Relaxation of selective constraints on avian mitochondrial DNA following the degeneration of flight ability

The evolution of flight is the most important feature of birds, and this ability has helped them become one of the most successful groups of vertebrates. However, some species have independently lost their ability to fly. The degeneration of flight abilit

Duplication-degeneration as a mechanism of gene fission and the origin of new genes in Drosophila species

Gene fission and fusion, the processes by which a single gene is split into two separate genes and two adjacent genes are fused into a single gene, respectively, are among the primary processes that generate new genes(1-4). Despite their seeming reversibi

Finite element analysis of compressor disc heat transfer using the transient conduction method with sparse boundary collocation points

Surface temperature measurements from two discs of a gas turbine compressor rig are used as boundary conditions for the transient conduction solution (inverse heat transfer analysis). The disc geometry is complex, and so the finite element method is used. There are often large radial temperature gradients on the discs, and the equations are therefore solved taking into account the dependence of thermal conductivity on temperature. The solution technique also makes use of a multigrid algorithm to reduce the solution time. This is particularly important since a large amount of data must be analyzed to obtain correlations of the heat transfer. The finite element grid is also used for a network analysis to calculate the radiant heat transfer in the cavity formed between the two compressor discs. The work discussed here proved particularly challenging as the disc temperatures were only measured at four different radial locations. Four methods of surface temperature interpolation are examined, together with their effect on the local heat fluxes. It is found that the choice of interpolation method depends on the available number of data points. Bessel interpolation gives the best results for four data points, whereas cubic splines are preferred when there are considerably more data points. The results from the analysis of the compressor rig data show that the heat transfer near the disc inner radius appears to be influenced by the central throughflow. However, for larger radii, the heat transfer from the discs and peripheral shroud is found to be consistent with that of a buoyancy-induced flow.

An investigation into numerical analysis alternatives for predicting reingestion in turbine disc rim cavities

Reliable means of predicting ingestion in cavities adjacent to the main gas path are increasingly being sought by engineers involved in the design of gas turbines. In this paper, analysis is to be presented that results from an extended research programme, MAGPI, sponsored by the EU and several leading gas turbine manufactures and universities. Extensive use is made of CFD modelling techniques to understand the aerodynamic behaviour of a turbine stator well cavity, focusing on the interaction of cooling air supply with the main annulus gas. The objective of the study has been to benchmark a number of CFD codes and numerical techniques covering RANS and URANS calculations with different turbulence models in order to assess the suitability of the standard settings used in the industry for calculating the mechanics of the flow travelling between cavities in a turbine through the main gas path. The modelling methods employed have been compared making use of experimental data gathered from a dedicated two-stage turbine rig, running at engine representative conditions. Extensive measurements are available for a range of flow conditions and alternative cooling arrangements. The limitations of the numerical methods in calculating the interaction of the cooling flow egress and the main stream gas, and subsequent ingestion into downstream cavities in the engine (i.e. re-ingestion), have been exposed. This has been done without losing sight of the validation of the CFD for its use for predicting heat transfer, which was the main objective of the partners of the MAGPI Work- Package 1 consortium. Copyright © 2012 by ASME.

Phylogenetic relationships of labeonine cyprinids of the disc-bearing group (Pisces : Teleostei)

Phylogenetic relationships of labeonine cyprinids of the disc-bearing group (Pisces. Teleostei). Zoological Studies 44 (1): 130-143. The disc-bearing group is composed of 4 currently recognized cyprinid genera: Discocheilus, Discogobio, Garra, and Placocheilus. This group is defined as having a lower lip modified to form a mental adhesive disc whose posterior margin is not continuous with the mental region, and includes 91 widely distributed species in tropical Africa and Asia. So far, it is represented in China by 28 species (about 1/3 of the total number) of all 4 genera. A phylogenetic analysis, based on 29 morphological characters scored from first-hand observations of 23 of the Chinese species examined, revealed that the disc-bearing group forms a monophyletic clade in which Garra is the basal lineage, and Placocheilus constitutes a subclade with the sister pair of Discocheilus and Discogobio. In such a phylogenetic framework, the validity of each genus of the disc-bearing group was evaluated. It was confirmed that Discocheilus, Discogobio and Placocheilus represent 3 valid cyprinid genera. Evidence provided in this phylogenetic analysis, incorporated with conclusions reached in the known literature, reveals that the monophyly and validity of Garra need to be further studied using observations of more Garra species. Additional characters should also be examined, as the characters utilized in this study and in Abebe's with Getahun's (1999) study are insufficient to resolve the monophyly of Garra.

Electronic structure of self-assembled InAs quantum discs in a magnetic field with varying orientation and two-electron quantum-disc qubits

We have studied the electronic structure of vertically assembled quantum discs in a magnetic field with varying orientation using the effective mass approximation. We calculate the four energy levels of single-electron quantum discs and the two lowest energy levels of two-electron quantum discs in a magnetic field with varying orientation. The change of the magnetic field as an effective potential strongly modifies the electronic structure, leading to splittings of the levels and anticrossings between the levels. The calculated results also demonstrate the switching between the ground states with the total spin S = 0 and 1. The switching induces a qubit controlled by varying the orientation of the magnetic field.

Design of a fibre-optic disc accelerometer: theory and experiment

Mechanical principles of fibre-optic disc accelerometers (FODA) different from those assumed in previous calculation methods are presented. An FODA with a high sensitivity of 82 rad/ g and a resonance frequency of 360 Hz is designed and tested. In this system, the minimum measurable demodulation phase of the phase-generated carrier (PGC) is 10(-5) rad, and the minimum acceleration reaches 120 ng theoretically. This kind of FODA, with its high responsivity, all-optic-fibre configuration, small size, light weight and stiff shell housing, ensures effective performance in practice.

Ultrastructure of the accessory podia of Laganum depressum (Echinoidea, Clypeasteroida) with special emphasis on the disc epidermis

info:eu-repo/semantics/published

Mitochondrial DNA polymorphism A4917G is independently associated with age-related macular degeneration.

The objective of this study was to determine if MTND2*LHON4917G (4917G), a specific non-synonymous polymorphism in the mitochondrial genome previously associated with neurodegenerative phenotypes, is associated with increased risk for age-related macular degeneration (AMD). A preliminary study of 393 individuals (293 cases and 100 controls) ascertained at Vanderbilt revealed an increased occurrence of 4917G in cases compared to controls (15.4% vs.9.0%, p = 0.11). Since there was a significant age difference between cases and controls in this initial analysis, we extended the study by selecting Caucasian pairs matched at the exact age at examination. From the 1547 individuals in the Vanderbilt/Duke AMD population association study (including 157 in the preliminary study), we were able to match 560 (280 cases and 280 unaffected) on exact age at examination. This study population was genotyped for 4917G plus specific AMD-associated nuclear genome polymorphisms in CFH, LOC387715 and ApoE. Following adjustment for the listed nuclear genome polymorphisms, 4917G independently predicts the presence of AMD (OR = 2.16, 95%CI 1.20-3.91, p = 0.01). In conclusion, a specific mitochondrial polymorphism previously implicated in other neurodegenerative phenotypes (4917G) appears to convey risk for AMD independent of recently discovered nuclear DNA polymorphisms.

Integrin-mediated interactions with extracellular matrix proteins for nucleus pulposus cells of the human intervertebral disc.

The extracellular matrix (ECM) of the human intervertebral disc is rich in molecules that interact with cells through integrin-mediated attachments. Porcine nucleus pulposus (NP) cells have been shown to interact with laminin (LM) isoforms LM-111 and LM-511 through select integrins that regulate biosynthesis and cell attachment. Since human NP cells lose many phenotypic characteristics with age, attachment and interaction with the ECM may be altered. Expression of LM-binding integrins was quantified for human NP cells using flow cytometry. The cell-ECM attachment mechanism was determined by quantifying cell attachment to LM-111, LM-511, or type II collagen after functionally blocking specific integrin subunits. Human NP cells express integrins β1, α3, and α5, with over 70% of cells positive for each subunit. Blocking subunit β1 inhibited NP cell attachment to all substrates. Blocking subunits α1, α2, α3, and α5 simultaneously, but not individually, inhibits NP cell attachment to laminins. While integrin α6β1 mediated porcine NP cell attachment to LM-111, we found integrins α3, α5, and β1 instead contributed to human NP cell attachment. These findings identify integrin subunits that may mediate interactions with the ECM for human NP cells and could be used to promote cell attachment, survival, and biosynthesis in cell-based therapeutics.