Performance Enhancement of Crystalline Silicon Solar Cells by Coating with Luminescent Silicon Nanostructures

In this work we report a technique that is potentially capable of increasing the efficiency of crystalline silicon solar cells, which dominate the present-day market of photovoltaic devices. The simple and cost-effective method involves coating the surface of a commercially procured silicon solar cell with luminescent silicon nanocrystals. Core/shell silicon/silicon-oxide nanostructures are fabricated by an inexpensive and reproducible technique, where coarse silicon powders are repeatedly milled, oxidized, and etched until their sizes are reduced so as to exhibit room-temperature photoluminescence under ultraviolet excitation. A thin coating of these nanostructures on a standard solar cell, obtained by a simple dip-coating method, increases the open-circuit voltage and short-circuit current, which consequently increases the maximum power delivered by ~16.3% and efficiency by almost ～39%. We propose that the core/shell nanostructures act as luminescent convertors that convert higher-energy photons to lower-energy photons, thereby leading to less thermal relaxation loss of photoexcited carriers.     

Proposed approach for defining climate regions for Turkey based on annual driving rain index and heating degree-days for building envelope design

Field surveys in Turkey indicate that a significant number of exterior wall assemblies in various regions of the country suffer from moisture degradation. These cases reveal that designers are in need for a climate scheme of Turkey, which indicates regions that require special provisions to prevent moisture degradation. Hence, this paper presents an approach for defining climate regions for Turkey. Initially, annual driving rain index (aDRI) based on monthly data is calculated and a driving rain map of Turkey is produced. Then, population-weighted heating degree-days (PW HDD) zones of Turkey are presented. Based on the aDRI and PW HDD zones, three climate regions of Turkey are established. Region 1 represents sheltered locations, i.e. locations which have aDRI less than 3. Region 2 represents locations (aDRI between 3 and 6 and PW HDD<1600), which are exposed to moderate driving rain between September and the end of May when the mean temperatures are above zero. Region 3 includes locations (aDRI between 3 and 6 and PW HDD between 1601 and 2500) which are moderately exposed to driving rain all throughout the year when the mean temperature is well above zero. As a conclusion, the proposed climate regions suggest that the design of wall assemblies located at Regions 2 and 3 must incorporate special provisions to prevent moisture degradation.     

Intermittent-low dose G-CSF treatment in a patient with chronic neutropenia

Tamoxifen induces apoptosis (programmed cell death) in human erythroleukemia K562 cells. Nitric oxide synthase activity and expression increased in apoptotic cells by 315% and 280%, respectively, compared to controls. The specific inhibitor of nitric oxide synthase, L-NAME, protected K562 cells from tamoxifen-induced apoptosis, whereas the nitric oxide donor, sodium nitroprusside (SNP), potentiated the apoptotic effect of the drug. In addition, 5-lipoxygenase was activated by tamoxifen and the specific enzyme inhibitor, MK886, protected K562 cells against the drug. Conversely, the 5-lipoxygenase product, 5-hydroperoxyeicosatetraenoic acid, enhanced the tamoxifen-induced apoptosis. Finally, tamoxifen altered also membrane properties of K562 cells.     

Processing of Carbon Fibers: Texture Enhancement Induced by Hot Stretching

A synchrotron radiation source has been used to monitor the x-ray diffraction patterns of a series of experimental PAN-based carbon fibers. The use of the synchrotron made feasible the collection of a substantial quantity of data on a reasonable time scale, by reducing the required exposure times by more than three orders of magnitude. The fibers considered in this report were hot stretched at temperatures in the range 2700°C to 3000°C for 5 minutes with stretching stresses between 5 MPa and 85 MPa. Measurement of the azimuthal and radial widths of the (00.2) reflections led to evaluation of figures for the preferred orientation parameter, Z, and the “apparent” crystallite size perpendicular to the graphitic rafts, L_c. The results showed that large increases in texturing can be achieved by hot stretching, so that from a starting value of ~38°, Z was reduced to between ~19° (2700°C and 5 MPa) and ~10° (3000°C and 85 MPa). Measurement of L_c was not possible for the as-received libers, since reflections were too diffuse, but the corresponding values for processed fibers were ~ 8 nm and ~11 nm respectively. It was found that the microstructural parameters depended on both the processing temperature and the stretching stress. Z showed substantial variation with both parameters, whereas Lc was far more sensitive to temperature than stress. Although the preferred orientation depended on a combination of extension and temperature, a close correlation was found between Z and the reduction in cross sectional area that occurred during processing. Similarly, within the range of conditions considered, Z varied approximately linearly with final fiber diameter, independently of the precise combination of processing parameters. A close correlation was also observed between the preferred orientation and Young's modulus of hot stretched fibers over the full range from ~330 GPa to ~690 GPa, compared with the untreated modulus value of ~180 GPa     

Lycopene content and antioxidant activity of fresh and processed tomatoes and in vitro bioavailability of lycopene

BACKGROUND: Lycopene, a phytochemical, has attracted a great deal of interest over the past few years. This has triggered research on the biological properties of lycopene and on the numerous factors that control these properties. Therefore, the aim of the study was to investigate lycopene content and antioxidant activity of fresh, sun‐dried and canned tomatoes. In addition, in vitro bioavailability of lycopene was determined. RESULTS: Lycopene contents of fresh, sun‐dried and canned tomatoes were found to be 1.74, 5.51 and 3.55 mg 100 g^?1, respectively, on a fresh wet basis. The highest lycopene bioavailability was obtained for sun‐dried tomatoes (58.05%) and this was followed by fresh (28.67%) and canned tomatoes (21.83%). Fresh tomatoes showed the highest antioxidant activity against ABTS radical oxidation. This was followed by sun‐dried tomatoes and canned tomatoes. The inhibition effect of intestinal dialysates of the samples on ABTS radical oxidation was between 51.34% and 92.96%. CONCLUSION: Maintenance antioxidant activity and existence of lycopene following an in vitro digestion process were the main findings, which might contribute forthcoming studies in this scientific field. Copyright © 2007 Society of Chemical Industry     

Modeling of gamma-ray energy absorption buildup factors using neural network

This paper presents a new approach based on multilayered perceptrons (MLPs) to compute energy absorption buildup factors. The MLP has been trained by a Levenberg–Marquardt learning algorithm. The model is fast and does not require tremendous computational efforts. The results obtained by using the proposed model are in good agreement with the ANSI/ANS-6.4.3 standard data set.     

陆上地震技术新进展

先进的地震采集和处理技术已经应用于陆上。一种高保真度、高分辨率集成式单传感器系统目前已在陆上使用。该技术的出现标志着在勘探、开发和生产应用方面取得了重大进展。     

Characterization of BPN Pyrotechnic Composition Containing Micro‐ and Nanometer‐Sized Boron Particles

The effect of micro‐ and nanometer‐sized boron particles on boron‐potassium nitrate (BPN) ignition composition was investigated in this paper. As a starting point, thermochemical calculations were made to determine the most promising ignition compositions. Both stoichiometric and fuel‐rich formulations of BPN were produced to observe the performance variation due to boron content. Particle morphology of boron particles and the surface structure of the ignition compositions were investigated by SEM. The influence of micro‐ and nanometer‐sized boron particles on the calorific value, sensitivity properties, and pressure buildup of compositions were investigated. Sensitivity tests showed that all compositions were safe enough for handling. It was seen that although nanometer‐sized boron particles enhanced calorific value and pressurization rate, they did not have a contribution on the maximum pressure level. The maximum adiabatic flame temperature was attained by the stoichiometric composition, but in practice, the stoichiometric composition resulted in much lower performance than the fuel rich composition. Possible reasons for these behaviors of the compositions were discussed in the paper.