Effect of Freshman Chemistry on Student Performance in Sophomore Engineering Courses

The role of first year chemistry courses in engineering programs varies somewhat across programs and disciplines. Clearly most engineering majors will encounter chemistry topics of a general nature in some of their upper-level course work. The purpose of requiring chemistry in the first year, however, goes well beyond learning chemical concepts. As a quantitative science, chemistry requires the use of math, principally algebra, on a regular basis in solving various problems. Students should gain an appreciation of the importance of units in solving problems should come to understand the difference between implicit and explicit properties and should develop other quantitative skills. Depending on how it is taught, chemistry can provide students with a wide range of opportunities to hone skills that will be required in their engineering courses. In discussions with students and even with many faculty, the role of chemistry is often viewed narrowly in terms of the chemistry topics alone. The purpose of this study is to explore how the number of chemistry courses taken and the performance in freshman chemistry affects performance in early engineering courses. Engineering students at the University of New Haven have different requirements for freshman chemistry depending on their particular discipline. All engineering students are required to take at least one freshman chemistry course. Students in chemical and civil engineering are required to take two, students in mechanical and system engineering have an option of biology or a second course in chemistry and students in electrical and computer engineering take only one freshman chemistry course. All engineering students take a sophomore engineering course, Introduction to Modeling of Engineering Systems, which includes topics drawn from electric circuits, mass and energy balances and force balances. The course is designed to help students develop an organized approach to solving problems and uses a conservation and accounting approach to provide a broad framework for the diverse topics. This course provides an opportunity to explore how their freshman chemistry background prepares studcents for engineering coursework. This study examines the impact of having one or two freshman chemistry courses on student performance in the first sophomore level engineering course. The methods used include standard statistical techniques, such as analysis of variance, correlation (eg., Pearson) and t-tests across groups

Limited metacognitive access to one’s own facial expressions

As humans we communicate important information through fine nuances in our facial expressions, but because conscious motor representations are noisy, we might not be able to report these fine but meaningful movements. Here we measured how much explicit metacognitive information young adults have about their own facial expressions. Participants imitated pictures of themselves making facial expressions and triggered a camera to take a picture of them while doing so. They then rated confidence (how well they thought they imitated each expression). We defined metacognitive access to facial expressions as the relationship between objective performance (how well the two pictures matched) and subjective confidence ratings. Metacognitive access to facial expressions was very poor when we considered all face features indiscriminately. Instead, machine learning analyses revealed that participants rated confidence based on idiosyncratic subsets of features. We conclude that metacognitive access to own facial expressions is partial, and surprisingly limited

Nanoscale mosaicity revealed in peptide microcrystals by scanning electron nanodiffraction.

Changes in lattice structure across sub-regions of protein crystals are challenging to assess when relying on whole crystal measurements. Because of this difficulty, macromolecular structure determination from protein micro and nanocrystals requires assumptions of bulk crystallinity and domain block substructure. Here we map lattice structure across micron size areas of cryogenically preserved three-dimensional peptide crystals using a nano-focused electron beam. This approach produces diffraction from as few as 1500 molecules in a crystal, is sensitive to crystal thickness and three-dimensional lattice orientation. Real-space maps reconstructed from unsupervised classification of diffraction patterns across a crystal reveal regions of crystal order/disorder and three-dimensional lattice tilts on the sub-100nm scale. The nanoscale lattice reorientation observed in the micron-sized peptide crystal lattices studied here provides a direct view of their plasticity. Knowledge of these features facilitates an improved understanding of peptide assemblies that could aid in the determination of structures from nano- and microcrystals by single or serial crystal electron diffraction

Hard X-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction

The Fe/MgO magnetic tunnel junction is a classic spintronic system, with current importance technologically and interest for future innovation. The key magnetic properties are linked directly to the structure of hard-to-access buried interfaces, and the Fe and MgO components near the surface are unstable when exposed to air, making a deeper probing, nondestructive, in-situ measurement ideal for this system. We have thus applied hard X-ray photoemission spectroscopy (HXPS) and standing-wave (SW) HXPS in the few kilo-electron-volt energy range to probe the structure of an epitaxially grown MgO/Fe superlattice. The superlattice consists of 9 repeats of MgO grown on Fe by magnetron sputtering on an MgO(001) substrate, with a protective Al2O3 capping layer. We determine through SW-HXPS that 8 of the 9 repeats are similar and ordered, with a period of 33 ± 4 Å, with the minor presence of FeO at the interfaces and a significantly distorted top bilayer with ca. 3 times the oxidation of the lower layers at the top MgO/Fe interface. There is evidence of asymmetrical oxidation on the top and bottom of the Fe layers. We find agreement with dark-field scanning transmission electron microscope (STEM) and X-ray reflectivity measurements. Through the STEM measurements, we confirm an overall epitaxial stack with dislocations and warping at the interfaces of ca. 5 Å. We also note a distinct difference in the top bilayer, especially MgO, with possible Fe inclusions. We thus demonstrate that SW-HXPS can be used to probe deep buried interfaces of novel magnetic devices with few-angstrom precision

Interpretable and efficient contrast in scanning transmission electron microscopy with a diffraction grating beamsplitter

Efficient imaging of biomolecules, 2D materials and electromagnetic fields depends on retrieval of the phase of transmitted electrons. We demonstrate a method to measure phase in a scanning transmission electron microscope using a nanofabricated diffraction grating to produce multiple probe beams. The measured phase is more interpretable than phase-contrast scanning transmission electron microscopy techniques without an off-axis reference wave, and the resolution could surpass that of off-axis electron holography. We apply the technique to image nanoparticles, carbon sub- strates and electric fields. The contrast observed in experiments agrees well with contrast predicted in simulations

Controlling biofilm growth using reactive ceramic ultrafiltration membranes

a b s t r a c t Fouling due to biofilms composed primarily of microorganisms and extracellular polymeric substances is a significant hindrance to membrane filtration in water treatment. The goal of this work was to use a reactive membrane surface to reduce membrane biofouling by coating a ceramic ultrafiltration membrane with the nanoparticulate photocatalyst, TiO 2 . 10-Day biofilm growth experiments were conducted to determine the effect of photocatalytic coatings on the formation of a Pseudomonas putida biofilm and subsequent changes in membrane flux. Results indicate that a highly hydrophilic, photoreactive coating of mixed phase TiO 2 nanoparticles is effective for the control of biofouling on ceramic ultrafiltration membranes

Multiple generations of grain aggregation in different environments preceded solar system body formation

Manuscript submitted to Proceedings of the National Academy of ScienceThe solar system formed from interstellar dust and gas in a molecular cloud. Astronomical observations show that typical interstellar dust consists of amorphous (a-) silicate and organic carbon. Bona fide physical samples for laboratory studies would yield unprecedented insight about solar system formation, but they were largely destroyed. The most likely repositories of surviving presolar dust are the least altered extraterrestrial materials, interplanetary dust particles (IDPs) with probable cometary origins. Cometary IDPs contain abundant submicron a-silicate grains called GEMS, believed to be carbon-free. Some have detectable isotopically anomalous a-silicate components from other stars, proving they are preserved dust inherited from the interstellar medium. However, it is debated whether the majority of GEMS predate the solar system or formed in the solar nebula by condensation of high-temperature (>1300K) gas. Here, we map IDP compositions with single nanometer-scale resolution and find that GEMS contain organic carbon. Mapping reveals two generations of grain aggregation, the key process in growth from dust grains to planetesimals, mediated by carbon. GEMS grains, some with a-silicate subgrains mantled by organic carbon, comprise the earliest generation of aggregates. These aggregates (and other grains) are encapsulated in lower density organic carbon matrix, indicating a second generation of aggregation. Since this organic carbon thermally decomposes above ~450K, GEMS cannot have accreted in the hot solar nebula and formed, instead, in the cold presolar molecular cloud and/or outer protoplanetary disk. We suggest that GEMS are consistent with surviving interstellar dust, condensed in situ, and cycled through multiple molecular clouds.Portions of this work were performed at the Molecular Foundry and the Advanced Light Source at Lawrence Berkeley National Laboratory, which are supported by the Office of Science, Basic Energy Sciences, U.S. Department of Energy under Contract No. DE-AC02-05CH11231. HAI acknowledges funding by NASA’s Laboratory Analysis of Returned Samples and Emerging Worlds Programs (NNX14AH86G and NNX16AK41G). JPB acknowledges funding by NASA’s Cosmochemistry Program (NNX14AI39G). CF acknowledges funding by NASA’s Cosmochemistry Program (NNX14AG25G)

Structure and morphology of hydroxylated nickel oxide (111) surfaces

We report an experimental and theoretical analysis of the sqrt(3)x sqrt(3)-R30 and 2x2 reconstructions on the NiO (111) surface combining transmission electron microscopy, x-ray photoelectron spectroscopy, and reasonably accurate density functional calculations using the meta-GGA hybrid functional TPSSh. While the main focus here is on the surface structure, we also observe an unusual step morphology with terraces containing only even numbers of unit cells during annealing of the surfaces. The experimental data clearly shows that the surfaces contain significant coverage of hydroxyl terminations, and the surface structures are essentially the same as those reported on the MgO (111) surface implying an identical kinetically-limited water-driven structural transition pathway. The octapole structure can therefore be all but ruled out for single crystals of NiO annealed in or transported through humid air. . The theoretical analysis indicates, as expected, that simple density functional theory methods for such strongly-correlated oxide surfaces are marginal, while better consideration of the metal d-electrons has a large effect although, it is still not perfect.Comment: Replaces previous submission with smaller PDF file size. 32 pages including 9 figures and 2 table