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Search Results: 1 - 10 of 224440 matches for " Shane R. Geisler "
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Controlling a Permanent State of Change – IT Management Framework (ITMF)
Janelle R. Pollard,Shane R. Geisler
Journal of Economics, Business and Management , 2014, DOI: 10.7763/joebm.2014.v2.97
Abstract: In acknowledgement that organisations are in a permanent state of change; that IT needs to deliver change at the pace of business; and the rejection of ‘one size fits all’ delivery model resulting in hybrid methodologies, a blended and encompassing management partnerships across an organisation have become even more pertinent in business. To this goal the IT Management Framework (ITMF) has established a framework that provides the organisation with the ability to identify and capture information across multiple level throughout the organisations structure without impacting delivery. ITMF forms a single delivery orientated ICT Environment which establishes methodology independent framework, without being prescriptive about the execution methodologies; simultaneously empowering leadership teams simplification of the governance touch points and reporting obligations into the delivery environment
Homology Modelling and Structural Comparisons of Capsid-Associated Proteins from Circoviruses Reveal Important Virus-Specific Surface Antigens  [PDF]
Edward I. Patterson, Jade K. Forwood, Shane R. Raidal
Crystal Structure Theory and Applications (CSTA) , 2012, DOI: 10.4236/csta.2012.12002
Abstract: Circoviridae represent a growing family of small animal viruses. Some of these viruses have veterinary and medical importance, although, a vast amount of these newly discovered viruses have unknown effects on their hosts. The capsid-associated protein (Cap) of circoviruses is of interest because of its role in viral structure, immune evasion, host cell entry, and nuclear shuttling of viral components. The structure of the porcine circovirus 2 (PCV2) Cap has been solved and offered insight to these functions. Based on the crystallographic PCV2 Cap structure, models from circoviruses isolated from avian, fish, and mammalian hosts have been constructed and analyzed to better understand the roles of these proteins in the virus family. A high degree of conservation is observed in the models, however, the surface antigens differ among viruses. This is likely a reflection of the small genome harbored by circoviruses, and therefore the requirement of their few proteins to carry out specific vital functions, while maintaining enough variation to successfully infect their hosts. Here we describe the putative structures of a range of Cap proteins from circoviruses based on the crystallographic determination of porcine Cap, identifying key regions for function and inhibition of crystal formation.
ESPRI: Astrometric planet search with PRIMA at the VLTI
Quirrenbach A.,Geisler R.,Henning T.,Launhardt R.
EPJ Web of Conferences , 2011, DOI: 10.1051/epjconf/20111607005
Abstract: The ESPRI consortium will conduct an astrometric survey for extrasolar planets, using the PRIMA facility at the Very Large Telescope Interferometer. Our scientific goals include determining orbital inclinations and masses for planets already known from radial-velocity surveys, searches for planets around nearby stars of all masses, and around young stars. The consortium has built the PRIMA differential delay lines, developed an astrometric operation and calibration plan, and will deliver astrometric data reduction software.
Dust and molecular shells in asymptotic giant branch stars - Mid-infrared interferometric observations of R Aql, R Aqr, R Hya, W Hya and V Hya
R. Zhao-Geisler,A. Quirrenbach,R. Koehler,B. Lopez
Physics , 2012, DOI: 10.1051/0004-6361/201118150
Abstract: Mid-IR (8 - 13 micron) interferometric data of four oxygen-rich AGB stars (R Aql, R Aqr, R Hya, and W Hya) and one carbon-rich AGB star (V Hya) were obtained with MIDI/VLTI between April 2007 and September 2009. The spectrally dispersed visibility data are analyzed by fitting a circular fully limb-darkened disk (FDD). Results. The FDD diameter as function of wavelength is similar for all oxygen-rich stars. The apparent size is almost constant between 8 and 10 micron and gradually increases at wavelengths longer than 10 micron. The apparent FDD diameter in the carbon-rich star V Hya essentially decreases from 8 to 12 micron. The FDD diameters are about 2.2 times larger than the photospheric diameters estimated from K-band observations found in the literature. The silicate dust shells of R Aql, R Hya and W Hya are located fairly far away from the star, while the silicate dust shell of R Aqr and the amorphous carbon (AMC) and SiC dust shell of V Hya are found to be closer to the star at around 8 photospheric radii. Phase-to-phase variations of the diameters of the oxygen-rich stars could be measured and are on the order of 15% but with large uncertainties. From a comparison of the diameter trend with the trends in RR Sco and S Ori it can be concluded that in oxygen-rich stars the overall larger diameter originates from a warm molecular layer of H2O, and the gradual increase longward of 10 micron can be most likely attributed to the contribution of a close Al2O3 dust shell. The chromatic trend of the Gaussian FWHM in V Hya can be explained with the presence of AMC and SiC dust. The observations suggest that the formation of amorphous Al2O3 in oxygen- rich stars occurs mainly around or after visual minimum. However, no firm conclusions can be drawn concerning the mass-loss mechanism.
A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea
Jonathan H Geisler, Michael R McGowen, Guang Yang, John Gatesy
BMC Evolutionary Biology , 2011, DOI: 10.1186/1471-2148-11-112
Abstract: We combined new nuclear DNA sequences, including segments of six genes (~2800 basepairs) from the functionally extinct Yangtze River dolphin, with an expanded morphological matrix and published genomic data. Diverse analyses of these data resolved the relationships of 74 taxa that represent all extant families and 11 extinct families of Cetacea. The resulting supermatrix (61,155 characters) and its sub-partitions were analyzed using parsimony methods. Bayesian and maximum likelihood (ML) searches were conducted on the molecular partition, and a molecular scaffold obtained from these searches was used to constrain a parsimony search of the morphological partition. Based on analysis of the supermatrix and model-based analyses of the molecular partition, we found overwhelming support for 15 extant clades. When extinct taxa are included, we recovered trees that are significantly correlated with the fossil record. These trees were used to reconstruct the timing of cetacean diversification and the evolution of characters shared by "river dolphins," a non-monophyletic set of species according to all of our phylogenetic analyses.The parsimony analysis of the supermatrix and the analysis of morphology constrained to fit the ML/Bayesian molecular tree yielded broadly congruent phylogenetic hypotheses. In trees from both analyses, all Oligocene taxa included in our study fell outside crown Mysticeti and crown Odontoceti, suggesting that these two clades radiated in the late Oligocene or later, contra some recent molecular clock studies. Our trees also imply that many character states shared by river dolphins evolved in their oceanic ancestors, contradicting the hypothesis that these characters are convergent adaptations to fluvial habitats.It has been 12 years since the publication of Messenger and McGuire [1], the first major effort to develop a phylogenetic hypothesis for crown Cetacea (Neoceti) based on a combined phylogenetic analysis of morphological and molecular charact
The helium content of globular clusters: NGC6121 (M4)
S. Villanova,D. Geisler,G. Piotto,R. Gratton
Physics , 2012, DOI: 10.1088/0004-637X/748/1/62
Abstract: He has been proposed as a key element to interpret the observed multiple MS, SGB, and RGB, as well as the complex horizontal branch (HB) morphology. Stars belonging to the bluer part of the HB, are thought to be more He rich (\Delta Y=0.03 or more) and more Na-rich/O-poor than those located in the redder part. This hypothesis was only partially confirmed in NGC 6752, where stars of the redder zero-age HB showed a He content of Y=0.25+-0.01, fully compatible with the primordial He content of the Universe, and were all Na-poor/O-rich. Here we study hot blue HB (BHB) stars in the GC NGC 6121 (M4) to measure their He plus O/Na content. We observed 6 BHB stars using the UVES@VLT2 spectroscopic facility. In addition to He, O, Na, and Fe abundances were estimated. Stars turned out to be all Na-rich and O-poor and to have a homogeneous enhanced He content with a mean value of Y=0.29+-0.01(random)+-0.01(systematic). The high He content of blue HB stars in M4 is also confirmed by the fact that they are brighter than red HB stars (RHB). Theoretical models suggest the BHB stars are He-enhanced by \Delta Y=0.02-0.03 with respect to the RHB stars. The whole sample of stars has a metallicity of [Fe/H]=-1.06+-0.02 (internal error). This is a rare direct measurement of the (primordial) He abundance for stars belonging to the Na-rich/O-poor population of GC stars in a temperature regime where the He content is not altered by sedimentation or extreme mixing as suggested for the hottest, late helium flash HB stars. Our results support theoretical predictions that the Na-rich/O-poor population is also more He-rich than the Na-poor/O-rich generation and that a leading contender for the 2^{nd} parameter is the He abundance.
The metallicity spread and the age-metallicity relation of Omega Centauri
S. Villanova,D. Geisler,R. G. Gratton,S. Cassisi
Physics , 2014, DOI: 10.1088/0004-637X/791/2/107
Abstract: Omega Centauri is a peculiar Globular Cluster formed by a complex stellar population. To shed light on this, we studied 172 stars belonging to the 5 SGBs that we can identify in our photometry, in order to measure their [Fe/H] content as well as estimate their age dispersion and the age-metallicity relation. The first important result is that all of these SGBs has a distribution in metallicity with a spread that exceeds the observational errors and typically displays several peaks that indicate the presence of several sub-populations. We were able to identified at least 6 of them based on their mean [Fe/H] content. These metallicity-based sub-populations are seen to varying extents in each of the 5 SGBs. Taking advantage of the age-sensitivity of the SGB we showed that, first of all, at least half of the sub-populations have an age spread of at least 2 Gyrs. Then we obtained an age-metallicity relation that is the most complete up to date for this cluster. The interpretation of the age-metallicity relation is not straightforward, but it is possible that the cluster (or what we can call its progenitor) was initially composed of two populations having different metallicities. Because of their age, it is very unlikely that the most metal-rich derives from the most metal-poor by some kind of chemical evolution process, so they must be assumed as two independent primordial objects or perhaps two separate parts of a single larger object, that merged in the past to form the present-day cluster.
Barrier Mechanisms in the Developing Brain
Norman R. Saunders,Shane A. Liddelow
Frontiers in Pharmacology , 2012, DOI: 10.3389/fphar.2012.00046
Abstract: The adult brain functions within a well-controlled stable environment, the properties of which are determined by cellular exchange mechanisms superimposed on the diffusion restraint provided by tight junctions at interfaces between blood, brain and cerebrospinal fluid (CSF). These interfaces are referred to as “the” blood–brain barrier. It is widely believed that in embryos and newborns, this barrier is immature or “leaky,” rendering the developing brain more vulnerable to drugs or toxins entering the fetal circulation from the mother. New evidence shows that many adult mechanisms, including functionally effective tight junctions are present in embryonic brain and some transporters are more active during development than in the adult. Additionally, some mechanisms present in embryos are not present in adults, e.g., specific transport of plasma proteins across the blood–CSF barrier and embryo-specific intercellular junctions between neuroependymal cells lining the ventricles. However developing cerebral vessels appear to be more fragile than in the adult. Together these properties may render developing brains more vulnerable to drugs, toxins, and pathological conditions, contributing to cerebral damage and later neurological disorders. In addition, after birth loss of protection by efflux transporters in placenta may also render the neonatal brain more vulnerable than in the fetus.
Revisitando o conceito de cidadania: notas para uma educa??o politécnica
Geisler, Adriana;
Trabalho, Educa??o e Saúde , 2006, DOI: 10.1590/S1981-77462006000200008
Abstract: in opposition to a community and school project which have been denying the effective citizenship to a great contingent of youth and brazilian workers, the polytechnic conception emerges as a part of an emancipating project which is far from the liberal ideology and from its reflexes on the education and work fields. retaking the issue of the citizenship meaning nowadays, this text aims to identify to which citizenship concept the polytechnic conception belongs, considering the educational practices field and its connection to the current aspect of the world of work.
Expression of a prokaryotic P-type ATPase in E. coli Plasma Membranes and Purification by Ni2+-affinity chromatography
Geisler Markus
Biological Procedures Online , 1998, DOI: 10.1251/bpo9
Abstract: In order to characterize the P-type ATPase from Synechocystis 6803 [Geisler (1993) et al. J. Mol. Biol. 234, 1284] and to facilitate its purification, we expressed an N-terminal 6xHis-tagged version of the ATPase in an ATPase deficient E. coli strain. The expressed ATPase was immunodetected as a dominant band of about 97 kDa localized to the E. coli plasma membranes representing about 20-25% of the membrane protein. The purification of the Synecho-cystis 6xHis-ATPase by single-step Ni-affinity chromatography under native and denaturating conditions is described. ATPase activity and the formation of phosphointermediates verify the full function of the enzyme: the ATPase is inhibited by vanadate (IC50= 119 &mgr;M) and the formation of phosphorylated enzyme intermediates shown by acidic PAGE depends on calcium, indicating that the Synechocystis P-ATPase functions as a calcium pump.
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