Interacting binaries in which a white dwarf accretes material from a companion-cataclysmic variables (CVs) in which the mass donor is a Roche-lobe filling star on or near the main sequence, and ...symbiotic stars in which the mass donor is a late type giant-are relatively commonplace. They display a wide range of behaviors in the optical, X-rays, and other wavelengths, which still often baffle observers and theorists alike. Here I review the existing body of research on X-ray emissions from these objects for the benefits of both experts and newcomers to the field. I provide introductions to the past and current X-ray observatories, the types of known X-ray emissions from these objects, and the data analysis techniques relevant to this field. I then summarize of our knowledge regarding the X-ray emissions from magnetic CVs, non-magnetic CVs and symbiotic stars, and novae in eruption. I also discuss space density and the X-ray luminosity functions of these binaries and their contribution to the integrated X-ray emission from the Galaxy. I then discuss open questions and future prospects.
Mast cells (MCs) are cells of hematopoietic origin that normally reside in mucosal tissues, often near epithelial cells, glands, smooth muscle cells, and nerves. Best known for their contributions to ...pathology during IgE-associated disorders such as food allergy, asthma, and anaphylaxis, MCs are also thought to mediate IgE-associated effector functions during certain parasite infections. However, various MC populations also can be activated to express functional programs--such as secreting preformed and/or newly synthesized biologically active products--in response to encounters with products derived from diverse pathogens, other host cells (including leukocytes and structural cells), damaged tissue, or the activation of the complement or coagulation systems, as well as by signals derived from the external environment (including animal toxins, plant products, and physical agents). In this review, we will discuss evidence suggesting that MCs can perform diverse effector and immunoregulatory roles that contribute to homeostasis or pathology in mucosal tissues.
The physical mechanism driving mass ejection during a nova eruption is still poorly understood. Possibilities include ejection in a single ballistic event, a common-envelope interaction, a continuous ...wind, or some combination of these processes. Here, we present a study of 12 Galactic novae, for which we have premaximum high-resolution spectroscopy. All 12 novae show the same spectral evolution. Before optical peak, they show a slow P Cygni component. After peak, a fast component quickly arises, while the slow absorption remains superimposed on top of it, implying the presence of at least two physically distinct flows. For novae with high-cadence monitoring, a third, intermediate-velocity component is also observed. These observations are consistent with a scenario where the slow component is associated with the initial ejection of the accreted material and the fast component with a radiation-driven wind from the white dwarf. When these flows interact, the slow flow is swept up by the fast flow, producing the intermediate component. These colliding flows may produce theγ-ray emission observed in some novae. Our spectra also show that the transient heavy-element absorption lines seen in some novae have the same velocity structure and evolution as the other lines in the spectrum, implying an association with the nova ejecta rather than a preexisting circumbinary reservoir of gas or material ablated from the secondary. While this basic scenario appears to qualitatively reproduce multiwavelength observations of classical novae, substantial theoretical and observational work is still needed to untangle the rich diversity of nova properties.
The X-rays in intermediate polars (IPs) originate in a compact region near the surface of a magnetic white dwarf (WD) and interact with the complex environment surrounding the emission region. Here ...we report a case study of two IPs, TV Col and V2731 Oph, with selected archival X-ray observations (NuSTAR, Swift, Suzaku, and XMM-Newton). For TV Col, we were successful in simultaneously accounting for the primary X-rays, the secondary X-rays due to Compton scattering and fluorescence, and the effects of local absorbers. In this case, we were able to demonstrate that the shock height is small, based on the high reflection amplitude; hence, the maximum temperature of the post-shock region can be used to derive the WD mass of 0.735 0.015 M . Despite the high specific accretion rate required to explain the small shock height, we do not detect any spin modulation in our NuSTAR data, consistent with the modest amount of complex absorption seen spectroscopically. We argue that our results are robust because they are based on the joint temporal-spectral analysis of broadband X-ray data. The spectrum of V2731 Oph is more highly absorbed. Through our analysis of the Suzaku data, we present a spectral model with nitrogen overabundance without the previously claimed soft blackbody that should be further explored. We have been unable to constrain the reflection amplitude for V2731 Oph; this and the detection of spin modulation above 10 keV suggest that it may have a tall shock. Hence, we only derive a lower limit to the mass of its WD (>0.9 M ).
Abstract
We propose a polarization-controlled ultrasmall single-photon emitter that combines a single photon source and an elliptical split ring (SR) type metamaterial element. Simulations using the ...finite difference time domain method showed that in elliptical metamaterial elements, the annular mode is suppressed and axial electric field oscillations occur preferentially, resulting in upward light emission from the photon source with controlled polarization. We fabricated prototype devices by focused ion beam lithography and PbS quantum dots. Evaluation of the optical properties of the devices revealed that the emission spectrum width was narrower and the emission lifetime was shorter than those of quantum dot ensemble, and that the polarization was controlled along the minor axis of ellipse. These suggested that the quantum dot emission and the metamaterial element resonated as expected. The combination of a single quantum dot and a single elliptical SR-type metamaterial element was shown to have the potential to operate as a polarization-controlled single-photon emitter.
A new type of self-sustained divertor oscillation is discovered in the Large Helical Device stellarator, where the peripheral plasma is detached from material diverters by means of externally applied ...perturbation fields. The divertor oscillation is found to be a self-regulation of an isolated magnetic field structure (the magnetic island) width induced by a drastic change in a poloidal inhomogeneity of the plasma radiation across the detachment-attachment transitions. A predator-prey model between the magnetic island width and a self-generated local plasma current (the bootstrap current) is introduced to describe the divertor oscillation, which successfully reproduces the experimental observations.
Key points
Following fish oil supplementation, omega‐3 fatty acids are incorporated into cellular membranes, which may affect lipid–protein interactions and therefore the function of embedded ...proteins.
As the components of the electron transport chain required for oxidative phosphorylation are contained in the mitochondrial membrane, omega‐3 supplementation may alter metabolic function.
We supplemented male participants for 12 weeks with fish oil eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) and analysed mitochondrial function and reactive oxygen species (ROS) emissions in permeabilized muscle fibres from the vastus lateralis muscle.
Supplementation incorporated EPA and DHA into mitochondrial membranes, but did not result in changes in maximal mitochondrial respiratory function or pyruvate respiration kinetics.
However, the apparent Km for ADP was decreased following supplementation, and was independent of creatine, changes in the protein content of ADP synthase or ANT transporters.
The propensity for ROS emissions increased with omega‐3 supplementation, although there were no changes in markers of lipid or protein oxidative damage.
These results demonstrate that omega‐3 supplementation improves mitochondrial ADP kinetics, suggesting post‐translational modification of existing proteins.
Studies have shown increased incorporation of omega‐3 fatty acids into whole skeletal muscle following supplementation, although little has been done to investigate the potential impact on the fatty acid composition of mitochondrial membranes and the functional consequences on mitochondrial bioenergetics. Therefore, we supplemented young healthy male subjects (n = 18) with fish oils 2 g eicosapentaenoic acid (EPA) and 1 g docosahexanoic acid (DHA) per day for 12 weeks and skeletal muscle biopsies were taken prior to (Pre) and following (Post) supplementation for the analysis of mitochondrial membrane phospholipid composition and various assessments of mitochondrial bioenergetics. Total EPA and DHA content in mitochondrial membranes increased (P < 0.05) ∼450 and ∼320%, respectively, and displaced some omega‐6 species in several phospholipid populations. Mitochondrial respiration, determined in permeabilized muscle fibres, demonstrated no change in maximal substrate‐supported respiration, or in the sensitivity (apparent Km) and maximal capacity for pyruvate‐supported respiration. In contrast, mitochondrial responses during ADP titrations demonstrated an enhanced ADP sensitivity (decreased apparent Km) that was independent of the creatine kinase shuttle. As the content of ANT1, ANT2, and subunits of the electron transport chain were unaltered by supplementation, these data suggest that prolonged omega‐3 intake improves ADP kinetics in human skeletal muscle mitochondria through alterations in membrane structure and/or post‐translational modification of ATP synthase and ANT isoforms. Omega‐3 supplementation also increased the capacity for mitochondrial reactive oxygen species emission without altering the content of oxidative products, suggesting the absence of oxidative damage. The current data strongly emphasize a role for omega‐3s in reorganizing the composition of mitochondrial membranes while promoting improvements in ADP sensitivity.
Abstract
WD 1145+017 was observed from 2016 November through 2017 June for the purpose of further characterizing the transit behaviour of the dusty debris clouds orbiting this white dwarf. The ...optical observations were carried out with a small ground-based telescope run by an amateur astronomer, and covered 53 different nights over the 8-month interval. We have found that the optical activity has increased to the highest level observed since its discovery with Kepler K2, with approximately 17 per cent of the optical flux extinguished per orbit. The source exhibits some transits with depths of up to 55 per cent and durations as long as 2 h. The dominant period of the orbiting dust clouds during 2016–2017 is 4.49126 h. We present ‘waterfall’ images for the entire 2016–2017 and 2015–2016 observing seasons. In addition, the white dwarf was observed with the Chandra X-ray Observatory for 10-ks on each of four different occasions, separated by about a month each. The upper limit on the average X-ray flux from WD 1145+017 is ≃ 5 × 10−15 erg cm−2 s−1 (unabsorbed over the range 0.1–100 keV), which translates to an upper limit on the X-ray luminosity, Lx, of ≃ 2 × 1028 erg s−1. If $L_{\rm x} \simeq G M_{\rm wd} \dot{M}_{\rm acc}/R_{\rm wd}$, where Mwd and Rwd are the mass and radius of the white dwarf, and $\dot{M}_{\rm acc}$ is the accretion rate, then $\dot{M}_{\rm acc} \lesssim 2 \times 10^{11}$ g s−1. This is just consistent with the value of $\dot{M}$ that is inferred from the level of dust activity.
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