Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical potential. It is possible to diffuse "uphill" from a region of lower concentration to a region of higher concentration, as in spinodal decomposition. Diffusion is a stochastic process due to the inherent randomness of the diffusing entity and can be used to model many real-life stochastic scenarios. Therefore, diffusion and the corresponding mathematical models are used in several fields beyond physics, such as statistics, probability theory, information theory, neural networks, finance, and marketing.

The concept of diffusion is widely used in many fields, including physics (particle diffusion), chemistry, biology, sociology, economics, statistics, data science, and finance (diffusion of people, ideas, data and price values). The central idea of diffusion, however, is common to all of these: a substance or collection undergoing diffusion spreads out from a point or location at which there is a higher concentration of that substance or collection.

A gradient is the change in the value of a quantity; for example, concentration, pressure, or temperature with the change in another variable, usually distance. A change in concentration over a distance is called a concentration gradient, a change in pressure over a distance is called a pressure gradient, and a change in temperature over a distance is called a temperature gradient.

The word diffusion derives from the Latin word, diffundere, which means "to spread out".

A distinguishing feature of diffusion is that it depends on particle random walk, and results in mixing or mass transport without requiring directed bulk motion. Bulk motion, or bulk flow, is the characteristic of advection. The term convection is used to describe the combination of both transport phenomena.

If a diffusion process can be described by Fick's laws, it is called a normal diffusion (or Fickian diffusion); Otherwise, it is called an anomalous diffusion (or non-Fickian diffusion).

When talking about the extent of diffusion, two length scales are used in two different scenarios:

 Brownian motion of an impulsive point source (for example, one single spray of perfume)—the square root of the mean squared displacement from this point. In Fickian diffusion, this is , where  is the dimension of this Brownian motion;
 Constant concentration source in one dimension—the diffusion length. In Fickian diffusion, this is .

Diffusion vs. bulk flow
"Bulk flow" is the movement/flow of an entire body due to a pressure gradient (for example, water coming out of a tap). "Diffusion" is the gradual movement/dispersion of concentration within a body, due to a concentration gradient, with no net movement of matter. An example of a process where both bulk motion and diffusion occur is human breathing.

First, there is a "bulk flow" process. The lungs are located in the thoracic cavity, which expands as the first step in external respiration. This expansion leads to an increase in volume of the alveoli in the lungs, which causes a decrease in pressure in the alveoli. This creates a pressure gradient between the air outside the body at relatively high pressure and the alveoli at relatively low pressure. The air moves down the pressure gradient through the airways of the lungs and into the alveoli until the pressure of the air and that in the alveoli are equal, that is, the movement of air by bulk flow stops once there is no longer a pressure gradient.

Second, there is a "diffusion" process. The air arriving in the alveoli has a higher concentration of oxygen than the "stale" air in the alveoli. The increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli. Oxygen then moves by diffusion, down the concentration gradient, into the blood. The other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases. This creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli, as fresh air has a very low concentration of carbon dioxide compared to the blood in the body.

Third, there is another "bulk flow" process. The pumping action of the heart then transports the blood around the body. As the left ventricle of the heart contracts, the volume decreases, which increases the pressure in the ventricle. This creates a pressure gradient between the heart and the capillaries, and blood moves through blood vessels by bulk flow down the pressure gradient.

Diffusion in the context of different disciplines

There are two ways to introduce the notion of diffusion: either a phenomenological approach starting with Fick's laws of diffusion and their mathematical consequences, or a physical and atomistic one, by considering the random walk of the diffusing particles.

In the phenomenological approach, diffusion is the movement of a substance from a region of high concentration to a region of low concentration without bulk motion. According to Fick's laws, the diffusion flux is proportional to the negative gradient of concentrations. It goes from regions of higher concentration to regions of lower concentration. Sometime later, various generalizations of Fick's laws were developed in the frame of thermodynamics and non-equilibrium thermodynamics.

From the atomistic point of view, diffusion is considered as a result of the random walk of the diffusing particles. In molecular diffusion, the moving molecules in a gas, liquid, or solid are self-propelled by kinetic energy. Random walk of small particles in suspension in a fluid was discovered in 1827 by Robert Brown, who found that minute particle suspended in a liquid medium and just large enough to be visible under an optical microscope exhibit a rapid and continually irregular motion of particles known as Brownian movement. The theory of the Brownian motion and the atomistic backgrounds of diffusion were developed by Albert Einstein.
The concept of diffusion is typically applied to any subject matter involving random walks in ensembles of individuals.

In chemistry and materials science, diffusion refers to the movement of fluid molecules in porous solids. Molecular diffusion occurs when the collision with another molecule is more likely than the collision with the pore walls. Under such conditions, the diffusivity is similar to that in a non-confined space and is proportional to the mean free path. Knudsen diffusion occurs when the pore diameter is comparable to or smaller than the mean free path of the molecule diffusing through the pore. Under this condition, the collision with the pore walls becomes gradually more likely and the diffusivity is lower. Finally there is configurational diffusion, which happens if the molecules have comparable size to that of the pore. Under this condition, the diffusivity is much lower compared to molecular diffusion and small differences in the kinetic diameter of the molecule cause large differences in diffusivity.

Biologists often use the terms "net movement"  or "net diffusion" to describe the movement of ions or molecules by diffusion. For example, oxygen can diffuse through cell membranes so long as there is a higher concentration of oxygen outside the cell. However, because the movement of molecules is random, occasionally oxygen molecules move out of the cell (against the concentration gradient). Because there are more oxygen molecules outside the cell, the probability that oxygen molecules will enter the cell is higher than the probability that oxygen molecules will leave the cell. Therefore, the "net" movement of oxygen molecules (the difference between the number of molecules either entering or leaving the cell) is into the cell. In other words, there is a net movement of oxygen molecules down the concentration gradient.

History of diffusion in physics
In the scope of time, diffusion in solids was used long before the theory of diffusion was created. For example, Pliny the Elder had previously described the cementation process, which produces steel from the element iron (Fe) through carbon diffusion. Another example is well known for many centuries, the diffusion of colors of stained glass or earthenware and Chinese ceramics.

In modern science, the first systematic experimental study of diffusion was performed by Thomas Graham. He studied diffusion in gases, and the main phenomenon was described by him in 1831–1833:

"...gases of different nature, when brought into contact, do not arrange themselves according to their density, the heaviest undermost, and the lighter uppermost, but they spontaneously diffuse, mutually and equally, through each other, and so remain in the intimate state of mixture for any length of time."

The measurements of Graham contributed to James Clerk Maxwell deriving, in 1867, the coefficient of diffusion for CO2 in the air. The error rate is less than 5%.

In 1855, Adolf Fick, the 26-year-old anatomy demonstrator from Zürich, proposed his law of diffusion. He used Graham's research, stating his goal as "the development of a fundamental law, for the operation of diffusion in a single element of space". He asserted a deep analogy between diffusion and conduction of heat or electricity, creating a formalism similar to Fourier's law for heat conduction (1822) and Ohm's law for electric current (1827).

Robert Boyle demonstrated diffusion in solids in the 17th century by penetration of zinc into a copper coin. Nevertheless, diffusion in solids was not systematically studied until the second part of the 19th century. William Chandler Roberts-Austen, the well-known British metallurgist and former assistant of Thomas Graham studied systematically solid state diffusion on the example of gold in lead in 1896. :
"... My long connection with Graham's researches made it almost a duty to attempt to extend his work on liquid diffusion to metals."

In 1858, Rudolf Clausius introduced the concept of the mean free path. In the same year, James Clerk Maxwell developed the first atomistic theory of transport processes in gases. The modern atomistic theory of diffusion and Brownian motion was developed by Albert Einstein, Marian Smoluchowski and Jean-Baptiste Perrin. Ludwig Boltzmann, in the development of the atomistic backgrounds of the macroscopic transport processes, introduced the Boltzmann equation, which has served mathematics and physics with a source of transport process ideas and concerns for more than 140 years.

In 1920–1921, George de Hevesy measured self-diffusion using radioisotopes. He studied self-diffusion of radioactive isotopes of lead in the liquid and solid lead.

Yakov Frenkel (sometimes, Jakov/Jacob Frenkel) proposed, and elaborated in 1926, the idea of diffusion in crystals through local defects (vacancies and interstitial atoms). He concluded, the diffusion process in condensed matter is an ensemble of elementary jumps and quasichemical interactions of particles and defects. He introduced several mechanisms of diffusion and found rate constants from experimental data.

Sometime later, Carl Wagner and Walter H. Schottky developed Frenkel's ideas about mechanisms of diffusion further. Presently, it is universally recognized that atomic defects are necessary to mediate diffusion in crystals.

Henry Eyring, with co-authors, applied his theory of absolute reaction rates to Frenkel's quasichemical model of diffusion. The analogy between reaction kinetics and diffusion leads to various nonlinear versions of Fick's law.

Basic models of diffusion

Diffusion flux
Each model of diffusion expresses the diffusion flux with the use of concentrations, densities and their derivatives. Flux is a vector  representing the quantity and direction of transfer. Given a small area  with normal , the transfer of a physical quantity  through the area  per time  is

where  is the inner product and  is the little-o notation. If we use the notation of vector area  then

The dimension of the diffusion flux is [flux] = [quantity]/([time]·[area]). The diffusing physical quantity  may be the number of particles, mass, energy, electric charge, or any other scalar extensive quantity. For its density, , the diffusion equation has the form

where  is intensity of any local source of this quantity (for example, the rate of a chemical reaction).
For the diffusion equation, the no-flux boundary conditions can be formulated as  on the boundary, where  is the normal to the boundary at point .

Fick's law and equations

Fick's first law: the diffusion flux is proportional to the negative of the concentration gradient:

The corresponding diffusion equation (Fick's second law) is

where  is the Laplace operator,

Onsager's equations for multicomponent diffusion and thermodiffusion
Fick's law describes diffusion of an admixture in a medium. The concentration of this admixture should be small and the gradient of this concentration should be also small. The driving force of diffusion in Fick's law is the antigradient of concentration, .

In 1931, Lars Onsager included the multicomponent transport processes in the general context of linear non-equilibrium thermodynamics. For
multi-component transport,

where  is the flux of the ith physical quantity (component) and  is the jth thermodynamic force.

The thermodynamic forces for the transport processes were introduced by Onsager as the space gradients of the derivatives of the entropy density  (he used the term "force" in quotation marks or "driving force"):

where  are the "thermodynamic coordinates".
For the heat and mass transfer one can take  (the density of internal energy) and  is the concentration of the th component. The corresponding driving forces are the space vectors
  because
where T is the absolute temperature and  is the chemical potential of the th component. It should be stressed that the separate diffusion equations describe the mixing or mass transport without bulk motion. Therefore, the terms with variation of the total pressure are neglected. It is possible for diffusion of small admixtures and for small gradients.

For the linear Onsager equations, we must take the thermodynamic forces in the linear approximation near equilibrium:

where the derivatives of  are calculated at equilibrium .
The matrix of the kinetic coefficients  should be symmetric (Onsager reciprocal relations) and positive definite (for the entropy growth).

The transport equations are

Here, all the indexes  are related to the internal energy (0) and various components. The expression in the square brackets is the matrix  of the diffusion (i,k > 0), thermodiffusion (i > 0, k = 0 or k > 0, i = 0) and thermal conductivity () coefficients.

Under isothermal conditions T = constant. The relevant thermodynamic potential is the free energy (or the free entropy). The thermodynamic driving forces for the isothermal diffusion are antigradients of chemical potentials, , and the matrix of diffusion coefficients is

(i,k > 0).

There is intrinsic arbitrariness in the definition of the thermodynamic forces and kinetic coefficients because they are not measurable separately and only their combinations  can be measured. For example, in the original work of Onsager the thermodynamic forces include additional multiplier T, whereas in the Course of Theoretical Physics this multiplier is omitted but the sign of the thermodynamic forces is opposite. All these changes are supplemented by the corresponding changes in the coefficients and do not affect the measurable quantities.

Nondiagonal diffusion must be nonlinear
The formalism of linear irreversible thermodynamics (Onsager) generates the systems of linear diffusion equations in the form

If the matrix of diffusion coefficients is diagonal, then this system of equations is just a collection of decoupled Fick's equations for various components. Assume that diffusion is non-diagonal, for example, , and consider the state with . At this state, . If  at some points, then  becomes negative at these points in a short time. Therefore, linear non-diagonal diffusion does not preserve positivity of concentrations. Non-diagonal equations of multicomponent diffusion must be non-linear.

Einstein's mobility and Teorell formula
The Einstein relation (kinetic theory) connects the diffusion coefficient and the mobility (the ratio of the particle's terminal drift velocity to an applied force). For charged particles:

where D is the diffusion constant, μ is the "mobility", kB is the Boltzmann constant, T is the absolute temperature, and q is the elementary charge, that is, the charge of one electron.

Below, to combine in the same formula the chemical potential μ and the mobility, we use for mobility the notation .

The mobility-based approach was further applied by T. Teorell. In 1935, he studied the diffusion of ions through a membrane. He formulated the essence of his approach in the formula:
the flux is equal to mobility × concentration × force per gram-ion.
This is the so-called Teorell formula. The term "gram-ion" ("gram-particle")  is used for a quantity of a substance that contains the Avogadro number of ions (particles). The common modern term is mole.

The force under isothermal conditions consists of two parts:
 Diffusion force caused by concentration gradient: .
 Electrostatic force caused by electric potential gradient: .
Here R is the gas constant, T is the absolute temperature, n is the concentration, the equilibrium concentration is marked by a superscript "eq", q is the charge and φ is the electric potential.

The simple but crucial difference between the Teorell formula and the Onsager laws is the concentration factor in the Teorell expression for the flux. In the Einstein–Teorell approach, if for the finite force the concentration tends to zero then the flux also tends to zero, whereas the Onsager equations violate this simple and physically obvious rule.

The general formulation of the Teorell formula for non-perfect systems under isothermal conditions is

where μ is the chemical potential, μ0 is the standard value of the chemical potential.
The expression  is the so-called activity. It measures the "effective concentration" of a species in a non-ideal mixture. In this notation, the Teorell formula for the flux has a very simple form

The standard derivation of the activity includes a normalization factor and for small concentrations , where  is the standard concentration. Therefore, this formula for the flux describes the flux of the normalized dimensionless quantity :

Fluctuation-dissipation theorem
Fluctuation-dissipation theorem based on the Langevin equation is developed to extend the Einstein model to the ballistic time scale. According to Langevin, the equation is based on Newton's second law of motion as

where
 x is the position.
 μ is the mobility of the particle in the fluid or gas, which can be calculated using the Einstein relation (kinetic theory).
 m is the mass of the particle.
 F is the random force applied to the particle.
 t is time.

Solving this equation, one obtained the time-dependent diffusion constant in the long-time limit and when the particle is significantly denser than the surrounding fluid,

where
 kB is the Boltzmann constant;
 T is the absolute temperature.
 μ is the mobility of the particle in the fluid or gas, which can be calculated using the Einstein relation (kinetic theory).
 m is the mass of the particle.
 t is time.

Teorell formula for multicomponent diffusion
The Teorell formula with combination of Onsager's definition of the diffusion force gives

where  is the mobility of the ith component,  is its activity,  is the matrix of the coefficients,  is the thermodynamic diffusion force, . For the isothermal perfect systems, . Therefore, the Einstein–Teorell approach gives the following multicomponent generalization of the Fick's law for multicomponent diffusion:

where  is the matrix of coefficients. The Chapman–Enskog formulas for diffusion in gases include exactly the same terms. Earlier, such terms were introduced in the Maxwell–Stefan diffusion equation.

Jumps on the surface and in solids

Diffusion of reagents on the surface of a catalyst may play an important role in heterogeneous catalysis. The model of diffusion in the ideal monolayer is based on the jumps of the reagents on the nearest free places. This model was used for CO on Pt oxidation under low gas pressure.

The system includes several reagents  on the surface. Their surface concentrations are  The surface is a lattice of the adsorption places. Each
reagent molecule fills a place on the surface. Some of the places are free. The concentration of the free places is . The sum of all  (including free places) is constant, the density of adsorption places b.

The jump model gives for the diffusion flux of  (i = 1, ..., n):

The corresponding diffusion equation is:

Due to the conservation law,  and we
have the system of m diffusion equations. For one component we get Fick's law and linear equations because . For two and more components the equations are nonlinear.

If all particles can exchange their positions with their closest neighbours then a simple generalization gives

where  is a symmetric matrix of coefficients that characterize the intensities of jumps. The free places (vacancies) should be considered as special "particles" with concentration .

Various versions of these jump models are also suitable for simple diffusion mechanisms in solids.

Diffusion in porous media
For diffusion in porous media the basic equations are (if Φ is constant):

where D is the diffusion coefficient, Φ is porosity, n is the concentration, m > 0 (usually m > 1, the case m = 1 corresponds to Fick's law).

Care must be taken to properly account for the porosity (Φ) of the porous medium in both the flux terms and the accumulation terms. For example, as the porosity goes to zero, the molar flux in the porous medium goes to zero for a given concentration gradient. Upon applying the divergence of the flux, the porosity terms cancel out and the second equation above is formed.

For diffusion of gases in porous media this equation is the formalization of Darcy's law: the volumetric flux of a gas in the porous media is

where k is the permeability of the medium, μ is the viscosity and p is the pressure.

The advective molar flux is given as

J = nq

and for  Darcy's law gives the equation of diffusion in porous media with m = γ + 1.

In porous media, the average linear velocity (ν), is related to the volumetric flux as:

Combining the advective molar flux with the diffusive flux gives the advection dispersion equation

For underground water infiltration, the Boussinesq approximation gives the same equation with m = 2.

For plasma with the high level of radiation, the Zeldovich–Raizer equation gives m > 4 for the heat transfer.

Diffusion in physics

Diffusion coefficient in kinetic theory of gases

The diffusion coefficient  is the coefficient in the Fick's first law , where J is the diffusion flux (amount of substance) per unit area per unit time, n (for ideal mixtures) is the concentration, x is the position [length].

Consider two gases with molecules of the same diameter d and mass m (self-diffusion). In this case, the elementary mean free path theory of diffusion gives for the diffusion coefficient

where kB is the Boltzmann constant, T is the temperature, P is the pressure,  is the mean free path, and vT is the mean thermal speed:

We can see that the diffusion coefficient in the mean free path approximation grows with T as T3/2 and decreases with P as 1/P. If we use for P the ideal gas law P = RnT with the total concentration n, then we can see that for given concentration n the diffusion coefficient grows with T as T1/2 and for given temperature it decreases with the total concentration as 1/n.

For two different gases, A and B, with molecular masses mA, mB and molecular diameters dA, dB, the mean free path estimate of the diffusion coefficient of A in B and B in A is:

The theory of diffusion in gases based on Boltzmann's equation
In Boltzmann's kinetics of the mixture of gases, each gas has its own distribution function, , where t is the time moment, x is position and c is velocity of molecule of the ith component of the mixture. Each component has its mean velocity . If the velocities  do not coincide then there exists diffusion.

In the Chapman–Enskog approximation, all the distribution functions are expressed through the densities of the conserved quantities:
 individual concentrations of particles,  (particles per volume),
 density of momentum  (mi is the ith particle mass),
 density of kinetic energy
The kinetic temperature T and pressure P are defined in 3D space as

where  is the total density.

For two gases, the difference between velocities,  is given by the expression:

where  is the force applied to the molecules of the ith component and  is the thermodiffusion ratio.

The coefficient D12 is positive. This is the diffusion coefficient. Four terms in the formula for C1−C2 describe four main effects in the diffusion of gases:
  describes the flux of the first component from the areas with the high ratio n1/n to the areas with lower values of this ratio (and, analogously the flux of the second component from high n2/n to low n2/n because n2/n = 1 – n1/n);
  describes the flux of the heavier molecules to the areas with higher pressure and the lighter molecules to the areas with lower pressure, this is barodiffusion;
  describes diffusion caused by the difference of the forces applied to molecules of different types. For example, in the Earth's gravitational field, the heavier molecules should go down, or in electric field the charged molecules should move, until this effect is not equilibrated by the sum of other terms. This effect should not be confused with barodiffusion caused by the pressure gradient.
  describes thermodiffusion, the diffusion flux caused by the temperature gradient.

All these effects are called diffusion because they describe the differences between velocities of different components in the mixture. Therefore, these effects cannot be described as a bulk transport and differ from advection or convection.

In the first approximation,
  for rigid spheres;
  for repulsing force
The number  is defined by quadratures (formulas (3.7), (3.9), Ch. 10 of the classical Chapman and Cowling book)

We can see that the dependence on T for the rigid spheres is the same as for the simple mean free path theory but for the power repulsion laws the exponent is different. Dependence on a total concentration n for a given temperature has always the same character, 1/n.

In applications to gas dynamics, the diffusion flux and the bulk flow should be joined in one system of transport equations. The bulk flow describes the mass transfer. Its velocity V is the mass average velocity. It is defined through the momentum density and the mass concentrations:

where  is the mass concentration of the ith species,  is the mass density.

By definition, the diffusion velocity of the ith component is , .
The mass transfer of the ith component is described by the continuity equation

where  is the net mass production rate in chemical reactions, .

In these equations, the term  describes advection of the ith component and the term  represents diffusion of this component.

In 1948, Wendell H. Furry proposed to use the form of the diffusion rates found in kinetic theory as a framework for the new phenomenological approach to diffusion in gases. This approach was developed further by F.A. Williams and S.H. Lam. For the diffusion velocities in multicomponent gases (N components) they used

Here,  is the diffusion coefficient matrix,  is the thermal diffusion coefficient,  is the body force per unit mass acting on the ith species,  is the partial pressure fraction of the ith species (and  is the partial pressure),  is the mass fraction of the ith species, and

Diffusion of electrons in solids

When the density of electrons in solids is not in equilibrium, diffusion of electrons occurs. For example, when a bias is applied to two ends of a chunk of semiconductor, or a light shines on one end (see right figure), electrons diffuse from high density regions (center) to low density regions (two ends), forming a gradient of electron density. This process generates current, referred to as diffusion current.

Diffusion current can also be described by Fick's first law

where J is the diffusion current density (amount of substance) per unit area per unit time, n (for ideal mixtures) is the electron density, x is the position [length].

Diffusion in geophysics
Analytical and numerical models that solve the diffusion equation for different initial and boundary conditions have been popular for studying a wide variety of changes to the Earth's surface. Diffusion has been used extensively in erosion studies of hillslope retreat, bluff erosion, fault scarp degradation, wave-cut terrace/shoreline retreat, alluvial channel incision, coastal shelf retreat, and delta progradation. Although the Earth's surface is not literally diffusing in many of these cases, the process of diffusion effectively mimics the holistic changes that occur over decades to millennia. Diffusion models may also be used to solve inverse boundary value problems in which some information about the depositional environment is known from paleoenvironmental reconstruction and the diffusion equation is used to figure out the sediment influx and time series of landform changes.

Dialysis

Dialysis works on the principles of the diffusion of solutes and ultrafiltration of fluid across a semi-permeable membrane. Diffusion is a property of substances in water; substances in water tend to move from an area of high concentration to an area of low concentration. Blood flows by one side of a semi-permeable membrane, and a dialysate, or special dialysis fluid, flows by the opposite side. A semipermeable membrane is a thin layer of material that contains holes of various sizes, or pores. Smaller solutes and fluid pass through the membrane, but the membrane blocks the passage of larger substances (for example, red blood cells and large proteins). This replicates the filtering process that takes place in the kidneys when the blood enters the kidneys and the larger substances are separated from the smaller ones in the glomerulus.

Random walk (random motion)
 One common misconception is that individual atoms, ions or molecules move randomly, which they do not. In the animation on the right, the ion in the left panel appears to have "random" motion in the absence of other ions. As the right panel shows, however, this motion is not random but is the result of "collisions" with other ions. As such, the movement of a single atom, ion, or molecule within a mixture just appears random when viewed in isolation. The movement of a substance within a mixture by "random walk" is governed by the kinetic energy within the system that can be affected by changes in concentration, pressure or temperature. (This is a classical description. At smaller scales, quantum effects will be non-negligible, in general. Thus, the study of the movement of a single atom becomes more subtle since particles at such small scales are described by probability amplitudes rather than deterministic measures of position and velocity.)

Separation of diffusion from convection in gases
While Brownian motion of multi-molecular mesoscopic particles (like pollen grains studied by Brown) is observable under an optical microscope, molecular diffusion can only be probed in carefully controlled experimental conditions. Since Graham experiments, it is well known that avoiding of convection is necessary and this may be a non-trivial task.

Under normal conditions, molecular diffusion dominates only at lengths in the nanometre-to-millimetre range. On larger length scales, transport in liquids and gases is normally due to another transport phenomenon, convection. To separate diffusion in these cases, special efforts are needed.

In contrast, heat conduction through solid media is an everyday occurrence (for example, a metal spoon partly immersed in a hot liquid). This explains why the diffusion of heat was explained mathematically before the diffusion of mass.

Other types of diffusion
 Anisotropic diffusion, also known as the Perona–Malik equation, enhances high gradients
 Atomic diffusion, in solids
 Bohm diffusion, spread of plasma across magnetic fields
 Eddy diffusion, in coarse-grained description of turbulent flow
 Effusion of a gas through small holes
 Electronic diffusion, resulting in an electric current called the diffusion current
 Facilitated diffusion, present in some organisms
 Gaseous diffusion, used for isotope separation
 Heat equation, diffusion of thermal energy
 Itō diffusion, mathematisation of Brownian motion, continuous stochastic process.
 Knudsen diffusion of gas in long pores with frequent wall collisions
 Lévy flight
 Molecular diffusion, diffusion of molecules from more dense to less dense areas
 Momentum diffusion ex. the diffusion of the hydrodynamic velocity field
 Photon diffusion
 Plasma diffusion
 Random walk, model for diffusion
 Reverse diffusion, against the concentration gradient, in phase separation
 Rotational diffusion, random reorientation of molecules
 Surface diffusion, diffusion of adparticles on a surface
 Taxis is an animal's directional movement activity in response to a stimulus
 Kinesis is an animal's non-directional movement activity in response to a stimulus
 Trans-cultural diffusion, diffusion of cultural traits across geographical area
 Turbulent diffusion, transport of mass, heat, or momentum within a turbulent fluid

See also

References

Articles containing video clips
Broad-concept articles

Diffusion


Blacks Fork, also known as Blacks Fork Commissary, is a ghost town in Summit County, Utah, United States. Named for the Blacks Fork River, it was a logging town that operated from 1870 to 1930.

History
Blacks Fork was established in 1870 as a logging camp that supplied lumber to the railroad and mining industries. A large barn was erected near the center of the town, and several businesses and homes were built around the barn. Tradition says that the town also served as a military commissary during the early part of its history, but Utah ghost towns researcher Stephen Carr concluded that "...this suggestion is very unlikely," citing the camp's remote location and harsh climate, as well as the fact that an army post called "Blacks Fork" already existed near Bryan, Wyoming. The population peaked at about 100, but the town was soon abandoned. Remaining are the barn, a post office, and a few homes.

See also

 List of ghost towns in Utah

References

External links

Ghost towns in Utah
Populated places established in 1870
1870 establishments in Utah Territory
Logging communities in the United States
Ghost towns in Summit County, Utah

Blacks Fork, Utah


Rotherhithe ( ) is a district of south-east London, England, and part of the London Borough of Southwark. It is on a peninsula on the south bank of the Thames, facing Wapping, Shadwell and Limehouse on the north bank, with the Isle of Dogs to the east. It borders Bermondsey to the west and Deptford to the south-east. The district is a part of the Docklands area.

Rotherhithe has a long history as a port, with Elizabethan shipyards and working docks until the 1970s. In the 1980s, the area along the river was redeveloped as housing through a mix of warehouse conversions and new-build developments. The Jubilee line was extended to the area in 1999, giving fast connections to the West End and to Canary Wharf; the East London underground line was converted to part of the London Overground network in 2010, which provides easy access to the City of London. As a result, Rotherhithe is now a gentrifying residential and commuter area, with urban regeneration progressing around Deal Porter Square at Canada Water; a new town centre with restaurant and retail units, as well as new residential developments, is emerging here around the existing freshwater dock and transport hub.

Rotherhithe is  east of London's centre point.

Etymology
The name "Rotherhithe" is thought to derive from the Anglo-Saxon Hrȳðer-hȳð and it is suggested it means "landing-place for cattle". The first recorded use of this name was in about 1105, as Rederheia. Other explanations of the name have been 'Red Rose Haven' and 'rehra' (mariner's) hythe (haven or landing place). In the past Rotherhithe was also known as Redriff or Redriffe, however until the early 19th century, this name was applied to the whole river front from St Saviour's Dock to Bull Head Dock, this near the entrance to Surrey Water. On the Ordnance Survey five feet to the mile, London 1893–1896 maps, Redriff appears in two places, by Beatson Street and by Nelson Dockyard to Durand's Wharf.

Description

The docks were closed and largely filled in during the 1980s, and have now been replaced by modern housing and commercial facilities, but Rotherhithe retains much of its character and its maritime heritage. The largest surviving dock on the south bank, Greenland Dock, is the focal point for the southern part of the district, while there are many preserved wharves along the riverside at the north end of Rotherhithe. St. Mary's Church is at the centre of the old Rotherhithe village, which contains various historic buildings including the Brunel Engine House at the south end of the Thames Tunnel.

Canada Dock was the dock basin furthest away from the River Thames in the Surrey Docks complex, and it was linked to Albion Dock and Greenland Dock at its northern and south-eastern extremities via the Albion Canal. The dock has been remodelled, and its northwest half retained as an ornamental lake, renamed Canada Water. The canal has remained as a walkway and water feature within the redeveloped area.

Southwark Council and the Greater London Authority have announced a significant regeneration project focused on Canada Water and Rotherhithe. Known as the 'Canada Water Masterplan', the project has proposed the development of an additional 3,500 homes, as well as a new high street, town square, parks, leisure centre and footpath links. The landmark Tesco store will also be relocated. The project would be developed in multiple phases over the coming 15 to 20 years. Some local community groups oppose the plan based on environmental and cost considerations.

Rotherhithe is the home of the football team Fisher F.C. and Ballers Football Academy, who train & play fixtures at St Pauls Stadium. The Championship team Millwall Football Club is nearby in the London Borough of Lewisham.

The sustainable transport charity Sustrans has proposed the construction of a bicycle and pedestrian swing bridge from Rotherhithe to Canary Wharf, and cost-benefit and feasibility studies were undertaken. In January 2009 the London Mayor Boris Johnson said he would not fund the bridge, citing budget cuts due to the credit crunch, with the result that the project was effectively put on ice. However the idea is still being supported by Sustrans.

There are two Anglican churches in Rotherhithe St. Mary's Church, and Trinity Church. There are two Roman Catholic churches: St Peter and the Guardian Angels, and Our Lady of the Immaculate Conception.

King's Stairs Gardens
King's Stairs Gardens is a small park on the river towards the Bermondsey boundary. In September 2011 Thames Water announced that they wanted to build an access shaft for the "super-sewer" Thames Tideway Tunnel. Due to local action by The Save King's Stairs Gardens Campaign, which collected over 5000 signatures, Thames Water decided to build the access shaft in Chambers Wharf instead.

Local landmarks and history

The Mayflower TRA Hall now occupies the site of the old Rotherhithe Town Hall. The building ceased to be a town hall in 1905 when the former Rotherhithe Council merged with the old Bermondsey Borough Council and the new council used premises in Spa Road. The old Rotherhithe Town Hall became a library and a museum. It was razed to the ground by repeated bomb hits and near misses during the Second World War (see below).

Rotherhithe had its own general hospital, St Olave's Hospital, on Lower Road close to the old town hall. Built originally in the early 1870s on land adjoining Rotherhithe Workhouse, it became the infirmary of St Olave's Union in 1875, and was renamed St Olave's Hospital in 1930. Subsequently, becoming part of the Guy's Hospital Teaching Group in 1966, it closed in 1985 and the site has been redeveloped into the residential Ann Moss Way.

The Terriss Theatre (named after the actor, William Terriss) opened in 1899 and was later renamed the Rotherhithe Hippodrome of Varieties. It stood on Lower Road by Culling Road. It was bombed in the 1940s and stood empty until demolition in 1955.

When the roundabout facing the Rotherhithe Tunnel was redeveloped in the early 1980s, several 19th century buildings were demolished including a school and a nunnery. A public house, the "Europa", described in an early 20th-century history of the area as one its oldest, was also demolished.

The Daily Mail and Evening Standard newspapers were printed at Harmsworth Quays in Rotherhithe from 1989 to 2012. The site is now the Printworks events venue.

Ecclesiastical parish

The ancient parish, dedicated to St Mary, was in the Diocese of Winchester until 1877, then the Diocese of Rochester until 1905, and then finally in the Diocese of Southwark. From 1840, as the population of Rotherhithe increased, a number of new parishes were formed:
 Christ Church, Rotherhithe in 1840
 All Saints, Rotherhithe in 1842
 Holy Trinity, Rotherhithe in 1842
 St Barnabas, Rotherhithe in 1873

In addition, as the population of neighbouring Deptford increased, parts of Rotherhithe parish were included in the new parish of:
 St Katherine, Rotherhithe in 1886 with parts of St James, Hatcham

Nordic connection

Because much of the former Surrey Docks had strong trade links to Scandinavia and the Baltic region, the area is still home to a thriving Scandinavian community. During World War II, in fact, it housed the Norwegian Government-in-Exile. Originally established as seafarers' missions, Rotherhithe is home to a Norwegian, a Finnish and a Swedish church. The Finnish Church and the Norwegian Church are both in Albion Street; they were built in 1958 and 1927 respectively (Rotherhithe Library is between them). There are also a number of "community centres" for the Nordic community in London, including hostels, shops and cafés and even a sauna, mostly linked closely to the churches.

Some of the redeveloped areas were built by Nordic architects, such as the Greenland Passage development by Danish Company Kjær & Richter. This gives some areas a distinctly "Nordic" feel in terms of house and street design.

The relationship with Scandinavia and the Baltic is also reflected in the names of some of the buildings (such as the King Frederik IX Tower), the street names (e.g. Finland Street, Sweden Gate, Baltic Quay, Norway Gate, Helsinki Square) or other place names (e.g. Greenland Dock). Another major influence factor was trade with Russia and Canada (mainly timber), reflected in names such as Canada Water and the Russia Dock Woodland.

Other connections
Rotherhithe is also a popular place to live with South Africans, according to the UK census of 2011, and there was a South African themed pub at 351 Rotherhithe Street.

The Mayflower
In July 1620, the Mayflower sailed from Rotherhithe and picked up 65 passengers, probably from Blackwall, then proceeded to Southampton on the south coast of England to begin loading food and supplies for the voyage to America. At that time, the English Separatists, who later became known as the "Pilgrim Fathers", were mostly still living in the city of Leiden, in the Netherlands. There they hired a ship called the Speedwell to take them from Delfshaven in the Netherlands to Southampton to join the Mayflower.

The ship's master, Christopher Jones, died shortly after his return in 1621 and is buried in an unmarked grave at St Mary's Church. No one can be sure where on the Rotherhithe peninsula the Mayflower was berthed, but the Mayflower pub near St Mary's Church claims the honour, and lists the names of the Mayflower passengers on their wall. The building itself, despite external and interior appearances, dates only from the 1950s. The extent to which the pub was damaged during the Second World War, and was rebuilt or simply restored is uncertain.

China Hall

On Lower Road, about halfway between Surrey Quays and Canada Water stations, there was a public house called the China Hall; at one time it was the entrance to a riparian playhouse visited by Samuel Pepys and mentioned in his diary. It is not known how long the theatre remained on the site, but it was reinvigorated in 1777 and George Frederick Cooke acted there the following year. In the winter of 1779, it was destroyed in fire. The site of the theatre became a well-known tea-gardens, with the "usual arbours and 'boxes'" during the Victorian period, but by the 1920s, most of the gardens had been absorbed into the Surrey Commercial Docks as part of a timber yard.

Second World War
Like the rest of the London Docks, the Surrey Commercial Docks were targeted by the Luftwaffe. On 7 September 1940, on the first day of the London Blitz, the deal yards of Surrey Docks were set ablaze. The raid ignited over a million tonnes of timber in Quebec Yard, causing the most intense single fire ever seen in Britain.

The bombing of the old Rotherhithe Town Hall during the Second World War gives an indication of how heavy the bombing in Rotherhithe was. The first damage to the building occurred when Luftwaffe bombs landed nearby in April 1941, and there was more bomb damage in February and June 1944. Later the same month (June 1944) the Town Hall was severely damaged by a direct hit from a V1 doodlebug. In November 1944 it was further damaged by near misses, and was finally destroyed by one of the last V1s to land on London.

King Haakon VII made many of his famous radio broadcasts to occupied Norway from Saint Olav's Norwegian Church in Rotherhithe, where the Norwegian royal family were regular worshippers during their exile.

Geography

Rotherhithe is joined to the north bank of the Thames by three tunnels. The Thames tunnel to Wapping was the first underwater tunnel in the world. Built by the Brunels, and originally intended to carry cross-river freight, it became a pedestrian tunnel due to the money running out to build the necessary ramps for vehicle traffic. It was used as a railway tunnel from 1869, and is now part of the London Overground network, which on 27 April 2010 started running trains on the route of the former East London Line. The later Rotherhithe Tunnel (opened 1908) carries a two-lane road to Limehouse. The Jubilee line extension (opened 1999) has a railway tunnel to Canary Wharf in the Isle of Dogs.

Parts of Rotherhithe Street were at one time or another called Jamaica Street, Lavender Street, Low Queen Street, Queen Street, Redriff Wall, Redriff, Rotherhithe Wall, Shipwright Street and Trinity Street.

Rotherhithe is part of the SE16 postcode district. Electorally, the western half is Rotherhithe ward of Southwark London Borough Council and the eastern half in Surrey Docks ward.

As much of Rotherhithe was occupied by the now-defunct Surrey Commercial Docks, the district is sometimes referred to as "Surrey Docks" or (since the late 1980s) "Surrey Quays", though the latter name tends to be used more for the southern half of the peninsula. An eastern part, which became an island when the docks were in use and the locks open, is called "Downtown". This name was never related to the idea of a "downtown" in the American sense, although there was a club of that name there for many years which has now closed. This part of Rotherhithe has since the 1980s been quiet and suburban in nature. Durand's Wharf is a park in Rotherhithe Street and holds an Outdoor Gym.

Notable people

 Marc Isambard Brunel (1769–1849) and his son Isambard Kingdom Brunel (1806–1859) built the Thames Tunnel between Rotherhithe and Wapping.
 John Short Hewett (1781–1835) cleric and academic, was Rector of Rotherhithe between 1817 and 1835
 Max Bygraves (1922–2012), entertainer, was born in Rotherhithe.
 Michael Caine (born 1933), actor, was born Maurice Joseph Micklewhite in Rotherhithe.
 Thomas Coram (1668–1751) a philanthropic sea captain, retired to Rotherhithe where he campaigned for establishment of the Foundling Hospital.
 Eliza Fay (1755 or 1756–1816), author of Original Letters from India (1817), was born in Rotherhithe.
 Malcolm Hardee (1950–2005), comedian, lived on a houseboat in Greenland Dock, Rotherhithe. He owned and ran the Wibbley Wobbley pub-boat on the same dock, and was drowned there.
Sir James Kemnal (1864-1927) industrialist
 Myleene Klass (born 1978), singer, lived in Rotherhithe in the early 2000s.
 George Lambourn (1900-1977), artist, was born in Rotherhithe.
 Aaron Manby (1776–1850) assembled and launched the world's first seagoing iron-hulled ship at Rotherhithe in 1822.
 Billy Mehmet (born 1985), professional footballer, attended Bacon's College in Rotherhithe in the 1990s.
King Mutesa II of Buganda (1925–1969) died in exile in his flat in Rotherhithe in 1969 following an interview with journalist John Simpson.
 James Townsend Saward (1798–c1875) Victorian English barrister and forger was born in Rotherhithe.
 James Walker (1781–1862) worked on the design and construction of Greenland Dock, where a memorial bust of him stands.
 Sean Lock (1963 - 2021), comedian, lived in Rotherhithe in the 1990s.

Main sights

Transport

Railway
Rotherhithe is served by three stations:
 Rotherhithe railway station was formerly a London Underground station on the East London Line; it was rebuilt as a London Overground station and reopened on 27 April 2010. It is located near to the river, to the north.
 Surrey Quays railway station is located to the south of the district. It was also an Underground station and was converted to the Overground network at the same time as Rotherhithe station.
 Canada Water tube station is located in central Rotherhithe. It is now an important transport interchange, as both London Overground's East London line and the Jubilee line of the London Underground serve it; there is also a bus station here. This station is at the centre of a major regeneration project, with rapid construction of new flats.
Other nearby stations are Bermondsey tube station (also on the Jubilee line), South Bermondsey railway station to the south-west and London Bridge railway station to the west.

Buses
The area is served by Transport for London bus services 1, 47, 188, 199, 225, 381, C10 and P12; night buses N1, N199 and N381 also stop here. Canada Water bus station is an important stop and interchange, given its proximity to the tube station.

Walking and cycling
The riverbank carries part of the Richmond - Thames Barrier (28 miles – 45 km) section of the Thames Path through London. Most of the riverbank is accessible, apart from sections where warehouses and estates have established rights to the riverside.

A new bridge for pedestrians and cyclists has been proposed between Rotherhithe and Canary Wharf.

Taxis
London Taxis (black cabs) can often be found on Salter Road.

River boat
 Greenland Dock Pier are served by Thames Clippers routes RB1, RB2, RB6 and RBS.
 Docklands Pier for Canary Wharf – Rotherhithe Ferry only

Gallery

References

Further reading
 BBC London Coast – Rotherhithe Walk
 Canada Water Campaign
 Canada Water Plaza
 Friends of Russia Dock Woodland
 LDDC Completion Booklets Surrey Docks
 London Voices Rotherhithe, Surrey Docks, Surrey Quays, London SE16
 Londonist Discovers Rotherhithe Picture Research Library
 Maritime Rotherhithe Walk A: Transport, Industry and the Docks by Stuart Rankin, Southwark, 2004,
 Maritime Rotherhithe Walk B: Shipyards, Granaries and Wharves by Stuart Rankin, Southwark, 2004,
 Save King's Stairs Gardens Campaign
 SE16 online community
 The Finnish Church in London
 The National Archives database record for St Olave's Hospital

Maps
 Google Maps: Map
 Google Maps: Satellite Photo

History
 British History Online The Environs of London: volume 1, Rotherhithe, County of Surrey, pp. 470–477, Daniel Lysons, 1792
 British History Online Old and New London: Volume 6, Rotherhithe, pp. 134–142, Edward Walford, 1878
 British History Online A History of the County of Surrey: Volume 4, Parishes: Rotherhithe, pp. 83–92, H.E. Malden (editor), 1912,

Areas of London
Districts of London on the River Thames
Districts of the London Borough of Southwark
Peninsulas of England
Port of London
Ports and harbours of the Thames Estuary
Redeveloped ports and waterfronts in London
Redevelopment projects in London
Shipbuilding in London

Rotherhithe


Synchronized diving (synchro diving) is a sport in which two divers dive at the same time as a team from a three-meter springboard or a ten-meter platform. It is one type of diving which has belonged to the Olympic games since 2000 Sydney Olympics. The competition consists of five or six rounds depending on the events. Divers dive two basic dives during the first two rounds. Then they dive more complex freestyle dives from the third to the fifth round. The winners are determined according to total scores from judges. There are two types of judges. One is a technical judge who evaluates degree of completion of their dives.  Another is a synchro judge who evaluates the synchronization of two divers. (synchro)

History of Synchronized Diving
Synchronized diving was internationally introduced at the 1995 FINA world cup. In 1999, four synchronized diving events were added as the Olympic programme at the IOC Executive Board meeting held in Lausanne. Then, it became an Olympic sport with its debut at the 2000 Sydney games with three-meter springboard and ten-meter platform events for both men and women.

Type of Dives

Dive Groups
There are six groups of dives. The first four show the direction the diver rotates.

1. Forward group: The diver faces the front of the board and jumps toward the water.

2. Backward group: Backward dives begin on the end of the board with divers back to the water.

3. Reverse group: Reverse dives begin with the diver facing the front of the board and then  rotates toward the board.

4. Inward group: these dives begin on the end of the board with divers' back to the water but then rotates toward the board.

5. Twisting group: Any dive that uses a twist excluding armstands.

6. Armstand group: The dives begin with a handstand position on the end of the platform before the dive.

Body Positions
A dive may be performed using one of the following four positions.

Pike: The legs are straight with the body bent at the waist. arm placement can be different according to the dives by each diver.

Tuck: The Body is bent at the waist and knees with thighs drawn to the chest.  Heels kept close to the buttocks, and feet should be kept together.

Straight: without bend at the waist or knees. Arm placement can be varied by diver's choice or is decided by the dive performed.

Free: using any of the above three positions, or combinations them, when performing a twisting dive.

Scoring & Judging

Scoring
While it takes seven judges to score individual events, 11 judges score synchronized diving. During a synchro event, three judges score the completion of Diver A's performance, while three other judges score the completion of Diver B's performance. The remaining five judges score the synchronization of two divers. Each judge scores a dive between 0 and 10 points, in half-point increments.

10: Excellent

8.5-9.5: Very good

7-8: Good

5-6.5: Satisfactory

2.5-4.5: Deficient

0.5-2: Unsatisfactory

0: Completely failed

Judging
Judges evaluate the following parts of a dive to determine an overall score:

Approach: several steps forward to the end of the board before takeoff. It should be smooth but forceful with good form.

Takeoff: A diver's jump from the board prior to execution of the dive. showing control and balance is important with appropriate angle and distance from the board.

Elevation: The amount of the jump has an effect on the appearance of the dive.A higher jump allows divers to dive with accuracy and smoothness of movement.

Execution: proper mechanical performance, skills, form, and grace.

Entry: The entry into the water is important because it's the last moment the judge watches. It should be vertical with a minimal amount of splash.

References

Diving
Summer Olympic sports

Synchronized diving


The Lia radiological accident began on December 2, 2001, with the discovery of two orphan radiation sources near the Enguri Dam in Tsalenjikha District in the country of Georgia. Three villagers from  were unknowingly exposed. All three men were injured, one of whom eventually died. The accident was a result of unlabeled radioisotope thermoelectric generator (RTG) cores which had been improperly dismantled and left behind from the Soviet era. The International Atomic Energy Agency (IAEA) led recovery operations and organized medical care.

Source of the radioactive material

In the early 1980s, a series of radio relays were built to connect the Enguri Dam with the Hudoni Dam, which was under construction. The relays were in remote territory with no reliable access to electricity, and thus were powered with a series of eight radioisotope thermoelectric generators (RTGs) manufactured in 1983. Each RTG was a Beta-M type powered by strontium-90, and contained some 12951480 TBq of radioactivity. However, the Hudoni dam's construction was stopped as Georgian independence from the Soviet Union drew near. The stations and their RTGs were abandoned and eventually dismantled. The RTGs became lost at this time. Two were rediscovered in 1998, leading to no injuries. Two more were found in 1999, and again led to no injuries or significant radiation exposure. Two more were rediscovered in 2001, which led to the accident. The other two sources remain unaccounted for. The sources were not marked, and had been removed from the rest of the generator housing. They were heavy for their size, weighing  despite being only . Upon their recovery, it was determined the radiation emitted at the surface of the sources was 4.6 Sieverts (Sv) per hour. A fully absorbed whole-body dose of 5 Sv has a 50% chance of death. The original dose output at the time of their construction would have been much higher, but said output had decreased 40% since their construction due to radioactive decay. The actual dose received per hour would be lower unless physically touching the source, as radiation decreases with distance according to the inverse-square law.

The accident
Three men from Lia (later designated as patients 1-DN, 2-MG, and 3-MB by the IAEA) had driven  to a forest overlooking the Enguri Dam reservoir to gather firewood. They drove up a nearly impassable road in snowy winter weather, and discovered two canisters at around 6 pm. Around the canisters there was no snow for about a  radius, and the ground was steaming. Patient 3-MB picked up one of the canisters and immediately dropped it, as it was very hot. Deciding that it was too late to drive back, and realizing the apparent utility of the devices as heat sources, the men decided to move the sources a short distance and make camp around them. Patient 3-MB used a stout wire to pick up one source and carried it to a rocky outcrop that would provide shelter. The other patients lit a fire, and then patients 3-MB and 2-MG worked together to move the other source under the outcrop. They ate dinner and had a small amount of vodka, while remaining close to the sources. Despite the small amount of alcohol, they all vomited soon after consuming it, the first sign of acute radiation syndrome (ARS), about three hours after first exposure. Vomiting was severe and lasted through the night, leading to little sleep. The men used the sources to keep them warm through the night, positioning them against their backs, and as close as . The next day, the sources may have been hung from the backs of Patient 1-DN and 2-MG as they loaded wood onto their truck. They felt very exhausted in the morning and only loaded half the wood they intended. They returned home that evening.

Aftermath

Medical
Two days after exposure, on December 4, patient 2-MG visited a local doctor but did not mention the mysterious heating source, and the doctor assumed he was drunk. The resulting treatment however did clear up the symptoms. On December 15, patient 1-DN and 2-MG developed burning and itching on the small of their backs, where the radiation source had been closest. Patient 1-DN lost his voice as well, but did not seek care at that time. The wife of patient 3-MB and the brother of patient 2-MG learned that all three men were ill with similar symptoms, including increasing desquamation, especially on their backs. The wife and brother reached out to the police, who suggested that all three men seek medical attention. All three patients were finally hospitalized on December 22, and it was determined they had ARS. Patient 3-MB was released on January 23, 2002, as his injury was mild. The other patients remained in serious condition, and the Government of Georgia petitioned the IAEA for help treating them. The IAEA intervened: patient 1-DN was sent to Burnasyan Federal Medical Biophysical Center in Moscow, and Patient 2-MG was sent to the Percy military hospital in Paris. Patient 2-MG was hospitalized for over a year, and required extensive skin grafts, but survived and was discharged on March 18, 2003. Patient 1-DN's injuries lingered. He had received the greatest exposure on his back, as well as damage to his heart and vital organs. A large radiation ulcer formed on much of his upper left back. Despite intensive care, repeated antibiotics, multiple surgeries, and an attempted skin graft, the wound did not heal. His condition was complicated by tuberculosis, which prevented effective treatment of lung injury. He developed sepsis, and died of heart failure on May 13, 2004, 893 days after first exposure.

Doses
Radiation doses were estimated in several different ways, but it was clear that Patient 2-MG received the greatest dose. Below, doses are measured in grays. A whole-body dose of 10 Gy is 99% fatal, a dose of 6 Gy is 50% fatal with treatment, and a dose of 2 Gy is 5% fatal with treatment. Localized doses, especially where the patients suffered radiation ulcers, may have been much higher. Patient 1-DN, despite a survivable whole-body dose of between 2.8 and 5.4 Gy, received 21-37 Gy to his shoulder, which eventually killed him. In the chart below, there is some uncertainty in the measurements. The calibration curve method is from an assumed exposure time, distance, and rate. This is close to the doses determined by the measurements of chromosome aberrations taken from blood samples analyzed by the Georgia Cytogenetics Laboratory. Also included are doses calculated by the Dolphin method, which uses a slightly different detector. No other people in the area were found to have been exposed.

Source recovery
The day after the hospitalization, Georgian authorities attempted to find the suspected radiation sources, but bad weather prevented them from reaching the site. On December 29 they tried again and ascertained the exact location, also shooting video footage. On January 4, 2002, the Georgian government appealed to the IAEA for help. A first attempt at recovering the sources was made two days later, but failed again due to weather. A fact-finding mission was led to determine how to best recover the sources, and their nature. The containers were extremely well built, which prevented the loss of radioactive material under all but the most extreme conditions. They had survived being abandoned in the woods for over a decade and had released no radioactive material. The radiation hazard was localized only, due to escaping ionizing radiation. For this reason, the IAEA had intended to wait until the spring thaw to recover the sources, but concerns by residents led the Georgian government to push for an early recovery. A tactically difficult recovery mission was successfully carried out on February 23, 2002.

The recovery mission faced numerous challenges, with winter weather being chief among them. The village of Potskho Etseri was used as the base of operations. A special container lined with  of lead and weighing  was built for the purpose. An old military truck was converted for hauling the container. Special handling tools were created to manipulate the source and put it in a container. A group of 41 people were organized to take turns handling the source, with each person spending not more than 40 seconds near it. In the end, only 24 people were needed to actually be near the sources, and only those 24 people received significant doses. Worker radiation doses were monitored, and the highest dose was not more than 1.16 mSv, less than 10% of the dose of a full-body CT scan. The sources were successfully recovered, and carefully escorted by police back to a permanent storage location. Doses received between placing the sources in the truck and closing the lid over them was higher than expected due to the presence of a tarp over the truck. Inclement weather had prevented its removal, and it acted to reflect and scatter radiation back at the workers. The IAEA also noted that better tool design, as well as the use of more workers at a time to provide spotting capabilities, would have made the process faster and safer. Overall, the IAEA considered the recovery a success with no major safety issues.

Analysis

The IAEA's final report concluded that the proximate cause of the accident was that the sources were unmarked and unlabeled, and thus their danger could not be known. It also chastised the illegal abandonment of the sources to begin with. The report stressed the importance of basic knowledge of radiation injuries by clinicians and called for increased programs to make them aware of the signs of radiation overexposure. The initial clinician who treated patient 2-MG did not accurately assess the injury (partly due to 2-MG's failure to mention the orphan source), thus delaying proper treatment for almost three weeks.

Between the fall of the Soviet Union and 2006, the IAEA had recovered some 300 orphan sources in Georgia, many lost from former industrial and military sites abandoned in the economic collapse after the Soviet breakup.

References

External links
 Video of the recovery
 Full IAEA report on the incident
2001 health disasters
2001 in Georgia (country)
Civilian nuclear power accidents
December 2001 events in Europe
Radiation accidents and incidents
Samegrelo-Zemo Svaneti
Strontium
Waste disposal incidents
2001 disasters in Georgia (country)

Lia radiological accident


Giorgio Pullicino (8 July 1779 – 25 October 1851) was a Maltese painter, architect, and professor of drawing and architecture at the University of Malta. He is known for his harbour views painted in a number of media, and he is also considered to be one of the first neoclassical architects in Malta. He produced designs for a number of buildings, but the only structure which is definitely proven to have been designed by him is a monumental obelisk known as the Spencer Monument. However, several other buildings including the Monument to Sir Alexander Ball are widely attributed to him.

Biography
Pullicino was born in Valletta on 8 July 1779, as the son of Pietro Paolo Pullicino and his wife Clara née Azzarillo. He was the nephew of the painter Alberto Pullicino. He had an inclination to drawing from a young age, and attended a design school run by Michele Busuttil before being sent to Rome in 1794 to study at the Accademia di San Luca. Pullicino studied the works of Raphael and Titian, and met a number of the leading artists of the time, including Antonio Canova. He became familiar with neoclassicism in both art and architecture, including the works of the French architect Claude Nicolas Ledoux. His father died in 1799, while he was still in Rome.

During Pullicino's six years abroad, Malta had been transformed by political turmoil. Hospitaller rule had ended in 1798 when the islands were invaded and occupied by the French. The Maltese later rebelled against French rule with British, Neapolitan and Portuguese assistance, and Malta became a British protectorate in September 1800. In that same month, Pullicino arrived in Malta from Rome and went to live with his mother in Valletta. He married Vincenza Attard in April 1807, with whom he had seven children.

In 1803, Pullicino became a professor of drawing and architecture within the University of Malta. He officially became qualified as perito agrimensore (architect and surveyor) in 1830. Pullicino was a representative of the Maltese body of architects in a petition to the Royal Commission on the Affairs of Malta in 1836. He retired in 1839, but continued to work in his private studio for another three years. For the last few years of his life, he was confined to his home in Valletta due to an illness. He died on 25 October 1851 at the age of 72.

Works

Paintings

Throughout his career, Pullicino produced paintings in a variety of media, including pen and wash, watercolours and oils. He had a picturesque, naturalistic style, and mainly painted scenes of Valletta, the Grand Harbour and Marsamxett Harbour. He also painted a few other places in Malta such as the Gozo Citadel and St. Julian's Bay. He also produced watercolours of local costumes.

He sold many of the landscape paintings in order to supplement his salary at the university, some of them to foreigners including British military personnel stationed in Malta. Many of his works can now be found in the National Museum of Fine Arts in Valletta or in private collections, both in Malta and abroad.

Architecture
In 1804, Pullicino produced a proposed design for rebuilding the Porto Salvo Church in Valletta, since the original church had been declared unsafe and was demolished. Pullicino's design was in a restrained form of Baroque which included a number of neoclassical elements. His design was not chosen, and the church was rebuilt to a Baroque design of Antonio Cachia. Pullicino also submitted a design for a small church in Luqa, and another for the reconstruction of the Mosta parish church, which was once again not chosen in favour of Giorgio Grognet de Vassé's neoclassical Rotunda.

The only existing structure for which there is historical evidence proving that it was designed by Pullicino is the Spencer Monument. The monumental obelisk was built in 1831 on Corradino Hill, and it was later relocated to Blata l-Bajda in 1893. The original architectural plans of the structure have survived, proving that Pullicino designed it.

Apart from the obelisk, a number of architectural works are attributed to Pullicino. The Monument to Sir Alexander Ball, built in the Lower Barrakka Gardens in 1810, was "with almost absolute certainty" designed by Pullicino, but the original plans have not been found. This monument is one of the first examples of Neoclassical architecture in Malta, and Pullicino is credited as one of the first exponents of this style on the island.

The Doric portico of Main Guard in Valletta, which was built in 1814, is also often attributed to Pullicino, although it might have alternatively been designed by Colonel George Whitmore of the Royal Engineers. Other structures which might have been designed by Pullicino include a fountain and exedra at Lower Saint Elmo, Villa Frere in Pietà, and the rear entrance of the Old University in Valletta. The latter is built in a style typical of Pullicino, and he is the likely designer since he was the professor of architecture at the University at the time of its construction in 1824.

Pullicino is also a possible candidate as the unknown architect of the now-destroyed Ponsonby's Column, built in 1838.

References

1779 births
1851 deaths
People from Valletta
19th-century Maltese architects
Neoclassical architects
Academic staff of the University of Malta
18th-century Maltese painters
18th-century male artists
19th-century Maltese painters
Maltese artists

Giorgio Pullicino


The abdominal aorta is the largest artery in the abdominal cavity.  It is part of the aorta. It is a direct continuation of the descending aorta (of the thorax).

The abdominal aorta begins at the level of the diaphragm, crossing it via the aortic hiatus, technically behind the diaphragm.

References

Torso

Abdominal aorta


The Queen's Tower (), also known as Quindah Tower; ) is a tower that was built by the British during their rule in Sri Lanka. They built it as a trigonometric point and a light navigation point for diurnally operated ships. It is located on the southeastern coast of Neduntheevu, also known as Delft Island.

It was used by the British as a tower to measure the land by setting up an instrument on the top of the tower. However, an incorrect theory suggests that this tower had been used as a lighthouse. According to it, a fire was lit at the bottom which created a vacuum, forcing air upwards. Its light was passed through the tower's chimney-like tube to the top where sailors would be able to see the light from a distance. Another tower known as the "King's Tower" was operated during the period of British rule in Sri Lanka, then Ceylon. Only the basement of the King's Tower survives to this day.

References

Neduntheevu
Tourist attractions in Northern Province, Sri Lanka
Archaeological protected monuments in Jaffna District
Buildings and structures in Jaffna District

Queen's Tower (Neduntheevu)


Dr. William Stout Chipley (October 16, 1810 – February 11, 1880) was an early American psychologist.

Chipley was born in Lexington, Kentucky, October 18, 1810, the only son of the
Reverend Stephen Chipley, a pioneer of Lexington. William Chipley graduated from the Transylvania University in 1832. He was later renowned for his work relating to brain diseases and held two jobs: a professor of medicine at Transylvania University and the warden of the Eastern Asylum for the Insane in Lexington. He married Georgia Elizabeth Fannin in 1837 while he lived in Columbus, Georgia. By this marriage he had four sons and one daughter.

When he took charge of the Eastern Kentucky Insane Asylum in 1855, he found that institution
overcrowded with incurables, epileptics, and feeble minded, huddled together without any
attempt at classification and separation. These defects were not only remedied by Dr. Chipley,
but largely through his efforts other institutions in Kentucky were erected.

William Stout Chipley published a paper on "sitomania," a type of insanity consisting of an
intense dread or loathing of food. Clinical research in Great Britain and France during the 1860s
and 1870s replaced sitomania with the term "anorexia nervosa" and distinguished the disorder
from other mental illnesses in which appetite loss was a secondary symptom and from physical
"wasting" diseases, such as tuberculosis, diabetes, and cancer.

References

Further reading
Sitiomania (intense dread of food), by William Stout Chipley

1810 births
1880 deaths
People from Lexington, Kentucky
Transylvania University alumni
Eating disorders

William Stout Chipley


The Huanren frog (Rana huanrensis) is a species of true frog found in East Asia. It was originally believed to be endemic to Huanren County, Liaoning, China, but was later also found in South Korea; it is presumed to be present in North Korea, as well. It is closely related to the Dybowski's frog, Rana dybowskii, and specimens collected before 1991 were incorrectly identified as that species. Distinguishing factors include the absence of a vocal sac.

The Huanren frog is found in and around rivers and streams in hilly terrain.  The type locality in Huanren is  above sea level, and specimens from Korea have also only been found at altitudes over . Specimens from South Korea have been collected in the provinces of Gangwon-do, Gyeongsangbuk-do, and eastern Gyeonggi-do. Egg clutches, which are small and clustered, are deposited on submerged rocks in the streams which this species favors.

References

Rana (genus)
Amphibians of China
Amphibians of Korea
Vertebrates of East Asia
Amphibians described in 1991

Huanren frog