Expressed sequence tags from the oomycete fish pathogen Saprolegnia parasitica reveal putative virulence factors

Peer reviewedPublisher PD

The Variable-Atmosphere Wave Tank

A facility was constructed for the study of water-entry, water-exit, and underwater trajectory behavior of small momentum-propelled missiles for varied trajectory launching angles, missile accelerations and velocities, wave fields and conditions of cavitation. A unique feature is the electromagnetic missile propulsion system. The facility is made principally of non-magnetic and electrically non-conducting materials to permit the determination of missile accelerating force from the reactive force on the launching coil

Fluid Free Surface Proximity Effect on a Sphere Vertically Accelerated from Rest

Theory is developed to estimate the effect of free surface proximity on the initial added mass of a sphere accelerated vertically upward from rest in an ideal fluid. It is assumed that the acceleration regime is sufficiently brief that inertial forces predominate and gravitational effects may be neglected. Results of tests in water indicate that while there are slight viscous and gravitational effects over the acceleration regime, the agreement between theory and experiment is good. It is concluded that over briefer acceleration regimes these effects would decrease and the agreement would improve

Volatile Analyzer for Lunar Polar Missions

One of the major questions remaining for the future exploration of the Moon by humans concerns the presence of volatiles on our nearest neighbor in space. Observational studies, and investigations involving returned lunar samples and using robotic spacecraft infer the existence of volatile compounds particularly water [1]. It seems very likely that a volatile component will be concentrated at the poles in circumstances where low-temperatures exist to provide cryogenic traps. However, the full inventory of species, their concentration and their origin and sources are unknown. Of particular importance is whether abundances are sufficient to act as a resource of consumables for future lunar expeditions especially if a long-term base involving humans is to be established. To address some of these issues requires a lander designed specifically for operation at a high-lunar latitude. A vital part of the payload needs to be a volatile analyzer such as the Gas Analysis Package specifically designed for identification quantification of volatile substances and collecting information which will allow the origin of these volatiles to be identified [1]. The equipment included, particularly the gas analyzer, must be capable of operation in the extreme environmental conditions to be encountered. No accurate information yet exists regarding volatile concentration even for sites closer to the lunar equator (because of contamination). In this respect it will be important to understand (and thus limit) contamination of the lunar surface by extraneous material contributed from a variety of sources. The only data for the concentrations of volatiles at the poles comes from orbiting spacecraft and whilst the levels at high latitudes may be greater than at the equator, the volatile analyzer package under consideration will be designed to operate at the highest specifications possible and in a way that does not compromise the data

Real Fluid Effects on an Accelerated Sphere Before Boundary-Layer Separation

Studies were made on the apparent increase in mass on acceleration (added mass) of a sphere accelerated from rest and before boundary-layer separation, in cylinders of various diameters filled with water or oil. From a comparison of theoretical and experimentally obtained added masses, the following conclusions were drawn: In the absence of wall effects on the boundary layer, the wall shear stress over elements of the sphere can be approximated by the solution for the flat plate moving parallel to itself and the potential flow over the elements outside the boundary layer. The impulse on the elements is obtained by integration with respect to time, and the wall drag and drag impulse on the sphere by integration over the sphere surface. Good theoretical and experimental agreement obtains under the assumption that a mass of fluid, estimated from the wall drag impulse, is carried in the boundary layer and may be university distributed over the sphere

Efficient Model Learning for Human-Robot Collaborative Tasks

We present a framework for learning human user models from joint-action demonstrations that enables the robot to compute a robust policy for a collaborative task with a human. The learning takes place completely automatically, without any human intervention. First, we describe the clustering of demonstrated action sequences into different human types using an unsupervised learning algorithm. These demonstrated sequences are also used by the robot to learn a reward function that is representative for each type, through the employment of an inverse reinforcement learning algorithm. The learned model is then used as part of a Mixed Observability Markov Decision Process formulation, wherein the human type is a partially observable variable. With this framework, we can infer, either offline or online, the human type of a new user that was not included in the training set, and can compute a policy for the robot that will be aligned to the preference of this new user and will be robust to deviations of the human actions from prior demonstrations. Finally we validate the approach using data collected in human subject experiments, and conduct proof-of-concept demonstrations in which a person performs a collaborative task with a small industrial robot

"5 Days in August" – How London Local Authorities used Twitter during the 2011 riots

© IFIP International Federation for Information Processing 2012This study examines effects of microblogging communications during emergency events based on the case of the summer 2011 riots in London. During five days in August 2011, parts of London and other major cities in England suffered from extensive public disorders, violence and even loss of human lives. We collected and analysed the tweets posted by the official accounts maintained by 28 London local government authorities. Those authorities used Twitter for a variety of purposes such as preventing rumours, providing official information, promoting legal actions against offenders and organising post-riot community engagement activities. The study shows how the immediacy and communicative power of microblogging can have a significant effect at the response and recovery stages of emergency events

Full capacitance matrix of coupled quantum dot arrays: static and dynamical effects

We numerically calculated the full capacitance matrices for both one-dimensional (1D) and two-dimensional (2D) quantum-dot arrays. We found it is necessary to use the full capacitance matrix in modeling coupled quantum dot arrays due to weaker screening in these systems in comparison with arrays of normal metal tunnel junctions. The static soliton potential distributions in both 1D and 2D arrays are well approximated by the unscreened (1/r) coulomb potential, instead of the exponential fall-off expected from the often used nearest neighbor approximation. The Coulomb potential approximation also provides a simple expression for the full inverse capacitance matrix of uniform quantum dot arrays. In terms of dynamics, we compare the current-voltage (I-V) characteristics of voltage biased 1D arrays using either the full capacitance matrix or its nearest neighbor approximation. The I-V curves show clear differences and the differences become more pronounced when larger arrays are considered.Comment: 8 pages preprint format, 3 PostScript figure