Formative time lags in nitrogen, oxygen and dry air In crossed electric and magnetic fields

Formative time lags in nitrogen, oxygen, and dry air are measured with and without a magnetic field over a range of gas pressures (0.05 ' p ' 20.2 torr 5 kPa to 2 MPa, electric field strengths (1.8xO14 EEs 60xlO V m l) and magnetic field strengths (85xl0-4 < B ' 16x10-2 Tesla). For experiments below the Paschen minimum, the electrodes are designed to ensure that breakdown occurs over longer gaps and for experiments above the Paschen minimum, a coaxial cylindrical system is employed. The experimental technique consists of applying pulse voltages to the gap at various constant values of E/p and B/p and measuring the time lags from which the formative time lags are separated. In the gases studed, formative time lags decrease on application of a magnetic field at a given pressure for conditions below the Paschen minimum. The voltages at which the formative time lags remain the same without and with magnetic fields are determined, and electron molecule collision frequencies (v/p) are determined using the Effective Reduced Electric Field [EREF] concept. With increasing ratio of E/p in crossed fields, v/p decreases in all the three gases. Measurements above the Paschen minimum yield formative time lags which increase on application of a magnetic field. Formative time lags in nitrogen in ExB fields are calculated assuming an average collision frequency of 8.5x109 sec-1 torr 1. It is concluded that the EREF concept can be applied to explain formative time lags in ExB fields.

Immunological studies on nucleic acids and their components.8.Antibodies specific to a deoxyribotrinucleotide sequence

Bovine serum albumin conjugates of two trinucleotides, dpTpTpA and dTpTpAp, were prepared by linking the trinucleotides through their end phosphates by the ‘carbodiimide method’. Antibodies were raised in rabbits by injecting the trinucleotide-bovine serum albumin conjugates. Analysis by double diffusion in agar gel, quantitative precipitin reaction and its inhibition by haptens showed clearly the presence of antibodies specific to the whole trinucleotide molecule. The titre of antibodies obtained by the trinucleotide-rabbit serum albumin conjugates with their respective antisera was approximately the same, indicating that linking the trinucleotide through either 5′ or 3′ phosphate does not have an appreciable effect on the titre of antibodies. The results also demonstrate that the nucleotide(s) away from the carrier protein is more immunodominant than the one linked directly to the protein.

Immunologic studies on nucleic acids and their components. I. An analysis of the specificity of anti-deoxyadenylate antibodies by a membrane-binding technique

Anti-deoxyadenylate antibodies were produced in rabbits by injecting a conjugate of deoxyadenosine 5′-phosphate with bovine serum albumin. The antisera, as analyzed by double diffusion in agar and the quantitative precipitin reaction, showed hapten-specific antibodies. The specific interaction between [3H]deoxyadenylate and antiserum was studied by a sensitive nitrocellulose membrane-binding assay. The specificity of the antibodies was analyzed by measuring the effectiveness of other nucleotides or derivatives to inhibit the hapten-antibody binding. The requirements for recognition by the antibody sites were studied by using a series of naturally occurring nucleic acid components as well as some synthetic derivatives as inhibitors. The antibodies were found to show a high degree of specificity for the whole nucleotide, the base, sugar and phosphate playing almost equally important roles. There was cross reactivity with other mononucleotides, although of a low order. The antibodies were able to react with DNA and tRNA.

Immunologic studies on nucleic acids and their components II. Reversible inhibition of anti-nucleoside antibodies in aqueous pyridine and its application in antibody

The effect of aqueous pyridine on a hapten—antihapten system was investigated by the quantitative precipitin reaction and by the membrane filtration method. It was found that dilute solutions of pyridine inhibited the reaction between isopentenyladenosine and its antiserum. Other solvents examined were less effective. The effect of pyridine was reversible at concentrations where complete inhibition occurred, thus indicating its use for the dissociation of antigen—antibody complexes. The inhibitory effect of pyridine was exploited in a single-step purification method for anti—isopentenyladenosine and antideoxy-adenylate antibodies. In addition, generally applicable methods for linking nucleosides and nucleotides to aminoethyl-Sepharose are described.

Immunologic studies on nucleic acids and their components II. Reversible inhibition of anti-nucleoside antibodies in aqueous pyridine and its application in antibody purification

The effect of aqueous pyridine on a hapten—antihapten system was investigated by the quantitative precipitin reaction and by the membrane filtration method. It was found that dilute solutions of pyridine inhibited the reaction between isopentenyladenosine and its antiserum. Other solvents examined were less effective. The effect of pyridine was reversible at concentrations where complete inhibition occurred, thus indicating its use for the dissociation of antigen—antibody complexes. The inhibitory effect of pyridine was exploited in a single-step purification method for anti—isopentenyladenosine and antideoxy-adenylate antibodies. In addition, generally applicable methods for linking nucleosides and nucleotides to aminoethyl-Sepharose are described.

Studies on Aspergillus niger glutamine synthetase: Regulation of enzyme levels by nitrogen sources and identification of active site residues

The specific activity of glutamine synthetase (L-glutamate: ammonia ligase, EC 6.3.1.2) in surface grown Aspergillus niger was increased 3-5 fold when grown on L-glutamate or potassium nitrate, compared to the activity obtained on ammonium chloride. The levels of glutamine synthetase was regulated by the availability of nitrogen source like NH4 + , and further, the enzyme is repressed by increasing concentrations of NH4 +. In contrast to other micro-organisms, the Aspergillus niger enzyme was neither specifically inactivated by NH4+ or L-glutamine nor regulated by covalent modification.Glutamine synthetase from Aspergillus niger was purified to homogenity. The native enzyme is octameric with a molecular weight of 385,000±25,000. The enzyme also catalyses Mn2+ or Mg2+-dependent synthetase and Mn2+-dependent transferase activity.Aspergillus niger glutamine synthetase was completely inactivated by two mol of phenylglyoxal and one mol of N-ethylmaleimide with second order rate constants of 3·8 M–1 min–1 and 760 M–1 min–1 respectively. Ligands like Mg. ATP, Mg. ADP, Mg. AMP, L-glutamate NH4+, Mn2+ protected the enzyme against inactivation. The pattern of inactivation and protection afforded by different ligands against N-ethylamaleimide and phenylglyoxal was remarkably similar. These results suggest that metal ATP complex acts as a substrate and interacts with an arginine ressidue at the active site. Further, the metal ion and the free nucleotide probably interact at other sites on the enzyme affecting the catalytic activity.

Immunological studies on nucleic-acids and their components .5. Antibodies specific to a deoxyribodinucleotide sequence

Antibodies were raised in rabbits against the bovine serum albumin conjugate of dpApT. Analysis by double diffusion in agar gel and quantitative precipitation test showed the presence of antibodies specific to the hapten in the antisera. Quantitative data on the specificity of the antibodies were obtained by studying the inhibition of the binding of 3H-dpApT to the anti-sera by various nonradioactive mono- and oligonucleotides, using a nitrocellulose membrane binding assay. The antibodies were found to be highly specific for the dinucleotide sequence dpApT. The antibodies were able to bind to synthetic oligonucleotides containing the sequence dpApT and to denatured calf thymus DNA.

Immunological studies on nucleic-acids and their components .6. Antibodies specific to two deoxyribotrinucleotide sequences

Antibodies to the deoxyribotrinucleotides dpApTpA and dpApApT were prepared by injecting the bovine serum albumin conjugates of the respective haptens in rabbits. The specificities of the antibodies were determined by estimating the inhibition of the binding of the tritiated haptens to the immunoglobulins by various nonradioactive mono- and oligonucleotides, using nitrocellulose membrane binding assay. Anti-dpApTpA and anti-dpApApT antisera were found to contain antibodies which were highly specific to the respective hapten sequence.

CO2-fertilization and potential future terrestrial carbon uptake in India

There is huge knowledge gap in our understanding of many terrestrial carbon cycle processes. In this paper, we investigate the bounds on terrestrial carbon uptake over India that arises solely due to CO (2) -fertilization. For this purpose, we use a terrestrial carbon cycle model and consider two extreme scenarios: unlimited CO2-fertilization is allowed for the terrestrial vegetation with CO2 concentration level at 735 ppm in one case, and CO2-fertilization is capped at year 1975 levels for another simulation. Our simulations show that, under equilibrium conditions, modeled carbon stocks in natural potential vegetation increase by 17 Gt-C with unlimited fertilization for CO2 levels and climate change corresponding to the end of 21st century but they decline by 5.5 Gt-C if fertilization is limited at 1975 levels of CO2 concentration. The carbon stock changes are dominated by forests. The area covered by natural potential forests increases by about 36% in the unlimited fertilization case but decreases by 15% in the fertilization-capped case. Thus, the assumption regarding CO2-fertilization has the potential to alter the sign of terrestrial carbon uptake over India. Our model simulations also imply that the maximum potential terrestrial sequestration over India, under equilibrium conditions and best case scenario of unlimited CO2-fertilization, is only 18% of the 21st century SRES A2 scenarios emissions from India. The limited uptake potential of the natural potential vegetation suggests that reduction of CO2 emissions and afforestation programs should be top priorities.

Study of symmetrical and related components through the theory of linear vector spaces

The paper proposes a study of symmetrical and related components, based on the theory of linear vector spaces. Using the concept of equivalence, the transformation matrixes of Clarke, Kimbark, Concordia, Boyajian and Koga are shown to be column equivalent to Fortescue's symmetrical-component transformation matrix. With a constraint on power, criteria are presented for the choice of bases for voltage and current vector spaces. In particular, it is shown that, for power invariance, either the same orthonormal (self-reciprocal) basis must be chosen for both voltage and current vector spaces, or the basis of one must be chosen to be reciprocal to that of the other. The original �¿, ��, 0 components of Clarke are modified to achieve power invariance. For machine analysis, it is shown that invariant transformations lead to reciprocal mutual inductances between the equivalent circuits. The relative merits of the various components are discussed.

Approaches to alpha-amino acids via rearrangement to electron-deficient nitrogen: Beckmann and Hofmann rearrangements of appropriate carboxyl-protected substrates

The titled approaches were effected with various 2-substituted benzoylacetic acid oximes 3 (Beckmann) and 2-substituted malonamic acids 9 (Hofmann), their carboxyl groups being masked as a 2,4,10-trioxaadamantane unit (an orthoacetate). The oxime mesylates have been rearranged with basic Al2O3 in refluxing CHCl3, and the malonamic acids with phenyliodoso acetate and KOH/MeOH. Both routes are characterized by excellent overall yields. Structure confirmation of final products was conducted with X-ray diffraction in selected cases. The final N-benzoyl and N-(methoxycarbonyl) products are alpha-amino acids with both carboxyl and amino protection; hence, they are of great interest in peptide synthesis.

On-line Estimation of Fundamental and Ripple Components of Line Currents in a Voltage-Source Inverter Operated at Low Switching Frequency

High-power voltage-source inverters (VSI) are often switched at low frequencies due to switching loss constraints. Numerous low-switching-frequency PWM techniques have been reported, which are quite successful in reducing the total harmonic distortion under open-loop conditions at such low operating frequencies. However, the line current still contains low-frequency components (though of reduced amplitudes), which are fed back to the current loop controller during closed-loop operation. Since the harmonic frequencies are quite low and are not much higher than the bandwidth of the current loop, these are amplified by the current controller, causing oscillations and instability. Hence, only the fundamental current should be fed back. Filtering out these harmonics from the measured current (before feeding back) leads to phase shift and attenuation of the fundamental component, while not eliminating the harmonics totally. This paper proposes a method for on-line extraction of the fundamental current in induction motor drives, modulated with low-switching-frequency PWM. The proposed method is validated through simulations on MATLAB/Simulink. Further, the proposed algorithm is implemented on Cyclone FPGA based controller board. Experimental results are presented for an R-L load.

Hexamethylenetetramine mediated simultaneous nitrogen doping and reduction of graphene oxide for a metal-free SERS substrate

We report a one-pot hydrothermal synthesis of nitrogen doped reduced graphene oxide (N-rGO) and Ag nanoparticle decorated N-rGO hybrid nanostructures from graphene oxide (GO), metal ions and hexamethylenetetramine (HMT). HMT not only reduces GO and metal ions simultaneously but also acts as the source for the nitrogen (N) dopant. We show that the N-rGO can be used as a metal-free surface enhanced Raman spectroscopy (SERS) substrate, while the Ag nano-particles decorated N-rGO can be used as an effective SERS substrate as well as a template for decorating various other nanostructures on N-rGO.

Estimates of site response based on spectral ratio between horizontal and vertical components of ambient vibrations in the source zone of 2001 Bhuj earthquake

We investigated the site response characteristics of Kachchh rift basin over the meizoseismal area of the 2001, Mw 7.6, Bhuj (NW India) earthquake using the spectral ratio of the horizontal and vertical components of ambient vibrations. Using the available knowledge on the regional geology of Kachchh and well documented ground responses from the earthquake, we evaluated the H/V curves pattern across sediment filled valleys and uplifted areas generally characterized by weathered sandstones. Although our HIV curves showed a largely fuzzy nature, we found that the hierarchical clustering method was useful for comparing large numbers of response curves and identifying the areas with similar responses. Broad and plateau shaped peaks of a cluster of curves within the valley region suggests the possibility of basin effects within valley. Fundamental resonance frequencies (f(0)) are found in the narrow range of 0.1-2.3 Hz and their spatial distribution demarcated the uplifted regions from the valleys. In contrary, low HIV peak amplitudes (A(0) = 2-4) were observed on the uplifted areas and varying values (2-9) were found within valleys. Compared to the amplification factors, the liquefaction indices (kg) were able to effectively indicate the areas which experienced severe liquefaction. The amplification ranges obtained in the current study were found to be comparable to those obtained from earthquake data for a limited number of seismic stations located on uplifted areas; however the values on the valley region may not reflect their true amplification potential due to basin effects. Our study highlights the practical usefulness as well as limitations of the HIV method to study complex geological settings as Kachchh. (C) 2014 Elsevier Ltd. All rights reserved.

Ratio of Diffusion Coefficient to Mobility for Electrons in SF6-Air and Freon-Nitrogen Mixtures

The ratio of diffusion coefficient to mobility (D/¿) for electrons has been measured in SF6-air and freon-nitrogen mixtures for various concentrations of SF6 and freon in the mixtures over the range 140¿ E/p¿ 220 V.cm-1 - torr-1. In SF6-air mixtures, the values of D/¿ were always observed to lie intermediate between the values for the pure gases. However, in freon-nitrogen mixtures, with a small concentration (10 percent) of freon in the mixture, the values of D/¿ are found to lie above the boundaries determined by the pure gases. In this mixture, over the lower E/p range (140 to 190) the electrons appear to lose a large fraction of their energy by the excitation of the complex freon molecules, while at higher E/p values (200 to 240), the excitation and consequent deexcitation of nitrogen molecules and its metastables seem to cause an increased rate of ionization of freon molecules.