750 research outputs found
Characterististics of plage fragments with photospheric network properties
Using data taken with the multi-channel magnetograph at KPNO, we demonstrate that plage regions surrounding a sunspot have thermal properties found in the photospheric network. These network-like regions existed up to the edge of the penumbra of the sunspot. Temperature gradients inferred from equivalent width fluctuations in our data do not conflict with the requirements of the theory (Parker, 1978) for flux tubes to exist at subphotospheric levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43752/1/11207_2004_Article_BF00146679.pd
Microbial Communities Under Distinct Thermal and Geochemical Regimes in Axial and Off-Axis Sediments of Guaymas Basin
Cold seeps and hydrothermal vents are seafloor habitats fueled by subsurface energy sources. Both habitat types coexist in Guaymas Basin in the Gulf of California, providing an opportunity to compare microbial communities with distinct physiologies adapted to different thermal regimes. Hydrothermally active sites in the southern Guaymas Basin axial valley, and cold seep sites at Octopus Mound, a carbonate mound with abundant methanotrophic cold seep fauna at the Central Seep location on the northern off-axis flanking regions, show consistent geochemical and microbial differences between hot, temperate, cold seep, and background sites. The changing microbial actors include autotrophic and heterotrophic bacterial and archaeal lineages that catalyze sulfur, nitrogen, and methane cycling, organic matter degradation, and hydrocarbon oxidation. Thermal, biogeochemical, and microbiological characteristics of the sampling locations indicate that sediment thermal regime and seep-derived or hydrothermal energy sources structure the microbial communities at the sediment surface
Capgras Syndrome: A Novel Probe for Understanding the Neural Representation of the Identity and Familiarity of Persons
Patients with Capgras syndrome regard people whom they know well such as their parents or siblings as imposters. Here we describe a case (DS) of this syndrome who presents several novel features. DS was unusual in that his delusion was modality-specific: he claimed that his parents were imposters when he was looking at them but not when speaking to them on the telephone. Unlike normals, DS's skin conductance responses to photographs of familiar people, including his parents, were not larger in magnitude than his responses to photographs of unfamiliar people. We suggest that in this patient connections from face-processing areas in the temporal lobe to the limbic system have been damaged, a loss which may explain why he calls his parents imposters. In addition, DS was very poor at judging gaze direction. Finally, when presented with a sequence of photographs of the same model's face looking in different directions, DS asserted that they were "different women who looked just like each other'. In the absence of limbic activation, DS creates separate memory "files' of the same person, apparently because he is unable to extract and link the common denominator of successive episodic memories. Thus, far from being a medical curiosity. Capgras syndrome may help us to explore the formation of new memories caught in flagrante delicto
Anisotropic spin freezing in the S=1/2 zigzag ladder compound SrCuO2
Using magnetic neutron scattering we characterize an unusual low temperature
phase in orthorhombic SrCuO2. The material contains zigzag spin ladders formed
by pairs of S=1/2 chains (J=180 meV) coupled through a weak frustrated
interaction |J'|<0.1J. At T<Tc1=5.0(4)K an elastic peak develops in a gapless
magnetic excitation spectrum indicating spin freezing on a time scale larger
than 200 picoseconds. While the frozen state has long range commensurate
antiferromagnetic order along the chains with the correlation length exceeding
200 lattice periods along the c-axis and a substantial correlation length of
60(25) spacings along the a-axis perpendicular to the zigzag plane, only 2
lattice units are correlated along the b-axis which is the direction of the
frustrated interactions. The frozen magnetic moment of each Cu ion is very
small, 0.033(7) Bohr magneton even at T=0.35K, and has unusual temperature
dependence with a cusp at Tc2=1.5K reminiscent of a phase transition. We argue
that slow dynamics of stripe-like cooperative magnetic defects in tetragonal
a-c planes yield this anisotropic frozen state.Comment: 4 pages, LaTeX, submitted to PR
Heat transport by lattice and spin excitations in the spin chain compounds SrCuO_2 and Sr_2CuO_3
We present the results of measurements of the thermal conductivity of the
quasi one-dimensional spin S=1/2 chain compound SrCuO_2 in the temperature
range between 0.4 and 300 K along the directions parallel and perpendicular to
the chains. An anomalously enhanced thermal conductivity is observed along the
chains. The analysis of the present data and a comparison with analogous recent
results for Sr_2CuO_3 and other similar materials demonstrates that this
behavior is generic for cuprates with copper-oxygen chains and strong
intrachain interactions. The observed anomalies are attributed to the
one-dimensional energy transport by spin excitations (spinons), limited by the
interaction between spin and lattice excitations. The energy transport along
the spin chains has a non-diffusive character, in agreement with theoretical
predictions for integrable models.Comment: 12 pages (RevTeX), 8 figure
Haematopoietic stem cell migration to the ischemic damaged kidney is not altered by manipulating the SDF-1/CXCR4-axis
Background. Haematopoietic stem cells (HSC) have been shown to migrate to the ischemic kidney. The factors that regulate the trafficking of HSC to the ischemic damaged kidney are not fully understood. The stromal cell-derived factor-1 (SDF-1)/CXCR4-axis has been identified as the central signalling axis regulating trafficking of HSC to the bone marrow. Therefore, we hypothesized that SDF-1/CXCR4 interactions are implicated in the migration of HSC to the injured kidney
Deep-sea hydrothermal vent sediments reveal diverse fungi with antibacterial activities
Relatively little is known about the diversity of fungi in deep-sea, hydrothermal sediments. Less thoroughly explored environments are likely untapped reservoirs of unique biodiversity with the potential to augment our current arsenal of microbial compounds with biomedical and/or industrial applications. In this study, we applied traditional culture-based methods to examine a subset of the morphological and phylogenetic diversity of filamentous fungi and yeasts present in 11 hydrothermally influenced sediment samples collected from eight sites on the seafloor of Guaymas Basin, Mexico. A total of 12 unique isolates affiliating with Ascomycota and Basidiomycota were obtained and taxonomically identified on the basis of morphological features and analyses of marker genes including actin, β-tubulin, small subunit ribosomal DNA (18S rRNA), internal transcribed spacer (ITS) and large subunit ribosomal DNA (26S rRNA) D1/D2 domain sequences (depending on taxon). A total of 11 isolates possess congeners previously detected in, or recovered from, deep-sea environments. A total of seven isolates exhibited antibacterial activity against human bacterial pathogens Staphylococcus aureus ATCC-35556 and/or Escherichia coli ATCC-25922. This first investigation suggests that hydrothermal environments may serve as promising reservoirs of much greater fungal diversity, some of which may produce biomedically useful metabolites
Soft solar X-rays and solar activity
Soft solar X-rays in the wavelength interval 8–12 Å were observed from OSO III. The totality of the observations that were made between 9 March, 1967, and 18 May, 1968, is summarized graphically and compared to the course of solar activity as observed at other wavelengths, with particular emphasis upon visible activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43715/1/11207_2004_Article_BF00146064.pd
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