On the viscosity and thermal conductivity of dense gases

The modified Enskog theory (MET) of transport in dense gases can be used to predict the density dependence of transport coefficients provided the function y, which is a product of a dimensionless density and a pair correlation function, is known as a function of density. In this communication we consider the inverse problem, extracting information on the y function from measured transport property data, both to resolve some peculiarities found by others, and to provide the basis for improved MET predictions.     

The benefits of multibit chaotic sigma delta modulation

Sigma delta modulation is a popular technique for high-resolution analog-to-digital conversion and digital-to-analog conversion. We investigate chaotic phenomena in multibit first-order sigma-delta modulators. Particular attention is placed on the occurrence of periodic orbits or limit cycles. These may result in idle tones audible to the listener when sigma-delta modulation is used for audio signal processing. One suggested method of eliminating idle tones is the operation of a sigma delta modulator in the chaotic regime. Unfortunately, chaotic modulation of a first order sigma delta modulator is a poor system for signal processing. We show that minor variations on a traditional first order sigma-delta modulator, together with a multibit implementation, may be used to produce an effective, stable chaotic modulator that accurately encodes the input and helps remove the presence of idle tones. (c) 2001 American Institute of Physics.     

Thermodynamic properties of binary mixtures containing aldehydes. II. Liquid-vapor equilibria in normal or branched alkanal + normal alkane mixtures: Analysis in terms of a quasichemical group-contribution model

Recent liquid-vapor equilibrium data for three alkanal + n-alkane mixtures are examined on the basis of the surface-interaction version of the quasichemical group-contribution theory used in Part I to correlate and predict excess enthalpies and excess Gibbs energies for such mixtures. The predictions prove to be accurate to better than 10%. Using the new data, revised interaction parameters are proposed for the estimation of liquid-vapor equilibrium for normal or branched alkanal + normal alkane mixtures.     

A cluster-variational investigation of static density waves in nuclear matter

A detailed comparison of the energy of the uniform phase and of phases exhibiting periodic density fluctuation is presented for extended nuclear systems. The short-range correlations are taken to be of Jastrow type and the calculations are carried through two-body cluster order. With semi-realistic central potentials containing hard cores, no energetic advantage of a non-uniform state is detected, either in symmetrical nuclear matter or in pure neutron matter. However, the analysis gives useful information on the conditions favoring an instability of the homogeneous phase and points to the essential role of the tensor force in the formation of spin-(isospin-) density waves.     

Measurement of the polarization in backward-angle π−p elastic scattering at 2.93 and 3.25 GeV/c

Polarization in π^?p elastic scattering, with emphasis over the backward region, has been measured at 2.93 and 3.25 GeV/c. We observe large changes in polarization compared with existing data above and below these energies. Our data may be useful in determining the properties of resonances and in understanding baryon exchanges.     

Synthesis and Biological Evaluation of 14‐Alkoxymorphinans. Part 19

The 14‐O‐benzylnaltrexones 3 – 6 were prepared from naltrexone ( 2 ) in several steps. The novel compounds were biologically evaluated in radioligand binding and in [³⁵S]GTPγS functional assays in comparison to the reference compound naltrexone. In the binding assay, compounds 3 – 6 exhibited preference for κ opioid receptors, while the parent compound naltrexone shows preference for μ receptors. In the functional assay, μ antagonist potency of compounds 3 – 6 was in the range of naltrexone, while κ antagonist potency was considerably higher for most novel compounds in comparison to naltrexone.     

The Moduli Space of n+1 Points in Complex Hyperbolic n-Space

The structure of the space of orbits of PU(n, 1) acting on (n+1)-tuples of points in complex hyperbolic space is characterized in terms of side lengths and angular invariants. The more general situation in which some of the points lie on the boundary of complex hyperbolic space is described in terms of other basic invariants.     

Cytotoxic macrolides from a new species of the deep-water marine sponge Leiodermatium

Chemical investigation of a new species of the deep-water marine sponge Leiodermatium, collected by manned submersible at a depth of 740 feet in Palau, resulted in the isolation of two cytotoxic macrolides, leiodolides A (1) and B (2). The leiodolides represent the first members of a new class of 19-membered ring macrolides, incorporating several unique functional groups including a conjugated oxazole ring, a bromine substituent, and an alpha-hydroxy-alpha-methyl carboxylic acid side-chain terminus. The structures of these new metabolites were established by spectroscopic analysis, chemical modification, and degradation. The relative and absolute stereochemistries at most chiral centers were assigned on detailed interpretation of spectroscopic data, coupled with chemical degradation and application of the modified Mosher ester method. Leiodolide A showed significant cytotoxicity (average GI(50) = 2.0 microM) in the National Cancer Institute's 60 cell line panel with enhanced activity against HL-60 leukemia and OVCAR-3 ovarian cancer cell lines.