477 research outputs found
An idiotypic cross-reaction between allotype a3 and allotype a negative rabbit antibodies to streptococcal carbohydrates
Two antibodies to Group C streptococcal carbohydrate isolated from an individual rabbit had similar relative binding affinities for a Group C immuno-adsorbent column. Their light chains were similar, if not identical, as were the constant regions of their heavy chains. Differences in the variable regions of the H chains of the two antibodies were detected by chemical analysis. The two antibodies had serologically identical idiotypic determinants although one antibody possessed the a3 allotype and the other had no detectable group a marker. The occurrence of such antibodies indicates the absence of obligatory associations between group a allotypes and idiotypic specificities, despite the fact that both determinants have antigenic components in the VH region of the H chain
The role of TcdB and TccC subunits in secretion of the photorhabdus Tcd toxin complex
The Toxin Complex (TC) is a large multi-subunit toxin encoded by a range of bacterial pathogens. The best-characterized examples are from the insect pathogens Photorhabdus, Xenorhabdus and Yersinia. They consist of three large protein subunits, designated A, B and C that assemble in a 5:1:1 stoichiometry. Oral toxicity to a range of insects means that some have the potential to be developed as pest control technology. The three subunit proteins do not encode any recognisable export sequences and as such little progress has been made in understanding their secretion. We have developed heterologous TC production and secretion models in E. coli and used them to ascribe functions to different domains of the crucial B+C sub-complex. We have determined that the B and C subunits use a secretion mechanism that is either encoded by the proteins themselves or employ an as yet undefined system common to laboratory strains of E. coli. We demonstrate that both the N-terminal domains of the B and C subunits are required for secretion of the whole complex. We propose a model whereby the N-terminus of the C-subunit toxin exports the B+C sub-complex across the inner membrane while that of the B-subunit allows passage across the outer membrane. We also demonstrate that even in the absence of the B-subunit, that the C-subunit can also facilitate secretion of the larger A-subunit. The recognition of this novel export system is likely to be of importance to future protein secretion studies. Finally, the identification of homologues of B and C subunits in diverse bacterial pathogens, including Burkholderia and Pseudomonas, suggests that these toxins are likely to be important in a range of different hosts, including man
Electrical switching of magnetic polarity in a multiferroic BiFeO3 device at room temperature
We have directly imaged reversible electrical switching of the cycloidal
rotation direction (magnetic polarity) in a (111)-BiFeO3 epitaxial-film device
at room temperature by non-resonant x-ray magnetic scattering. Consistent with
previous reports, fully relaxed (111)-BiFeO3 epitaxial films consisting of a
single ferroelectric domain were found to comprise a sub-micron-scale mosaic of
magneto-elastic domains, all sharing a common direction of the magnetic
polarity, which was found to switch reversibly upon reversal of the
ferroelectric polarization without any measurable change of the magneto-elastic
domain population. A real-space polarimetry map of our device clearly
distinguished between regions of the sample electrically addressed into the two
magnetic states with a resolution of a few tens of micron. Contrary to the
general belief that the magneto-electric coupling in BiFeO3 is weak, we find
that electrical switching has a dramatic effect on the magnetic structure, with
the magnetic moments rotating on average by 90 degrees at every cycle.Comment: 6 pages, 5 figures; corrected figure
The introduction and refinement of the assessment of digitally recorded audio presentations
This case study critically evaluates benefits and challenges of a form of assessment included in a final year undergraduate Religious Studies Open University module, which combines a written essay task with a digital audio recording of a short oral presentation. Based on the
analysis of student and tutor feedback and sample assignments, this study critically examines how teaching and learning practices linked to this novel form of assessment have been iteratively developed in
light of the project findings over a period of two years. It concludes that while this form of assessment poses a number of challenges, it can create valuable opportunities for the development of transferable twenty-first-century graduate employability skills as well as deep,
effective learning experiences, particularly â though not exclusively â in distance learning settings
Rethinking the social impacts of the arts
The paper presents a critical discussion of the current debate over the social impacts of the arts in the UK. It argues that the accepted understanding of the terms of the debate is rooted in a number of assumptions and beliefs that are rarely questioned. The paper goes on to present the interim findings of a threeâyear research project, which aims to rethink the social impact of the arts, with a view to determining how these impacts might be better understood. The desirability of a historical approach is articulated, and a classification of the claims made within the Western intellectual tradition for what the arts âdoâ to people is presented and discussed
Nematode Symbiont for Photorhabdus asymbiotica
Photorhabdus asymbiotica is an emerging bacterial pathogen that causes locally invasive soft tissue and disseminated bacteremic infections in the United States and Australia. Although the source of infection was previously unknown, we report that the bacterium is found in a symbiotic association with an insect-pathogenic soil nematode of the genus Heterorhabditis
Observation of magnetic vortex pairs at room temperature in a planar {\alpha}-Fe2O3/Co heterostructure
Vortices are among the simplest topological structures, and occur whenever a
flow field `whirls' around a one-dimensional core. They are ubiquitous to many
branches of physics, from fluid dynamics to superconductivity and
superfluidity, and are even predicted by some unified theories of particle
interactions, where they might explain some of the largest-scale structures
seen in today's Universe. In the crystalline state, vortex formation is rare,
since it is generally hampered by long-range interactions: in ferroic materials
(ferromagnetic and ferroelectric), vortices are only observed when the effects
of the dipole-dipole interaction is modified by confinement at the nanoscale,
or when the parameter associated with the vorticity does not couple directly
with strain. Here, we present the discovery of a novel form of vortices in
antiferromagnetic (AFM) hematite (-FeO) epitaxial films, in
which the primary whirling parameter is the staggered magnetisation.
Remarkably, ferromagnetic (FM) topological objects with the same vorticity and
winding number of the -FeO vortices are imprinted onto an
ultra-thin Co ferromagnetic over-layer by interfacial exchange. Our data
suggest that the ferromagnetic vortices may be merons (half-skyrmions, carrying
an out-of-plane core magnetisation), and indicate that the vortex/meron pairs
can be manipulated by the application of an in-plane magnetic field,
H, giving rise to large-scale vortex-antivortex annihilation.Comment: 16 pages, 4 figure
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