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The adsorption and desorption of cesium onto layered minerals, zeolite and geochemical reference samples were studied. 0.5 g of bentonite and mica were able to adsorb 71.2 and 51.5 mg of cesium, respectively, from 50 mL of deionized water containing 200 mg/L of cesium under neutral pH condition. These amounts of cesium adsorption were greater than those reported for vermiculites (8.9 and 5.6 mg, respectively). Additionally, the cesium adsorption on mica and vermiculite remained essentially unchanged under seawater conditions, but it decreased drastically on zeolite. The cesium desorption from the layered minerals was promoted by the addition of ammonium ions, namely trioctylmethylammonium chloride and zephiramine. These ammonium ions desorb cesium from the interlayers of the minerals without destroying the mineral structure. The cesium desorption procedure using quaternary ammonium ions would be extremely useful for decontamination of soil containing the layered minerals with adsorbed radioactive cesium.
We report on the spectral and temporal properties of the 50 ms pulsar PSR B0540–69 using ASCA archival data obtained during 1993 to 1995. From the spectral analysis it was found that the spectra of the whole (nebular and pulsed) emission and pulsed emission in the range 1-10 keV can be represented by a single power law of photon index, Γ = 2.00 ± 0.02 and Γpulsed = 1.7 ± 0.3 respectively. The parameters for pulse frequency change during 1993-1995 were obtained using the 9 pulse frequency measurements with ASCA. The parameters derived from the ASCA observations are consistent with the previous measurements, suggesting high stability of this pulsar, ΔΩ/Ω ≲ 0.5 × 10−7 over the past 10 years. These results confirm similarity of this pulsar with the Crab pulsar.
An overview of the Czech national R&D project HiLASE (High average power pulsed laser) is presented. The project focuses on the development of advanced high repetition rate, diode pumped solid state laser (DPSSL) systems with energies in the range from mJ to 100 J and repetition rates in the range from 10 Hz to 100 kHz. Some applications of these lasers in research and hi-tech industry are also presented.
Silver nanoparticle (AgNP) is one of the elegant material because its uses in various fields. In this study, AgNPs have been prepared by using Peltophorum pterocarpum (PP) flower extract as reducing and capping agent and aqueous silver nitrate (aq.AgNO3) as silver precursor. The synthesized nanoparticles were characterized using Ultra Violet - Visible (UV-Vis) spectroscopy, High Resolution Transmission Electron Microscope (HR-TEM) and Fourier Transform Infrared Spectroscopy (FT-IR), which reveals the formation of nanosized particles. The UV-Vis spectrum shows an absorption peak around 430nm. HR-TEM images of AgNPs with clear morphology and well dispersed prepared AgNPs.
In this paper, the authors have reported the structural and photoluminescence (PL) studies of pure and nickel (Ni) doped zinc oxide (ZnO) nanoparticles synthesized by the solution combustion method. The structural, morphological and optical studies are carried out by powder x-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and PL spectra, respectively. The XRD pattern indicates that the prepared particles are in hexagonal wurtzite structure with the average crystalline size is around 35-50nm. Room temperature PL shows the near band edge related emission and the results are related several intrinsic defects in the ZnO nanoparticles.
In this paper, the effect of shock compression on the synthesis of a Bi-based oxide superconductor was investigated. Bi1.85-Pb0.35-Sr1.90-Ca2.05-Cu3.05-Ox calcined powder was shock-compacted around 20 GPa and 30 GPa, and divided specimens were annealed at 845 °C for 1, 6 and 48 hours. The specimens were evaluated by x-ray diffraction and scanning electron microscope.
ZnO nanorods were grown up from as-deposited ZnO film on which the zinc self-catalysts generated by a novel reducing method. Well aligned ZnO nanorods with a uniform high aspect ratio were grown up on multi-annealed samples. The length of nanorods depended significantly on the reaction time in the hydrothermal synthesis.
A Mg(OH)2–C transparent conductive film was prepared using the sputtering method by the initial formation of a Mg-C film generated by the alternate layering of Mg and C on a rotating substrate and subsequent exposure of the film to atmospheric water vapor. To examine the influence exerted by the Mg/C layers of the starting film sample on semiconductivity,evaluations of the electrical conductivity properties of the film during the hydroxylation process and the optical properties after the hydroxylation process were carried out. As a result, although no effects on the characteristics of the electrical conductivity properties associated with the composition or number of layers in the films could be confirmed, it was determined that the films possessed the characteristics of semiconductors. On the other hand, the optical properties were found to be affected by the composition and number of layers of the Mg/C films.
During the development of oocytes from early antral follicles (EAFs) to antral follicles (AFs), the mitochondrial DNA copy number (Mt DNA number) increases, and granulosa cells markedly proliferate. This study examined the effect of supplementation of culture medium with estradiol-17β (E2) on the in vitro growth of oocytes, and increases in the Mt DNA number, and telomere length during the in vitro culture of oocytes derived from EAFs (0.4–0.7 mm in diameter). The E2 supplementation improved antrum formation and the ratio of oocytes reaching the metaphase II (MII) stage, and there was a significant difference in these values between addition E2 concentrations of 10 μg/ml and 0.1 μg/ml. When the oocytes were cultured in the medium containing 10 μg/ml E2, the Mt DNA number determined by real-time polymerase chain reaction (PCR) significantly increased, and the ratio of the Mt DNA number at the end of culture to the Mt DNA number at the beginning of the culture was greatly different among cows, and could be predicted by the degree of the difference between the Mt DNA number of oocytes derived from EAFs and that of oocytes derived from AFs (3–6 mm in diameter). When oocytes were cultured for 16 days in a medium containing 10 μg/ml E2 or 0.1 μg/ml E2, the Mt DNA number of oocytes grown in vitro did not differ, but the telomere length of the granulosa cells was significantly greater in the 10 μg/ml E2 group than in the 0.1 μg/ml group. In conclusion, E2 supplementation in culture medium improved the growth of oocytes derived from EAFs, and a high E2 concentration increased the telomere length of the granulosa cells.
A study of the ferroelectric and magnetic properties and of the magnetoelectric coupling effects of Pb(Fe0.5Nb0.5)O3 (PFN) thin films, grown on SrRuO3/Si [(100) or (111)] substrates by the rf-magnetron sputtering technique, is presented. Structural, morphological, and compositional characterization was realized using the XRD, AFM, XPS, and TEM techniques. Highly textured single phase films with different thickness (from 45 to 270 nm) were successfully grown without Fe2+ presence. A vertically  oriented grainy structure was observed. Polarization vs. electric field (P-E) hysteresis loops exhibit excellent and almost constant values of the maximum (∼ 60 μC/cm2) and remanent (∼ 22 μC/cm2) polarizations in the temperature range from 4 K to room temperature; small values of the coercive field, characteristic of soft ferroelectric materials, are observed in these samples. Measurements of the zero-field cooled (ZFC) and field cooled (FC) magnetization behavior and magnetic (M-H) hysteresis loops were realized at different temperatures between 5 and 300 K. Proof of the existence of ferromagnetic order in the low temperature region (below to 50 K) is discussed and reported for the first time. Values of the maximum (∼ 3 emu/g) and remanent (∼ 1.5 emu/g) magnetizations were obtained. dc magnetic field dependence of the ferroelectric hysteresis loops are shown as evidence of the magnetoelectric coupling.
Superconducting NMR pickup coils have to have a low surface resistance (Rs) under a high magnetic field. One way of reducing the Rs of superconducting thin films is adding artificial pins to the films. We examined the hetero-epitaxial growth of MgB2and YBCO thin films on decorated sapphire and MgO substrates while using nano-wires and nano-particles to add pins to the films.
We used ZnO nano-wire to add artificial grain boundary pins to MgB2 films. The tilted c-plane sapphire substrate with nano-step edges was used for these substrates. The terrace width with one lattice step edge can be controlled by changing the tilt angle. AFM images showed that the tilted c-plane sapphire substrate had straight nano-step edges. ZnO nono-wires were decorated on the nano-step edges by MOCVD, and then deposited on MgB2 films by sputtering. The Rs of the films was then measured with a sapphire rod resonator. The Rs of MgB2 thin films fabricated on the tilted c-plane sapphire substrate with ZnO nano-wires was lower than that of MgB2thin films on a conventional sapphire substrate under a high magnetic field.
We used BaZrO3(BZO) nano-particles to add the artificial pins to YBCO thin films. The BZO particles on the MgO substrates were fabricated by laser deposition. The size and density of these particles were controlled with a pulse number of laser shot. YBCO thin films were formed on decorated MgO substrate by laser deposition. The Rs of YBCO thin films on the decorated MgO substrate was lower than that of the YBCO films formed on a conventional MgO substrate under a high magnetic field.
We clarified that artificial pins in MgB2and YBCO thin films are useful for decreasing the Rs under a high magnetic field.
Recent trends in composite research include the development of structural materials with multiple functionalities. In new studies, novel materials are being designed, developed, modified, and implemented into composite designs. Typically, an increase in functionality requires additional material phases within one system. The presence of excessive phases can result in deterioration of individual or overall properties. True multi-functional materials must maintain all properties at or above the minimum operating limit. In this project, samples of Sb-doped SnO2(ATO) sol-gel solutions are used to coat carbon fibers and are heat treated at a temperature range of 200 – 500 °C. Results from this research are used to model the implementation of sol-gel coatings into carbon fiber reinforced multifunctional composite systems. This research presents a novel thermo-responsive sol-gel/ (dopant) combination and evaluation of the actuating responses due to various heat treatment temperatures. While ATO is a well-known transparent conductive material, the implementation of ATO on carbon fibers for infrared thermal reflectivity has not been examined. These coatings serve as actuators capable of reflecting thermal infrared radiation in mid-range and near-range wavelengths (λ). By altering the ATO sol gel thickness and heat treatment temperatures, optimal optical properties are obtained. While scanning electron microscopy (SEM) is used for imaging, electron diffraction spectroscopy (EDS) is used to verify the compounds present in the coatings. Fourier transform infrared (FT-IR) spectroscopy was performed to analyze the reflectivity in the infrared spectra and analyze the crystal structures after heat treatments.
Methane is an important explosive gas, used extensively at the domestic and industrial sites. It is the main constituent of natural gas, which is the main fuel supplied to homes and industries including automobiles. Detection of trace level of methane gas is very important to avoid any accidental explosion due to its leakage and may cause loss of valuable human life and property. The present paper is focused on the development of new sensing material in the form of composites to improve sensitivity, selectivity and stability. Present work shows the enhanced response of SnO2-ZnO composite structures for methane sensing and further increases its sensing response by loading appropriate catalyst on the sensor surface keeping in view of Fermi energy control mechanism and spillover mechanism. A stable sensor response of 77-85 % was obtained for SnO2-ZnO-Pd sensor structure over a wider range of temperature (160-260oC).
We have fabricated Bi2212 and Bi2223 bulk samples by shock compaction technique. Seed crystals were added to the starting materials in order to promote crystallization. The grain size of the prepared sample was increased by the addition of seed crystals to the starting material.
The changes are brought in the elemental semiconductors Si and Ge by replacing them with II-VI and III-V binary analogs or their ternary analogs I-III-VI2 chalcopyrides and II-IV-V2 pnictides respectively. Such compounds exhibit transitions from their parent compound in terms of nature of band gaps (Eg) as indirect to direct in addition to the changes in the values of the Eg. These changes have direct consequence in their optical properties with degenerate states being lifted leading to crystal field splitting and so on. The Eg in ternary bulk semiconducting materials is engineered as a function of certain structural parameters such as anion position parameter (u), tetragonal compression parameter (η) through effective alloying. The contributions to Eg due to these effects are studied as band gap anomalies. The present paper discusses the results of the band gap engineering in some of the bulk ABC2(A= Cd; B=Si,Ge,Sn; C= P,As) semiconductors using theoretical methods. The influence of each of A, B and C atom is also discussed. The dependence of morphology of nano semiconducting particles and the band gap on the chemical environment, temperature is reported by us. The confinement energy of a compound which is the difference in energy between the bulk and nano forms is investigated.
Enhanced near band-edge (NBE) emission was observed from composite structures fabricated from a PVA coated ZnO (PVA-ZnO) nanoparticle thin film embedded with multi-walled carbon nanotubes (MWCNTs). The enhancement is attributed to the resonant coupling between the bandgap transition of the semiconductor and the surface plasmon (SP) of MWCNTs. Moreover, the PVA-ZnO/MWCNTs/PVA-ZnO composite structures show faster transient response, which is due to the carrier transportation process in the composite structure. Reductions are observed for both photocurrent to dark current ratio and intensity of photoresponsivity, demonstrating a tradeoff between the time transient response and the detectivity.
Preparation of the CaTiO3:Pr (CTO:Pr) phosphor thin film on PET substrate was investigated by using the excimer laser-assisted metal organic decomposition(ELAMOD) and photo reaction of nano-particles (PRNP) process. The effects of the substrate material, starting materials, and UV sources on photoluminescence (PL) were investigated. By using the BaTiO3(BTO) nano-particles buffer layer and the CTO: Pr nano-particles as a starting material, CTO: Pr thin film on the PET substrate was successfully obtained by using the KrF laser and excimer lamp irradiation at 25°C. It was found that excimer lamp irradiation is effective for improving the PL of the films.