Detachment force of particles from fluid droplets

We calculate the deformation of a spherical droplet, resulting from the application of a pair of opposite forces to particles located diametrically opposite at the two ends of the droplet. The free-energy analysis is used to calculate the force–distance curves for the generated restoring forces, arising from the displacement of the particles relative to each other. While the logarithmic dependence of the “de Gennes–Hooke” constant on the particle to droplet size ratio, ν, is rather well known in the limit of very small ν, we find that for more realistic particle to droplet size ratios, i.e. ν = 0.001 to 0.01, the additional constant terms of O(1) constitute a significant correction to previously reported results. We derive the restoring force constant to be 2πγ[0.5 − ln(ν/2)]−1, in perfect agreement with the exact semi-numerical analysis of the same problem. The deviation from the linear force–displacement behaviour, occurring close to the point of detachment, is also investigated. A study of the energy dissipated shows it to be an increasingly dominant component of the work done during the detachment of the particles, as ν decreases. This indicates the existence of a significantly higher energy barrier to desorption of very small particles, compared to the one suggested by their adsorption energy alone. The influence of the line tension on the detachment force is also considered. It is shown that where line tension is important, the contact angle is no longer a constant but instead alters with the displacement of the particles from their equilibrium positions

Synthesis of 6-azaindoles via electrophilic [4+1]-cyclization of 3-amino-4-methyl pyridines: scope and limitations

A scalable and efficient synthesis of the 2-trifluoromethyl-3-trifluoroacetyl-6-azaindoles from 3-amino-4-methylpyridines under treatment with TFAA was disclosed. The reaction scope and limitation towards the pyridine and electrophilic components were investigated. Examining the pyridine components using trifluoroacetic anhydride (TFAA) as a model electrophile allowed us to divide them into three groups with different impacts on the reaction outcome. Among electrophilic components difluoroacetic anhydride (DFAA), trichloroacetic anhydride (TCAA) and Vilsmeier-Haack reagent (VHR) were inspected. The results superposition led to a cyclization mechanism rationalizing our observations

Selective laser spectroscopy of the bixbyite-type yttrium scandate doped by rare-earth ions

Yttrium scandate crystals doped by Nd3+ and Tm3+ ions have been obtained in the form of a fiber through the laser-heated pedestal growth (LHPG) method. Three types of optical centers of Nd3+ and Tm3+ have been recorded by the selective laser spectroscopy methods. Two dominant centers form due to substitution of the rare-earth ions for Y3+ and Sc3+ in the structural site of C2. In the case of Nd3+:YScO3, the third one is aggregate pair center Nd3+ - Nd3+ which forms due to substitution of basic ions (Y3+ or Sc3+) in neighboring MO6 polyhedra shared the edge. In the case of Tm3+:YScO3, the third optical center form due to substitution of Tm3+ for Y3+ or Sc3+ in the octahedra MO6 with symmetry site of C3i. The lifetime have been estimated for Nd3+ and Tm3+ ions occupied MO6 polyhedra with symmetry sites of C2 and C3i in the YScO3 crystal fibers. Stark level schematic of 2F3/2, 4I11/2, and 4I9/2 multiplets of Nd3+ ions have been built for both centers of C2 in the YScO3 crystal fibe

MEANS OF RESCUE FROM A HEIGHT DURING THE PERIOD OF SANCTIONS

The article discusses the means of rescue from a height, distributed on the territory of Russia over the past twenty years. A brief overview of devices and manufacturers depending on the part of imported content is carried out. There is made a forecast for the development of the situation of import substitution as for means of rescue of firefighters from the height

TRAINING TOWER BELAYING DEVICES

The article discusses the issue of using a belaying device on a training tower. The interpretation of normative documents in this area is given. There is presented the overview of possible belaying devices

Facet Appearance on the Lateral Face of Sapphire Single-Crystal Fibers during LHPG Growth

Results of the study of the lateral surface of single-crystal (SC) sapphire fibers grown along crystallographic directions [ 0001 ] and [ 11 2 ¯ 0 ] by the LHPG method are presented. The appearance or absence of faceting of the lateral surface of the fibers depending on the growth direction is analyzed. The crystallographic orientation of the facets is investigated. The microstructure of the samples is investigated with the help of an optical microscope and a JSM-5910LV scanning electronic microscope (JEOL). The crystallographic orientations of the facets on the SC sapphire fiber surface are determined by electron backscatter diffraction (EBSD). The seed orientation is studied by means of XRD techniques

Sulfamide instead urea in Biginelli reaction: from black box to reality

The scope and limitation of classical Biginelli reaction expanded to principally novel substrates: sulfamide and its monosubstituted analogues. The preparative procedure was optimized. The reasons for the unavailability of such compounds earlier were determined. The relationship between the structure and stability of final compounds and the nature of starting materials were detected. Some mechanistic observations were shown and discussed. The prospects for employing these compounds for new 3D-shape MedChem relevant libraries were disclosed