Multi-Step Cascade Annihilations of Dark Matter and the Galactic Center Excess

If dark matter is embedded in a non-trivial dark sector, it may annihilate and decay to lighter dark-sector states which subsequently decay to the Standard Model. Such scenarios - with annihilation followed by cascading dark-sector decays - can explain the apparent excess GeV gamma-rays identified in the central Milky Way, while evading bounds from dark matter direct detection experiments. Each 'step' in the cascade will modify the observable signatures of dark matter annihilation and decay, shifting the resulting photons and other final state particles to lower energies and broadening their spectra. We explore, in a model-independent way, the effect of multi-step dark-sector cascades on the preferred regions of parameter space to explain the GeV excess. We find that the broadening effects of multi-step cascades can admit final states dominated by particles that would usually produce too sharply peaked photon spectra; in general, if the cascades are hierarchical (each particle decays to substantially lighter particles), the preferred mass range for the dark matter is in all cases 20-150 GeV. Decay chains that have nearly-degenerate steps, where the products are close to half the mass of the progenitor, can admit much higher DM masses. We map out the region of mass/cross-section parameter space where cascades (degenerate, hierarchical or a combination) can fit the signal, for a range of final states. In the current work, we study multi-step cascades in the context of explaining the GeV excess, but many aspects of our results are general and can be extended to other applications.Comment: 18 pages, 15 figures, 2 tables; comments welcome. Updated to published versio

Text Messaging Between School Counselors and Students: An Exploratory Study

This exploratory case study examines the impact of text messaging on mentoring relationships when used as an outreach between school counselors and high school students, where established relationships are lacking. An SMS gateway was used to mediate communication between school counselors (N=2) and students (N=5) over a three-month timeframe. The SMS gateway converted email, sent from counselors, to text messages, which were received on mobile devices of students and allowed students to respond back to counselors. Findings indicate that the use of text messaging may ease scheduling of face-to-face meetings between counselors and students, but evidence does not support any conclusions about the impact of text messaging on mentoring relationships. Students prioritized transactional relationships and perceived direct access to counselors, via text messaging, as a way to mitigate help-seeking barriers and control the counseling process. Ethics of the counseling field, social perceptions of professional communications, and sensitivities to traditional counselor-student relationships are to be considered when applying these findings in practicum. Further study about the ways text messaging can impact relationships in a school setting is necessary to expand our understanding of text messaging as a potential communication tool between high school students and their school counselors

Model-Independent Indirect Detection Constraints on Hidden Sector Dark Matter

If dark matter inhabits an expanded "hidden sector", annihilations may proceed through sequential decays or multi-body final states. We map out the potential signals and current constraints on such a framework in indirect searches, using a model-independent setup based on multi-step hierarchical cascade decays. While remaining agnostic to the details of the hidden sector model, our framework captures the generic broadening of the spectrum of secondary particles (photons, neutrinos, e+e- and antiprotons) relative to the case of direct annihilation to Standard Model particles. We explore how indirect constraints on dark matter annihilation limit the parameter space for such cascade/multi-particle decays. We investigate limits from the cosmic microwave background by Planck, the Fermi measurement of photons from the dwarf galaxies, and positron data from AMS-02. The presence of a hidden sector can change the constraints on the dark matter annihilation cross section by up to an order of magnitude in either direction (although the effect can be much smaller). We find that generally the bound from the Fermi dwarfs is most constraining for annihilations to photon-rich final states, while AMS-02 is most constraining for electron and muon final states; however in certain instances the CMB bounds overtake both, due to their approximate independence of the details of the hidden sector cascade. We provide the full set of cascade spectra considered here as publicly available code with examples at http://web.mit.edu/lns/research/CascadeSpectra.html.Comment: Published version. Added analysis on interplay between indirect detection bounds and the Galactic Center GeV excess. Added antiproton ratio bound

Retinoic acid induces the differentiation of B cell hybridomas from patients with common variable immunodeficiency.

Human-human B cell hybridomas constructed from B lymphocytes of common variable immunodeficiency (CVI) patients and the nonsecreting cell line WIL2/729 HF consistently secrete low levels of Ig and appear to retain a defect characteristic of the CVI patient's B cells. We assessed the differentiative capacity of retinoic acid (RA) on these hybridomas, as well as on hybridomas constructed from normal B cells and from patients with selective IgA deficiency. RA at concentrations varying between 10(-5) and 10(-9) M augmented IgM secretion 4-20-fold from four of four CVI hybridomas tested, but did not affect Ig secretion from normal or IgA-deficiency hybridomas. In support of this elevated Ig secretion, RA enhanced the de novo synthesis of biosynthetically labeled light (kappa) and heavy (mu) Ig (up to 4- and 15-fold, respectively) in the CVI hybridoma line JK32.1. The increase in IgM synthesis/secretion could not be accounted for by RA-induced alteration in the cell cycle. In inducing this increase in IgM production, RA was found to affect two aspects of Ig gene expression: (a) the steady-state levels of heavy and light chain mRNAs were enhanced, and (b) the processing of mu heavy chain transcripts to the secreted mRNA form became favored over the membrane mRNA form. We also show that expression of Leu-17 (CD38), a surface marker that is re-expressed in the late pre-plasma stage of B cell development, was increased by RA from less than 20% to greater than 90% of the total cell population, with a concomitant 4-10-fold augmentation in the mean fluorescence intensity. Changes in both Leu-17 expression and de novo Ig synthesis were prominent by 24 h, but could be observed as early as 8 h after induction. Taken together, our study demonstrates that RA affects a marked alteration in the differentiated state of the CVI hybridoma clones. This finding suggests that retinoids can enhance the functional capabilities of B cells with defects in maturation and support further studies to evaluate their clinical potential in CVI

Spectroscopic Analysis and Image Processing of the Optically-Thin Solar Corona

This thesis examines the emission, radiative transfer, and interpretation of spectral observations of the optically-thin solar corona. The first half of this work presents a forward model called the Global Heliospheric Optically-thin Spectral Transport Simulation (GHOSTS), which uses data from other physical models to determine the plasma parameters in the solar environment. The model then performs optically-thin radiative transfer through the corona for a set of commonly observed coronal ions, generating ensembles of simulated lines. We develop GHOSTS starting with a timesteady model, and we focus on characterizing spectral lines that are influenced by three primary factors: solar wind outflow, preferential ion heating, and non-equilibrium ion populations along the Line-of-Sight (LOS) due to strong temperature gradients. We extend the GHOSTS model into the time domain to characterize how the spectral lines are affected by dynamic phenomena like dense magnetic polar plumes along the LOS shaken by Alfven waves propagating outward from the photosphere. The photosphere is very bright relative to the corona, so these two regions cannot be readily examined at the same time, even when they are both observed together. In the second half of this work, we review the literature regarding algorithms that are commonly applied to High Dynamic Range (HDR) filtergram imagery of the corona, like those recorded by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). We then present two new tools for examining these images, and evaluate them relative to algorithms from the literature: Quantile Radial Normalization (QRN) is a variation of a traditional Radial Graded Filter (RGF) that normalizes the image using percentile curves. The Radial Histogram Equalizing Filter (RHEF) is a more powerful algorithm, a hybrid of RGF and Adaptive Histogram Equalization (AHE), which equalizes the histogram of intensity at each radius. We conclude by offering a brief overview of the preliminary work we have performed modeling polarization observations for the PUNCH mission.</p

Complementarity for Dark Sector Bound States

We explore the possibility that bound states involving dark matter particles could be detected by resonance searches at the LHC, and the generic implications of such scenarios for indirect and direct detection. We demonstrate that resonance searches are complementary to mono-jet searches and can probe dark matter masses above 1 TeV with current LHC data. We argue that this parameter regime, where the bound-state resonance channel is the most sensitive probe of the dark sector, arises most naturally in the context of non-trivial dark sectors with large couplings, nearly-degenerate dark-matter-like states, and multiple force carriers. The presence of bound states detectable by the LHC implies a minimal Sommerfeld enhancement that is appreciable, and potentially also radiative bound state formation in the Galactic halo, leading to large signals in indirect searches. We calculate these complementary constraints, which favor either models where the bound-state-forming dark matter constitutes a small fraction of the total density, or models where the late-time annihilation is suppressed at low velocities or late times. We present concrete examples of models that satisfy all these constraints and where the LHC resonance search is the most sensitive probe of the dark sector.Comment: 22 pages plus appendices, 10 figures, comments welcom

Ressources cognitives et développement territorial : une analyse textuelle appliquée aux politiques locales de développement durable

International audienceThis paper focuses on how the development of a particular region consistently requires actors to share a certain level of cognitive resources. In the case studied here - the Nord Pas-de-Calais region, this cognitive proximity is built via the local policies involving sustainable development. In order to comprehend the way local communities of the region activate this resource, we used textual data treatment analyzing about thirty interviews. The results suggest that this cognitive proximity relies on two fundamentals elements: on the one hand, valuing the patrimonial infrastructures of the territory; and on the other hand, rebuilding the territorial identity of the region. Then the local policies lean both on the values that underlie these elements and on rhetorical modalities, to impulse in-depth changes that would have been more difficult to implement from the usual political levers.Cet article étudie comment un développement régional cohérent nécessite la mobilisation de ressources cognitives partagées. Dans le cas étudié - la région Nord Pas-de-Calais, cette proximité cognitive se construit via les politiques locales, sur la base du référentiel de développement durable. Pour saisir la manière dont les collectivités de la région activent cette ressource, nous avons mobilisé les outils d'analyse textuelle sur une trentaine d'entretiens auprès des acteurs publics du développement durabe. Les résultats mis en évidence suggèrent que cette proximité cognitive repose sur deux éléments fondamentaux : d'une part la mise en valeur d'un patrimoine infrastructurel territorialisé, et d'autre part la reconstruction d'une identité territoriale. Les politiques locales prennent ainsi appui sur les valeurs qui sous-tendent ces éléments ainsi que sur des modalités rhétoriques, pour impulser en profondeur une dynamique de changement, plus malaisée à mettre en œuvre partir des outils politiques habituels

The development and evaluation of ‘Farm Animal Welfare’ an educational computer game for children

Many children growing up in urban areas of Western countries have limited contact with and knowledge of farm animals and food production systems. Education can play an important role in children&rsquo;s understanding of farm animal welfare issues, however, most education provided focuses on pets. There is a need to develop new farm animal welfare interventions for young children. This study examines the process of designing, developing, and evaluating the effectiveness of a new theoretically-driven digital game to teach children, aged 6&ndash;13 years, about farm animal welfare. &lsquo;Farm Animal Welfare&rsquo; aimed to promote children&rsquo;s knowledge about animal welfare, promote beliefs about animal sentience, and promote positive attitudes and compassion. A quasi-experimental design was carried out, using self-report questionnaires that children (n = 133, test = 69, control = 64) completed in the classroom. Test and control groups were from different schools and the control group did not engage in the intervention. Findings indicate a positive impact on beliefs about animal minds, knowledge about animal welfare needs, and knowledge about welfare in different farming systems, but there was no change in compassion or attitudes about cruelty. This study presents the first evaluation of a digital animal welfare education intervention for children, demonstrating the benefits of incorporating &lsquo;serious games&rsquo; into farm animal welfare education. The findings will inform future practice around farm animal welfare education interventions for primary school children

The CAT Imaging Telescope for Very-High-Energy Gamma-Ray Astronomy

The CAT (Cherenkov Array at Themis) imaging telescope, equipped with a very-high-definition camera (546 fast phototubes with 0.12 degrees spacing surrounded by 54 larger tubes in two guard rings) started operation in Autumn 1996 on the site of the former solar plant Themis (France). Using the atmospheric Cherenkov technique, it detects and identifies very high energy gamma-rays in the range 250 GeV to a few tens of TeV. The instrument, which has detected three sources (Crab nebula, Mrk 421 and Mrk 501), is described in detail.Comment: 24 pages, 15 figures. submitted to Elsevier Preprin