Changes in ADC caused by tensile loading of rabbit achilles tendon: evidence for water transport

Water diffusion measurements were performed on rabbit Achilles tendons during static tensile loading and tendons in an unloaded state. The apparent diffusion coefficient (ADC) was measured along two directions: parallel and perpendicular to the long axis of the tendon. Tendons were studied after being prepared in two ways: (a) after being stored frozen in phosphate-buffered saline (PBS) and (b) freshly isolated. Statistically significant directional anisotropy was observed in the ADC in all tendons. The ADC was significantly greater in the direction parallel to the long axis of the tendon than in the perpendicular direction. The anisotropy is attributed to the greater restrictions seen by the water molecules in the perpendicular direction and is consistent with the known geometry of the tendon. Storage in PBS caused tendons to swell. This increased the ADC measured along both directions and reduced the anisotropy. The existence of anisotropy in the ADC was not related to the orientation of the specimen in the magnet. The ADC increased along both directions following the application of a 5-N tensile load; the increase was greatest along the perpendicular axis of the tendon. In order to determine whether load-related changes in the ADC reflected changes in interfibrilar spacing, we used electron microscopy to measure load-related changes in fibril spacing. Load-related changes in fiber spacing could not account for the observed changes in the ADC. The increase in ADC caused by loading was attributed to the extrusion of tendon water into a bulk phase along the outside surface of the tendon. In PBS-stored samples, enough fluid was extruded that it could be visualized. The transient response of the ADC to a 5-N tensile load was also studied. The absolute ADC in both directions increased with loading and recovered to baseline upon unloading. The transient changes in ADC, for both loading and unloading, had a mean time constant of approximately 15 min. The magnitude of the load-induced transient ADC changes was comparable to that seen in the static-loading experiments.     

Wasser

Analytical and Bioanalytical Chemistry -     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

Die Struktur des Anhydro-isocalebassin-methyläthers; Säurekatalysierte Umlagerungen des Curare-Alkaloids C-Calebassin. 60. Mitteilung über Calebassen-Alkaloide [1]

Treatment of the Calebash alkaloid C-calebassine ( 1 ), C₄₀H₄₈N₄O₂⁺⁺·2X^?, with hot mineral acid yielded the anhydro-isocalebassine acid adduct 3H , with the formula C₄₀H₄₇N₄O⁺⁺⁺·3X^?.H₂O. This was converted into anhydro-isocalebassine methyl ether salts ( 4 ) C₄₁H₄₈N₄O⁺⁺·2X^?·H₂O with alkaline dimethyl sulphate. A total X-ray analysis of the orthorhombic diiodide led to formula 4 . The conversion of C-calebassine ( 1 ) into 4 involves a radical change in the central part of the molecule. The structure of the acid adduct 3H can be deduced from the structure of 4. Treatment of 3 H with warm methanol or treatment of C-calebassine ( 1 ) with acetic acid yielded a pale yellow compound 2 , C₄₀, H₄₄N₄⁺⁺·2X^?·H₂O. The central part of the molecule 2 contains a pyrrole ring, and most probably this is an intermediate in the conversion of 1 into 3 H by mineral acid. The changes of 3 H and 2 in acidic, neutral and basic media can be shown by electronic spectroscopy. Reaction of 3 H with 1 mole of oxygen at pH 4 converted it into a stable blood-red oxidation product C₄₀H₄₄N₄O₂⁺⁺·2X^? containing a merocyanine system. The structure 7 , proposed for this compound, is discussed.     

Wasser

Ohne Zusammenfassung     

The channeling of light ions in the cubic and tetragonal (ferroelectrically polarized) phases of BaTiO3

Abstract

The channeling properties of thin BaTiO₃ crystals at temperatures both above and below the ferroelectric Curie point (T _c ? 120°C)have been measured with 3.8 MeV protons. In the cubic phase (T > T _c ), values for critical angles and minimum yields, have been measured for the major crystal axes and planes by detecting backscattered and transmitted protons, and characteristic X-rays. These values are compared with those predicted by current theories of ion channeling. In the tetragonal phase (T < T _c ), measurements were made with single ferroelectric domains. The channeling characteristics of the (100) planes in BaTiO₃ are found to be strongly dependent on the relative orientations of the electric polarization vector P, the (100) planes, and the beam direction. For example, when P lies in the channeling plane, strong channeling occurs; but when P is normal to the plane, the incident beam is rapidly dechanneled. These effects are attributed to the relatively large ionic displacements, and the strong internal electric fields in the ferroelectrically polarized state.     

Stereoselective entry to beta-linked C-disaccharides using a carbon-Ferrier reaction

[structure: see text] The synthesis of unsaturated beta-linked C-disaccharides by the Lewis acid-mediated reaction of 3-O-acetylated glycals with monosaccharide-derived alkenes is described. Deprotection and selective hydrogenation of an exocyclic carbon-carbon double, in the presence of an endocyclic double bond, for representative targets is also illustrated.