510 research outputs found
Null-steering LMS dual-polarised adaptive antenna arrays for GPS
No full textThe implementation of a null steering antenna array using dual polarised patch antennas is considered. The best optimality criterion for a dual polarised GPS antenna array is briefly discussed, followed by a description of the associated LMS algorithm. To prevent weight vector drift a version of the circular leakage LMS algorithm was used. The implementation details of a simplified circular leakage algorithm that is more suited to an FPGA implementation are presented.W C Cheuk, M Trinkle & D A Gra
*-Regularity and uniqueness of C*-norm for general *-algebras
No full textM.Phil.*-regularity property was first studied by J. Boidol in 1978. Let G be a locally compact group. We put PrimC*(G) and Prim L¹(G) the spaces of kernels of topologically irreducible representations of the group C*-algebra C*(G) and the L¹-algebra L¹(G) respectively, which both are endowed with the hull-kernel topologies. A locally compact group G is said to be *-regular if the canonical map from PrimC*(G) onto Prim*L¹(G), which is by definition a continuous surjection,is a homeomorphism. Therefore, a group G is *-regular if and only if the Fell topology and the hull-kernel topology on the set L¹(G) of all equivalence classes of topologically irreducible representations of L¹(G) coincide.In 1983, B. A. Barnes generalised the *-regularity property to a wider class of *-algebras, called reduced BG*-algebras. This is an algebraic property and is closely related to the C*-uniqueness property.We will give a survey about the ” *-regularity and uniqueness of C*-norm for general *-algebras ” in this thesis. First, we recall some basic tools in the Chapters 2,3. Next, these two properties will be introduced and discussed in Chapter 4. Most of the interesting results are collected in this last chapter from papers The properties *-regularity and uniqueness of C*-norm in a general *-algebra (B. A. Barnes, 1983), and *-regularity and uniqueness of C*-norm for tensor products of *-algebras (W. Hauenschild, E. Kaniuth, and A. Voigt, 1990).1978年，J.Boidol開始了關於*正則的研究。設G為局部緊群，記PrimC*(G)和Prim*L¹(G)由群C*代數C*(G)和群代數L¹(G)中的拓撲不可約*表⽰的核所組成(∗)的拓撲空間，依包核拓撲。我們稱⼀個局部緊群G為*正則，如果從PrimC*(G)到PrimL¹(G)的典範映射是同胚。由此可⾒，群G是*正則，當且僅當L¹(G)上的Fell拓撲等同於包核拓撲。1983年，B.A.Barnes將*正則性質推廣⾄更⼀般的 * 代數。在這篇綜述⽂章中，我們會綜合學術⽂章 The properties *-regularity and uniqueness of C*-norm in a general *-algebra (B. A. Barnes, 1983) 和 *-regularity and uniqueness of C*-norm for tensor products of *-algebras (W. Hauenschild, E. Kaniuth, and A. Voigt, 1990) 的結果。Cheuk, Tak Ming.Thesis M.Phil. Chinese University of Hong Kong 2019.Includes bibliographical references (leaves 98-100).Abstracts also in Chinese.Title from PDF title page (viewed on …)
The Mutagenic Plasticity of the Cholera Toxin B-Subunit Surface Residues: Stability and Affinity
No full textMastering selective molecule trafficking across human cell membranes poses a formidable challenge in healthcare biotechnology while offering the prospect of breakthroughs in drug delivery, gene therapy, and diagnostic imaging. The cholera toxin B-subunit (CTB) has the potential to be a useful cargo transporter for these applications. CTB is a robust protein that is amenable to reengineering for diverse applications; however, protein redesign has mostly focused on modifications of the N- and C-termini of the protein. Exploiting the full power of rational redesign requires a detailed understanding of the contributions of the surface residues to protein stability and binding activity. Here, we employed Rosetta-based computational saturation scans on 58 surface residues of CTB, including the GM1 binding site, to analyze both ligand-bound and ligand-free structures to decipher mutational effects on protein stability and GM1 affinity. Complimentary experimental results from differential scanning fluorimetry and isothermal titration calorimetry provided melting temperatures and GM1 binding affinities for 40 alanine mutants among these positions. The results showed that CTB can accommodate diverse mutations while maintaining its stability and ligand binding affinity. These mutations could potentially allow modification of the oligosaccharide binding specificity to change its cellular targeting, alter the B-subunit intracellular routing, or impact its shelf-life and in vivo half-life through changes to protein stability. We anticipate that the mutational space maps presented here will serve as a cornerstone for future CTB redesigns, paving the way for the development of innovative biotechnological tools
Protocolos tolerantes a faltas bizantinas para transações em bancos de dados
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2015.No âmbito de sistemas computacionais, a noção de transações constitui um dos elementos mais fundamentais para a especificação e implementação de aplicações com requisitos de confiabilidade e consistência, quanto à manipulação de dados. Ao longo dos anos, os sistemas de gerenciamento de banco de dados relacionais (SGBDR) têm sido considerados como componentes chave para o processamento de transações em sistemas computacionais; e, embora algumas alternativas aos SGBDRs tenham surgido nos últimos anos, há perspectivas de que um número significativo de sistemas computacionais permaneçam a utilizar os SGBDRs nos anos vindouros. Neste sentido, é imperioso que requisitos como confiabilidade, disponibilidade, desempenho, tolerância a faltas e consistência, sejam mantidos no SGBDR, com vista para o correto processamento de transações. Tais atributos podem ser obtidos por meio de replicação, sendo que a literatura é vasta em termos de soluções que visam a disponibilidade dos dados a despeito de faltas por parada intermitentes ou permanentes. Todavia, faltas oriundas da corrupção de dados em disco ou em memória RAM devido a efeitos físicos, ou decorrente de bugs no SGBDR, não afetam a disponibilidade dos dados, mas sim a integridade e a consistência destes. Estas faltas, que são caracterizadas como bizantinas, historicamente têm sido encontradas em SGBDRs, e elas afetam o processamento de transações comprometendo não apenas a exatidão, mas também o estado do banco de dados. A literatura dispõe de poucas soluções para lidar com faltas bizantinas em SGBDRs, onde algumas são baseadas em hipóteses difíceis de serem substanciadas na prática; ou em modelos de consistência mais relaxados, que podem causar problemas de integridade, consistência ou até mesmo corrupção de dados. Isto posto, elas não atendem plenamente todos os tipos de aplicações. Neste ensejo, esta tese versa sobre problemas relacionados ao processamento e a terminação de transações em SGBDRs e sistemas distribuídos, em ambientes com sujeição a faltas bizantinas. Para isso, esta tese apresenta duas grandes contribuições no âmbito de transações em SGBDRs. A primeira consiste num protocolo que permite o processamento e terminação de transações, a despeito de faltas bizantinas nas réplicas de bancos de dados  o primeiro da literatura a explorar a semântica de consistência mais forte de transações  , a partir de um protocolo de replicação tolerante a faltas bizantinas totalmente distribuído. A segunda investiga o problema da terminação de transações distribuídas em ambientes sujeitos a faltas bizantinas  um problema sem solução pela literatura  , que é conhecido como Validação Atômica Não-Bloqueante (NBAC) e visa assegurar uma decisão uniforme para os participantes da transação acerca da validação ou anulação das operações executadas num ambiente distribuído de banco de dados. A contribuição para este problema se baseia na investigação dos aspectos práticos necessários para resolvê-lo, onde é introduzido o conceito de Gerenciador Colaborativo de Transações em substituição ao Gerenciador de Transações, tradicionalmente empregado como agente num protocolo NBAC. A solução proposta para resolver o NBAC com faltas bizantinas baseia-se num conceito novo, que adota a tecnologia de virtualização como suporte para a especificação de uma arquitetura de sistema distribuído que permite circunscrever o problema. As soluções propostas foram comparadas de maneira analítica com soluções encontradas na literatura, bem como através de ensaios experimentais, a fim de comprovar a viabilidade das mesmas.Abstract : Within computer systems, the concept of transaction is one of the most fundamental elements for the specification and implementation of applications with reliability and consistency requirements concerning handling of data. Over the years, relational database management systems (RDBMS) have been considered key components for transaction processing in computer systems; and although some alternatives to RDBMSs have emerged in recent years, there are prospects that a significant number of computer systems will continute to use RDBMSs in coming years. In this sense, the need to provide reliability, availability, performance, fault tolerance and consistency, regarding transaction processing in RDBMS is imminent. Such attributes may be obtained through database replication. The literature is extensive in terms of solutions for data availability regardless of crash faults (e.g. intermittent or permanent). However, faults arising from the disk data corruption or RAM data corruption due to physical effects, or due to bugs in the RDBMS, do not affect the availability of data, though they affect their integrity and consistency. These faults, which are known as Byzantine, have historically been found in RDBMSs, and they affect transaction processing undermining not only the accuracy but also the database state. The literature offers few solutions to deal with Byzantine faults in RDBMSs, where some are based on difficult cases to be used in practice; or more relaxed consistency models, which can cause integrity, consistency or even data corruption problems. So, they are not addressed to all types of applications. As it is, this thesis deals with problems related to transaction processing and transaction termination on RDBMS and distributed systems, in environments subject to Byzantine fault. To this end, this thesis presents two major contributions to the transaction level in RDBMSs. The first is a protocol that allows the transaction processing and transaction, despite Byzantine faults in databases replicas  the first in literature that explores the strongest consistency semantics of transactions (e.g. serializability)  , by means of a fully distributed Byzantine fault tolerant database replication protocol. The second investigates the agreement problem related to transaction termination in distributed systems, also in environments subject to Byzantine fault  an unsolved problem in the literature. The Non Blocking Atomic Commitment (NBAC), as it known, aims to ensure a uniform decision for the transaction participants about the operations performed in a distributed database environment, that is, commit or abort them. The contribution to this problem is based on the investigation of practical and necessary conditions, to solve it. So, this thesis introduces the Collaborative Transaction Manager to replace the Transaction Manager, traditionally used as an agent on a NBAC protocol. The solution proposed to solve the NBAC with Byzantine fault is based on a new concept, adopting virtualization technology as a support for the specification of a distributed system architecture which makes the problem feasible. The proposed solutions were compared analytically with solutions found in the literature as well as through experimental tests in order to prove their feasibility
Mesobi: memória transacional em software tolerante a faltas bizantinas
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência da Computação, Florianópolis, 2015.Memória Transacional em Software (STM) é um modelo utilizado para tratar acesso concorrente a dados compartilhados, onde programadores não precisam lidar explicitamente com mecanismos de controle de concorrência, como locks. O programador, apenas delineia qual parte do código necessita ser tratado como concorrente e sua execução seguirá o modelo transacional, respeitando as propriedades: atomicidade, consistência e isolação. É proposto nessa dissertação um modelo denominado Mesobi: Memória Transacional em Software Tolerante a Faltas Bizantinas onde transações somente leitura não abortam. Existem algumas abordagens na literatura que utilizam Memória Transacional em Software, das quais grande parte tolera faltas de parada mas pouco se fala sobre faltas maliciosas. Somente o trabalho de Zhang 2012 faz tolerância a faltas Bizantinas no contexto de STM; sua proposta utiliza dois clusters para alcançar tolerância a faltas Bizantinas.No modelo de Zhang, transações somente leitura podem ser abortadas, não é suportada a execução de transações interativas e não é possível executar transações de forma otimista. O Mesobi permite alcançar tolerância a faltas Bizantinas utilizando (3f+1) réplicas, sendo que, f é o número de faltas toleradas. O modelo consiste em inicialmente tentar executar as transações de forma otimista sem a necessidade de executar o protocolo Bizantino. Transações conflitantes localmente não são iniciadas de imediato com isso evita-se trabalho improdutivo. É possível e viável a execução de transações pré-declaradas e interativas no mesmo ambiente, sendo que, transações interativas têm pior desempenho devido a sua maior troca de mensagens.Abstract : Software Transactional Memory (STM) is a model to deal concurrent accesses on shared data. With STM developers do not need to cope with explicit concurrency control mechanisms like locks. Instead developers can write parallel portions of code as transactions, which are garanteed to execute atomically and in isolation regardless of eventual data races. In this dissertation we propose a model named Mesobi: Memória Transacional em Software Tolerante a Faltas Bizantinas in which read-only transactions do not abort. There are some approaches in literature that use STM, but most of them treat crash faults, but few deal with arbitrary faults. The work presented by Zhang 2012 mentions Byzantine Fault Tolerance (BFT) in STM context, but two clusters are necessary, one for consensus and another to execute transactions. Zhang's model abort read-only transactions, does not use optimistic execution neither interactive transactions processing. It achieves BFT using (3f+1) replicas where f represents the number of tolerated faults. The model executes in an optimistic fashion the transactions without the BFT protocol. Conflicting local transactions are not executed immediately thereby saving wasted work. Execution and consistency tests showed that execution of interactive and pre-declared transactions on same environment are possible and practical. Interactive transactions have worse performance than pre-declared due to need of more message exchanges
Synthesis and structural characterization of monomeric heterobimetallic oxides with a Ge(II)-O-M skeleton (M = Yb, Y)
No full textThe germanium hydroxide complexes LGe(mu-O)M(THF)Cp(2) (M = Yb, 1; Y, 2; L = HC[C(Me)N(Ar)](2); Ar = 2,6-iPr(2)C(6)H(3)) were prepared by the reaction of LGeOH with Cp(3)M (M = Yb, Y) in THF at ambient temperature with the elimination of HCp. 1 and 2 are pale-yellow solids. Both compounds crystallize isotypically as monomers in a triclinic space group P (1) over bar (pseudo- merohedrally twinned, two independent molecules) and were found to be stable in the solid state and in solution at room temperature. The six-membered C(3)N(2)Ge rings in 1 and 2 display a boat conformation with the germanium and the gamma-C out-of-plane. The Ge-O-M skeleton exhibits a bent arrangement (angles 151-154 degrees). The (1)H NMR investigation of 2 confirmed that the solid-state structure is also found in solution
Efficient visible light photocatalytic oxidation of NO on F-, N-codoped spherical TiO₂ synthesized via ultrasonic spray pyrolysis
No full textAuthor name used in this publication: Frank S. C. LeeVersion of RecordPublishedC
Unimolecular dissociation of polyatomic ions by molecular beam photoionization mass spectrometry and collision-induced dissociation
No full textThe photoionization efficiency (PIE) specta for M(CO)n+ (n = 0-6) from M(CO)6, M = Cr, Mo, and W, have been measured in the photon energy range of 650-1600 A. Based on the ionization energies for M(CO)6 and appearance energies (AEs) for M(CO)n+ (n = 0-5) determined here, we have obtained estimates for the sequential bond dissociation energies (D0) for CO-M(CO)n-1+ (n = 1-6). The comparison of the first D0 values for M(CO)6+ obtained here and those for M(CO)6 provides strong support for the theoretical analysis that the importance of relativistic effects, which give rise to more efficient M to CO [pi]-back-donation in M(CO)6, is in the order W(CO)6>Mo(CO)6>Cr(CO)6.;The appearance energies for the formation of SF3+,sF4+, and SF5+ from SF6, and SF2+ and SF3+ from SF4 are reexamined by the molecular beam photoionization mass spectrometric method. Based on comparisons between G2 and G2(MP2) predictions and experimental measurements, we recommend a self-consistent set of experimental [delta]fH°0 for SFn,sFn+, and SFn- (n = 1-6). We have rationalized the theoretical structures for SFn,sFn+, and SFn- (n = 1-6) using the valence-shell-electron-pair-repulsion theory. The alternating patterns of high and low values observed for the SFn-1-F (n = 2-6), SFn-1+-F (n = 3-5), and SFn-1--F (n = 2-6) bond dissociation energies at 0 K and for the IEs and EAs of SFn (n = 1-6) are attributed to special stabilities for closed-shell molecular species with fully-filled valence electron shells around the central S atoms;Strong preference is observed for the C-S bond scission process, leading to the formation of CH3+ + SH, CH3CH2+ + SH, and CH2SH+ + CH3 in the collision induced dissociation (CID) reaction of CH3SH+, CH3CH2SH+, and CH3SCH3+ + Ar, respectively. Since the dissociation energies for C-S bond are significantly higher than that of H-elimination, this observation indicates that the CID process is non-statistical. The high yield for the C-S bond breakage is attributed to the more efficient translational to vibrational energy transfer for the C-S stretching mode than for C-H and S-H stretching modes via collisional activation, and to weak couplings between the low frequency C-S and high frequency C-H and S-H stretching vibrational modes of CH3SH+, CH3CH2SH+ and CH3SCH3+.</p
Changes in inflammatory response after endovascular treatment for type B aortic dissection
No full textThis present study aims to investigate the changes in the inflammatory markers after elective endovascular treatment of Type B aortic dissection with aneurysm, as related to different anatomical features of the dissection flap in the paravisceral perfusion. Consecutive patients with type B aortic dissections with elective endovascular stent graft repair were recruited and categorized into different groups. Serial plasma levels of cytokines (Interleukin-1β, -6, -8, -10, TNF-α), chemokines (MCP-1), and serum creatinine were monitored at pre-, peri- and post-operative stages. The length of stent graft employed in each surgery was retrieved and correlated with the change of all studied biochemical parameters. A control group of aortic dissected patients with conventional medication management was recruited for comparing the baseline biochemical parameters. In total, 22 endovascular treated and 16 aortic dissected patients with surveillance were recruited. The endovascular treated patients had comparable baseline levels as the non-surgical patients. There was no immediate or thirty day-mortality, and none of the surgical patients developed post-operative mesenteric ischaemia or clinically significant renal impairment. All surgical patients had detectable pro-inflammatory mediators, but none of the them showed any statistical significant surge in the peri-operative period except IL-1β and IL-6. Similar results were obtained when categorized into different groups. IL-1β and IL-6 showed maximal levels within hours of the endovascular procedure (range, 3.93 to 27.3 higher than baseline; p = 0.001), but returned to baseline 1 day post-operatively. The change of IL-1β and IL-6 at the stent graft deployment was statistically greater in longer stent graft (p>0.05). No significant changes were observed in the serum creatinine levels. In conclusion, elective endovascular repair of type B aortic dissection associated with insignificant changes in inflammatory mediators and creatinine. All levels fell toward basal levels post-operatively suggesting that thoracic endovascular aortic repair is rather less aggressive with insignificant inflammatory modulation. © 2012 Cheuk et al.published_or_final_versio
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