Formation of octacalcium phosphates with co-incorporated succinate and suberate ions

Octacalcium phosphates (OCPs) co-incorporated with various molar ratios of succinate and suberate ions were synthesized by wet processing. The interplanar spacings of the (100) planes (d(100)) of OCPs formed in the presence of succinic acid (Suc) or suberic acid (Sub) were larger than those of OCPs formed without addition of a dicarboxylic acid to the reaction solvent. The increases in the interplanar spacings of the (100) planes were caused by substitution of HPO(4)(2-) by dicarboxylate ions. The OCPs with co-incorporated succinate and suberate ions, i.e. solid solutions of OCP with incorporated Suc and Sub, were formed by reactions in the presence of Suc and Sub. When the Suc/(Suc + Sub) values in the starting compositions were in the range 0.45-1.0, Suc was preferentially incorporated into the OCP. In contrast, when the Sub/(Suc + Sub) values in the starting compositions were in the range 0.60-1.0, Sub was preferentially incorporated into the OCP crystals.     

Extreme points, support points and the Loewner variation in several complex variables

In this paper we consider extreme points and support points for compact subclasses of normalized biholomorphic mappings of the Euclidean unit ball Bn in Cn. We consider the class S0(Bn) of biholomorphic mappings on Bn which have parametric representation, i.e., they are the initial elements f (·, 0) of a Loewner chain f (z, t) = etz + ··· such that {e-tf (·, t)}t 0 is a normal family on Bn. We show that if f (·, 0) is an extreme point (respectively a support point) of S0(Bn), then e-tf (·, t) is an extreme point of S0(Bn) for t 0 (respectively a support point of S0(Bn) for t ∈[0, t0] and some t0 > 0). This is a generalization to the n-dimensional case of work due to Pell. Also, we prove analogous results for mappings which belong to S0(Bn) and which are bounded in the norm by a fixed constant. We relate the study of this class to reachable sets in control theory generalizing work of Roth. Finally we consider extreme points and support points for biholomorphic mappings of Bn generated by using extension operators that preserve Loewner chains.     

X-Ray Tube Voltage Dependence of Wiener Spectra of Screen Structure Mottle Recorded on Front and Back Emulsions

A low-speed screen/film system was used to investigate structure mottle, i.e., the density fluctuation of an x-ray film due to inhomogeneous screen structure. The tube voltage dependence of the Wiener spectra of the structure mottle was separately determined for front and back film emulsions. The Wiener spectral values of the structure mottle of the front emulsion were greater than those of the back emulsion at lower tube voltages. The spectral values of the structure mottle of the front emulsion decreased with tube voltage, while those of the back emulsion increased. We explain these phenomena by the behavior of the Wiener spectra of the relative spatial fluctuation of fluorescence intensity due to following reasons: (1) spatial thickness fluctuation of the screen produces a relative spatial fluctuation of x-ray energy absorbed in the screen, and (2) as the distance between the emulsion of the film and the average position of the x-ray absorption in the screen lengthens, the number of random scattering and absorption of light photons increase.Presented at the International Commission for Optics Topical Meeting, Kyoto, 1994.     

Novel negatively charged cyanocuprate(I) host [Cu4(CN)7]3− built of tetrahedral Cu(I) coordination centers: Crystal structure of [{NH2(CH2CH2)2NCH2CH2NH2}2H][Cu4(CN)7]

The title inclusion compound [{NH₂(CH₂CH₂)₂NCH₂CH₂NH₂}₂H][Cu₄(CN)₇] was obtained as single crystals from an aqueous solution containing CuCN, KCN, andN-(2-aminoethyl)piperazine. It crystallizes in the monoclinic space groupP2/n,a = 12.3829(9),b = 8.5970(9),c = 12.6633(7) Å, = 109.984(5)°,z = 2,R = 0.035 for 2921 independent reflections. The inclusion structure is composed of the hydrogen-bonded dimeric onium guest [{NH₂(CH₂CH₂)₂NCH₂CH₂NH₂}₂H]³⁺ and the negatively-charged three-dimensional host [CU₄(CN)₇]^3– in which the CN-bridged framework Cu(I) atoms are all tetrahedral. A polyacene-like one-dimensional array of hexagons cornered by Cu(I) atoms and edged by -CN- linkages is arrayed in parallel to theb axis and stacked approximately along the c axis. The Cu(I) corner shared in the one-dimensional array extends an N-coordinate CN group along the c axis to a pair of unshared Cu(I) corners for which the C end behaves as a bifurcated ligand to build up the three-dimensional host structure. The cavity is composed of two networks of the hexagons at the top and bottom and pillared by six >CN- groups and accommodates a dimeric guest ofN-(2-aminoethyl)piperazinium cations protonated at each 4-N with the cations being hydrogen-bonded to each other through the 2-NH₂ groups sharing another H⁺.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Conformational studies of poly(N5-Ω-hydroxyalkyl-L-glutamine)s in reversed micelles

The molecular conformations of poly(N⁵-dihydroxyethylaminopropyl-L-glutamine) and poly(N⁵-dihydroxyethyl-L-glutamine) were investigated in reversed micelles of AOT as well as in aqueous solutions. Both poly(-amino acid)s assume disordered structures in pure water. The conformation of poly(N⁵-dihydroxyethylaminopropyl-L-glutamine) transits into-helix in the reversed micelles as the molar ratio of water to AOT (w₀=[H₂O]/[AOT]) becomes smaller. A similar conformational transition was also observed in aqueous solutions when a certain amount of AOT was added. Under these conditions, however, poly(N⁵-dihydroxyethyl-L-glutamine) did not undergo a conformational transition into-helix.     

Morphology Change in Crystallization of α L-Glutamic Acid in the Presence of L-Phenylalanine

Abstract

Effect of L-phenylalanine(L-Phen) on the precipitation behavior and morphology of a L-glutamic acid (L-Glu) crystals, and inclusion of L-Phen in L-Glu crystals were investigated. L-Phen suppresses both nucleation rate and growth rate of L-Glu. The morphology of L-Glu was observed to change depending on L-Phen concentration. Two predominant morphologies were obtained, which have the large (111) face and the new face of (110), respectively. Irregular increase of the molar ratio of L-Phen to L-Glu in nucleated crystals was detected and it was attributed to the morphology change of L-Glu crystals. Dependence of R on L-Phen concentration appeared to be different between the nucleated crystals and seed crystals.     

A High‐Valent Iron(IV) Peroxo Core Derived from O2

Dioxygen‐tolerant [NiFe] hydrogenases catalyze not only the conversion of H₂ into 2 H⁺ and 2 e^? but also the reduction of O₂ to H₂O. Chemists have sought to mimic such bifunctional catalysts with structurally simpler compounds to facilitate analysis and improvement. Herein, we report a new [NiFe]‐based catalyst for O₂ reduction via an O₂ adduct. Structural investigations reveal the first example of a side‐on iron(IV) peroxo complex.     

Effects of Fluctuation and Segregation in the Rate Acceleration of ATRP Miniemulsion Polymerization

In the ATRP and SFRP miniemulsion polymerization, a particle size range may exist in which the polymerization rate is larger than that of the corresponding bulk polymerization. Here, MC simulations are applied to clarify the reason for the acceleration. It is shown that the statistical variation of the trapping agent concentration (fluctuation effect) dominates the acceleration for good living conditions, while the segregation effect is important when the bimolecular termination is significant. Even for the segregation‐dominated conditions, the polymerization rate cannot be predicted accurately without accounting for the fluctuation effect.

     

Molecular Weight Development in Free‐Radical Polymerization with Polyfunctional Chain‐Transfer Agents, 1. Equal Reactivity Model

The analytic expression for the weight‐average molecular weight development in free‐radical polymerization that involves a polyfunctional chain‐transfer agent is proposed. Free‐radical polymerization is kinetically controlled; therefore, the probability of chain connection with a polyfunctional chain‐transfer agent as well as the primary chain‐length distribution changes during the course of polymerization. We consider the primary chains formed at different times as different types of chains, and the heterochain branching model is used to obtain the weight‐average chain length at a given conversion level in a matrix formula, described as P_w = W { D _w + ( I + T ) SP ( I – TSP )^–1 D_f }. Because the primary chains are formed consecutively, the number of chain types N is extrapolated to infinity, but such extrapolation can be conducted with the calculated values for only three different N values. The criterion for the onset of gelation is simply described as a point at which the largest eigenvalue of the product of matrixes, TSP reaches unity, i. e., det  ( I – TSP ) = 0. The present model can readily be extended for the star‐shaped polyfunctional initiators, and the relationships between the model parameters and kinetic rate expression for such reaction systems are also shown.