Applicability of ToF-SIMS for monitoring compositional changes in bone in a long-term animal model

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a well-established technique in material sciences but has not yet been widely explored for implementation in life sciences. Here, we demonstrate the applicability and advantages of ToF-SIMS analysis for the study of minerals and biomolecules in osseous tissue. The locally resolved analysis of fragment ions deriving from the sample surface enables imaging and differentiation of bone tissue and facilitates histology on non-stained cross sections. In a rat model, bilateral ovariectomy combined with either a multi-deficiency diet or steroid treatment was carried out to create osteoporotic conditions. We focused our study on the Ca content of the mineralized tissue and monitored its decline. Calcium mass images of cross sections show the progressive degenerative changes in the bone. We observed a decreased Ca concentration in the edge region of the trabeculae and a decline in the Ca/P ratio. Additionally, we focused on the non-mineralized matrix and identified fragment ions that are characteristic for the collagen matrix. We observed trabeculae with wide ranges of non-mineralized collagen for the diet group owing to an impaired mineralization process. Here, the advantage of coeval monitoring of collagen and minerals indicated an osteomalacic model rather than an osteoporotic one.     

Microstructure of Molybdenum Disilicide-Silicon Carbide Nanocomposite Thin Films

Composite thin films of molybdenum disilicide-silicon carbide (MoSi₂-SiC) have been deposited via rf magnetron sputtering onto molybdenum substrates. An intermediate layer was deposited in the presence of nitrogen gas and evaluated as a potential diffusion barrier layer. The composite films have been characterized using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and Auger electron spectroscopy. The as-deposited films were amorphous but crystallized into nanometer-sized grains after annealing under vacuum at 1000°C for 30 min. There was a significant amount of interdiffusion between the film and substrate, which resulted in the formation of subsilicides such as Mo₅Si₃ and MoSi₃, as well as Mo₂C. The films that were deposited via reactive sputtering in a nitrogen ambient were amorphous in both the as-deposited and annealed conditions. Significantly fewer second phases were detected with the presence of the intermediate layer, which suggests the potential use of the nitrided (MoSi _x N _y C _z ) layer as a high-temperature diffusion barrier layer for the silicon and carbon.     

Control of chaos in SEPIC DC-DC converter

DC-DC converters are widely used in power electronic systems where there is a need for stabilizing a given dc voltage to a desired value. It has been reported that DC-DC converters exhibit different non-linear phenomena including bifurcations, quasi-periodicity and chaos under both voltage mode and current mode control schemes. In this work, current mode controlled SEPIC converter operating in continuous conduction mode is considered and by varying the reference current I_ref, the converter exhibits chaos. It has been observed that the system changes from a stable buck-like operation to an unstable boost-like operation by varying I_ref. Bifurcation diagram is plotted for control signal and capacitor voltage with I_ref as bifurcation parameter. Resonant parametric perturbation control technique has been applied to suppress chaos. Effects of phase shift and frequency mismatch are also analyzed. With phase shift, control power required for suppressing chaos has been reduced. Also intermittent chaotic stages are suppressed with the effect of frequency mismatch at the expense of increasing control power. The stability analysis in SEPIC converter is performed by means of discrete model and is validated through the simulated and experimental results.     

Understanding the Formation of Vertical Cracks in Solution Precursor Plasma Sprayed Yttria‐Stabilized Zirconia Coatings

Yttria‐stabilized zirconia (YSZ) deposition by the solution precursor plasma spraying (SPPS) route has been of interest for potential thermal barrier coating (TBC) applications. It has been surmised that realization of unique microstructural features like vertical cracks, nanosized pores and fine splats in the TBCs can significantly enhance coating durability and performance. However, satisfactory control over the YSZ coating microstructure has been elusive in the absence of an adequate understanding of the mechanism responsible for coating deposition in SPPS. This study demonstrates the ability to tailor microstructure of deposited YSZ coatings over a wide range, from nano‐porous coatings to a vertically cracked microstructure. Varying of precursor flow rate has been shown to dictate the pyrolysis events occurring in situ and, adopting this approach, YSZ coatings with widely varying microstructural features have been developed. The coatings have been characterized in detail and the observations correlated with in‐flight particle generation and splat formation. These studies also provide useful insights into the possible origin of vertical cracks in the coating for which a mechanism is proposed.     

Optimization of process parameters of polymer solution mediated growth of calcium carbonate nanoparticles

With the advent of nanotechnology, many methods of synthesis of nanoparticles have come into practice and the 'polymer mediated growth' technique is among them. In this route, ions of one of the reactants are allowed to diffuse from an external solution into a polymer matrix where the other reactant is complexed and bound. The exact role of ionic diffusion in the formation of nanoparticles was investigated in the current study by studying the patterns of kinetics of nanoparticle formation using UV vis spectroscopy. Typically, calcium carbonate nanoparticles were formed by the aforementioned technique using polyethylene glycol solution. The particle size was calculated using Scherrer's formula on x-ray diffraction plots and was reconfirmed with field emission scanning electron microscope and transmission electron microscope images. Energy-dispersive x-ray analysis was used to study the composition and purity of the nanoparticles formed. The reactant to polymer ratio, reaction temperature and molecular weight of polyethylene glycol affected the size of the particles formed. Through this knowledge we optimized these parameters to obtain particles as small as 20?nm and confirmed that this technique can be used to control the size of nanoparticles.     

Optimizing the search algorithm for protein engineering by directed evolution

An in silico protein model based on the Kauffman NK-landscape,where N is the number of variable positions in a protein andK is the degree of coupling between variable positions, wasused to compare alternative search strategies for directed evolution.A simple genetic algorithm (GA) was used to model the performanceof a standard DNA shuffling protocol. The search effectivenessof the GA was compared to that of a statistical approach calledthe protein sequence activity relationship (ProSAR) algorithm,which consists of two steps: model building and library design.A number of parameters were investigated and found to be importantfor the comparison, including the value of K, the screeningsize, the system noise and the number of replicates. The statisticalmodel was found to accurately predict the measured activitiesfor small values of the coupling between amino acids, K 1.The ProSAR strategy was found to perform well for small to moderatevalues of coupling, 0 K 3, and was found to be robust to noise.Some implications for protein engineering are discussed. Received January 2, 2003; revised May 13, 2003; accepted June 19, 2003.     

Evaluation of k-Nearest Neighbor classifier performance for direct marketing

Text data mining is a process of exploratory data analysis. Classification maps data into predefined groups or classes. It is often referred to as supervised learning because the classes are determined before examining the data. This paper describes the proposed k-Nearest Neighbor classifier that performs comparative cross-validation for the existing k-Nearest Neighbor classifier. The feasibility and the benefits of the proposed approach are demonstrated by means of data mining problem: direct marketing. Direct marketing has become an important application field of data mining. Comparative cross-validation involves estimation of accuracy by either stratified k-fold cross-validation or equivalent repeated random subsampling. While the proposed method may have a high bias; its performance (accuracy estimation in our case) may be poor due to a high variance. Thus the accuracy with the proposed k-Nearest Neighbor classifier was less than that with the existing k-Nearest Neighbor classifier, and the smaller the improvement in runtime the larger the improvement in precision and recall. In our proposed method we have determined the classification accuracy and prediction accuracy where the prediction accuracy is comparatively high.     

Synthesis,characterization, and catalytic activity of fluorescent polyimide nanocomposites

A fluorescent polyimide (PI) was synthesized by using perylene tetracarboxylic dianhydride (PTCDAH) and a oxydianiline (ODA) in N‐methyl pyrrolidone (NMP) solvent at 160 °C for 5 h under nitrogen atmosphere. Similarly, the fluorescent PI nanocomposites were prepared in the presence of silver (Ag) and vanadium pentoxide (V₂O₅) nanoparticles under identical experimental conditions. The above synthesized PI and its nanocomposites were characterized by FTIR spectroscopy, UV‐visible spectroscopy, Fluorescence emission spectroscopy, DSC, TGA, SEM, and FESEM. The data are carefully analyzed and compared with the literature values. The catalytic activity of the fluorescent nanocomposite fiber was tested towards the reduction of p‐nitrophenol (NiP), Cr(VI) and Rhodamine6G (R6G) dye. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44633.     

Characterization of Thermal Barrier Coatings Produced by Various Thermal Spray Techniques Using Solid Powder,Suspension, and Solution Precursor Feedstock Material

Use of a liquid feedstock in thermal spraying (an alternative to the conventional solid powder feedstock) is receiving an increasing level of interest due to its capability to produce the advanced submicrometer/nanostructured coatings. Suspension plasma spraying (SPS) and solution precursor plasma spraying (SPPS) are those advanced thermal spraying techniques which help to feed this liquid feedstock. These techniques have shown to produce better performance thermal barrier coatings (TBCs) than conventional thermal spraying. In this work, a comparative study was performed between SPS‐ and SPPS‐sprayed TBCs which then were also compared with the conventional atmospheric plasma‐sprayed (APS) TBCs. Experimental characterization included SEM, porosity analysis using weight difference by water infiltration, thermal conductivity measurements using laser flash analysis, and lifetime assessment using thermo‐cyclic fatigue test. It was concluded that SPS coatings can produce a microstructure with columnar type features (intermediary between the columnar and vertically cracked microstructure), whereas SPPS can produce vertically cracked microstructure. It was also shown that SPS coatings with particle size in suspension (D₅₀) <3 μm were highly porous with lower thermal conductivity than SPPS and APS coatings. Furthermore, SPS coatings have also shown a relatively better thermal cyclic fatigue lifetime than SPPS.     

Divalent metal complexes of formylhydrazine: Syntheses and crystal structures of M(CH4N2O)2(H2O)2·2NO3 (M = Zn,Co)

The syntheses and crystal structures of Zn(CH₄N₂O)₂(H₂O)₂·2(NO₃) (1) and Co(CH₄N₂O)₂(H₂O)₂·2(NO₃) (2), the first well-characterised metal complexes of formylhydrazine (fh), are described. In both compounds, the fh acts as an N,O-bidentate ligand in a centrosymmetric [M(fh)₂(H₂O)₂]²⁺ cation, with charge balance supplied by nitrate counter ions. The packing for the two compounds are quite different: in 1, chains of [Zn(fh)₂(H₂O)₂]²⁺ units are seen in the triclinic unit cell, whereas in the monoclinic structure of 2, sheets of cations occur. This might arise because the conformations of the five-membered chelate rings for the ligands are slightly different, with that for 2 showing a greater degree of puckering.