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Patterns Present (pattern + present)

Distribution by Scientific Domains

Life Sciences	50%
Chemistry	50%

Selected Abstracts

Brief communication: The distribution of perikymata on Qafzeh anterior teeth

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010
Debbie Guatelli-Steinberg
Abstract Recent studies have suggested that Neandertals and modern humans differ in the distribution of perikymata (enamel growth increments) over their permanent anterior tooth crowns. In modern humans, perikymata become increasingly more compact toward the cervix than they do in Neandertals. Previous studies have suggested that a more homogeneous distribution of perikymata, like that of Neandertals, characterizes the anterior teeth of Homo heidelbergensis and Homo erectus as well. Here, we investigated whether Qafzeh anterior teeth (N = 14) differ from those of modern southern Africans, northern Europeans, and Alaskans (N = 47,74 depending on tooth type) in the percentage of perikymata present in their cervical halves. Using the normally distributed modern human values for each tooth type, we calculated Z -scores for the 14 Qafzeh teeth. All but two of the 14 Qafzeh teeth had negative Z -scores, meaning that values equal to these would be found in the bottom 50% of the modern human samples. Seven of the 14 would be found in the lowest 5% of the modern human distribution. Qafzeh teeth therefore appear to differ from those of modern humans in the same direction that Neandertals do: with generally lower percentages of perikymata in their cervical regions. The similarity between them appears to represent the retention of a perikymata distribution pattern present in earlier members of the genus Homo, but not generally characteristic of modern humans from diverse regions of the world. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source]

Evolution of Courtship Behaviour Patterns and Reproductive Isolation in the Desmognathus ochrophaeus Complex

ETHOLOGY, Issue 5 2002
Louise S. Mead
The extent to which differences in courtship behaviour patterns act as mechanisms of reproductive isolation is critical to understanding both speciation and the evolution of these behaviour patterns. While numerous studies have investigated intraspecific and interspecific differences in courtship, fewer interpret results in a phylogenetic framework. We describe and analyse geographic variation in the courtship behaviour patterns of the Allegheny Dusky salamander (Desmognathus ochrophaeus). We then examine courtship among closely related species in the D. ochrophaeus complex in a phylogenetic context. We found that populations of D. ochrophaeus separated by extensive geographic distances show little variation in courtship behaviour patterns and are sexually compatible. This contrasts with significant levels of sexual isolation between D. ochrophaeus and other species in the complex. Mapping behaviour patterns onto a phylogeny that we generated from cytochrome b sequences indicates that two behaviour patterns present in the courtship sequence of other members in the complex have either been lost in D. ochrophaeus or gained independently in other species in the complex. Loss of these behaviour patterns may result in reproductive isolation between D. ochrophaeus and its sister taxon, D. orestes. [source]

Stereoselective Chemoenzymatic Preparation of ,-Amino Esters: Molecular Modelling Considerations in Lipase-Mediated Processes and Application to the Synthesis of (S)-Dapoxetine

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
María Rodríguez-Mata
Abstract A wide range of optically active 3-amino-3-arylpropanoic acid derivatives have been prepared by means of a stereoselective chemoenzymatic route. The key step is the kinetic resolution of the corresponding ,-amino esters. Although the enzymatic acylations of the amino group with ethyl methoxyacetate showed synthetically useful enantioselectivities, the hydrolyses of the ester group catalyzed by lipase from Pseudomonas cepacia have been identified as the optimal processes concerning both activity and enantioselectivity. The enantiopreference of this lipase in these reactions has been explained, at the molecular level, by using a fragment-based approach in which the most favoured binding site for a phenyl ring and the most stable conformation of the 3-aminopropanoate core nicely match the (S)-configuration of the major products. The conversion and enantioselectivity values of the enzymatic reactions have been compared in order to understand the influence of the different substitution patterns present in the phenyl ring. This chemoenzymatic route has been successfully applied to the preparation of a valuable intermediate in the synthesis of (S)-dapoxetine, which has been chemically synthesised in excellent optical purity. [source]

Holdup and Pressure Drop in Vertical and Near-Vertical Three-Phase Up-Flow: A Collection of Flow Regimes

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2002
P.L. Spedding
Three-phase oil, water and air data are reported for vertical and near vertical +86 5° upflow in a 0 026 m i d pipe In general, the liquid holdup for near vertical flow was greater than for the corresponding vertical upflow, the exception being at low liquid and superficial velocities under 0 6 m/s and high superficial gas velocities over 20 m/s Here the liquid holdup varied being sometimes below and other times above the corresponding vertical value These variations of liquid holdup were shown to depend on the fine structure of the flow patterns present The total pressure drop and its component parts showed significantly different patterns of behaviour depending on whether the superficial gas velocity was above or below the rise velocity of a Taylor bubble The total pressure drop generally was greater for near vertical flow compared to the vertical upflow case but reflected changes in the fine structure of the flow patterns A comprehensive collection of flow regimes is included in this paper [source]