161 research outputs found
D=11 SUGRA as the Low Energy Effective Action of Matrix Theory: Three Form Scattering
We employ the LSZ reduction formula for Matrix Theory introduced in our
earlier work to compute the t-pole S-matrix for three form-three form
scattering. The result agrees completely with tree level D=11 SUGRA. Taken
together with previous results on graviton-graviton scattering this shows that
Matrix Theory indeed reproduces the bosonic sector of the D=11 SUGRA action
including the Chern-Simons term. Furthermore we provide a detailed account of
our framework along with the technology to compute any Matrix Theory one-loop
t-pole scattering amplitude at vanishing p^- exchange.Comment: 24 pages, LaTex, no figures, Ref. added, typos correcte
On the quantum mechanics of M(atrix) theory
We present a study of M(atrix) theory from a purely canonical viewpoint. In
particular, we identify free particle asymptotic states of the model
corresponding to the supergraviton multiplet of eleven dimensional
supergravity. These states have a natural interpretation as excitations in the
flat directions of the matrix model potential. Furthermore, we provide the
split of the matrix model Hamiltonian into a free part describing the free
propagation of these particle states along with the interaction Hamiltonian
describing their interactions. Elementary quantum mechanical perturbation
theory then yields an effective potential for these particles as an expansion
in their inverse separation. Remarkably we find that the leading velocity
independent terms of the effective potential cancel in agreement with the fact
that there is no force between stationary D0 branes. The scheme we present
provides a framework in which one can perturbatively compute the M(atrix)
theory result for the eleven dimensional supergraviton S matrix.Comment: 28 pages, Latex2
Le porte Que Quelqu\u27un a Ouverte (The Door That Someone Opened)
This book was completed for Jan Baker\u27s artists\u27 book class, Printed Books.https://digitalcommons.risd.edu/specialcollections_bookmark_senses/1035/thumbnail.jp
The Matrix Theory S-Matrix
The technology required for eikonal scattering amplitude calculations in
Matrix theory is developed. Using the entire supersymmetric completion of the
v^4/r^7 Matrix theory potential we compute the graviton-graviton scattering
amplitude and find agreement with eleven dimensional supergravity at tree
level.Comment: 10 pages, RevTeX, no figure
Focusing a NIR adaptive optics imager, experience with GSAOI
The Gemini South Adaptive Optics Imager (GSAOI) to be used with the Multi-Conjugate Adaptive Optics (MCAO) system at Gemini South is currently in the final stages of assembly and testing. GSAOI uses a suite of 26 different filters, made from both BK7 and Fused Silica substrates. These filters, located in a non-collimated beam, work as active optical elements. The optical design was undertaken to ensure that both the filter substrates both focused longitudinally at the same point. During the testing of the instrument it was found that longitudinal focus was filter dependant. The methods used to investigate this are outlined in the paper. These investigations identified several possible causes for the focal shift including substrate material properties in cryogenic conditions and small amounts of residual filter power
Holes outperform electrons in group IV semiconductor materials
A recordâhigh mobility of holes, reaching 4.3 Ă 106 cm2 Vâ1 sâ1 at 300 mK in an epitaxial strained germanium (sâGe) semiconductor, grown on a standard silicon wafer, is reported. This major breakthrough is achieved due to the development of stateâofâtheâart epitaxial growth technology culminating in superior monocrystalline quality of the sâGe material platform with a very low density of background impurities and other imperfections. As a consequence, the hole mobility in sâGe appears to be â2 times higher than the highest electron mobility in strained silicon. In addition to the record mobility, this material platform reveals a unique combination of properties, which are a very large and tuneable effective g*âfactor (>18), a very low percolation density (5 Ă 109 cmâ2) and a small effective mass (0.054 m 0). This longâsought combination of parameters in one material system is important for the research and development of lowâtemperature electronics with reduced Joule heating and for quantumâelectronics circuits based on spin qubits
Comparison of microbiological diagnosis of urinary tract infection in young children by routine health service laboratories and a research laboratory: Diagnostic cohort study
OBJECTIVES: To compare the validity of diagnosis of urinary tract infection (UTI) through urine culture between samples processed in routine health service laboratories and those processed in a research laboratory. POPULATION AND METHODS: We conducted a prospective diagnostic cohort study in 4808 acutely ill children aged <5 years attending UK primary health care. UTI, defined as pure/predominant growth â„105 CFU/mL of a uropathogen (the reference standard), was diagnosed at routine health service laboratories and a central research laboratory by culture of urine samples. We calculated areas under the receiver-operator curve (AUC) for UTI predicted by pre-specified symptoms, signs and dipstick test results (the "index test"), separately according to whether samples were obtained by clean catch or nappy (diaper) pads. RESULTS: 251 (5.2%) and 88 (1.8%) children were classified as UTI positive by health service and research laboratories respectively. Agreement between laboratories was moderate (kappa = 0.36; 95% confidence interval [CI] 0.29, 0.43), and better for clean catch (0.54; 0.45, 0.63) than nappy pad samples (0.20; 0.12, 0.28). In clean catch samples, the AUC was lower for health service laboratories (AUC = 0.75; 95% CI 0.69, 0.80) than the research laboratory (0.86; 0.79, 0.92). Values of AUC were lower in nappy pad samples (0.65 [0.61, 0.70] and 0.79 [0.70, 0.88] for health service and research laboratory positivity, respectively) than clean catch samples. CONCLUSIONS: The agreement of microbiological diagnosis of UTI comparing routine health service laboratories with a research laboratory was moderate for clean catch samples and poor for nappy pad samples and reliability is lower for nappy pad than for clean catch samples. Positive results from the research laboratory appear more likely to reflect real UTIs than those from routine health service laboratories, many of which (particularly from nappy pad samples) could be due to contamination. Health service laboratories should consider adopting procedures used in the research laboratory for paediatric urine samples. Primary care clinicians should try to obtain clean catch samples, even in very young children
The Diagnosis of Urinary Tract infection in Young children (DUTY): a diagnostic prospective observational study to derive and validate a clinical algorithm for the diagnosis of urinary tract infection in children presenting to primary care with an acute illness
Background: It is not clear which young children presenting acutely unwell to primary care should be investigated for urinary tract infection (UTI) and whether or not dipstick testing should be used to inform antibiotic treatment.Objectives: To develop algorithms to accurately identify pre-school children in whom urine should be obtained; assess whether or not dipstick urinalysis provides additional diagnostic information; and model algorithm cost-effectiveness.Design: Multicentre, prospective diagnostic cohort study.Setting and participants: Children < 5 years old presenting to primary care with an acute illness and/or new urinary symptoms.Methods: One hundred and seven clinical characteristics (index tests) were recorded from the childâs past medical history, symptoms, physical examination signs and urine dipstick test. Prior to dipstick results clinician opinion of UTI likelihood (âclinical diagnosisâ) and urine sampling and treatment intentions (âclinical judgementâ) were recorded. All index tests were measured blind to the reference standard, defined as a pure or predominant uropathogen cultured at ? 105 colony-forming units (CFU)/ml in a single research laboratory. Urine was collected by clean catch (preferred) or nappy pad. Index tests were sequentially evaluated in two groups, stratified by urine collection method: parent-reported symptoms with clinician-reported signs, and urine dipstick results. Diagnostic accuracy was quantified using area under receiver operating characteristic curve (AUROC) with 95% confidence interval (CI) and bootstrap-validated AUROC, and compared with the âclinician diagnosisâ AUROC. Decision-analytic models were used toidentify optimal urine sampling strategy compared with âclinical judgementâ.Results: A total of 7163 children were recruited, of whom 50% were female and 49% were < 2 years old. Culture results were available for 5017 (70%); 2740 children provided clean-catch samples, 94% of whom were ? 2 years old, with 2.2% meeting the UTI definition. Among these, âclinical diagnosisâ correctly identified 46.6% of positive cultures, with 94.7% specificity and an AUROC of 0.77 (95% CI 0.71 to 0.83). Four symptoms, three signs and three dipstick results were independently associated with UTI with an AUROC (95% CI; bootstrap-validated AUROC) of 0.89 (0.85 to 0.95; validated 0.88) for symptoms and signs, increasing to 0.93 (0.90 to 0.97; validated 0.90) with dipstick results. Nappy pad samples were provided from the other 2277 children, of whom 82% were < 2 years old and 1.3% met the UTI definition.âClinical diagnosisâ correctly identified 13.3% positive cultures, with 98.5% specificity and an AUROC of 0.63 (95% CI 0.53 to 0.72). Four symptoms and two dipstick results were independently associated with UTI, with an AUROC of 0.81 (0.72 to 0.90; validated 0.78) for symptoms, increasing to 0.87 (0.80 to 0.94; validated 0.82) with the dipstick findings. A high specificity threshold for the clean-catch model was more accurate and less costly than, and as effective as, clinical judgement. The additional diagnostic utility of dipstick testing was offset by its costs. The cost-effectiveness of the nappy pad model was not clear-cut.Conclusions: Clinicians should prioritise the use of clean-catch sampling as symptoms and signs can cost-effectively improve the identification of UTI in young children where clean catch is possible. Dipstick testing can improve targeting of antibiotic treatment, but at a higher cost than waiting for a laboratory result. Future research is needed to distinguish pathogens from contaminants, assess the impact of the clean-catch algorithm on patient outcomes, and the cost-effectiveness of presumptive versus dipstick versus laboratory-guided antibiotic treatment.Funding: The National Institute for Health Research Health Technology Assessment programme.<br/
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
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