bluuebunny/crossref_metadata_2025 huggingface dataset:
Graft-induced Changes in MicroRNA Expression Patterns in Citrus Leaf Petioles
Authors: Tzarfati R. , Ben-Dor S. , Sela I. , Goldschmidt E.E.
Published: April 2013

Grafting is an important, widely used plant propagation technique but its physiological effects are as yet insufficiently understood. Recent studies indicate that movement of proteins and small RNAs through the graft union might be involved. MicroRNAs are known to play a significant role in regulation of higher plants’ developmental and metabolic traits. Extending this logic, we hypothesize that changes in activity of specific microRNAs are one of the mechanisms involved in physiological effects of grafting. The objective of the present study was to test this hypothesis. We determined the expression of a broad range of microRNAs in Citrus leaf petioles, as affected by grafting. Four stock/scion combinations (‘Merav’ mandarin and ‘Star Ruby‘ grapefruit scions X ‘Troyer’ citrange and ‘Volkamer’ lemon rootstocks), rootstock auto-grafts and plants of the variety used as rootstock (= non-grafted) were examined. Grafting caused a dramatic reduction in the expression of the major microRNAs, miR156 (and miR157), which appear to be associated with reduction of juvenility in perennial woody plants. This effect was strongest in hetero-grafts but evident also in auto-grafts. Expression of miR894 also declined upon grafting. Differences in the expression of miR397 were found among grafted scion cultivars, while in non-grafted rootstocks expression of miR397 was barely detectable. Bioinformatic analysis confirmed the presence of miR397 in the citrus genome, validated its sequence and demonstrated its ability to form a stem loop. The differences in miR397 expression might be related to specific copper and other micronutrient requirements of citrus stock-scion combinations.Thus, our results support the hypothesis, indicating the involvement of specific microRNAs in engendering physiological effects of grafting in Citrus. The precise, underlying mechanism needs to be elucidated.
Content Validity of the Comprehensive ICF Core Set for Chronic Obstructive Pulmonary Diseases: An International Delphi Survey
Authors: Jobst Andrea , Kirchberger Inge , Cieza Alarcos , Stucki Gerold , Stucki Armin
Published: April 2013

Introduction:

The “Comprehensive ICF Core Set for Chronic Obstructive Pulmonary Diseases (COPD)“ is an application of the International Classification of Functioning, Disability and Health (ICF) and represents the typical spectrum of problems in functioning of patients with COPD. The objective of this study was to validate this ICF Core Set from the perspective of physicians.

Materials and Methodology:

Physicians experienced in COPD treatment were asked about the patients’ problems treated by physicians in patients with COPD in a three-round electronic mail survey using the Delphi technique. Responses were linked to the ICF.

Results:

Seventy-six physicians in 44 countries gave a total of 1330 responses that were linked to 148 different ICF categories. Nine ICF categories were not represented in the Comprehensive ICF Core Set for COPD although at least 75% of the participants have rated them as important. Nineteen concepts were linked to the not yet developed ICF component personal factors and seventeen concepts were not covered by the ICF.

Conclusion:

The high percentage of ICF categories represented in the ICF Core Set for COPD indicates satisfactory content validity from the perspective of the physicians. However, some issues were raised that were not covered and need to be investigated further.
Virulence modulation of Streptococcus mutans biofilms by metal ions released from orthodontic appliances
Authors: Rymovicz Alinne Ulbrich Mores , Ronsani Maiara Medeiros , Grégio Ana Maria Trindade , Guariza-Filho Odilon Guariza , Tanaka Orlando , Rosa Edvaldo Antonio Ribeiro
Published: April 2013

Objectives:

To evaluate the impact of metal ions commonly shed from orthodontic appliances on the virulence of Streptococcus mutans ATCC®25175™ biofilms.

Materials and Methods:

Biofilms were grown in the presence of Ni2+, Fe3+, Cr3+, Co2+, and a metal ion pool at concentrations similar to those released in saliva of orthodontic patients for 72 hours. Once mature, biofilms were treated for up to 12 hours with 5% glucose.

Results:

Ions interfered with the growth of S mutans by reducing its biomass (Ni2+, Fe3+, Cr3+), raising its rates of sugar metabolism (Ni2+, Fe3+, Cr3+), and raising its secretion of lactate (Ni2+, Fe3+, Cr3+, pool).

Conclusion:

The laboratory data presented here point to the possibility of virulence increase of S mutans by metal ions commonly released during orthodontic therapy.
Ebselen Analogues Reduce 2-chloroethyl Ethyl Sulphide Toxicity in A-431 Cells
Authors: Pino Maria A. , Pietka-Ottlik Magdalena , Billack Blase
Published: April 2013

Vesicants are potent blistering agents. The prototype vesicant is sulphur mustard gas, first used in World War I, which still has no effective antidote. We used a mustard gas surrogate 2-chloroethyl ethyl sulphide (CEES) to study the ability of resveratrol (RES) and pterostilbene (PTS), two well-established stilbene antioxidants, ebselen (EB-1), an organoselenium compound, and three EB-1 analogues (EB-2, EB-3, and EB-4) to reduce CEES toxicity in human epidermoid carcinoma cells (A-431). Following a 24-hour incubation of a toxic concentration of CEES (1000 μmol L-1), we used the MTT [3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide] test to analyse cell viability. Different concentrations of test antioxidants alone (15 μmol L-1, 30 μmol L-1 or 60 μmol L-1) did not decrease cell viability. Treatment with CEES and test antioxidants for 24 h showed that only EB-1 and its analogues EB-2, EB-3, and EB-4 but not the stilbene compounds could rescue the cells from death. EB-1 and EB-4 were the most effective at reducing CEES cytotoxicity and did so in a concentration-dependent manner, while EB-2 and EB-3 demonstrated the least protective effect. In summary, the data described herein indicate that organoselenium antioxidants, especially EB-4, may prove useful as countermeasures to blistering agents.
Severe Renal Function Impairment in Adult Patients Acutely Poisoned with Concentrated Acetic Acid
Authors: Chibishev Andon , Sikole Aleksandar , Pereska Zanina , Chibisheva Vesna , Simonovska Natasha , Orovchanec Nikola
Published: April 2013

Acetic acid is a widely used organic acid with corrosive properties that depend on its concentration. If acetic acid is ingested in concentrations above 30 % it may severely damage the upper gastrointestinal tract and cause intravascular haemolysis, which can result in severe kidney and liver disorders and disseminated intravascular coagulation. In this retrospective study, we analysed acetic acid ingestion data collected at the University Clinic for Toxicology of Skopje, Macedonia from 1 January 2002 to 31 December 2011. The analysis included systemic complications, kidney damage, and the outcomes in particular. Over the ten years, 84 patients were reported at the Clinic to have ingested highly concentrated acetic acid. Twenty-eight developed kidney disorders, while the remaining 56 had no complications. Fatal outcome was reported for 11 patients, seven of whom had systemic complications and four severe gastrointestinal complications.
Effects of Acute Manganese Neurotoxicity in Young Chicks
Authors: Al-Zubaidy Muna H. I. , Mohammad Fouad K.
Published: April 2013

Manganese (Mn) is an industrial neurotoxicant in humans and animal models limited to rodent species. The present study analyses the potential neurotoxicity of acute Mn administration in young chicks. The acute (24 h) LD50 values of Mn following intraperitoneal, intramuscular, subcutaneous and oral administrations of MnCl2 in seven-day-old chicks were 21.3 mg kg-1, 28.1 mg kg-1, 28.1 mg kg-1 and 469.5 mg kg-1 body weight of Mn, respectively. Signs of Mn poisoning appeared in the chicks within 2 min and 13 min after parenteral administration and within 20 min and 32 min after oral administration. The signs demonstrated the depressant action of Mn in the chicks. The behavioural effects of Mn given at 5 mg kg-1, 10 mg kg-1 and 20 mg kg-1 intramuscularly were examined in 7 to 12 day old chicks using the three-minute open-field and tonic immobility tests. Manganese decreased the overall locomotor activity of the chicks in the open-field arena as manifested by a significant increase in the latency to move from the central square and decreases in line crossing, frequency of defecation and vocalization score when compared to control values. It also increased the duration of the chicks’ tonic immobility response. Pharmacological challenges of Mn-treated chicks with general anaesthetics xylazine-ketamine and thiopental caused the loss of right reflex at a faster rate in comparison with control values. Thiopental increased the duration of loss of righting reflex in Mn-treated chicks when compared with that of the control group. Chlorpromazine challenge of Mn-treated chicks significantly increased the depressant action of Mn in the open-field arena and increased the duration of tonic immobility response produced by the metal. The injections of Mn at 10 mg kg-1, 20 mg kg-1, 50 mg kg-1 and 100 mg kg-1 intramuscularly significantly increased the Mn levels in the plasma, liver, kidneys and entire brain of the chicks. The data suggests acute neurotoxicity of Mn chloride in the young chicks as a form of depressant action that could be determined by open-field and tonic immobility tests with further support from pharmacological challenges.
Accuracy of Ceramic Mould Filling with Liquid AlSi9 Aluminium Alloy in the Process Using Back-Pressure
Authors: Karwiński A. , Haratym R. , Biernacki R.
Published: April 2013

The paper presents the effect of suction pressure exerted on the liquid AlSi alloy when it is introduced into a ceramic mould made in the investment process and the results compared with data obtained on gravity poured castings. The study used special pattern sets and ceramic moulds made with the alternately applied soluble silicate binder and ethyl silicate. Additionally, self-supported moulds based entirely on the Ekosil binder were used. In the analysis of castings, the following parameters were examined: a linear dimensional accuracy, the state of surface microgeometry and the possibility of metal penetration into a complex ceramic mould, allowing also for the presence of capillary phenomena. In the process of casting with back-pressure, the pressure values of 500 hPa, 600 hPa and 700 hPa were applied in the chamber where the ceramic mould was located, with the temperature of the said mould kept at a level of 150 ± 10°C.
Microstructural Characterization of Cast Magnesium Matrix Composites by Raman Microscopy
Authors: Malika M.A. , Majchrzak K. , Braszczyńska-Malik K.N.
Published: April 2013

Cast magnesium matrix composites reinforced with silicon carbide particles were investigated by using Raman microscopy. 3C, 4H and 6H polytypes of SiC particles were identified in the investigated composites. Additionally, Mg2Si compound was detected by Raman microscopy in the composites microstructure.
Composite Zones Produced in Situ in the Ni3Al Phase
Authors: Olejnika E. , Janas A. , Sikora G. , Tokarski T. , Nowak J.
Published: April 2013

The study presents the results of research on the development of composite zones in castings based on the intermetallic phase of Ni3Al. Composite zones were obtained by placing packets with substrates for the reaction of titanium carbide in a foundry mould. To provide a variable carbides content in the composite zone, two compositions of the packets were prepared. The first packet contained only substrates for the reaction of TiC synthesis; the second one also contained a filler. The resulting composite zones in castings were examined for the filler effect on changes in the volume fraction, size and morphology of carbides in the zone. In addition, the effect of filler on the mechanical properties of the zone was verified, observing changes of Vickers hardness in this area. It was found that the presence of filler in the composition of the packet for synthesis reduced the content of carbides, as well as their size and morphology. Lower surface content of carbides reduced hardness of the zone, which enabled smooth control of the mechanical properties. At the same time, the use of the selected filler did not disturb the course of the TiC carbide synthesis.
The Influence of Silica Module of the Soluble Sodium Silicate Hardened by Ester on the Residual Strenght of Molding Sand
Authors: Baliński A.
Published: April 2013

Describes how to obtain a soluble sodium silicate with a density of 1.40 g/cm3, 1.45 g/cm3, 1.50 g/cm3, and silica module M = 2.1 obtained from the silica- sodium glass with module M = 3.3 and M = 2.1. Residual (final) strength of molding samples made with these binders, were determined at temperatures corresponding to the characteristic temperatures of phase and temperature transitions of silica gel. Indicated the type of soluble sodium silicate capable of obtain the smallest value of the final strength of molding sand in the specified range of temperatures.
Application of the Drazin inverse to the analysis of descriptor fractional discrete-time linear systems with regular pencils
Authors: Kaczorek Tadeusz
Published: April 2013

The Drazin inverse of matrices is applied to find the solutions of the state equations of descriptor fractional discrete-time systems with regular pencils. An equality defining the set of admissible initial conditions for given inputs is derived. The proposed method is illustrated by a numerical example.
A multivariable multiobjective predictive controller
Authors: Ben Aicha Faten , Bouani Faouzi , Ksouri Mekki
Published: April 2013

Predictive control of MIMO processes is a challenging problem which requires the specification of a large number of tuning parameters (the prediction horizon, the control horizon and the cost weighting factor). In this context, the present paper compares two strategies to design a supervisor of the Multivariable Generalized Predictive Controller (MGPC), based on multiobjective optimization. Thus, the purpose of this work is the automatic adjustment of the MGPC synthesis by simultaneously minimizing a set of closed loop performances (the overshoot and the settling time for each output of the MIMO system). First, we adopt the Weighted Sum Method (WSM), which is an aggregative method combined with a Genetic Algorithm (GA) used to minimize a single criterion generated by the WSM. Second, we use the Non- Dominated Sorting Genetic Algorithm II (NSGA-II) as a Pareto method and we compare the results of both the methods. The performance of the two strategies in the adjustment of multivariable predictive control is illustrated by a simulation example. The simulation results confirm that a multiobjective, Pareto-based GA search yields a better performance than a single objective GA.
A nonlinear dynamic inversion-based neurocontroller for unmanned combat aerial vehicles during aerial refuelling
Authors: Pedro Jimoh Olarewaju , Panday Aarti , Dala Laurent
Published: April 2013

The paper presents the development of modelling and control strategies for a six-degree-of-freedom, unmanned combat aerial vehicle with the inclusion of the centre of gravity position travel during the straight-leg part of an in-flight refuelling manoeuvre. The centre of gravity position travel is found to have a parabolic variation with an increasing mass of aircraft. A nonlinear dynamic inversion-based neurocontroller is designed for the process under investigation. Three radial basis function neural networks are exploited in order to invert the dynamics of the system, one for each control channel. Modal and time-domain analysis results show that the dynamic properties of the aircraft are strongly influenced during aerial refuelling. The effectiveness of the proposed control law is demonstrated through the use of simulation results for an F-16 aircraft. The longitudinal neurocontroller provided interesting results, and performed better than a baseline nonlinear dynamic inversion controller without neural network. On the other hand, the lateral-directional nonlinear dynamic inversion-based neurocontroller did not perform well as the longitudinal controller. It was concluded that the nonlinear dynamic inversion-based neurocontroller could be applied to control an unmanned combat aerial vehicle during aerial refuelling.
An efficient algorithm for estimating the parameters of superimposed exponential signals in multiplicative and additive noise
Authors: Bian Jiawen , Peng Huiming , Xing Jing , Liu Zhihui , Li Hongwei
Published: April 2013

This paper considers parameter estimation of superimposed exponential signals in multiplicative and additive noise which are all independent and identically distributed. A modified Newton-Raphson algorithm is used to estimate the frequencies of the considered model, which is further used to estimate other linear parameters. It is proved that the modified Newton- Raphson algorithm is robust and the corresponding estimators of frequencies attain the same convergence rate with Least Squares Estimators (LSEs) under the same noise conditions, but it outperforms LSEs in terms of the mean squared errors. Finally, the effectiveness of the algorithm is verified by some numerical experiments.
Stability analysis of high-order Hopfield-type neural networks based on a new impulsive differential inequality
Authors: Liu Yang , Yang Rongjiang , Lu Jianquan , Wu Bo , Cai Xiushan
Published: April 2013

This paper is devoted to studying the globally exponential stability of impulsive high-order Hopfield-type neural networks with time-varying delays. In the process of impulsive effect, nonlinear and delayed factors are simultaneously considered. A new impulsive differential inequality is derived based on the Lyapunov-Razumikhin method and some novel stability criteria are then given. These conditions, ensuring the global exponential stability, are simpler and less conservative than some of the previous results. Finally, two numerical examples are given to illustrate the advantages of the obtained results.
Mathematical modelling of molecule evolution in protocells
Authors: Myszor Dariusz , Cyran Krzysztof A.
Published: April 2013

In this article, we analyse the process of the emergence of RNA polynucleotides located in an enclosed environment, at an early stage of the RNA world. Therefore we prepared a mathematical model, composed of a set of differential equations, which simulates the behaviour of an early biological system bounded by a protocell membrane. There is evidence that enclosed environments were available on the primordial Earth. There are also experimental proofs that RNA strands can develop in these formations. The proposed model allows analysis of the influence of membrane permeability on the composition of internal material. It takes into account phenomena that lead to the elongation of an RNA strand (ligation), fission of molecules (phosphodiester bond breakage) and replication of polynucleotides. Results obtained from the model point out that the existence of protocells might support concentration of material and creation of longer molecules.
Individual Recognition from Gait Using Feature Value Method
Authors: Zhang Tianxiang , Venture Gentiane
Published: April 2013

We propose a novel framework to recognize individuals from gait, in order to improve HRI. We collected the motion data of the torso from 13 persons’ gait, using 2 IMU sensors. We developed Feature Value Method which is a PCA based classifier and we achieved an average individual recognition rate of 94% through cross-validation.
New Reference-Neighbourhood Scalarization Problem for Multiobjective Integer Programming
Authors: Genova Krasimira , Kirilov Leonid , Guljashki Vasil
Published: April 2013

Scalarization is a frequently used approach for finding efficient solutions that satisfy the preferences of the Decision Maker (DM) in multicriteria optimization. The applicability of a scalarization problem to solve integer multicriteria problems depends on the possibilities it provides for the decrease of the computing complexity in finding optimal solutions of this class of problems. This paper presents a reference-neighbourhood scalarizing problem, possessing properties that make it particularly suitable for solving integer problems. One of the aims set in this development has also been the faster obtaining of desired criteria values, defined by the DM, requiring no additional information by him/her. An illustrative example demonstrates the features of this scalarizing problem.
Pointwise a Posteriori Error Analysis for an Adaptive Penalty Finite Element Method for the Obstacle Problem
Authors: French Donald A. , Larsson Stig , Nochetto Ricardo H.
Published: April 2013

Finite element approximations based on a penalty formulation of the
elliptic obstacle problem are analyzed in the maximum norm. A posteriori error estimates,
which involve a residual of the approximation and a spatially variable penalty
parameter, are derived in the cases of both smooth and rough obstacles. An adaptive
algorithm is suggested and implemented in one dimension.
The Finite Difference Scheme for 3d Mathematical Modeling of a Wood Drying Process
Authors: Čiegis Raimondas , Starikovičius Vadimas
Published: April 2013

This work discusses issues on the design and analysis of finite difference
schemes for 3D modeling the process of moisture motion in the wood. A new finite
difference scheme is proposed. The stability and convergence in the maximum norm
are proved for Robin boundary conditions. The influence of boundary conditions is
investigated, and results of numerical experiments are presented.
Fractional Order Convergence Rate Estimates Of Finite Difference Method On Nonuniform Meshes
Authors: Bojović Dejan , Jovanović Boško
Published: April 2013

In this paper we show how the theory of interpolation of function
spaces can be used to establish convergence rate estimates for finite difference schemes
on nonuniform meshes. As a model problem we consider the first boundary value
problem for the Poisson equation. Using the interpolation theory we construct a
fractional-order convergence rate estimate which is consistent with the smoothness of
data.
The Maximum Principle and Some of Its Applications
Authors: Matus Piotr
Published: April 2013

The subject of this paper is the maximum principle and its application
for investigating the stability and convergence of finite difference schemes. To
some extent, this is a survey of the works on constructing and investigating certain
new classes of monotone difference schemes. In this connection the maximum principle
for the derivatives discussed in this paper is of fundamental importance. It is
used as a basis for proving the coefficient stability of difference schemes in Banach
spaces and the monotonicity of economical schemes of full approximation. New results
on unconditional stability of monotone difference schemes with weights, conservative
explicit-implicit schemes (staggered schemes), monotone schemes of second-order approximation
in arbitrary domains, and monotone difference schemes for multidimensional
elliptic equations with mixed derivatives are given.
On the Stability of Differential-operator Equations and Operator-difference Schemes as t → ∞
Authors: Jovanović Boško , Lemeshevsky Sergey , Matus Peter
Published: April 2013

For the abstract Cauchy problem for a parabolic equation a priori
estimates of the global and asymptotic stability in various energy norms have been
obtained. Similar problems are also considered for the second-order equation. In the
latter case, a priori estimates of the asymptotic stability by the initial data have been
obtained. The corresponding estimates of the global stability for three-level operator
difference schemes have been proved. Estimates of the asymptotic behavior of
the solution for quasi-linear multidimensional equations with unbounded nonlinearity
have been obtained. The corresponding mathematical apparatus permitting one to
prove unconditional monotonicity of the difference schemes approximating nonlinear
problems is presented.
The Two-sided FD-method of Solving the First Boundary Problem for Singular ODE of the Second Order in the Half-axis
Authors: Makarov V.L. , Lazurchak I.I.
Published: April 2013

To solve the boundary problems for singular ordinary differential equations
of the second order the functional-discrete (FD-) method is proposed. The method
gives the possibility of obtaining an approximate solution in the numerical-analytical
form in the whole half-axis with a guaranteed accuracy. Sufficient conditions of convergence
of the method at a rate of a geometrical progression are found. The two-sided
approximations are established and an explicit evaluation of the two-sided estimation
width is given. In conclusion the results of numerical experiments obtained by the
system of computer algebra are presented.
Non-conforming Computational Methods for Mixed Elasticity Problems
Authors: Belgacem Faker Ben , Chilton Lawrence K. , Seshaiyer Padmanabhan
Published: April 2013

In this paper, we present a non-conforming hp computational modeling methodology
for solving elasticity problems. We consider the incompressible elasticity model
formulated as a mixed displacement-pressure problem on a global domain which is
partitioned into several local subdomains. The approximation within each local
subdomain is designed using div-stable hp-mixed finite elements. The displacement
is computed in a mortared space while the pressure is not subjected to any constraints
across the interfaces. Our computational results demonstrate that the non-conforming
finite element method presented for the elasticity problem satisfies similar rates of
convergence as the conforming finite element method, in the presence of various h-version and p-version discretizations.
On a Nonlocal Boundary-value Problem for Two-dimensional Elliptic Equation
Authors: Berikelashvili Givi , Ionkin Nikolai I. , Morozova Valentina A.
Published: April 2013

A boundary-value problem with a nonlocal integral condition is considered for a two-dimensional elliptic
equation with constant coefficients and a mixed derivative. The existence and uniqueness of a weak solution
of this problem are proved in a weighted Sobolev space. A difference scheme is constructed using the Steklov averaging operators.
A Parallel High-accuracy Method for the First-order Evolution Equation in Hilbert and Banach Spaces
Authors: Garvrilyuk Ivan P. , Makarov Vladimir L. , Ryabichev Vyacheslav L.
Published: April 2013

We have developed a discretization method of an arbitrarily given order of accuracy with respect to the time discretization parameter for the first-order
evolution differential equation in Banach space. The method includes two levels of parallelism: the operator exponential needed for the calculation of the evolution operator
can be computed in parallel (inner parallelism) and then we can compute in parallel the evolution operator at various points of the time mesh (outer
parallelism).
Accuracy Estimates of Difference Schemes for Quasi-linear Parabolic Equations Taking into Account the Initial-boundary Effect
Authors: Makarov V. L. , Demkiv L. I.
Published: April 2013

For difference schemes the initial-boundary problem for quasi-linear parabolic-type equations, ’a priori weight estimates’ of the error have been found. These estimates show how much the accuracy of difference schemes near the boundary of a time rectangle is higher than in the middle of it. Sufficient conditions of smoothness of the coefficients and the right-hand side of the quasi-linear parabolic equation and the initial conditions have been found. These conditions ensure a correctness of these a priori estimates.
Numerical Study of Steady Flow Past a Sphere in an Aligned Magnetic Field
Authors: Sekhar T.V.S. , Sivakumar R. , Kumar Harish
Published: April 2013

The ﬂow of a steady, incompressible, viscous, electrically conducting
ﬂuid past a sphere in the presence of uniform magnetic ﬁeld parallel to the undisturbed
ﬂow is investigated using the ﬁnite difference method. The multigrid method with a
defect correction (DC) technique is used to achieve the second order accurate solution.
The Hartmann number M is used as the perturbation parameter. It has been found
that the increase of magnetic ﬁeld decreases the wake length (L) and increases the drag
coefficient. The graphs of streamlines, vorticity lines, drag coefficient, wake length,
surface pressure and surface vorticity are presented and discussed
A Generalized Relaxation Method for Transport and Diffusion of Pollutant Models in Shallow Water
Authors: Delis A.I. , Katsaounis Th.
Published: April 2013

We present a numerical method based on finite difference relaxation
approximations for computing the transport and diffusion of a passive pollutant by a
water flow. The flow is modeled by the well-known shallow water equations and the
pollutant propagation is described by a transport equation. The previously developed
nonoscillatory relaxation scheme is generalized to cover problems with pollutant trans-
port, in one and two dimensions and source terms, resulting in a class of methods of
the first and the second order of accuracy in space and time. The methods are based on
the classical relaxation models combined with a Runge-Kutta time splitting scheme,
where neither Riemann solvers nor characteristic decompositions are needed. Numerical
results are presented for several benchmark test problems. The schemes presented
are verified by comparing the results with documented ones, proving that no special
treatment is needed for the transport equation in order to obtain accurate results.
Error Estimates and Iterative Procedure for Mixed Finite Element Solution of Second-Order Quasi-Linear Elliptic Problems
Authors: Karchevsky Mikhail , Fedotov Alexander
Published: April 2013

The mixed finite element method for second-order quasi-linear elliptic
equations with nonlinearities of arbitrary power rate of growth is considered. Error
estimates are obtained. An iterative method for corresponding discrete problem is
proposed and investigated.
Instability and Collapse in Discrete Wave Equations
Authors: Carpio A. , Duro G.
Published: April 2013

Unstable growth phenomena in spatially discrete wave equations are
studied. We characterize sets of initial states leading to instability and collapse and
obtain analytical predictions for the blow-up time. The theoretical predictions are con-
trasted with the numerical solutions computed by a variety of schemes. The behavior
of the systems in the continuum limit and the impact of discreteness and friction are
discussed.
Stability Criterion of Difference Schemes for the Heat Conduction Equation with Nonlocal Boundary Conditions
Authors: Gulin A. , Ionkin N. , Morozova V.
Published: April 2013

The elements of the stability theory of nonselfadoint difference schemes
for nonstationary problems of mathematical physics are discussed. Difference schemes
for the heat conduction equation with nonlocal boundary conditions are considered in
detail from the viewpoint of the general stability theory of two-layer operator-difference
schemes. The necessary and sufficient stability conditions in the sense of the initial data
in special energy norm have been found. The equivalence of the energy norm to the
grid L2-norm has been proved. A priori estimates expressing the difference schemes
stability in the sense of the right-hand side have been constructed.
On Finite Volume Discretization of the Three-dimensional Biot Poroelasticity System in Multilayer Domains
Authors: Naumovich A.
Published: April 2013

In this paper we propose a finite volume discretization for the threedimensional
Biot poroelasticity system in multilayer domains. For stability reasons,
staggered grids are used. The discretization takes into account discontinuity of the
coefficients across the interfaces between layers with different physical properties. Numerical
experiments based on the proposed discretization showed second order convergence
in the maximum norm for the primary and flux unknowns of the system. An
application example is presented as well.
Sparse Radiographic Tomography and System Identification Imaging from Single View, Multiple Time Sample Density Plots
Authors: Asaki T.J. , Bollt E.M. , Vixie K.R.
Published: April 2013

Tomography is a classic inverse problem in which multiple density
projections of an object are processed to infer some approximation of the original. We
consider the highly sparse inverse problem of single angle projection, but seek to reduce
the ambiguity through multiple time observations in a dynamic system of known or
partially known dynamics. In this work we solve the planar problem by optimization
techniques based on a gradient-free multi-directional search algorithm to minimize our
nonlinear functional. We demonstrate convincingly successful numerical examples to
support our relatively simple technique.
Fedorenko Finite Superelement Method and Its Applications
Authors: Galanin M. , Lazareva S. , Savenkov E.
Published: April 2013

This paper considers the Fedorenko Finite Superelement Method
(FSEM) and some of its applications. The general idea, the main theoretical background,
and the results of the numerical investigation of the method are presented
using the model problem for the Laplace equation. Generalization to some other problems
using the general approach suggested by the authors is also considered.
A Weighted Residual Parabolic Acceleration Time Integration Method for Problems in Structural Dynamics
Authors: Razavi S.H. , Abolmaali A. , Ghassemieh M.
Published: April 2013

In the proposed method, the variation of displacement in each time step
is assumed to be a fourth order polynomial in time and its five unknown coefficients are
calculated based on: two initial conditions from the previous time step; satisfying the
equation of motion at both ends of the time step; and the zero weighted residual within
the time step. This method is non-dissipative and its dispersion is considerably less
than in other popular methods. The stability of the method shows that the critical time
step is more than twice of that for the linear acceleration method and its convergence
is of fourth order.
Exact Difference Schemes for Hyperbolic Equations
Authors: Matus P. , Kołodyńska A.
Published: April 2013

In the present paper, an exact difference scheme for the initial boundary-
value problem of the third kind for an inhomogeneous hyperbolic equation of the second
order with constant coefficients has been constructed on ordinary rectangular grids with
constant space and time steps, where the Courant number
γ=1. Later we proved a priori estimates of the stability in energy norm. For a quasi-linear wave
equation on the moving characteristic grid a difference scheme has been constructed,
which has the second order of approximation for the initial boundary-value problem
and is exact for the Cauchy problem. The computational results for smooth functions
and for a weak solution confirm the high accuracy of the introduced algorithm. We
have also constructed exact difference schemes for the Cauchy problem for a system
of two hyperbolic equations of the first order with constant coefficients on grids with
constant space and time steps. Stability in energy norm for one
of the constructed schemes has been proved. Using a method analogous to that used
for the nonlinear wave equation a difference scheme for a nonlinear gas dynamic system
has been constructed.
Sharp Expressions for the Stabilization Parameters in Symmetric Interior-penalty Discontinuous Galerkin Finite Element Approximations of Fourth-order Elliptic Problems
Authors: Mozolevski I. , Bösing P.R.
Published: April 2013

In this paper, we derive explicit expressions for the penalty parameters
appearing in symmetric and semi-symmetric interior-penalty discontinuous Galerkin
finite element method (DGFEM) for fourth-order elliptic problems. We demonstrate
the sharpness of the theoretically predicted penalty parameter values through numerical
experiments.
An hp-adaptive strategy for the solution Of the exact kernel curved wire pocklington Equation
Authors: HEMKER P.W. , LAHAYE D.J.P.
Published: April 2013

In this paper we introduce an adaptive method for the numerical solu-tion of the Pocklington integro-differential equation with exact kernel for the current induced in a smoothly curved thin wire antenna. The hp-adaptive technique is based on the representation of the discrete solution, which is expanded in a piecewise p-hierarchical basis. The key element in the strategy is an element-by-element criterion that controls the h- or p-refinement. Numerical results demonstrate both the simplicity and efficiency of the approach
Fully Discrete Galerkin Method For Fredholm Integro-Differential Equations With Weakly Singular Kernels
Authors: PEDAS A. , TAMME E.
Published: April 2013

Approximations to a solution and its derivatives of a boundary value problem of an nth order linear Fredholm integro-differential equation with weakly sin-gular or other nonsmooth kernels have been determined. These approximations are piecewise polynomial functions on special graded grids. To find them, a fully discrete version of the Galerkin method has been constructed. This version is based on a dis-crete inner product concept and some suitable product integration techniques. Optimal global convergence estimates have been derived and a collection of numerical results of a test problem is given.
An Alternating Potential-Based Approach To The Cauchy Problem For The Laplace Equation In A Planar Domain With A Cut
Authors: CHAPKO R. , JOHANSSON B.T.
Published: April 2013

We consider a Cauchy problem for the Laplace equation in a bounded region containing a cut, where the region is formed by removing a sufficiently smooth arc (the cut) from a bounded simply connected domain D. The aim is to reconstruct the solution on the cut from the values of the solution and its normal derivative on the boundary of the domain D. We propose an alternating iterative method which involves solving direct mixed problems for the Laplace operator in the same region. These mixed problems have either a Dirichlet or a Neumann boundary condition imposed on the cut and are solved by a potential approach. Each of these mixed problems is reduced to a system of integral equations of the first kind with logarithmic and hypersingular kernels and at most a square root singularity in the densities at the endpoints of the cut. The full discretization of the direct problems is realized by a trigonometric quadrature method which has super-algebraic convergence. The numerical examples presented illustrate the feasibility of the proposed method.
The Determinant Method for Nonselfadjoint Singular Sturm — Liouville Problems
Authors: Boumenir A.
Published: April 2013

We are concerned with the computation of eigenvalues of singular nonselfadjoint
Sturm — Liouville problems by the method of determinants. The representation
of a differential operator by an infinite matrix allows the use of Lidskii’s theorem
to define its determinant. The finite section is then used to compute eigenvalues in a
simple way. This direct method borrows stable methods from numerical linear algebra
to compute a large number of eigenvalues with high precision. Numerical examples
with nondifferentiable and complex valued coefficients are treated at the end.
Numerical Method for Finding Bifurcation Points of the Linear Two-parameter Eigenvalue Problem
Authors: Khlobystov V. V. , Podlevskyi B. M.
Published: April 2013

The iteration algorithm of finding bifurcation points of simple eigenvalue
curves of the linear algebraic two-parameter eigenvalue problem is considered. The
algorithm is based on the efficient numerical procedure of calculation of the derivative
of matrix determinant. Numerical results are given.
A Posteriori Error Estimators Based on Equilibrated Fluxes
Authors: Cochez-Dhondt Sarah , Nicaise Serge
Published: April 2013

We consider the conforming of finite element approximations of reactiondiffusion
problems. We propose new a posteriori error estimators based on H(div)-
conforming finite elements and equilibrated fluxes. It is shown that these estimators
give rise to an upper bound where the constant is one in front of the indicator, up to
higher order terms. Lower bounds can also be established with constants depending on
the shape regularity of the mesh and the local variation of the coefficients. We further
analyze the convergence of an adaptive algorithm. The reliability and efficiency of the
proposed estimators are confirmed by various numerical tests.
Diffeomorphic Matching and Dynamic Deformable Surfaces in 3d Medical Imaging
Authors: Azencott R. , Glowinski R. , He J. , Jajoo A. , Li Y. , Martynenko A. , Hoppe R.H.W. , Benzekry S. , Little S.H.
Published: April 2013

We consider optimal matching of submanifolds such as curves and
surfaces by a variational approach based on Hilbert spaces of diffeomorphic transformations.
In an abstract setting, the optimal matching is formulated as a minimization
problem involving actions of diffeomorphisms on regular Borel measures considered as
supporting measures of the reference and the target submanifolds. The objective functional
consists of two parts measuring the elastic energy of the dynamically deformed
surfaces and the quality of the matching. To make the problem computationally accessible,
we use reproducing kernel Hilbert spaces with radial kernels and weighted
sums of Dirac measures which gives rise to diffeomorphic point matching and amounts
to the solution of a finite dimensional minimization problem. We present a matching
algorithm based on the first order necessary optimality conditions which include an
initial-value problem for a dynamical system in the trajectories describing the deformation
of the surfaces and a final-time problem associated with the adjoint equations.
The performance of the algorithm is illustrated by numerical results for examples from
medical image analysis.
A Natural Adaptive Nonconforming FEM Of Quasi-Optimal Complexity
Authors: Rabus H.
Published: April 2013

In recent years, the question on the convergence and optimality in the
context of adaptive finite element methods has been the subject of intensive studies.
However, for nonstandard FEMs such as mixed or nonconforming ones, the lack of
Galerkin's orthogonality requires new mathematical arguments. The presented adap-
tive algorithm for the Crouzeix-Raviart finite element method and the Poisson model
problem is of quasi-optimal complexity. Furthermore it is natural in the sense that
collective marking rather than a separate marking is applied or the estimated error
and the volume term.
Quasi-optimality of an Adaptive Finite Element Method for an Optimal Control Problem
Authors: Becker Roland , Mao Shipeng
Published: April 2013

We prove quasi-optimality of an adaptive finite element algorithm for a model problem
of optimal control including control constraints. The quasi-optimility expresses the fact
that the decrease of error with respect to the number of mesh cells is optimal up to a
constant. The considered algorithm is based on an adaptive marking strategy which compares
a standard residualtype a posteriori error estimator with a data approximation term in each
step of the algorithm in order to adapt the marking of cells.
Energy Principles and Finite Element Methods for Pure Traction Linear Elasticity
Authors: Bochev Pavel , Lehoucq Richard
Published: April 2013

A conforming finite element discretization of the pure traction elasticity boundary value
problem results in a singular linear system of equations. The singularity of the linear
system is removed through various approaches. In this report, we consider an alternative
approach in which discrete finite element formulations are derived directly from the principle
of minimum potential energy. This point of view turns out to be particularly well suited to
handle the rigid body modes, which are the source of the singularity in the finite element
linear system. Our approach allows us to formulate a regularized potential energy principle
and show that the associated weak problem is coercive in H1(Ω). This guarantees nonsingular
problems, enables simplified solution algorithms and leads to more efficient and robust
preconditioners for the iterative solution linear equations.
Adaptive Finite Element Methods For Optimal Control Of Second Order Hyperbolic Equations
Authors: Kröner Axel
Published: April 2013

In this paper we consider a posteriori error estimates for space-time finite element
discretizations for optimal control of hyperbolic partial dierential equations of second
order. It is an extension of Meidner and Vexler (2007), where optimal control problems of
parabolic equations are analyzed. The state equation is formulated as a first order system
in time and a posteriori error estimates are derived separating the in uences of time, space,
and control discretization. Using this information the accuracy of the solution is improved
by local mesh refinement. Numerical examples are presented. Finally, we analyze the
conservation of energy of the homogeneous wave equation with respect to dynamically in time
changing spatial meshes.
Preface to the special issue, CMAM 2011, no. 3.
Authors: Gavrilyuk Ivan , Khoromskij Boris , Tyrtyshnikov Eugene
Published: April 2013

In the recent years, multidimensional numerical simulations with tensor-structured data formats have been
recognized as the basic concept for breaking the "curse of dimensionality".
Modern applications of tensor methods include the challenging high-dimensional
problems of material sciences, bio-science, stochastic modeling, signal processing,
machine learning, and data mining, financial mathematics, etc.
The guiding principle of the tensor methods
is an approximation of multivariate functions and operators
with some separation of variables to keep the computational process in
a low parametric tensor-structured manifold.
Tensors structures had been wildly used as models of data and
discussed in the contexts of differential geometry, mechanics,
algebraic geometry, data analysis etc. before tensor methods recently
have penetrated into numerical computations. On the one hand, the existing tensor
representation formats remained to be of a limited use in many high-dimensional problems
because of lack of sufficiently reliable and fast software.
On the other hand, for moderate dimensional problems (e.g. in
"ab-initio" quantum chemistry) as well as for selected model problems
of very high dimensions, the application of traditional canonical
and Tucker formats in combination with the ideas of multilevel methods
has led to the new efficient algorithms.
The recent progress in tensor numerical methods is achieved with new
representation formats now known as "tensor-train representations"
and "hierarchical Tucker representations". Note that the formats themselves could have
been picked up earlier in the literature on the modeling of quantum systems.
Until 2009 they lived in a closed world of those
quantum theory publications and never trespassed the territory of
numerical analysis. The tremendous progress
during the very recent years shows the new tensor tools in various
applications and in the development of these tools and study of
their approximation and algebraic properties.
This special issue treats tensors as a base for efficient
numerical algorithms in various modern applications and with special
emphases on the new representation formats.