2,123,716 research outputs found
On Schwarzschild's Topology in Brane-Worlds
The topological structure of Schwarzschild's space-time and its maximal
analytic extension are investigated in context of brane-worlds. Using the
embedding coordinates, these geometries are seen as different states of the
evolution of a single brane-world. Comparing the topologies and the embeddings
it is shown that this evolution must be followed by a signature change in the
bulk.Comment: 6 page
Multiperiodic Galactic field RR Lyrae stars in the ASAS catalog
The All Sky Automated Survey (ASAS) monitors bright stars (8 mag < V < 14
mag) south of declination +28 deg. The ASAS Catalogue of Variable Stars (ACVS)
presently contains 50,099 objects; among them are 2212 objects classified as RR
Lyrae pulsating variables. We use ASAS photometric V band data to search for
multiperiodicity in those stars. We find that 73 of 1435 RRab stars and 49 of
756 RRc stars exhibit the Blazhko effect. We observe a deficiency of RRab
Blazhko variables with main pulsation periods greater than 0.65 days. The
Blazhko periods of RRc stars exhibit a strongly bimodal distribution. During
our study we discovered the Blazhko effect with multiple periods in object ASAS
050747-3351.9 = SU Col. Blazhko periods of 89.3 d and 65.8 d and a candidate of
29.5 d were identified with periodogram peaks near the first three harmonics of
the main pulsation. These observations may inspire new models of the Blazhko
effect, which has eluded a consistent theory since its discovery about one
hundred years ago. Long term lightcurve changes were found in 29 stars. We also
found 19 Galactic double mode pulsators (RRd), of which 4 are new discoveries,
raising the number of ASAS discoveries of such objects to 16, out of 27 known
in the field of our Galaxy.Comment: 12 pages, 10 figures, published in MNRA
Obfuscation-based malware update: A comparison of manual and automated methods
IndexaciĂłn: Scopus; Web of Science.This research presents a proposal of malware classification and its update based on capacity and obfuscation. This article is an extension of [4]a, and describes the procedure for malware updating, that is, to take obsolete malware that is already detectable by antiviruses, update it through obfuscation techniques and thus making it undetectable again. As the updating of malware is generally performed manually, an automatic solution is presented together with a comparison from the standpoint of cost and processing time. The automated method proved to be more reliable, fast and less intensive in the use of resources, specially in terms of antivirus analysis and malware functionality checking times.http://univagora.ro/jour/index.php/ijccc/article/view/2961/112
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Image Transformations and Printing of Plaster Layers in Spiral Growth Manufacturing
Spiral growth manufacturing (SGM) is a high speed rapid manufacturing technique in
which objects are built up, layer by layer, by simultaneously depositing, levelling and selectively
consolidating thin powder layers onto a rotating build platform. The size and position of the
jetted droplets are mapped by the position and greyscale level of pixels within an 8 bit greyscale
bitmap image. This paper reports on the development of software in which mathematical
algorithms apply geometric transformations to images in preparation for printing onto a rotating
substrate. In support of this work, dimensional accuracy measurements of printed images and
methods to correct radial print density variations are reported. The accuracy of printed images
were found to be within ±0.2mm of their predicted size. The experimental work is briefly
extended to the direct printing of plaster layers, formed by mixing two reactive ink solutions.Mechanical Engineerin
Gene expression analysis in microdissected renal tissue - Current challenges and strategies
The architecture and compartmentalization of the kidney has stimulated the development of an array of microtechniques to study the functional differences between the distinct nephron segments. With the vast amounts of genomic sequence data now available, the groundwork has been laid for a comprehensive characterization of the molecular pathways defining the differences in nephron function. With the development of sensitive gene expression techniques the tools for a comprehensive molecular analysis of specific renal microenvironments have been provided: Quantitative RT-PCR technologies now allow the analysis of specific mRNAs from as little as single microdissected renal cells. A more global view of gene expression regulation is a logical development from the application of large scale profiling techniques. In this review, we will discuss the power and pitfalls of these approaches, including their potential for the functional characterization of nephron heterogeneity and diagnostic application in renal disease. Copyright (C) 2002 S. Karger AG, Basel
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