University of Minnesota

About: University of Minnesota is a education organization based out in Minneapolis, Minnesota, United States. It is known for research contribution in the topics: Population & Transplantation. The organization has 117432 authors who have published 257986 publications receiving 11944239 citations. The organization is also known as: University of Minnesota, Twin Cities & University of Minnesota-Twin Cities.

Current status of transition-state theory

Abstract: We present an overview of the current status of transition-state theory and its generalizations. We emphasize (i) recent improvements in available methodology for calculations on complex systems, including the interface with electronic structure theory, (ii) progress in the theory and application of transition-state theory to condensed-phase reactions, and (iii) insight into the relation of transition-state theory to accurate quantum dynamics and tests of its accuracy via comparisons with both experimental and other theoretical dynamical approximations.

Analysis of recommendation algorithms for e-commerce

Abstract: Re ommender systems apply statisti al and knowledge disovery te hniques to the problem of making produ t re ommendations during a live ustomer intera tion and they are a hieving widespread su ess in E-Commer e nowadays. In this paper, we investigate several te hniques for analyzing large-s ale pur hase and preferen e data for the purpose of produ ing useful re ommendations to ustomers. In parti ular, we apply a olle tion of algorithms su h as traditional data mining, nearest-neighbor ollaborative ltering, and dimensionality redu tion on two di erent data sets. The rst data set was derived from the web-pur hasing transa tion of a large Eommer e ompany whereas the se ond data set was olle ted from MovieLens movie re ommendation site. For the experimental purpose, we divide the re ommendation generation pro ess into three sub pro esses{ representation of input data, neighborhood formation, and re ommendation generation. We devise di erent te hniques for di erent sub pro esses and apply their ombinations on our data sets to ompare for re ommendation quality and performan e.

Transplantability and therapeutic effects of bone marrow-derived mesenchymal cells in children with osteogenesis imperfecta

Abstract: In principle, transplantation of mesenchymal progenitor cells would attenuate or possibly correct genetic disorders of bone, cartilage and muscle, but clinical support for this concept is lacking. Here we describe the initial results of allogeneic bone marrow transplantation in three children with osteogenesis imperfecta, a genetic disorder in which osteoblasts produce defective type I collagen, leading to osteopenia, multiple fractures, severe bony deformities and considerably shortened stature. Three months after osteoblast engraftment (1.5-2.0% donor cells), representative specimens of trabecular bone showed histologic changes indicative of new dense bone formation. All patients had increases in total body bone mineral content ranging from 21 to 29 grams (median, 28), compared with predicted values of 0 to 4 grams (median, 0) for healthy children with similar changes in weight. These improvements were associated with increases in growth velocity and reduced frequencies of bone fracture. Thus, allogeneic bone marrow transplantation can lead to engraftment of functional mesenchymal progenitor cells, indicating the feasibility of this strategy in the treatment of osteogenesis imperfecta and perhaps other mesenchymal stem cell disorders as well.

The ecological consequences of changes in biodiversity: a search for general principles101

Abstract: This paper uses theory and experiments to explore the effects of diversity on stability, productivity, and susceptibility to invasion. A model of resource competition predicts that increases in diversity cause com- munity stability to increase, but population stability to decrease. These opposite effects are, to a great extent, explained by how temporal variances in species abundances scale with mean abundance, and by the differential impact of this scaling on population vs. community stability. Community stability also depends on a negative covariance effect (competitive compensation) and on overyielding (ecosystem productivity increasing with diversity). A long-term study in Minnesota grasslands supports these predictions. Models of competition predict, and field experiments confirm, that greater plant diversity leads to greater primary productivity. This diversity-productivity relationship results both from the greater chance that a more productive species would be present at higher diversity (the sampling effect) and from the better ''coverage'' of habitat heterogeneity caused by the broader range of species traits in a more diverse community (the niche differentiation effect). Both effects cause more complete utilization of limiting resources at higher diversity, which increases resource retention, further increasing productivity. Finally, lower levels of available limiting resources at higher diversity are predicted to decrease the susceptibility of an ecosystem to invasion, supporting the diversity-invasibility hypothesis. This mechanism provides rules for community assembly and invasion resistance. In total, biodiversity should be added to species composition, disturbance, nutrient supply, and climate as a major controller of population and ecosystem dynamics and structure. By their increasingly great directional impacts on all of these controllers, humans are likely to cause major long-term changes in the functioning of ecosystems worldwide. A better understanding of these ecosystem changes is needed if ecologists are to provide society with the knowledge essential for wise management of the earth and its biological resources.