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  • 1
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ba3Ca1.18Nb1.82O9-δ (also referred to as BCN18) is a promising high-temperature proton conductor. In the dry state it contains an abundant amount of vacancies in the oxygen sublattice. Water may enter the compound occupying the vacancies and supplying protons to the lattice. The conductivity of these protons may be used in future applications of high-temperature proton conductors as electrolytes for SOFCs and in sensors. Chemical diffusion of water in this compound is described by the coupled outward flux of Ovacancies and the inward flux of protons (OH•). The chemical diffusivity is in general a complicated function of the concentrations and the individual diffusivities. In this work, the chemical diffusivity of water is determined by studying the kinetics of a) the weight increase in TG experiments, and b) of dilatometric length changes upon subjecting the samples to humid atmospheres. The chemical diffusivities determined using techniques a) and b) are in good agreement. Likewise, the present data are compatible with those determined in a previous thermal desorption study. The present data, however, only apply to situations where the initial proton concentration is rather low and where the proton content is not changed dramatically in the experiment.
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  • 2
    ISSN: 1432-0762
    Keywords: Fiddler crabs ; Condition dependence Sexual selection ; Handicap principle ; Sensory exploitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the fiddler crab (Uca beebei) males build a small mud pillar next to their burrow which increases their attractiveness to females. Three hypotheses were tested to explain inter-male variation in pillar-building. (1) The benefits of pillar-building are density dependent. The experimental addition of vertical structures did not support this hypothesis as there was no change in the level of pillar-building. (2) There are two classes of males (pillar-builders and non-pillar-builders). This could either be due to an alternative mating strategy, or because pillar building is age or size-dependent. There was also no support for this hypothesis. (3) Pillar-building is an honest signal of male quality dependent on body condition. A food supplementation experiment was performed. Addition of food affected several aspects of male behaviour and resulted in a two fold increase in the number of pillars built between control and food treatments (P 〈 0.001). However, the percentage of males building pillars did not increase significantly. Pillar building in this species has been attributed to sensory exploitation. Our results indicate that a trait which may well have evolved through sensory exploitation also appears to be condition-dependent. We emphasise that showing that an ornament or behaviour is condition-dependent does not necessarily mean that it evolved through “good gene” processes. However, in terms of its current selective value, pillar building may be maintained through female choice because it acts as a signal of male condition.
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  • 3
    ISSN: 1432-0762
    Keywords: Key words Fiddler crabs ; Condition dependence ; Sexual selection ; Handicap principle ; Sensory exploitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the fiddler crab (Uca beebei) males build a small mud pillar next to their burrow which increases their attractiveness to females. Three hypotheses were tested to explain inter-male variation in pillar-building. (1) The benefits of pillar-building are density dependent. The experimental addition of vertical structures did not support this hypothesis as there was no change in the level of pillar-building. (2) There are two classes of males (pillar-builders and non-pillar-builders). This could either be due to an alternative mating strategy, or because pillar building is age or size-dependent. There was also no support for this hypothesis. (3) Pillar-building is an honest signal of male quality dependent on body condition. A food supplementation experiment was performed. Addition of food affected several aspects of male behaviour and resulted in a two fold increase in the number of pillars built between control and food treatments (P 〈 0.001). However, the percentage of males building pillars did not increase significantly. Pillar building in this species has been attributed to sensory exploitation. Our results indicate that a trait which may well have evolved through sensory exploitation also appears to be condition-dependent. We emphasise that showing that an ornament or behaviour is condition-dependent does not necessarily mean that it evolved through “good gene” processes. However, in terms of its current selective value, pillar building may be maintained through female choice because it acts as a signal of male condition.
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  • 4
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    Age 19 (1996), S. 13-16 
    ISSN: 1574-4647
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A retrospective study over four years was performed reviewing the records of 1195 patients suffering from peripheral polyneuropathy without entrapment neuropathies. 613 patients over 60 years of age were compared with 582 patients under 60. Neurological diagnosis was made on the basis of personal and familyhistory, clinical examination, laboratory parameters, electrophysiology and in some cases by sural nerve biopsy. While diabetes was the most frequent etiology in both groups, it was more common in the old-age group (46.5% vs. 32.5%). Clinical manifestation of diabetic neuropathy did not differ. While alcoholism was not a major cause of late life polyneuropathy (2.6% vs. 15.5%), paraneoplastic neuropathy was somewhat more common in late life (3.4% vs. 2.4%) although this was not statistically significant. Paraproteinemic neuropathy as the only cause of neuropathy was found solely in the old-age group (0.8%). The percentage of cryptogenetic neuropathies was higher in late life (17.6% vs. 12.7%; p〈0.05) with only the outpatients showing a statistically significant difference (p〈0.05). From these findings, we concluded that there is a distinct etiological spectrum of neuropathies in late life, many with treatable causes. The higher percentage of cryptogenetic neuropathies in the elderly may be explained by a nonspecific neuropathy occurring in late life due to normal aging processes in the peripheral nerve.
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  • 5
    ISSN: 1619-7089
    Keywords: Single-photon emission tomography ; Iodine-123 iomazenil ; GABAA receptor ; Epilepsy ; Arachnoid cyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Imaging cerebral GABAA receptor density (GRD) with single-photon emission tomography (SPET) and iodine-123 iomazenil is highly accurate in lateralizing epileptogenic foci in patients with complex partial seizures of temporal origin. Limited knowledge exists on how iomazenil SPET compares with magnetic resonance imaging (MRI) in this regard. We present a patient with complex partial seizures in whom MRI had identified an arachnoid cyst anterior to the tip of the left temporal lobe. Contralaterally to this structural abnormality, interictal electroencephalography (EEG) performed after sleep deprivation disclosed an intermittent frontotemporal dysrhythmic focus with slow and sharp waves. On iomazenil SPET images GRD was significantly reduced in the right temporal lobe and thus contralaterally to the MRI abnormality, but ipsilaterally to the pathological EEG findings. These data suggest that iomazenil SPET may significantly contribute to the presurgical evaluation of epileptic patients even when MRI identifies potentially epileptogenic structural lesions.
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  • 6
    ISSN: 1619-7089
    Keywords: Brain neoplasms ; Amino acids ; Iodine-123-α-methyl tyrosine ; Radionuclide imaging ; Single-photon emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using single-photon emission tomography (SPET), the radiopharmaceuticall,-3-iodine-123-α-methyl tyrosine (IMT) has been applied to the imaging of amino acid transport into brain tumours. It was the aim of this study to investigate whether IMT SPET is capable of differentiating between high-grade gliomas, low-grade gliomas and non-neoplastic brain lesions. To this end, IMT uptake was determined in 53 patients using the triple-headed SPET camera MULTISPECT 3. Twenty-eight of these subjects suffered from high-grade gliomas (WHO grade III or IV), 12 from low-grade gliomas (WHO grade II), and 13 from non-neoplastic brain lesions, including lesions after effective therapy of a glioma (five cases), infarctions (four cases), inflammatory lesions (three cases) and traumatic haematoma (one case). IMT uptake was significantly higher in high-grade gliomas than in low-grade gliomas and non-neoplastic lesions. IMT uptake by low-grade gliomas was not significantly different from that by non-neoplastic lesions. Diagnostic sensitivity and specificity were 71% and 83% for differentiating high-grade from low-grade gliomas, 82% and 100% for distinguishing high-grade gliomas from non-neoplastic lesions, and 50% and 100% for discriminating low-grade gliomas from non-neoplastic lesions. Analogously to positron emission tomography with radioactively labelled amino acids and fluorine-18 deoxyglucose, IMT SPET may aid in differentiating high-grade gliomas from histologically benign brain tumours and non-neoplastic brain lesions; it is of only limited value in differentiating between non-neoplastic lesions and histologically benign brain tumours.
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  • 7
    ISSN: 1619-7089
    Keywords: Brain neoplasms ; Positron emission tomography ; Single-photon emission tomography ; Fluorine-18 fluorodeoxyglucose ; Iodine-123-α-methyl tyrosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Use of iodine-123-α-methyl tyrosine (123I-IMT) allows investigation of the amino acid transport rate in gliomas. It was the aim of this study to compare the value of measurement of glucose metabolism with that of measurement of123I-IMT uptake for the non-invasive grading of brain tumours. The study population comprised 23 patients with histopathologically proven primary brain tumours; 14 had high-grade gliomas, and nine low-grade brain neoplasms. Glucose metabolism was studied using an ECAT EXACT 47 positron emission tomography (PET) camera and fluorine-18 fluorodeoxyglucose (18F-FDG);123I-IMT uptake was measured with the triple-headed single-photon emission tomography (SPET) camera, MULTISPECT 3.18F-FDG and123I-IMT uptake was quantified as ratios between the uptake by the tumour and contralateral regions of reference. Glucose metabolism and amino acid uptake of the brain tumours correlated significantly (r=0.71,P 〈0.001). Assuming discrimination thresholds between high-grade and low-grade tumours of 0.8 for18F-FDG uptake and 1.8 for123I-IMT uptake, the accuracy values of18F-FDG PET and123I-IMT SPET for differentiating between high-grade and low-grade tumours were 21/23 (91%) and 19/23 (83%), respectively. The difference in diagnostic performance was not significant on receiver operating characteristic analysis (P 〉0.4). It is concluded that there is no major difference between the PET investigation of glucose metabolism and the less expensive SPET measurement of amino acid uptake in terms of their accuracy in evaluating the malignancy grade of primary brain tumours. This encourages the performance of further studies to analyse the potential impact of123I-IMT SPET on the therapeutic management of patients with brain tumours.
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  • 8
    ISSN: 1619-7089
    Keywords: Liver cirrhosis ; Portal hypertension ; Transjugular intrahepatic portosystemic shunt ; Liver perfusion scintigraphy ; Liver blood flow ; TIPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In patients with liver cirrhosis a transjugularly placed intrahepatic portocaval shunt (TIPS) is a non-surgical portosystemic device which aims to reduce portal venons pressure. In comparison with Doppler sonography, we evaluated in 28 patients the diagnostic impact of liver perfusion scintigraphy (with technetium-99m diethylene triamine penta-acetic acid) in the assessment of changes in the hepatic blood flow after TIPS shunting. The arterial and portal contributions to hepatic flow were calculated from the areas under the biphasic timeactivity curve. In the course of TIPS shunting, patency is threatened by reocclusion. Angiography is the gold standard for TIPS shunt reassessment. However, there is a need for a less invasive diagnostic procedure, such as scintigraphy or Doppler sonography, for the early detection of shunt insufficiency. Scintigraphy demonstrated that prior to TIPS shunting the portal venons contribution to hepatic perfusion was reduced to 29.2%, this reduction being due to portal hypertension. After TIPS placement a significant increase in portal venous perfusion was observed (38.2%;P〈0.02). TIPS shunt occlusion was identified in patients by a significant reduction in the scintigraphically measured portal venons contribution to hepatic blood flow. Hepatic perfusion scintigraphy appears to be a valuable method to determine the immediate effect of TIPS on hepatic blood flow. Post-TIPS follow-up studies of hepatic haemodynamics by liver perfusion scintigraphy appear able to contribute to the detection of TIPS shunt occlusion before the clinical consequences of this complication have become apparent.
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  • 9
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 10
    ISSN: 1619-7089
    Keywords: Key words: Thyroid cancer ; Fluorine-18 fluorodeoxyglucose ; Positron emission tomography ; Sestamibi ; Radioiodine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: n =222) and the group with negative radioiodine scan (n=166), respectively. Specificity was 90% in the whole patient group. Sensitivity and specificity of WBS were 50% and 99%, respectively. When the results of FDG-PET and WBS were considered in combination, tumour tissue was missed in only 7%. Sensitivity and specificity of MIBI/Tl were 53% and 92%, respectively (n=117). We conclude that FDG-PET is a sensitive method in the follow-up of thyroid cancer which should be considered in all patients suffering from differentiated thyroid cancer with suspected recurrence and/or metastases, and particularly in those with elevated thyroglobulin values and negative WBS.
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