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131.
We analyse anisotropy of acousto–optic figure of merit (AOFM) for Li2B4O7 crystals in order to estimate the prospects of these crystals in acousto–optics. We find that the maximal AOFM, 3.44 × 10?15 s3/kg, is peculiar for the isotropic acousto–optic interaction of the incident ordinary optical wave with the quasi-longitudinal acoustic wave. For the case of anisotropic diffraction in Li2B4O7, the maximum 1.87 × 10?15 s3/kg can be reached using the interaction of the extraordinary optical wave with the quasi-longitudinal acoustic wave. The case of collinear diffraction is characterized by small AOFMs, with the largest value 0.26 × 10?15 s3/kg. 相似文献
132.
Oksana Y. Dudaryeva Aurelia Bucciarelli Giovanni Bovone Florian Huwyler Shibashish Jaydev Nicolas Broguiere Marwa al-Bayati Marco Lütolf Mark W. Tibbitt 《Advanced functional materials》2021,31(52):2104098
Biophysical properties of the cellular microenvironment, including stiffness and geometry, have been shown to influence cell function. Recent findings have implicated 3D confinement as an important regulator of cell behavior. The understanding of how mechanical signals direct cell function is based primarily on 2D studies. To investigate how the extent of 3D confinement affects cell function, a single cell culture platform is fabricated with geometrically defined and fully enclosed microwells and it is applied to investigate how niche volume and stiffness affect human mesenchymal stem cells (hMSC) life and death. The viability and proliferation of hMSCs in confined 3D microniches are compared with unconfined cells in 2D. Confinement biases hMSC viability and proliferation, and this influence depends on the niche volume and stiffness. The rate of cell death increases and proliferation markedly decreases upon 3D confinement. The observed differences in hMSC behavior are correlated to changes in nuclear morphology and YES-associated protein (YAP) localization. In smaller 3D microniches, hMSCs display smaller and more rounded nuclei and primarily cytoplasmic YAP localization, indicating reduced mechanical activation upon confinement. Interestingly, these effects scale with the extent of 3D confinement. These results demonstrate that the extent of confinement in 3D can be an important regulator of cell function. 相似文献
133.
Syntheses of new adducts from glycidyl methacrylate and the following amines: aniline, p‐phenylenediamine, 4,4′‐oxydianiline, 4,4′‐diaminodiphenylmethane, 4,4′‐diaminodiphenyl sulfone, 4,4′‐thiodianiline, and 4,4′‐diaminodicyclohexylmethane, are presented. These adducts were copolymerized with glycidyl methacrylate. The curing process was initiated thermally and by UV light. Thermomechanical properties of the obtained compositions were studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2461–2466, 2005 相似文献
134.
Leonid V. Aseev Ludmila S. Koledinskaya Oksana S. Bychenko Irina V. Boni 《International journal of molecular sciences》2021,22(18)
The autogenous regulation of ribosomal protein (r-protein) synthesis plays a key role in maintaining the stoichiometry of ribosomal components in bacteria. In this work, taking the rpsO gene as a classic example, we addressed for the first time the in vivo regulation of r-protein synthesis in the mycobacteria M. smegmatis (Msm) and M. tuberculosis (Mtb). We used a strategy based on chromosomally integrated reporters under the control of the rpsO regulatory regions and the ectopic expression of Msm S15 to measure its impact on the reporter expression. Because the use of E. coli as a host appeared inefficient, a fluorescent reporter system was developed by inserting Msm or Mtb rpsO-egfp fusions into the Msm chromosome and expressing Msm S15 or E. coli S15 in trans from a novel replicative shuttle vector, pAMYC. The results of the eGFP expression measurements in Msm cells provided evidence that the rpsO gene in Msm and Mtb was feedback-regulated at the translation level. The mutagenic analysis showed that the folding of Msm rpsO 5′UTR in a pseudoknot appeared crucial for repression by both Msm S15 and E. coli S15, thus indicating a striking resemblance of the rpsO feedback control in mycobacteria and in E. coli. 相似文献
135.
Trushkevych O Xu H Lu T Zeitler JA Rungsawang R Gölden F Collings N Crossland WA 《Applied optics》2010,49(28):5212-5216
Tunable materials with high anisotropy of refractive index and low loss are of particular interest in the microwave and terahertz range. Nematic liquid crystals are highly sensitive to electric and magnetic fields and may be designed to have particularly high birefringence. In this paper we investigate birefringence and absorption losses in an isothiocyanate based liquid crystal (designed for high anisotropy) in a broad range of the electromagnetic spectrum, namely 0.1-4 GHz, 30 GHz, 0.5-1.8 THz, and in the visible and near-infrared region (400 nm-1600 nm). We report high birefringence (Δn = 0.19-0.395) and low loss in this material. This is attractive for tunable microwave and terahertz device applications. 相似文献
136.
Anderson JR Chemiavskaya O Gitlin I Engel GS Yuditsky L Whitesides GM 《Analytical chemistry》2002,74(8):1870-1878
A series of charge ladders of bovine carbonic anhydrase II were synthesized and the relative abundances of the rungs analyzed by capillary electrophoresis as a function of the quantity of acylating agent used. A simulation that models the kinetics of formation of the members of the charge ladders is described. The observed rate constants decreased as the extent of acylation increased. These rate constants correlated adequately with theoretical rate constants calculated using Debye-Hückel theory. The data are compatible with, but do not demand, a model for the formation of this charge ladder in which all unacetylated amino groups in each rung have indistinguishable reactivity and in which the reactivity of the amines in each rung decreases as the net charge on the protein increases; in this model, decreased reactivity is due to increased extent of protonation. This agreement between experiment and model suggests that the charge shielding that results from an ionic strength of 130 mM is not sufficient to suppress the influence of the increasingly negative charge of the protein with acetylation on the extent of protonation of Lys epsilon-NH2 groups. 相似文献
137.
Electrostatic force microscopy shows that the electric field gradients above pentacene monolayer islands on 2-nm SiO2/Si substrates, in a dark, dry nitrogen environment, display a wide distribution of signs and magnitude that is dependent on sample history. Under 12 mW/cm2 green (532 nm) illumination, pentacene islands accumulate positive charge because of photoexcited electron transfer across the oxide to the Si substrate. At a strong illumination of 60 mW/cm2, pentacene islands reform into small spherical particles, apparently because the positive charge Coulomb repulsion energy becomes comparable to the cohesive energy of the pentacene monolayer. 相似文献
138.
Kaupo Kukli Jaan Aarik Aleks Aidla Oksana Kohan Teet Uustare Vino Sammelselg 《Thin solid films》1995,260(2):135-142
Thin tantalum oxide films were deposited using atomic layer deposition from TaCl5 and H2O at temperatures in the range 80–500 °C. The films deposited at temperatures below 300 °C were predominantly amorphous, whereas those grown at higher temperatures were polycrystalline containing the phases TaO2 and Ta2O5. The oxygen to tantalum mass concentration ratio corresponded to that of TaO2 at all growth temperatures. The optical band gap was close to 4.2 eV for amorphous films and ranged from 3.9 to 4.5 eV for polycrystalline films. The refractive index measured at λ = 550 nm increased from 1.97 to 2.20 with an increase in growth temperature from 80 to 300 °C. The films deposited at 80 °C showed low absorption with absorption coefficients of less than 100 cm−1 in the visible region. 相似文献
139.
Bacherikov Yuriy Yu. Lytvyn Petro M. Mamykin Sergii V. Okhrimenko Olga B. Ponomarenko Valentyna V. Malyuta Serhiy V. Doroshkevich Aleksandr S. Danilenko Igor A. Gorban Oksana A. Gilchuk Andrii Baiova Yana Lyubchyk Andriy 《Journal of Materials Science: Materials in Electronics》2022,33(5):2753-2764
Journal of Materials Science: Materials in Electronics - The current transfer through a two-layer structure saturated with absorbed water, each layer of which consists of pressed ZrO2 nanoparticles... 相似文献
140.
Nikolai G. Dorbakov Vadim V. Grebenev Vladimir V. Titkov Evgeniya S. Zhukovskaya Sergey Y. Stefanovich Oksana V. Baryshnikova Dina V. Deyneko Vladimir A. Morozov Alexei A. Belik Bogdan I. Lazoryak 《Journal of the American Ceramic Society》2018,101(9):4011-4022
Solid solution of Ca9‐xMgxBi(VO4)7 in powder and ceramic forms are obtained by solid‐state reactions. Details of their crystal structures are determined for x = 0.25 and x = 0.5 by synchrotron radiation diffraction and the Rietveld method. The refinement has confirmed that Mg2+ is replacing Ca2+ in M5 position of a polar (S.G. R3c) β‐Ca3(PO4)2‐type structure. Thermal analysis, dielectric and second harmonic generation experiments in broad temperature regions have proved this polar structure is formed for 0 ≤ x ≤ 0.7. Magnesium for calcium substitution enhances optical nonlinear activity of Ca9‐xMgxBi(VO4)7 in 0 < x ≤ 0.5. Two phase transitions have been found, one of which from polar to centrosymmetric phase is accompanied by dielectric constant peak of ferroelectric type. The other is upper on temperature, marked with smaller dielectric anomaly, and goes between 2 centrosymmetric phases. Temperatures of the phase transition only slightly depend on x, the first being near 1050 K, the second near 1100 K. Electric conductivity quickly rises with temperature in the polar phase. At higher temperature it changes according to the Arrhenius law with small activation energy, Ea ~ 0.7 eV for bulk conductivity and Egb ~ 2.0‐2.5 eV for grain boundary conductivity. The analysis of bulk and grain boundary conductivities agrees with Ca2+‐ion fast transport in ceramics. The bulk conductivity slowly decreases with magnesium content, the grain boundary conductivity does not notably depend on the composition. 相似文献