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The photophysical properties of lead halide perovskite nanocrystals (NCs) are critical to their potential application in light emitting devices and other optoelectronics, and are typically characterized using optical spectroscopies. Measurements of nuclei and nascent NC photophysics during synthesis provide insight into how the reaction can be changed to control the properties of the resulting NCs. However, these measurements are typically only performed ex situ after growth is halted by centrifuging the reaction mixture for several minutes. Here, a method is reported to rapidly sample the reaction mixture during a solvation-limited synthesis to enable multiple spectroscopic measurements during nucleation and NC growth. Absorbance and fluorescence measurements of a reaction mixture during the formation of methylammonium lead triiodide perovskite NCs are reported. The changing positions of spectral features as a function of reaction time show the expected weakening of exciton confinement during NC growth. The evolving fluorescence spectra demonstrate that the capping and surface passivation of nascent NCs changes during the reaction. The species in the reaction mixture, particularly during the early stages of the synthesis, are shown to be unstable. This indicates that, even for a relatively slow solvation-limited reaction, the photophysics of the reaction mixture can only be accurately captured if spectroscopic measurements are completed within seconds of sampling. The common use of centrifugation to quench NC syntheses prior to spectroscopic measurement biases the NC population towards more stable, well-capped NCs and does not accurately report on the full NC population in a reaction mixture.
Staff training in positive behaviour support (PBS) is a widespread treatment approach for challenging behaviour in adults with intellectual disability.
To evaluate whether such training is clinically effective in reducing challenging behaviour during routine care (trial registration: NCT01680276).
We carried out a multicentre, cluster randomised controlled trial involving 23 community intellectual disability services in England, randomly allocated to manual-assisted staff training in PBS (n = 11) or treatment as usual (TAU, n = 12). Data were collected from 246 adult participants.
No treatment effects were found for the primary outcome (challenging behaviour over 12 months, adjusted mean difference = −2.14, 95% CI: −8.79, 4.51) or secondary outcomes.
Staff training in PBS, as applied in this study, did not reduce challenging behaviour. Further research should tackle implementation issues and endeavour to identify other interventions that can reduce challenging behaviour.
The appropriate medical treatment test (ATT), included in the Mental Health Act (MHA) (1983, as amended 2007), aims to ensure that detention only occurs when treatment with the purpose of alleviating a mental disorder is available.
As part of the Assessing the Impact of the Mental Health Act (AMEND) project, this qualitative study aimed to assess professionals' understanding of the ATT, and its impact on clinical practice.
Forty-one professionals from a variety of mental health subspecialties were interviewed. Interviews were coded related to project aims, and themes were generated in an inductive process.
We found that clinicians are often wholly relied upon for the ATT. Considered treatment varied depending on the patient's age rather than diagnosis. The ATT has had little impact on clinical practice.
Our findings suggest the need to review training and support for professionals involved in MHA assessments, with better-defined roles. This may enable professionals to implement the ATT as its designers intended.
Investigations of the stratigraphy and facies within a 2.69 m long gravity core (PS1423–2) from the southwestern Weddell Sea, Antarctica, indicate a significant change in the character of glaciomarine sedimentation since grounded ice withdrew from the continental shelf. Based on visual description, X-radiography, clast shape, particle-size analysis, physical properties and geochemical data, the core used in this analysis comprises five distinct units, from top to bottom: (i) massive diamicton, (ii) weakly to well-stratified diamicton, (iii) millimetre-scale laminated muds, with little or on coarse-clastic input, (iv) well- to weakly stratified diamicton, (v) massive diamicton. This succession is attributed to the variation in sedimentation associated with the recession of the grounding line of a previously advanced glacier. Grounded ice decoupled from the continental shelf to form an ice shelf, probably initiated by a rise in sea level in response to global climatic changes. Following disintegration of the ice shelf, sedimentation was influenced by marked variations in iceberg production. AMS-derived 14C ages from the upper 46 cm of the core indicate that the succession has been deposited since the end of the most recent glacial maximum (late Pleistocene), a conclusion supported by published data.
Mapping of the structural glaciology of Kongsvegen, Svalbard, reveals evidence for four main deformational structures. These are stratification, longitudinal foliation, thrusts and crevasse traces. These structures are considered in terms of their contribution to debris entrainment, transport and subsequent landform development. Stratification is associated with small amounts of supraglacial debris that has been folded with flow-parallel axes; longitudinal foliation in places incorporates basal glacial sediments along folds with flow-parallel axes; and thrusts transport basal debris to the glacier surface. Crevasse traces are not significant in terms of debris entrainment. The entrainment of basal debris along longitudinal foliation is not a universally recognised process. At Kongsvegen this process is attributed to the development of a transposition foliation, in combination with incorporation of debris-rich basal ice or soft basal sediment in the fold complex. Mapping of the landforms in the proglacial area shows that debris incorporated along longitudinal foliation is released as “foliation-parallel ridges” and that transverse ridges mark debris-bearing thrusts. The role of longitudinal foliation in landform development has never been documented in this manner. Although the preservation potential of such ridges may be limited, recognition of foliation-parallel ridges in the Pleistocene landform record has important implications for the interpretation of the dynamics of former ire masses.
We present the results of two 2.3 μm near-infrared (NIR) radial velocity (RV) surveys to detect exoplanets around 36 nearby and young M dwarfs. We use the CSHELL spectrograph (R ~ 46,000) at the NASA InfraRed Telescope Facility (IRTF), combined with an isotopic methane absorption gas cell for common optical path relative wavelength calibration. We have developed a sophisticated RV forward modeling code that accounts for fringing and other instrumental artifacts present in the spectra. With a spectral grasp of only 5 nm, we are able to reach long-term radial velocity dispersions of ~20–30 m s−1 on our survey targets.
The majority of children with Down syndrome (DS) develop Alzheimer's disease (AD) at an early age. Although long-chain n-3 fatty acids (FA) are protective of neurodegeneration, little is known about the FA status in DS. In the present study, we aimed to investigate whether children with DS presented altered plasma and erythrocyte membrane phospholipids (PL) FA composition, when compared with their non-affected siblings. Venous blood samples were analysed for plasma and erythrocyte membrane FA composition by TLC followed by GC techniques. Lipid molecular species were determined by electrospray ionisation/tandem MS (ESI-MS/MS). FA analysis measured by standard GC showed an increased concentration of MUFA and a decreased concentration of plasmalogens in major PL fractions, but there were no differences in the concentrations of arachidonic acid or DHA. However, as identified by ESI-MS/MS, children with DS had increased levels of the following erythrocyte PL molecular species: 16 : 0–16 : 0, 16 : 0–18 : 1 and 16 : 0–18 : 2n-6, with reduced levels of 16 : 0–20 : 4n-6 species. Children with DS presented significantly higher levels of MUFA in both plasma and erythrocyte membrane, as well as higher levels of saturated and monounsaturated molecular species. Of interest was the almost double proportion of 16 : 0–18 : 2n-6 and nearly half the proportion of 16 : 0–20 : 4n-6 of choline phosphoacylglycerol species in children with DS compared with their non-affected siblings. These significant differences were only revealed by ESI-MS/MS and were not observed in the GC analysis. Further investigations are needed to explore molecular mechanisms and to test the association between the pathophysiology of DS and the risk of AD.
Determine the prevalence and relatedness of Staphylococcus aureus anterior nares colonization in individuals with community-associated staphylococcal skin and soft-tissue infection (SSTI)
US Army soldiers undergoing infantry training.
Trainees who developed SSTI from May 2010 to January 2012.
Participants underwent anterior nares culture at the time of presentation for purulent SSTI. We determined the prevalence of S. aureus nasal colonization and strain relatedness between colonizing and clinical isolates with pulsed-field gel electrophoresis (PFGE).
We enrolled 1,203 SSTI participants, of whom 508 had culture-confirmed S. aureus SSTI. Overall, 70% (357/508) were colonized with S. aureus. Phenotypically, concordant colonization was more common with methicillin-susceptible S. aureus (MSSA; 56%; 122/218) than methicillin-resistant S. aureus (MRSA) SSTI (41%; 118/290; P < .01). With PFGE, 48% (121 of 254) of clinical-colonizing pairs were indistinguishable, and concordant colonization was more common with MRSA (53%; 92/173) than MSSA SSTI (36%; 29/81; P < .01). Restricting analysis to concomitant MRSA-MRSA or MSSA-MSSA pairs, 92% (92/100) of MRSA SSTI were indistinguishable, and 40% (29/72) MSSA SSTI were indistinguishable (P < .01). All 92 MRSA pairs were USA300.
On the phenotypic level, concordant anterior nares colonization with incident staphylococcal SSTI is more common in MSSA than MRSA; however, the opposite is observed when accounting for molecular typing, and MRSA SSTI displays greater concordance. USA300 was responsible for strain concordance with MRSA SSTI. Studies are needed to examine the roles of nasal and extra-nasal carriage, colonization preceding infection, and increased virulence in the pathogenesis of MRSA SSTI.
ClinicalTrials.gov identifier: NCT01105767.
Infect Control Hosp Epidemiol 2014;35(10):1251–1256
Growth kinetics, mechanisms, and material quality in GaN epitaxial lateral over-growth (ELO) were examined using a single mask of systematically varied patterns. A 2-D gas phase reaction/diffusion model describes how transport of the Ga precursor to the growth surface enhances the lateral rate in the early stages of growth. In agreement with SEM studies of truncated growth runs, the model also predicts the dramatic decrease in the lateral rate that occurs as GaN over-growth reduces the exposed area of the mask. At the point of convergence, a step-flow coalescence mechanism is observed to fill in the area between lateral growth-fronts. This alternative growth mode in which a secondary growth of GaN is nucleated along a single convergence line, may be responsible for producing smooth films observed to have uniform cathodoluminescence (CL) when using 1μm nucleation zones. Although emission is comprised of both UV (∼365nm) and yellow (∼550nm) components, the spectra suggest these films have reduced concentrations of threading dislocations normally associated with non-radiative recombination centers and defects known to accompany growth-front convergence lines.
We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant- PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GaInN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.
We are all products of human migration. Some of us migrated during our lifetimes from one part of the world to another, and had to learn different cultures, languages, diets, and systems of education. Others have parents who were forcibly relocated at different times, particularly during World War II and its sequelae, and experienced displaced persons camps, disease, and violence, and were uprooted to various corners of the world, such as the Americas and Australia. Yet others have ancestors who migrated hundreds or thousands of years ago and have lived in relatively undisturbed households for many generations. Finally, some people originated in Africa and migrated within the continent or were forcibly relocated by wars and the slave trade.
The authors of this volume are migrants and describe the human condition from their unique migratory experiences. Each author has a complex personal history of migration, often occurring in different generations, cultural traditions, and languages. All of the authors currently residing in the Americas are either recent migrants or have descended from ancestors who relocated to the Americas generations ago. Several of the authors have experienced extensive migration and relocation within their lifetimes, as the following examples show.
With its rich archaeological and historical record, Peru offers an exceptional opportunity for the study of human migration. While Amazonia comprises nearly 60% of the country’s national territory, most studies of Peru’s human populations have emphasized the Andean highlands. The selva baja, or lowland tropical forested region of Peru’s Lower Huallaga Valley, is particularly important for genetic studies on migration. A geographically significant crossroads of migration, the Lower Huallaga Valley is characterized by its degree of ethnic diversity among both indigenous and immigrant populations. Despite centuries of colonization, many contemporary indigenous societies reside in the selva baja region surrounding the city of Yurimaguas, including: Quechua-speaking populations (Kichwa Lamista, Kichwa del Pastaza); Jibaroan speakers (Achuar, Awajun, Kandozi, Wampis, and Jibaro); Tupi-Guarani speakers (Kukama-Kukamira); Cahuapanan speakers (Shawi and Shiwilu); Arawakan speakers (Chamicuro); and the Urarina (linguistic isolate).
In light of the region’s recent pattern of urbanization, this study evaluates the genetic consequences of migration using mitochondrial DNA (mtDNA) to characterize the maternal genetic structure of residents of the “new urban settlements” (or barriadas) enveloping Yurimaguas, one of the selva baja’s principal cities (Dean and Silverstein, 2011). Maternal markers were used to infer prominent source population and/or pattern of migration into the provincial capital city of Yurimaguas by comparing the focus sample with others from South America. By estimating the proportion of non-native maternal admixture and establishing estimates of a past population reduction we provide novel insights for understanding the effects of human migration in the Lower Huallaga Valley.