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941.
Akbar Ali Mohammad Huq Mirza Aminul Haji Iran Malai Shah Butcher Ray J. Tarafder M.T.H. Boon Keat Tan Manaf Ali A. 《Transition Metal Chemistry》2002,27(3):262-267
Copper(II) complexes of general formula, Cu(NNS)X
2 · nH2O (NNS = the 2-formylpyridine Schiff base of N-methyl-S-methyldithiocarbazate; X = Cl–, Br–, I–, NCS–; n = 0, 2) have been synthesized and characterized by elemental analysis and by magnetic and spectroscopic techniques. Based on magnetic and spectroscopic data, a monomeric five-coordinate square-pyramidal structure is assigned to these complexes. The crystal and molecular structure of [Cu(NNS)I2] has been determined by X-ray diffraction. The complex has a monomeric square-pyramidal structure with the ligand coordinated to the copper(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thione sulfur atom. The fourth and fifth coordination sites are occupied by the iodide ligands. Antimicrobial tests indicate that Schiff base is inactive against the bacteria, Bacillus subtilis (mutant defective DNA repair), Pseudomonas aeruginosa, methicillin resistant Staphylococcus aureus and Bacillus subtilis (wild type) and weakly active against the fungi, Candida albicans, Candida lypolytica, Saccharomyces cereviseae and Aspergillus ochraceous but its copper(II) complexes, Cu(NNS)X
2 are strongly active against these organisms. A cytotoxicity study of the compounds against leukemic and cervical cancer cells showed that the Schiff base is inactive, but the complexes, [Cu(NNS)I2] and [Cu(NNS)(NCS)2] · 2H2O exhibit significant activity against cervical cancer cells with CD50 values of 4.8 and 4.2 g, respectively. 相似文献
942.
S-Methyl 3-((2-hydroxyphenyl)methyl)dithiocarbazate (H(2)L(1)) and its bromo derivative (H(2)L(2)), which are traditionally biprotic tridentate (ONS) ligands, behave in an unprecedented manner when allowed to react with [VO(acac)(2)] under an oxidative environment in acetonitrile-water medium containing a catalytic amount of alkali metal ion. The products obtained are oxovanadium(V) compounds [VOL(L(cyclic))] (L = L(1), 1a, and L(2), 1b) that contain one molecule of ligand which undergoes metal-induced cyclization to form a thiadiazole ring. Compound 1a crystallizes in the triclinic space group P(-)1 with a = 9.1830(9) A, b = 9.4165(12) A, c = 12.700(2) A, alpha = 100.988(8)(o), beta = 100.195(7)(o), gamma = 78.774(8)(o), V = 1046.3(2) A(3), and Z = 2. With cobalt(III), however, the products [CoL(HL)].H(2)O (L = L(1), 2a, and L(2), 2b) have hydrogen-bonded dimeric structures with each ligand virtually carrying 1.5 units of negative charge as confirmed by X-ray crystal structure analysis of 2a. It also crystallizes in triclinic space group P(-)1 with a = 12.0842(8) A, b = 13.5251(9) A, c = 14.1960(10) A, alpha = 78.122(6)(o), beta = 73.888(6)(o), gamma = 78.255(6)(o), V = 2154.7(3) A(3), and Z = 4. In solution, 2a is a symmetric molecule as indicated by (1)H NMR, involving a characteristic hydrogen-bonded O-H-O broad feature in the downfield (at 14.5 ppm) connecting both monoprotonated (LH(-)) and deprotonated (L(2-)) forms of the ligand--a situation somewhat analogous to the classic H-F-H case as observed in bifluoride ion. 相似文献
943.
Vyas PV Ray P Trivedi GS Adhikary SK Rangarajan R 《Journal of colloid and interface science》2002,246(2):366-371
The variations of the selectivity coefficient K(A)(B) between Na(+)-H(+), Na(+)-K(+), and Na(+)-Cu(2+) systems and the separation factor alpha(A)(B) between Na(+)-Cu(2+) and K(+)-Cu(2+) systems in cation-exchange membranes as functions of loading and particle size of resin have been measured. The exchange affinities of all the membranes increase as H(+)相似文献
944.
S. Sinha A.K. Ray S. Kundu S. Sasikumar S.K.S. Nair K. Dasgupta 《Applied physics. B, Lasers and optics》2001,72(5):617-621
The photo-stability of laser dyes, Rhodamine-6G, Rhodamine-B, and Kiton-Red, under high repetition rate (6.3 kHz) Copper-vapour-laser
(CVL) irradiation has been investigated. Exhaustive photo-bleaching of these dyes in different solvents has been carried out
to study the extent to which the dye photo-degraded products would interfere with the lasing process in high-power CVL-pumped
dye lasers. Our results indicate that the photo-degradation of dyes occurs predominantly through excited-state intermolecular
reactions, involving the singlet state, rather than the process of nonlinear optical absorption in individual molecules.
Received: 13 March 2000 / Revised version: 2 August 2000 / Published online: 21 March 2001 相似文献
945.
The Iwasawa manifold is uplifted to seven‐folds of either G2 holonomy or SU(3) structure, explicit new metrics for the same having been constructed in this work. We uplift the Iwasawa manifold to a G2 manifold through “size” deformation (of the Iwasawa metric), via Hitchin's Flow equations, showing also the impossibility of the uplift for “shape” and “size” deformations (of the Iwasawa metric). Using results of Dall'Agata and Prezas, Phys. Rev. D 69 , 066004 (2004) [arXiv:hep‐th/0311146] [1], we also uplift the Iwasawa manifold to a 7‐fold with SU(3) structure through “size” and “shape” deformations via generalisation of Hitchin's Flow equations. For seven‐folds with SU(3)‐structure, the result could be interpreted as M5‐branes wrapping two‐cycles embedded in the seven‐fold (as in [1]) ‐ a warped product of either a special hermitian six‐fold or a balanced six‐fold with the unit interval. There can be no uplift to seven‐folds of SU(3) structure involving non‐trivial “size” and “shape” deformations (of the Iwasawa metric) retaining the “standard complex structure” ‐ the uplift generically makes one move in the space of almost complex structures such that one is neither at the standard complex structure point nor at the “edge”. Using the results of Konopelchenko and Landolfi, J. Geom. Phys. 29 , 319 (1999) [arXiv:math.DG/9804144] [2], we show that given two “shape deformation” functions, and the dilaton, one can construct a Riemann surface obtained via Weierstraß representation for the conformal immersion of a surface in R l, for a suitable l, with the condition of having conformal immersion being a quadric in CP l‐1. 相似文献
946.
Selected joaquinite minerals have been studied by Raman spectroscopy. The minerals are categorised into two groups depending upon whether bands occur in the 3250 to 3450 cm−1 region and in the 3450 to 3600 cm−1 region, or in the latter region only. The first set of bands is attributed to water stretching vibrations and the second set to OH stretching bands. In the literature, X‐ray diffraction could not identify the presence of OH units in the structure of joaquinite. Raman spectroscopy proves that the joaquinite mineral group contains OH units in their structure, and in some cases both water and OH units. A series of bands at 1123, 1062, 1031, 971, 912 and 892 cm−1 are assigned to SiO stretching vibrations. Bands above 1000 cm−1 are attributable to the νas modes of the (SiO4)4− and (Si2O7)6− units. Bands that are observed at 738, around 700, 682 and around 668, 621 and 602 cm−1 are attributed to O Si O bending modes. The patterns do not appear to match the published infrared spectral patterns of either (SiO4)4− or (Si2O7)6− units. The reason is attributed to the actual formulation of the joaquinite mineral, in which significant amounts of Ti or Nb and Fe are found. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
947.
Ray L. Frost Jií ejka Godwin A. Ayoko Matt L. Weier 《Journal of Raman spectroscopy : JRS》2007,38(10):1311-1319
Raman at 298 and 77 K and infrared spectra of two samples of sodium‐zippeite were studied and interpreted. U O bond lengths in uranyl were calculated and compared with those inferred from the X‐ray single crystal structure data of a synthetic sodium‐zippeite analogue. Hydrogen‐bonding network in the studied samples is discussed. O H…O bond lengths were calculated and compared with those predicted from the X‐ray single crystal structure analysis. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
948.
Infrared and Raman spectroscopy were used to characterise synthetic mixed carbonate and vanadate hydrotalcites of formula Mg6Al2(OH)16(CO3)2−, (VO4)3−·4H2 O. The spectra were used to assess the molecular assembly of the cations and anions in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based on (1) the carbonate anion (2) the hydroxyl units and (3) water units. Bands were assigned to the hydroxyl stretching vibrations of water. Three types of carbonate anions were identified: (1) carbonate hydrogen‐bonded to water in the interlayer, (2) carbonate hydrogen‐bonded to the hydrotalcite hydroxyl surface and (3) free carbonate anions. It is proposed that the water is highly structured in the hydrotalcite, as it is hydrogen‐bonded to both the carbonate and the hydroxyl surface. The spectra were used to assess the contamination of carbonate in an open reacting vessel in the synthesis of vanadate hydrotalcites of formula Mg6Al2(OH)16(CO3)2−, (VO4)3−·4H2 O. Bands have been assigned to vanadate anions in the infrared and Raman spectra associated with V O bonds. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
949.
We present a method for estimating the net traction and resistive wheel torques for a suspensionless, differential-steered robot on rigid or deformable terrain. The method, based on extended Kalman-Bucy filtering (EKBF), determines time histories of net traction and resistive wheel torques and wheel slips during steady or transient maneuvers. This method assumes good knowledge of the vehicle dynamics and treats the unknown forces and moments due to terrain response as random variables to be estimated. A proprioceptive sensor suite renders a subset of the unknown forces and associated wheel slip and slip angles observable. This methodology decouples semi-empirical terramechanics models from the net effect of the vehicle-terrain interaction, namely the net traction developed by the vehicle on the terrain. By collecting sensor data and processing data off-line, force-slip characteristics are identified irrespective of the underlying terramechanics. These characteristics can in turn support development or validation of terramechanics models for the vehicle-terrain system. For autonomous robots, real-time estimates of force-slip characteristics can provide setpoints for traction and steering control, increasing vehicle performance, speed, and maneuverability. Finally, force-slip estimation is the first step in identifying terrain parameters during normal maneuvering. The methodology is demonstrated through both simulation and physical testing using a 13-kg robot. 相似文献
950.
Grzegorz Litak Tomasz Kamiński Jacek Czarnigowski Asok K. Sen Mirosław Wendeker 《Meccanica》2009,44(1):1-11
In this paper we analyze the cycle-to-cycle variations of peak pressure p
max
and peak pressure angle α
pmax
in a four-cylinder spark ignition engine. We examine the experimental time series of p
max
and α
pmax
for three different spark advance angles. Using standard statistical techniques such as return maps and histograms we show
that depending on the spark advance angle, there are significant differences in the fluctuations of p
max
and α
pmax
. We also calculate the multiscale entropy of the various time series to estimate the effect of randomness in these fluctuations.
Finally, we explain how the information on both p
max
and α
pmax
can be used to develop optimal strategies for controlling the combustion process and improving engine performance. 相似文献