131 research outputs found
Power spectrum of the SDSS luminous red galaxies: constraints on cosmological parameters
In this paper we determine the constraints on cosmological parameters using
the CMB data from the WMAP experiment together with the recent power spectrum
measurement of the SDSS Luminous Red Galaxies (LRGs). Specifically, we focus on
spatially flat, low matter density models with adiabatic Gaussian initial
conditions. The spatial flatness is achieved with an additional quintessence
component whose equation of state parameter w_eff is taken to be independent of
redshift. Throughout most of the paper we do not allow any massive neutrino
contribution and also the influence of the gravitational waves on the CMB is
taken to be negligible. The analysis is carried out separately for two cases:
(i) using the acoustic scale measurements as presented in H\"utsi (2006), (ii)
using the full SDSS LRG power spectrum and its covariance matrix. We are able
to obtain a very tight constraint on the Hubble constant: H_0 = 70.8
^{+2.1}_{-2.0} km/s/Mpc, which helps in breaking several degeneracies between
the parameters and allows us to determine the low redshift expansion law with
much higher accuracy than available from the WMAP + HST data alone. The
positive deceleration parameter q_0 is found to be ruled out at 5.5 \sigma
confidence level. Finally, we extend our analysis by investigating the effects
of relaxing the assumption of spatial flatness and also allow for a
contribution from massive neutrinos.Comment: Final version accepted in A&A, added analysis for the models with
massive neutrinos and non-flat spatial geometrie
On the 3 dimensional structure of edge-on disk galaxies
A simple algorithm is employed to deproject the two dimensional images of a
pilot sample of 12 high-quality images of edge-on disk galaxies and to study
their intrinsic 3 dimensional stellar distribution. We examine the radial
profiles of the stars as a function of height above the plane and report a
general trend within our sample of an increasing radial scalelength with height
outside of the dustlane. This could be explained by the widespread presence of
a thick disk component in these galaxies. In addition, the 3 dimensional view
allows the study of the vertical distribution of the outer disk, beyond the
break region, where we detect a significant increase in scalelength with
vertical distance from the major axis for the truncated disks. This could be
regarded as a weakening of the "truncation" with increasing distance from the
plane. Furthermore, we conclude that the recently revised classification of the
radial surface brightness profiles found for face-on galaxies is indeed
independent of geometry. In particular, we find at least one example of each of
the three main profile classes as defined in complete samples of intermediate
to face-on galaxies: not-truncated, truncated and antitruncated. The position
and surface brightness that mark the break location in the radial light
distribution are found to be consistent with those of face-on galaxies.Comment: LaTeX, 25 pages, 10 figures (some low resolution), MNRAS accepted.
Version with all figures in full resolution (~6MB) available at
http://www.astro.rug.nl/~pohlen/pohlen_3Dedgeon.p
PG 1115+080: variations of the A2/A1 flux ratio and new values of the time delays
We report the results of our multicolor observations of PG 1115+080 with the
1.5-m telescope of the Maidanak Observatory (Uzbekistan, Central Asia) in
2001-2006. Monitoring data in filter R spanning the 2004, 2005 and 2006 seasons
(76 data points) demonstrate distinct brightness variations of the source
quasar with the total amplitude of almost 0.4 mag. Our R light curves have
shown image C leading B by 16.4d and image (A1+A2) by 12d that is inconsistent
with the previous estimates obtained by Schechter et al. in 1997 - 24.7d
between B and C and 9.4d between (A1+A2) and C. The new values of time delays
in PG 1115+080 must result in larger values for the Hubble constant, thus
reducing difference between its estimates taken from the gravitational lenses
and with other methods. Also, we analyzed variability of the A2/A1 flux ratio,
as well as color changes in the archetypal "fold" lens PG 1115+080. We found
the A1/A2 flux ratio to grow during 2001-2006 and to be larger at longer
wavelengths. In particular, the A2/A1 flux ratio reached 0.85 in filter I in
2006. We also present evidence that both the A1 and A2 images might have
undergone microlensing during 2001-2006, with the descending phase for A1 and
initial phase for A2. We find that the A2/A1 flux ratio anomaly in PG 1115 can
be well explained both by microlensing and by finite distance of the source
quasar from the caustic fold.Comment: 14 pages, 7 figures, 8 tables, Accepted for publication in MNRA
Extent of Social Inequalities in Disability in the Elderly: Results From a Population-based Study of British Men
Purpose
Little is known about social inequalities in disability in the elderly. We examined the extent and determinants of socioeconomic inequalities in disability and functional limitation in elderly men in Britain.
Methods
Disability was ascertained as problems with activities of daily living (ADLs) and instrumental ADL in a socioeconomically representative sample of 3981 men from 24 British towns who were between 63 to 82 years of age in 2003. We also examined functional limitation. Measures of socioeconomic position were social class, age at leaving full-time education, and car and house ownership.
Results
Men in lower social classes had greater risks of both ADL and instrumental ADL disability and functional limitation compared with higher social classes; odds ratios (95% CI) for social class V compared with I were 3.13 (1.64–5.97), 2.87 (1.49–5.51), and 2.65 (1.31–5.35), respectively. Behavioral risk factors (smoking, body mass index, physical activity) and particularly co-morbidity attenuated these differences; together, they reduced relative risks to 1.11 (0.49–2.51), 1.01 (0.45–2.25), and 1.05 (0.46–2.42). Age at leaving full-time education had no relation to functional limitations after taking social class into account. Men who were not house or car owners had greater odds of functional limitation and ADL disability compared with house or car owners, independent of behavioural risk factors, comorbidities and social class.
Conclusion
Strong socioeconomic inequalities in disability exist in the elderly, which were considerably explained by behavioral factors and comorbidity. Policy efforts are needed to reduce the social disparities in disability in the elderly
Symptomatic malaria enhances protection from reinfection with homologous Plasmodium falciparum parasites
A signature remains elusive of naturally-acquired immunity against Plasmodium falciparum. We identified P. falciparum in a 14-month cohort of 239 people in Kenya, genotyped at immunogenic parasite targets expressed in the pre-erythrocytic (circumsporozoite protein, CSP) and blood (apical membrane antigen 1, AMA-1) stages, and classified into epitope type based on variants in the DV10, Th2R, and Th3R epitopes in CSP and the c1L region of AMA-1. Compared to asymptomatic index infections, symptomatic malaria was associated with reduced reinfection by parasites bearing homologous CSP-Th2R (adjusted hazard ratio [aHR]:0.63; 95% CI:0.45–0.89; p = 0.008) CSP-Th3R (aHR:0.71; 95% CI:0.52–0.97; p = 0.033), and AMA-1 c1L (aHR:0.63; 95% CI:0.43–0.94; p = 0.022) epitope types. The association of symptomatic malaria with reduced hazard of homologous reinfection was strongest for rare epitope types. Symptomatic malaria provides more durable protection against reinfection with parasites bearing homologous epitope types. The phenotype represents a legible molecular epidemiologic signature of naturally-acquired immunity by which to identify new antigen targets
Near-Infrared Photometry of the Type IIn SN 2005ip: The Case for Dust Condensation
Near-infrared photometric observations of the Type IIn SN 2005ip in NGC 2906
reveal large fluxes (>1.3 mJy) in the K_s-band over more than 900 days. While
warm dust can explain the late-time K_s-band emission of SN 2005ip, the nature
of the dust heating source is ambiguous. Shock heating of pre-existing dust by
post-shocked gas is unlikely because the forward shock is moving too slowly to
have traversed the expected dust-free cavity by the time observations first
reveal the K_s emission. While an infrared light echo model correctly predicts
a near-infrared luminosity plateau, heating dust to the observed temperatures
of ~1400-1600 K at a relatively large distance from the supernova (> 10^{18}
cm) requires an extraordinarily high early supernova luminosity (~1 X 10^{11}
L_solar). The evidence instead favors condensing dust in the cool, dense shell
between the forward and reverse shocks. Both the initial dust temperature and
the evolutionary trend towards lower temperatures are consistent with this
scenario. We infer that radiation from the circumstellar interaction heats the
dust. While this paper includes no spectroscopic confirmation, the photometry
is comparable to other SNe that do show spectroscopic evidence for dust
formation. Observations of dust formation in SNe are sparse, so these results
provide a rare opportunity to consider SNe Type IIn as dust sources.Comment: 11 pages, 6 figures, 3 tables, Accepted for Publication to ApJ:
January 20, 200
Plasmodium falciparum importation does not sustain malaria transmission in a semi-arid region of Kenya
Human movement impacts the spread and transmission of infectious diseases. Recently, a large reservoir of Plasmodium falciparum malaria was identified in a semi-arid region of northwestern Kenya historically considered unsuitable for malaria transmission. Understanding the sources and patterns of transmission attributable to human movement would aid in designing and targeting interventions to decrease the unexpectedly high malaria burden in the region. Toward this goal, polymorphic parasite genes (ama1, csp) in residents and passengers traveling to Central Turkana were genotyped by amplicon deep sequencing. Genotyping and epidemiological data were combined to assess parasite importation. The contribution of travel to malaria transmission was estimated by modelling case reproductive numbers inclusive and exclusive of travelers. P. falciparum was detected in 6.7% (127/1891) of inbound passengers, including new haplotypes which were later detected in locally-transmitted infections. Case reproductive numbers approximated 1 and did not change when travelers were removed from transmission networks, suggesting that transmission is not fueled by travel to the region but locally endemic. Thus, malaria is not only prevalent in Central Turkana but also sustained by local transmission. As such, interrupting importation is unlikely to be an effective malaria control strategy on its own, but targeting interventions locally has the potential to drive down transmission
Recommended from our members
Admixture mapping of 15,280 African Americans identifies obesity susceptibility loci on chromosomes 5 and X
Isokinetic eccentric exercise substantially improves mobility, muscle strength and size, but not postural sway metrics in older adults, with limited regression observed following a detraining period
© 2020, The Author(s). Introduction: Eccentric exercise can reverse age-related decreases in muscle strength and mass; however, no data exist describing its effects on postural sway. As the ankle may be more important for postural sway than hip and knee joints, and with older adults prone to periods of inactivity, the effects of two 6-week seated isokinetic eccentric exercise programmes, and an 8-week detraining period, were examined in 27 older adults (67.1 ± 6.0 years). Methods: Neuromuscular parameters were measured before and after training and detraining periods with subjects assigned to ECC (twice-weekly eccentric-only hip and knee extensor contractions) or ECCPF (identical training with additional eccentric-only plantarflexor contractions) training programmes. Results: Significant (P \u3c 0.05) increases in mobility (decreased timed-up-and-go time [− 7.7 to − 12.0%]), eccentric strength (39.4–58.8%) and vastus lateralis thickness (9.8–9.9%) occurred after both training programmes, with low-to-moderate weekly rate of perceived exertion (3.3–4.5/10) reported. No significant change in any postural sway metric occurred after either training programme. After 8 weeks of detraining, mobility (− 8.2 to − 11.3%), eccentric strength (30.5–50.4%) and vastus lateralis thickness (6.1–7.1%) remained significantly greater than baseline in both groups. Conclusion: Despite improvements in functional mobility, muscle strength and size, lower-limb eccentric training targeting hip, knee and ankle extensor muscle groups was not sufficient to influence static balance. Nonetheless, as the beneficial functional and structural adaptations were largely maintained through an 8-week detraining period, these findings have important implications for clinical exercise prescription as the exercise modality, low perceived training intensity, and adaptive profile are well suited to the needs of older adults
- …