Analysis and Comparison of Parallel Plate Flow Chambers to Determine Consistency of Fluid forces on Cells

Biological cells are constantly exposed to fluid forces inside the body. These fluid forces aid in certain physical and chemical reactions that cells need to maintain physiological function. To observe these forces in vitro, parallel plate flow chambers (PPFC) are used, where cells are placed inside the chamber and a fluid medium runs through the device exposing the cells to fluid forces to initiate a response. This has aided in proving that fluid forces influence cell function and are factors in various disease and physiological processes, such as the development of atherosclerotic plaque in blood vessels or bone growth. Many designs for PPFCs have been used for various types of flow and simulation protocols, such as computational fluid dynamics (CFD), have sometimes been used to determine flow characteristics and to model chamber performance under a specific use; however, nearly all of these chambers are modeled without the presence of biological cells. In this thesis, a CFD protocol was used (i.e., STAR-CCM+) to compare the fluid performance of the most commonly published PPFC designs and to determine how reliably they may expose cells to specifically controlled flow conditions. In addition to simulating the published conditions of each chamber, they were each simulated at a respective flow rate that theoretically yielded a shear stress of 10 dyne/cm2 in their flow channel. For all CFD models, a uniform mesh size of 100 µm was used and all CFD calculations were obtained through 1,000 iterations or until convergence occurred. Machining tolerance was also applied to one of the designs in order to observe the effects of machining inconsistencies that would not normally be modeled in an ideal simulation. In addition, this thesis simulated biological cells (endothelial cells) within an arbitrary parallel plate PPFC system, in order to determine the effects of their presence on parallel plate flow patterns. Shear stress and velocity distributions were calculated at 1 µm above the bottom surface of the flow channel and yielded similar distribution patterns across the test areas of the flow channels (i.e., area where cells are placed). In addition, the percentage of a consistent shear stress was calculated and found to be 97%, 81%, 36%, 98%, and 89%, respectively, across the test section of five commonly used PPFCs. The pressure along the length of each flow channel was also calculated and showed that each chamber has different levels of fluid pressure that biological cells are exposed to. It was also found that altering the height of chamber by 25 µm resulted in changes in shear stress that varied ±0.3 dyne/cm2 from the original height. The simulations of arbitrary PPFCs with the inclusion of biological cells proved that there is a significant variation of shear stress on the biological cells. Shear stress levels on the biological cells ranged from 50 to 250% of the target value (i.e., 10 dyne/cm2) and showed that what has been published by PPFC researchers has to be reassessed, since most publications presented results of simulations without biological cells. A better understanding of the fluid flow would help determine if this wide range of shear stress levels is acceptable to the particular biological cells being exposed. It would also aid in making improvements to PPFCs in order to more accurately simulate in vitro conditions. In designing these chambers and accurately analyzing them, biological cells must be included into the simulation as the exposure forces are different from the forces seen in a “clean” chamber that contains no cells. Utilization of CFD aided in providing numerical data for comparison of PPFC designs and allowed for a better understanding of the flow regions and how biological cells would be exposed to fluid forces. The results of this thesis reaffirmed the need to better understand the level, or range of levels, of shear stress and pressure that is needed in order to invoke a cellular response. In addition, there is a need to better understand the amount of surface area on a cell exposed to fluid shear that also invokes a cellular response, including the amount of the response. Finally, CFD can be used to optimize the design of a chamber so that the performance is reliable and meets the need of an individual, or general, application especially at the cellular level

Effect of wettability on hydrodynamics and mass transfer in small capillaries

The wettability of the reactor wall has a significant effect on the interfacial liquid–liquid mass transfer rates in segmented flow. This work quantitatively demonstrates the importance of choosing the right material of construction of flow reactors to achieve the desired mass transfer performance. Glass and PTFE capillaries of identical diameter were used to study the effect of hydrophilic and hydrophobic surfaces on the hydrodynamics and mass transfer of the system. It was observed that for the overall mass transfer coefficient (kLa) changed by two orders of magnitude depending on the wettability of the continuous phase. The observations indicated that it is essential to achieve complete wetting of the capillary walls by the continuous phase for significant mass transfer enhancement. The observations are discussed on the basis of film thickness and slip velocity at the wall as well as the slip velocity at liquid–liquid interface. Predictions of the mass transfer coefficient using a model based on the interfacial and fluid properties showed excellent match with the experiments thereby allowing us to explore the effects of wettability on the overall mass transfer coefficient in greater detail

Interpenetrating Polymer Networks as Binders for Solid Composite Propellants

A new family of polymeric binders for solid composite propellants is proposed, based on two component interpenetrating polymer networks (IPNs). These networks comprise two different polyurethanes based on hydroxy terminated polybutadiene and ISRO polyol interpenetrated with two different vinyl polymers, viz poly methyl methacrylate and polystyrene. the networks synthesized by the simultaneous interpenetrating technique have been characterized for their properties, such as stress-strain, density, viscosity, thermal degradation, and heat of combustion. Phase morphologies have been determined using electron microscopy. Suitable explanations have been adduced to rationalize the properties of IPNs in terms of their structures and chain interactions. A study of the mechanical properties and burning rates of the ammonium perchlorate (AP)-based solid propellant using the newly synthesised IPNs as binders, has been carried out. The results show that both mechanical strength and burning rate of solid propellants could be suitably modified by simply changing the nature and/or the ratio of the two interpenetrating polymer components

Pooling signals from vertically and non-vertically orientation-tuned disparity mechanisms in human stereopsis

AbstractTo understand the role that orientation-tuned disparity-sensitive mechanisms play in the perception of stereoscopic depth, we measured stereothresholds using two sets of random-dot stimuli that produce identical stimulation of disparity mechanisms tuned to vertical orientation but dissimilar stimulation of disparity mechanisms tuned to non-vertical orientations. Either 1 or 1.5D of astigmatic blur was simulated in the random-dot images presented to both eyes, using two axis configurations. In the parallel-axis conditions, the axis of simulated astigmatic blur was same in the two eyes (0, 45 or 135 o[rientation]deg). In the orthogonal-axis conditions, the axes of astigmatic blur were orthogonal in the two eyes (LE: 180, RE: 90; LE: 90, RE: 180; LE: 45, RE: 135; and LE: 135, RE: 45). Whereas the stimulation of disparity mechanisms tuned to near-vertical orientations should be similar in the oblique parallel- and orthogonal-axis conditions, the stimulation of non-vertically tuned disparity mechanisms should be dissimilar. Measured stereothresholds were higher in the orthogonal compared to the parallel-axis condition by factors of approximately 2 and 5, for 1 and 1.5D of simulated oblique astigmatic blur, respectively. Further, for comparable magnitudes of simulated astigmatic blur, stereothresholds in the (LE: 180, RE: 90 and LE: 90, RE: 180) conditions were similar to those in the (LE: 45, RE: 135 and LE: 135, RE: 45) conditions. These results suggest that the computation of horizontal disparity includes substantial contributions from disparity mechanisms tuned to non-vertical orientations. Simulations using a modified version of a disparity-energy model [Qian, N., & Zhu, Y. (1997). Physiological computation of binocular disparity. Vision Research, 37, 1811–1827], show (1) that pooling across disparity mechanisms tuned to vertical and non-vertical orientations is required to account for our data and (2) that this pooling can provide the spatial resolution needed to encode spatially changing horizontal disparities

The Diffusion of Scientific Knowledge across Time and Space

This chapter discusses the consequences of academic mobility and the extent to which the movement of high-achieving faculty members affects both scientific and commercialization activities at their old and new schools. It looks at articles published by, and patents granted to, the mobile scientist before they departed for the new school, comparing these to similar outputs by scientists who did not move. The heterogeneity that can distort simpler comparisons can be limited. The analysis suggests that the citations to a departing scientist's articles from the university where he or she departs are barely affected by the move. However, citations to the departing scientist's patents (whether made in articles or patents) decline sharply at the originating school. This suggests that the physical proximity of the researcher is important to ensuring knowledge flows to industry. Citations to the scientist's work at his or her new location increase dramatically once the move is complete. Barriers to scientific mobility may actually be socially detrimental, as they prevent the kind of knowledge gains from the mixing of ideas. Keywords: diffusion; scientific knowledge; professional transitions; academic mobility; physical proximity; researche

Public R&D Investments and Private-sector Patenting: Evidence from NIH Funding Rules

We quantify the impact of scientific grant funding at the National Institutes of Health (NIH) on patenting by pharmaceutical and biotechnology firms. Our article makes two contributions. First, we use newly constructed bibliometric data to develop a method for flexibly linking specific grant expenditures to private-sector innovations. Second, we take advantage of idiosyncratic rigidities in the rules governing NIH peer review to generate exogenous variation in funding across research areas. Our results show that NIH funding spurs the development of private-sector patents: a $10 million boost in NIH funding leads to a net increase of 2.7 patents. Though valuing patents is difficult, we report a range of estimates for the private value of these patents using different approaches.National Science Foundation (U.S.) (Award SBE-0738142)National Institutes of Health (U.S.) (Grant P01-AG039347

The Diffusion of Scientific Knowledge Across Time and Space: Evidence from Professional Transitions for the Superstars of Medicine

Are scientific knowledge flows embodied in individuals, or "in the air"? To answer this question, we measure the effect of labor mobility in a sample of 9,483 elite academic life scientists on the citation trajectories associated with individual articles (resp. patents) published (resp. granted) before the scientist moved to a new institution. We find that article-to-article citations from the scientific community at the superstar's origin location are barely affected by their departure. In contrast, article-to-patent citations, and especially patent-to-patent citations, decline at the origin location following a star's departure, suggesting that spillovers from academia to industry are not completely disembodied. We also find that article-to-article citations at the superstar's destination location markedly increase after they move. Our results suggest that, to be realized, knowledge flows to industry may require more face-to-face interaction than those to academics. Moreover, to the extent that academic scientists do not internalize the effect of their location decisions on the circulation of ideas, our results raise the intriguing possibility that barriers to labor mobility in academic science limit the recombination of individual bits of knowledge, resulting in a suboptimal rate of scientific exploration.

Increased prevalence of val(66)met BDNF genotype among subjects with cervical dystonia

Abnormalities of cortical representational maps and their plasticity have been described in dystonia. A common polymorphism for BDNF has been associated with abnormal cortical plasticity, and thus might contribute to pathogenesis of dystonia in some subjects. As a first step towards this suggestion, the current study examined the prevalence of this polymorphism. BDNF genotype was examined in 34 subjects with cervical dystonia, 54 age-matched healthy controls, and 53 subjects with a different movement disorder, Parkinson\u27s disease. ApoE genotype, known to influence neurological outcome in some conditions, was also examined as a control. In subjects with cervical dystonia, the val(66)met polymorphism was approximately twice as prevalent when compared to either control group. This was not true of ApoE genotype, which was similarly distributed across subject groups. The current findings suggest that the BDNF val(66)met polymorphism might play a role in the pathogenesis of cervical dystonia in some subjects

Unique challenges accompany thick-shell CdSe/nCdS (n \u3e 10) nanocrystal synthesis

Thick-shell CdSe/nCdS (n \u3e10) nanocrystals were recently reported that show remarkably suppressed fluorescence intermittency or blinking at the single-particle level as well as slow rates of Auger decay. Unfortunately, whereas CdSe/nCdS nanocrystal synthesis is well-developed up to n \u3c 6 CdS monolayers (MLs), reproducible syntheses for n \u3e 10 MLs are less understood. Known procedures sometimes result in homogeneous CdS nucleation instead of heterogeneous, epitaxial CdS nucleation on CdSe, leading to broad and multimodal particle size distributions. Critically, obtained core/shell sizes are often below those desired. This article describes synthetic conditions specific to thick-shell growth (n\u3e 10 and n\u3e 20 MLs) on both small (sub2 nm) and large (\u3e4.5 nm) CdSe cores. We find added secondary amine and low concentration of CdSe cores and molecular precursors give desired core/shell sizes. Amine-induced, partial etching of CdSe cores results in apparent shell-thicknesses slightly beyond those desired, especially for very-thick shells (n \u3e20 MLs). Thermal ripening and fast precursor injection lead to undesired homogeneous CdS nucleation and incomplete shell growth. Core/shells derived from small CdSe (1.9 nm) have longer PL lifetimes and more pronounced blinking at single-particle level compared with those derived from large CdSe (4.7 nm). We expect our new synthetic approach will lead to a larger throughput of these materials, increasing their availability for fundamental studies and applications

Online Reviews System using Aspect Based Sentimental Analysis & Opinion Mining

Aspect extraction is the most critical and thoroughly researched process in SA (Sentiment Analysis) for conducting an accurate classification of feelings. Over the last decade, massive amounts of research have focused on identifying and removing elements. Products have centralized distribution channels, and certain apps may occasionally operate close to the most recent product to be created. Any e-commerce business enterprise must analyses user / customer feedback in order to provide better products and services to them. Because broad reviews frequently include remarks in a consolidated manner when a customer gives his thoughts on various product attributes within the same summary, it is difficult to determine the exact feeling. The key components of this software are included in their release, making it a valuable tool for management to improve the consistency of their own system's specifications. The goal was to categories the aspects of the target entities provided, as well as the feelings conveyed for each aspect. First, we are implementing a supervised classification framework that is tightly restricted and relies solely on training sets for knowledge. As a result, the key terms comes from associated at various elements of a thing within its entirety perform customer sentiment using certain elements. In contrast to current sentiment analysis approaches, synthetic and actual data set experiments yield positive results