Electron Population Aging Models for Wide-Angle Tails

Color-color diagrams have been useful in studying the spectral shapes in radio galaxies. At the workshop we presented color-color diagrams for two wide-angle tails, 1231+674 and 1433+553, and found that the standard aging models do not adequately represent the observed data. Although the JP and KP models can explain some of the observed points in the color-color diagram, they do not account for those found near the power-law line. This difficulty may be attributable to several causes. Spectral tomography has been previously used to discern two separate electron populations in these sources. The combination spectra from two such overlying components can easily resemble a range of power-laws. In addition, any non-uniformity in the magnetic field strength can also create a power-law-like spectrum. We will also discuss the effects that angular resolution has on the shape of the spectrum.Comment: 4 pages, 1 figure, proceedings from 1999 'Life Cycles of Radio Galaxies' workshop at STScI in Baltimore, M

Ubic: Bridging the gap between digital cryptography and the physical world

Advances in computing technology increasingly blur the boundary between the digital domain and the physical world. Although the research community has developed a large number of cryptographic primitives and has demonstrated their usability in all-digital communication, many of them have not yet made their way into the real world due to usability aspects. We aim to make another step towards a tighter integration of digital cryptography into real world interactions. We describe Ubic, a framework that allows users to bridge the gap between digital cryptography and the physical world. Ubic relies on head-mounted displays, like Google Glass, resource-friendly computer vision techniques as well as mathematically sound cryptographic primitives to provide users with better security and privacy guarantees. The framework covers key cryptographic primitives, such as secure identification, document verification using a novel secure physical document format, as well as content hiding. To make a contribution of practical value, we focused on making Ubic as simple, easily deployable, and user friendly as possible.Comment: In ESORICS 2014, volume 8712 of Lecture Notes in Computer Science, pp. 56-75, Wroclaw, Poland, September 7-11, 2014. Springer, Berlin, German

Self-Diffusion in Random-Tiling Quasicrystals

The first explicit realization of the conjecture that phason dynamics leads to self-diffusion in quasicrystals is presented for the icosahedral Ammann tilings. On short time scales, the transport is found to be subdiffusive with the exponent $\beta\approx0.57(1)$, while on long time scales it is consistent with normal diffusion that is up to an order of magnitude larger than in the typical room temperature vacancy-assisted self-diffusion. No simple finite-size scaling is found, suggesting anomalous corrections to normal diffusion, or existence of at least two independent length scales.Comment: 11 pages + 2 figures, COMPRESSED postscript figures available by anonymous ftp to black_hole.physics.ubc.ca directory outgoing/diffuse (use bi for binary mode to transfer), REVTeX 3.0, CTP-TAMU 21/9

On the complexity of strongly connected components in directed hypergraphs

We study the complexity of some algorithmic problems on directed hypergraphs and their strongly connected components (SCCs). The main contribution is an almost linear time algorithm computing the terminal strongly connected components (i.e. SCCs which do not reach any components but themselves). "Almost linear" here means that the complexity of the algorithm is linear in the size of the hypergraph up to a factor alpha(n), where alpha is the inverse of Ackermann function, and n is the number of vertices. Our motivation to study this problem arises from a recent application of directed hypergraphs to computational tropical geometry. We also discuss the problem of computing all SCCs. We establish a superlinear lower bound on the size of the transitive reduction of the reachability relation in directed hypergraphs, showing that it is combinatorially more complex than in directed graphs. Besides, we prove a linear time reduction from the well-studied problem of finding all minimal sets among a given family to the problem of computing the SCCs. Only subquadratic time algorithms are known for the former problem. These results strongly suggest that the problem of computing the SCCs is harder in directed hypergraphs than in directed graphs.Comment: v1: 32 pages, 7 figures; v2: revised version, 34 pages, 7 figure

Searching for the light dark gauge boson in GeV-scale experiments

We study current constraints and search prospects for a GeV scale vector boson at a range of low energy experiments. It couples to the Standard Model charged particles with a strength <= 10^-3 to 10^-4 of that of the photon. The possibility of such a particle mediating dark matter self-interactions has received much attention recently. We consider searches at low energy high luminosity colliders, meson decays, and fixed target experiments. Based on available data, searches both at colliders and in meson decays can discover or exclude such a scenario if the coupling strength is on the larger side. We emphasize that a dedicated fixed target experiment has a much better potential in searching for such a gauge boson, and outline the desired properties of such an experiment. Two different optimal designs should be implemented to cover the range of coupling strength 10^-3 to 10^-5, and < 10^-5 of the photon, respectively. We also briefly comment on other possible ways of searching for such a gauge boson.Comment: 33 pages, 5 figures; v2: corrected discussion of Upsilon decays, updates to discussion of fixed-target experiments and QED constraints, numerous minor changes, references added; v3: typo corrected relative to the JHEP published versio

Maternal obesity and major intraoperative complications during cesarean delivery

Background Multiple studies have demonstrated an association between maternal obesity and postoperative complications, but there is a dearth of information about the impact of obesity on intraoperative complications. Objective To estimate the association between maternal obesity at delivery and major intraoperative complications during cesarean delivery (CD). Methods This is a secondary analysis of the deidentified Maternal-Fetal Medicine Unit Cesarean Registry of women with singleton pregnancies. Maternal body mass index (BMI) at delivery was categorized as BMI 18.5 to 29.9 kg/m2, BMI 30 to 39.9 kg/m2, BMI 40 to 49.9 kg/m2, and BMI ≥ 50 kg/m2. The primary outcome, any intraoperative complication, was defined as having at least 1 major intraoperative complication, including perioperative blood transfusion, intraoperative injury (bowel, bladder, ureteral injury; broad ligament hematoma), atony requiring surgical intervention, repeat laparotomy, and hysterectomy. Log-binomial models were used to estimate risk ratios of intraoperative complication in 2 models: model 1 adjusting for maternal race, and preterm delivery &lt;37 weeks; and model 2 adjusting for confounders in Model 1 as well as emergency CD, and type of skin incision. Results A total of 51,218 women underwent CD; 38% had BMI 18.5 to 29.9 kg/m2, 47% BMI 30 to 39.9 kg/m2, 12% BMI 40 to 49.9 kg/m2 and 3% BMI ≥ 50 kg/m2. Having at least 1 intraoperative complication was uncommon (3.4%): 3.8% for BMI 18.5 to 29.9 kg/m2, 3.2% BMI 30 to 39.9 kg/m2, 2.6% BMI 40 to 49.9 kg/m2 and 4.3% BMI ≥ 50 kg/m2 (P &lt; .001). In the fully adjusted model 2, women with BMI 40 to 49.9 kg/m2 had a lower risk of any intraoperative complication (adjusted risk ratio [ARR], 0.76; 95% confidence interval [CI], 0.64 to 0.89) compared with women with BMI 18.5 to 29.9 kg/m2. Women with BMI 30 to 39.9 kg/m2 (ARR, 0.93; 95% CI, 0.84 to 1.03) had a similar risk of any intraoperative complication compared with nonobese women. Among super obese women, there was evidence of effect modification by emergency CD. Compared with nonobese women, neither super obese women undergoing nonemergency CD (ARR, 1.13; 95% CI, 0.84 to 1.52) nor those undergoing emergency CD (ARR, 0.59; 95% CI, 0.32 to 1.10) had an increased risk of intraoperative complication. Conclusion In contrast to the risk for postcesarean complications, the risk of intraoperative complication does not appear to be increased in obese women, even among those with super obesity

Maternal super obesity and neonatal morbidity after term cesarean delivery

Objective To estimate the association between maternal super obesity (body mass index [BMI] ≥ 50 kg/m2) and neonatal morbidity among neonates born via cesarean delivery (CD). Methods Retrospective cohort of singleton neonates delivered via CD ≥ 37 weeks in the Maternal-Fetal Medicine Unit Cesarean Registry. Maternal BMI at delivery was stratified as 18.5 to 29.9 kg/m2, 30 to 39.9 kg/m2, 40 to 49.9 kg/m2, and ≥ 50 kg/m2. Primary outcomes included acute (5-minute Apgar score &lt; 5, cardiopulmonary resuscitation and ventilator support &lt; 24 hours, neonatal injury, and/or transient tachypnea of the newborn) and severe (grade 3 or 4 intraventricular hemorrhage, necrotizing enterocolitis, seizure, respiratory distress syndrome, hypoxic ischemic encephalopathy, meconium aspiration, ventilator support ≥ 2 days, sepsis and/or neonatal death) neonatal morbidity. Odds of neonatal morbidity were estimated for each BMI category adjusting for clinical and operative characteristics. Results Of 41,262 maternal-neonatal dyads, 36% of women were nonobese, 49% had BMI of 30 to 39.9 kg/m2, 12% had BMI of 40 to 49.9 kg/m2, and 3% were super obese. Compared with nonobese women, super obese women had twofold odds of acute (5 vs. 10%; adjusted odds ratio [aOR]: 1.81, 95% confidence interval [CI]: 1.59-2.73) and severe (3 vs. 6%; aOR: 2.08; 95% CI: 1.59-2.73) neonatal morbidity. Conclusion Among term infants delivered via CD, maternal super obesity is associated with increased risk of neonatal morbidity

Ab initio density functional investigation of B_24 cluster: Rings, Tubes, Planes, and Cages

We investigate the equilibrium geometries and the systematics of bonding in various isomers of a 24-atom boron cluster using Born-Oppenheimer molecular dynamics within the framework of density functional theory. The isomers studied are the rings, the convex and the quasiplanar structures, the tubes and, the closed structures. A staggered double-ring is found to be the most stable structure amongst the isomers studied. Our calculations reveal that a 24-atom boron cluster does form closed 3-d structures. All isomers show staggered arrangement of nearest neighbor atoms. Such a staggering facilitates $sp^2$ hybridization in boron cluster. A polarization of bonds between the peripheral atoms in the ring and the planar isomers is also seen. Finally, we discuss the fusion of two boron icosahedra. We find that the fusion occurs when the distance between the two icosahedra is less than a critical distance of about 6.5a.u.Comment: 8 pages, 9 figures in jpeg format Editorially approved for publication in Phys. Rev.

GADGET: A code for collisionless and gasdynamical cosmological simulations

We describe the newly written code GADGET which is suitable both for cosmological simulations of structure formation and for the simulation of interacting galaxies. GADGET evolves self-gravitating collisionless fluids with the traditional N-body approach, and a collisional gas by smoothed particle hydrodynamics. Along with the serial version of the code, we discuss a parallel version that has been designed to run on massively parallel supercomputers with distributed memory. While both versions use a tree algorithm to compute gravitational forces, the serial version of GADGET can optionally employ the special-purpose hardware GRAPE instead of the tree. Periodic boundary conditions are supported by means of an Ewald summation technique. The code uses individual and adaptive timesteps for all particles, and it combines this with a scheme for dynamic tree updates. Due to its Lagrangian nature, GADGET thus allows a very large dynamic range to be bridged, both in space and time. So far, GADGET has been successfully used to run simulations with up to 7.5e7 particles, including cosmological studies of large-scale structure formation, high-resolution simulations of the formation of clusters of galaxies, as well as workstation-sized problems of interacting galaxies. In this study, we detail the numerical algorithms employed, and show various tests of the code. We publically release both the serial and the massively parallel version of the code.Comment: 32 pages, 14 figures, replaced to match published version in New Astronomy. For download of the code, see http://www.mpa-garching.mpg.de/gadget (new version 1.1 available

LexGLUE : a benchmark dataset for legal language understanding in English

Law, interpretations of law, legal arguments, agreements, etc. are typically expressed in writing, leading to the production of vast corpora of legal text. Their analysis, which is at the center of legal practice, becomes increasingly elaborate as these collections grow in size. Natural language understanding (NLU) technologies can be a valuable tool to support legal practitioners in these endeavors. Their usefulness, however, largely depends on whether current state-of-the-art models can generalize across various tasks in the legal domain. To answer this currently open question, we introduce the Legal General Language Understanding Evaluation (LexGLUE) benchmark, a collection of datasets for evaluating model performance across a diverse set of legal NLU tasks in a standardized way. We also provide an evaluation and analysis of several generic and legal-oriented models demonstrating that the latter consistently offer performance improvements across multiple tasks