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31.
Cary L. Perket Jean R. Krueger Donald A. Whitehurst 《Trends in analytical chemistry : TRAC》1982,1(14):342-347
Laboratory extraction test conditions do not accurately reflect the conditions within a land disposal facility. Current procedures lack the precision required for the results to be used as the basis for decision making. 相似文献
32.
Robert J. Krueger 《Applied mathematics and computation》1981,8(1):1-16
In a well-known generalization of the tautochrone problem, the shape of a monotone hill is determined by observing the travel time of a particle on the surface of the hill. In this paper we present a technique for uniquely determining the shape of any smooth hill, whether monotone or not, by observing collisions of particles on the hill. It is shown that this inverse problem is well posed. Error bounds for the solution are given for the case in which there are incomplete data. The efficiency of these bounds is shown by means of an example. 相似文献
33.
A technique is developed for solving multiple objective optimization programs. The approach decomposes the system into groups of objectives according to their priority in the model. A lexicographic ordering (goal programming) approach is used to analyse this system of groups, while the solution structure of each individual group is developed using the method of constraints. The technique is applied to a planning model for river basins. 相似文献
34.
35.
Franziska Preusse Elke van der Meer Dorothea Ullwer Martin Brucks Frank Krueger Isabell Wartenburger 《ZDM》2010,42(6):635-647
Intelligence is known to predict scholastic achievement and enables high performance in cognitive tasks. Fluid intelligence is strongly related to analogical reasoning abilities, which are fundamental to mathematical thinking. Geometric analogical reasoning is a prototypical measure of fluid intelligence. However, the cerebral correlates of geometric analogical reasoning and their developmental modulation over time are still rarely investigated. We report a 1-year follow-up functional magnetic resonance imaging study of a geometric analogical reasoning task in high fluid intelligence high-school students. This study was designed to characterise the cerebral correlates of geometric analogical reasoning and to improve our knowledge about the impact of general cognitive development on behavioural performance and on cerebral mechanisms underlying geometric analogical reasoning in adolescents. Our data indicate that a fronto-parietal network comprising the left and right parietal lobes and the left middle frontal gyrus was equally modulated by task difficulty at both measuring time points. At the behavioural level, however, participants showed improvements in performance at the second measuring time point. The behavioural improvements point to a more efficient task processing. As this is not accompanied by differential recruitment of fronto-parietal brain regions, the data suggest an increase in neural efficiency for these brain regions. 相似文献
36.
37.
Lutz I Kloas W Springer TA Holden LR Wolf JC Krueger HO Hosmer AJ 《Analytical and bioanalytical chemistry》2008,390(8):2031-2048
Xenopus laevis has been introduced as a model to study effects of endocrine-active compounds (EAC) on development and sexual differentiation.
However, variable and inconsistent data have raised questions about the reliability of the test methods applied. The current
study was conducted in two laboratories to develop, refine, and standardize procedures and protocols. Larvae were exposed
in flow-through systems to 17β-estradiol (E2), at concentrations from 0.2 to 6.0 μg E2 L−1 in Experiment 1A, and 0.015 to 2.0 μg E2 L−1 in Experiment 1B. In both studies survival (92%, 99%) and percentage of animals that completed metamorphosis (97%, 99%) indicated
reproducible biological performance. Furthermore, minor variations in husbandry led to significant differences in snout-to-vent
length, weight, and gonad size. In Experiment 1A, almost complete feminization occurred in all E2 treatment groups whereas
a concentration response was observed in Experiment 1B resulting in an EC50 of 0.12 μg E2 L−1. The final verified protocol is suitable for determining effects of EAC on development and sexual differentiation in X. laevis. 相似文献
38.
Krueger A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(5):1382-1390
Nanoscale diamond particles have become an interesting material. Due to their inertness, small size and surface structure, they are well-suited for biological applications, such as labelling and drug delivery. Here we discuss the surface structure and functionalisation of diamond nanoparticles. Non-covalent as well as covalent grafting of bioactive moieties is possible, and first applications of fluorescent diamond nanoparticles are described. 相似文献
39.
We have explored the impact of a number of basic simulation parameters on the results of a recently developed hybrid molecular dynamics-quantum mechanics (MD-QM) method (Mercer et al., J Phys Chem B 1999, 103, 7720). The method utilizes MD simulations to explore the ground-state configuration space of the system and QM evaluation of those structures to yield the time-dependent electronic transition energy, which is transformed into the optical line-broadening function using the second-order cumulant expansion. Both linear and nonlinear optical spectra can then be generated for comparison to experiment. The dependence of the resulting spectra on the length of the MD trajectory, the QM sampling rate, and the QM model chemistry have all been examined. In particular, for the system of oxazine-4 in methanol studied here, at least 20 ps of MD trajectory are needed for qualitative convergence of linear spectral properties, and >100 ps is needed for quantitative convergence. Surprisingly, little difference is found between the 3-21G and 6-31G(d) basis sets, and the CIS and TD-B3LYP methods yield remarkably similar spectra. The semiempirical INDO/s method yields the most accurate results, reproducing the experimental Stokes shift to within 5% and the FWHM to within 20%. Nonlinear 3-pulse photon echo peak shift (3PEPS) decays have also been simulated. Decays are generally poorly reproduced, though the initial peak shift which depends on the overall coupling of motions to the solute transition energy is within 15% of experiment for all model chemistries other than those using the STO-3G basis. 相似文献
40.
Sy-David Friedman John Krueger 《Transactions of the American Mathematical Society》2007,359(5):2407-2420
We describe two opposing combinatorial properties related to adding clubs to : the existence of a thin stationary subset of and the existence of a disjoint club sequence on . A special Aronszajn tree on implies there exists a thin stationary set. If there exists a disjoint club sequence, then there is no thin stationary set, and moreover there is a fat stationary subset of which cannot acquire a club subset by any forcing poset which preserves and . We prove that the existence of a disjoint club sequence follows from Martin's Maximum and is equiconsistent with a Mahlo cardinal.