6,270 research outputs found
Na/K pump regulation of cardiac repolarization: Insights from a systems biology approach
The sodium-potassium pump is widely recognized as the principal mechanism for active ion transport across the cellular membrane of cardiac tissue, being responsible for the creation and maintenance of the transarcolemmal sodium and potassium gradients, crucial for cardiac cell electrophysiology. Importantly, sodium-potassium pump activity is impaired in a number of major diseased conditions, including ischemia and heart failure. However, its subtle ways of action on cardiac electrophysiology, both directly through its electrogenic nature and indirectly via the regulation of cell homeostasis, make it hard to predict the electrophysiological consequences of reduced sodium-potassium pump activity in cardiac repolarization. In this review, we discuss how recent studies adopting the Systems Biology approach, through the integration of experimental and modeling methodologies, have identified the sodium-potassium pump as one of the most\ud
important ionic mechanisms in regulating key properties of cardiac repolarization and its rate-dependence, from subcellular to whole organ levels. These include the role of the pump in the biphasic modulation of cellular repolarization and refractoriness, the rate control of intracellular sodium and calcium dynamics and therefore of the adaptation of repolarization to changes in heart rate, as well as its importance in regulating pro-arrhythmic substrates through modulation of dispersion of repolarization and restitution. Theoretical findings are consistent across a variety of cell types and species including human, and widely in agreement with experimental findings. The novel insights and hypotheses on the role of the pump in cardiac electrophysiology obtained through this integrative approach could eventually lead to novel therapeutic and diagnostic strategies
Observations of solar scattering polarization at high spatial resolution
The weak, turbulent magnetic fields that supposedly permeate most of the
solar photosphere are difficult to observe, because the Zeeman effect is
virtually blind to them. The Hanle effect, acting on the scattering
polarization in suitable lines, can in principle be used as a diagnostic for
these fields. However, the prediction that the majority of the weak, turbulent
field resides in intergranular lanes also poses significant challenges to
scattering polarization observations because high spatial resolution is usually
difficult to attain. We aim to measure the difference in scattering
polarization between granules and intergranules. We present the respective
center-to-limb variations, which may serve as input for future models. We
perform full Stokes filter polarimetry at different solar limb positions with
the CN band filter of the Hinode-SOT Broadband Filter Imager, which represents
the first scattering polarization observations with sufficient spatial
resolution to discern the granulation. Hinode-SOT offers unprecedented spatial
resolution in combination with high polarimetric sensitivity. The CN band is
known to have a significant scattering polarization signal, and is sensitive to
the Hanle effect. We extend the instrumental polarization calibration routine
to the observing wavelength, and correct for various systematic effects. The
scattering polarization for granules (i.e., regions brighter than the median
intensity of non-magnetic pixels) is significantly larger than for
intergranules. We derive that the intergranules (i.e., the remaining
non-magnetic pixels) exhibit (9.8 \pm 3.0)% less scattering polarization for
0.2<u<0.3, although systematic effects cannot be completely excluded. These
observations constrain MHD models in combination with (polarized) radiative
transfer in terms of CN band line formation, radiation anisotropy, and magnetic
fields.Comment: Accepted for publication in A&
First test of a high voltage feedthrough for liquid Argon TPCs connected to a 300 kV power supply
Voltages above a hundred kilo-volt will be required to generate the drift
field of future very large liquid Argon Time Projection Chambers. The most
delicate component is the feedthrough whose role is to safely deliver the very
high voltage to the cathode through the thick insulating walls of the cryostat
without compromising the purity of the argon inside. This requires a
feedthrough that is typically meters long and carefully designed to be vacuum
tight and have small heat input. Furthermore, all materials should be carefully
chosen to allow operation in cryogenic conditions. In addition, electric fields
in liquid argon should be kept below a threshold to reduce risks of discharges.
The combination of all above requirements represents significant challenges
from the design and manufacturing perspective. In this paper, we report on the
successful operation of a feedthrough satisfying all the above requirements.
The details of the feedthrough design and its manufacturing steps are provided.
Very high voltages up to unprecedented voltages of -300 kV could be applied
during long periods repeatedly. A source of instability was observed, which was
specific to the setup configuration which was used for the test and not due to
the feedthrough itself.Comment: 13 pages, 9 figure
Noções sobre a teoria de vigotsky e observações sobre o professor como mediador: uma experiência vivenciada no PIBID
Anais do II Seminário Seminário Estadual PIBID do Paraná: tecendo saberes / organizado por Dulcyene Maria Ribeiro e Catarina Costa Fernandes — Foz do Iguaçu: Unioeste; Unila, 2014Este texto tem por finalidade discutir sobre algumas ideias da teoria de Vigotsky acerca da
formação de conceitos, bem como relatar uma experiência vivenciada em uma escola da rede
municipal pública do município de Guarapuava Paraná, a partir da participação no Programa
Institucional de Bolsas de Iniciação a Docência PIBID/CAPES/DEB, no Curso de Pedagogia, cujo
subprojeto é focado na Alfabetizaçã
Evaluation of insecticides for the control of Linepithema Micans (Hymenoptera: Formicidae).
Linepithema micans (Forel) (Hymenoptera: Formicidae) is the main ant species responsible for the spreading of Eurhizococcus brasiliensis (Wille) (Hemiptera: Margarodidae), a soil scale that damages grapevine plants in southern Brazil. The effect of contact and ingestion of insecticides on the control of L. micans was evaluated in a greenhouse using grapevines (Vitis spp.) infested by L. micans. The insecticides thiamethoxam (250, 187.5, and 125 g/ha), Þpronil (4, 5, and 50 ml/ha), and imidacloprid (650 g/ha) were sprayed on the ground, whereas toxic baits containing boric acid (0.5, 1.0, and 1.2%), pyriproxyfen (0.3 and 0.5%), and hydramethylnon (0.5%) were evaluated in different formulations. Hydramethylnon (toxic bait) and thiamethoxam (chemical barrier) were the most efÞcient active ingredients for the control of L. micans
Lepidopteran larva consumption of soybean foliage: basis for developing multiple-species economic thresholds for pest management decisions.
BACKGROUND: Defoliation by Anticarsia gemmatalis (H ¨ ubner), Pseudoplusia includens (Walker), Spodoptera eridania (Cramer), S. cosmioides (Walker) and S. frugiperda (JE Smith) (Lepidoptera: Noctuidae) was evaluated in four soybean genotypes. A multiple-species economic threshold (ET), based upon the species? feeding capacity, is proposed with the aim of improving growers? management decisions on when to initiate control measures for the species complex. RESULTS: Consumption by A. gemmatalis, S. cosmioides or S. eridania on different genotypes was similar. The highest consumption of P. includens was 92.7 cm2 on Codetec 219RR; that of S. frugiperda was 118 cm2 on Codetec 219RR and 115.1 cm2 on MSoy 8787RR. The insect injury equivalent for S. cosmoides, calculated on the basis of insect consumption, was double the standard consumption by A. gemmatalis, and statistically different from the other species tested, which were similar to each other. CONCLUSIONS: As S. cosmioides always defoliated nearly twice the leaf area of the other species, the injury equivalent would be 2 for this lepidopteran species and 1 for the other species. The recommended multiple-species ET to trigger the beginning of insect control would then be 20 insect equivalents per linear metre
Contribuição de espécies florestais para fins energéticos sobre algumas características químicas de um podzólico amarelo impactado por usos anteriores no município de Iranduba-AM.
O objetivo desse trabalho e selecionar especies nativas e/ou exoticas com potencial para produzir lenha e derivados, e estudar tecnicas de manejo adequadas a implantacao de producao de lenha em plantios ordenados.bitstream/CPAA-2009-09/6300/1/IT_11_2000.pd
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