bluuebunny/crossref_metadata_2025_split huggingface dataset:
Étude de la stabilité d'une équation différentielle non conservative du second ordre, à coefficients périodiques
Authors: Meckert C. 
Published: June 2007

AbstractVorgelegt sei die Gleichung (E) ẍ + p(t) ẋ + q(t) × = 0 mit Koeffizienten, die in jeder Halbperiode konstant sind und beziehungsweise die Werte p1 und p2 bzw. q1 und q2 haben. Dann läßt sich das folgende wesentliche Ergebnis erzielen: Bei gegebenen festen Werten p1, p2 und q1 – die notwendige Stabilitätsbedingung p1 + p2 ≧ 0 sei erfüllt – ist weder die Menge der Werte q1, für die (E) stabil ist, noch die Menge der Werte q1, für die (E) instabil ist, beschränkt, und diese Aussage gilt sogar für sehr große Werte p1 und p2.Überraschend ist noch folgende Eigenschaft: Ist (Ei), i = 1, 2, die Gleichung ẍ + piẋ + qix = 0 mit den konstanten Koeffizienten pi, qi, so ist die Stabilität von (E) weitgehend unabhängig von derjenigen von (Ei). Auf diese Weise kann es sein, daßIm Falle p1 + p2 = 0 konstruiert man das Stabilitätsdiagramm im (c1, c2, p1)‐Raum, wobei ci = qi ‐ pi2, i = 1, 2 ist.(E1) und (E2) stabil und sogar stark stabil sind, (E) aber instabil.(E1) und (E2) instabil sind, (E) aber asymptotisch stabil.
The Transient and Steady State Response of a Thick Membrane to Static and Dynamic Loading
Authors: Hutter K. , Olunloyo V. O. S. 
Published: June 2007

AbstractEs wird gezeigt, daß für anisotrop vorgespannte dicke Membranen oder dünne Platten mit kleiner Biegesteifigkeit die Methode der singulären Störungsrechnung geeignet ist, um die Durchbiegung der Membranen infolge statischer und dynamischer Belastungen zu bestimmen. Im speziellen wird die Durchbiegung eines Streifens (oder auch langen Rechtecks) konstruiert, wenn die äußere Belastung entweder statisch oder dynamisch ist. Zum ersten Mal in der Literatur dünner Platten wird hier die Technik der singulären Störungsrechnung verwendet, um stationäre erzwungene Schwingungen (im Gegensatz zum Eigenwertproblem) und das Verhalten unter Stoßlast zu bestimmen. Für den letzten Fall zeigt sich, daß sich eine Störung anfänglich mit einer Geschwindigkeit fortpflanzt, welche der Wurzel aus der Anisotropie in der Vorspannung proportional ist.Es wird weiter gezeigt, daß sich im allgemeinen, wenn die Störfunktion sowohl räumlich als auch zeitlich periodisch ist, der Charakter der Lösungen von exponentiellem Verhalten zu periodischem Verhalten ändert, je nachdem die Frequenz größer oder kleiner als die räumliche Wellenlänge ist.
Inertial Oscillations and Hydromagnetic Multiple Boundary Layers in a Rotating Fluid
Authors: Debnath L. 
Published: June 2007

AbstractA study is made of the non‐torsionally generated unsteady hydromagnetic flow in a semi‐infinite expanse of an electrically conducting rotating viscous fluid bounded by an infinite non‐conducting porous plate subjected to uniform suction or blowing in the presence of an external magnetic field. The structure of the steady and the unsteady velocity field and the associated multiple boundary layers are investigated. An asymptotic analysis of the solution is carried out for small and large times to describe the manner of the transient approach to the ultimate steady‐state flow including the various physical processes involved in it. The difficulty of the hydrodynamic solution associated with the case of blowing and resonant frequency is resolved in this paper. It is shown that the oscillatory boundary layer flows confined to the ultimate boundary layers are established through the inertial oscillations and the propagation of diffused hydromagnetic waves.
Vibration of Non‐Uniform Thin‐Walled Beams of Arbitrary Shape
Authors: Suryanarayan S. , Mürty A. V. Krishna 
Published: June 2007

AbstractA generalised theory for the natural vibration of non‐uniform thin‐walled beams of arbitrary cross‐sectional geometry is proposed. The governing equations are obtained as four partial, linear integro‐differential equations. The corresponding boundary conditions are also obtained in an integro‐differential form. The formulation takes into account the effect of longitudinal inertia and shear flexibility. A method of solution is presented. Some numerical illustrations and an exact solution are included.
Monotone Schrankenfolgen für gewöhnliche Randwertaufgaben bei schwach gekoppelten nichtlinearen Systemen
Authors: Spreuer H. , Adams E. , Srivastava U. N. 
Published: June 2007

AbstractEs werden in den Ableitungen lineare Systeme schwach gekoppelter gewöhnlicher DGL jeweils 2. Ordnung mit Randbedingungen 3. Art für magnified image: I ⊂ ℝ → ℝN betrachtet. Die nichtlinearen Funktionen von x und magnified image seien stetig und bzgl. magnified image Lipschitz‐stetig. Ohne Übergang zu einem äquivalenten System von Integralgleichungen werden monotone Folgen fallender oberer Schranken magnified imagen(x) und steigender unterer Schranken magnified imagen(x) mit n ϵ ℕ konstruiert, die zur Klasse Y mit den Eigenschaften klassischer Lösungen der vorgelegten Aufgabe gehören. Die Kontraktionsbedingung verlangt, daß Funktionen magnified image0(x) und magnified image0(x) bekannt sind, die strenge Ungleichungen erfüllen, welche durch Lipschitz‐Linearisierung aus dem gegebenen System gewonnen werden. Wenn diese Bedingungen erfüllt sind, konvergieren die Folgen (magnified imagen) und (magnified imagen) gleichmäßig gegen dieselbe Grenzfunktion magnified image ϵ Y, die die einzige ganz durch magnified image0 und magnified image0 eingeschlossene Lösung ist. Bei geeigneten Systemen können magnified image0 und magnified image0 durch eine Nebeniteration bestimmt werden. Der Schrankenabstand magnified imagen ‐ magnified imagen stellt mit n ϵ ℕ0 eine Fehlerabschätzung zur Verfügung, die i. a. günstiger als diejenige des Banachschen Fixpunktsatzes ist.
The Axisymmetric Distribution of Stresses in an Infinite Elastic Solid Containing a Flat Annular Crack under Internal Pressure
Authors: Shibuya T. , Nakahara I. , Koizumi T. 
Published: June 2007

AbstractThe authors analyze the axisymmetric distribution of stress in an infinite elastic solid containing a flat annular crack under internal pressure which is one of three‐part mixed boundary value problems. Assuming that the deformation on the crack surface is continuous, we may represent it by Fourier series, and reduce the problem to the solution of an infinite system of algebraic equations. The displacement and stress components obtained are given by series involving infinite integrals. In particular, the integrals on the crack plane are expressed in terms of Gaußian hypergeometric functions. The radial distributions of the displacement and the stress components and the variations of the stress intensity factors at the crack tips with the ratio of the inner to the outer radius of the crack are shown graphically.
Grundlagen zu einer Theorie des Ringflügels in axialsymmetrischer Scherströmung
Authors: Weissinger J. , Overlach B. 
Published: June 2007

AbstractAls Grundlage für eine Theorie des Ringflügels in ungleichförmiger Anströmung werden die grundlegenden Gleichungen für das axialsymmetrische, stationäre, inkompressible und reibungsfreie Strömungsfeld eines Wirbel‐ und eines Quellringes in axialsymmetrischer Scherströmung hergeleitet. Für das linearisierte Problem wird ein — auf einer Fourier‐Transformation beruhendes — Lösungsverfahren angegeben und für einige einfache Beispiele durchgeführt.
Some Aspects of Quadratic Programming in Complex Space
Authors: Das C. 
Published: June 2007

AbstractIn this paper a pair of quadratic programs (primal and its dual) has been formulated in complex space with an arbitrary square matrix A2 in the constraint sets. The paper establishes certain duality results without assuming any interdependence of the objective function and the constraint sets on a Hermitean positive‐semi‐definite matrix as considered in [3].
On a Quasi‐Conical Motion in Supersonic‐Hypersonic Flow, Considering the Entropy Effects
Authors: Berbente C. 
Published: June 2007

AbstractIn order to get analytical solutions for the supersonic‐hypersonic motion around a body of revolution, consisting of a cylinder and a truncated come, one proposes a perturbation method. Unlike the classical procedure where one considers small perturbations with respect to the general flow, parallel at upstream infinity, the basic state is a potential motion, close enough to the real one, that respresents an exact solution in several important limit cases. The method provides explicit formulae for the velocity field, as well as for the shock wave curve and for the entropy gradient.
A Direct Numerical Integration Method for Second‐Order Ordinary Differential Equations
Authors: Gupta R. G. 
Published: June 2007

AbstractThis paper describes a new direct method for the numerical integration of the initial value problem

.The method has a local truncation error O(h6) in y(x) and O(h5) in y'(x). For n integration steps, the present method requires 5n function evaluations while the method of Runge‐Kutta‐Butcher needs 6n for the same order of accuracy. Theoretical and computational comparisons of the present method with the existing methods are discussed.
Mixed Boundary Value Problems in Electrostatics
Authors: Gupta O. P. , Gupta S. K. 
Published: June 2007

AbstractThis paper deals with two problems. The first problem is to determine the electrostatic potential in the vicinity of two cross‐shaped charged strips, while in the second the study is made when these strips are situated inside a grounded cylinder. Both problems are first reduced to two sets of dual integral equations which are further reduced to two Fredholm integral equations of the second kind. These equations are solved numerically and quantities of physical interest are calculated.
Kinematic Hardening and Plastic Instability under Plane Stress
Authors: Shrivastava H. P. , Dubey R. N. 
Published: June 2007

AbstractThe main objective of this paper is to develop a criterion of tensile plastic instability which should be sufficiently general to include both the Bauschinger effect and anisotropy. The criterion so developed reduces to Moore and Wallace's condition for anisotropic materials, in case the Bauschinger effect is either completely neglected or it is negligible at the onset of deformation process. However, this analysis shows significant change in instability condition if the material exhibits the Bauschinger effect initially.It is also shown that localised neck can also take place in biaxial loading for stress ratios greater than half. This would depend upon the anisotropy coefficients and the degree of the Bauschinger effect initially exhibited by the material.
Unsteady Free Convection Flow from a Vertical Plate in the Presence of a Uniform Magnetic Field
Authors: Mishra S. P. , Moeapatra P. 
Published: June 2007

AbstractThe unsteady free convection flow of a viscous electrically conducting fluid from an infinite vertical plate in the presence of a uniform magmetic field has been studied. Simple closed form expressions for the velocity and the magnetic field are obtained for the case when the nzagnetic Prandtl number IS, is unity and the therncal Prandtl number Σ1 is arbitrary.
Dreidimensionale, instationäre Temperaturverteilung in durchströmten zylindrischen Rohren
Authors: Schenk R. 
Published: June 2007

AbstractIn dieser Arbeit werden eine numerische Methode und Ergebnisse einer instationären, dreidimensionalen Berechnung der Temperaturverteilung in durchströmten zylindrischen Rohren beschrieben. Der volle zylindrische Stab kann als Spezialfall für verschwindende Strömung mit diskutiert werden. Die Temperaturverteilung am Mantel ist eine Funktion des Ortes und der Zeit. Die Methode geht auf das Teilschrittverfahren zurück, welches für dreidimensionale Probleme auf volle Approximation erweitert wurde. Das Teilschrittverfahren gestattet mit Vorteil die direkte Integration der Differentialgleichungen. Auf eine Einführung von Hilfsfunktionen wird verzichtet. Als Ergebnis liegen Temperaturflächen vor, die ihre Lage im Raum zeitlich ändern.
Thermo‐Capillary‐Induced Axisymmetric Free Liquid Surface Oscillations in a Visco‐Elastic Liquid Column
Authors: Bauer H. F. 
Published: June 2007

AbstractThe response due to an axisymmetric time‐fluctuating temperature distribution applied at the free liquid surface of a viscoelastic cylindrical liquid column has been determined analytically. The amplitudes of the radial and axial velocity distributions as well as the free surface elevation have been presented as functions of the “reduced” forcing frequency of the oscillatory temperature and have numerically been evaluated for an axial sinusoidal temperature field for various surface‐tension parameters τ * v/v2, relaxation time parameters τ * v/v2 and axial wave number parameters ka. It was found, that visco‐elasticity as described by the Maxwell model has quite some influence upon the liquid motion. It shows for smaller relaxation more viscous, for larger relaxation times more elastic behavior. Larger relaxation time parameter exhibits increased amplitudes and fluctuating response behavior of the liquid. In addition there is a deflection of the liquid surface for vanishing oscillatory temperature frequency Ω. This means, that in the steadystate the surface is already deflected.
Biocatalytic synthesis of some chiral drug intermediates by oxidoreductases
Authors: Patel Ramesh N. , Hanson Ronald L. , Banerjee Amit , Szarka Laszlo J. 
Published: June 2007

AbstractChiral intermediates were prepared by biocatalytic processes with oxidoreductases for the chemical synthesis of some pharmaceutical drug candidates. These include: (i) the microbial reduction of 1‐(4‐fluorophenyl)‐4‐[4‐(5‐fluoro‐2‐pyrimidinyl)‐1‐piperazinyl]‐1‐butanone (1) to R‐(+)‐1‐(4‐fluorophenyl)‐4‐[4‐(5‐fluoro‐2‐pyrimidinyl)‐1‐piperazinyl]‐1‐butanol (2) [R‐(+)‐BMY 14802], an antipsychotic agent; (ii) the reduction of N‐4‐(1‐oxo‐2‐chloroacetyl ethyl) phenyl methane sulfonamide (3) to the corresponding chiral alcohol (4), an intermediate for d‐(+)‐N‐4‐{1‐hydroxy‐2‐[(‐methylethyl)amino]ethyl}phenyl methanesulfonamide [d‐(+) sotalol], a β‐blocker with class III antiarrhythmic properties; (iii) biotransformation of Nɛ‐carbobenzoxy (CBZ)‐l‐lysine (7) to Nɛ‐CBZ‐l‐oxylysine (5), an intermediate needed for synthesis of (S)‐1‐[6‐amino‐2‐{[hydroxy(4‐phenylbutyl)phosphinyl]oxy}1‐oxohexyl]‐l‐proline (ceronapril), a new angiotensin converting enzyme inhibitor (6) and (iv) enzymatic synthesis of l‐β‐hydroxyvaline (9) from α‐keto‐β‐hydroxyisovalerate (16). l‐β‐Hydroxyvaline (9) is a key chiral intermediate needed for the synthesis of S‐(Z)‐{[1‐(2‐amino‐4‐thiazolyl)‐2‐{[2,2‐dimethyl‐4‐oxo‐1‐(sulfooxy)‐3‐azetidinyl] amino}‐2‐oxoethylidene]amino}oxyacetic acid (tigemonam) (10), an orally active monobactam.
Chemoenzymatic approaches to SCH 56592, a new azole antifungal
Authors: Morgan Brian , Stockwell Brent R. , Dodds David R. , Andrews David R. , Sudhakar Anantha R. , Nielsen Christopher M. , Mergelsberg Ingrid , Zumbach Arne 
Published: June 2007

AbstractChemoenzymatic approaches to the synthesis of two key chiral‐precursors of a new azole antifungal agent, SCH 56592, are described. In particular, the enzymatic diastereoselective acylation of 2‐benzyloxy‐3‐pentanol (7) was developed to produce (2S;3R)‐7 in >97% diastereomeric excess (de) from otherwise unusable mixtures of (2S,3R)/(2S,3S)‐7 (40–80% de). The selectivity and reactivity of commercially available Candida rugosa and Mucor miehei lipases are compared for the acylation of 7 and the hydrolysis of the corresponding butyrate 16a. Of the 17 C. rugosa enzyme preparations that were examined for acylation of 7, two purified enzyme preparations showed no reactivity, five enzymes showed high diastereoselectivity with preference for the (2S,3R)‐isomer, and seven showed a slight preference for the (2S,3S)‐isomer.
Changes in hydrolysis specificities of lipase from Rhizomucor miehei to polyunsaturated fatty acyl ethyl esters in different aggregation states
Authors: Kosugi Yoshitsugu , Chang Qing‐long , Kanazawa Kenji , Nakanishi Hiroshi 
Published: June 2007

AbstractHydrolysis specificities of lipase from Rhizomucor miehei were compared for various fatty acyl ethyl esters. Activity yields of immobilized lipases, measured with 1 mM substrate, were more than 100%. Differences in hydrolysis rate and affinity for the substrates between lipase preparations were also typically higher during hydrolysis of substrates at 100 mM than at 1 mM, indicating better mass transfer effects for 1‐mM substrates. The native lipase showed higher affinity for polyunsaturated fatty acid substrates at 1 mM than at 100 mM. Hydrolysis rates for 1‐mM substrates were observed with immobilized lipases, fixed on anion exchange resin with glutaraldehyde and on cation exchange carrier with carbodiimide, and suggested some modification of the basic amino acid related to the lid of R. miehei lipase. Activation with these bifunctional reagents was not observed for 100‐mM substrates, indicating that interfacial activation always occurred because of aggregation of 100‐mM substrates. These results show that lipase from R. miehei recognizes molecular aggregation of lipids, and that various changes occur in the hydrolysis specificities for fatty acids.
The preparation of concentrates of eicosapentaenoic acid and docosahexaenoic acid by lipase‐catalyzed transesterification of fish oil with ethanol
Authors: Haraldsson Gudmundur G. , Kristinsson Björn , Sigurdardottir Ragnheidur , Gudmundsson Gudmundur G. , Breivik Harald 
Published: June 2007

AbstractThe objective of this study was to investigate the use of lipases as catalysts for producing concentrates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil as an alternative to conventional chemical procedures. Transesterification of fish oil with ethanol was conducted under anhydrous solvent‐free conditions with a stoichiometric amount of ethanol. Among the 17 lipases tested, the results showed that Pseudomonas lipases had the highest activity toward the saturated and monounsaturated fatty acids in the fish oil, much lower activity toward EPA and DHA and, at the same time, good tolerance toward the anhydrous alcoholic conditions. With 10 wt% of lipase, based on weight of the fish oil triacylglycerol substrate (15% EPA and 9% DHA initial content), a 50% conversion into ethyl esters was obtained in 24 h at 20°C, in which time the bulk of the saturated and monounsaturated fatty acids reacted, leaving the long‐chain n‐3 polyunsaturated fatty acids unreacted in the residual mixture as mono‐, di‐, and triacylglycerols. This mixture comprised approximately 50% EPA+DHA. Total recovery of DHA and EPA was high, over 80% for DHA and more than 90% for EPA. The observed fatty acid selectivity, favoring DHA as a substrate, was most unusual because most lipases favor EPA.
Purification of docosahexaenoic acid from tuna oil by a two‐step enzymatic method: Hydrolysis and selective esterification
Authors: Shimada Yuji , Maruyama Kazuaki , Sugihara Akio , Moriyama Shigeru , Tominaga Yoshio 
Published: June 2007

AbstractPurification of docosahexaenoic acid (DHA) was attempted by a two‐step enzymatic method that consisted of hydrolysis of tuna oil and selective esterification of the resulting free fatty acids (FFA). When more than 60% of tuna oil was hydrolyzed with Pseudomonas sp. lipase (Lipase‐AK), the DHA content in the FFA fraction coincided with its content in the original tuna oil. This lipase showed stronger activity on the DHA ester than on the eicosapentaenoic acid ester and was suitable for preparation of FFA rich in DHA. When a mixture of 2.5 g tuna oil, 2.5 g water, and 500 units (U) of Lipase‐AK per 1 g of the reaction mixture was stirred at 40°C for 48 h, 83% of DHA in tuna oil was recovered in the FFA fraction at 79% hydrolysis. These fatty acids were named tuna‐FFA‐Ps. Selective esterification was then conducted at 30°C for 20 h by stirring a mixture of 4.0 g of tuna‐FFA‐Ps/lauryl alcohol (1:2, mol/mol), 1.0 g water, and 1,000 U of Rhizopus delemar lipase. As a result, the DHA content in the unesterified FFA fraction could be raised from 24 to 72 wt% in an 83% yield. To elevate the DHA content further, the FFA were extracted from the reaction mixture with n‐hexane and esterified again under the same conditions. The DHA content was raised to 91 wt% in 88% yield by the repeated esterification. Because selective esterification of fatty acids with lauryl alcohol proceeded most efficiently in a mixture that contained 20% water, simultaneous reactions during the esterification were analyzed qualitatively. The fatty acid lauryl esters (L‐FA) generated by the esterification were not hydrolyzed. In addition, L‐FA were acidolyzed with linoleic acid, but not with DHA. These results suggest that lauryl DHA was generated only by esterification.
Kinetics of transesterification of soybean oil
Authors: Noureddini H. , Zhu D. 
Published: June 2007

AbstractTransesterification of soybean oil with methanol was investigated. Three stepwise and reversible reactions are believed to occur. The effect of variations in mixing intensity (Reynolds number=3,100 to 12,400) and temperature (30 to 70°C) on the rate of reaction were studied while the molar ratio of alcohol to triglycerol (6:1) and the concentration of catalyst (0.20 wt% based on soybean oil) were held constant. The variations in mixing intensity appear to effect the reaction parallel to the variations in temperature. A reaction mechanism consisting of an initial mass transfer‐controlled region followed by a kinetically controlled region is proposed. The experimental data for the latter region appear to be a good fit into a second‐order kinetic mechanism. The reaction rate constants and the activation energies were determined for all the forward and reverse reactions.
The Case of the Treasures of L'Ange Gardien: An Overview
Authors: Pelletier Benoît 
Published: June 2007

1 AbstractIt is clearly defined, in Quebec civil law, that ‘sacred things are excluded from being objects of commerce’. However, we might ask the following question: In order to determine how an object gets or loses its sacred character, do we have to refer to the internal rules of the various religious societies or instead, to the rules of civil law? It is that precise but difficult question, on which Quebec civil law does not say a word, that is raised principally by the case of the treasures of l'Ange-Gardien.
Law and Identity: Negotiating Meaning in the Native American Graves Protection and Repatriation Act
Authors: Fred Morris A. 
Published: June 2007

AbstractThe enactment of the Native American Graves Protection and Repatriation Act (NAGPRA) in 1990 represented the culmination of a long process of negotiation and ultimate compromise between representatives of Native American tribes and American museums. This paper focuses on the initial implementation stage of NAGPRA. That stage reveals that interaction between the two sides has entailed (and continues to entail) negotiations not only concerning the disposition of specific Native American cultural objects but also equally important concerning the professional identities of Native Americans and museum professionals, respectively. Viewed in this way, NAGPRA's post-enactment process is seen to illustrate the various functions of law (both symbolic and concrete) in maintaining the social and ideological dialectic of American society.