Density doubling of block copolymer templated features

Block copolymers can be used to template large arrays of nanopatterns with periodicities equal to the characteristic spacing of the polymer. Here we demonstrate a technique capitalizing on the multilayered arrangement of cylindrical domains to effectively double the pattern density templated by a given polymer. By controlling the initial thickness of the film and the solvent annealing conditions, it was possible to reproducibly create density doubled lines by swelling the film with solvent until bilayers of horizontal cylinders were obtained. This process was also demonstrated to be compatible with graphoepitaxy.     

Involving participants in the dissemination of HIV research results.

Participatory action research initiatives engage research participants as co-investigators and provide them with an avenue to explore their own experiences. It is not always easy, however, to determine how to involve participants in meaningful ways. Funding limitations and rigid methodological procedures pose barriers for creative approaches to inquiry. Nonetheless, the HIV program at the Hospital for Sick Children in collaboration with the University of Victoria, has taken an important step towards involving participants in a meaningful way--through the dissemination of research results. The present article describes the procedure used to share the role of researcher/author. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Finely tailored performance of inverted organic photovoltaics through layer-by-layer interfacial engineering

Control over interfacial properties in organic photovoltaics (OPVs) is critical for many aspects of their performance. Functionalization of the transparent conducting electrode, in this case, indium tin oxide (ITO), through an electrostatic layer by layer (eLbL) approach with cationic N,N'-bis[2-(trimethylammonium)ethylene] perylene-3,4,9,10-tetracarboxyldiimide (PTCDI(+)) and anionic poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonate) (PEDOT:PSS(-)), led to high control over the surface properties. The films were studied through a variety of surface and spectroscopic techniques, including X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, atomic force microscopy (AFM), and ellipsometry. The work function of modified ITO was measured by UV photoelectron spectroscopy (UPS) and showed oscillating values with respect to odd-even layer numbers; the strong odd-even effect is due to the differing electronic characteristics of the top layer, either PTCDI(+) or PEDOT:PSS(-). The modified ITO electrodes were then used as the cathode in a series of inverted organic photovoltaic architectures. The performance of inverted OPVs was, in parallel to the UPS results, found to be highly dependent on the layer number of coated films and showed an obvious oscillation based on layer number. Inverted OPVs were retested after 128 days of storage in air, and almost all devices maintained over 70% of original power conversion efficiency (PCE).     

Luminescence effects in reactive powder sintered silica glasses for radiation sensing

Silica glasses doped with rare-earth ions are potential materials for optical fiber radiation detection and dosimetry applications. High sensitivity to radiation requires fibers with large cores that can be reliably fabricated using glass made in a novel process from the reactive powder sintering of silica. The luminescence and dosimetric properties of a range of rare earth-doped silica materials produced using this novel technique are reported here. Radioluminescence and optically stimulated luminescence (OSL) are the fundamental mechanisms enabling radiation detection in optical fibers. It was found that thermoluminescence, radioluminescence, and OSL are observed if the glass contains luminescent transitions in the detection wavelength range. Cerium- and thulium-doped silica glasses were found to be promising candidates for optical fiber dosimetry. Samples showed intense luminescence signals in response to both photo-stimulation and irradiation from alpha and beta sources. OSL results for cerium are three times larger than results for irradiated fluoride phosphate glasses previously tested for dosimetry use. Spectroscopic measurements indicate emission in the 300-500 nm region, suitable for detection with photomultiplier tubes.     

Elimination of mercury by yellow perch in the wild

The rate of methylmercury (MeHg) elimination by fish is important in determining the extent of bioaccumulation and for predicting recovery times of MeHg-contaminated fisheries. Rates of MeHg elimination remain uncertain in existing bioaccumulation models due to a lack of field studies. We addressed this problem by monitoring fish that had naturally accumulated isotopically enriched MeHg (spike MeHg) during a whole-ecosystem experiment. We transported yellow perch (Perca flavescens) from the experimental lake to an untreated lake and monitored spike total mercury (THg, most of which was MeHg) losses over 440 d. Spike THg was distributed among fish tissues in a similar way as ambient THg (background non-spike THg). We observed rapid loss of spike THg from liver and other visceral tissues (approximately 90 d) followed by a plateau. Subsequently, there was prolonged redistribution of spike THg into muscle (180 d). Loss of spike THg from the whole fish occurred > 5 times slower (half-life of 489 d) than in past laboratory studies using this species. We determined that MeHg bioaccumulation models with laboratory-based elimination rates produced faster losses than those observed in wild fish. The present findings provide support for refining elimination rates in MeHg models and show the importance of examining biological processes under natural conditions.     

Child maltreatment history among newlywed couples: A longitudinal study of marital outcomes and mediating pathways.

Participants included 202 newlywed couples who reported retrospectively about child maltreatment experiences (sexual abuse, physical abuse, psychological abuse, and neglect) and whose marital functioning was assessed 3 times over a 2-year period. Decreased marital satisfaction at T1 was predicted by childhood physical abuse, psychological abuse, and neglect for husbands; only neglect predicted lower satisfaction for wives. Increased maltreatment of various types was also related to T1 difficulties with marital trust and partner aggression. Dyadic growth curve analyses showed that the marital difficulties reported at T1 tended to remain over the course of the study. Further, in several instances, maltreatment exerted an increasingly detrimental influence on marital functioning over time, particularly for husbands. Examination of possible mediators between maltreatment and reductions in marital satisfaction revealed pathways through decreased sexual activity, increased psychological aggression, and increased trauma symptoms reported by husbands. These findings suggest that clinicians should consider how an adult’s history of child maltreatment may contribute to current marital dysfunction. The authors also identify possible targets for intervention when working with this population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effectiveness of ergonomics interventions in reducing upper limb work-related musculoskeletal pain and dysfunction in sonographers,surgeons and dentists: a systematic review

Abstract

The aim of this systematic review was to summarise the effects of ergonomics interventions on work-related upper limb musculoskeletal pain and dysfunction, and on productivity in sonographers, surgeons and dentists. A total of 31 studies were included. All studies reported effects on upper limb pain. Nine studies reported effects on dysfunction and only two studies reported effects on productivity. Moderately strong evidence in reducing upper limb pain was found for instigation of microbreaks into long duration surgical procedures, and the use of wider, lighter handles in dental instruments. Moderate evidence was also found for use of prismatic glasses and favourable positioning in reducing upper limb pain. Weak, inconsistent or no evidence was found for all other ergonomics interventions in reducing upper limb pain and dysfunction and increasing productivity. The lack of high quality research, particularly in sonographers and in the outcome of productivity, should be addressed.

Practitioner summary: This systematic review investigates the effectiveness of ergonomics interventions on upper limb pain, dysfunction and productivity in sonographers, dentists and surgeons. Instigation of microbreaks during long duration procedures and the use of wider, lighter instrument handles were most effective in reducing upper limb work-related pain.

Abbreviations: ANOVA: analysis of variance; CLS: conventional laparoscopic surgery; DMAIC: define, measure, analyze, improve and control; GRADE: grading of recommendations, assessment, development and evaluations; HD: high definition; PRISMA: preferred reporting items for systematic reviews and meta-analyses; PROSPERO: The International Prospective Register of Systematic Reviews; RCT: randomised control trial; SILS: single incision laparoscopic surgery; VITOM: video telescopic operative microscope; WNSWLHD: Western New South Wales Local Health District; WMSD: work related musculoskeletal disorder     

Surface chemistry controls crystallinity of ZnS nanoparticles

Combined small-angle and high energy wide-angle X-ray scattering measurements of nanoparticle size and structure permit interior strain and disorder to be observed directly in the real-space pair distribution function (PDF). PDF analysis showed that samples of ZnS nanoparticles with similar mean diameters (3.2-3.6 nm) but synthesized and treated with different low-temperature procedures possess a dramatic range of interior disorder. We used Fourier transform infrared spectroscopy to detect the surface species and the nature of surface chemical interactions. Our results suggest that there is a direct correlation between the strength of surface-ligand interactions and interior crystallinity.     

High surface area silicon materials: fundamentals and new technology

Crystalline silicon forms the basis of just about all computing technologies on the planet, in the form of microelectronics. An enormous amount of research infrastructure and knowledge has been developed over the past half-century to construct complex functional microelectronic structures in silicon. As a result, it is highly probable that silicon will remain central to computing and related technologies as a platform for integration of, for instance, molecular electronics, sensing elements and micro- and nanoelectromechanical systems.Porous nanocrystalline silicon is a fascinating variant of the same single crystal silicon wafers used to make computer chips. Its synthesis, a straightforward electrochemical, chemical or photochemical etch, is compatible with existing silicon-based fabrication techniques. Porous silicon literally adds an entirely new dimension to the realm of silicon-based technologies as it has a complex, three-dimensional architecture made up of silicon nanoparticles, nanowires, and channel structures. The intrinsic material is photoluminescent at room temperature in the visible region due to quantum confinement effects, and thus provides an optical element to electronic applications.Our group has been developing new organic surface reactions on porous and nanocrystalline silicon to tailor it for a myriad of applications, including molecular electronics and sensing. Integration of organic and biological molecules with porous silicon is critical to harness the properties of this material. The construction and use of complex, hierarchical molecular synthetic strategies on porous silicon will be described.     

A Benchmark Quantum Yield for Water Photoreduction on Amorphous Carbon Nitride

Amorphous carbon nitride (a‐CN) is a less‐explored but promising photocatalyst for hydrogen production. Despite an extended visible light absorption (EVLA) its low quantum efficiency (QE) for water photoreduction is a long standing problem. This implies that EVLA is not proportionally translated into collection of large amounts of photogenerated electrons. Minimizing the mismatch between light‐absorption and charge‐collection remains a scientific challenge. Here a sponge‐like hierarchical structure of a‐CN that addresses this apparent mismatch is reported. Combined experimental and finite difference time domain simulations demonstrate the ability of the a‐CN sponge to induce scattering for total internal light reflection that promotes localized charge carrier generation. Diffused reflectance and transient fluorescence decay studies show good agreement with simulations with a 40% enhanced light‐trapping and an ≈23 times longer electron lifetime in spongy a‐CN compared with that of the bulk material. The result is a new high benchmark for hydrogen production of 203.5 µmol h^?1 with a QE of 6.1% at 420 nm in a reaction system of 10 vol% triethanolamine and 1 wt% Pt cocatalyst. The enhanced water photoreduction is a result of amenable photophysical and electrochemical attributes existing within the a‐CN sponge.