A comparative study on the modeling of sound pressure field distributions in a sonoreactor with experimental investigation

In sonochemical reactors the effect of emerging cavitation bubbles has significant influence on the amplitude and structure of the developing sound field. Calculations show that the damping parameter and the phase velocity may, depending on the pressure amplitude, change by several orders of magnitude. For example, the sound velocity in water comes to 1500 ms⁻¹, whereas in a bubbly liquid it may decrease to 20 ms⁻¹, which is much below the velocity of sound in air (about 340 ms⁻¹). In this paper, a method of calculating the time dependent three-dimensional pressure field in sonochemical reactors of various shapes is presented. It takes into account inhomogeneous distributed wave parameters which are a function of the spatial depending pressure amplitude. The modeled results are then compared with experimentally measured values of a certain kind of reaction vessel. The agreement is found to be satisfactory.     

φ production in In–In collisions at 158 A GeV

The NA60 experiment has measured muon pair production in In–In collisions at 158 AGeV at the CERN SPS. This paper presents a high statistics measurement of φ→μ μ meson production. Differential spectra, yields, mass and width are measured as a function of centrality and compared to previous measurements in other colliding systems at the same energy. The width of the rapidity distribution is found to be constant as a function of centrality, compatible with previous results. The decay muon polar angle distribution is measured in several reference frames. No evidence of polarization is found as a function of transverse momentum and centrality. The analysis of the p _T spectra shows that the φ has a small radial flow, implying a weak coupling to the medium. The T _eff parameter measured in In–In collisions suggests that the high value observed in Pb–Pb in the kaon channel is difficult to reconcile with radial flow alone. The absolute yield is compared to results in Pb–Pb collisions: though significantly smaller than measured by NA50 in the muon channel, it is found to exceed the NA49 and CERES data in the kaon channel at any centrality. The mass and width are found to be compatible with the PDG values at any centrality and at any p _T : no evidence for in-medium modifications is observed.     

Relationship between the Molecular Structure of Cyanine Dyes and the Vibrational Fine Structure of their Electronic Absorption Spectra

Vibronic sub‐bands in the electronic absorption spectra of symmetrical cyanine dyes (see picture) are attributed to the symmetric C? C valence vibration of the polymethine chain in the excited state. The ³J(H,H) coupling constants in the polymethine chain can be used to characterize the bond localization within the chain in the ground state and thus to explain the intensity distribution of the sub‐bands.

     

Combining reactive and configurational-bias Monte Carlo: confinement influence on the propene metathesis reaction system in various zeolites

In order to efficiently calculate chemical equilibria of large molecules in a confined environment the reactive Monte Carlo technique is combined with the configurational-bias Monte Carlo approach. To prove that detailed balance is fulfilled the acceptance rule for this combination of particular Monte Carlo techniques is derived in detail. Notably, by using this derivation all other acceptance rules of any Monte Carlo trial moves usually carried out in combination with the configurational-bias Monte Carlo approach can be deduced from it. As an application of the combination of reactive and configurational-bias Monte Carlo the influence of different zeolitic confinements (MFI, TON, LTL, and FER) on the reaction equilibrium and the selectivity of the propene metathesis reaction system was investigated. Compared to the bulk phase the conversion is increased significantly. The authors study this reaction system in the temperature range between 300 and 600 K, and the pressure range from 1 to 7 bars. In contrast to the bulk phase, pressure and temperature have a strong influence on the composition of the reaction mixture in confinement. At low pressures and temperatures both conversion and selectivity are highest. Furthermore, the equilibrium composition is strongly dependent on the type of zeolite. This demonstrates the important role of the host structure in catalytic systems.     

Perfect imaging through a disordered waveguide lattice

It is experimentally demonstrated that perfect imaging is possible in disordered wave guiding media, provided that the disorder is off-diagonal, i.e., that only the spacing varies randomly between the otherwise identical lattice sites. On-diagonal disorder or Kerr nonlinearity destroys the imaging.     

J/psi production in Indium-Indium collisions at 158 GeV/nucleon

The NA60 experiment studies muon pair production at the CERN Super Proton Synchrotron. In this Letter we report on a precision measurement of J/psi in In-In collisions. We have studied the J/psi centrality distribution, and we have compared it with the one expected if absorption in cold nuclear matter were the only active suppression mechanism. For collisions involving more than approximately 80 participant nucleons, we find that an extra suppression is present. This result is in qualitative agreement with previous Pb-Pb measurements by the NA50 experiment, but no theoretical explanation is presently able to coherently describe both results.     

Selektive Bestimmung von Niob durch Extraktion des Hydroxychinolinkomplexes

Zusammenfassung Eine selektive, relativ schnell durchführbare photometrische Mikrobestimmung von Mob in Zr-Nb-Legierungen und anderen Materialien wurde ausgearbeitet. Sie beruht auf der Extraktion des Niobs mit einer Oxin/Chloroformlösung und photometrischer Messung bei 385 nm. Störende Elemente werden vor der Extraktion aus H₂O₂-haltiger Lösung mit Natronlauge ausgefällt. Die relative Genauigkeit beträgt ± 3%, die kleinste bestimmbare Menge 1 Nb/10 ml.

---

Summary A selective and fairly rapid method has been worked out for the determination of micro amounts of niobium in Zr-Nb alloys and other materials. It is based on the extraction of Nb with a solution of hydroxyquinoline in chloroform and photometric measurement at 385 nm. Interfering elements are removed before the extraction by precipitation with sodium hydroxide in presence of hydrogen peroxide. The relative accuracy is ± 3%, the minimum quantity to be determined 1 Nb/10 ml.

---

---

Für die kritische Überprüfung meiner Arbeit möchte ich Herrn Dr. H. Züst danken.