Palladium catalyzed synthesis of mandelate derivatives from arylboronic acids and glyoxylate hemiacetals

NHC-coordinated cyclometalated palladium(II) catalyzed addition of arylboronic acids to methyl 2-hydroxy-2-methoxyacetate gave corresponding various functionalized methyl mandelate derivatives in good yields.     

Study on the Morphological Change of Growing Ag Crystallites by in-situ SEM Observation

The morphology of the initial growth stage of Ag thin films on Mo(110) substrate was investigated in-situ by the scanning electron microscope (SEM). A great majority of the Ag crystallites showed a truncated Wulff's equilibrium shape of the face-centered-cubic (fcc) structure with epitaxial orientation [1 0]Ag//[11 ]Mo, (111)Ag//(110)Mo with the substrate temperature of 400 °C. In-situ SEM observation during the growth revealed two kinds of particular morphological change of Ag crystallites, namely (1) rotation of an Ag crystallite and (2) reformation of the crystal faces of the Ag crystallite. However, a small number of Ag crystal particles showed Wulff-polyhedron truncated by the (100) plane parallel to the substrate surface (oriented to the 〈100〉 axis normal to the substrate surface).     

The Diameters of Some Transition Graphs Constructed from Hamilton Cycles

 A complete undirected graph of order n has Hamilton cycles. We consider the diameter of a transition graph whose vertices correspond to those Hamilton cycles and any of two vertices are adjacent if and only if the corresponding Hamilton cycles can be transformed each other by exchanging two edges. Moreover, we consider several transition graphs related to it. Received: November 4, 1999 Final version received: August 28, 2000     

Production, analysis, and application of spatially resolved shells in solid-phase polymer spheres

Two-photon fluorescence microscopy has been used to interrogate the interior functionality of polymer resin beads. By employing this technique, the spatial distribution of the initial functionality contained within the polymer matrix has been determined. Spatially resolved, concentric shells were then produced synthetically in these polymer spheres via a series of protection/deprotection reactions in which two-photon fluorescence microscopy was employed to monitor each successive step. To demonstrate the potential utility of these techniques in combinatorial screening, a set of beads was prepared containing a unique tripeptide sequence in each of the three concentric shells within each individual bead. The set was then screened for the binding affinity of each tripeptide toward a fluorescent ligand.     

CONFIGURATIONS OF NEUROSPORENE ISOMERS ISOLATED FROM THE REACTION CENTER AND THE LIGHT-HARVESTING COMPLEX OF Rhodobacter spheroides G1C. A RESONANCE RAMAN, ELECTRONIC ABSORPTION, AND 1H-NMR STUDY

Abstract— HPLC analysis of neurosporene extracted from the chromatophore membranes of Rhodobacter spheroides G1C showed two isomeric components 1 and 2. Extract from the light-harvesting complex (LH) gave only component 2, while extract from the reaction center (RC) mainly gave component 1. Both components were isolated, and their configurations were determined by means of (1) resonance Raman, (2) electronic absorption, and (3) ¹H-HMR spectroscopy. The configuration of component 2 originating from LH was determined to be all -trans and that of component 1 from RC was determined to be 15- cis . Thus, our previous configurational prediction of this particular carotenoid bound to RC, by means of resonance Raman spectroscopy, to be 15-cis [Y. Koyama, T. Takii, K. Saiki and K. Tsukida, Photobiochem. Photobiophys. 5 (1983)139–150] is confirmed.     

Some chemical transformations of 7a-cyanohexahydro-1H-pyrrolizine into 7a-substituted hexahydro-1H-pyrrolizines

Chemical transformations of 7a-cyanohexahydro-1H-pyrrolizine ( 2 ) into 7a-substituted hexahydro-1H-pyrrolizines are described. In the reaction of 2 with lithium aluminum hydride, the orientation of the lone pair of the bridgehead nitrogen against C-CN bond can be regarded as significant.     

Bijections Between Group Rings Preserving Character Sums

Generalizing an idea in [13], we exhibit some, in general nonhomomorphic, bijections between finite groups which preserve the absolute value of character sums. As a consequence, the existence of a single difference set, relative difference set, building set etc. in certain groups implies the existence of such objects in many other groups.     

Minimizing a monotone concave function with laminar covering constraints

Let V be a finite set with |V|=n. A family F⊆2^V is called laminar if for all two sets X,Y∈F, X∩Y≠∅ implies X⊆Y or X⊇Y. Given a laminar family F, a demand function , and a monotone concave cost function , we consider the problem of finding a minimum-cost such that x(X)?d(X) for all X∈F. Here we do not assume that the cost function F is differentiable or even continuous. We show that the problem can be solved in O(n²q) time if F can be decomposed into monotone concave functions by the partition of V that is induced by the laminar family F, where q is the time required for the computation of F(x) for any . We also prove that if F is given by an oracle, then it takes Ω(n²q) time to solve the problem, which implies that our O(n²q) time algorithm is optimal in this case. Furthermore, we propose an algorithm if F is the sum of linear cost functions with fixed setup costs. These also make improvements in complexity results for source location and edge-connectivity augmentation problems in undirected networks. Finally, we show that in general our problem requires Ω(2^n/2q) time when F is given implicitly by an oracle, and that it is NP-hard if F is given explicitly in a functional form.