Preparation of Cu2ZnSnS4 thin films by sulfurizing electroplated precursors

Cu₂ZnSnS₄ (CZTS) thin films were prepared by sulfurizing precursors deposited by electroplating. The precursors (Cu/Sn/Zn stacked layers) were deposited by electroplating sequentially onto Mo-coated glass substrates. Aqueous solutions containing copper sulfate for Cu plating, tin sulfate for Sn plating and zinc sulfate for Zn plating were used as the electrolytes. The precursors were sulfurized by annealing with sulfur at temperatures of 300, 400, 500 and 600 °C in an N₂ gas atmosphere. The X-ray diffraction peaks attributable to CZTS were detected in thin films sulfurized at temperatures above 400 °C. A photovoltaic cell using a CZTS thin film produced by sulfurizing an electroplated Sn-rich precursor at 600 °C exhibited an open-circuit voltage of 262 mV, a short-circuit current of 9.85 mA/cm² and an efficiency of 0.98%.     

Measurement of water thickness in PEM fuel cells and analysis of gas velocity distributions

Fuel gas (hydrogen gas) and oxidant gas (air) are supplied to a polymer electrolyte fuel cell (PEFC). Condensation may occur in the cathode side, since the air might be super-saturated by the fuel cell reactions. If condensed water exists in a gas diffusion layer (GDL) or the gas channels, it may affect the fuel cell performances because it blocks the oxygen from reaching the cathode reaction site. Thus, water management in the PEFC is important. In order to clarify water effects on performances of a PEFC, visualization and quantitative measurements of water distributions in a PEFC were carried out by means of neutron radiography. Two-dimensional water distributions were obtained, and water ejection was confirmed. It was found that the water easily accumulated in the GDL under the rib rather than under the channel at beginning of the operation. Furthermore, a network analysis of gas-velocity distribution is applied for the experimental results. It analyzes the gas-velocity distributions depending on the flow resistance, which is the pressure drop. Applying the measured data of water thickness, gas-velocity distributions were obtained in the channel and the GDL. From the calculation, air supply in the GDL dramatically decreased with increasing of water accumulation.     

Persistence and partitioning of eight selected pharmaceuticals in the aquatic environment: Laboratory photolysis, biodegradation, and sorption experiments

We selected eight pharmaceuticals with relatively high potential ecological risk and high consumption—namely, acetaminophen, atenolol, carbamazepine, ibuprofen, ifenprodil, indomethacin, mefenamic acid, and propranolol—and conducted laboratory experiments to examine the persistence and partitioning of these compounds in the aquatic environment. In the results of batch sunlight photolysis experiments, three out of eight pharmaceuticals—propranolol, indomethacin, and ifenprodil—were relatively easily photodegraded (i.e., half-life < 24 h), whereas the other five pharmaceuticals were relatively stable against sunlight. The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life > 24 h) for all eight pharmaceuticals, but the rate constant was dependent on sampling site and time. Batch sorption experiments were also conducted to determine the sorption coefficients to river sediments and a model soil sample. The determined coefficients (K_d values) were much higher for three amines (atenolol, ifenprodil, and propranolol) than for neutral compounds or carboxylic acids; the K_d values of the amines were comparable to those of a four-ring polycyclic aromatic hydrocarbon (PAH) pyrene. The coefficients were also higher for sediment/soil with higher organic content, and the organic carbon-based sorption coefficient (log K_oc) showed a poor linear correlation with the octanol-water distribution coefficient (log D_ow) at neutral pH. These results suggest other sorption mechanisms—such as electrochemical affinity, in addition to hydrophobic interaction—play an important role in sorption to sediment/soil at neutral pH.     

Hemodynamic characterization of YM435, a novel dopamine DA1 receptor agonist, in anesthetized dogs

In previous studies on experimental renal failure, hypertrophy of cardiomyocytes, diminished capillarization, and increased intercapillary distances had been observed, abnormalities that will expose the heart to reduced ischemia tolerance. It has not been established, however, whether such structural alterations are unique for the heart (eg, as a consequence of left ventricular hypertrophy) or are demonstrable in other tissues as well. Clarification of this point is important to test hypotheses on some potential mechanisms for cardiac undercapillarization. To address this issue further, we compared capillary length density (by stereologic techniques) in perfusion-fixed skeletal muscle (m. psoas) and hearts of subtotally nephrectomized (SNX) rats with moderate renal failure to those in sham-operated pair-fed controls. The duration of renal failure was 8 weeks. SNX rats had significantly higher mean systolic blood pressure (128 mm Hg v 109 mm Hg), serum creatinine, and urea levels. Despite pair feeding, the mean body weight was significantly lower in the SNX rats (409 g v 471 g), but the left ventricular weight to body weight ratio tended to be higher than in the sham-operated controls (2.39 mg/g v 2.13 mg/g). In the heart, myocyte mean cross-sectional area (675 +/- 112 microm2 v 545 +/- 111 microm2) and volume density of nonvascular interstitial tissue (3.47 +/- 1.04 v 1.33 +/- 0.22) were significantly higher in the SNX rats than in the controls. In parallel, myocardial capillary length density was significantly reduced after subtotal nephrectomy (3,036 +/- 535 mm/mm3 v 3,916 +/- 615 mm/mm3). In contrast, in skeletal muscle, myocyte cross-sectional area (3,109 +/- 783 microm2 v 3,042 +/- 639 microm2), capillary length density (718 +/- 248 mm/mm3 v 717 +/- 184 mm/mm3), and three-dimensional capillary fiber ratio (2.10 +/- 0.26 v 2.13 +/- 0.4) were similar in SNX and control rats. These data document a selective defect of capillarization in the heart of animals with moderate renal failure, pointing to tissue-specific abnormalities of cardiac capillarogenesis.     

Substance P- and calcitonin gene-related peptide-containing nerve fibers in the nasal mucosa of chronically hypoxic rats

Changes made in 1997 and 1998 in the U.S. childhood immunization schedule are discussed, with a focus on the use of poliovirus, pertussis, and combination vaccines. Oral poliovirus vaccine (OPV), the vaccine of choice for all four doses in the polio immunization series since 1962, can cause vaccine-associated paralytic poliomyelitis (VAPP). The inactivated poliovirus vaccine (IPV) has not been associated with VAPP but must be administered by injection and provides inferior intestinal immunity. With the reduced threat of poliovirus importation into the United States, the risk of VAPP, although low, has become less acceptable. The Centers for Disease Control and Prevention accordingly recommended a shift from OPV to IPV in the childhood immunization schedule for the United States, effective January 1997. A sequential OPV and IPV series is recommended, but the schedule includes an OPV-only option, which may be preferred in order to avoid the required injections, and an IPV-only option, which is recommended for immunocompromised persons and their contacts. Concern over local and systemic reactions associated with whole-cell pertussis vaccines, in addition to controversy over a possible relationship between the whole-cell vaccine and neurologic damage, has led to the development of new diphtheria and tetanus toxoids and acellular pertussis vaccine products for use in the diphtheria and tetanus toxoids and pertussis immunization series. Several combination products were licensed in 1997, and more are on the way. This will mean fewer inoculations for children. Increased use of IPV and acellular pertussis products could reduce the frequency of VAPP due to OPV and the local and systemic reactions associated with whole-cell pertussis vaccine.     

Realization of all-optical flip-flop using directionally coupled bistable laser diode

A novel all-optical flip-flop device has been realized using a directionally-coupled bistable laser diode (DC-BLD). We have fabricated the DC-BLD by a conventional fabrication technique of LDs. To separate the adjacent electrodes of the directional coupler, an oblique electron-beam evaporation technique was developed. By this self-align process, the two adjacent waveguides of the directional coupler were electrically isolated without employing any additional lithography step. Using the fabricated DC-BLD, all-optical flip-flop has been demonstrated due to the nonlinear effects of the saturable absorber and the directional coupler. The flip-flop operation has been achieved with sufficiently small input optical power level around 0 dBm.     

A New Approach to Humanitarian Demining

Humanitarian demining is an application in which the use of tele-operated machines and mechanisms has been gaining acceptance recently. Actually, demining is just one among many other field applications that require a high degree of mobility, manipulation of loads, robustness and, above all, high efficiency in terms of energy consumption. This paper will present the development and analysis of Field Arm, a pantographic manipulator especially designed for field works, focusing on its kinematic, static and dynamic properties. The novel features of Field Arm will be presented and discussed with results of simulations and experiments.     

Accumulation of Arsenic and Copper by Bryophytes Growing in an Aquatic Environment near Copper Mine Tailings

Bryophytes with high As accumulation affinity were identified in the aquatic environment. We surveyed a stream near copper mine tailings and then conducted laboratory experiments to confirm As accumulation in the bryophytes with high As affinity. We found that a moss, Scopelophila cataractae, accumulates As in addition to Cu in aquatic environments and confirmed it in laboratory experiments. The highest value for As in S. cataractae from the field survey was 1300 mg/kg dry weight at relatively low As concentrations in the stream water (0.005 mg/L). In addition, Brachythecium plumosum and Rhynchostegium riparioides may also be useful bryophytes for accumulation of Cu and As, though the mechanisms of As accumulation might differ between these two bryophytes and S. cataractae.     

Two Step Timing Synchronization Scheme for OFDM Signal in General Purpose Processor Based Software Defined Radio Receiver

Software defined radio (SDR) is a technology that allows a single terminal to support various kinds of wireless systems by changing its software to reconfigure itself. A general purpose processor (GPP) based SDR receiver platform named Sora has been recently developed by Microsoft. In the GPP based SDR receiver, timing synchronization of an OFDM signal consumes a significant amount of computational resources in the GPP. In this paper, a timing synchronization scheme which uses delayed correlation and matched filtering for the GPP based SDR platform is evaluated. The two stage timing synchronization scheme reduces the computational complexity by limiting the timing range of matched filtering. The proposed scheme reduces the amount of data transmission between the memory and the GPP of the SDR platform. It is shown through an experiment that the proposed scheme reduces the number of cycles for timing synchronization by up to 30 %.     

Crystal growth and scintillation properties of Nd-doped Lu3Al5O12 single crystals with different Nd concentrations

Nd 0.1%, 0.5%, 1% and 3% doped Lu₃Al₅O₁₂ (Nd:LuAG) single crystals were grown in the nitrogen atmosphere by the micro-pulling down (μ-PD) method. The grown crystals had a single-phase confirmed by powder XRD analysis. In absorption spectra, some weak absorption lines due to Nd³⁺ 4f-4f transitions were observed and their intensity increased with the increase of Nd concentration. When excited by ²⁴¹Am α-ray, a broad emission peak due to defects in the host lattice at 320 nm and some sharp lines due to Nd³⁺ 4f-4f transitions at wavelength longer than 400 nm were observed. The decay time profiles of Nd:LuAG under γ-ray excitation were well approximated by two exponential function of 340-760 ns and 3-5 μs for each sample. By pulse height measurement using ¹³⁷Cs, Nd 0.5%:LuAG showed the highest light yield of 7600 ± 760 photons/MeV.