goes through a sharp peak when the microwave frequency equals the cyclotron frequency formula_15. In recent years effective ... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) The optical Hall effect measures the analogue of the quasi-static electric-field-induced electrical Hall effect at optical frequencies in conductive and complex layered materials. The optical Hall effect also permits characterization of the anisotropy (tensor character) of the effec... | https://en.wikipedia.org/wiki?curid=156706 |
Effective mass (solid-state physics) Methods for assessing the electronic structures of different materials in this context have been developed. Certain group III-V compounds such as gallium arsenide (GaAs) and indium antimonide (InSb) have far smaller effective masses than tetrahedral group IV materials like silicon a... | https://en.wikipedia.org/wiki?curid=156706 |
X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystal structure, chemical composition, and physical properties of materials and thin films. These techniques are based on observing the scattered intensity of an X-ray beam hitting a sample as a functi... | https://en.wikipedia.org/wiki?curid=156962 |
X-ray scattering techniques In practice X-rays with small energy transfers are included with the diffraction spots due to elastic scattering, and X-rays with large energy transfers contribute to the background noise in the diffraction pattern. | https://en.wikipedia.org/wiki?curid=156962 |
MicroRNA A microRNA (abbreviated miRNA) is a small non-coding RNA molecule (containing about 22 nucleotides) found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression. miRNAs function via base-pairing with complementary sequences within mRNA molecu... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA However, miRNAs were not recognized as a distinct class of biological regulators until the early 2000s. miRNA research revealed different sets of miRNAs expressed in different cell types and tissues and multiple roles for miRNAs in plant and animal development and in many other biological processes. Aberrant m... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA The "let-7" RNA was found to be conserved in many species, leading to the suggestion that "let-7" RNA and additional "small temporal RNAs" might regulate the timing of development in diverse animals, including humans. A year later, the "lin-4" and "let-7" RNAs were found to be part of a large class of small RN... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA elegans" and "Drosophila," "Mir-1" in "Rattus norvegicus and MIR-25" in human. miRNAs with nearly identical sequences except for one or two nucleotides are annotated with an additional lower case letter. For example, miR-124a is closely related to miR-124b. For example: Pre-miRNAs, -miRNAs and genes that lead ... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Plant miRNAs usually have near-perfect pairing with their mRNA targets, which induces gene repression through cleavage of the target transcripts. In contrast, animal miRNAs are able to recognize their target mRNAs by using as few as 6–8 nucleotides (the seed region) at the 5' end of the miRNA, which is not eno... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA These are usually, though not exclusively, found in a sense orientation, and thus usually are regulated together with their host genes. The DNA template is not the final word on mature miRNA production: 6% of human miRNAs show RNA editing (IsomiRs), the site-specific modification of RNA sequences to yield prod... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA The double-stranded RNA (dsRNA) structure of the hairpins in a pri-miRNA is recognized by a nuclear protein known as DiGeorge Syndrome Critical Region 8 (DGCR8 or "Pasha" in invertebrates), named for its association with DiGeorge Syndrome. DGCR8 associates with the enzyme Drosha, a protein that cuts RNA, to fo... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA , by changing the seed region of miR-376 in the central nervous system). Pre-miRNA hairpins are exported from the nucleus in a process involving the nucleocytoplasmic shuttler Exportin-5. This protein, a member of the "karyopherin" family, recognizes a two-nucleotide overhang left by the RNase III enzyme Drosh... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA While the majority of miRNAs are located within the cell, some miRNAs, commonly known as circulating miRNAs or extracellular miRNAs, have also been found in extracellular environment, including various biological fluids and cell culture media. miRNA biogenesis in plants differs from animal biogenesis mainly in... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Generally, only one strand is incorporated into the miRISC, selected on the basis of its thermodynamic instability and weaker base-pairing on the 5' end relative to the other strand. The position of the stem-loop may also influence strand choice. The other strand, called the passenger strand due to its lower l... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Additional RISC components include TRBP [human immunodeficiency virus (HIV) transactivating response RNA (TAR) binding protein], PACT (protein activator of the interferon-induced protein kinase), the SMN complex, fragile X mental retardation protein (FMRP), Tudor staphylococcal nuclease-domain-containing prote... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Turnover of mature miRNA is needed for rapid changes in miRNA expression profiles. During miRNA maturation in the cytoplasm, uptake by the Argonaute protein is thought to stabilize the guide strand, while the opposite (* or "passenger") strand is preferentially destroyed. In what has been called a "Use it or l... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA An extra A added to the end of mammalian miR-122, a liver-enriched miRNA important in hepatitis C, stabilizes the molecule and plant miRNAs ending with an adenine residue have slower decay rates. The function of miRNAs appears to be in gene regulation. For that purpose, a miRNA is complementary to a part of on... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA miRNAs occasionally also cause histone modification and DNA methylation of promoter sites, which affects the expression of target genes. Nine mechanisms of miRNA action are described and assembled in a unified mathematical model: It is often impossible to discern these mechanisms using experimental data about ... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA miRNAs are well conserved in both plants and animals, and are thought to be a vital and evolutionarily ancient component of gene regulation. While core components of the microRNA pathway are conserved between plants and animals, miRNA repertoires in the two kingdoms appear to have emerged independently with di... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA nucleotide substitution) in recently originated microRNAs is comparable to that elsewhere in the non-coding DNA, implying evolution by neutral drift; however, older microRNAs have a much lower rate of change (often less than one substitution per hundred million years), suggesting that once a microRNA gains a f... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Focusing on the animals, the genome of "Mnemiopsis leidyi" appears to lack recognizable microRNAs, as well as the nuclear proteins Drosha and Pasha, which are critical to canonical microRNA biogenesis. It is the only animal thus far reported to be missing Drosha. MicroRNAs play a vital role in the regulation o... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA microRNAs can be both discovered and profiled by high-throughput sequencing methods (microRNA sequencing). The activity of an miRNA can be experimentally inhibited using a locked nucleic acid (LNA) oligo, a Morpholino oligo or a 2'-O-methyl RNA oligo. A specific miRNA can be silenced by a complementary antagom... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA A manually curated, publicly available database, miR2Disease, documents known relationships between miRNA dysregulation and human disease. A mutation in the seed region of miR-96 causes hereditary progressive hearing loss. A mutation in the seed region of miR-184 causes hereditary keratoconus with anterior pol... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA For instance, expression levels of miR-205 and miR-373 have been shown to be increased in mucinous colorectal cancers and mucin-producing Ulcerative Colitis-associated colon cancers, but not in sporadic colonic adenocarcinoma that lack mucinous components. In-vitro studies suggested that miR-205 and miR-373 ma... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA A significant number of cervical cancer samples were found to have downregulated expression of miR-506. Additionally, miR-506 works to promote apoptosis of cervical cancer cells, through its direct target hedgehog pathway transcription factor, Gli3. Cancer is caused by the accumulation of mutations from either... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA In glioblastomas without methylated MGMT promoters, the level of microRNA miR-181d is inversely correlated with protein expression of MGMT and the direct target of miR-181d is the MGMT mRNA 3'UTR (the three prime untranslated region of MGMT mRNA). Thus, in 28% of glioblastomas, increased expression of miR-181d... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA The global role of miRNA function in the heart has been addressed by conditionally inhibiting miRNA maturation in the murine heart. This revealed that miRNAs play an essential role during its development. miRNA expression profiling studies demonstrate that expression levels of specific miRNAs change in disease... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Within 24 hours, pre-existing immature miR-712 formed mature miR-712 suggesting that miR-712 is flow-sensitive. Coinciding with these results, miR-712 is also upregulated in endothelial cells exposed to naturally occurring d-flow in the greater curvature of the aortic arch. Pre-mRNA sequence of miR-712 is gene... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Activity of TNFα in turbulent flow was measured by the expression of TNFα-converting enzyme (TACE) in blood. TNFα decreased if miR-712 was inhibited or TIMP3 overexpressed, suggesting that miR-712 and TIMP3 regulate TACE activity in turbulent flow conditions. Anti-miR-712 effectively suppresses d-flow-induced ... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA p53 protein levels remained unchanged, suggesting that FoxD1 stromal miRNAs directly repress p53-effector genes. Using a lineage tracing approach followed by Fluorescent-activated cell sorting, miRNA profiling of the FoxD1-derived cells not only comprehensively defined the transcriptional landscape of miRNAs t... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA 87% of the cases are ischemic strokes, which results from blockage in the artery of the brain that carries oxygen-rich blood. The obstruction of the blood flow means the brain cannot receive necessary nutrients, such as oxygen and glucose, and remove wastes, such as carbon dioxide. miRNAs plays a role in postt... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA miRNAs can be either upregulated or downregulated in response to chronic alcohol use. miR-206 expression increased in the prefrontal cortex of alcohol-dependent rats, targeting the transcription factor brain-derived neurotrophic factor (BDNF) and ultimately reducing its expression. BDNF plays a critical role i... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Studies to determine what role pluripotent stem cells play in adipogenesis, were examined in the immortalized human bone marrow-derived stromal cell line hMSC-Tert20. Decreased expression of miR-155, miR-221, and miR-222, have been found during the adipogenic programming of both immortalized and primary hMSCs,... | https://en.wikipedia.org/wiki?curid=156964 |
MicroRNA Large scale studies of functional miRNA targeting have recently uncovered rationale therapeutic targets in the hemostatic system. When the human genome project mapped its first chromosome in 1999, it was predicted the genome would contain over 100,000 protein coding genes. However, only around 20,000 were even... | https://en.wikipedia.org/wiki?curid=156964 |
Action potential In physiology, an action potential occurs when the membrane potential of a specific cell location rapidly rises and falls: this depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, called excitable cells, which include neurons,... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential These channels are shut when the membrane potential is near the (negative) resting potential of the cell, but they rapidly begin to open if the membrane potential increases to a precisely defined threshold voltage, depolarising the transmembrane potential. When the channels open, they allow an inward f... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Sodium-based action potentials usually last for under one millisecond, but calcium-based action potentials may last for 100 milliseconds or longer. In some types of neurons, slow calcium spikes provide the driving force for a long burst of rapidly emitted sodium spikes. In cardiac muscle cells, on the ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential The electrical properties of a cell are determined by the structure of the membrane that surrounds it. A cell membrane consists of a lipid bilayer of molecules in which larger protein molecules are embedded. The lipid bilayer is highly resistant to movement of electrically charged ions, so it functions... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Recent studies have shown that the most excitable part of a neuron is the part after the axon hillock (the point where the axon leaves the cell body), which is called the initial segment, but the axon and cell body are also excitable in most cases. Each excitable patch of membrane has two important lev... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential However, some types are much quieter, and may go for minutes or longer without emitting any action potentials. Action potentials result from the presence in a cell's membrane of special types of voltage-gated ion channels. A voltage-gated ion channel is a cluster of proteins embedded in the membrane th... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Several types of channels capable of producing the positive feedback necessary to generate an action potential do exist. Voltage-gated sodium channels are responsible for the fast action potentials involved in nerve conduction. Slower action potentials in muscle cells and some types of neurons are gene... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential It tends then to stay inactivated for some time, but, if the membrane potential becomes low again, the channel will eventually transition back to the "deactivated" state. During an action potential, most channels of this type go through a cycle "deactivated"→"activated"→"inactivated"→"deactivated". Thi... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential The inward flow of sodium ions increases the concentration of positively charged cations in the cell and causes depolarization, where the potential of the cell is higher than the cell's resting potential. The sodium channels close at the peak of the action potential, while potassium continues to leave ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential This all-or-nothing property of the action potential sets it apart from graded potentials such as receptor potentials, electrotonic potentials, subthreshold membrane potential oscillations, and synaptic potentials, which scale with the magnitude of the stimulus. A variety of action potential types exis... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential In contrast to passive spread of electric potentials (electrotonic potential), action potentials are generated anew along excitable stretches of membrane and propagate without decay. Myelinated sections of axons are not excitable and do not produce action potentials and the signal is propagated passive... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential A neuron's ability to generate and propagate an action potential changes during development. How much the membrane potential of a neuron changes as the result of a current impulse is a function of the membrane input resistance. As a cell grows, more channels are added to the membrane, causing a decreas... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Second, the delayed rectifier, a potassium channel current, increases to 3.5 times its initial strength. In order for the transition from a calcium-dependent action potential to a sodium-dependent action potential to proceed new channels must be added to the membrane. If Xenopus neurons are grown in an... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Their protrusions, known as dendritic spines, are designed to capture the neurotransmitters released by the presynaptic neuron. They have a high concentration of ligand-gated ion channels. These spines have a thin neck connecting a bulbous protrusion to the dendrite. This ensures that changes occurring... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Although glial cells are not involved with the transmission of electrical signals, they communicate and provide important biochemical support to neurons. To be specific, myelin wraps multiple times around the axonal segment, forming a thick fatty layer that prevents ions from entering or escaping the a... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Action potentials are most commonly initiated by excitatory postsynaptic potentials from a presynaptic neuron. Typically, neurotransmitter molecules are released by the presynaptic neuron. These neurotransmitters then bind to receptors on the postsynaptic cell. This binding opens various types of ion c... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Due to the direct connection between excitable cells in the form of gap junctions, an action potential can be transmitted directly from one cell to the next in either direction. The free flow of ions between cells enables rapid non-chemical-mediated transmission. Rectifying channels ensure that action ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Some examples in humans include the olfactory receptor neuron and Meissner's corpuscle, which are critical for the sense of smell and touch, respectively. However, not all sensory neurons convert their external signals into action potentials; some do not even have an axon. Instead, they may convert the... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Although such pacemaker potentials have a natural rhythm, it can be adjusted by external stimuli; for instance, heart rate can be altered by pharmaceuticals as well as signals from the sympathetic and parasympathetic nerves. The external stimuli do not cause the cell's repetitive firing, but merely alt... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential This changes the membrane's permeability to those ions. Second, according to the Goldman equation, this change in permeability changes the equilibrium potential "E", and, thus, the membrane voltage "V". Thus, the membrane potential affects the permeability, which then further affects the membrane poten... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential This depolarization is often caused by the injection of extra sodium cations into the cell; these cations can come from a wide variety of sources, such as chemical synapses, sensory neurons or pacemaker potentials. For a neuron at rest, there is a high concentration of sodium and chloride ions in the e... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential If the depolarization is small (say, increasing "V" from −70 mV to −60 mV), the outward potassium current overwhelms the inward sodium current and the membrane repolarizes back to its normal resting potential around −70 mV. However, if the depolarization is large enough, the inward sodium current incre... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential At longer times, after some but not all of the ion channels have recovered, the axon can be stimulated to produce another action potential, but with a higher threshold, requiring a much stronger depolarization, e.g., to −30 mV. The period during which action potentials are unusually difficult to evoke ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential In addition, further potassium channels open in response to the influx of calcium ions during the action potential. The intracellular concentration of potassium ions is transiently unusually low, making the membrane voltage "V" even closer to the potassium equilibrium voltage "E". The membrane potentia... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Because the density and subtypes of potassium channels may differ greatly between different types of neurons, the duration of the relative refractory period is highly variable. The absolute refractory period is largely responsible for the unidirectional propagation of action potentials along axons. At ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential , to return to their closed state. There are many types of voltage-activated potassium channels in neurons. Some of them inactivate fast (A-type currents) and some of them inactivate slowly or not inactivate at all; this variability guarantees that there will be always an available source of current fo... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential , unfired; then two action potentials will be generated, one traveling towards the axon hillock and the other traveling towards the synaptic knobs. In order to enable fast and efficient transduction of electrical signals in the nervous system, certain neuronal axons are covered with myelin sheaths. Mye... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Action potentials cannot propagate through the membrane in myelinated segments of the axon. However, the current is carried by the cytoplasm, which is sufficient to depolarize the first or second subsequent node of Ranvier. Instead, the ionic current from an action potential at one node of Ranvier prov... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Also, since the ionic currents are confined to the nodes of Ranvier, far fewer ions "leak" across the membrane, saving metabolic energy. This saving is a significant selective advantage, since the human nervous system uses approximately 20% of the body's metabolic energy. The length of axons' myelinate... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Cable theory was developed in 1855 by Lord Kelvin to model the transatlantic telegraph cable and was shown to be relevant to neurons by Hodgkin and Rushton in 1946. In simple cable theory, the neuron is treated as an electrically passive, perfectly cylindrical transmission cable, which can be described... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential If the transmembrane resistance "r" is increased, that lowers the average "leakage" current across the membrane, likewise causing "λ" to become longer, increasing the conduction velocity. In general, action potentials that reach the synaptic knobs cause a neurotransmitter to be released into the synapt... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Hence, electrical synapses are used whenever fast response and coordination of timing are crucial, as in escape reflexes, the retina of vertebrates, and the heart. A special case of a chemical synapse is the neuromuscular junction, in which the axon of a motor neuron terminates on a muscle fiber. In su... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential The cardiac cells of the sinoatrial node provide the pacemaker potential that synchronizes the heart. The action potentials of those cells propagate to and through the atrioventricular node (AV node), which is normally the only conduction pathway between the atria and the ventricles. Action potentials ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Muscle action potentials are provoked by the arrival of a pre-synaptic neuronal action potential at the neuromuscular junction, which is a common target for neurotoxins. Plant and fungal cells are also electrically excitable. The fundamental difference from animal action potentials is that the depolari... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential The interaction of electrical and osmotic relations in plant cells appears to have arisen from an osmotic function of electrical excitability in the common, unicellular ancestors of plants and animals under changing salinity conditions, whereas the present function of rapid signal transmission is seen ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Part of this function is the tight coordination of mechanical events, such as the contraction of the heart. A second function is the computation associated with its generation. Being an all-or-none signal that does not decay with transmission distance, the action potential has similar advantages to dig... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential It focused on three goals: isolating signals from single neurons or axons, developing fast, sensitive electronics, and shrinking electrodes enough that the voltage inside a single cell could be recorded. The first problem was solved by studying the giant axons found in the neurons of the squid ("Loligo... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential The third problem, that of obtaining electrodes small enough to record voltages within a single axon without perturbing it, was solved in 1949 with the invention of the glass micropipette electrode, which was quickly adopted by other researchers. Refinements of this method are able to produce electrode... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential Tetrodotoxin from the pufferfish and saxitoxin from the "Gonyaulax" (the dinoflagellate genus responsible for "red tides") block action potentials by inhibiting the voltage-sensitive sodium channel; similarly, dendrotoxin from the black mamba snake inhibits the voltage-sensitive potassium channel. Such... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential , bundles of neurons) and demonstrated that nervous tissue was made up of cells, instead of an interconnected network of tubes (a "reticulum"). Carlo Matteucci followed up Galvani's studies and demonstrated that cell membranes had a voltage across them and could produce direct current. Matteucci's work... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential In 1907, Louis Lapicque suggested that the action potential was generated as a threshold was crossed, what would be later shown as a product of the dynamical systems of ionic conductances. In 1949, Alan Hodgkin and Bernard Katz refined Bernstein's hypothesis by considering that the axonal membrane migh... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential In the 21st century, researchers are beginning to understand the structural basis for these conductance states and for the selectivity of channels for their species of ion, through the atomic-resolution crystal structures, fluorescence distance measurements and cryo-electron microscopy studies. Julius ... | https://en.wikipedia.org/wiki?curid=156998 |
Action potential The properties of the Hodgkin–Huxley and FitzHugh–Nagumo models and their relatives, such as the Bonhoeffer–van der Pol model, have been well-studied within mathematics, computation and electronics. However the simple models of generator potential and action potential fail to accurately reproduce the n... | https://en.wikipedia.org/wiki?curid=156998 |
William Hyde Wollaston (; 6 August 1766 – 22 December 1828) was an English chemist and physicist who is famous for discovering the chemical elements palladium and rhodium. He also developed a way to process platinum ore into malleable ingots. He was born in East Dereham in Norfolk, the son of the Francis Wollaston (173... | https://en.wikipedia.org/wiki?curid=157164 |
William Hyde Wollaston He died in London in 1828 and was buried with his father in St Nicholas's Churchyard in Chislehurst, England. After having established a partnership with Smithson Tennant in 1800 in order to produce and sell chemical products, Wollaston became wealthy by developing the first physico-chemical meth... | https://en.wikipedia.org/wiki?curid=157164 |
William Hyde Wollaston During the last years of his life he performed electrical experiments, which resulted in his accidental discovery of electromagnetic induction 10 years prior to Michael Faraday, preceding the eventual design of the electric motor: Faraday constructed the first working electric motor and published... | https://en.wikipedia.org/wiki?curid=157164 |
William Hyde Wollaston Wollaston also devised a cryophorus, "a glass container containing liquid water and water vapor. It is used in physics courses to demonstrate rapid freezing by evaporation." He used his Bakerian lecture in 1805, "On the Force of Percussion", to defend Gottfried Leibniz's principle of "vis viva", ... | https://en.wikipedia.org/wiki?curid=157164 |
William Hyde Wollaston Jacobus Henricus van 't Hoff's "La Chimie dans l'Espace" was the first practical realisation of this prophecy. Wollaston was part of a royal commission that recommended adoption of the imperial gallon in 1814. He served on the government's Board of Longitude between 1818 and 1828 and was part of ... | https://en.wikipedia.org/wiki?curid=157164 |
Pepper spray (also known as capsaicin spray or capsicum spray) is a lachrymatory agent (a chemical compound that irritates the eyes to cause a burning sensation, pain, and temporary blindness) used in policing, riot control, crowd control, and self-defense, including defense against dogs and bears. Its inflammatory eff... | https://en.wikipedia.org/wiki?curid=157302 |
Pepper spray The solvent is then evaporated, and the remaining waxlike resin is the oleoresin capsaicin. An emulsifier such as propylene glycol is used to suspend OC in water, and the suspension is then pressurized to make an aerosol pepper spray. Determining the strength of pepper sprays made by different manufacturer... | https://en.wikipedia.org/wiki?curid=157302 |
Pepper spray Some manufacturers may show a very high percentage of OC and, although OC is the active ingredient within the formulation, it does not indicate pepper spray strength. High OC percentage also indicates that a spray has more oil content; which, can possibly use lower grade pepper oils (but, more of it), or l... | https://en.wikipedia.org/wiki?curid=157302 |
Pepper spray The "Journal of Investigative Ophthalmology and Visual Science" published a study that concluded that single exposure of the eye to OC is harmless, but repeated exposure can result in long-lasting changes in corneal sensitivity. They found no lasting decrease in visual acuity. The European Parliament Scien... | https://en.wikipedia.org/wiki?curid=157302 |
Pepper spray The US Army concluded, in a 1993 Aberdeen Proving Ground study, that pepper spray could cause "[m]utagenic effects, carcinogenic effects, sensitization, cardiovascular and pulmonary toxicity, neurotoxicity, as well as possible human fatalities. There is a risk in using this product on a large and varied po... | https://en.wikipedia.org/wiki?curid=157302 |
Pepper spray Some studies have found no harmful effects beyond the effects described above. Direct close-range spray can cause more serious eye irritation by attacking the cornea with a concentrated stream of liquid (the so-called "hydraulic needle" effect). Some brands have addressed this problem by means of an ellipt... | https://en.wikipedia.org/wiki?curid=157302 |
Pepper spray A study of five often-recommended treatments for skin pain (Maalox, 2% lidocaine gel, baby shampoo, milk, or water) concluded that: ...there was no significant difference in pain relief provided by five different treatment regimens. Time after exposure appeared to be the best predictor for decrease in pain... | https://en.wikipedia.org/wiki?curid=157302 |
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