840 research outputs found
Bayesian estimation of parameters in a regional hydrological model
International audienceThis study evaluates the applicability of the distributed, process-oriented Ecomag model for prediction of daily streamflow in ungauged basins. The Ecomag model is applied as a regional model to nine catchments in the NOPEX area, using Bayesian statistics to estimate the posterior distribution of the model parameters conditioned on the observed streamflow. The distribution is calculated by Markov Chain Monte Carlo (MCMC) analysis. The Bayesian method requires formulation of a likelihood function for the parameters and three alternative formulations are used. The first is a subjectively chosen objective function that describes the goodness of fit between the simulated and observed streamflow, as defined in the GLUE framework. The second and third formulations are more statistically correct likelihood models that describe the simulation errors. The full statistical likelihood model describes the simulation errors as an AR(1) process, whereas the simple model excludes the auto-regressive part. The statistical parameters depend on the catchments and the hydrological processes and the statistical and the hydrological parameters are estimated simultaneously. The results show that the simple likelihood model gives the most robust parameter estimates. The simulation error may be explained to a large extent by the catchment characteristics and climatic conditions, so it is possible to transfer knowledge about them to ungauged catchments. The statistical models for the simulation errors indicate that structural errors in the model are more important than parameter uncertainties. Keywords: regional hydrological model, model uncertainty, Bayesian analysis, Markov Chain Monte Carlo analysis</p
Generalized seniority scheme in light Sn isotopes
The yrast generalized seniority states are compared with the corresponding
shell model states for the case of the Sn isotopes Sn. For most of
the cases the energies agree within 100 keV and the overlaps of the wave
functions are greater than 0.7.Comment: 8 pages, revtex. Submitted to Phys. Rev.
Body size and thyroid cancer in two million Norwegian men and women
We investigated relations between measured body mass index (BMI) and stature and thyroid cancer (3046 cases) in a large Norwegian cohort of more than two million individuals. The risk of thyroid cancer, especially of the papillary and follicular types, increased moderately with increasing BMI and height in both sexes
Pharmacokinetics and Pharmacodynamic Effects of Flunixin after Intravenous, Intramuscular and Oral Administration to Dairy Goats
The pharmacokinetics and the prostaglandin (PG) synthesis inhibiting effect of flunixin were determined in 6 Norwegian dairy goats. The dose was 2.2 mg/kg body weight administered by intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) routes using a cross-over design. Plasma flunixin content was analysed by use of liquid chromatography and the PG synthesis was evaluated by measuring plasma 15-ketodihydro-PGF(2α )by a radioimmuno-assay. Results are presented as median (range). The elimination half-lives (t(1/2·λ)) were 3.6 (2.0–5.0), 3.4 (2.6–6.8) and 4.3 (3.4–6.1) h for i.v., i.m. and p.o. administration, respectively. Volume of distribution at steady state (Vd(ss)) was 0.35 (0.23–0.41) L/kg and clearance (CL), 110 (60–160) mL/h/kg. The plasma concentrations after oral administration showed a double-peak phenomenon with the two peaks occurring at 0.37 (0.25–1) and 3.5 (2.5–5.0) h, respectively. Both peaks were in the same order of magnitude. Bioavailability was 79 (53–112) and 58 (35%–120)% for i.m. and p.o. administration, respectively. 15-Ketodihydro-PGF(2α )plasma concentrations decreased after flunixin administration independent of the route of administration
Streamflow forecast sensitivity to air temperature forecast calibration for 139 Norwegian catchments
In this study, we used meteorological ensemble forecasts
as input to hydrological models to quantify the uncertainty in forecasted
streamflow, with a particular focus on the effect of temperature forecast
calibration on the streamflow ensemble forecast skill. In catchments with
seasonal snow cover, snowmelt is an important flood-generating process.
Hence, high-quality air temperature data are important to accurately
forecast streamflows. The sensitivity of streamflow ensemble forecasts to
the calibration of temperature ensemble forecasts was investigated using
ensemble forecasts of temperature from the European Centre for Medium-Range Weather Forecasts (ECMWF) covering a period of nearly
3 years, from 1 March 2013 to 31 December 2015. To improve the skill and reduce
biases of the temperature ensembles, the Norwegian Meteorological Institute
(MET Norway) provided parameters for ensemble calibration, derived using a standard
quantile mapping method where HIRLAM, a high-resolution regional weather
prediction model, was used as reference. A lumped HBV (Hydrologiska Byråns Vattenbalansavdelning)
model, distributed on 10 elevation zones, was used to estimate the streamflow. The results show
that temperature ensemble calibration affected both temperature and
streamflow forecast skill, but differently depending on season and region.
We found a close to 1:1 relationship between temperature and streamflow
skill change for the spring season, whereas for autumn and winter large
temperature skill improvements were not reflected in the streamflow
forecasts to the same degree. This can be explained by streamflow being less
affected by subzero temperature improvements, which accounted for the
biggest temperature biases and corrections during autumn and winter. The
skill differs between regions. In particular, there is a cold bias in the
forecasted temperature during autumn and winter along the coast, enabling a
large improvement by calibration. The forecast skill was partly related to
elevation differences and catchment area. Overall, it is evident that
temperature forecasts are important for streamflow forecasts in climates
with seasonal snow cover.</p
Shell-model calculation in 24Mg
A shell-model calculation is performed for 24Mg assuming wave functions with maximum symmetry in the spacial coordinates. Several interactions have been used including the Kallio-Kolltveit hard-core potential. A reasonable agreement is obtained for the energy levels, while the E2 branching ratios are in many cases different from the experimental values. The eigen-functions have large overlap with the predicted SU3 wave functons. The influence of particle-hole excitations in the spectrum is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33350/1/0000747.pd
Dominant g(9/2)^2 neutron configuration in the 4+1 state of 68Zn based on new g factor measurements
The factor of the state in Zn has been remeasured with
improved energy resolution of the detectors used. The value obtained is
consistent with the previous result of a negative factor thus confirming
the dominant neutron nature of the state. In addition, the
accuracy of the factors of the , and states has been
improved an d their lifetimes were well reproduced. New large-scale shell model
calculations based on a Ni core and an model space
yield a theoretical value, . Although the calculated value
is small, it cannot fully explain the experimental value, . The magnitude of the deduced B(E2) of the and
transition is, however, rather well described. These results demonstrate again
the importance of factor measurements for nuclear structure determination s
due to their specific sensitivity to detailed proton and neutron components in
the nuclear wave functions.Comment: 7 pages, 3 figs, submitted to PL
Interactions between p300 and multiple NF-Y trimers govern cyclin B2 promoter function
The CCAAT box is one of the most common elements in eukaryotic promoters and is activated by NF-Y, a conserved trimeric transcription factor with histone-like subunits. Usually one CCAAT element is present in promoters at positions between -60 and -100, but an emerging class of promoters harbor multiple NF-Y sites. In the triple CCAAT-containing cyclin B2 cell-cycle promoter, all CCAAT boxes, independently from their NF-Y affinities, are important for function. We investigated the relationships between NF-Y and p300. Chromatin immunoprecipitation analysis found that NF-Y and p300 are bound to the cyclin B2 promoter in vivo and that their binding is regulated during the cell cycle, positively correlating with promoter function. Cotransfection experiments determined that the coactivator acts on all CCAAT boxes and requires a precise spacing between the three elements. We established the order of in vitro binding of the three NF-Y complexes and find decreasing affinities from the most distal Y1 to the proximal Y3 site. Binding of two or three NF-Y trimers with or without p300 is not cooperative, but association with the Y1 and Y2 sites is extremely stable. p300 favors the binding of NF-Y to the weak Y3 proximal site, provided that a correct distance between the three CCAAT is respected. Our data indicate that the precise spacing of multiple CCAAT boxes is crucial for coactivator function. Transient association to a weak site might be a point of regulation during the cell cycle and a general theme of multiple CCAAT box promoters
Application of realistic effective interactions to the structure of the Zr isotopes
We calculate the low-lying spectra of the zirconium isotopes Z=40 with
neutron numbers from N=52 to N=60 using the 1p1/20g9/2 proton and
2s1d0g7/20h11/2 neutron sub-shells to define the model space. Effective
proton-proton, neutron--neutron and proton-neutron interactions have been
derived using 88Sr as closed core and employing perturbative many-body
techniques. The starting point is the nucleon-nucleon potential derived from
modern meson exchange models. The comprehensive shell-model calculation
performed in this work provides a qualitative reproduction of essential
properties such as the sub-shell closures in 96Zr and 98Zr.Comment: To appear in Phys Rev C, june 2000, 8 figs, Revtex latex styl
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