Forward flux sampling

Allen, R. Valerian , C., and ten Wolde, R R. (2009]. Forward flux sampling for rare event simulations, yournaf of Physics Condensed Matter 21,46, p. 463102. 

The forward flux sampling method (FFS) was conceived by Allen, Warren and ten Wolde [190-192] to deal with stochastic non-equilibrium systems in which the phase space distribution is not a priori known. Inspired by the TIS method, FFS employs the notion of a set of interfaces along a reaction coordinate (see Fig. 9), and even uses the same central reaction rate expression. 

Dahm and Dahm considered what happens when the thickness of the sample is doubled or halved, and computed the total backward flux, i co for an infinitely thick sample by an iterative solution of the latter set of equations. They showed that if the sample consists of an infinite number of layers, each with a forward flux of U, a backward flux of r and absorption of ai. 

Fig. 4 CGM sampling environment as introduced by Rebrin et al. [308]. Diffusion of glucose from plasma to ISP is in proportion to the concentration in each compartment, whereas ISF glucose is cleared by uptake of the surrounding cell. Cl glucose concentration in plasma, C2 ISF glucose concentration, kl2 forward flux rate for glucose transport across the capillary, k21 reverse flux rate for glucose transport across, k02 glucose uptake into the subcutaneous tissue, VI volume of plasma, V2 volume of ISP...

Angular distribution measurements of the SHG were carried out on BADP/PAA composites, in a manner similar to that described for mNA/PMMA. Analogous behaviour was observed, and Figure 3 illustrates the distribution obtained from a well-aligned sample. In this case, the angular distribution of the SH is very narrow, and most of the SH flux is confined to a narrow cone in the forward direction. 

Let us consider now that / and J are the fluxes of incident and disperse light traveling in the forward and reverse directions. The incident flux, /, decreases as it penetrates the solid powdered sample because not only is radiation absorbed, but because particles also disperse the incident light. At the same time / increases with J dispersion. The flux of disperse light, J, has an analogous variation, although in the opposite direction, as Figure 2 [8] shows. 

The quantity/i defined in Eq. (5.367) is just the a previously used and defined in Eq. (5.293). However, /2 is a new quantity which must be computed for each geometry of interest. Note that /2 is the fraction of neutrons transmitted by a sample upon which is incident a flux of neutrons whose angular distribution is an isotropic distribution weighted with a cosine factor which makes it more forward. For the cases of an infinite slab and a sphere, the quantities /2 are presented below no... 

There are quite a few different methods for the calibration of DSC instruments, of which the most popular are (a) calibration by Joule-effect and (b) calibration by heats of fusion.Joule-effect calibration is relatively simple and straight-forward in that it consists of an electrical heater inserted into the sample and reference compartments. A pulse of predetermined duration and intensity is sent to the sample, and the dissipated power is then measured. The disadvantage ofthis method is that some heat flux can be dissipated in the heater wires, and, therefore, not truly measured. Furthermore, the electrical heater is not necessarily composed of the same material as the sample and reference holders. Still, the accuracy of this calibration technique is better that 0.2%. 

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