Synthesis and Characterization of SrFe<Subscript>11.2</Subscript>Zn<Subscript>0.8</Subscript>O<Subscript>19</Subscript> Nanoparticles for Enhanced Microwave Absorption

SrFe₁₂O₁₉/ZnFe₂O₄ (SrFe_11.2Zn_0.8O₁₉) nanoparticles having superparamagnetic nature were synthesized by coprecipitation of chloride salts using 7.5 M sodium hydroxide solution. The resulting precursors were heat-treated at 900°C and 1200°C for 4 h in nitrogen atmosphere. During heat treatment (HT), transformation proceeds through instantaneous nucleation and three-dimensional diffusion-controlled growth with an activation energy of 175.9 kJ/mole. The hysteresis loops showed an increase in saturation magnetization from 1.044 emu/g to 61.227 emu/g with increasing HT temperature. As-synthesized particles had sizes in the range of 20 nm to 25 nm with spherical shape. Further, these spherically shaped nanoparticles tended to change their morphology to hexagonal plate and pyramidal shape with increasing HT temperature. The effects of this systematic morphological transformation of nanoparticles on dielectric (complex permittivity and permeability) and microwave absorption properties were estimated in the X-band (8.2 GHz to 12.2 GHz). The maximum reflection loss of the composite powder reached −29.81 dB at 10.37 GHz, making it suitable for application in radar-absorbing materials.     

Reaction kinetic studies of strontium hexaferrite nanoparticles synthesized by co-precipitation method

Nano crystalline strontium hexaferrite, SrFe₁₂O₁₉ powders have been synthesized using co-precipitation method. The ferrite precursors were obtained from aqueous mixtures of strontium chloride and ferric chloride by precipitating strontium and iron using 7.5 M sodium hydroxide solution. These precursors were heat treated at 800 and 1200°C in nitrogen atmosphere. The decomposition behaviour and reaction kinetics were investigated by means of DSC/DTG/TG for three heating rates. The various phases associated therein were identified by X-ray diffraction (XRD). From field emission scanning electron microscopy (FESEM) study, the formations of nonporous ultrafine particles have been confirmed. About 5 to 10% of the needle like crystals in the ‘as synthesized, condition were transformed to pyramidal structure and most of the crystals are found to have plate like hexagonal structures with increase in heat treatment temperatures. Activation energies and Avrami index ‘n’ were obtained using Johnson-Mehl-Avrami (JMA) equation. The reaction in the temperature range of 800 to 1200°C, proceeds as, instantaneous nucleation and three dimensional growth with activation energy of 168.33 kJ/mole.     

Effect of cyclosporine on fertility in male rats

The effect of cyclosporine (CsA) on fertility has assumed greater importance with the increasing numbers of pediatric transplantations being performed all over the world. Conflicting reports on the effects of CsA on sex hormones are available. This experimental animal study was designed to examine the effect of CsA on testicular weight, sperm counts, seminiferous tubular diameter (STD), testicular morphology, DNA flowcytometry, sex hormone levels, and fertility in male rats. Those rats who received CsA (20 mg/kg per day) showed significant reductions in testicular weight (P < 0.05), sperm count (P < 0.01), Johnsen score (P < 0.05), STD (P < 0.01), serum testosterone levels (P < 0.05), haploid cell population (P < 0. 001) in the testis, and fertility (P < 0.001) compared to those receiving CsA 10 mg/kg per day and control rats. These findings will have an important bearing for children receiving cyclosporine for long periods to guide the physician in optimally adjusting long-term treatment.     

选择性激光烧结金属零件的后处理

概述了选择性激光烧结(SLS)金属零件的后处理对改善结构完整性和诱导材料变形的影响.介绍了后处理液相烧结温度和时间对材料性能的影响.叙述了热等静压工艺,并论述了它在金属SLS零件中的应用.使用结果表明,热等静压适用于获得几乎全密实的零件.     

Electroless alloy/composite coatings: A review

Since the inception of electroless coating by Brenner & Riddell in 1946, it has been the subject of research interest and, in the past two decades, emphasis has shifted to the studies of its properties and applications. The co-deposition of paniculate matter or substance within the growing film has led to a new generation of electroless composite coatings, many of which possess excellent wear and corrosion resistance. This valuable process can coat not only electrically conductive materials including graphite but also fabrics, insulators like plastics, rubber etc. The low coating rates with these can provide better reflectivity of plated surfaces and many more applications. Coatings can be tailored for desired properties by selecting the composition of the coating alloy/composite/metallic to suit specific requirements. The market for these coatings is expanding fast as the potential applications are on the rise. In the present article, an attempt has been made to review different electroless alloy/composite coatings with respect to bath types and their composition, properties and applications. Different characterisation studies have been conducted on various electroless nickel-based coatings with emphasis on wear and corrosion properties.     

Effect of Pressure and Temperature on Phase Transformation and Properties of Titanium Aluminide Obtained through Reaction Synthesis

Reaction synthesis process has been used to develop γ titanium aluminide using elemental powders. Powder mixture of Ti-48 at. pct Al was prepared in ball mill and reaction synthesis was carried out in hot press with varying temperature and pressure. Titanium aluminide synthesized under high pressure and temperature resulted in better properties with respect to densification, homogenization response, mechanical properties and oxidation resistance as compared to that synthesized under low pressure and tempera...     

Style-based exploration of illustration datasets

Searching by style in illustration data sets is a particular problem in Information Retrieval which has received little attention so far. One of its main problems is that the perception of style is highly subjective, which makes labeling styles a very difficult task. Despite being difficult to predict computationally, certain properties such as colorfulness, line style or shading can be successfully captured by existing style metrics. However, there is little knowledge about how we distinguish between different styles and how these metrics can be used to guide users in style-based interactions. In this paper, we propose several contributions towards a better comprehension of illustration style and its usefulness for data exploration and retrieval. First, we provide new insights about how we perceive style in illustration. Second, we evaluate a handmade style clustering of clip art pieces with an existing style metric to analyze how this metric aligns with expert knowledge. Finally, we propose a method for efficient navigation and exploration of large clip art data sets which takes into account both semantic labeling of the data and its style. Our approach combines hierarchical clustering with dimensionality reduction techniques, and strategic sampling to obtain intuitive visualizations and useful visualizations.     

G‐Quadruplexes as Tools for Synthetic Biology

With the potential to engineer biological systems, synthetic biology is an emerging field that combines various disciplines of sciences. It encompasses combinations of DNA, RNA and protein modules for constructing desired systems and the “rewiring” of existing signalling networks. Despite recent advances, this field still lags behind in the artificial reconstruction of cellular processes, and thus demands new modules and switches to create “genetic circuits”. The widely characterised noncanonical nucleic acid secondary structures, G‐quadruplexes are promising candidates to be used as biological modules in synthetic biology. Structural plasticity and functional versatility are significant G‐quadruplex traits for its integration into a biological system and for diverse applications in synthetic circuits.     

Ductility prediction of Ti aluminide intermetallics through neuro-fuzzy set approach

Several studies have been conducted to improve the room temperature ductility of titanium aluminide intermetallics through alloy design and microstructure modifications. Ductility of two phase (α₂+γ) binary Ti aluminide intermetallics centered on Ti-48Al (at%) was reported as maximum (∼1.5%) in desirable heat treatment condition and so more studies were attempted near to this composition. In the present work also, ductility has been studied for the alloy variants of this composition through fuzzy modeling. Neuro-fuzzy models were developed through Adaptive Neural Fuzzy Inference System (ANFIS) using subtractive cluster techniques. The input parameters were fuzzified with Gaussian membership functions to develop the fuzzy rules. The output of each rule was obtained by the evaluation of the membership values. Finally the overall fuzzy model response was obtained as the weighted average of the individual rule response. Ductility database were prepared and three parameters viz. alloy type, grain size and heat treatment cycle were selected for modeling. Additional, ductility data were generated from literature based experimental data for training and validation of models on the basis of linearity and considering the primary effect of these three parameters. Adequacy of developed models was evaluated with the generated data sets. Different evaluation measures were considered and the resulting graphs from the developed model were analyzed. The results of the fuzzy models were found to be very close to the literature based generated data and it also showed the possibility of improving ductility upto 7% for multicomponent alloy with grain size of 10–50μm following a multistep heat treatment cycle.     

Institutions, routines, and crises: Post-earthquake housing recovery in Mexico City and Los Angeles

This is a study of how planning institutions deal with crisis recovery; that is, recovery from situations marked by complexity, uncertainty, and sudden change that increasingly characterize contemporary cities. Based on an analytical framework derived from institutional literature and planning theory, the study examines two successful housing recovery programs during crisis situations: the Renovación Habitacional Popular program in Mexico City following the 1985 earthquake, and the Ghost Town program in Los Angeles following the 1994 earthquake. The study addresses the following research questions: In what manner were the planning institutions successful, if at all? Which familiar and established institutional arrangements, policies, programs, and practices (ie routines) did they adopt when faced with large, unexpected shocks (ie crises)? How do institutional actors in different political-economic contexts respond to similar crisis situations? What are the lessons of these institutional actions for future crises, and for normal operations in planning? The study argues that planning institutions perform successfully during crises due primarily to routines, which are usually overlooked or decried as being bureaucratic. Planning institutions responded effectively to the crises by adapting institutional routines quickly and efficiently to new circumstances. While these routines can be constraints under normal conditions, they also act as powerful tools during exceptional times, serving as catalysts to release the disciplined energy of institutions to perform effectively, resolve problems, and re-establish order.