Extracting the depolarization coefficient D_NN from data measured with a full acceptance detector

The spin transfer from vertically polarized beam protons to Lambda or Sigma hyperons of the associated strangeness production pp -> pK Lambda (Sigma) is described with the depolarization coefficient D_NN. As the polarization of the hyperons is determined by their weak decays, detectors, which have a large acceptance for the decay particles, are needed. In this paper a formula is derived, which describes the depolarization coefficient D_NN by count rates of a 4 pi detector. It is shown, that formulas, which are given in publications for detectors with restricted acceptance, are specific cases of this formula for a 4 pi detector.Comment: Accepted for publication by Nuclear Instruments and Methods in Physics Research Section

A Special Homotopy Continuation Method For A Class of Polynomial Systems

A special homotopy continuation method, as a combination of the polyhedral homotopy and the linear product homotopy, is proposed for computing all the isolated solutions to a special class of polynomial systems. The root number bound of this method is between the total degree bound and the mixed volume bound and can be easily computed. The new algorithm has been implemented as a program called LPH using C++. Our experiments show its efficiency compared to the polyhedral or other homotopies on such systems. As an application, the algorithm can be used to find witness points on each connected component of a real variety

Bupivacaine concentrations in lumbar cerebrospinal fluid in patients with failed spinal anaesthesia

Background Spinal anaesthesia (SA) has high success rates. However, inadequate block after SA has been reported even in the absence of technical problems. Various mechanisms for failed SA (FSA) have been proposed, but reports of cerebrospinal fluid (CSF) concentrations of local anaesthetics (LA) after FSA are scarce. We report lumbar CSF concentrations of bupivacaine in 20 patients in whom adequate block after subarachnoid injection failed to develop. Methods All patients with inadequate block after subarachnoid injection of plain bupivacaine 0.5% and in whom a second subarachnoid injection of LA was to be performed as a rescue technique were eligible for entry into this study. A CSF sample was withdrawn immediately before injection of the second dose of LA. Patients in whom failure was obviously due to technical problems or inadequate dosage were excluded. Bupivacaine concentrations were assessed with high-performance liquid chromatography. Results During the study period of 15 months, 2600 spinal anaesthetics were performed. The failure rate was 2.7% (71 patients). In 20 patients (0.77%), CSF concentrations of bupivacaine were determined, which ranged from 3.36 to 1020 µg ml−1. Conclusions Inadequate CSF concentration of LA is a common reason for FSA. However, in 12 of our 20 patients, concentrations were above 73 µg ml−1, a concentration that should lead to an adequate block. In these patients, maldistribution of bupivacaine could be responsible for FSA. In view of the absence of sufficient block, despite adequate lumbar CSF concentrations of bupivacaine, concerns about neurotoxicity with repeat injections may be warrante

Center of Mass Motion of Short-Range Correlated Nucleon Pairs Studied Via the A(e, e\u27pp) Reaction

Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum (kF). A fundamental characteristic of SRC pairs is having large relative momenta as compared to kF, and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton (pp) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the A(e,e′pp) reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to 170  MeV/c , approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states

Ensamble de macroinvertebrados bentónicos como indicadores de calidad de agua a través de la aplicación de un índice biótico modificado en un contexto espacio-estacional en una cuenca costera del sur de Chile

Tapia, J (Tapia, Jaime).Univ Talca, Inst Chem & Nat Resources, Talca, Chile.The water quality in a Southern Chile river was characterized using the Biotic Index in a spatio-seasonal context, to analyze the composition and distribution of benthic macroinvertebrates and their correlation with 14 physico-chemical parameters. Sampling was done over a year at 5 sampling stations in the basin of the Boroa River. A total of 77 taxa were recorded, with the most represented orders being the Ephemeroptera (43.30%), Diptera (24.16%) and Plecoptera (18.03%). The most abundant species were Meridialaris diguillina, Nousia maculata (Ephemeroptera) and Limnoperla jaffueli (Plecoptera). According to the modified FBI (Family Biotic Index), the findings indicated excellent, very good and good water quality, the latter quality being registered principally in winter. Likewise, the physico-chemical parameters indicated exceptional water quality. These results suggested a low level of anthropogenic impact in the basin. Applying the modified Hilsenhoff Biotic Index based on macroinvertebrates, the influence of seasonality on water quality was evident

Accurate Determination of the Neutron Skin Thickness of \u3csup\u3e208\u3c/sup\u3ePb

We report a precision measurement of the parity-violating asymmetry Apv in the elastic scattering of longitudinally polarized electrons from 208Pb. We measure Apv = 550 ± 16(stat) ± 8(syst) parts per billion, leading to an extraction of the neutral weak form factor Fw (Q2 = 0.00616 GeV2) = 0.368 ± 0.013. Combined with our previous measurement, the extracted neutron skin thickness is Rn - Rp = 0.283 ± 0.071 fm. The result also yields the first significant direct measurement of the interior weak density of 208Pb: ρ0w = -0.0796 ± 0.0036(exp) ± 0.0013(theo) fm-3) leading to the interior baryon density ρ0b)= 0.1480 ± 0.0036(exp) ± 0.0013(theo) fm-3. The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars

First Measurement of Direct Photoproduction of the a\u3csub\u3e2\u3c/sub\u3e(1320)⁰ Meson on the Proton

We present the first measurement of the reaction p -\u3e a₂(1320)⁰ p in the photon energy range 3.5-5.5 GeV and four-momentum transfer squared 0.2 \u3c -t \u3c 2.0 GeV2. Data were collected with the CEBAF Large Acceptance Spectrometer detector at the Thomas Jefferson National Accelerator Facility. The a2resonance was detected by measuring the reaction p → π0ηp and reconstructing the π0η invariant mass. The most prominent feature of the differential cross section is a dip at -t ≈ 0.55 GeV2. This can be described in the framework of Regge phenomenology, where the exchange degeneracy hypothesis predicts a zero in the reaction amplitude for this value of the four-momentum transfer

Probing the Deuteron at Very Large Internal Momenta

We measure 2H(e,e′p)n cross sections at 4-momentum transfers of Q2 = 4.5 ± 0.5   (GeV/c)2 over a range of neutron recoil momenta pr, reaching up to ∼1.0  GeV/c. We obtain data at fixed neutron recoil angles θnq = 35°, 45°, and 75° with respect to the 3-momentum transfer →q. The new data agree well with previous data, which reached pr ∼ 500  MeV/c. At θnq = 35° and 45°, final state interactions, meson exchange currents, and isobar currents are suppressed and the plane wave impulse approximation provides the dominant cross section contribution. We compare the new data to recent theoretical calculations, where we observe a significant discrepancy for recoil momenta pr \u3e 700  MeV/c