PI-controlled bioreactor as a generalized Lienard system

It is shown that periodic orbits can occur in Cholette's bioreactor model working under the influence of a PI-controller. We find a diffeomorphic coordinate transformation that turns this controlled enzymatic reaction system into a generalized Lienard form. Furthermore, we give sufficient conditions for the existence and uniqueness of limit cycles in the new coordinates. We also perform numerical simulations illustrating the possibility of the existence of a local center (period annulus). A result with possible practical applications is that the oscillation frequency is a function of the integral control gain parameterComment: 15 pages, 5 figures, accepted version at Computers & Chem. En

Atenolol versus losartan in children and young adults with Marfan's syndrome

BACKGROUND : Aortic-root dissection is the leading cause of death in Marfan's syndrome. Studies suggest that with regard to slowing aortic-root enlargement, losartan may be more effective than beta-blockers, the current standard therapy in most centers. METHODS : We conducted a randomized trial comparing losartan with atenolol in children and young adults with Marfan's syndrome. The primary outcome was the rate of aortic-root enlargement, expressed as the change in the maximum aortic-root-diameter z score indexed to body-surface area (hereafter, aortic-root z score) over a 3-year period. Secondary outcomes included the rate of change in the absolute diameter of the aortic root; the rate of change in aortic regurgitation; the time to aortic dissection, aortic-root surgery, or death; somatic growth; and the incidence of adverse events. RESULTS : From January 2007 through February 2011, a total of 21 clinical centers enrolled 608 participants, 6 months to 25 years of age (mean [+/- SD] age, 11.5 +/- 6.5 years in the atenolol group and 11.0 +/- 6.2 years in the losartan group), who had an aorticroot z score greater than 3.0. The baseline-adjusted rate of change (+/- SE) in the aortic-root z score did not differ significantly between the atenolol group and the losartan group (-0.139 +/- 0.013 and -0.107 +/- 0.013 standard-deviation units per year, respectively; P = 0.08). Both slopes were significantly less than zero, indicating a decrease in the degree of aortic-root dilatation relative to body-surface area with either treatment. The 3-year rates of aortic-root surgery, aortic dissection, death, and a composite of these events did not differ significantly between the two treatment groups. CONCLUSIONS : Among children and young adults with Marfan's syndrome who were randomly assigned to losartan or atenolol, we found no significant difference in the rate of aorticroot dilatation between the two treatment groups over a 3-year period

Corpora Processing and Computational Scaffolding for a Web-based English Learning Environment: The Candle Project

This paper describes the development of an innovative web-based environment for English language learning with advanced data-driven and statistical approaches. The project uses various corpora, including a Chinese-English parallel corpus (Sinorama) and various natural language processing (NLP) tools to construct effective English learning tasks for college learners with adaptive computational scaffolding. It integrates the expertise of a group of researchers in four areas: (a) advances in NLP technologies and applications, (b) construction of a self-access reading environment, (c) exploration of English language learning through written exercises and translations, and (d) use of bilingual corpora for culture-based English learning. In this paper, the conceptualization of the system and its various reference tools (e.g., a bilingual concordancer) for English learning and pilot testing on various modules (e.g., a reading module, Text Grader, and Collocation Practice) are reported

Effects of mechanical milling on preparation and properties of CuAl1-xFexO2 thermoelectric ceramics

CuAl1-xFexO2 (x = 0, 0.1, and 0.2) thermoelectric ceramics produced by a reaction-sintering process were investigated. Pure CuAlO2 and CuAl0.9Fe0.1O2 were obtained. Minor CuAl2O4 phase formed in CuAl0.8Fe0.2O2. Addition of 10 mol% Fe lowered the sintering temperature obviously and enhanced the grain growth. At x = 0.1, electrical conductivity = 3.143 Omega(-1) cm(-1), Seebeck coefficient = 418 mu V K-1, and power factor = 5.49 x 10(-5) W m(-1) K-2 at 600 degrees C were obtained. The reaction-sintering process is simple and effective in preparing CuAlO2 and CuAl0.9Fe0.1O2 thermoelectric ceramics for applications at high temperatures. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Methodology for Ideation of Interaction Design

This paper explores new methodology, tools, and techniques for ideation of interaction design. On one hand, our work takes a mixed approach to developing design methodology by integrating usability tests and ethnographic studies in the ideation process. On the other hand, parallel design with user participation is attempted to reduce interactive design life cycle. An interaction design example is drawn from i-Awn project, an activity-coordination and reminding system in smart homes. This example demonstrates our mixed approach and shows how a new methodology is developed for validating the quality of user experience in a critical process of designing. The objective is to get the right interaction and the interaction right, provoking new ways of thinking about usability evaluation in the ideation process. The social, cultural and emotional uses of interactive systems in smart homes are discussed

A simple device for detecting impact time in impact-echo testing of concrete

The objective of this paper is to describe a simple device for detecting the time of an impact and to demonstrate its efficiency in measuring the depth of surface-opening cracks in concrete. Surface-opening cracks in concrete are relatively deep so that a mechanical impact instead of an ultrasonic transmitter is used to generate stress waves with enough energy for successful evaluation. A technique called the time-of-flight diffraction technique with impact-generated stress waves is an efficient method for detection of surface-opening cracks in concrete. Because the initial time of the impact is unavailable in a mechanical impact device, two receivers are employed in the test. One of the receivers is used to determine the time of the impact indirectly. The present study developed a simple device to record the time of impact initiation. The device comprises a conductive impact device, a sensing film, and an auxiliary circuit. With the device, stress waves are generated and the time of impact is detected so that the evaluation work needs only a single receiver. Laboratory studies were carried out on concrete specimens containing cracks with depths of 0.158 and 0.90 m. Field studies were performed on a dam damaged by an earthquake. Experimental results show that the new device can be used to accurately determine the crack depth in concrete. Using the device, the cost and effort for evaluation and signal analysis are reduced, which largely enhances the evaluation efficiency. (C) 2004 Elsevier Ltd. All rights reserved