Crystal Structure of [Co?6H2O][Co?4H2O?2Gly]?2SO4

The crystals of [Co6H₂O][Co4H₂O2Gly]2SO₄ were studied by X-ray diffraction analysis (triclinic, P , a = 5.975(5), b = 15.469(5), c = 6.765(5) , =120.71(5), =83.23(5), =98.77(5)°). The structure contains complex cations of two types: [Co6H₂O]²⁺ and [Co4H₂O2Gly]²⁺ and SO ₄ ^2– anions linked by hydrogen bonds and electrostatic forces. Three chemically nonequivalent charged layers can be distinguished in the structure: one layer is formed by cobalt hexaaqua complexes, another by [Co4H₂O2Gly]^2– complexes, and the third layer consists of sulfate anions interlaying the former two. The layers alternate along the b axis and are connected by a 3D system of hydrogen bonds.     

A simultaneous sucrose bioconversion into ethanol and levan byZymomonas mobilis

Two biotechnological systems were developed for sucrose conversion into levan and ethanol withZymomonas mobilis, ensuring a 66.7% transfer of substrate carbon in a batch and 61% carbon transfer in a continuous culture. The effect of glucose, ethanol, and medium pH on sucrose conversion byZ. mobilis was studied. The addition of ethanol to the fermentation medium, in the final conc. of 100 g/L, uncoupled levan synthesis from ethanol fermentation. For a continuous culture, the most efficient conversion of substrate carbon into levan was reached at pH 4.8, giving 64.2 g/L levan, with the levan yield of 0.22 g/g and the productivity of 3.2 g/L/h.     

On the possibility for synthesizing dihydrotriazolothiadiazoles by condensation of 4-amino-2,4-dihydro-3<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole-3-thiones with aromatic aldehydes

Regardless of the conditions, the condensation of 4-amino-2,4-dihydro-3H-1,2,4-triazole-3-thiones with aromatic aldehydes afforded the corresponding hydrazones as the only product. Both initial amines and resulting hydrazones exist as the thione rather than thiol tautomer. In no case bicyclic 5,6-dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles that are isomeric to the hydrazones were detected. DFT quantum chemical calculations at the B3LYP/6-31+g(d,p) level of theory with full geometry optimization showed that the hydrazone structure in methanol and DMF is more stable than the bicyclic isomer by 19–23 kcal/mol, which completely excluded the possibility for such cyclization. The thione tautomer of the hydrazones is more stable than the thiol structure by 11–13 kcal/mol.     

Regioselective Synthesis of 2-Trimethylsilyl-4H-pyran-4-ones from 1-Ethoxy(hydroxy)-5-(trimethylsilyl)pentenynones

Exclusive formation of 5-aryl-2-trimethylsilyl-4H-pyran-4-ones is accomplished by a regioselective cyclization of 2-aryl-1-ethoxy(hydroxy)-5-(trimethylsilyl)pent-1-en-4-yn-3-ones. This cyclization occurs in a 6-endo-dig mode through addition to the β-atom of the TMS substituted triple bond. The reaction was found to be general for a range of ethoxyenynones upon heating in glacial acetic acid and for analogous hydroxyenynones in diphenyl ether. Plausible mechanistic explanation and possible post-modifications of resulting pyranones are offered.     

Acoustic properties of glycine phosphite crystals with an admixture of glycine phosphate

Acoustic and dielectric anomalies in the region of the ferroelectric phase transition in crystals of glycine phosphite (GPI) with a 2 mol % admixture of glycine phosphate (GP) are studied. The acoustic anomalies were found to differ strongly from those observed in nominally pure glycine phosphite crystals. A theoretical analysis of the acoustic and dielectric properties of the crystals was carried out within the model of a pseudoproper ferroelectric phase transition. It is shown that the acoustic anomalies, as well as the temperature dependences of the dielectric constant (for various external electric fields) and pyroelectric current observed in the vicinity of the phase transition in GPI-GP crystals, can be adequately described when the macroscopic polarization present in these crystals above the phase transition temperature is taken into account. The thermodynamic-potential parameters describing electrostriction and the biquadratic relation between the polarization and strain turned out to be close to those characterizing a nominally pure GPI crystal. An irreversible phase transition was observed to occur in GPI-GP crystals at T = 240 K, i.e., above the ferroelectric phase transition temperature.     

Pyroelectric properties of some compounds based on protein aminoacids

Protein aminoacid-based compounds were synthesized, and their single crystals were grown. The dielectric and pyroelectric properties of the crystals were studied in the temperature ranges 80–340 and 140–340 K, respectively. It was established that three of the compounds studied (L-His(H₃PO₄)₂, L-TyrHCl, L-Ala₂H₃PO₃ · H₂O) are linear pyroelectrics, with their room-temperature pyroelectric figures of merit being close to those of ferroelectric triglycine sulfate crystals.     

Seeded polymerization as a method for producing hollow monodisperse microspheres

Crosslinked hollow monodisperse microspheres with diameters of 1.9–5.9 μm and one- or two-layer shells, with the layers being based on polymers of different natures, are produced by one- and two-stage seeded copolymerization of styrene and/or methyl methacrylate with ethylene glycol dimethacrylate or allyl methacrylate as crosslinking agents. Factors determining the morphology and dispersity of the microspheres are revealed. It is shown that, when, at the final stage of the synthesis, the content of a crosslinking agent in the reaction mixture is at least 50 wt %, the produced microspheres retain their size and morphology after exposure in toluene and dimethylformamide.     

Dielectric properties of thin films of partially deuterated betaine phosphite with large- and small-block structures

Ferroelectric thin films of partially deuterated betaine phosphite (DBPI) have been grown by evaporation on NdGaO₃ substrates with a preliminarily deposited structure of interdigitated electrodes. The block structure of the films is a texture in which the polar axis b is oriented in the plane of the film and the a* axis is perpendicular to this plane. Typical dimensions of the single-crystal blocks in DBPI films substantially exceeds the distance between the interdigitated electrodes (d = 50 μm). However, DBPI films in which the block structure has characteristic dimensions of the order of d have also been grown. Investigations of the dielectric properties of the films have demonstrated that the dimensions of the block structure have little effect on the behavior of a small-signal dielectric response, which, in the phase transition region, is characterized by a strong anomaly of the capacitance of the structure at T = T _c and by a glass-like behavior of the capacitance C and dielectric loss tangent tanδ in the temperature range of 120–200 K. By contrast, the low-frequency strong-signal dielectric response (dielectric hysteresis loops) in the structures with small blocks differs significantly from that observed for large-block structures. The difference in the frequency behavior of the hysteresis loops in the large-block and small-block structures is associated with the limitation of motion of domain walls in the case of small blocks.     

Synthesis of polyglutamine conjugates of lysine dendrimers in solution and polymer gel

The synthesis of polyglutamine conjugates of lysine dendrimers, in which carboxyl groups of polyglutamine chains are linked via one point to the amino groups of N-terminal lysine fragments of dendrimers, is studied. Lysine dendrimers of third, fourth, and fifth generations are preliminarily prepared via the solid-phase synthesis on a polymer support, crosslinked p-methylbenzohydrylaminopolystyrene. The first approach to the synthesis of polyglutamine conjugates of dendrimers consisted in that, after the synthesis of lysine dendrimers, their removal from the polymer support, their full unblocking, and their purification, γ-benzyl glutamate N-carboxyadhydride is involved in solution polymerization at the amino groups of lysine of the outer sphere of dendrimers. The second approach includes the polymerization of γ-benzyl glutamate N-carboxyadhydride on the amino groups of N-terminal lysine residues of lysine dendrimers performed before dendrimer removal from the polymer support. The structural study of star-shaped conjugate of lysine dendrimers makes it possible to for the first time estimate the similarities and differences in these two approaches to the synthesis of polyglutamine conjugates of lysine dendrimers.     

Characteristics of sound signals on a quasi-stationary track between the Josephine and Ampere Seamounts

Experimental data are presented on the measurement of the cross-correlation coefficients and the differences in the arrival times (temporal spectra) of acoustic signals transmitted through a 210-km-long quasi-stationary track in the Atlantic Ocean. At the summit of the Josephine Seamount, a continuous pseudonoise signal was emitted in the one-third-octave band with a mean frequency of 630 Hz. The signal was received at the Ampere Seamount by a 40-m flexible vertical array with a directivity pattern in the form of a static fan of 32 lobes. The width of each lobe was ～3°. At a signal-to-noise ratio of about 3 dB and with an incomplete resolution of multipath signals by the array, the correlation coefficients reached a value of 0.48. The rms fluctuations of the differences in the arrival times varied from 1.8 to 3.1 ms depending on the signal arrival angles. The factors responsible for the low correlation coefficients and the relatively high fluctuations of the arrival time differences are discussed. Apparently, one of the factors is the presence of short-period internal waves.