A rapid and sensitive method for the estimation of individual tRNA pools

A rapid and sensitive method is described to quantitatively compare tRNA pools for individual aminoacids in a single experiment. The procedure comprises of: (i) charging of total tRNA with a mixture of radiolabeled aminoacids, (ii) deacylation of the esterified tRNA with a volatile base and the recovery of the labeled aminoacid, (iii) derivatisation of the aminoacid with phenylisothiocyanate after mixing with excess of nonradioactive aminoacids, (iv) baseline separation of the phenylthiocarbamyl aminoacids by reverse phase high performance liquid chromatography monitored by A254nm and (v) quantitation of the radioactivity in individual aminoacid peaks. The radioactivity in the aminoacid peak corresponds to the quantity of the aminoacylated tRNA. The method has been successfully applied to quantitate the individual tRNA pools in the developing silk glands of Bombyx mori, a functionally adapted tissue which undergoes considerable variations in tRNA content. PSG, posterior silk gland; PITC, phenylisothiocyanate; DMAA, N,N-dimethyl-N-allylamine; APH, algal protein hydrolysate; ptc-, phenylthiocarbamyl; HPLC, high performance liquid chromatography.

A simple and rapid method for quantification of hapten specific antibodies

A sensitive and simple method for quantification of antibodies against small molecules is described using DNP-lysozyme as the enzyme conjugate. The anti-DNP antiserum was raised against DNP-bovin serum albumin conjugate. Anti-DNP antibody or its monovalent fragment (Fab) reduced the enzyme activity of DNP-lysozyme conjugate in a concentration-dependent manner. The inhibition of enzyme activity is a specific measure of the antibody and Fab content of the sample. The specificity of the reaction was assessed by reduction of antibody-induced inhibition by DNP-lysine. The ability of DNP-lysine to reduce the antibody-induced inhibition of DNP-lysozyme activity also makes possible a sensitive assay for DNP-lysine.

Studies on non-specific interference due to serum in the avidin-biotin microELISA for monkey chorionic gonadotropin and a method for its elimination

A study has been carried out on the non-specific interference due to serum in the avidin biotin micro-ELISA for monkey chorionic gonadotropin. Results suggest that it is not due to any proteolytic activity in the serum, but immunoglobulin or associated factors interfering at the level of antigen-antibody interaction. This interference was eliminated by heating samples at 60°C for 30 min.

Reduction of aromatic nitro compounds to amines using zinc and aqueous chelating ethers: Mild and efficient method for zinc activation

A mild, environmentally friendly method for reduction of aromatic nitro group to amine is reported, using zinc powder in aqueous solutions of chelating ethers. The donor ether acts as a ligand and also serves as a co-solvent. Water is the proton source. This procedure is also a new method for the activation of zinc for electron transfer reduction of aromatic nitro compounds. The reduction is accomplished in a neutral medium and other reducing groups remained unaffected. The ethers used are dioxolane, 1,4-dioxane, ethoxymethoxyethane, dimethoxymethane, 1,2-dimethoxyethane, and diglyme.

Filter Configuration and PWM Method For Single Phase Inverters with Reduced Conducted EMI Noise

Electromagnetic Interference (EMI) noise is one of the major issues during the design of the grid-tied power converters. Presence of high dv/dt in Common Mode (CM) voltage, excites the parasitic capacitances and causes injection of narrow peaky current to ground. This results in high EMI noise level. A topology consisting of a single phase PWM-rectifier with LCL filter, utilising bipolar PWM method is proposed which reduces the EMI noise level by more than 30dB. This filter topology is shown to be insensitive to the switching delays between the legs of the inverter. The proposed topology eliminates high dv/dt from the dc-bus CM voltage by making it sinusoidal. Hence, the high frequency CM current injection to ground is minimized.

Filter Configuration and PWM Method For Single-Phase Inverters With Reduced Conducted EMI Noise

Electromagnetic interference (EMI) noise is one of the major issues during design of grid-tied power converters. A novel LCL filter topology for a single-phase pulsewidth modulation (PWM) rectifier that makes use of bipolar PWM method is proposed for a single-phase to three-phase motor drive power converter. The proposed topology eliminates high dv/dt from the dc-bus common-mode (CM) voltage by making it sinusoidal. Hence, the high-frequency CM current injection to the ground and the motor-side CM current are minimized. The proposed filter configuration makes the system insensitive to circuit non-idealities such as mismatch in inductors values, unequal turn-on and turn-off delays, and dead-time mismatch between the inverter legs. Different variants of the filter topology are compared to establish the effectiveness of the proposed circuit. Experimental results based on the EMI measurement on the grid side and the CM current measurement on the motor side are presented for a 5-kW motor drive. It is shown that the proposed filter topology reduces the EMI noise level by about 35 dB.

A rapid and highly selective method for the estimation of pyro-,tri- and orthophosphates

A rapid, highly selective and simple method has been developed for the quantitative determination of pyro-, tri- and orthophosphates. The method is based on the formation of a solid complex of bis(ethylenediamine)cobalt(III) species with pyrophosphate at pH 4.2-4.3, with triphosphate at pH 2.0-2.1 and with orthophosphate at pH 8.2-8.6. The proposed method for pyro- and triphosphates differs from the available method, which is based on the formation of an adduct with tris(ethylenediamine)cobalt(III) species. The complexes have the composition [Co(en)(2)HP2O7]4H(2)O and [Co(en)(2)H2P3O10]2H(2)O, respectively. The precipitation is instantaneous and quantitative under the recommended optimum conditions giving 99.5% gravimetric yield in both cases. There is no interferences from orthophosphate, trimetaphosphate and pyrophosphate species in the triphosphate estimation up to 5% of each component. The efficacy of the method has been established by determining pyrophosphate and triphosphate contents in various matrices. In the case of orthophosphate, the proposed method differs from the available methods such as ammonium phosphomolybdate, vanadophosphomolybdate and quinoline phosphomolybdate, which are based on the formation of a precipitate, followed by either titrimetry or gravimetry. The precipitation is instantaneous and the method is simple. Under the recommended pH and other reaction conditions, gravimetric yields of 99.6-100% are obtainable. The method is applicable to orthophosphoric acid and a variety of phosphate salts.

Depth profile composition studies of thin film CdS: Cu,S solar cells using XPS and AES

Surface composition and depth profile studies of hemiplated thin film CdS:CuzS solar cells have been carried out using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. These studies indicate that the junction is fairly diffused in the as-prepared cell. However, heat treatment of the cell at 210°C in air relatively sharpens the junction and improves the cell performance. Using the Cu(2p3p)/S(2p) ratio as well as the Cu(LVV)/(LMM) Auger intensity ratio, it can be inferred that the nominal valency of copper in the layers above the junction is Cut and it is essentially in the CUSS form. Copper signals are observed from layers deep down in the cell. These seem to appear mostly from the grain boundary region. From the observed concentration of Cd, Cu and S in these deeper layers and the Cu(LVV)/(LMM) ratio it appears that the signals from copper essentially originate partly from copper in CuS and partly from Cu2t trapped in the lattice. It is significant to note that the nominal valence state of copper changes rather abruptly from Cut to Cuz+ across the junction.

A novel method of current efficiency determination

A simple and rapid method, based on the open-circuit decay of potential, is described for the determination of the current efficiency with which metals are electrodeposited. The advantages and disadvantages of the method are discussed.

Earth pressures on retaining walls due to Anisotropic and nonhomogeneous backfills

In this paper an attempt is made to study the lateral earth pressures on retaining walls as affected by anisotropy and non-homogeneity with respect to cohesion, of the backfill. Both the passive and active conditions are studied and the method of characteristics is used in the analysis. Numerical results show that, as the coeficient of anisotropy, k, defined as the ratio of vertical strength to horizontal strength, changes from 0-8 to 2, the pressure at the top of the wall decreases considerably.Also, as k changes fvom 0.8 to 2, the mod$ed passive and active earth pressure coeficients decrease when cohesion increases with depth and are unaffected by k when cohesion is constant with depth. On the other hand, when the rate of increase of cohesion with depth increares, the mod@ed earth pressure coefficients are found to increase considerably.

An FETI-preconditioned conjuerate gradient method for large-scale stochastic finite element problems

In the spectral stochastic finite element method for analyzing an uncertain system. the uncertainty is represented by a set of random variables, and a quantity of Interest such as the system response is considered as a function of these random variables Consequently, the underlying Galerkin projection yields a block system of deterministic equations where the blocks are sparse but coupled. The solution of this algebraic system of equations becomes rapidly challenging when the size of the physical system and/or the level of uncertainty is increased This paper addresses this challenge by presenting a preconditioned conjugate gradient method for such block systems where the preconditioning step is based on the dual-primal finite element tearing and interconnecting method equipped with a Krylov subspace reusage technique for accelerating the iterative solution of systems with multiple and repeated right-hand sides. Preliminary performance results on a Linux Cluster suggest that the proposed Solution method is numerically scalable and demonstrate its potential for making the uncertainty quantification Of realistic systems tractable.

A simple single-source precursor route to the nanostructures of AIN, GaN and InN

In an effort to find a simple and common single-source precursor route for the group 13 metal nitride semiconductor nanostructures, the complexes formed by the trichlorides of Al, Ga and In with urea have been investigated. The complexes, characterized by X-ray crystallography and other techniques, yield the nitrides on thermal decomposition. Single crystalline nanowires of AlN, GaN and InN have been deposited on Si substrates covered with Au islands by using the complexes as precursors. The urea complexes yield single crystalline nanocrystals under solvothermal conditions. The successful synthesis of the nanowires and nanocrystals of these three important nitrides by a simple single-precursor route is noteworthy and the method may indeed be useful in practice.

Analysis of the binding of polymyxin B to endotoxic lipid A and core glycolipid using a fluorescent displacement probe

Dansylcadaverine, a cationic fluorescent probe binds to bacterial lipopolysaccharide and lipid A, and is displaced competitively by other compounds which possess affinity toward endotoxins. The binding parameters of dansylcadaverine for lipid A were determined by Scatchard analysis to be two apparently equivalent sites with apparent dissociation constants (Kd) ranging between 16 μM to 26 μM, while that obtained for core glycolipid from Salmonella minnesota Re595 yielded a Kd of 22 μM to 28 μM with three binding sites. The Kd of polymyxin B for lipid A was computed from dansylcadaverine displacement by the method of Horovitz and Levitzki (Horovitz, A., and Levitzki, A. (1987) Proc. Natl. Acad. Sci. USA 84, 6654–6658). The applicability of this method for analyzing fluorescence data was validated by comparing the Kds of melittin for lipid A obtained by direct Scatchard analysis, and by the Horovitz-Levitzki method. The displacement of dansylcadaverine from lipid A by polymyxin B was distinctly biphasic with Kds for polymyxin B-lipid A interactions corresponding to 0.4 μM and 1.5 μM, probably resulting as a consequence of lipid A being a mixture of mono- and di-phosphoryl species. This was not observed with core glycolipid, for which the Kd for polymyxin was estimated to range from 1.1 μM to 5.8 μM. The use of dansylcadaverine as a displacement probe offers a novel and convenient method of quantitating the interactions of a wide variety of substances with lipid A.

On an asymptotic method of Krylov-Bogoliubov for overdamped nonlinear systems

A general asymptotic method based on the work of Krylov-Bogoliubov is developed to obtain the response of nonlinear over damped systems. A second-order system with both roots real is treated first and the method is then extended to higher-order systems. Two illustrative examples show good agreement with results obtained by numerical integration.