Untersuchungen zur Zerstäubung von höherviskosen Modelllebensmitteln mittels innenmischender pneumatischer Ringströmungsdüsen

Die Sprühtrocknung ist ein weit verbreitetes Verfahren zur Überführung von Lebens-mittelflüssigkeiten in einen festen, pulverförmigen Zustand. Da Trocknungsprozesse zu den energieintensivsten Prozessen der Lebensmittelverarbeitung zählen, gibt es hier ein hohes Energieeinsparpotenzial. Eine Möglichkeit zur Reduktion des Gesamtenergiebedarfs des Sprühtrocknungsprozesses ist die Aufkonzentrierung der verwendeten Konzentrate zu höheren Trockenmassen mittels energiesparender, vorgeschalteter Prozesse. Allerdings steigt mit steigender Trockenmasse auch die Viskosität der zu zerstäubenden Flüssigkeit, was die Zerteilung in feine Tropfen grundsätzlich erschwert. Eine Möglichkeit für die Zerstäubung höherviskoser Flüssigkeiten bei relativ geringem Energieeintrag stellen innenmischende pneumatische Zerstäuber dar, bei denen sich im Düsenauslasskanal eine stabile Ringströmung einstellt. Diese Erkenntnis resultiert unter anderem aus Arbeiten mit einem optisch zugänglichen Effervescent Atomizer [1]. Auf dieser Grundlage wurde ein neues Zerstäuberdesign vorgeschlagen, welches bei geringem Gaseinsatz über einen großen Viskositätsbereich gezielt eine Ringströmung im Düsenauslasskanal erzeugen kann. Bei diesem sogenannten Air-Core-Liquid-Ring Zerstäuber (ACLR) wird das Zerstäubungsgas kurz vor dem Düsenauslasskanal mittels einer Kapillaren zentral in den Flüssigkeitsstrom eingebracht. Dadurch wird gezielt eine Gaskernbildung erzwungen. In dieser Arbeit wurde der ACLR-Zerstäuber hinsichtlich der Zerstäubungseffizienz und –stetigkeit untersucht und mit dem zuvor genannten Effervescent Atomizer verglichen. Der ACLR-Zerstäuber erzielt dabei vergleichbare mittlere Tropfengrößen bei deutlich geringeren Fluktuationen des mittleren Sprühtropfendurchmessers, insbesondere bei gesteigerten Flüssigkeitsviskositäten. Diese geringe Fluktuation ist entscheidend für den Einsatz im Sprühtrocknungsbereich, da hier prozessbedingt eine enge Tropfengrößenverteilung erforderlich ist

Zircon U‐Pb Dating of a Lower Crustal Shear Zone: A Case Study From the Northern Sector of the Ivrea‐Verbano Zone (Val Cannobina, Italy)

A geochronological study was performed on zircon grains from a middle‐lower crustal shear zone exposed in the northern sector of the Ivrea‐Verbano Zone (Southern Alps, Italy) for the first time. The shear zone developed at the boundary between mafic rocks of the External Gabbro unit and ultramafic rocks of the Amphibole Peridotite unit. It is ~10–20 m wide, can be followed along a NE strike for several kilometers, and consists of an anastomosing network of mylonites and ultramylonites. Zircon grains were studied in thin sections and as separates from three representative outcrops along the shear zone. Zircon grains are more abundant in the shear zone compared to wall rocks and are generally equant, rounded to subrounded with dimensions up to 500 μm. U‐Pb data are mainly discordant, and the apparent ²⁰⁶Pb/²³⁸U dates show a large variation from Permian to Jurassic. Isotopic data, combined with microstructural, morphological, and internal features of zircon, reveal an inherited age component and suggest partial zircon recrystallization under high‐temperature conditions during Late Triassic to Early Jurassic. High‐temperature deformation in the shear zone, at lower crustal levels, was coeval with amphibolite to greenschist facies mylonitic deformation at upper crustal levels and is inferred to be related to Mesozoic rifting processes at the Adriatic margin

OCCURRENCE OF LOW-Ti AND HIGH-Ti FREUDENBERGITE IN ALKALI SYENITE

1609 Freudenbergite (Na2Fe 3+ 2Ti6O16) occurs in peralkaline alkali syenite dikes at Katzenbuckel, southwestern Germany, in association with lorenzenite, pyrochlore, landauite and Na–Zr silicates as rare, late-stage mineral phases. Freudenbergite shows a broad range in chemical composition; we recognize two varieties: 1) a “low-titanium ” type, with low concentrations of Ti and all iron in the trivalent state, as established by Mössbauer spectroscopy; this is the normal type of freudenbergite found in a syenite from the Katzenbuckel; 2) a “high-titanium ” type, with elevated concentrations of Ti and high contents of divalent cations (Mg 2+, Mn 2+, Zn 2+) substituting for Fe 2+. Increased concentrations of Nb are the cause of cation deficiency of sodium at the A site. Freudenbergite, up to 0.75 mm in size, is a sector-zoned mineral with selective enrichments in (Nb + Zr) and Ti in sectors (001) and (100), respectively. In one dike (Kb 45), freudenbergite metasomatically replaces primary ilmenite as well as thin exsolutionlamellae within hematite grains. Pseudobrookite, ilmenite, hematite or magnetite occur as Fe–Ti oxides in the freudenbergitebearing syenite samples. Ilmenite–hematite mineral pairs show large miscibility-gaps, and indicate conditions of formation in the range of 750–550°C at low pressures of about of 0.2–0.3 kbar. The unique occurrence of primary freudenbergite is mainly due to an efficient process of fractionation of the peralkaline syenitic melt, leading to a Na- and Ti-rich, but Ca-poor melt accompanied by a distinct enrichment in niobium and zirconium

Mutational analysis of the follicle-stimulating hormone (FSH) receptor in normal and infertile men: identification and characterization of two discrete FSH receptor isoforms.

In a search for pathophysiological causes of idiopathic male infertility we investigated the occurrence of mutations of the FSH receptor in 48 men with this disorder. The entire FSH receptor gene was analyzed by single stranded conformation polymorphism analysis (SSCP). A heterozygous point mutation without functional consequences, exchanging Val to Ala in codon 341, was found in one patient. SSCP analysis led to the identification of 2 polymorphisms in exon 10 associated in 2 discrete FSH receptor allelic variants, i.e. Thr307-Asn680 and Ala307-Ser680. The frequency and distribution of the two allelic variants was further analyzed in 86 proven fathers and 75 infertile men by SSCP (codon 307) and restriction fragment length polymorphism (codon 680). The 2 receptor isoforms showed similar Mendelian distribution in proven fathers and in infertile men. Serum FSH, inhibin B, and combined testicular volume did not differ between subjects with different receptor isoforms. Binding studies in transiently transfected COS-7 cells showed similar binding affinity for the two receptor variants. Moreover, the Ala307-Ser680 and the Thr307-Asn680 FSH receptors responded in vitro to FSH with comparable cAMP production. These data suggest that different isoforms of the FSH receptor with similar functional properties exist in normal and infertile men. We conclude that mutations of the FSH receptor or the FSH receptor genotype do not play a pathogenic role in male idiopathic infertility. The possibility that different FSH isoforms might interact differently with the 2 receptor variants remains to be investigated