bluuebunny/crossref_metadata_2025 huggingface dataset:
Luminescent silicon nanostructures synthesized by laser ablation
Authors: Riabinina D. , Durand C. , Rosei F. , Chaker M.
Published: May 2007

This paper describes the properties of silicon nanostructures synthesized by laser ablation. This is an extremely flexible technique allowing the fabrication of different kinds of nanostructures including porous films and Si nanocrystals embedded in Si oxide. Quantum confinement effects in nanostructures of indirect bandgap semiconductors have attracted great interest due to their new optical properties. This improvement of the efficiency of silicon in emitting light is a first step towards the integration of silicon in optoelectronics. Many groups are working on developing fabrication methods of Si nanocrystals and on the optimization of their luminescence properties. In particular, we describe in detail the mechanisms that govern nucleation and growth of these photoluminescent nanostructures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rapid separation and identification of phenolic and diterpenoid constituents from Radix Salvia miltiorrhizae by high‐performance liquid chromatography diode‐array detection, electrospray ionization time‐of‐flight mass spectrometry and electrospray ionization quadrupole ion trap mass spectrometry
Authors: Zhu Zhenyu , Zhang Hai , Zhao Liang , Dong Xin , Li Xiang , Chai Yifeng , Zhang Guoqing
Published: May 2007

High‐performance liquid chromatography‐diode array detection (HPLC‐DAD), electrospray ionization time‐of‐flight mass spectrometry (HPLC‐ESI‐TOF‐MS) and electrospray ionization quadrupole ion trap mass spectrometry (HPLC‐ESI‐MSn) were used for the isolation, identification and structural analysis of water‐soluble phenolic and nonpolar diterpenoid constituents in Dan‐shen (Radix Salvia miltiorrhizae) which was prepared by sonication in 70% methanol. Mass spectra were obtained by ESI‐TOF‐MS and electrospray ionization quadrupole ion trap mass spectrometry (ESI‐QIT‐MS). A formula database of known constituents in Dan‐shen was established and most constituents were rapidly identified by HPLC‐DAD/ESI‐TOF‐MS by matching their accurate molecular masses with the formulae of the compounds in the database. Compounds with the same molecular formula could not be differentiated by TOF‐MS; however, QIT‐MS could differentiate those compounds and elucidate their structures based on their characteristic fragmentation. HPLC‐DAD, HPLC/ESI‐TOF‐MS and HPLC/ESI‐MSn provided complementary information for the identification of the constituents in Dan‐shen. Forty constituents were identified in 30 min based on their positive and negative ion ESI mass spectra and liquid chromatographic information. Thus the method described is useful for the rapid analysis of multiple constituents in Dan‐shen. Copyright © 2007 John Wiley & Sons, Ltd.
Identification and quantitation of pyrethroid pesticide residues in vegetables by solid‐phase extraction and liquid chromatography/electrospray ionization ion trap mass spectrometry
Authors: Chen Tianwen , Chen Guonan
Published: May 2007

A quantitative method consisting of solid‐phase extraction (SPE) followed by liquid chromatography/electrospray ionization ion trap mass spectrometry (LC/ESI‐ITMS) analysis was developed for the identification and quantitation of ten pyrethroid pesticides commonly used in vegetables. The best HPLC separation was achieved using a gradient program of methanol/water mixture. For the vegetable samples, an SPE procedure to clean up the matrices was carried out prior to LC/MS analysis. Under the optimum conditions, the limits of quantification of the pyrethroid pesticides (tetramethrin, allethrin, fenpropathrin, lambda‐cyhalothrin, cypermethrin, deltamethrin, fenvalerate, bioresmethrin, permethrin and bifenthrin) ranged from 0.03 to 0.1 mg kg−1 with relative standard deviations <20%, and the mean recoveries ranged from 69.5 to 102.5%. The proposed method has been successfully applied to the determination of pyrethroids in six vegetables with satisfactory results. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of epoxidized soybean oil by gas chromatography/single quadrupole and tandem mass spectrometry stable isotope dilution assay
Authors: Rothenbacher Thorsten , Schwack Wolfgang
Published: May 2007

PVC lids of glass jars often contain epoxidized soybean oil (ESBO), able to migrate and contaminate food. To establish a stable isotope dilution assay (SIDA), the 13C18‐labelled internal standard ethyl 9,10,12,13‐diepoxyoctadecanoate (13C(18:2E)Et) was synthesized, providing after sample preparation the same retention time as methyl 9,10,12,13‐diepoxyoctadecanoate ((18:2E)Me), commonly used as a marker for ESBO in gas chromatographic (GC) analysis. For eleven different food matrices, the GC capillary columns VF‐17ms, DB1701 and DB1 were tested with single quadrupole (GC/MS) as well as tandem mass spectrometric detection (GC/MS/MS). Overall, the VF‐17ms column coupled with MS/MS detection showed the best results in terms of separation and sensitivity. The method validation for the matrix spiked olive oil resulted in a limit of detection (LOD) of 5 mg kg−1, a limit of quantification (LOQ) of 11 mg kg−1, a mean recovery (n = 5, c = 106.5 mg kg−1) of 99.7 ± 5.5%, with a repeatability (within‐run precision) of 6.0%. By means of GC/MS an LOQ of 21 mg kg−1 and a mean recovery (n = 5, c = 106.5 mg kg−1) of 103.3 ± 0.8% with a repeatability of 0.9% were determined. Copyright © 2007 John Wiley & Sons, Ltd.
Metabolic fingerprinting using direct flow injection electrospray ionization tandem mass spectrometry for the characterization of proanthocyanidins from the barks of Hancornia speciosa
Authors: Rodrigues Clenilson M. , Rinaldo Daniel , dos Santos Lourdes C. , Montoro Paola , Piacente Sonia , Pizza Cosimo , Hiruma‐Lima Clélia A. , Brito Alba R. M. Souza , Vilegas Wagner
Published: May 2007

Direct flow injection electrospray ionization ion trap tandem mass spectrometry (ESI‐IT‐MS/MS) was used to investigate the polyphenolic compounds present in an infusion from the barks of Hancornia speciosa Gom. (Apocynaceae), a native Brazilian plant popularly known as ‘mangabeira’, used as a source of nutrition and against gastric disorders. After a simple sample filtration pretreatment the characteristic fingerprint of the infusion was performed in negative ion ESI mode in a few minutes. At low capillary‐voltage activation, the deprotonated molecules ([MH]−) were observed and using collision‐induced dissociation the product ion spectra showed the presence of a homologous series of B‐type proanthocyanidins, as well as another series containing their respective C‐glycosylated derivatives, with a degree of polymerization from 1 up to 6 units of interlinked catechins. Therefore, direct flow injection allowed us to identify the key compounds without preparative isolation of the components. Copyright © 2007 John Wiley & Sons, Ltd.
Rapid screening assay of trimethylaminuria in urine with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Hsu Wei‐Yi , Lo Wan‐Yu , Lai Chien‐Chen , Tsai Fuu‐Jen , Tsai Chang‐Hai , Tsai Yuhsin , Lin Wei‐De , Chao Mei‐Chyn
Published: May 2007

Trimethyamine (TMA) and trimethylamine N‐oxide (TMAO) are the most important urine parameters for diagnosing and monitoring trimethylaminuria. A rapid, simple, and specific method based on matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) was developed to determine the presence of TMA and TMAO in urine samples from patients with trimethylaminuria. Formation of the quaternary tetramethylamino iodide by derivatization of TMA with methyl iodide allows measurement of TMA by MALDI‐TOFMS. The method is repeatable and reproducible, with coefficients of variance (CVs) <3%. This new method was used for direct determination of TMA and TMAO in urine specimens obtained from normal children and patients. The proposed method allows for rapid and reliable measurements of TMA and TMAO in urine specimens from patients affected by trimethylaminuria. Copyright © 2007 John Wiley & Sons, Ltd.
Rapid structural characterization of isomeric benzo[c]phenanthridine alkaloids from the roots of Zanthoxylum nitidium by liquid chromatography combined with electrospray ionization tandem mass spectrometry
Authors: Cai Min , Zhou Yan , Wang Xiaoling , Li Rui , Liao Xun , Ding Lisheng
Published: May 2007

The fragmentation mechanism of six alkaloids, namely: dihydronitidine, dihydrochelerythrine, 8‐acetonyldihydronitidine, 8‐acetonyldrochelerythrine, nitidine and 1,3‐bis(8‐dihydronitidinyl)acetone, was investigated by electrospray ionization multi‐stage tandem mass spectrometry (ESI‐MSn). Tandem mass spectrometry experiments indicated that different substitution sites of the methoxyl groups at C‐9 and C‐10 or at C‐10 and C‐11 determined the different abundances of the MS2 fragmentation ions using the same collision energy. According to the different abundances of MS2 product ions, positional isomeric benzo[c]phenanthridine alkaloids can be differentiated. Moreover, ten constituents in the crude alkaloidol extract from the roots of Zanthoxylum nitidium were rapidly identified by high‐performance liquid chromatography coupled with tandem mass spectrometry (HPLC/MSn), through comparing the retention times and ESI‐MSn spectra with the authentic standards. This work demonstrates that not only the characteristic fragments but also the characteristic abundances of the fragment ions can be used for detailed structural characterization. Copyright © 2007 John Wiley & Sons, Ltd.
Synchronicity and dissonance: nursing, spirituality and contemporary discourse
Authors: Greenstreet Wendy
Published: May 2007

Spirituality is a particularly intangible concept to define. Exploration and explanation of what is meant by spirituality result in varied discourses that can confuse by their differing use of similar terminology. As a result, despite the altruistic intent to provide clarity, understanding is further clouded. Therefore when complementary and alternative medicine are described as ‘holistic spirituality’ and a means of articulating ‘nursing spirituality’ (Heelas, 2006) this may erroneously be confused with ‘spirituality as a perspective of holistic nursing care’ (Greenstreet, 2006). This paper considers similarities and difference between these two discourses. A comparison of descriptions of the concept of spirituality within each discourse is followed by consideration of issues related to nurses' spirituality. Acknowledgement and interpretation of political and social drivers of nursing spirituality together with commonalities and difference in relation to spiritual care culminate in the conclusion that spirituality, as a perspective of holistic nursing care, is a wider, more comprehensive concept within which complementary and alternative medicine, or ‘holistic spirituality’, may provide an example of spiritual care. Copyright © 2007 John Wiley & Sons, Ltd.
Antenatal sonographic features of aneurysmal dilatation of a vitelline vein
Authors: Benoist G. , Gauthier F. , Belloy F. , Laloum D. , Herlicoviez M. , Dreyfus M.
Published: May 2007

We report a case of aneurysmal dilatation of a vitelline vein observed antenatally. Intra‐abdominal vascular dilatation was diagnosed on ultrasound examination at 24 weeks' gestation. The relationship with the umbilicus and portal vein suggested the diagnosis of umbilical vein varix. Fetal tolerance remained excellent in spite of a gradual increase in the size of the dilated vein. Postnatal ultrasound examination revealed thrombosis of the aneurysm with gradual extension to the portal vein and the onset of serious coagulation problems. Operative findings on postnatal day 9 included the absence of intra‐abdominal umbilical vein, and the presence of an abnormal, dilated and thrombosed vein connecting the umbilicus to the portal vein and following the trajectory of the right vitelline vein. Corrective surgery was attempted by resection of the aneurysm and portal thrombectomy, but this did not prevent the development of portal obstruction syndrome with cavernous hemangioma. This anomaly, in which the fetal venous return uses the vitelline vein in the absence of the umbilical vein, does not appear to have been described before. The mechanism in question could be anastomosis between the right vitelline vein and umbilical vein. Antenatal diagnosis should enable early surgical management before the formation of a portal thrombosis. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Lösungen der inhomogenen Mathieuschen Differentialgleichung mit periodischer Störfunktion beliebiger Frequenz (mit besonderer Berücksichtigung der Resonanzlösungen)
Authors: Kotowski Gertrud
Published: May 2007

Die vorliegende Arbeit ist der systematischen und vollständigen Unterschung der bis jetzt nur in allgemeinen Zügen bekannten Lösung der inhomogenen Mathieuschen Differentialgleichung mit und ohne Dämpfungsglied gewidmet. Es wird vor allem nach der Form der Lösungen (mit Einschluß der Resonanzlösungen) und nach der Lage der Kurven der Resonanzstellen gefragt. Da sich unendlich viele Kurven der Resonanzstellen ergeben, wird, bei gegebener Störfunktion und Dämpfungsfreiheit, eine numerische Untersuchung für gewisse Werte der Parameter vorgenommen, um aus der „Breite”︁ der Resonanzbereich eine Abschätzung für die Bedeutung der Resonanzstellen mit wachsender Ordnungszahl zu gewinnen. Ferner werden für einige Werte des Dämpfungskoeffizienten „Dämpfungskurven”︁, die zugleich die Kurven der Resonanzstellen bei gewissen Störfrequenzen sind, berechnet.
Über die Berechnung der Kräfte an einem in der reibungslosen Flüssigkeit beschleunigt bewegten Tragflügel
Authors: Müller Wilhelm
Published: May 2007

Die Arbeit bringt eine Anwendung einiger allgemeinen, vom Verfasser aufgestellten Beziehungen für die Kräfte n einem in der reibungslosen Flüssigkeit bewegten Körper auf die beschleunigte Bewegung eines Joukowskischen Tragflügels. Es werden Formeln für den Einfluß der verschiedenen Beschleunigungsarten, sowie der Drehung und Drehungsschwingung auf die Kraftwirkung angegeben. Die Rechnung besteht im wesentlichen in der Auswertung von komplexen Oberflächen, bzw. Randintegralen nach funktionen‐theoretischen Methoden.
Biegung gekrümmter, dünnwandiger Rohre
Authors: Karl Helmut
Published: May 2007

Unter Benutzung des Satzes vom Minimum der Formänderungsenergie und des Prinzipes von Castigliano werden obere und untere Schranken für die Größe der Biegung gekrümmter dünnwandiger Rohre gewonnen. Zunächst wird das Verfahren auf schwach gekrümmte Rohre bei Biegung in der Krümmungsebene unter der Annahme, daß die Querkontraktionszahl Null ist, angewendet. Weiter wird dann der Einfluß der Querdehnung berücksichtigt, stärker gekrümmte Röhren untersucht und die Biegung quer zur Krümmungsebene behandelt.
Die Geschwindigkeitsverteilung bei lokalen Überschallgebieten an flachen Profilen
Authors: Oswatitsch K.
Published: May 2007

Die Arbeit gibt eine erste kurze Darstellung einer Theorie zur Berechnung lokaler Überschallgebiete an flachen symmetrischen Profilen. Nach Vereinfachung der Ausgangsgleichungen wird eine Integralgleichung für die Geschwindigkeitsverteilung in der Strömungsebene aufgestellt. Diese Integralgleichung wird durch einen Näherungsansatz auf eine Integralgleichung für die Geschwindigkeitsverteilung am Profil reduziert. Die Lösung erfolgt durch Parameteransätze, wobei die Gleichung in einer Anzahl von Punkten exakt erfüllt wird. Es ergeben sich die experimentell bekannten Geschwindigkeitsverteilungen mit Verdichtungsstoß.
Berechnung des Spannungszustandes und Schlupfes beim Rollen deformierbarer Kugeln
Authors: Sonntag G.
Published: May 2007

Aufbauend auf die Arbeiten von H. Fromm2) über rollende Scheiben werden Spannungen, Schlupf und Reibungsarbeit in der Berührungsfläche rollender Kugeln bei Übertragung einer Tangentialkraft untersucht.
Die Temperaturverteilung in Schmierschichten zwischen parallelen wärmedurchlässigen Wänden
Authors: Vogelpohl G.
Published: May 2007

Vf. zeigt, daß für die Couette‐Strömung einer Flüssigkeit, deren Zähigkeit nicht von der Temperatur abhängt, für die Berechnung der Mittelwerte der Temperatur die Strömungsgeschwindigkeiten quer zur Schicht gemittelt werden dürfen, und daß dazu die Wärmeleitung quer zur Schicht vernachlässigt werden darf.
Maximalkorrelation und Korrelationsspektrum
Authors: Gebelein Hans
Published: May 2007

Die Theorie der Maximalkorrelation liefert für den Fall einer Korrelationstabelle mit k Zeilen und Spalten (k—1) ausgezeichnete Korrelationswerte, die das Korrelationsspektrum darstellen. Bei einer zwei parametrigen, kontinuierlichen Verteilung umfaßt dieses Spektrum sogar im allgemeinen unendlich viele Werte, z. B. bei der zweiparametrigen Gaußschen Verteilung die aufsteigenden Potenzen rn des gewöhnlichen Korrelationskoeffizienten r. Umgekehrt gibt es aber nicht zu jedem vorgegebenen Spektrum Häufigkeitsverteilungen, sondern die Korrelationswerte müssen auf gewisse Bereiche beschränkt sein.
Grenzschichten an zylindrischen Körpern mit nichtstationärer Querbewegung
Authors: Wuest Walter
Published: May 2007

Ein besonders ein facher Fall von nichtstationären dreidimensionalen Strömungsvorgängen in laminaren Grenzschichten ergibt sich bei der Anströmung zylindrischer Körper mit überlagerter zeitabhängiger Querbewegung. Ein allgemeines Lösungsverfahren wird angegeben und an mehreren numerisch berechneten Beispielen erläutert.
The Stress Distribution in a Shaft Press–fitted with a Collar
Authors: Okubo H.
Published: May 2007

This is the continuation of my previous study on the two‐dimensional problem of an elastic foundation compressed by a pillar with a rectangular cross section

H. Okubo: Quart. J. Mech. und Appl. Math. (1951).

. In this paper, we treat the problem of a shaft, press‐fitted with a collar or a wheel. The problem has long been left out of theoretical investigation, regardless of its importance from technical point of view. Considerable mathematical difficulties will be encountered in finding the exact solution of the problem, but an approximate solution can be obtained by a usual way, though the analysis becomes somewhat complicated.
Kugel mit normalgerichteten Einzelkräften
Authors: Weber C.
Published: May 2007

Untersucht wird die Kugel mit Einzelkraft normal zur Oberfläche. Die auftretende Belastungsfunktion wird durch Inversion bestimmt. Durch Überlagerung findet man den Belastungszustand durch mehrere Kräfte. Näher untersucht wird die Kugel mit zwei an den Polen wirkenden Druckkräften.
Das Problem der Jungfernquelle
Authors: Wendt H.
Published: May 2007

Es sei ein unendlich ausgebreitetes und unendlich tiefes Meer gegeben, das unter der Wirkung der Schwerkraft steht. Unterhalb der Meeresoberfläche befindet sich im endlichen Abstande h > 0 eine räumliche Quelle, die nach allen Richtungen gleichmäßig stationär pro Sekunde die Wassermenge e erzeugt. Im Unendlichen bleibt dabei das Meer in Ruhe. Es wird nach der Gestalt der Meeresoberfläche gefragt, wenn die Strömung stationär, inkompressibel, reibungs‐ und wirbelfrei vorausgesetzt wird.
Beiträge zur Theorie der achsensymmetrisch belasteten schweren dicken Kreisplatte
Authors: Szabö Istvän
Published: May 2007

Auf einige Resultate früherer Untersuchungen zurückgreifend, wird noch einmal das Problem der achsensymmetrisch belasteten dicken Kreisplatte unter exakter Berücksichtigung der Massenkräfte behandelt, wobei die zwischen Platte und Unterlage auftretenden Schubspannungen als Reibungskräfte im Sinne des Coulombschen Gesetzes erfaßt werden.
Eine neue Methode zur Berechnung der Strömungsfunktionen bei zeitlich veränderlicher Kontur
Authors: Gorup Guntram V.
Published: May 2007

Auf dem Weg über eine Funktionalgleichung werden die Strömungsfunktionen im Außenraum einer zeitlich veränderlichen Kontur unter der Voraussetzung einer meromorphen Abbildungsfunktion in geschlossener Form bestimmt. Als Beispiel für das Verfahren wird ein Joukowski‐Profil behandelt.
Zur Praxis der Biorthonormierung von Eigen‐ und Hauptvektoren
Authors: Unger Heinz
Published: May 2007

Die Biorthonormierung ist bei linearen Matrizeneigenwertproblemen im Falle von Mehrfachwurzeln bei nichtsymmetrischen Matrizen von Bedeutung. Zur praktischen Durchführung wird eine Vorgehensweise angegeben, die unter Verwendung der allgemeinen Gramschen Matrix mit dem modernisierten Gaußschen Algorithmus arbeitet. Lineare und nichtlineare Elementarteiler, sowie reelle und komplexe Eigenwerte werden getrennt, aber nach einheitlichen Gesichtspunkten bearbeitet.
Die Energieversorgung der Wandturbulenz
Authors: Reichardt H.
Published: May 2007

Es werden die Gesetzmäßigkeiten der Energieversorgung der Wandturbulenz am Beispiel der ebenen Kanalströmung behandelt. Ähnlich wie bei der Geschwindigkeitsverteilung kann man auch beim Energieumsatz zwischen einem Wandgesetz und einem Mittengesetz unterscheiden.
Der Wärmeaustausch zwischen einem geheizten Band und einer Konvektionsströmung
Authors: Herbeck M.
Published: May 2007

Es werden Lösungen bei verschiedenen Randbedingungen für die partielle elliptische Differentialgleichung Tξξ + Tηη = η Tξ aufgestellt, die unter gewissen vereinfachenden Annahmen das Temperaturfeld beim Wärmeaustausch zwischen einem geheizten Band und einer ihm parallelen Konvektionsströmung bestimmt. Der Vergleich zwischen Theorie und Experiment ergibt gute Übereinstimmung, er ist allerdings wegen der nicht genau bekannten Randbedingungen nur bei nicht zu kleinen Windgeschwindigkeiten möglich. Jedoch lassen sich umgekehrt mit Hilfe der Messung und der Lösungen der Differentialgleichung die Randbedingungen abschätzen, da die der Rechnung zugrunde liegenden Randbedingungen alle einen frei wählbaren Parameter enthalten.
Die Randwertaufgabe der Geoelektrik für Kugel und Zylinder
Authors: Huber A.
Published: May 2007

Die theoretische Grundlage der geoelektrischen Widerstandsmethoden bildet das im Unendlichen verschwindende Potential des von einer Punktquelle in einem inhomogenen Medium erzeugten Feldes. Es ist bestimmt durch die Ergiebigkeit der Quelle und durch zwei homogene lineare Randbedingungen entlang der Trennungsflächen elektrisch verschiedener Medien. Dieses Potential wird für eine kugel‐ und drehzylinderförmige Begrenzungsfläche konstruiert und für den durch einen Stollen mit kreisförmigem Querprofil realisierten Sonderfall eingehender diskutiert.
Beitrag zur Potentialströmung durch axiale Schaufelgitter
Authors: Isay Wolfgang‐Hermann
Published: May 2007

Es wird die Strömung durch Schaufelgitter nach der Singularitätenmethode behandelt. Dabei werden die Singularitätenverteilungen auf den Profilkonturen selbst angeordnet. Es ist möglich, sowohl Einzelgitter als auch Gitterstufen mit linienhaften und mit endlich dicken Profilen nach einer einheitlichen Methode zu behandeln.
Zur Torsion von Stäben
Authors: Herzig Alfred
Published: May 2007

Unterliegt ein Stab einer reinen Torsionsbeanspruchung, so wird ein beliebig herausgegriffener Stabquerschnitt bekanntlich im allgemeinen verwölbt. Gelingt es, bei vorgegebenem Querschnitt diese Verwölbung anzugeben, so lassen sich daraus die Drillungssteifigkeit und die Formänderungsarbeit des Stabes sowie die Schubspannungen innerhalb eines Querschnittes berechnen. Die Lösung dieser Torsionsaufgabe ist aber nur für wenige Querschnittsformen exakt durchführbar. Im folgenden soll gezeigt werden, daß man bei den Querschnittsformen Halbkreis, Viertelkreis und Kreis mit radialem Riß mit Hilfe der konformen Abbildung sofort zu geschlossenen Lösungen gelangt, die in völlig exakter Weise auswertbar sind.
Nonhydrostatic Standing Waves in a Parabolic Basin
Authors: Lundberg P.
Published: May 2007

Small‐amplitude standing oscillations of a fluid in a basin of parabolic bottom profile, but of such aspect ratio that the shallow‐water approximation is not valid, are examined. The eigenvalue problem determining the periods of the waves is solved using Frobenius series representations of the solutions in conjunction with the requirement that these be bounded. When this approach fails for large values of the aspect ratio, recourse is taken to a perturbation expansion of the problem. Finally the results of laboratory experiments are found to agree well with the predictions.
Frequenzmitnahme bei zwangs‐ und selbsterregten mechanischen Schwingungen
Authors: Hortel M. , Schmidt G.
Published: May 2007

For a general one‐degree‐of‐freedom system containing forced and self‐excitation as well as non‐linear damping and restoring forces, the vibration behaviour, especially the quenching of self‐excited vibrations in the synchronisation interval is investigated.
The Generalized Bang‐Bang‐Principle and the Numerical Solution of a Parabolic Boundary‐Control Problem with Constraints on the Control and the State
Authors: Tröltzsch F.
Published: May 2007

In this paper a numerical method is presented to solve a state‐constrained parabolic boundary control problem. The optimization technique is based on generalized bang‐bang‐properties of the optimal control, which were proved in earlier papers of the author. The effectivity of the corresponding algorithm is demonstrated by means of two examples, which were solved with high accuracy.
A Numerical Study of Mode Jumping of Rectangular Plates
Authors: Suchy H. , Troger H. , Weiss R.
Published: May 2007

A four parameter unfolding of the von Karman plate equations is used to study sudden qualitative changes (jumps) in the buckled deflection surface of a rectangular plate if parameters are varied. For the mode jumping to occur the linearized unperturbed problem has to have a double eigenvalue which leads to secondary bifurcations if small parameter perturbations are performed in the neighbourhood of the critical parameter value. As parameters we have the thrust p, the variation of the length of the plate and two types of transversal loads. Furthermore a detailed discussion is given whether the Liapunov‐Schmidt method has to be used to obtain the two dimensional algebraic system of bifurcation equations or whether a Galerkin approximation will also yield qualitatively correct bifurcation equations.
Buckling of an Elastic Strut Made of a Nonlocal Material
Authors: Nowinski J. L.
Published: May 2007

Buckling of a slender elastic strut built‐in at one end and loaded at the other is examined from the standpoint of the non‐local theory. Using the Strength of Materials Approach, the equation for the nonlocal longitudinal stress is derived. The governing equation obtained represents a sum of a number of difference equations with the coefficients provided by the dynamics of atomic lattices. Remarkably, both the first and the second approximation give the value of the buckling load coinciding with that of Euler.
Computation of Descent Directions in Stochastic Optimization Problems with Invariant Distributions
Authors: Marti K.
Published: May 2007

One of the main problems in stochastic optimization is the minimization of mean value functions F(x) = Eu(A(ω) x ‐ b(ω)) s.t. x ∈ D, where (A(ω), b(ω)) is a random matrix, u is a loss function on Rm and D is a convex subset of Rn. If the distribution μ of (A(ω), b(ω)) is invariant with respect to an affine transformation Λ of Rn(m+1), i.e. if Λ(μ) = μ, and if for a given x ∈ Rn there exists a vector y = y(x) such that \documentclass{article}\pagestyle{empty}\begin{document}$ \Lambda \left({A,b} \right)\left({\begin{array}{*{20}c} x \\ {- 1} \\ \end{array}} \right) = Ay - b $\end{document} a.s., then F(y) = F(x), and, consequently, d = y ‐ x is a descent direction of F at x, provided that F is not constant on the line segment joining x and y. For many practically important distributions μ the affine transformation Λ, a vector y(x) and therefore also a direction of decrease d = y(x) ‐ x is constructed without using any derivatives of F.
Totale Stabilität in der Plastokinetik
Authors: Vielsack P.
Published: May 2007

Permanente Störungen einer Gleichgewichtslage erfordern die Untersuchung der totalen Stabilität. Für ein Einfreiheitsgradsystem mit einer Rückführkraftcharakteristik, die makroskopisch elastisch‐plastisches Stoffverhalten beschreibt, werden die vollständigen Lösungen der nichtlinearen Störungsgleichungen bei harmonischer Erregung'angegeben. Mit Hilfe von Phasenportraits lassen sich totale Stabilität im Kleinen, praktische Stabilität (Einspielen), inkrementeller Kollaps, verzögerter Kollaps und plötzlicher Kollaps diskutieren.
Hydrodynamic Forces on Multiple Circular Cylinders Oscillating in a Viscous Incompressible Fluid
Authors: Lin W. H.
Published: May 2007

This paper presents a theoretical analysis and numerical results of the hydrodynamic force coefficients for groups of parallel, circular, rigid cylinders oscillating transversely and harmonically in an unbounded mass of viscous incompressible fluid at rest at infinity. The oscillatory amplitude of these cylinders is assumed to be small compared with their diameters, and the fluid motion is assumed due entirely to the oscillations of the cylinders. The motion of the perturbed fluid and the hydrodynamic forces on the cylinders are obtained by solving a fourth‐order partial differential equation for a stream function with Neumann conditions on the cylinders and the finiteness condition at infinity. The hydrodynamic forces are found to have a self‐excited part and a mutually excited part, each composes of an inertia force and a viscous dissipative force. Numerical results show that the viscous dissipative force predominates over the inertia force in the low‐frequency regime and that the hydrodynamic force coefficients (which are second‐order tensors) are symmetrical. The symmetrical property of hydrodynamic force coefficients is briefly proved by extending the Lorentz reciprocal theorem for steady flows to oscillatory flows. When the number of cylinders is set to one, the theory and numerical results agree very well with those of Stokes (1851) for a single cylinder.
Multibody Kinematical Equations in Terms of Relative Variables
Authors: Schwertassek R.
Published: May 2007

Formalisms for computer aided generation of multibody system equations are considered to start from a most simple set of data describing the system's mechanical properties and to apply to most general classes of systems. The generation of the right side of the dynamical equations and of additional relations describing closed loop control of the system motion has been discussed previously for formalisms yielding a state space representation and using relative variables. A state space representation of the system kinematics is gotten easily in case of tree configured systems only. In case of systems with closed circuits the system kinematics must be represented in the general case by a set of differential algebraic equations. These are developed here from data available in a joint kinematics library.
The Nonmonotone Skin Effects in Plane Elasticity Problems Obeying to Linear Elastic and Subdifferential Material Laws
Authors: Panagiotopoulos P. D. , Koltsakis E. K.
Published: May 2007

In the present paper two‐dimensional nonlinear elasticity problems subjected to nonmonotone skin friction effects are formulated and studied. General material laws derived from convex superpotentials are assumed. The friction forces are derived from nonconvex superpotentials through the generalised gradient of F. H. Clarke. The resulting variational‐hemivariational inequalities are studied and the existence and approximation of their solution is discussed by an appropriate combination of monotonicity with compactness arguments.
Umpolygone größten Flächeninhalts
Authors: Hartwig H. , Klötzler R.
Published: May 2007

Das geometrische Optimierungsproblem der Bestimmung des flächengrößten Umpolygons zu einem gegebenen konvexen Polygon Pn mit n Ecken ist weder konvex noch konkav. Die Aufgabe läßt sich jedoch im allgemeinen auf ein diskretes dynamisches Optimierungsproblem mit endlichen Zustandsbereichen zurückführen und im Spezialfall regulärer Pn elementar lösen.
The Mean Power of Forces and Moments in Unsteady Aerodynamics
Authors: Send W.
Published: May 2007

The balance of mechanical energy serves as the starting point for a unified and consistent approach to the two basic and inherent mechanisms in unsteady aerodynamics, propulsion and flutter. Both phenomena are mutually dependent and interchangeable with each other by a mere variation of the reduced frequency as the governing magnitude with respect to unsteady effects.
Numerical Analysis of the Thermocapillary Migration of a Fluid Particle under Zero‐Gravity
Authors: Ehmann M. , Wozniak G. , Siekmann J.
Published: May 2007

The present paper deals with the numerical investigation of the thermocapillary motion of a fluid sphere immersed in an unbounded region of a different liquid under weightlessness. The governing equations are solved by means of a finite difference scheme taking the nonlinear terms into account. The influence of inertia and convection on the flow pattern inside and outside the fluid particle is discussed. It is observed that the dimensionless velocity of a drop with fixed diameter decreases with increasing temperature gradient in the case of high temperature gradients. At smaller temperature gradients the dimensionless velocity can exhibit the opposite behavior. These results are in contrast to the analytical solution of the linearized governing equations, where the dimensionless velocity is a constant.
Elastic Stability of an Externally Pressurized Ring with Two Hinges
Authors: Wang C. Y.
Published: May 2007

A thin ring or cylinder with two hinges is buckled by external pressure. The buckling pressure is determined as a function or spacing between the hinges. In certain instances two hinges may be more stable than a single hinge. Optimum spacing is one quarter of the perimeter where the buckling pressure is as high as the ring without hinges.
A New Approximate Method for Numerically Solving of ODE Systems in Chemical Kinetics
Authors: Berndt T. , Picht R. , Scherzer K.
Published: May 2007

In a recent paper we described an algorithm to calculate analytical functions for the time‐dependence of concentrations based on a system of ODEs by Laplace transforms. In this paper, we extend the procedure to the case in which the analytical solutions are finished with an additional change function. The method is suitable for models containing first and second order steps. No differences between stiff and nonstiff ODEs are made. We show the application of our method to the case of propane conversion, a mechanism with 32 steps and 20 species. Comparisons with LARKIN (Deuflhard et al.) are made.
On a Self‐Consistent Method to the Analyses of Elastic and Elasto‐Plastic Materials with Inclusions
Authors: Mojia Huang , Bufler H.
Published: May 2007

In this paper, a self‐consistent method is used to estimate the overall properties of elastic and elasto‐plastic materials containing ellipsoidal elastic inclusions or voids. Two important properties of materials with voids are established. The general constitutive relations are derived in a clear form. For elastic problems, we present the relevant stiffness tensor for materials with spherical, penny‐shaped, and cylindrical voids. Further we work out analytically the constitutive behaviour of elasto‐plastic materials with voids under simple tension, pure shear, plane stress, and plane strain, respectively. These special cases illustrate the simplicity and applicability of the proposed method.
On Mathematical Aspects of Dual Variables in Continuum Mechanics. Part 1: Mathematical Principles
Authors: van der Giessen E. , Kollmann F. G.
Published: May 2007

In this paper consisting of two parts we consider mathematical aspects of dual variables appearing in continuum mechanics. Tensor calculus on manifolds as introduced into continuum mechanics by MARSDEN and HUGHES [1] is used as a point of departure. This mathematical formalism leads to additional structure of continuum mechanical theories. Specifically invariance of certain bilinear forms renders unambiguous transformation rules for tensors between the reference and the current configuration. These transformation rules are determined by push‐forwards and pull‐backs, respectively. — In Part 1 we consider the basic mathematical features of our theory. The key aspect of our approach is that, contrary to the usual considerations in this field, we distinguish carefully between inner products and scalar products. This discrimination is motivated by physical considerations and is subsequently given a firm mathematical basis. Inner products can only be formed with objects living in one and the same vector space. Scalar products, on the other hand, are formed between objects living in different spaces. The distinction between inner and scalar products lead to a distinction between transposes and duals of tensors. Therefore, we distinguish between symmetry and self‐duality. An important result of this approach are new formulae for the computation of push‐forwards and pull‐backs, respectively, of second‐order tensors, which are derived from invariance requirements of inner and scalar products, respectively. In contrast to prior approaches thse new formulae preserve symmetry of symmetric mixed tensors.
To the Analysis of Autoparametric Systems
Authors: Tondl A.
Published: May 2007

Autoparametric systems represent a special class of nonlinear systems. Such a system has at least two parts, i.e. two degrees of freedom at least. The first part — the oscillator — vibrates due to external or parametric excitations or due to self‐excitation. A typical feature is represented by the existence of the semi‐trivial solution, which means that only the oscillator vibrates. Under certain conditions the semi‐trivial solution is unstable, and autoparametric resonance is induced. Several examples of these systems together with a survey of the investigation results are presented. Typical properties like saturation effect and the occurrence of non‐periodic vibration are illustrated on examples.
Das Gaußsche Prinzip und das Lagrangesche — Notizen zu einer kaum beachteten Arbeit Paul Stäckels
Authors: Pfister F.
Published: May 2007

Die folgenden Ausführungen wurden angeregt durch eine — scheinbar vergessene(!) — Arbeit Paul Stäckels über das Prinzip des kleinsten Zwanges. Es zeigt sich, daß für zahlreiche Fälle, die auch in ihrer praktischen Anwendung von Relevanz sind, das d'Alembert/Lagrangesche Prinzip versagt, während das Gaußsche Prinzip ohne weiteres brauchbar ist. Wie es scheint, wurde diese Erkenntnis in der neueren Forschung bislang nirgendwo rezipiert. Die genannte Arbeit enthält ferner einen Hinweis auf den historischen Ursprung einer für die Mehrkörperdynamik besonders nützlichen Form der Lagrangeschen Gleichungen. Diese ist Gegenstand des Zweiten Teils des Aufsatzes.
Epoxy fatty acid ester plasticizers. Preparation and properties
Authors: Greenspan Frank P. , Gall Ralph J.
Published: May 2007

The preparation of epoxy fatty acid ester plasticizers has been reviewed. These plasticizers can be prepared by epoxidation reactions, utilizing a preformed peracid or anin‐situ technique. A newin‐situ epoxidation process, utilizing hydrogen peroxide and acetic acid in the presence of strong acid catalyst, has been described. Excellent conversions to epoxide have been achieved with a series of monounsaturated and polyunsaturated esters.

Epoxy fatty acid esters are excellent plasticizers for vinyl resins. Their performance in a series of additional epoxy plasticizers of vegetable and marine origin is described. Novel epoxy plasticizers based upon mixed acetylated mono‐ and di‐glyceride have been prepared and are found to have excellent plasticizer performance.
The hydrogenation of fatty oils with palladium catalyst. III. Hydrogenation of fatty oils for shortening stock
Authors: Zajcew Mykola
Published: May 2007

Palladium‐on‐carbon catalysts are exceedingly active for the hydrogenation of natural unsaturated oils when very mild conditions are used. Selectivity is usually good, andtrans content can be adequately controlled by the proper choice of conditions. In the range of operating variables used in this work,trans formation is lessened with increased agitation and pressure, decreased catalyst activity, decreased concentration of metal in oil and on carrier, and with decreased temperature. Some shortening stocks were obtained which have good physical properties, as expressed by their dilatometric curves.
Some factors in the measurement of the suspending power of aqueous detergent/fabric systems
Authors: Weatherburn A. S. , Bayley C. H.
Published: May 2007

The variability associated with the usual methods for measuring the suspending power of aqueous detergent solutions used to remove soil from textile fibers is pointed out, and a modified method, using multiple washes with very low concentrations of soil, is proposed. Two commonly used artificial soils are compared. Micronex, a typical fine particle carbon black, appears to give data in reasonable accord with practical experience while Aquadag, a suspension of graphite particles, tends to magnify some effects and therefore is more useful for specific tests. Aquadag is found to be highly dispersed in dilute aqueous suspension while Micronex (as well as other carbon blacks) forms relatively large aggregates in water. These aggregates are partially dispersed by vigorous agitation in a Waring Blendor but are more completely dispersed by rotation in the Launder‐Ometer in the presence of fabric, yarn, or fiber of cotton or other textile material. The influence of hard water and of other inorganic salts on suspending power data is discussed. The need for careful selection of type of soil and fabric and for careful interpretation of data is stressed.
Relations between oil, nitrogen, and gossypol in cottonseed kernels
Authors: Stansbury Mack F. , Pons Walter A. , Den Hartog G. T.
Published: May 2007

A study was made of the relations between oil, nitrogen, and gossypol contents of cottonseed kernels from the seed of eight commercial varieties of cotton grown at 13 locations during three years. Both variety of seed and environment had a highly significant influence on each constituent whether expressed as percentage of the kernel or as weight of constituent per 100 kernels. Each variety showed a significant positive correlation between oil and gossypol and significant negative correlations between oil and nitrogen and between gossypol and nitrogen, on the basis of percentage‐constituent in the kernel. The amount of both oil and nitrogen elaborated in the kernel tends to be related to the size of the kernel; each of these constituents increases with increased kernel size. The highly significant positive relationship between grams of oil and grams of gossypol per 100 kernels which is evident even when nitrogen is held constant can be explained on the basis that these two constituents are synthesized during the same stage of seed development.

Rainfall or temperature had no significant over‐all influence on the nitrogen content of the kernels. Grams of nitrogen per 100 kernels showed a significant negative correlation with mean minimum temperature for 5 of the varieties but was not significantly correlated with total rainfall during the maturation period for any of the varieties. Grams of oil and gossypol per 100 kernels tended to increase with increasing rainfall and decrease with increasing mean temperature.

The ratio of nitrogen to gossypol is negatively correlated with the oil content of the kernels. The variation attributed to varietal influence decreases as the oil content of the kernel increases. It is postulated that high ratios are desirable for the production of meals containing a low free‐gossypol content.
Thermal dimerization of fatty ester hypdroperoxides
Authors: Frankel E. N. , Evans C. D. , Cowan J. C.
Published: May 2007

When autoxidized fatty esters and purified fatty hydroperoxides were decomposed in the absence of oxygen at 210°C., the principal reaction was dimerization of the fatty acid chains with elimination of the hydroperoxide groups. Dimers isolated by molecular distillation (60 to 90% of the polymer) have approximately 1 mole hydroxyl, 0.5 mole carbonyl, and two double bonds per mole of dimer. Diene conjugation in the dimers from polyunsaturated fat hydroperoxides varied from 10 to 23%. The infrared spectra of the dimers were similar to those of the original fatty esters except for one striking band at 2.9 μ, which is attributed to the secondary hydroxyl group. Thecis‐trans diene in the polyunsaturated hydroperoxides was isomerized to thetrans‐trans configuration on dimerization. The methyl oleate hydroperoxide dimer showed only absorption for isolatedtrans double bond. The dimer was not split either by catalytic hydrogenation or by hydrogen iodide, indicating a carbon‐carbon bond between the monomer units. On oxidation with permanganate and periodate, the dimeric acids behaved like a monounsaturated mixture containing double bonds in the C6, C7, C8, C9, and C10 positions in the oleate dimer and in the C8, C9, and C10 positions in the safflower ester dimer. Although the dimers showed no peroxidic oxygen iodometrically with potassium iodide, a reduction occurred with hydriodic acid that may indicate the presence of intramolecular peroxide groups and/or allylic alcohol or carbonyl groups. Bromination with N‐bromosuc‐cinimide and dehydrobromination with N,N‐dimethyl aniline produced no aromatization. Subsequent oxidation of the dehydrobrominated dimer yielded 2.6% residue, which was not aromatic. This evidence indicates that the dimer does not have a six‐membered cyclic structure. Dimerization of the hydroperoxides is suggested as occurring through alkyl or alkoxy hydroperoxide radicals to give carbon‐carbon linked fatty acid dimers and some higher polymeric units.
Quantitative gas chromatography of fatty derivatives. Relative detector responses to C6−C14 saturated methyl esters
Authors: Killheffer J. V. , Jungermann Eric
Published: May 2007

The ralative response of a thermal conductivity cell, in terms of peak area produced per mole of compound, has been determined for the fatty methyl esters caproate through myristate. The values were found to be a linear function of molecular weight.
The biological consequences of feeding polyunsaturated fatty acids to antioxidant‐deficient animals
Authors: Machlin L. J.
Published: May 2007

The addition of polyunsaturated fatty acids (PUFA) to diets deficient in vitamin E and other effective antioxidants results in a variety of symptoms in animals. For example, the feeding of such diets to rats results in muscular dystrophy, testis degeneration, dental depigmentation, brown discoloration of the fat and and uterus and creatinuria Similar diets fed to rabbits and ruminants results in muscular dystrophy. In chickens the symptoms observed are encephalomalacia, lowered egg production, and poor hatchability. The addition of PUFA to diets is known to result in the destruction of vitamin E in the diet or in the tissues of animals as a result of free radicals produced during the autooxidation of the PUFA. However, in several studies, this possible explanation for the development of vitamin E deficiency symptoms has been made untenable. In such studies the more likely explanation for development of symptoms is thein vivo peroxidation of PUFA in the tissues of animals following incorporation of large amounts of PUFA in lipid structures and depletion from the tissues of vitamin E and other biologically effective antioxidants.
Alkyd resins from fumaric and maleic modified pine oleoresin
Authors: Halbrook Noah J. , Wells John A. , Lawrence Ray V.
Published: May 2007

Fumaric and maleic modified pine oleoresin can be used to prepare oil modified nonphthalic alkyd‐type surface coating vehicles. These vehicles may find use in trim enamels, concrete maintenance paints, and as a fortifier for linseed oil exterior paints. Processing of these resins requires that the temperature be raised to 285°C. for 1 to 1.5 hours and then lowered to 265°C. for a time during the procedure. Fumaric modifications may hold some advantages over maleic modifications. Clear films formed from these resins are characterized by good hardness, flexibility, adhesion, toughness, gloss, and color retention. The shorter oil length resins exhibit these properties to the greatest extent.