Čerenkov radiation and electromagnetic pulse produced by electron beams traversing a finite path in air

Coherent Čerenkov radiation has been investigated previously in the time domain for an infinite path. The present calculations for a finite path length show an effect analogous to diffraction (in the frequency domain) in which radiation fields appear both at Cerenkov angles and at other angles. The latter have previously been named electromagnetic pulse fields.Hydrodynamics Group, Los Alamos National Laboratory, For Fred R. Buskirk and the U.S. Naval Sea Systems Command.Approved for public release; distribution is unlimited

The Protective and Pathologic Roles of Toll-like Receptors in Arthritogenic Alphavirus Infection

Arthritogenic alphaviruses, including Chikungunya virus and Ross River virus (RRV), are mosquito-borne pathogens responsible for epidemics of debilitating polyarthritis in humans. The host inflammatory response plays an important role in the pathogenesis of arthritic alphaviruses, where some pathways, such as the complement cascade, exacerbate virus-induced disease, while type I IFN and other immune signaling pathways mediate protection from disease. Using a mouse model of alphavirus-induced arthritis/myositis, we demonstrated that toll-like receptor (TLR) signaling contributes to protection from and enhancement of alphavirus-induced disease. Myd88-dependent TLR7 signaling was critical for protection from severe RRV-induced morbidity and mortality. Additionally, TLR7 deficiency resulted in the production of low affinity, non-neutralizing RRV-specific antibodies that exacerbated virus-induced disease through systemic antibody- and complement-mediated mechanisms. Furthermore, TLR4 promoted RRV-induced morbidity and tissue damage in a complement-dependent manner, and complement-associated macrophage activation was dependent on TLR4 expression during RRV infection. Taken together, these studies establish the integral role that TLR pathways play in arthritic alphavirus pathogenesis and suggest that designing therapeutic strategies that target TLR signaling may aid in the treatment of RRV infection.Doctor of Philosoph

Chronicles of Oklahoma

Article describes the life of José Maria, a chief of the Anadarkos. Kenneth F. Neighbours discusses the life of the Anadarkos in Texas, relations with the United States government, and warfare with other tribes

Adiponectin and Risk Factors for Cardiovascular Disease and Type 2 Diabetes in Black and White Youth

This study was done to examine the relationships among adiponectin and multiple risk factors for CVD and T2D in a large, racially diverse sample of youth, and to determine if relationships were moderated by gender, race and overweight status. The sample consisted of 1215 Black and White children and adolescents, aged 7-18 years, selected from 2211 subjects who participated in the Cardiovascular Health in Children III Study. Subjects who were selected had frozen serum samples available for analysis, and had complete data on the following variables: race, age, gender, pubertal stage, cardiovascular fitness, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglyceride, insulin, glucose, systolic and diastolic blood pressure, body mass index (BMI), waist circumference, and sum of skinfolds. SAS 9.1.3 was used for all statistical analyses. Generalized Estimating Equations were used to account for the increased correlation among subjects within school clusters. Adiponectin means were lower in Black subjects and in male subjects overall, and specifically lower in Black males than in other race/gender groups. Adiponectin means were also lower in subjects with a family history of diabetes, but there were no differences in adiponectin means by Tanner stage or fitness level. BMI z-score, waist circumference and sum of skinfolds were each inversely related to adiponectin, but BMI z-score and waist circumference provided the best models for prediction of adiponectin when compared by the Quasi-Likelihood in Independence Model Criterion (QIC). Adiponectin was positively associated with HDL-C and inversely associated with insulin and systolic blood pressure in multivariate regression with other risk factors, but the relationships with insulin and systolic blood pressure were dependent on one or more measures of adiposity. There was an interaction between HDL-C and gender, in that the relationship between adiponectin and HDL-C was stronger in female than in males. Insulin was only related to adiponectin in female subjects. In summary, BMI z-score and waist circumference are strongly related to adiponectin. Race, gender and HDL-C are consistently related to adiponectin, independent of adiposity measures, but insulin and family history of diabetes are also important variables to consider in the study of adiponectin

Methylthiolate-induced reconstruction of Ag(1 1 1): A medium energy ion scattering study

Medium energy ion scattering (MEIS), using 100 keV H+ incident ions, has been used to investigate the structure of the Ag(1 1 1)(√7 × √7)R19° –CH3S surface phase. The results provide the first direct evidence that this structure does involve substantial reconstruction of the Ag surface layer. The measured absolute scattered ion yields and blocking curves are in generally good agreement with a specific structural model of the surface based on a reconstructed layer containing 3/7 ML Ag atoms, previously suggested on the basis of scanning tunnelling microscopy (STM) and normal incidence X-ray standing wave (NIXSW) studies. However, the MEIS data indicate that any rumpling of the thiolate layer, is small, and probably 0.2 Å. This value is smaller than the amplitude suggested in the STM and NIXSW studies, but could be entirely consistent with the earlier experimental data

Optimized Determination of Elastic Constants of Anisotropic Solids from Wavespeed Measurements

Ultrasonic measurements have been used for a long time to quantitatively determine the elastic properties of solids from wavespeed measurements. The determination is based on measuring the speeds of propagation of various wave modes, propagating in specific directions of the solid. Various methods have been developed for these measurements including both continuous wave and pulsed or burst techniques. A traditional distinction can be done in the way the transducer(s) interact with the solid to be characterized. Contact techniques [1,2] have been supplemented by immersion systems [3,4] which often yield more reproducible results and which permit measurements to be easily made along different directions in the test specimen. For instance, an advanced immersion system using the principle of digital interferometry with the help of a cross-correlation technique and normal mode tracking algorithms was recently designed [51. By using the mode conversion process at a liquid-solid interface, quasi-longitudinal and quasi-transverse bulk modes can be generated in numerous directions in the interior of the solid. The design and implementation of specialized optimization algorithms [6] permit a precise determination of the elastic constants for various synthetic and natural composite materials [7,8]. Nevertheless, a principal limitation of the existing optimization procedures for recovering a material’s elastic constants has been the requirement of wavespeed data measured in principal planes, where some analytical expressions, providing the slowness curves, generally exist [9]

Myd88-Dependent Toll-Like Receptor 7 Signaling Mediates Protection from Severe Ross River Virus-Induced Disease in Mice

Arthralgia-associated alphaviruses, including chikungunya virus (CHIKV) and Ross River virus (RRV), pose significant public health threats because of their ability to cause explosive outbreaks of debilitating arthralgia and myalgia in human populations. Although the host inflammatory response is known to contribute to the pathogenesis of alphavirus-induced arthritis and myositis, the role that Toll-like receptors (TLRs), which are major regulators of host antiviral and inflammatory responses, play in the pathogenesis of alphavirus-induced arthritis and myositis has not been extensively studied. Using a mouse model of RRV-induced myositis/arthritis, we found that myeloid differentiation primary response gene 88 (Myd88)-dependent TLR7 signaling is involved in protection from severe RRV-associated disease. Infections of Myd88- and TLR7-deficient mouse strains with RRV revealed that both Myd88 and TLR7 significantly contributed to protection from RRV-induced mortality, and both mouse strains exhibited more severe tissue damage than wild-type (WT) mice following RRV infection. While viral loads were unchanged in either Myd88 or TLR7 knockout mice compared to WT mice at early times postinfection, both Myd88 and TLR7 knockout mice exhibited higher viral loads than WT mice at late times postinfection. Furthermore, while high levels of RRV-specific antibody were produced in TLR7-deficient mice, this antibody had very little neutralizing activity and had lower affinity than WT antibody. Additionally, TLR7- and Myd88-deficient mice showed defects in germinal center activity, suggesting that TLR7-dependent signaling is critical for the development of protective antibody responses against RRV

Radio-Frequency Measurements of Coherent Transition and Cherenkov Radiation: Implications for High-Energy Neutrino Detection

We report on measurements of 11-18 cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultra high-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultra high-energy neutrinos.Comment: updated figure 10; fixed typo in equation 2.2; accepted by PR