Showing papers by "Technical University of Berlin published in 1974"

Implementation and efficiency of Moore-algorithms for the shortest route problem

Abstract: In the last 15 years, a good deal of effort has been devoted to the study of the shortest route problem. More than 200 publications are known but little has been reported concerning relative efficiencies. For a long time the Dijkstra method was considered the most efficient one. Programming work, using different data structures and implementation techniques for several algorithms, has shown that a variant of Moore's method seems to be most efficient for different types of graph structures.

Phase separation in urethane elastomers as judged by low-angle X-ray scattering. I. Fundamentals

Abstract: In thermoplastic urethane elastomers, phase separation between hard and soft segments resulting in a domain structure is an essential condition for a sufficiently high heat distortion temperature. The state of segregation, i.e., the domain structure, is characterized by the following aspects: 1) the size distribution, i.e., the dispersion level of the domains; 2) the sharpness of diffuseness of the domain boundaries, and 3) hard segments dissolved in the soft segment matrix or soft segments included in the domains. The state of segregation may be evaluated by means of low-angle X-ray scattering. The fundamental theory, based on Porod's theory of low-angle scattering, is given in this paper. Experimental findings will be discussed in a later paper.

X-ray investigations concerning the physical structure of crosslinking in urethane elastomers. III. Common structure principles for extensions with aliphatic diamines and diols

Abstract: Physical crosslinking of urethane elastomers is essentially based on statistical systems of hydrogen bonds within the hard segment domains. Two dimensional models of these systems, given in previous papers, are now replaced by three-dimensional models in the case of butane diol and pentane diol extenders, respectively. A suggestion is made for the transverse crosslinking mechanism with diamine extenders. Taking into account the conditions for three-dimensional hydrogen bonded systems a correlation between the cross-linking structure and heat-distortion temperature of diamine and diol extended elastomers is obtained.

Phase separation in urethane elastomers as Judged by low-angle X-Ray scattering. II. Experimental Results

Abstract: Supposing complete segregation, volume and density of the hard segment domains in thermoplastic urethane elastomers are easily calculated from the chemical composition of the elastomers. These hypothetical values may be compared with experimental small-angle X-ray findings, resulting in a realistic picture of the actual state of segregation. A similar situation holds true for the specific surface area of the domains. With respect to elastomers of MDI, hydrazine, and a linear polyester or a polyether with a hard segment volume fraction of about 15%, specific surface areas of the domains of about 220 m2/cm3 were found. They are characterized by diffuse transition zones, the width of which was about 20 A. The segregation was further more incomplete due to isolated MDI blocks dissolved in the soft segment matrix as well as to soft segments included in the domains.

Darstellung und Schwingungsspektren von Trimethylsilyl‐, Trimethylgermyl‐ und Trimethylstannyl‐tert‐butylphosphinen

Abstract: Trimethylchlorsilan reagiert mit Magnesium und Di-tert-butylchlorphosphin, tert- Butyl-dichlorphoshin oder PCl3 in Tetrahydrofuran unter Bildung von Di-tert-butyl(trimethylsilyl)phosphin, tert-Butylbis(trimethylsily)phosphin bzw. Tris(trimethylsilyl)phosphin in hohen Ausbeuten. Durch Umsetzung dieser Organosilylphosphine mit Trimethylgermaniumchlorid oder Trimethylzinnchlorid erhalt man die entsprechenden Trimethylgermanium-bzw. Trimethylzinn-phosphine. Die Infrarot-und Raman-Spektren werden diskutiert. Synthesis and Vibrational Spectra of Trimethylsilyl-, Trimethylgermyl-and Trimethylstannyl-tert-butylphosphines Trimethylchlorosilane reacts with magnesium and di-tert-butylchlorophosphine, tert-butyl-dichlorophosphine, or PCl3 in tetrahydrofurane to form di tert-butyl(trimethylsilyl)phosphine, tert-butylbis(trimethylsilyl) phosphine, or tris(trimethylsilyl)phosphine respectively in high yields. By reaction between these organosilylphosphines and trimethylgermanim chloride or trimethyltin chloride the corresponding trimethylgermanium - or trimethyltin-phosphines are formed. The i.r., and Raman spectra are discussed.

Natürlich vorkommende Terpen‐Derivate, XXXIX. Über die Inhaltsstoffe der Gattung Euryops

Abstract: Aus verschiedenen Vertretern der sudafrikanischen Gattung Euryops werden 35 neue Furanoeremophilane isoliert, fur die spektroskopische und chemische Methoden die Konstitutionsformeln 1–6, 14–16, 18–20, 27, 28, 31–33, 36–40, 42, 43, 45, 47, und 49–57 abzuleiten gestatten. Auserdem werden vier Eremophilan-Derivate isoliert, bei denen die Konfigurationsermittlung zu den Formeln 58, 59, 65, und 70 fuhrt. 58 und 65 lassen sich durch Chromsaureoxidation in Furanoeremophilane uberfuhren. Der Mechanismus durfte dem der Biogenese entsprechen. Die biogenetischen Beziehungen und die chemotaxonomische Bedeutung dieser Sesquiterpene werden diskutiert.

Natürlich vorkommende Terpen‐Derivate, XLII. Neue Sesquiterpene der Gattung Othonna

Abstract: Die Untersuchung von Vertretern aus funf Sektionen der Gattung Othonna zeigt, das hier relativ stark oxidierte Furanoeremophilane charakteristisch sind. Die Konstitutionen von 20 neuen Vertretern (1, 2, 6, 7, 9, 11, 12, 14, 16, 18, 28, 31, 34 und 37–43) werden durch ihre Spektren sowie durch chemische Reaktionen geklart. Daneben werden einige Sequiterpene (24, 35, 36) sowie eine Nor-Verbindung (22) isoliert und ihrer Struktur geklart. Die engen chemotaxonomischen Beziehungen zu den Nachbargattungen werden diskutiert. Naturally Occuring Terpene Derivatives, XLII. New Sesquiterpenes o the Genus Othonna The investigation of representatives from five sections of the genus Othonna shows that they are characterized by the presence of relatively strongly oxidized furanoeremophilanes. The constitution of 20 new members (1, 2, 6, 7, 9, 11, 12, 14, 16, 18, 28, 31, 34 and 37–43) has been established by means of their spectra as well as by chemical reactions. Besides these some sequiterpenes (24, 35, and 36) as well as a nor-compound (22) have been isolated and their structures elucidated. The close chemotaxonomical relationships to the neighbouring genera are discussed.

Polyacetylenverbindungen, 229. 13C‐NMR‐Spektren von Polyinen

Abstract: Die 13C-NMR-Spektren mehrerer Polyine zeigen, das die chemischen Verschiebungen aller Acetylen-13-C-Atome unterschiedlich sind, daher ist selbst beim Pentain 5, eine Zuordnung der Signale moglich Die Verschiebungen unsymmetrisch substituierter Verbindungen stehen nur teilweise in Ubereinstimmung mit den zu erwartenden Elekronendichten Bei Konjugation mit olefinischen C-Atomen beobachtet man eine Entschirmung des β-standigen Acetylen-C-Atoms Die Beziehungen zwischen den Kopplungskonstanten und der Struktur werden diskutiert Polyacetylenic Compounds, 229 13C NMR Spectra of Polyynes The 13C nmr spectra of several polyynes show that the chemical shifts of all acetylenic 13C-atoms differ from each other, so that even in the pentayne 5 a correlation of the signals is possible The chemical shifts of unsymmetrically substituted compounds are only partly in agreement with the electron densities In the case of conjugation with olefinic C-atoms a deshielding of the acetylenic C-atom in β-position is observed The relationship between coupling constants and structure is discussed

Calcium-transport in Wurzeln von Mais- und Bohnenkeimpflanzen

Abstract: Zur Untersuchung des Ca-Transportes in Wurzeln intakter Pflanzen wurde Wurzeln von 9 Tage alten Pflanzen von Mais (Zea mays L., Velox) und Bohnen (Phaseolus vulgaris L., Saxa) an einer 3 cm langen Zone Ca45-markierte Nahrlosung angeboten. Die ubrigen Zonen der Wurzeln (Gesamtlange der Primarwurzel 25–30 cm) befanden sich in nichtmarkierter Nahrlosung. Nach einer Versuchsdauer von 1–7 Tagen wurde die Verteilung von Ca45 in den einzelnen Wurzelzonen und im Spros ermittelt. Wachsende Wurzelspitzen mussen somit ihren gesamten Ca-Bedarf direkt durch Aufnahme aus der Ausenlosung decken, eine Durchwurzelung Ca-armer Bodenhorizonte ist deshalb erschwert oder nicht moglich. re]19730417

Natürlich vorkommende Terpen-Derivate, XLI. Über neue Sesquiterpene der Gattung Senecio

Abstract: Die Untersuchung mehrerer Arten der Gattung Senecio zeigt, das in einigen Sektionen Furanoeremophilane typisch sind. Die Konstitutionen von 19 neuen Furanen (6–16, 18, 20, 22–26 und 29) konnten hauptsachlich durch spektroskopische Methoden geklart werden. Weiterhin wurden ein Eremophilan-acetat (1) und eine Mischung von Diestern (32) isoliert. Naturally Occuring Terpene Derivatives, XLI. On New Sesquiterpenes from the Genus Senecio The investigation of several species of genus Senecio shows, that in some sections furanoeremophilanes are typical. The constitution of 19 new furanes (6–16, 18, 20, 22–26 and 29) could be elucidated mainly by spectroscopic methods. Furtheron an eremophilane acetate (1) and a mixture of diesters (32) have been isolated.

Polyacetylenverbindungen, 225. Weitere Amide aus der Tribus Anthemideae

Abstract: Otanthus maritimus (L.) Hoffm. et Link. enthalt drei neue Thiophenamide (8–10) und die neuen Amide 4, 5. Aus Achillea millefolium L. isoliert man ein weiteres Amid (25). Die Strukturen wurden durch spektroskopische Daten geklart. Die wahrscheinliche Biogenese wird diskutiert. Polyacetylenic Compounds, 225. Further Amides from the Tribe Anthemideae Otanthus maritimus (L.) Hoffm. et Link. contains three new thiophene amides (8–10) and the new amides. 4, 5. Form. 5. From Achillea millefolium L. a further amide (25) has been isolated. The structures are elucidated by spectroscopic data and the probable biogenesis is discussed.

Über das Vorkommen von Muscaflavin bei Hygroeyben (Agaricales) und seine Dihydro- azepin-Struktur 1,2 / Isolation of Muscaflavin from Hygrocybe Species (Agaricales) and Its Dihydroazepine Structure

Abstract: Abstract Sporophores of Hygrocybe species (Agaricales) contain muscaflavin, a pigment recently isolated from Amanita muscaria. Spectroscopic and chemical evidence for its dihydroazepine structure 5a is presented, indicating a close biogenetic relationship to betalamic acid 6a. The chemical nature of the water soluble pigments of Hygrocybe is dis cussed

Interaction between the antibiotic tyrocidine and DNA in vitro.

Abstract: VERY little is known about the natural function of the peptide antibiotics. The production of antibiotics may be related to sporulation as only sporulating microorganisms produce antibiotics1. In general, the synthesis of antibiotics occurs within a limited time at the end of the logarithmic growth of cell cultures2, concurrent with a change in the specificity of transcription3. Loss, through mutation, of the ability to synthesise the antibiotic leads to asporogeny, in some cases1. Specific inhibitors and changes in culture conditions affect both the synthesis of antibiotic and sporulation4. Sarkar and Paulus5 demonstrated that the cyclic peptide antibiotic, tyrocidine, produced by Bacillus brevis (ATCC 8185) effects RNA synthesis in vivo, whereas DNA synthesis continues. Moreover, these authors give evidence that tyrocidine inhibited an in vitro RNA transcriptional system using B. brevis DNA and B. brevis DNA-dependent RNA polymerase. Complete inhibition of RNA synthesis with a tyrocidine concentration comparable to that in a B. brevis cell at the end of the vegetative growing phase was observed. A strong binding of the oligopeptide antibiotics, neotropsin and distamycin A, to double-stranded DNA, resulting in a pronounced heat stabilisation of the double-strands, has been reported6. Compared with pure DNA, these peptide-DNA complexes exhibit a low template activity7.

Vibronic Spectra and the Dynamic Jahn‐Teller Effect of Cubic ZnS:Cu2+

Abstract: Near infrared absorption and emission spectra due to the transitions 2T2 2E of the Cu2+ ion in cubic ZnS have been measured at 4K. The distinct vibronic sidebands of the absorption spectrum exactly correspond to various critical point energies of TA, TO, and LO lattice modes, whereas the structure of the luminescence spectrum cannot be interpreted in terms of lattice phonon satellites. A dynamic Jahn-Teller interaction in the 2T2 ground state being in the same order of magnitude as static lattice spin-orbit splitting and phonon energy is shown to produce this deviation from the mirror symmetry. Weak and strong coupling approximations in the cluster limit have been extended to include vibronic states with up to six E-modes. Absorptions- und Emissions-Spektren im nahen Infrarot hervorgerufen, durch die Ubergange 2T2 2E des Cu2+in kubischem ZnS, wurden bei 4 K aufgenommen. Die aus- gepragten vibronischen Seitenbanden des Absorptionsspektrums entsprechen exakt den Energien verschiedener kritischer Punkte der TA-, TO- und LO- Gittermoden, wahrend das Emissionsspektrum nicht durch Phononenenergien des ungestorten Gitters zu erklaren ist. Es wird gezeigt, das eine dynamische Jahn-Teller-Wechselwirkung im 2T2-Grundzustand von der Grosenordnung der statischen Spin-Bahn- Aufspaltung und Phononenenergie diese Abweichung von der Spiegelsymmetrie hervorruft. Die Naherungen schwacher und starker Kopplung im Cluster-Mode11 werden auf vibronische Zustande mit bis zu sechs E-Moden ausgedehnt.

Zum Mechanismus der Desulfurierung von 1,3‐Benzodithiol‐2‐thion mit Triäthylphosphit

Abstract: Die Reaktion der Titelverbindung 1 mit Triathylphosphit in Gegenwart von Abfangreagentien wird untersucht. Mit Alkoholen werden 12 und 13, mit Piperidin 17, mit Carbonylverbindungen 20–23 und mit Enaminen 24 erhalten. Die Ergebnisse werden mit einem thiophilen Angriff des Phosphits auf 1 unter Bildung des 1,3-Dipols 14 und dessen Folgereaktionen erklart. On the Mechanism of Desulfuration of 1,3-Benzodithiole-2-thione with Triethyl Phosphite The reaction of title compound 1 with triethyl phosphite in the presence of capture-reagents is investigated. With alcohols the reaction yields 12 and 13, with piperidine 17, with carbonyl compounds 20–23, and with enamines 24. The results are explained by a thiophilic attack of triethyl phosphite on 1 with generation of the 1,3-dipole 14 and subsequent reactions.

Quantitative data on daylight for illuminating engineering

Abstract: Data are provided for the extraterrestrial radiation of the Sun, also for those quantities which are of interest to the illuminating engineer, namely luminance distribution, zenith luminance, illumination, spectral distribution and luminous efficacy of the overcast sky, clear sky and sunlight. Formulae for luminance and illuminance due to several authors are given and shown graphically. CIE recommendations are included.

Enhydrazine, 9. 1‐Alkyl‐3‐hydroxypyrazole aus Hydrazonen oder Hydrazinen

Abstract: Durch Umsetzung von Acetylendicarbonsaure- dimethylester mit Hydrazinen oder Alkyl-hydrazonen erhalt man die 1-Alkyl-3-hydroxy-5-pyrazolcarbonsaure-methylester 9 und 13a–e, durch Verseifung und Decarboxylierung hieraus die 1-Alkyl-3-hydroxypyrazole 11 und 15a–e. Die Cyclisierung von 13f zum Lacton 19a ist strukturbeweisend. Bei Verwendung von Benzaldehyd-hydrazonen entstehen hauptsachlich 2-Pyrazolin-4,5- dicarbonsaureester. Enehydrazines, 9. 1-Alkyl-3-hydroxypyrazoles from Hydrazones or Hydrazines Reaction of dimethyl acetylendicarboxylate with hydrazinen oder Alkyl hydrazonen gives the methyl 1-alkyl-3-hydroxy-5-pyrazolecarboxylats 9 and 13a–e, subsequent saponification and decarboxylation gives the 1-alkyl-3-hydroxypyrazoles 11 and 15a–e. The cyclization of 13f to lactone 19a is a structure proff. Starting from benzaldehyde hydrazones, 2-pyrazoline-4,5-dicarboxylic esters are the main products.

Basisches Verhalten von Epoxiden in Gegenwart von Halogenid‐Ionen, II. Dehydrohalogenierung von Phosphoniumhalogeniden durch Epoxide Teil 1: Bildung der Ylide und Umsetzung mit Carbonylverbindungen

Abstract: Epoxide und geeignete Phosphoniumhalogenide stehen im Gleichgewicht mit den entsprechenden Yliden und Alkoholen (Gleichungen (1) und (2)). Die im Gleichgewicht befindlichen Ylide reagieren mit Carbonylverbindungen zu olefinischen Verbindungen (Gleichung (3)). Auf diese Weise Konnen u. a. Vitamin-A-acetat und β-Carotin nach den Schemata C15 + C5 bzw. C20 + C 20 in guten Ausbeuten hergestellt werden (Tab. 1). – Mit 1-Chlor-2,3- epoxypropan (Epichlorhydrin) und Benzyltriphenylphosphoniumhalogenid, welche zum entsprechenden rot gefarbten Ylid miteinander reagieren, lassen sich sowohl die bekannte Reversibilitat der Ylid-Bildung als auch die Wittig-Reaktion eindrucksvoll vorfuhren (Demonstrationsexperiment, Abschnitt 2). Basic Behavior of Epoxides in the Presence of Halide Ions, II. Dehydrohalogenation of Phosphonium Halides by Epoxides Part 1: Formation of Ylides and Reaction with Carbonyl Compounds Epoxides and suitable phosphonium halides are in equilibrium with the corresponding ylids and alcohols (equations (1) and (2)). These ylids in equilibrium react with carbonyl compounds to yield derivatives of alkenes (equation (3)). Thus vitamin-A-acetate and β-carotene can be prepared in good yields according to the schemes C15 + C5 and C20 + C 20 resp. (table 1). – With the aid of 1-chloro-2,3-epoxypropane (epichlorohydrin) and benzyltri-phenylphosphonium halide, which react to the corresponding red ylid, both the well known reversibility of ylid formation and the Wittig reaction may be impressively demonstrated (demonstration experiment, section 2).

Improved Correlation of Film Condensation Data Based on a More Rigorous Application of Similarity Parameters

Abstract: It is shown that a most consistent application of similarity parameters reduces the “random error” of experimental results in film condensation by 90%, in extreme situations even more. On the basis of physical considerations a correlation of data is presented which shows the Nusselt number as a function not only of the Reynolds number but also in certain ranges of the Prandtl and Weber number. Although the latter parameters varied only moderately in the experiments presented here the general idea is supported clearly. Further experiments will have to provide for quantitatively more reliable results.