CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates

We describe a uniform all-sky survey of bright blazars, selected primarily by their flat radio spectra, that is designed to provide a large catalog of likely gamma-ray AGN. The defined sample has 1625 targets with radio and X-ray properties similar to those of the EGRET blazars, spread uniformly across the |b| > 10 deg sky. We also report progress toward optical characterization of the sample; of objects with known R < 23, 85% have been classified and 81% have measured redshifts. One goal of this program is to focus attention on the most interesting (e.g., high redshift, high luminosity, ...) sources for intensive multiwavelength study during the observations by the Large Area Telescope (LAT) on GLAST.Comment: 18 pages, 6 figures, 1 machine-readable table available at http://astro.stanford.edu/CGRaBS/ ; accepted for publication in ApJ

Various series expansions for a Heisenberg antiferromagnet model for SrCu2_2(BO3_3)2_2

We use a variety of series expansion methods at both zero and finite temperature to study an antiferromagnetic Heisenberg spin model proposed recently by Miyahara and Ueda for the quasi two-dimensional material SrCu$_2$(BO$_3$)$_2$. We confirm that this model exhibits a first-order quantum phase transition at T=0 between a gapped dimer phase and a gapless N\'eel phase when the ratio $x=J'/J$ of nearest and next-nearest neighbour interactions is varied, and locate the transition at $x_c=0.691(6)$. Using longer series we are able to give more accurate estimates of the model parameters by fitting to the high temperature susceptibility data.Comment: RevTeX, 13 figure

Magnetic Phase Transition of the Perovskite-type Ti Oxides

Properties and mechanism of the magnetic phase transition of the perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle distortion, are studied theoretically by using the effective spin and pseudo-spin Hamiltonian with strong Coulomb repulsion. It is shown that the A-type antiferromagnetic(AFM(A)) to ferromagnetic(FM) phase transition occurs as the Ti-O-Ti bond angle is decreased. Through this phase transition, the orbital state is hardly changed so that the spin-exchange coupling along the c-axis changes nearly continuously from positive to negative and takes approximately zero at the phase boundary. The resultant strong two-dimensionality in the spin coupling causes a rapid suppression of the critical temperature as is observed experimentally.Comment: 9 pages, 5 figure

Field dependent thermodynamics and Quantum Critical Phenomena in the dimerized spin system Cu2(C5H12N2)2Cl4

Experimental data for the uniform susceptibility, magnetization and specific heat for the material Cu2(C5H12N2)2Cl4 (abbreviated CuHpCl) as a function of temperature and external field are compared with those of three different dimerized spin models: alternating spin-chains, spin-ladders and the bilayer Heisenberg model. It is shown that because this material consists of weakly coupled spin-dimers, much of the data is insensitive to how the dimers are coupled together and what the effective dimensionality of the system is. When such a system is tuned to the quantum critical point by application of a field, the dimensionality shows up in the power-law dependences of thermodynamic quantities on temperature. We discuss the temperature window for such a quantum critical behavior in CuHpCl.Comment: Revtex, 5 pages, 4 figures (postscript

Magnetic and Orbital States and Their Phase Transition of the Perovskite-Type Ti Oxides: Strong Coupling Approach

The properties and mechanism of the magnetic phase transition of the perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle distortion, are studied theoretically by using the effective spin and pseudospin Hamiltonian with strong Coulomb repulsion. It is shown that the A-type antiferromagnetic (AFM(A)) to ferromagnetic (FM) phase transition occurs as the Ti-O-Ti bond angle is decreased. Through this phase transition, the orbital state changes only little whereas the spin-exchange coupling along the c-axis is expected to change from positive to negative nearly continuously and approaches zero at the phase boundary. The resultant strong two-dimensionality in the spin coupling causes rapid suppression of the critical temperature, as observed experimentally. It may induce large quantum fluctuations in this region.Comment: 13 pages, 15 figure

Success Rate of Embolization for Type II Endoleaks at a Major Tertiary Referral Center

Objective: The rise of endovascular aneurysm repair (EVAR) as the preferred treatment for abdominal aortic aneurysm (AAA) has introduced endoleaks as a major complication following AAA repair. The objective of this study is to assess the outcomes associated with endovascular embolization of type II endoleaks after EVAR. Methods: The institutional Radiology database at our tertiary referral hospital was queried for type II endoleak during the period 2006-2018. A retrospective chart review was then carried out. Only patients who underwent intervention for isolated type 2 endoleaks were analyzed. The primary outcome was success of the endoleak repair as determined by cessation of growth (i.e., ≤5mm change in diameter over follow-up period) of the native aneurysm sac. Patient outcomes for each failure of the above criterion were also collected. Other data pertaining to the location of endoleak, type of occlusion performed, type of embolic agent used, type of endograft used for EVAR, and incidence of aneurysm rupture were collected as secondary outcomes.Results:During this period 41 patients were treated for type II endoleaks. Demographics are shown in table 1. Cessation of growth was achieved in 28/41 (68.3%) of the patients after one embolization procedure. In 13/41 (31.7%) of patients, growth of the native aneurysm sac continued. Of the patients whose aneurysms continued to grow, 61.5% (8/13) did not undergo a second embolization. The remaining 38.5% (5/13) underwent a second embolization.Patient outcomes for both of these groups are presented in table II. None of the patients were found to have ruptured their aneurysm sac during follow-up after embolization. None of gender, race, the embolization site, or method of embolization were associated with embolization failure. Conclusions: Embolization of type II endoleaks is associated with a cessation of growth in the majority of cases and seems to be protective regarding the risk of aneurysm sac rupture. Future studies and additional follow-up will be important to elucidate the most significant risk factors for expansion and/or rupture of the endovascularly repaired abdominal aneurysm.Table I: Demographics for patients with type II endoleaks who underwent endovascular embolizationVariableValue Age (years +/- sd)75.66 +/- yearsAverage follow-up (months)62.65 monthsSex (%)71.7% male28.3% femaleRace (%)77.7% white17.8% black4.4% otherInflow vessel (%)43.2% lumbar only36.4% IMA only20.5% mixEmbolization site (%)40.5% vessel only14.3% cavity only20.5% mixEmbolization type (%)66.7% coil9.5% glue23.8% mixTable II: Outcomes for patients with continued growth after embolizationThose that did no undergo further embolizationThose that underwent a second embolization 3 were found to have type III endoleak and were successfully repaired with lining of the graft.2 whose aneurysm sac ceased growing. 2 who declined further treatment. 2 whose aneurysm sac continued to grow with persistent evidence of endoleak.1 who died from non-vascular complications. 1 who was lost to follow-up. 1 who is scheduled future surgical repair. 1 who was lost to follow-up.https://scholarlycommons.henryford.com/merf2019clinres/1026/thumbnail.jp

Lead Bullet Fragments in Venison from Rifle-Killed Deer: Potential for Human Dietary Exposure

Human consumers of wildlife killed with lead ammunition may be exposed to health risks associated with lead ingestion. This hypothesis is based on published studies showing elevated blood lead concentrations in subsistence hunter populations, retention of ammunition residues in the tissues of hunter-killed animals, and systemic, cognitive, and behavioral disorders associated with human lead body burdens once considered safe. Our objective was to determine the incidence and bioavailability of lead bullet fragments in hunter-killed venison, a widely-eaten food among hunters and their families. We radiographed 30 eviscerated carcasses of White-tailed Deer (Odocoileus virginianus) shot by hunters with standard lead-core, copper-jacketed bullets under normal hunting conditions. All carcasses showed metal fragments (geometric mean = 136 fragments, range = 15–409) and widespread fragment dispersion. We took each carcass to a separate meat processor and fluoroscopically scanned the resulting meat packages; fluoroscopy revealed metal fragments in the ground meat packages of 24 (80%) of the 30 deer; 32% of 234 ground meat packages contained at least one fragment. Fragments were identified as lead by ICP in 93% of 27 samples. Isotope ratios of lead in meat matched the ratios of bullets, and differed from background lead in bone. We fed fragment-containing venison to four pigs to test bioavailability; four controls received venison without fragments from the same deer. Mean blood lead concentrations in pigs peaked at 2.29 µg/dL (maximum 3.8 µg/dL) 2 days following ingestion of fragment-containing venison, significantly higher than the 0.63 µg/dL averaged by controls. We conclude that people risk exposure to bioavailable lead from bullet fragments when they eat venison from deer killed with standard lead-based rifle bullets and processed under normal procedures. At risk in the U.S. are some ten million hunters, their families, and low-income beneficiaries of venison donations

Potential Impact of the Development of Lignite Reserves on Water Resources of East Texas

This study was conducted for the Office of Water Resources Research and Technology in the U.S. Department of the Interior by the Texas Engineering Experiment Station at Texas A&M University. The project was concerned with identifying potential adverse effects of lignite strip mining and lignite utilization on the hydrology and water quality of the area. Both field and desk studies were conducted to evaluate the potential impact of lignite development on water resources of the area. Field studies included (1) monthly water sampling for a one-year period of streams, lakes and wells near the strip-mined areas at Fairfield and Rockdale and at control stations located away from the lignite development; (2) leaching studies of the lignite and overburden at Fairfield and Rockdale; (3) precipitation samples collected under the airborne waste plume from the lignite-fueled electric generating plant at Fairfield; and (4) a limited trace element enrichment study in the soils around the plant at Fairfield. Potential lignite reserves, as defined by the Bureau of Economic Geology, include about 41 percent of the outcrop area of the Wilcox Aquifer. Strip mining can change the hydrologic characteristics of the area and full development of the near-surface lignite reserves in east and east central Texas could have a significant impact on the groundwater resources of the region. Changes in the recharge rate of the Wilcox aquifer should be considered when identifying new lignite deposits for development. Also hydrologic characteristics should be considered when developing reclamation plans for the spoil area. Lignite-fired power plants cause environmental modifications of considerable magnitude and consume a significant quantity of water. During the 35-year expected life of a l,000-megawatt, lignite-fired power plant, about 21,000 acres of land would typically be strip mined. Approximately 25 percent of the identified near-surface lignite deposits are committed to existing and presently planned lignite-fired power plants in Texas. The Development of deep-basin lignite deposits in the near future appear inevitable. Lignite can contain elevated concentrations of certain trace elements and power plants tend to concentrate these elements. A l,OOO-megawatt plant requires approximately six million tons of lignite per year. When the lignite is fired at the plant some trace metals are concentrated in the fly ash (arsenic, iron, manganese and lead), while others are discharged from the stack primarily as a vapor (mercury and selenium). Improper handling and disposal of fly ash could result in pollution of water supplies. Precipitation samples collected at Fairfield under the airborne waste plume from the Big Brown plant had elevated concentrations of chromium, iron, manganese, selenium and phosphate when compared to background precipitation samples. A trace element enrichment study of the soils around the plant should be conducted to monitor the concentrations of those elements that could adversely affect the plant and animal life of the area. Small surface streams near Rockdale and Fairfield had elevated levels of zinc, selenium, manganese and sulfate as compared to other surface waters observed in the study. Strip mining or power generation was probably not the primary source of the elevated levels of these parameters. A water quality study should be initiated to accurately identify the source of these elevated parameters. Water quality in the cooling lakes at the Alcoa plant near Rockdale and the Big Brown plant near Fairfield was generally good. Highest observed values of many of the surface water quality parameters were in the spoil lake in the strip-mined area at Alcoa. Since there appears to be a direct hydraulic connection between water in the spoil lake and the shallow groundwater aquifer in the area, poor water quality in the lake could adversely affect the groundwater. Additional groundwater studies were recommended for both the Rockdale area and the Fairfield area

Why fencers should bounce: a new method of movement to engage the stretch-shortening cycle

While teaching a heel first contact style of footwork in fencing (also referred to as toe contribution avoidance) is in keeping with long standing traditions, it is not conducive to today’s modern style of fast paced and explosive fencing. Equally, fencers towards the elite-end seem to be gradually adopting a more spring-based style, as their body progressively and organically transitions to “ball of the foot” based footwork, in order for them to fence competitively in the manner they have intuitively associated with success. Therefore, if from a young age fencers are taught to make full use of the stretch shortening cycle (SSC) via “bouncing” or simply by initiating movement via the ball of the foot, this will expedite the learning process. It will demonstrate to them how the SSC can be used to move at greater speed, cover greater distances when advancing, retreating and lunging, and conserve the much-needed energy required to compete over day long competitions. This paper details the mechanistic underpinnings of the SSC and its application to the modern day fencer

Spectroscopy of Broad Line Blazars from 1LAC

We report on optical spectroscopy of 165 Flat Spectrum Radio Quasars (FSRQs) in the Fermi 1LAC sample, which have helped allow a nearly complete study of this population. Fermi FSRQ show significant evidence for non-thermal emission even in the optical; the degree depends on the gamma-ray hardness. They also have smaller virial estimates of hole mass than the optical quasar sample. This appears to be largely due to a preferred (axial) view of the gamma-ray FSRQ and non-isotropic (H/R ~ 0.4) distribution of broad-line velocities. Even after correction for this bias, the Fermi FSRQ show higher mean Eddington ratios than the optical population. A comparison of optical spectral properties with Owens Valley Radio Observatory radio flare activity shows no strong correlation.Comment: Accepted for publication in Ap