Spectroscopic evidence for temperature-dependent convergence of light and heavy hole valence bands of PbQ (Q=Te, Se, S)

We have conducted temperature dependent Angle Resolved Photoemission Spectroscopy (ARPES) study of the electronic structures of PbTe, PbSe and PbS. Our ARPES data provide direct evidence for the \emph{light} hole upper valence bands (UVBs) and hitherto undetected \emph{heavy} hole lower valence bands (LVBs) in these materials. An unusual temperature dependent relative movement between these bands leads to a monotonic decrease in the energy separation between their maxima with increasing temperature, which is referred as band convergence and has long been believed to be the driving factor behind extraordinary thermoelectric performances of these compounds at elevated temperatures.Comment: 6 pages, 4 figures. arXiv admin note: text overlap with arXiv:1404.180

The inexorable resistance of inertia determines the initial regime of drop coalescence

Drop coalescence is central to diverse processes involving dispersions of drops in industrial, engineering and scientific realms. During coalescence, two drops first touch and then merge as the liquid neck connecting them grows from initially microscopic scales to a size comparable to the drop diameters. The curvature of the interface is infinite at the point where the drops first make contact, and the flows that ensue as the two drops coalesce are intimately coupled to this singularity in the dynamics. Conventionally, this process has been thought to have just two dynamical regimes: a viscous and an inertial regime with a crossover region between them. We use experiments and simulations to reveal that a third regime, one that describes the initial dynamics of coalescence for all drop viscosities, has been missed. An argument based on force balance allows the construction of a new coalescence phase diagram

Formation of beads-on-a-string structures during break-up of viscoelastic filaments

Break-up of viscoelastic filaments is pervasive in both nature and technology. If a filament is formed by placing a drop of saliva between a thumb and forefinger and is stretched, the filament’s morphology close to break-up corresponds to beads of several sizes interconnected by slender threads. Although there is general agreement that formation of such beads-on-a-string (BOAS) structures occurs only for viscoelastic fluids, the underlying physics remains unclear and controversial. The physics leading to the formation of BOAS structures is probed by numerical simulation. Computations reveal that viscoelasticity alone does not give rise to a small, satellite bead between two much larger main beads but that inertia is required for its formation. Viscoelasticity, however, enhances the growth of the bead and delays pinch-off, which leads to a relatively long-lived beaded structure. We also show for the first time theoretically that yet smaller, sub-satellite beads can also form as seen in experiments.National Science Foundation (U.S.). ERC-SOPS (EEC-0540855)Nanoscale Interdisciplinary Research Thrust on 'Directed Self-assembly of Suspended Polymer Fibers' (NSF-DMS0506941

Abstract TP243: Emergency Transport of Stroke Patients in a Rural State: Opportunities for Improvement in Arkansas

Introduction: Time delay is the key obstacle for receiving effective stroke treatment. The requirement for Alteplase therapy to begin within 3 hours of an ischemic stroke onset (4.5 hours off-label) causes treatment ineligibility among many patients, such that only 3-5% receives treatment. Rapid transport to a stroke-care qualified facility is vital. Time and destination data for emergency medical system (EMS) first-responders transporting identified strokes in 2013 were provided by the EMS section of the Arkansas Department of Health and analyzed for regional location, mode of transport, transport time and the destination’s qualification for stroke care. Hypothesis: Rural regional EMS first-responders were transporting patients to non-qualified facilities even when there were nearby stroke-ready specialty centers available. We aimed at identifying potential areas for improvement within the system. Methods: The state’s 75 counties were placed into eight geographical regions (R1-R8). For each region transport times for stroke suspects and the destination’s qualification for stroke care were determined for all EMS 911 ground-transport calls. Destinations were ranked as a Primary Stroke Center (PSC), Acute Stroke Ready Hospital (ASRH), Non-Specialty or unknown Care Facility (NSCF), or out-of-state facility. Results: There were 9,688 verified EMS stroke ground transports with median within-region transport times ranging from 29.5 to 40 minutes. Statewide, only 65 percent of EMS-identified stroke 911-call patients were transported to either PSC (12%) or ASRH (53%) facilities. About one-third of the patients (30.4%) were delivered to NSCFs. In the regions (R6, R8) with the highest stroke suspects’ per-capita, up to 57% of transports were made to NSCFs. Conclusions: As a rural state with few PSCs, Arkansas benefits from a widespread network of ASRHs, yet almost a third of stroke suspects were delivered to NSCFs, where acute stroke therapy rates and outcomes are unknown. Further work is needed to enhance the ASRH network development and utilization, including EMS destination protocols. </jats:p

Abstract TP241: Concordance of Pre-hospital Stroke Recognition by Medical Dispatchers and Paramedics in an Urban County

Background: Immediately after a stroke, the time it takes to reach a designated stroke center can determine the patient’s chances of recovery or permanent disability. In pre-hospital care, the first level of care occurs when 911 is called, second when the paramedics arrive and triage, and third, transport to the nearest primary stroke center (PSC). When emergency medical dispatchers (EMD) initially recognize stroke they provide critical stroke triage codes guiding the paramedic’s decision in appropriate hospital choice, saving time and improving patient recovery. This study assessed EMD and paramedic stroke recognition and performance in an urban area. Hypothesis: EMD recognition of stroke would provide paramedics adequate codes for correct recognition and influence transports to area primary stroke centers (PSCs). Methods: All emergency medical service (EMS) transports in an urban county area (392,664 population) during 2014 were retrospectively analyzed. The transports encompassed True/Negatives, False/Positives, False/Negatives and True/Positives for data on the number and percentages of EMS correctly identified stroke ground transport 911 calls. Dispatch impressions of calls were compared to paramedic decisions and confirmed by hospital ICD-9-CM billing codes 430-438. Transports to area PSC and non-PSC hospitals were determined. Results: Over 12 months, in N=40,171 total transports, EMDs impression of strokes were n=942 with 51.3% confirmed as strokes by paramedics. The other 47.6% of calls reported as strokes by EMDs were coded by paramedics as syncope/fainting, altered level of consciousness, abdominal pain, diabetic, behavioral, cardiac rhythm disturbance and seizures. Paramedic reported strokes were coded by dispatchers as 52.0% strokes/CVA or as headaches, sick person, unconscious/fainting, fall victim, chest pain, convulsions/seizures and breathing problems. Significantly more stroke-related deliveries were made to PSCs (55%, p&lt;0.001) than other area facilities. Hospital confirmation by discharge data services of paramedic coded strokes provided a true positive predictive value of 44.8% and sensitivity of 25%. Conclusion: EMS dispatch and paramedic services could benefit from stroke recognition education. </jats:p