Dynamic crossover in hydration water of curing cement paste: the effect of superplasticizer

The influence of a new comb-shaped polycarboxylate-based superplasticizer (CSSP) on the hydration kinetics and transport properties of aged cement pastes has been investigated by high-resolution quasi-elastic neutron scattering (QENS) and low temperature differential scanning calorimetry (LT-DSC). A new method of analysis of QENS spectra is proposed. By applying the refined method we were able to access to four independent physical parameters including the self-diffusion coefficient of the hydration water confined in the cement paste. Mean squared displacement (MSD) of the hydrogen atom for mobile water molecules displays a dynamic crossover temperature in agreement with DSC data. The experimental results indicate that CSSP polymer added into cement paste moderates the hydration process and decreases the dynamic crossover temperature of the hydration water.     

Physicochemical characterization of acrylamide/bisacrylamide hydrogels and their application for the conservation of easel paintings

Acrylamide chemical gels have been synthesized to obtain systems with mechanic and hydrophilic properties suitable for the cleaning of works of art. The gel characteristics were tailored by changing the polymer percentage present in the final hydrogel formulation from 2 to 10% w/w. Two different hydrogels have been selected in this interval for an in depth characterization (i.e., S 4% w/w and H 6% w/w). Water retention properties of the gels along with the free water index have been determined by the combination of standard dehydration tests and differential scanning calorimetry (DSC) measurements. The gels' structure has been determined by scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS). The water retention capacity of hydrogel, H, was also determined. Cleaning tests on easel painting replicas, performed with both hydrogels loaded with an aqueous detergent system, showed good results in the removal of a widely used synthetic adhesive and hence offered these gels as a real alternative to the widely applied physical gel methodology with the advantage of being a residue-free technique. A preliminary SAXS investigation confirms the persistence of the detergent system nanostructure inside the hydrogel.     

Experimental implementation of a self-tuning control system for decentralised velocity feedback

Simulations have previously shown that, for broadband excitation, adjusting the gain of a local velocity feedback loop to maximise their absorbed power also tends to minimise the kinetic energy of the structure under control. This paper describes an experimental implementation of multiple velocity feedback loops on a flat panel, whose gains can be controlled automatically by an algorithm that maximises their local absorbed power. Taking care to remove excessive phase shift in the control loop allows a stable feedback gain that is high enough to experimentally demonstrate the transition in control action between optimum damping and pinning of the structure. A simple search algorithm is then used to adapt the feedback gains of two control loops to maximise their local absorbed powers, thus demonstrating self-tuning. By measuring the power absorbed by each of these loops and also estimation of the kinetic energy of the plate from velocity measurements for a wide range of the two feedback gains, it is shown that not only does the adaptive algorithm converge to a set of feedback gains that maximise total power absorbed by the two feedback loops, but also that this set of feedback gains is very close to those that minimise the measured kinetic energy of the panel.     

Modification of Cross-Linked Rubber Particles by Free Radical Polymerization

The synthesis of polystyrene chains covalently bound to the surface of cross-linked rubber particles from recycled tires (ground tire rubber, GTR) was investigated via free radical polymerization in situ by using azobisisobutyronitrile (AIBN) and dibenzoyl peroxide (BPO) as initiators. Indeed, the graft polymerization provides a significant route to modify the physical and chemical properties of these particles allowing to improve their compatibility with other polymers. Polymerization reactions were carried out in bulk by changing the styrene/GTR ratio as well as the amount of free radical initiator. Appreciable amounts of polystyrene (PS) were grafted on GTR when BPO was used as confirmed by particle characterizations.     

Nanostructured Polyelectrolyte-based System as a Toolbox for Metal Ions Detection

The capability of certain heavy metal ions to induce fluorescence decrease by a quenching mechanism suggested us to design and build a sensor potentially tunable for different ions at different concentrations. We propose a quenching-based sensor exploiting a nanostructured architecture in which fluorescent molecules (the sensing probe) are entrapped to recognize a specific analyte (heavy metal ions) through an optical transduction. The polyelectrolyte nanostructured system, named nanocapsule, improves the fluorophore-ion quenching sensitivity allowing a micromolar detection. Furthermore we couple our sensor with an electrical device in order to refine the sensing procedure: the electric field created allows a metal ions spatial gradient, necessary to detect a specific element on a single sample solution, avoiding a comparative analysis with an intensity reference value. Results obtained will show the advantages and the potentialities of our system as a smart toolbox for metal ions detection.     

Convergent synthesis of cis-α,β-epoxy-carboxylic acids from 1-halo-2-trimethylsilyloxy-3-aza-4-phenyl-1,3-butadiene

Reaction of a wide variety of aldehydes with the easily prepared 2-azadienes, in the presence of BF₃ etherate, furnishes the corresponding hetero Diels-Alder adducts which have been converted, mainly, to cis epoxides via N-Boc protection followed by one-pot two-step ring opening and nucleophilic displacement of the halogen atom, resulting in final formation of an oxirane ring.     

Modular DNA-programmed assembly of linear and branched conjugated nanostructures

A new strategy for self-assembly and covalent coupling of encoded molecular modules into nanostructures with predetermined connectivity has been developed. The method uses DNA-functionalized oligo(phenylene ethynylene)-derived organic modules for controlling the assembly and covalent coupling of multiple modules. Rigid linear modules (LM) and tripoidal modules (TM) were functionalized with short oligonucleotides at each terminus. They can hybridize and thereby link up modules containing complementary sequences. Each terminus of the oligo(phenylene ethynylene) modules also consists of a salicylaldehyde moiety, which can form metal-salen complexes with other modules. The salicylaldehyde groups of two modules are brought in proximity when their adjoining DNA sequences are complementary, and they selectively form a manganese-salen complex in the presence of ethylenediamine and manganese acetate. The resulting structures consist of a matrix of linear and branched oligo(phenylene ethynylene)s which are linked by conjugated and rigid manganese-salen complexes. These nanostructures are potential conductors for applications in molecular electronics.     

A green alternative method for analysis of ivermectin and moxidectin in environmental water samples using automatized preconcentration previous MEEKC

Antiparasitic drugs derived from macrocyclic lactones (MLs) are widely used in livestock activities around the world. An increasing concern for local authorities is the environmental pollution as a consequence of veterinary drugs widely used in rural areas. The purpose of environmental analysis is to monitor low levels of pollutant analytes in a large number of samples. Also, due to the lipophilic characteristic of these lactones, long‐chain solvents are usually required for performing sample treatment before and during the analysis. Therefore, sensitive, specific, robust, and environmentally friendly analytical methods are still required. In this paper, a new automatized preconcentration methodology followed by microemulsion electrokinetic chromatography analysis was developed for the simultaneous separation and determination of the most used MLs, ivermectin (IVM) and moxidectin (MXD) in environmental water. XAD‐4 resin was employed as an adsorbent for the preconcentration process and ethanol was used as the eluent. In contrast to traditional analysis for IVM and MXD, in this methodology nonpolluting solvents were involved during the whole process and therefore, it could be considered as a contribution to green analytical chemistry. Under optimal experimental conditions, LOD obtained for IVM and MXD were of 3 × 10^?3 and 3.6 × 10^?3 μg/L, respectively.     

Preliminary study of HCHO spatial and temporal distribution from Coastal to Plateau areas in Antarctica

Formaldehyde concentrations were determined in over 1800 snow samples (snowpit, firn cores and superficial snow) from Antarctica by a sensitive spectrofluorimetric Flow Injection Analysis method. The method performances (detection limit: 55?ng/L; reproducibility: 2.5% at 1?µg/L level; linear range: 0.1–3000?µg/L) allowed a reliable determination of formaldehyde content in all the collected samples. The range of determined concentrations was 0–70?µg/L with a mean concentration of 7.7?µg/L and a median concentration of 5.8?µg/L. The formaldehyde background level was estimated at a few micrograms per liter in coastal and plateau areas of Northern Victoria Land. In some stations the background values are modulated by HCHO deposition events recurring over relatively large time periods.