Globally smooth solutions of quasilinear hyperbolic systems in diagonal form

We prove the existence of a large class of globally smooth solutions of the Cauchy problem for the system of n equations u_t + Λ(x, t, u)u_x = 0, where Λ is a diagonal matrix. We show that, under certain monotonicity conditions on both Λ and the initial data u₀, the solution u will be locally Lipschitz continuous at positive times. Since u₀ is a function of locally bounded variation, our result thus provides both for the smoothing of discontinuities in u₀ as well as for the global preservation of smoothness. The global existence results from an a priori estimate of $\text{?u}\text{?x}$, which we obtain by a device which enables us to effectively uncouple the system of equations for $\text{?u}\text{?x}$. Finally, we prove a partial converse which demonstrates that our hypotheses are not overly restrictive.     

Decay schemes and total decay energies of89Br and90Br

Spectroscopical investigations of⁸⁹Br and⁹⁰Br have been performed, utilizing the formation of the molecular ion AlBr⁺ in the ion-source of an isotope separator on-line a reactor. Detailed level schemes have been constructed for⁸⁹Kr and⁹⁰Kr, and theβ-strength function of⁸⁹Br and⁹⁰Br below the neutron binding energy is presented. The total decay energy of^89,90Br, as well as of⁸⁹Kr, have been measured by means ofβ γ-coincidences, and the population of excited states in⁸⁹Kr via⁹⁰Br delayed neutrons has been deduced.     

Organometallic chemistry of the transition metals: XXXIII. Some new reactions of cyclopentadienyltetracarbonylniobium

Photolysis of C₅H₅Nb(CO)₄ with excess cycloheptatriene gives the dark brown tetrahapto complex C₅H₅Nb(CO)₂C₇H₈ but no C₅H₅NbC₇H₇ analogous to the corresponding reaction of C₅H₅V(CO)₄ with cycloheptatriene. Photolysis of C₅H₅Nb(CO)₄ with cyclooctatetraene gives the dark green tetrahapto complex C₅H₅Nb(CO)₂C₈H₈, the C₈H₈ ring in this complex remains fluxional below -86° C. Reaction of C₅H₅Nb(CO)₄ with I₂ gives re-brown C₅H₅Nb(CO)₃I₂ in which the carbonyl groups are relatively labile. Thus reaction of C₅H₅Nb-(CO)₃I₂ with (CH₃)₂PCH₂CH₂P(CH₃)₂ under ambient conditions results in the rapid replacement of two CO groups to give C₅H₅Nb(CO)[(CH₃)₂PCH₂CH₂ -P(CH₃)₂]I₂. Treatment of C₅H₅V(CO)₄ with I₂ at room temperature gives the carbonyl-free complex C₅H₅VI₂ with no evidence for any cyclopentadienyl-vanadium carbonyl iodide intermediates.     

ESR in zero field of the photoinduced triplet state in isolated reaction centers of rhodopseudomonas sphaeroides R-26 detected by the singlet ground-state absorbance

We have measured zero-field resonance transitions of the triplet state of the primary donor monitoring the transmittance at 890 nm at 1.2 K in isolated reaction centers of Rhodopseudomonas sphaeroides R-26. The transitions correspond to a decrease in transmittance, confirming the energy transfer model for the transitions detected via the antenna fluorescence in whole cells.     

Neue Strukturen in Polyäthylen-Einkristallen

Ohne Zusammenfassung     

Gross properties of delayed neutron spectra

Envelopes of energy spectra of delayed neutrons from 8 precursors are calculated, taking into account transitions to excited states in the final nuclei. Theoretical branching ratios to these states are presented and compared with the few observed data available.     

Detailed structure of delayed neutron spectra

Theoretical pulse-height spectra for delayed neutrons from 10 precursors are calculated using a Monte Carlo method based on a statistical model. The theoretical spectra are compared with experimental spectra, and rough values for the level density parameters of some of the neutron emitters are suggested.     

Experimental studies of the buckling of complete spherical shells

Complete spherical shells with radius-to-thickness ratios of from 1570 to 2120 were produced by electroforming. For specimens of good quality and for optimum testing conditions, buckling pressures up to 86 percent of the classical value were obtained.The effect of loading-system characteristics was examined by pressurizing spherical shells in rigid and soft systems and no difference in buckling pressure was observed. It was found that buckling behavior is strongly influenced by the nature and severity of flaws or imperfections; i.e., low buckling pressures can be correlated with the presence of severe flaws or nonuniformities.Paper was presented at 1967 SESA Spring Meeting held in Ottawa, Ontario, Can., on May 16–19.     

The postcritical behavior of compressed plates that creep

Summary The deformations of a simply supported rectangular plate are calculated when a uniaxial inplane compressive load is applied to it by means of a rigid platen of a testing machine. This kind of loading enforces a uniform in-plane displacement of the loaded edge and has the consequence that the distribution of the load along the edge becomes increasingly nonuniform as the buckling of the plate becomes more pronounced. The equilibrium, constitutive and compatibility equations are written for a material that deforms elastically and in consequence of steady-state creep but the numerical solution is given for a material that can deform only because of creep. The solution shows that the critical time of the simpler theory in which the load is distributed uniformly does not exist in the case treated here. Nevertheless the critical time is a good indicator of danger because the deformations of the plate increase much more rapidly after the critical time than before.

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Übersicht Es werden die Deformationen einer einfach gelagerten rechteckigen Platte berechnet, die über den starren Balken einer Prüfmaschine auf einachsigen Druck in der Plattenebene belastet wird. Der belastete Rand erleidet dabei eine gleichmäßige Verschiebung, jedoch wird die Lastverteilung längs dieses Randes um so ungleichförmiger, je mehr die Platte ausbeult. Zustandsgleichungen und die Bedingungen für Gleichgewicht und Verträglichkeit werden für elastisch verformbares und stationär kriechendes Material aufgestellt, wobei die numerische Lösung nur für den letztgenannten Fall angegeben wird. Die Ergebnisse zeigen, daß im vorliegenden Fall die kritische Zeit der einfachen Theorie, bei der eine gleichförmige Lastverteilung angenommen wird, nicht existiert. Dennoch ist die kritische Zeit ein gutes Gefahren-Kriterium, weil die Deformationen der Platte nach der kritischen Zeit erheblich rascher anwachsen als davor.

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Dedicated to Professor Dr. H. Görtier on the occasion of his 60th birthday.

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The work reported here was carried out under Contract AF 33 (615) 5115 awarded to Stanford University by the Air Force Flight Dynamics Laboratory at Wright-Patterson Air Force Base, Ohio.