Optimization of growth determinants of a potent cellulolytic bacterium isolated from lignocellulosic biomass for enhancing biogas production

Clean Technologies and Environmental Policy - Anaerobic digestion of lignocellulosic biomass is limited by inefficient hydrolysis of recalcitrant substrates, leading to low biogas yields where...     

Chemical evolution of alkali–silicate reaction (ASR) products: a Raman spectroscopic investigation

The objective of this study was to use Raman spectroscopy to study the morphology and chemical changes of alkali–silicate reaction (ASR) products over time. The reaction products induced by ASR on soda-lime glass slides in a high temperature alkaline environment (1 N NaOH at 80 °C) enriched with calcium hydroxide were studied at 0, 1, 4, 7, 14 and 28 days. The results show that the morphology of the granular-like and fan-like fascicles structure that formed at early ages was more ordered in terms of polymerization and dominated by Q³ and Q² units. This information implies that the ASR products were probably of mainly alkali silica composition with low content of calcium in the structure. As the reaction proceeded the products depolymerized, forming a cloud-like morphology of decreased structural order which surrounded the initial product particles. It can be hypothesized that more calcium ions in the soak solution entered into the particle structure, promoting a depolymerization and possible formation of a C–S–H phase which was indicated by the dominant presence of Q¹ units after 7 days of exposure. To corroborate the interpretation of Raman spectra, 28-day ASR products were verified by Fourier transform infrared.     

Engineered flux-pinning centers in Bi2Sr2CaCu2Ox and TIBa2Ca2Cu3Ox superconductors

Three methods were used to introduce flux-pinning centers into Bi₂Sr₂CaCu₂O_x (Bi-2212) and TlBa₂Ca₂Cu₃O_x (Tl-1223) samples. It was found that carbon induced local decomposition, that nanosized Al₂O₃ additions created stable reaction products, and that second phases could be isolated in Tl-1223 during synthesis. Each of these defects enhanced flux pinning and was of most benefit at temperatures ≤ 35K.     

An eco-friendly option for less-chrome and dye-free leather processing: in situ generation of natural colours in leathers tanned with Cr–Fe complex

A chromium–iron tanning agent has been prepared and used for tanning with the objective of high exhaustion of chromium. Chromium–iron tanned leathers exhibit comparable shrinkage temperature and strength properties with those of conventional chromium tanned leathers. There is no change in strength or colour on ageing the leathers for 1 year. Spent tan liquor analysis reveals that the exhaustion of both the metals is more than 90%. Dyes based on synthetic formulations are being widely used in the leather industry. However, it is known that many aryl amine dyes are banned because of their carcinogenic nature. Environmental concern leads one to look for dyes based on natural resources. A novel approach has been taken to achieve an eco-friendly coloration process utilizing the presence of iron in the tanning salt, which gives rise to various colours on reacting with vegetable tannins. Skins have been tanned with Cr–Fe tanning salt and complexed with different vegetable tanning materials such as myrobalan and quebracho at various concentrations. Colours such as brown, black and grey have been developed. The colour shades obtained have been quantified by reflectance measurements. Thus, the study provides not only clean processes for a greener environment but also clean leather without harmful synthetic dyes. Electronic Publication     

Formation of ceramic thin films using electrospray in cone-jet mode

An electrostatic atomization technique has been developed to generate ultrafine spray droplets of ZrO₂ and SiC ceramic suspensions in a range of a few micrometers with a narrow size distribution. The aim of this paper is to deposit uniform thin films (from a few micrometers to a few tens of micrometers) of these ceramic materials on alloy substrates. Compared to some other thin-film deposition techniques, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and plasma spray (PS), etc., the thin-film deposition process using electrostatic atomization is not only cheap but also capable of depositing a very thin multilayer with abrupt interfaces. CVD and PVD are expensive techniques. They require either a high vacuum, even an ultrahigh vacuum environment or complex gas handling system. Their deposition rate is also low. PS is normally used to grow thermal barrier coatings which usually have a thickness of a few tens to a few hundreds micrometers. Its application is limited by the quality of the coatings (high porosity, coarse and nonuniform microstructure). Preliminary results in this work have shown that, for low through-put atomization, the cone-jet is the most suitable method to produce a fine charged aerosol with a narrow size distribution, which is crucial to produce uniform thin films. It was found that the size of ceramic particles in ZrO₂ and SiC thin films is less than 10 μm. Microstructures of these thin films show very homogenous morphologies. These results indicate that ceramic thin films with high homogeneity can be deposited using electrostatic atomization. It was also observed that the morphology of the underlayer has some influence on the morphology of the top layer     

Advances in processing and characterizing Bi-based superconductors

Advances in the processing and fabrication of mono- and multifilament Bi-2223/2212 high-critical-temperature superconductors by the powder-in-tube technique continue to bring these materials closer to commercial applications. Consistently high critical- current densities (J_c) greater than 10⁴ A/cm₂ have been achieved along the entire length of a 1,260 m long, 37 filament Bi-2223 tape. Pancake-shaped coils, test magnets, and a prototype transformer were fabricated and characterized from such long conductors. Record high fields have been generated in prototype test magnets operated as inserts in the high background fields of conventional low-critical-temperature magnets. With an eye toward commercialization, this article reviews some of the recent advances in the processing and characterization of bismuth-based tapes.     

Nonlinear oscillations of a harmonically excited composite structure

An experimental study was conducted of the nonlinear forced response of an internally-resonant composite structure to primary resonant excitations. Coupling between the directly excited and indirectly excited modes of vibration of the structure leads to nonlinear periodic, periodically modulated, and chaotically modulated responses. Some of the observed nonlinear responses are nonplanar due to interaction between flexural and torsional modes of vibration. Experimental results are presented and compared with those obtained in earlier studies of a metallic structure having a similar form.     

Silicon-based microelectrodes for neurophysiology fabricated usinga gold metallization/nitride passivation system

The multimicroelectrode probe (microprobe) is a device used in neurophysiology to record signals from nerve cells. Microprobes typically have a number of gold recording sites supported on a narrow cantilever beam which is inserted into the tissue. Conducting tracks connect the recording sites to bonding pads on the body of the device. The metallization is insulated, except at the recording sites and bonding pads, by a passivation layer. Boron etch stop techniques can be used to produce narrow cantilever beams upon which recording sites are situated. Previously, polysilicon interconnects were used on microprobes fabricated using boron etch stop techniques, with gold inlaid onto the recording sites using a lift-off technique. This meant that mechanical jigging was required before the final shaping of the probes in potassium hydroxide (or other etch) to prevent the etch from attacking the polysilicon conductors beneath the inlaid gold. The process reported here incorporates a gold metallization layer, in conjunction with a plasma-enhanced chemical vapor deposition (PECVD) nitride passivation layer. Since both these materials etch very slowly in potassium hydroxide, no mechanical jigging, or other steps, need to be taken to protect the front of the wafer during the shaping stage. This simplifies the fabrication of these devices     

Nozzle extraction geometry of a liquid metal atomizer optimized bycomputer simulation of electric fields

Experimental measurements are compared with results obtained using a dedicated computer program for finite element modeling of electric fields in the vicinity of a liquid metal atomizer nozzle/tip. Good agreement between the experiment and the computer model has been achieved for two different nozzle geometries (Taylor cone and rounded tip), while paying particular attention to accuracy of the numerical solution near the tip (for equipotentials as well as derived values of field strength). In addition, the potential distribution has been calculated for several different positions of extractor voltage observed for each case. Finally, the assessment of suitability of the computer technique for qualitative consideration of the atomization process itself is presented