11,398 research outputs found
Detailed Topography of the Fermi Surface of Sr2RuO4
We apply a novel analysis of the field and angle dependence of the
quantum-oscillatory amplitudes in the unconventional superconductor Sr2RuO4 to
map its Fermi surface in unprecedented detail, and to obtain previously
inaccessible information on the band dispersion. The three quasi-2D Fermi
surface sheets not only exhibit very diverse magnitudes of warping, but also
entirely different dominant warping symmetries. We use the data to reassess
recent results on c-axis transport phenomena.Comment: REVTeX, 4 page
Phase transitions in a gas of anyons
We continue our numerical Monte Carlo simulation of a gas of closed loops on
a 3 dimensional lattice, however now in the presence of a topological term
added to the action corresponding to the total linking number between the
loops. We compute the linking number using certain notions from knot theory.
Adding the topological term converts the particles into anyons. Using the
correspondence that the model is an effective theory that describes the
2+1-dimensional Abelian Higgs model in the asymptotic strong coupling regime,
the topological linking number simply corresponds to the addition to the action
of the Chern-Simons term. We find the following new results. The system
continues to exhibit a phase transition as a function of the anyon mass as it
becomes small \cite{mnp}, although the phases do not change the manifestation
of the symmetry. The Chern-Simons term has no effect on the Wilson loop, but it
does affect the {\rm '}t Hooft loop. For a given configuration it adds the
linking number of the 't Hooft loop with all of the dynamical vortex loops to
the action. We find that both the Wilson loop and the 't Hooft loop exhibit a
perimeter law even though there are no massless particles in the theory, which
is unexpected.Comment: 6 pages, 5 figure
The worker branch in Yorkshire as a way of organising Polish migrants: exploring the process of carving out diasporic spaces within the trade union structure
While post-2004 Polish labour migration to the UK was underpinned by diasporic spaces instrumental in facilitating social and labour market adjustments, the institutions of the host society such as trade unions also sought to establish links with migrants. The analysis of interactions between UK unions and EU migrants focused on organising strategies and specific provisions such as English language learning. However, the discussion tended to ignore the impacts of diasporic influences, from ethnicity and native languages of migrants to the outcomes of migrant worker organising. Drawing on ethnographic and qualitative data, this paper discusses how Polishness, in its ethnic, historic and linguistic manifestations, has affected the internal dynamics of a migrant worker organisation created by a major UK trade union. The explicit acknowledgement of diasporic particularities of post-2004 Polish migrants not only enabled labour organising activities but also shaped the migrant worker organisation from within. The strength of diasporic influences on one hand and the chosen form of union organising on the other created conditions for the development of diasporic spaces within the institution of the host society
Rigid-Band Shift of the Fermi Level in a Strongly Correlated Metal: Sr(2-y)La(y)RuO(4)
We report a systematic study of electron doping of Sr2RuO4 by non-isovalent
substitution of La^(3+) for Sr^(2+). Using a combination of de Haas-van Alphen
oscillations, specific heat, and resistivity measurements, we show that
electron doping leads to a rigid-band shift of the Fermi level corresponding to
one doped electron per La ion, with constant many-body quasiparticle mass
enhancement over the band mass. The susceptibility spectrum is substantially
altered and enhanced by the doping but this has surprisingly little effect on
the strength of the unconventional superconducting pairing.Comment: 4 pages, 3 figure
Field theoretic description of the abelian and non-abelian Josephson effect
We formulate the Josephson effect in a field theoretic language which affords
a straightforward generalization to the non-abelian case. Our formalism
interprets Josephson tunneling as the excitation of pseudo-Goldstone bosons. We
demonstrate the formalism through the consideration of a single junction
separating two regions with a purely non-abelian order parameter and a sandwich
of three regions where the central region is in a distinct phase. Applications
to various non-abelian symmetry breaking systems in particle and condensed
matter physics are given.Comment: 10 pages no figure
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Weathering microenvironments on feldspar surfaces: implications for understanding fluid-mineral reactions in soils
The mechanisms by which coatings develop on weathered grain surfaces, and their potential impact on rates of fluid-mineral interaction, have been investigated by examining feldspars from a 1.1 ky old soil in the Glen Feshie chronosequence, Scottish highlands. Using the focused ion beam technique, electron-transparent foils for characterization by transmission electron microscopy were cut from selected parts of grain surfaces. Some parts were bare whereas others had accumulations, a few micrometres thick, of weathering products, often mixed with mineral and microbial debris. Feldspar exposed at bare grain surfaces is crystalline throughout and so there is no evidence for the presence of the amorphous 'leached layers' that typically form in acid-dissolution experiments and have been described from some natural weathering contexts. The weathering products comprise sub-μm thick crystallites of an Fe-K aluminosilicate, probably smectite, that have grown within an amorphous and probably organic-rich matrix. There is also evidence for crystallization of clays having been mediated by fungal hyphae. Coatings formed within Glen Feshie soils after ∼1.1 ky are insufficiently continuous or impermeable to slow rates of fluid-feldspar reactions, but provide valuable insights into the complex weathering microenvironments on debris and microbe-covered mineral surfaces
Analysis of Receptor Binding by the Channel-forming Toxin Aerolysin Using Surface Plasmon Resonance
Aerolysin is a channel-forming bacterial toxin that binds to glycosylphosphatidylinositol (GPI) anchors on host cell-surface structures. The nature of the receptors and the location of the receptor-binding sites on the toxin molecule were investigated using surface plasmon resonance. Aerolysin bound to the GPI-anchored proteins Thy-1, variant surface glycoprotein, and contactin with similar rate constants and affinities. Enzymatic removal of N-linked sugars from Thy-1 did not affect toxin binding, indicating that these sugars are not involved in the high affinity interaction with aerolysin. Aerolysin is a bilobal protein, and both lobes were shown to be required for optimal binding. The large lobe by itself bound Thy-1 with an affinity that was at least 10-fold weaker than that of the whole toxin, whereas the small lobe bound the GPI-anchored protein at least 1000-fold more weakly than the intact toxin. Mutation analyses provided further evidence that both lobes were involved in GPI anchor binding, with certain single amino acid substitutions in either domain leading to reductions in affinity of as much as 100-fold. A variant with single amino acid substitutions in both lobes of the protein was completely unable to bind the receptor. The membrane protein glycophorin, which is heavily glycosylated but not GPI-anchored, bound weakly to immobilized proaerolysin, suggesting that interactions with cell-surface carbohydrate structures other than GPI anchors may partially mediate toxin binding to host cells
Orthopedic management of the extremities in patients with Morquio A syndrome.
BackgroundMusculoskeletal involvement in Morquio A syndrome (mucopolysaccharidosis IVA; MPS IVA) contributes significantly to morbidity and mortality. While the spinal manifestations of the disorder have received considerable attention in the literature, there have been few reported studies to date to guide the management of the orthopedic problems associated with the lower and upper extremities.PurposeThe objective was to develop recommendations for the management of the extremities in patients with Morquio A syndrome.MethodsA group of specialists in orthopedics, pediatrics and genetics with experience in the management of Morquio A patients convened to review and discuss current clinical practices and to develop preliminary recommendations. Evidence from the literature was retrieved. Recommendations were further refined until consensus was reached.Results and conclusionsThis present article provides a detailed review and discussion of the lower and upper extremity deformities in Morquio A syndrome and presents recommendations for the assessment and treatment of these complications. Key issues, including the importance of early diagnosis and the implications of medical therapy, are also addressed. The recommendations herein represent an attempt to develop a uniform and practical approach to managing patients with Morquio A syndrome and improving their outcomes
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