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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 161 (1998), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: DnaK is known to be highly conserved in all species and is a major immunogen in Streptococcus pneumoniae. To elucidate the role of dnaK in S. pneumoniae, dnaK was cloned in Escherichia coli using a homologous dnaK probe generated by PCR. The His-tagged DnaK was overexpressed in soluble form and purified from E. coli. Alignment of the deduced DnaK amino acid sequence from nucleotide sequences of the cloned dnaK revealed high homology with DnaK analogs in E. coli (53%) and Staphylococcus aureus (73%). However, anti-pneumococcal DnaK antiserum did not crossreact with DnaK analogs in E. coli, S. aureus and human cells suggesting that pneumococcal DnaK might be a good candidate as a vaccine.
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 345-346 (Aug. 2007), p. 705-708 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The experimental investigation was performed to find the associated changes incharacteristics of fretting wear with various water temperatures. Fretting can be defined as theoscillatory motion with very small amplitudes, which usually occur between two contacting surfaces.The fretting wear, which occurs between cladding tubes of nuclear fuel rod and grids, causes indamages the cladding tubes by flow induced vibration in a nuclear reactor. In this paper, the frettingwear tests were carried out using the zirconium alloy tubes and the grids with increasing the watertemperature. The tube materials in water of 20[removed info], 50[removed info] and 80[removed info] were tested with the applied load of20N and the relative amplitude of 200[removed info]. The worn surfaces were observed by SEM, EDX and 2Dsurface profiler. As the water temperature increased, the wear volume was decreased. However, oxidelayer was increased on the worn surface. The abrasive wear mechanism was observed at watertemperature of 20[removed info] and adhesive wear mechanism occurred at water temperature of 50[removed info] and 80[removed info].As the water temperature increased, surface micro-hardness was decreased. Also, wear depth andwear width were decreased due to increasing stick phenomenon. Stick regime occurred due to theformation of oxide layer on the worn surface with increasing water temperatures
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 345-346 (Aug. 2007), p. 709-712 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fuel cladding tubes in nuclear fuel assembly are held up by supporting grids because thetubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes causeoscillating motions between tubes and supports. This is called as FIV (flow induced vibration), whichcauses fretting wear in contact parts of tube-support. The fretting wear of tube-support can threatenthe safety of nuclear power plant. Therefore, a research about the fretting wear characteristics oftube-support is required. The fretting wear tests were performed with supporting grids and claddingtubes, especially after corrosion treatment on tubes, in water. The tests were done using variousapplied loads with fixed amplitude. From the results of fretting tests, the wear amounts of tubematerials can be predictable by obtaining the wear coefficient using the work rate model. Due to stickphenomena the wear depth was changed as increasing load and temperature. The maximum weardepth was decreased as increasing the water temperatures. At high temperatures there are the regionsof some severe adhesion due to stick phenomena
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 119 (Jan. 2007), p. 231-234 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The Platinum catalysts on the carbon nanotubes(CNTs) supports of various diameterswere prepared by wet impregnation method using H2PtCl6 precursor. The samples using 100nm,15~20nm, 10~15nm and 5~10nm diameters of CNTs and carbon nanofibers(CNFs) are named Pt/t-CNFs, Pt/MWNTs20, Pt/MWNTs10 and Pt/MWNTs5, respectively. The effects of CNTs diameteron the Pt particle size and distribution were investigated by the means of powder XRD and TEMobservation. In addition, the electro-catalytic characteristics for methanol electro-oxidation wereestimated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS)techniques. The average size of Pt particles increases as follows; Pt/MWNTs10 〈 Pt/MWNTs5 〈Pt/MWNTs20 〈 Pt/t-CNFs. The electro-catalytic characteristics of Pt/MWNTs10 and Pt/MWNTs20are found to be superior in comparison with the others. For preparation of the most effectivesupported Pt catalyst, the optimum diameter of CNTs support in the range of 10-20nm, is needed
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 119 (Jan. 2007), p. 247-250 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Several methods for loading of Pt-Ni binary catalysts on the CNTs were tested. Using theCNTs treated HNO3, the catalysts supported Pt, Ni separately(Pt&Ni/CNT) and Pt-Ni alloy(Pt-Ni/CNTs) were made respectively. The results of supporting were confirmed by TEM and XRDanalysis. TEM images show that metal catalysts were loaded uniformly and finely on the CNTs. ByXRD analysis, the peaks of Pt&Ni/CNTs displayed Pt and Ni peaks respectively. Also it was foundthat the peaks of Pt were shifted to the higher 2theta angle in X-ray diffraction pattern whichindicated that Pt-Ni alloy was formed successfully(Pt-Ni/CNTs). In addition, electrochemical testsfor cathode catalysts of DMFC were performed. As the results, Pt-Ni/CNTs was most suitable forcathode catalysts of DMFC
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 118 (Dec. 2006), p. 479-484 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: This study investigated the microstructure and mechanical properties of the wide-gapregion brazed with various powder mixing ratios of additive powder (IN738) to filler metal powder(DF4B). The wide-gap brazing process was carried out in a vacuum of 2×10-5 torr at 1230ºC for 1 hr.The microstructure of the brazed region was analyzed by FESEM and AES. The wide-gap regionbrazed with 60wt.% IN738 additive powder and 40 wt.% DF 4B filler metal powder had amicrostructure consisting of Ni solid solution + γ' and (Cr, W)2B. The fracture strength of thewide-gap region brazed with 60 wt.% IN738 additive and 40 wt.% DF 4B powder was as high as 832MPa at room temperature. It was found that the (Cr, W)2B and pores in the brazed region areimportant microstructural factors affecting the mechanical properties of the wide-gap brazed region
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 297-300 (Nov. 2005), p. 250-256 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effects of adding Al, Y2O3 and the use of H2O as a PCA (process control agent), on the mechanical properties of mechanically alloyed Ni20Cr20Fe5Nb alloy were studied. The addition of Y2O3 and Al caused an increase in the tensile strength at room temperature, 400°C and 600°C. However, it was confirmed that the increase of tensile strength at room temperature and 400°C was predominantly caused by addition of Y2O3, while that at 600°C was mainly due to addition of Al.These results can be attributed to the dispersion strengthening of Y2O3, preventing the formation of Cr2O3 and the change of fracture mode at 600°C by the addition of Al. Therefore, the Ni20Cr20Fe5Nb2Al alloy using H2O as a PCA showed superior tensile strength at room temperature, 400°C and 600°C. The increase in the tensile strength at room temperature and 400°C can be attributed to the strengthening of the solid solution induced by the increase in the amount of Nb solid solution, resulting from the prevention of NbC formation, while the increase in the tensile strength at 600°C can be attributed to the strengthening of the grain boundary afforded by the presence of Al1.54Cr0.46O3 formed by the addition of Al. After aging treatment for 10 hours at 600°C, g²(Ni3Nb) precipitates were formed in the Ni20Cr20Fe5Nb2Al alloy in which H2O used as the PCA, and the formation of these precipitates caused an increase in hardness
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 297-300 (Nov. 2005), p. 2134-2139 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The cyclic deformation in Cu and Cu-35Zn alloy were studied using ultrasonicnondestructive evaluation (NDE) technique to measure the ultrasonic velocity, attenuation coefficient and a nonlinear parameter. These materials were cyclically deformed under total strain amplitude control to investigate their ultrasonic reaction to different dislocation substructures, depending on the stacking fault energy difference. The microstructure evolution was observed using a transmissionelectron microscope, and the ultrasonic NDE parameter was measured after several cycles of fatigue deformation, in order to clarify the relationship between them. In both materials, the ultrasonic velocity was observed to decrease as the fatigue life fraction increased, which was attributed to the increasing dislocation density caused by the cyclic deformation. In the case of Cu, with its cell structure evolving during cyclic deformation, the rate of increase of the ultrasonic attenuation coefficient and the ultrasonic nonlinear parameter was higher than that observed in the case of the Cu-35Zn alloy with its planar array structure. This result implies that the dislocation cell structure is more sensitive to the ultrasonic parameter changes than the planar array structure formed during cyclic deformation
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 297-300 (Nov. 2005), p. 2876-2882 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study investigated the microstructure and mechanical properties of a wide-gap region brazed with various process variables. The IN738 and DF 4B alloy powders were used as additive and filler metal powder for the brazing process. The wide-gap brazing process was carried out in a vacuum of 2×10-5 torr. The wide-gap region brazed with 60wt.% IN738 additive powder had a microstructure consisting of IN738 additive and (Cr, W)2B. The fracture strength of the wide-gap region (60 wt.%additive and 40 wt.% filler metal powder) brazed at 1230°C for 30hr was as high as 862MPa (93% of base material strength). It was observed that the brazing temperature was the main process variable affecting the mechanical properties of the wide-gap brazed region. The creep rupture life of the region brazed with 60wt.% additive and 40 wt.% was longer than that of other brazed samples. The Cracks inthe wide-gap brazed region initiated at the (Cr, W)2B and propagated through them. It was found that the (Cr, W)2B and the pore in the brazed region are important microstructural factors affecting the mechanical properties of the wide-gap brazed region
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  • 10
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effects of adding Y2O3, and the precipitation of Ni3Nb by heat treatment, on themechanical properties of mechanically alloyed Ni20Cr20Fe5Nb alloy were studied. The addition of Y2O3 caused an increase in the tensile strength at room temperature, 400°C and 600°C. The difference in the tensile strength between the Ni20Cr20Fe5Nb and Ni20Cr20Fe5Nb1Y2O3 alloys decreased gradually with increasing test temperature. The tensile strength of the Ni20Cr20Fe5Nb1Y2O3 alloy at relatively low temperature was increased by the addition of Y2O3, but decreased abruptly at temperature above 600°C. This seems to result from a change in the deformation mechanism due to the ultra-fine grain size, that is, grain boundary sliding is predominant at temperatures above 600°C while internal dislocation movement is predominant at temperatures below 600°C. Following the conventional heat treatment of the solution and subsequent aging, only a small amount of δ(Ni3Nb) phase was formed in the Ni20Cr20Fe5Nb alloy, whereas in a previous report it was indicated that a large amount of γ″(Ni3Nb) was formed in IN 718 alloy. The small amount of δ(Ni3Nb) phase formed in the present case is due to the exhaustion of the Nb content resulting from the formation of NbC during consolidation
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