Concomitant cocrystal and salt: no interconversion in the solid state

A cocrystal and a molecular salt of β‐alanine and dl ‐tartaric acid, C₃H₈NO₂⁺·C₄H₄O₆^?, of the same chemical composition, were studied over a wide temperature range by single‐crystal and powder X‐ray diffraction. Neither the interconversion between the two phases nor any polymorphic transitions were observed in the temperature range from 100 K to the melting points. This contrasts with the solvent‐mediated phase transition from the salt to the cocrystal in a slurry that has been documented earlier.     

Formation of Copper(I) mixed-ligand complexes with mercaptopropyl or dipropyl disulfide groups covalently bonded to the silica surface and Michler’s thioketone

Silica chemically modified with mercaptopropyl groups (MPS) is usable in copper(II) recovery from chloride and nitrate solutions, affording a recovery factor of 99%. With silica modified with dipropyl disulfide groups (DPDSS), the largest copper(II) recovery factor is 50% and is attained at pH 6–7. Copper in its mercaptopropyl and dipropyl disulfide complexes on the silica surface is in the oxidation states +1 and +2, respectively. Coordinatively unsaturated copper(I) complexes form on the MPS surface, and their amount depends on the quantity of functional groups grafted to the silica surface. These surface complexes of copper(I) can coordinate with Michler’s thioketone molecules from aqueous ethanol to yield intensely red mixed-ligand copper(I) complexes on the MPS or DPDSS surface (in the latter case, after copper(II) reduction to copper(I) with ascorbic acid). The diffuse reflectance spectrum of the mixed-ligand complexes shows a band at 520 nm.     

Prediction of the dispersity of ultrasonically treated starch hydrogels

Expressions for calculating the expected particle size of the colloid phase and the gain in the content of the water-soluble fraction in starch hydrogels upon their ultrasonic treatment were obtained.     

On fibers of algebraic invariant moment maps

In this paper we study some properties of fibers of the invariant moment map for a Hamiltonian action of a reductive group on an affine symplectic variety. We prove that all fibers have equal dimension. Further, under some additional restrictions, we show that the quotients of fibers are irreducible normal schemes.     

Low-temperature sorption-luminescence determination of platinum using silica chemically modified with dithiocarbamate groups

Application of silica chemically modified with dithiocarbamate groups (DTCS) has been proposed for the low-temperature sorption-luminescence determination of platinum. The establishment of a sorption equilibrium in the platinum(IV) and platinum(II) extraction with DTCS from hydrochloric acid solutions takes 20 and 2 min, respectively. If the duration of the phase contact is optimal, the recovery achieves 99% in the acidity range from 4 M of HCl to pH 5. The sorption of platinum(IV) and platinum(II) results in the formation of coordination compounds of platinum(II) on the surface of the adsorbent which are luminescent in ultraviolet light when frozen (77 K). A procedure has been developed for low-temperature sorption-luminescence determination of platinum with the detection limit of 0.5 ??g of platinum per 0.1 g of the adsorbent and linearity of the calibration curve to 25 ??g/0.1 g. The developed procedure has been applied to the determination of platinum in the samples of alumoplatinum catalyst.     

Completing the picture of tolazamide polymorphism under extreme conditions: a low‐temperature study

We present the results of an experimental and computational study of structural changes in two polymorphs of tolazamide {systematic name: 1‐[(azepan‐1‐ylamino)carbonyl]‐4‐methylbenzenesulfonamide}, C₁₄H₂₁N₃O₃S, on cooling to 100 K and reverse heating. No phase transitions occurred in this temperature range. The anisotropy of the thermal expansion was different for the two polymorphs and differed from that reported previously for the hydrostatic compression. The changes in different intermolecular contacts responsible for the strain anisotropy were analysed. Relative shortening of the contacts was related directly to their initial length and reversely to the steric density around them. Increasing steric density is likely to be the driving force for the conformational ordering of the azepane ring under compression.     

Pepper-Pot Emittance Measurement at Laser Plasma Ion Source for I-4 Accelerator

Physics of Atomic Nuclei - A computer code is developed for processing primary images obtained in the pepper-pot emittance measurement technique, which makes it possible to estimate emittance in a...     

Influence of a Fundamental Frequency Pulse Chirp on the Spectral and Temporal Second-Harmonic Characteristics

Russian Physics Journal - The results of investigation of the possibility of reducing the duration of the second-harmonic radiation pulse generated by the starting complex of an THL-100 laser...     

On the hyperbolicity criterion for noncompact Riemannian manifolds of special type

In this paper we study the behavior of bounded harmonic functions on complete Riemannian manifolds (of a certain special type) depending on the geometry of the manifold. Translated fromMatematicheskie Zametki, Vol. 59, No. 4, pp. 557–563, April, 1996.     

Spectroscopic study of the interaction between porphyrin and chlorin molecules of opposite charge in solutions

Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, Minsk, 220072, 70, F. Skorina Ave., Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 2, pp. 152–163, March–April, 1995.