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51.
We demonstrate large area two-dimensional arrays of patterned nanoporous gold for use as easy-to-fabricate, cost-effective, and stable surface enhanced Raman scattering (SERS) templates. Using a simple one-step direct imprinting process, subwavelength nanoporous gold (NPG) gratings are defined by densifying appropriate regions of a NPG film. Both the densified NPG and the two-dimensional grating pattern are shown to contribute to the SERS enhancement. The resulting substrates exhibit uniform SERS enhancement factors of at least 10(7) for a monolayer of adsorbed benzenethiol molecules. 相似文献
52.
We have applied an in vitro system that mimics thymic negative selection to investigate signaling pathways that may be important for the removal of autoreactive cells from the thymus. We sought to more precisely determine the contribution of calcium-dependent pathways to CD4+CD8+ thymocyte deletion that is mediated by either an antigenic peptide or a peptide analogue. We show that the requirement for external calcium influx is dependent upon the strength of the deleting ligand. Furthermore, these results correlate well with a requirement, under certain circumstances, for signaling through the calcium/calmodulin-dependent phosphatase calcineurin. The use of suboptimal stimuli may, therefore, be useful in revealing biochemical pathways important for CD4+CD8+ thymocyte negative selection. 相似文献
53.
Lee Y.J. Kane T. Lim J.-J. Schiano L. Kim Y.-B. Meyer F.J. Lombardi F. Max S. 《IEEE transactions on instrumentation and measurement》2003,52(6):1749-1755
This paper deals with the generation, measurement and modeling of the jitter encountered in the signals of a testhead board for automatic test equipment (ATE). A novel model is proposed for the jitter; this model takes into account the radiated electromagnetic interference (EMI) noise in the head of an ATE. The RMS value of the jitter is measured at the output signal of the testhead board to validate the proposed model. For measuring the RMS value, a novel circuitry has been designed on a daughter board to circumvent ground noise and connectivity problems arising from the head environment. An H-field is applied externally at the loop filter of a phase-locked loop (PLL), thus permitting the measurement of the RMS jitter to verify the transfer function between radiated EMI and jitter variation. The error between measured and predicted jitters is within a 15% level at both 200 kHz and 500 kHz. 相似文献
54.
55.
Gill D.M. Kane B.C. Svensson S.P. Tu D.-W. Uppal P.N. Byer N.E. 《Electron Device Letters, IEEE》1996,17(7):328-330
This letter describes the material characterization and device test of InAlAs/InGaAs high electron mobility transistors (HEMTs) grown on GaAs substrates with indium compositions and performance comparable to InP-based devices. This technology demonstrates the potential for lowered production cost of very high performance devices. The transistors were fabricated from material with room temperature channel electron mobilities and carrier concentrations of μ=10000 cm2 /Vs, n=3.2×1012 cm-2 (In=53%) and μ=11800 cm2/Vs, n=2.8×1012 cm-2 (In=60%). A series of In=53%, 0.1×100 μm2 and 0.1×50 μm2 devices demonstrated extrinsic transconductance values greater than 1 S/mm with the best device reaching 1.074 S/mm. High-frequency testing of 0.1×50 μm2 discrete HEMT's up to 40 GHz and fitting of a small signal equivalent circuit yielded an intrinsic transconductance (gm,i) of 1.67 S/mm, with unity current gain frequency (fT) of 150 GHz and a maximum frequency of oscillation (fmax) of 330 GHz. Transistors with In=60% exhibited an extrinsic gm of 1.7 S/mm, which is the highest reported value for a GaAs based device 相似文献
56.
Despite the acknowledged contribution of Small and Medium Enterprises (SMEs) to the food industry there is increasing evidence that Hazard Analysis Critical Control Point (HACCP) implementation is limited in this sector, with the burden of implementation perceived as potentially insurmountable. Using an action research methodology, this in-depth, government funded research project took the form of a two stage, 18 month investigation into methods of reducing burdens of HACCP on SMEs. Stage one indicted that SMEs see HACCP as a difficult, complex set of activities requiring great amounts of time effort and with few, if any, perceived benefits. In stage two, however, with the help of research tools developed, a number of SMEs completed HACCP and many made good progress on a tight timescale. This research thus concludes that SMEs can achieve HACCP if they are provided with sufficient guidance and support in a context of general consensus of HACCP terminology and requirements. Recommendations are made, many of which have been subsequently adopted by the UK Food Standards Agency. 相似文献
57.
TT Kane M Gueye I Speizer S Pacque-Margolis D Baron 《Canadian Metallurgical Quarterly》1998,29(3):309-323
An integrated multimedia campaign featuring family planning messages saturated the 900,000-person city of Bamako, Mali, for three months during the spring of 1993. With traditional theater and music, family planning messages were repeatedly broadcast on radio and television that conveyed information about modern contraceptive methods, the need for male sexual responsibility, the health and economic advantages of family planning, the need for communication between spouses, and that Islam, the predominant faith of Mali, does not oppose family planning. A separate sample pretest-post-test quasi-experimental research design was used to evaluate the effects of the campaign and exposure to specific messages on changes in contraceptive knowledge, attitudes, and practice. Results indicate a high level of exposure to and agreement with the messages. A dramatic drop was found in the proportion of men and women who believe that Islam opposes family planning. Logistic regression results indicate that contraceptive knowledge and use and more favorable attitudes toward family planning are positively associated with intensity of exposure to the project interventions, after controlling for relevant variables. 相似文献
58.
KT Sato NL Kane G Soos CV Gisolfi N Kondo K Sato 《Canadian Metallurgical Quarterly》1996,80(4):1233-1239
Controversies surrounding tympanic temperature (Tty) itself and techniques for measuring it have dampened the potential usefulness of Tty in determining core temperature (operationally defined here as the body temperature taken at a deep body site). The present study was designed to address the following questions. 1) Can a tympanic membrane probe be made that is safer and more reliable than its predecessors? 2) Why is the effect of facial cooling and heating on Tty so inconsistent in reports from different laboratories? 3) Is Tty still useful as a measure of core temperature? Data from this study, obtained with a modified thermocouple probe, suggest that the widely reported facial skin cooling effect on Tty is most probably due to thermal contamination from the surrounding ear canal wall and/or suboptimal contact of the probe sensor with the tympanic membrane because 1) Tty that fell during facial cooling was increased to the precooling level by the repositioning of the probe sensor; 2) Tty determined by using a probe with a larger sensor area (the sensor soldered to a steel wire ring)tended to fall in response to facial cooling, whereas Tty determined with a thermally insulated probe ring did not; and 3) Tty obtained under careful positioning of the insulated probe was relatively insensitive to facial cooling or heating. Because Tty was practically identical to esophageal temperature (Tes) in the steady state, i.e., 36.83 +/- 0.20 (SD) degrees C for Tty and 36.87 +/- 0.16 degrees C for Tes at room temperature (n = 11), and because facial cooling had little effect on both Tty and Tes (36.86 +/- 0.17 degrees C for Tty and 36.86 +/- 0.26 degrees C for Tes during facial or scalp skin cooling), we support the postulate that Tty is a good measure of core temperature. The temperature transient in response to foot warming was detected 5 min (n = 2) faster with Tty than with Tes. Thus, with further improvements in the design of the probe. Tty can become a standard for determination of core body temperature. 相似文献
59.
P Lebrun MH Antoine R Ouedraogo B Pirotte A Herchuelz KE Cosgrove C Kane MJ Dunne 《Canadian Metallurgical Quarterly》1997,40(12):1403-1410
Radioisotopic and electrophysiological techniques were used to assess the effects of verapamil, a phenylalkylamine Ca2+ channel blocker, on K+ permeability of insulin-secreting cells. Verapamil provoked a concentration-dependent inhibition of 86Rb (42K substitute) outflow from prelabelled and perifused rat pancreatic islets. This property appears to be inherent to the phenylalkylamine Ca2+ channel blockers since gallopamil, a methoxyderivative of verapamil, but not nifedipine, a 1,4-dihydropyridine Ca2+ channel blocker, inhibited 86Rb outflow. The experimental data further revealed that verapamil interacted with a Ca2+-independent, glucose- and glibenclamide-sensitive modality of 86Rb extrusion. Moreover, verapamil prevented the increase in 86Rb outflow brought about by BPDZ 44; a potent activator of the ATP-sensitive K+ channel. Single-channel current recordings by the patch clamp technique confirmed that verapamil elicited a dose-dependent inhibition of the ATP-dependent K+ channel. Lastly, under experimental conditions in which verapamil clearly inhibited the ATP-sensitive K+ channels, the drug did not affect 45Ca outflow, the cytosolic free Ca2+ concentration or insulin release. It is concluded that the Ca2+ entry blocker verapamil inhibits ATP-sensitive K+ channels in pancreatic beta cells. This effect was not associated with stimulation of insulin release. 相似文献
60.
The availability of inexpensive minicomputers and low cost digital/analog conversion equipment enables one to use interactive graphics in situations where such techniques were previously infeasible. The University of Tulsa is presently developing an interactive graphics package entitled BANDMARCH to assist the choreography of marching band drills. The graphics hardward consist of a 32K Interdata Model 70 minicomputer, a 5MB Diablo Disc system, a Tektronix 603 monitor with 256 × 256 point display provided by a pair of Detel 8 bit D/A converters. The program enables a band director who is most likely not computer oriented to prepare a routine in an existing language (About Face, Left Flank) and view the result of his ‘design’ in real time. The obvious interactive features of editing, cataloguing and accessing standard functions must be provided in a way that can be easily understood.
T.U.'s BANDMARCH (not an acromym) provides such features. Common data structures in a relatively novel environment are a demonstration of the soundness of these techniques to an interactive graphics situation. 相似文献