On the origin of electrical conductivity in the bio-electronic material melanin

The skin pigment melanin is one of a few bio-macromolecules that display electrical and photo-conductivity in the solid-state. A model for melanin charge transport based on amorphous semiconductivity has been widely accepted for 40 years. In this letter, we show that a central pillar in support of this hypothesis, namely experimental agreement with a hydrated dielectric model, is an artefact related to measurement geometry and non-equilibrium behaviour. Our results cast significant doubt on the validity of the amorphous semiconductor model and are a reminder of the difficulties of electrical measurements on low conductivity, disordered organic materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3688491

"Soft" graphene oxide-organopolysulfide nanocomposites for superior pseudocapacitive lithium storage

We report a “soft” graphene oxide-polymeric organosulfide nanocomposite with improved pseudocapacitive performance for high-potential (1–2.8 V vs. Li/Li), high-capacity (278 mAh/g) and stable (500 cycles) lithium storage

Focusing monochromator and imaging-plate camera for grazing-incidence diffraction studies of thin films

A multiple-imaging-plate detector system and focusing monochromator have been developed and successfully applied to the time-resolved study of phase transitions in Langmuir-Blodgett films by grazing-incidence X-ray diffraction (GIXD). The monochromator described here combines fixed-exit-beam height with sagittal focusing of the second crystal. The design is similar to that of Matsushita et nl. [Matsushita, Ishikawa & Oyanagi (1986). Nucl. Instrum. Methods, A246, 377-379], with the exception that the motion of the first crystal is achieved via a computer-controlled X-Y translation table rather than a set of cams. The second crystal is a ribbed Si(111) wafer mounted in a four-point bending mechanism. The first reported application of imaging plates to a GIXD study was carried out by our group and proved to be very successful in the determination of thin-film structure [Foran, Peng, Steitz, Barnes & Gentle (1996). Langmuir, 12, 774-777]. To extend the capabilities of this system, an imaging-plate camera was designed and built which can accommodate up to 13 imaging plates (40 x 20 cm) inside the vacuum chamber of the main diffractometer at the Australian Beamline at the Photon Factory

From Waste to Employment Opportunities and Wealth Creation: A Case Study of Utilization of Livestock By-Products in Hargeisa, Somaliland

This article was conducted to establish the involvement of vulnerable women and youths in creating alternative employment opportunities and diversify wealth creation livelihood activities through DFID UKaid Sustainable Employment and Economic Development (SEED) funded programme and implemented by FAO Somalia in the security fragile state of Somaliland.Mqaalkan waxaa loo sameeyey si haweenka nugul loogu abuuro shaqo ay ka heli karaan masaruufka reerka. Waxaana barnaamijlaas Hargeysa ku hirgeliyay FAO (DFID UK e SEED).Questo articolo è stato condotto per stabilire la partecipazione di donne vulnerabili e giovani nella creazione di opportunità di lavoro alternative e nella diversificazione delle attività creatrici di sostentamento attraverso programmi DFID UK e SEED sovvenzionati dalla FAO in Somaliland

Enhanced photocatalytic properties of reusable TiO2-loaded natural porous minerals in dye wastewater purification

Diatomite-based recyclable photocatalysts containing single lanthanide doped TiO nanoparticles (NPs) were synthesized by using simple sol–gel method. Photocatalytic activities of the prepared Ce- or La- single doped TiO/diatomite catalysts were estimated by the degradation of Rhodamine B (RhB) under simulated sunlight irradiation. The XRD and Raman spectra shown only anatase phase of TiO for the un-doped and Ce-doped samples. The TEM images revealed uniform distribution of TiO NPs on the matrix, indicating that diatomite played an important role to prevent the agglomeration of TiO NPs. Ce-TiO/diatomite showed a red shift in UV–visible light absorption edge with enhanced absorption intensity than un-doped sample, whereas La-TiO/diatomite showed a blue shift. The bandgap energy of 1.5%-Ce doped sample is as low as 2.75 eV. The XPS spectra showed the presence of both Ce and Ce oxidation states for Ce dopant. The photoluminescence spectra of the Ce-doped samples showed first decrease in the recombination centers with the maximum decrease for 1.5%-Ce doped sample and then started increase with the increasing Ce in the samples. As compared to the La-doped samples, a desired behavior was observed for the Ce-doped hybrid due to the redox Ce/Ce pairs acting as electron scavengers and localized unoccupied Ce 4f level narrowing the band gap. The incorporation with diatomite as support of TiO nanoparticles is contributed for the improved reusability and also gives a promising strategy to enable the application of nano-photocatalysts in a real wastewater remediation treatment

Dispersible percolating carbon nano-electrodes for improvement of polysulfide utilization in Li-S batteries

Percolating carbon nanoparticles were added into electrolyte to improve the performance of Li-S batteries. These percolating carbon nanoparticles acted as dispersible nanosized electrodes, allowed the direct electrochemical utilization of dissolved polysulfides in electrolyte, and mitigated the polysulfide shuttle. As a result, the polysulfide utilization was improved with the virtual sulfur capacity increasing from 538 mA h g(-1) to 1270 mA h g(-1). The increment in high plateau-sloping capacity is 43% while a much more significant 158% increment is observed in low plateau region. The percolating carbon nanoparticles also improved the battery stability. (C) 2015 Elsevier Ltd. All rights reserved

Differentiating between V‐ and G‐series nerve agent and simulant vapours using fluorescent film responses

In-field rapid and reliable identification of nerve agents is critical for the protection of Defence and National Security personnel as well as communities. Fluorescence-based detectors can be portable and provide rapid detection of chemical threats. However, most current approaches cannot differentiate between dilute vapors of nerve agent classes and are susceptible to false positives due to the presence of common acids. Here a fluorescence-based method is shown for rapid differentiation between the V-series and phosphonofluoridate G-series nerve agents and avoids false positives due to common acids. Differentiation is achieved through harnessing two different mechanisms. Detection of the V-series is achieved using photoinduced hole transfer whereby the fluorescence of the sensing material is quenched in the presence of the V-series agent. The G-series is detected using a turn-on mechanism in which a silylated excited state intramolecular proton transfer sensing molecule is selectively deprotected by hydrogen fluoride, which is typically found as a contaminant and/or breakdown product in G-series agents such as sarin. The strategy provided discrimination between classes, as the sensor for the G-series agent class is insensitive to the V-series agent, and vice versa, and neither responded to common acids

Elucidating the spatial arrangement of emitter molecules in organic light-emitting diode films

The effect of varying the emitter concentration on the structural properties of an archetypal phosphorescent blend consisting of 4,4′-bis(N-carbazolyl)biphenyl and tris(2-phenylpyridyl)iridium(III) has been investigated using non-equilibrium molecular dynamics (MD) simulations that mimic the process of vacuum deposition. By comparison with reflectometry measurements, we show that the simulations provide an accurate model of the average density of such films. The emitter molecules were found not to be evenly distributed throughout film, but rather they can form networks that provide charge and/or energy migration pathways, even at emitter concentrations as low as ≈5 weight percent. At slightly higher concentrations, percolated networks form that span the entire system. While such networks would give improved charge transport, they could also lead to more non-radiative pathways for the emissive state and a resultant loss of efficiency

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

On Perfect Sequence Covering Arrays

A PSCA$(v, t, \lambda)$ is a multiset of permutations of the $v$-element alphabet $\{0, \dots, v-1\}$ such that every sequence of $t$ distinct elements of the alphabet appears in the specified order in exactly $\lambda$ of the permutations. For $v \geq t \geq 2$, we define $g(v, t)$ to be the smallest positive integer $\lambda$ such that a PSCA$(v, t, \lambda)$ exists. We show that $g(6, 3) = g(7, 3) = g(7, 4) = 2$ and $g(8, 3) = 3$. Using suitable permutation representations of groups we make improvements to the upper bounds on $g(v, t)$ for many values of $v \leq 32$ and $3\le t\le 6$. We also prove a number of restrictions on the distribution of symbols among the columns of a PSCA