Establishing Partnerships for Science Outreach Inside and Outside the Undergraduate Classroom.

STEM outreach experiences provide aspiring scientists and healthcare professionals with opportunities to grow into new roles, integrate knowledge, and acquire soft skills. While STEM outreach publications often describe the outreach performed, few focus on how to establish strong partnerships, which are essential for outreach endeavors to succeed. Information on this is more important than ever before-grant agencies commonly require education and outreach plans that will reach a broader audience. Consequently, principal investigators who are not trained in education or outreach need tools to set up strong partnerships. To help fill this gap, here we outline the recommended steps for developing robust interdisciplinary STEM outreach programs that leverage institutional resources and community partnerships. This process yields strategic and sustainable opportunities for undergraduate students to learn as they engage with the STEM outreach team (students, faculty, university staff, and community partners) and the lay public. The outlined ideas broadly apply to creating outreach programs for trainees at any stage, not just undergraduates.

Colonic patch and colonic SILT development are independent and differentially regulated events.

Intestinal lymphoid tissues have to simultaneously ensure protection against pathogens and tolerance toward commensals. Despite such vital functions, their development in the colon is poorly understood. Here, we show that the two distinct lymphoid tissues of the colon-colonic patches and colonic solitary intestinal lymphoid tissues (SILTs)-can easily be distinguished based on anatomical location, developmental timeframe, and cellular organization. Furthermore, whereas colonic patch development depended on CXCL13-mediated lymphoid tissue inducer (LTi) cell clustering followed by LTα-mediated consolidation, early LTi clustering at SILT anlagen did not require CXCL13, CCR6, or CXCR3. Subsequent dendritic cell recruitment to and gp38(+)VCAM-1(+) lymphoid stromal cell differentiation within SILTs required LTα; B-cell recruitment and follicular dendritic cell differentiation depended on MyD88-mediated signaling, but not the microflora. In conclusion, our data demonstrate that different mechanisms, mediated mainly by programmed stimuli, induce the formation of distinct colonic lymphoid tissues, therefore suggesting that these tissues may have different functions.

Bond-order potentials with split-charge equilibration: application to C-, H-, and O-containing systems.

A method for extending charge transfer to bond-order potentials, known as the bond-order potential/split-charge equilibration (BOP/SQE) method [P. T. Mikulski, M. T. Knippenberg, and J. A. Harrison, J. Chem. Phys. 131, 241105 (2009)], is integrated into a new bond-order potential for interactions between oxygen, carbon, and hydrogen. This reactive potential utilizes the formalism of the adaptive intermolecular reactive empirical bond-order potential [S. J. Stuart, A. B. Tutein, and J. A. Harrison, J. Chem. Phys. 112, 6472 (2000)] with additional terms for oxygen and charge interactions. This implementation of the reactive potential is able to model chemical reactions where partial charges change in gas- and condensed-phase systems containing oxygen, carbon, and hydrogen. The BOP/SQE method prevents the unrestricted growth of charges, often observed in charge equilibration methods, without adding significant computational time, because it makes use of a quantity which is calculated as part of the underlying covalent portion of the potential, namely, the bond order. The implementation of this method with the qAIREBO potential is designed to provide a tool that can be used to model dynamics in a wide range of systems without significant computational cost. To demonstrate the usefulness and flexibility of this potential, heats of formation for isolated molecules, radial distribution functions of liquids, and energies of oxygenated diamond surfaces are calculated.

Merging bond-order potentials with charge equilibration.

A method is presented for extending any bond-order potential (BOP) to include charge transfer between atoms through a modification of the split-charge equilibration (SQE) formalism. Variable limits on the maximum allowed charge transfer between atomic pairs are defined by mapping bond order to an amount of shared charge in each bond. Charge transfer is interpreted as an asymmetry in how the shared charge is distributed between the atoms of the bond. Charge equilibration (QE) assesses the asymmetry of the shared charge, while the BOP converts this asymmetry to the actual amount of charge transferred. When applied to large molecules, this BOP/SQE method does not exhibit the unrealistic growth of charges that is often associated with QE models.

Molecular dynamics simulations on hydrogen adsorption in finite single walled carbon nanotube bundles.

Molecular dynamics simulations of the adsorption of hydrogen molecules in finite single-walled carbon nanotube bundles are presented using a curvature dependent force field. The heat of formation and the effective adsorption capacity are expressed as a function of H(2) distance from adsorbent. The heat of adsorption decreases rapidly with the distance and increasing H(2) loading results in weakening adsorption strength. The effects of nanotube packing and bundle thickness on hydrogen adsorption strength were investigated and the results show that the heat of adsorption can be improved slightly if hydrogen molecules are placed in thicker and inhomogeneously packed nanotube bundles. Only very small diameter nanotube bundles were found to hold promise for significant hydrogen storage for onboard applications.

The polymine spermine regulates osteogenic differentiation in adipose stem cells.

For bone tissue engineering, it is important that mesenchymal stem cells (MSCs) differentiate into osteoblasts. To develop a method for differentiation of adipose tissue-derived mesenchymal stem cells (AT-MSCs) along the osteogenic lineage, we studied the effect of polyamines, which are organic cations implicated in bone growth and development, on differentiation of AT-MSCs. Treatment of goat-derived AT-MSCs with 1,25-dihydroxyvitamin-D3 (1,25(OH)(2)D(3)), which stimulates osteogenic differentiation, for 7 days induced gene expression of the polyamine-modulated transcription factor-1 (PMF-1) and spermidine/spermine N (1)-acetyltransferase (SSAT), which are both involved in polyamine metabolism, suggesting that polyamines are involved in osteogenic differentiation of AT-MSCs. Furthermore, treatment of AT-MSCs with the polyamine spermine-regulated gene expression of runx-2, a transcription factor involved in early stages of osteogenic differentiation, and that of osteopontin, a bone matrix protein expressed in later stages of osteogenic differentiation. Runx-2 gene expression was increased 4 and 14 days after a short 30 min. treatment with spermine, while osteopontin gene expression was only increased 4 days after spermine treatment. Finally, alkaline phosphatase activity, which is intimately involved in the formation of extracellular matrix of bone, was increased 4 weeks after the 30 min.-spermine treatment of AT-MSCs. In conclusion, this study shows for the first time that the polyamine spermine regulates differentiation of AT-MSCs along the osteogenic lineage, which can be used as a new method for differentiation of AT-MSCs along the osteogenic lineage. Therefore, polyamines may constitute a promising tool for bone tissue engineering approaches using AT-MSCs, such as a one-step surgical procedure for spinal interbody fusion.

Friction between solids.

The theoretical examination of the friction between solids is discussed with a focus on self-assembled monolayers, carbon-containing materials and antiwear additives. Important findings are illustrated by describing examples where simulations have complemented experimental work by providing a deeper understanding of the molecular origins of friction. Most of the work discussed herein makes use of classical molecular dynamics (MD) simulations. Of course, classical MD is not the only theoretical tool available to study friction. In view of that, a brief review of the early models of friction is also given. It should be noted that some topics related to the friction between solids, i.e. theory of electronic friction, are not discussed here but will be discussed in a subsequent review.

Prostaglandins differentially affect osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells.

Adipose tissue-derived mesenchymal stem cells (AT-MSCs) are currently used for bone tissue engineering. AT-MSCs undergoing osteogenic differentiation respond to mechanical loading with increased cyclooxygenase-2 gene expression, a key enzyme in prostaglandin (PG) synthesis. PGs are potent multifunctional regulators in bone, exhibiting stimulatory and inhibitory effects on bone formation and resorption. PGE(2), but not PGI(2) or PGF(2), recruits osteoprogenitors from the bone marrow space and influences their differentiation. We hypothesize that PGE(2), PGI(2), and PGF(2) may differentially regulate osteogenic differentiation of human AT-MSCs. PGE(2), PGI(2), and PGF(2) (0.01-10 microM) affected osteogenic differentiation, but not proliferation of AT-MSCs after 4-14 days. Only PGF(2) (0.01-10 microM) increased alkaline phosphatase (ALP) activity at day 4. PGE(2) (10 microM), PGI(2) (0.01-10 microM), and PGF(2) (10 microM) decreased ALP activity, whereas PGF(2) (0.1 microM) increased ALP activity at day 14. PGF(2) (0.01-0.1 microM) and PGI(2) (0.01 microM) upregulated osteopontin gene expression, and PGF(2) (0.01 microM) upregulated alpha1(I)procollagen gene expression at day 4. PGE(2) and PGF(2) (10 microM) at day 4 and PGF(2) (1 microM) at day 14 downregulated runt-related transcription factor-2 gene expression. We conclude that PGE(2), PGI(2), and PGF(2) differentially affect osteogenic differentiation of AT-MSCs, with PGF(2) being the most potent. Thus, locally produced PGF(2) might be most beneficial in promoting osteogenic differentiation of AT-MSCs, resulting in enhanced bone formation for bone tissue engineering.

Physical adsorption strength in open systems.

For a physical adsorption system, the distances of adsorbates from the surface of a substrate can vary significantly, depending on particle loading and interatomic interactions. Although the total adsorption energy is quantified easily, the normalized, per-particle adsorption energies are more ambiguous if some of these particles are far away from the surface and are interacting only weakly with the substrate. A simple analytical procedure is proposed to characterize the distance dependence of the physisorption strength and effective adsorption capacity. As an example, the method is utilized to describe H2 physisorption in a finite bundle of single-walled carbon nanotubes.

Adipose tissue-derived mesenchymal stem cell yield and growth characteristics are affected by the tissue-harvesting procedure.

BACKGROUND: Adipose tissue contains a stromal vascular fraction that can be easily isolated and provides a rich source of adipose tissue-derived mesenchymal stem cells (ASC). These ASC are a potential source of cells for tissue engineering. We studied whether the yield and growth characteristics of ASC were affected by the type of surgical procedure used for adipose tissue harvesting, i.e. resection, tumescent liposuction and ultrasound-assisted liposuction. METHODS: Frequencies of ASC in the stromal vascular fraction were assessed in limiting dilution assays. The phenotypical marker profile of ASC was determined, using flow cytometry, and growth kinetics were investigated in culture. ASC were cultured under chondrogenic and osteogenic conditions to confirm their differentiation potential. RESULTS: The number of viable cells in the stromal vascular fraction was affected by neither the type of surgical procedure nor the anatomical site of the body from where the adipose tissue was harvested. After all three surgical procedures, cultured ASC did express a CD34+ CD31- CD105+ CD166+ CD45- CD90+ ASC phenotype. However, ultrasound-assisted liposuction resulted in a lower frequency of proliferating ASC, as well as a longer population doubling time of ASC, compared with resection. ASC demonstrated chondrogenic and osteogenic differentiation potential. DISCUSSION: We conclude that yield and growth characteristics of ASC are affected by the type of surgical procedure used for adipose tissue harvesting. Resection and tumescent liposuction seem to be preferable above ultrasound-assisted liposuction for tissue-engineering purposes.

Osteogenesis versus chondrogenesis by BMP-2 and BMP-7 in adipose stem cells.

Bone morphogenetic proteins (BMPs) initiate, promote, and maintain chondrogenesis and osteogenesis. We hypothesize that BMP-2 induces an osteogenic, and BMP-7 a chondrogenic phenotype in adipose tissue-derived mesenchymal stem cells (AT-MSCs). We compared the effects of a short 15min BMP-2 or BMP-7 (10ng/ml) treatment on osteogenic and chondrogenic differentiation of AT-MSCs. Gene expression was studied 4 and 14 days after BMP-treatment. At day 4 BMP-2, but not BMP-7, stimulated runx-2 and osteopontin gene expression, and at day 14 BMP-7 down-regulated expression of these genes. At day 4 BMP-2 and BMP-7 stimulated biglycan gene expression, which was down-regulated by BMP-7 at day 14. BMP-7 stimulated aggrecan gene expression at day 14. Our data indicate that BMP-2 treatment for 15min induces osteogenic differentiation, whereas BMP-7 stimulates a chondrogenic phenotype of AT-MSCs. Therefore, AT-MSCs triggered for only 15min with BMP-2 or BMP-7 provide a feasible tool for bone and cartilage tissue engineering.