80 research outputs found
LPMLE3 : a novel 1-D approach to study water flow in streambeds using heat as a tracer
We introduce LPMLE3, a new 1-D approach to quantify vertical water flow components at streambeds using temperature data collected in different depths. LPMLE3 solves the partial differential equation for coupled water flow and heat transport in the frequency domain. Unlike other 1-D approaches it does not assume a semi-infinite halfspace with the location of the lower boundary condition approaching infinity. Instead, it uses local upper and lower boundary conditions. As such, the streambed can be divided into finite subdomains bound at the top and bottom by a temperature-time series. Information from a third temperature sensor within each subdomain is then used for parameter estimation. LPMLE3 applies a low order local polynomial to separate periodic and transient parts (including the noise contributions) of a temperature-time series and calculates the frequency response of each subdomain to a known temperature input at the streambed top. A maximum-likelihood estimator is used to estimate the vertical component of water flow, thermal diffusivity, and their uncertainties for each streambed subdomain and provides information regarding model quality. We tested the method on synthetic temperature data generated with the numerical model STRIVE and demonstrate how the vertical flow component can be quantified for field data collected in a Belgian stream. We show that by using the results in additional analyses, nonvertical flow components could be identified and by making certain assumptions they could be quantified for each subdomain. LPMLE3 performed well on both simulated and field data and can be considered a valuable addition to the existing 1-D methods
Could hyponatremia be a marker of anastomotic leakage after colorectal surgery? A single center analysis of 1,106 patients over 5years
Purpose: The aim of this study is to define the significance of hyponatremia as a marker of anastomotic leakage after colorectal surgery. Methods: All anastomoses in colorectal surgery performed at a single institution between July 2007 and July 2012 (n = 1,106) were retrospectively identified. Serum sodium levels and leukocyte values measured when an anastomotic leak was diagnosed by CT scan and/or surgical reintervention (n = 81) were compared to the values preferably on postoperative day 5 in the absence of an anastomotic leak (n = 1,025). Results: The leak rate in anastomoses of the rectum was 9.0%, while the leak rate of the other anastomoses was 5.4%. Mean serum sodium level was 138.8mmol/l in the group with an anastomotic leak and 140.5mmol/l in the group without. Hyponatremia (<136mmol/l) was present in 23% of patients in the group with an anastomotic leak and in 15% in the group without (p < 0.001). In multivariate analysis, leukocytes and serum sodium level remained as significant markers of an anastomotic leak. As a marker of an anastomotic leak, hyponatremia had a specificity of 93% and a sensitivity of 23%, while the presence of either leukocytosis or hyponatremia had a sensitivity of 68%, a specificity of 75%, a positive predictive value of 18%, and a negative predictive value of 97%. Conclusions: Hyponatremia could be a specific and relevant marker of anastomotic leakage after colorectal surgery. If hyponatremia and leukocytosis are present after colorectal surgery, anastomotic leakage should be suspected and a CT scan with rectal contrast dye is recommended
The polarization observables T, P, and H and their impact on multipoles
Data on the polarization observables T, P, and H for the reaction are reported. Compared to earlier data from other experiments, our
data are more precise and extend the covered range in energy and angle
substantially. The results were extracted from azimuthal asymmetries measured
using a transversely polarized target and linearly polarized photons. The data
were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS
detector. Within the Bonn-Gatchina partial wave analysis, the new polarization
data lead to a significant narrowing of the error band for the multipoles for
neutral-pion photoproduction
The N(1520) 3/2- helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions
New data on the polarization observables T, P, and H for the reaction are reported. The results are extracted from azimuthal
asymmetries when a transversely polarized butanol target and a linearly
polarized photon beam are used. The data were taken at the Bonn electron
stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier
data are used to perform a truncated energy-independent partial wave analysis
in sliced-energy bins. This energy-independent analysis is compared to the
results from energy-dependent partial wave analyses
Photoproduction of eta mesons from the neutron: cross sections and double polarization observable E
Photoproduction of mesons from neutrons} \abstract{Results from
measurements of the photoproduction of mesons from quasifree protons and
neutrons are summarized. The experiments were performed with the CBELSA/TAPS
detector at the electron accelerator ELSA in Bonn using the
decay. A liquid deuterium target was used for the
measurement of total cross sections and angular distributions. The results
confirm earlier measurements from Bonn and the MAMI facility in Mainz about the
existence of a narrow structure in the excitation function of . The current angular distributions show a forward-backward
asymmetry, which was previously not seen, but was predicted by model
calculations including an additional narrow state. Furthermore, data
obtained with a longitudinally polarized, deuterated butanol target and a
circularly polarized photon beam were analyzed to determine the double
polarization observable . Both data sets together were also used to extract
the helicity dependent cross sections and . The
narrow structure in the excitation function of
appears associated with the helicity-1/2 component of the reaction
New data on with polarized photons and protons and their implications for decays
The polarization observables , and in photoproduction of
mesons off protons are measured for photon energies from threshold to
MeV (), 2280 MeV (), 1620 MeV (), or 1820 MeV (),
covering nearly the full solid angle. The data are compared to predictions from
the SAID, MAID, J\"uBo, and BnGa partial-wave analyses. A refit within the BnGa
approach including further data yields precise branching ratios for the
decay of nucleon resonances. A -branching ratio of for
is found, which reduces the large and controversially discussed
-branching ratio difference of the two lowest mass
-resonances significantly.Comment: 10 pages, 11 figure
Ubiquitous LEA29Y Expression Blocks T Cell Co-Stimulation but Permits Sexual Reproduction in Genetically Modified Pigs
We have successfully established and characterized a genetically modified pig line with ubiquitous expression of LEA29Y, a human CTLA4-Ig derivate. LEA29Y binds human B7.1/CD80 and B7.2/CD86 with high affinity and is thus a potent inhibitor of T cell co-stimulation via this pathway. We have characterized the expression pattern and the biological function of the transgene as well as its impact on the porcine immune system and have evaluated the potential of these transgenic pigs to propagate via assisted breeding methods. The analysis of LEA29Y expression in serum and multiple organs of CAG-LEA transgenic pigs revealed that these animals produce a biologically active transgenic product at a considerable level. They present with an immune system affected by transgene expression, but can be maintained until sexual maturity and propagated by assisted reproduction techniques. Based on previous experience with pancreatic islets expressing LEA29Y, tissues from CAG-LEA29Y transgenic pigs should be protected against rejection by human T cells. Furthermore, their immune-compromised phenotype makes CAG-LEA29Y transgenic pigs an interesting large animal model for testing human cell therapies and will provide an important tool for further clarifying the LEA29Y mode of action
Photoproduction of ηπ pairs off nucleons and deuterons
Quasi-free photoproduction of πη-pairs has been investigated from threshold up to incident photon energies of 1.4 GeV, respectively up to photon-nucleon invariant masses up to 1.9 GeV. Total cross sections, angular distributions, invariant-mass distributions of the πη and meson-nucleon pairs, and beamhelicity asymmetries have been measured for the reactions γp → pπ0η, γn → nπ0η, γp → nπ+η, and γn → pπ-n from nucleons bound inside the deuteron. For the γp initial-state data for free protons have also been analyzed. Finally, the total cross sections for quasi-free production of π0η pairs from nucleons bound in 3He nuclei have been investigated in view of final state interaction (FSI) effects. The experiments were performed at the tagged photon beam facility of the Mainz MAMI accelerator using an almost 4π covering electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. The shapes of all differential cross section data and the asymmetries are very similar for protons and neutrons and agree with the conjecture that the reactions are dominated by the sequential Δ*3/2- → ηΔ(1232) → πηN decay chain, mainly with Δ(1700)3/2- and Δ(1940)3/2-. The ratios of the magnitude of the total cross sections also agree with this assumption. However, the absolute magnitudes of the cross sections are reduced by FSI effects with respect to free proton data
Photon asymmetry measurements of γ→ p→ π0p for Eγ= 320-650 MeV
High-statistics measurements of the photon asymmetry Σ for the γ→ p→ π0p reaction have been made in the center-of-mass energy range W= 1214 - 1450 MeV. The data were measured with the MAMI A2 real photon beam and Crystal Ball/TAPS detector systems in Mainz, Germany. The results significantly improve the existing world data and are shown to be in good agreement with previous measurements, and with the MAID, SAID, and Bonn-Gatchina predictions. We have also combined the photon asymmetry results with recent cross-section measurements from Mainz to calculate the profile functions, Σˇ (= σ0Σ) , and perform a moment analysis. Comparison with calculations from the Bonn-Gatchina model shows that the precision of the data is good enough to further constrain the higher partial waves, and there is an indication of interference between the very small F-waves and the N(1520) 3 / 2 - and N(1535) 1 / 2 - resonances
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