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Search Results: 1 - 10 of 300331 matches for " J. Ryan "
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Minimal Bratteli diagrams and the dimension groups of AF -algebras
Ryan J. Zerr
International Journal of Mathematics and Mathematical Sciences , 2006, DOI: 10.1155/ijmms/2006/65737
Abstract: A method is described which identifies a wide variety of AF algebra dimension groups with groups of continuous functions. The results here generalize the well-known fact that commutative AF algebras have dimension groups which can be identified with groups of integer-valued continuous functions.
A topological isomorphism invariant for certain AF algebras
Ryan J. Zerr
International Journal of Mathematics and Mathematical Sciences , 2005, DOI: 10.1155/ijmms.2005.1665
Abstract: For certain AF algebras, a topological space is described which provides an isomorphism invariant for the algebras in this class. These AF algebras can be described in graphical terms by virtue of the existence of a certain type of Bratteli diagram, and the order-preserving automorphisms of the corresponding AF algebra's dimension group are then studied by utilizing this graph. This will also provide information about the automorphism groups of the corresponding AF algebras.
A.J. Ryan
Akroterion , 2012, DOI: 10.7445/52-0-57
Abstract: With the help of a generous donation from Miss Joan Law, the Museum of Classical Archaeology has recently acquired a small Roman bronze ithyphallic herm of Pan holding a pedum or shepherd’s crook (Figs. 1 & 2) from the 1st or 2nd century CE. 1 The bottom-most part of the base has broken off, but the object is otherwise in excellent condition with slight patination. The base is rectangular up to the waist. The buttocks are not sculpted but simply indicated by a single incised line. From the waist up the details, such as the musculature, face and hair, are very finely rendered. The figure arches his back and raises his right hand to his forehead while his left hand supports a pedum. He is bearded with short unkempt hair and visible horns.
A.j. Ryan
Akroterion , 2012, DOI: 10.7445/49-0-92
Abstract: Two Egyptian artefacts from the first millennium BC have recently been acquired by the Museum of Classical Archaeology at the University of KwaZulu-Natal, courtesy of a kind donation by Miss Joan Law. At a time when academia in South Africa is placing considerable emphasis on African-oriented scholarship, it is appropriate that the museum has on display a large selection of small Egyptian artefacts dating from as early as the 4th millennium BC. These items are of particular interest for teaching as they reflect a variety of different aspects of Egyptian life.
A.J. Ryan
Akroterion , 2012, DOI: 10.7445/47-0-112
Abstract: The Museum of Classical Archaeology has on loan from Dr. David Spurrett four arrowheads of varying antiquity, ranging from the late Neolithic to the Hellenistic period. Although small, these artefacts are of significant pedagogical value to a museum whose primary function is teaching. In particular, the Classics Programme at the University of Natal allows senior students, in lieu of a research essay, to submit web projects based on the artefacts in the museum.1 Ancient weaponry and warfare has always been a popular topic for students and these items offer considerable scope for new projects.
A.J. Ryan
Akroterion , 2012, DOI: 10.7445/51-0-69
Abstract: The Museum of Classical Archaeology has recently acquired a number of new Roman artefacts. Of these, the most interesting is a small fragment of a bronze Flavian Roman military diploma (Durban 2007.52), the subject of this contribution. The fragment is from Table I of a diploma and measures 5.39cm x 2.88cm, is 1.2mm thick with letters averaging 4.5mm high. Typically a complete diploma would be around 21cm x 16 cm. Not only is this diploma a valuable piece of documentary evidence, but it is also the first example of Roman writing in our museum. The acquisition of this new addition to our collection is thanks largely to a generous donation by Ms Joan Law.
S-glutathionylation reactions in mitochondrial function and disease
Ryan J. Mailloux
Frontiers in Cell and Developmental Biology , 2014, DOI: 10.3389/fcell.2014.00068
Abstract: Mitochondria are highly efficient energy-transforming organelles that convert energy stored in nutrients into ATP. The production of ATP by mitochondria is dependent on oxidation of nutrients and coupling of exergonic electron transfer reactions to the genesis of transmembrane electrochemical potential of protons. Electrons can also prematurely “spin-off” from prosthetic groups in Krebs cycle enzymes and respiratory complexes and univalently reduce di-oxygen to generate reactive oxygen species (ROS) superoxide (O2??) and hydrogen peroxide (H2O2), important signaling molecules that can be toxic at high concentrations. Production of ATP and ROS are intimately linked by the respiratory chain and the genesis of one or the other inherently depends on the metabolic state of mitochondria. Various control mechanisms converge on mitochondria to adjust ATP and ROS output in response to changing cellular demands. One control mechanism that has gained a high amount of attention recently is S-glutathionylation, a redox sensitive covalent modification that involves formation of a disulfide bridge between glutathione and an available protein cysteine thiol. A number of S-glutathionylation targets have been identified in mitochondria. It has also been established that S-glutathionylation reactions in mitochondria are mediated by the thiol oxidoreductase glutaredoxin-2 (Grx2). In the following review, emerging knowledge on S-glutathionylation reactions and its importance in modulating mitochondrial ATP and ROS production will be discussed. Major focus will be placed on Complex I of the respiratory chain since (1) it is a target for reversible S-glutathionylation by Grx2 and (2) deregulation of Complex I S-glutathionylation is associated with development of various disease states particularly heart disease. Other mitochondrial enzymes and how their S-glutathionylation profile is affected in different disease states will also be discussed.
What is a Systems Approach?
Alex J. Ryan
Physics , 2008,
Abstract: What is a systems approach? The first step towards answering this question is an understanding of the history of the systems movement, which includes a survey of contemporary systems discourse. In particular, I examine how systems researchers differentiated their contribution from mechanistic science - but also from holistic doctrines; and identify the similarities and sharpest differences between complex systems and other systems approaches. Having set the scene, the second step involves developing a definition of 'system' consistent with the spirit of the systems approach.
Kinematics and Host-Galaxy Properties Suggest a Nuclear Origin for Calcium-Rich Supernova Progenitors
Ryan J. Foley
Physics , 2015, DOI: 10.1093/mnras/stv789
Abstract: Calcium-rich supernovae (Ca-rich SNe) are peculiar low-luminosity SNe Ib with relatively strong Ca spectral lines at ~2 months after peak brightness. This class also has an extended projected offset distribution, with several members of the class offset from their host galaxies by 30 - 150 kpc. There is no indication of any stellar population at the SN positions. Using a sample of 13 Ca-rich SNe, we present kinematic evidence that the progenitors of Ca-rich SNe originate near the centers of their host galaxies and are kicked to the locations of the SN explosions. Specifically, SNe with small projected offsets have large line-of-sight velocity shifts as determined by nebular lines, while those with large projected offsets have no significant velocity shifts. Therefore, the velocity shifts must not be primarily the result of the SN explosion. There is an excess of SNe with blueshifted velocity shifts within two isophotal radii (5/6 SNe), indicating that the SNe are moving away from their host galaxies and redshifted SNe on the far sides of their galaxies are selectively missed in SN surveys. Additionally, nearly every Ca-rich SN is hosted by a galaxy with indications of a recent merger and/or is in a dense environment. We propose a progenitor model which fits all current data: The progenitor system for a Ca-rich SN is a double white dwarf (WD) system where at least one WD has a significant He abundance. This system, through an interaction with a super-massive black hole (SMBH) is ejected from its host galaxy and the binary is hardened, significantly reducing the merger time. After 10 - 100 Myr (on average), the system explodes with a large physical offset. The rate for such events is significantly enhanced for galaxies which have undergone recent mergers, potentially making Ca-rich SNe new probes of both the galaxy merger rate and (binary) SMBH population. (abridged)
Emergence is coupled to scope, not level
Alex J. Ryan
Physics , 2006,
Abstract: Since its application to systems, emergence has been explained in terms of levels of observation. This approach has led to confusion, contradiction, incoherence and at times mysticism. When the idea of level is replaced by a framework of scope, resolution and state, this confusion is dissolved. We find that emergent properties are determined by the relationship between the scope of macrostate and microstate descriptions. This establishes a normative definition of emergent properties and emergence that makes sense of previous descriptive definitions of emergence. In particular, this framework sheds light on which classes of emergent properties are epistemic and which are ontological, and identifies fundamental limits to our ability to capture emergence in formal systems.
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