Mesostructured island formation in sol-gel SiO2 films through controlled, concentration-dependent flocculation of colloidal silica particles

We have fabricated a number of films using various concentrations of colloidal silica particles in a sol-gel derived matrix. The particles were flocculated to tailor the surface properties of the film. Digital image analysis and profilometry were used to characterize the materials. We observe local maxima of floc size and film textural properties at 0.177 wt.% and within a very narrow range of particle concentration.     

Prolonged duration of craving, mood, and autonomic responses elicited by cues and imagery in smokers: Effects of tobacco deprivation and sex.

Increases in self-reported craving and changes in autonomic functioning are reliably elicited when smokers are exposed to tobacco-related stimuli compared with neutral stimuli. However, few studies have reported the time course of cue-elicited craving or have directly compared the effectiveness of smoking cues versus imagery to evoke a craving response. In addition to these two issues, we investigated the influence of tobacco deprivation and sex on craving, mood, and autonomic responses. Sixty cigarette smokers (30 men, 30 women) were tested in two counterbalanced sessions, one after overnight tobacco deprivation and one during ad libitum smoking. At each session, participants were exposed to four randomized experimental trials: smoking imagery, neutral imagery, smoking cues, and neutral cues. Tobacco craving and mood were assessed repeatedly and physiological measures were recorded continuously for 30 min after imagery or cue exposure. Compared with neutral trials, smoking cues and smoking imagery reliably increased tobacco craving, negative mood, heart rate, and blood pressure and decreased positive mood ratings. Changes were observed immediately after cue and imagery presentation and remained unchanged for 30 min. Responding was greater in the nondeprived condition, and cues elicited more robust responding than imagery for most measures. Women responded more robustly to smoking cues only in the nondeprived condition, whereas imagery evoked greater responses in men during both conditions. These findings provide new data on the time course, magnitude, and tobacco deprivation effects on elicited craving. Sex differences were dependent on stimulus type and deprivation condition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What We Want Is in That Room

Ilona Gaynor and Benedict Singleton , founding partners of design and research studio The Department of No, look beyond the specific technological possibilities of acute accuracy and explore the principle of zero tolerance as an aesthetic of precision. How is such an aesthetic at work when an architectural strategy places a heightened emphasis on the exact placement of objects in space and time? Could the precision in which a single spatial intervention is pursued have more fundamental and far-reaching consequences than we ever imagined?     

Tracking sources of unsaturated zone and groundwater nitrate contamination using nitrogen and oxygen stable isotopes at the Hanford site, Washington

The nitrogen and oxygen isotopic compositions of nitrate in pore water extracts from unsaturated zone (UZ) core samples and groundwater samples indicate at least four potential sources of nitrate in groundwaters at the U.S. DOE Hanford Site in south-central Washington. Natural sources of nitrate identified include microbially produced nitrate from the soil column (delta15N of 4 - 8 per thousand, delta18O of -9 to 2 per thousand) and nitrate in buried caliche layers (delta15N of 0-8 per thousand, delta 18O of -6to 42 per thousand). Isotopically distinctindustrial sources of nitrate include nitric acid in low-level disposal waters (delta15N approximately per thousand, delta 18O approximately 23%o) per thousandnd co-contaminant nitrate in high-level radioactive waste from plutonium processing (6'5delta1of 8-33 % o, per thousand18delta oO -9 to 7%0). per thousandThe isotopic compositions of nitrate from 97 groundwater wells with concentrations up to 1290 mg/L NO3- have been analyzed. Stable isotope analyses from this study site, which has natural and industrial nitrate sources, provide a tool to distinguish nitrate sources in an unconfined aquiferwhere concentrations alone do not. These data indicate that the most common sources of high nitrate concentrations in groundwater at Hanford are nitric acid and natural nitrate flushed out of the UZ during disposal of low-level wastewater. Nitrate associated with high-level radioactive UZ contamination does not appear to be a major source of groundwater nitrate at this time.     

Mechanical properties of ZnO thin films deposited on polyester substrates used in flexible device applications

ZnO is growing in importance as a functional film in flexible devices because of the wide range of electrical properties that can be achieved through appropriate doping and the relative abundance of Zn. We have deposited ZnO films with various thicknesses by sputtering on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) flexible substrates and measured their mechanical properties using compression and scratch tests coupled with in-situ optical microscopy. The cracking of ZnO, during compression, is thickness dependent and at lower thicknesses the films sputtered on PEN exhibit the highest crack onset strains, around 2%. During scratch testing, two major scratch failure mechanisms are observed, analyzed and discussed. It is also found that scratch resistance of ZnO is thickness dependent for both PET and PEN. At high scratch loads a secondary failure mechanism due to impregnation of film debris into the polymer substrates is observed.     

Stress-corrosion cracking of indium tin oxide coated polyethylene terephthalate for flexible optoelectronic devices

Stress corrosion cracking of transparent conductive layers of indium tin oxide (ITO), sputtered on polyethylene terephthalate (PET) substrates, is an issue of paramount importance in flexible optoelectronic devices. These components, when used in flexible device stacks, can be in contact with acid containing pressure-sensitive adhesives or with conductive polymers doped in acids. Acids can corrode the brittle ITO layer, stress can cause cracking and delamination, and stress-corrosion cracking can cause more rapid failure than corrosion alone.The combined effect of an externally-applied mechanical stress to bend the device and the corrosive environment provided by the acid is investigated in this work. We show that acrylic acid which is contained in many pressure-sensitive adhesives can cause corrosion of ITO coatings on PET. We also investigate and report on the combined effect of external mechanical stress and corrosion on ITO-coated PET composite films. Also, it is shown that the combination of stress and corrosion by acrylic acid can cause ITO cracking to occur at stresses less than a quarter of those needed for failure with no corrosion. In addition, the time to failure, under ~ 1% tensile strain can reduce the total time to failure by as much as a third.     

Identifying contemporary and historic sources of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in an industrial urban setting

A study of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) concentrations was undertaken in the vicinity of a municipal solid waste incinerator (MSWI) in Newcastle upon Tyne as a result of concerns raised by local residents about potential contamination from fugitive and stack emissions. The study area was divided into four sectors (north-east (NE), south-east (SE), north-west (NW) and south-west (SW)) around the MSWI, and sampling sites were located up to a distance of 2.25 km. Based on air dispersion modelling, the sampling density was four times greater in the NE (downwind) sector compared to the SW (upwind) direction, and twice as great in the NW and SE sectors. PCDD/F concentrations found in soil samples ranged from 6 to 1911 ng I-TEQ/kg DW with a median of 32 ng I-TEQ/kg DW. There was no evidence of elevated concentrations downwind of the MSWI compared to other directions, nor of any trend in concentration at increasing distance from the MSWI. We concluded, therefore, that the MSWI fugitive and stack emissions were not a major source of PCDD/F contamination. Analysis of PCDD/F homologue profiles showed that samples exhibiting furan-dominated and OCDD-dominated profiles and a profile characteristic of the MSWI ash occurred in distinct clusters. Those samples showing the furan-dominated profile had the largest PCDD/F concentrations measured as I-TEQ, followed by samples with the incinerator profile, the deposition profile, and the OCDD-dominated profile. We identified some contamination hotspots located in the SW and SE sampling sectors (upwind of the MSWI), and potential sources for these hotspots were sought by using historic land use data from maps of the locality dating back to 1856. We concluded that the cluster of very high concentrations of PCDD/F in soils showing the furan homologue profile were most likely to have resulted from the disposal of graphite electrode sludges from brine electrolysis carried out at a chemical works between the 1890s and the 1930s.     

Conserved residues are functionally distinct within transketolases of different species

Most of the amino acid residues which interact with thiamine pyrophosphate are highly conserved among enzymes which use this cofactor. The possible roles of several such residues in cofactor binding, catalysis, and/or substrate binding were examined for human transketolase. Mutations in H110 resulted in dramatic reductions to 2% or less of the normal activity. No alterations were found in the K(m)app's for the cofactor or for the donor and acceptor substrates. Alterations in Q428 resulted in a less severe loss of activity and also no changes in the K(m)app's. On the basis of the results, H110, an invariant residue, is proposed to function as a base which abstracts a proton from the protonated 4'-iminopyrimidine ring. The deprotonated 4'-imino moiety is required for generation of the C2-thiazolium carbanion which attacks the donor substrate. Interestingly, the function in the human enzyme of this invariant histidine is distinct from its role in yeast transketolase in which it aids in binding donor substrate and in subsequent catalytic events. Q428 is suggested to play a supportive role by stabilizing and orientating a water molecule which mediates the interaction between the 4'-amino group and H110. In other TPP-utilizing enzymes, the equivalent residue of Q428 is a histidine and is thought to deprotonate the 4'-amino group.