704 research outputs found
High resolution frequency analysis techniques with application to the redshift experiment
High resolution frequency analysis methods, with application to the gravitational probe redshift experiment, are discussed. For this experiment a resolution of .00001 Hz is required to measure a slowly varying, low frequency signal of approximately 1 Hz. Major building blocks include fast Fourier transform, discrete Fourier transform, Lagrange interpolation, golden section search, and adaptive matched filter technique. Accuracy, resolution, and computer effort of these methods are investigated, including test runs on an IBM 360/65 computer
New aperture photometry of QSO 0957+561; application to time delay and microlensing
We present a re-reduction of archival CCD frames of the doubly imaged quasar
0957+561 using a new photometry code. Aperture photometry with corrections for
both cross contamination between the quasar images and galaxy contamination is
performed on about 2650 R-band images from a five year period (1992-1997). From
the brightness data a time delay of 424.9 +/- 1.2 days is derived using two
different statistical techniques. The amount of gravitational microlensing in
the quasar light curves is briefly investigated, and we find unambiguous
evidence of both long term and short term microlensing. We also note the
unusual circumstance regarding time delay estimates for this gravitational
lens. Estimates by different observers from different data sets or even with
the same data sets give lag estimates differing by typically 8 days, and error
bars of only a day or two. This probably indicates several complexities where
the result of each estimate depends upon the details of the calculation.Comment: 14 pages, 16 figures (several in color
Selection Mapping Identifies Loci Underpinning Autumn Dormancy in Alfalfa (Medicago sativa).
Autumn dormancy in alfalfa (Medicago sativa) is associated with agronomically important traits including regrowth rate, maturity, and winter survival. Historical recurrent selection experiments have been able to manipulate the dormancy response. We hypothesized that artificial selection for dormancy phenotypes in these experiments had altered allele frequencies of dormancy-related genes. Here, we follow this hypothesis and analyze allele frequency changes using genome-wide polymorphisms in the pre- and postselection populations from one historical selection experiment. We screened the nondormant cultivar CUF 101 and populations developed by three cycles of recurrent phenotypic selection for taller and shorter plants in autumn with markers derived from genotyping-by-sequencing (GBS). We validated the robustness of our GBS-derived allele frequency estimates using an empirical approach. Our results suggest that selection mapping is a powerful means of identifying genomic regions associated with traits, and that it can be exploited to provide regions on which to focus further mapping and cloning projects
Estimating sunspot number
An empirical method is developed to predict certain parameters of future solar activity cycles. Sunspot cycle statistics are examined, and curve fitting and linear regression analysis techniques are utilized
Three photometric methods tested on ground-based data of Q 2237+0305
The Einstein Cross, Q~2237+0305, has been photometrically observed in four
bands on two successive nights at NOT (La Palma, Spain) in October 1995. Three
independent algorithms have been used to analyse the data: an automatic image
decomposition technique, a CLEAN algorithm and the new MCS deconvolution code.
The photometric and astrometric results obtained with the three methods are
presented. No photometric variations were found in the four quasar images.
Comparison of the photometry from the three techniques shows that both
systematic and random errors affect each method. When the seeing is worse than
1.0", the errors from the automatic image decomposition technique and the Clean
algorithm tend to be large (0.04-0.1 magnitudes) while the deconvolution code
still gives accurate results (1{sigma} error below 0.04) even for frames with
seeing as bad as 1.7". Reddening is observed in the quasar images and is found
to be compatible with either extinction from the lensing galaxy or colour
dependent microlensing. The photometric accuracy depends on the light
distribution used to model the lensing galaxy. In particular, using a numerical
galaxy model, as done with the MCS algorithm, makes the method less seeing
dependent. Another advantage of using a numerical model is that eventual
non-homogeneous structures in the galaxy can be modeled. Finally, we propose an
observational strategy for a future photometric monitoring of the Einstein
Cross.Comment: 9 pages, accepted for publication in A&
Research in psychobiology
Research in brain-behavior relationships, perception and learning, and comparative and developmental psycholog
Retreatment with interferon-alpha and ribavirin in primary interferon-alpha non-responders with chronic hepatitis C
Background/Aims: Combination therapy with interferon-alpha (IFN-alpha) plus ribavirin is more efficacious than IFN-alpha monotherapy in previously untreated patients with chronic hepatitis C and patients with IFN-alpha relapse. Only limited data are available in IFN-alpha non-responders. In a multicenter trial we therefore evaluated the efficacy of combination therapy in IFN-alpha-resistant chronic hepatitis C. Methods: Eighty-two patients (mean age 46.8 years, 54 males, 28 females) with chronic hepatitis C were treated with IFN-alpha-2a (3 x 6 MIU/week) and ribavirin (14 mg/kg daily) for 12 weeks. Thereafter, treatment was continued only in virological responders (undetectable serum HCV RNA at week 12) with an IFN-alpha dose of 3 x 3 MIU/week and without ribavirin for a further 9 months. The primary study endpoint was an undetectable HCV RNA by RT-PCR at the end of the 24-week follow-up period. Results: After 12 weeks of combination therapy, an initial virological response was observed in 29 of 82 (35.4%) patients. Due to a high breakthrough rate after IFN-a dose reduction and ribavirin discontinuation, an end-of-treatment response was only achieved in 12 of 82 (14.6%) patients. After the follow-up period, a sustained virological response was observed in 8 of 82 (9.8%) patients. Infection with HCV genotype 3 was the only pretreatment parameter, which could predict a sustained response (HCV-1, 5%; HCV-3, 57.1%; p < 0.001). Conclusions: Despite a high initial response rate of 35.4%, sustained viral clearance was achieved only in 9.8% of the retreated primary IFN-alpha non-responders. Higher IFN-alpha induction and maintenance dose, as well as prolonged ribavirin treatment may possibly increase the virological response rates in non-responders, particularly in those infected by HCV-1
Winter Survival and Physiology of Contrasting Fall Dormancy Selections of Alfalfa
Our objective was to determine the physiological changes that accompany selection from within a germplasm for contrasting fall dormancy reaction. Selection for greater fall dormancy improved winter survival of CUF 101 from 1 to 93%. The more fall dormant CUF 101 had higher sugar concentrations in buds and roots. Roots of the more fall dormant CUF 101 also contained higher soluble protein concentrations when compared to the other CUF 101 germplasms. Root protein extracts obtained in Dec. from the more fall dormant CUF 101 contained at least one polypeptide not found in protein extracts of the other CUF 101 germplasms. Efforts to characterize changes in gene expression that accompany winter hardening of these germplasms are underway
Upscaling the shallow water model with a novel roughness formulation
This study presents a novel roughness formulation
to conceptually account for microtopography
and compares it to four existing roughness models from
literature. The aim is to increase the grid size for computational
efficiency, while capturing subgrid scale effects
with the roughness formulation to prevent the loss
in accuracy associated with coarse grids. All roughness
approaches are implemented in the Hydroinformatics
Modeling System and compared with results of
a high resolution shallow water model in three test
cases: rainfall-runoff on an inclined plane with sinewave
shaped microtopography,
ow over an inclined
plane with random microtopography and rainfall-runoff
in a small natural catchment. Although the high resolution
results can not be reproduced exactly by the coarse
grid model, e.g. local details of
ow processes can not
be resolved, overall good agreement between the upscaled models and the high resolution model has been
achieved. The proposed roughness formulation generally
shows the best agreement of all compared models.
It is further concluded that the accuracy increases with
the number of calibration parameters available, however
the calibration process becomes more difficult. Using
coarser grids results in significant speedup in comparison
with the high resolution simulation. In the presented
test cases the speedup varies from 20 up to 2520,
depending on the size and complexity of the test case
and the difference in cell sizes.The authors thank the Alexander von
Humboldt-Foundation for the Humboldt Research Fellowship
granted to Dr. Dongfang Liang.This is the accepted manuscript. The final version is available at http://link.springer.com/article/10.1007%2Fs12665-015-4726-7
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