Elastocapillary instability under partial wetting conditions: bending versus buckling

The elastocapillary instability of a flexible plate plunged in a liquid bath is analysed theoretically. We show that the plate can bend due to two separate destabilizing mechanisms, when the liquid is partially wetting the solid. For contact angles $\theta_e > \pi/2$, the capillary forces acting tangential to the surface are compressing the plate and can induce a classical buckling instability. However, a second mechanism appears due to capillary forces normal to surface. These induce a destabilizing torque that tends to bend the plate for any value of the contact angle $\theta_e > 0$. We denote these mechanisms as "buckling" and "bending" respectively and identify the two corresponding dimensionless parameters that govern the elastocapillary stability. The onset of instability is determined analytically and the different bifurcation scenarios are worked out for experimentally relevant conditions.Comment: 12 pages, 13 figure

The use of animal models in multiple myeloma

Among biomaterials used for filling bone defects, beta-tricalcium phosphate (β-TCP) is suitable in non-bearing bones, particularly in dental implantology, oral and maxillofacial surgery. When β-TCP granules are placed in a bone defect, they occupy the void 3D volume. Little is known about the 3D arrangement of the granules, which depends on the nature and size of the granules. The aim of this study was to examine the 3D architecture of porous β-TCP granules. Granules were prepared with different concentrations of β-TCP powder in slurry (10, 11, 15, 18, 21, and 25 g of β-TCP powder in distilled water). Granules were prepared by the polyurethane foam method. They were analyzed by nano-computed tomography (nanoCT) and compared with scanning electron microscopy (SEM). Commercial granules of hydroxyapatite-β-TCP prepared by the same methodology were also used. The outer and inner architectures of the granules were shown by nanoCT which evidenced macroporosity, internal porosity and microporosity between the sintered grains. Macroporosity was reduced at high concentration and conversely, numerous concave surfaces were observed. Internal porosity, related to the sublimation of the polyurethane foam, was present in all the granules. Microporosity at the grain joints was evidenced by SEM and on 2D nanoCT sections. Granules presented a heterogeneous aspect due to the different mineralization degree of the sintered powder grains in the β-TCP granules; the difference between hydroxyapatite and β-TCP was also evidenced. NanoCT is an interesting method to analyze the fine morphology of biomaterials with a resolution close to synchrotron and better than microcomputed tomography

Multiangle observations of Arctic clouds from FIRE ACE: June 3, 1998, case study

In May and June 1998 the Airborne Multiangle Imaging Spectroradiometer (AirMISR) participated in the FIRE Arctic Cloud Experiment (ACE). AirMISR is an airborne instrument for obtaining multiangle imagery similar to that of the satellite-borne MISR instrument. This paper presents a detailed analysis of the data collected on June 3, 1998. In particular, AirMISR radiance measurements are compared with measurements made by two other instruments, the Cloud Absorption Radiometer (CAR) and the MODIS airborne simulator (MAS), as well as to plane-parallel radiative transfer simulations. It is found that the AirMISR radiance measurements and albedo estimates compare favorably both with the other instruments and with the radiative transfer simulations. In addition to radiance and albedo, the multiangle AirMISR data can be used to obtain estimates of cloud top height using stereoimaging techniques. Comparison of AirMISR retrieved cloud top height (using the complete MISR-based stereoimaging approach) shows excellent agreement with the measurements from the airborne Cloud Lidar System (CLS) and ground-based millimeterwave cloud radar

Behavior of macrophage and osteoblast cell lines in contact with the β-TCP biomaterial (beta-tricalcium phosphate)

Beta-tricalcium phosphate (β-TCP) is a synthetic ceramic used for filling bone defects. It is a good alternative to autologous grafts since it is biocompatible, resorbable and osteoconductive. Previous in vivo studies have shown that macrophages are one of the first cells coming in contact with the biomaterial followed by osteoclasts and osteoblasts that will elaborate new bone packets. Studies have focused on osteoclast morphology and very few of them have investigated the role of macrophages. The aims of this study were to characterize (i) the biomaterial surface; (ii) the in vitro behavior of macrophages (J774.2 and Raw264.7 cells) using the description of cell morphology by scanning electron microscopy (SEM) at 7 and 14 days; (iii) the behavior of osteoblasts (SaOs-2 and MC3T3-E1 cells) seeded at the surface of the biomaterial 24, 48 and 72hours by SEM and confocal microscopy. Cell proliferation was analyzed by MTT assays. Viability and affinity of the macrophages for β-TCP were found significantly increased after 7 and 14d. MC3T3-E1 cells were anchored and stretched onto the β-TCP surface as early as 24h with a high proliferation rate (+190%) when compared to the surface of a well plate. SaOs-2 exhibited the same morphological profile at 72h. Proliferation became significantly higher compared to the plastic surface at only 72h (+129%). This study emphasises the importance of choice of the cell line used in exploring the osteoconductive and osteoinductive properties of a biomaterial. Additional studies are needed to analyze differentiation of macrophages into giant multinucleated cells and how the biomaterial surface influences osteoblast differentiation