Hot Spine Loops and the Nature of a Late-Phase Solar Flare

The fan-spine magnetic topology is believed to be responsible for many curious features in solar explosive events. A spine field line links distinct flux domains, but direct observation of such feature has been rare. Here we report a unique event observed by the Solar Dynamic Observatory where a set of hot coronal loops (over 10 MK) connected to a quasi-circular chromospheric ribbon at one end and a remote brightening at the other. Magnetic field extrapolation suggests these loops are partly tracer of the evolving spine field line. Continuous slipping- and null-point-type reconnections were likely at work, energizing the loop plasma and transferring magnetic flux within and across the fan quasi-separatrix layer. We argue that the initial reconnection is of the "breakout" type, which then transitioned to a more violent flare reconnection with an eruption from the fan dome. Significant magnetic field changes are expected and indeed ensued. This event also features an extreme-ultraviolet (EUV) late phase, i.e. a delayed secondary emission peak in warm EUV lines (about 2-7 MK). We show that this peak comes from the cooling of large post-reconnection loops beside and above the compact fan, a direct product of eruption in such topological settings. The long cooling time of the large arcades contributes to the long delay; additional heating may also be required. Our result demonstrates the critical nature of cross-scale magnetic coupling - topological change in a sub-system may lead to explosions on a much larger scale.Comment: Accepted for publication in ApJ. Animations linked from pd

Data-constrained MHD simulation for the eruption of a filament-sigmoid system in solar active region 11520

The separation of a filament and sigmoid is observed during an X1.4 flare on July 12, 2012 in solar active region 11520, but the corresponding magnetic field change is not clear. We construct a data-constrained magnetohydrodynamic simulation of the filament-sigmoid system with the flux rope insertion method and magnetic flux eruption code, which produces the magnetic field evolution that may explain the separation of the low-lying filament and high-lying hot channel (sigmoid). The initial state of the magnetic model contains a magnetic flux rope with a hyperbolic flux tube, a null point structure and overlying confining magnetic fields. We find that the magnetic reconnections at the null point make the right footpoint of the sigmoid move from one positive magnetic polarity (P1) to another (P3). The tether-cutting reconnection at the hyperbolic flux tube occurs and quickly cuts off the connection of the low-lying filament and high-lying sigmoid. In the end, the high-lying sigmoid erupts and grows into a coronal mass ejection, while the low-lying filament stays stable. The observed double J-shaped flare ribbons, semi-circular ribbon, and brightenings of several loops are reproduced in the simulation, where the eruption of the magnetic flux rope includes the impulsive acceleration and propagation phases.Comment: This paper has been accepted for publication in the Ap

Diagnostic Utility of Ocular Symptoms and Vision for Cytomegalovirus Retinitis

Purpose: CMV retinitis remains a leading cause of blindness in countries with a high burden of AIDS. Although dilated fundus examinations are recommended for those with CD4 counts below 100 cells/µL, in practice only those with poor vision and/or symptoms are routinely referred for screening. Therefore, the predictive value of this common practice should be assessed. Methods: This is a prospective cross-sectional study. Patients with known HIV and a CD4 count of less than 100 cells/µL attending an HIV clinic in Chiang Mai, Thailand completed a standardized questionnaire about visual symptoms and underwent visual acuity testing and dilated fundus examination. Participants without CMV retinitis were invited for repeated examinations every 3 months until their CD4 count exceeded 100 cells/µL. Patient-level statistical analyses were conducted to calculate diagnostic test characteristics, with bootstrapping to account for correlated data. Results: HIV patients with CMV retinitis were more likely to complain of visual symptoms (p = 0.01) compared to those without CMV retinitis, including scotoma (p = 0.0002), itchy or watery eyes (p < 0.0001), and eye pain (p = 0.003); they were also more likely to have visual acuity worse than CF (p = 0.0003). However, the absence of eye symptoms and the absence of poor vision did not strongly affect the probability that a patient did not have disease (negative likelihood ratio 0.56 and 0.76, respectively). Conclusions: Ocular symptoms and poor visual acuity were poor diagnostic indicators for the presence of CMV retinitis. Systemic screening for HIV patients with CD4 count below 100 cells/µl should be carried out to catch the disease at its early stage to avoid blindnes

Barriers to HPV immunization among blacks and latinos: a qualitative analysis of caregivers, adolescents, and providers

Background: Despite recommendations that 11–12-year-olds receive the full three-shot Human papillomavirus (HPV) vaccine series, national HPV immunization coverage rates remain low. Disparities exist, with Blacks and Latinos being less likely than Whites to complete the series. We aimed to identify and compare barriers to HPV immunization perceived by healthcare providers, Black and Latino adolescents, and their caregivers to inform a clinic-based intervention to improve immunization rates. Methods: We conducted semi-structured interviews between March and July 2014 with Black and Latino adolescents (n = 24), their caregivers (n = 24), and nurses (n = 18), and 2 focus groups with 18 physicians recruited from two pediatric primary care clinics. Qualitative protocol topics included: general perceptions and attitudes towards vaccines; HPV knowledge; and perceived individual and systems-level barriers affecting vaccine initiation and completion. Results: Themes were identified and organized by individual and systems-level barriers to HPV immunization. Adolescents and their caregivers, particularly Blacks, expressed concerns about HPV being an untested, “newer” vaccine. All families felt they needed more information on HPV and found it difficult to return for multiple visits to complete the vaccine series. Providers focused on challenges related to administering multiple vaccines simultaneously, and perceptions of parental reluctance to discuss sexually transmitted infections. Conclusions: Optimizing HPV immunization rates may benefit from a multi-pronged approach to holistically address provider, structural, and individual barriers to care. Further research should examine strategies for providing multiple modalities of support for providers, including a routinized system of vaccine promotion and delivery, and for addressing families’ concerns about vaccine safety and efficacy

Solar Ring Mission: Building a Panorama of the Sun and Inner-heliosphere

Solar Ring (SOR) is a proposed space science mission to monitor and study the Sun and inner heliosphere from a full 360{\deg} perspective in the ecliptic plane. It will deploy three 120{\deg}-separated spacecraft on the 1-AU orbit. The first spacecraft, S1, locates 30{\deg} upstream of the Earth, the second, S2, 90{\deg} downstream, and the third, S3, completes the configuration. This design with necessary science instruments, e.g., the Doppler-velocity and vector magnetic field imager, wide-angle coronagraph, and in-situ instruments, will allow us to establish many unprecedented capabilities: (1) provide simultaneous Doppler-velocity observations of the whole solar surface to understand the deep interior, (2) provide vector magnetograms of the whole photosphere - the inner boundary of the solar atmosphere and heliosphere, (3) provide the information of the whole lifetime evolution of solar featured structures, and (4) provide the whole view of solar transients and space weather in the inner heliosphere. With these capabilities, Solar Ring mission aims to address outstanding questions about the origin of solar cycle, the origin of solar eruptions and the origin of extreme space weather events. The successful accomplishment of the mission will construct a panorama of the Sun and inner-heliosphere, and therefore advance our understanding of the star and the space environment that holds our life.Comment: 41 pages, 6 figures, 1 table, to be published in Advances in Space Researc

Propentofylline Targets TROY, a Novel Microglial Signaling Pathway

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain cancer, with a median survival of less than 2 years after diagnosis with current available therapies. The tumor microenvironment serves a critical role in tumor invasion and progression, with microglia as a critical player. Our laboratory has previously demonstrated that propentofylline, an atypical methylxanthine with central nervous system glial modulating and anti-inflammatory actions, significantly decreases tumor growth in a GBM rodent model by preferentially targeting microglia. In the present study, we used the CNS-1 rat glioma model to elucidate the mechanisms of propentofylline. Here we demonstrate that propentofylline targets TROY, a novel signaling molecule up-regulated in infiltrating microglia, and not macrophages, in response to CNS-1 cells. We identify Pyk2, Rac1 and pJNK as the downstream signaling molecules of TROY through western blot analysis and siRNA transfection. We demonstrate that inhibition of TROY expression in microglia by siRNA transfection significantly inhibits microglial migration towards CNS-1 cells similar to 10 µM propentofylline treatment. These results identify TROY as a novel molecule expressed in microglia, involved in their migration and targeted by propentofylline. Furthermore, these results describe a signaling molecule that is differentially expressed between microglia and macrophages in the tumor microenvironment

Old and New Methods of Glaucoma Diagnosis Using Spectral-Domain Optical Coherence Tomography: Testing Limitations of Older Retinal Nerve Fiber Layer Thickness Measurements and Diagnostic Potential of Newer Retinal Volume Measurements

Purpose: Optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurements are a reproducible and quantitative diagnostic modality widely used for glaucoma evaluations, but a high rate of testing artifacts limits its clinical utility. In Part I of this thesis, we aimed to characterize artifact types and assess artifact rates in two-dimensional (2D) RNFL thickness measurements obtained by the Spectralis OCT machine (Heidelberg Engineering, Heidelberg, Germany), as well as to determine patient factors and eye conditions associated with a higher artifact prevalence. In Part II of this thesis, we aimed to compare a new parameter, peripapillary retinal volume (RV), with the traditional 2D RNFL thickness parameter for diagnostic capability and artifact rates. Methods: Part I: The prevalence of 12 artifact types were described in this retrospective, cross sectional review of 2313 eye scans from 1188 patients who underwent a complete eye examination with Spectralis OCT scanning during the period of September 2009 to July 2013. Generalized estimating equations model was used to analyze associations between increased artifact prevalence and 10 patient characteristics, including age, sex, race, visual acuity, refractive error, astigmatism, cataract status, glaucoma staging, visual field reliability, and glaucoma diagnosis. Part II: This is a retrospective, cross-sectional review. A total of 180 subjects [113 open angle glaucoma (OAG) and 67 normal participants] had spectral domain optical coherence tomography (OCT) volume scans and RNFL thickness measurements (Spectralis, Heidelberg Engineering, Heidelberg, Germany). Peripapillary RV values were calculated using a custom-designed program with 4 different sized circumpapillary annuli (CA): CA1 had circle diameters of 2.5 and 3.5 mm; CA2, 3 and 4 mm; CA3, 3.5 and 4.5 mm; and CA4, 4 and 5 mm. Area under the receiver operating characteristic (AUROC) curves, sensitivity, and specificity were calculated for global, quadrant, and octant regions for RV (CA1 – CA4) and RNFL thickness. Pair-wise comparisons were conducted between RV and RNFL measurements. Artifacts rates were determined. Results: Part I: A total of 1070 or 46.3% of the 2313 2D eye scans had at least one artifact. De-centration error was the most common artifact (27.8%), followed by posterior vitreous detachment artifacts (14.4%). Visual acuity of less than 20/40 (p<0.0001), presence of moderate to severe cataracts (p<0.0001), advanced stage of glaucoma (p<0.0001), and a diagnosis of open angle glaucoma (p=0.0003) were associated with increased prevalence of artifacts. Part II: Of the 180 study subjects who had 3D eye scans, mean age was 62.6 ± 15.4 years and 41.7% were male. Among RV measurements, best diagnostic performances were for the smallest two annuli for inferior RV (CA1 0.964, CA2 0.955). Of the 4 annuli, the smallest CA1 had the highest diagnostic performance. Of specific regions, the inferior RV quadrant had the highest performance across CA1 to CA4. Peripapillary RV had similar diagnostic capability compared to RNFL thickness (p > 0.05). The artifact rate per B-scan for RV was 6.0%, and for 2D RNFL thickness scans was 32.2%. Conclusions: Clinicians should first assess scans for artifacts and pay attention to patient characteristics associated with a higher prevalence of artifacts before making therapeutic decisions based on RNFL thickness measurements. Meanwhile, the diagnostic capability of RV could be equal to that of RNFL thickness for diagnosing perimetric OAG, with fewer artifacts. RV may be a useful novel parameter in the evaluation of perimetric glaucoma