Adatom Emission From Nanoparticles: Implications for Ostwald Ripening

To achieve clean air in our cities, all modern means of ground transportation make use of catalytic converters. Precious metal-based catalysts such as Pt and Pd are currently used in catalytic converters. To achieve higher fuel efficiency, combustion can be carried out in excess air resulting in a reduction of greenhouse gas (GHG) emissions. Reduction of these emissions has emerged as a major challenge. Most of the pollutants are emitted within the first 30 seconds after starting an engine because the catalyst is cold. The development of catalysts which achieve high activity at low temperatures will improve fuel efficiency and therefore reduce the nations dependence on foreign fossil fuels. The supplies of precious metals are limited worldwide, but there is increasing demand for clean energy. Therefore, there is a need to develop more active catalysts that provide long-term stable performance at elevated temperatures with minimal use of precious metals such as platinum. A major problem is that catalysts lose activity during use. Pt particles sinter, leading to poor stability. There is universal agreement that addition of Pd improves the catalytic performance as well as the durability of the Pt catalysts; however, the mechanisms by which Pd improves the performance of Pt are less clear. Conventional supported catalysts (Pt, Pd, and Pt-Pd) have been used to explore the microstructure of diesel oxidation catalysts (DOCs) in their working state (i.e. under oxidizing conditions). Model catalysts have been used to study the evolution of platinum and palladium nanoparticles. Both a statistical and a microscopic approach have been used to understand the ways in which Pd affects Pt. The catalytic activity and kinetics of various monometallic as well as bimetallic powder catalysts aged under different conditions has also been studied. NO oxidation in the presence of NO, O2, and NO2 was the probe reaction used to distinguish between the differing activities of Pt/Al2O3 and Pt-Pd/Al2O3. The work described here focuses on important problems in the field of catalysis. A fundamental understanding of the role of palladium on both the catalytic activity and long-term performance of platinum catalysts has been gained.\u2

Rapt Admissions: Comparing Proposed Federal Rule of Evidence 416 “Rap Shield” with the Rule 412 “Rape Shield”

Creative expression depicting illicit activity can cause jurors to infer improper conclusions about a defendant, even when the jurors attempt to analyze such evidence objectively. When the government seeks to admit a defendant’s creative work into evidence in a criminal trial, courts use existing evidentiary rules to balance the work’s probative value against its risk of unfair prejudice. These rules are supposed to prevent unfair prejudice, but various scholars have shown that courts do not always appreciate how unfairly prejudicial art can be. Rap music presents unique challenges because jurors may fail to discern the work’s literal versus symbolic meaning. Similarly, several decades ago courts struggled to exclude improper evidence of victims’ sexual histories from the courtroom until social pressure encouraged legislators to pass “rape shield” laws. Now, legislators in several states as well as Congress have proposed “rap shield” laws to exclude improper artwork evidence. This Note analyzes proposed Federal Rule of Evidence 416, “Limitation on admissibility of defendant’s creative or artistic expression,” in the context of Federal Rule of Evidence 412, which governs admission of a victim’s sexual history in sex offense cases. Although proposed Rule 416 would protect artistic defendants and Rule 412 protects sexual assault victims, the two rules share various similarities; in particular, they both entail categorical rules of exclusion. This Note summarizes the Rule’s social and legal background and concludes by offering recommendations for its improvement

Shards

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Olfactory vocabulary and collocation in French

International audienceThis article is concerned with words pertaining to olfaction in first and second language French. Focusing on adjective collocates for odeur and parfumin word association tasks and in short written productions, the results show certain preferences for each of these words. A number of similarities and differences between natives and non-natives are noted. The question of typical nativelike language use is raised

The discovery of the nest of the Colima Warbler (Vermivora crissalis)

http://deepblue.lib.umich.edu/bitstream/2027.42/56278/4/MP033.pd

Calculus Students\u27 Reasoning About Slope and Derivative as Rates of Change

Students’ low success rates in college calculus courses are a factor that leads to high attrition rates from science, technology, engineering and mathematics (STEM) degree programs. To help reach our nation’s goal of one million additional STEM majors in the next decade, we must address the conceptual difficulties of our students. Studies have shown that students have difficulty with the concepts of slope and derivative, especially in cases when students are asked to utilize these concepts in real-life contexts. For this study, written surveys were collected from 69 differential (first semester) calculus students. Follow-up clinical interviews were performed on 13 integral (second semester) calculus students. Through the surveys and interviews, students’ understanding of slope and derivative using real-life contexts was explored. On the surveys, students answered questions about linear and nonlinear relationships and interpretations of slope and derivative. They also critiqued the reasoning and accuracy of a hypothetical person’s predictions based on values of slope and derivative. In interviews, students explained their thought process and reasoning for the problems, and answered follow-up questions. Results indicate that students struggle with knowing what the slope and derivative represent and how to use them appropriately to make predictions. The dominant incorrect reasoning by students (one-third of surveyed students and two-thirds of interviewed students) was to think of slope as the ratio-of-totals (y / x) instead of the ratio-of-differences ( Δ y / Δ x) . Thinking of slope as a ratio-of-totals implies that all linear relationships are directly proportional (of the form f(x)=mx, with a y-intercept of zero); students went on to interpret the slope as something that can be used to calculate the value of the dependent variable (by multiplying it by the value of the independent variable). This incorrect thinking about slope influences students’ understanding of the derivative. As a result, they often interpreted the derivative as something that could be used to find the value of the dependent variable (by multiplying the derivative by the value of the independent variable). This led to the incorrect relationship, f(x) = f\u27(x) * x . Furthermore, when students were asked to critique the reasoning of a hypothetical person’s predictions, they showed little knowledge of how the derivative can be used to make valid predictions. Instead of demonstrating understanding that the derivative can be used to estimate change only near the input value, 54% of interviewed students said once again that they could use the derivative to calculate the total value (f(x) = f\u27(x) * x). Students’ impoverished views of slope are adversely impacting their ability to understand the more advanced related topic of derivative. Knowing more about students’ understanding of slope and derivative as rates of change can help educators improve our instruction, with the overall goal of retaining our STEM majors. Instructional implications of this study, as well as limitations and future avenues for research, are discussed

The Effect of Teacher vs. Student-Set Performance Goals on Academic Achievement in a Middle School Science Classroom

Self-regulation and self-efficacy are both necessary for students to be independent learners. During middle school, students begin to yearn for academic autonomy, but lack the ability to regulate themselves and are unreasonable about their abilities. Goals have been proven to promote the development of these two skills. The purpose of this investigation was to determine which type of performance goal most efficiently promotes the development of self-regulation. The effects of performance goal source were analyzed to determine if teacher-assigned or student assigned performance goals produce greater growth in content knowledge for seventh grade life science students. The effects of goal source on goal attainment, test-anxiety, and goal orientation were also measured. Goal source did have a significant effect on normalized learning gains (nLGs). Students with teacher-set goals consistently had higher nLGs compared to students with self-assigned goals, these differences being significant for two units. It was also found that teacher-assigned performance goals produce greater nLGs amongst white students and female students. For all four units, a positive correlation between unit goals and nLGs could be found for students with teacher-set goals, indicating that assigning students higher assigned goals produces greater gains. This relationship could not be established for students with self-assigned goals. The mean goal set by the teacher was significantly lower than the mean student-set goal for three units. In the final unit, the mean goal for both groups were not statistically different, indicating that students were beginning to grasp the concept of what is a realistic goal. Both groups experienced an increase in goal attainment over the course of study, however the rate of attainment was greater for students with teacher-set goals. Test anxiety did not significantly increase over the course of the study. An inverse relationship between test anxiety and nLGs was initially established for students with self-set goals, but not for students with teacher-assigned goals. By the end of the experiment, no relationship between anxiety and normalized learning gains could be established for either group. Additionally, it was found that anxiety was not related to goal attainment. These results demonstrate a shift in the control anxiety had over achievement through the use of goals. While there was no significant change in performance-goal orientation for either group over the course of the experiment, both groups experienced a significant drop in mastery-goal orientation by the end of the experiment, suggesting students were more interested in letter grades than truly mastering content. The findings of this study suggest that performance goals are more efficient with seventh grade science students if they are assigned. Furthermore, the use of performance goals within the classroom shows promise as a tool to develop students’ self-efficacy and self-regulation

Effect of Exercise on Attentional Bias to Food in Restrained and Emotional Eaters

The goal of the current study was to determine the extent to which exercise or exposure to exercise through exercise-related reading material affect attentional bias to high- and low-calorie foods in restrained and emotional eaters. Ninety-three female undergraduates participated for 20 minutes in either an Exercise condition (n = 32), in which they exercised on a stationary bike; an Exercise magazine condition (n = 30), in which they read a magazine about exercise, or a Neutral magazine condition (n = 31), in which they read a magazine that was not about exercise. Attentional bias was assessed prior to and following the exercise manipulation through a dot probe paradigm that used picture pairs consisting of a high- or low-calorie food and a non-food object. Restrained eaters relative to unrestrained eaters exhibited an attentional bias away from images of high-calorie foods irrespective of time or condition. Non-emotional eaters, on the other hand, exhibited decreased attention bias towards both high- and low-calorie foods following exercise. They also exhibited decreased attentional bias to images of low-calorie foods after reading a neutral magazine. These results suggest responses to high- or low-calorie foods in females depend on levels of dietary restraint and that interventions, such as exercise, differentially affect attentional biases to foods depending on the eating habits of the individual

Unified approach for incompressible flows

A unified approach for solving incompressible flows has been investigated in this study. The numerical CTVD (Centered Total Variation Diminishing) scheme used in this study was successfully developed by Sanders and Li for compressible flows, especially for the high speed. The CTVD scheme possesses better mathematical properties to damp out the spurious oscillations while providing high-order accuracy for high speed flows. It leads us to believe that the CTVD scheme can equally well apply to solve incompressible flows. Because of the mathematical difference between the governing equations for incompressible and compressible flows, the scheme can not directly apply to the incompressible flows. However, if one can modify the continuity equation for incompressible flows by introducing pseudo-compressibility, the governing equations for incompressible flows would have the same mathematical characters as compressible flows. The application of the algorithm to incompressible flows thus becomes feasible. In this study, the governing equations for incompressible flows comprise continuity equation and momentum equations. The continuity equation is modified by adding a time-derivative of the pressure term containing the artificial compressibility. The modified continuity equation together with the unsteady momentum equations forms a hyperbolic-parabolic type of time-dependent system of equations. Thus, the CTVD schemes can be implemented. In addition, the physical and numerical boundary conditions are properly implemented by the characteristic boundary conditions. Accordingly, a CFD code has been developed for this research and is currently under testing. Flow past a circular cylinder was chosen for numerical experiments to determine the accuracy and efficiency of the code. The code has shown some promising results