Nonlinear wave propagation in locally dissipative metamaterials via Hamiltonian perturbation approach

Nonlinear Dynamics - The cellular microstructure of periodic architected materials can be enriched by local intracellular mechanisms providing innovative distributed functionalities. Specifically,...     

Quantification of glycoalkaloids in tomato plants by time-resolved fluorescence using a europium chelator entrapped in liposomes

In the control of tomato transgenic cultivars it is important to determine the glycoalkaloid content, which requires the screening of many samples. We have developed a simple method for the extraction and determination of glycoalkaloids in the leaf and fruit extracts of tomatoes using a europium chelator entrapped in phosphatidylcholine-cholesterol containing liposomes. The concentration values were quantified from liposome lysis effected by glycoalkaloid action. The fluorescent signal is linear between 1 and 10 micrograms of tomatine, which makes the method useful for the analysis of tomato samples.     

Acoustic waveguide filters made up of rigid stacked materials with elastic joints

Meccanica - The acoustic dispersion properties of monodimensional waveguide filters can be assessed by means of the simple prototypical mechanical system made of an infinite stack of periodic...     

Time-resolved fluoroimmunoassay for quantitative determination of ampicillin in cow milk samples with different fat contents

In this paper, we have reported an immunoassay with time-resolved revelation system for ampicillin in raw milk samples. Immunological methods appear to be a promising approach in the analysis of β-lactam compounds, because they do not need previous sample pre-treatments. In fact, β-lactam ring is not very stable in extensive sample pre-treatment procedures requested in conventional analytical techniques. Specimens were collected from lactating cows bred in various conditions and assayed for the fat contents. Ampicillin was assayed in samples with different fat concentrations. The assay was performed using ampicillin-specific polyclonal antibody raised in rabbit; the immunogen was synthesized using bovine thyroglobulin conjugated to ampicillin by glutaraldehyde reaction; as fluorescent marker we used goat anti-rabbit IgG conjugated with a chelating molecule complexed with Eu³⁺. Bovine serum albumin (BSA) conjugated with ampicillin was synthesized and used to prepare a solid phase on polystyrene microtiter plates. The use of a lanthanide chelate as label allowed to achieve 1 ng mL⁻¹ sensitivity, which is four times more sensitive than limits requested from European Community. Fat contents did not affect the assay performance.     

Second-gradient homogenized model for wave propagation in heterogeneous periodic media

The paper is focused on a homogenization procedure for the analysis of wave propagation in materials with periodic microstructure. By a reformulation of the variational-asymptotic homogenization technique recently proposed by Bacigalupo and Gambarotta (2012a), a second-gradient continuum model is derived, which provides a sufficiently accurate approximation of the lowest (acoustic) branch of the dispersion curves obtained by the Floquet–Bloch theory and may be a useful tool for the wave propagation analysis in bounded domains. The multi-scale kinematics is described through micro-fluctuation functions of the displacement field, which are derived by the solution of a recurrent sequence of cell BVPs and obtained as the superposition of a static and dynamic contribution. The latters are proportional to the even powers of the phase velocity and consequently the micro-fluctuation functions also depend on the direction of propagation. Therefore, both the higher order elastic moduli and the inertial terms result to depend by the dynamic correctors. This approach is applied to the study of wave propagation in layered bi-materials with orthotropic phases, having an axis of orthotropy parallel to the direction of layering, in which case, the overall elastic and inertial constants can be determined analytically. The reliability of the proposed procedure is analysed by comparing the obtained dispersion functions with those derived by the Floquet–Bloch theory.     

Time-resolved fluoroimmunoassay of progesterone by Eu-labelled protein-A

Summary A standard curve for progesterone using a solid phase time-resolved fluoroimmunoassay was obtained. The 11-hydroxyprogesterone hemisuccinate bonded to ovalbumin was adsorbed to the wells of polystyrene microtiter strips. After incubation of scalar quantities of free progesterone (from 12 to 5000 pg) with specific antibody and an excess of Eu-labelled protein-A, the wells were washed and the europium bound to the solid phase was measured as a 2-naphthoyltrifluoroacetone chelate using a time resolved fluorometer.

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Zeitaufgelöster Fluorescenzimmunoassay von Progesteron mit Hilfe von Eu-markiertem Protein-A

     

Radioimmunoassay of progesterone and estriol in plasma using antibodies immobilized onto protein A-sepharose CL-4B

Protein A-Sepharose CL-4B was used as a solid phase for antibodies in the radioimmunoassay of progesterone and estriol. The method was fast and easily standardizable. Immobilized antibodies had the same binding capacity as free antibodies and gave good correlation curves (r = 0.996 for progesterone andr = 0.989 for estriol). Sensitivity was 12.5 pg/tube for progesterone and 8.0 pg/tube for estriol. Comparison of progesterone radioimmunoassay with chemically immobilized antibody onto Sepharose CL-4B was also carried out.     

Analytical performance of luminescent immunoassays of different format for serum daidzein analysis

Two sensitive competitive-type solid-phase immunoassays for serum daidzein analysis have been developed and optimized. The first is a chemiluminescent enzyme immunoassay that uses black polystyrene microtiter wells in which daidzein-specific antibodies raised in rabbits are immobilized and a daidzein derivative is coupled to horseradish peroxidase (HRP) as a label. The HRP activity of the antibody-bound tracer is measured with an enhanced chemiluminescent system (luminol/H2O2/enhancer). The second immunoassay is based on the use of bovine serum albumin-daidzein derivative immobilized on microtiter plates and a secondary anti-rabbit IgG-Fc fragment conjugated with 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA). Formation of the complex Eu3+-BCPDA enables time-resolved fluorescence-mode detection of the amount of antibody bound to the immobilized antigen. Both methods fulfilled all the requirements of accuracy and precision. The detection limit was the same for each method, 10 pg/well; this is better than that of other immunoassays. The specificity of the two methods was different, because of their competitive-type mechanisms. The performance of the chemiluminescence method is better, because the cross-reactivity of the main interfering compound (genistein) was 5%, compared with 25% for the time-resolved fluoroimmunoassay.