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11.
Methyl 8-[2-(cis-pent-2′-enyl)-3-oxo-cis-cyclopent-4-enyl] octanoate (I) is the methyl ester of a cyclic fatty acid synthesized enzymically from an incubation of
linolenic acid with an extract of flaxseed (Linum usitatissimum L.). A proposed trivial name for I is methyl 12-oxo-cis-10, 15-phytodienoate (12-oxo-PDA). The evidence presented indicated that compound I has thecis configuration of the carbon chains with respect to the cyclopentenone ring. Treatment with acid, base, or heat isomerized
I to a second product (II) that has thetrans configuration of the carbon chains. Prolonged heat treatment of II yielded a third cyclic product, methyl 12-oxo-9(13),cis-15-phytodienoate (III). 相似文献
12.
3D Motion recovery via affine Epipolar geometry 总被引:10,自引:6,他引:4
Larry S. Shapiro Andrew Zisserman Michael Brady 《International Journal of Computer Vision》1995,16(2):147-182
Algorithms to perform point-based motion estimation under orthographic and scaled orthographic projection abound in the literature. A key limitation of many existing algorithms is that they operate on the minimum amount of data required, often requiring the selection of a suitable minimal set from the available data to serve as a local coordinate frame. Such approaches are extremely sensitive to errors and noise in the minimal set, and forfeit the advantages of using the full data set. Furthermore, attention is seldom paid to the statistical performance of the algorithms.We present a new framework that allowsall available features to be used in the motion computations, without the need to select a frame explicitly. This theory is derived in the context of theaffine camera, which preserves parallelism and generalises the orthographic, scaled orthographic and para-perspective models. We define the affine epipolar geometry for two such cameras, giving the fundamental matrix in this case. The noise resistant computation of the epipolar geometry is discussed, and a statistical noise model constructed so that confidence in the results can be assessed.The rigid motion parameters are then determineddirectly from the epipolar geometry, using the novel rotation representation of Koenderink and van Doorn (1991). The two-view partial motion solution comprises the scale factor between views, the projection of the 3D axis of rotation and the cyclotorsion angle, while the addition of a third view allows the true 3D rotation axis to be computed (up to a Necker reversal). The computed uncertainties in these parameters permit optimal estimates to be obtained over time by means of a linear Kalman filter. Our theory extends work by Huang and Lee (1989), Harris (1990), and Koenderink and van Doorn (1991), and results are given on both simulated and real data. 相似文献
13.
S Brady CM Hiam R Saemann L Humbert MZ Fleming K Dawkins-Brickhouse 《Canadian Metallurgical Quarterly》1996,32(6):573-578
The treatment of "dual diagnosis", co-occurring substance abuse and mental illness, calls for addressing two serious and often confounding problems. The authors introduce an expanded version of the transtheoretical model of change as formulated by J.O. Prochaska and C.C. DiClemente, and suggest that this new version offers a pragmatic approach to the conceptualization and treatment of dual diagnosis. The potential utility of the treatment model is presented through the authors' experiences in working with inner-city, chronic mentally ill individuals with substance abuse problems. Practical guidelines for dual diagnosis group therapy are discussed. 相似文献
14.
Combinatorial interaction testing (CIT) is a cost-effective sampling technique for discovering interaction faults in highly-configurable
systems. Constrained CIT extends the technique to situations where some features cannot coexist in a configuration, and is
therefore more applicable to real-world software. Recent work on greedy algorithms to build CIT samples now efficiently supports
these feature constraints. But when testing a single system configuration is expensive, greedy techniques perform worse than
meta-heuristic algorithms, because greedy algorithms generally need larger samples to exercise the same set of interactions.
On the other hand, current meta-heuristic algorithms have long run times when feature constraints are present. Neither class
of algorithm is suitable when both constraints and the cost of testing configurations are important factors. Therefore, we
reformulate one meta-heuristic search algorithm for constructing CIT samples, simulated annealing, to more efficiently incorporate
constraints. We identify a set of algorithmic changes and experiment with our modifications on 35 realistic constrained problems
and on a set of unconstrained problems from the literature to isolate the factors that improve performance. Our evaluation
determines that the optimizations reduce run time by a factor of 90 and accomplish the same coverage objectives with even
fewer system configurations. Furthermore, the new version compares favorably with greedy algorithms on real-world problems,
and, though our modifications were aimed at constrained problems, it shows similar advantages when feature constraints are
absent. 相似文献
15.
Non-Parametric Mixture Model Based Evolution of Level Sets and Application to Medical Images 总被引:1,自引:0,他引:1
We present a novel region-based curve evolution algorithm which has three primary contributions: (i) non-parametric estimation
of probability distributions using the recently developed NP windows method; (ii) an inequality-constrained least squares
method to model the image histogram with a mixture of nonparametric probability distributions; and (iii) accommodation of
the partial volume effect, which is primarily due to low resolution images, and which often poses a significant challenge
in medical image analysis (our primary application area). We first approximate the image intensity histogram as a mixture
of non-parametric probability density functions (PDFs), justifying its use with respect to medical image analysis. The individual
densities in the mixture are estimated using the recent NP windows PDF estimation method, which builds a continuous representation
of discrete signals. A Bayesian framework is then formulated in which likelihood probabilities are given by the non-parametric
PDFs and prior probabilities are calculated using an inequality constrained least squares method. The non-parametric PDFs
are then learnt and the segmentation solution is spatially regularised using a level sets framework. The log ratio of the
posterior probabilities is used to drive the level set evolution. As background to our approach, we recall related developments
in level set methods. Results are presented for a set of synthetic and natural images as well as simulated and real medical
images of various anatomical organs. Results on a range of images show the effectiveness of the proposed algorithm. 相似文献
16.
Saliency, Scale and Image Description 总被引:6,自引:0,他引:6
17.
An extremum principle is developed that determines three-dimensional surface orientation from a two-dimensional contour. The principle maximizes the ratio of the area to the square of the perimeter, a measure of the compactness or symmetry of the three-dimensional surface. The principle interprets regular figures correctly and it interprets skew symmetries as oriented real symmetries. The maximum likelihood method approximates the principle on irregular figures, but we show that it consistently overestimates the slant of an ellipse. 相似文献
18.
19.
In 2012 Arian Foster, a running back for the Houston Texans of the National Football League (NFL), announced via Twitter that he is “officially a vegan now” (Foster, July 6, 2012). Foster's announcement precipitated a torrent of attention by many who worriedly debated the impact that his new diet may have on his on-field performance. In this article, we unravel the threads that have woven together a picture of who Foster is and what his decision to go vegan means. We argue that a close look at the media response reveals deeply held beliefs about masculinity, race, class, and place and the ways in which food serves in the constitution of subjectivity in the context of pro-football in Texas. We conduct a contextual discourse analysis of the popular and sports media coverage of Foster's diet using an intersectional framework to elaborate how normative masculinity is further nuanced by the meanings attributed to race, place, sexuality, sport, aggression, violence, health, and productivity. 相似文献
20.