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151.
152.
Claire A. Krasinski Benjamin L. Solomon Firas F. Awwadi Christopher P. Landee Jan L. Wikaira 《Journal of Coordination Chemistry》2017,70(5):914-935
Reaction of 4-amino-2-fluoropyridine (2-F-4-AP) with copper halides produced the neutral coordination complexes: (2-F-4-AP)2CuX2 (X = Cl(1), Br(2)). 1 crystallizes in the orthorhombic space group Pccn in a distorted square planar geometry. Magnetic susceptibility data were fit to the uniform chain Heisenberg model resulting in C = 0.439(6)emu-K/mole-Oe and J = ?28(1) K. 2 crystallizes in the monoclinic space group C2/m and is closer to distorted tetrahedral. Intermolecular Br?Cu contacts generate a square layer. Magnetic data show very weak ferromagnetic interactions [C = 0.42(1)emu-K/mol-Oe, J = 0.71(2) K]. Similarly, reaction of 2-F-4-AP with copper halides and aqueous HX in alcohol solvents produced the salts (2-F-4-APH)2CuX4 (X = Cl(3), Br(4)). 3 crystallizes in the triclinic space group P-1. Crystal packing reveals short Cl?Cl contacts which generate a structural ladder. However, analysis of the magnetic data suggests that only the rails of the ladder produce a viable magnetic superexchange pathway; the uniform Heisenberg chain model provides C = 0.449(1)emu-K/mol-Oe and J = -6.9(1) K. 4 is isostructural and is also best fit by a chain model [J = ?2.7(4) K]. The brominated complex (2-F-3-Br-4-APH)2CuBr4·2H2O, 5, (2-F-3-Br-4-APH = 4-amino-3-bromo-2-fluoropyridinium) was serendipitously produced as a byproduct of the synthesis of 4 and was characterized by single-crystal X-ray diffraction. 相似文献
153.
NirmlaDevi Thakur Vilas G. Gaikar Debasis Sen Subhasish Mazumder Nancy S. Pandita 《Analytical letters》2017,50(4):690-711
A green method using Juglans regia bark extract was used to synthesize silver nanoparticles at room temperature with monitoring by absorption spectroscopy. The size and shape of the synthesized nanoparticles were characterized by infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and small-angle X-ray scattering. The average particle size was from 10 to 30?nm. Gas chromatography–mass spectrometry (GC–MS) was used for the separation, identification, and quantification of components of the plant extracts. A possible mechanism for the synthesis of nanoparticles was elucidated based on the GC–MS results. The synthesized silver nanoparticles showed effective inhibition against Streptococcus mutans, which is the main causative agent for dental caries. The nanoparticles also showed promising antibiofilm activity by inhibiting the glucosyltransferase enzyme. 相似文献
154.
Sara Luisa Rodríguez De Luna Luis Ángel GarzaSylvain Bernès Perla ElizondoBlanca Nájera Nancy Pérez 《Polyhedron》2010
A series of mononuclear complexes based on lanthanide ions has been synthesized and X-ray characterized. The compounds [LnIIIL2(NO3)3(H2O)2] (Ln = La, Ce, Pr, Nd, Sm, Gd and Tm; L = 2,6-bis(2-formylphenoxymethyl)pyridine) are found to be isomorphous and isostructural. Ligand L systematically coordinates through one carbonyl functionality, and the resulting complexes are placed on a twofold axis in crystals belonging to C2/c space-group. Emission spectra for Ln = La, Pr, Nd revealed a correlation between the Ln–O coordination bond length and the photoluminescent properties of the complexes, in line with a Förster–Dexter mechanism for intramolecular energy transfer. Ligand L is therefore a suitable sensitizer for lanthanide ions. 相似文献
155.
Brodie-Linder N Le Caër S Alam MS Renault JP Alba-Simionesco C 《Physical chemistry chemical physics : PCCP》2010,12(42):14188-14195
Measurement of H(2) production from electron irradiation (10 MeV) on SBA-15 materials has shown that adsorbed water is attacked preferentially. Silanol groups are only attacked when they are in the majority with respect to adsorbed water, however they are much less efficient at producing H(2). The comparison between water content before and after electron irradiation and the corresponding H(2) production indicates that water desorption is the main route to adsorbed water loss for SBA-15 materials. On the other hand, surface silanol groups are more susceptible to attack, leading to H(2) production when SBA-15 samples have undergone extensive thermal treatment. Electron irradiation of SBA-15-Cu materials has shown that the presence of Cu(II) on the surface reduces and inhibits the production of H(2.) This inhibiting power affects adsorbed water bonded to grafted copper but not surface silanol groups. 相似文献
156.
Jeng-Hao Pai Wei Xu Christopher E. Sims Nancy L. Allbritton 《Analytical and bioanalytical chemistry》2010,398(6):2595-2604
Cell microarrays with culture sites composed of individually removable microstructures or micropallets have proven benefits
for isolation of cells from a mixed population. The laser energy required to selectively remove these micropallets with attached
cells from the array depends on the microstructure surface area in contact with the substrate. Laser energies sufficient to
release micropallets greater than 100 μm resulted in loss of cell viability. A new three-dimensional culture site similar
in appearance to a table was designed and fabricated using a simple process that relied on a differential sensitivity of two
photoresists to UV-mediated photopolymerization. With this design, the larger culture area rests on four small supports to
minimize the surface area in contact with the substrate. Microtables up to 250 × 250 μm were consistently released with single
10-μJ pulses to each of the four support structures. In contrast, microstructures with a 150 × 150-μm surface area in contact
with the substrate could not be reliably released at pulse energies up to 212 μJ. Cassie–Baxter wetting is required to provide
a barrier of air to localize and sequester cells to the culture sites. A second asset of the design was an increased retention
of this air barrier under conditions of decreased surface tension and after prolonged culture of cells. The improved air retention
was due to the hydrophobic cavity created beneath the table and above the substrate which entrapped air when an aqueous solution
was added to the array. The microtables proved an efficient method for isolating colonies from the array with 100% of selected
colonies competent to expand following release from the array. 相似文献
157.
Wei Xu Alicia M. Luikart Christopher E. Sims Nancy L. Allbritton 《Analytical and bioanalytical chemistry》2010,397(8):3377-3385
A novel contact printing method utilizing a sacrificial layer of polyacrylic acid (PAA) was developed to selectively modify
the upper surfaces of arrayed microstructures. The method was characterized by printing polystyrene onto SU-8 microstructures
to create an improved substrate for a cell-based microarray platform. Experiments measuring cell growth on SU-8 arrays modified
with polystyrene and fibronectin demonstrated improved growth of NIH 3T3 (93% vs. 38%), HeLa (97% vs. 77%), and HT1080 (76%
vs. 20%) cells relative to that for the previously used coating method. In addition, use of the PAA sacrificial layer permitted
the printing of functionalized polystyrene, carboxylate polystyrene nanospheres, and silica nanospheres onto the arrays in
a facile manner. Finally, a high concentration of extracellular matrix materials (ECM), such as collagen (5 mg/mL) and gelatin
(0.1%), was contact-printed onto the array structures using as little as 5 μL of the ECM reagent and without the formation
of a continuous film bridge across the microstructures. Murine embryonic stem cells cultured on arrays printed with this gelatin
hydrogel remained in an undifferentiated state indicating an adequate surface gelatin layer to maintain these cells over time. 相似文献
158.
Yosef E. Maruvka Nadav M. Shnerb Sorin Solomon Gur Yaari David A. Kessler 《Journal of statistical physics》2011,142(6):1302-1316
The inference of past demographic parameters from current genetic polymorphism is a fundamental problem in population genetics.
The standard techniques utilize a reconstruction of the gene-genealogy, a cumbersome process that may be applied only to small
numbers of sequences. We present a method that compares the total number of haplotypes (distinct sequences) with the model
prediction. By chopping the DNA sequence into pieces we condense the immense information hidden in sequence space into a function
for the number of haplotypes versus subsequence size. The details of this curve are robust to statistical fluctuations and
are seen to reflect the process parameters. This procedure allows for a clear visualization of the quality of the fit and,
crucially, the numerical complexity grows only linearly with the number of sequences. Our procedure is tested against both
simulated data as well as empirical mtDNA data from China and provides excellent fits in both cases. 相似文献
159.
The structural evolution of orthorhombic CaTiO3 perovskite has been studied using high-pressure single-crystal x-ray diffraction under hydrostatic conditions up to 8.1 GPa and under a non-hydrostatic stress field formed in a diamond anvil cell (DAC) up to 4.7 GPa. Under hydrostatic conditions, the TiO6 octahedra become more tilted and distorted with increasing pressure, similar to other 2:4 perovskites. Under non-hydrostatic conditions, the experiments do not show any apparent difference in the internal structural variation from hydrostatic conditions and no additional tilts and distortions in the TiO6 octahedra are observed, even though the lattice itself becomes distorted due to the non-hydrostatic stress. The similarity between the hydrostatic and non-hydrostatic cases can be ascribed to the fact that CaTiO3 perovskite is nearly elastically isotropic and, as a consequence, its deviatoric unit-cell volume strain produced by the non-hydrostatic stress is very small; in other words, the additional octahedral tilts relevant to the extra unit-cell volume associated with the deviatoric unit-cell volume strain may be totally neglected. This study further addresses the role that three factors--the elastic properties, the crystal orientation and the pressure medium--have on the structural evolution of an orthorhombic perovskite loaded in a DAC under non-hydrostatic conditions. The influence of these factors can be clearly visualized by plotting the three-dimensional distribution of the deviatoric unit-cell volume strain in relation to the cylindrical axis of the DAC and indicates that, if the elasticity of a perovskite is nearly isotropic as it is for CaTiO3, the other two factors become relatively insignificant. 相似文献
160.
We prove that the length of the boundary of a J-holomorphic curve with Lagrangian boundary conditions is dominated by a constant times its area. The constant depends on the symplectic form, the almost complex structure, the Lagrangian boundary conditions and the genus. A similar result holds for the length of the real part of a real J-holomorphic curve. The infimum over J of the constant properly normalized gives an invariant of Lagrangian submanifolds. We calculate this invariant to be \({2\pi}\) for the Lagrangian submanifold \({\mathbb{R} P^n \subset \mathbb{C} P^n.}\) We apply our result to prove compactness of moduli of J-holomorphic maps to non-compact target spaces that are asymptotically exact. In a different direction, our result implies the adic convergence of the superpotential. 相似文献