Extracting the Weinberg angle at intermediate energies

A recent experiment by the NuTeV collaboration resulted in a surprisingly high value for the weak mixing angle $\sin^2 \theta_W$. The Paschos-Wolfenstein relation, relating neutrino cross sections to the Weinberg angle, is of pivotal importance in the NuTeV analysis. In this work, we investigate the sensitivity of the Paschos-Wolfenstein relation to nuclear structure aspects at neutrino energies in the few GeV range. Neutrino-nucleus cross sections are calculated for $^{16}$O and $^{56}$Fe target nuclei within a relativistic quasi-elastic nucleon-knockout model.Comment: To appear in the proceedings of International School of Nuclear Physics: 27th Course: "Neutrinos in Cosmology, in Astro, Particle and Nuclear Physics", Erice, Sicily, Italy, 16-24 Sep 200

Strangeness content of the nucleon in quasielastic neutrino-nucleus reactions

We present a systematic study of the sensitivity of quasielastic neutrino-nucleus cross sections at intermediate energies to the strange quark sea of the nucleon. To this end, we investigate the impact of the weak strangeness form factors on the ratio of proton-to-neutron knockout, the ratio of neutral-to-charged current cross sections, on the Paschos-Wolfenstein relation, and on the longitudinal helicity asymmetry. The influence of axial as well as vector strangeness effects is discussed. For the latter, we introduce strangeness parameters from various hadron models and from a recent fit to data from parity violating electron scattering. In our model, the nuclear target is described in terms of a relativistic mean-field approach. The effects of final-state interactions on the outgoing nucleon are quantified within a relativistic multiple-scattering Glauber approach. Our results are illustrated with cross sections for the scattering of 1 GeV neutrinos and antineutrinos off a $^{12}$C target. Folding with a proposed FINeSSE (anti)neutrino energy-distribution has no qualitative influence on the overall sensitivity of the cross-section ratios to strangeness mechanisms. We show that vector strangeness effects are large and strongly $Q^2$ dependent.Comment: 25 pages, 12 figures, submitted to Phys. Rev.

Quasi-elastic neutrino-nucleus scattering

In the energy region below 1 GeV, neutrino-scattering off nuclei is dominated by quasi-elastic processes. Several effects influence the outcome of these reactions, and the result of cross section calculations depends on choices in model and parameterization. We discuss the main sensitivities of quasi-elastic processes and their influence on cross section results

A relativistic model for neutrino pion production from nuclei in the resonance region

We present a relativistic model for electroweak pion production from nuclei, focusing on the $\Delta$ and the second resonance region. Bound states are derived in the Hartree approximation to the $\sigma-\omega$ Walecka model. Final-state interactions of the outgoing pion and nucleon are described in a factorized way by means of a relativistic extension of the Glauber model. Our formalism allows a detailed study of neutrino pion production through $Q^2$, $W$, energy, angle and out-of-plane distributions.Comment: 3 pages, 1 figure, poster presented at the NuInt07 conference on few-GeV neutrino physic

Potentialités des bioélectrodes et des bioréacteurs à biomasse fixée pour l'estimation rapide de la DBO

La méthode standard de détermination de la Demande Biochimique en Oxygène (DBO-5 jours par dilutions) présente certains inconvénients bien connus dont celui de ne pas être exploitable pour la gestion en temps réel d'un procédé d'épuration. De ce fait, divers types d'appareils d'estimation rapide de la DBO, basés sur des méthodes respirométriques, ont été imaginés dans le passé et même commercialisés pour certains.Dans cette étude, des appareils d'estimation rapide de la DBO de types bioélectrode et réacteurs à biomasse fixée (écoulement piston et parfaitement mélangé) ont été mis en oeuvre, après avoir été développés ou modifiés sur base de concepts déjà existants. Une attention particulière a été portée sur la validité de ces appareils, la crédibilité de leurs mesures et la définition de leur champ d'action.De par leur principe de fonctionnement (injection en flux), la bioélectrode et le bioréacteur piston sont des appareils qui doivent être calibrés et dont la biomasse immobilisée doit être préalablement adaptée à l'échantillon à analyser. La solution de calibration est essentielle et doit être qualitativement la plus proche possible de l'échantillon à analyser.Le bioréacteur parfaitement mélangé se distingue des deux premières méthodes car il travaille théoriquement en consommation totale du substrat. La méthode ne nécessite pas de calibration mais implique, avant toute mesure de respirogramme, la détermination d'un paramètre supplémentaire, le coefficient de transfert de l'oxygène.De manière générale, la principale conclusion de l'étude réside dans la difficulté de ces appareils à fournir une DO (Demande en oxygène) corrélable à la DBO5 conventionnelle. Leur champ d'application reste en effet limité aux substrats rapidement biodégradables.Leurs potentialités restent cependant conformes aux besoins de contrôle rapide des charges organiques polluantes en entrée et sortie des stations d'épuration.BOD (Biochemical Oxygen Demand) is an important parameter to characterize organic pollution in aquatic environments and sewage. The five-day period required by the classical dilution method (BOD5) is incompatible with real-time control of a sewage treatment plant. Moreover, the assay procedure (closed respirometer, very diluted samples) is not only far from real growing conditions but also far from conditions in sewage treatment plants.Several devices for rapid BOD estimation, all based on respirometric methods, have been developed and tested. These devices can be grouped into 2 categories:- an immobilized biomass plug-flow reactor and a bioelectrode, both based on a flow injection principle; - an immobilized biomass perfectly mixed reactor, based on an open respirometer principle. We have focused mainly on validating the principles, checking the measurement reliability, and defining more precisely the scope of the various devices.The bioelectrodeThe BOD bioelectrode that we developed relies on a classical configuration that uses a yeast strain (Trichosporon cutaneum) as the biological receptor and a Clark probe as the transducer. The main changes made in this system are as follows:- a second biomembraneless Clark probe was added to the 16-ml measuring cell to serve as a reference probe in order to remove experimental disturbances (temperature, oxygen transfer coefficient, dissolved oxygen concentration, etc.). - the second change was to include the respirogram area among the data available for processing. The signal utilized in this set-up is the difference between the signals provided by the two probes. Our conclusions are as follows:- Concerning the signal processing, manufacturers are currently guided by the desire to develop devices able to estimate the BOD of a large range of substrates or effluents in a very short time (a few minutes for the newest devices). However, it seems useful, even necessary in many cases (complex mixtures of components that are oxidized at variable rates), to use information provided by the respirogram shape and area. This approach allows one to maximize the BOD bioelectrode's range for a given immobilized strain, although the trade-off is a longer total run time. - Concerning the adaptation period for microorganisms, it is impossible to correctly estimate BOD from various effluents without first adapting the biomaterial to the type of substrate to be analyzed. Therefore it is dangerous to consider a BOD bioelectrode as an analytical instrument, because an adaptation period is required after any change in the composition or, even more so, type of effluent. - Concerning the correspondence between rapid BOD and BOD5, the BOD sensor can detect only the BOD of soluble compounds that can diffuse through the biomembrane and that will be metabolized during the time of analysis. The difference observed between BOD sensor and BOD5 depends on the calibration solution but also and even more on the structure and size of the molecules constituting the sample to be analyzed. - Concerning the choice of calibration solution, choosing the right calibration solution is crucial. The calibration solution should therefore be qualitatively as close as possible to the test sample. The immobilized biomass bioreactorsThe plug-flow reactorThe plug-flow reactor design was validated for simple substrates; its working principle is similar to the bioelectrodes, since it relies on flow-injection analysis (FIA). In the case of the plug-flow reactor, the only usable information for BOD estimation is the respirogram area, as the peak height quickly reaches a rather constant value due to saturation of the immobilized microorganisms. However, the importance of the many physical and biological processes that occur concomitantly in the system (transfer, adsorption, substrate consumption, substrate saturation phenomena, dilution rate, etc.) makes a theoretical mathematical model of the reactor more difficult to establish. A long-term, more fundamental study of various natural or artificial substrates might ultimately enable us to reach such a goal.On the other hand, a variant of this reactor that recirculates the partially-degraded effluent until it is completely consumed yielded a linear correlation between system response (respirogram area) and substrate amount. In this system, oxidation of the rapidly biodegradable substrates is total under our operating conditions. This alternative reactor seems to have some very interesting possibilities, especially with regard to the automation of the system.The perfectly mixed reactorThe utilization of the perfectly mixed reactor for rapid BOD estimation is based on two sequential experiments - although this has the disadvantage of increasing the total run time - to obtain the respirogram area (S) and oxygen transfer coefficient (KL.a), as the units of the product (KL.a x S) of these parameters are equivalent to those of oxygen demand and their product is the variable that best correlates with the substrate injection volume. This correlation was observed for a large range of substrates. In the case of the perfectly mixed reactor, unlike bioelectrodes,- diffusion processes have no effect on measurement, as the substrate is consumed completely during the experiment; - the substrate consumption rate does not affect the measurements, thereby freeing the method from the influence of various experimental parameters (air flow-rate, the quantity of biomass, the liquid volume in the reactor, etc.), as our tests have shown. For a given substrate, the linearity of the correlation between the product of KL.a x S and the amount of substrate is generally excellent. The attempt to correlate the system's response with the BOD5 measurements for a variety of substrates proved to be difficult, however. Although the bioreactor's analytical range is wider than that of bioelectrodes, the system still fails to give any measurable responses for complex substrates such as starch, cellulose, proteins, etc., and the KL.a x S values estimated by the bioreactor remained much lower than the corresponding BOD5 values. KL.a x S is probably characteristic of the portion of the substrate that is degraded rapidly by the microorganisms to meet their immediate energy needs, whereas the remaining substrate is probably kept for reserve and biomass synthesis

Stratigraphy and paleoenvironments of the early to middle Holocene Chipalamawamba Beds (Malawi Basin, Africa)

We describe the Chipalamawamba Beds, early to middle Holocene deposits at the southern margin of long-lived Lake Malawi. The beds are exposed because of downcutting of the upper Shire River. The Chipalamawamba sediments are medium to coarse, yellow to brown sands deposited in lenses varying in horizontal extent from a few meters to several hundreds of meters. Four units are recognized; the first three mainly contain lacustrine sediments deposited during lake high stands about 10.6–9.7 cal ka BP (Unit 1), 7.6–6.5 cal ka BP (Unit 2) and 5.9–5.3 cal ka BP (Unit 3). Sediments of Unit 4 overlay Units 1 to 3, are coarser and display regular foresets and oblique-bedding, suggesting deposition in riverine environments after installation of the Shire River (~ 5.5–5.0 ka BP). Freshwater mollusk assemblages and bioturbation regularly occur in the lacustrine sediments, but are largely absent from Unit 4. Diverse and often contradicting hypotheses on the lake levels of Lake Malawi have been proposed for the early and middle Holocene. The Chipalamawamba Beds allow straightforward recognition of water levels and provide strong evidence for oscillating lake levels during this period, rather than continuous high or low levels. Sedimentation rates have been high and individual shell beds have typically been deposited during a few decades. Because the Chipalamawamba Beds contain a sequence of mollusk assemblages with intervals between subsequent shell beds ranging from a century to a few millennia, they enable paleontological analysis of the fauna with an unusually high temporal resolution. That some mollusk lineages inhabiting Lake Malawi are in the early stages of diversification and radiation increases the paleobiological relevance of these beds

Minimally invasive atrioventricular valve surgery – current status and future perspectives

We are currently witnessing rapid evolution in minimally invasive and catheter-based atrioventricular valve interventions as acceptable alternatives to classic sternotomy access (CSA). Collectively, minimally invasive atrioventricular valve surgery (MIAS) is associated with significant learning curves and its routine application is met with varying degrees of enthusiasm in view of strict quality control, clinical governance and outcome reporting. Whether the reported potential benefits and comparable efficacy across a range of long-term outcome measures reported by experienced MIAS centres can be translated into general international surgical practice, are not well defined. This paper describes the historic evolution of MIAS, the contemporary clinical outcomes of MIAS compared with CSA, and the application of MIAS in “real-life” general practice

A low-energy rate-adaptive bit-interleaved passive optical network

Energy consumption of customer premises equipment (CPE) has become a serious issue in the new generations of time-division multiplexing passive optical networks, which operate at 10 Gb/s or higher. It is becoming a major factor in global network energy consumption, and it poses problems during emergencies when CPE is battery-operated. In this paper, a low-energy passive optical network (PON) that uses a novel bit-interleaving downstream protocol is proposed. The details about the network architecture, protocol, and the key enabling implementation aspects, including dynamic traffic interleaving, rate-adaptive descrambling of decimated traffic, and the design and implementation of a downsampling clock and data recovery circuit, are described. The proposed concept is shown to reduce the energy consumption for protocol processing by a factor of 30. A detailed analysis of the energy consumption in the CPE shows that the interleaving protocol reduces the total energy consumption of the CPE significantly in comparison to the standard 10 Gb/s PON CPE. Experimental results obtained from measurements on the implemented CPE prototype confirm that the CPE consumes significantly less energy than the standard 10 Gb/s PON CPE