Investigation on microstructure and tensile behaviour of stir cast LM13 aluminium alloy reinforced with copper coated short steel fibers using response surface methodology

Copper coated steel fibers reinforced LM13 aluminium alloy composites have been prepared using stir casting process. Experiments have been designed using response surface methodology by varying wt% of reinforcement (0–10), stirrer speed (350–800 rpm) and pouring temperature (700–800 °C). Microstructure, tensile strength and fracture surface of composites have been investigated. Analysis of variance, significance test and confirmation tests have been performed and regressions models have been developed to predict the tensile strength of composites. Response surface plots reveal that tensile strength of composites increases with increasing wt% of copper coated steel fibers reinforcement up to 6 wt%. Further increase in wt% of steel fibers decreases the tensile strength of composites. However tensile strength of composites increases with increasing stirrer speed due to the uniform and homogeneous dispersion of steel fibers in matrix. Optimum stir cast process parameters for obtaining higher tensile strength are found to be 5.9 wt% of reinforcement, 753 °C pouring temperature and stirrer speed of 633 rpm. Fracture mechanism is dominated by steel fiber pullouts in composites with higher wt% of reinforcement and dimples are observed in the surface of composites containing lower levels of wt% of reinforcement.     

Toasted soybean flour components with trypsin inhibitor activity

Compounds in toasted soybean flour having trypsin inhibitor (TI) activity were isolated and characterized. Sodium hydroxide (0.01N) extracts of toasted soybean flour had an average of 2.59 mg TI/g sample. These extracts, after trichloroacetic acid (TCA) precipitation and dialysis, yielded supernatant and precipitate fractions. Addition of polyvinylpyrrolidone to eliminate free tannins and phenolics in the extracts, which may lead to overestimation of TI activity, was unnecessary. Material balance studies revealed 91% protein recovery and 92% recovery of TI activity in the TCA supernatant (1.1% protein, 2.0% TI) and precipitate (89.8% protein, 90.0% TI) fractions. Column chromatography and electrophoresis showed the TCA supernatant and precipitate fractions to contain proteins, including those having TI activity. Kunitz type TI and Bowman-Birk type protease inhibitors accounted for most residual TI activity of toasted soybean flour, as verified by column chromatography, isoelectric focusing, sodium dodecyl sulfate polyacrylamide electrophoresis, and size-exclusion high performance liquid chromatography, using the two similarly treated protease inhibitors as standards. Immunoblotting was also used to detect and identify Kunitz type TI’s in toasted soybean meal extracts. This study established the proteinaceous nature of residual trypsin inhibitor activity in toasted soybean flour and the presence of both Kunitz and Bowman-Birk inhibitors. Presented in part at the AOCS meeting in Dallas, TX, in 1984.     

Self-induced field model for crystal twisting in spherulites

The observed twisting of crystals about the growth direction in spherulites is modeled as a response to fields generated during the crystal growth process. These fields can be compositional or mechanical. In either case, the high local field value in the melt near the interface acts to reduce the growth velocity. Twisting of the crystal about the growth direction places all portions of the growth surface in contact with melt of lower field value than would be the case for untwisted growth, thereby increasing the growth velocity. The effect of a compositional field is analyzed here, using an extension of the moving point source to compute the composition in the melt ahead of a twisting crystal. The retarding effect of the elastic twisting of the crystal is included in the analysis. Simulations using parameters for a crystallizable/uncrystallizable polyethylene blend are carried out for a crystal with thin, rectangular cross-section. The results are quantitatively and qualitatively consistent with observation. Comments on simplifications within and implications of the model are given.     

Aerosolization of Bacterial Spores with Pressurized Metered Dose Inhalers

Bioaerosol detection and identification systems need to be periodically checked for assurance that they are responsive to aerosol challenges. Herein, pressurized metered dose inhalers (pMDIs) containing ethanol suspensions of two simulants for B. anthracis spores are considered for providing suitable aerosols. Doses and shot weights from pMDIs with canisters having volumes equal to that of 200 metering-valve actuations were constant for ≤165 actuations, but drop beyond that range. There were statistically significant dose variations between replicate pMDIs and between two types of actuators used on the pMDIs. The storage half-lives of pMDIs filled with Bacillus atrophaeus (BG) and Bacillus thuringiensis subsp. israelensis (Bti) spore formulations are predicted to be 32 and 136 months, respectively, if the canisters are stored under refrigeration (4°C). The prediction is based on use of a logarithmic regression model relating CFU per actuation to storage time, with data taken at times of 1–12 months. Demonstration of the utility of the concept was provided by producing responses from a polymerase chain reaction (PCR) identifier with pMDI-generated BG and Bti aerosols that were collected with a 100 L/min wetted wall bioaerosol sampling cyclone.

Copyright 2013 American Association for Aerosol Research     

A Streamlined,High-Volume Particle Impactor for Trace Chemical Analysis

The design and characterization of a streamlined, high-volume particle impactor intended for use with trace chemical analysis is presented. The impactor has a single round jet and is designed to operate at a flow rate of 1000 L/min. Computational fluid dynamics (CFD) was used as a tool to optimize the aerodynamic performance of the impactor by iteratively redesigning the geometry and curvature of the internal walls. By eliminating recirculation zones within the flowfield of the impactor and using flowfield streamlines as new walls, successive designs revealed a significant reduction in the pressure drop across the impactor. Particle trajectories were simulated in the impactor and the 50% cutpoint was determined to be 1.05 μm. The impaction surface itself is easily removed from the body of the impactor assembly, potentially facilitating rapid trace chemical analysis using a variety of chemical detection techniques. A prototype impactor was fabricated with a 3D rapid prototyping printer and characterized in terms of particle cut-off diameter using test aerosols generated by an Ink Jet Aerosol Generator (IJAG) and fluorescence intensity measurements. The experimental particle cut-off diameter was not able to be measured because the smallest aerosol particles that could be tested were 1.86 μm which were collected at 100% efficiency. Particulate contamination from the high-explosive compound C4 was also collected with the impactor to demonstrate operational utility for trace explosives detection.

Copyright 2013 American Association for Aerosol Research     

Formation of banded and non-banded poly(l-lactic acid) spherulites during crystallization of films of poly(l-lactic acid)/poly(ethylene oxide) blends

In this study, a series of poly(l-lactic acid) (PLLA)/poly(ethylene oxide) (PEO) blends with different PLLA concentrations was prepared. Films of these blends crystallized with and without a coverslip were characterized by the presence and absence of banded structures, respectively. This difference in morphology was observed because the PEO component of the blends was oxidized at a high temperature (125 °C) in air without the protection of a coverslip. X-ray photoelectron spectroscopy (XPS) results showed that the surface of the blends crystallized in nitrogen without a coverslip contained mostly PLLA while the surfaces of the same blends crystallized under a coverslip contained only a moderately higher concentration of PLLA than their bulks. The migration of PLLA to the surface of the blends during crystallization in nitrogen when no coverslip was used was due to its low surface tension. Phase images obtained using atomic force microscopy (AFM) indicated that the banded structures consisted of valleys and ridges, which were in fact flat-on and edge-on lamellae, respectively. A detailed time-of-flight secondary ion mass spectrometry (ToF-SIMS) examination suggested that PLLA and PEO were located mainly on the surfaces of the ridges and valleys, respectively.     

The Rorschach: Toward a nomothetically based, idiographically applicable configurational model.

The authors argue that the Rorschach can and should be used best with a nomothetic foundation that adds an idiographic approach depending on the goal of the assessment. The research supporting this position is reviewed as are conceptual models that are advantageous to this conceptual position. The authors posit that method variance has a powerful impact on the measurement process. Each method is of value in some areas and of limited relevance in others. Self-report measures are most likely to be useful when interest is focused on consciously available and behavioral dimensions of functioning. Depth-oriented, indirect measures such as the Rorschach are most likely to be useful when interest is focused on unconscious, longitudinal, and structural dimensions of functioning. However, to have a full picture of human beings, heteromethod assessment is necessary to capture the full range of functioning and to implement the analytic model of assessment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Box–Behnken Design optimization of malachite green dye biosortpion using nano zero valent iron Sargassum swartzii biocomposite

This study reports the biosorption of MG using a novel nano zero valent iron Sargassum swartzii (nZVI-SS) biocomposite. Response surface methodology derived from Box–Behnken design (BBD) was applied for optimizing the essential variables such as pH, initial MG concentration, and biosorbent dosage. The results obtained from BBD design showed the maximum biosorption capacity of 73.5?mg/g at pH 10, initial MG concentration of 100?mg/L, and biosorbent dosage of 0.55?g/L. The biosorption was highly dependent on pH and initial dye concentration. The nZVI-SS biocomposite was characterized using SEM, FTIR, TGA, and DSC analysis. The experimental and analytical result shows that nZVI-SS biocomposite can be effectively used as prominent biosorbent for the removal of dye bearing wastewater.     

Competitive selection from single domain antibody libraries allows isolation of high-affinity antihapten antibodies that are not favored in the llama immune response

Single-domain antibodies (sdAbs) found in camelids lack a light chain, and their antigen-binding site sits completely in the heavy-chain variable domain (VHH). Their simplicity, thermostability, and ease in expression have made VHHs highly attractive. Although this has been successfully exploited for macromolecular antigens, their application to the detection of small molecules is still limited to a very few reports, mostly describing low-affinity VHHs. Using triclocarban (TCC) as a model hapten, we found that conventional antibodies, IgG1 fraction, reacted with free TCC with a higher relative affinity (IC(50) 51.0 ng/mL) than did the sdAbs (IgG2 and IgG3, 497 and 370 ng/mL, respectively). A VHH library was prepared, and by elution of phage with limiting concentrations of TCC and competitive selection of binders, we were able to isolate high-affinity clones, K(D) 0.98-1.37 nM (SPR), which allowed development of a competitive assay for TCC with an IC(50) = 3.5 ng/mL (11 nM). This represents a 100-fold improvement with regard to the performance of the sdAb serum fraction, and it is 100-fold better than the IC(50) attained with other antihapten VHHs reported thus far. Despite the modest overall antihapten sdAbs response in llamas, a small subpopulation of high-affinity VHHs is generated that can be isolated by careful design of the selection process.