An alternate derivation of the Herman—Kluk (coherent state) semiclassical initial value representation of the time evolution operator

It is shown that the Herman—Kluk (or coherent state) initial value representation (IVR) of the semiclassical propagator (time evolution operator) can be obtained by application of a modified Filinov filtering procedure to the standard Van Vleck (coordinate space) expression for the propagator. This further illustrates the effective equivalence, semiclassically, of these various IVRs.     

DEVELOPMENT AND VALIDATION OF REACTION WHEEL DISTURBANCE MODELS: EMPIRICAL MODEL

Accurate disturbance models are necessary to predict the effects of vibrations on the performance of precision space-based telescopes, such as the Space Interferometry Mission (SIM). There are many possible disturbance sources on such spacecraft, but mechanical jitter from the reaction wheel assembly (RWA) is anticipated to be the largest. A method has been developed and implemented in the form of a MATLAB toolbox to extract parameters for an empirical disturbance model from RWA micro-vibration data. The disturbance model is based on one that was used to predict the vibration behaviour of the Hubble Space Telescope (HST) wheels and assumes that RWA disturbances consist of discrete harmonics of the wheel speed with amplitudes proportional to the wheel speed squared. The MATLAB toolbox allows the extension of this empirical disturbance model for application to any reaction wheel given steady state vibration data. The toolbox functions are useful for analyzing RWA vibration data, and the model provides a good estimate of the disturbances over most wheel speeds. However, it is shown that the disturbances are under-predicted by a model of this form over some wheel speed ranges. The poor correlation is due to the fact that the empirical model does not account for disturbance amplifications caused by interactions between the harmonics and the structural modes of the wheel. Experimental data from an ITHACO Space Systems E-type reaction wheel are used to illustrate the model development and validation process.     

On the Location of Zeros of Certain Classes of Polynomials with Applications to Numerical Analysis

A polynomial is said to be of type (p₁, p₂, p₃) relative tothe unit circle if it has p₁ zeros interior to, p₂ on, and p₃exterior to the unit circle. Stability criteria frequently arisewhere a polynomial or a family of polynomials must be shownto be of type (p₁, p₂, 0) or of type (p₁, 0, 0). Here we reconsiderthe practical problem of showing that a polynomial is of oneor other of these types, and we show that the testing of a polynomialof degree n may always be reduced to the testing of one of degreen–1. The simplicity of the method is illustrated by itsapplication to several well known difference schemes for partialdifferential equations.     

A Finite Element Moving Boundary Computation with an Adaptive Mesh

The finite element method is used to obtain an accurate approximationto the solution of a well-known moving boundary problem. Thealgorithm uses the projective nature of the approximate solutionto follow the movement of the boundary, and the element notesare adapted as the region of the solution changes.     

Monte Carlo simulations of an amphiphilic polymer at a hydrophobic/hydrophilic interface

Monte Carlo simulations have been carried out for an off-lattice model of an amphiphilic polymer at a hydrophobic/hydrophilic interface. The model system consists of a polynorbornene backbone with poly(ethylene oxide) (PEO) grafts modelled atomistically at an idealized interface between hydrophobic and hydrophilic regions, which are represented by external potentials. Results are presented for the distribution of PEO chain ends, and the density of PEO segments perpendicular to the surface. The latter is used to provide predictions for neutron reflectivity profiles normal to the surface as a function of the lateral confinement of the PEO grafts. At low surface coverage the simulation results are found to be in good agreement with experimental neutron scattering results from similar polymers studied at the water/air interface.     

DIFFERENT EFFECTS OF RAD GENES OF SACCHAROMYCES CEREVISIAE ON INCISIONS OF INTERSTRAND CROSSLINKS AND MONOADDUCTS IN DNA INDUCED BY PSORALEN PLUS NEAR UV LIGHT TREATMENT

Abstract— The RAD1, RAD2, RAD3 and RAD4 genes of Saccharomyces cerevisiae are required for incising DNA containing UV induced pyrimidine dimers or psoralen plus 360 nm light induced interstrand crosslinks. We have now determined if these genes are also required for incising DNA at psoralen plus 360 nm light induced monoadducts. For distinguishing between incision breaks occurring at crosslinks and at monoadducts. we have used the cdc9-2 mutant, defective in DNA ligase activity at the restrictive temperature, and the radl-2 cdc9-2, rad2-5 cdc9-2 , rad3-2 cdc9-2 and rad4-4 cdc9-2 double mutant combinations. We conclude that the radl, rad2 , and rad4 mutants are defective in incising DNA both at crosslinks and monoadducts, whereas the rad3 mutant is proficient in incising DNA at monoadducts but not at crosslinks.     

DESIGN AND CHARACTERIZATION OF SEVELAMER HYDROCHLORIDE: A NOVEL PHOSPHATE-BINDING PHARMACEUTICAL

ABSTRACT

Sevelamer hydrochloride (polyallylamine crosslinked with epichlorohydrin) is a polymeric hydrogel that has been developed as an oral pharmaceutical to prevent the absorption of dietary phosphate by kidney dialysis patients. It has been found to bind to phosphate in vitro, and to do so more effectively than a wide range of other cationic polymers. It shows a preference for phosphate over other intestinal anions, such as chloride and bicarbonate. The preference for phosphate is believed to be due to its dianion character, and may also involve hydrogen bonding. The absorption of phosphate in vitro is rapid (less than a minute) relative to the time of passage of such a drug through the small intestine (hours). It has also been found to prevent the absorption of dietary phosphate in vivo and in humans, and is presently awaiting FDA approval.