No abstract

Supramolecular structure of initially wet bacterial cellulose of Acetobacter xylinum has been investigated by X‐ray scattering including synchrotron radiation, transmission electron microscopy, and 13C‐CP/MAS‐NMR‐spectroscopy. As a result a model is given of never dried swollen microfibrillar ribbons consisting of 5 to 12 waterfree Iα‐crystalline subunits with a cross‐section of about 7 nm × 13 nm and of water solvating the subunits. Lateral aggregation of these crystalline units was found along the smaller (110)‐lattice planes with a layer of water between adjacent crystallites. The NMR‐spectrum of wet bacterial cellulose exhibits an additional C‐1 line component indicating cellulose‐water interactions. During drying lateral dimensions of the microfibrillar ribbons, crystallite sizes, as well as the overall crystalline order decrease, whereas the Iα/Iβ‐ratio of about 80/20 remains approximately unchanged. Conclusions were drawn with regard to the early states of structure formation of bacterial cellulose.

The proposed cryofixation technique uses a tubule-shaped needle chilled in liquid propane for simultaneous excision and freezing of a tissue specimen. Due to this simultaneity, ionic shifts created by traumatic influences are avoided even in the outermost cells of the specimen.Moreover, it is shown here that stopping the blood flow for more than about 10 s results in notable ionic shifts between cells and extracellular space in rat heart and liver. Such preparative ischaemic injury is minimized by the Fast Cryofixation Technique because it can be easily performed on organs within the circulatory system, whilst the heart of the animal is still beating.Intracellular concentrations of the monovalent ions in rat heart and liver, obtained by this method, tally well with recent results from different independent techniques reported in the literature.As demonstrated by cross-sectioning and freeze-fracturing, the structural preservation of the freezing technique is sufficient for X-ray microanalytical work.

Amino resin microcapsules are prepared from partial etherified melamine-formaldehyde resins without other additives. As model substance for the core material mainly methylparathion was used. The influences of different parameters on the encapsulation process, the capsule morphology and some capsule properties were investigated. I t is shown that by this method capsules with average diameters between 5 and 50 pn and a wall thickness between 30 and 300 nm can be obtained. The encapsulation of liquids as well as solids is possible. First ideas to the mechanisms of the capsule formation are discussed. Aminoharz-Mikrokapseln. I I . Herstellung und MorphologieAminoharz-Mikrokapseln wurden aus partiell veretherten Melamin-Formaldehyd-Harzen ohne weitere Zusatzstoffe hergestellt. Als Modellsubstanz fur das Kernmaterial wurde Methylparathion verwendet. Die Einflusse verschiedener Parameter auf den VerkapselungsprozeS, die Kapselmorphologie und einige Kapseleigenschaften wurden untersucht. Mit der beschriebenen Methode lassen sich Kapseln mit mittleren Durchmessern zwischen 5 und 50 ym und Wanddicken zwischen 30 und 300 nm herstellen. Erste Vorstellungen zum Mechanismus der Kapselbildung werden diskutiert. MuKpoKanynbk na ocnoee afiunosoLi cfionbk. I I . H3zomosnenue u fiopgfionoeuw MAKpOHaIICyJIbI H a OCHOBe aMHHOBOfi CMOJIbI H3I'OTOBJIeHbI 113 9aCTM4HO 3TepH@HIJHpOBaHHbIX MenaMHH@OpMaJIjJe-rHjT,HbIX CMOJI Be3 AO6aBOK. B Ka4eCTBe MOjJeJIbHOFO BeweCTBa AJIH HQa HCnOJIb30BaJIH MeTHJIIIapaTHOH. ~CCJIe~O-Ba.IOCb BJIHJTHHe pa3JIH4HbIX IIapaMeTpOB H a IIpO~eCC 06pa30BaHHH KaIICyJI, H a HX MOp@OJIOFHH, H HeKOTOpbIe HX CBOfiCTBa. OnHCaHHbIM MeTOAOM MOXIHO I13I'OTOBHTb KaIlCyJIbI CO CpeAHHM AHaMeTpOM 5-50 MKM H C TOJILI(HH0m CTeHKH 30-300 HM. 06CYXIRalOTCR IIepBbIe COO6paxteHHf3 OTHOCHTeJIbHO MeXaHH3Ma 06pa30BaHHJT RaIICyJI.