The influence of yttrium on oxide scale growth and adherence

Alloys and coatings for high-temperature service are designed to form selectively chromia scales, alumina scales, or, to a limited extent, silica scales upon exposure to the environment. For such oxide scales to be protective, they should be both slow growing and adherent. It turns out that the addition of yttrium to such alloys can often impart both characteristics to the oxide scale. However, the actual operating mechanisms continue to be a matter of controversy among researchers in the area of oxidation. In the present study, the growth and adherence of alumina and chromia scales on alloys containing yttrium, either as an oxide dispersion or as an intermetallic phase, have been investigated in conjunction with detailed oxide scale characterization using the techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and secondary ion mass spectrometry (SIMS). The results of the study are used for critical assessment of the proposed mechanisms, especially the more recent ones, and to suggest some new mechanisms for adherence.     

A new input indicator for the assessment of science &; technology research?

Traditional input indicators of research performance, such as research funding, number of active scientists, and international collaborations, have been widely used to assess countries’ publication output. However, while publication in today’s English-only research world requires sound research in readable English, English proficiency may be a problem for the productivity of non-native English-speaking (NNES) countries. Data provided by the Brazilian National Research Council (CNPq) containing the academic profile of 51,223 Brazilian researchers show a correlation between English proficiency and publication output. According to our results, traditional input indicators may fall short of providing an accurate representation of the research performance of NNES developing countries.     

Friction and elasticity on a molecular scale

A molecular scale atomic force microscopy study of friction and elasticity is presented on a one-component lipid bilayer system - a model boundary lubricant. With a real area of contact on the order of the lattice spacings of the sample, the elastic compliances of single lipid molecules are recorded - the first report of a molecularly resolved elasticity map. The anisotropic and highly ordered structure of the lipid bilayer has been observed to cause contrast information in friction on molecularly flat areas, and to be dependent on the sliding direction. This anisotropic behavior of friction has been measured to be independent of normal elastic compliances. Only asymmetric indentation which causes in-plane compliances leads to heterogeneities in the elasticity map. In this fundamental study of friction, the effects of adhesion and elasticity are discussed.     

Fast computation of radiation integral for reflector antennas

A FORTRAN IV program to compute the field scattered by parabolic reflector antennas in a prescribed plane cut is presented. This program was executed on the UNIVAC 1100/80 at the University of Naples. A flowchart of the main program is provided     

Independent testing and validation of prototype hydrogen sensors

In this article, the independent testing and validation of a packaged, electrochemical prototype hydrogen sensor at the National Renewable Energy Laboratory (NREL) is reported. Custom electronics were developed to be compatible with the data acquisition system at NREL. The specialized hydrogen sensor-testing laboratory at NREL used a variety of standardized test protocols to assess sensor performance. The system controlled and monitored humidity, pressure, and hydrogen gas concentration and introduced interference gases such as methane, carbon dioxide, carbon monoxide and ammonia.     

A profile of science in Brazil

The Brazilian contribution to publications in science and humanities increased from 0.29% of the worldwide total in 1981 to 0.46% in 1993. In science, but not in humanities, Brazilian publications tend to follow the world publication trend; thus, during the period 1981–1993, 57.9% of Brazilian publications were in life sciences, 35.4% in exact sciences, 3.9% in earth sciences and 2.9% in humanities. The ten institutions with the largest number of publications are universities, which account for half of the all Brazilian publications. The total number of authors on the Brazilian 1981–1993 publications was 52,808. Among these 57.8% appear in only one publication and 17.5% have their publications cited more than 10 times.     

Phase transformations at steel/IN626 clad interfaces

The microstructures of 4130 and 2.25Cr-1Mo steels clad to nickel base IN625 by welding and HIPing were examined by Analytical Electron Microscopy (AEM) and Secondary Ion Mass Spectroscopy (SIMS) to determine the interfacial microstructural characteristics which could affect their mechanical properties and corrosion resistance. The interface microstructures of the clads produced by the two methods were considerably different. The clad produced by welding was characterized by a low density of carbide precipitates confined to a very narrow region (∼1 μm) at the interface of ferrite and austenite. In addition, a thin region of untempered martensite was present at the interface which could affect its resistance to hydrogen embrittlement as well as other mechanical properties. The interface of the HIP clad composite contained several regions of distinct microstructural characteristics with widely varying densities of carbide precipitates. Relative to the clad produced by welding, extensive precipitation was observed both in the steel and in the IN625 at the interface, separated by a region free from precipitation. The extent of precipitation at the interface regions appears to be controlled essentially by the extent of carbon transport across the interface. The article describes the detailed analysis of the interface characteristics, and models are proposed to explain the microstructural evolution at the interface of the HIP and weld clad composites.     

Science in Brazil. Part 1: A macro-level comparative study

Summary In the present paper, the evolution of publication activity and citation impact in Brazil is studied for the period 1991-2003. Besides the analysis of trends in publication and citation patterns and of national publication profiles, an attempt is made to find statistical evidences of the relation between international co-authorship and both research profile and citation impact in the Latin American region. Despite similarities and strong co-publication links with the other countries in the region, Brazil has nonetheless a specific research profile, and forms the largest potential in the region.     

Behavioral sensitization to cocaine, but not cocaine-conditioned behavior, is associated with increased dopamine occupation of its receptors in the nucleus accumbens.

Rats had repeated treatments with cocaine associated with a specific context (paired group). Evidence for classical conditioning of cocaine's motor-activity effects and context-specific behavioral sensitization to cocaine was obtained, relative to vehicle-treated (control) and pseudoconditioned (unpaired) groups. Only the paired group exhibiting context-specific behavioral sensitization had more dopamine bound to both D?-like and D?-like receptors in the nucleus accumbens than did rats in the control group receiving cocaine on the test day. No effects on receptor occupation were found in rats showing a classical conditioned response to a context previously paired with cocaine. Thus, sensitization to cocaine, but not classical conditioning of cocaine's behavioral effects, was associated with greater dopaminergic neurotransmission selectively in the nucleus accumbens. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recirculating immunomagnetic separation and optimal enrichment conditions for enhanced detection and recovery of low levels of Escherichia coli O157:H7 from fresh leafy produce and surface water

The objective of this study was to develop a rapid, simple method for enhanced detection and isolation of low levels of Escherichia coli O157:H7 from leafy produce and surface water using recirculating immunomagnetic separation (RIMS) coupled with real-time PCR and a standard culture method. The optimal enrichment conditions for the method also were determined. Analysis of real-time PCR data (C(T) values) suggested that incubation of lettuce and spinach leaves rather than rinsates provides better enrichment of E. coli O157:H7. Enrichment of lettuce or spinach leaves at 42 degrees C for 5 h provided better detection than enrichment at 37 degrees C. Extended incubation of surface water for 20 h at 42 degrees C did not improve the detection. The optimized enrichment conditions were also employed with modified Moore swabs, which were used to sample flowing water sites. Positive isolation rates and real-time PCR results indicated an increased recovery of E. coli O157:H7 from all samples following the application of RIMS. Under these conditions, the method provided detection and/or isolation of E. coli O157:H7 at levels as low as 0.07 CFU/g of lettuce, 0.1 CFU/g of spinach, 6 CFU/100 ml of surface water, and 9 CFU per modified Moore swab. During a 6-month field study, modified Moore swabs yielded high isolation rates when deployed in natural watershed sites. The method used in this study was effective for monitoring E. coli O157:H7 in the farm environment, during postharvest processing, and in foodborne outbreak investigations.