Force and hydrodynamic efficiency measurements of a three-dimensional flapping foil

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 69-70).Investigations into unsteady flapping foil propulsion have shown that it is an efficient and high thrust means of propulsion. Extensive work has been done to optimize the efficiency of two-dimensional flapping foils, varying both the kinematics of the motion and the flexibility of the foil. However, no thorough investigation into the hydrodynamic efficiency of three-dimensional flapping foils has been made. In this thesis, experimental hydrodynamic efficiency measurements and force measurements of a three-dimensional flapping foil are presented. These measurements were made by mounting a small, six-axis dynamometer directly onto the foil shaft of a flapping foil module. The module uses two computer controlled servo motors to actuate a foil in a sinusoidal pitch and roll motion, similar to the motion of a penguin's wing. The measured thrust coefficients compared well to previous experimental results, and the on-shaft dynamometer proved to be a valuable sensor. However, the experimental apparatus must be modified before reliable efficiency results can be made for the entire range of kinematics.(cont.) Once these improvements are made, a thorough investigation into the effects of foil geometry and flexibility can be done to find the optimum efficiency parameters of a three-dimensional flapping foil. These optimum efficiency parameters will be valuable for the development of flapping foil vehicles.by Karl-Magnus Weidmann McLetchie.S.M

Hyperactivation of B cells from Immunodeficient Patients

poster abstractChronic granulomatous disease (CGD) is an inherited immunodeficiency associated with defects in NADPH oxidase, an enzyme that produces oxygen radicals necessary to kill bacterial and fungal pathogens. NADPH oxidase, made up of six subunits, is located in endosomal and plasma membranes of immune cells. Although best studied in macrophages and neutrophils, the oxidase is expressed in B cells where we have shown its link to adaptive immunity and antigen presentation. Here, NADPH oxidase function was disrupted by mutations or gene knockdown in human B cells, and the role of the oxidase in innate immunity specifically Toll-like receptor (TLR) signaling tested. TLR7 and 9, which recognize viral single-stranded RNA and unmethylated CpG DNA respectively, potentially share an endosomal compartment with the oxidase in B cells. In this project, B cells were stimulated for 24 hours with TLR7 and 9 ligands along with a costimulator PMA. TLR7 signaling was significantly enhanced in oxidase deficient B cell lines compared with their respective control cells as evidenced by increased IL-6 secretion detected by an ELISA. CGD patients are incapable of producing oxygen radicals rendering them immunodeficient in terms of pathogen infection. Yet these patients also develop many autoimmune disorders associated with hyperactivation of the immune system. Thus, our studies on TLR activation using CGD cell lines may explain in part the development of autoimmunity in individuals with CGD. Additional studies are underway to examine the regulation of TLR including receptor expression levels and the subcellular localization of the NADPH oxidase in these B cells from CGD patients. This work has not yet been published and was supported by NIH 3R01AI079065-03S1

Age and sex-specific rates of leaf regeneration in the Mojave Desert moss Syntrichia caninervis

The extremely skewed female-biased sex ratio in the desert moss Syntrichia caninervis was investigated by assessing the regeneration capacity of detached leaves. Juvenile, green, yellow-green, and brown leaves equating to approximately 0, 2, 6, and 12 yr of age, respectively, were detached from individuals of S. caninervis collected from 10 field populations and grown in a growth chamber for 58 d at a light intensity of 33–128 µmol · m–2 · s–1. Younger leaves (0–2 yr old) tended to have a greater viability, regenerate more quickly, extend their protonemal filaments farther, produce shoots (gametophores) more quickly, produce more shoots, and accumulate a greater biomass than older leaves (6 and 12 yr old). Among younger leaf classes, regenerating female leaves were more likely to produce a shoot than male leaves and produced more shoots than male leaves. The sexes did not differ significantly in time until protonemal emergence, linear extension of protonemata, or rate of biomass accumulation. However, protonemata of male leaves tended to emerge more quickly and produce a greater total biomass, ultimately consisting mostly of protonemata, than did female leaves. The more rapid proliferation of shoots by female leaf regenerants may help to explain the rarity of males in this species

Local sex ratio : causes and reproductive consequences in a dioecious plant

I investigated the changes in sex ratio from germination to senescence in the dioecious liverwort, Sphaerocarpos texanus Aust. The mechanisms affecting these changes and the reproductive consequences of sex ratio are reported. Sphaerocarpos texanus is a winter ephemeral and disperses its spores as tetrads, each consisting of two males and two females. In the field, S. texanus can be found in pure male, pure female and mixed sex clumps. In the laboratory I examined the sex ratio at germination and proportions and sizes of the three clump types at the early and late gametophytic stages. I also examined the reproductive success of pure female and mixed sex clumps, and monitored the growth and survival of individuals in 20 plots over the four month growing season. I also completed a field manipulation experiment (different light conditions) to detect growth differences between males and females. Finally, in a series of laboratory experiments, I addressed specific questions raised by the field results. Two experiments explored the relationship between males and females within mixed sex clumps. In two reproductive experiments I examined the effects of male size and intermate distance on sporophyte production. Because I noted a lack of sporophytes in some mixed sex clumps, I investigated the possibility that some genetic combinations of males and females have higher reproductive output than other genetic combinations. I found both from the field census and the germination experiment that the most abundant clump type was pure female followed by mixed sex clumps. Pure male clumps were least abundant The relative proportion of males further decreased through time during the life cycle. Thus while the female bias begins at or before germination, it continues and becomes more pronounced. In the monitored plots, the most abundant clump type was mixed sex followed by pure female. Overall there was an increasing female bias. The increase in the female bias during the season was a consequence of high male mortality, which appears to result from the action of rain having a disproportionate effect on the smaller pure male clumps. The potential for pure male clumps to join other sex clumps and thus change clump affinity did not contribute to the large decrease of pure male clumps, nor did herbivory. Field studies showed that while the male part of mixed sex clumps were smaller than pure male clumps, males in mixed sex clumps may gain a survival benefit from growing with a female. However, females are competitively superior to males and both sexes are inhibited by leachates of the other sex. Males and females do not appear to exhibit different growth responses to various field manipulations. From the field work, females exhibited greater fecundity in mixed sex clumps than those in pure sex clumps. Reduced sporophyte numbers can be accounted for by sperm limitation due to increasing intermate distance. Smaller male size may also contribute to reduced sporophyte number. The failure of some mixed sex clumps to produce sporophytes may result from the infertility observed in some genetic crosses of S texanus. This infertility must have an underlying genetic mechanism since the individuals involved were fertile in other crosses. Any infertility caused by nuclear genes will not prevent inbreeding within spore tetrads. This pattern of infertility (between pairs of otherwise fertile mates) is unknown for dioecious organisms

LAMP-2C inhibits MHC class II presentation of cytoplasmic antigens by disrupting chaperone-mediated autophagy

Cells use multiple autophagy pathways to sequester macromolecules, senescent organelles, and pathogens. Several conserved isoforms of the lysosome-associated membrane protein-2 (LAMP-2) regulate these pathways influencing immune recognition and responses. LAMP-2A is required for chaperone-mediated autophagy (CMA), which promotes Ag capture and MHC class II (MHCII) presentation in B cells and signaling in T cells. LAMP-2B regulates lysosome maturation to impact macroautophagy and phagocytosis. Yet, far less is known about LAMP-2C function. Whereas LAMP2A and LAMP2B mRNA were broadly detected in human tissues, LAMP2C expression was more limited. Transcripts for the three LAMP2 isoforms increased with B cell activation, although specific gene induction varied depending on TLR versus BCR engagement. To examine LAMP-2C function in human B cells and specifically its role in Ag presentation, we used ectopic gene expression. Increased LAMP-2C expression in B cells did not alter MHCII expression or invariant chain processing, but did perturb cytoplasmic Ag presentation via CMA. MHCII presentation of epitopes from exogenous and membrane Ags was not affected by LAMP-2C expression in B cells. Similarly, changes in B cell LAMP-2C expression did not impact macroautophagy. The gene expression of other LAMP2 isoforms and proteasome and lysosomal proteases activities were unperturbed by LAMP-2C ectopic expression. LAMP-2C levels modulated the steady-state expression of several cytoplasmic proteins that are targeted for degradation by CMA and diminished peptide translocation via this pathway. Thus, LAMP-2C serves as a natural inhibitor of CMA that can selectively skew MHCII presentation of cytoplasmic Ags

Prison Education Programs and Their Impact on Recidivism in Canada

Prisoners are one of the most marginalized and vulnerable populations within any society. Education programs offered by Correctional Service Canada (CSC) and the Ontario Ministry of the Solicitor General (SOLGEN) have been critiqued for not adequately preparing prisoners to return to their communities. In this article, I explore the types of education programs available to Canadian prisoners and suggest how the federal and provincial governments can support new and innovative prison education policies using examples from the United States. I also discuss the benefits of post-secondary education to prisoners and its impact on recidivism

Studies on the Relationship of the Basophil Cells of the Hypophysis and the Adrenal Cortex

Abstract Not Provided

A Tragedy Exposed? Clear Growth Medium Reveals Competing Roots

Abstract Tragedy of the Commons (ToC) is the exploitation of an open-access resource that is exploited by selfish individuals to the detriment of all. Examples include open sea fisheries, cattle grazing, pollution, deforestation and plants competing over shared soil nutrients and space. Tragically, these resources become depleted and plants become severely resource limited. Our study seeks to determine if a ToC causes two plants sharing resources to reproduce less successfully than two plants owning the equivalent amount of personal resources. We predict that plant root competition creates a ToC by increasing root mass while reducing reproductive mass. Our study uses impermeable barriers to manipulate competition. We used transparent growth medium (Gellan Gum with Hoagland’s nutrient solution) in order to photograph roots as they grew in vivo. Root imaging allowed for computational analysis of root architecture which we expect to respond to the ToC. Our results from root and seed masses revealed no significant effects from competition. This could be explained by excessively high soil nutrient levels. Additionally, we failed to validate the photographic analysis platform (SmartRoot) with a hand measured model. Future direction includes optimizing soil nutrient levels and conducting a better photographic analysis based on multiple circumferential pictures