What Is STEM? A Discussion About Conceptions of STEM in Education and Partnerships

Educational reformation has proceeded slowly despite the many calls to improve science and mathematics for our students. The acronym STEM (science, technology, engineering, and mathematics) has been adopted by numerous programs as an important focus for renewed global competitiveness for the United States, but conceptions of what STEM entails often vary among stakeholders. This paper examines the conceptions of STEM held by faculty members from a public Research I institution in the middle of a regional “STEM movement.” Faculty members responded to two open‐ended questions: (1) What is STEM? and (2) How does STEM influence and/or impact your life? Although 72% of these faculty members possessed a relevant conception of STEM, the results suggest that they do not share a common conceptualization of STEM. Their conception is most likely based on their academic discipline or how STEM impacts their daily lives. STEM faculty members were likely to have a neutral or positive conception where non‐STEM faculty members often had negative feelings about STEM.     

Particles with spin in stationary flat spacetimes

We construct stationary flat three-dimensional Lorentzian manifolds with singularities that are obtained from Euclidean surfaces with cone singularities and closed one-forms on these surfaces. In the application to (2?+?1)-gravity, these spacetimes correspond to models containing massive particles with spin. We analyse their geometrical properties, introduce a generalised notion of global hyperbolicity and classify all stationary flat spacetimes with singularities that are globally hyperbolic in that sense. We then apply our results to (2?+?1)-gravity and analyse the causality structure of these spacetimes in terms of measurements by observers. In particular, we derive a condition on observers that excludes causality violating light signals despite the presence of closed timelike curves in these spacetimes.     

Pd(IPr*)(cinnamyl)Cl]: an efficient pre-catalyst for the preparation of tetra-ortho-substituted biaryls by Suzuki-Miyaura cross-coupling

The bigger the better: The new well-defined [Pd(IPr*)(cin)Cl] pre-catalyst is described. This complex proves to be highly active in the Suzuki-Miyaura cross-coupling for the synthesis of tetra-ortho-substituted biaryls under mild conditions. IPr* is reported as the largest N-heterocyclic carbene (NHC) to date for [Pd(NHC)(cin)Cl] complexes, explaining the high reactivity observed for this complex in this challenging transformation.     

Porous Polysaccharide‐Based Scaffolds for Human Endothelial Progenitor Cells

Human ECFCs contribute to vascular repair. For this reason, they are considered as valuable cell therapy products in ischemic diseases. Porous scaffolds are prepared that are composed of natural polysaccharides, pullulan and dextran, by chemical crosslinking without use of organic solvents. These porous scaffolds, which have pores with an average size of 42 µm and a porosity of 21%, preserve the viability and the proliferation of cord‐blood ECFCs. After 7 d of culture in porous scaffolds, ECFCs express endothelial markers (CD31 and vWf) and maintain endothelial functions. The cultured cells can be easily retrieved by enzymatic degradation of the porous scaffolds. In vitro results suggest that the porous scaffold could allow cell delivery of ECFCs for treatment of vascular diseases.

     

Biomimicking polysaccharide nanofibers promote vascular phenotypes: a potential application for vascular tissue engineering

The potential of electrospun pullulan/dextran (P/D) nanofibers (average diameter = 323 nm) for vascular tissue engineering applications is explored. The mechanical properties of the nanofibers are of the same order of magnitude as that of human arteries (Young's modulus ≈0.88 MPa; tensile strength ≈0.35 MPa). It is demonstrated that the nanofiber topography enables cell adhesion and that the endothelial phenotype is maintained on the nanofibers. Moreover, P/D nanofibers support a stable confluent monolayer of endothelial cells over 14 d. SMCs seeded on nanofibers display similar levels of alpha smooth muscle actin and a lower proliferation rate than cells on 2D cultures. The observations suggest that nanofibers promote a shift to a quiescent contractile phenotype in SMCs.

     

Total syntheses of (+)- and (−)-syringolides 3 and of (+)- and (−)-syributins 1, 2 and 3

The first total syntheses of (−)-syringolide 3, (+)-syributin 3 and their unnatural enantiomers (+)-syringolide 3 and (−)-syributin 3 using a common intermediate as starting material are described. In addition, total syntheses of (−)- and (+)-syributins 1 and 2 were accomplished by means of the same methodology.     

Effect of adding anionic surfactant on the stability of Pickering emulsions

We investigated the structure and stability of dodecane-in-water emulsions stabilised by partially hydrophobised silica particles after dilution of the emulsions in solutions of sodium dodecyl sulfate and sodium chloride. The emulsions were stable to coalescence on dilution in salt solutions, but did cream over time. The rate and extent of creaming gradually decreased as the salt concentration in the diluted emulsion increased. Dilution in low concentrations of the anionic surfactant did not affect the emulsion stability to coalescence or alter the creaming behaviour of the emulsion. At surfactant concentrations above the critical micelle concentration, however, the rate and extent of creaming and flocculation of the drops were enhanced.