The Case for a Low Extragalactic Gamma-ray Background

Measurements of the diffuse extragalactic gamma-ray background (EGRB) are complicated by a strong Galactic foreground. Estimates of the EGRB flux and spectrum, obtained by modeling the Galactic emission, have produced a variety of (sometimes conflicting) results. The latest analysis of the EGRET data found an isotropic flux I_x=1.45+-0.05 above 100 MeV, in units of 10^-5 s^-1 cm^-2 sr^-1. We analyze the EGRET data in search for robust constraints on the EGRB flux, finding the gamma-ray sky strongly dominated by Galactic foreground even at high latitudes, with no conclusive evidence for an additional isotropic component. The gamma-ray intensity measured towards the Galactic poles is similar to or lower than previous estimates of I_x. The high latitude profile of the gamma-ray data is disk-like for 40<|b[deg]|<70, and even steeper for |b|>70; overall it exhibits strong Galactic features and is well fit by a simple Galactic model. Based on the |b|>40 data we find that I_x<0.5 at a 99% confidence level, with evidence for a much lower flux. We show that correlations with Galactic tracers, previously used to identify the Galactic foreground and estimate I_x, are not satisfactory; the results depend on the tracers used and on the part of the sky examined, because the Galactic emission is not linear in the Galactic tracers and exhibits spectral variations across the sky. The low EGRB flux favored by our analysis places stringent limits on extragalactic scenarios involving gamma-ray emission, such as radiation from blazars, intergalactic shocks and production of ultra-high energy cosmic rays and neutrinos. We suggest methods by which future gamma-ray missions such as GLAST and AGILE could indirectly identify the EGRB.Comment: Accepted for publication in JCAP. Increased sizes of polar regions examined, and added discussion of spectral data. Results unchange

Observing the Sun with the Atacama Large Millimeter-submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping

The Atacama Large Millimeter-submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that utilizes the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions we derive quiet-Sun values at disk center of 7300 K at lambda=3 mm and 5900 K at lambda=1.3 mm. These values have statistical uncertainties of order 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of order 25 arcsec, the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range.Comment: Solar Physics, accepted: 24 pages, 13 figure

Inequalities in experiencing urban functions. An exploration of human digital (geo-)footprints

Studies on mobility inequalities have so far mostly relied on Survey data or Censuses. While such studies have demonstrated that inequalities strongly influence everyday mobility choices, these data sources lack granular information on people’s movements on a daily basis. By capitalising on high spatio-temporal resolution data provided by Spectus.ai, this study aims at investigating how the deprivation level of the area where people live influences the kinds of urban environment they are more likely to use for their everyday activities. To do this, raw GPS trajectories collected in 2019 in Great Britain (GB) are transformed into semantic trajectories where short-time changes and the functional nature of urban contexts are acknowledged as two key dimensions to understand human spatial behaviours. Hourly sequences of stops are extracted from GPS trajectories and enriched with contextual information based on a new area-based classification detecting urban functions. The data exploration shows that some human patterns are widely common across all levels of deprivation, such as the tendency to be mostly exposed to the urban context near the home location. At the same time, we show that differences exist, especially between those who live in the most deprived areas and those who live in the least deprived areas of GB. It appears that people living in the most deprived areas tend to have a less regular working pattern and be more exposed to urban-based functions and well-served areas, while those living in the least deprived areas have a more regular working patterns and are mostly exposed to the countryside and low-density areas. Our approach and results provide new insights on the temporal and contextual dimensions of mobility inequalities, informing on who is exposed to issues characterising certain urban environments. </jats:p

Correlates of Suicide Ideation and Attempt among Youth Living in the Slums of Kampala

While suicidal behavior is recognized as a growing public health problem world-wide, little is known about the prevalence and risk factors for suicidal behaviors among street and slum youth in Africa, and in Uganda, specifically. The number of youth who live on the streets and in the slums of Kampala appears to be growing rapidly, but their mental health needs have not been documented, which has hampered resource allocation and service implementation. This study of youth, ages 14–24, was conducted in May and June of 2011, to assess the prevalence and correlates of suicidal behavior. Participants (N = 457) were recruited for a 30-minute interviewer-administered survey through eight drop-in centers operated by the Uganda Youth Development Link for youth in need of services. Bivariate and multivariate logistic regression analyses were computed to determine associations between psychosocial correlates and suicide ideation and suicide attempt. Reporting both parents deceased Adj.OR = 2.36; 95% CI: 1.23–4.52), parental neglect due to alcohol use (Adj.OR = 2.09; 95% CI: 1.16–3.77), trading sex for food, shelter or money (Adj.OR = 1.95; 95% CI: 1.09–3.51), sadnesss (Adj.OR = 2.42; 95% CI: 1.20–4.89), loneliness (Adj.OR = 2.67; 95% CI: 1.12–6.40) and expectations of dying prior to age 30 (Adj.OR = 2.54; 95% CI: 1.53–4.23) were significantly associated with suicide ideation in multivariate analyses. Parental neglect due to alcohol use (Adj.OR = 2.04; 95% CI: 1.11–3.76), sadness (Adj.OR = 2.42; 95% CI: 1.30–7.87), and expectations of dying prior to age 30 (Adj.OR = 2.18; 95% CI: 1.25–3.79) were significantly associated with suicide attempt in multivariate analyses. Given the dire circumstances of this vulnerable population, increased services and primary prevention efforts to address the risk factors for suicidal behavior are urgently needed

Validity of the lactate 3.5 mmol x l*‘ threshold velocity identified by a test in the athletic track

Aerobic training for sportsmen, in particular, long and midlle distance runners, has had a great development in recent years, partially due to different types of laboratory tests, among them, measure of blood lactate. The great demand of athletes and specificity of the sports activity led to a search for track tests. 14 male long and middle distance runners, competing at national level, were studied in laboratory and field (track) conditions using gradual increasing tests, 3 min each level, with 30 s pause. The velocity of lactate threshold of 3.5 mmol x I*1 was determined by piecewise regression, with unknown intersection point; heart rate in this velocity was studied with linear or quadratic regression, depending on minimal residuals. These two summary measures were compaired using Pearson correlation coefficient (r), and parametric and non parametric inferential tests; r between track and laboratory results were 0.86 and 0.81 for velocity and heart rate, respectively. Significant differences between summary measures for track and laboratory were not found. Concluding, determination of lactate threshold for runners with incremental protocol in track is a valid estimation of laboratory resultsO treinamento acrôbio para atletas, cm especial para meio fundistas e fundistas, tem se desenvolvido muito nos últimos anos, embasado, entre outros fatores, em vários tipos de testes laboratoriais, dentre os quais a medida de iactnto sanguíneo para a determinação do limiar anaerôbio. A necessidade de atender a número mais elevado de esportistas, bem como a maior especificidade da atividade envolvida, levaram a procura de testes de pista. Foram analisados cm laboratório e em pista de atletismo, 14 atletas de fundo e meio íúndo, de nível nacional, utilizando-se testes escalonados de 3 min de duração por estágio, com pausas de 30 s. A velocidade de limiar de lactato de 3,5 mmol x l'1 foi determinada através de regressão segmentada, com ponto de intersecção desconhecido; a freqüência cardíaca nesse limiar foi calculada através de ajustes de curvas de primeiro ou segundo graus para obtenção de resíduos mínimos. Essas duas medidas resumo foram comparadas através do coeficiente de correlação de Pearson (r) c de testes inferenciais paramétricos c não paramétricos. O r entre laboratório c pista foi de 0,80 para a velocidade de limiar e de 0,81 para a freqüência cardíaca na velocidade de limiar. Não houve diferença significante entre os valores de laboratório c de pista, para nenhuma variável estudada, com nenhuma metodologia. Pode-sc concluir que, para atletas de corrida, a determinação da velocidade dc limiar de lactato cm pista, calculada por meio de regressão segmentada, através do teste escalonado intermitente, é uma metodologia válid

CXCL16-mediated cell recruitment to rheumatoid arthritis synovial tissue and murine lymph nodes is dependent upon the MAPK pathway

Objective Rheumatoid arthritis (RA) is characterized by profound mononuclear cell (MNC) recruitment into synovial tissue (ST), thought to be due in part to tumor necrosis factor Α (TNFΑ), a therapeutic target for RA. Although chemokines may also be involved, the mechanisms remain unclear. We undertook this study to examine the participation of CXCL16, a novel chemokine, in recruitment of MNCs to RA ST in vivo and to determine the signal transduction pathways mediating this process. Methods Using a human RA ST–SCID mouse chimera, immunohistochemistry, enzyme-linked immunosorbent assay, real-time reverse transcription–polymerase chain reaction, flow cytometry, and in vitro chemotaxis assays, we defined the expression and function of CXCL16 and its receptor, CXCR6, as well as the signal transduction pathways utilized by them for MNC homing in vitro and in vivo. Results CXCL16 was markedly elevated in RA synovial fluid (SF) samples, being as high as 145 ng/ml. Intense macrophage and lining cell staining for CXCL16 in RA ST correlated with increased CXCL16 messenger RNA levels in RA ST compared with those in osteoarthritis and normal ST. By fluorescence-activated cell sorting analysis, one-half of RA SF monocytes and one-third of memory lymphocytes expressed CXCR6. In vivo recruitment of human MNCs to RA ST implanted in SCID mice occurred in response to intragraft injection of human CXCL16, a response similar to that induced by TNFΑ. Lipofection of MNCs with antisense oligodeoxynucleotides for ERK-1/2 resulted in a 50% decline in recruitment to engrafted RA ST and a 5-fold decline in recruitment to regional lymph nodes. Interestingly, RA ST fibroblasts did not produce CXCL16 in response to TNFΑ in vitro, suggesting that CXCL16 protein may function in large part independently of TNFΑ. Conclusion Taken together, these results point to a unique role for CXCL16 as a premier MNC recruiter in RA and suggest additional therapeutic possibilities, targeting CXCL16, its receptor, or its signaling pathways.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49514/1/21662_ftp.pd

Imprint of Intergalactic Shocks on the Radio Sky

Strong intergalactic shocks are a natural consequence of structure formation in the universe. They are expected to deposit large fractions of their energy in relativistic electrons (xi_e~0.05 according to SNR observations) and magnetic fields (xi_B~0.01 according to cluster halo observations). We calculate the synchrotron emission from such shocks using an analytical model, calibrated with a hydrodynamical LCDM simulation. The resulting signal composes a large fraction of the extragalactic radio background (ERB) below 500 MHz. The associated angular fluctuations dominate the sky for frequencies nu<10 GHz and angular scales arcmin-deg (after a modest removal of point sources), provided that xi_e*xi_B>3*10^-4. The fluctuating signal is most pronounced for nu<500 MHz, dominating the sky even for xi_e*xi_B=5*10^-5. The signal will be easily observable by next generation radio telescopes such as LOFAR and SKA, and is marginally observable with present telescopes. It may be identified using cross-correlations with tracers of large scale structure, possibly even in existing <10 GHz CMB anisotropy maps and high resolution ~1 GHz radio surveys. Detection of the signal will provide the first identification of intergalactic shocks and of the WHIM, and gauge the unknown intergalactic magnetic field. We show that existing observations of the diffuse <500 MHz radio background are well fit by a simple, double-disk Galactic model, precluding a direct identification of the diffuse ERB. Modelling the frequency-dependent anisotropy pattern observed at very low (1-10 MHz) frequencies can disentangle the distributions of Galactic cosmic-rays, ionized gas and magnetic fields. Space missions such as ALFA will thus provide important insight into the structure and composition of our Galaxy (abridged).Comment: Accepted for publication in ApJ. Presentation improved and references adde

The Mirror of Anarchy: The Egoism of John Henry Mackay and Dora Marsden

The mirror of anarchy: the egoism of John Henry Mackay and Dora Marsde