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441.
Many of the current investigations on the environmental and human health risks of engineered nanomaterials focus on their
short-term acute toxicity. However, the long-term chronic effects of nanomaterials on living systems, and in particular, on
the genetic components of living systems, also warrant attention. An increasing number of nanomaterial safety studies include
an assessment of genotoxicity as part of the overall risk evaluation. The potential of nanomaterials to directly or indirectly
promote the formation of reactive oxygen species is one of the primary steps in their genotoxic repertoire. The subsequent
modification of genomic DNA by reactive oxygen species could lead to the development of mutagenesis, carcinogenesis, or other
age-related diseases if the DNA damage is not repaired. This review focuses on the interactions of nanomaterials with DNA
and specifically on the capacity of some nanomaterials to induce oxidative damage to DNA. A critical assessment of the analytical
methodology and the potential biochemical mechanisms involved in nanomaterial induction of oxidative damage to DNA is presented,
results obtained for the various studies with each nanomaterial are compared, and recommendations for future research are
discussed. Researchers should consider, among other experimental recommendations, (1) the application of more chromatography-based
and mass-spectrometry-based analytical techniques to the assessment of oxidative damage to DNA to facilitate an enhanced understanding
of DNA damage mechanisms and (2) the verification of cellular viability before conducting genotoxicity assays to reduce the
impact of fragmented DNA, formed as a consequence of cell death, on DNA damage measurements. 相似文献
442.
This paper concerns the reconstruction of possibly complex‐valued coefficients in a second‐order scalar elliptic equation that is posed on a bounded domain from knowledge of several solutions of that equation. We show that for a sufficiently large number of solutions and for an open set of corresponding boundary conditions, all coefficients can be uniquely and stably reconstructed up to a well‐characterized gauge transformation. We also show that in some specific situations, a minimum number of such available solutions equal to $I_n = {1 \over 2}n(n + 3)$ is sufficient to uniquely and globally reconstruct the unknown coefficients. This theory finds applications in several coupled‐physics medical imaging modalities including photo‐acoustic tomography, transient elastography, and magnetic resonance elastography. © 2013 Wiley Periodicals, Inc. 相似文献
443.
Gunther Schoeck 《哲学杂志》2013,93(14):1542-1551
In conventional dislocation theory based on the concept of Volterra dislocations, the energy of coplanar dislocation dipoles cannot be obtained without introducing an ill-defined ad hoc annihilation distance. When the dislocations are described more realistically by Peierls dislocations, absolute values for the dipole energy can be obtained from physical arguments. It is found that when dislocations in a dipole come close, they may not annihilate each other but the dipole can collapse when the dislocations have reached a critical separation of several lattice constants. 相似文献
444.
Gunther A. Uhlmann 《偏微分方程通讯》2013,38(7):713-779
Suppose G is a bounded C2domain in IR n, n ? 2 . We exam¬ine the regularity at the boundary of solutions to a class of quasi-linear elliptic equations having continuous boundary values ? . If ? has a modulus of continuity β , we give a modulus of continunity for the solution which depends on β and the generalized mean curvature of ?G . When the order of non-uniformity of the equation is between 0 and 1 , no curvature condition on ?G is needed. 相似文献
445.
Gunther Leobacher 《Applied Mathematical Finance》2013,20(1):71-91
Abstract We are interested in pricing rainfall options written on precipitation at specific locations. We assume the existence of a tradeable financial instrument in the market whose price process is affected by the quantity of rainfall. We then construct a suitable ‘Markovian gamma’ model for the rainfall process which accounts for the seasonal change of precipitation and show how maximum likelihood estimators can be obtained for its parameters. We derive optimal strategies for exponential utility from terminal wealth and determine the utility indifference price of the claim. The method is illustrated with actual measured data on rainfall from a location in Kenya and spot prices of Kenyan electricity companies. 相似文献
446.
The chemical potential of a surfactant in solution can be calculated from the Gibbs adsorption equation when the surface excess of the surfactant and the surface tension of the solution as a function of surfactant concentration are known. We have investigated a solution of the nonionic surfactant 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in the polar solvent 3-hydroxypropionitrile at concentrations below and above the critical micelle concentration (cmc). Neutral impact collision ion scattering spectroscopy was applied for the direct measurement of the surface excess of POPC as a function of concentration. The Gibbs adsorption equation was applied in conjunction with surface tension measurements to evaluate the chemical potential and the activity coefficients of POPC, respectively. We find that the solution shows ideal behavior up to the cmc and that the chemical potential remains constant at concentrations larger than the cmc. 相似文献
447.
Jan Baldeaux Josef Dick Gunther Leobacher Dirk Nuyens Friedrich Pillichshammer 《Numerical Algorithms》2012,59(3):403-431
We show how to obtain a fast component-by-component construction algorithm for higher order polynomial lattice rules. Such
rules are useful for multivariate quadrature of high-dimensional smooth functions over the unit cube as they achieve the near
optimal order of convergence. The main problem addressed in this paper is to find an efficient way of computing the worst-case
error. A general algorithm is presented and explicit expressions for base 2 are given. To obtain an efficient component-by-component
construction algorithm we exploit the structure of the underlying cyclic group. We compare our new higher order multivariate
quadrature rules to existing quadrature rules based on higher order digital nets by computing their worst-case error. These
numerical results show that the higher order polynomial lattice rules improve upon the known constructions of quasi-Monte
Carlo rules based on higher order digital nets. 相似文献
448.
J Pello J van der Tol S Keyvaninia R van Veldhoven H Ambrosius G Roelkens M Smit 《Optics letters》2012,37(17):3711-3713
An ultrasmall (<10 μm length) polarization converter in InP membrane is fabricated and characterized. The device relies on the beating between the two eigenmodes of chemically etched triangular waveguides. Measurements show a very high polarization conversion efficiency of >99% with insertion losses of <-1.2 dB at a wavelength of 1.53?μm. Furthermore, our design is found to be broadband and tolerant to dimension variations. 相似文献
449.
Alexey Karapetyants Elijah Liflyand 《Mathematical Methods in the Applied Sciences》2020,43(16):9487-9498
After 2000, an interest in the Hausdorff operators grew, first of all in the sense of a diversity of spaces on which these operators were considered. We try to introduce a ‘correct’ definition of the Hausdorff operator on Euclidean spaces. This is supplemented by a variety of known and possible applications. 相似文献
450.
We study inverse problems for the Einstein equations with source fields in a general form. Under a microlocal linearization stability condition, we show that by generating small gravitational perturbations and measuring the responses near a freely falling observer, one can uniquely determine the background Lorentzian metric up to isometries in a region where the gravitational perturbations can travel to and return. We apply the result to two concrete examples when the source fields are scalar fields (i.e., Einstein–scalar field equations) and electromagnetic fields (i.e., Einstein-Maxwell equations). © 2019 Wiley Periodicals, Inc. 相似文献