Trimetallic PtCoFe Alloy Monolayer Superlattices as Bifunctional Oxygen‐Reduction and Ethanol‐Oxidation Electrocatalysts

A synthesis strategy for the preparation of trimetallic PtCoFe alloy nanoparticle superlattices is reported. Trimetallic PtCoFe alloy monolayer array of nanoparticle superlattices with a large density of high index facets and platinum‐rich surface are successfully prepared by coreduction of metal precursors in formamide solvent. The concentration of cetyl trimethyl ammonium bromide plays a vital role for the formation of a monolayer array of nanoparticle superlattices, while the size of nanoparticles is determined by NaI. The prepared monolayer array of nanoparticle superlattices is the superior catalyst for oxygen reduction reaction as well as for ethanol oxidation owing to their specific structural and compositional characteristics.     

Three-dimensional macroscale assembly of Pd nanoclusters

Construction of macro-materials with highly oriented microstructures and well-connected interfaces between building blocks is significant for a variety of applications. However, it is still challenging to confine the desired structures. Thus, well-defined building blocks would be crucial to address this issue. Herein, we present a facile process based on 1.8 nm Pd nanoclusters (NCs) to achieve centimeter-size assemblages with aligned honeycomb structures, where the diameter of a single tubular moiety is ～4 μm. Layered and disordered porous assemblages were also obtained by modulating the temperature in this system. The reconciled interactions between the NCs were crucial to the assemblages. As a comparison, 14 nm Pd nanoparticles formed only aggregates. This work highlights the approach of confining the size of the building blocks in order to better control the assembly process and improve the stability of the structures.

Open image in new window

     

Chitosan/CNTs nanocomposite as green carrier material for pesticides controlled release

Chitosan-based nanocomposites containing gamma-treated carbon nanotubes (CNTs) were developed for controlled release of pesticide. The CNTs were irradiated under gamma irradiation in air at different doses. The transmission electron microscopic images of gamma-treated CNTs showed disentanglement of the tubes without distorting their tubular structure which effectively increased the dispersion properties of CNTs in nanocomposites. X-ray diffraction analysis of CNTs showed some structural changes, and an irradiation dose of 150 kGy is the most effective. Azinphos methyl (AZM) was selected as a model drug, and its release was studied using HPLC technique. Controlled release response of CNTs-based nanocomposites opens a new avenue for pesticides applications because it requires less quantity of pesticides. As a result, the side effects of pesticide in our environment are minimized.     

Conformational transition of Poly (vinylbenzyltrimethylammonium chloride) (PVBTMAC) brush in the presence of Hofmeister anions

This study pertains to the conformational changes of Poly (vinylbenzyltrimethylammonium chloride) (PVBTMAC) brush onto SiO₂-coated resonator; which was further incorporated by using quartz crystal microbalance with dissipation (QCM-D) in the presence of Hofmeister series of anions as a function of ionic strength. Gradual shrinkage of highly extended PVBTMAC followed by loose inhomogeneous layer was on account of change in frequency (?f) and dissipation (??D) at low ionic strength. On the contrary, the increase in ionic strength collapses chains and dense homogenous layer is formed. The chaotropic anions comparativley bring drastic change in frequency unlike kosmotropic anions. This is because weakly hydrated chaotropic anions form strong ion pair with weakly hydrated trimethyl ammonium group on the PVBTMAC brush and as a result strong counter ion condensation was observed on polymer chain. Thus, the apparent mass associated with PVBTMAC chains increases that accounts for large change in ?f.     

Quasi-maximum likelihood estimation of periodic GARCH and periodic ARMA-GARCH processes

Abstract.  This article establishes the strong consistency and asymptotic normality (CAN) of the quasi-maximum likelihood estimator (QMLE) for generalized autoregressive conditionally heteroscedastic (GARCH) and autoregressive moving-average (ARMA)-GARCH processes with periodically time-varying parameters. We first give a necessary and sufficient condition for the existence of a strictly periodically stationary solution of the periodic GARCH (PGARCH) equation. As a result, it is shown that the moment of some positive order of the PGARCH solution is finite, under which we prove the strong consistency and asymptotic normality of the QMLE for a PGARCH process without any condition on its moments and for a periodic ARMA-GARCH (PARMA-PGARCH) under mild conditions.     

Influence of germination techniques on sprout yield,biosynthesis of ascorbic acid and cooking ability,in chickpea (Cicer arietinum L.)

Effects of germination time and illuminations on sprout yield, biosynthesis of ascorbic acid, cooking ability and moisture accumulation in chickpeas were significant (p ? 0.01). Green light had the highest promoting effect on the ascorbic acid level (40.59 mg/100 g) as compared to other illuminations but significantly reduced the sprout yield (188.6 g) as compared to dark, fluorescence and γ-rays illuminations with significantly high sprout yield (196 g) and imbibing moisture (51%). Cooking time was reduced by 43% due to γ-rays in un-soaked seed. Cooking time increased in all treated chickpea samples after 24 h germination and thereafter decreased significantly. Red light significantly increased the cooking time (68.44 min) followed by fluorescent (64.5 min), yellow (61.8 min) and green light (60.9 min). The results indicated that germination of chickpea under green light was an effective process in enhancing ascorbic acid content while dark, fluorescence and γ-rays were effective in promoting sprout growth and to some extent biosynthesis of ascorbic acid.     

Pediatric flexible bronchoscopy

Between 1993-1996, 200 pediatric flexible bronchoscopies were performed. Indications were: chronic cough (158 children), persistent pulmonary infiltrates (89), recurrent stridor (28), suspected tracheobronchial foreign body (20), suspected tuberculosis (17) and hemoptysis (3). Some children had more than 1 indication. 124 patients were boys (mean 4.18 +/- 2.86 years; range 1 month-15 years) and 76 were girls (mean 4.39 +/- 2.7 years; range 4 months-15 years). The procedure included direct vision recorded by video-camera and bronchoalveolar lavage; the lavage fluid was sent for culture, Gram and Ziehl-Nielsen strains and for cytology. There were a few minor side effects: mild stridor which resolved within a few hours (10 children) and transient fever (3). This simple, flexible instrument was effective and helpful in the diagnosis and treatment of children with respiratory symptoms in a secondary hospital facility.     

新型本质阻燃高分子材料研究进展

综述了近年来国内外新型本质阻燃高分子材料的研究现状。简述了几种本质阻燃高分子材料如环氧树脂(EP)、聚酯(PET)、聚酰胺(PA)等阻燃材料的制备方法及通过实验对其性能的研究,阐述了几种自身具有阻燃性能的新型环保高分子材料,总结了现阶段阻燃高分子材料的制备方法和存在的不足,并提出了阻燃高分子材料的发展趋势。