4,115 research outputs found
The Spectroscopic Orbits of Five Solar Type, Single Lined Binaries
We have determined spectroscopic orbits for five single-lined spectroscopic
binaries, HD 100167, HD 135991, HD 140667, HD 158222, HD 217924. Their periods
range from 60.6 to 2403 days and the eccentricities, from 0.20 to 0.84. Our
spectral classes for the stars confirm that they are of solar type, F9 to G5,
and all are dwarfs. Their [Fe/H] abundances, determined spectroscopically, are
close to the solar value and on average are 0.12 greater than abundances from a
photometric calibration. Four of the five stars are rotating faster than their
predicted pseudosynchronous rotational velocities.Comment: 12 pages emulateap
Residual Stress Distributions in Arc, Laser and Electron-Beam Welds in 30 mm Thick SA508 Steel:A Cross-Process Comparison
Control via electron count of the competition between magnetism and superconductivity in cobalt and nickel doped NaFeAs
Using a combination of neutron, muon and synchrotron techniques we show how
the magnetic state in NaFeAs can be tuned into superconductivity by replacing
Fe by either Co or Ni. Electron count is the dominant factor, since Ni-doping
has double the effect of Co-doping for the same doping level. We follow the
structural, magnetic and superconducting properties as a function of doping to
show how the superconducting state evolves, concluding that the addition of 0.1
electrons per Fe atom is sufficient to traverse the superconducting domain, and
that magnetic order coexists with superconductivity at doping levels less than
0.025 electrons per Fe atom.Comment: 4 pages, 6 figure
Brain Activation Patterns during Visual Scene Encoding and Recognition fMRI Tasks in Early Phase Psychosis
poster abstractSchizophrenia is a chronic and disabling illness that is associated with significant impairments in areas such as independent living, social functioning, and vocational functioning. Cognitive dysfunction is a core facet of schizophrenia with deficits occurring in areas of abstraction, attention, language, and memory. Episodic memory (EM) is a cognitive domain that has been shown to be impaired in schizophrenia. EM combines event-specific autobiographical experiences and information regarding the context in which events took place. Patients with schizophrenia may exhibit broad impairments in EM, with deficits occurring during encoding and retrieval with both visual and verbal tasks. There are a number of inconsistencies in the EM fMRI literature and indicating a need for first episode psychosis (FEP) versus chronic phase schizophrenia research. FEP have fewer and less severe medical comorbidities, shorter durations of antipsychotic treatment exposure, and lower severity of illness, all of which can impact data interpretation. In this study, brain activation patterns were assessed during performance of visual scene encoding and recognition fMRI tasks in FEP patients and healthy control subjects. It is hypothesized that FEP patients would demonstrate decreased activation during encoding and recognition in the main areas that mediate EM function, namely the hippocampus, prefrontal, and parietal cortices. Within the FEP group correlations can be determined by comparing brain activation patterns with cognition (Brief Assessment of Cognition in Schizophrenia [BACS]) and symptom (Positive and Negative Syndrome Scale [PANSS]) outcome measures. Results indicate that during the encoding task FEP exhibited significantly lower activation in the hippocampus and fusiform gyrus when compared to controls. During the recognition task FEP showed a significantly weaker cortical response in the posterior cingulate cortex, the precuneus, and the left middle temporal cortex when compared to controls. These results demonstrate a pattern of alteration in hippocampal, parietal, and temporal activity during EM processes in FEP. Altered hippocampal response in FEP may reflect dysfunctional binding mechanisms and less efficient encoding
A breathing zirconium metal-organic framework with reversible loss of crystallinity by correlated nanodomain formation
The isoreticular analogue of the metal-organic framework UiO-66(Zr), synthesized with the flexible trans-1,4-cyclohexanedicarboxylic acid as linker, shows a peculiar breathing behavior by reversibly losing long-range crystalline order upon evacuation. The underlying flexibility is attributed to a concerted conformational contraction of up to two thirds of the linkers, which breaks the local lattice symmetry. X-ray scattering data are described well by a nanodomain model in which differently oriented tetragonal-type distortions propagate over about 7-10 unit cells
The Spectra of Red Quasars
We measure the spectral properties of a representative sub-sample of 187
quasars, drawn from the Parkes Half-Jansky, Flat-radio-spectrum Sample (PHFS).
Quasars with a wide range of rest-frame optical/UV continuum slopes are
included in the analysis: their colours range from 2 < B-K < 7.
The median H-beta and [O III] emission-line equivalent widths of the red
quasar sub-sample are a factor of ten weaker than those of the blue quasar
sub-sample. Both the colours and the emission-line equivalent widths of the red
quasars can be explained by the addition of a featureless red synchrotron
continuum component to an otherwise normal blue quasar spectrum. The relative
strengths of the blue and red components span two orders of magnitude at
rest-frame 500nm. The blue component is weaker relative to the red component in
low optical luminosity sources. This suggests that the fraction of accretion
energy going into optical emission from the jet is greater in low luminosity
quasars.
This synchrotron model does not, however, fit around 10% of the quasars,
which have both red colours and high equivalent width emission-lines. We
hypothesise that these red, strong-lined quasars have intrinsically weak Big
Blue Bumps.
There is no discontinuity in spectral properties between the BL Lac objects
in our sample and the other quasars. The synchrotron emission component only
dominates the spectrum at longer wavelengths, so existing BL Lac surveys will
be biassed against high redshift objects.Comment: 22 pages, 12 figures, accepted for publication in PASA. Data tables
and composite spectra from the paper can be found at
http://msowww.anu.edu.au/~pfrancis
Metacognition in Early Phase Psychosis: Toward Understanding Neural Substrates
Individuals in the early phases of psychotic illness have disturbed metacognitive capacity, which has been linked to a number of poor outcomes. Little is known, however, about the neural systems associated with metacognition in this population. The purpose of this study was to elucidate the neuroanatomical correlates of metacognition. We anticipated that higher levels of metacognition may be dependent upon gray matter density (GMD) of regions within the prefrontal cortex. Examining whole-brain structure in 25 individuals with early phase psychosis, we found positive correlations between increased medial prefrontal cortex and ventral striatum GMD and higher metacognition. These findings represent an important step in understanding the path through which the biological correlates of psychotic illness may culminate into poor metacognition and, ultimately, disrupted functioning. Such a path will serve to validate and promote metacognition as a viable treatment target in early phase psychosis
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