Heterojunctions between amorphous and crystalline niobium oxide with enhanced photoactivity for selective aerobic oxidation of benzylamine to imine under visible light

The formation of heterojunctions between two crystals with different band gap structures, acting as a tunnel for the unidirectional transfer of photo-generated charges, is an efficient strategy to enhance photocatalytic performance in semiconductor photocatalysts. The heterojunctions may also promote the photoactivity in the visible-light-response of any surface complex catalysts by influencing the transfer of photo-generated electrons. Herein, Nb2O5 microfibers, with a high surface area of interfaces between an amorphous phase and crystalline phase, were designed and synthesised by the calcination of hydrogen-form niobate while controlling the crystallization The photoactivity of these microfibers towards selective aerobic oxidation reactions was investigated. As predicted, the Nb2O5 microfibres containing heterojunctions exhibited the highest photoactivity. This could be due to the band gap difference between the amorphous phase and the crystalline phase, which shortened the charge mobile distance and improved the efficiency.

Vertical distribution of aerosols over the east coast of India inferred from airborne LIDAR measurements

The information on altitude distribution of aerosols in the atmosphere is essential in assessing the impact of aerosol warming on thermal structure and stability of the atmosphere.In addition, aerosol altitude distribution is needed to address complex problems such as the radiative interaction of aerosols in the presence of clouds. With this objective,an extensive, multi-institutional and multi-platform field experiment (ICARB-Integrated Campaign for Aerosols, gases and Radiation Budget) was carried out under the Geosphere Biosphere Programme of the Indian Space Research Organization (ISRO-GBP) over continental India and adjoining oceans during March to May 2006. Here, we present airborne LIDAR measurements carried out over the east Coast of the India during the ICARB field campaign. An increase in aerosol extinction (scattering + absorption) was observed from the surface upwards with a maximum around 2 to 4 km. Aerosol extinction at higher atmospheric layers (>2 km) was two to three times larger compared to that of the surface. A large fraction (75-85%) of aerosol column optical depth was contributed by aerosols located above 1 km. The aerosol layer heights (defined in this paper as the height at which the gradient in extinction coefficient changes sign) showed a gradual decrease with an increase in the offshore distance. A large fraction (60-75%) of aerosol was found located above clouds indicating enhanced aerosol absorption above clouds. Our study implies that a detailed statistical evaluation of the temporal frequency and spatial extent of elevated aerosol layers is necessary to assess their significance to the climate. This is feasible using data from space-borne lidars such as CALIPSO,which fly in formation with other satellites like MODIS AQUA and MISR, as part of the A-Train constellation.

Enhanced catharanthine and vindoline production in suspension cultures of Catharanthus roseus by ultraviolet-B light

Suspension cultures of Catharanthus roseus were used to evaluate ultraviolet-B (UV-B) treatment as an abiotic elicitor of secondary metabolites. A dispersed cell suspension culture from C. roseus leaves in late exponential phase and stationary phase were irradiated with UV-B for 5 min. The stationary phase cultures were more responsive to UV-B irradiation than late exponential phase cultures. Catharanthine and vindoline increased 3-fold and 12-fold, respectively, on treatment with a 5-min UV-B irradiation.

Substrate specificity plays an important role in uncoupling the catalytic and scaffolding activities of rat testis DNA topoisomerase IIalpha

Topoisomerase II (topo II) is a dyadic enzyme found in all eukaryotic cells. Topo II is involved in a number of cellular processes related to DNA metabolism, including DNA replication, recombination and the maintenance of genomic stability. We discovered a correlation between the development of postnatal testis and increased binding of topo IIalpha to the chromatin fraction. We used this observation to characterize DNA-binding specificity and catalytic properties of purified testis topo IIalpha. The results indicate that topo IIalpha binds a substrate containing the preferred site with greater affinity and, consequently, catalyzes the conversion of form I to form IV DNA more efficiently in contrast to substrates lacking such a site. Interestingly, topo IIalpha displayed high-affinity and cooperativity in binding to the scaffold associated region. In contrast to the preferred site, however, high-affinity binding of topo IIalpha to the scaffold-associated region failed to result in enhanced catalytic activity. Intriguingly, competition assays involving scaffold-associated region revealed an additional DNA-binding site within the dyadic topo IIalpha. These results implicate a dual role for topo IIalpha in vivo consistent with the notion that its sequestration to the chromatin might play a role in chromosome condensation and decondensation during spermatogenesis.

Zr4+ doping in Li4Ti5O12 anode for lithium-ion batteries: Open Li+ diffusion paths through structural imperfection

One-dimensional nanomaterials have short Li+ diffusion paths and promising structural stability, which results in a long cycle life during Li+ insertion and extraction processes in lithium rechargeable batteries. In this study, we fabricated one-dimensional spinel Li 4Ti5O12 (LTO) nanofibers using an electrospinning technique and studied the Zr4+ doping effect on the lattice, electronic structure, and resultant electrochemical properties of Li-ion batteries (LIBs). Accommodating a small fraction of Zr4+ ions in the Ti4+ sites of the LTO structure gave rise to enhanced LIB performance, which was due to structural distortion through an increase in the average lattice constant and thereby enlarged Li+ diffusion paths rather than changes to the electronic structure. Insulating ZrO2 nanoparticles present between the LTO grains due to the low Zr4+ solubility had a negative effect on the Li+ extraction capacity, however. These results could provide key design elements for LTO anodes based on atomic level insights that can pave the way to an optimal protocol to achieve particular functionalities. Distorted lattice: Zr4+ is doped into a 1 D spinel Li4Ti5O12 (LTO) nanostructure and the resulting electrochemical properties are explored through a combined theoretical and experimental investigation. The improved electrochemical performance resulting from incorporation of Zr4+ in the LTO is due to lattice distortion and, thereby, enlarged Li+ diffusion paths rather than to a change in the electronic structure.

Preparation of Y2Si2O7/ ZrO2 composites and their composition - Mechanical properties - Tribology relationships

In this work, novel Y2Si2O7/ZrO 2 composites were developed for structural and coating applications by taking advantage of their unique properties, such as good damage tolerance, tunable mechanical properties, and superior wear resistance. The γ-Y 2Si2O7/ZrO2 composites showed improved mechanical properties compared to the γ-Y2Si 2O7 matrix material, that is, the Young's modulus was enhanced from 155 to 188 GPa (121%) and the flexural strength from 135 to 254 MPa (181%); when the amount of ZrO2 was increased from 0 to 50 vol%, the γ-Y2Si2O7/ZrO2 composites also presented relatively high facture toughness (>1.7 MPa·m 1/2), but this exhibited an inverse relationship with the ZrO 2 content. The composition-mechanical property-tribology relationships of the Y2Si2O7/ZrO2 composites were elucidated. The wear resistance of the composites is not only influenced by the applied load, hardness, strength, toughness, and rigidity but also effectively depends on micromechanical stability properties of the microstructures. The easy growth of subcritical microcracks in Y 2Si2O7 grains and at grain boundaries significantly contributes to the macroscopic fracture toughness, but promotes the pull-out of individual grains, thus resulting in a lack of correlation between the wear rate and the macroscopic fracture toughness of the composites.

Aqueous colloidal stability evaluated by zeta potential measurement and resultant TiO2 for superior photovoltaic performance

Controlling the morphological structure of titanium dioxide (TiO 2) is crucial for obtaining superior power conversion efficiency for dye-sensitized solar cells. Although the sol-gel-based process has been developed for this purpose, there has been limited success in resisting the aggregation of nanostructured TiO2, which could act as an obstacle for mass production. Herein, we report a simple approach to improve the efficiency of dye-sensitized solar cells (DSSC) by controlling the degree of aggregation and particle surface charge through zeta potential analysis. We found that different aqueous colloidal conditions, i.e., potential of hydrogen (pH), water/titanium alkoxide (titanium isopropoxide) ratio, and surface charge, obviously led to different particle sizes in the range of 10-500 nm. We have also shown that particles prepared under acidic conditions are more effective for DSSC application regarding the modification of surface charges to improve dye loading and electron injection rate properties. Power conversion efficiency of 6.54%, open-circuit voltage of 0.73 V, short-circuit current density of 15.32 mA/cm2, and fill factor of 0.73 were obtained using anatase TiO 2 optimized to 10-20 nm in size, as well as by the use of a compact TiO2 blocking layer.

Sinteractivity, proton conductivity and chemical stability of BaZr 0.7In0.3O3-δ for solid oxide fuel cells (SOFCs)

In3+ was used as dopant for BaZrO3 proton conductor and 30 at%-doped BaZrO3 samples (BaZr0.7In 0.3O3-δ, BZI) were prepared as electrolyte materials for proton-conducting solid oxide fuel cells (SOFCs). The BZI material showed a much improved sinteractivity compared with the conventional Y-doped BaZrO 3. The BZI pellets reached almost full density after sintering at 1600 °C for 10 h, whereas the Y-doped BaZrO3 samples still remained porous under the same sintering conditions. The conductivity measurements indicated that BZI pellets showed smaller bulk but improved grain boundary proton conductivity, when compared with Y-doped BaZrO3 samples. A total proton conductivity of 1.7 × 10-3 S cm -1 was obtained for the BZI sample at 700 °C in wet 10% H 2 atmosphere. The BZI electrolyte material also showed adequate chemical stability against CO2 and H2O, which is promising for application in fuel cells.

Low-temperature synthesis and sintering of γ-Y2Si2O7

In this article, a novel pressureless solid-liquid reaction method is presented for preparation of yttrium disilicate (γ-Y2Si2O7). Single-phase γ-Y2Si2O7 powder was synthesized by calcination of SiO2 and Y2O3 powders with the addition of LiYO2 at 1400 °C for 4 h. The addition of LiYO2 significantly decreased the synthesis temperature, shortened the calcination time, and enhanced the stability of γ-Y2Si2O7. The sintering of these powders in air and O2 was studied by means of thermal mechanical analyzer. It is shown that the γ-Y2Si2O7 sintered in oxygen had a faster densification rate and a higher density than that sintered in air. Furthermore, single-phase γ-Y2Si2O7 with a density of 4.0 g/cm3 (99% of the theoretical density) was obtained by pressureless sintering at 1400 °C for 2 h in oxygen. Microstructures of the sintered samples are studied by scanning electron microscope.

Influence of spatial variability of permeability property on steady state seepage flow and slope stability analysis

In recent years, spatial variability modeling of soil parameters using random field theory has gained distinct importance in geotechnical analysis. In the present Study, commercially available finite difference numerical code FLAC 5.0 is used for modeling the permeability parameter as spatially correlated log-normally distributed random variable and its influence on the steady state seepage flow and on the slope stability analysis are studied. Considering the case of a 5.0 m high cohesive-frictional soil slope of 30 degrees, a range of coefficients of variation (CoV%) from 60 to 90% in the permeability Values, and taking different values of correlation distance in the range of 0.5-15 m, parametric studies, using Monte Carlo simulations, are performed to study the following three aspects, i.e., (i) effect ostochastic soil permeability on the statistics of seepage flow in comparison to the analytic (Dupuit's) solution available for the uniformly constant permeability property; (ii) strain and deformation pattern, and (iii) stability of the given slope assessed in terms of factor of safety (FS). The results obtained in this study are useful to understand the role of permeability variations in slope stability analysis under different slope conditions and material properties. (C) 2009 Elsevier B.V. All rights reserved.

Analysis of stability of earthen dams in kachchh region, Gujarat, India

The Kachchh region of Gujarat, India bore the brunt of a disastrous earthquake of magnitude M-w=7.6 that occurred on January 26, 2001. The major cause of failure of various structures including earthen dams was noted to be the presence of liquefiable alluvium in the foundation soil. Results of back-analysis of failures of Chang, Tappar, Kaswati and Rudramata earth dams using pseudo-static limit equilibrium approach presented in this paper confirm that the presence of liquefiable layer contributed to lesser factors of safety leading to a base type of failure that was also observed in the field. Following the earthquake, earth dams have been rehabilitated by the concerned authority and it is imperative that the reconstructed sections of earth dams be reanalyzed. It is also increasingly realized that risk assessment of dams in view of the large-scale investment made and probabilistic analysis is necessary. In this study, it is demonstrated that the probabilistic approach when used in conjunction with deterministic approach helps in providing a rational solution for quantification of safety of the dam and in the estimation of risk associated with the dam construction. (C) 2007 Elsevier B.V. All rights reserved.

Effect of residual stresses and metallographic stability on the over all performance of integral diaphragm material

The integral diaphragm pressure transducer consists of a diaphragm machined from precipitation hardened martensitic (APX4) steel. Its performance is quite significant as it depends upon various factors such as mechanical properties including induced residual stress levels, metallurgical and physical parameters due to different stages of processing involved. Hence, the measurement and analysis of residual stress becomes very important from the point of in-service assessment of a component. In the present work, the stress measurements have been done using the X-ray diffraction (XRD) technique, which is a non-destructive test (NDT). This method is more reliable and widely used compared to the other NDT techniques. The metallurgical aspects have been studied by adopting the conventional metallographic practices including examination of microstructure using light microscope. The dimensional measurements have been carried out using dimensional gauge. The results of the present investigation reveals that the diaphragm material after undergoing series of realization processes has yielded good amount of retained austenite in it. Also, the presence of higher compressive stresses induced in the transducer results in non-linearity, zero shift and dimensional instability. The problem of higher retained austenite content and higher compressive stress have been overcome by adopting a new realization process involving machining and cold and hot stabilization soak which has brought down the retained austenite content to about 5–6% and acceptable level of compressive stress in the range −100 to −150 MPa with fine tempered martensitic phase structure and good dimensional stability. The new realization process seems to be quite effective in terms of controlling retained austenite content, residual stress, metallurgical phase as well as dimensional stability and this may result in minimum zero shift of the diaphragm system.

An optimal weighted-average congestion based pricing scheme for enhanced QoS

Pricing is an effective tool to control congestion and achieve quality of service (QoS) provisioning for multiple differentiated levels of service. In this paper, we consider the problem of pricing for congestion control in the case of a network of nodes under a single service class and multiple queues, and present a multi-layered pricing scheme. We propose an algorithm for finding the optimal state dependent price levels for individual queues, at each node. The pricing policy used depends on a weighted average queue length at each node. This helps in reducing frequent price variations and is in the spirit of the random early detection (RED) mechanism used in TCP/IP networks. We observe in our numerical results a considerable improvement in performance using our scheme over that of a recently proposed related scheme in terms of both throughput and delay performance. In particular, our approach exhibits a throughput improvement in the range of 34 to 69 percent in all cases studied (over all routes) over the above scheme.

High-strength bulk Al-based bimodal ultrafine eutectic composite with enhanced plasticity

An in situ bulk ultrafine bimodal eutectic Al-Cu-Si composite was synthesized by solidification. This heterostructured composite with microstructural length scale hierarchy in the eutectic microstructure, which combines an ultrafine-scale binary cellular eutectic (alpha-Al + Al2Cu) and a nanometer-sized anomalous ternary eutectic (alpha-Al + Al2Cu + Si), exhibits high fracture strength (1.1 +/- 0.1 GPa) and large compressive plastic strain (11 +/- 2%) at room temperature. The improved compressive plasticity of the bimodal-nanoeutectic composite originates from homogeneous and uniform distribution of inhomogeneous plastic deformation (localized shear bands), together with strong interaction between shear bands in the spatially heterogeneous structure.