可装入很小空间的简单电源

随着便携设备应用的普及,对负极性电压电源的需求逐渐增加.用一个正电压输入源来产生一个负电压电源这一做法,成本既高,又比较复杂,特别是当设计需要正电压和负电压两种输出时更是如此.图1示出了一个经济实惠的简单解决方案,它将一个电压逆变器和一个倍压器组合成一个电荷泵电路.该电路能利用一个5～6V的输入电压来产生一个-5V稳压输出电压和一个10V非稳压输出电压.它除了需要一个SOT-23封装的电荷泵集成电路之外,只需5只很小的表面安装陶瓷电容器和两只二极管.     

Algorithm for tissue ischemia estimation based on electrical impedance spectroscopy

The purpose of this paper is to present an algorithm developed for real-time estimation of skeletal muscle ischemia, based on parameters extracted from in vivo obtained electrical impedance spectra. A custom impedance spectrometer was used to acquire data sets: complex impedance spectra measured at 27 frequencies in the range of 100 Hz-1 MHz, and tissue pH. Twenty-nine in vivo animal studies on rabbit anterior tibialis muscle were performed to gather data on the behavior of tissue impedance during ischemia. An artificial neural network (ANN) was used to quantitatively describe the relationship between the parameters of complex tissue impedance spectra and tissue ischemia via pH. The ANN was trained on 1249, and tested on 946 ischemic tissue impedance data sets. A correlation of 94.5% and a standard deviation of 0.15 pH units was achieved between the ANN estimated pH and measured tissue pH values.     

Failures induced by electromigration in ECL 100k devices

Reliability of ECL 100k devices using Al (4%wt Cu, 1%wt Si) double level metallization, isoplanar technology with shallow, 0.25 μm, base-emitter junctions was evaluated by means of high current and high temperature stresses. Three failure modes connected with electromigration phenomena were found in the output transistor: (a) base-emitter shunts owing to junction spiking caused by Al-Si interdiffusion enhanced by electromigration; (b) collector-emitter shorts due to the breaking of the dielectric oxide between two superimposed metal levels owing to material transport and pile-up in the underlying metallization; (c) open circuit of the output emitter due to void growth in the Cu-depleted areas of the Al interconnections. After B-E shunts, failure mechanism evolves towards two different sequences of failure modes, according to the different transistor structures; in fact C-E shorts were found to occur only when collector and emitter metals are superimposed, while the open circuit of the output emitter is the final failure for all configurations. The earlier and more frequent failure mode observed is the resistive shunt of the base-emitter junction of the output transistor, in agreement with previously reported data on electromigration effects in Al (Cu, Si) metallizations used both as interconnections and as contacts to shallow junctions.     

Synthesis and properties of fatty imidazolines and their N-(2-aminoethyl) derivatives

Cationic high molecular weight surfactants hold promise as water repellents for soil for water harvesting. Specifically, the products of the reaction of 2 moles of fatty acids with 1 mole of diethylenetria-mine were investigated. Optimum conditions for the formation of imidazolines as well as the open-chain N-(2-aminoethyl) derivatives, i.e., the diamides, were determined. Saturated fatty acids, pelargonic through behenic, oleic acid, elaidic acid as well as tallow, tallow fatty acids, and hydrogenated tallow fatty acids, were converted in 6 hr at 150 C to form the diamides. The fatty imidazolines were synthesized by cyclizing the diamides at 150 C for 2 hr under reduced pressure in a 92% yield. The crude imidazolines were purified by crystalliza-tion. The fatty imidazolines were readily hydrolyzed at the C=N bond of the imidazoline ring with water or dilute alcohol. The resulting diamides, RCON(CH₂ CH₂ NH₂)CH₂ CH₂ NHCOR, were also purified by crystallization. Water repellency of these com-pounds was evaluated by contact angle measurements and percola-tion tests. The surface properties of these series of compounds are determined by four parameters. The open-chain diamides are more hydrophobic than the analogous imidazolines, and hydrophobicity increases with increasing molecular weight of derivatives of saturated fatty acids. Oleic acid derivatives are far more hydrophilic than the saturated acid derivatives or the analogous elaidic acid derivatives. The latter are more hydrophilic than stearic derivatives. Presented at the 72nd AOCS annual meeting, New Orleans, 1981.     

Activity of two lignin biosynthesis enzymes during development of a maize internode

To ascertain the temporal relationships of phcnylpropanoid and lignin pathway enzymes, phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol- NADPH dehydrogenase(CAD), with lignin concentration, PAL and CAD activities and lignin concentrations were assessed during progressive development of the 10th internode in maize (Zea mays L). Enzyme activities were quantified and lignin concentrations were determined by the detergent system of fiber fractiona- tion from lower, middle, and upper sections of the elongating internode harvested 3, 5, 7, 9, 11, 13, and 15 days after the internode had reached 10 mm in length. Over 15 days, a coordinated, sequential, and basipetal pattern of enzyme activities and lignin accumulation evolved through the internode, spanning the stages of rapid elongation, cellular differentiation, and secondary cell wall formation. PAL activity was initiated first, rising to peak activity in elongating tissue, and falling basipetally in tissues as they matured. CAD activity rose in fully elongated, maturing internode tissue where PAL activity was waning following its peak activity. Lignin accumulated in tissues with high CAD activity. CAD activity and lignin deposition patterns were similar: simultaneously increasing in activity and deposition over time while activity and deposition also shifting basipetally through the internode, keeping pace with secondary cell wall formation. Lignin concentration correlated significantly with CAD, but not with PAL.     

Cathepsin D from horse spleen. I. Purification and study of certain physicochemical properties

Horse spleen cathepsin D (3.4.23.5.) was purified from crude extract by sodium chloride and ethanol precipitation, column chromatography fractionation on DEAE cellulose and CM Sephadex, re-chromatography on DEAE cellulose and gel filtration. The enzyme has been purified about 3.000 folds with a yield of 30 per cent. The purified enzyme seems to be homogeneous on Sephadex G100, one protein band is apparent on disc electrophoresis. Determined by dansylation the N-terminal amino acid is glycine. A molecular weight of 42,500 +/- 3,000 was obtained with Sephadex G100 gel filtration and light scattering measurements. Amino acid analysis and chemical determinations were performed: cathepsin D is a glycoprotein (2 or 3 osamine residues) including 344 amino acids and 4 disulfide bonds. Spectrophotometric data show that E1cm/1 mg/ml = 1.01 at lambda = 280 nm. ORD measurements indicate about 20 per cent of helicoidal content in the molecule.     

Presterilization interviewing: An evaluation.

The role of interviewing in diffusing possible harmful side effects of sterilization operations was evaluated in an acute general hospital. This hospital required an interview with a chaplain before either a vasectomy or a tubal-ligation operation. Two simultaneous field experiments were conducted with 50 vasectomy couples and 50 tubal-ligation couples. Couples applying for either operation were alternately assigned to either the interview or the control group. Questionnaires were mailed to all couples 6 mo after the operation. Results are based on the responses of 67 couples who followed through with the sterilization procedure. There were no significant differences between the interview and control groups. The vasectomy couples scored significantly higher than the tubal-ligation couples on 6 of 9 measures in the questionnaire. The wives in the vasectomy group had a significantly lower level than the wives in the tubal-ligation group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamic mechanical analysis of polymers in the liquid state: Use of a perforated shim stock support

This report summarizes some initial results on the use of a perforated brass shim stock support to extend the useful range of dynamic mechanical testing well over 100 degrees above the traditional limiting polymer softening points of T_g or T_m. Weak secondary relaxations were observed above T_g in both polyisobutylene (PIB) and polystyrene (PS) homopolymer, copolymer, and blend systems and above T_m in gutta percha (trans-polyisoprene). The DuPont 981 Dynamic Mechanical Analyzer (DMA)–990 Thermal Analyzer system was used to characterize these weak liquid state processes. The DMA instrument deforms the specimen in flexure, thus minimizing the shear component present in some other techniques. Specimen-coating weights are typically in the range 20–40 mg. The perforations are particularly useful for polymers having low inherent adhesion to metals or systems which are very brittle in the glassy state, e.g., low MW PS's and many methacrylates.     

Bioaccumulation of dioxin-like substances and selected brominated flame retardant congeners in the fat and livers of black pigs farmed within the Nebrodi Regional Park of Sicily

An observational study was designed to assess the bioaccumulation of polychlorodibenzodioxins (PCDD) and polychlorodibenzofurans (PCDF), dioxin-like polychlorobiphenyls (DL-PCB), and 13 selected polybromodiphenylethers (PBDE) in autochthonous pigs reared in the Nebrodi Park of Sicily (Italy). Perirenal fat and liver samples were drawn from animals representative of three different outdoor farming systems and from wild pigs and then analyzed for the chemicals mentioned previously. The highest concentrations of PCDD + PCDF and DL-PCB were detected in the fat (0.45 and 0.35 pg World Health Organization toxicity equivalents [WHO-TE] per g of fat base [FB], respectively) and livers (12.7 and 3.28 pg WHO-TE per g FB) of the wild group, whereas the free-ranging group showed the lowest levels (0.05 and 0.03 pg WHO-TE per g FB in fat and 0.78 and 0.27 pg WHO-TE per g FB in livers). The sum of PBDE congeners was highest in wild pigs (0.52 ng/g FB in fat and 5.64 ng/g FB in livers) and lowest in the farmed group (0.14 ng/g FB in fat and 0.28 ng/g FB in livers). The contamination levels in fat and livers of outdoor pigs had mean concentration values lower than those levels reported for intensively indoor-farmed animals. In wild pigs, bioaccumulation was associated with their free grazing in areas characterized by bush fires. The results of this study aid to emphasize the quality of the environment as a factor to guarantee food safety in typical processed pig meat products, specifically from outdoor and extensive Nebrodi farming systems.     

Effect of race on peer ratings in an industrial situation.

Examined the effect of race on the peer ratings of 43 black and 50 white industrial employees recently exposed to a foreman-training program which included intensive human relations training. Contrary to previous studies, no race effect was found. In addition, almost all the requirements for convergent and discriminant validity between the races were met. Possible explanations for these results and implications for the use of peer ratings in integrated settings are discussed. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)