1,220 research outputs found

    Pseudo Goldstone Bosons Phenomenology in Minimal Walking Technicolor

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    We construct the non-linear realized Lagrangian for the Goldstone Bosons associated to the breaking pattern of SU(4) to SO(4). This pattern is expected to occur in any Technicolor extension of the standard model featuring two Dirac fermions transforming according to real representations of the underlying gauge group. We concentrate on the Minimal Walking Technicolor quantum number assignments with respect to the standard model symmetries. We demonstrate that for, any choice of the quantum numbers, consistent with gauge and Witten anomalies the spectrum of the pseudo Goldstone Bosons contains electrically doubly charged states which can be discovered at the Large Hadron Collider.Comment: 25 pages, 5 figure

    Electrical activity of carbon-hydrogen centers in Si

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    The electrical activity of Cs-H defects in Si has been investigated in a combined modeling and experimental study. High-resolution Laplace capacitance spectroscopy with the uniaxial stress technique has been used to measure the stress-energy tensor and the results are compared with theoretical modeling. At low temperatures, implanted H is trapped as a negative-U center with a donor level in the upper half of the gap. However, at higher temperatures, H migrates closer to the carbon impurity and the donor level falls, crossing the gap. At the same time, an acceptor level is introduced into the upper gap making the defect a positive-U center

    DCO+^+, DCN and N2_2D+^+ reveal three different deuteration regimes in the disk around the Herbig Ae star HD163296

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    The formation pathways of deuterated species trace different regions of protoplanetary disks and may shed light into their physical structure. We aim to constrain the radial extent of main deuterated species; we are particularly interested in spatially characterizing the high and low temperature pathways for enhancing deuteration of these species. We observed the disk surrounding the Herbig Ae star HD 163296 using ALMA in Band 6 and obtained resolved spectral imaging data of DCO+^+ (JJ=3-2), DCN (JJ=3-2) and N2_2D+^+ (JJ=3-2). We model the radial emission profiles of DCO+^+, DCN and N2_2D+^+, assuming their emission is optically thin, using a parametric model of their abundances and radial excitation temperature estimates. DCO+^+ can be described by a three-region model, with constant-abundance rings centered at 70 AU, 150 AU and 260 AU. The DCN radial profile peaks at about ~60 AU and N2_2D+^+ is seen in a ring at ~160 AU. Simple models of both molecules using constant abundances reproduce the data. Assuming reasonable average excitation temperatures for the whole disk, their disk-averaged column densities (and deuterium fractionation ratios) are 1.6-2.6×1012\times 10^{12} cm2^{-2} (0.04-0.07), 2.9-5.2×1012\times 10^{12} cm2^{-2} (\sim0.02) and 1.6-2.5 ×1011\times 10^{11} cm2^{-2} (0.34-0.45) for DCO+^+, DCN and N2_2D+^+, respectively. Our simple best-fit models show a correlation between the radial location of the first two rings in DCO+^+ and the DCN and N2_2D+^+ abundance distributions that can be interpreted as the high and low temperature deuteration pathways regimes. The origin of the third DCO+^+ ring at 260 AU is unknown but may be due to a local decrease of ultraviolet opacity allowing the photodesorption of CO or due to thermal desorption of CO as a consequence of radial drift and settlement of dust grains

    SO and SiS Emission Tracing an Embedded Planet and Compact 12^{12}CO and 13^{13}CO Counterparts in the HD 169142 Disk

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    Planets form in dusty, gas-rich disks around young stars, while at the same time, the planet formation process alters the physical and chemical structure of the disk itself. Embedded planets will locally heat the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms such as Si from dust grains. This should cause chemical asymmetries detectable in molecular gas observations. Using high-angular-resolution ALMA archival data of the HD 169142 disk, we identify compact SO J=88_8-77_7 and SiS J=19-18 emission coincident with the position of a {\sim}2 MJup_{\rm{Jup}} planet seen as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at {\approx}38 au. The SiS emission is located along an azimuthal arc and has a similar morphology as a known 12^{12}CO kinematic excess. This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that the planet is driving sufficiently strong shocks to produce gas-phase SiS. We also report the discovery of compact 12^{12}CO and 13^{13}CO J=3-2 emission coincident with the planet location. Taken together, a planet-driven outflow provides the best explanation for the properties of the observed chemical asymmetries. We also resolve a bright, azimuthally-asymmetric SO ring at {\approx}24 au. While most of this SO emission originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations driven by a misaligned inner disk or planet-disk interactions. Overall, the HD 169142 disk shows several distinct chemical signatures related to giant planet formation and presents a powerful template for future searches of planet-related chemical asymmetries in protoplanetary disks.Comment: 22 pages, 12 figures, accepted for publication in ApJ

    Water formation at low temperatures by surface O2 hydrogenation II: the reaction network

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    Water is abundantly present in the Universe. It is the main component of interstellar ice mantles and a key ingredient for life. Water in space is mainly formed through surface reactions. Three formation routes have been proposed in the past: hydrogenation of surface O, O2, and O3. In a previous paper [Ioppolo et al., Astrophys. J., 2008, 686, 1474] we discussed an unexpected non-standard zeroth-order H2O2 production behaviour in O2 hydrogenation experiments, which suggests that the proposed reaction network is not complete, and that the reaction channels are probably more interconnected than previously thought. In this paper we aim to derive the full reaction scheme for O2 surface hydrogenation and to constrain the rates of the individual reactions. This is achieved through simultaneous H-atom and O2 deposition under ultra-high vacuum conditions for astronomically relevant temperatures. Different H/O2 ratios are used to trace different stages in the hydrogenation network. The chemical changes in the forming ice are followed by means of reflection absorption infrared spectroscopy (RAIRS). New reaction paths are revealed as compared to previous experiments. Several reaction steps prove to be much more efficient (H + O2) or less efficient (H + OH and H2 + OH) than originally thought. These are the main conclusions of this work and the extended network concluded here will have profound implications for models that describe the formation of water in space.Comment: 1 page, 1 figur

    Determinants of guideline use in primary care physical therapy: a cross-sectional survey of attitudes, knowledge, and behavior

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    Background Understanding of attitudes, knowledge, and behavior related to evidence-based practice (EBP) and use of evidence-based clinical practice guidelines in primary care physical therapy is limited. Objectives The objectives of this study were: (1) to investigate self-reported attitudes, knowledge, behavior, prerequisites, and barriers related to EBP and guideline use among physical therapists in primary care and (2) to explore associations of self-reported use of guidelines with these social cognitive factors along with demographic and workplace characteristics. Design This was a cross-sectional survey. Methods A web-based survey of 419 physical therapists in primary care in western Sweden was performed. Multiple logistic regression analysis was performed to examine factors associated with guideline use. Results The response rate was 64.7%. Most respondents had positive attitudes toward EBP and guidelines: 90% considered EBP necessary, and 96% considered guidelines important. Approximately two thirds reported confidence in finding and using evidence. One third reported being aware of guidelines. Thirteen percent knew where to find guidelines, and only 9% reported having easy access to guidelines. Fewer than half reported using guidelines frequently. The most important barriers to using guidelines were lack of time, poor availability, and limited access to guidelines. Young age and brief work experience were associated with positive attitudes toward EBP. A postgraduate degree was associated with higher application of EBP. Positive attitudes, awareness of guidelines, considering guidelines to facilitate practice, and knowing how to integrate patient preferences with guideline use were associated with frequent use of guidelines. Limitations Data were self-reported, which may have increased the risk of social desirability bias. Conclusions Use of guidelines was not as frequent as could be expected in view of the positive attitudes toward EBP and guidelines among physical therapists. Awareness of and perceived access to guidelines were limited. The identified determinants can be addressed when developing guideline implementation strategies

    Gastroesophageal Reflux after Vertical Banded Gastroplasty is Alleviated by Conversion to Gastric Bypass.

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    BACKGROUND: Conversion operations after vertical banded gastroplasty (VBG) are sometimes performed because of vomiting and/or acid regurgitation. Primary operation with gastric bypass (GBP) is known to reduce gastroesophageal reflux (GERD). Previous studies have not been designed to differentiate between the effects of the altered anatomy and of the ensuing weight loss. No series has reported data on acid reflux before and after conversion from VBG to GBP. METHODS: We invited eight VBG patients with current symptoms of GERD. All had intact staple lines as assessed by barium meal and gastroscopy. Acid reflux was quantified using 48-h Bravo capsule measurements. Conversion operations were performed creating an isolated 15-20-ml pouch; the previously banded part of gastric wall was excised. Gastrojejunostomy was made end to end with a 28-mm circular stapler. The study is based on five patients consenting to early postoperative endoscopy and pH measurement. RESULTS: All patients were women with a mean age of 49.5 years and BMI of 36.3. Time since VBG was 132.1 months. Time from conversion to second measurement was 46.6 days and BMI at that time 32.7. There was no mortality and no serious morbidity. All patients improved clinically and no patient had to go back on proton pump inhibition or antacids. Total time with pH < 4.0 was reduced from 18.4% to 3.3% (p < 0.05). DeMeester score was reduced from 58.1 to 15.9 (p < 0.05). CONCLUSIONS: The effect of converting VBG-operated patients to GBP results in a near-normalisation of acid reflux parameters and a discontinuation of proton pump inhibitor medication

    Calculus on the Sierpinski Gasket I: Polynomials, Exponentials and Power Series

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    We study the analog of power series expansions on the Sierpinski gasket, for analysis based on the Kigami Laplacian. The analog of polynomials are multiharmonic functions, which have previously been studied in connection with Taylor approximations and splines. Here the main technical result is an estimate of the size of the monomials analogous to x^n/n!. We propose a definition of entire analytic functions as functions represented by power series whose coefficients satisfy exponential growth conditions that are stronger than what is required to guarantee uniform convergence. We present a characterization of these functions in terms of exponential growth conditions on powers of the Laplacian of the function. These entire analytic functions enjoy properties, such as rearrangement and unique determination by infinite jets, that one would expect. However, not all exponential functions (eigenfunctions of the Laplacian) are entire analytic, and also many other natural candidates, such as the heat kernel, do not belong to this class. Nevertheless, we are able to use spectral decimation to study exponentials, and in particular to create exponentially decaying functions for negative eigenvalues
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