Synthetic Studies in Phytochrome Chemistry

An account is given of the author’s several approaches to the synthesis of the parent chromophore of phytochrome (1), a protein-bound linear tetrapyrrole derivative that controls photomorphogenesis in higher plants. These studies culminated in enantioselective syntheses of both (2R)- and (2S)-phytochromobilin (4), as well as several 13C-labeled derivatives designed to probe the site of Z,E-isomerization during photoexcitation. When reacted in vitro, synthetic 2R-4 and recombinant-derived phytochrome apoprotein N-C produced a protein-bound chromophore with identical difference spectra to naturally occurring 1

A Fisher-Rao Metric for curves using the information in edges

Two curves which are close together in an image are indistinguishable given a measurement, in that there is no compelling reason to associate the measurement with one curve rather than the other. This observation is made quantitative using the parametric version of the Fisher-Rao metric. A probability density function for a measurement conditional on a curve is constructed. The distance between two curves is then defined to be the Fisher-Rao distance between the two conditional pdfs. A tractable approximation to the Fisher-Rao metric is obtained for the case in which the measurements are compound in that they consist of a point x and an angle α which specifies the direction of an edge at x. If the curves are circles or straight lines, then the approximating metric is generalized to take account of inlying and outlying measurements. An estimate is made of the number of measurements required for the accurate location of a circle in the presence of outliers. A Bayesian algorithm for circle detection is defined. The prior density for the algorithm is obtained from the Fisher-Rao metric. The algorithm is tested on images from the CASIA Iris Interval database

Automatic processing of an orientation map into a finite element mesh that conforms to grain boundaries

A new procedure for image-based finite element models of materials is presented. This method is based on a conformal meshing strategy relying on (i) an efficient graph-based community detection algorithm for image segmentation and feature contour extraction as well as (ii) the generation of selectively refined meshes using the Gmsh suite. It provides a versatile and close to automatic environment for meshing complex microstructures. The procedure is illustrated with polycrystal microstructures obtained by orientation imaging microscopy. Hot deformation of a Duplex stainless steel is investigated based on ex-situ EBSD measurements performed on the same region of interest before and after deformation. A finite element mesh representing the initial microstructure is generated and then used in a crystal plasticity simulation of the plane strain compression. Simulation results and experiments are in relatively good agreement, confirming a large potential for such directly coupled experimental and modeling analyses, where the present image-based meshing procedure facilitates the task greatly

Converting Level Set Gradients to Shape Gradients

Abstract. The level set representation of shapes is useful for shape evolution and is widely used for the minimization of energies with respect to shapes. Many algorithms consider energies depending explicitly on the signed distance function (SDF) associated with a shape, and differentiate these energies with respect to the SDF directly in order to make the level set representation evolve. This framework is known as the “variational level set method”. We show that this gradient computation is actually mathematically incorrect, and can lead to undesirable performance in practice. Instead, we derive the expression of the gradient with respect to the shape, and show that it can be easily computed from the gradient of the energy with respect to the SDF. We discuss some problematic gradients from the literature, show how they can easily be fixed, and provide experimental comparisons illustrating the improvement.

Isolation, identification and evaluation of antimicrobial activity of streptomyces flavogriseus, strain actk2 from soil sample of Kodagu, Karnataka state (India)

Background: The search for novel antibiotics continues to be of immense importance in research programs around the world for pharmaceutical, industrial and agricultural applications. Filamentous soil bacteria, belonging to the Streptomyces genus, are widely used as an important biological tool for their ability to produce a wide range of novel secondary metabolites, such as ``antibiotics''. Objectives: The aim of the present study was to isolate and identify a strain of Streptomyces with high antibiotic production capability. Materials and Methods: The soil sample was collected randomly from the agricultural land of Kushalnagar Taluk of Kodagu district, Karnataka, India. The ACTK2 strain was isolated by serial dilution method and identified based on cultural, morphological, microscopic, biochemical and sequence analysis of 16S rRNA gene parameters. The isolated ACTK2 was analyzed for antimicrobial activities by perpendicular streak and disc diffusion methods, against the Gram-positive bacteria Staphylococcus aureus (MTCC 96), Bacillus subtilis (MTCC 121), Gram-negative Escherichia. coli (MTCC 729), Enterococcus aerogenes (MTCC 2829) and filamentous fungi (Trichoderma harizianum (MTCC6046), Fusarium proliferatum (MTCC 9375). Further, an antimicrobial metabolite from the ACTK2 strain was extracted by solvent extraction method, using n-butanol. The production of the antimicrobial compound by the ACTK2 strain was optimized by using different nutritional media and cultural conditions. Results: The strain Streptomyces flavogriseus designated as ACTK2 (Accession number KC990785) isolated from the soil sample of Kushalnagar Taluk, Kodagu, Karnataka, India, exhibited a broad spectrum of antimicrobial activity against test microorganisms. The optimum growth and antimicrobial compound production by strain ACTK2 was found to be a maximal pH 8, in the shaker incubator at 28 degrees C, for a period of 10 days. Conclusions: The crude n-butanol extract of the ACTK2 strain of S. flavogriseus showed a broad spectrum of antimicrobial activities against the test organisms and this opened further research investigations on purification and structural characterization of the active compounds from the crude extract