1,869 research outputs found
Variational Approximations in a Path-Integral Description of Potential Scattering
Using a recent path integral representation for the T-matrix in
nonrelativistic potential scattering we investigate new variational
approximations in this framework. By means of the Feynman-Jensen variational
principle and the most general ansatz quadratic in the velocity variables --
over which one has to integrate functionally -- we obtain variational equations
which contain classical elements (trajectories) as well as quantum-mechanical
ones (wave spreading).We analyse these equations and solve them numerically by
iteration, a procedure best suited at high energy. The first correction to the
variational result arising from a cumulant expansion is also evaluated.
Comparison is made with exact partial-wave results for scattering from a
Gaussian potential and better agreement is found at large scattering angles
where the standard eikonal-type approximations fail.Comment: 35 pages, 3 figures, 6 tables, Latex with amsmath, amssymb; v2: 28
pages, EPJ style, misprints corrected, note added about correct treatment of
complex Gaussian integrals with the theory of "pencils", matches published
versio
Internal delensing of cosmic microwave background polarization B-Modes with the POLARBEAR experiment
International audienceUsing only cosmic microwave background polarization data from the polarbear experiment, we measure B-mode polarization delensing on subdegree scales at more than 5σ significance. We achieve a 14% B-mode power variance reduction, the highest to date for internal delensing, and improve this result to 22% by applying for the first time an iterative maximum a posteriori delensing method. Our analysis demonstrates the capability of internal delensing as a means of improving constraints on inflationary models, paving the way for the optimal analysis of next-generation primordial B-mode experiments
Measurement of the cosmic microwave background polarization lensing power spectrum from two years of POLARBEAR data
We present a measurement of the gravitational lensing deflection power spectrum reconstructed with two seasons of cosmic microwave background polarization data from the POLARBEAR experiment. Observations were taken at 150 GHz from 2012 to 2014 and surveyed three patches of sky totaling 30 square degrees. We test the consistency of the lensing spectrum with a cold dark matter cosmology and reject the no-lensing hypothesis at a confidence of 10.9σ, including statistical and systematic uncertainties. We observe a value of AL = 1.33 ± 0.32 (statistical) ±0.02 (systematic) ±0.07 (foreground) using all polarization lensing estimators, which corresponds to a 24% accurate measurement of the lensing amplitude. Compared to the analysis of the first- year data, we have improved the breadth of both the suite of null tests and the error terms included in the estimation of systematic contamination
Towards a computer aided diagnosis system dedicated to virtual microscopy based on stereology sampling and diffusion maps
An original strategy is presented, combining stereological sampling methods based on test grids and data reduction methods based on diffusion maps, in order to build a knowledge image database with no bias introduced by a subjective choice of exploration areas. The practical application of the exposed methodology concerns virtual slides of breast tumors
Charge transfer in dissociating iodomethane and fluoromethane molecules ionized by intense femtosecond X-ray pulses
Citation: Boll, R., Erk, B., Coffee, R., Trippel, S., Kierspel, T., Bomme, C., . . . Rudenko, A. (2016). Charge transfer in dissociating iodomethane and fluoromethane molecules ionized by intense femtosecond X-ray pulses. Structural Dynamics, 3(4). doi:10.1063/1.4944344Additional Authors: Marchenko, T.;Miron, C.;Patanen, M.;Osipov, T.;Schorb, S.;Simon, M.;Swiggers, M.;Techert, S.;Ueda, K.;Bostedt, C.;Rolles, D.;Rudenko, A.Ultrafast electron transfer in dissociating iodomethane and fluoromethane molecules was studied at the Linac Coherent Light Source free-electron laser using an ultraviolet-pump, X-ray-probe scheme. The results for both molecules are discussed with respect to the nature of their UV excitation and different chemical properties. Signatures of long-distance intramolecular charge transfer are observed for both species, and a quantitative analysis of its distance dependence in iodomethane is carried out for charge states up to I21+. The reconstructed critical distances for electron transfer are in good agreement with a classical over-the-barrier model and with an earlier experiment employing a near-infrared pump pulse. © 2016 Author(s)
Functional determinants for general Sturm-Liouville problems
Simple and analytically tractable expressions for functional determinants are
known to exist for many cases of interest. We extend the range of situations
for which these hold to cover systems of self-adjoint operators of the
Sturm-Liouville type with arbitrary linear boundary conditions. The results
hold whether or not the operators have negative eigenvalues. The physically
important case of functional determinants of operators with a zero mode, but
where that mode has been extracted, is studied in detail for the same range of
situations as when no zero mode exists. The method of proof uses the properties
of generalised zeta-functions. The general form of the final results are the
same for the entire range of problems considered.Comment: 28 pages, LaTe
Operational experience, improvements, and performance of the CDF Run II silicon vertex detector
The Collider Detector at Fermilab (CDF) pursues a broad physics program at
Fermilab's Tevatron collider. Between Run II commissioning in early 2001 and
the end of operations in September 2011, the Tevatron delivered 12 fb-1 of
integrated luminosity of p-pbar collisions at sqrt(s)=1.96 TeV. Many physics
analyses undertaken by CDF require heavy flavor tagging with large charged
particle tracking acceptance. To realize these goals, in 2001 CDF installed
eight layers of silicon microstrip detectors around its interaction region.
These detectors were designed for 2--5 years of operation, radiation doses up
to 2 Mrad (0.02 Gy), and were expected to be replaced in 2004. The sensors were
not replaced, and the Tevatron run was extended for several years beyond its
design, exposing the sensors and electronics to much higher radiation doses
than anticipated. In this paper we describe the operational challenges
encountered over the past 10 years of running the CDF silicon detectors, the
preventive measures undertaken, and the improvements made along the way to
ensure their optimal performance for collecting high quality physics data. In
addition, we describe the quantities and methods used to monitor radiation
damage in the sensors for optimal performance and summarize the detector
performance quantities important to CDF's physics program, including vertex
resolution, heavy flavor tagging, and silicon vertex trigger performance.Comment: Preprint accepted for publication in Nuclear Instruments and Methods
A (07/31/2013
Feasibility, acceptability and effectiveness of integrated care for COPD patients: a mixed methods evaluation of a pilot community-based programme.
The aim of this study was to assess the feasibility, acceptability and effectiveness of a pilot COPD integrated care programme implemented in Valais, Switzerland.
The programme was adapted from the self-management programme Living Well with COPD, and included the following elements: self-management patient-education group sessions, telephone and medical follow-ups, multidisciplinary teams, training of healthcare professionals, and evidence-based COPD care. A process and outcome evaluation of the pilot phase of the programme was conducted by means of qualitative and quantitative methods. Reach (coverage, participation rates), dosage (interventions carried out), fidelity (delivered as intended) and stakeholders' acceptance of the programme were evaluated through data monitoring and conduct of focus groups with patients and healthcare professionals. Effectiveness was assessed with pre-post analyses (before and after the intervention). The primary outcome measures were; (1) generic and disease-specific quality of life (36-Item Short Form Health Survey, Chronic Respiratory Questionnaire); and (2) hospitalisations (all-cause and for acute exacerbations) in the past 12 months. Secondary outcomes included self-efficacy, number of exacerbations and exercise capacity. Finally, controlled pre-post comparisons were also made with patients from the Swiss COPD Cohort for three common outcome measures (dyspnoea [mMRC score], number of exacerbations and smoking status).
During the first 2 years of the programme, eight series of group-based education sessions were delivered to 57 patients with COPD in three different locations of the canton of Valais. Coverage objectives were achieved and attendance rate at the education sessions was high (83.6%). Patients' and healthcare professionals' reported a high degree of satisfaction, except for multidisciplinarity and transfer of information. Exploration of the effectiveness of this pilot programme suggested positive pre-post results at 12 months, with improvements in terms of health-related quality of life, self-efficacy, exercise capacity, immunisation coverage and Patient Assessment of Chronic Illness Care score. No other outcome, including the number of hospital admissions, differed significantly after 12 months. We observed no differences from the control group.
The evaluation demonstrated the feasibility and acceptability of the programme and confirmed the relevance of mixed method process evaluation to adjust and improve programme implementation. The introduction of multidisciplinary teams in a context characterised by fragmentation of care was identified as the main challenge in the programme implementation and could not be achieved as expected. Despite this area for improvement, patients' feedback and early effectiveness results confirmed the benefits of COPD integrated care programmes emphasising self-management education
Measurement of the Lifetime Difference Between B_s Mass Eigenstates
We present measurements of the lifetimes and polarization amplitudes for B_s
--> J/psi phi and B_d --> J/psi K*0 decays. Lifetimes of the heavy (H) and
light (L) mass eigenstates in the B_s system are separately measured for the
first time by determining the relative contributions of amplitudes with
definite CP as a function of the decay time. Using 203 +/- 15 B_s decays, we
obtain tau_L = (1.05 +{0.16}/-{0.13} +/- 0.02) ps and tau_H = (2.07
+{0.58}/-{0.46} +/- 0.03) ps. Expressed in terms of the difference DeltaGamma_s
and average Gamma_s, of the decay rates of the two eigenstates, the results are
DeltaGamma_s/Gamma_s = (65 +{25}/-{33} +/- 1)%, and DeltaGamma_s = (0.47
+{0.19}/-{0.24} +/- 0.01) inverse ps.Comment: 8 pages, 3 figures, 2 tables; as published in Physical Review Letters
on 16 March 2005; revisions are for length and typesetting only, no changes
in results or conclusion
Measurement of and Production in Collisions at = 1.96 TeV
The Standard Model predictions for and production are
tested using an integrated luminosity of 200 pb of \ppbar collision data
collected at the Collider Detector at Fermilab. The cross sections are measured
selecting leptonic decays of the and bosons, and photons with
transverse energy GeV that are well separated from leptons. The
production cross sections and kinematic distributions for the and
are compared to SM predictions.Comment: 7 pages, 4 figures, submitted to PR
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