Two Social Worlds: Social Correlates and Stability of Adolescent Status Groups

Examined adolescents\u27 peer group status in high school using self-report, peer nominations, and archival data collected during 2 consecutive school yrs. 408 students participated in the 1st yr, and 404 students participated in the 2nd yr. 60% of the 2nd yr Ss had also participated in the 1st yr. Higher status students (popular and controversial) had more close friends, engaged more frequently in peer activities, and self-disclosed more than lower status students (rejected and neglected). They were also more involved in extracurricular school activities and received more social honors from their schoolmates. Although the higher status students were more alike than different, controversial adolescents did report more self-disclosure and dating behavior than popular students. Lower status students were also highly similar, although rejected students reported lower grades

Cosmic Strings, Zero Modes and SUSY breaking in Nonabelian N=1 Gauge Theories

We investigate the microphysics of cosmic strings in Nonabelian gauge theories with N=1 supersymmetry. We give the vortex solutions in a specific example and demonstrate that fermionic superconductivity arises because of the couplings and interactions dictated by supersymmetry. We then use supersymmetry transformations to obtain the relevant fermionic zero modes and investigate the role of soft supersymmetry breaking on the existence and properties of the superconducting strings.Comment: 12 pages, RevTex, submitted to Phys. Rev.

Vacuum Decay on a Brane World

The bubble nucleation rate for a first order phase transition occurring on a brane world is calculated. Both the Coleman-de Luccia thin wall instanton and the Hawking-Moss instanton are considered. The results are compared with the corresponding nucleation rates for standard four-dimensional gravity.Comment: 5 page

Optimizing machine learning on Apache Spark in HPC environments

Machine learning has established itself as a powerful tool for the construction of decision making models and algorithms through the use of statistical techniques on training data. However, a significant impediment to its progress is the time spent training and improving the accuracy of these models – this is a data and compute intensive process, which can often take days, weeks or even months to complete. A common approach to accelerate this process is to employ the use of multiple machines simultaneously, a trait shared with the field of High Performance Computing (HPC) and its clusters. However, existing distributed frameworks for data analytics and machine learning are designed for commodity servers, which do not realize the full potential of a HPC cluster, and thus denies the effective use of a readily available and potentially useful resource. In this work we adapt the application of Apache Spark, a distributed data-flow framework, to support the use of machine learning in HPC environments for the purposes of machine learning. There are inherent challenges to using Spark in this context; memory management, communication costs and synchronization overheads all pose challenges to its efficiency. To this end we introduce: (i) the application of MapRDD, a fine grained distributed data representation; (ii) a task-based allreduce implementation; and (iii) a new asynchronous Stochastic Gradient Descent (SGD) algorithm using non-blocking all-reduce. We demonstrate up to a 2.6x overall speedup (or a 11.2x theoretical speedup with a Nvidia K80 graphics card), a 82- 91% compute ratio, and a 80% reduction in the memory usage, when training the GoogLeNet model to classify 10% of the ImageNet dataset on a 32-node cluster. We also demonstrate a comparable convergence rate using the new asynchronous SGD with respect to the synchronous method. With increasing use of accelerator cards, larger cluster computers and deeper neural network models, we predict a 2x further speedup (i.e. 22.4x accumulated speedup) is obtainable with the new asynchronous SGD algorithm on heterogeneous clusters

Concomitant presentation of carpal tunnel syndrome and trigger finger

<p>Abstract</p> <p>Background</p> <p>Carpal tunnel syndrome (CTS) and trigger finger (TF) are common conditions that may occur in the same patient. The etiology of most cases is unknown. The purpose of this study was to evaluate the rate of concomitant occurrence of these two conditions at presentation and to compare the concomitant occurrence in normal and diabetic patients.</p> <p>Methods</p> <p>One-hundred and eight consecutive subjects presenting to our hand clinic with CTS and/or TF were evaluated. The existence of both of these conditions was documented through a standard history and physical examination. The definition of trigger finger was determined by tenderness over the A1 pulley, catching, clicking or locking. CTS was defined in the presence of at least two of the following: numbness and tingling in a median nerve distribution, motor and sensory nerve loss (median nerve), a positive Tinel's or Phalen's test and positive electrophysiologic studies.</p> <p>Results</p> <p>The average age of the participants was 62.2 ± 13.6 years. Sixty-seven patients presented with symptoms and signs of CTS (62%), 41 (38%) subjects with signs and symptoms of TF. Following further evaluation, 66 patients (61%) had evidence of concomitant CTS and TF. Fifty-seven patients (53% of all study patients) had diabetes. The rate of subjects with diabetes was similar among the groups (p = 0.8, Chi-square test).</p> <p>Conclusion</p> <p>CTS and TF commonly occur together at presentation though the symptoms of one condition will be more prominent. Our results support a common local mechanism that may be unrelated to the presence of diabetes. We recommend evaluation for both conditions at the time of presentation.</p

Predictive analysis of a hydrodynamics application on large-scale CMP clusters

We present the development of a predictive performance model for the high-performance computing code Hydra, a hydrodynamics benchmark developed and maintained by the United Kingdom Atomic Weapons Establishment (AWE). The developed model elucidates the parallel computation of Hydra, with which it is possible to predict its runtime and scaling performance on varying large-scale chip multiprocessor (CMP) clusters. A key feature of the model is its granularity; with the model we are able to separate the contributing costs, including computation, point-to-point communications, collectives, message buffering and message synchronisation. The predictions are validated on two contrasting large-scale HPC systems, an AMD Opteron/ InfiniBand cluster and an IBM BlueGene/P, both of which are located at the Lawrence Livermore National Laboratory (LLNL) in the US. We validate the model on up to 2,048 cores, where it achieves a > 85% accuracy in weak-scaling studies. We also demonstrate use of the model in exposing the increasing costs of collectives for this application, and also the influence of node density on network accesses, therefore highlighting the impact of machine choice when running this hydrodynamics application at scale

Fermionic Zero Modes of Supergravity Cosmic Strings

Recent developments in string theory suggest that cosmic strings could be formed at the end of brane inflation. Supergravity provides a realistic model to study the properties of strings arising in brane inflation. Whilst the properties of cosmic strings in flat space-time have been extensively studied there are significant complications in the presence of gravity. We study the effects of gravitation on cosmic strings arising in supergravity. Fermion zero modes are a common feature of cosmic strings, and generically occur in supersymmetric models. The corresponding massless currents can give rise to stable string loops (vortons). The vorton density in our universe is strongly constrained, allowing many theories with cosmic strings to be ruled out. We investigate the existence of fermion zero modes on cosmic strings in supergravity theories. A general index theorem for the number of zero modes is derived. We show that by including the gravitino, some (but not all) zero modes disappear. This weakens the constraints on cosmic string models. In particular, winding number one cosmic D-strings in models of brane inflation are not subject to vorton constraints. We also discuss the effects of supersymmetry breaking on cosmic D-strings.Comment: 33 page

Keck Spectroscopy of Objects with Lens-like Morphologies in the Hubble Deep Field

We present spectroscopy from the Keck telescope of three sets of objects in the Hubble Deep Field which have lens-like morphologies. In the case of J123641+621204, which is composed of four objects with similar colors and a mean separation of <= 0.8", we find at least two distinct components at redshifts of z=3.209 and z=3.220 which are separated by 0.5" spatially. Each of these components has narrow Ly-alpha emission, and possibly NV emission and SiIV and CIV in absorption or with a P-Cygni profile. The second case is J123652+621227, which has an arc-like feature offset by 1.8" to the southwest of a red elliptical-like galaxy, and a ``counterimage'' offset 1.4" on the opposite side. We tentatively find a single line at 5301 AA at the spatial position of the counterimage, and no corresponding emission line at the position of the arc. The colors of the counterimage are consistent with the identification of this line as Ly-alpha at z=3.36. The colors of the arc are different than those of the counterimage, and thus both the colors and spectra indicate that this object is unlikely to be a gravitational lens. For a third lensing candidate (J123656+621221), which is a blue arc offset by 0.9" from a red, elliptical-like galaxy, our spectroscopy does not clearly resolve the system spatially, complicating the interpretation of the spectrum. We discuss possible identifications of features in the spectrum, and find that gravitational lensing remains a possibility in this case. We conclude that the frequency of strong gravitational lensing by galaxies in the HDF appears to be very low. This result is difficult to reconcile with the introduction of a cosmological constant to account for the large number of faint blue galaxies via a large volume element at high redshift.Comment: To be published in the Astrophysical Journal Letters. 10 pages, 3 Figures, 2 Plates. AAS LaTex v4.0. Paper+Figures+Plates also available at http://astro.berkeley.edu/davisgrp/HDF/ and via anonymous ftp at ftp://magicbean.berkeley.edu/pub/HDFLen