Dynamics of I-asterisk(P-2(1/2)) production inthe ultraviolet photodissociation of alkyn iodides

The relative quantum yields, phi*, for the production of I*(P-2(1/2)) at 266, 280, and similar to 305 nm are reported for a series of primary alkyl iodides using the technique of two-photon laser-induced fluorescence for the detection of I(P-2(3/2)) and I*(P-2(1/2)) atoms. Results are analyzed by invoking the impulsive energy disposal model, which summarizes the dynamics of dissociation as a single parameter. Comparison of our data with those calculated by a more sophisticated time-dependent quantum mechanical model is also made. Near the red edge of the alkyl iodide A band, absorption contribution from the (3)Q(1) state is important and the dynamics near the (3)Q(0)-(1)Q(1) curve-crossing region seem to be influenced by the kinematics of the dissociation process

Mechanism of gallic acid biosynthesis in bacteria (Escherichia coli) and walnut (Juglans regia)

Gallic acid (GA), a key intermediate in the synthesis of plant hydrolysable tannins, is also a primary anti-inflammatory, cardio-protective agent found in wine, tea, and cocoa. In this publication, we reveal the identity of a gene and encoded protein essential for GA synthesis. Although it has long been recognized that plants, bacteria, and fungi synthesize and accumulate GA, the pathway leading to its synthesis was largely unknown. Here we provide evidence that shikimate dehydrogenase (SDH), a shikimate pathway enzyme essential for aromatic amino acid synthesis, is also required for GA production. Escherichia coli (E. coli) aroE mutants lacking a functional SDH can be complemented with the plant enzyme such that they grew on media lacking aromatic amino acids and produced GA in vitro. Transgenic Nicotiana tabacum lines expressing a Juglans regia SDH exhibited a 500% increase in GA accumulation. The J. regia and E. coli SDH was purified via overexpression in E. coli and used to measure substrate and cofactor kinetics, following reduction of NADP(+) to NADPH. Reversed-phase liquid chromatography coupled to electrospray mass spectrometry (RP-LC/ESI-MS) was used to quantify and validate GA production through dehydrogenation of 3-dehydroshikimate (3-DHS) by purified E. coli and J. regia SDH when shikimic acid (SA) or 3-DHS were used as substrates and NADP(+) as cofactor. Finally, we show that purified E. coli and J. regia SDH produced GA in vitro.

Lossless and lossy image compression using Boolean function minimization

A novel approach for lossless as well as lossy compression of monochrome images using Boolean minimization is proposed. The image is split into bit planes. Each bit plane is divided into windows or blocks of variable size. Each block is transformed into a Boolean switching function in cubical form, treating the pixel values as output of the function. Compression is performed by minimizing these switching functions using ESPRESSO, a cube based two level function minimizer. The minimized cubes are encoded using a code set which satisfies the prefix property. Our technique of lossless compression involves linear prediction as a preprocessing step and has compression ratio comparable to that of JPEG lossless compression technique. Our lossy compression technique involves reducing the number of bit planes as a preprocessing step which incurs minimal loss in the information of the image. The bit planes that remain after preprocessing are compressed using our lossless compression technique based on Boolean minimization. Qualitatively one cannot visually distinguish between the original image and the lossy image and the value of mean square error is kept low. For mean square error value close to that of JPEG lossy compression technique, our method gives better compression ratio. The compression scheme is relatively slower while the decompression time is comparable to that of JPEG.

Magnetic Raman scattering from 1D antiferromagnets

We study Raman scattering from 1D antiferromagnets within the Fleury-Loudon scheme by applying a finite temperature Lanczos method to a 1D spin-half Heisenberg model with nearest-neighbor (J(1)) and second-neighbor (J(2)) interactions. The low-temperature spectra are analyzed in terms of the known elementary excitations of the system for J(2) = 0 and J(2) = 1/2. We find that the low-T Raman spectra are very broad for \J(2)/J(1)\ less than or equal to 0.3. This broad peak gradually diminishes and shifts with temperature, so that at T > J(1) the spectra are narrower and peaked at low frequencies. The experimental spectra for CuGeO3 are discussed in light of our calculations.

Purification and partial characterization of acyl carrier proteins from developing oil seeds of pisa (Actinodaphne hookeri) and ground nut (Arachis hypogaea)

Acyl carrier proteins (ACP) were purified to homogeneity in the active form from developing seeds of pisa (Actinodaphne hookeri) which synthesizes exclusively trilaurin and from ground nut (Arachis hypogaea) which synthesizes triacylglycerols containing long chain fatty acids. Two major isoforms of ACPs were purified from developing pisa seeds using DEAE-cellulose, Superose-6 FPLC and C-4 reversed phase HPLC chromatographic methods. In contrast, only a single form of ACP was present in ground nut seeds which was purified by anion-exchange and activated thiol-Sepharose 4B affinity chromatography. The two isoforms of ACPs from pisa showed nearly the same specific activity of 6,706 and 7,175 pmol per min per mg protein while ground nut ACP showed a specific activity of 3,893 pmol per min per mg protein when assayed using E. coli acyl-ACP synthetase and [1-C-14]palmitic acid. When compared with E. coli ACP, the purified ACPs from both the seeds showed considerable difference in their mobility in native PAGE, but showed similar mobility in SDS-PAGE under reducing conditions. In the absence of reducing agents formation of dimers was quite prominent. The ACPs from both the seed sources were acid- and heat-stable. The major isoform of pisa seed ACP and the ground nut ACP contain 91 amino acids with M(r) 11,616 and 1,228 respectively. However, there is significant variation in their amino acid composition. A comparision of the amino acid sequence in the N-terminal region of pisa and ground nut seed ACPs showed considerable homology between themselves and with other plant ACPs but not with E. coli ACP.

Nonlinear dynamics and chaotic motions in feedback-controlled two- and three-degree-of-freedom robots

The dynamics of a feedback-controlled rigid robot is most commonly described by a set of nonlinear ordinary differential equations. In this paper we analyze these equations, representing the feedback-controlled motion of two- and three-degrees-of-freedom rigid robots with revolute (R) and prismatic (P) joints in the absence of compliance, friction, and potential energy, for the possibility of chaotic motions. We first study the unforced or inertial motions of the robots, and show that when the Gaussian or Riemannian curvature of the configuration space of a robot is negative, the robot equations can exhibit chaos. If the curvature is zero or positive, then the robot equations cannot exhibit chaos. We show that among the two-degrees-of-freedom robots, the PP and the PR robot have zero Gaussian curvature while the RP and RR robots have negative Gaussian curvatures. For the three-degrees-of-freedom robots, we analyze the two well-known RRP and RRR configurations of the Stanford arm and the PUMA manipulator respectively, and derive the conditions for negative curvature and possible chaotic motions. The criteria of negative curvature cannot be used for the forced or feedback-controlled motions. For the forced motion, we resort to the well-known numerical techniques and compute chaos maps, Poincare maps, and bifurcation diagrams. Numerical results are presented for the two-degrees-of-freedom RP and RR robots, and we show that these robot equations can exhibit chaos for low controller gains and for large underestimated models. From the bifurcation diagrams, the route to chaos appears to be through period doubling.

Catalytic oxidative polymerization of 1,1-diphenylethylene at ambient temperature and potential application of peroxide macroinitiator

The Co(II)TPP(Py) complex was used as an efficient dioxygen carrier for the radical polymerization of 1,1-diphenylethylene (DPE), which has a low ceiling temperature, at ambient temperature and low oxygen pressure. The mechanism of polymerization is discussed' on the basis of kinetic data, W-vis, ESR, and H-1 NMR studies. The rate of polymerization (RP) and number-average molecular weights (M) of poly(1,1-diphenylethylene peroxide) (PDPEP) are higher and the polydispersity is lower than in 2,2'-azobis(isobutyronitrile) (AIBN) initiated polymerization. PDPEP was further. used as a macroinitiator for the polymerization of MMA. The polymerization obeys classical kinetics. The K-2 value of the PDPEP has been determined from the slope of R-P(2) VS [M](2)[I], which reveals that it can also be used at higher temperature for the polymerization. An "active" PMMA was also synthesized, containing initiating segments in the polymer backbone.

Chromatographic methods for determination of nimesulide and for stability studies

Simple and rapid HPLC, GC, and TLC procedures have been developed for detection and determination of nimesulide, a non-pharmacopeial drug, in preformulation and dosage form. Use of these techniques has enabled separation of impurities and the precursor in the bulk material and in formulations. Isocratic reversed-phase HPLC was performed on a C-18 column with methanol-water-acetic acid, 67:32:1 (v/v), as mobile phase and UV detection at 230 nm. Calibration curves were linear over the concentration range 100-1000 mug mL(-1) with a good correlation coefficient (0.9993) and a coefficient of variation of 1.5%. Gas chromatography was performed on an OV-17 packed column with temperature programming and flame-ionization detection. The lower limit of determination by HPLC and GC was 4 ppm. Thin-layer chromatography of nimesulide was performed on silica gel G with toluene-ethyl acetate, 8:2, as mobile phase. Stability testing of the drug was performed under different temperature, humidity, and UV-radiation conditions.

Microstructural, dielectric, pyroelectric and ferroelectric studies on partially grain-oriented SrBi2Ta2O9 ceramics

Partially grain-oriented (48%) ceramics of strontium bismuth tantalate (SrBi2Ta2O9) have been fabricated via conventional sintering. The grain-orientation factor of the ceramics was determined, as a function of both the sintering temperature and duration of sintering using X-ray powder diffraction (XRD) techniques. Variations in microstructural features (from acircular to plate like morphology) as a function of sintering temperature of the pellets were monitored by Scanning Electron Microscopy (SEM). The dielectric constant and loss measurements as functions of both frequency and temperature have been carried out along the directions parallel and perpendicular to the pressing axis. The anisotropy (epsilon(rn)/epsilon(rp)) associated was found to be 2.21. The effective dielectric constant of the samples with varying porosity was predicted using different dielectric mixture formulae. The grain boundary and grain interior contributions to the dielectric properties were rationalized using the impedance spectroscopy. The pyroelectric coefficient for strontium bismuth tantalate ceramic was determined along the parallel and perpendicular directions to the pressing axis and found to be -23 muC/m(2)K and -71 muC/m(2)K, respectively at 300 K. The ferroelectric properties of these partially grain-oriented ceramics are superior in the direction perpendicular to the pressing axis to that in the parallel direction.

Mapping of large scale 158 mu m [CII] line emission: Orion A

We present the first results of an observational programme undertaken to map the fine structure line emission of singly ionized carbon ([ CII] 157 : 7409 mum) over extended regions using a Fabry Perot spectrometer newly installed at the focal plane of a 100 cm balloon- borne far- infrared telescope. This new combination of instruments has a velocity resolution of similar to 200 km s(-1) and an angular resolution of 1.'5. During the first flight, an area of 30' x 15' in Orion A was mapped. These observations extend over a larger area than previous observations, the map is fully sampled and the spectral scanning method used enables reliable estimation of the continuum emission at frequencies adjacent to the [ CII] line. The total [ CII] line luminosity, calculated by considering up to 20% of the maximum line intensity is 0.04% of the luminosity of the far- infrared continuum. We have compared the [ CII] intensity distribution with the velocity- integrated intensity distributions of (CO)-C-13(1- 0), CI(1- 0) and CO( 3- 2) from the literature. Comparison of the [ CII], [ CI] and the radio continuum intensity distributions indicates that the largescale [ CII] emission originates mainly from the neutral gas, except at the position of M 43, where no [ CI] emission corresponding to the [ CII] emission is seen. Substantial part of the [ CII] emission from here originates from the ionized gas. The observed line intensities and ratios have been analyzed using the PDR models by Kaufman et al. ( 1999) to derive the incident UV flux and volume density at a few selected positions. The models reproduce the observations reasonably well at most positions excepting the [ CII] peak ( which coincides with the position of theta(1) Ori C). Possible reason for the failure could be the simplifying assumption of a homogeneous plane parallel slab in place of a more complicated geometry.

The effect of host glass on optical absorption and fluorescence of Nd3+ in xNa(2)O-(30-x)K2O-70B(2)O(3) glasses

The effect of host glass composition on the optical absorption and fluorescence spectra of Nd3+ has been studied in mixed alkali borate glasses of the type xNa(2)O-(30-x)K2O-69.5B(2)O(3)-0.5Nd(2)O(3) (X = 5,10,15,20 and 25). Various spectroscopic parameters such as Racah (E-1, E-2 and E-3), spin-orbit (xi(4f)) and configuration interaction (alpha, beta) parameters have been calculated. The Judd-Ofelt intensity parameters (Omega(lambda)) have been calculated and the radiative transition probabilities (A(rad)), radiative lifetimes (tau(r)), branching ratios (beta) and integrated absorption cross sections (Sigma) have been obtained for certain excited states of the Nd3+, ion and are discussed with respect to x. From the fluorescence spectra, the effective fluorescence line widths (Deltalambda(eff)) and stimulated emission cross sections (sigma(p)) have been obtained for the three transitions F-4(3/2) --> I-4(9/2), F-4(3/2) --> I-4(11/2) and F-4(3/2) --> I-4(13/2) of Nd3+. The stimulated emission cross section (sigma(p)) values are found to be in the range (2.0-4.8) x 10(-2)0 cm(2) and they are large enough to indicate that the mixed alkali borate glasses could be potential laser host materials.

From the Icosahedron to Natural Triangulations of CP(2) and S(2) x S(2)

We present two constructions in this paper: (a) a 10-vertex triangulation CP(10)(2) of the complex projective plane CP(2) as a subcomplex of the join of the standard sphere (S(4)(2)) and the standard real projective plane (RP(6)(2), the decahedron), its automorphism group is A(4); (b) a 12-vertex triangulation (S(2) x S(2))(12) of S(2) x S(2) with automorphism group 2S(5), the Schur double cover of the symmetric group S(5). It is obtained by generalized bistellar moves from a simplicial subdivision of the standard cell structure of S(2) x S(2). Both constructions have surprising and intimate relationships with the icosahedron. It is well known that CP(2) has S(2) x S(2) as a two-fold branched cover; we construct the triangulation CP(10)(2) of CP(2) by presenting a simplicial realization of this covering map S(2) x S(2) -> CP(2). The domain of this simplicial map is a simplicial subdivision of the standard cell structure of S(2) x S(2), different from the triangulation alluded to in (b). This gives a new proof that Kuhnel's CP(9)(2) triangulates CP(2). It is also shown that CP(10)(2) and (S(2) x S(2))(12) induce the standard piecewise linear structure on CP(2) and S(2) x S(2) respectively.

mRegistry: a registry representation for fault diagnosis

Microsoft Windows uses the notion of registry to store all configuration information. The registry entries have associations and dependencies. For example, the paths to executables may be relative to some home directories. The registry being designed with faster access as one of the objectives does not explicitly capture these relations. In this paper, we explore a representation that captures the dependencies more explicitly using shared and unifying variables. This representation, called mRegistry exploits the tree-structured hierarchical nature of the registry, is concept-based and obtained in multiple stages. mRegistry captures intra-block, inter-block and ancestor-children dependencies (all leaf entries of a parent key in a registry put together as an entity constitute a block thereby making the block as the only child of the parent). In addition, it learns the generalized concepts of dependencies in the form of rules. We show that mRegistry has several applications: fault diagnosis, prediction, comparison, compression etc.