Quantum theory of the far-off-resonance continuous-wave Raman laser: Heisenberg-Langevin approach

We present the quantum theory of the far-off-resonance continuous-wave Raman laser using the Heisenberg-Langevin approach. We show that the simplified quantum Langevin equations for this system are mathematically identical to those of the nondegenerate optical parametric oscillator in the time domain with the following associations: pump pump, Stokes signal, and Raman coherence idler. We derive analytical results for both the steady-state behavior and the time-dependent noise spectra, using standard linearization procedures. In the semiclassical limit, these results match with previous purely semiclassical treatments, which yield excellent agreement with experimental observations. The analytical time-dependent results predict perfect photon statistics conversion from the pump to the Stokes and nonclassical behavior under certain operational conditions.

Low-temperature single-crystal Raman and neutron-diffraction study of the hydrogenous ammonium copper(II) tutton salt and the deuterated analogue in the metastable state

Low-temperature (15 K) single-crystal neutron-diffraction structures and Raman spectra of the salts (NX4)(2)[CU(OX2)(6)](SO4)(2), where X = H or D, are reported. This study is concerned with the origin of the structural phase change that is known to occur upon deuteration. Data for the deuterated salt were measured in the metastable state, achieved by application of 500 bar of hydrostatic pressure at similar to303 K followed by cooling to 281 K and the subsequent release of pressure. This allows for the direct comparison between the hydrogenous and deuterated salts, in the same modification, at ambient pressure and low temperature. The Raman spectra provide no intimation of any significant change in the intermolecular bonding. Furthermore, structural differences are few, the largest being for the long Cu-O bond, which is 2.2834(5) and 2.2802(4) Angstrom for the hydrogenous and the deuterated salts, respectively. Calorimetric data for the deuterated salt are also presented, providing an estimate of 0.17(2) kJ/mol for the enthalpy difference between the two structural forms at 295.8(5) K. The structural data suggest that substitution of hydrogen for deuterium gives rise to changes in the hydrogen-bonding interactions that result in a slightly reduced force field about the copper(II) center. The small structural differences suggest different relative stabilities for the hydrogenous and deuterated salts, which may be sufficient to stabilize the hydrogenous salt in the anomalous structural form.

Effect of time of harvest of budded virus on the selection of baculovirus FP mutants in cell culture

Rapid formation and selection of FP (few polyhedra) mutants occurs during serial passaging of Helicoverpa armigera nucleopolyhedrovirus (HaSNPV) in insect cell culture. The production of HaSNPV for use as biopesticides requires the passaging of the virus over a number of passages to produce enough virus inoculum for large-scale fermentation. During serial passaging in cell culture, FP mutants were rapidly selected, resulting in declined productivity and reduced potency of virus. Budded virus (BV) is usually harvested between 72 and 96 h postinfection (hpi) in order to obtain a high titer virus stock. In this study, the effect of tine of harvest (TOH) for BV on the selection rate of HaSNPV FP mutants during serial passaging was investigated. BV were harvested at different times postinfection, and each series was serially passaged for six passages. The productivity and percentage of FP mutants at each passage were determined. It was found that the selection of FP mutants can he reduced by employing an earlier TOH for BV. Serial passaging with BV harvested at 48 hpi showed a slower accumulation of FP mutants compared to that of BV harvested after 48 hpi. Higher cell specific yields were also maintained when BV were harvested at 48 hpi. When BV that were formed between 48 and 96 hpi were harvested and serially passaged, FP mutants quickly dominated the virus population. This suggests that the V formed and released between 48 and 96 hpi are most likely from FP mutant infected cells.

Effect of pore-network connectivity on multicomponent adsorption of large molecules

The effect of pore-network connectivity on binary liquid-phase adsorption equilibria using the ideal adsorbed solution theory (LAST) was studied. The liquid-phase binary adsorption experiments used ethyl propionate, ethyl butyrate, and ethyl isovalerate as the adsorbates and commercial activated carbons Filtrasorb-400 and Norit ROW 0.8 as adsorbents. As the single-component isotherm, a modified Dubinin-Radushkevich equation was used. A comparison with experimental data shows that incorporating the connectivity of the pore network and considering percolation processes associated with different molecular sizes of the adsorptives in the mixture, as well as their different corresponding accessibility, can improve the prediction of binary adsorption equilibria using the LAST Selectivity of adsorption for the larger molecule in binary systems increases with an increase in the pore-network coordination number, as well with an increase in the mean pore width and in the spread of the pore-size distribution.