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  • 2000-2004
  • 1990-1994  (10)
  • 1960-1964
  • 1992  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1372-1374 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The atomic structure of the (1¯3¯3¯)CdTe/(2¯1¯1¯)GaAs interface is analyzed by high resolution transmission electron microscopy in order to elucidate the origin of the dual epitaxy in the growth of CdTe on (2¯1¯1¯)GaAs by molecular beam epitaxy. The analysis shows that the lattice mismatch at the interface is accommodated by a novel mechanism, which occurs with the combination of the 14.6% lattice mismatch between CdTe and GaAs and one wurtzite type bond sequence on the (2¯1¯1¯) substrate surface.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Lysyl-tRNA synthetases are synthesized in Escherichia coli from two distinct genes, lysS and lysU, which are regulated differentially. A strain which is null for lysS, the constitutive gene, was created by gene disruption (lysS1) and exhibited cold-sensitive lethality. Hence, lysS is dispensable at high temperatures. This cold sensitivity was suppressed by a multi-copy plasmid carrying lysU, the inducible gene. These data are interpreted as indicating that lysS is functionally replaceable by lysU for cell growth, and that the cold sensitivity of lysS1 is caused by insufficient expression of lysU at low temperatures. To investigate the mechanism of lysU expression, cold-resistant bypass mutations were isolated from lysS1, and named als (for abandonment of lysS.). Two als mutations which were linked to lysU contain IS2 insertions upstream of the lysU promoter. They caused a 16–19-fold increase in the lysU-mRNA level. Furthermore, deletion mutations created immediately upstream of the lysU promoter restored growth of lysS1. These results suggest that transcription of lysU is negatively controlled by a cis-element located upstream of the promoter.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0942-0940
    Keywords: Brain tumour ; chemotherapy ; induced hypertension ; xenon-enhanced CT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Changes in tumour blood flow under an induced hypertensive state were examined in malignant brain tumours to know if the precondition for the effectiveness of induced hypertensive chemotherapy — relative increase in tumour blood flow — are fulfilled. Tumour blood flow was measured under both a resting and an induced hypertensive state in 12 patients with various malignant brain tumours (6 gliomas, 6 metastatic brain tumours) using xenon-enhanced computed tomography. The blood pressure was elevated 40% above the systemic blood pressure of the resting state by the infusion of angiotensin II. Tumour blood flow increased 30% on average above the normal brain tissue blood flow after the induction of an induced hypertensive state (p 〈 0.05). The tumour blood flow increased in 11 cases of malignant tumours, but decreased in one case with massive brain oedema after induced hypertension. The increase in blood flow was higher in hypervascular tumours and less in hypovascular tumours. Therefore, induced hypertensive chemotherapy probably will be more effective in hypervascular malignant brain tumours with small mass effects.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 34 (1992), S. 162-167 
    ISSN: 1432-1920
    Keywords: Embolization ; Gelfoam powder ; Iodinated contrast medium ; Meningioma ; Polyvinyl alcohol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Study of the MRI changes that occur after superselective embolization of hypervascular meningiomas with Gelfoam powder (5 cases) and polyvinyl alcohol (PVA) particles 150–250 μm in size (4 cases) has indicated that, after embolization, meningiomas showed loss of the signal void, decrease in gadolinium-DTPA contrast enhancement, and prolonged T1 and T2. Shortening of T1 and T2 was seen in two patients with Gelfoam-embolized meningiomas in whom CT showed pooling of iodinated contrast medium in the tissue. In vitro experimental data demonstrated that the shortening of T1 and T2 was due to the iodinated contrast medium.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1920
    Keywords: Intracranial tumour ; Cerebral blood volume ; Dynamic computed tomography ; Extracellular fluid space ; Vascular permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cerebral vascular permeability is an important consideration in treatment for intracranial tumours. We have developed a new method to measure the cerebral vascular permeability quantitatively using a conventional X-ray CT scanner and iodinated contrast medium. We have already applied our method in 50 cases of intracranial tumour and 5 cases, which establish the methodology, are demonstrated. Dynamic CT scanning of a section including the tumour and the superior sagittal sinus was performed over 40 min after bolus injection of contrast medium, and 25 images were acquired. Our theoretical model of contrast enhancement was applied to analyse time-density curves, and the following parameters were obtained:K i (inward flux constant),K b (backward flux constant),V p (vascular plasma volume), and λ (extracellular fluid space volume). Furthermore, functional maps were generated from parameters for each pixel. Changes in intra-arterial iodine concentration, required in our model, were measured from CT numbers in the superior sagittal sinus. We have investigated several aspects of our method. Histological findings in surgical specimens of intracranial tumours agreed well with the parameters obtained by our method.V p was verified quantitatively by single photon emission computed tomography. Our method was shown to be reproducible. These results show that the parameters are useful for assessing tumours and in planning chemotherapy. Our method, which employs no special equipment, is readily available at any institution.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 27 (1992), S. 1926-1932 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Silicon nitride with thin sputter-deposited titanium and nickel films was joined to SUS304 stainless steel (18% Cr-8% Ni) using metallic buffers in a series of silicon nitride/nickel/ molybdenum/nickel/SUS304, and the joining strength and microstructures were investigated. Four-point bending tests showed fracture strength of the joints up to 169 MPa. Cracks were formed at the interface between the silicon nitride and its adjacent nickel buffer, and frequently extended into the silicon nitride. Microstructural analyses revealed that the silicon nitride reacted with the sputter-deposited titanium producing titanium nitride and isolated silicon atoms, and that silicon and titanium diffused into the nickel buffer. Calculations using a finite-element method indicated a marked reduction in thermal stress induced in the joined silicon nitride with increasing thickness of the molybdenum buffer. The strong interfacial bond inducing the fracture of the joined silicon nitride was interpreted in terms of a good interfacial reaction, the interdiffusions and the reduction of thermal stress being due to the insertion of the molybdenum buffer.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 11 (1992), S. 1534-1536 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 69 (1992), S. 595-598 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The chemical composition of ultrafine amorphous Fe−B powders prepared by a chemical reduction depends on the mixed molar ratio of KBH4 to Fe ions. We propose the following reaction processes for the formation of ultrafine Fe−B powders: (1) 4Fe2++2BH4−+6OH−→2Fe2B+6H2O+H2 and (2) 4Fe2++2BH4−+7OH−→2Fe3B+Fe+BO2+5H2O+5/2H2.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 69 (1992), S. 599-602 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ultrafine amorphous (Fe, Co, Ni) B powders have been prepared by a chemical reduction method. The influence of the Co and Ni atoms on the distribution of internal magnetic fields P(Bhf) has been investigated. The quadrupole splitting distribution P(QS) of ultrafine amorphous Fe−Ni−B powders has a form similar to that derived for the dense random packing of atoms.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 69 (1992), S. 447-450 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Zn−Fe intermediate phases have been investigated. The distribution of quadrupole splittings P(QS) was determined from the Mössbauer spectrum: the P(QS) gives evidence for two different iron sites in the γ phase. The analysis of Mössbauer spectrum taken in an applied magnetic field shows the negative sign of electrical field gradients is present.
    Type of Medium: Electronic Resource
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