Interactions between teaching assistants and students boost engagement in physics labs

Through in-class observations of teaching assistants (TAs) and students in the lab sections of a large introductory physics course, we study which TA behaviors can be used to predict student engagement and, in turn, how this engagement relates to learning. For the TAs, we record data to determine how they adhere to and deliver the lesson plan and how they interact with students during the lab. For the students, we use observations to record the level of student engagement and pre- and post-tests of lab skills to measure learning. We find that the frequency of TA-student interactions, especially those initiated by the TAs, is a positive and significant predictor of student engagement. Interestingly, the length of interactions is not significantly correlated with student engagement. In addition, we find that student engagement was a better predictor of post-test performance than pre-test scores. These results shed light on the manner in which students learn how to conduct inquiry and suggest that, by proactively engaging students, TAs may have a positive effect on student engagement, and therefore learning, in the lab.Comment: 27 pages, 8 figures. v2: Revised for clarity and concision. Version accepted to Physical Review Special Topics - Physics Education Researc

The Price Responsiveness of Salmon Supply in the Short and Long Run

Productivity growth and competitiveness indicate that salmon supply is price responsive. However, in the short run supply is likely to be constrained by the biological production process, regulations, and capacity constraints. In this article, we estimate a restricted profit function for Norwegian salmon producers, which allows us to examine the industry’s short-run and long-run supply responsiveness separately. Using data spanning 1985 to 2004, we find that there is close to zero, own-price supply responsiveness in the short run. In the long run, this changes substantially as supply becomes elastic. This result can contribute to explaining the observed cyclical profitability in the salmon farming industry.Restricted profit function, supply, salmon farming, profit cycles, Demand and Price Analysis, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies, Research Methods/ Statistical Methods, D24, Q21, Q22,

Wherry Revisited: An Empirical Examination of the Nonperformance Factors that Influence Variation in a Performance Rating

In a perfect performance rating system, both the recall and rating of an individual\u27s behavior would precisely mirror the performance of that ratee. However, the reality of performance rating systems is that often times the rater\u27s recall and subsequent rating fails to reflect the true performance of the individual. The difference between actual and perceived performance has been attributed in the literature to conscious or unconscious rater bias. In 1952, Wherry developed a rating theory based on a series of mathematical equations that precisely defined the relationship between the performance of the ratee and the recall of that observation. Key to his theoretical work was the fundamental rating equation, which stated that a rating score was equal to the actual performance of the ratee plus an observation and recall bias component as well as random error. As such, the goal of this study was to test the appropriateness of this framework by applying it to an actual performance rating system used by the United States Navy on board a particular ship. By utilizing Wherry\u27s basic theory, together with data on rater and ratee nonperformance characteristics (e.g. gender, race, education, height, smoker/non-smoker, etc.), multiple regression analysis was used to identify the nonperformance factors that affected the accuracy of a rating process for 423 individuals. The results of this study supported Wherry\u27s theory in that four of the eight variables contained in the study\u27s final regression model strongly indicated the existence of rater bias. Ratees that were either white, had personality types that matched the first raters, or were of the same race as the second raters generally received higher evaluation scores than ratees that were not, while ratees that smoked received lower evaluation scores. Even though more research is clearly needed to determine the factors that may have produced these biases, their existence in such a high-stakes performance appraisal system suggests that at a minimum, the Navy needs to develop a strategy that educates its raters on the possibility that they might be subconsciously discriminating against others based on their race, personality match, and smoking preference

MEASUREMENT OF DYNAMIC SURFACE TENSION IN BUBBLING SYSTEMS

The static and dynamic surface tension was measured for aqueous solutions of eleven surface-active agents for the purpose of studying the effect of surface tension upon boiling heat transfer. The surfactants were chosen from the Tween, Aerosol, and Hyonic series. Dynamic surface tension, at T = 90 deg C, was investigated by observing the volume and frequency for air bubbles forming from a submerged orifice. Static surface tension, at T = 100 deg C, was measured using a duNouy tensiometer. In all cases, the dynamic surface tension for solutions of these surface active agents was less than the value for pure water, greater than the static value for the same concentration, and was a smoothly decreasing function of concentration. (auth

The genetic architecture of emerging fungicide resistance in populations of a global wheat pathogen

Containing fungal diseases often depends on the application of fungicidal compounds. Fungicides can rapidly lose effectiveness due to the rise of resistant individuals in populations. However, the lack of knowledge about resistance mutations beyond known target genes challenges investigations into pathways to resistance. We used whole-genome sequencing data and association mapping to reveal the multilocus genetic architecture of fungicide resistance in a global panel of 159 isolates of Parastagonospora nodorum, an important fungal pathogen of wheat. We found significant differences in azole resistance among global field populations. The populations evolved distinctive combinations of resistance alleles which can interact when co-occurring in the same genetic background. We identified 34 significantly associated single nucleotide polymorphisms located in close proximity to genes associated with fungicide resistance in other fungi, including a major facilitator superfamily transporter. Using fungal colony growth rates and melanin production at different temperatures as fitness proxies, we found no evidence that resistance was constrained by genetic trade-offs. Our study demonstrates how genome-wide association studies of a global collection of pathogen strains can recapitulate the emergence of fungicide resistance. The distinct complement of resistance mutations found among populations illustrates how the evolutionary trajectory of fungicide adaptation can be complex and challenging to predict

VETA x ray data acquisition and control system

We describe the X-ray Data Acquisition and Control System (XDACS) used together with the X-ray Detection System (XDS) to characterize the X-ray image during testing of the AXAF P1/H1 mirror pair at the MSFC X-ray Calibration Facility. A variety of X-ray data were acquired, analyzed and archived during the testing including: mirror alignment, encircled energy, effective area, point spread function, system housekeeping and proportional counter window uniformity data. The system architecture is presented with emphasis placed on key features that include a layered UNIX tool approach, dedicated subsystem controllers, real-time X-window displays, flexibility in combining tools, network connectivity and system extensibility. The VETA test data archive is also described

DNMT3b overexpression contributes to a hypermethylator phenotype in human breast cancer cell lines

<p>Abstract</p> <p>Background</p> <p>DNA hypermethylation events and other epimutations occur in many neoplasms, producing gene expression changes that contribute to neoplastic transformation, tumorigenesis, and tumor behavior. Some human cancers exhibit a hypermethylator phenotype, characterized by concurrent DNA methylation-dependent silencing of multiple genes. To determine if a hypermethylation defect occurs in breast cancer, the expression profile and promoter methylation status of methylation-sensitive genes were evaluated among breast cancer cell lines.</p> <p>Results</p> <p>The relationship between gene expression (assessed by RT-PCR and quantitative real-time PCR), promoter methylation (assessed by methylation-specific PCR, bisulfite sequencing, and 5-aza-2'deoxycytidine treatment), and the DNA methyltransferase machinery (total DNMT activity and expression of DNMT1, DNMT3a, and DNMT3b proteins) were examined in 12 breast cancer cell lines. Unsupervised cluster analysis of the expression of 64 methylation-sensitive genes revealed two groups of cell lines that possess distinct methylation signatures: (i) hypermethylator cell lines, and (ii) low-frequency methylator cell lines. The hypermethylator cell lines are characterized by high rates of concurrent methylation of six genes (<it>CDH1, CEACAM6, CST6, ESR1, LCN2, SCNN1A</it>), whereas the low-frequency methylator cell lines do not methylate these genes. Hypermethylator cell lines coordinately overexpress total DNMT activity and DNMT3b protein levels compared to normal breast epithelial cells. In contrast, most low-frequency methylator cell lines possess DNMT activity and protein levels that are indistinguishable from normal. Microarray data mining identified a strong cluster of primary breast tumors that express the hypermethylation signature defined by <it>CDH1</it>, <it>CEACAM6, CST6, ESR1, LCN2</it>, and <it>SCNN1A</it>. This subset of breast cancers represents 18/88 (20%) tumors in the dataset analyzed, and 100% of these tumors were classified as basal-like, suggesting that the hypermethylator defect cosegregates with poor prognosis breast cancers.</p> <p>Conclusion</p> <p>These observations combine to strongly suggest that: (a) a subset of breast cancer cell lines express a hypermethylator phenotype, (b) the hypermethylation defect in these breast cancer cell lines is related to aberrant overexpression of DNMT activity, (c) overexpression of DNMT3b protein significantly contributes to the elevated DNMT activity observed in tumor cells expressing this phenotype, and (d) the six-gene hypermethylator signature characterized in breast cancer cell lines defines a distinct cluster of primary basal-like breast cancers.</p

Alternativas e consequências da debicagem em galinhas reprodutoras e poedeiras comerciais.

bitstream/item/58241/1/doc128.pd