Determination of amitraz and its transformation products in pears by ethyl acetate extraction and liquid chromatography–tandem mass spectrometry

A method has been developed for identification and quantification of the acaricide amitraz and its transformation products, 2,4-dimethylaniline (DMA), 2,4-dimethylformamidine (DMF) and N-2,4-dimethylphenyl-N-methylformamidine (DMPF) in pears. The analytes were extracted using ethyl acetate and anhydrous sodium sulphate. Analysis was performed by liquid chromatography–electrospray tandem mass spectrometry (LC–ESI-MS/MS) in the positive ion mode using a triple quadrupole (QqQ) instrument. Two precursor-product ion transitions were monitored for each compound in the selected reaction monitoring (SRM) mode. The method was validated with pears taken from the orchard before the amitraz treatment and spiked at the limit of quantification (LOQ), 10 times the LOQ and the maximum residue limit (MRL). Recoveries were between 70 and 106% and relative standard deviations were below 19% (n = 5 at each spiked level). Excellent sensitivity resulted in limits of detection (LODs) for all the compounds below 10 μg kg⁻¹. Quantification was carried out using matrix-matched standards calibration, response was a linear function of the concentration from the LOQs to, at least, three orders of magnitude. Recoveries and standard deviations were comparable to those obtained after hydrolysis of amitraz and its metabolites to DMA. Occurrence of amitraz and its metabolites in field-treated pears showed that, seven days after the treatment, DMPF and DMF are the main degradation products. This work reports for the first time the use of a conventional pesticide multiresidue method and LC–ESI-MS/MS for determining amitraz and its metabolites in pears.     

New long alkyl side-chain benzo[a]phenoxazines as micellisation probes

Several novel fluorescent benzo[a]phenoxazinium chlorides possessing a long aliphatic chain substituent at the 5-amino function of the heterocycle were efficiently synthesised. All compounds obtained absorbed and emitted at longer wavelengths with moderate to good fluorescent quantum yields. The photophysics of N-[10-methyl-5-(octylamino)-9H-benzo[a]phenoxazin-9-ylidene]ethanaminium chloride and N-[10-methyl-5-(dodecylamino)-9H-benzo[a]phenoxazin-9-ylidene]ethanaminium chloride was studied in Triton^® X-100 and in cetyltrimethylammonium bromide micellar media, demonstrating the capability of these fluorophores in detecting the micellisation process.     

Microimaging FT-IR spectroscopy on pathological breast tissues

Microimaging Fourier transform infrared spectroscopy is able to monitor differentiation between normal and malignant tissues. All the specimens, previously submitted to histological analysis, displayed abnormal spectra compared with the corresponding normal tissues with changes in many diagnostic bands like those arising from phosphate, C–O and CH stretching vibrational modes. The comparison between cancer (K) and connective (C) spectra evidenced the following differences: in the vCH region 3000–2800 cm⁻¹ no hypomethylation effect was evident in K; the convolution of the bands of connective indicated an expected higher membrane fluidity; in the neoplastic zone, Amide I and II modes showed convoluted bands with maxima at 1651 and 1547 cm⁻¹, respectively, indicating an α-helix conformation of proteins due to changes in the secondary structure proteins upon carcinogenesis. Other signature bands, such as the deformation O–P–O phosphate band at 965 cm⁻¹, suggested DNA conformational changes in solid cancer, infiltrating cancer and neoplasia in the region 1350–800 cm⁻¹. These characteristic bands have been monitored as a function of the degree of cancer progression. Chemometric methods, such as principal component analysis (PCA) and hierarchical clustering analysis (HCA) have been used in order to distinguish spectra of neoplastic and normal zones.     

Investigating the impact of an urban community school effort on middle school STEM-related student outcomes over time through propensity score matched methods

This study investigates the impact of an urban community school reform initiative that focuses on an immigrant and refugee population in middle school. A 6th–8th grade cohort of students in the community school are followed over time and compared to a propensity score matched group on overall GPA, mathematics, and science academic outcomes and traditional college preparedness indicators. Further, a deeper dive into the intersection of gender and race/ethnicity was examined on all outcomes. Findings revealed that students in the urban community school demonstrated significantly more preparedness to enroll in college and move into a STEM field if they desired compared to the matched students. All gender/racial groups in the community school performed significantly higher than those in the matched group. Further, all gender/racial groups of students in the urban community school defied standard academic achievement drops common over time in middle school, and instead increase overall, math, and science grades from 6th to 8th grade.     

Study of the interference effects in an optical cavity for organic light-emitting diode applications

The interference effects generated in a bottom-emitting electroluminescent device fabricated on a polymer underlayer introduced with the aim of improving the anode roughness have been studied. The analysis of the interference fringes at different detection angles and the spatial coherence demonstrates that this phenomenon is due to multiple internal reflections that propagate in the polymer layer. This effect can be eliminated by modifying the polymer thickness and the incidence angle of the electromagnetic radiation at the anode-polymer interface. Inkjet etching technology is adopted for microcavities-shaped polymer structuring to destroy the resonator effect of the optical cavity.     

Surface phenomena involved in the formation of Co nanoparticles on amorphous carbon and SiO2 deposited by magnetron sputtering

High-pressure DC magnetron sputtering was used for the deposition of cobalt on amorphous carbon (a-C) and SiO₂. Deposition conditions, substrate surface morphology and annealing parameters are investigated in order to promote the synthesis of large arrays of nanoparticles, with regular size and shape. Uniformly distributed Co nanoparticles a few nanometers in size were formed under annealing at 700°C in H₂. Particle nucleation and growth are discussed based on X-ray photoelectron spectroscopy, transmission and scanning electron microscopy and kinetic Monte Carlo modeling (KMC).     

Curve and surface construction using Hermite subdivision schemes

In this paper we present a very efficient Hermite subdivision scheme, based on rational functions, and outline its potential applications, with special emphasis on the construction of cubic-like B-splines — well suited for the design of constrained curves and surfaces.     

Properties and Characterization of Organoclay/Dimethacrylate Composites Obtained by In Situ Photopolymerization

Summary: Composites of dimethacrylates/organoclay were obtained by in situ photopolymerization of Bis-GMA (Bisphenol A glycidyl methacrylate) and TEGDMA (tetraethyleneglycol dimethacrylate) in the presence of camphorquinone and DEEMA (2-(diethylamino)ethyl methacrylate). The composites contained up to 10% wt/wt of organoclays. Monomer conversion and polymerization kinetics were determined by real time Fourier-Transform Infrared Spectroscopy – Attenuated Total Reflectance (FTIR-ATR), and showed an increase of conversion with addition of the clay. The storage modulus E' of the composites also had a marked dependence on the composite composition and increased with addition of clay at all temperatures. T_g also increases with clay content. X-Ray Diffraction (XRD) analysis shows that the clay is completely exfoliated for the composites with a lower proportion of clay, whereas for larger clay/polymer proportions peaks corresponding to the interlamellar distance of the clay are still observed. This is probably due to the fact that the amount of monomers in the initial formulation was not sufficient to delaminate the clay. Scanning Electron Microscopy (SEM) images indicate a quite homogenous copolymer, with some clay aggregates that increase in size and number for the higher filler loadings in agreement with the XRD results.     

Ultrasound-assisted extraction coupled with under vacuum distillation of flavour compounds from spearmint (carvone-rich) plants: Comparison with conventional hydrodistillation

Ultrasonically assisted extraction of flavour compounds from different varieties of Mentha spicata, using 70% ethanol, have been carried out for 5, 10 and 15 min and coupled with under vacuum distillation. The ultrasound distilled extracts have been analysed by GC–MS and compared with essential oils obtained by hydrodistillation. The results have showed that ultrasonically assisted extraction in combination with under vacuum distillation have provided extracts with higher flavouring strength due to the increased concentration of desirable oxygenated compounds (from 5 to 8 times) compared with hydrodistillation. Extraction yields of flavour volatiles have been calculated giving a range 0.04–0.13% by ultrasound and 0.01–0.02% by hydrodistillation.