On the Thermal Instability of Selected TLC-Type Alkyl Chemically Bonded Stationary Phases and on its Physical Implications

JPC – Journal of Planar Chromatography – Modern TLC - In this paper we report our most recent experimental results relating to the thermal instability of selected alkyl chemically...     

Coherent Generation and Detection of Continuous Terahertz Waves Using Two Photomixers Driven by Laser Diodes

We report on a completely coherent, tunable, continuous-wave THz system where, for the first-time, both the transmitter and receiver are log-periodic-antenna coupled LTG-GaAs based finger-photomixers. This compact room-temperature system exhibits signal-to-noise ratios (> 10³) comparable to or better than what is reported in the literature, and has potential applications in high-resolution spectroscopy and imaging. For the purpose of demonstration, we also present results of spectroscopy measurements carried out on fused silica, which are in agreement with previously published THz-TDS measurements.     

The effect of solvent on the reactions of allyltin (IV) compounds with singlet oxygen, 4-phenyl-1,2,4-triazoline-3,5-dione and diethyl azodicarboxylate

The effect of the influence on the increase of polarity of the solvent on the selectivity and rate of metalloene reactions of different allyltin compounds with singlet oxygen, 4-phenyl-1,2,4-triazoline-3,5-dione (TD) and diethyl azodicarboxylate has been studied.     

Molecular dynamics study of the influence of calcium ions on the conformation of gelsolin S2 domain

Gelsolin is an actin-severing protein whose action is promoted by Ca²⁺ ions and inhibited by binding to lipid phosphoinositides incorporated in the inner leaflet of the plasma membrane inner lipid bilayer. In this study, we carried out molecular dynamics (MD) simulations to investigate the influence of calcium cations on the conformation of gelsolin S2 domain. First, gelsolin S2 domain taken from the crystal structure of apo-gelsolin (PDB code: 1D0N) was subjected to three 1100 ps MD simulations in a periodic water box with the 5.0 force field at T=298 K. In the first simulation (S2_Ca²⁺) excess concentration of Ca²⁺ was applied, in the second one (S2_phys) the concentration of Ca²⁺ ions was physiological and in the third one (S2_w) no Ca²⁺ ions were added. The results of MD simulations showed high conformational flexibility of the N-terminal part of the S2 domain. S2_w deviated from the starting structure considerably more that S2_phys and S2_Ca²⁺ suggesting that Ca²⁺ ions stabilize the conformation of the S2 domain of gelsolin.     

A DFT/TD DFT study of the structure and spectroscopic properties of 5-methyl-2-(8-quinolinyl)benzoxazole and its complexes with Zn(II) ion

The structure and spectroscopic properties of 5-methyl-2-(8-quinolinyl)benzoxazole and its complexes with Zn(II) ion were studied using a DFT and TD DFT methods with def2-TZVP basis set. It was shown that the type of functional used (B3-LYP or pbe0) implemented in TURBOMOLE package does not have essential influence on the geometry (small differences in bond length, valence and dihedral angles) of studied compounds in both ground and excited states. However, significant differences were obtained for the position of vertical absorption and emission transition but not for the oscillator strength of transition. Application of pbe0 functional seems to reproduce better the experimental spectrum.     

On the Schröder equation and iterative sequences of C r diffeomorphisms in {\mathbb{R}^{N}} space

Let ${U \subset \mathbb{R}^{N}}$ be a neighbourhood of the origin and a function ${F:U\rightarrow U}$ be of class C ^r , r ≥ 2, F(0) = 0. Denote by F ⁿ the n-th iterate of F and let ${0<|s_1|\leq \cdots \leq|s_N| <1 }$ , where ${s_1, \ldots , s_N}$ are the eigenvalues of dF(0). Assume that the Schröder equation ${\varphi(F(x))=S\varphi(x)}$ , where S: = dF(0) has a C ² solution φ such that dφ(0) = id. If ${\frac{log|s_1|}{log|s_N|} <2 }$ then the sequence {S ^?n F ⁿ (x)} converges for every point x from the basin of attraction of F to a C ² solution φ of (1). If ${2\leq\frac{log|s_1|}{log|s_N|} }$ then this sequence can be diverging. In this case we give some sufficient conditions for the convergence and divergence of the sequence {S ^?n F ⁿ (x)}. Moreover, we show that if F is of class C ^r and ${r>\big[\frac{log|s_1|}{log|s_N|} \big ]:=p \geq 2}$ then every C ^r solution of the Schröder equation such that dφ(0) = id is given by the formula $$\begin{array}{ll}\varphi (x)={\lim\limits_{n \rightarrow \infty}} (S^{-n}F^n(x) + {\sum\limits _{k=2}^{p}} S^{-n}L_k (F^n(x))),\end{array}$$ where ${L_k:\mathbb{R}^{N} \rightarrow \mathbb{R}^{N}}$ are some homogeneous polynomials of degree k, which are determined by the differentials d ^(j) F(0) for 1 < j ≤  p.     

On some invariants of conjugacy of disjoint iteration groups

We give a necessary and sufficient condition for conjugacy of disjoint iteration groups of continuous functions defined on open real intervals. Moreover, we determine all homeomorphisms γ such that γ o ?^t = g ^t o γ, t ∈ R, where {?^t, t R} and {g1, t ∈ R} are given disjoint iteration groups.     

Cross-metathesis of vinylsilanes carrying electron-withdrawing substituents with olefins in the presence of the second-generation Grubbs catalyst

The efficient cross-metathesis of vinylsilanes carrying electron-withdrawing substituents with various olefins is described. High yields and selectivities were obtained when styrene, 1-hexene, and selective functional allyl derivatives were used as the olefins.     

Die Thiocyanatextraktion und Dithizonbestimmung von Zink in Eisen(III)-oxid

Zusammenfassung Eine Methode zur Zinkbestimmung in Eisen(III)-oxid wird vorgeschlagen. Sie beruht auf der Extraktion des Zinkthiocyanatkomplexes aus schwach saurer Lösung mit Isoamylalkohol. Eisen wird mit Ammoniumfluorid, Kupfer mit Natriumthiosulfat maskiert. Kobalt und Nickel stören nicht, wenn der Extrakt mit einer Waschlösung, die Nitroso-R-Salz enthält, gewaschen wird. Zink wird mit einer Pufferlösung (pH 9) re-extrahiert und mit Dithizon colorimetrisch bestimmt. Bei der Extraktion wird Zink gleichzeitig von gröeren Mengen Cd, Pb und Bi, die die colorimetrische Bestimmung in ammoniakalischer Lösung stören, abgetrennt.

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Thiocyanate extraction and dithizone determination of zinc in iron(III) oxide

A Separation of microgram amounts of zinc from large amounts of iron (100 mg) and from 100 g of Co, Cd, Ni, Cu and 200 g of Bi, Pb has been worked out. Zinc is extracted by isoamyl alcohol from a solution containing ammonium thiocyanate, ammonium fluoride (for masking iron) and sodium thiosulphate (for masking copper). Cobalt and nickel are removed from the extract by shaking with a washing solution containing nitroso-R-salt. Zinc is in this way also separated from Cd, Pb and Bi interfering with the colorimetric determination with dithizone. The method was applied to the determination of zinc in ferric oxide.