Dielectric response and its light-induced change in undoped alpha-Si : H films below 13 MHz

The low frequency (<13 MHz) dielectric response and its light-induced change in undoped a-Si:H were investigated in detail. The dielectric constant epsilon (the real part) in this range decreases with illumination time: following a stretched exponential law similar to that found for other light-induced changes. The saturation relative change was about 0.1-0.2 % for the measured samples. The change is fading away either after repeated illumination-annealing training or by aging at room temperature. The present results indicate some rearrangement of the whole Si network caused by light soaking.

Light-induced changes in diphasic nanocrystalline silicon films and solar cells

A series of diphasic nanocrystalline silicon films and solar cells was prepared using different hydrogen dilution ratios of silane by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). It was observed that after light soaking the open circuit voltage (V-oc) of the diphasic solar cells increased, while that of amorphous silicon solar cells decreased. Raman scattering spectroscopy was performed on the series of diphasic silicon films before and after light soaking. It was found that after light soaking the nanostruclures in the diphasic nanocrystalline silicon films were changed. Both the grain sizes and grain volume fraction reduced, while the grain boundary components increased. These results provide experimental evidence for the conjecture that the light-induced increase in V-oc of the diphasic nanocrystalline solar cells might be induced by the changes in the nanostructure of the intrinsic layer. (c) 2006 Elsevier B.V. All rights reserved.

Light induced rapid thermal diffusion of boron atom in silicon

国家自然科学基金

Light-induced change of Si-H bond absorption in hydrogenated amorphous silicon

Device-quality a-Si:H films were prepared by glow discharge CVD with pure or H-diluted silane as well as by hot-wire CVD. The hydrogen content was varied from similar to 2 to 15 at. %. The Si-H bond absorption and its light-soaking-induced changes were studied by IR and differential IR absorption spectroscopes. The results indicate that the more stable sample exhibits an increase of the absorption at wave number similar to 2000 cm(-1), and the less stable one exhibits a decrease at similar to 2040 cm(-1) and an increase at similar to 1880 cm(-1).

Gamma ray-induced bystander effect in tumour glioblastoma cells: a specific study on cell survival, cytokine release and cytokine receptors.

Recent experimental evidence has challenged the paradigm according to which radiation traversal through the nucleus of a cell is a prerequisite for producing genetic changes or biological responses. Thus, unexposed cells in the vicinity of directly irradiated cells or recipient cells of medium from irradiated cultures can also be affected. The aim of the present study was to evaluate, by means of the medium transfer technique, whether interleukin-8 and its receptor (CXCR1) may play a role in the bystander effect after gamma irradiation of T98G cells in vitro. In fact the cell specificity in inducing the bystander effect and in receiving the secreted signals that has been described suggests that not only the ability to release the cytokines but also the receptor profiles are likely to modulate the cell responses and the final outcome. The dose and time dependence of the cytokine release into the medium, quantified using an enzyme linked immunosorbent assay, showed that radiation causes alteration in the release of interleukin-8 from exposed cells in a dose-independent but time-dependent manner. The relative receptor expression was also affected in exposed and bystander cells.

Differential modulation of a radiation-induced bystander effect in glioblastoma cells by pifithrin-alpha and wortmannin

The implication of radiation-induced bystander effect (RIBE) for both radiation protection and radiotherapy has attracted significant attention, but a key question is how to modulate the RIBE. The present study found that, when a fraction of glioblastoma cells in T98G population were individually targeted with precise helium particles through their nucleus, micronucleus (MN) were induced and its yield increased non-linearly with radiation dose. After co-culturing with irradiated cells, additional MN could be induced in the non-irradiated bystander cells and its yield was independent of irradiation dose, giving direct evidence of a RIBE. Further results showed that the RIBE could be eliminated by pifithrin-alpha (p53 inhibitor) but enhanced by wortmannin (PI3K inhibitor). Moreover, it was found that nitric oxide (NO) contributed to this RIBE, and the levels of NO of both irradiated cells and bystander cells could be extensively diminished by pifithrin-alpha but insignificantly reduced by wortmannin. Our results indicate that RIBE can be modulated by p53 and PI3K through a NO-dependent and NO-independent pathway, respectively. (C) 2009 Elsevier B.V. All rights reserved.

OBSERVATION OF BIPHASIC KINETICS IN LIGHT-INDUCED SPIN-STATE CROSSOVER IN AN IRON(II) COMPLEX IN SOLUTION

Relaxation of the 1A1 half arrow right over half arrow left 5T2 spin equilibrium in acetonitrile of the complex of Fe(II) with the multidentate pyridyl macrocyclic ligand N,N',N''-tris(2-pyridylmethyl)-1,4,7-triazacyclodecane (tp[10]aneN3) after perturbation by a pulsed laser provides the first example of biphasic kinetics for spin crossover in solution with a fast (tau

Late-time supernova light curves:The effect of internal conversion and auger electrons

Energy release from radioactive decays contributes significantly to supernova light curves. Previous works, which considered the energy deposited by ?-rays and positrons produced by Ni, Co, Ni, Co, Ti and Sc, have been quite successful in explaining the light curves of both core collapse and thermonuclear supernovae. We point out that Auger and internal conversion electrons, together with the associated X-ray cascade, constitute an additional heat source. When a supernova is transparent to ?-rays, these electrons can contribute significantly to light curves for reasonable nucleosynthetic yields. In particular, the electrons emitted in the decay of Co, which are largely due to internal conversion from a fortuitously low-lying 3/2 state in the daughter Fe, constitute an additional significant energy-deposition channel. We show that when the heating by these electrons is accounted for, a slow-down in the light curve of SN 1998bw is naturally obtained for typical hypernova nucleosynthetic yields. Additionally, we show that for generic Type Ia supernova yields, the Auger electrons emitted in the ground-state to ground-state electron capture decay of Fe exceed the energy released by the Ti decay chain for many years after the explosion. © 2009 RAS.

Investigating the influence of respiratory motion on the radiation induced bystander effect in modulated radiotherapy

Respiratory motion introduces complex spatio-temporal variations in the dosimetry of radiotherapy and may contribute towards uncertainties in radiotherapy planning. This study investigates the potential radiobiological implications occurring due to tumour motion in areas of geometric miss in lung cancer radiotherapy. A bespoke phantom and motor-driven platform to replicate respiratory motion and study the consequences on tumour cell survival in vitro was constructed. Human non-small-cell lung cancer cell lines H460 and H1299 were irradiated in modulated radiotherapy configurations in the presence and absence of respiratory motion. Clonogenic survival was calculated for irradiated and shielded regions. Direction of motion, replication of dosimetry by multi-leaf collimator (MLC) manipulation and oscillating lead shielding were investigated to confirm differences in cell survival. Respiratory motion was shown to significantly increase survival for out-of-field regions for H460/H1299 cell lines when compared with static irradiation (p <0.001). Significantly higher survival was found in the in-field region for the H460 cell line (p <0.030). Oscillating lead shielding also produced these significant differences. Respiratory motion and oscillatory delivery of radiation dose to human tumour cells has a significant impact on in- and out-of-field survival in the presence of non-uniform irradiation in this in vitro set-up. This may have important radiobiological consequences for modulated radiotherapy in lung cancer. 

Realization of Optical Logic Gates Using the Thermal Lens Effect

A sensitive method based on the principle of photothermal phenomena to realize optical logic gates is presented. A dual beam thermal lens method using low power cw lasers in a dye-doped polymer can be very effectively used as an alternate technique to perform the logical function such as NAND, AND and OR.