3,537 research outputs found
Knots, Braids and Hedgehogs from the Eikonal Equation
The complex eikonal equation in the three space dimensions is considered. We
show that apart from the recently found torus knots this equation can also
generate other topological configurations with a non-trivial value of the
index: braided open strings as well as hedgehogs. In particular,
cylindric strings i.e. string solutions located on a cylinder with a constant
radius are found. Moreover, solutions describing strings lying on an arbitrary
surface topologically equivalent to cylinder are presented. We discus them in
the context of the eikonal knots. The physical importance of the results
originates in the fact that the eikonal knots have been recently used to
approximate the Faddeev-Niemi hopfions.Comment: 15 pages, 5 figure
The association among diet, dietary fiber, and bowel preparation at colonoscopy
BACKGROUND AND AIMS: Pre-colonoscopy dietary restrictions vary widely and lack evidence-based guidance. We investigated whether fiber and various other foods/macronutrients consumed during the 3 days before colonoscopy are associated with bowel preparation quality.
METHODS: This was a prospective observational study among patients scheduled for outpatient colonoscopy. Patients received instructions including split-dose polyethylene glycol, avoidance of vegetables/beans 2 days before colonoscopy, and a clear liquid diet the day before colonoscopy. Two 24-hour dietary recall interviews and 1 patient-recorded food log measured dietary intake on the 3 days before colonoscopy. The Nutrition Data System for Research was used to estimate dietary exposures. Our primary outcome was the quality of bowel preparation measured by the Boston Bowel Preparation Scale (BBPS).
RESULTS: We enrolled 201 patients from November 2015 to September 2016 with complete data for 168. The mean age was 59 years (standard deviation, 7 years), and 90% of colonoscopies were conducted for screening/surveillance. Only 17% and 77% of patients complied with diet restrictions 2 and 1 day(s) before colonoscopy, respectively. We found no association between foods consumed 2 and 3 days before colonoscopy and BBPS scores. However, BPPS was positively associated with intake of gelatin, and inversely associated with intake of red meat, poultry, and vegetables on the day before colonoscopy.
CONCLUSIONS: Our findings support recent guidelines encouraging unrestricted diets >1 day before colonoscopy if using a split-dose bowel regimen. Furthermore, we found no evidence to restrict dietary fiber 1 day before colonoscopy. We also found evidence to promote consumption of gelatin and avoidance of red meat, poultry, and vegetables 1 day before colonoscopy.Dr Jacobson has acted as a consultant for MOTUS GI and Remedy Partners. All other authors disclosed no financial relationships relevant to this publication. Supported by NIH/NIDDK R21DK105476. (R21DK105476 - NIH/NIDDK)Accepted manuscrip
Nontraditional Students, Multilingual Learners, and University Type: The Vital Missing Comparisons in our Basic Course Research
After the G.I. Bill was passed in 1944, the United States saw a massive expansion of higher education. The subsequent economic growth, expanding middle class, and support of public education meant that more Americans had access to college education than ever before (Bok, 2006).
In the decades that followed, a typical or “traditional” college student was a person who entered a four-year university at the age of eighteen immediately after completing high school, attended full time, considered their education a full-time responsibility, had no dependents, was employed part time or not at all, and graduated in four years (Center for Institutional Effectiveness, 2004; Ross-Gordon, 2011).
Most descriptions also assume that traditional students are born in the United States, speak English as their first language, and live in student housing on or near campus. However, the majority of students in college and university classrooms today do not reflect these “traditional” characteristics.
In 2014-2015, 886,052 international students were enrolled in U.S. colleges and universities (Institute for International Education, 2014), and many universities facing budget cuts are trying to increase international student recruiting.
Since the basic communication course is frequently required for most or all students at many colleges and universities as part of a general education requirement, and because the basic course is typically intended to help incoming undergraduate students build communication skills that they will use in other courses, their future careers, and in their communities, this diversity of student preparation and experience has important implications for how we approach the basic course
The Impact of Public Speaking and Hybrid Introductory Communication Courses on Student Perceptions of Homophily and Classroom Climate
This study examines whether public speaking and hybrid introductory communication courses contribute to whether students feel connected to one another as a result of taking the course. Results indicate that students develop stronger perceptions of homophily and connected classroom climate over time, and this growth is slightly larger in public speaking courses than in hybrid introductory communication courses. Attendance impacted the levels of perceived homophily and connected classroom climate at the end of the course. However, perceived homophily did not predict academic performance in either course, and perceptions of classroom connectedness only predicted the academic performance of students in the hybrid introduction to communication course
Persistent urinary incontinence and delivery mode history: a six-year longitudinal study.
Objective: To investigate the prevalence of persistent and long term postpartum urinary incontinence and associations with mode of first and subsequent delivery.
Setting: Maternity units in Aberdeen (Scotland), Birmingham (England) and Dunedin (New Zealand).
Design: Longitudinal study
Population: 4214 women who returned postal questionnaires 3 months and 6 years after the index birth.
Methods: Symptom data were obtained from both questionnaires and obstetric data from case-notes for the index birth and the second questionnaire for subsequent births. Logistic regression investigated the independent effects of mode of first delivery and delivery mode history.
Main outcome measures: Urinary incontinence – persistent (at 3 months and 6 years after index birth) and long-term (at 6 years after index birth).
Results: The prevalence of persistent urinary incontinence was 24%. Delivering exclusively by Caesarean section was associated with both less persistent (OR= 0.46, 95% CI 0.32 to 0.68) and long term urinary incontinence (OR=0.50, 95% CI 0.40 to 0.63). Caesarean section birth in addition to vaginal delivery however was not associated with significantly less persistent incontinence (OR 0.93, 95%CI 0.67 to 1.29). There were no significant associations between persistent or long-term urinary incontinence and forceps or vacuum extraction delivery. Other significantly associated factors were increasing number of births and older maternal age.
Conclusions: The risk of persistent and long term urinary incontinence is significantly lower following Caesarean section deliveries but not if there is another vaginal birth. Even when delivering exclusively by Caesarean section, the prevalence of persistent symptoms (14%) is still high
A Library of Integrated Spectra of Galactic Globular Clusters
We present a new library of integrated spectra of 40 Galactic globular
clusters, obtained with the Blanco 4-m telescope and the R-C spectrograph at
the Cerro Tololo Interamerican Observatory. The spectra cover the range ~ 3350
-- 6430 A with ~ 3.1 A (FWHM) resolution. The spectroscopic observations and
data reduction were designed to integrate the full projected area within the
cluster core radii in order to properly sample the light from stars in all
relevant evolutionary stages. The S/N values of the flux-calibrated spectra
range from 50 to 240/A at 4000 A and from 125 to 500/A at 5000 A. The selected
targets span a wide range of cluster parameters, including metallicity,
horizontal-branch morphology, Galactic coordinates, Galactocentric distance,
and concentration. The total sample is thus fairly representative of the entire
Galactic globular cluster population and should be valuable for comparison with
similar integrated spectra of unresolved stellar populations in remote systems.
For most of the library clusters, our spectra can be coupled with deep
color-magnitude diagrams and reliable metal abundances from the literature to
enable the calibration of stellar population synthesis models. In this paper we
present a detailed account of the observations and data reduction. The spectral
library is publicly available in electronic format from the National Optical
Astronomical Observatory website.Comment: 39 Pages, including 2 tables and 15 Figures. To appear in the
Astrophysical Journal, Supplement Serie
Simultaneous multi-band detection of Low Surface Brightness galaxies with Markovian modelling
We present an algorithm for the detection of Low Surface Brightness (LSB)
galaxies in images, called MARSIAA (MARkovian Software for Image Analysis in
Astronomy), which is based on multi-scale Markovian modeling. MARSIAA can be
applied simultaneously to different bands. It segments an image into a
user-defined number of classes, according to their surface brightness and
surroundings - typically, one or two classes contain the LSB structures. We
have developed an algorithm, called DetectLSB, which allows the efficient
identification of LSB galaxies from among the candidate sources selected by
MARSIAA. To assess the robustness of our method, the method was applied to a
set of 18 B and I band images (covering 1.3 square degrees in total) of the
Virgo cluster. To further assess the completeness of the results of our method,
both MARSIAA, SExtractor, and DetectLSB were applied to search for (i) mock
Virgo LSB galaxies inserted into a set of deep Next Generation Virgo Survey
(NGVS) gri-band subimages and (ii) Virgo LSB galaxies identified by eye in a
full set of NGVS square degree gri images. MARSIAA/DetectLSB recovered ~20%
more mock LSB galaxies and ~40% more LSB galaxies identified by eye than
SExtractor/DetectLSB. With a 90% fraction of false positives from an entirely
unsupervised pipeline, a completeness of 90% is reached for sources with r_e >
3" at a mean surface brightness level of mu_g=27.7 mag/arcsec^2 and a central
surface brightness of mu^0 g=26.7 mag/arcsec^2. About 10% of the false
positives are artifacts, the rest being background galaxies. We have found our
method to be complementary to the application of matched filters and an
optimized use of SExtractor, and to have the following advantages: it is
scale-free, can be applied simultaneously to several bands, and is well adapted
for crowded regions on the sky.Comment: 39 pages, 18 figures, accepted for publication in A
Experimental test of higher-order Laguerre–Gauss modes in the 10 m Glasgow prototype interferometer
Brownian noise of dielectric mirror coatings is expected to be one of the limiting noise sources, at the peak sensitivity, of next generation ground based interferometric gravitational wave (GW) detectors. The use of higher-order Laguerre–Gauss (LG) beams has been suggested to reduce the effect of coating thermal noise in future generations of gravitational wave detectors. In this paper we describe the first test of interferometry with higher-order LG beams in an environment similar to a full-scale gravitational wave detector. We compare the interferometric performance of higher-order LG modes and the fundamental mode beams, injected into a 10 m long suspended cavity that features a finesse of 612, a value chosen to be typical of future gravitational wave detectors. We found that the expected mode degeneracy of the injected LG3, 3 beam was resolved into a multiple peak structure, and that the cavity length control signal featured several nearby zero crossings. The break up of the mode degeneracy is due to an astigmatism (defined as |Rcy − Rcx|) of 5.25 ± 0.5 cm on one of our cavity mirrors with a radius of curvature (Rc) of 15 m. This observation agrees well with numerical simulations developed with the FINESSE software. We also report on how these higher-order mode beams respond to the misalignment and mode mismatch present in our 10 m cavity. In general we found the LG3, 3 beam to be considerably more susceptible to astigmatism and mode mismatch than a conventional fundamental mode beam. Therefore the potential application of higher-order Laguerre–Gauss beams in future gravitational wave detectors will impose much more stringent requirements on both mode matching and mirror astigmatism
Pressure-dependent transition from atoms to nanoparticles in magnetron sputtering: Effect on WSi2 film roughness and stress
We report on the transition between two regimes from several-atom clusters to
much larger nanoparticles in Ar magnetron sputter deposition of WSi2, and the
effect of nanoparticles on the properties of amorphous thin films and
multilayers. Sputter deposition of thin films is monitored by in situ x-ray
scattering, including x-ray reflectivity and grazing incidence small angle
x-ray scattering. The results show an abrupt transition at an Ar background
pressure Pc; the transition is associated with the threshold for energetic
particle thermalization, which is known to scale as the product of the Ar
pressure and the working distance between the magnetron source and the
substrate surface. Below Pc smooth films are produced, while above Pc roughness
increases abruptly, consistent with a model in which particles aggregate in the
deposition flux before reaching the growth surface. The results from WSi2 films
are correlated with in situ measurement of stress in WSi2/Si multilayers, which
exhibits a corresponding transition from compressive to tensile stress at Pc.
The tensile stress is attributed to coalescence of nanoparticles and the
elimination of nano-voids.Comment: 16 pages, 10 figures; v3: published versio
Sample size calculations for cluster randomised controlled trials with a fixed number of clusters
Background\ud
Cluster randomised controlled trials (CRCTs) are frequently used in health service evaluation. Assuming an average cluster size, required sample sizes are readily computed for both binary and continuous outcomes, by estimating a design effect or inflation factor. However, where the number of clusters are fixed in advance, but where it is possible to increase the number of individuals within each cluster, as is frequently the case in health service evaluation, sample size formulae have been less well studied. \ud
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Methods\ud
We systematically outline sample size formulae (including required number of randomisation units, detectable difference and power) for CRCTs with a fixed number of clusters, to provide a concise summary for both binary and continuous outcomes. Extensions to the case of unequal cluster sizes are provided. \ud
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Results\ud
For trials with a fixed number of equal sized clusters (k), the trial will be feasible provided the number of clusters is greater than the product of the number of individuals required under individual randomisation () and the estimated intra-cluster correlation (). So, a simple rule is that the number of clusters () will be sufficient provided: \ud
\ud
> x \ud
\ud
Where this is not the case, investigators can determine the maximum available power to detect the pre-specified difference, or the minimum detectable difference under the pre-specified value for power. \ud
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Conclusions\ud
Designing a CRCT with a fixed number of clusters might mean that the study will not be feasible, leading to the notion of a minimum detectable difference (or a maximum achievable power), irrespective of how many individuals are included within each cluster. \ud
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