Correlation between layer thickness and periodicity of long polytypes in silicon carbide

The layer widths and repeat spacing of long-period polytypes (LPPs) have been determined using synchrotron radiation source (SRS) X-ray diffraction topography (XRDT). This method has proved to be a powerful tool in investigating the spatial extent of one-dimensional disorder (1DD), long-period polytypes (LPPs) and the boundaries of polytype layers in silicon carbide (SiC). The resulting neighbourhood coalescence models have confirmed the validity of the sandwich rule even in the limit of two arbitrarily long LPPs, as well as the unique nature of the 6H polytype. A significant empirical trend is reported here that relates the thickness of LPP layers to the periodicity of the repeat stacking sequence measured on the topographs. A good correlation between the data suggests that this behaviour is governed by a simple mathematical expression t = kNn. Values for k and n have been determined that relate the polytype thickness (t in microns) to the number of hexagonal layers (N) in the polytype stacking repeat. These values can be used to prompt questions about the limits of polytypism and disorder in SiC

Video Didactic Preparation Augments Problem-Based Learning for First Year Medical Students.

Problem-based learning (PBL) utilizes a self-directed strategy. This process relies on group participation to succeed. Students without a background in biology or medicine can feel overwhelmed by the complexity of the subject matter and unable to participate in the group learning process. We incorporated curated educational videos in the PBL curriculum to help address this situation. First year medical students participated in this study in the form of a typical PBL session. They were then assessed on basic and clinical science knowledge and their learning experience. Student basic science and clinical knowledge were similar between the student groups. However, the students given a list of suggested videos scored higher in their learning experience, perception of feeling prepared, and participating in the group PBL experience than students who were not given the video list. Results from this study indicate that videos can be utilized to enhance the PBL process

The use of synchrotron edge topography to study polytype nearest neighbour relationships in SiC

A brief review of the phenomenon of polytypism is presented and its prolific abundance in Silicon Carbide discussed. An attempt has been made to emphasise modern developments in understanding this unique behaviour. The properties of Synchrotron Radiation are shown to be ideally suited to studies of polytypes in various materials and in particular the coalescence of polytypes in SiC. It is shown that with complex multipolytypic crystals the technique of edge topography allows the spatial extent of disorder to be determined and, from the superposition of Laue type reflections, neighbourhood relationships between polytypes can be deduced. Finer features have now been observed with the advent of second generation synchrotrons, the resolution available enabling the regions between adjoining polytypes to be examined more closely. It is shown that Long Period Polytypes and One Dimensionally Disordered layers often found in association with regions of high defect density are common features at polytype boundaries. An idealised configuration termed a "polytype sandwich" is presented as a model for the structure of SiC grown by the modified Lely technique. The frequency of common sandwich edge profiles are classified and some general trends of polytype neighbourism are summarised

Stepping onto the unknown: reflexes of the foot and ankle while stepping with perturbed perceptions of terrain

This is the author accepted manuscript. The final version is available from the Royal Society via e the DOI in this recordData availability: The data from this study and the code to generate the figures and statistics are publically available at 10.6084/m9.figshare.12986223Unanticipated variations in terrain can destabilize the body. The foot is the primary interface with the ground and we know that cutaneous reflexes provide important sensory feedback. However, little is known about the contribution of stretch reflexes from the muscles within the foot to upright stability. We used intramuscular electromyography measurements of the foot muscles flexor digitorum brevis (FDB) and abductor hallucis (AH) to show for the first time how their short latency stretch reflex response (SLR) may play an important role in responding to stepping perturbations. The SLR of FDB and AH was highest for downwards steps and lowest for upwards steps, with the response amplitude for level and compliant steps in between. When the type of terrain was unknown or unexpected to the participant, the SLR of AH and the ankle muscle soleus tended to decrease. We found significant relationships between the contact kinematics and forces of the leg and the SLR, but a person’s expectation still had significant effects even after accounting for these relationships. Motor control models of short latency body stabilization should not only include local muscle dynamics, but also predictions of terrain based on higher-level information such as from vision or memory

Physical and Social Contexts of Physical Activities Among Adolescent Girls

Background: With limited opportunities for physical activity during school hours, it is important to understand the contexts of physical activities done outside of school time. Given the importance of physical and social aspects of environments, the purpose of this study was to describe where and with whom girls participate in physical activities outside of school. Methods: Participants were 1925 sixth-grade girls in the Trial of Activity for Adolescent Girls (TAAG). At baseline, they completed a 3-day physical activity recall (3DPAR), reporting the main activity performed during 30-minute intervals and the physical and social contexts of physical activities. Results: The most frequently reported physical activities done outside of school time were house chores, walking (for transportation or exercise), dance, basketball, playing with younger children, and running or jogging. The most common location for these activities was at home or in the neighborhood. With the exception of household chores, these activities were typically done with at least one other person. Conclusions: Interventions that promote physical activities that can be done at or around home or developing supportive social networks for physical activity would be consistent with the current physical activity contexts of adolescent girls

Predictors of Academic Procrastination in Asian International College Students

This study examined the relationships among acculturative stress, coping styles, self-efficacy, English language proficiency, and various demographic characteristics as predictors of procrastination behavior in Asian International students (N = 255) studying in the United States. Results of multiple logistic regression indicated that a collective coping style, avoidant coping style, academic self-efficacy, and English language proficiency were the significant predictors of academic procrastination in non-Indian Asian international students. Implications for college student affairs professionals and researchers are addressed

North Dakota Refining Capacity Study

According to a 2008 report issued by the United States Geological Survey, North Dakota and Montana have an estimated 3.0 to 4.3 billion barrels of undiscovered, technically recoverable oil in an area known as the Bakken Formation. With the size and remoteness of the discovery, the question became 'can a business case be made for increasing refining capacity in North Dakota?' And, if so what is the impact to existing players in the region. To answer the question, a study committee comprised of leaders in the region's petroleum industry were brought together to define the scope of the study, hire a consulting firm and oversee the study. The study committee met frequently to provide input on the findings and modify the course of the study, as needed. The study concluded that the Petroleum Area Defense District II (PADD II) has an oversupply of gasoline. With that in mind, a niche market, naphtha, was identified. Naphtha is used as a diluent used for pipelining the bitumen (heavy crude) from Canada to crude markets. The study predicted there will continue to be an increase in the demand for naphtha through 2030. The study estimated the optimal configuration for the refinery at 34,000 barrels per day (BPD) producing 15,000 BPD of naphtha and a 52 percent refinery charge for jet and diesel yield. The financial modeling assumed the sponsor of a refinery would invest its own capital to pay for construction costs. With this assumption, the internal rate of return is 9.2 percent which is not sufficient to attract traditional investment given the risk factor of the project. With that in mind, those interested in pursuing this niche market will need to identify incentives to improve the rate of return

The Origin of Neutral Hydrogen Clouds in Nearby Galaxy Groups: Exploring the Range Of Galaxy Interactions

We combine high resolution N-body simulations with deep observations of neutral hydrogen (HI) in nearby galaxy groups in order to explore two well-known theories of HI cloud formation: HI stripping by galaxy interactions and dark matter minihalos with embedded HI gas. This paper presents new data from three galaxy groups, Canes Venatici I, NGC 672, and NGC 45, and assembles data from our previous galaxy group campaign to generate a rich HI cloud archive to compare to our simulated data. We find no HI clouds in the Canes Venatici I, NGC 672, or NGC 45 galaxy groups. We conclude that HI clouds in our detection space are most likely to be generated through recent, strong galaxy interactions. We find no evidence of HI clouds associated with dark matter halos above M_HI = 10^6 M_Sun, within +/- 700 km/s of galaxies, and within 50 kpc projected distance of galaxies.Comment: 35 pages, 10 figures, AJ accepte

Defining Components of the ßcatenin Destruction Complex and Exploring Its Regulation and Mechanisms of Action during Development

A subset of signaling pathways play exceptionally important roles in embryonic and post-embryonic development, and mis-regulation of these pathways occurs in most human cancers. One such pathway is the Wnt pathway. The primary mechanism keeping Wnt signaling off in the absence of ligand is regulated proteasomal destruction of the canonical Wnt effector ßcatenin (or its fly homolog Armadillo). A substantial body of evidence indicates that SCF(βTrCP) mediates βcat destruction, however, an essential role for Roc1 has not been demonstrated in this process, as would be predicted. In addition, other E3 ligases have also been proposed to destroy βcat, suggesting that βcat destruction may be regulated differently in different tissues.Here we used cultured Drosophila cells, human colon cancer cells, and Drosophila embryos and larvae to explore the machinery that targets Armadillo for destruction. Using RNAi in Drosophila S2 cells to examine which SCF components are essential for Armadillo destruction, we find that Roc1/Roc1a is essential for regulating Armadillo stability, and that in these cells the only F-box protein playing a detectable role is Slimb. Second, we find that while embryonic and larval Drosophila tissues use the same destruction complex proteins, the response of these tissues to destruction complex inactivation differs, with Armadillo levels more elevated in embryos. We provide evidence consistent with the possibility that this is due to differences in armadillo mRNA levels. Third, we find that there is no correlation between the ability of different APC2 mutant proteins to negatively regulate Armadillo levels, and their recently described function in positively-regulating Wnt signaling. Finally, we demonstrate that APC proteins lacking the N-terminal Armadillo-repeat domain cannot restore Armadillo destruction but retain residual function in negatively-regulating Wnt signaling.We use these data to refine our model for how Wnt signaling is regulated during normal development