Separation of betacyanins from flowers of Amaranthus cruentus L. in a polar solvent system by high‐speed counter‐current chromatography

Betacyanin extract of Amaranthus cruentus L. flowers was fractionated by semi‐preparative high‐speed counter‐current chromatography in a highly polar solvent system: propan‐1‐ol/acetonitrile/(NH₄)₂SO_{4satd. soln}/H₂O (1.0:0.5:1.2:1.0, v/v/v/v) in tail‐to‐head mode with 76% retention of the stationary phase. The crude extract as well as the fractions containing betacyanins were analyzed by liquid chromatography with tandem mass spectrometry as well as by high‐resolution ion‐trap time‐of‐flight mass spectrometry detection technique for the molecular formulae and multi‐step fragmentation pattern elucidation. Four betacyanins; namely, amaranthin, betanin, 6′‐O‐formyl‐amaranthin, and 6′‐O‐malonyl‐amaranthin as well as their diastereomeric forms differing in the configuration of the C‐15 carbon atom were identified in the fractions. Amaranthin was the dominant pigment in the extract and was additionally analyzed by nuclear magnetic resonance correlation techniques after the counter‐current chromatographic and high‐performance liquid chromatographic isolation. Betacyanins were highly enriched during a single high‐speed counter‐current chromatographic step; therefore, the tentative identification of new compounds for the whole Amaranthaceae family, 6′‐O‐formyl‐amaranthin and 6′‐O‐malonyl‐amaranthin was possible. Different elution profiles of the pigments observed in the counter‐current chromatographic system in comparison to high‐performance liquid chromatography system confirm a complementarity of both the techniques especially in the separation of diastereomeric pairs of betacyanins.     

Boron Phosphorus Nitride at Extremes: PN6 Octahedra in the High‐Pressure Polymorph β‐BP3N6

The high‐pressure behavior of non‐metal nitrides is of special interest for inorganic and theoretical chemistry as well as materials science, as these compounds feature intriguing elastic properties. The double nitride α‐BP₃N₆ was investigated by in situ single‐crystal X‐ray diffraction (XRD) upon cold compression to a maximum pressure of about 42 GPa, and its isothermal bulk modulus at ambient conditions was determined to be 146(6) GPa. At maximum pressure the sample was laser‐heated, which resulted in the formation of an unprecedented high‐pressure polymorph, β‐BP₃N₆. Its structure was elucidated by single‐crystal XRD, and can be described as a decoration of a distorted hexagonal close packing of N with B in tetrahedral and P in octahedral voids. Hence, β‐BP₃N₆ is the first nitride to contain PN₆ octahedra, representing the much sought‐after proof of principle for sixfold N‐coordinated P that has been predicted for numerous high‐pressure phases of nitrides.     

Centers and Uniform Isochronous Centers of Planar Polynomial Differential Systems

For planar polynomial vector fields of the form

$$\begin{aligned} (-y+X(x,y))\dfrac{\partial }{\partial x}+(x+Y(x,y))\dfrac{\partial }{\partial y}, \end{aligned}$$

where X and Y start at least with terms of second order in the variables x and y, we determine necessary and sufficient conditions under which the origin is a center or a uniform isochronous centers.

     

Liposomal Form of Tetra(Aryl)Tetracyanoporphyrazine: Physical Properties and Photodynamic Activity In Vitro

Tetra(aryl)tetracyanoporphyrazines are the promising group of dyes for photodynamic therapy of tumors with unique combination of photosensitizer properties and sensitivity of fluorescence parameters to the environment viscosity. However, in vivo application of such hydrophobic photosensitizers requires using of drug carriers ensuring efficient delivery to the tumor site. The present study is focused on obtaining liposomes loaded with tetrakis(4-benzyloxyphenyl)tetracyanoporphyrazine and examining their properties depending on lipid composition. An efficient loading of the dye and a high long-term stability were proved for the liposomes composed of phosphatidylcholine with cholesterol and phosphatidylglycerol. This can be explained by the presence of negatively charged lipids in the bilayer and, as a consequence, a high value of the surface potential. A high rate of cellular uptake and a strong photoinduced toxicity give the prerequisites for the further use of the liposomal form of the photosensitizer for photodynamic therapy of tumors.     

Collective magnetic response of inhomogeneous nanoisland FeNi films around the percolation transition

By using superconducting quantum interference device (SQUID) magnetometry, we investigated anisotropic high-field (H ? 7T) low-temperature (10 K) magnetization response of inhomogeneous nanoisland FeNi films grown by rf sputtering deposition on Sitall (TiO₂) glass substrates. In the grown FeNi films, the FeNi layer nominal thickness varied from 0.6 to 2.5 nm, across the percolation transition at the d _c ? 1.8 nm. We discovered that, beyond conventional spin-magnetism of Fe₂₁Ni₇₉ permalloy, the extracted out-of-plane magnetization response of the nanoisland FeNi films is not saturated in the range of investigated magnetic fields and exhibits paramagnetic-like behavior. We found that the anomalous out-of-plane magnetization response exhibits an escalating slope with increase in the nominal film thickness from 0.6 to 1.1 nm, however, it decreases with further increase in the film thickness, and then practically vanishes on approaching the FeNi film percolation threshold. At the same time, the in-plane response demonstrates saturation behavior above 1.5–2T, competing with anomalously large diamagnetic-like response, which becomes pronounced at high magnetic fields. It is possible that the supported-metal interaction leads to the creation of a thin charge-transfer (CT) layer and a Schottky barrier at the FeNi film/Sitall (TiO₂) interface. Then, in the system with nanoscale circular domains, the observed anomalous paramagnetic-like magnetization response can be associated with a large orbital moment of the localized electrons. In addition, the inhomogeneous nanoisland FeNi films can possess spontaneous ordering of toroidal moments, which can be either of orbital or spin origin. The system with toroidal inhomogeneity can lead to anomalously strong diamagnetic-like response. The observed magnetization response is determined by the interplay between the paramagnetic- and diamagnetic-like contributions.     

Crack reconstruction using a level-set strategy

We present a level-set based technique to recover key characteristics of a defect or crack (e.g. location, length and shape) in a two-dimensional material from boundary electrical measurements. The key feature of this work is to extend the usual level-set technique for modeling volumetric objects to very thin objects. Two level-set functions are employed: the first one models the location and form of the crack, and the second one models its length and connectivity. An efficient gradient based method is derived in order to define evolution laws for these two level-set functions which minimize the least squares data misfit. Numerical experiments show the utility of this method even in the presence of a significant noise level in the measurements. A finite element method is used to simulate the electric field behavior in the presence of very thin objects.     

Chern–Simons–Rozansky–Witten topological field theory

We construct and study a new topological field theory in three dimensions. It is a hybrid between Chern–Simons and Rozansky–Witten theory and can be regarded as a topologically-twisted version of the N=4$N=4$d=3$d=3$ supersymmetric gauge theory recently discovered by Gaiotto and Witten. The model depends on a gauge group G and a hyper-Kähler manifold X with a tri-holomorphic action of G. In the case when X is an affine space, we show that the model is equivalent to Chern–Simons theory whose gauge group is a supergroup. This explains the role of Lie superalgebras in the construction of Gaiotto and Witten. For general X, our model appears to be new. We describe some of its properties, focusing on the case when G is simple and X is the cotangent bundle of the flag variety of G. In particular, we show that Wilson loops are labeled by objects of a certain category which is a quantum deformation of the equivariant derived category of coherent sheaves on X.     

Three-dimensional particle imaging by defocusing method with an annular aperture

We propose an annular-aperture-based defocusing technique for three-dimensional (3D) particle metrology from a single camera view. This simple configuration has high optical efficiency and the ability to deal with overlapped defocused images. Initial results show that an uncertainty in depth of 23 microm can be achieved over a range of 10 mm for macroscopic systems. This method can also be applied in microscopy for the measurement of fluorescently doped microparticles, thus providing a promising solution for 3D flow metrology at both macroscales and microscales.     

A convenient synthesis of substituted 3-bromotetrahydrofurans from homoallylic alcohols

Substituted 3-bromotetrahydrofurans were prepared from homoallylic alcohols via bromination and cyclization in methanol in the presence of potassium carbonate.     

Sopra le estremali relative ad integrali curvilinei dello spazio in forma parametrica

Sunto Nel presente lavoro l' A. stabilisce le equazioni di Eulero relative agli integrali curvilinei e rileva alcune proprietà delle estremali relative alla funzione F, occupandosi in particolare dell'esistenza delle derivate successive delle funzioni da cui le estremali sono definite.