628 research outputs found
Discriminant Function Analysis Based on Principal Components for Rapid Discrimination of Metabolic Capabilities of New Isolates
The growing need for new microorganisms with novel metabolic capabilities has urged scientists to searchfor life in extreme environments. With the rapid progress in experimental methods, it is possible to isolate new microorganisms at high speeds but the
bottleneck in this process is the biochemical characterization due to time and financial limitations. Inferential hierarchical clustering of new isolates may help to overcome this problem. In this work, discriminant function analysis, used in conjunction with principal
component analysis (PCA) was able to rapidly discriminate eight new isolates using metabolic footprints (spectral data from electrospray injection mass spectrometry) and the results were compared with clustering based on the Euclidean distances computed both in the domain of original data and in the domain of PCA-transformed data. The presence of the replicates on the adjacent leaf nodes of dendrograms obtained by hierarchical cluster analysis confirmed the reliability of the method. This attractive tool is applicable to a chemical/biological system, which involves complex samples that can be analyzed by high-throughput instruments
Transversal torus knots
We classify positive transversal torus knots in tight contact structures up
to transversal isotopy.Comment: 16 pages. Published copy, also available at
http://www.maths.warwick.ac.uk/gt/GTVol3/paper11.abs.htm
Electrochemically Obtained Insulating and Conducting Polymers and Composites of Acrylonitrile
Electrochemically obtained polyacrylonitrile and a commercial polyacrylonitrile were heat treated to improve their conductivities. The parameters chosen for heat treatment conditions were the temperature, treatment medium (vacuum or air) and, doping agent. The conductivity of all heat treated polymers was measured. The characterization of the heat treated polymers was made by IR analysis. The composite films of polyacrylonitrile with polypyyrole and polythiophene were electrochemically prepared at different compositions. The change in the conductivity of composites was analyzed as a function of the percent composition of the insulating component. IR, DSC, TGA and SEM analyses were used to characterize the polymer composites
Solutions of the Einstein-Dirac and Seiberg-Witten Monopole Equations
We present unique solutions of the Seiberg-Witten Monopole Equations in which
the U(1) curvature is covariantly constant, the monopole Weyl spinor consists
of a single constant component, and the 4-manifold is a product of two Riemann
surfaces of genuses p_1 and p_2. There are p_1 -1 magnetic vortices on one
surface and p_2 - 1 electric ones on the other, with p_1 + p_2 \geq 2 p_1 =
p_2= 1 being excluded). When p_1 = p_2, the electromagnetic fields are
self-dual and one also has a solution of the coupled euclidean
Einstein-Maxwell-Dirac equations, with the monopole condensate serving as
cosmological constant. The metric is decomposable and the electromagnetic
fields are covariantly constant as in the Bertotti-Robinson solution. The
Einstein metric can also be derived from a K\"{a}hler potential satisfying the
Monge-Amp\`{e}re equations.Comment: 22 pages. Rep. no: FGI-99-
Witten's conjecture and Property P
Let K be a non-trivial knot in the 3-sphere and let Y be the 3-manifold
obtained by surgery on K with surgery-coefficient 1. Using tools from gauge
theory and symplectic topology, it is shown that the fundamental group of Y
admits a non-trivial homomorphism to the group SO(3). In particular, Y cannot
be a homotopy-sphere.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol8/paper7.abs.html Version 5: links
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Fake R^4's, Einstein Spaces and Seiberg-Witten Monopole Equations
We discuss the possible relevance of some recent mathematical results and
techniques on four-manifolds to physics. We first suggest that the existence of
uncountably many R^4's with non-equivalent smooth structures, a mathematical
phenomenon unique to four dimensions, may be responsible for the observed
four-dimensionality of spacetime. We then point out the remarkable fact that
self-dual gauge fields and Weyl spinors can live on a manifold of Euclidean
signature without affecting the metric. As a specific example, we consider
solutions of the Seiberg-Witten Monopole Equations in which the U(1) fields are
covariantly constant, the monopole Weyl spinor has only a single constant
component, and the 4-manifold M_4 is a product of two Riemann surfaces
Sigma_{p_1} and Sigma_{p_2}. There are p_{1}-1(p_{2}-1) magnetic(electric)
vortices on \Sigma_{p_1}(\Sigma_{p_2}), with p_1 + p_2 \geq 2 (p_1=p_2= 1 being
excluded). When the two genuses are equal, the electromagnetic fields are
self-dual and one obtains the Einstein space \Sigma_p x \Sigma_p, the monopole
condensate serving as the cosmological constant.Comment: 9 pages, Talk at the Second Gursey Memorial Conference, June 2000,
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A study of the Czernik 2 and NGC 7654 open clusters using CCD UBV photometric and Gaia EDR3 data
We analysed the open clusters Czernik 2 and NGC 7654 using CCD UBV
photometric and Gaia Early Data Release 3 (EDR3) photometric and astrometric
data. Structural parameters of the two clusters were derived, including the
physical sizes of Czernik 2 being r=5 and NGC 7654 as 8 min. We calculated
membership probabilities of stars based on their proper motion components as
released in the Gaia EDR3. To identify member stars of the clusters, we used
these membership probabilities taking into account location and the impact of
binarity on main-sequence stars. We used membership probabilities higher than
to identify 28 member stars for Czernik 2 and 369 for NGC 7654. We
estimated colour-excesses and metallicities separately using two-colour
diagrams to derive homogeneously determined parameters. The derived
colour excess is 0.46(0.02) mag for Czernik 2 and 0.57(0.04) mag for NGC 7654.
Metallicities were obtained for the first time for both clusters, -0.08(0.02)
dex for Czernik 2 and -0.05(0.01) dex for NGC 7654. Keeping the reddening and
metallicity as constant quantities, we fitted PARSEC models using
colour-magnitude diagrams, resulting in estimated distance moduli and ages of
the two clusters. We obtained the distance modulus for Czernik 2 as 12.80(0.07)
mag and for NGC 7654 as 13.20(0.16) mag, which coincide with ages of 1.2(0.2)
Gyr and 120(20) Myr, respectively. The distances to the clusters were
calculated using the Gaia EDR3 trigonometric parallaxes and compared with the
literature. We found good agreement between the distances obtained in this
study and the literature. Present day mass function slopes for both clusters
are comparable with the value of Salpeter (1955), being X=-1.37(0.24) for
Czernik 2 and X=-1.39(0.19) for NGC 7654.Comment: 22 pages, 13 figures and 9 tables, accepted for publication in
Astrophysics and Space Scienc
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