Novel approach for the simultaneous detection of DNA from different fish species based on a nuclear target: quantification potential

The development of DNA-based methods for the identification and quantification of fish in food and feed samples is frequently focused on a specific fish species and/or on the detection of mitochondrial DNA of fish origin. However, a quantitative method for the most common fish species used by the food and feed industry is needed for official control purposes, and such a method should rely on the use of a single-copy nuclear DNA target owing to its more stable copy number in different tissues. In this article, we report on the development of a real-time PCR method based on the use of a nuclear gene as a target for the simultaneous detection of fish DNA from different species and on the evaluation of its quantification potential. The method was tested in 22 different fish species, including those most commonly used by the food and feed industry, and in negative control samples, which included 15 animal species and nine feed ingredients. The results show that the method reported here complies with the requirements concerning specificity and with the criteria required for real-time PCR methods with high sensitivity.     

Thermal diesel-like analysis

Biofuel has been obtained by cracking of soybean (Glycine sp.) oil, which is characterized by acidity index, density, cetane index, copper corrosion, carbon residue, fulgor point, and heat of combustion. In order to evaluate the quality of biofuel as well as detect its adulteration with vegetable oil, partial least squares regression calibration models based on thermogravimetric (TG) analysis were used as a precise and an accurate method. Thirty mixtures of biofuel/diesel/vegetable oil standards were prepared. Twenty of them were used for calibration, and ten for validation. The results have shown that the thermogravimetric analysis, PLS/TG, presented the best performance for the detection of vegetable oil contamination with a root mean square error of prediction (RMSEC% w/w) of 0.23, with a relative error of prediction of 3.6%, corroborating with the success of TG analysis application to determine the quality of biofuels and diesel/biofuel blends, showing that the TG analysis is an excellent tool to control quality of biofuels.     

Stereoselective Synthesis of β-Hydroxy- and β-Ethoxy-δ-lactones: Model Structures for Compounds Isolated from Otoba parvifolia

Abstract: In this paper we describe a very short stereoselective synthesis of the β-ethoxylactone 13, a model structure for compounds isolated from Otoba parvifolia. The method, which also produces β-hydroxy-esters and β-hydroxy-lactones, is based on a chemo- and stereoselective Reformatsky reaction.     

Mechanical Properties and Failure Behavior of Physically Assembled Triblock Copolymer Gels with Varying Midblock Length

Mechanical properties including the failure behavior of physically assembled gels or physical gels are governed by their network structure. To investigate such behavior, we consider a physical gel system consisting of poly(styrene)‐poly(isoprene)‐poly(styrene)[PS‐PI‐PS] in mineral oil. In these gels, the endblock (PS) molecular weights are not significantly different, whereas, the midblock (PI) molecular weight has been varied such that we can access gels with and without midblock entanglement. Small angle X‐ray scattering data reveals that the gels are composed of collapsed PS aggregates connected by PI chains. The gelation temperature has been found to be a function of the endblock concentration. Tensile tests display stretch‐rate dependent modulus at high strain for the gels with midblock entanglement. Creep failure behavior has also been found to be influenced by the entanglement. Fracture experiments with predefined cracks show that the energy release rate scales linearly with the crack‐tip velocity for all gels considered here. In addition, increase of midblock chain length resulted in higher viscous dissipation leading to a higher energy release rate. The results provide an insight into how midblock entanglement can possibly affect the mechanical properties of physically assembled triblock copolymer gels in a midblock selective solvent. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1014–1026     

Magnetic Anisotropy of Cyanide‐Bridged Core and Core–Shell Coordination Nanoparticles Probed by X‐ray Magnetic Circular Dichroism

The local symmetry and local magnetic properties of 6 nm‐sized, bimetallic, cyanide‐bridged CsNiCr(CN)₆ coordination nanoparticles 1 and 8 nm‐sized, trimetallic, CsNiCr(CN)₆@CsCoCr(CN)₆ core–shell nanoparticles 2 were studied by X‐ray absorption spectroscopy (XAS) and X‐ray magnetic circular dichroism (XMCD). The measurements were performed at the Ni^II, Co^II, and Cr^III L_2,3 edges. This study revealed the presence of distorted Ni^II sites located on the particle surface of 1 that account for the uniaxial magnetic anisotropy observed by SQUID measurements. For the core–shell particles, a combination of the exchange anisotropy between the core and the shell and the pronounced anisotropy of the Co^II ions is the origin of the large increase in coercive field from 120 to 890 Oe on going from 1 to 2 . In addition, XMCD allows the relative orientation of the magnetic moments throughout the core–shell particles to be determined. While for the bimetallic particles of 1 , alignment of the magnetic moments of Cr^III ions with those of Ni^II ions leads to uniform magnetization, in the core–shell particles 2 the magnetic moments of the isotropic Cr^III follow those of Co^II ions in the shell and those of Ni^II ions in the core, and this leads to nonuniform magnetization in the whole nanoobject, mainly due to the large difference in local anisotropy between the Co^II ions belonging to the surface and the Ni^II ions in the core.     

Aqueous micro and nanoreactors based on alternating copolymers of phenylmaleimide and vinylpyrrolidone bearing pendant l‐proline stabilized with PEG grafted chains

Proline may work efficiently in water as catalyst of aldol reactions if it is hydrophobically activated. In this work, we have maximized this hydrophobic activation by the preparation of linear alternating copolymers of hydrophobic phenylmaleimide and a vinylpyrrolidone derivative bearing proline. These copolymers were water soluble above pH 5.0 and, unlike the free proline, exhibited efficient catalysis at pH 7.0. Moreover, they catalyzed and presented enantioselectivity in an aggregated form at pH 4.0 (close to the isoelectric point, IEP, of the polymer). This enantioselectivity has been related to the exclusion of water at this IEP. To control the size and stabilize the aggregates, PEG grafted copolymers were prepared by the incorporation of a PEG‐macromer (2–10 mol%), which rendered stable nano‐aggregates in water at the IEP. At this pH they catalyzed the aldol reaction in a higher rate than the non‐grafted polymer, but the enantioselectivity was decreased. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1228–1236     

Direct amplification of ultrashort pulses in μ-pulling-down Yb:YAG single crystal fibers

We demonstrated that Yb:YAG single crystal fibers have a strong potential for the amplification of femtosecond pulses. Seeded by 230?fs pulses with an average power of 400?mW at 30?MHz delivered by a passively mode-locked Yb:KYW oscillator, the system produced 330?fs pulses with an average power of 12?W. This is the shortest pulse duration ever produced by an Yb:YAG amplifier. The gain in the single crystal fiber reached a value as high as 30 in a simple double-pass configuration.     

Hall-effect measurements probing the degree of charge-carrier delocalization in solution-processed crystalline molecular semiconductors

Intramolecular structure and intermolecular packing in crystalline molecular semiconductors should have profound effects on the charge-carrier wave function, but simple drift mobility measurements are not very sensitive to this. Here we show that differences in the Hall resistance of two soluble pentacene derivatives can be explained with different degrees of carrier delocalization being limited by thermal lattice fluctuations. A combination of Hall measurements, optical spectroscopy, and theoretical simulations provides a powerful probe of structure-property relationships at a molecular level.     

Multi-hump bright solitons in a Schrödinger–mKdV system

We consider the problem of energy transport in a Davydov model along an anharmonic crystal medium obeying quartic longitudinal interactions corresponding to rigid interacting particles. The Zabusky and Kruskal unidirectional continuum limit of the original discrete equations reduces, in the long wave approximation, to a coupled system between the linear Schrödinger (LS) equation and the modified Korteweg–de Vries (mKdV) equation. Single- and two-hump bright soliton solutions for this LS–mKdV system are predicted to exist by variational means and numerically confirmed. The one-hump bright solitons are found to be the anharmonic supersonic analogue of the Davydov's solitons while the two-hump (in both components) bright solitons are found to be a novel type of soliton consisting of a two-soliton solution of mKdV trapped by the wave function associated to the LS equation. This two-hump soliton solution, as a two component solution, represents a new class of polaron solution to be contrasted with the two-soliton interaction phenomena from soliton theory, as revealed by a variational approach and direct numerical results for the two-soliton solution.