A simple model for electron plasma heating in supernova remnants

Context: Multiwavelength observations of supernova remnants can be explained within the framework of diffusive shock acceleration theory, which allows effective conversion of the explosion energy into cosmic rays. Although the models of nonlinear shocks describe reasonably well the nonthermal component of emission, certain issues, including the heating of the thermal electron plasma and the related X-ray emission, still remain open. Methods: Numerical solution of the equations of the Chevalier model for supernova remnant evolution, coupled with Coulomb scattering heating of the electrons. Results: The electron temperature and the X-ray thermal Bremsstrahlung emission from supernova remnants have been calculated as functions of the relevant parameters. Since only the Coulomb mechanism was considered for electron heating, the values obtained for the electron temperatures should be treated as lower limits. Results from this work can be useful to constrain model parameters for observed SNRs.Comment: Accepted to A&A as a research not

Interferometric fibre grating characterisation

One of the most important fibre-optic devices to have emerged in the recent years is the fibre grating. It finds applications in DFB and DBR fibre lasers, dispersion compensation and fibre sensors. Full and accurate amplitude and phase (dispersion) characterization of this device is therefore needed. We have demonstrated such a system based on an interferometric technique (figure 1). The signal arm of a fibre Michelson interferometer is phase-modulated with a saw-tooth function to generate an electric signal at the photodetector which carries the optical phase and amplitude information of the reflective fibre device under test (DUT). The amplitude response of the interferometer is directly proportional to the field reflection coefficient, whereas the measured relative phase is related to the time delay response of the device. The set-up is fully automated and uses a Hewlett Packard tunable laser source (1470-1560nm) with wavelength accuracy are high resonance piezoelectric ceramic cylinders which are wrapped round with some turns of fibre

Demonstration of early functional compromise of bone marrow derived hematopoietic progenitor cells during bovine neonatal pancytopenia through in vitro culture of bone marrow biopsies

<p>Abstract</p> <p>Background</p> <p>Bovine neonatal pancytopenia (BNP) is a syndrome characterised by thrombocytopenia associated with marked bone marrow destruction in calves, widely reported since 2007 in several European countries and since 2011 in New Zealand. The disease is epidemiologically associated with the use of an inactivated bovine virus diarrhoea (BVD) vaccine and is currently considered to be caused by absorption of colostral antibody produced by some vaccinated cows (“BNP dams”). Alloantibodies capable of binding to the leukocyte surface have been detected in BNP dams and antibodies recognising bovine MHC class I and β-2-microglobulin have been detected in vaccinated cattle. In this study, calves were challenged with pooled colostrum collected from BNP dams or from non-BNP dams and their bone marrow hematopoietic progenitor cells (HPC) cultured <it>in vitro</it> from sternal biopsies taken at 24 hours and 6 days post-challenge.</p> <p>Results</p> <p>Clonogenic assay demonstrated that CFU-GEMM (colony forming unit-granulocyte/erythroid/macrophage/megakaryocyte; pluripotential progenitor cell) colony development was compromised from HPCs harvested as early as 24 hour post-challenge. By 6 days post challenge, HPCs harvested from challenged calves failed to develop CFU-E (erythroid) colonies and the development of both CFU-GEMM and CFU-GM (granulocyte/macrophage) was markedly reduced.</p> <p>Conclusion</p> <p>This study suggests that the bone marrow pathology and clinical signs associated with BNP are related to an insult which compromises the pluripotential progenitor cell within the first 24 hours of life but that this does not initially include all cell types.</p

Hubungan Tinggi Badan Dengan Ukuran Lebar Panggul Pada Mahasiswi Angkatan 2010 Fakultas Kedokteran Universitas Sam Ratulangi

: Body weight is one of growth indicators. The result of previous research show that women with less than 145 centimeter body weight are potentially has a pelvic stricture. Pelvic stricture is able to cause a coccygeal presentation that can cause natal death. The purpose is to know the correlation of body height and pelvic width which are distansia spinarum and distansia tuberum. The method of this research is observational – analytic using cross – sectional design. The study was conducted for three weeks. The amount of the subject is 80 subjects. The measure of body height and pelvic width of the subjects was being analyzed by the Pearson Correlation Analysis with α = 0,05. The result show that there was a significant correlation of body height and measure of distansia spinarum with correlation coefficient +0,479. In the other side, there was nothing significant correlation of body height and measure of distansia tuberum with correlation coefficient +0,088. Conclusion: There have significant correlation of body height and measure of distansia spinarum but there have no significant correlation of body height and measure of distansia tuberum

The curse of conservation: empirical evidence demonstrating that changes in land-use legislation drove catastrophic bushfires in Southeast Australia

Protecting &ldquo;wilderness&rdquo; and removing human involvement in &ldquo;nature&rdquo; was a core pillar of the modern conservation movement through the 20th century. Conservation approaches and legislation informed by this narrative fail to recognise that Aboriginal people have long valued, used, and shaped most landscapes on Earth. Aboriginal people curated open and fire-safe Country for millennia with fire in what are now forested and fire-prone regions. Settler land holders recognised the importance of this and mimicked these practices. The Land Conservation Act of 1970 in Victoria, Australia, prohibited burning by settler land holders in an effort to protect natural landscapes. We present a 120-year record of vegetation and fire regime change from Gunaikurnai Country, southeast Australia. Our data demonstrate that catastrophic bushfires first impacted the local area immediately following the prohibition of settler burning in 1970, which allowed a rapid increase in flammable eucalypts that resulted in the onset of catastrophic bushfires. Our data corroborate local narratives on the root causes of the current bushfire crisis. Perpetuation of the wilderness myth in conservation may worsen this crisis, and it is time to listen to and learn from Indigenous and local people, and to empower these communities to drive research and management agendas.1. Introduction 1.1. Study Region 1.2. A confluence of Factors 2. Materials and Methods 2.1. Core Collection & Chronology 2.2. Pollen 2.3. Macroscopic Charcoal & Charanalysis 2.4. Magnetic Susceptibility 2.5. Numerical Data Analysis 3. Results 3.1. Chronology 3.2. Pollen 3.3. Macroscopic Charcoal & Charanalysis 3.4. Magnetic Susceptibility 3.5. Numerical Data Analysis 4. Discussion 4.1. Landscape Change between ca. 1900–2021 4.2. The Environmental Impact of Legislation 4.3. The Curse of Conservation That Ignores People as Managers and History as a Prelud

Line intensity enhancements in stellar coronal X-ray spectra due to opacity effects

Context. The I(15.01 A)/I(16.78 A) emission line intensity ratio in Fe XVII has been reported to deviate from its theoretical value in solar and stellar X-ray spectra. This is attributed to opacity in the 15.01 A line, leading to a reduction in its intensity, and was interpreted in terms of a geometry in which the emitters and absorbers are spatially distinct. Aims. We study the I(15.01 A)/I(16.78 A) intensity ratio for the active cool dwarf EV Lac, in both flare and quiescent spectra. Methods. The observations were obtained with the Reflection Grating Spectrometer on the XMM-Newton satellite. The emission measure distribution versus temperature reconstruction technique is used for our analysis. Results. We find that the 15.01 A line exhibits a significant enhancement in intensity over the optically thin value. To our knowledge, this is the first time that such an enhancement has been detected on such a sound statistical basis. We interpret this enhancement in terms of a geometry in which the emitters and absorbers are not spatially distinct, and where the geometry is such that resonant pumping of the upper level has a greater effect on the observed line intensity than resonant absorption in the line-of-sight.Comment: accepted for publication in A&

A Deep Chandra Observation of Kepler's Supernova Remnant: A Type Ia Event with Circumstellar Interaction

We present initial results of a 750 ks Chandra observation of the remnant of Kepler's supernova of AD 1604. The strength and prominence of iron emission, together with the absence of O-rich ejecta, demonstrate that Kepler resulted from a thermonuclear supernova, even though evidence for circumstellar interaction is also strong. We have analyzed spectra of over 100 small regions, and find that they fall into three classes. (1) The vast majority show Fe L emission between 0.7 and 1 keV and Si and S K alpha emission; we associate these with shocked ejecta. A few of these are found at or beyond the mean blast wave radius. (2) A very few regions show solar O/Fe abundance rations; these we associate with shocked circumstellar medium (CSM). Otherwise O is scarce. (3) A few regions are dominated by continuum, probably synchrotron radiation. Finally, we find no central point source, with a limit about 100 times fainter than the central object in Cas A. The evidence that the blast wave is interacting with CSM may indicate a Ia explosion in a more massive progenitor.Comment: Accepted by ApJ Letter

On Collisionless Electron-Ion Temperature Equilibration in the Fast Solar Wind

We explore a mechanism, entirely new to the fast solar wind, of electron heating by lower hybrid waves to explain the shift to higher charge states observed in various elements in the fast wind at 1 A.U. relative to the original coronal hole plasma. This process is a variation on that previously discussed for two temperature accretion flows by Begelman & Chiueh. Lower hybrid waves are generated by gyrating minor ions (mainly alpha-particles) and become significant once strong ion cyclotron heating sets in beyond 1.5 R_sun. In this way the model avoids conflict with SUMER electron temperature diagnostic measurements between 1 and 1.5 R_sun. The principal requirement for such a process to work is the existence of density gradients in the fast solar wind, with scale length of similar order to the proton inertial length. Similar size structures have previously been inferred by other authors from radio scintillation observations and considerations of ion cyclotron wave generation by global resonant MHD waves.Comment: 32 pages including 11 figures, 4 tables, accepted by Ap