Pilus antigenic variation in Neisseria gonorrhoeae occurs by the high-frequency, unidirectional transfer of DNA sequences from one of several silent pilin loci (pilS) into the expressed pilin gene (pilE), resulting in a change in the primary pilin protein sequence. Previously, we investigated the effects of large or small heterologous insertions in conserved and variable portions of a pilS copy...

An analytical model has been developed for the airborne sound pressure waveform radiated when an offshore steel pipe pile is struck by a short hammer. The model is based on the coupled equations of motion for axial and radial vibration of a thin shell, and yields frequency-dependent phase velocity and attenuation of these vibrations. A harmonic solution is obtained for the radiated sound pressu...

The evaluation of liquefaction effect on the dynamic moment of stabilizing piles is potentially significant. Based on the dynamic centrifuge modeling of a slope reinforced with a row of copper model pile, this paper not only analyzed the response of dynamic pore pressure, earthquake deformation and macroscopic phenomenon measured in the response of the reinforced slope, but also simulated the r...

Mechanical mastication is increasingly prescribed for wildfire mitigation, yet little is known about the ecological impacts of this fuels treatment. Mastication shreds trees into woodchips as an alternative to tree thinning and burning the resulting slash, which can create soil disturbances that favor exotic plants. Previous research on mastication has not simultaneously considered both the res...

It is a common belief that power-law distributed avalanches are inherently unpredictable. This idea affects phenomena as diverse as evolution, earthquakes, superconducting vortices, stock markets, etc., from atomic to social scales. It mainly comes from the concept of "self-organized criticality" (SOC), where criticality is interpreted in the way that, at any moment, any small avalanche can eve...

This paper describes the digital control of a vibratory pile driver in which the vibration is generated via two tandem pairs of electrically driven, geared, contra-rotating eccentrics. Experimental results are included to show the controller-induced system dynamics for a variety of load conditions, and to highlight the fact that, if the relative phase of the eccentric pairs is not controlled, t...

Marine renewable developments have raised concerns over impacts of underwater noise on marine species, particularly from pile-driving for wind turbines. Environmental assessments typically use generic sound propagation models, but empirical tests of these models are lacking. In 2006, two 5MW wind turbines were installed off NE Scotland. The turbines were in deep (>40m) water, 25km from the Mora...

For several decades vibratory pile driving has been extensively applied in civil engineering, e.g. in the construction of bulkheads. On urban construction sites shock waves occur which could damage nearby building structures and annoy humans. State-of-the-art machinery provides three control inputs (frequency, excitation force and surcharge force) to achieve two almost contradictory goals: fast...

We study the evolution of a one-dimensional pile, empty at rst, which receives a grain in its rst stack at each iteration. The nal position of grains is singular: grains are sorted according to their parity. They are sorted on trapezoidal areas alternating on both sides of a diagonal line of slope p 2. This is explained and proved by means of a local study. Each generated pile, encoded in heigh...

Sand Pile Models are discrete dynamical systems emphasizing the phenomenon of Self-Organized Criticality. From a configuration composed of a finite number of stacked grains, we apply on every possible positions (in parallel) two grain moving transition rules. The transition rules permit one grain to fall to its right or left (symmetric) neighboring column if the difference of height between tho...