SSME main combustion chamber life prediction

Typically, low cycle fatigue life is a function of the cyclic strain range, the material properties, and the operating temperature. The reusable life is normally defined by the number of strain cycles that can be accrued before severe material degradation occurs. Reusable life is normally signified by the initiation or propagation of surface cracks. Hot-fire testing of channel wall combustors has shown significant mid-channel wall thinning or deformation during accrued cyclic testing. This phenomenon is termed cyclic-creep and appears to be significantly accelerated at elevated surface temperatures. This failure mode was analytically modelled. The cyclic life of the baseline SSME-MCC based on measured calorimeter heat transfer data, and the life sensitivity of local hot spots caused by injector effects were determined. Four life enhanced designs were assessed

Innermost stable circular orbits around relativistic rotating stars

We investigate the innermost stable circular orbit (ISCO) of a test particle moving on the equatorial plane around rotating relativistic stars such as neutron stars. First, we derive approximate analytic formulas for the angular velocity and circumferential radius at the ISCO making use of an approximate relativistic solution which is characterized by arbitrary mass, spin, mass quadrupole, current octapole and mass $2^4$-pole moments. Then, we show that the analytic formulas are accurate enough by comparing them with numerical results, which are obtained by analyzing the vacuum exterior around numerically computed geometries for rotating stars of polytropic equation of state. We demonstrate that contribution of mass quadrupole moment for determining the angular velocity and, in particular, the circumferential radius at the ISCO around a rapidly rotating star is as important as that of spin.Comment: 12 pages, 2 figures, accepted for publication in Phys. Rev.

Different populations of RNA polymerase II in living mammalian cells

RNA polymerase II is responsible for transcription of most eukaryotic genes, but, despite exhaustive analysis, little is known about how it transcribes natural templates in vivo. We studied polymerase dynamics in living Chinese hamster ovary cells using an established line that expresses the largest (catalytic) subunit of the polymerase (RPB1) tagged with the green fluorescent protein (GFP). Genetic complementation has shown this tagged polymerase to be fully functional. Fluorescence loss in photobleaching (FLIP) reveals the existence of at least three kinetic populations of tagged polymerase: a large rapidly-exchanging population, a small fraction resistant to 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) but sensitive to a different inhibitor of transcription (i.e. heat shock), and a third fraction sensitive to both inhibitors. Quantitative immunoblotting shows the largest fraction to be the inactive hypophosphorylated form of the polymerase (i.e. IIA). Results are consistent with the second (DRB-insensitive but heat-shock-sensitive) fraction being bound but not engaged, while the third (sensitive to both DRB and heat shock) is the elongating hyperphosphorylated form (i.e. IIO)

Oncogenic K-Ras suppresses IP₃-dependent Ca²⁺ release through remodeling of IP₃Rs isoform composition and ER luminal Ca²⁺ levels in colorectal cancer cell lines

The GTPase Ras is a molecular switch engaged downstream of G-protein coupled receptors and receptor tyrosine inases that controls multiple cell fate-determining signalling athways. Ras signalling is frequently deregulated in cancer underlying associated changes in cell phenotype. Although Ca2+ signalling pathways control some overlapping functions with Ras, and altered Ca2+ signalling pathways are emerging as important players in oncogenic transformation, how Ca2+ signalling is remodelled during transformation and whether it has a causal role remains unclear. We have investigated Ca2+ signalling in two human colorectal cancer cell lines and their isogenic derivatives in which the mutated K-Ras allele (G13D) has been deleted by homologous recombination. We show that agonist-induced Ca2+ release from intracellular stores is enhanced by loss of K-RasG13D through an increase in the ER store content and a modification of IP3R subtype abundance. Consistently, uptake of Ca2+ into mitochondria and sensitivity to apoptosis was enhanced as a result of KRasG13D loss. These results suggest that suppression of Ca2+ signalling is a common response to naturally occurring levels of K-RasG13D that contributes to a survival advantage during oncogenic transformation

Evaluation of surface water resources from machine-processing of ERTS multispectral data

The surface water resources of a large metropolitan area, Marion County (Indianapolis), Indiana, are studied in order to assess the potential value of ERTS spectral analysis to water resources problems. The results of the research indicate that all surface water bodies over 0.5 ha were identified accurately from ERTS multispectral analysis. Five distinct classes of water were identified and correlated with parameters which included: degree of water siltiness; depth of water; presence of macro and micro biotic forms in the water; and presence of various chemical concentrations in the water. The machine processing of ERTS spectral data used alone or in conjunction with conventional sources of hydrological information can lead to the monitoring of area of surface water bodies; estimated volume of selected surface water bodies; differences in degree of silt and clay suspended in water and degree of water eutrophication related to chemical concentrations

Statistical Issues in Modeling Chronic Disease in Cohort Studies

The final publication (Cook, R. J., & Lawless, J. F. (2014). Statistical issues in modeling chronic disease in cohort studies. Statistics in Biosciences, 6(1), 127-161. DOI: 10.1007/s12561-013-9087-8) is available at Springer via http://link.springer.com/article/10.1007/s12561-013-9087-8Observational cohort studies of individuals with chronic disease provide information on rates of disease progression, the effect of fixed and time-varying risk factors, and the extent of heterogeneity in the course of disease. Analysis of this information is often facilitated by the use of multistate models with intensity functions governing transition between disease states. We discuss modeling and analysis issues for such models when individuals are observed intermittently. Frameworks for dealing with heterogeneity and measurement error are discussed including random effect models, finite mixture models, and hidden Markov models. Cohorts are often defined by convenience and ways of addressing outcome-dependent sampling or observation of individuals are also discussed. Data on progression of joint damage in psoriatic arthritis and retinopathy in diabetes are analysed to illustrate these issues and related methodology.Natural Sciences and Engineering Research Council of Canada (RGPIN 155849); Canadian Institutes for Health Research (FRN 13887

The 2′-Phosphate of NADP Is Critical for Optimum Productive Binding to 6-Phosphogluconate Dehydrogenase from Candida Utilis

Initial velocity studies obtained with alternative dinucleotide substrates for the 6-phosphogluconate dehydrogenase reaction suggest that the 2′-phosphate is critical for the optimum productive binding of the dinucleotide substrate. Initial velocity patterns obtained by varying 6-phosphogluconate at different fixed levels of NAD are nearly parallel with apparent competitive substrate inhibition by 6-phosphogluconate at pH 7 and below but intersect to the left of the ordinate at pH 8 and above. Dead-end inhibition studies indicate that the mechanism is random at all pH values. Data are interpreted in terms of a random mechanism with marked antagonism in the binding of NAD and 6-phosphogluconate at low pH. Deuterium isotope effects on V and V/K for either substrate are equal at pH 8, indicating that the kinetic mechanism is rapid equilibrium random. A decrease in the pH and the subsequent protonation of the active site general base or some other enzyme residue with a similar pK apparently results in the ineffective binding of NAD. The latter suggests either a link between the protonation state of this group and the conformation of the dinucleotide binding site or an interaction between the two

The 2′-Phosphate of NADP Is Critical for Optimum Productive Binding to 6-Phosphogluconate Dehydrogenase from Candida Utilis

Initial velocity studies obtained with alternative dinucleotide substrates for the 6-phosphogluconate dehydrogenase reaction suggest that the 2′-phosphate is critical for the optimum productive binding of the dinucleotide substrate. Initial velocity patterns obtained by varying 6-phosphogluconate at different fixed levels of NAD are nearly parallel with apparent competitive substrate inhibition by 6-phosphogluconate at pH 7 and below but intersect to the left of the ordinate at pH 8 and above. Dead-end inhibition studies indicate that the mechanism is random at all pH values. Data are interpreted in terms of a random mechanism with marked antagonism in the binding of NAD and 6-phosphogluconate at low pH. Deuterium isotope effects on V and V/K for either substrate are equal at pH 8, indicating that the kinetic mechanism is rapid equilibrium random. A decrease in the pH and the subsequent protonation of the active site general base or some other enzyme residue with a similar pK apparently results in the ineffective binding of NAD. The latter suggests either a link between the protonation state of this group and the conformation of the dinucleotide binding site or an interaction between the two

Can a combination of the conformal thin-sandwich and puncture methods yield binary black hole solutions in quasi-equilibrium?

We consider combining two important methods for constructing quasi-equilibrium initial data for binary black holes: the conformal thin-sandwich formalism and the puncture method. The former seeks to enforce stationarity in the conformal three-metric and the latter attempts to avoid internal boundaries, like minimal surfaces or apparent horizons. We show that these two methods make partially conflicting requirements on the boundary conditions that determine the time slices. In particular, it does not seem possible to construct slices that are quasi-stationary and avoid physical singularities and simultaneously are connected by an everywhere positive lapse function, a condition which must obtain if internal boundaries are to be avoided. Some relaxation of these conflicting requirements may yield a soluble system, but some of the advantages that were sought in combining these approaches will be lost.Comment: 8 pages, LaTeX2e, 2 postscript figure