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Ultrasound Doppler methods are widely used in clinical practice as prospective investigational tool to study the vascular system and soft biological tissues. Meanwhile, the most general relationship between the power Doppler spectra, spectral characteristics of the scattering fluctuations and the probing ultrasound field parameters for some clinical implementations are still unexplored. Based upon the continuum model of scattering inhomogeneities, a set of the closed-form expressions for the correlation functions and the spectra of Doppler response of soft tissues and blood have been derived. The influence of the correlation among inhomogeneities and the diffusion processes on the Doppler power spectra formed by stationary flows have been examined. Computer simulations of Doppler spectra were performed for different values of correlation radius and diffusion coefficient. With simulation results the effects of the correlation among inhomogeneities and the diffusion processes on the spectral width and mean frequency are established and discussed in respect to turbulent flows. Closed-form expressions for correlation functions and Doppler spectra for the vibrational sonoelastography technique for visualizing malignant tumors in tissues have been derived. Based on the peculiarities of the obtained Doppler spectra, it is shown that the differentiation of soft tissues with respect to the amplitude value of constrained oscillations is feasible. The expressions were derived for the cases of non-stationary accelerated blood movement. It has been found that the frequency dependence reveals solely at a finite time of observation and depends on the initial phase of the accelerated movement. 相似文献
73.
Sergii Demchenko Roman Lesyk Oleh Yadlovskyi Johannes Zuegg Alysha G. Elliott Iryna Drapak Yuliia Fedchenkova Zinaida Suvorova Anatolii Demchenko 《Molecules (Basel, Switzerland)》2021,26(14)
A series of novel 3-aryl-5H-pyrrolo[1,2-a]imidazole and 5H-imidazo[1,2-a]azepine quaternary salts were synthesized in 58–85% yields via the reaction of 3-aryl-6, 7-dihydro-5H-pyrrolo[1,2-a]imidazoles or 3-aryl-6,7,8,9-tetrahydro-5H-imidazo[1,2-a]azepines and various alkylating reagents. All compounds were characterized by 1H NMR, 13C NMR, and LC-MS. The conducted screening studies of the in vitro antimicrobial activity of the new quaternary salts derivatives established that 15 of the 18 newly synthesized compounds show antibacterial and antifungal activity. Synthesized 3-(3,4-dichlorohenyl)-1-[(4-phenoxyphenylcarbamoyl)-methyl]-6,7-dihydro-5H-pyrrolo[1,2-a]imidazol-1-ium chloride 6c possessed a broad activity spectrum towards Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Cryptococcus neoformans, with a high hemolytic activity against human red blood cells and cytotoxicity against HEK-293. However, compound 6c is characterized by a low in vivo toxicity in mice (LD50 > 2000 mg/kg). 相似文献
74.
Tokareva I Tokarev I Minko S Hutter E Fendler JH 《Chemical communications (Cambridge, England)》2006,(31):3343-3345
An ultrathin novel nanosensor (31.5 +/- 4.1 nm thick in the absence of analytes), employing a molecularly imprinted polymer as a recognition element for cholesterol and gold nanoparticle enhanced transmission surface plasmon resonance spectroscopy for detection, was constructed. 相似文献
75.
Tandem Deprotection–Dimerization–Macrocyclization Route to C2 Symmetric cyclo‐Tetrapeptides 下载免费PDF全文
Khanh Ha Dr. Iryna Lebedyeva Sadra Hamedzadeh Zhiliang Li Ryan Quiñones Girinath G. Pillai Byron Williams Amir Nasajpour Kristin Martin Prof. Dr. Abdullah M. Asiri Prof. Dr. Alan R. Katritzky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):4874-4879
Dimerization–macrocyclization has been a long‐standing problem in the cyclization of peptides since, together with the desired cyclic product, many cyclic oligomers and linear polymers may also be formed during the reaction. Therefore, the development of a process that affords the cyclic dimer predominantly is difficult. A novel and versatile strategy for the synthesis of symmetric cyclo‐tetrapeptides by palladium‐promoted tandem deprotection/cyclo‐dimerization from readily available Cbz‐dipeptidoyl benzotriazolides is reported (Cbz=carboxybenzyl). 相似文献
76.
Iryna Pohrelyuk Oleh Tkachuk Roman Proskurnyak 《Central European Journal of Chemistry》2014,12(2):260-265
The corrosion properties of Ti-6Al-4V alloy with oxidized thermodiffusion nitride coatings were investigated in isotonic 0.9% solution of NaCl at temperature of 40°C. It was shown that modification of nitride coatings by oxygen leads to a deterioration of the protective properties of nitrided surface of Ti-6Al-4V alloy. The protective properties of the alloy with nitride coatings modified by oxygen are determined by the composition of formed surface oxynitride film. 相似文献
77.
Maryna V. Murlykina Yana I. Sakhno Sergey M. Desenko Iryna S. Konovalova Oleg V. Shishkin Dmytro A. Sysoiev Maryna N. Kornet Valentin A. Chebanov 《Tetrahedron》2013
Three-component reactions of 5-aminopyrazoles and salicylic aldehydes with pyruvic acids were studied. The method of tuning of the selectivity of the heterocyclizations allowing to change its direction by variation of the reaction parameters was worked out. The treatment involving pyruvic acid can be selectively directed to the formation to either 3-aryl-10,11-dihydro-4,10-methano-pyrazolo[4,3-c][1,5]benzoxazocine-4-carboxylic acids or 3,6-diarylpyrazolo[3,4-b]pyridine-4-carboxylic acids, while the reaction involving arylpyruvic acid leads only to 7-hydroxy-2,5,6-triaryl-4,5,6,7-tetrahydro-pyrazolo[1,5-a]pyrimidine-7-carboxylic acids. Antimicrobial activity of the compounds obtained was also studied: Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) were found sensitive to the substances tested, however, only in the highest concentration. 相似文献
78.
Iryna Antonyshyn Ana M. Barrios Jimnez Olga Sichevych Ulrich Burkhardt Igor Veremchuk Marcus Schmidt Alim Ormeci Ioannis Spanos Andrey Tarasov Detre Teschner Gerardo Algara‐Siller Robert Schlgl Yuri Grin 《Angewandte Chemie (International ed. in English)》2020,59(38):16770-16776
The production of hydrogen via water electrolysis is feasible only if effective and stable catalysts for the oxygen evolution reaction (OER) are available. Intermetallic compounds with well‐defined crystal and electronic structures as well as particular chemical bonding features are suggested here to act as precursors for new composite materials with attractive catalytic properties. Al2Pt combines a characteristic inorganic crystal structure (anti‐fluorite type) and a strongly polar chemical bonding with the advantage of elemental platinum in terms of stability against dissolution under OER conditions. We describe here the unforeseen performance of a surface nanocomposite architecture resulting from the self‐organized transformation of the bulk intermetallic precursor Al2Pt in OER. 相似文献
79.
Zhenzhen Cai Anja Kastell Claire Speiser Iryna Smetanska 《Applied biochemistry and biotechnology》2013,171(2):330-340
The effects of heavy metal ions (Co2+, Ag+, Cd2+) on cell viability and secondary metabolite production, particularly anthocyanins and phenolic acids in Vitis vinifera cell suspension cultures, were investigated. Of these, Co at all three used concentrations (5.0, 25, and 50 μM), Ag, and Cd at low concentration (5.0 μM) were most effective to stimulate the phenolic acid production, increasing the 3-O-glucosyl-resveratrol up to 1.6-fold of the control level (250.5 versus 152.4 μmol/g), 4 h after the treatments. Meanwhile, the elicitors at effective concentrations did not suppress cell growth, while the cell viability maintained. In contrast, Ag and Cd at high concentrations (25 and 50 μM) remarkably reduced the cell viability, decreasing the cell viability up to about 15 % of the control level, 24 h after the treatments. The heavy metal ions did not affect the anthocyanin production. These observations show how, in a single system, different groups of secondary products can show distinct differences in their responses to potential elicitors. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, peroxidase activity, medium pH value, and conductivity were only slightly elevated by the heavy metal ions. The results suggest that some of the secondary metabolites production was stimulated by the used elicitors, but there was not a stress response of the cells. 相似文献
80.
Iryna Ryzhkova 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,58(2):246-261
We discuss the problem of non-linear oscillations of a clamped thermoelastic plate in a subsonic gas flow. The dynamics of
the plate is described by von Kármán system in the presence of thermal effects. No mechanical damping is assumed. To describe
the influence of the gas flow we apply the linearized theory of potential flows. Our main result states that each weak solution
of the problem considered tends to the set of the stationary points of the problem.
A similar problem was considered in [27], but with rotational inertia accounted for, i.e. with the additional term −αΔutt,α > 0, and the same result on stabilization was obtained. There was introduced the decomposition of the solution such that
the one term tends to zero and the other is compact in special (“local energy”) topology. This decomposition enables us to
prove the main result. But the case of rotational inertia neglected (α = 0) appears more difficult. Low a priori smoothness
of ut in the case α = 0 prevents us to construct such a decomposition. In order to prove additional smoothness of ut we use analyticity of the corresponding thermoelastic semigroup proved in [25].
The isothermal variant of this problem with additional mechanical damping term −εΔut
, ε > 0 was considered in [13] and stabilization to the set of stationary solutions to the problem was proved. The problem,
considered in the present work can also be regarded as an extension of the result of [18] to the case when gas occupies an
unbounded domain. 相似文献