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1.
We show that the isotropy types of the singularities of Riemannian orbifolds are not determined by the Laplace spectrum. Indeed,
we construct arbitrarily large families of mutually isospectral orbifolds with different isotropy types. Finally, we show
that the corresponding singular strata of two isospectral orbifolds may not be homeomorphic.
Received: 6 October 2005 相似文献
2.
A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of iron, copper and cadmium is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of iron, copper and cadmium were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 2.0 μM, pH of 9.5, and accumulation potential at ?0.4 V vs. Ag/AgCl with an accumulation time of 60 s. The peak currents are proportional to the concentration of iron, copper and cadmium over the 1–80, 0.5–100 and 1–100 ng mL?1 ranges with detection limits of 0.5, 0.4 and 0.9 ng mL?1, respectively. The R.S.D. at a concentration level of 20 ng mL?1 of iron, copper and cadmium were 2.5%, 0.9% and 1.5% (n=6), respectively. The procedure was applied to the simultaneous determination of iron, copper and cadmium in the tap water and some synthetic samples with satisfactory results. 相似文献
3.
M.A. Shams El-Din M. KoerdtC. Wochnowski F. VollertsenA.M. Sadik 《Optics and Lasers in Engineering》2012,50(3):405-412
Polymeric integrated-optical waveguides are prepared in a planar polymer chip by UV-laser lithographic methods. The waveguide samples are irradiated by an excimer laser at a wavelength Λ=248 nm with various irradiation parameters (different fluencies and irradiation doses). Mach-Zehnder interferometer is employed and the refractive index depth profiles of the waveguide samples are obtained. This profile covers two regions having exponential and Gaussian shapes. The model field distributions strongly depend on the refractive index of each region. The mode field distribution and the effective mode indices for each region have been calculated on the basis of a theoretical model and the experimentally measured data. 相似文献
4.
JPC – Journal of Planar Chromatography – Modern TLC - The merits of chemometrics in categorizing different Egyptian olive chemovarieties based on their compositional integrity were... 相似文献
5.
Pyrimidine and purine nucleosides have a remarkable and comprehensive impact on medicinal chemistry and pharmaceutical industries. They become key parts of the growing interdisciplinary area of antimetabolites. The paramount importance of the nucleoside analogs triggered their broader use in treatment of critical diseases such as cancer, malignancies, microbial infection, and autoimmune diseases. Recent advances in their synthetic strategies through microwave-assisted organic synthesis (MAOS) have been reviewed. 相似文献
6.
Yarn defect evaluation, since they can drastically deteriorate the quality of the product, is one of the most important problems in textile industry. In this work, the yarn defects are evaluated by image processing technique. Initially, images were taken by scanner, later the obtained images were modified by using several filters. Then, the yarn defects were identified base on their geometric shape and surface area. As the results show, image processing methods is excellently reliable in evaluating number and type of yarn defects. 相似文献
7.
Mohammad Anary-Abbasinejad Nasim Shams Alireza Hassanabadi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):1823-1829
The reaction between arylglyoxalmonohydrates, dialkyl acetylenedicarboxylates, and triphenylphosphine is described as a simple and efficient method for the synthesis of 5-hydroxy-4-aryl-2,5-dihydrofuran-2,3-dicarboxylate derivatives. 相似文献
8.
Mounir A. I. Salem Wafaa M. Abdou Tarik E. Ali Azza A. Kamal Reham F. Barghash 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1007-1016
Abstract Fragmentation pathways of 14 organophosphorus compounds derived from diethyl spiro[pyrimidino[5,3][1,2]oxazole] phosphonates, diethyl (oxazolo[5,4-d]pyrimidine-4,6-dione)phosphonates, and diethyl (pyrimidino[4,5-b][1,4] oxazine)phosphonates were investigated by electron impact mass spectrometry (EI-MS). The intensity of the recorded molecular ion peaks showed various values depending on the nature of the compounds. Characteristic fragment ions were formed by successive loss of simple functional groups followed by decomposition of heterocycles connected to pyrimidine rings. 相似文献
9.
Treatment of 2-methoxyisoindoline-1,3-dione with resonance-stabilized alkylidenephosphoranes afforded the corresponding monoalkenes as the sole reaction product, in ~58–63% yields, whereas more than 80% yields of the same monoolefin products were obtained when the reactions were carried out under microwave conditions. Similarly, 2-(phenylamino)isoindoline-1,3-dione reacted under either thermal or microwave conditions to give only the corresponding monoalkene derivatives. The alkene products from both substrates were further reduced to the corresponding isoindoles using Zn-dust in EtOH. Prediction of the designed compounds and the in vivo anti-inflammation activity of the products in the rat adjuvant model were also studied. The work is the first demonstration of the anti-inflammatory activity of phthalimide derivatives. 相似文献
10.
Awalekar Ramchandra Mohire Priyanka Patravale Ajinkya Salunkhe Shilpa Usmani Shams Jamale Dattatray Hangirgekar Shankar Kolekar Govind Anbhule Prashant 《Chemistry of Natural Compounds》2021,57(6):1000-1004
Chemistry of Natural Compounds - (3E,7Z)-Tetradecadienyl acetate, the major sex pheromone component of the potato pest Symmetrischema tangolias (Gyen), was stereoselectively synthesized from the... 相似文献