bluuebunny/crossref_metadata_2025 huggingface dataset:
Preservation of Steatotic Livers
Authors: Bessems Maud , Doorschodt Benedict M. , Kolkert Joe L.P. , Vetelainen Reeta L. , van Vliet Arlene K. , Vreeling Heleen , van Marle Jan , van Gulik Thomas M.
Published: March 2007

Liver grafts are frequently discarded due to steatosis. Steatotic livers can be classified as suboptimal and deteriorate rapidly during hypothermic static preservation, often resulting in graft nonfunction. Hypothermic machine perfusion (MP) has been introduced for preservation of donor livers instead of cold storage (CS), resulting in superior preservation outcomes. The aim of this study was to compare CS and MP for preservation of the steatotic donor rat liver. Liver steatosis was induced in male Wistar rats by a choline-methionine-deficient diet. After 24 hours hypothermic CS using the University of Wisconsin solution (UW) or MP using UW-Gluconate (UW-G), liver damage (liver enzymes, perfusate flow, and hyaluronic acid clearance) and liver function (bile production, ammonia clearance, urea production, oxygen consumption, adenosine triphosphate [ATP] levels) were assessed in an isolated perfused rat liver model. Furthermore, liver biopsies were visualized by hematoxylin and eosin staining. Animals developed 30 to 60% steatosis. Livers preserved by CS sustained significantly more damage as compared to MP. Bile production, ammonia clearance, urea production, oxygen consumption, and ATP levels were significantly higher after MP as compared to CS. These results were confirmed by histology. In conclusion, MP improves preservation results of the steatotic rat liver, as compared to CS. Liver Transpl 13:497–504, 2007. © 2007 AASLD.
Combined HLA-DR and -DQ Disparity is Associated with a Stable Course of Ulcerative Colitis After Liver Transplantation for Primary Sclerosing Cholangitis
Authors: Cholongitas Evangelos , Papatheodoridis George V. , Zappoli Paola , Giannakopoulos Athanasios , Patch David , Marelli Laura , Shusang Vibhakorn , Kalambokis George , Shirling Graham , Rolando Nancy , Burroughs A. K.
Published: March 2007

Combined disparity of human leukocyte antigen (HLA)-DR and -DQ between mother and fetus is associated with less severe ulcerative colitis (UC) during pregnancy. We evaluated whether donor-recipient HLA disparity after liver transplantation (LT) affects UC in patients with primary sclerosing cholangitis (PSC). Sixty-nine consecutive patients with PSC underwent LT; all underwent colonoscopy before LT; 48 had UC before and 3 had de novo UC after LT. Clinical and laboratory data, activity and treatment of UC, post-LT cytomegalovirus infection, and disparity of HLA-A, -B, -DR, and -DQ for each donor-recipient pair were evaluated. Pre-LT quiescent UC was present in 26 patients. Post-LT UC activity was evaluated in 36 of 51 patients with UC who had not undergone pre-LT colectomy and who had >12 months' post-LT survival. Of these, 16 were stable, 17 had worsened, and 3 had de novo UC. Seven required colectomy (4 for dysplasia or cancer) after LT. Post-LT cytomegalovirus viremia was neither associated with worse UC activity (P = 0.58) nor de novo UC. Disparity with respect to HLA-A, -B, -DR, and -DQ was found in 58%, 27%, 44%, and 39% donor-recipient pairs, respectively. Post-LT UC course was similar with respect to single HLA disparity. However, disparity in none or only one HLA-DR or -DQ was significantly associated with worse activity compared with patients with disparity at both (65% vs. 0%, P = 0.009). Logistic regression found that the disparity for both -DR and -DQ was the only factor statistically significantly associated with post-LT UC activity. We conclude that disparity in both HLA-DR and -DQ between donor and recipient is associated with stable UC activity after LT. Liver Transpl 13:552–557, 2007. © 2007 AASLD.
Recurrent Hepatocellular Carcinoma After Transplantation
Authors: Parfitt Jeremy R. , Marotta Paul , AlGhamdi Mohammed , Wall William , Khakhar Anand , Suskin Neville G. , Quan Douglas , McAllister Vivian , Ghent Cam , Levstik Mark , McLean Carolyn , Chakrabarti Subrata , Garcia Bertha , Driman David K.
Published: March 2007

Milan and University of California at San Francisco (UCSF) criteria are used to select patients with hepatocellular carcinoma (HCC) for liver transplantation (LT). Recurrent HCC is a significant cause of death. There is no widely accepted pathological assessment strategy to predict recurrent HCC after transplantation. This study compares the pathology of patients meeting Milan and UCSF criteria and develops a pathological score and nomogram to assess the risk of recurrent HCC after transplantation. All explanted livers with HCC from our center over the 18-yr period 1985 to 2003 were assessed for multiple pathological features and relevant clinical data were recorded; multivariate analysis was performed to determine features associated with recurrent HCC. Using pathological variables that independently predicted recurrent HCC, a pathological score and nomogram were developed to determine the probability of recurrent HCC. Of 75 cases analyzed, 50 (67%) met Milan criteria, 9 (12%) met only UCSF criteria and 16 (21%) met neither criteria based on explant pathology. There were 20 cases of recurrent HCC and the mean follow-up was 8 yr. Recurrent HCC was more common (67 vs. 12%; P < 0.001) and survival was lower (15 vs. 83% at 5 yr; 15 vs. 55% at 8 yr; P < 0.001) with those who met only UCSF criteria, compared to those who met Milan criteria. Cryptogenic cirrhosis (25 vs. 5%; P = 0.015), preoperative AFP >1,000 ng/mL (20 vs. 0%; P < 0.001) and postoperative OKT3 use (40 vs. 15%; P = 0.017) were more common among patients with recurrent HCC. While microvascular invasion was the strongest pathological predictor of recurrent HCC, tumor size ≥3 cm (P = 0.004; odds ratio [OR] = 7.42), nuclear grade (P = 0.044; OR = 3.25), microsatellitosis (P = 0.020; OR = 4.82), and giant/bizarre cells (P = 0.028; OR = 4.78) also predicted recurrent HCC independently from vascular invasion. The score and nomogram stratified the risk of recurrent HCC into 3 tiers: low (<5%), intermediate (40–65%), and high (>95%). In conclusion, compared to patients meeting Milan criteria, patients who meet only UCSF criteria have a worse survival and an increased rate of recurrent HCC with long-term follow-up, as well as more frequent occurrence of adverse histopathological features, such as microvascular invasion. Application of a pathological score and nomogram could help identify patients at increased risk for tumor recurrence, who may benefit from increased surveillance or adjuvant therapy. Liver Transpl, 2007. © 2007 AASLD.
Induction of Long-Term Liver Allograft Survival by Delayed Immunosuppression is Dependent on Interleukin-10
Authors: Yang Zhen Fan , Ngai Patricia , Lau Chi Keung , Ho David W. , Tam Ka Ho , Lam Chi Tat , Poon Ronnie T. , Fan Sheung Tat
Published: March 2007

This study aims to investigate the potential role of endogenous interleukin (IL)-10 in long-term liver allograft survival induced by delayed immunosuppression (FK506 days 2-7). Liver transplantation was performed by using Dark Agouti and Lewis rats as donors and recipients, respectively. The delayed immunosuppression protocol induced indefinite allograft survival. A transient upregulation of plasma IL-10 levels was detected in the nontreatment and FK506 treatment groups. Macrophages were found to be one of the major sources of IL-10 produced from the liver allografts. Administration of IL-10–neutralizing antibody shortened the long-term isograft survival and FK506-induced indefinite allograft survival, particularly in the FK506 group. Damaged liver graft histology and increase of plasma alanine aminotransferase levels were detected in the groups with IL-10 antibody treatment. In an ex vivo setting, IL-10 recombinant protein augmented the expression of Foxp3, downregulated the expression of IL-2 and interferon gamma, and induced the generation of CD4+CD25+Foxp3+ and CD8+CD25+Foxp3+ cells, but this effect was blocked by the administration of IL-10 antibody. Finally, administration of IL-10 recombinant protein after the decline of endogenous IL-10 levels improved allograft survival, and a 100% long-term allograft survival was achieved by the combination of IL-10 with low-dose FK506. In conclusion, the delayed immunosuppression could induce long-term liver allograft survival in the presence of endogenous IL-10 produced by the tissue macrophages. Supplementary exogenous IL-10 administration combined with low-dose immunosuppressive drug may be a useful strategy to induce long-term liver allograft survival. Liver Transpl 13:571–578, 2007. © 2007 AASLD.
Antiinflammatory Properties of IL-10 Rescue Small-for-Size Liver Grafts
Authors: Yang Zhen Fan , Ho David Wing Yuen , Ngai Patricia , Lau Chi Keung , Zhao Yi , Poon Ronnie Tung Ping , Fan Sheung Tat
Published: March 2007

The present study aims to investigate the potential therapeutic role of interleukin-10 (IL-10) in small-for-size liver transplantation. A syngenic rat orthotopic liver transplantation model was performed using either whole or 40% liver volume of Lewis rats as grafts according to the experimental design. IL-10 was given to the 40% grafts right after reperfusion, and also at 24 and 48 hours after transplantation. When no treatment was given, less than 40% of the small-for-size grafts survived indefinitely, whereas IL-10 treatment could increase the long-term survival rate of the small-for-size grafts to 80%. The 40% grafts presented with extensive areas of necrosis and increased number of apoptotic cells at the early phases after reperfusion. In addition, upregulation of plasma protein carbonyl content (PCC) levels was also detected in the 40% graft group. IL-10 treatment suppressed the upregulation of allograft inflammatory factor-1 (AIF-1) on macrophages in the 40% grafts, and at the same time, decreased the levels of plasma PCC, and improved the histology and function of the 40% grafts. The expression of inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)-α, and caspase 9 in the 40% grafts were upregulated after reperfusion, whereas the augmentation could be suppressed by the administration of IL-10. Finally, IL-10 culture could block AIF-1-mediated NO production and downregulate the expression of iNOS and TNF-α in a macrophage cell line. In conclusion, IL-10 rescued the small-for-size liver grafts by its antiinflammatory properties, through inhibition of AIF-1 mediated proinflammatory and proapoptotic activities of the macrophages during the early period after ischemia/reperfusion. Liver Transpl 13:558–565, 2007. © 2007 AASLD.
Risk Factors for Invasive Aspergillosis in Living Donor Liver Transplant Recipients
Authors: Osawa Makoto , Ito Yutaka , Hirai Toyohiro , Isozumi Rie , Takakura Shunji , Fujimoto Yasuhiro , Iinuma Yoshitsugu , Ichiyama Satoshi , Tanaka Koichi , Mishima Michiaki
Published: March 2007

Invasive aspergillosis (IA) is a severe complication of liver transplantation. Risk factors for IA after deceased donor liver transplantation (DDLT) have been presented in several reports, but are not well established for living donor liver transplant recipients. Here, a retrospective case-control study was performed. Five cases with IA were investigated after living donor liver transplantation (LDLT) between January 1999 and December 2002 at Kyoto University Hospital. For comparison, living donor liver transplant recipients without IA were taken as controls. These patients had undergone LDLT 1 month before or after each IA case and had the same survival times as the latter. We evaluated the clinical and laboratory findings for both groups up until their demise. Patients with IA after LDLT had a very poor prognosis. By univariate analysis, risk factors for IA were preoperative intensive care unit stay (P = 0.02) and preoperative steroid administration (P = 0.02). Preoperative steroid administration for fulminant hepatitis possibly predisposed to the development of IA after LDLT. Liver Transpl 13:566–570, 2007. © 2007 AASLD.
Tissue Factor-Dependent Procoagulant Activity of Isolated Human Hepatocytes
Authors: Stéphenne Xavier , Vosters Olivier , Najimi Mustapha , Beuneu Claire , Ngoc Dung Khuu , Wijns Walter , Goldman Michel , Sokal Etienne M.
Published: March 2007

Liver cell transplantation (LCT) aims to correct inborn liver function defects by infusing metabolically active cells into the diseased liver. Further improvement in LCT might depend on the prevention of early loss of transplanted cells. As tissue factor (TF)-dependent activation of coagulation was found to contribute to a low rate of beta cell engraftment in islet transplantation, we investigated the potential procoagulant activity (PCA) of hepatocyte preparations. TF expression on hepatocyte preparations was assessed by flow cytometry, reverse-transcription polymerase chain reaction and immunofluorescence. PCA depending on TF was evaluated in human plasma and in whole blood systems. Coagulation parameters were followed by routine techniques in a LCT recipient Crigler-Najjar patient. We determined that hepatocytes express soluble and membrane-bound forms of TF. We showed that hepatocytes exert a TF-dependent PCA. In parallel, delayed increase in D-dimer levels was observed following the hepatocyte infusions in the Crigler-Najjar patient. Furthermore, in vitro experiments demonstrated that TF-dependent PCA of hepatocytes is inhibited by N-acetyl-L-cysteine. In conclusion, hepatocytes exert TF-dependent PCA, which may contribute to early loss of infused cells. Addition of N-acetyl-L-cysteine to the suspensions of hepatocytes might be beneficial in LCT by inhibiting activation of coagulation. Liver Transpl 13:599–606, 2007. © 2007 AASLD.
The Continuing Controversy Regarding the Antiviral Effect of Mycophenolate Mofetil on Hepatitis C†
Authors: Perkins James D.
Published: March 2007

End-stage liver disease caused by the hepatitis C virus (HCV) is a major indication for liver transplantation. HCV re-infection after LT is constant, and it significantly impairs patient and graft survival. Factors that may influence histological recurrence in the graft remain unclear. The aim of our study is to analyse the factors that influence the histological recurrence of HCV in a series of 142 patients undergoing orthotopic liver transplantation. In this series, donors age until 1995 were mostly younger than 30 years, however, from 2000 onwards most of the cases had graft implants from elderly donors. Histological recurrence was 92% after a mean follow-up of 60 months (12-120 months), 17% of which had poor prognostic recurrence. Half of the patients presenting with recurrence did so in the first six months and more than two thirds developing hepatitis in the graft did so in the first year. The accumulated probability of histological recurrence is 40.1%, 51.5%, 70.3%, 83.5% and 92% at 6, 12, 24, 36 and 60 months respectively. In our experience, the variables associated with the development of histological recurrence in the graft, in the multivariate analysis, are donors age ≥31 years and immunosuppressive treatment without mycophenolate mophetil (MMF). Treatment with MMF still acts as a protection factor and is associated with histological non-recurrence. (Transpl Immunol 2006;17:47-50.)
Mood stability during acute stimulator challenge in Parkinson's disease patients under long‐term treatment with subthalamic deep brain stimulation
Authors: Berney Alexandre , Panisset Michel , Sadikot Abbas F. , Ptito Alain , Dagher Alain , Fraraccio Maria , Savard Ghislaine , Pell Marc , Benkelfat Chawki
Published: March 2007

Acute and chronic behavioral effects of subthalamic stimulation (STN‐DBS) for Parkinson's disease (PD) are reported in the literature. As the technique is relatively new, few systematic studies on the behavioral effects in long‐term treated patients are available. To further study the putative effects of STN‐DBS on mood and emotional processing, 15 consecutive PD patients under STN‐DBS for at least 1 year, were tested ON and OFF stimulation while on or off medication, with instruments sensitive to short‐term changes in mood and in emotional discrimination. After acute changes in experimental conditions, mood core dimensions (depression, elation, anxiety) and emotion discrimination processing remained remarkably stable, in the face of significant motor changes. Acute stimulator challenge in long‐term STN‐DBS–treated PD patients does not appear to provoke clinically relevant mood effects. © 2007 Movement Disorder Society
Lösung von Randwertproblemen der Schwingungsgleichung für ein Modell eines Triebwerkeinlaufs
Authors: Friedrich N. , Meister E
Published: March 2007

We consider a simple model of a jet engine inlet consisting of two coaxial cylinders. The inner cylinder extends in both directions to infinity and represents the hub of a jet engine. The outer cylinder is assumed to be semiinfinite representing the engine's jacket. This arrangement is approached by a compressible and invisced gas moving at a velocity U less than the speed of sound. Two problems are formulated. In problem A a normal speed distribution is given in the compressor‐inlet plane, in problem B we are given a pressure distribution. We look for the induced pressure and velocity fields. Using the acoustical approximation of the fundamental equations the Wiener‐Hopf‐method is applied then leading, after a multiplicative and additive decomposition procedure, to an infinite system of linear equations. These involve the expansion coefficients of the solution with respect to the eigenfunctions of the concentric cylindrical duct. Applying arguements from perturbation theory it is possible to extract the essential information from this system of equations. Apart from the possible exception of a denumerable set of values of the distance L of the blade‐row from the inlet the problem has a unique solution.
Asymptotic expansions for central limit theorems for general linear stochastic processes. I: General theorems on rates of convergence
Authors: Butzer P. L. , Gather U. , Törnig W.
Published: March 2007

This paper deals with so‐called general linear stochastic processes (GLSP), defined by T. Kawata in 1972 in generalization of work of R. Lugannani and J. B. Thomas of 1967/71. These second order processes (which are not necessarily stationary nor have independent increments) are described by rather weak requirements, so that several processes such as some random noise and pulse train processes are specific models of these GLSP. Part I is concerned with two general theorems giving asymptotic expansions (including those for the density function) in the central limit theorem for such GLSP, together with error rates. The assumptions for the corresponding θ– ando–error estimates seem rather natural: in the former, apart from assumptions on the inherent structure of such GLSP, the existence of certain moments of higher order as well as a Cramer‐type condition are assumed, in the latter in addition a Lindeberg‐type condition of higher order. Fourier analytic machinery is used for the proofs.
Conform and mixed finite element schemes for the Dirichlet problem for the Bilaplacian in plane domains with corners
Authors: Stephan E. , Meister E.
Published: March 2007

In plane domains with corners for the Bilaplacian a uniquely solvable conform variational principle is studied on weighted Sobolev spaces which is equivalent to the standard Dirichlet problem in the weak form. Clamped plates under point forces near corners are handled by this approach. With weighted Hsieh‐Clough‐Tocher elements on regular triangulations as conform C1‐finite elements a new error analysis is performed without higher regularity assumptions on the exact solution than given by the data and the boundary. The rate of convergence of the error depends on the eigenvalue with smallest imaginary part of a clamped infinite wedge since this eigenvalue describes the singularity of the exact solution in a sector with same angle. Using different spaces of trial and test functions in the standard Galerkin procedure it is shown that the error in the weighted energy norm does not pollute. For convex corners asymptotic error estimates, are proved yielding convergence for a mixed method in hydrodynamics where the solution of a system of 2nd order and its Laplacian are approximated simultaneously by C0‐finite elements being piecewise polynomials.
Über eine Verallgemeinerung des Begriffs „Charakteristik”︁ bei partiellen Differentialgleichungen erster Ordnung
Authors: Wick J. , Neunzert H.
Published: March 2007

As, in general, the projections of characteristics into the x‐space intersect for finite values of t, the global solution of a conservation law

equation image

cannot be determined from the characteristic system of the equation,

equation image

is considered. Only in the linear case, this equation coincides with the equation of the projections of characteristics. For convex h and all x0 this equation has a solution almost everywhere, and the properties of this solution permit to construct a global solution of the conservation law using strips, in the same way as this is done for linear problems by the method of characteristics.
Exotische Lösungen des Bénardschen Problems
Authors: Kirchgässner K.
Published: March 2007

A bifurcation analysis is given for the generalized Bénard problem near the critical value of the Grashoff number. In contrast to earlier investigations where symmetry arguments were used to reduce the boundary‐value‐problem to a simple‐eigenvalue‐bifurcation, we only require double periodicity and treat high multiplicity bifurcation. It is shown that solutions of a yet unknown type exist.
Separation of variables and commuting operators
Authors: Hainzl J. , Kirchgässner K.
Published: March 2007

For any differential operator L, separable in some coordinate system, we construct a set of commuting operators Si such that 1) each Si maps solutions of Lu = 0 into solutions, and 2) the separated solutions of Lu = 0 are simultaneous eigenfunctions of Si. Moreover, a certain description of the separable coordinate system by Si is possible. The paper generalizes results obtained by W. Miller and others on many equations of mathematical physics.
On the time‐dependent Nernst‐Planck equations
Authors: Lange H. , Kirchgässner K.
Published: March 2007

For the one‐dimensional Nernst‐Planck equations of the theory of ion‐transport in thin layers or membranes which mathematically represent a nonlinear coupled parabolic integro‐differential system some global existence and uniqueness theorems for inner and outer problems are given using a priori estimates of the maximum principle type.
An existence theorem for the unmodified Vlasov Equation
Authors: Illner R. , Neunzert H.
Published: March 2007

The initial value problem for the modified Vlasov equation with a mollification parameter δ > 0, as introduced by Batt, has a unique global solution in the weak sense whenever f0 ε L1 and f0 ≧ 0 λ‐a.e. Assuming boundedness of f0 and boundedness of the kinetic energy, it is shown that, as δ → 0, there are subsequences δn → 0 such that the corresponding solutions converge weakly in the measure‐theoretical sense. The limits are shown to be global weak solutions of the initial value problem for Vlasov's equation, and these solutions are seen to be weakly continuous with respect to t. For the plasma physical case, boundedness of the kinetic energy is a consequence of energy conservation.
Solutions for systems of nonlinear elliptic equations with nonlinear boundary conditions
Authors: Rothe F. , Hadeler K. P.
Published: March 2007

We look for solutions of systems of nonlinear elliptic equations with nonlinear boundary conditions and values in some compact convex set M. If the nonlinear terms satisfy a sign condition on the boundary of M and the inhomogeneous terms assume their values in this set existence of solutions is proved.

The proof is based on the homotopy invariance of the Leray‐Schauder degree and Weinberger's strong maximum principle.
On the bifurcation diagram of discrete analogues for ordinary bifurcation problems
Authors: Bohl E. , Kirchgässner K.
Published: March 2007

Ordinary bifurcation problems of the form (1) typically have at most one nontrivial, nonnegative solution for λ > 0. The paper shows that this is in general not true for discrete analogues to (1) no matter how small the step width h > 0 is chosen.
Asymptotic study of the macroscopic behaviour of a solid‐fluid mixture
Authors: Sanchez‐Hubert J. , Eckhaus W.
Published: March 2007

In the framework of homogenization theory we study a mixture of an elastic solid and a viscous compressible fluid with periodic structure and its limit behaviour as the period tends to zero Existence, uniqueness and convergence theorems are given. The limit behaviour is viscoelastic.
Existence and uniqueness of solutions of quasilinear transmission problems of both elliptic and pseudoparabolic type simulating oxygen transport in capillary and tissue
Authors: Großmann U. , Brosowski B.
Published: March 2007

Quasilinear transmission problems of both the elliptic and pseudoparabolic type with differential operators in divergence form simulating oxygen transport in capillary and tissue are investigated. Using recent methods of the theory of pseudomonotone operators and singular perturbations (elliptic regularization) the existence of weak solutions for both problems has been proven. Moreover, the weak solution of the elliptic problem proves to be a solution in the classical sense. Finally, at most one classical solution of a slightly modified pseudoparabolic problem exists.
Scattering by moving bodies: The quasi stationary approximation
Authors: Cooper J. , Wilcox C. H.
Published: March 2007

The scattered field produced by a rotating or vibrating object in the presence of a time harmonic plane wave is usually approximated by a time dependent sequence of stationary fields, called a quasi stationary field. Recently the mathematical theory of scattering of scalar fields of Lax and Phillips has been extended to cover moving bodies. Within this framework the quasi stationary approximation is shown to be valid in each sphere of finite radius which contains the body. Far fields for the exact field and the quasi stationary field are defined and the difference is estimated in terms of a small parameter.
A finite element method for the double‐layer potential solutions of the Neumann exterior problem
Authors: Duong Tuong Ha , Nedelec J. C.
Published: March 2007

A variational formulation for the integral equation used for the double layer potential solution of the Neumann exterior problem in the Laplace equation was proposed in [4]. This formulation allows the use of a finite element method which we describe and experiment here.
Convergence of semigroups with an application to the carleman equation
Authors: Kaper H. G. , Leaf G. K. , Reich S. , Gilbert R. T.
Published: March 2007

We present a simple proof of a convergence result for nonlinear semigroups which can be applied to obtain the fluid dynamical limit of Carleman's equation. In addition, we explicitly identify a closed exponential generator of the limit semigroup. Our results are closely related to those of T. G. Kurtz and H. P. McKean.
Die Lösung der Prae‐Maxwellschen Gleichungen mit Hilfe vollständiger Lösungssysteme
Authors: Hermann P. , Kersten H. , Leis R.
Published: March 2007

This paper deals with the Neumann problem of the pre‐Maxwell partial differential equations

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for a vector field v defined in a region G ⊂ R3. We approximate its uniquely determined solution (integrability conditions assumed) uniformly on G by explicitly computable particular integrals and linear combinations of vector fields with a “fundamental” sequence of points .
Zur numerischen Lösung gewöhnlicher Differential‐gleichungen mit Splines in einem Sonderfall
Authors: Mülthei H. N. , Leis R.
Published: March 2007

In an earlier paper [1] a general procedure has been presented to obtain polynomial spline approximations for the solution of the initial value problem for ordinary differential equations. In this paper the general procedure is described by an equivalent one step method. Furthermore two convergence theorems are proved for a special case which is not included in the general convergence or divergence theory given in [1].
A monotonicity property of bessel functions
Authors: Richberg R. , Leis R.
Published: March 2007

Some monotonicity results are given for the remainder terms in the asymptotic expansion for x → ∞ of the function Jv(x)Jv+n(x) + Yv(x Yv+n(x), v ε R, n ε Z.
Eine abstrakte Theorie der Kegel‐ und Segmentbedingungen
Authors: König H. , Loch H. , Leis R.
Published: March 2007

We develop an abstract theory of geometric regularity conditions for subsets of normed linear spaces, of the type which occurs in the theory of Sobolev spaces (cone conditions, …). The theory is to systematize the diversity of existing conditions, to replace complicated conditions by simpler ones, and to clarify the interplay between different conditions. Our main result is a very general decomposition theorem.
On the boundary value problem of the biharmonic operator on domains with angular corners
Authors: Blum H. , Rannacher R. , Leis R.
Published: March 2007

The paper is concerned with boundary singularities of weak solutions of boundary value problems governed by the biharmonic operator. The presence of angular corner points or points at which the type of boundary condition changes in general causes local singularities in the solution. For that case the general theory of V. A. Kondrat'ev provides a priori estimates in weighted Sobolev norms and asymptotic singular representations for the solution which essentially depend on the zeros of certain transcendental functions. The distribution of these zeros will be analysed in detail for the biharmonic operator under several boundary conditions. This leads to sharp a priori estimates in weighted Sobolev norms where the weight function is characterized by the inner angle of the boundary corner. Such estimates for “negative” Sobolev norms are used to analyse also weakly nonlinear perturbations of the biharmonic operator as, for instance, the von Kármán model in plate bending theory and the stream function formulation of the steady state Navier‐Stokes problem. It turns out that here the structure of the corner singularities is essentially the same as in the corresponding linear problem.
Eine Integralgleichungsmethode für akustische Reflexionsprobleme an lokal gestörten Ebenen
Authors: Gartmeier O. , Werner P.
Published: March 2007

In this paper we consider the reflection of acoustic waves at an unbounded surface which coincides with a plane outside a sufficiently large sphere. We prove uniqueness and existence theorems for the corresponding boundary value problems for the reduced wave equation with Dirichlet and Neumann data by employing integral equation methods.
On the construction of minimizing sequences for convex functionals with upper and lower bounding functionals
Authors: Smith P. , Roach G. F.
Published: March 2007

A method is described for constructing upper and lower bounds for the stationary values of a general class of convex functionals. The method relies of the existence of approximating convex functionals whose Gâteaux derivatives are presumed to have simpler structure than the original. The method is iterative in that convergent sequences of bounds can be constructed. Some applications to the Laplacian operator are included.
On the existence of small‐amplitude optimum hydrofoil propulsion
Authors: Sparenberg J. A. , Thomas E. G. F. , van de Vooren A. I.
Published: March 2007

The trust production by means of a periodic heaving motion of a rigid profile is discussed. It is proved by using Bauer's maximum principle, that when a constraint is put on the magnitude of the amplitude, optimum motions do exist.
On the convexity of equilibrium plasma configurations
Authors: Acker A. , Payne L.
Published: March 2007

We investigate the problem of plasma confinement by a magnetic field in an infinite cylinder. We show that if the cylinder has convex cross‐section, then there exists an equilibrium plasma configuration with convex cross‐section.
An integral equation approximation of the mixed problem for the laplacian in R3
Authors: Baldino R. R. , Nedelec J. C.
Published: March 2007

An integral representation for the solutions of the interior and exterior homogeneous mixed problems on a regular bounded open set in R3 is given in terms of a potential of simple layer on the Dirichlet data and of double layer on the Neumann data. A coercive non‐symmetric bilinear form is provided. Singular finite elements containing the first terms of the assymptotic expansion of the singularity are built and error estimates for the surface distributions are given.
Stability and instability of the energy dependent diffusion system in reactor dynamics
Authors: Pao C. V. , Meister E.
Published: March 2007

The purpose of this paper is to give a systematic analysis for the linear energy dependent diffusion system in reactor dynamics, taking into consideration of delayed neutrons. This analysis includes the existence of a unique positive solution for the time dependent system, the asymptotic behaviour of the solution as t → ∞, the stability and instability of steady‐state solutions, and the existence and uniqueness of a steady‐state solution for the time‐independent system. Using the notion of upper and lower solution, we establish some threshold conditions for insuring the asymptotic behaviour of the solution and the stability and the instability of any given unperturbed solution, including steady‐state solution. In fact, these conditions characterize the stability and the instability property of the solution, and yield a bifurcation result in terms of either the size of the diffusion domain or the physical parameters of the diffusion medium. We also discuss the case without the effect of delayed neutrons.
On the classical solutions of the initial value problem for the unmodified non‐linear vlasov equation II special cases
Authors: Horst E. , Neunzert H.
Published: March 2007

The theory of part I is applied to prove several existence and non‐existence results for special cases. If N = 3, a global classical solution of P° exists, if φ ⩾ 0 has rotational symmetry. If N ⩾ 4, global classical solutions of P° do not always exist.
On complete recovery of geophysical data
Authors: Carroll Robert , Santosa Fadil , Payne L.
Published: March 2007

One considers an elastic halfspace with depth (x1) dependent density Q and Lamé moduli (λ,m̈). Impulsive stresses τli = δ(x2, x3)δ(t) for x1 = 0 are applied with displacement responses ui = gi(t, x2, x3) at x1 = 0 (i = 1, 2, 3). Let vi(t, x1) = ∫∫uidx2dx3 (i = 1, 2 is enough) and set w(t, x1) = ∫∫x2u1dx2dx3. One obtains a system of 3 differential equations for v1, v2, and w to which the spectral techniques of inverse scattering theory are applied as in [25]. The inverse problems for the uncoupled vi can then be solved to produce 2 functions A1 and A2 involving (Q, λ, μ) as functions of “bound” variables y1 and y2 containing (Q, λ, μ), between which a relation then is determined. Analysis of the coupled equation for w then leads to a Fredholm integral equation whose solution provides an additional relation between (Q, λ, μ) from which (Q, λ, μ) can be determined as functions of x1. The integral equation is reduced to a Volterra type equation by results and techniques of transmutation and then solved by a modification of standard techniques. A number of features and results of independent mathematical interest arise from the transmutation theory.
Crank‐nicolsen‐Galerkin approximation for Maxwell's equations
Authors: Hoppe Ronald H. W. , Brosowski B.
Published: March 2007

The Maxwell equations are formulated as an evolution equation in a suitable chosen Hilbert space involving a densely defined closed skew‐Hermitian operator which generates a unitary group. A Crank‐Nicolsen‐Galerkin approximation is then established and convergence is shown by arguments from the theory of approximation of groups of operators.
On the transition from supercritical to subcritical Hopf bifurcations
Authors: Chow Shui.‐Ne E. , White Robert G. , Hadeler K. P.
Published: March 2007

By using the method of averaging, we give a complete Hopf bifurcation diagram when the differential equation has more than one parameter. The method is applied to a system of parabolic equations with nonlinear coupling on the boundary. This set of equations is a mathematical model which describes the normalized concentrations of substances in a solution produced by two enzymes.
Ein gemischtes randwertproblem der kreiszylinderschale mit beliebigen ausschnitten
Authors: Hein J. C. , Meister E.
Published: March 2007

The problem of stress determination in the area of cut‐outs in circular cylindrical shells at given loads is of great interest in industrial practice. This work deals with a mixed boundary value problem of a differential equation derived according to the theory of shallow shells. On partCt1of the boundary, the displacements are given, whereas the stresses are specified on the remaining partCt2. Starting from the Betti‐Maxwell principle and with the aid of the fundamental solutions for unit loads and unit displacements, integral representations can be derived for the displacement functions as well as the stress functions.

The problem is then transformed into an equivalent system of Fredholm integral equations of the first kind with logarithmic kernels as the main part. As the integral equations together with the auxiliary conditions form a strongly elliptical system of pseudo‐differential operators, the Galerkin method converges. Assuming that curvesCt1andCt1do not have points of intersection and that the data are sufficiently regular, the required functions are approximated by cubic splines and, for simplicity's sake, the integral equation system is solved by approximation with a collocation method. In view of the complicated terms of the kernel functions, the kernels are split into a regular and a singular part, the regular part being in turn replaced by cubic splines. The remaining integrations are done numerically by means of Gaussian quadrature formulae. The applicability of the method is demonstrated with the example of a cylinder under internal pressure.
Approximation von extremalflächenstücken (hyperbolischen typs) durch charakteristische räumliche vierecke
Authors: Hölder Ernst , Wendland W.
Published: March 2007

We consider solutions z of the Cauchy‐problem for hyperbolic Euler‐Lagrange equations derived from a general Lagrangian f(x, y, z; zx, zy) in two independent variables x, y. z is supposed to be an extremal of the corresponding variational problem. Visualizing z as a surface in R3 we give a geometric interpretation of Lewy's well‐known characteristic approximation scheme for the numerical solution of second order hyperbolic equations by approximating z via a polyhedral construction built up from subunits which consist of two characteristic triangles having one side in common but lying on different planes in R3. Utilizing ideas from Cartan‐geometry one can (in an appropriate sense) introduce the “mean curvature” of these subunits and it is seen that this curvature vanishes (up to terms of higher order). That is a highly plausible result for the polyhedral approximation of “minimal surfaces”.
Ein nichtlineares Glättungsverfahren zur rekonstruktion von flugbahnen aus radardaten
Authors: Mieth H.‐J. , Wendland W.
Published: March 2007

Data processing is an important tool in airspace surveillance and air traffic control today. In this paper the problem is treated how to reconstruct a flown trajectory from its correlated radar plots subject to a certain knowledge of the aircraft manoeuverability and the radar measurement statistics. A variational approach leads to a generalized smoothing spline method. Simulation results are presented.
Über die existenz und eindeutigkeit einer lösung für ein randwertproblem für eine gleichung vom gemischten typ in einem rechteck
Authors: Müller‐Rettkowski Andreas , Schneider Manfred , Wendland W.
Published: March 2007

In the paper a boundary value problem is studied for the equation of mixed typek(y)uxx+uyy+r(x, y)u=f(x, y)in the rectangular domain {(x, y)| −1 <x< +1,yc<y<yH} withyc< 0,yH> 0,k(y)= signy|y|m,m> 0 (and more generally for a functionk = k(y)withk(O) = 0,k(y)y> O fory≠ O). Specific for the stated problem is that no data are prescribed on the line {(x, yc), −1 <x< +1}. It is proved that the formulated problem is well‐posed in the sense that there is at most one quasi‐regular solution and that a generalized solution exists. The energy‐integral‐(abc‐)method is used to show uniqueness and to obtain an apriori estimate for the solution of the adjoint problem whence the existence statement follows.
Half‐stable solution branches for ordinary bifurcation problems
Authors: Beyn W.‐J. , Kirchgassner K.
Published: March 2007

It is shown that second order bifurcation problems with a positive, autonomous nonlinearity have a smooth branch of positive solutions which tends to infinity. Moreover, this branch satisfies a stability rule saying that the solutions are stable if the branch turns to the right and unstable if it turns to the left.
The sommerfeld half‐plane problem revisited, II the factoring of a matrix of analytic functions
Authors: Heins A. E. , Mmeister E.
Published: March 2007

A half‐plane under plane wave excitation obeys a Dirichlet boundary condition on one side and a Neumann boundary condition on the other. These boundary conditions contrast the ones used by A. Sommerfeld in his classical paper. The present problem leads to a system of integral equations of the Wiener‐Hopf type which may be solved by a matrix factoring method suggested by A. E. Heins in 1950.
An existence theorem for a non linear shell model in large displacements analysis
Authors: Destuynder Ph. , Nedelec J.C.
Published: March 2007

A non linear shell model is considered in this paper. An existence theorem is proved under suitable assumptions on the applied forces or on the geometry.
Dual‐band patch antenna on magnetic substrate for WLAN communication
Authors: Encheng Wang , Shaojun Fang
Published: March 2007

This article introduces a novel dual‐band patch antenna printed on organic magnetic substrate for WLAN communication, operating at 2.45 and 5 GHz. The dual‐band operation is obtained through embedding a pair of L‐shaped slots. The antenna has smaller size for the use of magnetic material, compared with rectangular microstrip antennas on normal dielectric substrate. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1445–1447, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22405
Analysis of multilayer substrates by multilayer contribution of wave concept iterative process
Authors: Hajlaoui El Amjed , Trabelsi Hichem , Zairi Hassen , Gharsallah Ali , Baudrand Henri
Published: March 2007

An efficient iterative technique based on the concept of wave is presented for computing multilayer substrates. This article presents an extensible approach of the iterative method to study substrates with n layers. To validate our theory, we intend to study multilayer dielectric substrates. The approach involves the mixed magnetic and electric filed equation technique and the multilayer contribution of wave concept iterative process, which involves S‐parameters extraction technique based on a simple form of Matched Load Simulation. In this sense, a program in FORTRAN has been elaborated to determine different parameters Sijcharacterizing the studied structure. The numerical results are compared with the published data. Good agreement will be important to establish the validity and usefulness of the iterative method given in this article. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1439–1445, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22406
A wideband circularly polarized 2 × 2 sequentially rotated patch antenna array
Authors: Lu Y. , Fang D. G. , Wang H.
Published: March 2007

A wideband circularly polarized 2 × 2 sequentially rotated patch antenna array is presented. This array applies the wideband circularly polarized elements to the sequential rotated feeding to realize wide bandwidth by a simple structure. A measured −10‐dB return loss bandwidth of 102% and an AR < 3‐dB bandwidth of 43.7% are obtained. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1405–1407, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22409
Characterization of on‐human‐body UWB radio propagation channel
Authors: Zhang Y. P. , Bin Li , Qi Cao
Published: March 2007

Wireless body area network (WBAN) has begun to receive attention recently. Ultra wideband (UWB) is a promising technology for WBAN applications. This article presents the results of UWB radio channel measurements performed on human bodies from 3.1 to 10.6 GHz in indoor environments. The measurements were devised to generate the radiographs of path loss and delay spread for the first time. The radiographs contain both qualitative and quantitative information on the channel. They clearly display the influence of the body on the channel and thus reveal where the network nodes should be strategically placed on the body in the design of the UWB WBAN systems. They directly give such channel parameters as path loss and delay spread. They also reflect variations of the channel on and in close proximity to the body. In addition, the measurements were made in an anechoic chamber to expose the impact of the body and to study the effect of different environments on the channel. It is shown that for the UWB channel on the body the path loss exponent n = 2.7 can be used, while for the UWB channel through the body the path loss exponent increases to n = 3.7. The maximum value of the rms delay spread is 12 ns. The rms delay spread values are less than 6 ns 50% of the time. The number of multipath components increases with the separation between transmit and receive antennas. Because of the nonreflecting mechanism, the path loss is larger and the delay spread is smaller in the anechoic chamber environment. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1365–1371, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22411
A study of printed monopole antenna for ultra wideband applications
Authors: Lee Yi‐Chieh , Sun Jwo‐Shiun , Huang Wei‐Jiun
Published: March 2007

A printed monopole with coplanar waveguide‐fed antenna for ultra‐wideband applications is proposed. The proposed antenna includes a rectangle‐shaped patch as a radiator, two ground planes with symmetrical notch, and feed excitation. It covers the all ultra wideband (UWB 3.1–10.6 GHz) and has 7.8 GHz (2.8–10.6 GHz) measured return loss bandwidth. In modifiable design, we choose to design the notches on the ground plane, the height of the proposed antenna, and the width of the radiator, and have to obtain broad impedance bandwidth and accessible measurement parameters. The experiment results have shown acceptable omnidirectional radiation pattern and fine gain in this paper. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1435–1438, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22420
Switchable dual wavelength erbium‐doped fiber laser at room temperature
Authors: Han Young‐Geun , Lee Ju Han
Published: March 2007

A simple technique of a switchable dual wavelength erbium‐doped fiber laser based on fiber Bragg gratings is proposed and demonstrated by using both the linear cavity loss controlling and the homogeneous gain broadening of EDF. The single or dual lasing wavelength can be also obtained by controlling of two linear cavity losses at room temperature. The stability response time for the small‐amplitude stability of less than 1% is measured to be less than 0.27 ms. High‐quality EDF laser output with a high extinction ratio of more than ∼40 dB is achieved for all wavelength switching cases. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1433–1435, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22421