COS-Weak: Probing the CGM using analogs of weak Mg II absorbers at z < 0.3

We present a sample of 34 weak metal line absorbers at $z< 0.3$ complied via the simultaneous detections ($3\sigma$) of the SiII$\lambda1260$ and CII$\lambda1334$ absorption lines, with $W_{r}$(SiII)$<0.2$ \AA\ and $W_{r}$(CII)$<0.3$ \AA, in archival HST/COS spectra. Our sample increases the number of known low-$z$ "weak absorbers" by a factor of $>5$. The column densities of HI and low-ionization metal lines obtained from Voigt profile fitting are used to build simple photoionization models using CLOUDY. The inferred densities and total hydrogen column densities are in the ranges of $-3.3 < \log n_{\rm H}/{\rm cm^{-3}} < -2.4$ and $16.0 < \log N_{\rm H}/{\rm cm^{-2}}<20.3$, respectively. The line of sight thicknesses of the absorbers have a wide range of $\sim$1 pc$-$50 kpc with a median value of $\sim$500 pc. The high-ionization OVI absorption, detected in 12/18 cases, always stems from a different gas-phase. Most importantly, 85% (50%) of these absorbers show a metallicity of $\rm [Si/H] > -1.0$ (0.0). The fraction of systems showing high metallicity (i.e., $\rm [Si/H]>-1.0$) in our sample is significantly higher than the HI-selected sample (Wotta et al. 2016) and the galaxy-selected sample (Prochaska et al. 2017) of absorbers probing the circum-galactic medium (CGM) at similar redshift. A search for galaxies has revealed a significant galaxy-overdensity around these weak absorbers compared to random places with a median impact parameter of 166 kpc to the nearest galaxy. Moreover, we find the presence of multiple galaxies in $\sim80$% of the cases, suggesting group environments. The observed $d\mathcal{N}/dz$ of $0.8\pm0.2$ indicates that such metal-enriched, compact, dense structures are ubiquitous in the halos of low-$z$ galaxies that are in groups. We suggest that these are transient structures that are related to outflows and/or stripping of metal-rich gas from galaxies.Comment: Published (2018MNRAS.476.4965M) after minor revision. Appendix A is newly added

Behind the Technology: CT Perfusion in the Setting of Acute Stroke Management

Computed Tomography Perfusion (CTP) is an imaging modality that generates parametric maps of cerebral hemodynamics which are useful in the assessment of suspected acute ischemic stoke. However, the technology underlying CTP is complex and serious controversy surrounds the safety of CTP tests and the reproducibility and validity of CTP results. This report briefly outlines the history of CTP, its current clinical applications for stroke management, the main controversies surrounding CTP, and future directions for this technology

Nitric oxide production and antioxidant function during viral infection of the coccolithophore Emiliania huxleyi

Emiliania huxleyi is a globally important marine phytoplankton that is routinely infected by viruses. Understanding the controls on the growth and demise of E. huxleyi blooms is essential for predicting the biogeochemical fate of their organic carbon and nutrients. In this study, we show that the production of nitric oxide (NO), a gaseous, membrane-permeable free radical, is a hallmark of early-stage lytic infection in E. huxleyi by Coccolithoviruses, both in culture and in natural populations in the North Atlantic. Enhanced NO production was detected both intra- and extra-cellularly in laboratory cultures, and treatment of cells with an NO scavenger significantly reduced viral production. Pre-treatment of exponentially growing E. huxleyi cultures with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) prior to challenge with hydrogen peroxide (H2O2) led to greater cell survival, suggesting that NO may have a cellular antioxidant function. Indeed, cell lysates generated from cultures treated with SNAP and undergoing infection displayed enhanced ability to detoxify H2O2. Lastly, we show that fluorescent indicators of cellular ROS, NO, and death, in combination with classic DNA- and lipid-based biomarkers of infection, can function as real-time diagnostic tools to identify and contextualize viral infection in natural E. huxleyi blooms

Effective Hub-Spoke Relationships: Lessons from the Jefferson Neuroscience Network Experience

Introduction: The stroke public health crisis is increasingly addressed by regional TeleStroke networks comprised of Hub and Spoke treatment sites. Functional Hub-Spoke (H-S) relationships are fundamental to network success. The purpose was to report on our experience developing and maintaining H-S relationships, and to propose a H-S relationship model. Methods: Jefferson Neuroscience Network (JNN) was launched in July 2010. By June 2011 it had 1 Hub and 28 Spoke sites across 2 states (PA, NJ), and had performed 836 TeleStroke consultations. Key Hub and Spoke personnel were consulted regarding H-S relationships. Feedback was organized. Results: A Hub team was assembled and trained. Three key steps to developing H-S relationships were identified: Secure Spoke physician and administration commitment; Train Spoke team; Address Spoke-specific obstacles. Two key steps to maintaining H-S relationships were identified: Continual education; Institutionalize bi-directional communication. Specific JNN initiatives are described. The proposed H-S relationship model is a patient-centered, physician-driven, voluntary collaboration between treatment sites. Hubs offer Spokes education, and access to clinical expertise, clinical trials, and a higher level of care. As a result, Spokes may increase evidence-based practice, become more comfortable administering tPA, experience stroke center accreditation opportunities, and decrease transfer of inappropriate patients. In turn, Spokes offer Hubs community partnership, meaning they choose to solicit Hub expert opinion regarding patient management. As a result, Hubs may increase their community reputation and research opportunities. Furthermore, appropriate patients may be rapidly identified and treated in the community or, if necessary, transferred to comprehensive stroke centers within time constraints. Conclusions: JNN-identified key steps for developing and maintaining H-S relationships may assist other stroke networks to build and sustain relationships between treatment sites. Different treatment sites can collaborate to improve stroke care while simultaneously achieving their own independent goals. Additional practical advice about designing and implementing functional and sustainable TeleStroke programs is needed