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On the Fourier Spectra of Distributions in Clifford Analysis 总被引:1,自引:1,他引:0
In recent papers by Brackx, Delanghe and Sommen, some fundamental higher dimensional distributions have been reconsidered in the framework of Clifford analysis, eventually leading to the introduction of four broad classes of new distributions in Euclidean space. In the current paper we continue the in-depth study of these distributions, more specifically the study of their behaviour in frequency space, thus extending classical results of harmonic analysis. 相似文献
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Nanoscale Confinement Controls the Crystallization of Calcium Phosphate: Relevance to Bone Formation
Bram Cantaert Dr. Elia Beniash Prof. Fiona C. Meldrum 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):14918-14924
A key feature of biomineralization processes is that they take place within confined volumes, in which the local environment can have significant effects on mineral formation. Herein, we investigate the influence of confinement on the formation mechanism and structure of calcium phosphate (CaP). This is of particular relevance to the formation of dentine and bone, structures of which are based on highly mineralized collagen fibrils. CaP was precipitated within 25–300 nm diameter, cylindrical pores of track etched and anodised alumina membranes under physiological conditions, in which this system enables systematic study of the effects of the pore size in the absence of a structural match between the matrix and the growing crystals. Our results show that the main products were polycrystalline hydroxapatite (HAP) rods, together with some single crystal octacalcium phosphate (OCP) rods. Notably, we demonstrate that these were generated though an intermediate amorphous calcium phosphate (ACP) phase, and that ACP is significantly stabilised in confinement. This effect may have significance to the mineralization of bone, which can occur through a transient ACP phase. We also show that orientation of the HAP comparable, or even superior to that seen in bone can be achieved through confinement effects alone. Although this simple experimental system cannot be considered, a direct mimic of the in vivo formation of ultrathin HAP platelets within collagen fibrils, our results show that the effects of physical confinement should not be neglected when considering the mechanisms of formation of structures, such as bones and teeth. 相似文献
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Dhooge W Arijs K D'Haese I Stuyvaert S Versonnen B Janssen C Verstraete W Comhaire F 《Analytical and bioanalytical chemistry》2006,386(5):1419-1428
In vitro assays are considered as the first step in a tiered approach to compound screening for hormonal activity. Although
many new assays have been developed in recent years, little attention has been paid towards assay validation. Our objective
was to identify critical experimental parameters in a yeast estrogen screen (YES) that affect its sensitivity and specificity.
We investigated the role of incubation time, solvent type, yeast inoculum growth stage and concentration on the outcome of
the YES. Compounds tested included new and established agonists, antagonists and negative controls, and results were evaluated
according to prefixed statistical criteria. In addition, we assessed the assay’s performance in a blind interlaboratory validation
exercise (IVE). An incubation time of five days was necessary to positively identify the estrogenic properties of all agonists
tested, when dissolved in DMSO. Longer incubation times were required when using an ethanol protocol. Similar estrogenic activity
was reported for benzyl butyl phthalate, bisphenol-A, methoxychlor, permethrin and genistein in the IVE. One out of the three
laboratories did not classify α,β-endosulfan, dissolved in DMSO, as an estrogen. The same was true for 4,4′-DDE and lindane, dissolved in ethanol, a result
that might be attributable to an inappropriate yeast start concentration and/or growth stage. These validation experiments
show that under appropriate experimental conditions the YES yields sensitive, specific and reliable results. Therefore it
fulfills the requirements as a first step screening assay to evaluate the capacity of chemicals to interact with the estrogen
receptor. 相似文献
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Dr. Peter Spannring Dr. Indrek Reile M. Sc. Meike Emondts Dr. Philipp P. M. Schleker M. Sc. Niels K. J. Hermkens M. Sc. Nick G. J. van der Zwaluw M. Sc. Bram J. A. van Weerdenburg Dr. Paul Tinnemans Dr. Marco Tessari Prof. Dr. Bernhard Blümich Prof. Dr. Floris P. J. T. Rutjes Prof. Dr. Martin C. Feiters 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9277-9282
NMR signal amplification by reversible exchange (SABRE) has been observed for pyridine, methyl nicotinate, N‐methylnicotinamide, and nicotinamide in D2O with the new catalyst [Ir(Cl)(IDEG)(COD)] (IDEG=1,3‐bis(3,4,5‐tris(diethyleneglycol)benzyl)imidazole‐2‐ylidene). During the activation and hyperpolarization steps, exclusively D2O was used, resulting in the first fully biocompatible SABRE system. Hyperpolarized 1H substrate signals were observed at 42.5 MHz upon pressurizing the solution with parahydrogen at close to the Earth's magnetic field, at concentrations yielding barely detectable thermal signals. Moreover, 42‐, 26‐, 22‐, and 9‐fold enhancements were observed for nicotinamide, pyridine, methyl nicotinate, and N‐methylnicotinamide, respectively, in conventional 300 MHz studies. This research opens up new opportunities in a field in which SABRE has hitherto primarily been conducted in CD3OD. This system uses simple hardware, leaves the substrate unaltered, and shows that SABRE is potentially suitable for clinical purposes. 相似文献
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The relative ranks of the monoid of endomorphisms of a strong independence algebra of infinite rank modulo two distinguished
subsets are calculated. These subsets are the group of automorphisms and the endomorphisms α satisfying α2 = α. The extra generators are characterised in each case. 相似文献
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