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Background Dual antiplatelet therapy (DAPT), aspirin plus a P2Y12-i (clopidorel, prasugrel or ticagrelor), is recommended for one year after myocardial infarction (MI) for secondary prevention of cardiovascular disease (SP-CVD). Beyond one year maintaining DAPT is controversial. Purpose To compare the 3-year risk of a composite of MI, ischemic stroke (IS), major bleeding (MB) and death between DAPT and single antiplatelet therapy with aspirin (SAPT) beyond one year after MI. Methods All adults hospitalized in 2013 or 2014 for acute MI (trigger event) with intensive care unit stay were identified in the French SDNS nationwide claims database. Patients who survived at least one year without MI or MB, and with a DAPT medication possession ratio (MPR) ≥80% were included in a cohort study. All patients were followed for 3 years after the index date (defined 365 days after the MI trigger event), except right-censored observations for those who died or discontinued aspirin with a 60-day grace period. The 3-year hazard ratios (HR [95% CI]) were estimated using Cox proportional hazards risk model for outcomes including death, and Fine and Gray competing risks model for non-fatal outcomes, with a time-dependent variable for DAPT-SAPT exposure, and adjusted on a high-dimensional disease risk score (hdDRS) plus time dependent variables for SP-CVD drugs, oral antidiabetics, insulin, anticoagulants, NSAIDs, corticoids and proton pump inhibitors. HdDRS were estimated for the composite outcome, a composite of ischemic outcomes, and MB alone, and variables were selected using a combination of Principal Component Analysis and Lasso regression. Results From the 105,080 adults admitted in intensive care units for acute MI in 2013 or 2014, 53,399 were included in the cohort. The most common reasons for non-inclusion were death (n=12,012) and a DAPT MPR Conclusions In this nationwide real-life population-based study in France, DAPT maintained beyond one year after MI is significantly associated with increased harm compared to SAPT with increased risks of 21% (IC95% [13–30]) for the composite of MI, IS, MB and death (net clinical benefit), 22% [7–38] for MI, 89% [55–130] for MB, 16% [6–27] for death, and no difference for IS. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): French Ministry of Health (PHRCN-18-0745)

Background Myocardial infarction (MI), stroke, peripheral arterial disease (PAD), heart failure (HF) and chronic kidney disease (CKD) are common cardiovascular renal disease (CVRD) complications for type 2 diabetes (T2D). However, for those with a single CVRD comorbidity, the incidence of a new CVRD complication and death is not well known. Purpose To assess the 5-year CVRD complication and mortality incidence for T2D patients with a single CVRD comorbidity or without CVRD at baseline. Methods A cohort study of all T2D patients with a single CVRD or without CVRD (disease-free) at baseline (January 1st, 2014) identified and followed-up for 5 years within the French SNDS nationwide claims database. Incidence rates were estimated for 5 years and the risk of all-cause death was compared to the disease-free population using Cox proportional hazards risk model: hazard ratio (HR) with [95% confidence interval]. Results From about 2 million T2D patients without cancer or transplantation at baseline, 76.5% were disease-free, 7.9% with a single CVRD and the others having several CVRD comorbidities history. Five-year CVRD complication and mortality incidence rates for 1,000 patient-years are presented in the table. CKD and HF were the most frequent CVRD complications for the disease-free and all CVRD comorbid populations, far ahead of MI, stroke and PAD, except PAD complication for PAD population and to a lesser degree stroke complication for stroke population. The incidence rate of all-cause death was the highest for HF+CKD patients, followed by HF patients, then PAD, stroke and CKD patients. Compared to disease-free patients with same sex and age, the HR of death was 4.3 [4.2–4.5] higher for HF+CKD patients, 2.7 [2.7–2.8], 2.1 [2.0–2.1], 2.1 [2.0–2.1], 1.9 [1.9–1.9] and 1.4 [1.3–1.4] for HF, CKD, PAD, stroke and MI patients, respectively. Conclusions While MI, stroke and PAD comorbidities remain major risks of complications for T2D patients, HF and CKD nowadays represent a clearly higher risk of CVRD complications and death, that needs improved preventive strategies. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): Study performed with unconditional funding from AstraZeneca

This paper deals with the extraction of wave features in elastic media. An inverse approach is proposed for the identification of wave dispersion characteristics (e.g. k-space) in one- and two-dimensional structures (1D, 2D). The proposed method is similar to the ESPRIT algorithm and the Prony series method and can be considered as an extension of the latter, specifically when applied to 1D problems. By using a convolution framework, the method is extended to the 2D case for which it allows the estimation of the full k-space by solving a linear problem. The method is called INverse COnvolution MEthod (INCOME). The formulation of INCOME is first detailed and mathematically justified. Both the 1D and 2D cases are detailed and explained. Then several examples are presented for assessing the validity domain of INCOME. These numerical tests clearly show the relevance of INCOME for structured inputs with periodic characteristics ispartof: Journal Of Sound And Vibration vol:520 status: Published online

Uncertainty quantification has always been an important topic in model reduction and simulation of complex systems. In this aspect, global sensitivity analysis (GSA) methods such as Fourier amplitude sensitivity test (FAST) are well recognized as effective algorithms. Recently, some data-based metamodeler such as Random Forest (RF) also developed their own variable importance selection solutions for parameters with perturbations. This paper proposes a visual comparison of these two uncertainty quantification methods, using datasets retrieved from vibroacoustic models. Their results have a lot in common and are capable to explain many results. The remarkable agreement between methods under fundamentally different definitions can potentially improve their compatibility in various occasions.

International audience; In this article, the Second Strain Gradient (SSG) theory proposed by Mindlin is used within a Wave Finite Element Method (WFEM) framework for dynamic analysis of one-dimensional Euler-Bernoulli bending beam and torsional bar. Firstly, strong forms of continuum models including governing equations and boundary conditions for bending and torsion cases, respectively, are derived using Hamilton's principle. New "non-local" Lattice Spring Models (LSM) are expounded, giving unified description of the SSG models for bending and torsion. These LSM can be regarded as a discrete micro-structural description of SSG continuum models and the resulting dynamic equations are transformed using Fourier series. Weak forms for both bending and torsion are established based on SSG theory. Subsequently, the WFEM is used to formulate the spectral problem and compute wave dispersion characteristics from one-dimensional unit-cell structures. Finally, dispersion relations and forced responses for bending and torsion in micro-sized structures are calculated by SSG and Classical Theory (CT), and some useful conclusions are discussed.

International audience; The scattering of guided waves through a complex structure is of great importance in predicting vibration energy transmission and reflection across structures. Multi-scale models based on generalized continuum theory have been developed recently to investigate the vibration behavior of complex media in the frame of continuum mechanics. In this study, models based on the second strain gradient theory are employed together with a scattering matrix method to study the wave transmission and reflection through non-classical coupling regions between two waveguides. Numerical results are presented for longitudinal and bending waves through 1-D coupling interfaces. Upon which we discuss the local behavior of the internal heterogeneity in the complex coupling region and its impact on wave scattering properties at coupling interfaces. The results obtained also show that the proposed approach is of great potential in the investigation of vibration transmission control by enriching a waveguide's internal structure.

International audience; In this paper, a Floquet Model Order Reduction (MOR) method is proposed for the modelling of finite periodic structures subjected to harmonic or transient loads. This Floquet MOR generates frequency-independent projection matrices of the full-scale structure using a Floquet expansion of the local state-vectors computed on a single unit-cell with the Forced Wave Finite Element framework. This two-step MOR method can handle large multi-scale waveguides regardless of the scale and the number of unit-cells. A comparison with a standard sub-structuring approach based on unit-cell wave-mode reduction demonstrates that Floquet MOR is able to create reduced models of finite periodic structures with an unequaled computational efficiency. The method's ability to produce small and accurate models suitable for time-domain simulations presents a high potential for virtual sensing, real-time Structural Health Monitoring (SHM) and digital twins for large periodic structures and metamaterials.

In this work, we develop a numerical framework for analyzing Bloch waves and their interactions with localized damages. A reduced Bloch expansion technique is first used to sub-structure the waveguide’s healthy part, while a detailed finite element description of the damaged regions can be applied. A remarkable strength of this modelling technique lies in the possibility to compute the dynamic response of the overall structure (finite or infinite) subjected to harmonic or transient loads. The damage model and its location on the waveguide can both be updated with almost negligible additional computational effort. The performances compared with standard finite element analysis of a similar problem are outstanding (i.e. faster by at least 3 orders of magnitude). Two types of indicators can therefore be computed over a large number of possible waveguide-damage configurations: (i) the local transmission, reflection and conversions of Bloch waves at the interfaces of the damaged region, and (ii) the global harmonic or transient response of a loaded waveguide. This approach is used to extend the detectability of small-scaled damages in large-scaled periodic waveguides by exploiting the frequency-conversions of the Bloch scattering coefficients. These so-called ’diffusion features’ are eventually used to improve sub-wavelength damage quantification and localization. ispartof: pages:870-877 ispartof: Proceedings of the International Conference on Structural Dynamic , EURODYN pages:870-877 ispartof: EURODYN 2020: XI International Conference on Structural Dynamics location:Athens, Greece date:23 Nov - 26 Nov 2020 status: published

The present work deals with multi-layer rectangular core topology systems built up by stacking layers made of different rectangular core geometries. Multi-layer systems have been intensively studied in terms of mechanical performances whereas their vibroacoustic behavior, acoustic efficiency and design is however still an open issue. Several design parameters should be considered to fully understand the dynamic and acoustic behaviour of such structures. Therefore, this paper focuses on controlling the transition frequency and the Sound Transmission Loss (STL) by modifying geometrical parameters of the unit cell, while keeping the mass constant. Infinite panels and real wavenumbers will be considered in the study. The Wave Finite Element Method (WFEM) is used to obtain the targeted indicators. The proposed designs give the opportunity to shift the transition frequency and to control the flexural waves propagating in the structure. Besides, the STL is highly improved in the full frequency range of interest compared to a standard sandwich panel made of a single core. ispartof: Mechanical Systems And Signal Processing vol:143 status: Published online

International audience; This paper deals with the theoretical, numerical and ex perimental behavior of periodic orthogonally ribbed plates. It ex tends the paper (Fossat et al., 2018) in which a comprehensive homogenized model has been established for flex ural and torsional motion of periodic 1D-ribbed plates. New theoretical results describing the out-of-plane behavior of cellular plates involving inner resonance phenomena, are derived using an asymptotic approach. In this aim, the out-of-plane model of beam grids accounting for local bending and torsion is first established through the asymptotic method of homogenization of periodic discrete media. Then, the coupling between the beam grid and the internal plates (fully or partially connected to it) is detailed. This lead to an explicit analytical formulation of the equivalent plate model whose effective parameters arise from the geometry and mechanical properties of the unit cell. The unconventional features of the flex ural wave dispersion are shown to be straightforwardly related to inner-resonance phenomena. These theoretical results are successfully compared to numerical computations conducted using WFEM. Furthermore, ex periments performed on two prototypes of ribbed plates evidence the ability of the homogenized model to describe their complex dynamic behavior. The latter is characterized by the co-ex istence of a dynamic regime at both the micro-scale of the period and the macro-scale of the whole structure, that results in an inhomogeneous kinematics where the plate and beam displacements differ at the leading order. These unique features depart from the usual assumptions retained in plate mechanics and generates the observed non-conventional features. In conclusion, it is stressed that the study yields design rules to tailor cellular panels having specific atypical features in a given frequency range.

The implementation of increasingly complex periodic structures for vibro-acoustic purposes in civil engineering and transportation industry creates new modeling and computational challenges, mainly due to the multi-scale nature of the structures. Homogenization techniques able to describe the local dynamics effects appearing in periodic structures have therefore received significant attention in the past years. In this paper, a homogenization technique is proposed for 1D periodic media, where the equivalent material properties are determined using the local wave scattering characteristics of the periodic medium. A Wave Finite Element scheme is used to retrieve the multi-modal interface diffusion coefficients based on a unit-cell FE model of the periodic structure. The homogenized model is then used to derive wavenumbers and Frequency Response Function of the waveguide. Four examples are proposed, including a 3D periodic waveguide exhibiting locally resonant bandgaps. Good agreement is observed. Also limitations of the method are discussed.

International audience; In this work, an enriched model describing the longitudinal wave propagation is established based on Mindlin’s Second Strain Gradient (SSG) theory, which can describe the heterogeneity caused by the micro-structure interactions in the frame of continuum mechanics. The governing equation and associated boundary conditions are derived based on Hamilton's principle, then the dispersion relation of non-classical longitudinal wave together with the extra-waves appearing exclusively in SSG theory model are investigated. The investigations are based on the modal density, energy flow, and forced response of the rod. Wave transmission and reflection through planar interfaces based on the proposed model have been calculated. Finally, the results of the enriched model are well interpreted by comparing with the classical theory results, and some useful conclusions are derived on the SSG theory based model in the wave propagation characterization.

International audience; Periodic structures have properties of controlling mechanical waves. These solutions are used in aircraft, trains, submarines, space structures where high level of robustness has to be ensured in presence of uncertainty in the numerical models. The paper presents a stochastic formulation for the Bloch analysis of periodic structures, based on the quadratic 1D and 2D forms of the Wave Finite Element method. In 1D case, numerical examples of periodic rod and metamaterial rod systems are considered; for the 2D case, homogeneous and periodic plates considered. In both cases, the effect of uncertainties on wavenumber variation is studied. The accuracy and performance of the developed method is compared with Monte Carlo simulation (MCS) results. It is found that the uncertainties affects the wavenumber scattering. Maximum variation of wavenumber occurs at the band gap edge frequencies and trends are increasing in higher frequency. In terms of computational cost, the presented formulation offers computational advantages over MCS. The computational cost savings can be a good point for the optimization and reliability study under uncertainties of complex structures. Highlights • A stochastic quadratic eigenvalue formulation for the periodic media is presented. • The longitudinal and flexural waves in the 1D and 2D periodic media are simulated. • In the case of flexural wave, only out of plane flexural wave are generated. • The formulation offers computational advantages over the Monte Carlo simulation.

An inverse wavenumber identification tool is used to characterize the vibration behavior of three structures and meta-structures with different complexity levels: a plane steel panel, a curved thick composite sandwich shell and a stiffened aluminum aircraft sidewall panel. Bare structures are first studied and then equipped with spatially distributed small-scale resonators, leading to meta-structures. For the two curved panels, tests are conducted under diffuse acoustic field and point mechanical excitations. For each studied case, the effect of the industrially-oriented small-scale resonators is highlighted using frequency and wavenumber analysis, showing general attenuation of the vibration level and even band gaps occurrence. The complex wavenumber identification allows also estimating the structural loss factor in the composite sandwich panel, while the multi-modal behavior is captured in the aluminum aircraft sidewall panel. ispartof: Mechanical Systems And Signal Processing vol:135 status: Published online

International audience; In the framework of vibrational analysis of 2D periodic waveguides, Floquet-Bloch theorem is widely applied for the determination of wave dispersion characteristics. In this context, the Wave Finite Element Method (WFEM) combines Periodic Structure Theory (PST) with standard FE packages, enabling wave dispersion analysis of waveguides involving structurally realistic unit-cells. For such applications, the computational efficiency of the WFEM, depends on the choice of the formulation and can lead to numerical issues, worsen by extensive computational cost. This paper presents a coupled wave-mode approach for the determination of wave dispersion characteristics in structurally advanced periodic structures. It combines two scales of model order reduction. At the unit-cell's scale, Component Mode Synthesis (CMS) provides the displacement field associated with local resonances of the periodic structure, while the free wave propagation is considered using a spectral problem projection on a reduced set of shape functions associated with propagating waves, thus providing considerable reduction of the computational cost. An application is provided for a bi-directionally stiffened panel and the influence of reduction parameters is discussed, as well as the robustness of the numerical results.

After presenting with nonspecific symptoms, a 52-year-old female was found to have a 3.4 × 2.6 cm retroperitoneal mass resulting in hydronephrosis on abdominal computed tomography scan. After extensive workup including surgical debulking, excisional biopsy, and autoimmune panel, she was found to have idiopathic retroperitoneal fibrosis (IRF) with negative staining for immunoglogulin G4 (IgG4). Two years after presentation, the patient developed dyspnea, cough, and xerostomia. Repeat anti-Sjögren Syndrome A and anti-Sjögren Syndrome B titers and labial gland biopsy confirmed the diagnosis of concomitant Sjögren's syndrome (SS). The patient was treated with mycophenolate mofetil with improvement in her symptoms. Most cases of retroperitoneal fibrosis are associated with IgG4-related disease or other autoimmune disease. To our knowledge, this is only the second reported case of SS associated with IRF. Because symptoms of IRF are nonspecific, there is often a delay in diagnosis resulting in end-organ disease such as ureteral obstruction or hydronephrosis. Although IRF is uncommon, it should be considered in patients presenting with abdominal or flank pain, especially in patients with concomitant autoimmune disorders. Early recognition of disease can prevent end-organ damage and, as more cases are diagnosed, its relationship to SS may be elucidated leading to further advances in treatment and surveillance.

Summary The identification of structural damage in composite waveguides is a critical issue in aerospace and transportation industries. Frequently, these structures involve periodic patterns or dissipative components that considerably reduce the range, robustness, and available bandwidth of ultrasonic structural health monitoring techniques. On the other hand, wave-based methods provide more accurate information on a defect's type, size, and location than modal analysis techniques. This paper focuses on a low-frequency wave-based method for structural integrity assessment of complex waveguides. The wave finite element method is employed to compute the dispersion curves of non-standard cross-sectional waves exhibiting increased strain energy. The spectral results are used to analyse the diffusion of guided elastic waves through representative localized defects in a laminated sandwich panel. To validate the diffusion model, reflection and transmission coefficients are determined for several wave pulses on typical defects using time-domain virtual experiments and cross-sectional energy acquisition. Results demonstrate that using cross-sectional waves provides a sensitivity to damage up to 2.8× higher than flexural waves in the low-frequency range. These results are explained by the presence of local resonances within the cross section, producing wavelengths in the transverse direction of propagation. These waves may prove suitable for cost-effective structural health monitoring applications because they can travel long distances through heterogeneous and periodic structures.

We present for the first time an approach for identifying the geometric and material characteristics of layered composite structures through an inverse wave and finite element approach. More specifically, this Non-Destructive Evaluation (NDE) approach is able to recover the thickness, density, as well as all independent mechanical characteristics such as the tensile and shear moduli for each layer of the composite structure under investigation. This is achieved through multi-frequency single shot measurements. It is emphasized that the success of the approach is independent of the employed excitation frequency regime, meaning that both structural dynamics and ultrasound frequency spectra can be employed. It is demonstrated that more efficient convergence of the identification process is attained closer to the bending-to-shear transition range of the layered structure. Since a full FE description is employed for the periodic composite, the presented approach is able to account for structures of arbitrary complexity. The procedure is applied to a sandwich panel with composite facesheets and results are compared with two wave-based characterization techniques: the Inhomogeneous Wave Correlation method and the Transition Frequency Characterization method. Numerical simulations and experimental results are presented to verify the robustness of the proposed method.

International audience; This paper presents a new wave-based material identification strategy for sandwich panels, able to estimate their tensile and equivalent shear moduli from single shot measurements. The proposed algorithm is based on the determination of the maximal wave speed in the bending-to-shear transition bandwidth. A definition is proposed for the transition phenomenon resulting from the conversion of flexural waves in the composite waveguide, and the existence of a local energy velocity maxima is demonstrated using the 4 th-order sandwich theory. Analytical expressions are derived for the equivalent bending and shear parameters in terms of the transition frequency and the maximal group velocity. An practical iterative procedure is also proposed for the experimental identification of the transition bandwidth, while a Hilbert Transform magnitude is employed to measure time of arrivals of the flexural wave pulses. The robustness of the method is highlighted using a numerical case study and an experimental validation is finally conducted on a sandwich panel with composite faces. Results are compared with static measurements and a wave-based technique (Inhomogeneous Wave Correlation) and show significant accuracy improvements while ensuring reduced post-processing times.

Objectif La prise en charge du cancer de la prostate metastatique resistant a la castration (mCRPC) a fortement evolue depuis 2011. L’etude CAMERRA vise a decrire cette evolution via l’identification des cas prevalents de mCRPC dans le SNDS. En l’absence de marqueur direct du mCRPC au sein du SNDS, l’identification des cas necessite la construction d’un algorithme complexe. Methodes Un algorithme d’identification des patients mCRPC a ete construit a partir d’une extraction d’hommes âges de plus de 40 ans, couverts par le Regime general de l’Assurance maladie, avec un indicateur de cancer de la prostate (ALD, hospitalisations et actes CCAM, medicaments) et disposant d’un historique de soins de cinq ans sans absence de remboursement > 1 an. L’identification des mCRPC repose sur la construction de deux indicateurs : la date de premiere prise en charge des metastases se basant sur des actes specifiques (radiotherapie, hospitalisations, traitements ciblant les metastases [denosumab, acide zoledronique, radio-isotopes, radiofrequences, etc.], et des traitements specifiques du mCRPC (acetate d’abiraterone, enzalutamide, docetaxel et cabazitaxel) associes a des actes d’imageries ; la date de resistance a la castration s’appuyant sur les changements entre les sequences de traitements par anti-androgenes et analogues de la LH-RH, les actes chirurgicaux (orchidectomie et pulpectomie) ou la premiere delivrance d’estramustine ou d’un traitement specifique du mCRPC. Un patient est considere comme mCRPC a partir du moment ou il dispose d’une date de premiere prise en charge des metastases et d’une date de resistance a la castration. Resultats En 2014, 3192 patients avec un cancer de la prostate ont ete identifies dans l’EGB, parmi lesquels 499 metastatiques et 254 resistants a la castration. Chez ces 3192 patients, 141 ont ete identifies comme ayant un mCRPC. Par extrapolation, 468 142 cancers de la prostate sont attendus dans le SNDS en 2014. Cette estimation concorde avec celle de l’Institut national du cancer (INCa) : 508 699 en 2008. Parmi ces cas prevalents de cancer de la prostate, 20 137 devraient etre des mCRPC. Conclusion Cette etude preliminaire a permis de construire un algorithme fonctionnel d’identification des mCRPC en tenant compte d’elements complexes et de leur sequence, permettant une premiere estimation de la prevalence des mCRPC dans la population francaise d’apres le SNDS. La prise en charge des patients selectionnes sera par la suite decrite afin de rendre compte de l’evolution du parcours de soin.

International audience; This paper investigates the use of a wave-based method in the framework of structural optimisation of composite panels involving advanced components. The wave/finite element method (WFEM) is used to evaluate the influence of a core's geometry on the transition frequency of a sandwich panel involving composite skins. This transition occurs is a sandwich panel when the transverse shear stiffness has a significant influence on the flexural motion, compared to the bending stiffness. It follows that the modal density and the acoustic radiation will considerably increase above this frequency. The periodic waveguide is modelled at the mesoscopic scale using a 3D finite element model of the unit-cell. Therefore this method does not require an homogenisation of the core based on Gibson and Ashby formulations to provide the wave dispersion characteristics. Although the cellular cores compared in this study share the same mass-to-stiffness ratio, a significant alteration of the transition frequency and modal density can be observed compared to honeycomb cores. A periodic octagonal core is designed, providing up to 70 % increase of the transition frequency and a significant reduction of the modal density.

The determination of the crystalline volume fraction from the Raman spectra of microcrystalline silicon involves the knowledge of a material parameter called the Raman emission cross-section ratio y. This value is still debated in the literature. In the present work, the determination of y has been carried out on the basis of quantitative analysis of medium-resolution transmission electron microscopy (TEM) micrographs performed on one layer deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) close to the amorphous/microcrystalline transition. Subsequent comparison of these data with the crystallinity as evaluated from measured Raman spectra yields a surprisingly high value of y = 1.7. This result is discussed in relation to previously published values (that range from 0.1 to 0.9).

This contribution describes the introduction of hydrogenated microcrystalline silicon (μc-Si:H) as novel absorber material for thin-film silicon solar cells. Work done at IMT Neuchâtel in connection with deposition of μc-Si:H layers by very high frequency glow discharge deposition is related in detail. Corresponding layer properties w.r.t. material microstructure, hydrogen content, stability and electronic transport are referred to. Basic properties of single-junction, entirely microcrystalline, thin-film silicon solar cells are related: Spectral response, stability w.r.t. light-induced degradation, basic solar cell parameters (Voc, Jsc and FF) obtained by IMT Neuchâtel and by other laboratories are listed and commented; the deposition rate issue is addressed. Finally, microcrystalline/amorphous, i.e. "micromorph" silicon tandem solar cells, are described, together with recent developments on the research and industrial front. © 2002 Elsevier Science B.V. All rights reserved.

The microstructure and open-circuit voltage of n-i-p microcrystalline silicon solar cells were discussed. A mixed phase layer consisting of amorphous plus microcrystalline material was observed at the bottom of the solar cell and identified as one of the key microstructural features of the device. Results underlined the importance of the first stages of growth of the intrinsic (i) layer for the fabrication of high- Voc n-i-p microcrystalline solar cells.

The case for thin-film silicon as one of the main future options for cost-effective photovoltaic solar cells is outlined. The limitations of present amorphous silicon (a-Si:H) solar cells are briefly mentioned. Hydrogenated microcrystalline silicon (μc-Si:H) deposited by PECVD (plasma-enhanced chemical vapor deposition) at low substrate temperatures (approx. 200 °C) constitutes a new and additional possibility for solar cells. Properties of intrinsic μc-Si:H layers deposited by PECVD at VHF (very high frequency) excitation frequencies are listed, together with the necessary conditions for obtaining device-grade material. Performances obtained so far with μc-Si:H solar cells are given; the latter are compared with estimated limits for pn- and pin-type devices with Eg = 1.1 eV. Finally, present performances and future perspectives for 'micromorph' (μc-Si:H/a-Si:H) tandem solar cells are discussed. © 2002 Elsevier Science B.V. All rights reserved.

International audience; This paper presents an improved numerical strategy for the broadband analysis of wave propagation in composite or complex cross-sectional waveguides using the wave finite element method (WFE). Numerical analysis of such structures require highly discretized finite element models and leads to extensive computations. The proposed formulation relies on a projection of the cross-sectional transfer matrices on a reduced set of shape functions associated to propagating waves. Dispersion curves are then predicted only using a reduced number of eigenvectors. The performances and stability of this method are evaluated using the wavenumbers and wave shapes. Validations are provided for a sandwich composite beam and a cylindrical elasto-acoustic waveguide.

The aim of this communication is to show that it is possible to extend the model of the electronic transport developed for amorphous silicon (a-Si:H) to microcrystalline silicon (μc-Si:H). By describing the electronic transport with the μ0τR products (mobility×recombination time) as a function of the Fermi level, we observed the same behaviour for both materials, indicating a similar type of recombination. Moreover, applying the normalized μ0τ0 product (mobility×life-time) obtained by combining the photoconductivity (σphoto) and the ambipolar diffusion length (Lamb) measured in individual layers, we are able, as in the case of a-Si:H, to predict the quality of the solar cells incorporating these layers as the active 〈i〉 layer.

Undoped hydrogenated microcrystalline silicon (μc-Si:H) layers were grown by the very high frequency glow discharge (VHF-GD) technique under various deposition conditions. The electronic transport properties under illumination were investigated by means of steady-state photoconductivity and steady-state photocarrier grating methods. Similarly to hydrogenated amorphous silicon (a-Si:H), power law dependencies as a function of the generation rate are observed for the photoconductivity, for the ambipolar diffusion length, and for the parameter b (indicating the Fermi level). For μc-Si:H, as for a-Si:H, nearly constant product of (mobility × recombination time) of majority and minority carriers is observed as a function of the parameter b. Based on these similarities, we assume that the electronic transport model developed for a-Si:H remains valid for μc-Si:H.

Theoretical: Limits for Jsc, Voc, FF and efficiency of single-junction solar cells and tandems are derived, as a function of Eg, showing that: (1) double-junction ‘micromorph' solar cells constitute an optimum combination of bandgap values; (2) main future gain for thin-film silicon solar cells will be increasing Jsc, by light trapping. Spectral ranges where light trapping has to act are presented, separately for a:Si:H and μc-Si:H. Experimental: For glass-pin type cells, light trapping is obtained at the front end, by use of rough TCO layers. For plastic-nip type solar cells, light trapping is obtained by texturing of the back reflector, which acts as basic layer for further growth. Both random texturing and periodic gratings have been used, but results presented are limited to single-junction a-Si:H and μc-Si:H solar cells. So far, the highest Jsc-enhancement obtained is approximately 20%.

Microcrystalline silicon growth using very high frequency-glow discharge PECVD has been studied under conditions of high pressure and high VHF-power conditions. Hereby, the influence of the total gas flow and the silane concentration on the deposition rate has been investigated. Deposition rates of over 25 Å/s have been achieved at relatively low total gas flows of 100 sccm. These high-rate films show device-grade quality with respect to subband gap absorption and microcrystalline structure. Dark conductivity measurements reveal midgap character and transmission electron microscopy investigations confirm a highly crystalline microstructure from the bottom to the top of the μc-Si:H films. These high-rate μc-Si:H layers are very interesting candidates for solar cell and other devices. © 2002 Elsevier Science B.V. All rights reserved.

The development of μc-Si:H technology and the introduction of intrinsic μc-Si:H as photovotaically active material is retraced. Special emphasis is laid on the use of very high frequency glow discharge as a particularly propitious deposition method for μc-Si:H. Thereby, the use of a gas purifier to reduce oxygen content and obtain intrinsic layers with ‘midgap’ character is described. Recent results obtained with single-junction μc-Si:H solar cells and a-Si:H/μc-Si:H tandem solar cells are given. The analysis of carrier collection in single-junction μc-Si:H solar cells is undertaken with the variable intensity measurements method. It yields effective mobility×lifetime (μτ)eff products for the i-layer in p–i–n and n–i–p solar cells in the range 10−7–10−6 cm2 V−1. Similar values have been found for μτ-products in individual layers based on photoconductivity and ambipolar diffusion length measurements. Transmission electron microscopy images for μc-Si:H layers are given. They display a complex microstructure not suspected before. On the other hand, atomic force microscopy data reveal a pronounced surface roughness that correlates well with the optical light scattering and with the pronounced enhancement of the apparent optical absorption coefficient, in the 1–2 eV region, as already observed before.

Inks used for printing paper and cardboard are dispersions of synthetic organic pigments in a bonding agent system built up essentially of resins, vegetable oils and high-boiling-point mineral oil products (b.p. >250°C). The proportion of mineral oil material in the ink ranges between 20 and 30%. The more volatile mineral oil components slowly evaporate from the printed cardboard box and may migrate into the food product. They contaminated cereals and dry baby-food products at concentrations between 10 and 150 mg/kg.

Patients who are physically dependent on prescription drugs often create clinical management problems during hospitalization. Identifying those patients who have prescription drug problems can be difficult at the time of admission, but the information of the Kentucky All Schedule Prescription Electronic Reporting (KASPER) system can be useful clinically. The purpose of this study was to examine the value of the KASPER system in the management of patients admitted to an acute care hospital. A convenience sample of 58 hospitalized patients was evaluated. The patients' clinical and demographic data were abstracted from the medical record. The KASPER data were used to confirm the patients' history of drug use. In this sample, the KASPER data supplied additional, clinically useful information that was not available from the clinical history or screening toxicology from 30 (51.7%) of these patients. We conclude that the KASPER system has the potential to assist physicians in the care of hospitalized patients who take controlled drugs that are obtained by physician prescription and filled in Kentucky pharmacies.

The complete resection for NSCLC is analyzed through the study of a series of retrospective surgical reports upon the incomplete resection, due to a microscopic residual tumor at the resection margin. Following Shields' statement in 1974, the incomplete resection represents, in fact, the basic study protocol for the local recurrence following the resection of primary NSCLC. First of all, the obligation for a careful intraoperative pathologic assessment upon the resection margins, clearly emerges from this study. Secondly, two main aspects featuring the incomplete resection have also been pointed out. The first is represented by the historical microscopic residual tumor at the bronchial resection margin, while the second, more recently recognized, is represented by the critical resection margin within the involved ipsilateral mediastinal lymphatic area. The analysis of such different figures leads to different considerations when dealing with the basic matter of the local-regional completeness of resection and the oncological result in terms of cure. In fact, while the problem of the bronchial remnant appears amenable to further improvement by activating the surgical attention, the second, instead, is to be considered unmodifiable by the surgery alone. It basically depends on the extended microvascularity of the large lymphatic mediastinal network which appears to be the crucial factor of risk for such a "lymphatic" resection margin. In conclusion, the matter of complete resection is still open to further research provided that the design is strictly prospective. As a matter of fact, so far the expectation for cure in any apparently completely resected NSCLC is ruled by other well-known factors of prognosis which do not consider the quality of the resected margin at all.

We assessed the correlations between some plasma markers of immune activation (soluble receptors of interleukin 2 (sIL2-R) and TNFap75 (sTNFII-R) and usual markers of HIV infection in patients treated with protease-inhibitors (PI). Forty-six PI-naive HIV-1-infected adults were included in a 1-year prospective cohort from the initiation of a P1-containing regimen (M0). Measurements of CD4+cell count, plasma HIV-RNA, sIL2-R and sTNFII-R were performed at M0, M6, and M12. The evolution of sIL2-R from baseline to M12 was significantly different between immunological responders (IR) (CD4+count above 200/mm3 for subject having less than 200 CD4 +/mm3 at inclusion, or increase of at least 50 CD4+/mm3 for others) (58 UI/ml) and non-IR (+28 UI/ml) (P =0.01). The evolution of sTNFII-R between M0 and M12 was significantly different between virological responders (VR) (plasma HIV-1 RNA less than 500 copies/ml at M12) (-2.5 ng/ml) and non-VR (+0.2 ng/ml) (P = 0.02). Our study shows significative correlations between the evolutions of soluble interleukin-2 and TNFR-II receptors and those of CD4+T-lymphocytes or HIV-RNA responses in patients under HAART.

Growth of intrinsic micro-crystalline silicon layers by means of VHF-PECVD, assisted by remote microwave (MW) plasma has been investigated. The aim of the MW plasma is to enhance the deposition rate by introducing excited hydrogen and Ar atoms from the MW plasma in the VHF deposition zone. For this purpose a remote microwave plasma source was constructed in which a H2/Ar plasma is generated in a 20 mm diameter quartz tube. A gasshower has been constructed for homogeneous distribution of the flow of excited gas species from the microwave source into the deposition zone of the VHF-PECVD reactor where the dissociation of silane takes place. In a first series of experiments we applied high microwave power (< 500 W) and pure hydrogen in the MW source. This resulted in a larger deposition rate, but all layers – even grown at low silane concentrations – were amorphous and had a high oxygen content. The oxygen contamination was partly due to reduction of the quartz tube by the hydrogen plasma. In a second series of experiments Ar dilution and reduced MW power were used to eliminate the effect of etching of the tube by the microwave hydrogen plasma. In this series of experiments an increase of the growth rate of micro-crystalline silicon by about 15 % due to assistance of the microwave plasma was found. Optical emission spectroscopy indicates that – in these experiments – the main mechanism for the increased dissociation of silane is through molecular quenching reaction of Ar* metastables.