Classification of biodiesel using NIR spectrometry and multivariate techniques

This article describes the classification of biodiesel samples using NIR spectroscopy and chemometric techniques. A total of 108 spectra of biodiesel samples were taken (being three samples each of four types of oil, cottonseed, sunflower, soybean and canola), from nine manufacturers. The measurements for each of the three samples were in the spectral region between 12,500 and 4000 cm⁻¹. The data were preprocessed by selecting a spectral range of 5000-4500 cm⁻¹, and then a Savitzky-Golay second-order polynomial was used with 21 data points to obtain second derivative spectra. Characterization of the biodiesel was done using chemometric models based on hierarchical cluster analysis (HCA), principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) elaborated for each group of biodiesel samples (cotton, sunflower, soybean and canola). For the HCA and PCA, the formation of clusters for each group of biodiesel was observed, and SIMCA models were built using 18 spectral measurements for each type of biodiesel (training set), and nine spectral measurements to construct a classification set (except for the canola oil which used eight spectra). The SIMCA classifications obtained 100% accurate identifications. Using this strategy, it was feasible to classify biodiesel quickly and nondestructively without the need for various analytical determinations.     

Differential Pulse Voltammetric Determination of Paraquat Using a Bismuth‐Film Electrode

A bismuth‐film electrode (BiFE) ex situ electrochemically deposited onto a copper substrate has been presented for paraquat determination. The bismuth film was electrochemically deposited at an applied potential of ?0.18 V vs. Ag/AgCl (3.0 M KCl) for 200 s. The analytical curve was linear in the paraquat concentration range from 6.6×10^?7 M to 4.8×10^?5 M with a limit of detection of 9.3×10^?8 M. The method presented satisfactory results at a confidence level of 95% and the performance was evaluated in water samples.     

Toward the discovery of functional transthyretin amyloid inhibitors: application of virtual screening methods

Inhibition of amyloid fibril formation by stabilization of the native form of the protein transthyretin (TTR) is a viable approach for the treatment of familial amyloid polyneuropathy that has been gaining momentum in the field of amyloid research. The TTR stabilizer molecules discovered to date have shown efficacy at inhibiting fibrilization in vitro but display impairing issues of solubility, affinity for TTR in the blood plasma and/or adverse effects. In this study we present a benchmark of four protein- and ligand-based virtual screening (VS) methods for identifying novel TTR stabilizers: (i) two-dimensional (2D) similarity searches with chemical hashed, pharmacophore, and UNITY fingerprints, (ii) 3D searches based on shape, chemical, and electrostatic similarity, (iii) LigMatch, a new ligand-based method which uses multiple templates and combines 3D geometric hashing with a 2D preselection process, and (iv) molecular docking to consensus X-ray crystal structures of TTR. We illustrate the potential of the best-performing VS protocols to retrieve promising new leads by ranking a tailored library of 2.3 million commercially available compounds. Our predictions show that the top-scoring molecules possess distinctive features from the known TTR binders, holding better solubility, fraction of halogen atoms, and binding affinity profiles. To the best of our knowledge, this is the first attempt to rationalize the utilization of a large battery of in silico screening techniques toward the identification of a new generation of TTR amyloid inhibitors.     

Superluminal neutrinos from Lorentz-violating dimension-5 operators

We consider Lorentz- and CPT-violating dimension-5 operators to address the issue of superluminal neutrinos recently pointed out in OPERA experiments. We assume these operators in the photon and neutrino sectors to be coupled to Lorentz-violating backgrounds in a preferred frame defined by a time-like direction. We show that such operators can produce a curve with OPERA’s slope that fits OPERA, MINOS and supernova SN1987a data.     

Interior Proximal Algorithm for Quasiconvex Programming Problems and Variational Inequalities with Linear Constraints

In this paper, we propose two interior proximal algorithms inspired by the logarithmic-quadratic proximal method. The first method we propose is for general linearly constrained quasiconvex minimization problems. For this method, we prove global convergence when the regularization parameters go to zero. The latter assumption can be dropped when the function is assumed to be pseudoconvex. We also obtain convergence results for quasimonotone variational inequalities, which are more general than monotone ones.     

Antifungal activity, toxicity and chemical composition of the essential oil of Coriandrum sativum L. fruits

The aims of this study were to test the antifungal activity, toxicity and chemical composition of essential oil from C. sativum L. fruits. The essential oil, obtained by hydro-distillation, was analyzed by gas chromatography/mass spectroscopy. Linalool was the main constituent (58.22%). The oil was considered bioactive, showing an LC?? value of 23 μg/mL in the Artemia salina lethality test. The antifungal activity was evaluated against Microsporum canis and Candida spp. by the agar-well diffusion method and the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) were established by the broth microdilution method. The essential oil induced growth inhibition zones of 28 ± 5.42 and 9.25 ± 0.5 for M. canis and Candida spp. respectively. The MICs and MFCs for M. canis strains ranged from 78 to 620 and 150 to 1,250 μg/mL, and the MICs and MFCs for Candida spp strains ranged from 310 to 620 and 620 to 1,250 μg/mL, respectively. C. sativum essential oil is active in vitro against M. canis and Candida spp. demonstrating good antifungal activity.     

Evidence of the participation of electronic excited states in the mechanism of positronium formation in substitutional Tb(1-x)Eu(x)(dpm)3 solid solutions studied by optical and positron annihilation spectroscopies

Positronium formation in the bimary molecular solid solutions Tb(1-x)Eu(x) (dpm)(3) (dpm = dipivaloylmethanate) has been investigated. A strong linear correlation between the (5)D(4) Tb(iii) energy level excited state lifetime and the positronium formation probability has been observed. This correlation indicates that the ligand-to-metal charge transfer LMCT states act in both luminescence quenching and positronium formation inhibition, as previously proposed. A kinetic mechanism is proposed to explain this correlation and shows that excited electronic states have a very important role in the positronium formation mechanism.     

Self-assembly in a catanionic mixture with an aminoacid-derived surfactant: from mixed micelles to spontaneous vesicles

The aqueous self-assembly of a novel lysine-derived surfactant with a gemini-like architecture, designated here as 12-Lys-12, has been experimentally investigated for the amphiphile alone in water and in a mixture with dodecyltrimethylammonium bromide (DTAB). The neat surfactant forms interesting micrometer-sized rigid tubules in the dilute region, resulting in very viscous solutions. For the catanionic mixture with DTAB, various single and multiphase regions were identified (up to a total surfactant concentration of 1.5 wt %) by means of combined polarizing light microscopy, cryo-TEM, and NMR. In the DTAB-rich side, for a mixing molar ratio in the range 2 < DTAB/12-Lys-12 < 4, a region of stable, unilamellar vesicles can be found. Furthermore, it was found that upon addition of 12-Lys-12 to pure DTAB solutions, the mixed micelles grow and beyond a given mixing ratio, vesicles assemble and coexist with small micelles. The transition is not continuous, since there is a narrow mixing range where phase separation occurs. Self-diffusion measurements and cryo-TEM imaging show that the average vesicle radius is on the order of 30-40 nm.     

Aplysiadiol from Aplysia dactylomela suggested a key intermediate for a unified biogenesis of regular and irregular marine algal bisabolene-type metabolites

The rearranged compound 1, the regular 2 and 3 and the degraded 4 are novel bisabolene-type metabolites that along with the known compounds caespitol, 8-acetylcaespitol, caespitane, caespitenone, laucapyranoid A, and furocaespitane have been isolated from the sea hare Aplysia dactylomela. The structures of these compounds were determined on the basis of spectroscopic evidence. The irregular network of 1 suggested that the halogenated epoxide 6 is a key intermediate for a unified biogenetic pathway of naturally occurring marine algal bisabolene-type metabolites.     

Fluctuation-induced casimir forces in granular fluids

We numerically investigate the behavior of driven noncohesive granular media and find that two fixed large intruder particles, immersed in a sea of small particles, experience, in addition to a short-range depletion force, a long-range repulsive force. The observed long-range interaction is fluctuation-induced and we propose a mechanism similar to the Casimir effect that generates it: The hydrodynamic fluctuations are geometrically confined between the intruders, producing an unbalanced renormalized pressure. An estimation based on computing the possible Fourier modes explains the repulsive force and is in qualitative agreement with the simulations.