Possibility of Recoating of Impurities on Product Kaolin during Froth Flotation - HRTEM-EDS Study

Attempts were made to remove the Fe, Ti minerals from Gujarat kaolin by SC-HGMS and ultraflotation to improve the optical properties. The removal of Fe was higher by SC-HGMS, but that of Ti was almost the same by both techni-ques. The Fe content of the products was relatively low, but the brightness was lower than the expected. A drastic improvement in brightness was observed for the SC-HGMS product compared to the ultra flotation product. One of the probable reasons for the low enhancement in brightness by flotation was thought to be recoating of the impurities on the clay surface during flotation. XPS study conducted on the flotation product ruled out the possibility of such a coating. HRTEM-EDS analyses showed that most of the titania is present in the form of anatase particles of very small size. A part of the Fe forms independent parti-cles of goethite /hematite having nano size. Rest of the Fe is found to be closer to anatase or kaolinite particles either as a part of the structure or nano sized independ-ent particles adhering to the surface and hence is not easily separated. The ultra fine grains of Fe stained ana-tase remaining in the kaolinite surface after flotation is found to have a strong pigment effect. During flotation, high shear energy is given for dispersion and conditioning which is possibly reducing the particle size to sub-micron / nano level. The dissatisfying brightness of the flotation product is attributed to the presence of these fine / colloidal impurities. Fe content in the product samples is relatively low and its influence on brightness is probably smaller than that of the Fe stained anatase. The organic matter and ferriferous smectite identified in the sample even at small percentages may also have a pig-ment effect due to their dark color and colloidal distri-bution

Mechanochemical synthesis of nanocrystalline lead selenide

Mechanochemical synthesis of lead selenide PbSe nanoparticles has been performed by high-energy milling of lead and selenium powder in a planetary ball mill Pulverisette 6 (Fritsch, Germany) and in an industrial eccentric vibratory mill ESM 654 (Siebtechnik GmbH, Germany). Structural properties of the synthesized lead selenide were characterized by X-ray diffraction, which confirms crystalline nature of PbSe nanoparticles (JCPDS 6-354). The average size of PbSe crystallites of 37 nm was calculated from XRD data by Williamson-Hall method. The methods of particle size distribution analysis, specific surface area measurement, scanning electron microscopy and transmission electron microscopy were used for characterization of surface, mean particle size, and morphology of PbSe. An application of industrial mill verified a possibility of the synthesis of a narrowband-gap semiconductor PbSe at ambient temperature and in a relatively short reaction time

Is there a common water-activity limit for the three domains of life?

Archaea and Bacteria constitute a majority of life systems on Earth but have long been considered inferior to Eukarya in terms of solute tolerance. Whereas the most halophilic prokaryotes are known for an ability to multiply at saturated NaCl (water activity (a w) 0.755) some xerophilic fungi can germinate, usually at high-sugar concentrations, at values as low as 0.650-0.605 a w. Here, we present evidence that halophilic prokayotes can grow down to water activities of <0.755 for Halanaerobium lacusrosei (0.748), Halobacterium strain 004.1 (0.728), Halobacterium sp. NRC-1 and Halococcus morrhuae (0.717), Haloquadratum walsbyi (0.709), Halococcus salifodinae (0.693), Halobacterium noricense (0.687), Natrinema pallidum (0.681) and haloarchaeal strains GN-2 and GN-5 (0.635 a w). Furthermore, extrapolation of growth curves (prone to giving conservative estimates) indicated theoretical minima down to 0.611 a w for extreme, obligately halophilic Archaea and Bacteria. These were compared with minima for the most solute-tolerant Bacteria in high-sugar (or other non-saline) media (Mycobacterium spp., Tetragenococcus halophilus, Saccharibacter floricola, Staphylococcus aureus and so on) and eukaryotic microbes in saline (Wallemia spp., Basipetospora halophila, Dunaliella spp. and so on) and high-sugar substrates (for example, Xeromyces bisporus, Zygosaccharomyces rouxii, Aspergillus and Eurotium spp.). We also manipulated the balance of chaotropic and kosmotropic stressors for the extreme, xerophilic fungi Aspergillus penicilloides and X. bisporus and, via this approach, their established water-activity limits for mycelial growth (∼0.65) were reduced to 0.640. Furthermore, extrapolations indicated theoretical limits of 0.632 and 0.636 a w for A. penicilloides and X. bisporus, respectively. Collectively, these findings suggest that there is a common water-activity limit that is determined by physicochemical constraints for the three domains of life

Intraoperative Flüssigkeitstherapie bei Pankreasresektionen - Die Sicht des Chirurgen

Obwohl die intra- und perioperative Infusionstherapie bei großen chirurgischen Eingriffen in der Vergangenheit mehrfach thematisiert wurde, bestehen nach wie vor keine Evidenz-basierten Empfehlungen zu Art und Menge der empfohlenen Infusionslösungen. Der vorliegende Beitrag erläutert die Thematik aus Sicht des Chirurgen. Für den Chirurgen sind vor allem der Einfluss größerer Flüssigkeitsmengen auf Wund- und Anastomosenheilung, Blutungskomplikationen sowie den postoperativen Verlauf (Extubationszeitpunkt, postoperative Darmfunktion, Krankenhausverweildauer, usw.) von Interesse. Zur Klärung der Frage, wie eine aus chirurgischer Sicht anzustrebende intraoperative Infusionstherapie beschaffen sein sollte, werden Angaben aus der Literatur und eigene Daten herangezogen. Die retrospektive Analyse von 98 Pankreasresektionen an unserer Klink ergab keine signifikanten Unterschiede bezüglich der Häufigkeit von Nachblutung (8,2 %), Wundheilungsstörung (4,1 %), Pankreasfisteln (9,4 %) und Mortalität (2,0 %) in Abhängigkeit von der Flüssigkeitsgabe. Die Komplikationsrate war vergleichbar mit der anderer Autoren. Die durchschnittliche Infusionsmenge betrug 13,9 ± 0,9 mL / kg / h. In 74 % aller Operationen wurden Katecholamine und in 54 % Noradrenalin appliziert. Auch wenn diese Qualitätsmessgrößen weiteren Variablen unterworfen sind, lässt sich anhand dieser Ergebnisse ableiten, dass die intraoperative Gabe von 10-15 mL / kg / h keinen negativen Einfluss auf das Outcome nach Pankreasresektionen hat und sich somit die intraoperative Volumentherapie an diesen Werten orientieren sollte