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This work clearly demonstrates that the X Ray Reflectometry technique (XRR), extensively used to assess the quality of microelectronic devices can be a useful tool to study the first stages of ion beam mixing. This technique allows measuring the evolution of the Si concentration profile in irradiated Cr/Si layers. From the analysis of the XRR profiles, it clearly appears that the Si profile cannot be described by a simple error function.
To examine the prevalence of human pathogens carried by rats in urban areas in Hanoi and Hai Phong, Vietnam, we live-trapped 100 rats in January 2011 and screened them for a panel of bacteria and viruses. Antibodies against Leptospira interrogans (22·0%), Seoul virus (14·0%) and rat hepatitis E virus (23·0%) were detected in rats, but antibodies against Yersinia pestis were not detected. Antibodies against L. interrogans and Seoul virus were found only in adult rats. In contrast, antibodies to rat hepatitis E virus were also found in juvenile and sub-adult rats, indicating that the transmission mode of rat hepatitis E virus is different from that of L. interrogans and Seoul virus. Moreover, phylogenetic analyses of the S and M segments of Seoul viruses found in Rattus norvegicus showed that Seoul viruses from Hai Phong and Hanoi formed different clades. Human exposure to these pathogens has become a significant public health concern.
We have investigated microstructures in both the antiferroelectric (AFE) and relaxor states of Pb(In1/2Nb1/2)O3 (PIN) with the perovskite structure by a transmission electron microscopy (TEM). Electron diffraction (ED) experiments revealed that the AFE state is characterized as the modulated structure with the modulation vector of q=1/4 1/4 0. High-resolution TEM images clearly show the coexistence of two types of domains consisting of the modulated and the nonmodulated structures with the 100 ∼ 200 nm size. On the other hand, in the relaxor state there appear two types of diffuse scatterings in the ED patterns. One is diffuse spots at the 1/2 1/2 0-type reciprocal positions and the other is diffuse streaks elongating along the <110> direction around the fundamental spots. The real-space TEM images clearly demonstrate the presence of nanodomains with the average size of ∼ 5 nm. These nanodomains in the relaxor state should be responsible for the characteristic dielectric properties.
Effect of non-thermal plasma (NTP) on bio-particles has been studied using Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and bacteriophages. NTP has been used, and states of different biological components were monitored during the course of the exposure. Analysis of green fluorescent protein (GFP), introduced into E.coli cells proved that NTP causes a prominent protein damages without cutting peptide bonds. We have developed a biological assay which evaluates in vivo DNA damage of the bacteriophages. Different doses of the plasma were applied to wet state of λ phages. From the plasma-exposed λ phages, DNA was purified and subjected to in vitro DNA packaging reactions. The re-packaged phages consist of the DNA from discharged phages and brand-new coat proteins. Survival curves of the re-packaged phages showed extremely large D value (D = 25 s) compared to the previous D value (D = 3 s) from the discharged phages. The results indicate that DNA damage hardly contributed to the inactivation, and the damage in coat proteins is responsible for inactivation of the phages. We also report a single-molecule-based analysis of strand breakages on large DNA molecules induced by the plasma exposure. Single-molecule observation of DNA that involved molecular combing was used to measure the length of individual DNA molecules. The measured DNA length showed that plasma exposure caused a marked change in length of DNA molecules. The rate of plasmainduced strand breakage on large random-coiled DNA molecules was determined using a simple mathematical model. The measured rate shows good relation with the plasma exposure time, and could be used for safety evaluation of the plasma treated water.
We propose a novel concept of optical detection of thermal neutrons in a passive device that exploits transmutation of Dy-164, a dominant, naturally occurring isotope of dysprosium, into a stable isotope of either holmium Ho-165 or erbium Er-166. Combination of the high thermal neutron capture cross section of ~2,650 barns and transmutation into two other lanthanides makes Dy-164 a very attractive alternative to traditional methods of neutron detection that will be completely insensitive to gamma irradiation, thus reducing greatly the likelihood of false alarms. The optically enabled neutron detection relies on significant differences in optical properties of Dy, Ho, and Er that are not sensitive to a particular isotope, but change considerably from one element to another. While the concept applies equally well to bulk materials and to nanocrystals, nanocrystalline approach is much more attractive due to its significantly lower cost, relative ease of colloidal synthesis of high quality nanocrystals (NCs), and superior optical and mechanical properties of NCs compared to their bulk counterparts. We report on colloidal synthesis of DyF3 NCs, both doped and undoped with Ho and co-doped with Ce and Eu to enhance their optical properties. We also report on DyF3:10%Ce and DyF3:10%Eu NCs irradiated with thermal neutrons from a Cf-252 source and their optical characterization.
Synthetic CdZnTe or “CZT” crystals are highly suitable for γ-spectrometers operating at the room temperature. Secondary phases (SP) in CZT are known to inhibit detector performance, particularly when they are present in large numbers or dimensions. These SP may exist as voids or composites of non-cubic phase metallic Te layers with bodies of polycrystalline and amorphous CZT material and voids. Defects associated with crystal twining may also influence detector performance in CZT. Using transmission electron microscopy, we identify two types of defects that are on the nano scale. The first defect consists of 40 nm diameter metallic Pd/Te bodies on the grain boundaries of Te-rich composites. Although the nano-Pd/Te bodies around these composites may be unique to the growth source of this CZT material, noble metal impurities like these may contribute to SP formation in CZT. The second defect type consists of atom-scale grain boundary dislocations. Specifically, these involve inclined “finite-sized” planar defects or interfaces between layers of atoms that are associated with twins. Finite-sized twins may be responsible for the subtle but observable striations that can be seen with optical birefringence imaging and synchrotron X-ray topographic imaging.
In this present work we report the growth of Cd0.9Zn0.1Te doped with In by a modified THM technique. It has been demonstrated that by controlling the microscopically flat growth interface, the size distribution and concentration of Te inclusions can be drastically reduced in the as-grown ingots. This results in as-grown detector-grade CZT by the THM technique. The three-dimensional size distribution and concentrations of Te inclusions/precipitations were studied. The size distributions of the Te precipitations/inclusions were observed to be below the 10-μm range with the total concentration less than 105 cm-3. The relatively low value of Te inclusions/precipitations results in excellent charge transport properties of our as-grown samples. The (μτ)e values for different as-grown samples varied between 6-20 x10-3 cm2/V. The as-grown samples also showed fairly good detector response with resolution of ∼1.5%, 2.7% and about 3.8% at 662 keV for quasi-hemispherical geometry for detector volumes of 0.18 cm3, 1 cm3 and 4.2 cm3, respectively.
Pre-irradiated thermodynamic and microstructural properties of nuclear fuels form the necessary set of data against which to gauge fuel performance and irradiation damage evolution. This paper summarizes recent efforts in mixed-oxide and minor actinide-bearing mixed-oxide ceramic fuels fabrication and characterization at Los Alamos National Laboratory. Ceramic fuels (U1-x-y-zPuxAmyNpz)O2 fabricated in the compositional ranges of 0.19≤x≤0.3 Pu, 0≤y≤0.05 Am, and 0≤z≤0.03 Np exhibited a uniform crystalline face-centered cubic phase with an average grain size of 14μm; however, electron microprobe analysis revealed segregation of NpO2 in minor actinide-bearing fuels. Immersion density and porosity analysis demonstrated an average density of 92.4% theoretical for mixed-oxide fuels and an average density of 89.5% theoretical density for minor actinide-bearing mixed-oxide fuels. Examined fuels exhibited mean thermal expansion value of 12.56×10−6/°C-1 for temperature range (100°C<T<1500°C) and ambient temperature Young's modulus and Poisson's ratio of 169 GPa and of 0.327, respectively. Internal dissipation as determined from mechanical resonances of these ceramic fuels has shown promise as a tool to gauge microstructural integrity and to interrogate fundamental properties.
This paper summarizes research activities in National Institute of Radiological Sciences (NIRS) for evaluation of the radiation effects on selected terrestrial and aquatic organisms as well as the ecosystems. Seven organisms, conifers, fungi, earthworms, springtails, algae, daphnia and Medaka are presently selected to study. For the estimation of possible radiation dose, transfers of radionuclides and related elements from medium to organisms are evaluated. Dose-effect relationships of acute gamma radiation on the survival, growth, and reproduction of selected organisms have been studied. Studies on the effect of chronic gamma radiation at low dose rate were also started. In order to understand the mechanism of radiation effects and to find possible indicators of the effects, information of genome- and metagenome-wide gene expression has been collected. Evaluation of ecological effects of radiation is more challenging task. Study methods by using three-species microcosm were established, and an index for the holistic evaluation of effects on various ecological parameters was proposed. The microcosm has been simulated as a computer simulation code. Developments of more complicated and practical model ecosystems have been started. The Denaturant Gradient Gel Electrophoresis (DGGE) has been applied on soil bacterial community in order to evaluate the radiation effects on soil ecosystems.
We report the results of mid- to far-infrared spectroscopic
observations of Galactic star-forming regions with ISO, Spitzer, and
AKARI. Owing to the high sensitivity of the IRS onboard Spitzer, we
detected [Si II] 35 μm, [Fe II] 26 μm, and [Fe III] 23 μm lines widely
in low-density star-forming regions, and derived gas-phase Si and Fe
abundances as 3–100% and <22%, respectively. With the FTS
onboard AKARI, we obtained the spatial distribution of
the [O III] 88 μm emission in two star-forming regions.
We have started a VLBI monitoring program for Asymptotic Giant Branch (AGB) stars at 22 and 43 GHz as part of a project of the VLBI Exploration of Radio Astrometry (VERA) for precisely obtaining the period-luminosity (PL) relation of Galactic Mira variables. Using accurate distances measured with VERA, we reveal PL relation in the Galaxy based on the absolute magnitudes of the sources. We selected the sources for VLBI monitoring so that they have a good coverage of various pulsation periods. Photometry in the infrared J, H, and K bands for over 600 AGB stars has also started since 2003 with the 1m telescope of Kagoshima University to obtain the pulsation periods and magnitudes. Current analysis of the phase referencing VLBI observations of S Crt shows that the parallax of 2.3±0.2 milliarcsec (mas) corresponds to a distance of 435+41−35 pc. From the infrared monitoring data, pulsation periods and magnitudes in K band for 248 sources were obtained.
The internal friction of a silicon nitride with a sintering aid of yttrium oxide was measured from room temperature to 1400 °C. A mechanical loss peak was typically observed at 1000 °C on heating the as-sintered specimen; however, it disappeared on cooling. Also, the peak was not observed upon heating a specimen that had been heated above 1400 °C. When we carried out thermal cycling, raising terminal temperatures from 1050 to 1400 °C, the integrated intensity of the peak gradually decreased due to the progressive crystallization of a grain-boundary amorphous phase.
We have investigated the flat-band voltage (VFB) shifts of tantalum nitride gate MOS capacitors prepared by two methods. One is CVD-tantalum nitride (CVD-TaN) deposited by the chemical vapor deposition technique using Ta[NC(CH3)2C2H5][N(CH3)2]3 as a precursor, and the other one is sputtered tantalum nitride (sp-TaN) electrodes deposited by reactive DC magnetron sputtering. In the case of the CVD-TaN electrodes, the effective work function estimated from the relationship between VFB and the equivalent oxide thickness (EOT) of the MOS capacitors was about 4.4eV after post metallization annealing (PMA) at 400°C, and shifted to the mid-gap after PMA at 950°C. Moreover, the VFB values of MOS capacitors with sp-TaN electrodes also showed the same behavior after PMA. This shift is mainly dependent on the PMA temperature, regardless of the deposition method used. Similar VFB shifts induced by PMA were also observed in sp-TaN/ Al2O3/ SiO2/ p-Si and sp-TaN/ TaOx/ SiO2/ p-Si capacitors. However, in the case of the sp-TaN/ TaOx/ SiO2/ p-Si capacitors, the VFB shift was also observed when the PDA temperature after the TaOx deposition was 800°C and the PMA temperature after the TaN deposition was only 400°C. These results strongly suggest that this VFB shift caused by the PMA originates from a thin interfacial oxide layer between the TaN gate electrode and the dielectrics. Therefore, the maximum processing temperature after gate electrode deposition is important in order to control the threshold voltage of tantalum nitride gate MOSFETs.
We report a simple and mild fabrication of flexible organic field-effect transistors (OFETs) by an electrode-peeling transfer method. Firstly, fine patterns of source-drain metal electrodes were formed on a solid substrate, where a micro-patterning process such as photolithography is applicable. An organic dielectric layer (poly-chloro-p-xylylene) was deposited by a chemical vapor deposition. Then patterned gate electrode was deposited using a shadow mask. On the top surface of the gate electrode, another adhesive flexible substrate was fixed and the stack of the flexible substrate/gate electrode /dielectric layer /source-drain electrode was peeled away from the solid substrate. The peeling-transfer was completed with a help of a self-assembled monolayer of n-decyl mercaptan as a connecting buffer layer between the gold electrodes and the dielectric layer. Then an organic semiconductor material was deposited on the fresh peeled-off surface on the flexible substrate. When pentacene was used as the semiconductor material, the OFETs exhibited a hole mobility of 0.1 cm2/Vs and a current on/off ratio of 105.
mechanism of general flowering in Dipterocarpaceae in the Malay
Peninsula is revealed through field survey and meteorological data
analyses. The regions of general flowering coincide with those which
experienced a low night-time temperature (LNT) c. 2 mo before
flowering. This supports the hypothesis that low air temperature induces
the development of floral buds of dipterocarps. LNT was found to be
caused by radiative cooling during dry spells in winter when the
northern subtropical ridge (STR) occasionally migrates southwards with a
dry air mass into the equatorial region. LNT events usually occur in La
Niña episodes, not in El Niño episodes as believed
previously. This is because the southward migration of the STR is
associated with the intensification of local meridional Hadley
Circulation in the western Pacific, which is strengthened in a La
Niña episode. Results suggest that El Niño-like climate
change in increased atmospheric carbon dioxide concentrations may be
critical for the tropical rain forest biome in south-east Asia.
We study the total luminosity function (LF) and the type-specific LF of 7 nearby clusters of galaxies (A1060, S805, A2063, A1736, A1644, A1631, and A754) using the R-band image (1.0 × 0.5 deg2) taken with our mosaic CCD camera mounted on 1-m telescope at the Las Campanas Observatory.
We observed three 0.44 square degree fields centered on the Coma cluster center (Coma-1), about 1 degree SW of the Coma center (Coma-3), and on a control field in SA57 with the mosaic CCD camera at the prime focus of the 4.2-m William Herschel Telescope. We detected 5628, 5020, and 4323 galaxies down to R = 22 mag in Coma-1, Coma-3, and SA57 fields, respectively. We measure the magnitude and color within the variable aperture r90 in which about 90% of the total flux is included. The histograms of (B–R) colors of galaxies are made for four magnitude bins of width ΔR = 2 mag covering 13 < R < 21 mag for each of the three fields. The mean colors and the 1σ scatters of the Coma galaxies are obtained by a histogram subtraction technique (Coma-1/3 minus SA57). We find a very shallow slope of the color-magnitude relation (CMR), Δ(B–R)/ΔR=−0.0037, which indicates nearly a constant (B–R) color over 6 magnitude in 15 < R < 21 mag (−19.5 < MR < −13.5 at Coma cluster). Dwarf galaxies are dominant in this magnitude range, and we conclude that the mean color of dwarf galaxies in the Coma clusters is nearly constant at (B–R) ∼ 1.6–1.7, which is similar to the color of the faint end of giant elliptical galaxies.
The effects of freeze-dried soya milk (SM) and Bifidobacterium-fermented soya milk (FSM) on plasma and liver lipids, and faecal steroid excretion were estimated in hamsters fed on a cholesterol-free or cholesterol-enriched diet. Hamsters fed on the cholesterol-free diet containing 300 g FSM/kg had lower levels of plasma VLDL + LDL cholesterol than the animals fed on the control diet. SM in the diet produced a similar pattern without significant differences. In the cholesterol-enriched diet group, SM and FSM decreased the levels of plasma total cholesterol and VLDL + LDL-cholesterol. SM and FSM decreased the plasma triacylglycerol level in both the cholesterol-free and -enriched diet groups. The liver total cholesterol contents in the SM and FSM groups were lower than that in the control group, for hamsters fed on the cholesterol-free diet. The liver triacylglycerol content was not modified by SM or FSM in hamsters fed on either the cholesterol-free or -enriched diet. SM and FSM increased the total bile acid excretion and the proportion of cholesterol entering the cholic acid biosynthesis pathway in both the cholesterol-free and -enriched diet groups. SM and FSM did not affect neutral steroid excretion in the cholesterol-free or -enriched diet group. There was an inverse relationship between VLDL + LDL-cholesterol and faecal bile acid excretion in hamsters fed on the cholesterol-free (r −0.670, P < 0.01) and cholesterol-enriched (r −0.761, P < 0.001) diets respectively. These results indicated that SM had an anti-atherogenic effect, and that this effect was not diminished by prior fermentation.
At present, the photometric data for clusters at z ≲ 0.2 mainly come from photographic photometry. The lack of CCD data for such clusters is simply due to the fact that no CCD camera had been available until recently that covers the wide extension of clusters within a reasonable amount of observing time. We have developed a large mosaic CCD camera and conducted multicolor imaging observations of z ≲ 0.2 clusters using the 40-inch Swope telescope at Las Campanas Observatory.