羧甲基纤维素钠水凝胶的制备及其生物降解性研究

用羧甲基纤维素钠(CMC—Na)制得了含水量高达98％的水凝胶，考察了防腐剂、交联剂、无机态氮素、有机态氮素、碳水化合物的加入量以及环境中pH值等因素对生物降解性的影响。结果表明：制备条件不同，水凝胶的生物降解性不同；环境中一定量铵根离子的存在有利于水凝胶的生物降解；在pH=5．2的环境中纤维素酶活性最高，降解程度最大。     

Formulation of Quaternized Aminated Chitosan Nanoparticles for Efficient Encapsulation and Slow Release of Curcumin

An effective drug nanocarrier was developed on the basis of a quaternized aminated chitosan (Q-AmCs) derivative for the efficient encapsulation and slow release of the curcumin (Cur)-drug. A simple ionic gelation method was conducted to formulate Q-AmCs nanoparticles (NPs), using different ratios of sodium tripolyphosphate (TPP) as an ionic crosslinker. Various characterization tools were employed to investigate the structure, surface morphology, and thermal properties of the formulated nanoparticles. The formulated Q-AmCs NPs displayed a smaller particle size of 162 ± 9.10 nm, and higher surface positive charges, with a maximum potential of +48.3 mV, compared to native aminated chitosan (AmCs) NPs (231 ± 7.14 nm, +32.8 mV). The Cur-drug encapsulation efficiency was greatly improved and reached a maximum value of 94.4 ± 0.91%, compared to 75.0 ± 1.13% for AmCs NPs. Moreover, the in vitro Cur-release profile was investigated under the conditions of simulated gastric fluid [SGF; pH 1.2] and simulated colon fluid [SCF; pH 7.4]. For Q-AmCs NPs, the Cur-release rate was meaningfully decreased, and recorded a cumulative release value of 54.0% at pH 7.4, compared to 73.0% for AmCs NPs. The formulated nanoparticles exhibited acceptable biocompatibility and biodegradability. These findings emphasize that Q-AmCs NPs have an outstanding potential for the delivery and slow release of anticancer drugs.     

Thermal stability and crystallization phenomena of low cost Ti-based bulk metallic glass

The thermal stability, kinetics of crystallization, and glass forming ability of a Ti₄₈Ni₃₂Cu₈Si₈Sn₄ bulk amorphous alloy have been studied by differential scanning calorimetry using both isothermal and non-isothermal experiments. The activation energy, frequency factor, and reaction rate for the crystallization cascade were determined via the Kissinger method. X-ray diffractometry and transmission electron microscopy studies revealed that crystallization starts with the primary precipitation of Ti(Ni,Cu), followed by the nucleation of Cu₃Ti from the amorphous precursor. The kinetics of nucleation of the primary crystalline phase was also investigated using the Johnson–Mehl-Avrami method and the Avrami exponent, n, was determined. This new alloy possesses a significantly larger supercooled liquid region than any other non beryllium- or non rare earth – containing titanium-based bulk metallic glass to date.     

Electrochemical reduction of oxygen at a porous flow-through electrode

The electrochemical reduction of oxygen at a porous flow-through electrode is described with emphasis on the effects of concentration, flow speed and surface area. On a packed bed copper electrode in sulfuric acid, it was found that oxygen undergoes a two electron reduction process giving rise to H₂O₂.     

The Nambu Sum Rule in the Composite Two Higgs Doublet Model

Physics of Particles and Nuclei Letters - The spectrum of spinless modes in a model with the $$SU{{(2)}_{L}} times U{{(1)}_{R}}$$ symmetrical four-quark-interaction proposed by Miransky,...     

Synthesis and antioxidant activity of some thiazolidin-4-one derivatives

Abstract  4-Fluorobenzaldehyde was used for the preparation of 2-(4-fluorophenyl)thiazolidin-4-one derivatives which were allowed to react with chloroacetonitrile and acrylonitrile to produce 3-(2-(4-fluorophenyl)-4-oxothiazolidine3-yl)acetonitrile and 3-(2-(4-fluorophenyl)-4-oxothiazoledine-3-yl)propanenitrile. Biological evaluation of some of the compounds showed that many had promising antioxidant activity. Graphical Abstract        

Pallatriazo — A sensitive and selective reagent for the spectrometric determination of palladium(II)

Summary Based on an investigation of the functional and active analytical groups, a new trisazo derivative, pallatriazo, is proposed as a reagent for determining Pd(II) spectrometrically. This reagent shows high sensitivity, allowing palladium determination in the concentration range 0.05–4g Pd(II)/ml even if platinum is present up to the ratio Pd(II)Pt(IV)=130.

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Pallatriazo — ein empfindliches und selektives Reagens für die spektrometrische Bestimmung von Palladium(II) (Vorläufige Mitteilung)

Zusammenfassung Auf der Grundlage einer Untersuchung der funktionellen und analytischaktiven Gruppen wurde ein neues Trisazo-Derivat, Pallatriazo, als Reagens für die spektrometrische Bestimmung von Pd(II) vorgeschlagen. Es zeigt hohe Empfindlichkeit und gestattet die Pd-Bestimmung im Gebiet 0,05–4g Pd(II)/ml, auch wenn Platin in 30fachem Überschuß anwesend ist.

     

Pterin chemistry. 45. A new and clear synthesis of isomer-free pteroyl-gamma-L-glutamyl-L-glutamic acid

A new and unequivocal synthesis of pteroyl-λ-L-glutamyl-L-glutamic acid free of isomers is described. A melt of N(2′)-acetyl-6-formylpterine and trimethyl-N-(p-amino-benzoyl)-λ-L-glutamyl-L-glutamate was quantitatively converted to 6-azomethin-pterine-trimethylester XI. NaBH₄-reduction followed by basic hydrolysis of acetyl and methyl ester groups gives pure pteroyl-λ-glutamyl-glutamic acid in good yield.