Passage of Particles

The probability of passage decreases as the particle size tends to approach the size of the aperture. Thus, to ensure that efficient screening of particles takes place, many opportunities to pass through the screen must be provided to them. This is accomplished by moving the screen. For efficient screening both horizontal and vertical movements are required. The vertical movement is intended to lift the particles out of the blocking positions in the apertures and the horizontal movement ensures that when the particles fall they are presented at different positions on the screen surface. For any given aperture size the optimum conditions of the horizontal movement (vibration frequency) and the vertical movement (stroke) of the screen are related. 

---

So far we have derived an expression for the overall rate constant k. As with the copper system, we should also like an expression for the first-order rate constant k, describing the passage of particles from the secondary minimum over the barrier. The equilibrium constant describing the population of the secondary minimum is given by the same expression (49) as (36), where, as in Fig. 14, xR describes the width... 

The efficiency of screening is defined as the ratio of the mass of material which passes the screen to that which is capable of passing. This will differ according to the size of the material. It may be assumed that the rate of passage of particles of a given size through the screen is proportional to the number or mass of particles of that size on the screen at any... 

Another use of the term diffusion is to denote the passage of particles through mauer in such circumstances that the probability of scattering is large compared with thal of leakage or absorption. It is often limited to phenomena described by a member of the class of differential equations known as diffusion equations. 

The addition of NLS in a non viral gene delivery system is expected to favor the nuclear import (nuclear pores allow the passage of particles of 24 nm) by using the karyopherin and importin machinery. Where should the NLS be linked, on the pDNA or on the carrier For the latter strategy, polyplexes must not dissociate before their import in the cell nucleus. Both strategies have been prospected but with only limited success. 

We may consider this equation as signifying the passage of particles with an average velocity v in the x-direction defined by the expression. 

Volkheimer G. 1974. Passage of particles through the wall of the gastrointestinal tract. Environ Health... 

Fractionation by sieving is a function of two particle dimensions only, maximum breadth and maximum thickness for, unless the particles are excessively elongated, the length does not affect the passage of particles through the sieve apertures (Figure 4.1). Particles, having two dimensions... 

Sieving procedures are standardized in BS 1796 [14], Dry sieving by machine is used for coarse separation but other procedures are necessary as the powder becomes finer and more cohesive. Conventional dry sieving is not recommended for brittle material since attrition takes place and an endpoint is difficult to define. If the rate of passage of particles does not decrease with sieving time, it may be due to particle attrition, deagglomeration or a damaged sieve [72]. 

The term selectively permeable or differentially permeable is used to describe biological membranes because they restrict passage of particles based both on size and charge. Even small ions, such as H, cannot pass freely across a cell membrane. 

Screening involves passage of particles over apertures in a screen deck (or mat ), which allow particles smaller than the aperture size to pass through the deck, thereby dividing the product into undersize and oversize fractions [5.4-5.6]. The apertures may be square, rectangular, or circular. 

Figure fi. Plot of the proportion of particles liner than the sieve mesh that have passed through the sieve per time (modified from Irani Callis, 1963). Phase 1 is due to the passage of particles which are smaller than the sieve mesh in all dimensions Phase 2 is due to the more gradual passage of particles which at least one dimension larger than the sieve mesh. 

Aerosol delivery via mechanical ventilation using nebulizers seems more complex than conventional nebulization. How should the nebulizer be powered Where in the circuit should it be connected Early studies in the ICU suggested that nebulized particles could be delivered to the lungs of intubated patients only with great difficulty. Compared to other devices such as MDIs, nebulizers were inefficient (30) and the endotracheal tube presented an additional barrier to the passage of particles into the respiratory tract (31). However, by taking the same... 

Casley-Smith J.R. 1964. Endothelial permeability— the passage of particles into and out of diaphragmatic lymphatics. Q. J. Exp. Physiol. 49 365. 

---