5,931 research outputs found
A fast and portable Re-Implementation of Piskunov and Valenti's Optimal-Extraction Algorithm with improved Cosmic-Ray Removal and Optimal Sky Subtraction
We present a fast and portable re-implementation of Piskunov and Valenti's
optimal-extraction algorithm (Piskunov & Valenti, 2002} in C/C++ together with
full uncertainty propagation, improved cosmic-ray removal, and an optimal
background-subtraction algorithm. This re-implementation can be used with IRAF
and most existing data-reduction packages and leads to signal-to-noise ratios
close to the Poisson limit. The algorithm is very stable, operates on spectra
from a wide range of instruments (slit spectra and fibre feeds), and has been
extensively tested for VLT/UVES, ESO/CES, ESO/FEROS, NTT/EMMI, NOT/ALFOSC,
STELLA/SES, SSO/WiFeS, and finally, P60/SEDM-IFU data.Comment: 23 pages, 12 figure
The Inclusive-Exclusive Connection and the Neutron Negative Central Charge Density
We find an interpretation of the recent finding that the central charge
density of the neutron is negative by using models of generalized parton
distributions at zero skewness to relate the behavior of deep inelastic
scattering quark distributions, evaluated at large values of Bjorken x, to the
transverse charge density evaluated at small distances. The key physical input
of these models is the Drell-Yan-West relation We find that the d quarks
dominate the neutron structure function for large values of Bjorken x, where
the large longitudinal momentum of the struck quark has a significant impact on
determining the center-of-momentum of the system, and thus the "center" of the
nucleon in the transverse position plane.Comment: 17 pages, 8 figures. Text of an invited talk presented by G. A.
Miller at the 2008 Division of Nuclear Physics Meeting in Oakland. Prepared
for Int. Journ. Mod. Phys.
Conformational transformations induced by the charge-curvature interaction at finite temperature
The role of thermal fluctuations on the conformational dynamics of a single
closed filament is studied. It is shown that, due to the interaction between
charges and bending degrees of freedom, initially circular aggregates may
undergo transformation to polygonal shape. The transition occurs both in the
case of hardening and softening charge-bending interaction. In the former case
the charge and curvature are smoothly distributed along the chain while in the
latter spontaneous kink formation is initiated. The transition to a
non-circular conformation is analogous to the phase transition of the second
kind.Comment: 23 pages (Latex), 10 figures (Postscript), 2 biblio file (bib-file
and bbl-file
Biometric analysis of the foetal meconium pattern using T1 weighted 2D gradient echo MRI
OBJECTIVES:
Foetal MRI is used to assess abnormalities after ultrasonography. Bowel anomalies are a significant cause of neonatal morbidity, however there are little data concerning its normal appearance on antenatal MRI. This study aims to investigate the pattern of meconium accumulation throughout gestation using its hyperintense appearance on T1 weighted scans and add to the current published data.
METHODS:
This was a retrospective cohort study in a tertiary referral clinical MRI centre. Foetal body MRI scans of varying gestational ages were obtained dating between October 2011 and March 2018. The bowel was visualised on T1 weighted images. The length of the meconium and the width of the meconium at the rectum, sigmoid colon, splenic flexure and hepatic flexure was measured. Presence or absence of meconium in the small bowel was noted. Inter- and intrarater reliability was assessed.
RESULTS:
181 foetal body scans were reviewed. 52 were excluded and 129 analysed. Visualisation of the meconium in the large bowel became increasingly proximal with later gestations, and small bowel visualisation was greater at earlier gestations. There was statistically significant strong (r = 0.6–0.8) or very strong (r = 0.8–1.0) positive correlation of length and width with increasing gestation. Interrater reliability was moderate to excellent (r = 0.4–1.0).
CONCLUSION:
This study provides new information regarding the pattern of meconium accumulation throughout gestation. With care, the results can be used in clinical practice to aid diagnosis of bowel pathology.
ADVANCES IN KNOWLEDGE:
The findings of this study provide further information concerning the normal accumulation of foetal meconium on MR imaging, an area where current research is limited
Selecting children for head CT following head injury
OBJECTIVE: Indicators for head CT scan defined by the 2007 National Institute for Health and Care Excellence (NICE) guidelines were analysed to identify CT uptake, influential variables and yield. DESIGN: Cross-sectional study. SETTING: Hospital inpatient units: England, Wales, Northern Ireland and the Channel Islands. PATIENTS: Children (3 years were much more likely to have CT than those <3 years (OR 2.35 (95% CI 2.08 to 2.65)). CONCLUSION: Compliance with guidelines and diagnostic yield was variable across age groups, the type of hospital and region where children were admitted. With this pattern of clinical practice the risks of both missing intracranial injury and overuse of CT are considerable
First year student radiographers’ perceptions of a one-week simulation-based education package designed to increase clinical placement capacity
The radiography workforce is short-staffed and under increasing pressure to meet service
pressures. Combined with the impact of Covid-19, where student face-to-face clinical time was abruptly
halted for safety, there is cause to change the pedagogical approach to teaching diagnostic radiography to
students, increasing capacity and ensuring the continuance of qualifying radiographers to support the
profession. This paper shares the perceptions of first year student radiographers on a one-week simulation-based education package designed to replace one week of clinical placement experience.
Two cohorts of first-year radiography students engaged in a one-week simulation-based education package. Simulations increased in complexity throughout the week and included conventional
imaging techniques, mobile and theatre radiography, and cross-sectional imaging. Thirty-six students
consented to the thematic analysis of their reflective blogs.
Five themes emerged from the data: feeling anxious, understanding and skill development,
building confidence, communication, and patient-centred care.
The simulation package had a positive impact on students learning, no matter the stage at
which it was incorporated into their clinical placement block. Students engaged well with the activities
and saw value in the experience. The findings indicate that the simulation-based education package is a
suitable replacement for one week of clinical placement, supporting skills development in students and
providing increased placement capacity.
A successful, engaging simulation-based education package is presented, which
first year student radiographers perceived as a suitable replacement for one-week of clinical placement.
Further research into the acceptability of use of simulation-based education packages in second- and
third-year student radiographers would be a useful next step
The Value of Bt Corn in Southwest Kansas: A Monte Carlo Simulation Approach
While most Corn Belt farmers consider planting Bt corn to control European corn borer, southwestern Kansas farmers must also take into account an array of other insect pests, including corn rootworm, spider mites, and southwestern corn borer. This research uses a decision analysis framework to estimate the expected economic value of Bt corn in southwest Kansas. Mean per acre Bt values ranged from 34.60, well above the technology fee assumed to be 5.25 per acre at a seeding rate of 30,000 seeds per acre. The minimum value over all scenarios was $8.69 per acre. Using Monte Carlo simulation, it was shown that European and southwestern corn borer infestation probabilities, expected corn price, and expected pest-free yields are important determinants of the value of Bt corn.Bt corn, decision analysis, European corn borer, integrated pest management, Monte Carlo simulation, southwestern corn borer, Crop Production/Industries,
Target-Based Coherent Beam Combining of an Optical Phased Array Fed by a Broadband Laser Source
The target-based phasing of an optical phased array (OPA) fed by a broadband master oscillator laser source is investigated. The specific scenario examined here considers an OPA phasing through atmospheric turbulence on a rough curved object. An analytical expression for the detected or received intensity is derived. Gleaned from this expression are the conditions under which target-based phasing is possible. A detailed OPA wave optics simulation is performed to validate the theoretical findings. Key aspects of the simulation set-up as well as the results are thoroughly discussed
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Near-Infrared Spectroscopy Shows Right Parietal Specialization for Number in Pre-Verbal Infants
Bilateral regions of the intraparietal sulcus (IPS) appear to be functionally selective for both rudimentary non-symbolic number tasks and higher-level symbolic number tasks in adults and older children. Furthermore, the ability to mentally represent and manipulate approximate non-symbolic numerical quantities is present from birth. These factors leave open whether the specialization of the IPS develops through the experience of learning a symbolic number system or if it is already specialized before symbolic number acquisition. Using the newly emerging technique of functional Near-Infrared Spectroscopy (fNIRS) over left and right parietal and lateral occipital regions, we show right parietal specialization for number in 6-month-old infants. These results extend the current literature in three ways: by successfully implementing an event-related NIRS design in infants, by showing parietal specialization for number occurs before the acquisition of language, and by suggesting number representation may be initially right lateralized and become bilateral through experience.Psycholog
Unconventional magnetism in all-carbon nanofoam
We report production of nanostructured carbon foam by a high-repetition-rate,
high-power laser ablation of glassy carbon in Ar atmosphere. A combination of
characterization techniques revealed that the system contains both sp2 and sp3
bonded carbon atoms. The material is a novel form of carbon in which
graphite-like sheets fill space at very low density due to strong hyperbolic
curvature, as proposed for ?schwarzite?. The foam exhibits ferromagnetic-like
behaviour up to 90 K, with a narrow hysteresis curve and a high saturation
magnetization. Such magnetic properties are very unusual for a carbon
allotrope. Detailed analysis excludes impurities as the origin of the magnetic
signal. We postulate that localized unpaired spins occur because of topological
and bonding defects associated with the sheet curvature, and that these spins
are stabilized due to the steric protection offered by the convoluted sheets.Comment: 14 pages, including 2 tables and 7 figs. Submitted to Phys Rev B 10
September 200
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