Elastohydrodynamic Lift at a Soft Wall

We study experimentally the motion of nondeformable microbeads in a linear shear flow close to a wall bearing a thin and soft polymer layer. Combining microfluidics and 3D optical tracking, we demonstrate that the steady-state bead-to-surface distance increases with the flow strength. Moreover, such lift is shown to result from flow-induced deformations of the layer, in quantitative agreement with theoretical predictions from elastohydrodynamics. This study thus provides the first experimental evidence of “soft lubrication” at play at small scale, in a system relevant, for example, to the physics of blood microcirculation

A Cross-National Investigation of First-Generation, Second-Generation, and Third-Generation Family Businesses: A Four Country Anova Comparison

This study compared first, second, and third-generation family businesses in the United States, Croatia, France, and India - countries with significant differences in cultures, economies, levels of entrepreneurial activity, and family business demographics. Contrary to much of the existing literature, the results indicate that owner-managers of all three generational categories of family businesses, in all four countries, generally shared the same managerial characteristics and practices. Implications for theory development and further research are presented

Change in acetabular version after lumbar pedicle subtraction osteotomy to correct post-operative flat back: EOS® measurements of 38 acetabula

AbstractBackgroundAbnormalities in acetabular orientation can promote the development of hip osteoarthritis, femoro-acetabular impingement, or even acetabular cup malposition. The objective of the present study was to determine whether pedicle substraction osteotomy (PSO) to correct sagittal spinal imbalance affected acetabular orientation.HypothesisPSO performed to correct sagittal spinal imbalance affects acetabular orientation by changing the pelvic parameters.Materials and methodsThis was a descriptive study in which two observers measured the acetabular parameters on both sides in 19 patients (38 acetabula) before and after PSO for post-operative flat-back syndrome. Mean time from PSO to post-operative measurements was 19months. Measurements were taken twice at a 2-week interval, on standing images obtained using the EOS® imaging system and sterEOS® software to obtain 3D reconstructions of synchronised 2D images. Acetabular anteversion and inclination were measured relative to the vertical plane. Mean pre-PSO and post-PSO values were compared using the paired t-test, and P values lower than 0.05 were considered significant. To assess inter-observer and intra-observer reproducibility, we computed the intra-class correlation coefficients (ICCs).ResultsThe measurements showed significant acetabular retroversion after PSO, of 7.6° on the right and 6.5° on the left (P<0.001). Acetabular inclination diminished significantly, by 4.5° on the right and 2.5° on the left (P<0.01). Inclination of the anterior pelvic plane decreased by 8.4° (P<0.01). Pelvic incidence was unchanged, whereas sacral slope increased by 10.5° (P<0.001) and pelvic tilt decreased by 10.9° (P<0.001). The ICC was 0.98 for both inter-observer and intra-observer reproducibility.ConclusionChanging the sagittal spinal alignment modifies both the pelvic and the acetabular parameters. PSO significantly increases sacral slope, thus inducing anterior pelvic tilt with significant acetabular retroversion. The measurements obtained using sterEOS® showed good inter-observer and intra-observer reproducibility. To our knowledge, this is the first study of changes in acetabular version after PSO

Peculiar scaling of self-avoiding walk contacts

The nearest neighbor contacts between the two halves of an N-site lattice self-avoiding walk offer an unusual example of scaling random geometry: for N going to infinity they are strictly finite in number but their radius of gyration Rc is power law distributed, ~ Rc^{-\tau}, where \tau>1 is a novel exponent characterizing universal behavior. A continuum of diverging lengths scales is associated to the Rc distribution. A possibly super-universal \tau=2 is also expected for the contacts of a self-avoiding or random walk with a confining wall.Comment: 4 pages, 5 Postscript figures, uses psfig.sty; some sentences clarifie

Verdier specialization via weak factorization

Let X in V be a closed embedding, with V - X nonsingular. We define a constructible function on X, agreeing with Verdier's specialization of the constant function 1 when X is the zero-locus of a function on V. Our definition is given in terms of an embedded resolution of X; the independence on the choice of resolution is obtained as a consequence of the weak factorization theorem of Abramovich et al. The main property of the specialization function is a compatibility with the specialization of the Chern class of the complement V-X. With the definition adopted here, this is an easy consequence of standard intersection theory. It recovers Verdier's result when X is the zero-locus of a function on V. Our definition has a straightforward counterpart in a motivic group. The specialization function and the corresponding Chern class and motivic aspect all have natural `monodromy' decompositions, for for any X in V as above. The definition also yields an expression for Kai Behrend's constructible function when applied to (the singularity subscheme of) the zero-locus of a function on V.Comment: Minor revision. To appear in Arkiv f\"or Matemati

Paper Session I-C - Non-Destructive Detection of Corrosion Under Paint on Critical Surfaces

We describe our proof-of-concept demonstration of the well-known thermal diffusion imaging technique *\u3e 2\u3e3 for detection of corrosion under paint on critical surfaces. Our first application will be the detection and mapping of corrosion on arbiter vehicle wing spars and rudder speed brakes. The technique will also used for the evaluation of doubler plate bond integrity on the rudder speed brakes

An integrated assay to probe endothelial glycocalyx-blood cell interactions under flow in mechanically and biochemically well-defined environments

Cell-cell and cell-glycocalyx interactions under flow are important for the behaviour of circulating cells in blood and lymphatic vessels. However, such interactions are not well understood due in part to a lack of tools to study them in defined environments. Here, we develop a versatile in vitro platform for the study of cell-glycocalyx interactions in well-defined physical and chemical settings under flow. Our approach is demonstrated with the interaction between hyaluronan (HA, a key component of the endothelial glycocalyx) and its cell receptor CD44. We generate HA brushes in situ within a microfluidic device, and demonstrate the tuning of their physical (thickness and softness) and chemical (density of CD44 binding sites) properties using characterisation with reflection interference contrast microscopy (RICM) and application of polymer theory. We highlight the interactions of HA brushes with CD44-displaying beads and cells under flow. Observations of CD44+ beads on a HA brush with RICM enabled the 3-dimensional trajectories to be generated, and revealed interactions in the form of stop and go phases with reduced rolling velocity and reduced distance between the bead and the HA brush, compared to uncoated beads. Combined RICM and bright-field microscopy of CD44+ AKR1 T-lymphocytes revealed complementary information about the dynamics of cell rolling and cell morphology, and highlighted the formation of tethers and slings, as they interacted with a HA brush under flow. This platform can readily incorporate more complex models of the glycocalyx, and should permit the study of how mechanical and biochemical factors are orchestrated to enable highly selective blood cell-vessel wall interactions under flow

Precise Measurement of the b-Quark Fragmentation Function in Z0 Boson Decays

We have developed a new technique for inclusive reconstruction of the energy of B hadrons. The excellent efficiency and resolution of this technique allow us to make the most precise determination of the b-quark fragmentation function, using e[superscript +]e[superscript -]→Z[superscript 0] decays recorded in the SLAC Large Detector experiment. We compared our measurement with the predictions of a number of fragmentation models. We excluded several of these models and measured the average scaled energy of weakly decaying B hadrons to be 〈x[subscript B]〉 = 0.714±0.005(stat)±0.007(syst)±0.002 (model dependence).Istituto Nazionale di Fisica Nucleare of ItalyJapan-U.S. Cooperative Research Project on High Energy PhysicsDepartment of EnergyU.K. Particle Physics and Astronomy Research CouncilKorea Science and Engineering Foundatio

The SciCryo Project and Cryogenic Scintillation of Al2O3Al_2O_3 for Dark Matter

International audienceWe discuss cryogenic scintillation of Al2O3. Room-temperature measurements with α particles are first carried out to study effect of Ti concentration on response. Measurements under X-rays between room temperature and 10 K confirm a doubling of light output. The integration of a scintillation-phonon detector into an ionization-phonon dark matter search is underway, and the quenching factor for neutrons has been verified