Largely enhanced ductility of immiscible high density polyethylene/polyamide 6 blends via nano‐bridge effect of functionalized multiwalled carbon nanotubes

Immiscible polymer blends usually exhibit negative deviation in mechanical properties compared with the corresponding pure polymers due to the weak interfacial bonding between the two polymers. Due to the bridge effect of the oriented carbon nanotubes (CNTs) on the craze and crack development at the load of stress, CNTs have been proved to be efficient toughening agent for polymers. In this work, functionalized multiwalled carbon nanotubes (FMWCNTs) have been introduced into immiscible high density polyethylene/polyamide 6 (HDPE/PA6) blends through different sample preparation methods. The mechanical measurements demonstrate that, when the nanocomposite is prepared from the HDPE master batch, the sample exhibits excellent tensile strength and toughness simultaneously. For all the nanocomposites, FMWCNTs tend to migrate and/or maintain in PA6 particles, leading to the variation of the crystallization behavior in PA6 phase. Further results based on morphologies characterization indicate that the intensified interfacial adhesion between HDPE and PA6, which is realized by the nano‐bridge effect of FMWCNTs in the interfaces, is the main reason for the largely improved ductility. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation and characterization of porous calcium titanate-based coated glass fiber filter material and its application in determination of lead and cadmium ion concentrations in water

Glass fiber filter coated with a porous block adsorption agent of calcium titanate (GPCTO) was prepared by the citric acid sol-gel method, and characterized by X-ray diffraction, scanning electron microscopy, and FTIR spectrophotometry. Its Pb2+ and Cd2+ adsorption properties from water were studied. Adsorption and elution were investigated under different conditions, as were the thermodynamics and kinetics of adsorption, using Cd ion as representative. Calcium titanate may react with glass fiber, forming Si-O-Ti and B-O-Ti bonds and becoming a composite adsorbent. The Pb and Cd ions were quantitatively retained at pH 4-9; their adsorption capacities by the GPCTO were 199.72 and 19.68 mg/g, respectively. The isothermal data were described by the Langmuir equation. The dynamic data followed the pseudo-second-order kinetic model well. The enthalpy change (AH) of the adsorption process was 37.160 kJ/mol. At various temperatures, Gibbs free energy changes (delta G) were negative, and entropy changes (delta S) were positive. The activation energy (Ea) was 38.127 kJ/mol for the adsorption. Cd ion adsorption by the GPCTO was endothermic and spontaneous. The adsorbed Pb and Cd ions were completely recovered by elution with 2 M HNO3. The Pb+ and Cd2+ concentration factors were up to 200. The method has been applied to the preconcentration for flame atomic absorption spectrometric determinations of trace Pb and Cd ions in water samples. The recoveries were 95.2 to 102.4% for Pb and 92.2 to 98.0% for Cd.     

AAK1 identified as an inhibitor of neuregulin-1/ErbB4-dependent neurotrophic factor signaling using integrative chemical genomics and proteomics

Target identification remains challenging for the field of chemical biology. We describe an integrative chemical genomic and proteomic approach combining the use of differentially active analogs of small molecule probes with stable isotope labeling by amino acids in cell culture-mediated affinity enrichment, followed by subsequent testing of candidate targets using RNA interference-mediated gene silencing. We applied this approach to characterizing the natural product K252a and its ability to potentiate neuregulin-1 (Nrg1)/ErbB4 (v-erb-a erythroblastic leukemia viral oncogene homolog 4)-dependent neurotrophic factor signaling and neuritogenesis. We show that AAK1 (adaptor-associated kinase 1) is a relevant target of K252a, and that the loss of?AAK1?alters ErbB4 trafficking and expression levels,?providing evidence for a previously unrecognized role for AAK1 in Nrg1-mediated neurotrophic?factor signaling. Similar strategies should lead to the discovery of novel targets for therapeutic development.     

Direct ab initio dynamics study of radical C4H (X̃2Σ+) + CH4 reaction

The methane (CH(4)) hydrogen abstraction reaction by linear butadiynyl radical C(4)H (CCCCH) has been investigated by direct ab initio dynamics over a wide temperature range of 100-3000 K, theoretically. The potential energy surfaces (PESs) have been constructed at the CCSD(T)/aug-cc-pVTZ//BB1K/6-311G(d,p) levels of theory. Two different hydrogen abstraction channels by C(1) and C(4) of C(4)H (C(1)C(2)C(3)C(4)H) have been considered. The results indicate that the C(1) position of C(4)H is a more reactive site. The electron transfer behaviors of two possible channels are also analyzed by quasi-restricted orbital (QRO) in detail. The rate constants calculated by canonical variational transition-state theory (CVT) with the small-curvature tunneling correction (SCT) are in excellent agreement with available experimental values. The normal and three-parameter expressions of Arrhenius rate constants are also provided within 100-3000 K. It is expected to be helpful for further studies on the reaction dynamics behaviors over a wide temperature range where no experimental data is available so far.     

A local average connectivity-based method for identifying essential proteins from the network level

Identifying essential proteins is very important for understanding the minimal requirements of cellular survival and development. Fast growth in the amount of available protein-protein interactions has produced unprecedented opportunities for detecting protein essentiality from the network level. Essential proteins have been found to be more abundant among those highly connected proteins. However, there exist a number of highly connected proteins which are not essential. By analyzing these proteins, we find that few of their neighbors interact with each other. Thus, we propose a new local method, named LAC, to determine a protein's essentiality by evaluating the relationship between a protein and its neighbors. The performance of LAC is validated based on the yeast protein interaction networks obtained from two different databases: DIP and BioGRID. The experimental results of the two networks show that the number of essential proteins predicted by LAC clearly exceeds that explored by Degree Centrality (DC). More over, LAC is also compared with other seven measures of protein centrality (Neighborhood Component (DMNC), Betweenness Centrality (BC), Closeness Centrality (CC), Bottle Neck (BN), Information Centrality (IC), Eigenvector Centrality (EC), and Subgraph Centrality (SC)) in identifying essential proteins. The comparison results based on the validations of sensitivity, specificity, F-measure, positive predictive value, negative predictive value, and accuracy consistently show that LAC outweighs these seven previous methods.     

A simple solution combustion route for the preparation of metal-doped TiO2 nanoparticles and their photocatalytic degradation properties

In this paper, we report the successful synthesis of metal ion-doped TiO(2) nanoparticles via a simple solution combustion method employing a mixture of ethanol and ethyleneglycol (v/v = 30/20) as the solvent, tetra-n-butyl titanate [Ti(OC(4)H(9))(4), TBOT] as the titanium source and oxygen gas in the atmosphere as the oxygen source, in the presence of small amounts of metal ions such as Cu(2+), Mn(2+), Ce(3+) and Sn(4+). The as-obtained products were characterized by means of powder X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS) and scanning electron microscopy (SEM). The UV-vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra of various metal ion-doped products were investigated. Experiments showed that the metal ion-doped TiO(2) nanoparticles presented a stronger photocatalytic ability for the degradation of organic dyes, including Pyronine B, Safranine T and Methylene blue (MB), under visible light/254 nm UV light irradiation than commercial P25 within the same time.     

Catalytic asymmetric construction of spirocyclopentaneoxindoles by a combined Ru-catalyzed cross-metathesis/double Michael addition sequence

Biologically important and synthetically challenging spirocyclopentaneoxindoles with four contiguous stereocenters including one spiroquaternary stereocenter have been constructed in good yields (72-87%) with excellent diastereoselectivity (16:1→30:1 dr) and enantioselectivity (93→99% ee) by a combined Ru-catalyzed cross-metathesis/organocatalyzed asymmetric double-Michael addition sequence.     

Qualitative and quantitative analyses of Epimedium wushanense by high-performance liquid chromatography coupled with diode array detection and electrospray ionization tandem mass spectrometry

A new HPLC-DAD-ESI-MS(n) method was developed for rapid separation, characterization and quantitation of flavonoids in Epimedium wushanense, a popular Chinese herbal medicine. For qualitative identification, a total of 37 compounds were characterized from the underground and aerial parts of E. wushanense. Among them, 28 compounds were prenylated flavonoids, and 23 were confirmed by comparing with reference standards. For quantitative analysis, 12 major flavonoids including kaempferol glycosides, desmethylicaritin glycosides, and icaritin glycosides were simultaneously determined by HPLC/UV. Samples were separated on a Waters Symmetry C(18) column at 35 °C eluted with a gradient three-component mobile phase of acetonitrile, methanol, and water containing 0.03% v/v formic acid. All the flavonoids showed good linearity (r(2) ≥0.9997). The recoveries varied from 92.6 to 106.1% at three concentration levels. This method was applied to the determination of 20 samples of different geographical sources, harvesting time, and plant parts. Contents of the predominant flavonoid, epimedin C, ranged from 1.4 to 5.1% in aerial parts and 1.0 to 2.8% in underground parts. The methods established in this paper were simple and reliable and could be used for the quality control of E. wushanense.     

Micelles from amphiphilic block copolyphosphates for drug delivery

Amphiphilic block copolyphosphates (PEP-b-PIPPs) are synthesized by two-step ROP of cyclic phosphate monomers with different pedant groups. They can spontaneously self-assemble into approximately spherical micelles ranging in size between 89 and 198 nm in water. A typical hydrophobic anti-cancer drug DOX is encapsulated into the micelles. The release rate of DOX slows down with increasing hydrophobic block length of PIPP. DOX-loaded micelles are investigated for the proliferation inhibition of Hela cells and the DOX dose required for 50% cellular growth inhibition is found to be 0.8 μg mL(-1). It is demonstrated that PEP-b-PIPP micelles can be used as a safe and promising drug delivery system.     

Solving diffusion equation using wavelet method

A wavelet-based numerical method based on wavelets of Hermite cubic splines is presented for computing singularly perturbed convection-dominated diffusion equation. The advantages of the method are explained. To improve the accuracy of singular areas, wavelets are configured hierarchically for solving algebraic equations. Numerical examples show that the proposed method has good efficiency and precision.