Investigation of an axial-excursion transducer for squeeze-film bearings

Resonant frequencies and characteristic bearing cone motion of axial-excursion transducer for squeeze-film gas bearing - drive voltage, preload, bearing mass, and mounting ring effect

Consistent and contrasting properties of lineage-specific genes in the apicomplexan parasites Plasmodium and Theileria

<p>Abstract</p> <p>Background</p> <p>Lineage-specific genes, the genes that are restricted to a limited subset of related organisms, may be important in adaptation. In parasitic organisms, lineage-specific gene products are possible targets for vaccine development or therapeutics when these genes are absent from the host genome.</p> <p>Results</p> <p>In this study, we utilized comparative approaches based on a phylogenetic framework to characterize lineage-specific genes in the parasitic protozoan phylum Apicomplexa. Genes from species in two major apicomplexan genera, <it>Plasmodium </it>and <it>Theileria</it>, were categorized into six levels of lineage specificity based on a nine-species phylogeny. In both genera, lineage-specific genes tend to have a higher level of sequence divergence among sister species. In addition, species-specific genes possess a strong codon usage bias compared to other genes in the genome. We found that a large number of genus- or species-specific genes are putative surface antigens that may be involved in host-parasite interactions. Interestingly, the two parasite lineages exhibit several notable differences. In <it>Plasmodium</it>, the (G + C) content at the third codon position increases with lineage specificity while <it>Theileria </it>shows the opposite trend. Surface antigens in <it>Plasmodium </it>are species-specific and mainly located in sub-telomeric regions. In contrast, surface antigens in <it>Theileria </it>are conserved at the genus level and distributed across the entire lengths of chromosomes.</p> <p>Conclusion</p> <p>Our results provide further support for the model that gene duplication followed by rapid divergence is a major mechanism for generating lineage-specific genes. The result that many lineage-specific genes are putative surface antigens supports the hypothesis that lineage-specific genes could be important in parasite adaptation. The contrasting properties between the lineage-specific genes in two major apicomplexan genera indicate that the mechanisms of generating lineage-specific genes and the subsequent evolutionary fates can differ between related parasite lineages. Future studies that focus on improving functional annotation of parasite genomes and collection of genetic variation data at within- and between-species levels will be important in facilitating our understanding of parasite adaptation and natural selection.</p

Counseling College Student-Athletes: A Working Alliance Model Approach

Student-athletes often represent a highly visible, yet decidedly misunderstood population on college and university campuses. In the general student population, the combination of multiple stressors often leads students to seek professional counseling services. Unfortunately, student-athletes, who are often faced with a multitude of psychosocial stressors germane to balancing athletic and academic responsibilities, seldom seek out professional counseling services. However, when they do seek services, the authors posited that an understanding of the construct of the therapeutic working alliance and the application of the working alliance model (Bordin, 1979) offered a useful template for fostering positive counseling outcomes with student-athletes. In this article, the major elements of this construct and model were presented along with a discussion and implications for its application to a college or university student-athlete population

Thermodynamic Data from Drug-DNA Footprinting Experiments

Sequence-dependent thermodynamic quantities for the antiviral agent netropsin and a related bis(N-methylimidazole) dipeptide, lexitropsin, have been determined by DNase I footprinting techniques. The primary data are autoradiographic spot intensities derived from 10 footprinting experiments carried out in the temperature range 0-45 OC. After exclusion effects due to overlapped drug sites on DNA and redistribution phenomena associated with the enzyme were accounted for, sequence-dependent binding constants for the two ligands were calculated. Our approach does not require an independent determination of the free drug concentration, which is calculated, with individual site binding constants, by using only footprinting data. The temperature dependence of the binding constants for netropsin implied that the binding enthalpies for all the sites but one on a 139 base pair restriction fragment of pBR 322 DNA are exothermic. Their values roughly correlate with the free energies of binding, which are smaller for sites including a 5’-TA-3’ sequence. The binding enthalpies for the lexitropsin to all its sites were exothermic and more negative than those of netropsin. This may be due to the greater ability of the lexitropsin, when compared to netropsin, to form hydrogen bonds with sites on DNA. The binding constants of the lexitropsin toward its GC interaction sequences were much lower than those of netropsin, as can be explained by the reduced charge of the former ligand. Although it is difficult to determine the specific origin of the thermodynamic effects measured, comparison between netropsin and the lexitropsin suggests that the degree of solvation in the minor groove of DNA may be a factor influencing the entropy of the binding process

Identification and functional characterization of cis-regulatory elements in the apicomplexan parasite Toxoplasma gondii

Mining of genomic sequence data of the apicomplexan parasite Toxoplasma gondii identifies putative cis-regulatory elements using a de novo approach

A glycosylphosphatidylinositol-anchored carbonic anhydrase-related protein of Toxoplasma gondii is important for rhoptry biogenesis and virulence

Carbonic anhydrase-related proteins (CARPs) have previously been described as catalytically inactive proteins closely related to α-carbonic anhydrases (α-CAs). These CARPs are found in animals (both vertebrates and invertebrates) and viruses as either independent proteins or domains of other proteins. We report here the identification of a new CARP (TgCA_RP) in the unicellular organism Toxoplasma gondii that is related to the recently described η-class CA found in Plasmodium falciparum. TgCA_RP is posttranslationally modified at its C terminus with a glycosylphosphatidylinositol anchor that is important for its localization in intracellular tachyzoites. The protein localizes throughout the rhoptry bulbs of mature tachyzoites and to the outer membrane of nascent rhoptries in dividing tachyzoites, as demonstrated by immunofluorescence and immunoelectron microscopy using specific antibodies. T. gondii mutant tachyzoites lacking TgCA_RP display a growth and invasion phenotype in vitro and have atypical rhoptry morphology. The mutants also exhibit reduced virulence in a mouse model. Our results show that TgCA_RP plays an important role in the biogenesis of rhoptries

Finite size effects in nonequilibrium wetting

Models with a nonequilibrium wetting transition display a transition also in finite systems. This is different from nonequilibrium phase transitions into an absorbing state, where the stationary state is the absorbing one for any value of the control parameter in a finite system. In this paper, we study what kind of transition takes place in finite systems of nonequilibrium wetting models. By solving exactly a microscopic model with three and four sites and performing numerical simulations we show that the phase transition taking place in a finite system is characterized by the average interface height performing a random walk at criticality and does not discriminate between the bounded-KPZ classes and the bounded-EW class. We also study the finite size scaling of the bKPZ universality classes, showing that it presents peculiar features in comparison with other universality classes of nonequilibrium phase transitions.Comment: 14 pages, 6figures, major change

Identification of putative cis-regulatory elements in Cryptosporidium parvum by de novo pattern finding

BACKGROUND: Cryptosporidium parvum is a unicellular eukaryote in the phylum Apicomplexa. It is an obligate intracellular parasite that causes diarrhea and is a significant AIDS-related pathogen. Cryptosporidium parvum is not amenable to long-term laboratory cultivation or classical molecular genetic analysis. The parasite exhibits a complex life cycle, a broad host range, and fundamental mechanisms of gene regulation remain unknown. We have used data from the recently sequenced genome of this organism to uncover clues about gene regulation in C. parvum. We have applied two pattern finding algorithms MEME and AlignACE to identify conserved, over-represented motifs in the 5' upstream regions of genes in C. parvum. To support our findings, we have established comparative real-time -PCR expression profiles for the groups of genes examined computationally. RESULTS: We find that groups of genes that share a function or belong to a common pathway share upstream motifs. Different motifs are conserved upstream of different groups of genes. Comparative real-time PCR studies show co-expression of genes within each group (in sub-sets) during the life cycle of the parasite, suggesting co-regulation of these genes may be driven by the use of conserved upstream motifs. CONCLUSION: This is one of the first attempts to characterize cis-regulatory elements in the absence of any previously characterized elements and with very limited expression data (seven genes only). Using de novo pattern finding algorithms, we have identified specific DNA motifs that are conserved upstream of genes belonging to the same metabolic pathway or gene family. We have demonstrated the co-expression of these genes (often in subsets) using comparative real-time-PCR experiments thus establishing evidence for these conserved motifs as putative cis-regulatory elements. Given the lack of prior information concerning expression patterns and organization of promoters in C. parvum we present one of the first investigations of gene regulation in this important human pathogen

TcruziKB: Enabling Complex Queries for Genomic Data Exploration

We developed a novel analytical environment to aid in the examination of the extensive amount of interconnected data available for genome projects. Our focus is to enable flexibility and abstraction from implementation details, while retaining the expressivity required for post-genomic research. To achieve this goal, we associated genomics data to ontologies and implemented a query formulation and execution environment with added visualization capabilities. We use ontology schemas to guide the user through the process of building complex queries in a flexible Web interface. Queries are serialized in SPARQL and sent to servers via Ajax. A component for visualization of the results allows researchers to explore result sets in multiple perspectives to suit different analytical needs. We show a use case of semantic computing with real world data. We demonstrate facilitated access to information through expressive queries in a flexible and friendly user interface. Our system scores 90.54% in a user satisfaction evaluation with 30 subjects. In comparison with traditional genome databases, preliminary evaluation indicates a reduction of the amount of user interaction required to answer the provided sample queries