Applications of Latent Heat Storage using Phase Change Materials

Thermal Storage Systems are gaining more attention in recent years with the increased emphasis on more renewable energy sources. Energy storage is necessary whenever there is greater amounts of energy being produced than is required. Various improvements to the conventional heat storage system can be made by integrating latent heat storage into the conventional heat storage system. Latent heat storage can be utilized for thermal storage applications by using phase change materials, materials that will undergo a change in their physical state in the temperature range desired for heat storage. Analysis was conducted on four different waxes considering the waxes for use in a latent heat storage unit. Benchmark experiments analyzing the cooling curves of the waxes were conducted. In addition, data was collected using a differential scanning calorimeter to measure the latent heat of the phase change material as well as the onset temperature of melting in the waxes. The latent heat value of paraffin wax was found to be approximately .Based on the analysis, palm wax was chosen as the phase change material to be used in a prototype latent heat storage. A small prototype latent heat storage unit was constructed using a 1 gallon steel can with copper tube coils in the container. The container was then filled with palm wax, which serves as the heat storage medium in the system. Based on some initial testing, it was found that when operating between and , the palm wax was able to store approximately of energy

Engineering characterization of a versatile vertical-wheel bioreactor for cell and gene therapy

An ideal, versatile bioreactor for cell and gene therapy should be capable of growing cells across a range of formats, such as freely floating in suspension, in aggregates of various target sizes, and also on porous or solid carriers of various sizes. It should work well with cells and multi-cellular structures that are particularly shear sensitive. Ideally, it should be a well-mixed vessel with a homogenous culture environment. To achieve these low shear and mixing objectives, the bioreactor should be capable of suspending aggregates and solid carriers, as well as provide good mixing, at low power inputs per volume. Furthermore, in order to harvest attached cells when needed, it should also be capable of rapidly applying a uniform target high shear environment to viably remove cells from solid carriers. To achieve these objectives, a single-use bioreactor system using an innovative Vertical-Wheel technology has been developed. The first design hypothesis was that a large vertical wheel, when rotated at relatively close clearance to a circular tank bottom, could provide homogeneous liquid mixing, as well as uniform suspension of solid carriers or cellular aggregates, at lower power input per volume than traditional stirred tanks. The second design hypothesis was that the same vertical wheel design could be used to viably harvest cells from solid carriers by simply turning up the rotation speed to a target level for a short period of time. In this talk, we present data directly testing both of these hypotheses. Experimental data will be presented showing the measured power curves for the novel vertical wheel design, as well as the resulting power levels required to achieve uniform fluid mixing and suspension of solid microcarriers across a range of scales, from 0.5 liters to 80 liters. Data will also be shown regarding the ability of this system to viably harvest cells from solid microcarriers. Data regarding the performance of this system for the culture of several different cell types is presented as part of other talks and posters at this conference. In summary, clear evidence will be presented on whether Vertical-Wheel technology provides the most ideal, versatile bioreactor for cell and gene therapy applications

Chord diagrams, contact-topological quantum field theory, and contact categories

We consider contact elements in the sutured Floer homology of solid tori with longitudinal sutures, as part of the (1+1)-dimensional topological quantum field theory defined by Honda--Kazez--Mati\'{c} in \cite{HKM08}. The $\Z_2$ $SFH$ of these solid tori forms a "categorification of Pascal's triangle", and contact structures correspond bijectively to chord diagrams, or sets of disjoint properly embedded arcs in the disc. Their contact elements are distinct and form distinguished subsets of $SFH$ of order given by the Narayana numbers. We find natural "creation and annihilation operators" which allow us to define a QFT-type basis of $SFH$, consisting of contact elements. Sutured Floer homology in this case reduces to the combinatorics of chord diagrams. We prove that contact elements are in bijective correspondence with comparable pairs of basis elements with respect to a certain partial order. The algebraic and combinatorial structures in this description have intrinsic contact-topological meaning. In particular, the QFT-basis of $SFH$ and its partial order have a natural interpretation in pure contact topology, related to the contact category of a disc: the partial order enables us to tell when the sutured solid cylinder obtained by "stacking" two chord diagrams has a tight contact structure. This leads us to extend Honda's notion of contact category to a "bounded" contact category, containing chord diagrams and contact structures which occur within a given contact solid cylinder. We compute this bounded contact category in certain cases. Moreover, the decomposition of a contact element into basis elements naturally gives a triple of contact structures on solid cylinders which we regard as a type of "distinguished triangle" in the contact category. We also use the algebraic structures arising among contact elements to extend the notion of contact category to a 2-category.Comment: v.2: 74 pages, 51 figures. Much new material added, especially about contact categories, hence title change; much rewritten/restructured; some minor corrections; some details/background/exposition removed/shortened in the interest of concision. v.1: 89 pages, 42 figure

Mixed-proxy extensions for the NVIDIA PTX memory consistency model

In recent years, there has been a trend towards the use of accelerators and architectural specialization to continue scaling performance in spite of a slowing of Moore's Law. GPUs have always relied on dedicated hardware for graphics workloads, but modern GPUs now also incorporate compute-domain accelerators such as NVIDIA's Tensor Cores for machine learning. For these accelerators to be successfully integrated into a general-purpose programming language such as C++ or CUDA, there must be a forward- and backward-compatible API for the functionality they provide. To the extent that all of these accelerators interact with program threads through memory, they should be incorporated into the GPU's memory consistency model. Unfortunately, the use of accelerators and/or special non-coherent paths into memory produces non-standard memory behavior that existing GPU memory models cannot capture. In this work, we describe the "proxy" extensions added to version 7.5 of NVIDIA's PTX ISA for GPUs. A proxy is an extra tag abstractly applied to every memory or fence operation. Proxies generalize the notion of address translation and specialized non-coherent cache hierarchies into an abstraction that cleanly describes the resulting non-standard behavior. The goal of proxies is to facilitate integration of these specialized memory accesses into the general-purpose PTX programming model in a fully composable manner. This paper characterizes the behaviors that proxies can capture, the microarchitectural intuition behind them, the necessary updates to the formal memory model, and the tooling that we built in order to ensure that the resulting model both is sound and meets the needs of business-critical workloads that they are designed to support

Development of a scale-down approach to the scalable culture of induced Pluripotent Stem Cells on microcarriers using single-use Vertical-Wheel™ bioreactors under xeno-free conditions

Induced Pluripotent Stem Cells (iPSC) are capable of extensive self-renewal while retaining the ability to differentiate into virtually all cell types of the body. These cells are the subject of much research and development activity aimed at the development of cell-based tools, which may speed drug discovery, and cell-based medical therapies that are being developed to address unmet medical needs. However, development of these therapies is hampered by manufacturing bottlenecks including production scale up to meet the anticipated demand. PBS Biotech, Inc. has developed a single use bioreactor with an innovative Vertical-Wheel™ design that promotes more homogenous and gentle particle suspension, under lower hydrodynamic shear environment than traditional bioreactor vessel design. Vertical-Wheel bioreactors are available from lab-scale vessels (PBS MINI) to larger production units (up to 500L). This study describes the culture of human iPSCs on microcarriers under xeno-free conditions using Vertical-Wheel bioreactors. Human iPSCs were cultured on microcarriers to provide surface for cell attachment using the chemically defined Essential 8 culture medium, a xeno-free, feeder-free culture medium. The culture conditions were optimized in terms of 1) initial cell/microcarrier ratio, 2) inoculation method and 3) agitation rate, in the PBS-0.1 vessel using 80 mL working volume. The cells were successfully expanded, up to a 7-fold increase in cell number, after 6 days in the bioreactor. Glucose consumption and lactate production were analyzed to prevent glucose starvation or excessive lactate accumulation. These optimized culture conditions were successfully repeated in a larger vessel, the PBS-0.5 using 300 mL working volume, demonstrating the scalability of the Vertical-Wheel system. With this PBS-0.5 bioreactor, 3 x 108 cells were produced after 6 days of operation, and the specific growth rate (0.72 day-1) was similar to the one observed with the PBS-0.1 (0.68 day-1). The applications of iPSC cells and their progeny, especially in clinical settings, will require a guarantee of cell quality. After PBS-MINI bioreactor culture, the expression of pluripotency markers, such as Oct4, Nanog, and SSEA4 was assessed by immunocytochemistry and flow cytometry. The directed differentiation into the neural lineage of the expanded cells was performed and the pluripotency of the cells was further tested after embryoid body formation. The robustness of this process method was evaluated by cultivating another iPSC cell line under the same process conditions, resulting in identical growth kinetics in the PBS MINI-0.1. The methodology developed herein, which grows human iPSC on microcarriers in single-use bioreactors using chemically defined xeno-free cultivation reagents provides a foundation upon which further refinement and scale-up of processes can be built for large scale production of iPSCs

Radio parlée, élections et démocratie.

Le Centre d'étude s'est intéressé au rôle qu'ont joué les deux radios privées de format parlé de Québec lors des élections à la mairie à l'automne 2007. Nous avons analysé ce que CHOI et le 93,3 ont proposé à leurs nombreux auditeurs pendant les trois semaines officielles de cette campagne électorale. Nos travaux montrent clairement que les deux stations de Québec n’ont pas respecté les consignes du CRTC ni les normes qu’on retrouve dans le Code de déontologie de l’Association canadienne des radiodiffuseurs, auquel elles ont pourtant adhéré. Elles n’ont pas traité de manière équitable la candidate du RMQ, Ann Bourget. Elles n’ont pas assuré une couverture « complète, juste et appropriée » de cette campagne à la mairie de Québec. Au contraire, des animateurs se sont servis abusivement du pouvoir que leur confère l’accès quotidien aux micros de stations très écoutées, et les dirigeants de ces stations ont laissé faire

Numerical modeling of a two-dimensional aerated cavitation in a symmetrical venturi nozzle

Cavitation is a well-known physical phenomenon occurring in various technical applications. Its coupling with the aeration, is a recent technique, which allows the control of the overall effect of the cavitation. The aeration is achieved by introducing air bubbles into the flow. In order to reveal and explore the behaviour of air in the vicinity of the cavitation regions, the paper is oriented towards the physics of the colliding vapour phase in the presence of cavitation. By penalizing the strain rate tensor in the Homogeneous Equilibrium Model, a two-way cavitation-aeration coupling is achieved. The contact-handling algorithm is based on the projections of the velocity fields of the injected bubbles over the velocity field of the fluid flow. At each time step the gradient of the distance between the bubbles, is kept non-negative, as a guarantee of the physical non overlapping. The bubbles are considered as non-deformable. The differential equations system is composed of the 2D Navier-Stokes equations, implemented with the Homogeneous Equilibrium Model. A high-order Finite Volume solver based on Moving Least Squares approximations is used. The code uses a SLAU-type Riemann solver for the accurate calculation of the low Mach numbers. The computational domain is a symmetrical 2D venturi nozzle, with 18/ 8 convergent/divergent angles respectively

Itsy bitsy topological field theory

We construct an elementary, combinatorial kind of topological quantum field theory, based on curves, surfaces, and orientations. The construction derives from contact invariants in sutured Floer homology and is essentially an elaboration of a TQFT defined by Honda--Kazez--Matic. This topological field theory stores information in binary format on a surface and has "digital" creation and annihilation operators, giving a toy-model embodiment of "it from bit".Comment: 54 pages, 35 figures. Minor edits, extra figures adde

Impacts of agriculture on the parasite communities of northern leopard frogs (Rana pipiens) in southern Quebec, Canada

Given that numerous amphibians are suffering population declines, it is becoming increasingly important to examine the relationship between disease and environmental disturbance. Indeed, while many studies relate anthropogenic activity to changes in the parasitism of snails and fishes, little is known of the impact on the parasites of amphibians, particularly from agriculture. For 2 years, the parasite communities of metamorphic northern leopard frogs from 7 agricultural wetlands were compared with those from 2 reference wetlands to study differences in parasite community diversity and abundance of various species under pristine conditions and 3 categories of disturbance: only agricultural landscape, only pesticides, and agricultural landscape with pesticides. Agricultural (and urban) area was negatively related to species richness, and associated with the near absence of adult parasites and species that infect birds or mammals. We suggest that agriculture and urbanization may hinder parasite transmission to frogs by limiting access of other vertebrate hosts of their parasites to wetlands. The only parasite found at all localities was an unidentified echinostome infecting the kidneys. This parasite dominated communities in localities surrounded by the most agricultural land, suggesting generalist parasites may persist in disrupted habitats. Community composition was associated with dissolved organic carbon and conductivity, but few links were found with pesticides. Pollution effects may be masked by a strong impact of land use on parasite transmission

Deweyan tools for inquiry and the epistemological context of critical pedagogy

This article develops the notion of resistance as articulated in the literature of critical pedagogy as being both culturally sponsored and cognitively manifested. To do so, the authors draw upon John Dewey\u27s conception of tools for inquiry. Dewey provides a way to conceptualize student resistance not as a form of willful disputation, but instead as a function of socialization into cultural models of thought that actively truncate inquiry. In other words, resistance can be construed as the cognitive and emotive dimensions of the ongoing failure of institutions to provide ideas that help individuals both recognize social problems and imagine possible solutions. Focusing on Dewey\u27s epistemological framework, specifically tools for inquiry, provides a way to grasp this problem. It also affords some innovative solutions; for instance, it helps conceive of possible links between the regular curriculum and the study of specific social justice issues, a relationship that is often under-examined. The aims of critical pedagogy depend upon students developing dexterity with the conceptual tools they use to make meaning of the evidence they confront; these are background skills that the regular curriculum can be made to serve even outside social justice-focused curricula. Furthermore, the article concludes that because such inquiry involves the exploration and potential revision of students\u27 world-ordering beliefs, developing flexibility in how one thinks may be better achieved within academic subjects and topics that are not so intimately connected to students\u27 current social lives, especially where students may be directly implicated