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21.
Many estimation problems amount to minimizing a piecewise Cm objective function, with m ≥ 2, composed of a quadratic data-fidelity term and a general regularization term. It is widely
accepted that the minimizers obtained using non-convex and possibly non-smooth
regularization terms are frequently good estimates. However, few facts are known on the ways to control properties of these
minimizers. This work is dedicated to the stability of the minimizers of such objective functions with respect to variations
of the data. It consists of two parts: first we consider all local minimizers, whereas in a second part we derive results
on global minimizers. In this part we focus on data points such that every local minimizer is isolated and results from a
Cm-1 local minimizer function, defined on some neighborhood. We demonstrate that all data points for which this fails form a set
whose closure is negligible. 相似文献
22.
23.
Deyanka Nikolova 《Journal of Thermal Analysis and Calorimetry》2007,89(2):579-581
A new cobalt(II) tetrahydrogen hexaoxoiodate tetrahydrate Co(H4IO6)2·4H2O is prepared by crystallization from an acidic aqueous solution. This compound is identified by quantitative analysis, TG,
DTA, DSC and IR spectra. A thermal decomposition scheme is proposed. Some phase transitions are identified and the corresponding
enthalpy changes are determined. 相似文献
24.
Let the Lie groups G and H act on the manifold P in such a way that P fibres as a principal G-bundle over P/G and as an H-bundle over P/H. We find that every pair (,) where is an H-invariant connection form in PP/G and is a G-invariant connection form in PP/H corresponds uniquely to a connection form in PP/(H×G) and a cross-section of a vector bundle with base P/(H×G). 相似文献
25.
Bojidarka Ivanova Rositca Nikolova Marc Lamshöft Penka Tsanova Ivan Petkov Petko Ivanov Michael Spiteller 《Journal of inclusion phenomena and macrocyclic chemistry》2010,67(3-4):317-324
The interaction of seven novel substituted merocyanine dyes, i.e. 1-methyl-4-[2-(3-methoxy-4-hydroxyphenyl)ethenyl)]pyridinium iodide, 1-methyl-4-[2-(3,5-dimethoxy-4-hydroxyphenyl)ethenyl)]pyridinium iodide, 1-methyl-4-[2-(4-dimethylaminophenyl)ethenyl)]pyridinium iodide, their quinoide forms as well as 1-methyl-4-[2-(3-methoxy-4-oxocyclohexadienilydene)ethylidene]-1,4-dihydropyridine, 1-methyl-4-[2-(3,5-dimethoxy-4-oxocyclohexadienilydene)ethylidene]-1,4-dihydropyridine, with α-CD, γ-CD as well as functionalized γ-cyclodextrin phosphate sodium salt is studied by the methods such as UV–Vis and fluorescence spectroscopy, linear-polarized infrared (IR-LD) spectroscopy of oriented colloids in nematic host, 1H- and 13C-NMR spectroscopy, HPLC ESI tandem mass spectrometry, scanning electron and tunneling microscopy, powder X-ray diffraction as well as thermal methods. A formation of the 1D and 2D “supramolecular polymers” with nanosizes is found. The dyes are adsorbed on the CDs surface and form a hexagonal microcrystalline sub-structures. Remarkable fluorescence properties depending of the type of the substituent in the dyes, in solid-state are observed. 相似文献
26.
Ts. Kolev B.B. Koleva R. Nikolova R.W. Seidel H. Mayer-Figge M. Spiteller W.S. Sheldrick 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,73(5):929-935
Four different dimethyltin(IV) complexes of Schiff bases derived from 2-amino-3-hydroxypyridine and different substituted salicylaldehydes have been synthesized. The compounds, with the general formula [Me2Sn(2-OArCHNC5H3NO)], where Ar = –C6H3(5-CH3) [Me2SnL1], –C6H3(5-NO2) [Me2SnL2], –C6H2(3,5-Cl2) [Me2SnL3], and –C6H2(3,5-I2) [Me2SnL4], were characterized by IR, NMR (1H and 13C), mass spectroscopy and elemental analysis. Me2SnL3 was also characterized by X-ray diffraction analysis and shows a fivefold C2NO2 coordination with distorted square pyramidal geometry. H3C–Sn–CH3 angles in the complexes were calculated using Lockhart's equations with the 1J(117/119Sn–13C) and 2J(117/119Sn–1H) values (from the 1H-NMR and 13C-NMR spectra). The in vitro antibacterial and antifungal activities of dimethyltin(IV) complexes were also investigated. 相似文献
27.
Yana Nikolova Georgi M. Dobrikov Zhanina Petkova Pavletta Shestakova 《Molecules (Basel, Switzerland)》2021,26(22)
A series of squaric acid amides (synthesized in 66–99% isolated yields) and a set of chiral aminoalcohols were comparatively studied as ligands in a model reaction of reduction of α-chloroacetophenone with BH3•SMe2. In all cases, the aminoalcohols demonstrated better efficiency (up to 94% ee), while only poor asymmetric induction was achieved with the corresponding squaramides. A mechanistic insight on the in situ formation and stability at room temperature of intermediates generated from ligands and borane as possible precursors of the oxazaborolidine-based catalytic system has been obtained by 1H DOSY and multinuclear 1D and 2D (1H, 10/11B, 13C, 15N) NMR spectroscopy of equimolar mixtures of borane and selected ligands. These results contribute to better understanding the complexity of the processes occurring in the reaction mixture prior to the possible oxazaborolidine formation, which play a crucial role on the degree of enantioselectivity achieved in the borane reduction of α-chloroacetophenone. 相似文献
28.
Martinez-Ponce G Petrova T Tomova N Dragostinova V Todorov T Nikolova L 《Optics letters》2004,29(9):1001-1003
We present a holographic lens with novel features recorded in an azopolymer film. Two holographic modulations, bulk birefringence and surface relief, are induced in the medium at the same time. The resultant holographic element has two focal planes, and the polarization of light in the focal points depends on the polarization of the incident light. Applications of this device for writing-reading information in two planes simultaneously or separately are described. 相似文献
29.
Neronov A Mazgalova J Cholakova M Dimitrova M Deligiozova I Kovatcheva S Nikolova E 《Cryo letters》2005,26(2):131-136
The aim of the present study was to elaborate an optimal method for cryopreservation of human donor cornea for transplantation and to follow the morphological changes in the structure of the endothelial cell layer using scanning electron microscopy (SEM). Sixteen groups, with four donor cornea each, were cryopreserved at cooling rates of 1 degree C per min and 5 degree C per min. Four cryoprotectants (glycerol, dimethyl sulfoxide, 1,2-propanediol, polyethylene glycol-400) in two concentrations (5% and 10% v/v) were prepared on the bases of medium Optisol GS supplied with 20% v/v human serum albumin. Four additional human cornea were used as controls. Endothelial cell recovery of the cornea after thawing and 24 hours culture, was calculated as a percent of the preserved recovered cells. Sufficient recovery of the endothelial cell layer, making the cornea suitable for transplantation was obtained using the cryoprotectants dimethyl sulfoxide and especially polyethylene glycol-400. 相似文献
30.
N. Krasnobaeva N. Nedyalkova P. Peshev E. Kirkova L. Nikolova S. Velichkov 《Spectrochimica Acta Part B: Atomic Spectroscopy》1982,37(9):829-833
The application of atomic emission spectrometric methods (AES) to the different stages of preparation of white sapphire and neodymium doped yttrium-aluminium garnet (Y3Al5O12 : Nd3+) single crystals is discussed. Optimum conditions for d.c. arc analysis of NH4Al(SO4)2·12H2O and Al2O3 were established and the detection limits for impurities were determined. The applicability of laser spectral microanalysis for monitoring the distribution of neodymium in the single crystals is shown. 相似文献