Dengue virus binding to human leukocyte cell lines: receptor usage differs between cell types and virus strains

Monocyte macrophages (M phi) are thought to be the principal target cells for the dengue viruses (DV), the cause of dengue fever and hemorrhagic fever. Cell attachment is mediated by the virus envelope (E) protein, but the host-cell receptors remain elusive. Currently, candidate receptor molecules include proteins, Fc receptors, glycosaminoglycans (GAGs) and lipopolysaccharide binding CD14-associated molecules. Here, we show that in addition to M phi, cells of the T- and B-cell lineages, and including cells lacking GAGs, can bind and become infected with DV. The level of virus binding varied widely between cell lines and, notably, between virus strains within a DV serotype. The latter difference may be ascribable to one or more amino acid differences in domain II of the E protein. Heparin had no significant effect on DV binding, while heparinase treatment of cells in all cases increased DV binding, further supporting the contention that GAGs are not required for DV binding and infection of human cells. In contrast to a recent report, we found that lipopolysaccharide (LPS) had either no effect or enhanced DV binding to, and infection of various human leukocyte cell lines, while in all virus-cell combinations, depletion of Ca2+/Mg2+ enhanced DV binding. This argues against involvement of beta (2) integrins in virus-host cell interactions, a conclusion in accord with the demonstration of three virus binding membrane proteins of < 75 kDa. Collectively, the results of this study question the purported exclusive importance of the E protein domain III in DV binding to host cells and point to a far more complex interaction between various target cells and, notably, individual DV strains. (C) 2001 Elsevier Science B.V. All rights reserved.

How different is Mediterranean Caulerpa taxifolia (Caulerpales : Chlorophyta) to other populations of the species?

The green macroalgal species Caulerpa taxifolia is indigenous to tropical/subtropical Australia, ranging as far south as 28degrees and 29degrees 15' S on the Australian mainland east and west coasts, respectively. The origin of disjunct populations of the species, discovered in 2000 on the Australian mainland east coast at localities to 35degrees S remains unknown, variously attributed to introduced exotic strains or range extensions from other eastern Australian populations. Some naturally occurring Australian populations of C. taxifolia are similar to Mediterranean C. taxifolia. In Australia, large broad forms of the species, which have been known in the region since 1860, grow luxuriantly in sheltered seagrass meadows, with some of these populations tolerating minimum surface seawater temperatures in winter of 12.5 to 14.5degreesC. Accordingly, the contention that the Mediterranean has been invaded by a genetically-modified, large, cold-adapted strain of C. taxifolia may be incorrect. It is crucial that genetic markers (DNA fingerprinting, microsatellites) sensitive at the population level are used to accurately determine the genetic relatedness of C. taxifolia populations.

Sediment yield and impacts from river catchments to the Great Barrier Reef lagoon

Land use intensification is estimated to result in an overall increase in sediment delivery to the Great Barrier Reef lagoon by a factor of approximately four. Modelling suggests that, following land use intensification, croplands cause the greatest increase of sediment yield and sediment concentration, whereas erosion of grazing land is the main contemporary source of sediments, primarily owing to the large spatial extent of this land use. The spatial pattern of sediment yield to the coast after land use intensification is strongly correlated with the pattern under natural conditions, although the greatest increase is estimated to have occurred in the wet-dry catchments. Sediment transport and resuspension processes have led to the development of a strongly sediment-partitioned shelf, with modern mud-rich sediments almost exclusively restricted to the inner and inner-middle shelf, northward-facing embayments and in the lee of headlands. Elevated sediment concentrations increase the potential transport rates of nutrients and other pollutants. Whether increased sediment supply to the coastal zone has impacted on reefs remains a point of contention. More sediment load data need to be collected and analysed in order to make detailed estimates of catchment yields and establish the possible sediment impact on the Great Barrier Reef.

When social psychology became less social: Prasad and the history of rumor research

Rumor research, in general, and its delayed incorporation of the work, of rumor researcher Jamuna Prasad, in particular, exemplify how the intellectual climate of American social psychology discouraged the development of social approaches. In the present paper, we explain his conceptualization of how rumors start and spread, and explore findings from subsequent research supporting or negating his propositions. It is our contention that, although Prasad had identified the basic variables involved in rumor generation and transmission correctly, mainstream social psychological research in the 1940s did not incorporate his contributions. Instead, mirroring the Zeitgeist of American social psychology, rumor research was approached from a predominantly individual level of analysis. In the present paper, the authors have tried to resurrect some of the group-level variables from Prasad's treatment of rumor and to suggest that social psychology adopt a more 'social' approach to rumor.

Nuclear weapons as obstacles to international security

This article argues that nuclear weapons serve no useful purpose in military calculations; moreover, their continued retention invites the dangers of further proliferation and of accidental use. They are thus defined here as obstacles to, rather than as facilitators of, international security. Seven reasons are presented to support this contention, including an assessment of the moral implications and the strategic limitations of nuclear weapons. Despite these limitations, and the recent commitments made by the nuclear weapon states to eliminate their arsenals, nuclear weapons remain central to the strategic doctrines of these states. Several reasons are put forward to explain why this retention continues, including the unchanging nature of strategic mindsets, the presence of vested interests, and now, in the case of the USA at least, a renewed reliance on nuclear weapons, regardless of how appropriate and effective such a strategy might be against emerging terrorist or `rogue state' threats.

But what if I don't want to wait forever?

We present an abstract model of the leader election protocol used in the IEEE 1394 High Performance Serial Bus standard. The model is expressed in the probabilistic Guarded Command Language. By formal reasoning based on this description, we establish the probability of the root contention part of the protocol successfully terminating in terms of the number of attempts to do so. Some simple calculations then allow us to establish an upper bound on the time taken for those attempts.

Dos cl��ssicos aos hereges : Keynes e a economia de seu tempo

O artigo trata da posi����o te��rica de Keynes relativamente �� economia cl��ssica e �� abordagem denominada her��tica. A primeira se����o resgata os tra��os distintivos das escolas cl��ssica e neocl��ssica segundo a demarca����o proposta por Keynes, bem como as cr��ticas por ele dirigidas ��s principais teses defendidas por essas linhagens te��ricas. A seguir, retoma-se a sua avalia����o dos argumentos subconsumistas, indicando-se os seus pontos de converg��ncia e distanciamento dessa vis��o econ��mica. Na continua����o, apresentam-se as interpreta����es neocl��ssicas ao problema da demanda, comentando-se a rela����o da obra de Keynes com a tradi����o marshalliana. A ��ltima se����o avalia a teoria neocl��ssica do produto real sob condi����es c��clicas e introduz a vers��o de Keynes para o equil��brio agregado definido pelas propens��es a gastar e a investir, al��m de indicar o componente de fragilidade da leitura marshalliana de sua estrutura te��rica. Por fim, comenta-se a contribui����o de Keynes ao conhecimento econ��mico da ��poca perante a escola cl��ssica e os hereges.

Remote Patient Monitoring Based on ZigBee: Lessons from a Real-World Deployment

AIM: This work presents detailed experimental performance results from tests executed in the hospital environment for Health Monitoring for All (HM4All), a remote vital signs monitoring system based on a ZigBee�� (ZigBee Alliance, San Ramon, CA) body sensor network (BSN). MATERIALS AND METHODS: Tests involved the use of six electrocardiogram (ECG) sensors operating in two different modes: the ECG mode involved the transmission of ECG waveform data and heart rate (HR) values to the ZigBee coordinator, whereas the HR mode included only the transmission of HR values. In the absence of hidden nodes, a non-beacon-enabled star network composed of sensing devices working on ECG mode kept the delivery ratio (DR) at 100%. RESULTS: When the network topology was changed to a 2-hop tree, the performance degraded slightly, resulting in an average DR of 98.56%. Although these performance outcomes may seem satisfactory, further investigation demonstrated that individual sensing devices went through transitory periods with low DR. Other tests have shown that ZigBee BSNs are highly susceptible to collisions owing to hidden nodes. Nevertheless, these tests have also shown that these networks can achieve high reliability if the amount of traffic is kept low. Contrary to what is typically shown in scientific articles and in manufacturers' documentation, the test outcomes presented in this article include temporal graphs of the DR achieved by each wireless sensor device. CONCLUSIONS: The test procedure and the approach used to represent its outcomes, which allow the identification of undesirable transitory periods of low reliability due to contention between devices, constitute the main contribution of this work.

Avalia����o do impacto da contrata����o p��blica eletr��nica na efici��ncia do processo de compras do Hospital Distrital de Santar��m

Mestrado em Interven����o S��cio-Organizacional na Sa��de. ��rea de especializa����o: Pol��ticas de Administra����o e Gest��o de Servi��os de Sa��de.

Supporting intra-task parallelism in real-time multiprocessor systems

Os sistemas de tempo real modernos geram, cada vez mais, cargas computacionais pesadas e din��micas, come��ando-se a tornar pouco expect��vel que sejam implementados em sistemas uniprocessador. Na verdade, a mudan��a de sistemas com um ��nico processador para sistemas multi- processador pode ser vista, tanto no dom��nio geral, como no de sistemas embebidos, como uma forma eficiente, em termos energ��ticos, de melhorar a performance das aplica����es. Simultaneamente, a prolifera����o das plataformas multi-processador transformaram a programa����o paralela num t��pico de elevado interesse, levando o paralelismo din��mico a ganhar rapidamente popularidade como um modelo de programa����o. A ideia, por detr��s deste modelo, �� encorajar os programadores a exporem todas as oportunidades de paralelismo atrav��s da simples indica����o de potenciais regi��es paralelas dentro das aplica����es. Todas estas anota����es s��o encaradas pelo sistema unicamente como sugest��es, podendo estas serem ignoradas e substitu��das, por construtores sequenciais equivalentes, pela pr��pria linguagem. Assim, o modo como a computa����o �� na realidade subdividida, e mapeada nos v��rios processadores, �� da responsabilidade do compilador e do sistema computacional subjacente. Ao retirar este fardo do programador, a complexidade da programa����o �� consideravelmente reduzida, o que normalmente se traduz num aumento de produtividade. Todavia, se o mecanismo de escalonamento subjacente n��o for simples e r��pido, de modo a manter o overhead geral em n��veis reduzidos, os benef��cios da gera����o de um paralelismo com uma granularidade t��o fina ser��o meramente hipot��ticos. Nesta perspetiva de escalonamento, os algoritmos que empregam uma pol��tica de workstealing s��o cada vez mais populares, com uma efici��ncia comprovada em termos de tempo, espa��o e necessidades de comunica����o. Contudo, estes algoritmos n��o contemplam restri����es temporais, nem outra qualquer forma de atribui����o de prioridades ��s tarefas, o que impossibilita que sejam diretamente aplicados a sistemas de tempo real. Al��m disso, s��o tradicionalmente implementados no runtime da linguagem, criando assim um sistema de escalonamento com dois n��veis, onde a previsibilidade, essencial a um sistema de tempo real, n��o pode ser assegurada. Nesta tese, �� descrita a forma como a abordagem de work-stealing pode ser resenhada para cumprir os requisitos de tempo real, mantendo, ao mesmo tempo, os seus princ��pios fundamentais que t��o bons resultados t��m demonstrado. Muito resumidamente, a ��nica fila de gest��o de processos convencional (deque) �� substitu��da por uma fila de deques, ordenada de forma crescente por prioridade das tarefas. De seguida, aplicamos por cima o conhecido algoritmo de escalonamento din��mico G-EDF, misturamos as regras de ambos, e assim nasce a nossa proposta: o algoritmo de escalonamento RTWS. Tirando partido da modularidade oferecida pelo escalonador do Linux, o RTWS �� adicionado como uma nova classe de escalonamento, de forma a avaliar na pr��tica se o algoritmo proposto �� vi��vel, ou seja, se garante a efici��ncia e escalonabilidade desejadas. Modificar o n��cleo do Linux �� uma tarefa complicada, devido �� complexidade das suas fun����es internas e ��s fortes interdepend��ncias entre os v��rios subsistemas. N��o obstante, um dos objetivos desta tese era ter a certeza que o RTWS �� mais do que um conceito interessante. Assim, uma parte significativa deste documento �� dedicada �� discuss��o sobre a implementa����o do RTWS e �� exposi����o de situa����es problem��ticas, muitas delas n��o consideradas em teoria, como �� o caso do desfasamento entre v��rios mecanismo de sincroniza����o. Os resultados experimentais mostram que o RTWS, em compara����o com outro trabalho pr��tico de escalonamento din��mico de tarefas com restri����es temporais, reduz significativamente o overhead de escalonamento atrav��s de um controlo de migra����es, e mudan��as de contexto, eficiente e escal��vel (pelo menos at�� 8 CPUs), ao mesmo tempo que alcan��a um bom balanceamento din��mico da carga do sistema, at�� mesmo de uma forma n��o custosa. Contudo, durante a avalia����o realizada foi detetada uma falha na implementa����o do RTWS, pela forma como facilmente desiste de roubar trabalho, o que origina per��odos de inatividade, no CPU em quest��o, quando a utiliza����o geral do sistema �� baixa. Embora o trabalho realizado se tenha focado em manter o custo de escalonamento baixo e em alcan��ar boa localidade dos dados, a escalonabilidade do sistema nunca foi negligenciada. Na verdade, o algoritmo de escalonamento proposto provou ser bastante robusto, n��o falhando qualquer meta temporal nas experi��ncias realizadas. Portanto, podemos afirmar que alguma invers��o de prioridades, causada pela sub-pol��tica de roubo BAS, n��o compromete os objetivos de escalonabilidade, e at�� ajuda a reduzir a conten����o nas estruturas de dados. Mesmo assim, o RTWS tamb��m suporta uma sub-pol��tica de roubo determin��stica: PAS. A avalia����o experimental, por��m, n��o ajudou a ter uma no����o clara do impacto de uma e de outra. No entanto, de uma maneira geral, podemos concluir que o RTWS �� uma solu����o promissora para um escalonamento eficiente de tarefas paralelas com restri����es temporais.

Cycle time properties of the PROFIBUS timed-token protocol

A recent trend in distributed computer-controlled systems (DCCS) is to interconnect the distributed computing elements by means of multi-point broadcast networks. Since the network medium is shared between a number of network nodes, access contention exists and must be solved by a medium access control (MAC) protocol. Usually, DCCS impose real-time constraints. In essence, by real-time constraints we mean that traffic must be sent and received within a bounded interval, otherwise a timing fault is said to occur. This motivates the use of communication networks with a MAC protocol that guarantees bounded access and response times to message requests. PROFIBUS is a communication network in which the MAC protocol is based on a simplified version of the timed-token protocol. In this paper we address the cycle time properties of the PROFIBUS MAC protocol, since the knowledge of these properties is of paramount importance for guaranteeing the real-time behaviour of a distributed computer-controlled system which is supported by this type of network.

Convex optimization framework for intermediate deadline assignment in soft and hard real-time distributed systems

It is generally challenging to determine end-to-end delays of applications for maximizing the aggregate system utility subject to timing constraints. Many practical approaches suggest the use of intermediate deadline of tasks in order to control and upper-bound their end-to-end delays. This paper proposes a unified framework for different time-sensitive, global optimization problems, and solves them in a distributed manner using Lagrangian duality. The framework uses global viewpoints to assign intermediate deadlines, taking resource contention among tasks into consideration. For soft real-time tasks, the proposed framework effectively addresses the deadline assignment problem while maximizing the aggregate quality of service. For hard real-time tasks, we show that existing heuristic solutions to the deadline assignment problem can be incorporated into the proposed framework, enriching their mathematical interpretation.

Real-time scheduling of parallel tasks in the Linux Kernel

This paper proposes a global multiprocessor scheduling algorithm for the Linux kernel that combines the global EDF scheduler with a priority-aware work-stealing load balancing scheme, enabling parallel real-time tasks to be executed on more than one processor at a given time instant. We state that some priority inversion may actually be acceptable, provided it helps reduce contention, communication, synchronisation and coordination between parallel threads, while still guaranteeing the expected system���s predictability. Experimental results demonstrate the low scheduling overhead of the proposed approach comparatively to an existing real-time deadline-oriented scheduling class for the Linux kernel.

Software transactional memory as a building block for parallel embedded realtime systems

The recent trends of chip architectures with higher number of heterogeneous cores, and non-uniform memory/non-coherent caches, brings renewed attention to the use of Software Transactional Memory (STM) as a fundamental building block for developing parallel applications. Nevertheless, although STM promises to ease concurrent and parallel software development, it relies on the possibility of aborting conflicting transactions to maintain data consistency, which impacts on the responsiveness and timing guarantees required by embedded real-time systems. In these systems, contention delays must be (efficiently) limited so that the response times of tasks executing transactions are upper-bounded and task sets can be feasibly scheduled. In this paper we assess the use of STM in the development of embedded real-time software, defending that the amount of contention can be reduced if read-only transactions access recent consistent data snapshots, progressing in a wait-free manner. We show how the required number of versions of a shared object can be calculated for a set of tasks. We also outline an algorithm to manage conflicts between update transactions that prevents starvation.

An Explicit GTS allocation algorithm for IEEE 802.15.4

The IEEE 802.15.4 standard provides appealing features to simultaneously support real-time and non realtime traffic, but it is only capable of supporting real-time communications from at most seven devices. Additionally, it cannot guarantee delay bounds lower than the superframe duration. Motivated by this problem, in this paper we propose an Explicit Guaranteed time slot Sharing and Allocation scheme (EGSA) for beacon-enabled IEEE 802.15.4 networks. This scheme is capable of providing tighter delay bounds for real-time communications by splitting the Contention Free access Period (CFP) into smaller mini time slots and by means of a new guaranteed bandwidth allocation scheme for a set of devices with periodic messages. At the same the novel bandwidth allocation scheme can maximize the duration of the CFP for non real-time communications. Performance analysis results show that the EGSA scheme works efficiently and outperforms competitor schemes both in terms of guaranteed delay and bandwidth utilization.