Synchronization problems for unidirectional feedback coupled nonlinear systems

In this paper we consider three different synchronization problems consisting in designing a nonlinear feedback unidirectional coupling term for two (possibly chaotic) dynamical systems in order to drive the trajectories of one of them, the slave system, to a reference trajectory or to a prescribed neighborhood of the reference trajectory of the second dynamical system: the master system. If the slave system is chaotic then synchronization can be viewed as the control of chaos; namely the coupling term allows to suppress the chaotic motion by driving the chaotic system to a prescribed reference trajectory. Assuming that the entire vector field representing the velocity of the state can be modified, three different methods to define the nonlinear feedback synchronizing controller are proposed: one for each of the treated problems. These methods are based on results from the small parameter perturbation theory of autonomous systems having a limit cycle, from nonsmooth analysis and from the singular perturbation theory respectively. Simulations to illustrate the effectiveness of the obtained results are also presented.Comment: To appear in Dyn. Contin. Discrete Impuls. Syst., Ser. A, Math. Ana

Positive periodic solutions and optimal control for a distributed biological model of two interacting species

The paper deals with the existence of positive periodic solutions to a system of degenerate parabolic equations with delayed nonlocal terms and Dirichlet boundary conditions. Taking in each equation a meaningful function as a control parameter, we show that for a suitable choice of a class of such controls we have, for each of them, a time-periodic response of the system under different assumptions on the kernels of the nonlocal terms. Finally, we consider the problem of the minimization of a cost functional on the set of pairs: control-periodic response. The considered system may be regarded as a possible model for the coexistence problem of two biological populations, which dislike crowding and live in a common territory, under different kind of intra- and inter-specific interferences. \ua9 2010 Elsevier Ltd. All rights reserved

Non-trivial non-negative periodic solutions of a system of doubly degenerate parabolic equations with nonlocal terms

The aim of the paper is to provide conditions ensuring the ex- istence of non-trivial non-negative periodic solutions to a system of doubly degenerate parabolic equations containing delayed nonlocal terms and satis- fying Dirichlet boundary conditions. The employed approach is based on the theory of the Leray-Schauder topological degree theory, thus a crucial purpose of the paper is to obtain a priori bounds in a convenient functional space, here L 2(QT ), on the solutions of certain homotopies. This is achieved under different assumptions on the sign of the kernels of the nonlocal terms. The considered system is a possible model of the interactions between two biologi- cal species sharing the same territory where such interactions are modeled by the kernels of the nonlocal terms. To this regard the obtained results can be viewed as coexistence results of the two biological populations under different intra and inter specific interferences on their natural growth rates

From the sugar platform to biofuels and biochemicals. Final report for the European Commission Directorate-General Energy NENER

Numerous potential pathways to biofuels and biochemicals exist via the sugar platform1. This study uses literature surveys, market data and stakeholder input to provide a comprehensive evidence base for policymakers and industry – identifying the key benefits and development needs for the sugar platform. The study created a company database for 94 sugar-based products, with some already commercial, the majority at research/pilot stage, and only a few demonstration plants crossing the “valley of death”. Case studies describe the value proposition, market outlook and EU activity for ten value chains (acrylic, adipic & succinic acids, FDCA, BDO, farnesene, isobutene, PLA, PHAs and PE). Most can deliver significant greenhouse savings and drop-in (or improved) properties, but at an added cost to fossil alternatives. Whilst significant progress has been made, research barriers remain around lignocellulosic biomass fractionation, product separation energy, biological inhibition, chemical selectivity and monomer purity, plus improving whole chain process integration. An assessment of EU competitiveness highlights strengths in R&D, but a lack of strong commercial activity, due to the US, China and Brazil having more attractive feedstock and investment conditions. Further policy development, in particular for biochemicals, will be required to realise a competitive European sugar-based bioeconomy

Creation, Contingency, and Early Modern Science: The Impact of Voluntarist Theology on Seventeenth-Century Natural Philosophy

Could God have made it true that 2 + 2 = 5? Was he bound to make the best of all possible worlds? Is he able at this moment to alter the course of nature, either in whole or in part? Questions like these are often associated with medieval theology, not with early modern science. But science is done by people, and people have not always practiced the rigorous separation of science and theology that has come to characterize the modern world. Although many 17th century scientists sought validity for their work apart from revelation, divorcing science from religion was something they never intended. Indeed most natural philosophers of the scientific revolution assumed without question that the world and the human mind had been created by God. This was no small admission, for it meant that both the manner in which and the degree to which the world could be understood depended upon how God had acted in creating it and how he continued to act in sustaining it. Fifty years ago the late British philosopher M.B. Foster identified two different theologies of creation which differ profoundly in their implications for natural science. Rationalist theology, which assigns to God the activity of pure reason, involves both a rationalist X philosophy of nature and a rationalist theory of knowledge of nature. Voluntarist theology, which attributes to God an activity of will not wholly determined by reason, implies that the products of his creative activity are contingent and can be known only empirically. By a careful analysis of four natural philosophies of the early modern period--those of Galileo, Descartes, Boyle, and Newton--! intend to show that there was indeed a connection between theological voluntarism and empirical science in the 17th century

Differential diagnosis between Marfan syndrome and Loeys–Dietz syndrome type 4: A novel chromosomal deletion covering tgfb2

Marfan syndrome (MFS) and Loeys–Dietz syndrome type 4 (LDS4) are two hereditary connective tissue disorders. MFS displays ectopia lentis as a distinguishing, characterising feature, and thoracic aortic ectasia, aneurysm, dissection, and systemic features as manifestations overlapping with LDS4. LDS4 is characterised by the presence of hypertelorism, cleft palate and/or bifid uvula, with possible ectasia or aneurysms in other arteries. The variable age of onset of clinical manifestations makes clinical diagnosis more difficult. In this study, we report the case of a patient with Marfan syndrome diagnosed at our centre at the age of 33 on the basis of typical clinical manifestations of this syndrome. At the age of 38, the appearance of ectasia of the left common iliac artery and tortuosity of the iliac arteries suggested the presence of LDS4. Next Generation Sequencing (NGS) analysis, followed by Array-CGH, allowed the detection of a novel chromosomal deletion including the entire TGFB2 gene, confirming not only the clinical suspicion of LDS4, but also the clinical phenotype associated with the haploinsufficiency mechanism, which is, in turn, associated with the deletion of the entire gene. The same mutation was detected in the two young sons. This emblematic case confirms that we must be very careful in the differential diagnosis of these two pathologies, especially before the age of 40, and that, in young subjects suspected to be affected by MFS in particular, we must verify the diagnosis, extending genetic analysis, when necessary, to the search for chromosomal alterations. Recently, ectopia lentis has been reported in a patient with LDS4, confirming the tight overlap between the two syndromes. An accurate revision of the clinical parameters both characterising and overlapping the two pathologies is highly desirable

Prevalence and clinical significance of acquired left coronary artery fistulas after surgical myectomy in patients with hypertrophic cardiomyopathy

ObjectivesThe relevance of iatrogenic left coronary artery fistulas complicating surgical myectomy in patients with hypertrophic cardiomyopathy is not known. We prospectively defined the echocardiographic features, prevalence, and clinical significance of left coronary artery fistulas in 40 consecutive patients with hypertrophic cardiomyopathy undergoing extended septal myectomy.MethodsEchocardiographic analysis was performed preoperatively and 1 and 6 months after surgical intervention. Diagnosis of left coronary artery fistulas required evidence of diastolic flow draining from the left ventricular wall into the left ventricular cavity according to prespecified criteria.ResultsLeft coronary artery fistulas were detected in 9 (23%) of the 40 study patients as a single occurrence in all except 1 patient, who had multiple fistulas. At 6 months, left coronary artery fistulas could still be detected in only 2 of the 9 patients. Of these, 1 patient remained asymptomatic but continued to show left coronary artery fistula persistence at 37 months postoperatively. The other, a woman with prior alcohol septal ablation, had progressive severe symptoms that required percutaneous closure of the fistula with a covered stent after angiographic identification of a large first septal branch fistula associated with distal left anterior descending coronary artery steal.ConclusionsIn patients with hypertrophic cardiomyopathy, left coronary artery fistulas are common in the early period after surgical myectomy, although their echocardiographic prevalence is dependent on operator awareness. Most left coronary artery fistulas heal spontaneously. Occasionally, however, fistulas can persist and cause symptoms requiring therapeutic intervention