[en] The repair of radiation-induced DNA double-strand breaks (DSBs) is analyzed kinetically. It is assumed that a fraction of the damaged sites in the DNA duplex are irreparable. The kinetic model takes the effect of radiation dose into account. The analysis of the available experimental data reveals that, although the number of irreparable DSBs is a quadratic function of radiation dose, the normalized number of irreparable DSBs correlates linearly with this variable

[en] Letter to the editor

[en] Selective tungsten deposition was carried out in a Varian/Torrex radiantly heated single-wafer cold wall 5101 CVD reactor. The wafer holder configuration is such that the wafer is heated directly by halogen lamps, allowing the use of a variety of wafer heating rates. A unique feature of this system is that the wafer temperature is measured directly by the use of an infra-red sensor mounted on the bottom plate. This configuration results in maximum process flexibility, which the authors show as essential for selective tungsten process. The deposition of one micron of selective tungsten has been realized in a reproducible basis, and, in a limited set of experiments, selective deposition was carried out for oxide thickness of up to --1.7 microns. Silicon consumption is kept to a minimum by insuring good nucleation of tungsten on the contact at the beginning of the process. In this manner a one micron deposition results in less than 300 angstroms of silicon loss. Deposition rate versus temperature data is presented for a limited set of process conditions. These data illustrate the behavior of selective tungsten kinetics for a cold wall chamber in which the wafer temperature is known. Data are also presented on the temperature uniformity of this system. Wafer cleaning prior to selective tungsten deposition will be discussed in reference to contact size and type of clean used

[en] Flavonoids exist extensively in plants and Chinese herbs, and several biological effects of flavonoids have been demonstrated. The antitumor effects in colorectal carcinoma cells (HT29, COLO205, and COLO320HSR) of eight flavanones including flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone, 7-OH flavanone, naringenin, nargin, and taxifolin were investigated. Results of the MTT assay indicate that 2'-OH flavanone showed the most potent cytotoxic effect on these three cells, and cell death induced by 2'-OH flavanone was via the occurrence of DNA ladders, apoptotic bodies, and hypodiploid cells, all characteristics of apoptosis. Induction of caspase 3 protein processing and enzyme activity associated with cleavage of poly(ADP-ribose) polymerase (PARP) was identified in 2'-OH flavanone-treated cells, and a peptidyl inhibitor (Ac-DEVD-FMK) of caspase 3 attenuated the cytotoxicity of 2'-OH flavanone in COLO205 and HT-29 cells. Elevation of p21 (but not p53) and a decrease in Mcl-1 protein were found in 2'-OH flavanone-treated COLO205 and HT-29 cells. Elevation of intracellular reactive oxygen species (ROS) was detected in 2'-OH flavanone-treated cells by the 2',7'-dichlorodihydrofluorescein diacetate (DCHF-DA) assay, and ROS scavengers including 4,5-dihydro-1,3-benzene disulfonic acid (tiron), catalase, superoxide dismutase (SOD), and pyrrolidine dithiocarbamate (PDTC) suppressed the 2'-OH flavanone-induced cytotoxic effect. Subcutaneous injection of COLO205 induced tumor formation in nude mice, and 2'-OH flavanone showed a significant inhibitory effect on tumor formation. The appearance of apoptotic cells with H and E staining, and an increase in p21, but not p53, protein by immunohistochemistry were observed in tumor tissues under 2'-OH flavanone treatment. Primary tumor cells (COLO205-X) derived from a tumor specimen elicited by COLO205 were established, and 2'-OH flavanone showed an significant apoptotic effect in COLO205-X cells in accordance with the appearance of DNA ladders, caspase 3 protein processing, PARP protein cleavage, and increasing p21 protein. These results revealed in vitro, ex vivo, and in vivo antitumor activities of 2'-OH flavanone via apoptosis induction, and indicates that 2'-OH flavanone is an active compound worthy of development for cancer chemotherapy

[en] Two types of double gate electrodes were fabricated by several steps such as photolithography and thin-film deposition methods. The electron sources of these double gate electrodes were generated by multi-walled carbon nanotubes (MWCNTs). The aspect ratio of the MWCNTs grown via thermal chemical vapor deposition method was very high. Thus, the field emission performances of double gate electrodes were excellent and met the demand for application. At an applied voltage 10 V, the current reached 29 μA. (authors)

[en] To understand the feasibility and characteristics of a depth-of-interaction (DOI) imaging detector with an ends-read edge-on configuration, a prototype detector unit having a long crystal array was developed and tested in this study. A test platform providing precise positioning and equipped with a collimated line positron source was installed for the experiments and data acquisition. Methods for event (3D) position estimations were implemented and the acquired data were processed and analyzed. The results show that good event position distinguishability is performed in y (along line source distributions) and z (along gamma-ray incident, i.e. the depth) directions. While in x (along the long crystals) direction, results of position estimations (i.e. the x-coordinates) show accurate correspondence to their target locations, but with poor precision, i.e. wide distribution (average 15 mm) of the estimated positions. With photopeak-index filtering, the estimation error of x-coordinates was improved (average 0.8 mm). For the imprecise x-coordinate estimations, the behavior and characteristics of the detector unit were understood by analyzing the experimental data. Energy resolutions and attenuation lengths were found to be essential factors influencing the precision of x-coordinate estimations. It is also found that by changing a scintillation material with better energy resolution and performing a proper crystal surface treatment, an ends-read edge-on imaging detector which is practical for applications can be developed.

[en] Carbonaceous adsorbents with controllable surface areas were chemically activated with KOH at 780 deg. C from char that had been carbonized from cane pith at 450 deg. C. The pore properties including the BET surface area, pore volume, pore size distribution, and mean pore diameter of these activated carbons were characterized and derived using the t-plot method based on N₂ adsorption isotherms. The activated cane pith carbons, with KOH/char ratios of 2-6, exhibited BET surface areas ranging from 912 to 2299 m² g^-1. The scanning electron microscopic (SEM) observations revealed that the surface morphology of honeycombed holes on all activated cane pith carbons was significantly influenced by the KOH/char ratio. The adsorption kinetics and equilibrium isotherms of acid blue 74, methylene blue, basic brown 1, p-nitrophenol, p-chlorophenol, p-cresol, and phenol from water at 30 deg. C on the activated carbons were studied. The adsorption kinetics were suitably described by a simplified kinetic model, the Elovich equation. All adsorption equilibrium isotherms were in agreement with the Langmuir equation, and were used to compare the covered area (S _c/S _p) of the activated carbons at different KOH/char ratios. The high-surface-area activated carbons were proven to be promising adsorbents for pollution control and for other applications

[en] The strong coupling between the spin, orbital and lattice leads to abundant phenomena in oxide SC/FM superlattice films, such as a magnetic proximity effect, a giant magnetoresistance and a SC induced magnetic depletion in the FM layers. In this study, superlattice of [YBCO(10nm)/LSMO (10nm)]4 multilayer film were grown on SrTiO₃ (001) substrates by a UHV pulse laser deposition technique. To reveal the magnetic structure fluctuation at SC/FM interfaces, a polarized neutron reflectometry (PNR) measurements were carried out at 300 K (applied magnetic field 1.4mT & 1T) and at 8 K (applied magnetic field 1.4mT field cooled under 1T) in the Platypus beam line of ANSTO. The reflectivity intensities of each curve span over 5 orders of magnitude which reflect good interface quality with very low roughness. PNR data at 300 K where YBCO layers are in normal metal states shows presence of depletion layers at the SC/FM interfaces near the YBCO side. This depletion layers acts like YBCO in a normal metal state and is independent of the polarization of the incident Neutron beam. At low temperature, the depletion layer transfers to a magnetic layer with characteristics very similar both on the scattering length density and magnetization to LSMO layers. A thin interface layer near the YBCO/LSMO interface on the YBCO side shows destruction of superconductivity and induces a mall magnetic moment antiparallel to Mn moment FM layers. This phenomena can be explained on the basis of inverse proximity effect, where the suppression of superconductivity accompanying a Cu magnetic moment can be induced antiparallel to Mn moment as observed earlier by D. K. Satapathy et al.

[en] Quantum dots (QDs) are semiconducting nanocrystals that have photoluminescent (PL) properties brighter than fluorescent molecules and do not photo-bleach, ideal for in vivo imaging of diseased tissues or monitoring of biological processes. Near-infrared (NIR) fluorescent light within the window of 700–1000 nm, which is separated from the major absorption peaks of hemoglobin and water, has the potential to be detected several millimeters under the surface with minimal interference from tissue autofluorescence. Here we report the synthesis and bioimaging demonstration of a new NIR QDs system, namely, CdPbS, made by an aqueous approach with 3-mercaptopropionic acid (MPA) as the capping molecule. The aqueous-synthesized, MPA-capped CdPbS QDs exhibited an NIR emission in the range of 800–950 nm with x_i ≥ 0.3, where x_i denotes the initial Pb molar fraction during the synthesis. Optimal PL performance of the CdPbS QDs occurred at x_i = 0.7, which was about 4 nm in size as determined by transmission electron microscopy, had a rock salt structure and a quantum yield of 12%. Imaging of CdPbS QDs was tested in membrane staining and transfection studies. Cells transfected with CdPbS QDs were shown to be visible underneath a slab of chicken muscle tissue of up to 0.7 mm in thickness without the use of multiple-photon microscopy. (paper)

[en] Despite the fact that polystyrene (PS) spheres have been developed as polymeric carriers or matrices for various biomedical applications, the synthesis of PS spheres is time-consuming. This work describes the fabrication of a uniform PS sphere, coated with silver nanoparticles (Ag–PS), by simultaneous photoinduced polymerization and reduction fabricated using x-rays in aqueous solution without any initiator. The solution contains only styrene, silver ions (Ag⁺), and poly(vinyl pyrrolidone) (PVP) as a stabilizer. The proposed mechanism of the formation of the Ag–PS nanocomposite spheres involves the generation of radicals in the aqueous solution to induce PS polymerization and the reduction of Ag. The distribution of the sizes of the core PS spheres in the Ag–PS nanocomposite spheres was systematically examined as a function of irradiation time, concentration of styrene, and amount of PVP. Ag–PS nanocomposite spheres exhibit antimicrobial activity against bacteria (Escherichia coli and Staphylococcus aureus). Additionally, the cationic (vinylbenzyl)trimethylammonium (TMA) monomer was photopolymerized to form positively charged TMA–PS spheres as gene carriers with uniquely low cytotoxicity. Given these design advantages, the method proposed herein is simpler than typical approaches for synthesizing PS spheres with functionalized groups and PS spheres coated with Ag nanoparticles. (paper)