Schwingungsspektren des käfigstrukturierten PAs3S3

Vibrational Spectra of the Cage Compound PAs₃S₃ The vibrational spectrum of crystalline PAs₃S₃ and the raman spectrum of the molten title compound have been recorded. The assignment of the frequencies is proposed mainly based on polarization data of a PAs₃S₃ solution in white phosphorus. In the molten state a partial decomposition takes place according to 2 PAs₃S₃ ? P₂As₂S₃ + α-As₄S₃.     

Diffusion of macromolecular solutions in the boundary layer

Summary This paper concerns the study of a diffusion layer of macromolecular solutions annularly injected in a cylindric pipe in turbulent flow. The study includes firstly the analysis of the longitudinal and transversal projections of the concentration gradient, secondly the study of the state of turbulence in the diffusion layer.The concentrations are determined by the measurement of the concentration salt (salt was added to the injected solution). A mathematical model of the development of concentration is proposed.The turbulent state of diffusion layer has been studied with Laser-Doppler-Anemometry. An analysis of Eulerian autocorrelation and the power spectral density has been done.

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Zusammenfassung Es werden Ergebnisse über die turbulente Diffusionsschicht von nicht-newtonschen Flüssigkeiten (PÄO) mitgeteilt, die an der Wand eines kreiszylindrischen Rohrs injiziert werden. Diese Untersuchungen betreffen die Analyse der Längs- und Querkomponenten des Konzentrationsgradienten in der Diffusionsschicht und im Turbulenzfeld.Die Konzentrationen werden mit Hilfe von Salz (NaCl) gemessen, das der injizierten Polymerlösung beigefügt worden ist. Ein mathematisches Modell für die Konzentrationsverteilung wird vorgeschlagen.Der Turbulenzzustand der Diffusionsschicht wird mit Hilfe der Laser-Doppler-Anemometrie untersucht. Die Eulersche Autokorrelation und das Intensitätsspektrum werden analysiert.

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Nomenclature c polymer concentration (wppm) - c ₀ wall value ofc - c _i value ofc at the slot - D diameter of the pipe - e slot thickness - L ₀ distance from the slot at which the wall concentration drops toe ^–1of its original value - m distance in meter from the slot - U means freestream velocity - u _i injection velocity - x distance from the slot - y normal distance from the surface - boundary layer thickness - characteristic height of the diffusion, i. e. the value ofy at whichc/c ₀ = 0.5 With 4 figures     

Diffusion of macromolecular solutions in the turbulent boundary layer of a cylindrical pipe

A model is presented describing the changes that occur in the diffusion boundary layer upon injection of a macromolecular solution (PEO) into a cylindrical pipe under turbulent flow conditions (Re 40,000). A shape parameter was introduced to describe the shape of the turbulent plume. The value of this parameter was found to be the same for water and various dilute PEO solutions. The proposed model gives a good approximation at low homogeneous concentrations. x downstream distance from the slot - y normal distance from the wall - R radius of the pipe - C concentration - C _w wall concentration - Q _i flow rate injection - Q _t flow rate - C _j =C _i *Q _i /Q _t equivalent homogeneous polymer concentration - L _tf characteristic length of the diffusion plume - characteristic height of the diffusion plume, i.e. the value ofy at whichC/C _w = 0.5 - thickness of the diffusion boundary layer - x ₀ characteristic distance from the slot, i.e. the value ofx at which/R = 1/2 - ⁺ shape parameter of the diffusion boundary layer - ⁺ —/R nondimensionalized variables - x ⁺ —x/L _tf nondimensionalized variables     

Über die Struktur von geschmolzenem Selendioxid

About the Structure of Molten Selenium Dioxide The Raman spectra of molten and gaseous selenium dioxide are nearly identical. The number of bands indicates the existence of a temperature depending equilibrium of monomeric and dimeric selenium dioxide in the molten and the gaseous state. A chain structure as in the crystal could not be found. An oxygen-bridged planar ring seems most likely for the structure of the dimer. Broadening of bands two intense, polarized lines at ν = 955/966 cm^?1 indicate an equilibrium of the trans-(C_2h) with the cis-structure (C_2v).     

Schwingungsspektren von β-P4S5 und P4S7

Vibrational Spectra of β-P₄S₅ and P₄S₇ The vibrational spectra of the solid and liquid cage compounds β-P₄S₅ and P₄S₇ have been recorded. The assignments of the frequencies are proposed mainly based on polarization data. β-P₄S₅ decomposes during melting into P₄S₃ α-P₄S₇ and β-P₄S₆. Molten α-P₄S₇ dissociates to some extent into β-P₄S₆ and sulphur. An association of β-P₄S₆ with α-P₄S₇ is discussed for the molten state. All reactions in molten P₄S₇ are reversible.     

Diffusion of macromolecular solutions in the turbulent boundary layer of a cylindrical pipe — Evolution of wall concentration

Summary In this paper, we are presenting a model of the evolution of the wall concentration of a macromolecular solution (PEO) annularly injected in a cylindrical pipe in a turbulent flow. This model valid for all diffusion zones is based on mathematical and physical considerations and proves to be in good agreement with the experimental data.

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Zusammenfassung Es wird ein Modell der Entwicklung der Wandkonzentration einer makromolekularen Lösung (PÄO) vorgestellt, die in einem wandnahen Ringspalt in die turbulente Strömung durch ein zylindrisches Rohr injiziert worden ist. Dieses für alle Diffusionszonen gültige Modell basiert auf mathematischen und physikalischen Betrachtungen und erweist sich für die Beschreibung der experimentellen Daten als gut geeignet.

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C _w wall concentration - C _i initial concentration before injection - L ₀ distance from the slot at which the wall concentration drops toe ^-1 of its original value - L _IT ,L _IF ,L _F characteristic lengths - L _I length scale of the second region - x downstream distance from the source - n _I ,n _T ,n _F characteristic exponents - K ₀,K _I ,K _F characteristic constants - ln natural logarithm - q _i flow rate of injection - Q _T flow rate - C _j =C _{i · q i} /Q _T concentration in homogeneous medium - A, B, C, m constants - p andq annex variables - Re Reynolds number With 7 figures     

Diffusion of macromolecular solutions in the turbulent boundary layer of a cylindrical pipe

This paper presents a model for the evolution of a transversal concentration profile of a macromolecular solution (PEO) injected into a cylindrical pipe at turbulent flow conditions (R 40000). This model, based on the diffusion of a scalar quantity emitted by two diametrically opposed point sinks, proves to be in good agreement with the experimental data. C concentration - C _w wall concentration - C _i initial concentration before injection - x downstream distance from the slot - y normal distance from the wall - characteristic height of diffusion, i.e. the value ofg at whichC/C _w = 0.5 - n characteristic exponent - R radius of pipe - D diameter of pipe - a, b constants - L _m mixing length, i.e. the value ofx at whichC _w /C _i =Q _i /Q _T - Q _i flow rate of injection - Q _T flow rate - f, g annex functions - n ₀ maximal value ofn     

Analysis of ionic fragments from 308 nm photoablation of polyimide

The ionic products from excimer laser photoablation (=308 nm) of polyimide (Kapton) film have been studied as a function of fluence. Large ion masses up to about 900a.m.u. are easily observed, the mass distribution depending strongly on the fluence. Velocities of the emitted particles lie between 1400 and 10 000 ms^–1, again dependent on the fluence. A mechanism to explain the high velocities is suggested consisting of ionisation of the surface polymer molecules followed by a Coulomb explosion combined with expansion of the high density gas formed by the photoablation.     

Schwingungsspektren von As4S4 und As4Se4

Vibrational Spectra of As₄S₄ and As₄Se₄ The vibrational spectra of solid α- and β-As₄S₄ and the Raman spectrum of molten As₄S₄ have been recorded. The assignments of the frequencies are proposed mainly based on polarization data. The Raman melt spectra suggest that As₄S₄ molecules (symmetry D_2d) are retained in the molten state. A partial decomposition of the melt by prolonged laser irradiation was observed. The Raman spectrum of solid As₄Se₄ is presented and the frequencies are tentatively assigned to an As₄Se₄ molecule of the cradle type, possessing D_2d symmetry.