2,802 research outputs found
Tidally-Triggered Star Formation in Close Pairs of Galaxies
We analyze new optical spectra of a sample of 502 galaxies in close pairs and
n-tuples, separated by <= 50/h kpc. We extracted the sample objectively from
the CfA2 redshift survey, without regard to the surroundings of the tight
systems. We probe the relationship between star formation and the dynamics of
the systems of galaxies. The equivalent widths of H\alpha (EW(H\alpha) and
other emission lines anti-correlate strongly with pair spatial separation
(\Delta D) and velocity separation. We use the measured EW(H\alpha) and the
starburst models of Leitherer et al. to estimate the time since the most recent
burst of star for- mation began for each galaxy. In the absence of a large
contribution from an old stellar population to the continuum around H\alpha,
the observed \Delta D -- EW(H\alpha) correlation signifies that starbursts with
larger separations on the sky are, on average, older. By matching the dynamical
timescale to the burst timescale, we show that the data support a simple
picture in which a close pass initiates a starburst; EW(H\alpha) decreases with
time as the pair separation increases, accounting for the anti-correlation.
This picture leads to a method for measuring the duration and the initial mass
function of interaction-induced starbursts: our data are compatible with the
starburst and orbit models in many respects, as long as the starburst lasts
longer than \sim10^8 years and the delay between the close pass and the
initiation of the starburst is less than a few \times 10^7 years. If there is
no large contribution from an old stellar population to the continuum around
H\alpha the Miller-Scalo and cutoff (M <= 30 M_\sun) Salpeter initial mass
functions fit the data much better than a standard Salpeter IMF. (Abridged.)Comment: 43 pages, 22 figures, to appear in the ApJ; we correct an error which
had minor effects on numerical values in the pape
The risk, burden, and management of non-communicable diseases in cerebral palsy: a scoping review.
AIM: To examine the risk, burden, and management of non-communicable diseases (NCDs) among people with cerebral palsy (CP). METHOD: Databases (Ovid MEDLINE, Embase Ovid, CINAHL Plus) were systematically searched up to August 2017. Data on the prevalence of risk factors for, and the burden and management of, cardiovascular diseases, diabetes, cancers, and respiratory diseases were extracted. RESULTS: Thirty-six studies that examined the prevalence of risk factors among people with CP were identified. There was inconsistent evidence that people with CP had higher prevalence of metabolic risk factors such as hypertension, hyperlipidaemia, and obesity, but strong evidence that they participated in low levels of physical activity, compared with people without CP. Seven studies reported on the burden of NCDs. Adults with CP had a higher risk of NCDs, including stroke, chronic obstructive pulmonary disease, and other heart conditions, and death due to NCDs, including cancers, chronic obstructive pulmonary disease, stroke, and ischaemic heart disease, compared with the general population. Only one study reported on the management of NCD, specifically the uptake of breast cancer screening among females. INTERPRETATION: The burden of NCDs is higher among adults with CP compared with the general population. Further research is required to determine the prevalence of metabolic risk factors and management of NCDs among people with CP. WHAT THIS PAPER ADDS: Adults with cerebral palsy (CP) have an increased risk of non-communicable diseases (NCDs) and increased risk of death because of NCDs. Evidence is inconsistent about the elevated prevalence of metabolic risk factors for NCDs. Evidence is consistent that people with CP participate in reduced physical activity. Only one study reported on management of NCD among people with CP. Available evidence suggests people with CP are less likely to receive preventive medicine
Overview of C/C-SiC Composite Development for the Orion Launch Abort System
Past and present efforts by the authors to further understanding of the ceramic matrix composite (CMC) material used in the valve components of the Orion Launch Abort System (LAS) Attitude Control Motor (ACM) will be presented. The LAS is designed to quickly lift the Orion Crew Exploration Vehicle (CEV) away from its launch vehicle in emergency abort scenarios. The ACM is a solid rocket motor which utilizes eight throttleable nozzles to maintain proper orientation of the CEV during abort operations. Launch abort systems have not been available for use by NASA on manned launches since the last Apollo ]Saturn launch in 1975. The CMC material, carbon-carbon/silicon-carbide (C/C-SiC), is manufactured by Fiber Materials, Inc. and consists of a rigid 4-directional carbon-fiber tow weave reinforced with a mixed carbon plus SiC matrix. Several valve and full system (8-valve) static motor tests have been conducted by the motor vendor. The culmination of these tests was the successful flight test of the Orion LAS Pad Abort One (PA ]1) vehicle on May 6, 2010. Due to the fast pace of the LAS development program, NASA Marshall Space Flight Center assisted the LAS community by performing a series of material and component evaluations using fired hardware from valve and full ]system development motor tests, and from the PA-1 flight ACM motor. Information will be presented on the structure of the C/C-SiC material, as well as the efficacy of various non ]destructive evaluation (NDE) techniques, including but not limited to: radiography, computed tomography, nanofocus computed tomography, and X-ray transmission microscopy. Examinations of the microstructure of the material via scanning electron microscopy and energy dispersive spectroscopy will also be discussed. The findings resulting from the subject effort are assisting the LAS Project in risk assessments and in possible modifications to the final ACM operational design
Factors associated with dietary diversity and length-for-age z-score in rural Ethiopian children aged 6-23Â months: A novel approach to the analysis of baseline data from the Sustainable Undernutrition Reduction in Ethiopia evaluation.
Infants and young children need diets high in nutrient density and diversity to meet the requirements of rapid growth and development. Our aim was to evaluate sociodemographic, agricultural diversity, and women's empowerment factors associated with child dietary diversity and length-for-age z-score (LAZ) in children 6-23Â months using data collected as part of the Sustainable Undernutrition Reduction in Ethiopia (SURE) evaluation study baseline survey in May-June 2016. We here present a novel analysis using directed acyclic graphs (DAGs) to represent our assumptions about the causal influences between the factors of interest and the outcomes. The causal diagrams enabled the identification of variables to be included in multivariable analysis to estimate the total effects of factors of interest using ordinal logistic/linear regression models. We found that child dietary diversity was positively associated with LAZ with children consuming 4 or more food groups having on average an LAZ score 0.42 (95% CI [0.08, 0.77]) higher than those consuming no complementary foods. Household production of fruits and vegetables was associated with both increased child dietary diversity (adjusted OR 1.16; 95% CI [1.09, 1.24]) and LAZ (adjusted mean difference 0.05; 95% CI [0.005, 0.10]). Other factors positively associated with child dietary diversity included age in months, socio-economic status, maternal education, women's empowerment and dietary diversity, paternal childcare support, household food security, fruit and vegetable cultivation, and land ownership. LAZ was positively associated with age, socio-economic status, maternal education, fruit and vegetable production, and land ownership
Ariel - Volume 9 Number 4
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IMPACT OF PASSIVE LEG MOVEMENT ON LOWER LIMB VASCULAR FUNCTION IN PATIENTS WITH A SPINAL CORD INJURY
Background: Individuals with spinal cord injuries (SCI) are at a greater risk for developing cardiovascular diseases. Of note, post injury mediated increases in physical inactivity leads to muscle atrophy, which also results in vascular dysfunction in this population. Although a growing body of evidence suggests that passive leg movement (PLM) may be a useful exercise modality to improve peripheral blood flow and skeletal muscle activation in individuals with limited mobility, few studies have examined the impact of PLM on local skeletal muscle blood flow. Therefore, there is a need to examine the impact of PLM on lower limb vascular function and skeletal muscle oxygen utilization capacity in patients with SCI. Methods: Individuals with SCI (n=2) and healthy age-matched controls (CON, n=5) were recruited for this study. Participants were fitted with a standard knee brace and were instructed to rest in the seated position for 20 minutes with their legs bent at 90. PLM was performed by flexion and extension of the lower leg (90-180) at a rate of 1 Hz (60 bpm) for 5 minutes. A Doppler ultrasound was located on the superficial femoral artery, and blood flow and diameter were measured for 5 minutes at rest and during the PLM protocol. Following the PLM protocol, the leg was held in the extended position (180) for 5 minutes of recovery. Results: We found that the SCI group had a significantly lower blood flow response to PLM compared to the CON group (p=0.004). Furthermore, post-PLM femoral artery blood velocity and shear rate significantly increased in both SCI and CON compared to pre-PLM (p=0.014, and p=0.016, respectively) but no differences were found between groups. Finally, the SCI group had significantly smaller vessel diameters compared with CON (pConclusion: We found that PLM could efficiently increase blood flow and blood velocity in SCI. Although the magnitude of this increase was significantly lower in SCI compared to healthy age-matched control, PLM produced shear rates in the leg arteries that were similar between SCI and CON, which indicates that PLM may potentially be an efficient exercise modality to improve leg vascular function in individuals with SCI
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Women’s responses to changes in U.S. preventive task force’s mammography screening guidelines: results of focus groups with ethnically diverse women
Background: The 2009 U.S. Preventive Services Task Force (USPSTF) changed mammography guidelines to recommend routine biennial screening starting at age 50. This study describes women’s awareness of, attitudes toward, and intention to comply with these new guidelines. Methods: Women ages 40–50 years old were recruited from the Boston area to participate in focus groups (k = 8; n = 77). Groups were segmented by race/ethnicity (Caucasian = 39%; African American = 35%; Latina = 26%), audio-taped, and transcribed. Thematic content analysis was used. Results: Participants were largely unaware of the revised guidelines and suspicious that it was a cost-savings measure by insurers and/or providers. Most did not intend to comply with the change, viewing screening as obligatory. Few felt prepared to participate in shared decision-making or advocate for their preferences with respect to screening. Conclusions: Communication about the rationale for mammography guideline changes has left many women unconvinced about potential disadvantages or limitations of screening. Since further guideline changes are likely to occur with advances in technology and science, it is important to help women become informed consumers of health information and active participants in shared decision-making with providers. Additional research is needed to determine the impact of the USPSTF change on women’s screening behaviors and on breast cancer outcomes
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