Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation

The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm （diameter） polystyrene. The liquid mixtures, in the proper proportions of water （H2O）, deuterium oxide （D2O） and methanol （MeOH） as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes （reduction） in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.     

Physiologically active bis(dialkylamides) of phosphoryl-substituted α,ω-dicarboxylic acids

Bis(dialkylamides) of phosphoryl-substituted α,ω-dicarboxylic acids were synthesized and their biological activity was studied.     

Measuring the cross sections of heavy-metal spallation induced by deuterons with energies of 2, 2.94, and 3.5 GeV per nucleon

The cross sections for the spallation of the heavy-metal nuclei ¹⁸¹Ta, ¹⁹⁷Au, ²⁰⁷Pb, ²⁰⁹Bi, ²³²Th, and ²³⁸U induced by relativistic deuterons with energies of 2, 2.94, and 3.5 GeV per nucleon are measured using the deuteron beam from the Nuclotron accelerator of the JINR Laboratory of High Energy Physics in Dubna, Russia. The cross-section measurements employ a combined experimental technique involving the solidstate nuclear-track detectors and the activation gamma spectrometry. Adding our measurements to the database of experimental nuclear data will make it possible to test the computer codes used for selecting the parameters of the ADS-type facilities.     

Z-dependences of atomic characteristics of ions in Be- and O-isoelectronic sequences (2s−2p transition)

Transition energies and probabilities are presented for ions of the Be(Z = 4?100) and O(Z = 8?100) isoelectronic sequences. Dipole transitions are considered between all low-lying states constructed from 2s², 2s2p, and 2p² configuration in the case of Be-like ions, and between all low lying states from 2s²2p⁴, 2s2p⁵, and 2p⁶ configurations in the case of O-like ions. The calculations are based on the $\text{1}\text{Z}$ expansion technique and are carried out in the intermediate coupling scheme. Relativistic effects are incorporated using the Breit operator. For Z > 40, it is shown that jj-coupling is applicable. Results of the present calculations are compared with those of other authors over a broad range of nuclear charges.     

Synthesis and crystal structure of triphenyl[tris(tetrahydrofuran)]ytterbium, Ph3Yb(THF)3

Triphenyl[tris(tetrahydrofuran)]ytterbium, Ph₃Yb(THF)₃ (1), was synthesized in high yields by the reaction of Yb with an excess of Ph₂Hg or Ph₃Bi in the presence of catalytic amounts of YbI₂(THF)₄ as well as by the reaction of Ph₂Yb(THF)₂ (2) with Ph₂Hg or Ph₃Bi. The crystal structure of complex1 was studied by X-ray structural analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 163–166, January, 1998.     

Distortion of Configuration of the Nitrogen Atom in 3-Trimethylsilylpropynamides

Analysis of the IR spectral parameters and the results of AM1 quantum-chemical calculations indicated distortion of the planar structure of the amide fragment and destabilization of the nitrogen configuration in new N-functionalized 3-trimethylsilylpropynamides Me₃SiCCC(O)NHR. This effect is most pronounced in N-hydroxy-3-trimethylsilylpropynamide upon formation of intramolecular hydrogen bond C=O···H-O.     

Intramolecular Diels—Alder reaction of 4-(N-furfuryl)aminobut-1-enes. New approach to the synthesis of 6,8a-epoxyoctahydroisoquinoline (3-aza-11-oxatricyclo[6.2.1.01,6]undec-9-ene) derivatives

The intramolecular Diels—Alder reaction of readily accessible 4-substituted 4-(N-furfuryl)aminobut-1-enes was studied and a new one-step method was developed for the synthesis of 6,8a-epoxy-1,2,3,4,4a,5,6,8a-octahydroisoquinoline (3-aza-11-oxatricyclo[6.2.1.0^1,6]undec-9-ene) derivatives. The [4+2]-cycloaddition proceeds stereoselectively to form exo-adducts. The influence of substituents at the nitrogen atom in 4-(N-furfuryl)aminobut-1-enes on the cycloaddition pathway was examined.