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Endothelialization of arterial vascular grafts by circulating monocytes
Recently our group demonstrated that acellular tissue engineered vessels (A-TEVs) comprised of small intestinal submucosa (SIS) immobilized with heparin and vascular endothelial growth factor (VEGF) could be implanted into the arterial system of a pre-clinical ovine animal model, where they endothelialized within one month and remained patent. Here we report that immobilized VEGF captures blood circulating monocytes (MC) with high specificity under a range of shear stresses. Adherent MC differentiate into a mixed endothelial (EC) and macrophage (Mφ) phenotype and further develop into mature EC that align in the direction of flow and produce nitric oxide under high shear stress. In-vivo, newly recruited cells on the vascular lumen express MC markers and at later times they co-express MC and EC-specific proteins and maintain graft patency. This novel finding indicates that the highly prevalent circulating MC contribute directly to the endothelialization of acellular vascular grafts under the right chemical and biomechanical cues.
Acellular tissue engineered vessels functionalised with VEGF are coated with a layer of endothelial cells after in vivo implantation, but the source of the cells are unknown. Here the authors provide evidence that monocytes expressing VEGF receptors can transdifferentiate into endothelial cells via a macrophage intermediate.
Journal Article
Flux Contribution and Geometry of Charge Exchange Emission in the Starburst Galaxy M82
Recent X-ray studies of starburst galaxies have found that charge exchange (CX) commonly occurs between outflowing hot plasma and cold gas, possibly from swept-up clouds. However, the total CX flux and the regions where CX occurs have been poorly understood. We present an analysis of XMM-Newton observations of M82, a prototype starburst galaxy, aiming to investigate these key properties of CX emission. We have used a blind source separation method in an image analysis of CCD data, which identified a component with the enhanced O–K lines expected from the CX process. Analyzing the XMM-Newton/RGS spectra from the regions identified by the image analysis, we have detected a high forbidden-to-resonance ratio of the O vii Heα triplet as well as several emission lines from K-shell transitions of C, N, and O that are enhanced by the CX process. CX is less responsible for the emission lines of Ne and Mg, and accurate estimation of the CX contribution is confirmed to be crucial in measuring chemical abundances. The temperature of the plasma acting as an electron receiver in the CX process is significantly lower compared to that of the plasma components responsible for most of the X-rays. From the low temperature and an estimation of the CX-emitting volume, we find that the CX primarily occurs in a limited region at interfaces between plasma and gas whose temperatures rapidly decrease due to thermal conduction.
Journal Article
The Lure of Academic and Social Reputations Versus Athletic Success
Colleges and universities face pressure to maintain enrollments in a time of demographic shifts in the college-going population and reductions in state funding. One indicator of successfully maintaining enrollments is the percentage of accepted students who matriculate —the enrollment yield. Factors known to contribute to yield include school size, cost, research, and reputation. Of interest in the present study is the import of academic reputation as measured by U. S. News and World Report rankings and social reputation as measured by designation as a ‘party school’ relative to accomplishments of the school’s high-profile athletic teams. I use a 21 year panel to model yield for all institutions competing at the highest level of intercollegiate athletics. The results show that yield rates consistently respond to USNWR rankings, but being named a party school has a more sporadic influence. Athletic success has little effect on a school’s enrollment yield. The findings suggest that the signals sent by academic rankings are stronger and better received than the signals sent by social or sports accomplishments.
Journal Article
Unveiling the Cosmic Chemistry. II. “Direct” Te-based Metallicity of Galaxies at 3 < z < 10 with JWST/NIRSpec
We report the detection of the [O iii] auroral line in 42 galaxies within the redshift range of 3 < z < 10. These galaxies were selected from publicly available JWST data releases, including the JADES and PRIMAL surveys, and observed using both the low-resolution PRISM/CLEAR configuration and medium-resolution gratings. The measured electron temperatures in the high-ionization regions of these galaxies range from Te([O iii]) = 12,000 to 24,000 K, consistent with temperatures observed in local metal-poor galaxies and previous JWST studies. In 10 galaxies, we also detect the [O ii] auroral line, allowing us to determine electron temperatures in the low-ionization regions, which range between Te([O ii]) = 10,830 and 20,000 K. The direct Te-based metallicities of our sample span from 12 + log(O/H) = 7.2 to 8.4, indicating these high-redshift galaxies are relatively metal-poor. By combining our sample with 25 galaxies from the literature, we expand the data set to a total of 67 galaxies within 3 < z < 10, effectively more than doubling the previous sample size for direct Te-based metallicity studies. This larger data set allows us to derive empirical metallicity calibration relations based exclusively on high-redshift galaxies, using six key line ratios: R3, R2, R23, Ne3O2, O32, and O3N2. Notably, we derive a novel metallicity calibration relation for the first time using high-redshift Te-based metallicities: Rˆ = 0.18log R2 + 0.98log R3. This new calibration significantly reduces the scatter in high-redshift galaxies compared to the Rˆ relation previously calibrated for low-redshift galaxies.
Journal Article
Ionized outflows from active galactic nuclei as the essential elements of feedback
Outflows from active galactic nuclei (AGNs) are one of the fundamental mechanisms by which the central supermassive black hole interacts with its host galaxy. Detected in ≥50% of nearby AGNs, these outflows have been found to carry kinetic energy that is a large fraction of the AGN power, and thereby give ‘negative’ feedback to their host galaxies. To understand the physical processes that regulate them, it is important to have a robust estimate of their physical and dynamical parameters. In this Review Article, we summarize our current understanding of the physics of the ionized outflows detected via absorption in the ultraviolet and X-ray wavelength bands. We discuss the most relevant observations and our current knowledge and uncertainties in the measurements of the outflow parameters, as well as their origin and acceleration mechanisms. The commissioning and concept studies of large telescope missions with high-resolution spectrographs in ultraviolet/optical and X-rays along with rapid advancements in simulations offer great promise for discoveries in this field over the next decade.
This Review Article summarizes our current understanding of ionized outflows in active galactic nuclei, observed in absorption in the ultraviolet and X-ray wavelengths, including the most relevant observations as well as their origin and acceleration mechanisms.
Journal Article
New Resonance Scattering Model in AtomDB: Application to Line Suppression in Galaxy Clusters and Elliptical Galaxies
In this paper, we present the simple, one-step, self-consistent, and fast resonance scattering model rsapec based on the AtomDB database. This model can be used as an alternative to the commonly used APEC model for fitting X-ray spectra with optically thick lines. The current model is intended, in general, for verifying the presence of the effect and for spectral modeling of galaxy clusters and elliptical galaxies under applicable assumptions. We test rsapec to derive the line suppression in the elliptical galaxy NGC 4636 and the Perseus cluster of galaxies and obtain resonance suppressions of ∼1.24 and ∼1.30, respectively.
Journal Article
XRISM Reveals Complex Ionization and Velocity Structures in the GX 340+0 X-Ray Binary
We present the first high-resolution XRISM spectrum of the neutron star low-mass X-ray binary GX 340+0, revealing unprecedented detail in its emission and absorption features. The spectrum reveals a rich and complex Fe xxv Heα line profile and a P Cygni profile from Ca xx. We use the state-of-the-art spectral synthesis code Cloudy to model the emission and absorption features in detail. Our analysis reveals multi-ionization and multivelocity structures, where the combination of broad (∼800 km s−1) and narrow (∼360 km s−1) line components, along with rest-frame and blueshifted emission and absorption lines, accounts for the observed line profile complexity. We identify a modest ∼2735 km s−1 accretion disk wind exhibiting both absorption and emission features. We also detect a relativistic reflection feature in the spectrum, which we model using relxillNS, specifically designed to characterize X-ray reprocessing in accretion disks around neutron stars. Furthermore, we examine the detailed physics of the Fe xxv Heα complex, focusing on the forbidden-to-resonance line ratio under the influence of continuum pumping and optical depth effects.
Journal Article
X-Ray Performance of Critical-angle Transmission Grating Prototypes for the Arcus Mission
Arcus is a proposed Explorer Class soft X-ray grating spectrometer. It aims to explore cosmic feedback by mapping hot gases within and between galaxies and galaxy clusters and characterizing jets and winds from supermassive black holes and to investigate the dynamics of protoplanetary disks and stellar accretion. Arcus features 12 m focal-length grazing-incidence silicon pore optics (SPO) developed for the Athena mission. Critical-angle transmission (CAT) gratings efficiently disperse high diffraction orders onto CCDs. We report new and improved X-ray performance results for Arcus-like CAT gratings, including a record resolving power for two coaligned CAT gratings. Multiple Arcus prototype grating facets were illuminated by an SPO at the PANTER facility. The facets consist of 32 × 32.5 mm2 patterned silicon membranes, bonded to metal frames. The bonding angle is adjusted according to the measured average tilt angle of the grating bars in the membrane. Two simultaneously illuminated facets show a minor broadening of the Al-K α doublet in the 18th and 21st orders with the best-fit record effective resolving power of RG≈1.3−0.5+∞×104 (3σ), about three to four times the Arcus requirement. We measured the diffraction efficiency of quasi-fully illuminated gratings at O-K wavelengths in orders 4–7 in an Arcus-like configuration and compare results with synchrotron spot measurements. After corrections for geometrical effects and bremsstrahlung continuum, we find agreement between full and spot illumination at the two different facilities, as well as with the models used for Arcus effective area predictions. We find that these flight-like gratings meet the diffraction efficiency and greatly exceed the resolving power Arcus requires.
Journal Article
Shortwave infrared imaging increases the number of lymph nodes and improves cancer staging: a 104-patient study
AimsAdequate lymph node examination is key to accurate cancer staging. This study investigates the effectiveness of shortwave infrared imaging in increasing the overall and positive lymph node numbers.MethodsSpecimens from various anatomic sites, including colorectal, pancreatic, breast, gastric, skin and small bowel resections, were evaluated. 104 specimens were first grossed with manual palpation and then grossed with the assistance of shortwave infrared imaging. The overall and positive lymph node numbers were documented.ResultsIn 90 of the 104 cases (86.5%), shortwave infrared imaging helped identify additional lymph nodes. On average, 4.81 additional lymph nodes were found. In 11 of the 104 cases (10.6%), additional positive lymph nodes were found. In 4 of the 104 cases (3.8%), cancer stages were changed.ConclusionsShortwave infrared imaging may increase the number of lymph nodes identified and has the potential to improve cancer staging accuracy. Further validation in larger, randomised or prospective studies is warranted.
Journal Article