Comparison of dynamic mechanical and dielectric thermal analysis on cure studies for composites

Dielectric measurements covering a wide frequency range provide one of the few practical methods for monitoring the cure of thermosets (epoxy, etc.) using relatively non-intrusive sensors. The measurements form the basis of a manufacturing control cycle, in the autoclave, provided the rheological state of the thermoset can be related to the dielectric constant (¹) and loss factor (tan). The present paper concerns further investigations in our laboratory of the correlation between mechanical and dielectric behaviour during cure (1).

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Zusammenfassung Dielektrische Messungen über einem weiten Frequenzbereich stellen die eine Methode dar, um unter Anwendung verhältnismässig nicht-intrusiver Fühler die Aushärtung von Duroplasten /Epoxid usw./ verfolgen zu können. Die Messungen bilden die Grundlage für einen Pertigungsüberwachungskreis des Autoklaven, da der rheologische Zustand des Duroplast mit der Dielektrizitätskonstanten // und dem dielektrischen Verlustfaktor /tan/ in Verbindung gebracht werden kann. Vorliegende Arbeit berichtet über weitere Untersuchungen unseres Laboratoriums über den Zusammenhang zwischen mechanischem und dielektrischen Verhaltens während der Aushärtung.

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120–230°. 2 3590 . . . 150°, . .

     

Rotating flow past an elliptic-cylindrical bump of large aspect ratio

Summary Very slow flow of a rapidly rotating fluid past a right cylindrical obstacle of heightd on one of two co-rotating parallel planes, separated by a distanceh, is studied. The elliptic boundaryvalue problem for the geostrophic flow is formulated quite generally, and solutions are given for an infinitely-long ridge and an elliptic cylinder. A modified Ekman number,E _*v/d ², where is the inverse aspect ratio of the cylinder, characterizes the latter solution. ForE _*<1, the fluid flows around a stagnant Taylor column over the elliptic cylinder; forE _*1, the fluid flows over the cylinder as though it were an infinitely-long ridge;E _*=O(1) shows part of the fluid flowing over, and part around, the cylinder. The drag increases from orderE ^–1/4 to orderE ^–1 asE _* increases from small to large values.

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Zusammenfassung In dieser Arbeit wird die sehr langsame Strömung in einem rasch rotierenden Fluid untersucht um einen zylindrischen Körper, dessen Höhed die viel kleiner ist als die Distanzh der zwei unendlich ausgedehnten mitrotierenden parallelen Platten, welche das Fluid begrenzen; der Körper sitzt auf der unteren Platte. Eine allgemeine Formulierung des elliptischen Randwertproblems wurde für die geostrophische Strömung angegeben. Lösungen wurden für ein unendlich langes Wehr und einen elliptischen Zylinder gefunden. Eine modifizierte Ekman-Zahl,E _*=v/d ² E, in welcher das reziproke Verhältnis von Länge zu Durchmesser darstellt, charakterisiert die Lösung für den elliptischen Zylinder. WennE _*1, umgeht die Flüssigkeit die stagnierende Taylorsäule, die auf dem elliptischen Zylinder ruht; wennE _*1, geht die Flüssigkeit über den Zylinder, als ob er ein unendlich langes Wehr wäre; wennE _*=0(1), geht ein Teil der Flüssigkeit über den Zylinder und ein anderer um ihn herum. Der Reibungswiderstand erhöht sich von 0(E ^–1/4) zu 0(E ^–1), wennE _* von kleinen zu grossen Werten ansteigt.

     

Structural Characterization of the Condensation Polymer of Dipyridine Manganese II Dichloride with 1,3-Di-4-piperidy I propane

The synthesis of polymers derived from the condensation of dipyridine manganese II dichloride with 1,3-di-4-piperidylpro-pane is described. Structural analysis of the polyamines is detailed utilizing results based on infrared, thermal, elemental and solution analyses.     

Uranyl peroxide ((UO2)(O2)·4H2O; UO4) precipitation for uranium sequestering: formation and physicochemical characterization

Journal of Radioanalytical and Nuclear Chemistry - Applicability of uranium peroxide ((UO2)(O2)·4H2O; UO4) precipitation to remove uranium from secondary wastewaters, generated as part of a...     

Uncovering the Stoichiometry of Pyrococcus furiosus RNase P,a Multi‐Subunit Catalytic Ribonucleoprotein Complex,by Surface‐Induced Dissociation and Ion Mobility Mass Spectrometry

We demonstrate that surface‐induced dissociation (SID) coupled with ion mobility mass spectrometry (IM‐MS) is a powerful tool for determining the stoichiometry of a multi‐subunit ribonucleoprotein (RNP) complex assembled in a solution containing Mg²⁺. We investigated Pyrococcus furiosus (Pfu) RNase P, an archaeal RNP that catalyzes tRNA 5′ maturation. Previous step‐wise, Mg²⁺‐dependent reconstitutions of Pfu RNase P with its catalytic RNA subunit and two interacting protein cofactor pairs (RPP21⋅RPP29 and POP5⋅RPP30) revealed functional RNP intermediates en route to the RNase P enzyme, but provided no information on subunit stoichiometry. Our native MS studies with the proteins showed RPP21⋅RPP29 and (POP5⋅RPP30)₂ complexes, but indicated a 1:1 composition for all subunits when either one or both protein complexes bind the cognate RNA. These results highlight the utility of SID and IM‐MS in resolving conformational heterogeneity and yielding insights on RNP assembly.     

Bright quasi-phase-matched soft-X-ray harmonic radiation from argon ions

Selective enhancement (>10(3)) of harmonics extending to the water window (approximately 4 nm) generated in an argon gas filled straight bore capillary waveguide is demonstrated. This enhancement is in good agreement with modeling which indicates that multimode quasi-phase-matching is achieved by rapid axial intensity modulations caused by beating between the fundamental and higher-order capillary modes. Substantial pulse energies (>10 nJ per pulse per harmonic order) at wavelengths beyond the carbon K edge (approximately 4.37 nm, approximately 284 eV) up to approximately 360 eV are observed from argon ions for the first time.     

Uncovering the Stoichiometry of Pyrococcus furiosus RNase P,a Multi‐Subunit Catalytic Ribonucleoprotein Complex,by Surface‐Induced Dissociation and Ion Mobility Mass Spectrometry

We demonstrate that surface‐induced dissociation (SID) coupled with ion mobility mass spectrometry (IM‐MS) is a powerful tool for determining the stoichiometry of a multi‐subunit ribonucleoprotein (RNP) complex assembled in a solution containing Mg²⁺. We investigated Pyrococcus furiosus (Pfu) RNase P, an archaeal RNP that catalyzes tRNA 5′ maturation. Previous step‐wise, Mg²⁺‐dependent reconstitutions of Pfu RNase P with its catalytic RNA subunit and two interacting protein cofactor pairs (RPP21?RPP29 and POP5?RPP30) revealed functional RNP intermediates en route to the RNase P enzyme, but provided no information on subunit stoichiometry. Our native MS studies with the proteins showed RPP21?RPP29 and (POP5?RPP30)₂ complexes, but indicated a 1:1 composition for all subunits when either one or both protein complexes bind the cognate RNA. These results highlight the utility of SID and IM‐MS in resolving conformational heterogeneity and yielding insights on RNP assembly.     

Portable capillary liquid chromatography for pharmaceutical and illicit drug analysis

A newly developed portable capillary liquid chromatograph was investigated for the separation of various pharmaceutical and illicit drug compounds. The system consists of two high‐pressure syringe pumps capable of delivering capillary‐scale flow rates at pressures up to 10 000 psi. Capillary liquid chromatography columns packed with sub‐2 μm particles are housed in cartridges that can be inserted into the system and easily connected through high‐pressure fluidic contact points by simply applying a specific, predetermined torque rather than using standard fittings and less precise sealing protocols. Several over‐the‐counter analgesic drug separations are demonstrated, along with a simple online measurement of tablet dissolution. Twenty illicit drug compounds were also separated across six targeted drug panels. The results described in this study demonstrate the capability of this compact liquid chromatography instrument to address several important drug‐related applications while simplifying system operation, and greatly reducing solvent usage and waste generation essential for onsite analysis.     

Toward high-performance computational chemistry: I. Scalable Fock matrix construction algorithms

Several parallel algorithms for Fock matrix construction are described. The algorithms calculate only the unique integrals, distribute the Fock and density matrices over the processors of a massively parallel computer, use blocking techniques to construct the distributed data structures, and use clustering techniques on each processor to maximize data reuse. Algorithms based on both square and row-blocked distributions of the Fock and density matrices are described and evaluated. Variants of the algorithms are discussed that use either triple-sort or canonical ordering of integrals, and dynamic or static task clustering schemes. The algorithms are shown to adapt to screening, with communication volume scaling down with computation costs. Modeling techniques are used to characterize algorithm performance. Given the characteristics of existing massively parallel computers, all the algorithms are shown to be highly efficient for problems of moderate size. The algorithms using the row-blocked data distribution are the most efficient. © 1996 by John Wiley & Sons, Inc.