1,244 research outputs found
Pseudo Goldstone Bosons Phenomenology in Minimal Walking Technicolor
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
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 ND reveal three different deuteration regimes in the disk around the Herbig Ae star HD163296
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 (=3-2), DCN (=3-2) and ND
(=3-2). We model the radial emission profiles of DCO, DCN and
ND, 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
ND 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 cm
(0.04-0.07), 2.9-5.2 cm (0.02) and 1.6-2.5 cm (0.34-0.45) for DCO, DCN and ND, respectively.
Our simple best-fit models show a correlation between the radial location of
the first two rings in DCO and the DCN and ND 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 CO and CO Counterparts in the HD 169142 Disk
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=8-7 and
SiS J=19-18 emission coincident with the position of a 2 M
planet seen as a localized, Keplerian NIR feature within a gas-depleted,
annular dust gap at 38 au. The SiS emission is located along an
azimuthal arc and has a similar morphology as a known 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
CO and 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 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
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
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.
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
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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