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51.
Franciszek Herold Jerzy Kleps Beata Szczsna Romana Anulewicz‐Ostrowska 《Journal of heterocyclic chemistry》2002,39(4):773-782
A series of new 4‐aryloctahydropyrido[1,2‐c]pyrimidine‐1,3‐diones 6a,b,d‐h and j were synthesized by intramolecular cyclization of α‐aryl‐α‐(1‐ethoxycarbonyl‐2‐piperidyl)‐acetamide derivatives 5a,b,d‐h and j . The structures of compounds were determined by 1H and 13C nmr spectroscopy. Nmr and X‐ray diffraction data indicate that the configuration at the C4, C4a stereocenters constitute RR and SS pair. 相似文献
52.
Speciation of vanadium in soil 总被引:1,自引:0,他引:1
A method for speciation of vanadium in soil is presented in this work. The sequential extraction analysis procedure of Tessier et al. for heavy metals was used for the vanadium separation. The method consists of sequential leaching of the soil samples to separate five fractions of metals: (1) exchangeable, (2) bound to carbonates, (3) bound to Fe-Mn oxides, (4) bound to organic matter and (5) residual. The leaching solutions of Tessier were used for the vanadium extraction, only for the residual fraction the HClO4 was replaced with H2SO4. The optimum conditions for leaching of vanadium from soil (weight of sample, concentration and volume of extractants, time of extraction) were chosen for each fraction. A sensitive, spectrophotometric method based on the ternary complex V(IV) with Chrome Azurol S and benzyldodecyldimethylammonium bromide (ε=7.1×104 l mol−1 cm−1) was applied for the vanadium determination after separation of V(V) by solvent extraction using mesityl oxide and reduction of V(V) using ascorbic acid. This method was applied for vanadium speciation in soil from two different regions of Poland: Upper Silesia (industrial region) and Podlasie (agricultural region). The content of vanadium in the fractions of Upper Silesia soil was respectively (in 10−3%): I, 3.39; III, 4.53; IV, 10.70; V, 8.70 and it was the highest in the organic fraction, indicating input by anthropogenic activities. The content of vanadium in Podlasie soil was clearly lower and it was (in 10−3%): I, 2.07; III, 0.92; IV, 0.69; V, 1.23. The concentration of vanadium in fraction 2 of both soils was less than detection limit of applied method. The total content of vanadium in the five soil fractions was in good correlation with the total content of this element in both soils found after HF-H2SO4 digestion. Analysis using the ICP-AES method gave comparable results. 相似文献
53.
54.
Rob Moss Ed Kazmierczak Michael Kirley Peter Harris 《Physica D: Nonlinear Phenomena》2009,238(22):2166-2176
The kidney is one of the major organs involved in whole-body homeostasis, and exhibits many of the properties of a complex system. The functional unit of the kidney is the nephron, a complex, segmented tube into which blood plasma is filtered and its composition adjusted. Although the behaviour of individual nephrons can fluctuate widely and even chaotically, the behaviour of the kidney remains stable.In this paper, we investigate how the filtration rate of a multi-nephron system is affected by interactions between nephrons. We introduce a discrete-time multi-nephron network model. The tubular mechanisms that have the greatest effect on filtration rate are the transport of sodium and water, consequently our model attempts to capture these mechanisms. Multi-nephron systems also incorporate two competing coupling mechanisms–vascular and hemodynamic–that enforce in-phase and anti-phase synchronisations respectively. Using a two-nephron model, we demonstrate how changing the strength of the hemodynamic coupling mechanism and changing the arterial blood pressure have equivalent effects on the system. The same two-nephron system is then used to demonstrate the interactions that arise between the two coupling mechanisms. We conclude by arguing that our approach is scalable to large numbers of nephrons, based on the performance characteristics of the model. 相似文献
55.
Zuzanna Molęda Anna Zawadzka Małgorzata Żytek Daria Madej Franciszek Pluciński Jan K. Maurin Zbigniew Czarnocki 《Comptes Rendus Chimie》2013,16(9):807-813
A series of carbamate melatonin derivatives was treated with performic acid, providing tricyclic products with a 3-hydroxytetrahydropyrrolo[2,3-b]indole skeleton. An unusual migration of carbamate groups was observed in some cases, and the reaction appeared to be strongly dependent on the type of substituent in the phenyl ring of the phenylcarbamate group. Theoretical calculations suggest that the reaction is kinetically controlled. 相似文献
56.
Mahdi Hormozi Franciszek Prus-Wiśniowski Hjalmar Rosengren 《Journal of Mathematical Analysis and Applications》2014
The characterization of the inclusion of Waterman–Shiba spaces ΛBV(p) into generalized Wiener classes of functions BV(q;δ) is given. It uses a new and shorter proof and extends an earlier result of U. Goginava. 相似文献
57.
Karolina Kazmierczak 《Journal of solid state chemistry》2010,183(9):2087-2094
The potassium lanthanide double sulphates KLn(SO4)2·H2O (Ln=La, Nd, Sm, Eu, Gd, Dy) were obtained by evaporation of aqueous reaction mixtures of rare earth (III) sulphates and potassium thiocyanate at 298 K. X-ray single-crystal investigations show that KLn(SO4)2·H2O (Ln=Nd, Sm, Eu, Gd, Dy) crystallise monoclinically (Ln=Sm: P21/c, Z=4, a=10.047(1), b=8.4555(1), c=10.349(1) Å, wR2=0.060, R1=0.024, 945 reflections, 125 parameters) while KLa(SO4)2·H2O adopts space group P3221 (Z=3, a=7.1490(5), c=13.2439(12) Å, wR2=0.038, R1=0.017, 695 reflections, 65 parameters). The coordination environment of the lanthanide ions in KLn(SO4)2·H2O is different in the case of the Nd/Sm/Gd and the Eu/Dy compounds, respectively. In the first case the Ln atoms are nine-fold coordinated in contrast to the latter where the Ln ions are eight-fold coordinated by oxygen atoms. The vibrational spectra of KLn(SO4)2·H2O and the UV-vis reflection spectra of KEu(SO4)2·H2O and KNd(SO4)2·H2O are also reported. 相似文献
58.
Several rare‐earth cyclotriphosphate hydrates were obtained from mixtures of sodium cyclotriphosphates and the respective rare‐earth chlorides. Nd(P3O9) · 3H2O [P$\bar{6}$ , Z = 3, a = 677.90(9), c = 608.67(9) pm, R1 = 0.016, wR2 = 0.038, 312 data, 36 parameters] was obtained by a solid state reaction and is isotypic with respective rare‐earth phosphate hydrates, while all the others adopt new structure types. Nd(P3O9) · 4.5H2O [C2/c, Z = 8, a = 1644.6(3), b = 756.11(15), c = 1856.1(4) pm, β = 97.25(3)°, R1 = 0.032, wR2 = 0.081, 1763 data, 194 parameters], Nd(P3O9) · 5H2O [P21/c, Z = 4, a = 773.75(15), b = 1149.1(2), c = 1394.9(3) pm, β = 106.07(3)°, R1 = 0.042, wR2 = 0.082, 1338 data, 194 parameters], Pr(P3O9) · 5H2O [P$\bar{1}$ , Z = 2, a = 745.64(15), b = 889.07(18), c = 934.55(19) pm, α = 79.00(3), β = 80.25(3), γ = 66.48(3), R1 = 0.059, wR2 = 0.089, 1468 data, 193 parameters], Na3Nd(P3O9)2 · 6H2O [P21/n, Z = 4, a = 1059.78(18), b = 1207.25(15), c = 1645.7(4) pm, β = 99.742(17), R1 = 0.047, wR2 = 0.119, 1109 data, 351 parameters] and Na3Pr(P3O9)2 · 6H2O [P21/n, Z = 4, a = 1061.42(16), b = 1209.0(2), c = 1635.5(3) pm, β = 99.841(13), R1 = 0.035, wR2 = 0.062, 1323 data, 350 parameters] were obtained by careful crystallization at room temperature. A thorough structure discussion is given. The infrared spectrum of Nd(P3O9) · 4.5H2O is also reported. 相似文献
59.
Ruben Mirzoyan Nathanael P. Kazmierczak Prof. Ryan G. Hadt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(37):9482-9494
In the past decade, transition metal complexes have gained momentum as electron spin-based quantum bit (qubit) candidates due to their synthetic tunability and long achievable coherence times. The decoherence of magnetic quantum states imposes a limit on the use of these qubits for quantum information technologies, such as quantum computing, sensing, and communication. With rapid recent development in the field of molecular quantum information science, a variety of chemical design principles for prolonging coherence in molecular transition metal qubits have been proposed. Here the spin-spin, motional, and spin-phonon regimes of decoherence are delineated, outlining design principles for each. It is shown how dynamic ligand field models can provide insights into the intramolecular vibrational contributions in the spin-phonon decoherence regime. This minireview aims to inform the development of molecular quantum technologies tailored for different environments and conditions. 相似文献
60.