Structural Integrity Testing Method for PRSEUS Rod-Wrap Stringer Design

NASA Langley Research Center and The Boeing Company are developing an innovative composite structural concept, called PRSEUS, for the flat center section of a future environmentally friendly hybrid wing body (HWB) aircraft. The PRSEUS (Pultruded Rod Stitched Efficient Unitized Structure) concept uses dry textile preforms for the skins, frames, and stiffener webs. The highly loaded stiffeners are made from precured unidirectional carbon/epoxy rods and dry fiber preforms. The rods are wrapped with the dry fiber preforms and a resin infusion process is used to form the rod-wrap stiffeners. The structural integrity of the rod-wrap interface is critical for maintaining the panel s high strength and bending rigidity. No standard testing method exists for testing the strength of the rod-wrap bondline. Recently, Boeing proposed a rod push-out testing method and conducted some preliminary tests using this method. This paper details an analytical study of the rod-wrap bondline. The rod-wrap interface is modeled as a cohesive zone for studying the initiation and growth of interfacial debonding during push-out testing. Based on the correlations of analysis results and Boeing s test data, the adequacy of the rod-wrap testing method is evaluated, and potential approaches for improvement of the test method are proposed

Applicant perspectives during selection

We provide a comprehensive but critical review of research on applicant reactions to selection procedures published since 2000 (n = 145), when the last major review article on applicant reactions appeared in the Journal of Management. We start by addressing the main criticisms levied against the field to determine whether applicant reactions matter to individuals and employers (“So what?”). This is followed by a consideration of “What’s new?” by conducting a comprehensive and detailed review of applicant reaction research centered upon four areas of growth: expansion of the theoretical lens, incorporation of new technology in the selection arena, internationalization of applicant reactions research, and emerging boundary conditions. Our final section focuses on “Where to next?” and offers an updated and integrated conceptual model of applicant reactions, four key challenges, and eight specific future research questions. Our conclusion is that the field demonstrates stronger research designs, with studies incorporating greater control, broader constructs, and multiple time points. There is also solid evidence that applicant reactions have significant and meaningful effects on attitudes, intentions, and behaviors. At the same time, we identify some remaining gaps in the literature and a number of critical questions that remain to be explored, particularly in light of technological and societal changes

Effect of Phosphorus Amendments on Present Day Plankton Communities in Pelagic Lake Erie

To address questions regarding the potential impact of elevated total phosphorus (TP) inputs (due to relaxed regulations of TP loading), a series of TP enrichment experiments were conducted at pelagic stations in the 3 hydrologically distinct basins of Lake Erie. Results of nutrient assimilation measurements and assays for nutrient bioavailability suggest that the chemical speciation, and not concentration, of nitrogenous compounds may influence phytoplankton community structure; this in turn may lead to the selective proliferation of cyanobacteria in the eastern basin of the lake. Assays with cyanobacterial bioluminescent reporter systems for P and N availability as well as N-tot:P-tot assimilation ratios from on-deck incubation experiments support this work. Considered in the context of a microbial food web relative to a grazing food web, the results imply that alterations in current TP loading controls may lead to alterations in the phytoplankton community structure in the different basins of the Lake Erie system

Colorectal Cancer Stem Cells Are Enriched in Xenogeneic Tumors Following Chemotherapy

Patients generally die of cancer after the failure of current therapies to eliminate residual disease. A subpopulation of tumor cells, termed cancer stem cells (CSC), appears uniquely able to fuel the growth of phenotypically and histologically diverse tumors. It has been proposed, therefore, that failure to effectively treat cancer may in part be due to preferential resistance of these CSC to chemotherapeutic agents. The subpopulation of human colorectal tumor cells with an ESA(+)CD44(+) phenotype are uniquely responsible for tumorigenesis and have the capacity to generate heterogeneous tumors in a xenograft setting (i.e. CoCSC). We hypothesized that if non-tumorigenic cells are more susceptible to chemotherapeutic agents, then residual tumors might be expected to contain a higher frequency of CoCSC.Xenogeneic tumors initiated with CoCSC were allowed to reach approximately 400 mm(3), at which point mice were randomized and chemotherapeutic regimens involving cyclophosphamide or Irinotecan were initiated. Data from individual tumor phenotypic analysis and serial transplants performed in limiting dilution show that residual tumors are enriched for cells with the CoCSC phenotype and have increased tumorigenic cell frequency. Moreover, the inherent ability of residual CoCSC to generate tumors appears preserved. Aldehyde dehydrogenase 1 gene expression and enzymatic activity are elevated in CoCSC and using an in vitro culture system that maintains CoCSC as demonstrated by serial transplants and lentiviral marking of single cell-derived clones, we further show that ALDH1 enzymatic activity is a major mediator of resistance to cyclophosphamide: a classical chemotherapeutic agent.CoCSC are enriched in colon tumors following chemotherapy and remain capable of rapidly regenerating tumors from which they originated. By focusing on the biology of CoCSC, major resistance mechanisms to specific chemotherapeutic agents can be attributed to specific genes, thereby suggesting avenues for improving cancer therapy

Investigations of a fibre-reinforced composite used for an ankle-foot orthosis

An Ankle-Foot Orthosis (AFO) provides mediolateral support to the ankle and foot for individuals with abnormal gait patterns. New manufacturing methods using light-curable composite laminate materials are under development for improved AFOs. A comprehensive approach must be applied to the AFO design, because of the effect of weave patterns and matrix adhesions in composite laminate structures. In this study, fibres were tested with a light-curable vinylester resin to investigate the interface behavior using the Microbond Test. From the preliminary Microbond Testing, Kevlar fibres and the vinylester displayed the highest interfacial shear strength and energy absorption capabilities. The Four-Point Bend test was used to determine the flexural properties of the composite. Both the Microbond and Four-Point Bend test samples were examined by Scanning Electron Microscopy to confirm interface properties and failure mechanisms. After investigation of the results, E-glass and S-glass fibres were selected for future AFO experiments with the matrix.M.A.Sc

Investigating the Effects of Organic Ligands on Iron and Copper Availability to Coastal and Oceanic Phytoplankton Using Continuous Cultures

The chemical speciation of Fe and Cu in marine waters impart a strong selective pressure on phytoplankton assemblages by influencing the availability and partitioning of these essential trace nutrients among taxa. Consequently, trace metal speciation establishes interspecific competitive interactions that largely determine the phytoplankton community structure in natural marine waters. The aim of this dissertation was to broaden the understanding of Fe and Cu availability to different phytoplankton by examining the effects of organic complexation on natural community assemblages from coastal and oceanic waters using continuous cultures. Continuous cultures provide an effective platform for investigating subtle responses in natural populations to consistent nutrient flux and speciation, as the community trajectory is amplified by dilution losses of slow-growing and noncompetitive organisms. The successful design and implementation of a novel continuous culture system for shipboard experiments with natural mixed communities is detailed here. Domoic acid (DA), a potent phycotoxin produced by the diatom genus Pseudo-nitzschia, is an Fe and Cu chelator. Dissolved DA (dDA) additions to natural phytoplankton communities from coastal and offshore regions enhanced diatom growth more than Fe or Cu additions alone, and principally selected for Pseudo-nitzschia over all other phytoplankton. These findings are consistent with evidence that Pseudo-nitzschia release dDA to enhance the Cu acquisition needed to initiate an inducible high-affinity Fe uptake mechanism. These experiments provide the first direct evidence that the production of dDA by Pseudo-nitzschia may facilitate a competitive advantage, and explain its success in coastal and offshore assemblages. Three commercially available strong Fe(III)-binding siderophores isolated from terrestrial organisms (desferrioxamine B, ferrichrome and rhodotorulic acid) were used as analogs to marine siderophores to determine Fe availability to different coastal phytoplankton taxa. While all have high conditional constants for Fe(III) in seawater, the complexation characteristics greatly influenced Fe availability, reflected in their effects on chlorophyll biomass, Fe uptake and photophysiology. Although the specific compounds comprising strong Fe and Cu complexing organic ligands in seawater are unknown, these findings strongly suggest their specific chemical nature is likely more important than their metal affinities in determining Fe availability to phytoplankton

Injected Versus Oral Deep Vein Thrombosis Prophylactic Therapy: A Patient Satisfaction Study

Deep vein thrombosis (DVT) is a serious complication of total knee replacement (TKA). While the need for post op prophylaxis is accepted, controversy exists as to which regimen(s) to use. ASA use has seen resurgence due to its efficacy, safety profile, and easy administration. To date no study has evaluated patient satisfaction and compliance with ASA chemoprophylaxis after TKA. Ninety-six TKA patients were surveyed after randomization to receive either oral ASA or injected low molecular weight heparin. Satisfaction was significantly greater in the ASA group. Confidence in treatment was equivalent between the groups. Patient satisfaction withanticoagulation after TKA should not be overlooked. We have demonstrated increased satisfaction with ASA treatment without affecting perceptions of efficacy. Our findings should be considered when prescribing postoperative prophylaxi