Cavity ignition and flameholding of ethylene–air and hydrogen–air flows by a repetitively pulsed nanosecond discharge

Repetitive nanosecond pulse plasma assisted ignition and flameholding of premixed and non-premixed ethylene–air and hydrogen–air flows are studied in a cavity flow at a pressure of 0.2 atm and flow velocities of up to 100 m/s. Ignition occurs via formation of multiple filaments in the fuel–air plasma, although air plasma remains diffuse until the fuel is added. After ignition occurs in the cavity, with ignition delay time of a few milliseconds, the plasma becomes diffuse and the flame couples out to the main flow. The use of a short cavity (length-to-depth ratio L/D = 1) results in repetitive ignition and flame blow-off, caused by slow mixing between the main flow and the cavity. Increasing the length-to-depth ratio to L/D = 3, as well as choking inlet air and fuel flows resulted in stable flameholding and nearly complete combustion in both premixed and non-premixed ethylene–air and hydrogen–air flows at u = 35–100 m/s. Air plasma temperature before fuel is added ranges from 70 °C to 200 °C. When the nanosecond pulse discharge is operated in repetitive burst mode, continuous ethylene–air flame is maintained only at a high duty cycle, which increases with the flow velocity. In hydrogen–air, the flame remains stable after the plasma is turned off. Nanosecond pulse discharge ignition of ethylene–air is compared with ignition by DC arc discharge of approximately the same power. DC arc discharge results in sporadic ignition and flame blow-off, much lower burned fuel fraction, and significantly lower flow velocity at which ignition can be achieved. Kinetic modeling is used to identify the reduced mechanism of plasma chemical oxidation and ignition of hydrogen, and to demonstrate the mechanism of energy release low-temperature reactions of radicals generated in the plasma (primarily O and H atoms).     

VOLTAGE-MEDIATED CONFORMATIONAL CHANGES OF A POLYELECTROLYTE IN A LINEAR ELASTIC MEMBRANE

The wall of the cylindrically-shaped outer hair cell is piezoelectric, which allows the cell to function as an electromechanical transducer in the mammalian inner ear. Polyelectrolytes, which are located in the cell wall, may be responsible for the cell's piezoelectric properties. The polyelectrolytes can change conformation in response to a change in the external electric field; this conformational change can cause the cell to change its length. We have developed a model to predict the voltage response of a cylindrical cell whose wall contains conformationally-mobile polyelectrolytes. The cell wall is modeled as a rectangular lattice of polyelectrolytes connected by springs. The springs represent the (non-piezoelectric) elastic portion of the cell wall. The polyelectrolytes can exist in one of two possible conformations. The energy of the polyelectrolyte is a function of both the trans-wall electric potential difference and the forces which are applied by the surrounding elastic material in the wall. The fraction of polyelectrolytes in a given conformation is determined by the relative energies of the two conformations, by means of a Boltzmann distribution. If the electric potential difference and the pressure difference between the inside and outside of the cell are known, the model can predict the cell's radius, the length, the fraction of polyelectrolytes in a given conformation, and the electrical capacitance of the cell wall (due to the polyelectrolyte activity). We also propose an experimental scheme which would provide data that could be used to evaluate the parameters in our model. Our simulations predict that the electrical capacitance vs. voltage function should exhibit a peak which simply shifts its location (without a significant change in height) when the intracellular pressure is changed. In addition, we demonstrate that electrical stimulation of the cell, under conditions of constant cell volume, could result in a significant change in the intracellular pressure.     

Hot-air drying of whole fruit Chinese jujube (Zizyphus jujuba Miller): physicochemical properties of dried products

Drying characteristics of whole fruit was studied as distinct from fruit slices. Taking Chinese jujube as an example, shrinkage, density, vitamin C, colour and rehydration of whole fruit were measured in hot-air drying at 50, 60 and 70 °C. Unlike fruit slices or lumps where shrinkage volume typically equals the volume of removed water, volumetric shrinkage of Chinese jujube was much more than the volume of removed water. Change in shrinkage with moisture content was described using three linear regions. Increased drying temperature increases the retention of vitamin C and the extent of browning, while decreasing shrinkage and the density. The findings are useful for industrial drying of whole fruit of Chinese jujube but also possibly extend to drying of other drupes.     

Book reviews

Applied Environmetrics Hydrological Tables. Tom Beer. Victoria, Australia, Applied Environmetrics, 1991, 73 pp. + 1 diskette 360 Kb, US$ 124.95.

Drainage Guidelines. Walter J. Ochs & Bishay G. Bishay. Washington, DC, The International Bank for Reconstruction and Development/The World Bank (Technical Paper Number 195), 1992, 186 pp., price not given.

Groundwater Treatment Technology (2nd edn). Evan K. Nyer. New York, Van Nostrand Reinhold, 1992, 306 pp., £36.50.

Surveillance of Drinking Water Quality in Rural Areas. Barry Lloyd & Richard Helmer. Harlow, UK, Longman Scientific & Technical, 1991, xvi +171 pp., £9.99.

Disinfection Alternatives For Safe Drinking Water. Edward A. Bryant, George P. Fulton & George C. Budd. New York, Van Nostrand Reinhold, 1992, 518pp., £43.50, ISBN 0–442–31841–3.     

Abundance and nutrient limiting growth rate of heterotrophic bacterio-plankton in Himalayan foot hill Lake Phewa, Nepal

We examined heterotrophic bacterial abundance, chlorophyll- a concentration and resources limiting bacterial growth from October 2004 to August 2005 in Lake Phewa. The lake has a large watershed that covers ≈435 ha of water surface surrounded by ≈23-time large catchment area that might receive up to 4850 mm annual precipitation. During the study, bacterial abundance ranged from 3.2 to 9.9 × 10⁶ cells mL⁻¹, and chlorophyll- a varied from 2 to 32 μg L⁻¹. Bacterial abundance and chlorophyll- a weakly correlated ( r  = 0.40, n  = 77, P  < 0.1) in the lake. Experiments on resources, glucose (C), nitrogen (N), phosphorus (P) alone and in combination (CNP) limiting bacterial growth rate, were examined using dilution bioassays. Experimental bottles enriched with resources and controls without enrichment (in triplicate) were incubated in situ for 48 h at collection depth. Results showed that C, N and P in combination significantly (at 5% level) stimulated bacterial growth rate. Bioassays with single resource additions showed P as main nutrient limiting bacterial growth comparing with C and N, implying that rainfall received in the catchment might convey adequate resources causing increased P deficiency for bacterial growth in Himalayan foot hill Lake Phewa.     

Densification of Pond Ash by Blasting

Fly ash from thermal power plants is disposed, in huge quantities in ash ponds, which occupy large land areas otherwise useful for agriculture, housing, or other development. For effective rehabilitation of ash ponds, densification of the slurry deposit is essential to increase the bearing capacity and to improve its resistance to liquefaction. Extensive field trials were carried out to evaluate the effectiveness of deep blasting for densification of deposited fly ash. Ninety explosions comprising 15 single blasts, with varying depths and quantities of charges, and 3 group blasts, each having 25 charges placed at various spacings, were carried out. The compaction achieved in terms of an increase in relative density was evaluated from surface settlement measurements. Extensive field monitoring was undertaken through pore-water pressure measurements, vibration measurements, penetration tests, and block vibration tests. For the average charge of 2–4 g of explosive per cubic meter of untreated deposit, the average relative density was found to improve from 50% to 56–58%. Analysis of the test results indicates that deep blasting may be an effective technique for modest compaction of loose fly ash deposits. The field testing program presented in this paper provides valuable information that can be used for planning blast densification of fly ash deposits.     

Identifying Genetic Biomarkers Predicting Response to Anti-Vascular Endothelial Growth Factor Injections in Diabetic Macular Edema

Intraocular anti-vascular endothelial growth factor (VEGF) therapies are the front-line treatment for diabetic macular edema (DME); however, treatment response varies widely. This study aimed to identify genetic determinants associated with anti-VEGF treatment response in DME. We performed a genome-wide association study on 220 Australian patients with DME treated with anti-VEGF therapy, genotyped on the Illumina Global Screening Array, and imputed to the Haplotype Reference Consortium panel. The primary outcome measures were changes in central macular thickness (CMT in microns) and best-corrected visual acuity (BCVA in ETDRS letters) after 12 months. Association between single nucleotide polymorphism (SNP) genotypes and DME outcomes were evaluated by linear regression, adjusting for the first three principal components, age, baseline CMT/BCVA, duration of diabetic retinopathy, and HbA1c. Two loci reached genome-wide significance (p < 5 × 10⁻⁸) for association with increased CMT: a single SNP on chromosome 6 near CASC15 (rs78466540, p = 1.16 × 10⁻⁹) and a locus on chromosome 12 near RP11-116D17.1 (top SNP rs11614480, p = 2.69 × 10⁻⁸). Four loci were significantly associated with reduction in BCVA: two loci on chromosome 11, downstream of NTM (top SNP rs148980760, p = 5.30 × 10⁻⁹) and intronic in RP11-744N12.3 (top SNP rs57801753, p = 1.71 × 10⁻⁸); one near PGAM1P1 on chromosome 5 (rs187876551, p = 1.52 × 10⁻⁸); and one near TBC1D32 on chromosome 6 (rs118074968, p = 4.94 × 10⁻⁸). In silico investigations of each locus identified multiple expression quantitative trait loci and potentially relevant candidate genes warranting further analysis. Thus, we identified multiple genetic loci predicting treatment outcomes for anti-VEGF therapies in DME. This work may potentially lead to managing DME using personalized treatment approaches.     

THE INFLUENCE OF AXIAL LOADING ON THE ELECTROMECHANICAL RESPONSE OF THE OUTER HAIR CELL

The cylindrically-shaped outer hair cell functions as an active support beam in the inner ear. We develop a model for electromechanical transduction when the cell supports a load. The model is an extension of Jerry and Dutta [Chemical Engineering Communications, 166 (1998), 81 -110]. We use our model to simulate a “tensile test” on the cell, similar to that used to measure the elastic modulus for plastic, metal and ceramic specimens. Our work demonstrates the importance of accurate control of cell volume or intracellular pressure during experiments, and also suggests that voltage clamping may not be necessary when measuring the elastic properties of the cell. A plot of the polyelectrolyte-associated charge (that is moved across the wall) vs. the load reveals a charge reversal effect: at a particular value of the load, the direction of charge movement changes. The effect can be explained using our model.     

Dynamic Threshold Based Throughput Enhancement in Cognitive Radio Network Using Hidden Markov Model with State Prediction

Wireless Personal Communications - The enhancement of throughput is one of the key issues in the cognitive radio network. In this paper, a channel status prediction scheme based on hidden Markov...     

A novel improved whale optimization algorithm to solve numerical optimization and real-world applications

Artificial Intelligence Review - Whale optimization algorithm (WOA) has been developed based on the hunting behavior of humpback whales. Though it has a considerable convergence speed, WOA suffers...