Strain specific motility patterns and surface adhesion of virulent and probiotic Escherichia coli

Bacterial motility provides the ability for bacterial dissemination and surface exploration, apart from a choice between surface colonisation and further motion. In this study, we characterised the movement trajectories of pathogenic and probiotic Escherichia coli strains (ATCC43890 and M17, respectively) at the landing stage (i.e., leaving the bulk and approaching the surface) and its correlation with adhesion patterns and efficiency. A poorly motile strain JM109 was used as a control. Using specially designed and manufactured microfluidic chambers, we found that the motion behaviour near surfaces drastically varied between the strains, correlating with adhesion patterns. We consider two bacterial strategies for effective surface colonisation: horizontal and vertical, based on the obtained results. The horizontal strategy demonstrated by the M17 strain is characterised by collective directed movements within the horizontal layer during a relatively long period and non-uniform adhesion patterns, suggesting co-dependence of bacteria in the course of adhesion. The vertical strategy demonstrated by the pathogenic ATCC43890 strain implies the individual movement of bacteria mainly in the vertical direction, a faster transition from bulk to near-surface swimming, and independent bacterial behaviour during adhesion, providing a uniform distribution over the surface.

Temperature distribution in the three-layered upper mantle beneath a continent

Temperature distribution in the upper mantle underneath the continent, as well as temperature distribution in the lower mantle, is obtained. In the continental lithosphere, the solution to the heat transfer equation is obtained in the model of conduction heat transfer with inner heat within the crust. To calculate the temperature distribution in the upper and lower mantle, we use the results of laboratory and theoretical modeling of free convective heat transfer in a horizontal layer heated from below and cooled from above.

Numerical studies of the advective flow of heptadecane in a horizontal layer with a longitudinal temperature gradient at the lower boundary

Numerical studies of the convective flow of heptadecane in a horizontal layer with a suddenly applied longitudinal temperature gradient at the lower high-thermal conductivity boundary have been carried out by the finite element method. A system of nonstationary dimensionless equations of free convection containing stream function, velocity vortex, and temperature as variables was solved. The calculations were carried out with a free upper boundary with and without taking into account the influence of the thermocapillary effect.

Experimental study of heat transfer during boiling in a thin layer of liquid on surfaces with structured porous coatings

The paper presents the results of the study of evaporation and boiling in a thin horizontal layer of liquid on microstructured surfaces in a wide range of changes in pressure. It is found that the thermal conductivity of materials of microstructured surfaces significantly affects the mechanism of steam removal from the pores and circulation of liquid along the heat transfer surface. It is determined that the pressure change leads to three regimes of heat transfer: evaporation, transition regime, and bubble boiling. The lowest values of the heat transfer coefficients and CHF were obtained in the transition regime; the highest ones were obtained in the bubble regime on both surfaces. Due to the higher thermal conductivity, the higher heat transfer coefficients and CHF were obtained on the bronze coating than on stainless steel over the entire pressure range.

The effect of controlled vibrations on Rayleigh-Benard convection

The paper presents the results of a numerical study of convective heat transfer in a long horizontal layer heated from below with and without the vibration effect of the lower wall. The simulation was carried out on the basis of solving the Navier-Stokes 2D equations for an incompressible fluid in the Boussinesq approximation. It is shown that the influence of vibrations of the lower heated wall on the wave number of the convective flow roll structure, on the time and on the critical Rayleigh number of convection. The influence of controlled harmonic vibrations of wall on the structure of convective flow in the Rayleigh-Benard problem has been investigated. It is shown that the wave number of the periodic convective structure, the critical Rayleigh number, and the time of occurrence of Rayleigh-Benard convection under the vertical vibration effect on the horizontal layer from the lower wall are reduced.

The onset of magnetic nanofluid convection because of selective absorption of radiation

This article reports a linear stability analysis of the onset of convection stimulated by selective absorption of radiation in a horizontal layer of magnetic nanofluid (MNF) under the impact of an external magnetic field. The Chebyshev pseudospectral method is utilized to obtain the numerical solution for water-based magnetic nanofluids (MNFs). The confining boundaries of the magnetic nanofluid layer are considered to be rigid–rigid, rigid–free, and free–free. The results are derived for two different conditions, viz., when the system is heated from the below and when the system is heated from the above. It is observed that an increase in the value of the Langevin parameter , diffusivity ratio and a decrease in the value of nanofluid Lewis number , the parameter which represents the impact of selective absorption of radiation and modified diffusivity ratio delays the onset of MNF convection for both the two configurations. Moreover, as the value of concentration Rayleigh number increases, the convection commences easily when the system is heated from the below, whereas the onset of MNF convection gets delayed as the system is heated from the above.

Studies on compressive strength of sandy clay soil samples with different percentages of lime and nylon fibres

To develop economically feasible and durable methods of ground improvement are some of the major challenges faced by geotechnical engineers. Many commonly available stabilisers like lime, fly ash, rice husk ash has been used in many studies. These stabilisers are known to improve the compressive strength of soil. But in order to improve the tensile properties of soil and increase the ductility characteristics, fibres can be included along with the commonly used stabilisers. In this paper values of compressive strength of sandy clay soil treated with different concentrations of lime and nylon fibre is studied and compared with the values of untreated native soil. The compressive strength of soil increases with increase in lime content up to 10%. The compressive strength of soil also increases with nylon fibre inclusion up to a concentration of 0.3%. With further increase in nylon fibre content, compressive strength decreases in the studied samples. In the present study the difference in the increase in compressive strength shown by composites with random and horizontal layers of nylon fibres as inclusions appears to be very small. The present study concludes that a combination of lime and nylon fibre can be a better stabilizer for ground improvement. Keywords—unconfined compressive strength, lime, horizontal layer, nylon fibre

Oscillatory Bifurcations in Porous Layers with Stratified Porosity, Driven by Each Coefficient of the Spectrum Equation

The onset of oscillatory bifurcations in a porous horizontal layer L, uniformly rotating about a vertical axis, with vertically stratified porosity, heated from below and salted from above and below, is investigated. Denoting by Pi,(i=1,2), the Prandtl numbers of the salt Si salting L from below (i=1) and above (i=2) respectively, it is shown that: (i) in L the oscillatory bifurcations can occur only if one of the structural conditions P1>1,P2<1 or P1=1,P2<1 or P1>1,P2=1 is verified; (ii) exists a bound R¯2 for the Rayleigh number R2 of S2 such that R2<R¯2 guarantees the absence of cold convection; (iii) via a new approach based on the instability power of each coefficient of the spectrum equation, criteria of existence, location and frequency of oscillatory (Hopf) bifurcations are furnished for any porosity stratification law. These criteria, as far as we know are, for the case at stake, the first criteria of Hopf bifurcations appearing in literature. We are confident that, via experimental results, will be validated.