210Pb-Derived Bioturbation Rates in Sediments Around Seamounts in the Tropical Northwest Pacific

To evaluate bioturbation coefficients (DB) and mixing depths (L), 210Pb and 226Ra activity was measured in two sediments cores (from water depths of 5,398 m and 4,428 m), which were collected from seamount areas in the Northwest Pacific. Using a steady-state diffusion mode, we estimated DB values of 16.8 and 24.1 cm2/a, higher than those in abyssal sediments and those predicted by traditional empirical equations. Corresponding L values varied between 19.3 and 23.1 cm. These high values indicate that seamounts are the area of active bioturbation. A one-dimensional model for the transport of total organic carbon (TOC) from the surface layer of sediments to the deep layer was developed using the distribution pattern of the specific activity of excess 210Pb (210Pbex) and its relationship with TOC. The model showed that the TOC flux transmitted downward by bioturbation was 0.09 mmol/(cm2⋅a) and 0.12 mmol/(cm2⋅a).

Study of the diffusion process in films sodium salt of carboxymethyl cellulose – drug

The transport properties of medicinal films based on sodium salt of carboxymethylcellulose and the antibiotic amikacin sulfate have been studied in this work. It has been shown that the process of sorption of water vapor by such films and the release of a drug from them proceeds in an abnormal diffusion mode, which is explained by the slowdown of relaxation processes in glassy polymers, which include the sodium salt of carboxymethylcellulose. An increase of the amount of the introduced drug is accompanied by a regular decrease in the diffusion coefficients of both the process of sorption of water vapor and the release of amikacin from the films. It is noted that the formed films of sodium salt of carboxymethylcellulose-amikacin sulfate dissolve in water during the day and do not provide a prolonged release of the drug. To reduce the solubility of the films in water, the surface modification of the polymer film with calcium chloride has been carried out. It has been found that the modification does not lead to a change in the diffusion mode, but is accompanied by a regular change in the diffusion coefficients – the longer the formed films were kept in a calcium chloride solution, the lower the diffusion coefficients of the sorption of water vapor by medicinal films and the diffusion coefficients of the release of the drug amikacin from the film. It is argued that the surface modification of polymer films based on the sodium salt of carboxymethylcellulose is an effective way of imparting to them the effect of prolonging the release of a drug.

Aluminum diffusion during laser-stimulated crystallization of thin silicon films

Diffusion of aluminum in amorphous silicon films during crystallization through infrared laser irradiation was studied. Diffusion regime was found to change from limited source to abundant source diffusion at higher laser source power. At the same time, crystalline structure of the obtained samples becomes more perfect, which is more characteristic to limited source diffusion mode.

Effective field theory for hydrodynamics without boosts

We formulate the Schwinger-Keldysh effective field theory of hydrodynamics without boost symmetry. This includes a spacetime covariant formulation of classical hydrodynamics without boosts with an additional conserved particle/charge current coupled to Aristotelian background sources. We find that, up to first order in derivatives, the theory is characterised by the thermodynamic equation of state and a total of 29 independent transport coefficients, in particular, 3 hydrostatic, 9 non-hydrostatic non-dissipative, and 17 dissipative. Furthermore, we study the spectrum of linearised fluctuations around anisotropic equilibrium states with non-vanishing fluid velocity. This analysis reveals a pair of sound modes that propagate at different speeds along and opposite to the fluid flow, one charge diffusion mode, and two distinct shear modes along and perpendicular to the fluid velocity. We present these results in a new hydrodynamic frame that is linearly stable irrespective of the boost symmetry in place. This provides a unified covariant stable approach for simultaneously treating Lorentzian, Galilean, and Lifshitz fluids within an effective field theory framework and sets the stage for future studies of non-relativistic intertwined patterns of symmetry breaking.

Lipid tracking at kilohertz sampling rates on live cell membranes through Interferometric Scattering microscopy

The lateral dynamics of lipids on the cellular membranes are one of the most challenging topics to study in membrane biophysics, needing simultaneously high spatial and temporal resolution. In this study, we have employed Interferometric scattering Microscopy (ISCAT) to explore the dynamics of a biotinylated lipid analogue labelled with streptavidin-coated gold nanoparticles (20 and 40nm in diameter) at 2kHz sampling rate. We developed a statistics-driven analysis pipeline to analyse both ensemble average and single trajectory Mean Squared Displacements from each dataset, and to discern the most likely diffusion mode. We found that the use of larger tags slows down the target motion without affecting the diffusion mode. Moreover, we determined from our statistical analysis that the prevalent diffusion mode of the tracked gold-labelled lipids is compartmentalized diffusion. This model describes the motion of particles diffusing on a corralled surface, with a certain probability of changing compartment. This is compatible with the picket-fence model of membrane structure, already observed by similar studies. Through our analysis, we could determine significant physical parameters, such as average compartment size, dynamic localization uncertainty, and the intra- and inter-compartmental diffusion rates. We then simulated diffusion in an environment compatible with the experimentally-derived parameters and model. The closeness of the results from the analysis of experimental and simulated trajectories validates our analysis and the proposed description of the cell membrane. Finally, we introduce the confinement strength metric to compare diffusivity measurements across techniques and experimental conditions, which we used to successfully compare the present results with other related studies.

Computational analysis on the stability and characteristics of partially premixed butane air open flames in tubular burner

Partially premixed combustion is one of the developing areas of combustion research that has the advantages of both premixed and diffusion mode of combustion. The present work involves a computational study on the stability and characteristics of partially premixed butane-air flames. The effect of operating parameters like fuel-air ratio, primary aeration, and the presence of co-flow and co-swirl on the stability and flame characteristics has been studied. The simulation results show that the height of the flame decreases with an increase in primary aeration and also in the presence of a co-swirl stream. It has also been found that the stability of flames increases with co-swirl air but deteriorates with the presence of the co-flow air. The flame temperature increases with primary aeration and it has been observed that the peak flame temperature shifts away from the burner mouth for lower primary aeration. It has been observed that the flame stability improves with co-swirl air which is attributed to the recirculation zone created due to the swirl motion which acts as a heat source. The poor stability in the presence of co-flow air is attributed to flame stretching and aerodynamic quenching of the stretched flame lets. The lift off velocity and the stable operating range increases with equivalence ratio and also with co-swirl air.

Evaluation of the Porosity of a Coke Particle According to Its Combustion Data

The dependence of the density of a porous coke particle on its diameter at the particle combustion in the external diffusion mode is analyzed. It is shown that, for the large values of the internal diffusion-kinetic ratio, Sev > 5, the required dependence can be obtained in the analytic form. The analytic formulas are found to be different for the bulk and Knudsen diffusion modes inside the pores. A graphical comparison of the obtained dependences with the empirical power-law dependence is carried out to evaluate the power exponents in the analytic dependences. The corresponding results make it possible to evaluate the effective specific surface area of the pores.

Displacement of Slow-Turnover DNA Glycosylases by Molecular Traffic on DNA

In the base excision repair pathway, the initiating enzymes, DNA glycosylases, remove damaged bases and form long-living complexes with the abasic DNA product, but can be displaced by AP endonucleases. However, many nuclear proteins can move along DNA, either actively (such as DNA or RNA polymerases) or by passive one-dimensional diffusion. In most cases, it is not clear whether this movement is disturbed by other bound proteins or how collisions with moving proteins affect the bound proteins, including DNA glycosylases. We have used a two-substrate system to study the displacement of human OGG1 and NEIL1 DNA glycosylases by DNA polymerases in both elongation and diffusion mode and by D4, a passively diffusing subunit of a viral DNA polymerase. The OGG1–DNA product complex was disrupted by DNA polymerase β (POLβ) in both elongation and diffusion mode, Klenow fragment (KF) in the elongation mode and by D4. NEIL1, which has a shorter half-life on DNA, was displaced more efficiently. Hence, both possibly specific interactions with POLβ and nonspecific collisions (KF, D4) can displace DNA glycosylases from DNA. The protein movement along DNA was blocked by very tightly bound Cas9 RNA-targeted nuclease, providing an upper limit on the efficiency of obstacle clearance.

The Determination of Radon Diffusion Coefficient and Radon Speed Advection in the Conditions of Instantaneous Source with Diffusion-Advective Transfer in Rocks

Experimental determination of diffusion parameters in the upper part of geological section (presented by clayey weathering crust) was made by a point instantaneous source method in a diffusion mode and a linear instantaneous source diffusion-advective mode. The results obtained by these methods showed a fairly good coincidence of the obtained diffusion characteristics of the medium. The time to determine the diffusion characteristics of the medium is significantly reduced by more than an order of magnitude when using the advective method. This is a prerequisite for the widespread use of methods for determining radon hazard based on measurements of the vertical distribution of radon volume activity in the upper part of the geological section.