Molecular Hydrogen Emission from Protoplanetary Disks

We have modeled self-consistently the density and temperature profiles of gas and dust in protoplanetary disks, taking into account irradiation from a central star. Making use of this physical structure, we have calculated the level populations of molecular hydrogen and the line emission from the disks. As a result, we can reproduce the observed strong line spectra of molecular hydrogen from protoplanetary disks, both in the ultraviolet (UV) and the near-infrared, but only if the central star has a strong UV excess radiation.

Staurosporine-induced apoptosis and hydrogen peroxide-induced necrosis in two human breast cell lines.

The use of apoptosis-inducing agents in the treatment of malignant cancer is increasingly being considered as a therapeutic approach. In this study, the induction of apoptosis and necrosis was examined in terms of temporal dose responses, comparing a malignant and nonmalignant breast cell line. Staurosporine (SSP)-induced apoptosis and H2O2-induced necrosis were evaluated by two cytotoxicity assays, neutral red (NR) and methyl-thiazolyl tertrazolium (MTT), in comparison with a differential dye uptake assay, using Hoechst33342/propidium iodide (Hoechst/PI). Confirmatory morphological assessment was also performed by routine resin histology and transmission electron microscopy. Cell viability was assessed over a 0.5-48 h time course. In nonmalignant HBL-100 cells, 50 nM SSP induced 100% apoptosis after a 48 h exposure, while the same exposure to SSP caused only 4% apoptosis in metastatic T47D cells. Although complete apoptosis of both cell lines was induced by 50 M SSP, this effect was delayed in T47D (24 h) compared with HBL-100 (4 h). Results also showed that neither MTT or NR can distinguish between the modes of cell death, nor detect the early onset of apoptosis revealed by Hoechst/PI.

Positronium scattering by atomic hydrogen with inclusion of target excitation channels

Calculations are reported for positronium (Ps) scattering by atomic hydrogen (H) in the energy range 0-6.5 eV in a coupled- pseudostate approximation in which excitation and ionization channels of both the Ps and the H are taken into account. The approximation contains an accurate representation of the van der Waals coefficient. Results are presented for phase shifts, scattering lengths, effective ranges, and various cross sections including partial wave, total, and ortho-para conversion cross sections. An analysis of the possible spin transitions is provided and the energy of the positronium hydride (PsH) bound state is determined. Substantial differences are found from earlier work within the frozen target approximation, now clearly confirming the importance of target excitation channels. Good agreement is obtained with recent calculations of S-wave phase shifts and scattering lengths using the stabilization method. Convergence to the exact binding energy for PsH appears to be slow. Resonances corresponding to unstable states of the positron orbiting H- are seen in the electronic spin singlet partial waves. The importance of the H- formation channel is discussed.