14,432 research outputs found

    The Physical State of Potassium Ion in the Living Cell

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    This review summarizes more than 30 years of experimental testing (and confirmation) of a key postulate of the association-induction (AI) hypothesis: most K+ ions in resting cells are adsorbed on -and -carboxyl group of cell proteins in a close-contact one ion-one site manner. Failure of healthy, cytoplasm-free, squid axon-membrane sacs to selectively accumulate K+ over Na+ and success of muscle cells without a functional cell membrane (and postulated pumps) to achieve the same, point to the cytoplasm as the seat of selective K+ accumulation. Four independent techniques unanimously confirmed the predicted localization in striated muscle cells, of the bulk of cell K+ in the A-bands where 65% of the -and -carboxyl groups are located. Strict adherence to the Langmuir adsorption isotherm in the equilibrium distribution of K+ in muscle cells in the absence and presence of competing ions, proved one ion-one site, close contact adsorption of cell K+ on anionic groups. The effectively membrane-pumpless open-ended cell (EMOC) technique, further helped to establish close contact adsorption of K+ to take place in the cytoplasm rather than the cell membrane. A pKa of 3.9 obtained by titration of the cytoplasmic anions groups and a sensitivity to specific carboxyl group-reagent, 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide HCl combine to establish that the cytoplasmic anionic sites adsorbing K+ are indeed -and -carboxyl groups

    Solute Exclusion by Polymer and Protein-Dominated Water: Correlation with Results of Nuclear Magnetic Resonance (NMR) and Calorimetric Studies and Their Significance for the Understanding of the Physical State of Water in Living Cells

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    According to the polarized multilayer (PM) theory of cell water proteins with their back-bones fully extended and their NHCO groups directly exposed to bulk water, polarize water in multilayers. Experimental testing of the theory led to a new understanding of the uniqueness of gelatin, due to its permanently maintained fully extended conformation and its ability to polarize the bulk phase water in multilayers with reduced solubilities for solutes in a size dependent manner ( size rule ). Other models which behave like gelatin are urea-denatured proteins, synthetic polymers like polyethylene oxide (PEO), and polyvinylpyrrolidine (PVP), but not native proteins. NMR studies showed that the majority of water molecules dominated by these polymers does indeed suffer rotational (and translational) motional restriction as predicted by the PM theory. In conjunction with ultra-high frequency dielectric studies but particularly quasielastic neutron scattering of both model systems (e.g., PEO) and living cells (i.e., brine shrimp cysts and frog muscle), this finding offers confirmation of the PM theory of living cell water and model systems. Studies of the freezing point depression showed that the presence of as much as 50% of native proteins had no effect on the freezing point of water while inclusion of gelatin, PEO, etc., caused concentration-dependent lowering of the freezing temperature. These findings demonstrate the key role of polarized water in the phenomena of freezing point depression and the unusual ice forms seen in living cells

    A Physical Theory of the Living State: Application to Water and Solute Distribution

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    This review begins with a summary of the disproof of the membrane-pump theory and the alternative theory of the living cell, the association-induction (AI) hypothesis. Being alive in the AI hypothesis represents the maintenance of a high (negative) energy-low entropy state in which the two major components K+ and water of the living cell are closely associated with the third major component of the living cells, proteins. K+ is adsorbed singly on -and γ-carboxyl groups and the bulk of cell water in multilayers on the exposed NHCO groups of fully extended polypeptide chains of cell proteins. These adsorptions account for both the constancy of cell K+ and cell water per unit of cell proteins. ATP plays a key role in the maintenance of the cooperatively linked protein-ion-water assembly at the living state by its adsorption on key protein site and exercises the controlling influence through its strong inductive effects. Water polarized in multilayers demonstrates size-dependent exclusion of solutes, e.g., large (hydrated) Na+ is excluded from water in living cells or model systems while smaller urea that fits into the dynamic water structure is not excluded. The confirmation of the polarized multilayer theory of cell water by nuclear magnetic resonance (NMR), dielectric, neutron scattering, and other studies not only reverses the conventional belief of the existence of the cell water as normal liquid water; it also gives a new definition to colloids

    Little String Theory from Double-Scaling Limits of Field Theories

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    We show that little string theory on S^5 can be obtained as double-scaling limits of the maximally supersymmetric Yang-Mills theories on RxS^2 and RxS^3/Z_k. By matching the gauge theory parameters with those in the gravity duals found by Lin and Maldacena, we determine the limits in the gauge theories that correspond to decoupling of NS5-brane degrees of freedom. We find that for the theory on RxS^2, the 't Hooft coupling must be scaled like ln^3(N), and on RxS^3/Z_k, like ln^2(N). Accordingly, taking these limits in these field theories gives Lagrangian definitions of little string theory on S^5.Comment: 16 pages, 5 figures. Minor change

    Bounces/Dyons in the Plane Wave Matrix Model and SU(N) Yang-Mills Theory

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    We consider SU(N) Yang-Mills theory on the space R^1\times S^3 with Minkowski signature (-+++). The condition of SO(4)-invariance imposed on gauge fields yields a bosonic matrix model which is a consistent truncation of the plane wave matrix model. For matrices parametrized by a scalar \phi, the Yang-Mills equations are reduced to the equation of a particle moving in the double-well potential. The classical solution is a bounce, i.e. a particle which begins at the saddle point \phi=0 of the potential, bounces off the potential wall and returns to \phi=0. The gauge field tensor components parametrized by \phi are smooth and for finite time both electric and magnetic fields are nonvanishing. The energy density of this non-Abelian dyon configuration does not depend on coordinates of R^1\times S^3 and the total energy is proportional to the inverse radius of S^3. We also describe similar bounce dyon solutions in SU(N) Yang-Mills theory on the space R^1\times S^2 with signature (-++). Their energy is proportional to the square of the inverse radius of S^2. From the viewpoint of Yang-Mills theory on R^{1,1}\times S^2 these solutions describe non-Abelian (dyonic) flux tubes extended along the x^3-axis.Comment: 11 pages; v2: one formula added, some coefficients correcte

    MeV Right-handed Neutrinos and Dark Matter

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    We consider the possibility of having a MeV right-handed neutrino as a dark matter constituent. The initial reason for this study was the 511 keV spectral line observed by the satellite experiment INTEGRAL: could it be due to an interaction between dark matter and baryons? Independently of this, we find a number of constraints on the assumed right-handed interactions. They arise in particular from the measurements by solar neutrino experiments. We come to the conclusion that such particles interactions are possible, and could reproduce the peculiar angular distribution, but not the rate of the INTEGRAL signal. However, we stress that solar neutrino experiments are susceptible to provide further constraints in the future.Comment: 7 pages, figure 1 changed, added reference

    The electronic and magnetic properties of La0.85Zr0.15MnO3 deposited on SrTiO3 and MgO substrates

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    [[abstract]]The electronic and magnetic properties of tetravalent-ion-doped La0.85Zr0.15MnO3 (LZMO) thin films that were epitaxially grown on SrTiO3 (STO) and MgO substrates were studied using temperature-dependent x-ray diffraction (XRD), x-ray absorption near-edge structure, x-ray linear dichroism, and x-ray magnetic circular dichroism at the Mn L 3,2- and K-edge. XRD studies reveal that the LZMO thin films have compressive and tensile strains (along the c -axis) on the STO and MgO substrates, respectively. As the temperature is reduced from room temperature to below magnetic transition temperature, the preferentially occupied Mn majority-spin e g orbital changes from the in-plane dx 2 -y 2 to the out-of-plane d 3 z 2 -r 2 orbital for LZMO/STO, and vice versa for LZMO/MgO. Experimental results suggest that the new hopping path that is mediated by the Mn2+ ions triggers a stronger d 3 z 2 -r 2 orbital ordering of Mn3+ ions and enhances the ferromagnetic coupling between the Mn spin moments of t 2g electrons in LZMO/STO, whereas the strong tensile strain stabilizes the dx 2 -y 2 orbital by inducing lattice distortions of the MnO6 octahedra in LZMO/MgO.[[notice]]補正完畢[[incitationindex]]SCI[[cooperationtype]]國

    Luminosity dependent clustering of star-forming BzK galaxies at redshift 2

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    We use the BzK color selection proposed by Daddi et al. (2004) to obtain a sample of 1092 faint star-forming galaxies (hereafter sBzKs) from 180 arcmin^2 in the Subaru Deep Field. This sample represents star-forming galaxies at 1.4 < z < 2.5 down to K(AB)=23.2, which roughly corresponds to a stellar-mass limit of ~ 1 x 10^{10} Msun. We measure the angular correlation function (ACF) of these sBzKs to be w(theta) = (0.58 +- 0.13) x theta["]^{-0.8} and translate the amplitude into the correlation length assuming a reasonable redshift distribution. The resulting value, r0 = 3.2^{+0.6}_{-0.7} h^{-1} Mpc, suggests that our sBzKs reside in haloes with a typical mass of 2.8 x 10^{11} Msun. Combining this halo mass estimate with those for brighter samples of Kong et al. (2006), we find that the mass of dark haloes largely increases with K brightness, a measure of the stellar mass. Comparison with other galaxy populations suggests that faint sBzKs (K(AB)<23.2) and Lyman Break Galaxies at z ~ 2 are similar populations hosted by relatively low-mass haloes, while bright sBzKs (K(AB)<21) reside in haloes comparable to or more massive than those of Distant Red Galaxies and Extremely Red Objects. Using the extended Press-Schechter formalism, we predict that present-day descendants of haloes hosting sBzKs span a wide mass range depending on K brightness, from lower than that of the Milky Way up to those of richest clusters.Comment: 14 pages, 9 figures, accepted for publication in Ap
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