183 research outputs found
Network coding for speedup in switches
No full textThesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 69-71).Network coding, which allows mixing of data at intermediate network nodes, is known to increase the throughput of networks. In particular, it is known that linear network coding in a crossbar switch can sustain traffic patterns that cannot be served if network coding were not allowed. Thus, network coding leads to a larger rate region in a multicast crossbar switch. This thesis quantities the gain in rate region in a multicast crossbar switch in terms of speedup. We present a graph theoretic upper bound on speedup needed to achieve 100% throughput in a multicast switch using network coding. By bounding speedup, we show the equivalence between network coding and speedup in multicast switches - i.e. network coding, which is usually implemented using software, can in many cases substitute speedup, which is often achieved by adding extra switch fabrics. This bound is based on an approach to network coding problems called the "enhanced conflict graph". We show that the "imperfection ratio" of the enhanced conflict graph gives an upper bound on speedup. In particular, we apply this result to K x N switches with traffic patterns consisting of unicasts and broadcasts only to obtain an upper bound of min(2K-1/K, 2N/N+1).by MinJi Kim.M.Eng
Silver-halophenylethynide and silver-nitrophenylethynide supramolecular synthons for the construction of coordination networks.
No full textWang, Minji.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.Includes bibliographical references (leaves 91-97).Abstracts in English and Chinese.Acknowledgement --- p.iAbstract --- p.ii摘要 --- p.iiiChapter Chapter 1. --- Introduction --- p.1Chapter 1.1 --- Weak Intermolecular Interactions --- p.1Chapter 1.1.1 --- Van der Waals Interaction --- p.1Chapter 1.1.2 --- Hydrogen Bonds --- p.2Chapter 1.1.3 --- π…π Interactions --- p.4Chapter 1.1.4 --- Lone-Pair…Aromatic Interactions --- p.5Chapter 1.1.5 --- Halogen…Halogen Interactions --- p.6Chapter 1.2 --- Argentophilic Interaction --- p.7Chapter 1.3 --- Silver Acetylenediide and Silver Arylethynide --- p.11Chapter 1.3.1 --- "C2@Agn(n = 6, 7, 8, 9, 10)" --- p.11Chapter 1.3.2 --- "Ag4eC=C-C=Cz>Ag4 and R-C=C@=)Agn, (n = 4, 5; R = Aryl, t-Bu)" --- p.12Chapter 1.4 --- Research Strategy --- p.14Chapter Chapter 2. --- "Coordination Networks Constructed with the Supramolecular Synthon System Rx-CsCzAgn (n = 4,5; Rx = halophenyl)" --- p.16Chapter 2.1 --- Crystal Structure of AgC=CC6H4l-4 ´Ø 2AgCF3COO (2.1) --- p.17Chapter 2.2 --- Crystal Structure of AgC=CC6H4l-4 . 3AgNO3 (2.2) --- p.20Chapter 2.3 --- "Crystal Structure of 2AgC=CC6H3Cl2-3,4 . 5AgCF3COO ´Ø 2CH3CN . H20 (2.3)" --- p.25Chapter 2.4 --- Crystal Structure of 4AgC=CC6H4Cl-3 . 6AgC2F5COO ´Ø 5CH3CN (2.4) & 4AgOCC6H4Br-3 ´Ø 6AgC2F5COO ´Ø 5CH3CN (2.5) --- p.28Chapter 2.5 --- Crystal Structure of 2AgC=CC6H4Cl-2 . 4AgCF3COO ´Ø NC(CH2)4CN (2.6) & 2AgOCC6H4Cl-2 ´Ø 4AgCF3COO ´Ø 2CH3CN (2.7) --- p.32Chapter 2.6 --- Crystal Structure of AgC=CC6H4F-2 ´Ø 2CF2(CF2COOAg)2 ´Ø 2CH3CN (2.8) --- p.36Chapter 2.7 --- Crystal Structure of 4AgC=CC6H4N02-2 ´Ø 10AgC3F7COO ´Ø 4CH3CN . 4H20 (2.9) --- p.39Chapter 2.8 --- Summary --- p.41Chapter Chapter 3. --- Network Assembly with the Supramolecular Synthon System Rx-C=C3Agw (/i = 3 to 5; Rx = nitrophenyl) --- p.43Chapter 3.1 --- Crystal Structure of AgC=CC6H4N02-2 ´Ø 3AgC2F5COO . 2CH3CN (3.1) --- p.44Chapter 3.2 --- Crystal Structure of AgC=CC6H4N02-4 ´Ø 3AgC2F5COO ´Ø CH3CN (3.2) --- p.47Chapter 3.3 --- Crystal Structure of AgC=CC6H4N02-4 ´Ø 4AgCF3COO ´Ø 2CH3CN (3.3) --- p.50Chapter 3.4 --- Crystal Structure of AgC=CC6H4N02-4 ´Ø 3AgCF3COO . CH3CN ´Ø 0.5NC(CH2)4CN (3.4) --- p.53Chapter 3.5 --- Crystal Structure of AgC=CC6H4N02-4 ´Ø 3AgC2F5COO ´Ø 2CH3CN (3.5) --- p.56Chapter 3.6 --- Crystal Structure of AgC=CC6H4N02-4 ´Ø 3AgC2F5COO ´Ø CH3CN ´Ø NC(CH2)4CN (3.6) --- p.59Chapter 3.7 --- Crystal Structure of 4AgC三CC6H4NOr4 ´Ø 4AgC3F7COO ´Ø 3CH3CN (3.7) --- p.62Chapter 3.8 --- Crystal Structure of 3AgC=CC6H4N02-4 ´Ø 3AgCF3COO ´Ø 3CH3CN (3.8) --- p.66Chapter 3.9 --- Crystal Structure of 7AgC三CC6H4NOr4 ´Ø 17AgCF3COO ´Ø 11CH3CN ´Ø H20 (3.9) --- p.68Chapter 3.10 --- Crystal Structure of AgC=CC6H4N02-4 ´Ø CF2(CF2COOAg)2. AgCFsCOO . H2O (3.10) --- p.72Chapter 3.11 --- Summary --- p.76Chapter 3.12 --- Further Development --- p.77Chapter 3.12.1 --- Elongation of Ethynide Ligands --- p.77Chapter 3.12.2 --- Incorporating More Ethynide Ligands into One Compound --- p.78Chapter Chapter 4. --- Experimental --- p.79Chapter 4.1 --- Synthesis --- p.79Chapter 4.2 --- X-Ray Crystallography --- p.84References --- p.9
Puerto Rico’s Attempts to Address a Public Health Crisis Struck Down by the United States Court of Appeals for the First Circuit
No full textThis RCD discusses a recent decision by the United States Court of Appeals for the First Circuit that struck down Puerto Rico’s Act 90-2019, which aimed to regulate pay structures for Medicare Advantage insurers in Puerto Rico. The court found that the provision in Act 90, known as the “Mandated Price Provision,” is preempted by federal law. However, the author argues that the court’s decision did not adequately consider the congressional intent of the Medicare Advantage Act in weighing the public health crisis in Puerto Rico. The RCD provides background on the Medicare Advantage program and Act 90 and explains how Act 90 aimed to eliminate insurers’ practice of paying providers at rates below the CMS’s minimum reimbursement rates under the traditional Medicare program. The article concludes that the court’s decision inadequately considered the larger purpose of the Medicare Advantage Act and the relevant public health crisis in Puerto Rico.Published versio
Are Clinical Findings Of Systemic Titanium Dispersion Following Implantation Explained By Available In Vitro Evidence? An Evidence-based Analysis.
No full textAlthough the presence of titanium wear particles released into tissues is known to induce local inflammation following the therapeutic implantation of titanium devices into humans, the role that titanium ions play in adverse tissue responses has received little attention. Support that ongoing titanium ion release occurs is evidenced by the presence of ionic titanium bound to transferrin in blood, and ongoing excretion in the urine of patients with titanium devices. However, as reports documenting the presence of titanium within tissues do not distinguish between particulate and ionic forms due to technical challenges, the degree to which ionic titanium is released into tissues is unknown. To determine the potential for titanium ion release into tissues, this study evaluates available in vitro evidence relating to the release of ionic titanium under physiological conditions. This is a systematic literature review of studies reporting titanium ion release into solutions from titanium devices under conditions replicating the interstitial pH and constituents. Inclusion and exclusion criteria were defined. Of 452 articles identified, titanium ions were reported in nine media relevant to human biology in seventeen studies. Only one study, using human serum replicated both physiological pH and the concentration of constituents while reporting the presence of titanium ions. While there is insufficient information to explain the factors that contribute to the presence of titanium ions in serum of humans implanted with titanium devices, currently available information suggests that areas of future inquiry include the role of transferrin and organic acids
Author Correction: Multi-target mode of action of silver against Staphylococcus aureus endows it with capability to combat antibiotic resistance
No full textThe original version of this Article contained an error in the author affiliations. Affiliation 1 incorrectly read “Department of Chemistry, The University of Hong Kong, Hong Kong S.A.R., People’s Republic of China”. This has now been corrected to “Department of Chemistry, State Key Laboratory of Synthetic Chemistry, CAS-HKU Joint Laboratory of Metallomics on Health and Environment, The University of Hong Kong, Hong Kong S.A.R., People’s Republic of China”. in both the PDF and HTML versions of the Article.link_to_OA_fulltex
Corroborating information from multiple sources
No full textInformation on the Internet is abundant but often inaccurate. Given a query that has a unique answer (as opposed to a Web query against a search engine), different Web sources might provide multiple conflicting answers. As a result, users are left with the burden of validating the correctness of the answer from each source. In order to tackle this problem, corroboration techniques have been proposed in order to identify the correct answer given a set of candidate answers extracted from the sources. Corroboration is the technique that evaluates the quality of the answers by considering the trustworthiness of the sources from which the answers are extracted. Intuitively, an answer extracted from a trustworthy source is more likely to be the correct answer. In return, the more correct answers it reports, the more trustworthy a source is. Unfortunately, several challenges arise before we can successfully apply a corroboration technique to find the correct answer to a query. First of all, the prime challenge is how to evaluate the trustworthiness of the sources and henceforth derive the quality of an answer based on the sources reporting it. Secondly, in a case where all the sources agree on a single candidate answer, how to validate the correctness of the answer. Third, in an application in which each source only provides a partial answer and the final answer is a combination of partial answers from multiple sources, how to evaluate the quality of answers and how to efficiently compute the correct answer. This thesis investigates several real world problems and proposes novel corroboration techniques that address each of the challenges presented above.
We first studied the problem of using corroboration for the task of question answering. With many web sources providing conflicting information on the Internet, users often have to rummage through a large number of different sites to both retrieve the information and ascertain the correctness of the retrieved information. While a naive approach that returns the most frequent answer can eliminate outlier answers such as typos, it fails to consider the fact that answers extracted from different pages are rarely equally important in answering the query. By ranking the answers based on the number, relevance and similarity of the web sources reporting them, as well as the prominence of the answers within the sources, our algorithm is able to efficiently identify accurate answers for most queries. We investigated the problem of verifying the correctness of claims that are unanimously agreed upon among all sources. Intuitively, a claim supported by all the sources must be true, simply because there is no other source rebutting it. However, it might not be the case in real world scenarios since agreeing sources might be out-dated or due to copy/paste. In such a scenario, existing corroboration approaches tend to reach consensus quickly and conclude that all claims are true since there is little conflict among the sources. We studied this problem in a real world scenario (restaurant listings) and proposed a novel corroboration algorithm that evaluates the claims on a gradual basis. More specifically, our approach divides the claims into multiple sets and evaluates each set of claims using a different trust score from each source. Different from existing algorithms that assign a single trust score to each source, our approach computes a set of finer-grained trust scores for each source that is used to evaluate different set of claims. In real world scenarios there often exist queries in which a single source is insufficient to provide a candidate answer. To answer these queries, users have to fetch and combine information from multiple sources and derive a potential final answer. Such cases are similar to the case of finding air ticket between two points without direct flight, and differs in that there is no centralized source (e.g., Expedia.com) that provides the information of all connecting flights. The process of combining information from two sources is similar to the join operation in relational databases and therefore this problem can be viewed as a join query processing over multiple web-accessible databases. The main bottleneck of join query processing is tuple accessing of web databases, which typically exhibit high and variable latency. In order to find the top-k answers for a join query, a branch-and-bound algorithm has to be developed to avoid computing scores of all candidates exhaustively. Our method efficiently computes bounds for partial query results and determines a good order in which it accesses the tables so as to minimize wasted efforts in the computation of top-k answers. In summary, this thesis studies real world problems that involve information from multiple sources. We demonstrate that using information from a single source is often of low quality and in some cases insufficient. We discuss the challenges in each individual problem and present novel corroboration algorithms that efficiently compute scores for the answers by taking into consideration of the trustworthiness of the sources.Ph.D.Includes bibliographical referencesby Minji W
Application of next generation sequencing for detection of protozoan pathogens in shellfish
No full textFood and waterborne protozoan pathogens can cause serious disease in people. Three common species Cryptosporidium parvum, Giardia enterica and Toxoplasma gondii can contaminate diverse shellfish species, including commercial oysters. Current methods of protozoan detection in shellfish are not standardized, and few are able to simultaneously identify multiple species. Here, we present a novel metabarcoding assay targeting the 18S rRNA gene followed by next generation sequencing (NGS) for simultaneous detection of Cryptosporidium spp., Giardia spp. and T. gondii spiked into oyster samples. We further developed a bioinformatic pipeline to process and analyze 18S rRNA data for protozoa classification. The ability of the NGS assay to detect protozoa was later compared with conventional PCR. Results demonstrated that background amplification of oyster and other eukaryotic DNA competed with that of protozoa for obtained sequence reads. Sequences of target protozoans were obtained across all spiking levels; however, low numbers of target sequences in negative controls imply that a threshold for true positives must be defined for assay interpretation. While this study focused on three target parasites, the ability of this approach to detect numerous known and potentially unknown protozoan pathogens make it a promising screening tool for monitoring protozoan contamination in food and water.Natural Science and Engineering Research Council of CanadaUniversity of Guelp
Network coding for robust wireless networks
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 157-167).Wireless networks and communications promise to allow improved access to services and information, ubiquitous connectivity, and mobility. However, current wireless networks are not well-equipped to meet the high bandwidth and strict delay requirements of future applications. Wireless networks suffer from frequent losses and low throughput. We aim to provide designs for robust wireless networks. This dissertation presents protocols and algorithms that significantly improve wireless network performance and effectively overcome interference, erasures, and attacks. The key idea behind this dissertation is in understanding that wireless networks are fundamentally different from wired networks, and recognizing that directly applying techniques from wired networks to wireless networks limits performance. The key ingredient underlying our algorithms and protocols is network coding. By recognizing the algebraic nature of information, network coding breaks the convention of routing networks, and allows mixing of information in the intermediate nodes and routers. This mixing has been shown to have numerous performance benefits, e.g. increase in throughput and robustness against losses and failures. We present three protocols and algorithms, each using network coding to harness a different characteristic of the wireless medium. We address the problem of interference, erasures, and attacks in wireless networks with the following network coded designs. -- Algebraic NC exploits strategic interference to provide a distributed, randomized code construction for multi-user wireless networks. Network coding framework simplifies the multi-user wireless network model, and allows us to describe the multi-user wireless networks in an algebraic framework. This algebraic framework provides a randomized, distributed code construction, which we show achieves capacity for multicast connections as well as a certain set of non-multicast connections. -- TCP/NC efficiently and reliably delivers data over unreliable lossy wireless networks. TCP, which was designed for reliable transmission over wired networks, often experiences severe performance degradation in wireless networks. TCP/NC combines network coding's erasure correction capabilities with TCP's congestion control mechanism and reliability. We show that TCP/NC achieves significantly higher throughput than TCP in lossy networks; therefore, TCP/NC is well suited for reliable communication in lossy wireless networks. -- Algebraic Watchdog takes advantage of the broadcast nature of wireless networks to provide a secure global self-checking network. Algebraic Watchdog allows nodes to detect malicious behaviors probabilistically, and police their neighbors locally using overheard messages. Unlike traditional detection protocols which are receiver-based, this protocol gives the senders an active role in checking the nodes downstream. We provide a trellis-based inference algorithm and protocol for detection, and analyze its performance. The main contribution of this dissertation is in providing algorithms and designs for robust wireless networks using network coding. We present how network coding can be applied to overcome the challenges of operating in wireless networks. We present both analytical and simulation results to support that network coded designs, if designed with care, can bring forth significant gains, not only in terms of throughput but also in terms of reliability, security, and robustness.by MinJi Kim.Ph.D
The influence of Korean culture in the Ethiopian entertainment industry
No full textDie "Welle" der südkoreanischen Kultur im Ausland wird als Hallyu bezeichnet und wurde anfangs von Unternehmen in der Unterhaltungsbranche initiiert, die auch als Talentmanagement-Agentur für junge, aufstrebende Künstler agieren. Das Hallyu-Syndrom ist auch zu einem effektiven Instrument der öffentlichen Diplomatie von der koreanischen Regierung geworden und hat nicht nur zur Stärkung der Jugend, sondern auch zur Entwicklung der Unterhaltungsindustrie und zum allgemeinen Wachstum des Landes anderer relevanter Industrien beigetragen. Die koreanische Regierung kennt den Nutzen von Hallyu und hat Entwicklungsländer mit einer sogenannten "Hallyu Kulturelle ODA" versorgt. In dieser Klausurarbeit wird untersucht, wie solche Entwicklungsmechanismen in Äthiopien am besten eingesetzt werden können. Für die Forschung wurde eine einjährige, partizipative Fallstudie an einer von einigen äthiopischen Hallyu-Fans gegründeten Firma namens MOM Entertainment durchgeführt. Diese Firma setzte als Richtwert, die Werte von anderen koreanischen Unternehmen in der Unterhaltungsbranche und wandte das TalentInkubationssystemen dieser Firmen in Äthiopien an, wobei sie ihren eigenen Entwicklungsmechanismus dabei nutzten. Die in dieser Arbeit verwendeten Forschungsmethoden beinhalten unter anderem Interviews, Fragebögen und statistische Analysen der Umfrageergebnisse, sowie die partizipative Beobachtung. Aus den Forschungsergebnissen analysiert der Autor, den neuen Mechanismus und die beobachtete Entwicklung in Äthiopien und beantwortet damit die Hauptforschungsfrage, wie die Stärkung der Jugend und die Emanzipation der Frauen in Äthiopien zu einer nachhaltigen Entwicklung der Unterhaltungsindustrie und zur Verbreitung ihrer eigenen “Kultur-Welle” führen könnte.The overseas ‘wave’ of South Korean culture, so called hallyu, was initiated by entertainment companies, also known as talent management agencies, for young aspiring artists. The hallyu syndrome has also become the Korean government’s most effective public diplomacy tool and has largely contributed not only to the empowerment of the youth but also to the development of the entertainment industry along with an overall growth of the country in relevant industries. Recognizing the impact of hallyu, the Korean government has provided “hallyu cultural ODA” to developing countries. This paper examines how such a developing mechanism can be best adopted in Ethiopia. For research, a year-long participatory case study was done on a company called MOM Entertainment established by Ethiopian hallyu fans, who benchmarked Korean entertainment companies and applied their talent incubating system to a new development mechanism for Ethiopia. The research methods used in this paper are interviews, questionnaires and statistical analysis of the survey results, as well as the participatory observation. From the research findings, the author analyzes the new mechanism and the movement observed in Ethiopia that answers the main research question of how empowering the youth and females could result in the sustainable development of the entertainment industry in Ethiopia along with the spread of their own wave of culture
Crystallographic studies of Helicobacter pylori chaperone HspB and human serum transferrin : metalloprotein as a template for heavy metal ions and their relevance to bismuth antiulcer drug
No full textIron is important for human health and serves as a co-factor in a variety of proteins and enzymes. Human serum transferrin (hTF) is an Fe(III) transporter in blood plasma which delivers metal to cells via a receptor-mediated endocytosis.
In the first part, crystal structures of FeNFeC-hTF and BiNFeC-hTF have been characterized. The N-lobes of the two structures adopt “partially opened” conformations between holo-hTF’s “closed” and apo-hTF’s “fully-opened” states. The N-lobe of BiNFeC-hTF opens wider than FeNFeC-hTF. Their metal-bound C-lobes are totally closed. Rigid-body movement and different inter-lobal hydrogen bonds for the “partially opened” conformations are observed. The binding affinities of four putative binding residues are in the order: Tyr188>Tyr95>Asp63~His249. In the N-lobe of BiNFeC-hTF, Tyr188, bicarbonate and a nitrilotriacetate (NTA) ion bind to Bi(III), whilst Tyr95 and Asp63 interact with NTA ligand. One (BiNFeC-hTF) or two (FeNFeC-hTF) glycan molecules are identified on the surface area of C-lobe.
In the second part, biocoordination chemistry of selected metal ions was investigated using hTF as a template. The Al(III), Fe(III), Ga(III), Dy(III) and Yb(III)-bound hTF exhibit closed conformations in the C-lobe and “fully-opened” conformations in the N-lobe. In these structures, malonate serves as an anion in the C-lobe and provides two tunable ligation sites that lead to a less distorted octahedral coordination geometry. As a result, the large lanthanide ions (Dy(III) and Yb(III)) turn from their favored high coordination numbers (8~12) and fit into the protein’s hexadental pocket. Unexpectedly, in the presence of malonate ion and the excess amount of Dy(III) ion, the Ga(III) can be partially replaced by Dy(III), although Ga(III) has a much higher affinity than Dy(III) towards the protein.
The chaperone system in Helicobacter pylorithat helps protein refold is assembled with HspB and HspA. In the third part, preliminary crystallographic work is reported for HspB and HspA. The chaperone HspB has been crystallized under various conditions and currently the diffraction resolution is 6.8Å. The co-chaperone HspA, which binds Bi(III) tightly, although its crystals diffract to 1.6Å, still needs improvement for data collection due to radiation damage.The crystal structure of HspB revealed that HspB presents as a single-ring heptamer, though it is a mixture of dimer, tetramer and a higher oligomer in solution. The interactions between HspB monomers in crystal structure are significantly weaker than that of GroEL (counterpart in Escherichia coli) monomers which may makes the HspB heptamer easier to dissociate in solution.published_or_final_versionChemistryDoctoralDoctor of Philosoph
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