The nucleon-sigma coupling constant in QCD Sum Rules

The external-field QCD Sum Rules method is used to evaluate the coupling constant of the light isoscalar-scalar meson (``$\sigma$'' or \epsilon) to the nucleon. The contributions that come from the excited nucleon states and the response of the continuum threshold to the external field are calculated. The obtained value of the coupling constant is compatible with the large value required in one-boson exchange potential models of the two-nucleon interaction.Comment: 11 pages, 4 figure

An interacting quark-diquark model of baryons

A simple quark-diquark model of baryons with direct and exchange interactions is constructed. Spectrum and form factors are calculated and compared with experimental data. Advantages and disadvantages of the model are discussed.Comment: 13 pages, 3 eps-figures, accepted by Phys.Rev. C Rapid Communication

Evaluating Local Community Methods in Networks

We present a new benchmarking procedure that is unambiguous and specific to local community-finding methods, allowing one to compare the accuracy of various methods. We apply this to new and existing algorithms. A simple class of synthetic benchmark networks is also developed, capable of testing properties specific to these local methods.Comment: 8 pages, 9 figures, code included with sourc

\pi N scattering in relativistic baryon chiral perturbation theory revisited

We have analyzed pion-nucleon scattering using the manifestly relativistic covariant framework of Infrared Regularization up to {\cal O}(q^3) in the chiral expansion, where q is a generic small momentum. We describe the low-energy phase shifts with a similar quality as previously achieved with Heavy Baryon Chiral Perturbation Theory, \sqrt{s}\lesssim1.14 GeV. New values are provided for the {\cal O}(q^2) and {\cal O}(q^3) low-energy constants, which are compared with previous determinations. This is also the case for the scattering lengths and volumes. Finally, we have unitarized the previous amplitudes and as a result the energy range where data are reproduced increases significantly.Comment: 26 pages, 5 figures, 5 table

Pertinent Dirac structure for QCD sum rules of meson-baryon coupling constants

Using general baryon interpolating fields $J_B$ for $B= N, \Xi, \Sigma,$ without derivative, we study QCD sum rules for meson-baryon couplings and their dependence on Dirac structures for the two-point correlation function with a meson i\int d^4x e^{iqx} \bra 0|{\rm T}[J_B(x)\bar{J}_B(0)] |{\cal M}(p)\ket. Three distinct Dirac structures are compared: $i\gamma_5$, i\gamma_5\fslash{p}, and $\gamma_5\sigma_{\mu\nu}q^\mu p^\nu$ structures. From the dependence of the OPE on general baryon interpolating fields, we propose criteria for choosing an appropriate Dirac structure for the coupling sum rules. The $\gamma_5\sigma_{\mu\nu}q^\mu p^\nu$ sum rules satisfy the criteria while the $i\gamma_5$ sum rules beyond the chiral limit do not. For the i\gamma_5\fslash{p} sum rules, the large continuum contributions prohibit reliable prediction for the couplings. Thus, the $\gamma_5\sigma_{\mu\nu}q^\mu p^\nu$ structure seems pertinent for realistic predictions. In the SU(3) limit, we identify the OPE terms responsible for the $F/D$ ratio. We then study the dependence of the ratio on the baryon interpolating fields. We conclude the ratio $F/D \sim 0.6-0.8$ for appropriate choice of the interpolating fields.Comment: To be published in Phys.Rev.C ; 21 pages,8 figures, revtex ; references are adde

Contaminant-related suppression of delayed-type hypersensitivity and antibody responses in harbor seals fed herring from the Baltic Sea.

Recent mass mortalities among several marine mammal populations have led to speculation about increased susceptibility to viral infections as a result of contaminant-induced immunosuppression. In a 2.5-year study, we fed herring from either the relatively uncontaminated Atlantic Ocean or the contaminated Baltic Sea to two groups of captive harbor seals and monitored immune function in the seals. Seals fed the contaminated fish were less able to mount a specific immunological response to ovalbumin, as measured by in vivo delayed-type hypersensitivity (DTH) reactions and antibody responses. The skin reaction to this protein antigen was characterized by the appearance of mononuclear cells which peaked at 24 hr after intradermal administration, characteristic of DTH reactions in other animals studied. These DTH responses correlated well with in vitro tests of T-lymphocyte function, implicating this cell type in the reaction. Aryl-hydrocarbon (Ah) receptor-dependent toxic equivalent (TEQ) profiles in blubber biopsies taken from the seals implicated polychlorinated biphenyls rather than dioxins or furans in the observed immunosuppression. Marine mammal populations currently inhabiting polluted coastal environments in Europe and North America may therefore have an increased susceptibility to infections, and pollution may have played a role in recent virus-induced mass mortalities

LC determination of propylene glycol in human plasma after pre-column derivatization with benzoyl chloride

A simple high-performance liquid chromatographic method, using photodiode array detection was developed for the determination of propylene glycol in human plasma and in the fluid retreived after continuous veno-venous hemofiltration. The method entailed alkaline derivatization with benzoyl chloride and ethylene glycol as internal standard. The separation of the compounds, after extraction with pentane, was carried out on a Pursuit C8 column with UV-detection at 230 nm. Validation samples were analyzed with an accuracy between 95 and 105%, and intra- and inter-day coefficients of variation of less than 8%. The calibration curve was linear over a concentration range of 5-100 mg

Diagnostic performance of dobutamine stress echocardiography: A South African experience

Background. Dobutamine stress echocardiography (DSE) is a well-established modality for the diagnosis of coronary artery disease, but there are no reported diagnostic data in southern Africa. Objectives. To compare the safety, sensitivity and specificity of a South African (SA) DSE programme with larger, international series. Methods. All patients undergoing DSE from 2019 to 2021 at a single SA centre were included. A new wall motion abnormality (≥2 segments) signified inducible ischaemia. Results. A total of 106 patients (mean (standard deviation) age 61 (11) years, 68% male) were analysed. Six patients (6%) experienced chest pain during DSE and 4 (4%) developed an atrial arrhythmia. The sensitivity and specificity for epicardial coronary stenosis were 77% and 74%, respectively, changing to 82% and 72% when excluding those who had previous coronary artery bypass surgery. Conclusion. The sensitivity, specificity and safety of an SA DSE programme were comparable to international series. A DSE programme is feasible in a resource-constrained environment

Metal and Metal Oxide Transformation and Texturing Using Pulsed Fiber Laser

Thin films of amorphous vanadium metal were deposited on a glass substrate using the electron beam evaporator, these thin films were then exposed to a focused 1064 nm wavelength nanosecond laser pulses. The laser fluence was selected such that it was below the ablation threshold of the films, x-ray diffraction measurement revealed the formation of an oxide phase of vanadium after the laser exposure. The time of flight-secondary ion mass spectrometry data analysis showed a uniform elemental distribution of the elements on the films, whereas the Rutherford backscattering spectrometry results showed that the concentration of oxygen as a function of the laser fluence was increasing, hinting to the incorporation of the oxygen atoms in the films as the laser fluence increases. UV-Vis-NIR percentage reflectance measurements showed small evolution in the visible part of the spectrum due to laser exposure