Common subgraph isomorphism detection by backtracking search

Graph theory offers a convenient and highly attractive approach to various tasks of pattern recognition. Provided there is a graph representation of the object in question (e.g. a chemical structure or protein fold), the recognition procedure is reduced to the problem of common subgraph isomorphism (CSI). Complexity of this problem shows combinatorial dependence on the size of input graphs, which in many practical cases makes the approach computationally intractable. Among the optimal algorithms for CSI, the leading place in practice belongs to algorithms based on maximal clique detection in the association graph. Backtracking algorithms for CSI, first developed two decades ago, are rarely used. We propose an improved backtracking algorithm for CSI, which differs from its predecessors by better search strategy and is therefore more efficient. We found that the new algorithm outperforms the traditional maximal clique approach by orders of magnitude in computational time. Copyright © 2004 John Wiley & Sons, Ltd.     

The use of local entropy measures in edge detection for cytological image analysis

Accurate edge detection is a fundamental problem in the areas of image processing and pattern recognition/classification. The lack of effective edge detection methods has slowed the application of image processing to many areas, in particular diagnostic cytology, and is a major factor in the lack of acceptance of image processing in service orientated pathology. In this paper, we present a two-step procedure which detects edges. Since most images are corrupted by noise and often contain artefacts, the first step is to clean up the image. Our approach is to use a median filter to reduce noise and background artefacts. The second operation is to locate image pixels which are ‘information rich’ by using local statistics. This step locates the regions of the image most likely to contain edges. The application of a threshold can then pin-point those pixels forming the edge of structures of interest. The procedure has been tested on routine cytologic specimens.     

Oleochemicals as a fuel: Mechanical and economic feasibility

The status of vegetable oils as diesel fuel substitutes is currently dubious. Although it is fair to consider them as short-term emergency fuels (or, more desirably, low proportion supplements to diesel fuels), they present mechanical problems in long-term use that have not yet been solved. It is preferable to use these oils blended in small proportions with diesel fuels. Indirect-injection diesel engines have had fewer problems than direct-injection engines, whether the tests were performed with pure vegetable oil fuel or with vegetable oil/diesel fuel blends. The economic prospect for these fuels is not promising. In general, they are not and have not been economical alternatives to diesel fuel. Exceptions appear to have occurred recently in Brazil and the Philippines where low local prices for vegetable oils combined with high petroleum prices encouraged officials to use low proportion vegetable oil/diesel fuel blends. Nonetheless, current and long-term trends in petroleum and oilseed prices indicate that these fuels will probably not be price competitive within the near future. Emergency disruption of petroleum supplies completely changes the economic situation. Vegetable oils would be worth much more as a fuel during disruptions than otherwise; thus incentives could be strong to include these oils in the fuel supply, diverting them from the food supply.     

Identification of the California red scale sex pheromone

Pheromone components of female California red scale,Aonidiella aurantii (Maskell) were isolated from airborne collections and found to be 3-methyl-6-isopropenyl-9-decen-1-yl acetate and (Z)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate. Both enantiomers of the latter compound as well as the corresponding enantiomers of theE isomer were prepared from (S)- or (R)-carvone. Bioassays with each of the four isomers showed that only theR,Z isomer attracted male red scale. Aonidiella aurantii (Maskell) (Homoptera: Diaspididae).This research was supported by a USDA Cooperative Research Grant.     

Comparison of backbone structures of glucose isomerase from Streptomyces and Arthrobacter

The C backbones of the glucose isomerase molecules of Streptomycesrubiginosus and Arthrobacter have been determined by X-ray crystallographyand compared. Each molecule is a tetramer of eight-stranded/ß barrels, and the mode of association of the tetramersis identical in each case. The Arthrobacter electron densityshows four additional amino acids at the carboxyl terminus.There is also an insertion of six amino acids at position 277,and two individual insertions at about positions 348 and 357(numbering according to the Streptomyces structure). There isa close structural homology throughout the whole molecule, whichis most accurate up to position 325. The r.m.s. displacementfor 315 homologous C positions up to this position is 0.92 Å.     

Synthesis of 7-methyl-3-methylene-7-octen 1-yl propanoate and (z)-3,7-dimethyl-2, 7-octadien-1-yl propanoate,components of the sex pheromone of the san jose scale

The two components of the sex pheromone of the San Jose scale,Quadraspidiotus perniciosus (Comstock) were synthesized. The first component, 7-methyl-3-methylene-7-octen-1-yl propanoate, was obtained by the addition of a 4-methyl-4-penten-1-yl copper complex to 3-butyn-1-yl propanoate (or 3-butyn-1-yl trimethylsilyl ether). Reaction of the same copper complex with propyne followed by treatment with carbon dioxide gave a key intermediate in the stereoselective synthesis of (Z)-3,7-dimethyl-2,7-octadien-1-yl propanoate, the second component of the pheromone.Quadraspidiotus perniciosus (Comstock) (Homoptera: Diaspididae).Contribution No. 73 from the Research Laboratory of Zoecon Corporation.     

Fingerprinting <Emphasis Type="Italic">Cynara scolymus</Emphasis> L. (Artichoke) by Means of a Green Statistically Developed HPLC-PAD Method

The process to develop a chromatographic method for fingerprinting complex matrices should be performed through a multiparameter approach that could lead to the desired separation and save environmental resources such as organic solvents and energy. In other words, this process should be pursued by employing an optimized experimental design and having a response function which takes into consideration separation parameters together with environmental parameters. Green Analytical Chemistry principles should be pursued during all steps of the research. This work presents a heuristic approach to develop a high-performance liquid chromatography method for fingerprinting an extract from leaves of Cynara scolymus L., a food plant consumed worldwide. A fractional factorial design was used to identify relevant chromatographic variables followed by a comprehensive design for optimization purposes (Doehlert design). A response function called green chromatographic fingerprinting response was employed to obtain a compromise between fingerprint quality and low environmental impact of the method. This optimized approach led to the development of a robust and green method for fingerprinting C. scolymus by HPLC-PAD. This method proved to be greener than the reference method reported in literature and compatible even with no state of art HPLC instruments because the system backpressure did not exceed 15 MPa and the column temperature was 35 °C.     

Evaluation of enzymatic activity of commercial inulinase from Aspergillus niger immobilized in polyurethane foam

The objective of this work was to evaluate the stability of the activity of commercial inulinase from Aspergillus niger immobilized in polyurethane foam. The activity of the enzyme was measured in the hydrolysis reaction of both sucrose and inulin at 50 °C and pH 5.5. The enzyme reuse was evaluated during 59 days and 29 reuse cycles. The inulinase immobilized in polyurethane kept 49.7% and 49.4% of its initial activity during 1008 h and 24 reuse cycles for sucrose and inulin, respectively. In this work, enzyme immobilization was accomplished together with the formation of the polyurethane foam, which is an interesting characteristic, differing from several works found in the literature. Taking into account the promising results obtained, the low cost of the immobilization support employed and the whole technique developed, this work may comprise an innovative contribution.     

Synthesis of stereoisomers of 8-methyl-2-decanol and esters attractive to severalDiabrotica sp.

Details of the syntheses of the four stereoisomers of 8-methyl-2-decanol and its propanoate ester are given. The racemic ester, two of its stereoisomers, and one stereoisomer as an acetate are attractive to several species ofDiabrotica. The key steps in the syntheses involve high-performance liquid chromatograpic resolutions of diastereomers to achieve high configurational enrichment of each site and generation of (R)-2-methylbutyric acid by chemical degradation ofd-isoleucine.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Synthesis and identification of a third component of the San Jose scale sex pheromone

Two components of the San Jose scale sex pheromone had previously been identified as 7-methyl-3-methylene-7-octen-1-yl propanoate (I) and (Z)-3,7-dimethyl-2,7-octadien-1-yl propanoate (II). An isomer and various homologs have subsequently been synthesized and tested in a greenhouse bioassay. TheE isomer of II (XI) was found to be attractive to male scales. This compound has now been isolated and identified from airborne extracts of virgin female scales. The composition of the natural pheromone was 48.5%, 46.7%, and 4.8% of I, II, and XI, respectively. In field tests in California and New York, synthetic XI was found to be attractive to male scales alone and in combination with I and II, but there was no obvious increase in trap catch when the synthetic isomers were present in the same ratio as in the natural blend. Quadraspidiotus perniciosm (Comstock) (Homoptera: Diaspididae)