Cloud point extraction of disulfiram for its HPLC-MS/MS determination in synthetic urine

A new simple cloud point extraction/preconcentration method was developed for the HPLCMS/MS determination of disulfiram in synthetic urine. Some parameters with an effect on the extraction, such as the concentration of Triton X-114, pH influence, incubation time, equilibration temperature and centrifuging parameters, were studied and optimised. The method proposed for the HPLC-MS/MS determination of disulfiram in synthetic urine with preliminary cloud point extraction was validated. The calibration curve was linear in the range of 0.025–15.4 ng mL?1. The limits of detection (3σ) and quantification (10σ) were 0.008 ng mL^?1 and 0.025 ng mL^?1, respectively. The matrix effect (96 %), recovery of the extraction procedure (95 %) and overall “process efficiency” (91 %) were also estimated. The results show that the sensitivity, metrological characteristics, ecological safety, simplicity and convenience of the suggested procedure exceed its analogues based on extraction using organic solvents.     

Silver particles growth by pulse electrolysis in acetonitrile solutions

The morphology of silver particles deposited on ITO-glass surface by pulse electrolysis in acetonitrile solutions of AgNO₃ has been analyzed. The influences of potential value (E) as well pulse duration (τ_on) and pause (τ_off) on the size and geometry of the particles has been discussed. It has been shown that in the range of 0.0 ≤ E ≤ ?1.5 V at τ_on = 6 ms and 90 ≤ τ_off ≤ 490 ms formation of silver particles (～20–50 nm) and their agglomeration (～0.2–2 µm) take place. The tendency to increase size of the particles in 3D has been observed with the increase of cathode potential. Decreasing of duty cycle leads to more discrete deposited particles.      

On group operations on homogeneous spaces

It is proved that every countably infinite homogeneous regular space admits a structure of any countably infinite group with continuous left shifts.

     

Ultrafilter semigroups generated by direct sums

Let λ be an infinite cardinal and for every ordinal α<λ, let A _α be a set with a distinguished element 0 _α ∈A _α . The direct sum of sets A _α , α<λ, is the subset \(X=\bigoplus_{\alpha<\lambda}A_{\alpha}\) of the Cartesian product ∏_α<λ A _α consisting of all x with finite supp?(x)={α<λ:x(α)≠0 _α }. Endow X with a topology by taking as a neighborhood base at x∈X the subsets of the form {y∈X:y(α)=x(α) for all α<γ} where γ<λ. Let Ult?(X) denote the set of all nonprincipal ultrafilters on X converging to 0∈X. There is a natural partial semigroup operation on X which induces a semigroup operation on Ult?(X). We show that if direct sums X and Y are homeomorphic, then the semigroups Ult?(X) and Ult?(Y) are isomorphic.     

Free groups in the smallest ideal of β G

Let G be an infinite group with cardinality κ embeddable into a direct sum of countable groups and let β G be the Stone-Čech compactification of G as a discrete semigroup. We show that the structural group of the smallest ideal of β G contains copies of the free group on generators. Supported by NRF grants FA2007041200005 and IFR2008041600015, respectively, and The John Knopfmacher Centre for Applicable Analysis and Number Theory.     

Symmetric colorings of the dihedral group

Let G be a finite group and let r∈?. An r-coloring of G is any mapping χ:G→{1,…,r}. Colorings χ and ψ are equivalent if there exists g∈G such that χ(xg^?1) = ψ(x) for every x∈G. A coloring χ is symmetric if there exists g∈G such that χ(gx^?1g) = χ(x) for every x∈G. Let S_r(G) denote the number of symmetric r-colorings of G and s_r(G) the number of equivalence classes of symmetric r-colorings of G. We count S_r(G) and s_r(G) in the case where G is the dihedral group D_n.     

Pressure-Induced Perovskite-to-non-Perovskite Phase Transition in CsPbBr3

The expanding range of optoelectronic applications of lead-halide perovskites requires their production in diverse forms (single crystals, thin- and thick-films or even nanocrystals), motivating the development of diverse materials processing and deposition routes that are specifically suited for these structurally soft, low-melting semiconductors. Pressure-assisted deposition of compact pellets or thick-films are gaining popularity, necessitating studies on the pressure effects on the atomic structure and properties of the resulting material. Herein we report the phase transformation in bulk polycrystalline cesium lead bromide from its three-dimensional perovskite phase (γ-CsPbBr₃) into the one-dimensional polymorph (δ-CsPbBr₃) upon application of hydrostatic pressure (0.35 GPa). δ-CsPbBr₃ is characterized by a wide bandgap of 2.9 eV and broadband yellow luminescence at 585 nm (2.1 eV) originating from self-trapped excitons. The formation of δ-CsPbBr₃ was confirmed and characterized by Raman spectroscopy, ²⁰⁷Pb and ¹³³Cs solid-state nuclear magnetic resonance, X-ray diffraction, absorption spectroscopy, and temperature-dependent and time-resolved photoluminescence spectroscopy. No such phase transition was observed in colloidal CsPbBr₃ nanocrystals.     

Formyl MIDA Boronate: C1 Building Block Enables Straightforward Access to α‐Functionalized Organoboron Derivatives

Formyl MIDA boronate has been known to be an elusive type of acylboronate that has not been obtained to date. In this work, an approach to the one‐pot preparation and chemical transformations of formyl MIDA boronate were developed to provide new types of α‐functionalized organoboron compounds. Among them are acylboronate reagents which present boron‐substituted analogues of ynones and β‐dicarbonyl compounds. The developed synthetic procedures, utilizing formyl MIDA boronate, are tolerant to diverse functional groups, making this reagent an advantageous C₁ building block for extending the scope of organoboron chemistry.     

Interpolation with Specified Error of a Point Series Belonging to a Monotone Curve

The paper addresses the problem of modeling a smooth contour interpolating a point series belonging to a curve containing no special points, which represents the original curve with specified accuracy. The contour is formed within the area of possible location of the parts of the interpolated curve along which the curvature values are monotonously increased or decreased. The absolute interpolation error of the point series is estimated by the width of the area of possible location of the curve. As a result of assigning each intermediate point, the location of two new sections of the curve that lie within the area of the corresponding output section is obtained. When the interpolation error becomes less than the given value, the area of location of the curve is considered to be formed, and the resulting point series is interpolated by a contour that lies within the area. The possibility to shape the contours with arcs of circles specified by characteristics is investigated.