Polymerase chain reaction-mediated characterization of molds belonging to the Aspergillus flavus group and detection of Aspergillus parasiticus in peanut kernels by a multiplex polymerase chain reaction

The Aspergillus flavus group covers species of A. flavus and Aspergillus parasiticus as aflatoxin producers and Aspergillus oryzae and Aspergillus sojae as koji molds. Genetic similarity among these species is high, and aflatoxin production of a culture may be affected by cultivation conditions and substrate composition. Therefore, a polymerase chain reaction (PCR)-mediated method of detecting the aflatoxin-synthesizing genes to indicate the degree of risk a genotype has of being a phenotypic producer was demonstrated. In this study, 19 strains of the A. flavus group, including A. flavus, A. parasiticus, A. oryzae, A. sojae, and one Aspergillus niger, were subjected to PCR testing in an attempt to detect four genes, encoding for norsolorinic acid reductase (nor-1), versicolorin A dehydrogenase (ver-1), sterigmatocystin O-methyltransferase (omt-1), and a regulatory protein (apa-2), involved in aflatoxin biosynthesis. Concurrently, the strains were cultivated in yeast-malt (YM) broth for aflatoxin detection. Fifteen strains were shown to possess the four target DNA fragments. With regard to aflatoxigenicity, all seven aflatoxigenic strains possessed the four DNA fragments, and five strains bearing less than the four DNA fragments did not produce aflatoxin. When peanut kernels were artificially contaminated with A. parasiticus and A. niger for 7 days, the contaminant DNA was extractable from a piece of cotyledon (ca. 100 mg), and when subjected to multiplex PCR testing using the four pairs of primers coding for the above genes, they were successfully detected. The target DNA fragments were detected in the kernels infected with A. parasiticus, and none was detected in the sound (uninoculated) kernels or in the kernels infected with A. niger.     

A study of multi-angles knife-edge method applied to digital modulation transfer function measurement

Microsystem Technologies - The objective of this study was to propose a newly-developed method to calculate digital modulation transfer function (DMTF) of digital image system which integrates with...     

On the parallel-decomposability of geometric problems

There is a large and growing body of literature concerning the solutions of geometric problems on mesh-connected arrays of processors. Most of these algorithms are optimal (i.e., run in timeO(n ^1/d ) on ad-dimensionaln-processor array), and they all assume that the parallel machine is trying to solve a problem of sizen on ann-processor array. Here we investigate the situation where we have a mesh of sizep and we are interested in using it to solve a problem of sizen >p. The goal we seek is to achieve, when solving a problem of sizen >p, the same speed up as when solving a problem of sizep. We show that for many geometric problems, the same speedup can be achieved when solving a problem of sizen >p as when solving a problem of sizep.     

Role of Ca2+ in differentiation mediated by nerve growth factor and dibutyryl cyclic AMP in PC12 cells

Nerve growth factor (NGF) and dibutyryl cyclic AMP (dbcAMP) have synergistic effects on the neurite outgrowth of rat pheochromocytoma PC12 cells. The sites of interaction between NGF and dbcAMP have been studied extensively; however, the role of Ca2+ in differentiation induced by the two agents remains unclear. To understand whether intracellular Ca2+ is involved in the differentiation induced by the two agents, PC12 cells were treated with NGF, dbcAMP, or NGF plus dbcAMP for 2 days, and then effects on neurite outgrowth, ATP-induced Ca2+ influx, and Ca2+ mobilization from intracellular Ca2+ pools were examined. NGF or dbcAMP alone enhanced neurite outgrowth and Ca2+ accumulation by nonmitochondrial Ca2+ pools or the thapsigargin (TG)-sensitive Ca2+ pool. The dbcAMP acted synergistically with NGF to increase neurite outgrowth and to enlarge the TG-sensitive Ca2+ pool. The synergistic effect occurred within the first hour of treatment with dbcAMP plus NGF. On the other hand, dbcAMP abolished NGF's ability to enhance ATP-induced influx of extracellular Ca2+ . Therefore, NGF and dbcAMP induced different effects on Ca2+ signaling pathways through two different but interacting pathways. In PC12 cells pretreated with TG to deplete the TG-sensitive Ca2+ pool, the dbcAMP- or dbcAMP plus NGF-mediated neurite outgrowth was significantly inhibited, whereas NGF-mediated neurite outgrowth was not affected by TG pretreatment. Our results suggest that the intracellular nonmitochondrial Ca2+ pools were changed in the differentiation process and were necessary for the synergistic effect of NGF and dbcAMP.     

Dynamics of the phase inversion process

An analysis of the dynamics of phase inversion based on mathematical modeling and in situ experimental observations is presented. Calculations based on ternary diffusion models illustrate the effects of casting film composition, evaporation time, and film thickness on the precipitation time and resulting polymer film profiles, which correlate with observed final morphologies. An experimental method based on the use of dark ground optics, interface visualization, and reflected light illumination is used for in situ monitoring of the mass transfer and phase separation dynamics during the quench step. Observations on the systems water—dimethylsulfoxide cellulose acetate and water—dioxane—cellulose acetate show regions in the films corresponding to gel formation and growth, instabilities associated with finger formation, and homogeneous ternary diffusion. Data for the kinetics of the diffusion and gel front motions show that both propagate as the square root of time with rates dependent on the bath—film compositions. Examples of interface structures characteristic of deep quenching and nucleated droplet growth are also shown. Semiquantitative analyses in terms of the ternary models developed earlier and a phenomenological model for diffusion in the growing gel are used to explain the trends seen. © 1992 John Wiley & Sons, Inc.     

Gaseous hydrogen embrittlement of T-250 laser welds

The tensile properties of laser-welded T-250 maraging steel are measured, with attention paid to the influence of strain rate and gaseous hydrogen on the fracture behavior of welded specimens. Post-weld heat treatments are performed on laser-welded specimens to obtain underaged (WU), peak-aged (WP), and overaged (WO) specimens. Hydrogen embrittlement (HE) affects the tensile fracture behavior of the welded specimens; HE changes not only the fracture mode but also the fracture location. Without the influence of hydrogen, the fracture location is at the softest region, the weld metal (WM), and the fracture appearance reveals a ductile dimple fracture. For welds sensitive to HE, the fracture is initiated at the heat-affected zone (HAZ) with coarse grain size, and the associated fracture surface exhibits intergranular and quasi-cleavage fractures that are brittle in nature. In addition, the HAZ with coarse grain size is more prone to HE, as compared to other regions in the welded specimens. The WU specimens are susceptible to HE in air under a low strain rate, while the WP specimens are only susceptible to gaseous hydrogen embrittlement (GHE). However, the WO specimens are immune to GHE and insensitive to strain rate.     

Notch tensile properties of laser-surface-annealed 17-4 PH stainless steel in hydrogen-related environments

Slow displacement rate tensile tests were performed to determine the notched tensile strength (NTS) of 17-4 PH stainless steel with various microstructures in hydrogen-related environments. Solution-annealed (SA), peak-aged (H900), over-aged (H1025), and laser-annealed (LA) specimens were included in the study. Based on the results of NTS in air, the NTS loss in both gaseous hydrogen and H₂S-saturated solution was used to access the detrimental effects of hydrogen in 17-4 PH steel subjected to different treatments. Electrochemical permeation tests were also employed to determine the hydrogen permeation characteristics of the 17-4 PH steel plate with various microstructures. The result indicates that all the specimens have low NTS loss in gaseous hydrogen but significantly suffer from sulfide stress corrosion cracking (SCC), especially for the soft SA specimen. It was deduced that high hydrogen diffusivity and less trapped hydrogen atoms in the SA matrix provided rapid transport of massive hydrogen atoms into highly stressed region, and deteriorated the NTS tested in the saturated sulfide solution. On the other hand, H1025 specimen consists of the blocky austenite together with Cu-rich precipitates uniformly distributed in the grain interior; dense and coarse precipitates are also observed along prior austenite grain boundaries. Hydrogen atoms tend to be trapped along grain boundaries, and lead to the formation of intergranular fracture for H1025 specimen tested in the H₂S solution. Fine and homogeneously distributed precipitates in the H900 matrix result in uniformly trapping of hydrogen atoms, so it behaves superior properties than other specimens. The decohesion of precipitate/matrix interfaces induces quasi-cleavage fracture of the H900 specimen tested in H₂S solution. Finally, the application of laser-annealing treatment on the H900 specimen cannot improve its resistance to sulfide SCC, because the laser-annealed zone is susceptible to hydrogen embrittlement in the H₂S solution.     

Behavioristic image-based pose control of mobile manipulators using an uncalibrated eye-in-hand vision system

In the execution of material handling, the mobile manipulator is controlled to reach a station by its mobile base. This study adopts an uncalibrated eye-in-hand vision system to provide visual information for the manipulator to pick up a workpiece on the station. A novel vision-guided control strategy with a behavior-based look-and-move structure is proposed. This strategy is based on six image features, predefined by image moment method. In the designed neural-fuzzy controllers with varying learning rate, each image feature error is taken to generate intuitively one DOF motion command relative to the camera coordinate frame using fuzzy rules, which define a particular visual behavior. These behaviors are then fused to produce a final command action to perform grasping tasks using the proposed behavior fusion scheme. Finally, the proposed control strategy is experimentally applied to control the end-effector to approach and grasp a workpiece in various locations on a station.     

PROPERTIES OF UV-CURED POLYURETHANE ACRYLATES: EFFECT OF POLYOL TYPE AND MOLECULAR WEIGHT

Several families of UV-cured polyurethane acrylates were synthesized and the effects of polyol type and molecular weight on their physical properties were investigated. Increasing polyol molecular weight led to a lower polyol glass transition temperature, a smaller amount of a separate urethane acrylate phase, and a larger chain length between crosslinks. The first two effects were reflected in lower modulus and strength at room temperature while the larger chain length between crosslinks led to higher elongation at break (room temperature) and lower modulus at high temperatures. The use of different polyols (polycarbonate, polytetramethylene oxide, polypropylene oxide, and polycaprolactone) primarily affected the room temperature modulus due to differences in the position and breadth of the polyol glass transition. The properties of materials based on isocyanatoethyl methacrylate (IEM) and toluene diisocyanate-2-hydroxyethyl melhacrylate (TDI-HEMA) were also compared.