Helical Magnetic Fields from Inflation

We analyze the generation of seed magnetic fields during de Sitter inflation considering a non-invariant conformal term in the electromagnetic Lagrangian of the form $-\frac14 I(\phi) F_{\mu \nu} \widetilde{F}^{\mu \nu}$, where $I(\phi)$ is a pseudoscalar function of a non-trivial background field $\phi$. In particular, we consider a toy model, that could be realized owing to the coupling between the photon and either a (tachyonic) massive pseudoscalar field and a massless pseudoscalar field non-minimally coupled to gravity, where $I$ follows a simple power-law behavior $I(k,\eta) = g/(-k\eta)^{\beta}$ during inflation, while it is negligibly small subsequently. Here, $g$ is a positive dimensionless constant, $k$ the wavenumber, $\eta$ the conformal time, and $\beta$ a real positive number. We find that only when $\beta = 1$ and $0.1 \lesssim g \lesssim 2$ astrophysically interesting fields can be produced as excitation of the vacuum, and that they are maximally helical.Comment: 17 pages, 1 figure, subsection IIc and references added; accepted for publication in IJMP

Tables of Hyperonic Matter Equation of State for Core-Collapse Supernovae

We present sets of equation of state (EOS) of nuclear matter including hyperons using an SU_f(3) extended relativistic mean field (RMF) model with a wide coverage of density, temperature, and charge fraction for numerical simulations of core collapse supernovae. Coupling constants of Sigma and Xi hyperons with the sigma meson are determined to fit the hyperon potential depths in nuclear matter, U_Sigma(rho_0) ~ +30 MeV and U_Xi(rho_0) ~ -15 MeV, which are suggested from recent analyses of hyperon production reactions. At low densities, the EOS of uniform matter is connected with the EOS by Shen et al., in which formation of finite nuclei is included in the Thomas-Fermi approximation. In the present EOS, the maximum mass of neutron stars decreases from 2.17 M_sun (Ne mu) to 1.63 M_sun (NYe mu) when hyperons are included. In a spherical, adiabatic collapse of a 15$M_\odot$ star by the hydrodynamics without neutrino transfer, hyperon effects are found to be small, since the temperature and density do not reach the region of hyperon mixture, where the hyperon fraction is above 1 % (T > 40 MeV or rho_B > 0.4 fm^{-3}).Comment: 23 pages, 6 figures (Fig.3 and related comments on pion potential are corrected in v3.

Circular Polarization from Gamma-ray Burst Afterglows

We investigate the circular polarization (CP) from Gamma-Ray Burst (GRB) afterglows. We show that a tangled magnetic field cannot generate CP without an ordered magnetic field because there is always an oppositely directed field, so that no handedness exists. This implies the observation of CP could be a useful probe of an ordered field, which carries valuable information on the GRB central engine. By solving the transfer equation of polarized radiation, we find that the CP reaches 1% at radio frequencies and 0.01% at optical for the forward shock, and 10-1% at radio and 0.1-0.01% at optical for the reverse shock.Comment: 12 pages, 3 figure

Bioprocessing in Microgravity: Applications of Continuous Flow Electrophoresis to Rat Anterior Pituitary Particles

In this report we describe the results of a continuous flow electrophoresis (CFE) experiment done on STS-65 in which we tested the idea that intracellular growth hormone (GH) particles contained in a cell lysate prepared from cultured rat anterior pituitary cells in microgravity might have different electrophoretic mobilities from those in a synchronous ground control cell lysate. Collectively, the results suggested that CFE processing in microgravity was better than on earth; more samples could be processed at a time (6 x) and more variant forms of GH molecules could be resolved as well. We had also hoped to carry out a pituitary cell CFE experiment, but failure of the hardware required that the actual cell electrophoresis trials be done on earth shortly after Shuttle landing. Data from these experiments showed that space-flown cells possessed a higher electrophoretic mobility than ground control cells, thereby offering evidence for the idea that exposure of cultured cells to microgravity can change their net surface charge-density especially when the cells are fed. Collectively, the results from this pituitary cell experiment document the advantage of using coupled cell culture and CFE techniques in the microgravity environment

A diffuse scattering model of ultracold neutrons on wavy surfaces

Metal tubes plated with nickel-phosphorus are used in many fundamental physics experiments using ultracold neutrons (UCN) because of their ease of fabrication. These tubes are usually polished to a average roughness of 25-150 nm. However, there is no scattering model that accurately describes UCN scattering on such a rough guide surface with a mean-square roughness larger than 5 nm. We therefore developed a scattering model for UCN in which scattering from random surface waviness with a size larger than the UCN wavelength is described by a microfacet Bidirectional Reflectance Distribution Function model (mf-BRDF model), and scattering from smaller structures by the Lambert's cosine law (Lambert model). For the surface waviness, we used the statistical distribution of surface slope measured by an atomic force microscope on a sample piece of guide tube as input of the model. This model was used to describe UCN transmission experiments conducted at the pulsed UCN source at J-PARC. In these experiments, a UCN beam collimated to a divergence angle smaller than $\pm 6^{\circ}$ was directed into a guide tube with a mean-square roughness of 6.4 nm to 17 nm at an oblique angle, and the UCN transport performance and its time-of-flight distribution were measured while changing the angle of incidence. The mf-BRDF model combined with the Lambert model with scattering probability $p_{L} = 0.039\pm0.003$ reproduced the experimental results well. We have thus established a procedure to evaluate the characteristics of UCN guide tubes with a surface roughness of approximately 10 nm.Comment: 15 pages, 11 figure

Structure of an archaeal PCNA1-PCNA2-FEN1 complex: elucidating PCNA subunit and client enzyme specificity.

The archaeal/eukaryotic proliferating cell nuclear antigen (PCNA) toroidal clamp interacts with a host of DNA modifying enzymes, providing a stable anchorage and enhancing their respective processivities. Given the broad range of enzymes with which PCNA has been shown to interact, relatively little is known about the mode of assembly of functionally meaningful combinations of enzymes on the PCNA clamp. We have determined the X-ray crystal structure of the Sulfolobus solfataricus PCNA1-PCNA2 heterodimer, bound to a single copy of the flap endonuclease FEN1 at 2.9 A resolution. We demonstrate the specificity of interaction of the PCNA subunits to form the PCNA1-PCNA2-PCNA3 heterotrimer, as well as providing a rationale for the specific interaction of the C-terminal PIP-box motif of FEN1 for the PCNA1 subunit. The structure explains the specificity of the individual archaeal PCNA subunits for selected repair enzyme 'clients', and provides insights into the co-ordinated assembly of sequential enzymatic steps in PCNA-scaffolded DNA repair cascades

Primordial Power Spectrum Reconstruction

In order to reconstruct the initial conditions of the universe it is important to devise a method that can efficiently constrain the shape of the power spectrum of primordial matter density fluctuations in a model-independent way from data. In an earlier paper we proposed a method based on the wavelet expansion of the primordial power spectrum. The advantage of this method is that the orthogonality and multiresolution properties of wavelet basis functions enable information regarding the shape of $P_{\rm in}(k)$ to be encoded in a small number of non-zero coefficients. Any deviation from scale-invariance can then be easily picked out. Here we apply this method to simulated data to demonstrate that it can accurately reconstruct an input $P_{\rm in}(k)$, and present a prescription for how this method should be used on future data.Comment: 4 pages, 2 figures. JCAP accepted versio

Reconstructing the primordial power spectrum - a new algorithm

We propose an efficient and model independent method for reconstructing the primordial power spectrum from Cosmic Microwave Background (CMB) and large scale structure observations. The algorithm is based on a Monte Carlo principle and therefore very simple to incorporate into existing codes such as Markov Chain Monte Carlo. The algorithm has been used on present cosmological data to test for features in the primordial power spectrum. No significant evidence for features is found, although there is a slight preference for an overall bending of the spectrum, as well as a decrease in power at very large scales. We have also tested the algorithm on mock high precision CMB data, calculated from models with non-scale invariant primordial spectra. The algorithm efficiently extracts the underlying spectrum, as well as the other cosmological parameters in each case. Finally we have used the algorithm on a model where an artificial glitch in the CMB spectrum has been imposed, like the ones seen in the WMAP data. In this case it is found that, although the underlying cosmological parameters can be extracted, the recovered power spectrum can show significant spurious features, such as bending, even if the true spectrum is scale invariant.Comment: 22 pages, 12 figures, matches JCAP published versio

New chiral organosulfur donors related to bis(ethylenedithio)tetrathiafulvalene

Six new enantiopure chiral organosulfur donors, with structures related to BEDT-TTF, have been synthesised for use in the preparation of organic metals, starting either by double nucleophilic substitutions on the bis-mesylate of 2R,4Rpentane-2,4-diol or by a cycloaddition with subsequent elimination of acetic acid on the enol acetate of (+)-nopinone. Crystal structures of some of their radical cation triiodides salts and TCNQ complexes are reported