bluuebunny/crossref_metadata_2025 huggingface dataset:
End user voltage regulation to ease urban low‐voltage distribution congestion
Authors: Connor Gordon , Jones Catherine E. , Finney Stephen J.
Published: March 2014

Owing to the increasing demand in the urban areas for new technologies such as heat pumps and electric vehicles (EVs), greater power capacity in low voltage (LV) distribution networks is becoming increasingly important. This study will investigate how to improve the power capacity through the implementation of point of use voltage regulation (PUVR). PUVR relies on a power electronics converter at each end‐user. Most LV network cabling has a voltage limit of 1 kV, PUVR exploits this voltage rating to increase the network capacity. This study will describe and discuss the results from a viability study using data from a utility company, which shows that the capacity in the LV network could be increased by an additional 500 kVA. However, it was also found that PUVR using present off‐the‐shelf converters is not as cost‐effective as replacing the LV network cables. Two power electronics topologies have been investigated in the simulation studies to date: the AC chopper circuit and the back‐to‐back inverter circuit. These two topologies were compared and the AC chopper was found to be a cheaper, more efficient topology. Therefore the AC chopper is more suitable for this application and may increase the viability of the PUVR.
Ferromagnetism and magneto-transport properties of Mn0.92Ca0.08As thin film grown on Al2O3(0001) substrate
Authors: Dung Dang Duc , Van Thiet Duong , Anh Tuan Duong , Feng Wuwei , Cho Sunglae
Published: March 2014

The epitaxial Mn0.92Ca0.08As thin film was grown on Al2O3(0001) substrate by molecular beam epitaxy. The Curie temperature (TC) around 340 K was enhanced with the addition of Ca, compared to that of bulk MnAs (TC ∼ 318 K). The maxima magnetoresistance, ∼2.08% at 0.7 T, was observed near the critical magnetic transition temperature. Moreover, the giant magnetocaloric effect was found with the maximum magnetic entropy change, ∼200 J/kgK, around 330 K at 5 T.
Amyloid oligomer structure characterization from simulations: A general method
Authors: Nguyen Phuong H. , Li Mai Suan , Derreumaux Philippe
Published: March 2014

Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ9−40, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.
Shear-induced diffusion in dilute curved fiber suspensions in simple shear flow
Authors: Wang Jianghui , Graham Michael D. , Klingenberg Daniel J.
Published: March 2014

Shear-induced self-diffusion of fibers suspended in an incompressible Newtonian fluid in simple shear flow at low Reynolds number is studied by simulation. Two models are employed: a linked rigid rod model and a bead chain model. Hydrodynamic interactions are neglected in both models. The shear-induced diffusivity of suspensions of fibers increases with increasing concentration and increasing static friction between contacts. The diffusivities in both the gradient and vorticity directions are larger for suspensions of curved fibers than for suspensions of straight fibers. For suspensions of curved fibers, significant enhancements in the diffusivity in the gradient direction are observed. The enhanced diffusivities are attributed to fiber drift observed in prior work for isolated curved fibers [J. Wang, E. J. Tozzi, M. D. Graham, and D. J. Klingenberg, “Flipping, scooping, and spinning: Drift of rigid curved nonchiral fibers in simple shear flow,” Phys. Fluids 24, 123304 (2012)]. Here, for some initial orientations, curved fibers will drift in the positive or negative gradient direction with nearly constant speed. In dilute suspensions, this drift occurs for a fraction of the fibers, which increases the mean-squared displacement in the gradient direction, and thus increases the diffusivity in the gradient direction.
A note on the application of the Prigogine theorem to rotation of tokamak-plasmas in absence of external torques
Authors: Sonnino Giorgio , Cardinali Alessandro , Sonnino Alberto , Nardone Pasquale , Steinbrecher György , Zonca Fulvio
Published: March 2014

Rotation of tokamak-plasmas, not at the mechanical equilibrium, is investigated using the Prigogine thermodynamic theorem. This theorem establishes that, for systems confined in rectangular boxes, the global motion of the system with barycentric velocity does not contribute to dissipation. This result, suitably applied to toroidally confined plasmas, suggests that the global barycentric rotations of the plasma, in the toroidal and poloidal directions, are pure reversible processes. In case of negligible viscosity and by supposing the validity of the balance equation for the internal forces, we show that the plasma, even not in the mechanical equilibrium, may freely rotate in the toroidal direction with an angular frequency, which may be higher than the neoclassical estimation. In addition, its toroidal rotation may cause the plasma to rotate globally in the poloidal direction at a speed faster than the expression found by the neoclassical theory. The eventual configuration is attained when the toroidal and poloidal angular frequencies reaches the values that minimize dissipation. The physical interpretation able to explain the reason why some layers of plasma may freely rotate in one direction while, at the same time, others may freely rotate in the opposite direction, is also provided. Invariance properties, herein studied, suggest that the dynamic phase equation might be of the second order in time. We then conclude that a deep and exhaustive study of the invariance properties of the dynamical and thermodynamic equations is the most correct and appropriate way for understanding the triggering mechanism leading to intrinsic plasma-rotation in toroidal magnetic configurations.
Extinction properties of single-walled carbon nanotubes: Two-fluid model
Authors: Moradi Afshin
Published: March 2014

The extinction spectra of a single-walled carbon nanotube are investigated, within the framework of the vector wave function method in conjunction with the hydrodynamic model. Both polarizations of the incident plane wave (TE and TM with respect to the x-z plane) are treated. Electronic excitations on the nanotube surface are modeled by an infinitesimally thin layer of a two-dimensional electron gas represented by two interacting fluids, which takes into account the different nature of the σ and π electrons. Numerical results show that strong interaction between the fluids gives rise to the splitting of the extinction spectra into two peaks in quantitative agreement with the π and σ + π plasmon energies.
Alternative understanding for the enthalpy vs volume change upon structural relaxation of metallic glasses
Authors: Khonik V. A. , Kobelev N. P.
Published: March 2014

It has been argued that the densification observed upon structural relaxation of metallic glasses can be explained not by the “free volume annihilation,” as it is custom to consider, but by the annealing of interstitialcy-like “defects” frozen-in upon glass production. A simple expression for the enthalpy release due to relaxation of defect-induced dilatational energy has been proposed. The expression is shown to be in agreement with recent detailed experimental data on the heat release occurring upon structural relaxation of Au-based metallic glass [J. Bünz and G. Wilde, J. Appl. Phys. 114, 223503 (2013)].
All-thin-film multilayered multiferroic structures with a slot-line for spin-electromagnetic wave devices
Authors: Nikitin Andrey A. , Ustinov Alexey B. , Semenov Alexander A. , Kalinikos Boris A. , Lähderanta E.
Published: March 2014

Spin-electromagnetic waves propagating in thin-film multilayered multiferroic structures containing a slot transmission line have been investigated both experimentally and theoretically. The thin-film structure was composed of a ferrite film, a ferroelectric film, and a slot-line. It was shown that the spectrum of the spin-electromagnetic wave was formed as a result of hybridization of the spin wave in the ferrite film with the electromagnetic wave in the slot-line and was electrically and magnetically tunable. For the experimental investigations, a microwave phase shifter based on the multiferroic structure has been fabricated. Performance characteristics are presented.
Non-linear dynamic characteristics and optimal control of giant magnetostrictive film subjected to in-plane stochastic excitation
Authors: Zhu Z. W. , Zhang W. D. , Xu J.
Published: March 2014

The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF) subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.
Effective terahertz-to-near-infrared photon conversion in slant-stripe-type periodically poled LiNbO3
Authors: Nawata K. , Notake T. , Ishizuki H. , Qi F. , Takida Y. , Fan S. , Hayashi S. , Taira T. , Minamide H.
Published: March 2014

We propose a slant-stripe-type periodically poled LiNbO3 crystal for the construction of a practical quasi-phase-matched (QPM) device for terahertz (THz) detection. A minimum detectable THz-wave energy of 25 fJ/pulse is demonstrated, and a linear input-output property with a dynamic range of 60 dB is achieved. The working frequency range of 0.15 THz for THz detection is obtained, and the central frequency of the sensitivity can be controlled by the design of the periodically poled structure. THz detection using this QPM device is a promising technique that may allow the detection of a coherent THz photon.
Understanding the Use of Ecosystem Service Knowledge in Decision Making: Lessons from International Experiences of Spatial Planning
Authors: McKenzie Emily , Posner Stephen , Tillmann Patricia , Bernhardt Joanna R , Howard Kirsten , Rosenthal Amy
Published: March 2014

The limited understanding of how ecosystem service knowledge (ESK) is used in decision making constrains our ability to learn from, replicate, and convey success stories. We explore use of ESK in decision making in three international cases: national coastal planning in Belize; regional marine spatial planning on Vancouver Island, Canada; and regional land-use planning on the island of Oahu, Hawaii. Decision makers, scientists, and stakeholders collaborated in each case to use a standardized ecosystem service accounting tool to inform spatial planning. We evaluate interview, survey, and observation data to assess evidence of ‘conceptual’, ‘strategic’, and ‘instrumental’ use of ESK. We find evidence of all modes: conceptual use dominates early planning, while strategic and instrumental uses occur iteratively in middle and late stages. Conceptual and strategic uses of ESK build understanding and compromise that facilitate instrumental use. We highlight attributes of ESK, characteristics of the process, and general conditions that appear to affect how knowledge is used. Meaningful participation, scenario development, and integration of local and traditional knowledge emerge as important for particular uses.
Modelling canopy fuel variables for Pinus radiata D. Don in NW Spain with low-density LiDAR data
Authors: González-Ferreiro Eduardo , Diéguez-Aranda Ulises , Crecente-Campo Felipe , Barreiro-Fernández Laura , Miranda David , Castedo-Dorado Fernando
Published: March 2014

Crown fire initiation and spread are key elements in gauging fire behaviour potential in conifer forests. Crown fire initiation and spread models implemented in widely used fire behaviour simulation systems such as FARSITE and FlamMap require accurate spatially explicit estimation of canopy fuel complex characteristics. In the present study, we evaluated the potential use of very low-density airborne LiDAR (light detection and ranging) data (0.5 first returns m–2) – which is freely available for most of the Spanish territory – to estimate canopy fuel characteristics in Pinus radiata D. Don stands in north-western Spain. Regression analysis indicated strong relationships (R2=0.82–0.98) between LiDAR-derived metrics and field-based fuel estimates for stand height, canopy fuel load, and average and effective canopy base height Average and effective canopy bulk density (R2=0.59–0.70) were estimated indirectly from a set of previously modelled forest variables. The LiDAR-based models developed can be used to elaborate geo-referenced raster files to describe fuel characteristics. These files can be generated periodically, whenever new freely available airborne LiDAR data are released by the Spanish National Plan of Aerial Orthophotography, and can be used as inputs in fire behaviour simulation systems.
Oxidized Low‐Density Lipoprotein Alters the Effect of Matrix Stiffness on the Formation of Endothelial Networks and Capillary Lumens
Authors: Gundavaram Madhu S. , Shentu Tzu Pin , Kowalsky Gregory B. , Volkov Suncica , Schraufnagel Dean E. , Levitan Irena
Published: March 2014

Formation of new blood vessels is essential for vascular repair and remodeling, and it is known that biomechanical properties of extracellular matrix play a major role in this process. Our earlier studies have also shown that exposing endothelial cells to oxidized modification of low‐density lipoproteins (oxLDL) increases endothelial stiffness and facilitates their ability to form cellular networks, suggesting that it facilitates endothelial angiogenic potential. The goal of this study, therefore, was to test the interrelationship between matrix stiffness and oxLDL in the regulation of angiogenesis. Our results show that, as expected, an increase in matrix stiffness inhibited endothelial network formation and that exposure to oxLDL significantly facilitated this process. We also show, however, that oxLDL‐induced facilitation of endothelial networks was observed only in stiff (3 mg/mL) but not in soft (1 mg/mL) collagen gels, resulting in blunting the effect of matrix stiffness. Also unexpectedly, we show that an increase in matrix stiffness results in a significant increase in the number of capillary lumens that are formed by single cells or pairs of cells, suggesting that while endothelial connectivity is impaired, formation of single‐cell lumens is facilitated. oxLDL facilitates lumen formation, but this effect is also matrix dependent and is observed only in soft gels and not in stiff gels. Finally, an increase in both matrix stiffness and oxLDL exposure results in changes in capillary morphology, with the formation of larger capillary lumens. Overall, our study suggests that oxLDL plays an important role in formation of new capillaries and their morphology and that this effect is critically dependent on the extracellular environment's compliance, thereby underlining the importance of the interdependence of these parameters.
Interaction between Bone Morphogenetic Protein Receptor Type 2 and Estrogenic Compounds in Pulmonary Arterial Hypertension
Authors: Fessel Joshua P. , Chen Xinping , Frump Andrea , Gladson Santhi , Blackwell Tom , Kang Christie , Johnson Jennifer , Loyd James E. , Hemnes Anna , Austin Eric , West James
Published: March 2014

The majority of heritable pulmonary arterial hypertension (HPAH) cases are associated with mutations in bone morphogenetic protein receptor type 2 (BMPR2). BMPR2 mutation carries about a 20% lifetime risk of PAH development, but penetrance is approximately three times higher in females. Previous studies have shown a correlation between estrogen metabolism and penetrance, with increased levels of the estrogen metabolite 16α‐hydroxyestrone (16αOHE) and reduced levels of the metabolite 2‐methoxyestrogen (2ME) associated with increased risk of disease. The goal of this study was to determine whether 16αOHE increased and 2ME decreased penetrance of disease in Bmpr2 mutant mice and, if so, by what mechanism. We found that 16αOHE:2ME ratio was high in male human HPAH patients. Bmpr2 mutant male mice receiving chronic 16αOHE had doubled disease penetrance, associated with reduced cardiac output. 2ME did not have a significant protective effect, either alone or in combination with 16αOHE. In control mice but not in Bmpr2 mutant mice, 16αOHE suppressed bone morphogenetic protein signaling, probably directly through suppression of Bmpr2 protein. Bmpr2 mutant pulmonary microvascular endothelial cells were insensitive to estrogen signaling through canonical pathways, associated with aberrant intracellular localization of estrogen receptor α. In both control and Bmpr2 mutant mice, 16αOHE was associated with suppression of cytokine expression but with increased alternate markers of injury, including alterations in genes related to thrombotic function, angiogenesis, planar polarity, and metabolism. These data support a causal relationship between increased 16αOHE and increased PAH penetrance, with the likely molecular mechanisms including suppression of BMPR2, alterations in estrogen receptor translocation, and induction of vascular injury and insulin resistance–related pathways.
Short‐Term Improvement in Pulmonary Hemodynamics is Strongly Predictive of Long‐Term Survival in Patients with Pulmonary Arterial Hypertension
Authors: Tiede Henning , Sommer Natascha , Milger Katrin , Voswinckel Robert , Bandorski Dirk , Schermuly Ralph T. , Weissmann Norbert , Grimminger Friedrich , Seeger Werner , Ghofrani Hossein A.
Published: March 2014

Hemodynamic measurements provide important parameters for determining prognosis and therapy in patients with pulmonary arterial hypertension (PAH). Current guidelines do not incorporate the possible predictive value of individual changes in hemodynamic variables during the disease time course, and there is no consensus about the time point for hemodynamic reevaluation. We aimed to assess the long‐term prognostic value of short‐term changes in hemodynamic parameters. The study included 122 patients with PAH from the Giessen Pulmonary Hypertension Registry who underwent hemodynamic evaluation at baseline and at 16 weeks (±2.5 standard deviations [SDs]; range: 4–29 weeks) after initial assessment. At baseline, mean pulmonary vascular resistance (PVR) was 1,109 dyn s cm−5, and 82% of patients were in World Health Organization (WHO) functional class III or IV. Fifty patients died, and 2 underwent lung transplantation during long‐term observation (≤10 years; mean: 4.7 years). Kaplan‐Meier estimates for transplant‐free survival were 93.3%, 76.1%, 57.8%, and 53.1% at 1, 3, 5, and 7 years, respectively. When assigned to prognostic groups, improvements in cardiac output of >0.22 L min−1 (hazard ratio [HR]: 2.05; P = 0.015) and a decrease in PVR of >176 dyn s cm−5 (HR: 1.89; P = 0.044) at 4–29 weeks were associated with long‐term transplant‐free survival. Changes in mean pulmonary arterial pressure did not predict long‐term prognosis. Of 2 noninvasive parameters assessed in this selected patient group, change in WHO functional class, but not in 6‐minute walk distance, predicted long‐term prognosis. Short‐term assessment of changes in hemodynamic parameters at 16 weeks ± 2.5 SDs after initial invasive evaluation is useful to determine long‐term prognosis in patients with PAH.
Looking beyond PPHN: The Unmet Challenge of Chronic Progressive Pulmonary Hypertension in the Newborn
Authors: Fike Candice D. , Aschner Judy L.
Published: March 2014

Infants with forms of pulmonary hypertension (PH) that persist or develop beyond the first week of life are an understudied group of patients with up to 40%–60% mortality. The clinical management of the progressive PH that develops in these infants is challenging because of the nonspecific signs and symptoms of clinical presentation, the limited diagnostic sensitivity of standard echocardiographic techniques, and the lack of proven therapies. The signaling mechanisms that underlie the structural and functional abnormalities in the pulmonary circulation of these infants are not yet clear. The ability to improve outcomes for these patients awaits technological advances to improve diagnostic capabilities and therapeutic discoveries made in basic science laboratories that can be tested in randomized clinical trials.
Perioperative Pharmacological Management of Pulmonary Hypertensive Crisis during Congenital Heart Surgery
Authors: Brunner Nathan , Perez Vinicio A. de Jesus , Richter Alice , Haddad François , Denault André , Rojas Vanessa , Yuan Ke , Orcholski Mark , Liao Xiaobo
Published: March 2014

Pulmonary hypertensive crisis is an important cause of morbidity and mortality in patients with pulmonary arterial hypertension secondary to congenital heart disease (PAH‐CHD) who require cardiac surgery. At present, prevention and management of perioperative pulmonary hypertensive crisis is aimed at optimizing cardiopulmonary interactions by targeting prostacyclin, endothelin, and nitric oxide signaling pathways within the pulmonary circulation with various pharmacological agents. This review is aimed at familiarizing the practitioner with the current pharmacological treatment for dealing with perioperative pulmonary hypertensive crisis in PAH‐CHD patients. Given the life‐threatening complications associated with pulmonary hypertensive crisis, proper perioperative planning can help anticipate cardiopulmonary complications and optimize surgical outcomes in this patient population.
Perspective: Ambient Air Pollution: Inflammatory Response and Effects on the Lung's Vasculature
Authors: Grunig Gabriele , Marsh Leigh M. , Esmaeil Nafiseh , Jackson Katelin , Gordon Terry , Reibman Joan , Kwapiszewska Grazyna , Park Sung‐Hyun
Published: March 2014

Particulates from air pollution are implicated in causing or exacerbating respiratory and systemic cardiovascular diseases and are thought to be among the leading causes of morbidity and mortality. However, the contribution of ambient particulate matter to diseases affecting the pulmonary circulation, the right heart, and especially pulmonary hypertension is much less documented. Our own work and that of other groups has demonstrated that prolonged exposure to antigens via the airways can cause severe pulmonary arterial remodeling. In addition, vascular changes have been well documented in a typical disease of the airways, asthma. These experimental and clinical findings link responses in the airways with responses in the lung's vasculature. It follows that particulate air pollution could cause, or exacerbate, diseases in the pulmonary circulation and associated pulmonary hypertension. This perspective details the literature for support of this concept. Data regarding the health effects of particulate matter from air pollution on the lung's vasculature, with emphasis on the lung's inflammatory responses to particulate matter deposition and pulmonary hypertension, are discussed. A deeper understanding of the health implications of exposure to ambient particulate matter will improve our knowledge of how to improve the management of lung diseases, including diseases of the pulmonary circulation. As man‐made ambient particulate air pollution is typically linked to economic growth, a better understanding of the health effects of exposure to particulate air pollution is expected to integrate the global goal of achieving healthy living for all.
Formation of the Ring-Like Structure in the SN 1987A Nebula due to the Magnetic Pressure of the Toroidal Field
Authors: Washimi Haruichi , Shibata Shinpei , Mori Masao
Published: March 2014

Several weeks after the explosion of supernova (SN) 1987A, the UV flash of the SN illuminated a ring-like structure in the circumstellar material at about 0.65 ly from the SN. The interaction between the stellar winds from the SN progenitor is considered to be the candidate for the formation of the circumstellar structure. In the case that the stellar winds are spherically symmetric, the interaction should result in a shell-like structure. However, in this paper we show that the magnetic field in the winds causes an anisotropy which leads to the formation of a ring-like structure. When the fast wind of the blue supergiant phase of the progenitor sweeps up the surrounding slow wind of the red-supergiant phase, the magnetic field as well as the wind material are piled up in the interaction region. Since the magnetic energy increases in proportion to the square of the amplitude, the magnetic field exhibits its effect prominently at the interaction region; due to the magnetic pressure force the material at lower latitudes is compressed into a ring-like structure. It is suggested that this magnetic process can also explain the newly observed pair of rings of the SN 1987A nebula.
Enhanced He I Absorption at the Feet of Solar X-Ray Loops
Authors: Venkatakrishnan P. , Sakurai Takashi , Suematsu Yoshinori , Ichimoto Kiyoshi
Published: March 2014

A comparison of He I spectroheliograms and Yohkoh soft X-ray images of active regions indicates that He I absorption is enhanced at the feet of hot X-ray loops. It is suggested that the conduction of heat from the loops into the transition region at their feet would produce enhanced transition-region emission around 50 eV that would in turn cause enhanced excitation of He I leading to the excess He I absorption that is observed.
X-Ray Observations of NGC 2110 with Ginga and ASCA
Authors: Hayashi Ichizo , Koyama Katsuji , Awaki Hisamitsu , Ueno Shiro , Yamauchi Shigeo
Published: March 2014

We present the Ginga and ASCA results for the narrow emission line galaxy NGC 2110. Using Ginga data we found a fast time-variability of a few hours, superimposed on a relatively constant X-ray flux. The X-ray spectrum was well fitted with an absorbed power- law plus iron K emission-line model, in which no significant reflection component w as required. Using ASCA data we confirmed the previous detection of extra soft X-ray emission and a K-shell emission line from “cold” iron in the simple absorbed power-law spectrum. For the first time we detected a K-shell absorption edge of “cold” iron. This edge feature, combined with the Ginga results, indicates that the reflection process is not dominant in NGC 2110. We propose that these iron line and edge features are due to a partial covering material with NH ∼ 1023 cm−2 , which presumably comprises “hidden” broad line region (BLR) clouds.
ASCA Observations of Soft X-Ray Transients in Quiescence : X1608–52 and Cen X-4
Authors: Asai Kazumi , Dotani Tadayasu , Mitsuda Kazuhisa , Hoshi Reiun , Vaughan Brian , Tanaka Yasuo , Inoue Hajime
Published: March 2014

We observed soft X-ray transients, X1608–52 and Cen X-4, in quiescence with ASCA at X-ray luminosities on the order of 1032–33 erg s−1. The energy spectra were rather soft for both sources. Blackbody fits to the data required characteristic temperatures of 0.2–0.3 keV and emission regions of ∼ 10 km2. A conspicuous hard tail remained after fitting Cen X-4 with a blackbody curve. An extremely soft spectrum in quiescence seems to be a common property of soft X-ray transients.
CO-to-H2 Conversion Factor in Galaxies
Authors: Arimoto Nobuo , Sofue Yoshiaki , Tsujimoto Takuji
Published: March 2014

A general method and formulae to derive the CO-to-H2 conversion factor in galaxies as a function of the metallicity are presented based on an analysis of the observed data for the conversion factor obtained for nearby spiral and dwarf irregular galaxies. From the CO data for eight galaxies we obtained the following formula, which gives the conversion factor (X*) as a function of metallicity:

log X*= −1.0 (12 +log O/H)+ A,

where X* = NH2 / ICO × 10−20 H2/(K km s−1) and A is a constant. Since the metallicity is dependent on the luminosity of galaxies, we derived a correlation between the conversion factor and the absolute magnitude of galaxies. We also investigated dependence of the conversion factor on the distance from the center of individual galaxies. We also present a formula to calculate X* as a function of the radius in a galaxy.
Discovery of Two Types of Superhumps in WZ Sge-Type Dwarf Nova AL Comae Berenices
Authors: Kato Taichi , Nogami Daisaku , Baba Hajime , Matsumoto Katsura , Arimoto Jun'ichi , Tanabe Kazuhito , Ishikawa Kaoru
Published: March 2014

A dwarf nova, AL Com, was photometrically observed during an outburst in 1995 April, which occurred for the first time since 1975. The star showed two distinct types of periodic variation: (1) a 0.05666-day variation with decaying amplitudes during the earliest stage of the outburst, and (2) 0.0572-day super humps which grew ∼ 11 d after the onset of the outburst. The present observations are the one first to clearly established the SU UMa-type nature of AL Com. Furthermore, the appearance of these two periods, together with the whole course of the superoutburst, makes AL Com an almost perfect twin of an enigmatic dwarf nova, WZ Sge. We attributed the former period to be the orbital period of this cataclysmic binary. The double-humped profile of this variation seems to preclude an explantion based on an enhanced hot spot by a mass-transfer burst from the secondary, which has been believed to be the best observational evidence of a mass-transfer burst in WZ Sge obtained during its 1978 outburst.
ASCA Observation of NGC 1808
Authors: Awaki Hisamitsu , Ueno Shiro , Koyama Katsuji , Tsuru Takeshi , Iwasawa Kazushi
Published: March 2014

The Japanese X-ray satellite ASCA observed NGC 1808, which is known to exhibit both Seyfert and starburst activities. In the soft X-ray band, ASCA detected emission lines from highly ionized Mg and Si, which confirmed the presence of a thin thermal plasma, due possibly to starburst activity. The thin thermal plasma consists of two temperature components of kT ∼ 0.78 keV and kT ∼ 0.35 keV. We found that the intrinsic absorption toward the 0.78 keV plasma is NH ∼ 7 × 1021 cm−2, which is greater than the galactic foreground value of 2.8 × 1020 cm−2 (Dickey, Lockman 1990, AAA 53.155.163). This result implies that most of the X-ray emission from this plasma comes from the central region. The absorption toward the 0.35 keV plasma, on the other hand, shows a low value compared to the galactic absorption. This indicates that the plasma is more extended like an X-ray halo. The metal abundance of about 1 solar value found in the thin thermal plasma is larger than that of the archetypical starburst galaxy M82. In addition to the thin hot plasma, ASCA detected a hard X-ray component from NGC 1808, with a luminosity of 2×1040 erg s−1 (0.5–10 keV band), obscured by an absorbing column of 1.0×1022 cm−2. The hard X-ray flux and spectrum may also be attributable to starburst activity. However, the hard X-rays exhibited a long-term variability from the Ginga and ASCA observations, suggesting the presence of a low-luminosity AGN in NGC 1808.
Growth of Velocity Dispersions for Collapsing Spherical Stellar Systems
Authors: Hozumi Shunsuke , Fujiwara Takao , Kan-ya Yukitoshi
Published: March 2014

First, we have ensured that spherical nonrotating collisionless systems collapse while almost retaining their spherical configurations during the initial contraction phases, even if they are allowed to collapse three-dimensionally. Next, based on the assumption of spherical symmetry, we examine the evolution of the velocity dispersions with collapse for those systems having uniform or power-law density profiles with Maxwellian velocity distributions by directly integrating the collisionless Boltzmann equation. The results show that as far as the initial contraction phases are concerned, the radial velocity dispersion never grows faster than the tangential velocity dispersion, except at small radii, where the nearly isothermal nature remains, irrespective of the density profiles and virial ratios. This implies that the velocity anisotropy as an initial condition should be a poor indicator of the radial orbit instability. The growing behavior of the velocity dispersions is briefly discussed from the viewpoint that phase-space density is conserved in collisionless systems.
Measurement of the Coronal Electron Temperature at the Total Solar Eclipse on 1994 November 3
Authors: Ichimoto Kiyoshi , Kumagai Kazuyoshi , Sano Issei , Kobiki Toshihiko , Sakurai Takashi , Muñoz Alberto
Published: March 2014

A spectroscopic observation was carried out at the total solar eclipse on 1994 November 3 in Putre, Chile, in order to investigate the electron temperature and the expanding motion of the corona. The shape of weak depressions at 3900 Å and 4300 Å in the continuous coronal spectra was compared with the theoretical electron-scattered coronal spectra; thus, the magnitude of the electron thermal motion was determined directly. It was found that a coronal streamer on the eastern limb and a coronal hole on the south-pole have overall temperatures of about 1.5–1.7 MK and 0.9–1.1 MK, respectively. No significant height variation in the temperature was found in the streamer, while the coronal hole shows evidence of increasing temperature with height. An acceleration of the expanding motion between 1.1 R⊙ and 2.0 R⊙ by ∼ 80 km s−1 was found in the streamer.
Radial Distributions of the Temperature and Metal Abundances in the Ophiuchus Cluster of Galaxies
Authors: Matsuzawa Hideyuki , Matsuoka Masaru , Ikebe Yasushi , Mihara Tatehiro , Yamashita Koujun
Published: March 2014

We report on the first result concerning the Ophiuchus cluster of galaxies observed with ASCA during the performance-verification phase. The obtained image in the energy range of 0.7–10 keV is nearly circular, and the peak of the X-ray surface brightness is coincident with the position of the cD galaxy. We analyzed the ASCA GIS data within a 13′.8 radius of the cluster center while considering the energy-dependent flux-contaminated effect due to ASCA X-ray telescope. This data can be well explained with the isothermal β model, in which the density profile is expressed with a β profile of rcore = 3′.8 and β = 0.62, and the temperature and metal abundances are constant at kT = 9.8 keV and Z = 0.24 Z⊙. The central excess density profile obtained with Einstein HRI is also consistent with the ASCA GIS data.
Discovery of a Large-Amplitude SU UMa-Type Dwarf Nova, CT Hydrae
Authors: Nogami Daisaku , Kato Taichi , Hirata Ryuko
Published: March 2014

A faint dwarf nova, CT Hya, was observed for seven nights during its long outburst in 1995 February–March and during quiescence on 1995 December 15. V-band CCD photometry revealed superhumps with a period of 0.06505 (±0.00010) d or its aliases, 0.06358 (±0.00010) d or 0.06649 (±0.00010) d, and with a total amplitude of about 0.25 mag. This discovery confirms CT Hya as being a new member of SU UMa-type dwarf novae. We have concluded that CT Hya is an intermediate object between ordinary SU UMa stars and WZ Sge stars based on its peculiar behavior.
Relativistic Radiative Winds from an Accretion Disk under Radiation Drag
Authors: Fukue Jun
Published: March 2014

We examine the steady relativistic winds which are emanating from a luminous accretion disk and driven by disk radiation fields under the influence of radiation drag. For wind flows we use a streamline approach where the dynamical equations are expressed by the streamline coordinates, and a cold approximation where the pressure-gradient force is ignored. For radiation fields, on the other hand, we use a near-disk approximation where the radiation stress-energy tensors are evaluated from the disk region just below the flows. The streamlines may widen, since the wind flows gain angular momentum from the disk radiation field just below them. The wind terminal speed is smaller than the Icke's magic speed of (4-√7)c/3 ∼ 0.45c, because the streamlines are generally inclined, and therefore the radiative force is smaller than in the case of vertical streamlines. The conditions that the radiative wind blows are obtained for the control parameters: the radius of the wind base and the normalized disk luminosity. The radiative wind can blow from the inner region (r0 ∼ 5–8 rg) if the disk is sufficiently luminous. We also briefly discuss pure electron-positron pair winds, where the acceleration takes place very close to the disk.
A Search for Galaxies behind the Milky Way at Aquila and Sagittarius
Authors: Roman Adel T. , Nakanishi Kouichiro , Tomita Akihiko , Saitō Mamoru
Published: March 2014

We searched for galaxies using Schmidt atlases in a Milky Way region of about 800 square degrees around l ≃ 8° to 43° and b ≃ −17° to 17°. The surveyed region is located between the northern Local void and the Ophiuchus void. We detected about 5300 galaxy candidates, which have galaxy-like images with sizes larger than 0′.1. Of these, only 30 have been given in galaxy catalogs and another 74 are associated with IRAS point sources containing 18 IRAS galaxies with known redshifts. We made a catalog of detected objects in which the position in (α, δ) and (l, b), size, and features of image and multiplicity are given. The sky distribution of detected objects shows the presence of two clusters of galaxies and a group of nearby galaxies located around l = 33°, b = −15° with cz = 1500 km s−1.
Spectral Variability and Iron Line Emission in the ASCA Observations of the Seyfert 1 Galaxy NGC 4051
Authors: Guainazzi Matteo , Mihara Tatehiro , Otani Chiko , Matsuoka Masaru
Published: March 2014

We present the results of an extensive analysis of the ASCA AO2 observation of the Seyfert 1 galaxy NGC 4051. The target exhibits broadband [0.5–10 keV] variability by a factor ∼ 8 on time scales ∼ 104 s, with a typical doubling time ∼ 500 s. The spectrum is characterized by a strong emission excess over the extrapolated power law at energies E ≤ 1 keV. Absorption edges due to ionized oxygen species O VII and O VIII are detected together with an emission-like feature at E ∼ 0.93 keV. The O VII edge undergoes significant variability on a timescale as low as ∼ 104 s, whilst no contemporary variability of the O VIII feature is detected. Typical variability time scales place constraints on the location and the density of the absorbing matter. In the self-consistent hypothesis of a high energy (E ≥ 2.3 keV) power law reflected by an infinite plane-parallel cold slab, a photon index change (ΔΓ = 0.4) has also been observed; a natural explanation can be found in the framework of non-thermal Comptonization models. The iron line is redshifted (centroid energy E ∼ 6.1 keV) and broad (σ > 0.2 keV); multicomponent structure is suggestive of emission from a relativistic accretion disk; however if the disk is not ionized a contribution by a molecular torus or an iron overabundance by a factor ∼ 1.5 are required.
Post-Periastron ASCA Observation of the PSR B1259–63 System
Authors: Hirayama Masaharu , Nagase Fumiaki , Tavani Marco , Kaspi Victoria M. , Kawai Nobuyuki , Arons Jonathan
Published: March 2014

We report on the results of a post-periastron ASCA observation of the PSR B1259–63 system, containing a 48 ms pulsar orbiting a Be star in an eccentric 3.4 yr orbit. The ASCA observation was carried out on 1994 February 28 when the radio pulsar was again visible after a prolonged 40-day radio eclipse near to periastron. The source was clearly detected with an X-ray luminosity (1–10 keV) LX of (1.03 ± 0.09) × 1034 (d/2 kpc)2 erg s−1, where d is the pulsar's distance. The X-ray spectrum is well-represented by a single power-law model of the photon index, α = 1.61 ± 0.06, and a small photoelectric absorption, NH = (5.6 ± 0.6) × 1021 cm−2. No significant X-ray pulsations were detected, and the upper limit for the pulsed component was estimated to be 15% of the total X-ray flux, assuming sinusoidal modulation. The characteristics of the X-ray emission detected on 1994 February 28 are similar to those detected by ASCA near periastron when the pulsed radio emission from PSR B1259-63 was eclipsed. Our results strongly favor a non-thermal model of X-ray emission driven by synchrotron radiation from relativistic shocked particles in the pulsar wind interacting with the outflow from the Be star companion.
Accretion-Disk Corona Advected by External Radiation Drag II. Relativistic Case
Authors: Watanabe Yoichi , Fukue Jun
Published: March 2014

We examined the accretion-disk corona (β-corona) for a relativistic case under the pseudo-Newtonian approximation. The β-corona is dynamically driven via radiation drag exerted by a central luminous source and an α accretion disk, itself. The corona is assumed to be geometrically thin and optically thin. When the central source is sufficiently luminous, the specific angular momentum of the corona gas is lost by radiation drag of the radiation field produced by the central source. As a result, the rotational velocity of the corona gas becomes smaller than the Keplerian one, and the corona gas is advected inward on a dynamical timescale — a dynamical disk corona. When the accretion disk is luminous, on the other hand, the corona gas tends to corotate with the underlying disk by radiation drag of the radiation field produced by the α -disk. As a result, the advection of the corona gas is suppressed. Emission-line profiles expected from such an advected disk corona were also calculated, particularly bearing in mind the recently observed X-ray line of MCG–6–30–15. The line profiles are generally double peaked where the blue peaks are stronger than the red peaks because of relativistic effects. The separation of the two peaks depends on the brightness of the central source as well as the size of the emitting regions. The best-fit parameters for MCG–6–30–15 are the followings: the central luminosity normalized by the Eddington luminosity 0.6, the normalized disk luminosity also 0.6, the central radius of the emitting region 5 Schwarzschild radii, the width of the emitting region also 5 Schwarzschild radii, and the inclination angle 30°.
A New Method to Estimate Cosmological Parameters Using the Baryon Fraction of Clusters of Galaxies
Authors: Sasaki Shin
Published: March 2014

We propose a new method to estimate cosmological parameters using the baryon fraction of clusters of galaxies for a range of redshifts. The basic assumption is that the baryon fraction of clusters is constant, which is a reasonable assumption when it is averaged within a Mpc scale. We find that the baryon fraction vs. redshift diagram can estimate the cosmological parameters, since the derived value of the baryon fraction from observations depends on the adopted value of the cosmological parameters. We also discuss some points in comparing theoretical calculations with observations.
CII Diffuse Emission Observed by IRTS
Authors: Shibai Hiroshi , Okuda Haruyuki , Nakagawa Takao , Makiuti Sin'itirou , Matsuhara Hideo , Hiromoto Norihisa , Okumura Ken'ichi
Published: March 2014

The CII 158 μm line emission and the far-infrared continuum emission at 155 μm were observed by the Far-Infrared Line Mapper (FILM) aboard the Infrared Telescope in Space (IRTS) with its high sensitivity and resolution. The observation was made along a great circle crossing the galactic plane at l = 50° and 230°. Two components were found in their intensity distributions. The first component concentrates on the galactic plane. It is prominent on the plane at l = 50°, but is very faint at 230°. The second component extends over at least 20° in galactic latitude, and has nearly the same intensity at both crossing parts of the galactic plane. Therefore, the first one can be ascribed to emission from the galactic disk, and the second component to emission from the local interstellar gas. The intensity distribution of the [CII] line of the second component is similar to that of the HI 21 cm integrated intensity. This fact suggests that the local [CII] emission component arises in the HI 21 cm line emitting gas. From the ratio of the CII line luminosity to the hydrogen column density, the interstellar cooling rate of the HI gas is (5.6 ± 2.6) × 10−27 erg s−1/H-atom, corresponding to the cold neutral gas whose pressure is a few hundred cm−3 K.
Nuclear-to-Outer Rotation Curves of Galaxies in the CO and HI Lines
Authors: Sofue Yoshiaki
Published: March 2014

We have derived rotation curves of nearby galaxies, which are almost completely sampled from the inner to outer regions. We used high-resolution position–velocity diagrams in the CO line along the major axes for the inner regions, and HI-line data for the outer regions. We combined the CO and HI data to obtain total rotation curves from the nuclear to outer regions. The rotation curves show a steep nuclear rise within a radius smaller than the resolutions of the CO-line observations, indicating a compact massive concentration near the nucleus. We show that the nuclear steep rise is general and universal, and that a rigid body-like gentle rise is exceptional.
Graph-Theoretical Approach for Quantifying the Large-Scale Structure of the Universe
Authors: Ueda Haruhiko , Itoh Makoto
Published: March 2014

We propose a graph-theoretical approach for quantifying the galaxy distributions in the universe. In order to examine the validity of this approach, we construct graphs based on our cosmological N-body simulations with scale-free power-law spectra, and apply graph theory to them. First we construct a constellation graph from our simulations, which is one of the most basic graphs. We then calculate the distribution function of the edge-length, order, degree, and the eigenvalue of the adjacency matrix of the constellation graph. From our analysis we find that the eigenvalue of the adjacency matrix is a good statistical measure for quantifying the galaxy distributions in a clear manner. For supplementary purposes we also construct a separated minimal spanning tree and a group graph, and examine the usefulness of the graph-theoretical approach.