Crystallization kinetics of Sn40Se60 thin films for phase change memory applications

The crystallization kinetics of Sn₄₀Se₆₀ thin films has been successfully investigated using sheet resistance versus temperature measurements. Thermal evaporation was used to deposit the films on ordinary glass substrates. The crystallization temperature for Sn₄₀Se₆₀ thin film was found to be 156.6 ± 0.3 ℃. In the as-deposited state, the sheet resistance was found to be 195 MΩ, this value declined to 1560 Ω/口 upon annealing. The value of activation energy obtained from the Kissinger plot was 0.62 ± 0.07 eV. From the results obtained, Sn₄₀Se₆₀ is a promising alloy for PCM application because of its high electrical contrast, high crystallization temperature, and relatively high activation energy.     

Silk proteins for biomedical applications: Bioengineering perspectives

Biomaterials of either natural or synthetic origin are used to fabricate implantable devices, as carriers for bioactive molecules or as substrates to facilitate tissue regeneration. For the design of medical devices it is fundamental to use materials characterized by non-immunogenicity, biocompatibility, slow and/or controllable biodegradability, non-toxicity, and structural integrity. The success of biomaterial-derived biodevices tends to be based on the biomimetic architecture of the materials. Recently, proteins from natural precursors that are essentially structural and functional polymers, have gained popularity as biomaterials. The silks produced by silkworms or spiders are of particular interest as versatile protein polymers. These form the basis for diverse biomedical applications that exploit their unique biochemical nature, biocompatibility and high mechanical strength. This review discusses and summarizes the latest advances in the engineering of silk-based biomaterials, focusing specifically on the fabrication of diverse bio-mimetic structures such as films, hydrogels, scaffolds, nanofibers and nanoparticles; their functionalization and potential for biomedical applications.     

Gas holdup in tapered bubble column using pseudoplastic non-Newtonian liquids

Experimental studies on the gas holdup in two tapered bubble columns using non-Newtonian pseudoplastic liquid have been reported. The effects of different variables such as gas flow rate, liquid viscosity, bed height, and orifice diameter of sieve plate on gas holdup have been investigated. An empirical correlation has been developed for the prediction of the gas holdup as a function of various measurable parameters of the system. The correlation is statistically acceptable.     

Isolation and identification of phosphate‐solubilizing microorganisms and distribution of orthophosphate in different seasons from sewage‐fed East Kolkata Wetland

This study focused on isolation and identification of possible phosphate‐solubilizing bacteria (PSB ) from the sewage‐fed East Kolkata Wetland (EKWL ), a prospective water resource for pisciculture. In addition, different limnological parameters have been correlated with orthophosphate and seasonal variations. PSB have been isolated in Pikovskaya medium and identified morphologically and biochemically and finally analysed by 16S rDNA gene sequence. Limnological studies involving temperature (potentiometric), pH (potentiometric), dissolved oxygen (iodometric), ammonia‐nitrogen (spectrophotometric) and orthophosphate (spectrophotometric) concentrations were conducted. The results of this study established the presence of Bacillus megaterium , a potential PSB in EKWL . The activity of B. megaterium is also supported by the seasonal orthophosphate variations. The changes in concentration of other limnological parameters were also prominent. The water quality parameters of temperature (r  = 0.886), dissolved oxygen (r  = 0.729) and ammonia‐nitrogen (r  = 0.396) concentrations exhibited a positive correlation with orthophosphate and a negative correlation with pH (r  = ?0.699). The B. megaterium obtained in this study, exhibited a significant alteration in regard to orthophosphate content and relationships with other factors. Further experiment on the soluble phosphorus solubilization potential of B. megaterium revealed the biological availability of phosphorus was increased by threefold after 120 hr of incubation, with the decreasing pH value, although the phytase activity was 0.419 U/ml. PSB have a vital function in plant nutrition in supplying phosphate, essential nutrients and its uptake results in appropriate functioning and metabolism of different aquatic plants and organisms. PSB are competent biofertilizer to amplify aquaculture production for sustainable development.     

ISGP: Iterative sequential geometric programming for precise and robust CMOS analog circuit sizing

In this paper, a fast yet accurate CMOS analog circuit sizing method, referred to as Iterative Sequential Geometric Programming (ISGP), has been proposed. In this methodology, a correction factor has been introduced for each parameter of the geometric programming (GP) compatible device and performance model. These correction factors are updated using a SPICE simulation after every iteration of a sequential geometric programming (SGP) optimization. The proposed methodology takes advantage of SGP based optimization, namely, fast convergence and effectively optimum design and at the same time it uses SPICE simulation to fine tune the design point by rectifying inaccuracy that may exists in the GP compatible device and performance models. In addition, the ISGP considers the requirement of common centroid layout and yield aware design centering for robust final design point specifying the number of fingers and finger widths for each transistor which makes the design point ready for layout.     

Biocompatible composites of fibrous nanohydroxyapatite embedded in a polydimethylsiloxane

Silicone elastomers have the potential to be a valuable biomaterial due to their mechanical and chemical properties, easy processing, and high gas permeability. Some inherent properties of the pure silicone implant such as high hydrophobicity and low load bearing capacity can be problematic for biomedical applications. The issues were addressed by fabricating hydroxyapatite nanofiber/polydimethylsiloxane nanocomposites. The morphology of nanocomposite structures was visualized by high resolution transmission electron microscopy and field emission scanning electron microscopy. Improved mechanical strength and compliance of the prepared nanocomposite structures were obtained by frequency sweep and creep measurements. Surface hydrophilicity of polydimethylsiloxane was enhanced by hydroxyapatite nanofiber incorporation into the polymer matrix. The cytotoxicity and biocompatibility of the structures were analyzed using breast epithelial cells (MDA MB 231 cell line). These studies showed that the nanocomposite scaffold did not leach any cytotoxic material and showed better cell adhesion and cell proliferation compared to the unfilled elastomer.     

Grain Size Distributions after Single Hit Deformation of a Segregated, Commercial Nb-Containing Steel: Prediction and Experiment

The present investigation examines the applicability of the Dutta–Sellars equations in predicting the recrystallized grain sizes following deformation for a 0.046 wt pct Nb-bearing, commercially produced steel with a segregated solute content (from continuous casting). The investigation considered initial unimodal and bimodal grain size distributions before deformation that were generated by reheating the steel to 1498 K and 1423 K (1225 °C and 1150 °C), respectively. It was found that the reheated grain size distribution (separated into grain size classes) could be related to the solute-rich (smaller grain size classes) and solute-depleted (larger grain size classes) regions. The use of these relationships and a simple halving of the grain size within the distribution on recrystallization (used previously for homogenized samples of this steel) were found to be appropriate in the grain size class-based use of the Dutta–Sellars equations with respect to mode and maximum grain sizes after hot deformation and holding. This approach successfully predicted (confirmed by experiment) the grain size distribution after deformation in the presence of Nb segregation from continuous casting.     

Physicochemical Investigation of Biocompatible Mixed Surfactant Reverse Micelles: III. Aqueous NaCl Solubilization, Thermodynamic Parameters of Desolubilization Process and Conductometric Studies

Solubilization of water and aqueous NaCl in mixed reverse micelles (RMs) comprising sodium bis(2‐ethylhexyl) sulfosuccinate (AOT), and polyoxyethylene (20) sorbitan trioleate or polyoxyethylene (20) sorbitan monooleate has been studied at different compositions (X_nonionic = 0–1.0) at a total surfactant concentration, S_T = 0.10 × 10³ mol m^?3 in biocompatible oils of different chemical structures; viz., ethyl oleate (EO), isopropyl myristate (IPM) and isopropyl palmitate (IPP) at 303 K. The enhancement in water solubilization (i.e., synergism) has been evidenced by the addition of nonionic surfactant to dioctyl sulfosuccinate/oil(s)/water systems. Addition of NaCl in these systems at different X_nonionic enhances their solubilization capacities further until a maximum, ω_NaCl,max is reached. ω_NaCl,max and [NaCl]_max (concentration at which maximization of NaCl solubilization occurs) depend on type of nonionic surfactant, its content (X_nonionic) and oil. A new solubilization efficiency parameter (SP*_water or SP*_NaCl) has been proposed to compare solubilization phenomena in these oils. The energetic parameters of the desolubilization process of water or aqueous NaCl in single and mixed RMs have been estimated. Energetically, the water dissolution process in oil has been found to be more exothermic as well as more organized in IPP. Overall, the dissolution of water and aqueous NaCl in mixed RMs is entropically driven process. Conductance behavior of these systems in the presence of NaCl has been investigated under different [NaCl] at 303 K. An attempt has been made to give an insight to the mechanism of solubilization phenomena, percolation in conductance and microstructures vis‐à‐vis role of biocompatible oils in these systems.