Snake method

Some earlier segmentation methods are characterized as explicit. This means the front representing the boundary of the preliminary object is moved explicitly, point by point. A popular explicit segmentation method is the active contours, or snake method. As both these names indicate, the front (the contour) is active in crawling to find the true boundary. The points indicating the front are updated by a minimization of the energy formulation. More on theory and applications can be found in [2] and [8]. 

For semi-dilute and dense solutions the generalized reptation (or, sHther-ing snake ) algorithm [59] is probably among the most efficient ones. In this method one takes at random an end monomer and tries to add it at the other... 

Clearly, both the pivot and the slithering snake algorithms are incapable of reproducing true chain dynamics at molecular basis, covering the time range of typical chain relaxation times. Therefore, in the following we focus on two alternative methods, broadly used at present to this end. 

The bearing which these discoveries have had on the elucidation of the structure of ribopolynucleotides will be discussed later. It is important to stress here, however, that, for most purposes, the older methods of preparing nucleotides have been superseded by procedures which yield separate isomers of each. Of the techniques mentioned above, paper chromatography iB mainly of analytical value, and is the most convenient method for the qualitative detection of isomeric adenylic acids. The only disadvantage of this method is that the isomers are not completely separable from muscle adenylic acid. The presence of the latter, however, can be readily detected by hydrolyzing it to adenosine by means of the specific 5-nucleotidase present in snake venoms,66 or by deamination by a specific enzyme... 

To examine variation in the quality of methyl ketones expressed by females and newly-emerged males, we determined the number of unique methyl ketones expressed by individual snakes and compared the relative concentrations of individual methyl ketones comprising the overall pheromone profiles for the two groups. The methyl ketones present in the pheromone extracts were identified by gas chromatography / mass spectrometry (Hewlett Packard 5890 Series II gas chromatograph coupled with a Hewlett Packard 5971 Series mass selective detector— see LeMaster and Mason 2003 for full description of the GC/MS platform and methods). 

Using phosphotriester methods, dinucleoside (3 - 50-monophosphates containing 6-methyl-2,-deoxyuridine at the 3 - or 5 -end have been prepared.44 N.m.r. spectroscopy indicates that this nucleoside possesses the syn conformation in these compounds, and, on treatment with snake venom phosphodiesterase, d(m6UpT) is degraded, while d(Apm6U) is not, indicating that this enzyme, a 3 -exonuclease, requires the anti conformation to be present in the substrate. Two modified nucleo-side-5 -monophosphates, (20) and (21), which are resistant to 5 -nucleotidase, have been isolated from tRNA snake venom hydrolysates.45 A synthesis of (20) has been reported.46... 

The polymer literature yields a variety of specialized move types in particular for lattice homopolymers [110]. Sampling methods like the slithering snake and reptation algorithms (see ref. Ill and references therein) or the original configurational-bias/chain growth algorithms [112,113] were specifically... 

The existence of photoreversible, but not of heat-reversible, absorbance change in irradiated poly dI dC was taken to prove that the photoproducts are entirely dimers (in contrast to those in poly C irradiations where the product is almost entirely the hydrate82a). It was possible to detect dimers of uracil as well as those of cytosine, by means of the much slower photoreversal of uracil dimers. In the acid hydrolysates of irradiated dl-dC, both uracil dimers and uracil could be identified. Enzymatic hydrolysis (snake venom phosphodiesterase) does not split pyrimidine dimers, and the products of such hydrolysis of irradiated tritium-labeled poly dl dC contained trinucleotides shown by radioactivity to contain cytosine dimers. Thymine dimers were formed in the photolysis of the poly dA dT, and were detected and assayed by the same methods. The yield of thymine dimers in irradiated poly... 

Snake-holing. Blasting method for removing deeply buried boulders or rocks. It consists of digging a hole under the boulder and placing a Dynamite charge immediately below it. As the expl charge is confined by the earth, when detonated, it will exert sufficient force on the... 

Axelrod DI (1965) A method for determining the altitudes of Tertiary floras. Paleobotanist 14 144-171 Axelrod DI (1968) Tertirary floras and topographic history of the Snake River basin, Idaho. Geol Soc Am Bull 79 713-734... 

Flavonoids are well known as inhibitors of hyaluronidase. Li 1950 Rodney et al, reported the effect of several flavonoids on hyaluronidase using in vitro and in vivo methods [79], Knppusamy et al. investigated the structure-activity relationship of die flavonoids as inhibitors of testicular hyaluronidase [80] and hyaluronidase from snake, scorpion, and bee venom [81]. They showed that flavones. flavanols. and chalcones possess the general ability to inhibit hyaluronidase Kinetic investigations showed that these compounds acted as competitive inhibitors [80]. Several hyaluronidase inhibitors were shown to be able to delay the action of snake venom when injected into mice [8ll One caimnt rule out the possible interaction of the flavonoids with other components of the venom, as the inhibitory effects of flavonoids are not specific to hyaluronidase... 

In the biochemical method, the enzyme phospholipase A2, isolated from Naja naja snake venom can attack the native alkenylacylglycerophosphocho-line and liberate completely the esterified fatty acid and the alkenyl(lyso)glyc-erophosphocholine. On the basis of the stereospecific mode of attack of this enzyme on the 2-acyl ester position of sn-3 phosphoglycerides, it can be concluded that the naturally occurring alkenylacylglycerophosphocholine possessed the sn-3 stereochemical configuration. 

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