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  • Computed tomography  (3)
  • Picea abies  (3)
  • Thermodynamics  (3)
  • genes  (3)
  • 1
    Electronic Resource
    Electronic Resource
    A thermodynamic analysis of the secondary transition in the spontaneous precipitation of calcium phosphate (1978)
    Springer
    Calcified tissue international 25 (1978), S. 209-216 
    Details
    ISSN: 1432-0827
    Keywords: Thermodynamics ; Kinetics ; Apatite ; Octacalcium phosphate ; Tricalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A thermodynamic analysis has been made of the secondary transition stage in the spontaneous precipitation of calcium phosphate following the amorphous-crystalline transformation. The first formed crystalline material has a solubility similar to that of octacalcium phosphate (OCP) and the computed thermodynamic solubility product remains invariant in the pH range 7.00–8.60. The duration of the secondary stage is sensitive to pH and the transition appears to occur by hydrolysis of the first formed OCP-like phase to a more basic apatitic phase with a tricalcium phosphate (TCP) stoichiometry. The crystalline material at the end of this transition has an invariant solubility product, in the pH range 7.00 to 8.60, when the TCP-like molecular formula is assumed. Changes in the solution chemistry which accompany the solid-tosolid transitions are consistent with the above conclusions. The results of this study are also consistent with those of a previous study which suggest that the stability of the amorphous calcium phosphate phase is dependent upon the instability of the solution phase with respect to OCP formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010771
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  • 2
    Electronic Resource
    Electronic Resource
    A thermodynamic analysis of the amorphous to crystalline calcium phosphate transformation (1978)
    Springer
    Calcified tissue international 25 (1978), S. 59-68 
    Details
    ISSN: 1432-0827
    Keywords: Amorphous calcium phosphate ; Thermodynamics ; Apatite ; Octacalcium phosphate ; Tricalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A thermodynamic analysis of the precipitation of amorphous calcium phosphate (ACP) and its transformation to crystalline apatite has been made. A nearly constant ion product, over a wide variety of conditions, was obtained for a tricalcium phosphate (TCP)-like phase suggesting that the molecular unit which governs the solubility of ACP may be similar in composition to TCP. The introduction of 10% acid phosphate into the formula for the TCP ion product improves the fit of experimental data and results in an invariant ion product. The stability of ACP in solution was found to be dependent upon its thermodynamic instability with respect to an octacalcium phosphate (OCP)-like phase. The dependence of the induction period for the amorphous to crystalline transformation upon the pH and the Ca/P ratio of the solution is best explained by the assumption that an OCP-like phase is initially nucleated on the surfaces of the ACP particles. The events that occur in the immediate post-transition period suggest the hydrolysis of this OCP-like material to an apatitic phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010752
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  • 3
    Electronic Resource
    Electronic Resource
    Hydroxyl content of solution-precipitated calcium phosphates (1979)
    Springer
    Calcified tissue international 27 (1979), S. 153-160 
    Details
    ISSN: 1432-0827
    Keywords: Hydroxide ; Hydroxyapatite ; Titration ; Precipitation ; Thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A method is described for determination of the titratable hydroxide ion in calcium phosphate precipitates. The procedure requires accurate analysis of the other titratable species in the crystal lattice but is unaffected by the presence of other lattice constituents or impurities. The method was applied to precipitates that had been previously analyzed by solution thermodynamic techniques, and the results were consistent with the earlier observations. The hydroxide content of the precipitates increased with crystal maturity and with increasing pH of the precipitation medium. The hydroxide content of the amorphous phase and the immediate post-amorphous-crystalline transformation phase was shown to be nearly zero. After 3 to 4 days' maturation, the hydroxide content of precipitates prepared at pH values of 7, 8, and 9 was shown to increase to approximately 23, 40, 56% of that required for pure hydroxyapatite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441178
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  • 4
    Electronic Resource
    Electronic Resource
    Imaging local cerebral blood flow by Xenon-enhanced computed tomography — Technical optimization procedures (1988)
    Springer
    Neuroradiology 30 (1988), S. 283-292 
    Details
    ISSN: 1432-1920
    Keywords: Cerebral blood flow ; Computed tomography ; Partition coefficients ; Xenon contrast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Methods are described for non-invasive, computer-assisted serial scanning throghout the human brain during eight minutes of inhalation of 27%–30% Xenon gas in order to measure local cerebral blood flow (LCBF). Optimized Xenonenhanced computed tomography (XeCT) was achieved by 5-second scanning at one-minute intervals utilizing a state-of-the-art CT scanner and rapid delivery of Xenon gas via a face mask. Values for local brain-blood partition coefficients (Lλ) measured in vivo were utilized to calculate LCBF values. Previous methods assumed Lλ values to be normal, introducing the risk of systematic errors, because Lλ values differ throughout normal brain and may be altered by disease. Color-coded maps of Lλ and LCBF values were formatted directly onto CT images for exact correlation of function with anatomic and pathologic observations (spatial resolution: 26.5 cubic mm). Results were compared among eight normal volunteers, aged between 50 and 88 years. Mean cortical gray matter blood flow was 46.3±7.7, for subcortical gray matter was 50.3±13.2 and for white matter was 18.8±3.2. Modern CT scanners provide stability, improved signal to noise ratio and minimal radiation scatter. Combining these advantages with rapid Xenon saturation of the blood provides correlations of Lλ and LCBF with images of normal and abnormal brain in a safe, useful and non-invasive manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328177
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  • 5
    Electronic Resource
    Electronic Resource
    Potential of a new laser target system for percutaneous CT-guided nerve blocks: technical note (2000)
    Springer
    Neuroradiology 42 (2000), S. 838-841 
    Details
    ISSN: 1432-1920
    Keywords: Key words Nerve block ; technology ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A prototype of a laser target device was used for CT-guided nerve blocks in a preliminary series of nine interventions. The system provides guidance from any possible approach. High accuracy of needle insertion was achieved; the average deviation of the planned from the actual angle was 1.4°. The target device is valuable for facilitating minimally invasive therapy and can decrease the time required for the procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340000433
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  • 6
    Electronic Resource
    Electronic Resource
    LCBF values decline while Lλ values increase during normal human aging measured by stable xenon-enhanced computed tomography (1988)
    Springer
    Neuroradiology 30 (1988), S. 463-472 
    Details
    ISSN: 1432-1920
    Keywords: Cerebral blood flow ; Partition coefficient ; Computed tomography ; Stable xenon ; Aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Results of measurements of LCBF and Lλ values utilizing optimal CT-CBF methods under resting conditions are reported among thirty-two neurologically normal volunteers aged between 20 and 88 years. Measurements were made during inhalation of 26–30% stable xenon gas for 8 min and serial scanning utilizing a state-of the-art CT scanner with both eyes closed and ears unplugged. LCBF values for cortical gray matter were lowest in occipital cortex and highest in frontal cortex. Gray matter flow values were also high in subcortical structures with highest values measured in the thalamus. For white matter, highest flow values were measured in the internal capsule. Changes in LCBF and Lλ values were analyzed with respect to advancing age. Significant age-related declines in LCBF values were observed in occipital cortex and frontal white matter. Significant age-related increases in Lλ values were measured in frontal and temporal cortex, caudate nucleus and thalamus. Possible explanations are offered for these age-related increases in Lλ values for gray matter, such as accumulation of lipofuscin in neurons and relative compacting of gray matter with advancing age. The latter increases the numbers of nerve cells sampled per volume of gray matter measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00339684
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  • 7
    Electronic Resource
    Electronic Resource
    Performance of two Picea abies (L.) Karst. stands at different stages of decline (1988)
    Springer
    Oecologia 75 (1988), S. 25-37 
    Details
    ISSN: 1432-1939
    Keywords: Forest decline ; Carbohydrates ; Picea abies ; Growth ; Leaf area index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This is the first in a series of papers on the growth, photosynthetic rate, water and nutrient relations, root distribution and mycorrhizal frequency of two Norway spruce forests at different stages of decline. One of the stands was composed of green trees only while the other included trees ranging in appearance from full green crowns to thin crowns with yellow needles. In this paper we compare the growth and carbohydrate relations of the two stands and examine relationships among growth variables in ten plots. The declining stand produced 65 percent of the wood per ground area compared with the stand in which all trees were green because its foliage produced less wood at any level of leaf area index. The difference in foliage efficiency between the sites could not be explained by differeneces in climate, competition or stand structure. The declining stand appeared to have lower carbon gain as indicated by a smaller increase in reserve carbohydrates before bud break, and weaker sinks for carbohydrates as indicated by less use of the stored carbohydrates than the healthy stand. Thus, growth reduction was probably related to factors which affect both photosynthesis and, even more, the sinks for carbohydrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378810
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  • 8
    Electronic Resource
    Electronic Resource
    Performance of two Picea abies (L.) Karst. stands at different stages of decline (1988)
    Springer
    Oecologia 76 (1988), S. 519-524 
    Details
    ISSN: 1432-1939
    Keywords: Picea abies ; Forest decline ; Xylem flow ; Whole tree transpiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The water relations of Picea abies in a healthy stand with green trees only and a declining stand with trees showing different stages of needle yellowing were investigated in northern Bavaria. The present study is based on observations of trees differing in their nutritional status but apparently green on both sites in order to identify changes in the response pattern which might be caused by atmospheric concentrations of air pollutants and could lead to the phenomenon of decline. Transpiration was measured as water flow through the hydroactive xylem using an equilibrium mass-flow measurement system. Total tree transpiration was monitored diurnally, from July 1985 until October 1985 at both sites. The relationship between transpiration and meteorological measurements indicated that transpiration was a linear function of the vapor pressure deficit. No differences in transpiration of green trees were observed between the two sites. Canopy transpiration was 57%–68% of total throughfall and 41%–54% of total rainfall. Due to this positive water balance, soil water potential at 10 and 20 cm depths remained close to-0.02 MPa (max.-0.09 MPa) for most of the summer. Soil water potential was correlated with the difference between the weekly precipitation and transpiration. No differences in the water relations of apparently healthy trees in the two P. abies stands were observed. It is concluded that differences between green trees at the two sites in terms of nutrient relations or growth rate cannot be explained by changes in whole-tree transpiration or soil water status.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397863
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  • 9
    Electronic Resource
    Electronic Resource
    Performance of two Picea abies (L.) Karst. stands at different stages of decline (1988)
    Springer
    Oecologia 77 (1988), S. 7-13 
    Details
    ISSN: 1432-1939
    Keywords: Forest decline ; Ectomycorrhizas ; Fine roots ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of root tips and apparent ectomycorrhizas was compared in the Fichtelgebirge (FRG) over one growing season in two 30-year-old Picea abies stands, both on soils derived from phyllite but showing varying symptoms of decline. Visual symptoms of tree decline reflected a lower relative and absolute mycorrhizal frequency, a lower number of ectomycorrhizas per m2 leaf area and an uneven vertical distribution of root tips and ectomycorrhizas. The number of apparent ectomycorrhizas per ground area was correlated with the amount of magnesium, calcium, and ammonium, and the pH in the free-drainage soil solution, and with the molar calcium to aluminium ratio in mineral soil extracts. The foliage concentrations of magnesium and calcium were correlated with the numbers of apparent ectomycorrhizas per m2 leaf or ground area. These observations were used to formulate testable hypotheses concerning the role of the root system and the soil environment in forest decline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380917
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  • 10
    Electronic Resource
    Electronic Resource
    Resolving causes of developmental continuity or “tracking.” I. Longitudinal twin studies during growth (1988)
    Springer
    Behavior genetics 18 (1988), S. 133-151 
    Details
    ISSN: 1573-3297
    Keywords: genes ; environment ; development ; growth ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Models of developmental continuity and change in quantitative phenotypes may be tested using longitudinal data from twins. We illustrate a procedure for establishing the power and required sample sizes for detecting developmental transmission against an alternative common-factor hypothesis. We explore the general effects of different heritabilities, different fidelities of environmental and genetic developmental transmission, and varying numbers of occasions of measurement. In addition, a constraint of wide application is postulated for the action of the environment; either environmental effects are transmitted (learned) and occasion specific or they exert a constant influence which is not transmitted (learned). While the situations we examine are necessarily restricted here, our explorations of power show that, providing that we measure on at least four occasions, it is easy to detect developmental transmission with workable sample sizes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067836
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