Quasi-two-dimensional diamond crystals: Deposition from a gaseous phase and structural–morphological properties

Diamond films predominantly consisting of plane micrometer-size crystallites with a thickness of several dozen nanometers have been deposited from a methane–hydrogen gas mixture activated by a dc gas discharge. The crystallite structure has been studied by scanning and transmission electron microscopy and diffraction. A possible mechanism of formation of plane crystallites during deposition of diamond from the gas phase has been discussed. It has been shown that the results agree with the theoretical concepts of formation of crystals with a face-centered cubic lattice.     

Experience on using titanium as a structural material for a solar neutrino lithium detector

Data obtained by the radiotracer method on a specially designed test bench show that a lithium oxide film serves as a trap for beryllium extracted from lithium. No tangible chemisorption of beryllium on the titanium surface is observed. These finding are used to design and fabricate a lithium detector for solar neutrinos. They will also find application in designing power nuclear facilities with liquid-metal heat carriers.     

Calorimetric study of polyvinyl alcohols used as emulsifiers in suspension polymerization of vinyl chloride

The heat effects of dissolution of two pairs of polyvinyl alcohols used as emulsifiers in suspension polymerization of vinyl chloride and the optical transmission of their stirred aqueous solutions as a function of time were determined.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1917–1919.Original Russian Text Copyright © 2004 by Kiryanov, Semchikov, Kronman, Ganyukhina, Leshina, Orekhov.     

Multiple-site exchange in proteins studied with a suite of six NMR relaxation dispersion experiments: an application to the folding of a Fyn SH3 domain mutant

The three-site exchange folding reaction of an (15)N-labeled, highly deuterated Gly48Met mutant of the Fyn SH3 domain has been characterized at 25 degrees C using a suite of six CPMG-type relaxation dispersion experiments that measure exchange contributions to backbone (1)H and (15)N transverse relaxation rates in proteins. It is shown that this suite of experiments allows the extraction of all the parameters of this multisite exchange process in a robust manner, including chemical shift differences between exchanging states, from a data set recorded at only a single temperature. The populations of the exchanging folded, intermediate, and unfolded states that are fit are 94, 0.7, and 5%, respectively. Despite the small fraction of the intermediate, structural information is obtained for this state that is consistent with the picture of SH3 domain folding that has emerged from other studies. Taken together, the six dispersion experiments facilitate the complete reconstruction of (1)H-(15)N correlation spectra for the unfolded and intermediate states that are "invisible" in even the most sensitive of NMR experiments.     

Processing of heteronuclear NMR relaxation data with the new software DASHA

The new program DASHA is an efficient implementation of common data processing steps for the protein internal dynamic analysis. The “model-free” parameters and their uncertainties (Lipari G., Szabo A.: J. Am. Chem. Soc.104, 4546–4559 (1982) can be calculated from an arbitrary combination of experimental data sets (i.e. heteronuclear¹H?¹⁵N or¹H?¹³C relaxation times and NOE values at different spectrometer frequencies). Anisotropy of the molecular rotational diffusion could be also taken into account without introduction of the new adjustable parameters into the spectral density functionJ(ω), provided the structure of the molecule is known. Parameters of chemical (conformational) exchange can be estimated from the CPMG spin-lock frequency dependences (Bloomet al.: J. Chem. Phys.42, 1615–1624 (1965); Orekhovet al.: Eur. J. Biochem.219, 887–896 (1994). The program can be used both in the interactive and batch modes. It has sophisticated PostScript plotting facilities.     

Microstructure of eutectic composites Ln 1?x Ln′ x MnO3 (Ln = Eu or Tb; Ln′ = Y or Ho) near the transition between the orthorhombic structure and hexagonal structures

Multiferroic crystals Ln _{1 ? x} MnO₃ (Ln = Eu or Tb; Ln?? = Y or Ho) have been grown by floating-zone melting; the compositions of these crystals are close to the point of concentration transition from the orthorhombic structure to the hexagonal phase. Scanning microscopy has revealed that the crystal boules have a regular lamellar structure in the form of alternating layers of the orthorhombic and hexagonal phases; this structure is typical of the materials obtained by the directional solidification of eutectic composites. The local chemical and phase compositions and the unit-cell parameters of the phases have been determined. The microstructure and morphology of the lamellar structures are described for different growth conditions. The mutual orientation of the crystallographic axes of the orthorhombic and hexagonal phases in the neighboring layers has been determined by electron backscatter diffraction. The orientational features are considered from the point of view of the crystal structure of both phases.     

Method for recording of solar neutrinos with a lithium detector

A method for solar neutrino recording on a laboratory bench with a lithium detector is developed. The efficiency of extraction of beryllium from lithium as high as 96.4% is achieved, and it is shown that lithium extraction losses are less than 1%. The results of a full-scale experiment with a 10-t lithium detector consisting of 20 500-kg modules are presented. Technical solutions based on the experimental results open the way to designing a pilot facility intended for 500 kg of lithium.     

Accurate relaxation parameters for large proteins

The practical applicability, performance, and robustness of three-way decomposition (TWD) for the extraction of relaxation parameters are demonstrated for a large protein with 370 residues, the maltose binding protein. An ordinary set of seven relaxation-modulated (15)N HSQC spectra, recorded at another site, is systematically analyzed. For all 341 assigned backbone amide groups, including 21 pairs and one group of three overlapped peaks, T1 decay values were determined. On isolated peaks, TWD extracts T1 values with systematically lower error bounds compared to conventional tools, although for these simple cases the improvements remain limited. However, in the presence of spectral artifacts, the decrease in errors can become significant, demonstrating the higher robustness of TWD. For about half of the peaks in overlapped regions, the decomposition allowed separation of the signals, yielding significantly different T1 values between overlapping signals. For the rest, similarity of the decay times for the two or three overlapping signals could be confirmed within usually low error bounds. The use of TWD thus leads to a significant increase in the number of accessible relaxation probes in large proteins. With a newly implemented graphical user interface, the application of TWD requires merely a peak list, and thus no additional effort compared to conventional approaches is needed.