Position Paper On Use Of Stereoscopy To Support Science Learning: Ten Years Of Research

Stereoscopys potential as a tool for science education has been largely eclipsed by its popularity as an entertainment platform and marketing gimmick. Dozens of empirical papers have been published in the last decade about the impact of stereoscopy on learning. As a result, a corpus of research now points to a coherent message about how, when, and where stereoscopy can be most effective in supporting science education. This position paper synthesizes that research with examples from three studies recently completed and published by the authors of this paper. Results of the synthesis point towards generally limited successful uses of stereoscopic media in science education with a pocket of potentially beneficial applications. Our position is that stereoscopy should be used only where its unique properties can accommodate specific requirements of understanding topics and tasks namely visualizations where the spatial sense of depth is germane to conveying core ideas and cognitive load is high. Stereoscopys impact on learning is also related to the spatial ability of the viewer. More research is needed on the effect of novelty, long-term learning and possible learning differences between the various methods of implementing stereoscopy

Biochemical and structural characterization of Cdc14 phosphatases from pathogenic fungi

Cyclin-dependent kinases (Cdk) drive cell cycle progression and reversal of Cdk phosphorylation is essential for mitotic exit. Cdc14 is a widely conserved family of protein phosphatases that reverse Cdk phosphorylation. Recently, Cdc14 was also found to be essential for pathogenicity of some fungal plant pathogens. Fungal pathogens, like Ustilago maydis, decrease agricultural crop yield costing global agriculture by some accounts $60 billion per year. Since Cdc14 is absent in plants, a fungi specific Cdc14 inhibitor could be made to reduce the pathogenicity of U. maydis and other fungal plant pathogens to increase crop yields. To guide inhibitor development, a three-dimensional structural model of fungal Cdc14 is needed. Therefore, we recombinantly expressed Ustilago maydis Cdc14 (UmCdc14) and a catalytically inactive substrate trapping mutant (UmCdc14C318S) with N-terminal hexa-histidine tags in E. coli. Recombinant UmCdc14 and UmCdc14C318S were successfully purified using immobilized metal affinity chromatography. We screened the purified proteins by sitting drop crystallography. Two conditions yielded small crystals for UmCdc14. One condition yielded a crystal for UmCdc14C318S. These conditions were used for large scale crystal growth by hanging drop crystallography. If ideal conditions are found, UmCdc14C318S will be crystallized bound to a peptide substrate to capture the molecular binding determinants that will help guide inhibitor design. Wild-type UmCdc14 will be crystallized bound to small molecule inhibitors identified by a previous high throughput library screen. In the future, we will also explore crystallization of Cdc14 orthologs from other plant pathogens

Chemical and Electrochemical Lithiation of van der Waals Tetrel Arsenides

A lithiation of van der Waals tetrel‐arsenides GeAs and SiAs has been investigated. Electrochemical lithiation demonstrated large initial capacities of over 950 mAh g‐1 accompanied by rapid fading over successive cycling in the voltage range of 0.01‐2 V. Limiting the voltage range to 0.5‐2 V achieved more stable cycling attributed to the intercalation process with lower capacities. Ex‐situ powder X‐ray diffraction confirmed complete amorphization of the samples after lithiation, as well as recrystallization of the binary tetrel‐arsenide phases after full de‐lithiation in the voltage range of 0.5‐2 V. Solid‐state synthetic methods produces layered phases, where Si‐As or Ge‐As layers are separated by Li cations. The first layered compounds in the corresponding ternary systems were discovered, Li0.9Ge2.9As3.1 and Li3Si7As8, which crystallize in the Pbam (No. 55) and P2/m (No. 10) space groups, respectively. Semiconducting layered GeAs and SiAs accommodate extra charge from Li cations through structural rearrangement in the Si‐As or Ge‐As layers and eventually by replacement of the tetrel dumbbells with sets of Li atoms. Ge and Si monoarsenides demonstrated high structural flexibility and a mild ability for reversible lithiation

Photoreversible interconversion of a phytochrome photosensory module in the crystalline state.

A major barrier to defining the structural intermediates that arise during the reversible photointerconversion of phytochromes between their biologically inactive and active states has been the lack of crystals that faithfully undergo this transition within the crystal lattice. Here, we describe a crystalline form of the cyclic GMP phosphodiesterases/adenylyl cyclase/FhlA (GAF) domain from the cyanobacteriochrome PixJ in Thermosynechococcus elongatus assembled with phycocyanobilin that permits reversible photoconversion between the blue light-absorbing Pb and green light-absorbing Pg states, as well as thermal reversion of Pg back to Pb. The X-ray crystallographic structure of Pb matches previous models, including autocatalytic conversion of phycocyanobilin to phycoviolobilin upon binding and its tandem thioether linkage to the GAF domain. Cryocrystallography at 150 K, which compared diffraction data from a single crystal as Pb or after irradiation with blue light, detected photoconversion product(s) based on Fobs - Fobs difference maps that were consistent with rotation of the bonds connecting pyrrole rings C and D. Further spectroscopic analyses showed that phycoviolobilin is susceptible to X-ray radiation damage, especially as Pg, during single-crystal X-ray diffraction analyses, which could complicate fine mapping of the various intermediate states. Fortunately, we found that PixJ crystals are amenable to serial femtosecond crystallography (SFX) analyses using X-ray free-electron lasers (XFELs). As proof of principle, we solved by room temperature SFX the GAF domain structure of Pb to 1.55-Å resolution, which was strongly congruent with synchrotron-based models. Analysis of these crystals by SFX should now enable structural characterization of the early events that drive phytochrome photoconversion

Identification of pre-leukaemic haematopoietic stem cells in acute leukaemia.

In acute myeloid leukaemia (AML), the cell of origin, nature and biological consequences of initiating lesions, and order of subsequent mutations remain poorly understood, as AML is typically diagnosed without observation of a pre-leukaemic phase. Here, highly purified haematopoietic stem cells (HSCs), progenitor and mature cell fractions from the blood of AML patients were found to contain recurrent DNMT3A mutations (DNMT3A(mut)) at high allele frequency, but without coincident NPM1 mutations (NPM1c) present in AML blasts. DNMT3A(mut)-bearing HSCs showed a multilineage repopulation advantage over non-mutated HSCs in xenografts, establishing their identity as pre-leukaemic HSCs. Pre-leukaemic HSCs were found in remission samples, indicating that they survive chemotherapy. Therefore DNMT3A(mut) arises early in AML evolution, probably in HSCs, leading to a clonally expanded pool of pre-leukaemic HSCs from which AML evolves. Our findings provide a paradigm for the detection and treatment of pre-leukaemic clones before the acquisition of additional genetic lesions engenders greater therapeutic resistance

HL‐TWiM Empirical Model of High‐Latitude Upper Thermospheric Winds

We present an empirical model of thermospheric winds (High‐latitude Thermospheric Wind Model [HL‐TWiM]) that specifies F region high‐latitude horizontal neutral winds as a function of day of year, latitude, longitude, local time, and geomagnetic activity. HL‐TWiM represents the large‐scale neutral wind circulation, in geomagnetic coordinates, for the given input conditions. The model synthesizes the most extensive collection to date of historical high‐latitude wind measurements; it is based on statistical analyses of several decades of F region thermospheric wind measurements from 21 ground‐based stations (Fabry‐Perot Interferometers and Scanning Doppler Imaging Fabry‐Perot Interferometers) located at various northern and southern high latitudes and two space‐based instruments (UARS WINDII and GOCE). The geomagnetic latitude and local time dependences in HL‐TWiM are represented using vector spherical harmonics, day of year and longitude variations are represented using simple harmonic functions, and the geomagnetic activity dependence is represented using quadratic B splines. In this paper, we describe the HL‐TWiM formulation and fitting procedures, and we verify the model against the neutral wind databases used in its formulation. HL‐TWiM provides a necessary benchmark for validating new wind observations and tuning our physical understanding of complex wind behaviors. Results show stronger Universal Time variation in winds at southern than northern high latitudes. Model‐data intra‐annual comparisons in this study show semiannual oscillation‐like behavior of GOCE winds, rarely observed before in wind data.Key PointsWe developed a comprehensive empirical model of high‐latitude F region thermospheric winds (HL‐TWiM)Universal Time variations in high‐latitude winds are stronger in the Southern than Northern HemisphereHL‐TWiM provides a necessary benchmark for validating new high‐latitude wind observations and tuning first principal modelsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153588/1/jgra55363_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153588/2/jgra55363-sup-0001-Figure_SI-S01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153588/3/jgra55363.pd