2,209 research outputs found
Polarisation properties of Milky-Way-like galaxies
(Abridged) We study the polarisation properties, magnetic field strength, and
synchrotron emission scale-height of Milky-Way-like galaxies in comparison with
other spiral galaxies. We use our 3D-emission model of the Milky Way Galaxy for
viewing the Milky Way from outside at various inclinations as spiral galaxies
are observed. When seen edge-on the synchrotron emission from the Milky Way has
an exponential scale-height of about 0.74 kpc, which is much smaller than the
values obtained from previous models. We find that current analysis methods
overestimate the scale-height of synchrotron emission of galaxies by about 10%
at an inclination of 80 degree and about 40% at an inclination of 70 degree
because of contamination from the disk. The observed RMs for face-on galaxies
derived from high-frequency polarisation measurements approximate to the
Faraday depths (FDs) when scaled by a factor of two. For edge-on galaxies, the
observed RMs are indicative of the orientation of the large-scale magnetic
field, but are not well related with the FDs. Assuming energy equipartition
between the magnetic field and particles for the Milky Way results in an
average magnetic-field strength, which is about two times larger than the
intrinsic value for a K factor of 100. The number distribution of the
integrated polarisation percentages of a large sample of unresolved
Milky-Way-like galaxies peaks at about 4.2% at 4.8 GHz and at about 0.8% at
1.4GHz. Integrated polarisation angles rotated by 90 degree align very well
with the position angles of the major axes, implying that unresolved galaxies
do not have intrinsic RMs.Comment: 10 pages, 11 figures, accepted for publication in A&
Crystal Chute Moves on Pipe Dreams
Schubert polynomials represent a basis for the cohomology of the complete
flag variety and thus play a central role in geometry and combinatorics. In
this context, Schubert polynomials are generating functions over various
combinatorial objects, such as rc-graphs or reduced pipe dreams. By restricting
Bergeron and Billey's chute moves on rc-graphs, we define a Demazure crystal
structure on the monomials of a Schubert polynomial. As a consequence, we
provide a method for decomposing Schubert polynomials as sums of key
polynomials, complementing related work of Assaf and Schilling via reduced
factorizations with cutoff, as well as Lenart's coplactic operators on biwords.Comment: 29 pages, 15 figures best viewed in colo
The Galactic halo magnetic field revisited
Recently, Sun et al. (2008) published new Galactic 3D-models of magnetic
fields in the disk and halo of the Milky Way and the distribution of cosmic-ray
electron density by taking into account the thermal electron density model
NE2001 by Cordes & Lazio (2002, 2003). The models successfully reproduce
observed continuum and polarization all-sky maps and the distribution of
rotation measures of extragalactic sources across the sky. However, the model
parameters obtained for the Galactic halo, although reproducing the
observations, seem physically unreasonable: the magnetic field needs to be
significantly stronger in the Galactic halo than in the plane and the
cosmic-ray distribution must be truncated at about 1 kpc to avoid excessive
synchrotron emission from the halo. The reason for these unrealistic parameters
was the low scale-height of the warm thermal gas of about 1 kpc adapted in the
NE2001 model. However, this scale-height seemed well settled by numerous
investigations. Recently, the scale-height of the warm gas in the Galaxy was
revised by Gaensler et al. (2008) to about 1.8 kpc, by showing that the 1 kpc
scale-height results from a systematic bias in the analysis of pulsar data.
This implies a higher thermal electron density in the Galactic halo, which in
turn reduces the halo magnetic field strength to account for the observed
rotation measures of extragalactic sources. We slightly modified the NE2001
model for the new scale-height and revised the Sun et al. (2008) model
parameters accordingly: the strength of the regular halo magnetic field is now
2 microG or lower, and the physically unrealistic cutoff in z for the
cosmic-ray electron density is removed. The simulations based on the revised
3D-models reproduce all-sky observations as before.Comment: 11 pages, 6 figures, accepted for publication in Research in
Astronomy and Astrophysics (RAA
Picornavirus RNA is protected from cleavage by ribonuclease during virion uncoating and transfer across cellular and model membranes
Picornaviruses are non-enveloped RNA viruses that enter cells via receptor-mediated endocytosis. Because they lack an envelope, picornaviruses face the challenge of delivering their RNA genomes across the membrane of the endocytic vesicle into the cytoplasm to initiate infection. Currently, the mechanism of genome release and translocation across membranes remains poorly understood. Within the enterovirus genus, poliovirus, rhinovirus 2, and rhinovirus 16 have been proposed to release their genomes across intact endosomal membranes through virally induced pores, whereas one study has proposed that rhinovirus 14 releases its RNA following disruption of endosomal membranes. For the more distantly related aphthovirus genus (e.g. foot-and-mouth disease viruses and equine rhinitis A virus) acidification of endosomes results in the disassembly of the virion into pentamers and in the release of the viral RNA into the lumen of the endosome, but no details have been elucidated as how the RNA crosses the vesicle membrane. However, more recent studies suggest aphthovirus RNA is released from intact particles and the dissociation to pentamers may be a late event. In this study we have investigated the RNase A sensitivity of genome translocation of poliovirus using a receptor-decorated-liposome model and the sensitivity of infection of poliovirus and equine-rhinitis A virus to co-internalized RNase A. We show that poliovirus genome translocation is insensitive to RNase A and results in little or no release into the medium in the liposome model. We also show that infectivity is not reduced by co-internalized RNase A for poliovirus and equine rhinitis A virus. Additionally, we show that all poliovirus genomes that are internalized into cells, not just those resulting in infection, are protected from RNase A. These results support a finely coordinated, directional model of viral RNA delivery that involves viral proteins and cellular membranes
The Parkes Galactic Meridian Survey (PGMS): observations and CMB polarization foreground analysis
We present observations and CMB foreground analysis of the Parkes Galactic
Meridian Survey (PGMS), an investigation of the Galactic latitude behaviour of
the polarized synchrotron emission at 2.3 GHz with the Parkes Radio Telescope.
The survey consists of a 5-deg wide strip along the Galactic meridian l=254-deg
extending from Galactic plane to South Galactic pole. We identify three zones
distinguished by polarized emission properties: the disc, the halo, and a
transition region connecting them. The halo section lies at latitudes |b| >
40-deg and has weak and smooth polarized emission mostly at large scale with
steep angular power spectra of median slope . The
disc region covers the latitudes |b|<20-deg and has a brighter, more complex
emission dominated by the small scales with flatter spectra of median slope
. The transition region has steep spectra as in the
halo, but the emission increases toward the Galactic plane from halo to disc
levels. The change of slope and emission structure at b \sim -20\degr is
sudden, indicating a sharp disc-halo transition. The whole halo section is just
one environment extended over 50-deg with very low emission which, once scaled
to 70GHz, is equivalent to the CMB B-Mode emission for a tensor-to-scalar
perturbation power ratio r_halo = 3.3 +/- 0.4 x 10^{-3}. Applying a
conservative cleaning procedure, we estimate an r detection limit of at 70~GHz (3-sigma C.L.) and, assuming a dust polariztion
fraction <12%, at 150~GHz. The 150-GHz limit
matches the goals of planned sub-orbital experiments, which can therefore be
conducted at this high frequency. The 70-GHz limit is close to the goal of
proposed next generation space missions, which thus might not strictly require
space-based platforms.Comment: 23 pages, 22 Figures. Accepted for publication on MNRAS. Some figures
have been reduced in resolution. Replaced with the accepted version, 3
figures, more details on instrument performances, and map of polarization
spectral index adde
The experience of long-term opiate maintenance treatment and reported barriers to recovery: A qualitative systematic review
Background/Aim: To inform understanding of the experience of long-term opiate maintenance and identify barriers to recovery. Methods: A qualitative systematic review. Results: 14 studies in 17 papers, mainly from the USA (65%), met inclusion criteria, involving 1,088 participants. Studies focused on methadone prescribing. Participants reported stability; however, many disliked methadone. Barriers to full recovery were primarily ‘inward focused'. Conclusion: This is the first review of qualitative literature on long-term maintenance, finding that universal service improvements could be made to address reported barriers to recovery, including involving ex-users as positive role models, and increasing access to psychological support. Treatment policies combining harm minimisation and abstinence-orientated approaches may best support individualised recovery
DNA Product Formation in Female Sprague–Dawley Rats Following Polyhalogenated Aromatic Hydrocarbon (PHAH) Exposure
DNA oxidation damage has been regarded as one of the possible mechanisms for the hepatic carcinogenesis of dioxin-like compounds (DLCs). In this study, we evaluated the toxic equivalency factor (TEF) from the standpoint of induced DNA oxidation products and their relationship to toxicity and carcinogenicity. Nine DNA oxidation products were analyzed in the liver of female Sprague-Dawley rats exposed to 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD) alone or the tertiary mixture of TCDD, 3,3',4,4',5-pentachlorobiphenyl (PCB 126), and 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) by gavage for 14, 31, and 53 weeks (5 days/week) by LC-MS/MS: 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo); 1,N6-etheno-2'-deoxyadenosine (1,N6-εdAdo); N2,3-ethenoguanine (N2,3-εG); 7-(2-oxoethly)guanine (7-OEG); 1,N2-etheno-2'-deoxyguanosine (1,N2-εdGuo); malondialdehyde (M1dGuo); acrolein (AcrdGuo); crotonaldehyde (CrdGuo); and 4-hydroxynonenal (HNEdGuo) derived 2'-deoxyguanosine adducts. Exposure to TCDD (100 ng/kg/day) significantly induced 1,N6-εdAdo at 31 and 53 weeks, while no increase of 8-oxo-dGuo was observed. Significant increases were observed for 8-oxo-dGuo and 1,N6-εdAdo at all time points following exposure to the tertiary mixture (TEQ 100 ng/kg/day). Exposure to TCDD for 53 weeks only significantly increased 1,N6-εdAdo, while increases of N2,3-εG and 7-OEG were only found in the highest dose group (100 ng/kg/day). Exposure to the tertiary mixture for 53 weeks had no effect on N2,3-εG in any exposure group (TEQ 0, 22, 46, or 100 ng/kg/day), while significant increases were observed for 1,N6-εdAdo (all dose groups), 8-oxo-dGuo (46 and 100 ng/kg/day), and 7-OEG (100 ng/kg/day). While no significant increase was observed at 53 weeks for 1,N2-εdGuo, M1dGuo, AcrdGuo, or CrdGuo following exposure to TCDD (100 ng/kg/day), all of them were significantly induced in animals exposed to the tertiary mixture (TEQ 100 ng/kg/day). This oxidation DNA product data suggest that the simple TEF methodology cannot be applied to evaluate the diverse patterns of toxic effects induced by DLCs
Association of Menopausal Vasomotor Symptoms With Increased Bone Turnover During the Menopausal Transition
The purpose of this study was to determine the longitudinal association between menopausal vasomotor symptoms (VMS) and urinary N-telopeptide level (NTX) according to menopausal stage. We analyzed data from 2283 participants of the Study of Women's Health Across the Nation, a longitudinal community-based cohort study of women aged 42 to 52 years at baseline. At baseline and annually through follow-up visit 8, participants provided questionnaire data, urine samples, serum samples, and anthropometric measurements. Using multivariable repeated-measures mixed models, we examined associations between annually assessed VMS frequency and annual NTX measurements. Our results show that mean adjusted NTX was 1.94 nM of bone collagen equivalents (BCE)/mM of creatinine higher among early perimenopausal women with any VMS than among early perimenopausal women with no VMS (p < .0001). Mean adjusted NTX was 2.44 nM BCE/mM of creatinine higher among late perimenopausal women with any VMS than among late perimenopausal women with no VMS (p = .03). Among premenopausal women, VMS frequency was not significantly associated with NTX level. When NTX values among women with frequent VMS (≥6 days in past 2 weeks) were expressed as percentages of NTX values among women without frequent VMS, the differences were 3% for premenopausal women, 9% for early perimenopausal women, 7% for late perimenopausal women, and 4% for postmenopausal women. Adjustment for serum follicle-stimulating hormone (FSH) level greatly reduced the magnitudes of associations between VMS and NTX level. We conclude that among early perimenopausal and late perimenopausal women, those with VMS had higher bone turnover than those without VMS. Prior to the final menstrual period, VMS may be a marker for risk of adverse bone health. © 2011 American Society for Bone and Mineral Research
Joint 3D modelling of the polarized Galactic synchrotron and thermal dust foreground diffuse emission
We present for the first time a coherent model of the polarized Galactic
synchrotron and thermal dust emissions which are the main diffuse foreground
for the measurement of the polarized power spectra of the CMB fluctuations with
the Planck satellite mission. We produce 3D models of the Galactic magnetic
field including regular and turbulent components, and of the distribution of
matter in the Galaxy, relativistic electrons and dust grains. By integrating
along the line of sight we construct maps of the polarized Galactic synchrotron
and thermal dust emission for each of these models and compare them to
currently available data. We consider the 408 MHz all-sky continuum survey, the
23 GHz band of the Wilkinson Microwave Anisotropy Probe and the 353 GHz
Archeops data.}{The best-fit parameters obtained are consistent with previous
estimates in the literature based only on synchrotron emission and pulsar
rotation measurements. They allows us to reproduce the large scale structures
observed on the data. Poorly understood local Galactic structures and
turbulence make difficult an accurate reconstruction of the observations in the
Galactic plane. Finally, using the best-fit model we are able to estimate the
expected polarized foreground contamination at the Planck frequency bands. For
the CMB bands, 70, 100, 143 and 217 GHz, at high Galactic latitudes although
the CMB signal dominates in general, a significant foreground contribution is
expected at large angular scales. In particular, this contribution will
dominate the CMB signal for the B modes expected from realistic models of a
background of primordial gravitational waves
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