2,011 research outputs found
Topography and lithology of the Mendocino Ridge
Twenty-two slope-corrected bathymetric profiles of the Mendocino Ridge between 125°W and 129°W are presented, and the method of their development is discussed. The crest of this Ridge lies at an average depth of 2000 m, falling off to 3200 m on the north and to 4400 m on the south. A short, steep scarp, fresh dredge-haul material lacking manganiferous crusts, and earthquake epicenters suggest recent faulting on the north...
Gravitational Lensing as Signal and Noise in Lyman-alpha Forest Measurements
In Lyman-alpha forest measurements it is generally assumed that quasars are
mere background light sources which are uncorrelated with the forest.
Gravitational lensing of the quasars violates this assumption. This effect
leads to a measurement bias, but more interestingly it provides a valuable
signal. The lensing signal can be extracted by correlating quasar magnitudes
with the flux power spectrum and with the flux decrement. These correlations
will be challenging to measure but their detection provides a direct measure of
how features in the Lyman-alpha forest trace the underlying mass density field.
Observing them will test the fundamental hypothesis that fluctuations in the
forest are predominantly driven by fluctuations in mass, rather than in the
ionizing background, helium reionization or winds. We discuss ways to
disentangle the lensing signal from other sources of such correlations,
including dust, continuum and background residuals. The lensing-induced
measurement bias arises from sample selection: one preferentially collects
spectra of magnified quasars which are behind overdense regions. This
measurement bias is ~0.1-1% for the flux power spectrum, optical depth and the
flux probability distribution. Since the effect is systematic, quantities such
as the amplitude of the flux power spectrum averaged across scales should be
interpreted with care.Comment: 22 pages, 8 figures; v2: references added, discussion expanded,
matches PRD accepted versio
[OI] disk emission in the Taurus star forming region
The structure of protoplanetary disks is thought to be linked to the
temperature and chemistry of their dust and gas. Whether the disk is flat or
flaring depends on the amount of radiation that it absorbs at a given radius,
and on the efficiency with which this is converted into thermal energy. The
understanding of these heating and cooling processes is crucial to provide a
reliable disk structure for the interpretation of dust continuum emission and
gas line fluxes. Especially in the upper layers of the disk, where gas and dust
are thermally decoupled, the infrared line emission is strictly related to the
gas heating/cooling processes. We aim to study the thermal properties of the
disk in the oxygen line emission region, and to investigate the relative
importance of X-ray (1-120 Angstrom) and far-UV radiation (FUV, 912-2070
Angstrom) for the heating balance there. We use [OI] 63 micron line fluxes
observed in a sample of protoplanetary disks of the Taurus/Auriga star forming
region and compare it to the model predictions presented in our previous work.
The data were obtained with the PACS instrument on board the Herschel Space
Observatory as part of the Herschel Open Time Key Program GASPS (GAS in
Protoplanetary diskS), published in Howard et al. (2013). Our theoretical grid
of disk models can reproduce the [OI] absolute fluxes and predict a correlation
between [OI] and the sum Lx+Lfuv. The data show no correlation between the [OI]
line flux and the X-ray luminosity, the FUV luminosity or their sum. The data
show that the FUV or X-ray radiation has no notable impact on the region where
the [OI] line is formed. This is in contrast with what is predicted from our
models. Possible explanations are that the disks in Taurus are less flaring
than the hydrostatic models predict, and/or that other disk structure aspects
that were left unchanged in our models are important. ..abridged..Comment: 9 pages, accepted for publication in A&
Randomized Clinical Trial of Azithromycin vs. Erythromycin for the Treatment of Chlamydia Cervicitis in Pregnancy
Objective: The purpose of this study was to prospectively test the null hypothesis that there is no
difference in the clinical effectiveness of azithromycin and erythromycin for the treatment of chlamydia
cervicitis in pregnancy
Confinement effects on glass forming liquids probed by DMA
Many molecular glass forming liquids show a shift of the glass transition T-g
to lower temperatures when the liquid is confined into mesoporous host
matrices. Two contrary explanations for this effect are given in literature:
First, confinement induced acceleration of the dynamics of the molecules leads
to an effective downshift of T-g increasing with decreasing pore size. Second,
due to thermal mismatch between the liquid and the surrounding host matrix,
negative pressure develops inside the pores with decreasing temperature, which
also shifts T-g to lower temperatures. Here we present dynamic mechanical
analysis measurements of the glass forming liquid salol in Vycor and Gelsil
with pore sizes of d=2.6, 5.0 and 7.5 nm. The dynamic complex elastic
susceptibility data can be consistently described with the assumption of two
relaxation processes inside the pores: A surface induced slowed down relaxation
due to interaction with rough pore interfaces and a second relaxation within
the core of the pores. This core relaxation time is reduced with decreasing
pore size d, leading to a downshift of T-g proportional to 1/d in perfect
agreement with recent differential scanning calorimetry (DSC) measurements.
Thermal expansion measurements of empty and salol filled mesoporous samples
revealed that the contribution of negative pressure to the downshift of T-g is
small (<30%) and the main effect is due to the suppression of dynamically
correlated regions of size xi when the pore size xi approaches
Early risk factors for adolescent antisocial behaviour: an Australian longitudinal study
Objective: This investigation utilizes data from an Australian longitudinal study to identify early risk factors for adolescent antisocial behaviour. Method: Analyses are based on data from the Mater University Study of Pregnancy, an on-going longitudinal investigation of women’s and children’s health and development involving over 8000 participants. Five types of risk factors (child characteristics, perinatal factors, maternal/familial characteristics, maternal pre- and post-natal substance use and parenting practices) were included in analyses and were based on maternal reports, child assessments and medical records. Adolescent antisocial behaviour was measured when children were 14 years old, using the delinquency subscale of the Child Behaviour Checklist. Results: Based on a series of logistic regression models, significant risk factors for adolescent antisocial behaviour included children’s prior problem behaviour (i.e. aggression and attention/restlessness problems at age 5 years) and marital instability, which doubled or tripled the odds of antisocial behaviour. Perinatal factors, maternal substance use, and parenting practices were relatively poor predictors of antisocial behaviour. Conclusions: Few studies have assessed early predictors of antisocial behaviour in Australia and the current results can be used to inform prevention programs that target risk factors likely to lead to problem outcomes for Australian youth
Magnetic topologies of cool stars
Stellar magnetic fields can be investigated using several, very complementary
approaches. While conventional spectroscopy is capable of estimating the
average magnetic strength of potentially complex field configurations thanks to
its low sensitivity to the vector properties of the field, spectropolarimetry
can be used to map the medium- and large-scale structure of magnetic
topologies. In particular, the latter approach allows one to retrieve
information about the poloidal and toroidal components of the large-scale
dynamo fields in low-mass stars, and thus to investigate the physical processes
that produce them. Similarly, this technique can be used to explore how
magnetic fields couple young stars to their massive accretion disc and thus to
estimate how much mass and angular momentum are transfered to the newly-born
low-mass star. We present here the latest results in this field obtained with
spectropolarimetry, with special emphasis on the surprising discoveries
obtained on very-low mass fully-convective stars and classical T Tauri stars
thanks to the ESPaDOnS spectropolarimeter recently installed on the 3.6m
Canada-France-Hawaii Telescope.Comment: 10p invited review paper, 3 figures, to be published in the
proceedings of the 14th Cambridge Workshop on Cool Stars, Stellar Systems,
and the Sun, November 6-10, 2006, ed. G. van Belle (ASP Conf Ser
Association of Checklist Use in Endotracheal Intubation With Clinically Important Outcomes: A Systematic Review and Meta-analysis
Importance: The ε4 allele of the apolipoprotein E (APOE) gene and lower apolipoprotein E (apoE) protein levels in plasma are risk factors for Alzheimer disease, but the underlying biological mechanisms are not fully understood. Half of plasma apoE circulates on high-density lipoproteins (HDLs). Higher apoE levels in plasma HDL were previously found to be associated with lower coronary heart disease risk, but the coexistence of another apolipoprotein, apoC3, modified this lower risk.
Objective: To investigate associations between the presence of apoE in different lipoproteins with cognitive function, particularly the risk of dementia.
Design, Setting, and Participants: This prospective case-cohort study embedded in the Ginkgo Evaluation of Memory Study (2000-2008) analyzed data from 1351 community-dwelling participants 74 years and older. Of this group, 995 participants were free of dementia at baseline (recruited from September 2000 to June 2002) and 521 participants were diagnosed with incident dementia during follow-up until 2008. Data analysis was performed from January 2018 to December 2019.
Exposures: Enzyme-linked immunosorbent assay–measured concentration of apoE in whole plasma, HDL-depleted plasma (non-HDL), HDL, and HDL subspecies that contain or lack apoC3 or apoJ.
Main Outcomes and Measures: Adjusted hazard ratios for risk of dementia and Alzheimer disease during follow-up and adjusted differences (β coefficients) in Alzheimer Disease Assessment–Cognitive Subscale (ADAS-cog) and Modified Mini-Mental State Examination scores at baseline.
Results: Among 1351 participants, the median (interquartile range) age was 78 (76-81) years; 639 (47.3%) were women. The median (interquartile range) follow-up time was 5.9 (3.7-6.5) years. Higher whole plasma apoE levels and higher apoE levels in HDL were associated with better cognitive function assessed by ADAS-cog (whole plasma, β coefficient, −0.15; 95% CI, −0.24 to −0.06; HDL, β coefficient, −0.20; 95% CI, −0.30 to −0.10) but were unassociated with dementia or Alzheimer disease risk. When separated by apoC3, a higher apoE level in HDL that lacks apoC3 was associated with better cognitive function (ADAS-cog per SD: β coefficient, 0.17; 95% CI, −0.27 to −0.07; Modified Mini-Mental State Examination score per SD: β coefficient, 0.25; 95% CI, 0.07 to 0.42) and lower risk of dementia (hazard ratio per SD, 0.86; 95% CI, 0.76 to 0.99). In contrast, apoE levels in HDL that contains apoC3 were unassociated with any of these outcomes.
Conclusions and Relevance: In a prospective cohort of older adults with rigorous follow-up of dementia, the apoE level in HDL that lacked apoC3 was associated with better cognitive function and lower dementia risk. This finding suggests that the cardioprotective associations of this novel lipoprotein extend to dementia
Customer Referral Behavior: Do Switchers and Stayers Differ?
In today’s highly competitive market environment, service providers are beginning to recognize that customer referral plays an important role in enhancing firm value through cost-effective acquisition of new customers. While a significant body of research has focused on exploring customer referral, surprisingly limited research to date has addressed how customer referral may vary for different customer groups, particularly among switchers and stayers. This article examines the moderating effect of switchers and stayers on the relationships between service quality and perceived value on customer referral behavior. Actual referral data were collected from 441 customers of an Internet Service Provider in two waves for this study. The results show that the effects of positive changes in service quality and perceived value on customer referral behavior are stronger for recently acquired customers (switchers) than for long-term customers (stayers). The findings of the study suggest that investment in service quality and value improvements yield significantly higher returns (through greater customer referrals) for switchers than for stayers. Based on the findings, the authors recommend that service managers should identify and target newly acquired customers, who have switched from different service providers, right from the outset of the relationship with service offerings that signify higher quality and value in order to maximize customer referrals
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