Brane-Antibrane Systems at Finite Temperature and Phase Transition near the Hagedorn Temperature

In order to study the thermodynamic properties of brane-antibrane systems, we compute the finite temperature effective potential of tachyon T in this system on the basis of boundary string field theory. At low temperature, the minimum of the potential shifts towards T=0 as the temperature increases. In the D9-antiD9 case, the sign of the coefficient of |T|^2 term of the potential changes slightly below the Hagedorn temperature. This means that a phase transition occurs near the Hagedorn temperature. On the other hand, the coefficient is kept negative in the Dp-antiDp case with p <= 8, and thus a phase transition does not occur. This leads us to the conclusion that only a D9-antiD9 pair and no other (lower dimensional) brane-antibrane pairs are created near the Hagedorn temperature. We also discuss a phase transition in NS9B-antiNS9B case as a model of the Hagedorn transition of closed strings.Comment: 28 pages, 3 figures, minor errors correcte

Stable Exact Solutions in Cosmological Models with Two Scalar Fields

The stability of isotropic cosmological solutions for two-field models in the Bianchi I metric is considered. We prove that the sufficient conditions for the Lyapunov stability in the Friedmann-Robertson-Walker metric provide the stability with respect to anisotropic perturbations in the Bianchi I metric and with respect to the cold dark matter energy density fluctuations. Sufficient conditions for the Lyapunov stability of the isotropic fixed points of the system of the Einstein equations have been found. We use the superpotential method to construct stable kink-type solutions and obtain sufficient conditions on the superpotential for the Lyapunov stability of the corresponding exact solutions. We analyze the stability of isotropic kink-type solutions for string field theory inspired cosmological models.Comment: 23 pages, v3:typos corrected, references adde

Finite Temperature Systems of Brane-Antibrane on a Torus

In order to study the thermodynamic properties of brane-antibrane systems in the toroidal background, we compute the finite temperature effective potential of tachyon T in this system on the basis of boundary string field theory. We first consider the case that all the radii of the target space torus are about the string scale. If the Dp-antiDp pair is extended in all the non-compact directions, the sign of the coefficient of |T|^2 term of the potential changes slightly below the Hagedorn temperature. This means that a phase transition occurs near the Hagedorn temperature. On the other hand, if the Dp-antiDp pair is not extended in all the non-compact directions, the coefficient is kept negative, and thus a phase transition does not occur. Secondly, we consider the case that some of the radii of the target space torus are much larger than the string scale and investigate the behavior of the potential for each value of the radii and the total energy. If the Dp-antiDp pair is extended in all the non-compact directions, a phase transition occurs for large enough total energy.Comment: 23 pages, 3 figures, minor errors corrected, version to appear in JHE

The Schr\"odinger Wave Functional and S-branes

In this paper we will consider the minisuperspace approach to S-branes dynamics in the Schr\"odinger picture description. Time-evolution of vacuum wave functional for quantum field theory on S-brane is studied. Open string pair production is calculated. The analysis of density matrix for mixed states is also performed.Comment: 27 page

Suspension high velocity oxy-fuel spraying of TiO2: a quantitative approach to phase composition

A range of coatings from a water based suspension of anatase has been prepared by suspension high velocity oxy-fuel spraying with the aim to study effects of heat power of the flame on phase composition, microstructure and surface topography. Three most commonly used approaches of quantitative phase analysis have been scrutinized with respect to their applicability and as some of the coatings showed presence of preferred orientation and it was argued that quantitative Rietveld refinement is the most accurate method for phase composition determination. Coatings had a layered duplex anatase/rutile microstructure with fraction of rutile increasing exponentially with heat power. Spraying at the lower heat power led to a lower surface roughness and higher power resulted in surfaces with pronounced humps, which were distributed homogeneously on the surface. The emergence of humps is related to an increase in macroscopic surface area of up to 30% with respect to the flat coating

Transmission electron microscopic observations of nanobubbles and their capture of impurities in wastewater

Unique properties of micro- and nanobubbles (MNBs), such as a high adsorption of impurities on their surface, are difficult to verify because MNBs are too small to observe directly. We thus used a transmission electron microscope (TEM) with the freeze-fractured replica method to observe oxygen (O2) MNBs in solutions. MNBs in pure water and in 1% NaCl solutions were spherical or oval. Their size distribution estimated from TEM images close to that of the original solution is measured by light-scattered methods. When we applied this technique to the observation of O2 MNBs formed in the wastewater of a sewage plant, we found the characteristic features of spherical MNBs that adsorbed surrounding impurity particles on their surface

An algebraic approach to the scattering equations

We employ the so-called companion matrix method from computational algebraic geometry, tailored for zero-dimensional ideals, to study the scattering equations. The method renders the CHY-integrand of scattering amplitudes computable using simple linear algebra and is amenable to an algorithmic approach. Certain identities in the amplitudes as well as rationality of the final integrand become immediate in this formalism

Regulation of expression of Na+,K+-ATPase in androgen-dependent and androgen-independent prostate cancer

The β1-subunit of Na+,K+-ATPase was isolated and identified as an androgen down-regulated gene. Expression was observed at high levels in androgen-independent as compared to androgen-dependent (responsive) human prostate cancer cell lines and xenografts when grown in the presence of androgens. Down-regulation of the β1-subunit was initiated at concentrations between 0.01 nM and 0.03 nM of the synthetic androgen R1881 after relatively long incubation times (> 24 h). Using polyclonal antibodies, the concentration of β1-subunit protein, but not of the α1-subunit protein, was markedly reduced in androgen-dependent human prostate cancer cells (LNCaP-FGC) cultured in the presence of androgens. In line with these observations it was found that the protein expression of total Na+,K+-ATPase in the membrane (measured by 3H-ouabain binding) was also markedly decreased. The main function of Na+,K+-ATPase is to maintain sodium and potassium homeostasis in animal cells. The resulting electrochemical gradient is facilitative for transport of several compounds over the cell membrane (for example cisplatin, a chemotherapeutic agent experimentally used in the treatment of hormone-refractory prostate cancer). Here we observed that a ouabain-induced decrease of Na+,K+-ATPase activity in LNCaP-FGC cells results in reduced sensitivity of these cells to cisplatin-treatment. Surprisingly, androgen-induced decrease of Na+,K+-ATPase expression, did not result in significant protection against the chemotherapeutic agent. © 1999 Cancer Research Campaig