921 research outputs found

    The Future Theater-Level Model: A Research Project Update

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    Proceedings of the 1994 Winter Simulation Conference ed. J. D. Tew, S. Manivannan, D. A. Sadowski, and A. F. SeilaResearch has been conducted at the Naval Postgraduate School into new methodologies for joint theater-level combat simulation modeling, emphasizing C3I, operational intelligence, decisionmaking under uncertainty, and aggregated stochastic process modeling. Research outcomes to date as well as a prototype software tool are described in this paper

    The surface area and reactivity of granitic soils: I. Dissolution rates of primary minerals as a function of depth and age deduced from field observations

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    Surface area-normalised dissolution rates of the primary minerals in two distinct granitic soils located in 1) the Dartmoor National Park, England and 2) Glen Dye, Scotland were determined as a function of depth. Each soil was sampled to a depth of ~ 1 m. The maximum soil ages based on 14C analysis of the humin fraction of the soil are 15,600 and 4400 years for the Dartmoor and Glen Dye soil profiles, respectively. The measured BET surface areas of the soil minerals are close to 5 m2/g in the B and C horizons, but decrease to less than 1 m2/g close to the surface. Retrieved geometric surface area normalised mineral dissolution rates are most rapid at the surface and at the bedrock–soil interface; this behaviour is interpreted to stem from a combination of the approach to equilibrium of the soil waters with depth and more rapid dissolution rates of fresh versus weathered surfaces. At the soil surface, the relative mineral dissolution rate order is found to be quartz > feldspar > mica, with quartz geometric surface area dissolution rates as fast as 2.6 to 4.1 × 10− 13 mol/m2/s. As observed in a number of past studies, field based rates obtained in this study are significantly slower than corresponding rates obtained from laboratory studies, suggesting that these latter rates may not accurately describe the reactivity of primary minerals in soils

    Sleep During Pregnancy: The nuMoM2b Pregnancy and Sleep Duration and Continuity Study

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    Study Objectives: To characterize sleep duration, timing and continuity measures in pregnancy and their association with key demographic variables. Methods: Multisite prospective cohort study. Women enrolled in the nuMoM2b study (nulliparous women with a singleton gestation) were recruited at the second study visit (16-21 weeks of gestation) to participate in the Sleep Duration and Continuity substudy. Women <18 years of age or with pregestational diabetes or chronic hypertension were excluded from participation. Women wore a wrist activity monitor and completed a sleep log for 7 consecutive days. Time in bed, sleep duration, fragmentation index, sleep efficiency, wake after sleep onset, and sleep midpoint were averaged across valid primary sleep periods for each participant. Results: Valid data were available from 782 women with mean age of 27.3 (5.5) years. Median sleep duration was 7.4 hours. Approximately 27.9% of women had a sleep duration of 9 hours. In multivariable models including age, race/ethnicity, body mass index, insurance status, and recent smoking history, sleep duration was significantly associated with race/ethnicity and insurance status, while time in bed was only associated with insurance status. Sleep continuity measures and sleep midpoint were significantly associated with all covariates in the model, with the exception of age for fragmentation index and smoking for wake after sleep onset. Conclusions: Our results demonstrate the relationship between sleep and important demographic characteristics during pregnancy

    Loss of placental growth factor ameliorates maternal hypertension and preeclampsia in mice

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    Preeclampsia remains a clinical challenge due to its poorly understood pathogenesis. A prevailing notion is that increased placental production of soluble fms-like tyrosine kinase-1 (sFlt-1) causes the maternal syndrome by inhibiting proangiogenic placental growth factor (PlGF) and VEGF. However, the significance of PlGF suppression in preeclampsia is uncertain. To test whether preeclampsia results from the imbalance of angiogenic factors reflected by an abnormal sFlt-1/PlGF ratio, we studied PlGF KO (Pgf-/-) mice and noted that the mice did not develop signs or sequelae of preeclampsia despite a marked elevation in circulating sFLT-1. Notably, PlGF KO mice had morphologically distinct placentas, showing an accumulation of junctional zone glycogen. We next considered the role of placental PlGF in an established model of preeclampsia (pregnant catechol-O-methyltransferase-deficient [COMT-deficient] mice) by generating mice with deletions in both the Pgf and Comt genes. Deletion of placental PlGF in the context of COMT loss resulted in a reduction in maternal blood pressure and increased placental glycogen, indicating that loss of PlGF might be protective against the development of preeclampsia. These results identify a role for PlGF in placental development and support a complex model for the pathogenesis of preeclampsia beyond an angiogenic factor imbalance

    Objectively measured short sleep duration and later sleep midpoint in pregnancy are associated with a higher risk of gestational diabetes

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    BACKGROUND: Experimental and epidemiologic data suggest that among nonpregnant adults, sleep duration may be an important risk factor for chronic disease. Although pregnant women commonly report poor sleep, few studies objectively evaluated the quality of sleep in pregnancy or explored the relationship between sleep disturbances and maternal and perinatal outcomes. OBJECTIVE: Our objective was to examine the relationship between objectively assessed sleep duration, timing, and continuity (measured via wrist actigraphy) and maternal cardiovascular and metabolic morbidity specific to pregnancy. STUDY DESIGN: This was a prospective cohort study of nulliparous women. Women were recruited between 16 0/7 and 21 6/7 weeks' gestation. They were asked to wear a wrist actigraphy monitor and complete a daily sleep log for a period of 7 consecutive days. The primary sleep exposure variables were the averages of the following over the total valid nights (minimum 5, maximum 7 nights): short sleep duration during the primary sleep period (5 am), and top quartile of minutes of wake time after sleep onset and sleep fragmentation index. The primary outcomes of interest were a composite of hypertensive disorders of pregnancy (mild, severe, or superimposed preeclampsia; eclampsia; or antepartum gestational hypertension) and gestational diabetes mellitus. We used χ2 tests to assess associations between sleep variables and categorical baseline characteristics. Crude odds ratios and 95% confidence intervals were estimated from univariate logistic regression models to characterize the magnitude of the relationship between sleep characteristics and hypertensive disorders of pregnancy and gestational diabetes. For associations significant in univariate analysis, multiple logistic regression was used to explore further the association of sleep characteristics with pregnancy outcomes. RESULTS: In all, 901 eligible women consented to participate; 782 submitted valid actigraphy studies. Short sleep duration and a later sleep midpoint were associated with an increased risk of gestational diabetes (odds ratio, 2.24; 95% confidence interval, 1.11-4.53; and odds ratio, 2.58; 95% confidence interval, 1.24-5.36, respectively) but not of hypertensive disorders. A model with both sleep duration and sleep midpoint as well as their interaction term revealed that while there was no significant interaction between these exposures, the main effects of both short sleep duration and later sleep midpoint with gestational diabetes remained significant (adjusted odds ratio, 2.06; 95% confidence interval, 1.01-4.19; and adjusted odds ratio, 2.37; 95% confidence interval, 1.13-4.97, respectively). Additionally, after adjusting separately for age, body mass index, and race/ethnicity, both short sleep duration and later sleep midpoint remained associated with gestational diabetes. No associations were demonstrated between the sleep quality measures (wake after sleep onset, sleep fragmentation) and hypertensive disorders or gestational diabetes. CONCLUSION: Our results demonstrate a relationship between short sleep duration and later sleep midpoint with gestational diabetes. Our data suggest independent contributions of these 2 sleep characteristics to the risk for gestational diabetes in nulliparous women

    Association of Adverse Pregnancy Outcomes With Hypertension 2 to 7 Years Postpartum

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    Background Identifying pregnancy-associated risk factors before the development of major cardiovascular disease events could provide opportunities for prevention. The objective of this study was to determine the association between outcomes in first pregnancies and subsequent cardiovascular health. Methods and Results The Nulliparous Pregnancy Outcomes Study Monitoring Mothers-to-be Heart Health Study is a prospective observational cohort that followed 4484 women 2 to 7 years (mean 3.2 years) after their first pregnancy. Adverse pregnancy outcomes (defined as hypertensive disorders of pregnancy, small-for-gestational-age birth, preterm birth, and stillbirth) were identified prospectively in 1017 of the women (22.7%) during this pregnancy. The primary outcome was incident hypertension (HTN). Women without adverse pregnancy outcomes served as controls. Risk ratios (RR) and 95% CIs were adjusted for age, smoking, body mass index, insurance type, and race/ethnicity at enrollment during pregnancy. The overall incidence of HTN was 5.4% (95% CI 4.7% to 6.1%). Women with adverse pregnancy outcomes had higher adjusted risk of HTN at follow-up compared with controls (RR 2.4, 95% CI 1.8-3.1). The association held for individual adverse pregnancy outcomes: any hypertensive disorders of pregnancy (RR 2.7, 95% CI 2.0-3.6), preeclampsia (RR 2.8, 95% CI 2.0-4.0), and preterm birth (RR 2.7, 95% CI 1.9-3.8). Women who had an indicated preterm birth and hypertensive disorders of pregnancy had the highest risk of HTN (RR 4.3, 95% CI 2.7-6.7). Conclusions Several pregnancy complications in the first pregnancy are associated with development of HTN 2 to 7 years later. Preventive care for women should include a detailed pregnancy history to aid in counseling about HTN risk

    Measurement of the Branching Fraction for B- --> D0 K*-

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    We present a measurement of the branching fraction for the decay B- --> D0 K*- using a sample of approximately 86 million BBbar pairs collected by the BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the K*- through its decay to K0S pi-. We measure the branching fraction to be B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid Communications

    Evidence for the Rare Decay B -> K*ll and Measurement of the B -> Kll Branching Fraction

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    We present evidence for the flavor-changing neutral current decay B→K∗ℓ+ℓ−B\to K^*\ell^+\ell^- and a measurement of the branching fraction for the related process B→Kℓ+ℓ−B\to K\ell^+\ell^-, where ℓ+ℓ−\ell^+\ell^- is either an e+e−e^+e^- or μ+μ−\mu^+\mu^- pair. These decays are highly suppressed in the Standard Model, and they are sensitive to contributions from new particles in the intermediate state. The data sample comprises 123×106123\times 10^6 Υ(4S)→BBˉ\Upsilon(4S)\to B\bar{B} decays collected with the Babar detector at the PEP-II e+e−e^+e^- storage ring. Averaging over K(∗)K^{(*)} isospin and lepton flavor, we obtain the branching fractions B(B→Kℓ+ℓ−)=(0.65−0.13+0.14±0.04)×10−6{\mathcal B}(B\to K\ell^+\ell^-)=(0.65^{+0.14}_{-0.13}\pm 0.04)\times 10^{-6} and B(B→K∗ℓ+ℓ−)=(0.88−0.29+0.33±0.10)×10−6{\mathcal B}(B\to K^*\ell^+\ell^-)=(0.88^{+0.33}_{-0.29}\pm 0.10)\times 10^{-6}, where the uncertainties are statistical and systematic, respectively. The significance of the B→Kℓ+ℓ−B\to K\ell^+\ell^- signal is over 8σ8\sigma, while for B→K∗ℓ+ℓ−B\to K^*\ell^+\ell^- it is 3.3σ3.3\sigma.Comment: 7 pages, 2 postscript figues, submitted to Phys. Rev. Let

    Study of e+e- --> pi+ pi- pi0 process using initial state radiation with BABAR

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    The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum we have obtained the products of branching fractions for the omega and phi mesons, B(omega --> e+e-)B(omega --> 3pi)=(6.70 +/- 0.06 +/- 0.27)10-5 and B(phi --> e+e-)B(phi --> 3pi)=(4.30 +/- 0.08 +/- 0.21)10-5, and evaluated the e+e- --> pi+ pi- pi0 cross section for the e+e- center-of-mass energy range 1.05 to 3.00 GeV. About 900 e+e- --> J/psi gamma --> pi+ pi- pi0 gamma events have been selected and the branching fraction B(J/psi --> pi+ pi- pi0)=(2.18 +/- 0.19)% has been measured.Comment: 21 pages, 37 postscript figues, submitted to Phys. Rev.
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