808 research outputs found

    Equivalence of the sine-Gordon and massive Thirring models at finite temperature

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    Using the path-integral approach, the quantum massive Thirring and sine-Gordon models are proven to be equivalent at finite temperature. This result is an extension of Coleman's proof of the equivalence between both theories at zero temperature. The usual identifications among the parameters of these models also remain valid at T0T \neq 0.Comment: 9 pages, standard LaTe

    Concluding remarks

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    Hadronic Phases and Isospin Amplitudes in D(B)ππD(B) \to \pi \pi and D(B)KKˉD(B) \to K \bar K Decays

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    Hadronic phase in ππ\pi \pi and KKˉK \bar K channels are calculated a la Regge. At the D mass one finds δπππ/3\delta_{\pi \pi} \approx \pi/3 and δKKˉπ/6\delta_{K \bar K} \approx -\pi/6 in good agreement with the CLEO data while at the B mass these angles are predicted to be, respectively, 1111^\circ and 7-7^\circ. With the hadronic phase eiδKKˉe^{i \delta_{K \bar K}} taken into account, a quark diagram decomposition of the isospin invariant amplitudes in DKKˉD \to K \bar K decays fits the data provided the exchange diagram contribution is about 1/3 of the tree level one.Comment: 10pages,late

    Effect of explicitly teaching expository text structure to learning disabled and at-risk readers

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    This study examined comprehension effects of explicitly teaching expository text structures to four Caucasian male students in a sixth grade general education classroom in a rural Minnesota town. The criteria to participate in the study required participants to possess a learning disability or have been identified as an at-risk reader by standardized testing data. The researcher used leveled expository text passages from Leslie and Caldwell\u27s (2010) Qualitative Reading Inventory – 5 as pre- and post-assessments to gauge growth. The researcher guided the students through a five-week intervention focusing on a new nonfiction text structure each week. The nonfiction text structures that were covered included: Goal/Action/Outcome, Problem/Solution, Concept/Definition, Cause/Effect, and Proposition/Support. The results of the study showed all four students exhibiting a two or three level growth in their nonfiction instructional reading levels throughout the intervention. The results of the study paralleled the findings of similar research on the benefits of expository text structure training

    Final State Interaction Phases in BKπ B \to K \pi Decay Amplitudes

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    A simple Regge pole model for KπK\pi scattering explains the large eiδe^{i \delta} between isospin amplitudes which is observed at the D meson mass (δπ/2\delta \approx \pi/2). It predicts δ1420\delta \approx 14^{\circ}- 20^{\circ} at the B mass. Implications for (BKπB \to K \pi) decays and extensions of the model to other two-body decay channels are briefly discussed.Comment: 8pages,late

    Comparative evaluation of existing expendable upper stages for space shuttle

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    The use of existing expendable upper stages in the space shuttle during its early years of operation is evaluated. The Burner 2, Scout, Delta, Agena, Transtage, and Centaur were each studied under contract by their respective manufacturers to determine the extent and cost of the minimum modifications necessary to integrate the stage with the shuttle orbiter. A comparative economic analysis of thirty-five different families of these stages is discussed. Results show that the overall transportation system cost differences between many of the families are quite small. However, by considering several factors in addition to cost, it is possible to select one family as being representative of the capability of the minimum modification existing stage approach. The selected family meets all of the specified mission requirements during the early years of shuttle operation

    TOP-INDUCED ELECTROWEAK BREAKING IN THE MINIMAL SUPERSYMMETRIC STANDARD MODEL

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    Severe constraints on parameters of the minimal supersymmetric standard model follow from a dynamical electroweak symmetry breaking mechanism dominated by top and stop loops. In particular, the lightest Higgs boson mass is expected to be smaller than 100 GeV.Comment: 10 pages, Latex, 6 Postcript Figure

    Interrogation of caesium atoms in a fountain clock by a femtosecond laser microwave oscillator

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    A caesium fountain clock is operated utilizing a microwave oscillator that derives its frequency stability from a stable laser by means of a fiber-laser femtosecond frequency comb. This oscillator is based on the technology developed for optical clocks and replaces the quartz based microwave oscillator commonly used in fountain clocks. As a result, a significant decrease of the frequency instability of the fountain clock is obtained, reaching 0.74E-14 at 100 s averaging time. We could demonstrate that for a significant range of detected atom numbers the instability is limited by quantum projection noise only, and that for the current status of this fountain clock the new microwave source poses no limit on the achievable frequency instability.Comment: 4 pages, 4 figure

    Hysteroscopy for treating subfertility associated with suspected major uterine cavity abnormalities

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    Background : Observational studies suggest higher pregnancy rates after the hysteroscopic removal of endometrial polyps, submucous fibroids, uterine septum or intrauterine adhesions, which are detectable in 10% to 15% of women seeking treatment for subfertility. Objectives : To assess the effects of the hysteroscopic removal of endometrial polyps, submucous fibroids, uterine septum or intrauterine adhesions suspected on ultrasound, hysterosalpingography, diagnostic hysteroscopy or any combination of thesemethods inwomenwith otherwise unexplained subfertility or prior to intrauterine insemination (IUI), in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI). Search methods : We searched theCochraneMenstrualDisorders and Subfertility SpecialisedRegister (8 September 2014), theCochrane Central Register of Controlled Trials (The Cochrane Library 2014, Issue 9), MEDLINE (1950 to 12 October 2014), EMBASE (inception to 12 October 2014), CINAHL (inception to 11 October 2014) and other electronic sources of trials including trial registers, sources of unpublished literature and reference lists. We handsearched the American Society for Reproductive Medicine (ASRM) conference abstracts and proceedings (from January 2013 to October 2014) and we contacted experts in the field. Selection criteria : Randomised comparisons between operative hysteroscopy versus control in women with otherwise unexplained subfertility or undergoing IUI, IVF or ICSI and suspected major uterine cavity abnormalities diagnosed by ultrasonography, saline infusion/ gel instillation sonography, hysterosalpingography, diagnostic hysteroscopy or any combination of these methods. Primary outcomes were live birth and hysteroscopy complications. Secondary outcomes were pregnancy and miscarriage. Data collection and analysis : Two review authors independently assessed studies for inclusion and risk of bias, and extracted data. We contacted study authors for additional information. Main results : We retrieved 12 randomised trials possibly addressing the research questions. Only two studies (309 women) met the inclusion criteria. Neither reported the primary outcomes of live birth or procedure related complications. In women with otherwise unexplained subfertility and submucous fibroids there was no conclusive evidence of a difference between the intervention group treated with hysteroscopic myomectomy and the control group having regular fertility-oriented intercourse during 12 months for the outcome of clinical pregnancy. A large clinical benefit with hysteroscopic myomectomy cannot be excluded: if 21% of women with fibroids achieve a clinical pregnancy having timed intercourse only, the evidence suggests that 39% of women (95% CI 21% to 58%) will achieve a successful outcome following the hysteroscopic removal of the fibroids (odds ratio (OR) 2.44, 95% confidence interval (CI) 0.97 to 6.17, P = 0.06, 94 women, very low quality evidence). There is no evidence of a difference between the comparison groups for the outcome of miscarriage (OR 0.58, 95% CI 0.12 to 2.85, P = 0.50, 30 clinical pregnancies in 94 women, very low quality evidence). The hysteroscopic removal of polyps prior to IUI can increase the chance of a clinical pregnancy compared to simple diagnostic hysteroscopy and polyp biopsy: if 28% of women achieve a clinical pregnancy with a simple diagnostic hysteroscopy, the evidence suggests that 63% of women (95% CI 50% to 76%) will achieve a clinical pregnancy after the hysteroscopic removal of the endometrial polyps (OR 4.41, 95% CI 2.45 to 7.96, P < 0.00001, 204 women, moderate quality evidence). Authors' conclusions : A large benefit with the hysteroscopic removal of submucous fibroids for improving the chance of clinical pregnancy in women with otherwise unexplained subfertility cannot be excluded. The hysteroscopic removal of endometrial polyps suspected on ultrasound in women prior to IUI may increase the clinical pregnancy rate. More randomised studies are needed to substantiate the effectiveness of the hysteroscopic removal of suspected endometrial polyps, submucous fibroids, uterine septum or intrauterine adhesions in women with unexplained subfertility or prior to IUI, IVF or ICSI

    Cancellation of the collisional frequency shift in caesium fountain clocks

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    We have observed that the collisional frequency shift in primary caesium fountain clocks varies with the clock state population composition and, in particular, is zero for a given fraction of the |F = 4, mF = 0> atoms, depending on the initial cloud parameters. We present a theoretical model explaining our observations. The possibility of the collisional shift cancellation implies an improvement in the performance of caesium fountain standards and a simplification in their operation. Our results also have implications for test operation of fountains at multiple pi/2 pulse areas
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