University of Groningen

About: University of Groningen is a education organization based out in Groningen, Groningen, Netherlands. It is known for research contribution in the topics: Population & Context (language use). The organization has 36346 authors who have published 69116 publications receiving 2940370 citations. The organization is also known as: Rijksuniversiteit Groningen & RUG.

Antimicrobial effects of positively charged surfaces on adhering Gram-positive and Gram-negative bacteria

Abstract: The infection of biomaterials is determined by an interplay of adhesion and surface growth of the infecting organisms. In this study, the antimicrobial effects on adhering bacteria of a positively charged poly(methacrylate) surface (xi potential +12 mV) were compared with those of negatively charged poly(methyl methacrylate) (-12 mV) and a highly negatively charged poly(methacrylate) (-18 mV) surface. Initial adhesion of Staphylococcus aureus ATCC 12600, Staphylococcus epidermidis HBH(2) 102, Escherichia coli O2K2 and Pseudomonas aeruginosa AK1 to these surfaces was measured in a parallel plate flow chamber in phosphate-buffered saline. Adhering bacteria were allowed to multiply by perfusing the flow chamber with growth medium. All bacteria adhered most rapidly to the positively charged surface, but there was no subsequent surface growth of the Gram-negative strains. On the negatively charged surfaces, despite a slower initial adhesion, surface growth of the adhering bacteria was exponential for both Gram-positive and Gram-negative strains. These results suggest that positively charged biomaterial surfaces exert an antimicrobial effect on adhering Gram-negative bacteria, but not on Gram-positive ones.

X-ray photoelectron and Auger spectroscopy study of some vanadium oxides

Abstract: A detailed investigation of ${\mathrm{V}}_{2}$${\mathrm{O}}_{5}$, V${\mathrm{O}}_{2}$, ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$, and V metal is presented. The vanadium core lines in the x-ray photoelectron spectra are anomalously wide for ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ and V${\mathrm{O}}_{2}$. It is shown that this is a consequence of the narrow $3d$ band in these materials and the relatively strong core-hole $3d$ Coulomb interaction. The influence of electron correlation effects in the $3d$ band on the core linewidths is discussed. The valence bands are compared to band-structure calculations and the difference in the band structure above and below the semiconductor-metal transition is discussed. The Auger results are discussed in terms of the $3d$ partial density of states. It is found that there is a large amount of $d$ character in the $\mathrm{O}\ensuremath{-}2p$ region of the valence band. Also the average "on-site" Coulomb interaction of $3d$ electrons is obtained from the Auger spectra and is discussed in terms of electron correlation effects.

Loneliness Across the Life Span

Abstract: Most people have experienced loneliness and have been able to overcome it to reconnect with other people. In the current review, we provide a life-span perspective on one component of the evolutionary theory of loneliness—a component we refer to as the reaffiliation motive (RAM). The RAM represents the motivation to reconnect with others that is triggered by perceived social isolation. Loneliness is often a transient experience because the RAM leads to reconnection, but sometimes this motivation can fail, leading to prolonged loneliness. We review evidence of how aspects of the RAM change across development and how these aspects can fail for different reasons across the life span. We conclude with a discussion of age-appropriate interventions that may help to alleviate prolonged loneliness.

Phosphoramidites: Privileged Ligands in Asymmetric Catalysis

Abstract: Asymmetric catalysis with transition-metal complexes is the basis for a vast array of stereoselective transformations and has changed the face of modern synthetic chemistry. Key to this success has been the design of chiral ligands to control the regio-, diastereo-, and enantioselectivity. Phosphoramidites have emerged as a highly versatile and readily accessible class of chiral ligands. Their modular structure enables the formation of ligand libraries and easy fine-tuning for a specific catalytic reaction. Phosphoramidites frequently show exceptional levels of stereocontrol, and their monodentate nature is essential in combinatorial catalysis, where a ligand-mixture approach is used. In this Review, recent developments in asymmetric catalysis with phosphoramidites used as ligands are discussed, with a focus on the formation of carbon-carbon and carbon-heteroatom bonds.

Seed size, shape and vertical distribution in the soil: Indicators of seed longevity

Abstract: 1. We investigated the vertical distribution of seeds in the soil, using data from nine studies in five European countries. We discovered significant correlations between seed shape and distributio ...