Microscopic Description of Deeply Virtual Compton Scattering off Spin-0 Nuclei

We evaluate within a microscopic calculation the contributions of both coherent and incoherent deeply virtual Compton scattering from a spin-0 nucleus. The coherent contribution is obtained when the target nucleus recoils as a whole, whereas for incoherent scattering break-up configurations for the final nucleus into a an outgoing nucleon and an $A-1$ system are considered. The two processes encode different characteristics of generalized parton distributions.Comment: 7 pages, 3 figure

Cerenkov counters for high energy nuclei: Some new developments

A method to determine with gas Cerenkov counters the Lorentz factor, gamma = E/mc, of cosmic ray nuclei with high accuracy over the range gamma approx. 20 to 100 is discussed. The measurement of the Cerenkov emission angle theta, by use of a suitable imaging system is considered. Imaging counters, the ring imaging Cerenkov counters (RICH), were developed for use on accelerators. The image of off-axis particles to determine the amount of image distortion as a function of the direction of the incoming nucleus is examined and an acceptance solid angle, relative to the optical axis, within which the nucleus produces an image with an acceptable level of distortion is defined. The properties of the image, which becomes elliptical, for off-axis particles are analyzed

Nuclear Medium Modifications of Hadrons from Generalized Parton Distributions

We study the structure of generalized parton distributions in spin 0 nuclei within a microscopic approach for nuclear dynamics. GPDs can be used on one side as tools to unravel the deep inelastic transverse structure of nuclei in terms of both transverse spatial and transverse momentum degrees of freedom. On the other, one can obtain information on GPDs themselves by observing how they become modified in the nuclear environment. We derive the structure of the nuclear deeply virtual Compton scattering tensor and generalized parton distributions at leading order in $Q$ in a field-theoretical framework. The nuclear generalized parton distributions are calculated using a two step process -- the convolution approach -- where the scattering process happens from a quark inside a nucleon, itself inside a nucleus, disregarding final state interactions with both the nuclear and nucleon debris. We point out that details of the nuclear long range interactions such as two-body currents, can be disregarded compared to the deep inelastic induced modifications of the bound GPDs. We show how the pattern of nuclear modifications predicted, and in particular the deviations of off-shell effects from the longitudinal convolution provide clear signals to be sought in experimental measurements. Finally, we find interesting relationships by studying Mellin moments in nuclei: in particular we predict the $A$-dependence for the $D$-term of GPDs within a microscopic approach, and the behavior with $t$ of the total momentum carried by quarks in a nucleus. The latter provides an important element for the evaluation of nuclear hadronization phenomena which are vital for interpreting current and future data at RHIC, HERMES and Jefferson Lab.Comment: 29 pages, 10 figure

Indigenous sovereignties: relational ontologies and environmental management

© 2019 Institute of Australian Geographers Indigenous nations have always and continue to assert their sovereignties to resist colonialism. This paper makes explicit the ways in which environmental management has been and continues to act as a tool of colonialism, particularly by privileging Western science, institutions, and administrative procedures. We argue that to decolonise environmental management, it is crucial to understand and challenge the power relations that underlie it—asking who makes decisions and on what worldview those decisions are based. Indigenous ways of being deeply challenge the foundations of environmental management and the colonising power structures that underlie it, and invite further thought about posthuman and relational ontologies. We provide a range of case studies that showcase the role of Indigenous nations in redefining and reimagining environmental management based on Indigenous sovereignties, knowledges, and ways of being. The case studies emphasise the crucial connection between Indigenous decision-making authority and self-governance for the enhanced protection and health of the environment. We argue that Indigenous agency, grounded in Indigenous governance and sovereignties, is driving innovation and decolonising environmental management by making space for new ways of thinking and being “in place”

Solvable senescence model with positive mutations

We build upon our previous analytical results for the Penna model of senescence to include positive mutations. We investigate whether a small but non-zero positive mutation rate gives qualitatively different results to the traditional Penna model in which no positive mutations are considered. We find that the high-lifespan tail of the distribution is radically changed in structure, but that there is not much effect on the bulk of the population. Th e mortality plateau that we found previously for a stochastic generalization of the Penna model is stable to a small positive mutation rate.Comment: 3 figure

Carrier scattering, mobilities and electrostatic potential in mono-, bi- and tri-layer graphenes

The carrier density and temperature dependence of the Hall mobility in mono-, bi- and tri-layer graphene has been systematically studied. We found that as the carrier density increases, the mobility decreases for mono-layer graphene, while it increases for bi-layer/tri-layer graphene. This can be explained by the different density of states in mono-layer and bi-layer/tri-layer graphenes. In mono-layer, the mobility also decreases with increasing temperature primarily due to surface polar substrate phonon scattering. In bi-layer/tri-layer graphene, on the other hand, the mobility increases with temperature because the field of the substrate surface phonons is effectively screened by the additional graphene layer(s) and the mobility is dominated by Coulomb scattering. We also find that the temperature dependence of the Hall coefficient in mono-, bi- and tri-layer graphene can be explained by the formation of electron and hole puddles in graphene. This model also explains the temperature dependence of the minimum conductance of mono-, bi- and tri-layer graphene. The electrostatic potential variations across the different graphene samples are extracted.Comment: 18 pages, 7 figure

Self-reported domain-specific and accelerometer-based physical activity and sedentary behaviour in relation to psychological distress among an urban Asian population

Background: The interpretation of previous studies on the association of physical activity and sedentary behaviour with psychological health is limited by the use of mostly self-reported physical activity and sedentary behaviour, and a focus on Western populations. We aimed to explore the association of self-reported and devise-based measures of physical activity and sedentary behaviour domains on psychological distress in an urban multi-ethnic Asian population. Methods: From a population-based cross-sectional study of adults aged 18-79 years, data were used from an overall sample (n = 2653) with complete self-reported total physical activity/sedentary behaviour and domain-specific physical activity data, and a subsample (n = 703) with self-reported domain-specific sedentary behaviour and accelerometry data. Physical activity and sedentary behaviour data were collected using the Global Physical Activity Questionnaire (GPAQ), a domain-specific sedentary behaviour questionnaire and accelerometers. The Kessler Screening Scale (K6) and General Health Questionnaire (GHQ-12) were used to assess psychological distress. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals, adjusted for socio-demographic and lifestyle characteristics. Results: The sample comprised 45.0% men (median age = 45.0 years). The prevalence of psychological distress based on the K6 and GHQ-12 was 8.4% and 21.7%, respectively. In the adjusted model, higher levels of self-reported moderate-to-vigorous physical activity (MVPA) were associated with significantly higher odds for K6 (OR = 1.47 [1.03-2.10]; p-trend = 0.03) but not GHQ-12 (OR = 0.97 [0.77-1.23]; p-trend = 0.79), when comparing the highest with the lowest tertile. Accelerometry-assessed MVPA was not significantly associated with K6 (p-trend = 0.50) nor GHQ-12 (p-trend = 0.74). The highest tertile of leisure-time physical activity, but not work- or transport-domain activity, was associated with less psychological distress using K6 (OR = 0.65 [0.43-0.97]; p-trend = 0.02) and GHQ-12 (OR = 0.72 [0.55-0.93]; p-trend = 0.01). Self-reported sedentary behaviour was not associated with K6 (p-trend = 0.90) and GHQ-12 (p-trend = 0.33). The highest tertile of accelerometry-assessed sedentary behaviour was associated with significantly higher odds for K6 (OR = 1.93 [1.00-3.75]; p-trend = 0.04), but not GHQ-12 (OR = 1.34 [0.86-2.08]; p-trend = 0.18). Conclusions: Higher levels of leisure-time physical activity and lower levels of accelerometer-based sedentary behaviour were associated with lower psychological distress. This study underscores the importance of assessing accelerometer-based and domain-specific activity in relation to mental health, instead of solely focusing on total volume of activity

Dynamics of the Solar Magnetic Network. II. Heating the Magnetized Chromosphere

We consider recent observations of the chromospheric network, and argue that the bright network grains observed in the Ca II H & K lines are heated by an as yet unidentified quasi-steady process. We propose that the heating is caused by dissipation of short-period magnetoacoustic waves in magnetic flux tubes (periods less than 100 s). Magnetohydrodynamic (MHD) models of such waves are presented. We consider wave generation in the network due to two separate processes: (a) by transverse motions at the base of the flux tube; and (b) by the absorption of acoustic waves generated in the ambient medium. We find that the former mechanism leads to an efficient heating of the chromosphere by slow magnetoacoustic waves propagating along magnetic field lines. This heating is produced by shock waves with a horizontal size of a few hundred kilometers. In contrast, acoustic waves excited in the ambient medium are converted into transverse fast modes that travel rapidly through the flux tube and do not form shocks, unless the acoustic sources are located within 100 km from the tube axis. We conclude that the magnetic network may be heated by magnetoacoustic waves that are generated in or near the flux tubes.Comment: 30 pages, 8 figures, Accepted in Astrophysical Journa