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851.
Janusz W. Strzelecki Joanna Strzelecka Karolina Mikulska Mariusz Tszydel Aleksander Balter Wiesław Nowak 《Central European Journal of Physics》2011,9(2):482-491
Caddisfly (Trichopera) can glue diverse material underwater with a silk fiber. This makes it a particularly interesting subject
for biomimetcs. Better understanding of silk composition and structure could lead to an adhesive capable to close bleeding
wounds or to new biomaterials. However, while spiderweb or silkworm secretion is well researched, caddisfly silk is still
poorly understood. Here we report a first nanomechanical analysis of H. Angustipennis caddisfly silk fiber. An Atomic Force
Microscope (AFM) imaging shows dense 150 nm bumps on silk surface, which can be identified as one of features responsible
for its outstanding adhesive properties. AFM force spectroscopy at the fiber surface showed, among others, characteristic
saw like pattern. This pattern is attributed to sacrificial bond stretching and enhances energy dissipation in mechanical
deformation. Similarities of some force curves observed on Tegenaria domestica spiderweb and caddisfly silk are also discussed.
Steered Molecular Dynamics simulations revealed that the strength of short components of Fib-H HA species molecules, abundant
in Trichoptera silk is critically dependent on calcium presence. 相似文献
852.
Dr. Dimitrije Mara Prof. Anna M. Kaczmarek Dr. Flavia Artizzu Anatolii Abalymov Prof. Andre G. Skirtach Prof. Kristof Van Hecke Prof. Rik Van Deun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(21):6479-6488
In recent years, luminescent materials doped with Ln3+ ions have attracted much attention for their application as optical thermometers based on both downshifting and upconversion processes. This study presents research done on the development of highly sensitive optical thermometers in the physiological temperature range based on poly(methyl methacrylate) (PMMA) films doped with two series of visible Ln3+ complexes (Ln3+=Tb3+, Eu3+, and Sm3+) and SiO2 nanoparticles (NPs) coated with these PMMA films. The best performing PMMA film doped with Tb3+ and Eu3+ complexes was the PMMA[TbEuL1tppo]1 film (L1=4,4,4-trifluoro-1-phenyl-1,3-butadionate; tppo=triphenylphosphine oxide), which showed good temperature sensing of Sr=4.21 % K−1 at 313 K, whereas for the PMMA films doped with Tb3+ and Sm3+ complexes the best performing was the PMMA[TbSmL2tppo]3 film (L2=4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butadionate), with Sr=3.64 % K−1 at 313 K. Additionally, SiO2 NPs coated with the best performing films from each of the series of PMMA films (Tb–Eu and Tb–Sm) and their temperature-sensing properties were studied in water, showing excellent performance in the physiological temperature range (PMMA[TbEuL1tppo]1@SiO2: Sr=3.84 % °C at 20 °C; PMMA[TbSmL2tppo]3@SiO2: Sr=3.27 % °C at 20 °C) and the toxicity of these nanoparticles on human cells was studied, showing that they were nontoxic. 相似文献
853.
Damian Wojcieszak Danuta Kaczmarek Jaroslaw Domaradzki Eugeniusz L. Prociow Antoni W. Morawski Magdalena Janus 《Central European Journal of Physics》2011,9(2):354-359
In this work photocatalytic properties of TiO2 thin films doped with different amount of Tb have been described. Thin films were prepared by high energy reactive magnetron
sputtering process. Comparable photocatalytic activity has been found for all doped TiO2 thin films, while different amounts of Tb dopant (0.4 and 2.6 at. %) results in either an anatase or rutile structure. It
was found that the terbium dopant incorporated into TiO2 was also responsible for the amount of hydroxyl groups and water particles adsorbed on the thin film surfaces and thus photocatalytic
activity was few times higher in comparison with results collected for undoped TiO2 thin films. 相似文献
854.
Evelyne Flandrin Antoni Marczyk Jakub Przybyło Jean-François Saclé Mariusz Woźniak 《Graphs and Combinatorics》2013,29(5):1329-1336
We consider proper edge colorings of a graph G using colors of the set {1, . . . , k}. Such a coloring is called neighbor sum distinguishing if for any pair of adjacent vertices x and y the sum of colors taken on the edges incident to x is different from the sum of colors taken on the edges incident to y. The smallest value of k in such a coloring of G is denoted by ndiΣ(G). In the paper we conjecture that for any connected graph G ≠ C 5 of order n ≥ 3 we have ndiΣ(G) ≤ Δ(G) + 2. We prove this conjecture for several classes of graphs. We also show that ndiΣ(G) ≤ 7Δ(G)/2 for any graph G with Δ(G) ≥ 2 and ndiΣ(G) ≤ 8 if G is cubic. 相似文献
855.
The Spectral Analysis of Surface Waves (SASW) is a popular technique in seismics for imaging the ground subsurface. It uses the dispersive properties of Rayleigh waves in a transversely homogeneous, multilayered medium. The SASW approach is being transposed into the civil engineering domain to characterize subsurface damage in concrete structures. Such a damage consists in a few millimeters thick surface layer with porosity slightly higher than in the sound material. It is induced by contact with moisture or chemicals at the surface of the structure and may facilitate penetration of aggressive agents. In this study, two-layered mortar samples are made to mimic concrete cover damage in real structures. The dispersive behavior of Rayleigh waves arises when the wavelength is comparable to the thickness of the first layer. Given the small thickness of this layer, it requires increasing the frequency up to several hundreds of kHz, which means high attenuation and low signal-to-noise ratio. Rayleigh waves with 0.5 MHz central frequency are generated into the samples by the wedge method. Phase velocity dispersion curves are obtained by broadband phase spectroscopy from signals received at various distances from the source. The signal processing is first validated on simulated signals with known dispersion law. Then, the measured dispersion curves are compared with the theoretical curve for a two-layered medium, following Haskell's approach. The measured curve displays the general behavior expected from theory. However, a three-layered, visco-elastic model would be necessary to get a better fit and to estimate more accurately the parameters of each layer. 相似文献
856.
Matejícek P Uchman M Lokajova J Stepanek M Prochazka K Spírkova M 《The journal of physical chemistry. B》2007,111(29):8394-8401
The size and structural changes of nanoparticles formed after the addition of poly(2-vinylpyridine), PVP, to block copolymer micelles of polystyrene-block-poly(methacrylic acid), PS-PMA, were studied by light scattering and atomic force microscopy. Due to the strong hydrogen bonding between PVP and PMA segments, complex structures based on the core/shell micelles form in mixed selective solvents. As proven by a combination of light scattering and atomic force microscopy, individual PS-PMA micelles are "glued" together by PVP chains. The dialysis against solvents with a high content of water results in transient increase in polydispersity and turbidity of originally clear solutions. However, the precipitated polymer material dissolves in basic buffers and stable soluble nanoparticles reform in aqueous media. The behavior of their solutions was studied in a broad pH range by light scattering, atomic force microscopy and capillary zone electrophoresis. 相似文献
857.
858.
Kulszewicz-Bajer I Zagórska M Wielgus I Pawłowski M Gosk J Twardowski A 《The journal of physical chemistry. B》2007,111(1):34-40
Three alternating poly(m-p-anilines) have been synthesized via palladium-catalyzed amination reactions. Polymers were oxidized to radical cations by the use of chemical and electrochemical methods. The presence of radical cations was manifested by the appearance of two new bands in UV-vis spectra and a strong EPR signal. Moreover, EPR spectra at low temperatures confirmed the formation of a high-spin state. The magnetization measurements of polymers oxidized to radical cations revealed the paramagnetic-type behavior with weak antiferromagnetic interactions. Radical cations underwent the degradation processes in the presence of air, which led to the decrease of spin concentration. 相似文献
859.
Sylwia Zielińska Joanna Kolniak-Ostek Mariusz Dziadas Jan Oszmiański Adam Matkowski 《液相色谱法及相关技术杂志》2016,39(4):209-219
The accurate profiling of Agastache rugosa phenolic compounds is an indispensable step toward better understanding of the medicinal properties of the species. The applied method based on coupling fast centrifugal partition chromatography and UPLC–qTOF–MS is an alternative and rapid method for the separation and preliminary purification of compounds included in crude extract and can facilitate the detection of minor compounds. Samples were prepared by the extraction of leaves and inflorescences with methanol, dichloromethane, and ethyl acetate. Polyphenolic compounds were separated using fast centrifugal partition chromatography (FCPC) and analyzed by UPLC–qTOF–MS. Rosmarinic acid, chlorogenic acid, and tilianin content were determined in aerial parts during the growth season and in plants of different age. The developed analytical method used in our experiments improved the identification of phenolic compounds and led to the detection of compounds that had not been found in A. rugosa previously. 相似文献
860.
Dr. Mariusz Tasior Dr. Małgorzata Czichy Prof. Mieczysław Łapkowski Prof. Daniel T. Gryko 《化学:亚洲杂志》2018,13(4):449-456
Dibenzothienopyrrolo[3,2‐b]pyrrole and the corresponding bis(S,S‐dioxide) were synthesized by using a concise synthetic strategy. Despite the presence of six fused aromatic rings, π‐expanded pyrrolo[3,2‐b]pyrroles of this type absorb and emit at relatively short wavelengths, which reflects inefficient π conjugation due to the angular arrangement of the aromatic rings. They exhibit interesting and complex electrochemical behavior, which highlights their potential in organic electronics. Both heteroacenes undergo two‐stage oxidation while retaining the independence of each 1‐phenyl‐1H‐[1]benzothieno[3,2‐b]pyrrole, which was proved by in situ electron spin resonance measurements. Interestingly, electrochemically generated dicationdiradicals are not only distributed over the pyrrolo[3,2‐b]pyrrole scaffold, but also over the phenyl substituents located on nitrogen atoms. 相似文献