Thermal stability of nanocrystalline Pd81Zr19

Grain growth stability in mechanically alloyed nanocrystalline Pd₈₁Zr₁₉ was investigated. Previous research suggested that the alloy is thermodynamically stable to very high temperatures. When X-ray diffraction (XRD) is used to estimate the grain size of annealed samples the alloy appears to have remarkable resistance to growth. Microscopy done here on the same alloy indicated that the XRD estimates are not accurate for samples annealed above 600 °C. It appears that when this alloy is annealed at high temperatures XRD peak broadening is retained for reasons that are unrelated to the grain size. The alloy still has much improved grain growth stability compared with pure Pd, but not as significant as suggested by the XRD results. A similar phenomenon was observed in Fe–Zr alloys.     

Multiplexed protein analysis using encoded antibody-conjugated microbeads

We describe a method for multiplexed analysis of proteins using fluorescently encoded microbeads. The sensitivity of our method is comparable to the sensitivity obtained by enzyme-linked immunosorbent assay while only 5 µl sample volumes are needed. Streptavidin-coated, 1 µm beads are encoded with a combination of fluorophores at different intensity levels. As a proof of concept, we demonstrate that 27 microbead populations can be readily encoded by affinity conjugation using three intensity levels for each of three different biotinylated fluorescent dyes. Four populations of encoded microbeads are further conjugated with biotinylated capture antibodies and then combined and immobilized in a microfluidic flow cell for multiplexed protein analysis. Using four uniquely encoded microbead populations, we show that a cancer biomarker and three cytokine proteins can be analysed quantitatively in the picogram per millilitre range by fluorescence microscopy in a single assay. Our method will allow for the fabrication of high density, bead-based antibody arrays for multiplexed protein analysis using integrated microfluidic devices and automated sample processing.     

Photosensitized amino acid degradation in the presence of riboflavin and its derivatives

The addition of photosensitizers to water can accelerate disinfection in sunlight-based systems by enhancing oxidation of target compounds through direct reaction with the excited sensitizer or through production of another oxidant, such as singlet oxygen (1O?). The kinetics of the oxidation of selected amino acids in the presence of the sensitizer riboflavin (Vitamin B2), its primary photoproduct lumichrome, and its derivative riboflavin tetraacetate (2',3',4',5'-tetraacetylriboflavin; RTA) were quantified and the mechanisms of reaction were determined during exposure to 365 ± 9 nm light. 1O?-mediated reactions contributed to the rapid photodegradation of the four amino acids, but its contribution was sensitizer-dependent and varied from 5.4-10.2% for tyrosine, 7.1-12.4% for tryptophan, 18.7-69.0% for methionine, and 64.7-100.2% for histidine. Riboflavin was subject to rapid photodegradation (t? < 8 min), while the half-lives of lumichrome and RTA were 100 and 30 times longer, respectively. Lumichrome and RTA also were more efficient 1O? sensitizers (quantum yield (Φ) = 0.63 and 0.66) compared to riboflavin (Φ = 0.48). Of the three flavin-based compounds, RTA shows the most promise as a sensitizer in sunlight-based disinfection systems because it absorbs both visible and UV light, is an efficient 1O? sensitizer, is a strong oxidant in its triplet state, and exhibits greater photostability.     

Secondhand smoke exposure and the risk of hearing loss

Hearing loss has been associated with tobacco smoking, but its relationship with secondhand smoke is not known. We sought to investigate the association between secondhand smoke exposure and hearing loss in a nationally representative sample of adults. The National Health and Nutrition Examination Survey (NHANES), a nationally representative cross-sectional dataset, was utilised to investigate the association between secondhand smoke exposure and hearing loss. Data collected from non-smoking participants aged 20-69 years were included in the analysis if they had completed audiometric testing, had a valid serum continue value, and provided complete smoking, medical co-morbidity and noise exposure histories (N=3307). Hearing loss was assessed from averaged pure-tone thresholds over low- or mid-frequencies (500, 1000 and 2000 Hz) and high-frequencies (3000, 4000, 6000 and 8000 Hz), and was defined as mild or greater severity (pure-tone average in excess of 25 dB HL). Second-Hand Smoke (SHS) exposure was significantly associated with increased risk of hearing loss for low-/mid-frequencies (adjusted OR=1.14; 95% CI 1.02-1.28 for never smokers and 1.30; 1.10-1.54 for former smokers) and high-frequencies (1.40; 1.22-1.81 for former smokers), after controlling for potential confounders. Findings from the present analysis indicate that SHS exposure is associated with hearing loss in non-smoking adults.     

Performance of bolted joints in Discontinuous Ceramic Cored Sandwich Structures – Static experimental testing

Thick section composites that consist of discontinuous ceramic tile arrays as a core represent a unique class of sandwich structures. They have been developed to provide a balance of structural, impact, and penetration resistance at minimum weight. Bolted joints are often used to fasten the Discontinuous Ceramic Cored Sandwich Structures (DCCSS) to other structures. Extensive experimental testing has been completed in order to better understand the performance of bolted joints in DCCSS. In this study, pin-loaded specimens are subjected to static in-plane tensile loading to establish the sequence and severity of failure modes and ultimate joint capacity. Static testing was completed on various geometric ratios such as edge distance effects, as well as the influence of tile gaps that exist in the discontinuous tile array. The results from this study establish guidelines for design of bolted joints in DCCSS.     

A parametric study of golf car and personal transport vehicle braking stability and their deficiencies

This paper describes research and parametric analyses of braking effectiveness and directional stability for golf cars, personal transport vehicles (PTVs) and low speed vehicles (LSVs). It is shown that current designs, which employ brakes on only the rear wheels, can lead to rollovers if the brakes are applied while traveling downhill. After summarizing the current state of existing safety standards and brake system designs, both of which appear deficient from a safety perspective, a previously developed dynamic simulation model is used to identify which parameters have the greatest influence on the vehicles’ yaw stability. The simulation results are then used to parametrically quantify which combination of these factors can lead to yaw induced rollover during hard braking. Vehicle velocity, steering input, path slope and tire friction are all identified as important parameters in determining braking stability, the effects of which on rollover propensity are presented graphically. The results further show that when vehicles are equipped with front brakes or four-wheel brakes, the probability of a yaw induced rollover is almost entirely eliminated. Furthermore, the parametric charts provided may be used as an aid in developing guidelines for golf car and PTV path design if rear brake vehicles are used.     

Watershed influences on the transport, fate and bioavailability of mercury in Lake Superior: Field measurements and modelling approaches

The issuance of fish consumption advisories in US states bordering Lake Superior has heightened the need for understanding the biogeochemical cycling and transformations of mercury in this great lake. Major routes of mercury (Hg) transport to lakes include atmospheric deposition (wet and dry), direct discharges and riverine (watershed) inputs. The specific objectives of this ongoing study are to: (i) determine the speciation and bioavailability of Hg transported to Lake Superior (ii) determine the importance of watershed‐specific characteristics that control physical and chemical forms of Hg; (iii) identify key mechanisms controlling Hg bioavailability and speciation in near‐shore zones relative to open lake regions; and (iv) provide process‐level information to compliment concurrent development of Hg fate and transport models of the Lake Superior ecosystem. Three tributaries of Lake Superior were chosen for detailed field study based on previous results and particular watershed characteristics. Mixing zones represent a potentially important zone of Hg entry into the food chain, and were sampled for biota, water and sediment in transects between the tributary mouth and the lake end member. Sampling of open‐water sites was conducted during Environmental Protection Agency‐sponsored cruises on the research vessel Lake Guardian. Results from our work on Lake Superior tributaries demonstrate that dissolved organic carbon and methylmercury (MeHg) export was greatest from watersheds containing wetlands. In Lake Superior, concentrations of Hg species were small at pelagic stations (total mercury (HgT) averaged 0.49 ng/L, MeHg averaged 6.4 pg/L). In contrast, MeHg concentrations in tributaries ranged from 100 to 250 pg/L. Watershed sites dominated by wetlands exhibited the greatest MeHg concentrations, occasionally in excess of 12 ng/L. Samples of bulk zooplankton ranged from 20 to 130 ng/g dry weight HgT and from 15 to 45 ng/g dry weight MeHg, and demonstrated typical bioacculmulation of mercury as well as distinct seasonality in concentrations.     

Integrity of emotional and motivational states during the prodromal, first-episode, and chronic phases of schizophrenia.

Emotional and motivational dysfunction is fundamental to schizophrenia, and yet, the nature and scope of associated deficits are not well understood. This study assessed the integrity of emotional responding from the perspective of its underlying motivational systems during different phases of schizophrenia. Evaluative, somatic, and autonomic responses were measured during viewing of pictures categorized by emotional content, including threat, mutilation, contamination, illness, pollution, mild erotica, families, food, and nature. Participants were 13 patients at ultra high risk or prodromal for psychosis, 40 first-episode schizophrenia patients, 37 chronic schizophrenia patients, and 74 healthy comparison subjects. Irrespective of phase of illness, schizophrenia patients showed a robust and normal pattern of response across multiple systems, with differential engagement of the defensive and appetitive systems as a function of the motivational significance assigned to specific emotional contexts. Although the integrity of core motivational states also appeared to be intact in prodromal patients, a less consistent pattern of response was observed. As continuing efforts are made to identify emotional and motivational abnormalities in schizophrenia, identified deficits will likely be independent of a fundamental dysfunction in basic emotion and motivation response systems and involve integration with higher order processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of stitch incline angle on mode I fracture toughness – Experimental and modelling

In this study, double cantilever beam (DCB) experiments were conducted to determine the effect of stitch incline angle on fracture toughness. The laminates were stitched with a square wave pattern having a pitch and spacing of 4 mm and three different angles being 0°, 22.5° and 45°. A semi-analytical model for DCB specimens was developed based on the Timoshenko beam theory and validated against the experiment results using a previously developed traction law. The results were also compared against a finite element analysis (FEA).