3,319 research outputs found

    Improving processor efficiency through thermal modeling and runtime management of hybrid cooling strategies

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    One of the main challenges in building future high performance systems is the ability to maintain safe on-chip temperatures in presence of high power densities. Handling such high power densities necessitates novel cooling solutions that are significantly more efficient than their existing counterparts. A number of advanced cooling methods have been proposed to address the temperature problem in processors. However, tradeoffs exist between performance, cost, and efficiency of those cooling methods, and these tradeoffs depend on the target system properties. Hence, a single cooling solution satisfying optimum conditions for any arbitrary system does not exist. This thesis claims that in order to reach exascale computing, a dramatic improvement in energy efficiency is needed, and achieving this improvement requires a temperature-centric co-design of the cooling and computing subsystems. Such co-design requires detailed system-level thermal modeling, design-time optimization, and runtime management techniques that are aware of the underlying processor architecture and application requirements. To this end, this thesis first proposes compact thermal modeling methods to characterize the complex thermal behavior of cutting-edge cooling solutions, mainly Phase Change Material (PCM)-based cooling, liquid cooling, and thermoelectric cooling (TEC), as well as hybrid designs involving a combination of these. The proposed models are modular and they enable fast and accurate exploration of a large design space. Comparisons against multi-physics simulations and measurements on testbeds validate the accuracy of our models (resulting in less than 1C error on average) and demonstrate significant reductions in simulation time (up to four orders of magnitude shorter simulation times). This thesis then introduces temperature-aware optimization techniques to maximize energy efficiency of a given system as a whole (including computing and cooling energy). The proposed optimization techniques approach the temperature problem from various angles, tackling major sources of inefficiency. One important angle is to understand the application power and performance characteristics and to design management techniques to match them. For workloads that require short bursts of intense parallel computation, we propose using PCM-based cooling in cooperation with a novel Adaptive Sprinting technique. By tracking the PCM state and incorporating this information during runtime decisions, Adaptive Sprinting utilizes the PCM heat storage capability more efficiently, achieving 29\% performance improvement compared to existing sprinting policies. In addition to the application characteristics, high heterogeneity in on-chip heat distribution is an important factor affecting efficiency. Hot spots occur on different locations of the chip with varying intensities; thus, designing a uniform cooling solution to handle worst-case hot spots significantly reduces the cooling efficiency. The hybrid cooling techniques proposed as part of this thesis address this issue by combining the strengths of different cooling methods and localizing the cooling effort over hot spots. Specifically, the thesis introduces LoCool, a cooling system optimizer that minimizes cooling power under temperature constraints for hybrid-cooled systems using TECs and liquid cooling. Finally, the scope of this work is not limited to existing advanced cooling solutions, but it also extends to emerging technologies and their potential benefits and tradeoffs. One such technology is integrated flow cell array, where fuel cells are pumped through microchannels, providing both cooling and on-chip power generation. This thesis explores a broad range of design parameters including maximum chip temperature, leakage power, and generated power for flow cell arrays in order to maximize the benefits of integrating this technology with computing systems. Through thermal modeling and runtime management techniques, and by exploring the design space of emerging cooling solutions, this thesis provides significant improvements in processor energy efficiency.2018-07-09T00:00:00

    Microfluidics: a new look at cell migration analysis

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    This thesis explores the development and employment of microfluidic devices as a tool for studying the effect of the surrounding environment on embryonic stem cells during the migration phenomena. Different single-cell microchips were designed and manufactured to study mouse embryonic fibroblasts (MEFs) migration towards an environmental variation (increase of serum concentration in the culture medium) that was expected to function as a motility stimuli. Considering the experimental, cells were injected into the microchips chambers and individually isolated by dedicated cell traps with view to a single-cell analysis. Once fribroblasts were attached to the surface, culture medium with an increased serum level was subsequently injected in an adjacent chamber to promote the formation of a serum concentration gradient. The gradient established between the chambers could be sensed by the fibroblasts and thus triggered the cells mobilization towards and in the direction of the richer serum medium. Additionally, the experiment allowed the observation of MEFs’ structural reorganization when migrating through micro-tunnels containing widths below the cell size, suggesting a cytoskeleton rearrangement on account of the nutritional stimulus introduced. Furthermore, results indicate that fibronectin promotes MEFs adhesion to the substrate and that MEFs migration is characterized as haptotactic

    Internet of Things Strategic Research Roadmap

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    Internet of Things (IoT) is an integrated part of Future Internet including existing and evolving Internet and network developments and could be conceptually defined as a dynamic global network infrastructure with self configuring capabilities based on standard and interoperable communication protocols where physical and virtual “things” have identities, physical attributes, and virtual personalities, use intelligent interfaces, and are seamlessly integrated into the information network

    DEVELOPMENT OF HIGH-THROUGHPUT IMPEDANCE SPECTROSCOPY-BASED MICROFLUIDIC PLATFORM FOR DETECTING AND ANALYZING CELLS AND PARTICLES

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    Impedance spectroscopy based microfluidics have the capability to characterize the dielectric properties of mediums, particles, cellular and sub-cellular contents in response to stimulating voltage signals over a frequency range. This label-free technology has broad ranges of applications in life sciences where there is a need for high-throughput, label-free, non-contact, and low-cost microsystems. To address these limitations, three innovative impedance spectroscopy microfluidic platforms have been developed and presented in this dissertation. The first platform was developed for detecting and characterizing the transverse position of a single cell flowing within a microfluidic channel using a single impedance spectroscopy electrode pair. Regardless of the cell separation methods used, identifying and quantifying the position of cells and particles within a microchannel are important, as these information indicate both the degree of separation as well as how many cells are separated into each position. Using a single pair of non-parallel surface microelectrodes, five different transverse positions of single cells flowing through a microfluidic channel were successfully identified at a throughput of more than 400 particles/s using the detected impedance peak height and width. The second platform utilizes the above technology to count and quantify cells flowing through multiple outlets of microfluidic cell separation systems. A single pair of step-shaped electrodes was developed by integrating five different electrode-to-electrode gaps within a single pair of electrodes. Using this platform, an overall misclassification error rate of only 1.85% was achieved. The result shows the technology’s capability in achieving efficient on-chip cell counting and quantification, regardless of the cell separation methods used, making it a promising on-chip, low-cost and label-free quantification method for cell and particle sorting and separation applications. The third platform was developed for counting cells and particles encapsulated in water-in-oil emulsion droplets using microfluidic based impedance spectroscopy systems. Impedance signal peak height and width were utilized to successfully quantify the number of cells encapsulated within a droplet, and was successfully applied for various cell types and growth media. In addition, the developed platform has been also successfully tested for identifying and discriminating filamentous fungal cell growth, where single fungal spores and filamentous fungi of different lengths could be discriminated inside droplets. Overall in this research, several impedance spectroscopy based microfluidic systems have been successfully developed to solve current limitations in technologies that need high-throughput, low-cost and label-free detection and characterization method for a broad range of cell/particle screening applications

    Acute Myeloid Leukemia

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    Acute myeloid leukemia (AML) is the most common type of leukemia. The Cancer Genome Atlas Research Network has demonstrated the increasing genomic complexity of acute myeloid leukemia (AML). In addition, the network has facilitated our understanding of the molecular events leading to this deadly form of malignancy for which the prognosis has not improved over past decades. AML is a highly heterogeneous disease, and cytogenetics and molecular analysis of the various chromosome aberrations including deletions, duplications, aneuploidy, balanced reciprocal translocations and fusion of transcription factor genes and tyrosine kinases has led to better understanding and identification of subgroups of AML with different prognoses. Furthermore, molecular classification based on mRNA expression profiling has facilitated identification of novel subclasses and defined high-, poor-risk AML based on specific molecular signatures. However, despite increased understanding of AML genetics, the outcome for AML patients whose number is likely to rise as the population ages, has not changed significantly. Until it does, further investigation of the genomic complexity of the disease and advances in drug development are needed. In this review, leading AML clinicians and research investigators provide an up-to-date understanding of the molecular biology of the disease addressing advances in diagnosis, classification, prognostication and therapeutic strategies that may have significant promise and impact on overall patient survival

    Microfluidic Devices with Engineered Micro-/Nanostructures for Cell Isolation

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    Isolation of cells from blood is critical for vast biomedical applications. The focus of this dissertation is on the isolation of circulating tumor cells (CTCs) from patient blood, which contains important prognostic and diagnostic information. Challenges in this field originates from the striking contrast between the rare amount of CTCs (1-10 per mL) and vast other normal cells (millions of white blood cells (WBCs) and billions of red blood cells per mL). Various techniques have been developed to isolate CTCs in the recent decades, while the most demanding clinical requirements lie in two aspects: higher capture efficiency meaning the strong ability to isolate the rare CTCs and higher purity meaning the strong ability to repel all other normal cells. In order to better serve clinical practice, we developed four microfluidic platforms aiming at high capture efficiency and high purity, thus advancing the cancer patient care. By extending the concept of the hallmark immunoaffinity based grooved-herringbone (HB) chip, we first developed a wavy-HB chip by smoothing the grooved patterns to wavy patterns. The wavy-HB chip was demonstrated to not only achieve high capture efficiency (up to 85.0%) by micro-vortexes induced by HB structures, but achieve high purity (up to 39.4%) due to the smooth wavy microstructures. The HB structures were then further optimized through a refined computational model implemented with cell adhesion probability. The particulate cell transport dynamics was shown to be crucial in determining the optimized geometry for CTC capture. To further enhance the CTC capture, integration of nanostructures was examined due to their intrinsic large surface area-to-volume ratio. By exploring the geometric effects of nanopillars on CTC capture, we unraveled an interesting linear relationship between CTC capture efficiency and effective nanopillar contact area. We then developed a fabrication approach to deposit nanoparticles on the wavy-HB patterns to form hierarchical micro/nanostructures. The hierarchical wavy-HB chip was demonstrated to achieve a capture efficiency up to ~98% and a high purity performance (only ~680 WBCs per 1 mL blood). Over the course of the above-mentioned work, there emerges another clinical need which requires captured CTCs to be released and re-cultured for post-analysis such as drug screening. We thus developed two microfluidic chips attempting to achieve this goal. The first platform is an integration of immunomagnetic particles on the developed wavy-HB chip. In addition to the good device performance brought by the wavy-HB patterns, CTCs were able to be released from the capture bed by removing the magnetic field. The collected CTCs labeled with magnetic particles were able to be re-cultured and it was found that these magnetic particles were subject to self-removal during cell proliferations. The second platform was an inclined wavy patterns coated with E-selectin, which was able to form weak adhesion forces with WBCs and CTCs. A proof-of-concept work was performed to demonstrate that WBCs and CTCs were able to be separated along different pathways due to the different adhesion forces and the inclined direction guidance. With all these developed cancer cell isolation microfluidic chips, we showed our contributions toward effective cancer cell isolation and eventually cancer treatment

    High Throughput Screening of Clopidogrel Resistance Using Microfluidic Technology

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    The pre-treatment of patients with clopidogrel before primary percutaneous coronary intervention (PCI) has been shown to lower the risk of complications that could lead to heart attack or stroke during the procedure. However, the proper administration of clopidogrel requires the measurement of the patient’s drug resistance due to its inherent variation across the population. Approximately 1.1 million PCIs were performed in the US alone in 2008. As the patient population is becoming increasingly aware of the benefits of clopidogrel treatment prior to PCI, there is an ever-expanding market potential for clopidogrel resistance screening devices. As most of the existing devices utilize traditional test-tube-scale bench-top technology that usually sets limitations on the throughput and applicability of the test itself, the market demands a device that not only minimizes the cost per test but also produces consistent and comprehensive results. In this report, guided by the innovation map, we are able to link soft lithography in combination with micro-patterning technology to the customer’s requirements, and come up with a higher-throughput system that meets the market demand. Our system consists of two parts: the chip and the device. We focus our design effort primarily on the chip, in which micro-channel layout, dry reagent dissolution, reagent mixing and reservoir volume design are carefully worked out. On the other hand, the design of the device is discussed briefly, but production is assumed to be outsourced. With the cost estimates from suppliers and the assumed expected market share to be 50%, the net present value is computed to be about 45 million, indicating a lucrative return to investors
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