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31.
Slater D.B. Jr. Enquist P.M. Hutchby J.A. Reed F.E. Morris A.S. Kolbas R.M. Trew R.J. Lujan A.S. Swart J.W. 《Photonics Technology Letters, IEEE》1993,5(7):791-794
An AlGaAs/GaAs nan heterojunction bipolar transistor (HBT) laser driver circuit and a pseudomorphic InGaAs/GaAs/AlGaAs graded index single-quantum-well (SQW) laser have been laterally integrated to maintain surface planarity using selective organometallic vapor-phase epitaxy (OMVPE) regrowth of the HBT. The self-aligned HBTs exhibit a DC current gain of 30 and an f t (f max ) of 45(60) GHz. The 980-nm lasers exhibit room-temperature threshold current densities as low as 420(320) A/cm2 for CW (pulsed) operation. The cavities are 40(7) μm×500 μm and have less than 1(2) Ω of series resistance. SPICE simulations of the integrated driver indicate that operating speeds of over 10 Gb/s are possible 相似文献
32.
The relationship of a member of the transmembrane dystrophin-associated glycoprotein (DAG) complex to acetylcholine receptors (AChRs) was investigated using immunofluorescence techniques at rat neuromuscular junctions (NMJs) viewed en face. These results were compared with those from a similar previous study of dystrophin and an autosomal homologue (utrophin or dystrophin-related protein, DRP) (Bewick et al. Neuro Report 1992; 3: 857-860). The region of highest 43 K DAG (43DAG) labelling projected beyond the AChRs by approximately 0.3 microns, as does that for dystrophin. By contrast DRP labelling precisely co-localizes with the AChRs. These results suggest that at the NMJ, the region of high 43DAG concentration encompasses the area of highest intensity labelling for both DRP and dystrophin. 相似文献
33.
Edge M; Forder C; Hennam J; Lee I; Tonge D; Hardern I; Fitton J; Eckersley K; East S; Shufflebotham A; Blakey D; Slater A 《Protein engineering, design & selection : PEDS》1998,11(12):1229-1234
Variants of human pancreatic carboxypeptidase B (HCPB), with specificityfor hydrolysis of C-terminal glutamic acid and aspartic acid, were preparedby site-directed mutagenesis of the human gene and expressed in theperiplasm of Escherichia coli. By changing residues in the lining of theS1' pocket of the enzyme, it was possible to reverse the substratespecificity to give variants able to hydrolyse prior to C- terminal acidicamino acid residues instead of the normal C-terminal basic residues. Thiswas achieved by mutating Asp253 at the base of the S1' specificity pocket,which normally interacts with the basic side- chain of the substrate, toeither Lys or Arg. The resulting enzymes had the desired reversed polarityand enzyme activity was improved significantly with further mutations atresidue 251. The [G251T,D253K]HCPB double mutant was 100 times more activeagainst hippuryl-L-glutamic acid (hipp-Glu) as substrate than was thesingle mutant, [D253K]HCPB. Triple mutants, containing additional changesat Ala248, had improved activity against hipp-Glu substrate when position251 was Asn. These reversed-polarity mutants of a human enzyme have thepotential to be used in antibody-directed enzyme prodrug therapy of cancer. 相似文献
34.
Eduardo J. Cavanagh Mariano J. Savelski C. Stewart Slater 《Chemical Engineering Research and Design》2014
The environmental impact reduction and operating costs savings associated with the purification and recovery of solvent waste in the manufacture of active pharmaceutical ingredients (API's) were investigated. A software toolbox has been developed that combines Aspen Plus® process simulation with SimaPro® and Ecosolvent life cycle assessment (LCA) databases. A LCA approach was used in order to consider the environmental impact beyond pharmaceutical production plant boundaries. The feasibility of a relatively small flexible equipment-skid capable of recovering multiple solvent waste streams was evaluated. Distillation and pervaporation were considered to separate binary waste solvent mixtures. Optimum distillation reflux ratio and feed stage were determined to maximize the environmental impact reductions and operating cost savings. The optimum reflux ratio was significantly higher than 1.2 times the minimum reflux ratio suggested by traditional heuristics. The emissions and cost reductions obtained were as much as 49% and 56% higher, respectively, as compared to using the conventional optimum reflux ratio. A comprehensive cash flow analysis showed that the recovery of low volume solvent waste streams is economically feasible, despite traditional thinking. Three case studies from Pfizer are presented to show how our software tool can aid in green engineering decision making. 相似文献
35.
Evaluating the Vulnerability of Network Traffic Using Joint Security and Routing Analysis 总被引:1,自引:0,他引:1
Tague Patrick Slater David Rogers Jason Poovendran Radha 《Dependable and Secure Computing, IEEE Transactions on》2009,6(2):111-123
Joint analysis of security and routing protocols in wireless networks reveals vulnerabilities of secure network traffic that remain undetected when security and routing protocols are analyzed independently. We formulate a class of continuous metrics to evaluate the vulnerability of network traffic as a function of security and routing protocols used in wireless networks. We develop two complementary vulnerability definitions using set theoretic and circuit theoretic interpretations of the security of network traffic, allowing a network analyst or an adversary to determine weaknesses in the secure network. We formalize node capture attacks using the vulnerability metric as a nonlinear integer programming minimization problem and propose the GNAVE algorithm, a Greedy Node capture Approximation using Vulnerability Evaluation. We discuss the availability of security parameters to the adversary and show that unknown parameters can be estimated using probabilistic analysis. We demonstrate vulnerability evaluation using the proposed metrics and node capture attacks using the GNAVE algorithm through detailed examples and simulation. 相似文献
36.
This study compares the effectiveness of group health supervision (three or four families counseled simultaneously) with traditional visits in conveying knowledge of child health and development, increasing perceived maternal support, and mitigating maternal depression. Subjects were recruited from a predominantly white, middle-class, suburban/rural pediatric practice. Twenty-five families were allocated to group health supervision and 25 to individual visits. A questionnaire covering knowledge of child health and development (CHDQ), the Maternal Social Support Index (MSSI), and the Center for Epidemiologic Studies Depression Scale (CESD) were administered to both groups before their 2-month and after their 10-month visits. A subset of these charts was reviewed for problem visits between 2 and 6 months. As compared with families having traditional visits, families who received the group intervention did at least as well in acquiring knowledge of child care and development and, although not statistically significant, tended to recover from postpartum depression faster and deal better with minor illnesses. The investigators found group child health supervision to be a pleasant and effective method of health care delivery. 相似文献
37.
An organizational prototype is a forum to address simultaneously process, behavioral, and cultural change pursuant to business process redesign (BPR). in this case study, IS personnel facilitated organizational prototypes, thereby extending their knowledge of business systems to a new sphere, facilitating business process redesign. Success of the prototypes led to success in obtaining corporate funding for new client/server systems to support the changes in business operations. 相似文献
38.
Sheffert Sonya M.; Pisoni David B.; Fellowes Jennifer M.; Remez Robert E. 《Canadian Metallurgical Quarterly》2002,28(6):1447
In 5 experiments, the authors investigated how listeners learn to recognize unfamiliar talkers and how experience with specific utterances generalizes to novel instances. Listeners were trained over several days to identify 10 talkers from natural, sinewave, or reversed speech sentences. The sinewave signals preserved phonetic and some suprasegmental properties while eliminating natural vocal quality. In contrast, the reversed speech signals preserved vocal quality while distorting temporally based phonetic properties. The training results indicate that listeners learned to identify talkers even from acoustic signals lacking natural vocal quality. Generalization performance varied across the different signals and depended on the salience of phonetic information. The results suggest similarities in the phonetic attributes underlying talker recognition and phonetic perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
Apatite-type lanthanum silicates/germanates have been attracting considerable interest as a new class of oxide ion conductors, whose conductivity is mediated by oxide ion interstitials. For the germanates, it has been shown that, depending on composition, the cell can be either hexagonal or triclinic, with evidence for reduced low-temperature conductivities for the latter, attributed to increased defect trapping in this lower symmetry cell. In this paper we show that site selective doping of Y into the triclinic apatite-type oxide ion conductors, La9.33+z(GeO4)6O2+3z/2 (0.33 ≤ z ≤ 0.67) results in a hexagonal lattice for the complete series with correspondingly enhanced low-temperature conductivity. 相似文献
40.
Mel Slater 《Software》1986,16(11):965-980
The problems associated with using picture segments in interactive applications on workstations with bit-mapped displays are discussed. A method for displaying and updating segments is introduced. 相似文献