Steady-state composition of a two-component gas bubble growing in a liquid solution: self-similar approach

The paper presents an analytical description of the growth of a two-component bubble in a binary liquid-gas solution. We obtain asymptotic self-similar time dependence of the bubble radius and analytical expressions for the non-steady profiles of dissolved gases around the bubble. We show that the necessary condition for the self-similar regime of bubble growth is the constant, steady-state composition of the bubble. The equation for the steady-state composition is obtained. We reveal the dependence of the steady-state composition on the solubility laws of the bubble components. Besides, the universal, independent from the solubility laws, expressions for the steady-state composition are obtained for the case of strong supersaturations, which are typical for the homogeneous nucleation of a bubble.Comment: 12 pages, 2 figure

Dynamics of gas bubble growth in a supersaturated solution with Sievert's solubility law

This paper presents a theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution. We study systems where gas molecules completely dissociate in the solvent into two parts, thus making Sievert's solubility law valid. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux is steady we obtain a differential equation on bubble radius. Bubble dynamics equation is solved analytically for the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop. We also obtain conditions of diffusion flux steadiness. The fulfillment of these conditions is studied for the case of nucleation of water vapor bubbles in magmatic melts.Comment: 22 pages, 3 figure

КОРЕКЦІЯ ПОТЕНЦІЙНО МОДИФІКОВАНИХ ФАКТОРІВ РИЗИКУ ПРИ ЛІКУВАННІ МЕТОДОМ ГЕМОДІАЛІЗУ: СТАНДАРТИ ЛІКУВАННЯ І ІНДИВІДУАЛЬНІ ДІАЛІЗНІ ПРОГРАМИ

In the effect prognosis of dialysis a possible adjustment of the modified potential death risk factors of patients who are on renal replacement therapy by hemodialysis techniques are discussed. The conclusions about the possibility of modern dialysis techniques to effectively influence on arterial hypertension of patients with chronic kidney disease stage 5 - D and the need for further study in order to develop treatment standards using mathematical models for individualised dialysis programs.Изучены возможности корректировки потенциально модифицированного фактора риска смерти пациентов, находящихся на заместительной почечной терапии, методиками проведения гемодиализа. Сделаны выводы о возможности современных диализных методик эффективно влиять на артериальную гипертензию больных с хроническойболезнью почек V Д стадии и необходимость дальнейшего их изучения с целью разработки стандартов лечения с применением математических моделей индивидуальных диализных программ.Для створення системи прогнозування ефективності гемодіалізу вивчено можливості коригування потенційно модифікованого фактора ризику смерті пацієнтів, які перебувають на замісній нирковій терапії, методиками проведення гемодіалізу. Зроблено висновки про можливість сучасних діалізних методик ефективно впливати на артеріальну гіпертензію хворих із хронічною хворобою нирок V Д стадії та необхідність подальшого їх вивчення з метою розроблення стандартів лікування із застосуванням математичних моделей індивідуальних діалізних програм

МОДИФІКАЦІЯ ФАКТОРІВ РИЗИКУ СЕРЦЕВО-СУДИННИХ УСКЛАДНЕНЬ В ПЛАНІ ОПТИМІЗАЦІЇ ЛІКУВАННЯ ХВОРИХ ІЗ ХРОНІЧНОЮ ХВОРОБОЮ НИРОК СЕАНСАМИ ПРОГРАМНОГО ГЕМОДІАЛІЗУ

The number of patients with chronic kidney disease (CKD) in substitution therapy sessions dialysis program in Ukraine is growing. Improvement of methods of renal replacement therapy (RRT), chronic kidney disease, in particular, the use of modern dialysis technology has led to a significant increase in the life expectancy of patients. However, the mortality of the disease remains high. In its structure heavily reliant on cardiovascular disease, according to the National registry of patients with chronic kidney disease in 2011 it was 72 %. In this regard, there is actual determination of risk factors for these complications and the search for new methods to ensure their prevention. The author studied the effect of individually tailored and standard hemodialysis treatment programs on the risk factors of cardiovascular complications in patients with CKD. It is concluded that the custom-fitted options at the time of hemodialysis and ultrafiltration properties klirensovyh dialyzer electrolyte composition of the dialysate can achieve better results in the management of risk factors in patients with CKD.про­граммного диализа в Украине, постоянно увеличивается. Усовершенствование методов почечной заместительной терапии (ПЗТ) хронической болезни почек, в частности использование современных диализных технологий, приве­ло к значительному увеличению продолжительности жизни пациентов. Вместе с тем, смертность от этого заболева­ния остается довольно высокой. В ее структуре значительное место занимают сердечно-сосудистые заболевания - по данным Национального реестра больных с хронической болезнью почек, в 2011 году она составила 72%. В этой связи становится актуальным определение факторов риска возникновения этих осложнений и поиск новых мето­дик, обеспечивающих их профилактику. Автором изучено влияние индивидуально подобранных и стандартных лечебных программ гемодиализа на факторы риска возникновения сердечно-сосудистых осложнений у больных с ХБП. Сделаны выводы о том, что индивидуально подобранные параметры по времени проведения гемодиализа, клиренсовых и ультрафильтрационных свойствах диализатора, электролитному составу диализирующего раствора позволяют достигать лучших результатов в коррекции факторов риска у пациентов с ХБП.Вивчено вплив індивідуально підібраних та стандартних лікувальних програм гемодіалізу на фактори ризику виникнення серцево-судинних ускладнень у хворих із хронічною хворобою нирок. Зроблено висновки про те, що індивідуально підібрані параметри по часу проведення діалізу, площі, кліренсових та ультрафільтраційних власти­востей діалізатора, електролітного складу діалізуючого розчину дозволяють отримувати кращі результати по ко­рекції потенційно модифікованих факторів ризику у пацієнтів з хронічною хворобою нирок, котрі лікуються сеан­сами програмного гемодіалізу

ПОРІВНЯЛЬНА ОЦІНКА ЯКОСТІ ЖИТТЯ ПАЦІЄНТІВ, ЯКІ ОТРИМУЮТЬ НИРКОВУ ЗАМІСНУ ТЕРАПІЮ, ПРИ ВИКОРИСТАННІ СТАНДАРТНИХ ТА ІНДИВІДУАЛЬНИХ ПРОГРАМ ЛІКУВАННЯ

Improvement of methods of renal replacement therapy (RRT), chronic kidney disease (CKD), in particular, the use of modern dialysis technology, the introduction into clinical practice of new methods of providing adequate and gentle treatment led to a significant increase in the life expectancy of patients. At the same time, comes to the fore the problem of quality of life (QOL) of patients. Therefore, the approach of QoL parameters in patients with CKD receiving RRT, to the level of a healthy population is one of the main goals of modern nephrology. In this context, it becomes urgent the choice of method and technique of dialysis. The author studied the basic parameters of the quality of life of patients receiving renal replacement therapy, their relationship to the method of dialysis. The conclusions about the need for further study of correlations uremic, hematological parameters with quality of life and the development of mathematical models of individual dialysis programs.Изучены основные параметры качества жизни пациентов с хронической болезнью почек (ХБП), получающих заместительную почечную терапию, их связь с методикой проведения диализа. Сделаны выводы о необходимости дальнейшего изучения корре­ляционных связей уремических, гематологических показателей с показателями качества жизни и разработки математических моделей индивидуальных диализных программ.Вивчено основні параметри якості життя пацієнтів із хронічною хворобою нирок (ХХН), які отримують замісну ниркову терапію, їх зв’язок із методикою проведення діалізу. Зроблено висновки про необхідність подальшого вивчення кореляційних зв’язків уремічних, гематологічних показників із показниками якості життя та розроблення математичних моделей індивіду­альних діалізних програм

Minor Pilins of the Type IV Pilus System Participate in the Negative Regulation of Swarming Motility

Pseudomonas aeruginosa exhibits distinct surface-associated behaviors, including biofilm formation, flagellum-mediated swarming motility, and type IV pilus-driven twitching. Here, we report a role for the minor pilins, PilW and PilX, components of the type IV pilus assembly machinery, in the repression of swarming motility. Mutating either the pilW or pilX gene alleviates the inhibition of swarming motility observed for strains with elevated levels of the intracellular signaling molecule cyclic di-GMP (c-di-GMP) due to loss of BifA, a c-di-GMP-degrading phosphodiesterase. Blocking PilD peptidase-mediated processing of PilW and PilX renders the unprocessed proteins defective for pilus assembly but still functional in c-di-GMP-mediated swarming repression, indicating our ability to separate these functions. Strains with mutations in pilW or pilX also fail to exhibit the increase in c-di-GMP levels observed when wild-type (WT) or bifA mutant cells are grown on a surface. We also provide data showing that c-di-GMP levels are increased upon PilY1 overexpression in surface-grown cells and that this c-di-GMP increase does not occur in the absence of the SadC diguanylate cyclase. Increased levels of endogenous PilY1, PilX, and PilA are observed when cells are grown on a surface compared to liquid growth, linking surface growth and enhanced signaling via SadC. Our data support a model wherein PilW, PilX, and PilY1, in addition to their role(s) in type IV pilus biogenesis, function to repress swarming via modulation of intracellular c-di-GMP levels. By doing so, these pilus assembly proteins contribute to P. aeruginosa\u27s ability to coordinately regulate biofilm formation with its two surface motility systems

Surface Attachment Induces Pseudomonas aeruginosa Virulence

Pseudomonas aeruginosa infects every type of host that has been examined by deploying multiple virulence factors. Previous studies of virulence regulation have largely focused on chemical cues, but P. aeruginosa may also respond to mechanical cues. Using a rapid imaging-based virulence assay, we demonstrate that P. aeruginosa activates virulence in response to attachment to a range of chemically distinct surfaces, suggesting that this bacterial species responds to mechanical properties of its substrates. Surface-activated virulence requires quorum sensing, but activating quorum sensing does not induce virulence without surface attachment. The activation of virulence by surfaces also requires the surface-exposed protein PilY1, which has a domain homologous to a eukaryotic mechanosensor. Specific mutation of the putative PilY1 mechanosensory domain is sufficient to induce virulence in non-surface-attached cells, suggesting that PilY1 mediates surface mechanotransduction. Triggering virulence only when cells are both at high density and attached to a surface—two host-nonspecific cues—explains how P. aeruginosa precisely regulates virulence while maintaining broad host specificity

A Three-Component Regulatory System Regulates Biofilm Maturation and Type III Secretion in Pseudomonas aeruginosa

Biofilms are structured communities found associated with a wide range of surfaces. Here we report the identification of a three-component regulatory system required for biofilm maturation by Pseudomonas aeruginosa strain PA14. A transposon mutation that altered biofilm formation in a 96-well dish assay originally defined this locus, which is comprised of genes for a putative sensor histidine kinase and two response regulators and has been designated sadARS. Nonpolar mutations in any of the sadARS genes result in biofilms with an altered mature structure but do not confer defects in growth or early biofilm formation, swimming, or twitching motility. After 2 days of growth under flowing conditions, biofilms formed by the mutants are indistinguishable from those formed by the wild-type (WT) strain. However, by 5 days, mutant biofilms appear to be more homogeneous than the WT in that they fail to form large and distinct macrocolonies and show a drastic reduction in water channels. We propose that the sadARS three-component system is required for later events in biofilm formation on an abiotic surface. Semiquantitative reverse transcription-PCR analysis showed that there is no detectable change in expression of the sadARSgenes when cells are grown in a planktonic culture versus a biofilm, indicating that this locus is not itself induced during or in response to biofilm formation. DNA microarray studies were used to identify downstream targets of the SadARS system. Among the genes regulated by the SadARS system are those required for type III secretion. Mutations in type III secretion genes result in strains with enhanced biofilm formation. We propose a possible mechanism for the role that the SadARS system plays in biofilm formation

Seismic Performance of Slender C-Shaped Walls Subjected to UniI- and Bi-Directional Loading

Reinforced concrete structural walls are common as the primary lateral load resisting system in modern mid- and high-rise buildings constructed in seismic regions, yet few research programs have investigated the seismic performance of modern, slender walls with nonplanar cross-sectional geometries. Three large-scale, C-shaped wall specimens, designed per ACI 318-08, were tested under uni- and bi-directional loading at the University of Illinois at Urbana-Champaign (UIUC). This paper presents experimental results including the cyclic load-deformation response and measured versus nominal flexural/shear strengths as well as a description of damage sequence. Final failure occurs due to a flexure-tension failure of boundary elements where multiple previously buckled bars fracture. From these tests, it is possible to conclude that with respect to uni- versus bi-directionally loading C-shaped walls have similar strong-axis load-deformation response until 0.75% drift as well as effective flexure/shear stiffness; however, there is a notable reduction in strong-axis ductility due to bi-directional loading. When comparing C-shaped walls to planar walls, the C-shaped specimens exhibit a more ductile flexural-tension controlled response where wall flanges contribute significantly to carrying compressive loads. Additionally, wall flanges and boundary elements are noted to be critical to resisting shear demands after the lightly-reinforced wall web has deteriorated