Dynamics of cryogenic jets: non-rayleigh breakup and onset of nonaxisymmetric motions

We report development of generators for periodic, satellite-free fluxes of monodisperse drops with diameters down to 10 microm from cryogenic liquids such as H2, N2, Ar, and Xe (and, as a reference fluid, water). While the break up of water jets can be described well by Rayleigh's linear theory, we find jet regimes for H2 and N2 which reveal deviations from this behavior. Thus, Rayleigh's theory is inappropriate for thin jets that exchange energy and/or mass with the surrounding medium. Moreover, at high evaporation rates, the axial symmetry of the dynamics is lost. When the drops pass into vacuum, frozen pellets form due to surface evaporation. The narrow width of the pellet flux paves the way towards various industrial and scientific applications.     

Droplet cluster

A new phenomenon consisting of the formation of an ordered layer of condensate microdroplets at the water free surface was observed upon the irradiation of an open horizontal water layer (and layers of some organic fluids) by a light beam that causes local heating and evaporation of the fluid.     

Structural relaxation in the CoP-CoNiP system upon low-temperature annealing

The atomic structure of alloys in the CoP-CoNiP system in the initial state and its behavior upon low-temperature annealing is investigated. It is shown that structural relaxation starts at temperatures of 150–200°C and results in local atomic ordering at the network boundaries. Crystals 2–5 nm in size start to undergo nucleation at the boundaries of structural heterogeneities when heated further to 250–300°C. The nanocrystal structure corresponds to the metastable phase delta-Co (ICSD 42684) and the unknown phase Co_{1 ? x} P _x . The estimated diffusion coefficient for CoP alloy is 10^?14 m² s^?1, according to the experimental data.     

Modified Tilting-Plate Method for Measuring Contact Angles

The additivity of the dynamic curvature of a thermocapillary depression and the static curvature of liquid meniscus is experimentally confirmed. A high sensitivity of response shape to the static curvature of liquid surface is used to improve the tilting-plate method. The results of measuring contact angles by this method are well consistent with the data obtained by the sessile drop method. The behavior of meniscus is analyzed in the tilting of a plate with various positioning of its rotation axis in relation to the liquid–gas interface. The applicability limits of the modified method are indicated.     

Luminosity determination for the pd reaction at 2.14 GeV with WASA-at-COSY

The luminosity for a WASA-at-COSY experiment involving the pd reaction at 2.14 GeV proton-beam energy is determined by the forward pd elastic scattering, which yields an average beam-on-target value of [5.2 ± 0.3(stat) ± 0.3syst] × 10³⁰s^-1cm^-2. In addition, the forward pd elastic-scattering angular distribution is obtained with four-momentum transfer squared -t between 0.16 (GeV/c)² and 0.78 (GeV/c)² at this beam energy, which is compared with other experimental data and the pd double scattering model.     

On the role of capillary waves in the mechanism of coalescence of a droplet cluster

Packets of capillary waves on the surface of a horizontal water layer generated at coalescence with a layer of microdroplets (with a characteristic diameter of 50–100 μm) of the dissipative structure “droplet cluster” have been detected by high-speed video recording and the schlieren method. The shortest experimentally observed waves have a length of about 130 μm and their phase velocity exceeds 1.8 m/s. It has been found that the coalescence of a single drop initiates a self-sustained wave process, which induces the coalescence of hundreds of droplets in a time shorter than 1 ms, which form a cluster.     

Mechanism of energy dissipation in a droplet cluster

It has been shown that thermocapillary processes on the surface of the drops in a drop cluster that appears above a locally heated liquid ensure additional energy transfer. Thus, the drop cluster is a typical dissipative structure. The energy dissipated by an individual drop of the cluster has been estimated.     

Dispersive power and crossover temperature,TCO, of two polar nematic liquid crystals in the visible spectral region

Refractive index studies are carried out on two highly polar liquid crystals: 1. N-(p-n-methoxy benzylidene)-p-amino benzonitrile, PmBAB, 2. N-(p-n-ethoxy benzylidene)-p-amino benzonitrile, PeBAB. The experimental investigations are carried out in the visible region at four different wavelengths, namely, 633, 589, 546 and 436 nm. The two compounds exhibit only the nematic liquid crystalline phase in between the isotropic and crystalline solid. The dispersive power ω is estimated for two consecutive wavelengths for the case of <n>, n_e and n_o for different wavelengths and found to be constant with temperature. Further the temperature gradients of n_e and n_o are estimated, and the crossover temperature is obtained using dn_o/dT for all the wavelengths.