Solar Gamma Rays Powered by Secluded Dark Matter

Secluded dark matter models, in which WIMPs annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the solar system, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.Comment: 22 pages, 3 figure

Shock Geometry and Spectral Breaks in Large SEP Events

Solar energetic particle (SEP) events are traditionally classified as "impulsive" or "gradual." It is now widely accepted that in gradual SEP events, particles are accelerated at coronal mass ejection-driven (CME-driven) shocks. In many of these large SEP events, particle spectra exhibit double power law or exponential rollover features, with the break energy or rollover energy ordered as (Q/A)^α, with Q being the ion charge in e and A the ion mass in units of proton mass m_p . This Q/A dependence of the spectral breaks provides an opportunity to study the underlying acceleration mechanism. In this paper, we examine how the Q/A dependence may depend on shock geometry. Using the nonlinear guiding center theory, we show that α ~ 1/5 for a quasi-perpendicular shock. Such a weak Q/A dependence is in contrast to the quasi-parallel shock case where α can reach 2. This difference in α reflects the difference of the underlying parallel and perpendicular diffusion coefficients κ_(||) and κ ⊥. We also examine the Q/A dependence of the break energy for the most general oblique shock case. Our analysis offers a possible way to remotely examine the geometry of a CME-driven shock when it is close to the Sun, where the acceleration of particle to high energies occurs

The role of interplanetary scattering in western hemisphere large solar energetic particle events

Using high-sensitivity instruments on the ACE spacecraft, we have examined the intensities of O and Fe in 14 large solar energetic particle events whose parent activity was in the solar western hemisphere. Sampling the intensities at low (~273 keV nucleon to the -1) and high (~12 MeV nucleon to the -1) energies, we find that at the same kinetic energy per nucleon, the Fe/O ratio decreases with time, as has been reported previously. This behavior is seen in more than 70% of the cases during the rise to maximum intensity and continues in most cases into the decay phase. We find that for most events if we compare the Fe intensity with the O intensity at a higher kinetic energy per nucleon, the two time-intensity profiles are strikingly similar. Examining alternate scenarios that could produce this behavior, we conclude that for events showing this behavior the most likely explanation is that the Fe and O share similar injection profiles near the Sun, and that scattering in the interplanetary medium dominates the profiles observed at 1 AU

Genetic Variation and the Fate of Beneficial Mutations in Asexual Populations

The fate of a newly arising beneficial mutation depends on many factors, such as the population size and the availability and fitness effects of other mutations that accumulate in the population. It has proved difficult to understand how these factors influence the trajectories of particular mutations, since experiments have primarily focused on characterizing successful clones emerging from a small number of evolving populations. Here, we present the results of a massively parallel experiment designed to measure the full spectrum of possible fates of new beneficial mutations in hundreds of experimental yeast populations, whether these mutations are ultimately successful or not. Using strains in which a particular class of beneficial mutation is detectable by fluorescence, we followed the trajectories of these beneficial mutations across 592 independent populations for 1000 generations. We find that the fitness advantage provided by individual mutations plays a surprisingly small role. Rather, underlying “background” genetic variation is quickly generated in our initially clonal populations and plays a crucial role in determining the fate of each individual beneficial mutation in the evolving population

Seed populations for large solar particle events of cycle 23

Using high-resolution mass spectrometers on board the Advanced Composition Explorer (ACE), we surveyed the event-averaged ~0.1-60 MeV/nuc heavy ion elemental composition in 64 large solar energetic particle (LSEP) events of cycle 23. Our results show the following: (1) The rare isotope ^3He is greatly enhanced over the corona or the solar wind values in 46% of the events. (2) The Fe/O ratio decreases with increasing energy up to ~10 MeV/nuc in ~92% of the events and up to ~60 MeV/nuc in ~64% of the events. (3) Heavy ion abundances from C-Fe exhibit systematic M/g-dependent enhancements that are remarkably similar to those seen in ^3He-rich SEP events and CME-driven interplanetary (IP) shock events. Taken together, these results confirm the role of shocks in energizing particles up to ~60 MeV/nuc in the majority of large SEP events of cycle 23, but also show that the seed population is not dominated by ions originating from the ambient corona or the thermal solar wind, as previously believed. Rather, it appears that the source material for CME-associated large SEP events originates predominantly from a suprathermal population with a heavy ion enrichment pattern that is organized according to the ion's mass-per-charge ratio. These new results indicate that current LSEP models must include the routine production of this dynamic suprathermal seed population as a critical pre-cursor to the CME shock acceleration process

Particle acceleration in the heliosphere

The heliosphere is filled with supersonic solar wind that forms shocks wherever it encounters obstacles, be they a high speed Coronal Mass Ejection (CME), or regions where fastsolar wind encounters slower-moving solar wind. Energetic particles (> 10s of keV/nuc to 10s of MeV/nuc) associated with these shocks form a test bed for understanding particle acceleration since the shock properties can often be measured and energetic particle composition compared to candidate seed populations. Over the past 15-20 years a wide body of evidence has emerged showing that generally the seed population is the suprathermal ion pool at energies above the bulk solar wind. Understanding the interplanetary suprathermal ion population is therefore a critical step in fully understanding the physical mechanisms that accelerate particles in interplanetary space

Development Discourse and Popular Articulations in Urban Gujarat

This article discusses how marginalized groups in the Indian state of Gujarat make sense of hegemonic discourses about national development in light of their own experiences and material circumstances. For many, the idea of development resonates even when they do not experience material progress in their lives. This partial hegemony of development discourse can be explained by utilizing the concept of ‘political articulation’. This captures the political process by which parties succeed, at specific historical moments and under certain circumstances, in joining together different, even potentially conflictual interests by referring to a common idea and project. The article focuses on Ahmedabad city where the Bharatiya Janata Party (BJP) has created a cross-caste bloc through the trope of development. The Party has been particularly effective in linking the idea of development to people’s mundane concerns of security, identity and spatial order. However, anxieties about the degradation of labour and its conditions such as casualization, informalization, and socio-spatial marginalization disrupts this common sense and has weakened the hegemony of the BJP’s model of development.This research was funded by a Leverhulme Research Project Grant (2011-13) titled Beyond Identity? Markets and Logics of Democratization in India, 1991-Present.This is the author accepted manuscript. The final version is available from Taylor & Francis via http://dx.doi.org/10.1080/14672715.2015.112040

A case of inferior lumbar hernia

In this article we report a case of inferior lumbar hernia. The patient underwent preperitoneal meshplasty. The patient is well on follow up with no recurrence. The relevant literature has been reviewed and management discussed in brief

The Star Formation Histories of z ~ 2 Dust-obscured Galaxies and Submillimeter-selected Galaxies

The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z ~ 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M_*) of two populations of Spitzer-selected ULIRGs that have extremely red R – [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 μm associated with stellar emission ("bump DOGs"), while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ("power-law DOGs"). We measure M_* by applying Charlot & Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M_* values for SMGs, bump DOGs, and power-law DOGs are log(M_*/M_☉) = 10.42^(+0.42)_(–0.36), 10.62^(+0.36)_(–0.32), and 10.71^(+0.40)_(–0.34), respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z ~ 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z ~ 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M_*, a situation that arises more naturally in major mergers than in smooth accretion-powered systems

Obesity, oxidative DNA damage and vitamin D as predictors of genomic instability in children and adolescents

Background/objectives Epidemiological evidence indicates obesity in childhood and adolescence to be an independent risk factor for cancer and premature mortality in adulthood. Pathological implications from excess adiposity may begin early in life. Obesity is concurrent with a state of chronic inflammation, a well-known aetiological factor for DNA damage. In addition, obesity has been associated with micro-nutritional deficiencies. Vitamin D has attracted attention for its anti-inflammatory properties and role in genomic integrity and stability. The aim of this study was to determine a novel approach for predicting genomic instability via the combined assessment of adiposity, DNA damage, systemic inflammation, and vitamin D status. Subjects/methods We carried out a cross-sectional study with 132 participants, aged 10–18, recruited from schools and paediatric obesity clinics in London. Anthropometric assessments included BMI Z-score, waist and hip circumference, and body fat percentage via bioelectrical impedance. Inflammation and vitamin D levels in saliva were assessed by enzyme-linked immunosorbent assay. Oxidative DNA damage was determined via quantification of 8-hydroxy-2′-deoxyguanosine in urine. Exfoliated cells from the oral cavity were scored for genomic instability via the buccal cytome assay. Results As expected, comparisons between participants with obesity and normal range BMI showed significant differences in anthropometric measures (p < 0.001). Significant differences were also observed in some measures of genomic instability (p < 0.001). When examining relationships between variables for all participants, markers of adiposity positively correlated with acquired oxidative DNA damage (p < 0.01) and genomic instability (p < 0.001), and negatively correlated with vitamin D (p < 0.01). Multiple regression analyses identified obesity (p < 0.001), vitamin D (p < 0.001), and oxidative DNA damage (p < 0.05) as the three significant predictors of genomic instability. Conclusions Obesity, oxidative DNA damage, and vitamin D deficiency are significant predictors of genomic instability. Non-invasive biomonitoring and predictive modelling of genomic instability in young patients with obesity may contribute to the prioritisation and severity of clinical intervention measures