Density fluctuations as door-opener for diffusion on crowded surfaces.

How particles can move on a catalyst surface that, under the conditions of an industrial process, is highly covered by adsorbates and where most adsorption sites are occupied has remained an open question. We have studied the diffusion of O atoms on a fully CO-covered Ru(0001) surface by means of high-speed/variable-temperature scanning tunneling microscopy combined with density functional theory calculations. Atomically resolved trajectories show a surprisingly fast diffusion of the O atoms, almost as fast as on the clean surface. This finding can be explained by a "door-opening" mechanism in which local density fluctuations in the CO layer intermittently create diffusion pathways on which the O atoms can move with low activation energy.

Detection of Bacteria Colonizing Titanium Spinal Implants in Children.

BACKGROUND: Bacterial colonization of spinal implants may cause severe complications in patients with early-onset scoliosis. Correct diagnosis and detection of microbiologic formation is crucial to prevent delayed infections caused by bacterial colonization. The purposes of this study were to estimate the rate and risk factors of colonization of vertical expandable prosthetic titanium rib (VEPTR) implants in children and to compare the different methods for detecting microbiologic formation on the spinal implants. METHODS: We evaluated prospectively a group of 42 children with spinal deformities with an overall of 95 lengthening surgeries and applied different methods to detect potential bacterial colonization of VEPTR implants: swab of the implant, swab with culture of tissue, analysis of the removed lock, polymerase chain reaction (PCR), and confocal microscopy. Potential risk factors were evaluated. RESULTS: Of 42 patients, 17 (40%) were rated positive for bacterial colonization with Propionibacterium acnes and coagulase-negative staphylococci being the most commonly found bacteria. Risk factors for colonization were increasing age, body height, and weight. The swab with culture of removed tissue yielded most positive results, whereas direct microscopy and PCR were the least sensitive detection methods. Furthermore, commonly used infectious blood parameters were inconclusive. CONCLUSIONS: Although the impact of bacterial colonized implants on the health of the patients is not fully elucidated, clinicians aim for prevention of microbiologic formation on implanted devices. Therefore, reliable, inexpensive, and easy to apply diagnostic tools are indispensable to detect colonization. Based on our data, the swab together with tissue culture has the potential to become the method of choice for future diagnosis.

Stable Redox-Cycling Nitroxide Tempol Inhibits NET Formation.

To prevent the spread of pathogens neutrophils as the first line of defense are able to release Neutrophil Extracellular Traps (NETs), a recently discovered form of immune response. Reactive oxygen species (ROS) have been shown to be essential for many different induction routes of NET formation. Therefore, pharmacological inhibition of ROS generation has implications for research and medicine related to NETs. The application of diphenylene iodonium (DPI), an inhibitor of NADPH oxidase activity, is limited due to its toxicity to host cells as well as microbes. Therefore, we investigated the effect of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol) a membrane-permeable radical scavenger on NET formation triggered by phorbol esters and Candida albicans. We quantified the amount of NETs with two complementary methods, using a microscopic analysis and an online fluorescence-based assay. In line with removal of ROS, Tempol reduced the amount of NET formation by neutrophils challenged with those stimuli significantly. Since Tempol efficiently blocks NET formation in vitro, it might be promising to test the effect of Tempol in experimental models of disorders in which NETs probably have hazardous effects.