Measuring Learning Gains in Chemical Education: A Comparison of Two Methods

Evaluating the effect of a pedagogical innovation is often done by looking for a significant difference in a content measure using a pre−post design. While this approach provides valuable information regarding the presence or absence of an effect, it is limited in providing details about the nature of the effect. A measure of the magnitude of the pre−post change, commonly called learning gain, could provide this additional information to chemical education researchers. In this paper, we compare two methods of measuring learning gains using data from large-scale administrations of the Chemical Concepts Inventory at four universities. The intent of this study is to compare various measures of learning gain, not to contrast the teaching effectiveness at the four universities. In this gain analysis, we introduce a method based on Rasch modeling and discuss the advantages offered by this type of analysis over more commonly used measures of learning gain

Application of Two-Parameter Item Response Theory for Determining Form-Dependent Items on Exams Using Different Item Orders

Using multiple versions of an assessment has the potential to introduce item environment effects. These types of effects result in version dependent item characteristics (i.e., difficulty and discrimination). Methods to detect such effects and resulting implications are important for all levels of assessment where multiple forms of an assessment are created. This report describes a novel method for identifying items that do and do not display form dependence. The first two steps identify form dependent items using a differential item functioning (DIF) analysis of item parameters estimated by Item Response Theory. The method is illustrated using items that appeared in four forms (two trial and two released versions) of a first semester general chemistry examination. Eighteen of fifty-six items were identified as having item parameters that were form dependent. Thirteen of those items displayed a form dependence consistent with reasons previously identified in the literature: preceding item difficulty, content priming, and a combination of preceding item difficulty and content priming. The remaining five items had form dependence that did not align reasons reported in the literature. An analysis was done to determine if all possible instances of predicted form dependence could be found. Several instances where form dependence could have been found, based on the preceding item difficulty or content priming, were identified, and those items did not display form dependence. We identify and rationalize form dependence for thirteen of the eighteen items flagged; however, we are unable to predict form dependence for items

Electron Affinity of Chlorine Dioxide

The flowing afterglow technique was used to determine the electron affinity of chlorine dioxide. A value of 2.37 ± 0.10 eV was found by bracketing between the electron affinities of HS° and SF4 as a lower limit and that of NO2 as an upper limit. This value is in excellent agreement with 2.32 eV predicted from a simple thermodynamic cycle involving the reduction potential of the C102/C102- couple and a Gibbs hydration energy identical with that of SO2-

PLD1 is overexpressed in an ER-negative MCF-7 cell line variant and a subset of phospho-Akt-negative breast carcinomas

We have used a novel variant of the human oestrogen receptor (ER)-positive MCF-7 cell line, TMX2-28, as a model to study breast cancer. TMX2-28 cells show no detectable levels of mRNA or protein expression for the ER and express basal cytokeratins (CKs) 5, 14, and 17. cDNA microarray comparison between TMX2-28 and its parent cell line, MCF-7, identified 1402 differentially expressed transcripts, one of which was, phospholipase D1 (PLD1). Using real-time RT–PCR, we confirmed that PLD1 mRNA levels are 10-fold higher in TMX2-28 cells than in MCF-7 cells. We next examined PLD1 expression in human breast carcinomas. Phospholipase D1 mRNA levels were higher in breast tumours that expressed high-mRNA levels of basal CKs 5 and/or 17, but PLD1 mRNA levels were not significantly higher in ER-negative tumours. Phospholipase D1 protein was overexpressed in 10 of 42 (24%) breast tumours examined by IHC. Phospholipase D1 was overexpressed in 6 of 31 ER-positive tumours and 4 of 11 ER-negative tumours. Phospholipase D1 was overexpressed in three of the four tumours that showed high CK5/17 expression. Five PLD1-positive tumours were negative for phospho-Akt expression, but positive for phospho-mammalian target of rapamycin (mTOR) expression. The other five PLD1-positive breast tumours showed positive expression for phospho-Akt; however, only two of these cases were positive for phospho-mTOR. In this study, we report that PLD1 and phospho-mTOR are coexpressed in a subset of phospho-Akt-negative breast carcinomas

Recombinant Probiotic Expressing Listeria Adhesion Protein Attenuates Listeria monocytogenes Virulence In Vitro

BACKGROUND: Listeria monocytogenes, an intracellular foodborne pathogen, infects immunocompromised hosts. The primary route of transmission is through contaminated food. In the gastrointestinal tract, it traverses the epithelial barrier through intracellular or paracellular routes. Strategies to prevent L. monocytogenes entry can potentially minimize infection in high-risk populations. Listeria adhesion protein (LAP) aids L. monocytogenes in crossing epithelial barriers via the paracellular route. The use of recombinant probiotic bacteria expressing LAP would aid targeted clearance of Listeria from the gut and protect high-risk populations from infection. METHODOLOGY/PRINCIPAL FINDINGS: The objective was to investigate the ability of probiotic bacteria or LAP-expressing recombinant probiotic Lactobacillus paracasei (Lbp(LAP)) to prevent L. monocytogenes adhesion, invasion, and transwell-based transepithelial translocation in a Caco-2 cell culture model. Several wild type probiotic bacteria showed strong adhesion to Caco-2 cells but none effectively prevented L. monocytogenes infection. Pre-exposure to Lbp(LAP) for 1, 4, 15, or 24 h significantly (P<0.05) reduced adhesion, invasion, and transepithelial translocation of L. monocytogenes in Caco-2 cells, whereas pre-exposure to parental Lb. paracasei had no significant effect. Similarly, Lbp(LAP) pre-exposure reduced L. monocytogenes translocation by as much as 46% after 24 h. Lbp(LAP) also prevented L. monocytogenes-mediated cell damage and compromise of tight junction integrity. Furthermore, Lbp(LAP) cells reduced L. monocytogenes-mediated cell cytotoxicity by 99.8% after 1 h and 79% after 24 h. CONCLUSIONS/SIGNIFICANCE: Wild type probiotic bacteria were unable to prevent L. monocytogenes infection in vitro. In contrast, Lbp(LAP) blocked adhesion, invasion, and translocation of L. monocytogenes by interacting with host cell receptor Hsp60, thereby protecting cells from infection. These data show promise for the use of recombinant probiotics in preventing L. monocytogenes infection in high-risk populations

Clarity on Cronbach’s Alpha Use

The Cronbach’s alpha (α) statistic is regularly reported in science education studies. However, recent reviews have noted that it is not well-understood. Therefore, this commentary provides additional clarity regarding the language used when describing and interpreting alpha and other estimates of reliability