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  • 1
    ISSN: 1434-601X
    Schlagwort(e): PACS: 21.10.Re Collective levels – 21.10.Tg Lifetimes – 23.20.En Angular distribution and correlation measurements – 23.20.Lv Gamma transitions and level energies – 27.70.+q 150 ≤ A ≤ 189
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: High-spin states in 181Ta have been studied via the 176Yb(11B,α2n) reaction at 52 MeV using the PEX array and at 57 MeV using the NORDBALL array, with α-particle detection. The previously known, Kπ=(7/2)+ ground state band and Kπ=(9/2)− band have been extended to spins (29/2)+ and (31/2)−, respectively. Two new one-quasiparticle bands, the Kπ=(5/2)+ band built on the known (5/2)+ isomer and a Kπ=((1/2)−) band have been observed. Two other rotational bands with three-quasiparticle structure, Kπ=(15/2)− and ((19/2)+ with π(7/2)[404]ν2(1/2)[510](9/2)[624] and π(9/2)[514]ν2(1/2)[510](9/2)[624] configurations, respectively, have been newly observed. The half-life of the Kπ=((19/2)+) bandhead which decays to the head of the (15/2)− band has been measured to be 140(36) ns. However, transitions from the ((19/2)+) state to the (15/2)− band have not been observed.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 2 (1998), S. 327-330 
    ISSN: 1434-601X
    Schlagwort(e): PACS:21.10.Tg Lifetimes – 23.20.Lv Gamma transitions and level energies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstact: High-spin states in 183Re have been studied using the 176Yb(11B,4n) reaction at 52 and 57 MeV. Two high-K bands have been observed directly by a time-correlated γ-γ coincidence measurement. One of the bands is built on an isomeric K π=(25/2)+ state at E x= 1908 keV with a half-life of 0.82(2) ms. The other band, assigned as K π=(29/2)− at E x= 2739 keV, decays to the (25/2)+ band. These bands are interpreted as three-quasiparticle structures, π(5/2)+[402] &⊗ν(9/2)+[624] ⊗ν(11/2)+[615] for the (25/2)+ band and π(9/2)−[514] ⊗ν(9/2)+[624] ⊗ν(11/2)+[615] for the (29/2)− band. The K π= (29/2)− band becomes strongly Coriolis mixed with increasing spin and is gradually changing into a low-K s-band structure.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1434-601X
    Schlagwort(e): PACS:21.10.Re Collective levels – 27.60+j 90 ≤ A ≤ 149
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: Excited states of the nucleus ν123Xe have been investigated with the fusion–evaporation-reaction ν110Pd(ν18O,5n)ν123Xe at 86 MeV beam energy, using the compton-suppressed Nordball-multidetector-system at the Niels-Bohr-Institute in Risø, Denmark. The level scheme of ν123Xe was extended up to a level of tentative 53/2+ħ. Four excited bands of 3-quasiparticle-character were observed. Analyzing the directional correlation information, we could assign spin- and parity-values to all observed bands in ν123Xe. The observed band structures fit well into systematics of the neighboring nuclei ν125Xe and ν127Xe.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1434-601X
    Schlagwort(e): PACS:21.10.Tg Lifetimes – 25.70.Gh Compound nucleus – 27.60.+j 90 ≤ A ≤ 149
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: An in-beam experiment with the reaction 122Sn(27Al,4np) at 127 MeV was performed at the Nordball multi-detector array in Roskilde. It provided evidence for a new high-spin isomer in 144Sm. This isomer with T 1/2= (2.6 ± 0.5) ns at an excitation energy E x= 9232 keV seems to belong to a family of isomers of similar configuration in neighbouring N= 82 nuclei.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1434-601X
    Schlagwort(e): PACS:21.10.Re Collective levels – 23.20.Lv Gamma transitions and level energies – 27.80.+w 190 ≤ A ≤ 219
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract: Three high energy γ rays have been observed to connect the two yrast signature-partners superdeformed bands in 193Tl to the normal deformed states. Thereby, both excitation energy and spin of these bands are proposed for the first time in an odd-proton nucleus.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-2161
    Schlagwort(e): Key words Skeletal metastases ; PET ; Fluoride ; CT
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Objective. To characterise the uptake of 18F in skeletal metastases from breast cancer using positron emission tomography (PET) and to relate these findings to the appearance on CT. Patients and design. PET with 18F and CT were performed in five patients with multiple skeletal metastases from breast cancer. The CT characteristics were analysed in areas with high uptake on the PET study. Dynamic PET imaging of the skeletal kinetics of the 18F-fluoride ion were included. Results. The areas of abnormal high accumulation of 18F correlated well with the pathological appearance on CT. Lytic as well as sclerotic lesions had markedly higher uptake than normal bone, with a 5–10 times higher transport rate constant for trapping of the tracer in the metastatic lesions than in normal bone. Conclusion. PET with 18F-fluoride demonstrates very high uptake in lytic and sclerotic breast cancer metastases.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-1041
    Schlagwort(e): Key words Positron emission tomography ; Esuprone; antidepressive drugs ; MAO-A ; moclobemide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: The aim of the study was to investigate whether or not esuprone binds substantially to MAO-A in the human brain. Methods: In a randomised double-blind placebo-controlled study 16 male healthy volunteers were examined␣with positron emission tomography (PET) with [11C]harmine. Eight of the volunteers were given daily doses of 800 mg esuprone, four were given bi-daily doses of 300 mg moclobemide, and four volunteers were given placebo tablets. PET was performed before initiation of a 7-day treatment period. On day 7, one investigation was made immediately before administration of the drug, representing 23 h after the previous day's treatment for esuprone and 11 h after the last tablets of moclobemide. Further investigations were made 4 h and 8 h after the morning dose on day 7. Results: PET showed a high degree of binding of [11C]harmine, a high-affinity ligand for MAO-A, before the start of treatment, and a marked and similar reduction after treatment with esuprone and moclobemide. A slight tendency for normalisation of enzyme binding was observed at the last time point. In the placebo group no change was observed. Plasma kinetics of esuprone showed a rapid elimination with a half-life of about 4 h. Conclusion: The study demonstrates that esuprone was comparable to moclobemide in its effect on MAO-A inhibition in the brain at the doses given. This is an illustration of the potential of PET to monitor drug effects directly on target biochemical systems in the brain in human volunteers, and the possibility of using these data, rather than pharmacokinetic data, for the determination of dosing intervals.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-2072
    Schlagwort(e): Key words PET ; Pharmacokinetics ; Dopamine D2 receptor ; Serotonin 5HT2 receptor ; Atypical antipsychotic ; Quetiapine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Quetiapine (Seroquel) is a novel antipsychotic with an atypical profile in animal models and a relatively short plasma half-life of 2.5–5 h. In the present study, we used PET to compare the time course of blockade of dopamine D2 and serotonin 5HT2 receptors of quetiapine using C11-raclopride and C11-N-methyl-spiperone as ligands, parallel to monitoring plasma drug concentrations. It was an open study in 11 schizophrenic men using a fixed dose of 450 mg quetiapine. Eight men completed the 29 days treatment, followed by four PET scans performed over a 26-h period after withdrawal of the compound. Quetiapine was shown to bind to dopamine D2 receptors in striatum and 2 h (tmax) after the last dose, 44% receptor occupancy was calculated. After 26 h it had dropped to the same level as was found in untreated healthy volunteers. Serotonin 5HT2 receptor blockade in the frontal cortex was 72% after 2 h, which declined to 50% after 26 h. The terminal plasma half-life of quetiapine was 5.3 h. Clinically, our eight patients had good antipsychotic effect without any extrapyramidal side-effects. Our data shows that quetiapine has a relatively low affinity for dopamine D2 receptors, with an occupancy half-life (10 h), which was about twice as long as that for plasma. A more prolonged blockade of the serotonin 5HT2 receptors was found in the frontal cortex, with receptor occupancy half-life of 27 h. Compared to clozapine, as demonstrated in other studies, quetiapine has much the same ratio of D2/5HT2 occupancy. This could suggest that the combination of D2/5HT2 receptor blockade contributes to the antipsychotic effect and a low incidence of EPS seen with quetiapine in comparative phase three trials. Our results also confirm the clinical data that quetiapine can be administered twice daily.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1435-1463
    Schlagwort(e): Keywords: NMDA-receptor ; cyano-dizocilpine ; positron emission tomography ; in vitro investigation ; in vivo investigation.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary. (+)-3-[11C]Cyano-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine ([11C]MKC) was successfully synthesized as a potential radiotracer for PET studies on the NMDA receptor channel complex. In vitro binding properties of [11C]MKC were investigated with newly developed techniques for efficient evaluation of 11C-labeled compounds. The association curve of [11C]MKC binding in rat forebrain membranes showed that the specific binding reached an equilibrium within 30 min. Specific binding was saturable with affinity constant KD = 8.2 ± 0.4 nM and Bmax = 1.62 ± 0.04 pmol/mg protein with glutamate and glycine included in the incubation medium. The binding of [11C]MKC was decreased by extensive washing of the membrane preparation. (+)- and (−)-Dizocilpine, 3-cyano-dizocilpine, and ketamine inhibited the specific binding of [11C]MKC with IC50 values of 37.3, 445.0, 65.8 nM and 3.91 μM, respectively. High specific binding in in vitro autoradiography was distributed predominantly in telencephalic regions (the hippocampus, cerebral cortex, and striatum) followed by thalamus. PET studies using rhesus monkeys under anesthesia showed high uptake of [11C]MKC in the temporoparietal and frontal cerebral cortices, striatum, and thalamic regions, although it is problematic to verify the specific binding in vivo by PET.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1435-1463
    Schlagwort(e): Keywords: Brain slice ; positron emitting tracer ; triazolam ; muscarinic acetylcholine receptor ; amnesia.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary. The effect of triazolam, a potent benzodiazepine (BZ) agonist, on muscarinic acetylcholinergic receptor (mAChR) binding was investigated in living brain slices by use of a novel positron-based imaging technique. Fresh rat brain slices were incubated with [11C]N-methyl-4-piperidylbenzilate ([11C]NMPB), a mAChR antagonist, in oxygenated Krebs-Ringer solution at 37°C. During incubation, time-resolved imaging of [11C]NMPB binding in the slices was constructed on the storage phosphor screens. Addition of triazolam (1 μM) plus muscimol (30 μM), a GABAA receptor agonist, to the incubation mixture decreased the specific binding of [11C]NMPB. Ro15-1788, a BZ receptor antagonist, prevented this effect, indicating that the effect was exerted through the GABAA/BZ receptor complex. These results demonstrated that stimulation of the GABAA/BZ receptor lowers the affinity of the mAChR for its ligand, which may underlie the BZ-induced amnesia, a serious clinical side effect of BZ. No such effect in the P2-fraction instead implies that the integrity of the neuronal cells and/or their environment is prerequisite for the modulation of mAChR by GABAA/BZ stimulation.
    Materialart: Digitale Medien
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