9,375 research outputs found

    A theory of the infinite horizon LQ-problem for composite systems of PDEs with boundary control

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    We study the infinite horizon Linear-Quadratic problem and the associated algebraic Riccati equations for systems with unbounded control actions. The operator-theoretic context is motivated by composite systems of Partial Differential Equations (PDE) with boundary or point control. Specific focus is placed on systems of coupled hyperbolic/parabolic PDE with an overall `predominant' hyperbolic character, such as, e.g., some models for thermoelastic or fluid-structure interactions. While unbounded control actions lead to Riccati equations with unbounded (operator) coefficients, unlike the parabolic case solvability of these equations becomes a major issue, owing to the lack of sufficient regularity of the solutions to the composite dynamics. In the present case, even the more general theory appealing to estimates of the singularity displayed by the kernel which occurs in the integral representation of the solution to the control system fails. A novel framework which embodies possible hyperbolic components of the dynamics has been introduced by the authors in 2005, and a full theory of the LQ-problem on a finite time horizon has been developed. The present paper provides the infinite time horizon theory, culminating in well-posedness of the corresponding (algebraic) Riccati equations. New technical challenges are encountered and new tools are needed, especially in order to pinpoint the differentiability of the optimal solution. The theory is illustrated by means of a boundary control problem arising in thermoelasticity.Comment: 50 pages, submitte

    Role of EGFR in the Nervous System

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    Epidermal growth factor receptor (EGFR) is the first discovered member of the receptor tyrosine kinase superfamily and plays a fundamental role during embryogenesis and in adult tissues, being involved in growth, differentiation, maintenance and repair of various tissues and organs. The role of EGFR in the regulation of tissue development and homeostasis has been thoroughly investigated and it has also been demonstrated that EGFR is a driver of tumorigenesis. In the nervous system, other growth factors, and thus other receptors, are important for growth, differentiation and repair of the tissue, namely neurotrophins and neurotrophins receptors. For this reason, for a long time, the role of EGFR in the nervous system has been underestimated and poorly investigated. However, EGFR is expressed both in the central and peripheral nervous systems and it has been demonstrated to have specific important neurotrophic functions, in particular in the central nervous system. This review discusses the role of EGFR in regulating differentiation and functions of neurons and neuroglia. Furthermore, its involvement in regeneration after injury and in the onset of neurodegenerative diseases is examined

    A study of environmental characterization of conventional and advanced aluminum alloys for selection and design. Phase 2: The breaking load test method

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    A technique is demonstrated for accelerated stress corrosion testing of high strength aluminum alloys. The method offers better precision and shorter exposure times than traditional pass fail procedures. The approach uses data from tension tests performed on replicate groups of smooth specimens after various lengths of exposure to static stress. The breaking strength measures degradation in the test specimen load carrying ability due to the environmental attack. Analysis of breaking load data by extreme value statistics enables the calculation of survival probabilities and a statistically defined threshold stress applicable to the specific test conditions. A fracture mechanics model is given which quantifies depth of attack in the stress corroded specimen by an effective flaw size calculated from the breaking stress and the material strength and fracture toughness properties. Comparisons are made with experimental results from three tempers of 7075 alloy plate tested by the breaking load method and by traditional tests of statistically loaded smooth tension bars and conventional precracked specimens

    Effectiveness of surgical procedures in the acceleration of orthodontic tooth movement: Findings from systematic reviews and meta-analyses

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    The current overview aimed to summarise the findings provided by systematic reviews (SRs) on the effect of surgical procedures in the acceleration of tooth movement and to assess the methodological quality of the included SRs. Three electronic databases have been explored. SRs addressing the effects of surgical procedures on the acceleration of tooth movement were included. The methodological quality of the included SRs was assessed using the updated version of “A Measurement Tool to Assess Systematic Review” (AMSTAR-2). Twenty-eight (28) SRs were included. The methodological quality of the included reviews ranged between critically low (6 studies) and high (12 studies). The most common critical weakness in the included reviews was the absence of clearly a-prior established review methods and any significant deviations from the protocol. The most studied surgical procedure was corticotomy, followed by micro-osteoperforation, piezocision and periodontally accelerated osteogenic orthodontics. The majority of the included SRs supported short-term favourable effects of corticotomy on treatment time and tooth movement rate, in the short-term. However, the authors of the included SRs reported that results were based on weak quality evidence. Conflicting results arise from the existent SRs with regards to the effectiveness of piezocision and micro-osteoperforation. Few SRs summarised complications and side effects of surgical techniques, supporting absence of loss of tooth vitality, periodontal problems, or severe root resorption. The current overview of SRs highlighted the need of high quality SRs comparing different surgical approaches for tooth movement acceleration though network meta-analysis, in order to determine the most efficient instrument for orthodontic movement acceleration

    Flora and Fauna in East Asian Art

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    Flora and Fauna in East Asian Art is the fourth annual exhibition curated by students enrolled in the Art History Methods course. This exhibition highlights the academic achievements of six student curators: Samantha Frisoli ’18, Daniella Snyder ’18, Gabriella Bucci ’19, Melissa Casale ’19, Keira Koch ’19, and Paige Deschapelles ’20. The selection of artworks in this exhibition considers how East Asian artists portrayed similar subjects of flora and fauna in different media including painting, prints, embroidery, jade, and porcelain. This exhibition intends to reveal the hidden meanings behind various representations of flora and fauna in East Asian art by examining the iconography, cultural context, aesthetic and function of each object.https://cupola.gettysburg.edu/artcatalogs/1025/thumbnail.jp

    Effect of orthopedic and functional orthodontic treatment in children with obstructive sleep apnea: A systematic review and meta-analysis

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    Orthodontic treatment is suggested in growing individuals to correct transverse maxillary deficiency and mandibular retrusion. Since, as a secondary effect, these orthodontic procedures may improve pediatric obstructive sleep apnea (OSA), this systematic review assessed their effects on apnea-hypopnea index (AHI) and oxygen saturation (SaO2). Twenty-five (25) manuscripts were included for qualitative synthesis, 19 were selected for quantitative synthesis. Five interventions were analyzed: rapid maxillary expansion (RME, 15 studies), mandibular advancement (MAA, five studies), myofunctional therapy (MT, four studies), and RME combined with MAA (one study). RME produced a significant AHI reduction and minimum SaO2 increase immediately after active treatment, at six and 12 months from baseline. A significant AHI reduction was also observed six and 12 months after the beginning of MAA treatment. MT showed positive effects, with different protocols. In this systematic review and meta-analysis of data from mainly uncontrolled studies, interceptive orthodontic treatments showed overall favorable effects on respiratory outcomes in pediatric OSA. However, due to the low to very low level of the body evidence, this treatment cannot be suggested as elective for OSA treatment. An orthodontic indication is needed to support this therapy and a careful monitoring is required to ensure positive improvement in OSA parameters

    Class II functional orthopaedic treatment: a systematic review of systematic reviews

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    This Systematic Review (SR) aims to assess the quality of SRs and Meta-Analyses (MAs) on functional orthopaedic treatment of Class II malocclusion and to summarise and rate the reported effects. Electronic and manual searches were conducted until June 2014. SRs and MAs focusing on the effects of functional orthopaedic treatment of Class II malocclusion in growing patients were included. The methodological quality of the included papers was assessed using the AMSTAR (Assessment of Multiple Systematic Reviews). The design of the primary studies included in each SR was assessed with Level of Research Design scoring. The evidence of the main outcomes was summarised and rated according to a scale of statements. 14 SRs fulfilled the inclusion criteria. The appliances evaluated were as follows: Activator (2 studies), Twin Block (4 studies), headgear (3 studies), Herbst (2 studies), Jasper Jumper (1 study), Bionator (1 study) and Fränkel-2 (1 study). Four studies reviewed several functional appliances, as a group. The mean AMSTAR score was 6 (ranged 2-10). Six SRs included only controlled clinical trials (CCTs), three SRs included only randomised controlled trials (RCTs), four SRs included both CCTs and RCTs and one SR included also expert opinions. There was some evidence of reduction of the overjet, with different appliances except from headgear; there was some evidence of small maxillary growth restrain with Twin Block and headgear; there was some evidence of elongation of mandibular length, but the clinical relevance of this results is still questionable; there was insufficient evidence to determine an effect on soft tissues

    Growth and dissection of a fold and thrust belt: the geological record of the High Agri Valley, Italy

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    We present a 130 km2 wide geological map for the NE side of the fault-bounded High Agri Valley Southern Italy, that formed in the Quaternary in response to extensional tectonics dissecting the folds and thrusts of the Lucanian Apennine. To prepare the map, at 1:25,000 scale, we integrated information obtained through field surveys and the review of pre-existing geological data. Our work describes a number of significant map-scale structures, which can be related to well-constrained tectonic episodes. The new geological map provides important constraints that can be used to distinguish ancient structures from those that were active during the Quaternary, allowing a more detailed reconstruction of the processes that operate during the development of a post-orogenic trough. We expect that the new map will be used for different types of geological investigations, including studies of inversion tectonics, active tectonics, geosite mapping, 3D modelling of geological structures. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps
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