105,736 research outputs found
Hydrodynamic Response of the Intergalactic Medium to Reionization
No full textThe intergalactic medium is expected to clump on scales down to 104 V108 Me before the onset of reionization. The impact of these small-scale structures on reionization is poorly understood despite the modern understanding that gas clumpiness limits the growth of H II regions. We use a suite of radiation-hydrodynamics simulations that capture the ~104M Jeans mass of unheated gas to study density fluctuations during reionization. Our simulations track the complex ionization and hydrodynamical response of gas in the wake of ionization fronts. The clumping factor of ionized gas (proportional to the recombination rate) rises to a peak value of 5 V20 approximately ?t= 10 Myr after ionization front passage, depending on the incident intensity, redshift, and degree to which the gas had been preheated by the first X-ray sources. The clumping factor reaches its relaxed value of .3 by ?t=300 Myr. The mean free path of Lyman-limit photons evolves in unison, being up to several times shorter in unrelaxed, recently reionized regions compared to those that were reionized much earlier. Assessing the impact of this response on the global reionization process, we find that unrelaxed gaseous structures boost the total number of recombinations by .50% and lead to spatial fluctuations in the mean free path that persist appreciably for several hundred million years after the completion of reionization
A locally adaptive perceptual masking threshold model for image coding
No full textThesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 95-97).by Trac Duy Tran.M.S
STRIP, a modified TRAC implementation for the PDP-8/1
No full textSTRIP is a small modified TRAC version implemented for use on a PDP/8 computer with 8K of core memory only and a Teletype. This publication has been initiated by the lecture "The Programming Language TRAC and its Implementation", presented at IBM Germany Computer Science Seminar, Stuttgart, Sept. 1971, by Prof. Dr. W.L. van der Poel, University of Technology, Delft. An other base of this report has been the publication "TRAC, A Procedure-Describing Language for the Reactive Typewriter" in Communications of the ACM, Volume 9/Number 3/ March 1966, by C.N. MOOERS. The implementation and some STRIP applications have been supported by useful discussions with my colleagues D. Bartel, H.W. Homrighausen, Dr. Th. Meis, H. Peters, and S. Rafflenbeul. The interpretive and machine- independent language TRAC (Text Reckoning And Compiling) is very compact and concise and therefore well-suited for small computers, too. The development of TRAC began in 1960. The language was written as the basis of a software package for the reactive typewriter. "In the TRAC language, one can write procedures for accepting, naming and storing any character string from the reactive typewriter; for modifying any string in any way; for treating any string at any time as an executableprocedure, or as a name, or as text; and for printing out any string", (see C.N. MOOERS). Iterative and recursive programs can be written in a short form. All of input is treated as a character string and at first there is no difference in text strings and functions. During input every character is put into the working area in ASCII-Code
Damage Analysis Modified TRAC Computer Program (DAMTRAC)
No full textA computer program tailored for EMP damage analysis of solid-state circuitry has been developed by modifying the existing TRAC network analysis program. Modification of the TRAC diode and transistor models to include breakdown parameters and the addition of a semiconductor device parameter library have greatly simplified the analyst\u27s task. An added feature is a subroutine that automatically calculates the amplitude and duration of transient power dissipated in electronic circuit components
Metabolic priming of GD2 TRAC-CAR T cells during manufacturing promotes memory phenotypes while enhancing persistence
No full textManufacturing chimeric antigen receptor (CAR) T cell therapies is complex, with limited understanding of how medium composition impacts T cell phenotypes. CRISPR-Cas9 ribonucleoproteins can precisely insert a CAR sequence while disrupting the endogenous T cell receptor alpha constant (TRAC) gene resulting in TRAC-CAR T cells with an enriched stem cell memory T cell population, a process that could be further optimized through modifications to the medium composition. In this study we generated anti-GD2 TRAC-CAR T cells using ''metabolic priming'' (MP), where the cells were activated in glucose/glutamine-low medium and then expanded in glucose/glutamine-high medium. T cell products were evaluated using spectral flow cytometry, metabolic assays, cytokine production, cytotoxicity assays in vitro, and potency against human GD2+ xenograft neuroblastoma models in vivo. Compared with standard TRAC-CAR T cells, MP TRAC-CAR T cells showed less glycolysis, higher CCR7/CD62L expression, more bound NAD(P)H activity, and reduced IFN-γ, IL-2, IP-10, IL-1β, IL-17, and TGF-β production at the end of manufacturing ex vivo, with increased central memory CAR T cells and better persistence observed in vivo. MP with medium during CAR T cell biomanufacturing can minimize glycolysis and enrich memory phenotypes ex vivo, which could lead to better responses against solid tumors in vivo
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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One-dimensional TRAC calculations of a pump-trip scram for the PIUS 600 advanced reactor design
No full textOne dimensional TRAC transient calculations of the process inherent ultimate safety (PIUS) advanced reactor design were performed for a pump-trip SCRAM. The TRAC calculations showed that the reactor power response and shutdown were in qualitative agreement with the one-dimensional analyses presented in the PIUS Preliminary Safety Information Document (PSID) submitted by Asea Brown Boveri (ABB) to the US Nuclear Regulatory Commission for preapplication safety review. The PSID analyses were performed with the ABB-developed RIGEL code. The TRAC-calculated phenomena and trends were also similar to those calculated with another one-dimensional PIUS model, the Brookhaven National Laboratory developed PIPA code. A TRAC pump-trip SCRAM transient has also been calculated with a TRAC model containing a multi-dimensional representation of the PIUS intemal flow structures and core region. The results obtained using the TRAC fully one-dimensional PIUS model are compared to the RIGEL, PIPA, and TRAC multi-dimensional results
Comparison of reionization models: radiative transfer simulations and approximate, seminumeric models
No full textWe compare the predictions of four different algorithms for the distribution of ionized gas during the Epoch of Reionization. These algorithms are all used to run a 100Mpch-1 simulation of reionization with the same initial conditions. Two of the algorithms are state-of-the-art ray-tracing radiative transfer codes that use disparate methods to calculate the ionization history. The other two algorithms are fast but more approximate schemes based on iterative applications of a smoothing filter on the underlying source and density fields. We compare these algorithms' resulting ionization and 21-cm fields using several different statistical measures. The two radiative transfer schemes are in excellent agreement judging by the power spectra of both the ionization fields and the 21-cm emission fields (agreeing to better than 10 per cent) and are in good agreement with the analytic schemes (better than 50 per cent) over the range of ionized fractions and wavevectors we compare (Mpc-1). This agreement suggests that the different approximations involved in the ray-tracing algorithms are sensible and that seminumerical schemes provide a numerically inexpensive, yet fairly accurate, description of the reionization process. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Event traffic forecast for metropolitan areas based on microscopic simulation
No full textIt is shown that a traditional travel demand forecast combined with a simulationbased approach can serve as a short-term forecast for the traffic situation. The approach presented was developed and tested during the Soccer World Cup 2006 in the city of Cologne as a service for the action forces to react as fast as possible to developing aberrations. This paper discusses the merits and the short-comings of the approach
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