Effect of constant magnetic field on the microhardness of LiIO3 single crystals

The microhardness of LiIO₃ crystals is found to decrease after action of a constant magnetic field B. The maximum change in the microhardness is observed within an hour after the magnetic treatment. Then, the microhardness demonstrates a gradual relaxation return to the initial value. The change in the microhardness is dependent on the orientation of magnetic inductance vector with respect to the polar axis. The effect is pronounced at B ⊥ [0001] and is absent at B ‖ [0001]. The sensitivity of the microhardness of LiIO₃ to a constant magnetic field has a threshold character: the effect appears at the magnetic induction higher than 1 T, increases quickly, and reaches the saturation even at 1.3 T. The reversibility of the magnetically induced decrease in the microhardness has been justified: the effect is exactly reproduced during repeated tests after two weeks. The study of the crystals doped with chromium shows that the increase in the Cr concentration enhances the magnetoplastic effect in LiIO₃, i.e., favors the softening of the material after the magnetic treatment.     

Vibrational dynamics of pyrrole via frequency-domain spectroscopy

The N-H stretch overtones of pyrrole, a key constituent of biologic building blocks, were studied by room temperature photoacoustic and jet-cooled action spectroscopies to unravel their intramolecular dynamics. Contrary to "isolated" states excited with two and three N-H stretch quanta, the one with four quanta shows strong accidental resonances with two other states involving three quanta of N-H stretch and one quantum of C-H stretch. The inhomogeneously reduced features in the action spectra provide the means for getting insight into the intramolecular interactions and the factors controlling energy flow within pyrrole. The time dependence of the survival probability of the 4ν(1) N-H stretch, deduced from the vibrational Hamiltonian, shows an initial decay in ~0.3 ps with ensuing quantum beats from the N-H-C-H resonance and their decay with a time constant of about 5 ps as a result of weaker coupling to bath states.     

Effect of impurity adsorption on the growth of Rochelle salt crystals

The influence of impurities of copper compounds on the growth of Rochelle salt crystals of the composition KNaC₄H₄O₄ · 4H₂O is studied. The growth rates of the faces of various simple forms experimentally measured as functions of the CuCO₃ concentration in solution at a constant supersaturation and temperature are compared with the theoretical models of impurity adsorption on the faces of a growing crystal. Deceleration of the growth of various faces of a Rochelle salt crystal is satisfactorily described by the Bliznakov equation with the use of the Langmuir, Frumkin-Fowler, and de Boor adsorption isotherms for all the faces except for {010}. However, such a comparison does not allow one to reveal the cause of adsorption or its type on different faces. Photometric scanning of Rochelle salt solutions with copper-compound impurity showed that a small addition of alkali (0.06–0.4 g/l) to the solution results in the appearance in the absorption spectra of both the solution nd the crystal grown from it of a maximum at the wavelength 660–670 nm. The intensity of this maximum increases with an increase in the copper concentration. The EPR data, the absorption spectra of the solution and the crystal, and the modified crystal shape showed that the addition of alkali to the solution results in the formation of new copper complexes that more actively decelerate the growth of Rochelle salt faces.     

Effect of the character of ring fusion on the basicity of bicyclic hydrazides

The ionization constants of a number of 1,2-diazabicyclo-3-alkanones were measured. It was found that the basicity of 2-aza-3-quinuclidones is 1.5–2 orders of magnitude lower than in the remaining compounds. An assumption was made regarding the substantial effect of the character of ring fusion on the basicity of bicyclic hydrazides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 220–221, February, 1972.     

Kinetics of the growth of filamentary KH2PO4 crystals on a seed crystal

Physics of the Solid State - At oversaturations exceeding the inert range end for face {101} due to the presence of admixture Al(NO3)3 · 9H2O, a new phase is observed during the growth of this...     

Vibrational overtone spectroscopy and intramolecular dynamics of ethene

The first through fourth C-H stretching overtone regions of ethene were measured by photoacoustic spectroscopy of room-temperature molecules and action spectroscopy of jet-cooled molecules. The rotational cooling led to improved resolution in the action spectra, turning these spectra into key players in determining the multiple band appearance in each region, their types, and origins. These manifolds arise from strong couplings of the C-H stretches to doorway states and were analyzed in terms of a simplified joint local-mode/normal-mode (LM)/(NM) model and an equivalent NM model, accounting for principal resonances. The diagonalization of the LM/NM and NM vibrational Hamiltonians and the least-square fittings revealed model parameters, enabling assignment of A- and B-type bands. These bands behave differently through the V = 2-4 manifolds, showing coupling to doorway states for the former but not for the latter. The energy flow out of the fourth C-H overtone is governed by the interaction with bath states due to the increase in the density of states.     

Anchoring and a Load Transfer Technique in Uniaxial Tension of Unidirectional High-Strength Composites

A simplified analytical method for calculating the stress-strain state in uniaxial tension of unidirectional composite specimens with glued wedges is developed. A numerical analysis of the influence of geometry and mechanical parameters of the specimens on the maximum stresses is carried out. The calculations are refined by finite-element modeling. Tests of the specimens have proved the suitability of the suggested technique of anchoring and load transfer in uniaxial tension of unidirectional high-strength composites.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 3, pp. 319–334, May–June, 2005.