In the electrochemistry , the diffusion layer contains the material that is analyzed. According to IUPAC , the diffusion layer is defined as the region in the vicinity of an electrode where the concentrations are different from their value in the bulk solution. The definition of the thickness of the diffusion layer is arbitrary because the concentration approaches asymptotically the value in the bulk solution . ref GoldBookRef file D01725 title diffusion layer concentration boundary layer ref The diffusion layer thus depends on the diffusion coefficient D of the analyte and on the scan rate V sec . It is usually considered to be some multiple of Dt sup 1 2 sup where 1 t scan rate . At slow scan rates, the diffusion layer is large, on the order of microns, whereas at fast scan rates the diffusion layer is nanometers in thickness. The relationship is described in part by the Cottrell equation . ref Bard, A. J. Faulkner, L. R. Electrochemical Methods. Fundamentals and Applications 2nd Ed. Wiley, New York. 2001. ISBN 0 471 04372 9 ref Relevant to cyclic voltammetry , the diffusion layer has negligible volume compared the volume of the bulk solution. For this reason, cyclic voltammetry experiments have an inexhaustible supply of fresh analyte. References references ru Category Diffusion ... more details
Orphan date September 2008 Diffusion networks are continuous time, continuous state recurrent neural network neural networks with a stochastic component. They are neural networks and stochastic diffusion processes, thus their name. Diffusion networks are related to a wide range of popular algorithms in the neural network and machine learning literature. For example Boltzmann machine Boltzmann machines are binary state versions of diffusion networks. Kalman filter Kalman filters are linear versions of diffusion networks. Diffusion networks can be trained using a variety of approaches, including minimum velocity, contrastive divergence, and standard maximum likelihood estimation ref Movellan2008 . The goal of learning in general is to learn entire probability distributions. One of the main advantages of this approach, when compared to other generative approaches, is that once a distribution has been learned, optimal inference is trivial. All it takes is to clamp the observable units and let the unobservable units settle to stochastic equilibrium. References note Movellan2008 1 Movellan J. R. Contrastive Divergence in Gaussian Diffusion Processes http mplab.ucsd.edu Neural Computation. In Press. Category Computational neuroscience ... more details
Jump diffusion is a stochastic process that involves jump discontinuity jumps and diffusion . It has important applications in condensed matter physics and in option pricing . In physics In crystals, atomic diffusion typically consists of jumps between vacant lattice sites. On time and length scales that average over many single jumps, the net motion of the jumping atoms can be described as regular diffusion . Jump diffusion can be studied on a microscopic scale by inelastic neutron scattering and by M bauer spectroscopy . Closed expressions for the autocorrelation function have been derived for several jump diffusion models Singwi, Sj lander 1960 full alternation between oscillatory motion and directed motion Chudley, Elliot 1961 ref cite journal last Chudley first C. T. coauthors R. J. Elliot title Neutron Scattering from a Liquid on a Jump Diffusion Model journal Proc. Phys. Soc. year 1961 volume 77 pages 353 doi 10.1088 0370 1328 77 2 319 ref jumps on a lattice Sears 1966, 1967 full jump diffusion of rotational degrees of freedom Hall, Ross 1981 full jump diffusion within a restricted volume Reflist In economics and finance In option pricing , a jump diffusion model is a form of mixture model , mixing a jump process and a diffusion process . Jump diffusion models have been introduced by Robert C. Merton as an extension of jump model s. Due to their computational tractability, the special case of a basic affine jump diffusion is popular for some credit risk and short rate model s. Derivatives market Volatility Category Stochastic processes Category Options economics stub physics stub ... more details
likely kerosene , combined with strong convection flows due to intense heat gives a turbulent diffusion flame. In combustion , a diffusion flame is a flame in which the oxidizer combines with the fuel by diffusion . As a result, the flame speed is limited by the rate of diffusion. cn date October 2011 Diffusion flames tend to burn slower and to produce more soot than premixed flame s because there may ... to the rule. The soot typically produced in a diffusion flame becomes incandescent from the heat of the flame and lends the flame its readily identifiable orange yellow color. Diffusion flames ... for diffusion may vary somewhat. For instance, a candle uses the heat of the flame itself to vaporize .... Diffusion flames are often studied in Counter flow burner counter flow also called opposed jet ... on their axis because of the high strain rates in the vicinity of the stagnation point. Diffusion ... front, such as in the candle seen here. This is a rare example of a diffusion flame which does not produce ... The common flame of a candle is a classic example of a diffusion flame. Its yellow color owing to the large ... Image Australia Cairns Flame.jpg A nearly turbulent diffusion flame File Fire breathing 2 Luc Viatour.jpg A turbulent diffusion flame Image Candlespace.jpg A candle in a microgravity environment. This is a rare example of a diffusion flame which does not produce much soot and does not therefore have ... process External links http microgravity.grc.nasa.gov combustion lsp lsp overview.htm Diffusion ... date October 2011 , NASA http www.andreaciani.net research.htm Diffusion and edge flames in opposed ... more details
notability Companies date March 2009 unreferenced date March 2009 infobox record label name Diffusion Records image Image Diffusion Records.jpg 220px parent founded 2001 founder Andrew Sega status Active distributor genre Electronica , electronic rock , electropop country United States US url http www.diffusionrecords.com Official website Diffusion Records is an American independent record label founded by Andrew Sega in 2001. Initially started as a label for Sega s first Alpha Conspiracy album Cipher album Cipher , Diffusion Records went on growing into a more full featured label, so far releasing albums by artists such as Iris Texas band Iris , CTRL band CTRL , Low Technicians , and Kilowatts and Vanek . Releases 2001 The Alpha Conspiracy Cipher album Cipher 2001 The Alpha Conspiracy vs Low Technicians Forward Rewinding 2002 Iris Texas band Iris Unknown 2002 Low Technicians Remembrance 2003 Iris Awakening Iris album Awakening Limited 2003 Iris Awakening 2004 The Alpha Conspiracy Aura The Alpha Conspiracy album Aura 2004 CTRL band CTRL Lose The Image 2005 Kilowatts and Vanek Rawq 2005 Iris Wrath Iris album Wrath 2006 CTRL Loaded Weapons And Darkened Days 2008 Iris Hydra 2009 CTRL Lost In Static 2009 Low Technicians Riga 2010 CTRL Lost In Static 2010 Iris Blacklight Iris album Blacklight External links http www.diffusionrecords.com Official website http www.allrecordlabels.com db 1 8301.html Diffusion Records at allrecordlabels.com http www.discogs.com label Diffusion Records Diffusion Records Discography at Discogs http www.emusic.com listen label Diffusion Records IODA MP3 Download 139350.html Diffusion Records at eMusic http www.connexionbizarre.net interviews diffusion records an interview with andrew sega Diffusion Records an interview with Andrew Sega at Connexionbizarre.net Category Record labels established in 2001 Category Electronic music record labels Category American independent record labels sq Diffusion Records ... more details
Eddy diffusion , eddy dispersion , or turbulence turbulent diffusion is any diffusion process by which substances are mixed in the atmosphere or in any fluid system due to eddy motion . ref IUPAC Compendium of Chemical Terminology 2nd Edition 1997 Gold Book http www.iupac.org goldbook E01889.pdf Link ref ref Science world, wolframe ref In another definition ref Glossary of Meteorology http amsglossary.allenpress.com glossary browse?s e&p 9 Link ref it is mixing that is caused by eddy fluid dynamics eddies that can vary in size from the small Kolmogorov microscales to subtropical gyre s. Because the microscopic processes responsible for atmospheric mixing are too complex to model in detail, atmospheric modelers generally treat atmospheric mixing as a macroscopic eddy diffusion process. In this approach, the diffusion rate at each pressure level is parameterized by a quantity known as the eddy diffusion coefficient , K ref Chamberlain and Hunten 1987, pp. 75 and 90 ref also sometimes called eddy diffusivity , with units of math m 2 s 1 math . References Reflist Category diffusion de Eddy Diffusion nl Eddy diffusie nn Eddy diffusjon pt Difus o turbulenta ... more details
Unreferenced stub auto yes date December 2009 Photon diffusion is a situation where photon s travel through a material without being absorbed, but rather undergoing repeated scattering events which change the direction of their path. The path of any given photon is then effectively a random walk . A large statistical ensemble ensemble of such photons can be said to exhibit diffusion in the material, and can be described with a diffusion equation . Astrophysics In astrophysics , photon diffusion occurs inside a stellar atmosphere . To describe this phenomenon, one should develop the transfer equation in moments and use the Eddington approximation to radiative transfer i.e. the diffusion approximation . In 3D the results are two equations for the photon energy flux math vec F frac c 12 pi sigma vec nabla U, math math vec nabla cdot vec F 0, math where math sigma math is the opacity. By substituting the first equation into the second, one obtains the diffusion equation for the photon energy density math nabla 2 U frac 1 sigma vec nabla U cdot vec nabla sigma 0. math Medical science In medicine , the diffusion of photons can be used to create images of the body mainly brain and breast and has contributed much to the advance of certain fields of research, such as neuroscience. This technique is known as diffuse optical imaging . See also Global dimming Radiative transfer equation and diffusion theory for photon transport in biological tissue Diffusion damping Diffuse reflection DEFAULTSORT Photon Diffusion Category Diffusion Category Photonics Physics stub it Diffusione fotonica ... more details
Multiple issues unreferenced November 2006 orphan November 2009 context May 2011 technical May 2011 wikify March 2012 Streamline diffusion , given an advection equation advection diffusion equation , refers to all diffusion going on along the advection direction. Explanation If we take an advection equation, for simplicity of writing we have assumed math nabla cdot bold u 0 math , and math bold u 1 math math frac partial psi partial t bold u cdot nabla psi 0. math we may add a diffusion term, again for simplicty, we assume the diffusion to be constant over the entire field. math D nabla 2 psi math , Giving us an equation of the form math frac partial psi partial t bold u cdot nabla psi D nabla 2 psi 0 math We may now rewrite the equation on the following form math frac partial psi partial t bold u cdot nabla psi bold u bold u cdot D nabla 2 psi D nabla 2 psi bold u bold u cdot D nabla 2 psi 0 math The term below is called streamline diffusion. math bold u bold u cdot D nabla 2 psi math Crosswind diffusion Any diffusion orthogonal to the streamline diffusion is called crosswind diffusion, for us this becomes the term math D nabla 2 psi bold u bold u cdot D nabla 2 psi math Category Fluid dynamics Category Diffusion Category Partial differential equations Math stub ... more details
About spontaneous dispersion of mass a more generic treatment of diffusionDiffusion File DiffusionMicroMacro.gif thumb 250px Diffusion from a microscopic and macroscopic point of view. Initially, there are solution ... to low concentration areas, following Fick s laws. Molecular diffusion , often called simply diffusion .... Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration, but it is important to note that diffusion also occurs when there is no concentration gradient. The result of diffusion is a gradual mixing of material. In a Phase matter phase with uniform temperature, absent external net forces acting on the particles, the diffusion process ... s of the Diffusion diffusing substance in the two compartments becomes equal. Consider two systems ... it would be of equal color to system B. Molecular diffusion is typically described mathematically using Fick s laws of diffusion . Applications Diffusion is of fundamental importance in many disciplines of physics, chemistry, and biology. Some example applications of diffusion Sintering to produce ... its properties Doping semiconductor Doping during production of semiconductor s. Significance File Diffusion 1 .png thumb 280px Schematic representation of mixing of two substances by diffusionDiffusion is part of the transport phenomena . Of mass transport mechanisms, molecular diffusion is known as a slower one. Biology In cell biology , diffusion is a main form of transport for necessary materials ... url doi id isbn ref Diffusion of water H sub 2 sub O through a partially permeable membrane is classified as osmosis . Metabolism and Respiration physiology respiration rely in part upon diffusion in addition ... this gas exchange process. Tracer, self and chemical diffusion File Diffusion self1.svg thumb 340px Self diffusion, exemplified with an isotopic tracer of radioactive isotope sup 22 sup Na File Diffusion4.svg thumb 340px Example of chemical classical, Fick s, or Fickian diffusion of sodium chloride ... more details
Cleanup article date March 2008 Bohm diffusion is the diffusion of Plasma physics plasma across a magnetic field . Description Bohm diffusion is charactrerized with a diffusion coefficient equal to math D Bohm frac 1 16 , frac k BT eB math , where B is the magnetic field strength, T is the temperature, and e is the elementary charge . It was first observed in 1949 by David Bohm , E. H. S. Burhop , and Harrie Massey while studying magnetic arcs for use in isotope separation . ref D. Bohm The characteristics ... there are exceptions where the diffusion rate is lower, otherwise there would be no hope of achieving ... the exact value of the diffusion coefficient is uncertain within a factor of 2 or 3. Lyman ... Diffusion across a Magnetic Field, Physics of Fluids, Vol. 3, pp. 659 660 1960 . ref Generally diffusion can be modelled as a random walk of steps of length and time . If the diffusion is collisional, then is the mean free path and is the inverse of the collision frequency. The diffusion coefficient ... with the thermal velocity v sub th sub between collisions, and the diffusion coefficient takes the form D v sub th sub . Evidently the classical collisional diffusion is maximum when the collision frequency ... of order unity, Bohm diffusion is always greater than classical diffusion. In the common low collisionality regime, classical diffusion scales with 1 B , compared with the 1 B dependence of Bohm diffusion. This distinction is often used to distinguish between the two. In light of the calculation above, it is tempting to think of Bohm diffusion as classical diffusion with an anomalous collision rate that maximizes the transport, but the physical picture is different. Anomalous diffusion is the result ... velocity equal to E B . These eddies play a similar role to the gyro orbits in classical diffusion ... T e . The turbulent diffusion constant D v is then independent of the scale length and is approximately ... Diffusion Category Plasma physics pt Difus o de Bohm ru ... more details
Unreferenced stub auto yes date December 2009 Momentum diffusion refers to the diffusion , or spread of momentum between particles atom s or molecule s of matter , usually in the liquid state. In the case of the laminar flow of a liquid past a solid surface, momentum diffuses across the boundary layer which forms at the boundary where the solid meets the liquid. The gradient in this case occurs between the liquid in contact with the surface, which does not move at all and has zero momentum see no slip condition , and the liquid far away from the wall, which has momentum proportional to the speed at which it is flowing. The rate of transport is governed by the viscosity of the fluid and the momentum gradient. DEFAULTSORT Momentum Diffusion Category Diffusion Category Fluid dynamics Fluiddynamics stub ... more details
The diffusion equation is a partial differential equation which describes density fluctuations in a material undergoing diffusion . It is also used to describe processes exhibiting diffusive like behaviour, for instance the diffusion of alleles in a population in population genetics . Statement The equation ... r and time t and D , r is the collective diffusion coefficient for density at location r and represents the vector differential operator del . If the diffusion coefficient depends on the density ... definite matrix , the equation describes Anisotropy anisotropic diffusion, which is written for three dimensional diffusion as Equation box 1 equation math frac partial phi mathbf r ,t partial t sum ... origin The Fick s law of diffusion particle diffusion equation was originally derived by Adolf Fick in 1855. ref A. Fick, Ueber Diffusion , Pogg. Ann. Phys. Chem. 170 4. Reihe 94 , 59 86 1855 . ref Derivation The diffusion equation can be derived in a straightforward way from the continuity equation .... The diffusion equation can be obtained easily from this when combined with the phenomenological .... Discretization see also Discrete Gaussian kernel The diffusion equation is continuous ... tensor diffusion equation, in standard discretization schemes. Because direct discretization of the diffusion .... The rewritten diffusion equation used in image filtering math frac partial phi mathbf r ,t partial ... diffusion algorithm can be written as an image convolution with a varying kernel stencil of size 3 3 in 2D and 3 3 3 in 3D. See also Heat equation Fick s law of diffusion Fick s law of diffusion Second law Fick s Second Law Radiative transfer equation and diffusion theory for photon transport in biological ... in Solids. Oxford Clarendon Press 3. Crank, J. 1956 . The Mathematics of Diffusion. Oxford Clarendon Press 4. Thambynayagam, R. K. M 2011 . The Diffusion Handbook Applied Solutions for Engineers McGraw Hill External links http www.ee.byu.edu cleanroom DopConCalc.phtml Diffusion Calculator for Impurities ... more details
File Diffusion welding animation.gif thumb right Animation of the Diffusion Welding process Diffusion welding DFW is a solid state welding process by which two metal s which may be dissimilar can be bonded together. Diffusion involves the migration of atom s across the joint, due to concentration gradients. The two materials are pressed together at an elevated temperature usually between 50 and 70 of the melting point . The pressure is used to relieve the void that may occur due to the different surface topographies. The method was invented by the Soviet scientist N.F. Kazakov in 1953. ref cite web url http www.msm.cam.ac.uk phase trans 2005 Amir bond.html title Diffusion Bonding of Materials last Kazakov first N.F year 1985 publisher Pergamon Press ref Specific tooling is made for each welding application to mate the welder to the workpieces. ref http www.welding advisers.com Diffusion welding.html ref Applications DFW is usually used on sheet metal structures. Typical materials that are welded include titanium , beryllium , and zirconium . It is usually used on low volume workpieces mainly for aerospace , Nuclear power nuclear , and electronics industries. In many military aircraft diffusion bonding will help to allow for the conservation of expensive strategic materials and the reduction of manufacturing costs. Some aircraft have over 100 diffusion bonded parts, including fuselage s, outboard and inboard actuator fittings, landing gear trunnions, and nacelle frames. Notes Reflist Further reading Kalpakjian, Serope, Schmid, Steven R. Manufacturing Engineering and Technology, Fifth Edition , pp. 996 998 External links http www.key to metals.com Article51.htm Cast Nonferrous Solid State Welding, at http www.keytometals.com page.aspx?ID Home&LN EN Key to Metals http www.msm.cam.ac.uk phase trans 2005 Amir bond.html An excellent discussion of diffusion bonding by Amir Shirzadi for the UK Centre for Materials Education DEFAULTSORT Diffusion Welding Category Welding ... more details
Image Surface diffusion hopping.gif thumb 288px right Figure 1. Model of a single adatom diffusing across ... diffusion is a general process involving the motion of adatom s, molecule s, and atomic clusters ... adjacent adsorption sites on a surface, as in figure 1. Just as in bulk diffusion , this motion is typically ... display diffusion behavior that deviates from the conventional model of nearest neighbor jumps. ref Antczak, Ehrlich 2007, p.39 ref Tunneling diffusion is a particularly interesting example of an unconventional ... tunneling effect. Various analytical tools may be used to wikt elucidate elucidate surface diffusion ... diffusion are limited to well below the melting point of the substrate materials science substrate .... ref Antczak, Ehrlich 2007, p. 50, 59 ref Surface diffusion rates and mechanisms are affected by a variety ..., p. 109 ref As such, the principles of surface diffusion are critical for the chemical industry chemical ... salts used in photographic film . ref name Shust109 Kinetics Image Diffusion energy landscape.png thumb 300px right Figure 2. Diagram of the energy landscape for diffusion in one dimension. x is displacement ... adsorption sites E sub diff sub is the barrier to diffusion. Surface diffusion kinetics can be thought ... , the potential energy barrier to diffusion. Equation 1 describes the relationship math Gamma nu e E ... be smaller than the energy of desorption for diffusion to occur, otherwise desorption processes .... The manner in which diffusion takes place is dependent on the relationship between E sub diff ... factor approaches unity and E sub diff sub ceases to be a meaningful barrier to diffusion. This case, known as mobile diffusion , is relatively uncommon and has only been observed in a few ... of Fick s law of diffusion Fickian diffusion it is possible to extract both the and E sub diff sub from an Arrhenius plot of the logarithm of the diffusion coefficient, D , versus 1 T . For cases where more than one diffusion mechanism is present see below , there may be more than one E ... more details
Image M6 Diffusion Pump.jpg right 250 px thumb Six inch oil diffusion pump. Diffusion pumps use a high ... Physik volume 46 pages 357 author Gaede, W. doi 10.1002 andp.19153510304 title Die Diffusion der Gase ... as diffusion than by conventional fluid dynamics . Gaede used the name diffusion pump since his design ... with it to the exhaust. ref cite journal author D. G. Avery and R. Witty title Diffusion pumps a critical ... might be more precisely described as gas jet pump , since diffusion plays a role also in other high vacuum pumps. In modern text books, the diffusion pump is categorized as a vacuum pump Momentum transfer momentum transfer pump. The diffusion pump is widely used in both industrial and research applications. Most modern diffusion pumps use silicone oil or polyphenyl ethers as the working fluid ... pages 729 doi 10.1038 122729c0 issue 3080 bibcode 1928Natur.122..729B ref Oil diffusion pumps The oil diffusion pump is operated with an oil of low vapor pressure. Its purpose is to achieve higher ... sup 9 sup mbar , diffusion pumps today can produce pressures approaching 10 sup 10 sup mbar when properly used with modern fluids and accessories. The features that make the diffusion pump attractive ... pumping speed when compared with other types of pump used in the same vacuum range. Diffusion pumps ... an outlet pressure around 0.1 mbar. Image Calutron diffusion pumps.jpg left thumb 250 px Diffusion pumps used on the Calutron mass spectrometer s during the Manhattan Project . Image Diffusion pump schematic.svg thumb right 250 px Diagram of an oil diffusion pump The high speed jet is generated by boiling ... action. The outside of the diffusion pump is cooled using either air flow or a water line. As the vapor jet impacts the outer cooled shell of the diffusion pump, the working fluid condenses and is recovered ... pressure, flowing out through the diffusion pump outlet, where they are compressed to ambient ... s, diffusion pumps have no moving parts and as a result are quite durable and reliable. They can ... more details
Noref date August 2011 Numerical diffusion is a difficulty with computer simulation s of continua such as fluid s wherein the simulated medium exhibits a higher diffusivity than the true medium. This phenomenon can be particularly egregious when the system should not be diffusive at all, for example an ideal fluid acquiring some spurious viscosity in a numerical model. Explanation In Eulerian method Eulerian simulations , time and space are divided into a discrete grid and the continuous differential equation s of motion such as the Navier Stokes equation are discretization discretized into finite difference equation s. The discrete equations are in general more diffusion diffusive than the original differential equations, so that the simulated system behaves differently than the intended physical system. The amount and character of the difference depends on the system being simulated and the type of discretization that is used. Most fluid dynamics or Magnetohydrodynamics magnetohydrodynamic simulations seek to reduce numerical diffusion to the minimum possible, to achieve high fidelity but under certain circumstances diffusion is added deliberately into the system to avoid mathematical singularity singularities . For example, shock wave s in fluids and current sheet s in plasma physics plasma s are in some approximations infinitely thin this can cause difficulty for numerical codes. A simple way to avoid the difficulty is to add diffusion that smooths out the shock or current sheet. Higher order numerical methods including spectral methods tend to have less numerical diffusion than low order methods. Example As an example of numerical diffusion, consider an Eulerian simulation using an explicit time advance of a drop of green dye diffusing through water. If the water is flowing ... due to this sideways transfer. This numerical effect takes the form of an extra high diffusion rate. When numerical diffusion applies to the components of the momentum vector, it is called numerical ... more details
context date October 2009 Spin diffusion describes a situation wherein the individual nuclear spin physics spins undergo continuous exchange of energy. ref name durham http www.dur.ac.uk a.m.kenwright kenwright spindiff.html EPS2 Spin Diffusion Bot generated title ref This permits Spin polarization polarization differences within the sample to be reduced on a timescale much shorter than relaxation time relaxation effects. ref name durham Notes references Category Quantum field theory Nuclear stub ... more details
refimprove date March 2010 Image Scheme facilitated diffusion in cell membrane en.svg thumb 300px right Facilitated diffusion in cell membrane, showing ion channel s and carrier proteins Not to be confused with diffusion . Facilitated diffusion is not a type of diffusion thermal motion but a type of transport process. Facilitated diffusion also known as facilitated transport or passive mediated transport is a process of passive transport as opposed to active transport , with this passive transport aided by integral membrane proteins. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane integral proteins. The facilitated diffusion may occur either across biological membrane s or through aqueous compartments of an organism. ref name isbn0 471 41759 9 cite book author Pratt, Charlotte Amerley Voet, Donald Voet, Judith G. title Fundamentals of biochemistry upgrade publisher Wiley location New York year 2002 pages 264 266 isbn 0 471 41759 9 oclc doi accessdate ref Polar molecules and charged ions are dissolved in water but they can not diffuse freely across the plasma membrane due to the hydrophobe hydrophobic nature of the fatty acid tails of phospholipid s that make up the lipid bilayer s. Only small nonpolar molecules, such as oxygen can diffuse easily across the membrane. All polar molecules are transported across cell membrane membranes by proteins that form transmembrane channels. These channels are gated so they can open and close, thus regulating the flow of ions or small polar molecules. Larger molecules are transported by transmembrane carrier proteins, such as permease s that change ... binding protein . The metabolites are not changed because no energy is required for facilitated diffusion ... Facilitated Diffusion Description and Animation Membrane transport Category Diffusion Category Transport proteins ca Difusi facilitada fr Diffusion facilit e nl Gefaciliteerde diffusie pl Dyfuzja ... more details
orphan date December 2011 A diffusion map is a Machine learning machine learning algorithm for dealing .... year 2006 title Diffusion maps url http www.pnas.org content 102 21 7426.long journal Applied and Computational Harmonic Analysis ref and Diffusion Maps and Geometric Harmonics . ref cite journal last Lafon first S.S. year 2004 title Diffusion Maps and Geometric Harmonics journal PhD thesis, Yale ... Principle Component Analysis PCA and Multi Dimensional Scaling MDS , diffusion mapping is a non linear ... local similarities at different scales, the diffusion map gives a global description of the data set. Compared with other methods, diffusion maps are robust to noise perturbation and are computationally inexpensive. Definition of Diffusion Map As explained in An Introduction to Diffusion ... to Diffusion Maps journal Techniques ref diffusion maps can be defined in four steps. Connectivity Diffusion maps try to find a relation between distance in the feature space and probability ... be guided by the application that one has in mind. Diffusion Process With the definition of connectivity between two points, we can define the diffusion matrix math L math which is also a version of Laplacian ... of math t math , we observe the data set at different scales. This is the diffusion process. The diffusion ... structure of the data set have high probability. Diffusion Distance The diffusion distance at time ... Diffusion Process Now, we can give the definition of diffusion map as math Psi t x lambda 1 t psi ... 2005 title Diffusion Maps, Spectral Clustering and Eigenfunctions of Fokker Planck Operators url ... Eigenvalues and eigenvectors eigenvectors and eigenvalues , we get the diffusion map from the original ... framework of a diffusion map is as Step 1. Given the similarity matrix L Step 2. Form the normalized ... Step 4. Use diffusion map to get the embedding matrix Y Application The paper Diffusion Maps, Spectral ... that reproduces the diffusion induced by a Fokker Planck equation . It is also explained that when ... more details
Diffusion maps,introduced by R.R. Coifman and S. Lafon in ref name DifussionMap ref name Diffusion ,is a machine ... MDS , diffusion maps is a non linear method and focus on discovering the underlying manifold that the data is embedded. By integrating local similarities at different scales, diffusion maps gives a global description of the data set. Compared with other methods, diffusion maps is robust to noise perturbation and is computationally inexpensive. Definition of Diffusion Maps Follow by ref name Introduction , Diffusion Maps can be defined in four steps. Connectivity Diffusion maps leverages the relationship between heat diffusion and random walk Markov Chain . The basic observation is that if we take ... choice should be guided by the application that one has in mind. Diffusion Process With the definition of connectivity between two points, we can define the diffusion matrix math L math it is also a version ... values of math t math , we observe the data set at different scales. This is the diffusion process. Diffusion process reveals the global geometric structure of a data set as paths along the true geometric structure of the data set have high probability. Diffusion Distance The diffusion distance at time ... y math here math w y math is a weighted function which can often treated as math w y 1 math Diffusion Process Now, we can give the definition of diffusion map as math Psi t x lambda 1 t psi 1 x , lambda ... get the diffusion map from the original data to a k dimension space which is embedded in the original space. Algorithm The basic algorithm framework of Diffusion Map is as Step 1. Given the similarity ... and eigenvalues of math M t math Step 4. Use Diffusion Map to get the embedding matrix Y Application ... the diffusion induced by a Fokker Planck equation.Also, they explained that when the data approximate ... and therefore provides a separation of the statistics and the geometry of the data. Since Diffusion ... points in the manifold the data is embedded. Based on diffusion map, there are many applications ... more details
Diagnostic infobox Name Diffusion MRI Image Illus dti.gif Caption DTI Color Map ICD10 ICD9 MeshID D038524 OPS301 OtherCodes Diffusion MRI or dMRI is a Magnetic Resonance Imaging MRI method which came into existence .... Breton title Imagerie de diffusion in vivo par r sonance journal C R Acad Sci Paris year 1985 volume ..., J title Self diffusion NMR imaging using stimulated echoes journal Journal of Magnetic Resonance ... last Taylor first D G coauthors Bushell, M C title The spatial mapping of translational diffusion coefficients ... issue 4 pages 345 349 doi 10.1088 0031 9155 30 4 009 pmid 4001161 ref It allows the mapping of the diffusion ... diffusion in tissues is not free, reflecting interactions of molecules with many obstacles, such as macromolecules ... diffusion MRI images of the normal and diseased brain were made public in 1985. ref cite journal last ... to diffusion and perfusion in neurologic disorders journal Annual Meeting of the RSNA, Chicago ... SMRM meeting, London year 1985 ref During the last 25 years, diffusion MRI has been extraordinarily ... matter disorders, as diffusion tensor imaging DTI can reveal abnormalities in white matter fiber structure and provide outstanding maps of brain connectivity ref Hagmann et al, Understanding Diffusion MR Imaging Techniques From Scalar Diffusion weighted Imaging to Diffusion Tensor Imaging and Beyond ... emerged, diffusion functional MRI DfMRI as it was suggested that with dMRI one could also get images ... detection of neuronal activation in the human brain with diffusion MRI journal Proceedings of the National ... ref Finally, the method of diffusion MRI has been shown to be also sensitive to perfusion, as the movement ..., Laval Jeantet, M title Separation of diffusion and perfusion in intravoxel incoherent motion MR imaging ... doi 10.1148 radiol.2493081301 ref In diffusion weighted imaging DWI , each image voxel three dimensional pixel has an image intensity that reflects a single best measurement of the rate of water diffusion ... traditional MRI measurements such as T1 or T2 relaxation rates. A variant of diffusion weighted ... more details
Knudsen diffusion is a means of diffusion that occurs in a long pore with a narrow diameter 2 50 nm because molecules frequently collide with the pore wall. ref cite web url http sinnott.mse.ufl.edu Backgrounds theo02 diff.html title Transport in Small Pores accessdate 2009 10 20 ref Consider the diffusion of gas molecules through very small capillary pores. If the Porosity pore diameter is smaller than the mean free path of the diffusing gas molecules and the density of the gas is low, the gas molecules collide with the pore walls more frequently than with each other. This process is known as Knudsen flow or Knudsen diffusion. The Knudsen number is a good measure of the relative importance of Knudsen diffusion. A Knudsen number much greater than one indicates Knudsen diffusion is important. In practice, Knudsen diffusion applies only to gases because the mean free path for molecules in the liquid state is very small, typically near the diameter of the molecule itself. The diffusivity for Knudsen diffusion is obtained from the self diffusion coefficient derived from the kinetic theory of gases. ref cite book first James R. last Welty first2 Charles E. last2 Wicks first3 Robert E. last3 Wilson first4 Gregory L. last4 Rorrer title Fundamentals of Momentum, Heat and Mass Transfer ... lambda u over 3 lambda over 3 sqrt 8 kappa NT over pi M A math For Knudsen diffusion, path length .... However there may be instances where both Knudsen diffusion and molecular diffusion math D AB ... to zero, the equation reduces to, math frac 1 D Ae frac 1 D AB frac 1 D KA math Knudsen self diffusion In the Knudsen diffusion regime, the molecules do not interact with one another, so that they move ... Diffusion in Rough Nanoporous Media url http www.uni leipzig.de diffusion pdf MalekCoppens JCP 031.pdf ref See also Knudsen Flow Knudsen number Diffusion Atomic diffusion Mass diffusivity References reflist Category Diffusion de Knudsen Diffusion fa pl Dyfuzja Knudsena pt Difus o ... more details
Merge from Barrier metal date October 2009 A diffusion barrier is a thin layer usually micrometres thick of metal usually placed between two other metals. It is done to act as a barrier to protect either one of the metals from corrupting the other. ref Citation last Cahn first Robert W. title Physical metallurgy page 1355 publisher Elsevier year 1996 volume 1 edition 4th url http books.google.com books?id IuEq0S4sO0wC&lpg PA1355 isbn 9780444898753 . ref Adhesion of a electroplating plated metal layer to its substrate requires a physical interlocking, inter diffusion of the deposit or a chemical bond ing between plate and substrate in order to work. The role of a diffusion barrier is to prevent or to retard the inter diffusion of the two superposed metals. Therefore, to be effective, a good diffusion barrier requires inertness with respect to adjacent materials. To obtain good adhesion and a diffusion barrier simultaneously, the bonding between layers needs to come from a chemical reaction of limited range at both boundaries. Materials providing good adhesion are not necessarily good diffusion barriers and vice versa. Consequently there are cases where two or more separate layers must be used to provide a proper interface between substrates. Selection While the choice of diffusion barrier depends on the final function, anticipated operating temperature and service life are critical parameters to select diffusion barrier materials. Many thin film metal combinations have been evaluated for their adhesion and diffusion barrier properties. Aluminum provides good conductivity Disambiguation needed date June 2011 thermal or electrical? , adhesion and reliability because of its oxygen reactivity and the self passivation properties of its oxide. Copper also easily reacts with oxygen but its oxides have poor adhesion properties. As for gold its virtue relies in its inertness, and ease ... used to form diffusion barriers for specific applications. Conductive ceramic s can be also used ... more details
Gnawa Diffusion is a France French and Algeria n Gnawa music band based in Paris , France . ref http www.timesonline.co.uk tol sport related reports article668436.ece Fashion Tribes , The Times . ref The group s lead singer, Amazigh literally meaning Free Man in Berber languages Tamazight , is the son of the Algeria n writer and poet Kateb Yacine . Although there is a strong Gnawa influence, the band is noted for its mix of reggae and roots music. Gnawa Diffusion is very popular in Algeria and is also well known in many other countries including Morocco and France. The band s lyrics are in Arabic language Arabic , berber languages Tamazight , French language French and English language English . Gnawa Diffusion started their career in 1993 with the release of the album L gitime diff rence . Members of the band Amazigh Kateb vocal and gimbri Mohamed Abdenour mandolin , banjo , krakebs , choir Pierre Bonnet bass guitar bass Philippe Bonnet drums Salah Meguiba Keyboard, oriental percussion , choir Pierre Feugier guitar , choir, krakebs Abdel Aziz Maysour Amar Chaoui percussionist, choir The lead singer s lyrics are often controversial. Themes range from discussions of poverty in Algeria or corruption in government to denunciations of global military actions and perceived imperialism. Nevertheless, in spite of a strong political direction, this band also has more entrancing numbers which focus on self determination and improvement. Discography 2007 Fucking Cowboys D JAMAZ Production 2003 Souk System Warner Music Group Warner 2002 DZ Live Next Musique 1999 Bab el Oued Kingston Musisoft ref http allmusic.com album bab el oued kingston r450221 review Review , Allmusic ref 1997 Algeria Melodie 1993 L gitime diff rence References reflist External links http www.gnawa diffusion.com ... gnawa diffusion 551.php French interview. Category Algerian musical groups de Gnawa Diffusion fr Gnawa Diffusion ru Gnawa Diffusion tr Gnawa Diffusion ... more details
orphan date February 2010 Diffusion curves are Vector graphics vector graphic primitives for creating smooth shaded images. Each diffusion curve partitions the 2D computer graphics 2D graphics space through which it is drawn, defining different colors on either side. When Rasterisation rendered , these colors then spread into the regions on either side of the curve in a way analogous to diffusion . The colors may also be defined to vary smoothly along the curve and the sharpness of the color transition from one side of the curve to the other may also be specified. ref name Orzan2008 cite journal title Diffusion Curves A Vector Representation for Smooth Shaded Images url http artis.imag.fr Publications 2008 OBWBTS08 diffusion curves.pdf format PDF last Orzan first Alexandrina coauthors Adrien Bousseau, Holger Winnem ller, Pascal Barla, Joë lle Thollot, David Salesin journal ACM Transactions on Graphics Proceedings of SIGGRAPH 2008 volume 27 year 2008 accessdate 2009 05 25 ref Diffusion curves have been discussed in relation to being a possible addition to the SVG specification. ref cite web url http www.svgopen.org 2008 papers 104 SVG in KDE title SVG in KDE Freedom of Beauty last Rusin first Zack publisher svgopen.org year 2008 accessdate 2009 05 25 ref Motivations In the original paper introducing the concept of diffusion curves, Orzan et al. describe two main motivations for them. ref name Orzan2008 Freehand Drawing Artists traditionally begin by sketching lines and shapes that represent the major, and some of the lesser, colour boundaries of the envisioned work. The use of diffusion curves supports this practice accurately as color would be added later, up to and between these sketched lines, so the lines color values are specified and their diffusion like behaviors produce an image in a manner similar to the way a traditional artist works with brushes or other ... detection integrate well with the construction of diffusion curves and so they can facilitate ... more details
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