Copolymerization of glycidylmethacrylate–methylmethacrylate–divinylbenzene in cyclohexane

The copolymerization of glycidylmethacrylate–methylmethacrylate–divinylbenzene in cyclohexane was studied as an example of crosslinking precipitation copolymerization. The resultant copolymer is fine spheroidal. The copolymerization proceeds acceleratively at first, then steadily, and gradually slows down. The larger the divinylbenzene concentration, the smaller is the copolymerization rate. Glycidylmethacrylate is preferentially incorporated in the copolymer.     

Occurrence,horizontal transfer and degeneration of VDE intein family in Saccharomycete yeasts

VDE is a homing endonuclease gene originally discovered as an intervening element in VMA1s of Saccharomyces cerevisiae. There have been two independent subfamilies of VDE, one from S. cerevisiae strain X2180-1A and the other from Saccharomyces sp. DH1-1A in the host VMA1 gene, and they share the identity of 96.3%. In order to search the occurrence, intra/interspecies transfer and molecular degeneration of VDE, complete sequences of VMA1 in 10 strains of S. cerevisiae, eight species of saccharomycete yeasts, Candida glabrata and Kluyveromyces lactis were determined. We found that six of 10 S. cerevisiae strains contain VDEs 99.7-100% identical to that of the strain X2180-1A, one has no VDE, whereas the other three harbour VDEs 100% identical to that of the strain DH1-1A. S. carlsbergensis has two VMA1s, one being 99.8% identical to that of the strain X2180-1A with VDE 100% identical to that of the strain DH1-1A and the other containing the same VMA1 in S. pastorianus with no VDE. This and other evidence indicates that intra/interspecies transmissions of VDEs have occurred among saccharomycete yeasts. Phylogenetic analyses of VMA1 and VDE suggest that the S. cerevisiae VDEs had branched earlier than other VDEs from an ancestral VDE and had invaded into the host loci as relatively late events. The two VDEs seemed to degenerate in individual host loci, retaining their splicing capacity intact. The degeneration of the endonuclease domains was distinct and, if compared, its apparent rate was much faster than that of the protein-splicing domains.     

Determination of captafol,cyhexatin, 1-naphthylacetic acid and quintozene in apple,Japanese pear and melon by simultaneous extraction

A simple and rapid method is described for the determination of the non-registered pesticides, captafol, quintozene (PCNB), cyhexatin and 1-naphthylacetic acid (NAA), in fruits. These pesticides were extracted with acidified acetone, then captafol and PCNB were purified with a Florisil mini column and analyzed by GC-ECD. Cyhexatin was ethylated with ethylmagnesium bromide, and the ethyl derivative was analyzed by GC-FPD (Sn filter). NAA was purified with liquid-liquid extraction and determined by HPLC equipped with a fluorescence detector. These analytes were identified with GC/MS or LC/MS. The minimum identified concentration of the pesticides was below 0.2 ng per injection, which corresponds to a detection limit of below 0.02 microgram/g in the original samples. Recoveries of the pesticides spiked at 0.1 microgram/g into apple, Japanese pear and melon were greater than 61%.     

Analysis and evaluations of logical instructions called in parallel digital optical operations based on optical array logic

The authors have analysed and evaluated a two-dimensional instruction set of parallel operation based on optical array logic (OAL), which is a digital optical computing paradigm, to clarify efficient composition of an optical computing system based on OAL. To evaluate parallel operation based on OAL, the author have introduced new indices and evaluated a logical instruction set of various parallel operations with the indices, so that a guideline for composing a simple and efficient OAL computing system is clarified. Also, the authors have proposed the reduced operation kernel set correlation technique to perform parallel operations more efficiently by a simple OAL computing system. It has been clarified that the technique can reduce the required hardware necessary for an OAL computing system for efficient general-purpose processing.     

Effects of steroid hormones on vascular functions

The purpose of this review is to present reported findings of effects of steroids on vascular function and to discuss the biological significance in vascular physiology and pathology. Steroid hormones play various roles in vascular functions through the specific receptor localized in the endothelium and underlying vascular smooth muscle cells (VSMCs). Estrogen replacement therapy in postmenopausal women is in general associated with a reduction in mortality from cardiovascular disease and the beneficial effects of estrogens are caused by modulation of lipid metabolism, expression of leukocyte adhesion molecules, and migration of VSMCs in the vascular wall. Estrogens also play a role as vasodilators through an increment in nitric oxide (NO) production in endothelium or modulation of calcium homeostasis in VSMCs. Some progestin molecules partially oppose the effects of estrogens on vascular functions, but striking differences exist among the types of molecules. Testosterone shows a vasorelaxant response, but detailed actions of androgens on vascular functions remain unknown. Glucocorticoids act on vasoconstriction through reduced prostacyclin production, increased alpha-adrenoceptor numbers, and inhibition of NO synthase, while mineralocorticoids induce hypertrophy and hyperplasia of VSMCs and perivascular fibrosis and cause peripheral vascular resistance, in addition to changes in vascular electrocyte permeability. Some rapid actions of steroids are mediated by "nongenomic" responses in vascular tissues. Recent studies have also demonstrated that steroid-producing or -metabolizing enzymes are expressed in the vascular wall, suggesting the local regulation of steroids in the vascular system. Thus, steroid hormones greatly influence vascular functions and an understanding of the mechanisms may provide new means to prevent vascular diseases.     

Simulated crepitus and its reality-based specification using wearable patient dummy

Physical therapists are trained in manual examination techniques to test the impaired motor functions of patients. In this study, we have introduced a wearable robotic dummy joint to simulate disordered joint resistances or behaviors to support physical therapists in learning such techniques. We developed a discontinuous joint friction model based on a stick-slip phenomenon to simulate knee joint resistances caused by crepitus, a typical symptom accompanied by osteoarthritis. Practicing therapists participated in a reality-based evaluation test and specified acceptable parameter sets to adjust the simulated crepitus for the exoskeletal patient robot. The simulated crepitus and wearable dummy joint are expected to support the training of physical therapists.     

Fracture Energy of an Aligned Porous Silicon Nitride

The fracture energy of a porous silicon nitride with aligned fibrous grains was investigated, using a chevron-notched-beam technique. A crack was constrained to propagate normal to the grain alignment. The obtained fracture energy was ∼500 J/m², which was ∼7 times larger than that of a dense silicon nitride with randomly oriented fibrous grains. The large fracture energy was attributable primarily to the sliding resistance associated with interlocking grains.     

Vapor generation model for flashing in the initial blowdown phase

A vapor generation model for flashing in the initial blowdown phase is proposed based on a wall nucleation theory and a bubble transport model. Comparisons are made between the proposed model and the TRAC-PF1 model by using the MINCS code through analyses of three blowdown experiments with different scales. The present model well predicts the pressure undershoot in the vessel, while the TRAC model can not predict this typical thermodynamic nonequilibrium phenomenon.     

The leaching of chalcopyrite with cupric chloride

A comparative study of electrochemical leaching and chemical leaching of chalcopyrite was performed mainly at 343 K to elucidate the leaching mechanism of chalcopyrite with CuCl₂. Also, the morphology of the leached chalcopyrite surface was studied by using a single chalcopyrite crystal. The leaching with CuCl₂ produced a porous elemental sulfur layer on the chalcopyrite surface, showing a similar morphology to that produced during leaching with FeCl₃. The leaching kinetics were found to be linear over an extended period, followed by an acceleration stage, as a result of an increase in the reaction surface area. The leaching rate of chalcopyrite was proportional to C(CuCl₂)^0.5, whereas it was inversely proportional to C(CuCl)^0.5. The mixed potential of chalcopyrite exhibited a 66 mV decade⁻¹ dependency upon C(CuCl₂), and—69 mV decade⁻¹ upon C(CuCl). Based on these observations together with other findings, an electrochemical mechanism involving the oxidation of chalcopyrite and CuCl ₋ ² and the reduction of CuCl⁺ was proposed. The Tafel plot between the mixed potential and the current density obtained by converting the rate of chemical leaching gave a straight line whose slope was in good agreement with that of the electrochemical leaching. These findings strongly support the electrochemical mechanism of chalcopyrite leaching with cupric chloride.     

Cast Your Vote for the 2002 IEEE Division VII Director

A simple and low-cost method of generating the pulse width modulation specific harmonic elimination (PWM-SHE) switching signals to drive the three-phase voltage source inverter (VSI) is presented. This novel approach computes the switching angles online using a PC and provides the flexibility of eliminating different sets of VSI output harmonics in a quick and easy manner without any hardware change. The validity of selected results has been verified experimentally.