An Unsplit Godunov Method for Ideal MHD via Constrained Transport in Three Dimensions

We present a single step, second-order accurate Godunov scheme for ideal MHD which is an extension of the method described by Gardiner & Stone (2005) to three dimensions. This algorithm combines the corner transport upwind (CTU) method of Colella for multidimensional integration, and the constrained transport (CT) algorithm for preserving the divergence-free constraint on the magnetic field. We describe the calculation of the PPM interface states for 3D ideal MHD which must include multidimensional ``MHD source terms'' and naturally respect the balance implicit in these terms by the ${\bf\nabla\cdot B}=0$ condition. We compare two different forms for the CTU integration algorithm which require either 6- or 12-solutions of the Riemann problem per cell per time-step, and present a detailed description of the 6-solve algorithm. Finally, we present solutions for test problems to demonstrate the accuracy and robustness of the algorithm.Comment: Extended version of the paper accepted for publication in JC

Surface detonation in type Ia supernova explosions?

We explore the evolution of thermonuclear supernova explosions when the progenitor white dwarf star ignites asymmetrically off-center. Several numerical simulations are carried out in two and three dimensions to test the consequences of different initial flame configurations such as spherical bubbles displaced from the center, more complex deformed configurations, and teardrop-shaped ignitions. The burning bubbles float towards the surface while releasing energy due to the nuclear reactions. If the energy release is too small to gravitationally unbind the star, the ash sweeps around it, once the burning bubble approaches the surface. Collisions in the fuel on the opposite side increase its temperature and density and may -- in some cases -- initiate a detonation wave which will then propagate inward burning the core of the star and leading to a strong explosion. However, for initial setups in two dimensions that seem realistic from pre-ignition evolution, as well as for all three-dimensional simulations the collimation of the surface material is found to be too weak to trigger a detonation.Comment: 5 pages, 3 figures, in: Proceedings of the SciDAC 2006 Meeting, Denver June 25-26 2006, also available at http://herald.iop.org/jpcs46/m51/gbr//link/40

Innovative Approaches to Emergency Medical Services Fellowship Challenges

Introduction: Since the development of an Accreditation Council of Graduate Medical Education (ACGME)-accredited emergency medical services (EMS) fellowship, there has been little published literature on effective methods of content delivery or training modalities. Here we explore a variety of innovative approaches to the development and revision of the EMS fellowship curriculum.Methods: Three academic, university-based ACGME-accredited EMS fellowship programs each implemented an innovative change to their existing training curricula. These changes included the following: a novel didactic curriculum delivery modality and evaluation; implementation of a distance education program to improve EMS fellows’ rural EMS experiences; and modification of an existing EMS fellowship curriculum to train a non-emergency medicine physician.Results: Changes made to each of the above EMS fellowship programs addressed unique challenges, demonstrating areas of success and promise for more generalized implementation of these curricula. Obstacles remain in tailoring the described curricula to the needs of each unique institution and system.Conclusion: Three separate curricula and program changes were implemented to overcome specific challenges and achieve educational goals. It is our hope that our shared experiences will enable others in addressing common barriers to teaching the EMS fellowship core content and share similar innovative approaches to educational challenges

Spin 0 and spin 1/2 particles in a constant scalar-curvature background

We study the Klein-Gordon and Dirac equations in the presence of a background metric ds^2 = -dt^2 + dx^2 + e^{-2gx}(dy^2 + dz^2) in a semi-infinite lab (x>0). This metric has a constant scalar curvature R=6g^2 and is produced by a perfect fluid with equation of state p=-\rho /3. The eigenfunctions of spin-0 and spin-1/2 particles are obtained exactly, and the quantized energy eigenvalues are compared. It is shown that both of these particles must have nonzero transverse momentum in this background. We show that there is a minimum energy E^2_{min}=m^2c^4 + g^2c^2\hbar^2$ for bosons E_{KG} > E_{min}, while the fermions have no specific ground state E_{Dirac}>mc^2.Comment: LateX, 10 page

Spin 0 and spin 1/2 quantum relativistic particles in a constant gravitational field

The Klein-Gordon and Dirac equations in a semi-infinite lab ($x > 0$), in the background metric \ds^2 = u^2(x) (-\dt^2 + \dx^2) + \dy^2 + \dz^2, are investigated. The resulting equations are studied for the special case $u(x) = 1 + g x$. It is shown that in the case of zero transverse-momentum, the square of the energy eigenvalues of the spin-1/2 particles are less than the squares of the corresponding eigenvalues of spin-0 particles with same masses, by an amount of $mg\hbar c$. Finally, for nonzero transverse-momentum, the energy eigenvalues corresponding to large quantum numbers are obtained, and the results for spin-0 and spin-1/2 particles are compared to each other.Comment: 12 pages, LaTeX 2

Monitoring prohemostatic treatment in bleeding patients

Acutely bleeding patients are commonly found in the trauma and major surgery scenarios. They require prompt and effective treatment to restore an adequate hemostatic pattern, to avoid serious and sometimes life-threatening complications.Different prohemostatic treatments are available, including allogeneic blood derivatives (fresh frozen plasma, platelet concentrates, and cryoprecipitates), prothrombin complex concentrates, specific coagulation factors (fibrinogen, recombinant factor XIII, recombinant activated factor VII), and drugs (protamine for patients under heparin treatment, desmopressin, antifibrinolytics).For decades, prohemostatic treatment of the acutely bleeding patient was based on empirical strategies and clinical judgment, both in terms of a correct diagnosis of the mechanism(s) leading to bleeding, and of an assessment of the effects of the treatment. This empirical strategy may lead to excessive or unnecessary use of allogeneic blood products, as well as to an incorrect, inefficacious, or even dangerous treatment. Different monitoring devices are nowadays available for guiding the diagnostic and therapeutic decision-making process in an acutely bleeding patient. This review addresses the available tools for monitoring prohemostatic treatment of the bleeding patient, with a specific respect for point-of-care tests (thromboelastography, thromboelastometry, platelet function tests, and heparin monitoring systems) at the light of the existing evidence

Continuous flow synthesis of heterocycles: A recent update on the flow synthesis of indoles

Indole derivatives are among the most useful and interesting heterocycles employed in drug discovery and medicinal chemistry. In addition, flow chemistry and flow technology are changing the synthetic paradigm in the field of modern synthesis. In this review, the role of flow technology in the preparation of indole derivatives is showcased. Selected examples have been described with the aim to provide readers with an overview on the tactics and technologies used for targeting indole scaffolds

Multidimensional hydrodynamic simulations of the hydrogen injection flash

The injection of hydrogen into the convection shell powered by helium burning during the core helium flash is commonly encountered during the evolution of metal-free and extremely metal-poor low-mass stars. With specifically designed multidimensional hydrodynamic simulations, we aim to prove that an entropy barrier is no obstacle for the growth of the helium-burning shell convection zone in the helium core of a metal-rich Pop I star, i.e. convection can penetrate into the hydrogen-rich layers for these stars, too. We further study whether this is also possible in one-dimensional stellar evolutionary calculations. Our hydrodynamical simulations show that the helium-burning shell convection zone in the helium core moves across the entropy barrier and reaches the hydrogen-rich layers. This leads to mixing of protons into the hotter layers of the core and to a rapid increase of the nuclear energy production at the upper edge of the helium-burning convection shell - the hydrogen injection flash. As a result a second convection zone appears in the hydrogen-rich layers. Contrary to 1D models, the entropy barrier separating the two convective shells from each other is largely permeable to chemical transport when allowing for multidimensional flow, and consequently, hydrogen is continuously mixed deep into the helium core. We find it difficult to achieve such a behavior in one-dimensional stellar evolutionary calculations.Comment: 8 pages, 8 figures - accepted for publication in Astronomy and Astrophysics. Animations related to the manuscript can be downloaded from http://www-astro.ulb.ac.be/~mocak/index.php/Main/AnimationsHeFlas

Evidence on Problematic Online Gaming and Social Anxiety over the Past Ten Years: a Systematic Literature Review

Purpose of Review: The present study aimed to review the literature concerning the relationship between problematic online gaming (POG) and social anxiety, taking into account the variables implicated in this relationship. This review included studies published between 2010 and 2020 that were indexed in major databases with the following keywords: Internet gaming, disorder, addiction, problematic, social phobia, and social anxiety. Recent Findings: In recent years, scientific interest in POG has grown dramatically. Within this prolific research field, difficulties associated with social anxiety have been increasingly explored in relation to POG. Indeed, evidence showed that individuals who experience social anxiety are more exposed to the risk of developing an excessive or addictive gaming behavior. Summary: A total of 30 studies satisfied the initial inclusion criteria and were included in the present literature review. Several reviewed studies found a strong association between social anxiety and online gaming disorder. Furthermore, the relationships among social anxiety, POG, age, and psychosocial and comorbid factors were largely explored. Overall, the present review showed that socially anxious individuals might perceive online video games as safer social environments than face-to-face interactions, predisposing individuals to the POG. However, in a mutually reinforcing relationship, individuals with higher POG seem to show higher social anxiety. Therefore, despite online gaming might represent an activity able to alleviate psychopathological symptoms and/or negative emotional states, people might use online gaming to counterbalance distress or negative situations in everyday life, carrying out a maladaptive coping strategy