234 research outputs found
Morphology and kinematics of Lynds 1642
The high latitude translucent molecular cloud L1642 has been mapped in the
J=1-0 and J=2-1 transitions of 12CO, 13CO and C18O using the SEST radio
telescope. We have analysed the morphology and velocity structure of the cloud
using the Positive Matrix Factorization (PMF) method. The results show that
L1642 is composed of a main structure at radial velocity 0.2 km/s while the
higher velocity components at ~0.5 and 1.0 km/s form an incomplete ring around
it, suggesting an expanding shell structure. Fainter emission extends to the
north with a still higher velocity of up to 1.6 km/s. Such a velocity structure
suggests an elongated morphology in the line of sight direction. The physical
properties of the cloud have been investigated assuming LTE conditions, but
non-LTE radiative transfer models are also constructed for the 13CO
observations. We confirm that L1642 follows an r^-1 density distribution in its
outer parts while the distribution is considerably flatter in the core. The
cloud is close to virial equilibrium. In an Appendix the PMF results are
compared with the view obtained through the analysis of channel maps and by the
use of Principal Component Analysis (PCA). Both PMF and PCA present the
observations as a linear combination of basic spectral shapes that are
extracted from the data. Comparison of the methods shows that the PMF method in
particular is able to produce a presentation of the complex velocity that is
both compact and easily interpreted.Comment: Accepted to A&
Cortical beta burst dynamics are altered in Parkinson's disease but normalized by deep brain stimulation
Exaggerated subthalamic beta oscillatory activity and increased beta range cortico-subthalamic synchrony have crystallized as the electrophysiological hallmarks of Parkinson's disease. Beta oscillatory activity is not tonic but occurs in 'bursts' of transient amplitude increases. In Parkinson's disease, the characteristics of these bursts are altered especially in the basal ganglia. However, beta oscillatory dynamics at the cortical level and how they compare with healthy brain activity is less well studied. We used magnetoencephalography (MEG) to study sensorimotor cortical beta bursting and its modulation by subthalamic deep brain stimulation in Parkinson's disease patients and age-matched healthy controls. We show that the changes in beta bursting amplitude and duration typical of Parkinson's disease can also be observed in the sensorimotor cortex, and that they are modulated by chronic subthalamic deep brain stimulation, which, in turn, is reflected in improved motor function at the behavioural level. In addition to the changes in individual beta bursts, their timing relative to each other was altered in patients compared to controls: bursts were more clustered in untreated Parkinson's disease, occurring in 'bursts of bursts', and re-burst probability was higher for longer compared to shorter bursts. During active deep brain stimulation, the beta bursting in patients resembled healthy controls' data. In summary, both individual bursts' characteristics and burst patterning are affected in Parkinson's disease, and subthalamic deep brain stimulation normalizes some of these changes to resemble healthy controls' beta bursting activity, suggesting a non-invasive biomarker for patient and treatment follow-up.Peer reviewe
Properties of dust in the high-latitude translucent cloud L1780 I: Spatially distinct dust populations and increased dust emissivity from ISO observations
We have analyzed the properties of dust in the high galactic latitude
translucent cloud Lynds 1780 using ISOPHOT maps at 100 and 200 micrometers and
raster scans at 60, 80, 100, 120, 150 and 200 micrometers. In far-infrared
(FIR) emission, the cloud has a single core that coincides with the maxima of
visual extinction and 200um optical depth. At the resolution of 3.0 arcmin, the
maximum visual extinction is 4.0 mag. At the cloud core, the minimum
temperature and the maximum 200um optical depth are 14.9+/-0.4 K and
2.0+/-0.2x10^{-3}, respectively, at the resolution of 1.5 arcmin. The cloud
mass is estimated to be 18M_{SUN}. The FIR observations, combined with IRAS
observations, suggest the presence of different, spatially distinct dust grain
populations in the cloud: the FIR core region is the realm of the "classical"
large grains, whereas the very small grains and the PAHs have separate maxima
on the Eastern side of the cold core, towards the "tail" of this
cometary-shaped cloud. The color ratios indicate an overabundance of PAHs and
VSGs in L1780. Our FIR observations combined with the optical extinction data
indicate an increase of the emissivity of the big grain dust component in the
cold core, suggesting grain coagulation or some other change in the properties
of the large grains. Based on our observations, we also address the question,
to what extent the 80um emission and even the 100um and the 120um emission
contain a contribution from the small-grain component.Comment: 12 pages, 9 figures, minor changes, one table adde
Crystalline cyclophane-protein cage frameworks
open10siCyclophanes are macrocyclic supramolecular hosts famous for their ability to bind atomic or molecular guests via noncovalent interactions within their well-defined cavities. In a similar way, porous crystalline networks, such as metal organic frameworks, can create microenvironments that enable controlled guest binding in the solid state. Both types of materials often consist of synthetic components, and they have been developed within separate research fields. Moreover, the use of biomolecules as their structural units has remained elusive. Here, we have synthesized a library of organic cyclophanes and studied their electrostatic self-assembly with biological metal-binding protein cages (ferritins) into ordered structures. We show that cationic pillar[S]arenes and ferritin cages form biohybrid cocrystals with an open protein network structure. Our cyclophane-protein cage frameworks bridge the gap between molecular frameworks and colloidal nanoparticle crystals and combine the versatility of synthetic supramolecular hosts with the highly selective recognition properties of biomolecules. Such host-guest materials are interesting for porous material applications, including water remediation and heterogeneous catalysis.openBeyeh N.K.; Nonappa; Liljestrom V.; Mikkila J.; Korpi A.; Bochicchio D.; Pavan G.M.; Ikkala O.; Ras R.H.A.; Kostiainen M.A.Beyeh, N. K.; Nonappa, ; Liljestrom, V.; Mikkila, J.; Korpi, A.; Bochicchio, D.; Pavan, G. M.; Ikkala, O.; Ras, R. H. A.; Kostiainen, M. A
Water and ammonia abundances in S140 with the Odin satellite
We have used the Odin satellite to obtain strip maps of the ground-state
rotational transitions of ortho-water and ortho-ammonia, as well as CO(5-4) and
13CO(5-4) across the PDR, and H218O in the central position. A physi-chemical
inhomogeneous PDR model was used to compute the temperature and abundance
distributions for water, ammonia and CO. A multi-zone escape probability method
then calculated the level populations and intensity distributions. These
results are compared to a homogeneous model computed with an enhanced version
of the RADEX code. H2O, NH3 and 13CO show emission from an extended PDR with a
narrow line width of ~3 kms. Like CO, the water line profile is dominated by
outflow emission, however, mainly in the red wing. The PDR model suggests that
the water emission mainly arises from the surfaces of optically thick, high
density clumps with n(H2)>10^6 cm^-3 and a clump water abundance, with respect
to H2, of 5x10^-8. The mean water abundance in the PDR is 5x10^-9, and between
~2x10^-8 -- 2x10^-7 in the outflow derived from a simple two-level
approximation. Ammonia is also observed in the extended clumpy PDR, likely from
the same high density and warm clumps as water. The average ammonia abundance
is about the same as for water: 4x10^-9 and 8x10^-9 given by the PDR model and
RADEX, respectively. The similarity of water and ammonia PDR emission is also
seen in the almost identical line profiles observed close to the bright rim.
Around the central position, ammonia also shows some outflow emission although
weaker than water in the red wing. Predictions of the H2O(110-101) and
(111-000) antenna temperatures across the PDR are estimated with our PDR model
for the forthcoming observations with the Herschel Space Observatory.Comment: 13 pages, 14 figures, 10 tables. Accepted for publication in
Astronomy & Astrophysics 14 November 200
Comparison of the efficacy of early versus late viral proteins in vaccination against SIV.
The immune response against early regulatory proteins of simian- and human immunodeficiency virus (SIV, HIV) has been associated with a milder course of infection. Here, we directly compared vaccination with Tat/Rev versus Pol/Gag. Challenge infection with SIVmac32H (pJ5) suggested that vaccination with Tat/Rev induced cellular immune responses that enabled cynomolgus macaques to more efficiently control SIV replication than the vaccine-induced immune responses against Pol/Gag. Vaccination with Tat/Rev resulted in reduced plasma SIV loads compared with control (P=0.058) or Pol/Gag-vaccinated (P
Reynolds stresses from hydrodynamic turbulence with shear and rotation
To study the Reynolds stresses which describe turbulent momentum transport
from turbulence affected by large-scale shear and rotation. Three-dimensional
numerical simulations are used to study turbulent transport under the
influences of large-scale shear and rotation in homogeneous, isotropically
forced turbulence. We study three cases: one with only shear, and two others
where in addition to shear, rotation is present. These cases differ by the
angle (0 or 90\degr) the rotation vector makes with respect to the z-direction.
Two subsets of runs are performed with both values of \theta where either
rotation or shear is kept constant. When only shear is present, the
off-diagonal stress can be described by turbulent viscosity whereas if the
system also rotates, nondiffusive contributions (\Lambda-effect) to the stress
can arise. Comparison of the direct simulations are made with analytical
results from a simple closure model. We find that the turbulent viscosity is of
the order of the first order smoothing result in the parameter regime studied
and that for sufficiently large Reynolds numbers the Strouhal number,
describing the ratio of correlation to turnover times, is roughly 1.5. This is
consistent with the closure model based on the minimal tau-approximation which
produces a reasonable fit to the simulation data for similar Strouhal numbers.
In the cases where rotation is present, separating the diffusive and
nondiffusive components of the stress turns out to be challenging but taking
the results at face value, we can obtain nondiffusive contributions of the
order of 0.1 times the turbulent viscosity. We also find that the simple
closure model is able to reproduce most of the qualitative features of the
numerical results provided that the Strouhal number is of the order of unity.Comment: 19 pages, 12 figures, published versio
Far-infrared and molecular line observations of Lynds 183 - studies of cold gas and dust
We have mapped the dark cloud L183 in the far-infrared at 100um and 200um
with the ISOPHOT photometer aboard the ISO satellite. The observations make it
possible for the first time to study the properties of the large dust grains in
L183 without confusion from smaller grains. The observations show clear colour
temperature variations which are likely to be caused by changes in the emission
properties of the dust particles. In the cloud core the far-infrared colour
temperature drops below 12K. The data allow a new determination of the cloud
mass and the mass distribution. The mass within a radius of 10 arcmin from the
cloud centre is 25 Msun. We have mapped the cloud in several molecular lines
including DCO+(2-1) and H13CO+(1-0). These species are believed to be tracers
of cold and dense molecular material and we detect a strong anticorrelation
between the DCO+ emission and the dust colour temperatures. In particular, the
DCO+(2-1) emission is not detected towards the maximum of the 100um emission
where the colour temperature rises above 15K. The H13CO+ emission follows the
DCO+ distribution but CO isotopes show strong emission even towards the 100um
peak. A comparison of the DCO+ and C18O maps shows sharp variations in the
relative intensities of the species. Morphologically the 200um dust emission
traces the distribution of dense molecular material as seen e.g. in C18O lines.
A comparison with dust column density shows that C18O is depleted by a factor
of 1.5 in the cloud core. We present results of R- and B-band starcounts. The
extinction is much better correlated with the 200um than with the 100um
emission. Based on the 200um correlation at low extinction values we deduce a
value of ~17mag for the visual extinction towards the cloud centre.Comment: to be published in A&
Water maser variability over 20 years in a large sample of star-forming regions: the complete database
Context. Water vapor emission at 22 GHz from masers associated with
star-forming regions is highly variable. Aims. We present a database of up to
20 years of monitoring of a sample of 43 masers within star-forming regions.
The sample covers a large range of luminosities of the associated IRAS source
and is representative of the entire population of H2O masers of this type. The
database forms a good starting point for any further study of H2O maser
variability. Methods. The observations were obtained with the Medicina 32-m
radiotelescope, at a rate of 4-5 observations per year. Results. To provide a
database that can be easily accessed through the web, we give for each source:
plots of the calibrated spectra, the velocity-time-flux density plot, the light
curve of the integrated flux, the lower and upper envelopes of the maser
emission, the mean spectrum, and the rate of the maser occurrence as a function
of velocity. Figures for just one source are given in the text for
representative purposes. Figures for all the sources are given in electronic
form in the on-line appendix. A discussion of the main properties of the H2O
variability in our sample will be presented in a forthcoming paper.Comment: 11 pages, 9 figures, to be published in Astronomy and Astrophysics;
all plots in appendix (not included) can be downloaded from
http://www.arcetri.astro.it/~starform/water_maser_v2.html or
http://www.ira.inaf.it/papers/masers/water_maser_v2.htm
- âŠ