Numerical study of rich catalytic combustion of syngas

The rich catalytic combustion of syngas/air mixtures over platinum has been investigated numerically in a two-dimensional circular channel using steady simulations and detailed hetero-homogeneous chemistry. The channel dimensions are representative of a catalytic monolith. Simulations have been conducted in the pressure range of 1–10 bar and Φ = 3–5 with varying inlet velocities, residence time, H₂/CO ratio and CH₄ percentage. Detailed kinetic studies including the reaction path diagram (RPD) in a plug flow reactor have also been conducted to understand the kinetic interactions between H₂, CO, and CH₄. It has been observed that the homogeneous reaction rates are significant at higher pressures and cannot be neglected, although they were highly localized. The channel temperature significantly affected the relative conversion of H₂ and CO. The kinetic coupling between H₂ and CO oxidation was studied and the reason for the differential consumption of O₂ by the reactants was addressed by analyzing the reaction pathways. The residence time in the channel affected the species oxidation and four operation regimes were identified. Both the water-gas shift reaction and the reverse water-gas shift reaction were observed under varying conditions of pressure and equivalence ratio. The effect of H₂/CO ratio has also been investigated. The present study shows that rich catalytic combustion of syngas is fundamentally different from lean combustion.     

Progress of key strategies in development of electrospun scaffolds: bone tissue

There has been unprecedented development in tissue engineering (TE) over the last few years owing to its potential applications, particularly in bone reconstruction or regeneration. In this article, we illustrate several advantages and disadvantages of different approaches to the design of electrospun TE scaffolds. We also review the major benefits of electrospun fibers for three-dimensional scaffolds in hard connective TE applications and identify the key strategies that can improve the mechanical properties of scaffolds for bone TE applications. A few interesting results of recent investigations have been explained for future trends in TE scaffold research.     

Effect of photocatalytic activities of nano-sized copper molybdate (CuMoO4)-doped bismuth titanate (Bi2Ti4O11) (CMBT) alloy

Different compositions of [CuMoO₄]_x-doped Bi₂Ti₄O₁₁ nanophotocatalyst (x = 0.05, 0.1, 0.5) have been prepared by chemical precursor decomposition (CPD) method using triethanolamine (TEA) and HNO₃. Cu(II) is one of reactive species on the catalyst surface and Mo(VI) ion helps to generate charge compensation of lattice having poor catalytic properties. The photocatalytic properties based on the prepared samples for photodecolorization of thymol blue (TB) solutions are examined by Hg-lamp. The crystal structures of the prepared nano-powders are characterized by XRD, EDAX, UV-vis spectra, specific surface area (BET), and HRTEM analyses. The average particle size of copper molybdate-doped bismuth titanate ranges 32 ± 5 nm measured from TEM. Results show doping of copper molybdate of 5 mol% with bismuth titanate can significantly increase the photoactivity of bismuth titanate compared all the compositions studied except degussa P25 titania. The observed increased photocatalytic activity of copper molybdate-doped bismuth titanate ((CuMoO4)_x(Bi₂Ti₄O₁₁)_1−x; CM_xBT_1−x) is attributed to the strong absorption of OH groups at the surface of the catalyst.     

Classification of black tea liquor using cyclic voltammetry

Tea quality evaluation is a complex task and is carried out qualitatively in the industry by experienced tea tasters. But, the unpredictable and inconsistent nature of human panel tasting demands instrumental methods to assess the quality of black tea in an objective manner. For discrimination between different black tea samples and instrumental evaluation of their quality, a new method employing the principle of cyclic voltammetry is proposed in this paper. The technique has been investigated using platinum and glassy carbon as working electrodes and the resultant current from the potentiostat has been considered for data analysis. First, principal component analysis (PCA) and linear discriminant analysis (LDA) has been performed for visualization of underlying clusters and finally, a neural network model has been used to classify the data. The performance of the classifier has been established using 10-fold cross-validation method.     

Multifunctional carbon-nanotube cellular endoscopes

Glass micropipettes, atomic force microscope tips and nanoneedles can be used to interrogate cells, but these devices either have conical geometries that can damage cells during penetration or are incapable of continuous fluid handling. Here, we report a carbon-nanotube-based endoscope for interrogating cells, transporting fluids and performing optical and electrochemical diagnostics at the single organelle level. The endoscope, which is made by placing a multiwalled carbon nanotube (length, 50-60?μm) at the tip of a glass pipette, can probe the intracellular environment with a spatial resolution of ～100?nm and can also access organelles without disrupting the cell. When the nanotube is filled with magnetic nanoparticles, the endoscope can be remotely manoeuvered to transport nanoparticles and attolitre volumes of fluids to and from precise locations. Because they are mounted on conventional glass micropipettes, the endoscopes readily fit standard instruments, creating a broad range of opportunities for minimally invasive intracellular probing, drug delivery and single-cell surgery.     

Folate receptor targeted, carboxymethyl chitosan functionalized iron oxide nanoparticles: a novel ultradispersed nanoconjugates for bimodal imaging

This article delineates the design and synthesis of a novel, bio-functionalized, magneto-fluorescent multifunctional nanoparticles suitable for cancer-specific targeting, detection and imaging. Biocompatible, hydrophilic, magneto-fluorescent nanoparticles with surface-pendant amine, carboxyl and aldehyde groups were designed using o-carboxymethyl chitosan (OCMC). The free amine groups of OCMC stabilized magnetite nanoparticles on the surface allow for the covalent attachment of a fluorescent dye such as rhodamine isothiocyanate (RITC) with the aim to develop a magneto-fluorescent nanoprobe for optical imaging. In order to impart specific cancer cell targeting properties, folic acid and its aminated derivative was conjugated onto these magneto-fluorescent nanoparticles using different pendant groups (-NH(2), -COOH, -CHO). These newly synthesized iron-oxide folate nanoconjugates (FA-RITC-OCMC-SPIONs) showed excellent dispersibility, biocompatibility and good hydrodynamic sizes under physiological conditions which were extensively studied by a variety of complementary techniques. The cellular internalization efficacy of these folate-targeted and its non-targeted counterparts were studied using a folate-overexpressed (HeLa) and a normal (L929 fibroblast) cells by fluorescence microscopy and magnetically activated cell sorting (MACS). Cell-uptake behaviors of nanoparticles clearly demonstrate that cancer cells over-expressing the human folate receptor internalized a higher level of these nanoparticle-folate conjugates than normal cells. These folate targeted nanoparticles possess specific magnetic properties in the presence of an external magnetic field and the potential of these nanoconjugates as T(2)-weighted negative contrast MR imaging agent were evaluated in folate-overexpressed HeLa and normal L929 fibroblast cells.     

Influence of crystallographic texture and microstructure on elastic modulus of steels

In this paper the effects of crystallographic texture and microstructure on the elastic modulus of different grades of steel have been collected from the available literature and put in one place. It is expected that this will help researchers in their understanding of both the fundamental and the practical aspects of the different grades of steel used for various purposes.

Dans cet article, on a recueilli à partir de la littérature disponible et rassemblé en un seul lieu les effets de la texture cristallographique et de la microstructure sur le module l’élasticité de différentes nuances d’acier. On s’attend à ce que cela aide les chercheurs dans leur compréhension tant des aspects fondamentaux que pratiques des différentes nuances d’acier utilisées à diverses fins.     

Preparation and characterization of modified telechelic natural rubber-based pressure-sensitive adhesive

Telechelic natural rubber (TNR) was prepared by the use of potassium persulfate and propanal at 70 °C and various degradation times from 0 to 30 h. These samples were then grafted by maleic anhydride (MA) in toluene solution before modification with 3-amino-1,2,4-triazole (ATA) to produce modified TNRs (AMTNRs). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the chemical compositions. Carboxyl and hydroxyl groups of TNRs were clearly observed, due to chain scission, oxidation, and modified chain ends. The viscosities of TNRs were dropped greatly after 5 h and then decreased slowly as a function of degradation time. ATR-FTIR spectra of AMTNRs showed amide bonds between ATA and MA groups, and then the multiple hydrogen bonding arrays were formed. The glass transition temperatures (T_g) of AMTNRs were determined by differential scanning calorimetry. The T_g of AMTNR_0 moved to a higher temperature of –55 °C after modification by ATA, confirming the formation of multiple hydrogen bonding arrays. However, the T_g of AMTNR_5 to AMTNR_30 decreased slightly due to chain scission in the degradation process. The adhesive properties of AMTNR-based pressure-sensitive adhesive were evaluated by a Lloyd adhesion tester. The tack of AMTNRs depended on wettability whereas peel and shear strengths were responded by a combination between wettability and multiple hydrogen bonding arrays.     

Processing and properties of nano‐ and macro‐hydroxyapatite/poly(ethylene‐co‐acrylic acid) composites

Hydroxyapatite (HAp)/poly(ethylene‐co‐acrylic acid) composites have been synthesized by a solution‐based method, using nanosized (n‐HAp) and coarse hydroxyapatite (c‐HAp) particles, respectively. X‐ray diffraction study has indicated the development of compressive and tensile stresses in composites because of the thermal expansion mismatch between the particles and polymer matrix. Fourier transform infrared absorption spectra and thermal analysis have showed the presence of strong interfacial bonding between the particles and polymer. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. A comparison in mechanical properties between composites prepared with n‐HAp and c‐HAp particles, respectively, has been studied. Nanosized particles contribute excellent improvement of mechanical properties of the composites rather than the coarse particles. The uniform dispersion of HAp particles, followed by the improvement in mechanical properties of the composite, provides a means of preparing HAp/polymer composites for low load‐bearing implant applications. POLYM. COMPOS., 27:633–641, 2006. © 2006 Society of Plastics Engineers