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  • Articles  (1,635)
  • Engineering  (937)
  • Rats  (698)
  • 1980-1984  (1,635)
  • Mathematics  (936)
  • Physics  (699)
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  • Articles  (1,635)
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  • 1
    Electronic Resource
    Electronic Resource
    Immobilization osteoporosis and active vitamin D: Effect of active vitamin D analogs on the development of immobilization osteoporosis in rats (1981)
    Springer
    Calcified tissue international 33 (1981), S. 623-630 
    Details
    ISSN: 1432-0827
    Keywords: Osteoporosis ; Immobilization ; Rats ; Vitamin D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The therapeutic effects of vitamin D analogs, 1,24(R)-dihydroxycholecalciferol [1,24(R)(OH)2D3], 1,24(S)-dihydroxycholecalciferol [1,24(S)(OH)2D3], and 1,25-dihydroxycholecalciferol [1,25(OH)2D3] on immobilization osteoporosis were studied in rats. The right hind limb was immobilized through application of a plaster cast following the section of the sciatic nerve. The left hind limb was intact. Vitamin D analogs were orally administered for 6 weeks at dose levels of 0.02 and 0.10µg/kg/day, respectively. The mean lengths of the immobilized femurs were not significantly different from those of the intact femurs in all the experimental groups. In the immobilized femur of animals treated with 1,24(R)(OH)2D3, 0.10µg/kg, dry and ash weights were heavier and calcium and phosphorus contents greater than those in the nontreated group. Furthermore, the amount of calcified bone mass and the cortical thickness of the femurs of the immobilized limb in 1,24(R)(OH)2D3-treated animals were greater than those in the nontreated animals. Treatment with 1,25(OH)2D3 at 0.10µg/kg caused an increase of the bone mass in both immobilized and intact femurs when compared with those of the control group. It was concluded that the administration of 1,24(R)(OH)2D3 diminished the effect of immobilization in the development of osteoporosis without any side effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409500
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  • 2
    Electronic Resource
    Electronic Resource
    Scanning electron microscopy of castrate rat bone (1982)
    Springer
    Calcified tissue international 34 (1982), S. 547-552 
    Details
    ISSN: 1432-0827
    Keywords: Rats ; Osteoporosis ; Anorganic ; Femur ; Castrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The study describes the SEM appearances of endosteal and periosteal surfaces of anorganic femoral diaphyses from 16-month-old normal and castrate male rats. Different types of surfaces could be recognized in both groups. Percentage areas occupied by each surface type were analyzed with a Ladd Data Analyzing Digitizer. Endosteal surfaces were composed of significantly more (P〈0.05) incompletely mineralized, forming surface and significantly less (P〈0.05) completely mineralized, resting surface in castrates than in controls. Both endosteal and periosteal surfaces from experimental bone demonstrated significantly more (P〈0.05) osteoblast lucunae than did control surfaces, and vascular canal entrances were significantly wider (P〈0.001) on castrate endosteal surfaces than on control endosteal surfaces. There was a greater proportion of small nodule forming surface/large nodule forming surface in castrate endosteal bone than in control, and a greater proportion prolonged resting surface/fibrous resting surface in control periosteal bone than in castrate. The results indicate that, when viewed in the SEM, anorganic endosteal and periosteal bone surfaces from femoral diaphyses of old castrate male rats demonstrate appearances characteristic of changes in bone turnover that occur with osteoporosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411302
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  • 3
    Electronic Resource
    Electronic Resource
    Use of dermestid beetles for cleaning bones (1980)
    Springer
    Calcified tissue international 31 (1980), S. 45-47 
    Details
    ISSN: 1432-0827
    Keywords: Dermestid beetles ; Cleaning bones ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Various parts of the skeleton of normal and osteoporotic rats were compared with respect to their dry weight, ash weight, and calcium content when the bones were cleaned byDermestes maculatus beetles or manually. Both techniques gave similar results. This was also true when whole body calcium measured by neutron activation and total skeletal calcium from bones cleaned by the beetles were compared. Thus dermestid beetles are useful as a technique to clean bones, especially for the parts of the skeleton which are difficult to dissect by hand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407166
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of castration on the bone structure of male rats: A model of osteoporosis (1980)
    Springer
    Calcified tissue international 32 (1980), S. 77-82 
    Details
    ISSN: 1432-0827
    Keywords: Osteoporosis ; Castration ; Density ; Femur ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Forty young (23-day-old) and thirty old (1-year-old) male rats were castrated and sacrificed with controls at intervals up to 18 months of age. No differences were observed between femurs or mandibles of rats castrated at 23 days and those of controls. Year-old castrate rats developed femoral osteoporosis after 2 months, which became more pronounced 4 months after castration. This was characterized by reductions in femoral density, dry weight, dry weight per unit length, and ash weight, and by the appearance of resorption cavities in diaphyseal walls and a sparsity of trabeculae in metaphyses and epiphyses of castrate femurs. These results indicate that the year-old castrate male rat may be a valuable experimental model for studies of the treatment of osteoporosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408524
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  • 5
    Electronic Resource
    Electronic Resource
    Role of parathyroid hormone and 1,25-dihydroxyvitamin D3 in the development of osteopenia in oophorectomized rats (1982)
    Springer
    Calcified tissue international 34 (1982), S. 510-514 
    Details
    ISSN: 1432-0827
    Keywords: Rats ; Osteopenia of oophorectomy ; 1,25-Dihydroxyvitamin D3 ; Parathyroid hormone ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effect of ovarian insufficiency on calcium metabolism has been thought to involve an increased bone resorptive effect of parathyroid hormone and possible impaired synthesis of 1,25-dihydroxyvitamin D3. In the present study a rat model allowing for controlled serum levels of parathyroid hormone and 1,25-dihydroxyvitamin D3 was used. Oophorectomy in this species is associated with increased serum levels of 1,25-dihydroxyvitamin D3 and decreased bone mass. Although thyroparathyroidectomy increased bone mass, an increased sensitivity of bone to parathyroid hormone in oophorectomized rats was not observed. Thus the development of the osteopenia did not seem to be related to increased parathyroid hormone sensitivity or to reduced levels of 1,25-dihydroxyvitamin D3. Exogenous 1,25-dihydroxyvitamin D3 increased bone mass in oophorectomized as well as intact rats. Intestinal calcium transport was increased by moderate doses of 1,25-dihydroxyvitamin D3. Intestinal calcium transport was also reduced by thyroparathyroidectomy and increased by the administration of parathyroid extract. A tendency for increased accumulation of 1,25-dihydroxyvitamin D3 in blood in oophorectomized rats has been noted. It is suggested that the tendency to hypercalcemia in ovarian-insufficient females given 1-hydroxylated vitamin D compounds may be related to a diminished metabolism of 1,25-dihydroxyvitamin D3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411294
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  • 6
    Electronic Resource
    Electronic Resource
    A comparative study on the occurrence and activity of extracellular matrix vesicles in young and adult rat maxillary bone (1981)
    Springer
    Calcified tissue international 33 (1981), S. 129-134 
    Details
    ISSN: 1432-0827
    Keywords: Matrix vesicles ; Young/adult ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The occurrence of matrix vesicles in the maxillary bone of normal young and adult rats was demonstrated by both ultrastructural and enzymatic studies. Transmission electron microscopy revealed that the vesicles are invested in trilaminar membranes. Occasionally, crystals were found both within the vesicles and in the surrounding matrix. Separated fractions of vesicles, membranes, and cells were studied biochemically. The amounts of vesicular protein and enzymatic activity per gram bone in the adult rats were significantly lower than in the young. This coincides with the higher number of vesicles observed in the TEM specimens of young rats when compared to that in the old ones. The specific activities of all enzymes examined in the three bone fractions obtained from both young and adult rats were similar. This indicates that no significant difference exists in the enzymatic characteristics of matrix vesicles from the maxillary bone of young and adult rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409425
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  • 7
    Electronic Resource
    Electronic Resource
    Derivation of first-passage time distribution of a single lift for arbitrary traffic (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1-11 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The distribution of the first-passage time is of decisive importance in lift (elevator) design. It yields the easure of performance of the system, the expected number of stops, the interval (i. e. time elapsed between two successive departures from a given floor) and many other parameters and factors determining the required number of lifts in a building. The derivation is based on the transition probability matrix of the operation policy, and consists in solving a system of linear equations.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150102
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  • 8
    Electronic Resource
    Electronic Resource
    On the analysis of accuracy for two-equation transient problems (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 55-62 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Fourier analysis of numerical accuracy has traditionally concentrated on the propagation behaviour of various methods. When systems of equations in more than one unknown are involved, analysis of propagation accuracy alone is shown to be incomplete. A distribution factor is introduced to complement the Fourier analysis in these cases, and application of the concept to two problems commonly encountered in the water resources field is demonstrated. The distribution factor is shown to provide important information which cannot be obtained from the customary analysis of propagation accuracy.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150106
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  • 9
    Electronic Resource
    Electronic Resource
    The limitations of the patch test (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 177-188 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple approximation by nonconforming finite elements is presented that passes the patch test of Irons and Strang but does not yield approximate solutions converging to the solution of the given boundary value problem. It is constructed from continuous piecewise linear functions perturbed by step functions. Further, strange convergence properties of such approximations are explained in all details because they may be typical for the behaviour of nonconforming finite elements violating the basic precondition for convergence.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150203
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  • 10
    Electronic Resource
    Electronic Resource
    Primitive variable finite element formulations for steady viscous flows (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 209-223 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The solution of incompressible, viscous flow problems using the primitive variable finite element approach is formulated in a coherent and physically reasoned exposition. In particular, it is shown that terms associated with changes in momentum caused by lack of mass conservation should logically be included in the governing equations. Previous formulations have not considered this possibility. Numerical results are presented to show the effect of inclusion of these extra terms; however, it is concluded from the numerical results for the specific case which was tested that there is no obvious benefit obtained by including these terms.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150205
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