305,417 research outputs found
Multi-line detection of O_2 toward Ï Ophiuchi A
Context. Models of pure gas-phase chemistry in well-shielded regions of molecular clouds predict relatively high levels of molecular oxygen, O_2, and water, H_(2)O. These high abundances imply high cooling rates, leading to relatively short timescales for the evolution of gravitationally unstable dense cores, forming stars and planets. Contrary to expectations, the dedicated space missions SWAS and Odin typically found only very small amounts of water vapour and essentially no O_2 in the dense star-forming interstellar medium.
Aims. Only toward ÏOph â A did Odin detect a very weak line of O_2 at 119 GHz in a beam of size 10 arcmin. The line emission of related molecules changes on angular scales of the order of some tens of arcseconds, requiring a larger telescope aperture such as that of the Herschel Space Observatory to resolve the O2 emission and pinpoint its origin.
Methods. We use the Heterodyne Instrument for the Far Infrared (HIFI) aboard Herschel to obtain high resolution O_2 spectra toward selected positions in the ÏOph A â core. These data are analysed using standard techniques for O_2 excitation and compared to recent PDR-like chemical cloud models.
Results. The N_J = 3_(3) â 1_(2) line at 487.2 GHz is clearly detected toward all three observed positions in the ÏOph A âcore. In addition, an oversampled map of the 5_(4)â3_(4) transition at 773.8 GHz reveals the detection of the line in only half of the observed area. On the basis of their ratios, the temperature of the O_2 emitting gas appears to vary quite substantially, with warm gas (âł 50K) being adjacent to a much colder region, of temperatures lower than 30 K.
Conclusions. The exploited models predict that the O_2 column densities are sensitive to the prevailing dust temperatures, but rather insensitive to the temperatures of the gas. In agreement with these models, the observationally determined O_2 column densities do not seem to depend strongly on the derived gas temperatures, but fall into the range N(O_2) = 3 to âł 6 Ă 10^(15) cm^(-2). Beam-averaged O2 abundances are about 5 Ă 10^(-8) relative to H_2. Combining the HIFI data with earlier Odin observations yields a source size at 119 GHz in the range of 4 to 5 arcmin, encompassing the entire ÏOph A core. We speculate that one of the reasons for the generally very low detection rate of O2 is the short period of time during which O_2 molecules are reasonably abundant in molecular clouds
Implantable RF-coiled chip packaging
In this paper, we present an embedded chip integration
technology that utilizes silicon housings and flexible
parylene radio frequency (RF) coils. As a demonstration
of this technology, a flexible parylene RF coil has been
integrated with an RF identification (RFID) chip. The coil
has an inductance of 16 ÎŒH, with two layers of metal
completely encapsulated in parylene-C. The functionality
of the embedded chip is verified using an RFID reader
module. Accelerated-lifetime soak testing has been
performed in saline, and the results show that the silicon
chip is well protected and the lifetime of our
parylene-encapsulated RF coil at 37 °C is more than 20
years
Correlated Spectral and Temporal Variability in the High-Energy Emission from Blazars
Blazar flare data show energy-dependent lags and correlated variability
between optical/X-ray and GeV-TeV energies, and follow characteristic
trajectories when plotted in the spectral-index/flux plane. This behavior is
qualitatively explained if nonthermal electrons are injected over a finite time
interval in the comoving plasma frame and cool by radiative processes.
Numerical results are presented which show the importance of the effects of
synchrotron self-Compton cooling and plasmoid deceleration. The use of INTEGRAL
to advance our understanding of these systems is discussed.Comment: 8 pages, 5 figures, uses epsf.sty, rotate.sty Invited paper in "The
Extreme Universe," 3rd INTEGRAL Workshop, 14-18 September 1998, Taorimina,
Ital
Optoelectronic control of spin dynamics at near-THz frequencies in magnetically doped quantum wells
We use time-resolved Kerr rotation to demonstrate the optical and electronic
tuning of both the electronic and local moment (Mn) spin dynamics in
electrically gated parabolic quantum wells derived from II-VI diluted magnetic
semiconductors. By changing either the electrical bias or the laser energy, the
electron spin precession frequency is varied from 0.1 to 0.8 THz at a magnetic
field of 3 T and at a temperature of 5 K. The corresponding range of the
electrically-tuned effective electron g-factor is an order of magnitude larger
compared with similar nonmagnetic III-V parabolic quantum wells. Additionally,
we demonstrate that such structures allow electrical modulation of local moment
dynamics in the solid state, which is manifested as changes in the amplitude
and lifetime of the Mn spin precession signal under electrical bias. The large
variation of electron and Mn-ion spin dynamics is explained by changes in
magnitude of the sp−d exchange overlap.Comment: 4 pages, 3 figure
Reward modulates spatial neglect
Copyright @ 2012 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and 85 reproduction in any medium, provided the original author and source are credited. The article was made available through the Brunel University Open Access Publishing Fund.BACKGROUND: Reward has been shown to affect attention in healthy individuals, but there have been no studies addressing whether reward influences attentional impairments in patients with focal brain damage. METHODS: Using two novel variants of a widely-used clinical cancellation task, we assessed whether reward modulated impaired attention in 10 individuals with left neglect secondary to right hemisphere stroke. RESULTS: Reward exposure significantly reduced neglect, as measured by total targets found, left-sided targets found and centre of cancellation, across the patient group. Lesion analysis showed that lack of response to reward was associated with damage to the ipsilateral striatum. CONCLUSIONS: This is the first experimental evidence that reward can modulate attentional impairments following brain damage. These results have significant implications for the development of behavioural and pharmacological therapies for patients with attentional disorders.PM is supported by a HEFCE Clinical Senior Lectureship Award and this research was funded by grants from the UK Academy of Medical Sciences/Wellcome Trust and the NIHR Biomedical Research Centre at Imperial College London. DS is supported by a grant from the UK Medical Research Council (89631). CR is supported by a Brunel Research Initiative Award (BRIEF) and a scientific bursary from the Bial foundation, Portugal
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