2,890 research outputs found
Identification of stable endogenous reference genes for real-time PCR in the human fetal gonad using an external standard technique
Peer reviewedPostprin
Severity scoring of manganese health effects for categorical regression
Characterizing the U-shaped exposure response relationship for manganese (Mn) is necessary for estimating the risk of adverse health from Mn toxicity due to excess or deficiency. Categorical regression has emerged as a powerful tool for exposure-response analysis because of its ability to synthesize relevant information across multiple studies and species into a single integrated analysis of all relevant data. This paper documents the development of a database on Mn toxicity designed to support the application of categorical regression techniques. Specifically, we describe (i) the conduct of a systematic search of the literature on Mn toxicity to gather data appropriate for dose-response assessment; (ii) the establishment of inclusion/exclusion criteria for data to be included in the categorical regression modeling database; (iii) the development of a categorical severity scoring matrix for Mn health effects to permit the inclusion of diverse health outcomes in a single categorical regression analysis using the severity score as the outcome variable; and (iv) the convening of an international expert panel to both review the severity scoring matrix and assign severity scores to health outcomes observed in studies (including case reports, epidemiological investigations, and in vivo experimental studies) selected for inclusion in the categorical regression database. Exposure information including route, concentration, duration, health endpoint(s), and characteristics of the exposed population was abstracted from included studies and stored in a computerized manganese database (MnDB), providing a comprehensive repository of exposure-response information with the ability to support categorical regression modeling of oral exposure data
Dynamical models for sand ripples beneath surface waves
We introduce order parameter models for describing the dynamics of sand
ripple patterns under oscillatory flow. A crucial ingredient of these models is
the mass transport between adjacent ripples, which we obtain from detailed
numerical simulations for a range of ripple sizes. Using this mass transport
function, our models predict the existence of a stable band of wavenumbers
limited by secondary instabilities. Small ripples coarsen in our models and
this process leads to a sharply selected final wavenumber, in agreement with
experimental observations.Comment: 9 pages. Shortened version of previous submissio
Effect of H on the crystalline and magnetic structures of the YCo3-H(D) system. I. YCo3 from neutron powder diffraction and first-principles calculations
This paper reports investigations into the influence of hydrogen on the magnetic properties of the YCo3-H
system. We report results on the magnetic structure and magnetic transitions of YCo3 using a combination of
neutron powder diffraction measurements and first-principles full potential augmented plane wave + local
orbital calculations under the generalized gradient approximation. The ferromagnetic and ferrimagnetic structures
are examined on an equal footing. However, we identify that, no matter which structure is used as the
starting point, the neutron diffraction data always refines down to the ferrimagnetic structure with the Co2
atoms having antiparallel spins. In the ab initio calculations, the inclusion of spin-orbit coupling is found to be
important in the prediction of the correct magnetic ground state. Here, the results suggest that, for zero external
field and sufficiently low temperatures, the spin arrangement of YCo3 is ferrimagnetic rather than ferromagnetic
as previously believed. The fixed spin moment calculation technique has been employed to understand
the two successive field-induced magnetic transitions observed in previous magnetization measurements under
increasing ultrahigh magnetic fields. We find that the magnetic transitions start from the ferrimagnetic phase
�0.61�B/Co� and terminate with the ferromagnetic phase �1.16�B/Co�, while the spin on the Co2 atoms
progressively changes from antiparallel ferrimagnetic to paramagnetic and then to ferromagnetic. Our neutron
diffraction measurements, ab initio calculations, and the high field magnetization measurements are thus
entirely self-consistent
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