Predicting Math Success in an Online Tutoring System Using Language Data and Click-Stream Variables: A Longitudinal Analysis

Previous studies have demonstrated strong links between students\u27 linguistic knowledge, their affective language patterns and their success in math. Other studies have shown that demographic and click-stream variables in online learning environments are important predictors of math success. This study builds on this research in two ways. First, it combines linguistics and click-stream variables along with demographic information to increase prediction rates for math success. Second, it examines how random variance, as found in repeated participant data, can explain math success beyond linguistic, demographic, and click-stream variables. The findings indicate that linguistic, demographic, and click-stream factors explained about 14% of the variance in math scores. These variables mixed with random factors explained about 44% of the variance

Tumor Vascular Permeability to a Nanoprobe Correlates to Tumor-Specific Expression Levels of Angiogenic Markers

© 2009 Karathanasis et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.DOI: 10.1371/journal.pone.0005843Background. Vascular endothelial growth factor (VEGF) receptor-2 is the major mediator of the mitogenic, angiogenic, and vascular hyperpermeability effects of VEGF on breast tumors. Overexpression of VEGF and VEGF receptor-2 is associated with the degree of pathomorphosis of the tumor tissue and unfavorable prognosis. In this study, we demonstrate that non-invasive quantification of the degree of tumor vascular permeability to a nanoprobe correlates with the VEGF and its receptor levels and tumor growth. Methodology/Principal Findings. We designed an imaging nanoprobe and a methodology to detect the intratumoral deposition of a 100 nm-scale nanoprobe using mammography allowing measurement of the tumor vascular permeability in a rat MAT B III breast tumor model. The tumor vascular permeability varied widely among the animals. Notably, the VEGF and VEGF receptor-2 gene expression of the tumors as measured by qRT-PCR displayed a strong correlation to the imaging-based measurements of vascular permeability to the 100 nm-scale nanoprobe. This is in good agreement with the fact that tumors with high angiogenic activity are expected to have more permeable blood vessels resulting in high intratumoral deposition of a nanoscale agent. In addition, we show that higher intratumoral deposition of the nanoprobe as imaged with mammography correlated to a faster tumor growth rate. This data suggest that vascular permeability scales to the tumor growth and that tumor vascular permeability can be a measure of underlying VEGF and VEGF receptor-2 expression in individual tumors. Conclusions/Significance. This is the first demonstration, to our knowledge, that quantitative imaging of tumor vascular permeability to a nanoprobe represents a form of a surrogate, functional biomarker of underlying molecular markers of angiogenesi

Reduced Levels of Membrane-Bound Alkaline Phosphatase Are Common to Lepidopteran Strains Resistant to Cry Toxins from Bacillus thuringiensis

Development of insect resistance is one of the main concerns with the use of transgenic crops expressing Cry toxins from the bacterium Bacillus thuringiensis. Identification of biomarkers would assist in the development of sensitive DNA-based methods to monitor evolution of resistance to Bt toxins in natural populations. We report on the proteomic and genomic detection of reduced levels of midgut membrane-bound alkaline phosphatase (mALP) as a common feature in strains of Cry-resistant Heliothis virescens, Helicoverpa armigera and Spodoptera frugiperda when compared to susceptible larvae. Reduced levels of H. virescens mALP protein (HvmALP) were detected by two dimensional differential in-gel electrophoresis (2D-DIGE) analysis in Cry-resistant compared to susceptible larvae, further supported by alkaline phosphatase activity assays and Western blotting. Through quantitative real-time polymerase chain reaction (qRT-PCR) we demonstrate that the reduction in HvmALP protein levels in resistant larvae are the result of reduced transcript amounts. Similar reductions in ALP activity and mALP transcript levels were also detected for a Cry1Ac-resistant strain of H. armigera and field-derived strains of S. frugiperda resistant to Cry1Fa. Considering the unique resistance and cross-resistance phenotypes of the insect strains used in this work, our data suggest that reduced mALP expression should be targeted for development of effective biomarkers for resistance to Cry toxins in lepidopteran pests

Damage prediction of carbon-epoxy composite laminates using finite element analysis

Continuous growth in the use of composite materials in advanced structural applications, such as aerospace, marine, and automotive, has been observed in the past two decades. This has motivated efficient design and manufacturing of composite products so as to obtain lighter structures with higher strength, durability and life. To contribute to develop an efficient design methodology, the present research has been undertaken. The accuracy and predictive capabilities of finite element models and failure analysis of a specific composite material using the commercial finite element program ABAQUS are evaluated. A set of unidirectional carbon-epoxy composite laminates are modelled under monotonic tensile and compressive loading, and their failure is assessed using the Hashin's failure criterion. The numerical results are compared against carefully conducted experimental test data. The differences between the experimental and numerically predicted values of the maximum principle stress are used to evaluate the accuracy of the finite element models. In the unidirectional (0-degree) composite laminates after the initial ply failure, a varied damage pattern is observed with a difference of 17.7% and 10.5% under tension and compression, respectively. The unidirectional composites under transverse loading (90-degree) show a difference of 10.8% and 0.4% under tensile and compressive loading, respectively. The variations between the experimental and the modelled results are mainly due to approximating and analysing the model in its 2D behaviour, which excludes delamination. Specifically, a composite tested under compression suffers from Brooming Gage Bottom (BGB); so the variation is expected. The Hashin's damage criterion is not suitable when delamination occurs as a dominant failure mode

Damage prediction of carbon-epoxy composites under shear loads using the finite element method

Carbon fiber reinforced polymer composite (CFRP) laminates are used in many applications of the aerospace industry, particularly, in aircraft structural components due to their good stiffness to weight ratios compared to traditionally used aluminium. The ability of accurate prediction of the structural response of composites under complex loadings is crucially important for high-end designs and optimisation of composite structures. The accuracy and predictive capabilities of finite element models in the failure analysis of the carbon-epoxy (IM7/977-3) composite laminates have been evaluated. The cross ply composite laminate with the layup configuration [0,90]4S was numerically modelled under shear loads, and the commercial finite element program ABAQUS was utilised. The failure due to shear loads were analysed using the Hashin's failure criterion. The numerical results were validated by comparing them against the carefully conducted experimental test data. The difference between the experimental and numerically predicted values of the stress and strain were compared to evaluate the accuracy of the finite element models