Mechanical and thermal properties of green polylactide composites with natural fillers

Green composites of PLA with micropowders derived from agricultural by-products such as oat husks, cocoa shells, and apple solids that remain after pressing have been prepared by melt mixing. The thermal and mechanical properties of the composites, including the effect of matrix crystallization and plasticization with poly(propylene glycol), have been studied. All fillers nucleated PLA crystallization and decreased the cold-crystallization temperature. They also affected the mechanical properties of the compositions, increasing the modulus of elasticity but decreasing the elongation at break and tensile impact strength although with few exceptions. Plasticization of the PLA matrix improved the ductility of the composites.     

Thermal degradation of bisphenol a polycarbonate

Bisphenol A polycarbonate (Makrolon 3000) has been purified and fractionated. Thin films of these samples have been degraded by heating at 200° under continuous evacuation (pressure less than 0- 1 Pa) for periods of several hours. The molecular weight is observed (by gel permeation chromatography) to increase with time at 200°. Eventually gel is formed. The variation of the number- and weight-average molecular weights with heating time and the effect of the initial molecular weights of the polycarbonate samples are consistent, in the main, with the Davis-Golden mechanism of thermal degradation of bisphenol A polycarbonate; i.e. the principal reactions are condensation and trifunctional branching. Chain scission due to hydrolysis of the carbonate linkage is absent under our conditions.     

Sticking probability for oxygen adsorption and readsorption on thin iron films

Sticking probability for oxygen adsorption on thin iron films and readsorption on surface sites liberated due to incorporation of the adsorbate adatoms below the surface during thermal treatment has been studied by means of the Wagener flow method. Sticking probability for oxygen adsorption on oxidized thin iron films has also been measured for comparison.

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On the generalized Fréchet functional equation with constant coefficients and its stability

We study a generalization of the Fréchet functional equation, stemming from a characterization of inner product spaces. We show, in particular, that under some weak additional assumptions each solution of such an equation is additive. We also obtain a theorem on the Ulam type stability of the equation. In its proof we use a fixed point result to show the existence of an exact solution of the equation that is close to a given approximate solution.     

A look at multiparticle production via modified combinants

The European Physical Journal A - The transverse momentum ($$p_{T}$$) distribution of strange hadrons ($$K_{S}^{0}$$ and $$\varLambda $$) and multi-strange hadrons( $$\varXi $$ and $$\varOmega $$)...     

Experimental and computational study on the reactivity of 2,3-bis[(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile, a key intermediate for the synthesis of tribenzoporphyrazine bearing peripheral methyl(3-pyridylmethyl)amino substituents

Abstract  

An earlier developed alkylating path leading to tetraalkylated diaminomaleonitrile derivatives was explored. Attempts to explain the reactivity of the representative dialkylated diaminomaleonitrile 2,3-bis[(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile during the alkylation reaction were performed using X-ray and density functional theory (DFT) studies. The condensed Fukui functions accompanied by softness indices were found to be useful in explaining its reactivity observed during the reaction. The values of the Fukui functions and condensed softness for electrophilic attack calculated from Mulliken, L?wdin, and natural population analyses closely corresponded to the experimental observations. When 2,3-bis[(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile disodium salt was treated with dimethyl sulfate at lower temperatures the alkylation reaction prevailed, whereas at higher temperatures the alkylating agent acted as a hydride anion acceptor, which favored the elimination reaction. The tetraalkylated dinitrile 2,3-bis[methyl(3-pyridylmethyl)amino]-2(Z)-butene-1,4-dinitrile was used in the synthesis of tribenzoporphyrazine bearing methyl(3-pyridylmethyl)amino groups, which was subsequently subjected to solvatochromic and metallation studies. The changes observed during metallation seem to result from the coordination of the 3-pyridyl group by a palladium ion. This could influence the configuration of the methyl(3-pyridylmethyl)amino moiety, causing more effective donation of a lone pair of electrons from peripheral nitrogen to the macrocyclic ring.     

Activity changes of glassy carbon electrodes caused by their exposure to OH• radicals

GC electrodes were exposed to Fenton solutions. The surface changes produced by the OH^? radicals of these solution were inspected using SEM, XPS, Raman spectroscopy and electrochemistry. The OH^? radicals caused erosion and roughening of the surface, selective oxidation and dissolution of sp² carbon, and reduction of the number of nucleation sites for silver deposition.     

On uniform estimate in Calabi-Yau theorem

We show that the uniform estimate in the Calabi-Yau theorem easily follows from the local stability of the complex Monge-Ampère equation.

     

Synthesis of betulin derivatives and the determination of their relative lipophilicities using reversed‐phase thin‐layer chromatography

A series of superlipophilic or highly lipophilic semisynthetic betulin derivatives was prepared and their relative lipophilicity was measured by reversed‐phase thin‐layer chromatography (RP‐TLC) at different pH values using 1,4‐dioxane–acetate buffer mixtures as mobile phases. Cholesterol, 17β‐estradiol and pure betulin were used as the reference compounds. Linear relationships were found between R_M values and 1,4‐dioxane concentrations in the mobile phases. LogP values were also calculated with computer programs ACD/LogP (ChemSketch 11.0, Advanced Chemistry Development Inc.) and ClogP (Daylight Chemical Information Systems Inc.). The empirical and theoretical data were compared, and the R_M0 values correlated well with logP. Two of the synthesized betulin derivatives are reported for the first time. Copyright © 2009 John Wiley & Sons, Ltd.