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81.
[structure: see text] Bis-Tr?ger's base derivatives are a new family of molecular tweezers. A major drawback to their study is a lack of commercially available precursors, ortho-nitrocarboxylic acids. A reverse synthetic strategy starting from known dinitrodicarboxylic acids, which circumvents this problem, is presented. Via this methodology regioisomeric bis-TB derivatives can be prepared selectively, using only common aromatic amines that are typically commercially available. 相似文献
82.
Bohumil Barda Petr Machá? Stanislav Cichoň Marie Kudrnová Jakub Siegel 《Applied Surface Science》2010,257(2):414-4421
Ni, Ni2Si and Pd contacts were prepared on n-type 4H-SiC and annealed in the temperature range of 750-1150 °C. The annealed contacts were analyzed before and after acid etching, and different features were found in unetched and etched contacts. Carbon left on the SiC surface after the acid etching of Ni2Si contacts annealed at 960 °C was highly graphitized. In nickel contacts, the graphitization of interface carbon began at 960 °C and increased after annealing at higher temperatures. In palladium contacts, the onset of the interface carbon graphitization was observed after annealing at 1150 °C. For all three types of metallization, the minimal values of contact resistivity were achieved only when the sharp first-order peak at 1585 cm−1 and distinct second-order peak at ∼2700 cm−1 related to the presence of graphitized carbon were detected by Raman spectroscopy after the acid etching of contacts. The properties of unannealed secondary contacts deposited onto etched primary contacts were similar to the properties of the primary contacts unless carbon was selectively etched. The results show that ohmic behavior of Ni-based and Pd contacts on n-type SiC originates from the formation of graphitic carbon at the interface with SiC. 相似文献
83.
Jonathan Bould Annette Brownless Colin A. Kilner Michael G. S. Londesborough Bohumil Štíbr John D. Kennedy Mark Thornton-Pett 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(1):52-54
The title compound, μ-6,9-chloro-8-methoxy-6,9-bis(η5-pentamethylcyclopentadienyl)-6,9-dirhoda-5-thia-arachno-decaborane(7), [Rh2(CH10B7OS)(C10H15)2Cl], has a single Cl atom bridging the two remote rhodium `prow' vertices of an arachno ten-vertex dirhodathiadecaborane cluster, with Rh—Cl distances of 2.3475 (11) and 2.3536 (11) Å, and an Rh—Cl—Rh angle of 106.82 (4)°. 相似文献
84.
Ludk Toman Miroslav Janata Jií Spv
ek Petr Vl
ek Petra Ltalov Antonín Sikora Bohumil Masa 《Journal of polymer science. Part A, Polymer chemistry》2005,43(17):3823-3830
ABCBA‐type pentablock copolymers of methyl methacrylate, styrene, and isobutylene (IB) were prepared by the cationic polymerization of IB in the presence of the α,ω‐dichloro‐PS‐b‐PMMA‐b‐PS triblock copolymer [where PS is polystyrene and PMMA is poly(methyl methacrylate)] as a macroinitiator in conjunction with diethylaluminum chloride (Et2AlCl) as a coinitiator. The macroinitiator was prepared by a two‐step copper‐based atom transfer radical polymerization (ATRP). The reaction temperature, ?78 or ?25 °C, significantly affected the IB content in the resulting copolymers; a higher content was obtained at ?78 °C. The formation of the PIB‐b‐PS‐b‐PMMA‐b‐PS‐b‐PIB copolymers (where PIB is polyisobutylene), prepared at ?25 (20.3 mol % IB) or ?78 °C (61.3 mol % IB; rubbery material), with relatively narrow molecular weight distributions provided direct evidence of the presence of labile chlorine atoms at both ends of the macroinitiator capable of initiation of cationic polymerization of IB. One glass‐transition temperature (Tg), 104.5 °C, was observed for the aforementioned triblock copolymer, and the pentablock copolymer containing 61.3 mol % IB showed two well‐defined Tg's: ?73.0 °C for PIB and 95.6 °C for the PS–PMMA blocks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3823–3830, 2005 相似文献
85.
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87.
Štíbr B Bakardjiev M Holub J Růžička A Padělková Z Olejník R Švec P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13156-13159
88.
Bohumil Zítka 《Czechoslovak Journal of Physics》1957,7(2):175-189
. , . . - , 500 10 000 30 500 . - , . 相似文献
89.
90.
Imaging of human meiotic chromosomes by scanning near-field optical microscopy (SNOM) 总被引:2,自引:0,他引:2
Hausmann M Liebe B Perner B Jerratsch M Greulich KO Scherthan H 《Micron (Oxford, England : 1993)》2003,34(8):441-447
Centromeres and telomeres are key structures of mitotic and meiotic chromosomes. Especially telomeres develop particular structural properties at meiosis. Here, we investigated the feasibility of scanning near-field optical microscopy (SNOM) for light-microscopic imaging of meiotic telomeres in the sub-hundred nanometer resolution regime. SNOM was applied to visualise the synaptonemal complex (SC) and telomere proteins (TRF1, TRF2) after differential immuno-fluorescent labelling. We tested and compared two different preparation protocols for their applicability in a SNOM setting using micro-fabricated silicon nitride aperture tips. Protocol I consisted of differential labelling of meiotic chromosome cores (SC) by SCP3 immuno-fluorescence and telomeres by TRF1 or TRF2 immuno-fluorescence, while protocol II combined absorption labelling with alkaline phosphatase substrates of cores with fluorescent labelling of telomeres. The results obtained indicate that protocol I reveals a better visualisation of structural (topographic) details than protocol II. By means of SNOM, meiotic chromosome cores could be visualised at a resolution overtopping that of far-field light microscopy. 相似文献