Showing papers by "Technical University of Berlin published in 1973"

Structure-borne sound

Abstract: Although sound waves in structures cannot be heard directly, and only be felt at low frequencies, they play an important role in noise control, because many sound signals are generated or transmitted in structures before they are radiated into the surrounding medium. In several respects sound waves in structures and sound waves in gases or liquids are similar, there are, however, also fundamental differences, which are due to the fact that solids have a certain shear stiffness, wheras gases or liquids show practically none. As a consequence acoustic energy can be transported not only by the normal compressional waves but also by shear waves and many combinations of compressional (sometimes loosely called longitudinal) and shear waves . For noise control purposes bending waves (which are a special combination of compressional and shear waves) are of primary importance; for some special cases (quasi-) longitudinal waves and torsional waves also have to be considered.

Rotation and Translation of Regular and Irregular Solid Spherical Harmonics

Abstract: Publisher Summary Quantum-mechanical calculations of molecular properties and reactions require the introduction of atomic orbitals (AO's) that are centered on the nuclei of the different atoms of the investigated molecule or molecular complex. Each atomic orbital is a certain mathematical function of the coordinates of one electron with respect to a coordinate system that has its origin in the nucleus of the considered atom. The main difficulties of quantum-mechanical theories are because of operators that may be considered as special cases of irregular solid spherical harmonics. The formulas derived to describe the transformation properties of solid spherical harmonics under rotations and translations have been found useful for the calculation of molecular integrals. The chapter describes the solid spherical harmonics and presents certain relations that are to be used in the sequel. The behavior of spherical harmonics under rotations is discussed to obtain a set of uniform formulas useful for subsequent considerations. The derivation of the transformation of solid spherical harmonics under translations is facilitated by the translation of general functions and by deriving some auxiliary identities needed in the sequel.

Natürlich vorkommende Terpenderivate, XXVI. Über die Inhaltsstoffe von Artemisia fragrans Willd

Abstract: Die Wurzeln von Arternisia fragrans Willd. enthalten ein komplexes Gemisch von Terpenen, deren Strukturen geklart werdcn. Neben Lavandulol und Nerol und verschiedener ihrer Ester enthalt die Pflanze ein Cyclobutan-Derivat, das ebenfalls ala Alkohol und verestert vorkommt (5 und 15–18). Naturally Occuring Terpene Derivatives, XXVI. On the Constituents of Artemisia fragrans Willd The roots of Artemisia fragrans Willd. contain a complex mixture of terpenes, their structure being elucidated. Besides lavandulol and nerol and different esters there from the plant contains a cyclobutane derivative, which also occurs as alcohol and esterified (5 and 15–18).

Polyacetylenverbindungen, 215. Neue Inhaltsstoffe aus Achillea-Arten

Abstract: Eine erneute Untersuchung von Achillea-Arten zeigt, das hier neben bereits bekannten Acetylenverbindungen mehrere neue Amide (4, 12, 13, 20, 21 und 22) vorkommen, deren Strukturen durch spektroskopische Daten geklart werden. Durch Synthese des Piperideids 4 wird dessen Struktur gesichert. Bemerkenswert ist das Vorherrschen derartiger cyclischer Amin-Derivate in der Gattung Achillea. Polyacetylenic Compounds, 215. New Constituents of Achillea Species A reinvestigation of Achillea species shows that besides already known acetylenic compounds several new amides (4,12, 13, 20, 21, and 22) are present, their structures being elucidated by spectroscopie data. The structure of the piperideide 4 has been established by synthesis. The predominance of these cyclic amine derivatives in the genus Achillea is remarkable.

Eine neue Synthese von Cyclohexadien‐Derivaten

Abstract: Die Reaktion α,β-ungesattigter Carbonylverbindungen mit Phosphoranen vom Typ 3.14, 21, 27 oder 29 fuhrt an Stelle der zu erwartenden Trienester zu 1.3-Cyclohexadien-Derivaten (5, 9, 11, 13, 15, 17, 19, 22, 24, 26, 28 und 30). Auch das Phosphonat-Anion 37 reagiert in gleicher Weise. Der Mechanismus dieser Reaktion wird diskutiert. A New Synthesis of Cyclohexadiene Derivatives The reaction of α,β-unsaturated carbonyl compounds with phosphoranes of types 3, 14, 21, 27, or 29 leads instead of the expected triene esters to 1,3-cyclohexadiene derivative (5,9,11, 13, 15, 17, 19, 22, 24, 26,28 and 30). The phosphonate anion 37 reacts in the same manner. The mechanism of this reaction is discussed.

Natürlich vorkommende Cumarin‐Derivate, IX1) Über die Inhaltsstoffe der Gattung Gerbera

Abstract: Die Wurzeln mehrerer Gerbera-Arten enthalten die bekannten Polyine 1 und 2. Aus Gerbera crocea wurden zusatzlich das Acetophenon-Derivat 3 und zwei neue Cumarine (4 und 7) isoliert, deren Strukturen durch spektroskopische Daten sowie durch Synthese geklart werden. Naturally Occuring Coumarin Derivatives, IX1) On the Constituents of the Genus Gerbera The roots of several Gerbera species contain the known polyynes 1 and 2. In addition from Gerbera crocea the acetophenon derivative 3 and two new coumarins (4 and 7) were isolated, the structures being elucidated by spectroscopic data as well as by synthesis.

Fracture mechanism of lower legs under impact load

Abstract: The increasing number of injured or even killed pedestrians in urban traffic accidents demands the attention of automobile designers to improve the outside safety operation of the vehicles. To incorporate an effective pedestrian-protection system~such as bumper, engine hood, etc.~in the vehicle, one needs the relevant information about the injury limits of the pedestrians. It is also well known that most pedestrians, particularly at lower speeds, are injured in the region of the lower legs; therefore, it is necessary to know the injury limits between vehicle and pedestrian, and hence this investigation has been initiated. This paper reports on the mechanism of injuries of the tibia under dynamic load conditions. Some 209 tests with cadavers of recently deceased people representing the normal pedestrian population were carried out on a twin-pendulum catapult. Impact load has been brought up by bumper-shaped impact bodies; the point of impact was varied between the patella and the distal end of the tibia. During the tests, the time histories of the leg decelerations were recorded, and a pathological dissection just after the tests gave us the details of the incurred injuries. These data are further evaluated using a digital computer. The relation between the mechanical and biological properties of the test specimens were thus determined, and the influence of constitution, age, and sex as well as loading form, center of impact, and energy during the impact was analyzed. The breaking forces are shown as a function of impact velocity as well as the particulars of the injuries, depending upon physiological parameters thus describing critical limits, from which the risk of being severely injured will sharply rise. The relations between mechanical and physiological parameters allow estimation of the severity of real-world injuries through the dummy tests.

Birefringence of Compensated Cholesteric Liquid Crystals

Abstract: The temperature dependence of refractive indices of three compensated cholesteric mixtures has been measured using a commercial Abbe-refractometer. At compensation temperature Tn a homeotropic nematic texture was achieved indicated by exchange of ordinary and extraordinary ray and strong increase of birefringence. A comparison is given between nematic and cholesteric birefringence yielding good agreement with the de Vries model of cholesteric structure. Es wurde die Temperaturabhangigkeit der Brechungsindizes dreier kompensierter cholesterischer Mischungen mit einem handelsublichen Abbe-Refraktometer bestimmt. Bei der Kompensationstemperatur Tn, wurde eine homootrope nematische Textur erzeugt, die an dem Austausch von auserordentlichem und ordentlichem Strahl und einem starken Anstieg der Doppelbrechung zu erkennen war. Der Vergleich der Doppelbrechung im cholesterischen und nematischen Zustand fuhrt zu einer guten Ubereinstimmung mit dem Struktur-modell cholesterischer Phasen von de Vries.

Impuls-, Stoff- und Wärmetransport durch die Grenzfläche kugelförmiger Partikeln

Abstract: Der stationare Stoff- und Warmetransport wird bei zunehmender Reynolds-Zahl durch den Ubergang von der schleichenden Stromung zur Grenzschichtstromung gepragt. Bei festen Kugeln wird durch die Wirbelbewegung im Ablosegebiet auch auf der Kugelruckseite ein Grenzschichtcharakter hervorgerufen. Die mitgeteilte Stoffubergangsgleichung stimmt mit Meswerten gut uberein. Sie berucksichtigt auch den Einflus des Turbulenzgrades der Ausenstromung, durch den der Stoffubergang erheblich verstarkt wird. Bei der Umstromung von Kugelblasen ergeben sich vollig andere Verhaltnisse fur den Stofftransport. Mit steigender Reynolds-Zahl erfolgt eine Annaherung an die Gesetze fur die Potentialstromung. Die mitgeteilten Gesetze gelten nur fur Kugelblasen. Oberhalb ihrer Gultigkeitsgrenze, die angegeben wurde, verliert die Blase ihre Kugelform und erfahrt stochastische Formanderungen. Der instationare Stofftransport durch die Grenzflache einer Kugel unter Berucksichtigung eines stationaren konvektiven Anteils wird an einem Beispiel erortert. Fur sehr kurze und fur sehr lange Zeiten verliert der konvektive Anteil seine Bedeutung fur den instationaren Transport.

Theory of chirality functions, generalized for molecules with chiral ligands

Abstract: The theory of chirality functions described in a previous publication is generalized to allow for chiral ligands. In the earlier theory, all symmetry operations of the molecular frame could be thought of as permutations of the ligands among the sites; in the present work, improper rotations not only permute the ligands, but convert them into mirror images. The group that generates all isomers from a given ordered molecule belonging to a frame with n sites is now the “hyperoctahedral” group of order 2n n! consisting of all possible combinations of permutations and site reflections. The representation theory of these groups is described, and applied to the problem of constructing qualitatively complete chirality functions, and of deciding which ligand partitions, and which isomer mixtures, are chiral. It is found useful to classify chiral representations of the covering group as “ligand specific” and “class specific”. The ligand specific representations describe chiral properties which are common to all frames and arise purely from the chirality of the ligands, while the class specific representations describe the chiral properties of the frame. A number of examples are explicitly worked out.

Approximation von Eigenwertproblemen bei nichtlinearer Parameterabhängigkeit

Abstract: We consider in this paper the approximation of the eigenvalues of the problem $$A(z)u = 0$$ by means of the eigenvalues of a sequence of approximating problems $$A_l (z)u_l = 0, l\varepsilon \Lambda _0 ,$$ where the functions A∶G→C(E, F) and leΛ0, are defined in a domain G⊂ℂ with values in the set of closed linear operators from the Banach space E resp. El into the Banach space F resp. Fl, leΛ0. Beside theorems concerning the convergence of spectra we give connections between the structure of spectra resp. analyticity properties of the resolvents of the operator A and the elements of the sequence (Al). As an application of our abstract results we treat difference approximations of the Dirichlet-problem for strongly elliptic partial differential equations with coefficients depending analytically on a complex parameter.

The Modification of the Trapping Properties within the Photosynthetic Watersplitting Enzyme System Y

Abstract: The modification of the trapping properties for oxidizing equivalents (holes) within the watersplitting enzyme system Y by chemicals (ADRY agents) has been investigated. It is shown: (1) The ADRY agents decrease significantly the storage life time of the higher trapped hole accumulation states. (2) The acidic NH-or OH-group is a functional indispensable element for substances to be able to act as ADRY agents. (3) The trapping efficiency of the watersplitting enzyme system Y for holes is not correlated with the transmembrane electrochemical gradient. (4) As electron donor for the discharge of the trapped holes acts an andogeneous carrier of the electron transport chain located either between the photosystems I and II respectively or on the reducing side of system I. A special electron donor is not required for the ADRY effect.