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  • 1
    Electronic Resource
    Electronic Resource
    Sequential tunneling due to intersubband scattering in double-barrier resonant tunneling devices (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 212-214 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetoquantum oscillations in the tunnel current of double-barrier n-GaAs/(AlGa)As/GaAs/(AlGa)As/GaAs resonant tunneling devices reveal evidence of sequential tunneling in the voltage range corresponding to the resonance when electrons tunnel into the second subband of the GaAs quantum well. The sequential tunneling arises from intersubband scattering between two quasi-bound states of the well. Near this resonance, the charge buildup in the well can be estimated from the magnetoquantum oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99522
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  • 2
    Electronic Resource
    Electronic Resource
    Edge effects in a gated submicron resonant tunneling diode (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2508-2510 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the current-voltage [I(V)] characteristics of a gated GaAs/(AlGa)As resonant tunneling diode. As the negative gate voltage is progressively increased I(V) becomes asymmetric. In particular the peak-to-valley ratio in forward bias is decreased from (approximately-equal-to)20 to (approximately-equal-to)1, but in reverse bias remains constant (approximately-equal-to)20. This arises from a lateral variation of the voltage drop across the emitter tunnel barrier, which in forward bias leads to a smearing of the resonance. We discuss the relationship between our experiment and the low peak-to-valley ratios of two-terminal submicron resonant tunneling diodes observed by other groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106949
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  • 3
    Electronic Resource
    Electronic Resource
    Submicrometer resonant tunnelling diodes fabricated by photolithography and selective wet etching (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1124-1126 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new process based on photolithography and selective wet etching has been used to fabricate small area resonant tunnelling diodes. The low-temperature current-voltage (I-V) characteristics of diodes with conducting widths less than 0.1 μm show additional peaks due to 1D lateral quantum confinement. We observe a pronounced asymmetry in I-V which we explain in terms of tunnelling from emitter states which have a different degree of lateral quantum confinement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112117
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of a school visit dental health programme upon the attitudes of undergraduate dental students in England (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Community dentistry and oral epidemiology 10 (1982), S. 0 
    Details
    ISSN: 1600-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract A programme of structured school visits during the dental undergraduate course was used to assess attitudes and changes of attitudes of dental students to aspects of dental health education. Participating students showed the greater changes of attitude towards community dental health education and developed better understanding of correct dietary and oral hygien advice. However, in spite of these attitude changes the participating students were not convince of that this type of dental health education was very effective in the prevention of dental disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0528.1982.tb00372.x
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  • 5
    Electronic Resource
    Electronic Resource
    Ectopic Meningothelial Hamartoma of the Scalp (2005)
    Oxford, UK; Malden, USA : Blackwell Publishing Ltd/Inc.
    Journal of cutaneous pathology 32 (2005), S. 0 
    Details
    ISSN: 1600-0560
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A 7-month-old male infant presented with a 2 month history of a solitary, well circumscribed, 1.2 cm right parietal scalp lesion. An MRI excluded intracranial extension of the lesion. Grossly the excised lesion was tan-grey, soft to rubbery with focal areas of hemorrhage. On histology, the lesion demonstrated elongated strands of haphazardly arranged fibrous tissue and meningothelial elements with clusters of plump, cuboidal epitheloid cells extending along connective tissue planes in the dermis and subcutaneous tissue. The meningothelial elements were intimately admixed with mature adipose tissue and proliferation of small to medium sized vessels. The overlying epidermis was unremarkable. No mitotic figures or areas of necrosis were identified. The meningothelial cells were positive for Vimentin and Epithelial Membrane Antigen. S-100 protein was negative and CD-34 was positive only in the endothelial cells. The gross, histologic and immunohistochemical features are consistent with ectopic meningothelial hamartoma of the scalp. The meningothelial elements characteristic of this entity are believed to arise from displaced, ectopic meningothelial rests in the scalp and are thus regarded as simply representing a proliferation of the hamartomatous process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0303-6987.2005.320fe.x
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  • 6
    Electronic Resource
    Electronic Resource
    Dental study of handicapped children attending special schools in Birmingham, UK (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Community dentistry and oral epidemiology 14 (1986), S. 0 
    Details
    ISSN: 1600-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract The prevalence of dental caries, the levels of oral hygiene and the periodontal treatment requirements were assessed in 3562 handicapped children and 1344 randomly selected normal children attending schools in Birmingham, UK. The effect of different types of handicapping condition on these parameters was also evaluated. This investigation showed that there were few differences in caries prevalence when comparing handicapped children with children attending normal schools. However, the provision of dental care showed significant differences, with the handicapped children receiving less restorative treatment. There were also significantly poorer levels of oral hygiene and a greater prevalence of periodontal disease in the handicapped children attending special schools. The type of handicapping condition had a significant effect on the periodontal problems observed; those children with mental retardation having the poorest levels of oral hygiene and the greatest periodontal treatment requirements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0528.1986.tb01488.x
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  • 7
    Electronic Resource
    Electronic Resource
    Identification of the ligand-binding domain of the surface-located fibrinogen receptor (clumping factor) of Staphylococcus aureus (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 16 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ability of Staphylococcus aureus to bind to fibrinogen and fibrin is believed to be an important factor in the initiation of foreign-body and wound Infections. Recently, we reported the cloning and sequencing of the gene clfA encoding the fibrinogen receptor (clumping factor, ClfA) of S. aureus strain Newman and showed that the gene product was responsible for the clumping of bacteria in soluble fibrinogen and for the adherence of bacteria to solid-phase fibrinogen. This was confirmed here by showing that antibodies raised against purified Region A inhibited both of these properties. Also, immunofluorescent microscopic analysis of wild-type Newman and a clfA::Tn917 mutant of Newman with anti-ClfA Region A sera confirmed that Region A is exposed on the bacterial cell surface. Furthermore, polystyrene beads coated with the Region A protein formed clumps in soluble fibrinogen showing that the ClfA protein alone is sufficient for the clumping phenotype. Western immunoblotting with anti-ClfA Region A antibodies identified the native ClfA receptor as a 185 kDa protein that was released from the cell wall of S. aureus by lysostaphin treatment. A single extensive ligand-binding site was located within Region A of the ClfA protein. Truncated ClfA proteins were expressed in Escherichia coli. Lysates of E. coli and proteins that had been purified by affinity chromatography were tested for (i) their ability to bind fibrinogen in Western ligand blotting experiments, (ii) for their ability to inhibit clumping of bacteria in fibrinogen solution and adherence of bacteria to solid-phase fibrinogen, and (iii) for their ability to neutralize the blocking activity of anti-ClfA Region A antibody. These tests allowed the ligand-binding domain to be localized to a 218-residue segment (residues 332-550) within Region A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.tb02316.x
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular characterization of the clumping factor (fibrinogen receptor) of Staphylococcus aureus (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 11 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Four mutants of Staphylococcus aureus strain Newman that were defective in the fibrinogen receptor (clumping factor) were isolated by transposon Tn917 mutagenesis. Southern hybridization analysis of the mutants identified transposon-host DNA junction fragments, one of which was cloned and used to generate a probe to identify and clone the wild-type clumping factor locus (clfA). The mutants failed to form clumps in soluble fibrinogen and adhered poorly to polymethylmethacrylate (PMMA) coverslips coated with fibrinogen. A single copy of the clfA gene, when introduced into the chromosome of the mutant strains, fuily compiemented the ciumping deficiency of these strains and restored the ability of these mutants to adhere to fibrinogen-coated PMMA. in addition, the cloned clfA gene on a shuttle plasmid aiiowed the weakiy ciumping strain 8325-4 to form clumps with the same avidity as the wild-type strain Newman and also significantly enhanced the adherence of 8325-4 strains. Thus the formation of clumps in soluble fibrinogen correlated with adherence of bacteria to solid-phase fibrinogen. The clfA gene encodes a fibrinogen-binding protein with an apparent molecular mass of c. 130 kDa. The amino acid sequence of the protein was deduced from the DNA sequence; it was predicted that a 896 residue protein (molecular mass 92 kDa) would be expressed. The putative ClfA protein has features that suggest that it is associated with the ceil surface. Furthermore it contains a novel 308 residue region comprising dipeptide repeats predominantly of Asp and Ser ending 28 residues upstream from the LPXTG motif common to wall-associated proteins. Significant homology was found between the ClfA protein and the fibronectin-binding proteins of S. S. aureus, particularly in the N-and C-termini.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00304.x
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  • 9
    Electronic Resource
    Electronic Resource
    The coagulase of Staphylococcus aureus 8325-4. Sequence analysis and virulence of site-specific coagulase-deficient mutants (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The sequence of the coagulase gene (coa) from Staphylococcus aureus strain 8325-4 is reported. The deduced amino acid sequence of the coagulase protein is compared with previously reported sequences of coagulases from strains 213 and BB. The secreted mature forms of coagulase proteins are composed of three distinct segments: (i) the N-terminal 150–270 residues, which are c. 50% identical, (ii) a central region with high (〉90%) residue identities, and (iii) a C-terminal region composed of repeated 27-amino-acid residue sequences. The variable N-terminal sequences are probably responsible for antigenic differences among coagulases of different serotype. The region of coagulase which binds to prothrombin and activates it to form staphylothrombin is also located in the N-terminal half of the protein.A site-specific substitution mutation in the coa gene, which abolished plasma clotting activity, was isolated by recombinational allele-replacement in strains 8325-4 and M60. The Coa− mutants did not show diminished virulence in subcutaneous and intramammary infections of mice. No evidence for a role for coagulase in virulence of toxigenic or non-toxigenic strains was obtained. This contradicts findings of several groups using Coa− mutants generated by chemical mutagenesis and suggests that the earlier results were obtained with strains that had suffered additional mutations in virulence-related genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb00606.x
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  • 10
    Electronic Resource
    Electronic Resource
    Cryptic α-toxin gene in toxic shock syndrome and septicaemia strains of Staphylococcus aureus (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The majority of clinical isolates of Staphylococcus aureus that produce toxic shock syndrome toxin-1 (TSST-1) fail to express α-toxin, despite having a copy of the hla gene in the chromosome. The hla gene was cloned from an Hla- TSST-1+ strain, Todd 555, which had been isolated from a case of toxic shock syndrome in the USA. Of the 630 bases of the Todd 555 gene sequenced, 46 differed from the hla gene sequence of strain Wood 46. The defect in α-toxin expression was shown to be due to a nonsense mutation which converted a CAG glutamine codon in the equivalent position in the functional Wood 46 sequence to a TAG stop codon. The same mutation was present in the hla gene cloned from a human septicaemia strain (V37) isolated in Dublin. The nonsense mutation of Todd 555 was suppressed by the supE 44 mutation in Escherichia coli resulting in haemolytic activity in cell lysates. Hybrid hla genes were formed by splicing fragments of hla from Todd 555 and Wood 46. Expression of one such chimaeric hla gene in S. aureus demonstrated that the Todd 555 hla gene has a functional agr-regulated promoter. The silent hla gene may be a cryptic gene in S. aureus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb02044.x
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