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991.
Daria Larowska Dr. Aleksandra Wojcik Dr. Marta Mazurkiewicz-Pawlicka Dr. Artur Malolepszy Dr. Leszek Stobiński Prof. Bronislaw Marciniak Dr. Anna Lewandowska-Andralojc 《Chemphyschem》2019,20(8):1054-1066
Non-covalent nanohybrids composed of cationic 5,10,15,20-tetra(4-trimethylammoniophenyl)porphyrin tetra(p-toluenesulfonate) (TMAP) and the graphene oxide sheets were prepared under two pH values (6.2 vs. 1.8). The TMAP molecule was positively charged, regardless of the pH value during preparation. However, protonation of the imino nitrogens increased the overall charge of the porphyrin molecule from +4 to +6 (TMAP4+ and TMAP6+). It was found that at acidic pH, interaction of TMAP6+ with GO was largely suppressed. On the other hand, results of FTIR, Raman spectroscopy, thermogravimetric analysis, atomic force microscopy (AFM) and elemental analysis confirmed effective non-covalent functionalization of graphene oxide with cationic porphyrin at pH 6.2. The TMAP4+-GO hybrids exhibited well defined structure with a monolayer of TMAP4+ on the GO sheets as confirmed by AFM. Formation of the ground-state TMAP4+-GO complex in solution was monitored by the red-shift of the porphyrin Soret absorption band. This ground-state interaction between TMAP4+ and GO is responsible for the static quenching of the porphyrin emission. Fluorescence was not detected for the nanohybrid which indicated that a very fast deactivation process had to take place. Ultrafast time-resolved transient absorption spectroscopy clearly demonstrated the occurrence of electron transfer from the photoexcited TMAP4+ singlet state to GO sheets, as proven by the formation of a porphyrin radical cation. 相似文献
992.
Ricardo García-Pelayo 《Journal of statistical physics》2008,133(2):401-404
It was recently shown (Physica A 216:299–315, 1995) that in two dimensions the sum of three vectors each of whose lengths is exponentially distributed, whose direction is uniformly
distributed and such that the sum of their lengths is l, is uniformly distributed on a disk of radius l. We state here this random walk result in terms of scattering of particles as follows: in two dimensions twice isotropically
scattered particles by random (i.e., Poisson distributed) scatterers are uniformly distributed. We show that there is no other
dimension d and no other number of scatterings s for which the corresponding result (i.e., uniform distribution on a d-dimensional sphere after s scatterings) holds. 相似文献
993.
Estrada H Candelas P Uris A Belmar F García de Abajo FJ Meseguer F 《Physical review letters》2008,101(8):084302
We report extraordinary effects in the transmission of sound through periodically perforated plates, supported by both measurements and theory. In agreement with recent observations in slit arrays, M. H. Lu et al. [Phys. Rev. Lett. 99, 174301 (2007)10.1103/PhysRevLett.99.174301], nearly full transmission is observed at certain resonant frequencies, pointing out similarities of the acoustic phenomena and their optical counterpart. However, acoustic screening well beyond that predicted by the mass law is achieved over a wide range of wavelengths in the vicinity of the period of the array, resulting in fundamentally unique behavior of the sound as compared to light. 相似文献
994.
García J Giruzzi G Artaud JF Basiuk V Decker J Imbeaux F Peysson Y Schneider M 《Physical review letters》2008,100(25):255004
Burning tokamak plasmas with internal transport barriers are investigated by means of integrated modeling simulations. The barrier sustainment in steady state, differently from the barrier formation process, is found to be characterized by a critical behavior, and the critical number of the phase transition is determined. Beyond a power threshold, alignment of self-generated and noninductively driven currents occurs and steady state becomes possible. This concept is applied to simulate a steady-state scenario within the specifications of the International Thermonuclear Experimental Reactor. 相似文献
995.
A reliable technique for cryopreservation by encapsulation was developed for two suspension cultures of gentian species (Gentiana tibetica and G. cruciata) of different ages and embryogenic potential. The effect of water content, aggregate size and the subculture time on viability was determined by the 2,3,5-triphenyltetrazolium chloride (TTC) test. Regrowth of a proembryogenic mass (PEM) on agar, liquid or agar/liquid media was assayed by measuring the increase in biomass. A water content of 24-30% (fresh weight basis) after 5-6 h dehydration of encapsulated cells of gentians yielded the highest survival (68% for G. tibetica and 83% for G. cruciata) after cryopreservation. Regardless of species, aggregate size and subculture time, the lowest PEM survival was 44%. These parameters did not influence the survival of G. tibetica PEM, but the survival of G. cruciata was higher when the smaller aggregates were cryopreserved on the 5th day of culture. Agar/liquid culture caused the greatest biomass increase. Cryopreservation did not affect the characteristics of suspension cultures and their regrowth after thawing, nor the number and dynamics of somatic embryos formed. Flow cytometry showed that cryopreservation did not change the genome size of the PEMs or regenerants. 相似文献
996.
D. Kasprowicz T. Runka A. Speghini D. Falcomer J. García Solé M. Bettinelli 《Journal of luminescence》2008,128(5-6):985-987
Vibrational Raman spectra have been measured for strontium barium niobate (Sr0.5Ba0.5Nb2O6, SBN50) single crystals and nanopowders doped with 1 mol% of the luminescent ions Eu3+ and Er3+. The nanocrystalline materials show slightly broader spectra with respect to the single crystals with the same composition. The presence of the Eu3+ and Er3+ ions at the 1 mol% doping level, and the present particle size (200 nm) do not appear to affect the ferro-to-paraelectric phase transition temperature typical of undoped SBN50 single crystals, as detected from anomalies in the dependence of the position of the Raman peak around 635 cm?1 as a function of the temperature. 相似文献
997.
S. García-Revilla R. Valiente Y.E. Romanyuk M. Pollnau 《Journal of luminescence》2008,128(5-6):934-936
Crystalline Er3+ and Yb3+ singly and doubly doped KY(WO4)2 thin films were grown by low-temperature liquid-phase epitaxy. Absorption, luminescence, excitation and temporal evolution measurements were carried out for both Er3+ and Yb3+ transitions from 10 K to room temperature. Green Er3+ upconversion luminescence was observed after Yb3+ and Er3+ excitation. The mechanisms responsible for the upconversion phenomena detected in each case were identified. 相似文献
998.
999.
Karásek V Cizmár T Brzobohatý O Zemánek P Garcés-Chávez V Dholakia K 《Physical review letters》2008,101(14):143601
We create extended longitudinally optically bound chains of microparticles with the use of counterpropagating "nondiffracting" light fields, the so-called Bessel beams. The beam homogeneity and extended propagation range allow the creation of 200 microm long chains of organized microparticles. We observe short-range multistability within a single chain and long-range multistability between several distinct chains. Our observations are supported by theoretical results of the coupled dipole method. 相似文献
1000.
Magdalena Krcisz Bogdan Stpie Marta Pasawska Jarosaw Poposki Kinga Dulak 《Molecules (Basel, Switzerland)》2021,26(15)
The aim of this study was to determine the effects that the type of impregnating solution and drying method (freeze drying (FD) and vacuum drying (VD) at 45 °C and convective drying (CD) at 50, 60, and 70 °C) had on the physicochemical and quality properties of courgettes. Courgette slices were vacuum-impregnated (6 kPa) in freshly squeezed onion, kale, and onion and kale (50:50) juices with 3% NaCl solution (N). The application of vacuum impregnation (VI) with impregnating solutions from freshly squeezed onions and kale had a beneficial effect on the bioactive values of courgette. The highest contents of quercetin (41.84 μg/g d.m.) and carotenoids (276.04 μg/g d.m.) were found in courgette impregnated with onion juice after freeze drying. The highest values of lutein and zeaxanthin (216.42 μg/g d.m.) were recorded for courgette impregnated with kale juice and convective dried. By analysing the kinetics of convective drying, the best matching of the logistic model was found. Increasing the drying process temperature from 50 to 70 °C reduced the drying time from 15% to 36%, depending on the type of impregnating solution used. Water activity < 0.6 was recorded for courgette dried by freezing, vacuum, and convection at 60 and 70 °C. Conclusions: The vacuum impregnation process and the impregnation solutions from freshly squeezed vegetables can be used to develop new snacks with high levels of bioactive compounds. The FD method is the most appropriate considering both the bioactive compounds content and the obtained colour and water activity. 相似文献