Sequence Clustering

Fig. 1. Various color-magnitude diagrams for NGC 1851 obtained with uvby filters at the Danish 1.54m telescope on La Silla. Seven stars in our sample have previous low-resolution spectroscopy from [2] which classified them into CN strong (open squares) and CN normal (plusses) groups. Note how the CN strong stars stand out clearly from the cluster sequences when using filter combinations involving the u and v filters. We see from the lower righthand panel that the RGB stars in this cluster also show a large scatter in the mi index at a fixed luminosity - this is the only cluster in our sample of 20 which show mi scatter. This points to very large C variations (larger than for other clusters). Could this be related to the bimodality of the cluster horizontal branch ...

A complication, however, arises from the fact that these anomalies are also due to proton nucleosynthesis (though operating at higher temperatures) and thus that some primordial CNO-abundance anomalies should be expected, too. In fact, 47 Tuc has been for a long time the example for a CN/CH dichotomy all along the cluster sequence, and by now, CN-variations have been found -mainly by Cohen, Briley and coworkers - in unevolved stars of other clusters as well (47 Tuc [3,2], M71 [1], M5 [9],. ..). This complicates the task to identify the purely evolutionary effect due to extra-mixing, which is needed to develop and test physical models. 

So far, three types of i-QCs appear in the literature Mackay [17], Bergman [18], and Tsai types [19], which have been differentiated on the basis of the polyhedral cluster sequences observed in the respective 1/1 AC structures. These are commonly represented as shown in Fig. 2. An i-QC is concluded to be Mackay-type if its 1/1 AC contains a 54-atom multiply endohedral cluster ordered, from the center out, as a small icosahedron (12 atoms), a larger icosahedron (12), and an icosidodecahe-dron (30). This motif occurs in ACs that consist of transition metals and main-group elements on the right side of the periodic table such as Al-(Pd,Mn)-Si [17,20]. In... 

Tibehus KH, Du L, Tito D, Stejskal F. 1993. The Azotobacter chroococcum hydrogenase gene cluster sequences and genetic analysis of four accessory genes, hup A, hupB,hupY, and hup C. Gene 127 53-61. 

HaarmannT The ergot alkaloid gene cluster in Clavicepspurpurea. Extension of the cluster sequence and intra species evolution. Phytochemistry 66 1312— 1320, 2005. 

Haarmann, T., Machado, C., Lubbe, Y., Correia, T., Schardl, C. L., Panaccione, D. G. and Tudzynski, P. 2005. The ergot alkaloid gene cluster in Clavicepspurpure Extension of the cluster sequence and intra species evolution. Phytochemistry, 66(11) 1312-1320. 

Figure 5 Violacein (18) and deoxyviolacein (19) are produced by a blue clone that was found in a soil DNA library hosted in Escherichia coii. A four-gene cluster iyioA-D) captured on this clone is responsible for the biosynthesis of both metabolites (GenBank accession No AF367409). The eDNA-derived biosynthetic gene cluster and the violacein biosynthetic gene cluster sequenced from the cultured bacterium Chromobacterium violaceum have the same gene organization but show low amino acid sequence identity. ...

Clusters may be held together by a variety of different forces, strong enough to hold the atoms together, but weak enough to allow some flexibility in the interatomic angles, which allows further atoms to be added to the system. If clusters are characterised by their stackability, not all binding forces are suitable to build up a cluster sequence. 

As of July 2000, the human subset of UniGene contained 1.7 million sequences in 82,000 clusters 98% of these clustered sequences were ESTs, and the remaining... 

Character-state weight matrices have usually been estimated more or less by eye, but they can also be derived from a rate matrix. For example, if it is presumed that each of the two transitions occurs at double the frequency of each transversion, a weight matrix can simply specify, for example, that the cost of A-G is 1 and the cost of A-T is 2 (Fig. 14.5). (The parsimony method dictates that the diagonal elements of the matrix, or the cost of having the same base in different sequences, be zero. This proves to be a shortcoming of parsimony this will be discussed further below.) In the subsequent tree-building step, this set of assumptions will minimize the overall number of transversions and tend to cluster sequences differing mainly by transitions. 

Step six, to compute the fitting sequence of clustering sequence = 1,2,...,10 and then... 

Calculations for the time required to reach equilibrium can be made for selected systems using the kinetic data in Tables I-III. For systems for which no kinetic data are available, estimates can be made. Thus for ion-solvent molecule equilibria studies in which the clustering molecules are polyatomic, as a rule of thumb one can assume that the achievement of equilibrium is determined by the rate of the slowest reaction, which has a rate constant k 10 cm molecule sec This value corresponds to the rate constant for the attachment of HjO to Cl with O2 as third body (Table I). With this value one calculates a half-life for the reaction at 0.5 Torr HjO and 5 Torr third body equal to 4 x 10 sec. The subsequent steps in the clustering sequence require considerably less time since... 

Cluster Sequence logo Binding domain (Pfam ID) Corresponding transcription factor Conserved binding motif ... 

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