The periodic variations of a white-light flare observed with ULTRACAM

High time resolution observations of a white-light flare on the active star EQ PegB show evidence of intensity variations with a period of ≈10 s. The period drifts to longer values during the decay phase of the flare. If the oscillation is interpreted as an impulsively-excited, standing-acoustic wave in a flare loop, the period implies a loop length of ≈3.4 Mm and ≈6.8 Mm for the case of the fundamental mode and the second harmonic, respectively. However, the small loop lengths imply a very high modulation depth making the acoustic interpretation unlikely. A more realistic interpretation may be that of a fast-MHD wave, with the modulation of the emission being due to the magnetic field. Alternatively, the variations could be due to a series of reconnection events. The periodic signature may then arise as a result of the lateral separation of individual flare loops or current sheets with oscillatory dynamics (i.e., periodic reconnection).

White-light oscillations during a flare on II Peg

We analyse the intensity oscillations observed in the gradual phase of a white-light flare on the RS CV n binary II Peg. Fast Fourier Transform power spectra and Wavelet analysis reveal a period of 220 s. The reliability of the oscillation is tested using several criteria. Oscillating coronal loop models are used to derive physical parameters such as temperature, electron density and magnetic field strength associated with the coronal loop. The derived parameters are consistent with the near-simultaneous X-ray observations of the flare. There is no evidence for oscillations in the quiescent state of the binary.

Absence of aquaporin-4 expression in lesions of neuromyelitis optica but increased expression in multiple sclerosis lesions and normal-appearing white matter.

Aquaporin-4 (AQP4) has recently been implicated in the pathogenesis of neuromyelitis optica(NMO) where it has been identifed as the first defined autoantigen pertinent to an infammatory demyelinating disorder of the human CNS. Furthermore, a recent case report has shown a lack of AQP4 expression in the spinal cord lesions of NMO. However, the pattern of AQP4 expression in multiple sclerosis (MS) tissues has not been well-defned. In the present investigation we have confirmed a lack of expression of AQP4 in optic and spinal cord lesions in NMO which contrasted sharply with the increased levels of AQP4 expression seen in MS lesions. Furthermore a detailed immunohistochemical and semi-quantitative analysis is used to describe the expression pattern of AQP4 on well-characterized tissue microarray samples of MS and control white matter. Anatomically AQP4 was more highly expressed in all categories of MS tissue compared to normal control tissues with the most abundant expression in active lesions. Within active lesions AQP4 expression was significantly correlated with expression of the pro-infammatory cytokine osteopontin. At the cellular level dual-labelling immunofluoresence demonstrated that increased expression of AQP4 was most pronounced at the astrocytic endfeet but was also associated with the cell bodies of astrocytes in the tissue parenchyma. The finding of increased AQP4 expression in MS lesions in contrast to the lack of expression in NMO lesions may suggest different mechanisms of initiation and progression between the two disease states.

Novel frenatins from the skin of the Australasian Giant White-lipped tree frog, Litoria infrafrenata: cloning of precursor cDNAs and identification in defensive skin secretion.

The Australasian anuran amphibian genus Litoria, contains many phenotypically-diverse species as a result of radial evolution of an ancestral species into different biotopes much in the manner of the indigenous marsupial mammals. In common with members of the Central/South American genus Phyllomedusa, their specialized skin granular glands are factories for the production of a plethora of biologically-active peptides. Here we report a more detailed study of those present in the defensive skin secretion of the Australasian giant white-lipped tree frog, Litoria infrafrenata, and, for the first time, we have identified three novel frenatins by deduction of primary structures from cDNAs that were cloned from a library constructed from lyophilized skin secretion using a recently-developed technique. All open-reading frames consisted of a putative signal peptide and an acidic pro-region followed by a single copy of a frenatin peptide. Processed peptides corresponding in molecular mass to the deduced molecular masses of frenatins (named 1.1, 3, 3.1 and 4.1) were identified in the same secretion sample using HPLC and mass spectroscopy. The application of this technique thus permits parallel peptidomic and transcriptomic analyzes on the same lyophilized skin secretion sample circumventing sacrifice of specimens from endangered herpetofauna.

A new look at the pulsating DB white dwarf GD 358: Line-of-sight velocity measurements and constraints on model atmospheres

We report on our findings of the bright, pulsating, helium atmosphere white dwarf GD 358, based on time-resolved optical spectrophotometry. We identify 5 real pulsation modes and at least 6 combination modes at frequencies consistent with those found in previous observations. The measured Doppler shifts from our spectra show variations with amplitudes of up to 5.5 km s-1 at the frequencies inferred from the flux variations. We conclude that these are variations in the line-of-sight velocities associated with the pulsational motion. We use the observed flux and velocity amplitudes and phases to test theoretical predictions within the convective driving framework, and compare these with similar observations of the hydrogen atmosphere white dwarf pulsators (DAVs). The wavelength dependence of the fractional pulsation amplitudes (chromatic amplitudes) allows us to conclude that all five real modes share the same spherical degree, most likely, l=1. This is consistent with previous identifications based solely on photometry. We find that a high signal-to-noise mean spectrum on its own is not enough to determine the atmospheric parameters and that there are small but significant discrepancies between the observations and model atmospheres. The source of these remains to be identified. While we infer Teff =24 kK and log g ~ 8.0 from the mean spectrum, the chromatic amplitudes, which are a measure of the derivative of the flux with respect to the temperature, unambiguously favour a higher effective temperature, 27 kK, which is more in line with independent determinations from ultra-violet spectra.

Characterization of White bream virus reveals a novel genetic cluster of nidoviruses.

The order Nidovirales comprises viruses from the families Coronaviridae (genera Coronavirus and Torovirus), Roniviridae (genus Okavirus), and Arteriviridae (genus Arterivirus). In this study, we characterized White bream virus (WBV), a bacilliform plus-strand RNA virus isolated from fish. Analysis of the nucleotide sequence, organization, and expression of the 26.6-kb genome provided conclusive evidence for a phylogenetic relationship between WBV and nidoviruses. The polycistronic genome of WBV contains five open reading frames (ORFs), called ORF1a, -1b, -2, -3, and -4. In WBV-infected cells, three subgenomic RNAs expressing the structural proteins S, M, and N were identified. The subgenomic RNAs were revealed to share a 42-nucleotide, 5' leader sequence that is identical to the 5'-terminal genome sequence. The data suggest that a conserved nonanucleotide sequence, CA(G/A)CACUAC, located downstream of the leader and upstream of the structural protein genes acts as the core transcription-regulating sequence element in WBV. Like other nidoviruses with large genomes (>26 kb), WBV encodes in its ORF1b an extensive set of enzymes, including putative polymerase, helicase, ribose methyltransferase, exoribonuclease, and endoribonuclease activities. ORF1a encodes several membrane domains, a putative ADP-ribose 1"-phosphatase, and a chymotrypsin-like serine protease whose activity was established in this study. Comparative sequence analysis revealed that WBV represents a separate cluster of nidoviruses that significantly diverged from toroviruses and, even more, from coronaviruses, roniviruses, and arteriviruses. The study adds to the amazing diversity of nidoviruses and appeals for a more extensive characterization of nonmammalian nidoviruses to better understand the evolution of these largest known RNA viruses.

SDSS J150722.30+523039.8: a cataclysmic variable formed directly from a detached white dwarf/brown dwarf binary?

We present high-speed, three-colour photometry of the eclipsing cataclysmic variable SDSS J150722.30+523039.8 (hereafter SDSS J1507). This system has an orbital period of 66.61 min, placing it below the observed `period minimum' for cataclysmic variables. We determine the system parameters via a parametrized model of the eclipse fitted to the observed lightcurve by ?2 minimization. We obtain a mass ratio of q = 0.0623 +/- 0.0007 and an orbital inclination . The primary mass is Mw = 0.90 +/- 0.01Msolar. The secondary mass and radius are found to be Mr = 0.056 +/- 0.001Msolar and Rr = 0.096 +/- 0.001Rsolar, respectively. We find a distance to the system of 160 +/- 10pc. The secondary star in SDSS J1507 has a mass substantially below the hydrogen burning limit, making it the second confirmed substellar donor in a cataclysmic variable. The very short orbital period of SDSS J1507 is readily explained if the secondary star is nuclearly evolved, or if SDSS J1507 formed directly from a detached white dwarf/brown dwarf binary. Given the lack of any visible contribution from the secondary star, the very low secondary mass and the low HeI ?6678/Ha emission-line ratio, we argue that SDSS J1507 probably formed directly from a detached white dwarf/brown dwarf binary. If confirmed, SDSS J1507 will be the first such system identified. The implications for binary star evolution, the brown dwarf desert and the common envelope phase are discussed.