The importance of demonstratively restoring order.
Ontology highlight
ABSTRACT:
SUBMITTER: Keizer K
PROVIDER: S-EPMC3673976 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Different types of tasks exist, including tasks for research purposes or exams assessing knowledge. According to expectation-value theory, tests are related to different levels of effort and importance within a test taker. Test-taking effort and importance in students decreased over the course of high-stakes tests or low-stakes-tests in research on test-taking motivation. However, whether test-order changes affect effort, importance, and response processes of education students have seldomly been experimentally examined. We aimed to examine changes in effort and importance resulting from variations in test battery order and their relations to response processes. We employed an experimental design assessing N = 320 education students' test-taking effort and importance three times as well as their performance on cognitive ability tasks and a mock exam. Further relevant covariates were assessed once such as expectancies, test anxiety, and concentration. We randomly varied the order of the cognitive ability test and mock exam. The assumption of intraindividual changes in education students' effort and importance over the course of test taking was tested by one latent growth curve that separated data for each condition. In contrast to previous studies, responses and test response times were included in diffusion models for examining education students' response processes within the test-taking context. The results indicated intraindividual changes in education students' effort or importance depending on test order but similar mock-exam response processes. In particular effort did not decrease, when the cognitive ability test came first and the mock exam subsequently but significantly decreased, when the mock exam came first and the cognitive ability test subsequently. Diffusion modeling suggested differences in response processes (separation boundaries and estimated latent trait) on cognitive ability tasks suggesting higher motivational levels when the cognitive ability test came first than vice versa. The response processes on the mock exam tasks did not relate to condition.
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Project description:Four multicomponent charge gradients containing acidic and basic functionalities were prepared via sol-gel processes and the controlled-rate infusion (CRI) method to more clearly understand how preparation conditions influence macroscopic properties. CRI is used to form gradients by infusing reactive alkoxysilanes into a glass vial housing a vertically oriented modified silicon wafer. The concentration and time of infusion of the silane solutions were kept constant. Only the sequence of infusion of the silane solutions was changed. The first set of samples was prepared by initially infusing a solution containing 3-aminopropyltriethoxysilane (APTES) followed by a mercaptopropyltrimethoxysilane (MPTMS) solution. The individual gradients were formed either in an aligned or opposed fashion with respect to the initial gradient. The second set of samples was prepared by infusing the MPTMS solution first followed by the APTES solution, again in either an aligned or opposed fashion. To create charge gradients (NH3 +, SO3 -), the samples were immersed into H2O2. The extent of modification, the degree of protonation of the amine, and the thicknesses of the individual layers were examined by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. The wettability of the individual gradients was assessed via static contact angle measurements. The results demonstrate the importance of infusion order and how it influences the macroscopic and microscopic properties of gradient surfaces including the surface concentration, packing density, degree of protonation, and ultimately wettability. When the gradient materials are prepared via infusion of the APTES sol first, it results in increased deposition of both the amine and thiol groups as evidenced by XPS. Interestingly, the total thickness evaluated from ellipsometry was independent of the infusion order for the aligned gradients, indicative of significant differences in the film density. For the opposed gradients, however, the infusion of APTES first leads to a significantly thicker composite film. Furthermore, it also leads to a more pronounced gradient in the protonation of the amine, which introduces a very different surface wettability. The use of aminosilanes provides a viable approach to create gradient surfaces with different functional group distributions. These studies demonstrate that the controlled placement of functional groups on a surface can provide a new route to prepare gradient materials with improved performance.
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Project description:We revisit a dangling theoretical question of whether the surface reconstruction of the Si(100) surface would energetically favor the symmetric or buckled dimers on the intrinsic potential energy surfaces at 0 K. This seemingly simple question is still unanswered definitively since all existing density functional based calculations predict the dimers to be buckled, while most wavefunction based correlated treatments prefer the symmetric configurations. Here, we use the doubly hybrid density functional (DHDF) geometry optimizations, in particular, XYGJ-OS, complete active space self-consistent field theory, multi-reference perturbation theory, multi-reference configuration interaction (MRCI), MRCI with the Davidson correction (MRCI + Q), multi-reference average quadratic CC (MRAQCC), and multi-reference average coupled pair functional (MRACPF) methods to address this question. The symmetric dimers are still shown to be lower in energy than the buckled dimers when using the CASPT2 method on the DHDF optimized geometries, consistent with the previous results using B3LYP geometries [Y. Jung, Y. Shao, M. S. Gordon, D. J. Doren, and M. Head-Gordon, J. Chem. Phys. 119, 10917 (2003)]. Interestingly, however, the MRCI + Q, MRAQCC, and MRACPF results (which give a more refined description of electron correlation effects) suggest that the buckled dimer is marginally more stable than its symmetric counterpart. The present study underlines the significance of having an accurate description of the electron-electron correlation as well as proper multi-reference wave functions when exploring the extremely delicate potential energy surfaces of the reconstructed Si(100) surface.
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