Direct evidence for efficient ultrafast charge separation in epitaxial WS₂/graphene heterostructures

We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to investigate ultrafast charge transfer in an epitaxial heterostructure made of monolayer WS2 and graphene. This heterostructure combines the benefits of a direct-gap semiconductor with strong spin-orbit coupling and strong light-matter interaction with those of a semimetal hosting massless carriers with extremely high mobility and long spin lifetimes. We find that, after photoexcitation at resonance to the A-exciton in WS2, the photoexcited holes rapidly transfer into the graphene layer while the photoexcited electrons remain in the WS2 layer. The resulting charge-separated transient state is found to have a lifetime of ∼1 ps. We attribute our findings to differences in scattering phase space caused by the relative alignment of WS2 and graphene bands as revealed by high-resolution ARPES. In combination with spin-selective optical excitation, the investigated WS2/graphene heterostructure might provide a platform for efficient optical spin injection into graphene

Direct evidence for efficient ultrafast charge separation in epitaxial WS2_2/graphene heterostructure

We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to investigate ultrafast charge transfer in an epitaxial heterostructure made of monolayer WS$_2$ and graphene. This heterostructure combines the benefits of a direct gap semiconductor with strong spin-orbit coupling and strong light-matter interaction with those of a semimetal hosting massless carriers with extremely high mobility and long spin lifetimes. We find that, after photoexcitation at resonance to the A-exciton in WS$_2$, the photoexcited holes rapidly transfer into the graphene layer while the photoexcited electrons remain in the WS$_2$ layer. The resulting charge transfer state is found to have a lifetime of $\sim1$\,ps. We attribute our findings to differences in scattering phase space caused by the relative alignment of WS$_2$ and graphene bands as revealed by high resolution ARPES. In combination with spin-selective excitation using circularly polarized light the investigated WS$_2$/graphene heterostructure might provide a new platform for efficient optical spin injection into graphene.Comment: 28 pages, 14 figure

Grid services for the MAGIC experiment

Exploring signals from the outer space has become an observational science under fast expansion. On the basis of its advanced technology the MAGIC telescope is the natural building block for the first large scale ground based high energy gamma-ray observatory. The low energy threshold for gamma-rays together with different background sources leads to a considerable amount of data. The analysis will be done in different institutes spread over Europe. Therefore MAGIC offers the opportunity to use the Grid technology to setup a distributed computational and data intensive analysis system with the nowadays available technology. Benefits of Grid computing for the MAGIC telescope are presented.Comment: 5 pages, 1 figures, to be published in the Proceedings of the 6th International Symposium ''Frontiers of Fundamental and Computational Physics'' (FFP6), Udine (Italy), Sep. 26-29, 200

INCIDENCE OF PSYCHOTIC DISORDERS IN PALERMO: PRELIMINARY DATA

Background: The incidence of psychotic disorders varies in different geographical areas (McGrath 2004). Recent data suggest that the incidence is higher in males, migrant minorities and in urban areas. There aren\u2019t many available epidemiological data on the incidence of psychotic disorders in Italy. This is the first incidence study on psychotic disorders carried out in Palermo, the capital of Sicily. Methods: we screened all patients presenting with their first episode of psychosis to the mental health services of our catchment area (5 inpatient, 5 outpatient units and 3 private psychiatric hospitals) over a period of three years (2008-2011). The diagnosis of psychosis was defined using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN Wing, J. K., et al., 1990).The main socio-demographic data were collected using the MRC Social Data Schedule. When subjects were not available (did not consent) for interview, information was collected from clinical notes. The population at risk referred to the people aged from 18-65 who were resident in the same catchment area (Palermo Municipality) in the period considered, according to the data of the Statistic Office of Palermo Municipality). Results: we identified 216 patients affected by a first episode of psychosis (FEP): 135 M (62.5%) and 81 F (37.5%), mean age 31.42 years (SD: 11.44). 77.1% of FEP had a diagnosis of non affective psychosis, 12.8% of affective psychosis and 10.1% received a diagnosis of other psychosis. 204 subjects were Caucasian, 12 non Caucasian belonging to various ethnicities and they were all first generation migrants (4 Indian, 3 African, 2 Bangladeshi, and 3 Mixed). Population at risk is 425.194 people. The mean age of onset was lower in men than women M: 29.98 years (SD: 10.41) vs. F: 34.28 (SD:12.64) (p=0.013)The incidence of psychotic disorders in our catchment area is 16,9 per 100.000 person years. It was higher in men 21,9 per 100.000 than women 12,2 per 100.000. Discussion: Our study is the first epidemiological study in Sicily investigating the incidence of psychotic disorders. In our population men have a higher incidence of psychotic disorders than women and an earlier age of onset

Integrated Nitrogen CAtchment model (INCA) applied to a tropical catchment in the Atlantic Forest, São Paulo, Brazil

International audienceStream-water flows and in-stream nitrate and ammonium concentrations in a small (36.7 ha) Atlantic Forest catchment were simulated using the Integrated Nitrogen in CAtchments (INCA) model version 1.9.4. The catchment, at Cunha, is in the Serra do Mar State Park, SE Brazil and is nearly pristine because the nearest major conurbations, São Paulo and Rio, are some 450 km distant. However, intensive farming may increase nitrogen (N) deposition and there are growing pressures for urbanisation. The mean-monthly discharges and NO3-N concentration dynamics were simulated adequately for the calibration and validation periods with (simulated) loss rates of 6.55 kg.ha?1 yr?1 for NO3-N and 3.85 kg.ha?1 yr?1 for NH4-N. To investigate the effects of elevated levels of N deposition in the future, various scenarios for atmospheric deposition were simulated; the highest value corresponded to that in a highly polluted area of Atlantic Forest in Sao Paulo City. It was found that doubling the atmospheric deposition generated a 25% increase in the N leaching rate, while at levels approaching the highly polluted São Paulo deposition rate, five times higher than the current rate, leaching increased by 240%, which would create highly eutrophic conditions, detrimental to downstream water quality. The results indicate that the INCA model can be useful for estimating N concentration and fluxes for different atmospheric deposition rates and hydrological conditions

The copy number variant involving part of the \u3b17 nicotinic receptor gene contains a polymorphic inversion.

The \u3b17 nicotinic acetylcholine receptor gene (CHRNA7) is located at 15q13\u2013q14 in a region that is strongly linked to the P50 sensory gating deficit, an endophenotype of schizophrenia and bipolar disorder. Part of the gene is a copy number variant, due to a duplication of exons 5\u201310 and 3\u2032 sequence in CHRFAM7A, which is present in many but not all humans. Maps of this region show that the two genes are in opposite orientation in the individual mainly represented in the public access human DNA sequence database (Build 36), suggesting that an inversion had occurred since the duplication. We have used fluorescent in situ hybridization to investigate this putative inversion. Analysis of interphase chromosomes in 12 individuals confirms the occurrence of an inversion and indicates that CHRFAM7A exists in both orientations with similar frequency. We showed that the 2\u2009bp deletion polymorphism in exon 6 of CHRFAM7A is in strong linkage disequilibrium with the inversion polymorphism (r2=0.82, CI 0.53\u20131.00, P=0.00003), which can therefore be used as a surrogate marker. Previous associations of endophenotypes of schizophrenia with the 2\u2009bp deletion might therefore be due to the orientation of the duplicon containing CHRFAM7A

Cannabis consumption and the risk of psychosis

Summary Objectives: Cannabis is the most widely used illicit drug globally and its use has been linked to an increased risk for psychotic disorders. An association between cannabis consumption and psychotic symptoms was consistently reported by several studies. This case-control study aimed to widen the current findings about the impact of cannabis exposure on the risk of psychosis, by investigating the pattern of cannabis consumption in a sample of first-episode of psychosis (FEP) patients compared to healthy controls. Material and methods: 68 individuals who presented for the first time to mental health services of Palermo (Italy) with an ICD-10 diagnosis of psychotic disorders and 74 healthy were enrolled as part of the Sicilian Genetics and Psychosis study. Psychopathological assessment and diagnosis were carried out by the Schedule for Clinical Assessment in Neuropsychiatry (SCAN). Socio-demographic data were collected by the modified version of the Medical Research Council (MRC) socio-demographic scale. All participants were interviewed using the Cannabis Experience Questionnaire \u2013 Modified Version to obtain a detailed assessment of lifetime patterns of cannabis and other illicit drug consumption. Logistic regression was applied to investigate the relationships between various aspects of cannabis use (lifetime use, age at first use, duration, and frequency of use) and case-control status while controlling for potential confounders. Results: Patients started cannabis consumption about 3 years earlier than the control group (t = 3.1, p = 0.002) and were 8 times more likely to having started using cannabis before 15 years (adjusted OR = 8.0, 95% CI 2.4-27) than controls. Furthermore cases were more likely to smoke more frequently than controls (adjusted OR = 4.4, 95% CI 1.08-18). We did not find a difference in duration of cannabis use between cases and controls. Conclusions: The findings suggest that cannabis exposure, and especially daily cannabis consumption, is associated with the risk for psychosis; however, the retrospective study design does not allow drawing firm conclusions about causality

Approximate Homomorphisms of Ternary Semigroups

A mapping $f:(G_1,[ ]_1)\to (G_2,[ ]_2)$ between ternary semigroups will be called a ternary homomorphism if $f([xyz]_1)=[f(x)f(y)f(z)]_2$. In this paper, we prove the generalized Hyers--Ulam--Rassias stability of mappings of commutative semigroups into Banach spaces. In addition, we establish the superstability of ternary homomorphisms into Banach algebras endowed with multiplicative norms.Comment: 10 page