The Cause of Photospheric and Helioseismic Responses to Solar Flares: High-Energy Electrons or Protons?

Analysis of the hydrodynamic and helioseismic effects in the photosphere during the solar flare of July 23, 2002, observed by Michelson Doppler Imager (MDI) on SOHO, and high-energy images from RHESSI shows that these effects are closely associated with sources of the hard X-ray emission, and that there are no such effects in the centroid region of the flare gamma-ray emission. These results demonstrate that contrary to expectations the hydrodynamic and helioseismic responses (''sunquakes") are more likely to be caused by accelerated electrons than by high-energy protons. A series of multiple impulses of high-energy electrons forms a hydrodynamic source moving in the photosphere with a supersonic speed. The moving source plays a critical role in the formation of the anisotropic wave front of sunquakes.Comment: 13 pages, 5 figures, ApJL in pres

News By Association: Designing a Way Out of the Echo Chamber

This thesis is an investigation of the echo chamber phenomenon in news consumption on social networking sites. It incorporates elements of actor-network theory, Bruno Latour’s ‘matters-of-concern’ and Participatory Design methodology to identify and unpack contributing factors to the formation of echo chambers. As part of the research, a web tool called Echology was conceptualized during a series of workshops with news industry professionals. This paper describes the making of Echology, from ideation to actualization. The goal of this document and its accompanying design piece is to challenge readers to think critically about the forces at play in an online news experience

Does the Sun Shrink with Increasing Magnetic Activity?

We have analyzed the full set of SOHO/MDI f- and p-mode oscillation frequencies from 1996 to date in a search for evidence of solar radius evolution during the rising phase of the current activity cycle. Like Antia et al. (2000), we find that a significant fraction of the f-mode frequency changes scale with frequency; and that if these are interpreted in terms of a radius change, it implies a shrinking sun. Our inferred rate of shrinkage is about 1.5 km/y, which is somewhat smaller than found by Antia et al. We argue that this rate does not refer to the surface, but rather to a layer extending roughly from 4 to 8 Mm beneath the visible surface. The rate of shrinking may be accounted for by an increasing radial component of the rms random magnetic field at a rate that depends on its radial distribution. If it were uniform, the required field would be ~7 kG. However, if it were inwardly increasing, then a 1 kG field at 8 Mm would suffice. To assess contribution to the solar radius change arising above 4Mm, we analyzed the p-mode data. The evolution of the p-mode frequencies may be explained by a magnetic^M field growing with activity. The implications of the near-surface magnetic field changes depend on the anisotropy of the random magnetic field. If the field change is predominantly radial, then we infer an additional shrinking at a rate between 1.1-1.3 km/y at the photosphere. If on the other hand the increase is isotropic, we find a competing expansion at a rate of 2.3 km/y. In any case, variations in the sun's radius in the activity cycle are at the level of 10^{-5} or less, hence have a negligible contribution to the irradiance variations.Comment: 10 pages (ApJ preprint style), 4 figures; accepted for publication in Ap

The relationship between oestrogen receptor-alpha phosphorylation and the tumour microenvironment in patients with primary operable ductal breast cancer

Aims: Although the role of phosphorylation of oestrogen receptor (ER) at serines 118 (p-S118) and 167 (p-S167) has been studied, the relationship between p-S118, p-S167 and the tumour microenvironment in ER-positive primary operable ductal breast cancers have not been investigated. The aims of this study are to investigate (i) the relationship between p-S118/p-S167 and the tumour microenvironment, and (ii) the effect of p-S118/167 on survival and recurrence in ER-positive primary operable ductal breast cancers. Methods and results: Patients presenting at three Glasgow hospitals between 1995 and 1998 with invasive ductal ER-positive primary breast cancers were studied (n = 294). Immunohistochemical staining of p-S118 and p-S167 was performed and their association with clinicopathological characteristics, cancer-specific survival (CSS) and recurrence-free interval (RFI) were examined. In the whole cohort, tumour size (P < 0.05) and microvessel density (P < 0.05) were associated with high p-S118 while increased micovessel density (P < 0.05), apoptosis (P < 0.05), general inflammatory infiltrate measured using the Klintrup–Makinen score (P < 0.05) and macrophage infiltrate (P < 0.05) were found to be associated with high p-S167. Only high p-S167 was associated with shorter CSS (P < 0.005) and shorter RFI in the whole cohort (P = 0.001) and separately in the luminal A (P < 0.05) and B tumours (P < 0.05). Conclusions: This study showed that both p-S118 and p-S167 were associated with several microenvironmental factors, including increased microvessel density. In particular, p-S167 was associated with reduced RFI and CSS in the whole cohort and RFI in luminal A and B tumours and could possibly be employed to predict response to kinase inhibitors

The origin of pine pollen grains captured from air at Calypsobyen, Svalbard

Spitsbergen is the largest island in the Svalbard Archipelago (Norway) that has been permanently populated. The harsh Arctic climate prevents development of large vascular plants such as trees. A two-year aerobiological survey was conducted within the framework of two consecutive polar expeditions (2014 and 2015) in Spitsbergen (Calypsobyen, Bellsund). The air quality was measured continuously from June/July to August using a 7-day volumetric air sampler, Tauber trap and moss specimens. Collected air samples and gravimetric pollen deposits were processed following transfer to sterile laboratory conditions and analyzed with the aid of light microscopy. Days when pine pollen grains were detected in the air were selected for further analysis. Clusters of back-trajectories, computed using the Hybrid Single Particle Lagrangian Integrated Trajectory model in combination with ArcGIS software as well as the Flextra trajectory model, showed the movement of air masses to the sampling location at Hornsund, and thus indicated the likely origin of pollen grains. The GlobCover 2009 and CORINE Land Cover 2012 datasets were employed to establish the distribution of coniferous forests in the areas of interest. Conclusions were drawn based on the analyses of the circulation of air masses, using visualization of global weather conditions forecast to supercomputers. For the first time, we have demonstrated that pine pollen grains occurring in pine-free Spitsbergen, could originate from numerous locations, including Scandinavia, Iceland, Siberia and northern Canada. Pollen grains were transported via air masses for distances exceeding ~2000 km. Both air samples and gravimetric pollen deposits revealed the same pattern of Pinus pollen distributio

Properties of Flares-Generated Seismic Waves on the Sun

The solar seismic waves excited by solar flares (``sunquakes'') are observed as circular expanding waves on the Sun's surface. The first sunquake was observed for a flare of July 9, 1996, from the Solar and Heliospheric Observatory (SOHO) space mission. However, when the new solar cycle started in 1997, the observations of solar flares from SOHO did not show the seismic waves, similar to the 1996 event, even for large X-class flares during the solar maximum in 2000-2002. The first evidence of the seismic flare signal in this solar cycle was obtained for the 2003 ``Halloween'' events, through acoustic ``egression power'' by Donea and Lindsey. After these several other strong sunquakes have been observed. Here, I present a detailed analysis of the basic properties of the helioseismic waves generated by three solar flares in 2003-2005. For two of these flares, X17 flare of October 28, 2003, and X1.2 flare of January 15, 2005, the helioseismology observations are compared with simultaneous observations of flare X-ray fluxes measured from the RHESSI satellite. These observations show a close association between the flare seismic waves and the hard X-ray source, indicating that high-energy electrons accelerated during the flare impulsive phase produced strong compression waves in the photosphere, causing the sunquake. The results also reveal new physical properties such as strong anisotropy of the seismic waves, the amplitude of which varies significantly with the direction of propagation. The waves travel through surrounding sunspot regions to large distances, up to 120 Mm, without significant decay. These observations open new perspectives for helioseismic diagnostics of flaring active regions on the Sun and for understanding the mechanisms of the energy release and transport in solar flares.Comment: 12 pages, 4 figures, submitted to Ap

Our Sun. IV. The Standard Model and Helioseismology: Consequences of Uncertainties in Input Physics and in Observed Solar Parameters

Helioseismology provides a powerful tool to explore the deep interior of the Sun: for example, the adiabatic sound speed can be inferred with an accuracy of a few parts in 10,000. This has become a serious challenge to theoretical models of the Sun. Therefore, we have undertaken a self-consistent, systematic study of sources of uncertainties in the standard solar model, which must be understood before the helioseismic observations can be used as constraints on theory. We find that the largest uncertainty in the sound speed in the solar interior, namely, 3 parts in 1000, arises from uncertainties in the observed photospheric abundances of the elements; uncertainties of 1 part in 1000 arise from (1) the 4% uncertainty in the OPAL opacities, (2) the 5% uncertainty in the basic pp nuclear reaction rate, (3) the 15% uncertainty in the diffusion constants for the gravitational settling of helium, and (4) the 50% uncertainties in diffusion constants for the heavier elements. (Other investigators have shown that similar uncertainties arise from uncertainties in the interior equation of state and in rotation-induced turbulent mixing.) The predicted pre-main-sequence solar lithium depletion is a factor of order 20 (an order of magnitude larger than that predicted by earlier models that neglected gravitational settling and used older opacities), and is uncertain by a factor of 2. The predicted neutrino capture rate is uncertain by 30% for the Cl-37 experiment and by 3% for the Ga-71 experiments (not including uncertainties in the capture cross sections), while the B-8 neutrino flux is uncertain by 30%.Comment: LaTeX, 38 pages (including 8 figures); ApJ, in press. Added figures/color figurea available at http://www.cita.utoronto.ca/~boothroy/sun4.htm

Autosomal dominant inheritance of a predisposition to thoracic aortic aneurysms and dissections and intracranial saccular aneurysms

A genetic predisposition for thoracic aortic aneurysms and dissections (TAAD) can be inherited in an autosomal dominant manner with decreased penetrance and variable expression. Four genes identified to date for familial TAAD account for approximately 20% of the heritable predisposition. In a cohort of 514 families with two or more members with presumed autosomal dominant TAAD, 48 (9.3%) families have one or more members who were at 50% risk to inherit the presumptive gene causing TAAD had an intracranial vascular event. In these families, gender is significantly associated with disease presentation ( P  < 0.001), with intracranial events being more common in women (65.4%) while TAAD events occurred more in men (64.2%,). Twenty‐nine of these families had intracranial aneurysms (ICA) that could not be designated as saccular or fusiform due to incomplete data. TGFBR1 , TGFBR2 , and ACTA2 mutations were found in 4 families with TAAD and predominantly fusiform ICAs. In 15 families, of which 14 tested negative for 3 known TAAD genes, 17 family members who were at risk for inheriting TAAD had saccular ICAs. In 2 families, women who harbored the genetic mutation causing TAAD had ICAs. In 2 additional families, intracranial, thoracic and abdominal aortic aneurysms were observed. This study documents the autosomal dominant inheritance of TAADs with saccular ICAs, a previously recognized association that has not been adequately characterized as heritable. In these families, routine cerebral and aortic imaging for at risk members could prevent cerebral hemorrhages and aortic dissections. © 2011 Wiley‐Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87019/1/34050_ftp.pd

Everything you always wanted to know about systemic sclerosis but were afraid to ask: Part 2. Intermediate pathophenotypes: the best pathogenetic background in systemic sclerosis

Systemic sclerosis (SSc, scleroderma) is a chronic systemic connective tissue disease with a complex pathogenesis that is still not fully understood, in the course of which attention is increasingly drawn to the dynamic, sequential pathogenetic mechanisms according to disease stage. An increasing understanding of the diversity of mechanisms underlying this disease, as well as the prevalence of certain pathogenetic elements that depend i.a. on disease stage, will enable more effective therapeutic interventions in the future. Systemic sclerosis can thus be seen as a complex process, where the main players are immune cells, endothelial cells and fibroblasts, and the focal point is probably impaired function and subsequent damage to endothelial cells. Systemic sclerosis is also the final stage of a certain continuum of events, starting with a state of susceptibility to the development of the disease (dependent on genetic conditions and environmental influences), followed by disruption of homeostasis and initiation of pathological processes (e.g. as a result of viral infections), progression of pathological responses (inflammation, endothelial damage, fibrosis) and consequently organ damage. According to most authors, the key event and focal point of the cascade of phenomena is endothelial cell damage, and the mechanisms that lead to this damage are related to the activation of the immune system. There is growing acceptance of the thesis of an autoimmune origin of the disease involving mechanisms of innate and acquired immunity, both cellular and humoral.Systemic sclerosis (SSc, scleroderma) is a chronic systemic connective tissue disease with a complex pathogenesis that is still not fully understood, in the course of which attention is increasingly drawn to the dynamic, sequential pathogenetic mechanisms according to disease stage. An increasing understanding of the diversity of mechanisms underlying this disease, as well as the prevalence of certain pathogenetic elements that depend i.a. on disease stage, will enable more effective therapeutic interventions in the future. Systemic sclerosis can thus be seen as a complex process, where the main players are immune cells, endothelial cells and fibroblasts, and the focal point is probably impaired function and subsequent damage to endothelial cells. Systemic sclerosis is also the final stage of a certain continuum of events, starting with a state of susceptibility to the development of the disease (dependent on genetic conditions and environmental influences), followed by disruption of homeostasis and initiation of pathological processes (e.g. as a result of viral infections), progression of pathological responses (inflammation, endothelial damage, fibrosis) and consequently organ damage. According to most authors, the key event and focal point of the cascade of phenomena is endothelial cell damage, and the mechanisms that lead to this damage are related to the activation of the immune system. There is growing acceptance of the thesis of an autoimmune origin of the disease involving mechanisms of innate and acquired immunity, both cellular and humoral