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  • Scanning electron microscopy  (3)
  • Composition  (2)
  • Physical Chemistry  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 56 (1995), S. 118-122 
    ISSN: 1432-0827
    Keywords: Osteogenesis imperfecta ; Mineral ; Composition ; Microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract A semiquantitative electron probe X-ray microan-alytical (XRMA) technique, in conjunction with transmission electron microscopy, was used to compare the calcium to phosphorus (Ca/P) molar ratios in calcium phosphate standards of known composition, in normal bone and in bone from patients with osteogenesis imperfecta (OI). Using a modified routine processing and resin embedding schedule, the measured Ca/P molar ratio of calcium phosphates standards of known composition were found to correlate well with the Ca/P molar ratio based on their respective chemical formulae. This technique was then used to compare the Ca/P molar ratio in normal human bone and in OI bone. The Ca/P ratio values for normal bone (Ca/P=1.631) correlated well with those for chemically prepared hydroxyapatite (Ca/P=1.602), but in bone from OI patients, the Ca/P molar ratio was significantly lower (Ca/P=1.488). This study has shown that there is a lower Ca/P molar ratio in OI bone compared with normal, matched bone. This suggests that the mineral deviates from the carbanoapatite usually found in bone. Isomorphous substitutions in the carbanoapatite lattice could account for this although this study has neither proved nor disproved this. The altered bone mineral is an-other factor that could contribute to the increased fracture rate observed in OI.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Islets of Langerhans ; Microangioarchitecture ; Corrosion casts ; Scanning electron microscopy ; Naja naja, Vipera russelli, Echis carinatus (Serpentes)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Due to a decided lack in the literature of reports on the microangioarchitecture of the pancreas of snakes, an analysis was performed in three different species of two different ophidian families with the use of cast preparations and complementary scanning electron microscopy. The vascular architecture reflects the lobular substructure of the pancreas; the organ is supplied by branches of the superior mesentric artery. Coiled lobular arteries and arterioles continue into a meshwork of capillaries. Dilated capillaries of the endocrine portion of the pancreas are an integral component of this fine capillary network. A few very small capillaries establish a connection between the endocrine and the exocrine pancreas. The other capillaries drain into venules, which ultimately join their respective veins. No interspecific differences were noted in the vascularization of the pancreas of the three ophidian species examined. The present results suggest the existence of arterio-venous anastomoses and speak against the presence of a portal system, but establish a feed-forward capillary connection from the endocrine to the exocrine component of the ophidian pancreas.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 250 (1987), S. 425-429 
    ISSN: 1432-0878
    Keywords: Pineal organ ; Angioarchitecture (capillaries,arteries, veins) ; Corrosion-cast preparation method ; Scanning electron microscopy ; Salmo gairdneri
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The angioarchitecture of the pineal organ of the rainbow trout (Salmo gairdneri) was investigated by means of the corrosion-cast preparation method and scanning electron microscopy. Two main arteries (aa. epiphyseales) supply the pineal parenchyma. They emerge from the aa. cerebri anteriores and run in the fissure between the prosencephalon and the mesencephalon. After entering the pineal stalk, the aa. epiphyseales branch off into several arterioles, most of which extend to the pineal end-vesicle where they give rise to a lobular, bilaterally symmetric capillary network. Capillaries establishing the main portion of the pineal vessels appear widened in comparison to those supplying other portions of the brain and resemble capillaries in other endocrine organs. In Salmo gairdneri, no specialized system of portal vessels appears to exist between the pineal organ and other portions of the brain.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-5604
    Keywords: Key words Osteogenesis imperfecta ; Mineral ; Composition ; FTIR ; 31P-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fourier transform infrared spectroscopy and 31P solid-state nuclear magnetic resonance spectroscopy were used to determine if any structural or compositional differences in osteogenesis imperfecta (OI) bone mineral could be detected that might help to explain the bone fragility observed in this disease. A previous study by Cassella et al. used an electron probe X-ray microanalytical technique to compare the calcium to phosphorus (Ca/P) molar ratios in normal bone and bone from patients with OI. It was demonstrated that bone from OI patients had a lower Ca/P molar ratio. This study demonstrated that OI bone mineral had a general hydroxyapatite structure and that isomorphous substitutions in the carbanoapatite lattice could account for the low Ca/P molar ratio.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 223 (1982), S. 231-234 
    ISSN: 1432-0878
    Keywords: Pancreas (cat) ; Islet of Langerhans ; Vascularization ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pathways of microcirculation in the pancreas of the cat were investigated by scanning electron microscopy of Mercox preparations of the vascular bed. A portal system from islet to exocrine vessels as well as a direct arterial flow to the exocrine pancreas have been observed. Sphincters appear to exist in portal capillaries at the border between the endocrine and exocrine portions of the pancreas. Islets possess an independent venous drainage.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 28 (1996), S. 705-711 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dioxotetracyanomolybdate(IV) has been found to form a 1 : 2 complex with 2,2′-bipyridyl. The kinetics of the reaction has been studied over the pH range 5.3-8.7 by visible spectrophotometry under pseudo conditions. The effect of the 2,2′-bipyridyl and dioxotetracyanomolybdate(IV), temperature, ionic strength, and pH on the reaction rate was determined. The reaction follows first-order kinetics with respect to dioxotetracyanomolybdate(IV) ion and fractional-order kinetics with respect to 2,2′-bipyridyl. Values for the outer-sphere complex formation constant (Kos2) and rate constants (k2) were also calculated from the kinetic data. It was found that rate of the reaction increases with the decreasing pH. The following rate equation based on the outersphere complexation equilibrium preceding the associative interchange has been derived.\documentclass{article}\pagestyle{empty}\begin{document}$$\rm {{1}\over{{\it k}_{obs}}}={{1+K_{a2}[H^+]}\over{B_1[2,2\prime-bipyridyl]}}+B_2$$ ${\rm where}$ $\rm B_1={\it k}_1K_{os1}+{\it k}_2K_{os2}[H^+]K_{a2}$ ${\rm and}$ $\rm B_2={{K_{os1}+K_{a2}K_{os2}[H^+]}\over {{\it k}_1K_{os1}+{\it k}_2K_{os2}[H^+]K_{a2}}}.$\end{document}On the basis of the observed results probable mechanism has been proposed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 29 (1997), S. 819-824 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An investigation is presented on the kinetics of complexation of aqueous solution of octacyanomolybdate (IV) and -tungstate (IV) after photoinitiation with one of the mixed group ligands containing both N and O, diethanolamine (DEOA), [NH(CH2CH2OH)2]. Under the steady state conditions and with approximation k3 〉 k4 over a range of concentrations, the observed rate law is:\documentclass{article}\pagestyle{empty}\begin{document}$$ \cal{k}_{\rm obs.}={\cal{k}_{2}\cal{k}_{4}\rm {I}_{a}[\rm {OH}^{-}][\rm {NH}(\rm{CH}_{2}\rm{CH}_{2}\rm{OH})_{2}]\over \rm{I}+\it \cal{k}_{2}[\rm {OH}^{-}]} $$\end{document}The complexes show shift in electronic transition supporting the mechanism of association of the ligand followed by the abstraction of some small molecules and then substitution by the ligand. The presence of the specific isobestic point also contributes towards the stability of the complex. The rate constant and quantum yield values are dependent on both the concentration of the metal cyanide and the ligand predicting the mechanism to be an associative one. The complexes have strong absorption in the visible range and are assigned metal-to-ligand electron transfer transition. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 819-824, 1997
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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