X-ray Phase-Resolved Spectroscopy of PSRs B0531+21, B1509-58, and B0540-69 with RXTE

The Rossi X-ray Timing Explorer ({\sl RXTE}) has made hundreds of observations on three famous young pulsars (PSRs) B0531+21 (Crab), B1509-58, and B0540-69. Using the archive {\sl RXTE} data, we have studied the phase-resolved spectral properties of these pulsars in details. The variation of the X-ray spectrum with phase of PSR B0531+21 is confirmed here much more precisely and more details are revealed than the previous studies: the spectrum softens from the beginning of the first pulse, turns to harden right at the pulse peak and becomes the hardest at the bottom of the bridge, softens gradually until the second peak, and then softens rapidly. Different from the previous studies, we found that the spectrum of PSR B1509-58 is significantly harder in the center of the pulse, which is also in contrast to that of PSR B0531+21. The variation of the X-ray spectrum of PSR B0540-69 seems similar to that of PSR B1509-58, but with a lower significance. Using the about 10 years of data span, we also studied the real time evolution of the spectra of these pulsars, and no significant evolution has been detected. We have discussed about the constraints of these results on theoretical models of pulsar X-ray emission.Comment: 42 pages, 24 figure

NGC 3627: a galaxy-dwarf collision?

Group galaxies very often show distinct signs of interaction with both companion galaxies and the intragroup medium. X-ray observations are particularly helpful because they provide information on the temperatures and the densities of the hot gas in galaxies and intergalactic space. This can put important constraints on the nature and timescales of these interactions. We use the XMM-Newton X-ray observations of NGC 3627 in the Leo Triplet galaxy group to explain peculiar features visible in the polarized radio maps. We analyzed soft X-ray (0.2-1 keV) emission from NGC 3627 to study the distribution of the hot gas and its temperature in different areas of the galaxy. Any change throughout the disk can reflect distortions visible in the radio polarized emission. We also studied two bright point sources that are probably tightly linked to the evolution of the galaxy. We find an increase in the temperature of the hot gas in the area of the polarized radio ridge in the western arm of the galaxy. In the eastern part of the disk we find two ultra-luminous X-ray sources. We note a large hot gas temperature difference (by a factor of 2) between the two bar ends. The polarized radio ridge in the western arm of NGC 3627 is most likely formed by ram-pressure effects caused by the movement of the galaxy through the intragroup medium. To explain the distortions visible in the eastern part of the disk in polarized radio maps, the asymmetry of the bar, and the distortion of the eastern arm, we propose a recent collision of NGC 3627 with a dwarf companion galaxy.Comment: 8 pages, 6 figures, 5 tables. Accepted for publication in Astronomy and Astrophysic

Observational Constraints on the Ages of Molecular Clouds and the Star-Formation Timescale: Ambipolar-Diffusion--Controlled or Turbulence-Induced Star Formation?

We revisit the problem of the star formation timescale and the ages of molecular clouds. The apparent overabundance of star-forming molecular clouds over clouds without active star formation has been thought to indicate that molecular clouds are "short-lived" and that star formation is "rapid". We show that this statistical argument lacks self-consistency and, even within the rapid star-formation scenario, implies cloud lifetimes of approximately 10 Myr. We discuss additional observational evidence from external galaxies that indicate lifetimes of molecular clouds and a timescale of star formation of approximately 10 Myr . These long cloud lifetimes in conjunction with the rapid (approximately 1 Myr) decay of supersonic turbulence present severe difficulties for the scenario of turbulence-controlled star formation. By contrast, we show that all 31 existing observations of objects for which the linewidth, the size, and the magnetic field strength have been reliably measured are in excellent quantitative agreement with the predictions of the ambipolar-diffusion theory. Within the ambipolar-diffusion-controlled star formation theory the linewidths may be attributed to large-scale non-radial cloud oscillations (essentially standing large-amplitude, long-wavelength Alfven waves), and the predicted relation between the linewidth, the size, and the magnetic field is a natural consequence of magnetic support of self-gravitating clouds.Comment: 7 pages, 2 figures, uses emulateapj; accepted for publication in Ap

Regulatory Impact Assessment: A survey of selected developing and emerging economies

Regulatory impact assessment (RIA) involves a systematic appraisal of the social, economic and environmental impacts of proposed regulations and other kinds of policy instruments before they are adopted. A vast amount of academic literature in the last decade has charted the diffusion of RIA in OECD countries and EU member states. However, relatively little is known about the extent to which RIA has been adopted and implemented in developing countries. The last research attempting to shed light on this issue over a decade ago found that a number of were beginning to apply some form of regulatory assessment but that its development was at an early stage. Since then RIA has become almost universally adopted in OECD and EU member states as well as promoted as a tool for good (regulatory) governance in developing countries by international donors and organizations such as OECD, the International Finance Corporation of the World Bank Group (IFC). What, then, is the extent of RIA adoption and implementation in these countries today? This working paper addresses this question through a survey of RIA in 14 developing and emerging economies based on documentary analysis as well as semi-structured interviews with key stakeholders. The survey explores topics such as the legal and institutional framework of RIA, organizational capacity, and use of tools and methods (e.g. Cost Benefit Analysis). The results suggest that while an increasing number of developing countries have made efforts to introduce RIA in their decision making processes, these efforts have not yet led to a sustainable RIA system which significantly contributes to the good regulatory governance of these countries

Simultaneous Absolute Timing of the Crab Pulsar at Radio and Optical Wavelengths

The Crab pulsar emits across a large part of the electromagnetic spectrum. Determining the time delay between the emission at different wavelengths will allow to better constrain the site and mechanism of the emission. We have simultaneously observed the Crab Pulsar in the optical with S-Cam, an instrument based on Superconducting Tunneling Junctions (STJs) with $\mu$s time resolution and at 2 GHz using the Nan\c{c}ay radio telescope with an instrument doing coherent dedispersion and able to record giant pulses data. We have studied the delay between the radio and optical pulse using simultaneously obtained data therefore reducing possible uncertainties present in previous observations. We determined the arrival times of the (mean) optical and radio pulse and compared them using the tempo2 software package. We present the most accurate value for the optical-radio lag of 255 $\pm$ 21 $\mu$s and suggest the likelihood of a spectral dependence to the excess optical emission asociated with giant radio pulses.Comment: 8 pages; accepted for publication in Astronomy and Astrophysic

Updating the orbital ephemeris of Her X-1; rate of decay and eccentricity of the orbit

We present an update of the orbital ephemeris of the binary X-ray pulsar Her X-1 and determine an improved value for the rate of orbital decay. In addition, we report the first measurement of the orbital eccentricity. We have analyzed pulse timing data of Her X-1 from X-ray observations by RXTE (Rossi X-Ray Timing Explorer) and INTEGRAL over the period 1996-2007. Accurate pulse arrival times were determined from solar system bary-centered photon arrival times by generating pulse profiles averaged over appropriately short integration times. Applying pulse phase connection techniques, it was possible to determine sufficiently accurate local ephemeris data for seven observation periods distributed over 12 years. Combining the new local T90 values with historical values from the literature we update the orbital ephemeris of Her X-1 to T90 = MJD 46359.871940(6) and Porb = 1.700167590(2) d and measure a continuous change of the orbital period of dPorb/dt = -(4.85 +/- 0.13) x 10-11 s/s. For the first time, a value for the eccentricity of the orbit of Her X-1 is measured to be e = (4.2 +/- 0.8) x 10-4.Comment: 7 pages, 4 figures, accepted by A&A on 30.03.200

Preventie op de camping:Resultaten van twee pilots in West-Brabant in het souterrain van de woningmarkt

Vanwege tekorten op de woningmarkt enerzijds en de moeizame exploitatie van recreatieparken anderzijds, is permanente bewoning op recreatieparken een structureel maatschappelijk verschijnsel geworden. Permanente bewoning is wettelijk niet toegestaan en kan samengaan met diverse vormen van sociale problematiek. De sociale crisis die ontstond op camping Fort Oranje is voor de GGD WestBrabant aanleiding geweest preventieve werkwijzen voor recreatieparken te ontwikkelen. Dit artikel beschrijft twee pilots die in dit verband werden opgezet. De ambitie was bewoners van recreatieparken in beeld te krijgen en waar nodig te ondersteunen, en om een stem te geven aan hun verhaal

The Eastern Arm of M83 Revisited: High-Resolution Mapping of 12CO 1-0 Emission

We have used the Owens Valley Millimeter Array to map 12CO (J=1-0) along a 3.5 kpc segment of M83's eastern spiral arm at resolutions of 6.5"x3.5", 10", and 16". The CO emission in most of this segment lies along the sharp dust lane demarking the inner edge of the spiral arm, but beyond a certain point along the arm the emission shifts downstream from the dust lane to become better aligned with the young stars seen in blue and H-beta images. This morphology resembles that of the western arm of M100. Three possibilities, none of which is wholly satisfactory, are considered to explain the deviation of the CO arm from the dust lane: heating of the CO by UV radiation from young stars, heating by low-energy cosmic rays, and a molecular medium consisting of two (diffuse and dense) components which react differently to the density wave. Regardless, the question of what CO emission traces along this spiral arm is a complicated one. Strong tangential streaming is observed where the arm crosses the kinematic major axis of the galaxy, implying that the shear becomes locally prograde in the arms. Inferred from the streaming is a very high gas surface density of about 230 solar masses/pc**2 and an arm-interarm contrast greater than 2.3 in the part of the arm near the major axis. Using two different criteria, we find that the gas at this location is well above the threshold for gravitational instability -- much more clearly so than in either M51 or M100.Comment: Accepted for publication in ApJ. 25 pages, 5 figures. Manuscript in LaTeX, figures in pdf. Fig 3 in colo

KRAB-Induced Heterochromatin Effectively Silences <i>PLOD2</i> Gene Expression in Somatic Cells and is Resilient to TGFβ1 Activation

Epigenetic editing, an emerging technique used for the modulation of gene expression in mammalian cells, is a promising strategy to correct disease-related gene expression. Although epigenetic reprogramming results in sustained transcriptional modulation in several in vivo models, further studies are needed to develop this approach into a straightforward technology for effective and specific interventions. Important goals of current research efforts are understanding the context-dependency of successful epigenetic editing and finding the most effective epigenetic effector(s) for specific tasks. Here we tested whether the fibrosis- and cancer-associated PLOD2 gene can be repressed by the DNA methyltransferase M.SssI, or by the non-catalytic Krüppel associated box (KRAB) repressor directed to the PLOD2 promoter via zinc finger- or CRISPR-dCas9-mediated targeting. M.SssI fusions induced de novo DNA methylation, changed histone modifications in a context-dependent manner, and led to 50%-70% reduction in PLOD2 expression in fibrotic fibroblasts and in MDA-MB-231 cancer cells. Targeting KRAB to PLOD2 resulted in the deposition of repressive histone modifications without DNA methylation and in almost complete PLOD2 silencing. Interestingly, both long-term TGFβ1-induced, as well as unstimulated PLOD2 expression, was completely repressed by KRAB, while M.SssI only prevented the TGFβ1-induced PLOD2 expression. Targeting transiently expressed dCas9-KRAB resulted in sustained PLOD2 repression in HEK293T and MCF-7 cells. Together, these findings point to KRAB outperforming DNA methylation as a small potent targeting epigenetic effector for silencing TGFβ1-induced and uninduced PLOD2 expression