One-dimensional rigorous hole theory of fluids: Internally constrained ensembles

A hole in a fluid is specified in a well-defined manner. The concentration of holes is a thermodynamic property of the fluid and we derive this concentration in three different ensembles for a one-dimensional fluid of hard rods. The thermodynamics of these rigorously defined holes is developed, and the properties of holes are explored. The ensemble in which the concentration of holes is maintained fixed exhibits dramatic properties. Finally, pair correlation functions for hard rods in the various ensembles are computed. Contrary to a frequently made assumption, the equilibrium number of holes is found to never be proportional to the probability of finding a single hole in the fluid. Constraining the concentration of holes as well as the density leads to dramatic structural effects prominently displayed by the pair correlation function. The ensemble in which the concentration of holes is fixed is an example of an internally constrained metastable system.     

A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

Background  

Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.     

Temperature-controlled change of charge transport mechanisms in nonionic water-in-oil microemulsions

 The temperature-controlled transition from the Stokes charge transport of aqueous nanodroplets to the intrinsic conduction of nanodroplet clusters in nonionic microemulsions was studied. Two different charge transport processes apparent from a minimum value of the conductance have been simulated based on straightforward physical models. Their predictions compare favourably with the observations. Received: 4 September 2001 Accepted: 20 September 2001     

Fourier analysis,correlation functions and nonadiabatic electron transfer: Wavepackets and exact representations

Summary We investigate the validity of several common approximations in the analysis of nonadiabatic intramolecular electron transfer rate constants. Utilizing the Fourier representation of the golden rule form, we study the evolution of the vibrational correlation function that represents the density-of-states-weighted Franck-Condon factor. In particular, we test the validity of the perturbation theoretic golden rule form and of the Gaussian wavepacket representation for the vibrational wavefunctions against numerically exact quantum mechanical propagations. Although specific cases are found in which both of these break down, for a wide range of conditions (including anharmonic behavior and frequency changes), both the Gaussian wavepacket representation and the golden rule are excellent approximations.     

Second-harmonic and sum-frequency generation in AgGaSe2 with tunable waveguide CO2 lasers

A tunable source is described, giving extensive coverage of a spectral region around 2000 cm^–1. A frequency self-calibration routine allows for the recording of Doppler-limited absorption profiles with an absolute accuracy of better than 10 MHz. The applicability of the source is demonstrated through measurements on the¹²C¹⁶O,¹²C¹⁷O, and¹²C¹⁸O isotopomers. Collision-broadening parameters and line strengths are determined, some of the data showing evidence of motional narrowing. Sensitivity limits are determined for linear absorption measurements as well as for photoacoustic absorption, and the feasibility of monitoring all three isotopomers with ppm sensitivity is demonstrated.Work supported by the Danish Science Research Council under grants no. 11-6866, 11-0116, and 11-0920     

Computational Prediction of 1H and 13C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

Prediction of chemical shifts in organic cations is known to be a challenge. In this article we meet this challenge for α-protonated alkylpyrroles, a class of compounds not yet studied in this context, and present a combined experimental and theoretical study of the ¹³C and ¹H chemical shifts in three selected pyrroles. We have investigated the importance of the solvation model, basis set, and quantum chemical method with the goal of developing a simple computational protocol, which allows prediction of ¹³C and ¹H chemical shifts with sufficient accuracy for identifying such compounds in mixtures. We find that density functional theory with the B3LYP functional is not sufficient for reproducing all ¹³C chemical shifts, whereas already the simplest correlated wave function model, Møller–Plesset perturbation theory (MP2), leads to almost perfect agreement with the experimental data. Treatment of solvent effects generally improves the agreement with experiment to some extent and can in most cases be accomplished by a simple polarizable continuum model. The only exception is the NH proton, which requires inclusion of explicit solvent molecules in the calculation.     

Compressing a Non-Planar Aromatic Heterocyclic [7]Helicene to a Planar Hetero[8]Circulene

This work describes a synthetic approach where a non-planar aromatic heterocyclic [7]helicene is compressed to yield a hetero[8]circulene containing an inner antiaromatic cyclooctatetraene (COT) core. This [8]circulene consists of four benzene rings and four heterocyclic rings, and it is the first heterocyclic [8]circulene containing three different heteroatoms. The synthetic pathway proceeds via a the flattened dehydro-hetero[7]helicene, which is partially a helicene and partially a circulene: it is non-planar and helically chiral as helicenes, and contains a COT motif like [8]circulenes. The antiaromaticity of the COT core is confirmed by nucleus independent chemical shift (NICS) calculations. The planarization from a helically π-conjugated [7]helicene to a fully planar heterocyclic [8]circulene significantly alters the spectroscopic properties of the molecules. Post-functionalization of the [7]helicenes and the [8]circulenes by oxygenation of the thiophene rings to the corresponding thiophene-sulfones allows an almost complete fluorescence emission coverage of the visible region of the optical spectrum (400–700 nm).