116 research outputs found
Cold Atom Physics Using Ultra-Thin Optical Fibers: Light-Induced Dipole Forces and Surface Interactions
The strong evanescent field around ultra-thin unclad optical fibers bears a
high potential for detecting, trapping, and manipulating cold atoms.
Introducing such a fiber into a cold atom cloud, we investigate the interaction
of a small number of cold Caesium atoms with the guided fiber mode and with the
fiber surface. Using high resolution spectroscopy, we observe and analyze
light-induced dipole forces, van der Waals interaction, and a significant
enhancement of the spontaneous emission rate of the atoms. The latter can be
assigned to the modification of the vacuum modes by the fiber.Comment: 4 pages, 4 figure
Implementation of a Standardized Handoff System for a General Surgery Residency Program
Introduction:
The I-PASS Handoff Bundle is an evidence based standardized set of educational materials designed to decrease handoff failures in patient care.
Two of every three sentinel events , the most serious events reported to the Joint Commission, are due to failures of communication, including miscommunication during patient care handoffs.
Implementation of the I-PASS method results in decreased medical errors and preventable adverse events
There are few studies that evaluate this validated method in the context of a General Surgery resident program
We aim to implement the I-PASS system into the transition of care process for General Surgery residents at our institution, and to analyze of the quality of the handoff process before and after the implementation.https://jdc.jefferson.edu/patientsafetyposters/1047/thumbnail.jp
Selective Reflection Spectroscopy on the UV Third Resonance Line of Cs : Simultaneous Probing of a van der Waals Atom-Surface Interaction Sensitive to Far IR Couplings and of Interatomic Collisions
We report on the analysis of FM selective reflection experiments on the
6S1/2->8P3/2 transition of Cs at 388 nm, and on the measurement of the surface
van der Waals interaction exerted by a sapphire interface on Cs(8P3/2). Various
improvements in the systematic fitting of the experiments have permitted to
supersede the major difficulty of a severe overlap of the hyperfine components,
originating on the one hand in a relatively small natural structure, and on the
other hand on a large pressure broadening imposed by the high atomic density
needed for the observation of selective reflection on a weak transition. The
strength of the van der Waals surface interaction is evaluated to be 7310
kHz.m3. An evaluation of the pressure shift of the transition is also
provided as a by-product of the measurement. We finally discuss the
significance of an apparent disagreement between the experimental measurement
of the surface interaction, and the theoretical value calculated for an
electromagnetic vacuum at a null temperature. The possible influence of the
thermal excitation of the surface is evoked, because, the dominant
contributions to the vW interaction for Cs(8P3/2) lie in the far infrared
range.Comment: submitted to Laser Physics - issue in the memory of Herbert Walther
Phenotypic spectrum of MFN2 mutations in the Spanish population
INTRODUCTION: The most common form of axonal Charcot-Marie-Tooth (CMT) disease is type 2A, caused by mutations in the mitochondrial GTPase mitofusin 2 (MFN2). OBJECTIVE: The objective of our study is to establish the incidence of MFN2 mutations in a cohort of Spanish patients with axonal CMT neuropathy. MATERIAL AND METHODS: Eighty-five families with suspected axonal CMT were studied. All MFN2 exons were studied through direct sequencing. A bioenergetics study in fibroblasts was conducted using a skin biopsy taken from a patient with an Arg468His mutation. RESULTS: Twenty-four patients from 14 different families were identified with nine different MFN2 mutations (Arg94Trp, Arg94Gln, Ile203Met, Asn252Lys, Gln276His, Gly296Arg, Met376Val, Arg364Gln and Arg468His). All mutations were found in the heterozygous state and four of these mutations had not been described previously. MFN2 mutations were responsible for CMT2 in 16% +/- 7% of the families studied and in 30.8 +/- 14.2% (12/39) of families with known dominant inheritance. The bioenergetic studies in fibroblasts show typical results of MFN2 patients with a mitochondrial coupling defect (ATP/O) and an increase of the respiration rate linked to complex II. CONCLUSION: It is concluded that mutations in MFN2 are the most frequent cause of CMT2 in this region. The Arg468His mutation was the most prevalent (6/14 families), and our study confirms that it is pathological, presenting as a neuropathy in a mild to moderate degree. This study also demonstrates the value of MFN2 studies in cases of congenital axonal neuropathy, especially in cases of dominant inheritance, severe clinical symptoms or additional symptoms such as optic atrophy
Observation of modified radiative properties of cold atoms in vacuum near a dielectric surface
We have observed a distance-dependent absorption linewidth of cold Rb
atoms close to a dielectric-vacuum interface. This is the first observation of
modified radiative properties in vacuum near a dielectric surface. A cloud of
cold atoms was created using a magneto-optical trap (MOT) and optical molasses
cooling. Evanescent waves (EW) were used to observe the behavior of the atoms
near the surface. We observed an increase of the absorption linewidth with up
to 25% with respect to the free-space value. Approximately half the broadening
can be explained by cavity-quantum electrodynamics (CQED) as an increase of the
natural linewidth and inhomogeneous broadening. The remainder we attribute to
local Stark shifts near the surface. By varying the characteristic EW length we
have observed a distance dependence characteristic for CQED.Comment: 6 pages, 6 figures, some minor revision
L\'evy flights of photons in hot atomic vapours
Properties of random and fluctuating systems are often studied through the
use of Gaussian distributions. However, in a number of situations, rare events
have drastic consequences, which can not be explained by Gaussian statistics.
Considerable efforts have thus been devoted to the study of non Gaussian
fluctuations such as L\'evy statistics, generalizing the standard description
of random walks. Unfortunately only macroscopic signatures, obtained by
averaging over many random steps, are usually observed in physical systems. We
present experimental results investigating the elementary process of anomalous
diffusion of photons in hot atomic vapours. We measure the step size
distribution of the random walk and show that it follows a power law
characteristic of L\'evy flights.Comment: This final version is identical to the one published in Nature
Physic
Selective Reflection Spectroscopy at the Interface between a Calcium Fluoride Window and Cs Vapour
A special vapour cell has been built, that allows the measurement of the
atom-surface van der Waals interaction exerted by a CaF2 window at the
interface with Cs vapour. Mechanical and thermal fragility of fluoride windows
make common designs of vapour cells unpractical, so that we have developed an
all-sapphire sealed cell with an internal CaF2 window. Although impurities were
accidentally introduced when filling-up the prototype cell, leading to a
line-broadening and shift, the selective reflection spectrum on the Cs D1 line
(894 nm) makes apparent the weak van der Waals surface interaction. The
uncertainties introduced by the effects of these impurities in the van der
Waals measurement are nearly eliminated when comparing the selective reflection
signal at the CaF2 interface of interest, and at a sapphire window of the same
cell. The ratio of the interaction respectively exerted by a sapphire interface
and a CaF2 interface is found to be 0.55 0.25, in good agreement with the
theoretical evaluation of ~0.67.Comment: soumis \`a Appl Phys B MS 4734
The accumulation of assembly intermediates of the mitochondrial complex I matrix arm is reduced by limiting glucose uptake in a neuronal-like model of MELAS syndrome
Ketogenic diet (KD) which combined carbohydrate restriction and the addition of ketone bodies has emerged as an alternative metabolic intervention used as an anticonvulsant therapy or to treat different types of neurological or mitochondrial disorders including MELAS syndrome. MELAS syndrome is a severe mitochondrial disease mainly due to the m.3243AâŻ>âŻG mitochondrial DNA mutation. The broad success of KD is due to multiple beneficial mechanisms with distinct effects of very low carbohydrates and ketones. To evaluate the metabolic part of carbohydrate restriction, transmitochondrial neuronal-like cybrid cells carrying the m.3243AâŻ>âŻG mutation, shown to be associated with a severe complex I deficiency was exposed during 3âŻweeks to glucose restriction. Mitochondrial enzyme defects were combined with an accumulation of complex I (CI) matrix intermediates in the untreated mutant cells, leading to a drastic reduction in CI driven respiration. The severe reduction of CI was also paralleled in post-mortem brain tissue of a MELAS patient carrying high mutant load. Importantly, lowering significantly glucose concentration in cell culture improved CI assembly with a significant reduction of matrix assembly intermediates and respiration capacities were restored in a sequential manner. In addition, OXPHOS protein expression and mitochondrial DNA copy number were significantly increased in mutant cells exposed to glucose restriction. The accumulation of CI matrix intermediates appeared as a hallmark of MELAS pathophysiology highlighting a critical pathophysiological mechanism involving CI disassembly, which can be alleviated by lowering glucose fuelling and the induction of mitochondrial biogenesis, emphasizing the usefulness of metabolic interventions in MELAS syndrome
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