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201.
202.
The synthesis of the Rhodococcus erythropolis siderophores heterobactins A and B, and the structurally related Nocardia heterobactin, is described. Two approaches for the assembly of these asymmetric ligand donor chelators are explored. In the first approach, a scheme predicated on the biosynthesis of the Paracoccus denitrificans siderophore, parabactin, is employed. In this approach, the central donor synthon is added last. In the second scheme, the central donor and the terminal 2,3-dihydroxybenzoyl fragment are first fixed to the ligand’s d-ornithine backbone. This is followed by condensation with the cyclic ornithine hydroxamate glycine segment. The schemes offer a flexible approach to other heterobactins. Job’s plots suggest that heterobactin A and Nocardia heterobactin form 1:1 ligand/metal complexes, while heterobactin B forms a 3:2 ligand/metal complex. 相似文献
203.
204.
Cover Picture: Sequential Anion and Cation Exchange Reactions for Complete Material Transformations of Nanoparticles with Morphological Retention (Angew. Chem. Int. Ed. 30/2015)
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205.
Jyh-Kang Chen Jeng-Rong Ho Yu-Hsuan Lin Raymond Chien-Chao Tsiang 《Applied Physics A: Materials Science & Processing》2011,105(1):249-254
This study characterizes electrical properties of silver thin films with meshed nanostructures fabricated through the photoreduction
of solid silver nitrate thin films using excimer laser irradiation. Variations of mesh morphology as functions of laser irradiation
time and fluences are examined; and the relationship between the film’s electrical resistance and mesh structure are addressed.
The course of nanomesh formation can be separated into two main phases: precipitation of silver nanoparticles as a result
of photoreduction; and, formation of mesh nanostructures through the photothermal effect. The resulting electrical resistance
depends strongly on the mesh nanostructure. With a suitable arrangement of laser fluence and irradiation time, silver thin
films with well interconnected nanomeshes can be fabricated. Results show that silver thin films with low electrical resistivity,
down to 8.5×10−8 Ω m, are easily obtainable. The laser reduction approach takes advantage of the flexibility in local patterning. Moreover,
the reduction is from a solid silver nitrate thin film and is executed in the ambient environment that renders this approach
a potential method for low-temperature fabrication of metallic electrode conductors for organic electronics. 相似文献
206.
We consider the diffraction of a time-harmonic acoustic plane wave by a rigid half-plane in a viscous fluid medium. The linearized equations of viscous fluid flow and the no-slip condition on the half-plane are used to derive a pair of disjoint Wiener-Hopf equations for the fluid stresses and velocities. The Wiener-Hopf equations are solved in conjunction with a requirement that the stresses are integrable near the edge of the half-plane. Specific wave components of the scattered velocity field are given analytically. A Padé approximation to the Wiener-Hopf kernel function is used to derive numerical results that show the effect of viscosity on the velocity field in the immediate vicinity of the edge of the half-plane. 相似文献
207.
A reversed-phase liquid chromatographic method was developed and validated for the determination of the content of free acetic acid, free succinic acid, acetyl substituents, and succinoyl substituents in hydroxypropyl methylcellulose acetate succinate (HPMCAS; Chemical Abstracts Service Registry No. 71138-97-1) polymer. This single new method gave accurate and precise measurement of both acetyl and succinoyl substituents, which had previously required 3 Japanese Pharmaceutical Excipients (JPE) methods to accomplish. Consequently, analysis time and turnaround time are decreased significantly. Furthermore, this method can also separate and determine the free acetic and succinic acids in HPMCAS polymer, a task that the corresponding JPE method cannot achieve. The values for accuracy (average recovery from 12 standard samples) were 99.9% for acetic acid and 99.8% for succinic acid. The values for injection precision (relative standard deviation [RSD]) were 0.11% for acetic acid and 0.28% for succinic acid. The values for intermediate precision (RSD) were 1.25% for determination of the acetyl content at the 8.78% (w/w) level and 1.33% for determination of the succinoyl content at the 10.9% (w/w) level. The values for intermediate precision (RSD) were 5.98% for determination of free acetic acid at the 0.12% (w/w) level and 5.13% for determination of free succinic acid at the 0.029% (w/w) level. The method was proven to be robust with respect to variation in the pH of the mobile phase, the concentration of potassium dihydrogen phosphate, and the flow rate. The method is well suited for quality control in today's fast-paced pharmaceutical laboratories. 相似文献
208.
A series of molecules of therapeutic interest, possessing the new skeleton of 1H-benzo[c]pyrido[2,3,4-kl]acridine with acyl or aminoacyl and methoxy or aminoalkoxy substituents on the aromatic homocycles were synthesized by means of a Friedl?nder-type reaction. The requisite 5-aminodihydroquinoline-4-ones 1, whose preparation is described, were reacted with the appropriate alpha-tetralones 2 using an acidic catalyst (PPTS) under azeotropic conditions. Optimized reaction time and yield depend on temperature, which must not be below 90 degrees C. 相似文献
209.
Mund G Gabert AJ Batchelor RJ Britten JF Leznoff DB 《Chemical communications (Cambridge, England)》2002,(24):2990-2991
An unusual metal-ligand binding motif is found in dimeric cobalt(II) complexes coordinated by diamidoether ligands that bridge the metals in a 'serpentine' fashion through the ether donors of the ligand backbone rather than the amido groups. 相似文献
210.
The concept of supported ionic liquid catalysis (silc) has successfully been applied to hydrogenation reactions, which significantly reduced the required amounts of ionic liquid phase and enabled the usage of fixed-bed technology; the resulting catalysts exhibited high activity and outstanding stability. 相似文献