1,029 research outputs found
Landau-fluid simulations of Alfvén-wave instabilities in a warm collisionless plasma
A dispersive Landau-fluid model is used to study the decay and modulational instabilities of circularly-polarized Alfvén waves in a collisionless plasma, as well as their nonlinear developments. Comparisons are presented with the drift-kinetic approximation for the dispersionless regime and with hybrid simulations in more general conditions. The effect of the nature of the instability on particle heating is discussed, together with the formation of coherent structures or the development of an inverse cascade
Atomic and Electronic Structure of a Rashba - Junction at the BiTeI Surface
The non-centrosymmetric semiconductor BiTeI exhibits two distinct surface
terminations that support spin-split Rashba surface states. Their ambipolarity
can be exploited for creating spin-polarized - junctions at the
boundaries between domains with different surface terminations. We use scanning
tunneling microscopy/spectroscopy (STM/STS) to locate such junctions and
investigate their atomic and electronic properties. The Te- and I-terminated
surfaces are identified owing to their distinct chemical reactivity, and an
apparent height mismatch of electronic origin. The Rashba surface states are
revealed in the STS spectra by the onset of a van Hove singularity at the band
edge. Eventually, an electronic depletion is found on interfacial Te atoms,
consistent with the formation of a space charge area in typical -
junctions.Comment: 5 pages, 4 figure
Ultrafast Optical Control of the Electronic Properties of
We report on the temperature dependence of the electronic
properties, studied at equilibrium and out of equilibrium, by means of time and
angle resolved photoelectron spectroscopy. Our results unveil the dependence of
the electronic band structure across the Fermi energy on the sample
temperature. This finding is regarded as the dominant mechanism responsible for
the anomalous resistivity observed at T* 160 K along with the change of
the charge carrier character from holelike to electronlike. Having addressed
these long-lasting questions, we prove the possibility to control, at the
ultrashort time scale, both the binding energy and the quasiparticle lifetime
of the valence band. These experimental evidences pave the way for optically
controlling the thermoelectric and magnetoelectric transport properties of
High-Pressure Stopped-Flow Study of Inclusion Reactions with α-Cyclodextrin: Dynamic Aspects in Host-Guest Interactions
The full volume and entropy profiles of the inclusion reaction between α-cyclodextrin and the guest molecules, ethylorange (1) and mordant yellow 7 (2), have been constructed from variable-pressure and -temperature stopped-flow kinetic experiments
BiTeCl and BiTeBr: a comparative high-pressure optical study
We here report a detailed high-pressure infrared transmission study of BiTeCl
and BiTeBr. We follow the evolution of two band transitions: the optical
excitation between two Rashba-split conduction bands, and the
absorption across the band gap. In the low pressure range, ~GPa,
for both compounds is approximately constant with pressure and
decreases, in agreement with band structure calculations. In BiTeCl, a clear
pressure-induced phase transition at 6~GPa leads to a different ground state.
For BiTeBr, the pressure evolution is more subtle, and we discuss the
possibility of closing and reopening of the band gap. Our data is consistent
with a Weyl phase in BiTeBr at 56~GPa, followed by the onset of a structural
phase transition at 7~GPa.Comment: are welcom
High-rate deposition of microcrystalline silicon in a large-area PECVD reactor and integration in tandem solar cells
We study the high-rate deposition of microcrystalline silicon in a large-area plasma-enhanced chemical-vapor-deposition (PECVD) reactor operated at 40.68 MHz, in the little-explored process conditions of high-pressure and high-silane concentration and depletion. Due to the long gas residence time in this process, the silane gas is efficiently depleted using moderate feed-in power density, thus facilitating up-scaling of the process to large surfaces. As observed in more traditional deposition processes, the deposition rate and performance of device-quality material are limited by the inter-electrode gap of the reactor. We significantly increase the cell performances by reducing this gap. X-ray diffractometry (XRD) and secondary ion mass spectroscopy (SIMS) are used to characterize the microcrystalline material deposited in the modified reactor at a rate of 1 nm/s. Comparison with a microcrystalline process at a low deposition rate demonstrates that the crystallographic orientation of the absorbing layer of the cell and the concentrations of contaminants are strongly correlated and dependent on the process. We use microcrystalline cells with absorber layer grown at a rate of 1 nm/s integrated as bottom cells in amorphous-microcrystalline (micromorph) tandem solar cells using the superstrate configuration. We report an initial efficiency of 10.8% (9.6% stabilized) for a tandem cell with 1.2 cm2 surface. Copyright # 2010 John Wiley & Sons, Ltd
Antibiotic consumption in nursing homes of the Canton of Vaud: trends over the years 2009 - 2014
Background & Objectives: Excessive use of antibiotics in nursing homes was reported in several studies1-3. Surveillance of their use in nursing homes is essential to plan interventions fostering an appropriate use and to measure the impact of these interventions. The aims of the study were to describe the antibiotic consumption in nursing homes of the Canton of Vaud and to examine whether the antibiotic consumption was correlated to the urinary catheter use and to methicillin-resistant Staphylococcus aureus (MRSA) colonization.
Methods: Data on the use of systemic antibiotics (class J01 of WHO Anatomical Therapeutic Chemical (ATC) system, 2015) were collected from the community pharmacies' annual invoice data including 13 nursing homes in 2009. The number of nursing homes in the database increased to 67 in 2014, representing 46% of all nursing homes of the Canton of Vaud and 54% of the available beds. Aggregated data were converted into defined daily doses (DDD) and antibiotic consumption expressed in number of defined daily doses per 1000 beds and per day (DDD/1000B/D). Proportion of urinary catheter use and MRSA colonization data were provided through a point prevalence study.
Results: The total consumption of systemic antibiotics was 52.2 DDD/1000B/D in 2009 and 48.3 in 2014. Beta-lactam antibacterials other than penicillins, macrolides and other antibacterials (including nitrofurantoin) consumption increased resp. by 80%, 45% and 187% between 2009 and 2014, while the use of sulfonamides and trimethoprim decreased by 41%. Penicillin and quinolone use remained relatively stable between 2009 and 2014. Amoxicillin and clavulanic acid (oral) was the most common antibiotic prescribed (31% of the total use), followed by ciprofloxacin (oral) (20%) and nitrofurantoin (10%). Among nursing homes, we reported a large variation in antibiotic consumption from 6.8 to 164.6 DDD/1000B/D in 2014. No correlation was found between global antibiotic consumption and urinary catheter use and between quinolone consumption and proportion of MRSA in 2010 and 2011 (p>0.05).
Discussion & Conclusions: This study is the first that analyzes longitudinal data of antibiotic consumption in nursing homes of the Canton of Vaud. The findings suggest that a large variation in antibiotic consumption exists among nursing homes. Thus, antibiotic stewardship programs should be implemented to promote a more accurate use
The momentum and photon energy dependence of the circular dichroic photoemission in the bulk Rashba semiconductors BiTeX (X = I, Br, Cl)
Bulk Rashba systems BiTeX (X = I, Br, Cl) are emerging as important
candidates for developing spintronics devices, because of the coexistence of
spin-split bulk and surface states, along with the ambipolar character of the
surface charge carriers. The need of studying the spin texture of strongly
spin-orbit coupled materials has recently promoted circular dichroic Angular
Resolved Photoelectron Spectroscopy (cd-ARPES) as an indirect tool to measure
the spin and the angular degrees of freedom. Here we report a detailed photon
energy dependent study of the cd-ARPES spectra in BiTeX (X = I, Br and Cl). Our
work reveals a large variation of the magnitude and sign of the dichroism.
Interestingly, we find that the dichroic signal modulates differently for the
three compounds and for the different spin-split states. These findings show a
momentum and photon energy dependence for the cd-ARPES signals in the bulk
Rashba semiconductor BiTeX (X = I, Br, Cl). Finally, the outcome of our
experiment indicates the important relation between the modulation of the
dichroism and the phase differences between the wave-functions involved in the
photoemission process. This phase difference can be due to initial or final
state effects. In the former case the phase difference results in possible
interference effects among the photo-electrons emitted from different atomic
layers and characterized by entangled spin-orbital polarized bands. In the
latter case the phase difference results from the relative phases of the
expansion of the final state in different outgoing partial waves.Comment: 6 pages, 4 figure
Giant ambipolar Rashba effect in a semiconductor: BiTeI
We observe a giant spin-orbit splitting in bulk and surface states of the
non-centrosymmetric semiconductor BiTeI. We show that the Fermi level can be
placed in the valence or in the conduction band by controlling the surface
termination. In both cases it intersects spin-polarized bands, in the
corresponding surface depletion and accumulation layers. The momentum splitting
of these bands is not affected by adsorbate-induced changes in the surface
potential. These findings demonstrate that two properties crucial for enabling
semiconductor-based spin electronics -- a large, robust spin splitting and
ambipolar conduction -- are present in this material.Comment: 4 pages, 3 figure
Clinical evaluation of IDAS II, a new electronic device enabling drug adherence monitoring.
OBJECTIVE: The goal of this study was to evaluate clinically the acceptability of the IDAS II (Intelligent Drug Administration System), a new electronic device that enables drug adherence monitoring.
METHODS: IDAS II was compared to another electronic monitor, the Medication Event Monitoring System (MEMS) in a randomised two-way cross-over study involving 24 hypertensive patients treated with irbesartan. Patients used each device for 2 months. The main parameter of evaluation was the patients' opinion on both devices. Rates of adherence and blood pressure were also assessed.
RESULTS: Most patients considered both devices to be reliable reminders (IDAS II: 75%;MEMS: 84%, p = ns). Ten patients (42%) preferred the MEMS, while 11 (46%) preferred the IDAS II; three (12%) expressed no preference. Patients found the MEMS device easier to use than the IDAS device (p < 0.001) but appreciated the IDAS blister packs better than the MEMS bulk packaging (p < 0.01). Over the 4-month period, the median "taking adherence" was excellent (99.2%) and comparable with both devices. However, the regularity of drug intake timing was higher with the IDAS II (p < 0.01).
CONCLUSION: IDAS II, a new electronic device enabling drug adherence monitoring without reconditioning of the drugs appears to be a well-accepted device. Overall, practicability and acceptability of the IDAS II and the MEMS device were similar. Thus, IDAS II could be a useful tool for the management of long-term therapies
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