Homogenization method for microscopic characterization of the composite magnetoelectric multiferroics.

Tuning of magnetization or electrical polarization using external fields other than their corresponding conjugate fields (i.e., magnetic field for the former or electric field for the latter response) attracts renewed interest due to its potential for applications. The magnetoelectric effect in multiferroic 1-3 composite composed of alternating magnetic and ferroelectric layers operating in linear regime consequent to external biasing fields is simulated and analysed theoretically. Two-scale homogenization procedure to arrive at the equilibrium overall physical properties of magnetoelectric multiferroic composite is formulated using variational analysis. This procedure is extended to quantify the underlying local (microscopic) electric, magnetic and elastic fields and thereby compute local distribution of stresses and strains, electrical and magnetic potentials, the electric and magnetic fields as well as the equivalent von Mises stresses. The computational model is implemented by modifying the software POSTMAT (material postprocessing). Computed local stress/strain profiles and the von Mises stresses consequent to biasing electrical and magnetic fields provide insightful information related to the magnetostriction and the ensuing electrical and magnetic polarization. Average polarization and magnetization against magnetic and electric fields respectively are computed and found to be in reasonable limits of the experimental results on similar composite systems. The homogenization model covers multiferroics and its composites regardless of crystallographic symmetry (with the caveat of assuming an ideal and semi-coherent interface connecting the constituent phases) and offer computational efficiency besides unveiling the nature of the underlying microscopic field characteristics.

Numerical and experimental evaluation of TPMS Gyroid scaffolds for bone tissue engineering.

The combination of computational methods with 3D printing allows for the control of scaffolds microstructure. Lately, triply periodic minimal surfaces (TPMS) have been used to design porosity-controlled scaffolds for bone tissue engineering (TE). The goal of this work was to assess the mechanical properties of TPMS Gyroid structures with two porosity levels (50 and 70%). The scaffold stiffness function of porosity was determined by the asymptotic homogenisation method and confirmed by mechanical testing. Additionally, microCT analysis confirmed the quality of the printed parts. Thus, the potential of both design and manufacturing processes for bone TE applications is here demonstrated.

Solutions for maximum coupling in multiferroic magnetoelectric composites by material design.

Electrical control of magnetization offers an extra degree of freedom in materials possessing both electric and magnetic dipole moments. A stochastic optimization combined with homogenization is applied for the solution for maximum magnetoelectric (ME) coupling coefficient α of a laminar ME composite with the thickness and orientation of ferroelectric phase as design variables. Simulated annealing with a generalized Monte Carlo scheme is used for optimization problem. Optimal microstructure with single and poly-crystalline configurations that enhances the overall α is identified. It is found that juxtaposing a preferentially oriented ferroelectric material with a ferromagnetic ferrite into a composite would result in manifold increase in magnetoelectric coupling. The interface shear strains are found to be richly contributing to the ME coupling. The preferential orientation of the ferroelectric phase in the optimal ME composite laminate is demonstrated using the optimal pole figure analyses.

Correlation between the body mass index of patients with breast cancer before and after chemotherapy.

The objective of this work was to show how the influence of the microenvironment in tumor cells and consequently the onset and tumor progression is becoming increasingly more evident. Cancer is the second leading cause of death in the developed world, surpassed only by heart disease and obesity, and is increasingly recognised as an oncogenic factor in the genesis of this tumor. Inflammatory me- diators related to obesity are suspected to play a role in oncogenic modification of substrates metabolism of nutrients, most patients diagnosed with breast cancer underwent chemotherapy treatment, and this may be an aggravating factor of obesity. The authors selected 49 patients with previous diagnosis of breast cancer who had undergone chemotherapy and evaluated data regarding body mass index (BMI) before and after chemotherapy. They observed that there was statistical difference of BMI of patients before and after chemotherapy with p = 0.03. Comparing the groups, a statistical difference was found between overweight and obesity grade II and overweight and obesity grade III. Patients with a diagnosis of breast cancer usually showed on average a BMI 27.84, worsening after chemotherapy to 28.64. These findings can help to accelerate the division and cell reproduction, because obesity is a risk factor for breast cancer, and weight gain seems to be a major factor after treatment and may influence the prognosis of these women.

Is the treatment of the small saphenous veins with foam sclerotherapy at risk of deep vein thrombosis?

OBJECTIVE: To assess the deep vein thrombosis risk of the treatment of the small saphenous veins depending on the anatomical pattern of the veins. METHOD: A multicenter, prospective and controlled study was carried out in which small saphenous vein trunks were treated with ultrasound-guided foam sclerotherapy. The anatomical pattern (saphenopopliteal junction, perforators) was assessed by Duplex ultrasound before the treatment. All patients were systematically checked by Duplex ultrasound 8 to 30 days after the procedure to identify a potential deep vein thrombosis. RESULTS: Three hundred and thirty-one small saphenous veins were treated in 22 phlebology clinics. No proximal deep vein thrombosis occurred. Two (0.6%) medial gastrocnemius veins thrombosis occurred in symptomatic patients. Five medial gastrocnemius veins thrombosis and four cases of extension of the small saphenous vein sclerosis into the popliteal vein, which all occurred when the small saphenous vein connected directly into the popliteal vein, were identified by systematic Duplex ultrasound examination in asymptomatic patients. Medial gastrocnemius veins thrombosis were more frequent (p = 0.02) in patients with medial gastrocnemius veins perforator. A common outlet or channel between the small saphenous vein and the medial gastrocnemius veins did not increase the risk of deep vein thrombosis. CONCLUSION: Deep vein thrombosis after foam sclerotherapy of the small saphenous vein are very rare. Only 0.6% medial gastrocnemius veins thrombosis occurred in symptomatic patients. However, the anatomical pattern of the small saphenous vein should be taken into account and patients with medial gastrocnemius veins perforators and the small saphenous vein connected directly into the popliteal vein should be checked by Duplex ultrasound one or two weeks after the procedure. Recommendations based on our everyday practice and the findings of this study are suggested to prevent and treat deep vein thrombosis.

Permeability analysis of scaffolds for bone tissue engineering.

Porous artificial bone substitutes, especially bone scaffolds coupled with osteobiologics, have been developed as an alternative to the traditional bone grafts. The bone scaffold should have a set of properties to provide mechanical support and simultaneously promote tissue regeneration. Among these properties, scaffold permeability is a determinant factor as it plays a major role in the ability for cells to penetrate the porous media and for nutrients to diffuse. Thus, the aim of this work is to characterize the permeability of the scaffold microstructure, using both computational and experimental methods. Computationally, permeability was estimated by homogenization methods applied to the problem of a fluid flow through a porous media. These homogenized permeability properties are compared with those obtained experimentally. For this purpose a simple experimental setup was used to test scaffolds built using Solid Free Form techniques. The obtained results show a linear correlation between the computational and the experimental permeability. Also, this study showed that permeability encompasses the influence of both porosity and pore size on mass transport, thus indicating its importance as a design parameter. This work indicates that the mathematical approach used to determine permeability may be useful as a scaffold design tool.

Pathophysiology of visual disturbances occurring after foam sclerotherapy.

BACKGROUND: Visual disturbances (VDs) are reported with an average rate of 1.4% after foam sclerotherapy (FS). Some clinical clues indicate that they could correspond to migraine with aura (MA). AIMS: To validate the hypothesis that VDs occurring after FS correspond to MA and are not transient ischaemic cerebro-vascular events. METHOD: A prospective multicentre study was carried out by the French Society of Phlebology in collaboration with the Neurology Department of the Marseille University Hospital (France). We included prospectively and consecutively all patients who experienced VDs after FS using air to make the foam. The patients were assessed (1) clinically with a specific form describing procedures of FS and recording neurological symptoms, later analysed by a neurologist specialized in migraine; and (2) by a brain diffusion-weighted magnetic resonance imaging (MRI) (T1, T2, T2*, diffusion) carried out within two weeks and analysed by a neuroradiologist. RESULTS: Twenty patients, 16 women and four men, were included in 11 phlebology clinics. All kinds of veins were treated. VDs occurred in average seven minutes after FS. Clinical assessment showed that VDs presented characteristics of MA in all patients, with headache in 10 and without in 10. Paresthesia was observed in five patients and dysphasic speech disturbance in one. Fifteen patients (75%) had a personal history of migraine. Fifteen MRIs were performed within two weeks (mean: 8 days) and three were late (26 days). All of them were normal. MRI was not performed in two patients. CONCLUSION: These results show that VDs occurring after FS correspond to MA and are not transient ischaemic cerebro-vascular events. We suggest a pathophysiological hypothesis resting on the release of endothelin that would reach the cerebral cortex through a paten foramen ovale.

Side-effects and complications of foam sclerotherapy of the great and small saphenous veins: a controlled multicentre prospective study including 1,025 patients.

OBJECTIVES: Increasing interest in foam sclerotherapy (FS) for saphenous insufficiency has highlighted the need to study the side-effects and complications of this treatment. The aim of this study is to better assess their nature and incidence. METHODS: A multicentre, prospective and controlled study was carried out in which patients treated with FS for great (GSV) and small saphenous veins (SSV) trunk incompetence were included. Immediate untoward events were reported. Duplex ultrasound (DUS) examination was carried out to assess all patients between the eighth and 30th day. In addition, 20% of patients were called by an external auditor. RESULTS: In total, 818 GSV and 207 SSV were treated in 1025 patients in 20 phlebology clinics. Ninety-nine percent of patients were controlled with DUS and non-duplex-checked patients were all called. The saphenous trunk was occluded in 90.3% of patients. Twenty-seven (2.6%) side-effects were reported: migraine (n = 8, 4 with visual disturbance); visual disturbance alone (n = 7); chest pressure alone (n = 7); and chest pressure associated with visual disturbance (n = 5). Eleven thrombo-embolic events occurred: 10 deep vein thrombosis (DVT) but only five in symptomatic patients, and one pulmonary embolism that occurred 19 days following the FS without DVT identified by DUS. One transient ischaemic stroke, with complete clinical recovery in 30 minutes, and one septicaemia with satisfactory outcome were reported as well. CONCLUSION: This study demonstrates in a large sample of patients a low rate of adverse reactions after FS of great and small saphenous trunks. However, but the eventuality of exceptional but more serious complications has to be taken into account in the management of patients. A multicentre study like this one takes into account different practices and reports all possible complications, thus demonstrating the need for a common validated protocol.

Numerical modeling of bone tissue adaptation--a hierarchical approach for bone apparent density and trabecular structure.

In this work, a three-dimensional model for bone remodeling is presented, taking into account the hierarchical structure of bone. The process of bone tissue adaptation is mathematically described with respect to functional demands, both mechanical and biological, to obtain the bone apparent density distribution (at the macroscale) and the trabecular structure (at the microscale). At global scale bone is assumed as a continuum material characterized by equivalent (homogenized) mechanical properties. At local scale a periodic cellular material model approaches bone trabecular anisotropy as well as bone surface area density. For each scale there is a material distribution problem governed by density-based design variables which at the global level can be identified with bone relative density. In order to show the potential of the model, a three-dimensional example of the proximal femur illustrates the distribution of bone apparent density as well as microstructural designs characterizing both anisotropy and bone surface area density. The bone apparent density numerical results show a good agreement with Dual-energy X-ray Absorptiometry (DXA) exams. The material symmetry distributions obtained are comparable to real bone microstructures depending on the local stress field. Furthermore, the compact bone porosity is modeled giving a transversal isotropic behavior close to the experimental data. Since, some computed microstructures have no permeability one concludes that bone tissue arrangement is not a simple stiffness maximization issue but biological factors also play an important role.