1,047 research outputs found
Predicting cesarean section and uterine rupture among women attempting vaginal birth after prior cesarean section
<p><b>Background:</b> There is currently no validated method for antepartum prediction of the risk of failed vaginal birth after cesarean section and no information on the relationship between the risk of emergency cesarean delivery and the risk of uterine rupture.</p>
<p><b>Methods and Findings:</b> We linked a national maternity hospital discharge database and a national registry of perinatal deaths. We studied 23,286 women with one prior cesarean delivery who attempted vaginal birth at or after 40-wk gestation. The population was randomly split into model development and validation groups. The factors associated with emergency cesarean section were maternal age (adjusted odds ratio [OR] = 1.22 per 5-y increase, 95% confidence interval [CI]: 1.16 to 1.28), maternal height (adjusted OR = 0.75 per 5-cm increase, 95% CI: 0.73 to 0.78), male fetus (adjusted OR = 1.18, 95% CI: 1.08 to 1.29), no previous vaginal birth (adjusted OR = 5.08, 95% CI: 4.52 to 5.72), prostaglandin induction of labor (adjusted OR = 1.42, 95% CI: 1.26 to 1.60), and birth at 41-wk (adjusted OR = 1.30, 95% CI: 1.18 to 1.42) or 42-wk (adjusted OR = 1.38, 95% CI: 1.17 to 1.62) gestation compared with 40-wk. In the validation group, 36% of the women had a low predicted risk of caesarean section (<20%) and 16.5% of women had a high predicted risk (>40%); 10.9% and 47.7% of these women, respectively, actually had deliveries by caesarean section. The predicted risk of caesarean section was also associated with the risk of all uterine rupture (OR for a 5% increase in predicted risk = 1.22, 95% CI: 1.14 to 1.31) and uterine rupture associated with perinatal death (OR for a 5% increase in predicted risk = 1.32, 95% CI: 1.02 to 1.73). The observed incidence of uterine rupture was 2.0 per 1,000 among women at low risk of cesarean section and 9.1 per 1,000 among those at high risk (relative risk = 4.5, 95% CI: 2.6 to 8.1). We present the model in a simple-to-use format.</p>
<p><b>Conclusions:</b> We present, to our knowledge, the first validated model for antepartum prediction of the risk of failed vaginal birth after prior cesarean section. Women at increased risk of emergency caesarean section are also at increased risk of uterine rupture, including catastrophic rupture leading to perinatal death.</p>
Breeding Ecology of Birds at Teshekpuk Lake: A Key Habitat Site on the Arctic Coastal Plain of Alaska
The Teshekpuk Lake Special Area in the National Petroleum Reserve â Alaska (NPR-A) currently has no long-term protection from oil development. In this study, we provide novel information on nest density, productivity, and habitat use at Teshekpuk relative to a developed oilfield site at Prudhoe Bay, Alaska, to assess the importance of Teshekpuk for tundra-nesting birds and to provide recommendations regarding potential oil development. Mean annual nest density of all bird species combined was significantly higher at Teshekpuk than at Prudhoe Bay and was higher than any of five other sites with comparable data on the Alaskan Arctic Coastal Plain. Nest densities were significantly higher at Teshekpuk than at Prudhoe Bay for Lapland longspurs (Calcarius lapponicus) and long-billed dowitchers (Limnodromus scolopaceus), although those for semipalmated sandpipers (Calidris pusilla) were higher at Prudhoe Bay. Total shorebird nest densities at Teshekpuk were among the highest of any sites in the region. At Teshekpuk, shorebirds nested preferentially in wet and emergent habitats, including flooded low-center polygons, non-patterned tundra, and Carex aquatilis-dominated habitats. Therefore, we recommend that future oil infrastructure placement in this region avoid these habitats. Using data collected at Teshekpuk and Prudhoe Bay from 2005 to 2008, we modeled nest survivorship for 11 shorebird species and for Lapland longspurs. For longspurs, the best-supported models based on AICc values indicated that nest survival was always higher at Teshekpuk, but it was also higher elsewhere in years of high lemming abundance and later in the nesting season. For shorebirds, the best-supported models indicated that nest survivorship was highly variable among years and sites. Uniparental-nesting shorebirds had lower nest survivorship shortly after nest initiation followed by a rapid increase, while biparental survivorship was consistently high throughout the nest lifetime. We recommend that disturbances to nesting habitat be minimized during early June, when vulnerability to nest failure is higher. Because of their high importance to Arctic breeding birds, we recommend that areas within the Teshekpuk Lake Special Area, including our study area and those that are currently under 10-year deferral, be considered for permanent protection.La zone spĂ©ciale du lac Teshekpuk situĂ©e dans la rĂ©serve nationale de pĂ©trole de lâAlaska (NPR-A) nâest dotĂ©e dâaucune protection Ă long terme en matiĂšre de mise en valeur pĂ©troliĂšre. Dans la prĂ©sente Ă©tude, nous fournissons de nouveaux renseignements sur la densitĂ© des nids, la productivitĂ© et lâutilisation de lâhabitat Ă Teshekpuk Ă la lumiĂšre dâun chantier de mise en valeur pĂ©troliĂšre Ă la baie Prudhoe, en Alaska et ce, dans le but dâĂ©valuer lâimportance de Teshekpuk pour les oiseaux qui nichent dans la toundra ainsi que de fournir des recommandations en matiĂšre de mise en valeur pĂ©troliĂšre future. La densitĂ© moyenne annuelle des nids de toutes les espĂšces dâoiseaux prises ensemble Ă©tait considĂ©rablement supĂ©rieure Ă Teshekpuk quâĂ la baie Prudhoe et Ă©tait plus Ă©levĂ©e que dans nâimporte quel des cinq autres sites aux donnĂ©es comparables sur la plaine cĂŽtiĂšre arctique de lâAlaska. La densitĂ© des nids Ă©tait considĂ©rablement supĂ©rieure Ă Teshekpuk quâĂ la baie Prudhoe dans le cas du bruant lapon (Calcarius lapponicus) et du bĂ©casseau Ă long bec (Limnodromus scolopaceus), tandis que les densitĂ©s du bĂ©casseau semipalmĂ© (Calidris pusilla) Ă©taient plus Ă©levĂ©es Ă la baie Prudhoe. Les densitĂ©s totales de nids dâoiseaux de rivage Ă Teshekpuk comptaient parmi les densitĂ©s les plus Ă©levĂ©es de nâimporte quel des sites de la rĂ©gion. Ă Teshekpuk, les oiseaux de rivage nichaient, de prĂ©fĂ©rence, dans des habitats humides et Ă©mergents, ce qui comprend les polygones concaves inondĂ©s et la toundra non rĂ©ticulĂ©e de mĂȘme que les habitats dominĂ©s par le Carex aquatilis. Nous recommandons donc que lâemplacement dâinfrastructures pĂ©troliĂšres futures dans cette rĂ©gion Ă©vite ces habitats. Ă lâaide de donnĂ©es recueillies Ă Teshekpuk et Ă la baie Prudhoe de 2005 Ă 2008, nous avons modĂ©lisĂ© la prĂ©somption de survie en nid de 11 espĂšces dâoiseaux de rivage et des bruants lapons. Dans le cas des bruants lapons, les modĂšles les mieux soutenus dâaprĂšs les valeurs AICc laissent entrevoir que la survie en nid Ă©tait constamment supĂ©rieure Ă Teshekpuk, mais quâelle Ă©tait Ă©galement plus Ă©levĂ©e ailleurs pendant les annĂ©es de grande abondance de lemmings de mĂȘme quâĂ une pĂ©riode plus tardive de la saison de nidification. Dans le cas des oiseaux de rivage, les modĂšles les mieux soutenus indiquent que la survie en nid varie beaucoup dâune annĂ©e Ă lâautre et dâun emplacement Ă lâautre. Les oiseaux de rivage en mode de nidification monoparental affichaient un taux de survie en nid moins Ă©levĂ© peu aprĂšs lâinitiation du nid, ce qui Ă©tait suivi dâune augmentation rapide, tandis que le taux de survie des oiseaux en mode de nidification biparental Ă©tait constamment Ă©levĂ© pendant toute la durĂ©e dâexistence du nid. Nous recommandons donc que les perturbations Ă lâhabitat de nidification soient rĂ©duites au minimum au dĂ©but de juin car câest Ă ce moment-lĂ que la nidification est plus vulnĂ©rable. Compte tenu de leur grande importance pour les oiseaux nicheurs de lâArctique, nous recommandons que les aires faisant partie de la zone spĂ©ciale du lac Teshekpuk, ce qui comprend lâaire visĂ©e par notre Ă©tude et les aires faisant couramment lâobjet dâun report de 10 ans, soient considĂ©rĂ©es Ă titre de protection permanente
Electrical activation of the ventricular myocardium of the crocodile Crocodylus johnstoni: A combined microscopic and electrophysiological study
We mapped the sequence of ventricular depolarization in the crocodile Crocodylus johnstoni. We also attempted to find specialized conduction tissue within the ventricular myocardium. Electrical recordings with miniature multi-point electrodes revealed two strands of rapidly conducting tissue (channels) within the interventricular septum, suggestive of conductive tissue pathways. From these septal channels, wavefronts of excitation swept around each ventricle. Electrical recordings did not indicate that there was conductive tissue in the wall of either ventricle. Similarly, microscopic studies of the septal channels provided no indication of specialized conductive tissue. We suggest that the channels of early septal depolarization provide the crocodile heart with a high speed depolarization pathway functionally analogous to a rudimentary conductive system
Cost-effectiveness of new cardiac and vascular rehabilitation strategies for patients with coronary artery disease
Objective: Peripheral arterial disease (PAD) often hinders the cardiac rehabilitation program. The aim of this study was evaluating the relative cost-effectiveness of new rehabilitation strategies which include the diagnosis and treatment of PAD in patients with coronary artery disease (CAD) undergoing cardiac rehabilitation. Data Sources: Best-available evidence was retrieved from literature and combined with primary data from 231 patients. Methods: We developed a Markov decision model to compare the following treatment strategies: 1. cardiac rehabilitation only; 2. ankle-brachial index (ABI) if cardiac rehabilitation fails followed by diagnostic work-up and revascularization for PAD if needed; 3. ABI prior to cardiac rehabilitation followed by diagnostic work-up and revascularization for PAD if needed. Quality-adjusted-life years (QALYs), life-time costs (US 75 000 was used. Results: ABI if cardiac rehabilitation fails was the most favorable strategy with an ICER of 75 000/ QALY. After sensitivity analysis, a combined cardiac and vascular rehabilitation program increased the success rate and would dominate the other two strategies with total lifetime costs of $30 246 a quality-adjusted life expectancy of 3.84 years, and an incremental NHB of 0.06 QALYs (95%CI:-0.24, 0.46) compared to current practice. The results were robust for other different input parameters. Conclusion: ABI measurement if cardiac rehabilitation fails followed by a diagnostic work-up and revascularization for PAD if needed are potentially cost-effective compared to cardiac rehabilitation only
Calcification in the soft tissues of the chest after thoracotomy
We have observed soft-tissue calcification of the chest in 4 of 54 patients following thoracotomy in the neonatal period for a Blalock-Taussig or a Blalock-Hanlon procedure. The time of appearance ranged from 2 weeks to 11 months. This calcification is similar to myositis ossificans in having a traumatic origin. In one of the patients, it resolved spontaneously.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46812/1/256_2004_Article_BF00347331.pd
Species-specific responses of planktivorous fish to the introduction of a new piscivore: implications for prey fitness
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75539/1/j.1365-2427.2007.01810.x.pd
Sub-surface Oxygen and Surface Oxide Formation at Ag(111): A Density-functional Theory Investigation
To help provide insight into the remarkable catalytic behavior of the
oxygen/silver system for heterogeneous oxidation reactions, purely sub-surface
oxygen, and structures involving both on-surface and sub-surface oxygen, as
well as oxide-like structures at the Ag(111) surface have been studied for a
wide range of coverages and adsorption sites using density-functional theory.
Adsorption on the surface in fcc sites is energetically favorable for low
coverages, while for higher coverage a thin surface-oxide structure is
energetically favorable. This structure has been proposed to correspond to the
experimentally observed (4x4) phase. With increasing O concentrations, thicker
oxide-like structures resembling compressed Ag2O(111) surfaces are
energetically favored. Due to the relatively low thermal stability of these
structures, and the very low sticking probability of O2 at Ag(111), their
formation and observation may require the use of atomic oxygen (or ozone, O3)
and low temperatures. We also investigate diffusion of O into the sub-surface
region at low coverage (0.11 ML), and the effect of surface Ag vacancies in the
adsorption of atomic oxygen and ozone-like species. The present studies,
together with our earlier investigations of on-surface and
surface-substitutional adsorption, provide a comprehensive picture of the
behavior and chemical nature of the interaction of oxygen and Ag(111), as well
as of the initial stages of oxide formation.Comment: 17 pages including 14 figures, Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances
1. Movements of many animals along a life-path can be separated into repetitive ones within home ranges and transitions between home ranges. We sought relationships of social and environmental factors with initiation and distance of transition movements in 114 buzzards Buteo buteo that were marked as nestlings with long-life radio tags.
2. Ex-natal dispersal movements of 51 buzzards in autumn were longer than for 30 later in their first year and than 35 extra-natal movements between home ranges after leaving nest areas. In the second and third springs, distances moved from winter focal points by birds that paired were the same or less than for unpaired birds. No post-nuptial movement exceeded 2 km.
3. Initiation of early ex-natal dispersal was enhanced by presence of many sibs, but also by lack of worm-rich loam soils. Distances travelled were greatest for birds from small broods and with relatively little short grass-feeding habitat near the nest. Later movements were generally enhanced by the absence of loam soils and short grassland, especially with abundance of other buzzards and probable poor feeding habitats (heathland, long grass).
4. Buzzards tended to persist in their first autumn where arable land was abundant, but subsequently showed a strong tendency to move from this habitat.
5. Factors that acted most strongly in œ-km buffers round nests, or round subsequent focal points, usually promoted movement compared with factors acting at a larger scale. Strong relationships between movement distances and environmental characteristics in œ-km buffers, especially during early ex-natal dispersal, suggested that buzzards became primed by these factors to travel far.
6. Movements were also farthest for buzzards that had already moved far from their natal nests, perhaps reflecting genetic predisposition, long-term priming or poor habitat beyond the study area
Asteroseismology of red giants & galactic archaeology
Red-giant stars are low- to intermediate-mass (~M)
stars that have exhausted hydrogen in the core. These extended, cool and hence
red stars are key targets for stellar evolution studies as well as galactic
studies for several reasons: a) many stars go through a red-giant phase; b) red
giants are intrinsically bright; c) large stellar internal structure changes as
well as changes in surface chemical abundances take place over relatively short
time; d) red-giant stars exhibit global intrinsic oscillations. Due to their
large number and intrinsic brightness it is possible to observe many of these
stars up to large distances. Furthermore, the global intrinsic oscillations
provide a means to discern red-giant stars in the pre-helium core burning from
the ones in the helium core burning phase and provide an estimate of stellar
ages, a key ingredient for galactic studies. In this lecture I will first
discuss some physical phenomena that play a role in red-giant stars and several
phases of red-giant evolution. Then, I will provide some details about
asteroseismology -- the study of the internal structure of stars through their
intrinsic oscillations -- of red-giant stars. I will conclude by discussing
galactic archaeology -- the study of the formation and evolution of the Milky
Way by reconstructing its past from its current constituents -- and the role
red-giant stars can play in that.Comment: Lecture presented at the IVth Azores International Advanced School in
Space Sciences on "Asteroseismology and Exoplanets: Listening to the Stars
and Searching for New Worlds" (arXiv:1709.00645), which took place in Horta,
Azores Islands, Portugal in July 201
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