Enzyme-amplified amperometric sandwich test for RNA and DNA.

A one-step enzyme-amplified amperometric sandwich hybridization test for RNA and DNA is described. The test utilizes a carbon electrode, modified with a film of co-electrodeposited avidin and redox polymer; the redox polymer electrically "wiring" horseradish peroxidase (HRP) reaction centers upon contact. The film is made specific for the particular RNA or DNA sequence tested by conjugating its avidin with a biotinylated oligonucleotide, complementary to the assayed sequence. This oligonucleotide-modified redox polymer film, prepared prior to the test, forms the base of the sandwich. The center layer of the sandwich, added in the test, is the analyte RNA or DNA; its top is a second complemetary oligonucleotide, which is HRP-labeled, and is cohybridized in the test. The test consists of mixing the analyte DNA or RNA solution, the HRP-labeled oligonucleotide solution, and a hydrogen peroxide solution, immersing the base-layer carrying electrode applying a potential of 0 V versus Ag/AgCl, and measuring the H2O2 electroreduction current. Completion of the sandwich brings the HRP label into electrical contact with the redox polymer, converting the nonelectrocatalytic base layer into an electrocatalyst for the electroreduction of H2O2 to water. Flow of H2O2 electroreduction current when the electrode is poised near Ag/AgCl potential indicates the presence of the analyte RNA or DNA. The current density for the maximally sandwich-covered electrode was 250 microA cm(-2), exceeding more than a 100-fold the current density flowing upon nonspecific binding of the HRP-labeled oligonucleotide. High concentrations of irrelevant DNA and diluted serum did not interfere with the assay. When the electrodes were rotated in order to make the solution-phase mass transport rapid, the test was completed in approximately 30 min. The test was applied in probing for the presence of a 60-base E. coli mRNA sequence.     

Pit formation observed in a multilayer dielectric coating as a result of simulated space environmental exposure

Certain spaceborne telescope designs require that dielectric-coated lenses be exposed to the energetic electrons and protons associated with the space environment. Test coupons that were exposed to a simulated space environment showed extensive pitting as a result of dielectric breakdown. A typical pit was 50-100 microm at the surface and extended to the substrate material, in which a 10-microm-diameter melt region was found. Pitting was not observed on similar samples that had also been overcoated with a transparent conductive thin film. Measurement of the bidirectional reflectance distribution transfer function showed that pitting caused a fivefold to tenfold increase in the scattering of visible light.     

Software Process Improvement Motivators: An Analysis using Multidimensional Scaling

In this paper we present an analysis of software practitioners' motivations for software process improvement (SPI). Our findings are based on an empirical study of SPI in 13 software companies where we conducted focus groups with nearly 200 software practitioners. Our aim is to better understand how companies can maximise practitioner support for SPI. This insight should help SPI managers establish more effective SPI implementation strategies. In this paper we introduce the use of multidimensional scaling (MDS) in SPI research. MDS is a social science data analysis technique designed to generate a rich visual understanding of human issues. By using MDS we found evidence to suggest distinct clusters of punitive and rewarding SPI motivators. Furthermore our analysis also suggests that different clusters of motivations exist for different staff groups.     

Estimating the chance expectancies of diadic relationships within a group.

"This paper discusses the use of a mathematical model for computing the chance frequency and variance of the diadic relationships obtained within relational analysis. This procedure defines the diads within a group in terms of the pattern of choices, rejections, and perceptions of choice and rejection between pairs of members… . Examples are given of the application of this model to various problems requiring the comparison of observed data against a theoretical base line." A nomograph is provided for estimating the chance expectancies of diadic relationships within a group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The structural dependence of light sensitivity in (Al,Ga)As/GaAs modulation doped heterostructures

Understanding the origin and nature of light sensitivity in (Al,Ga)As/GaAs modulation doped heterostructures is becoming important as modulation doped field effect transistors move from the research laboratories into practical application. Control of threshold voltage in an integrated circuit is crucial. If these devices are to be operated at cryogenic temperatures to take advantage of their enhanced transport properties then the persistent photoconductive effects associated with these structures cannot be ignored. This paper examines the dependence of light sensitivity on the thicknesses of the doped (Al, Ga)As layer and the undoped GaAs buffer layer. The use of As₂ as opposed to As₄ is investigated. Based upon these results, the origin and behavior of the persistent photoconductivity is reexamined.     

Organizational structure and roles of psychologists in schools of medicine.

Conducted a questionnaire survey of medical school psychologists to assess attitudes toward work, advantages and disadvantages of working in medical schools, organizational structure, job satisfaction, and salary, from which 794 usable responses were obtained. 90% of Ss preferred that psychology be represented as an independent department or as part of an autonomous department of behavioral science. (6 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infrared Multiphoton Induced Isomerization of cis-3,4-Dichlorocyclobutene. III. Pressure Dependence of the Yield

The multiphoton induced isomerization of cis-3,4-dichlorocyclobutene (DCCB) was studied as a function of pressure. Three experiments indicated the existence of a nonthermal mechanism at neat pressures below 60 mtorr. These were: (i) the leveling off of the fractional yield of isomerization products at low pressures; (ii) the absence of dissociation products from 2-iodo-2-methyl propane, which served as a chemical thermometer in the presence of a large excess of DCCB; and (iii) a break in the power-law dependence of the optoacoustic signal produced by neat DCCB. The increased yield at higher DCCB pressures is believed to be due partly to a thermal reaction and partly to increased absorption caused by rotational or vibrational hole filling. Optoacoustic measurements also showed that at constant fluence the absorbed energy was greater for long, low intensity pulses, as might be expected for inhomogeneous excitation. However, the present experiments did not reveal an intensity dependence of the reaction yield. Addition of argon as a buffer gas monotonically decreased the yield, indicating that vibrational quenching more than offsets any hole-filling effects.     

Does social exclusion motivate interpersonal reconnection? Resolving the "porcupine problem."

Evidence from 6 experiments supports the social reconnection hypothesis, which posits that the experience of social exclusion increases the motivation to forge social bonds with new sources of potential affiliation. Threat of social exclusion led participants to express greater interest in making new friends, to increase their desire to work with others, to form more positive impressions of novel social targets, and to assign greater rewards to new interaction partners. Findings also suggest potential boundary conditions to the social reconnection hypothesis. Excluded individuals did not seem to seek reconnection with the specific perpetrators of exclusion or with novel partners with whom no face-to-face interaction was anticipated. Furthermore, fear of negative evaluation moderated responses to exclusion such that participants low in fear of negative evaluation responded to new interaction partners in an affiliative fashion, whereas participants high in fear of negative evaluation did not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low-temperature materials and thin-film transistors for electronics on flexible substrates

The deposition processes and electronic properties of thin-film semiconductors and insulators based on silicon in relation to the fabrication of electronic devices on flexible plastic substrates are considered. The films of amorphous hydrogenated silicon (a-Si:H), nanocrystalline silicon (nc-Si), and amorphous silicon nitride (a-SiN_x), and also thin-film transistors are fabricated at comparatively low temperatures (120°C, 75°C) using existing commercial plasma-chemical equipment. The parameters of thin-film transistors based on a-Si:H and fabricated at the aforementioned relatively low temperatures are compatible with those of high-temperature analogues.