Probing the structure of the cold dark matter halo with ancient mica

Mica can store (for >1 Gy) etchable tracks caused by atoms recoiling from WIMPs. Ancient mica is a directional detector despite the complex motions it makes with respect to the WIMP "wind". We can exploit the properties of directionality and long integration time to probe for structure in the dark matter halo of our galaxy. We compute a sample of possible signals in mica for a plausible model of halo structure.Comment: 7 pages, 2 figure

XMM-Newton discovery of O VII emission from warm gas in clusters of galaxies

XMM-Newton recently discovered O VII line emission from ~2 million K gas near the outer parts of several clusters of galaxies. This emission is attributed to the Warm-Hot Intergalactic Medium. The original sample of clusters studied for this purpose has been extended and two more clusters with a soft X-ray excess have been found. We discuss the physical properties of the warm gas, in particular the density, spatial extent, abundances and temperature.Comment: 8 pages, 3 figures, conference "Soft X-ray emission from clusters of galaxies and related phenomena", ed. R. Lieu, Kluwer, in pres

OVII and OVIII line emission in the diffuse soft X-ray background: heliospheric and galactic contributions

We study the 0.57 keV (O VII triplet) and 0.65 keV (O VIII) diffuse emission generated by charge transfer collisions between solar wind (SW) oxygen ions and interstellar H and He neutral atoms in the inner Heliosphere. These lines which dominate the 0.3-1.0 keV energy interval are also produced by hot gas in the galactic halo (GH) and possibly the Local Interstellar Bubble (LB). We developed a time-dependent model of the SW Charge-Exchange (SWCX) X-ray emission, based on the localization of the SW Parker spiral at each instant. We include input SW conditions affecting three selected fields, as well as shadowing targets observed with XMM-Newton, Chandra and Suzaku and calculate X-ray emission fot O VII and O VIII lines. We determine SWCX contamination and residual emission to attribute to the galactic soft X-ray background. We obtain ground level intensities and/or simulated lightcurves for each target and compare to X-ray data. The local 3/4 keV emission (O VII and O VIII) detected in front of shadowing clouds is found to be entirely explained by the CX heliospheric emission. No emission from the LB is needed at these energies. Using the model predictions we subtract the heliospheric contribution to the measured emission and derive the halo contribution. We also correct for an error in the preliminary analysis of the Hubble Deep Field North (HDFN).Comment: 21 pages (3 on-line), 10 figures (4 on-line), accepted for publication in Astronomy and Astrophysic

Local ISM 3D Distribution and Soft X-ray Background Inferences for Nearby Hot Gas

Three-dimensional (3D) interstellar medium (ISM) maps can be used to locate not only interstellar (IS) clouds, but also IS bubbles between the clouds that are blown by stellar winds and supernovae, and are filled by hot gas. To demonstrate this, and to derive a clearer picture of the local ISM, we compare our recent 3D IS dust distribution maps to the ROSAT diffuse Xray background maps after removal of heliospheric emission. In the Galactic plane, there is a good correspondence between the locations and extents of the mapped nearby cavities and the soft (0.25 keV) background emission distribution, showing that most of these nearby cavities contribute to this soft X-ray emission. Assuming a constant dust to gas ratio and homogeneous 106 K hot gas filling the cavities, we modeled in a simple way the 0.25 keV surface brightness along the Galactic plane as seen from the Sun, taking into account the absorption by the mapped clouds. The data-model comparison favors the existence of hot gas in the solar neighborhood, the so-called Local Bubble (LB). The inferred mean pressure in the local cavities is found to be approx.9,400/cu cm K, in agreement with previous studies, providing a validation test for the method. On the other hand, the model overestimates the emission from the huge cavities located in the third quadrant. Using CaII absorption data, we show that the dust to CaII ratio is very small in those regions, implying the presence of a large quantity of lower temperature (non-X-ray emitting) ionized gas and as a consequence a reduction of the volume filled by hot gas, explaining at least part of the discrepancy. In the meridian plane, the two main brightness enhancements coincide well with the LB's most elongated parts and chimneys connecting the LB to the halo, but no particular nearby cavity is found towards the enhancement in the direction of the bright North Polar Spur (NPS) at high latitude. We searched in the 3D maps for the source regions of the higher energy (0.75 keV) enhancements in the fourth and first quadrants. Tunnels and cavities are found to coincide with the main bright areas, however no tunnel nor cavity is found to match the low-latitude b > or approx. 8deg, brightest part of the NPS. In addition, the comparison between the 3D maps and published spectral data favors a NPS central source region location beyond 230 pc, i.e. at larger distance than usually considered. Those examples illustrate the potential use of more detailed 3D distributions of the nearby ISM for the interpretation of the diffuse soft X-ray background

Changes in Oxidised Phospholipids in Response to Oxidative Stress in Microtubule-Associated Protein Tau ( MAPT ) Mutant Dopamine Neurons

Microtubule-associated protein Tau (MAPT) is strongly associated with the development of neurodegenerative diseases. In addition to driving the formation of neurofibrillary tangles (NFT), mutations in the MAPT gene can also cause oxidative stress through hyperpolarisation of the mitochondria. This study explores the impact that MAPT mutation is having on phospholipid metabolism in iPSC-derived dopamine neurons, and to determine if these effects are exacerbated by mitochondrial and endoplasmic reticulum stress. Neurons that possessed a mutated copy of MAPT were shown to have significantly higher levels of oxo-phospholipids (Oxo-PL) than wild-type neurons. Oxidation of the hydrophobic fatty acid side chains changes the chemistry of the phospholipid leading to disruption of membrane function and potential cell lysis. In wild-type neurons, both mitochondrial and endoplasmic reticulum stress increased Oxo-PL abundance; however, in MAPT mutant neurons mitochondrial stress appeared to have a minimal effect. Endoplasmic reticulum stress, surprisingly, reduced the abundance of Oxo-PL in MAPT mutant dopamine neurons, and we postulate that this reduction could be modulated through hyperactivation of the unfolded protein response and X-box binding protein 1. Overall, the results of this study contribute to furthering our understanding of the regulation and impact of oxidative stress in Parkinson’s disease pathology

Measuring Cluster Temperature Profiles with XMM/EPIC

Using the PV observation of A1795, we illustrate the capability of XMM-EPIC to measure cluster temperature profiles, a key ingredient for the determination of cluster mass profiles through the equation of hydrostatic equilibrium. We develop a methodology for spatially resolved spectroscopy of extended sources, adapted to XMM background and vignetting characteristics. The effect of the particle induced background is discussed. A simple unbiased method is proposed to correct for vignetting effects, in which every photon is weighted according to its energy and location on the detector. We were able to derive the temperature profile of A1795 up to 0.4 times the virial radius. A significant and spatially resolved drop in temperature towards the center (r<200 kpc) is observed, which corresponds to the cooling flow region of the cluster. Beyond that region, the temperature is constant with no indication of a fall-off at large radii out to 1.2 Mpc.Comment: 7 pages, 8 figures, Accepted for publication in A&A (special Letter issue on XMM

X-ray observations of the galaxy cluster Abell 2029 to the virial radius

We present Suzaku observations of the galaxy cluster Abell 2029, which exploit Suzaku's low particle background to probe the ICM to radii beyond those possible with previous observations (reaching out to the virial radius), and with better azimuthal coverage. We find significant anisotropies in the temperature and entropy profiles, with a region of lower temperature and entropy occurring to the south east, possibly the result of accretion activity in this direction. Away from this cold feature, the thermodynamic properties are consistent with an entropy profile which rises, but less steeply than the predictions of purely gravitational hierarchical structure formation. Excess emission in the northern direction can be explained due to the overlap of the emission from the outskirts of Abell 2029 and nearby Abell 2033 (which is at slightly higher redshift). These observations suggest that the assumptions of spherical symmetry and hydrostatic equilibrium break down in the outskirts of galaxy clusters, which poses challenges for modelling cluster masses at large radii and presents opportunities for studying the formation and accretion history of clusters.Comment: 15 pages, 14 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Societ

GEM Operation in Negative Ion Drift Gas Mixtures

The first operation of GEM gas gain elements in negative ion gas mixtures is reported. Gains up to several thousand were obtained from single-stage GEMs in carbon disulfide vapor at low pressure, and in mixtures of carbon disulfide with Argon and Helium, some near 1 bar total pressure.Comment: 7 pages, 3 figure

The pupil's response to affective pictures: Role of image duration, habituation, and viewing mode

The pupil has been shown to be sensitive to the emotional content of stimuli. We examined this phenomenon by comparing fearful and neutral images carefully matched in the domains of luminance, image contrast, image color, and complexity of content. The pupil was more dilated after viewing affective pictures, and this effect was (a) shown to be independent of the presentation time of the images (from 100–3,000 ms), (b) not diminished by repeated presentations of the images, and (c) not affected by actively naming the emotion of the stimuli in comparison to passive viewing. Our results show that the emotional modulation of the pupil is present over a range of variables that typically vary from study to study (image duration, number of trials, free viewing vs. task), and encourages the use of pupillometry as a measure of emotional processing in populations where alternative techniques may not be appropriate