CiteULike: Author Dao

Differential H3K4 Methylation Identifies Developmentally Poised Hematopoietic Genes

Keith Orford — 2008-08-05T08:50:23-00:00

Developmental Cell, Vol. 14, No. 5. (13 May 2008), pp. 798-809.

Summary Throughout development, cell fate decisions are converted into epigenetic information that determines cellular identity. Covalent histone modifications are heritable epigenetic marks and are hypothesized to play a central role in this process. In this report, we assess the concordance of histone H3 lysine 4 dimethylation (H3K4me2) and trimethylation (H3K4me3) on a genome-wide scale in erythroid development by analyzing pluripotent, multipotent, and unipotent cell types. Although H3K4me2 and H3K4me3 are concordant at most genes, multipotential hematopoietic cells have a subset of genes that are differentially methylated (H3K4me2+/me3-). These genes are transcriptionally silent, highly enriched in lineage-specific hematopoietic genes, and uniquely susceptible to differentiation-induced H3K4 demethylation. Self-renewing embryonic stem cells, which restrict H3K4 methylation to genes that contain CpG islands (CGIs), lack H3K4me2+/me3- genes. These data reveal distinct epigenetic regulation of CGI and non-CGI genes during development and indicate an interactive relationship between DNA sequence and differential H3K4 methylation in lineage-specific differentiation.

Biomolecular network motif counting and discovery by color coding

Noga Alon — 2008-06-27T15:15:51-00:00

Bioinformatics, Vol. 24, No. 13. (1 July 2008), pp. i241-249.

Protein-protein interaction (PPI) networks of many organisms share global topological features such as degree distribution, k-hop reachability, betweenness and closeness. Yet, some of these networks can differ significantly from the others in terms of local structures: e.g. the number of specific network motifs can vary significantly among PPI networks. Counting the number of network motifs provides a major challenge to compare biomolecular networks. Recently developed algorithms have been able to count the number of induced occurrences of subgraphs with k[≤] 7 vertices. Yet no practical algorithm exists for counting non-induced occurrences, or counting subgraphs with k[≥] 8 vertices. Counting non-induced occurrences of network motifs is not only challenging but also quite desirable as available PPI networks include several false interactions and miss many others. In this article, we show how to apply the color coding' technique for counting non-induced occurrences of subgraph topologies in the form of trees and bounded treewidth subgraphs. Our algorithm can count all occurrences of motif G' with k vertices in a network G with n vertices in time polynomial with n, provided k=O(log n). We use our algorithm to obtain treelet' distributions for k[≤] 10 of available PPI networks of unicellular organisms (Saccharomyces cerevisiae Escherichia coli and Helicobacter Pyloris), which are all quite similar, and a multicellular organism (Caenorhabditis elegans) which is significantly different. Furthermore, the treelet distribution of the unicellular organisms are similar to that obtained by the duplication model' but are quite different from that of the preferential attachment model'. The treelet distribution is robust w.r.t. sparsification with bait/edge coverage of 70% but differences can be observed when bait/edge coverage drops to 50%. Contact:cenk@cs.sfu.ca 10.1093/bioinformatics/btn163

Development of a microscopic traffic simulator for inter-vehicle communication application research

Keith — 2008-06-03T10:27:19-00:00

Intelligent Transportation Systems Conference, 2006. ITSC '06. IEEE (2006), pp. 1286-1291.

This paper describes the development of a microscopic traffic simulator purposely designed for ITS researchers studying inter-vehicle communication (IVC) concepts and applications in large traffic networks. The simulator can represent real life vehicles within the simulation by using data from vehicle Global Positioning System (GPS) receivers, enabling validation of theories with real vehicle data. The software is developed on top of the existing microscopic traffic simulator VISSIM with the added flexibility of modelling and efficiently handling communication between large numbers of vehicles. This along with the software architecture was discussed in detail

Measurement of the phase and amplitude distributions of coupled oscillator arrays

PF Maccarini — 2008-05-09T23:55:44-00:00

Microwave Symposium Digest., 2000 IEEE MTT-S International, Vol. 1 (2000), pp. 593-596 vol.1.

This paper describes the analysis, design, implementation and characterization of a computer-controlled system that accurately measures the phase and amplitude distributions of a phased antenna array. The proposed setup allows `on board' measurements and far field radiation pattern collection at the same time. We have measured the phase and amplitude distributions of a coupled oscillator array at 2.4-2.6 GHz. The results are coherent with the theoretical expectations. The amplitude error is less than 5% and the phase error is less than 5°. This simple and inexpensive measurement system can be used for automated diagnostics of linear and nonlinear antenna arrays

Evolutionary and Biomedical Insights from the Rhesus Macaque Genome

Rhesus — 2007-04-13T05:22:30-00:00

Science, Vol. 316, No. 5822. (13 April 2007), pp. 222-234.

The rhesus macaque (Macaca mulatta) is an abundant primate species that diverged from the ancestors of Homo sapiens about 25 million years ago. Because they are genetically and physiologically similar to humans, rhesus monkeys are the most widely used nonhuman primate in basic and applied biomedical research. We determined the genome sequence of an Indian-origin Macaca mulatta female and compared the data with chimpanzees and humans to reveal the structure of ancestral primate genomes and to identify evidence for positive selection and lineage-specific expansions and contractions of gene families. A comparison of sequences from individual animals was used to investigate their underlying genetic diversity. The complete description of the macaque genome blueprint enhances the utility of this animal model for biomedical research and improves our understanding of the basic biology of the species. 10.1126/science.1139247

The genome of the model beetle and pest Tribolium castaneum.

2008-04-09T04:32:41-00:00

Nature (23 March 2008)

Tribolium castaneum is a member of the most species-rich eukaryotic order, a powerful model organism for the study of generalized insect development, and an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved the ability to interact with a diverse chemical environment, as shown by large expansions in odorant and gustatory receptors, as well as P450 and other detoxification enzymes. Development in Tribolium is more representative of other insects than is Drosophila, a fact reflected in gene content and function. For example, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, some being expressed in the growth zone crucial for axial elongation in short-germ development. Systemic RNA interference in T. castaneum functions differently from that in Caenorhabditis elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets for selective insect control.

Competing superfluid and density-wave ground-states of fermionic mixtures with mass imbalance in optical lattices

Tung Dao — 2008-03-10T14:22:40-00:00

Physical Review B (Condensed Matter and Materials Physics), Vol. 76, No. 10. (2007)

We study the effect of mass imbalance on the phase diagram of a two-component fermionic mixture with attractive interactions in optical lattices. Using static and dynamical mean-field theories, we show that the pure superfluid phase is stable for all couplings when the mass imbalance is smaller than a limiting value. For larger imbalance, phase separation between a superfluid and a charge-density wave takes place when the coupling exceeds a critical strength. The harmonic trap induces a spatial segregation of the two phases, with a rapid variation of the density at the boundary.

Axin1 and Axin2 Are Regulated by TGF- and Mediate Cross-talk between TGF- and Wnt Signaling Pathways.

Debbie Y Dao — 2008-01-03T08:24:09-00:00

Ann N Y Acad Sci, Vol. 1116 (December 2007), pp. 82-99.

Chondrocyte maturation during endochondral bone formation is regulated by a number of signals that either promote or inhibit maturation. Among these, two well-studied signaling pathways play crucial roles in modulating chondrocyte maturation: transforming growth factor-beta (TGF-beta)/Smad3 signaling slows the rate of chondrocyte maturation, while Wingless/INT-1-related (Wnt)/beta-catenin signaling enhances the rate of chondrocyte maturation. Axin1 and Axin2 are functionally equivalent and have been shown to inhibit Wnt/beta-catenin signaling and stimulate TGF-beta signaling. Here we show that while Wnt3a stimulates Axin2 in a negative feedback loop, TGF-beta suppresses the expression of both Axin1 and Axin2 and stimulates beta-catenin signaling. In Axin2 -/- chondrocytes, TGF-beta treatment results in a sustained increase in beta-catenin levels compared to wild-type chondrocytes. In contrast, overexpression of Axin enhanced TGF-beta signaling while overexpression of beta-catenin inhibited the ability of TGF-beta to induce Smad3-sensitive reporters. Finally, the suppression of the Axins is Smad3-dependent since the effect is absent in Smad3 -/- chondrocytes. Altogether these findings show that the Axins act to integrate signals between the Wnt/beta-catenin and TGF-beta/Smad pathways. Since the suppression Axin1 and Axin2 expression by TGF-beta reduces TGF-beta signaling and enhances Wnt/beta-catenin signaling, the overall effect is a shift from TGF-beta toward Wnt/beta-catenin signaling and an acceleration of chondrocyte maturation.

Decoding, Performance Analysis, and Optimal Signal Designs for Coordinate Interleaved Orthogonal Designs

DN Dao — 2008-02-13T15:08:35-00:00

IEEE Transactions on Wireless Communications, Vol. 7, No. 1. (January 2008), pp. 54-59.

A New Markov Model for Non-Saturated 802.11 Networks

Nghia Dao — 2008-02-09T05:57:30-00:00

Consumer Communications and Networking Conference, 2008. CCNC 2008. 5th IEEE (2008), pp. 420-424.

Nanoscale effects leading to non-Einstein-like decrease in viscosity

Michael Mackay — 2007-12-12T00:02:22-00:00

Nat Mater, Vol. 2, No. 11. (November 2003), pp. 762-766.

Power Management for Throughput Enhancement in Wireless Ad-Hoc Networks

Tamer Elbatt — 2006-08-24T23:47:15-00:00

(2000), pp. 1506-1513.

In this paper we introduce the notion of power management within the context of wireless ad-hoc networks. More specifically, we investigate the effects of using different transmit powers on the average power consumption and end-to-end network throughput in a wireless ad-hoc environment. This power management approach would help in reducing the system power consumption and hence prolonging the battery life of mobile nodes. Furthermore, it improves the end-to-end network throughput as compared to ...

Throughput Performance of Saturated 802.11g Networks

Nghia Dao — 2007-11-25T01:21:29-00:00

Wireless Broadband and Ultra Wideband Communications, 2007. AusWireless 2007. The 2nd International Conference on (2007), pp. 31-31.

In this paper we evaluate the throughput properties of 802.11g networks in the saturated limit. Using a modification to existing analytical models we show how our new results solve previously reported dicrepancies between anlaytical throughput predictions and measured throughputs. We investigate the performance of saturated 802.11g networks as a function of various 802.11g PHY parameters, including the transmission rate of ACK frames, the slot size, the use of EIFS (Extended Inter-Frame Spacing) and the total PCLP (Physical Convergence Layer Protocol) overhead. We also investigate the throughput performance as a function of important MAC layer parameters. An interesting result we find is the how the predicted throughput depends on the Contention Window value and the number of stations. The results reported here will be of value to the ongoing study of multimedia application deployments over high PHY data rate 802.11g networks.

Differential VoIP service in Wi-Fi networks and priority QoS maps

Nghia Dao — 2007-10-18T13:14:09-00:00

Global Telecommunications Conference, 2005. GLOBECOM '05. IEEE, Vol. 5 (2005), pp. 2653-2657.

Positioning range extension gateways in mobile ad hoc wireless networks to improve connectivity and throughput

M Ahmed — 2007-10-02T10:57:20-00:00

Military Communications Conference, 2001. MILCOM 2001. Communications for Network-Centric Operations: Creating the Information Force. IEEE, Vol. 1 (2001), pp. 331-335 vol.1.

The dynamic nature of a mobile ad hoc network (MANET) may result in a cluster of nodes being isolated from the remaining network, especially when deployed in a terrain with blockages. In order to facilitate scalability and to provide connectivity between partitions that might occur in wireless networks as a consequence of mobility, we can envision a 'range extension' network that consists of airborne communication platforms, or geostationary/low-Earth-orbit satellites. These airborne/satellite nodes maintain communication links with specific 'gateway' nodes among the mobile ground nodes. To communicate with a node that is geographically distant or belongs to a different network partition, an ad hoc node can relay its data packets through an appropriate mobile gateway and via the range extension network. If we envision that the MANET is divided into different groups and a mobile gateway is deployed for each such group, an objective then is to determine the trajectory of the mobile gateway to best serve the ad hoc group to which it belongs, in terms of network performance metrics such as throughput and latency. In this paper, this problem of computing the optimal position for a gateway is reduced to a linear optimization problem by means of some simplifying but realistic assumptions. We suggest methods that may be deployed to enable the gateway to follow this optimal trajectory as closely as possible (within the practical constraints imposed by its velocity and maneuverability). Simulation results for various scenarios show a 10-15% improvement in the throughput and latency, per gateway domain, if a gateway has a dynamic trajectory whose locus follows the computed optimal position, as compared to a gateway that is statically placed at a regular position, or to a gateway that has a random trajectory.

An architecture for providing range extension by deploying mobile gateways in ad hoc networks

M Ahmed — 2007-10-02T09:22:27-00:00

Personal, Indoor and Mobile Radio Communications, 2002. The 13th IEEE International Symposium on, Vol. 4 (2002), pp. 1660-1664 vol.4.

The dynamic nature of a mobile ad hoc network (MANET) may result in a cluster of nodes being isolated from the rest of the network, especially when deployed in a terrain with blockages. To provide connectivity between the partitions of an ad hoc network that might occur due to mobility, a 'range extension' network can be employed. Such a network might consist of airborne communication platforms, or geostationary/low-Earth-orbit satellites maintaining communication links with specific 'gateway' nodes that are dispersed among the mobile ground nodes. Thus, to communicate with a node that is geographically distant or belongs to a different network partition, an ad hoc node can relay its data packets through an appropriate mobile gateway and via the range extension network. In such an architecture, MANET is divided into different domains with a mobile gateway deployed for each domain. The objective, then, is to determine the position and trajectory of the gateways to optimize network performance metrics such as throughput and latency. In this paper, computation of the optimal position for a gateway is shown to be equivalent to a linear optimization problem by means of some simplifying but realistic assumptions. An algorithm is proposed for the control of the gateway trajectory. The practical constraints imposed by the velocity and maneuverability of the gateways are taken into account. Simulation results show a 10-15% improvement in the throughput and latency, per gateway domain, if a gateway has a dynamic trajectory whose locus follows the computed optimal position, as compared to a gateway that is statically placed at a fixed position, or to a gateway that has a random trajectory.

Effect of plasmodial RESA protein on deformability of human red blood cells harboring Plasmodium falciparum

JP Mills — 2007-08-09T19:35:17-00:00

PNAS, Vol. 104, No. 22. (29 May 2007), pp. 9213-9217.

During intraerythrocytic development, Plasmodium falciparum exports proteins that interact with the host cell plasma membrane and subplasma membrane-associated spectrin network. Parasite-exported proteins modify mechanical properties of host RBCs, resulting in altered cell circulation. In this work, optical tweezers experiments of cell mechanical properties at normal physiological and febrile temperatures are coupled, for the first time, with targeted gene disruption techniques to measure the effect of a single parasite-exported protein on host RBC deformability. We investigate Pf155/Ring-infected erythrocyte surface antigen (RESA), a parasite protein transported to the host spectrin network, on deformability of ring-stage parasite-harboring human RBCs. Using a set of parental, gene-disrupted, and revertant isogenic clones, we found that RESA plays a major role in reducing deformability of host cells at the early ring stage of parasite development, but not at more advanced stage. We also show that the effect of RESA on deformability is more pronounced at febrile temperature, which ring-stage parasite-harboring RBCs can be exposed to during a malaria attack, than at normal body temperature. 10.1073/pnas.0703433104

Cytoskeletal dynamics of human erythrocyte.

J Li — 2007-07-15T03:48:22-00:00

Proc Natl Acad Sci U S A, Vol. 104, No. 12. (20 March 2007), pp. 4937-4942.

The human erythrocyte (red blood cell, RBC) demonstrates extraordinary ability to undergo reversible large deformation and fluidity. Such mechanical response cannot be consistently rationalized on the basis of fixed connectivity of the cell cytoskeleton that comprises the spectrin molecular network tethered to phospholipid membrane. Active topological remodeling of spectrin network has been postulated, although detailed models of such dynamic reorganization are presently unavailable. Here we present a coarse-grained cytoskeletal dynamics simulation with breakable protein associations to elucidate the roles of shear stress, specific chemical agents, and thermal fluctuations in cytoskeleton remodeling. We demonstrate a clear solid-to-fluid transition depending on the metabolic energy influx. The solid network's plastic deformation also manifests creep and yield regimes depending on the strain rate. This cytoskeletal dynamics model offers a means to resolve long-standing questions regarding the reference state used in RBC elasticity theory for determining the equilibrium shape and deformation response. In addition, the simulations offer mechanistic insights into the onset of plasticity and void percolation in cytoskeleton. These phenomena may have implication for RBC membrane loss and shape change in the context of hereditary hemolytic disorders such as spherocytosis and elliptocytosis.

Toward a quantitative understanding of mechanical behavior of nanocrystalline metals

M Dao — 2007-06-21T00:25:49-00:00

Acta Materialia, Vol. 55, No. 12. (July 2007), pp. 4041-4065.

Focusing on nanocrystalline (nc) pure face-centered cubic metals, where systematic experimental data are available, this paper presents a brief overview of the recent progress made in improving mechanical properties of nc materials, and in quantitatively and mechanistically understanding the underlying mechanisms. The mechanical properties reviewed include strength, ductility, strain rate and temperature dependence, fatigue and tribological properties. The highlighted examples include recent experimental studies in obtaining both high strength and considerable ductility, the compromise between enhanced fatigue limit and reduced crack growth resistance, the stress-assisted dynamic grain growth during deformation, and the relation between rate sensitivity and possible deformation mechanisms. The recent advances in obtaining quantitative and mechanics-based models, developed in line with the related transmission electron microscopy and relevant molecular dynamics observations, are discussed with particular attention to mechanistic models of partial/perfect-dislocation or deformation-twin-mediated deformation processes interacting with grain boundaries, constitutive modeling and simulations of grain size distribution and dynamic grain growth, and physically motivated crystal plasticity modeling of pure Cu with nanoscale growth twins. Sustained research efforts have established a group of nanocrystalline and nanostructured metals that exhibit a combination of high strength and considerable ductility in tension. Accompanying the gradually deepening understanding of the deformation mechanisms and their relative importance, quantitative and mechanisms-based constitutive models that can realistically capture experimentally measured and grain-size-dependent stress-strain behavior, strain-rate sensitivity and even ductility limit are becoming available. Some outstanding issues and future opportunities are listed and discussed.

Liver adenomatosis: reappraisal, diagnosis, and surgical management: eight new cases and review of the literature.

L Chiche — 2006-07-12T20:37:48-00:00

Ann Surg, Vol. 231, No. 1. (January 2000), pp. 74-81.

OBJECTIVE: Liver adenomatosis (LA) is a rare disease originally defined by Flejou et al in 1985 from a series of 13 cases. In 1998, 38 cases were available for analysis, including eight personal cases. The aim of this study was to review and reappraise the characteristics of this rare liver disease and to discuss diagnosis and therapeutic options. BACKGROUND: LA was defined as the presence of >10 adenomas in an otherwise normal parenchyma. Neither female predominance nor a relation with estrogen/progesterone intake has been noted. Natural progression is poorly known. METHODS: The clinical presentation, evolution, histologic characteristics, and therapeutic options and results were analyzed based on a personal series of eight new cases and an updated review of the literature. RESULTS: From a diagnostic standpoint, two forms of liver adenomatosis with different presentations and evolution can be defined: a massive form and a multifocal form. The role of estrogen and progesterone is reevaluated. The risks of hemorrhage and malignant transformation are of major concern. In the authors' series, liver transplantation was indicated in two young women with the massive, aggressive form, and good results were obtained. CONCLUSION: Liver adenomatosis is a rare disease, more common in women, where outcome and evolution vary and are exacerbated by estrogen intake. Most often, conservative surgery is indicated. Liver transplantation is indicated only in highly symptomatic and aggressive forms of the disease.

OPC strategies to minimize mask cost and writing time

Michael Rieger — 2006-06-29T14:19:36-00:00

21st Annual BACUS Symposium on Photomask Technology, Vol. 4562, No. 1. (2002), pp. 154-160.

As k1 factors decline, optical proximity correction (OPC) treatments required to maintain dimensional tolerances involve increasingly complex correction shapes. This translates to more detailed, larger mask pattern databases. Intricate, dense mask-layouts increase mask writing time and cost. OPC employment within a growing number of lithography layers compounds the issue, leading to skyrocketing mask-set costs and long turn-times. ASIC manufacturing, where average chip life cycles consume less than 500 wafers, is particularly hard hit by elevated mask manufacturing costs. OPC increases mask data mainly by adding geometric detail - serifs, hammerheads, jogs, etc - to the design layout. The vertex count, a measure of shape complexity, typically expands by a factor of 2 to 5, depending on OPC objectives and accuracy requirements. OPC can also increase hierarchic data file size through loss of hierarchic compression. In this paper we outline several alternatives for reducing OPC data base size and for making OPC layout configurations friendlier to mask fabrication tools. An underlying assumption is that there is an optimum OPC treatment dictated by the behavior of the process, and that approximations to this ideal involve trade-offs with OPC accuracy. To whatever extent OPC effectiveness can be maintained while accuracy is compromised, mask complexity can be reduced.

HLA-A2 supertype-restricted cell-mediated immunity by peripheral blood mononuclear cells derived from Malian children with severe or uncomplicated Plasmodium falciparum malaria and healthy controls.

KE Lyke — 2006-06-06T19:00:17-00:00

Infect Immun, Vol. 73, No. 9. (September 2005), pp. 5799-5808.

Understanding HLA-restricted adaptive host immunity to defined epitopes of malarial antigens may be required for the development of successful malaria vaccines. Fourteen epitopes of preerythrocytic malarial antigens known to mediate cytotoxic T-lymphocyte responses against target cells expressing HLA-A2-restricted epitopes were synthesized and pooled based on antigen: thrombospondin-related anonymous protein (TRAP), circumsporozoite protein (CSP), and export protein 1 (Exp-1) peptides. HLA-A2 supertype (*0201, *0202, *0205, *6802) peripheral blood mononuclear cells collected from 774 Malian children, aged 3 months to 14 years, with severe Plasmodium falciparum malaria matched to uncomplicated malaria or healthy controls were stimulated with the HLA-A2-restricted peptide pools. Significant gamma interferon production, determined by enzyme-linked immunospot assay to at least one of the three peptide pools, was observed in 24/58 (41%) of the severe malaria cases, 24/57 (42%) of the uncomplicated malaria cases, and 34/51 (67%) of the healthy controls. Significant lymphoproliferation to these peptides was observed in 12/44 (27%) of the severe malaria cases, 13/55 (24%) of the uncomplicated malaria cases, and 18/50 (36%) of the healthy controls. Responses to individual peptide pools were limited. These studies confirm the presence of adaptive cell-mediated immunity to preerythrocytic malaria antigens in volunteers from Mali and demonstrate that suballeles of the HLA-A2 supertype can effectively present antigenic epitopes. However, whether these immune responses to TRAP, CSP, and Exp-1 malarial proteins play a substantial role in protection remains a matter of controversy.

Serum levels of the proinflammatory cytokines interleukin-1 beta (IL-1beta), IL-6, IL-8, IL-10, tumor necrosis factor alpha, and IL-12(p70) in Malian children with severe Plasmodium falciparum malaria and matched uncomplicated malaria or healthy controls.

KE Lyke — 2006-06-06T18:59:49-00:00

Infect Immun, Vol. 72, No. 10. (October 2004), pp. 5630-5637.

Inflammatory cytokines play an important role in human immune responses to malarial disease. However, the role of these mediators in disease pathogenesis, and the relationship between host protection and injury remains unclear. A total of 248 cases of severe Plasmodium falciparum malaria among children aged 3 months to 14 years residing in Bandiagara, Mali, were matched to cases of uncomplicated malaria and healthy controls. Using modified World Health Organization criteria for defining severe malaria, we identified 100 cases of cerebral malaria (coma, seizure, and obtundation), 17 cases of severe anemia (hemoglobin, <5 g/dl), 18 cases combined cerebral malaria with severe anemia, and 92 cases with hyperparasitemia (asexual trophozoites, >500,000/mm3). Significantly elevated levels (given as geometric mean concentrations in picograms/milliliter) of interleukin-6 (IL-6; 485.2 versus 54.1; P = <0.001), IL-10 (1,099.3 versus 14.1; P = <0.001), tumor necrosis factor alpha (10.1 versus 7.7; P = <0.001), and IL-12(p70) (48.9 versus 31.3; P = 0.004) in serum were found in severe cases versus healthy controls. Significantly elevated levels of IL-6 (485.2 versus 141.0; P = <0.001) and IL-10 (1,099.3 versus 133.9; P = <0.001) were seen in severe malaria cases versus uncomplicated malaria controls. Cerebral malaria was associated with significantly elevated levels of IL-6 (754.5 versus 311.4; P = <0.001) and IL-10 (1,405.6 versus 868.6; P = 0.006) compared to severe malaria cases without cerebral manifestations. Conversely, lower levels of IL-6 (199.2 versus 487.6; P = 0.03) and IL-10 (391.1 versus 1,160.9; P = 0.002) were noted in children with severe anemia compared to severe malaria cases with hemoglobin at >5 g/dl. Hyperparasitemia was associated with significantly lower levels of IL-6 (336.6 versus 602.1; P = 0.002). These results illustrate the complex relationships between inflammatory cytokines and disease in P. falciparum malaria.

The distribution of hatching time in Anopheles gambiae.

Alpha Yaro — 2006-03-26T12:46:21-00:00

Malar J, Vol. 5, No. 1. (22 March 2006)

ABSTRACT: BACKGROUND: Knowledge of the ecological differences between the molecular forms of Anopheles gambiae and their sibling species, Anopheles arabiensis might lead to understanding their unique contribution to disease transmission and to better vector control as well as to understanding the evolutionary forces that have separated them. METHODS: The distributions of hatching time of eggs of wild An. gambiae and An. arabiensis females were compared in different water types. Early and late hatchers of the S molecular form were compared with respect to their total protein content, sex ratio, development success, developmental time and adult body size. RESULTS: Overall, the distribution of hatching time was strongly skewed to the right, with 89% of the eggs hatching during the second and third day post oviposition, 10% hatching during the next four days and the remaining 1% hatching over the subsequent week. Slight, but significant differences were found between species and between the molecular forms in all water types. Differences in hatching time distribution were also found among water types (in each species and molecular form), suggesting that the eggs change their hatching time in response to chemical factors in the water. Early hatchers were similar to late hatchers except that they developed faster and produced smaller adults than late hatchers. CONCLUSIONS: Differences in hatching time and speed of development among eggs of the same batch may be adaptive if catastrophic events such as larval site desiccation are not rare and the site's quality is unpredictable. The egg is not passive and its hatching time depends on water factors. Differences in hatching time between species and molecular forms were slight, probably reflecting that conditions in their larval sites are rather similar.

Semantic multicast: intelligently sharing collaborative sessions

Son Dao — 2006-02-19T19:07:41-00:00

ACM Comput. Surv., Vol. 31, No. 2es. (1999)

International management skills for success in Asia: A needs-based determination of skills for foreign managers and local managers

E Neupert — 2005-03-22T12:18:51-00:00

Journal of European Industrial Training, Vol. 29, No. 2. (February 2005), pp. 165-180.

Spectrin-level modeling of the cytoskeleton and optical tweezers stretching of the erythrocyte.

J Li — 2005-07-31T11:48:13-00:00

Biophys J, Vol. 88, No. 5. (May 2005), pp. 3707-3719.

We present a three-dimensional computational study of whole-cell equilibrium shape and deformation of human red blood cell (RBC) using spectrin-level energetics. Random network models consisting of degree-2, 3, ..., 9 junction complexes and spectrin links are used to populate spherical and biconcave surfaces and intermediate shapes, and coarse-grained molecular dynamics simulations are then performed with spectrin connectivities fixed. A sphere is first filled with cytosol and gradually deflated while preserving its total surface area, until cytosol volume consistent with the real RBC is reached. The equilibrium shape is determined through energy minimization by assuming that the spectrin tetramer links satisfy the worm-like chain free-energy model. Subsequently, direct stretching by optical tweezers of the initial equilibrium shape is simulated to extract the variation of axial and transverse diameters with the stretch force. At persistence length p = 7.5 nm for the spectrin tetramer molecule and corresponding in-plane shear modulus mu(0) approximately 8.3 microN/m, our models show reasonable agreement with recent experimental measurements on the large deformation of RBC with optical tweezers. We find that the choice of the reference state used for the in-plane elastic energy is critical for determining the equilibrium shape. If a position-independent material reference state such as a full sphere is used in defining the in-plane energy, then the bending modulus kappa needs to be at least a decade larger than the widely accepted value of 2 x 10(-19) J to stabilize the biconcave shape against the cup shape. We demonstrate through detailed computations that this paradox can be avoided by invoking the physical hypothesis that the spectrin network undergoes constant remodeling to always relax the in-plane shear elastic energy to zero at any macroscopic shape, at some slow characteristic timescale. We have devised and implemented a liquefied network structure evolution algorithm that relaxes shear stress everywhere in the network and generates cytoskeleton structures that mimic experimental observations.

Mechanics of the human red blood cell deformed by optical tweezers

M Dao — 2005-07-17T17:36:32-00:00

Journal of the Mechanics and Physics of Solids, Vol. 51, No. 11-12. ( 2003), pp. 2259-2280.

The mechanical deformation characteristics of living cells are known to influence strongly their chemical and biological functions and the onset, progression and consequences of a number of human diseases. The mechanics of the human red blood cell (erythrocyte) subjected to large deformation by optical tweezers forms the subject of this paper. Video photography of the cell deformed in a phosphate buffered saline solution at room temperature during the imposition of controlled stretching forces, in the tens to several hundreds picoNewton range, is used to assess experimentally the deformation characteristics. The mechanical responses of the cell during loading and upon release of the optical force are then analysed to extract the elastic properties of the cell membrane by recourse to several different constitutive formulations of the elastic and viscoelastic behavior within the framework of a fully three-dimensional finite element analysis. A parametric study of various geometric, loading and structural factors is also undertaken in order to develop quantitative models for the mechanics of deformation by means of optical tweezers. The outcome of the experimental and computational analyses is then compared with the information available on the mechanical response of the red blood cell from other independent experimental techniques. Potential applications of the optical tweezers method described in this paper to the study of mechanical deformation of living cells under different stress states and in response to the progression of some diseases are also highlighted. (60009 K)Movie_1.mov Quicktime movie 1. Direct stretch experiment of a human red blood cell using laser tweezers (movie). (128984 K)Movie_2.mov Quicktime movie 2. Computational modeling of a human red blood cell undergoing uniaxial direct stretch (movie showing shape changes). (128984 K)Movie_3.mov Quicktime movie 3. Computational modeling of a human red blood cell undergoing uniaxial direct stretch (movie showing the evolution of the maximum principle strain).