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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Decisions in economics and finance 7 (1984), S. 67-77 
    ISSN: 1129-6569
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Description / Table of Contents: Riassunto Si risolve il problema della sostituzione ottimale perdue en componenti con un singolo pezzo di «unloaded standby». La soluzione è determinata dai costi relativi del guasto per ogni componente ed è indipendente dal tempo specifico in cui il guasto è avvenuto, salvo che sia assunta l'immediata sostituzione. Si derivano condizioni per l'esistenza di una politica basata su un solo numero critico e si studia la politica generale.
    Notes: Abstract The problem of optimal replacement for two andn components with a single unloaded standby is solved. The solution is determined by the relative costs of failure for each component and is independent of the actual failure time, other than immediate replacement being specified. Conditions for the existence of a single critical number policy are derived and the general policy is described.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 52 (1993), S. 263-268 
    ISSN: 1432-0827
    Keywords: Osteoporosis ; Bone density ; Postmenopausal ; Vertebral collapse ; Bisphosphonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Bone mineral density (BMD) at the lumbar spine, femoral neck, trochanteric region, and Ward's triangle was measured using dual-energy X-ray absorptiometry (DXA) in 118 women with osteoporotic vertebral collapse (average age 65 years), divided into four groups according to numbers and SD of vertebral deformation below norms: group 1:-3SD deformations only; group 2: one-4SD deformation; group 3: two-four-4SD deformations; and group 4: 5 or more-4SD deformations. There were no significant differences between the groups. Results were compared with those from 80 premenopausal (average age 32 years, range 20–40 years) and 109 postmenopausal normal women (average age 64, range 60–70 years). Mean BMD in osteoporotic group 1 was lower than premenopausal normal women by 32% at the lumbar spine, 31% femoral neck, 30% trochanteric region, and 44% at Ward's triangle, and postmenopausal controls by 17% lumbar spine, 16% femoral neck, 17% trochanter, and 14% Ward's triangle. There was a clear trend to reduction in mean BMD between osteoporotic groups 1 and 4 at all four measured sites with significant differences at the spine of 0.102 g/cm2 (P〈0.01) and Ward's triangle 0.059 g/cm2 (P〈0.01). When compared with premenopausal controls, there was a reduction in mean BMD between osteoporotic groups 1 and 4 of 10% at the lumbar spine, 7% femoral neck, 8% trochanteric region, and 13% Ward's triangle. Receiver operating characteristic analysis showed no significant differences in diagnostic sensitivities among the four measured sites for vertebral fractures. We conclude from this crosssectional data that the majority of bone loss in spinal osteoporosis occurs before the onset of fractures.
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  • 13
    ISSN: 1433-2965
    Keywords: Key words:Bisphosphonate – Bone density – Osteoporosis – Pamidronate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: The effect of oral pamidronate on bone mineral density and its adverse effect profile was investigated by a double-masked placebo-controlled study of 122 patients aged 55–75 years with established vertebral osteoporosis. Patients on active therapy received disodium pamidronate 300 mg/day (group A) for 4 weeks every 16 weeks, 150 mg/day (group B) for 4 weeks every 8 weeks or placebo (group C). All patients additionally received 500 mg of calcium and 400 IU vitamin D daily. Dual-energy X-ray absorptiometry measurements of the spine, hip, forearm and total body were performed at baseline and 6-monthly for 2 years using a Hologic QDR 1000 device at two sites. Serum osteocalcin and urinary deoxypyridinoline were measured at the above visits and at 3 months. The percentage change (SEM) in spine bone mineral density (BMD) at 2 years based on intention-to-treat analysis was 4.64 (1.01) in group A, 6.10 (0.87) in group B and 1.13 (1.32) in group C. Analysis of variance showed significant increases in group A and B compared with placebo (p〈0.01). There were also significant rises in femoral neck BMD for group A (p = 0.005), trochanter BMD for groups A and B (p〈0.01) and total-body BMD for groups A and B (p〈0.001). There was a significant reduction in serum osteocalcin and urinary deoxypyridinoline for groups A and B (p〈0.01). There was an excess of gastrointestinal side-effects in the treated groups, particularly group A. We conclude that intermittent pamidronate therapy can prevent bone loss at both the lumbar spine and femoral neck in patients with established vertebral osteoporosis, although due to gastrointestinal side-effects the 300 mg dose in particular does not appear suitable for clinical usage.
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  • 14
    ISSN: 1433-2965
    Keywords: Bone mineral measurements ; Broadband ultrasonic attenuation ; Ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a study of broadband ultrasonic attenuation (BUA) in the calcaneus in 248 women. Measurements were performed with a Walker-Sonix UBA-575 ultrasonic bone analyser. The populations studied were 15 healthy young volunteers (group 1, mean age 26 years), 200 healthy pre- and postmenopausal women (group 2, mean age 53 years) and 33 osteoporotic women with vertebral crush fractures (group 3, mean age 66 years). Subjects in group 1 each had 10 repeated measurements of their right heel. Duplicate BUA measurements in the right heel were performed in 96 subjects and bilateral scans in a further 87 women in group 2. The remaining 17 subjects in group 2 and those in group 3 had a single scan of the right heel. All women in groups 2 and 3 had dual X-ray absorptiometry (DXA) scans of the lumbar spine and femoral neck. The precision study on the women in group 1 gave a root mean square (RMS) coefficient of variation (CV) of 4.2%. Individual CV results showed statistically significant differences (range 1.3%–7.6%). Duplicate scans in subjects in group 2 gave a RMS CV of 4.6% while the bilateral measurements showed no significant difference between the two heels. Linear regression analysis gave the following relationship between BUA and age: BUA=87.1−0.76 (Age −40) dB/MHz (r=−0.31,p〈0.001, SEE=14.0 dB/MHz). Multivariate regression analysis showed that, in addition to age, years since the menopause was also a significant factor in predicting BUA. In the first 5 years following the menopause BUA decreased by 2.5%/year, while in the next 5 years the decrease fell to 0.5%/year. The BUA measurements in the osteoporotic subjects in group 3 gave a mean T-score of −2.1 compared with 66 premenopausal normal women and a mean Z-score of −1.0 compared with 27 age-matched elderly normal women in group 2. In comparison the lumbar spine DXA measurements for the same women gave a mean T-score of −3.2 and a mean Z-score of −1.8. DXA therefore gave substantially better discrimination between osteoporotic and normal subjects than the BUA measurements.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Osteoporosis international 4 (1994), S. 67-71 
    ISSN: 1433-2965
    Keywords: Bone mineral density ; DXA ; Osteoporosis ; Spine ; Vertebrae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The significance of variability in bone mineral density (BMD) between lumbar vertebrae L1 to L4 in the same individual was investigated by dual-energy X-ray absorptiometry in 1000 normal women aged 40–60 years (average 52 years) and 145 women aged 45–80 years (average 65 years) with vertebral osteoporosis. The mean BMD increased from L1 to L4 in normal women from 0.841 g/cm2 to 1.017 g/cm2, and in osteoporotics from 0.562 g/cm2 to 0.709 g/cm2.Z scores for osteoporotic women (Z = osteoporotic BMD — age-normal BMD/normal SD) were significantly lower for individual vertebrae compared with Ll–4 and at L4 compared with L1, L2 and L3 (p〈0.001). The mean difference betweenZ scores for the highest and lowest vertebrae in an individual was 0.70 for normals (SD=0.40) and 0.64 for osteoporotics (SD=0.36). The mean Z score difference between the L1–4Z score and the lowest individual vertebralZ score was 0.36 for normals (SD=0.23) and 0.06 for osteoporotics (SD=0.31). However, receiver operating analysis (ROC) curves showed that the lowestZ score for any individual vertebra did not provide improved discrimination between normals and osteoporotics when compared with the L1–4Z score. The area under the ROC curve for L1–4 was significantly greater than for individual vertebrae (p〈0.05) and that for L4 was significantly smaller than for L1, L2 or L3 (p〈0.001). In conclusion, L1–4 BMD gives greater diagnostic sensitivity for osteoporosis than individual vertebrae, and L1, L2 and L3 are better than L4. Although there is considerable individual variation inZ scores for different vertebrae in the same individual, the lowest vertebralZ score does not offer improved diagnostic sensitivity over the L1–4Z score.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 252 (1974), S. 501-503 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the light of these findings and the known existence of sulphated polysaccharides and proteoglycans in connective tissue, it is appropriate to seek a role for such polyanions in growth control in such tissues. We have obtained dextran sulphate resistant cultures of normal hamster BHK/21 cells and ...
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  • 17
    ISSN: 1432-0827
    Keywords: Bone mineral measurements ; Broadband ultrasonic attenuation ; Calcaneus ; Ultrasonic velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Measurements of broadband ultrasonic attenuation (BUA) and velocity of ultrasound through the heel (heel velocity, HV) were performed with a Contact Ultrasonic Bone Analyzer (CUBA-Research model) in 229 women. The subjects consisted of 16 healthy young volunteers (Group 1, mean age 26 years), 170 healthy pre- and postmenopausal women (Group 2, mean age 53 years), and 43 osteoporotic women with radiographically defined vertebral crush fracture (Group 3, mean age 66 years). Subjects in Group 1 had 10 repeated measurements in a study of short-term precision. Women in Groups 2 and 3 also had dual X-ray absorptiometry (DXA) scans to measure lumbar spine and femoral neck bone mineral density (BMD). The BUA and HV measurements for all 229 women showed a significant correlation (r = 0.75,P 〈 0.001). The precision study on the subjects in Group 1 gave a root mean square coefficient of variation of 6.3% for BUA and 1.04% for HV. Linear regression analysis gave the following relationship between BUA and age for the 170 normal women in Group 2: BUA = 83.6 − 0.86 (age 40) dB/MHz (r = −0.31,P 〈 0.001, SEE = 16.3 dB/MHz). The relationship between HV and age was as follows: HV = 1614 − 2.3 (age 40) m/s (r = −0.33,P 〈 0.001, SEE = 42 m/s). Multivariate regression analysis showed that in addition to age, years since the menopause was also a significant factor in determining both BUA and HV. In the first 5 years following the menopause, BUA and HV decreased by 2.2% and 0.3%/year, respectively, whereas in the next 10 years the rates of decrease fell to 0.5% and 0.03%/year. The BUA and HV measurements on the 43 osteoporotic subjects in Group 3 gave mean T-scores of −2.1 and −1.9 compared with 59 premenopausal women, and mean Z-scores of −1.3 and −0.9 compared with 26 age-matched normal women in Group 2, respectively. In comparison, the lumbar spine and femoral neck DXA measurements in the same subjects gave mean T-scores of −2.9 and −2.1 and mean Z-scores of −1.7 and −1.0, respectively. Lumbar spine BMD gave the best discrimination between women with osteoporotic vertebral fractures and normal subjects. However, the difference between the lumbar spine and BUA Z-scores was not statistically significant. Femoral neck BMD was equivalent to the ultrasound parameters in T-score and Z-score values.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 23 (1996), S. 1634-1635 
    ISSN: 1619-7089
    Keywords: Breast milk ; Hexamethylpropylene amine oxime ; Labelling efficiency ; Technetium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There are no published data for the activity of technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) found 1in breast milk. The amount of radioactivity in breast milk following the administration of 500 MBq99mTc-HMPAO for a brain perfusion study has been measured. The effective dose to the infant was calculated to be 0.26 mSv, so necessitating no interruption of breast feeding. Unbound99mTc is readily secreted into breast milk and the effective dose will remain less than 1 mSv if the99mTc-HMPAO labelling effici ency is ≥99% for the worse reported case, and could remain 〈1 mSv for the mean reported case for99mTc-HMPAO labelling efficiencies down to 94%.
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 1619-7089
    Keywords: Meniscal tears ; Single-photon emission tomography ; Arthroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Bone single-photon emission tomography (SPET) was performed in 40 patients within 6 months of acute knee injury where internal derangement of the knee was suspected, and the results related to the arthroscopy findings. Scan features with high sensitivity, specificity, and predictive accuracy for a meniscal tear could not be obtained on planar imaging. However, a half-crescent or more of increased tibial plateau activity on transaxial SPET gave a sensitivity of 89%, a specificity of 76%, a positive predictive accuracy of 77% and a negative predictive value of 89%. For longitudinal (bucket handle) tears alone the optimum scan pattern was a full crescent of increased tibial plateau activity with adjacent femoral activity and increased blood pool activity which gave corresponding values of 78%, 94%, 78% and 93%. It is concluded that the inclusion of tibial plateau activity of less than a full crescent and the presence of femoral condyle and blood pool activity in the diagnostic criteria improves the ability of bone SPET to detect meniscal tears. The value of bone SPET in the diagnosis of meniscal tears suggests that it could have a significant role to play in the management of knee injuries.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Clinical rheumatology 13 (1994), S. 455-458 
    ISSN: 1434-9949
    Keywords: Bone Density ; Fracture ; Menopause ; Bisphophanate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Clinical experience with cyclical etidronate for the treatment of osteoporosis was reviewed in 69 consecutive patients. Six patients stopped treatment either due to adverse effects (5) or the decision to take hormone replacement therapy (HRT) (1). Bone mineral density (BMD) measurements using dual energy X-ray absorptiometry (DXA) were obtained in 63 patients (33 with spinal osteoporotic fractures and 30 with osteopenia) before and 1 year after treatment. BMD increased by an average of 4.50% (p〈0.001) in the lumbar spine (range +14% to −12%) and 5.5% (p〈0.01) at Ward's triangle (range +31% to −13%) while there was no significant change at the femoral neck (range +11% to −12%) and greater trochanter (range +12% to −15%). Significant rises in BMD were found at the lumbar spine and Ward's triangle in both osteoporotic and osteopenic groups. Of patients analysed after 1 year, 83% had an increased bone mass at the lumbar spine and 55% at the femoral neck. We conclude that there is a whide variation in the bone mass response to cyclical etidronate therapy, and in a minority of patients bone mass does not increase. For the majority of osteoporotic patients, however, we confirm the efficacy and tolerability of cyclical etidronate for the preservation of bone mass over 1 year in a clinical setting.
    Type of Medium: Electronic Resource
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