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1.
Hybrid numerical—experimental approach for investigation of dynamics of microcantilever relay system
V. Ostasevicius S. Tamulevicius A. Palevicius M. Ragulskis R. Palevicius V. Grigaliunas 《Optics and Lasers in Engineering》2005,43(1):199
The time average holography measurements of the vibrating microelectromechanical switch (MEMS) were performed in this study. Experimental measurement results exhibit good agreement with computer generated holographic interferogram analysis. The validation of experimental investigations versus numerical analysis provides the necessary background to analyze the dynamical characteristics of micromechanical systems in virtual numerical environments. Direct application of fringe counting techniques for reconstruction of motion from time average holograms cannot be straightforward if the analyzed micromechanical systems contain motion limiters. Modifications of a classical time average holographic technique enable qualitative analysis of MEMS and can be applied for investigation of dynamical properties of much broader classes of MEMS systems. 相似文献
2.
Sigitas Tumkevicius Linas LabanauskasVirginija Bucinskaite Algirdas BrukstusGintaras Urbelis 《Tetrahedron letters》2003,44(35):6635-6638
(1-Amino-1H-benzimidazol-2-yl)methanol 1 with thionyl chloride at reflux afforded 3-chlorobenzimidazo[1,2-c][1,2,3]thiadiazole 4, which reacted with various nucleophiles to give different products depending on the nature of the solvent. The structures of 4 and di(benzimidazo[1,2-c][1,2,3]thiadiazol-3-yl)sulfide 8 were confirmed by single-crystal X-ray analysis. 相似文献
3.
Prof. Dr. Andrei V. Malkov Dr. Sigitas Stončius Dr. Mark Bell Dr. Fabiomassimo Castelluzzo Dr. Pedro Ramírez‐López Dr. Lada Biedermannová Prof. Dr. Vratislav Langer Dr. Lubomír Rulíšek Prof. Dr. Pavel Kočovský 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(28):9167-9185
Detailed kinetic and computational investigation of the enantio‐ and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5 , employing the pyridine N‐oxides METHOX ( 9 ) and QUINOX ( 10 ) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate‐ and selectivity‐determining step, which is supported by both experimental and computational data. 相似文献
4.
Karolina Maleckait Domantas Narkevi
ius Rugil
ilnait Jelena Dodonova-Vaitknien Stepas Toliautas Sigitas Tumkevi
ius Aurimas Vyniauskas 《Molecules (Basel, Switzerland)》2022,27(1)
Mapping microviscosity, temperature, and polarity in biosystems is an important capability that can aid in disease detection. This can be achieved using fluorescent sensors based on a green-emitting BODIPY group. However, red fluorescent sensors are desired for convenient imaging of biological samples. It is known that phenyl substituents in the position of the BODIPY core can shift the fluorescence spectra to longer wavelengths. In this research, we report how electron-withdrawing (EWG) and -donating (EDG) groups can change the spectral and sensory properties of -phenyl-substituted BODIPYs. We present a trifluoromethyl-substituted (EWG) conjugate with moderate temperature sensing properties and a methoxy-substituted (EDG) molecule that could be used as a lifetime-based polarity probe. In this study, we utilise experimental results of steady-state and time-resolved fluorescence, as well as quantum chemical calculations using density functional theory (DFT). We also explain how the energy barrier height () for non-radiative relaxation affects the probe’s sensitivity to temperature and viscosity and provide appropriate ranges for the best possible sensitivity to viscosity and temperature. 相似文献
5.
Lina Skardžiūtė Karolis Kazlauskas Jelena Dodonova Jonas Bucevičius Sigitas Tumkevičius Saulius Juršėnas 《Tetrahedron》2013
Pyrrolo[2,3-d]pyrimidine derivatives possessing different sterically-hindered end-groups at position 7 of the heterocycle were studied and compared with respect to nanoaggregate formation ability by the reprecipitation method in aqueous solutions. The emergence of nanoaggregates with an increasing water fraction in THF/water mixture was traced by observing sudden changes in spectral and transient fluorescence dynamics accompanied by fluorescence efficiency turn-on. The aggregation induced emission with a maximal 20-fold emission efficiency enhancement was obtained. Tuning of the nanoaggregates sizes from about 50 nm to 600 nm by increasing the THF/water ratio was revealed by electron microscopy. Almost perfect spherical shapes of the nanoaggregates and their structureless fluorescence bands similar to those of their neat amorphous films suggested an amorphous-like nature of the pyrrolo[2,3-d]pyrimidine-based nanoparticles. 相似文献
6.
Dr. Stepas Toliautas Dr. Jelena Dodonova Audrius Žvirblis Ignas Čiplys Artūras Polita Dr. Andrius Devižis Prof. Sigitas Tumkevičius Prof. Juozas Šulskus Dr. Aurimas Vyšniauskas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10342-10349
Molecular rotors are a class of fluorophores that enable convenient imaging of viscosity inside microscopic samples such as lipid vesicles or live cells. Currently, rotor compounds containing a boron-dipyrromethene (BODIPY) group are among the most promising viscosity probes. In this work, it is reported that by adding heavy-electron-withdrawing −NO2 groups, the viscosity-sensitive range of a BODIPY probe is drastically expanded from 5–1500 cP to 0.5–50 000 cP. The improved range makes it, to our knowledge, the first hydrophobic molecular rotor applicable not only at moderate viscosities but also for viscosity measurements in highly viscous samples. Furthermore, the photophysical mechanism of the BODIPY molecular rotors under study has been determined by performing quantum chemical calculations and transient absorption experiments. This mechanism demonstrates how BODIPY molecular rotors work in general, why the −NO2 group causes such an improvement, and why BODIPY molecular rotors suffer from undesirable sensitivity to temperature. Overall, besides reporting a viscosity probe with remarkable properties, the results obtained expand the general understanding of molecular rotors and show a way to use the knowledge of their molecular action mechanism for augmenting their viscosity-sensing properties. 相似文献
7.
Mickevicius S Bondarenka V Grebinskij S Tvardauskas H Andriulevicius M Tamulevicius S Kaciulis S 《Micron (Oxford, England : 1993)》2009,40(1):126-129
The X-ray photoelectron spectroscopy (XPS) spectra of hydrated vanadium oxides (VO)Mo(x)V(12-x).nH(2)O (x=0, 1, 2, 3) were studied to provide the vanadium ions reduction ratio (RR)=V(4+)/(V(4+)+V(5+)) dependence on the molybdenum ions concentration and thermal treatment. The vanadium valence does not depend on Mo doping (x=3) and is strongly dependent on calcinations above the oxygen desorption temperature. 相似文献
8.
Sourbh Thakur Jyoti Chaudhary Bhawna Sharma Ankit Verma Sigitas Tamulevicius Vijay Kumar Thakur 《Current Opinion in Green and Sustainable Chemistry》2018
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9.
The synthesis of chiral 1'H-spiro[1,3-benzodioxole-2,12'-[6',10']methanocyclooct[b]indole] 3, a fused polycyclic structure derived from bicyclo[3.3.1]nonane, was accomplished via the Fisher indolization reaction. Enantiomers of this structure were obtained by chiral HPLC enantiomer separation on a swollen microcrystalline triacetylcellulose column. Chiroptical properties of the resolved enantiomers containing indole and 1,2-methylenedioxybenzene chromophores were studied. Application of the sector rule to the 1,2-methylenedioxybenzene chromophore to establish the absolute configuration of this polycyclic structure did not lead to an unequivocal conclusion which is likely to be due to the transannular interaction of the chromophores. The enantiospecific synthesis from enantiomerically enriched (-)-(1R,5S)-bicyclo[3.3.1]nonane-2,9-dione 1 was performed to prove unequivocally the (+)-(6'R,10'S)-configuration of the title structure. This study demonstrates that semiempirical rules should be applied cautiously to the determination of the absolute configuration of molecules containing several chromophores. 相似文献
10.
Inga Cikotiene Erika Pudziuvelyte Algirdas Brukstus Sigitas Tumkevicius 《Tetrahedron》2007,63(34):8145-8150
Reactions of 4-amino-5-nitro-6-phenylethynylpyrimidines with amines and thiols have been investigated. Pyridine catalyzes rearrangement of the title compounds into 6-phenyl-7-oxo-7H-pyrrolo[3,2-d]pyrimidine-5-oxides. Primary and secondary amines and thiols take part in a regio- and stereoselective addition reaction to the triple bond of 5-nitro-6-phenylethynylpyrimidines to form the corresponding syn-addition (in the case of secondary amines) or anti-addition (in the case of primary amines or thiols) products. 相似文献