Diffeomorphic 3D Image Registration via Geodesic Shooting Using an Efficient Adjoint Calculation

In the context of large deformations by diffeomorphisms, we propose a new diffeomorphic registration algorithm for 3D images that performs the optimization directly on the set of geodesic flows. The key contribution of this work is to provide an accurate estimation of the so-called initial momentum, which is a scalar function encoding the optimal deformation between two images through the Hamiltonian equations of geodesics. Since the initial momentum has proven to be a key tool for statistics on shape spaces, our algorithm enables more reliable statistical comparisons for 3D images.     

Comparison between Immunocytochemistry,FISH and NGS for ALK and ROS1 Rearrangement Detection in Cytological Samples

The detection of ROS1 and ALK rearrangements is performed for advanced-stage non-small cell lung cancer. Several techniques can be used on cytological samples, such as immunocytochemistry (ICC), fluorescence in situ hybridization (FISH) and, more recently, next-generation sequencing (NGS), which is gradually becoming the gold standard. We performed a retrospective study to compare ALK and ROS1 rearrangement results from immunocytochemistry, FISH and NGS methods from 131 cytological samples. Compared to NGS, the sensitivity and specificity of ICC were 0.79 and 0.91, respectively, for ALK, and 1 and 0.87 for ROS1. Regarding FISH, the sensitivity and specificity were both at 1 for ALK and ROS1 probes. False-positive cases obtained by ICC were systematically corrected by FISH. When using ICC and FISH techniques, results are very close to NGS. The false-positive cases obtained by ICC are corrected by FISH, and the true-positive cases are confirmed. NGS has the potential to improve the detection of ALK and ROS1 rearrangements in cytological samples; however, the cost of this technique is still much higher than the sequential use of ICC and FISH.     

Immunothrombosis and the Role of Platelets in Venous Thromboembolic Diseases

Venous thromboembolism (VTE) is the third leading cardiovascular cause of death and is conventionally treated with anticoagulants that directly antagonize coagulation. However, recent data have demonstrated that also platelets play a crucial role in VTE pathophysiology. In the current review, we outline how platelets are involved during all stages of experimental venous thrombosis. Platelets mediate initiation of the disease by attaching to the vessel wall upon which they mediate leukocyte recruitment. This process is referred to as immunothrombosis, and within this novel concept inflammatory cells such as leukocytes and platelets directly drive the progression of VTE. In addition to their involvement in immunothrombosis, activated platelets can directly drive venous thrombosis by supporting coagulation and secreting procoagulant factors. Furthermore, fibrinolysis and vessel resolution are (partly) mediated by platelets. Finally, we summarize how conventional antiplatelet therapy can prevent experimental venous thrombosis and impacts (recurrent) VTE in humans.     

Physicochemical and consolidation properties of compacted lateritic soil treated with cement

The consolidation of a fine-grained lateritic soil, treated with compound Portland cement (CEMII/BM 32.5 N) up to 9% by weight of the dry soil and prepared at three different molding water contents (ω_DRY, OMC, and ω_WET), was investigated by means of a one-dimensional consolidation test. The physicochemical and microstructural properties of the compacted lateritic soil-cement mixture were investigated using Raman spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), and pH measurement. The results show that cement admixtures resulted in the formation of tobermorite, afwillite, ettringite, portlandite, and calcite. However, tobermorite and afwilite, which are calcium silicate hydrates (CSH) whose mechanisms of formation are the pozzolanic and alkali silica reactions, appear from 6% added cement. The fixing point of the pH (12.4) is also obtained from 6% added cement. It is the threshold value at which the material begins to develop an adequate mechanical performance. In general, as the content of cement in the soil is increased, the yield stress increases from 1 to 3 times in comparison to untreated soil. For effective vertical stresses smaller than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is 2–7 times faster than that for specimens not treated with cement, while for effective vertical stresses higher than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is about 0.5–1.5 times faster than that for specimens not treated with cement. Permeability and secondary compression are reduced 1–9 times and 2–11 times that of the untreated samples, respectively. These changes are attributed to the creation of chemical bonds and aggregation that accompany the addition of cement. The results also show that it would be desirable for soil samples to be prepared at the dry side of optimum (ω_DRY) when the optimum moisture content (OMC) is not reached at the site. These results indicate that significant and desirable changes in soil behavior can be achieved when the soil is admixed with CEM II/BM 32.5 N cement, thus providing the possibility of using the tested lateritic soil in road construction.     

Estimating the poroelastic properties of cracked materials

We present a comparative study of the ability of some micromechanics estimates to predict the overall properties of heterogeneous materials. We focus mainly on cracked materials, for which this task is difficult and many estimates fail. We study particularly the interaction direct derivative estimate, proposed by Zheng and Du, which is an approximation of the generalized self-consistent scheme, but has the very convenient property to be always explicit. A modified version of this estimate, called full-range IDD by Zheng and Du, yields good results when comparing all poromechanical coefficients predicted by the estimate to finite element simulations of a 2D cracked material in plane strain, up to crack density factors of 1 for aligned cracks and 0.60 for randomly oriented cracks. The accuracy of finite element computations of the overall moduli is also commented by plotting the convergence of the average of the properties as well as the confidence intervals on these averages.     

Collapses and Watersheds in Pseudomanifolds of Arbitrary Dimension

This work is settled in the framework of abstract simplicial complexes. We propose a definition of a watershed and of a collapse (i.e., a homotopic retraction) for maps defined on pseudomanifolds of arbitrary dimension. Then, we establish two important results linking watersheds and homotopy. The first one generalizes a property known for distance transforms in a continuous setting to any map on pseudomanifolds: a watershed of any map is a subset of an ultimate collapse of the support of this map. The second result establishes, through an equivalence theorem, a deep link between watershed and collapse of maps: any watershed of any map can be straightforwardly obtained from an ultimate collapse of this map, and conversely any ultimate collapse of the initial map straightforwardly induces a watershed.