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NiO-TiO2 (TN) nanocomposite is synthesized from an assembly of p-type nickel oxide (NiO) and n-type titanium oxide (TiO2) in an ultrasound assisted operation. Transmission electron microscopy (TEM) demonstrates the existence of hexagonal particles in the nanocomposite. Dynamic light scattering (DLS) measurements show stable TN nanoparticles (NPs) at a negative zeta potential (−18.5 ± 0.8 mV). The nanocomposite is tested for its catalytic activity towards degrading malachite green (MG), a known water toxicant and methylene blue (MB) under ultraviolet (UV) irradiation. Response surface methodology (RSM) is employed to optimise the influence of significant variables such as initial dye concentration, catalyst dose and time. Their mutual interactions are mapped by response surface and contour plots and correlated with degradation process by a designed model. The best photocatalytic efficiency (87%) is observed at an optimised concentration of 5 ppm dye with 10 ppm catalyst. The presence of inorganic ions and organic matter hardly affected the aggregate size of TN but caused a decline in photoactivity. The catalyst is found effective even in real water system (Hooghly River). A (Fluorine doped tin oxide) FTO/TN/Al heterojunction is fabricated. TN showed enhanced carrier mobility (1.03.10−4 m2V-1s-1) and low transit time (1.76.10-6 s) evaluated using space charge limited current (SCLC) theory. The nanocomposite appears suitable for energy preservation and environmental applications.

A novel methodology was developed that uniquely employs alternating current (AC) electric field to fabricate ice-templated ceramics. In the methodology, AC field was applied to an aqueous ceramic suspension, and then ice-templating was performed. Field application to an aqueous ceramic suspension resulted in a net motion of ceramic particles due to DC voltage generation. Suspension concentration increased near one of the electrodes, which was controllable through AC frequency and field duration. Density of the very bottommost regions in sintered materials increased with field duration, attributed to increased local suspension concentration. In sintered materials, the thickness of non-templated region increased with field duration, whereas templated microstructure turned increasingly dendritic with field duration, suggesting a strong influence of AC field on the growth characteristics of ice crystals. AC-field assisted materials exhibited remarkably enhanced compressive strength without any change in porosity. This work contributes to advancing the ice-templating technology using externally energized fields.

We investigated the effects of platelets and strain rate on the compressive response of ice-templated porous alumina, processed from ultrafine, equiaxed particles and from a mixture of ultrafine, equiaxed and large platelet particles. Results revealed a remarkable enhancement of the quasistatic and dynamic compressive mechanical properties of the templated ceramics in the presence of platelets. Specific compressive mechanical properties of the ice-templated alumina containing platelets are superior in comparison to those of the various metallic, syntactic and natural cellular solids. In the presence of platelets, compressive strength exhibited contrasting strain rate sensitivity between the elastic and inelastic stages of deformation.

We investigated and thoroughly analyzed compressive response of ice-templated ceramics in quasistatic and dynamic regimes of strain rate. In the high pore volume regime, sintered scaffolds exhibited highly lamellar pore morphology and pore architecture transitioned to dendritic with the decreasing pore volume. Mechanical property measurements in the quasistatic regime of strain rate revealed that with increasing density, compressive response transitioned from a damageable, cellular-like failure to a brittle-like failure. We rationalized the measured results in terms of the propensity of the lamella walls to undergo buckling. Our conjecture is that in the high pore volume regime, lamella walls of the scaffolds are prone to buckling-induced elastic instability, which leads to a compressive response that manifests a gradual decrease of stress beyond peak stress. In contrast, we suggest that in the low pore volume regime thick lamella walls and extensive transverse bridging exhibit marked resistance to buckling-induced instability and scaffolds undergo a global failure, which is manifested in the measured quasistatic compressive response as a sharp drop of stress beyond peak stress. Dynamic compressive response of the scaffolds exhibited measurable differences relative to the quasistatic compressive response. Scaffolds exhibited a relatively gradual decrease of dynamic compressive stress beyond peak stress, and an overall improvement of compressive response and energy absorption capacity was measured under the dynamic loading conditions. We rationalized the measured differences in between the strain rate regimes in terms of the micro-inertia and other effects. This study is of critical significance for applications of ice-templated structures in dynamic environments.

We attempted to develop a phenomenological understanding of the evolution of the fracture events within fine-grained lamella walls of partially deformed ice-templated sintered Al 2 O 3 scaffolds and revealed the effects of the platelets on the crack propagation characteristics. Detailed microstructural analyses suggest that intergranular cracks within the walls evolved at two orientations, parallel and perpendicular to the loading direction. We proposed probable mechanisms including one based on the so-called wing-crack model to rationalize the observed crack orientations. We presented crack propagation behavior in lamella walls in presence of the platelets and discussed the effects in terms of the crack deflection mechanism.

Ice-templated ceramics have unique lamellar pore morphology that offers better compressive mechanical properties in comparison to the typical ceramic foams with isotropic pore morphology. However, for very high-level porosity (>65 vol%) strength difference diminishes. This investigation reveals that by inducing anisotropic grains within the matrix of a fine-grained ceramic, uniaxial compressive response of the ice-templated sintered scaffolds can be markedly enhanced without causing any considerable modification of the total porosity. To address this innovative materials design strategy, we synthesized a series of microstructures by systematically varying the anisotropic grains content in an aqueous suspension and the freezing kinetics to investigate the process-microstructure correlations and understand the structure-property relationships. Microstructural investigations revealed the unique arrangements of the platelets within and out of the lamella walls, where the upward moving ice fronts aligned the platelets' in-plane direction to the ice-growth direction. In the low freezing front velocity regime, platelets were observed to be mainly within the lamella walls, whereas platelets started to develop lamellar bridges with the increasing velocity. As a result, a transition of the pore morphology occurred with the increasing platelets content and the freezing front velocity. A novel method based on the rigorous microstructural analysis is developed to estimate the distribution of the platelets within and out of the walls and the variation of the platelets distribution with the composition and freezing front velocity. A drastic improvement of the compressive mechanical properties (stiffness, strength, energy absorption capacity) was measured due to the platelets' addition, which has been related to the platelets' distribution within and out of the walls and the pore morphology modifications. Results are rationalized based on the role of the platelets during the compressive deformation.

This paper describes the effects of the grain-level anisotropy on the microstructure and uniaxial compressive response of the ice-templated alumina scaffolds. Highly porous (~ 80 vol.%) scaffolds were fabricated from alumina powders of equiaxed morphology as well as from powder mixtures containing equiaxed and small amount of platelet particles. Presence of the platelets (diameter 8 μm and thickness 400 nm) led to the formation of the interlamellae bridges, and significantly enhanced the stiffness and compressive strength of the scaffolds. Measured improvement of the mechanical response is rationalized based on the stiffening and strengthening effects exhibited by the intralamella and interlamella platelets.

The ice-templating technique enables the fabrication of multilayered ceramic-based composite materials. Very little is known on the inelastic deformation mechanisms that evolve in this class of composite materials under compressive loading conditions and cause macroscopic failure. The current investigation is motivated by a recent study by the authors, which revealed that the uniaxial compressive response of ice-templated ceramic–polymer composites is strongly dependent on the loading direction relative to the layer orientation. The current investigation reveals that the inelastic deformation mechanisms in ice-templated alumina–epoxy composites are strongly influenced by the compressive loading orientation relative to the growth direction of ice crystals. The deformation mechanisms were investigated for the loading directions of 0° (parallel to the growth direction), 45° (to the growth direction), and 90° (to the growth direction). For 0°, kink band formation and longitudinal splitting were observed to be the primary strength limiting mechanisms. Kink band formation could be the primary strength limiting factor and responsible for the catastrophic-type compressive failure response. For the loading directions of 45° and 90°, interface delamination and fracture within the lamella walls and across the alumina–epoxy interfaces were the main deformation mechanisms. These mechanisms significantly reduced the compressive strength but attributed progressive-type failure behavior in ice-templated composites. The knowledge of the inelastic deformation mechanisms in ice-templated ceramic–polymer composites under compressive loading is vital for an improved understanding of structure–mechanical property relationships and hierarchical materials design.

This work is motivated by the structural gradient observed in natural materials to investigate the influence of the loading direction on the compressive response of ice-templated alumina-epoxy composites. Although this investigation is not on the development of multilayered composites with a structural gradient, the current results can help understand the mechanical behavior and design of such materials. Ice-templated alumina materials were developed from 20 vol% suspensions at high freezing-front velocity (FFV) and from 30 vol% suspensions at high and low FFVs. From porous ceramics, specimens were extracted at different orientations relative to the growth direction of ice crystals and infiltrated with epoxy. The resultant composites varied in ceramic fraction and morphology. For compression along the growth direction of ice crystals, specimens exhibited either high strength with brittle-like (catastrophic) failure or low strength with ductile-like (progressive) failure. Away from growth direction, strength decreased significantly, and failure was ductile-type. The strength exhibited a strong dependence on ceramic fraction and morphology. At each orientation, strength data of both porous ceramics and composites showed significant variability, and Weibull analysis suggested a connection between their strength. Direct visualization revealed the influence of loading orientation and morphology on deformation and failure in composites. Using the Tsai-Hill failure criterion, the role of competitive failure mechanisms on the compressive response of composites was evaluated. From the knowledge of composition, compressive and bend strength of ceramic phase, and yield strength of polymer phase, upper bound and lower bound of strength were predicted, which encompassed the strength of composites.

Ice-templating technique enables the synthesis of novel ceramic materials with directional, anisotropic pores, and the templated structure is highly tunable. Another factor that also drives interest in ice-templated ceramics is that for a comparable level of porosity, the uniaxial compressive strength of these materials can be significantly greater in comparison to that of the conventional open-cell foams. However, the strength advantage is significantly reduced in the materials templated from low solid loading suspensions. Toward this limitation, this study sheds insights into the influence of sucrose (a water-soluble additive) and freezing front velocity (FFV) on microstructure and the uniaxial compressive response of ice-templated sintered lithium titanate (LTO, composition Li4Ti5O12). This study used LTO as a model material. Materials were ice-templated from aqueous suspensions with 20 vol.% LTO powder and sucrose content was varied between 1–4 wt.%. The porosity of the sintered materials was in the range of 60–65 vol.%. Materials processed without sucrose exhibited lamellar morphology and low compressive strength. Sucrose had a marked influence on the connectivity between lamella walls, which significantly increased with sucrose content, and morphology became highly dendritic. The microstructural changes remarkably impacted compressive strength, which increased as high as eight-fold. Moreover, materials processed with sucrose exhibited a significant increase in strength in the continuous brittle crushing regime. By adjusting sucrose content in aqueous suspension and FFV, it is possible to synthesize ice-templated sintered LTO materials with tailored connectivity between lamella walls and harness compressive strength within a wide range of 4–80 MPa.

This study investigates the effects of two different particle sizes (0.3 μ m vs. 0.9 μ m ) on the microstructure and uniaxial compressive response of ice-templated sintered alumina scaffolds as a function of the solids loading of the ceramic suspensions and freezing front velocity (FFV). For a comparable solids loading and FFV, variation of the particle size is observed to have a significant effect on the microstructure of the fabricated scaffolds. Moreover, transition of the pore morphology with the increasing solids loading and FFV is observed to be more drastic for the scaffolds processed from the 0.9 μ m size powder particles compared to the scaffolds processed from the 0.3 μ m size powder particles. Similarly, particle size variation also influenced significantly the relative density and porosity of the scaffolds. Interestingly, in spite of the observed significant differences of the microstructure and relative density, uniaxial compressive stress-strain measurements revealed marginal effects of the particle size variation on the compressive strength. The measured comparable uniaxial compressive response of the sintered alumina scaffolds fabricated from two different particle sizes are rationalized based on the relative density, pore aspect ratio, and interlamellae bridge density.

A number of single and two parameter variational approximations for the LP 01 mode are reported in the literature which has been used to compute the various propagation characteristic parameters, such as, propagation constant, normalised dispersion, splice loss, bending loss etc. for single mode fibers. These studies are limited to optically linear fibers. To our knowledge, these variational approximations have not been used to study the nonlinear optical processes in such fibers. In the present work, using these variational approximations, the generation of self-similar parabolic pulses in graded-index single mode normal dispersive active fibers has been studied. The optimum length L opt of the fiber, after which an input Gaussian pulse turns into a self-similar parabolic pulse, has been computed and the accuracies obtained from these variational approximations have been compared.

This study investigates the effects of the size of hollow glass microspheres (20 μm vs. 40 μm) and composition on the energy absorption capacity of the silicate glass foams under both the quasistatic (∼10^(−3) s^(−1)) and high-strain rate (∼10^3 s^(−1)) loading conditions. These measurements revealed that while the size difference of the hollow glass microspheres and the foam composition have negligible effects on the uniaxial quasistatic response, their effects were significant under the dynamic loading conditions. The results suggest that the smaller glass microspheres (20 μm) dominated the dynamic behavior of the glass foams in comparison to the larger glass microspheres (40 μm), leading to a significant increase of the energy absorption capacity of the 20 μm-based glass foams at high-strain rates. Glass foams exhibited energy absorption capacity of about 54 kJ/kg under the dynamic loading that is greater in comparison to that of the typical metallic and syntactic foams.

Let $A$ be a Noetherian standard $\mathbb{N}$-graded algebra over an Artinian local ring $A_0$. Let $I_1,\ldots,I_t$ be homogeneous ideals of $A$ and $M$ a finitely generated $\mathbb{N}$-graded $A$-module. We prove that there exist two integers $k$ and $k'$ such that \[ \mathrm{reg}(I_1^{n_1} \cdots I_t^{n_t} M) \leq (n_1 + \cdots + n_t) k + k' \quad\mbox{for all }~n_1,\ldots,n_t \in \mathbb{N}. \], 9 pages

The isolation of ten different cyanobacteria were carried out from northern parts of India and among them the cyanobacterium with maximum specific growth rate (0.246 day−1) was selected for the present study. The strain was further identified using morphometric and molecular analysis using 16S rDNA sequencing and was found to be related with Leptolyngbya sp. (GenBank accession no.: KF953500). The analysis of biomass composition showed ash content, amount of carbohydrate, lipid content, amount of protein, and moisture were found to be 6.8, 27.20, 18.30, 45.70, and 2% respectively. Over 26.6% increment in lipid content was evidenced when the strain was grown in BG11 medium augmented with salinity (25 mM sodium chloride) as compared to BG11 medium without sodium chloride. The unsaturated fatty acids was found 1.39 times higher than saturated fatty acids in KF953500. The lipid separated from cyanobacteria showed saponification value of 220.28, iodine value of 84.08, cetane number of 52.16, degree of unsaturation of 84.04 (%), long-chain saturation factor of 3.09 (%) and cold-filter plugging point of −6.76 °C which are generally in covenant with international standards of biodiesel. Other biodiesel properties such as pour point, flash point, acid number, viscosity, specific gravity, and density were found to be −18 °C, 126 °C, 0.34 mg KOH/g, 4.08 mm2 s−1, 0.812, and 854 kg m−3 respectively which falls within the acceptable ranges as per ASTM D6751 and EN 14214 standards, signifying the aptness of the microalga as promising sustainable feedstock for biodiesel.

The present research work was aimed at improving the high field dielectric properties of silicone rubber (SR) composites used for power cable insulation. Liquid silicone rubber composites were developed using two types of clays as filler materials; organically modified montmorillonite (ommt) and calcined, surface treated kaolin with the commercial name Translink 37 (T37). The results revealed that the surface chemistry of the clay had a distinct effect on both dispersion as well as electrical performance of silicone rubber-clay composites. We observed that surface treated kaolin (T37) were well dispersed in the SR matrix, but had adverse impact on the crosslinking kinetics of liquid silicone rubber resulting in higher dielectric loss at low frequencies. On the other hand, organically modified clay showed poor dispersion in the silicone rubber matrix while exhibiting much lower dc conductivity characteristics at high temperature. The agglomerated ommt macroparticles introduced the interfacial traps in SR matrix and charge carriers migration was limited within the matrix.

The current investigation provides insights into microstructure development as a function of sintering temperature within lamella walls of ice-templated ceramics, effects of ceramic platelets on wall microstructure, and the influence of those developments on the compressive mechanical response. The results revealed a profound influence of both on the several aspects of ice-templated ceramics, enabling an improved understanding of the structure-mechanical property relationships in these materials and limitations in the development of the ice-templated ceramic structure. In the materials without platelets, at low-temperature walls were highly porous, at intermediate temperature a pore-free lamella wall with fine-grained microstructure developed, and at high-temperature along with grain growth significant abnormal grain growth occurred as well. More dramatic was the combined effects of temperature and platelets. The effects of platelets were realized at two length scales. Some of the platelets developed lamellar bridges, whereas the platelets that became part of the lamella walls remarkably impacted wall microstructure. The current results strongly suggest that there are significant structural and mechanical strength advantages in the incorporation of large anisometric particles in ice-templated ceramics. The addition of large platelets resulted in a marked increase of compressive strength. A significant structural advantage is that the materials containing platelets exhibited improved stability to structural deformation at higher temperatures compared to the materials without the platelets. Thus, this study shows the importance of deeply probing into the structure-mechanical property relationships of ice-templated ceramics as a function of temperature and composition, providing valuable guidance into the microstructure design of these materials.

Managers are influenced in their decisions by the information provided by managerial accountants. Two typical examples from textbooks are the irrelevance of sunk costs and, more recently, the affect of knowing the outcome of a decision or revised budget forecast. Individual differences in the cognitive ability of decision makers to use information can lead to systematic differences in judgments. We identify and label one of these individual cognitive differences comprehensive thinking ability: the ability to think about multiple paths, branches or alternatives. Significant comprehensive thinking ability is likely to mitigate systematic differences in judgment in many contexts. We report the results of a series of studies using a variation on the investment trap (sunk cost or irrelevant cost) problem and a probability revision task. The findings suggest that comprehensive thinking ability may also explain other common systematic differences in judgment.

Microalgae are being investigated as potential candidates for biodiesel production since they can be grown without competition with food production, have an inherently fast growth rate, and can have a high lipid content under different nutrient limiting conditions. However, large scale production will best be carried out with indigenous strains, well adapted to local conditions. This study reports on the characterization of the novel microalga Chlorella sp. PCH90, isolated in Quebec. Its molecular phylogeny was established and lipid production studies as a function of the initial concentrations of nitrate, phosphate, and sodium chloride were carried out using response surface methodology. Under the appropriate conditions this microalga could produce up to 36% lipid and grew well in both synthetic medium and secondary effluent from a wastewater treatment plant at both 22 and 10 °C. Thus, this strain is promising for further development as a potential biofuels producer under local climatic conditions.

Mg–Al 2 O 3 nanocomposite powders, with Al 2 O 3 particles of 50 nm size, were synthesized by mechanical alloying starting from a mixture of 70 vol.% pure Mg and 30 vol.% Al 2 O 3 powders. A steady-state condition was obtained on milling the powder mix for about 20 h, when the crystallite size of the Mg powder was about 10 nm. The structural evolution during milling was monitored using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction methods. The results showed that a mixture of Mg, Al 2 O 3 , and MgO phases were obtained on mechanical alloying. On annealing the milled powders at 600 °C for 30 min, a displacement reaction occurred between the Mg and Al 2 O 3 phases, when the formation of a mixture of pure Al and MgO phases was observed. Also, a reaction occurred between the initial Mg powder and Al formed as a result of the displacement reaction, leading to the formation of Mg 17 Al 12 , Al 0.58 Mg 0.42 , and Al 3 Mg 2 phases. Thus, the powder annealed after milling the Mg + Al 2 O 3 powder mix for 25 h consisted of Al, MgO and Al 3 Mg 2 phases.

Hydrogen production from glucose via single-stage photofermentation was examined with the photosynthetic bacterium Rhodobacter capsulatus JP91 (hup-). Response surface methodology with Box–Behnken design was used to optimize the independent experimental variables of glucose concentration, glutamate concentration and light intensity, as well as examining their interactive effects for maximization of molar hydrogen yield. Under optimal condition with a light intensity of 175 W/m 2 , 35 mM glucose, and 4.5 mM glutamate, a maximum hydrogen yield of 5.5 (±0.15) mol H 2 /mol glucose, and a maximum nitrogenase activity of 246 (±3.5) nmol C 2 H 4 /ml/min were obtained. Densitometric analysis of nitrogenase Fe-protein expression under different conditions showed significant variation in Fe-protein expression with a maximum at the optimized central point. Even under optimum conditions for hydrogen production, a significant fraction of the Fe-protein was found in the ADP-ribosylated state, suggesting that further improvement in yields might be possible.

Calculation of bend loss for single-mode graded-index fibers utilizes the fundamental modal field. Using some of the single and two parameter scalar variational approximations available in the literature for this mode, the bend loss has been computed. The exact results are obtained using a well known numerical method. The accuracies of the results obtained from the use of these variational fields have been compared.

Biological hydrogen production presents a possible avenue for the large scale sustainable generation of hydrogen needed to fuel a future hydrogen economy. Amongst the possible approaches that are under active investigation and that will be briefly discussed; biophotolysis, photofermentation, microbial electrolysis, and dark fermentation, dark fermentation has the additional advantages of largely relying on already developed bioprocess technology and of potentially using various waste streams as feedstock. However, the major roadblock to developing a practical process has been the low yields, typically around 25%, well below those achievable for the production of other biofuels from the same feedstocks. Moreover, low yields also lead to the generation of side products whose large scale production would generate a waste disposal problem. Here recent attempts to overcome these barriers are reviewed and recent progress in efforts to increase hydrogen yields through physiological manipulation, metabolic engineering and the use of two-stage systems are described.

Replacement of fossil fuels with alternative energies is increasingly imperative in light of impending climate change and fossil fuel shortages. Biohydrogen has several potential advantages over other biofuels. Dark fermentation as a means of producing biohydrogen is attractive since a variety of readily available waste streams can be used. However, at present its practical application is prevented by the low yields obtained. Here the basic metabolisms leading to hydrogen production are outlined and current research to increase yields, either through modification of existing pathways, or by metabolic engineering to create new, higher yielding, pathways, is discussed. Inactivation of competing reactions and manipulation of culture conditions has lead to higher hydrogen yields, near those predicted by metabolic schemes. However, to be useful, hydrogen production must be increased beyond present limits. Several possibilities for surpassing those limits using metabolic engineering are presented.

Biodiesel manufacture produces crude glycerol as a major byproduct. At the scale estimated for future biodiesel production, extensive quantities of crude glycerol fraction will be generated, creating a large waste stream with potentially significant environmental impacts. The magnitude of projected future crude glycerol supplies suggests that its conversion to a biofuel is the only viable route to producing a product that does not cause market saturation. Previously it was shown that crude glycerol could be converted to hydrogen, a possible future clean energy carrier, by photofermentation using Rhodopseudomonas palustris through photofermentation. Here, the effects of nitrogen source and different concentrations of crude glycerol on this process were assessed. At 20 mM glycerol, 4 mM glutamate, 6.1 mol hydrogen/mole of crude glycerol were obtained under optimal conditions, a yield of 87% of the theoretical, and significantly higher than what was achieved previously.

The extent of dislocation-based plasticity in ceramics is limited and often accompanied by microcracking. This limitation has precluded the investigation of post-yield plastic response in ceramics. Using low-load nanoindentations and by tracking the hardness of selected grains before and after plastic deformation, the influence of microcracking and variability in microhardness due to grain orientation were minimized and the post-yield response of polycrystalline ZrB 2 ceramic was determined. The observed increase in nanoindentation hardness after plastically deforming isolated ZrB 2 grains indicates conclusively the existence of post-yield strain hardening.

Photosynthetic bacteria have been extensively investigated for biohydrogen production due to their high intrinsic substrate conversion efficiency. Many studies have examined different aspects of photo fermentative hydrogen production using various volatile organic fatty acids under nitrogen limited conditions, and in some cases nearly stoichiometric hydrogen yields have been obtained. In addition, there has been great interest in using photosynthetic bacteria to increase the yields of dark fermentation of glucose through either two stage or co-culture approaches. Although these processes can achieve yields of about 7 mol of H2 per mole of glucose, there have many drawbacks. Thus, we have begun the systematic investigation of a simple one stage system for the conversion of glucose to hydrogen through photofermentation by Rhodobacter capsulatus. Yields of about 3 mol of H2 per moles of glucose have been obtained, which represents a yield of 25% yield. Thus improvement is needed and can be sought through a variety of means, including. process optimization and gene inactivation. These approaches could allow the development of a single stage process for the complete stoichiometric conversion of glucose, or glucose containing wastes, to hydrogen with a minimal lag phase and relative insensitivity to inhibition by fixed nitrogen. This would present an attractive simple alternative to either two stage or co-culture fermentations for the complete conversion of carbohydrate substrates to hydrogen.

The parabolic similariton pulse formation by alternate arrangements of passive and active dispersion compensating fibers (DCFs) is presented here. These combinations of passive and active DCFs with constant core radii and constant nonlinearities are suggested as equivalent profiles of a dispersion tailored fiber amplifier in normal dispersion regime. The dispersion tailored fibers, usually known as dispersion decreasing fibers (DDFs) in normal dispersion regime, are capable of producing linearly chirped parabolic self-similar pulses. The DDF is designed and optimized with proper choice of fiber parameters so that considerable variation of nonlinearity can be achieved, which in turn enhances the effective gain coefficient of the fiber. Inclusion of this nonlinear variation along the DDF amplifier length leads to obtain the simulated output pulses with very small misfit parameters with respect to perfect parabolic pulse at sufficiently reduced optimum length. At the same time to avoid the fabrication difficulties of the DDF, the alternately arranged passive and active DCFs are suggested as suitable alternatives of the DDF. The performances of the cascaded systems for generation of self-similar parabolic pulses are compared with that of the DDF amplifier as well as combined systems consisting of DCFs with equal gain. The results show that the proposed alternately arranged cascaded system with less pumping requirements, are efficient enough to produce similar parabolic pulses as compared to the previously designed DDF, even when considerable amount of splice loss at each joint is included.

Macroscopic manifestation of microscale plasticity at room temperature in the form of slip-lines has been elusive in brittle solids. Recently, such a phenomenon has been reported in ZrB2 ceramics and ZrB2–SiC composites, where slip-lines were detected in room-temperature deformation. Here we show that the slip-line spacing increases with grain size in these ceramics and their composites. Such behavior has been rationalized on the basis of geometrically necessary dislocations and the role of grain boundaries and interfaces.

Ceramics such as ZrB 2 and HfB 2 are potential candidates for ultra-high-temperature applications. Their electrical conductivity values are comparable to those of metals. Such unusual electrical properties arise from the presence of metallic bonds in their crystal structure. We argue that the metallicity in chemical bonding is also reflected in their room-temperature mechanical deformation, which was investigated through indentation-induced slip bands and the resulting dislocation activity. These observations were rationalized on the basis of metallic character of their dislocation core structure.

Inelastic deformation features induced in an ultra-high temperature ceramic composite, ZrB 2 –SiC, due to static indentation (rate of deformation of the order of 10 −5 s −1 ), dynamic indentation (rate of deformation of the order of 10 3 s −1 ), and high-velocity scratch (500 mm/s) experiments are presented. It was found that this ceramic composite has up to 30% higher dynamic hardness compared to static hardness. Dynamic indentations resulted in extensive transgranular microcracking within the indented regions compared to static indentations. In addition, significant plastic deformation features in terms of slip-line formation were observed within statically and dynamically indented regions. The high-velocity scratch studies revealed extensive transgranular microcracking perpendicular to the scratch direction and slip-lines in and around the scratch path. Preliminary transmission electron microscopy (TEM) observations from regions of slip-lines surrounding the scratch grooves revealed dislocation activity in the composite.

Future sustainable production of biofuels will depend upon the ability to use complex substrates present in biomass if the use of simple sugars derived from food crops is to be avoided. Therefore, organisms capable of using a variety of fermentable carbon sources must be found or developed for processes that could produce hydrogen via fermentation. Here we have examined the ability of a metabolically engineered strain of Escherichia coli, DJT135, to produce hydrogen from glucose as well as various other carbon sources, including pentoses. The effects of pH, temperature and carbon source were investigated in batch experiments. Maximal hydrogen production from glucose was obtained at an initial pH of 6.5 and temperature of 35 °C. Kinetic growth studies showed that the μmax was 0.0495 h−1 with a Ks of 0.0274 g L−1 when glucose was the sole carbon source in M9 (1X) minimal medium. Among the many sugar and sugar derivatives tested, hydrogen yields were highest with fructose, sorbitol and d -glucose; 1.27, 1.46 and 1.51 mol H2 mol−1 substrate respectively.

Alpha-melanocyte stimulating hormone (alpha-MSH) is an endogenous anti-inflammatory peptide reported to possess antimicrobial properties, however their role as antibacterial peptides is yet to be established. In the present study, we examined in vitro antibacterial activity of alpha-MSH against S. aureus strain ISP479C and several methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) S. aureus strains. Antibacterial activity was examined by varying several parameters, viz., bacterial cell densities, growth phase, pH, salt concentration, and temperature. Antibacterial activity was also examined in complex biomatrices of rat whole blood, plasma and serum as well as in biofilm form of bacteria. Our results showed that alpha-MSH possessed significant and rapid antibacterial activity against all the studied strains including MRSA (84% strains were killed on exposure to 12 microM of alpha-MSH for 2h). pH change from 7.4 to 4 increased alpha-MSH staphylocidal activity against ISP479C by 21%. Antibacterial activity of alpha-MSH was dependent on bacterial cell density and independent of growth phase. Moreover, antimicrobial activity was retained when alpha-MSH was placed into whole blood, plasma, and serum. Most importantly, alpha-MSH exhibited antibacterial activity against staphylococcal biofilms. Multiple membrane permeabilization assays suggested that membrane damage was, at least in part, a major mechanism of staphylocidal activity of alpha-MSH. Collectively the above findings suggest that alpha-MSH could be a promising candidate of a novel class of antimicrobial agents.

A computational method for arbitrary crack motion through a finite element mesh, termed as the generalized cohesive element technique, is presented. In this method, an element with an internal discontinuity is replaced by two superimposed elements with a combination of original and imaginary nodes. Conventional cohesive zone modeling, limited to crack propagation along the edges of the elements, is extended to incorporate the intra-element mixed-mode crack propagation. Proposed numerical technique has been shown to be quite accurate, robust and mesh insensitive provided the cohesive zone ahead of the crack tip is resolved adequately. A series of numerical examples is presented to demonstrate the validity and applicability of the proposed method.

Although an organization’s environmental uncertainty may induce greater variability in reported earnings, managers have incentives to reduce this variability. The flexibility accorded by generally accepted accounting principles (GAAP) provides managers the means to accomplish this via exercising discretion in recognizing accounting accruals. Thus, we examine the relation between managers’ use of discretionary accruals and environmental uncertainty. Overall, evidence suggests managers use discretionary accruals to reduce the variability in reported earnings more when firms operate in high uncertainty.

An analytical framework for determination of scratch-induced residual stress within SiC grains of ZrB2–SiC composite is developed. Using a ‘‘secular equation” that relates strain to Raman-peak shift for zinc-blende structures and the concept of sliding blister field model for scratch-induced residual stress, explicit expressions are derived for residual stress calculation in terms of phonon deformation potentials and Raman peak shift. It is determined that, in the as-processed composite, thermal expansion coefficient mismatch between ZrB2 and SiC induces compressive residual stress of 1.731 GPa within the SiC grains and a tensile tangential stress of 1.126 GPa at the ZrB2– SiC interfaces. With increasing scratch loads, the residual stress within the SiC grains becomes tensile and increases in magnitude with scratch load. At a scratch load of 250 mN, the calculated residual stress in SiC was 2.6 GPa. Despite this high value, no fracture was observed in SiC grains, which has been rationalized based on fracture strength calculations from Griffith theory.

A ZrB2–5 wt.%SiC composite, consolidated using the plasma pressure compaction technique, was subjected to scratch loads in the range of 50–250 mN using a Berkovich nanoindenter. Microstructural analysis revealed that the scratch grooves consisted of numerous slip bands oriented at random angles to the scratch direction and microcracks oriented perpendicular to the scratch direction. The observed features were rationalized using an elastic stress field due to the combined Boussinesq- and Cerruti-field solutions. The analysis revealed that maximum shear stress occurs ahead of the scratch tool whereas the maximum principal tensile stress occurs in the wake of the scratch tool. Accordingly, it was argued that the slip bands occurred first in the region ahead of the scratch tool due to maximum shear stress while the microcracks developed later due to maximum tensile stress in the wake of the scratch tool. This result was further confirmed by the existence of slip bands ahead of the scratch tip at the exit end of the scratch grooves.

A parabolic index dispersion decreasing fiber (DDF) has been designed and optimized to produce high capacity soliton communication system. Variation of different fiber parameters such as core radius, effective core area and GVD factor along the 25 km of DDF length has been carried out to optimize a best possible DDF which can sustain the propagation of fundamental soliton. The variation of non-linearity with length along with the conventional power and GVD factor variation has been included in the generalized non-linear Schrodinger equation (NLSE). This NLSE has been solved numerically by split step Fourier method for shorter pulse propagation, incorporating the term for third order dispersion and intrapulse Raman scattering. Stable soliton pulses in transmission system have been achieved by our simulation, when a correction factor due to Raman induced soliton mean frequency shift is incorporated to the GVD profile predicted by the fundamental soliton condition. The interaction of neighboring soliton pulse pair through the proposed fiber has also been studied.

Non-zero dispersion shifted fibers (NZ-DSFs) find extensive use in wavelength division multiplexed (WDM) system as it reduces the non-linear effects like four-wave mixing (FWM) generation. A depressed clad graded index fiber with a central dip in the refractive index profile, as well as without dip, has been modeled to perform as an NZ-DSF using the spot size optimization technique. The performance characteristics of the proposed NZ-DSF have been studied by changing different fiber parameters; such as inner core radius (a), relative refractive index differences (Δ+), normalized end position of depressed clad (C), depression parameter (ρ), etc. for a given value of Petermann-2 spot size ( W ¯ ) . By suitably adjusting the fiber parameters, the effective core areas (Aeff) as simulated here are very large (∼80 μm2) so that the effect of non-linearities upon them can be minimized. These NZ-DSFs have also been optimized for WDM transmission system. The dispersion slopes of the proposed fibers with and without dip have been estimated which are comparable with the reported results.

Interdigitated capacitors containing the field-tunable ferroelectric Ba0.75Sr0.25TiO3, polycrystalline alumina substrates, and copper metallization have been fabricated. Dielectric layers were prepared by magnetron sputtering, while the Cu metallization was evaporated. The dielectric tunability of the Ba0.75Sr0.25TiO3 was 40% at an applied electric field of 12 V/μm. This corresponds to a 3-μm electrode gap width and a 35 V dc bias. Low-frequency (1 MHz) loss tangent measurements indicate a dielectric Q (quality factor) of ∼100 while microwave measurements reveal a zero bias device Q of ∼30 at 26 GHz. These values are comparable or superior to numerous reports of barium strontium titanate interdigitated capacitors prepared using single crystalline substrates and noble metallization. As such, this technology is significantly less expensive and more amenable to large-volume manufacturing.

A segmented core central step index dispersion compensating fiber (DCF) has been modeled by using spot size optimization technique. We have designed and optimized the DCF by suitably adjusting different fiber parameters, i.e. inner core radius (a), central relative refractive index difference (Δ), normalized outer core position (p), width (b) and height (h) at different values of given Petermann-II spot sizes ( W ¯ ) . The studies on the propagation behavior as well as bendloss and other losses of the DCF have been presented here. The proposed design of the DCF can possess improved bend performances over single core DCFs. At the same time higher negative dispersion coefficient in the single mode region as well as considerably high value of figure of merit (FOM) for optimized fiber parameters can be achieved for smaller spot sizes ( W ¯ ) of the DCF. Further, inclusion of length independent splice loss modified this conventional FOM to a slightly lesser value of modified FOM.