5,391 research outputs found
Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field
The magnetic response of irreversible type-II superconductor slabs subjected
to in-plane rotating magnetic field is investigated by applying the circular,
elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state
models. Specifically, the models have been applied to explain experiments on a
PbBi rotating disk in a fixed magnetic field , parallel to the flat
surfaces. Here, we have exploited the equivalency of the experimental situation
with that of a fixed disk under the action of a parallel magnetic field,
rotating in the opposite sense. The effect of both the magnitude of the
applied magnetic field and its angle of rotation upon the
magnetization of the superconductor sample is analyzed. When is smaller
than the penetration field , the magnetization components, parallel and
perpendicular to , oscillate with increasing the rotation angle. On
the other hand, if the magnitude of the applied field, , is larger than
, both magnetization components become constant functions of at
large rotation angles. The evolution of the magnetic induction profiles inside
the superconductor is also studied.Comment: 12 pages, 29 figure
Morphological and geological features of Drake Passage, Antarctica, from a new digital bathymetric model
The Drake Passage is an oceanic gateway of about 850 km width located between South America
and the Antarctic Peninsula that connects the southeastern Pacific Ocean with the southwestern
Atlantic Ocean. It is an important gateway for mantle flow, oceanographic water masses, and
migrations of biota. This sector developed within the framework of the geodynamic evolution of
the Scotia Arc, including continental fragmentation processes and oceanic crust creation, since
the oblique divergence of the South American plate to the north and the Antarctic plate to the
south started in the Eocene. As a consequence of its complex tectonic evolution and subsequent
submarine processes, as sedimentary infill and erosion mainly controlled by bottom currents and
active tectonics, this region shows a varied physiography. We present a detailed map of the
bathymetry and geological setting of the Drake Passage that is mainly founded on a new
compilation of precise multibeam bathymetric data obtained on 120 cruises between 1992 and
2015, resulting in a new Digital Bathymetric Model with 200 × 200 m cell spacing. The map
covers an area of 1,465,000 km2 between parallels 52°S and 63°S and meridians 70°W and 50°W
at scale 1:1,600,000 allowing the identification of the main seafloor features. In addition, the map
includes useful geological information related to magnetism, seismicity and tectonics. This work
constitutes an international cooperative effort and is part of the International Bathymetric Chart
of the Southern Ocean project, under the Scientific Committee on Antarctic Research umbrella.This work was supported through projects CTM2014-
60451-C2-02/01, CTM2017-89711-C2-2/1-P and special
action CTM2011-13970-E from “Ministerio de Ciencia,
Innovación y Universidades” of Spain
Diatom Proteomics Reveals Unique Acclimation Strategies to Mitigate Fe Limitation
Phytoplankton growth rates are limited by the supply of iron (Fe) in approximately one third of the open ocean, with major implications for carbon dioxide sequestration and carbon (C) biogeochemistry. To date, understanding how alteration of Fe supply changes phytoplankton physiology has focused on traditional metrics such as growth rate, elemental composition, and biophysical measurements such as photosynthetic competence (Fv/Fm). Researchers have subsequently employed transcriptomics to probe relationships between changes in Fe supply and phytoplankton physiology. Recently, studies have investigated longer-term (i.e. following acclimation) responses of phytoplankton to various Fe conditions. In the present study, the coastal diatom, Thalassiosira pseudonana, was acclimated (10 generations) to either low or high Fe conditions, i.e. Fe-limiting and Fe-replete. Quantitative proteomics and a newly developed proteomic profiling technique that identifies low abundance proteins were employed to examine the full complement of expressed proteins and consequently the metabolic pathways utilized by the diatom under the two Fe conditions. A total of 1850 proteins were confidently identified, nearly tripling previous identifications made from differential expression in diatoms. Given sufficient time to acclimate to Fe limitation, T. pseudonana up-regulates proteins involved in pathways associated with intracellular protein recycling, thereby decreasing dependence on extracellular nitrogen (N), C and Fe. The relative increase in the abundance of photorespiration and pentose phosphate pathway proteins reveal novel metabolic shifts, which create substrates that could support other well-established physiological responses, such as heavily silicified frustules observed for Fe-limited diatoms. Here, we discovered that proteins and hence pathways observed to be down-regulated in short-term Fe starvation studies are constitutively expressed when T. pseudonana is acclimated (i.e., nitrate and nitrite transporters, Photosystem II and Photosystem I complexes). Acclimation of the diatom to the desired Fe conditions and the comprehensive proteomic approach provides a more robust interpretation of this dynamic proteome than previous studies.This work was supported by National Science Foundation grants OCE1233014 (BLN) and the Office of Polar Programs Postdoctoral Fellowship grant 0444148 (BLN). DRG was supported by National Institutes of Health 5P30ES007033-10. AH and MTM were supported by Natural Sciences and Engineering Research Council of Canada. RFS and PWB were supported by the New Zealand Royal Society Marsden Fund and the Ministry of Science. This work is supported in part by the University of Washington's Proteomics Computer Resource Centre (UWPR95794). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Just Keep Tweeting: Emergency Responder\u27s Social Media Use Before and During Emergencies
This study investigates how emergency response organizations use social media during emergency preparedness and response. Using qualitative (interviews and documents) and quantitative (Facebook posts) data, the study identifies several uses of social media in emergency preparedness and emergency management, as well as the organizational context that affects this use. Findings indicate that social media support various purposes of use, including information dissemination, obtaining input from the public and other organizations, and participation by other emergency response organizations. Branding of the organization during the emergency preparedness phase was found to be an important aspect of information dissemination, and helps social media to be useful tool to connect with the public and other organizations during the emergency response phase. Nevertheless, social media use in the emergency response domain still has to overcome leadership and staff adoption barriers
Coordinated X-ray and Optical observations of Star-Planet Interaction in HD 17156
The large number of close-in Jupiter-size exoplanets prompts the question
whether star-planet interaction (SPI) effects can be detected. We focused our
attention on the system HD 17156, having a Jupiter-mass planet in a very
eccentric orbit. Here we present results of the XMM-Newton observations and of
a five months coordinated optical campaign with the HARPS-N spectrograph. We
observed HD 17156 with XMM-Newton when the planet was approaching the apoastron
and then at the following periastron passage, quasi simultaneously with
HARPS-N. We obtained a clear () X-ray detection only at the
periastron visit, accompanied by a significant increase of the
chromospheric index. We discuss two possible scenarios for the activity
enhancement: magnetic reconnection and flaring or accretion onto the star of
material tidally stripped from the planet. In any case, this is possibly the
first evidence of a magnetic SPI effect caught in action
PReS-FINAL-2280: Lupus disease activity in a pediatric Colombian cohort with systemic lupus erytematosus
In vitro regeneration of Calophyllum brasiliense Cambess: A valuable medicinal tree
Calophyllum brasiliense (Calophyllaceae) is a medicinal tree known mainly for producing calanolides, secondary metabolites against HIV-1 reverse transcriptase. This wild plant is listed as threatened and despite its outstanding medicinal value, no studies have been conducted on its propagation or preservation. This study standardized a procedure for the micropropagation of C. brasiliense with nodal segments from in vitro seedlings. The in vitro seed germination was 48.6%. The nodal explants displayed a high percentage of shoot induction (77.5%), shoots per segment (6.9), nodes per shoot (3.8), leaves per shoot (8.0) and shoot length (4.2 cm) when 0.5 mg L-1 indole-3-butyric acid plus 0.1 mg L-1 thidiazuron were used. Furthermore, maximum shoot rooting (63.5%) and root length (2.2 cm) were recovered using 1.0 mg L-1 indole-3-acetic acid. More than three-quarters of the acclimatized plants (77.5%) grew successfully in pots. Thus, this study developed an in vitro propagation protocol for C. brasiliense that can be used as a potential resource for restoring wild populations or performing phytopharmacological studies.Key words: Seed germination, plant growth regulators, micropropagation, nodal segments, medicinal plants
Fermion dynamics in torsion theories
In this work we have studied the non-geodesical behaviour of particles with
spin 1/2 in Poincar\'e gauge theories of gravity, via the WKB method and the
Mathisson-Papapetrou equation. We have analysed the relation between the two
approaches and we have argued the different advantages associated with the WKB
approximation. Within this approach, we have calculated the trajectories in a
particular Poincar\'e gauge theory, discussing the viability of measuring such
a motion.Comment: 17 pages, 2 figures, minor changes, conclusions unchanged. It matches
the version published in JCA
Strain balanced quantum posts
Quantum posts are assembled by epitaxial growth of closely spaced quantum dot
layers, modulating the composition of a semiconductor alloy, typically InGaAs.
In contrast with most self-assembled nanostructures, the height of quantum
posts can be controlled with nanometer precision, up to a maximum value limited
by the accumulated stress due to the lattice mismatch. Here we present a strain
compensation technique based on the controlled incorporation of phosphorous,
which substantially increases the maximum attainable quantum post height. The
luminescence from the resulting nanostructures presents giant linear
polarization anisotropy.Comment: Submitted to Applied Physics Letters (7th March 2011). 4 pages, 4
figure
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