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排序方式: 共有41条查询结果,搜索用时 15 毫秒
1.
Manju Rajeswaran Thomas N. Blanton David R. Whitcomb Nicholas Zumbulyadis Brian J. Antalek Scott T. Misture 《Journal of solid state chemistry》2006,179(4):1053-1059
In continuation of our interest in solid-state structures of silver complexes of photographic importance, the structure for silver benzotriazole (AgBZT), has now been obtained. The preferred method for solving crystal structures is via single-crystal X-ray diffraction (XRD). However, for some materials, growing single crystals of appropriate size and quality is often difficult or even impossible. AgBZT is an example of such a silver complex with poor solubility. The usual routes to preparing single crystals using recrystallization from a cooperating solvent resulted in polycrystalline powder samples. We propose a crystal structure for AgBZT, solved from synchrotron X-ray powder diffraction data, using a direct-space Monte Carlo simulated annealing approach. AgBZT crystals are monoclinic, (P21/c), with unit cell dimensions, a=14.8052(3) Å, b=3.7498(4) Å, c=12.3495(12) Å, and β=114.200(6)°. The AgBZT complex is constructed from all three of the Benzotriazole (BZT) nitrogens bonding to a separate silver atom. As a consequence of this bonding mode, the structure is a highly cross-linked, coordination polymer. 相似文献
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Tom Otieno Jaime R. Blanton M. Jason Hatfield Sherry L. Asher Sean Parkin 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):m182-m185
The reaction of Cu(ClO4)2·6H2O, NaAsF6 and excess pyrazole yields hexakis(pyrazole‐κN2)copper(II) bis(hexafluoroarsenate), [Cu(C3H4N2)6](AsF6)2 or [Cu(pzH)6](AsF6)2 (pzH is pyrazole), (I). The analogous hexakis(pyrazole‐κN2)copper(II) hexafluorophosphate perchlorate complex, [Cu(C3H4N2)6](PF6)1.29(ClO4)0.71 or [Cu(pzH)6](PF6)1.29(ClO4)0.71, (II), is obtained in a similar fashion, using KPF6 in place of NaAsF6. Both compounds contain the hitherto unknown [Cu(pzH)6]2+ complex cation, in which the copper(II) ion lies at the center of a regular octahedron of coordinated N atoms. The cation has crystallographically imposed symmetry. The X‐ray data indicate that the lack of the expected distortion can be accounted for by the presence of either static Jahn–Teller disorder or dynamic Jahn–Teller distortion. 相似文献
5.
Ana C. Stephens Eric J. Knuth Maria L. Blanton Isil Isler Angela Murphy Gardiner Tim Marum 《The Journal of Mathematical Behavior》2013
This paper reports results from a written assessment given to 290 third-, fourth-, and fifth-grade students prior to any instructional intervention. We share and discuss students’ responses to items addressing their understanding of equation structure and the meaning of the equal sign. We found that many students held an operational conception of the equal sign and had difficulty recognizing underlying structure in arithmetic equations. Some students, however, were able to recognize underlying structure on particular tasks. Our findings can inform early algebra efforts by highlighting the prevalence of the operational view and by identifying tasks that have the potential to help students begin to think about equations in a structural way at the very beginning of their early algebra experiences. 相似文献
6.
TN Ruckmongathan 《Pramana》1999,53(1):199-212
Liquid crystal displays had a humble beginning with wrist watches in the seventies. Continued research and development in
this multi-disciplinary field have resulted in displays with increased size and complexity. After three decades of growth
in performance, LCDs now offer a formidable challenge to the cathode ray tubes (CRT).
A major contribution to the growth of LCD technology has come from the developments in addressing techniques used for driving
matrix LCDs. There are several approaches like passive matrix addressing, active matrix addressing and plasma addressing to
drive a matrix display.
Passive matrix LCD has a simple construction and uses the intrinsic non-linear characteristic of the LCD for driving. Departure
from conventional line by line addressing of a passive matrix has resulted in improved performance of the display. Orthogonal
functions have played a crucial role in the development of passive matrix addressing. Simple orthogonal functions that are
useful for driving a matrix LCD are introduced. The basics of driving several rows simultaneously (multi-line addressing)
are discussed by drawing analogies from multiplexing in communication. The impact of multi-line addressing techniques on the
performance of the passive matrix LCDs in comparison with the conventional technique will be discussed. 相似文献
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Conor J. Twomey Shaw H. Chen Thomas N. Blanton Ansgar Schmid Kenneth L. Marshall 《Journal of Polymer Science.Polymer Physics》1994,32(10):1687-1695
In view of the residual crystallinity in PEO found to limit the solubility of some Nd3+-compounds, amorphous PEO (aPEO) was synthesized for exploration as an alternative host. Complexation, solubility limit, morphology, and response to moisture absorption in the doped systems were investigated using FTIR, DSC, TGA, and WAXD techniques. Representing a perturbation to the structural regularity present in PEO, aPEO was found to present lower solubilities for dopants (Nd(act)3 and Nd(acac)3, both characterized by a weak Nd3+–ether oxygen interaction. On the other hand, no difference in solubility was observed for dopant Nd(NO3)3, characterized by a strong Nd3+–ether oxygen interaction. Laser interferometry was employed to assess film homogeneity of the Nd(NO3)3-doped systems across a 20-mm diameter, and the measured peak-to-valley distortion values were observed to be encouraging for practical applications. © 1994 John Wiley & Sons, Inc. 相似文献
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Blanton WB 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,162(2):269-283
Computational power, speed, and algorithmic complexity are increasing at a continuing rate. As a result, scientific simulations continue to investigate more and more complex systems. Nuclear magnetic resonance (NMR) is no exception. NMR theory and language is extremely well developed, that simulations have become a standard by which experiments are measured. Nowadays, complex computations can be performed on normal workstations and workstation clusters. Basic numerical operations have also become extremely optimized and new computer language paradigms have become implemented. Currently there exists no complete NMR tool kit which uses these newer techniques. This paper describes such a tool kit, BlochLib. BlochLib is designed to be the next generation of NMR simulation packages; however, the basic techniques implemented are applicable to almost any problem. BlochLib enables the user to simulate almost any NMR idea both experimental or theoretical in nature. Both classical and quantum mechanical techniques are included and demonstrated, as well as several powerful user interface tools. The total tool kit and documentation can be found at http://waugh.cchem.berkeley.edu/blochlib/. 相似文献
10.
Rajeswaran M Blanton TN Zumbulyadis N Giesen DJ Conesa-Moratilla C Misture ST Stephens PW Huq A 《Journal of the American Chemical Society》2002,124(48):14450-14459
The three-dimensional structure, conformation, and packing of molecules in the solid state are crucial components used in the optimization of many technologically useful materials properties. Single-crystal X-ray diffraction is the traditional and most effective method of determining 3-D structures in the solid state. Obtaining single crystals that are sufficiently large and free of imperfections is often laborious, time-consuming, and, occasionally, impossible. The feasibility of an integrated approach to the determination and verification of a complete three-dimensional structure for a medium-sized organic molecule without using single crystals is demonstrated for the case of an organic stabilizer compound N-(p-tolyl)-dodecylsulfonamide. The approach uses a combination of powder XRD data, several computational packages involving Monte Carlo simulations and ab initio quantum mechanical calculations, and experimental solid-state NMR chemical shifts. Structure elucidation of N-(p-tolyl)-dodecylsulfonamide revealed that the Bravais lattice is monoclinic, with cell dimensions of a = 38.773 A, b = 5.507 A, c = 9.509 A, and beta = 86.35 degrees, and a space group of P21/c. 相似文献