Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars

A closed-form description is proposed to explain nonlinear and slow dynamics effects exhibited by sandstone bars in longitudinal resonance experiments. Along with the fast subsystem of longitudinal nonlinear displacements we examine the strain-dependent slow subsystem of broken intergrain and interlamina cohesive bonds. We show that even the simplest but phenomenologically correct modelling of their mutual feedback elucidates the main experimental findings typical for forced longitudinal oscillations of sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both its up- and down-slopes, (ii) linear softening of resonant frequency with increase of driving level, and (iii) gradual recovery (increase) of resonant frequency at low dynamical strains after the sample was conditioned by high strains. In order to reproduce the highly nonlinear elastic features of sandstone grained structure a realistic non-perturbative form of strain potential energy was adopted. In our theory slow dynamics associated with the experimentally observed memory of peak strain history is attributed to strain-induced kinetic changes in concentration of ruptured inter-grain and inter-lamina cohesive bonds causing a net hysteretic effect on the elastic Young's modulus. Finally, we explain how enhancement of hysteretic phenomena originates from an increase in equilibrium concentration of ruptured cohesive bonds that are due to water saturation.Comment: 5 pages, 3 figure

First isolation report of Arcobacter cryaerophilus from a human diarrhea sample in Costa Rica

ABSTRACT Arcobacter cryaerophilus is an emerging enteropathogen and potential zoonotic agent transmitted by food and water. In Costa Rica, this bacterium has not been associated with cases of human gastroenteritis, even though it has been isolated from farm animals, especially poultry. This paper reports the first isolation of A. cryaerophilus from a human case of bloody watery diarrhea and the virulence genes associated with this isolate

Ambient-aware continuous care through semantic context dissemination

Background: The ultimate ambient-intelligent care room contains numerous sensors and devices to monitor the patient, sense and adjust the environment and support the staff. This sensor-based approach results in a large amount of data, which can be processed by current and future applications, e. g., task management and alerting systems. Today, nurses are responsible for coordinating all these applications and supplied information, which reduces the added value and slows down the adoption rate. The aim of the presented research is the design of a pervasive and scalable framework that is able to optimize continuous care processes by intelligently reasoning on the large amount of heterogeneous care data. Methods: The developed Ontology-based Care Platform (OCarePlatform) consists of modular components that perform a specific reasoning task. Consequently, they can easily be replicated and distributed. Complex reasoning is achieved by combining the results of different components. To ensure that the components only receive information, which is of interest to them at that time, they are able to dynamically generate and register filter rules with a Semantic Communication Bus (SCB). This SCB semantically filters all the heterogeneous care data according to the registered rules by using a continuous care ontology. The SCB can be distributed and a cache can be employed to ensure scalability. Results: A prototype implementation is presented consisting of a new-generation nurse call system supported by a localization and a home automation component. The amount of data that is filtered and the performance of the SCB are evaluated by testing the prototype in a living lab. The delay introduced by processing the filter rules is negligible when 10 or fewer rules are registered. Conclusions: The OCarePlatform allows disseminating relevant care data for the different applications and additionally supports composing complex applications from a set of smaller independent components. This way, the platform significantly reduces the amount of information that needs to be processed by the nurses. The delay resulting from processing the filter rules is linear in the amount of rules. Distributed deployment of the SCB and using a cache allows further improvement of these performance results

Photon-induced proton knockout from 208Pb

No abstract available

Inferring the degradation of pultruded composites from dynamic nonlinear resonance measurement

The Chemical resistance of pultruded polyester composites to various chemical immersion solutions is investigated as a function of the exposure time, and the observations from static tests are compared with the results from nonlinear dynamic vibration experiments. The mechanical properties were measured according to ASTM standards, both in flexural and tensile tests. Barcol hardness and sorption measurements provide complemntary information. In addition, a novel nondestructive (NDE) method, called Single Mode Nonlinear Resonance Acoustic Spectroscopy (SIMONRAS), was applied to measure the linear and nonlinear dynamical properties of the samples as a funtion of exposure time. This new NDE method focuses on the strain amplitude dependence of the resonance frequency while driving a sample at relatively low excitation levels. The obtained relative frequency shift is a measure of the internal microstructural properties of the material. The correlation between this nonlinearity parameter and the mechanical properties is extremely good, which implies that the SIMONRAS technique can be applied to predict the chemo-mechanical degradation of composites in a nondestructive manner