Jitter reduction through feedback for picosecond pulsed InGaAsPlasers

Following a comparison of picosecond-pulse generation techniques, feedback schemes are reported for the generation of picosecond pulse trains with improved jitter for both multicontact and conventional single-contact InGaAsP-InP lasers. Subpicosecond jitter is achieved for Q-switched laser sources using a novel optoelectronic feedback scheme. The use of resonant electrical feedback is shown to improve the timing jitter of gain-switched pulses by up to six times. Pulse-to-pulse timing jitter as low as 250 fs is demonstrated for a hybrid of optical and electrical feedback schemes. Limits for timing jitter in diode lasers are established for optoelectronic, electrical, and optical feedback schemes, and the key picosecond pulse generation schemes are compared in terms of timing jitter for the first time     

Clinical and historical predictors of dental caries on radiographs

Jet injection can be used to introduce genes into the cells of differentiated tissues of living animals and organ cultures. When a solution of plasmid DNA is jet injected into a selected tissue or organ, cells lying in or near the path of the jet injection are transfected with the DNA and the introduced gene(s) are expressed. Since there is minimal morbidity from each jet injection, multiple injections can be performed at the same or nearby sites. Both mRNA and protein expression from transfected genes can be quantitated using standard methods. In addition, the technique is an efficient means of DNA immunization. Methodology for using jet injection to transfer plasmid DNA into the cells of skin, fat, mammary gland, and muscle are described.     

The effects of plasma etching induced gate oxide degradation onMOSFET's 1/f noise

The effects of the plasma etching process induced gate oxide damages on device's low frequency noise behavior are investigated on MOSFET's fabricated with different field plate perimeter to gate area ratio antennas. Abnormal 1/f noise spectrum with a shoulder centered in the frequency range of 100 and to 1 kHz was frequently observed in small geometry devices, and it is attributable to a nonuniform distribution of oxide traps induced by plasma etching process     

A set of electrophoretic molecular markers for strain typing and population genetic studies of Histoplasma capsulatum

A set of eleven biallelic and three multiallelic molecular markers have been developed to analyze populations of Histoplasma capsulatum. All markers are amplified by polymerase chain reaction (PCR) and can be readily scored using minimal amounts of template DNA. The 11 biallelic loci have polymorphic restriction endonuclease sites or small insertions or deletions which may be assessed by agarose gel electrophoresis. These markers are inherited in an unambiguous manner and are ideal for assessing structure and gene flow within US populations of H. capsulatum, but are monomorphic in non-US populations. Both length and sequence variation are present in the multiallelic loci, which can be scored by direct sequencing, polyacrylamide gel electrophoresis, or single-strand conformation polymorphism (SSCP): As they are hypervariable, the multiallelic loci can be used to type isolates and to assess the level of genetic variation within populations. Preliminary results indicate that the three multiallelic markers presented are sufficient to distinguish isolates at the individual level and are polymorphic in both US and non-US populations. This collection of molecular markers will be a useful tool in population and epidemiology studies of H. capsulatum.     

Indoor temperature changes in retrofit homes

The behavioral response (e.g. changes in indoor temperatures, attention to window and door openings) to residential technical efficiency improvements (e.g. attic insulation, storm windows) is an important and largely unresolved issue. Although there is considerable discussion concerning the extent to which households take back some of the energy savings due to technical efficiency improvements in increased comfort, there is almost no empirical evidence on the subject.Detailed electricity billing data (from mid-1981 to mid-1983) were analyzed for 79 households that received financial assistance from the Bonneville Power Administration to retrofit their homes in mid-1982. The mean retrofit expenditure in these homes was $1900; the mean reduction in annual electricity use was 4700 kWh, of which 83% was due to reductions in space heating electricity use. Analysis of the electricity billing data suggests that these households increased their indoor temperature settings after retrofit by almost 1 °F on average. This temperature increase led to an estimated average loss of almost 600 kWh of electricity saving. In other words, roughly 10% of the energy saving due to retrofit was taken back in terms of increased comfort. These results concerning changes in indoor temperatures should be viewed cautiously because of limitations in the analytical method and the large variation across households.     

A new technique for on-line and off-line high speed computation

A novel technique for both online and offline computation is presented. With this technique, a reconstruction analysis in elementary particle physics, otherwise prohibitively long, has been accomplished. It will be used online in an upcoming Fermilab experiment to reconstruct more than 100000 events per second and to trigger on the basis of that information. The technique delivers 40 gigaoperations per second, has a bandwidth on the order of gigabytes per second, and has a modest cost. An overview of the program, details of the system, and performance measurements are presented     

Metabolism of lysophosphatidylcholine by swine platelets

Incubation of intact platelets from Sinclair(S-1) miniature swine with³²P-labeled lysophosphatidylcholine (lyso PC) indicated the presence of an active lysophospholipase with a pH optimum of 8.0 for hydrolysis of the substrate. However, lyso PC was incorporated into the membrane phosphatidylcholines by the acyltransferase pathway upon addition of ATP, Mg⁺⁺ and CoA to the platelet suspension. These results suggest that intact platelets are able to resist the cytotoxic effects of lyso PC in plasma, and the phospholipids in platelet membranes are not readily affected by the lipid environment of the plasma. The acyltransfer reaction apparently is saturated with endogenous free fatty acids since arachidonic acid added exogenously did not further enhance the incorporation activity. Neither the acyltransferase nor the lysophospholipase activity was affected by Ca⁺⁺, but divalent metal ions such as Zn⁺⁺ inhibited the lysophospholipase activity. Cholesterol but not cholesteryl esters elicited a biphasic effect on both enzymes, stimulating at low concentration but inhibiting at a cholesterol to lyso PC ratio greater than 1. Serum albumin inhibited the lysophospholipase but gave a small biphasic effect to the acyltransferase.     

Working memory and articulation rate in children with spastic diplegic cerebral palsy.

A. D. Baddeley, N. Thomson, and M. Buchanan (1975) suggested that articulatory rehearsal rate determines the amount of verbal material that can be maintained in working memory. In the current study, 12 children with spastic diplegic cerebral palsy (SDCP) and 38 normal children were tested on measures of articulation rate and memory span for 1-, 2-, and 3-syllable words. Across all conditions, articulation rate for the SDCP group was significantly slower than for the normal group; nonetheless, memory span was equivalent for both groups. This finding implies that covert rehearsal proceeded normally for the SDCP group, in spite of decrements in speech rate. Thus, the relationship between overt and covert rehearsal rates differs for children with SDCP compared with normal children. Findings from the current study further suggest that normal speech rates are not necessary for development of normal covert rehearsal rates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Theory and application of charge pumping for the characterizationof Si-SiO2 interface and near-interface oxide traps

A generalized charge pumping model has been developed which extends the use of charge pumping from a study of traps at the Si-SiO ₂ interface to a study of traps in the oxide. The analytical model, based on tunneling theory, allows the spatial distribution of near-interface oxide traps to be determined from variable frequency charge pumping data. Profiling of near-interface oxide traps in irradiated MOSFET's as well as SONOS nonvolatile memory devices is presented     

Selective interactions among the multiple connexin proteins expressed in the vertebrate lens: the second extracellular domain is a determinant of compatibility between connexins

Gap junctions are collections of intercellular channels composed of structural proteins called connexins (Cx). We have examined the functional interactions of the three rodent connexins present in the lens, Cx43, Cx46, and Cx50, by expressing them in paired Xenopus oocytes. Homotypic channels containing Cx43, Cx46, or Cx50 all developed high conductance. heterotypic channels composed of Cx46 paired with either Cx43 or Cx50 were also well coupled, whereas Cx50 did not form functional channels with Cx43. We also examined the functional response of homotypic and heterotypic channels to transjunctional voltage and cytoplasmic acidification. We show that all lens connexins exhibited sensitivity to cytoplasmic acidification as well as to voltage, and that voltage-dependent closure of heterotypic channels for a given connexin was dramatically influenced by its partner connexins in the adjacent cell. Based on the observation that Cx43 can discriminate between Cx46 and Cx50, we investigated the molecular determinants that specify compatibility by constructing chimeric connexins from portions of Cx46 and Cx50 and testing them for their ability to form channels with Cx43. When the second extracellular (E2) domain in Cx46 was replaced with the E2 of Cx50, the resulting chimera could no longer form heterotypic channels with Cx43. A reciprocal chimera, where the E2 of Cx46 was inserted into Cx50, acquired the ability to functionally interact with Cx43. Together, these results demonstrate that formation of intercellular channels is a selective process dependent on the identity of the connexins expressed in adjacent cells, and that the second extracellular domain is a determinant of heterotypic compatibility between connexins.