Auto-aggregation in zoospores of Phytophthora infestans: the cooperative roles of bioconvection and chemotaxis

Phytophthora infestans is a highly destructive plant pathogen. It was the cause of the infamous Irish potato famine in the nineteenth century and remains to this day a significant global problem with associated costs estimated at $3 billion annually. Key to the success of this pathogen is the dispersal of free-swimming cells called zoospores. A poorly understood aspect of zoospore behaviour is auto-aggregation—the spontaneous formation of large-scale patterns in cell density. Current competing hypotheses suggest that these patterns are formed by one of two distinct mechanisms: chemotaxis and bioconvection. In this paper, we present mathematical and experimental results that together provide strong evidence that auto-aggregation can only result from a combination of these mechanisms, each having a distinct, time-separated role. A better understanding of the underlying infection mechanisms of P. infestans and potentially other Phytophthora species will in the longer term lead to advances in preventative treatment and thus potentially significant savings in socio-economic costs.     

Behavioral event data and their analysis

Social science is broadly defined as the analysis of human behavior whether it be at an individual or a group level. In this work, we explore the analysis of human behavior encoded as a trail of their events over time and space, which we refer to as behavioral event data. We show that such data offers challenges to data mining algorithm designers as the data to analyze is naturally multi-way, involves complex patterns that form/reform over time, and has complex interactions between groups in the population. Though the data naturally lends itself to be represented as graphs and tensors we show how existing techniques are limited in their usefulness and outline our own algorithms to overcome these challenges. In this paper, using the adversarial event behavior of blue and red forces, we show three core problems and solutions in event behavior analysis: (1) Decomposing behavior to identify areas of intense activity, (2) Predicting what groups of events are likely to occur, and (3) Analysis to identify interacting behavior given a known template.     

Development and use of specific polymerase reaction for the detection of an organism resembling Ehrlichia sp. in white-tailed deer

OBJECTIVE: To establish the pharmacodynamic and safety equivalence between 2 sustained-release forms of leuprorelin 11.25 mg and 3.75 mg, in the treatment of metastatic prostatic carcinoma. METHODS: 44 patients received subcutaneous injections of leuprorelin for 9 months (randomization: 2/l): either 11.25 mg every three months (n = 29) or 3.75 mg monthly (n = 15). Main criterion: centralized monthly assay of plasma testosterone (T). RESULTS: The equivalence of the 2 forms in terms of mean plasma testosterone was demonstrated (p = 0.002): 1 month: T = 0.19 +/- 0.03 ng/ml; 3 months: T = 0.27 +/- 0.04 ng/ml. Exploratory analysis did not reveal any significant difference between the groups for the number of patients castrated at each visit or for the number of patients with all T values < or = 0.5 ng/ml, or for clinical responses or safety. CONCLUSION: The 2 forms have a comparable efficacy and safety.     

Interaction of the adaptor protein Shc and the adhesion molecule cadherin

In mitogenic signaling pathways, Shc participates in the growth factor activation of Ras by interacting with activated receptors and/or the Grb-2.Sos complex. Using several experimental approaches we demonstrate that Shc, through its SH2 domain, forms a complex with the cytoplasmic domain of cadherin, a transmembrane protein involved in the Ca2+-dependent regulation of cell-cell adhesion. This interaction is demonstrated in a yeast two-hybrid assay, by co-precipitation from mammalian cells, and by direct biochemical analysis in vitro. The Shc-cadherin association is phosphotyrosine-dependent and is abrogated by addition of epidermal growth factor to A-431 cells maintained in Ca2+-free medium, a condition that promotes changes in cell shape. Shc may therefore participate in the control of cell-cell adhesion as well as mitogenic signaling through Ras.     

Analysis of Load Average and its Relationship to Program Run Time on Networks of Workstations

Parallel processing systems using networks of workstations are being used to provide an alternative to expensive parallel processors. Scheduling of tasks on these networks is an important and practical problem that must be addressed. Although CPU load is an important parameter to many of the proposed scheduling schemes, no quantitative analysis of CPU load and its precise relation to the run time of application programs has to date been presented. The work in this paper describes the experimental analysis of one common load measure, the UNIX load average, and its relationship to the run time of computation-bound parallel programs. Data was gathered using a test application program designed to mimic common applications, performing long bursts of computation with occasional interprocess data exchange over the network. The resulting execution times and measured load averages were then analyzed using regression analysis to detect load-run time trends. This paper describes the test program and the experiments, then details the results of the data analysis. A technique is then presented for the evaluation of the load-run time relationship for a computation-bound program on a network of workstations.     

Addition of the MSA1 signal and anchor sequences to the malaria merozoite surface antigen 1 C-terminal region enhances immunogenicity when expressed by recombinant vaccinia virus

Genes encoding four different C-terminal fragments of a Plasmodium falciparum merozoite surface antigen were generated: MSA1C-(Si,A), containing signal and anchor regions of MSA1; MSA1C-(Si,nA), containing the signal but not the anchor; MSA1C-(nSi,A), containing the anchor but not the signal, and MSA1C-(nSi,nA) containing neither the signal nor the anchor region. Each gene was inserted into the thymidine kinase region of vaccinia virus, under the control of a synthetic strong early/ late promoter. When the plasmodial genes were expressed in cells infected by the recombinant vaccinia virus, the two proteins containing the signal region were transported to the surface of infected cells. Infection of mice and rabbits with the latter recombinant viruses stimulated C-terminal-specific antibody levels that were 10-80-fold higher than those induced by the two recombinant viruses without the signal region. The combination of the signal and anchor regions with the C-terminal MSA1 protein also generated the most effective neutralization in a P. falciparum invasion assay.     

Optimizing nitrogen incorporation in nanodiamond film for bio-analyte sensing

Nitrogen incorporated nanodiamond electrodes were fabricated using microwave plasma enhanced chemical vapor deposition. The N₂ incorporation was achieved by the introduction of N₂ gas along with H₂ and CH₄ gases in the plasma. In the context of this work, the H₂:CH₄ ratio was held fixed at 9:1 and the N₂ content was varied. Three different levels of N₂ incorporation were examined: 30 sccm (S1), 60 sccm (S2) and 90 sccm (S3). The Fe(CN)₆^3?/4? redox couple in 0.1 M KCl was used for initial evaluation of the electrochemical properties of the 3 electrodes. Cyclic voltammetry was then used to study the detection of dopamine (DA), which is an important neurotransmitter, in 0.1 M phosphate buffered saline (PBS) at the physiologic pH of 7.4. Electrode S1, which has a microstructure resembling that of ‘ridges’, showed excellent electrochemical response as compared to the other two electrodes, S2 and S3 which exhibited sluggish reaction kinetics. Cyclic voltammograms from S1 show well defined and closely spaced redox peaks, not only for dopamine, but also for its redox active metabolites which are produced due to reactions downstream of DA oxidation. The calibration curves for the three electrodes show linear behavior but S1 shows superior sensitivity towards DA detection. Also, a linear relationship between the DA concentration and √scan rate was observed which is consistent with semi-infinite linear diffusion limited mass transport mechanism for planar electrodes. These results have been achieved without the need of functionalization or modification of the electrode surface, using optimum N₂ incorporated nanodiamond electrode.     

Room-temperature diffusion in Cu/Ag thin-film couples caused by anodic dissolution

Thin, 100-nm films of first silver and then copper were deposited consecutively onto inert substrates by magnetron sputter deposition. Constant anodic current densities were applied at room temperature to dissolve the outer copper film to varying depths. The 50Cu/50Ag interface, derived from the auger electron spectroscopic concentration-depth profile, initially moved into the copper toward the outer dissolving surface, indicating enhanced diffusion of copper into silver. After longer times at all anodic current densities, the interface reversed and moved back toward the underlying silver-rich layer, indicating that eventually diffusion of silver into copper predominated. The reversal time was inversely proportional to the anodic current density. These effects are explained by anodic formation of subsurface vacancies which migrate as divacancies to the copper/silver interface where they affect interface movements by the well-known Kirkendall mechanism. Calculated diffusivities up to 10⁻¹² cm²/s at maximum anodic current densities of 900 μA/cm² are dramatically above any that are normally observed at room temperature.