On The Origin of Super-Hot Electrons from Intense Laser Interactions with Solid Targets having Moderate Scale Length Preformed Plasmas

We use PIC modeling to identify the acceleration mechanism responsible for the observed generation of super-hot electrons in ultra-intense laser-plasma interactions with solid targets with pre-formed plasma. We identify several features of direct laser acceleration (DLA) that drive the generation of super-hot electrons. We find that, in this regime, electrons that become super-hot are primarily injected by a looping mechanism that we call loop-injected direct acceleration (LIDA)

Enhancing Bremsstrahlung Production From Ultraintense Laser-Solid Interactions With Front Surface Structures

We report the results of a combined study of particle-in-cell and Monte Carlo modeling that investigates the production of Bremsstrahlung radiation produced when an ultraintense laser interacts with a tower-structured target. These targets are found to significantly narrow the electron angular distribution as well as produce significantly higher energies. These features combine to create a significant enhancement in directionality and energy of the Bremstrahlung radiation produced by a high-Z converter target. These studies employ short-pulse, high intensity laser pulses, and indicate that novel target design has potential to greatly enhance the yield and narrow the directionality of high energy electrons and $\gamma$-rays. We find that the peak $\gamma$-ray brightness for this source is 6.0$\times$10$^{19}$ ${\rm s^{-1}mm^{-2}mrad^{-2}}$ at 10MeV and 1.4$\times$10$^{19}$ ${\rm s^{-1}mm^{-2}mrad^{-2}}$ at 100MeV (0.1$\%$ bandwidth).Comment: arXiv admin note: text overlap with arXiv:1310.328

Bandpass Dependence of X-ray Temperatures in Galaxy Clusters

We explore the band dependence of the inferred X-ray temperature of the intracluster medium (ICM) for 192 well-observed galaxy clusters selected from the Chandra Data Archive. If the hot ICM is nearly isothermal in the projected region of interest, the X-ray temperature inferred from a broad-band (0.7-7.0 keV) spectrum should be identical to the X-ray temperature inferred from a hard-band (2.0-7.0 keV) spectrum. However, if unresolved cool lumps of gas are contributing soft X-ray emission, the temperature of a best-fit single-component thermal model will be cooler for the broad-band spectrum than for the hard-band spectrum. Using this difference as a diagnostic, the ratio of best-fitting hard-band and broad-band temperatures may indicate the presence of cooler gas even when the X-ray spectrum itself may not have sufficient signal-to-noise to resolve multiple temperature components. To test this possible diagnostic, we extract X-ray spectra from core-excised annular regions for each cluster in our archival sample. We compare the X-ray temperatures inferred from single-temperature fits when the energy range of the fit is 0.7-7.0 keV (broad) and when the energy range is 2.0/(1+z)-7.0 keV (hard). We find that the hard-band temperature is significantly higher, on average, than the broad-band temperature. Upon further exploration, we find this temperature ratio is enhanced preferentially for clusters which are known merging systems. In addition, cool-core clusters tend to have best-fit hard-band temperatures that are in closer agreement with their best-fit broad-band temperatures. We show, using simulated spectra, that this diagnostic is sensitive to secondary cool components (TX = 0.5-3.0 keV) with emission measures >10-30% of the primary hot component.Comment: Accepted for publication in Ap

Efecto de diferentes condiciones de tostado sobre el valor nutritivo y la estabilidad oxidativa de aceites de semillas de Brassica napus alto oleico y semillas amarillas

This study was conducted to evaluate the possibility of enhancing the nutritional value and oxidative stability of rapeseed oil obtained from seeds subjected to thermal treatment prior to pressing. The yellowseeded and high-oleic B. napus lines, harvested in Poland, were roasted prior to pressing for 1 h at 100 and 150 °C. This study highlighted how rapeseed breeding lines affect the quality profile of the oils obtained both before and after the roasting process. In principle, the high-oleic B. napus was accompanied by a nearly 2-fold increase in oxidative stability compared to the yellow-seeded B. napus, most likely due to a higher content of oxidation-resistant oleic fatty acids (~74.24% vs. ~60.76%) and a decreased concentration of oxidizable PUFAs (~16.32% vs. ~31.09%). Similar to the case of roasting black-seeded rapeseed, the thermal pre-treatment of yellow-seeded and high-oleic B. napus prior to pressing did not alter the composition of their fatty acids. Based on the results obtained in this study, it can be concluded that roasting seeds prior to pressing does not reduce the amount of tocopherols in the oil; moreover, a slight increase in γ-tocopherol content was observed.Este estudio se realizó para evaluar la posibilidad de aumentar el valor nutritivo y la estabilidad oxidativa del aceite de colza obtenido a partir de semillas sometidas a tratamiento térmico antes del prensado. Las líneas de B. napus sembrados amarillos y alto oleico, cosechadas en Polonia, fueron tostadas antes de ser prensadas durante 1 hora a 100 y 150 °C. Este estudio pone de relieve cómo las líneas de colza mejoradas ven afectado el perfil de calidad de los aceites obtenidos antes y después del proceso de tostado. En principio, el alto oleico B. napus aumenta casi 2 veces la estabilidad a la oxidación en comparación con semilla amarilla B. napus, muy probablemente debido a un mayor contenido de ácido graso oleico resistente a la oxidación (~74,24% vs. ~60,76%) y una concentración menor de PUFAs oxidables (~16,32% frente a ~31,09%). Similar al caso de tostar semillas de colza-negro, las semillas amarillas y las alto oleico de B. napus antes tratadas térmicamente antes del prensado no alteran su composición de ácidos grasos. También Basándonos en los resultados obtenidos en este estudio, se puede concluir que el tostado semillas antes del prensado no reduce la cantidad de tocoferol en aceite; Además, se observó ligero aumento en el contenido de γ-tocoferol

Selective Deuterium Ion Acceleration Using the Vulcan PW Laser

We report on the successful demonstration of selective acceleration of deuterium ions by target-normal sheath acceleration (TNSA) with a high-energy petawatt laser. TNSA typically produces a multi-species ion beam that originates from the intrinsic hydrocarbon and water vapor contaminants on the target surface. Using the method first developed by Morrison, et al.,$^{1}$ an ion beam with $>$99$\%$ deuterium ions and peak energy 14 MeV/nucleon is produced with a 200 J, 700 fs, $>10^{20} W/cm^{2}$ laser pulse by cryogenically freezing heavy water (D$_{2}$O) vapor onto the rear surface of the target prior to the shot. Within the range of our detectors (0-8.5$^{\circ}$), we find laser-to-deuterium-ion energy conversion efficiency of 4.3$\%$ above 0.7 MeV/nucleon while a conservative estimate of the total beam gives a conversion efficiency of 9.4$\%$.Comment: 5 pages, 5 figure

The Butcher-Oemler Effect at Moderate Redshift

We present the results of Butcher-Oemler-style analysis of three moderate- redshift (0.1<z<0.2) clusters which have bimodal X-ray surface brightness profiles. We find that at least two of these clusters exhibit unusually high fractions of blue galaxies as compared to clusters at comparable redshifts studied by Butcher and Oemler (1984). This implies that star formation is occurring in a high fraction of the galaxies in the two clusters. Our results are consistent with hierarchical clustering models in which subcluster- subcluster mergers create shocks in the intracluster medium. The shocks, in turn, induce simultaneous starbursts in a large fraction of cluster galaxies. Our study therefore lends weight to the hypothesis that the Butcher-Oemler effect is an environmental, as well as evolutionary, phenomenon.Comment: 22 pages, 8 figures; accepted for publication in A

Escaping the pushpin paradigm in geographic information science: (re)presenting national crime data

In 2011 the Home Office released the police.uk website, which provided a high-resolution map of recent crime data for the national extents of England, Wales and Northern Ireland. Through this free service, crimes were represented as points plotted on top of a Google map, visible down to a street level of resolution. However, in order to maintain confidentiality and to comply with data disclosure legislation, individual-level crimes were aggregated into points that represented clusters of events that were located over a series of streets. However, with aggregation the representation of crimes as points becomes problematic, engendering spurious precision over where crimes occurred. Given obvious public sensitivity to such information, there are social imperatives for appropriate representation of crime data, and as such, in this paper we present a method of translating the ‘point’ crime events into a new representational form that is tied to street network geography; presenting these results in an alternate national crime mapping portal http://www.policestreets.co.u