Proper motion, spectra, and timing of PSR J1813-1749 using Chandra and NICER.

PSR J1813-1749 is one of the most energetic rotation-powered pulsars known, producing a pulsar wind nebula (PWN) and gamma-ray and TeV emission, but whose spin period is only measurable in X-ray. We present analysis of two Chandra datasets that are separated by more than ten years and recent NICER data. The long baseline of the Chandra data allows us to derive a pulsar proper motion µ R.A. = - ( 0 . ″ 067 ± 0 . ″ 010 ) yr-1 and µ decl. = - ( 0 . ″ 014 ± 0 . ″ 007 ) yr-1 and velocity v ⊥ ≈ 900-1600 km s-1 (assuming a distance d = 3 - 5 kpc), although we cannot exclude a contribution to the change in measured pulsar position due to a change in brightness structure of the PWN very near the pulsar. We model the PWN and pulsar spectra using an absorbed power law and obtain best-fit absorption N H = (13.1 ± 0.9) × 1022 cm-2, photon index Γ = 1.5 ± 0.1, and 0.3-10 keV luminosity L X ≈ 5.4 × 1034 erg s-1(d/ 5 kpc)2 for the PWN and Γ = 1.2 ± 0.1 and L X « 9.3 × 1033 erg s-1(d/ 5 kpc)2 for PSR J1813-1749. These values do not change between the 2006 and 2016 observations. We use NICER observations from 2019 to obtain a timing model of PSR J1813-1749, with spin frequency ν = 22.35 Hz and spin frequency time derivative v . = ( - 6.428 ± 0.003 ) × 10 - 11 Hz s-1. We also fit ν measurements from 2009-2012 and our 2019 value and find a long-term spin-down rate v . = ( - 6.3445 ± 0.0004 ) × 10 - 11 Hz s-1. We speculate that the difference in spin-down rates is due to glitch activity or emission mode switching.

An anti-glitch in a magnetar.

Magnetars are neutron stars with X-ray and soft γ-ray outbursts thought to be powered by intense internal magnetic fields. Like conventional neutron stars in the form of radio pulsars, magnetars exhibit 'glitches' during which angular momentum is believed to be transferred between the solid outer crust and the superfluid component of the inner crust. The several hundred observed glitches in radio pulsars and magnetars have involved a sudden spin-up (increase in the angular velocity) of the star, presumably because the interior superfluid was rotating faster than the crust. Here we report X-ray timing observations of the magnetar 1E 2259+586 (ref. 8), which exhibited a clear 'anti-glitch'--a sudden spin-down. We show that this event, like some previous magnetar spin-up glitches, was accompanied by multiple X-ray radiative changes and a significant spin-down rate change. Such behaviour is not predicted by models of neutron star spin-down and, if of internal origin, is suggestive of differential rotation in the magnetar, supporting the need for a rethinking of glitch theory for all neutron stars.

Characterization of GCY1 in Saccharomyces cerevisiae by metabolic profiling.

AIMS: The analytical study of intracellular (IC) metabolites has developed with advances in chromatography-linked mass spectrometry and fast sampling procedures. We applied the IC metabolite analysis to characterize the role of GCY1 in the glycerol (GLY) catabolic pathway in Saccharomyces cerevisiae. METHODS AND RESULTS: Strains with disrupted or overexpressing GLY catabolic genes such as GCY1, DAK1 and DAK2 were constructed. The strains were cultivated under different aeration conditions and quickly quenched using a novel rapid sampling port. IC concentrations of GLY, dihydroxyacetone (DHA), glycerol 3-phosphate and dihydroxyacetone phosphate were analysed in the strains by gas chromatography/mass spectrometry. DHA was not detected in the gcy1 gene-disrupted strain but accumulated 225.91 µmol g DCW(-1) in a DHA kinase gene-deficient strain under micro-aerobic conditions. Additionally, a 16.1% increase in DHA occurred by overexpressing GCY1 in the DHA kinase-deficient strain. CONCLUSIONS: Metabolic profiling showed that the GCY1 gene product functions as a GLY dehydrogenase in S. cerevisiae, particularly under micro-aerobic conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: Metabolic profiling of the GLY dissimilation pathway was successfully demonstrated in S. cerevisiae, and the function of GCY1 was explained by the results.

Breast cancer screening: How knowledgeable are female staff of a public university?

Breast cancer is the most common cancer among women worldwide and in Malaysia. It has better cure rate if detected early. However, the practice of breast cancer screening in Malaysia is still low. The objective of this study is to determine the knowledge and its associated factors as well as sources of information on breast cancer and breast cancer screening among female staff in a public university in Malaysia. Materials and Methods: This was a cross sectional study conducted in 2005 involving 394 female staff including academic and non-academic staff, which was selected by cluster sampling. A self-administered questionnaire on socioeconomic characteristics and family history of breast cancer was used for data collection. Chi-square Test and Fisher’s Exact Test was used for testing an association using SPSS 12.0. Results: The response rate was 84.3%. Only 50.9% had high knowledge on breast cancer and breast cancer screening and this was significantly associated with occupational status, monthly family income and educational level (p<0.05). The usual source of information was mass media (92.2%) while the most preferred source is the health team (71.4%). Conclusion: As mass media was a major source of information, all types of mass media could efficiently be utilized to disseminate knowledge by presenting specific programmes associated with breast cancer and breast cancer screening.

Pulsed field ionization-photoelectron photoion coincidence spectroscopy with synchrotron radiation: the heat of formation of the C2H5+ ion

Pulsed field ionization photoelectron (PFI-PE) spectroscopy combined with ion coincidence detection has been used with multi-bunch synchrotron radiation at the Advance Light Source (ALS) to energy select ions and to measure their breakdown diagram. The resolution for ion state selection achieved with Ar+ (2P3/2, 1/2) employing this PFI-PE-photoion coincidence apparatus is 0.6 meV (full width at half maximum). The production of C2H5+ from C2H5Br was investigated near the dissociative photoionization limit with this pulsed field ionization-threshold photoelectron photoion coincidence (PFI-PEPICO) scheme. Although the PFI-PE spectra of C2H5Br, C2H5I, and benzene show that the production of ions in the Franck-Condon gap regions is quite low, the selectivity for PFI-PE detection and the suppression of prompt electrons is such that we can detect 1 PFI-PE out of 25,000 total electrons s-1. The derived C2H5+ heat of formation from the analysis of the C2H5Br+ breakdown diagram and a critical analysis of other results is 900.5 +/- 2.0 kJ mol-1 at 298 K, or 913.2 +/- 2.0 kJ mol-1 at 0 K. This leads to an ethylene proton affinity at 298 K of 682.0 kJ mol-1. The measured IE of C2H5Br is 10.307 eV.

Ion-pair formation observed in a pulsed-field ionization photoelectron spectroscopic study of HF

The pulsed-field ionization (PFI) photoelectron (PE) spectrum of HF has been recorded at the chemical dynamics beamline of the advanced light source over the photon energy range 15.9-16.5 eV using a time-of-flight selection scheme at a resolution of 0.6 meV. Rotationally-resolved structure in the HF+(X 2 pi 3/2, 1/2, v+ = 0, 1) band systems are assigned. The spectral appearance of these systems agrees with a previous VUV laser PFI-PE study. Importantly, extensive rotationally-resolved structure between these two vibrational band systems is also observed. This is attributed to ion-pair formation via Rydberg states converging on the v+ = 1 vibrational levels of the HF+(X 2 pi 3/2, 1/2) spin-orbit states. These Rydberg states are assigned to the 1 sigma+ part of the nd-complexes (sigma, pi, and delta). Ion-pair formation is observed in this study by the detection of F- ions. Some partially rotationally-resolved structure in a previously published threshold photoelectron spectrum is similarly attributed to ion-pair formation (F- detection) through a combination of the v+ = 17 level of the (A 2 sigma+) 3s sigma Rydberg state and the (X 2 pi 3/2, 1/2, v+ = 1) 7d Rydberg states. On the basis of the present study, an accurate experimental value for the dissociation energy of the ground state of HF has been obtained, D0(HF) = 5.8650(5) eV.