Yang-Baxter equation in spin chains with long range interactions

We consider the $su(n)$ spin chains with long range interactions and the spin generalization of the Calogero-Sutherland models. We show that their properties derive from a transfer matrix obeying the Yang-Baxter equation. We obtain the expression of the conserved quantities and we diagonalize them.Comment: Saclay-t93/00

CamFlow: Managed Data-sharing for Cloud Services

A model of cloud services is emerging whereby a few trusted providers manage the underlying hardware and communications whereas many companies build on this infrastructure to offer higher level, cloud-hosted PaaS services and/or SaaS applications. From the start, strong isolation between cloud tenants was seen to be of paramount importance, provided first by virtual machines (VM) and later by containers, which share the operating system (OS) kernel. Increasingly it is the case that applications also require facilities to effect isolation and protection of data managed by those applications. They also require flexible data sharing with other applications, often across the traditional cloud-isolation boundaries; for example, when government provides many related services for its citizens on a common platform. Similar considerations apply to the end-users of applications. But in particular, the incorporation of cloud services within `Internet of Things' architectures is driving the requirements for both protection and cross-application data sharing. These concerns relate to the management of data. Traditional access control is application and principal/role specific, applied at policy enforcement points, after which there is no subsequent control over where data flows; a crucial issue once data has left its owner's control by cloud-hosted applications and within cloud-services. Information Flow Control (IFC), in addition, offers system-wide, end-to-end, flow control based on the properties of the data. We discuss the potential of cloud-deployed IFC for enforcing owners' dataflow policy with regard to protection and sharing, as well as safeguarding against malicious or buggy software. In addition, the audit log associated with IFC provides transparency, giving configurable system-wide visibility over data flows. [...]Comment: 14 pages, 8 figure

Expression of MHC Class II Antigens During Xenopus Development

Larval and adult forms of the amphibian Xenopus differ in their MHC class II .expression. In tadpoles, class II epitopes can be detected by monoclonal antibodies only on B cells, macrophages (whatever their location), spleen reticulum, thymus epithelium, and the pharyngobuccal cavity. In contrast, all adult T cells express class II on their surface. The transitions in class II expression occur at metamorphosis and are accompanied by other changes. The skin is invaded by class II positive dendritic cells, and the skin glands differentiate and also express class II. The gut, which expressed class II in discrete areas of the embryonic tissue, becomes invaded with B cells, and its epithelium also becomes class II positive

Less is more ? The Commission proposal on access to EU documents and the proper limits of transparency

Transparency is now seen as a key tool of democratic governance. The European Union's commitment to transparency is now at the centre of a crucial debate between the Commission and the Parliament on the future of citizen's right of access to information. This article presents the main characteristics of the current regime and questions the pertinence of the proposed changes in light of the international drive at modernising access to information laws and the attempt at identifying the ̳proper limits of transparency'. The questions raised range from the identification of what can be accessed to the definition of exemption and the protection of competing interests

Unconventional continuous phase transition in a three dimensional dimer model

Phase transitions occupy a central role in physics, due both to their experimental ubiquity and their fundamental conceptual importance. The explanation of universality at phase transitions was the great success of the theory formulated by Ginzburg and Landau, and extended through the renormalization group by Wilson. However, recent theoretical suggestions have challenged this point of view in certain situations. In this Letter we report the first large-scale simulations of a three-dimensional model proposed to be a candidate for requiring a description beyond the Landau-Ginzburg-Wilson framework: we study the phase transition from the dimer crystal to the Coulomb phase in the cubic dimer model. Our numerical results strongly indicate that the transition is continuous and are compatible with a tricritical universality class, at variance with previous proposals.Comment: 4 pages, 3 figures; v2: minor changes, published versio

Identification of a Candidate CD5 Homologue in the Amphibian Xenopus laevis

We identified a novel T cell Ag in the South African clawed toad (Xenopus laevis) by a mAb designated 2B1. This Ag is present in relatively high levels on most thymocytes, approximately 65% of splenocytes, 55% of PBL, and 65% of intestinal lymphocytes, but is rarely seen on IgM+ B cells in any of these tissues. Lymphocytes bearing the 2B1 Ag proliferate in response to stimulation with Con A or PHA, whereas the 2B1- lymphocytes are reactive to LPS. Biochemical analysis indicates that this Ag is a differentially phosphorylated glycoprotein of 71 to 82 kDa. The protein core of 64 kDa bears both N- and O-linked carbohydrate side chains. The amino-terminal protein sequence of the 2B1 Ag shares significant homology with both the macrophage scavenger receptor type 1 motif and the mammalian CD5/CD6 family. The biochemical characteristics and cellular distribution of the 2B1 Ag suggest that it represents the CD5 homologue in X. laevis. While T cells constitutively express this highly conserved molecule, Xenopus B cells acquire the CD5 homologue only when they are stimulated in the presence of T cell

Evidence for the coexistence of Dirac and massive carriers in a-(BEDT-TTF)2I3 under hydrostatic pressure

Transport measurements were performed on the organic layered compound \aI3 under hydrostatic pressure. The carrier types, densities and mobilities are determined from the magneto-conductance of \aI3 . While evidence of high-mobility massless Dirac carriers has already been given, we report here, their coexistence with low-mobility massive holes. This coexistence seems robust as it has been found up to the highest studied pressure. Our results are in agreement with recent DFT calculations of the band structure of this system under hydrostatic pressure. A comparison with graphene Dirac carriers has also been done.Comment: 5 pages 5 figure

Opening wedge high tibial osteotomy performed without filling the defect but with locking plate fixation (TomoFix™) and early weight-bearing: Prospective evaluation of bone union, precision and maintenance of correction in 51 cases

SummaryIntroductionA medial opening wedge high tibial osteotomy (HTO), where the osteotomy site is filled, is often preferred to a lateral closing osteotomy, but filling the defect can lead to certain complications.HypothesisA medial opening HTO can be performed without filling the bone defect if fixation is carried out with a specially-designed stiff locking plate.Patients and methodsFifty-one patients, 37 to 72 years of age where followed prospectively and continuously from 2003 to 2006. A single surgical technique was used: medial opening HTO with locked plate fixation (TomoFix™, Synthes) but without filling the defect. The preoperative genu varum could not exceed 15°. The following were evaluated: time to return to weight-bearing, IKS functional score, long-leg standing film performed preoperative, postoperative and at follow-up to evaluate limb alignment and validate the precision of the correction and its stability over time. A measurement of the area of bone union in the osteotomy site was used to quantify the rate of union.ResultsBone union occurred at 4.5 months on average; two cases of incomplete union (7%) were found and revised with an autograft at 7 and 9 months. Lower-limb alignment was 7.5° of varus on average before surgery (3° to 15° varus, SD=2.85) and 1.2° of valgus on average after the surgery (4° varus to 5° valgus, SD=1.78). The correction was maintained at 1 year post-surgery. The average IKS knee score went from 69±15.5 (range 25 to 96) before surgery to 90±7.4 (range 66 to 98) at follow-up (P=0.0001). Full weight-bearing without assistance was possible after 3 months on average (range 1.5 to 8, SD=1.21). Forty-seven patients (92%) were fully weight-bearing after 2 months. Forty-eight patients were able to return to work and sporting activities at the same or a higher level than before the procedure.DiscussionBone union seems to happen more slowly when the defect is filled; however, there are doubts about radiological evaluation of bone union in different published studies. When osteotomy defect was left unfilled in this study, union and filling of 4/5 of the osteotomy site was obtained in 4.2 months for 49 of the 51 cases. Fixation with the locking plate is reliable and provides stable correction and the option for early weight-bearing.Level of proofLevel IV, prospective cohort study

Quantum spin chains of Temperley-Lieb type: periodic boundary conditions, spectral multiplicities and finite temperature

We determine the spectra of a class of quantum spin chains of Temperley-Lieb type by utilizing the concept of Temperley-Lieb equivalence with the S=1/2 XXZ chain as a reference system. We consider open boundary conditions and in particular periodic boundary conditions. For both types of boundaries the identification with XXZ spectra is performed within isomorphic representations of the underlying Temperley-Lieb algebra. For open boundaries the spectra of these models differ from the spectrum of the associated XXZ chain only in the multiplicities of the eigenvalues. The periodic case is rather different. Here we show how the spectrum is obtained sector-wise from the spectra of globally twisted XXZ chains. As a spin-off, we obtain a compact formula for the degeneracy of the momentum operator eigenvalues. Our representation theoretical results allow for the study of the thermodynamics by establishing a TL-equivalence at finite temperature and finite field.Comment: 29 pages, LaTeX, two references added, redundant figures remove