Lorentzian homogeneous spaces admitting a homogeneous structure of type T1+T3

We show that a Lorentzian homogeneous space admitting a homogeneous structure of type T1 + T3 is either a (locally) symmetric space or a singular homogeneous plane wave.Comment: 7 pages, Latex2e, a small note and a reference adde

Photonic-Doppler-Velocimetry, Paraxial-Scalar Diffraction Theory and Simulation

Author Institution: Lawrence Livermore National Laborator

Ill-posedness of degenerate dispersive equations

In this article we provide numerical and analytical evidence that some degenerate dispersive partial differential equations are ill-posed. Specifically we study the K(2,2) equation $u_t = (u^2)_{xxx} + (u^2)_{x}$ and the "degenerate Airy" equation $u_t = 2 u u_{xxx}$. For K(2,2) our results are computational in nature: we conduct a series of numerical simulations which demonstrate that data which is very small in $H^2$ can be of unit size at a fixed time which is independent of the data's size. For the degenerate Airy equation, our results are fully rigorous: we prove the existence of a compactly supported self-similar solution which, when combined with certain scaling invariances, implies ill-posedness (also in $H^2$)

Serfati solutions to the 2D Euler equations on exterior domains

We prove existence and uniqueness of a weak solution to the incompressible 2D Euler equations in the exterior of a bounded smooth obstacle when the initial data is a bounded divergence-free velocity field having bounded scalar curl. This work completes and extends the ideas outlined by P. Serfati for the same problem in the whole-plane case. With non-decaying vorticity, the Biot-Savart integral does not converge, and thus velocity cannot be reconstructed from vorticity in a straightforward way. The key to circumventing this difficulty is the use of the Serfati identity, which is based on the Biot-Savart integral, but holds in more general settings.Comment: 50 page

Management of Agitation During the COVID-19 Pandemic

The coronavirus disease 2019 (COVID-19) pandemic caused by the coronavirus SARS-CoV-2 has radically altered delivery of care in emergency settings. Unprecedented hardship due to ongoing fears of exposure and threats to personal safety, along with societal measures enacted to curb disease transmission, have had broad psychosocial impact on patients and healthcare workers alike. These changes can significantly affect diagnosing and managing behavioral emergencies such as agitation in the emergency department. On behalf of the American Association for Emergency Psychiatry, we highlight unique considerations for patients with severe behavioral symptoms and staff members managing symptoms of agitation during COVID-19. Early detection and treatment of agitation, precautions to minimize staff hazards, coordination with security personnel and psychiatric services, and avoidance of coercive strategies that cause respiratory depression will help mitigate heightened risks to safety caused by this outbreak

Influence of relative humidity on tensile and compressive creep of concrete amended with ground granulated blast-furnace slag

This paper presents an experimental study on the influence of ambient relative humidity on tensile creep of plain concrete amended with Ground Granulated Blast - furnace Slag and compares it with its influence on compressive creep. Tensile and compressive creep tests were carried out on concrete specimens of 34.49 MPa compressive strength and 0.56 water/binder ratio at 51, 68 and 100% relative humidity. The results show a linear relationship between compressive creep and relative humidity; this cannot be said about tensile creep. Tensile creep was observed to be more sensitive to change in ambient humidity than compressive creep. Based on equal applied stress, tensile creep was found to be several times higher than compressive creep and the difference was great er in drying creep than in basic creep. On the basis of equal stress/strength ratio, tensile - to - compressive creep ratio was slightly less than 1 for drying creep and much less for basic creep. Keywords: Compressive Creep, Concrete, Relative Humidity, Strain, Strength, Tensile Cree

Melting of hexagonal skyrmion states in chiral magnets

Skyrmions are spiral structures observed in thin films of certain magnetic materials (Uchida et al 2006 Science 311 359–61). Of the phases allowed by the crystalline symmetries of these materials (Yi et al 2009 Phys. Rev. B 80 054416), only the hexagonally packed phases (SCh) have been observed. Here the melting of the SCh phase is investigated using Monte Carlo simulations. In addition to the usual measure of skyrmion density, chiral charge, a morphological measure is considered. In doing so it is shown that the low-temperature reduction in chiral charge is associated with a change in skyrmion profiles rather than skyrmion destruction. At higher temperatures, the loss of six-fold symmetry is associated with the appearance of elongated skyrmions that disrupt the hexagonal packing

Grabežljiva stjenica Rhynocoris fuscipes (FABRICIUS) učinkovito potinula zaraženost mahuna Cajanus cajan od štetnika Helicoverpa armigera (HÜBNER), Nezara viridula (L.) i Riptortus clavatus Thunberg u kavezima u polju

Rhynocoris fuscipes effectively suppressed the infestation of Helicoverpa armigera, Nezara viridula and Riptortus clavatus in pigeonpea field cages. Reduced pod and flower damages were observed in R. fuscipes released field cages. R. fuscipes release significantly enhanced the yield of healthy pods (grains). Field observations suggested this predator\u27s pest suppression and grain damage reduction efficacy.Predator Rhynocoris fuscipes učinkovito je potisnuo zarazu vrstama Helicoverpa armigera, Nezara viridula i Riptortus clavatus u poljskim kavezima. Zapaženo je smanjenje šteta na mahunama i cvjetovima biljke kajan (Cajanus cajan) u kavezima u koje su ispušteni R. fuscipes. Prisutnost predatora signifikantno je povećala prirod zdravih mahuna i zrna. Poljski pokusi ukazuju na učinak predatora na smanjenje zaraze štetnicima i sniženje šteta