673 research outputs found
Cold inelastic collisions between lithium and cesium in a two-species magneto-optical trap
We investigate collisional properties of lithium and cesium which are
simultaneously confined in a combined magneto-optical trap. Trap-loss
collisions between the two species are comprehensively studied. Different
inelastic collision channels are identified, and inter-species rate
coefficients as well as cross sections are determined. It is found that loss
rates are independent of the optical excitation of Li, as a consequence of the
repulsive Li-Cs interaction. Li and Cs loss by inelastic inter-species
collisions can completely be attributed to processes involving optically
excited cesium (fine-structure changing collisions and radiative escape). By
lowering the trap depth for Li, an additional loss channel of Li is observed
which results from ground-state Li-Cs collisions changing the hyperfine state
of cesium.Comment: submitted to Euro. Phys. J. D, special issue on Laser Cooling and
Trappin
Nuclear Resonance Vibrational Spectroscopy of Iron Sulfur Proteins
Nuclear inelastic scattering in conjunction with density functional theory
(DFT) calculations has been applied for the identification of vibrational modes
of the high-spin ferric and the high-spin ferrous iron-sulfur center of a
rubredoxin-type protein from the thermophylic bacterium Pyrococcus abysii
Density functional theory calculations and vibrational spectroscopy on iron spin-crossover compounds
Iron complexes with a suitable ligand field undergo spin-crossover (SCO),
which can be induced reversibly by temperature, pressure or even light.
Therefore, these compounds are highly interesting candidates for optical
information storage, for display devices and pressure sensors. The SCO
phenomenon can be conveniently studied by spectroscopic techniques like Raman
and infrared spectroscopy as well as nuclear inelastic scattering, a technique
which makes use of the M\"ossbauer effect. This review covers new developments
which have evolved during the last years like, e.g. picosecond infrared
spectroscopy and thin film studies but also gives an overviewon newtechniques
for the theoretical calculation of spin transition phenomena and vibrational
spectroscopic data of SCO complexes
Dogs distinguish human intentional and unintentional action
When dogs interact with humans, they often show appropriate reactions to human intentional action. But it is unclear from these everyday observations whether the dogs simply respond to the action outcomes or whether they are able to discriminate between different categories of actions. Are dogs able to distinguish intentional human actions from unintentional ones, even when the action outcomes are the same? We tested dogs’ ability to discriminate these action categories by adapting the so-called “Unwilling vs. Unable” paradigm. This paradigm compares subjects’ reactions to intentional and unintentional human behaviour. All dogs received three conditions: In the unwilling-condition, an experimenter intentionally withheld a reward from them. In the two unable-conditions, she unintentionally withheld the reward, either because she was clumsy or because she was physically prevented from giving the reward to the dog. Dogs clearly distinguished in their spontaneous behaviour between unwilling- and unable-conditions. This indicates that dogs indeed distinguish intentional actions from unintentional behaviour. We critically discuss our findings with regard to dogs’ understanding of human intentional action.Results - Analysis of waiting - Other behavioural reactions Discussion Methods - Ethical statement - Subjects - Experimental set‑up - Procedure - Codin
Elucidating the structural composition of a Fe-N-C catalyst by nuclear and electron resonance techniques
Fe–N–C catalysts are very promising materials for fuel cells and metal–air batteries. This work gives fundamental insights into the structural composition of an Fe–N–C catalyst and highlights the importance of an in‐depth characterization. By nuclear‐ and electron‐resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of α‐iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end‐on bonded oxygen as one of the axial ligands
Certainty ranges facilitated explicit and transparent judgments regarding evidence credibility
Objectives: The Grading of Recommendations Assessment, Development and Evaluation approach to rating certainty of evidence includes five domains of reasons for rating down certainty. Only one of these, precision, is easily amenable through the confidence interval to quantitation. The other four (risk of bias, inconsistency, indirectness, and publication bias) are not. Nevertheless, conceptually, one could consider a quantified "certainty range" within which the true effect lies. The certainty range would be at least as wide as the confidence interval and would expand with each additional reason for uncertainty. Study Design and Setting: We have applied this concept to rating the certainty of evidence in the baseline risk of venous thromboembolism (VTE) and bleeding in patients undergoing urological surgery. We considered rating up moderate or low quality evidence when the net benefit of VTE prophylaxis was unequivocally positive, that is, when the smallest plausible value of VTE reduction was greater than the largest plausible value of increased bleeding. To establish whether the net benefit was unequivocally positive, we expanded the range of plausible values by 20% for each of the four nonquantitative domains in which there were serious limitations. Results: We present how we applied these methods to examples of open radical cystectomy and laparoscopic partial nephrectomy. In high-VTE risk laparoscopic partial nephrectomy patients and high-and medium-VTE risk open radical cystectomy patients, results proved robust to expanded certainty intervals, justifying rating up quality of evidence. In low -risk patients, the results were not robust, and rating up was therefore not appropriate. Conclusion: This work represents the first empirical application in a decision -making context of the previously suggested concept of certainty ranges and should stimulate further exploration of the associated theoretical and practical issues. (C) 2018 Elsevier Inc. All rights reserved.Peer reviewe
Developing clinical practice guidelines: target audiences, identifying topics for guidelines, guideline group composition and functioning and conflicts of interest
Clinical practice guidelines are one of the foundations of efforts to improve health care. In 1999, we authored a paper about methods to develop guidelines. Since it was published, the methods of guideline development have progressed both in terms of methods and necessary procedures and the context for guideline development has changed with the emergence of guideline clearing houses and large scale guideline production organisations (such as the UK National Institute for Health and Clinical Excellence). It therefore seems timely to, in a series of three articles, update and extend our earlier paper. In this first paper we discuss: the target audience(s) for guidelines and their use of guidelines; identifying topics for guidelines; guideline group composition (including consumer involvement) and the processes by which guideline groups function and the important procedural issue of managing conflicts of interest in guideline development
Resonator-Enhanced Optical Dipole Trap for Fermionic Lithium Atoms
We demonstrate a novel optical dipole trap which is based on the enhancement
of the optical power density of a Nd:YAG laser beam in a resonator. The trap is
particularly suited for experiments with ultracold gases, as it combines a
potential depth of order 1 mK with storage times of several tens of seconds. We
study the interactions in a gas of fermionic lithium atoms in our trap and
observe the influence of spin-changing collisions and off-resonant photon
scattering. A key element in reaching long storage times is an ultra-low noise
laser. The dependence of the storage time on laser noise is investigated.Comment: 4 pages 3 figures Revised 17.07.2001; Corrected calibration of noise
measm
Interpreting the results of patient reported outcome measures in clinical trials: The clinician's perspective
This article deals with the problem of interpreting health-related quality of life (HRQL) outcomes in clinical trials. First, we will briefly describe how dichotomization and item response theory can facilitate interpretation. Based on examples from the medical literature for the interpretation of HRQL scores we will show that dichotomies may help clinicians understand information provided by HRQL instruments in RCTs. They can choose thresholds to calculate proportions of patients benefiting based on absolute scores or change scores. For example, clinicians interpreting clinical trial results could consider the difference in the proportion of patients who achieve a mean score of 50 before and after an intervention on a scale from 1 to 100. For the change score approach, they could consider the proportion of patients who have changed by a score of 5 or more. Finally, they can calculate the proportion of patients benefiting and transform these numbers into a number needed to treat or natural frequencies. Second, we will describe in more detail an approach to the interpretation of HRQL scores based on the minimal important difference (MID) and proportions. The MID is the smallest difference in score in the outcome of interest that informed patients or informed proxies perceive as important, either beneficial or harmful, and that would lead the patient or clinician to consider a change in the management. Any change in management will depend on the downsides, including cost and inconvenience, associated with the intervention. Investigators can help with the interpretation of HRQL scores by determining the MID of an HRQL instrument and provide mean differences in relation to the MID. For instance, for an MID of 0.5 on a seven point scale investigators could provide the mean change on the instrument as well as the proportion of patients with scores greater than the MID. Thus, there are several steps investigators can take to facilitate this process to help bringing HRQL information closer to the bedside
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