3,042 research outputs found

    Primordial Black Hole as a Source of the Boost Factor

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    Primordial black holes (PBHs) accumulate weakly interacting massive particles (WIMPs) around them and form ultracompact minihalos (UCMHs), if the WIMP is a dominant component of the dark matter (DM). In this paper, we discuss that the UCMHs seeded by the PBHs with sub-earth mass enhance the WIMP annihilation in the present Universe and can successfully explain the positron and/or electron excess in cosmic ray observed by PAMELA/Fermi experiments. The signal is very similar to that from a decaying dark matter, which can explain the PAMELA and/or Fermi anomaly without conflict with any constraints as long as the decay mode is proper. In this scenario, the boost factor can be as large as 10^5. In addition, we discuss testability of our scenario by gamma-ray point source and gravitational-wave experiments.Comment: 17 pages, 3 figur

    Selected topics on parton distribution functions

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    We report recent studies on structure functions of the nucleon and nuclei. First, clustering effects are investigated in the structure function F_2 of Be-9 for explaining an unusual nuclear correction found in a JLab experiment. We propose that high densities created by formation of clustering structure like 2*alpha+neutron in Be-9 is the origin of the unexpected JLab result by using the antisymmetrized molecular dynamics (AMD). There is an approved proposal at JLab to investigate the structure functions of light nuclei including the cluster structure, so that much details will become clear in a few years. Second, tensor-polarized quark and antiquark distributions are obtained by analyzing HERMES measurements on the structure function b_1 for the deuteron. The result suggests a finite tensor polarization for antiquark distributions, which is an interesting topic for further theoretical and experimental investigations. An experimental proposal exists at JLab for measuring b_1 of the deuteron as a new tensor-structure study in 2010's. Furthermore, the antiquark tensor polarization could be measured by polarized deuteron Drell-Yan processes at hadron facilities such as J-PARC and GSI-FAIR. Third, the recent CDF dijet anomaly is investigated within the standard model by considering possible modifications of the strange-quark distribution. We find that the shape of a dijet-mass spectrum changes depending on the strange-quark distribution. It indicates that the CDF excess could be partially explained as a PDF effect, particularly by the strangeness in the nucleon, within the standard model if the excess at m_{jj}~140 GeV is not a sharp peak.Comment: 8 pages, LaTeX, to be published in AIP proceedings, 8th Circum-Pan-Pacific Symposium on High Energy Spin Physics, June 20-24, 2011, Cairns, Australi

    ABO-incompatible living-donor pediatric kidney transplantation in Japan

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    The Japanese ABO-Incompatible Transplantation Committee officially collected and analyzed data on pediatric ABO-incompatible living-donor kidney transplantation in July 2012. The age of a child was defined a

    How should cardiac xenotransplantation be initiated in Japan?

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    The version of record of this article, first published in Surgery Today, is available online at Publisher’s website: https://doi.org/10.1007/s00595-024-02861-7.The world's first clinical cardiac xenotransplantation, using a genetically engineered pig heart with 10 gene modifications, prolonged the life of a 57-year-old man with no other life-saving options, by 60 days. It is foreseeable that xenotransplantation will be introduced in clinical practice in the United States. However, little clinical or regulatory progress has been made in the field of xenotransplantation in Japan in recent years. Japan seems to be heading toward a "device lag", and the over-importation of medical devices and technology in the medical field is becoming problematic. In this review, we discuss the concept of pig-heart xenotransplantation, including the pathobiological aspects related to immune rejection, coagulation dysregulation, and detrimental heart overgrowth, as well as genetic modification strategies in pigs to prevent or minimize these problems. Moreover, we summarize the necessity for and current status of xenotransplantation worldwide, and future prospects in Japan, with the aim of initiating xenotransplantation in Japan using genetically modified pigs without a global delay. It is imperative that this study prompts the initiation of preclinical xenotransplantation research using non-human primates and leads to clinical studies

    Spectral detection of grazing degradation in the Xilingol Steppe, Inner Mongolia

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    In order to detect the grazing degradation of steppe vegetation, spectral reflectance was measured using a portable spectral radiometer in the Xilingol steppe, Inner Mongolia. There is only one main drinking place for animals, which is supplied by a water tank at the center of Branch No.4 site-00. In addition to the measurement of surface reflectance, vegetation surveys were carried out involving floristic composition and plant growth parameters as a function of the distance from site-00 at every 1-km interval until the 5-km point. It becomes clear that the effects of grazing on vegetation and soil mitigated according to the distance from site-00. Negative plant indicators of grazing intensity such as Stipa grandis and Filifolium sibiricum increased in dominance with distance from site-00, whereas positive indicators of grazing intensity, such as Cleistogenens squarrosa and Agropyron cristatum, decreased in dominance. Changes in growth parameters along the environmental gradients were reflected on NDVI (Normalized Difference Vegetation Index), in which NDVI was positively correlated with the aboveground biomass (r=0.77, P<0.001), plant height (r=0.69, P<0.001) and coverage (r=0.89, P<0.001), respectively. These results suggested that a spectral vegetation index is effective in the detection of the degradation of grazing grassland in a non-destruction way.Original Pape
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