3,323 research outputs found
Analysis of total urinary catecholamines by liquid chromatography: methodology, routine experience and clinical interpretations of results
A simple routine method is described for simultaneous assay of total urinary adrenaline, noradrenaline and dopamine. The catecholamines are pre-purified on a small ion-exchange column, separated by reversed phase ion-pair liquid chromatography, and are quantitated by electrochemical detection. The method was routinely applied to 422 urines. Elevated values were found in four urine specimens obtained from patients with histologically proven phaeochromocytomas. Virtually no interference by endogenous or exogenous compounds was found. Values for urinary catecholamines determined by fluorimetric analysis agreed with those obtained by high pressure liquid chromatography with electrochemical detection. Within-day CVs for the compounds ranged from 5.2-11.9%, between-day CVs from 3.3-6.6%. The normal range (95% confidence level) was 20-230 micrograms/24 h for noradrenaline and 1-35 micrograms/24 h for adrenaline
Low-lying dipole response in the unstable Ni 70 nucleus
The Coulomb excitation of the neutron-rich nucleus Ni70 was measured in inverse kinematics at 260AMeV bombarding energy and with a Au197 target. The beam energy allowed us to study the dipole response around the neutron separation energy (up to about 12 MeV). The experiment was performed at the RIKEN Radioactive Isotope Beam Factory (RIBF). The γ decay from the scattered Ni70 ions at around zero degree was measured with a scintillator detection system composed of large volume LaBr3:Ce detectors (HECTOR+ array) and NaI(Tl) detectors (DALI2 array). Results were obtained for the E1 strength in the region where the dipole response is characterized by the presence of the pygmy dipole resonance. The measured E1 strength is found to be larger as compared with that of Ni68 below the neutron binding energy. The measured E1 strength as a function of energy is compared with available predictions based on relativistic and nonrelativistic approaches, and only in some cases does theory give a reasonable account of the data
Space Station CMIF extended duration metabolic control test
The Space Station Extended Duration Metabolic Control Test (EMCT) was conducted at the MSFC Core Module Integration Facility. The primary objective of the EMCT was to gather performance data from a partially-closed regenerative Environmental Control and Life Support (ECLS) system functioning under steady-state conditions. Included is a description of the EMCT configuration, a summary of events, a discussion of anomalies that occurred during the test, and detailed results and analysis from individual measurements of water and gas samples taken during the test. A comparison of the physical, chemical, and microbiological methods used in the post test laboratory analyses of the water samples is included. The preprototype ECLS hardware used in the test, providing an overall process description and theory of operation for each hardware item. Analytical results pertaining to a system level mass balance and selected system power estimates are also included
Microbiological Characterization and Concerns of the International Space Station Internal Active Thermal Control System
Since January 1999, the chemical the International Space Station Thermal Control System (IATCS) and microbial state of (ISS) Internal Active fluid has been monitored by analysis of samples returned to Earth. Key chemical parameters have changed over time, including a drop in pH from the specified 9.5 +/- 0.5 ta = 58.4, an increase in the level of total inorganic carbon (TIC), total organic carbon (TOC) and dissolved nickel (Ni) in the fluid, and a decrease in the phosphate (PO,) level. In addition, silver (AS) ion levels in the fluid decreased rapidly as Ag deposited on internal metallic surfaces of the system. The lack of available Ag ions coupled with changes in the fluid chemistry has resulted in a favorable environment for microbial growth. Counts of heterotrophic bacteria have increased from less than 10 colony-forming units (CFUs)/l00 mL to l0(exp 6) to l0(exp 7) CFUs/100 mL. The increase of the microbial population is of concern because uncontrolled microbiological growth in the IATCS can contribute to deterioration in the performance of critical components within the system and potentially impact human health if opportunistic pathogens become established and escape into the cabin atmosphere. Micro-organisms can potentially degrade the coolant chemistry; attach to surfaces and form biofilms; lead to biofouling of filters, tubing, and pumps; decrease flow rates; reduce heat transfer; initiate and accelerate corrosion; and enhance mineral scale formation. The micro- biological data from the ISS IATCS fluid, and approaches to addressing the concerns, are summarized in this paper
PROGRESS IN THE STUDY OF THE γ-DECAY OF THE GIANT DIPOLE RESONANCE IN HOT NUCLEI
The problem of the damping of the Giant Dipole Resonance (GDR) at finite temperature at T>2 MeV is discussed here. The experimental results are based on fusion evaporation reactions. The most recent results on the mass region A = 132 ( Ce isotopes) obtained in exclusive measurements are compared with the existing results on the A = 110–120 region ( Sn isotopes). The comparison with the theoretical predictions based on thermal shape fluctuations is also discussed. The GDR width is found to increase also in the region T>2 MeV and this is accounted by the combined effect of the increase of the compound nucleus width (smaller lifetime) and to the increase of the average deformation of the nucleus
Pulse distributions and tracking in segmented detectors
Abstract A study of the performance of a cylindrical HPGe detector segmented in 25 segments is presented. It is based on simulations made with the computer code GEANT and focuses on the reconstruction of a γ-ray path. The effects of the segmentation are initially discussed in terms of Doppler correction. The role of the pulse shape analysis and its effects on tracking algorithms are discussed as a function of the capability to reconstruct a γ-ray path when multiple signals (direct and induced) are present in a single segment. It is found that it is critical to identify correctly at least two signals in a segment in order to have a reasonable efficiency and Compton suppression in the spectra and to make a good use of this type of detectors
Money in monetary policy design: monetary cross-checking in the New-Keynesian model
In the New-Keynesian model, optimal interest rate policy under uncertainty is formulated without reference to monetary aggregates as long as certain standard assumptions on the distributions of unobservables are satisfied. The model has been criticized for failing to explain common trends in money growth and inflation, and that therefore money should be used as a cross-check in policy formulation (see Lucas (2007)). We show that the New-Keynesian model can explain such trends if one allows for the possibility of persistent central bank misperceptions. Such misperceptions motivate the search for policies that include additional robustness checks. In earlier work, we proposed an interest rate rule that is near-optimal in normal times but includes a cross-check with monetary information. In case of unusual monetary trends, interest rates are adjusted. In this paper, we show in detail how to derive the appropriate magnitude of the interest rate adjustment following a significant cross-check with monetary information, when the New-Keynesian model is the central bank’s preferred model. The cross-check is shown to be effective in offsetting persistent deviations of inflation due to central bank misperceptions. Keywords: Monetary Policy, New-Keynesian Model, Money, Quantity Theory, European Central Bank, Policy Under Uncertaint
Analysis of cold worked holes for structural life extension
Cold working holes for improved fatigue life of fastener holes are widely used on aircraft. This paper presents methods used by the authors to determine the percent of cold working to be applied and to analyze fatigue crack growth of cold worked fastener holes. An elastic, perfectly-plastic analysis of a thick-walled tube is used to determine the stress field during the cold working process and the residual stress field after the process is completed. The results of the elastic/plastic analysis are used to determine the amount of cold working to apply to a hole. The residual stress field is then used to perform damage tolerance analysis of a crack growing out of a cold worked fastener hole. This analysis method is easily implemented in existing crack growth computer codes so that the cold worked holes can be used to extend the structural life of aircraft. Analytical results are compared to test data where appropriate
- …