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  • 1
    Electronic Resource
    Electronic Resource
    Distinctive Degradation Behaviors of Electrospun PGA, PLGA and P(LLA-CL) Nanofibers Cultured with/without Cell Culture (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 1327-1330 
    Details
    ISSN: 1662-8985
    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: Biodegradable nanofiber has become a popular candidate as tissue engineering scaffolds due to itsbiomimic structure as natural extracellular matrix (ECM). Certain tissue regeneration may requireprolonged in vitro culture time for cellular reorganization and tissue remodeling. Therefore, longterm understanding of cellular effects on scaffold degradation is needed. Although there are somedegradation studies on nanofiber, degradation study of nanofibers with cell culture is rare. In ourstudy, polyglycolide (PGA), poly(DL-lactide-co-glycolide) (PLGA), poly(L-lactide-co-ε-caprolactone) [P(LLA-CL)] were electrospun into nanofiber scaffolds. The scaffolds were culturedwith porcine smooth muscle cells (PSMC) for up to 3 months to evaluate their degradation behaviorand cellular response. The results showed that their degradation rates were in the order ofPGA〉〉PLGA〉P(LLA-CL). PGA nanofiber degraded in 3 weeks and only supported cell growth inthe first few days. Cell culture accelerated the surface erosion of PLGA and P(LLA-CL) nanofiberwhile the bulk degradation remained unaffected. Furthermore, the cell culture did not significantlyreduce the mechanical strength of PLGA and P(LLA-CL) during degradation
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/41/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.47-50.1327.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of Step Aging on Creep Behavior and Microstructural Evolution of Fine-Grained Fully Lamellar XD TiAl Alloys (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 539-543 (Mar. 2007), p. 1525-1530 
    Details
    ISSN: 1662-9752
    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: Fine-grained fully lamellar (FGFL) structures of XD TiAl alloys (Ti-45 and47Al-2Nb-2Mn+0.8vol.%TiB2) (at.%) were stabilized to varying degrees by different agingtreatments. Specimens with and without aging were creep tested at 760°C and 207 MPa. It wasfound that during creep deformation, degradation of the lamellar structure involving coarseningwithin the colonies and spheroidization at colony boundaries occurred, forming fine globularstructures at the colony boundaries and increasing the creep rate. Aging treatments stabilized thelamellar structure and retarded the coarsening and spheroidization processes during creepdeformation. As a result, the aged specimens exhibited lower minimum creep rates and longer creeplives than the unaged specimens. A multiple step aging stabilized the lamellar structure to thegreatest extent and suppressed other degradation processes during aging, resulting in the best creepresistance. These results demonstrate that the multiple step aging is the optimal aging condition forstabilizing FGFL XD TiAl alloys
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/15/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.539-543.1525.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Microstructure and Creep of γ-TiAl Containing β-Stabilizer (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 539-543 (Mar. 2007), p. 1543-1548 
    Details
    ISSN: 1662-9752
    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: Fully lamellar structures of powder metallurgy (PM), investment cast, and directionallysolidified (DS) TiAl alloys containing β stabilizer were produced after stepped cool heat treatment,and interface β precipitates were formed after aging at 950°C. In addition, a columnar grainstructure combined with a fully lamellar structure aligned with the load direction and interface βprecipitates were formed by directional solidification and subsequent heat treatments. Creep testresults of PM TiAl indicate that controlling the initial microstructures is also critical for balancingthe primary and steady-state creep resistance during short and long-term tests. DS TiAl alloyexhibits a significant reduction of the primary strain and creep rate compared to polycrystalline TiAldue to the unique DS microstructure. Therefore, a DS microstructure with proper lamellarorientation and controlled interface β precipitation is the ideal if maximum time to a relatively small(〈0.5%) strain is the design criterion of merit
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/15/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.539-543.1543.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Microstructures and Mechanical Properties of Ti-48Al-2Cr-2Nb-xW (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 561-565 (Oct. 2007), p. 481-486 
    Details
    ISSN: 1662-9752
    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 microstructures and mechanical properties of three powder metallurgy Ti-48Al-2Cr-2Nb-xW alloys (where x=0, 0.5, and 1 atomic percent (at.%)) are presented. The results indicate thata solution heat treatment combined with controlled cooling generate a fully lamellar (FL)microstructure without the formation of detrimental Widmanstätten or massively transformed γphases. Aging causes coarsening of the FL microstructure in the alloys containing 0%W and0.5%W, while almost no coarsening occurs in the 1%W sample. The addition of W to the basecomposition results in the formation of precipitates at the lamellar interfaces and grain boundariesduring aging which helps stabilize the FL microstructure. The amount of W and the aging timeaffect the room temperature hardness values and tensile properties
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/17/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.561-565.481.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray analysis of luffaculin, a ribosome-inactivating protein from sponge-gourd seeds (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 185-186 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Luffaculin is a ribosome-inactivating protein. Crystals suitable for X-ray diffraction were first obtained using the hanging-drop vapour-diffusion method. X-ray studies show that the crystals belong to space group C2, with unit-cell parameters a = 89.90, b = 59.82, c = 55.18 Å, β = 120.81°, and have one molecule in the crystallographic asymmetric unit. The crystals diffract X-rays to at least 2.0 Å resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444999014110
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  • 6
    Electronic Resource
    Electronic Resource
    VqsM, a novel AraC-type global regulator of quorum-sensing signalling and virulence in Pseudomonas aeruginosa (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 58 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Human pathogen Pseudomonas aeruginosa uses quorum-sensing (QS) signalling systems to synchronize the production of virulence factors. There are two interrelated QS systems, las and rhl, in P. aeruginosa. In addition to this complexity, a number of transcriptional regulators were shown to have complicated interplays with las and rhl central QS components. Here, we describe a novel virulence and QS modulator (VqsM) that positively regulates the QS systems in P. aeruginosa. Mutation in vqsM resulted in much reduced production of N-acylhomoserine lactones (AHLs) and extracellular enzymes. Sequence analysis revealed that vqsM encodes a transcriptional regulator with an AraC-type helix–turn–helix DNA binding domain at the C-terminal of the peptide. Global gene expression profile analysis showed at least a total of 302 genes to be influenced, directly or indirectly, by VqsM. Among the 203 VqsM-promoted genes, 52.2% were known to be QS upregulated. Several genes encoding the key regulators implicated in QS, such as rhlR, rsaL, vqsR, mvfR, pprB and rpoS, and two AHL synthesis genes, lasI and rhlI, were suppressed in the vqsM mutant. Similar to the ‘AHL-blind’ phenotype of vqsR and pprB mutants, vqsM mutant did not respond to external addition of N-3-oxo-dodecanoyl-homoserine lactone signals. Moreover, overexpression of vqsR in vqsM mutant more or less restored the production of both AHL and virulence factors. The results demonstrate that VqsM, largely through modulation of vqsR expression, plays a vital role in regulation of QS signalling in P. aeruginosa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04851.x
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  • 7
    Electronic Resource
    Electronic Resource
    Quenching quorum-sensing-dependent bacterial infection by an N -acyl homoserine lactonase (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 411 (2001), S. 813-817 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Bacterial cells sense their population density through a sophisticated cell–cell communication system and trigger expression of particular genes when the density reaches a threshold. This type of gene regulation, which controls diverse biological functions including virulence, is known as ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35081101
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  • 8
    Electronic Resource
    Electronic Resource
    A rapid variation in the H-alpha profile of gamma cassiopeiae
    Amsterdam : Elsevier
    Chinese Astronomy and Astrophysics 9 (1985), S. 259-260 
    Details
    ISSN: 0275-1062
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0275-1062(85)90048-7
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  • 9
    Electronic Resource
    Electronic Resource
    The two-component response regulator PprB modulates quorum-sensing signal production and global gene expression in Pseudomonas aeruginosa (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 56 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The response regulator PprB and its cognate sensor PprA were recently reported as a two-component regulatory system that controls membrane permeability and antibiotic sensitivity of Pseudomonas aeruginosa. We found that a Tn5 insertion mutation in pprB caused a drastic reduction in virulence factor production and cell motility. A transcriptome analysis revealed that 175 genes were regulated by PprB. Among the 113 PprB-activated genes, 85.5% are known to be activated by N-3-oxo-dodecanoyl-homoserine lactone (OdDHL) and N-butanoyl-homoserine lactone (BHL). In particular, the expression of lasI, rhlI and rhlR, which encode key components of the las and rhl quorum-sensing (QS) systems, were significantly decreased in the pprB mutant. These data suggest that PprB might regulate QS signal production. Measurement of OdDHL and BHL in cultures of the mutant sustained this hypothesis. By using various OdDHL- or BHL-responsive QS reporter systems, including lasB–lacZ, lasI–lacZ and rsaL–lacZ, we found that the mutation in pprB resulted in a large decrease in the sensitivity of P. aeruginosa to exogenous OdDHL. However, there was no difference in sensitivity to BHL. Further analysis showed that the OdDHL influx was significantly reduced in the pprB mutant. We conclude that PprB is a novel QS modulator that positively regulates N-acylhomoserine lactone production probably by affecting the OdDHL signal influx and thereby influences global expression of the QS-dependent genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04612.x
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  • 10
    Electronic Resource
    Electronic Resource
    Quorum sensing and signal interference: diverse implications (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Quorum sensing (QS) is a community genetic regulation mechanism that controls microbiological functions of medical, agricultural and industrial importance. Discovery of microbial QS signals and the signalling mechanisms led to identification of numerous enzymatic and non-enzymatic signal interference mechanisms that quench microbial QS signalling. Evidence is accumulating that such signal interference mechanisms can be developed as promising approaches to control microbial infection and biofilm formation. In addition, these mechanisms exist not only in microorganisms but also in the host organisms of bacterial pathogens, highlighting their potential implications in microbial ecology and in host–pathogen interactions. Investigation of QS and signal interference mechanisms might significantly broaden the scope of research in microbiology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04234.x
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