| 1. |
- Makarova, Tatiana L, et al.
(författare)
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Conductivity of two-dimensional C60 polymers
- 2000
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Ingår i: Proceedings of the 4th International Workshop on Fullerenes and Atomic Clusters (IWFAC'99), St. Petersburg 1999. - : Overseas Publishers Association N.V.. ; , s. 151-156
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Konferensbidrag (refereegranskat)abstract
- The general trend in the shift of electronic properties as the result of polymerization has been studied with the aid of temperature dependences of conductivity. Samples representing the pure rhombohedral phase exhibit great anisotropy in their electrical properties. The main features of the behaviour of these samples are: (i) in the z-direction the resistivity is of the order of several kOhm cm and decreases with temperature; (ii) in the x-y direction resistivity is less than 1 Ohm cm and shows a minimum at a certain temperature.
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| 2. |
- Makarova, Tatiana L, et al.
(författare)
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Electrical properties of the rhombohedral C60 polymers
- 1999
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Ingår i: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 7. - Pennington, NJ : The Electrochemical Society. - 1566772346 ; , s. 628-639
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Konferensbidrag (refereegranskat)abstract
- Electrical properties of polymerized fullerenes C60 are governed by the type of polymerization which is in turn determined by the initial (P or H) orientation of molecules, the pressure and the temperature of polymerization. The mixed tetragonal - rhombohedral polymerized structure shows a semiconductor-like behavior. An increase in the polymerization temperature results in a decrease in the activation energy and an increase in conductivity. The conductivity prefactor and the activation energy are interconnected by the Meyer-Neldel rule. The pure rhombohedral phase shows highly anisotropic electrical properties. The conductivity in the polymerized (111) planes exhibits a metal-insulator transition and shows the features of 2D weak localization.
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| 3. |
- Galkina, Olga, et al.
(författare)
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Antibacterial and photochemical properties of cellulose nanofiber-titania nanocomposites loaded with two different types of antibiotic medicines
- 2015
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Ingår i: Journal of materials chemistry. B. - : Royal Society of Chemistry (RSC). - 2050-750X .- 2050-7518. ; 3:35, s. 7125-7134
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite dermal drug delivery systems based on cellulose nanofibers with grafted titania nanoparticles loaded by two antibiotic medicines from different classes, i.e. tetracycline (TC) and phosphomycin (Phos), were successfully produced by a "green chemistry'' approach in aqueous media. The influence of a different surface binding mechanism between the drug molecule and modified cellulose nanofibers on the release of the drug and, as a result, on antimicrobial properties against common pathogens Gram-positive, Staphylococcus aureus and Gram-negative Escherichia coli was investigated. The disk diffusion method and broth culture tests using varying concentrations of drugs loaded to nanocomposites were carried out to investigate the antibacterial effects. The influence of UV irradiation on the stability of the obtained nanocomposites and their antibacterial properties after irradiation were also investigated, showing enhanced stability especially for the TC loaded materials. These findings suggest that the obtained nanocomposites are promising materials for the development of potentially useful antimicrobial patches.
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| 4. |
- Moret, Roger, et al.
(författare)
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Single-crystal structural study of the pressure-temperature induced dimerization of C60
- 2004
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Ingår i: European Physics Journal B. - Berlin : Springer. - 1434-6028 .- 1434-6036. ; 37:1, s. 25-37
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Tidskriftsartikel (refereegranskat)abstract
- We present a study by Raman spectroscopy and X-ray diffraction/diffuse scattering of C60 single-crystals treated at high-pressure and high-temperature. This allowed us to obtain structural information on the C60 dimer state which can be considered as an intermediate state in the polymerization process. In the 1-6 GPa pressure range the crystals are primarily formed of dimers with additional minor fractions of monomers, 1D and 2D polymers, as shown by the analysis of the Raman spectra. The dimers are disordered within an average cubic lattice derived from that of the monomer. Single-crystal diffraction patterns reveal a characteristic diffuse scattering intensity distribution which has been simulated by calculating the diffuse scattering produced by dimer and trimer model structures. Satisfactory agreement is obtained for random positional and orientational disorder of the C60-C60 dimers although a small concentration of similarly disordered trimers is likely. In a first approximation the dimer/trimer disorder can be considered as random but various inter-dimer correlations are probably present, as discussed.
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| 5. |
- Zashikhin, A L, et al.
(författare)
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Organization of the muscular component of the lymphangion wall in different parts of the lymphatic bed
- 2005
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Ingår i: Morfologiia. - 1026-3543. ; 127:1, s. 29-32
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Complex comparative analysis of the organization of smooth muscle (SM) forming the wall of lymphatic vessels in bovine small intestinal mesenterium was performed using the methods of morphometry, quantitative histochemistry (including the analysis of nuclear DNA content, and cytoplasmic protein content) and electron microscopy. SM cells (SMC) isolated by dissociation were studied and were found to possess various levels of differentiation, associated with specific morphometric and metabolic characteristics. The structure of SMC population was shown to vary in both different parts of lymphatic bed and within the wall of an individual lymphangion. The results obtained indicate the cellular heteromorphism of lymphatic bed SM. The peculiarities of SM organization in lymphatic vessels are functionally dependent and are determined not only by the level of SM representation in their wall but also by the proportions of different SMC types.
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| 6. |
- Benavides, Vicente, et al.
(författare)
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Tuning structure and mechanical properties of nanoclustered graphene phase by controlled disorder of precursor C60 fullerite
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The paper compares the Raman spectroscopy, HRSTEM, and indentation hardness results of disordered systems synthesized by squeezing (8 GPa, 850 °C) C60 and ball-milled C60. Mechanical activation introduces substantial damage to the C60 crystal leading to the rupture of van der Waals interaction between the C60 units and a chemical reaction between the balls creating C60 dimers. The multi-wavelength Raman spectra of both, the compressed mechanical activated phase (MA-Phase) and without the mechanical activation phase (wMA phase) reveal that fused aromatic rings with a low fraction of nanographene clusters dominate the MA phase, whereas wMA phase is composed of nanographene clusters. Moreover, a Raman model is presented which introduces fullerene-like structures because of fivefold (F-band) and sevenfold carbon rings-like defects for the wMA phase and part of fused aromatic rings for the MA phase. HRSTEM-EELS data confirm that: nanographene clusters present in wMA (I) are smaller and not abundant in the MA phase (II). (III) EELS data reveal a higher fraction of sp3 bonds in the MA phase compared to that in wMA. The hardness of the MA Phase (37 GPa) is twice its value (18 GPa) in the wMA (IV). The extensive analysis of the Raman data yielded empirical dependences of Hardness vs ID/IG/Hardness vs ID/IF that can be useful for prediction of the hardness of sp2-dominant disordered carbon systems based on their spectroscopic data.
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| 7. |
- Hellmann, Lena, et al.
(författare)
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Diverse growth trends and climate responses across Eurasia's boreal forest
- 2016
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 11:7
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Tidskriftsartikel (refereegranskat)abstract
- The area covered by boreal forests accounts for similar to 16% of the global and 22% of the Northern Hemisphere landmass. Changes in the productivity and functioning of this circumpolar biome not only have strong effects on species composition and diversity at regional to larger scales, but also on the Earth's carbon cycle. Although temporal inconsistency in the response of tree growth to temperature has been reported from some locations at the higher northern latitudes, a systematic dendroecological network assessment is still missing for most of the boreal zone. Here, we analyze the geographical patterns of changes in summer temperature and precipitation across northern Eurasia >60 degrees N since 1951 AD, as well as the growth trends and climate responses of 445 Pinus, Larix and Picea ring width chronologies in the same area and period. In contrast to widespread summer warming, fluctuations in precipitation and tree growth are spatially more diverse and overall less distinct. Although the influence of summer temperature on ring formation is increasing with latitude and distinct moisture effects are restricted to a few southern locations, growth sensitivity to June-July temperature variability is only significant at 16.6% of all sites (p <= 0.01). By revealing complex climate constraints on the productivity of Eurasia's northern forests, our results question the a priori suitability of boreal tree-ring width chronologies for reconstructing summer temperatures. This study further emphasizes regional climate differences and their role on the dynamics of boreal ecosystems, and also underlines the importance of free data access to facilitate the compilation and evaluation of massively replicated and updated dendroecological networks.
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| 8. |
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