The effect of corona discharge on free convection heat transfer from a horizontal cylinder

Free convection heat transfer from an isothermal horizontal cylinder in the presence of DC positive corona discharge with a blade edge emitter electrode has been studied experimentally and numerically. A Mach–Zehnder interferometer was used to determine the local Nusselt numbers. The effect of corona discharge on heat transfer from the cylinder was investigated at Rayleigh numbers in the range between 1500 and 5000. To find the details of the flow patterns and to further verify the experimental results, numerical simulations were also performed. It was found that the numerical results are in good agreement with experimental data. By increasing the applied voltage up to 15.5 kV, the corona discharge generates a recirculation zone around the blade and below the lower stagnation point of the cylinder. The effect of the recirculation zone becomes stronger near the breakdown voltage (17 kV) and it is responsible for a local decrease in the cooling of the cylinder around the lower stagnation point. The results indicate that corona discharge has a significant effect on the average Nusselt number at lower Rayleigh numbers whereas it has smaller effect at higher Rayleigh numbers.     

Generating of quadratic gray scale beam profile using binary gray scale masks

Generating beams with a desired quadratic lateral intensity distribution using 1D binary masks was analyzed, in detail. Effect of width of the first bar as well as the gray scale increment rate on the generated shaped beam was examined. It is shown that increasing the gray scale rate produces smoother and broaden profile. Besides, it was demonstrated that width of the first bar has great impact on the generated profile, so by increasing the width, the generated profile becomes sharper. Theoretical results are confirmed by experiment, as well.     

Devitrification behaviour of Cu-Zr-Ti-Pd bulk glassy alloys

The glass formation, mechanical properties and devitrification of the Cu-Zr-Ti-Pd glassy alloys are studied. The formation of a nanoscale icosahedral phase in Cu-based alloys is observed. The nanoscale particles with icosahedral symmetry are primarily formed in the Cu-Zr-Ti-Pd glassy alloys in the initial stage of the devitrification process. As the icosahedral phase is metastable it transforms to the equilibrium oC68 (Cu, Pd)₁₀(Zr, Ti)₇ single phase or its mixture with the oP44 Cu₈Zr₃ phase, depending upon the alloy composition, through an intermediate crystalline compound. The structure changes on heating were studied by X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry.     

Comparison of the performance of different hybrid catalysts for direct synthesis of dimethyl ether from synthesis gas

Nine hybrid catalysts have been prepared, characterized and tested in a micro reactor for the direct synthesis of dimethyl ether. The physical mixtures of H-MFI-90 with ICI or KMT catalysts showed better performance.     

Automated mass spectrometric sequence determination of cyclic peptide library members

Cyclic peptides have come under scrutiny as potential antimicrobial therapeutic agents. Combinatorial split-and-pool synthesis of cyclic peptides can afford single compound per well libraries for antimicrobial screening, new lead identification, and construction of quantitative structure-activity relationships (QSAR). Here, we report a new sequencing protocol for rapid identification of the members of a cyclic peptide library based on automated computer analysis of mass spectra, obviating the need for library encoding/decoding strategies. Furthermore, the software readily integrates with common spreadsheet and database packages to facilitate data visualization and archiving. The utility of the new MS-sequencing approach is demonstrated using sonic spray ionization ion trap MS and MS/MS spectrometry on a single compound per bead cyclic peptide library and validated with individually synthesized pure cyclic D,L-alpha-peptides.     

Preparation and characterization of aqueous polyaniline battery using a modified polyaniline electrode

A rechargeable battery of the type Zn/ZnCl₂, NH₄Cl/polyaniline (PAn)-reticulated vitreous carbon was successfully prepared based on a PAn modified electrode. Voltage of the battery was 1.2 V. Charge-discharge behavior at a constant load of 2.5 k, recycle ability and the rate of self-discharge were measured. The results showed that the battery has a capacity of 121 mA h g⁻¹ polymer weight and coulombic efficiency was in the range between 75% and 100%. Self-discharge rate was less than 1% per day and the battery showed a good recycle ability. It was also found that even after 70 cycles, the decrease in the open-circuit voltage was less than 5%.     

Automatic Controls for Nonlinear Dynamical Systems with Lipschitzian Trajectories

We would like to investigate on the solution to the automatic control problem given by the differential equation y′(t) = f(t, y(t), w(t)) for a given initial function x in the initial domain D(x, ω, Y) for almost all t in the interval I, with controls given by w(t) = g(t, y(t), T(y)(t)), where T is a nonanticipating and Lipschitzian operator. The result will be generalized for a dynamical system y′(t) = f(t, y(t), T(y), u(t)).     

A Spectral Representation for Weakly Periodic Sequences F Bounded Linear Transformations

A spectral representation for certain sequences of bounded linear transformations between two Hilbert spaces, namely; weakly periodic, is given. In this representation the elements of a weakly periodic sequence, {An, n Z} L(X, Y), are viewed, in the weak sense, as the Fourier coefficients of a certain set function on the Borel sets of [0, 2) with values in L(X, Y).     

Study on interaction of alpha-amylase from Bacillus subtilis with cetyl trimethylammonium bromide

The interaction of cetyl trimethylammonium bromide (CTAB) with alpha-amylase from Bacillus subtilis was investigated at 25 degrees C and various experimental conditions, such as pH, ionic strength and urea concentration. The binding data were measured using CTAB-membrane selective electrodes as a simple, fast, cheap and accurate method. The obtained binding isotherms were analyzed using Wyman binding potential concept. The results represent the highest binding affinity at 10(-3) M of NaBr respect to other salt concentrations. The less binding affinity at pH 9.7 with respect to pH 6.5 is related to increasing of protein self aggregation with pH. The binding data analysis at various urea concentrations also shows that the predominate unfolding of alpha-amylase occurred in the urea concentration range of 3-5 M.