Rheological characteristics of coal tar and petroleum pitches with and without additives

An extensive study of rheological characteristics of coal tar and petroleum pitches with and without additives, namely, petroleum coke, natural graphite and carbon black has been made. It is found that all pitches, pure or mixed with a carbon additive are not Newtonian as reported in the literature, but behave Theologically as Bingham plastics with certain yield stress and plastic viscosity at all temperatures of measurement between 85–180°C. The yield stress and plastic viscosity both decrease with increase in temperature of the pitch. A pure petroleum pitch having the same softening point as that of a coal tar pitch is found to have a lower viscosity compared to that of the latter at all temperatures of measurement. This suggests that the criterion of softening point as a measure of suitability of a coal tar pitch binder in the manufacture of artificial carbon is not sufficient for petroleum pitches. Addition of ten parts of carbon black by weight of pitch results in a considerable decrease in viscosity change with temperature of the coal tar pitch compared to almost insignificant change in the case of the petroleum pitch of the same softening point. However, the addition of petroleum coke or natural graphite makes the pitch more viscous but does not change the temperature dependence of viscosity of either of the two types of pitches. The implications are discussed.     

Synthesis of Nanoparticles in High Temperature Ceramic Microreactors: Design, Fabrication and Testing

Microreactors as a novel concept in chemical technology enable the introduction of new reaction procedures in chemistry, pharmaceutical industry, and molecular biology. These miniaturized reaction systems offer many exceptional technical advantages for a large number of applications. One major application is in the bulk synthesis of nanoparticles. Despite the availability of a plethora of nanoparticle synthesis processes, there exist many difficulties in controlling the shape, size, and purity of nanoparticles in large quantities in a safe and cost-effective manner. These difficulties have been the principal factors adversely limiting the applications of ceramic nanoparticles. Recent experiments have shown that to study the process of growth and formation of nanoparticles, a reactor having much smaller dimensions, namely a microreactor is more appropriate. These studies have also shown that a microchannel reactor provides control over the mean residence time and hence over the nanoparticle size and shape. This paper deals with the design, fabrication, and testing issues related to a high temperature, ceramic microreactor by investigating the use of reactive gas streams in arrays of microchannel reactors. These innovations offer the potential to overcome the barriers associated with synthesis of ceramic nanoparticles in large quantities.     

Fly ash supported calcium oxide as recyclable solid base catalyst for Knoevenagel condensation reaction

A new type of solid base catalyst has been prepared by loading of CaO on thermally activated fly ash, with the aim of being used as heterogeneous catalyst for fine chemical production. The prepared fly ash supported calcium oxide catalyst (FAC) was characterized by FT-IR spectroscopy, X-ray diffraction analysis, Scanning Electron Microscopy and atomic absorption spectroscopy. The catalytic activity of FAC was evaluated by Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate as model test reaction under optimized conditions. The catalyst gave very high conversion (87%) of benzaldehyde to desired product ethyl (E)-α-cyanocinnamate with high purity. The catalyst was completely recyclable without significant loss in activity up to three reaction cycles, which confers its stability during reaction unlike commercial catalysts. Moreover this catalyst shows a promising future in providing environmentally clean process for the industrial sector.     

Sterile keratitis after corneal collagen crosslinking in a child

Corneal collagen crosslinking (CXL) is a non invasive technique used in halting the progression of keratoconus. Complications with this modality are rare. We report a case of an 8-year-old child who developed sterile infiltrates in the immediate postoperative period after uneventful corneal collagen crosslinking for keratoconus. The infiltrates resolved with topical steroid therapy. There was also present coexisting vernal keratoconjunctivitis (VKC) which was controlled with topical 2% cyclosporine A eye drops prior to crosslinking treatment. This case highlights importance of controlling VKC prior to CXL in keratoconus as it adds to the risk of developing post operative sterile keratitis.     

Fabrication and Circuit Modeling of NMOS Inverter Based on Quantum Dot Gate Field-Effect Transistors

This paper presents the fabrication of a negative-channel metal–oxide–semiconductor (NMOS) inverter based on quantum dot gate field-effect transistors (QDG-FETs). A QDG-FET produces one intermediate state in its transfer characteristic. NMOS inverters based on a QDG-FET produce three states in their transfer characteristic. The generation of the third state in the inverter characteristic makes this a promising circuit element for multivalued logic implementation. A circuit simulation result based on the Berkley simulation (BSIM) circuit model of the QDG-FET is also presented in this paper, predicting the fabricated device characteristic.     

Non-dendritic Structural Changes in Al–7Si Alloy Cast Through Rapid Slurry Formation (RSF) Process

Rapid slurry formation (RSF) is a semi-solid metal forming technique, which is based on a so-called solid enthalpy exchange material. The beauty of the process is that the slurry is controlled by relative added amounts of the alloy system used. It is not necessary to accurately control the heat flux to surrounding media such as, crucible or mould. In the present investigation 15?% solid fraction in Al?C7Si alloy slurry has been produced by RSF method. The slurry so prepared was cast in gravity die cast mould with water cooling arrangement. Thus ingot of size 30?cm?×?5?cm?×?2.5?cm could be produced. The microstructure showed rosette and globular type ??-Al morphology. Tensile properties evaluated were higher than as cast Al?C7Si alloy. During slurry formation coarsening of particles was experimentally investigated and also theoretically described by Lifshitz-Slyozov-Wagner (LSW) theory and convective mass flow equations.     

A correlation study on the phenolic profiles and corrosion inhibition properties of mangrove tannins (Rhizophora apiculata) as affected by extraction solvents

The objective of this study was to investigate the correlation of phenolic compositions and corrosion inhibition properties of Rhizophora apiculata bark extracts as affected by nine solvent systems. Several phenolic compositions, namely, total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC) were investigated. In addition, the inhibitive actions of tannin extracts on mild steel in 1 M HCl solution were studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that extraction solvents had significant effects on TPC, TFC, CTC and inhibition properties of extracts. A correlation between CTC and inhibition properties of R. apiculata bark extracts was revealed.     

Solubility and dissolution enhancement strategies: current understanding and recent trends

Identification of lead compounds with higher molecular weight and lower aqueous solubility has become increasingly prevalent with the advent of high throughput screening. Poor aqueous solubility of these lipophilic compounds can drastically affect the dissolution rate and subsequently the drug absorbed in the systemic circulation, imposing a significant burden of time and money during drug development process. Various pre-formulation and formulation strategies have been applied in the past that can improve the aqueous solubility of lipophilic compounds by manipulating either the crystal lattice properties or the activity coefficient of a solute in solution or both, if possible. However, despite various strategies available in the armor of formulation scientist, solubility issue still remains an overriding problem in the drug development process. It is perhaps due to the insufficient conceptual understanding of solubility and dissolution phenomenon that hinders the judgment in selecting suitable strategy for improving aqueous solubility and/or dissolution rate. This article, therefore, focuses on (i) revisiting the theoretical and mathematical concepts associated with solubility and dissolution, (ii) their application in making rationale decision for selecting suitable pre-formulation and formulation strategies and (iii) the relevant research performed in this field in past decade.     

Humble,humane and harmonious houses of Laurie Baker

Laurie Baker (1917–2007) was an architect from Birmingham, who settled and worked in India, where he met and was profoundly influenced by Gandhi. In India, he developed simple and indigenous principles of design of houses, which are comfortable and affordable by the poor. Laurie Baker is often called the Mahatma Gandhi of domestic architecture. His work is truly sustainable architecture – ecological, economic and social.     

Gonflement de la chaux dans les briques

Le problème de l'éclatement des briques dû à l'action de la chaux devient grave dans la fabrication des briques en différents endroits de l'lnde et d'ailleurs. Des briques cuites tombent en poussière lorsqu'elles sont exposées à l'air libre, du fait de la présence de particules de chaux. L'Institut central de recherche de la construction de Roorkee s'est attachée à l'étude du mécanisme par lequel les chlorures peuvent prévenir cet inconvénient.