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31.
The reactions of 5‐nitriminotetrazole ( 4 ) with 1‐methyl‐5‐aminotetrazole ( 2 ) as well as 2‐methyl‐5‐aminotetrazole ( 3 ) were investigated. In the first reaction 2 was protonated yielding 1‐methyl‐5‐aminotetrazolium 5‐nitrimino‐1H‐tetrazolate monohydrate ( 7 ). In the latter case no protonation could be observed and a co‐crystallization of 5‐nitraminotetrazole and 2‐methyl‐5‐aminotetrazole was obtained. In this compound a new tautomer of 4 could be found. Both products were determined by low temperature single crystal X‐ray diffraction, IR, Raman and multinuclear (1H, 13C, 15N) NMR spectroscopy, elemental analysis as well as differential scanning calorimetry. In addition the heats of formation were calculated using experimentally obtained heats of combustion. With these and the X‐ray densities several detonation parameter were computed using the EXPLO5 software. In addition the sensitivities towards impact, friction and electrostatic discharge were determined. Further, two crystal structures of the important starting materials in energetic research 5‐nitriminotetrazole monohydrate ( 4 ·H2O) and 1‐methyl‐5‐nitriminotetrazolemonohydrate ( 5 ·H2O) are presented and compared with the water‐free compounds. The heats of formation of 4 , 4 ·H2O, 5 , 5 ·H2O have been calculated by the atomization method using the CBS basis set. Inclusion of crystal water decrease heats of formation about 265 kJ mol?1. Also the influence of crystal water on sensitivities (impact, friction, electrostatic discharge) but also performance is discussed. 相似文献
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33.
High and low molecular weight (Mw) carboxymethyl celluloses (CMC) were adsorbed on a well-characterized fiber substrate (long fibers of a commercial bleached birch kraft pulp with the carboxylic acid groups in Na-form) to increase the charge of the fibers in a controlled fashion. The Mw played a role in the utilization of CMCs as a strength additive in paper sheets nearly doubling the tensile strength with the high Mw CMC. Swelling properties of the CMC treated fibers were measured with water retention value (WRV). The WRV increased more with the high Mw CMC. The swelling was further tuned by two highly cationic polyelectrolytes; high Mw poly(diallyldimethyl ammonium chloride) (PDADMAC) and low Mw polybrene (hexadimethrine bromide, [3,6]-ionene). They were chosen because of their known ability to neutralize the anionic charge either exclusively on the surface or in the whole fiber, respectively. Adsorption of PDADMAC could reduce WRV of the CMC pre-treated fibers to the level of the untreated reference, while polybrene adsorbed pulps with 3–10 times more cationic polyelectrolyte deswelled the fibers only slightly more than the surface neutralized fibers. These results indicated surface conformation differences with low and high Mw CMCs. While the conformation did play a role after physical alteration (drying and rewetting) of the fibers, the paper sheets produced from these fibers showed remarkable differences. In extreme cases, the strength of the paper could be retained after drying (low Mw CMC + PDADMAC) or paper, resistant to disintegration, could be achieved (CMC + polybrene). 相似文献
34.
Niko Guskos Spiros Glenis Janusz Typek Grzegorz Zolnierkiewicz Pawel Berczynski Kamil Wardal Aleksander Guskos Daniel Sibera Dariusz Moszyński Witold Lojkowski Urszula Narkiewicz 《Central European Journal of Physics》2012,10(2):470-477
Fine particles of ZnFe2O4 were synthesized by a wet chemical method in the (80 wt.% Fe2O3 + 20 wt.% ZnO) system. The morphological and structural properties of the mixed system were investigated by scanning electron microscopy, X-ray diffraction, inductively coupled plasma atomic emission, and X-ray photoelectron spectroscopy. The major phase was determined to be the ZnFe2O4 spinel with particle size of 11 nm. The magnetic properties of the material were investigated by ferromagnetic resonance (FMR) in the temperature range from liquid helium to room temperature. A very intense, asymmetric FMR signal from ZnFe2O4 nanoparticles was recorded, which has been analyzed in terms of two Callen-lineshape lines. Temperature dependence of the FMR parameters was obtained from fitting the experimental lines with two component lines. Analysis of the FMR spectra in terms of two separate components indicates the presence of strongly anisotropic magnetic interactions. 相似文献
35.
Niko Prasetyo Alberto Krishna Ksatria Winning Kusuma La Ode Muhammad Iqbal 《International journal of quantum chemistry》2024,124(1):e27236
The spin component scale MP2/molecular mechanics molecular dynamics simulation investigated the hydration shell formation and hydrated Cd2+ dynamics in the water environment. At the first hydration shell, six water molecules with 2.27 Å for the average distance between water and Cd2+. Dynamical properties were analyzed by computing the water molecule's mean residence time (MRT) in its first and second hydration shells. The MRT of each shell was determined to be 31.8 and 1.92 ps, suggesting the strong influence of Cd2+ in the first hydration shell. The second shell was labile, with an average number of water molecules being 18. Despite the strong interaction between Cd2+ and water molecules in the first shell, the influence of ions in the second hydration shell remained weak. 相似文献
36.
Klika KD Kivelä H Ovcharenko VV Nieminen V Sillanpää R Arpalahti J 《Dalton transactions (Cambridge, England : 2003)》2007,(35):3966-3970
The reaction of tetrapyrazine Pt(II) with adenine under basic conditions yielded two products both disubstituted by adenine and bound in all cases to the N-9 nitrogen of adenine. Crystals amenable to X-crystallographic analysis were obtained for one product which was consequently identified as trans-[Pt(II)(N9-adeH)2(pz)2](NO3)(4).H2O. The other product, though, was identified as the cis isomer based on extensive and comparative NMR structural studies whereby the two compounds were examined as both neutral and tetraprotonated species in solution. The major product of the reaction was unexpectedly the cis isomer, thus obtained in contrast to the trans effect, and the reason for this result is speculated on. Computational calculations using DFT at the B3LYP/TZVP-MARI-J level of theory provided the head-to-tail conformer as the overwhelmingly more stable species over the head-to-head conformer for both compounds whilst the trans product was found to be more stable than the cis. Thus the reaction does not follow a thermodynamic course and rather is kinetically controlled in concert with the speculated mode of reaction. 相似文献
37.
Dr. Yuriy Rebets Dr. Elke Brötz Niko Manderscheid Dr. Bogdan Tokovenko Dr. Maksym Myronovskyi Prof. Dr. Peter Metz Dr. Lutz Petzke Dr. Andriy Luzhetskyy 《Angewandte Chemie (International ed. in English)》2015,54(7):2280-2284
Pamamycins are macrodiolides of polyketide origin with antibacterial activities. Their biosynthesis has been proposed to utilize succinate as a building block. However, the mechanism of succinate incorporation into a polyketide was unclear. Here, we report identification of a pamamycin biosynthesis gene cluster by aligning genomes of two pamamycin‐producing strains. This unique cluster contains polyketide synthase (PKS) genes encoding seven discrete ketosynthase (KS) enzymes and one acyl‐carrier protein (ACP)‐encoding gene. A cosmid containing the entire set of genes required for pamamycin biosynthesis was successfully expressed in a heterologous host. Genetic and biochemical studies allowed complete delineation of pamamycin biosynthesis. The pathway proceeds through 3‐oxoadipyl‐CoA, a key intermediate in the primary metabolism of the degradation of aromatic compounds. 3‐Oxoadipyl‐CoA could be used as an extender unit in polyketide assembly to facilitate the incorporation of succinate. 相似文献
38.
Niko Naumann 《Comptes Rendus Mathematique》2003,336(4):289-292
R. Pellikaan (Arithmetic, Geometry and Coding Theory, Vol. 4, Walter de Gruyter, Berlin, 1996, pp. 175–184) introduced a two variable zeta-function Z(t,u) for a curve over a finite field which, for u=q, specializes to the usual zeta-function and he proved rationality: Z(t,u)=(1?t)?1(1?ut)?1P(t,u) with . We prove that P(t,u) is absolutely irreducible. This is motivated by a question of J. Lagarias and E. Rains about an analogous two variable zeta-function for number fields. To cite this article: N. Naumann, C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
39.
A self-consistent method for calculating the chiral anomaly in dimensional regularization without the four-dimensional symbols 5 and is proposed. The method is applied to the calculation and analysis of chiral symmetry in massless quantum electrodynamics.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 109, No. 3, pp. 372–380, December, 1996. 相似文献
40.
Niko Ernsting 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1994,106(5):608-609