Isolation of microparticles and biological cells from mixtures and suspensions is a central problem in a variety of biomedical applications. This problem, for instance, is of an immense importance ...for microfluidic devices manipulating with whole blood samples. It is instructive to know how the mobility and dynamics of rigid microparticles is altered by the presence of micrometer-size roughness on walls. The presented theoretical study addresses this issue via computer simulations. The approach is based on a combination of the Lattice Boltzmann method for calculating hydrodynamics and the Lagrangian Particle dynamics method to describe the dynamics of cell membranes. The effect of the roughness on the mobility of spheroidal microparticles in a shear fluid flow was quantified. We conclude that mechanical and hydrodynamic interactions lift the particles from the surface and change their mobility. The effect is sensitive to the shape of particles.
We show that an electro-osmotic flow near the slippery hydrophobic surface depends strongly on the mobility of surface charges, which are balanced by counterions of the electrostatic diffuse layer. ...For a hydrophobic surface with immobile charges, the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges, it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this, we formulate electrohydrodynamic boundary conditions at the slipping interface, which should be applied to quantify electro-osmotic flows instead of hydrodynamic boundary conditions. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new interpretation of zeta potential of hydrophobic surfaces.
Issues associated with the lack of promptness and accuracy of nondestructive testing (NDT) methods for determining the diffusion coefficient in thin porous materials are studied. Since the ...calibration of diffusant concentration transducers in a porous material takes a long time, the productivity of research on the diffusion coefficient is low when using conventional methods. The authors examine two methods enabling determination of the diffusion coefficient without the actual static characteristic of the used diffusant concentration transducer. The first method relies on recording the time point that corresponds to the maximum concentration of the diffusant following pulse application. When determining the target coefficient via the second method, it is possible to select two identical values of the transducer output characteristic following the pulse application with the recording of corresponding time points. The specified methods are compared. The errors in determining the target coefficient are studied under comparable conditions using both methods. The paper also analyzes the possibility of reducing the resulting error of Method II by selecting quantities included in the calculation expression. The study results can be useful in the production and use of items made of porous materials.
A brief description of scientific program and papers of International Conference "Physics of Dispersed Media for Electronics and IT devices" is presented. It is an annual conference of Moscow Region ...State University (MRSU).
The work is devoted to the study of a MEMS resonator dynamics under the action of phase-locked and automatic gain control loops. Particular attention is directed to the study of the nonlinearity ...factor of the resonator elastic restoring force. It was found that the determination of control system parameters based on the stability analysis of the operating resonant mode, in the general case, does not provide the required phase adjustment and stabilization of the oscillation amplitude. Stable multifrequency modes of oscillations are found, and an analytical study of the mechanisms of their appearance and evolution is carried out under variation of the key parameters of the system. The real regions of the control system stable operation are determined (which do not coincide, as was found, with the regions of stability of the operating resonant mode, due to the presence of hidden attractors in the phase space of the system). A methodology has been developed for identifying such areas of stable operation. A significant complication of the structure of possible motions in the system with an increase in the Q-factor of the resonator is revealed.
The results of studying the spatial structure of the plasma flows that appear when a laser pulse of relativistic intensity (above 10
18
W/cm
2
) is incident on the surface of a solid target are ...presented. The ring structure experimentally observed in the cross section of a plasma flow is shown to correspond to the toroidal equilibrium plasma configuration that appears in the strong magnetic fields of laser plasma. A model is proposed to describe astrophysical current jets consisting of a discrete sequence of toroidal equilibrium plasma structures.
The pathogenesis of malocclusions, which are common among the population of all countries, is well represented in the professional literature. The occurrence of malocclusions is associated with ...genetic and various environmental factors. Among the latter, fluorides which affect the prevalence of some dental diseases are of particular interest. However, there are few publications reflecting the frequency of malocclusion among the population in the regions with different levels of fluoride in drinking water. This problem seems to be significant in the context of the increasing impact of fluorine compounds on human health, including dental health.
The aim of the study.
To analyze the literature on the frequency of malocclusion among the population living in conditions of variable fluoride content in drinking water. A manual search of domestic and foreign literature was performed in the search databases PubMed, Medline and Google Scholar. From the initial list of publications, eighteen articles that met the inclusion criteria for the study were selected for analysis. We revealed significant variability of the research results. Some authors note a higher prevalence of malocclusions among the population under conditions of increased fluoride intake, others note a lower one, and still others did not reveal any differences between the values obtained in both samples. Most of the assessed publications did not methodologically meet modern international standards, and therefore were of little evidence.
The literature data do not provide grounds for an unambiguous assessment of fluorine compounds as an environmental factor that indirectly affects the process of occlusion formation in humans and animals.
The review did not allow to make a definitive conclusion on the possible impact of systemic fluorides on the prevalence and pattern of malocclusion in humans and animals. It requires the implementation of studies that comply with the principles of evidence-based medicine.
This study deals with an assessment of radiation dose dynamics to fish and higher aquatic plants (helophytes) in Glyboke Lake (10-km exclusion zone) during the early phase of the Chernobyl accident. ...Models of radioactive contamination of water and sediment and models of radioactive contamination and radiation dose to fish and aquatic plants were developed. It was found that, in 1986, the total dose rate to fish reached 0.25 Gy d−1. Within 6 months after the accident, the dose rate due to 90Sr, 134Cs and 137Cs had increased. The absorbed dose to prey fish of Glyboke Lake for this period was estimated as being 27–81 Gy of which 4–40 Gy was formed by 131I exposure. The radiation dose rate due to 90Sr, 106Ru, 134+137Cs and 144Ce to aquatic plants reached its quasi-equilibrium values approximately 50 days after the accident and remained virtually unchanged until the end of the 1986 growing season. The highest levels of 89Sr, 91Y, 95Zr, 103Ru, 141Ce exposure were observed between 30 and 50 days with a decrease by 2–3 times at the end of the growing season. Radiation exposure of the short-lived 131I, 140Ba, 140La, 239Np reached its maximum within 5–15 days after the accident. The absorbed dose rate to aquatic plants reached 0.69 Gy d−1, while the contribution of cerium radionuclides to the total dose rate formed 50% in the initial period and reached 90% at the end of the growing season. The magnitude of the radiation dose rate to plant roots was 2.4 times higher than aboveground organs, and that of rhizomes was 1.6 times higher. During the growing season of 1986 the total dose of exposure of plants in Glyboke Lake was about 78 Gy. The results of this study emphasise the necessity to consider the history of exposure of past generation of living organisms as part of the assessment of current radiation effects.
•Dynamics of radiation dose to aquatic biota during the early phase of the Chernobyl accident in lake of the Exclusion Zone was estimated.•During 6 months after accident the contribution of external exposure to the total dose of aquatic biota did not exceed 5%.•During 6 months after accident the highest radiation dose rate to fish in lake was 0.25 Gy d−1, and the total dose - 27–81 Gy.•During the growing season of 1986 the highest radiation dose rate to aquatic plants in lake was 0.69 Gy d−1, and total dose - 78 Gy.
A full set of the energy characteristics describing dissociation (
D
o
(Sr–OH) = 401.8 ± 3.0 kJ/mol), ionization (
I
o
(SrOH) = 5.372 ± 0.042 eV), and radiation power in the visible spectrum where ...the brightest bands with momenta
R
e
(au) of transitions
A
2
Π →
X
2
Σ (2.08 ± 0.15) and
B
2
Σ →
X
2
Σ (1.79 ± 0.13) are located is determined for strontium monohydroxide via spectrophotometry, and from a physical model.
The treatment of tuberculosis is still a challenging process due to the widespread of pathogen strains resistant to antibacterial drugs, as well as the undesirable effects of anti-tuberculosis ...therapy. Hence, the development of safe and effective new anti-antitubercular agents, in addition to suitable nanocarrier systems, has become of utmost importance and necessity. Our research aims to develop liposomal vesicles that contain newly synthesized compounds with antimycobacterial action. The compound being studied is a derivative of imidazo-tetrazine named 3-(3,5-dimethylpyrazole-1-yl)-6-(isopropylthio) imidazo 1,2-b 1,2,4,5 tetrazine compound. Several factors that affect liposomal characteristics were studied. The maximum encapsulation efficiency was 53.62 ± 0.09. The selected liposomal formulation T8* possessed a mean particle size of about 205.3 ± 3.94 nm with PDI 0.282, and zeta potential was + 36.37 ± 0.49 mv. The results of the in vitro release study indicated that the solubility of compound I was increased by its incorporation in liposomes. The free compound and liposomal preparation showed antimycobacterial activity against Mycobacterium tuberculosis H
R
(ATCC 27294) at MIC value 0.94-1.88 μg/ml. We predict that the liposomes may be a good candidate for delivering new antitubercular drugs.
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