3,509 research outputs found
Cluster spacecraft observations of a ULF wave enhanced by Space Plasma Exploration by Active Radar (SPEAR)
Space Plasma Exploration by Active Radar (SPEAR) is a high-latitude ionospheric heating facility capable of exciting ULF waves on local magnetic field lines. We examine an interval from 1 February 2006 when SPEAR was transmitting a 1 Hz modulation signal with a 10 min on-off cycle. Ground magnetometer data indicated that SPEAR modulated currents in the local ionosphere at 1 Hz, and enhanced a natural field line resonance with a 10 min period. During this interval the Cluster spacecraft passed over the heater site. Signatures of the SPEAR-enhanced field line resonance were present in the magnetic field data measured by the magnetometer on-board Cluster-2. These are the first joint ground- and space-based detections of field line tagging by SPEAR
Changes in intracellular ion activities induced by adrenaline in human and rat skeletal muscle
To study the stimulating effect of adrenaline (ADR) on active Na+/K+ transport we used double-barrelled ion-sensitive micro-electrodes to measure the activities of extracellular K+ (aKe) and intracellular Na+ (aNai) in isolated preparations of rat soleus muscle, normal human intercostal muscle and one case of hyperkalemic periodic paralysis (h.p.p.). In these preparations bath-application of ADR (10−6 M) resulted in a membrane hyperpolarization and transient decreasesaKe andaNai which could be blocked by ouabain (3×10−4 M). In the h.p.p. muslce a continuous rise ofaNai induced by elevation ofaKe to 5.2 mM could be stopped by ADR. In addition, the intracellular K+ activity (aKi), the free intracellular Ca2+ concentration (pCai) and intracellular pH (pHi) were monitored in rat soleus muscle. During ADRaKi increased, pHi remained constant and intracellular Ca2+ apparently decreased. In conclusion, our data show that ADR primarily stimulates the Na+/K+ pump in mammalian skeletal muscle. This stimulating action is not impaired in the h.p.p. muscle
Fossil Mobiles: Exploring the Process of Art as Science Inquiry for Elementary Students through a Grounded Theory Study
Arts integration into Science, Technology, Engineering, and Mathematics (STEM) subject areas is currently an important area of investigation. This study developed a grounded theory of how artmaking of a mobile related to fossil life of the Devonian period engendered geoscience inquiry. Data were collected from elementary students entering fourth to sixth grade (7 male, 9 female) attending a week-long summer camp at a Midwestern university. Students engaged in a daily hour-long class creating fossil mobiles and learning geoscience content through illustrated slide shows, form and function sets of materials related to Devonian fossils, fossil books, and a fossil hunter- fossil find matching game. The art fossil mobile was constructed of painted dowel rods suspended from a beaded string with four craft fossils (traced onto clear plastic and back-painted or stenciled onto canvas) attached to the ends of the rods. The grounded theory research design identified seven major repeating interactions among the triad of art, science, and students: (1) art promoting science inquiry, (2) art aspects positively influencing science learning, (3) science learning increasing interest in fossils, (4) science influencing art, (5) student-centered artwork increasing desire for more art knowledge, (6) student-centered art providing connections to science, and (7) student-centered science increasing interest in fossils. Implications for educators include integrating art activities into science lessons, thereby providing engagement and motivation for students, supporting students’ fine motor skills development, and building a community of learners. Geoscience educators should consider the positive cyclical effects of art-science-student interactions identified in this study
Impacts of Extension Education on Improving Residential Stormwater Quality: Monitoring Results
The project reported in this article evaluated whether stormwater quality could be improved by educating homeowners and implementing best management practices in a suburban neighborhood. Nitrogen, phosphorus, and bacteria levels from two watersheds were compared using the paired watershed approach. Resident surveys, property site assessments, soil tests, and water quality and quantity monitoring were conducted. A x2-analysis of survey data indicated no significant changes in measured behavior. Significant (p=0.01) reductions in NO3-N and fecal coliform bacteria concentrations occurred; however, total nitrogen concentrations did not change significantly
Engineered nonlinear lattices
We show that with the quasi-phase-matching technique it is possible to fabricate stripes of nonlinearity that trap and guide light like waveguides. We investigate an array of such stripes and find that when the stripes are sufficiently narrow, the beam dynamics is governed by a quadratic nonlinear discrete equation. The proposed structure therefore provides an experimental setting for exploring discrete effects in a controlled manner. In particular, we show propagation of breathers that are eventually trapped by discreteness. When the stripes are wide the beams evolve in a structure we term a quasilattice, which interpolates between a lattice system and a continuous system.Peer ReviewedPostprint (published version
Brorfelde Schmidt CCD Catalog (BSCC)
The Brorfelde Schmidt CCD Catalog (BSCC) contains about 13.7 million stars,
north of +49 deg Declination with precise positions and V, R photometry. The
catalog has been constructed from the reductions of 18,667 CCD frames observed
with the Brorfelde Schmidt Telescope between 2000 and 2007. The Tycho-2 catalog
was used for astrometric and photometric reference stars. Errors of individual
positions are about 20 to 200 mas for stars in the R = 10 to 18 mag range.
External comparisons with 2MASS and SDSS reveal possible small systematic
errors in the BSCC of up to about 30 mas. The catalog is supplemented with J,
H, and K_s magnitudes from the 2MASS catalog. The catalog data file (about 550
MB ASCII, compressed) will be made available at the Strasbourg Data Center
(CDS).Comment: 16 pages, 22 figures, 2 tables, accepted by A
Chest computed tomography findings in HIV-infected individuals in the era of antiretroviral therapy
Background: Chest radiographic abnormalities were common in HIV-infected individuals in the pre-combination antiretroviral therapy era, but findings may differ now due to a changing spectrum of pulmonary complications. Copyright
Predicting local adaptation in fragmented plant populations: Implications for restoration genetics
Understanding patterns and correlates of local adaptation in heterogeneous landscapes can provide important information in the selection of appropriate seed sources for restoration. We assessed the extent of local adaptation of fitness components in 12 population pairs of the perennial herb Rutidosis leptorrhynchoides (Asteraceae) and examined whether spatial scale (0.7-600 km), environmental distance, quantitative (QST) and neutral (FST) genetic differentiation, and size of the local and foreign populations could predict patterns of adaptive differentiation. Local adaptation varied among populations and fitness components. Including all population pairs, local adaptation was observed for seedling survival, but not for biomass, while foreign genotype advantage was observed for reproduction (number of inflorescences). Among population pairs, local adaptation increased with QST and local population size for biomass. QST was associated with environmental distance, suggesting ecological selection for phenotypic divergence. However, low FST and variation in population structure in small populations demonstrates the interaction of gene flow and drift in constraining local adaptation in R. leptorrhynchoides. Our study indicates that for species in heterogeneous landscapes, collecting seed from large populations from similar environments to candidate sites is likely to provide the most appropriate seed sources for restoration
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