Memory optimization techniques for embedded systems

Embedded systems have become ubiquitous and as a result optimization of the design and performance of programs that run on these systems have continued to remain as significant challenges to the computer systems research community. This dissertation addresses several key problems in the optimization of programs for embedded systems which include digital signal processors as the core processor. Chapter 2 develops an efficient and effective algorithm to construct a worm partition graph by finding a longest worm at the moment and maintaining the legality of scheduling. Proper assignment of offsets to variables in embedded DSPs plays a key role in determining the execution time and amount of program memory needed. Chapter 3 proposes a new approach of introducing a weight adjustment function and showed that its experimental results are slightly better and at least as well as the results of the previous works. Our solutions address several problems such as handling fragmented paths resulting from graph-based solutions, dealing with modify registers, and the effective utilization of multiple address registers. In addition to offset assignment, address register allocation is important for embedded DSPs. Chapter 4 develops a lower bound and an algorithm that can eliminate the explicit use of address register instructions in loops with array references. Scheduling of computations and the associated memory requirement are closely inter-related for loop computations. In Chapter 5, we develop a general framework for studying the trade-off between scheduling and storage requirements in nested loops that access multi-dimensional arrays. Tiling has long been used to improve the memory performance of loops. Only a sufficient condition for the legality of tiling was known previously. While it was conjectured that the sufficient condition would also become necessary for large enough tiles, there had been no precise characterization of what is large enough. Chapter 6 develops a new framework for characterizing tiling by viewing tiles as points on a lattice. This also leads to the development of conditions under the legality condition for tiling is both necessary and sufficient

An empirical framework for user mobility models: Refining and modeling user registration patterns

AbstractIn this paper, we examine user registration patterns in empirical WLAN traces, identify elusive patterns that are abused as user movements in constructing empirical mobility models, and analyze them to build up a realistic user mobility model. The examination shows that about 38–90% of transitions are irrelevant to actual user movements. In order to refine the elusive movements, we investigate the geographical relationships among APs and propose a filtering framework for removing them from the trace data. We then analyze the impact of the false-positive movements on an empirical mobility model. The numerical results indicate that the proposed framework improves the fidelity of the empirical mobility model. Finally, we devise an analytical model for characterizing realistic user movements, based on the analysis on the elusive user registration patterns, which emulates elusive user registration patterns and generates true user mobile patterns

MICROPOLYHEDRA AND THEIR APPLICATIONS AS A CHEMICAL DISPLAY

Inspired by the readily observed phenomenon of self-assembly in nature, multiple self-assembling microfabrication techniques have been developed to fabricate various 3D structures in both micro and nanoscale. Among the structures that can be fabricated via self-assembly are polyhedra, an attractive model system for studying a wide range of disciplines including mathematics, chemistry and biology. While polyhedra have been considered as an attractive model system with a wide range of implications in multiple fields of study, they are also an effective choice of encapsulant in particle technology to enable spatially controlled chemical reactions. From the formation of milk from fat globules to the development of the central nervous system (CNS) through diffusible chemoattractants, nature has benefitted from selecting and fine-tuning particles to enable spatially controlled chemistry. In past studies, scientists have mainly utilized particle technology to develop an effective system of drug delivery in micro and nanoscale. However, the potential application of particle technology is unlimited; we were inspired to develop a novel application of a chemical display in addition to other existing applications of particle technology. We herein describe a concept of a chemical display system that can generate a dynamic pattern based on a controlled chemical release from an array of porous self-assembled micropolyhedra with various tunable properties such as dimensions, pore sizes, chemical concentrations and arrangements. Based on the idea of controlled chemical release via particle technology, our goal is to develop a chemical display system that would be able to address an inherent limitation that exists in conventional electronic display. A concept of a chemical display would benefit from the absence of components or interfaces that connect each pixel, allowing increased freedom in both design and utility. We fabricated our chemical display system based on an array of self-assembled micropolyhedra, a structure that can be produced in parallel at high efficiency. In this study, we have successfully demonstrated the viability of a chemical display system by loading porous self-folded metallic cubes with chemicals and by precisely controlling the porosity, volume and chemical concentration. We expect that our highly tunable chemical display system based on a self-assembled micropolyhedra would be able to benefit current display systems by complementing currently existing electronic displays. We also anticipate that the technology could open up new possibilities in other fields such as biotechnology, benefitting from a sequential release of chemicals, cells and more. Advisor: Dr. David H. Gracias Reader: Dr. Honggang Cu

The Economics of All-You-Can-Read Pricing: Tariff Choice, Contract Renewal, and Switching for E-Book Purchases

E-book markets are currently moving through a period of disequilibrium as new pricing structures (i.e., flat-fee subscriptions) are rapidly embraced by major vendors. On the basis of a novel dataset, we investigate how the availability of “all-you-can-read” pricing programs influences consumers’ tariff choice, contract renewal, and switching behaviors. Consistent with the rational choice framework, the findings suggest that most e-book consumers significantly gain from subscription-based tariffs. However, we also find some other intriguing results. Among the three subscription designs examined, the 1-week plan affords consumers more economic benefits than do 1-day or 1-month programs. The economic gains derived from subscription-based tariffs diminish as consumers renew their subscriptions under the same contract duration. Consumers who switch to other plans also suffer from reduced savings. Finally, iOS users are more inclined to select subscription models than are Android users because of the absence of in-app purchase functionalities for the former

Imiquimod enhances excitability of dorsal root ganglion neurons by inhibiting background (K2P) and voltage-gated (Kv1.1 and Kv1.2) potassium channels

<p>Abstract</p> <p>Background</p> <p>Imiquimod (IQ) is known as an agonist of Toll-like receptor 7 (TLR7) and is widely used to treat various infectious skin diseases. However, it causes severe itching sensation as its side effect. The precise mechanism of how IQ causes itching sensation is unknown. A recent report suggested a molecular target of IQ as TLR7 expressed in dorsal root ganglion (DRG) neurons. However, we recently proposed a TLR7-independent mechanism, in which the activation of TLR7 is not required for the action of IQ in DRG neurons. To resolve this controversy regarding the involvement of TLR7 and to address the exact molecular identity of itching sensation by IQ, we investigated the possible molecular target of IQ in DRG neurons.</p> <p>Findings</p> <p>When IQ was applied to DRG neurons, we observed an increase in action potential (AP) duration and membrane resistance both in wild type and TLR7-deficient mice. Based on these results, we tested whether the treatment of IQ has an effect on the activity of K⁺channels, K_v1.1 and K_v1.2 (voltage-gated K⁺channels) and TREK1 and TRAAK (K_2Pchannels). IQ effectively reduced the currents mediated by both K⁺channels in a dose-dependent manner, acting as an antagonist at TREK1 and TRAAK and as a partial antagonist at K_v1.1 and K_v1.2.</p> <p>Conclusions</p> <p>Our results demonstrate that IQ blocks the voltage-gated K⁺channels to increase AP duration and K_2Pchannels to increase membrane resistance, which are critical for the membrane excitability of DRG neurons. Therefore, we propose that IQ enhances the excitability of DRG neurons by blocking multiple potassium channels and causing pruritus.</p

Long-term prenatal stress increases susceptibility of N-methyl-D-aspartic acid-induced spasms in infant rats

PurposeInfantile spasms, also known as West syndrome, is an age-specific epileptic seizure. Most patients with this condition also exhibit delayed development. This study aimed to determine the effect of long-term prenatal stress on susceptibility to infantile spasms.MethodsWe subjected pregnant rats to acute or chronic immobilization stress. Resulting offspring received N-methyl-D-aspartic acid (15 mg/kg, intraperitoneally) on postnatal day 15, and their behaviors were observed 75 minutes after injection. The expression of KCC2 and GAD67 was also determined using immunohistochemistry.ResultsExposure to long-term prenatal stress increased the frequency of spasms and decreased the latency to onset of spasms compared with offspring exposed to short-term prenatal stress. Expression of KCC2 and GAD67 also decreased in the group exposed to long-term prenatal stress compared with the group exposed to short-term prenatal stress.ConclusionOur study suggests that exposure to long-term prenatal stress results in increased susceptibility to seizures

Surface energy-mediated construction of anisotropic semiconductor wires with selective crystallographic polarity.

ZnO is a wide band-gap semiconductor with piezoelectric properties suitable for opto-electronics, sensors, and as an electrode material. Controlling the shape and crystallography of any semiconducting nanomaterial is a key step towards extending their use in applications. Whilst anisotropic ZnO wires have been routinely fabricated, precise control over the specific surface facets and tailoring of polar and non-polar growth directions still requires significant refinement. Manipulating the surface energy of crystal facets is a generic approach for the rational design and growth of one-dimensional (1D) building blocks. Although the surface energy is one basic factor for governing crystal nucleation and growth of anisotropic 1D structures, structural control based on surface energy minimization has not been yet demonstrated. Here, we report an electronic configuration scheme to rationally modulate surface electrostatic energies for crystallographic-selective growth of ZnO wires. The facets and orientations of ZnO wires are transformed between hexagonal and rectangular/diamond cross-sections with polar and non-polar growth directions, exhibiting different optical and piezoelectrical properties. Our novel synthetic route for ZnO wire fabrication provides new opportunities for future opto-electronics, piezoelectronics, and electronics, with new topological properties

TLR2-induced astrocyte MMP9 activation compromises the blood brain barrier and exacerbates intracerebral hemorrhage in animal models

Background: The innate immune response plays an important role in the pathogenesis of intracerebral hemorrhage (ICH). Recent studies have shown that Toll-like receptor 2 (TLR2) is involved in the innate immune response in various neurological diseases, yet neither its role in ICH nor the mechanisms by which it functions have yet been elucidated. We examined these in this study using a collagenase-induced mouse ICH model with TLR2 knock-out (KO) mice. Results: TLR2 expression was upregulated in the ipsilateral hemorrhagic tissues of the collagenase-injected mice. Brain injury volume and neurological deficits following ICH were reduced in TLR2 KO mice compared to wild-type (WT) control mice. Heterologous blood-transfer experiments show that TLR2 signaling in brain-resident cells, but not leukocytes, contributes to the injury. In our study to elucidate underlying mechanisms, we found that damage to blood-brain barrier (BBB) integrity following ICH was attenuated in TLR2 KO mice compared to WT mice, which may be due to reduced matrix metalloproteinase-9 (MMP9) activation in astrocytes. The reduced BBB damage accompanies decreased neutrophil infiltration and proinflammatory gene expression in the injured brain parenchyma, which may account for the attenuated brain damage in TLR2 KO mice after ICH. Conclusions: TLR2 plays a detrimental role in ICH-induced brain damage by activating MMP9 in astrocytes, compromising BBB, and enhancing neutrophils infiltration and proinflammatory gene expression. © 2015 Min et al.; licensee BioMed Central.1