Phase-contrast microscopy at high x-ray energy with a laboratory setup

We report on the design and realization of an x-ray imaging system for quantitative phase-contrast microscopy at high x-ray energy with laboratory-scale instrumentation. Phase and amplitudewere separated quantitatively at x-ray energies up to 80 keV with micrometric spatial resolution. The accuracy of the results was tested against numerical simulations, and the spatial resolution was experimentally quantified by measuring a Siemens star phase object. This simple setup should find broad application in those areas of x-ray imaging where high energy and spatial resolution are simultaneously required and in those difficult cases where the sample contains materials with similar x-ray absorption

High Energy Gamma-Ray Emission From Blazars: EGRET Observations

We will present a summary of the observations of blazars by the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO). EGRET has detected high energy gamma-ray emission at energies greater than 100 MeV from more that 50 blazars. These sources show inferred isotropic luminosities as large as $3\times 10^{49}$ ergs s$^{-1}$. One of the most remarkable characteristics of the EGRET observations is that the gamma-ray luminosity often dominates the bolometric power of the blazar. A few of the blazars are seen to exhibit variability on very short time-scales of one day or less. The combination of high luminosities and time variations seen in the gamma-ray data indicate that gamma-rays are an important component of the relativistic jet thought to characterize blazars. Currently most models for blazars involve a beaming scenario. In leptonic models, where electrons are the primary accelerated particles, gamma-ray emission is believed to be due to inverse Compton scattering of low energy photons, although opinions differ as to the source of the soft photons. Hardronic models involve secondary production or photomeson production followed by pair cascades, and predict associated neutrino production.Comment: 16 pages, 7 figures, style files included. Invited review paper in "Observational Evidence for Black Holes in the Universe," 1999, ed. S. K. Chakrabarti (Dordrecht: Kluwer), 215-23

High Energy Cosmic Rays From Supernovae

Cosmic rays are charged relativistic particles that reach the Earth with extremely high energies, providing striking evidence of the existence of effective accelerators in the Universe. Below an energy around $\sim 10^{17}$ eV cosmic rays are believed to be produced in the Milky Way while above that energy their origin is probably extragalactic. In the early '30s supernovae were already identified as possible sources for the Galactic component of cosmic rays. After the '70s this idea has gained more and more credibility thanks to the the development of the diffusive shock acceleration theory, which provides a robust theoretical framework for particle energization in astrophysical environments. Afterwards, mostly in recent years, much observational evidence has been gathered in support of this framework, converting a speculative idea in a real paradigm. In this Chapter the basic pillars of this paradigm will be illustrated. This includes the acceleration mechanism, the non linear effects produced by accelerated particles onto the shock dynamics needed to reach the highest energies, the escape process from the sources and the transportation of cosmic rays through the Galaxy. The theoretical picture will be corroborated by discussing several observations which support the idea that supernova remnants are effective cosmic ray factories.Comment: Final draft of a chapter in "Handbook of Supernovae" edited by Athem W. Alsabti and Paul Murdi

Benzyne in V4334 Sqr: A Quest for the Ring with SOFIA/EXES

Large aromatic molecules are ubiquitous in both circumstellar and interstellar environments. Detection of small aromatic molecules, such as benzene (C6H6) and benzyne (C6H4), are rare in astrophysical environments. Detection of such species will have major implications for our understanding of the astrochemistry involved in the formation of the molecules necessary for life, including modeling the chemical pathways to the formation of larger hydrocarbon molecules. We conducted a search for the infrared 18 μm spectral signature of benzyne in V4334 Sgr with the Stratospheric Observatory for Infrared Astronomy (SOFIA)/Echelon-Cross-Echelle Spectrograph (EXES) finding no evidence for a feature at the sensitivity of our observations

Heroes and villains of world history across cultures

© 2015 Hanke et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedEmergent properties of global political culture were examined using data from the World History Survey (WHS) involving 6,902 university students in 37 countries evaluating 40 figures from world history. Multidimensional scaling and factor analysis techniques found only limited forms of universality in evaluations across Western, Catholic/Orthodox, Muslim, and Asian country clusters. The highest consensus across cultures involved scientific innovators, with Einstein having the most positive evaluation overall. Peaceful humanitarians like Mother Theresa and Gandhi followed. There was much less cross-cultural consistency in the evaluation of negative figures, led by Hitler, Osama bin Laden, and Saddam Hussein. After more traditional empirical methods (e.g., factor analysis) failed to identify meaningful cross-cultural patterns, Latent Profile Analysis (LPA) was used to identify four global representational profiles: Secular and Religious Idealists were overwhelmingly prevalent in Christian countries, and Political Realists were common in Muslim and Asian countries. We discuss possible consequences and interpretations of these different representational profiles.This research was supported by grant RG016-P-10 from the Chiang Ching-Kuo Foundation for International Scholarly Exchange (http://www.cckf.org.tw/). Religion Culture Entropy China Democracy Economic histor

Growth in Children with Cerebral Palsy during five years after Selective Dorsal Rhizotomy: a practice-based study

Background: Overweight is reported as a side effect of SDR. The aims were to study the development of weight, height and body mass index (BMI) during five years after SDR. Methods: This prospective, longitudinal and practice-based study included all 56 children with CP spastic diplegia undergoing SDR from the start in March 1993 to April 2003 in our hospital. The preoperative Gross Motor Function Classification System (GMFCS) levels were I-II in 17, III in 15, IV-V in 24 children. Median age at SDR was 4.3 years (range 2.4-7.4 years). Weight and height/recumbent length were measured. Swedish growth charts for typically developing children generated weight, height and BMI z-scores for age and gender. Results: The preoperative median z-scores were for height-1.92 and for body mass index (BMI)-0.22. Five years later, the median BMI z-score was increased by + 0.57 (p + 2 SD) increased (p < 0.05). Baseline BMI and age at the start of follow-up influenced the BMI change during the five years (p < 0.001 and p < 0.05 respectively). The individual growth was highly variable, but a tendency towards increasing stunting with age was seen in severe gross motor dysfunction (GMFCS levels IV-V) and the opposite, a slight catch-up of height in children with walking ability (GMFCS levels I-III). Conclusions: These are the first available subtype-and GMFCS-specific longitudinal growth data for children with CP spastic diplegia. Their growth potential according to these data should be regarded as a minimum, as some children were undernourished. It is unknown whether the spasticity reduction through SDR increased the weight gain velocity, or if the relative weight increase was part of the general "obesity epidemic". For some children the weight increase was highly desirable. In others, it resulted in overweight and obesity with risk of negative health effects. Weight and height should be monitored to enable early prevention of weight aberrations also causing problems with mobility, activity and participation

Cultivation of a novel cold-adapted nitrite oxidizing betaproteobacterium from the Siberian Arctic

Permafrost-affected soils of the Siberian Arctic were investigated with regard to identification of nitrite oxidizing bacteria active at low temperature. Analysis of the fatty acid profiles of enrichment cultures grown at 4°C, 10°C and 17°C revealed a pattern that was different from that of known nitrite oxidizers but was similar to fatty acid profiles of Betaproteobacteria. Electron microscopy of two enrichment cultures grown at 10°C showed prevalent cells with a conspicuous ultrastructure. Sequence analysis of the 16S rRNA genes allocated the organisms to a so far uncultivated cluster of the Betaproteobacteria, with Gallionella ferruginea as next related taxonomically described organism. The results demonstrate that a novel genus of chemolithoautotrophic nitrite oxidizing bacteria is present in polygonal tundra soils and can be enriched at low temperatures up to 17°C. Cloned sequences with high sequence similarities were previously reported from mesophilic habitats like activated sludge and therefore an involvement of this taxon in nitrite oxidation in nonarctic habitats is suggested. The presented culture will provide an opportunity to correlate nitrification with nonidentified environmental clones in moderate habitats and give insights into mechanisms of cold adaptation. We propose provisional classification of the novel nitrite oxidizing bacterium as 'Candidatus Nitrotoga arctica'

The Citation Field of Evolutionary Economics

Evolutionary economics has developed into an academic field of its own, institutionalized around, amongst others, the Journal of Evolutionary Economics (JEE). This paper analyzes the way and extent to which evolutionary economics has become an interdisciplinary journal, as its aim was: a journal that is indispensable in the exchange of expert knowledge on topics and using approaches that relate naturally with it. Analyzing citation data for the relevant academic field for the Journal of Evolutionary Economics, we use insights from scientometrics and social network analysis to find that, indeed, the JEE is a central player in this interdisciplinary field aiming mostly at understanding technological and regional dynamics. It does not, however, link firmly with the natural sciences (including biology) nor to management sciences, entrepreneurship, and organization studies. Another journal that could be perceived to have evolutionary acumen, the Journal of Economic Issues, does relate to heterodox economics journals and is relatively more involved in discussing issues of firm and industry organization. The JEE seems most keen to develop theoretical insights