989 research outputs found
Antifreeze in the hot core of Orion - First detection of ethylene glycol in Orion-KL
Comparison of their chemical compositions shows, to first order, a good
agreement between the cometary and interstellar abundances. However, a complex
O-bearing organic molecule, ethylene glycol (CHOH), seems to depart
from this correlation because it was not easily detected in the interstellar
medium although it proved to be rather abundant with respect to other O-bearing
species in comet Hale-Bopp. Ethylene glycol thus appears, together with the
related molecules glycolaldehyde CHOHCHO and ethanol CHCHOH,
as a key species in the comparison of interstellar and cometary ices as well as
in any discussion on the formation of cometary matter. We focus here on the
analysis of ethylene glycol in the nearest and best studied hot core-like
region, Orion-KL. We use ALMA interferometric data because high spatial
resolution observations allow us to reduce the line confusion problem with
respect to single-dish observations since different molecules are expected to
exhibit different spatial distributions. Furthermore, a large spectral
bandwidth is needed because many individual transitions are required to
securely detect large organic molecules. Confusion and continuum subtraction
are major issues and have been handled with care. We have detected the aGg'
conformer of ethylene glycol in Orion-KL. The emission is compact and peaks
towards the Hot Core close to the main continuum peak, about 2" to the
south-west; this distribution is notably different from other O-bearing
species. Assuming optically thin lines and local thermodynamic equilibrium, we
derive a rotational temperature of 145 K and a column density of 4.6 10
cm. The limit on the column density of the gGg' conformer is five times
lower.Comment: 19 pages, 10 figures, A&A accepte
HCOOCH3 as a probe of temperature and structure of Orion-KL
We studied the O-bearing molecule HCOOCH3 to characterize the physical
conditions of the different molecular source components in Orion-KL. We
identify 28 methyl formate emission peaks throughout the 50" field of
observations. The two strongest peaks are in the Compact Ridge (MF1) and in the
SouthWest of the Hot Core (MF2). Spectral confusion is still prevailing as half
of the expected transitions are blended over the region. Assuming that the
transitions are thermalized, we derive the temperature at the five main
emission peaks. At the MF1 position we find a temperature of 80K in a 1.8"x0.8"
beam size and 120K on a larger scale (3.6" x2.2"), suggesting an external
source of heating, whereas the temperature is about 130K at the MF2 position on
both scales. Transitions of HCOOCH3 in vt=1 are detected as well and the good
agreement of the positions on the rotational diagrams between the vt=0 and the
vt=1 transitions suggests a similar temperature. The velocity of the gas is
between 7.5 and 8.0km/s depending on the positions and column density peaks
vary from 1.6x10^16 to 1.6x10^17cm^-2. A second velocity component is observed
around 9-10 km/s in a North-South structure stretching from the Compact Ridge
up to the BN object; this component is warmer at the MF1 peak. The two other
C2H4O2 isomers are not detected and the derived upper limit for the column
density is <3x10^14cm^-2 for glycolaldehyde and <2x10^15cm^-2 for acetic acid.
From the 223GHz continuum map, we identify several dust clumps with associated
gas masses in the range 0.8 to 5.8Msun. Assuming that the HCOOCH3 is spatially
distributed as the dust, we find relative abundances of HCOOCH3 in the range
<0.1x10^-8 to 5.2x10^-8. We suggest a relation between the methyl formate
distribution and shocks as traced by 2.12 mum H2 emission.Comment: Accepted for publication in A&
Gamma and beta frequency oscillations in response to novel auditory stimuli: A comparison of human electroencephalogram (EEG) data with in vitro models
Investigations using hippocampal slices maintained in vitro have demonstrated that bursts of oscillatory field potentials in the gamma frequency range (30-80 Hz) are followed by a slower oscillation in the beta 1 range (12-20 Hz). In this study, we demonstrate that a comparable gamma-to-beta transition is seen in the human electroencephalogram (EEG) in response to novel auditory stimuli. Correlations between gamma and beta 1 activity revealed a high degree of interdependence of synchronized oscillations in these bands in the human EEG. Evoked (stimulus-locked) gamma oscillations preceded beta 1 oscillations in response to novel stimuli, suggesting that this may be analogous to the gamma-to-beta shift observed in vitro. Beta 1 oscillations were the earliest discriminatory responses to show enhancement to novel stimuli, preceding changes in the broad-band event-related potential (mismatch negativity). Later peaks of induced beta activity over the parietal cortex were always accompanied by an underlying gamma frequency oscillation as seen in vitro. A further analogy between in vitro and human recordings was that both gamma and beta oscillations habituated markedly after the initial novel stimulus presentation
Modelling and simulation of operation and maintenance strategy for offshore wind farms based on multiagent system
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Maintenance of offshore wind turbines is a complex and costly undertaking which acts as a barrier to the development of this source of energy. Factors such as the size of the turbines, the size of the wind farms, their distance from the coast and meteorological conditions make it difficult for the stakeholders to select the optimal maintenance strategy. With the objective of reducing costs and duration of such operations it is important that new maintenance techniques are investigated. In this paper we propose a hybrid model of maintenance that is based on multi-agent systems; this allows for the modelling of systems with dynamic interactions between multiple parts. A multi-criteria decision algorithm has been developed to allow analysis and selection of different maintenance strategies. A cost model that includes maintenance action cost, energy loss and installation of monitoring system cost has been presented. For the purposes of this research we have developed a simulator using NetLogo software and have provided experimental results. The results show that employing the proposed hybrid maintenance strategy could increase wind farm productivity and reduce maintenance cost.Acknowledgement is made to European Union for the support of this research through the
European Program INTERREG IVA France-Channel-UK by funding project entitled MER
Innovate
Editorial: Neuromechanics in Movement and Disease With Physiological and Pathophysiological Implications: From Fundamental Experiments to Bio-Inspired Technologies.
SCOPUS: ed.jinfo:eu-repo/semantics/publishe
Formation of disclination lines near a free nematic interface
We have studied the nucleation and the physical properties of a -1/2 wedge
disclination line near the free surface of a confined nematic liquid crystal.
The position of the disclination line has been related to the material
parameters (elastic constants, anchoring energy and favored anchoring angle of
the molecules at the free surface). The use of a planar model for the structure
of the director field (whose predictions have been contrasted to those of a
fully three-dimensional model) has allowed us to relate the experimentally
observed position of the disclination line to the relevant properties of the
liquid crystals. In particular, we have been able to observe the collapse of
the disclination line due to a temperature-induced anchoring angle transition,
which has allowed us to rule out the presence of a real disclination line near
the nematic/isotropic front in directional growth experiments.
61.30.Jf,61.30.G
The wonderful complexity of the Mira AB system
We have mapped the CO(3-2) line emission around the Mira AB system at 0.5
resolution using the Atacama Large Millimeter/submillimeter Array (ALMA). The
CO map shows amazing complexity. The circumstellar gas has been shaped by
different dynamical actors during the evolution of the system and several
morphological components can be identified. The companion is marginally
resolved in continuum emission and is currently at 0.4870.006 separation.
In the main line component, centered on the stellar velocity, spiral arcs
around Mira A are found. The spiral appears to be relatively flat and oriented
in the orbital plane. An accretion wake behind the companion is clearly visible
and the projected arc separation is of order 5''. In the blue wing of the line
emission, offset from the main line, several large (5-10''), opposing
arcs are found. We tentatively suggest that this structure is created by the
wind of Mira B blowing a bubble in the expanding envelope of Mira A.Comment: Letter accepted in A&
Defects in the CAPN1 Gene Result in Alterations in Cerebellar Development and Cerebellar Ataxia in Mice and Humans
A CAPN1 missense mutation in Parson Russell Terrier dogs is associated with spinocerebellar ataxia. We now report that homozygous or heterozygous CAPN1-null mutations in humans result in cerebellar ataxia and limb spasticity in four independent pedigrees. Calpain-1 knockout (KO) mice also exhibit a mild form of ataxia due to abnormal cerebellar development, including enhanced neuronal apoptosis, decreased number of cerebellar granule cells, and altered synaptic transmission. Enhanced apoptosis is due to absence of calpain-1-mediated cleavage of PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1), which results in inhibition of the Akt pro-survival pathway in developing granule cells. Injection of neonatal mice with the indirect Akt activator, bisperoxovanadium, or crossing calpain-1 KO mice with PHLPP1 KO mice prevented increased postnatal cerebellar granule cell apoptosis and restored granule cell density and motor coordination in adult mice. Thus, mutations in CAPN1 are an additional cause of ataxia in mammals, including humans
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