[en] Past work by or group and others has shown the modulation of specific genes following exposure of cells to ionizing radiation. Many classes of genes have been found to be modulated in response to ionizing radiation, including those encoding cytoskeletal elements, cell growth arresting proteins, cytokines, and cellular oncogenes. The functions of this specific modulation of gene expression are currently being investigated by several groups: it has been suggested that gene modulation in response to radiation plays a role in the cellular repair of DNA damage, cell survival, or cellular transformation. Several groups have examined induction of nuclear proto-oncogenes following exposure to DNA-damaging agents. In all experiments, we examined modulation of gene expression by ionizing radiations in Syrian hamster embryo (SHE) fibroblasts, which are normal diploid cells that can be neoplastically transformed by low doses of ionizing radiations. Cells plated in 100-mm Petri plates containing 10 ml of medium were irradiated with ⁶⁰C γ-rays or fission-spectrum neutrons (0.85 MeV) from the JANUS reactor. All irradiations were performed at 37 degrees C on cycling cells; equitoxic doses of neutrons and γ-rays were selected on the basis of survival data

[en] ZnS crystallites with a core–shell heterostructure (ZnO–ZnS core–shell rods) and tube-like architecture were synthesized through a facile chemical solution route. Many tiny ZnS particles were clustered and compacted to form the shell layer of the ZnO–ZnS core–shell rods and the wall of the ZnS tubes during sulfidation of vertically aligned ZnO rods. X-ray diffraction and transmittance electron microscopy images revealed that the ZnS shell layer of the ZnO–ZnS core–shell rods and the wall of the tubes were polycrystalline, and that many domains or grain boundaries were present in the ZnS layers. The sensitivities of ZnO–ZnS core–shell rods and ZnS tubes to reducing and oxidizing gases differed. The ZnO–ZnS core–shell rods were more sensitive to reducing gases, whereas the ZnS tubes were more sensitive to oxidizing gases. The different gas sensing properties of the ZnS-based heterostructures and tubes are further discussed in relation to their microstructures. The heterojunction at the ZnO/ZnS interfacial region resulted in the differing gas sensing properties of the ZnS-based heterostructures and tubes in this study

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[en] Experiments were designed to examine the effects of radiation quality on specific gene expression within the first 3 h following radiation exposure in Syrian hamster embryo (SHE) cells. Preliminary work demonstrated the induction of c-fos and alpha-interferon genes following exposure to low-linear-energy-transfer (low-LET) radiations (X rays or gamma rays). More detailed experiments revealed induction of c-fos mRNA within the first 3 h following exposure to either X rays (75 cGy) or gamma rays (90 cGy). We could not detect induction of c-fos following exposure of SHE cells to fission-spectrum neutrons (high-LET) from the JANUS reactor administered at either high (12 cGy/min) or low (0.5 cGy/min) dose rates. Expression of alpha-interferon mRNA was similarly induced by low-LET radiations but only modestly by JANUS neutrons. The induction by gamma rays was dose-dependent, while induction by neutrons was specific for low doses and low dose rates. These experiments demonstrate the differential gene inductive response of cells following exposure to high- and low-LET radiations. These experiments suggest that these different qualities of ionizing radiation may have different mechanisms for inducing many of the cellular consequences of radiation exposure, such as cell survival and cell transformation

[en] JANUS fission-spectrum neutrons of Argonne National Laboratory's JANUS reactor administered at high (12cGy/min) dose-rates had little effect on Syrian hamster embryo resting cells, but at very low dose-rates (0.1 cGy/min) had a repressive effect on γ-actin mRNA accumulation. Increased accumulation of β-actin mRNA was detected following exposure of cells to neutrons administered at high dose-rates, but repression of β-actin mRNA was observed when neutrons were administered at low dose-rates. Cycling cells (unexposed and neutron irradiated) in all cases expressed higher levels of all actin-specific mRNAs than resting cells; β-actin mRNA (but not γ-actin mRNA) has induced to a greater extent in cycling cells than in resting cells during the first hour following neutron exposure. In resting cells, low dose-rate neutrons were more effective than low dose-rate γ-rays at repressing both γ- and β-actin mRNA accumulation. (author)

[en] In this study, oligomeric phenylsilsesquioxane (OPSQ)-titania optical thin films were synthesized and characterized. OPSQ with the end group of Si-OR was prepared first. Then, it was reacted with titanium (IV) n-butoxide, followed by spin-coating and multi-step curing to form the optical thin films. Highly homogeneous and transparent films were obtained at the titania content of 0-54.8 wt.%. The titania domain in the prepared films was estimated to be 8 nm from the TEM diagram. The optical properties of the prepared hybrid films could be tuned by the titania content. By increasing the titania content from 0 to 54.8 wt.%, the absorption edge and refractive index of the prepared film were increased from 277 to 322 nm and 1.527 to 1.759, respectively. These results could be explained from the growing size effect of the titania domain. The optical loss of the studied planar waveguide by using the OPSQ-titania as the core layer decreased from 0.568 to 0.415 dB cm^-1 as increasing the titania content from 0 to 15.9 wt.%. It is resulted from the reduction of the C-H bonding density of the hybrid materials by increasing the titania composition. The prepared films could have potential applications for high refractive index coating or optical waveguides

[en] The flow structures, drag coefficients (C_d) and vortex shedding characteristics around a single square cylinder and twin side-by-side square cylinders were experimentally investigated with various Reynolds numbers (Re) and gap ratios (g^*) in a vertical water tunnel. The Reynolds number (Re) and gap ratio (g^*) were 178 < Re < 892 and 0 ≤ g^* ≤ 2.5, respectively. The flow patterns and vortex shedding frequency were determined using the particle tracking flow visualization (PTFV). The flow structures, velocity properties, and drag coefficients were calculated using the particle image velocimetry (PIV). The topological flow patterns of vortex evolution processes were plotted and analyzed based on critical point theory. Furthermore, the flow structures behind twin side-by-side square cylinders were classified into three modes - single vortex-street mode, gap-flow mode and couple vortex-streets mode. The maximum C_d occurred in the single vortex-street mode, and the minimum C_d occurred in the gap-flow mode. The highest Strouhal number (St) occurred in the single vortex-street mode, and the lowest St occurred in the gap-flow mode

[en] Members of the protein kinase C (PKC) gene family have been shown to play an important role in tumor promotion and regulation of cell growth. Experiments were designed to examine the effects of different qualities of ionizing radiation administered at a variety of doses and dose rates on the expression of PKC-specific mRNA in confluent Syrian hamster embryo cells. The results of these experiments showed that low-linear energy of transfer (LET) radiations (such as X-rays and gamma-rays) can induce increased expression of PKC mRNA within 1 h after radiation exposure. Levels of expression of PKC mRNA were increased 4- to 6-fold over unirradiated controls. Dose effects were evident, with increased accumulation of PKC mRNA at higher doses (ranging from 6 to 200 cGy). Induction of PKC mRNA occurred at a time when total cellular transcription was reduced following irradiation. Similar exposure of the cells to fission spectrum JANUS neutrons, however, had little effect on PKC mRNA expression. Modest induction (2-fold compared to untreated cells) occurred when irradiations were at very low dose rates (0.5 cGy/min). These results suggest that induction of PKC mRNA may be a step in the transformation process caused by ionizing radiation. In addition, they demonstrate that different qualities of radiation may regulate PKC differently

[en] The relationship has been examined between the survival curves obtained with UV light (254 nm) and those obtained with a near UV source (Westinghouse Sun Lamps, FS20) simulating sunlight for cultured Chinese hamster cells, C3H mouse cells, and HeLa cells. In no case do the 'sunlight' survival curves have the same shape as the UV survival curves. Also, the combined lethal effects of UV and near-UV, sunlight-like exposures are not entirely additive. Hence it is concluded that (1) the cell-killing photolesions induced by these radiations are at most only partly the same, and (2) in view of (1), caution should be exercised in predicting near UV-induced dose-dependencies of other end points based upon observations with UV. (author)