Economic evaluation of the routine use of echocardiography versus natriuretic peptide and ECG-targeted echocardiography in the diagnosis of heart failure

Objectives: To investigate the most efficient use of echocardiography and natriuretic peptide testing in the diagnosis of heart failure. Design: An economic model comparing two strategies: (A) provide echocardiography and electrocardiogram (ECG) for all individuals who present to a GP with symptoms that may be due to heart failure; (B) carry out B-type natriuretic peptide (BNP) blood test and ECG on all such individuals and provide echocardiography only where an abnormality is detected in one of more of these tests. Setting: Primary care in the UK NHS. Subjects: Individuals who present to a GP with new symptoms of heart failure. Main outcome measures: Cost per life year gained. Results: Baseline cost per life year gained by strategy A compared with strategy B is £3,987. Conclusions: Immediate echocardiography is the most cost-effective option. Where echocardiography is a scarce resource, efficient use can be obtained by using BNP and ECG tests to identify patients most likely to have heart failure

Marine environmental monitoring programmes in South Africa: a review

South Africa uniquely lies at the junction of two major currents, the Agulhas and the Benguela. The waters overlying the continental shelf exhibit exceptionally high short-, medium- and long-term (days to inter-decadal) variability compared with most other shelf areas, and strongly contrasting oceanographic conditions are observed on the east and west coasts. South Africa is rich in fisheries resources and associated environmental data collected over more than a century. The South African marine scientific community has a history of multidisciplinary studies of marine foodwebs, from the driving forces such as wind, currents and solar heating, to the top predators, with the development of kelp bed, sub-tidal reefs and estuarine ecosystem studies in the 1970s; the Benguela Ecology Programme, which ran through four successive five-year stages, focused on the pelagic marine resources. Various approaches have been used to observe the continental shelf at different time and space scales, including: macroscale but frequent satellite imagery, mesoscale environmental and fishery surveys, dedicated crossshelf transects in key areas, measurements of dynamic processes, use of moored buoys and coastal weather stations, and integrated monitoring approaches, including modelling and simulation studies. Between 30 and 50 years of comprehensive marine data now exist, which are proving useful in the application of an ecosystem approach to fisheries monitoring and management, as decadal changes become discernible. These observations need to continue; even though the single-species stock assessment and operational management procedures have not yet formally used environmental factors for fisheries management advice, they help us to understand the factors affecting fish population fluctuations and early life histories and to identify large-scale regime shifts where marine trophic structure and functioning alter to a new state

Nonperturbative Aspect of Axial Vector Vertex in the Global Color Symmetry Model

It is shown how the axial vector current of current quarks is related to that of constituent quarks within the framework of the global color symmetry model. Gluon dressing of the axial vector vertex and the quark self-energy functions is described by the inhomogeneous Bethe-Salpeter equation in the ladder approximation and the Schwinger-Dyson equation in the rainbow approximation, respectively.Comment: 10 page

Mesons as qbar-q Bound States from Euclidean 2-Point Correlators in the Bethe-Salpeter Approach

We investigate the 2-point correlation function for the vector current. The gluons provide dressings for both the quark self energy as well as the vector vertex function, which are described consistently by the rainbow Dyson-Schwinger equation and the inhomogeneous ladder Bethe-Salpeter equation. The form of the gluon propagator at low momenta is modeled by a 2-parameter ansatz fitting the weak pion decay constant. The quarks are confined in the sense that the quark propagator does not have a pole at timelike momenta. We determine the ground state mass in the vector channel from the Euclidean time Fourier transform of the correlator, which has an exponential falloff at large times. The ground state mass lies around 590 MeV and is almost independent of the model form for the gluon propagator. This method allows us to stay in Euclidean space and to avoid analytic continuation of the quark or gluon propagators into the timelike region.Comment: 21 pages (REVTEX), 8 Postscript figure

Low-energy QCD: Chiral coefficients and the quark-quark interaction

A detailed investigation of the low-energy chiral expansion is presented within a model truncation of QCD. The truncation allows for a phenomenological description of the quark-quark interaction in a framework which maintains the global symmetries of QCD and permits a $1/N_c$ expansion. The model dependence of the chiral coefficients is tested for several forms of the quark-quark interaction by varying the form of the running coupling, $\alpha (q^2)$, in the infrared region. The pattern in the coefficients that arises at tree level is consistent with large $N_c$ QCD, and is related to the model truncation.Comment: 28 pages, Latex, 6 postscript figures available on request to [email protected]

Should the Pomeron and imaginary parts be modelled by two gluons and real quarks?

We illustrate that solution of the Schwinger-Dyson equation for the gluon propagator in QCD does not support an infrared softened behaviour, but only an infrared enhancement. This has consequences for the modelling of the Pomeron in terms of dressed gluon exchange. It highlights that an understanding of the Pomeron within QCD must take account of the bound state nature of hadrons.Comment: 7 pages, latex, 2 figures, replaced ~\epsfig... by \mbox{\epsfig...

Nonperturbative aspects of the quark-photon vertex

The electromagnetic interaction with quarks is investigated through a relativistic, electromagnetic gauge-invariant treatment. Gluon dressing of the quark-photon vertex and the quark self-energy functions is described by the inhomogeneous Bethe-Salpeter equation in the ladder approximation and the Schwinger-Dyson equation in the rainbow approximation respectively. Results for the calculation of the quark-photon vertex are presented in both the time-like and space-like regions of photon momentum squared, however emphasis is placed on the space-like region relevant to electron scattering. The treatment presented here simultaneously addresses the role of dynamically generated $q\bar{q}$ vector bound states and the approach to asymptotic behavior. The resulting description is therefore applicable over the entire range of momentum transfers available in electron scattering experiments. Input parameters are limited to the model gluon two-point function, which is chosen to reflect confinement and asymptotic freedom, and are largely constrained by the obtained bound-state spectrum.Comment: 8 figures available on request by email, 25 pages, Revtex, DOE/ER/40561-131-INT94-00-5

Dissecting the Re-Os molybdenite geochronometer

Rhenium and osmium isotopes have been used for decades to date the formation of molybdenite (MoS2), a common mineral in ore deposits and the world’s main source of molybdenum and rhenium. Understanding the distribution of parent 187Re and radiogenic daughter 187Os isotopes in molybdenite is critical in interpreting isotopic measurements because it can compromise the accurate determination and interpretation of mineralization ages. In order to resolve the controls on the distribution of these elements, chemical and isotope mapping of MoS2 grains from representative porphyry copper-molybdenum deposits were performed using electron microprobe and nano-scale secondary ion mass spectrometry. Our results show a heterogeneous distribution of 185,187Re and 192Os isotopes in MoS2, and that both 187Re and 187Os isotopes are not decoupled as previously thought. We conclude that Re and Os are structurally bound or present as nanoparticles in or next to molybdenite grains, recording a complex formation history and hindering the use of microbeam techniques for Re-Os molybdenite dating. Our study opens new avenues to explore the effects of isotope nuggeting in geochronometers

(No) dynamical constraints on the mass of the black hole in two ULXs

We present the preliminary results of two Gemini campaigns to constrain the mass of the black hole in an ultraluminous X-ray source (ULX) via optical spectroscopy. Pilot studies of the optical counterparts of a number of ULXs revealed two candidates for further detailed study, based on the presence of a broad He II 4686 Å emission line. A sequence of 10 long-slit spectra were obtained for each object, and the velocity shift of the ULX counterpart measured. Although radial velocity variations are observed, they are not sinusoidal, and no mass function is obtained. However, the broad He II line is highly variable on timescales shorter than a day. If associated with the reprocessing of X-rays in the accretion disc, its breadth implies that the disc must be close to face-on

K -> pi pi and a light scalar meson

We explore the Delta-I= 1/2 rule and epsilon'/epsilon in K -> pi pi transitions using a Dyson-Schwinger equation model. Exploiting the feature that QCD penguin operators direct K^0_S transitions through 0^{++} intermediate states, we find an explanation of the enhancement of I=0 K -> pi pi transitions in the contribution of a light sigma-meson. This mechanism also affects epsilon'/epsilon.Comment: 7 pages, REVTE