Infinite Dimensional Slow Modulations In A Delayed Model For Orthogonal Cutting Vibrations

We apply the method of multiple scales (MMS) to a well known model of regenerative cutting vibrations in the large delay regime. By ``large'' we mean the delay is much larger than the time scale of typical cutting tool oscillations. The MMS upto second order for such systems has been developed recently, and is applied here to study tool dynamics in the large delay regime. The second order analysis is found to be much more accurate than first order analysis. Numerical integration of the MMS slow flow is much faster than for the original equation, yet shows excellent accuracy. The main advantage of the present analysis is that infinite dimensional dynamics is retained in the slow flow, while the more usual center manifold reduction gives a planar phase space. Lower-dimensional dynamical features, such as Hopf bifurcations and families of periodic solutions, are also captured by the MMS. Finally, the strong sensitivity of the dynamics to small changes in parameter values is seen clearly.

Determination of beta-turn conformation by laser Raman spectroscopy

To correlate the Raman frequencies of the amide I and III bands to beta-turn structures, three peptides shown to contain beta-turn structure by x-ray diffraction and NMR were examined. The compounds examined were tertiary (formula: see text). The amide I band of these compounds is seen at 1,668, 1,665, and 1,677 cm-1, and the amide III band appears at 1,267, 1,265, and 1,286 cm-1, respectively. Thus, it is concluded that the amide I band for type III beta-turn structure appears in the range between 1,665 and 1,677 cm-1 and the amide III band between 1,265 and 1,286 cm-1.

Transient state work fluctuation theorem for a classical harmonic oscillator linearly coupled to a harmonic bath

Based on a Hamiltonian description we present a rigorous derivation of the transient state work fluctuation theorem and the Jarzynski equality for a classical harmonic oscillator linearly coupled to a harmonic heat bath, which is dragged by an external agent. Coupling with the bath makes the dynamics dissipative. Since we do not assume anything about the spectral nature of the harmonic bath the derivation is not restricted only to the Ohmic bath, rather it is more general, for a non-Ohmic bath. We also derive expressions of the average work done and the variance of the work done in terms of the two-time correlation function of the fluctuations of the position of the harmonic oscillator. In the case of an Ohmic bath, we use these relations to evaluate the average work done and the variance of the work done analytically and verify the transient state work fluctuation theorem quantitatively. Actually these relations have far-reaching consequences. They can be used to numerically evaluate the average work done and the variance of the work done in the case of a non-Ohmic bath when analytical evaluation is not possible.

Phase transition in ammonium aluminium and ammonium chromium alums-A high pressure EPR study

An investigation of the phase transitions at high pressures in the alums mentioned in the title has been carried out using EPR of the Cr3+ ion (at the trivalent metal ion site). It is observed that at ambient as well as at high pressures there is a change of slope in the linear variations of the zero field splitting with temperature and that the low temperature phase is characterised by a large number of lines in the EPR spectra. The transition temperature shows a large positive shift with pressure, for both the alums. All these facts are explained in terms of our model of the origin of the trigonal field at the trivalent metal ion site as well as the details of the motion of NH4+ ion.

Multiresolution Area-based Fractal Dimension Estimation of Signals Applied to EEG Data

In this paper, we present an approach to estimate fractal complexity of discrete time signal waveforms based on computation of area bounded by sample points of the signal at different time resolutions. The slope of best straight line fit to the graph of log(A(rk)A / rk(2)) versus log(l/rk) is estimated, where A(rk) is the area computed at different time resolutions and rk time resolutions at which the area have been computed. The slope quantifies complexity of the signal and it is taken as an estimate of the fractal dimension (FD). The proposed approach is used to estimate the fractal dimension of parametric fractal signals with known fractal dimensions and the method has given accurate results. The estimation accuracy of the method is compared with that of Higuchi's and Sevcik's methods. The proposed method has given more accurate results when compared with that of Sevcik's method and the results are comparable to that of the Higuchi's method. The practical application of the complexity measure in detecting change in complexity of signals is discussed using real sleep electroencephalogram recordings from eight different subjects. The FD-based approach has shown good performance in discriminating different stages of sleep.

Inhibition of H2O2 generation in rat liver mitochondria by radical quenchers and phenolic compounds

Generation of H2O2 by rat liver mitochondria with choline, glycerol 1-phosphate and proline as substrates has been shown by using high-concentration phosphate buffer. Rates obtained under these conditions were higher and more consistent as compared with the earlier reports with high-concentration mannitol/sucrose/Tris buffer. Sulphate ions could replace phosphate indicating a requirement for a high concentration of oxygen-containing anions. H2O2 generation was dependent on the presence of native mitochondria and substrate. Maximal rates with various substrates were found to be the same as with succinate. Values of Km and Vmax for H2O2 generation were considerably less than those obtained for respective dehydrogenase activities, measured by dye reduction. Scavengers of O2-. and OH. inhibited generation of H2O2. ATP, ADP, thyronine derivatives and a number of phenolic compounds also showed very potent inhibitory effects of H2O2 generation, whereas phenyl compound had no effect. Phenolic compounds did not have any effect on mitochondrial superoxide dismutase and choline dehydrogenase activities as well as on O2-. generation by the xanthine-xanthine oxidase system. Inhibition by phenolic compounds may have potential for regulation of the intracellular concentration of H2O2, that is not considered to have a "second messenger' function.

Comments on a decentralized control of linear multivariable systems

A strongly connected decentralized control system may be made single channel controllable and observable with respect to any channel by decentralized feedbacks. It is noted here that the system example considered by Corfmat and Morse to illustrate this fact is already single channel controllable and observable, with respect to one of the channels. An alternate example which fits into the situation is presented in this item.

Unique presence of 2-methylthio-ribosylzeatin in the transfer ribonucleic acid of the bacterium Pseudomonas-Aeruginosa

Analysis of 35S labled nucleosides prepared from tRNA of Pseudomonas aeruginosa by phosphocellulose column chromatography, thin layer chromatography and Sephadex LH-20 column chromatography revealed the presence of 2-methylthioribosylzeatin in it. 2iPA, 6-(3-methyl-2-butenylamino)-9-β-D-ribofuranosyl purine; ms-2iPA, 6-(3-methyl-2-butenylamino)-2-methylthio-9-β-D-ribofuranosylpurine; ribosyl-cis-zeatin, 6-(4-hydroxy-3-methyl-cis-2-butenylamino)-9-β-D-ribofuranosylpurine; ribosyl-trans-zeatin, 6-(4-hydroxy-3-methyl-trans-2-butenylamino)-9-β-D-ribofuranosylpurine; ms-ribosylzeatin, 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9-β-D-ribofuranosylpurine; s4U2, 4-thiouridine; s2U*, 5-methylaminomethyl-2-thiouridine; s2C, 2-thiocytidine; TLC — thin layer chromatography.

Unique presence of 2-methylthio-ribosylzeatin in the transfer ribonucleic acid of the bacterium Pseudomonas-aeruginosa

Analysis of 35S labled nucleosides prepared from tRNA of Pseudomonas aeruginosa by phosphocellulose column chromatography, thin layer chromatography and Sephadex LH-20 column chromatography revealed the presence of 2-methylthioribosylzeatin in it. 2iPA, 6-(3-methyl-2-butenylamino)-9-β-D-ribofuranosyl purine; ms-2iPA, 6-(3-methyl-2-butenylamino)-2-methylthio-9-β-D-ribofuranosylpurine; ribosyl-cis-zeatin, 6-(4-hydroxy-3-methyl-cis-2-butenylamino)-9-β-D-ribofuranosylpurine; ribosyl-trans-zeatin, 6-(4-hydroxy-3-methyl-trans-2-butenylamino)-9-β-D-ribofuranosylpurine; ms-ribosylzeatin, 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9-β-D-ribofuranosylpurine; s4U2, 4-thiouridine; s2U*, 5-methylaminomethyl-2-thiouridine; s2C, 2-thiocytidine; TLC — thin layer chromatography.

Gas-crystal photoreaction: the structures of 4,4'-dimethoxy(thiobenzophenone) (I), C15H14O2S, and 4,4'-bis(dimethylamino)thiobenzophenone (II), C17H20N2S

(I): M r = 258.34, triclinic, Pi, a = 9.810 (3), b=9.635(3), e=15.015(4)A, a=79.11(2), #= 102.38 (3), y = 107.76 (3) o, V= 1308.5 A 3, Z = 4, Din= 1.318 (3) (by flotation in KI solution), D x = 1.311 g cm -3, Cu Ka, 2 = 1.5418/~, g = 20-05 cm -1, F(000) = 544, T---- 293 K, R = 0.074 for 2663 reflections. (II): M r = 284.43, monoclinic, P2~/c, a= 17.029 (5), b=6.706 (5), c= 14.629 (4), t= 113.55 (2) ° , V=1531.4A 3, Z=4, Dm=1.230(5) (by flotation in KI solution), Dx= 1.234gem -3, Mo Ka, 2 = 0.7107 A, g = 1.63 cm-1; F(000) = 608, T= 293 K, R = 0.062 for 855 reflections. The orientation of the C=S chromophores in the crystal lattice and their reactivity in the crystalline state are discussed. The C--S bonds are much shorter than the normal bond length [1.605 (4) (I), 1.665 (8) A (II) cf. 1.71 A].

Stimulation of hepatic 3-hydroxy-3-methylglutaryl CoA reductase on administration of ATP

The depressed activity of hepatic 3-hydroxy-3-methylglutaryl CoA reductase in starved or cholesterol fed rats was stimulated on intraperitoneally administering small quantities of ATP.

Melting of an Anchored Bilayer: Molecular Dynamics Simulations of the Structural Transition in (CnH2n+1NH3)(2)PbI4 (n=12, 14, 16, 18)

The thermally driven Structural phase transition in the organic-inorganic hybrid perovskite (CnH2n+1NH3)(2)PbI4 has been investigated using molecular dynamics (MD) simulations. This system consists of positively charged alkyl-amine chains anchored to a rigid negatively charged PbI4 sheet with the chains organized as bilayers with a herringbone arrangement. Atomistic simulations were performed using ail isothermal-isobaric ensemble over a wide temperature range from 65 to 665 K for different alkyl chain lengths, n = 12, 14, 16, and 18. The simulations are able to reproduce the essential Features of the experimental observations of this system, including the existence of a transition, the linear variation of the transition temperature with alkyl chain length, and the expansion of the bilayer thickness at the transition. By use of the distance fluctuation Criteria, it is Shown that the transition is associated With a Melting of the alkyl chains of the anchored bilayer. Ail analysis of the conformation of the alkyl chains shows increased disorder in the form of gauche defects above due melting transition. Simulations also show that the melting transition is characterized by the complete disappearance of all-trans alkyl chains in the anchored bilayer, in agreement with experimental observations. A conformationally disordered chain has a larger effective cross-sectional area, and above due transition a uniformly tilted arrangement of the anchored chains call no longer be Sustained. At the melt the angular distribution of the orientation of the chains are 110 longer uniform; the chains are splayed allowing for increased space for individual chains of the anchored bilayer. This is reflected in a sharp rise in the ratio of the mean head-to-head to tail-to-tail distance of the chains of the bilayer at the transition resulting in in expansion of the bilayer thickness. The present MD simulations provide a simple explanation as to how changes in conformation of individual alkyl-chains gives rise to the observed increase in the interlayer lattice spacing of (CnH2n+1NH3)(2)PbI4 at the melting transition.

Synthesis and Densification of Monolithic Zirconium Carbide by Reactive Hot Pressing

Synthesis and densification of monolithic zirconium carbide (ZrC) has been carried out by reactive hot pressing of zirconium (Zr) and graphite (C) powders in the molar ratios 1:1, 1.25:1, 1.5:1, and 2:1 at 40 MPa, 1200 degrees-1600 degrees C. Monolithic ZrC could be synthesized with a C/Zr ratio similar to 0.5-1.0 and the post heat-treated samples have the lattice parameter in the range 4.665 to 4.698 A. Densification improves with an increasing deviation from the stoichiometry. Fine-grained (similar to 1 mu m) and nearly fully dense material (99% RD) could be obtained at a temperature as low as 1200 degrees C with C/Zr similar to 0.67. Microstructural and XRD observations suggest that densification occurred at low temperatures with nonstoichiometric Zr-C powder mixtures.