Frictional Properties of Fault Gouge in HIgh Velocity/Long Distance Shear Experiments

The present objective is the characterization of the dynamic friction and seismic stability of fault gouge in high-velocity/long-distance shear experiments. The study has two parts based on the gouge source: A) Reservoir rocks and mixtures of quartz-calcite-clay to determine the effect of gouge composition on frictional properties; and B) gouge of the Alpine Fault zone, New Zealand, which is a major plate boundary in the later stage of the seismic cycle. Accordingly, the abstract includes two parts. DYNAMIC FRICTION AS FUNCTION OF FAULT-GOUGE COMPOSITION The seismic stability of a fault and its likelihood to generate earthquakes are controlled by its frictional properties (Brace and Byerlee, 1966). This project focuses on experimental characterization of the frictional properties of rocks and sediments. The results will contribute to a better understanding of the seismicity associated with hydrocarbon production and wastewater injection, which are known to trigger seismic slip on faults and fractures (Segall, 1989, Ellsworth, 2013). The experimental analysis is based on shearing rock gouge samples at slip-velocities up to 0.5 m/s, which is comparable to seismic slip velocity. The samples were placed in a confined rotary cell, and were sheared as either room-dry or water-saturated. Two types of samples were used: (1) core samples from six oil reservoirs comprised of approximately equal amounts of quartz and clay, and calcite that varies between 10% and 90%; and (2) mixtures of quartz-calcite-clay grains that cover a wide range of sedimentary rock compositions. The core samples were ground into aggregates of 150-450 µm before testing. The 93 experiments were conducted at slip velocities of 0.001-0.5 m/s with either stepped-velocity or constant velocity to distances up to 15 m. The main results are: (1) the friction coefficient ranges widely from very low (~ 0.1) to very high (~1.2) with low strength of the water saturated samples, and weakening intensity proportional to the relative abundance of calcite in the samples; (2) The velocity-dependence of friction showed complex trends of velocity-weakening, velocity-strengthening, or velocity-neutral behavior. DYNAMIC STRENGTH OF ALPINE FAULT GOUGE The Alpine Fault, New Zealand, is a large plate boundary fault with slip rate of ~ 37 mm/y, and a documented history of M~8 seismic events (Sutherland, 2007). Trench analyses have shown that slip frequently ruptures to the surface, and suggest that a large earthquake occurs approximately every 300 years (Wells et al., 1999; Berryman, 2012). As the last known event occurred in 1717, the Alpine Fault is late in the seismic cycle (Sutherland, 2007). To better understand the slip behavior and related hazards of the Alpine Fault, we analyze the frictional properties of its gouge that was collected at three field exposures (Waikukupa, Cataclasite, and Gaunt) along 40 km stretch of the Alpine Fault. The bulk samples (1-3 kg) were first manually disintegrated without shear, and then sieved to the 250-350 µm fractions. The gouge was sheared at natural, moisture-rich conditions at slip-velocity range of 0.01-1.5 m/s in stepped-velocity style with a constant normal stress of ~3 MPa. Data collection included monitoring the CO2 and H2O emission, in addition to the standard mechanical parameters. The results show an initial friction coefficient of µ ~0.6. Initial slip at low velocities (0.01 m/s) displays gentle velocity strengthening that changed to a drastic weakening (~50%) at velocity of 0.5 m/s. This weakening was associated with intense slip localization along a hard, dark slip surface within the gouge zone. After the establishment of this slip surface, there was no strength recovery and the sample remains weakened. If such behavior occurs during a natural earthquake, it will allow the release of a significant amount of the accumulated energy, which may result in a stronger earthquake with larger displacement

L’agriculture libre

Les principes fondateurs de l’open source – la capacité de partager, distribuer, modifier et reproduire des informations – sont-ils transposables à l’agriculture ? Si dans le domaine informatique, les logiciels libres sont maintenant une réalité, cela est-il transposable au domaine de l’agriculture ? Cet article examine l’hypothèse et la manière de créer et de diffuser des outils agricoles à travers des processus « libres ». Deux cas d’étude seront présentés : un logiciel de gestion pour les exploitants agricoles développé par la société éponyme, Ekylibre ; et une coopérative qui développe auprès des agriculteurs des techniques d’auto-construction d’outils agricoles, l’Atelier Paysan. Ces deux structures seront étudiées à travers leur histoire et leur forme d’organisation, la façon dont elles mettent en pratique les principes de l’open source, et en décrivant les outils qu’ils fabriquent dans leur contexte économique et social.Ekylibre et l’Atelier Paysan se réfèrent tous les deux au mouvement open source et s’investissent dans le partage des connaissances – lesquelles sont diffusées via des sites web, des démonstrations, des formations, et des forums. Ce sont des structures intimement liées à des communautés d’utilisateurs. Toutefois, en y regardant de plus près, on s’aperçoit que l’architecture, la matérialité et l’aspect financier des outils développés par Ekylibre et l’Atelier Paysan présentent des différences.Dans la littérature académique, l’open source est généralement conceptualisé comme un projet politique et éthique, tributaire d’une forme de sociabilité et de communautarité bien particulière. L’article montre qu’il faut problématiser et détailler davantage en retraçant empiriquement comment l’open source se matérialise au cas par cas. Si on peut concevoir certains outils comme des objets politiques, le terme politique ne renvoie pas à la même chose. Bien que Ekylibre et l’Atelier Paysan soient tous les deux liés à des communautés d’usagers, ces dernières sont organisées différemment et les échanges monétaires se font de façon distincte. L’idée d’open source ne se traduit, dans la pratique, pas seulement par des outils visant à être libres, partageables, collectifs, etc. Il faut aussi, selon nous, examiner de quelle manière et jusqu’à quel degré des outils open source peuvent être qualifiés comme tel et ainsi préciser ce qu’on entend par “politique” au cas par cas.Are the founding principles of open source – the ability to share, distribute, modify and reproduce information – transferable to agriculture? If in the computer field, free software is now a reality, this paper examines whether and how agricultural tools can be created and disseminated through ‘free’ processes. We look at two case studies: a management software for farmers developed by – and called – Ekylibre; and a cooperative that provides farmers with machines that can be self-constructed, l’Atelier Paysan. Both structures are studied by retracing their history and form of organization, studying how they enact the principles of open source, and by describing their tools within their economic and political context.Ekylibre and Atelier Paysan refer both to the open source movement and are devoted to knowledge sharing - knowledge that is disseminated via websites, demonstrations, trainings, and forums. They are both structures that are closely related to communities of users. However, at a closer look, we observe that the social architecture, the materiality and the economics of the tools developed by Ekylibre and Atelier Paysan differ. In the academic literature, open source is usually conceptualized as a political and ethical project, depending on a specific form of sociability and community. The article argues that we need to empirically describe and analytically problematize how open source is materialized in individual cases. If we can see open source tools as political objects, the term political does not refer to the same thing. While Ekylibre and Atelier Paysan are both related to user communities, they are organized and ‘economicized’ differently. The idea of open source is not only, in practice, translated into tools that aim to be free, shareable, collective, etc. We need, so we argue, to examine how and to what extent open source tools can be qualified as such and thereby show what the term ‘political’ signifies from case to case

L’agriculture libre

Image d’ouverture Le tracteur de LifeTrac est une machine open source qui pourrait coûter moitié moins qu’un tracteur conventionnel ; et il est conçu pour durer toute une vie... Open Source Ecology Les outils agricoles pourront-ils, à l’image des logiciels libres, devenir « libres » ? Les principes fondateurs de l’open source – la capacité de partager, distribuer, modifier et reproduire librement des informations – sont-ils transposables à l’agriculture ? Si dans le domaine informatique, les..

2015-2016 Sanctuary Series March 16, 2016

Watch video of the performance here.https://spiral.lynn.edu/sanctuary_series/1000/thumbnail.jp

Two-photon excited autofluorescence imaging of freshly isolated frog retinas

The purpose of this study was to investigate cellular sources of autofluorescence signals in freshly isolated frog (Rana pipiens) retinas. Equipped with an ultrafast laser, a laser scanning two-photon excitation fluorescence microscope was employed for sub-cellular resolution examination of both sliced and flat-mounted retinas. Two-photon imaging of retinal slices revealed autofluorescence signals over multiple functional layers, including the photoreceptor layer (PRL), outer nuclear layer (ONL), outer plexiform layer (OPL), inner nuclear layer (INL), inner plexiform layer (IPL), and ganglion cell layer (GCL). Using flat-mounted retinas, depth-resolved imaging of individual retinal layers further confirmed multiple sources of autofluorescence signals. Cellular structures were clearly observed at the PRL, ONL, INL, and GCL. At the PRL, the autofluorescence was dominantly recorded from the intracellular compartment of the photoreceptors; while mixed intracellular and extracellular autofluorescence signals were observed at the ONL, INL, and GCL. High resolution autofluorescence imaging clearly revealed mosaic organization of rod and cone photoreceptors; and sub-cellular bright autofluorescence spots, which might relate to connecting cilium, was observed in the cone photoreceptors only. Moreover, single-cone and double-cone outer segments could be directly differentiated

Ferrous iron release from transferrin by human neutrophil-derived superoxide anion: Effect of pH and iron saturation

The ability of superoxide anion (O2-) from stimulated human neutrophils (PMNs) to release ferrous iron (Fe2+) from transferrin was assessed. At pH 7.4, unstimulated PMNs released minimal amounts of O2- and failed to facilitate the release of Fe2+ from holosaturated transferrin. In contrast, incubation of phorbol myristate acetate (PMA)-stimulated PMNs with holosaturated transferrin at pH 7.4 enhanced the release of Fe2+ from transferrin eightfold in association with marked generation of O2-. The release of Fe2+ was inhibited by addition of superoxide dismutase (SOD), indicating that the release of Fe2+ was dependent on PMN-derived extracellular O2-. In contrast, at physiologic pH (7.4), incubation of transferrin at physiological levels of iron saturation (e.g. 32%) with unstimulated or PMA stimulated PMNs failed to facilitate the release of Fe2+. The effect of decreasing the pH on the release of Fe2+ from transferrin by PMN-derived O2- was determined. Decreasing the pH greatly facilitated the release of Fe2+ from both holosaturated transferrin and from transferrin at physiological levels of iron saturation by PMN-derived O2-. Release of Fe2+ occurred despite a decrease in the amount of extracellular O2- generated by PMNs in an acidic environment. These results suggest that transferrin at physiologic levels of iron saturation may serve as a source of Fe2+ for biological reactions in disease states where activated phagocytes are present and there is a decrease in tissue pH. The unbound iron could participate in biological reactions including promoting propagation of lipid peroxidation reactions or hydroxyl radical formation following reaction with phagocytic cell-derived hydrogen peroxide.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29537/1/0000625.pd

An extreme value theory approach to calculating minimum capital risk requirements

This paper investigates the frequency of extreme events for three LIFFE futures contracts for the calculation of minimum capital risk requirements (MCRRs). We propose a semiparametric approach where the tails are modelled by the Generalized Pareto Distribution and smaller risks are captured by the empirical distribution function. We compare the capital requirements form this approach with those calculated from the unconditional density and from a conditional density - a GARCH(1,1) model. Our primary finding is that both in-sample and for a hold-out sample, our extreme value approach yields superior results than either of the other two models which do not explicitly model the tails of the return distribution. Since the use of these internal models will be permitted under the EC-CAD II, they could be widely adopted in the near future for determining capital adequacies. Hence, close scrutiny of competing models is required to avoid a potentially costly misallocation capital resources while at the same time ensuring the safety of the financial system

Subcomplex Iλ Specifically Controls Integrated Mitochondrial Functions in Caenorhabditis elegans

Complex I dysfunction is a common, heterogeneous cause of human mitochondrial disease having poorly understood pathogenesis. The extensive conservation of complex I composition between humans and Caenorhabditis elegans permits analysis of individual subunit contribution to mitochondrial functions at both the whole animal and mitochondrial levels. We provide the first experimentally-verified compilation of complex I composition in C. elegans, demonstrating 84% conservation with human complex I. Individual subunit contribution to mitochondrial respiratory capacity, holocomplex I assembly, and animal anesthetic behavior was studied in C. elegans by RNA interference-generated knockdown of nuclear genes encoding 28 complex I structural subunits and 2 assembly factors. Not all complex I subunits directly impact respiratory capacity. Subcomplex Iλ subunits along the electron transfer pathway specifically control whole animal anesthetic sensitivity and complex II upregulation, proportionate to their relative impairment of complex I-dependent oxidative capacity. Translational analysis of complex I dysfunction facilitates mechanistic understanding of individual gene contribution to mitochondrial disease. We demonstrate that functional consequences of complex I deficiency vary with the particular subunit that is defective

Pathophysiology and treatment of inflammatory anorexia in chronic disease

Decreased appetite and involuntary weight loss are common occurrences in chronic disease and have a negative impact on both quality of life and eventual mortality. Weight loss in chronic disease comes from both fat and lean mass, and is known as cachexia. Both alterations in appetite and body weight loss occur in a wide variety of diseases, including cancer, heart failure, renal failure, chronic obstructive pulmonary disease and HIV. An increase in circulating inflammatory cytokines has been implicated as a uniting pathogenic mechanism of cachexia and associated anorexia. One of the targets of inflammatory mediators is the central nervous system, and in particular feeding centers in the hypothalamus located in the ventral diencephalon. Current research has begun to elucidate the mechanisms by which inflammation reaches the hypothalamus, and the neural substrates underlying inflammatory anorexia. Research into these neural mechanisms has suggested new therapeutic possibilities, which have produced promising results in preclinical and clinical trials. This review will discuss inflammatory signaling in the hypothalamus that mediates anorexia, and the opportunities for therapeutic intervention that these mechanisms present