27,863 research outputs found
Undulatory swimming in fluids with polymer networks
The motility behavior of the nematode Caenorhabditis elegans in polymeric
solutions of varying concentrations is systematically investigated in
experiments using tracking and velocimetry methods. As the polymer
concentration is increased, the solution undergoes a transition from the
semi-dilute to the concentrated regime, where these rod-like polymers entangle,
align, and form networks. Remarkably, we find an enhancement in the nematode's
swimming speed of approximately 65% in concentrated solutions compared to
semi-dilute solutions. Using velocimetry methods, we show that the undulatory
swimming motion of the nematode induces an anisotropic mechanical response in
the fluid. This anisotropy, which arises from the fluid micro-structure, is
responsible for the observed increase in swimming speed.Comment: Published 1 November 2013 in Europhysics Letter
Thermodynamics with density and temperature dependent particle masses and properties of bulk strange quark matter and strangelets
Thermodynamic formulas for investigating systems with density and/or
temperature dependent particle masses are generally derived from the
fundamental derivation equality of thermodynamics. Various problems in the
previous treatments are discussed and modified. Properties of strange quark
matter in bulk and strangelets at both zero and finite temperature are then
calculated based on the new thermodynamic formulas with a new quark mass
scaling, which indicates that low mass strangelets near beta equilibrium are
multi-quark states with an anti-strange quark, such as the pentaquark
(u^2d^2\bar{s}) for baryon nmber 1 and the octaquark (u^4d^3\bar{s}) for
dibaryon etc.Comment: 14 pages, 12 figures, Revtex4 styl
Valosin-containing protein regulates the proteasome-mediated degradation of DNA-PKcs in glioma cells.
DNA-dependent protein kinase (DNA-PK) has an important role in the repair of DNA damage and regulates the radiation sensitivity of glioblastoma cells. The VCP (valosine-containing protein), a chaperone protein that regulates ubiquitin-dependent protein degradation, is phosphorylated by DNA-PK and recruited to DNA double-strand break sites to regulate DNA damage repair. However, it is not clear whether VCP is involved in DNA-PKcs (DNA-PK catalytic subunit) degradation or whether it regulates the radiosensitivity of glioblastoma. Our data demonstrated that DNA-PKcs was ubiquitinated and bound to VCP. VCP knockdown resulted in the accumulation of the DNA-PKcs protein in glioblastoma cells, and the proteasome inhibitor MG132 synergised this increase. As expected, this increase promoted the efficiency of DNA repair in several glioblastoma cell lines; in turn, this enhanced activity decreased the radiation sensitivity and prolonged the survival fraction of glioblastoma cells in vitro. Moreover, the VCP knockdown in glioblastoma cells reduced the survival time of the xenografted mice with radiation treatment relative to the control xenografted glioblastoma mice. In addition, the VCP protein was also downregulated in ~25% of GBM tissues from patients (WHO, grade IV astrocytoma), and the VCP protein level was correlated with patient survival (R(2)=0.5222, P<0.05). These findings demonstrated that VCP regulates DNA-PKcs degradation and increases the sensitivity of GBM cells to radiation
Low-Energy Electronic Structure of the High-Tc Cuprates La2-xSrxCuO4 Studied by Angle-resolved Photoemission Spectroscopy
We have performed a systematic angle-resolved photoemission spectroscopy
(ARPES) study of the high-Tc cuprates La2-xSrxCuO4, ranging from the underdoped
insulator to the superconductor to the overdoped metal. We have revealed a
systematic doping evolution of the band dispersions and (underlying) Fermi
surfaces, pseudogap and quasi-particle features under the influence of strong
electron-electron interaction and electron-phonon interaction. The unusual
transport and thermodynamic properties are explained by taking into account the
pseudogap opening and the Fermi arc formation, due to which the carrier number
decreases as the doped hole concentration decreases.Comment: 27 pages, 17 figures, accepted in Journal of Physics Condensed Matte
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