Nanocomposites of crosslinked starch phthalate and silane modified nanoclay: Study of mechanical, thermal, morphological, and biodegradable characteristics

Biodegradable composites comprising of modified starch and modified nanoclay have been prepared. Starch has been modified by esterification and subsequently crosslinked. The thermal, mechanical, and biodegradation characteristics of the composites have been investigated. The compressive properties of the composites with the addition of nanoclay were twice that of crosslinked starch phthalate without addition of nanoclay. Predictive theories were used to analyze the obtained experimental results. SEM studies on fracture morphology indicated quasi-brittle fracture. Flexural properties showed considerable improvement due to nanoclay addition. The water uptake increased up to 6% nanoclay, beyond which the uptake decreased. Biodegradation studies showed an initial time lag prior to the onset of degradation.

Anomalous magnetic behavior of La0.6Sr0.4MnO3 nano-tubes constituted with 3-12 nm particles

Uniform La0.6Sr0.4MnO3 (LSMO) nanotubes of an average diameter 180 nm were synthesized by a modified sol-gel method employing nanochannel porous anodic alumina templates. The nanotubes were characterized chemically and structurally by XRD, SEM, EDX, and TEM. Postannealed (700 degrees C for 1 h hour) nanotubes were found to be polycrystalline from XRD and SAED studies. To get further insight into the nanotube structure, HRTEM studies were done, which revealed that obtained LSMO nanotubes were structurally constituted with nanoparticles of 3-12 nm size. These constituent nanoparticles were randomly aligned and self-knitted to build the nanotube wall. Investigation of magnetic properties at this structured nanoscale revealed remarkable irreversibility between the zero field cooling (ZFC) and field cooling (FC) magnetization curves accompanied with a peak in the ZFC curve indicating spin-glass-like behavior. Structural defects and compositional variations at surfaces and grain-boundaries of constituent nanoparticles might be responsible for this anomalous magnetic behavior.

Composite cyclodextrin-calcium carbonate porous microparticles and modified multilayer capsules: novel carriers for encapsulation of hydrophobic drugs

Novel composite cyclodextrin (CD)-CaCO3 spherical porous microparticles have been synthesized through Ca2+-CD complex formation, which influences the crystal growth of CaCO3. The CDs are entrapped and distributed uniformly in the matrix of CaCO3 microparticles during crystallization. The hydrophobic fluorescent molecules coumarin and Nile red (NR) are efficiently encapsulated into these composite CD-CaCO3 porous particles through supramolecular inclusion complexation between entrapped CDs and hydrophobic molecules. Thermogravimetric (TGA) and infrared spectroscopy (IR) analysis of composite CD-CaCO3 particles reveals the presence of large CDs and their strong interaction with calcium carbonate nanoparticles. The resulting composite CD-CaCO3 microparticles are utilized as sacrificial templates for preparation of CD-modified layer-by-layer (LbL) capsules. After dissolution of the carbonate core, CDs are retained in the interior of the capsules in a network fashion and assist in the encapsulation of hydrophobic molecules. The efficient encapsulation of the hydrophobic fluorescent dye, coumarin, was successfully demonstrated using CD-modified capsules. In vitro release of the encapsulated coumarin from the CD-CaCO3 and CD-modified capsules has been demonstrated.

Effect of hydrogen charging on tensile properties of B-modified Ti-6Al-4V alloy

Trace addition of B to Ti and its alloys leads to a marked microstructural refinement, which in turn enhances the tensile and fatigue properties of the as-cast alloys. This can be particularly advantageous in applications wherein Ti alloys are used in the as-cast form. In some of these, the environment containing H and Ti alloy components is susceptible to embrittlement due to H uptake. Whether the addition of B to Ti-6Al-4V improves the relative mechanical performance of such cast components used in H environments is examined in this work. Cast Ti-6Al-4V-xB (0 <= x <= 0.55 wt%) alloys were H charged at 500 and 700 degrees C for up to 4 h. Microstructures and room temperature tensile properties of the resulting alloys have been evaluated. Experimental results show that charging at 700 degrees C for 2 h leads to the formation of titanium hydride in the microstructure, which in turn causes severe embrittlement. For shorter durations of charging, a marginal increase in strength was noted, which is attributed to the solid solution strengthening by H. The mechanical performance of the B modified alloys was found to be relatively higher, implying that B addition not only refines the as-cast microstructure but also is beneficial in applications that involve H environment A direct correlation between the volume fraction of TiB particles in the microstructure and the relative reduction in the strength of H-embrittled alloys suggests that the addition of B to Ti alloys, in optimum quantities, can be utilized as a strategy to design alloys that are more resistant to H embrittlement.

Modified current space vector based powerline communication method for distributed inverters interfaced smart grids

The following paper presents a Powerline Communication (PLC) Method for grid interfaced inverters, for smart grid application. The PLC method is based on the concept of the composite vector which involves multiple components rotating at different harmonic frequencies. The pulsed information is modulated on the fundamental component of the grid current as a specific repeating sequence of a particular harmonic. The principle of communication is same as that of power flow, thus reducing the complexity. The power flow and information exchange are simultaneously accomplished by the interfacing inverters based on current programmed vector control, thus eliminating the need for dedicated hardware. Simulation results have been shown for inter-inverter communication, both under ideal and distorted conditions, using various harmonic modulating signals.

Flexible poly(vinyl alcohol-co-ethylene)/modified MMT moisture barrier composite for encapsulating organic devices

Flexible, nano-composite moisture barrier films of poly(vinyl alcohol-co-ethylene) with surface modified montmorillonite fabricated by solution casting were used to encapsulate organic devices. The composite films were characterized by FTIR, UV-visible spectroscopy and SEM imaging. Thermal and mechanical properties of the composite films were studied by DSC and UTM. Calcium degradation test was used to determine the transmission rate of water vapour through the composite films, which showed a gradual reduction from similar to 0.1 g m(-2) day(-1) to 0.0001 g m(-2) day(-1) with increasing modified montmorillonite loading in the neat copolymer. The increase in moisture barrier performance is attributed to the decreased water vapour diffusivity due to matrix-filler interactions in the composite. The accelerated aging test was carried out for non-encapsulated and encapsulated devices to evaluate the efficiency of the encapsulants. The encapsulated devices exhibited longer lifetimes indicating the efficacy of the encapsulant.

Graphene composites containing chemically bonded metal oxides

Composites of graphene involving chemically bonded nano films of metal oxides have been prepared by reacting graphene containing surface oxygen functionalities with metal halide vapours followed by exposure to water vapour. The composites have been characterized by electron microscopy, atomic force microscopy and other techniques. Magnetite particles chemically bonded to graphene dispersible in various solvents have been prepared and they exhibit fairly high magnetization.

Anomalous piezoelectric response due to stabilization of two ferroelectric phases in Zr-modified BaTiO3

The lead-free Ba (Ti1-xZrx)O-3 ceramic has shown enhanced piezo-response (d(33)) in a narrow composition interval (0.01 <= x <= 0.03) exhibiting the coexistence of two ferroelectric phases. The system presents two electric-field-dependent-property regimes: (i) a low field regime (E < 1.7 kV mm(-1)) where d(33) is nearly independent of the poling field, and (ii) (E > 1.7 kV mm(-1)) for which d(33) drops sharply. X-ray diffraction studies revealed that the later phenomenon is related to field driven irreversible structural transformation, which tends to drive the system away from an equilibrium two phase state to a nearly single phase metastable state.

The Modified Selenenyl Amide, M-hydroxy Ebselen, Attenuates Diabetic Nephropathy and Diabetes-Associated Atherosclerosis in ApoE/GPx1 Double Knockout Mice

Seleno-organic glutathione peroxidase (GPx) mimetics, including ebselen (Eb), have been tested in in vitro studies for their ability to scavenge reactive oxygen and nitrogen species, including hydrogen peroxide and peroxynitrite. In this study, we investigated the efficacies of two Eb analogues, m-hydroxy ebselen (ME) and ethanol-ebselen (EtE) and compared these with Eb in cell based assays. We found that ME is superior in attenuating the activation of hydrogen peroxide-induced pro-inflammatory mediators, ERK and P38 in human aortic endothelial cells. Consequently, we investigated the effects of ME in an in vivo model of diabetes, the ApoE/GPx1 double knockout (dKO) mouse. We found that ME attenuates plaque formation in the aorta and lesion deposition within the aortic sinus of diabetic dKO mice. Oxidative stress as assessed by 8-OHdG in urine and nitrotyrosine immunostaining in the aortic sinus and kidney tubules, was reduced by ME in diabetic dKO mice. ME also attenuated diabetes-associated renal injury which included tubulointerstitial fibrosis and glomerulosclerosis. Furthermore, the bioactivity of the pro-fibrotic cytokine transforming growth factor-beta (TGF-beta) as assessed by phospho-Smad2/3 immunostaining was attenuated after treatment with ME. TGF-beta-stimulated increases in collagen I and IV gene expression and protein levels were attenuated by ME in rat kidney tubular cells. However, in contrast to the superior activity of ME in in vitro and cell based assays, ME did not further augment the attenuation of diabetes-associated atherosclerosis and renal injury in our in vivo model when compared with Eb. In conclusion, this study strengthens the notion that bolstering GPx-like activity using synthetic mimetics may be a useful therapeutic strategy in lessening the burden of diabetic complications. However, these studies highlight the importance of in vivo analyses to test the efficacies of novel Eb analogues, as in vitro and cell based assays are only partly predictive of the in vivo situation.

Strain-controlled fatigue in B-modified Ti-6Al-4V alloys

The strain-controlled fatigue behaviour of Ti-6Al-4V alloy with up to 0.11 wt.% B addition was investigated. Results show significant softening when the strain amplitudes, Delta epsilon(T)/2, are >= 0.75%. B addition was found to improve the fatigue life for Delta epsilon(T)/2 <= 0.75% as it corresponds to the elastic regime and hence is strength dominated. At Delta epsilon(T)/2 = 1%, in contrast, the base alloy exhibits higher fatigue life as TiB particle cracking due to strain incompatibility causes easy crack nucleation in the B-modified alloys. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Modified particle swarm optimization for pattern clustering

Data clustering is a common technique for statistical data analysis, which is used in many fields, including machine learning and data mining. Clustering is grouping of a data set or more precisely, the partitioning of a data set into subsets (clusters), so that the data in each subset (ideally) share some common trait according to some defined distance measure. In this paper we present the genetically improved version of particle swarm optimization algorithm which is a population based heuristic search technique derived from the analysis of the particle swarm intelligence and the concepts of genetic algorithms (GA). The algorithm combines the concepts of PSO such as velocity and position update rules together with the concepts of GA such as selection, crossover and mutation. The performance of the above proposed algorithm is evaluated using some benchmark datasets from Machine Learning Repository. The performance of our method is better than k-means and PSO algorithm.

AZ91C magnesium alloy modified by Cd

In the present work, the effect of Cd on the microstructure, mechanical properties and general corrosion behaviour of AZ91C alloys was investigated. Addition of Cd was found not to be efficient in modifying/refining the microstructure or beta-phase. A morphology change in beta-phase from fine continuous precipitates to discontinuous beta-phase upon the addition of Cd was observed. A marginal increment in mechanical properties was observed. General corrosion behaviour was followed with weight loss measurements, potentiostatic polarisation studies and surface studies in 3.5% sodium chloride solution and 3.5% sodium chloride with 2% potassium dichromate solution. Cd addition deteriorated the corrosion behaviour of AZ91C. This behaviour was attributed to the formation of chunks of beta-phase upon the addition of Cd. AZ91C with refined beta-phase distribution, performed rather better in the NaCl solutions. (C) 2013 Elsevier Ltd. All rights reserved.

Jeans instability criterion modified by external tidal field

The well-known Jeans criterion describes the onset of instabilities in an infinite, homogeneous, self-gravitating medium supported by pressure. Most realistic astrophysical systems, however, are not isolated - instead they are under the influence of an external field such as the tidal field due to a neighbour. Here, we do a linear perturbation analysis for a system in an external field and obtain a generalized dispersion relation that depends on the wavenumber, the sound speed and also the magnitude of the tidal field. A typical, disruptive tidal field is shown to make the system more stable against perturbations, and results in a higher effective Jeans wavelength. The minimum mass that can become unstable is then higher (super-Jeans) than the usual Jeans mass. Conversely, in a compressive tidal field, perturbations can grow even when the mass is lower (sub-Jeans). This approach involving the inclusion of tidal field opens up a new way of looking at instabilities in gravitating systems. The treatment is general and the simple analytical form of the modified Jeans criterion obtained makes it easily accessible.

Is chemically synthesized Graphene `really' a unique substrate for SERS and fluorescence quenching?

We demonstrate observation of Raman signals of different analytes adsorbed on carbonaceous materials, such as, chemically reduced graphene, graphene oxide (GO), multi-walled carbon nanotube (MWCNT), graphite and activated carbon. The analytes selected for the study were Rhodamine 6G (R6G) (in resonant conditions), Rhodamine B (RB), Nile blue (NBA), Crystal Violet (CV) and acetaminophen (paracetamol). All the analytes except paracetamol absorb and fluoresce in the visible region. In this article we provide experimental evidence of the fact that observation of Raman signals of analytes on such carbonaceous materials are more due to resonance effect, suppression of fluorescence and efficient adsorption and that this property in not unique to graphene or nanotubes but prevalent for various type of carbon materials.

Compressibility behaviour of bentonite and organically modified bentonite slurry

Bentonite in slurry walls needs to be amended with organo-clay to control the migration of organic contaminants. Consolidation behaviour of the slurry is important because it will reduce the total effective stress owing to mobilisation of frictional force between the side wall of the trench and the slurry. Compressibility of the slurry of bentonite is expected to undergo significant changes owing to amendment with organo-clay and according to the nature of the fluid. Standard one-dimensional consolidation tests were carried out on slurries of bentonite, organo-clay and their mixtures by remoulding them to their respective liquid limit consistency with water as well as fluids of low polarity, such as carbon tetrachloride, and inundating with different fluids. Organo-clay and its mixture with bentonite when moulded with water exhibit lower compressibility than bentonite in any pore fluid, but their compressibility increases when moulded with carbon tetrachloride and inundated with the same fluid. These changes in the compressibility of bentonite amended with organo-clay are explained by particle rearrangements, changes in the development of the diffuse double layer and contribution from the water adsorbed in the inter-lamellar space of the clay.