A study of fine-dispersed silver powders for conductive adhesive compositions

Results of granulometric investigations of fine-dispersed silver powders are presented, and they are evaluated for use in compositions of conductive adhesives. The optimal brand of nanodispersed powder for the obtaining of conductive adhesive of EKS-2 brand characterized by ρ_v × 10^–7 Ω m is chosen.     

Peculiarities of section topograms for the multiple diffraction of X rays

The distortion of interference fringes on the section topograms of single crystal due to the multiple diffraction of X rays has been investigated. The cases of the 220 and 400 reflections in a silicon crystal in the form of a plate with a surface oriented normally to the [001] direction are considered both theoretically and experimentally. The same section topogram exhibits five cases of multiple diffraction at small azimuthal angles for the 400 reflection and MoK_α radiation, while the topogram for the 220 reflection demonstrates two cases of multiple diffraction. All these cases correspond to different combinations of reciprocal lattice vectors. Exact theoretical calculations of section topograms for the aforementioned cases of multiple diffraction have been performed for the first time. The section topograms exhibit two different distortion regions. The distortions in the central region of the structure are fairly complex and depend strongly on the azimuthal angle. In the tails of the multiple diffraction region, there is a shift of two-beam interference fringes, which can be observed even with a laboratory X-ray source.     

Thermodynamic properties of a second-generation poly(phenylene-pyridyl) dendron with a dodecyl-decorated periphery

The heat capacity of a partially crystalline second-generation poly(phenylene-pyridyl) dendron with a dodecyl-decorated periphery is studied by high-precision adiabatic vacuum and differential scanning calorimetry in the temperature range of 6 to 530 K. The thermodynamic characteristics of the glass’s transition and melting are determined from the calorimetric data and the degree of its crystallinity is estimated (α = 30%). Standard thermodynamic functions (C_p°, H°-H°(0), S°-S°(0), and G°-H°(0)) for a partially crystalline dendron in the range of T → 0 to 480 K are calculated.     

Solvation of decane and benzene in mixtures of 1-octanol and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylformamide

The heats of dissolution of decane and benzene in a model system of octanol-1 (OctOH) and N,N-dimethylformamide (DMF) at 308 K are measured using a variable temperature calorimeter equipped with an isothermal shell. Standard enthalpies are determined and standard heat capacities of dissolution in the temperature range of 298–318 K are calculated using data obtained in [1, 2]. The state of hydrocarbon molecules in a binary mixture is studied in terms of the enhanced coordination model (ECM). Benzene is shown to be preferentially solvated by DMF over the range of physiological temperatures. The solvation shell of decane is found to be strongly enriched with 1-octanol. It is obvious that although both hydrocarbons are nonpolar, the presence of the aromatic π-system in benzene leads to drastic differences in their solvation in a lipid–protein medium.     

On the T-old quark fragmentation function and on transversal handedness

The first probe of the correlation of the T-odd one-particle fragmentation function responsible for the left-right asymmetry of fragmentation of a transversely polarized quark is done by using the 1991–95 DELPHI data for Z→2-jet decay. Integrated over the fraction of longitudinal and transversal momenta, this correlation is of 1.5% order, which means order of 13% for the analyzing power.A rather large (≈ 10%) handedness transversal to the production plane was observed in the diffractive production of (π^?+π⁺π^?) triples from nuclei by the 40 GeV/c π^?-beam. It was shown that the phenomenon has a clear dynamic origin and resembles the single spin asymmetry behavior. All this makes us hope to use this effects in polarized DIS experiments for transversity measurement.     

Multiblock (segmented) shape memory copolymers containing Polyurethane and rigid-chain polyimide blocks

Russian Chemical Bulletin - Multiblock (segment) shape memory poly(urethane-imide) copolymers (PUIC) were studied by thermogravimetric analysis, differential scanning calorimetry, and dynamic...     

SYNTHESIS AND CRYSTAL STRUCTURE OF PENTANUCLEAR HETEROMETALLIC Pd(II)–La(III) ACETATE COMPLEX

Journal of Structural Chemistry - The structure of a novel pentanuclear heterometallic complex [Pd3La2(OOCMe)12(MeCOOH)4] with an unusual ratio of metals 3Pd:2La is studied by XRD. The complex is...     

Intramolecular sensitization of photocleavage of the photolabile 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) protecting group: photoproducts and photokinetics of the release of nucleosides

Novel photolabile protecting groups based on the 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) group with a covalently linked thioxanthone as an intramolecular triplet sensitizer exhibit significantly enhanced light sensitivity under continuous illumination. Herein we present a detailed study of the photokinetics and photoproducts of nucleosides caged with these new protecting groups. Relative to the parent NPPOC group, the light sensitivity of the new photolabile protecting groups is enhanced by up to a factor of 21 at 366 nm and is still quite high at 405 nm, the wavelength at which the sensitivity of the parent compound is practically zero. A new pathway for deprotection of the NPPOC group proceeding through a nitroso benzylalcohol intermediate has been discovered to complement the main mechanism, which involves beta elimination. Under standard conditions of lithographic DNA-chip synthesis, some of the new compounds, while maintaining the same chip quality, react ten times faster than the unmodified NPPOC-protected nucleosides.     

Terahertz time-domain and Raman spectroscopy of the sulfur-containing peptide dimers: Low-frequency markers of disulfide bridges

The terahertz time-domain and Raman spectra of sulfur-containing cystein-based peptides in the region of the low-frequency infrared vibrations have been measured at room temperature. The low-frequency bands that can be assigned to the S–S bridges are observed. The vibrational modes found in molecular crystalline materials should be described as phonon modes with strong coupling to the intra molecular vibrations.     

Thermodynamic properties, intermolecular interaction parameters, and structure of aqueous amide solutions of ammonium and tetraalakylammonium bromides

The thermal effects of dissolution of ammonium bromide in water and its mixtures with formamide (FA) at 277–328 K were studied by the calorimetry method in the region of small additions of the nonaqueous component. The standard values of enthalpy and heat capacity of solution, as well as the temperature changes in the solution entropy and reduced dimensionless Gibbs energy, were calculated. The parameters of electrolyte-amide pair interactions were calculated using the McMillan-Mayer formalism. The contributions of the cation and anion to the pair interaction parameters were determined by the group additivity method. The results are compared with the data obtained previously for solutions of tetrabutyl-and tetraethylammonium bromides in aqueous solutions of FA and hexamethylphoshotriamide (HMPT). At elevated temperatures the system becomes less structured in amide solutions of tetraalkylammonium bromides (except solutions of Et₄NBr in aqueous HMPT) but more structured in solutions of ammonium bromide and in aqueous FA and HMPT.