Mode stability on the real axis

A generalization of the mode stability result of Whiting (1989) for the Teukolsky equation is proved for the case of real frequencies. The main result of the paper states that a separated solution of the Teukolsky equation governing massless test fields on the Kerr spacetime, which is purely outgoing at infinity, and purely ingoing at the horizon, must vanish. This has the consequence, that for real frequencies, there are linearly independent fundamental solutions of the radial Teukolsky equation which are purely ingoing at the horizon, and purely outgoing at infinity, respectively. This fact yields a representation formula for solutions of the inhomogenous Teukolsky equation.Comment: 20 pages, 4 figures. Reference added, revtex4-1 forma

R-mode oscillations and rocket effect in rotating superfluid neutron stars. I. Formalism

We derive the hydrodynamical equations of r-mode oscillations in neutron stars in presence of a novel damping mechanism related to particle number changing processes. The change in the number densities of the various species leads to new dissipative terms in the equations which are responsible of the {\it rocket effect}. We employ a two-fluid model, with one fluid consisting of the charged components, while the second fluid consists of superfluid neutrons. We consider two different kind of r-mode oscillations, one associated with comoving displacements, and the second one associated with countermoving, out of phase, displacements.Comment: 10 page

Examining User Acceptance of Computer Technology: An Empirical Study of Student Teachers

The use of computer technology in schools has made slow progress since the mid-1980s even though governments have been generous in funding. It is therefore important to understand how and when teachers use computer technology in order to devise implementation strategies to encourage them. This study investigates student teachers\u27 perceptions of computer technology in relation to their intention to use computers. The purpose is to shed light on more effective ways to motivate the use of computer technology in schools. Based on an expanded variation of the Technology Acceptance Model, 84 completed surveys of student teachers were collected at a local university in Sweden. Overall, the results indicated that (1) student teachers\u27 perceived usefulness of computer technology had a direct significant effect on their intention to use it; (2) student teachers\u27 perceived ease of use had only an indirect significant effect on intention to use; however, (3) student teachers\u27 subjective norm, that is the possible influence of external expectations, did not have any direct or indirect significant effects on their intention to use computer technology. Theoretical and practical implications that follow from the results are discussed

Stability for linearized gravity on the Kerr spacetime

In this paper we prove integrated energy and pointwise decay estimates for solutions of the vacuum linearized Einstein equation on the domain of outer communication of the Kerr black hole spacetime. The estimates are valid for the full subextreme range of Kerr black holes, provided integrated energy estimates for the Teukolsky Master Equation holds. For slowly rotating Kerr backgrounds, such estimates are known to hold, due to the work of one of the authors. The results in this paper thus provide the first stability results for linearized gravity on the Kerr background, in the slowly rotating case, and reduce the linearized stability problem for the full subextreme range to proving integrated energy estimates for the Teukolsky equation. This constitutes an essential step towards a proof of the black hole stability conjecture, i.e. the statement that the Kerr family is dynamically stable, one of the central open problems in general relativity.Comment: 99 pages, 5 figures. Minor revision

Revisiting spin alignment of heavy mesons in its inclusive production

In the heavy quark limit inclusive production rate of a heavy meson can be factorized, in which the nonperturbative effect related to the heavy meson can be characterized by matrix elements defined in the heavy quark effective theory. Using this factorization, predictions for the full spin density matrix of a spin-1 and spin-2 meson can be obtained and they are characterized only by one coefficient representing the nonperturbative effect. Predictions for spin-1 heavy meson are compared with experiment performed at $e^+e^-$ colliders in the energy range from $\sqrt{s}=10.5$GeV to $\sqrt{s}=91$GeV, a complete agreement is found for $D^*$- and $B^*$-meson. For $D^{**}$ meson, our prediction suffers a large correction, as indicated by experimental data. There exists another approach by taking heavy mesons as bound systems, in which the total angular momentum of the light degrees of freedom is 1/2 and 3/2 for spin-1 and spin-2 meson respectively, then the diagonal parts of spin density matrices can be obtained. However, there are distinct differences in the predictions from the two approaches and they are discussed in detail.Comment: 14 pages with one figur

Density functional theory for freezing transition of vortex-line liquid with periodic layer pinning

By the density functional theory for crystallization, it is shown that for vortex lines in an underlying layered structure a smectic phase with period m=2 can be stabilized by strong layer pinning. The freezing of vortex liquid is then two-step, a second-order liquid-smectic transition and a first-order smectic-lattice transition. DFT also indicates that a direct, first-order liquid-lattice transition preempts the smectic order with m>2 irrespectively of the pinning strength. Possible H-T phase diagrams are mapped out. Implications of the DFT results to the interlayer Josephson vortex system in high-Tc cuprates are given.Comment: 4 pages, 5 figures, references adde

Stability for linearized gravity on the Kerr spacetime

In this paper we prove integrated energy and pointwise decay estimates for solutions of the vacuum linearized Einstein equation on the Kerr black hole exterior. The estimates are valid for the full, subextreme range of Kerr black holes, provided integrated energy estimates for the Teukolsky Master Equation holds. For slowly rotating Kerr backgrounds, such estimates are known to hold, due to the work of one of the authors arXiv:1708.07385. The results in this paper thus provide the first stability results for linearized gravity on the Kerr background, in the slowly rotating case, and reduce the linearized stability problem for the full subextreme range to proving integrated energy estimates for the Teukolsky equation. This constitutes an essential step towards a proof of the black hole stability conjecture, i.e. the statement that the Kerr family is dynamically stable, one of the central open problems in general relativity. The proof relies on three key steps. First, there are energy decay estimates for the Teukolsky equation, proved by applying weighted multiplier estimates to a system of spin-weighted wave equations derived from the Teukolsky equation, and making use of the pigeonhole principle for the resulting hierarchy of weighted energy estimates. Second, working in the outgoing radiation gauge, the linearized Einstein equations are written as a system of transport equations, driven by one of the Teukolsky scalars. Third, expansions for the relevant curvature, connection, and metric components can be made near null infinity. An analysis of the dynamics on future null infinity, together with the Teukolsky Starobinsky Identity plays an important role in the argument

Influence of hyperhomocysteinemia on the cellular redox state - Impact on homocysteine-induced endothelial dysfunction

Hyperhomocysteinemia is an independent risk factor for the development of atherosclerosis. An increasing body of evidence has implicated oxidative stress as being contributory to homocysteines deleterious effects on the vasculature. Elevated levels of homocysteine may lead to increased generation of superoxide by a biochemical mechanism involving nitric oxide synthase, and, to a lesser extent, by an increase in the chemical oxidation of homocysteine and other aminothiols in the circulation. The resultant increase in superoxide levels is further amplified by homocysteinedependent alterations in the function of cellular antioxidant enzymes such as cellular glutathione peroxidase or extracellular superoxide dismutase. One direct clinical consequence of elevated vascular superoxide levels is the inactivation of the vasorelaxant messenger nitric oxide, leading to endothelial dysfunction. Scavenging of superoxide anion by either superoxide dismutase or 4,5-dihydroxybenzene 1,3-disulfonate (Tiron) reverses endothelial dysfunction in hyperhomocysteinemic animal models and in isolated aortic rings incubated with homocysteine. Similarly, homocysteineinduced endothelial dysfunction is also reversed by increasing the concentration of the endogenous antioxidant glutathione or overexpressing cellular glutathione peroxidase in animal models of mild hyperhomocysteinemia. Taken together, these findings strongly suggest that the adverse vascular effects of homocysteine are at least partly mediated by oxidative inactivation of nitric oxide

Synergistic interaction in simultaneous exposure to Streptomyces californicus and Stachybotrys chartarum.

The microbial exposure associated with health complaints in moldy houses consists of a heterogeneous group of components, including both living and dead bacteria, fungi, and their metabolites and active compounds. However, little is known about the interactions between different microbes and their metabolites, although the cytotoxicity and inflammatory potential of certain individual microbes have been reported. In this study, we investigated the inflammatory responses of mouse RAW264.7 macrophages after exposure to six indoor air microbes (Aspergillus versicolor, Penicillium spinulosum, Stachybotrys chartarum, Bacillus cereus, Mycobacterium terrae, and Pseudomonas fluorescens) alone and together with the actinomycete Streptomyces californicus. The production of nitric oxide, levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6), and cytotoxicity were measured. The coexposure to Sta. chartarum and Str. californicus caused a synergistic increase in the production of IL-6 but not other cytokines. In further experiments, the metabolites from Sta. chartarum or from closely related fungi (atranones B and E, satratoxin G, trichodermin, 7-alpha-hydroxytrichodermol, staplabin, and SMTP-7) and the known fungal toxins sterigmatocystin, citrinin, and ochratoxin A were each tested with Str. californicus. The testing revealed a synergistic response in TNF-alpha and IL-6 production after coexposure to Str. californicus with both trichodermin and 7-alpha-hydroxytrichodermol. Finally, the synergistic inflammatory response caused by Str. californicus and trichodermin together was studied by analyzing for the presence of nuclear factor-kappa-B (NF-kappa-B) in nuclear extracts of the exposed cells. The exposure to Str. californicus induced the binding of NF-kappa-B proteins to the NF-kappa-B consensus sequence as well as to the natural NF-kappa-B site of the IL-6 promoter. Adding trichodermin to the exposure did not increase the DNA binding

System-size scan of dihadron azimuthal correlations in ultra-relativistic heavy ion collisions

System-size dependence of dihadron azimuthal correlations in ultra-relativistic heavy ion collision is simulated by a multi-phase transport model. The structure of correlation functions and yields of associated particles show clear participant path-length dependences in collision systems with a partonic phase. The splitting parameter and root-mean-square width of away-side correlation functions increase with collision system size from $^{14}$N+$^{14}$N to $^{197}$Au+$^{197}$Au collisions. The double-peak structure of away-side correlation functions can only be formed in sufficient "large" collision systems under partonic phase. The contrast between the results with partonic phase and with hadron gas could suggest some hints to study onset of deconfinment.Comment: 8 pages, 4 figures, 1 table; Nucl. Phys. A (accepted