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1. chinaXiv:201605.01569 [pdf]

STRONG SOLAR WIND DYNAMIC PRESSURE PULSES: INTERPLANETARY SOURCES AND THEIR IMPACTS ON GEOSYNCHRONOUS MAGNETIC FIELDS

Zuo, Pingbing; Feng, Xueshang; Xie, Yanqiong; Wang, Yi; Xu, Xiaojun
Subjects: Geosciences >> Space Physics

In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic pressure pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector.

submitted time 2016-05-12 Hits357Downloads219 Comment 0

2. chinaXiv:201605.01558 [pdf]

AUTOMATIC DETECTION ALGORITHM OF DYNAMIC PRESSURE PULSES IN THE SOLAR WIND

Zuo, Pingbing; Feng, Xueshang; Xie, Yanqiong; Wang, Yi; Li, Huijun; Xu, Xiaojun
Subjects: Geosciences >> Space Physics

Dynamic pressure pulses (DPPs) in the solar wind are a significant phenomenon closely related to the solar-terrestrial connection and physical processes of solar wind dynamics. In order to automatically identify DPPs from solar wind measurements, we develop a procedure with a three-step detection algorithm that is able to rapidly select DPPs from the plasma data stream and simultaneously define the transition region where large dynamic pressure variations occur and demarcate the upstream and downstream region by selecting the relatively quiet status before and after the abrupt change in dynamic pressure. To demonstrate the usefulness, efficiency, and accuracy of this procedure, we have applied it to the Wind observations from 1996 to 2008 by successfully obtaining the DPPs. The procedure can also be applied to other solar wind spacecraft observation data sets with different time resolutions.

submitted time 2016-05-12 Hits339Downloads205 Comment 0

3. chinaXiv:201605.01556 [pdf]

A STATISTICAL SURVEY OF DYNAMIC PRESSURE PULSES IN THE SOLAR WIND BASED ON WIND OBSERVATIONS

Zuo, Pingbing; Feng, Xueshang; Xie, Yanqiong; Wang, Yi; Xu, Xiaojun
Subjects: Geosciences >> Space Physics

Solar wind dynamic pressure pulse (DPP) structures, across which the dynamic pressure changes abruptly over timescales from a few seconds to several minutes, are often observed in the near-Earth space environment. The space weather effects of DPPs on the magnetosphere-ionosphere coupling system have been widely investigated in the last two decades. In this study, we perform a statistical survey on the properties of DPPs near 1 AU based on nearly 20 years of observations from the WIND spacecraft. It is found that only a tiny fraction of DPPs (around 4.2%) can be regarded as interplanetary shocks. For most DPPs, the total pressure (the sum of the thermal pressure and magnetic pressure) remains in equilibrium, but there also exists a small fraction of DPPs that are not pressure-balanced. The overwhelming majority of DPPs are associated with solar wind disturbances, including coronal mass ejection-related flows, corotating interaction regions, as well as complex ejecta. The annual variations of the averaged occurrence rate of DPPs are roughly in phase with the solar activity during solar cycle 23, and during the rising phase of solar cycle 24.

submitted time 2016-05-12 Hits335Downloads197 Comment 0

4. chinaXiv:201605.01343 [pdf]

V1 neurons respond to luminance changes faster than contrast changes

Wang, Wen-Liang; Li, Ran; Li, Da-Peng; Wang, Yi; Wang, Wen-Liang; Li, Ran; Ding, Jian; Tao, Louis; Tao, Louis
Subjects: Biology >> Biophysics

Luminance and contrast are two major attributes of objects in the visual scene. Luminance and contrast information received by visual neurons are often updated simultaneously. We examined the temporal response properties of neurons in the primary visual cortex (V1) to stimuli whose luminance and contrast were simultaneously changed by 50 Hz. We found that response tuning to luminance changes precedes tuning to contrast changes in V1. For most V1 neurons, the onset time of response tuning to luminance changes was shorter than that to contrast changes. Most neurons carried luminance information in the early response stage, while all neurons carried both contrast and luminance information in the late response stage. The early luminance response suggests that cortical processing for luminance is not as slow as previously thought.

submitted time 2016-05-11 Hits318Downloads189 Comment 0

5. chinaXiv:201605.01311 [pdf]

Recombinant Murine Gamma Herpesvirus 68 Carrying KSHV G Protein-Coupled Receptor Induces Angiogenic Lesions in Mice

Zhang, Junjie; Zhu, Lining; Lu, Xiaolu; Wang, Yi; Gao, Shou-jiang; Feng, Pinghui; Feldman, Emily R.; Keyes, Lisa R.; Tibbetts, Scott A.; Fan, Hui; Feng, Hao; Xia, Zanxian; Xia, Zanxian; Sun, Jiya; Jiang, Taijiao; Sun, Jiya; Jiang, Taijiao; Sun, Jiya; Jiang, Taijiao; Jiang, Taijiao
Subjects: Biology >> Biophysics

Human gamma herpesviruses, including Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are capable of inducing tumors, particularly in in immune-compromised individuals. Due to the stringent host tropism, rodents are resistant to infection by human gamma herpesviruses, creating a significant barrier for the in vivo study of viral genes that contribute to tumorigenesis. The closely-related murine gamma herpesvirus 68 (gamma HV68) efficiently infects laboratory mouse strains and establishes robust persistent infection without causing apparent disease. Here, we report that a recombinant gamma HV68 carrying the KSHV G protein-coupled receptor (kGPCR) in place of its murine counterpart induces angiogenic tumors in infected mice. Although viral GPCRs are conserved in all gamma herpesviruses, kGPCR potently activated downstream signaling and induced tumor formation in nude mouse, whereas gamma HV68 GPCR failed to do so. Recombinant gamma HV68 carrying kGPCR demonstrated more robust lytic replication ex vivo than wild-type gamma HV68, although both viruses underwent similar acute and latent infection in vivo. Infection of immunosuppressed mice with gamma HV68 carrying kGPCR, but not wild-type gamma HV68, induced tumors in mice that exhibited angiogenic and inflammatory features shared with human Kaposi's sarcoma. Immunohistochemistry staining identified abundant latently-infected cells and a small number of cells supporting lytic replication in tumor tissue. Thus, mouse infection with a recombinant gamma HV68 carrying kGPCR provides a useful small animal model for tumorigenesis induced by a human gamma herpesvirus gene in the setting of a natural course of infection.

submitted time 2016-05-11 Hits302Downloads184 Comment 0

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