186 research outputs found

    Vulnerability of Roof and Building Walls Under a Translating Tornado Like Vortex

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    Exposure of a building to a tornado often proves fatal, resulting in massive destruction of property and structures. The effect of disasters can be minimized by understanding the nature of fluid-structure interactions when a tornado hits a building on its path. Earlier researchers have investigated extensively on building models exposed to stationary type vortex generated in a laboratory type tornado simulator; however studies using translating type vortex are few. In the present investigation, the external and internal pressures experienced by a building model are discussed based on experiments conducted using a translating tornado-like flow simulator at Tokyo Polytechnic University, Japan. The swirl ratio which characterizes the strength of vortices generated is kept constant. The investigation attempts to explore the opening locations which can result in higher internal pressures and net roof forces in building and the vulnerability of roof structures of buildings when exposed to tornado-like flow. The effect of translating speed on internal pressure fluctuations when compared to those of external pressures are investigated using aerodynamic admittance functions. Results indicate that there is an increased amount of internal pressure fluctuations at higher translating speeds

    aPKC and DOC2b in glucose transport

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    Aims/introduction: Double C2 domain protein b (DOC2b), one of the synaptotagmins, has been shown to translocate to the plasma membrane, and to initiate membrane-fusion processes of vesicles containing glucose transporter 4 proteins on insulin stimulation. However, the mechanism by which DOC2b is regulated remains unclear. Herein, we identified the upstream regulatory factors of DOC2b in insulin signal transduction. We also examined the role of DOC2b on systemic homeostasis using DOC2b knockout (KO) mice. Materials and Methods: We first identified DOC2b binding proteins by immunoprecipitation and mutagenesis experiments. Then, DOC2b KO mice were generated by disrupting the first exon of the DOC2b gene. In addition to the histological examination, glucose metabolism was assessed by measuring parameters on glucose/insulin tolerance tests. Insulin-stimulated glucose uptake was also measured using isolated soleus muscle and epididymal adipose tissue. Results: We identified an isoform of atypical protein kinase C (protein kinase C iota) that can bind to DOC2b and phosphorylates one of the serine residues of DOC2b (S34). This phosphorylation is essential for DOC2b translocation. DOC2b KO mice showed insulin resistance and impaired oral glucose tolerance on insulin and glucose tolerance tests, respectively. Insulin-stimulated glucose uptake was impaired in isolated soleus muscle and epididymal adipose tissues from DOC2b KO mice. Conclusions: We propose a novel insulin signaling mechanism by which protein kinase C iota phosphorylates DOC2b, leading to glucose transporter 4 vesicle translocation, fusion and facilitation of glucose uptake in response to insulin. The present results also showed DOC2b to play important roles in systemic glucose homeostasis

    Suppression of NSAID-induced small intestinal inflammation by orally administered redox nanoparticles

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    Patients regularly taking non-steroidal anti-inflammatory drugs (NSAIDs) such as indomethacin (IND) have a risk of small intestinal injuries. In this study, we have developed an oral nanotherapeutics by using a redox nanoparticle (RNPO), which is prepared by self-assembly of an amphiphilic block copolymer that possesses nitroxide radicals as side chains of hydrophobic segment via ether linkage, to reduce inflammation in mice with IND-induced small intestinal injury. The localization and accumulation of RNPO in the small intestine were determined using fluorescent-labeled RNPO and electron spin resonance. After oral administration, the accumulation of RNPO in both the jejunum and ileum tissues was about 40 times higher than those of low-molecular-weight nitroxide radical compounds, and RNPO was not absorbed into the bloodstream via the mesentery, thereby avoiding the adverse effects of nitroxide radicals in the entire body. RNPO remarkably suppressed inflammatory mediators such as myeloperoxidase, superoxide anion, and malondialdehyde in the small intestines of IND-treated mice. Compared to low-molecular-weight nitroxide radical compounds, RNPO also significantly increased the survival rate of mice treated daily with IND. On the basis of these results, RNPO is promising as a nanotherapeutics for treatment of inflammation in the small intestine of patients receiving NSAIDs

    Quark Spectrum above but near Critical Temperature of Chiral Transition

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    We explore the quark properties at finite temperature near but above the critical temperature of the chiral phase transition. We investigate the effects of the precursory soft mode of the phase transition on the quark dispersion relation and the spectral function. It is found that there appear novel excitation spectra of quasi-quarks and quasi-antiquarks with a three-peak structure, which are not attributed to the hard-thermal-loop approximation. We show that the new spectra originate from the mixing between a quark (anti-quark) and an anti-quark hole (quark hole) caused by a ``resonant scattering'' of the quasi-fermions with the thermally-excited soft mode which has a small but finite excitation energy.Comment: 6 pages, 12 eps figures, typos corrected and references updated, version to appear in Phys. Lett.
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