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  • Springer  (150)
  • International Union of Crystallography (IUCr)  (14)
  • Royal Society  (11)
  • 1
    ISSN: 1432-0630
    Keywords: 61.10 ; 68.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Single crystals of iodine-intercalated C60 have been examined by transmission electron microscopy. Tilting series of Electron Diffraction Patterns (EDP) confirm that it has a simple hexagonal structure with c/a≈1 in accordance with the results of X-ray diffraction, which allows higher precision c/a=1.0024. Cooling and heating experiments were performed in the vacuum of the microscope to investigate the order — disorder phenomena. High-Resolution Electron Microscopy (HREM) images and electron diffraction patterns reveal that the c/2-displacement along the c-direction plays an important role in the transition from the simple hexagonal structure into the fcc structure when iodine is lost from the specimen or “vice versa”. The orientation relationship between the intercalate and the C60 structure is [01 $$\overline {\text{1}}$$ 10]h∥[1 $$\overline {\text{1}}$$ 10]fcc and (001)h∥(110)fcc. A model is proposed to interpret the features observed in EDP and HREM consistently.
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  • 2
    ISSN: 1432-0738
    Keywords: Aluminum ; Toxicokinetics ; Rat ; Parenterals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The toxicokinetics of aluminum (Al) in male Wistar rats was studied after single intragastric (IG) doses of 1000 and 12000 μg Al/kg and intravenous (IV) doses of 10, 100, 1000, and 12000 μg Al/kg. Serial blood samples, daily samples of urine and feces as well as brain, liver, kidney, spleen, quadriceps muscle, and femur samples were collected. Al was measured by atomic absorption spectrometry. Al blood profiles after IV doses were adequately described by a two-compartment open model. Al toxicokinetics was dose dependent and appeared to plateau at 12000 μg/kg. At IV doses between 10 and 1000 μg/kg the terminal half-life of elimination from whole blood (t1/2β) increased from 29.9±7.8 to 209.3±32.6 min, and the total body clearance (CL) decreased from 2.45±0.64 to 0.28±0.03 ml min−1 kg−1. Following an IV bolus of 10 and 100 μg/kg the administered Al was recovered completely from urine (94.4%±9.9% and 98.5%±3.2%). Twenty-nine days after the IV dose of 1000 μg/kg daily renal excretion decreased to baseline values while only 55.1%±8.0% of the dose was excreted. Nineteen days after the single IV dose of 1000 μg/kg Al accumulated in liver (28.1±7.7 versus 1.7±0.5 μg/g of control rats) and spleen (72.5±21.1 versus 〈0.4 μg/g). After the single 1000 μg/kg IG dose no absorption of Al was detectable. The IG dose of 12000 μg/kg resulted in a maximum blood Al level of 47.9±12.4 μg/l after 50 min. The blood concentration time curve fitted a one-compartment open model with a half-life of absorption of 28.2±3.6 min and a t1/2β of 81.2±20.2 min. Cumulative renal Al excretion was 0.18%±0.10% of the dose and oral bioavailability was 0.02%. Seventeen days after the 12000 μg/kg IG dose the Al content in femur samples was increased (2.7±1.3 versus 0.6±0.4 μg/g). In no case was fecal elimination of incorporated Al observed.
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  • 3
    ISSN: 1432-1106
    Keywords: Electrophysiology ; Medulla oblongata ; Spinal cord ; Interneurons ; Respiratory control ; Intracellular labelling ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Upper cervical inspiratory neurons form a distinct neuronal column located near the lateral edge of the intermediate grey matter in the rostral spinal segments. Previous studies conducted in cats have demonstrated synaptic inputs to these neurons from several respiratory related regions of the medulla, and long descending axonal projections mainly towards the motoneurons supplying the intercostal muscles. The aim of this study was to examine the electrophysiological and morphological properties of this propriospinal system in the rat. Extracellular recordings were made from 127 cervical inspiratory units, mainly in the C1 and C2 segments. Eighty-two percent could be antidromically activated from the C7/C8 border. No evidence of monosynaptic connection was obtained by cross-correlating the activity of some of these units with the discharge of the phrenic nerve. Intracellular recordings were made from seven neurons, three of which were labelled with biotinamide (neurobiotin). Long “survival times” after intracellular injections (up to 23 h) resulted in staining of axons for long distances, at least to the C5 segment. Each of the three labelled axons issued only one short collateral which arborized in the region of the phrenic nucleus. These results demonstrate that upper cervical inspiratory neurons in the rat have features similar to those previously described in the cat, including only a limited projection to the phrenic nucleus. In addition, this study provides the first morphological identification of these neurons.
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  • 4
    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 wird über Ergebnisse einer numerischen Studie berichtet, welche die Ermittlung des Gleichgewichtszustandes bei Konvektion von Wasser in Gegenwart von Eis in einem geneigten, rechteckigen, mit porösem Medium befüllten Behälter zum Ziele hatte. Eine Seite des Behälters wird über Schmelztemperatur, die andere darunter gehalten, während die übrigen zwei Seiten wärmedicht sind. Die Auswertung der Resultate erfolgt hinsichtlich des Dichteinversionsparameters, des Neigungswinkels und der Kühlplattentemperatur. Unterhalb einer Heiztemperatur von 25°C wird der Gleichgewichtszustand des Eis/Wasser-Systems entscheidend durch das Phänomen der Dichteanomalie beeinflußt. In einem Vertikalbehälter verursacht letztere die Ausbildung von zwei gegensinnig drehenden Walzen, was zu einer Verbreiterung der Wasserzone am Boden gegenüber der im oberen Bereich führt. Bei geneigtem Behälter existieren zwei Lösungszweige, welche die Boden-bzw. die Seitenheizungscharakteristik repräsentieren (Bénard- und Seitenheizungszweig). Aufgrund der Dichteinversion kann die Lösung auf dem Bénardzweig bei kleinen Neigungswinkeln oszillatorisches Verhalten anstatt Konvergenz liefern. Auf dem anderen Zweig ergibt sich bei 70° Neigungswinkel ein Maximum des Wärmestroms. Das Volumen der Wasserzone zeigt nur schwache Abhängigkeit vom Neigungswinkel. Bei Berücksichtigung des Unterkühlungseffektes führt die Wechselwirkung zwischen Leitung in der festen und Konvektion in der flüssigen Phase zu einer Gleichgewichtsstruktur der Eis/Wasser-Grenzfläche, welche bei einigen intermediären Kühlungsplattentemperaturen äußerst starke Unregelmäßigkeiten aufweist.
    Notes: Abstract This paper reports on the results of a numerical study on the equilibrium state of the convection of water in the presence of ice in an inclined rectangular cavity filled with a porous medium. One side of the cavity is maintained at a temperature higher than the fusion temperature while the opposite side is cooled to a temperature lower than the fusion temperature. The two remaining sides are insulated. Results are analysed in terms of the density inversion parameter, the tilt angle, and the cooling temperature. It appears that the phenomenon of density inversion plays an important role in the equilibrium of an ice-water system when the heating temperature is below 20°. In a vertical cavity, the density inversion causes the formation of two counterrotating vortices leading to a water volume which is wider at the bottom than at the top. When the cavity is inclined, there exist two branches of solutions which exhibit the bottom heating and the side heating characteristics, respectively (the Bénard and side heating branches). Due to the inversion of density, the solution on the Bénard branch may fail to converge to a steady state at small tilt angles and exhibits an oscillating behavior. On the side heating branch, a maximum heat transfer rate is obtained at a tilt angle of about 70° but the water volume was found to depend very weakly on the inclination of the cavity. Under the effect of subcooling, the interplay between conduction in the solid phase and convection in the liquid leads to an equilibrium ice-water interface which is most distorted at some intermediate cooling temperature.
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  • 5
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Receptors of 12 lectins in 25 cases of human hepatocellular carcinomas (HCC) were histochemically investigated by avidin-biotin-peroxidase complex (ABC) methol. Liver tissues of five cirrhotic patients and five normal subjects were used as controls. SJA receptor was absent both in HCC and controls, while LCA and PSA receptors were present in all tissues studied here. Receptors of DBA, PHA, PNA, UEAI and SBA which did not bind to normal, cirrhotic and pericarcinomatous liver tissues had the positive rates of 4%, 44%, 16%, 4% and 12% in HCC, respectively. Four lectins which strongly bound to the non-cancer liver tissues had their receptors in 96% (ConA, WGA, RCAI) and 36% (BSAI) of HCC. The pretreatment of tissue sections with neuraminidase abolished most of WGA receptors and exposed some PNA binding sites. There were many differences in lectin distribution between HCC and noncancer liver tissues. The changes of glycoconjugates in HCC were discussed.
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  • 6
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. In order to detect aneuploidy in interphase human lymphocytes, both in vivo and in vitro, fluorescence in situ hybridization (FISH) was carried out on binucleated cells cytokinesis-blocked by cytochalasin B at the first mitosis after phytohemagglutinin stimulation. A pericentric chromosome-21-specific DNA probe prepared from yeast artificial chromosome clone 881D2 by the polymerase chain reaction was employed. One thousand binucleated cells per individual were scored from cultures from twelve trisomy 21 patients aged 0.01–8.9 years (mean 4.3 years) and 20 normal children of similar age. Of trisomy 21 patients, increased frequencies of disomic cells in vivo (1.690±1.070%) and cells containing six signals with nondisjunction (0.822±0.554%) were found, compared with those of monosomic 21 cells in vivo (0.265±0.130%) and cells containing four signals with nondisjunction in normal children (0.369±0.250%; P=0.000 and P=0.000, respectively). These results show that malsegregation of chromosome 21 occurs more often in trisomic 21 cells than in disomic cells from normal children. The frequency of nondisjunction was significantly higher than the loss of chromosome 21 in both cultured trisomic (0.822±0.554% vs 0.043±0.049%, P=0.000) and disomic (0.369±0.250% vs 0.010±0.030%, P=0.000) cells. Comparisons of in vivo and in vitro data on aneuploidy indicate that a cell selection mechanism may exist in vivo. All these results show that FISH, with a chromosome-specific probe, on binucleated lymphocytes is a powerful tool for simultaneously detecting mosaic cell lines in vivo and malsegregation (loss and nondisjunction) of a corresponding chromosome in vitro in the same cell population.
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  • 7
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A polymorphic BamHI site was located in the coding region of the human T cell receptor delta gene TCRDV2. Two alleles defined by the absence or the presence of the BamHI site were detected by the polymerase chain reaction.
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  • 8
    ISSN: 1432-1106
    Keywords: Plasticity ; Enkephalin ; Vasoactive intestinal polypeptide ; Somatostatin ; Neuropeptide tyrosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The extent to which the plasticity in peptide expression observed in developing spinal motoneurons occurs following proximal peripheral axotomy in the adult rat was examined using in situ hybridization and immunohistochemical techniques to visualize the changes. Transient upregulation of galanin, vasoactive intestinal polypeptide (VIP) and substance P messenger ribonucleic acids (mRNAs) was observed within subpopulations of motoneurons ipsilateral to lesion for periods lasting 2–3 weeks after injury. In contrast, the axotomy-induced heterogenous increases in somatostatin and neuropeptide tyrosine mRNA expression in ipsilateral motoneurons remained elevated, or, in the case of somatostatin, continued to increase for the time period studied (1 month). Immunohistochemical analysis agreed with the in situ hybridization results, showing some motoneurons within the injured ventral horn to contain galanin-, VIP-or somatostatin-like immunoreactivity. In some instances, galanin-immunoreactive motoneurons colocalized with calcitonin gene-related peptide immunoreactivity. Most of the neurons expressing the injury-induced peptides appeared large, presumably alpha-motoneurons, but there were also many small neurons expressing galanin in the ventral horn ipsilateral to lesion. This may represent evidence for peptide synthesis in gamma-motoneurons. The only peptide mRNA studied to be downregulated in response to axotomy was enkephalin. The results show that peptide expression in injured motoneurons is dramatically altered, the significance of which remains to be determined.
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  • 9
    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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  • 10
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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