Threshold behavior of the formation of nanometer islands in a Ge/Si(100) system in the presence of Sb

Atomic-force microscopy is used to study the behavior of an array of Ge islands formed by molecular-beam epitaxy on an Si (100) surface in the presence of an antimony flux incident on the surface. It is shown that, as the Sb flux increases to a certain critical level, the surface density of the islands increases; however, if this critical level is exceeded, nucleation of the islands is suppressed and mesoscopic small-height clusters are observed on the surface. This effect is explained qualitatively in the context of a kinetic model of the islands’ formation in heteroepitaxial systems mismatched with respect to their lattice parameters.     

Comparison of different methods to determine the spreadability and firmness of processed cheese

Summary Current texture-measuring instruments and a recently developed measuring method (two-dimensional measuring of the force necessary to spread a sample) were compared in measuring the spreadability of processed cheese. How far subjective assessment by a qualified panel correlates with the instrumental results in determining spreadability and firmness was also investigated. Samples of processed cheese with various consistencies were measured by an Universal testing machine, a buttermeasuring instrument (DIN 10331), a rotational-type rheometer (oscillation mode) and a two-dimensional force measuring instrument. The evaluation of the results shows that an oscillating rheometer is most suitable to measure the spreadability of processed cheese; the correlation coefficient (r) between the dynamic Weissenberg number, calculated from parameters of the rheometer, and the subjective judgement by the panel wasr=0.91. For the determination of firmness the two-dimensional force measuring instrument is most suitable. The correlation coefficient between the parameter tangential energy (S _t) and the sensorially evaluated firmness wasr=0.95.

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Vergleich verschiedener Bestimmungsmethoden für die Streichfähigkeit und Festigkeit von Schmelzkäse

Zusammenfassung Verschiedene gebräuchliche Meßinstrumente und ein neu entwickeltes Gerät zur zweidimensionalen Messung der Kräfte, die zum Ausstreichen einer Probe erforderlich sind, wurden vergleichend zur Charakterisierung der Streichfähigkeit von Schmelzkäse erprobt. Dabei wurde auch geprüft, inwieweit die subjektiven Beurteilungen eines qualifizierten Prüferpanels mit den Meßwerten für Streichfähigkeit und Festigkeit korrelierten. Gemessen wurde mit einer Universalprüfmaschine, dem Butterprüfgerät (DIN 10331), einem Rotationsrheometer und mit dem zweidimensional registrierenden Kraftmeßgerät. Dabei zeigte sich, daß das Rheometer im oscillierenden Modus die Streichfähigkeit am besten zu charakterisieren vermag. Die Korrelation zwischen den Rheometerwerten, berechnet als dynamische Weissenbergzahl, und den sensorisch ermittelten Werten für die Streichfähigkeit betrugr=0,91. Zur Bestimmung der Festigkeit ist das zweidimensional registrierende Kraftmeßgerät am besten geeignet, was sich in einem Korrelationskoeffizienten vonr=0,95 zwischen dem ParameterS _t und den im Sensoriktest ermittelten Werten für dieFestigkeit ausdrückt.

     

Zur Analytik von Zuckercouleuren I. Mitteilung: Differenzierung der Couleurklassen mittels Curiepunkt-Pyrolyse-Capillargaschromatographie-Massenspektrometrie

Summary After an introduction on the production, classification, legislative regulations, toxicology, and analysis of caramel colours, a report is given on the examination of these colourings by Curie-point pyrolysis-capillary gas chromatography-mass spectrometry. This method enables the differentiation between the four classes of caramel colours on the basis of the most concentrated of more than 100 identified pyrolysis products, which requires small quantities of substance (100 g) and short periods of time (1 h).

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Zur Analytik von Zuckercouleuren I. Mitteilung: Differenzierung der Couleurklassen mittels Curiepunkt-Pyrolyse-Capillargaschromatographie-Massenspektrometrie

Zusammenfassung Nach einer Einführung zur Herstellung, Klassifizierung, rechtlichen Stellung, Toxikologie und Analytik der Zuckercouleure wird über die Untersuchung dieser Farbstoffe mittels Curiepunkt-Pyrolyse-Capillargaschromatographie-Massenspektrometrie berichtet. Anhand der konzentrationsstärksten der über 100 identifizierten Pyrolyseprodukte ist es möglich, die vier Couleurklassen bei geringem Substanz- (100 g) and Zeitbedarf (1 h) sicher zu differenzieren.

     

A note on the aerodynamic diameter and the mobility of non-spherical aerosol particles

The aerodynamic diameter of a non-spherical aerosol particle is primarily related to the final settling velocity of the particle. The aerodynamic diameter is not obtained directly from mobility measurements by formally calculating a sphere diameter from the mobility equation for a spherical particle. Instead, a correction factor involving the dynamic shape factor of the non-spherical particle must be applied.     

Unterscheidung von Palmölen und Palmöl-Fraktionen durch HPLC der Triglyceride

Analytical Characterisation of Palm Oil Fractions by HPLC of Triglycerides The increasing importance of palm oils and palm oil fractions in international trade makes it necessary to develop analytical criteria for the characterisation of these products. One problem is the correct identification of palm oleins, which are often difficult to distinguish from palm oils. These products frequently exhibit similar fatty acid by GLC and similar iodine values. The correct identification of palm stearins by GLC is comparatively more easy. Palm oleins and palm oils can be characterized by HPLC using conditions that permit not only the separation of triolein from less unsaturated triglycerides of the same carbon number, but also, at the same time, a separation of tripalmitin from triglycerides containing oleic acid. By establishing the peak area ratios for a number of selected triglycerides a clear differentiation between palm oils and palm oleins, as well as various other palm oil fractions and their mixtures is obtained.     

Einfluß der Produkteigenschaften auf die Trocknung

Influence of Product Properties on Drying. A number of items of information are required for selection and design of a drying process. Thermodynamic equilibrium as well as heat and mass transfer are the traditional prerequisites for describing the drying operation. In the development of a drying process further specific properties of the product must be known. These properties, such as chemical reactions or sticking properties, greatly reduce the number of possible drying processes. For this reason, the measurement of these properties plays an important role in the development of a drying process. Many of the bench scale tests in use do not have a physical basis, but have been developed empirically because the physical context is often unknown. Yet a number of physically well-defined methods are available for product characterization. In practical work a combination of empirical and scientifically defined methods is used.     

A Complete and Highly Effective Mothproofing Agent Comprising a Pyrethroid and a Hexahydropyrimidine

Pyrethroids, considered as a general class of compounds, have been shown to provide effective protection from the larvae of the keratin-digesting insects Tineola bisselliella H., Tinea pellionella Linn., Hofmannophila pseudo-spretella Station and Attagenus piceus Oliv. The position regarding the susceptibility of the furniture carpet beetle to pyrethroids is less clear, however. It has been reported that both deltamethrin and permethrin are effective against Anthrenus flavipes Le Conte, whilst permethrin is also reported elsewhere to be effective against the same species. Results obtained in our laboratory, however, have indicated that pyrethroids may offer inadequate protection against Anthrenus vorax Waterh. [1, 2]. This latter species is identical to Anthrenus flavipes var. seminiveus Casey, a colour variety of Anthrenus flavipes Le Conte. The 1,3-disubstituted5-phenylcarbamoyl-2,4,6-trioxo- and 4,6-dioxo-2-thione-hexahydropyrimidine derivatives described in this paper exhibit a surprisingly high and selective toxicity to the Anthrenus species. Thus, a combination of an appropriate hexahydropyrimidine with a suitable pyrethroid, e.g. permethrin, provides complete control of a wide range of commonly encountered textile insect pests. The influence of substituents on the mothproofing activity is discussed.