A sol‐gel based solid phase microextraction fiber for the analysis of aliphatic alcohols in apple juices

A new fiber based on titania‐chitin sol‐gel coated on a silver wire for the headspace solid phase microextraction of aliphatic alcohols from apple juice samples was developed. The influences of fiber coating composition and microextraction conditions (extraction temperature, extraction time, and ionic strength of the sample matrix) on the fiber performance were investigated. Also, the influence of temperature and time on desorption of analytes from fiber were studied. Under the optimized conditions, a porous fiber with a high extraction capacity and good thermal stability (up to 250°C) was obtained. The proposed headspace solid‐phase microextraction‐GC method was successfully used for the analysis of aliphatic alcohols in apple juice and concentrate samples. The recovery values were from 92.8 to 98.6%. The RSD (n=5) for all analytes were below 7.8%.     

Synthesis and molecular modelling of double-functionalised nucleosides with aromatic moieties in the 5'-(S)-position and minor groove interactions in DNA zipper structures

A series of six double-functionalised nucleosides, in which aromatic moieties were inserted into the 5'-(S)-C-position, were synthesised and incorporated into DNA duplexes. The aromatic moieties were thymine-1-yl, phenyl, 1,2,3-triazol-1-yl, 1,2,3-triazol-4-yl, 4-(uracil-5-yl)-1,2,3-triazol-1-yl and 4-phenyl-1,2,3-triazol-1-yl. The DNA duplexes were studied with UV melting curves, CD spectroscopy and molecular modelling. The results showed that the aromatic moieties in some cases interact in the minor groove forming DNA zipper structures. The strongest specific interaction was found between two thymines or between a thymine and a phenyl group in a crossed (-3)-zipper motif (i.e., with two base pairs interspacing the modifications). Modelling revealed that the interaction is aromatic stacking across the minor groove. Also, the extended uracil-triazole moiety demonstrated zipper contacts in the minor groove as well as binding to the floor of the groove.     

Pseudo almost automorphic solutions for some partial functional differential equations with infinite delay

In this work, we study the existence of pseudo almost automorphic solution for some partial functional differential equations with infinite delay. We assume that the undelayed part is not necessarily densely defined and satisfies the Hille–Yosida condition. We use the variation of constant formula developed recently in 1 Hino, Y, Murakami, S and Naito, T. 1991. “Functional Differential Equations with Infinite Delay”. In Lecture Notes in Mathematics, Vol. 1473, New York: Springer-Verlag.  [Google Scholar] to get the existence and uniqueness of pseudo almost automorphic solution when the linear equation has an exponential dichotomy. We also give an application of the abstract results to a Lotka–Volterra model with diffusion.     

Dynamics and stability of a hybrid serial-parallel mobile robot

Kinematics, dynamics, and stability analysis of a hybrid serial-parallel wheeled mobile robot is detailed in this paper. Privileging the advantages of both serial and parallel robots, the suggested structure will provide higher stability for heavy object manipulation by a mobile robotic system. The proposed system is made of a differentially-driven wheeled platform, a planar parallel manipulator, which is called here as star-triangle (ST) mechanism, and a serial Puma-type manipulator arm. In order to develop a comprehensive kinematics model of the robot; first it is divided into three modules, i.e. a mobile platform, a parallel ST mechanism, and a serial robot. Next, a closed-form dynamics model is derived for the whole hybrid system based on a combined Newton–Euler and Lagrange formulation. Then, a careful validation procedure is presented to verify the obtained dynamics model. Finally, using the new postural stability metric named as moment-height stability (MHS), the important role of the parallel ST mechanism for stabilizing the mobile robotic system is demonstrated. The obtained results show that the proposed hybrid serial–parallel arrangement effectively enhances the tip-over stability of the overall mobile robotic system. Hence, it can be successfully exploited to prevent tip-over instability particularly during heavy object manipulation tasks.     

New Mn12 single-molecule magnets from edge-sharing bioctahedra

Dodecanuclear Mn clusters based on edge-sharing bioctahedra display the scan-rate- and temperature-dependent hysteresis loops that are indicative of single-molecule magnetism behaviour.     

An unexpected reaction of trimethylsilyl fluorosulfonyldifluoroacetate (TFDA) with imidazoles. Formation of N-difluoromethylthioureas

A new reaction of the efficient difluorocarbene-generating reagent trimethylsilyl fluorosulfonyldifluoroacetate (TFDA) is reported in which molecules containing an N-alkylimidazole or benzimidazole structure undergo an unexpected one-pot conversion to N-difluoromethylthioureas. [reaction: see text].     

Concentration and multiplicity of solutions for a fourth-order equation with critical nonlinearity

In this paper, we consider the problem (_Pε)$(P_{\epsilon })$ : Δ²u=u^n+4/n-4+εu,u>0${\mathrm{\Delta }}^{2}u=u^{n+4/n-4}+\epsilon u,u>0$ in Ω,u=Δu=0$\Omega ,u=\mathrm{\Delta }u=0$ on ∂Ω$\mathrm{\partial }\Omega$, where Ω$\Omega$ is a bounded and smooth domain in Rⁿ,n>8${\mathbb{R}}^n,n>8$ and ε>0$\epsilon >0$. We analyze the asymptotic behavior of solutions of (_Pε)$(P_{\epsilon })$ which are minimizing for the Sobolev inequality as ε→0$\epsilon \to 0$ and we prove existence of solutions to (_Pε)$(P_{\epsilon })$ which blow up and concentrate around a critical point of the Robin's function. Finally, we show that for ε$\epsilon$ small, (_Pε)$(P_{\epsilon })$ has at least as many solutions as the Ljusternik–Schnirelman category of Ω$\Omega$.     

Zeolite‐SiC in PVC Matrix as a New SPME Fiber for Gas Chromatographic Determination of BTEX in Water and Soil Samples

A new SPME fiber based on mixture of zeolite and silicon carbide in PVC matrix was made and its application for sampling of BTEX compounds from headspace of water and soil samples was studied. After optimization of conditions, the proposed fiber was used for determination of BTEX in real samples obtained from rivers and soils of gasoline reservoirs surroundings. The method has good linearity (0.991‐0.999) over wide concentration range. Detection limits of the method are in the range of 0.66–1.66 μg L^? and 0.01–0.12 μg kg^? for water and soil samples, respectively.