LC–MS/MS analysis of coccidiostats in meat supply chain safety

The presence of coccidiostats in meat products represents an important topic because of the animal administration of these substances, authorized as feed additives for targeted species, in order to prevent and inhibit coccidiosis. Coccidiostats include both ionophores and synthetic molecules characterized by different chemical–physical properties such as polarity. Meat is a matrix characterized by many interfering compound groups, such as proteins, phospholipids, and fats. High-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) analysis allows the required selectivity and sensitivity for discriminating analytes and matrix interferences. For these reasons, an LC–MS/MS method for the analysis of coccidiostats in meat products was developed without SPE purification steps. The correct analyte quantification is allowed by matrix-matched calibration. The method validation was performed by the replicated analysis of spiked meat samples at two different concentration levels (limit of quantification—LOQ—and a 10 times LOQ) in order to evaluate method recovery and repeatability, plus spiked samples at higher concentrations up to 10,000 μg/kg. Moreover, the metrological approach was used for the calculation of method uncertainty. The application of the developed method to real samples evidenced the presence of some non-ionophores coccidiostats in the meat and liver of chicken and rabbit species. Although, the determined concentration was below the established MRLs, the monitoring of coccidiostats in the meat supply chain is confirmed as a good strategy in order to safeguard consumer health.     

Piezoelectric PVDF-TrFE nanocomposite mats filled with BaTiO3 nanofibers: The effect of poling conditions

BaTiO₃ nanofibers (BT NFs), prepared by electrospinning, were used as a filler for electrospun poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) nanocomposite mats. The phase structure and the effect of poling conditions on the piezoelectric properties of PVDF-TrFE/BT nanocomposites were investigated. The results showed an improved degree of crystallinity (78.6%) and a high β-crystal phase (up to 98.3%) in all electrospun samples, independent of the nanofiber content. The two-step poling method, applying electric fields of opposite polarity, led to significantly improved piezoelectric constants d₃₃ (−31.7 pC N⁻¹), strongly dependent on the added BaTiO₃ nanofibers. The inclusion of piezoelectric ceramic nanofibers into a polymer matrix, easily carried out by means of electrospinning, followed by an ad hoc optimized poling treatment, allowed to develop flexible materials with enhanced piezoelectric properties, potentially exploitable in innovative conversion systems used in wearable and sensing devices.     

Molecular force field study concerning the host properties of carbosilane dendrimers

The effect of structural variations at the core of carbosilane dendrimers has been studied using Molecular Dynamics. Several derivatives of the parent dendrimer have been modeled and characterized with respect to the dimensions of the inner cavities which lie on the order of 5–15 Å. The “denseness” of the outer shell has been studied by calculating solvent accessible surfaces and excluded volumes as a function of the radius of the probe sphere. The higher generation dendrimers were found to possess dense outer shells with holes of the order of 2–3 Å. Dendron separation especially with respect to clefts in the molecule is discussed. It was found that in low generation carbosilane dendrimers the dendrons are clearly separated while at higher generations a substantial amount of interpenetration occurs. In addition, results are presented showing that carbosilane dendrimer surfaces are fractal only over a narrow range of length scales. In this range, the fractal dimensions of the surfaces are of the order of 2.1.     

Nanosized T1 MRI Contrast Agent Based on a Polyamidoamine as Multidentate Gd Ligand

A linear polyamidoamine (PAA) named BAC-EDDS, containing metal chelating repeat units composed of two tert-amines and four carboxylic groups, has been prepared by the aza-Michael polyaddition of ethylendiaminodisuccinic (EDDS) with 2,2-bis(acrylamido)acetic acid (BAC). It was characterized by size exclusion chromatography (SEC), FTIR, UV–Vis and NMR spectroscopies. The pK_a values of the ionizable groups of the repeat unit were estimated by potentiometric titration, using a purposely synthesized molecular ligand (Agly-EDDS) mimicking the structure of the BAC-EDDS repeat unit. Dynamic light scattering (DLS) and ζ-potential analyses revealed the propensity of BAC-EDDS to form stable nanoaggregates with a diameter of approximately 150 nm at pH 5 and a net negative charge at physiological pH, in line with an isoelectric point <2. BAC-EDDS stably chelated Gd (III) ions with a molar ratio of 0.5:1 Gd (III)/repeat unit. The stability constant of the molecular model Gd-Agly-EDDS (log K = 17.43) was determined as well, by simulating the potentiometric titration through the use of Hyperquad software. In order to comprehend the efficiency of Gd-BAC-EDDS in contrasting magnetic resonance images, the nuclear longitudinal (r₁) and transverse (r₂) relaxivities as a function of the externally applied static magnetic field were investigated and compared to the ones of commercial contrast agents. Furthermore, a model derived from the Solomon–Bloembergen–Morgan theory for the field dependence of the NMR relaxivity curves was applied and allowed us to evaluate the rotational correlation time of the complex (τ = 0.66 ns). This relatively high value is due to the dimensions of Gd-BAC-EDDS, and the associated rotational motion causes a peak in the longitudinal relaxivity at ca. 75 MHz, which is close to the frequencies used in clinics. The good performances of Gd-BAC-EDDS as a contrast agent were also confirmed through in vitro magnetic resonance imaging experiments with a 0.2 T magnetic field.     

Finite Dimensional Global Attractor for 3D MHD-α Models: A Comparison

We consider two magnetohydrodynamic-α (MHDα) models with kinematic viscosity and magnetic diffusivity for an incompressible fluid in a three-dimensional periodic box (torus). More precisely, we consider the Navier–Stokes-α-MHD and the Modified Leray-α-MHD models. Similar models are useful to study the turbulent behavior of fluids in presence of a magnetic field because of the current impossibility to handle non-regularized systems neither analytically nor via numerical simulations. In both cases, the global existence of the solution and of a global attractor can be shown. We provide an upper bound for the Hausdorff and the fractal dimension of the attractor. This bound can be interpreted in terms of degrees of freedom of the long-time dynamics of the involved system and gives information about the numerical stability of the model. We get the same bound that holds for the Simplified Bardina-MHD model, considered in a previous paper (this result provides, in some sense, an intermediate bound between the number of degrees of freedom for the Simplified Bardina model and the Navier–Stokes-α equation in the nonmagnetic case). However, the Navier–Stokes-α-MHD system is preferable since, in the ideal case, it conserves more quadratic invariants derived from the standard MHD model.     

Visible‐Light‐Promoted Polycyclizations of Dienynes

A variety of linear dienynes can deliver complex tetracyclic frameworks in the presence of an Ir^III complex and visible light. Product formation involves the generation of four new C?C bonds and six contiguous stereocenters, which decorate two [3.1.0] bicyclic units tethered through their bridging quaternary carbon atoms. The internal alkyne acts as a formal dicarbenoid for the generation of two cyclopropanes in these radical cation cascades. This behavior has not been previously observed for organic reactive intermediates and can be extended to intermolecular reactions and diendiynes.     

Viscoelastic melt rheology and time–temperature superposition of polycarbonate–multi-walled carbon nanotube nanocomposites

This work investigates the linear and non-linear viscoelastic melt rheology of four grades of polycarbonate melt compounded with 3 wt% Nanocyl NC7000 multi-walled carbon nanotubes and of the matching matrix polymers. Amplitude sweeps reveal an earlier onset of non-linearity and a strain overshoot in the nanocomposites. Mastercurves are constructed from isothermal frequency sweeps using vertical and horizontal shifting. Although all nanocomposites exhibit a second plateau at ～10⁵ Pa, the relaxation times estimated from the peak in loss tangent are not statistically different from those of pure melts estimated from cross-over frequencies: all relaxation timescales scale with molar mass in the same way, evidence that the relaxation of the polymer network is the dominant mechanism in both filled and unfilled materials. Non-linear rheology is also measured in large amplitude oscillatory shear. A comparison of the responses from frequency and amplitude sweep experiments reveals the importance of strain and temperature history on the response of such nanocomposites.     

Effects of Traditional and Modern Post-Harvest Withering Processes on the Composition of the Vitis v. Corvina Grape and the Sensory Profile of Amarone Wines

In the Valpolicella area (Verona, Italy) Vitis vinifera cv. Corvina is the main grape variety used to produce Amarone wine. Before starting the winemaking process, the Corvina grapes are stored in a withering (i.e., dehydrating) warehouse until about 30% of the berry weight is lost (WL). This practice is performed to concentrate the metabolites in the berry and enrich the Amarone wine in aroma and antioxidant compounds. In compliance with the guidelines and strict Amarone protocol set by the Consorzio of Amarone Valpolicella, withering must be carried out by setting the grapes in a suitable environment, either under controlled relative air humidity (RH) conditions and wind speed (WS)—no temperature modification is to be applied—or, following the traditional methods, in non-controlled environmental conditions. In general, the two processes have different dehydration kinetics due to the different conditions in terms of temperature, RH, and WS, which affect the accumulation of sugars and organic acids and the biosynthesis of secondary metabolites such as stilbenes and glycoside aroma precursors. For this study, the two grape-withering processes were carried out under controlled (C) and non-controlled (NC) conditions, and the final compositions of the Corvina dried grapes were compared also to evaluate the effects on the organoleptic characteristics of Amarone wine. The findings highlighted differences between the two processes mainly in terms of the secondary metabolites of the dried grapes, which affect the organoleptic characteristics of Amarone wine. Indeed, by the sensory evaluation, wines produced by adopting the NC process were found more harmonious, elegant, and balanced. Finally, we can state how using a traditional system, grapes were characterised by higher levels of VOCs (volatile compounds), whilst wines had a higher and appreciable complexity and finesse.