Synthesis of Fe–SiC Nanowires via Precursor Route

Magnetic SiC nanowires were obtained by the pyrolysis of iron containing polycarbosilane (PCS) which in turn was synthesized by the reaction of polycarbosilane and iron (III) acetylacetonate [Fe(acac)₃] in solvent. Characterization of synthesized polycarbosilane and Fe–SiC were performed with Fourier transformation infrared spectroscopy, energy dispersive X-ray spectrometry, powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, electron spin resonance and vibrating sample magnetometer.     

Cichoric acid production from hairy root cultures of Echinacea purpurea grown in a modified airlift bioreactor

BACKGROUND: Hairy root cultures of Echinacea offer great potential for the production of valuable cichoric acid, but scale‐up of the culture in the bioreactor represents a big challenge. Therefore, there is great interest in developing a suitable bioreactor for hairy root culture of Echinacea and novel bioprocessing strategies for intensifying cichoric acid production. RESULTS: Homogenous distribution of inoculum roots and high cichoric acid production were observed in a bioreactor modified by installing a mesh draught tube with an average pore size 700 µm, slightly larger than the hairy root, about 500 µm. Improved root growth and cichoric acid production were improved by increasing the aeration rate from 0.002 m³ h^?1 to 0.012 m³ h^?1. The hairy root cultures in the modified bioreactor exposed once to 6 min of ultrasound treatment at day 20 gave the highest biomass accumulation of 12.8 ± 0.3 g L^?1, which resulted in the maximum cichoric acid production of 178.2 ± 4.9 mg L^?1 at day 30. CONCLUSION: The present work demonstrated the effectiveness of hairy root culture in a modified airlift bioreactor. The biomass distribution remained homogenous in the modified airlift bioreactor, and the cichoric acid production was improved owing to the even root growth at optimal air flow rate. An interesting finding of this investigation was that ultrasound stimulated root growth and cichoric acid production considerably in the modified airlift bioreactor. Copyright © 2009 Society of Chemical Industry     

Novel Three Dimensional Cubic Fm3m Mesoporous Aluminosilicates with Tailored Cage Type Pore Structure and High Aluminum Content

Novel three dimensional cubic Fm3m mesoporous aluminosilicates (AlKIT‐5) with very high structural order and unprecedented loadings of Al in the silica framework have been successfully prepared for the first time by using non ionic surfactant as a template in a highly acidic medium. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques such as XRD, N₂ adsorption, HRTEM, HRSEM, EDS, elemental mapping, ²⁷Al MAS NMR, and NH₃‐TPD. We also demonstrate that the nature, and the amount of Al incorporation in the silica framework can easily be controlled by simply varying the n_H2O/n_HCl and the n_Si/n_Al ratios, and the Al sources in the synthesis gel. Among the Al sources examined, the Al isopropoxide (AiPr) is superior over other Al sources. ²⁷Al MAS NMR results reveal that the amount of tetrahedral Al in the framework can be controlled by simply adjusting the n_Si/n_Al ratio in the synthesis gel, which increases with increasing the Al incorporation. One of the interesting findings in the work is the increase of the specific surface area, specific pore volume and the pore diameter of AlKIT‐5 with increasing the Al incorporation in the silica framework (up to n_Si/n_Al ratio of 10) while retaining the well‐ordered three dimensional cage type porous structure, and the mechanism for the unusual behavior has been discussed in detail. Finally, the acidity and the catalytic activity in the acetylation of veratrole of the AlKIT‐5 catalysts have been studied and the results have been compared with the several zeolites catalysts. Among the catalysts examined, AlKIT‐5(10) is found to be superior over the zeolites catalysts such as mordenite, zeolite H‐Y, zeolite H‐β, and ZSM‐5.     

Biodiesel production from palm oil via heterogeneous transesterification

This paper presents the study of the transesterification of palm oil via heterogeneous process using montmorillonite KSF as heterogeneous catalyst. This study was carried out using a design of experiment (DOE), specifically response surface methodology (RSM) based on four-variable central composite design (CCD) with α (alpha) = 2. The transesterification process variables were reaction temperature, x₁ (50–190 °C), reaction period, x₂ (60–300 min), methanol/oil ratio, x₃ (4–12 mol mol^?1) and amount of catalyst, x₄ (1–5 wt%). It was found that the yield of palm oil fatty acid methyl esters (FAME) could reach up to 79.6% using the following reaction conditions: reaction temperature of 190 °C, reaction period at 180 min, ratio of methanol/oil at 8:1 mol mol^?1 and amount of catalyst at 3%.     

Laser assisted surface modification of AZ91 alloy: Microstructural and electrochemical study

Laser assisted surface modification has been used to produce variety of surface/sub-surface microstructures in AZ91 alloy. Refined microstructures thus produced have been characterized by metallography. Electrochemical corrosion behaviour of these variations is studied using polarization curves and compared to that of sand-cast alloy. Scanning electron microscope is used to determine post corrosion morphology. The corrosion behaviour is correlated to refined microstructures developed upon laser treatment.     

Compressing Two-Dimensional Routing Tables

We consider an algorithmic problem that arises in the context of routing tables used by Internet routers. The Internet addressing scheme is hierarchical, where a group of hosts are identified by a prefix that is common to all the hosts in that group. Each host machine has a unique 32-bit address. Thus, all traffic between a source group s and a destination group d can be routed along a particular route c by maintaining a routing entry (s, d, c) at all intermediate routers, where s and d are binary bit strings. Many different routing tables can achieve the same routing behavior. In this paper we show how to compute the most compact routing table. In particular, we consider the following optimization problem: given a routing table D with N entries of the form (s, d, c) , determine a conflict-free routing table with fewest entries that has the same routing behavior as D. If the source and destination fields have up to w bits, and there are at most K different route values, then our algorithm runs in worst-case time O( NK w ² ) .     

Multidimensional Test Escape Rate Modeling

Today's SoC designs contain many types of circuitry, each with various test types. This article revisits the classic test escape models and highlights their limitations in a test environment with different types of circuits and different test types with overlapping coverage. A new methodology for test escape rate prediction is presented.     

Al2O3 nanoparticles with and without polyoxometalates as reactive sorbents for the removal of sulphur mustard

Nanoparticles of AP–Al₂O₃ (aerogel produced alumina) have been produced by an alkoxide based synthesis involving aluminum powder, methanol, toluene and water. Thus produced alumina nanoparticles were characterized by N₂-BET, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transformed infra-red spectroscopy and thermogravimetry techniques. The data indicated the formation of nanoparticles of alumina in the size range of 2–30 nm with high surface area (375 m²/g) and microporous–mesoporous characteristics. Thereafter, these nanoparticles were impregnated with polyoxometalates and other reactive chemicals, which have already proven to be effective against sulphur mustard (HD). Adsorptive removal kinetics for HD was monitored by GC–FID (gas chromatograph coupled with flame ionization detector) technique and found to be following pseudo first order reaction kinetics. Among polyoxometalates impregnated alumina nanoparticles based novel mesoporous reactive sorbent systems AP–Al₂O₃ impregnated with 9-molybdo-3-vanadophosphoric acid (10%, w/w) was found to be the most reactive with least half life value (214 min). In addition to this, degradation products of sulphur mustard on prepared mesoporous reactive sorbents were identified using GC/MS technique. Hydrolysis, dehydrohalogenation and oxidation reactions were found to be the route of degradation of sulphur mustard.     

Performance study of modified ZSM‐5 as support for bimetallic chromium–copper catalysts for VOC combustion

The catalytic performance of bimetallic chromium–copper supported over untreated ZSM‐5 (Cr? Cu/Z), ZSM‐5 treated with silicon tetrachloride (Cr–Cu/SiCl₄‐Z) and ZSM‐5 treated with steam (Cr–Cu/H₂O‐Z) is reported. The activity is based on the combustion of ethyl ethanoate and benzene at a feed concentration of 2000 ppm and a gas hourly space velocity (GHSV) of 32 000 h^?1. Due to higher reactivity and larger molecular size compared with that of water molecules, SiCl₄ reacted at the external surface of ZSM‐5 crystals. Cr–Cu/SiCl₄‐Z and Cr–Cu/H₂O‐Z both gave slightly lower conversion and carbon dioxide yield compared with Cr–Cu/Z. This was attributed to larger active metal crystallites formed in the mesopores and narrowing pore mouth and pore intersection by extraframework species. Cr–Cu/SiCl₄‐Z and Cr–Cu/H₂O‐Z both had reduced concentration and strength of acid sites, thus making them less susceptible to deactivation by coking. The coke accumulated by these two catalysts was relatively softer and more easily decomposed in oxygen during catalyst regeneration. Copyright © 2004 Society of Chemical Industry     

Two-dimensional analytical threshold voltage model for DMG Epi-MOSFET

A two-dimensional (2-D) analytical model of a dual material gate (DMG) epitaxial (Epi)-MOSFET for improved, SCEs, hot electron effects, and carrier transport efficiency is presented. Using a two-region polynomial potential distribution and a universal boundary condition, we calculated the 2-D potential and electric field distribution along the channel. An expression for threshold voltage for short-channel DMG Epi-MOSFETs is also derived. The ratio of gate lengths has been varied to show which gate length ratio gives the best performance. The analytical results have been validated by the 2-D device simulator ATLAS over a wide range of device parameters and bias conditions.