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  • Springer  (51)
  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The analysis of total Hg in various environmental matrices was investigated using energy dispersive X-ray fluorescence (EDXRF) for both powdered and digested samples and cold vapor atomic absorption (CV-AAS) for digested samples. Several microwave decomposition procedures were evaluated with respect to the determination of Hg by CV-AAS and EDXRF. The use of different acid mixtures, microwave power settings and decomposition times were compared as well as the analysis on wet and freeze-dried samples. A set of standard reference samples were used to evaluate the procedures: NBS Citrus leaves (1572), NRC Pine needles (1575), NRC Dogfish muscle tissue (DORM-2), NRC Dogfish liver tissue (DOLM-2), BCR Human hair (397), BCR Coking coal (181) and NRC Marine sediment (PACS-1). An H2SO4/HNO3/H2O2 acid mixture was found to be optimal for the complete mineralization and digestion of biological samples for Hg by CV-AAS whereas for EDXRF both the HNO3/H2O2 and H2SO4/HNO3/H2O2 acid mixture gave good results. The detection limit of EDXRF could significantly be decreased (from 0.2 μg/g to 0.058 μg/g) by performing the analysis with digested samples. A good agreement was obtained between CV-AAS and EDXRF analysis. The obtained results were also in good agreement with certified values. The methods were applied to environmental samples (coal, trees, leaves, spinach, fish, sediments) and human hair in a coal mining area and in places where they use coal for cooking in Vietnam.
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  • 2
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es wurde eine numerische Untersuchung über den Wärmeverlust durch freie Konvektion mit Wasser in einem horizontalen Kreiszylinder mit konstant fallender Wandtemperatur angestellt. Die besondere Situation bei Wasser mit dem Dichtemaximum bei 4 °C wurde mit dimensionslosen Relationen formuliert, ausgehend von der linearen Beziehung zwischen dem Wärmeausdehnungskoeffizienten von Wasser und der Temperatur. Diese Näherung führt zu einer erschöpfenden Lösung in Termen einer nichtlinearen Rayleigh-Zahl. Die Verknüpfung zur üblichen Situation, in der die Hypothese der linearen Beziehung zwischen Dichte und Temperatur anwendbar ist, wird ebenso hergestellt. Im einzelnen wird gezeigt, daß die Ergebnisse des quasi-stationären Zustands, die durch die Normalsituation erreicht werden, zu Gleichgewichtskurven werden, in die das System mit steigender Differenz zwischen Begrenzungstemperatur und 4 °C einläuft. Eine vollständige numerische Lösung kann für den nichtlinearen Bereich der Rayleigh-Zahl von 0 bis 107 angegeben werden. Vorläufige numerische und experimentelle Ergebnisse am waagerechten Kreiszylinder werden diskutiert und umgerechnet auf die Terme der derzeitigen dimensionsbehafteten Näherung.
    Notes: Abstract A numerical study is made of the heat loss by natural convection of water within a horizontal circular cylinder with wall temperature decreasing at a constant rate. The particular situation of water with maximum density at 4 °C is formulated in dimensionless relations based on a linear relationship between the water thermal expansion coefficient and the temperature. Such an approach leads to an exhaustive solution in terms of a non linear Rayleigh number. The link is also established with the standard situation where the hypothesis of a linear relationship between density and temperature is applicable. In particular it is shown that the quasi steady state results obtained for a standard situation become equilibrium curves to which the system tends with increasing difference between the temperature of the boundary and 4 °C. A complete numerical solution is obtained for non linear Rayleigh numbers ranging between 0 and 107. Previous numerical and experimental results on the horizontal circular cylinder are also discussed and recast in terms of the present dimensional approach.
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  • 3
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung  In der Arbeit wird über die Ergebnisse einer numerischen Studie, betreffend die stationäre Konvektionsströmung und den stationären Wärmeübergang in einer rechteckigen, mit einem porösen, phasenveränderlichen Medium (PCM) verfüllten Kavität, berichtet. Den zwei vertikalen Berandungen der Kavität sind zwei, den Schmelzpunkt des PCM einschließende Temperaturen aufgeprägt, während die beiden horizontalen Berandungen adiabat gehalten werden. Das poröse Medium ist durch einen anisotropen Permeabilitätstensor charakterisiert, dessen Hauptachsen bezüglich des Gravitationsvektors beliebig orientiert sein können. Das Problem ist durch das Seitenverhältnis A, die Rayleigh–Zahl Ra, das Anisotropienverhältnis R und den Orientierungswinkel Θ des Permeabilitätstensor bestimmt. Hauptaugenmerk gilt dem Einfluß der anisotropen Permeabilität auf das Strömungsverhalten und den Wärme-übergang beim Phasenwechselprozeß flüssig/fest. Die Lösungsmethode basiert auf dem Kontrollvolumenprinzip in Verbindung mit der Landau-Transformation über welche das irreguläre Strömungsgebiet in ein rechteckiges abgebildet wird. Ergebnisse bezüglich Strömungsfeld, Temperaturverteilung, Phasengrenzenort und Wärmeübergang werden fürA=2, 5;Ra=40; 0≤Θ≤π; 0, 25≤R≤4 mitgeteilt. Es zeigte sich, daß der Gleichgewichtszustand des Phasenwechselsprozesses fest/flüssig sowohl durch das Anisotropieverhältnis R als auch durch den Orientierungswinkel Θ des Permeabilitätstensors wesentlich beeinflußt werden kann. Zum einen existiert bei festgehaltenen ParameternA, Ra undR eine optimale Orientierung Θmax, bei der die Stromstärke, das Flüssigkeitsvolumen und der Wärmestrom Maximalwerte erreichen, während für Θmin=Θmax+π/2 Minimalwerte resultieren. Ist das anisotrope Medium entlang der Optimalrichtung Θmax orientiert, so ergibt sich zum anderen, daß eine Vergrößerung der in diese Richtung fallenden Permeabilitätskomponente die Stromstärke und den Wärmestrom in gleichem Maße erhöht, während eine Vergrößerung der anderen Permeabilitätskomponente nur vernachlässigbaren Einfluß hat. In den untersuchten Parameterbereichen lag die Optimalrichtung zwischen dem Gravitationsvektor und der Hauptstromrichtung.
    Notes: Abstract  This paper reports on the results of a numerical study of convection flow and heat transfer in a rectangular porous cavity filled with a phase change material under steady state conditions. The two vertical walls of the cavity are subject respectively to temperatures below and above the melting point of the PCM while adiabatic conditions are imposed on the horizontal walls. The porous medium is characterized by an anisotropic permeability tensor with the principal axes arbitrarily oriented with respect to the gravity vector. The problem is governed by the aspect ratioA, the Rayleigh numberRa, the anisotropy ratioR and the orientation angle θ of the permeability tensor. Attention is focused on these two latter parameters in order to investigate the effects of the anisotropic permeability on the fluid flow and heat transfer of the liquid/solid phase change process. The method of solution is based on the control volume approach in conjunction with the Landau-transformation to map the irregular flow domain into a rectangular one. The results are obtained for the flow field, temperature distribution, interface position and heat transfer rate forA=2.5,Ra=40, 0≤θ≤π, 0.25≤R≤4. It was found that the equilibrium state of the solid/liquid phase change process may be strongly influenced by the anisotropy ratioR as well as by the orientation angle θ of the permeability tensor. First, for a given set of parametersA,Ra andR, there exists an optimum orientation θmax for which the flow strength, the liquid volume and the heat transfer rate are maximum. There also exists an orientation θmin=θmax+π/2 for which these quantities are minimum. Second, when an anisotropic medium is oriented along the optimum direction θmax, an increase of the permeability component along that direction will increase the flow and heat transfer rate in a same order while an increase of the other permeability component only has a negligible effect. For the parameter ranges considered in the present study, it was found that the optimum direction is lying between the gravity vector and the dominant flow direction.
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  • 4
    ISSN: 1433-2965
    Keywords: Key words:Hip fracture – Morbidity – Osteoporosis – Quality of life
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: To examine longitudinal change in health- related quality of life (HRQoL) following hip fracture in elderly subjects, 32 patients with hip fractures and 29 sex-matched non-fracture control subjects (mean ± SD age 82 ± 8 and 86 ± 6 years respectively) were enrolled in a prospective, case–control study. Fracture subjects completed a generic questionnaire, Short Form 36 (SF-36), and a disease-targeted measure, the revised Osteoporosis Assessment Questionnaire (OPAQ2), on two separate occasions, within 1 week of fracture and 12–15 weeks after fracture. Controls completed both questionnaires on two occasions 12 weeks apart. SF-36 scores were significantly correlated with OPAQ2 in comparable domains of Physical Function (r= 0.76), General Health (r= 0.70) and Mental Health/Tension (r = 0.86). Control subjects had stable scores with the OPAQ2 and SF-36. At 3 months after fracture there was a significant reduction in HRQoL in the SF-36 domains Physical Function (–51%), Vitality (–24%) and Social Function (–26%) and in the OPAQ2 domains Physical Function (–20%), Social Activity (–49%) and General Health (–24%). Hip fracture patients thus had a lower baseline HRQoL and experienced a significant deterioration in HRQoL after hip fracture on both the SF-36 and OPAQ2. HRQoL should be part of a comprehensive assessment of the costs of osteoporosis including fracture-associated morbidity.
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  • 5
    ISSN: 1433-2965
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prolonged corticosteroid therapy is known to result in an increased risk of osteoporotic fracture, probably as a consequence of enhanced bone resorption and depressed bone formation. We examined the effects of prophylactic treatment with 1,25-dihydroxyvitamin D3 (calcitonin) and nasal salmon calcitonin on corticosteroid-induced bone loss in 103 patients being treated with long-term corticosteroids for the first time in a randomized, double-masked prospective study. Patients were randomly allocated to one of three groups receiving either calcium supplementation alone, calcium plus calcitriol, or calcium plus calcitriol and nasal salmon calcitonin. Treatment was given for 12 months. Bone mineral density (BMD) was measured every 4 months by dual-photon absorptiometry in the lumbar spine and femoral neck. Calcium supplementation alone did not prevent bone loss at either site. In the lumbar spine calcitriol, with or without nasal calcitonin, significantly reduced bone loss (p〈0.0001). Neither calcitriol alone nor calcitriol with calcitonin prevented bone loss at the femoral neck. These data suggest that treatment with calcium and calcitriol, or with calcium and intranasal calcitonin, greatly reduced or prevented corticosteroid-induced bone loss in the lumbar spine.
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  • 6
    ISSN: 1433-2965
    Keywords: Corticosteroids ; Cyclosporine ; Hydroxyproline ; Osteocalcin ; Testosterone ; Transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rapid bone loss after orthoptic cardiac transplantation (OHTX) is a major problem; however, the mechanisms are poorly understood. To investigate these mechanisms we measured biochemical and hormonal indices of bone turnover serially in 25 patients (21 men, 4 women) after OHTX. Serum osteocalcin was reduced immediately post-OHTX (2.2±0.5 ng/ml) but rose significantly by 6 and 12 months (14.1±2.5 and 15.7±2.2 respectively). Bone resorption indices (urinary hydroxyproline/creatinine and calcium/creatinine ratios) were increased immediately post-OHTX but fell by 6 months. Serum testosterone was reduced in males but recovered towards normal values by 6–12 months. Regression analysis showed lumbar bone loss was predicted independently by the change in both serum osteocalcin and testosterone. The data suggest that bone loss post-OHTX is due to a combination of accelerated turnover and hypogonadism.
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  • 7
    ISSN: 1433-2965
    Keywords: Elderly ; Epidemiology ; Fracture ; Incidence ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This longitudinal population-based study documents the incidence of all symptomatic fractures from 1989 to 1992 in an elderly, predominantly Caucasian population of males and females (⩾60 years as at 1 January 1989) living in the geographically isolated region of the city of Dubbo, NSW, Australia. Fractures were ascertained by reviewing reports from all radiology services in the region. There were 306 fractures in 271 patients during the study period representing 11 401 person-years of observation. In the 60–80 year age group only 10% of fractures involved the hip, while in the over-80 age group this proportion rose to 41%. Incidence of distal forearm, hip and total fractures increased exponentially in both sexes with increasing age. Rib fractures were relatively common, with incidence rates for rib fractures similar to those for humeral fractures. Overall fracture incidence was 2685 per 100000 person-years (males 1940 per 100000 and females 3250 per 100000). Residual lifetime fracture risk in a person aged 60 years with average life expectancy was 29% for males and 56% for females. Symptomatic fracture rates with the improved methodology in this study were higher than previously reported in both elderly males and females, with a marked preponderance of non-hip fractures in the 60–80 year age group. These symptomatic fractures have previously been underestimated, if not largely ignored, in public health approaches including cost—benefit analyses of osteoporosis prevention and treatment. Total fracture risk during later life is substantial, with fractures other than hip fractures constituting the majority of morbid fracture events, especially in the 60–80 year age group.
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  • 8
    ISSN: 1433-2965
    Keywords: Direct costs ; Epidemiology ; Fractures ; Health economics ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Osteoporosis is an increasing health care problem in all aging populations, but overall direct costs associated with the total fracture burden of osteoporosis remain uncertain. We have examined direct costs associated with 151 osteoporotic fractures occurring between 1989 and 1992 in a large cohort of elderly men and women followed prospectively as part of the Dubbo Osteoporosis Epidemiology Study. The median cost of hospital treated fractures was $A10 511 per fracture and for fractures treated on an outpatient basis $A455 in 1992 Australian dollars. Femoral neck fractures were the most expensive fractures ($15984 median cost). There was no significant difference in costs between men and women for either hospital- or outpatient-treated fractures. Rehabilitation hospital costs comprised the largest proportion of costs (49%) for hospital-treated fractures. Community services comprised the major cost (40%) of outpatient-treated fractures. Univariate predictors of costs were quadriceps strength and bone density, although multivariate analysis showed quadriceps strength to be the best overall predictor of costs. The predicted annual treatment costs in Australia for atraumatic fractures occurring in subjects ⩾60 years was $A779 million or approximately $A44 million per million of population per annum. Estimated total osteoporotic fracture-related costs for the Australian population were much higher than previously reported. The majority of direct costs (95%) were incurred by hospitalized patients and related to hospital and rehabilitation costs. Extrapolation of these data suggests that the direct costs for hip fracture alone will increase approximately twofold in most Western countries by 2025. Improving the cost-effectiveness of treating osteoporotic fractures should involve reduced hospitalization and/or greater efficiency in community rehabilitation services. The costs of various approaches to osteoporosis prevention must be placed into the context of these direct costs and prevention should target men as well as women.
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  • 9
    ISSN: 1433-2965
    Keywords: Biochemical assay ; Bone densitometry ; Bone turnover ; Menopause ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A number of recent studies have suggested that non-invasive measures of bone turnover are associated with bone loss at the forearm in postmenopausal women. Whether bone turnover markers are predictive of bone loss from the clinically important sites of lumbar spine and femoral neck remain unclear, and was the aim of this 4-year prospective study. One hundred and forty-one normal, postmenopausal women (mean age 52.0±3.3 years, mean menopause duration 20.4±5.7 months) were recruited for the study in 1988. Fasting early morning samples of blood and urine were collected at the baseline visit and stored at −20 °C prior to analysis. Serum was assayed for osteocalcin, oestradiol, oestrone, oestrone sulphate, testosterone, sex hormone binding globulin, dehydroepiandrosterone sulphate and total alkaline phosphatase. Urine was assayed for calcium, hydroxyproline, oestrone glucuronide and the collagen cross-links pyridinoline and deoxypyridinoline using high-performance liquid chromatography. Bone density was measured at the lumbar spine and femoral neck using dual photon absorptiometry at time 0, 12, 24 and 48 months. The mean annual percentage change in bone density (SE) was −1.41% (0.18) at the lumbar spine and −0.86% (0.22) at the femoral neck. There was no evidence of bimodality or a fast loser subgroup as the rates of change were normally distributed. Both simple and multiple stepwise regression analyses revealed no significant correlation between the rates of change in bone density with any biochemical marker, either individually or in combination, despite the study having sufficient power (80%) to detect a correlation of 0.5 between any biochemical marker levels and bone loss. We conclude that single measurements of these markers of bone turnover and endogenous sex hormones appear unlikely to be clinically useful in predicting early postmenopausal bone loss from either the spine or the hip.
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  • 10
    ISSN: 1433-7339
    Keywords: Key words Low-energy laser ; Mucositis ; Radiotherapy ; Head and neck cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Use of the low-energy helium-neon laser (LEL) appears to be a simple atraumatic technique for the prevention and treatment of mucositis of various origins. Preliminary findings, and significant results obtained for chemotherapy-induced mucositis in a previous phase III study, prompted a randomized multicenter double-blind trial to evaluate LEL in the prevention of acute radiation-induced stomatitis. Irradiation by LEL corresponds to local application of a high-photon-density monochromatic light source. Activation of epithelial healing for LEL-treated surfaces, the most commonly recognized effect, has been confirmed by numerous in vitro studies. The mechanism of action at a molecular and enzymatic level is presently being studied. From September 1994 to March 1998, 30 patients were randomized. Technical specification: 60 mW (25 mW at Reims, 1 patient), He-Ne, wavelength 632.8 nm. The trial was open to patients with carcinoma of the oropharynx, hypopharynx and oral cavity, treated by radiotherapy alone (65 Gy at a rate of 2 Gy/fraction, 5 fractions per week) without prior surgery or concomitant chemotherapy. The malignant tumor had to be located outside the tested laser application areas (9 points): posterior third of the internal surfaces of the cheeks, soft palate and anterior tonsillar pillars. Patients were randomized to LEL or placebo light treatment, starting on the first day of radiotherapy and before each session. The treatment time (t) for each application point was given by the equation : t (s)=energy (J/cm2)×surface (cm2)/Power (W). Objective assessment of the degree of mucositis was recorded weekly by a physician blinded to the type of treatment, using the WHO scale for grading of mucositis and a segmented visual analogue scale for pain evaluation. Protocol feasibility and compliance were excellent. Grade 3 mucositis occured with a frequency of 35.2% without LEL and of 7.6% with LEL (P〈0.01). The frequency of "severe pain" (grade 3) was 23.8% without LEL, falling to 1.9% with LEL (P〈0.05). Pain relief was significantly reduced throughout the treatment period (weeks 2–7). LEL therapy is capable of reducing the severity and duration of oral mucositis associated with radiation therapy. In addition, there is a tremendous potential for using LEL in combined treatment protocols utilizing concomitant chemotherapy and radiotherapy.
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