Performance of an industrial biofilter from a composting plant in the removal of ammonia and VOCs after material replacement

BACKGROUND: Biofiltration is a suitable odor reduction technique for the treatment of gaseous emissions from composting processes, but little is known about the start‐up of full‐scale biofilters after material replacement and their performance after several years of operation. RESULTS: Biofilter material (wood chips used previously as bulking agent in a composting process) can effectively remove ammonia and most of the volatile organic compounds (VOCs) content, achieving removal efficiencies greater than 70% for VOCs and near 90% for ammonia immediately after material replacement. These removal efficiencies were maintained for several months after material replacement. In the studied full‐scale biofilter no lag phase was observed in the removal of ammonia whereas in the case of VOCs different patterns were detected during biofilter start‐up. For the old biofilter material, after 4 years of operation, a statistically significant decrease of removal efficiency for ammonia in comparison with the new material was detected. No statistically significant differences were found in the case of VOCs. CONCLUSIONS: Data on the emissions of several pollutants from biofilters treating composting exhaust gases have been systematically obtained. The tested filtering media presented adequate properties for biofiltration of gases emitted during the composting process. Copyright © 2009 Society of Chemical Industry     

Improved magnetic trapped field in thin-wall YBCO single-domain samples by high-pressure oxygen annealing

Oxygen high pressure (up to 16 MPa) has been introduced in the oxygen-annealing step necessary to make the YBa₂Cu₃O_x phase superconducting (change x from 6 to about 7). It enables a displacement in the equilibrium phase diagram towards higher temperatures, which means the possibility to achieve the same final oxygen content as the one at low temperature, but with the benefit of higher diffusion rates. Initial development made on thin bars (1.5–3 mm thick) has confirmed the interest of using a high pressure of oxygen. TEM observations have shown an increase of twin density associated with higher Jc. This is in agreement with other works claiming the possibility of higher Jc by twin engineering, and more precisely by twin refinement while annealing at high temperature. We report the successful application of this process without any adjustment to so-called thin-wall single-domain samples. These samples are obtained by growing a crystal on a pellet already shaped with an array of holes. The advantage is that, as far as diffusion processes are concerned, the typical length is not anymore the diameter of the sample, but the thickness of the walls between holes. The trapped field of 16 mm diameter Y123 thin-wall single-domain samples was doubled (0.6 T vs. 0.3 T at 77 K) in a rather short annealing time (about 3 days). Microstructures as well as magneto-optical observations of plain and thin-wall samples evidenced a reduction of cracks in the thin-wall samples. Improved performances were confirmed by further characterizations performed from 77 down to 20 K using the pulse-field facilities of the LNCMP at Toulouse.     

Conduction mechanism of metal-free phthalocyanine single crystals as a function of temperature

Metal-free phthalocyanine (H₂Pc) single crystals grown by vacuum sublimation were investigated for their conductivity (both in dark and light). The investigations consisted of dark- and photo-current variations with (i) applied electric field and (ii) temperature. The applied electric field ranged from 0·8 kV/cm to 6 kV/cm. The temperature range was from 300°K to around 570°K. The crystals were found to be photoconductive. Based on activation energies calculated from photoconductivity due to temperature dependence, an energy level scheme for H₂Pc single crystals is proposed. The model consists of two trapping levels within the forbidden gap — one at 0·4 eV below the conduction band edge from which electrons are thermally excited into the conduction band and the other acts as recombination centre at 0·3 eV above the valence band edge. The band gap is calculated to be 1·4 eV. Comparative study of the proposed model with that of earlier investigations on the same crystals of the H₂Pc is in good agreement, thereby indicating that H₂Pc is thermally stable even at relatively higher temperature as semiconductor.     

Seed-mediated electrochemical growth of gold nanostructures on indium tin oxide thin films

Two-dimensional gold nanostructures (Au NSs) were fabricated on amine-terminated indium tin oxide (ITO) thin films using constant potential electrolysis. By controlling the deposition time and by choosing the appropriate ITO surface, Au NSs with different shapes were generated. When Au NSs were formed directly on aminosilane-modified ITO, the surface roughness of the interface was largely enhanced. Modification of such Au NSs with n-tetradecanethiol resulted in a highly hydrophobic interface with a water contact angle of 144°. Aminosilane-modified ITO films further modified with colloidal Au seeds before electrochemical Au NSs formation demonstrated interesting optical properties. Depending on the deposition time, surface colors ranging from pale pink to beatgold-like were observed. The optical properties and the chemical stability of the interfaces were characterized using UV-vis absorption spectroscopy. Well-defined localized surface plasmon resonance signals were recorded on Au-seeded interfaces with λ_max = 675 ± 2 nm (deposition time 180 s). The prepared interfaces exhibited long-term stability in various solvents and responded linearly to changes in the corresponding refractive indices.     

Effect of gate length in InAs/AlSb HEMTs biased for low power or high gain

The effect of gate-length variation on DC and RF performance of InAs/AlSb HEMTs, biased for low DC power consumption or high gain, is reported. Simultaneously fabricated devices, with gate lengths between 225 nm and 335 nm, have been compared. DC measurements revealed higher output conductance g_ds and slightly increased impact ionization with reduced gate length. When reducing the gate length from 335 nm to 225 nm, the DC power consumption was reduced by approximately 80% at an f_T of 120 GHz. Furthermore, a 225 nm gate-length HEMT biased for high gain exhibited an extrinsic f_T of 165 GHz and an extrinsic f_max of 115 GHz, at a DC power consumption of 100 mW/mm. When biased for low DC power consumption of 20 mW/mm the same HEMT exhibited an extrinsic f_T and f_max of 120 GHz and 110 GHz, respectively.     

Modeling of a bacterial and fungal biofilter applied to toluene abatement: Kinetic parameters estimation and model validation

Biofiltration has been established as a promising alternative to conventional air pollution control technologies. However, gas biofilters modeling has been less developed than experimental research due to the complexity of describing the fundamental processes and the lack of globally accepted physical, chemical and biological parameters. In addition, biofiltration modeling based on degradation activity of fungi has been rarely considered. For this reason, in this work, a dynamic model describing toluene abatement by a bacterial and fungal biofilter is developed, calibrated and validated. The mathematical model is based on detailed mass balances which include the main processes involved in the system: convection, absorption, diffusion and biodegradation. The model was calibrated and validated using experimental data obtained from two equal lab-scale biofilters packed with coconut fiber and pine leaves, respectively. Both reactors were operated under similar conditions during 100 days at an empty bed residence time of 60 s and an average inlet load of 77 g toluene m⁻³ h⁻¹. Biofilters were initially inoculated with a bacterial consortium, even though reactors were mostly colonized by fungi after 60 days of operation according to microscopic observation and reactors pH. Removal efficiency increased notably from 20% for the bacterial period to 80% for the fully developed fungal biofilters. Since kinetic parameters are strongly dependent on the biological population, semi-saturation constants for toluene and maximum growth rates were determined for bacterial and fungal operation periods. Kinetic parameters were fitted by means of an optimization routine using either outlet concentrations or removal efficiency data from the coconut fiber biofilter. A novel procedure in gas biofilters modeling was considered for checking the model calibration, by the assessment of the parameters confidence interval based on the Fisher Information Matrix (FIM). Kinetic parameters estimated in the coconut fiber reactor were validated in the pine leaves biofilter for bacterial and fungal operation. Adequate model fitting to the experimental outlet gas concentration for both bacterial and fungal operation periods was verified by using a standard statistical test.     

Different strategies to recover the activity of monomeric triosephosphate isomerase by directed evolution

A monomeric version of triosephosphate isomerase from Trypanosomabrucei, MonoTIM, has very low activity, and the same is truefor all of the additional monomeric variants so far constructed.Here, we subjected MonoTIM to directed evolution schemes toachieve an activity improvement. The construction of a suitablestrain for genetic selection provided an effective way to obtainactive catalysts from a diverse population of protein variants.We used this tool to identify active mutants from two differentstrategies of mutagenesis: random mutagenesis of the whole geneand randomization of loop 2. Both strategies converged in theisolation of mutations Ala43 to Pro and Thr44 to either Alaor Ser, when randomizing the entire gene or to Arg in the caseof randomization of loop 2. The kinetic characterization ofthe two more active mutants showed an increase of 11-fold ink_cat and a reduction of 4-fold in K_m for both of them, demonstratingthe sensitivity of the selection method. A small differencein growth rate is observed when both mutant genes are compared,which seems to be attributable to a difference in solubilityof the expressed proteins.     

High temperature deformation of oxide scale

Samples of ultra low carbon steel were oxidized in a chamber designed to control the thickness of the scale layer prior to their deformation by plane strain compression. The specimens were reheated within the temperature range of 950-1150 °C for different periods of time to vary the scale thickness; compression was conducted at temperatures that vary from 650 to 1150 °C. Metallographic analyses were conducted on deformed and undeformed scales to evaluate the integrity of the oxide crust that is made almost exclusively of wustite. It was found that the integrity of the crust depends on the temperature at which deformation is carried out and on the amount of deformation imparted. It is concluded that thin scales exhibit a plastic behaviour when deformed at temperatures above 900 °C and a brittle behaviour at temperatures below 700 °C; mixed behaviour was observed within this temperature range, as the scale was found to resist limited amounts of deformation.     

Novel TTLL5 Variants Associated with Cone-Rod Dystrophy and Early-Onset Severe Retinal Dystrophy

Variants of the TTLL5 gene, which encodes tubulin tyrosine ligase-like family member five, are a rare cause of cone dystrophy (COD) or cone-rod dystrophy (CORD). To date, only a few TTLL5 patients have been clinically and genetically described. In this study, we report five patients harbouring biallelic variants of TTLL5. Four adult patients presented either COD or CORD with onset in the late teenage years. The youngest patient had a phenotype of early onset severe retinal dystrophy (EOSRD). Genetic analysis was performed by targeted next generation sequencing of gene panels and assessment of copy number variants (CNV). We identified eight variants, of which six were novel, including two large multiexon deletions in patients with COD or CORD, while the EOSRD patient harboured the novel homozygous p.(Trp640*) variant and three distinct USH2A variants, which might explain the observed rod involvement. Our study highlights the role of TTLL5 in COD/CORD and the importance of large deletions. These findings suggest that COD or CORD patients lacking variants in known genes may harbour CNVs to be discovered in TTLL5, previously undetected by classical sequencing methods. In addition, variable phenotypes in TTLL5-associated patients might be due to the presence of additional gene defects.     

Slag corrosion of dolomite-carbon refractories

Seven industrial doloma refractory samples, coming from three European suppliers, and with different carbon, or graphite, or binder content, are subjected to the action of a slag required for the desulfurization of the steel in the secondary metallurgy at 1600°C. Three tests have been carried out within two induction furnaces. The corrosion depth, at the slag-steel interface, has been measured; the graphite-containing samples display a better resistance than the graphite-free pitch or resin-bonded refractories. Among the graphite-containing samples correlations have been found with the carbon content and with the resistance to oxidation by CO–CO₂ at 1100–1200°C. The slag-refractory interface has been investigated by X-ray diffraction, optical microscopy and electron microprobe analysis; the observed phases are CaO, MgO, Ca₂SiO₄, Ca₃SiO₅ and Ca₁₂Al₁₄O₃₃ (outside graphite and iron). The corrosion mechanism is linked to the reaction of slag with lime, followed by infiltration of the refractory and dispersion of periclase grains in the slag.