First Detection of Ar-K Line Emission from the Cygnus Loop

We observed the Cygnus Loop with XMM-Newton (9 pointings) and Suzaku (32 pointings) between 2002 and 2008. The total effective exposure time is 670.2 ks. By using all of the available data, we intended to improve a signal-to-noise ratio of the spectrum. Accordingly, the accumulated spectra obtained by the XIS and the EPIC show some line features around 3 keV that are attributed to the S He$\beta$ and Ar He$\alpha$ lines, respectively. Since the Cygnus Loop is an evolved ($\sim$10,000 yr) supernova remnant whose temperature is relatively low ($<$1 keV) compared with other young remnants, its spectrum is generally faint above 3.0 keV, no emission lines, such as the Ar-K line have ever been detected. The detection of the Ar-K line is the first time and we found that its abundance is significantly higher than that of the solar value; 9.0$^{+4.0}_{-3.8}$ and 8.4$^{+2.5}_{-2.7}$ (in units of solar), estimated from the XIS and the EPIC spectra, respectively. We conclude that the Ar-K line originated from the ejecta of the Cygnus Loop. Follow-up X-ray observations to tightly constrain the abundances of Ar-rich ejecta will be useful to accurately estimate the progenitor's mass.Comment: 12 pages, 9 figures, accepted for publication in PAS

The Co-Ni distribution in decagonal Al69.7(4)Co10.0(4)Ni20.3(4)

The Co-Ni distribution in d-Al69.7(4)Co10.0(4)Ni20.3(4) was investigatedbased on X-ray and neutron diffraction data. The structure was modelledin higher dimensional space using the ‘charge-flipping’ and ‘low-densityelimination’ methods and it was quantitatively refined inthree-dimensional space employing a pseudo-approximant approach. Inhigher-dimensional description, the Co atoms are found at the centre ofone of the two symmetry independent occupation domains, enclosed byregions mainly occupied by Ni. The other occupation domain is mostlyoccupied by Al. In physical space Co atoms are located in the centres ofsmall Al pentagons and form pentagonal units, which are arranged indecagonal rings. On these sites Co is partly substituted by Ni, whileall other transition metal sites are occupied by Ni and to a minordegree by Al. The fraction of Co found on transition metal sitesdecreases with decreasing Co-Co distances, whereby Co is replaced by Ni

Hybridization Mechanism for Cohesion of Cd-based Quasicrystals

Cohesion mechanism of cubic approximant crystals of newly discovered binary quasicrystals, Cd$_6$M (M=Yb and Ca), are studied theoretically. It is found that stabilization due to alloying is obtained if M is an element with low-lying unoccupied $d$ states. This leads to conclusion that the cohesion of the Cd-based compounds is due to the hybridization of the $d$ states of Yb and Ca with a wide $sp$ band. %unlike known stable quasicrystals without transition elements %such as Al-Li-Cu and Zn-Mg-RE (RE:rare earth). Although a diameter of the Fermi sphere coincides with the strong Bragg peaks for Cd-Yb and Cd-Ca, the Hume-Rothery mechanism does not play a principal role in the stability because neither distinct pseudogap nor stabilization due to alloying is obtained for isostructural Cd-Mg. In addition to the electronic origin, matching of the atomic size is very crucial for the quasicrystal formation of the Cd-based compounds. It is suggested that the glue atoms, which do not participate in the icosahedral cluster, play an important role in stabilization of the compound.Comment: 4 pages, 2 figure

Pretransplant serum ferritin and C-reactive protein as predictive factors for early bacterial infection after allogeneic hematopoietic cell transplantation.

Although fluoroquinolones or other antibiotics are commonly used to prevent bacterial infections after hematopoietic cell transplantation (HCT), because of the growing presence of multidrug-resistant microorganisms, it is important to identify patients who are more likely to benefit from antibacterial prophylaxis. To evaluate risk factors for early bacterial infection after allogeneic HCT, we retrospectively analyzed clinical data for 112 consecutive adult patients with hematological malignancies who received transplants without any antibacterial prophylaxis. The cumulative incidence of bacterial infection at 30 days after transplantation was 16%. Among various pre-transplant factors, only high serum ferritin (>700 ng/mL, 47 patients) and high C-reactive protein (CRP) (>0.3 mg/dL, 28 patients) levels were significantly associated with the development of bacterial infection in a multivariate analysis (hazard ratio (95% confidence interval): ferritin, 4.00 (1.32-12.17); CRP, 3.64 (1.44-9.20)). In addition, septic shock and sepsis with organ failure were exclusively observed in patients who had high ferritin and/or high CRP levels. These results suggest that pretransplant serum ferritin and CRP levels can be useful markers for predicting the risk of early bacterial infection after allogeneic HCT. It may be prudent to limit antibacterial prophylaxis to patients with predefined risk factors to ensure the safety of HCT with the use of fewer antibiotics

Characterization of a half-wave plate for cosmic microwave background circular polarization measurement with POLARBEAR

A half-wave plate (HWP) is often used as a modulator to suppress systematic error in the measurements of cosmic microwave background (CMB) polarization. A HWP can also be used to measure circular polarization (CP) through its optical leakage from CP to linear polarization. The CP of the CMB is predicted from various sources, such as interactions in the Universe and extension of the standard model. Interaction with supernova remnants of population III stars is one of the brightest CP sources. Thus, the observation of the CP of CMB is a new tool for searching for population III stars. In this paper, we demonstrate the improved measurement of the leakage coefficient using the transmission measurement of an actual HWP in the laboratory. We measured the transmittance of linearly polarized light through the HWP used in \textsc{Polarbear} in the frequency range of \SIrange{120}{160}{GHz}. We evaluate properties of the HWP by fitting the data with a physical model using the Markov Chain Monte Carlo method. We then estimate the band-averaged CP leakage coefficient using the physical model. We find that the leakage coefficient strongly depends on the spectra of CP sources. We thus calculate the maximum fractional leakage coefficient from CP to linear polarization as $0.133 \pm 0.009$ in the Rayleigh--Jeans spectrum. The nonzero value shows that \textsc{Polarbear} has sensitivity to CP. Additionally, because we use the bandpass of detectors installed in the telescope to calculate the band-averaged values, we also consider systematic effects in the experiment.Comment: 27 pages, 7 figure

The surface science of quasicrystals

The surfaces of quasicrystals have been extensively studied since about 1990. In this paper we review work on the structure and morphology of clean surfaces, and their electronic and phonon structure. We also describe progress in adsorption and epitaxy studies. The paper is illustrated throughout with examples from the literature. We offer some reflections on the wider impact of this body of work and anticipate areas for future development. (Some figures in this article are in colour only in the electronic version