Non-equilibrium solidification of undercooled droplets during atomization process

Thermal history of droplets associated with gas atomization of melt has been investigated. A mathematical model, based on classical theory of heterogeneous nucleation and volume separation of nucleants among droplets size distribution, is described to predict undercooling of droplets. Newtonian heat flow condition coupled with velocity dependent heat transfer coefficient is used to obtain cooling rate before and after nucleation of droplets. The results indicate that temperature profile of droplets in the spray during recalescence, segregated and eutectic solidification regimes is dependent on their size and related undercooling. The interface temperature during solidification of undercooled droplets rapidly approaches the liquidus temperature of the alloy with a subsequent decrease in solid-liquid interface velocity. A comparison in cooling rates of atomized powder particles estimated from secondary dendrite arm spacing measurements are observed to be closer to those predicted from the model during segregated solidification regime of large size droplets.     

High ferromagnetic transition temperature in PbS and PbS:Mn nanowires

Spontaneous magnetization measured in the temperature range 5-300 K with high ferromagnetic transition temperature (T(c)) has been observed in both undoped and Mn doped (2-8 mol %) PbS nanowires (diameter 30 nm) in polymer. For undoped sample, we find T(c) ~ 290 K while for doped samples T(c) varies between 310-340 K depending on Mn concentrations. Both T(c) and coercive fields are critically dependent on Mn concentrations. Coercive fields show a T(0.5) dependence with temperature for a moderate concentration of Mn (4 mol %) in PbS while it deviates from T(0.5) behavior for higher Mn concentrations. Anionic defects arising out of nonstoichiometric growth is solely responsible for the observed magnetism in undoped PbS nanowires. The role of intrinsic strain along with reduced dimensionality in determining such high T(c) and overall magnetizations has been discussed.     

Microstructural design of neodymium-doped lanthanum–magnesium hexaaluminate synthesized by aqueous sol–gel process

Aqueous sol–gel processing was used to synthesize neodymium-doped magnesium hexaaluminate (La_1?x Nd _x MgAl₁₁O₁₉; x = 0, 0.3, 0.4, 0.5) ceramic powder and subsequently calcined at 1450 and 1600 °C for 2 h. Randomly grown platelets of lanthanum–magnesium hexaaluminate formed a porous interlocking structure. Presence of various percentages of neodymium oxide significantly modifies the porous interlocking microstructure into self-reinforced, card-house-like microstructure. Platelets of rare earth-rich magnesium hexaaluminate were grown preferentially more than the stoichiometric rare earth magnesium hexaaluminate at elevated temperature greater than 1450 °C. Rare earth-rich magnesium hexaaluminate platelets form the skeleton of a card-house structure and the tiny platelets of stoichiometric rare earth magnesium hexaaluminate fill the house. The specific heat capacities, micro-hardness, and fracture toughness were studied in details.     

Macro-to-micro porous special bioactive glass and ceftriaxone-sulbactam composite drug delivery system for treatment of chronic osteomyelitis: an investigation through in vitro and in vivo animal trial

A systematic and extensive approach incorporating in vitro and in vivo experimentation to treat chronic osteomyelitis in animal model were made using antibiotic loaded special bioactive glass porous scaffolds. After thorough characterization for porosity, distribution, surface charge, a novel drug composite were infiltrated by using vacuum infiltration and freeze-drying method which was subsequently analyzed by SEM-EDAX and studied for in vitro drug elution in PBS and SBF. Osteomyelitis in rabbit was induced by inoculation of Staphylococcus aureus and optimum drug-scaffold were checked for its efficacy over control and parenteral treated animals in terms of histopathology, radiology, in vivo drug concentration in bone and serum and implant-bone interface by SEM. It was optimized that 60P samples with 60-65% porosity (bimodal distribution of macro- to micropore) with average pore size ~60 μm and higher interconnectivity, moderately high antibiotic adsorption efficiency (~49%) was ideal. Results after 42 days showed antibiotic released higher than MIC against S. aureus compared to parenteral treatment (2 injections a day for 6 weeks). In vivo drug pharmacokinetics and SEM on bone-defect interface proved superiority of CFS loaded porous bioactive glass implants over parenteral group based on infection eradication and new bone formation.     

Four-dimensional structural description of phase transformations in titanium alloys

Journal of Materials Science - Titanium alloys display formation of $$\beta$$ , $$\alpha$$ , and $$\omega$$ phases under different processing conditions. Understanding structural transformations...     

Predicted modifications in the direct and indirect gaps of Ge

The charge density of Ge was studied at various k-points and for various bands, by the ab initio pseudopotential method, using additionally the interstitial sites. The lowest X_c conduction-band points were found to be unique in having a high charge density in the interstitial site. It has been therefore predicted and verified that the X_c points move up in energy relative to the Γ_c point when closed-shell atoms (like H) are substituted at the interstitial sites. The calculations also indicate the change of the band-gap for HGeH.     

Distribution of IgG subclasses in antimonial unresponsive Indian kala-azar patients

BACKGROUND: Interleukin 10 (IL-10) decreases the severity of experimental acute pancreatitis. The role of endogenous IL-10 in modulating the course of pancreatitis is currently unknown. AIMS: To examine the systemic release of IL-10 and its messenger RNA production in the pancrease, liver, and lungs and analyse the effects of IL-10 neutralisation in caerulein induced acute pancreatitis in mice. METHODS: Acute necrotising pancreatitis was induced by intraperitoneal caerulein. Serum levels of IL-10 and tumour necrosis factor (TNF), and tissue IL-10 and TNF-alpha gene expression were assessed. After injecting control antibody or after blocking the activity of endogenous IL-10 by a specific monoclonal antibody, the severity of acute pancreatitis was assessed in terms of serum enzyme release, histological changes, and systemic and tissue TNF production. RESULTS: In control conditions, serum IL-10 levels increased and correlated with the course of pancreatitis, with a maximal value eight hours after induction. Both IL-10 and TNF-alpha messengers showed a similar course, and were identified in the pancreas, liver, and lungs. Neutralisation of endogenous IL-10 significantly increased the severity of pancreatitis and associated lung injury as well as serum TNF protein levels (+75%) and pancreatic, pulmonary, and hepatic TNF messenger expression (+33%, +29%, +43%, respectively). CONCLUSIONS: In this non-lethal model, systemic release of IL-10 correlates with the course of acute pancreatitis. This anti-inflammatory response parallels the release of TNF and both cytokines are produced multisystemically. Endogenous IL-10 controls TNF-alpha production and plays a protective role in the local and systemic consequences of the disease.     

Wavelet-based image coding using nonlinear interpolative vectorquantization

We propose a reduced complexity wavelet-based image coding technique. Here, 64-D (for three stages of decomposition) vectors are formed by combining appropriate coefficients from the wavelet subimages, 16-D feature vectors are then extracted from the 64-D vectors on which vector quantization (VQ) is performed. At the decoder, 64-D vectors are reconstructed using a nonlinear interpolative technique. The proposed technique has a reduced complexity and has the potential to provide a superior coding performance when the codebook is generated using the training vectors drawn from similar images.     

Effect of elevated temperatures and cooling regimes on normal strength concrete

The compressive strength of normal strength concrete at elevated temperatures up to 700^°C and the effect of cooling regimes were investigated and compared in this study. Thus, two different mixture groups with initial strengths of 20 and 35 MPa were produced by using river sand, normal aggregate and portland cement. Thirteen different temperature values were chosen from 50 to 700^°C. The specimens were heated for 3 h at each temperature. After heating, concretes were cooled to room temperature either in water rapidly or in laboratory conditions gradually. The residual strengths were determined by an axial compressive strength test. Strength and unit weight losses were compared with the initial values. Throughout this study, ASTM and Turkish Standards were used. It was observed that concrete properties deteriorated with the heat; however, a small increase in strength was observed from 50 to 100^°C. Strength loss was more significant on the specimens rapidly cooled in water. Both concrete mixtures lost a significant part of their initial strength when the temperature reached 700^°C. Copyright © 2008 John Wiley & Sons, Ltd.     

Three-dimensional finite element analysis to predict the effects of SAW process parameters on temperature distribution and angular distortions in single-pass butt joints with top and bottom reinforcements

Achieving adequate top and bottom reinforcement is important to minimize angular distortions in single-pass submerged arc welded (SAW) butt joints. This is achieved in the present work by using a reusable flux-filled backing strip and proper SAW process parameters without resorting to costly distortion mitigation techniques. The butt joints were made without edge (square butts) preparation. The process was also modeled by using three-dimensional finite element analysis by incorporating the top and bottom reinforcements into the modeling. Filler material deposition was also simulated. Temperature distributions and angular distortions obtained from the modeling closely matched with the experimental values. Thus, the cost effective experimental methodology established in the present work can be utilized for minimizing angular distortions in SAW square butts. The modeling methodology adopted can be used for predicting the angular distortions in SAW square butts with top and bottom reinforcements.