1,101 research outputs found
Unusual Shubnikov-de Haas oscillations in BiTeCl
We report measurements of Shubnikov-de Haas (SdH) oscillations in single
crystals of BiTeCl at magnetic fields up to 31 T and at temperatures as low as
0.4 K. Two oscillation frequencies were resolved at the lowest temperatures,
Tesla and Tesla. We also measured the
infrared optical reflectance and Hall effect; we
propose that the two frequencies correspond respectively to the inner and outer
Fermi sheets of the Rashba spin-split bulk conduction band. The bulk carrier
concentration was cm and the effective
masses for the inner and for the
outer sheet. Surprisingly, despite its low effective mass, we found that the
amplitude of is very rapidly suppressed with increasing temperature,
being almost undetectable above K
Ultrafast photodoping and effective Fermi-Dirac distribution of the Dirac particles in Bi2Se3
We exploit time- and angle- resolved photoemission spectroscopy to determine
the evolution of the out-of-equilibrium electronic structure of the topological
insulator Bi2Se. The response of the Fermi-Dirac distribution to ultrashort IR
laser pulses has been studied by modelling the dynamics of the hot electrons
after optical excitation. We disentangle a large increase of the effective
temperature T* from a shift of the chemical potential mu*, which is consequence
of the ultrafast photodoping of the conduction band. The relaxation dynamics of
T* and mu* are k-independent and these two quantities uniquely define the
evolution of the excited charge population. We observe that the energy
dependence of the non-equilibrium charge population is solely determined by the
analytical form of the effective Fermi-Dirac distribution.Comment: 5 Pages, 3 Figure
Evidence of reduced surface electron-phonon scattering in the conduction band of Bi_{2}Se_{3} by non-equilibrium ARPES
The nature of the Dirac quasiparticles in topological insulators calls for a
direct investigation of the electron-phonon scattering at the \emph{surface}.
By comparing time-resolved ARPES measurements of the TI Bi_{2}Se_{3} with
different probing depths we show that the relaxation dynamics of the electronic
temperature of the conduction band is much slower at the surface than in the
bulk. This observation suggests that surface phonons are less effective in
cooling the electron gas in the conduction band.Comment: 5 pages, 3 figure
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
Spin-resolved electronic response to the phase transition in MoTe
The semimetal MoTe is studied by spin- and angle- resolved photoemission
spectroscopy to probe the detailed electronic structure underlying its broad
range of response behavior. A novel spin-texture is uncovered in the bulk Fermi
surface of the non-centrosymmetric structural phase that is consistent with
first-principles calculations. The spin-texture is three-dimensional, both in
terms of momentum dependence and spin-orientation, and is not completely
suppressed above the centrosymmetry-breaking transition temperature. Two types
of surface Fermi arc are found to persist well above the transition
temperature. The appearance of a large Fermi arc depends strongly on thermal
history, and the electron quasiparticle lifetimes are greatly enhanced in the
initial cooling. The results indicate that polar instability with strong
electron-lattice interactions exists near the surface when the bulk is largely
in a centrosymmetric phase
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
Medication reviews led by community pharmacists in Switzerland: a qualitative survey to evaluate barriers and facilitators.
1) To evaluate the participation rate and identify the practical barriers to implementing a community pharmacist-led medication review service in francophone Switzerland and, 2) To assess the effectiveness of external support.
A qualitative survey was undertaken to identify barriers to patient inclusion and medication review delivery in daily practice among all contactable independent pharmacists working in francophone Switzerland (n=78) who were members of a virtual chain (pharmacieplus), regardless of their participation in a simultaneous cross-sectional study. This study analyzed the dissemination of a medication review service including a prescription and drug utilization review with access to clinical data, a patient interview and a pharmaceutical report to the physicians. In addition, we observed an exploratory and external coaching for pharmacists that we launched seven months after the beginning of the cross-sectional study.
Poor motivation on the part of pharmacists and difficulties communicating with physicians and patients were the primary obstacles identified. Lack of time and lack of self-confidence in administering the medication review process were the most commonly perceived practical barriers to the implementation of the new service. The main facilitators to overcome these issues may be well-planned workflow organization techniques, strengthened by an adequate remuneration scheme and a comprehensive and practice-based training course that includes skill-building in pharmacotherapy and communication. External support may partially compensate for a weak organizational framework.
To facilitate the implementation of a medication review service, a strong local networking with physicians, an effective workflow management and a practice- and communications-focused training for pharmacists and their teams seem key elements required. External support can be useful to help some pharmacists improve their service management skills. Adequate remuneration seems necessary to encourage initial investments to provide such a service. Future research in this area may help improve the process and design of training programs, as well as the monitoring of implementation for each new pharmaceutical service
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
Momentum resolved spin dynamics of bulk and surface excited states in the topological insulator
The prospective of optically inducing a spin polarized current for spintronic
devices has generated a vast interest in the out-of-equilibrium electronic and
spin structure of topological insulators (TIs). In this Letter we prove that
only by measuring the spin intensity signal over several order of magnitude in
spin, time and angle resolved photoemission spectroscopy (STAR-PES) experiments
is it possible to comprehensively describe the optically excited electronic
states in TIs materials. The experiments performed on
reveal the existence of a Surface-Resonance-State in the 2nd bulk band gap
interpreted on the basis of fully relativistic ab-initio spin resolved
photoemission calculations. Remarkably, the spin dependent relaxation of the
hot carriers is well reproduced by a spin dynamics model considering two
non-interacting electronic systems, derived from the excited surface and bulk
states, with different electronic temperatures.Comment: 5 pages and 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
- …