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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7079-7081 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single-crystalline and nontextured polycrystalline thin films of La0.7Pb0.3MnO3−δ (LPMO) and La0.7Ca0.3MnO3−δ (LCMO) have been prepared by pulsed laser deposition and by magnetron sputtering, respectively. The oxygen deficiency δ of the samples was controlled by heat treatments under defined oxygen pressure. For δ(approximate)0, the polycrystalline as well as the single-crystalline films are ferromagnetic metals with Curie temperatures Tc of 220–270 K. At low temperatures T(very-much-less-than)Tc, the polycrystalline LCMO films show a negative magnetoresistance ratio (MR) at T=20, 77, and 180 K of −30%, −20%, and −8%, respectively, for a field of 1.5 kOe. At 20 K, around 200 Oe, the field sensitivity is as high as −0.5% (Oe)−1. A possible mechanism for this phenomenon is the spin-polarized tunneling through grain boundaries. For the single-crystalline films, the change of δ from 0 to about 0.1 has a similar effect as changing the doping level x from 0.3 to 0.1, namely, a transition from a ferromagnetic metal to a ferromagnetic insulator. By variation of δ, the low-temperature resistivity of these samples can be controlled within many orders of magnitude. The negative MR of oxygen-deficient single-crystalline LPMO and LCMO films was found to be as large as −20% at T=0.2Tc. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Orthorhombic Ba3Cu2O4Cl2 contains folded Cu2O4 chains along the crystallographic a direction with two different Cu sites. In single crystals of this compound the magnetization measured for a field applied parallel to the a axis shows a spin-flop transition at a threshold field of 2.6 T for temperatures below TN(approximate)20 K. Above TN a Curie–Weiss behavior is found with a paramagnetic moment of 2.0 μB per Cu atom. Parallel to the b or c axis the magnetization increases linearly with the field strength, and no metamagnetic transition was detected for these directions. It is concluded that Ba3Cu2O4Cl2 has localized magnetic moments which, at low temperatures, order antiferromagnetically parallel to the a axis. The bulklike magnetic behavior of this compound is probably caused by a strong coupling between the Cu2O4 chains. Tetragonal Ba2Cu3O4Cl2 is built up of Cu3O4 planes, also with two types of copper atoms (CuA,CuB). Its magnetization increases nearly linearly with the field. Below TNA=337 K single-crystalline Ba2Cu3O4Cl2 shows a spontaneous magnetization and ferromagnetic hysteresis for fields applied parallel to the tetragonal [100] or [110] directions. For T〈TNB(approximate)33 K, the coercive field is more than one order of magnitude larger compared to that measured in the temperature range TNB〈T〈TNA. The spontaneous magnetization observed in TNB〈T〈TNA may be attributed to weak ferromagnetism of the Dzyaloshinsky–Moriya type. The behavior of Ba2Cu3O4Cl2 at lower temperatures, T≤TNB, is not yet understood. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6905-6907 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to apply the hydrogenation-disproportionation-desorption-recombination process for the preparation of highly coercive Sm2Fe15Ga2Cy, which exhibits excellent magnetic properties together with a high thermal stability, the disproportionation of Sm2Fe17−xGax was investigated. A systematic study of the hydrogen absorption behavior of Sm2Fe17−xGax (x=0, 0.5, 1, and 2) at hydrogen pressures between 0.5 and 8 bar by means of hydrogen differential thermal analysis (HDTA) showed that increased hydrogen pressures promote the disproportionation of the stabilized 2:17 phase. X-ray diffraction investigations of the HDTA samples showed a decreasing content of the 2:17 phase for increasing hydrogen pressures. It was possible to achieve a nearly full disproportionation even for the most stable compound Sm2Fe15Ga2 by applying a pressure of 8 bar. Microstructural changes within the disproportionated mixture as a result of the applied pressure have been documented in detail by high resolution scanning electron microscopy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1056-1058 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel principle for cooling by adiabatic pressure application in the mixed crystalline compound Pr1−xLaxNiO3 is described and experimentally verified. Cooling occurs in the vicinity of the structural phase transition where the electronic ground state of the Pr3+ ions changes from a singlet to a doublet state. By properly choosing the La concentration x, the cooling effect can be achieved down to some 100 mK. Furthermore, Pr1−xLaxNiO3 can be used for second and third stage cooling down to the μK region by classical paramagnetic and nuclear demagnetization techniques, respectively. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3001-3003 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sm–Co-type alloys were disproportionated by milling in hydrogen at enhanced temperatures. X-ray diffraction confirmed the disproportionation of the SmCo5 and Sm2Co17 phases into Sm hydride and α-Co. This "reactive milling" procedure facilitates the disproportionation of these alloys which are characterized by a very high thermodynamic stability, and therefore are not available for a standard hydrogenation disproportionation desorption recombination treatment. Recombination of the reactively milled powders leads to the formation of the original phases, now with dramatically refined grain sizes of around 25 nm and significant coercivities such as μ0JHC=3.7 T in the case of the SmCo5 alloy. Exchange coupling between the nanoscaled grains resulted in magnetically single phase behavior despite a multiphase microstructure. In particular, for the Sm2Co17 alloy, a remanence enhancement was observed for recombination temperatures ≤700 °C. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2307
    Keywords: Key words Vascular endothelial growth factor ; flt ; Pulmonary sarcoidosis ; Activated macrophage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Vascular endothelial growth factor (VEGF) is a multifunctional cytokine, which has recently been reported to enhance the activation and migration of monocytes through the flt receptor in vitro, which are key events in granuloma formation of granulomatous disorders and in sarcoidosis. Since activated macrophages and monocytes are known to be involved in sarcoid granuloma formation in sarcoidosis, we investigated the expression of VEGF and its receptor flt in 33 paraffin-embedded lung tissue biopsies of patients with pulmonary sarcoidosis. VEGF-mRNA was localized by nonradioactive in situ hybridization, VEGF and flt expression were visualized immunohistochemically. We found an increased transcription and protein production of VEGF and an overexpression of flt in activated alveolar macrophages, in epitheloid cells, and in multinuclear giant cells of pulmonary sarcoid granulomas.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Der Pathologe 19 (1998), S. 308-312 
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Myositis proliferans ; Weichteilerkrankung ; Muskulatur ; Myofibroblasten ; Riesenzellen ; Key words Myositis proliferans ; Soft tissue disorder ; Muscles ; Myofibroblasts ; Giant cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Myositis proliferans is a reactive, intramuscular soft tissue disease characterized by fibroblast and myofibroblast proliferation, showing similarities to the phase-like development seen in the general pathology of wound healing and hypertrophic scars. Immunohistochemically, a combined expression of vimentin and alpha-sm actin is seen in the spindle-shaped cell formations. The decisive histological preparation is supported by immunohistochemical techniques, especially in the differentiation from sarcoma. If a definite diagnosis is made, incomplete excision may suffice.
    Notes: Zusammenfassung Die Myositis proliferans ist eine reaktive intramuskuläre Weichteilerkrankung, die durch eine Proliferation von Fibroblasten und Myofibroblasten, mit Übereinstimmungen zum phasenhaften Verlauf der allgemeinen Pathologie von Wundheilungsvorgängen und hypertrophen Narben charakterisiert ist. Immunhistochemisch zeigt sich eine kombinierte Expression von Vimentin und alpha-sm-Aktin im Bereich der spindeligen Zellformationen. Die entscheidende histologische Aufarbeitung erfährt durch immunhistochemische Verfahren eine sinnvolle Unterstützung insbesondere bei der Abgrenzung zu Sarkomen. Gelingt eine sichere Zuordnung, kann auch eine inkomplette Exzision ausreichend sein.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Der Pathologe 19 (1998), S. 134-140 
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Placentoide Malformation Lunge ; Makroskopie ; Histologische/ elektronenmikroskopische Befunde ; Pathogenese ; Key words Placentoid malformation lung ; Macroscopy ; Histologic/electronmicroscopic findings ; Pathogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The differential diagnosis of bullous and cystiform lung alterations comprises a relatively calculable number of various diseases, in which the most important are rare cystic tumors and congential malformations, such as adenomatoid cystic malformation. We report on a rare clinical picture. In this case, the clinical diagnosis of localized unilateral emphysema caused by local displacement and with subsequent complications had led to ”bullectomies” and pneumonectomy. Macroscopi-cally, spongiform solid areas in association with areas of physaliform transformation were seen, corresponding histomorphologi-cally to villous, placentalike formations. The ”villous stroma” revealed focally regressive alterations, fatty islets and leiomyomatous areas. So far, the pathogenesis of this lesion, described as ”placentoid malformation” due to its pathognomonic histological appear-ance, remains unclear. In contradiction to the much discussed hypothesis that this lesion may develop from pre-existing lung emphysema, our results suggest that this may be an independent lesion, possibly congenital hamartous malformation with self-developing progression. The clinically predominant emphysematic alterations are considered to be caused by a valve mechanism due to unphysiological traction forces, the lymphatic path-ways regularly found in the border areas towards the original lung tissue, possibly playing an important etiological part.
    Notes: Zusammenfassung Die Differentialdiagnose bullöser und zystiformer Lungenveränderungen umfaßt eine relativ überschaubare Zahl unterschiedlicher Krankheitsbilder, wobei insbesondere seltene zystische Tumoren und kongenitale Fehlbildungen wie die adenomatoidzystische Malformation abgegrenzt werden müssen. Wir berichten über ein bisher seltenes Krankheitsbild, bei dem unter der klinischen Diagnose eines lokalisierten einseitigen Emphysems aufgrund lokaler Verdrängungserscheinungen mit daraus resultierenden Komplikationen „Bullektomien” und eine Pneumonektomie durchgeführt wurden. Den makroskopisch imponierenden schwammartig-soliden Bezirken in Assoziation zu blasig transformierten Arealen entspricht das histomorphologische Korrelat zottig-villöser, plazentaähnlicher Formationen. Das „Zottenstroma” zeigt fokale regressive Veränderungen, daneben können fakultativ Fettinseln sowie leiomyomatöse Bezirke abgegrenzt werden. Die kausale Pathogenese der aufgrund des pathognomonischen feingeweblichen Bildes deskriptiv als „plazentoide Malformation” bezeichneten Läsion ist bisher nicht geklärt. Unsere Untersuchungen weisen im Gegensatz zu der vielfach diskutierten Hypothese der Entwicklung dieser Läsion aus einem vorbestehenden Lungenemphysem das Krankheitsbild als eigenständige Läsion im Sinne einer mög- licherweise kongenitalen hamartösen Malformation mit progredienter Eigendynamik aus. Die klinisch meist im Vordergrund stehenden emphysematischen Veränderungen werden als Folge eines durch unphysiologische Zugkräfte entstandenen Ventilmechanismus gewertet, wobei den regelmäßig in den Grenzzonen zum originären Lungengewebe zu beobachtenden Lymphbahnen möglicherweise eine ätiologisch bedeut- same Rolle zukommt.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Der Pathologe 19 (1998), S. 214-220 
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Talkum ; Pleurodese ; Rasterelektronenmikroskopie ; Maligne Pleuraerkrankungen ; Key words Talcum ; Pleurodesis ; Scan electron microscopy ; Malignant pleural diseases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Because of the rising importance of talcum pleurodesis in the therapeutic management of malignant and benign pleural effusions in Germany, pleural samples after talcum pleurodesis were compared to microscopic, immunohistochemical, and scanning electron microscopy findings after Tetracyclin and Novantron pleurodesis in 24 patients up to 18 months after intrapleural therapy. The histomorphological findings after talcum pleurodesis show an early phase of up to 4 weeks, characterized by the presence of talcum-containing granulation tissue with giant-cell foreign-body reaction, and a subsequent late phase with organization of the granulation tissue and connective tissue formation and obliteration of the pleura sheets. The resulting characteristic linear talcum zone in the pleural connective tissue is missing in cases with tumorous infiltration of the pleura. Continuous fibroblast activation, e.g., by macrophage or foreign-body giant-cell-released mediators, seems to be the decisive factor in the fibrosing process. No therapy-related tumor growth alterations could be demonstrated.
    Notes: Zusammenfassung Aufgrund der auch in Deutschland zunehmenden Bedeutung von Talkumpleurodesen für die Therapie von malignen und benignen Pleuraergüssen wurden Präparate der Pleura nach Talkumpleurodesen vergleichend mit Befunden nach Tetracyclin- und Novantron®-Pleurodesen von 24 Patienten bis zu einem Zeitraum von maximal 18 Monaten nach intrapleuraler Therapie mikroskopisch, immunhistochemisch und rasterelektronenmikroskopisch untersucht. Die histomorphologischen Befunde nach Talkumpleurodese können eingeteilt werden in eine bis zu 4 Woche dauernde Frühphase, welche sich durch ein talkumhaltiges Granulationsgewebe mit riesenzelliger Fremdkörperinfiltration auszeichnet, sowie eine daran anschließende Spätphase, in der es in wechselnden zeitlichen Verläufen zu einer Organisation des Granulationsgewebes mit bindegewebiger Durchbauung und zur Obliteration der Pleurablätter kommt. Die daraus resultierende charakteristische lineare Talkumzone im pleuralen Bindegewebe ist bei tumoröser Infiltration der Pleura aufgehoben. Eine kontinuierliche Fibroblastenaktivierung u.a. durch von Makrophagen und Fremdkörperriesenzellen freigesetzte Mediatoren scheint für den Fibrosierungsprozeß die entscheidende Rolle zu spielen. Eine Änderung des Tumorwachstums durch die Therapie konnte nicht belegt werden.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1963
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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