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101.
Sandgren N Selén Y Stoica P Li J 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,168(2):13-272
Accurate quantitation of the spectral components in a pre-selected frequency band for magnetic resonance spectroscopy (MRS) signals is a frequently addressed problem in the MR community. One obvious application for such a frequency-selective technique is to lower the computational burden in situations when the measured data sequence contains too many samples to be processed using a standard full-spectrum method. Among the frequency-selective methods previously proposed in the literature, only a few possess the two features of primary concern: high robustness against interferences from out-of-band components and low computational complexity. In this survey paper we consider five spectral analysis methods which can be used for MRS signal parameter estimation in a selected frequency band. We re-derive the filter diagonalization method (FDM) in a new way that allows an easy comparison to the other methods presented. Then we introduce a frequency-selective version of the method of direction estimation (MODE) which has not been applied to MR-spectroscopy before. In addition, we present a filtering and decimation technique using a maximum phase bandpass FIR-filter and relate it to a similar ARMA-modeling approach known as SB-HOYWSVD (sub-band high-order Yule-Walker singular value decomposition). Finally, we study the numerical performances of these four methods and compare them to that of the recently introduced SELF-SVD (Singular Value Decomposition-based method usable in a SELected Frequency band) in several examples using simulated MR data, and discuss the benefits and disadvantages of each technique. 相似文献
102.
Dmitriy Khoroshev Przemyslaw Kolek Petre Birza Andrei Chirokolava John P. Maier 《Journal of Molecular Spectroscopy》2004,227(1):81-89
Rotationally resolved electronic spectrum of the origin band in the 2A″-X2A″ transition of a nonlinear carbon chain radical C6H4+ has been recorded in the 604 nm region using cw cavity ring down spectroscopy. The radical was produced by a discharge through an acetylene-helium mixture in a supersonic planar expansion. The rotational structure has been analysed and precisely determined. A band having a-type prolate rotational structure has also been observed near 581 nm. By considering the results of ab initio calculations this band is assigned to a transition involving the excitation of the ν12 fundamental in the upper 2A″ electronic state of the same C6H4+ isomer. 相似文献
103.
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105.
Aurora Reiss Mariana Carmen Chifiriuc Emilia Amzoiu Nicoleta Cioateră Irina Dăbuleanu Petre Rotaru 《Journal of Thermal Analysis and Calorimetry》2018,131(3):2073-2085
Complexes of Co(II), Ni(II) and Cu(II) with the Schiff base (LH) derived from ceftazidime and salicylaldehyde were synthesized. The proposed structures of the new metal complexes based on the results of elemental analyses, molar conductivity, IR, DRUV and 1H NMR spectra, effective magnetic moment and thermal analysis were discussed. The surface morphology of Schiff base and metal complexes was studied by SEM. The composition of the metal complexes was ML2, where L is the deprotonated Schiff base ligand and M = Co(II), Ni(II) and Cu(II). IR spectral data indicated the Schiff base ligand being bidentately coordinated to the metallic ions with N and O atoms from azomethine and phenolic groups. All the complexes have square-planar geometry and are nonelectrolytes. The thermal analysis recorded that TG, DTG, DTA and DSC experiments confirmed the assigned composition and gave information about the thermal stability of complexes in dynamic air atmosphere. Theoretical investigation of the molecular structure of Schiff base ligand and its complexes was studied using programs dedicated to chemical modeling and quantomolecular calculation of chemical properties. The newly synthesized complexes were tested for in vitro antibacterial activity against selected Gram-negative and Gram-positive bacterial strains, and they exhibited an antibacterial activity superior to that of the Schiff base ligand. 相似文献
106.
Tero Harju Ion Petre Vladimir Rogojin Grzegorz Rozenberg 《Discrete Applied Mathematics》2008,156(14):2581-2597
The intramolecular model for gene assembly in ciliates considers three operations, , , and that can assemble any gene pattern through folding and recombination: the molecule is folded so that two occurrences of a pointer (short nucleotide sequence) get aligned and then the sequence is rearranged through recombination of pointers. In general, the sequence rearranged by one operation can be arbitrarily long and consist of many coding and noncoding blocks. We consider in this paper simple variants of the three operations, where only one coding block is rearranged at a time. We characterize in this paper the gene patterns that can be assembled through these variants. Our characterization is in terms of signed permutations and dependency graphs. Interestingly, we show that simple assemblies possess rather involved properties: a gene pattern may have both successful and unsuccessful assemblies and also more than one successful assembling strategy. 相似文献
107.
Petre A. L. Auroux A. Gervasini A. Caldararu M. Ionescu N. I. 《Journal of Thermal Analysis and Calorimetry》2001,64(1):253-260
The surface properties of supported gallium oxide catalysts prepared by impregnation of various supports (γ-Al2O3, SiO2, TiO2, ZrO2) were investigated by adsorption microcalorimetry, using ammonia and water as probe molecules. In the case of acidic supports
(γ-Al2O3, ZrO2, TiO2), the acidic character of supported gallium catalysts always decreased in comparison with gallium-free supports; on very
weakly acidic SiO2, new acidic centers were created when depositing Ga2O3. The addition of gallium oxide decreased the hydrophilic properties of alumina, titania and zirconia, but increased the amount
of water adsorbed on silica. The catalytic performances in the selective catalytic reduction of NO by C2H4 in excess oxygenwere in the order Ga/Al2O3>Ga/TiO2>Ga/ZrO2>>Ga/SiO2. This order is more related to the quality of the dispersion of Ga2O3 on the support than to the global acidity of the solids.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
108.
The thermal degradation of a sort of polyvinyl chloride was investigated. Complex processes for polyvinyl chloride degradation
were evidenced. The kinetic analysis of dehydrochlorination and of subsequent processes was carried out. A change of mechanism
was detected when dehydrochlorination goes to completion. The values of non-isothermal kinetic parameters determined by various
methods are in a satisfactory agreement. The obtained results allowed some clarifications concerning the thermal degradation
steps.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
109.
L. Pintilie I. Pintilie D. Petre T. Botila M. Alexe 《Applied Physics A: Materials Science & Processing》1999,69(1):105-109
Thermally stimulated current (TSC) measurements performed in the 100 K–400 K temperature range on Bi4Ti3O12 (BiT) thin films annealed at 550 °C and 700 °C had revealed two trapping levels having activation energies of 0.55 eV and
0.6 eV. The total trap concentration was estimated at 1015 cm−3 for the samples annealed at 550 °C and 3×1015 cm−3 for a 700 °C annealing and the trap capture cross-section was estimated about 10−18 cm2. From the temperature dependence of the dark current in the temperature range 20 °C–120 °C the conduction mechanism activation
energy was found to be about 0.956–0.978 eV. The electrical conductivity depends not only on the sample annealing temperature
but also whether the measurement is performed in vacuum or air. The results on the dark conductivity are discussed considering
the influence of oxygen atoms and oxygen vacancies.
Received: 28 January 1998 / Accepted: 8 January 1999 / Published online: 5 May 1999 相似文献
110.
Ema Stojchevska Petre Makreski Michele Zanoni Leonardo Gasperini Giacomo Selleri Davide Fabiani Chiara Gualandi Aleksandra Bužarovska 《先进技术聚合物》2024,35(2):e6333
BaTiO3 nanofibers (BT NFs), prepared by electrospinning, were used as a filler for electrospun poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) nanocomposite mats. The phase structure and the effect of poling conditions on the piezoelectric properties of PVDF-TrFE/BT nanocomposites were investigated. The results showed an improved degree of crystallinity (78.6%) and a high β-crystal phase (up to 98.3%) in all electrospun samples, independent of the nanofiber content. The two-step poling method, applying electric fields of opposite polarity, led to significantly improved piezoelectric constants d33 (−31.7 pC N−1), strongly dependent on the added BaTiO3 nanofibers. The inclusion of piezoelectric ceramic nanofibers into a polymer matrix, easily carried out by means of electrospinning, followed by an ad hoc optimized poling treatment, allowed to develop flexible materials with enhanced piezoelectric properties, potentially exploitable in innovative conversion systems used in wearable and sensing devices. 相似文献