Thermogravimetric Analysis of Aromatic Polyamides with Benzimidazolyl Side Group

The TG studies are presented for isomers of benzimidazolyl-substituted polyamides (BIPA). The TG data are compared with those polyamides (PA) of identical backbones without substitution, in view of the mechanism of thermal degradation. The TG mass loss curves divided to three temperature ranges reflect the decomposition reactions in the respective temperature ranges: (1) cleavage of single bonds of nitrogen to aromatic ring, (2) random scission of single bonds, (3) condensation of the remained rings. Liberation of benzimidazole rings occurs in the temperature range (2). The final product, char, contains benzimidazole rings. Terephthaloyl-rich BIPA's retard liberation of benzimidazole from the decomposed polymer. This revised version was published online in August 2006 with corrections to the Cover Date.     

A model proposal for the chaotic structure of Istanbul stock exchange

Chaos theory is considered a novel way of understanding the behaviour of nonlinear dynamic systems. It is well known that the evaluation of chaotic systems is dependent on initial conditions since exponential growth error is a common characteristic. This present paper evaluates the effects of a nonlinear dynamic system in Istanbul Stock Exchange, based on time series. The reliability of predicting stock behaviour depends on this fact. In other words, the aim is to prove that if ISE daily index return shows chaotic behaviour.     

Synthesis of phenoxyacetic acid derivatives as highly potent antagonists of gastrin/cholecystokinin-B receptors. III.

In order to improve the biological characteristics of DA-3934 (5), a novel gastrin/cholecystokinin (CCK)-B receptor antagonist, phenoxyacetic acid derivatives replacing the N-methyl-N-phenylcarbamoylmethyl moiety of 5 with various alkyl chains have been synthesized and their biological activity evaluated. The relationship between the structure of these compounds and their human gastrin receptor binding affinity showed that there should be the optimal size among the various N-alkyl chains. Also a significant increase in the receptor binding affinity was achieved by several compounds. Among those compounds, 2-[3-[3- [N-cyclohexylmethyl-N-[2-(N-methyl- N-phenylcarbamoylmethoxy)phenyl]carbamoylmethyl]ureido]pheny l]acetic acid (22c) and (+/-)-2-[3-[3-[N-[2-(N-methyl-N- phenylcarbamoylmethoxy)phenyl]-N-(3-methylpentyl)carbamoy lmethyl]ureido] phenyl]acetic acid (22h) exhibited high affinity for human gastrin receptors and were also more potent inhibitors in a pentagastrin-induced gastric acid secretion model than the parent compound, 5. The ED50 values of these compounds when administered intraduodenally to rats were 0.12 and 0.63 mg/kg, respectively.     

Analyzing Power in Elastic Scattering of Polarized Protons from Neutron-rich Helium Isotopes

The vector analyzing power has been measured for the elastic scattering of neutron-rich ⁶He from polarized protons at 71 MeV/nucleon. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a ⁶He nucleus. An optical model analysis revealed that the spin-orbit potential for ⁶He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semi-microscopic analysis with a α + n + n cluster folding model suggests that the inclusion of realistic interaction between a proton and the α core is important in describing the p-⁶He elastic scattering.     

On the existence of minimal surfaces with singular boundaries

In 1931, Jesse Douglas showed that in , every set of rectifiable Jordan curves, with , bounds an area-minimizing minimal surface with prescribed topological type if a ``condition of cohesion' is satisfied. In this paper, it is established that under similar conditions, this result can be extended to non-Jordan curves.

     

Dual Catalysis of Gold Nanoclusters: Photocatalytic Cross-Dehydrogenative Coupling by Cooperation of Superatomic Core and Molecularly Modified Staples**

Thiolate-protected gold nanoclusters (AuNCs) have attracted significant attention as nano-catalysts, revealing a superatomic core and gold-thiolate staples as distinct structural units. Here, we demonstrate the unprecedented dual catalytic activity of thiolate-protected [Au₂₅(SR)₁₈]⁻ nanoclusters, involving both photosensitized ¹O₂ generation by the Au₁₃ superatomic core and catalytic carbon-carbon bond formation facilitated by Au₂(SR)₃ staples. This synergistic combination of two different catalytic units enables efficient cross-dehydrogenative coupling of terminal alkynes and tertiary aliphatic amines to afford propargylamines in high yields of up to 93 %. Mixed-ligand AuNCs bearing both thiolate and alkynyl ligands revealed the intermediacy of the alkynyl-exchanged AuNCs toward both photosensitization and C−C bond-forming catalytic cycles. Density functional theory calculations also supported the intermediacy of the alkynyl-exchanged AuNCs. Thus, the use of ligand-protected metal nanoclusters has enabled the development of an exceptional multifunctional catalyst, wherein distinct nanocluster components facilitate cooperative photo- and chemo-catalysis.