289 research outputs found
Disorderly Histories: An Anthropology of Decolonization in Western Sahara
This dissertation situates the disputed geopolitical territory of Western Sahara in a broader, regional history of decolonization. Eschewing the conceptual framework of methodological nationalism, and pushing beyond the period of Moroccan-Sahrawi political conflict, it examines how decolonization has generated multiple, unresolved political projects in this region of the Sahara, dating back to the 1950s. These formations, encompassing southern Morocco, Moroccan-occupied Western Sahara, Sahrawi refugee camps in Algeria, and northern Mauritania, include a zone of militarized occupation, a movement for nation-state sovereignty based in refugee camps, and the borderlands in between. By considering the overlapping processes that emerge through these unresolved political projects, this study considers how the “disorderly histories” of decolonization have produced multiple forms of political space, time and subjectivity in the Sahara, from the late 1950s, through the 1970s, and to today. The ongoing effects of these projects in the Sahara bring several tensions underlying post-World War II political formations – between borders and belonging, dependence and autonomy, sovereignty and international law – into particularly sharp relief
Multidimensional simulations of magnetic field amplification and electron acceleration to near-energy equipartition with ions by a mildly relativistic quasi-parallel plasma collision
The energetic electromagnetic eruptions observed during the prompt phase of
gamma-ray bursts are attributed to synchrotron emissions. The internal shocks
moving through the ultrarelativistic jet, which is ejected by an imploding
supermassive star, are the likely source of this radiation. Synchrotron
emissions at the observed strength require the simultaneous presence of
powerful magnetic fields and highly relativistic electrons. We explore with one
and three-dimensional relativistic particle-in-cell simulations the transition
layer of a shock, that evolves out of the collision of two plasma clouds at a
speed 0.9c and in the presence of a quasi-parallel magnetic field. The cloud
densities vary by a factor of 10. The number densities of ions and electrons in
each cloud, which have the mass ratio 250, are equal. The peak Lorentz factor
of the electrons is determined in the 1D simulation, as well as the orientation
and the strength of the magnetic field at the boundary of the two colliding
clouds. The relativistic masses of the electrons and ions close to the shock
transition layer are comparable as in previous work. The 3D simulation shows
rapid and strong plasma filamentation behind the transient precursor. The
magnetic field component orthogonal to the initial field direction is amplified
in both simulations to values that exceed those expected from the shock
compression by over an order of magnitude. The forming shock is
quasi-perpendicular due to this amplification. The simultaneous presence of
highly relativistic electrons and strong magnetic fields will give rise to
significant synchrotron emissions.Comment: 8 pages, 5 figures. This work was presented at 21st International
Conference on Numerical Simulation of Plasmas (ICNSP'09). Accepted for
publication IEEE Trans. on Plasma Scienc
Global Futures and Government Towns: Phosphates and the Production of Western Sahara as a Space of Contention
The study of natural resources lends itself to theorizing the politics of nature and the politics of time. The space of Western Sahara, where both remain highly contested, provides an opportunity to consider the ramifications of resources in political conflict at different historical moments. Drawing from environmental histories of North Africa and the Sahara, as well as the anthropology of time, the author focuses on two historical moments. The first, from 1945 to 1972, concerns the discovery of phosphate deposits during the Spanish colonial period and the implications of this discovery for political authority in the Sahara more broadly. The second, contemporary moment is characterized by intensifying interest in plotting the future use and reserves of phosphates, with potential implications for the political futures of Western Sahara. These two moments are considered in three parts: the first situates the discovery of phosphates in Western Sahara within the regional process of decolonization; the second considers the configuration and reconfiguration of an urban space, Laâyoune, during these two moments of phosphate production; and the third discusses the contemporary dynamics of determining the future of phosphates in the present
Field amplification, vortex formation, and electron acceleration in a plasma protoshock: effect of asymmetric density profile
Gamma ray bursts (GRBs) are thought to originate from highly relativistic
jets. The fireball model predicts internal shocks in the jets, causing magnetic
field to be amplified and particles to be accelerated. We model the effects of
an asymmetric density configuration for an internal plasma collision in a
quasi-parallel magnetic field. We measured electron acceleration and found that
a tenuous population of electrons is accelerated to Lorentz factors of \sim 300
- close to energy equipartition with ions. We found that the filaments did not
remain static, but were deflected by the Lorentz force and rolled up into small
vortices, which themselves merge to form a larger current vortex.Comment: 4 pages, 5 figures; Procceedings of the workshop "High Energy
Phenomena in Relativistic Outflows III" (HEPRO III), Barcelona, June 27 -
July 1, 201
Recommended from our members
Risk-taking that signals trust increases social identification
ocial identification predicts many important phenomena; however, its determinants have received comparably little research attention. We argue that people are more likely to socially identify with others who engage in risky behavior that implies trust than with those who act cautiously, and test this in four experiments with over 900 participants. The experiments found support for the hypotheses across diverse risk contexts – specifically, risk of physical injury, disease risk, and financial risk. These findings indicate that others’ risk taking can strengthen shared psychological group membership
Effects of Equal Volume But Different Plyometric Jump Training Intensities on Components of Physical Fitness in Physically Active Young Males
Ramirez-Campillo, R, Moran, J, Drury, B, Williams, M, Keogh, JW, Chaabene, H, and Granacher, U. Effects of equal volume but different plyometric jump training intensities on components of physical fitness in physically active young males. J Strength Cond Res XX(X): 000–000, 2019—An 8-week single-blind randomized controlled trial was conducted to compare the effects of separate programs of equal volume, but different intensity, plyometric jump training (PJT), on physical fitness in healthy adults. Thirty-eight physically active males (mean age: 21.8 6 2.5 years) participated. Subjects were randomly assigned to one of 3 PJT groups or a control (CON, n = 9) according to their jump performance. Plyometric jump training was conducted at maximal (PJT-100, n = 10), high (PJT-80, n = 9), or moderate (PJT-65, n = 10) intensity within each group. Baseline and follow-up tests were performed for the assessment of countermovement jump (CMJ) height, CMJ height with arm swing (CMJA), and drop jump height from a 20-cm drop box (DJ20), linear speed (30 m), and change-of-direction speed (CODS) (the Illinois CODS test). Results revealed significant group 3 time interactions for CMJ, CMJA, DJ20, 30-m sprint, and CODS (all p , 0.001; d = 0.39–0.76). Post hoc analyses showed significant improvements in all 5 fitness measures for PJT-100 (all p , 0.01, D3.7–13.5%, d = 0.26–1.4). For PJT-80, 3 of 5 fitness tests demonstrated significant change (CMJ: p , 0.001, D5.9%, d = 0.33; CMJA: p , 0.001, D7.0%, d = 0.43; CODS: p , 0.001, D3.9%, d = 0.9), and for PJT-65, only 1 test was significant (CMJ: p , 0.05, D2.8%, d = 0.15). No significant changes were observed in CON. Except for similar gains in DJ20 and 30-m sprint in PJT-100 and PJT-80, gains in physical fitness were, in general, greater (p , 0.05) after PJT-100 vs. PJT-80 vs. PJT-65 vs. CON. Therefore, maximal PJT intensity may induce larger physical fitness gains, although high and moderate intensities may also be useful, but to a lesser exten
Widespread recombination, reassortment, and transmission of unbalanced compound viral genotypes in natural arenavirus infections.
Arenaviruses are one of the largest families of human hemorrhagic fever viruses and are known to infect both mammals and snakes. Arenaviruses package a large (L) and small (S) genome segment in their virions. For segmented RNA viruses like these, novel genotypes can be generated through mutation, recombination, and reassortment. Although it is believed that an ancient recombination event led to the emergence of a new lineage of mammalian arenaviruses, neither recombination nor reassortment has been definitively documented in natural arenavirus infections. Here, we used metagenomic sequencing to survey the viral diversity present in captive arenavirus-infected snakes. From 48 infected animals, we determined the complete or near complete sequence of 210 genome segments that grouped into 23 L and 11 S genotypes. The majority of snakes were multiply infected, with up to 4 distinct S and 11 distinct L segment genotypes in individual animals. This S/L imbalance was typical: in all cases intrahost L segment genotypes outnumbered S genotypes, and a particular S segment genotype dominated in individual animals and at a population level. We corroborated sequencing results by qRT-PCR and virus isolation, and isolates replicated as ensembles in culture. Numerous instances of recombination and reassortment were detected, including recombinant segments with unusual organizations featuring 2 intergenic regions and superfluous content, which were capable of stable replication and transmission despite their atypical structures. Overall, this represents intrahost diversity of an extent and form that goes well beyond what has been observed for arenaviruses or for viruses in general. This diversity can be plausibly attributed to the captive intermingling of sub-clinically infected wild-caught snakes. Thus, beyond providing a unique opportunity to study arenavirus evolution and adaptation, these findings allow the investigation of unintended anthropogenic impacts on viral ecology, diversity, and disease potential
U.S. Department of Energy Commercial Reference Building Models of the National Building Stock
The U.S. Department of Energy (DOE) Building Technologies Program has set the aggressive goal of producing marketable net-zero energy buildings by 2025. This goal will require collaboration between the DOE laboratories and the building industry. We developed standard or reference energy models for the most common commercial buildings to serve as starting points for energy efficiency research. These models represent fairly realistic buildings and typical construction practices. Fifteen commercial building types and one multifamily residential building were determined by consensus between DOE, the National Renewable Energy Laboratory, Pacific Northwest National Laboratory, and Lawrence Berkeley National Laboratory, and represent approximately two-thirds of the commercial building stock
- …