8,514 research outputs found
Perturbation Approach to the Self Energy of non-S Hydrogenic States
We present results on the self-energy correction to the energy levels of
hydrogen and hydrogenlike ions. The self energy represents the largest QED
correction to the relativistic (Dirac-Coulomb) energy of a bound electron. We
focus on the perturbation expansion of the self energy of non-S states, and
provide estimates of the so-called A60 perturbative coefficient, which can be
considered as a relativistic Bethe logarithm. Precise values of A60 are given
for many P, D, F and G states, while estimates are given for other electronic
states. These results can be used in high-precision spectroscopy experiments in
hydrogen and hydrogenlike ions. They yield the best available estimate of the
self-energy correction of many atomic states.Comment: 18 pages (in 2-column format), 21 figures. Version 2 (June 20, 2003)
includes minor modification
Bottomonium spectroscopy with mixing of eta_b states and a light CP-odd Higgs
The mass of the eta_b(1S), measured recently by BABAR, is significantly lower
than expected from QCD predictions for the Upsilon(1S) - eta_b(1S) hyperfine
splitting. We suggest that the observed eta_b(1S) mass is shifted downwards due
to a mixing with a CP-odd Higgs scalar A with a mass m_A in the range 9.4 -
10.5 GeV compatible with LEP, CLEO and BABAR constraints. We determine the
resulting predictions for the spectrum of the eta_b(nS) - A system and the
branching ratios into tau^+ tau^- as functions of m_A.Comment: 4 pages, 4 figures, submitted to PRL, misprint correcte
Trypsin inhibition by macrocyclic and open-chain variants of the squash inhibitor MCoTI-II
MCoTl-I and MCoTl-II from the seeds of Momordica cochinchinensis are inhibitors of trypsin-like proteases and the only known members of the large family of squash inhibitors that are cyclic and contain an additional loop connecting the amino- and the carboxy-terminus. To investigate the contribution of macrocycle formation to biological activity, we synthesized a set of open-chain variants of MCoTl-II that lack the cyclization loop and contain various natural and non-natural amino acid substitutions in the reactive-site loop. Upon replacement of P1 lysine residue \#10 within the open-chain variant of MCoTl-II by the non-natural isosteric nucleo amino acid AlaG{[}beta-(guanin-9-yl)-L-alanine], a conformationally restricted arginine mimetic, residual inhibitory activity was detected, albeit reduced by four orders of magnitude. While the cyclic inhibitors MCoTl-I and MCoTl-II were found to be very potent trypsin inhibitors, with picomolar inhibition constants, the open-chain variants displayed an approximately 10-fold lower affinity. These data suggest that the formation of a circular backbone in the MCoTI squash inhibitors results in enhanced affinity and therefore is a determinant of biological activity
A multi-case study on Industry 4.0 for SMEâs in Brandenburg, Germany
Industry 4.0 is still in its development phase and it promises to bring remarkable benefits to the manufacturing industry around the world when employing the Smart Factory application in large organizations and their supply chains. However, there is a risk of a miss-match when trying to introduce Industry 4.0 to Small and Medium Enterprises (SME) as the concept is mainly being developed around large manufacturing companies. The purpose of this research is to analyze the readiness level and feasibility of implementing Industry 4.0 technologies for SMEâs in the federal state of Brandenburg (Germany). The work is based on the survey of 20 SMEâs assessing their current problems emphasizing on automation, Enterprise Resource Planning (ERP), CAD/CAM, factory layout planning and logistics. Five SMEâs from different domains out of the 20 surveyed are taken as case studies to evaluate the potential benefits, trade-offs and barriers from an implementation of these integrated technologies. The findings revealed that the companies are still coping with the issues relating to planning, logistics and automation. It was also found that all the concepts of i4.0 may not be necessary or even beneficial to an enterprise in the current scenario and new strategies need to be developed for its realization in SMEâs
Improved energy resolution for VHE gamma-ray astronomy with systems of Cherenkov telescopes
We present analysis techniques to improve the energy resolution of
stereoscopic systems of imaging atmospheric Cherenkov telescopes, using the
HEGRA telescope system as an example. The techniques include (i) the
determination of the height of the shower maximum, which is then taken into
account in the energy determination, and (ii) the determination of the location
of the shower core with the additional constraint that the direction of the
gamma rays is known a priori. This constraint can be applied for gamma-ray
point sources, and results in a significant improvement in the localization of
the shower core, which translates into better energy resolution. Combining both
techniques, the HEGRA telescopes reach an energy resolution between 9% and 12%,
over the entire energy range from 1 TeV to almost 100 TeV. Options for further
improvements of the energy resolution are discussed.Comment: 13 Pages, 7 figures, Latex. Astroparticle Physics, in pres
Fluorescence optical imaging for treatment monitoring in patients with early and active rheumatoid arthritis in a 1-year follow-up period
BACKGROUND:
Fluorescence optical imaging (FOI) enables visualization of inflammation in the hands in rheumatic joint diseases with currently a lack of long-term follow-up studies.
OBJECTIVE:
To investigate FOI for treatment monitoring in a homogenous cohort of patients with early (disease duration â3.2) RA over a period of 12âmonths.
METHODS:
Thirty-five RA patients (24 (68.6%) females, mean age 53.3âyears (SD 13.6)) were investigated clinically by DAS28, tender joint count (TJC) and swollen joint count (SJC) and by FOI in phases 1-3 and PrimaVistaMode (PVM) before therapy change and after 12âmonths. The FOI activity score (FOIAS) was calculated based on individual joint scores from 0 to 3 in 30 joints per patient, adding up to a sum score (0-90).
RESULTS:
We found a statistically significant reduction of FOIAS in phase 1 from baseline (median 5.0, IQR 24.96) to follow-up (median 1.0, IQR 4.0) in all patients (pâ=â0.0045), both in responders and non-responders according to EULAR response criteria by DAS28. Statistically significant reductions over 12âmonths were found for median DAS28(ESR) 5.61 to 3.31, TJC 7.0 to 1.0, and SJC 5.0 to 1.0 (each pâ<â 0.001). No statistically significant correlations were detected between the FOIAS change in phase 1 and DAS28(ESR), TJC, or SJC. Correlations between the other phases and clinical outcomes were weak to moderate.
CONCLUSION:
Reduced early enhancement in FOI phase 1 can be observed in clinically responding and non-responding early RA patients under treatment. Regarding potential marker performance, FOI probably shows a reduction of inflammation more objectively
Quantitative linear and nonlinear Resonance Inspection Techniques and Analysis for material characterization: Application to concrete thermal damage.
International audienceDeveloped in the late 80's, Nonlinear Resonant Ultrasound Spectroscopy (NRUS) has been widely employed in the field of material characterization. Most of the studies assume the measured amplitude to be proportional to the strain amplitude which drives nonlinear phenomena. In 1D resonant bar experiments, the configuration for which NRUS was initially developed, this assumption holds. However, it is not true for samples of general shape which exhibit several resonance mode shapes. This paper proposes a methodology based on linear resonant ultrasound spectroscopy, numerical simulations and nonlinear resonant ultrasound spectroscopy to provide quantitative values of nonlinear elastic moduli taking into account the 3D nature of the samples. In the context of license renewal in the field of nuclear energy, this study aims at providing some quantitative information related to the degree of micro-cracking of concrete and cement based materials in the presence of thermal damage. The resonance based method is validated as regard with concrete microstructure evolution during thermal exposure
Precise calculation of transition frequencies of hydrogen and deuterium based on a least-squares analysis
We combine a limited number of accurately measured transition frequencies in
hydrogen and deuterium, recent quantum electrodynamics (QED) calculations, and,
as an essential additional ingredient, a generalized least-squares analysis, to
obtain precise and optimal predictions for hydrogen and deuterium transition
frequencies. Some of the predicted transition frequencies have relative
uncertainties more than an order of magnitude smaller than that of the g-factor
of the electron, which was previously the most accurate prediction of QED.Comment: 4 pages, RevTe
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