11,185 research outputs found

    Kodaira Dimension of Subvarieties

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    In this article we study how the birational geometry of a normal projective variety XX is influenced by a normal subvariety A⊂X.A \subset X. One of the most basic examples in this context is provided by the following situation. Let f:X→Yf:X\to Y be a surjective holomorphic map with connected fibers between compact connected complex manifolds. It is well known that given a general fiber AA of ff we have Îș(X)≀Îș(A)+dim⁥Y. \kappa(X)\le \kappa(A)+\dim Y. This article grew out of the realization that this result should be true with dim⁥Y\dim Y replaced by the codimension \cod_X A for a pair (X,A)(X,A) consisting of a normal subvariety AA of a compact normal variety XX under weak semipositivity conditions on the normal sheaf of AA and the weak singularity condition \cod_A (A\cap\sing X)\ge 2. We shall now state our main results in the special case of a submanifold AA in a projective manifold XX and we also simplify the semipositivity notion

    Comparison of Abstinence and Coital Frequency between Two Natural Methods of Family Planning

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    Problem Statement: The length of periodic abstinence, due to overestimation of the fertile phase of the menstrual cycle is often a reason for dissatisfaction, discontinuation, and user error with natural family planning (NFP) methods. The objective of this research was to compare the length of required abstinence (i.e., estimated fertility) and coital frequency between two NFP methods. Study Design: Analysis of existing data from a 12 month prospective comparison study in which participants were randomized into either an electronic hormonal fertility monitor (EHFM) group or a cervical mucus monitoring (CMM) group, both of which included a fertility algorithm as a double check for the beginning and end of the estimated FW. The current study involved 197 women (mean age 29.7, SD=5.4) who used the EHFM to estimate the FW and 162 women (mean age 30.4, SD=5.3) who used CMM to estimate the FW. They produced 1,669 menstrual cycles of data. Number of days of estimated fertility and coitus was extracted from each cycle and t-tests were used to compare the means of these two variables between the two NFP methods. Results: After six months of use, the EHFM group had statistically fewer days of estimated fertility than the CMM group (13.25 days, SD=2.79 versus 13.65 days, SD=2.99; t=2.07, p = .04) and significantly more coitus (4.22 coital acts, SD=3.16 versus 4.05 acts, SD=2.88, t=1.17, p=.026). Conclusion: The use of the EHFM seems to provide more objectivity and confidence in self-estimating the FW and use of non-fertile days for intercourse when avoiding pregnancy

    Promoting Partnerships for Student Success: Lessons from the SSPIRE Initiative

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    The Student Support Partnership Integrating Resources and Education (SSPIRE) initiative aimed to increase the success of young, low-income, and academically underprepared California community college students by helping colleges strengthen their support services and better integrate these services with academic instruction. This report describes what the nine participating community colleges did to meet the goals of SSPIRE and offers lessons for other institutions drawn from MDRC's research on the initiative

    Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations

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    We have carried out an extensive survey of magnetic field strengths toward dark cloud cores in order to test models of star formation: ambipolar-diffusion driven or turbulence driven. The survey involved ∌500\sim500 hours of observing with the Arecibo telescope in order to make sensitive OH Zeeman observations toward 34 dark cloud cores. Nine new probable detections were achieved at the 2.5-sigma level; the certainty of the detections varies from solid to marginal, so we discuss each probable detection separately. However, our analysis includes all the measurements and does not depend on whether each position has a detection or just a sensitive measurement. Rather, the analysis establishes mean (or median) values over the set of observed cores for relevant astrophysical quantities. The results are that the mass-to-flux ratio is supercritical by ∌2\sim 2, and that the ratio of turbulent to magnetic energies is also ∌2\sim 2. These results are compatible with both models of star formation. However, these OH Zeeman observations do establish for the first time on a statistically sound basis the energetic importance of magnetic fields in dark cloud cores at densities of order 103−410^{3-4} cm−3^{-3}, and they lay the foundation for further observations that could provide a more definitive test.Comment: 22 pages, 2 figures, 2 table

    Risk Stratification in Post-MI Patients Based on Left Ventricular Ejection Fraction and Heart-Rate Turbulence

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    Objectives: Development of risk stratification criteria for predicting mortality in post-infarction patients taking into account LVEF and heart-rate turbulence (HRT). Methods: Based on previous results the two parameters LVEF (continuously) and turbulence slope (TS) as an indicator of the HRT were combined for risk stratification. The method has been applied within two independent data sets (the MPIP-trial and the EMIAT-study). Results: The criteria were defined in order to match the outcome of applying LVEF ( 30 % in sensitivity. In the MPIP trial the optimal criteria selected are TS normal and LVEF ( 21 % or TS abnormal and LVEF ( 40 %. Within the placebo group of the EMIAT-study the corresponding criteria are: TS normal and LVEF ( 23 % or TS abnormal and LVEF ( 40 %. Combining both studies the following criteria could be obtained: TS normal and LVEF ( 20 % or TS abnormal and LVEF ( 40 %. In the MPIP study 83 out of the 581 patients (= 14.3 %) are fulfilling these criteria. Within this group 30 patients have died during the follow-up. In the EMIAT-trial 218 out of the 591 patients (= 37.9 %) are classified as high risk patients with 53 deaths. Combining both studies the high risk group contains 301 patients with 83 deaths (ppv = 27.7 %). Using the MADIT-criterion as classification rule (LVEF ( 30 %) a sample of 375 patients with 85 deaths (ppv = 24 %) can be selected. Conclusions: The stratification rule based on LVEF and TS is able to select high risk patients suitable for implanting an ICD. The rule performs better than the classical one with LVEF alone. The high risk group applying the new criteria is smaller with about the same number of deaths and therefor with a higher positive predictive value. The classification criteria have been validated within a bootstrap study with 100 replications. In all samples the rule based on TS and LVEF (= NEW) was superior to LVEV alone, the high risk group has been smaller (( s: 301 ( 14.5 (NEW) vs. 375 ( 14.5 (LVEF)) and the positive predictive value was larger (( s: 27.2 ( 2.6 % (NEW) vs. 23.3 ( 2.2 % (LVEF)). The new criteria are less expensive due to a reduced number of high risk patients selected

    Weak gravitational lensing in the standard Cold Dark Matter model, using an algorithm for three-dimensional shear

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    We investigate the effects of weak gravitational lensing in the standard Cold Dark Matter cosmology, using an algorithm which evaluates the shear in three dimensions. The algorithm has the advantage of variable softening for the particles, and our method allows the appropriate angular diameter distances to be applied to every evaluation location within each three-dimensional simulation box. We investigate the importance of shear in the distance-redshift relation, and find it to be very small. We also establish clearly defined values for the smoothness parameter in the relation, finding its value to be at least 0.88 at all redshifts in our simulations. From our results, obtained by linking the simulation boxes back to source redshifts of 4, we are able to observe the formation of structure in terms of the computed shear, and also note that the major contributions to the shear come from a very broad range of redshifts. We show the probability distributions for the magnification, source ellipticity and convergence, and also describe the relationships amongst these quantities for a range of source redshifts. We find a broad range of magnifications and ellipticities; for sources at a redshift of 4, 97{1/2}% of all lines of sight show magnifications up to 1.3 and ellipticities up to 0.195. There is clear evidence that the magnification is not linear in the convergence, as might be expected for weak lensing, but contains contributions from higher order terms in both the convergence and the shear.Comment: 14 pages, LaTeX, 15 figures include

    On the role of shake-off in single-photon double ionization

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    The role of shake-off for double ionization of atoms by a single photon with finite energy has become the subject of debate. In this letter, we attempt to clarify the meaning of shake-off at low photon energies by comparing different formulations appearing in the literature and by suggesting a working definition. Moreover, we elaborate on the foundation and justification of a mixed quantum-classical ansatz for the calculation of single-photon double ionization

    Effectiveness of a Postpartum Breastfeeding Protocol for Avoiding Pregnancy

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    The uses of cervical mucus and basal body temperature as indicators of return to fertility postpartum have resulted in high unintended pregnancy rates. In 2013, a study found that when women used urine hormone signs in a postpartum/breastfeeding protocol this resulted in fewer pregnancies. To improve the original protocol\u27s effectiveness, three revisions were made: (1) women were to increase the number of days tested with the Clearblue Fertility Monitor, (2) an optional second luteinizing hormone test could be done in the evening, and (3) instructions were given to manage the beginning of the fertile window for the first six cycles postpartum. The purpose of this study was to determine the correct and typical use effectiveness rates to avoid pregnancy in women who used a revised postpartum/breastfeeding protocol. A cohort review of an established data set from 207 postpartum breastfeeding women who used the protocol to avoid pregnancy was completed using Kaplan-Meier survival analysis. Total pregnancy rates that included correct and incorrect use pregnancies were eighteen per one hundred women over twelve cycles of use. For the pregnancies that met a priori criteria, the correct use pregnancy rates were two per one hundred over twelve months and twelve cycles of use and typical use rates were four per one hundred women at twelve cycles of use. The protocol had fewer unplanned pregnancies than the original, however, the cost of the method increased

    A Statistical Model for Risk Stratification on the Basis of Left Ventricular Ejection Fraction and Heart-Rate Turbulence

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    The MPIP data set was used to obtain a model for mortality risk stratification of acute myocardial infarction patients. The predictors heart rate turbulence (HRT) and left-ventricular ejection fraction (LVEF) were employed. HRT was a categorical variable of three levels; LVEF was continuous and its influence on the relative risk was explained by the natural logarithm function (found using fractional polynomials). Cox - PH model with HRT and lnLVEF was constructed and used for risk stratification. The model can be used to divide the patients into two or more groups according to mortality risk. It also describes the relationship between risk and predictors by a (continuous) function, which allows the calculation of individual mortality risk
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