3,007 research outputs found
Finite element model to simulate impact on a soft tissue simulant
A finite element model of an impact test on a soft tissue simulant, used as part of a shoulder surrogate, was developed in Ansys© LS-DYNA®. The surrogate consisted of a metal hemicylindrical core, with a diameter of 75 mm, covered with a 15 mm thick relaxed muscle simulant. The muscle simulant consisted of a 14 mm thick layer of silicone covered with 1 mm thick chamois leather to represent skin. The material properties of the silicone were obtained via quasi-static compression testing (curve fit with hyperelastic models) and compressive stress relaxation testing (curve fit with a Prony series). Outputs of the finite element models were compared against experimental data from impact tests on the shoulder surrogate at energies of 4.9, 9.8 and 14.7 J. The accuracy of the finite element models was assessed using four parameters: peak impact force, maximum deformation, impact duration and impulse. A 5-parameter Mooney-Rivlin material model combined with a 2-term Prony series was found to be suitable for modelling the soft tissue simulant of the shoulder surrogate. This model had under 10% overall mean deviation from the experimental values for the four assessment parameters across the three impact energies. Overall, the model provided a repeatable test method that can be adapted to help predict injuries to skin tissue and the performance/efficacy of personal protective equipment
Cotunneling-mediated transport through excited states in the Coulomb blockade regime
We present finite bias transport measurements on a few-electron quantum dot.
In the Coulomb blockade regime, strong signatures of inelastic cotunneling
occur which can directly be assigned to excited states observed in the
non-blockaded regime. In addition, we observe structures related to sequential
tunneling through the dot, occuring after it has been excited by an inelastic
cotunneling process. We explain our findings using transport calculations
within the real-time Green's function approach, including diagrams up to fourth
order in the tunneling matrix elements.Comment: 4 pages, 3 figure
Universal behavior of quantum Green's functions
We consider a general one-particle Hamiltonian H = - \Delta_r + u(r) defined
in a d-dimensional domain. The object of interest is the time-independent Green
function G_z(r,r') = . Recently, in one dimension (1D),
the Green's function problem was solved explicitly in inverse form, with
diagonal elements of Green's function as prescribed variables. The first aim of
this paper is to extract from the 1D inverse solution such information about
Green's function which cannot be deduced directly from its definition. Among
others, this information involves universal, i.e. u(r)-independent, behavior of
Green's function close to the domain boundary. The second aim is to extend the
inverse formalism to higher dimensions, especially to 3D, and to derive the
universal form of Green's function for various shapes of the confining domain
boundary.Comment: 46 pages, the shortened version submitted to J. Math. Phy
Effective Vortex Pinning in MgB2 thin films
We discuss pinning properties of MgB2 thin films grown by pulsed-laser
deposition (PLD) and by electron-beam (EB) evaporation. Two mechanisms are
identified that contribute most effectively to the pinning of vortices in
randomly oriented films. The EB process produces low defected crystallites with
small grain size providing enhanced pinning at grain boundaries without
degradation of Tc. The PLD process produces films with structural disorder on a
scale less that the coherence length that further improves pinning, but also
depresses Tc
Acclimation of adaxial and abaxial stomatal structure and function to increased CO2 availability in maize leaves
Pharmacological interventions for sleepiness and sleep disturbances caused by shift work
BACKGROUND: Shift work results in sleep-wake disturbances, which cause sleepiness during night shifts and reduce sleep length and quality in daytime sleep after the night shift. In its serious form it is also called shift work sleep disorder. Various pharmacological products are used to ameliorate symptoms of sleepiness or poor sleep length and quality. OBJECTIVES: To evaluate the effects of pharmacological interventions to reduce sleepiness or to improve alertness at work and decrease sleep disturbances whilst of work, or both, in workers undertaking shift work. METHODS: Search methods: We searched CENTRAL, MEDLINE, EMBASE, PubMed and PsycINFO up to 20 September 2013 and ClinicalTrials.gov up to July 2013. We also screened reference lists of included trials and relevant reviews. Selection criteria: We included all eligible randomised controlled trials (RCTs), including cross-over RCTs, of pharmacological products among workers who were engaged in shift work (including night shifts) in their present jobs and who may or may not have had sleep problems. Primary outcomes were sleep length and sleep quality while of work, alertness and sleepiness, or fatigue at work. Data collection and analysis: Two authors independently selected studies, extracted data and assessed risk of bias in included trials. We performed meta-analyses where appropriate. MAIN RESULTS: We included 15 randomised placebo-controlled trials with 718 participants. Nine trials evaluated the effect of melatonin and two the effect of hypnotics for improving sleep problems. One trial assessed the effect of modafinil, two of armodafinil and one examined cafeine plus naps to decrease sleepiness or to increase alertness
Research data supporting the publication "Under Pressure: Offering Fundamental Insight into Structural Changes on Ball Milling Battery Materials"
Data depository includes the following:
Powder X-ray diffraction (PXRD) of the ball-milled Li2MoO4 (at 40Hz and 50Hz, with varying ball size of 7 and 10 mm).
PXRD of H-Nb2O5 ball-milled at 40 Hz and 50 Hz (7 mm ball)
Electrochemical data of Li2MoO4 and Li2MnO3 (ball-milled samples).
TEM of Li2MoO4 and the ball-milled equivalent.
Li and Mo NMR of Li2MoO4 and the ball-milled equivalent
A Byzantine-Fault Tolerant Self-Stabilizing Protocol for Distributed Clock Synchronization Systems
Embedded distributed systems have become an integral part of safety-critical computing applications, necessitating system designs that incorporate fault tolerant clock synchronization in order to achieve ultra-reliable assurance levels. Many efficient clock synchronization protocols do not, however, address Byzantine failures, and most protocols that do tolerate Byzantine failures do not self-stabilize. Of the Byzantine self-stabilizing clock synchronization algorithms that exist in the literature, they are based on either unjustifiably strong assumptions about initial synchrony of the nodes or on the existence of a common pulse at the nodes. The Byzantine self-stabilizing clock synchronization protocol presented here does not rely on any assumptions about the initial state of the clocks. Furthermore, there is neither a central clock nor an externally generated pulse system. The proposed protocol converges deterministically, is scalable, and self-stabilizes in a short amount of time. The convergence time is linear with respect to the self-stabilization period. Proofs of the correctness of the protocol as well as the results of formal verification efforts are reported
Protein-losing enteropathy after the Fontan operation
AbstractPatients were observed after the Fontan operation to determine the frequency and severity of protein-losing enteropathy. A total of 427 patients who survived for 30 days after the Fontan operation, performed between 1973 and January 1987, were analyzed and, thus far, protein-losing enteropathy has developed in 47 of 427. The cumulative risk for the development of protein-losing enteropathy by 10 years was 13.4% among 30-day survivors, and 5-year survival after the diagnosis was 46%. Hemodynamic studies done coincident with the diagnosis of protein-losing enteropathy have shown increased systemic venous pressure, decreased cardiac index, increased pulmonary vascular resistance, and increased ventricular end-diastolic pressure. Medical management of protein-losing enteropathy was only partially successful. Statistical analysis has shown that factors related to protein-losing enteropathy were ventricular anatomy, increased preoperative ventricular end-diastolic pressure, longer operative bypass time, increased length of hospital stay, and postoperative renal failure. This study suggests that scrupulous selection of cases for the Fontan operation is mandatory and that certain perioperative factors may predispose to this serious complication of the Fontan procedure. (J THORAC CARDIOVASC SURG 1996;112:672-80
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