VICAR image processing system guide to system use

The functional characteristics and operating requirements of the Video Image Communication and Retrieval System are detailed

Direct Measurement of 2D and 3D Interprecipitate Distance Distributions from Atom-Probe Tomographic Reconstructions

Edge-to-edge interprecipitate distance distributions are critical for predicting precipitation strengthening of alloys and other physical phenomena. A method to calculate this 3D distance and the 2D interplanar distance from atom-probe tomographic data is presented. It is applied to nanometer-sized Cu-rich precipitates in an Fe-1.7 at.% Cu alloy. Experimental interprecipitate distance distributions are discussed

Piecewise smooth systems near a co-dimension 2 discontinuity manifold: can one say what should happen?

We consider a piecewise smooth system in the neighborhood of a co-dimension 2 discontinuity manifold $\Sigma$. Within the class of Filippov solutions, if $\Sigma$ is attractive, one should expect solution trajectories to slide on $\Sigma$. It is well known, however, that the classical Filippov convexification methodology is ambiguous on $\Sigma$. The situation is further complicated by the possibility that, regardless of how sliding on $\Sigma$ is taking place, during sliding motion a trajectory encounters so-called generic first order exit points, where $\Sigma$ ceases to be attractive. In this work, we attempt to understand what behavior one should expect of a solution trajectory near $\Sigma$ when $\Sigma$ is attractive, what to expect when $\Sigma$ ceases to be attractive (at least, at generic exit points), and finally we also contrast and compare the behavior of some regularizations proposed in the literature. Through analysis and experiments we will confirm some known facts, and provide some important insight: (i) when $\Sigma$ is attractive, a solution trajectory indeed does remain near $\Sigma$, viz. sliding on $\Sigma$ is an appropriate idealization (of course, in general, one cannot predict which sliding vector field should be selected); (ii) when $\Sigma$ loses attractivity (at first order exit conditions), a typical solution trajectory leaves a neighborhood of $\Sigma$; (iii) there is no obvious way to regularize the system so that the regularized trajectory will remain near $\Sigma$ as long as $\Sigma$ is attractive, and so that it will be leaving (a neighborhood of) $\Sigma$ when $\Sigma$ looses attractivity. We reach the above conclusions by considering exclusively the given piecewise smooth system, without superimposing any assumption on what kind of dynamics near $\Sigma$ (or sliding motion on $\Sigma$) should have been taking place.Comment: 19 figure

k-core organization of complex networks

We analytically describe the architecture of randomly damaged uncorrelated networks as a set of successively enclosed substructures -- k-cores. The k-core is the largest subgraph where vertices have at least k interconnections. We find the structure of k-cores, their sizes, and their birth points -- the bootstrap percolation thresholds. We show that in networks with a finite mean number z_2 of the second-nearest neighbors, the emergence of a k-core is a hybrid phase transition. In contrast, if z_2 diverges, the networks contain an infinite sequence of k-cores which are ultra-robust against random damage.Comment: 5 pages, 3 figure

Effects of surface damage on rf cavity operation

We describe a model of damage in rf cavities and show how this damage can limit cavity operation. We first present a review of mechanisms that may or may not affect the ultimate fields that can be obtained in rf cavities, assuming that mechanical stress explains the triggers of rf breakdown events. We present a method of quantifying the surface damage caused by breakdown events in terms of the spectrum of field enhancement factors, , for asperities on the surface. We then model an equilibrium that can develop between damage and conditioning effects, and show how this equilibrium can determine cavity performance and show experimental evidence for this mechanism. We define three functions that quantify damage, and explain how the parameters that determine performance can be factored out and measured. We then show how this model can quantitatively explain the dependence of cavity performance on material, frequency, pulse length, gas, power supply, and other factors. The examples given in this paper are derived from a variety of incomplete data sets, so we outline an experimental program that should improve these predictions, provide mechanisms for comparing data from different facilities, and fill in many gaps in the existing data

Study of defects, radiation damage and implanted gases in solids by field-ion and atom-probe microscopy

The ability of the field-ion microscope to image individual atoms has been applied, at Cornell University, to the study of fundamental properties of point defects in irradiated or quenched metals. The capability of the atom probe field-ion microscope to determine the chemistry - that is, the mass-to-charge ratio - of a single ion has been used to investigate the behavior of different implanted species in metals. A brief review is presented of: (1) the basic physical principles of the field-ion and atom-probe microscopes; (2) the many applications of these instruments to the study of defects and radiation damage in solids; and (3) the application of the atom-probe field-ion microscope to the study of the behavior of implanted /sup 3/He and /sup 4/He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interests in detail

The evolution of interdisciplinarity in physics research

Science, being a social enterprise, is subject to fragmentation into groups that focus on specialized areas or topics. Often new advances occur through cross-fertilization of ideas between sub-fields that otherwise have little overlap as they study dissimilar phenomena using different techniques. Thus to explore the nature and dynamics of scientific progress one needs to consider the large-scale organization and interactions between different subject areas. Here, we study the relationships between the sub-fields of Physics using the Physics and Astronomy Classification Scheme (PACS) codes employed for self-categorization of articles published over the past 25 years (1985-2009). We observe a clear trend towards increasing interactions between the different sub-fields. The network of sub-fields also exhibits core-periphery organization, the nucleus being dominated by Condensed Matter and General Physics. However, over time Interdisciplinary Physics is steadily increasing its share in the network core, reflecting a shift in the overall trend of Physics research.Comment: Published version, 10 pages, 8 figures + Supplementary Informatio

Antidepressants for cognitive impairment in schizophrenia - A systematic review and meta-analysis

Background: Cognitive impairment in schizophrenia is disabling, but current treatment options remain limited. Objective: To meta-analyze the efficacy and safety of adjunctive antidepressants for cognitive impairment in schizophrenia. Data sources and study selection: PubMed, MEDLINE, PsycINFO, and Cochrane Library databases were searched until 12/2013 for randomized controlled trials comparing antidepressant augmentation of antipsychotics with placebo regarding effects on cognitive functioning in schizophrenia. Data extraction: Two authors independently extracted data. Standardized mean differences (SMDs) were calculated for continuous outcomes and risk ratios for categorical outcomes. SMDs of individual cognitive tests were pooled on a study level within domains (primary outcome) and across domains. When results were heterogeneous, random instead of fixed effects models were used. Results: We meta-analyzed 11 studies (duration=8.7 +/- 3.7 weeks) including 568 patients (mean age=39.5 +/- 6.9 years, males=67.2%, illness duration=12.5 +/- 8.0 years). Antidepressants included mirtazapine (4 studies; n=126), citalopram (2 studies; n=231), fluvoxamine (1 study; n=47), duloxetine (1 study; n=40), mianserin (1 study; n=30), bupropion (1 study; n=61), and reboxetine (1 study; n=33). Statistically significant, but clinically negligible, advantages were found for pooled antidepressants compared to placebo in executive function (Hedges\u27 g=0.17, p=0.02) and a composite cognition score (Hedges\u27 g=0.095, p=0.012). Depression improved with serotonergic antidepressants (p=0.0009) and selective serotonin reuptake inhibitors (p=0.009), but not with pooled antidepressants (p=0.39). Sedation was more common with pooled antidepressants (p=0.04). Conclusion: Adjunctive antidepressants do not demonstrate clinically significant effects on cognition in schizophrenia patients, however, larger studies, preferably in euthymic schizophrenia patients and using full neurocognitive batteries, are needed to confirm this finding. (C) 2014 Elsevier B. V. All rights reserved