Automated microwave device characterization set-up based on a technology-independent generalized Bias System

In this paper an automated laboratory set-up for the characterization of micro- and millimeter-wave electron devices under DC, small- and large-signal operation is described, which is based on a generalized, technology-independent bias system. The biasing parameters adopted, which are a linear combination between currents and voltages at the device ports, allow for a complete characterization of the desired empirical data (e.g. multi-frequency S-matrix) throughout all the regions in which the quiescent operation of the device can be conventionally divided, without any need for the switch between different biasing strategies. The look-up tables of experimental data obtained, which are carried out homogeneously with respect to the same couple of bias parameters, independently of the quiescent regions investigated, are particularly suitable for the characterization of empirical non-linear dynamic models for the electron device

Statistical characterization of residual noise in the low-rank approximation filter framework, general theory and application to hyperpolarized tracer spectroscopy

The use of low-rank approximation filters in the field of NMR is increasing due to their flexibility and effectiveness. Despite their ability to reduce the Mean Square Error between the processed signal and the true signal is well known, the statistical distribution of the residual noise is still undescribed. In this article, we show that low-rank approximation filters are equivalent to linear filters, and we calculate the mean and the covariance matrix of the processed data. We also show how to use this knowledge to build a maximum likelihood estimator, and we test the estimator's performance with a Montecarlo simulation of a 13C pyruvate metabolic tracer. While the article focuses on NMR spectroscopy experiment with hyperpolarized tracer, we also show that the results can be applied to tensorial data (e.g. using HOSVD) or 1D data (e.g. Cadzow filter).Comment: 26 pages, 7 figure

Reinforcement-matrix interactions and their consequences on the mechanical behavior of basalt fibers-cement composites

In order to prepare basalt fibers-reinforced cement-based mortars with higher compatibility between reinforcement and matrix, basalt fibers with new surface treatments (sizing) were studied looking for enhanced interaction at the interphase between basalt fibers and cement matrix. As-received, calcinated, activated and silanized (by three silane aqueous solutions: i) aminopropyltriethoxysilane, APTES; ii) ¿-aminopropylmethyldiethoxysilane, APDES and iii) a mixture APTES APDES 50% by weight) basalt fibers were dispersed in Portland cement matrix. Performances of the composites were evaluated by mechanical tests. Final correlation between the fibers surface characteristics and mechanical performance was carried out considering the induced microstructural changes and adhesion at the interface. Fractographic analysis by SEM and laser and optical profilometry were performed. A clear improvement in mechanical properties was obtained when basalt fibers were dispersed in cement matrix. Results suggest that better behavior is achieved when basalt fibers modified with a complex mixture of silanes are dispersed in cement matrix.This work was financially supported by the Projects MAT2014-59116-C2 (Ministerio de Economía y Competitividad); 2012/00130/004 (Fondos de Investigación de Fco. Javier GonzalezBenito, política de reinversión de costes generales, Universidad Carlos III de Madrid) and 2011/00287/002 (Acción Estratégica en Materiales Compuestos Poliméricos e Interfases, Universidad Carlos III de Madrid). The research was financially supported also by the Project Bando per il Finanzia- mento di Progetti di Ricerca Congiunti per la Mobilit`a all Estero di Studenti di Dottorato prot. n 0051266 (Universit`a degli Studi di Roma, La Sapienza) in the frame the PhD Thesis of Morena Iorio. Finally, the authors would like to thank the group In-service Material Performance (Universidad Carlos III de Madrid) for supporting the project in the mechanical tests

Improvement of phemt intermodulation prediction through the accurate modelling of low-frequency dispersion effects

Large-signal dynamic modelling of III-V FETs cannot be simply based on de i/v characteristics, when accurate performance prediction is needed. In fact, dispersive phenomena due to self-heating and/or traps (surface state densities and deep level traps) must be taken into account since they cause important deviations in the dynamic drain current. In this paper, a recently proposed large-signal i/v measurement setup is exploited to extract an empirical model for lowfrequency dispersive phenomena in microwave electron devices. This i/v model is then embedded into a microwave large-signal PHEMT model. Eventually, a Ka-band highly linear power amplifier, designed by Ericsson using the Triquint GaAs 0.25pm PHEMT process, is used for model validation. Excellent intermodulation distortion predictions are obtained with different loads despite the extremely low power level of IMD products involved. This entitles the proposed model to be also used in the PA design process instead of conventional loadpull techniques whenever the high-linearity specifications play a major role

Mechanism of miR-222 and miR-126 regulation and its role in asbestos-induced malignancy

MiR-222 and miR-126 are associated with asbestos exposure and the ensuing malignancy, but the mechanism(s) of their regulation remain unclear. We evaluated the mechanism by which asbestos regulates miR-222 and miR-126 expression in the context of cancer etiology. An ‘in vitro’ model of carcinogen-induced cell transformation was used based on exposing bronchial epithelium BEAS-2B cells to three different carcinogens including asbestos. Involvement of the EGFR pathway and the role of epigenetics have been investigated in carcinogen-transformed cells and in malignant mesothelioma, a neoplastic disease associated with asbestos exposure. Increased expression of miR-222 and miR-126 were found in asbestos-transformed cells, but not in cells exposed to arsenic and chrome. Asbestos-mediated activation of the EGFR pathway and macrophages-induced inflammation resulted in miR-222 upregulation, which was reversed by EGFR inhibition. Conversely, asbestos-induced miR-126 expression was affected neither by EGFR modulation nor inflammation. Rather than methylation of the miR-126 host gene EGFL7, epigenetic mechanism involving DNMT1- and PARP1-mediated chromatin remodeling was found to upregulate of miR-126 in asbestos-exposed cells, while miR-126 was downregulated in malignant cells. Analysis of MM tissue supported the role of PARP1 in miR-126 regulation. Therefore, activation of the EGFR pathway and the PARP1-mediated epigenetic regulation both play a role in asbestos-induced miRNA expression, associated with in asbestos-induced carcinogenesis and tumor progression

Preliminary study of the mechanical and hygrothermal performance of concrete reinforced with fibrillated cellulose

Cement, being the most widely used building material, is the responsible for a large share of greenhouse gas emissions. To reduce the environmental impact of its production, natural fibres can be used as eco-friendly additives. Moreover, their potential use in traditional lime-based mortars makes them an ideal choice for green buildings as well as for the retrofit of historical buildings. An innovative cementitious composite reinforced with fibrillated cellulose (hereafter called «green concrete») was tested to assess its mechanical and physical properties. Samples were casted using Portland cement and natural hydraulic lime and varying the ratios among the constituents. Viscosity and setting time of the fresh pastes were determined with a viscosimeter and a Vicat apparatus, while their hydration was studied by thermal analysis. The influence of the fibres on the flexural strength of the final composite was determined through mechanical tests. The expected hygrothermal performance of the «green concrete» was explored through dynamic hygrothermal simulation to investigate its potential use as a retrofit material. A sensitivity analysis (SA), based on the hygrothermal properties of natural-based building materials similar to the «green concrete», was conducted to identify the parameters influencing more the simulation of annual internal temperature and moisture variations. The preliminary assessment of the mechanical properties of the «green concrete» showed that at higher percentages the cellulose fibres can negatively affect the workability/setting time of the fresh pastes and the flexural strength. The most promising samples were identified and will undergo further investigation. The SA results outlined that the «green concrete» might not be effective for thermal insulation, although it might be used as a moisture-buffering layer by adjusting the values of the free water saturation moisture content, the equilibrium moisture content at RH=80% and the dry vapour diffusion resistance factor of the final composite

Glass-ceramic sealants for SOEC: Thermal characterization and electrical resistivity in dual atmosphere

A Ba-based glass-ceramic sealant is designed and tested for solid oxide electrolysis cell (SOEC) applications. A suitable SiO2/BaO ratio is chosen in order to obtain BaSi2O5 crystalline phase and subsequently favorable thermo-mechanical properties of the glass-ceramic sealant. The glass is analyzed in terms of thermal, thermo-mechanical, chemical, and electrical behavior. Crofer22APU-sealant-Crofer22APU joined samples are tested for 2000 h at 850 ◦C in a dual atmosphere test rig having reducing atmosphere of H2:H2O 50/50 (mol%) and under the applied voltage of 1.6 V. In order to simulate the SOEC dynamic working conditions, thermal cycles are performed during the long-term electrical resistivity test. The glass-ceramic shows promising behavior in terms of high density, suitable CTE, and stable electrical resistivity (106–107 Ω cm) under SOEC conditions. The SEM-EDS post mortem analysis confirms excellent chemical and thermo-mechanical compatibility of the glass-ceramic with Crofer22APU

MOLECULAR IDENTIFICATION AND GENOTYPING OF CIAUSCOLO AUTOCHTHONOUS MICROFLORA: PRELIMINARY STUDY

The present study reports the results of a preliminary characterization of the bacterial population of Ciauscolo, a typical Italian fermented sausage, traditionally manufactured in Marche region. The bacterial community involved in Ciauscolo fermentation was investigated using both molecular and culturebased methods. The estimation of genotypic intra-species variation of the autochthonous bacteria isolated was also evaluated by using randomly amplified polymorphic DNA (RAPD) analysis and unweighted pairgroup method with arithmetic averages (UPGMA) cluster analysis. Our findings revealed an high diversity of the autochthonous bacterial population investigated, both at species and strain level