Research into the stress-strained state of the concrete dam given the variability of the linear expansion coefficient of concrete

The article has summarized findings of the research into the stress-strained state of the concrete dam. Within the framework of this project, the co-authors have analyzed particular features accompanying field data processing, if the concrete dam serves as the data source. The co-authors have derived average linear expansion coefficients for frozen concrete samples originating from varied dam zones. The findings of numerical studies are provided with the account for the variable value of the linear expansion coefficient of the concrete exposed to negative temperatures. Specialized contact methods in finite elements simulations were employed to simulate the casting joints, with the monolith height being equal to 1.5 m, to take account of the non-linear shear strain of joints and their opening. The analysis performed by the co-authors is based on the combinations of loads and other exposures typical for January as the coldest month of an average year. Casting joints were only simulated in the bottom of the finite element dam model, while no joints were simulated for the dam top. The findings have proven, that the 1.53-fold rise in the value of α accompanying concrete freezing, influences the strain state of the dam at Bogouchanskaya hydropower plant. However no effect was produced by the change in the α value onto the strain state of the dam face. Besides, the rock-to-concrete contact depth and width increased. Although, given the small value of the aforementioned increase (decimal points of a millimeter), it will produce no effect on the filtration underway within the bedrock base of the dam. Changes in the value of the linear expansion coefficient of concrete must be taken into account when physico-mechanical characteristics of concrete are identified for the purpose of the finite element analysis

The Organic Ammonium Counterion Effect on Slow Magnetic Relaxation of the [Er(hfac)₄]⁻ Complexes

The first mononuclear anionic erbium complex [Er(hfac)4]− (hfac = hexafluoroacetylacetone) with an organic ammonium cation [(CH3)4N+] as the counterion was synthesized and structurally and magnetically characterized. The coordination geometries around the Er ions are square antiprisms with pseudo-D4d symmetry. The complex shows distinct field-induced slow magnetization relaxation, which is described by a combination of Orbach (Ueff/kB~28.54(8) K.) and direct mechanisms. Quantum chemical calculations were performed to analyze the magnetic properties of the complex under consideration

Effect of Ligand Substitution on Zero-Field Slow Magnetic Relaxation in Mononuclear Dy(III) β-Diketonate Complexes with Phenanthroline-Based Ligands

Herein, we report the synthesis, structure and magnetic properties of two mononuclear complexes of general formula [Dy(acac)3(L)], where L = 2,2-dimethyl-1,3-dioxolo[4,5-f][1,10] phenanthroline (1) or 1,10-phenanthroline-5,6-dione (2), and acac− = acetylacetonate anion. A distorted square-antiprismatic N2O6 environment around the central Dy(III) ion is formed by three acetylacetonate anions and a phenanthroline-type ligand. Both complexes display a single-molecule magnet (SMM) behavior at zero applied magnetic field. Modification of the peripheral part of ligands L provide substantial effects both on the magnetic relaxation barrier Ueff and on the quantum tunneling of magnetization (QTM). Ab initio quantum-chemical calculations are used to analyze the electronic structure and magnetic properties

Zero-Field Slow Magnetic Relaxation in Binuclear Dy Acetylacetonate Complex with Pyridine-N-Oxide

A new complex [Dy(C5H7O2)3(C5H5NO)]2·2CHCl3 (1) has been synthesized by the reaction of pyridine-N-oxide with dysprosium (III) acetylacetonate in an n-heptane/chloroform mixture (1/20). X-ray data show that each dysprosium atom is chelate-like coordinated by three acetylacetonate ligands and the oxygen atom from two bridging molecules of pyridine-N-oxide, which unite the dysprosium atoms into a binuclear complex. Static (constant current) and dynamic (alternating current) investigations and ab initio calculations of the magnetic properties of complex 1 were performed. The complex was shown to exhibit a frequency maximum under alternating current. At temperatures above 10 K, the maximum shifts to a higher frequency, which is characteristic of SMM behavior. It is established that the dependence of ln(τ) on 1/T for the relaxation process is nonlinear, which indicates the presence of Raman relaxation mechanisms, along with the Orbach mechanism

Solubility Enhancement of Dihydroquercetin via “Green” Phase Modification

Dihydroquercetin (DHQ) is a promising antioxidant for medical applications. The poor water solubility of this flavanonol at ambient conditions inhibits its implementation in clinical practice as an injectable dosage form. Thus, increasing water solubility is a critical step toward solving this problem. Herein we attempted to deal with this problem via DHQ phase modification while at the same time adhering to the principles of green chemistry as much as possible. Lyophilization is an appropriate method to achieve phase modification in an environment-friendly way. This method was employed to generate new phase modifications of DHQ that were then characterized. Mixtures of water with ethanol or acetonitrile were used as solvents for the preparation of the lyophilizates, DHQE, and DHQA, respectively. The results of dissolution testing of the obtained DHQE and DHQA demonstrated that the lyophilization increased water solubility at least 30-fold times. These new DHQ modifications were studied by scanning electron microscopy, mass-spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy, X-ray powder diffraction, and thermal analysis. Their solid-state phases were confirmed to differ from the initial DHQ substance without any changes in the molecular structure. Both DHQE and DHQA showed as high antioxidant activity as the initial DHQ. These data demonstrate the potential of DHQE and DHQA as active pharmaceutical ingredients for injectable dosage forms

New Radical-Cation Salts Based on the TMTTF and TMTSF Donors with Iron and Chromium Bis(Dicarbollide) Complexes: Synthesis, Structure, Properties

New radical-cation salts based on tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenefulvalene (TMsTSF) with metallacarborane anions (TMTTF)[3,3′-Cr(1,2-C2B9H11)2], (TMTTF)[3,3′-Fe(1,2-C2B9H11)2], and (TMTSF)2[3,3′-Cr(1,2-C2B9H11)2] were synthesized by electrocrystallization. Their crystal structures were determined by single crystal X-ray diffraction, and their electrophysical properties in a wide temperature range were studied. The first two salts are dielectrics, while the third one is a narrow-gap semiconductor: σRT = 5 × 10−3 Ohm−1cm−1; Ea ≈ 0.04 eV (aprox. 320 cm−1)

Mononuclear Heptacoordinated 3d-Metal Helicates as a New Family of Single Ion Magnets

The series of Co(II), Fe(II), and Ni(II) mononuclear coordination compounds of [CoL(NCS)2]·3DMSO (1), [CoL(H2O)2](ClO4)2·DMSO (2), [CoL(H2O)(EtOH)][CoCl4]·2H2O (2a), [FeL(NCS)2]·DMSO (3), and [NiL(NCS)2]·CH3CN (4) composition (where L is 2,6-bis(1-(2-(4,6-dimethylpyrimidin-2-yl)hydrazineylidene)ethyl)pyridine), with an [MLA2] coordination unit (where A is a pair of apical monodentate ligands), was synthesized. In compounds 1, 2, 2a, and 3, the ligand L is pentadentate, and cobalt and iron ions are placed in a heavily distorted pentagonal pyramidal coordination environment, while in 4 the Ni(II) ion is hexacoordinated. Easy plane-type magnetic anisotropy (D = 13.69, 11.46, 19.5, and 6.2 cm−1 for 1, 2, 2a, and 4, respectively) was established for cobalt and nickel compounds, while easy axis-type magnetic anisotropy (D = −14.5 cm−1) was established for iron compound 3. The cobalt coordination compounds 1 and 2 show SIM behavior under a 1500 Oe external magnetic field, with effective magnetization reversal barriers of 65(1) and 60(1) K for 1 and 2, respectively. The combination of Orbach and Raman relaxation mechanisms was shown to adequately describe the temperature dependence of relaxation times for 1 and 2. CASSCF/NEVPT2 calculations were performed to model the parameters of the effective spin Hamiltonian for the compounds under study

A new member of the cationic dinitrosyl iron complexes family incorporating N-ethylthiourea is effective against human HeLa and MCF-7 tumor cell lines

<p>A new analog of the active site of mononuclear dinitrosyl [1Fe–2S] proteins, [C₃N₂H₈SFe(NO)₂Cl][Fe(NO)₂(C₃N₂H₈S)₂]⁺Cl⁻ (<b>I</b>), has been synthesized by reacting NO with an aqueous mixture of iron(II) sulfate and N-ethylthiourea in acidic medium. The structure and properties of the complex were studied by X-ray diffraction, IR, Mössbauer, and EPR spectroscopy, in addition to quantum chemical calculations. Complex <b>I</b> spontaneously generates NO in protic media. The cytotoxicity of <b>I</b> was investigated against human cervical carcinoma (HeLa), breast cancer (MCF7), and non-immortalized (FetMCS) cell lines. The cytotoxicity of <b>I</b> against HeLa is similar to that of anticancer agents currently used clinically (platinum complexes), but <b>I</b> is 10 times less toxic in normal cells. The cytotoxicity of MCF7 cells to <b>I</b> is low.</p

Single-Ion Magnet Et₄N[Co^II(hfac)₃] with Nonuniaxial Anisotropy: Synthesis, Experimental Characterization, and Theoretical Modeling

In this article we report the synthesis and structure of the new Co­(II) complex Et₄N­[Co^II­(hfac)₃] (<b>I</b>) (hfac = hexafluoroacetylacetonate) exhibiting single-ion magnet (SIM) behavior. The performed analysis of the magnetic characteristics based on the complementary experimental techniques such as static and dynamic magnetic measurements, electron paramagnetic resonance spectroscopy in conjunction with the theoretical modeling (parametric Hamiltonian and ab initio calculations) demonstrates that the SIM properties of <b>I</b> arise from the nonuniaxial magnetic anisotropy with strong positive axial and significant rhombic contributions