Development of a photosystem II-based optical microfluidic sensor for herbicide detection

Herbicides are highly toxic for both human and animal health. The increased application of herbicides in agriculture during the last decades has resulted in the contamination of both soil and water. Herbicides, under illumination, can inhibit photosystem II electron transfer. Photosynthetic membranes isolated from higher plants and photosynthetic micro-organisms, immobilized and stabilized, can serve as a biorecognition element for a biosensor. The inhibition of photosystem II causes a reduced photoinduced production of hydrogen peroxide, which can be measured by a chemiluminescence reaction with luminol and the enzyme horseradish peroxidase. In the present work, a compact and portable sensing device that combines the production and detection of hydrogen peroxide in a single flow assay is proposed for herbicide detection.     

Chemical engineering approach to regenerative medicine

The intrinsically multi-factorial pathological trend of spinal cord injury is probably the most important reason behind the absence of efficient therapeutic strategies. Therefore, recent studies suggest the use of new tools combining the delivery of both cells and drugs. Systems which are able to perform multiple controlled delivery of different therapeutic agents have gained particularly strong interest. Hence, in order to avoid trial and error approaches, several studies were performed following the classic chemical engineering multiscale approach: tuning microchemistry to manipulate macro properties in order to satisfy specific medical needs as injectability, low stress on target tissues, ability to retain liquids, capability of carrying living cells, and possibility to control the delivery of drugs. In this framework we focused on injectable agarose-carbomer based hydrogels applying he results of our studies performed in the past two years: in vitro biocompatibility, physical chemical studies, drug delivery transport phenomena investigation, and in vivo biocompatibility in uninjured Brainbow mice.     

The problem of the critical angle for edge and center V-notched structures

In the present paper, the problem of detecting the critical notch angle, i.e. the angle providing the minimum failure load, for brittle or quasi-brittle structures containing either edge or center V-notches is investigated. The expression of the generalized fracture toughness is obtained according to Finite Fracture Mechanics. It is shown that a critical angle is always present: its value depends, through the brittleness number, on both material and geometric characteristics. Thus, the crack is not the most dangerous configuration. The result is supported by experimental results presented in the Literature.     

Structural identification of fatty acid methyl esters by collision spectra of their [M ? H]− species

Negative ion chemical ionization linked to collisionally activated decomposition (CAD) experiments has proved to be an efficient analytical tool in mass spectrometric characterization of fatty acids. The CAD mass-analysed ion kinetic energy spectra of [M ? H]^? species, obtained by OH^? reaction with a selection of six C₁₈ fatty acid methyl esters, reveal useful correlations with the original structure of the neutrals, giving evidence of both chain branching and double bond positions.     

On the magnitude of the Li + He → B + n reaction cross section at the Big-Bang temperature

The ⁸Li + ⁴He → ¹¹B + n reaction at Ecm<2 MeV$E_{\mathrm{cm}}<2\text{MeV}$ is a process of relevant astrophysical interest for which a remarkable experimental discrepancy between inclusive and exclusive cross-section measurements exists. In this Letter, a new inclusive neutron measurement at Ecm=1.05±0.16 MeV$E_{\mathrm{cm}}=1.05\pm 0.16\text{MeV}$ is given. The radioactive ⁸Li beam was delivered by the EXCYT facility. The cross section was determined by a low-background measurement of the time correlation between the ⁸Li projectile arrival to the target and the following neutron capture in a threshold-less 4π thermalization counter. This new data strengthens the reliability of the previous inclusive reaction cross-section data and altogether are consistent with a significant population of ¹¹B levels at high excitation energy.     

Infrared digital reflective-holographic 3D shape measurements

We present a series of experiments to demonstrate digital holography on reflective objects at wavelength 10.6 μm of a CO₂ laser using a pyrocam array. Fresnel holograms of reflective objects are recorded by a Mach-Zehnder interferometer. We describe a method for improving the accuracy of the numerical reconstructions and for compensating the loss of resolution at longer wavelength by Fresnel reconstruction of digitally recorded infrared holograms.     

Colloidal assembly on magnetically vibrated stripes

We investigate the collective organization of paramagnetic colloidal particles externally driven above the periodic stripes of a uniaxial ferrimagnetic garnet film. An external field modulation induces vibration of the stripe walls and produces random motion of the particles. Defects in the stripe pattern break the symmetry of the potential and favor particle nucleation into large clusters above a critical density. Mismatch between particle size and pattern wavelength generates assemblies with different morphological order. At even higher field strengths, repulsive dipolar interactions between the particles induce cluster melting. We propose a novel approach to generate and externally control a variety of colloidal assemblies.     

Pegylated silica nanoparticles: cytotoxicity and macrophage uptake

Here, we present a thorough study of pegylated silica nanoparticle (SNP) interaction with different biological environments. The SNPs have a mean diameter of about 40 nm and are coated with polyethylene glycol (PEG) of different molecular weights. The physicochemical characterization of SNPs allowed the confirmation of the binding of PEG chains to the silica surface, the reproducibility of the synthesis and the narrow size-dispersion. In view of clarifying the SNP interaction with biological environments, we first assessed the SNP reactivity after the incubation with two cell lines (macrophages RAW 264.7 and primary human fibroblasts), observing a reduced toxicity of pegylated SNPs compared to the bare ones. Then, we investigated the effect of the protein adsorption on the SNP surface using the model serum protein, bovine serum albumin (BSA). We found that the protein adsorption takes place more heavily on poorly pegylated SNPs, promoting the uptake of the latter by macrophages and leading to an increased mortality of these cells. To better understand this mechanism by means of flow cytometry, the dye Ru(bpy)₃Cl₂ was incorporated in the SNPs. The overall results highlight the SNP potentialities as a drug delivery system, thanks to the low interactions with the macrophages.     

Generation and Application of Ultra-High-Intensity Magnetic Field Gradient Pulses for NMR Spectroscopy

Two different concepts of gradient current power supplies are introduced, which are suitable for the generation of ultra-high intensity pulsed magnetic field gradients of alternating polarity. The first system consists of a directly binary coded current source (DBCCS). It yields current pulses of up to ±120 A and a maximum voltage across the gradient coil of ±400 V. The second system consists of two TECHRON 8606 power supplies in push–pull configuration (PSPPC). It yields current pulses of up to ±100 A and a maximum voltage across the gradient coil of ±300 V. In combination with actively shielded anti-Helmholtz gradient coils, both systems are used routinely in NMR diffusion studies with unipolar pulsed field gradients of up to 35 T/m. Until now, alternating pulsed field gradient experiments were successfully performed with gradient intensities of up to ±25 T/m (DBCCS) and ±35 T/m (PSPPC), respectively. Based on the observation of the NMR spin echo in the presence of a small read gradient, procedures to test the stability and the matching of such ultra-high pulsed field gradient intensities as well as an automated routine for the compensation of possible mismatches are introduced. The results of these procedures are reported for the PSPPC system.