We consider the scattering of a plane time-harmonic electromagnetic wave by a perfectly conducting infinite cylinder with axis in the direction k , where k is the unit vector along the z axis. Suppose the incident wave propagates in a direction perpendicular to the cylinder. For a given observation angle θ, let FD(θ, α) k be the far-field pattern of the electric field corresponding to an incident wave with direction angle α polarized perpendicular to the axis and let FN(θ; α) k be the far-field pattern of the magnetic field corresponding to an incident wave with direction angle α polarized parallel to the z axis. Let {αn}n=1∞ be a distinct set of angles in [ ? π, π] and μ a complex number. Then, necessary and sufficient conditions are given for the set {(1 ? μ)FD(θ;αn) + μFN(θ;αn)}n = 1∞ to be complete in L2[ ? π, π]. Applications, together with numerical examples, are given to the inverse scattering problem of determining the shape of the cylinder from a knowledge of the far-field data. 相似文献
Summary In this paper we study the use of Nédélec's curl conforming finite elements to approximate the time-harmonic Maxwell equations on a bounded domain. The analysis is complicated by the fact that the bilinear form is not coercive, and the principle part has a very large null-space. This difficulty is circumvented by using a discrete Helmholtz decomposition of the error vector. Numerical results are presented that compare two different linear elements.Research supported in part by grants from AFOSR and NSF 相似文献
Synthesis and biological activity of γ-lactam analogues of penicillanic and carboapenicillanic acids, and the sodium periodate mediated rearrangement of pyrrolidine-2,3-diones are described. 1,3- Dipolar addition of cyclic nitrone (6) and methyl acrylate afforded the bicyclic adducts (7a) and (7b). Reductive cleavage of the N-O bond and subsequent cyclisation of a regioisomer (11a) gave the γ-lactams (12a) and (12b) in a ratio of 85 : 15. They are transformed to the carbapenam analogues (1)-(4). Their stereochemistry was assigned according to the X-ray structure of the γ-lactam (12b). Benzyl 6-oxopenicillanate (20) was directly transformed to the γ-lactam analogue (5) a novel ring expansion. These synthetic analogues did not show antibiotic activity or β-lactamase inhibition. Treatment of pyrro1idine-2,3-diones (25a) and (25b) with sodium periodate gave ring contracted β-lactams (26a) and (26b) respectively. Similar treatment of (27) followed by diazomethane afforded an unexpected spiro epoxide. 相似文献
A Boolean algebra is constructed having only those endomorphisms corresponding to prime ideals, which are present in any BA. The BA constructed is of powerc, has 2c endomorphisms, and is not rigid in Bonnet’s sense. 相似文献
We report here a novel approach for the extraction and analysis of thyroid hormones (TH) and their metabolites (THM) from human serum samples. Our method features a compact, 96-well micro-titre plate-based pre-analytic extraction/clean-up workflow combined with an isotope dilution LC-MS/MS-MS3 analytical method. In particular, these features make possible the detection of iodothyronines at their endogenous concentrations in serum differing by a factor of ca. 104, with potential to semi-automate the pre-analytics. The method was validated by the assessment of linearity, lower limits of quantification and detection (LLOQ and LLOD respectively), intra- and inter-day accuracy, precision, process efficiency (PE), matrix effect (ME) and relative recovery (RE). Calibration curves were linear in the concentration range in sample matrix from 0.1–250 nM for T3, rT3, T4 and 3-T1AM and from 0.005–1 nM for 3,5-T2 and 3,3′-T2. Using a 200-μL sample volume, the analyte dependant LLOQ were in the range 0.005 (3,5-T2) to 0.25 (T4) nM and LLOD were between 0.002 (3,5-T2) and 0.052 nM (T4). We applied the LC-MS/MS-MS3 method to the analysis of a cross section of patients with disorders of the thyroid hormone axis. T4, T3 and rT3 concentrations (± standard deviation) were 120 ± 18, 1.9 ± 0.4 and 0.45 ± 0.09 nM respectively. 3,3′-T2 concentrations (± standard deviation) were 0.079 ± 0.022 nM; 3,5-T2 concentrations were below the LLOQ and/or LLOD in all but a single sample (0.013 nM). This method expands the analytical spectrum to endogenous thyroid hormone metabolites such as 3,5-T2 which exert biological actions and rT3 which may act as surrogate markers for disturbed thyroid hormone metabolism.