Equilibrium sedimentation profiles of charged colloidal suspensions

We investigate the sedimentation equilibrium of a charge stabilized colloidal suspension in the regime of low ionic strength. We analyze the asymptotic behaviour of the density profiles on the basis of a simple Poisson--Boltzmann theory and show that the effective mass we can deduce from the barometric law corresponds to the actual mass of the colloidal particles, contrary to previous studies.Comment: 13 pages, 4 figures, 1 tabl

An analytical analysis of vesicle tumbling under a shear flow

Vesicles under a shear flow exhibit a tank-treading motion of their membrane, while their long axis points with an angle < 45 degrees with respect to the shear stress if the viscosity contrast between the interior and the exterior is not large enough. Above a certain viscosity contrast, the vesicle undergoes a tumbling bifurcation, a bifurcation which is known for red blood cells. We have recently presented the full numerical analysis of this transition. In this paper, we introduce an analytical model that has the advantage of being both simple enough and capturing the essential features found numerically. The model is based on general considerations and does not resort to the explicit computation of the full hydrodynamic field inside and outside the vesicle.Comment: 19 pages, 9 figures, to be published in Phys. Rev.

INDICATION AND IDENTIFICATION OF SPORE-FORMING BACTERIA WITH PROBIOTIC POTENCY

З фекалій здорових підсвинків та об'єктів зовнішнього середовища рутинними методами були ізольовані 12 культур сінних бацил у чистому вигляді та вивчені їх основні біологічні властивості. При цьому тільки дві культури були повністю апатогенні, у них були відсутні ферменти патогенності - гемолізини та лецитіназа, а при зараженні, у лабораторних тварин інфекційна патологія не розвивалась.Культури бацил володіли типовими для виду морфо-тинкторіальними, культуральними та біохімічними властивостями, на підставі чого згідно короткого визначника бактерій Берджі були ідентифіковані як Bacillus subtilis і зареєстровані як штами BI-9 і BI-12. Культури депоновані і проводиться процедура патентування та паспортизації.Депоновані штами сінних бацил проявили виражену антагоністичну активність щодо широкого кола патогенних і умовно-патогенних мікроорганізмів та можуть бути використані як основа для створення пробіотичних препаратів.Из фекальных масс и объектов внешней среды рутинными методами были изолированы 12 культур сенных бацилл в чистом виде и изучены их основные свойства. При этом только две культуры были полностью апатогенны, а именно у них отсутствовали ферменты патогенности – гемолизины и лецитиназа, и при заражении лабораторных животных не возникала инфекционная патология.Культуры бацилл обладали типичными для вида морфо-тинкториальными, культуральными и биохимическим свойствами, на основании чего согласно ключа краткого определителя бактерий Берджи были идентифицированы как Bacillus subtilis и зарегистрированы как штаммы BI-9 и BI-12. Культуры депонированы и проводится процедура патентования и паспортизации.Депонированные штаммы сенных бацилл проявили выраженную антагонистическую активность в отношении широкого круга патогенных и условно-патогенных микроорганизмов и могут быть использованы как основа для создания пробиотических препаратов.Of fecal and environmental objects routine methods were isolated 12 culture bacillus in pure form and study their basic properties. However, only two crops were completely nonpathogenic, namely they have no enzymes pathogenicity - hemolysin and lecithinase, and infection of laboratory animals emerging infectious pathology.Culture bacilli had typical type of morpho-tinctorial, cultural and biochemical properties, whereby according to a key determinant of short Burgi bacteria were identified as Bacillus subtilis strains and registered as BI‑9 and BI-12. Culture deposited and held patents and certification procedure.Deposited strains hay bacillus showed pronounced antagonistic activity against a wide range of pathogenic and conditionally pathogenic microorganisms and can be used as a foundation for probiotics

New analytical progress in the theory of vesicles under linear flow

Vesicles are becoming a quite popular model for the study of red blood cells (RBCs). This is a free boundary problem which is rather difficult to handle theoretically. Quantitative computational approaches constitute also a challenge. In addition, with numerical studies, it is not easy to scan within a reasonable time the whole parameter space. Therefore, having quantitative analytical results is an essential advance that provides deeper understanding of observed features and can be used to accompany and possibly guide further numerical development. In this paper shape evolution equations for a vesicle in a shear flow are derived analytically with precision being cubic (which is quadratic in previous theories) with regard to the deformation of the vesicle relative to a spherical shape. The phase diagram distinguishing regions of parameters where different types of motion (tank-treading, tumbling and vacillating-breathing) are manifested is presented. This theory reveals unsuspected features: including higher order terms and harmonics (even if they are not directly excited by the shear flow) is necessary, whatever the shape is close to a sphere. Not only does this theory cure a quite large quantitative discrepancy between previous theories and recent experiments and numerical studies, but also it reveals a new phenomenon: the VB mode band in parameter space, which is believed to saturate after a moderate shear rate, exhibits a striking widening beyond a critical shear rate. The widening results from excitation of fourth order harmonic. The obtained phase diagram is in a remarkably good agreement with recent three dimensional numerical simulations based on the boundary integral formulation. Comparison of our results with experiments is systematically made.Comment: a tex file and 6 figure

Wetting on Nanorough Surfaces

We present in this Letter a free-energy approach to the dynamics of a fluid near a nanostructured surface. The model accounts both for the static phase equilibrium in the vicinity of the surface (wetting angles, Cassie-Wenzel transition) and the dynamical properties like liquid slippage at the boundary. This method bridges the gap between phenomenological phase-field approaches and more macroscopic lattice-Boltzmann models

Clinical Aspects of Combination of Ceramic and Acrylic Occlusal Surfaces

The objective of the research was to develop and substantiate the methods of constructing the occlusal surfaces when manufacturing aesthetic fixed restorations through the combination of different materials.Materials and methods. The study included 65 patients with ceramic and acrylic occlusal surfaces of aesthetic fixed dental prostheses. Group I included 21 patients with a combination of ceramic and acrylic occlusal surfaces. Group II included 22 patients with a combination of ceramic occlusal surfaces. Group III included 22 patients with a combination of acrylic occlusal surfaces. The patients were observed 3, 6 and 12 months after prosthetic repair.Results. The greatest increase in the occlusal contact surface area of fixed restorations was observed in Group I, that is, when combining dental prostheses with ceramic and acrylic occlusal surfaces. Considering uneven abrasion of the occlusal surfaces, we do not recommend to combine different materials when veneering the occlusal surface of the antagonistic teeth.Conclusions. This study demonstrated the important role of the correct combination of materials when veneering the occlusal surfaces. Physical and chemical properties of materials, namely the abrasion resistance play a significant role in the long-term denture functioning.The smallest increase in the occlusal contact surface area was observed in Group II when combining ceramic occlusal surfaces. It was due to a good abrasion resistance of ceramics as compared to acrylic resin as well as the presence of the glazed layer which prevents the premature abrasion of the occlusal surfaces of the antagonistic teeth due to lower surface roughness.The combination of acrylic resin and ceramics when constructing the occlusal surfaces of fixed restorations in Group I demonstrated the highest rate of the increase in the occlusal contact surface area – 9.93%. It was due to a low hardness of acrylic resin and its high surface roughness. In addition, there was observed an uneven abrasion of the occlusal surfaces resulting in periodontal tissue overload, thereby negatively affecting denture functioning

Quality Assessment of Prosthetic Rehabilitation Using Aesthetic Fixed Restorations

The objective of the research was to study and assess the quality of prosthetic treatment using aesthetic fixed restorations.Materials and methods. The study included 79 patients without a comorbidity who underwent prosthetic rehabilitation. All the patients were divided into 3 groups: Group I included 25 patients with metal-plastic restorations; Group II comprised 34 patients with porcelain-fused-to-metal restorations; Group III consisted of 20 patients with a combined occlusal surface of prosthetic restorations. The patients were observed 6 months after prosthetic repair. Only patients with single molar and premolar crowns were examined. Bridge prostheses were not taken into account in order to eliminate the effect of masticatory force redistribution on the abutment crowns.Results. In Group I, 11 (44%) patients were satisfied with the results of prosthetic treatment. In Group II, 25 (78.12%) patients reported that they were satisfied with their treatment. In Group III, there were 17 (85%) patients satisfied with their outcome. However, the patients’ complaints are often subjective and do not fully reflect the objective state of the dentoalveolar system. An objective examination revealed that in indirect restorations, marginal periodontium pathology is typical. Conclusions. Aesthetic fixed restorations with a combined occlusal surface have demonstrated good clinical results, even at long-term follow-up. Combining positive properties of two different construction materials, namely zirconium dioxide and ceramics, they reduce the risk of complications such as marginal periodontium pathology and chipping along the occlusal surface as well as contribute to minimal abrasion of the occlusal surfaces of the antagonistic teeth. We cannot recommend metal-plastic restorations due to their low clinical effectiveness, poor aesthetic qualities as well as a high level of marginal periodontium pathology

Clinical Effectiveness of Using Aesthetic Fixed Prosthetic Appliances with Combined Occlusal Surface

The objective of the research was to evaluate the clinical effectiveness of using aesthetic fixed prosthetic appliances with combined occlusal surface.Materials and methods. The study included 30 patients who were divided into 2 groups: Group I included 20 patients with combined occlusal surface of the crowns; Group II included 22 patients with ceramic occlusal surface of the crowns. The patients were observed 3, 6 and 12 months after prosthetic repair.Results. 6 months after prosthetic repair, the occlusal contact surface area in Group I increased by 0.79%, while in Group II, it increased by 1.4%.12 months after prosthetic repair, the occlusal contact surface area in Group I and Group II increased by 2.37% and 5%, respectively.The aforementioned data indicated that the occlusal contact surface area increased as the period of ceramic fixed prosthetic appliance wearing increased.When combining the occlusal surface in dental prostheses, the occlusal contact surface area increased approximately 2 times slower. The study demonstrated convincingly that crowns burnt on a zirconium dioxide frame were a better choice as compared to cast framework made of nickel-cobalt-chrome alloy. In case of cast frameworks, the indicators of crown margin discrepancy were worse than in case of milled frameworks - 15% versus 5%, respectively. In addition, one cast framework crown (5%) in Group II was remodeled and one crown (5%) was recemented.Conclusions. Aesthetic fixed prosthetic appliances with combined occlusal surface demonstrated high functional and aesthetic characteristics. The use of the USHPS system showed a decisive advantage of milled frameworks and combined occlusal surface over traditional cast ceramic frameworks.The combination of high mechanical, strength and tribological properties of zirconium dioxide and high biological as well as aesthetic properties of ceramic materials helped reveal high clinical characteristics of aesthetic appliances with combined occlusal surface.