How Flow Changes Polymer Depletion in a Slit

A theoretical model is developed for predicting dynamic polymer depletion effects under the influence of fluid flow. The results are established by combining the two-fluid model and the self-consistent field theory. We consider a uniform fluid flow across a slit containing a solution with polymer chains. The two parallel and infinitely long walls are permeable to solvent only and the polymers do not adsorb to these walls. For a weak flow and a narrow slit in Theta-solvent conditions, an analytic expression is derived to describe the steady state polymer concentration profiles. In both Theta- and good-solvents, we compute the time evolution of the concentration profiles for various flow rates characterized by the Peclet number. The model reveals the interplay of depletion, solvent condition, slit width, and relative strength of the fluid flow.Comment: 12 pages, 12 figure

Система единого генератора

Выдвигается принципиально новая идея синхронизации частот управления передающего и приемного устройств. В случае ее практической реализации может быть достигнуто значительное повышение эффективности новых (модернизированных) систем информационного комплекса при значительном снижении его себестоимости. Представленные соображения могут быть рассмотрены именно в качестве идеи, при положительной оценке которой потребуется разработка оптимальных путей реализации комплекса в целом, отдельных его составляющих и методов реализации.Висувається принципово нова ідея синхронізації частот управління передавального і приймального пристроїв. У разі її практичної реалізації може бути досягнуто значне підвищення ефективності нових (модернізованих) систем інформаційного комплексу при значному зниженні його собівартості. Представлені міркування можуть бути розглянуті саме як ідея, при позитивній оцінці якої потрібна буде розробка оптимальних шляхів реалізації комплексу в цілому, окремих його складових і методів реалізації.Suggested in the article is a brand new concept of the synchronization of control frequencies of the transmitting and receiving devices. In the case of its implementation a significant increase can be achieved in the efficiency of the new (upgraded) information systems while significantly reducing their cost. The presented considerations may be regarded merely as an idea, which being positively assessed will require the development of optimal ways to implement the system as a whole, its individual components and methods of implementation

Stochastic Interactions of Two Brownian Hard Spheres in the Presence of Depletants

A quantitative analysis is presented for the stochastic interactions of a pair of Brownian hard spheres in non-adsorbing polymer solutions. The hard spheres are hypothetically trapped by optical tweezers and allowed for random motion near the trapped positions. The investigation focuses on the long-time correlated Brownian motion. The mobility tensor altered by the polymer depletion effect is computed by the boundary integral method, and the corresponding random displacement is determined by the fluctuation-dissipation theorem. From our computations it follows that the presence of depletion layers around the hard spheres has a significant effect on the hydrodynamic interactions and particle dynamics as compared to pure solvent and pure polymer solution (no depletion) cases. The probability distribution functions of random walks of the two interacting hard spheres that are trapped clearly shifts due to the polymer depletion effect. The results show that the reduction of the viscosity in the depletion layers around the spheres and the entropic force due to the overlapping of depletion zones have a significant influence on the correlated Brownian interactions.Comment: 30 pages, 9 figures, 1 appendix, 40 formulas inside the text, 5 formulas in appendi

Оценка влияния противотурбулентной присадки на параметры течения транспортируемой нефти по магистральному трубопроводу

В работе определяется эффективность применения противотурбулентной присадки на участке магистрального нефтепровода.The paper determines the efficiency gains of the use of anti-turbulent additives in the section of the main oil pipeline

Fluid mechanics and bio-transport phenomena in imaging of biological membranes using AFM-integrated microelectrode

Ph.D.Committee Chair: Andrei G. Federo

Beliefs about aging and later life health and well-being among the elderly in Taiwan

textMost of the empirical research on later life well-being in Taiwan has focused on demographic, structural factors and resources flow, and tended to ignore the meaning and beliefs older Taiwanese assign to aging and the consequences. In light of dramatic social transformation and the changing nature of elderly support, the empirical test of the values and beliefs about later life and their effects may provide a significant viewpoint in understanding why some older adults in Taiwan are healthier and live longer than others. This project employs a national representative data drawn from the Survey of Health and Living Status of the Elderly in Taiwan in year 1996 and 1999. Beliefs about aging are conceptualized into several constructs and each is linked to three dimensions of health outcomes: physical health, mental health and mortality. In addition, I tested whether engagement in healthy habits, supportive social relationships, and greater involvement in social activities account for the associations. Results suggest that general higher levels of positive beliefs about aging are predictive of improved health and longevity over time. When I divide general beliefs into positive and negative domains, I find that positive beliefs improve health largely through life style factors. While, compared to positive beliefs, negative beliefs seem to exert stronger effects on health through pathways well beyond an individual's lifestyle. That is, pessimistic views on aging may be more detrimental to health because domains related to negative beliefs (e.g., "boredom and uselessness" and "financial insecurity") directly challenge an individual's desires to search for a sense of meaning, purpose and security later in life. Taken together, this study shows that positive beliefs about aging shape proactive behaviors and translate limited resources into opportunities, eventually leading to better health outcomes. In contrast, viewing aging in an unfavorable way may limit an individual's pursuit for a better life, and, in turn, impact health and well-being, regardless the actual resources possessed by the individuals. Therefore, this study suggests despite physically intact, generally active, and supportive relationships, the individual's subjective perception of aging is another important determinant in securing a healthy later life among elderly Taiwanese.Sociolog