Size-dependent oxygen-related electronic states in silicon nanocrystals

Silicon nanocrystals embedded in SiO2 were isolated with a selective etching procedure, and the isolated nanocrystals' excitonic emission energy was studied during controlled oxidation. Nanocrystals having initial diameters, d(0), of similar to 2.9-3.4 nm showed a photoluminescence (PL) blueshift upon oxidatively induced size reduction, as expected from models of quantum confinement. Oxidation of smaller Si nanocrystals (d(0)similar to 2.5-2.8 nm) also initially resulted in a PL blueshift, but a redshift in the PL was then observed after growth of similar to 0.3 monolayers of native oxide. This decrease in excitonic emission energy during oxidation is consistent with the theoretically predicted formation of an oxygen-related excitonic recombination state

Erbium in crystal silicon: Optical activation, excitation, and concentration limits

7 pags.; 7 figs.The optical activation, excitation, and concentration limits of erbium in crystal Si are studied. Preamorphized surface layers of Czochralski-grown (Cz) Si(100), containing 1.7×1018 O/cm3, were implanted with 250 keV Er at fluences in the range 8×1011-8×10 14 cm-2. After thermal solid-phase epitaxy of the Er-doped amorphous layers at 600°C, Er is trapped in the crystal at concentrations ranging from 3×1016 to 7×1019 Er/cm 3, as measured by secondary-ion-mass spectrometry. Photoluminescence spectra taken at 77 K show the characteristic Er3+ intra-4f luminescence at 1.54 ¿m. Photoluminescence excitation spectroscopy shows that Er is excited through a photocarrier-mediated process. Rapid thermal annealing at 1000°C for 15 s increases the luminescence intensity, mainly due to an increase in minority-carrier lifetime, which enhances the excitation efficiency. Luminescent Er forms clusters with oxygen: the maximum Er concentration that can be optically activated is determined by the O content, and is (3±1)×1017 Er/cm3 in Cz-Si. The internal quantum efficiency for electrical excitation of Er in Cz-Si is larger than 3×10-6. © 1995 American Institute of Physics.This work is part of the research program of the Foundation for Fundamental Research on Matter (FOM) and was made possible by financial support from the Dutch Organization for the Advancement of Pure Research @IWO), the Netherlands Technology Foundation (STW), and the IC Technology Program (IOP Electra-Optics) of the Ministry of Economic Affairs. R.S. acknowIedges financial support from CSIC, Spain.Peer Reviewe

Verdienmodellen voor natuurinclusieve landbouw:Wat ondernemers al doen, en wat de overheid kan doen om opschaling te bevorderen

De Rijksnatuurvisie 2014 breekt een lans voor natuurinclusieve landbouw waarbij veel nadruk ligt op de rol van markt en maatschappij. Zulke landbouw behelst wat de nota noemt ‘natuurcombinaties’ waarbij natuur en economische activiteiten met elkaar vervlochten zijn. Een natuurinclusieve landbouw heeft een wezenlijk andere oriëntatie dan gangbare landbouw. In dit essay gaan we in op de voorwaarden waaronder natuurinclusieve verdienmodellen op middellange termijn op grote schaal kunnen worden gerealiseerd. Dit wordt uiteengezet op basis van de ervaringen van koplopers, die al langer aan natuurinclusieve landbouw doen

The effect of a multi-component school-based social network intervention on children's body mass index:a four-arm intervention study

Objective: Schools are considered an important setting for stimulating healthy weight. The current study is unique in examining effects of a multi-component school-based social network intervention on children’s body mass index z-scores (zBMI).Methods: Four schools were randomly allocated to one of four conditions: a social network intervention using influence agents focusing on water consumption, physical activity, a combination of the two, or a passive control condition. Participants included a total of 201 6- to-11-year-old children (53.7% girls; Mage = 8.51, SDage = 0.93). At baseline, 149 (76.0%) participants had a healthy weight, 29 (14.8%) had overweight and 18 (9.2%) had obesity.Results: Linear mixed effect models indicated that a multi-component school-based social network intervention targeting both water consumption and physical activity was most effective in decreasing children’s zBMI.Conclusion: This study suggests that schools can contribute to the intervention of childhood obesity—even without involving the parents—by targeting both children’s water consumption and physical activity through influential peers, but more research is needed to identify mechanisms of change

Paired hormone response elements predict caveolin-1 as a glucocorticoid target gene

Abstract Glucocorticoids act in part via glucocortocoid receptor binding to hormone response elements (HREs), but their direct target genes in vivo are still largely unknown. We developed the criterion that genomic occurrence of paired HREs at an inter-HRE distance less than 200 bp predicts hormone responsiveness, based on synergy of multiple HREs, and HRE information from known target genes. This criterion predicts a substantial number of novel responsive genes, when applied to genomic regions 10 kb upstream of genes. Multiple-tissue in situ hybridization showed that mRNA expression of 6 out of 10 selected genes was induced in a tissue-specific manner in mice treated with a single dose of corticosterone, with the spleen being the most responsive organ. Caveolin-1 was strongly responsive in several organs, and the HRE pair in its upstream region showed increased occupancy by glucocorticoid receptor in response to corticosterone. Our approach allowed for discovery of novel tissue specific glucocorticoid target genes, which may exemplify responses underlying the permissive actions of glucocorticoids

Mindfulness based interventions in multiple sclerosis: a systematic review

<b>Background</b> Multiple sclerosis (MS) is a stressful condition; depression, anxiety, pain and fatigue are all common problems. Mindfulness based interventions (MBIs) mitigate stress and prevent relapse in depression and are increasingly being used in healthcare. However, there are currently no systematic reviews of MBIs in people with MS. This review aims to evaluate the effectiveness of MBIs in people with MS.<p></p> <b>Methods</b> Systematic searches were carried out in seven major databases, using both subject headings and key words. Papers were screened, data extracted, quality appraised, and analysed by two reviewers independently, using predefined criteria. Study quality was assessed using the Cochrane Collaboration risk of bias tool. Perceived stress was the primary outcome. Secondary outcomes include mental health, physical health, quality of life, and health service utilisation. Statistical meta-analysis was not possible. Disagreements were adjudicated by a third party reviewer.<p></p> <b>Results</b> Three studies (n = 183 participants) were included in the final analysis. The studies were undertaken in Wales (n = 16, randomised controlled trial - (RCT)), Switzerland (n = 150, RCT), and the United States (n = 17, controlled trial). 146 (80%) participants were female; mean age (SD) was 48.6 (9.4) years. Relapsing remitting MS was the main diagnostic category (n = 123, 67%); 43 (26%) had secondary progressive disease; and the remainder were unspecified. MBIs lasted 6–8 weeks; attrition rates were variable (5-43%); all employed pre- post- measures; two had longer follow up; one at 3, and one at 6 months. Socio-economic status of participants was not made explicit; health service utilisation and costs were not reported. No study reported on perceived stress. All studies reported quality of life (QOL), mental health (anxiety and depression), physical (fatigue, standing balance, pain), and psychosocial measures. Statistically significant beneficial effects relating to QOL, mental health, and selected physical health measures were sustained at 3- and 6- month follow up.<p></p> <b>Conclusion</b> From the limited data available, MBIs may benefit some MS patients in terms of QOL, mental health, and some physical health measures. Further studies are needed to clarify how MBIs might best serve the MS population.<p></p&gt

The Impact of Gymnastics on Children’s Physical Self-Concept and Movement Skill Development in Primary Schools

This study evaluated the effectiveness of an 8-week gymnastics curriculum on children’s movement competence and their physical self-concept. There were 113 children (46% girls, 49% intervention) with a mean age of 9.4 years (SD = 1.8) that participated. Intervention children underwent 8 weeks of gymnastics and the comparison group continued with their standard curriculum. Age was a significant co-variate, a separate analysis was conducted on the lower (grades 2 and 4) and upper (grade 6) groups. The lower age group showed significant improvement in favor of the gymnastic group in fundamental movement skills. The upper age group showed a significant improvement for the control group in general body coordination and fundamental movement skills. For all grades, the physical self-concept showed a significant main effect in favor of the gymnastics group. The gymnastics intervention was found to be of particular benefit for developing children’s movement competence and physical self-concept in younger children

DNA-based Self-Assembly of Chiral Plasmonic Nanostructures with Tailored Optical Response

Surface plasmon resonances generated in metallic nanostructures can be utilized to tailor electromagnetic fields. The precise spatial arrangement of such structures can result in surprising optical properties that are not found in any naturally occurring material. Here, the designed activity emerges from collective effects of singular components equipped with limited individual functionality. Top-down fabrication of plasmonic materials with a predesigned optical response in the visible range by conventional lithographic methods has remained challenging due to their limited resolution, the complexity of scaling, and the difficulty to extend these techniques to three-dimensional architectures. Molecular self-assembly provides an alternative route to create such materials which is not bound by the above limitations. We demonstrate how the DNA origami method can be used to produce plasmonic materials with a tailored optical response at visible wavelengths. Harnessing the assembly power of 3D DNA origami, we arranged metal nanoparticles with a spatial accuracy of 2 nm into nanoscale helices. The helical structures assemble in solution in a massively parallel fashion and with near quantitative yields. As a designed optical response, we generated giant circular dichroism and optical rotary dispersion in the visible range that originates from the collective plasmon-plasmon interactions within the nanohelices. We also show that the optical response can be tuned through the visible spectrum by changing the composition of the metal nanoparticles. The observed effects are independent of the direction of the incident light and can be switched by design between left- and right-handed orientation. Our work demonstrates the production of complex bulk materials from precisely designed nanoscopic assemblies and highlights the potential of DNA self-assembly for the fabrication of plasmonic nanostructures.Comment: 5 pages, 4 figure