Clinical and molecular characterization of both methicillin-resistant andsensitive staphylococcus aureus mastitis

NO ABSTRACT AVAILABLEThis study targeted bovine mastitis as a possible source of livestock-associated methicillin-resistant Staphylococcus aureus (MRSA), to identify clinical signs associated with MRSA- and non-MRSA-associated mastitis. Thirty-eight mastitis cases (68 infected quarters) were investigated. Gram-positive cocci-shaped isolates were selected based on Baird Parker agar growth as well as Gram-stained bacterial smears. Molecular screening for Staphylococcus aureus (S. aureus) yielded 17 isolates, of which five (29.41%) were methicillin resistant. The five isolates were mecA positive, but mecC negative. Multilocus sequence typing (MLST) indicated that sequence type 1 (ST1) was the identified type of all isolates of MRSA. S. aureus-associated cases showed different clinical forms of mastitis, including subclinical, acute, chronic, and gangrenous. Additionally, subclinical mastitis was the only detected condition associated with MRSA, which may represent a potential hidden risk for humans. Phenotypically, isolates of MRSA showed resistance to all of the tested β-lactam antimicrobials, with marked resistance to tetracycline and gentamycin. Based on our knowledge, this is the first report to identify MRSA ST1 in Egypt. Bovine mastitis could be a source for the dissemination of MRSA to humans and other animals. Additionally, while methicillin-resistance may have no effect on the clinical outcome of mastitis, it does affect therapeutic success, particularly when β-lactam antimicrobials are used

Second Annual AEC Scientific Computer Information Exhange Meeting. Proceedings of the Technical Program Theme: Computer Graphics

The topic of computer graphics serves well to illustrate that AEC affiliated scientific computing installations are well represented in the forefront of computing science activities. The participant response to the technical program was overwhelming--both in number of contributions and quality of the work described. Session I, entitled Advanced Systems, contains presentations describing systems that contain features not generally found in graphics facilities. These features can be roughly classified as extensions of standard two-dimensional monochromatic imaging to higher dimensions including color and time as well as multidimensional metrics. Session II presents seven diverse applications ranging from high energy physics to medicine. Session III describes a number of important developments in establishing facilities, techniques and enhancements in the computer graphics area. Although an attempt was made to schedule as many of these worthwhile presentations as possible, it appeared impossible to do so given the scheduling constraints of the meeting. A number of prospective presenters 'came to the rescue' by graciously withdrawing from the sessions. Some of their abstracts have been included in the Proceedings

Axial crack propagation and arrest in pressurized fuselage

The crack arrest capability of a tear strap in a pressurized precracked fuselage was studied through instrumented axial rupture tests of small scale models of an idealized fuselage. Upon pressurization, rapid crack propagation initiated at an axial through crack along the stringer and immediately kinked due to the mixed modes 1 and 2 state caused by the one-sided opening of the crack flap. The diagonally running crack further turned at the tear straps. Dynamic finite element analysis of the rupturing cylinder showed that the crack kinked and also ran straight in the presence of a mixed mode state according to a modified two-parameter crack kinking criterion

Frictional melting of peridotite and seismic slip

The evolution of the frictional strength along a fault at seismic slip rates (about 1 m/s) is a key factor controlling earthquake mechanics. At mantle depths, friction-induced melting and melt lubrication may influence earthquake slip and seismological data. We report on laboratory experiments designed to investigate dynamic fault strength and frictional melting processes in mantle rocks. We performed 20 experiments with Balmuccia peridotite in a high-velocity rotary shear apparatus and cylindrical samples (21.8 mm in diameter) over a wide range of normal stresses (5.4–16.1 MPa), slip rates (0.23–1.14 m/s), and displacements (1.5–71 m). During the experiments, shear stress evolved with cumulative displacement in five main stages (stages 1–5). In stage 1 (first strengthening), the coefficient of friction m increased up to 0.4–0.7 (first peak in friction). In stage 2 (abrupt firstweakening), m decreased to about 0.25–0.40. In stage 3 (gradual second strengthening), shear stress increased toward a second peak in friction (m = 0.30–0.40). In stage 4 (gradual second weakening), the shear stress decreased toward a steady state value (stage 5) with m = 0.15. Stages 1 and 2 are of too short duration to be investigated in detail with the current experimental configuration. By interrupting the experiments during stages 3, 4, and 5, microstructural (Field Emission Scanning Electron Microscope) and geochemical (Electron Probe Micro-Analyzer and Energy Dispersive X-Ray Spectroscopy) analysis of the slipping zone suggest that second strengthening (stage 3) is associated with the production of a grain-supported melt-poor layer, while second weakening (stage 4) and steady state (stage 5) are associated with the formation of a continuous melt-rich layer with an estimated temperature up to 1780 C. Microstructures formed during the experiments were very similar to those found in natural ultramafic pseudotachylytes. By performing experiments at different normal stresses and slip rates, (1) the ‘‘thermal’’ (as it includes the thermally activated first and second weakening) slip distance to achieve steady state from the first peak in strength decreased with increasing normal stress and slip rate and (2) the steady state shear stress slightly increased with increasing normal stress and, for a given normal stress, decreased with increasing slip rate. The ratio of shear stress versus normal stress was about 0.15, well below the typical friction coefficient of rocks (0.6–0.8). The dependence of steady state shear stress with normal stress was described by means of a constitutive equation for melt lubrication. The presence of microstructures similar to those found in natural pseudotachylytes and the determination of a constitutive equation that describes the experimental data allows extrapolation of the experimental observations to natural conditions and to the study of rupture dynamics in mantle rocks

Morphological hysteresis in the evolution of beach profiles under sequences of wave climates - Part 1; observations

Novel series of experiments are presented that demonstrate morphological hysteresis in the evolution to equilibrium of beach profiles under sequences of different wave climates. The experiments were conducted in a wave flume at medium scale using both monochromatic and random waves, representing 2D conditions. Beach profiles were obtained with high spatial resolution at frequent intervals with a laser profiler, from which shoreline location, bar position and sediment transport rates were derived. Experiments were conducted for sequences of wave climates, where a sequence comprised of 6-13 sequential tests, each commencing with the beach profile from the preceding test. Each test was run until equilibrium conditions were obtained and had a constant wave height, increased or decreased relative to the preceding test. Cyclical conditions were also included, with erosive and accretive wave conditions of short durations alternating through multiple cycles, so that equilibrium conditions were not reached during a test. With a sequence of increasing wave heights, the relationship between the shoreline position and the bulk cross-shore sediment transport, at equilibrium, was non-monotonic, indicating a maximum in the landward sediment transport rate. For test series comprised of a sequence of increasing wave heights followed by a sequence of decreasing wave heights, morphological hysteresis was observed in the equilibrium shoreline position and bulk cross-shore sediment transport, such that shoreline recession, or offshore transport, continued in some instances after reductions in wave height. This is inconsistent with classical equilibritim type shoreline evolution models. However, when equilibrium conditions were not reached, in the cyclic sequences, no such morphological hysteresis was observed and a dynamic equilibrium is reached. The morphological hysteresis occurs because of the decay, stranding, or increased relative depth, of the breaker bar following a reduction in wave height, often in conjunction with a new breaker bar generated by further offshore transport in the inner surf zone. Similar sequences of morphological response are evident in field data and larger scale tests in the literature. Finally, it is shown that the morphological hysteresis can be explained using the classical equilibrium beach state model of Wright et al. (1985) by introducing the concept of a subsequent alternate active beach state, which may occur following a change in wave conditions