Microstructure,mechanical properties,and in vitro biocompatibility of spark plasma sintered hydroxyapatite–aluminum oxide–carbon nanotube composite

In the present work, HA reinforced with Al₂O₃ and multiwalled carbon nanotubes (CNTs) is processed using spark plasma sintering (SPS). Vickers micro indentation and nanoindentation of the samples revealed contrary mechanical properties (hardness of 4.0, 6.1, and 4.4 GPa of HA, HA–Al₂O₃ and HA–Al₂O₃–CNT samples at bulk scale, while that of 8.0, 9.0, and 7.0 GPa respectively at nanoscale), owing to the difference in the interaction of the indenter with the material at two different length scales. The addition of Al₂O₃ reinforcement has been shown to enhance the indentation fracture toughness of HA matrix from 1.18 MPa m^1/2 to 2.07 MPa m^1/2. Further CNT reinforcement has increased the fracture toughness to 2.3 times (2.72 MPa m^1/2). In vitro biocompatibility of CNT reinforced HA–Al₂O₃ composite has been evaluated using MTT assay on mouse fibroblast L929 cell line. Cell adhesion and proliferation have been characterized using scanning electron microscopy (SEM), and have been quantified using UV spectrophotometer. The combination of cell viability data as well as microscopic observations of cultured surfaces suggests that SPS sintered HA–Al₂O₃–CNT composites exhibit the ability to promote cell adhesion and proliferation on their surface and prove to be promising new biocompatible materials.     

Multiscale micro-patterned polymeric and carbon substrates derived from buckled photoresist films: fabrication and cytocompatibility

We report here a novel and simple buckling-based multiscale patterning of negative photoresist films which were subsequently pyrolyzed to yield complex micro-patterned carbon surfaces. Unlike other polymers, the use of a photoresist layer allows the overall pattern definition by photolithography on which the geometry and length scale of the buckling-instability are superimposed. The photoresist film swells anisotropically during developing and buckles after subsequent drying due to the difference in the shrinkage of the hard cross-linked layer on top of a softer native pre-polymer. We studied the conditions for the formation of a wide variety of complex, fractal buckling patterns as well as directionally aligned zigzag patterns over a large area. For example, the buckling diminished for the films below a critical thickness and after a prolonged UV exposure, both of which eliminate the softer under-layer. These patterned carbon substrates are also shown to be biocompatible for the cellular adhesion and viability by using L929 mouse fibroblast cells, thus indicating their potential use in bio-MEMS platforms with a conductive substrate. The buckled carbon patterns were found to be a better choice of a substrate for cell growth and viability as compared to flat and simply periodic patterned carbon surfaces.     

Enhanced production of glutaminase free L-asparaginase II by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> WB800N through media optimization

We studied the crucial components which elevate the expression of recombinant novel glutaminase free L-asparaginase II (rL-asp II) from Bacillus subtilis WB800N. The Plackett-Burman tool identified sucrose, NH₄Cl, NaH₂-PO₄ and MgSO₄ as the significant influencing factors (p<0.05). Further investigations showed that artificial neural network-genetic algorithm (ANN-GA) was more effective than central composite design (CCD) in optimizing the influencing factors. The maximum rL-asp II expression was found to be 389.56 IU/ml and 525.98 IU/ml using CCD (R²=90.4%) and ANN-GA (R²=96.2%), respectively. The validation experiments were carried out in a 3 L batch bioreactor where kinetic modelling of the obtained data was done. The rL-asp II expressed effectively inhibiting the polyacrylamide formation in vitro where no solidification was observed, when 2ml of purified rL-asp II used even after 60 min of incubation. This is the first study to report highest production of rL-asp II in B. subtilis WB800N (525.98 IU/ml) till date by combining statistical designs with consecutive intermittent addition of IPTG in batch reactor.     

Mapping of rice-cropping pattern and cultural type using remote-sensing and ancillary data: a case study for South and Southeast Asian countries

A geospatial database on the spatial distribution of rice areas and rice cultural types of major rice-producing countries of South and Southeast Asia has been developed in this study using remote-sensing and ancillary data sets. Multitemporal SPOT VGT normalized difference vegetation index (NDVI) data for the period 2009–2010 were used for the analysis. The classification was performed adopting ISODATA clustering to build a non-agricultural area mask followed by rice area mapping. The derived rice area was stratified by logical modelling of ancillary data sets into five rice cultural types: irrigated wet, upland, flood-prone, drought-prone, and deep-water. The uniqueness of this study is a synergistic approach based solely on single-source, high-temporal remote-sensing data coupled with ancillary data, which demonstrate the application of SPOT VGT NDVI data in building a geospatial database for rice crops over a wide spatial extent. This approach was adopted for cost effectivity as the study extent was vast and thus lacking ground truth information. Comparison of the derived rice area against the reported literature values for validation yielded a good correlation (linear coefficient of determination, R² = 0.95–0.99). The high-temporal resolution NDVI data enabled effective characterization of vegetation phenology. The derived spatial outputs can be used in various studies associated with the assessment of greenhouse gas emissions from paddy fields, change detection, and inputs to crop simulation models, which are significantly related to different rice cultural types.     

Feasibility of vermicomposting in biostabilization of sludge from a distillery industry

The feasibility of vermicomposting technology to stabilize the distillery industry sludge mixed with a bulking agent (cow dung) in different proportions viz. 20% (T1), 40% (T2), 60% (T3) and 80% (T4), was tested using composting earthworm Perionyx excavatus for 90 days. The vermitreated sludge was evaluated for different physico-chemical parameters and all vermibeds expressed a significant decrease in pH (10.5-19.5%) organic C contents (12.8-27.2%), and an increase in total N (128.8-151.9%), available P (19.5-78.3%) as well as exchangeable K (95.4-182.5%), Ca (45.9-115.6%), and Mg contents (13.2-58.6%). Data suggested that inoculated earthworms could maximize the decomposition and mineralization rate, if sludge is used with appropriate bulking material for earthworm feed. Vermicomposting also caused significant reduction in total concentration of metals: Zn (15.1-39.6%), Fe (5.2-29.8%), Mn (2.6-36.5%) and Cu (8.6-39.6%) in sludge. Bioconcentration factors (BCFs) for metals in different treatments were also calculated and the greater values of BCFs indicate the capability of earthworms to accumulate a considerable amount of metals in their tissues from substrate. The reproduction biology of P. excavatus in different treatments was also monitoring during experimentation and they showed the maximum rate of biomass gain, growth (mg weight worm(-1) week(-1)) and cocoon production rate in T2, while least values of these parameters were in T4 treatment. The feasibility of earthworms to mitigate the metal toxicity and to enhance the nutrient profile in sludge might be useful in sustainable land restoration practices at low-input basis.     

A Comparative Biocompatibility Analysis of Ternary Nitinol Alloys

Nitinol alloys are rapidly being utilized as the material of choice in a variety of applications in the medical industry. It has been used for self-expanding stents, graft support systems, and various other devices for minimally invasive interventional and endoscopic procedures. However, the biocompatibility of this alloy remains a concern to many practitioners in the industry due to nickel sensitivity experienced by many patients. In recent times, several new Nitinol alloys have been introduced with the addition of a ternary element. Nevertheless, there is still a dearth of information concerning the biocompatibility and corrosion resistance of these alloys. This study compared the biocompatibility of two ternary Nitinol alloys prepared by powder metallurgy (PM) and arc melting (AM) and critically assessed the influence of the ternary element. ASTM F 2129-08 cyclic polarization in vitro corrosion tests were conducted to evaluate the corrosion resistance in phosphate buffered saline (PBS). The growth of endothelial cells on NiTi was examined using optical microscopy.     

Energy transfer and photoluminescent analysis of a novel color-tunable Ba2Y1-xV3O11:xSm3+ nanophosphor for single-phased phosphor-converted white LEDs

Metal nitrates are used to synthesize a series of novel Ba₂Y_1-xV₃O₁₁:xSm³⁺ nanophosphors via urea-assisted solution combustion route. X-ray diffraction (XRD), diffuse reflectance (DR), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were employed to analyse the structure, morphology, photoluminescent behaviour and energy transfer mechanism. Rietveld analysis over Ba₂Y_0.98Sm_0.02V₃O₁₁ showed that Y³⁺ ions can be well-replaced by trivalent samarium ions without resulting any major alteration in the crystal structure of host lattice. Furthermore, the lattice parameters were determined for both the host as well as the doped composition. The Scherrer equation yielded an average particle size of 44?nm, which in turn was further confirmed by TEM micrographs. The optical band-gap of the host (3.92?eV) was calculated from the diffuse reflectance spectra. Moreover, the photoluminescence spectral studies showed that under near ultra-violet (NUV) excitation of 340?nm, our nanophosphor powder exhibits the characteristic emission peaks of trivalent samarium along with the emission of VO₄^3? (501?nm) group. The excitation energy transfer from vanadate group to Sm³⁺ produced a systematic color tunablity in white region itself. The optimum Sm³⁺ concentration for better luminescence was found to be 2?mol%. The critical distance for energy transfer was calculated to be 29.02?Å, which in turn assisted to shortlist the mechanism responsible for luminescence-quenching (dipole-dipole) arising from the over-doping of the activator. The photoluminescence decay curves revealed the decay kinetics of ⁴G_5/2 electronic state. Finally, the calculation of CIE color coordinates from emission spectra in MATLAB program unveiled a somewhat white-light emitter which may find potential applications in phosphor-converted white light emitting diodes (PC-WLED) under near-ultraviolet (NUV) excitation.