WorldWideScience

Sample records for quadratic helix approach

  1. On Algebraic Approach in Quadratic Systems

    Directory of Open Access Journals (Sweden)

    Matej Mencinger

    2011-01-01

    Full Text Available When considering friction or resistance, many physical processes are mathematically simulated by quadratic systems of ODEs or discrete quadratic dynamical systems. Probably the most important problem when such systems are applied in engineering is the stability of critical points and (nonchaotic dynamics. In this paper we consider homogeneous quadratic systems via the so-called Markus approach. We use the one-to-one correspondence between homogeneous quadratic dynamical systems and algebra which was originally introduced by Markus in (1960. We resume some connections between the dynamics of the quadratic systems and (algebraic properties of the corresponding algebras. We consider some general connections and the influence of power-associativity in the corresponding quadratic system.

  2. Constrained neural approaches to quadratic assignment problems.

    Science.gov (United States)

    Ishii, S; Sato, M

    1998-08-01

    In this paper, we discuss analog neural approaches to the quadratic assignment problem (QAP). These approaches employ a hard constraints scheme to restrict the domain space, and are able to obtain much improved solutions over conventional neural approaches. Since only a few strong heuristics for QAP have been known to date, our approaches are good alternatives, capable of obtaining fairly good solutions in a short period of time. Some of them can also be applied to large-scale problems, say of size N>/=300.

  3. A polyhedral approach to quadratic assignment problem

    OpenAIRE

    Köksaldı, Ahmet Sertaç Murat

    1994-01-01

    Ankara : Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent University, 1994. Thesis (Master's) -- Bilkent University, 1994. Includes bibliographical references. In this thesis, Quadratic Assignment Problem is considered. Since Quadratic Assignment Problem is JVP-bard, no polynomial time exact solution method exists. Proving optimality of solutions to Quadratic Assignment Problems has been limited to instances of small dimension. In...

  4. New Heuristic Rounding Approaches to the Quadratic Assignment Problem

    CERN Document Server

    Gharibi, Wajeb

    2011-01-01

    Quadratic assignment problem is one of the great challenges in combinatorial optimization. It has many applications in Operations research and Computer Science. In this paper, the author extends the most-used rounding approach to a one-parametric optimization model for the quadratic assignment problems. A near-optimum parameter is also predestinated. The numerical experiments confirm the efficiency.

  5. Quadratic function approaching method for magnetotelluric soundingdata inversion

    Energy Technology Data Exchange (ETDEWEB)

    Liangjun, Yan; Wenbao, Hu; Zhang, Keni

    2004-04-05

    The quadratic function approaching method (QFAM) is introduced for magnetotelluric sounding (MT) data inversion. The method takes the advantage of that quadratic function has single extreme value, which avoids leading to an inversion solution for local minimum and ensures the solution for global minimization of an objective function. The method does not need calculation of sensitivity matrix and not require a strict initial earth model. Examples for synthetic data and field measurement data indicate that the proposed inversion method is effective.

  6. NMR-based approach to measure the free energy of transmembrane helix-helix interactions.

    Science.gov (United States)

    Mineev, Konstantin S; Lesovoy, Dmitry M; Usmanova, Dinara R; Goncharuk, Sergey A; Shulepko, Mikhail A; Lyukmanova, Ekaterina N; Kirpichnikov, Mikhail P; Bocharov, Eduard V; Arseniev, Alexander S

    2014-01-01

    Knowledge of the energetic parameters of transmembrane helix-helix interactions is necessary for the establishment of a structure-energy relationship for α-helical membrane domains. A number of techniques have been developed to measure the free energies of dimerization and oligomerization of transmembrane α-helices, and all of these have their advantages and drawbacks. In this study we propose a methodology to determine the magnitudes of the free energy of interactions between transmembrane helices in detergent micelles. The suggested approach employs solution nuclear magnetic resonance (NMR) spectroscopy to determine the population of the oligomeric states of the transmembrane domains and introduces a new formalism to describe the oligomerization equilibrium, which is based on the assumption that both the dimerization of the transmembrane domains and the dissociation of the dimer can occur only upon the collision of detergent micelles. The technique has three major advantages compared with other existing approaches: it may be used to analyze both weak and relatively strong dimerization/oligomerization processes, it works well for the analysis of complex equilibria, e.g. when monomer, dimer and high-order oligomer populations are simultaneously present in the solution, and it can simultaneously yield both structural and energetic characteristics of the helix-helix interaction under study. The proposed methodology was applied to investigate the oligomerization process of transmembrane domains of fibroblast growth factor receptor 3 (FGFR3) and vascular endothelium growth factor receptor 2 (VEGFR2), and allowed the measurement of the free energy of dimerization of both of these objects. In addition the proposed method was able to describe the multi-state oligomerization process of the VEGFR2 transmembrane domain.

  7. A Riccati approach for constrained linear quadratic optimal control

    Science.gov (United States)

    Sideris, Athanasios; Rodriguez, Luis A.

    2011-02-01

    An active-set method is proposed for solving linear quadratic optimal control problems subject to general linear inequality path constraints including mixed state-control and state-only constraints. A Riccati-based approach is developed for efficiently solving the equality constrained optimal control subproblems generated during the procedure. The solution of each subproblem requires computations that scale linearly with the horizon length. The algorithm is illustrated with numerical examples.

  8. Geometric Approaches to Quadratic Equations from Other Times and Places.

    Science.gov (United States)

    Allaire, Patricia R.; Bradley, Robert E.

    2001-01-01

    Focuses on geometric solutions of quadratic problems. Presents a collection of geometric techniques from ancient Babylonia, classical Greece, medieval Arabia, and early modern Europe to enhance the quadratic equation portion of an algebra course. (KHR)

  9. A Neurodynamic Optimization Approach to Bilevel Quadratic Programming.

    Science.gov (United States)

    Qin, Sitian; Le, Xinyi; Wang, Jun

    2016-08-19

    This paper presents a neurodynamic optimization approach to bilevel quadratic programming (BQP). Based on the Karush-Kuhn-Tucker (KKT) theorem, the BQP problem is reduced to a one-level mathematical program subject to complementarity constraints (MPCC). It is proved that the global solution of the MPCC is the minimal one of the optimal solutions to multiple convex optimization subproblems. A recurrent neural network is developed for solving these convex optimization subproblems. From any initial state, the state of the proposed neural network is convergent to an equilibrium point of the neural network, which is just the optimal solution of the convex optimization subproblem. Compared with existing recurrent neural networks for BQP, the proposed neural network is guaranteed for delivering the exact optimal solutions to any convex BQP problems. Moreover, it is proved that the proposed neural network for bilevel linear programming is convergent to an equilibrium point in finite time. Finally, three numerical examples are elaborated to substantiate the efficacy of the proposed approach.

  10. The generalized quadratic knapsack problem. A neuronal network approach.

    Science.gov (United States)

    Talaván, Pedro M; Yáñez, Javier

    2006-05-01

    The solution of an optimization problem through the continuous Hopfield network (CHN) is based on some energy or Lyapunov function, which decreases as the system evolves until a local minimum value is attained. A new energy function is proposed in this paper so that any 0-1 linear constrains programming with quadratic objective function can be solved. This problem, denoted as the generalized quadratic knapsack problem (GQKP), includes as particular cases well-known problems such as the traveling salesman problem (TSP) and the quadratic assignment problem (QAP). This new energy function generalizes those proposed by other authors. Through this energy function, any GQKP can be solved with an appropriate parameter setting procedure, which is detailed in this paper. As a particular case, and in order to test this generalized energy function, some computational experiments solving the traveling salesman problem are also included.

  11. A Unified Approach to Teaching Quadratic and Cubic Equations.

    Science.gov (United States)

    Ward, A. J. B.

    2003-01-01

    Presents a simple method for teaching the algebraic solution of cubic equations via completion of the cube. Shows that this method is readily accepted by students already familiar with completion of the square as a method for quadratic equations. (Author/KHR)

  12. Twistless Version of Thirring's Approach to the KAM Theorem for Quadratic Hamiltonians

    CERN Document Server

    Chandre, C

    1998-01-01

    We give a proof of the KAM theorem on the existence of invariant tori for weakly perturbed Hamiltonian systems, based on Thirring's approach for Hamiltonians that are quadratic in the action variables. The main point of this approach is that the iteration of canonical transformations on which the proof is based stays within the space of quadratic Hamiltonians. We show that Thirring's proof for nondegenerate Hamiltonians can be adapted to twistless Hamiltonians. This twistless assumption, in fact, drastically simplifies Thirring's proof.

  13. Wind turbine power tracking using an improved multimodel quadratic approach.

    Science.gov (United States)

    Khezami, Nadhira; Benhadj Braiek, Naceur; Guillaud, Xavier

    2010-07-01

    In this paper, an improved multimodel optimal quadratic control structure for variable speed, pitch regulated wind turbines (operating at high wind speeds) is proposed in order to integrate high levels of wind power to actively provide a primary reserve for frequency control. On the basis of the nonlinear model of the studied plant, and taking into account the wind speed fluctuations, and the electrical power variation, a multimodel linear description is derived for the wind turbine, and is used for the synthesis of an optimal control law involving a state feedback, an integral action and an output reference model. This new control structure allows a rapid transition of the wind turbine generated power between different desired set values. This electrical power tracking is ensured with a high-performance behavior for all other state variables: turbine and generator rotational speeds and mechanical shaft torque; and smooth and adequate evolution of the control variables. 2010 ISA. Published by Elsevier Ltd. All rights reserved.

  14. Linearly and Quadratically Separable Classifiers Using Adaptive Approach

    Institute of Scientific and Technical Information of China (English)

    Mohamed Abdel-Kawy Mohamed Ali Soliman; Rasha M. Abo-Bakr

    2011-01-01

    This paper presents a fast adaptive iterative algorithm to solve linearly separable classification problems in Rn.In each iteration,a subset of the sampling data (n-points,where n is the number of features) is adaptively chosen and a hyperplane is constructed such that it separates the chosen n-points at a margin e and best classifies the remaining points.The classification problem is formulated and the details of the algorithm are presented.Further,the algorithm is extended to solving quadratically separable classification problems.The basic idea is based on mapping the physical space to another larger one where the problem becomes linearly separable.Numerical illustrations show that few iteration steps are sufficient for convergence when classes are linearly separable.For nonlinearly separable data,given a specified maximum number of iteration steps,the algorithm returns the best hyperplane that minimizes the number of misclassified points occurring through these steps.Comparisons with other machine learning algorithms on practical and benchmark datasets are also presented,showing the performance of the proposed algorithm.

  15. QUADRATIC BI-LEVEL PROGRAMMING PROBLEM BASED ON FUZZY GOAL PROGRAMMING APPROACH

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    Partha Pratim Dey

    2011-11-01

    Full Text Available This paper presents fuzzy goal programming approach to quadratic bi-level programming problem. Inthe model formulation of the problem, we construct the quadratic membership functions by determiningindividual best solutions of the quadratic objective functions subject to the system constraints. Thequadratic membership functions are then transformed into equivalent linear membership functions byfirst order Taylor series approximation at the individual best solution point. Since the objectives of upperand lower level decision makers are potentially conflicting in nature, a possible relaxation of each leveldecisions are considered by providing preference bounds on the decision variables for avoiding decisiondeadlock. Then fuzzy goal programming approach is used for achieving highest degree of each of themembership goals by minimizing deviational variables. Numerical examples are provided in order todemonstrate the efficiency of the proposed approach.

  16. A Role-Based Approach to Adult Development: The Triple-Helix Model.

    Science.gov (United States)

    Juhasz, Anne McCreary

    1989-01-01

    Presents triple-helix model of adult development which incorporates three major roles: family, work, and self, each powered by drive for self-esteem. Asserts that this approach accommodates wide range of possible patterns and varied timing of life events relative to career options, family and relationship choices, and emphasis on self-development.…

  17. A linear quadratic regulator approach to the stabilization of uncertain linear systems

    Science.gov (United States)

    Shieh, L. S.; Sunkel, J. W.; Wang, Y. J.

    1990-01-01

    This paper presents a linear quadratic regulator approach to the stabilization of uncertain linear systems. The uncertain systems under consideration are described by state equations with the presence of time-varying unknown-but-bounded uncertainty matrices. The method is based on linear quadratic regulator (LQR) theory and Liapunov stability theory. The robust stabilizing control law for a given uncertain system can be easily constructed from the symmetric positive-definite solution of the associated augmented Riccati equation. The proposed approach can be applied to matched and/or mismatched systems with uncertainty matrices in which only their matrix norms are bounded by some prescribed values and/or their entries are bounded by some prescribed constraint sets. Several numerical examples are presented to illustrate the results.

  18. The Portfolio Selection by Using Quadratic Programming Approach Case Study of Malaysia Stock Exchange

    Directory of Open Access Journals (Sweden)

    Ali YOUSFAT

    2015-08-01

    Full Text Available This paper uses the quadratic approach to select the optimum portfolio of the Malaysian stovk exchange. This framework deals with ten biggest firms posted on the stock exchange during 2014. The result shows that the optimum portfolio includes 22 % of Axiata Group shares, 11% of Genting shares, 30 % of Petronas Chemicals shares, 1% of Sime Darbi shares and 36 % of Tenaga Nasional shares.

  19. A New Finite-Time Bounded Control of Stochastic Itô Systems with (x,u,v)-Dependent Noise: Different Quadratic Function Approach

    National Research Council Canada - National Science Library

    Yan, Zhiguo; Lin, Zhongwei

    2014-01-01

    .... Then a different quadratic function approach is proposed to give a sufficient condition for finite-time boundedness of such a class of systems, and its superiority to common quadratic approach is shown...

  20. A novel neural dynamical approach to convex quadratic program and its efficient applications.

    Science.gov (United States)

    Xia, Youshen; Sun, Changyin

    2009-12-01

    This paper proposes a novel neural dynamical approach to a class of convex quadratic programming problems where the number of variables is larger than the number of equality constraints. The proposed continuous-time and proposed discrete-time neural dynamical approach are guaranteed to be globally convergent to an optimal solution. Moreover, the number of its neurons is equal to the number of equality constraints. In contrast, the number of neurons in existing neural dynamical methods is at least the number of the variables. Therefore, the proposed neural dynamical approach has a low computational complexity. Compared with conventional numerical optimization methods, the proposed discrete-time neural dynamical approach reduces multiplication operation per iteration and has a large computational step length. Computational examples and two efficient applications to signal processing and robot control further confirm the good performance of the proposed approach.

  1. Measurement of the quadratic hyperpolarizability of the collagen triple helix and application to second harmonic imaging of natural and biomimetic collagenous tissues

    Science.gov (United States)

    Deniset-Besseau, A.; Strupler, M.; Duboisset, J.; De Sa Peixoto, P.; Benichou, E.; Fligny, C.; Tharaux, P.-L.; Mosser, G.; Brevet, P.-F.; Schanne-Klein, M.-C.

    2009-09-01

    Collagen is a major protein of the extracellular matrix that is characterized by triple helical domains. It plays a central role in the formation of fibrillar and microfibrillar networks, basement membranes, as well as other structures of the connective tissue. Remarkably, fibrillar collagen exhibits efficient Second Harmonic Generation (SHG) so that SHG microscopy proved to be a sensitive tool to probe the three-dimensional architecture of fibrillar collagen and to assess the progression of fibrotic pathologies. We obtained sensitive and reproducible measurements of the fibrosis extent, but we needed quantitative data at the molecular level to further process SHG images. We therefore performed Hyper- Rayleigh Scattering (HRS) experiments and measured a second order hyperpolarisability of 1.25 10-27 esu for rat-tail type I collagen. This value is surprisingly large considering that collagen presents no strong harmonophore in its aminoacid sequence. In order to get insight into the physical origin of this nonlinear process, we performed HRS measurements after denaturation of the collagen triple helix and for a collagen-like short model peptide [(Pro-Pro- Gly)10]3. It showed that the collagen large nonlinear response originates in the tight alignment of a large number of weakly efficient harmonophores, presumably the peptide bonds, resulting in a coherent amplification of the nonlinear signal along the triple helix. To illustrate this mechanism, we successfully recorded SHG images in collagenous biomimetic matrices.

  2. A Genetic-Algorithms-Based Approach for Programming Linear and Quadratic Optimization Problems with Uncertainty

    Directory of Open Access Journals (Sweden)

    Weihua Jin

    2013-01-01

    Full Text Available This paper proposes a genetic-algorithms-based approach as an all-purpose problem-solving method for operation programming problems under uncertainty. The proposed method was applied for management of a municipal solid waste treatment system. Compared to the traditional interactive binary analysis, this approach has fewer limitations and is able to reduce the complexity in solving the inexact linear programming problems and inexact quadratic programming problems. The implementation of this approach was performed using the Genetic Algorithm Solver of MATLAB (trademark of MathWorks. The paper explains the genetic-algorithms-based method and presents details on the computation procedures for each type of inexact operation programming problems. A comparison of the results generated by the proposed method based on genetic algorithms with those produced by the traditional interactive binary analysis method is also presented.

  3. Global asymptotic stability analysis for delayed neural networks using a matrix-based quadratic convex approach.

    Science.gov (United States)

    Zhang, Xian-Ming; Han, Qing-Long

    2014-06-01

    This paper is concerned with global asymptotic stability for a class of generalized neural networks with interval time-varying delays by constructing a new Lyapunov-Krasovskii functional which includes some integral terms in the form of ∫(t-h)(t)(h-t-s)(j)ẋ(T)(s)Rjẋ(s)ds(j=1,2,3). Some useful integral inequalities are established for the derivatives of those integral terms introduced in the Lyapunov-Krasovskii functional. A matrix-based quadratic convex approach is introduced to prove not only the negative definiteness of the derivative of the Lyapunov-Krasovskii functional, but also the positive definiteness of the Lyapunov-Krasovskii functional. Some novel stability criteria are formulated in two cases, respectively, where the time-varying delay is continuous uniformly bounded and where the time-varying delay is differentiable uniformly bounded with its time-derivative bounded by constant lower and upper bounds. These criteria are applicable to both static neural networks and local field neural networks. The effectiveness of the proposed method is demonstrated by two numerical examples.

  4. An iterative method for tri-level quadratic fractional programming problems using fuzzy goal programming approach

    Science.gov (United States)

    Kassa, Semu Mitiku; Tsegay, Teklay Hailay

    2017-08-01

    Tri-level optimization problems are optimization problems with three nested hierarchical structures, where in most cases conflicting objectives are set at each level of hierarchy. Such problems are common in management, engineering designs and in decision making situations in general, and are known to be strongly NP-hard. Existing solution methods lack universality in solving these types of problems. In this paper, we investigate a tri-level programming problem with quadratic fractional objective functions at each of the three levels. A solution algorithm has been proposed by applying fuzzy goal programming approach and by reformulating the fractional constraints to equivalent but non-fractional non-linear constraints. Based on the transformed formulation, an iterative procedure is developed that can yield a satisfactory solution to the tri-level problem. The numerical results on various illustrative examples demonstrated that the proposed algorithm is very much promising and it can also be used to solve larger-sized as well as n-level problems of similar structure.

  5. Knowledge-enhancing Helix: An Approach for Developing Key Academic Skills at Universities. A Case Study

    Directory of Open Access Journals (Sweden)

    Nadja Boeller

    2008-08-01

    Full Text Available In an increasingly e-literate society, new and media technologies are proliferating and traditional teaching approaches are challenged to meet new requirements. Other aspects such as teamwork and knowledge exchange are also becoming more important. Collaborative working methods are more dominant in the networked business environment. The vocational training at universities is therefore continuously facing with new challenges. The objective of this paper is to show how the implementation of a holistic teaching approach including the idea of blended learning can be an effective way to train students in collaborative and academic working skills, methodological expertise, information literacy, as well as making students aware of new developments in media literacy. This approach follows our proposed concept DIAMOND (Didactical Approach for Media Competence Development with a main focus on the implementation of the "knowledgeenhancing helix." This pedagogical concept was developed corresponding the requirements for "good online learning." The paper accordingly discusses the theoretical framework and presents a case study where the concept was implemented in practice.

  6. Knowledge-enhancing Helix: An Approach for Developing Key Academic Skills at Universities. A Case Study

    Directory of Open Access Journals (Sweden)

    Nadja Boeller

    2008-08-01

    Full Text Available In an increasingly e-literate society, new and media technologies are proliferating and traditional teaching approaches are challenged to meet new requirements. Other aspects such as teamwork and knowledge exchange are also becoming more important. Collaborative working methods are more dominant in the networked business environment. The vocational training at universities is therefore continuously facing with new challenges. The objective of this paper is to show how the implementation of a holistic teaching approach including the idea of blended learning can be an effective way to train students in collaborative and academic working skills, methodological expertise, information literacy, as well as making students aware of new developments in media literacy. This approach follows our proposed concept DIAMOND (Didactical Approach for Media Competence Development with a main focus on the implementation of the "knowledgeenhancing helix." This pedagogical concept was developed corresponding the requirements for "good online learning." The paper accordingly discusses the theoretical framework and presents a case study where the concept was implemented in practice.

  7. Innovative Development of Kazakhstan on The Basis of Triple Helix and Cluster Approach

    Directory of Open Access Journals (Sweden)

    Farkhat Musayevich Dnishev

    2015-06-01

    Full Text Available The aim of the research is to study the Triple Helix model feasibility in developing innovations and using cluster approach in Kazakhstan. There are possible points of the emergence of clusters in Kazakhstan. However, there are a lot of constraining factors. First of all, institutional and social factors: the culture of business, unfair competition, low trust of economic agents to each other and to power institutes, low psychological readiness for cooperation of the enterprises of various branches and regions, poor development of chambers of commerce, and industrial associations. For the time being, the majority of regions of Kazakhstan are characterized by a limited set of high technology industrial branches, and a sharp shortage of universities generating innovation and research institutes. The research results show that the open innovation model is realized in a limited scale that does not allow to export innovations into external markets, to participate in global technology chains and international research networks. At the same time, some interaction schemes and preconditions for the development of the Triple Helix model are emerging. However, in general, the innovation policy is not systemic; it does not unite actions in the sphere of science and technology, education, industry, and regional initiatives. As the result of the research, some policy implications are given. For the development of clusters in Kazakhstan, it is desirable to use such a way, as integration into global cluster networks. It is necessary to make use of foreign experience at which various specialized state agencies become participants of clusters. It is necessary to focus not only on science but also industry, which should play the central role in the innovation process.

  8. An inner-outer nonlinear programming approach for constrained quadratic matrix model updating

    Science.gov (United States)

    Andretta, M.; Birgin, E. G.; Raydan, M.

    2016-01-01

    The Quadratic Finite Element Model Updating Problem (QFEMUP) concerns with updating a symmetric second-order finite element model so that it remains symmetric and the updated model reproduces a given set of desired eigenvalues and eigenvectors by replacing the corresponding ones from the original model. Taking advantage of the special structure of the constraint set, it is first shown that the QFEMUP can be formulated as a suitable constrained nonlinear programming problem. Using this formulation, a method based on successive optimizations is then proposed and analyzed. To avoid that spurious modes (eigenvectors) appear in the frequency range of interest (eigenvalues) after the model has been updated, additional constraints based on a quadratic Rayleigh quotient are dynamically included in the constraint set. A distinct practical feature of the proposed method is that it can be implemented by computing only a few eigenvalues and eigenvectors of the associated quadratic matrix pencil.

  9. Scalable Effective Approaches for Quadratic Assignment Problems Based on Conic Optimization and Applications

    Science.gov (United States)

    2012-02-09

    several optimization models and algorithm design for problems from computer vision and learning , research on sparse solutions in quadratic optimization...following papers: [9] L. Mukherjee, V. Singh, J. Peng and C. Hinrichs. Learning kernels for variants of normalized cuts: Convex relaxations and...are very small gaps compared to state-of-the-art knowledge in comunications . Table 1. Bounds for adjacency matrix

  10. Fitting timeseries by continuous-time Markov chains: A quadratic programming approach

    Science.gov (United States)

    Crommelin, D. T.; Vanden-Eijnden, E.

    2006-09-01

    Construction of stochastic models that describe the effective dynamics of observables of interest is an useful instrument in various fields of application, such as physics, climate science, and finance. We present a new technique for the construction of such models. From the timeseries of an observable, we construct a discrete-in-time Markov chain and calculate the eigenspectrum of its transition probability (or stochastic) matrix. As a next step we aim to find the generator of a continuous-time Markov chain whose eigenspectrum resembles the observed eigenspectrum as closely as possible, using an appropriate norm. The generator is found by solving a minimization problem: the norm is chosen such that the object function is quadratic and convex, so that the minimization problem can be solved using quadratic programming techniques. The technique is illustrated on various toy problems as well as on datasets stemming from simulations of molecular dynamics and of atmospheric flows.

  11. Robust stabilization of linear descriptor systems. Quadratic stabilization approach of equivalent systems; Descriptor system no robust anteika. Toka system ni taisuru 2 ji anteika kara no approach

    Energy Technology Data Exchange (ETDEWEB)

    Uezato, E. [Ryukyu Univ., Nishihara, Okinawa (Japan)] Ikeda, M. [Osaka Univ., Suita (Japan)] Toyama, R. [Kobe Univ. (Japan)

    1998-11-30

    This paper presents two sufficient conditions as linear and bilinear matrix conditions for a system with polytopic uncertainties to be robustly stabilizable by an approach of quadratic stabilization of equivalent systems as regards closed system and robust stabilization. For the purpose, two systems are assumed which are equivalent concerning closed loop system and robust stabilization and contains no uncertainty in the coefficient matrix of the differential of descriptor variables. The robust stability conditions for the original system are obtained by deriving quadratic stabilization conditions of the equivalent systems because the original closed system is robustly stable if those equivalent systems are quadratically stable. Robust stabilizability conditions for a system with polytopic uncertainties in the coefficient matrix are given in terms of linear and bilinear matrix inequalities. In addition, an algorithm based on the idea of the homotopy method is proposed to solve the bilinear matrix inequality. 13 refs., 1 fig.

  12. Robust and minimum norm partial quadratic eigenvalue assignment in vibrating systems: A new optimization approach

    Science.gov (United States)

    Bai, Zheng-Jian; Datta, Biswa Nath; Wang, Jinwei

    2010-04-01

    The partial quadratic eigenvalue assignment problem (PQEVAP) concerns reassigning a few undesired eigenvalues of a quadratic matrix pencil to suitably chosen locations and keeping the other large number of eigenvalues and eigenvectors unchanged (no spill-over). The problem naturally arises in controlling dangerous vibrations in structures by means of active feedback control design. For practical viability, the design must be robust, which requires that the norms of the feedback matrices and the condition number of the closed-loop eigenvectors are as small as possible. The problem of computing feedback matrices that satisfy the above two practical requirements is known as the Robust Partial Quadratic Eigenvalue Assignment Problem (RPQEVAP). In this paper, we formulate the RPQEVAP as an unconstrained minimization problem with the cost function involving the condition number of the closed-loop eigenvector matrix and two feedback norms. Since only a small number of eigenvalues of the open-loop quadratic pencil are computable using the state-of-the-art matrix computational techniques and/or measurable in a vibration laboratory, it is imperative that the problem is solved using these small number of eigenvalues and the corresponding eigenvectors. To this end, a class of the feedback matrices are obtained in parametric form, parameterized by a single parametric matrix, and the cost function and the required gradient formulas for the optimization problem are developed in terms of the small number of eigenvalues that are reassigned and their corresponding eigenvectors. The problem is solved directly in quadratic setting without transforming it to a standard first-order control problem and most importantly, the significant "no spill-over property" of the closed-loop eigenvalues and eigenvectors is established by means of a mathematical result. These features make the proposed method practically applicable even for very large structures. Results on numerical experiments show

  13. An optimization approach for minimum norm and robust partial quadratic eigenvalue assignment problems for vibrating structures

    Science.gov (United States)

    Brahma, Sanjoy; Datta, Biswa

    2009-07-01

    The partial quadratic eigenvalue assignment problem (PQEVAP) concerns the reassignment of a small number of undesirable eigenvalues of a quadratic matrix pencil, while leaving the remaining large number of eigenvalues and the corresponding eigenvectors unchanged. The problem arises in controlling undesirable resonance in vibrating structures and in stabilizing control systems. The solution of this problem requires computations of a pair of feedback matrices. For practical effectiveness, these feedback matrices must be computed in such a way that their norms and the condition number of the closed-loop eigenvector matrix are as small as possible. These considerations give rise to the minimum norm partial quadratic eigenvalue assignment problem (MNPQEVAP) and the robust partial quadratic eigenvalue assignment problem (RPQEVAP), respectively. In this paper we propose new optimization based algorithms for solving these problems. The problems are solved directly in a second-order setting without resorting to a standard first-order formulation so as to avoid the inversion of a possibly ill-conditioned matrix and the loss of exploitable structures of the original model. The algorithms require the knowledge of only the open-loop eigenvalues to be replaced and their corresponding eigenvectors. The remaining open-loop eigenvalues and their corresponding eigenvectors are kept unchanged. The invariance of the large number of eigenvalues and eigenvectors under feedback is guaranteed by a proven mathematical result. Furthermore, the gradient formulas needed to solve the problems by using the quasi-Newton optimization technique employed are computed in terms of the known quantities only. Above all, the proposed methods do not require the reduction of the model order or the order of the controller, even when the underlying finite element model has a very large degree of freedom. These attractive features, coupled with minimal computational requirements, such as solutions of small

  14. A triple Helix Approach to the Future Innovation Flagship of Europe:

    DEFF Research Database (Denmark)

    Jofre, Sergio; Andersen, Per Dannemand

    2009-01-01

    , are transforming the profile of the triple helix relationships. This transformation is bringing the American and the Japanese innovation system to an unprecedented level of commonality and the EU to a yet uncertain stage of transition characterized by the conflict between national and supranational priorities...

  15. IFSM fractal image compression with entropy and sparsity constraints: A sequential quadratic programming approach

    Science.gov (United States)

    Kunze, Herb; La Torre, Davide; Lin, Jianyi

    2017-01-01

    We consider the inverse problem associated with IFSM: Given a target function f , find an IFSM, such that its fixed point f ¯ is sufficiently close to f in the Lp distance. Forte and Vrscay [1] showed how to reduce this problem to a quadratic optimization model. In this paper, we extend the collage-based method developed by Kunze, La Torre and Vrscay ([2][3][4]), by proposing the minimization of the 1-norm instead of the 0-norm. In fact, optimization problems involving the 0-norm are combinatorial in nature, and hence in general NP-hard. To overcome these difficulties, we introduce the 1-norm and propose a Sequential Quadratic Programming algorithm to solve the corresponding inverse problem. As in Kunze, La Torre and Vrscay [3] in our formulation, the minimization of collage error is treated as a multi-criteria problem that includes three different and conflicting criteria i.e., collage error, entropy and sparsity. This multi-criteria program is solved by means of a scalarization technique which reduces the model to a single-criterion program by combining all objective functions with different trade-off weights. The results of some numerical computations are presented.

  16. Quadratic choreographies

    CERN Document Server

    Ryckelynck, Philippe

    2011-01-01

    This paper addresses the classical and discrete Euler-Lagrange equations for systems of $n$ particles interacting quadratically in $\\mathbb{R}^d$. By highlighting the role played by the center of mass of the particles, we solve the previous systems via the classical quadratic eigenvalue problem (QEP) and its discrete transcendental generalization. The roots of classical and discrete QEP being given, we state some conditional convergence results. Next, we focus especially on periodic and choreographic solutions and we provide some numerical experiments which confirm the convergence.

  17. On the algebraic approach to the time-dependent quadratic Hamiltonian

    Energy Technology Data Exchange (ETDEWEB)

    Urdaneta, Ines; Palma, Alejandro [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico); Sandoval, Lourdes, E-mail: urdaneta@sirio.ifuap.buap.m [Facultad de Ciencias de la Computacion, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico)

    2010-09-24

    The unitary operator V(t) that diagonalizes the time-dependent quadratic Hamiltonian (TDQH) into a time-dependent harmonic oscillator (TDHO) is obtained using a Lie algebra. The method involves a factorization of the TDQH into a TDHO through a unitary Bogoliubov transformation in terms of creation and annihilation operators with time-dependent coefficients. It is shown that this operator can be easily achieved by means of the factorization, together with the commonly known Wei-Norman theorem. We discuss the conditions under which this unitary operator converges to the evolution operator U(t) of the Schroedinger equation for the TDQH, giving then a straightforward calculation of the evolution operator with respect to the procedures published in the literature.

  18. Helix Nebula and CERN: A Symbiotic approach to exploiting commercial clouds

    CERN Multimedia

    Barreiro Megino, Fernando Harald; Kucharczyk, Katarzyna; Medrano Llamas, Ramón; van der Ster, Daniel

    2013-01-01

    The recent paradigm shift toward cloud computing in IT, and general interest in "Big Data" in particular, have demonstrated that the computing requirements of HEP are no longer globally unique. Indeed, the CERN IT department and LHC experiments have already made significant R&D; investments in delivering and exploiting cloud computing resources. While a number of technical evaluations of interesting commercial offerings from global IT enterprises have been performed by various physics labs, further technical, security, sociological, and legal issues need to be address before their large-scale adoption by the research community can be envisaged. Helix Nebula - the Science Cloud is an initiative that explores these questions by joining the forces of three European research institutes (CERN, ESA and EMBL) with leading European commercial IT enterprises. The goals of Helix Nebula are to establish a cloud platform federating multiple commercial cloud providers, along with new business models, which can sustain...

  19. Helix Nebula and CERN: A Symbiotic approach to exploiting commercial clouds

    CERN Document Server

    Barreiro Megino, Fernando Harald; Kucharczyk, Katarzyna; Medrano Llamas, Ramón; van der Ster, Daniel

    2014-01-01

    The recent paradigm shift toward cloud computing in IT, and general interest in "Big Data" in particular, have demonstrated that the computing requirements of HEP are no longer globally unique. Indeed, the CERN IT department and LHC experiments have already made significant R&D investments in delivering and exploiting cloud computing resources. While a number of technical evaluations of interesting commercial offerings from global IT enterprises have been performed by various physics labs, further technical, security, sociological, and legal issues need to be address before their large-scale adoption by the research community can be envisaged. Helix Nebula - the Science Cloud is an initiative that explores these questions by joining the forces of three European research institutes (CERN, ESA and EMBL) with leading European commercial IT enterprises. The goals of Helix Nebula are to establish a cloud platform federating multiple commercial cloud providers, along with new business models, which can sustain ...

  20. Helix Nebula and CERN: A Symbiotic approach to exploiting commercial clouds

    Science.gov (United States)

    Barreiro Megino, Fernando H.; Jones, Robert; Kucharczyk, Katarzyna; Medrano Llamas, Ramón; van der Ster, Daniel

    2014-06-01

    The recent paradigm shift toward cloud computing in IT, and general interest in "Big Data" in particular, have demonstrated that the computing requirements of HEP are no longer globally unique. Indeed, the CERN IT department and LHC experiments have already made significant R&D investments in delivering and exploiting cloud computing resources. While a number of technical evaluations of interesting commercial offerings from global IT enterprises have been performed by various physics labs, further technical, security, sociological, and legal issues need to be address before their large-scale adoption by the research community can be envisaged. Helix Nebula - the Science Cloud is an initiative that explores these questions by joining the forces of three European research institutes (CERN, ESA and EMBL) with leading European commercial IT enterprises. The goals of Helix Nebula are to establish a cloud platform federating multiple commercial cloud providers, along with new business models, which can sustain the cloud marketplace for years to come. This contribution will summarize the participation of CERN in Helix Nebula. We will explain CERN's flagship use-case and the model used to integrate several cloud providers with an LHC experiment's workload management system. During the first proof of concept, this project contributed over 40.000 CPU-days of Monte Carlo production throughput to the ATLAS experiment with marginal manpower required. CERN's experience, together with that of ESA and EMBL, is providing a great insight into the cloud computing industry and highlighted several challenges that are being tackled in order to ease the export of the scientific workloads to the cloud environments.

  1. Controller design approaches for large space structures using LQG control theory. [Linear Quadratic Gaussian

    Science.gov (United States)

    Joshi, S. M.; Groom, N. J.

    1979-01-01

    The paper presents several approaches for the design of reduced order controllers for large space structures. These approaches are shown to be based on LQG control theory and include truncation, modified truncation regulators and estimators, use of higher order estimators, selective modal suppression, and use of polynomial estimators. Further, the use of direct sensor feedback, as opposed to a state estimator, is investigated for some of these approaches. Finally, numerical results are given for a long free beam.

  2. Analytic derivative couplings in time-dependent density functional theory: Quadratic response theory versus pseudo-wavefunction approach

    Science.gov (United States)

    Zhang, Xing; Herbert, John M.

    2015-02-01

    We revisit the formalism for analytic derivative couplings between excited states in time-dependent density functional theory (TDDFT). We derive and implement these couplings using quadratic response theory, then numerically compare this response-theory formulation to couplings implemented previously based on a pseudo-wavefunction formalism and direct differentiation of the Kohn-Sham determinant. Numerical results, including comparison to full configuration interaction calculations, suggest that the two approaches perform equally well for many molecular systems, provided that the underlying DFT method affords accurate potential energy surfaces. The response contributions are found to be important for certain systems with high symmetry, but can be calculated with only a moderate increase in computational cost beyond what is required for the pseudo-wavefunction approach. In the case of spin-flip TDDFT, we provide a formal proof that the derivative couplings obtained using response theory are identical to those obtained from the pseudo-wavefunction formulation, which validates our previous implementation based on the latter formalism.

  3. Elastic Model Transitions: a Hybrid Approach Utilizing Quadratic Inequality Constrained Least Squares (LSQI) and Direct Shape Mapping (DSM)

    Science.gov (United States)

    Jurenko, Robert J.; Bush, T. Jason; Ottander, John A.

    2014-01-01

    A method for transitioning linear time invariant (LTI) models in time varying simulation is proposed that utilizes both quadratically constrained least squares (LSQI) and Direct Shape Mapping (DSM) algorithms to determine physical displacements. This approach is applicable to the simulation of the elastic behavior of launch vehicles and other structures that utilize multiple LTI finite element model (FEM) derived mode sets that are propagated throughout time. The time invariant nature of the elastic data for discrete segments of the launch vehicle trajectory presents a problem of how to properly transition between models while preserving motion across the transition. In addition, energy may vary between flex models when using a truncated mode set. The LSQI-DSM algorithm can accommodate significant changes in energy between FEM models and carries elastic motion across FEM model transitions. Compared with previous approaches, the LSQI-DSM algorithm shows improvements ranging from a significant reduction to a complete removal of transients across FEM model transitions as well as maintaining elastic motion from the prior state.

  4. Analytic derivative couplings in time-dependent density functional theory: Quadratic response theory versus pseudo-wavefunction approach.

    Science.gov (United States)

    Zhang, Xing; Herbert, John M

    2015-02-14

    We revisit the formalism for analytic derivative couplings between excited states in time-dependent density functional theory (TDDFT). We derive and implement these couplings using quadratic response theory, then numerically compare this response-theory formulation to couplings implemented previously based on a pseudo-wavefunction formalism and direct differentiation of the Kohn-Sham determinant. Numerical results, including comparison to full configuration interaction calculations, suggest that the two approaches perform equally well for many molecular systems, provided that the underlying DFT method affords accurate potential energy surfaces. The response contributions are found to be important for certain systems with high symmetry, but can be calculated with only a moderate increase in computational cost beyond what is required for the pseudo-wavefunction approach. In the case of spin-flip TDDFT, we provide a formal proof that the derivative couplings obtained using response theory are identical to those obtained from the pseudo-wavefunction formulation, which validates our previous implementation based on the latter formalism.

  5. Solvable quadratic Lie algebras

    Institute of Scientific and Technical Information of China (English)

    ZHU; Linsheng

    2006-01-01

    A Lie algebra endowed with a nondegenerate, symmetric, invariant bilinear form is called a quadratic Lie algebra. In this paper, the author investigates the structure of solvable quadratic Lie algebras, in particular, the solvable quadratic Lie algebras whose Cartan subalgebras consist of semi-simple elements, the author presents a procedure to construct a class of quadratic Lie algebras from the point of view of cohomology and shows that all solvable quadratic Lie algebras can be obtained in this way.

  6. Quantum quadratic operators and processes

    CERN Document Server

    Mukhamedov, Farrukh

    2015-01-01

    Covering both classical and quantum approaches, this unique and self-contained book presents the most recent developments in the theory of quadratic stochastic operators and their Markov and related processes. The asymptotic behavior of dynamical systems generated by classical and quantum quadratic operators is investigated and various properties of quantum quadratic operators are studied, providing an insight into the construction of quantum channels. This book is suitable as a textbook for an advanced undergraduate/graduate level course or summer school in quantum dynamical systems. It can also be used as a reference book by researchers looking for interesting  problems to work on, or useful techniques and discussions of particular problems. Since it includes the latest developments in the fields of quadratic dynamical systems, Markov processes and quantum stochastic processes, researchers at all levels are likely to find the book inspiring and useful.

  7. From the double-helix to novel approaches to the sequencing of large genomes.

    Science.gov (United States)

    Szybalski, W

    1993-12-15

    Elucidation of the structure of DNA by Watson and Crick [Nature 171 (1953) 737-738] has led to many crucial molecular experiments, including studies on DNA replication, transcription, physical mapping, and most recently to serious attempts directed toward the sequencing of large genomes [Watson, Science 248 (1990) 44-49]. I am totally convinced of the great importance of the Human Genome Project, and toward achieving this goal I strongly favor 'top-down' approaches consisting of the physical mapping and preparation of contiguous 50-100-kb fragments directly from the genome, followed by their automated sequencing based on the rapid assembly of primers by hexamer ligation together with primer walking. Our 'top-down' procedures totally avoids conventional cloning, subcloning and random sequencing, which are the elements of the present 'bottom-up' procedures. Fragments of 50-100 kb are prepared in sufficient quantities either by in vitro excision with rare-cutting restriction systems (including Achilles' heel cleavage [AC] or the RecA-AC procedures of Koob et al. [Nucleic Acids Res. 20 (1992) 5831-5836]) or by in vivo excision and amplification using the yeast FRT/Flp system or the phage lambda att/Int system. Such fragments, when derived directly from the Escherichia coli genome, are arranged in consecutive order, so that 50 specially constructed strains of E. coli would supply 50 end-to-end arranged approx. 100-kb fragments, which will cover the entire approx. 5-Mb E. coli genome. For the 150-Mb Drosophila melanogaster genome, 1500 of such consecutive 100-kb fragments (supplied by 1500 strains) are required to cover the entire genome. The fragments will be sequenced by the SPEL-6 method involving hexamer ligation [Szybalski, Gene 90 (1990) 177-178; Fresenius J. Anal. Chem. 4 (1992) 343] and primer walking. The 18-mer primers are synthesized in only a few minutes from three contiguous hexamers annealed to the DNA strand to be sequenced when using an over 100-fold

  8. A Novel Approach for Modeling and Simulation of Helix Twisting Structure Based on Mass-Spring Model

    Directory of Open Access Journals (Sweden)

    Zhongbin Wang

    2013-01-01

    Full Text Available In order to improve the modeling efficiency and realize the deformation simulation of helix twisting structure, a computer-aided design system based on mass-spring model is developed. The geometry structure of helix twisting structure is presented and mass-spring model is applied in the deformation simulation. Moreover, the key technologies such as coordinate mapping, system render and system architecture are elaborated. Finally, a prototype system is developed with Visual C++ and OpenGL, and the proposed system is proved efficient through a comparison experiment.

  9. 创新三螺旋模型的计量研究与实践进展*%A Review of Measuring the Triple Helix Using Quantitative Approach

    Institute of Scientific and Technical Information of China (English)

    邹益民; 张智雄

    2013-01-01

    Triple Helix model has become the new innovation paradigm. We can measure the national innovation system and predict the effect of the implementation of the innovation and technology policy using quantitative indicators and approaches based on this model. On the basis of the theoretical analysis of the Triple Helix, mutual information,φcoefficient and partial correlation and the indicators based on vector space model are studied. In accordance with the data used,Triple Helix quantitative methods are divided into Scientometrics,Web-metrics and Social Informetics, and the advantages and disadvantages of each method are compared and analyzed. In addition,the quantita-tive approach of N Helix is also discussed in this paper.%  三螺旋模型已成为创新研究的新范式,如何利用其对国家创新系统的状态进行识别,并预测创新和技术政策的执行效果,需要定量化的指标和方法对其进行测度。在三螺旋理论分析的基础上,分别对互信息、φ系数和偏相关以及基于向量空间的三螺旋计量指标进行了研究,按照采用的数据和方法不同将三螺旋的计量化研究分为科学计量法、网络计量法以及社会信息计量法三类进行综述,对各个方法的优缺点进行了对比和分析,并对N螺旋的计量方法进行了研究。

  10. Successive quadratic programming multiuser detector

    Institute of Scientific and Technical Information of China (English)

    Mu Xuewen; Zhang Yaling; Liu Sanyang

    2007-01-01

    Based on the semidefinite programming relaxation of the CDMA maximum likelihood multiuser detection problem,a detection strategy by the successive quadratic programming algorithm is presented. Coupled with the randomized cut generation scheme, the suboptimal solution of the multiuser detection problem in obtained. Compared to the interior point methods previously reported based on semidefinite programming, simulations demonstrate that the successive quadratic programming algorithm often yields the similar BER performances of the multiuser detection problem. But the average CPU time of this approach is significantly reduced.

  11. The quadratic Fock functor

    CERN Document Server

    Accardi, Luigi

    2009-01-01

    We construct the quadratic analogue of the boson Fock functor. While in the first order case all contractions on the 1--particle space can be second quantized, the semigroup of contractions that admit a quadratic second quantization is much smaller due to the nonlinearity. Within this semigroup we characterize the unitary and the isometric elements.

  12. Quadratic eigenvalue problems.

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, Timothy Francis; Day, David Minot

    2007-04-01

    In this report we will describe some nonlinear eigenvalue problems that arise in the areas of solid mechanics, acoustics, and coupled structural acoustics. We will focus mostly on quadratic eigenvalue problems, which are a special case of nonlinear eigenvalue problems. Algorithms for solving the quadratic eigenvalue problem will be presented, along with some example calculations.

  13. Criterion for the simultaneous selection of a working correlation structure and either generalized estimating equations or the quadratic inference function approach.

    Science.gov (United States)

    Westgate, Philip M

    2014-05-01

    Generalized estimating equations (GEE) are commonly used for the marginal analysis of correlated data, although the quadratic inference function (QIF) approach is an alternative that is increasing in popularity. This method optimally combines distinct sets of unbiased estimating equations that are based upon a working correlation structure, therefore asymptotically increasing or maintaining estimation efficiency relative to GEE. However, in finite samples, additional estimation variability arises when combining these sets of estimating equations, and therefore the QIF approach is not guaranteed to work as well as GEE. Furthermore, estimation efficiency can be improved for both analysis methods by accurate modeling of the correlation structure. Our goal is to improve parameter estimation, relative to existing methods, by simultaneously selecting a working correlation structure and choosing between GEE and two versions of the QIF approach. To do this, we propose the use of a criterion based upon the trace of the empirical covariance matrix (TECM). To make GEE and both QIF versions directly comparable for any given working correlation structure, the proposed TECM utilizes a penalty to account for the finite-sample variance inflation that can occur with either version of the QIF approach. Via a simulation study and in application to a longitudinal study, we show that penalizing the variance inflation that occurs with the QIF approach is necessary and that the proposed criterion works very well. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. The explicit dependence of quadrat variance on the ratio of clump size to quadrat size.

    Science.gov (United States)

    Ferrandino, Francis J

    2005-05-01

    ABSTRACT In the past decade, it has become common practice to pool mapped binary epidemic data into quadrats. The resultant "quadrat counts" can then be analyzed by fitting them to a probability distribution (i.e., betabinomial). Often a binary form of Taylor's power law is used to relate the quadrat variance to the quadrat mean. The fact that there is an intrinsic dependence of such analyses on quadrat size and shape is well known. However, a clear-cut exposition of the direct connection between the spatial properties of the two-dimensional pattern of infected plants in terms of the geometry of the quadrat and the results of quadrat-based analyses is lacking. This problem was examined both empirically and analytically. The empirical approach is based on a set of stochastically generated "mock epidemics" using a Neyman-Scott cluster process. The resultant spatial point-patterns of infected plants have a fixed number of disease foci characterized by a known length scale (monodisperse) and saturated to a known disease level. When quadrat samples of these epidemics are fit to a beta-binomial distribution, the resulting measures of aggregation are totally independent of disease incidence and most strongly dependent on the ratio of the length scale of the quadrat to the length scale of spatial aggregation and to a lesser degree on disease saturation within individual foci. For the analytical approach, the mathematical form for the variation in the sum of random variates is coupled to the geometry of a quadrat through an assumed exponential autocorrelation function. The net result is an explicit equation expressing the intraquadrat correlation, quadrat variance, and the index of dispersion in terms of the ratio of the quadrat length scale to the correlative length scale.

  15. Quantum bouncer with quadratic dissipation

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, G. [NanoScience Technology Center, University of Central Florida, Orlando, FL 32826 (United States)]. e-mail: ggonzalez@physics.ucf.edu

    2008-07-01

    The energy loss due to a quadratic velocity-dependent force on a quantum particle bouncing off a perfectly reflecting surface is obtained for a full cycle of motion. We approach this problem by means of a new, effective, phenomenological Hamiltonian which corresponds to the actual energy of the system and obtain the correction to the eigenvalues of the energy in first-order quantum perturbation theory for the case of weak dissipation. (Author)

  16. Quantum bouncer with quadratic dissipation

    Science.gov (United States)

    González, G.

    2008-02-01

    The energy loss due to a quadratic velocity dependent force on a quantum particle bouncing on a perfectly reflecting surface is obtained for a full cycle of motion. We approach this problem by means of a new effective phenomenological Hamiltonian which corresponds to the actual energy of the system and obtained the correction to the eigenvalues of the energy in first order quantum perturbation theory for the case of weak dissipation.

  17. A Mixed-Binary Convex Quadratic Reformulation for Box-Constrained Nonconvex Quadratic Integer Program

    OpenAIRE

    Xia, Yong; Han, Ying-Wei

    2014-01-01

    In this paper, we propose a mixed-binary convex quadratic programming reformulation for the box-constrained nonconvex quadratic integer program and then implement IBM ILOG CPLEX 12.6 to solve the new model. Computational results demonstrate that our approach clearly outperform the very recent state-of-the-art solvers.

  18. Multistage quadratic stochastic programming

    Science.gov (United States)

    Lau, Karen K.; Womersley, Robert S.

    2001-04-01

    Quadratic stochastic programming (QSP) in which each subproblem is a convex piecewise quadratic program with stochastic data, is a natural extension of stochastic linear programming. This allows the use of quadratic or piecewise quadratic objective functions which are essential for controlling risk in financial and project planning. Two-stage QSP is a special case of extended linear-quadratic programming (ELQP). The recourse functions in QSP are piecewise quadratic convex and Lipschitz continuous. Moreover, they have Lipschitz gradients if each QP subproblem is strictly convex and differentiable. Using these properties, a generalized Newton algorithm exhibiting global and superlinear convergence has been proposed recently for the two stage case. We extend the generalized Newton algorithm to multistage QSP and show that it is globally and finitely convergent under suitable conditions. We present numerical results on randomly generated data and modified publicly available stochastic linear programming test sets. Efficiency schemes on different scenario tree structures are discussed. The large-scale deterministic equivalent of the multistage QSP is also generated and their accuracy compared.

  19. A new numerical approach to solve Thomas-Fermi model of an atom using bio-inspired heuristics integrated with sequential quadratic programming.

    Science.gov (United States)

    Raja, Muhammad Asif Zahoor; Zameer, Aneela; Khan, Aziz Ullah; Wazwaz, Abdul Majid

    2016-01-01

    In this study, a novel bio-inspired computing approach is developed to analyze the dynamics of nonlinear singular Thomas-Fermi equation (TFE) arising in potential and charge density models of an atom by exploiting the strength of finite difference scheme (FDS) for discretization and optimization through genetic algorithms (GAs) hybrid with sequential quadratic programming. The FDS procedures are used to transform the TFE differential equations into a system of nonlinear equations. A fitness function is constructed based on the residual error of constituent equations in the mean square sense and is formulated as the minimization problem. Optimization of parameters for the system is carried out with GAs, used as a tool for viable global search integrated with SQP algorithm for rapid refinement of the results. The design scheme is applied to solve TFE for five different scenarios by taking various step sizes and different input intervals. Comparison of the proposed results with the state of the art numerical and analytical solutions reveals that the worth of our scheme in terms of accuracy and convergence. The reliability and effectiveness of the proposed scheme are validated through consistently getting optimal values of statistical performance indices calculated for a sufficiently large number of independent runs to establish its significance.

  20. Azithromycin assay in drug formulations: Validation of a HPTLC method with a quadratic polynomial calibration model using the accuracy profile approach.

    Science.gov (United States)

    Bouklouze, A; Kharbach, M; Cherrah, Y; Vander Heyden, Y

    2017-03-01

    Many different assaying high performance thin layer chromatography (HPTLC) methods have been developed and validated in order to be used in routine analysis in different analytical fields. Validation often starts by the evaluation of the linearity of the calibration curve. Frequently, if the correlation coefficient is close to one, the linear calibration curve model is considered to be proper to predict the unknown concentration in the sample. But is this simple model effective to assess the behavior of the response of an HPTLC method as a function of concentration. To answer this question, a method for the determination of azithromycin by HPTLC has been developed and validated following both the classical approach and that based on the accuracy profile. Silica gel plates with fluorescence indicator F254 and chloroform - ethanol - 25% ammonia 6:14:0.2 (v/v/v) as mobile phase were used. Analysis was carried out in reflectance mode at 483nm. The RF of azithromycin was 0.53. The validation based on the classical approach, shows that the behavior is not linear, even though r(2)=0.999 because the lack of fit test is significant (Pquadratic regression model, show that the former results is a β-expectation tolerance interval outside the acceptance limits, while with the latter, this interval is within the limits of ±5% acceptability for a range which extends from 0.2 to 1.0μg/zone. With the quadratic model, the method showed to be precise and accurate. Copyright © 2016 Académie Nationale de Pharmacie. Published by Elsevier Masson SAS. All rights reserved.

  1. Semidefinite programming for quadratically constrained quadratic programs

    Science.gov (United States)

    Olkin, Julia A.; Titterton, Paul J., Jr.

    1995-06-01

    We consider the linear least squares problem subject to multiple quadratic constraints, which is motivated by a practical application in controller design. We use the techniques of convex optimization, in particluar, interior-point methods for semi-definite programming. We reduce a quasi-convex potential function. Each iteration requires calculating a primal and dual search direction and minimizing along the plane defined by these search directions. The primal search direction requires solving a least squares problem whose matrix is composed of a block- Toeplitz portion plus other structured matrices. We make use of Kronecker products and FFTs to greatly reduce the calculation. In addition, the matrix updates and matrix inverses in the plane search are actually low-rank updates to structured matrices so we are able to further reduce the flops required. Consequently, we can design controllers for problems of considerable size.

  2. On Convex Quadratic Approximation

    NARCIS (Netherlands)

    den Hertog, D.; de Klerk, E.; Roos, J.

    2000-01-01

    In this paper we prove the counterintuitive result that the quadratic least squares approximation of a multivariate convex function in a finite set of points is not necessarily convex, even though it is convex for a univariate convex function. This result has many consequences both for the field of

  3. On Convex Quadratic Approximation

    NARCIS (Netherlands)

    den Hertog, D.; de Klerk, E.; Roos, J.

    2000-01-01

    In this paper we prove the counterintuitive result that the quadratic least squares approximation of a multivariate convex function in a finite set of points is not necessarily convex, even though it is convex for a univariate convex function. This result has many consequences both for the field of

  4. On Quadratic Differential Forms

    NARCIS (Netherlands)

    Willems, J.C.; Trentelman, H.L.

    1998-01-01

    This paper develops a theory around the notion of quadratic differential forms in the context of linear differential systems. In many applications, we need to not only understand the behavior of the system variables but also the behavior of certain functionals of these variables. The obvious cases w

  5. Aspects of Quadratic Gravity

    CERN Document Server

    Alvarez-Gaume, Luis; Kounnas, Costas; Lust, Dieter; Riotto, Antonio

    2016-01-01

    We discuss quadratic gravity where terms quadratic in the curvature tensor are included in the action. After reviewing the corresponding field equations, we analyze in detail the physical propagating modes in some specific backgrounds. First we confirm that the pure $R^2$ theory is indeed ghost free. Then we point out that for flat backgrounds the pure $R^2$ theory propagates only a scalar massless mode and no spin-two tensor mode. However, the latter emerges either by expanding the theory around curved backgrounds like de Sitter or anti-de Sitter, or by changing the long-distance dynamics by introducing the standard Einstein term. In both cases, the theory is modified in the infrared and a propagating graviton is recovered. Hence we recognize a subtle interplay between the UV and IR properties of higher order gravity. We also calculate the corresponding Newton's law for general quadratic curvature theories. Finally, we discuss how quadratic actions may be obtained from a fundamental theory like string- or M-...

  6. quadratic spline finite element method

    Directory of Open Access Journals (Sweden)

    A. R. Bahadir

    2002-01-01

    Full Text Available The problem of heat transfer in a Positive Temperature Coefficient (PTC thermistor, which may form one element of an electric circuit, is solved numerically by a finite element method. The approach used is based on Galerkin finite element using quadratic splines as shape functions. The resulting system of ordinary differential equations is solved by the finite difference method. Comparison is made with numerical and analytical solutions and the accuracy of the computed solutions indicates that the method is well suited for the solution of the PTC thermistor problem.

  7. Hidden conic quadratic representation of some nonconvex quadratic optimization problems

    NARCIS (Netherlands)

    Ben-Tal, A.; den Hertog, D.

    2014-01-01

    The problem of minimizing a quadratic objective function subject to one or two quadratic constraints is known to have a hidden convexity property, even when the quadratic forms are indefinite. The equivalent convex problem is a semidefinite one, and the equivalence is based on the celebrated S-lemma

  8. A Constructive Transition from Linear to Quadratic Functions.

    Science.gov (United States)

    Movshovitz-Hadar, Nitsa

    1993-01-01

    Presents an approach to quadratic functions that draws upon knowledge of linear functions by looking at the product of two linear functions. Then considers the quadratic function as the sum of three monomials. Potential advantages of each approach are discussed. (Contains 17 references.) (MDH)

  9. Extended gcd of quadratic integers

    CERN Document Server

    Miled, Abdelwaheb

    2010-01-01

    Computation of the extended gcd of two quadratic integers. The ring of integers considered is principal but could be euclidean or not euclidean ring. This method rely on principal ideal ring and reduction of binary quadratic forms.

  10. On Characterization of Quadratic Splines

    DEFF Research Database (Denmark)

    Chen, B. T.; Madsen, Kaj; Zhang, Shuzhong

    2005-01-01

    A quadratic spline is a differentiable piecewise quadratic function. Many problems in numerical analysis and optimization literature can be reformulated as unconstrained minimizations of quadratic splines. However, only special cases of quadratic splines are studied in the existing literature...... between the convexity of a quadratic spline function and the monotonicity of the corresponding LCP problem. It is shown that, although both conditions lead to easy solvability of the problem, they are different in general......., and algorithms are developed on a case by case basis. There lacks an analytical representation of a general or even a convex quadratic spline. The current paper fills this gap by providing an analytical representation of a general quadratic spline. Furthermore, for convex quadratic spline, it is shown...

  11. PSQP: Puzzle Solving by Quadratic Programming.

    Science.gov (United States)

    Andalo, Fernanda A; Taubin, Gabriel; Goldenstein, Siome

    2017-02-01

    In this article we present the first effective method based on global optimization for the reconstruction of image puzzles comprising rectangle pieces-Puzzle Solving by Quadratic Programming (PSQP). The proposed novel mathematical formulation reduces the problem to the maximization of a constrained quadratic function, which is solved via a gradient ascent approach. The proposed method is deterministic and can deal with arbitrary identical rectangular pieces. We provide experimental results showing its effectiveness when compared to state-of-the-art approaches. Although the method was developed to solve image puzzles, we also show how to apply it to the reconstruction of simulated strip-shredded documents, broadening its applicability.

  12. Guises and disguises of quadratic divergences

    Energy Technology Data Exchange (ETDEWEB)

    Cherchiglia, A.L., E-mail: adriano@fisica.ufmg.br [Departamento de Física, ICEx, Universidade Federal de Minas Gerais, P.O. BOX 702, 30.161-970, Belo Horizonte, MG (Brazil); Vieira, A.R., E-mail: arvieira@fisica.ufmg.br [Departamento de Física, ICEx, Universidade Federal de Minas Gerais, P.O. BOX 702, 30.161-970, Belo Horizonte, MG (Brazil); Hiller, Brigitte, E-mail: brigitte@teor.fis.uc.pt [Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-516 Coimbra (Portugal); Baêta Scarpelli, A.P., E-mail: scarpelli.apbs@dpf.gov.br [Setor Técnico-Científico, Departamento de Polícia Federal, Rua Hugo D’Antola, 95 - Lapa, São Paulo (Brazil); Sampaio, Marcos, E-mail: marcos.sampaio@durham.ac.uk [Departamento de Física, ICEx, Universidade Federal de Minas Gerais, P.O. BOX 702, 30.161-970, Belo Horizonte, MG (Brazil); Centre for Particle Theory, Department of Mathematical Sciences, Durham University, South Road Durham DH1 3LE (United Kingdom)

    2014-12-15

    In this contribution, we present a new perspective on the control of quadratic divergences in quantum field theory, in general, and in the Higgs naturalness problem, in particular. Our discussion is essentially based on an approach where UV divergences are parameterized, after being reduced to basic divergent integrals (BDI) in one internal momentum, as functions of a cutoff and a renormalization group scale λ. We illustrate our proposal with well-known examples, such as the gluon vacuum self energy of QCD and the Higgs decay in two photons within this approach. We also discuss frameworks in effective low-energy QCD models, where quadratic divergences are indeed fundamental.

  13. Quadratic forms and Clifford algebras on derived stacks

    OpenAIRE

    Vezzosi, Gabriele

    2013-01-01

    In this paper we present an approach to quadratic structures in derived algebraic geometry. We define derived n-shifted quadratic complexes, over derived affine stacks and over general derived stacks, and give several examples of those. We define the associated notion of derived Clifford algebra, in all these contexts, and compare it with its classical version, when they both apply. Finally, we prove three main existence results for derived shifted quadratic forms over derived stacks, define ...

  14. Quadratic Interpolation Algorithm for Minimizing Tabulated Function

    Directory of Open Access Journals (Sweden)

    E. A. Youness

    2008-01-01

    Full Text Available Problem statement: The problem of finding the minimum value of objective function, when we know only some values of it, is needed in more practical fields. Quadratic interpolation algorithms are the famous tools deal with this kind of these problems. These algorithms interested with the polynomial space in which the objective function is approximated. Approach: In this study we approximated the objective function by a one dimensional quadratic polynomial. This approach saved the time and the effort to get the best point at which the objective is minimized. Results: The quadratic polynomial in each one of the steps of the proposed algorithm, accelerate the convergent to the best value of the objective function without taking into account all points of the interpolation set. Conclusion: Any n-dimensional problem of finding a minimal value of a function, given by some values, can be converted to one dimensional problem easier in deal.

  15. Double-helix stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Moroz, P.E.

    1997-09-01

    A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A {approx} 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-{beta} MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications.

  16. Waardecreatie in triple helix : Recepten voor triple helix samenwerking

    NARCIS (Netherlands)

    Vos, P.M.; Vries, F. de

    2016-01-01

    Om innovaties in het veiligheidsdomein te realiseren worden triple helix samenwerkingen gezien als een belangrijke motor. Een triple helix samenwerking is een tijdelijk samenwerkingsverband tussen drie of meer organisaties die middelen, risico’s en opbrengsten delen om individuele organisatiedoelen,

  17. The Wiener maximum quadratic assignment problem

    CERN Document Server

    Cela, Eranda; Woeginger, Gerhard J

    2011-01-01

    We investigate a special case of the maximum quadratic assignment problem where one matrix is a product matrix and the other matrix is the distance matrix of a one-dimensional point set. We show that this special case, which we call the Wiener maximum quadratic assignment problem, is NP-hard in the ordinary sense and solvable in pseudo-polynomial time. Our approach also yields a polynomial time solution for the following problem from chemical graph theory: Find a tree that maximizes the Wiener index among all trees with a prescribed degree sequence. This settles an open problem from the literature.

  18. Range-based estimation of quadratic variation

    DEFF Research Database (Denmark)

    Christensen, Kim; Podolskij, Mark

    In this paper, we propose using realized range-based estimation to draw inference about the quadratic variation of jump-diffusion processes. We also construct a new test of the hypothesis that an asset price has a continuous sample path. Simulated data shows that our approach is efficient, the test...

  19. Range-based estimation of quadratic variation

    DEFF Research Database (Denmark)

    Christensen, Kim; Podolskij, Mark

    This paper proposes using realized range-based estimators to draw inference about the quadratic variation of jump-diffusion processes. We also construct a range-based test of the hypothesis that an asset price has a continuous sample path. Simulated data shows that our approach is efficient...

  20. A CLASS OF QUADRATIC HAMILTONIAN SYSTEMS UNDER QUADRATIC PERTURBATION

    Institute of Scientific and Technical Information of China (English)

    丰建文; 陈士华

    2001-01-01

    This paper deals with a class of quadratic Hamiltonian systems with quadratic perturbation. The authors prove that if the first order Melnikov function M1(h) = 0 and the second order Melnikov function M2(h) ≡ 0, then the origin of the Hamiltonian system with small perturbation is a center.

  1. 可行逐步二次规划方法解非线性方程组%FEASIBLE SEQUENTIAL QUADRATIC PROGRAMMING APPROACHES TO THE SYSTEM OF NONLINEAR EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    聂普焱; 彭小飞

    2004-01-01

    We transform the system of nonlinear equations into a nonlinear programming problem, which is attacked by feasible sequential quadratic programming(FSQP) method.We do not employ standard least square approach.We divide the equations into two groups. One group, which contains the equations with zero residual,is treated as equality constraints. The square of other equations is regarded as objective function. Two groups are updated in every step.Therefore, the subproblem is updated at every step, which avoids the difficulty that it is required to lie in feasible region for FSQP.

  2. Helix reactor: great potential for flow chemistry

    NARCIS (Netherlands)

    Geerdink, P.; Runstraat, A. van den; Roelands, C.P.M.; Goetheer, E.L.V.

    2009-01-01

    The Helix reactor is highly suited for precise reaction control based on good hydrodynamics. The hydrodynamics are controlled by the Dean vortices, which create excellent heat transfer properties, approach plug flow and avoid turbulence. The flexibility of this reactor has been demonstrated using a

  3. Quadratic solitons as nonlocal solitons

    DEFF Research Database (Denmark)

    Nikolov, Nikola Ivanov; Neshev, D.; Bang, Ole

    2003-01-01

    We show that quadratic solitons are equivalent to solitons of a nonlocal Kerr medium. This provides new physical insight into the properties of quadratic solitons, often believed to be equivalent to solitons of an effective saturable Kerr medium. The nonlocal analogy also allows for analytical...

  4. On Characterization of Quadratic Splines

    DEFF Research Database (Denmark)

    Chen, B. T.; Madsen, Kaj; Zhang, Shuzhong

    2005-01-01

    that the representation can be refined in a neighborhood of a non-degenerate point and a set of non-degenerate minimizers. Based on these characterizations, many existing algorithms for specific convex quadratic splines are also finite convergent for a general convex quadratic spline. Finally, we study the relationship...

  5. SMOOTHING BY CONVEX QUADRATIC PROGRAMMING

    Institute of Scientific and Technical Information of China (English)

    Bing-sheng He; Yu-mei Wang

    2005-01-01

    In this paper, we study the relaxed smoothing problems with general closed convex constraints. It is pointed out that such problems can be converted to a convex quadratic minimization problem for which there are good programs in software libraries.

  6. Quadratic Tangles in Planar Algebras

    CERN Document Server

    Jones, Vaughan F R

    2010-01-01

    In planar algebras, we show how to project certain simple "quadratic" tangles onto the linear space spanned by "linear" and "constant" tangles. We obtain some corollaries about the principal graphs and annular structure of subfactors.

  7. Nonlinear predictive control of a boiler-turbine unit: A state-space approach with successive on-line model linearisation and quadratic optimisation.

    Science.gov (United States)

    Ławryńczuk, Maciej

    2017-03-01

    This paper details development of a Model Predictive Control (MPC) algorithm for a boiler-turbine unit, which is a nonlinear multiple-input multiple-output process. The control objective is to follow set-point changes imposed on two state (output) variables and to satisfy constraints imposed on three inputs and one output. In order to obtain a computationally efficient control scheme, the state-space model is successively linearised on-line for the current operating point and used for prediction. In consequence, the future control policy is easily calculated from a quadratic optimisation problem. For state estimation the extended Kalman filter is used. It is demonstrated that the MPC strategy based on constant linear models does not work satisfactorily for the boiler-turbine unit whereas the discussed algorithm with on-line successive model linearisation gives practically the same trajectories as the truly nonlinear MPC controller with nonlinear optimisation repeated at each sampling instant. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  8. Quadratic Hedging of Basis Risk

    Directory of Open Access Journals (Sweden)

    Hardy Hulley

    2015-02-01

    Full Text Available This paper examines a simple basis risk model based on correlated geometric Brownian motions. We apply quadratic criteria to minimize basis risk and hedge in an optimal manner. Initially, we derive the Föllmer–Schweizer decomposition for a European claim. This allows pricing and hedging under the minimal martingale measure, corresponding to the local risk-minimizing strategy. Furthermore, since the mean-variance tradeoff process is deterministic in our setup, the minimal martingale- and variance-optimal martingale measures coincide. Consequently, the mean-variance optimal strategy is easily constructed. Simple pricing and hedging formulae for put and call options are derived in terms of the Black–Scholes formula. Due to market incompleteness, these formulae depend on the drift parameters of the processes. By making a further equilibrium assumption, we derive an approximate hedging formula, which does not require knowledge of these parameters. The hedging strategies are tested using Monte Carlo experiments, and are compared with results achieved using a utility maximization approach.

  9. Ion-mediated nucleic acid helix-helix interactions.

    Science.gov (United States)

    Tan, Zhi-Jie; Chen, Shi-Jie

    2006-07-15

    Salt ions are essential for the folding of nucleic acids. We use the tightly bound ion (TBI) model, which can account for the correlations and fluctuations for the ions bound to the nucleic acids, to investigate the electrostatic free-energy landscape for two parallel nucleic acid helices in the solution of added salt. The theory is based on realistic atomic structures of the helices. In monovalent salt, the helices are predicted to repel each other. For divalent salt, while the mean-field Poisson-Boltzmann theory predicts only the repulsion, the TBI theory predicts an effective attraction between the helices. The helices are predicted to be stabilized at an interhelix distance approximately 26-36 A, and the strength of the attractive force can reach -0.37 k(B)T/bp for helix length in the range of 9-12 bp. Both the stable helix-helix distance and the strength of the attraction are strongly dependent on the salt concentration and ion size. With the increase of the salt concentration, the helix-helix attraction becomes stronger and the most stable helix-helix separation distance becomes smaller. For divalent ions, at very high ion concentration, further addition of ions leads to the weakening of the attraction. Smaller ion size causes stronger helix-helix attraction and stabilizes the helices at a shorter distance. In addition, the TBI model shows that a decrease in the solvent dielectric constant would enhance the ion-mediated attraction. The theoretical findings from the TBI theory agree with the experimental measurements on the osmotic pressure of DNA array as well as the results from the computer simulations.

  10. Students' understanding of quadratic equations

    Science.gov (United States)

    López, Jonathan; Robles, Izraim; Martínez-Planell, Rafael

    2016-05-01

    Action-Process-Object-Schema theory (APOS) was applied to study student understanding of quadratic equations in one variable. This required proposing a detailed conjecture (called a genetic decomposition) of mental constructions students may do to understand quadratic equations. The genetic decomposition which was proposed can contribute to help students achieve an understanding of quadratic equations with improved interrelation of ideas and more flexible application of solution methods. Semi-structured interviews with eight beginning undergraduate students explored which of the mental constructions conjectured in the genetic decomposition students could do, and which they had difficulty doing. Two of the mental constructions that form part of the genetic decomposition are highlighted and corresponding further data were obtained from the written work of 121 undergraduate science and engineering students taking a multivariable calculus course. The results suggest the importance of explicitly considering these two highlighted mental constructions.

  11. Finite dimensional quadratic Lie superalgebras

    CERN Document Server

    Jarvis, Peter; Yates, Luke

    2010-01-01

    We consider a special class of Z_2-graded, polynomial algebras of degree 2, which we call quadratic Lie superalgebras. Starting from the formal definition, we discuss the generalised Jacobi relations in the context of the Koszul property, and give a proof of the PBW basis theorem. We give several concrete examples of quadratic Lie superalgebras for low dimensional cases, and discuss aspects of their structure constants for the `type I' class. Based on the factorisation of the enveloping algebra, we derive the Kac module construction for typical and atypical modules, and a related direct construction of irreducible modules due to Gould. We investigate the method for one specific case, the quadratic generalisation gl_2(n/1) of the Lie superalgebra sl(n/1). We formulate the general atypicality conditions at level 1, and present an analysis of zero-and one-step atypical modules for a certain family of Kac modules.

  12. Folding pathways of a helix-turn-helix model protein

    CERN Document Server

    Hoffmann, D

    1997-01-01

    A small model polypeptide represented in atomic detail is folded using Monte Carlo dynamics. The polypeptide is designed to have a native conformation similar to the central part of the helix-turn-helix protein ROP. Starting from a beta-strand conformation or two different loop conformations of the protein glutamine synthetase, six trajectories are generated using the so-called window move in dihedral angle space. This move changes conformations locally and leads to realistic, quasi-continuously evolving trajectories. Four of the six trajectories end in stable native-like conformations. Their folding pathways show a fast initial development of a helix-bend-helix motif, followed by a dynamic behaviour predicted by the diffusion-collision model of Karplus and Weaver. The phenomenology of the pathways is consistent with experimental results.

  13. Integer Quadratic Quasi-polyhedra

    Science.gov (United States)

    Letchford, Adam N.

    This paper introduces two fundamental families of 'quasi-polyhedra' - polyhedra with a countably infinite number of facets - that arise in the context of integer quadratic programming. It is shown that any integer quadratic program can be reduced to the minimisation of a linear function over a quasi-polyhedron in the first family. Some fundamental properties of the quasi-polyhedra are derived, along with connections to some other well-studied convex sets. Several classes of facet-inducing inequalities are also derived. Finally, extensions to the mixed-integer case are briefly examined.

  14. Impurity solitons with quadratic nonlinearities

    DEFF Research Database (Denmark)

    Clausen, Carl A. Balslev; Torres, Juan P-; Torner, Lluis

    1998-01-01

    We fmd families of solitary waves mediated by parametric mixing in quadratic nonlinear media that are localized at point-defect impurities. Solitons localized at attractive impurities are found to be dynamically stable. It is shown that localization at the impurity modifies strongly the soliton p...

  15. Unramified extensions of quadratic fields

    Institute of Scientific and Technical Information of China (English)

    Wei Li; Dong Yang; Xianke Zhang

    2008-01-01

    Let K be a global quadratic field, then every unramified abelian extension of K is proved to be absolutely Galois when K is a number field or under some natural conditions when K is a function field. The absolute Galois group is also determined explicitly.

  16. Quadratic prediction of factor scores

    NARCIS (Netherlands)

    Wansbeek, T

    1999-01-01

    Factor scores are naturally predicted by means of their conditional expectation given the indicators y. Under normality this expectation is linear in y but in general it is an unknown function of y. II is discussed that under nonnormality factor scores can be more precisely predicted by a quadratic

  17. Quadratic Variation by Markov Chains

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Horel, Guillaume

    We introduce a novel estimator of the quadratic variation that is based on the the- ory of Markov chains. The estimator is motivated by some general results concerning filtering contaminated semimartingales. Specifically, we show that filtering can in prin- ciple remove the effects of market...

  18. Range-based estimation of quadratic variation

    DEFF Research Database (Denmark)

    Christensen, Kim; Podolskij, Mark

    In this paper, we propose using realized range-based estimation to draw inference about the quadratic variation of jump-diffusion processes. We also construct a new test of the hypothesis that an asset price has a continuous sample path. Simulated data shows that our approach is efficient, the te...... is well-sized and more powerful than a return-based t-statistic for sampling frequencies normally used in empirical work. Applied to equity data, we find that the intensity of the jump process is not as high as previously reported....

  19. Range-based estimation of quadratic variation

    DEFF Research Database (Denmark)

    Christensen, Kim; Podolskij, Mark

    This paper proposes using realized range-based estimators to draw inference about the quadratic variation of jump-diffusion processes. We also construct a range-based test of the hypothesis that an asset price has a continuous sample path. Simulated data shows that our approach is efficient, the ......, the test is well-sized and more powerful than a return-based t-statistic for sampling frequencies normally used in empirical work. Applied to equity data, we show that the intensity of the jump process is not as high as previously reported....

  20. The Quadratic Graver Cone, Quadratic Integer Minimization, and Extensions

    CERN Document Server

    Lee, Jon; Romanchuk, Lyubov; Weismantel, Robert

    2010-01-01

    We consider the nonlinear integer programming problem of minimizing a quadratic function over the integer points in variable dimension satisfying a system of linear inequalities. We show that when the Graver basis of the matrix defining the system is given, and the quadratic function lies in a suitable {\\em dual Graver cone}, the problem can be solved in polynomial time. We discuss the relation between this cone and the cone of positive semidefinite matrices, and show that none contains the other. So we can minimize in polynomial time some non-convex and some (including all separable) convex quadrics. We conclude by extending our results to efficient integer minimization of multivariate polynomial functions of arbitrary degree lying in suitable cones.

  1. Consensus-ADMM for General Quadratically Constrained Quadratic Programming

    Science.gov (United States)

    Huang, Kejun; Sidiropoulos, Nicholas D.

    2016-10-01

    Non-convex quadratically constrained quadratic programming (QCQP) problems have numerous applications in signal processing, machine learning, and wireless communications, albeit the general QCQP is NP-hard, and several interesting special cases are NP-hard as well. This paper proposes a new algorithm for general QCQP. The problem is first reformulated in consensus optimization form, to which the alternating direction method of multipliers (ADMM) can be applied. The reformulation is done in such a way that each of the sub-problems is a QCQP with only one constraint (QCQP-1), which is efficiently solvable irrespective of (non-)convexity. The core components are carefully designed to make the overall algorithm more scalable, including efficient methods for solving QCQP-1, memory efficient implementation, parallel/distributed implementation, and smart initialization. The proposed algorithm is then tested in two applications: multicast beamforming and phase retrieval. The results indicate superior performance over prior state-of-the-art methods.

  2. Clustered Self Organising Migrating Algorithm for the Quadratic Assignment Problem

    Science.gov (United States)

    Davendra, Donald; Zelinka, Ivan; Senkerik, Roman

    2009-08-01

    An approach of population dynamics and clustering for permutative problems is presented in this paper. Diversity indicators are created from solution ordering and its mapping is shown as an advantage for population control in metaheuristics. Self Organising Migrating Algorithm (SOMA) is modified using this approach and vetted with the Quadratic Assignment Problem (QAP). Extensive experimentation is conducted on benchmark problems in this area.

  3. Semismooth Newton method for quadratic programs with bound constraints

    Science.gov (United States)

    Daryina, A. N.; Izmailov, A. F.

    2009-10-01

    Convex quadratic programs with bound constraints are proposed to be solved by applying a semismooth Newton method to the corresponding variational inequality. Computational experiments demonstrate that, for strongly convex problems, this approach can be considerably more efficient than more traditional approaches.

  4. The triple helix frame for Small and Medium-sized Enterprises for innovation and development of offshore wind energy

    DEFF Research Database (Denmark)

    Brink, Tove; Madsen, Svend Ole

    2016-01-01

    from integrating SMEs in a triple helix context. The triple helix approach with government, university and industry participants typically include larger organisations. The research indicates that SMEs could join the triple helix and both contribute and receive benefit from their presence. The findings...

  5. The use of approaches the history of science in the teaching of Biology: A proposal to work the participation of scientist Rosalind Franklin in building the model of the DNA double helix

    Directory of Open Access Journals (Sweden)

    Etiane Ortiz

    2016-04-01

    Full Text Available In this article we present the results of an investigation conducted with academics from a course of Biological Sciences of North University of Paraná. We sought to investigate the virtues and difficulties encountered in the process of contextualization the episode of "discovery" of the DNA double helix. Therefore, an educational proposal was developed with the goal of working context of that episode emphasizing controversies in the history regarding the participation of scientist Rosalind Franklin in the construction of DNA model, based on a traditional approach and alternative in History of Science. Data were collected through questionnaires and records were analyzed according to the procedures of content analysis. The use of an approach based on the History of Science has proven effective in contextualizing the historical episode presented in this study, since, from the analysis of the data, it was observed that the students were able to understand the controversial episode at the end of didactic intervention and knew in general, how to differentiate the two types of approaches in the history of science that were used to treat the historical episode. However, this research also showed that the use of this approach is no easy task, since some difficulties were encountered during the investigation.

  6. Quadratic and 2-Crossed Modules of Algebras

    Institute of Scientific and Technical Information of China (English)

    Z. Arvasi; E. Ulualan

    2007-01-01

    In this work, we define the quadratic modules for commutative algebras and give relations among 2-crossed modules, crossed squares, quadratic modules and simplicial commutative algebras with Moore complex of length 2.

  7. Team Decision Problems with Convex Quadratic Constraints

    OpenAIRE

    Gattami, Ather

    2015-01-01

    In this paper, we consider linear quadratic team problems with an arbitrary number of quadratic constraints in both stochastic and deterministic settings. The team consists of players with different measurements about the state of nature. The objective of the team is to minimize a quadratic cost subject to additional finite number of quadratic constraints. We first consider the problem of countably infinite number of players in the team for a bounded state of nature with a Gaussian distributi...

  8. Thermal stability of collagen triple helix.

    Science.gov (United States)

    Xu, Yujia

    2009-01-01

    Chief among the challenges of characterizing the thermal stability of the collagen triple helix are the lack of the reversibility of the thermal transition and the presence of multiple folding-unfolding steps during the thermal transition which rarely follows the simple two-state, all-or-none mechanism. Despite of the difficulties inherited in the quantitative depiction of the thermal transition of collagen, biophysical studies combined with proteolysis and mutagenesis approaches using full-chain collagens, short synthetic peptides, and recombinant collagen fragments have revealed molecular features of the thermal unfolding of the subdomains of collagen and led to a better understanding of the diverse biological functions of this versatile protein. The subdomain of collagen generally refers to a segment of the long, rope-like triple helical molecule that can unfold cooperatively as an independent unit whose properties (their size, location, and thermal stability) are considered essential for the molecular recognition during the self-assembly of collagen and during the interactions of collagen with other macromolecules. While the unfolding of segments of the triple helix at temperatures below the apparent melting temperature of the molecule has been used to interpret much of the features of the thermal unfolding of full-chain collagens, the thermal studies of short, synthetic peptides have firmly established the molecular basis of the subdomains by clearly demonstrating the close dependence of the thermal stability of a triple helix on the constituent amino acid residues at the X and the Y positions of the characteristic Gly-X-Y repeating sequence patterns of the triple helix. Studies using recombinant collagen fragments further revealed that in the context of the long, linear molecule, the stability of a segment of the triple helix is also modulated by long-range impact of the local interactions such as the interchain salt bridges. Together, the combined approaches

  9. Quadratic forms for Feynman-Kac semigroups

    Energy Technology Data Exchange (ETDEWEB)

    Hibey, Joseph L. [Department of Electrical Engineering, University of Colorado at Denver, Campus Box 110, Denver, CO 80217 (United States)]. E-mail: joseph.hibey@cudenver.edu; Charalambous, Charalambos D. [Electrical and Computer Engineering Department, University of Cyprus, 75 Kallipoleos Avenue, Nicosia (Cyprus)]. E-mail: chadcha@ucy.ac.cy

    2006-05-15

    Some problems in a stochastic setting often involve the need to evaluate the Feynman-Kac formula that follows from models described in terms of stochastic differential equations. Equivalent representations in terms of partial differential equations are also of interest, and these establish the well-known connection between probabilistic and deterministic formulations of these problems. In this Letter, this connection is studied in terms of the quadratic form associated with the Feynman-Kac semigroup. The probability measures that naturally arise in this approach, and thus define how Brownian motion is killed at a specified rate while exiting a set, are interpreted as a random time change of the original stochastic differential equation. Furthermore, since random time changes alter the diffusion coefficients in stochastic differential equations while Girsanov-type measure transformations alter their drift coefficients, their simultaneous use should lead to more tractable solutions for some classes of problems. For example, the minimization of some quadratic forms leads to solutions that satisfy certain partial differential equations and, therefore, the techniques discussed provide a variational approach for finding these solutions.

  10. Orthogonality preserving infinite dimensional quadratic stochastic operators

    Energy Technology Data Exchange (ETDEWEB)

    Akın, Hasan [Department of Mathematics, Faculty of Education, Zirve University, Gaziantep, 27260 (Turkey); Mukhamedov, Farrukh [Department of Computational & Theoretical Sciences Faculty of Science, International Islamic University Malaysia P.O. Box, 141, 25710, Kuantan Pahang (Malaysia)

    2015-09-18

    In the present paper, we consider a notion of orthogonal preserving nonlinear operators. We introduce π-Volterra quadratic operators finite and infinite dimensional settings. It is proved that any orthogonal preserving quadratic operator on finite dimensional simplex is π-Volterra quadratic operator. In infinite dimensional setting, we describe all π-Volterra operators in terms orthogonal preserving operators.

  11. Extending the Scope of Robust Quadratic Optimization

    NARCIS (Netherlands)

    Marandi, Ahmadreza; Ben-Tal, A.; den Hertog, Dick; Melenberg, Bertrand

    2017-01-01

    In this paper, we derive tractable reformulations of the robust counterparts of convex quadratic and conic quadratic constraints with concave uncertainties for a broad range of uncertainty sets. For quadratic constraints with convex uncertainty, it is well-known that the robust counterpart is, in ge

  12. Global Optimization of a Class of Nonconvex Quadratically Constrained Quadratic Programming Problems

    Institute of Scientific and Technical Information of China (English)

    Yong XIA

    2011-01-01

    In this paper we study a class of nonconvex quadratically constrained quadratic programming problems generalized from relaxations of quadratic assignment problems.We show that each problem is polynomially solved.Strong duality holds if a redundant constraint is introduced.As an application,a new lower bound is proposed for the quadratic assignment problem.

  13. Quadratic 0-1 programming: Geometric methods and duality analysis

    Science.gov (United States)

    Liu, Chunli

    The unconstraint quadratic binary problem (UBQP), as a classical combinatorial problem, finds wide applications in broad field and human activities including engineering, science, finance, etc. The NP-hardness of the combinatorial problems makes a great challenge to solve the ( UBQP). The main purpose of this research is to develop high performance solution method for solving (UBQP) via the geometric properties of the objective ellipse contour and the optimal solution. This research makes several contributions to advance the state-of-the-art of geometric approach of (UBQP). These contributions include both theoretical and numerical aspects as stated below. In part I of this dissertation, certain rich geometric properties hidden behind quadratic 0-1 programming are investigated. Especially, we derive new lower bounding methods and variable fixation techniques for quadratic 0-1 optimization problems by investigating geometric features of the ellipse contour of a (perturbed) convex quadratic function. These findings further lead to some new optimality conditions for quadratic 0-1 programming. Integrating these novel solution schemes into a proposed solution algorithm of a branch-and-bound type, we obtain promising preliminary computational results. In part II of this dissertation, we present new results of the duality gap between the binary quadratic optimization problem and its Lagrangian dual. We first derive a necessary and sufficient condition for the zero duality gap and discuss its relationship with the polynomial solvability of the problem. We then characterize the zeroness of duality gap by the distance, delta, between the binary set and certain affine space C. Finally, we discuss a computational procedure of the distance delta. These results provide new insights into the duality gap and polynomial solvability of binary quadratic optimization problems.

  14. Simultaneous quadratic performance stabilization for linear time-delay systems

    Institute of Scientific and Technical Information of China (English)

    Chen Yuepeng; Zhou Zude; Liu Huanbin; Zhang Qingling

    2006-01-01

    A newly designed approach of simultaneous stabilization is given for linear discrete time-delay systems. The problem of stabilization for a collection of systems is discussed initially. Adequate condition are obtained in terms of linear matrix inequalities (LMIs) which are independent of time delays such that the resultant collection of discrete time-delay systems are stable with an upper bound of the quadratic performance index. Subsequently, controllers are designed such that the resultant closed-loop discrete time-delay systems are simultaneously stabilized with the upper bound of the quadratic performance index. Finally,a numerical example is given to illustrate the design method.

  15. ANOTHER LOOK AT LINEAR-QUADRATIC OPTIMIZATION PROBLEMS OVER TIME

    NARCIS (Netherlands)

    NIEUWENHUIS, JW

    1995-01-01

    We will study deterministic quadratic optimization problems over time with linear constraints by means of the behavioral approach of linear systems as developed by Willems (1986, 1989). We will start with a simple example from economics and embed this in a general framework. Then we will develop the

  16. Finding the Best Quadratic Approximation of a Function

    Science.gov (United States)

    Yang, Yajun; Gordon, Sheldon P.

    2011-01-01

    This article examines the question of finding the best quadratic function to approximate a given function on an interval. The prototypical function considered is f(x) = e[superscript x]. Two approaches are considered, one based on Taylor polynomial approximations at various points in the interval under consideration, the other based on the fact…

  17. Asymptotic Normality of Quadratic Estimators.

    Science.gov (United States)

    Robins, James; Li, Lingling; Tchetgen, Eric; van der Vaart, Aad

    2016-12-01

    We prove conditional asymptotic normality of a class of quadratic U-statistics that are dominated by their degenerate second order part and have kernels that change with the number of observations. These statistics arise in the construction of estimators in high-dimensional semi- and non-parametric models, and in the construction of nonparametric confidence sets. This is illustrated by estimation of the integral of a square of a density or regression function, and estimation of the mean response with missing data. We show that estimators are asymptotically normal even in the case that the rate is slower than the square root of the observations.

  18. Optimal control linear quadratic methods

    CERN Document Server

    Anderson, Brian D O

    2007-01-01

    This augmented edition of a respected text teaches the reader how to use linear quadratic Gaussian methods effectively for the design of control systems. It explores linear optimal control theory from an engineering viewpoint, with step-by-step explanations that show clearly how to make practical use of the material.The three-part treatment begins with the basic theory of the linear regulator/tracker for time-invariant and time-varying systems. The Hamilton-Jacobi equation is introduced using the Principle of Optimality, and the infinite-time problem is considered. The second part outlines the

  19. Factorization method of quadratic template

    Science.gov (United States)

    Kotyrba, Martin

    2017-07-01

    Multiplication of two numbers is a one-way function in mathematics. Any attempt to distribute the outcome to its roots is called factorization. There are many methods such as Fermat's factorization, Dixońs method or quadratic sieve and GNFS, which use sophisticated techniques fast factorization. All the above methods use the same basic formula differing only in its use. This article discusses a newly designed factorization method. Effective implementation of this method in programs is not important, it only represents and clearly defines its properties.

  20. Quadratic reactivity fuel cycle model

    Energy Technology Data Exchange (ETDEWEB)

    Lewins, J.D.

    1985-11-01

    For educational purposes it is highly desirable to provide simple yet realistic models for fuel cycle and fuel economy. In particular, a lumped model without recourse to detailed spatial calculations would be very helpful in providing the student with a proper understanding of the purposes of fuel cycle calculations. A teaching model for fuel cycle studies based on a lumped model assuming the summability of partial reactivities with a linear dependence of reactivity usefully illustrates fuel utilization concepts. The linear burnup model does not satisfactorily represent natural enrichment reactors. A better model, showing the trend of initial plutonium production before subsequent fuel burnup and fission product generation, is a quadratic fit. The study of M-batch cycles, reloading 1/Mth of the core at end of cycle, is now complicated by nonlinear equations. A complete account of the asymptotic cycle for any order of M-batch refueling can be given and compared with the linear model. A complete account of the transient cycle can be obtained readily in the two-batch model and this exact solution would be useful in verifying numerical marching models. It is convenient to treat the parabolic fit rho = 1 - tau/sup 2/ as a special case of the general quadratic fit rho = 1 - C/sub tau/ - (1 - C)tau/sup 2/ in suitably normalized reactivity and cycle time units. The parabolic results are given in this paper.

  1. A sequential quadratically constrained quadratic programming method with an augmented Lagrangian line search function

    Science.gov (United States)

    Tang, Chun-Ming; Jian, Jin-Bao

    2008-10-01

    Based on an augmented Lagrangian line search function, a sequential quadratically constrained quadratic programming method is proposed for solving nonlinearly constrained optimization problems. Compared to quadratic programming solved in the traditional SQP methods, a convex quadratically constrained quadratic programming is solved here to obtain a search direction, and the Maratos effect does not occur without any other corrections. The "active set" strategy used in this subproblem can avoid recalculating the unnecessary gradients and (approximate) Hessian matrices of the constraints. Under certain assumptions, the proposed method is proved to be globally, superlinearly, and quadratically convergent. As an extension, general problems with inequality and equality constraints as well as nonmonotone line search are also considered.

  2. An Algorithm for Solving Quadratic Programming Problems

    Directory of Open Access Journals (Sweden)

    V. Moraru

    1997-08-01

    Full Text Available Herein is investigated the method of solution of quadratic programming problems. The algorithm is based on the effective selection of constraints. Quadratic programming with constraints-equalities are solved with the help of an algorithm, so that matrix inversion is avoided, because of the more convenient organization of the Calculus. Optimal solution is determined in a finite number of iterations. It is discussed the extension of the algorithm over solving quadratic non-convex programming problems.

  3. A review of fast circle and helix fitting

    CERN Document Server

    Frühwirth, R; Waltenberger, W; Wroldsen, J

    2003-01-01

    Circle and helix fitting is of paramount importance in the data analysis of LHC experiments. We review several approaches to exact but fast fitting, including a recent development based on the projection of the measured points onto a second-order surface in space (a sphere or a paraboloid). We present results of a comparison with global and recursive linearized least-squares estimators.

  4. The Knowledge-Based Economy and the Triple Helix Model

    CERN Document Server

    Leydesdorff, Loet

    2012-01-01

    1. Introduction - the metaphor of a "knowledge-based economy"; 2. The Triple Helix as a model of the knowledge-based economy; 3. Knowledge as a social coordination mechanism; 4. Neo-evolutionary dynamics in a Triple Helix of coordination mechanism; 5. The operation of the knowledge base; 6. The restructuring of knowledge production in a KBE; 7. The KBE and the systems-of-innovation approach; 8. The KBE and neo-evolutionary theories of innovation; 8.1 The construction of the evolving unit; 8.2 User-producer relations in systems of innovation; 8.3 'Mode-2' and the production of scientific knowledge; 8.4 A Triple Helix model of innovations; 9. Empirical studies and simulations using the TH model; 10. The KBE and the measurement; 10.1 The communication of meaning and information; 10.2 The expectation of social structure; 10.3 Configurations in a knowledge-based economy

  5. The Random Quadratic Assignment Problem

    Science.gov (United States)

    Paul, Gerald; Shao, Jia; Stanley, H. Eugene

    2011-11-01

    The quadratic assignment problem, QAP, is one of the most difficult of all combinatorial optimization problems. Here, we use an abbreviated application of the statistical mechanics replica method to study the asymptotic behavior of instances in which the entries of at least one of the two matrices that specify the problem are chosen from a random distribution P. Surprisingly, the QAP has not been studied before using the replica method despite the fact that the QAP was first proposed over 50 years ago and the replica method was developed over 30 years ago. We find simple forms for C min and C max , the costs of the minimal and maximum solutions respectively. Notable features of our results are the symmetry of the results for C min and C max and their dependence on P only through its mean and standard deviation, independent of the details of P.

  6. Binary Quadratic Forms: A Historical View

    Science.gov (United States)

    Khosravani, Azar N.; Beintema, Mark B.

    2006-01-01

    We present an expository account of the development of the theory of binary quadratic forms. Beginning with the formulation and proof of the Two-Square Theorem, we show how the study of forms of the type x[squared] + ny[squared] led to the discovery of the Quadratic Reciprocity Law, and how this theorem, along with the concept of reduction relates…

  7. Quadratic Boost A-Source Impedance Network

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; Blaabjerg, Frede; Chub, Andrii

    2016-01-01

    A novel quadratic boost type A-source impedance network is proposed in this paper for realizing converters that demand a very high voltage gain. To achieve that, the proposed network uses an auto-transformer, whose obtained gain is quadratically dependent on the duty ratio and is presently not ma...

  8. Quadratic Boost A-Source Impedance Network

    DEFF Research Database (Denmark)

    Siwakoti, Yam Prasad; Blaabjerg, Frede; Chub, Andrii

    2016-01-01

    A novel quadratic boost A-source impedance network is proposed to realize converters that demand very high voltage gain. To satisfy the requirement, the network uses an autotransformer where the obtained gain is quadratically dependent on the duty ratio and is unmatched by any existing impedance ...

  9. Factorising a Quadratic Expression with Geometric Insights

    Science.gov (United States)

    Joarder, Anwar H.

    2015-01-01

    An algorithm is presented for factorising a quadratic expression to facilitate instruction and learning. It appeals to elementary geometry which may provide better insights to some students or teachers. There have been many methods for factorising a quadratic expression described in school text books. However, students often seem to struggle with…

  10. An example in linear quadratic optimal control

    NARCIS (Netherlands)

    Weiss, George; Zwart, Heiko J.

    1998-01-01

    We construct a simple example of a quadratic optimal control problem for an infinite-dimensional linear system based on a shift semigroup. This system has an unbounded control operator. The cost is quadratic in the input and the state, and the weighting operators are bounded. Despite its extreme

  11. An example in linear quadratic optimal control

    NARCIS (Netherlands)

    Weiss, George; Zwart, Heiko J.

    1998-01-01

    We construct a simple example of a quadratic optimal control problem for an infinite-dimensional linear system based on a shift semigroup. This system has an unbounded control operator. The cost is quadratic in the input and the state, and the weighting operators are bounded. Despite its extreme sim

  12. Molecular structure of the collagen triple helix.

    Science.gov (United States)

    Brodsky, Barbara; Persikov, Anton V

    2005-01-01

    The molecular conformation of the collagen triple helix confers strict amino acid sequence constraints, requiring a (Gly-X-Y)(n) repeating pattern and a high content of imino acids. The increasing family of collagens and proteins with collagenous domains shows the collagen triple helix to be a basic motif adaptable to a range of proteins and functions. Its rodlike domain has the potential for various modes of self-association and the capacity to bind receptors, other proteins, GAGs, and nucleic acids. High-resolution crystal structures obtained for collagen model peptides confirm the supercoiled triple helix conformation, and provide new information on hydrogen bonding patterns, hydration, sidechain interactions, and ligand binding. For several peptides, the helix twist was found to be sequence dependent, and such variation in helix twist may serve as recognition features or to orient the triple helix for binding. Mutations in the collagen triple-helix domain lead to a variety of human disorders. The most common mutations are single-base substitutions that lead to the replacement of one Gly residue, breaking the Gly-X-Y repeating pattern. A single Gly substitution destabilizes the triple helix through a local disruption in hydrogen bonding and produces a discontinuity in the register of the helix. Molecular information about the collagen triple helix and the effect of mutations will lead to a better understanding of function and pathology.

  13. Fusion arrest and collapse phenomena due to Kerr-nonlinearity in quadratic media

    DEFF Research Database (Denmark)

    Johansen, Steffen Kjær; Bang, Ole; Sørensen, Mads Peter

    2000-01-01

    Emphasizing collapse phenomena it is investigated to what extend the always present cubic nonlinearity affects the properties of soliton interaction in quadratic bulk media. An effective particle approach is applied and verified by numerical simulations....

  14. Microfluidic 3D Helix Mixers

    Directory of Open Access Journals (Sweden)

    Georgette B. Salieb-Beugelaar

    2016-10-01

    Full Text Available Polymeric microfluidic systems are well suited for miniaturized devices with complex functionality, and rapid prototyping methods for 3D microfluidic structures are increasingly used. Mixing at the microscale and performing chemical reactions at the microscale are important applications of such systems and we therefore explored feasibility, mixing characteristics and the ability to control a chemical reaction in helical 3D channels produced by the emerging thread template method. Mixing at the microscale is challenging because channel size reduction for improving solute diffusion comes at the price of a reduced Reynolds number that induces a strictly laminar flow regime and abolishes turbulence that would be desired for improved mixing. Microfluidic 3D helix mixers were rapidly prototyped in polydimethylsiloxane (PDMS using low-surface energy polymeric threads, twisted to form 2-channel and 3-channel helices. Structure and flow characteristics were assessed experimentally by microscopy, hydraulic measurements and chromogenic reaction, and were modeled by computational fluid dynamics. We found that helical 3D microfluidic systems produced by thread templating allow rapid prototyping, can be used for mixing and for controlled chemical reaction with two or three reaction partners at the microscale. Compared to the conventional T-shaped microfluidic system used as a control device, enhanced mixing and faster chemical reaction was found to occur due to the combination of diffusive mixing in small channels and flow folding due to the 3D helix shape. Thus, microfluidic 3D helix mixers can be rapidly prototyped using the thread template method and are an attractive and competitive method for fluid mixing and chemical reactions at the microscale.

  15. On Quadratic Variation of Martingales

    Indian Academy of Sciences (India)

    Rajeeva L Karandikar; B V Rao

    2014-08-01

    We give a construction of an explicit mapping $$\\Psi: D([0,∞),\\mathbb{R})→ D([0,∞),\\mathbb{R}),$$ where $D([0,∞), \\mathbb{R})$ denotes the class of real valued r.c.l.l. functions on $[0,∞)$ such that for a locally square integrable martingale $(M_t)$ with r.c.l.l. paths, $$\\Psi(M.())=A.()$$ gives the quadratic variation process (written usually as $[M,M]_t$) of $(M_t)$. We also show that this process $(A_t)$ is the unique increasing process $(B_t)$ such that $M_t^2-B_t$ is a local martingale, $B_0=0$ and $$\\mathbb{P}(( B)_t=[( M)_t]^2, 0 < ∞)=1.$$ Apart from elementary properties of martingales, the only result used is the Doob’s maximal inequality. This result can be the starting point of the development of the stochastic integral with respect to r.c.l.l. martingales.

  16. Multiple helix ecosystems for sustainable competitiveness

    CERN Document Server

    Ferreira, João; Farinha, Luís; Fernandes, Nuno

    2016-01-01

    This book discusses the main issues, challenges, opportunities, and trends involving the interactions between academia, industry, government and society. Specifically, it aims to explore how these interactions enhance the ways in which companies deliver products and services in order to achieve sustainable competitiveness in the marketplace. Sustainable competitiveness has been widely discussed by academics and practitioners, considering the importance of protecting the environment while sustaining the economic goals of organizations. The Quintuple Helix innovation model is a framework for facilitating knowledge, innovation and sustainable competitive advantage. It embeds the Triple and the Quadruple Helix models by adding a fifth helix, the “natural environment.” The Triple Helix model focuses on the university-industry-government triad, while the Quadruple adds civil society (the media- and culture-driven public) as a fourth helix. The Quintuple Helix model facilitates research, public policy, and pract...

  17. The Pure Virtual Braid Group Is Quadratic

    CERN Document Server

    Lee, Peter

    2011-01-01

    If an augmented algebra K over Q is filtered by powers of its augmentation ideal I, the associated graded algebra gr_I K need not in general be quadratic: although it is generated in degree 1, its relations may not be generated by homogeneous relations of degree 2. In this paper we give a criterion which is equivalent to gr_I K being quadratic. We apply this criterion to the group algebra of the pure virtual braid group (also known as the quasi-triangular group), and show that the corresponding associated graded algebra is quadratic.

  18. Specialization of Quadratic and Symmetric Bilinear Forms

    CERN Document Server

    Knebusch, Manfred

    2010-01-01

    The specialization theory of quadratic and symmetric bilinear forms over fields and the subsequent generic splitting theory of quadratic forms were invented by the author in the mid-1970's. They came to fruition in the ensuing decades and have become an integral part of the geometric methods in quadratic form theory. This book comprehensively covers the specialization and generic splitting theories. These theories, originally developed for fields of characteristic different from 2, are explored here without this restriction. In addition to chapters on specialization theory, generic splitting t

  19. Quadratic stabilization of switched nonlinear systems

    Institute of Scientific and Technical Information of China (English)

    DONG YaLi; FAN JiaoJiao; MEI ShengWei

    2009-01-01

    In this paper, the problem of quadratic stabilization of multi-input multi-output switched nonlinear systems under an arbitrary switching law is investigated. When switched nonlinear systems have uniform normal form and the zero dynamics of uniform normal form is asymptotically stable under an arbitrary switching law, state feedbacks are designed and a common quadratic Lyapunov function of all the closed-loop subsystems is constructed to realize quadratic stabilizability of the class of switched nonlinear systems under an arbitrary switching law. The results of this paper are also applied to switched linear systems.

  20. Parameter Optimization of Linear Quadratic Controller Based on Genetic Algorithm

    Institute of Scientific and Technical Information of China (English)

    LI Jimin; SHANG Chaoxuan; ZOU Minghu

    2007-01-01

    The selection of weighting matrix in design of the linear quadratic optimal controller is an important topic in the control theory. In this paper, an approach based on genetic algorithm is presented for selecting the weighting matrix for the optimal controller. Genetic algorithm is adaptive heuristic search algorithm premised on the evolutionary ideas of natural selection and genetic. In this algorithm, the fitness function is used to evaluate individuals and reproductive success varies with fitness. In the design of the linear quadratic optimal controller, the fitness function has relation to the anticipated step response of the system. Not only can the controller designed by this approach meet the demand of the performance indexes of linear quadratic controller, but also satisfy the anticipated step response of close-loop system. The method possesses a higher calculating efficiency and provides technical support for the optimal controller in engineering application. The simulation of a three-order single-input single-output (SISO) system has demonstrated the feasibility and validity of the approach.

  1. Collagen model peptides: Sequence dependence of triple-helix stability.

    Science.gov (United States)

    Persikov, A V; Ramshaw, J A; Brodsky, B

    2000-01-01

    The triple helix is a specialized protein motif, found in all collagens as well as in noncollagenous proteins involved in host defense. Peptides will adopt a triple-helical conformation if the sequence contains its characteristic features of Gly as every third residue and a high content of Pro and Hyp residues. Such model peptides have proved amenable to structural studies by x-ray crystallography and NMR spectroscopy, suitable for thermodynamic and kinetic analysis, and a valuable tool in characterizing the binding activities of the collagen triple helix. A systematic approach to understanding the amino acid sequence dependence of the collagen triple helix has been initiated, based on a set of host-guest peptides of the form, (Gly-Pro-Hyp)(3)-Gly-X-Y-(Gly-Pro-Hyp)(4). Comparison of their thermal stabilities has led to a propensity scale for the X and Y positions, and the additivity of contributions of individual residues is now under investigation. The local and global stability of the collagen triple helix is normally modulated by the residues in the X and Y positions, with every third position occupied by Gly in fibril-forming collagens. However, in collagen diseases, such as osteogenesis imperfecta, a single Gly may be substituted by another residue. Host-guest studies where the Gly is replaced by various amino acids suggest that the identity of the residue in the Gly position affects the degree of destabilization and the clinical severity of the disease.

  2. Structure of Solvable Quadratic Lie Algebras

    Institute of Scientific and Technical Information of China (English)

    ZHU Lin-sheng

    2005-01-01

    @@ Killing form plays a key role in the theory of semisimple Lie algebras. It is natural to extend the study to Lie algebras with a nondegenerate symmetric invariant bilinear form. Such a Lie algebra is generally called a quadratic Lie algebra which occur naturally in physics[10,12,13]. Besides semisimple Lie algebras, interesting quadratic Lie algebras include the Kac-Moody algebras and the Extended Affine Lie algebras.

  3. Compression limits in cascaded quadratic soliton compression

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Krolikowski, Wieslaw;

    2008-01-01

    Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency.......Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency....

  4. Radiotherapy treatment planning linear-quadratic radiobiology

    CERN Document Server

    Chapman, J Donald

    2015-01-01

    Understand Quantitative Radiobiology from a Radiation Biophysics PerspectiveIn the field of radiobiology, the linear-quadratic (LQ) equation has become the standard for defining radiation-induced cell killing. Radiotherapy Treatment Planning: Linear-Quadratic Radiobiology describes tumor cell inactivation from a radiation physics perspective and offers appropriate LQ parameters for modeling tumor and normal tissue responses.Explore the Latest Cell Killing Numbers for Defining Iso-Effective Cancer TreatmentsThe book compil

  5. Quadratic stabilization for uncertain stochastic systems

    Institute of Scientific and Technical Information of China (English)

    Jun'e FENG; Weihai ZHANG

    2005-01-01

    This paper discusses the robust quadratic stabilization control problem for stochastic uncertain systems,where the uncertain matrix is norm bounded,and the external disturbance is a stochastic process.Two kinds of controllers are designed,which include state feedback case and output feedback case.The conditions for the robust quadratic stabilization of stochastic uncertain systems are given via linear matrix inequalities.The detailed design methods are presented.Numerical examples show the effectiveness of our results.

  6. Cascaded quadratic soliton compression at 800 nm

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Moses, Jeffrey;

    2007-01-01

    We study soliton compression in quadratic nonlinear materials at 800 nm, where group-velocity mismatch dominates. We develop a nonlocal theory showing that efficient compression depends strongly on characteristic nonlocal time scales related to pulse dispersion.......We study soliton compression in quadratic nonlinear materials at 800 nm, where group-velocity mismatch dominates. We develop a nonlocal theory showing that efficient compression depends strongly on characteristic nonlocal time scales related to pulse dispersion....

  7. A NEW INEXACT SEQUENTIAL QUADRATIC PROGRAMMING ALGORITHM

    Institute of Scientific and Technical Information of China (English)

    倪勤

    2002-01-01

    This paper represents an inexact sequential quadratic programming (SQP ) algorithm which can solve nonlinear programming (NLP ) problems. An inexact solution of the quadratic programming subproblem is determined by a projection and contraction method such that only matrix-vector product is required. Some truncated criteria are chosen such that the algorithm is suitable to large scale NLP problem. The global convergence of the algorithm is proved.

  8. Optimal power flow using sequential quadratic programming

    Science.gov (United States)

    Nejdawi, Imad M.

    1999-11-01

    Optimal power flow (OPF) is an operational as well as a planning tool used by electric utilities to help them operate their network in the most economic and secure mode of operation. Various algorithms to solve the OPF problem evolved over the past three decades; linear programming (LP) techniques were among the major mathematical programming methods utilized. The linear models of the objective function and the linearization of the constraints are the main features of these techniques. The main advantages of the LP approach are simplicity and speed. Nonlinear programming techniques have been applied to OPF solution. The major drawback is the expensive solution of large sparse systems of equations. This research is concerned with the development of a new OPF solution algorithm using sequential quadratic programming (SQP). In this formulation, a small dense system the size of which is equal to the number of control variables is solved in an inner loop. The Jacobian and Hessian terms are calculated in an outer loop. The total number of outer loop iterations is comparable to those in an ordinary load flow in contrast to 20--30 iterations in other nonlinear methods. In addition, the total number of floating point operations is less than that encountered in direct methods by two orders of magnitude. We also model dispatch over a twenty four-hour time horizon in a transmission constrained power network that includes price-responsive loads where large energy customers can operate their loads in time intervals with lowest spot prices.

  9. Square Helix TWT for THz Frequencies

    DEFF Research Database (Denmark)

    Kotiranta, Mikko; Krozer, Viktor; Zhurbenko, Vitaliy

    2010-01-01

    A helix slow-wave structure with a square shape has been designed for use in traveling-wave tubes operating at terahertz frequencies. The square shape makes it compatible with microfabrication methods. A 3-D particle-in-cell simulation of a traveling-wave tube with such a helix indicates a gain...

  10. Kevlar: Transitioning Helix from Research to Practice

    Science.gov (United States)

    2015-04-01

    KEVLAR : TRANSITIONING HELIX FROM RESEARCH TO PRACTICE UNIVERSITY OF VIRGINIA APRIL 2015 FINAL TECHNICAL REPORT...DATES COVERED (From - To) FEB 2013 – NOV 2014 4. TITLE AND SUBTITLE KEVLAR : TRANSITIONING HELIX FROM RESEARCH TO PRACTICE 5a. CONTRACT NUMBER...possible exploitation. Our technology, called Kevlar , includes key security technologies are protective transformations and targeted recovery. The

  11. Thioamides in the collagen triple helix.

    Science.gov (United States)

    Newberry, Robert W; VanVeller, Brett; Raines, Ronald T

    2015-06-14

    To probe noncovalent interactions within the collagen triple helix, backbone amides were replaced with a thioamide isostere. This subtle substitution is the first in the collagen backbone that does not compromise thermostability. A triple helix with a thioamide as a hydrogen bond donor was found to be more stable than triple helices assembled from isomeric thiopeptides.

  12. Helix-packing motifs in membrane proteins.

    Science.gov (United States)

    Walters, R F S; DeGrado, W F

    2006-09-12

    The fold of a helical membrane protein is largely determined by interactions between membrane-imbedded helices. To elucidate recurring helix-helix interaction motifs, we dissected the crystallographic structures of membrane proteins into a library of interacting helical pairs. The pairs were clustered according to their three-dimensional similarity (rmsd universe of common transmembrane helix-pairing motifs is relatively simple. The largest cluster, which comprises 29% of the library members, consists of an antiparallel motif with left-handed packing angles, and it is frequently stabilized by packing of small side chains occurring every seven residues in the sequence. Right-handed parallel and antiparallel structures show a similar tendency to segregate small residues to the helix-helix interface but spaced at four-residue intervals. Position-specific sequence propensities were derived for the most populated motifs. These structural and sequential motifs should be quite useful for the design and structural prediction of membrane proteins.

  13. Soliton solutions for Davydov solitons in α-helix proteins

    Science.gov (United States)

    Taghizadeh, N.; Zhou, Qin; Ekici, M.; Mirzazadeh, M.

    2017-02-01

    The propagation equation for describing Davydov solitons in α-helix proteins has been investigated analytically. There are seven integration tools to extract analytical soliton solutions. They are the Ricatti equation expansion approach, ansatz scheme, improved extended tanh-equation method, the extend exp(-Ψ(τ)) -expansion method, the extended Jacobi elliptic function expansion method, the extended trial equation method and the extended G ' / G - expansion method.

  14. A Tight Linearization Strategy for Zero-One Quadratic Programming Problems

    CERN Document Server

    gharibi, Wajeb

    2012-01-01

    In this paper, we present a new approach to linearizing zero-one quadratic minimization problem which has many applications in computer science and communications. Our algorithm is based on the observation that the quadratic term of zero-one variables has two equivalent piece-wise formulations, convex and concave cases. The convex piece-wise objective function and/or constraints play a great role in deducing small linearization. Further tight strategies are also discussed.

  15. Two Reformulations for the Dynamic Quadratic Assignment Problem

    Directory of Open Access Journals (Sweden)

    Sirirat Muenvanichakul

    2010-01-01

    Full Text Available Problem statement: The Dynamic Quadratic Assignment Problem (DQAP, an NP-hard problem, is outlined and reformulated in two alternative models: Linearized model and logic-based model. Approach: The solution methods for both models based on combinatorial methods (Benders’ Decomposition and Approximate Dynamic Programming and constraint logic programming, respectively, are proposed. Results: Proofs of model equivalence and solution methodology are presented. Conclusion: Both proposed models are more simplified leading to possible hybrid adaptations of existing techniques for more practical approaches.

  16. Polyhedral combinatorics of the cardinality constrained quadratic knapsack problem and the quadratic selective travelling salesman problem

    DEFF Research Database (Denmark)

    Mak, Vicky; Thomadsen, Tommy

    2006-01-01

    This paper considers the cardinality constrained quadratic knapsack problem (QKP) and the quadratic selective travelling salesman problem (QSTSP). The QKP is a generalization of the knapsack problem and the QSTSP is a generalization of the travelling salesman problem. Thus, both problems are NP...

  17. Linear-quadratic control and quadratic differential forms for multidimensional behaviors

    NARCIS (Netherlands)

    Napp, D.; Trentelman, H.L.

    2011-01-01

    This paper deals with systems described by constant coefficient linear partial differential equations (nD-systems) from a behavioral point of view. In this context we treat the linear-quadratic control problem where the performance functional is the integral of a quadratic differential form. We look

  18. Comparative Study on the Adaptation and Growth Dynamics of the Helix pomatia and Helix aspersa Muller Terrestrial Snails Under Different Feeding Regimes

    Directory of Open Access Journals (Sweden)

    Adrian Toader-Williams

    2010-05-01

    Full Text Available We used Helix pomatia and Helix aspersa species and measure their growth as the snails were approaching the hibernation season. Helix pomatia 2yo shown a decrease in weight while being raised in enclosed parcels of 4sqm the younger Helix pomatia 1yo as well as Helix aspersa Muller demonstrated the ability to adapt relatively fast to the same conditions. We established 5 experimental lots in a Helix pomatia farm, GPS coordinates N46.606040 E23.599950. Control lot contained Taraxacum officinales, Sonchus oleraceus, Equisetum arvense and Atriplex hortensis, wild flora found within the farm. The other lots contained the same plants as the control lot plus different combinations of imported plants from other areals. The H. pomatia 2yo weight decreased in the control lot by a mean of -3.86% while H. aspersa 1yo marked an increase of +16.89% in the same lot during the same period. The lot containing lupinus polyphyllus delivered snails with weight gain of +24.66% for H. pomatia 2yo and an increase of only +1.98% for H. aspersa 1yo. As a contrast, H. pomatia 2yo gained only +7.72% while H. aspersa 1yo gained +28.89%, in the lot containing Lavanda officinalis, Foeniculum vulgare and Hyssopus officinalis among the other plants.

  19. Binary classification posed as a quadratically constrained quadratic programming and solved using particle swarm optimization

    Indian Academy of Sciences (India)

    DEEPAK KUMAR; A G RAMAKRISHNAN

    2016-03-01

    Particle swarm optimization (PSO) is used in several combinatorial optimization problems. In this work, particle swarms are used to solve quadratic programming problems with quadratic constraints. The central idea is to use PSO to move in the direction towards optimal solution rather than searching the entire feasibleregion. Binary classification is posed as a quadratically constrained quadratic problem and solved using the proposed method. Each class in the binary classification problem is modeled as a multidimensional ellipsoid to forma quadratic constraint in the problem. Particle swarms help in determining the optimal hyperplane or classification boundary for a data set. Our results on the Iris, Pima, Wine, Thyroid, Balance, Bupa, Haberman, and TAE datasets show that the proposed method works better than a neural network and the performance is close to that of a support vector machine

  20. Fast approximate quadratic programming for graph matching.

    Directory of Open Access Journals (Sweden)

    Joshua T Vogelstein

    Full Text Available Quadratic assignment problems arise in a wide variety of domains, spanning operations research, graph theory, computer vision, and neuroscience, to name a few. The graph matching problem is a special case of the quadratic assignment problem, and graph matching is increasingly important as graph-valued data is becoming more prominent. With the aim of efficiently and accurately matching the large graphs common in big data, we present our graph matching algorithm, the Fast Approximate Quadratic assignment algorithm. We empirically demonstrate that our algorithm is faster and achieves a lower objective value on over 80% of the QAPLIB benchmark library, compared with the previous state-of-the-art. Applying our algorithm to our motivating example, matching C. elegans connectomes (brain-graphs, we find that it efficiently achieves performance.

  1. Fast approximate quadratic programming for graph matching.

    Science.gov (United States)

    Vogelstein, Joshua T; Conroy, John M; Lyzinski, Vince; Podrazik, Louis J; Kratzer, Steven G; Harley, Eric T; Fishkind, Donniell E; Vogelstein, R Jacob; Priebe, Carey E

    2015-01-01

    Quadratic assignment problems arise in a wide variety of domains, spanning operations research, graph theory, computer vision, and neuroscience, to name a few. The graph matching problem is a special case of the quadratic assignment problem, and graph matching is increasingly important as graph-valued data is becoming more prominent. With the aim of efficiently and accurately matching the large graphs common in big data, we present our graph matching algorithm, the Fast Approximate Quadratic assignment algorithm. We empirically demonstrate that our algorithm is faster and achieves a lower objective value on over 80% of the QAPLIB benchmark library, compared with the previous state-of-the-art. Applying our algorithm to our motivating example, matching C. elegans connectomes (brain-graphs), we find that it efficiently achieves performance.

  2. Quadratic gravity: from weak to strong

    CERN Document Server

    Holdom, Bob

    2016-01-01

    More than three decades ago quadratic gravity was found to present a perturbative, renormalizable and asymptotically free theory of quantum gravity. Unfortunately the theory appeared to have problems with a spin-2 ghost. In this essay we revisit quadratic gravity in a different light by considering the case that the asymptotically free interaction flows to a strongly interacting regime. This occurs when the coefficient of the Einstein-Hilbert term is smaller than the scale $\\Lambda_{\\mathrm{QG}}$ where the quadratic couplings grow strong. Here QCD provides some useful insights. By pushing the analogy with QCD, we conjecture that the nonperturbative effects can remove the naive spin-2 ghost and lead to the emergence of general relativity in the IR.

  3. Modulation of the oligomerization of myelin proteolipid protein by transmembrane helix interaction motifs.

    Science.gov (United States)

    Ng, Derek P; Deber, Charles M

    2010-08-17

    Proteolipid protein (PLP) is a highly hydrophobic 276-residue integral membrane protein that constitutes more than 50% of the total protein in central nervous system myelin. Previous studies have shown that this protein exists in myelin as an oligomer rather than as a monomer, and mutations in PLP that lead to neurological disorders such as Pelizaeus-Merzbacher disease and spastic paraplegia type 2 have been reported to affect its normal oligomerization. Here we employ peptide-based and in vivo approaches to examine the role of the TM domain in the formation of PLP quaternary structure through homo-oligomeric helix-helix interactions. Focusing on the TM4 alpha-helix (sequence (239)FIAAFVGAAATLVSLLTFMIAATY(262)), the site of several disease-causing point mutations that involve putative small residue helix-helix interaction motifs in the TM4 sequence, we used SDS-PAGE, fluorescence resonance energy transfer, size-exclusion chromatography, and TOXCAT assays in an Escherichia coli membrane to show that the PLP TM4 helix readily assembles into varying oligomeric states. In addition, through targeted studies of the PLP TM4 alpha-helix with point mutations that selectively eliminate these small residue motifs via substitution of Gly, Ala, or Ser residues with Ile residues, we describe a potential mechanism through which disease-causing point mutations can lead to aberrant PLP assembly. The overall results suggest that TM segments in misfolded PLP monomers that expose and/or create surface-exposed helix-helix interaction sites that are normally masked may have consequences for disease.

  4. A CART extention using Quadratic Decision Borders

    DEFF Research Database (Denmark)

    Hartelius, Karsten

    1999-01-01

    In this article we put forward an extention to the hierarchical CART classification method which uses quadratic decision borders. The original CART applies univariate splits on individual variables as well as splits on combinations of variables to recursively partition the feature......-space into subsets which are successively more class-homogeneous. Guided by the fact that class-distributions in feature-space are very often hyper-elliptical shaped, we give an extension to the original CART which also uses quadratic shaped decision borders which can be modelled by a mean-vector and a dispersion...

  5. A CART extension using Quadratic Decision Borders

    DEFF Research Database (Denmark)

    Hartelius, Karsten

    1999-01-01

    In this article we put forward an extention to the hierarchical CART classification method which uses quadratic decision borders. The original CART applies univariate splits on individual variables as well as splits on combinations of variables to recursively partition the feature......-space into subsets which are successively more class-homogeneous. Guided by the fact that class-distributions in feature-space are very often hyper-elliptical shaped, we give an extension to the original CART which also uses quadratic shaped decision borders which can be modelled by a mean-vector and a dispersion...

  6. Quintessence with quadratic coupling to dark matter

    CERN Document Server

    Boehmer, Christian G; Chan, Nyein; Lazkoz, Ruth; Maartens, Roy

    2009-01-01

    We introduce a new form of coupling between dark energy and dark matter that is quadratic in their energy densities. Then we investigate the background dynamics when dark energy is in the form of exponential quintessence. The three types of quadratic coupling all admit late-time accelerating critical points, but these are not scaling solutions. We also show that two types of coupling allow for a suitable matter era at early times and acceleration at late times, while the third type of coupling does not admit a suitable matter era.

  7. Indirect quantum tomography of quadratic Hamiltonians

    Energy Technology Data Exchange (ETDEWEB)

    Burgarth, Daniel [Institute for Mathematical Sciences, Imperial College London, London SW7 2PG (United Kingdom); Maruyama, Koji; Nori, Franco, E-mail: daniel@burgarth.de, E-mail: kmaruyama@riken.jp [Advanced Science Institute, RIKEN, Wako-shi, Saitama 351-0198 (Japan)

    2011-01-15

    A number of many-body problems can be formulated using Hamiltonians that are quadratic in the creation and annihilation operators. Here, we show how such quadratic Hamiltonians can be efficiently estimated indirectly, employing very few resources. We found that almost all the properties of the Hamiltonian are determined by its surface and that these properties can be measured even if the system can only be initialized to a mixed state. Therefore, our method can be applied to various physical models, with important examples including coupled nano-mechanical oscillators, hopping fermions in optical lattices and transverse Ising chains.

  8. Lambda-Lifting in Quadratic Time

    DEFF Research Database (Denmark)

    Danvy, Olivier; Schultz, Ulrik Pagh

    2004-01-01

    Lambda-lifting is a program transformation that is used in compilers, partial evaluators, and program transformers. In this article, we show how to reduce its complexity from cubic time to quadratic time, and we present a flow-sensitive lambda-lifter that also works in quadratic time. Lambda...... on the simple observation that all functions in each component need the same extra parameters and thus a transitive closure is not needed. We therefore simplify the search for extra parameters by treating each strongly connected component instead of each function as a unit, thereby reducing the time complexity...

  9. Lambda-lifting in Quadratic Time

    DEFF Research Database (Denmark)

    Danvy, O.; Schultz, U.P.

    2004-01-01

    Lambda-lifting is a program transformation that is used in compilers, partial evaluators, and program transformers. In this article, we show how to reduce its complexity from cubic time to quadratic time, and we present a flow-sensitive lambda-lifter that also works in quadratic time. Lambda...... on the simple observation that all functions in each component need the same extra parameters and thus a transitive closure is not needed. We therefore simplify the search for extra parameters by treating each strongly connected component instead of each function as a unit, thereby reducing the time complexity...

  10. On orthogonality preserving quadratic stochastic operators

    Energy Technology Data Exchange (ETDEWEB)

    Mukhamedov, Farrukh; Taha, Muhammad Hafizuddin Mohd [Department of Computational and Theoretical Sciences, Faculty of Science International Islamic University Malaysia, P.O. Box 141, 25710 Kuantan, Pahang Malaysia (Malaysia)

    2015-05-15

    A quadratic stochastic operator (in short QSO) is usually used to present the time evolution of differing species in biology. Some quadratic stochastic operators have been studied by Lotka and Volterra. In the present paper, we first give a simple characterization of Volterra QSO in terms of absolutely continuity of discrete measures. Further, we introduce a notion of orthogonal preserving QSO, and describe such kind of operators defined on two dimensional simplex. It turns out that orthogonal preserving QSOs are permutations of Volterra QSO. The associativity of genetic algebras generated by orthogonal preserving QSO is studied too.

  11. Discrete fractional Radon transforms and quadratic forms

    CERN Document Server

    Pierce, Lillian B

    2010-01-01

    We consider discrete analogues of fractional Radon transforms involving integration over paraboloids defined by positive definite quadratic forms. We prove sharp results for this class of discrete operators in all dimensions, providing necessary and sufficient conditions for them to extend to bounded operators from $\\ell^p$ to $\\ell^q$. The method involves an intricate spectral decomposition according to major and minor arcs, motivated by ideas from the circle method of Hardy and Littlewood. Techniques from harmonic analysis, in particular Fourier transform methods and oscillatory integrals, as well as the number theoretic structure of quadratic forms, exponential sums, and theta functions, play key roles in the proof.

  12. Rosalind Franklin and the Double Helix

    Science.gov (United States)

    Elkin, Lynne Osman

    2003-03-01

    Although she made essential contributions toward elucidating the structure of DNA, Rosalind Franklin is known to many only as seen through the distorting lens of James Watson's book, The Double Helix.

  13. The triple helix perspective of innovation systems

    NARCIS (Netherlands)

    Leydesdorff, L.; Zawdie, G.

    2010-01-01

    Alongside the neo-institutional model of networked relations among universities, industries, and governments, the triple helix can be provided with a neo-evolutionary interpretation as three selection environments operating upon one another: markets, organisations and technological opportunities. Ho

  14. Cylindrical Helix Spline Approximation of Spatial Curves

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, we present a new method for approximating spatial curves with a G1 cylindrical helix spline within a prescribed tolerance. We deduce the general formulation of a cylindrical helix,which has 11 freedoms. This means that it needs 11 restrictions to determine a cylindrical helix. Given a spatial parametric curve segment, including the start point and the end point of this segment, the tangent and the principal normal of the start point, we can always find a cylindrical segment to interpolate the given direction and position vectors. In order to approximate the known parametric curve within the prescribed tolerance, we adopt the trial method step by step. First, we must ensure the helix segment to interpolate the given two end points and match the principal normal and tangent of the start point, and then, we can keep the deviation between the cylindrical helix segment and the known curve segment within the prescribed tolerance everywhere. After the first segment had been formed, we can construct the next segment. Circularly, we can construct the G1 cylindrical helix spline to approximate the whole spatial parametric curve within the prescribed tolerance. Several examples are also given to show the efficiency of this method.

  15. Test-assignment: a quadratic coloring problem

    NARCIS (Netherlands)

    Duives, Jelle; Lodi, Andrea; Malaguti, Enrico

    2013-01-01

    We consider the problem of assigning the test variants of a written exam to the desks of a classroom in such a way that desks that are close-by receive different variants. The problem is a generalization of the Vertex Coloring and we model it as a binary quadratic problem. Exact solution methods bas

  16. Experimental results on quadratic assignment problem

    Directory of Open Access Journals (Sweden)

    N.P. Nikolov

    1999-08-01

    Full Text Available The paper presents experimental results on quadratic assignment problem. The "scanning area" method formulated for radioelectronic equipment design is applied. For all more complex tests ours results are better or coincident with the ones known in literature. Conclusion concerning the effectiveness of method are given.

  17. Quadratic Forms%二次型

    Institute of Scientific and Technical Information of China (English)

    谭亚茹

    2016-01-01

    The quadratic Higher Algebra is an important part of this paper, the definition of quadratic forms, introduces the second type of representation, and then describes how to use the allocation method, elementary transformation, orthogonal transformation method, etc. II second type into the standard form, and the second type of normal form, finally introduced posi-tive definite quadratic form and method for determining positive definite quadratic form.%二次型是高等代数的重要组成部分,本文从二次型的定义出发,介绍了二次型的表示方法,然后介绍了如何用配方法、初等变换法、正交变换法等将二次型化为标准形,以及二次型的规范形,最后介绍了正定二次型和判定正定二次型的方法。

  18. On Quadratic Programming with a Ratio Objective

    CERN Document Server

    Bhaskara, Aditya; Manokaran, Rajsekar; Vijayaraghavan, Aravindan

    2011-01-01

    Quadratic Programming (QP) is the well-studied problem of maximizing over {-1,1} values the quadratic form \\sum_ij a_ij x_i x_j. QP captures many known combinatorial optimization problems and SDP techniques have given optimal approximation algorithms for many of these problems. We extend this body of work by initiating the study of Quadratic Programming problems where the variables take values in the domain {-1,0,1}. The specific problem we study is: QP-Ratio: max_{-1,0,1}^n (x^T A x) / (x^T x). This objective function is a natural relative of several well studied problems. Yet, it is a good testbed for both algorithms and complexity because the techniques used for quadratic problems for the {-1,1} and {0,1} domains do not seem to carry over to the {-1,0,1} domain. We give approximation algorithms and evidence for the hardness of approximating the QP-Ratio problem. We consider an SDP relaxation obtained by adding constraints to the natural SDP relaxation for this problem and obtain an O(n^{2/7}) algorithm for...

  19. Distortion control of conjugacies between quadratic polynomials

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We use a new type of distortion control of univalent functions to give an alternative proof of Douady-Hubbard’s ray-landing theorem for quadratic Misiurewicz polynomials. The univalent maps arise from Thurston’s iterated algorithm on perturbation of such polynomials.

  20. Target manifold formation using a quadratic SDF

    Science.gov (United States)

    Hester, Charles F.; Risko, Kelly K. D.

    2013-05-01

    Synthetic Discriminant Function (SDF) formulation of correlation filters provides constraints for forming target subspaces for a target set. In this paper we extend the SDF formulation to include quadratic constraints and use this solution to form nonlinear manifolds in the target space. The theory for forming these manifolds will be developed and demonstrated with data.

  1. The GCD property and irreduciable quadratic polynomials

    Directory of Open Access Journals (Sweden)

    Saroj Malik

    1986-01-01

    Full Text Available The proof of the following theorem is presented: If D is, respectively, a Krull domain, a Dedekind domain, or a Prüfer domain, then D is correspondingly a UFD, a PID, or a Bezout domain if and only if every irreducible quadratic polynomial in D[X] is a prime element.

  2. Modulational instability in periodic quadratic nonlinear materials

    DEFF Research Database (Denmark)

    Corney, Joel Frederick; Bang, Ole

    2001-01-01

    We investigate the modulational instability of plane waves in quadratic nonlinear materials with linear and nonlinear quasi-phase-matching gratings. Exact Floquet calculations, confirmed by numerical simulations, show that the periodicity can drastically alter the gain spectrum but never complete...

  3. Integration of the Quadratic Function and Generalization

    Science.gov (United States)

    Mitsuma, Kunio

    2011-01-01

    We will first recall useful formulas in integration that simplify the calculation of certain definite integrals with the quadratic function. A main formula relies only on the coefficients of the function. We will then explore a geometric proof of one of these formulas. Finally, we will extend the formulas to more general cases. (Contains 3…

  4. Solitons in quadratic nonlinear photonic crystals

    DEFF Research Database (Denmark)

    Corney, Joel Frederick; Bang, Ole

    2001-01-01

    We study solitons in one-dimensional quadratic nonlinear photonic crystals with modulation of both the linear and nonlinear susceptibilities. We derive averaged equations that include induced cubic nonlinearities, which can be defocusing, and we numerically find previously unknown soliton families...

  5. Solving the quadratic assignment problem with clues from nature.

    Science.gov (United States)

    Nissen, V

    1994-01-01

    This paper describes a new evolutionary approach to solving quadratic assignment problems. The proposed technique is based loosely on a class of search and optimization algorithms known as evolution strategies (ES). These methods are inspired by the mechanics of biological evolution and have been applied successfully to a variety of difficult problems, particularly in continuous optimization. The combinatorial variant of ES presented here performs very well on the given test problems as compared with the standard 2-Opt heuristic and results with simulated annealing and tabu search. Extensions for practical applications in factory layout are described.

  6. A Solution Proposal To Indefinite Quadratic Interval Transportation Problem

    Directory of Open Access Journals (Sweden)

    Hasan Dalman

    2013-12-01

    Full Text Available The data of real world applications generally cannot be expressed strictly. An efficient way of handling this situation is expressing the data as intervals. Thus, this paper focus on the Indefinite Quadratic Interval Transportation Problem (IQITP in which all the parameters i.e. cost and risk coefficients of the objective function, supply and demand quantities are expressed as intervals. A Taylor series approach is presented for the solution of IQITP by means of the expression of intervals with its left and right limits. Also a numerical example is executed to illustrate the procedure.

  7. Unambiguous demonstration of triple-helix-directed gene modification.

    Science.gov (United States)

    Barre, F X; Ait-Si-Ali, S; Giovannangeli, C; Luis, R; Robin, P; Pritchard, L L; Helene, C; Harel-Bellan, A

    2000-03-28

    Triple-helix-forming oligonucleotides (TFOs), which can potentially modify target genes irreversibly, represent promising tools for antiviral therapies. However, their effectiveness on endogenous genes has yet to be unambiguously demonstrated. To monitor endogenous gene modification by TFOs in a yeast model, we inactivated an auxotrophic marker gene by inserting target sequences of interest into its coding region. The genetically engineered yeast cells then were treated with psoralen-linked TFOs followed by UV irradiation, thus generating highly mutagenic covalent crosslinks at the target site whose repair could restore gene function; the number of revertants and spectrum of mutations generated were quantified. Results showed that a phosphoramidate TFO indeed reaches its target sequence, forms crosslinks, and generates mutations at the expected site via a triplex-mediated mechanism: (i) under identical conditions, no mutations were generated by the same TFO at two other loci in the target strain, nor in an isogenic control strain carrying a modified target sequence incapable of supporting triple-helix formation; (ii) for a given target sequence, whether the triplex was formed in vivo on an endogenous gene or in vitro on an exogenous plasmid, the nature of the mutations generated was identical, and consistent with the repair of a psoralen crosslink at the target site. Although the mutation efficiency was probably too low for therapeutic applications, our results confirm the validity of the triple-helix approach and provide a means of evaluating the effectiveness of new chemically modified TFOs and analogs.

  8. A 20 GHz, 75 watt, helix TWT for space communications

    Science.gov (United States)

    Heney, J. F.; Tamashiro, R. N.

    A space-qualified, helix-type traveling wave tube is being developed for satellite communication systems in the frequency band of 17.7 to 21.2 GHz. The design approach stresses very high efficiency operation, but with very low distortion. The tube provides multi-mode operation, permitting CW saturated power output levels of 75, 40, and 7.5 W. Operation is also anticipated at 5 dB below these saturation levels to achieve the required low distortion levels. Advanced construction features include a five-stage depressed collector, a diamond supported helix slow-wave circuit, and a type M dispenser cathode. High reliability and long life (10 yr) are objectives of the tube design. Preliminary test results on early developmental models of this tube are very encouraging. An output power of 75 to 90 W has been achieved over the full bandwidth with about 40 dB of saturated gain. More importantly, the basic electronic efficiency of the interaction process has been increased from about 7.5-11 percent by the use of the diamond helix support compared to earlier tubes using BeO support rods. This effort is supported by NASA Lewis Research Center and is aimed toward application in the NASA Advanced Communications Satellite Technology Program.

  9. Challenges in Targeting a Basic Helix-Loop-Helix Transcription Factor with Hydrocarbon-Stapled Peptides

    NARCIS (Netherlands)

    Edwards, Amanda L; Meijer, Dimphna H; Guerra, Rachel M; Molenaar, Remco J; Alberta, John A; Bernal, Federico; Bird, Gregory H; Stiles, Charles D; Walensky, Loren D

    2016-01-01

    Basic helix-loop-helix (bHLH) transcription factors play critical roles in organism development and disease by regulating cell proliferation and differentiation. Transcriptional activity, whether by bHLH homo- or heterodimerization, is dependent on protein-protein and protein-DNA interactions mediat

  10. Biochemical analysis of the basic helix-loop-helix transcription factor Olig2

    NARCIS (Netherlands)

    Meijer, D.H.M.

    2014-01-01

    The basic helix-loop-helix (bHLH) transcription factors oligodendrocyte transcription factor 1 (Olig1) and Olig2 are structurally similar and, to a first approximation, coordinately expressed in the developing CNS and postnatal brain. Notwithstanding these similarities, it was apparent from early on

  11. Quadratically constrained quadratic programs on acyclic graphs with application to power flow

    CERN Document Server

    Bose, Subhonmesh; Low, Steven H; Chandy, K Mani

    2012-01-01

    This paper proves that non-convex quadratically constrained quadratic programs have an exact semidefinite relaxation when their underlying graph is acyclic, provided the constraint set satisfies a certain technical condition. When the condition is not satisfied, we propose a heuristic to obtain a feasible point starting from a solution of the relaxed problem. These methods are then demonstrated to provide exact solutions to a richer class of optimal power flow problems than previously solved.

  12. Advanced Nonlinear Latent Variable Modeling: Distribution Analytic LMS and QML Estimators of Interaction and Quadratic Effects

    Science.gov (United States)

    Kelava, Augustin; Werner, Christina S.; Schermelleh-Engel, Karin; Moosbrugger, Helfried; Zapf, Dieter; Ma, Yue; Cham, Heining; Aiken, Leona S.; West, Stephen G.

    2011-01-01

    Interaction and quadratic effects in latent variable models have to date only rarely been tested in practice. Traditional product indicator approaches need to create product indicators (e.g., x[superscript 2] [subscript 1], x[subscript 1]x[subscript 4]) to serve as indicators of each nonlinear latent construct. These approaches require the use of…

  13. Optimal linear-quadratic missile guidance laws with penalty on command variability

    NARCIS (Netherlands)

    Weiss, M.; Shima, T.

    2015-01-01

    This paper proposes a new approach to the derivation of homing guidance laws for interceptor missiles that makes use of linear-quadratic optimal control in a different manner than the traditional approaches. Instead of looking only for the minimization of the miss distance and the integral square of

  14. Prokaryotic transcription regulators: more than just the helix-turn-helix motif.

    Science.gov (United States)

    Huffman, Joy L; Brennan, Richard G

    2002-02-01

    Over the past two years, the structures of many prokaryotic transcriptional regulators have been solved, and several of them have revealed the structural mechanism of gene regulation. The crystal structure of BmrR-TPP-DNA reveals a novel mechanism of transcription activation, whereby the drug-bound protein activates the bmr promoter by local DNA unwinding and base pair disruption. Myristoyl-CoA induces FadR by a three-helix pushing mechanism, whereas TetR employs a helical pendulum motion to regulate expression. The structures of AbrB, and DNA complexes of Rob and MuR unveil a novel DNA-binding motif, 'the looped-hinge helix', and new uses of the helix-turn-helix and winged helix motifs in DNA binding.

  15. The collagen triple-helix structure.

    Science.gov (United States)

    Brodsky, B; Ramshaw, J A

    1997-03-01

    Recent advances, principally through the study of peptide models, have led to an enhanced understanding of the structure and function of the collagen triple helix. In particular, the first crystal structure has clearly shown the highly ordered hydration network critical for stabilizing both the molecular conformation and the interactions between triple helices. The sequence dependent nature of the conformational features is also under active investigation by NMR and other techniques. The triple-helix motif has now been identified in proteins other than collagens, and it has been established as being important in many specific biological interactions as well as being a structural element. The nature of recognition and the degree of specificity for interactions involving triple helices may differ from globular proteins. Triple-helix binding domains consist of linear sequences along the helix, making them amenable to characterization by simple model peptides. The application of structural techniques to such model peptides can serve to clarify the interactions involved in triple-helix recognition and binding and can help explain the varying impact of different structural alterations found in mutant collagens in diseased states.

  16. [Study of collagen mimetic peptide's triple-helix structure and its thermostability by circular dichroism].

    Science.gov (United States)

    Zhang, Zhi-Bao; Wang, Jing-Jie; Chen, Hui-Juan; Xiong, Qing-Qing; Liu, Ling-Rong; Zhang, Qi-Qing

    2014-04-01

    In the present study, the authors explore the triple-helix conformation and thermal stability of collagen mimetic peptides (CMPs) as a function of peptide sequence and/or chain length by circular dichroism(CD). Five CMPs were designed and synthetized varying the number of POG triplets or incorporating an integrin alpha2beta1 binding motif Gly-Phe-Hyp-Gly-Glu-Arg (GFOGER). CD spectroscopy from 260 to 190 nm was recorded to confirm the existence of triple-helix conformation at room temperature, while thermal melting and thermal annealing of triple-helix (thermal unfolding and refolding of triple-helix, respectively) was characterized by monitoring ellipticity at 225 nm as a function of temperature. The results demonstrated that all the CMPs adopted triple-helix conformation, and the thermal stability of the CMPs was enhanced with increasing the number of POG triplets. In contrast to natural collagen, the thermal denaturation processes of CMPs were reversible, i. e. the triple-helix unfolded upon heating while refolded upon cooling. Meanwhile, the phenomenon of "hysteresis" was observed by comparing melting and thermal curves. These findings add new insights to the mechanisms of collagen and CMPs assembly, as well as provide an alternative approach to the fabrication of artificial collagen-likes biomaterials.

  17. Triple helix interactions for eco-innovation

    DEFF Research Database (Denmark)

    Hermann, Roberto Rivas; Riisgaard, Henrik; Remmen, Arne

    Authority with insights from consultants, universities and donnor agencies. The proximity of the science park to the canal, has hitherto not yielded with the creation of a “green cluster”, which could be a precedent to promote eco-innovations. These findings suggest that, Triple Helix interactions...... the role of science parks in promoting eco-innovation. This study uses qualitative data gathered in two units of analysis: Panama Canal Authority and City of Knowledge Science Park. The study examines how Triple Helix interactions have built the regional system of eco-innovation at the Panama Canal...... are not institutionalized but take place through adhoc projects. Further, science parks could become mediators in Triple Helix interactions between industry, universities and governments....

  18. On quadratic residue codes and hyperelliptic curves

    Directory of Open Access Journals (Sweden)

    David Joyner

    2008-01-01

    Full Text Available For an odd prime p and each non-empty subset S⊂GF(p, consider the hyperelliptic curve X S defined by y 2 =f S (x, where f S (x = ∏ a∈S (x-a. Using a connection between binary quadratic residue codes and hyperelliptic curves over GF(p, this paper investigates how coding theory bounds give rise to bounds such as the following example: for all sufficiently large primes p there exists a subset S⊂GF(p for which the bound |X S (GF(p| > 1.39p holds. We also use the quasi-quadratic residue codes defined below to construct an example of a formally self-dual optimal code whose zeta function does not satisfy the ``Riemann hypothesis.''

  19. Higgsed Stueckelberg vector and Higgs quadratic divergence

    Directory of Open Access Journals (Sweden)

    Durmuş Ali Demir

    2015-01-01

    Full Text Available Here we show that, a hidden vector field whose gauge invariance is ensured by a Stueckelberg scalar and whose mass is spontaneously generated by the Standard Model Higgs field contributes to quadratic divergences in the Higgs boson mass squared, and even leads to its cancellation at one-loop when Higgs coupling to gauge field is fine-tuned. In contrast to mechanisms based on hidden scalars where a complete cancellation cannot be achieved, stabilization here is complete in that the hidden vector and the accompanying Stueckelberg scalar are both free from quadratic divergences at one-loop. This stability, deriving from hidden exact gauge invariance, can have important implications for modeling dark phenomena like dark matter, dark energy, dark photon and neutrino masses. The hidden fields can be produced at the LHC.

  20. Linear quadratic output tracking and disturbance rejection

    Science.gov (United States)

    Karimi-Ghartemani, Masoud; Khajehoddin, S. Ali; Jain, Praveen; Bakhshai, Alireza

    2011-08-01

    This article introduces the problem of linear quadratic tracking (LQT) where the objective is to design a closed-loop control scheme such that the output signal of the system optimally tracks a given reference signal and rejects a given disturbance. Different performance indices that have been used to address the tracking problem are discussed and an appropriate new form is introduced. It is shown that a solution to the proposed optimality index exists under very mild conditions of stabilisability and detectability of the plant state-space equations. The solution is formulated based on converting the LQT problem to a standard linear quadratic regulation problem. The method is applied to two examples, a first-order plant and a third-order plant, and their simulation results are presented and discussed.

  1. Estimating quadratic variation using realized variance

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Shephard, N.

    2002-01-01

    This paper looks at some recent work on estimating quadratic variation using realized variance (RV) - that is, sums of M squared returns. This econometrics has been motivated by the advent of the common availability of high-frequency financial return data. When the underlying process is a semimar......This paper looks at some recent work on estimating quadratic variation using realized variance (RV) - that is, sums of M squared returns. This econometrics has been motivated by the advent of the common availability of high-frequency financial return data. When the underlying process...... have to impose some weak regularity assumptions. We illustrate the use of the limit theory on some exchange rate data and some stock data. We show that even with large values of M the RV is sometimes a quite noisy estimator of integrated variance. Copyright © 2002 John Wiley & Sons, Ltd....

  2. Lambda-Lifting in Quadratic Time

    DEFF Research Database (Denmark)

    Danvy, Olivier; Schultz, Ulrik Pagh

    2002-01-01

    Lambda-lifting is a program transformation that is used in compilers, partial evaluators, and program transformers. In this article, we show how to reduce its complexity from cubic time to quadratic time, and we present a flow-sensitive lambda-lifter that also works in quadratic time. Lambda-lifting...... that yields the cubic factor in the traditional formulation of lambda-lifting, which is due to Johnsson. This search is carried out by computing a transitive closure. To reduce the complexity of lambda-lifting, we partition the call graph of the source program into strongly connected components, based...... of lambda-lifting from O(n^3) to O(n^2) . where n is the size of the program. Since a lambda-lifter can output programs of size O(n^2), our algorithm is asympotically optimal....

  3. Lambda-Lifting in Quadratic Time

    DEFF Research Database (Denmark)

    Danvy, Olivier; Schultz, Ulrik Pagh

    2004-01-01

    Lambda-lifting is a program transformation that is used in compilers, partial evaluators, and program transformers. In this article, we show how to reduce its complexity from cubic time to quadratic time, and we present a flow-sensitive lambda-lifter that also works in quadratic time. Lambda-lifting...... that yields the cubic factor in the traditional formulation of lambda-lifting, which is due to Johnsson. This search is carried out by computing a transitive closure. To reduce the complexity of lambda-lifting, we partition the call graph of the source program into strongly connected components, based...... of lambda-lifting from O(n^3) to O(n^2) . where n is the size of the program. Since a lambda-lifter can output programs of size O(n^2), our algorithm is asympotically optimal....

  4. Lambda-Lifting in Quadratic Time

    DEFF Research Database (Denmark)

    Danvy, Olivier; Schultz, Ulrik Pagh

    2003-01-01

    Lambda-lifting is a program transformation that is used in compilers, partial evaluators, and program transformers. In this article, we show how to reduce its complexity from cubic time to quadratic time, and we present a flow-sensitive lambda-lifter that also works in quadratic time. Lambda-lifting...... that yields the cubic factor in the traditional formulation of lambda-lifting, which is due to Johnsson. This search is carried out by computing a transitive closure. To reduce the complexity of lambda-lifting, we partition the call graph of the source program into strongly connected components, based...... of lambda-lifting from O(n^3) to O(n^2) . where n is the size of the program. Since a lambda-lifter can output programs of size O(n^2), our algorithm is asympotically optimal....

  5. Lambda-lifting in Quadratic Time

    DEFF Research Database (Denmark)

    Danvy, O.; Schultz, U.P.

    2004-01-01

    Lambda-lifting is a program transformation that is used in compilers, partial evaluators, and program transformers. In this article, we show how to reduce its complexity from cubic time to quadratic time, and we present a flow-sensitive lambda-lifter that also works in quadratic time. Lambda-lifting...... that yields the cubic factor in the traditional formulation of lambda-lifting, which is due to Johnsson. This search is carried out by computing a transitive closure. To reduce the complexity of lambda-lifting, we partition the call graph of the source program into strongly connected components, based...... of lambda-lifting from O(n^3) to O(n^2) . where n is the size of the program. Since a lambda-lifter can output programs of size O(n^2), our algorithm is asympotically optimal....

  6. Quaternion orders, quadratic forms, and Shimura curves

    CERN Document Server

    Alsina, Montserrat

    2004-01-01

    Shimura curves are a far-reaching generalization of the classical modular curves. They lie at the crossroads of many areas, including complex analysis, hyperbolic geometry, algebraic geometry, algebra, and arithmetic. The text provides an introduction to the subject from a theoretic and algorithmic perspective. The main topics covered in it are Shimura curves defined over the rational number field, the construction of their fundamental domains, and the determination of their complex multiplication points. The study of complex multiplication points in Shimura curves leads to the study of families of binary quadratic forms with algebraic coefficients and to their classification by arithmetic Fuchsian groups. In this regard, the authors develop a theory full of new possibilities which parallels Gauss' theory on the classification of binary quadratic forms with integral coefficients by the action of the modular group. Each topic covered in the book begins with a theoretical discussion followed by carefully worked...

  7. A Finite Continuation Algorithm for Bound Constrained Quadratic Programming

    DEFF Research Database (Denmark)

    Madsen, Kaj; Nielsen, Hans Bruun; Pinar, Mustafa C.

    1999-01-01

    The dual of the strictly convex quadratic programming problem with unit bounds is posed as a linear $\\ell_1$ minimization problem with quadratic terms. A smooth approximation to the linear $\\ell_1$ function is used to obtain a parametric family of piecewise-quadratic approximation problems...

  8. Elementary Components of the Quadratic Assignment Problem

    CERN Document Server

    Chicano, Francisco; Alba, Enrique

    2011-01-01

    The Quadratic Assignment Problem (QAP) is a well-known NP-hard combinatorial optimization problem that is at the core of many real-world optimization problems. We prove that QAP can be written as the sum of three elementary landscapes when the swap neighborhood is used. We present a closed formula for each of the three elementary components and we compute bounds for the autocorrelation coefficient.

  9. Cubic Lienard Equations with Quadratic Damping (Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    Yu-quan Wang; Zhu-jun Jing

    2002-01-01

    Applying Hopf bifurcation theory and qualitative theory, we show that the general cubic Lienard equations with quadratic damping have at most three limit cycles. This implies that the guess in which the system has at most two limit cycles is false. We give the sufficient conditions for the system has at most three limit cycles or two limit cycles. We present two examples with three limit cycles or two limit cycles by using numerical simulation.

  10. Characterization of a Quadratic Function in Rn

    Science.gov (United States)

    Xu, Conway

    2010-01-01

    It is proved that a scalar-valued function "f"(x) defined in "n"-dimensional space must be quadratic, if the intersection of tangent planes at x[subscript 1] and x[subscript 2] always contains the midpoint of the line joining x[subscript 1] and x[subscript 2]. This is the converse of a result of Stenlund proved in this JOURNAL in 2001.

  11. Quadratic forms representing all odd positive integers

    CERN Document Server

    Rouse, Jeremy

    2011-01-01

    We consider the problem of classifying all positive-definite integer-valued quadratic forms that represent all positive odd integers. Kaplansky considered this problem for ternary forms, giving a list of 23 candidates, and proving that 19 of those represent all positive odds. (Jagy later dealt with a 20th candidate.) Assuming that the remaining three forms represent all positive odds, we prove that an arbitrary, positive-definite quadratic form represents all positive odds if and only if it represents the odd numbers from 1 up to 451. This result is analogous to Bhargava and Hanke's celebrated 290-theorem. In addition, we prove that these three remaining ternaries represent all positive odd integers, assuming the generalized Riemann hypothesis. This result is made possible by a new analytic method for bounding the cusp constants of integer-valued quaternary quadratic forms $Q$ with fundamental discriminant. This method is based on the analytic properties of Rankin-Selberg $L$-functions, and we use it to prove...

  12. Optimal Approximation of Quadratic Interval Functions

    Science.gov (United States)

    Koshelev, Misha; Taillibert, Patrick

    1997-01-01

    Measurements are never absolutely accurate, as a result, after each measurement, we do not get the exact value of the measured quantity; at best, we get an interval of its possible values, For dynamically changing quantities x, the additional problem is that we cannot measure them continuously; we can only measure them at certain discrete moments of time t(sub 1), t(sub 2), ... If we know that the value x(t(sub j)) at a moment t(sub j) of the last measurement was in the interval [x-(t(sub j)), x + (t(sub j))], and if we know the upper bound D on the rate with which x changes, then, for any given moment of time t, we can conclude that x(t) belongs to the interval [x-(t(sub j)) - D (t - t(sub j)), x + (t(sub j)) + D (t - t(sub j))]. This interval changes linearly with time, an is, therefore, called a linear interval function. When we process these intervals, we get an expression that is quadratic and higher order w.r.t. time t, Such "quadratic" intervals are difficult to process and therefore, it is necessary to approximate them by linear ones. In this paper, we describe an algorithm that gives the optimal approximation of quadratic interval functions by linear ones.

  13. Piece-wise quadratic approximations of arbitrary error functions for fast and robust machine learning.

    Science.gov (United States)

    Gorban, A N; Mirkes, E M; Zinovyev, A

    2016-12-01

    Most of machine learning approaches have stemmed from the application of minimizing the mean squared distance principle, based on the computationally efficient quadratic optimization methods. However, when faced with high-dimensional and noisy data, the quadratic error functionals demonstrated many weaknesses including high sensitivity to contaminating factors and dimensionality curse. Therefore, a lot of recent applications in machine learning exploited properties of non-quadratic error functionals based on L1 norm or even sub-linear potentials corresponding to quasinorms Lp (0basic universal data approximation algorithms (k-means, principal components, principal manifolds and graphs, regularized and sparse regression), based on piece-wise quadratic error potentials of subquadratic growth (PQSQ potentials). We develop a new and universal framework to minimize arbitrary sub-quadratic error potentials using an algorithm with guaranteed fast convergence to the local or global error minimum. The theory of PQSQ potentials is based on the notion of the cone of minorant functions, and represents a natural approximation formalism based on the application of min-plus algebra. The approach can be applied in most of existing machine learning methods, including methods of data approximation and regularized and sparse regression, leading to the improvement in the computational cost/accuracy trade-off. We demonstrate that on synthetic and real-life datasets PQSQ-based machine learning methods achieve orders of magnitude faster computational performance than the corresponding state-of-the-art methods, having similar or better approximation accuracy. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Optimization Design of Helix Pitch for Efficiency Enhancement in the Helix Travelling Wave Tubes

    Institute of Scientific and Technical Information of China (English)

    DUAN Zhao-Yun; GONG Yu-Bin; L(U) Ming-Yi; WEI Yan-Yu; WANG Wen-Xiang

    2008-01-01

    @@ The output section of a helix travelling wave tube usually contains a helix pitch taper for high rf electron efficiency.By keeping the rf field as synchronous as possible with the decelerating electron beam bunches,the rf field can extract much more energy from the beam,and thus the maximum electron efficiency can be realized.Recently,a global simulated annealing algorithm has been employed to design the helix pitch profile so as to improve the electron efficiency as much as possible.From the numerical results,it is concluded that the electron efficiency can be enhanced by about 4%-8%.

  15. Chirality-specific lift forces of helix under shear flows: Helix perpendicular to shear plane.

    Science.gov (United States)

    Zhang, Qi-Yi

    2017-02-01

    Chiral objects in shear flow experience a chirality-specific lift force. Shear flows past helices in a low Reynolds number regime were studied using slender-body theory. The chirality-specific lift forces in the vorticity direction experienced by helices are dominated by a set of helix geometry parameters: helix radius, pitch length, number of turns, and helix phase angle. Its analytical formula is given. The chirality-specific forces are the physical reasons for the chiral separation of helices in shear flow. Our results are well supported by the latest experimental observations.

  16. Heterogeneity of myotubes generated by the MyoD and E12 basic helix-loop-helix transcription factors in otherwise non-differentiation growth conditions.

    Science.gov (United States)

    Grubišić, Vladimir; Gottipati, Manoj K; Stout, Randy F; Grammer, J Robert; Parpura, Vladimir

    2014-02-01

    We used a synthetic biology approach to produce myotubes from mammalian C2C12 myoblasts in non-differentiation growth conditions using the expression of basic helix-loop-helix transcription factors, MyoD and E12, in various combinations and configurations. Our approach not only recapitulated the basics of muscle development and physiology, as the obtained myotubes showed qualities similar to those seen in striated muscle fibers in vivo, but also allowed for the synthesis of populations of myotubes which assumed distinct morphology, myofibrillar development and Ca(2+) dynamics. This fashioned class of biomaterials is suitable for the building blocks of soft actuators in micro-scale biomimetic robotics. This production line strategy can be embraced in reparative medicine as synthetic human myotubes with predetermined morphological/functional properties could be obtained using this very approach. This methodology can be adopted beyond striated muscle for the engineering of other tissue components/cells whose differentiation is governed by the principles of basic helix-loop-helix transcription factors, as in the case, for example, of neural or immune cell types.

  17. A triple helix-loop-helix/basic helix-loop-helix cascade controls cell elongation downstream of multiple hormonal and environmental signaling pathways in Arabidopsis.

    Science.gov (United States)

    Bai, Ming-Yi; Fan, Min; Oh, Eunkyoo; Wang, Zhi-Yong

    2012-12-01

    Environmental and endogenous signals, including light, temperature, brassinosteroid (BR), and gibberellin (GA), regulate cell elongation largely by influencing the expression of the paclobutrazol-resistant (PRE) family helix-loop-helix (HLH) factors, which promote cell elongation by interacting antagonistically with another HLH factor, IBH1. However, the molecular mechanism by which PREs and IBH1 regulate gene expression has remained unknown. Here, we show that IBH1 interacts with and inhibits a DNA binding basic helix-loop-helix (bHLH) protein, HBI1, in Arabidopsis thaliana. Overexpression of HBI1 increased hypocotyl and petiole elongation, whereas dominant inactivation of HBI1 and its homologs caused a dwarf phenotype, indicating that HBI1 is a positive regulator of cell elongation. In vitro and in vivo experiments showed that HBI1 directly bound to the promoters and activated two EXPANSIN genes encoding cell wall-loosening enzymes; HBI1's DNA binding and transcriptional activities were inhibited by IBH1, but the inhibitory effects of IBH1 were abolished by PRE1. The results indicate that PREs activate the DNA binding bHLH factor HBI1 by sequestering its inhibitor IBH1. Altering each of the three factors affected plant sensitivities to BR, GA, temperature, and light. Our study demonstrates that PREs, IBH1, and HBI1 form a chain of antagonistic switches that regulates cell elongation downstream of multiple external and endogenous signals.

  18. Molecular recognition in helix-loop-helix and helix-loop-helix-leucine zipper domains. Design of repertoires and selection of high affinity ligands for natural proteins.

    Science.gov (United States)

    Ciarapica, Roberta; Rosati, Jessica; Cesareni, Gianni; Nasi, Sergio

    2003-04-04

    Helix-loop-helix (HLH) and helix-loop-helix-leucine zipper (HLHZip) are dimerization domains that mediate selective pairing among members of a large transcription factor family involved in cell fate determination. To investigate the molecular rules underlying recognition specificity and to isolate molecules interfering with cell proliferation and differentiation control, we assembled two molecular repertoires obtained by directed randomization of the binding surface in these two domains. For this strategy we selected the Heb HLH and Max Zip regions as molecular scaffolds for the randomization process and displayed the two resulting molecular repertoires on lambda phage capsids. By affinity selection, many domains were isolated that bound to the proteins Mad, Rox, MyoD, and Id2 with different levels of affinity. Although several residues along an extended surface within each domain appeared to contribute to dimerization, some key residues critically involved in molecular recognition could be identified. Furthermore, a number of charged residues appeared to act as switch points facilitating partner exchange. By successfully selecting ligands for four of four HLH or HLHZip proteins, we have shown that the repertoires assembled are rather general and possibly contain elements that bind with sufficient affinity to any natural HLH or HLHZip molecule. Thus they represent a valuable source of ligands that could be used as reagents for molecular dissection of functional regulatory pathways.

  19. Helix aspersa Müller in Holland

    NARCIS (Netherlands)

    Vernhout, J.H.

    1912-01-01

    In „Nachrichtsblatt der Deutschen Malakozool. Gesellsch. 1910, p. 134” Mr. V. Franz (Helgoland) gives a note on the occurrence of Helix aspersa in Holland at Vlissingen. He suggests that the animals have been transported fortuitously to that locality. Now I will not discuss the possibility this havi

  20. Analytical Solution of Projectile Motion with Quadratic Resistance and Generalisations

    CERN Document Server

    Ray, Shouryya

    2013-01-01

    The paper considers the motion of a body under the influence of gravity and drag of the surrounding fluid. Depending on the fluid mechanical regime, the drag force can exhibit a linear, quadratic or even more general dependence on the velocity of the body relative to the fluid. The case of quadratic drag is substantially more complex than the linear case, as it nonlinearly couples both components of the momentum equation, and no explicit analytic solution is known for a general trajectory. After a detailed account of the literature, the paper provides such a solution in form of a series expansion. This result is discussed in detail and related to other approaches previously proposed. In particular, it is shown to yield certain approximate solutions proposed in the literature as limiting cases. The solution technique employs a strategy to reduce systems of ordinary differential equations with a triangular dependence of the right-hand side on the vector of unknowns to a single equation in an auxiliary variable....

  1. Thermodynamics of helix-coil transitions studied by multicanonical algorithms

    CERN Document Server

    Okamoto, Y; Okamoto, Yuko; Hansmann, Ulrich H.E.

    1995-01-01

    Thermodynamics of helix-coil transitions in amino-acid homo-oligomers are studied by the recently proposed multicanonical algorithms. Homo-oligomers of length 10 are considered for three characteristic amino acids, alanine (helix former), valine (helix indifferent), and glycine (helix breaker). For alanine other lengths (15 and 20) are also considered in order to examine the length dependence. From one multicanonical production run with completely random initial conformations, we have obtained the lowest-energy conformations and various thermodynamic quantities (average helicity, Zimm-Bragg $s$ and $\\sigma$ parameters, free energy differences between helix and coil states, etc.) as functions of temperature. The results confirm the fact that alanine is helix-forming, valine is helix-indifferent, and glycine is helix-breaking.

  2. Inelastic scattering in a local polaron model with quadratic coupling to bosons

    DEFF Research Database (Denmark)

    Olsen, Thomas

    2009-01-01

    We calculate the inelastic scattering probabilities in the wide band limit of a local polaron model with quadratic coupling to bosons. The central object is a two-particle Green's function which is calculated exactly using a purely algebraic approach. Compared with the usual linear interaction term...... a quadratic interaction term gives higher probabilities for inelastic scattering involving a large number of bosons. As an application we consider the problem hot-electron-mediated energy transfer at surfaces and use the delta self-consistent field extension of density-functional theory to calculate...

  3. An application of nonlinear programming to the design of regulators of a linear-quadratic formulation

    Science.gov (United States)

    Fleming, P.

    1983-01-01

    A design technique is proposed for linear regulators in which a feedback controller of fixed structure is chosen to minimize an integral quadratic objective function subject to the satisfaction of integral quadratic constraint functions. Application of a nonlinear programming algorithm to this mathematically tractable formulation results in an efficient and useful computer aided design tool. Particular attention is paid to computational efficiency and various recommendations are made. Two design examples illustrate the flexibility of the approach and highlight the special insight afforded to the designer. One concerns helicopter longitudinal dynamics and the other the flight dynamics of an aerodynamically unstable aircraft.

  4. Quadratic partial eigenvalue assignment problem with time delay for active vibration control

    Science.gov (United States)

    Pratt, J. M.; Singh, K. V.; Datta, B. N.

    2009-08-01

    Partial pole assignment in active vibration control refers to reassigning a small set of unwanted eigenvalues of the quadratic eigenvalue problem (QEP) associated with the second order system of a vibrating structure, by using feedback control force, to suitably chosen location without altering the remaining large number of eigenvalues and eigenvectors. There are several challenges of solving this quadratic partial eigenvalue assignment problem (QPEVAP) in a computational setting which the traditional pole-placement problems for first-order control systems do not have to deal with. In order to these challenges, there has been some work in recent years to solve QPEVAP in a computationally viable way. However, these works do not take into account of the practical phenomenon of the time-delay effect in the system. In this paper, a new "direct and partial modal" approach of the quadratic partial eigenvalue assignment problem with time-delay is proposed. The approach works directly in the quadratic system without requiring transformation to a standard state-space system and requires the knowledge of only a small number of eigenvalues and eigenvectors that can be computed or measured in practice. Two illustrative examples are presented in the context of active vibration control with constant time-delay to illustrate the success of our proposed approach. Future work includes generalization of this approach to a more practical complex time-delay system and extension of this work to the multi-input problem.

  5. A semidefinite programming based branch-and-bound framework for the quadratic assignment problem

    NARCIS (Netherlands)

    Truetsch, U.

    2014-01-01

    The practical approach to calculate an exact solution for a quadratic assignment problem (QAP) via a branch-and-bound framework depends strongly on a "smart" choice of different strategies within the framework, for example the branching strategy, heuristics for the upper bound or relaxations for the

  6. Automatic differentiation for reduced sequential quadratic programming

    Institute of Scientific and Technical Information of China (English)

    Liao Liangcai; Li Jin; Tan Yuejin

    2007-01-01

    In order to slove the large-scale nonlinear programming (NLP) problems efficiently, an efficient optimization algorithm based on reduced sequential quadratic programming (rSQP) and automatic differentiation (AD) is presented in this paper. With the characteristics of sparseness, relatively low degrees of freedom and equality constraints utilized, the nonlinear programming problem is solved by improved rSQP solver. In the solving process, AD technology is used to obtain accurate gradient information. The numerical results show that the combined algorithm, which is suitable for large-scale process optimization problems, can calculate more efficiently than rSQP itself.

  7. Bianchi I solutions of effective quadratic gravity

    CERN Document Server

    Müller, Daniel

    2012-01-01

    It is believed that soon after the Planck time, Einstein's general relativity theory should be corrected to an effective quadratic theory. Numerical solutions for the anisotropic generalization of the Friedmann "flat" model $E^3$ for this effective gravity are given. It must be emphasized that although numeric, these solutions are exact in the sense that they depend only on the precision of the machine. The solutions are identified asymptotically in a certain sense. It is found solutions which asymptote de Sitter space, Minkowski space and a singularity. This work is a generalization for non diagonal spatial metrics of a previous result obtained by one of us and a collaborator for Bianchi $I$ spaces.

  8. Linear Stability Analysis of Dynamical Quadratic Gravity

    CERN Document Server

    Ayzenberg, Dimitry; Yunes, Nicolas

    2013-01-01

    We perform a linear stability analysis of dynamical, quadratic gravity in the high-frequency, geometric optics approximation. This analysis is based on a study of gravitational and scalar modes propagating on spherically-symmetric and axially-symmetric, vacuum solutions of the theory. We find dispersion relations that do no lead to exponential growth of the propagating modes, suggesting the theory is linearly stable on these backgrounds. The modes are found to propagate at subluminal and superluminal speeds, depending on the propagating modes' direction relative to the background geometry, just as in dynamical Chern-Simons gravity.

  9. Relaxed Constraint and Evolutionary Rate Variation between Basic Helix-Loop-Helix Floral Anthocyanin Regulators in Ipomoea

    National Research Council Canada - National Science Library

    Streisfeld, Matthew A; Rausher, Mark D

    2007-01-01

    .... We cloned the full-length coding region from 2 basic helix-loop-helix transcription factors from several species of Ipomoea with diverse flower colors and determined the selective forces operating on them...

  10. Geometric Methods in the Algebraic Theory of Quadratic Forms : Summer School

    CERN Document Server

    2004-01-01

    The geometric approach to the algebraic theory of quadratic forms is the study of projective quadrics over arbitrary fields. Function fields of quadrics have been central to the proofs of fundamental results since the renewal of the theory by Pfister in the 1960's. Recently, more refined geometric tools have been brought to bear on this topic, such as Chow groups and motives, and have produced remarkable advances on a number of outstanding problems. Several aspects of these new methods are addressed in this volume, which includes - an introduction to motives of quadrics by Alexander Vishik, with various applications, notably to the splitting patterns of quadratic forms under base field extensions; - papers by Oleg Izhboldin and Nikita Karpenko on Chow groups of quadrics and their stable birational equivalence, with application to the construction of fields which carry anisotropic quadratic forms of dimension 9, but none of higher dimension; - a contribution in French by Bruno Kahn which lays out a general fra...

  11. The Quintuple Helix innovation model: Global warming as a challenge and driver for innovation

    OpenAIRE

    Carayannis, Elias G.; Thorsten D. Barth; Campbell David F. J.

    2012-01-01

    The Triple Helix innovation model focuses on university-industry-government relations. The Quadruple Helix embeds the Triple Helix by adding as a fourth helix the media-based and culture-based public and civil society. The Quintuple Helix innovation model is even broader and more comprehensive by contextualizing the Quadruple Helix and by additionally adding the helix (and perspective) of the natural environments of society. The Triple Helix acknowledges explicitly the importance of higher ed...

  12. Facets for the Cardinality Constrained Quadratic Knapsack Problem and the Quadratic Selective Travelling Salesman Problem

    DEFF Research Database (Denmark)

    Mak, Vicky; Thomadsen, Tommy

    2004-01-01

    A well-known extension of the Travelling Salesman Problem (TSP) is the Selective (or Prize-collecting) TSP: In addition to the edge-costs, each node has an associated reward (denoted the node-reward) and instead of visiting all nodes, only profitable nodes are visited. The Quadratic Selective TSP...

  13. Integrability of Quadratic Non-autonomous Quantum Linear Systems

    Science.gov (United States)

    Lopez, Raquel

    The Quantum Harmonic Oscillator is one of the most important models in Quantum Mechanics. Analogous to the classical mass vibrating back and forth on a spring, the quantum oscillator system has attracted substantial attention over the years because of its importance in many advanced and difficult quantum problems. This dissertation deals with solving generalized models of the time-dependent Schrodinger equation which are called generalized quantum harmonic oscillators, and these are characterized by an arbitrary quadratic Hamiltonian of linear momentum and position operators. The primary challenge in this work is that most quantum models with timedependence are not solvable explicitly, yet this challenge became the driving motivation for this work. In this dissertation, the methods used to solve the time-dependent Schrodinger equation are the fundamental singularity (or Green's function) and the Fourier (eigenfunction expansion) methods. Certain Riccati- and Ermakov-type systems arise, and these systems are highlighted and investigated. The overall aims of this dissertation are to show that quadratic Hamiltonian systems are completely integrable systems, and to provide explicit approaches to solving the time-dependent Schr¨odinger equation governed by an arbitrary quadratic Hamiltonian operator. The methods and results established in the dissertation are not yet well recognized in the literature, yet hold for high promise for further future research. Finally, the most recent results in the dissertation correspond to the harmonic oscillator group and its symmetries. A simple derivation of the maximum kinematical invariance groups of the free particle and quantum harmonic oscillator is constructed from the view point of the Riccati- and Ermakov-type systems, which shows an alternative to the traditional Lie Algebra approach. To conclude, a missing class of solutions of the time-dependent Schrodinger equation for the simple harmonic oscillator in one dimension is

  14. Solving Large Quadratic|Assignment Problems in Parallel

    DEFF Research Database (Denmark)

    Clausen, Jens; Perregaard, Michael

    1997-01-01

    Quadratic Assignment problems are in practice among the most difficult to solve in the class of NP-complete problems. The only successful approach hitherto has been Branch-and-Bound-based algorithms, but such algorithms are crucially dependent on good bound functions to limit the size of the space...... searched. Much work has been done to identify such functions for the QAP, but with limited success.Parallel processing has also been used in order to increase the size of problems solvable to optimality. The systems used have, however, often been systems with relatively few, but very powerful vector...... processors, and have hence not been ideally suited for computations essentially involving non-vectorizable computations on integers.In this paper we investigate the combination of one of the best bound functions for a Branch-and-Bound algorithm (the Gilmore-Lawler bound) and various testing, variable binding...

  15. Quadratic time dependent Hamiltonians and separation of variables

    Science.gov (United States)

    Anzaldo-Meneses, A.

    2017-06-01

    Time dependent quantum problems defined by quadratic Hamiltonians are solved using canonical transformations. The Green's function is obtained and a comparison with the classical Hamilton-Jacobi method leads to important geometrical insights like exterior differential systems, Monge cones and time dependent Gaussian metrics. The Wei-Norman approach is applied using unitary transformations defined in terms of generators of the associated Lie groups, here the semi-direct product of the Heisenberg group and the symplectic group. A new explicit relation for the unitary transformations is given in terms of a finite product of elementary transformations. The sequential application of adequate sets of unitary transformations leads naturally to a new separation of variables method for time dependent Hamiltonians, which is shown to be related to the Inönü-Wigner contraction of Lie groups. The new method allows also a better understanding of interacting particles or coupled modes and opens an alternative way to analyze topological phases in driven systems.

  16. DEALING WITH INCONSISTENT QUADRATIC PROGRAMS IN A SQP BASED ALGORITHM

    Directory of Open Access Journals (Sweden)

    M.T. de Gouvêa

    1997-03-01

    Full Text Available In this paper we present a new sequential quadratic programming SQP algorithm that does not need any preprocessing phase. Its main features consist of not enforcing the Hessian to be positive definite and of dealing with infeasible QP problems in a novel way. The linearized constraints are analyzed and all those that do not belong to the minimal representation of the feasible region are eliminated. In the approach used the convergence rate of the algorithm may be adjusted by the user by properly selecting some tuning parameters that are also used to improve the robustness of the algorithm. The SQP code presented here is also able to deal with bound constraints that may be linearly dependent on the linearized equality or original constraints. The algorithm is shown to be robust and to perform well for small to medium-sized problems

  17. Frequency weighted system identification and linear quadratic controller design

    Science.gov (United States)

    Horta, Lucas G.; Phan, Minh; Juang, Jer-Nan; Longman, Richard W.; Sulla, Jeffrey L.

    1991-01-01

    Application of filters for frequency weighting of Markov parameters (pulse response functions) is described in relation to system/observer identification. The time domain identification approach recovers a model which has a pulse response weighted according to frequency. The identified model is composed of the original system and filters. The augmented system is in a form which can be used directly for frequency weighted linear quadratic controller design. Data from either single or multiple experiments can be used to recover the Markov parameters. Measured acceleration signals from a truss structure are used for system identification and the model obtained is used for frequency weighted controller design. The procedure makes the identification and controler design complementary problems.

  18. Optimal Piecewise-Linear Approximation of the Quadratic Chaotic Dynamics

    Directory of Open Access Journals (Sweden)

    J. Petrzela

    2012-04-01

    Full Text Available This paper shows the influence of piecewise-linear approximation on the global dynamics associated with autonomous third-order dynamical systems with the quadratic vector fields. The novel method for optimal nonlinear function approximation preserving the system behavior is proposed and experimentally verified. This approach is based on the calculation of the state attractor metric dimension inside a stochastic optimization routine. The approximated systems are compared to the original by means of the numerical integration. Real electronic circuits representing individual dynamical systems are derived using classical as well as integrator-based synthesis and verified by time-domain analysis in Orcad Pspice simulator. The universality of the proposed method is briefly discussed, especially from the viewpoint of the higher-order dynamical systems. Future topics and perspectives are also provided

  19. Helix Scan: A Scan Design for Diagnosis

    Institute of Scientific and Technical Information of China (English)

    WANG Fei; HU Yu; LI Xiaowei

    2007-01-01

    Scan design is a widely used design-for-testability technique to improve test quality and efficiency. For the scan-designed circuit, test and diagnosis of the scan chain and the circuit is an important process for silicon debug and yield learning. However, conventional scan designs and diagnosis methods abort the subsequent diagnosis process after diagnosing the scan chain if the scan chain is faulty. In this work, we propose a design-for-diagnosis scan strategy called helix scan and a diagnosis algorithm to address this issue. Unlike previous proposed methods, helix scan has the capability to carry on the diagnosis process without losing information when the scan chain is faulty. What is more, it simplifies scan chain diagnosis and achieves high diagnostic resolution as well as accuracy. Experimental results demonstrate the effectiveness of our design.

  20. FPGA helix tracking algorithm for PANDA

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Yutie; Galuska, Martin; Gessler, Thomas; Kuehn, Wolfgang; Lange, Jens Soeren; Muenchow, David; Spruck, Bjoern [II. Physikalisches Institut, Giessen University (Germany); Ye, Hua [Institute of High Energy Physics, Beijing (China); Collaboration: PANDA-Collaboration

    2015-07-01

    The PANDA detector is a general-purpose detector for physics with high luminosity cooled antiproton beams, planed to operate at the FAIR facility in Darmstadt, Germany. The central detector includes a silicon Micro Vertex Detector (MVD) and a Straw Tube Tracker (STT). Without any hardware trigger, large amounts of raw data are streaming into the data acquisition system. The data reduction task is performed in the online system by reconstruction algorithms programmed on FPGAs (Field Programmable Gate Arrays) as first level and on a farm of GPUs or PCs as a second level. One important part in the system is the online track reconstruction. In this presentation, an online tracking algorithm for helix tracking reconstruction in the solenoidal field is shown. The tracking algorithm is composed by two parts, a road finding module followed by an iterative helix parameter calculation module. A performance study using C++ and the status of the VHDL implementation are presented.

  1. On a general class of quadratic hopping sequences

    Institute of Scientific and Technical Information of China (English)

    JIA HuaDing; YUAN Ding; PENG DaiYuan; GUO Ling

    2008-01-01

    Based upon quadratic polynomials over the finite field, a new class of frequency hopping sequences with large family size suitable for applications in time/frequency hopping CDMA systems, multi-user radar and sonar systems is proposed and investigated. It is shown that the new time/frequency hopping sequences have at most one hit in their autocorrelation functions and at most two hits in their crosscorrelation functions except for a special case, and their family size is much larger than the conventional quadratic hopping sequences. The percentage of full collisions for the new quadratic hopping sequences is discussed. In addition, the average number of hits for the new quadratic hopping sequences, quadratic congruence sequences, extended quadratic congruence sequences and the general linear hopping sequences are also derived.

  2. Quadratic residues and non-residues selected topics

    CERN Document Server

    Wright, Steve

    2016-01-01

    This book offers an account of the classical theory of quadratic residues and non-residues with the goal of using that theory as a lens through which to view the development of some of the fundamental methods employed in modern elementary, algebraic, and analytic number theory. The first three chapters present some basic facts and the history of quadratic residues and non-residues and discuss various proofs of the Law of Quadratic Reciprosity in depth, with an emphasis on the six proofs that Gauss published. The remaining seven chapters explore some interesting applications of the Law of Quadratic Reciprocity, prove some results concerning the distribution and arithmetic structure of quadratic residues and non-residues, provide a detailed proof of Dirichlet’s Class-Number Formula, and discuss the question of whether quadratic residues are randomly distributed. The text is a valuable resource for graduate and advanced undergraduate students as well as for mathematicians interested in number theory.

  3. Monosaccharide templates for de novo designed 4-alpha-helix bundle proteins: template effects in carboproteins

    DEFF Research Database (Denmark)

    Brask, Jesper; Dideriksen, J.M.; Nielsen, John;

    2003-01-01

    De novo design and total chemical synthesis of proteins provide powerful approaches to critically test our understanding of protein folding, structure, and stability. The 4-alpha-helix bundle is a frequently studied structure in which four amphiphilic alpha-helical peptide strands form a hydropho......)) and melting points in chemical and thermal denaturation experiments....

  4. The double helix and the 'wronged heroine'.

    Science.gov (United States)

    Maddox, Brenda

    2003-01-23

    In 1962, James Watson, Francis Crick and Maurice Wilkins received the Nobel prize for the discovery of the structure of DNA. Notably absent from the podium was Rosalind Franklin, whose X-ray photographs of DNA contributed directly to the discovery of the double helix. Franklin's premature death, combined with misogynist treatment by the male scientific establishment, cast her as a feminist icon. This myth overshadowed her intellectual strength and independence both as a scientist and as an individual.

  5. Nanoparticle biofabrication using English ivy (Hedera helix)

    OpenAIRE

    Burris Jason N; Lenaghan Scott C; Zhang Mingjun; Stewart C

    2012-01-01

    Abstract Background English ivy (Hedera helix) is well known for its adhesive properties and climbing ability. Essential to its ability to adhere to vertical surfaces is the secretion of a nanocomposite adhesive containing spherical nanoparticles, 60–85 nm in diameter, produced exclusively by root hairs present on adventitious roots. These organic nanoparticles have shown promise in biomedical and cosmetic applications, and represent a safer alternative to metal oxide nanoparticles currently ...

  6. On Quadratic BSDEs with Final Condition in L2

    OpenAIRE

    Yang, Hanlin

    2015-01-01

    This thesis consists of three parts. In the first part, we study $\\mathbb{L}^p$ solutions of a large class of BSDEs. Existence, comparison theorem, uniqueness and a stability result are proved. In the second part, we establish the solvability of quadratic semimartingale BSDEs. In contrast to current literature, we use Lipschitz-quadratic regularization and obtain the existence and uniqueness results with minimal assumptions. The third part is a brief summary of quadratic semimartingales and t...

  7. Robust Solutions of Uncertain Complex-valued Quadratically Constrained Programs

    Institute of Scientific and Technical Information of China (English)

    Da Chuan XU; Zheng Hai HUANG

    2008-01-01

    In this paper,we discuss complex convex quadratically constrained optimization with uncertain data.Using S-Lemma,we show that the robust counterpart of complex convex quadratically constrained optimization with ellipsoidal or intersection-of-two-ellipsoids uncertainty set leads to a complex semidefinite program.By exploring the approximate S-Lemma,we give a complex semidefinite program which approximates the NP-hard robust counterpart of complex convex quadratic optimization with intersection-of-ellipsoids uncertainty set.

  8. Some Aspects of Quadratic Generalized White Noise Functionals

    Science.gov (United States)

    Si, Si; Hida, Takeyuki

    2009-02-01

    We shall discuss some particular roles of quadratic generalized white noise functionals. First observation is made from the viewpoint of the so-called "la passage du fini à l'infini". We then come to a dual pairing of spaces formed by quadratic generalized white noise functionals. In this line, we can further discuss quadratic forms of differential operators acting on the space of white noise functionals.

  9. Damping effect of helix-like pili

    CERN Document Server

    Zakrisson, Johan; Axner, Ove; Andersson, Magnus

    2014-01-01

    Biopolymers are vital structures for many living organisms; for a variety of bacteria, adhesion polymers play a crucial role for the initiation of colonization. Some bacteria express, on their surface, attachment organelles (pili) that comprise subunits formed into stiff helix-like structures that possess unique biomechanical properties. These helix-like structures possess a high degree of flexibility that gives the biopolymers a unique extendibility. This has been considered beneficial for piliated bacteria adhering to host surfaces in the presence of a fluid flow. We show in this work that helix-like pili have the ability to act as efficient dampers of force that can, for a limited time, lower the load on the force-mediating adhesin-receptor bond on the tip of an individual pilus. The model presented is applied to bacteria adhering with a single pilus of either of the two most common types expressed by uropathogenic Escherichia coli, P or type 1 pili, subjected to realistic flows. The results indicate that ...

  10. Alterations in tumorigenicity of embryonal carcinoma cells by IGF-I triple-helix induced changes in immunogenicity and apoptosis.

    Science.gov (United States)

    Ly, A; Francois, J C; Upegui-Gonzalez, L C; Swiercz, B; Bedel, C; Duc, H T; Bout, D; Trojan, J

    2000-12-08

    IGF-I antisense gene therapy has been applied successfully to animal models of glioma, hepatoma and teratocarcinoma. The antisense strategy has shown that tumor cells transfected with vectors encoding IGF-I antisense RNA lose tumorigenicity, become immunogenic and are associated with tumor specific immune response involving CD8+ lymphocytes. An IGF-I triple helix approach to gene therapy for glioma was recently described. The approach we have taken is to establish parameters of change using the IGF-I triple helix strategy. PCC-3 embryonal carcinoma cells derived from murine teratocarcinoma which express IGF-I were used as a model. The cells were transfected with vector which encodes an oligoribonucleotide that forms RNA-IGF-I DNA triple-helix structure. The triple-helix stops the production of IGF-I. Cells transfected in this manner underwent changes in phenotype and an increase in MHC-I and B-7 cell surface molecules. They also showed enhancement in the production of apoptotic cells (60-70%). The "triple helix" transfected cells lost the ability to induce tumor when injected subcutaneously in syngeneic 129 Sv mice. When co-transfected in vitro with expression vectors encoding both MHC-I and B-7 cDNA in antisense orientation, the "triple-helix" transfected cells were down-regulated in expression of MHC-I and B-7 and the number of apoptotic cells was significantly decreased. Injection of the doubly co-transfected cells into 129 Sv mice was associated with induction of teratocarcinoma. Comparison between antisense and triple-helix transfected cells strategies showed similar immunogenic and apoptotic changes. The findings suggest that triple-helix technology may offer a new clinical approach to treatement of tumors expressing IGF-I.

  11. Obstacle avoidance for autonomous land vehicle navigation in indoor environments by quadratic classifier.

    Science.gov (United States)

    Ku, C H; Tsai, W H

    1999-01-01

    A vision-based approach to obstacle avoidance for autonomous land vehicle (ALV) navigation in indoor environments is proposed. The approach is based on the use of a pattern recognition scheme, the quadratic classifier, to find collision-free paths in unknown indoor corridor environments. Obstacles treated in this study include the walls of the corridor and the objects that appear in the way of ALV navigation in the corridor. Detected obstacles as well as the two sides of the ALV body are considered as patterns. A systematic method for separating these patterns into two classes is proposed. The two pattern classes are used as the input data to design a quadratic classifier. Finally, the two-dimensional decision boundary of the classifier, which goes through the middle point between the two front vehicle wheels, is taken as a local collision-free path. This approach is implemented on a real ALV and successful navigations confirm the feasibility of the approach.

  12. Quadratic dynamical decoupling with nonuniform error suppression

    Energy Technology Data Exchange (ETDEWEB)

    Quiroz, Gregory; Lidar, Daniel A. [Department of Physics and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089 (United States); Departments of Electrical Engineering, Chemistry, and Physics, and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089 (United States)

    2011-10-15

    We analyze numerically the performance of the near-optimal quadratic dynamical decoupling (QDD) single-qubit decoherence errors suppression method [J. West et al., Phys. Rev. Lett. 104, 130501 (2010)]. The QDD sequence is formed by nesting two optimal Uhrig dynamical decoupling sequences for two orthogonal axes, comprising N{sub 1} and N{sub 2} pulses, respectively. Varying these numbers, we study the decoherence suppression properties of QDD directly by isolating the errors associated with each system basis operator present in the system-bath interaction Hamiltonian. Each individual error scales with the lowest order of the Dyson series, therefore immediately yielding the order of decoherence suppression. We show that the error suppression properties of QDD are dependent upon the parities of N{sub 1} and N{sub 2}, and near-optimal performance is achieved for general single-qubit interactions when N{sub 1}=N{sub 2}.

  13. The Quadratic Selective Travelling Salesman Problem

    DEFF Research Database (Denmark)

    Thomadsen, Tommy; Stidsen, Thomas K.

    2003-01-01

    complication that each pair of nodes have an associated profit which can be gained only if both nodes are visited. The QSTSP is a subproblem when constructing hierarchical ring networks. We describe an integer linear programming model for the QSTSP. The QSTSP is solved by two construction heuristics...... solutions at a cost of much higher running time. All problems with up to 50 nodes are solved within one hour.......A well-known extension of the Travelling Salesman Problem (TSP) is the Selective TSP (STSP): Each node has an associated profit and instead of visiting all nodes, the most profitable set of nodes, taking into account the tour cost, is visited. The Quadratic STSP (QSTSP) adds the additional...

  14. Compact stars with quadratic equation of state

    CERN Document Server

    Ngubelanga, Sifiso A; Ray, Subharthi

    2015-01-01

    We provide new exact solutions to the Einstein-Maxwell system of equations for matter configurations with anisotropy and charge. The spacetime is static and spherically symmetric. A quadratic equation of state is utilised for the matter distribution. By specifying a particular form for one of the gravitational potentials and the electric field intensity we obtain new exact solutions in isotropic coordinates. In our general class of models, an earlier model with a linear equation of state is regained. For particular choices of parameters we regain the masses of the stars PSR J1614-2230, 4U 1608-52, PSR J1903+0327, EXO 1745-248 and SAX J1808.4-3658. A comprehensive physical analysis for the star PSR J1903+0327 reveals that our model is reasonable.

  15. Low-rank quadratic semidefinite programming

    KAUST Repository

    Yuan, Ganzhao

    2013-04-01

    Low rank matrix approximation is an attractive model in large scale machine learning problems, because it can not only reduce the memory and runtime complexity, but also provide a natural way to regularize parameters while preserving learning accuracy. In this paper, we address a special class of nonconvex quadratic matrix optimization problems, which require a low rank positive semidefinite solution. Despite their non-convexity, we exploit the structure of these problems to derive an efficient solver that converges to their local optima. Furthermore, we show that the proposed solution is capable of dramatically enhancing the efficiency and scalability of a variety of concrete problems, which are of significant interest to the machine learning community. These problems include the Top-k Eigenvalue problem, Distance learning and Kernel learning. Extensive experiments on UCI benchmarks have shown the effectiveness and efficiency of our proposed method. © 2012.

  16. Directed animals, quadratic and rewriting systems

    CERN Document Server

    Marckert, Jean-François

    2011-01-01

    A directed animal is a percolation cluster in the directed site percolation model. The aim of this paper is to exhibit a strong relation between in one hand, the problem of computing the generating function $\\G$ of directed animals on the square lattice, counted according to the area and the perimeter, and on the other hand, the problem to find a solution to a system of quadratic equations involving unknown matrices. The matrices solution of this problem can be finite or infinite. We were unable to find finite solutions. We present some solid clues that some infinite explicit matrices, fix points of a rewriting like system are the natural solutions of this system of equations: some strong evidences are given that the problem of finding $\\G$ reduces then to the problem of finding an eigenvector to an explicit infinite matrix. Similar properties are shown for other combinatorial questions concerning directed animals, and for different lattices.

  17. Lambda-Lifting in Quadratic Time

    DEFF Research Database (Denmark)

    Danvy, Olivier; Schultz, Ulrik Pagh

    2002-01-01

    Lambda-lifting is a program transformation used in compilers and in partial evaluators and that operates in cubic time. In this article, we show how to reduce this complexity to quadratic time. Lambda-lifting transforms a block-structured program into a set of recursive equations, one for each...... local function in the source program. Each equation carries extra parameters to account for the free variables of the corresponding local function and of all its callees. It is the search for these extra parameters that yields the cubic factor in the traditional formulation of lambda-lifting, which...... is not needed. We therefore simplify the search for extra parameters by treating each strongly connected component instead of each function as a unit, thereby reducing the time complexity of lambda-lifting from O(n 3 log n)toO(n2 log n), where n is the size of the program. Since a lambda-lifter can output...

  18. A SPLITTING METHOD FOR QUADRATIC PROGRAMMING PROBLEM

    Institute of Scientific and Technical Information of China (English)

    魏紫銮

    2001-01-01

    A matrix splitting method is presented for minimizing a quadratic programming (QP)problem, and a general algorithm is designed to solve the QP problem and generates a sequence of iterative points. We prove that the sequence generated by the algorithm converges to the optimal solution and has an R-linear rate of convergence if the QP problem is strictly convex and nondegenerate, and that every accumulation point of the sequence generated by the general algorithm is a KKT point of the original problem under the hypothesis that the value of the objective function is bounded below on the constrained region, and that the sequence converges to a KKT point if the problem is nondegenerate and the constrained region is bounded.

  19. Linear ultrasonic motor using quadrate plate transducer

    Institute of Scientific and Technical Information of China (English)

    Jiamei JIN; Chunsheng ZHAO

    2009-01-01

    A linear ultrasonic motor using a quadrate plate transducer was developed for precision positioning. This motor consists of two pairs of Pb(Zr, Ti)O3 piezo-electric ceramic elements, which are piezoelectrically excited into the second-bending mode of the motor stator's neutral surface in two orthogonal directions, on which the tops of four projections move along an elliptical trajectory, which in turn drives a contacted slider into linear motion via frictional forces. The coincident frequency of the stator is easily obtained for its coincident characteristic dimen-sion in two orthogonal directions. The performance characteristics achieved by the motor are: 1) a maximum linear speed of more than 60 mm/s; 2) a stroke of more than 150 mm; 3) a driving force of more than 5.0 N; and 4) a response time of about 2 ms.

  20. Large-scale sequential quadratic programming algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Eldersveld, S.K.

    1992-09-01

    The problem addressed is the general nonlinear programming problem: finding a local minimizer for a nonlinear function subject to a mixture of nonlinear equality and inequality constraints. The methods studied are in the class of sequential quadratic programming (SQP) algorithms, which have previously proved successful for problems of moderate size. Our goal is to devise an SQP algorithm that is applicable to large-scale optimization problems, using sparse data structures and storing less curvature information but maintaining the property of superlinear convergence. The main features are: 1. The use of a quasi-Newton approximation to the reduced Hessian of the Lagrangian function. Only an estimate of the reduced Hessian matrix is required by our algorithm. The impact of not having available the full Hessian approximation is studied and alternative estimates are constructed. 2. The use of a transformation matrix Q. This allows the QP gradient to be computed easily when only the reduced Hessian approximation is maintained. 3. The use of a reduced-gradient form of the basis for the null space of the working set. This choice of basis is more practical than an orthogonal null-space basis for large-scale problems. The continuity condition for this choice is proven. 4. The use of incomplete solutions of quadratic programming subproblems. Certain iterates generated by an active-set method for the QP subproblem are used in place of the QP minimizer to define the search direction for the nonlinear problem. An implementation of the new algorithm has been obtained by modifying the code MINOS. Results and comparisons with MINOS and NPSOL are given for the new algorithm on a set of 92 test problems.

  1. Quadratic elongation: A quantitative measure of distortion in coordination polyhedra

    Science.gov (United States)

    Robinson, Kelly F.; Gibbs, G.V.; Ribbe, P.H.

    1971-01-01

    Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrahedral coordination complexes, both of which show variations in bond length and bond angle. The quadratic elonga tion is dimensionless, giving a quantitative measure of polyhedral distortion which is independent of the effective size of the polyhedron.

  2. Binary GCD like Algorithms for Some Complex Quadratic Rings

    DEFF Research Database (Denmark)

    Agarwal, Saurabh; Frandsen, Gudmund Skovbjerg

    2004-01-01

    binary gcd like algorithms for the ring of integers in and , one now has binary gcd like algorithms for all complex quadratic Euclidean domains. The running time of our algorithms is O(n 2) in each ring. While there exists an O(n 2) algorithm for computing the gcd in quadratic number rings by Erich...

  3. Geometric quadratic stochastic operator on countable infinite set

    Energy Technology Data Exchange (ETDEWEB)

    Ganikhodjaev, Nasir; Hamzah, Nur Zatul Akmar [Department of Computational and Theoretical Sciences, Kulliyyah of Science, International Islamic University, Jalan Sultan Ahmad Shah, Bandar InderaMahkota, 25200 Kuantan, Pahang (Malaysia)

    2015-02-03

    In this paper we construct the family of Geometric quadratic stochastic operators defined on the countable sample space of nonnegative integers and investigate their trajectory behavior. Such operators can be reinterpreted in terms of of evolutionary operator of free population. We show that Geometric quadratic stochastic operators are regular transformations.

  4. Quadratic Twists of Rigid Calabi–Yau Threefolds Over

    DEFF Research Database (Denmark)

    Gouvêa, Fernando Q.; Kiming, Ian; Yui, Noriko

    2013-01-01

    We consider rigid Calabi–Yau threefolds defined over Q and the question of whether they admit quadratic twists. We give a precise geometric definition of the notion of a quadratic twists in this setting. Every rigid Calabi–Yau threefold over Q is modular so there is attached to it a certain newfo...

  5. Immunizing Conic Quadratic Optimization Problems Against Implementation Errors

    NARCIS (Netherlands)

    Ben-Tal, A.; den Hertog, D.

    2011-01-01

    We show that the robust counterpart of a convex quadratic constraint with ellipsoidal implementation error is equivalent to a system of conic quadratic constraints. To prove this result we first derive a sharper result for the S-lemma in case the two matrices involved can be simultaneously diagonali

  6. Approximate *-derivations and approximate quadratic *-derivations on C*-algebras

    Directory of Open Access Journals (Sweden)

    Park Choonkil

    2011-01-01

    Full Text Available Abstract In this paper, we prove the stability of *-derivations and of quadratic *-derivations on Banach *-algebras. We moreover prove the superstability of *-derivations and of quadratic *-derivations on C*-algebras. 2000 Mathematics Subject Classification: 39B52; 47B47; 46L05; 39B72.

  7. AdS Waves as Exact Solutions to Quadratic Gravity

    CERN Document Server

    Gullu, Ibrahim; Sisman, Tahsin Cagri; Tekin, Bayram

    2011-01-01

    We give an exact solution of the quadratic gravity in D dimensions. The solution is a plane fronted wave metric with a cosmological constant. This metric solves not only the full quadratic gravity field equations but also the linearized ones which include the linearized equations of the recently found critical gravity.

  8. Fuzzy Programming With Quadratic Membership Functions For Multi-objective Transportation Problem

    Directory of Open Access Journals (Sweden)

    Satyanarayana Murthy Akkapeddi

    2015-08-01

    Full Text Available In the present paper, a fuzzy programming model with quadratic membership functions has been developed for the solution of a Multi-Objective Transportation problem. In literature, several fuzzy programming approaches exist with various types of membership functions such as linear, exponential, hyperbolic etc. These membership functions are defined, by taking the lower and upper values of the objective functions into account.  In some cases, these methods fail to obtain an integer compromise optimal solution. In the present method, two coefficients of the quadratic membership functions are determined by the lower and upper values of the objective functions. The other coefficient is taken as a variable in the fuzzy programming approach. This means that the membership curve is fixed at the two end points and set free in between. Application of the method on numerical examples proved that the approach could generate integer compromise optimal solutions.  

  9. De novo design of protein-protein interactions through modification of inter-molecular helix-helix interface residues.

    Science.gov (United States)

    Yagi, Sota; Akanuma, Satoshi; Yamagishi, Manami; Uchida, Tatsuya; Yamagishi, Akihiko

    2016-05-01

    For de novo design of protein-protein interactions (PPIs), information on the shape and chemical complementarity of their interfaces is generally required. Recent advances in computational PPI design have allowed for de novo design of protein complexes, and several successful examples have been reported. In addition, a simple and easy-to-use approach has also been reported that arranges leucines on a solvent-accessible region of an α-helix and places charged residues around the leucine patch to induce interactions between the two helical peptides. For this study, we adopted this approach to de novo design a new PPI between the helical bundle proteins sulerythrin and LARFH. A non-polar patch was created on an α-helix of LARFH around which arginine residues were introduced to retain its solubility. The strongest interaction found was for the LARFH variant cysLARFH-IV-3L3R and the sulerythrin mutant 6L6D (KD=0.16 μM). This artificial protein complex is maintained by hydrophobic and ionic interactions formed by the inter-molecular helical bundle structure. Therefore, by the simple and easy-to-use approach to create de novo interfaces on the α-helices, we successfully generated an artificial PPI. We also created a second LARFH variant with the non-polar patch surrounded by positively charged residues at each end. Upon mixing this LARFH variant with 6L6D, mesh-like fibrous nanostructures were observed by atomic force microscopy. Our method may, therefore, also be applicable to the de novo design of protein nanostructures. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Chatter Prediction for Variable Pitch and Variable Helix Milling

    Directory of Open Access Journals (Sweden)

    Yong Wang

    2015-01-01

    Full Text Available Regenerative chatter is a self-excited vibration that can occur during milling, which shortens the lifetime of the tool and results in unacceptable surface quality. In this paper, an improved semidiscretization method for modeling and simulation with variable pitch and variable helix milling is proposed. Because the delay between each flute varies along the axial depth of the tool in milling, the cutting tool is discrete into some axial layers to simplify calculation. A comparison of the predicted and observed performance of variable pitch and variable helix against uniform pitch and uniform helix milling is presented. It is shown that variable pitch and variable helix milling can obtain larger stable cutting area than uniform pitch and uniform helix milling. Thus, it is concluded that variable pitch and variable helix milling are an effective way for suppressing chatter.

  11. Control of Collagen Triple Helix Stability by Phosphorylation.

    Science.gov (United States)

    Acevedo-Jake, Amanda M; Ngo, Daniel H; Hartgerink, Jeffrey D

    2017-03-10

    The phosphorylation of the collagen triple helix plays an important role in collagen synthesis, assembly, signaling, and immune response, although no reports detailing the effect this modification has on the structure and stability of the triple helix exist. Here we investigate the changes in stability and structure resulting from the phosphorylation of collagen. Additionally, the formation of pairwise interactions between phosphorylated residues and lysine is examined. In all tested cases, phosphorylation increases helix stability. When charged-pair interactions are possible, stabilization via phosphorylation can play a very large role, resulting inasmuch as a 13.0 °C increase in triple helix stability. Two-dimensional NMR and molecular modeling are used to study the local structure of the triple helix. Our results suggest a mechanism of action for phosphorylation in the regulation of collagen and also expand upon our understanding of pairwise amino acid stabilization of the collagen triple helix.

  12. A potential smoothing algorithm accurately predicts transmembrane helix packing.

    Science.gov (United States)

    Pappu, R V; Marshall, G R; Ponder, J W

    1999-01-01

    Potential smoothing, a deterministic analog of stochastic simulated annealing, is a powerful paradigm for the solution of conformational search problems that require extensive sampling, and should be a useful tool in computational approaches to structure prediction and refinement. A novel potential smoothing and search (PSS) algorithm has been developed and applied to predict the packing of transmembrane helices. The highlight of this method is the efficient manner in which it circumvents the combinatorial explosion associated with the large number of minima on multidimensional potential energy surfaces in order to converge to the global energy minimum. Here we show how our potential smoothing and search method succeeds in finding the global minimum energy structure for the glycophorin A (GpA) transmembrane helix dimer by optimizing interhelical van der Waals interactions over rigid and semi-rigid helices. Structures obtained from our ab initio predictions are in close agreement with recent experimental data.

  13. QUADRATIC ADMISSIBLE ESTIMATE OF COVARIANCE IN PSEUDO-ELLIPTICAL CONTOURED DISTRIBUTION

    Institute of Scientific and Technical Information of China (English)

    Hengjian CUI; Xiuhong GAO

    2006-01-01

    This article mainly discusses the admissibility of quadratic estimate of covariance in pseudoelliptical distribution. Under the quadratic loss function, the necessary and sufficient conditions that a quadratic estimator is an admissible estimator of covariance in the class of quadratic estimators are obtained. A complete class of the quadratic estimator class is also given.

  14. Site-specific unfolding thermodynamics of a helix-turn-helix protein.

    Science.gov (United States)

    Amunson, Krista E; Ackels, Loren; Kubelka, Jan

    2008-07-01

    The thermal unfolding of a 40-residue helix-turn-helix subdomain of the P22 viral coat protein was investigated using circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) with site-specific 13C isotopic labeling. Helix-turn-helix is the simplest alpha-helical structural motif that combines both secondary and tertiary structural elements. The CD of individual helical fragments reveals that the P22 subdomain is stabilized by tertiary interhelical interactions. Overall the temperature-dependent CD and FTIR data can be described by a three-state process with a partially folded intermediate. However, the analysis of the site-specific 13C IR signals reveals distinct unfolding thermodynamics for each of the labeled sites. The thermodynamic parameters of the thermal unfolding of each of the labeled segments were obtained using singular value decomposition in combination with target transformation and global fitting. The P22 subdomain unfolds from the N-terminus toward the helical segments near the turn. Our results show that as few as two 13C labeled residues can be detected in a 40 residue protein and provide local, site-specific structural information about protein unfolding, which is not resolved by standard, nonsite-specific spectroscopic probes.

  15. A Classification of Basic Helix-Loop-Helix Transcription Factors of Soybean

    Directory of Open Access Journals (Sweden)

    Karen A. Hudson

    2015-01-01

    Full Text Available The complete genome sequence of soybean allows an unprecedented opportunity for the discovery of the genes controlling important traits. In particular, the potential functions of regulatory genes are a priority for analysis. The basic helix-loop-helix (bHLH family of transcription factors is known to be involved in controlling a wide range of systems critical for crop adaptation and quality, including photosynthesis, light signalling, pigment biosynthesis, and seed pod development. Using a hidden Markov model search algorithm, 319 genes with basic helix-loop-helix transcription factor domains were identified within the soybean genome sequence. These were classified with respect to their predicted DNA binding potential, intron/exon structure, and the phylogeny of the bHLH domain. Evidence is presented that the vast majority (281 of these 319 soybean bHLH genes are expressed at the mRNA level. Of these soybean bHLH genes, 67% were found to exist in two or more homeologous copies. This dataset provides a framework for future studies on bHLH gene function in soybean. The challenge for future research remains to define functions for the bHLH factors encoded in the soybean genome, which may allow greater flexibility for genetic selection of growth and environmental adaptation in this widely grown crop.

  16. Counting Quadratic Nonresidues in Shifted Subsets of the Set of Quadratic Nonresidues for Primes p=4k+1

    Directory of Open Access Journals (Sweden)

    Rocío Meza-Moreno

    2015-01-01

    Full Text Available Let p=4k+1 be a prime number and Fp the finite field with p elements. For x∈1,n, Nx will denote the set of quadratic nonresidues less than or equal to x. In this work we calculate the number of quadratic nonresidues in the shifted set N(p-1/2+a.

  17. Interaction of Spatial Visualization and General Reasoning Abilities with Instructional Treatment in Quadratic Inequalities: A Further Investigation

    Science.gov (United States)

    Eastman, Phillip M.; Carry, L. Ray

    1975-01-01

    Subjects were randomly assigned to a deductively structured verbal-symbolic-numeric treatment or an inductively structured verbal-spatial-numeric treatment for a unit on quadratic inequalities. Success on the deductive symbolic approach was associated with general reasoning ability; success on the inductive spatial approach was associated with…

  18. The bridge helix coordinates movements of modules in RNA polymerase

    Directory of Open Access Journals (Sweden)

    Landick Robert

    2010-11-01

    Full Text Available Abstract The RNA polymerase 'bridge helix' is a metastable α-helix that spans the leading edge of the enzyme active-site cleft. A new study published in BMC Biology reveals surprising tolerance to helix-disrupting changes in a region previously thought crucial for translocation, and suggests roles for two hinge-like segments of the bridge helix in coordinating modules that move during the nucleotide-addition cycle. See Research article: http://www.biomedcentral.com/1741-7007/8/134

  19. Approximate Graph Edit Distance in Quadratic Time.

    Science.gov (United States)

    Riesen, Kaspar; Ferrer, Miquel; Bunke, Horst

    2015-09-14

    Graph edit distance is one of the most flexible and general graph matching models available. The major drawback of graph edit distance, however, is its computational complexity that restricts its applicability to graphs of rather small size. Recently the authors of the present paper introduced a general approximation framework for the graph edit distance problem. The basic idea of this specific algorithm is to first compute an optimal assignment of independent local graph structures (including substitutions, deletions, and insertions of nodes and edges). This optimal assignment is complete and consistent with respect to the involved nodes of both graphs and can thus be used to instantly derive an admissible (yet suboptimal) solution for the original graph edit distance problem in O(n3) time. For large scale graphs or graph sets, however, the cubic time complexity may still be too high. Therefore, we propose to use suboptimal algorithms with quadratic rather than cubic time for solving the basic assignment problem. In particular, the present paper introduces five different greedy assignment algorithms in the context of graph edit distance approximation. In an experimental evaluation we show that these methods have great potential for further speeding up the computation of graph edit distance while the approximated distances remain sufficiently accurate for graph based pattern classification.

  20. A Quadratic Closure for Compressible Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Futterman, J A

    2008-09-16

    We have investigated a one-point closure model for compressible turbulence based on third- and higher order cumulant discard for systems undergoing rapid deformation, such as might occur downstream of a shock or other discontinuity. In so doing, we find the lowest order contributions of turbulence to the mean flow, which lead to criteria for Adaptive Mesh Refinement. Rapid distortion theory (RDT) as originally applied by Herring closes the turbulence hierarchy of moment equations by discarding third order and higher cumulants. This is similar to the fourth-order cumulant discard hypothesis of Millionshchikov, except that the Millionshchikov hypothesis was taken to apply to incompressible homogeneous isotropic turbulence generally, whereas RDT is applied only to fluids undergoing a distortion that is 'rapid' in the sense that the interaction of the mean flow with the turbulence overwhelms the interaction of the turbulence with itself. It is also similar to Gaussian closure, in which both second and fourth-order cumulants are retained. Motivated by RDT, we develop a quadratic one-point closure for rapidly distorting compressible turbulence, without regard to homogeneity or isotropy, and make contact with two equation turbulence models, especially the K-{var_epsilon} and K-L models, and with linear instability growth. In the end, we arrive at criteria for Adaptive Mesh Refinement in Finite Volume simulations.

  1. Designing Camera Networks by Convex Quadratic Programming

    KAUST Repository

    Ghanem, Bernard

    2015-05-04

    ​In this paper, we study the problem of automatic camera placement for computer graphics and computer vision applications. We extend the problem formulations of previous work by proposing a novel way to incorporate visibility constraints and camera-to-camera relationships. For example, the placement solution can be encouraged to have cameras that image the same important locations from different viewing directions, which can enable reconstruction and surveillance tasks to perform better. We show that the general camera placement problem can be formulated mathematically as a convex binary quadratic program (BQP) under linear constraints. Moreover, we propose an optimization strategy with a favorable trade-off between speed and solution quality. Our solution is almost as fast as a greedy treatment of the problem, but the quality is significantly higher, so much so that it is comparable to exact solutions that take orders of magnitude more computation time. Because it is computationally attractive, our method also allows users to explore the space of solutions for variations in input parameters. To evaluate its effectiveness, we show a range of 3D results on real-world floorplans (garage, hotel, mall, and airport). ​

  2. Linear quadratic regulator for laser beam shaping

    Science.gov (United States)

    Escárate, Pedro; Agüero, Juan C.; Zúñiga, Sebastián; Castro, Mario; Garcés, Javier

    2017-07-01

    The performance of an adaptive optics system depends on multiple factors, including the quality of the laser beam before being projected to the mesosphere. In general, cumbersome procedures are required to optimize the laser beam in terms of amplitude and phase. However, aberrations produced by the optics of the laser beam system are still detected during the operations due to, for example, uncertainty in the utilized models. In this paper we propose the use of feedback to overcome the presence of model uncertainty and disturbances. In particular we use a Linear Quadratic Regulator (LQR) for closed loop laser beam shaping using a setup of two deformable mirrors. The proposed method is studied and simulated to provide an automatic optimization of the Amplitude of the laser beam. The performance of the LQR control algorithm is evaluated via numerical simulations using the root mean square error (RMSE). The results show an effective amplitude correction of the laser system aberrations after 20 iterations of the algorithm, a RMSE less than 0.7 was obtained, with about 140 actuators per mirror and a separation of z=3 [m] among the mirrors.

  3. HELIX: The High Energy Light Isotope Experiment

    Science.gov (United States)

    Wakely, Scott

    This is the lead proposal for a new suborbital program, HELIX (High-Energy Light Isotope eXperiment), designed to make measurements of the isotopic composition of light cosmic-ray nuclei from ~200 MeV/nuc to ~10 GeV/nuc. Past measurements of this kind have provided profound insights into the nature and origin of cosmic rays, revealing, for instance, information on acceleration and confinement time scales, and exposing some conspicuous discrepancies between solar and cosmic-ray abundances. The most detailed information currently available comes from the ACE/CRIS mission, but is restricted to energies below a few 100 MeV/nuc. HELIX aims at extending this energy range by over an order of magnitude, where, in most cases, no measurements of any kind exist, and where relativistic time dilation affects the apparent lifetime of radioactive clock nuclei. The HELIX measurements will provide essential information for understanding the propagation history of cosmic rays in the galaxy. This is crucial for properly interpreting several intriguing anomalies reported in recent cosmic-ray measurements, pertaining to the energy spectra of protons, helium, and heavier nuclei, and to the anomalous rise in the positron fraction at higher energy. HELIX employs a high-precision magnet spectrometer to provide measurements which are not achievable by any current or planned instrument. The superconducting magnet originally used for the HEAT payload in five successful high-altitude flights will be combined with state-of-the-art detectors to measure the charge, time-of-flight, magnetic rigidity, and velocity of cosmic-ray particles with high precision. The instrumentation includes plastic scintillators, silicon-strip detectors repurposed from Fermilab's CDF detector, a high-performance gas drift chamber, and a ring-imaging Cherenkov counter employing aerogel radiators and silicon photomultipliers. To reduce cost and technical risk, the HELIX program will be structured in two stages. The first

  4. On the Distribution of Indefinite Quadratic Forms in Gaussian Random Variables

    KAUST Repository

    Al-Naffouri, Tareq Y.

    2015-10-30

    © 2015 IEEE. In this work, we propose a unified approach to evaluating the CDF and PDF of indefinite quadratic forms in Gaussian random variables. Such a quantity appears in many applications in communications, signal processing, information theory, and adaptive filtering. For example, this quantity appears in the mean-square-error (MSE) analysis of the normalized least-meansquare (NLMS) adaptive algorithm, and SINR associated with each beam in beam forming applications. The trick of the proposed approach is to replace inequalities that appear in the CDF calculation with unit step functions and to use complex integral representation of the the unit step function. Complex integration allows us then to evaluate the CDF in closed form for the zero mean case and as a single dimensional integral for the non-zero mean case. Utilizing the saddle point technique allows us to closely approximate such integrals in non zero mean case. We demonstrate how our approach can be extended to other scenarios such as the joint distribution of quadratic forms and ratios of such forms, and to characterize quadratic forms in isotropic distributed random variables.We also evaluate the outage probability in multiuser beamforming using our approach to provide an application of indefinite forms in communications.

  5. Importance of Hydrophilic Hydration and Intramolecular Interactions in the Thermodynamics of Helix-Coil Transition and Helix-Helix Assembly in a Deca-Alanine Peptide.

    Science.gov (United States)

    Tomar, Dheeraj S; Weber, Valéry; Pettitt, B Montgomery; Asthagiri, D

    2016-01-14

    For a model deca-alanine peptide the cavity (ideal hydrophobic) contribution to hydration favors the helix state over extended states and the paired helix bundle in the assembly of two helices. The energetic contributions of attractive protein-solvent interactions are separated into quasi-chemical components consisting of a short-range part arising from interactions with solvent in the first hydration shell and the remaining long-range part that is well described by a Gaussian. In the helix-coil transition, short-range attractive protein-solvent interactions outweigh hydrophobic hydration and favor the extended coil states. Analysis of enthalpic effects shows that it is the favorable hydration of the peptide backbone that favors the unfolded state. Protein intramolecular interactions favor the helix state and are decisive in favoring folding. In the pairing of two helices, the cavity contribution outweighs the short-range attractive protein-water interactions. However, long-range, protein-solvent attractive interactions can either enhance or reverse this trend depending on the mutual orientation of the helices. In helix-helix assembly, change in enthalpy arising from change in attractive protein-solvent interactions favors disassembly. In helix pairing as well, favorable protein intramolecular interactions are found to be as important as hydration effects. Overall, hydrophilic protein-solvent interactions and protein intramolecular interactions are found to play a significant role in the thermodynamics of folding and assembly in the system studied.

  6. On nondecomposable positive definite Hermitian forms over imaginary quadratic fields

    Institute of Scientific and Technical Information of China (English)

    ZHU; Fuzu

    2001-01-01

    [1]Mordell, L. J., The representation of a definite quadratic form as a sum of two others, Ann. of Math., 937, 38: 75.[2]Erds, P., Ko Chao, On definite quadratic forms, which are not the sum of two definite or semidefinite forms, Acta Arith., 939, 3: 02.[3]Erds, P., Ko Chao, Some results on definite quadratic forms, J. London Math. Soc., 938, 3: 27.[4]Zhu Fu-zu, Construction of nondecomposable positive definite quadratic forms, Sci. Sinica, Ser. A, 987, 30(): 9.[5]Zhu Fuzu, On nondecomposability and indecomposability of quadratic forms, Sci. Sinica, Ser. A, 988, 3(3): 265.[6]Pleskin, W., Additively indecomposable positive integral quadratic forms, J. Number Theory, 994, 47: 273.[7]Zhu Fuzu, An existence theorem on positive definite unimodular even Hermitian forms, Chinese Ann. of Math., Ser. A, 984, 5: 33.[8]Zhu Fu-Zu, On the construction of positive definite indecomposable unimodular even Hermitian forms, J. Number Theory, 995, 30: 38.[9]O'Meara, O. T., Introduction to Quadratic Forms, Berlin, New York: Springer-Verlag, 973.[10]Zhu Fuzu, Construction of indecomposable definite Hermitian forms, Chinese Ann. of Math., Ser. B, 994, 5: 349.[11]Zhu Fuzu, On nondecomposable Hermitian forms over Gaussian domain, Acta Math. Sinica, New Ser., 998, 4: 447.

  7. The Cyclicity of the Period Annulus Around the Quadratic Isochronous Center

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The number of the limit cycles bifurcating in small quadratic perturbations of quadratic systems with an isochronous center is studied, it turns out that the cyclicity of the period annulus around one kind of quadratic isochronous center is two.

  8. Predicting transmembrane helix packing arrangements using residue contacts and a force-directed algorithm.

    Science.gov (United States)

    Nugent, Timothy; Jones, David T

    2010-03-19

    Alpha-helical transmembrane proteins constitute roughly 30% of a typical genome and are involved in a wide variety of important biological processes including cell signalling, transport of membrane-impermeable molecules and cell recognition. Despite significant efforts to predict transmembrane protein topology, comparatively little attention has been directed toward developing a method to pack the helices together. Here, we present a novel approach to predict lipid exposure, residue contacts, helix-helix interactions and finally the optimal helical packing arrangement of transmembrane proteins. Using molecular dynamics data, we have trained and cross-validated a support vector machine (SVM) classifier to predict per residue lipid exposure with 69% accuracy. This information is combined with additional features to train a second SVM to predict residue contacts which are then used to determine helix-helix interaction with up to 65% accuracy under stringent cross-validation on a non-redundant test set. Our method is also able to discriminate native from decoy helical packing arrangements with up to 70% accuracy. Finally, we employ a force-directed algorithm to construct the optimal helical packing arrangement which demonstrates success for proteins containing up to 13 transmembrane helices. This software is freely available as source code from http://bioinf.cs.ucl.ac.uk/memsat/mempack/.

  9. Predicting transmembrane helix packing arrangements using residue contacts and a force-directed algorithm.

    Directory of Open Access Journals (Sweden)

    Timothy Nugent

    2010-03-01

    Full Text Available Alpha-helical transmembrane proteins constitute roughly 30% of a typical genome and are involved in a wide variety of important biological processes including cell signalling, transport of membrane-impermeable molecules and cell recognition. Despite significant efforts to predict transmembrane protein topology, comparatively little attention has been directed toward developing a method to pack the helices together. Here, we present a novel approach to predict lipid exposure, residue contacts, helix-helix interactions and finally the optimal helical packing arrangement of transmembrane proteins. Using molecular dynamics data, we have trained and cross-validated a support vector machine (SVM classifier to predict per residue lipid exposure with 69% accuracy. This information is combined with additional features to train a second SVM to predict residue contacts which are then used to determine helix-helix interaction with up to 65% accuracy under stringent cross-validation on a non-redundant test set. Our method is also able to discriminate native from decoy helical packing arrangements with up to 70% accuracy. Finally, we employ a force-directed algorithm to construct the optimal helical packing arrangement which demonstrates success for proteins containing up to 13 transmembrane helices. This software is freely available as source code from http://bioinf.cs.ucl.ac.uk/memsat/mempack/.

  10. A Finite Continuation Algorithm for Bound Constrained Quadratic Programming

    DEFF Research Database (Denmark)

    Madsen, Kaj; Nielsen, Hans Bruun; Pinar, Mustafa C.

    1999-01-01

    The dual of the strictly convex quadratic programming problem with unit bounds is posed as a linear $\\ell_1$ minimization problem with quadratic terms. A smooth approximation to the linear $\\ell_1$ function is used to obtain a parametric family of piecewise-quadratic approximation problems. The u....... The unique path generated by the minimizers of these problems yields the solution to the original problem for finite values of the approximation parameter. Thus, a finite continuation algorithm is designed. Results of extensive computational experiments are reported....

  11. "Special Issue": Regional Dimensions of the Triple Helix Model

    Science.gov (United States)

    Todeva, Emanuela; Danson, Mike

    2016-01-01

    This paper introduces the rationale for the special issue and its contributions, which bridge the literature on regional development and the Triple Helix model. The concept of the Triple Helix at the sub-national, and specifically regional, level is established and examined, with special regard to regional economic development founded on…

  12. Regional Dimensions of the Triple Helix Model: Setting the Context

    Science.gov (United States)

    Todeva, Emanuela; Danson, Mike

    2016-01-01

    This paper introduces the rationale for the special issue and its contributions, which bridge the literature on regional development and the Triple Helix model. The concept of the Triple Helix at the sub-national, and specifically regional, level is established and examined, with special regard to regional economic development founded on…

  13. Government and Governance of Regional Triple Helix Interactions

    Science.gov (United States)

    Danson, Mike; Todeva, Emanuela

    2016-01-01

    This conceptual paper contributes to the discussion of the role of regional government and regional Triple Helix constellations driving economic development and growth within regional boundaries. The impact of regionalism and subsidiarity on regional Triple Helix constellations, and the questions of governmentality, governance and institutional…

  14. Time-programmed helix inversion in phototunable liquid crystals.

    Science.gov (United States)

    Asshoff, Sarah J; Iamsaard, Supitchaya; Bosco, Alessandro; Cornelissen, Jeroen J L M; Feringa, Ben L; Katsonis, Nathalie

    2013-05-14

    Doping cholesteric liquid crystals with photo-responsive molecules enables controlling the colour and polarisation of the light they reflect. However, accelerating the rate of relaxation of these photo-controllable liquid crystals remains challenging. Here we show that the relaxation rate of the cholesteric helix is fully determined by helix inversion of the molecular dopants.

  15. An FPGA helix tracking algorithm for PANDA

    Energy Technology Data Exchange (ETDEWEB)

    Muenchow, David; Galuska, Martin; Gessler, Thomas; Kuehn, Wolfgang; Lange, Jens Soeren; Liang, Yutie; Liu, Ming; Spruck, Bjoern [Justus Liebig University Giessen (Germany); Spataro, Stefano [University of Torino (Italy)

    2010-07-01

    An online track finder for the PANDA experiment at the future FAIR facility was developed and tested. The central Panda tracking detectors for charged particles will consist of a silicon based micro vertex detector (MVD, 5-7 hits/track) and possibly of a straw tube tracker (STT, 15 double layers of straws). Due to the solenoidal magnetic field, tracks of charged particles can be parametrized by a helix (if neglecting energy loss). The algorithm works in several steps. Perpendicular to the beam direction the projection of the tracks is equivalent to a circle. Thus, first a conformal transformation will be used to convert the circles to straight lines. Second, a Hough transform is used to find the straight lines by a peak finding algorithm. Along the beam direction, a different Hough transformation is used. As the algorithm was developed for an FPGA, it uses lookup tables. Possible FPGA implementation is discussed.

  16. FPGA helix tracking algorithm for PANDA

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Yutie; Galuska, Martin; Gessler, Thomas; Hu, Jifeng; Kuehn, Wolfgang; Lange, Jens Soeren; Muenchow, David; Spruck, Bjoern [II. Physikalisches, Giessen University (Germany); Ye, Hua [II. Physikalisches, Giessen University (Germany); Institute of High Energy Physics, Beijing (China); Collaboration: PANDA-Collaboration

    2014-07-01

    The PANDA detector is a general-purpose detector for physics with high luminosity cooled antiproton beams, planed to operate at the FAIR facility in Darmstadt, Germany. The central detector includes a silicon Micro Vertex Detector (MVD) and a Straw Tube Tracker (STT). Without any hardware trigger, large amounts of raw data are streaming into the data acquisition system. The data reduction task is performed in the online system by reconstruction algorithms programmed in VHDL (Very High Speed Integrated Circuit Hardware Description Language) on FPGAs (Field Programmable Gate Arrays) as first level and on a farm of GPUs or PCs as a second level. One important part in the system is the online track reconstruction. In this presentation, an online tracking finding algorithm for helix track reconstruction in the solenoidal field is shown. A performance study using C++ and the status of the VHDL implementation are presented.

  17. The Triple Helix Perspective of Innovation Systems

    CERN Document Server

    Leydesdorff, Loet

    2010-01-01

    Alongside the neo-institutional model of networked relations among universities, industries, and governments, the Triple Helix can be provided with a neo-evolutionary interpretation as three selection environments operating upon one another: markets, organizations, and technological opportunities. How are technological innovation systems different from national ones? The three selection environments fulfill social functions: wealth creation, organization control, and organized knowledge production. The main carriers of this system-industry, government, and academia-provide the variation both recursively and by interacting among them under the pressure of competition. Empirical case studies enable us to understand how these evolutionary mechanisms can be expected to operate in historical instance. The model is needed for distinguishing, for example, between trajectories and regimes.

  18. The Triple Helix of the Organizational Knowledge

    Directory of Open Access Journals (Sweden)

    Contantin BRĂTIANU

    2013-09-01

    Full Text Available The purpose of this paper is to present the inner triple helix dynamics of the organizationalknowledge. This is a new perspective of the classical view of tacit knowledge– explicit knowledge dyad of the organizational knowledge promoted by Nonaka and hisco-workers. The new perspective is based on the metaphor that organizational knowledge isa "eld rather than a stock, or stocks and flows. It is a complex metaphor using the thermodynamicsprinciples. The organizational knowledge is composed of three different "elds: cognitiveknowledge, emotional knowledge and spiritual knowledge. These "elds are nonuniform,nonhomogeneous and they interact in a dynamic way. Cognitive "eld contains knowledgeabout what is, emotional "eld contains knowledge about how we feel, and the spiritual "eldcontains knowledge about people’s aspirations and life values. This new perspective opens anew opportunity in understanding the challenges for the 21st century management.

  19. Hexa Helix: Modified Quad Helix Appliance to Correct Anterior and Posterior Crossbites in Mixed Dentition

    Directory of Open Access Journals (Sweden)

    Syed Mohammed Yaseen

    2012-01-01

    Full Text Available Among the commonly encountered dental irregularities which constitute developing malocclusion is the crossbite. During primary and mixed dentition phase, the crossbite is seen very often and if left untreated during these phases then a simple problem may be transformed into a more complex problem. Different techniques have been used to correct anterior and posterior crossbites in mixed dentition. This case report describes the use of hexa helix, a modified version of quad helix for the management of anterior crossbite and bilateral posterior crossbite in early mixed dentition. Correction was achieved within 15 weeks with no damage to the tooth or the marginal periodontal tissue. The procedure is a simple and effective method for treating anterior and bilateral posterior crossbites simultaneously.

  20. Combinatorics on Words in Symbolic Dynamics: The Quadratic Map

    Institute of Scientific and Technical Information of China (English)

    Wan Ji DAI; Kebo L(U); Jun WANG

    2008-01-01

    This paper is contributed to the combinatorial properties of the MSS sequences, which are the periodic kneading words of quadratic maps denned on a interval. An explicit expression of adjacency relations on MSS sequences of given lengths is established.

  1. Modulational stability and dark solitons in periodic quadratic nonlinear media

    DEFF Research Database (Denmark)

    Corney, Joel Frederick; Bang, Ole

    2000-01-01

    We show that stable dark solitons exist in quadratic nonlinear media with periodic linear and nonlinear susceptibilities. We investigate the modulational stability of plane waves in such systems, a necessary condition for stable dark solitons....

  2. Reconsideration on Homogeneous Quadratic Riemann Boundary Value Problem

    Institute of Scientific and Technical Information of China (English)

    Lu Jian-ke

    2004-01-01

    The homogeneous quadratic Riemann boundary value problem (1) with Hǒlder continuous coefficients for the normal case was considered by the author in 1997. But the solutions obtained there are incomplete. Here its general method of solution is obtained.

  3. A Trust-region-based Sequential Quadratic Programming Algorithm

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian; Poulsen, Niels Kjølstad

    This technical note documents the trust-region-based sequential quadratic programming algorithm used in other works by the authors. The algorithm seeks to minimize a convex nonlinear cost function subject to linear inequalty constraints and nonlinear equality constraints....

  4. Geometric structure of pseudo-plane quadratic flows

    Science.gov (United States)

    Sun, Che

    2017-03-01

    Quadratic flows have the unique property of uniform strain and are commonly used in turbulence modeling and hydrodynamic analysis. While previous applications focused on two-dimensional homogeneous fluid, this study examines the geometric structure of three-dimensional quadratic flows in stratified fluid by solving a steady-state pseudo-plane flow model. The complete set of exact solutions reveals that steady quadratic flows have an invariant conic type in the non-rotating frame and a non-rotatory vertical structure in the rotating frame. Three baroclinic solutions with vertically non-aligned formulation disprove an earlier conjecture. All elliptic and hyperbolic solutions, except for the inertial ones, exhibit vertical concentricity. The rich geometry of quadratic flows stands in contrast to the depleted geometry of high-degree polynomial flows. A paradox in the steady solutions of shallow-water reduced-gravity models is also explained.

  5. Finite dimensional semigroup quadratic algebras with minimal number of relations

    CERN Document Server

    Iyudu, Natalia

    2011-01-01

    A quadratic semigroup algebra is an algebra over a field given by the generators $x_1,...,x_n$ and a finite set of quadratic relations each of which either has the shape $x_jx_k=0$ or the shape $x_jx_k=x_lx_m$. We prove that a quadratic semigroup algebra given by $n$ generators and $d\\leq \\frac{n^2+n}{4}$ relations is always infinite dimensional. This strengthens the Golod--Shafarevich estimate for the above class of algebras. Our main result however is that for every $n$, there is a finite dimensional quadratic semigroup algebra with $n$ generators and $\\delta_n$ generators, where $\\delta_n$ is the first integer greater than $\\frac{n^2+n}{4}$. This shows that the above Golod-Shafarevich type estimate for semigroup algebras is sharp.

  6. Democracy and environment as references for quadruple and quintuple helix innovation systems

    Science.gov (United States)

    Carayannis, Elias G.; Campbell, David F. J.; Orr, Barron J.

    2015-04-01

    The perspective of democracy and the ecological context define key references for knowledge production and innovation in innovation systems. Particularly under conditions of environmental change where enhancing the potential for adaptation is critical, this requires a closer look at ecological responsibility and sensitivity in the different innovation models and governance regimes. The "Quintuple Helix" innovation model is an approach that stresses the necessary socio-ecological transition of society and economy by adding an environment helix to an innovation system already made up of three (university-industry-government) or four (civil society relations) helices in a way that supports adaptation by incorporating global warming as both a challenge to and a driver of innovation. There is the proposition that knowledge production and innovation co-evolve with democracy (Carayannis and Campbell, 2014). In the Triple Helix model (Etzkowitz and Leydesdorff, 2000) the existence of a democracy does not appear to be necessary for knowledge production and innovation. However, the Quadruple Helix (Carayannis and Campbell, 2009, 2010 and 2014) is defined and represented by additional key attributes and components: "media-based and culture-based public", "civil society" and "arts, artistic research and arts-based innovation" (Bast, Carayannis and Campbell, 2015). Implications of this are that the fourth helix in the Quadruple Helix innovation systems brings in and represents the perspective of "dimension of democracy" or the "context of democracy" for knowledge in general and knowledge production and innovation in more particular. Within theories of democracy there is a competition between narrow and broader concepts of democracy (Campbell, 2013). This is particularly true when democracy is to be understood to transcend more substantially the narrow understanding of being primarily based on or being primarily rooted in government institutions (within a Triple Helix

  7. Assembly of liposomes controlled by triple helix formation.

    Science.gov (United States)

    Jakobsen, Ulla; Vogel, Stefan

    2013-09-18

    Attachment of DNA to the surface of different solid nanoparticles (e.g., gold and silica nanoparticles) is well established, and a number of DNA-modified solid nanoparticle systems have been applied to thermal denaturation analysis of oligonucleotides. We report herein the noncovalent immobilization of oligonucleotides on the surface of soft nanoparticles (i.e., liposomes) and the subsequent controlled assembly by DNA triple helix formation. The noncovalent approach avoids tedious surface chemistry and necessary purification procedures and can simplify and extend the available methodology for the otherwise difficult thermal denaturation analysis of complex triple helical DNA assemblies. The approach is based on lipid modified triplex forming oligonucleotides (TFOs) which control the assembly of liposomes in solution in the presence of single- or double-stranded DNA targets. The thermal denaturation analysis is monitored by ultraviolet spectroscopy at submicromolar concentrations and compared to regular thermal denaturation assays in the absence of liposomes. We report on triplex forming oligonucleotides (TFOs) based on DNA and locked nucleic acid (LNA)/DNA hybrid building blocks and different target sequences (G or C-rich) to explore the applicability of the method for different triple helical assembly modes. We demonstrate advantages and limitations of the approach and show the reversible and reproducible formation of liposome aggregates during thermal denaturation cycles. Nanoparticle tracking analysis (NTA) and dynamic light scattering (DLS) show independently from ultraviolet spectroscopy experiments the formation of liposome aggregates.

  8. Quadratic measurement and conditional state preparation in an optomechanical system

    DEFF Research Database (Denmark)

    A. Brawley, George; Vanner, Michael A.; Bowen, Warwick P.;

    2014-01-01

    We experimentally demonstrate, for the first time, quadratic measurement of mechanical motion in an optomechanical system. We use this nonlinear easurement to conditionally prepare classical non-Gaussian states of motion of a micro-mechanical oscillator.......We experimentally demonstrate, for the first time, quadratic measurement of mechanical motion in an optomechanical system. We use this nonlinear easurement to conditionally prepare classical non-Gaussian states of motion of a micro-mechanical oscillator....

  9. An Interval Maximum Entropy Method for Quadratic Programming Problem

    Institute of Scientific and Technical Information of China (English)

    RUI Wen-juan; CAO De-xin; SONG Xie-wu

    2005-01-01

    With the idea of maximum entropy function and penalty function methods, we transform the quadratic programming problem into an unconstrained differentiable optimization problem, discuss the interval extension of the maximum entropy function, provide the region deletion test rules and design an interval maximum entropy algorithm for quadratic programming problem. The convergence of the method is proved and numerical results are presented. Both theoretical and numerical results show that the method is reliable and efficient.

  10. On wave-packet dynamics in a decaying quadratic potential

    DEFF Research Database (Denmark)

    Møller, Klaus Braagaard; Henriksen, Niels Engholm

    1997-01-01

    We consider the time-dependent Schrodinger equation for a quadratic potential with an exponentially decaying force constant. General analytical solutions are presented and we highlight in particular, the signatures of classical mechanics in the wave packet dynamics.......We consider the time-dependent Schrodinger equation for a quadratic potential with an exponentially decaying force constant. General analytical solutions are presented and we highlight in particular, the signatures of classical mechanics in the wave packet dynamics....

  11. DERIVATIVES OF EIGENPAIRS OF SYMMETRIC QUADRATIC EIGENVALUE PROBLEM

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Derivatives of eigenvalues and eigenvectors with respect to parameters in symmetric quadratic eigenvalue problem are studied. The first and second order derivatives of eigenpairs are given. The derivatives are calculated in terms of the eigenvalues and eigenvectors of the quadratic eigenvalue problem, and the use of state space representation is avoided, hence the cost of computation is greatly reduced. The efficiency of the presented method is demonstrated by considering a spring-mass-damper system.

  12. Scale-Invariant Rotating Black Holes in Quadratic Gravity

    Directory of Open Access Journals (Sweden)

    Guido Cognola

    2015-07-01

    Full Text Available Black hole solutions in pure quadratic theories of gravity are interesting since they allow the formulation of a set of scale-invariant thermodynamics laws. Recently, we have proven that static scale-invariant black holes have a well-defined entropy, which characterizes equivalent classes of solutions. In this paper, we generalize these results and explore the thermodynamics of rotating black holes in pure quadratic gravity.

  13. Ideal Class Groups and Subgroups of Real Quadratic Function Fields

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, we study the real quadratic function fields K=k(D), given a necessary and sufficient condition for the ideal class group H(K) of any real quadratic function field K to have a cyclic subgroup of order n, and obtained eight series of such fields. The ideal class numbers h(OK) of K in the series all have a factor n.

  14. Burgers' turbulence problem with linear or quadratic external potential

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Leonenko, N.N.

    2005-01-01

    We consider solutions of Burgers' equation with linear or quadratic external potential and stationary random initial conditions of Ornstein-Uhlenbeck type. We study a class of limit laws that correspond to a scale renormalization of the solutions.......We consider solutions of Burgers' equation with linear or quadratic external potential and stationary random initial conditions of Ornstein-Uhlenbeck type. We study a class of limit laws that correspond to a scale renormalization of the solutions....

  15. On Integers, Primes and UniqueFactorization in Quadratic Fields

    OpenAIRE

    Hedenlund, Alice

    2013-01-01

    Abstract. This thesis will deal with quadratic elds. The prob- lem is to study such elds and their properties including, but not limited to, determining integers, nding primes and deciding which quadratic elds have unique factorization. The goal is to get famil- iar with these concepts and to provide a starting point for students with an interest in algebra to explore eld extensions and inte- gral closures in relation to elementary number theory. The reader will be assumed to have a basic kn...

  16. Stability of a Generalized Quadratic Functional Equation in Schwartz Distributions

    Institute of Scientific and Technical Information of China (English)

    Jae-Young CHUNG

    2009-01-01

    We consider the Hyers-Ulam stability problem of the generalized quadratic functional equation u(o)A+v(o)B-2w(o)P1-2k(o)P2=0, which is a distributional version of the classical generalized quadratic functional equation f(x + y) + g(x - y) - 2h(x) - 2k(y) = 0.

  17. On the use of simplex methods in constructing quadratic models

    Institute of Scientific and Technical Information of China (English)

    Qing-hua ZHOU

    2007-01-01

    In this paper, we investigate the quadratic approximation methods. After studying the basic idea of simplex methods, we construct several new search directions by combining the local information progressively obtained during the iterates of the algorithm to form new subspaces. And the quadratic model is solved in the new subspaces. The motivation is to use the information disclosed by the former steps to construct more promising directions. For most tested problems, the number of function evaluations have been reduced obviously through our algorithms.

  18. Mutations in TWIST, a basic helix-loop-helix transcription factor, in Saethre-Chotzen syndrome.

    Science.gov (United States)

    Howard, T D; Paznekas, W A; Green, E D; Chiang, L C; Ma, N; Ortiz de Luna, R I; Garcia Delgado, C; Gonzalez-Ramos, M; Kline, A D; Jabs, E W

    1997-01-01

    Saethre-Chotzen syndrome is one of the most common autosomal dominant disorders of craniosynostosis in humans and is characterized by craniofacial and limb anomalies. The locus for Saethre-Chotzen syndrome maps to chromosome 7p21-p22. We have evaluated TWIST, a basic helix-loop-helix transcription factor, as a candidate gene for this condition because its expression pattern and mutant phenotypes in Drosophila and mouse are consistent with the Saethre-Chotzen phenotype. We mapped TWIST to human chromosome 7p21-p22 and mutational analysis reveals nonsense, missense, insertion and deletion mutations in patients. These mutations occur within the basic DNA binding, helix I and loop domains, or result in premature termination of the protein. Studies in Drosophila indicate that twist may affect the transcription of fibroblast growth factor receptors (FGFRs), another gene family implicated in human craniosynostosis. The emerging cascade of molecular components involved in craniofacial and limb development now includes TWIST, which may function as an upstream regulator of FGFRs.

  19. Personal Pornography Viewing and Sexual Satisfaction: A Quadratic Analysis.

    Science.gov (United States)

    Wright, Paul J; Bridges, Ana J; Sun, Chyng; Ezzell, Matthew; Johnson, Jennifer A

    2017-09-08

    Personal pornography viewing has been associated with lower sexual satisfaction in both experimental and observational research. The language used to hypothesize this relationship typically suggests that it is frequent viewing, rather than infrequent or only occasional viewing, that is responsible for any adverse effects. When the nature of the relationship between a predictor and a criterion depends on the levels of the predictor, a curvilinear relationship is indicated. Nevertheless, studies have assumed linearity in their analytical approach. Curvilinear relationships will go undetected unless they are specifically tested. This article presents results from a survey of approximately 1,500 U.S. adults. Quadratic analyses indicated a curvilinear relationship between personal pornography viewing and sexual satisfaction in the form of a predominately negative, concave downward curve. The nature of the curvilinearity did not differ as a function of participants' gender, relationship status, or religiosity. But the negative acceleration was slightly more pronounced for men than for women, for people not in a relationship than for people in a relationship, and for religious people than for nonreligious people. For all groups, negative simple slopes were present when viewing reached once a month or more. These results are correlational only. However, if an effects perspective were adopted, they would suggest that consuming pornography less than once a month has little or no impact on satisfaction, that reductions in satisfaction tend to initiate once viewing reaches once a month, and that additional increases in the frequency of viewing lead to disproportionately larger decrements in satisfaction.

  20. Can synergy in Triple Helix relations be quantified? A review of the development of the Triple Helix indicator

    NARCIS (Netherlands)

    Leydesdorff, L.; Park, H.W.

    2014-01-01

    Triple Helix arrangements of bi- and trilateral relations can be considered as adaptive ecosystems. During the last decade, we have further developed a Triple Helix indicator of synergy as reduction of uncertainty in niches that can be shaped among three or more sets of relations. Reduction of uncer

  1. Differential regulation of granulopoiesis by the basic helix-loop-helix transcriptional inhibitors Id1 and Id2

    NARCIS (Netherlands)

    Buitenhuis, M; van Deutekom, HWM; Verhagen, LP; Castor, A; Jacobsen, SEW; Lammers, JWJ; Koenderman, L; Coffer, PJ

    2005-01-01

    Inhibitor of DNA binding (Id) proteins function as inhibitors of members of the basic helix-loop-helix family of transcription factors and have been demonstrated to play an important role in regulating lymphopoiesis. However, the role of these proteins in regulation of myelopoiesis is currently

  2. From Family Based to Industrial Based Production: Local Economic Development Initiatives and the HELIX Model

    Directory of Open Access Journals (Sweden)

    Bartjan W Pennink

    2013-01-01

    Full Text Available To build a strong local economy, good practice tells us that each community should undertake a collaborative, strategically planned process to understand and then act upon its own strengths, weaknesses, opportunities and threats. From this perspective we start with the local communities but how is this related to the perspective from the Helix model in which three actors are explicitly introduced: the Government, the Industry and the Universities? The purpose of local economic development (LED is to build up the economic capacity of a local area to improve its economic future and the quality of life for all. To support  the Local Economic Development in remote areas,   a program  has been developed based on the LED frame work of the world bank. This approach and  the experiences over  the past years with this program are  described in the first part.  In the second part of the paper, We analyse work done with that program with the help of the social capital concept and the triple helix model.  In all cases it is important to pay attention to who is taken the initiative after the first move (and it is not always the governance as actor and for the triple helix we suggest  that the concepts of (national Government, Industry and University need a translation to Local Governance Agency, Cooperation or other ways of cooperation of local communities and Local Universities. Although a push from outside might help  a local region in development the endogenous factors are  also needed. Keywords: Triple Helix model, Local Economic Development, Local Actors, Double Triangle within the Helix Model

  3. A Quadratic precision generalized nonlinear global optimization migration velocity inversion method

    Institute of Scientific and Technical Information of China (English)

    Zhao Taiyin; Hu Guangmin; He Zhenhua; Huang Deji

    2009-01-01

    An important research topic for prospecting seismology is to provide a fast accurate velocity model from pre-stack depth migration. Aiming at such a problem, we propose a quadratic precision generalized nonlinear global optimization migration velocity inversion. First we discard the assumption that there is a linear relationship between residual depth and residual velocity and propose a velocity model correction equation with quadratic precision which enables the velocity model from each iteration to approach the real model as quickly as possible. Second, we use a generalized nonlinear inversion to get the global optimal velocity perturbation model to all traces. This method can expedite the convergence speed and also can decrease the probability of falling into a local minimum during inversion. The synthetic data and Marmousi data examples show that our method has a higher precision and needs only a few iterations and consequently enhances the practicability and accuracy of migration velocity analysis (MVA) in complex areas.

  4. The Thermo Scientific HELIX-SFT noble gas mass spectrometer: (preliminary) performance for 40Ar/39Ar geochronology

    Science.gov (United States)

    Barfod, D. N.; Mark, D. F.; Morgan, L. E.; Tomkinson, T.; Stuart, F.; Imlach, J.; Hamilton, D.

    2011-12-01

    The Thermo Scientific HELIX-platform Split Flight Tube (HELIX-SFT) noble gas mass spectrometer is specifically designed for simultaneous collection of helium isotopes. The high mass spur houses a switchable 1011 - 1012 Ω resistor Faraday cup and the low mass spur a digital pulse-counting secondary electron multiplier (SEM). We have acquired the HELIX-SFT with the specific intention to measure argon isotopes for 40Ar/39Ar geochronology. This contribution will discuss preliminary performance (resolution, reproducibility, precision etc.) with respect to measuring argon isotope ratios for 40Ar/39Ar dating of geological materials. We anticipate the greatest impact for 40Ar/39Ar dating will be increased accuracy and precision, especially as we approach the techniques younger limit. Working with Thermo Scientific we have subtly modified the source, alpha and collector slits of the HELIX-SFT mass spectrometer to improve its resolution for resolving isobaric interferences at masses 36 to 40. The enhanced performance will allow for accurate and precise measurement of argon isotopes. Preliminary investigations show that we can obtain a valley resolution of >700 and >1300 (compared to standard HELIX-SFT specifications of >400 and >700) for the high and low mass spurs, respectively. The improvement allows for full resolution of hydrocarbons (C3+) at masses 37 - 40 and almost full resolution at mass 36. The HELIX-SFT will collect data in dual collection mode with 40Ar+ ion beams measured using the switchable 1011 - 1012 Ω resistor Faraday cup and 39Ar through 36Ar measured using the SEM. The HELIX-SFT requires Faraday-SEM inter-calibration but negates the necessity to inter-calibrate multiple electron multipliers. We will further present preliminary data from the dating of mineral standards: Alder Creek sanidine, Fish Canyon sanidine and Mount Dromedary biotite (GA1550).

  5. A one-layer recurrent neural network with a discontinuous hard-limiting activation function for quadratic programming.

    Science.gov (United States)

    Liu, Q; Wang, J

    2008-04-01

    In this paper, a one-layer recurrent neural network with a discontinuous hard-limiting activation function is proposed for quadratic programming. This neural network is capable of solving a large class of quadratic programming problems. The state variables of the neural network are proven to be globally stable and the output variables are proven to be convergent to optimal solutions as long as the objective function is strictly convex on a set defined by the equality constraints. In addition, a sequential quadratic programming approach based on the proposed recurrent neural network is developed for general nonlinear programming. Simulation results on numerical examples and support vector machine (SVM) learning show the effectiveness and performance of the neural network.

  6. A transient, quadratic nodal method for triangular-Z geometry

    Energy Technology Data Exchange (ETDEWEB)

    DeLorey, T.F.

    1993-06-01

    Many systematically-derived nodal methods have been developed for Cartesian geometry due to the extensive interest in Light Water Reactors. These methods typically model the transverse-integrated flux as either an analytic or low order polynomial function of position within the node. Recently, quadratic nodal methods have been developed for R-Z and hexagonal geometry. A static and transient quadratic nodal method is developed for triangular-Z geometry. This development is particularly challenging because the quadratic expansion in each node must be performed between the node faces and the triangular points. As a consequence, in the 2-D plane, the flux and current at the points of the triangles must be treated. Quadratic nodal equations are solved using a non-linear iteration scheme, which utilizes the corrected, mesh-centered finite difference equations, and forces these equations to match the quadratic equations by computing discontinuity factors during the solution. Transient nodal equations are solved using the improved quasi-static method, which has been shown to be a very efficient solution method for transient problems. Several static problems are used to compare the quadratic nodal method to the Coarse Mesh Finite Difference (CMFD) method. The quadratic method is shown to give more accurate node-averaged fluxes. However, it appears that the method has difficulty predicting node leakages near reactor boundaries and severe material interfaces. The consequence is that the eigenvalue may be poorly predicted for certain reactor configurations. The transient methods are tested using a simple analytic test problem, a heterogeneous heavy water reactor benchmark problem, and three thermal hydraulic test problems. Results indicate that the transient methods have been implemented correctly.

  7. Concentration-temperature superposition of helix folding rates in gelatin.

    Science.gov (United States)

    Gornall, J L; Terentjev, E M

    2007-07-13

    Using optical rotation as the primary technique, we have characterized the kinetics of helix renaturation in water solutions of gelatin. By covering a wide range of solution concentrations we identify a universal exponential dependence of folding rate on concentration and quench temperature. We demonstrate a new concentration-temperature superposition of data at all temperatures and concentrations, and build the corresponding master curve. The normalized rate constant is consistent with helix lengthening. Nucleation of the triple helix occurs rapidly and contributes less to the helical onset than previously thought.

  8. Electrostatic free energy landscapes for nucleic acid helix assembly

    OpenAIRE

    Tan, Zhi-Jie; Chen, Shi-Jie

    2006-01-01

    Metal ions are crucial for nucleic acid folding. From the free energy landscapes, we investigate the detailed mechanism for ion-induced collapse for a paradigm system: loop-tethered short DNA helices. We find that Na + and Mg2+ play distinctive roles in helix–helix assembly. High [Na+] (>0.3 M) causes a reduced helix–helix electrostatic repulsion and a subsequent disordered packing of helices. In contrast, Mg2+ of concentration >1 mM is predicted to induce helix–helix attraction and results i...

  9. CAD of control systems: Application of nonlinear programming to a linear quadratic formulation

    Science.gov (United States)

    Fleming, P.

    1983-01-01

    The familiar suboptimal regulator design approach is recast as a constrained optimization problem and incorporated in a Computer Aided Design (CAD) package where both design objective and constraints are quadratic cost functions. This formulation permits the separate consideration of, for example, model following errors, sensitivity measures and control energy as objectives to be minimized or limits to be observed. Efficient techniques for computing the interrelated cost functions and their gradients are utilized in conjunction with a nonlinear programming algorithm. The effectiveness of the approach and the degree of insight into the problem which it affords is illustrated in a helicopter regulation design example.

  10. Silver conical helix broadband plasmonic nanoantenna

    Science.gov (United States)

    Sobhkhiz, Nader; Moshaii, Ahmad

    2014-01-01

    The discrete dipole approximation method is used to investigate the optical extinction spectra and the electric field enhancement of Ag conical helix (CH) nanostructures. Based on an expected similarity between the radio frequency response of the antenna with the infrared and the visible response of the nanoantenna, the Ag CH nanostructures were designed as a broadband nanoantenna. It is shown that with engineering the structure parameters of the CH nanostructure the plasmonic response of the nanostructure can be designed for a desirable application. In addition, the change of the substrate material for the nanohelix growth is shown to have infinitesimal effect on the resonance peaks of the conical nanohelix. However, varying the surrounding medium can lead to considerable red-shifting of the plasmonic resonance peaks (up to 230 nm). Calculations of the near field around the helical nanoantenna show that the smaller and the larger sides of the CH are related to the plasmonic resonance peaks at low and high wavelengths, respectively. The calculation result for the extinction spectrum has also been compared with similar experimental data for a 2-pitch Ag conical nanohelix and a relatively good agreement between the numerical calculation and the experiment has been obtained.

  11. Role of hydration and intramolecular interactions in the helix-coil transition and helix-helix assembly in a deca-alanine peptide

    CERN Document Server

    Tomar, Dheeraj S; Pettitt, B M; Asthagiri, D

    2015-01-01

    For a model deca-alanine peptide the cavity (ideal hydrophobic) contribution to hydration favors the helix state in the coil-to-helix transition and the paired helix bundle in the assembly of two helices. The energetic contributions of attractive protein-solvent interactions are separated into a short-range part arising from interactions with solvent in the first hydration shell and the remaining long-range part. In the helix-coil transition, short-range attractive protein-solvent interactions outweigh hydrophobic hydration and favor the unfolded coil states. Analysis of enthalpic effects shows that it is the favorable hydration of the peptide backbone that favors the unfolded state. Protein intramolecular interactions favor the helix state and are decisive in folding. In the pairing of two helices, the cavity contribution outweighs short-range attractive protein-water interactions. However, long-range, protein-solvent attractive interactions can either enhance or reverse this trend depending on the mutual or...

  12. Statistical mechanical model for a closed loop plectoneme with weak helix specific forces.

    Science.gov (United States)

    Lee, Dominic J O'

    2017-04-12

    We develop a statistical mechanical framework, based on a variational approximation, to describe closed loop plectonemes. This framework incorporates weak helix structure dependent forces into the determination of the free energy and average structure of a plectoneme. Notably, due to their chiral nature, helix structure dependent forces break the symmetry between left and right handed supercoiling. The theoretical approach, presented here, also provides a systematic way of enforcing the topological constraint of closed loop supercoiling in the variational approximation. At large plectoneme lengths, by considering correlation functions in an expansion in terms of the spatial mean twist density about its thermally averaged value, it can be argued that topological constraint may be approximated by replacing twist and writhe by their thermal averages. A Lagrange multiplier, containing the sum of average twist and writhe, can be added to the free energy to conveniently inforce this result. The average writhe can be calculated through the thermal average of the Gauss' integral in the variational approximation. Furthermore, this approach allows for a possible way to calculate finite size corrections due to the topological constraint. Using interaction energy terms from the mean-field Kornyshev-Leikin theory, for parameter values that correspond to weak helix dependent forces, we calculate the free energy, fluctuation magnitudes and mean geometric parameters for the plectoneme. We see a slight asymmetry, where interestingly, left handed supercoils have a looser structure than right handed ones, although with a lower free energy, unlike what the previous ground state calculations would suggest.

  13. On the solution of nonconvex cardinality Boolean quadratic programming problems: a computational study

    KAUST Repository

    Lima, Ricardo

    2016-06-16

    This paper addresses the solution of a cardinality Boolean quadratic programming problem using three different approaches. The first transforms the original problem into six mixed-integer linear programming (MILP) formulations. The second approach takes one of the MILP formulations and relies on the specific features of an MILP solver, namely using starting incumbents, polishing, and callbacks. The last involves the direct solution of the original problem by solvers that can accomodate the nonlinear combinatorial problem. Particular emphasis is placed on the definition of the MILP reformulations and their comparison with the other approaches. The results indicate that the data of the problem has a strong influence on the performance of the different approaches, and that there are clear-cut approaches that are better for some instances of the data. A detailed analysis of the results is made to identify the most effective approaches for specific instances of the data. © 2016 Springer Science+Business Media New York

  14. Data on diverse roles of helix perturbations in membrane proteins

    Directory of Open Access Journals (Sweden)

    Ashish Shelar

    2016-12-01

    Full Text Available The various structural variations observed in TM helices of membrane proteins have been deconstructed into 9 distinct types of helix perturbations. These perturbations are defined by the deviation of TM helices from the predominantly observed linear α-helical conformation, to form 310- and π-helices, as well as adopting curved and kinked geometries. The data presented here supplements the article ‘Helix perturbations in Membrane Proteins Assist in Inter-helical Interactions and Optimal Helix Positioning in the Bilayer’ (A. Shelar, M. Bansal, 2016 [1]. This data provides strong evidence for the role of various helix perturbations in influencing backbone torsion angles of helices, mediating inter-helical interactions, oligomer formation and accommodation of hydrophobic residues within the bilayer. The methodology used for creation of various datasets of membrane protein families (Sodium/Calcium exchanger and Heme Copper Oxidase has also been mentioned.

  15. Structural alignment of RNA with triple helix structure.

    Science.gov (United States)

    Wong, Thomas K F; Yiu, S M

    2012-04-01

    Structural alignment is useful in identifying members of ncRNAs. Existing tools are all based on the secondary structures of the molecules. There is evidence showing that tertiary interactions (the interaction between a single-stranded nucleotide and a base-pair) in triple helix structures are critical in some functions of ncRNAs. In this article, we address the problem of structural alignment of RNAs with the triple helix. We provide a formal definition to capture a simplified model of a triple helix structure, then develop an algorithm of O(mn(3)) time to align a query sequence (of length m) with known triple helix structure with a target sequence (of length n) with an unknown structure. The resulting algorithm is shown to be useful in identifying ncRNA members in a simulated genome.

  16. Hedera helix L. and damages in Tlos Ancient City

    Directory of Open Access Journals (Sweden)

    Elinç, Z.K.

    2013-03-01

    Full Text Available There are various plant types in Tlos Ancient City of Fethiye district in the Province of Mugla, a city where different residential ruins of Lycia Civilization starting from Classical Age until Byzantine Period. Tlos is an important city in West-Lycia and is situated right on the control point of Lycia Way. Hedera helix L. is one of the plants living in this area, which attracts the attention as it mostly harms the ancient ruins. One of the most important reasons why Hedera helix L. is growing commonly in this region is the perfect ecological circumstances for the growth of this plant of the location where this ancient city is situated in. Additionally the fact that the ruins of the city are left on their fate, is another perfect circumstance for the Hedera helix L. to grow. Climbing or creeping stems of Hedera helix L. stick easily to the objects it touches and encircle them. Due to this characteristic, the walls of the ancient city are covered by this plant. Nevertheless, Hedera helix L. does not only harm the ancient constructions and natural rocks but also woody plants. The harm caused by dried out or cut Hedera helix L. are more than the harm caused by them when they were untouched. The subject of this study is to prove the shape and level of the harm caused by Hedera helix L. on ancient ruins of Tlos. At the same time, this study will underline the fighting methods against Hedera helix L. by comparing similar studies in other countries. Knowledge collected after this study will offer an insight into the excavation and restoration studies undertaken in all Mediterranean countries.

  17. The Triple Helix of University-Industry-Government Relations

    OpenAIRE

    Leydesdorff, Loet

    2012-01-01

    Etzkowitz & Leydesdorff (2000) further elaborated the Triple Helix of University-Industry-Government Relations (cf. Etzkowitz & Leydesdorff, 1995; Lowe, 1982) into a model for studying knowledge-based economies. A series of workshops, conferences, and special issues of journals have developed under this title since 1996. In various countries, the Triple Helix concept has also been used as an operational strategy for regional development and to further the knowledge-based economy. This short r...

  18. Slow Wave Characteristics of Helix Structure with Elliptical Cross Section

    Institute of Scientific and Technical Information of China (English)

    XIE Jian-Xiang; WEI Yan-Yu; GONG Yu-Bin; Fu Cheng-Fang; YUE Ling-Na; WANG Wen-Xiang

    2007-01-01

    We present a novel helix slow wave structure with an elliptical cross section shielded by an elliptical waveguide.The rf characteristics including dispersion properties,interaction impedance of zero mode in this structure have been studied in detail.The theoretical results reveal that weaker dispersion even abnormal dispersion characteristics is obtained with the increasing eccentricity of the elliptical waveguide,while the interaction impedance is enhanced by enlarging the eccentricity of elliptical helix.

  19. Symmetric quadratic Hamiltonians with pseudo-Hermitian matrix representation

    Energy Technology Data Exchange (ETDEWEB)

    Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar

    2016-06-15

    We prove that any symmetric Hamiltonian that is a quadratic function of the coordinates and momenta has a pseudo-Hermitian adjoint or regular matrix representation. The eigenvalues of the latter matrix are the natural frequencies of the Hamiltonian operator. When all the eigenvalues of the matrix are real, then the spectrum of the symmetric Hamiltonian is real and the operator is Hermitian. As illustrative examples we choose the quadratic Hamiltonians that model a pair of coupled resonators with balanced gain and loss, the electromagnetic self-force on an oscillating charged particle and an active LRC circuit. -- Highlights: •Symmetric quadratic operators are useful models for many physical applications. •Any such operator exhibits a pseudo-Hermitian matrix representation. •Its eigenvalues are the natural frequencies of the Hamiltonian operator. •The eigenvalues may be real or complex and describe a phase transition.

  20. The quadratic reciprocity law a collection of classical proofs

    CERN Document Server

    Baumgart, Oswald

    2015-01-01

    This book is the English translation of Baumgart’s thesis on the early proofs of the quadratic reciprocity law (“Über das quadratische Reciprocitätsgesetz. Eine vergleichende Darstellung der Beweise”), first published in 1885. It is divided into two parts. The first part presents a very brief history of the development of number theory up to Legendre, as well as detailed descriptions of several early proofs of the quadratic reciprocity law. The second part highlights Baumgart’s comparisons of the principles behind these proofs. A current list of all known proofs of the quadratic reciprocity law, with complete references, is provided in the appendix. This book will appeal to all readers interested in elementary number theory and the history of number theory.

  1. Parametric localized modes in quadratic nonlinear photonic structures

    DEFF Research Database (Denmark)

    Sukhorukov, Andrey A.; Kivshar, Yuri S.; Bang, Ole;

    2001-01-01

    We analyze two-color spatially localized nonlinear modes formed by parametrically coupled fundamental and second-harmonic fields excited at quadratic (or chi2) nonlinear interfaces embedded in a linear layered structure-a quadratic nonlinear photonic crystal. For a periodic lattice of nonlinear...... interfaces, we derive an effective discrete model for the amplitudes of the fundamental and second-harmonic waves at the interfaces (the so-called discrete chi2 equations) and find, numerically and analytically, the spatially localized solutions-discrete gap solitons. For a single nonlinear interface...... in a linear superlattice, we study the properties of two-color localized modes, and describe both similarities to and differences from quadratic solitons in homogeneous media....

  2. On Volterra quadratic stochastic operators with continual state space

    Energy Technology Data Exchange (ETDEWEB)

    Ganikhodjaev, Nasir; Hamzah, Nur Zatul Akmar [Department of Computational and Theoretical Sciences, Faculty of Science, International Islamic University, Jalan Sultan Ahmad Shah, Bandar Indera Mahkota, 25200 Kuantan, Pahang (Malaysia)

    2015-05-15

    Let (X,F) be a measurable space, and S(X,F) be the set of all probability measures on (X,F) where X is a state space and F is σ - algebraon X. We consider a nonlinear transformation (quadratic stochastic operator) defined by (Vλ)(A) = ∫{sub X}∫{sub X}P(x,y,A)dλ(x)dλ(y), where P(x, y, A) is regarded as a function of two variables x and y with fixed A ∈ F . A quadratic stochastic operator V is called a regular, if for any initial measure the strong limit lim{sub n→∞} V{sup n }(λ) is exists. In this paper, we construct a family of quadratic stochastic operators defined on the segment X = [0,1] with Borel σ - algebra F on X , prove their regularity and show that the limit measure is a Dirac measure.

  3. Amalgamated Products of Ore and Quadratic Extensions of Rings

    CERN Document Server

    Johnson, Garrett

    2012-01-01

    We study the ideal theory of amalgamated products of Ore and quadratic extensions over a base ring R. We prove an analogue of the Hilbert Basis theorem for an amalgamated product Q of quadratic extensions and determine conditions for when the one-sided ideals of Q are principal or doubly-generated. We also determine conditions that make Q a principal ideal ring. Finally, we show that the double affine Hecke algebra $H_{q,t}$ associated to the general linear group GL_2(k) (here, k is a field with characteristic not 2) is an amalgamated product of quadratic extensions over a three-dimensional quantum torus and give an explicit isomorphism. In this case, it follows that $H_{q,t}$ is a noetherian ring.

  4. A Projection Neural Network for Constrained Quadratic Minimax Optimization.

    Science.gov (United States)

    Liu, Qingshan; Wang, Jun

    2015-11-01

    This paper presents a projection neural network described by a dynamic system for solving constrained quadratic minimax programming problems. Sufficient conditions based on a linear matrix inequality are provided for global convergence of the proposed neural network. Compared with some of the existing neural networks for quadratic minimax optimization, the proposed neural network in this paper is capable of solving more general constrained quadratic minimax optimization problems, and the designed neural network does not include any parameter. Moreover, the neural network has lower model complexities, the number of state variables of which is equal to that of the dimension of the optimization problems. The simulation results on numerical examples are discussed to demonstrate the effectiveness and characteristics of the proposed neural network.

  5. Quadratic relativistic invariant and metric form in quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Pissondes, Jean-Claude [DAEC, Observatoire de Paris-Meudon, Meudon (France)

    1999-04-16

    The Klein-Gordon equation is recovered in the framework of the theory of scale-relativity, first in the absence, then in the presence of an electromagnetic field. In this framework, spacetime at quantum scales is characterized by non-differentiability and continuity, which involves the introduction of explicit resolution-dependent fractal coordinates. Such a description leads to the notion of scale-covariance and its corresponding tool, a scale-covariant; derivative operator {theta}/ds. Due to it, the Klein-Gordon equation is written as an equation of free motion and interpreted as a geodesic equation in fractal spacetime. However, we obtain a new form for the corresponding relativistic invariant, which differs from that of special and general relativity. Characterizing quantum mechanics in the present approach, it is not simply quadratic in terms of velocities, but contains an extra term of divergence, which is intrinsically present in its expression. Moreover, in spite of the scale-covariance statements of the present theory, we find an extra term of current in addition to the Lorentz force, within the equations of motion with electromagnetic field written in this framework. Finally, we introduce another tool - a 'symmetric product' - from the requirement of recovering the usual form of the Leibniz rule written with the operator {theta}/ds. This tool allows us to write most equations in this framework in their usual classical form; in particular the simple rules of differentiation, the equations of motion with field and also our new relativistic invariant. (author)

  6. Quadratic adaptive algorithm for solving cardiac action potential models.

    Science.gov (United States)

    Chen, Min-Hung; Chen, Po-Yuan; Luo, Ching-Hsing

    2016-10-01

    An adaptive integration method is proposed for computing cardiac action potential models accurately and efficiently. Time steps are adaptively chosen by solving a quadratic formula involving the first and second derivatives of the membrane action potential. To improve the numerical accuracy, we devise an extremum-locator (el) function to predict the local extremum when approaching the peak amplitude of the action potential. In addition, the time step restriction (tsr) technique is designed to limit the increase in time steps, and thus prevent the membrane potential from changing abruptly. The performance of the proposed method is tested using the Luo-Rudy phase 1 (LR1), dynamic (LR2), and human O'Hara-Rudy dynamic (ORd) ventricular action potential models, and the Courtemanche atrial model incorporating a Markov sodium channel model. Numerical experiments demonstrate that the action potential generated using the proposed method is more accurate than that using the traditional Hybrid method, especially near the peak region. The traditional Hybrid method may choose large time steps near to the peak region, and sometimes causes the action potential to become distorted. In contrast, the proposed new method chooses very fine time steps in the peak region, but large time steps in the smooth region, and the profiles are smoother and closer to the reference solution. In the test on the stiff Markov ionic channel model, the Hybrid blows up if the allowable time step is set to be greater than 0.1ms. In contrast, our method can adjust the time step size automatically, and is stable. Overall, the proposed method is more accurate than and as efficient as the traditional Hybrid method, especially for the human ORd model. The proposed method shows improvement for action potentials with a non-smooth morphology, and it needs further investigation to determine whether the method is helpful during propagation of the action potential. Copyright © 2016 Elsevier Ltd. All rights

  7. A directional nucleation-zipping mechanism for triple helix formation.

    Science.gov (United States)

    Alberti, Patrizia; Arimondo, Paola B; Mergny, Jean-Louis; Garestier, Thérèse; Hélène, Claude; Sun, Jian-Sheng

    2002-12-15

    A detailed kinetic study of triple helix formation was performed by surface plasmon resonance. Three systems were investigated involving 15mer pyrimidine oligonucleotides as third strands. Rate constants and activation energies were validated by comparison with thermodynamic values calculated from UV-melting analysis. Replacement of a T.A base pair by a C.G pair at either the 5' or the 3' end of the target sequence allowed us to assess mismatch effects and to delineate the mechanism of triple helix formation. Our data show that the association rate constant is governed by the sequence of base triplets on the 5' side of the triplex (referred to as the 5' side of the target oligopurine strand) and provides evidence that the reaction pathway for triple helix formation in the pyrimidine motif proceeds from the 5' end to the 3' end of the triplex according to the nucleation-zipping model. It seems that this is a general feature for all triple helices formation, probably due to the right-handedness of the DNA double helix that provides a stronger base stacking at the 5' than at the 3' duplex-triplex junction. Understanding the mechanism of triple helix formation is not only of fundamental interest, but may also help in designing better triple helix-forming oligonucleotides for gene targeting and control of gene expression.

  8. Hydration dynamics of the collagen triple helix by NMR.

    Science.gov (United States)

    Melacini, G; Bonvin, A M; Goodman, M; Boelens, R; Kaptein, R

    2000-07-28

    The hydration of the collagen-like Ac-(Gly-Pro-Hyp)(6)-NH(2) triple-helical peptide in solution was investigated using an integrated set of high-resolution NMR hydration experiments, including different recently developed exchange-network editing methods. This approach was designed to explore the hydration dynamics in the proximity of labile groups, such as the hydroxyproline hydroxyl group, and revealed that the first shell of hydration in collagen-like triple helices is kinetically labile with upper limits for water molecule residence times in the nanosecond to sub-nanosecond range. This result is consistent with a "hopping" hydration model in which solvent molecules are exchanged in and out of solvation sites at a rate that is not directly correlated to the degree of site localization. The hopping model thus reconciles the dynamic view of hydration revealed by NMR with the previously suggested partially ordered semi-clathrate-like cylinder of hydration. In addition, the nanosecond to sub-nanosecond upper limits for water molecule residence times imply that hydration-dehydration events are not likely to be the rate-limiting step for triple helix self-recognition, complementing previous investigations on water dynamics in collagen fibers. This study has also revealed labile proton features expected to facilitate the characterization of the structure and folding of triple helices in collagen peptides.

  9. Photo-active collagen systems with controlled triple helix architecture.

    Science.gov (United States)

    Tronci, Giuseppe; Russell, Stephen J; Wood, David J

    2013-08-14

    The design of photo-active collagen systems is presented as a basis for establishing biomimetic materials with varied network architecture and programmable macroscopic properties. Following in-house isolation of type I collagen, reaction with vinyl-bearing compounds of varied backbone rigidity, i.e. 4-vinylbenzyl chloride (4VBC) and glycidyl methacrylate (GMA), was carried out. TNBS colorimetric assay, (1)H-NMR and ATR-FTIR confirmed covalent and tunable functionalization of collagen lysines. Depending on the type and extent of functionalization, controlled stability and thermal denaturation of triple helices were observed via circular dichroism (CD), whereby the hydrogen-bonding capability of introduced moieties was shown to play a major role. Full gel formation was observed following photo-activation of functionalized collagen solutions. The presence of a covalent network only slightly affected collagen triple helix conformation (as observed by WAXS and ATR-FTIR), confirming the structural organization of functionalized collagen precursors. Photo-activated hydrogels demonstrated an increased denaturation temperature (DSC) with respect to native collagen, suggesting that the formation of the covalent network successfully stabilized collagen triple helices. Moreover, biocompatibility and mechanical competence of obtained hydrogels were successfully demonstrated under physiologically-relevant conditions. These results demonstrate that this novel synthetic approach enabled the formation of biocompatible collagen systems with defined network architecture and programmable macroscopic properties, which can only partially be obtained with current synthetic methods.

  10. Challenges in Targeting a Basic Helix-Loop-Helix Transcription Factor with Hydrocarbon-Stapled Peptides.

    Science.gov (United States)

    Edwards, Amanda L; Meijer, Dimphna H; Guerra, Rachel M; Molenaar, Remco J; Alberta, John A; Bernal, Federico; Bird, Gregory H; Stiles, Charles D; Walensky, Loren D

    2016-11-18

    Basic helix-loop-helix (bHLH) transcription factors play critical roles in organism development and disease by regulating cell proliferation and differentiation. Transcriptional activity, whether by bHLH homo- or heterodimerization, is dependent on protein-protein and protein-DNA interactions mediated by α-helices. Thus, α-helical decoys have been proposed as potential targeted therapies for pathologic bHLH transcription. Here, we developed a library of stabilized α-helices of OLIG2 (SAH-OLIG2) to test the capacity of hydrocarbon-stapled peptides to disrupt OLIG2 homodimerization, which drives the development and chemoresistance of glioblastoma multiforme, one of the deadliest forms of human brain cancer. Although stapling successfully reinforced the α-helical structure of bHLH constructs of varying length, sequence-specific dissociation of OLIG2 dimers from DNA was not achieved. Re-evaluation of the binding determinants for OLIG2 self-association and stability revealed an unanticipated role of the C-terminal domain. These data highlight potential pitfalls in peptide-based targeting of bHLH transcription factors given the liabilities of their positively charged amino acid sequences and multifactorial binding determinants.

  11. A genome-wide survey on basic helix-loop-helix transcription factors in giant panda.

    Directory of Open Access Journals (Sweden)

    Chunwang Dang

    Full Text Available The giant panda (Ailuropoda melanoleuca is a critically endangered mammalian species. Studies on functions of regulatory proteins involved in developmental processes would facilitate understanding of specific behavior in giant panda. The basic helix-loop-helix (bHLH proteins play essential roles in a wide range of developmental processes in higher organisms. bHLH family members have been identified in over 20 organisms, including fruit fly, zebrafish, mouse and human. Our present study identified 107 bHLH family members being encoded in giant panda genome. Phylogenetic analyses revealed that they belong to 44 bHLH families with 46, 25, 15, 4, 11 and 3 members in group A, B, C, D, E and F, respectively, while the remaining 3 members were assigned into "orphan". Compared to mouse, the giant panda does not encode seven bHLH proteins namely Beta3a, Mesp2, Sclerax, S-Myc, Hes5 (or Hes6, EBF4 and Orphan 1. These results provide useful background information for future studies on structure and function of bHLH proteins in the regulation of giant panda development.

  12. An exploration of alternative visualisations of the basic helix-loop-helix protein interaction network

    Directory of Open Access Journals (Sweden)

    Amoutzias Grigoris D

    2007-08-01

    Full Text Available Abstract Background Alternative representations of biochemical networks emphasise different aspects of the data and contribute to the understanding of complex biological systems. In this study we present a variety of automated methods for visualisation of a protein-protein interaction network, using the basic helix-loop-helix (bHLH family of transcription factors as an example. Results Network representations that arrange nodes (proteins according to either continuous or discrete information are investigated, revealing the existence of protein sub-families and the retention of interactions following gene duplication events. Methods of network visualisation in conjunction with a phylogenetic tree are presented, highlighting the evolutionary relationships between proteins, and clarifying the context of network hubs and interaction clusters. Finally, an optimisation technique is used to create a three-dimensional layout of the phylogenetic tree upon which the protein-protein interactions may be projected. Conclusion We show that by incorporating secondary genomic, functional or phylogenetic information into network visualisation, it is possible to move beyond simple layout algorithms based on network topology towards more biologically meaningful representations. These new visualisations can give structure to complex networks and will greatly help in interpreting their evolutionary origins and functional implications. Three open source software packages (InterView, TVi and OptiMage implementing our methods are available.

  13. Hydroxyproline Ring Pucker Causes Frustration of Helix Parameters in the Collagen Triple Helix

    Science.gov (United States)

    Ying Chow, W.; Bihan, Dominique; Forman, Chris J.; Slatter, David A.; Reid, David G.; Wales, David J.; Farndale, Richard W.; Duer, Melinda J.

    2015-07-01

    Collagens, the most abundant proteins in mammals, are defined by their triple-helical structures and distinctive Gly-Xaa-Yaa repeating sequence, where Xaa is often proline and Yaa, hydroxyproline (Hyp/O). It is known that hydroxyproline in the Yaa position stabilises the triple helix, and that lack of proline hydroxylation in vivo leads to dysfunctional collagen extracellular matrix assembly, due to a range of factors such as a change in hydration properties. In addition, we note that in model peptides, when Yaa is unmodified proline, the Xaa proline has a strong propensity to adopt an endo ring conformation, whilst when Yaa is hydroxyproline, the Xaa proline adopts a range of endo and exo conformations. Here we use a combination of solid-state NMR spectroscopy and potential energy landscape modelling of synthetic triple-helical collagen peptides to understand this effect. We show that hydroxylation of the Yaa proline causes the Xaa proline ring conformation to become metastable, which in turn confers flexibility on the triple helix.

  14. Dermatitis from common ivy (Hedera helix L. subsp. helix) in Europe: past, present, and future.

    Science.gov (United States)

    Paulsen, Evy; Christensen, Lars P; Andersen, Klaus E

    2010-04-01

    Common ivy (Hedera helix subsp. helix) is a well-known native and ornamental plant in Europe. Reports on contact dermatitis from ivy have regularly appeared since 1899. Recently, it has been suggested that allergic contact dermatitis from the plant may be under-diagnosed, partly due to lack of commercial patch test allergens. The objective of the article is to present the results of aimed patch testing with the main common ivy allergen, falcarinol, during a 16-year period and review the newer literature. Consecutive patients tested with falcarinol 0.03% petrolatum from May 1993 to May 2009 were included. Cases published since 1987 were retrieved from the PubMed database. One hundred and twenty-seven Danish patients were tested with falcarinol and 10 (7.9%) tested positive. Seven were occupationally sensitized. Between 1994 and 2009, 28 new cases of contact dermatitis from ivy were reported, 2 of which were occupational. Only 11 of the 28 patients were tested with pure allergens. Falcarinol is not only widely distributed in the ivy family, but also in the closely related Apiaceae. Sensitization may occur in childhood or in adults pruning ivy plants or handling them in an occupational setting. In view of the ubiquity of falcarinol-containing plants and the relatively high prevalence of positive reactions in aimed patch testing, falcarinol should be the next plant allergen to be commercially available and included in the plant series worldwide.

  15. Hydroxyproline Ring Pucker Causes Frustration of Helix Parameters in the Collagen Triple Helix.

    Science.gov (United States)

    Chow, W Ying; Bihan, Dominique; Forman, Chris J; Slatter, David A; Reid, David G; Wales, David J; Farndale, Richard W; Duer, Melinda J

    2015-07-29

    Collagens, the most abundant proteins in mammals, are defined by their triple-helical structures and distinctive Gly-Xaa-Yaa repeating sequence, where Xaa is often proline and Yaa, hydroxyproline (Hyp/O). It is known that hydroxyproline in the Yaa position stabilises the triple helix, and that lack of proline hydroxylation in vivo leads to dysfunctional collagen extracellular matrix assembly, due to a range of factors such as a change in hydration properties. In addition, we note that in model peptides, when Yaa is unmodified proline, the Xaa proline has a strong propensity to adopt an endo ring conformation, whilst when Yaa is hydroxyproline, the Xaa proline adopts a range of endo and exo conformations. Here we use a combination of solid-state NMR spectroscopy and potential energy landscape modelling of synthetic triple-helical collagen peptides to understand this effect. We show that hydroxylation of the Yaa proline causes the Xaa proline ring conformation to become metastable, which in turn confers flexibility on the triple helix.

  16. Nanoparticle biofabrication using English ivy (Hedera helix

    Directory of Open Access Journals (Sweden)

    Burris Jason N

    2012-10-01

    Full Text Available Abstract Background English ivy (Hedera helix is well known for its adhesive properties and climbing ability. Essential to its ability to adhere to vertical surfaces is the secretion of a nanocomposite adhesive containing spherical nanoparticles, 60–85 nm in diameter, produced exclusively by root hairs present on adventitious roots. These organic nanoparticles have shown promise in biomedical and cosmetic applications, and represent a safer alternative to metal oxide nanoparticles currently available. Results It was discovered that the maximum adventitious root production was achieved by a 4 h application of 1 mg/ml indole-3 butyric acid (IBA to juvenile English ivy shoot segments cultured in custom vessels. After incubation of the shoots under continuous light at 83 μmol/m2 s at 20°C for 2 weeks, the adventitious roots were harvested from the culture system and it was possible to isolate 90 mg of dry weight nanoparticles per 12 g of roots. The nanoparticle morphology was characterized by atomic force microscopy, and found to be similar to previous studies. Conclusions An enhanced system for the production of English ivy adventitious roots and their nanoparticles by modifying GA7 Magenta boxes and identifying the optimal concentration of IBA for adventitious root growth was developed. This system is the first such platform for growing and harvesting organic nanoparticles from plants, and represents an important step in the development of plant-based nanomanufacturing. It is a significant improvement on the exploitation of plant systems for the formation of metallic nanoparticles, and represents a pathway for the generation of bulk ivy nanoparticles for translation into biomedical applications.

  17. Nanoparticle biofabrication using English ivy (Hedera helix).

    Science.gov (United States)

    Burris, Jason N; Lenaghan, Scott C; Zhang, Mingjun; Stewart, C Neal

    2012-10-24

    English ivy (Hedera helix) is well known for its adhesive properties and climbing ability. Essential to its ability to adhere to vertical surfaces is the secretion of a nanocomposite adhesive containing spherical nanoparticles, 60-85 nm in diameter, produced exclusively by root hairs present on adventitious roots. These organic nanoparticles have shown promise in biomedical and cosmetic applications, and represent a safer alternative to metal oxide nanoparticles currently available. It was discovered that the maximum adventitious root production was achieved by a 4 h application of 1 mg/ml indole-3 butyric acid (IBA) to juvenile English ivy shoot segments cultured in custom vessels. After incubation of the shoots under continuous light at 83 μmol/m2 s at 20°C for 2 weeks, the adventitious roots were harvested from the culture system and it was possible to isolate 90 mg of dry weight nanoparticles per 12 g of roots. The nanoparticle morphology was characterized by atomic force microscopy, and found to be similar to previous studies. An enhanced system for the production of English ivy adventitious roots and their nanoparticles by modifying GA7 Magenta boxes and identifying the optimal concentration of IBA for adventitious root growth was developed. This system is the first such platform for growing and harvesting organic nanoparticles from plants, and represents an important step in the development of plant-based nanomanufacturing. It is a significant improvement on the exploitation of plant systems for the formation of metallic nanoparticles, and represents a pathway for the generation of bulk ivy nanoparticles for translation into biomedical applications.

  18. Convergence properties of the softassign quadratic assignment algorithm.

    Science.gov (United States)

    Rangarajan, A; Vuille, A; Mjolsness, E

    1999-08-15

    The softassign quadratic assignment algorithm is a discrete-time, continuous-state, synchronous updating optimizing neural network. While its effectiveness has been shown in the traveling salesman problem, graph matching, and graph partitioning in thousands of simulations, its convergence properties have not been studied. Here, we construct discrete-time Lyapunov functions for the cases of exact and approximate doubly stochastic constraint satisfaction, which show convergence to a fixed point. The combination of good convergence properties and experimental success makes the softassign algorithm an excellent choice for neural quadratic assignment optimization.

  19. Robust quadratic assignment problem with budgeted uncertain flows

    Directory of Open Access Journals (Sweden)

    Mohammad Javad Feizollahi

    2015-12-01

    Full Text Available We consider a generalization of the classical quadratic assignment problem, where material flows between facilities are uncertain, and belong to a budgeted uncertainty set. The objective is to find a robust solution under all possible scenarios in the given uncertainty set. We present an exact quadratic formulation as a robust counterpart and develop an equivalent mixed integer programming model for it. To solve the proposed model for large-scale instances, we also develop two different heuristics based on 2-Opt local search and tabu search algorithms. We discuss performance of these methods and the quality of robust solutions through extensive computational experiments.

  20. Selectable linear or quadratic coupling in an optomechanical system

    CERN Document Server

    Xuereb, André

    2012-01-01

    There has been much interest recently in the analysis of optomechanical systems incorporating dielectric nano- or microspheres inside a cavity field. We analyse here the situation when one of the mirrors of the cavity itself is also allowed to move. We reveal that the interplay between the two oscillators yields a cross-coupling that results in, e.g., appreciable cooling and squeezing of the motion of the sphere, despite its nominal quadratic coupling. We also discuss a simple modification that would allow this cross-coupling to be removed at will, thereby yielding a purely quadratic coupling for the sphere.

  1. The size of quadratic $p$-adic linearization disks

    OpenAIRE

    Lindahl, Karl-Olof

    2013-01-01

    We find the exact radius of linearization disks at indifferent fixed points of quadratic maps in $\\mathbb{C}_p$. We also show that the radius is invariant under power series perturbations. Localizing all periodic orbits of these quadratic-like maps we then show that periodic points are not the only obstruction for linearization. In so doing, we provide the first known examples in the dynamics of polynomials over $\\mathbb{C}_p$ where the boundary of the linearization disk does not contain any ...

  2. On the use of simplex methods in constructing quadratic models

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper,we investigate the quadratic approximation methods.After studying the basic idea of simplex methods,we construct several new search directions by combining the local information progressively obtained during the iterates of the algorithm to form new subspaces.And the quadratic model is solved in the new subspaces.The motivation is to use the information disclosed by the former steps to construct more promising directions.For most tested problems,the number of function evaluations have been reduced obviously through our algorithms.

  3. New robust chaotic system with exponential quadratic term

    Institute of Scientific and Technical Information of China (English)

    Bao Bo-Cheng; Li Chun-Biao; Xu Jian-Peing; Liu Zhong

    2008-01-01

    This paper proposes a new robust chaotic system of three-dimensional quadratic autonomous ordinary differential equations by introducing an exponential quadratic term.This system can display a double-scroll chaotic attractor with only two equilibria,and can be found to be robust chaotic in a very wide parameter domain with positive maximum Lyapunov exponent.Some basic dynamical properties and chaotic behaviour of novel attractor are studied.By numerical simulation,this paper verifies that the three-dimensional system can also evolve into periodic and chaotic behaviottrs by a constant controller.

  4. Approximation algorithms for indefinite complex quadratic maximization problems

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper,we consider the following indefinite complex quadratic maximization problem: maximize zHQz,subject to zk ∈ C and zkm = 1,k = 1,...,n,where Q is a Hermitian matrix with trQ = 0,z ∈ Cn is the decision vector,and m 3.An (1/log n) approximation algorithm is presented for such problem.Furthermore,we consider the above problem where the objective matrix Q is in bilinear form,in which case a 0.7118 cos mπ 2approximation algorithm can be constructed.In the context of quadratic optimization,various extensions and connections of the model are discussed.

  5. PORTAL SUPPLY TO CAUDATE LOBE AND QUADRATE LOBE OF LIVER

    Directory of Open Access Journals (Sweden)

    Maheswari

    2015-09-01

    Full Text Available The precise knowledge of intra hepatic branching pattern of portal vein to caudate lobe and quadrate lobe is important for Gastroenterologist during hepatic segmental and subsegmental resection. The study was done in 47 adult human liver specimens. In this study methods like Manual dissection and Contrast study were used. During this study the portal branches to caudate l obe, Quadrate lobe and accessory branches to segment IV in addition to its branches were observed. The results were compared with previous studies

  6. Sparse Signal Recovery from Quadratic Measurements via Convex Programming

    OpenAIRE

    Li, Xiaodong; Voroninski, Vladislav

    2012-01-01

    In this paper we consider a system of quadratic equations ||^2 = b_j, j = 1, ..., m, where x in R^n is unknown while normal random vectors z_j in R_n and quadratic measurements b_j in R are known. The system is assumed to be underdetermined, i.e., m < n. We prove that if there exists a sparse solution x, i.e., at most k components of x are non-zero, then by solving a convex optimization program, we can solve for x up to a multiplicative constant with high probability, provided that k

  7. Exact solutions to quadratic gravity generated by a conformal method

    CERN Document Server

    Pravda, Vojtech; Podolsky, Jiri; Svarc, Robert

    2016-01-01

    We study the role of conformal transformations in constructing vacuum solutions to quadratic gravity. We find that such solutions can be obtained by solving one non-linear partial differential equation for the conformal factor on any Einstein spacetime or, more generally, on any background with vanishing Bach tensor. We show that all spacetimes conformal to Kundt are either Kundt or Robinson--Trautmann, and we provide explicit Kundt and Robinson--Trautman solutions to quadratic gravity by solving the above mentioned equation on certain Kundt backgrounds.

  8. Alpha-helix <-> random coil phase transition: analysis of ab initio theory predictions

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Yakubovich, Alexander V.; Solov'yov, Andrey V.

    2008-01-01

    In the present paper we present results of calculations obtained with the use of the theoretical method described in our preceding paper [Eur. Phys. J. D, DOI 10.1140/epjd/e2007-00328-9] and perform detail analysis of -helix random coil transition in alanine polypeptides of different length. We...... have obtained same thermodynamical characteristics from the use of molecular dynamics simulations and compared them with the results of the new statistical mechanics approach. The comparison proves the validity of the statistical mechanic approach and establishes its accuracy....

  9. Role of side chains in collagen triple helix stabilization and partner recognition.

    Science.gov (United States)

    Berisio, Rita; De Simone, Alfonso; Ruggiero, Alessia; Improta, Roberto; Vitagliano, Luigi

    2009-03-01

    Collagen is a widespread protein family involved in a variety of biological processes. The complexity of collagen and its fibrous nature prevent detailed investigations on the full-length protein. Reductionist approaches conducted by dissecting the protein complexity through the use of model peptides have proved to be quite effective. There are, however, several issues regarding structure-stability relationships, aggregation in higher-order assemblies, and partner recognition that are still extensively investigated. In this review, we discuss the role that side chains play in triple helix stabilization and in partner recognition. On the basis of recent literature data, we show that collagen triple helix stability is the result of the interplay of different factors. As a general trend, interactions established by amino/imino acid side chains within the triple helix scaffold effectively modulate the intrinsic residue propensity for this common structural motif. The use of peptide models has also highlighted the role that side chains play in collagen self-association and in its interactions with receptors. Valuable examples in these fields are illustrated. Finally, future actions required to obtain more detailed information on the structure and the function of this complex protein are also delineated.

  10. Contact Stress Analysis for Gears of Different Helix Angle Using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Patil Santosh

    2014-07-01

    Full Text Available The gear contact stress problem has been a great point of interest for many years, but still an extensive research is required to understand the various parameters affecting this stress. Among such parameters, helix angle is one which has played a crucial role in variation of contact stress. Numerous studies have been carried out on spur gear for contact stress variation. Hence, the present work is an attempt to study the contact stresses among the helical gear pairs, under static conditions, by using a 3D finite element method. The helical gear pairs on which the analysis is carried are 0, 5, 15, 25 degree helical gear sets. The Lagrange multiplier algorithm has been used between the contacting pairs to determine the stresses. The helical gear contact stress is evaluated using FE model and results have also been found at different coefficient of friction, varying from 0.0 to 0.3. The FE results have been further compared with the analytical calculations. The analytical calculations are based upon Hertz and AGMA equations, which are modified to include helix angle. The commercial finite element software was used in the study and it was shown that this approach can be applied to gear design efficiently. The contact stress results have shown a decreasing trend, with increase in helix angle.

  11. Beyond the nearest-neighbor Zimm-Bragg model for helix-coil transition in peptides.

    Science.gov (United States)

    Murza, Adrian; Kubelka, Jan

    2009-02-01

    The nearest-neighbor (micro = 1) variant of the Zimm and Bragg (ZB) model has been extensively used to describe the helix-coil transition in biopolymers. In this work, we investigate the helix-coil transition for a 21-residue alanine peptide (AP) with the ZB model up to fourth nearest neighbor (micro = 1, 2, 3, and 4). We use a matrix approach that takes into account combinations of any number of helical stretches of any length and therefore gives the exact statistical weight of the chain within the assumptions of the ZB model. The parameters of the model are determined by fitting the temperature-dependent circular dichroism and Fourier transform infrared experimental spectra of the AP. All variants of the model fit the experimental data, thus giving similar results in terms of the macroscopic observables, such as temperature-dependent fractional helicity. However, the resulting microscopic parameters, such as distributions of the individual residue helical probabilities and free energy surfaces, vary significantly depending on the variant of the model. Overall, the mean residue enthalpy and entropy (in the absolute value) both increase with micro, but combined yield essentially the same "effective" value of the ZB propagation parameters for all micro. Greater helical probabilities for individual residues are predicted for larger micro, in particular, near the center of the sequence. The ZB nucleation parameters increase with increasing micro, which results in a lower free energy barrier to helix nucleation and lower apparent "cooperativity" of the transition. The significance of the long-range interactions for the predictions of ZB model for helix-coil transition, the calculated model parameters and the limitations of the model are discussed.

  12. Effect of Hedera helix on lung histopathology in chronic asthma.

    Directory of Open Access Journals (Sweden)

    Arzu Babayigit Hocaoglu

    2012-12-01

    Full Text Available Hedera helix  is widely used to treat bronchial asthma for many years. However, effects of this herb on lung histopathology is still far from clear. We aimed to determine the effect of oral administration of Hedera helix on lung histopathology in a murine model of chronic asthma.BALB/c  mice  were  divided  into  four  groups;   I  (Placebo,  II  (Hedera  helix, III (Dexamethasone and IV (Control. All mice except controls were sensitized and challenged with ovalbumin. Then, mice in group I received saline, group II 100 mg/kg Hedera helix and group III 1 mg/kg  dexamethasone via orogastic gavage once daily for one week. Airway histopathology was evaluated by using light and electron microscopy in all groups.Goblet  cell numbers and thicknesses of basement membrane were found  significantly lower in group II, but there was no statistically significant difference in terms of number of mast cells, thicknesses of epithelium and subepithelial smooth muscle layers between group I and II. When Hedera helix and dexamethasone groups were compared with each other, thickness of epithelium, subepithelial muscle layers, number of mast cells and goblet cells of group III were significantly ameliorated when compared with the group II.Although Hedera helix administration reduced only goblet cell counts and the thicknesses of basement membrane  in the  asthmatic airways, dexamethasone ameliorated all histopathologic parameters except thickness of  basement  membrane  better  than  Hedera helix.

  13. Structure, stability and folding of the alpha-helix.

    Science.gov (United States)

    Doig, A J; Andrew, C D; Cochran, D A; Hughes, E; Penel, S; Sun, J K; Stapley, B J; Clarke, D T; Jones, G R

    2001-01-01

    Pauling first described the alpha-helix nearly 50 years ago, yet new features of its structure continue to be discovered, using peptide model systems, site-directed mutagenesis, advances in theory, the expansion of the Protein Data Bank and new experimental techniques. Helical peptides in solution form a vast number of structures, including fully helical, fully coiled and partly helical. To interpret peptide results quantitatively it is essential to use a helix/coil model that includes the stabilities of all these conformations. Our models now include terms for helix interiors, capping, side-chain interactions, N-termini and 3(10)-helices. The first three amino acids in a helix (N1, N2 and N3) and the preceding N-cap are unique, as their amide NH groups do not participate in backbone hydrogen bonding. We surveyed their structures in proteins and measured their amino acid preferences. The results are predominantly rationalized by hydrogen bonding to the free NH groups. Stabilizing side-chain-side-chain energies, including hydrophobic interactions, hydrogen bonding and polar/non-polar interactions, were measured accurately in helical peptides. Helices in proteins show a preference for having approximately an integral number of turns so that their N- and C-caps lie on the same side. There are also strong periodic trends in the likelihood of terminating a helix with a Schellman or alpha L C-cap motif. The kinetics of alpha-helix folding have been studied with stopped-flow deep ultraviolet circular dichroism using synchrotron radiation as the light source; this gives a far superior signal-to-noise ratio than a conventional instrument. We find that poly(Glu), poly(Lys) and alanine-based peptides fold in milliseconds, with longer peptides showing a transient overshoot in helix content.

  14. Polyproline and triple helix motifs in host-pathogen recognition.

    Science.gov (United States)

    Berisio, Rita; Vitagliano, Luigi

    2012-12-01

    Secondary structure elements often mediate protein-protein interactions. Despite their low abundance in folded proteins, polyproline II (PPII) and its variant, the triple helix, are frequently involved in protein-protein interactions, likely due to their peculiar propensity to be solvent-exposed. We here review the role of PPII and triple helix in mediating hostpathogen interactions, with a particular emphasis to the structural aspects of these processes. After a brief description of the basic structural features of these elements, examples of host-pathogen interactions involving these motifs are illustrated. Literature data suggest that the role played by PPII motif in these processes is twofold. Indeed, PPII regions may directly mediate interactions between proteins of the host and the pathogen. Alternatively, PPII may act as structural spacers needed for the correct positioning of the elements needed for adhesion and infectivity. Recent investigations have highlighted that collagen triple helix is also a common target for bacterial adhesins. Although structural data on complexes between adhesins and collagen models are rather limited, experimental and theoretical studies have unveiled some interesting clues of the recognition process. Interestingly, very recent data show that not only is the triple helix used by pathogens as a target in the host-pathogen interaction but it may also act as a bait in these processes since bacterial proteins containing triple helix regions have been shown to interact with host proteins. As both PPII and triple helix expose several main chain non-satisfied hydrogen bond acceptors and donors, both elements are highly solvated. The preservation of the solvation state of both PPII and triple helix upon protein-protein interaction is an emerging aspect that will be here thoroughly discussed.

  15. Analyzing Quadratic Unconstrained Binary Optimization Problems Via Multicommodity Flows.

    Science.gov (United States)

    Wang, Di; Kleinberg, Robert D

    2009-11-28

    Quadratic Unconstrained Binary Optimization (QUBO) problems concern the minimization of quadratic polynomials in n {0, 1}-valued variables. These problems are NP-complete, but prior work has identified a sequence of polynomial-time computable lower bounds on the minimum value, denoted by C(2), C(3), C(4),…. It is known that C(2) can be computed by solving a maximum-flow problem, whereas the only previously known algorithms for computing C(k) (k > 2) require solving a linear program. In this paper we prove that C(3) can be computed by solving a maximum multicommodity flow problem in a graph constructed from the quadratic function. In addition to providing a lower bound on the minimum value of the quadratic function on {0, 1}(n), this multicommodity flow problem also provides some information about the coordinates of the point where this minimum is achieved. By looking at the edges that are never saturated in any maximum multicommodity flow, we can identify relational persistencies: pairs of variables that must have the same or different values in any minimizing assignment. We furthermore show that all of these persistencies can be detected by solving single-commodity flow problems in the same network.

  16. A new heuristic for the quadratic assignment problem

    OpenAIRE

    Zvi Drezner

    2002-01-01

    We propose a new heuristic for the solution of the quadratic assignment problem. The heuristic combines ideas from tabu search and genetic algorithms. Run times are very short compared with other heuristic procedures. The heuristic performed very well on a set of test problems.

  17. HOMOCLINIC CYCLES OF A QUADRATIC SYSTEM DESCRIBED BY QUARTIC CURVES

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    This paper is devoted to discussing the topological classification of the quartic invariant algebraic curves for a quadratic system. We obtain sufficient and necessary conditions which ensure that the homoclinic cycle of the system is defined by the quartic invariant algebraic curve. Finally, the corresponding global phase diagrams are drawn.

  18. Diagonalization of bosonic quadratic Hamiltonians by Bogoliubov transformations

    DEFF Research Database (Denmark)

    Nam, Phan Thanh; Napiorkowski, Marcin; Solovej, Jan Philip

    2016-01-01

    We provide general conditions for which bosonic quadratic Hamiltonians on Fock spaces can be diagonalized by Bogoliubov transformations. Our results cover the case when quantum systems have infinite degrees of freedom and the associated one-body kinetic and paring operators are unbounded. Our...

  19. Positivity and storage functions for quadratic differential forms

    NARCIS (Netherlands)

    Trentelman, Hendrikus; Willems, Jan C.

    1996-01-01

    Differential equations and one-variable polynomial matrices play an essential role in describing dynamics of systems. When studying functions of the dynamical variables or specifying performance criteria in optimal control, we invariably encounter quadratic expressions in the variables and their der

  20. Canonical realization of Bondi-Metzner-Sachs symmetry: Quadratic Casimir

    Science.gov (United States)

    Gomis, Joaquim; Longhi, Giorgio

    2016-01-01

    We study the canonical realization of Bondi-Metzner-Sacks symmetry for a massive scalar field introduced by Longhi and Materassi [J. Math. Phys. 40, 480 (1999)]. We construct an invariant scalar product for the generalized momenta. As a consequence we introduce a quadratic Casimir with the supertranslations.

  1. Second Order Backward Stochastic Differential Equations with Quadratic Growth

    CERN Document Server

    Dylan, Possamai

    2012-01-01

    We prove the existence and uniqueness of a solution for one-dimensionnal second order backward stochastic differential equations introduced by Soner, Touzi and Zhang (2010), with a bounded terminal condition and a generator which is continuous with quadratic growth in z. We also prove a Feyman-Kac formula and a probabilistic representation for fully nonlinear PDEs in this setting.

  2. Quantum electroweak symmetry breaking through loop quadratic contributions

    Directory of Open Access Journals (Sweden)

    Dong Bai

    2015-06-01

    Full Text Available Based on two postulations that (i the Higgs boson has a large bare mass mH≫mh≃125 GeV at the characteristic energy scale Mc which defines the Standard Model (SM in the ultraviolet region, and (ii quadratic contributions of Feynman loop diagrams in quantum field theories are physically meaningful, we show that the SM electroweak symmetry breaking is induced by the quadratic contributions from loop effects. As the quadratic running of Higgs mass parameter leads to an additive renormalization, which distinguishes from the logarithmic running with a multiplicative renormalization, the symmetry breaking occurs once the sliding energy scale μ moves from Mc down to a transition scale μ=ΛEW at which the additive renormalized Higgs mass parameter mH2(Mc/μ gets to change the sign. With the input of current experimental data, this symmetry breaking energy scale is found to be ΛEW≃760 GeV, which provides another basic energy scale for the SM besides Mc. Studying such a symmetry breaking mechanism could play an important role in understanding both the hierarchy problem and naturalness problem. It also provides a possible way to explore the experimental implications of the quadratic contributions as ΛEW lies within the probing reach of the LHC and the future Great Collider.

  3. Bandit-Inspired Memetic Algorithms for Solving Quadratic Assignment Problems

    NARCIS (Netherlands)

    Puglierin, Francesco; Drugan, Madalina M.; Wiering, Marco

    2013-01-01

    In this paper we propose a novel algorithm called the Bandit-Inspired Memetic Algorithm (BIMA) and we have applied it to solve different large instances of the Quadratic Assignment Problem (QAP). Like other memetic algorithms, BIMA makes use of local search and a population of solutions. The novelty

  4. The Quadratic Assignment Problem is Easy for Robinsonian Matrices

    NARCIS (Netherlands)

    Laurent, M.; Seminaroti, M.

    2014-01-01

    We present a new polynomially solvable case of the Quadratic Assignment Problem in Koopmans-Beckman form QAP(A;B), by showing that the identity permutation is optimal when A and B are respectively a Robinson similarity and dissimilarity matrix and one of A or B is a Toeplitz matrix. A Robinson (dis)

  5. A bilinear programming solution to the quadratic assignment problem

    NARCIS (Netherlands)

    J.F. Kaashoek (Johan); J.H.P. Paelinck (Jean)

    1999-01-01

    textabstractThe quadratic assignment problem (QAP) or maximum acyclical graph problem is well documented (see e.g. Pardalos and Wolkowicz, 1994). One of the authors has published some material, in which it was tried, by structuring the problem additionally, to bring it as closely as possible in the

  6. The quadratic assignment problem is easy for robinsonian matrices

    NARCIS (Netherlands)

    Laurent, M.; Seminaroti, M.

    2015-01-01

    We present a new polynomially solvable case of the Quadratic Assignment Problem in Koopmans–Beckman form QAP(A,B), by showing that the identity permutation is optimal when AA and BB are respectively a Robinson similarity and dissimilarity matrix and one of AA or BB is a Toeplitz matrix. A Robinson (

  7. Solving quadratic programming problems by delayed projection neural network.

    Science.gov (United States)

    Yang, Yongqing; Cao, Jinde

    2006-11-01

    In this letter, the delayed projection neural network for solving convex quadratic programming problems is proposed. The neural network is proved to be globally exponentially stable and can converge to an optimal solution of the optimization problem. Three examples show the effectiveness of the proposed network.

  8. A Result on Output Feedback Linear Quadratic Control

    NARCIS (Netherlands)

    Engwerda, J.C.; Weeren, A.J.T.M.

    2006-01-01

    In this note we consider the static output feedback linear quadratic control problem.We present both necessary and sufficient conditions under which this problem has a solution in case the involved cost depend only on the output and control variables.This result is used to present both necessary and

  9. Nonlocal description of X waves in quadratic nonlinear materials

    DEFF Research Database (Denmark)

    Larsen, Peter Ulrik Vingaard; Sørensen, Mads Peter; Bang, Ole

    2006-01-01

    We study localized light bullets and X-waves in quadratic media and show how the notion of nonlocality can provide an alternative simple physical picture of both types of multi-dimensional nonlinear waves. For X-waves we show that a local cascading limit in terms of a nonlinear Schrodinger equation...

  10. ON WEIGHTED GENERALIZED FUNCTIONS ASSOCIATED WITH QUADRATIC FORMS

    Directory of Open Access Journals (Sweden)

    E. L. Shishkina

    2016-12-01

    Full Text Available In this article we consider certain types of weighted generalized functions associated with nondegenerate quadratic forms. Such functions and their derivatives are used for constructing fundamental solutions of iterated ultra-hyperbolic equations with the Bessel operator and for constructing negative real powers of ultra-hyperbolic operators with the Bessel operator.

  11. Quadratic Lyapunov Function and Exponential Dichotomy on Time Scales

    Institute of Scientific and Technical Information of China (English)

    ZHANG JI; LIU ZHEN-XIN

    2011-01-01

    In this paper, we study the relationship between exponential dichotomy and quadratic Lyapunov function for the linear equation x△ = A(t)x on time scales.Moreover, for the nonlinear perturbed equation x△ = A(t)x + f(t,x) we give the instability of the zero solution when f is sufficiently small.

  12. Radar Rainfall Estimation using a Quadratic Z-R equation

    Science.gov (United States)

    Hall, Will; Rico-Ramirez, Miguel Angel; Kramer, Stefan

    2016-04-01

    The aim of this work is to test a method that enables the input of event based drop size distributions to alter a quadratic reflectivity (Z) to rainfall (R) equation that is limited by fixed upper and lower points. Results will be compared to the Marshall-Palmer Z-R relation outputs and validated by a network of gauges and a single polarisation weather radar located close to Essen, Germany. The time window over which the drop size distribution measurements will be collected is varied to note any effect on the generated quadratic Z-R relation. The new quadratic algorithm shows some distinct improvement over the Marshall-Palmer relationship through multiple events. The inclusion of a minimum number of Z-R points helped to decrease the associated error by defaulting back to the Marshall-Palmer equation if the limit was not reached. More research will be done to discover why the quadratic performs poorly in some events as there appears to be little correlation between number of drops or mean rainfall amount and the associated error. In some cases it seems the spatial distribution of the disdrometers has a significant effect as a large percentage of the rain bands pass to the north of two of the three disdrometers, frequently in a slightly north-easterly direction. However during widespread precipitation events the new algorithm works very well with reductions compared to the Marshall-Palmer relation.

  13. Entanglement entropy of fermionic quadratic band touching model

    Science.gov (United States)

    Chen, Xiao; Cho, Gil Young; Fradkin, Eduardo

    2014-03-01

    The entanglement entropy has been proven to be a useful tool to diagnose and characterize strongly correlated systems such as topologically ordered phases and some critical points. Motivated by the successes, we study the entanglement entropy (EE) of a fermionic quadratic band touching model in (2 + 1) dimension. This is a fermionic ``spinor'' model with a finite DOS at k=0 and infinitesimal instabilities. The calculation on two-point correlation functions shows that a Dirac fermion model and the quadratic band touching model both have the asymptotically identical behavior in the long distance limit. This implies that EE for the quadratic band touching model also has an area law as the Dirac fermion. This is in contradiction with the expectation that dense fermi systems with a finite DOS should exhibit LlogL violations to the area law of entanglement entropy (L is the length of the boundary of the sub-region) by analogy with the Fermi surface. We performed numerical calculations of entanglement entropies on a torus of the lattice models for the quadratic band touching point and the Dirac fermion to confirm this. The numerical calculation shows that EE for both cases satisfy the area law. We further verify this result by the analytic calculation on the torus geometry. This work was supported in part by the NSF grant DMR-1064319.

  14. Kronecker limit formula for real quadratic number fields(III)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    For a kind of L-function of the real quadratic number fields, we prove a Kronecker limit formula which generalized a result of Hecke. And taking an example we give an interesting identity on a fundamental unit of such a field.

  15. A realised volatility measurement using quadratic variation and ...

    African Journals Online (AJOL)

    the instantaneous volatility does not change too much as a result of a weighted average ... method is also based on quadratic variation theory, but the underlying return model is ..... [3] Barndorff-Nielsen OE & Shepard N, 2001, Non-Gaussian ...

  16. The strong law of large numbers for random quadratic forms

    NARCIS (Netherlands)

    Mikosch, T

    1996-01-01

    The paper establishes strong laws of large numbers for the quadratic forms [GRAPHICS] and the bilinear forms [GRAPHICS] where X = (X(n)) is a sequence of independent random variables and Y = (Y-n) is an independent copy of it. In the case of independent identically distributed symmetric p-stable ran

  17. Confidence set interference with a prior quadratic bound. [in geophysics

    Science.gov (United States)

    Backus, George E.

    1989-01-01

    Neyman's (1937) theory of confidence sets is developed as a replacement for Bayesian interference (BI) and stochastic inversion (SI) when the prior information is a hard quadratic bound. It is recommended that BI and SI be replaced by confidence set interference (CSI) only in certain circumstances. The geomagnetic problem is used to illustrate the general theory of CSI.

  18. Optimization with quadratic support functions in nonconvex smooth optimization

    Science.gov (United States)

    Khamisov, O. V.

    2016-10-01

    Problem of global minimization of twice continuously differentiable function with Lipschitz second derivatives over a polytope is considered. We suggest a branch and bound method with polytopes as partition elements. Due to the Lipschitz property of the objective function we can construct a quadratic support minorant at each point of the feasible set. Global minimum of of this minorant provides a lower bound of the objective over given partition subset. The main advantage of the suggested method consists in the following. First quadratic minorants usually are nonconvex and we have to solve auxiliary global optimization problem. This problem is reduced to a mixed 0-1 linear programming problem and can be solved by an advanced 0-1 solver. Then we show that the quadratic minorants are getting convex as soon as partition elements are getting smaller in diameter. Hence, at the final steps of the branch and bound method we solve convex auxiliary quadratic problems. Therefore, the method accelerates when we are close to the global minimum of the initial problem.

  19. Stochastic level-value approximation for quadratic integer convex programming

    Institute of Scientific and Technical Information of China (English)

    PENG Zheng; WU Dong-hua

    2008-01-01

    We propose a stochastic level value approximation method for a quadratic integer convex minimizing problem in this paper. This method applies an importance sampling technique, and make use of the cross-entropy method to update the sample density functions. We also prove the asymptotic convergence of this algorithm, and re-port some numerical results to illuminate its effectiveness.

  20. Diagonalization of bosonic quadratic Hamiltonians by Bogoliubov transformations

    DEFF Research Database (Denmark)

    Nam, Phan Thanh; Napiorkowski, Marcin; Solovej, Jan Philip

    2016-01-01

    We provide general conditions for which bosonic quadratic Hamiltonians on Fock spaces can be diagonalized by Bogoliubov transformations. Our results cover the case when quantum systems have infinite degrees of freedom and the associated one-body kinetic and paring operators are unbounded. Our...

  1. Sub-quadratic decoding of one-point hermitian codes

    DEFF Research Database (Denmark)

    Nielsen, Johan Sebastian Rosenkilde; Beelen, Peter

    2015-01-01

    We present the first two sub-quadratic complexity decoding algorithms for one-point Hermitian codes. The first is based on a fast realization of the Guruswami-Sudan algorithm using state-of-the-art algorithms from computer algebra for polynomial-ring matrix minimization. The second is a power...

  2. Cosmological Vorticity in a Gravity with Quadratic Order Curvature Couplings

    CERN Document Server

    Hwang, J

    1998-01-01

    We analyse the evolution of the rotational type cosmological perturbation in a gravity with general quadratic order gravitational coupling terms. The result is expressed independently of the generalized nature of the gravity theory, and is simply interpreted as a conservation of the angular momentum.

  3. The strong law of large numbers for random quadratic forms

    NARCIS (Netherlands)

    Mikosch, T

    1996-01-01

    The paper establishes strong laws of large numbers for the quadratic forms [GRAPHICS] and the bilinear forms [GRAPHICS] where X = (X(n)) is a sequence of independent random variables and Y = (Y-n) is an independent copy of it. In the case of independent identically distributed symmetric p-stable

  4. Searchless tuning of linear controllers for the minimum of quadratic criterion

    Science.gov (United States)

    Pikina, G. A.; Burtseva, Yu. S.

    2014-03-01

    A searchless method of calculating the tunings of typical controllers is developed for linear plants with a time delay, the use of which makes it possible to minimize the quadratic criterion I 2 with respect to an internal disturbance. The basic idea of the method consists in obtaining the complex frequency response of a suboptimal linear controller, followed by approaching the characteristic of a typical controller to this frequency response in the essential frequency band using the least squares method. Recommendations on selecting the smoothing filter time constant and the suboptimal system's dynamic error are given for a system comprising a PID controller and a second-order plant with a time delay.

  5. Steady-state solution of the PTC thermistor problem using a quadratic spline finite element method

    Directory of Open Access Journals (Sweden)

    Bahadir A. R.

    2002-01-01

    Full Text Available The problem of heat transfer in a Positive Temperature Coefficient (PTC thermistor, which may form one element of an electric circuit, is solved numerically by a finite element method. The approach used is based on Galerkin finite element using quadratic splines as shape functions. The resulting system of ordinary differential equations is solved by the finite difference method. Comparison is made with numerical and analytical solutions and the accuracy of the computed solutions indicates that the method is well suited for the solution of the PTC thermistor problem.

  6. A sequential quadratic programming algorithm using an incomplete solution of the subproblem

    Energy Technology Data Exchange (ETDEWEB)

    Murray, W. [Stanford Univ., CA (United States). Systems Optimization Lab.; Prieto, F.J. [Universidad `Carlos III` de Madrid (Spain). Dept. de Estadistica y Econometria

    1993-05-01

    We analyze sequential quadratic programming (SQP) methods to solve nonlinear constrained optimization problems that are more flexible in their definition than standard SQP methods. The type of flexibility introduced is motivated by the necessity to deviate from the standard approach when solving large problems. Specifically we no longer require a minimizer of the QP subproblem to be determined or particular Lagrange multiplier estimates to be used. Our main focus is on an SQP algorithm that uses a particular augmented Lagrangian merit function. New results are derived for this algorithm under weaker conditions than previously assumed; in particular, it is not assumed that the iterates lie on a compact set.

  7. Quadratically consistent projection from particles to mesh

    CERN Document Server

    Duque, Daniel

    2016-01-01

    The advantage of particle Lagrangian methods in computational fluid dynamics is that advection is accurately modeled. However, this complicates the calculation of space derivatives. If a mesh is employed, it must be updated at each time step. On the other hand, fixed mesh, Eulerian, formulations benefit from the mesh being defined at the beginning of the simulation, but feature non-linear advection terms. It therefore seems natural to combine the two approaches, using a fixed mesh to perform calculations related to space derivatives, and using the particles to advect the information with time. The idea of combining Lagrangian particles and a fixed mesh goes back to Particle-in-Cell methods, and is here considered within the context of the finite element method (FEM) for the fixed mesh, and the particle FEM (pFEM) for the particles. Our results, in agreement with recent works, show that interpolation ("projection") errors, especially from particles to mesh, are the culprits of slow convergence of the method if...

  8. An unusual helix turn helix motif in the catalytic core of HIV-1 integrase binds viral DNA and LEDGF.

    Directory of Open Access Journals (Sweden)

    Hayate Merad

    Full Text Available BACKGROUND: Integrase (IN of the type 1 human immunodeficiency virus (HIV-1 catalyzes the integration of viral DNA into host cellular DNA. We identified a bi-helix motif (residues 149-186 in the crystal structure of the catalytic core (CC of the IN-Phe185Lys variant that consists of the alpha(4 and alpha(5 helices connected by a 3 to 5-residue turn. The motif is embedded in a large array of interactions that stabilize the monomer and the dimer. PRINCIPAL FINDINGS: We describe the conformational and binding properties of the corresponding synthetic peptide. This displays features of the protein motif structure thanks to the mutual intramolecular interactions of the alpha(4 and alpha(5 helices that maintain the fold. The main properties are the binding to: 1- the processing-attachment site at the LTR (long terminal repeat ends of virus DNA with a K(d (dissociation constant in the sub-micromolar range; 2- the whole IN enzyme; and 3- the IN binding domain (IBD but not the IBD-Asp366Asn variant of LEDGF (lens epidermal derived growth factor lacking the essential Asp366 residue. In our motif, in contrast to the conventional HTH (helix-turn-helix, it is the N terminal helix (alpha(4 which has the role of DNA recognition helix, while the C terminal helix (alpha(5 would rather contribute to the motif stabilization by interactions with the alpha(4 helix. CONCLUSION: The motif, termed HTHi (i, for inverted emerges as a central piece of the IN structure and function. It could therefore represent an attractive target in the search for inhibitors working at the DNA-IN, IN-IN and IN-LEDGF interfaces.

  9. TOWARDS UNDERSTANDING OF HELIX B BASED CONFORMATIONAL DISEASES IN SERPIN

    Directory of Open Access Journals (Sweden)

    Mohamad Aman Jairajpuri

    2012-12-01

    Full Text Available Serine protease inhibitors (serpins are a unique family of protease inhibitors that are prone to polymer formation due to their metastable nature and a complex inhibition mechanism that involves large scale conformational change. Helix B is in the shutter region near the strand 2A and strand 3A of �-sheet A, where reactive centre loop inserts during the serpin inhibition mechanism. Helix B region in serpins is a mutation hotspot for naturally occurring variants that result in pathological conditions due to polymerization. Helix B residues are completely buried in the native state and loop inserted latent state but not in the inhibitory loop inserted cleaved conformation. Native to cleaved transition during inhibition forms a large cavity in the shutter region, which invariably is the largest cavity in most serpins in native state. In a recent paper we had for the first time hypothesized that exposure of helix B at the N-terminal end is important for smooth insertion of the reactive center loop during serpin inhibition mechanism. It is therefore possible that natural variant that induces conformational deformation of helix B probably alter the cavity size which increases the rate of loop-sheet interaction between the monomers resulting in increased polymerization.

  10. The Other Double Helix--The Fascinating Chemistry of Starch

    Science.gov (United States)

    Hancock, Robert D.; Tarbet, Bryon J.

    2000-08-01

    Current textbooks deal only briefly with the chemistry of starch. A short review with 21 references is presented, describing the structure of starch and indicating the double helix structure of A-type and B-type starch. The structure of the starch granule is examined, pointing out the existence of growth rings of alternating crystalline and noncrystalline starch, with growing amylopectin molecules extending from the hilum (point of origin) to the surface of the starch granule. The swelling of starch granules in water, above the gelatinization temperature of about 60 °C, is discussed. The process of gelatinization involves unraveling of the starch helix and a manyfold increase in volume of the starch granule as water is imbibed and bound to the unraveled starch polymer by hydrogen bonding. Baking bread or pastries causes unraveling of the starch helix, and the process by which these products become stale corresponds primarily to the re-forming of the starch helix. The importance of this phenomenon in food science is discussed. The absorption of nonpolar linear molecules such as I2, or linear nonpolar portions of molecules such as n-butanol or fats and phospholipids, by the C-type helix of starch is examined. The way in which starch is structurally modified to retard staling is discussed in relation to food technology.

  11. Sample Extraction Bsaed on Helix Scattering for Polarimetric SAR Calibratio

    Science.gov (United States)

    Chang, Y.; Yang, J.; Li, P.; Zhao, L.; Shi, L.

    2017-09-01

    Polarimetric calibration (PolCAL) of Synthetic Aperture Radar (SAR) images is a significant preprocessing for further applications. Since the reflection symmetry property of distributed objects can provide stable constraints for PolCAL. It is reasonable to extract these reference samples before calibration. The helix scattering generally appears in complex urban area and disappears for a natural scatterer, making it a good measure to extract distributed objects. In this paper, a novel technique that extracts reflecting symmetry samples is proposed by using helix scattering. The helix scattering information is calculated by Yamaguchi four-component decomposition algorithm. An adaptive threshold selection algorithm based on generalized Gaussian distribution is also utilized to scale the helix scattering components automatically, getting rid of the problem of various numerical range. The extracting results will be taken as PolCAL reference samples and the Quegan method are utilized to calibrate these PolSAR images. A C-band airborne PolSAR data was taken as examples to evaluate its ability in improving calibration precision. Traditional method i.e. extracting samples with span power was also evaluated as contrast experiment. The results showed that the samples extracting method based on helix scattering can improve the Polcal precision preferably.

  12. Development of a log-quadratic model to describe microbial inactivation, illustrated by thermal inactivation of Clostridium botulinum.

    Science.gov (United States)

    Stone, G; Chapman, B; Lovell, D

    2009-11-01

    In the commercial food industry, demonstration of microbiological safety and thermal process equivalence often involves a mathematical framework that assumes log-linear inactivation kinetics and invokes concepts of decimal reduction time (D(T)), z values, and accumulated lethality. However, many microbes, particularly spores, exhibit inactivation kinetics that are not log linear. This has led to alternative modeling approaches, such as the biphasic and Weibull models, that relax strong log-linear assumptions. Using a statistical framework, we developed a novel log-quadratic model, which approximates the biphasic and Weibull models and provides additional physiological interpretability. As a statistical linear model, the log-quadratic model is relatively simple to fit and straightforwardly provides confidence intervals for its fitted values. It allows a D(T)-like value to be derived, even from data that exhibit obvious "tailing." We also showed how existing models of non-log-linear microbial inactivation, such as the Weibull model, can fit into a statistical linear model framework that dramatically simplifies their solution. We applied the log-quadratic model to thermal inactivation data for the spore-forming bacterium Clostridium botulinum and evaluated its merits compared with those of popular previously described approaches. The log-quadratic model was used as the basis of a secondary model that can capture the dependence of microbial inactivation kinetics on temperature. This model, in turn, was linked to models of spore inactivation of Sapru et al. and Rodriguez et al. that posit different physiological states for spores within a population. We believe that the log-quadratic model provides a useful framework in which to test vitalistic and mechanistic hypotheses of inactivation by thermal and other processes.

  13. Universal kinetics of helix-coil transition in gelatin.

    Science.gov (United States)

    Gornall, J L; Terentjev, E M

    2008-03-01

    By covering a much wider concentration range than previous studies we find a very unusual exponential dependence of the rate of helix formation on concentration of gelatin in water and ethylene glycol solutions. By applying a procedure of concentration-temperature superposition we build a master curve describing the initial renaturation rates in both solvents. The growth of the normalized helical fraction chi(t) is a first-order process, with a rate constant consistent with cis-trans isomerization, in most situations. We propose that association of three separate chains to form a triple helical nucleus occurs rapidly and contributes less to the helical onset than previously thought. The measured helix content is a result of lengthening of the triple helix after nucleation, by zipping from the associated nuclei.

  14. Stabilization of magnetic helix in exchange-coupled thin films.

    Science.gov (United States)

    Dzemiantsova, L V; Meier, G; Röhlsberger, R

    2015-11-05

    Based on micromagnetic simulations, we report on a novel magnetic helix in a soft magnetic film that is sandwiched between and exchange-coupled to two hard magnetic layers with different anisotropies. We show that such a confined helix stays stable without the presence of an external magnetic field. The magnetic stability is determined by the energy minimization and is a result of an internal magnetic field created by the exchange interaction. We show that this internal field stores a magnetic energy density of a few kJ/m(3). We also find that it dramatically modifies ferromagnetic resonances, such that the helix can be used as a ferromagnetic resonance filter and a fast acting attenuator.

  15. Prediction of transmembrane helix orientation in polytopic membrane proteins

    Directory of Open Access Journals (Sweden)

    Liang Jie

    2006-06-01

    Full Text Available Abstract Background Membrane proteins compose up to 30% of coding sequences within genomes. However, their structure determination is lagging behind compared with soluble proteins due to the experimental difficulties. Therefore, it is important to develop reliable computational methods to predict structures of membrane proteins. Results We present a method for prediction of the TM helix orientation, which is an essential step in ab initio modeling of membrane proteins. Our method is based on a canonical model of the heptad repeat originally developed for coiled coils. We identify the helical surface patches that interface with lipid molecules at an accuracy of about 88% from the sequence information alone, using an empirical scoring function LIPS (LIPid-facing Surface, which combines lipophilicity and conservation of residues in the helix. We test and discuss results of prediction of helix-lipid interfaces on 162 transmembrane helices from 18 polytopic membrane proteins and present predicted orientations of TM helices in TRPV1 channel. We also apply our method to two structures of homologous cytochrome b6f complexes and find discrepancy in the assignment of TM helices from subunits PetG, PetN and PetL. The results of LIPS calculations and analysis of packing and H-bonding interactions support the helix assignment found in the cytochrome b6f structure from green alga but not the assignment of TM helices in the cyanobacterium b6f structure. Conclusion LIPS calculations can be used for the prediction of helix orientation in ab initio modeling of polytopic membrane proteins. We also show with the example of two cytochrome b6f structures that our method can identify questionable helix assignments in membrane proteins. The LIPS server is available online at http://gila.bioengr.uic.edu/lab/larisa/lips.html.

  16. A statistically derived parameterization for the collagen triple-helix.

    Science.gov (United States)

    Rainey, Jan K; Goh, M Cynthia

    2002-11-01

    The triple-helix is a unique secondary structural motif found primarily within the collagens. In collagen, it is a homo- or hetero-tripeptide with a repeating primary sequence of (Gly-X-Y)(n), displaying characteristic peptide backbone dihedral angles. Studies of bulk collagen fibrils indicate that the triple-helix must be a highly repetitive secondary structure, with very specific constraints. Primary sequence analysis shows that most collagen molecules are primarily triple-helical; however, no high-resolution structure of any entire protein is yet available. Given the drastic morphological differences in self-assembled collagen structures with subtle changes in assembly conditions, a detailed knowledge of the relative locations of charged and sterically bulky residues in collagen is desirable. Its repetitive primary sequence and highly conserved secondary structure make collagen, and the triple-helix in general, an ideal candidate for a general parameterization for prediction of residue locations and for the use of a helical wheel in the prediction of residue orientation. Herein, a statistical analysis of the currently available high-resolution X-ray crystal structures of model triple-helical peptides is performed to produce an experimentally based parameter set for predicting peptide backbone and C(beta) atom locations for the triple-helix. Unlike existing homology models, this allows easy prediction of an entire triple-helix structure based on all existing high-resolution triple-helix structures, rather than only on a single structure or on idealized parameters. Furthermore, regional differences based on the helical propensity of residues may be readily incorporated. The parameter set is validated in terms of the predicted bond lengths, backbone dihedral angles, and interchain hydrogen bonding.

  17. Encoding physico-chemical cues in synthetic hydrogels by triple helix assembly of collagen mimetic peptides

    Science.gov (United States)

    Stahl, Patrick

    The ECM is a complex natural system evolved to promote proliferation and differentiation of cells during tissue development. In order to create synthetic biomaterials for studying cell-scaffold interactions and ultimately for engineering tissues, scientists strive to recapitulate many characteristics of ECM by developing hydrogels that contain mechanical cues and biochemical signals such as adhesion moieties and cell growth factors. While synthetic hydrogels bypass limitations of naturally-derived materials (e.g. transfer of pathogens), nature provides inspiration to enhance the functionality of synthetic hydrogels through biomimetic approaches. The collagen triple helix is the basis for the supramolecular structure of collagen in the ECM, and its adaptation in collagen mimetic peptides (CMPs) has provided hybridization mechanisms that can be employed in the formation and functionalization of synthetic hydrogels. The aim of this dissertation is to develop novel poly(ethylene glycol) (PEG)-based hydrogels that employ CMP triple helix assembly as a non-covalent yet target-specific tool to encode physical and chemical cues into the hydrogel with spatial control. We demonstrate that multi-arm PEG functionalized with CMPs form hydrogels supported by physical crosslinks mediated by CMP triple helix. Particle tracking microrheology shows that these physical crosslinks are sensitive to temperature as well as addition of exogenous CMPs that can disrupt crosslinks by competing for triple helix formation. This physical crosslink disruption enables the modulation of bulk hydrogel elasticity and the introduction of local stiffness gradients in PEG-CMP hydrogels. We also present photopolymerized PEG diacrylate (PEGDA) hydrogels displaying CMPs that can be further conjugated to CMPs with bioactive moieties via triple helix hybridization. Encoding these hydrogels with cell-adhesive CMPs induces cell spreading and proliferation. We further demonstrate generation of gradients and

  18. Parametric-Resonance Ionization Cooling in Twin-Helix.

    Energy Technology Data Exchange (ETDEWEB)

    V.S. Morozov, Ya.S. Derbenev, A. Afanasev, R.P. Johnson, Erdelyi. B., J.A. Maloney

    2011-09-01

    Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a highluminosity muon collider. For the implementation of PIC, we developed an epicyclic twin-helix channel with correlated optics. Wedge-shaped absorbers immediately followed by short rf cavities are placed into the twin-helix channel. Parametric resonances are induced in both planes using helical quadrupole harmonics. We demonstrate resonant dynamics and cooling with stochastic effects off using GEANT4/G4beamline. We illustrate compensation of spherical aberrations and benchmark COSY Infinity, a powerful tool for aberration analysis and compensation.

  19. DNA-like double helix formed by peptide nucleic acid

    DEFF Research Database (Denmark)

    Wittung, P; Nielsen, Peter E.; Buchardt, O;

    1994-01-01

    Although the importance of the nucleobases in the DNA double helix is well understood, the evolutionary significance of the deoxyribose phosphate backbone and the contribution of this chemical entity to the overall helical structure and stability of the double helix is not so clear. Peptide nucleic...... acid (PNA) is a DNA analogue with a backbone consisting of N-(2-aminoethyl)glycine units (Fig. 1) which has been shown to mimic DNA in forming Watson-Crick complementary duplexes with normal DNA. Using circular dichroism spectroscopy we show here that two complementary PNA strands can hybridize to one...

  20. MODIFIED BERNOULLI ITERATION METHODS FOR QUADRATIC MATRIX EQUATION

    Institute of Scientific and Technical Information of China (English)

    Zhong-Zhi Bai; Yong-Hua Gao

    2007-01-01

    We construct a modified Bernoulli iteration method for solving the quadratic matrix equation AX2+BX+C=0,where A,B and C are square matrices.This method is motivated from the Gauss-Seidel iteration for solving linear systems and the ShermanMorrison-Woodbury formula for updating matrices.Under suitable conditions, we prove the local linear convergence of the Dew method.An algorithm is presented to find the solution of the quadratic matrix equation and some numerical results are given to show the feasibility and the effectiveness of the algorithm.In addition,we also describe and analyze the block version of the modified Bernoulli iteration method.

  1. Gravitomagnetic effects in quadratic gravity with a scalar field

    CERN Document Server

    Finch, Andrew

    2016-01-01

    The two gravitomagnetic effects which influence bodies orbiting around a gravitational source are the geodetic effect and the Lense-Thirring effect. The former describes the precession angle of the axis of a spinning gyroscope while in orbit around a nonrotating gravitational source whereas the latter provides a correction for this angle in the case of a spinning source. In this paper we derive the relevant equations in quadratic gravity and relate them to their equivalents in general relativity. Starting with an investigation into Kepler's third law in quadratic gravity with a scalar field, the effects of an axisymmetric and rotating gravitational source on an orbiting body in a circular, equatorial orbit are introduced.

  2. Induced motion of domain walls in multiferroics with quadratic interaction

    Energy Technology Data Exchange (ETDEWEB)

    Gerasimchuk, Victor S., E-mail: viktor.gera@gmail.com [National Technical University of Ukraine “Kyiv Polytechnic Institute”, Peremohy Avenue 37, 03056 Kiev (Ukraine); Shitov, Anatoliy A., E-mail: shitov@mail.ru [Donbass National Academy of Civil Engineering, Derzhavina Street 2, 86123 Makeevka, Donetsk Region (Ukraine)

    2013-10-15

    We theoretically study the dynamics of 180-degree domain wall of the ab-type in magnetic materials with quadratic magnetoelectric interaction in external alternating magnetic and electric fields. The features of the oscillatory and translational motions of the domain walls and stripe structures depending on the parameters of external fields and characteristics of the multiferroics are discussed. The possibility of the domain walls drift in a purely electric field is established. - Highlights: • We study DW and stripe DS in multiferroics with quadratic magnetoelectric interaction. • We build up the theory of oscillatory and translational (drift) DW and DS motion. • DW motion can be caused by crossed alternating electric and magnetic fields. • DW motion can be caused by alternating “pure” electric field. • DW drift velocity is formed by the AFM and Dzyaloshinskii interaction terms.

  3. Quadratic Serendipity Finite Elements on Polygons Using Generalized Barycentric Coordinates

    CERN Document Server

    Rand, Alexander; Bajaj, Chandrajit

    2011-01-01

    We introduce a finite element construction for use on the class of convex, planar polygons and show it obtains a quadratic error convergence estimate. On a convex n-gon satisfying simple geometric criteria, our construction produces 2n basis functions, associated in a Lagrange-like fashion to each vertex and each edge midpoint, by transforming and combining a set of n(n+1)/2 basis functions known to obtain quadratic convergence. The technique broadens the scope of the so-called `serendipity' elements, previously studied only for quadrilateral and regular hexahedral meshes, by employing the theory of generalized barycentric coordinates. Numerical evidence is provided on a trapezoidal quadrilateral mesh, previously not amenable to serendipity constructions, and applications to adaptive meshing are discussed.

  4. QUADRATIC SERENDIPITY FINITE ELEMENTS ON POLYGONS USING GENERALIZED BARYCENTRIC COORDINATES.

    Science.gov (United States)

    Rand, Alexander; Gillette, Andrew; Bajaj, Chandrajit

    2014-01-01

    We introduce a finite element construction for use on the class of convex, planar polygons and show it obtains a quadratic error convergence estimate. On a convex n-gon, our construction produces 2n basis functions, associated in a Lagrange-like fashion to each vertex and each edge midpoint, by transforming and combining a set of n(n + 1)/2 basis functions known to obtain quadratic convergence. The technique broadens the scope of the so-called 'serendipity' elements, previously studied only for quadrilateral and regular hexahedral meshes, by employing the theory of generalized barycentric coordinates. Uniform a priori error estimates are established over the class of convex quadrilaterals with bounded aspect ratio as well as over the class of convex planar polygons satisfying additional shape regularity conditions to exclude large interior angles and short edges. Numerical evidence is provided on a trapezoidal quadrilateral mesh, previously not amenable to serendipity constructions, and applications to adaptive meshing are discussed.

  5. Quadratic differentials in low genus: exceptional and non-varying

    CERN Document Server

    Chen, Dawei

    2012-01-01

    We give an algebraic way of distinguishing the components of the exceptional strata of quadratic differentials in genus three and four. The complete list of these strata is (9, -1), (6,3,-1), (3,3,3, -1) in genus three and (12), (9,3), (6,6), (6,3,3) and (3,3,3,3) in genus four. This result is part of a more general investigation of disjointness of Teichmueller curves with divisors of Brill-Noether type on the moduli space of curves. As a result we show that for many strata of quadratic differentials in low genus the sum of Lyapunov exponents for the Teichmueller geodesic flow is the same for all Teichmueller curves in that stratum.

  6. QUADRATIC INVARIANTS AND SYMPLECTIC STRUCTURE OF GENERAL LINEAR METHODS

    Institute of Scientific and Technical Information of China (English)

    Ai-guo Xiao; Shou-fu Li; Min Yang

    2001-01-01

    In this paper, we present some invariants and conservation laws of general linear methods applied to differential equation systems. We show that the quadratic invariants and symplecticity of the systems can be extended to general linear methods by a tensor product, and show that general linear methods with the matrix M=0 inherit in an extended sense the quadratic invariants possessed by the differential equation systems being integrated and preserve in an extended sense the symplectic structure of the phase space in the integration of Hamiltonian systems. These unify and extend existing relevant results on Runge-Kutta methods, linear multistep methods and one-leg methods. Finally, as special cases of general linear methods, we examine multistep Runge-Kutta methods, one-leg methods and linear two-step methods in detail.

  7. Large Deviation Principle for Benedicks-Carleson Quadratic Maps

    Science.gov (United States)

    Chung, Yong Moo; Takahasi, Hiroki

    2012-11-01

    Since the pioneering works of Jakobson and Benedicks & Carleson and others, it has been known that a positive measure set of quadratic maps admit invariant probability measures absolutely continuous with respect to Lebesgue. These measures allow one to statistically predict the asymptotic fate of Lebesgue almost every initial condition. Estimating fluctuations of empirical distributions before they settle to equilibrium requires a fairly good control over large parts of the phase space. We use the sub-exponential slow recurrence condition of Benedicks & Carleson to build induced Markov maps of arbitrarily small scale and associated towers, to which the absolutely continuous measures can be lifted. These various lifts together enable us to obtain a control of recurrence that is sufficient to establish a level 2 large deviation principle, for the absolutely continuous measures. This result encompasses dynamics far from equilibrium, and thus significantly extends presently known local large deviations results for quadratic maps.

  8. On Jannsen's conjecture for Hecke characters of imaginary quadratic fields

    CERN Document Server

    Bars, Francesc

    2007-01-01

    We present a collection of results on a conjecture of Jannsen about the $p$-adic realizations associated to Hecke characters over an imaginary quadratic field $K$ of class number 1. The conjecture is easy to check for Galois groups purely of local type. We prove the conjecture under a geometric regularity condition for the imaginary quadratic field $K$ at $p$, which is related to the property that a global Galois group is purely of local type. Without this regularity assumption at $p$, we present a review of the known situations in the critical case and in the non-critical case for the realizations associated to Hecke characters over $K$. We relate the conjecture to the non-vanishing of some concrete non-critical values of the associated $p$-adic $L$-function of the Hecke character. Finally, we prove that the conjecture follows from a general conjecture on Iwasawa theory for almost all Tate twists.

  9. Identity-based signature scheme based on quadratic residues

    Institute of Scientific and Technical Information of China (English)

    CHAI ZhenChuan; CAO ZhenFu; DONG XiaoLei

    2007-01-01

    Identity-based (ID-based) cryptography has drawn great concerns in recent years, and most of ID-based schemes are constructed from bilinear parings. Therefore, ID-based scheme without pairing is of great interest in the field of cryptography. Up to now,there still remains a challenge to construct ID-based signature scheme from quadratic residues. Thus, we aim to meet this challenge by proposing a concrete scheme. In this paper, we first introduce the technique of how to calculate a 2lth root of a quadratic residue, and then give a concrete ID-based signature scheme using such technique.We also prove that our scheme is chosen message and ID secure in the random oracle model, assuming the hardness of factoring.

  10. Time-Inconsistent Stochastic Linear--Quadratic Control

    CERN Document Server

    Hu, Ying; Zhou, Xun Yu

    2011-01-01

    In this paper, we formulate a general time-inconsistent stochastic linear--quadratic (LQ) control problem. The time-inconsistency arises from the presence of a quadratic term of the expected state as well as a state-dependent term in the objective functional. We define an equilibrium, instead of optimal, solution within the class of open-loop controls, and derive a sufficient condition for equilibrium controls via a flow of forward--backward stochastic differential equations. When the state is one dimensional and the coefficients in the problem are all deterministic, we find an explicit equilibrium control. As an application, we then consider a mean-variance portfolio selection model in a complete financial market where the risk-free rate is a deterministic function of time but all the other market parameters are possibly stochastic processes. Applying the general sufficient condition, we obtain explicit equilibrium strategies when the risk premium is both deterministic and stochastic.

  11. A Special Role of Boolean Quadratic Polytopes among Other Combinatorial Polytopes

    Directory of Open Access Journals (Sweden)

    A. N. Maksimenko

    2016-01-01

    Full Text Available We consider several families of combinatorial polytopes associated with the following NP-complete problems: maximum cut, Boolean quadratic programming, quadratic linear ordering, quadratic assignment, set partition, set packing, stable set, 3-assignment. For comparing two families of polytopes we use the following method. We say that a family

  12. A new semidefinite programming relaxation for the quadratic assignment problem and its computational perspectives

    NARCIS (Netherlands)

    de Klerk, E.; Sotirov, R.; Truetsch, U.

    2015-01-01

    Recent progress in solving quadratic assignment problems (QAPs) from the QAPLIB (Quadratic Assignment Problem Library) test set has come from mixed-integer linear or quadratic programming models that are solved in a branch-and-bound framework. Semidefinite programming (SDP) bounds for QAPs have also

  13. UNIFORM SUPERAPPROXIMATION OF THE DERIVATIVE OF TETRAHEDRAL QUADRATIC FINITE ELEMENT APPROXIMATION

    Institute of Scientific and Technical Information of China (English)

    Jing-hong Liu; Qi-ding Zhu

    2005-01-01

    In this paper,we will prove the derivative of tetrahedral quadratic finite element approximation is superapproximate to the derivative of the quadratic Lagrange interpolant of the exact solution in the L∞-norm, which can be used to enhance the accuracy of the derivative of tetrahedral quadratic finite element approximation to the derivative of the exact solution.

  14. A Hamiltonian-based solution to the linear quadratic consensus control problem

    NARCIS (Netherlands)

    Weiss, M.

    2012-01-01

    The Linear Quadratic Consensus Control (LQCC) problem is a relaxation of the classical Linear Quadratic Regulation (LQR) problem, that consists of asymptotically driving the state of the system to a "consensus" point in which all coordinates are equal, in such a way that a quadratic cost function on

  15. Quadratic and Cubic Nonlinear Oscillators with Damping and Their Applications

    Science.gov (United States)

    Li, Jibin; Feng, Zhaosheng

    We apply the qualitative theory of dynamical systems to study exact solutions and the dynamics of quadratic and cubic nonlinear oscillators with damping. Under certain parametric conditions, we also consider the van der Waals normal form, Chaffee-Infante equation, compound Burgers-KdV equation and Burgers-KdV equation for explicit representations of kink-profile wave solutions and unbounded traveling wave solutions.

  16. Solving the Quadratic Assignment Problem by a Hybrid Algorithm

    Directory of Open Access Journals (Sweden)

    Aldy Gunawan

    2011-01-01

    Full Text Available This paper presents a hybrid algorithm to solve the Quadratic Assignment Problem (QAP. The proposed algorithm involves using the Greedy Randomized Adaptive Search Procedure (GRASP to obtain an initial solution, and then using a combined Simulated Annealing (SA and Tabu Search (TS algorithm to improve the solution. Experimental results  indicate that the hybrid algorithm is able to obtain good quality solutions for QAPLIB test problems within reasonable computation time.

  17. Developing A Combined Strategy For Solving Quadratic Assignment Problem

    Directory of Open Access Journals (Sweden)

    Faiz Ahyaningsih

    2015-08-01

    Full Text Available Abstract The quadratic assigment problem QAP is one of the most interesting and most challenging combinatorial optimization problems in existence. In this paper we propose a random point strategy to get a starting point and then we use a combination methods to get optimal solution. As a computational experience weve solved QAP 30 x 30 adopted from Nugent and backboard wiring problem 42 amp61620 42 adopted from Skorin-Kapov.

  18. A new genetic representation for quadratic assignment problem

    Directory of Open Access Journals (Sweden)

    Kratica Jozef

    2011-01-01

    Full Text Available In this paper, we propose a new genetic encoding for well known Quadratic Assignment Problem (QAP. The new encoding schemes are implemented with appropriate objective function and modified genetic operators. The numerical experiments were carried out on the standard QAPLIB data sets known from the literature. The presented results show that in all cases proposed genetic algorithm reached known optimal solutions in reasonable time.

  19. Observers for Systems with Nonlinearities Satisfying an Incremental Quadratic Inequality

    Science.gov (United States)

    Acikmese, Ahmet Behcet; Corless, Martin

    2004-01-01

    We consider the problem of state estimation for nonlinear time-varying systems whose nonlinearities satisfy an incremental quadratic inequality. These observer results unifies earlier results in the literature; and extend it to some additional classes of nonlinearities. Observers are presented which guarantee that the state estimation error exponentially converges to zero. Observer design involves solving linear matrix inequalities for the observer gain matrices. Results are illustrated by application to a simple model of an underwater.

  20. Linear Quadratic Controller with Fault Detection in Compact Disk Players

    DEFF Research Database (Denmark)

    Vidal, Enrique Sanchez; Hansen, K.G.; Andersen, R.S.

    2001-01-01

    The design of the positioning controllers in Optical Disk Drives are today subjected to a trade off between an acceptable suppression of external disturbances and an acceptable immunity against surfaces defects. In this paper an algorithm is suggested to detect defects of the disk surface combined...... with an observer and a Linear Quadratic Regulator. As a result, the mentioned trade off is minimized and the playability of the tested compact disk player is considerably enhanced....

  1. On a linear-quadratic problem with Caputo derivative

    Directory of Open Access Journals (Sweden)

    Dariusz Idczak

    2016-01-01

    Full Text Available In this paper, we study a linear-quadratic optimal control problem with a fractional control system containing a Caputo derivative of unknown function. First, we derive the formulas for the differential and gradient of the cost functional under given constraints. Next, we prove an existence result and derive a maximum principle. Finally, we describe the gradient and projection of the gradient methods for the problem under consideration.

  2. Information sets as permutation cycles for quadratic residue codes

    Directory of Open Access Journals (Sweden)

    Richard A. Jenson

    1982-01-01

    Full Text Available The two cases p=7 and p=23 are the only known cases where the automorphism group of the [p+1,   (p+1/2] extended binary quadratic residue code, O(p, properly contains PSL(2,p. These codes have some of their information sets represented as permutation cycles from Aut(Q(p. Analysis proves that all information sets of Q(7 are so represented but those of Q(23 are not.

  3. A quadratic rate of asymptotic regularity for CAT(0)-spaces

    OpenAIRE

    Leustean, Laurentiu

    2005-01-01

    In this paper we obtain a quadratic bound on the rate of asymptotic regularity for the Krasnoselski-Mann iterations of nonexpansive mappings in CAT(0)-spaces, whereas previous results guarantee only exponential bounds. The method we use is to extend to the more general setting of uniformly convex hyperbolic spaces a quantitative version of a strengthening of Groetsch's theorem obtained by Kohlenbach using methods from mathematical logic (so-called ``proof mining'').

  4. Adomian solution of a nonlinear quadratic integral equation

    Directory of Open Access Journals (Sweden)

    E.A.A. Ziada

    2013-04-01

    Full Text Available We are concerned here with a nonlinear quadratic integral equation (QIE. The existence of a unique solution will be proved. Convergence analysis of Adomian decomposition method (ADM applied to these type of equations is discussed. Convergence analysis is reliable enough to estimate the maximum absolute truncated error of Adomian’s series solution. Two methods are used to solve these type of equations; ADM and repeated trapezoidal method. The obtained results are compared.

  5. New sequential quadratic programming algorithm with consistent subproblems

    Institute of Scientific and Technical Information of China (English)

    贺国平; 高自友; 赖炎连

    1997-01-01

    One of the most interesting topics related to sequential quadratic programming algorithms is how to guarantee the consistence of all quadratic programming subproblems. In this decade, much work trying to change the form of constraints to obtain the consistence of the subproblems has been done The method proposed by De O. Panto-ja J F A and coworkers solves the consistent problem of SQP method, and is the best to the authors’ knowledge. However, the scale and complexity of the subproblems in De O. Pantoja’s work will be increased greatly since all equality constraints have to be changed into absolute form A new sequential quadratic programming type algorithm is presented by means of a special ε-active set scheme and a special penalty function. Subproblems of the new algorithm are all consistent, and the form of constraints of the subproblems is as simple as one of the general SQP type algorithms. It can be proved that the new method keeps global convergence and local superhnear convergence.

  6. Measurement of quadratic electrogyration effect in castor oil

    Science.gov (United States)

    Izdebski, Marek; Ledzion, Rafał; Górski, Piotr

    2015-07-01

    This work presents a detailed analysis of electrogyration measurement in liquids with the usage of an optical polarimetric technique. Theoretical analysis of the optical response to an applied electric field is illustrated by experimental data for castor oil which exhibits natural optical activity, quadratic electro-optic effect and quadratic electrogyration effect. Moreover, the experimental data show that interaction of the oil with a pair of flat electrodes induces a significant dichroism and natural linear birefringence. The combination of these effects occurring at the same time complicates the procedure of measurements. It has been found that a single measurement is insufficient to separate the contribution of the electrogyration effect, but it is possible on the basis of several measurements performed with various orientations of the polarizer and the analyser. The obtained average values of the quadratic electrogyration coefficient β13 in castor oil at room temperature are from - 0.92 ×10-22 to - 1.44 ×10-22m2V-2 depending on the origin of the oil. Although this study is focused on measurements in castor oil, the presented analysis is much more general.

  7. Design of a quadratic filter for contrast - assisted ultrasonic imaging based on 2D gaussian filters

    Directory of Open Access Journals (Sweden)

    Tosaporn Nilmanee

    2010-05-01

    Full Text Available We present a novel design of quadratic filters (QFs in the frequency domain in order to improve the quality of contrastassisted ultrasound images for medical diagnosis. The QF is designed as a 2D linear-phase filter. In addition, the magnitude is based on the sum of two 2D Gaussian filters. The centers of the Gaussian filters are placed at the locations where the power strength of signals from ultrasound contrast agent over surrounding tissue is maximal. The design parameters consist of two centers and a standard deviation (SD of the Gaussian filters. The coefficients of the QF are obtained using the inverse discreteFourier transform. The QFs from the proposed design method are evaluated using in vivo ultrasound data, i.e., the kidney of aguinea pig. We find that the appropriate SD and two center points of the QF for the in vivo data are at 0.34, (3.30, 3.30 and (-3.30,-3.30 MHz, respectively. Results show that the images produced from the output signals of the new design are superior to theoriginal B-mode both in terms of contrast and spatial resolution. The quadratic image provides clear visualization of thekidney shape and large vascular structures inside the kidney. The contrast-to-tissue ratio value of quadratic image is 24.8 dBcompared to -1.5 dB from the B-mode image. In addition, we can use this new design approach as an efficient tool to furtherimprove the QF in producing better contrast-assisted ultrasound images for medical diagnostic purposes.

  8. Binary Quadratic Programing for Online Tracking of Hundreds of People in Extremely Crowded Scenes.

    Science.gov (United States)

    Dehghan, Afshin; Shah, Mubarak

    2017-03-24

    Multi-object tracking has been studied for decades. However, when it comes to tracking pedestrians in extremely crowded scenes, we are limited to only few works. This is an important problem which gives rise to several challenges. Pre-trained object detectors fail to localize targets in crowded sequences. This consequently limits the use of data-association based multi-target tracking methods which rely on the outcome of an object detector. Additionally, the small apparent target size makes it challenging to extract features to discriminate targets from their surroundings. Finally, the large number of targets greatly increases computational complexity which in turn makes it hard to extend existing multi-target tracking approaches to high-density crowd scenarios. In this paper, we propose a tracker that addresses the aforementioned problems and is capable of tracking hundreds of people efficiently. We formulate online crowd tracking as Binary Quadratic Programing. Our formulation employs target's individual information in the form of appearance and motion as well as contextual cues in the form of neighborhood motion, spatial proximity and grouping, and solves detection and data association simultaneously. In order to solve the proposed quadratic optimization efficiently, where state-of art commercial quadratic programing solvers fail to find the solution in a reasonable amount of time, we propose to use the most recent version of the Modified Frank Wolfe algorithm, which takes advantage of SWAP-steps to speed up the optimization. We show that the proposed formulation can track hundreds of targets efficiently and improves state-of-art results by significant margins on eleven challenging high density crowd sequences.

  9. Type VIa β-turn-fused helix N-termini: A novel helix N-cap motif containing cis proline.

    Science.gov (United States)

    Dasgupta, Rubin; Ganguly, Himal K; Modugula, E K; Basu, Gautam

    2017-01-01

    Helix N-capping motifs often form hydrogen bonds with terminal amide groups which otherwise would be free. Also, without an amide hydrogen, proline (trans) is over-represented at helix N-termini (N1 position) because this naturally removes the need to hydrogen bond one terminal amide. However, the preference of cisPro, vis-à-vis helix N-termini, is not known. We show that cisPro (αR or PPII ) often appears at the N-cap position (N0) of helices. The N-cap cisPro(αR ) is associated with a six-residue sequence motif - X(-2) -X(-1) -cisPro-X(1) -X(2) -X(3) - with preference for Glu/Gln at X(-1) , Phe/Tyr/Trp at X(1) and Ser/Thr at X(3) . The motif, formed by the fusion of a helix and a type VIa β-turn, contains a hydrogen bond between the side chain of X(-1) and the side chain/backbone of X(3) , a α-helical hydrogen bond between X(-2) and X(2) and stacking interaction between cisPro and an aromatic residue at X(1) . NMR experiments on peptides containing the motif and its variants showed that local interactions associated with the motif, as found in folded proteins, were not enough to significantly tilt the cis/trans equilibrium towards cisPro. This suggests that some other evolutionary pressure must select the cisPro motif (over transPro) at helix N-termini. Database analysis showed that >C = O of the pre-cisPro(αR ) residue at the helix N-cap, directed opposite to the N→C helical axis, participates in long-range interactions. We hypothesize that the cisPro(αR ) motif is preferred at helix N-termini because it allows the helix to participate in long-range interactions that may be structurally and functionally important.

  10. Solution structure of the ETS domain from murine Ets-1: a winged helix-turn-helix DNA binding motif.

    OpenAIRE

    Donaldson, L W; Petersen, J.M.; Graves, B J; McIntosh, L. P.

    1996-01-01

    Ets-1 is the prototypic member of the ets family of transcription factors. This family is characterized by the conserved ETS domain that mediates specific DNA binding. Using NMR methods, we have determined the structure of a fragment of murine Ets-1 composed of the 85 residue ETS domain and a 25 amino acid extension that ends at its native C-terminus. The ETS domain folds into a helix-turn-helix motif on a four-stranded anti-parallel beta-sheet scaffold. This structure places Ets-1 in the win...

  11. A class of stochastic optimization problems with one quadratic & several linear objective functions and extended portfolio selection model

    Science.gov (United States)

    Xu, Jiuping; Li, Jun

    2002-09-01

    In this paper a class of stochastic multiple-objective programming problems with one quadratic, several linear objective functions and linear constraints has been introduced. The former model is transformed into a deterministic multiple-objective nonlinear programming model by means of the introduction of random variables' expectation. The reference direction approach is used to deal with linear objectives and results in a linear parametric optimization formula with a single linear objective function. This objective function is combined with the quadratic function using the weighted sums. The quadratic problem is transformed into a linear (parametric) complementary problem, the basic formula for the proposed approach. The sufficient and necessary conditions for (properly, weakly) efficient solutions and some construction characteristics of (weakly) efficient solution sets are obtained. An interactive algorithm is proposed based on reference direction and weighted sums. Varying the parameter vector on the right-hand side of the model, the DM can freely search the efficient frontier with the model. An extended portfolio selection model is formed when liquidity is considered as another objective to be optimized besides expectation and risk. The interactive approach is illustrated with a practical example.

  12. Talent Development as a University Mission: The Quadruple Helix

    Science.gov (United States)

    Holm-Nielsen, Lauritz B.; Thorn, Kristian; Olesen, Jeppe Dorup; Huey, Tina

    2013-01-01

    In this paper, the authors discuss the rationale behind making talent development at the PhD, post-doctoral and early career levels an equal fourth pillar of the university's mission, alongside the more traditional pillars of the triple helix. Using Denmark and Aarhus University as a case study, the paper describes how increased institutional…

  13. Design of GEO helix tourist orbit based on perturbation compensation

    Science.gov (United States)

    Xu, Yanli; Zhou, Haijun; Dai, Huayu

    2017-05-01

    Constrained by country area and technology level, GEO target and environment's detection become practical difficulty which restrict development of our country's space technology. Helix tourist orbit is introduced; orbit formation effect from perturbation of nonsphericfigure of the Earth, the solar and lunar attraction is analyzed; orbit design method based on perturbation compensation is put forward.

  14. The Triple Helix Model and the Knowledge-Based Economy

    NARCIS (Netherlands)

    Leydesdorff, L.; Meyer, M.

    2010-01-01

    The Triple Helix model of university-industry-government relations can be generalized from a neo-institutional model of networks of relations to a neo-evolutionary model of how three selection environments operate upon one another. Two selection mechanisms operating upon each other can mutually

  15. Alpha- and beta-hemocyanin of Helix pomatia

    NARCIS (Netherlands)

    Dijk, Jan

    1971-01-01

    This thesis deals with several aspects of the protein structure of Alpha- and Beta -hemocyanin of Helix pomatia. a- and 0-hemocyanin possess a virtually identical amino acid composition; it closely resembles the amino acid com- positions of hemocyanins of other MOLLUSCA and ARTHROPODA. All hemocyani

  16. The Triple Helix Model and the Knowledge-Based Economy

    NARCIS (Netherlands)

    Leydesdorff, L.; Meyer, M.

    2010-01-01

    The Triple Helix model of university-industry-government relations can be generalized from a neo-institutional model of networks of relations to a neo-evolutionary model of how three selection environments operate upon one another. Two selection mechanisms operating upon each other can mutually shap

  17. Spontaneous Helix Hand Reversal and Tendril Perversion in Climbing Plants

    Science.gov (United States)

    Goriely, Alain; Tabor, Michael

    1998-02-01

    The helix hand reversal exhibited by the tendrils of climbing plants when attached to a support is investigated. Modeled as a thin elastic rod with intrinsic curvature, a linear and nonlinear stability analysis shows the problem to be a paradigm for curvature induced morphogenesis in which symmetry breaking is constrained by a global invariant.

  18. Targeting intracellular bacteria with an extended cationic amphiphilic polyproline helix.

    Science.gov (United States)

    Nepal, Manish; Thangamani, Shankar; Seleem, Mohamed N; Chmielewski, Jean

    2015-06-07

    An extended cationic and amphiphilic polyproline helix (CAPH) is described with a dual mode of action: effective cell penetration of human macrophages, and potent antimicrobial activity in vitro against both Gram-positive and negative pathogens, including Acinetobacter baumannii, Escherichia coli O157 and Bacillus anthracis. This dual action was successfully combined to clear pathogenic bacteria (Brucella and Salmonella) residing within macrophages.

  19. Organizing product innovation: hierarchy, market or triple-helix networks?

    Science.gov (United States)

    Fitjar, Rune Dahl; Gjelsvik, Martin; Rodríguez-Pose, Andrés

    This paper assesses the extent to which the organization of the innovation effort in firms, as well as the geographical scale at which this effort is pursued, affects the capacity to benefit from product innovations. Three alternative modes of organization are studied: hierarchy, market and triple-helix-type networks. Furthermore, we consider triple-helix networks at three geographical scales: local, national and international. These relationships are tested on a random sample of 763 firms located in five urban regions of Norway which reported having introduced new products or services during the preceding 3 years. The analysis shows that firms exploiting internal hierarchy or triple-helix networks with a wide range of partners managed to derive a significantly higher share of their income from new products, compared to those that mainly relied on outsourcing within the market. In addition, the analysis shows that the geographical scale of cooperation in networks, as well as the type of partner used, matters for the capacity of firms to benefit from product innovation. In particular, firms that collaborate in international triple-helix-type networks involving suppliers, customers and R&D institutions extract a higher share of their income from product innovations, regardless of whether they organize the processes internally or through the network.

  20. A catastrophe theory model of the conflict helix, with tests.

    Science.gov (United States)

    Rummel, R J

    1987-10-01

    Macro social field theory has undergone extensive development and testing since the 1960s. One of these has been the articulation of an appropriate conceptual micro model--called the conflict helix--for understanding the process from conflict to cooperation and vice versa. Conflict and cooperation are viewed as distinct equilibria of forces in a social field; the movement between these equilibria is a jump, energized by a gap between social expectations and power, and triggered by some minor event. Quite independently, there also has been much recent application of catastrophe theory to social behavior, but usually without a clear substantive theory and lacking empirical testing. This paper uses catastrophe theory--namely, the butterfly model--mathematically to structure the conflict helix. The social field framework and helix provide the substantive interpretation for the catastrophe theory; and catastrophe theory provides a suitable mathematical model for the conflict helix. The model is tested on the annual conflict and cooperation between India and Pakistan, 1948 to 1973. The results are generally positive and encouraging.

  1. Surface simulation synthesis: a new strategy to spy alpha-helix structure.

    Science.gov (United States)

    Dong, Xiao-Nan; Chen, Yu; Chen, Ying-Hua

    2007-09-04

    In key proteins, there are always some alpha-helix structures, which play important role in the structure and functions. Many epitopes lie on the surface of alpha-helix. These epitopes are not easy to be recruited into the vaccine development, because they are conformation dependent epitopes. Can such epitopes on alpha-helix be mimicked synthetically? Our findings undoubtedly validate the feasibility of surface simulation synthesis with short linear peptide to mimic the antigenic side of alpha-helix structure.

  2. Rigid-Plastic Post-Buckling Analysis of Columns and Quadratic Plates

    DEFF Research Database (Denmark)

    Jönsson, Jeppe

    2008-01-01

    The objective of this paper is to show the application of a novel approach to the rigid plastic hinge and yield line theory in post-buckling analysis of slender plates and columns. The upper bound theorem of plasticity theory and the associated flow law of plasticity are used to find...... of the post-buckling behaviour. The rigid plastic theory of plates, referred to as yield line theory, involves large rigid parts of the plate mutually rotating about yielding hinge lines, however in order to accommodate in plane plastic deformations area “collapse” yield lines have been introduced. The hinge...... yield lines accommodate differential rotations of rigid parts and the area “collapse” yield lines accommodate local area changes of the rigid parts thereby preserving compatibility of the rigid parts of a plate. The approach will be illustrated for rigid plastic column analysis and for a quadratic plate...

  3. Npas4, a novel helix-loop-helix PAS domain protein, is regulated in response to cerebral ischemia

    DEFF Research Database (Denmark)

    Shamloo, Mehrdad; Soriano, Liza; von Schack, David

    2006-01-01

    Basic helix-loop-helix PAS domain proteins form a growing family of transcription factors. These proteins are involved in the process of adaptation to cellular stresses and environmental factors such as a change in oxygen concentration. We describe the identification and characterization of a rec......Basic helix-loop-helix PAS domain proteins form a growing family of transcription factors. These proteins are involved in the process of adaptation to cellular stresses and environmental factors such as a change in oxygen concentration. We describe the identification and characterization...... of a recently cloned PAS domain protein termed Npas4 in ischemic rat brain. Using gene expression profiling following middle cerebral artery occlusion, we showed that the Npas4 mRNA is differentially expressed in ischemic tissue. The full-length gene was cloned from rat brain and its spatial and temporal...... expression characterized with in situ hybridization and Northern blotting. The Npas4 mRNA is specifically expressed in the brain and is highly up-regulated in ischemic tissues following both focal and global cerebral ischemic insults. Immunohistochemistry revealed a strong expression in the limbic system...

  4. Archaeal MBF1 binds to 30S and 70S ribosomes via its helix-turn-helix domain

    NARCIS (Netherlands)

    Blombach, F.; Launay, H.; Snijders, A.P.; Zorraquino, V.; Wu, H.; Koning, de B.; Brouns, S.J.J.; Ettema, T.J.; Camilloni, C.; Cavalli, A.; Vendruscolo, M.; Dickman, M.J.; Cabrita, L.D.; Teana, La A.; Benelli, D.; Londei, P.; Christodoulou, J.; Oost, van der J.

    2014-01-01

    MBF1 (multi-protein bridging factor 1) is a protein containing a conserved HTH (helix–turn–helix) domain in both eukaryotes and archaea. Eukaryotic MBF1 has been reported to function as a transcriptional co-activator that physically bridges transcription regulators with the core transcription initia

  5. Iron-binding E3 ligase mediates iron response in plants by targeting basic helix-loop-helix transcription factors.

    Science.gov (United States)

    Selote, Devarshi; Samira, Rozalynne; Matthiadis, Anna; Gillikin, Jeffrey W; Long, Terri A

    2015-01-01

    Iron uptake and metabolism are tightly regulated in both plants and animals. In Arabidopsis (Arabidopsis thaliana), BRUTUS (BTS), which contains three hemerythrin (HHE) domains and a Really Interesting New Gene (RING) domain, interacts with basic helix-loop-helix transcription factors that are capable of forming heterodimers with POPEYE (PYE), a positive regulator of the iron deficiency response. BTS has been shown to have E3 ligase capacity and to play a role in root growth, rhizosphere acidification, and iron reductase activity in response to iron deprivation. To further characterize the function of this protein, we examined the expression pattern of recombinant ProBTS::β-GLUCURONIDASE and found that it is expressed in developing embryos and other reproductive tissues, corresponding with its apparent role in reproductive growth and development. Our findings also indicate that the interactions between BTS and PYE-like (PYEL) basic helix-loop-helix transcription factors occur within the nucleus and are dependent on the presence of the RING domain. We provide evidence that BTS facilitates 26S proteasome-mediated degradation of PYEL proteins in the absence of iron. We also determined that, upon binding iron at the HHE domains, BTS is destabilized and that this destabilization relies on specific residues within the HHE domains. This study reveals an important and unique mechanism for plant iron homeostasis whereby an E3 ubiquitin ligase may posttranslationally control components of the transcriptional regulatory network involved in the iron deficiency response.

  6. A kind of signature scheme based on class groups of quadratic fields

    Institute of Scientific and Technical Information of China (English)

    董晓蕾; 曹珍富

    2004-01-01

    Quadratic-field cryptosystem is a cryptosystem built from discrete logarithm problem in ideal class groups of quadratic fields(CL-DLP). The problem on digital signature scheme based on ideal class groups of quadratic fields remained open, because of the difficulty of computing class numbers of quadratic fields. In this paper, according to our researches on quadratic fields, we construct the first digital signature scheme in ideal class groups of quadratic fields, using q as modulus, which denotes the prime divisors of ideal class numbers of quadratic fields. Security of the new signature scheme is based fully on CL-DLP. This paper also investigates realization of the scheme, and proposes the concrete technique. In addition, the technique introduced in the paper can be utilized to realize signature schemes of other kinds.

  7. Sensitivity Analysis of Linear Programming and Quadratic Programming Algorithms for Control Allocation

    Science.gov (United States)

    Frost, Susan A.; Bodson, Marc; Acosta, Diana M.

    2009-01-01

    The Next Generation (NextGen) transport aircraft configurations being investigated as part of the NASA Aeronautics Subsonic Fixed Wing Project have more control surfaces, or control effectors, than existing transport aircraft configurations. Conventional flight control is achieved through two symmetric elevators, two antisymmetric ailerons, and a rudder. The five effectors, reduced to three command variables, produce moments along the three main axes of the aircraft and enable the pilot to control the attitude and flight path of the aircraft. The NextGen aircraft will have additional redundant control effectors to control the three moments, creating a situation where the aircraft is over-actuated and where a simple relationship does not exist anymore between the required effector deflections and the desired moments. NextGen flight controllers will incorporate control allocation algorithms to determine the optimal effector commands and attain the desired moments, taking into account the effector limits. Approaches to solving the problem using linear programming and quadratic programming algorithms have been proposed and tested. It is of great interest to understand their relative advantages and disadvantages and how design parameters may affect their properties. In this paper, we investigate the sensitivity of the effector commands with respect to the desired moments and show on some examples that the solutions provided using the l2 norm of quadratic programming are less sensitive than those using the l1 norm of linear programming.

  8. An improved quadratic inference function for parameter estimation in the analysis of correlated data.

    Science.gov (United States)

    Westgate, Philip M; Braun, Thomas M

    2013-08-30

    Generalized estimating equations (GEE) are commonly employed for the analysis of correlated data. However, the quadratic inference function (QIF) method is increasing in popularity because of its multiple theoretical advantages over GEE. We base our focus on the fact that the QIF method is more efficient than GEE when the working covariance structure for the data is misspecified. It has been shown that because of the use of an empirical weighting covariance matrix inside its estimating equations, the QIF method's realized estimation performance can potentially be inferior to GEE's when the number of independent clusters is not large. We therefore propose an alternative weighting matrix for the QIF, which asymptotically is an optimally weighted combination of the empirical covariance matrix and its model-based version, which is derived by minimizing its expected quadratic loss. Use of the proposed weighting matrix maintains the large-sample advantages the QIF approach has over GEE and, as shown via simulation, improves small-sample parameter estimation. We also illustrated the proposed method in the analysis of a longitudinal study. Copyright © 2012 John Wiley & Sons, Ltd.

  9. Structural and functional aspects of winged-helix domains at the core of transcription initiation complexes.

    Science.gov (United States)

    Teichmann, Martin; Dumay-Odelot, Hélène; Fribourg, Sébastien

    2012-01-01

    The winged helix (WH) domain is found in core components of transcription systems in eukaryotes and prokaryotes. It represents a sub-class of the helix-turn-helix motif. The WH domain participates in establishing protein-DNA and protein-protein-interactions. Here, we discuss possible explanations for the enrichment of this motif in transcription systems.

  10. Playing with peptides: how to build a supramolecular peptide nanostructure by exploiting helix···helix macrodipole interactions.

    Science.gov (United States)

    Gatto, E; Porchetta, A; Scarselli, M; De Crescenzi, M; Formaggio, F; Toniolo, C; Venanzi, M

    2012-02-07

    A novel method to build bicomponent peptide self-assembled monolayers (SAMs) has been developed, by exploiting helix···helix macrodipole interactions. In this work, a peptide-based self-assembled monolayer composed of two helical peptides was immobilized on a gold surface. Specifically, a pyrene-containing octapeptide, devoid of any sulfur atom (A8Pyr), and a hexapeptide, functionalized at the N-terminus with (S,R) lipoic acid, for binding to gold substrates (SSA4WA) via a Au-S linkage, have been employed. Both peptides investigated attain a helical structure, because they are almost exclusively formed by strongly folding inducer C(α)-tetrasubstituted α-amino acids. We demonstrate that the two peptides generate a stable supramolecular nanostructure (a densely packed bicomponent peptide monolayer), where A8Pyr is incorporated into the SSA4WA palisade by exploiting helix···helix macrodipole interactions. The presence of both peptides on the gold surface was investigated by spectroscopic and electrochemical techniques, while the morphology of the monolayer was analyzed by ultra high-vacuum scanning tunnelling microscopy. The composition of the bicomponent SAM on the surface was studied by a combination of electrochemical and spectroscopic techniques. In particular, the amount of Au-S linkages from the sulfur-containing peptides was quantified from reductive desorption of the peptide-based SAM, while the amount of A8Pyr was estimated by fluorescence spectroscopy. The antiparallel orientation of the A8Pyr and SSA4WA peptide chains minimizes the interaction energy between the helix dipoles, suggesting that this kind of electrostatic phenomenon is the driving force that stabilizes the bicomponent SAM.

  11. Helix-helix interconversion rates of short 13C-labeled helical peptides as measured by dynamic NMR spectroscopy.

    Science.gov (United States)

    Kubasik, Matthew; Kotz, James; Szabo, Christopher; Furlong, Theresa; Stace, Justin

    2005-06-05

    The rates at which a peptide hexamer and a peptide octamer interconvert between left- and right-handed helical forms in CD2Cl2 solution have been characterized by 13C dynamic NMR (DNMR) spectroscopy. The peptide esters studied are Fmoc-(Aib)n-OtBu (n = 6 and 8), where Fmoc is 9-fluorenylmethyoxycarbonyl and Aib is the strongly helix-forming residue alpha-aminoisobutyric acid. Because the Aib residue is itself achiral, homooligomers of this residue form a 50/50 mixture of enantiomeric 3(10)-helices in solution. It has been demonstrated (R.-P. Hummel, C. Toniolo, and G. Jung, Angewandte Chemie International Edition, 1987, Vol. 26, pp. 1150-1152) that oligomers of Aib interconvert on the millisecond timescale. We have performed lineshape analysis of 13C-NMR spectra collected for our peptides enriched with 13C at a single residue. Rate constants for the octamer range from 6 s(-1) at 196 K to about 56,500 s(-1) at 320 K. At all temperatures, the hexamer interconverts about three times faster than the octamer. Eyring plots of the data reveal experimentally indistinguishable DeltaH++ values for the hexamer and octamer of 37.8 +/- 0.6 and 37.6 +/- 0.4 kJ mol(-1) respectively. The difference in the rates of interconversion is dictated by entropic factors. The hexamer and octamer exhibit negative DeltaS++ values of -29.0(-1) +/- 2.5 and -37.3 +/- 1.7 J K(-1) mol(-1), respectively. A mechanism for the helix-helix interconversion is proposed. and calculated DeltaG++ values are compared to the estimate for a decamer undergoing a helix-helix interconversion.

  12. EXACT SOLUTION FOR SPHERICAL FLOW AND TRANSIENT BEHAVIOR OF PRESSURE WITH CONSIDERATION OF EFFECTS OF QUADRATIC-GRADIENT TERM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Conventional models for fluid flow in well tests have not been consistent with material balance. According to the slightly compressible fluid assumption, the quadratic gradient term in the nonlinear partial differential equation has been usually neglected. This approach is questionable for live oil and low permeability reservoirs. We have already known that linearization by neglecting quadratic gradient terms may lead to errors for large values of well-test time. In this paper, a method that is consistent with material balance was proposed on the spherical flow system. All terms in the nonlinear partial eqiation were retained. Exact solution for the resulting nonlinear partial differential equation in an infinite reservoir was obtained by using the Laplace transform considering wellbore storage. Analytical solution for nonlinear partial differential equation are resulted by using orthogonal transforms under both closed and constant-pressure outer boundary conditions. The law of pressure changes for a fluid compressibility α and a storage coefficient CD were discussed.

  13. Evaluation of a photovoltaic energy mechatronics system with a built-in quadratic maximum power point tracking algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Chao, R.M.; Ko, S.H.; Lin, I.H. [Department of Systems and Naval Mechatronics Engineering, National Cheng Kung University, Tainan, Taiwan 701 (China); Pai, F.S. [Department of Electronic Engineering, National University of Tainan (China); Chang, C.C. [Department of Environment and Energy, National University of Tainan (China)

    2009-12-15

    The historically high cost of crude oil price is stimulating research into solar (green) energy as an alternative energy source. In general, applications with large solar energy output require a maximum power point tracking (MPPT) algorithm to optimize the power generated by the photovoltaic effect. This work aims to provide a stand-alone solution for solar energy applications by integrating a DC/DC buck converter to a newly developed quadratic MPPT algorithm along with its appropriate software and hardware. The quadratic MPPT method utilizes three previously used duty cycles with their corresponding power outputs. It approaches the maximum value by using a second order polynomial formula, which converges faster than the existing MPPT algorithm. The hardware implementation takes advantage of the real-time controller system from National Instruments, USA. Experimental results have shown that the proposed solar mechatronics system can correctly and effectively track the maximum power point without any difficulties. (author)

  14. Exact solution of the classical mechanical quadratic Zeeman effect

    Indian Academy of Sciences (India)

    Sambhu N Datta; Anshu Pandey

    2007-06-01

    We address the curious problem of quadratic Zeeman effect at the classical mechanical level. The problem has been very well understood for decades, but an analytical solution of the equations of motion is still to be found. This state of affairs persists because the simultaneous presence of the Coulombic and quadratic terms lowers the dynamical symmetry. Energy and orbital angular momentum are still constants of motion. We find the exact solutions by introducing the concept of an image ellipse. The quadratic effect leads to a dilation of space–time, and a one-to-one correspondence is observed for pairs of physical quantities like energy and angular momentum, and the maximum and minimum distances from the Coulomb center for the Zeeman orbit and the corresponding pairs for the image ellipse. Thus, instead of finding additional conserved quantities, we find constants of motion for an additional dynamics, namely, the image problem. The trajectory is open, in agreement with Bertrand's theorem, but necessarily bound. A stable unbound trajectory does not exist for real values of energy and angular momentum. The radial distance, the angle covered in the plane of the orbit, and the time are uniquely determined by introducing further the concept of an image circle. While the radial distance is defined in a closed form as a transcendental function of the image-circular angle, the corresponding orbit angle and time variables are found in the form of two convergent series expansions. The latter two variables are especially contracted, thereby leading to a precession of the open cycles around the Coulomb center. It is expected that the space–time dilation effect observed here would somehow influence the solution of the quantum mechanical problem at the non-relativistic level.

  15. Vacuum solutions of Bianchi cosmologies in quadratic gravity

    Energy Technology Data Exchange (ETDEWEB)

    Deus, Juliano Alves de; Muller, Daniel [Universidade de Brasilia (UnB), DF (Brazil)

    2011-07-01

    Full text: In this work we solve numerically the vacuum solutions of field equations of Bianchi homogeneous universes in the context of Semiclassical theory. Our interest is to study the quadratic theory of gravity with regard in the cosmological description of our universe in periods of intense fields. Bianchi cosmologies are anisotropic homogeneous cosmological models, but can include the isotropic models as particular cases (Bianchi I, VII and IX include homogeneous and isotropic Friedmann models plane, hyperbolic and spherical, respectively). Homogeneous models are good cosmological representations of our universe. With focus in solutions for intense fields, like the early universe, where isotropy is not necessarily required, the adopted scenario is the vacuum solutions, where the geometry is dominant in determining the gravitation. Still following in this way, the Semiclassical theory, which considers quantum matter fields propagating in classical geometrical background, is addressed to give the field equations. This formalism leads to fourth-order ordinary differential equations, in contrast to second-order equations from General Relativity. The Lagrangian of the theory is quadratic in the Ricci scalar and in the Ricci tensor. The equations system is highly non-linear and can be only numerically solved, except perhaps for few particular cases. We obtained numerical solutions for Bianchi V II{sub A} evolving to Minkowski and to de Sitter solutions, and also to singularities. The both first and second solutions were obtained choosing initial conditions near from respective exact vacuum solutions from Einstein theory, which are also exact solutions of the quadratic theory. Other Bianchi types are still under study. (author)

  16. Creepers: Real quadratic orders with large class number

    Science.gov (United States)

    Patterson, Roger

    2007-03-01

    Shanks's sequence of quadratic fields Q(sqrt{S_{n}}) where S_{n}=(2^n+1)^2 + 2^{n+2} instances a class of quadratic fields for which the class number is large and, therefore, the continued fraction period is relatively short. Indeed, that period length increases linearly with n, that is: in arithmetic progression. The fields have regulator O(n^2). In the late nineties, these matters intrigued Irving Kaplansky, and led him to compute period length of the square root of sequences a^2x^{2n}+bx^{n}+c for integers a, b, c, and x. In brief, Kap found unsurprisingly that, generically, triples (a,b,c) are `leapers': they yield sequences with period length increasing at exponential rate. But there are triples yielding sequences with constant period length, Kap's `sleepers'. Finally, there are triples, as exemplified by the Shanks's sequence, for which the period lengths increase in arithmetic progression. Felicitously, Kaplansky called these `creepers'. It seems that the sleepers and creepers are precisely those for which one is able to detail the explicit continued fraction expansion for all n. Inter alia, this thesis noticeably extends the known classes of creepers and finds that not all are `kreepers' (of the shape identified by Kaplansky) and therefore not of the shape of examples studied by earlier authors looking for families of quadratic number fields with explicitly computable unit and of relatively large regulator. The work of this thesis includes the discovery of old and new families of hyperelliptic curves of increasing genus g and torsion divisor of order O(g^2). It follows that the apparent trichotomy leaper/sleeper/creeper coincides with the folk belief that the just-mentioned torsion is maximum possible.

  17. STOCHASTIC LINEAR QUADRATIC OPTIMAL CONTROL PROBLEMS WITH RANDOM COEFFICIENTS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper studies a stochastic linear quadratic optimal control problem (LQ problem, for short), for which the coefficients are allowed to be random and the cost functional is allowed to have a negative weight on the square of the control variable. The authors introduce the stochastic Riccati equation for the LQ problem. This is a backward SDE with a complicated nonlinearity and a singularity. The local solvability of such a backward SDE is established, which by no means is obvious. For the case of deterministic coefficients, some further discussions on the Riccati equations have been carried out. Finally, an illustrative example is presented.

  18. Restart-Based Genetic Algorithm for the Quadratic Assignment Problem

    Science.gov (United States)

    Misevicius, Alfonsas

    The power of genetic algorithms (GAs) has been demonstrated for various domains of the computer science, including combinatorial optimization. In this paper, we propose a new conceptual modification of the genetic algorithm entitled a "restart-based genetic algorithm" (RGA). An effective implementation of RGA for a well-known combinatorial optimization problem, the quadratic assignment problem (QAP), is discussed. The results obtained from the computational experiments on the QAP instances from the publicly available library QAPLIB show excellent performance of RGA. This is especially true for the real-life like QAPs.

  19. Gilmore-Lawler bound of quadratic assignment problem

    Institute of Scientific and Technical Information of China (English)

    Yong XIA

    2008-01-01

    The Gilmore-Lawler bound (GLB) is one of the well-known lower bound of quadratic assignment problem (QAP). Checking whether GLB is tight is an NP-complete problem. In this article, based on Xia and Yuan linearization technique, we provide an upper bound of the complexity of this problem, which makes it pseudo-polynomial solvable. We also pseudo-polynomially solve a class of QAP whose GLB is equal to the optimal objec-tive function value, which was shown to remain NP-hard.

  20. Neural network for solving convex quadratic bilevel programming problems.

    Science.gov (United States)

    He, Xing; Li, Chuandong; Huang, Tingwen; Li, Chaojie

    2014-03-01

    In this paper, using the idea of successive approximation, we propose a neural network to solve convex quadratic bilevel programming problems (CQBPPs), which is modeled by a nonautonomous differential inclusion. Different from the existing neural network for CQBPP, the model has the least number of state variables and simple structure. Based on the theory of nonsmooth analysis, differential inclusions and Lyapunov-like method, the limit equilibrium points sequence of the proposed neural networks can approximately converge to an optimal solution of CQBPP under certain conditions. Finally, simulation results on two numerical examples and the portfolio selection problem show the effectiveness and performance of the proposed neural network.

  1. Rigorous Performance Bounds for Quadratic and Nested Dynamical Decoupling

    CERN Document Server

    Xia, Yuhou; Lidar, Daniel A

    2011-01-01

    We present rigorous performance bounds for the quadratic dynamical decoupling (QDD) pulse sequence which protects a qubit from general decoherence, and for its nested generalization to an arbitrary number of qubits. Our bounds apply under the assumption of instantaneous pulses and of bounded perturbing environment and qubit-environment Hamiltonians such as those realized by baths of nuclear spins in quantum dots. We prove that if the total sequence time is fixed then the trace-norm distance between the unperturbed and protected system states can be made arbitrarily small by increasing the number of applied pulses.

  2. Analysis of electroperforated materials using the quadrat counts method

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, E; Garzon, C; Garcia-Garcia, J [Departament d' Enginyeria Electronica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); MartInez-Cisneros, C; Alonso, J, E-mail: enrique.miranda@uab.cat [Departament de Quimica AnalItica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)

    2011-06-23

    The electroperforation distribution in thin porous materials is investigated using the quadrat counts method (QCM), a classical statistical technique aimed to evaluate the deviation from complete spatial randomness (CSR). Perforations are created by means of electrical discharges generated by needle-like tungsten electrodes. The objective of perforating a thin porous material is to enhance its air permeability, a critical issue in many industrial applications involving paper, plastics, textiles, etc. Using image analysis techniques and specialized statistical software it is shown that the perforation locations follow, beyond a certain length scale, a homogeneous 2D Poisson distribution.

  3. Bianchi $VII_A$ solutions of quadratic gravity

    CERN Document Server

    de Deus, Juliano A

    2011-01-01

    It is believed that soon after the Planck time, Einstein's general relativity theory should be corrected to an effective quadratic theory. Numerical solutions for the anisotropic generalization of the Friedmann "open" model $H^ 3$ for this effective gravity are given. It must be emphasized that although numeric, these solutions are exact in the sense that they depend only on the precision of the machine. The solutions are identified asymptotically in a certain sense. It is found solutions which asymptote de Sitter space, Minkowski space and a singularity.

  4. Quadratic controller syntheses for the steam generator water level

    Energy Technology Data Exchange (ETDEWEB)

    Arzelier, D.; Daafouz, J.; Bernussou, J.; Garcia, G

    1998-06-01

    The steam generator water level, (SGWL), control problem in the pressurized water reactor of a nuclear power plant is considered from robust control techniques point of view. The plant is a time-varying system with a non minimum phase behavior and an unstable open-loop response. The time-varying nature of the plant due to change in operating power is taken into account by including slowly time-varying uncertainty in the model. A linear Time-Invariant, (LTI) guaranteed cost quadratic stabilizing controller is designed in order to address some of the particular issues arising for such a control problem. (author) 17 refs.

  5. SPEECH EMOTION RECOGNITION USING MODIFIED QUADRATIC DISCRIMINATION FUNCTION

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Quadratic Discrimination Function(QDF)is commonly used in speech emotion recognition,which proceeds on the premise that the input data is normal distribution.In this Paper,we propose a transformation to normalize the emotional features,then derivate a Modified QDF(MQDF) to speech emotion recognition.Features based on prosody and voice quality are extracted and Principal Component Analysis Neural Network (PCANN) is used to reduce dimension of the feature vectors.The results show that voice quality features are effective supplement for recognition.and the method in this paper could improve the recognition ratio effectively.

  6. FaSa: A Fast and Stable Quadratic Placement Algorithm

    Institute of Scientific and Technical Information of China (English)

    HOU WenTing(侯文婷); HONG XianLong(洪先龙); WU WeiMin(吴为民); CAI YiCi(蔡懿慈)

    2003-01-01

    Placement is a critical step in VLSI design because it dominates overall speed andquality of design flow. In this paper, a new fast and stable placement algorithm called FaSa is pro-posed. It uses quadratic programming model and Lagrange multiplier method to solve placementproblems. And an incremental LU factorization method is used to solve equations for speeding up.The experimental results show that FaSa is very stable, much faster than previous algorithms andits total wire length is comparable with other algorithms.

  7. Quadratic growth and stability in convex programming problems

    OpenAIRE

    Bonnans, J. Frederic; Ioffe, Alexander D.

    1994-01-01

    Projet PROMATH; Given a convex program with $C^2$ functions and a convex set $S$ of solutions to the problem, we give a second order condition which guarantees that the problem does not have solutions outside of $S$. This condition is interpreted as a characterization for the quadratic growth of the cost function. The crucial role in the proofs is played by a theorem describing a certain uniform regularity property of critical cones in smooth convex programs. We apply these results to the dis...

  8. Asymmetric Simple Exclusion Process with Open Boundaries and Quadratic Harnesses

    Science.gov (United States)

    Bryc, Włodek; Wesołowski, Jacek

    2017-04-01

    We show that the joint probability generating function of the stationary measure of a finite state asymmetric exclusion process with open boundaries can be expressed in terms of joint moments of Markov processes called quadratic harnesses. We use our representation to prove the large deviations principle for the total number of particles in the system. We use the generator of the Markov process to show how explicit formulas for the average occupancy of a site arise for special choices of parameters. We also give similar representations for limits of stationary measures as the number of sites tends to infinity.

  9. Linear and quadratic in temperature resistivity from holography

    CERN Document Server

    Ge, Xian-Hui; Wu, Shang-Yu; Wu, Shao-Feng

    2016-01-01

    We present a new black hole solution in the Lifshitz spacetime with a hyperscaling violating factor. We analytically compute all of the DC thermoelectric conductivities in this theory. We find that both the linear-T and quadratic-T contributions to the resistivity can be realized, indicating that a more detailed comparison with experimental phenomenology can be performed in this scenario. At zero temperature, the Lorenz ratios are a constant, obeying the Wiedemann-Franz law, indications of a Fermi-liquid ground state.

  10. Health and Environment Linked for Information Exchange (HELIX)-Atlanta: A CDC-NASA Joint Environmental Public Health Tracking Collaborative Project

    Science.gov (United States)

    Al-Hamdan, Mohammad; Luvall, Jeff; Crosson, Bill; Estes, Maury; Limaye, Ashutosh; Quattrochi, Dale; Rickman, Doug

    2008-01-01

    HELIX-Atlanta was developed to support current and future state and local EPHT programs to implement data linking demonstration projects which could be part of the CDC EPHT Network. HELIX-Atlanta is a pilot linking project in Atlanta for CDC to learn about the challenges the states will encounter. NASA/MSFC and the CDC are partners in linking environmental and health data to enhance public health surveillance. The use of NASA technology creates value added geospatial products from existing environmental data sources to facilitate public health linkages. Proving the feasibility of the approach is the main objective

  11. Design and synthesis of DNA four-helix bundles

    Energy Technology Data Exchange (ETDEWEB)

    Rangnekar, Abhijit; Gothelf, Kurt V [Department of Chemistry, Centre for DNA Nanotechnology (CDNA) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark); LaBean, Thomas H, E-mail: kvg@chem.au.dk, E-mail: thl@cs.duke.edu [Department of Chemistry, Duke University, Durham, NC 27708 (United States)

    2011-06-10

    The field of DNA nanotechnology has evolved significantly in the past decade. Researchers have succeeded in synthesizing tile-based structures and using them to form periodic lattices in one, two and three dimensions. Origami-based structures have also been used to create nanoscale structures in two and three dimensions. Design and construction of DNA bundles with fixed circumference has added a new dimension to the field. Here we report the design and synthesis of a DNA four-helix bundle. It was found to be extremely rigid and stable. When several such bundles were assembled using appropriate sticky-ends, they formed micrometre-long filaments. However, when creation of two-dimensional sheet-like arrays of the four-helix bundles was attempted, nanoscale rings were observed instead. The exact reason behind the nanoring formation is yet to be ascertained, but it provides an exciting prospect for making programmable circular nanostructures using DNA.

  12. Crowding effect on helix-coil transition: Beyond entropic stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Koutsioubas, A.; Lairez, D.; Combet, S.; Longeville, S. [Laboratoire Leon Brillouin, CEA/CNRS UMR 12, CEA-Saclay, 91191 Gif-sur-Yvette Cedex (France); Fadda, G. C. [Laboratoire Leon Brillouin, CEA/CNRS UMR 12, CEA-Saclay, 91191 Gif-sur-Yvette Cedex (France); Universite Paris 13, UFR SMBH, 93017 Bobigny (France); Zalczer, G. [Service de Physique de l' Etat Condense, CEA-Saclay, 91191 Gif-sur-Yvette Cedex (France)

    2012-06-07

    We report circular dichroism measurements on the helix-coil transition of poly(L-glutamic acid) in solution with polyethylene glycol (PEG) as a crowding agent. The PEG solutions have been characterized by small angle neutron scattering and are well described by the picture of a network of mesh size {xi}, usual for semi-dilute chains in good solvent. We show that the increase of PEG concentration stabilizes the helices and increases the transition temperature. But more unexpectedly, we also notice that the increase of concentration of crowding agent reduces the mean helix extent at the transition, or in other words reduces its cooperativity. This result cannot be taken into account for by an entropic stabilization mechanism. Comparing the mean length of helices at the transition and the mesh size of the PEG network, our results strongly suggest two regimes: helices shorter or longer than the mesh size.

  13. Rational design of a triple helix-specific intercalating ligand.

    Science.gov (United States)

    Escudé, C; Nguyen, C H; Kukreti, S; Janin, Y; Sun, J S; Bisagni, E; Garestier, T; Hélène, C

    1998-03-31

    DNA triple helices offer new perspectives toward oligonucleotide-directed gene regulation. However, the poor stability of some of these structures might limit their use under physiological conditions. Specific ligands can intercalate into DNA triple helices and stabilize them. Molecular modeling and thermal denaturation experiments suggest that benzo[f]pyrido[3, 4-b]quinoxaline derivatives intercalate into triple helices by stacking preferentially with the Hoogsteen-paired bases. Based on this model, it was predicted that a benzo[f]quino[3,4-b]quinoxaline derivative, which possesses an additional aromatic ring, could engage additional stacking interactions with the pyrimidine strand of the Watson-Crick double helix upon binding of this pentacyclic ligand to a triplex structure. This compound was synthesized. Thermal denaturation experiments and inhibition of restriction enzyme cleavage show that this new compound can indeed stabilize triple helices with great efficiency and specificity and/or induce triple helix formation under physiological conditions.

  14. Triple Helix Formation in a Topologically Controlled DNA Nanosystem.

    Science.gov (United States)

    Yamagata, Yutaro; Emura, Tomoko; Hidaka, Kumi; Sugiyama, Hiroshi; Endo, Masayuki

    2016-04-11

    In the present study, we demonstrate single-molecule imaging of triple helix formation in DNA nanostructures. The binding of the single-molecule third strand to double-stranded DNA in a DNA origami frame was examined using two different types of triplet base pairs. The target DNA strand and the third strand were incorporated into the DNA frame, and the binding of the third strand was controlled by the formation of Watson-Crick base pairing. Triple helix formation was monitored by observing the structural changes in the incorporated DNA strands. It was also examined using a photocaged third strand wherein the binding of the third strand was directly observed using high-speed atomic force microscopy during photoirradiation. We found that the binding of the third strand could be controlled by regulating duplex formation and the uncaging of the photocaged strands in the designed nanospace.

  15. Potential triple helix-mediated inhibition of IGF-I gene expression significantly reduces tumorigenicity of glioblastoma in an animal model.

    Science.gov (United States)

    Shevelev, A; Burfeind, P; Schulze, E; Rininsland, F; Johnson, T R; Trojan, J; Chernicky, C L; Hélène, C; Ilan, J; Ilan, J

    1997-01-01

    Oligonucleotide-directed triple helix formation is a powerful approach to block transcription of specific genes. Although the oligonucleotide triplex approach is efficient for inhibiting gene expression in cultured cells, suppression is transient. We developed an approach which inhibits insulin-like growth factor-I (IGF-I) expression following stable transfection of C6 rat glioblastoma cells with a plasmid from which an RNA is transcribed that codes for the third strand of a potential triple helix. We tested the ability of this expression vector to inhibit IGF-I gene expression in vitro as well as tumorigenesis in an animal. A dramatic reduction of IGF-I RNA and protein levels in cultured cells occurred following transfection of rat C6 cells with a eukaryotic expression plasmid encoding the oligopurine variant of the triple helix but not the oligopyrimidine or a control sequence. The cells transfected with the oligopurine variant displayed morphological changes, upregulation of major histocompatibility complex I, and increased expression of protease nexin I. Dramatic inhibition of tumor growth occurred in nude mice following injection of transfected C6 cells. To our knowledge, this is the first example of tumor growth inhibition in an animal model employing a triple helix approach.

  16. AND BUSINESS INCUBATORS INTO THE TRIPLE HELIX CONCEPT

    Directory of Open Access Journals (Sweden)

    Sizova, Y.S.

    2016-04-01

    Full Text Available The article’s author endeavors to create a practical model of the Russian economy’s development while integrating such tools of supporting and stimulating entrepreneurship as business incubators and research and technology parks into the Triple Helix concept. The article points out that configurations fusing together the nation-state, business and science/education, possess a greater potential for development.

  17. Chiral transformation: From single nanowire to double helix

    KAUST Repository

    Wang, Yong

    2011-12-21

    We report a new type of water-soluble ultrathin Au-Ag alloy nanowire (NW), which exhibits unprecedented behavior in a colloidal solution. Upon growth of a thin metal (Pd, Pt, or Au) layer, the NW winds around itself to give a metallic double helix. We propose that the winding originates from the chirality within the as-synthesized Au-Ag NWs, which were induced to untwist upon metal deposition. © 2011 American Chemical Society.

  18. Exigência de proteína para o escargot francês, Helix aspersa maxima em fase de crescimento Protein requirement for Helix aspersa maxima during the growing phase

    Directory of Open Access Journals (Sweden)

    Claudemir Martins Soares

    2002-04-01

    Full Text Available Com o objetivo de determinar a exigência de proteína bruta (PB em dietas para o "escargot" francês (Helix aspersa maxima, 200 animais com peso inicial médio de 2,00 g foram distribuídos em um experimento inteiramente casualizado com quatro tratamentos [12,00; 15,00; 18,00 e 21,00% de PB] e cinco repetições, com 10 animais por unidade experimental, durante 90 dias. Foi observado efeito quadrático dos teores de PB sobre o peso final médio, a conversão alimentar, taxa de eficiência protéica, porcentagem de concha e rendimento de carcaça com os melhores valores nos teores de 16,23; 16,95; 14,79; 16,07 e 15,87% de PB, respectivamente. A taxa de sobrevivência não foi afetada pelos teores de PB utilizados. Concluiu-se que a exigência de PB em dietas para "escargot" francês é de 16,23%.Aiming to determinate the dietary crude protein (CP requirements for Helix aspersa maxima snail, 200 animals, with average initial weight of 2.00 g were used, and assigned to a completely randomized design with four treatments [12.00, 15.00, 18.00, and 21.00% CP] and five replicates of 10 animals per experimental unit, during a period of 90 days. It was observed a quadratic effect of CP levels on final mean weight, feed conversion, protein efficiency rate, shell percentage and carcass yield with the best values for 16.23, 16.95, 14.79, 16.07, and 15.87% CP, respectively. The CP levels did not affect the survival rate. It may be concluded that the requirement of CP on diets for the Helix aspersa maxima is 16.23%.

  19. Electroweak vacuum stability and finite quadratic radiative corrections

    Energy Technology Data Exchange (ETDEWEB)

    Masina, Isabella [Ferrara Univ. (Italy). Dipt. di Fisica e Scienze della Terra; INFN, Sezione di Ferrara (Italy); Southern Denmark Univ., Odense (Denmark). CP3-Origins; Southern Denmark Univ., Odense (Denmark). DIAS; Nardini, Germano [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quiros, Mariano [Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona (Spain); IFAE-IAB, Barcelona (Spain)

    2015-07-15

    If the Standard Model (SM) is an effective theory, as currently believed, it is valid up to some energy scale Λ to which the Higgs vacuum expectation value is sensitive throughout radiative quadratic terms. The latter ones destabilize the electroweak vacuum and generate the SM hierarchy problem. For a given perturbative Ultraviolet (UV) completion, the SM cutoff can be computed in terms of fundamental parameters. If the UV mass spectrum involves several scales the cutoff is not unique and each SM sector has its own UV cutoff Λ{sub i}. We have performed this calculation assuming the Minimal Supersymmetric Standard Model (MSSM) is the SM UV completion. As a result, from the SM point of view, the quadratic corrections to the Higgs mass are equivalent to finite threshold contributions. For the measured values of the top quark and Higgs masses, and depending on the values of the different cutoffs Λ{sub i}, these contributions can cancel even at renormalization scales as low as multi-TeV, unlike the case of a single cutoff where the cancellation only occurs at Planckian energies, a result originally obtained by Veltman. From the MSSM point of view, the requirement of stability of the electroweak minimum under radiative corrections is incorporated into the matching conditions and provides an extra constraint on the Focus Point solution to the little hierarchy problem in the MSSM. These matching conditions can be employed for precise calculations of the Higgs sector in scenarios with heavy supersymmetric fields.

  20. On the Content Bound for Real Quadratic Field Extensions

    Directory of Open Access Journals (Sweden)

    Robert G. Underwood

    2012-12-01

    Full Text Available Let K be a finite extension of Q and let S = {ν} denote the collection of K normalized absolute values on K. Let V+K denote the additive group of adeles over K and let K ≥0   c : V + → R denote the content map defined as c({aν } = Q K   ν ∈S ν (aν for {aν } ∈ V+K A classical result of J. W. S. Cassels states that there is a constant c > 0 depending only on the field K  with the following property: if {aν } ∈ V+K with c({aν }  > c, then there exists a non-zero element b  ∈ K for which ν (b ≤ ν (aν , ∀ν  ∈ S. Let cK be the greatest lower bound of the set of all c that satisfy this property. In the case that K is a real quadratic extension there is a known upper bound for cK due to S. Lang. The purpose of this paper is to construct a new upper bound for cK in the case that K has class number one. We compare our new bound with Lang’s bound for various real quadratic extensions and find that our new bound is better than Lang’s in many instances.