Effective elastic properties of planar SOFCs: A non-local dynamic homogenization approach

The focus of the article is on the analysis of effective elastic properties of planar Solid Oxide Fuell Cell (SOFC) devices. An ideal periodic multi-layered composite (SOFC-like) reproducing the overall properties of multi-layer SOFC devices is defined. Adopting a non-local dynamic homogenization method, explicit expressions for overall elastic moduli and inertial terms of this material are derived in terms of micro-fluctuation functions. These micro-fluctuation function are then obtained solving the cell problems by means of finite element techniques. The effects of the temperature variation on overall elastic and inertial properties of the fuel cells are studied. Dispersion relations for acoustic waves in SOFC-like multilayered materials are derived as functions of the overall constants, and the results obtained by the proposed computational homogenization approach are compared with those provided by rigorous Floquet-Boch theory. Finally, the influence of the temperature and of the elastic properties variation on the Bloch spectrum is investigated

Multiscale asymptotic homogenization analysis of thermo-diffusive composite materials

In this paper an asymptotic homogenization method for the analysis of composite materials with periodic microstructure in presence of thermodiffusion is described. Appropriate down-scaling relations correlating the microscopic fields to the macroscopic displacements, temperature and mass concentration are introduced. The effects of the material inhomogeneities are described by perturbation functions derived from the solution of recursive cell problems. Exact expressions for the overall elastic and thermodiffusive constants of the equivalent first order thermodiffusive continuum are derived. The proposed approach is applied to the case of a two-dimensional bi-phase orthotropic layered material, where the effective elastic and thermodiffusive properties can be determined analytically. Considering this illustrative example and assuming periodic body forces, heat and mass sources acting on the medium, the solution performed by the first order homogenization approach is compared with the numerical results obtained by the heterogeneous model.Comment: 40 pages, 13 figure

Design of acoustic metamaterials through nonlinear programming

The dispersive wave propagation in a periodic metamaterial with tetrachiral topology and inertial local resonators is investigated. The Floquet-Bloch spectrum of the metamaterial is compared with that of the tetrachiral beam lattice material without resonators. The resonators can be designed to open and shift frequency band gaps, that is, spectrum intervals in which harmonic waves do not propagate. Therefore, an optimal passive control of the frequency band structure can be pursued in the metamaterial. To this aim, a suitable constrained nonlinear optimization problem on a compact set of admissible geometrical and mechanical parameters is stated. According to functional requirements, the particular set of parameters which determines the largest low-frequency band gap between a pair of consecutive branches of the Floquet-Bloch spectrum is obtained. The optimization problem is successfully solved by means of a version of the method of moving asymptotes, combined with a quasi-Monte Carlo multi-start technique. Subjects: Materials Science (cond-mat.mtrl-sci) Cite as: arXiv:1603.07717 [cond-mat.mtrl-sci] (or arXiv:1603.07717v2 [cond-mat.mtrl-sci] for this version

Multi-field asymptotic homogenization approach for Bloch wave propagation in periodic thermodiffusive elastic materials

Multi-field asymptotic homogenization methods are proposed to describe the behaviour of periodic Cauchy materials subject to several physical phenomena, focusing on thermodiffusion. The resulting homogenized models provide the overall constitutive tensors and overall inertial terms. Moreover, they allow one to investigate the complex band structures associated with damped Bloch waves travelling in periodic materials, avoiding the challenging computations needed by the adoption of micromechanical approaches

Asymptotic approximation of the band structure for tetrachiral metamaterials

Tetrachiral materials are characterized by a cellular microstructure made by a periodic pattern of stiff rings and flexible ligaments. Their mechanical behaviour can be described by a planar lattice of rigid massive bodies and elastic massless beams. Therefore, the periodic cell dynamics is governed by a monoatomic structural model, conveniently reduced to the only active degrees-of-freedom. The paper presents an explicit parametric description of the Floquet-Bloch spectrum (or band structure) governing the propagation of elastic waves through the tetrachiral material. By virtue of multiparametric perturbation techniques, an analytical asymptotic approximation is achieved for the dispersion surfaces in the Brillouin zone. Since different optimization strategies tend to fail in opening low-frequency band gaps in the material spectrum, this specific design purpose is commonly pursued by introducing interring inertial resonators. The paper demonstrates that multiparametric perturbation methods can efficiently deal with the consequent enlargement of the parameter space, necessary to describe the resulting inertial metamaterial. Indeed, paying due attention to the doubling of internal resonance conditions, an accurate parametric approximations of the enriched band structure can be achieved. From the applicative perspective, the research findings furnish suited analytical tools for the optimal design of pass and stop bands

Metamaterial filter design via surrogate optimization

Recently, an increasing research effort has been dedicated to analyse transmission and dispersion properties of periodic metamaterials containing resonators, and to optimize the amplitude of selected acoustic band gaps between consecutive dispersion curves in the Floquet-Bloch spectrum. Potential novel applications of this research are in the design of passive mechanical filters/diodes. The present work proposes a way to interpolate the objective functions in such band gap optimization problems, using Radial Basis Functions. The study is motivated by the high computational effort often needed for an exact evaluation of the original objective functions, when using iterative optimization algorithms. By replacing such functions with surrogate objective functions, well-performing suboptimal solutions can be obtained with a small computational effort. Numerical results demonstrate the feasibility of the approach

Early hemopoietic progenitors in the peripheral blood of patients with severe aplastic anemia (SAA) after treatment with antilymphocyte globulin (ALG), cyclosporin-A and G-CSF

ABSTRACT © F e r r a t a S t o r t i F o u n d a t i o n A. Bacigalupo et al. 134 administration of G-CSF in SAA patients leads to mobilization of hemopoietic progenitors, which are then available for analysis and can actually be harvested at weekly leukophereses and cryopreserved. 14,15 Human LTC-ICs share many of the characteristics of murine LTC-ICs, which have proven in vivo long-term repopulating ability. Materials and Methods Patients Clinical data on the patients are presented in Response Patients were classified as complete responders if they were transfusion independent with a hemoglobin level of ≥ 11 g/dL, a neutrophil count greater than 1.5ϫ10 9 /L, and a platelet count greater than 100ϫ10 9 /L; partial responders were transfusion independent with a hemoglobin level of ≥ 8 g/dL, a neutrophil count of >0.5ϫ10 9 /L, and a platelet count of >20ϫ10 9 /L. Persistence of transfusion dependence was taken as evidence of no response. Normal donors Sixteen leukaphereses from 7 normal donors treated with G-CSF (10 ug/kg/day for 5 days) were used as controls. These volunteers underwent the procedure as matched donors for their HLA-identical sibling. Informed consent was obtained from SAA patients and normal donors, and investigations were approved by our Ethical Committee. Flow cytometry PB cells recovered from each leukaphereses were processed with a work station Coulter Q-Prep (Coulter Corporated Hialeah, FL) in order to lyse erythrocytes and to fix white blood cells. Cell surface antigens were detected by direct immunofluorescence using a CD34 HPCA-2 for progenitor cells (Becton Dickinson, Mountainview, CA). Fluorescence was analyzed with an XL Coulter. Isotypically matched mouse Ig directly conjugated to fluorescein isothiocyanate (FITC) or phycoerythrin (PE) were used as negative controls in all experiments. Overall, 10 4 events were acquired on an FS (Forward Scatter) x SS (Side Scatter) diagram on all populations except platelets and debris. Immediately after staining, cells were sorted on a Coulter Epics 753 dual laser flow cytometer (Coulter Electronics, Hialeah, FL) equipped with a CICERO high-speed computer (Cytomation, Fort Collins, CO). FITC and PE were excited using the 488nm wavelength from a dedicated 5 W argon laser. In this staining protocol, it was still possible to obtain CD34 + HLA-DR + cells, even though both HLA-DR (IgG1 isotype, Becton-DickinsonImmunocytometry System) and CD15 were FITC conjugated (FITC-conjugated mouse antihuman-LeuM1, Becton-Dickinson). 18 Functional assays Light density cells from each leukapheresis were assayed for clonogenic precursors. Briefly 10 5 MNC were plated in: A. 1.1 mL consisting of Iscove's modified Dulbecco's medium (IMDM, GIBCO BRL, Life Technologies LTD, UK) + 0.9% methylcellulose (Sigma Chemical, St.Louis, MO, USA) + 30% fetal calf serum (FCS, Gibco) + 100 ng of rhGM-CSF (Sandoz, Basel, CH); B. 1.5 ml consisting of IMDM + 0.9%methylcellulose + 30% FCS + 1% bovine serum albumin (BSA, Sigma) + 10 -4 M mercaptoethanol (ME, Sigma) + rhGM-CSF (10 ng) + rhIL3 (10 ng Sandoz) + rhG-CSF (10 ng) + rhEPO (4U Cilag AG, Schaffhauser, CH) + SCF (50 ng Genzyme Corporation, Cambridge, UK). After 14 days of incubation in a humidified atmosphere at 37°C in 5% CO 2 , colonies were classified and counted using an inverted microscope (Zeiss, Germany). Sorted cells were cultured in the presence of PIXY and SCF as described. 18 MNC and freshly sorted cells were cultured in suspensions containing different cytokines and scored according to previously established criteria. 19 LTC-IC assays were performed by seeding an aliquot (usually 5ϫ10 6 MNC/flask) of light density cells over a feeder layer of irradiated (1.5 cGy) normal marrow cells. These were subcultured from adherent layers of previously established 4-week-old LTCs. LTC-ICs were maintained for 3 days at 37°C, then switched to 33°C and fed weekly by replacing half the growth medium (IMDM + 12.5% horse serum (HS, Gibco) + 12.5% FCS + 10 -4 M ME + 10 -6 M hydrocortisone, Sigma) containing half of the nonadherent cells with fresh growth medium. After 5 weeks, adherent cells were trypsinized and combined with the nonadherent fraction. These harvested cells were washed and assayed for clonogenic precursors in standard methylcellulose cultures (B). As previously reported, 14 the number of LTC-ICs present in the starting cell suspension was shown to be equal to the total CFC content of the 5-week-old LTC assay divided by 4. Statistical analysis Chi-square, Student's t-test and Mann-Whitney rank sum test were used to analyze the data. Results Patients All patients completed the designed course of IS treatment and underwent leukaphereses, which © F e r r a t a S t o r t i F o u n d a t i o n Early hemopietic progenitors in PB of treated SAA patients 135 were scheduled weekly starting on day +30 of treatment. One patient who did not become transfusion independent after a first course was treated again with a second course of ALG, CyA and G-CSF, and then a third time with CyA and G-CSF. He therefore underwent 3 courses of leukaphereses ( Flow cytometry Flow cytometry demonstrated a higher frequency of CD3 + cells Committed progenitors Samples from each apheresis were assayed for in vitro granulocytic, erythroid and multipotent progenitors (CFU-GM, BFU-E and CFU-GEMM). In our experiments we were able to grow mainly CFU-GM, with very low numbers of other colonies (in percentages: 25-100% CFU-GM, 0-30% BFU-E and 0-19% CFU-GEMM). Five patients showed significant increments in white blood cell (WBC) counts (>10ϫ10 9 /L, Early progenitors HPP-CFC were studied in 4 patients (#1, 4, 5, 6); they grew at a frequency of 0-3.4/10 5 MNC, in one case in the absence of committed progenitors. In addition, we studied LTC-ICs in 18 leukaphereses from 4 patients: in 7/18 samples LTC-ICs were present at low frequency (range: 0.4-2/10 6 MNC) when compared with collections from G-CSF-treated normal donors (range: 5.4-130/10 6 MNC); p<0.00001) Cell sorting Cells derived from 3 aphereses were sorted into CD34 + DR + and CD34+DR -CD15 -; these were then cultured in vitro with different cytokine combinations. CD34 + DR + cells showed evident increments in GM, GEMM, BFU-E and HPP colony formation Discussion It has been always difficult to design in vitro colony assays in patients with SAA, mainly because of the lack of bone marrow cells to initiate such studies. We have described the presence of hemopoietic progenitors in the peripheral blood of many SAA patients after treatment with ALG-CyA and prolonged administration of rhG-CSF. 13 By performing weekly leukaphereses in such patients, one can collect large numbers of cells which can be cryopreserved and are, at the same time, available for in vitro assays. The aim of the present study was to assess phenotypic and functional properties of such PBHP. As regards the phenotype, SAA PB cells contained large numbers of CD3 + cells, significantly more than 136 controls (p=0.006), with an inverted CD4/CD8 ratio. This is in keeping with reports of an excess of suppressor cells in SAA, When SAA cells were plated in vitro we grew prevalently CFU-GM in numbers which were significantly lower than in normal controls, with a median 28-fold reduction. BFU-E and CFU-GEMM were seen less frequently in both SAA patients and normal controls, possibly as a result of in vivo triggering with G-CSF. LTC-ICs were studied in 18 leukaphereses and scored in 7 of these, though in small numbers: they were significantly fewer than in controls (0-2 vs 5-130/10 6 MNC). In one of these patients LTC-ICs were present in the blood in the absence of peripheral blood and marrow CFU-GM, and this was also seen for HPP colonies. Therefore primitive progenitors may be present in the absence of committed progenitors, as previously suggested by hematologic reconstitution in most SAA patients in spite of no colony formation from bone marrow cells. © F e r r a t a S t o r t i F o u n d a t i o n or whether their survival is limited. When we assessed the total yield of leukaphereses from SAA patients we recovered reduced numbers of CFU-GM (p=0.05), although SAA patients underwent a median of 5 vs 2 leukaphereses performed with normal controls. It is difficult to say whether these cryopreserved cells are suitable for an autotransplant, a possibility one may wish to consider in the case of poor or absent hematologic reconstitution or in the case of evolution of the disease into overt myelodysplasia or leukemia. Highdose chemotherapy has been shown do induce complete remissions when given to SAA patients, though at a cost of prolonged periods of neutropenia; 24 the infusion of autologous cryopreserved progenitors may shorten the duration of chemotherapy-induced aplasia. The total CFU-GM content recovered from leukaphereses was in the range reported to allow hemopoietic reconstitution if infused after ablative chemo-radiotherapy, and so was the LTC-IC content in 2 out of 4 patients studied. Another important issue may be to consider blood progenitor cell mobilization as a prediction or as a measure of clinical improvement. Indeed two complete responders (#5 and #6) mobilized high numbers of CFU-GM; one patient (#2) mobilized very few CFU-GM and showed no response. In patient #3 clonogenic progenitors appeared in the blood after the second course of IS treatment and he achieved a durable response after the third course. This suggests that the presence of committed and early progenitors in the blood during IS treatment may be predictive of clinical response, in keeping with data reported by Finally, early hemopoietic progenitors mobilized with G-CSF may reseed the marrow 26 and contribute to hematologic recovery in SAA patients undergoing treatment with ALG and Cy A, as indicated by the high response rate seen with this regimen and a survival rate greater than 90%. 9 It may be possible to prove this hypothesis by using the neomycin resistance gene to mark circulating progenitors. 27 In conclusion, this study suggests that very early progenitors are found in the peripheral blood of patients with SAA after prolonged G-CSF administration and after treatment with IS therapy. The number of such early precursors is small, and the majority of cells exhibit the features of committed progenitors. It remains to be determined whether these cells contribute to hematologic recovery and whether they can be used for autografting. Early hemopietic progenitors in PB of treated SAA patients References 137 © F e r r a t a S t o r t i F o u n d a t i o

A systematic review and meta-analysis on the prevalence of dementia in europe. estimates from the highest-quality studies adopting the dsm iv diagnostic criteria

BACKGROUND: Dementia, including Alzheimer's disease (AD), is one of the most burdensome medical conditions. Usually, the reviews that aim at calculating the prevalence of dementia include estimates from studies without assessing their methodological quality. Alzheimer's Disease International (ADI) proposed a score to assess the methodological quality of population-based studies aimed at estimating the prevalence of dementia. During the last three years, the European Commission has funded three projects (Eurodem, EuroCoDe, and ALCOVE) in order to estimate the prevalence of dementia in Europe. OBJECTIVE: The aim of this study was to perform a systematic review and meta-analysis of data on the prevalence of dementia in Europe derived from studies that included only subjects with a diagnosis of dementia according to the DSM IV criteria, and that had a high quality score according to ADI criteria. METHODS: We considered the studies selected by the two projects EuroCoDe (1993-2007) and Alcove (2008-2011), and we performed a new bibliographic search. For the systematic review, we only selected the subset of articles that included subjects with a diagnosis of dementia according to the DSM IV criteria. The studies were qualitatively assessed using the ADI tool. RESULTS: The meta-analysis considered 9 studies that were carried out in Europe between 1993 and 2018 including a total of 18,263 participants, of which 2,137 were diagnosed with dementia. The prevalence rate standardized for age and sex resulted 7.1%. DISCUSSION: This is the first systematic review on the prevalence of dementia in Europe considering only high-quality studies adopting the same diagnostic criteria (i.e., DSM IV)

A phase field approach for damage propagation in periodic microstructured materials

In the present work, the evolution of damage in periodic composite materials is investigated through a novel finite element-based multiscale computational approach. The proposed methodology is developed by means of the original combination of asymptotic homogenization with the phase field approach to nonlocal damage. This last is applied at the macroscale level on the equivalent homogeneous continuum, whose constitutive properties are obtained in closed form via a two-scale asymptotic homogenization scheme. The formulation considers different assumptions on the evolution of damage at the microscale (e.g., damage in the matrix and not in the inclusion/fiber), as well as the role played by the microstructural reinforcement, i.e. its volumetric content and shape. Numerical results show that the proposed formulation leads to an apparent tensile strength and a post-peak branch of unnotched and notched specimens dependent not only on the internal length scale of the phase field approach, as for homogeneous materials, but also on microstructural features. Down-scaling relations provide the full reconstruction of the microscopic fields at any point of the macroscopic model, as a simple post-processing operation