Abstract
Excitons, Coulomb bound electron–hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb ...interaction in transition metal dichalcogenides such as WSe
2
monolayers combined with the presence of the valley degree of freedom is expected to provide new opportunities for controlling excitonic effects. But so far the bosonic character of exciton scattering processes remains largely unexplored in these two-dimensional materials. Here we show that scattering between B-excitons and A-excitons preferably happens within the same valley in momentum space. This leads to power dependent, negative polarization of the hot B-exciton emission. We use a selective upconversion technique for efficient generation of B-excitons in the presence of resonantly excited A-excitons at lower energy; we also observe the excited A-excitons state 2
s
. Detuning of the continuous wave, low-power laser excitation outside the A-exciton resonance (with a full width at half maximum of 4 meV) results in vanishing upconversion signal.
Abstract In the present work new highly biocompatible nanovesicles were developed using polyanion sodium hyaluronate to form polymer immobilized vesicles, so called hyalurosomes. Curcumin, at high ...concentration was loaded into hyalurosomes and physico-chemical properties and in vitro/in vivo performances of the formulations were compared to those of liposomes having the same lipid and drug content. Vesicles were prepared by direct addition of dispersion containing the polysaccharide sodium hyaluronate and the polyphenol curcumin to a commercial mixture of soy phospholipids, thus avoiding the use of organic solvents. An extensive study was carried out on the physico-chemical features and properties of curcumin-loaded hyalurosomes and liposomes. Cryogenic transmission electron microscopy and small-angle X-ray scattering showed that vesicles were spherical, uni- or oligolamellar and small in size (112–220 nm). The in vitro percutaneous curcumin delivery studies on intact skin showed an improved ability of hyalurosomes to favour a fast drug deposition in the whole skin. Hyalurosomes as well as liposomes were biocompatible, protected in vitro human keratinocytes from oxidative stress damages and promoted tissue remodelling through cellular proliferation and migration. Moreover, in vivo tests underlined a good effectiveness of curcumin-loaded hyalurosomes to counteract 12-O-tetradecanoilphorbol (TPA)-produced inflammation and injuries, diminishing oedema formation, myeloperoxydase activity and providing an extensive skin reepithelization. Thanks to the one-step and environmentally-friendly preparation method, component biocompatibility and safety, good in vitro and in vivo performances, the hyalurosomes appear as promising nanocarriers for cosmetic and pharmaceutical applications.
The strong light-matter interaction and the valley selective optical selection rules make monolayer (ML) MoS2 an exciting 2D material for fundamental physics and optoelectronics applications. But, so ...far, optical transition linewidths even at low temperature are typically as large as a few tens of meV and contain homogeneous and inhomogeneous contributions. This prevented in-depth studies, in contrast to the better-characterized ML materials MoSe2 and WSe2 . In this work, we show that encapsulation of ML MoS2 in hexagonal boron nitride can efficiently suppress the inhomogeneous contribution to the exciton linewidth, as we measure in photoluminescence and reflectivity a FWHM down to 2 meV at T=4K . Narrow optical transition linewidths are also observed in encapsulated WS2 , WSe2 , and MoSe2 MLs. This indicates that surface protection and substrate flatness are key ingredients for obtaining stable, high-quality samples. Among the new possibilities offered by the well-defined optical transitions, we measure the homogeneous broadening induced by the interaction with phonons in temperature-dependent experiments. We uncover new information on spin and valley physics and present the rotation of valley coherence in applied magnetic fields perpendicular to the ML.
The intricate interplay between optically dark and bright excitons governs the light-matter interaction in transition metal dichalcogenide monolayers. We have performed a detailed investigation of ...the “spin-forbidden” dark excitons in WSe2 monolayers by optical spectroscopy in an out-of-plane magnetic field Bz. In agreement with the theoretical predictions deduced from group theory analysis, magnetophotoluminescence experiments reveal a zero-field splitting δ=0.6±0.1meV between two dark exciton states. The low-energy state is strictly dipole forbidden (perfectly dark) at Bz=0, while the upper state is partially coupled to light with z polarization (“gray” exciton). The first determination of the dark neutral exciton lifetime τD in a transition metal dichalcogenide monolayer is obtained by time-resolved photoluminescence. We measure τD∼110±10ps for the gray exciton state, i.e., two orders of magnitude longer than the radiative lifetime of the bright neutral exciton at T=12K.
Excitons, Coulomb bound electron-hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb ...interaction in transition metal dichalcogenides such as WSe
monolayers combined with the presence of the valley degree of freedom is expected to provide new opportunities for controlling excitonic effects. But so far the bosonic character of exciton scattering processes remains largely unexplored in these two-dimensional materials. Here we show that scattering between B-excitons and A-excitons preferably happens within the same valley in momentum space. This leads to power dependent, negative polarization of the hot B-exciton emission. We use a selective upconversion technique for efficient generation of B-excitons in the presence of resonantly excited A-excitons at lower energy; we also observe the excited A-excitons state 2s. Detuning of the continuous wave, low-power laser excitation outside the A-exciton resonance (with a full width at half maximum of 4 meV) results in vanishing upconversion signal.
Niche and neutral processes drive community assembly and metacommunity dynamics, but their relative importance might vary with the spatial scale. The contribution of niche processes is generally ...expected to increase with increasing spatial extent at a higher rate than that of neutral processes. However, the extent to what community composition is limited by dispersal (usually considered a neutral process) over increasing spatial scales might depend on the dispersal capacity of composing species. To investigate the mechanisms underlying the distribution and diversity of species known to have great powers of dispersal (hundreds of kilometres), we analysed the relative importance of niche processes and dispersal limitation in determining beta‐diversity patterns of aquatic plants and cladocerans over regional (up to 300 km) and continental (up to 3300 km) scales. Both taxonomic groups were surveyed in five different European regions and presented extremely high levels of beta‐diversity, both within and among regions. High beta‐diversity was primarily explained by species replacement (turnover) rather than differences in species richness (i.e. nestedness). Abiotic and biotic variables were the main drivers of community composition. Within some regions, small‐scale connectivity and the spatial configuration of sampled communities explained a significant, though smaller, fraction of compositional variation, particularly for aquatic plants. At continental scale (among regions), a significant fraction of compositional variation was explained by a combination of spatial effects (exclusive contribution of regions) and regionally‐structured environmental variables. Our results suggest that, although dispersal limitation might affect species composition in some regions, aquatic plant and cladoceran communities are not generally limited by dispersal at the regional scale (up to 300 km). Species sorting mediated by environmental variation might explain the high species turnover of aquatic plants and cladocerans at regional scale, while biogeographic processes enhanced by dispersal limitation among regions might determine the composition of regional biotas.
Abstract The aims of this study were to investigate the rates of deliberate self-harm (DSH) behavior among an Italian adolescent sample, as well as to explore its clinical correlates. On a sample of ...234 adolescents in Italian secondary schools (Mean age = 16.47; SD = 1.7) were assessed the DSH as well as externalizing symptoms (including both conduct disorder CD and oppositional defiant disorder ODD symptoms), borderline personality disorder BPD symptoms, dissociative symptoms, and the incidence of life-stressors. Consistent with past research on DSH in youth, 42% of the adolescents in this sample engaged in DSH. Results indicate a positive association between DSH and all psychopathological correlates, including BPD, dissociative, and ODD and CD symptoms. Further, findings revealed an association between DSH and specific life-stressors (i.e., psychological and sexual abuse, natural disasters and serious accidents, the loss of someone important, and the witnessing of family violence or a serious accident).
Abstract
Background
The BETTER (Building on Existing Tools to Improve Chronic Disease Prevention and Screening in Primary Care) intervention was designed to integrate the approach to chronic disease ...prevention and screening in primary care and demonstrated effective in a previous randomized trial.
Methods
We tested the effectiveness of the BETTER HEALTH intervention, a public health adaptation of BETTER, at improving participation in chronic disease prevention and screening actions for residents of low-income neighbourhoods in a cluster randomized trial, with ten low-income neighbourhoods in Durham Region Ontario randomized to immediate intervention vs. wait-list. The unit of analysis was the individual, and eligible participants were adults age 40–64 years residing in the neighbourhoods. Public health nurses trained as “prevention practitioners” held one prevention-focused visit with each participant. They provided participants with a tailored prevention prescription and supported them to set health-related goals. The primary outcome was a composite index: the number of evidence-based actions achieved at six months as a proportion of those for which participants were eligible at baseline.
Results
Of 126 participants (60 in immediate arm; 66 in wait-list arm), 125 were included in analyses (1 participant withdrew consent). In both arms, participants were eligible for a mean of 8.6 actions at baseline. At follow-up, participants in the immediate intervention arm met 64.5% of actions for which they were eligible versus 42.1% in the wait-list arm (rate ratio 1.53 95% confidence interval 1.22–1.84).
Conclusion
Public health nurses using the BETTER HEALTH intervention led to a higher proportion of identified evidence-based prevention and screening actions achieved at six months for people living with socioeconomic disadvantage.
Trial registration
NCT03052959
, registered February 10, 2017.
Transitions metal dichalcogenides (TMDs) are direct gap semiconductors in the monolayer (ML) limit with fascinating optical and spin-valley properties. The strong optical absorption of up to 20% for ...a single ML is governed by excitons, electron-hole pairs bound by Coulomb attraction. Excited exciton states inMoSe2andMoTe2monolayers have so far been elusive because of their low oscillator strength and strong inhomogeneous broadening. Here, we show that encapsulation in hexagonal boron nitride results in an emission line width of theA:1sexciton below 1.5 meV and 3 meV in ourMoSe2andMoTe2monolayer samples, respectively. This allows us to investigate the excited exciton states by photoluminescence upconversion spectroscopy for both monolayer materials. The excitation laser is tuned into resonance with theA:1stransition, and we observe emission of excited exciton states up to 200 meV above the laser energy. We demonstrate bias control of the efficiency of this nonlinear optical process. We discuss the origin of the upconversion effect. Our model calculations suggest an exciton-exciton (Auger) scattering mechanism specific to TMD MLs involving an excited conduction band, thus generating high-energy excitons with small wave vectors. The optical transitions are further investigated by white light reflectivity, photoluminescence excitation, and resonant Raman scattering, confirming their origin as excited excitonic states in monolayer thin semiconductors.
•Roux-en-Y Gastric Bypass significantly reduced and sustained glycated haemoglobin (HbA1c) levels compared to medical therapy at ten-year follow-up.•The short duration of diabetes is of fundamental ...importance to achieve long-term remission of diabetes after bariatric surgery.•Weight loss impacts the short-term remission of type 2 diabetes, but has a marginal role in long-term relapse.
: To assess the impact of bariatric surgery on remission and relapse of type 2 diabetes mellitus (T2DM) at 10 years of follow-up and analyze predictive factors.
: Eighty-eight obese subjects undergoing Roux-en-Y gastric bypass (RYGB) and 25 subjects assigned to medical therapy (MT) were evaluated every year for 10 years. T2DM remission was defined by the American Diabetes Association criteria.
: Body mass index (BMI), fasting glucose, and haemoglobin A1c (HbA1c) improved more markedly in RYGB than MT patients throughout the 10-year period. Post-surgery remission rates were 74% and 53% at 1 and 10 years, respectively, while remission did not occur in MT patients. One-year post-surgery, BMI decreased more in subjects with remission than in those without, but no further decrease was observed thereafter. By partial-least-squares analysis, T2DM duration, baseline HbA1c, and ensuing insulin therapy were the strongest predictors of remission. Remission was achieved at one year in 91% of patients with T2DM duration < 4 years, and 79% of them remained in remission at 10 years. On the contrary only 42% of patients with T2DM duration ≥ 4 years achieved remission, which was maintained only in 6% at the end of 10 years. By survival analysis, patients with T2DM duration < 4 years had higher remission rates than those with duration ≥ 4 years (hazards ratio (HR) 3.1 95%CI 1.8–5.7). Relapse did not occur before two years post-surgery and was much less frequent in patients with < 4- vs ≥ 4-year duration (HR 11.8 4.9–29.4).
: Short T2DM duration and good glycemic control before RYGB surgery were the best requisites for a long-lasting T2DM remission, whereas weight loss had no impact on the long-term relapse of T2DM.
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