Particle tracking

The task of particle tracking breaks easily into two parts locating the particles in a particular image frame (location) and determining where a particle has moved from one frame to the next (connection). 

Connection The second task is generally straightforward and will not be discussed in depth. The general outline consists of finding the permutation of particle indices from frame n to frame n + l, which minimizes the maximum distance traveled by a particle. If the particles move less than half a particle diameter D from one frame to the next then the process is relatively easy. Find the permutation of m, P m), such that = xw(nA)-xp( ,)(( + 1)A) D/2 for all m, where A is 

The typical approach finds all m,k) pairs with L, where L is the maximum distance that a particle might travel. Then test all possible k = Pq m) for 

Another case that can occur when L D/2 is that all or some of the particles have a mean motion which when corrected for would yield smaller frame-to-frame distances. In this case, modify = xm( S) +V(x)-xp( ,)((n +1)6),  

To be concrete, assume that the image to be tracked is of the form 

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Hollomon s ethos, combined with his ferocious energy and determination, and his sustained determination to recruit only the best researchers to join his group, over the next 15 years led to a sequence of remarkable innovations related to materials, including man-made diamond, high-quality thermal insulation, a vacuum circuit-breaker, products based on etched particle tracks in irradiated solids, polycarbonate plastic and, particularly, the Lucalox alumina envelope for a metal-vapour lamp. (Of course many managers besides Hollomon were involved.) A brilliant, detailed account of these innovations and the arrangements that made them possible was later written by Guy Suits and his successor as director, Arthur Bueche (Suits and Bueche 1967). Some of these specific episodes will feature later in this book, but it helps to reinforce the points made here about Hollomon s coneeption of broad research on materials if I point out that the invention of translucent alumina tubes for lamps was... 

Particle tracking can often be very helpful. Sometimes the particle distribution is directly asked for in other cases, it is an attractive way of illustrating the effectiveness of the ventilation system. 

In practice, particle tracking is usually performed in a Lagrangian frame of reference, and the motion of a particle is governed by... 

Devasenathipathy, S., Santiago, J. G., andTakehara, K., "Particle Tracking Techniques for Electrokinetic Micro-channel Elows, AnaZ. Chem.,Wo. 74,No. 15,2002,pp.3704-3713. 

Radioactive particle tracking (RPT) can be used to map the velocity field by tracking the position of a single radioactive tracer particle in a reactor. The particle which may consist of a polypropylene shell contains a radionuclide that emits y-rays. 

Direct measurement of particle velocity and velocity fluctuations in fluidized beds or riser reactors is necessary for validating multiphase models. Dudukovic [14] and Roy and Dudukovic [28] have used computer-automated radioactive particle tracking (CARPT) to foUow particles in a riser reactor. From their measurements, it was possible to calculate axial and radial solids diffusion as well as the granular temperature from a multiphase KTGF model. Figure 15.10 shows one such measurement... 

Kasumi A, Sako Y, Yamamoto M (1993) Confined lateral diffusion of membrane receptors as studied by single particle tracking (nanovid microscopy. Effects of calcium-induced differentiation in cultured epithelial cells. Biophys J 65 2021-2040... 

Single-particle tracking of endocytosis and exocytosis of single-walled carbon nanotubes in NIH-3T3 cells. Nano Letters, 8 (6), 1577-1585. 

Venkat, R. V., Stock, L. R., and Chalmers, J. J., Study of Hydrodynamics in Microcarrier Culture Spinner Vessels A Particle Tracking Velocimetry Approach, Biotechnol. Bioeng., 49 456 (1996)... 

Burch (1983) suggests that repair mechanisms cause a non neglectible complication for extrapolation from high to low doses and presents a modification of the linear-quadratic formula given above. Katz and Hofmann (1982) carried out an analysis of particle tracks with the result that they find no basis for a linear or linear-quadratic extrapolation to low doses. Van Bekkum and Bentvelzen (1982) present a hypothesis of the gene transfer-... 

Katz, R. and W. Hofmann, Biological Effects of Low Doses of Ionizing Radiations Particle Tracks in Radiobiology, Nuclear Instruments and Methods 203 433-442 (1982). 

Structure of Charged Particle Tracks in Condensed Media... 

Charged particle tracks in liquids are formally similar to cloud chamber or bubble chamber tracks. In detail, there are great differences in track lifetime and observability. Tracks in the radiation chemistry of condensed media are extremely short-lived and are not amenable to direct observation. Also, it must be remembered that in the cloud or bubble chamber, the track is actually seen at a time that is many orders of magnitude longer than the formation time of the track. The manifestation occurs through processes extraneous to track formation, such as condensation, formation of bubbles, and so forth. In a real sense, therefore, charged particle tracks in radiation chemistry are metaphysical constructs. 

In radiation chemistry, the track effect is synonymous with LET variation of product yield. Usually, the product measured is a new molecule or a quasi-stable radical, but it can also be an electron that has escaped recombination or a photon emitted in a luminescent process. Here LET implies, by convention, the initial LET, although the actual LET varies along the particle track also, the secondary electrons frequently represent regions of heterogeneous LET against the background of the main particle. 

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