14,099 research outputs found

    Flow properties of suspensions rich in solids

    Get PDF
    Mathematical evaluation of flow properties of fluids carrying high concentrations of solids in suspension relates suspension viscosity to physical properties of the solids and liquids, and provides a means for predicting flow behavior. A technique for calculating a suspensions flow rates is applicable to the design of pipelines

    Dynamics of the peel front and the nature of acoustic emission during peeling of an adhesive tape

    Full text link
    We investigate the peel front dynamics and acoustic emission of an adhesive tape within the context of a recent model by including an additional dissipative energy that mimics bursts of acoustic signals. We find that the nature of the peeling front can vary from smooth to stuck-peeled configuration depending on the values of dissipation coefficient, inertia of the roller, mass of the tape. Interestingly, we find that the distribution of AE bursts shows a power law statistics with two scaling regimes with increasing pull velocity as observed in experiments. In this regimes, the stuck-peeled configuration is similar to the `edge of peeling' reminiscent of a system driven to a critical state.Comment: Accepted for publication in Phys. Rev. Let

    Tip cap for a rotor blade

    Get PDF
    A replaceable tip cap for attachment to the end of a rotor blade is described. The tip cap includes a plurality of walls defining a compartment which, if desired, can be divided into a plurality of subcompartments. The tip cap can include inlet and outlet holes in walls thereof to permit fluid communication of a cooling fluid there through. Abrasive material can be attached with the radially outer wall of the tip cap

    Aspects of the Unitarized Soft Multipomeron Approach in DIS and Diffraction

    Get PDF
    We study in detail the main features of the unitarized Regge model (CFKS), recently proposed to describe the small-Q2Q^2 domain. It takes into account a two-component description with two types of unitarized contributions: one is the multiple pomeron exchange contribution, interacting with the large dipole configurations, and the other one consists of a unitarized dipole cross section, describing the interaction with the small size dipoles. We analyze the ratio between soft and hard pieces as a function of the virtuality, and also compare the resulting dipole cross section to that from the saturation model. Diffraction dissociation is also considered, showing the scaling violations in diffractive DIS and estimating the corresponding logarithmic slope.Comment: 14 pages, 5 postscript figures. Version to be published in Eur. Phys. J.

    Unitarity Corrections to the Proton Structure Functions through the Dipole Picture

    Full text link
    We study the dipole picture for the description of the deep inelastic scattering, focusing on the structure functions which are driven directly by the gluon distribution. One performs estimates using the effective dipole cross section given by the Glauber-Mueller approach in QCD, which encodes the corrections due to the unitarity effects associated with the saturation phenomenon. We also address issues about frame invariance of the calculations when analysing the observables.Comment: 16 pages, 8 figures. Version to be published in Phys. Rev.

    Molekulare Signalwege der aseptischen Endoprothesenlockerung (Molecular pathways in aseptic loosening of orthopaedic endoprosthesis)

    Full text link
    Abstract Operative joint replacement to treat disabling joint conditions secondary to degenerative and inflammatory arthritides has become one of the most efficacious and cost-effective procedures to relieve pain and restore joint function. However, prosthetic implants are not built to last forever and osteolysis and aseptic loosening has been associated with prosthetic arthroplasties since their introduction. The functional life of a synthetic joint is influenced by many factors including the material of the implant, operation procedures and the surgeon involved, as well as patient-related factors. Although promising developments have been achieved in this field, more than 10% of all implants still have to undergo operative revision within 15 years after the initial operation. Failure due to sepsis, fractures and dislocations has become rare; premature loosening of implants on the other hand is becoming much more important. Prosthetic loosening without concurrent infection or trauma is called aseptic loosening. It is generally accepted that small particles ("wear debris") and activated macrophages play a key role in aseptic loosening. The pathophysiology of this condition, however, is still not very well characterized. In this article, we review the molecular mechanisms and signal pathways that were unravelled as responsible factors for loosening orthopaedic implants. Finally, we discuss possible novel strategies for future therapeutic approaches

    Molekulare Signalwege der aseptischen Endoprothesenlockerung

    Get PDF
    Die Behandlung von immobilisierenden degenerativen und entzündlichen Gelenkerkrankungen mit der Implantation von Endoprothesen ist ein großer Erfolg und Fortschritt in der Medizin und hat stark zur Verbesserung der Lebensqualität der betroffenen Patienten beigetragen. Jährlich werden weltweit ca. 1,3 Mio. Endoprothesen implantiert, davon allein 500.000 in den USA. Dennoch sind die einmal implantierten Prothesen nicht von lebenslanger Dauer und unterliegen multiplen Einflüssen. Trotz immer neuer Entwicklungen müssen innerhalb der ersten 15 Jahre bis zu 10% der Implantate aufgrund vorzeitiger Prothesenlockerung gewechselt werden. Bei vorzeitiger Lockerung ohne Infekt oder Trauma spricht man von aseptischer Lockerung. Es ist allgemein bekannt, dass durch Abrieb entstandene Kleinstpartikel und aktivierte Makrophagen die Hauptrolle im Prozess der aseptischen Lockerung spielen. Die Pathophysiologie ist jedoch noch nicht vollständig erklärt. Die vorliegende Arbeit gibt eine Übersicht über die anerkannten molekularen Mechanismen und die Signalwege, die zur aseptischen Prothesenlockerung führen. Außerdem werden neue Therapieoptionen zur Vermeidung der aseptischen Lockerung diskutier

    Synovial fibroblasts: key players in rheumatoid arthritis

    Get PDF
    Rheumatoid arthritis (RA) is a chronic autoimmune-disease of unknown origin that primarily affects the joints and ultimately leads to their destruction. The involvement of immune cells is a general hallmark of autoimmune-related disorders. In this regard, macrophages, T cells and their respective cytokines play a pivotal role in RA. However, the notion that RA is a primarily T-cell-dependent disease has been strongly challenged during recent years. Rather, it has been understood that resident, fibroblast-like cells contribute significantly to the perpetuation of disease, and that they may even play a role in its initiation. These rheumatoid arthritis synovial fibroblasts (RASFs) constitute a quite unique cell type that distinguishes RA from other inflammatory conditions of the joints. A number of studies have demonstrated that RASFs show alterations in morphology and behaviour, including molecular changes in signalling cascades, apoptosis responses and in the expression of adhesion molecules as well as matrix-degrading enzymes. These changes appear to reflect a stable activation of RASFs, which occurs independently of continuous exogenous stimulation. As a consequence, RASFs are no longer considered passive bystanders but active players in the complex intercellular network of R

    Overexpression of toll-like receptors 3 and 4 in synovial tissue from patients with early rheumatoid arthritis: Toll-like receptor expression in early and longstanding arthritis

    Full text link
    OBJECTIVE: To analyze the expression, regulation, and biologic relevance of Toll-like receptors (TLRs) 1-10 in synovial and skin fibroblasts and to determine the expression levels of TLRs 2, 3, and 4 in synovial tissues from patients with early rheumatoid arthritis (RA), longstanding RA, and osteoarthritis (OA). METHODS: Expression of TLRs 1-10 in RA synovial fibroblasts (RASFs), OASFs, and skin fibroblasts was analyzed by real-time polymerase chain reaction (PCR). Fibroblasts were stimulated with tumor necrosis factor alpha, interleukin-1beta (IL-1beta), bacterial lipopeptide, poly(I-C), lipopolysaccharide, and flagellin. Production of IL-6 was determined by enzyme-linked immunosorbent assay and induction of TLRs 2-5, matrix metalloproteinases (MMPs) 3 and 13 messenger RNA by real-time PCR. Expression of TLRs 2-4 in synovial tissues was analyzed by immunohistochemistry. RESULTS: Synovial fibroblasts expressed TLRs 1-6, but not TLRs 7-10. Among the expressed TLRs, TLR-3 and TLR-4 were the most abundant in synovial fibroblasts, and stimulation of synovial fibroblasts with the TLR-3 ligand poly(I-C) led to the most pronounced increase in IL-6, MMP-3, and MMP-13. In contrast, skin fibroblasts did not up-regulate MMP-3 or MMP-13 after stimulation with any of the tested stimuli. In synovial tissues from patients with early RA, TLR-3 and TLR-4 were highly expressed and were comparable to the levels of patients with longstanding RA. These expression levels were elevated as compared with those in OA. CONCLUSION: Our findings of high expression of TLRs, particularly TLRs 3 and 4, at an early stage of RA and the reactivity of synovial fibroblasts in vitro to TLR ligands suggest that TLR signaling pathways resulting in persistent inflammation and joint destruction are activated early in the disease process

    Un-reduction

    Full text link
    This paper provides a full geometric development of a new technique called un-reduction, for dealing with dynamics and optimal control problems posed on spaces that are unwieldy for numerical implementation. The technique, which was originally concieved for an application to image dynamics, uses Lagrangian reduction by symmetry in reverse. A deeper understanding of un-reduction leads to new developments in image matching which serve to illustrate the mathematical power of the technique.Comment: 25 pages, revised versio
    corecore