A general backwards calculus of variations via duality

We prove Euler–Lagrange and natural boundary necessary optimality conditions for problems of the calculus of variations which are given by a composition of nabla integrals on an arbitrary time scale. As an application, we get optimality conditions for the product and the quotient of nabla variational functionals.     

Off-axis metallic diffractive lens for terahertz beams

A diffractive optical element for off-axis focusing of terahertz radiation is presented. It was designed in a nonparaxial regime and manufactured in a metal slab by laser cutting of curved stripes. The optical function of the structure includes focusing and deflecting the illuminating beam of a chosen frequency in a particular place. Therefore, the element acts as both a spatial and a spectral filter; hence it is especially suitable for separating the terahertz signal from a broadband thermal load in passive detection devices. The experimental evaluation of the proposed diffractive lens by means of time-domain spectroscopy is presented and discussed.     

Characterization of nanomaterials in food by electron microscopy

Engineered nanomaterials (ENMs) are increasingly being used in the food industry. In order to assess the efficacy and the risks of these materials, it is essential to have access to methods that not only detect the nanomaterials, but also provide information on the characteristics of the materials (e.g., size and shape).This review presents an overview of electron microscopy (EM)-based methods that have been, or have the potential to be, applied to imaging ENMs in foodstuffs. We provide an overview of approaches to sample preparation, including drying, chemical treatment, fixation and cryogenic methods. We then describe standard and non-standard EM-based approaches that are available for imaging prepared samples. Finally, we present a strategy for selecting the most appropriate method for a particular foodstuff.     

New phosphorus-containing spherical carbon adsorbents as promising materials in drug adsorption and release

A simple method of preparation of new high surface area spherical carbon adsorbents is presented. The phosphoric acid activation upon hydrothermally formed spherules was employed to produce carbons having controlled high specific surface area (over 2100m(2)/g), large volumes of pores (1.2cm(3)/g), and high acidity. Prepared from sucrose materials show high adsorption capacities (i.e. 220mg/g(C)) toward paracetamol. It is proved that for these materials the contents of surface phosphorus are responsible for the reversibility of drug adsorption/release process.     

Fluid streaming above interdigitated electrodes in dielectrophoresis experiments

For the investigation of alternating current electrokinetic effects, a system is presented that allows for the simultaneous observation of fluid flow above and around microelectrodes in all three directions in space. Beside the usual microscopical view from top, lateral observation through the same objective is made possible by two small mirrors that are placed next to the electrodes. Fluid flow and movement of fluorescent nanoparticles above interdigitated electrodes are monitored by fluorescence microscopy and digital imaging and are further analysed by image processing. Field frequencies are varied from 10 Hz to 1 GHz at up to 10V(rms) . Electrical conductivity of the fluid is monitored in situ in the actual measuring chamber.     

Synthesis, crystal structure, spectroscopic, magnetic, theoretical, and microbiological studies of a nickel(II) complex of L-tyrosine and imidazole, [Ni(Im)2(L-tyr)2]·4H2O

The [Ni(Im)(2)(L-tyr)(2)]·4H(2)O (1) complex was obtained in crystalline form as a product of interaction of L-tyrosine sodium salt, imidazole, and NiSO(4). The X-ray structure was determined, and the spectral (IR, FIR, NIR-vis-UV, HF EPR) and magnetic properties were studied. The Ni(2+) ion is hexacoordinated by the N and O atoms from two L-tyrosine molecules and by two N atoms of imidazole, resulting in a slightly distorted octahedral [NiN(2)N(2)'O(2)] geometry with a tetragonality parameter T = 0.995. The bands observed in the electronic spectra were ascribed to the six spin-allowed electronic transitions (3)B(1g) → (3)E(g) and (3)B(2g), (3)B(1g) → (3)A(2g) and (3)E(g), and (3)B(1g) → (3)A(2g) and (3)E(g). The spin Hamiltonian parameters g, D, and E, which were determined from high-field HF EPR spectra, excellently reproduced the magnetic properties of the complex. Calculation of the zero-field splitting in the S = 1 state of nickel(II) using DFT and UHF was attempted. The biological activity of the complexes has been tested for antifungal and antibacterial effects against Aspergillus flavus, Fusarium solani, Penicillium verrucosu, Bacillus subtilis, Serratia marcescens, Pseudomonas fluorescens, and Escherichia coli.     

Optimization of Co2+ ions removal from water solutions via polymer enhanced ultrafiltration with application of PVA and sulfonated PVA as complexing agents

The paper presents the results of the studies of UF-complexation process applied for the removal of Co(2+) ions from water solutions. As binding agents for cobalt ions, the PVA polymer (M(w)=10,000) and its sulfonated form, synthesized in the laboratory, have been used. The method of experimental design and response surface methodology have been employed to find out the optimal conditions for the complexation process and to evaluate the interaction between the input variables, i.e., initial cobalt concentration, pH and amount of the polymer used, expressed as a polymer/Co(2+) ratio r. The data collected by the designed experiments showed that sulfonation of polymer has improved significantly the binding ability of PVA. The optimal conditions of cobalt ions complexation established by response surface model for non-sulfonated PVA polymer have been found to be as follows: the initial concentration of Co(2+)=5.70 mg L(-1), the ratio between polymer and metal ions, r=8.58 and pH=5.93. The removal efficiency of Co(2+) in these conditions was 31.81%. For sulfonated PVA polymer, the optimal conditions determined are as follows: initial concentration of [Co(2+)](0)=10 mg L(-1), r=1.2 and pH=6.5. For these conditions, a removal efficiency of 99.98% has been determined. The experiments showed that Co(2+) removal ability of sulfonated PVA was much higher than its non-sulfonated precursor. Although the polymer concentrations used in the tests with sulfonated PVA were approximately ten times lower than the non-sulfonated one, the removal efficiency of cobalt ions was significantly higher.     

Ionic liquids as silica deactivating agents in gas chromatography for direct analysis of primary amines in water

Analysis of primary amines in aqueous samples remains a challenging analytical issue. The preferred approach by gas chromatography is hampered by interactions of free silanol groups with the highly reactive amine groups, resulting in inconsistent measurements. Here, we report a method for direct analysis of aliphatic amines and diamines in aqueous samples by gas chromatography (GC) with silanol deactivation using ionic liquids (ILs). ILs including trihexyl(tetradecyl)phosphonium bis 2,4,4-(trimethylpentyl)phosphinate (Cyphos IL-104), 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide [pmim][Tf(2)N] and N″-ethyl-N,N,N',N'-tetramethylguanidinium tris(pentafluoroethyl)trifluorophosphate [etmg][FAP] were tested as deactivating media for the GC liner. Solutions of these ILs in methanol were injected in the system prior to the analysis of primary amines. Butane-1,4-diamine (putrescine, BDA) was used as a reference amine. The best results were obtained using the imidazolium IL [pmim][Tf(2)N]. With this deactivator, excellent reproducibility of the analysis was achieved, and the detection limit of BDA was as low as 1mM. The applicability of the method was proven for the analysis of two different primary amines (C4-C5) and pentane-1,5-diamine.     

Rapid identification of novel antigens of Salmonella Enteritidis by microarray-based immunoscreening

We report on an approach to rapidly screen thousands of Salmonella Enteritidis proteins with the goal of identifying novel immunodominant proteins. We used a microarray-based system that warrants high throughput and easy handling. Seven immunogenic candidates were selected after screening. Comparative analyses by ELISA and microarrays manifested their immunodominant character. The large repetitive protein (SEN4030) that plays a role as a putative adhesin in initial cell surface interaction and is highly specific to Salmonella is considered to be the most suitable protein for a diagnostic approach. The results further demonstrate that the strategy applied herein is convenient for specifically identifying immunogenic proteins of pathogenic microorganisms. Consequently, it enables a sound assessment of promising candidates for diagnostic applications and vaccine development. Moreover, the elucidation of immunogenic proteins may assist in unveiling unknown virulence-associated factors, thus furthering the understanding of the underlying pathogenicity of Salmonella in general, and of S. Enteritidis, one of the most frequently detected serovars of this pathogen, in particular. Figure

The microarray-based approach was aimed at identifying novel immunodominant proteins of S. Enteritidis. Seven antigens were revealed by screening a cDNA expression library. SEN4030, a large repetitive protein specific for salmonella, is considered an optimal candidate for future applications.     

New olefin metathesis catalysts bearing polyether clamp in N-heterocyclic carbenes ligands

Synthesis of new type of the Hoveyda–Grubbs catalysts containing modified N-heterocyclic carbene ligands is described herein. New catalysts bear different in size polyether clamp embracing N,N′-2,4-dimethylphenyl substituents in N-heterocyclic carbene. New complexes were tested in model RCM, enyne and CM reactions. They showed comparable activity to that of commercially available Grubbs second generation and Hoveyda–Grubbs second generation complexes. Complex with larger polyether clamp proved Z-stereoselective in a macrocycle formation and yielded more Z isomers than commercial complexes in CM reactions. The catalysts are stable and easy to purify.