Brittle fracture and spinnability of viscous materials

Conclusion In both cases, brittle fracture and dropping breakdown, only very little deformation or elongation was observed in the experiments mentioned above, and limiting conditions were obtained reproducibly with respect to rate of extension and temperature. The brittle limits give the condition where the viscous resistance due to locally concentrated stress, i. e. the grip effect (5) exceeds cohesion of the materials, and development of the surface of separation is followed. At the dropping limits, the viscosities of the liquids may be too small to resist shrinking by surface tension with respect to the rate of extension. Although the theory of spinnability proposed here may be only tentative, it can be pointed out that surface tension plays some important role in spinning of viscous liquids of lower molecules. Concerning higher molecules, rubber-like elasticity as well as viscosity may become more important (6).

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Zusammenfassung Für beide Fälle, spröden Bruch und stufenweiser Bruch, wurde nur sehr geringe Deformation oder Verlängerung beobachtet und Grenzbedingungen hinsichtlich Dehnungsgeschwindigkeit und Temperatur reproduzierbar erhalten. Die Bruchgrenzen geben die Bedingungen, bei denen der viskose Widerstand entsprechend den lokalen Spannungskonzentrationen, d. h. entsprechend den grip-Effekt die Kohäsion des Materials übersteigt, und die Entwickelung der Trennfläche wird verfolgt. Bei der Grenzbelastung für das Absinken der Spannung mag die Viskosität der Flüssigkeiten zu gering sein, um dem Schrumpfen durch Oberflächenspannung im Vergleich mit der Dehnungsgeschwindigkeit entgegen zu wirken. Obgleich die Theorie der Spinnbarkeit, hier vorgeschlagen, nur einen Versuch darstellt, kann behauptet werden, daß die Oberflächenspannung beim Spinnen viskoser Flüssigkeiten mit kleineren Molekülen eine wichtige Rolle spielt. Für höhermolekulare Substanzen wird neben der Viskosität auch die Gummielastizität ausschlaggebend.

     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. II. Properties of acrylonitrile–styrene copolymer

The properties of the acrylonitrile–styrene copolymer prepared in the presence of zinc chloride were investigated in comparison with those of a copolymer having the same overall composition and prepared by the ordinary radical procedure. The characteristics of the polymer prepared with ZnCl₂ were as follows: (1) less coloration by alkali treatment, (2) less coloration by thermal treatment and (3) higher glass transition temperature. These features may be attributed principally to the structure of the copolymer, which has more unlike bonds and less long sequences as described in the first article of this series. The effects of residual salt in the copolymer on the properties were also investigated.     

10-Gbit/s Serial Optical Interconnection for an ATM Switch

Serial optical interconnection is proposed for connections in a Torus asynchronous transfer mode switch. A cross-point switch was developed that operates at a bit rate of 20 Gbit/s. The switching operation was successfully performed using cascaded cross-point switches through an optical interconnection configuration consisting of commercial optoelectronics devices. The measured switching rate was 10 Gbit/s, and it was limited by the responses of the optoelectronics devices.     

Phase transition in ammonium hexafluorovanadate (III)

Heat capacity of ammonium hexafluorovanadate (NH₄)₃ [VF₆] has been measured with a miniaturized adiabatic calorimeter from 20 to 300 K. A phase transition was found at 280.44 ± 0.05 K with the associated entropy change Δ_trs S = 24.9 ± 0.5 JK^?1 mol^?1. The entropy transition is accounted for by the orientational order-disorder changes of hexafluorovanadate ion and ammonium ion occupying respective octahedral sites, as in the cases of (NH₄)₃AlF₆ and (NH₄)₃FeF₆ crystals. Changes in infrared spectra relative to v₃ vibrational mode of [VF₆]^3? ion can be explained by an orientational disorder of the anions in the high-temperature phase (HTP). The dependence of cubic root of the unit-cell volume of a family of ammonium cryolites on their transition temperatures is discussed in relation to the nature of interactions which induce the phase transition.     

Regularized determinants for quantum field theories with fermions

A new type of regularized determinant for the ratio of two Dirac operators is presented. Some of its properties with application to the chiral anomaly are given.     

Radical cyclopolymerizations of diallylsilanes and triallylsilanes

The radical polymerizations of diallylsilanes such as diallyldimethylsilane ( 1 ) and diallylmethylphenylsilane ( 2 ) have been conducted. Both poly(diallyldimethylsilane) ( 3 ) and poly(diallylmethylphenylsilane) ( 4 ) are soluble in benzene, methyl ethyl keton (MEK), and chloroform, slightly soluble in acetone, and insoluble in methanol and ethanol. No insoluble fraction of either polymer was obtained. Very little evidence of vinyl protons in the ¹H-NMR spectra can indicate that both polymerizations predominantly proceed with intramolecular cyclization. In order to study the ring size of cyclic structure in the repeating unit of the polymers, a model compound, allyl(2-chloropropyl)dimethylsilane ( 5 ), was synthesized and cyclized with Bu₃SnH in the presence of azobisisobutyronitrile (AIBN) in benzene, under similar condition of those for the cyclopolymerizations. The product was analyzed with GC–MS which showed that the five-membered ring compound, 1,1,3,4-tetramethylsilacyclopentane, was not formed. From the result of the cyclization of the model compound, it can be suggested that the polymerizations undergo with only h–t intramolecular cyclization to form a six-membered ring in the repeated unit. The ¹³C-NMR spectra of 3 and 4 were measured to study the ring size and the configuration of the cyclic structures. The two peaks at ?1.6 and ?3.4 ppm of the spectrum of 3 show that there are two kinds of methyl carbons in the repeating unit. From consideration of the model reaction and the number of the peaks of the NMR spectrum, it can be considered that the polymer main chain is assembled with the six-membered ring in cis-form, and the two signals are assigned to equatorial and axial methyl carbons, respectively. The two peaks at -1.5 and -5.1 ppm of the ¹³C-NMR spectrum of 4 can be assigned similarly. The radical cyclopolymerizations of triallylsilanes such as methyltriallylsilane ( 6 ) and phenyltriallylsilane ( 7 ) were conducted. The ¹H-NMR spectra of poly(methyltriallylsilane) ( 8 ) and poly(phenyltriallylsilane) ( 9 ) show broad peak around 5 ppm for vinyl protons and around 2 ppm for alkyl protons. Comparisons of the relative intensities of the peaks indicate that both polymerizations undergo with single ring closure to form a polymer with monocyclic structure moiety, cyclosilahexane, and an allyl group in a repeating unit of 8 and 9 .     

The absorption spectrum of localized electrons in crystalline 1,8-octanediol, γ-irradiated at 4.2 K

Crystalline 1.8-octanediol has been γ-irradiated and its optical absorption spectrum has been measured at 4.2 K. The spectrum consists of three partially resolved peaks with maxima at 740, 590, and 490 nm. The peaks cannot be separated by photobleaching or annealing. It is suggested that they arise from transitions inherent in each localized electron.     

E 6,7,8 magnetized extra-dimensional models

We study 10D super Yang–Mills theory with the gauge groups E ₆, E ₇ and E ₈. We consider the torus/orbifold compactification with magnetic fluxes and Wilson lines. They lead to 4D interesting models with three families of quarks and leptons, whose profiles in extra dimensions are quasi-localized because of magnetic fluxes.