3,609 research outputs found

    Black Hole as a Wormhole Factory

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    On general grounds, one may argue that a black hole stops radiation at the Planck mass, where the radiated energy is comparable to the black hole's mass. And also, it has been argued that there would be a "wormhole-like" structure, known as "space-time foam", due to large fluctuations below the Planck length. In this paper, as an explicit example, we consider an exact classical solution which represents nicely those two properties in a recently proposed quantum gravity model based on different scaling dimensions between space and time coordinates. The solution, called "Black Wormhole", consists of two different states, depending on its mass M and an IR parameter omega: For the black hole state, a non-traversable wormhole occupies the interior region of the black hole around the singularity at the origin, whereas for the wormhole state, the interior wormhole is exposed to an outside observer as the black hole horizon is disappeared from evaporation. The black hole state becomes thermodynamically stable as it approaches to the merge point where the interior wormhole throat and the black hole horizon merges, and the Hawking temperature vanishes at the exact merge point. This solution suggests the "Generalized Cosmic Censorship" by the existence of a wormhole-like structure which protects the naked singularity even after the black hole evaporation. One could understand the would-be wormholes inside the black hole horizon as the results of microscopic wormholes created by "negative" energy quanta which have entered the black hole horizon in Hawking radiation processes: The quantum black hole could be a wormhole factory. It is found that this speculative picture may be consistent with the recent "ER=EPR" proposal for resolving the recent black hole entanglement debates.Comment: Added some more words on (1) the transition between the black hole phase and wormhole phase and (2) the notion of a wormhole "factory" in Fig. 5. Updated references, Accepted in PL

    Improving Prediction Quality in Collaborative Filtering Based on Clustering

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    In this paper we present the recommender systems that use the k-means clustering method in order to solve the problems associated with neighbor selection. The first method is to solve the problem in which customers belong to different clusters due to the distance-based characteristics despite the fact that they are similar customers, by properly converting data before performing clustering. The second method explains the k-prototype algorithm performing clus-tering by expanding not only the numeric data but also the categorical data. The experimental results show that better prediction quality can be obtained when both methods are used together. 1

    To the Edge of M87 and Beyond: Spectroscopy of Intracluster Globular Clusters and Ultra Compact Dwarfs in the Virgo Cluster

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    We present the results from a wide-field spectroscopic survey of globular clusters (GCs) in the Virgo Cluster. We obtain spectra for 201 GCs and 55 ultracompact dwarfs (UCDs) using the Hectospec on the Multiple Mirror Telescope, and derive their radial velocities. We identify 46 genuine intracluster GCs (IGCs), not associated with any Virgo galaxies, using the 3D GMM test on the spatial and radial velocity distribution.They are located at the projected distance 200 kpc ≲\lesssim R ≲\lesssim 500 kpc from the center of M87. The radial velocity distribution of these IGCs shows two peaks, one at vrv_{\rm r} = 1023 km sβˆ’1^{-1} associated with the Virgo main body, and another at vrv_{\rm r} = 36 km sβˆ’1^{-1} associated with the infalling structure. The velocity dispersion of the IGCs in the Virgo main body is ΟƒGC∼\sigma_{\rm{GC}} \sim 314 km sβˆ’1^{-1}, which is smoothly connected to the velocity dispersion profile of M87 GCs, but much lower than that of dwarf galaxies in the same survey field, Οƒdwarf∼\sigma_{\rm{dwarf}} \sim 608 km sβˆ’1^{-1}. The UCDs are more centrally concentrated on massive galaxies, M87, M86, and M84. The radial velocity dispersion of the UCD system is much smaller than that of dwarf galaxies. Our results confirm the large-scale distribution of Virgo IGCs indicated by previous photometric surveys. The color distribution of the confirmed IGCs shows a bimodality similar to that of M87 GCs. This indicates that most IGCs are stripped off from dwarf galaxies and some from massive galaxies in the Virgo.Comment: 19 pages, 20 figures, 8 tables, accepted for publication in Ap

    Low-power hybrid structure of digital matched filters for direct sequence spread spectrum systems

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    ABSTRACT 1 This paper presents a low-power structure of digital matched filters (DMFs), which is proposed for direct sequence spread spectrum systems. Traditionally, low-power approaches for DMFs are based on either the transposedform structure or the direct-form one. A new hybrid structure that employs the direct-form structure for local addition and the transposed-form structure for global addition is used to take advantages of both structures. For a 128-tap DMF, the proposed DMF that processes 32 addends a cycle consumes 46 % less power at the expense of 6 % area overhead as compared to the state-of-the-art low-power DM

    Ectopic Pancreas with Hemorrhagic Cystic Change in the Anterior Mediastinum

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    A 31-year-old female was referred from other hospital due to migrating chest pain, mild cough, and blood-tinged sputum for three days before admission. Laboratory tests were unremarkable. Chest computed tomography revealed an elliptical necrotic mass at the left anterior mediastinum, measuring 7Γ—3Γ—4 cm. With the impression of mediastinal abscess or loculated empyema, thoracoscopic resection was performed. There was severe pleural adhesion around the mass. The mass could be resected by the wedge resection of the adhesed upper lobe tissue of left lung around the mass. Final pathologic diagnosis was ectopic pancreas

    Rapid quantification of DNA methylation through dNMP analysis following bisulfite-PCR

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    We report a novel method for rapid quantification of the degree of DNA methylation of a specific gene. Our method combined bisulfite-mediated PCR and quantification of deoxyribonucleoside monophosphate (dNMP) contents in the PCR product through capillary electrophoresis. A specific bisulfite-PCR product was enzymatically hydrolyzed to dNMP monomers which were quantitatively analyzed through subsequent capillary electrophoresis. PCR following bisulfite treatment converts unmethylated cytosines to thymines while leaving methyl-cytosines unchanged. Then the ratio of cytosine to thymine determined by capillary electrophoresis represents the ratio of methyl-cytosine to cytosine in genomic locus of interest. Pure oligonucleotides with known sequences were processed in parallel as standards for normalization of dNMP peaks in capillary electrophoresis. Sources of quantification uncertainty such as carryovers of dNTPs or primers and incomplete hydrolysis were examined and ruled out. When the method was applied to samples with known methylation levels (by bisulfite-mediated sequencing) as a validation, deviations were within Β±5%. After bisulfite-PCR, the analytical procedure can be completed within 1.5 h

    Large area deep ultraviolet light of Al0.47_{0.47}Ga0.53_{0.53}N/Al0.56_{0.56}Ga0.44_{0.44}N multi quantum well with carbon nanotube electron beam pumping

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    Large area deep ultraviolet (DUV) light is generated by carbon nanotube (CNT) cold cathode electron beam (C-beam) irradiation on Al0.47_{0.47}Ga0.53_{0.53}N/Al0.56_{0.56}Ga0.44_{0.44}N multi quantum wells (MQWs) anode. We developed areal electron beam (EB) with CNT cold cathode emitters. The CNT emitters on silicon wafer were deposited with an area of 188 mm2^2 , and these were vertically aligned and had conical structures. We optimized the C-beam irradiation conditions to effectively excite AlGaN MQWs. When AlGaN MQWs were excited using an anode voltage of 3 kV and an anode current of 0.8 mA, DUV with a wavelength of 278.7 nm was generated in a large area of 303 mm2^2 . This DUV area is more than 11 times larger than the light emitting area of conventional EB pumped light sources and UV-LEDs
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