Non trivial generalizations of the Schwinger pair production result II

It is suggested that Schwinger's (1951) vacuum persistence probability against pair production by an intense but constant electric field is a very good approximation to the corresponding quantity if the field does not vary appreciably over distances less than m/e/E/5 pagesComment: 5 page

The formation of ion acoustic shocks

Recent experiments performed in the double plasma (DP) device have verified the existence of electrostatic ion acoustic laminar shocks. The influence of the piston on the shock structure is investigated by modeling the DP device and by numerically solving the temporal and spatial evolution of the shock. In order to isolate piston effects, as opposed to kinetic theory effects such as reflected ions and trapped electrons, the DP plasma is modeled as a cold ion fluid with isothermal Boltzmann electrons. It is shown that laminar shock transitions with structure agreeing with DP shock experiments can be excited

Differential image motion in the short exposure regime

Whole atmosphere seeing \beta_0 is the most important parameter in site testing measurements. Estimation of the seeing from a variance of differential image motion is always biased by a non-zero DIMM exposure, which results in a wind smoothing. In the paper, the wind effects are studied within short exposure approximation, i.e. when the wind shifts turbulence during exposure by distance lesser than device aperture. The method of correction for this effect on the base of image motion correlation between adjacent frames is proposed. It is shown that the correlation can be used for estimation of the mean wind speed V_2 and atmospheric coherence time \tau_0. Total power of longitudinal and transverse image motion is suggested for elimination of dependence on the wind direction. Obtained theoretical results were tested on the data obtained on Mount Shatdjatmaz in 2007--2010 with MASS/DIMM device and good agreement was found.Comment: 11 pages, 8 figures. Accepted for publication in MNRA

Restitution for Haiti, Reparations for All: Haiti’s Place in the Global Reparations Movement

Haiti’s claim for restitution of the debt coerced by France in exchange for Haiti’s 1804 independence has unique legal advantages that can open the door to broader reparations for the descendants of all people harmed by slavery. But in order to assert the claim, Haiti first needs help reclaiming its democracy from a corrupt, repressive regime propped up by the powerful countries that prospered through slavery and overthrew the Haitian President who dared to assert his country’s legal claim. This article explores Haiti’s Independence Debt, and the fight for restitution of it, in the context of two centuries of continued struggle between Haitians asserting their independence and countries enriched by slavery trying to limit the power of Haiti’s example

Assessment of PlanIQ Feasibility DVH for head and neck treatment planning

INTRODUCTION: Designing a radiation plan that optimally delivers both target coverage and normal tissue sparing is challenging. There are limited tools to determine what is dosimetrically achievable and frequently the experience of the planner/physician is relied upon to make these determinations. PlanIQ software provides a tool that uses target and organ at risk (OAR) geometry to indicate the difficulty of achieving different points for organ dose-volume histograms (DVH). We hypothesized that PlanIQ Feasibility DVH may aid planners in reducing dose to OARs. METHODS AND MATERIALS: Clinically delivered head and neck treatments (clinical plan) were re-planned (re-plan) putting high emphasis on maximally sparing the contralateral parotid gland, contralateral submandibular gland, and larynx while maintaining routine clinical dosimetric objectives. The planner was blinded to the results of the clinically delivered plan as well as the Feasibility DVHs from PlanIQ. The re-plan treatments were designed using 3-arc VMAT in Raystation (RaySearch Laboratories, Sweden). The planner was then given the results from the PlanIQ Feasibility DVH analysis and developed an additional plan incorporating this information using 4-arc VMAT (IQ plan). The DVHs across the three treatment plans were compared with what was deemed "impossible" by PlanIQ's Feasibility DVH (Impossible DVH). The impossible DVH (red) is defined as the DVH generated using the minimal dose that any voxel outside the targets must receive given 100% target coverage. RESULTS: The re-plans performed blinded to PlanIQ Feasibilty DVH achieved superior sparing of aforementioned OARs compared to the clinically delivered plans and resulted in discrepancies from the impossible DVHs by an average of 200-700 cGy. Using the PlanIQ Feasibility DVH led to additionalOAR sparing compared to both the re-plans and clinical plans and reduced the discrepancies from the impossible DVHs to an average of approximately 100 cGy. The dose reduction from clinical to re-plan and re-plan to IQ plan were significantly different even when taking into account multiple hypothesis testing for both the contralateral parotid and the larynx (P < 0.004 for all comparisons). No significant differences were observed between the three plans for the contralateral parotid when considering multiple hypothesis testing. CONCLUSIONS: Clinical treatment plans and blinded re-plans were found to suboptimally spare OARs. PlanIQ could aid planners in generating treatment plans that push the limits of OAR sparing while maintaining routine clinical target coverage goals

FORMATION AND CHARACTERIZATION OF NITROGEN IMPLANTED SILICON-ON-INSULATOR STRUCTURE

Silicon wafer has been implanted with 200keV14N+ ions to a dose of 0.75 x 10 18N+ /cm2 at a temperature of 600°C and has been annealed at 1300°C for 2 hours. During post-annealing rapid redistribution of the implanted nitrogen results in formation of buried polycrystalline nitride layer under the damage-free (except for few dislocations < 10⁵/cm2) single crystal silicon layer, which is characterized by n type conduction. The buried dielectric has a resistivity of approximately 10⁸ Ωcm. P channel integrated circuit transistors have been fabricated in the buried nitrid area. The measurements of these transistor devices demonstrate the suitability of nitrogen implanted SOl structure for integrated circuit application

Quantum shutter approach to tunneling time scales with wave packets

The quantum shutter approach to tunneling time scales (G. Garc\'{\i }a-Calder\'{o}n and A. Rubio, Phys. Rev. A \textbf{55}, 3361 (1997)), which uses a cutoff plane wave as the initial condition, is extended in such a way that a certain type of wave packet can be used as the initial condition. An analytical expression for the time evolved wave function is derived. The time-domain resonance, the peaked structure of the probability density (as the function of time) at the exit of the barrier, originally found with the cutoff plane wave initial condition, is studied with the wave packet initial conditions. It is found that the time-domain resonance is not very sensitive to the width of the packet when the transmission process is in the tunneling regime.Comment: 6 page

Coronavirus peplomer charge heterogeneity

Recent advancements in viral hydrodynamics afford the calculation of the transport properties of particle suspensions from first principles, namely, from the detailed particle shapes. For coronavirus suspensions, for example, the shape can be approximated by beading (i) the spherical capsid and (ii) the radially protruding peplomers. The general rigid bead-rod theory allows us to assign Stokesian hydrodynamics to each bead. Thus, viral hydrodynamics yields the suspension rotational diffusivity, but not without first arriving at a configuration for the cationic peplomers. Prior work considered identical peplomers charged identically. However, a recent pioneering experiment uncovers remarkable peplomer size and charge heterogeneities. In this work, we use energy minimization to arrange the spikes, charged heterogeneously to obtain the coronavirus spike configuration required for its viral hydrodynamics. For this, we use the measured charge heterogeneity. We consider 20 000 randomly generated possibilities for cationic peplomers with formal charges ranging from 30 to 55. We find the configurations from energy minimization of all of these possibilities to be nearly spherically symmetric, all slightly oblate, and we report the corresponding breadth of the dimensionless rotational diffusivity, the transport property around which coronavirus cell attachment revolves.journal articl