Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures

We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to $25$ mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two dimensional system of electron spins. We approach the sample with a $3.43$ $\mu$m-diameter magnetic particle attached to an ultrasoft cantilever, and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time $T_1=0.39\pm0.08$ ms and spin density $\sigma=0.14\pm0.01$ spins per nm$^2$. Our analysis shows that at temperatures $\leq500$ mK magnetic dissipation is an important source of non-contact friction.Comment: 5 pages, 3 figure

ICT: New Opportunities for Higher Education Institutions to Train Employees?

Higher education institutions are confronted with a declining growth in the number of students in initial education. At the same time, the market for training of employees has increased significantly. Between 1993 and 1999, the total training volume on this market has doubled. However, at least in the Netherlands, higher education institutes altogether have only a small and stable share in the training of employees of about 2%. The central question of this paper is to what extent the growing possibilities of using ICT as a training tool can help higher education institutes to enhance their position in the market of training of employees. The empirical evidence presented does not support the expectation that ICTis already the vehicle leading to drastic changes. A large scale survey among companies at the end of the nineties in the Netherlands showed that the use of ICT as a training tool was at that time limited to only 12% of all training incidences. Moreover, the companies did not expect a strong growth. This has to do with a large variety of bottlenecks companies perceive. Succesful implementation means dealing with considerations from many angles: pedagogical, technical, organisational and last but least cost-efficiency. Even if the use of ICT as a training tool would rise considerable, this would not automatically mean an improvement of the position of higher education institutes. The survey results do not give indications that higher education institutions have a relative large share in ICT-based training.In: A.J. Kallenberg and M.J.J.M. van de Ven (Eds), 2002, The New Educational Benefits of ICT in Higher Education: Proceedings. Rotterdam: Erasmus Plus BV, OECR ISBN 90-9016127-

Loneliness, Social Isolation, and Objectively Measured Physical Activity in Rural-Living Older Adults

This cross-sectional, observational study examined whether objectively measured physical activity (PA) and specific activities are associated with loneliness and social isolation (SI) in rural-living older adults. A total of 112 participants (Mage = 72.8 [SD = 6.6], 51.8% female) from 23 villages in Wiltshire, United Kingdom, completed questionnaires, 7-day accelerometry, and activity diaries. Regression analysis was used to test associations between objectively measured light PA, moderate to vigorous PA, and total PA; loneliness; and SI from family, neighbors, or friends and to explore these associations using specific activities. Daily mean light, moderate to vigorous, and total PA were not associated with loneliness or SI. Volunteering, accompanying others, and sports/exercise were associated with lower SI from neighbors (odds ratio = 0.23, 95% CI [0.06, 0.91]), family (odds ratio = 0.39, 95% CI [0.22, 0.68]), and friends (odds ratio = 0.56, 95% CI [0.33, 0.97]), respectively. There were no associations between loneliness, SI, and objectively measured PA. The contribution of PA to loneliness and SI needs to be further investigated with larger and diverse samples of rural-living older adults

Finite temperature molecular dynamics study of unstable stacking fault free energies in silicon

We calculate the free energies of unstable stacking fault (USF) configurations on the glide and shuffle slip planes in silicon as a function of temperature, using the recently developed Environment Dependent Interatomic Potential (EDIP). We employ the molecular dynamics (MD) adiabatic switching method with appropriate periodic boundary conditions and restrictions to atomic motion that guarantee stability and include volume relaxation of the USF configurations perpendicular to the slip plane. Our MD results using the EDIP model agree fairly well with earlier first-principles estimates for the transition from shuffle to glide plane dominance as a function of temperature. We use these results to make contact to brittle-ductile transition models.Comment: 6 pages revtex, 4 figs, 16 refs, to appear in Phys. Rev.

Early onset ataxia with comorbid myoclonus and epilepsy:A disease spectrum with shared molecular pathways and cortico-thalamo-cerebellar network involvement

OBJECTIVES: Early onset ataxia (EOA) concerns a heterogeneous disease group, often presenting with other comorbid phenotypes such as myoclonus and epilepsy. Due to genetic and phenotypic heterogeneity, it can be difficult to identify the underlying gene defect from the clinical symptoms. The pathological mechanisms underlying comorbid EOA phenotypes remain largely unknown. The aim of this study is to investigate the key pathological mechanisms in EOA with myoclonus and/or epilepsy.METHODS: For 154 EOA-genes we investigated (1) the associated phenotype (2) reported anatomical neuroimaging abnormalities, and (3) functionally enriched biological pathways through in silico analysis. We assessed the validity of our in silico results by outcome comparison to a clinical EOA-cohort (80 patients, 31 genes).RESULTS: EOA associated gene mutations cause a spectrum of disorders, including myoclonic and epileptic phenotypes. Cerebellar imaging abnormalities were observed in 73-86% (cohort and in silico respectively) of EOA-genes independently of phenotypic comorbidity. EOA phenotypes with comorbid myoclonus and myoclonus/epilepsy were specifically associated with abnormalities in the cerebello-thalamo-cortical network. EOA, myoclonus and epilepsy genes shared enriched pathways involved in neurotransmission and neurodevelopment both in the in silico and clinical genes. EOA gene subgroups with myoclonus and epilepsy showed specific enrichment for lysosomal and lipid processes.CONCLUSIONS: The investigated EOA phenotypes revealed predominantly cerebellar abnormalities, with thalamo-cortical abnormalities in the mixed phenotypes, suggesting anatomical network involvement in EOA pathogenesis. The studied phenotypes exhibit a shared biomolecular pathogenesis, with some specific phenotype-dependent pathways. Mutations in EOA, epilepsy and myoclonus associated genes can all cause heterogeneous ataxia phenotypes, which supports exome sequencing with a movement disorder panel over conventional single gene panel testing in the clinical setting