Low energy neutron physics research with a gamma multiplicity detector

A sixteen-segment NaI(Tl) multiplicity gamma ray detector is used at the Rensselaer Polytechnic Institute Gaerttner LINAC Laboratory for neutron cross section measurements. This detector consists of an annulus of NaI(Tl) divided into two sets of 8 pie-shaped segments, each segment optically isolated and viewed by a photomultiplier. The neutron beam passes along the axis of the detector and impinges upon a sample placed in the center. Time-of-flight data are taken as a function of the number of sections which detect a gamma and which is defined as the detected multiplicity. This detector can simultaneously acquire a neutron scattering, capture and fission data by placing suitable limits on the total detected gamma ray energy deposited in the detector. Scattering and capture measurements have been performed on samples of holmium, erbium, and tungsten and experimental results are presented. The experimental multiplicity for capture is analyzed by assuming the single particle model, stochastically calculating the gamma ray cascades from neutron capture, and transporting each gamma ray into the detector using the Monte Carlo method. The detection efficiency for neutron capture is over 90% and is relatively insensitive to different isotopes of the same element or different spins of the compound nuclear resonances. A status report on experimental and analytical activities at the Laboratory is presented

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

The focus of this work is to determine the resonance parameters for stable hafnium isotopes in the 0.005 - 200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. Accurate hafnium cross sections and resonance parameters are needed in order to quantify the effects of hafnium found in zirconium, a metal commonly used in reactors. The accuracy of the cross sections and the corresponding resonance parameters used in current nuclear analysis tools are rapidly becoming the limiting factor in reducing the overall uncertainty on reactor physics calculations. Experiments measuring neutron capture and transmission are routinely performed at the Rensselaer Polytechnic Institute (RPI) LINAC using the time-of flight technique. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m, respectively. Capture experiments were performed using a sixteen section NaI multiplicity detector at a flight path length of 25 m. These experiments utilized several thicknesses of metallic and isotope-enriched liquid Hf samples. The liquid Hf samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analyses were performed using the R-matrix Bayesian code SAMMY. A combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005 - 200 eV. Additionally, resonance integrals were calculated, along with errors for each hafnium isotope, using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previous values. The {sup 176}Hf resonance integral, based on this work, is approximately 73% higher than the ENDF/B-VI value. This is due primarily to the changes to resonance parameters in the 8 eV resonance, the neutron width presented in this work is more than twice that of the previous value. The calculated elemental hafnium resonance integral however, changed very little

EQ-5D in Central and Eastern Europe : 2000-2015

Objective: Cost per quality-adjusted life year data are required for reimbursement decisions in many Central and Eastern European (CEE) countries. EQ-5D is by far the most commonly used instrument to generate utility values in CEE. This study aims to systematically review the literature on EQ-5D from eight CEE countries. Methods: An electronic database search was performed up to July 1, 2015 to identify original EQ-5D studies from the countries of interest. We analysed the use of EQ-5D with respect to clinical areas, methodological rigor, population norms and value sets. Results: We identified 143 studies providing 152 country-specific results with a total sample size of 81,619: Austria (n=11), Bulgaria (n=6), Czech Republic (n=18), Hungary (n=47), Poland (n=51), Romania (n=2), Slovakia (n=3) and Slovenia (n=14). Cardiovascular (20%), neurologic (16%), musculoskeletal (15%) and endocrine/nutritional/metabolic diseases (14%) were the most frequently studied clinical areas. Overall 112 (78%) of the studies reported EQ VAS results and 86 (60%) EQ-5D index scores, of which 27 (31%) did not specify the applied tariff. Hungary, Poland and Slovenia have population norms. Poland and Slovenia also have a national value set. Conclusions: Increasing use of EQ-5D is observed throughout CEE. The spread of health technology assessment activities in countries seems to be reflected in the number of EQ-5D studies. However, improvement in informed use and methodological quality of reporting is needed. In jurisdictions where no national value set is available, in order to ensure comparability we recommend to apply the most frequently used UK tariff. Regional collaboration between CEE countries should be strengthened

Dynamic thylakoid stacking regulates the balance between linear and cyclic photosynthetic electron transfer

An Author Correction to this article was published on 29 May 2018 https://www.nature.com/articles/s41477-018-0163-4 http://eprints.whiterose.ac.uk/131699/ Upon transition of plants from darkness to light the initiation of photosynthetic linear electron transfer (LET) from H2O to NADP+ precedes the activation of CO2 fixation, creating a lag period where cyclic electron transfer (CET) around photosystem I (PSI) has an important protective role. CET generates ΔpH without net reduced NADPH formation, preventing overreduction of PSI via regulation of the cytochrome b 6 f (cytb 6 f) complex and protecting PSII from overexcitation by inducing non-photochemical quenching. The dark-to-light transition also provokes increased phosphorylation of light-harvesting complex II (LHCII). However, the relationship between LHCII phosphorylation and regulation of the LET/CET balance is not understood. Here, we show that the dark-to-light changes in LHCII phosphorylation profoundly alter thylakoid membrane architecture and the macromolecular organization of the photosynthetic complexes, without significantly affecting the antenna size of either photosystem. The grana diameter and number of membrane layers per grana are decreased in the light while the number of grana per chloroplast is increased, creating a larger contact area between grana and stromal lamellae. We show that these changes in thylakoid stacking regulate the balance between LET and CET pathways. Smaller grana promote more efficient LET by reducing the diffusion distance for the mobile electron carriers plastoquinone and plastocyanin, whereas larger grana enhance the partition of the granal and stromal lamellae plastoquinone pools, enhancing the efficiency of CET and thus photoprotection by non-photochemical quenching

Energetic control of intact chloroplast photosynthesis

The induction phase of photosynthesis was studied in intact chloroplasts isolated from spinach. Within 15 sec of illumination, stromal ADP is phosphorylated to give an ATP/ADP ratio of 1.4. A transthylakoid pH gradient of about 4.1 units developed during the first min, and was associated with a low note of linear electron flow from H/sub 2/O to NADP/sup +/. In the following 2 to 3 min, both the pH gradient and ATP/ADP ratio declined to new steady state levels (3.9 pH units and a ratio of 0.9), whereas O/sub 2/ evolution rose rapidly to 110 ..mu..mol/mg chlorophyll-h. Prolonging the induction phase by omission of catalase or by addition of 2 mM phosphate resulted in a high pH gradient and ATP/ADP ratio. Ribose 5-phosphate is known to reverse partial inhibition resulting from catalase omission or high phosphate, hence its effect on the pH gradient and ATP/ADP ratio was investigated. Ribose 5-phosphate was found to lower both these parameters under conditions chosen to restrict turnover of the carbon cycle. This result with ribose 5-phosphate underscores the importance of its product, ribulose 5-phosphate and the carboxylation product, 3-phosphoglycerate, in serving as sinks for ATP and thereby preventing inhibition of electron flow by an excessive pH gradient

Measurement of the fission cross section of /sup 238/Pu

The fission cross sections of /sup 238/Pu have been measured from 0.1 eV to 80 keV energy range using the Rensselaer Intense Neutron Spectrometer. The cross sections were normalized to the /sup 235/U ENDF/B-V data broadened to the resolution of the Rensselaer Intense Neutron Spectrometer system. The fission areas and widths were determined for the resolved low-energy resonances. The ENDF/B-V fission cross sections for the /sup 238/Pu isotope are, in general, not in good agreement with the measured cross sections and a new evaluation is recommended. The observations of structure in the unresolved fission cross sections is suggestive of the existence of intermediate structure. 18 refs., 1 fig., 1 tab

Function and mechanism of cyclic electron transport

In isolated intact chloroplasts from spinach, maximal rates of photosynthetic O/sub 2/ evolution (in saturating HCO/sub 3//sup -/) are associated with a critical transthylakoid pH gradient of about 3.9 units. O/sub 2/ evolution is inhibited by higher ..delta..pH values that arise when catalase is omitted from the medium; NH/sub 4/Cl and actimycin, but not the energy transfer inhibitor quercetin, decrease ..delta..pH and relieve this inhibition. The same low amount NH/sub 4/Cl added to control chloroplasts (..delta..pH=3.9) has little effect on ..delta..pH or the O/sub 2/ evolution rate. This resistance to uncoupling is due to an increase in the pumping of protons by cyclic electron flow. It suggests operation of feedback control in maintaining an optimal ATP/NADPH ratio. A general mechanism is proposed that allows the chloroplast to divert electrons from ferredoxin:NADP/sup +/ reductase into the cyclic pathway to provide a ..delta..pH appropriate to the ATP/NADPH ratio needed in the stroma. The stromal NADPH/NADP/sup +/ ratio is probably sensed indirectly by membrane components with redox mid point potentials around - 50 mV, such that reduction of these components causes partial loss of linear electron flow and commencement of cyclic turnover