7,707 research outputs found
Direct evidence for efficient ultrafast charge separation in epitaxial WS/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 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, the photoexcited holes
rapidly transfer into the graphene layer while the photoexcited electrons
remain in the WS layer. The resulting charge transfer state is found to
have a lifetime of \,ps. We attribute our findings to differences in
scattering phase space caused by the relative alignment of WS and graphene
bands as revealed by high resolution ARPES. In combination with spin-selective
excitation using circularly polarized light the investigated WS/graphene
heterostructure might provide a new platform for efficient optical spin
injection into graphene.Comment: 28 pages, 14 figure
Direct evidence for efficient ultrafast charge separation in epitaxial WS<sub>2</sub>/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
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
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
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
Measurement of the Charge Collection Efficiency after Heavy Non-Uniform Irradiation in BaBar Silicon Detectors
We have investigated the depletion voltage changes, the leakage current
increase and the charge collection efficiency of a silicon microstrip detector
identical to those used in the inner layers of the BaBar Silicon Vertex Tracker
(SVT) after heavy non-uniform irradiation. A full SVT module with the front-end
electronics connected has been irradiated with a 0.9 GeV electron beam up to a
peak fluence of 3.5 x 10^14 e^-/cm^2, well beyond the level causing substrate
type inversion. We irradiated one of the two sensors composing the module with
a non-uniform profile with sigma=1.4 mm that simulates the conditions
encountered in the BaBar experiment by the modules intersecting the horizontal
machine plane. The position dependence of the charge collection properties and
the depletion voltage have been investigated in detail using a 1060 nm LED and
an innovative measuring technique based only on the digital output of the chip.Comment: 7 pages, 13 figures. Presented at the 2004 IEEE Nuclear Science
Symposium, October 18-21, Rome, Italy. Accepted for publication by IEEE
Transactions on Nuclear Scienc
Polymerizable deep eutectic solvents: Convenient reactive dispersion media for the preparation of novel multi-walled carbon nanotubes-based functional materials
A new straightforward and green approach for the covalent functionalization of multi-walled carbon nanotubes (MWCNTs) was developed. This carbon nanostructure was efficiently derivatized by polymerizing proper deep eutectic monomers (DEM), a subclass of deep eutectic solvents (DES), based on a series of mono- and bis-vinyl imidazolium salts endowed with different functional groups (–OH, –NH2, –NH3+Br–) in the side chain or in the spacer. Herein, DEM systems played a triple role as convenient dispersion media for MWCNTs, efficient reactive systems, and also as structure-directing agents for the radical-initiated polymerization process onto the surface of MWCNTs. In addition, the new methodology allowed obtaining highly functionalized hybrid materials, as shown by thermogravimetric analyses, in short reaction times (<1h). Transmission electron microscopy (TEM) revealed that the polymeric network orderly develops along the surface of the nanotubes, which act as templating agent for both mono- and bis-vinyl imidazolium salts, despite the random nature of the polymerization process for the latter species. This new functionalization strategy of MWCNTs stands out for its environmentally friendly and time-saving nature leading to the formation of materials with significant potential for applications in a plethora of research fields. As a proof of their possible application, we tested these new hybrid materials as recoverable and recyclable catalysts for the conversion of CO2 into cyclic carbonates under solvent-free conditions, showing good catalytic performances, even in the absence of additional co-catalysts
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