Kinetics of the reduction of wilt-type and mutant cytochrome c-550 by methylamin dehydrogenase and amicyanin from thiobacillus-versutus

Macromolecular Biochemistr

Optical spectroscopy of the radio pulsar PSR B0656+14

We have obtained the spectrum of a middle-aged PSR B0656+14 in the 4300-9000 AA range with the ESO/VLT/FORS2. Preliminary results show that at 4600-7000 AA the spectrum is almost featureless and flat with a spectral index $\alpha_nu ~ -0.2 that undergoes a change to a positive value at longer wavelengths. Combining with available multiwavelength data suggests two wide, red and blue, flux depressions whose frequency ratio is about 2 and which could be the 1st and 2nd harmonics of electron/positron cyclotron absorption formed at magnetic fields ~10^8G in upper magnetosphere of the pulsar.Comment: 4 pages, 4 figures, To appear in Astrophysics and Space Science, Proceedings of "Isolated Neutron Stars: from the Interior to the Surface", eds. D. Page, R. Turolla and S. Zan

Characterization of mutant met100lys of cytochrome c-550 from thibacillus-versutus with Lysine-histidine heme ligation

Macromolecular Biochemistr

On slip pulses at a sheared frictional viscoelastic/ non deformable interface

We study the possibility for a semi-infinite block of linear viscoelastic material, in homogeneous frictional contact with a non-deformable one, to slide under shear via a periodic set of ``self-healing pulses'', i.e. a set of drifting slip regions separated by stick ones. We show that, contrary to existing experimental indications, such a mode of frictional sliding is impossible for an interface obeying a simple local Coulomb law of solid friction. We then discuss possible physical improvements of the friction model which might open the possibility of such dynamics, among which slip weakening of the friction coefficient, and stress the interest of developing systematic experimental investigations of this question.Comment: 23 pages, 3 figures. submitted to PR

Optical observations of the young supernova remnant SNR 0540-69.3 and its pulsar

We have used the ESO NTT/EMMI and VLT/FORS1 instruments to examine the LMC supernova remnant 0540-69.3 as well as its pulsar (PSR B0540-69) and pulsar-powered nebula in the optical range.Spectroscopic observations of the remnant covering the range of 3600-7350 A centered on the pulsar produced results consistent with those of Kirshner et al. (1989), but also revealed many new emission lines. The most important are [Ne III] 3869, 3967 and Balmer lines of hydrogen. In both the central part of the remnant, as well as in nearby H II regions, the [O III] temperature is higher than about 20 000 K, but lower than previously estimated. For PSR B0540-69, previous optical data are mutually inconsistent: HST/FOS spectra indicate a significantly higher absolute flux and steeper spectral index than suggested by early time-resolved groundbased UBVRI photometry. We show that the HST and VLT spectroscopic data for the pulsar have more then about 50% nebular contamination, and that this is the reason for the previous difference. Using HST/WFPC2 archival images obtained in various bands from the red part of the optical to the NUV range we have performed an accurate photometric study of the pulsar, and find that the spectral energy distribution of the pulsar emission has a negative slope with 1.07 +/- 0.2. This is steeper than derived from previous UBVRI photometry, and also different from the almost flat spectrum of the Crab pulsar. We also estimate that the proper motion of the pulsar is 4.9 +/- 2.3 mas/yr, corresponding to a transverse velocity of 1190 +/- 560 km/s, projected along the southern jet of the pulsar nebula.Comment: To appear in the conference proceedings '35th COSPAR Scientific Assembly. E1.4-0058-04, Paris, France, 18 - 25 July 2004'. Paper with full resolution images can be found at ftp://ftp.astro.su.se/pub/supernova/natalia/0540psr_snr_fin.pd

Effects of Pore Walls and Randomness on Phase Transitions in Porous Media

We study spin models within the mean field approximation to elucidate the topology of the phase diagrams of systems modeling the liquid-vapor transition and the separation of He$^3$--He$^4$ mixtures in periodic porous media. These topologies are found to be identical to those of the corresponding random field and random anisotropy spin systems with a bimodal distribution of the randomness. Our results suggest that the presence of walls (periodic or otherwise) are a key factor determining the nature of the phase diagram in porous media.Comment: REVTeX, 11 eps figures, to appear in Phys. Rev.

Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review

New hadrons as ultra-high energy cosmic rays

Ultra-high energy cosmic ray (UHECR) protons produced by uniformly distributed astrophysical sources contradict the energy spectrum measured by both the AGASA and HiRes experiments, assuming the small scale clustering of UHECR observed by AGASA is caused by point-like sources. In that case, the small number of sources leads to a sharp exponential cutoff at the energy E<10^{20} eV in the UHECR spectrum. New hadrons with mass 1.5-3 GeV can solve this cutoff problem. For the first time we discuss the production of such hadrons in proton collisions with infrared/optical photons in astrophysical sources. This production mechanism, in contrast to proton-proton collisions, requires the acceleration of protons only to energies E<10^{21} eV. The diffuse gamma-ray and neutrino fluxes in this model obey all existing experimental limits. We predict large UHE neutrino fluxes well above the sensitivity of the next generation of high-energy neutrino experiments. As an example we study hadrons containing a light bottom squark. These models can be tested by accelerator experiments, UHECR observatories and neutrino telescopes.Comment: 17 pages, revtex style; v2: shortened, as to appear in PR

Large enhancement of deuteron polarization with frequency modulated microwaves

We report a large enhancement of 1.7 in deuteron polarization up to values of 0.6 due to frequency modulation of the polarizing microwaves in a two liters polarized target using the method of dynamic nuclear polarization. This target was used during a deep inelastic polarized muon-deuteron scattering experiment at CERN. Measurements of the electron paramagnetic resonance absorption spectra show that frequency modulation gives rise to additional microwave absorption in the spectral wings. Although these results are not understood theoretically, they may provide a useful testing ground for the deeper understanding of dynamic nuclear polarization.Comment: 10 pages, including the figures coming in uuencoded compressed tar files in poltar.uu, which also brings cernart.sty and crna12.sty files neede