Frequency comb spectroscopy on trapped calcium ions

Ubachs, W.M.G. [Promotor]Eikema, K.S.E. [Promotor]Berg, S. van den [Copromotor

Characterising Dutch forests, wetlands and cultivated lands on the basis of phytolith assemblages

Palaeoecological reconstructions in the Netherlands are commonly based on pollen and macrofossil analysis, but can be limited if the preservation of organic material is poor. Phytoliths, biogenic silica, do not have this limitation and preserve in settings where other macro- and microfossils do not. Little is known about how phytolith assemblages preserved in soils and sediments reflect the parent vegetation in north-western European systems, so it is currently difficult to contextualise past environments. Here, we characterise phytolith assemblages for soil samples recovered from three major vegetation types in the Netherlands to provide reference data for future reconstructions of past vegetation change. We collected 42 soil surface samples from forests, wetlands and agricultural fields across the Netherlands and characterised the phytolith assemblages they contained. We identified the different phytolith morphotypes and quantified the percentages and concentrations (#phytoliths/cm3 soil) in each sample. We used non-metric multidimensional scaling to assess the variation in phytolith assemblage composition within, and between, the three vegetation types. The phytolith assemblages analysed from the forests, wetlands and agricultural fields were clearly distinguishable from each other. Agricultural fields were dominated by four phytolith morphotypes of grass silica short cells (GSSCs): rondel (tabular), cross type 1 (>15 µm), rondel (elongated) and disturbance or crop phytoliths. Forests settings had significantly higher amounts of different arboreal phytoliths (large and small spheroid rugose) compared with other vegetation types. Wetlands could be identified by significantly higher amounts of Cyperaceae phytoliths (papillate) and other GSSCs (saddle and bilobates with thick castula). Phytolith assemblages could distinguish different subtypes of vegetation within forest and wetland areas, while differences between agricultural systems could not be identified. Our study demonstrates that phytoliths preserved in soils or sediments can be used to separate major vegetation types across the Netherlands. Thus, these results support the hypothesis that phytoliths can be used to infer past environmental conditions in palaeoecological reconstructions. We suggest that future work should: (1) focus on characterising which phytolith types are produced by the commonest tree, wetland, shrub and herb species in the Netherlands and (2) characterise phytolith assemblages across a wider array of vegetation types in north-western European systems to increase the capability for quantitative reconstructions using phytolith assemblages

Improving caring quality for people with dementia in nursing homes using IPOS-Dem: A stepped-wedge cluster randomized controlled trial protocol.

We aim to evaluate the effectiveness of the Integrated Palliative Care Outcome Scale for people with dementia-based case studies to improve the caring quality for people with dementia in nursing homes by frontline staff and family members. Swiss nursing homes mostly care for people with dementia. This population is at high risk of receiving little to no palliation for their complex needs. The majority of Swiss frontline healthcare staff do not systematically report on the needs of their residents. Additionally, family members do not routinely participate in assessment processes. We will conduct a stepped-wedge cluster randomized trial of repeated assessment using the Integrated Palliative Care Outcome Scale for people with dementia (IPOS-Dem) and subsequent case studies. Clusters will consist of Swiss nursing homes randomly assigned to one of three sequential intervention time points. The study population will consist of people with dementia living in nursing homes with and without specialized dementia care facilities. Over 16 months, staff working at the frontline and family members will assess the needs and concerns of people with dementia using IPOS-Dem. Depending on sequence allocation, facilitated case studies will start after 3, 6 or 9 months. The primary outcome will be caring quality measured by QUALIDEM. The secondary outcome will be symptoms and concerns, as indicated by the IPOS-Dem sum-score. The Zürich Ethics Committee approved the study in 2019 (2019-01847). The results of this study will contribute to improving the effectiveness of person-centred care for people with dementia. Collaboration between healthcare staff and family members will be systematically developed and built upon thorough assessment using the IPOS-Dem and related case studies. The use of IPOS-Dem will offer all frontline staff a systematic approach to have an independent voice within the nursing process, regardless of their qualification or grade

Phase stability of terawatt-class ultrabroadband parametric amplification

The phase stability of broadband (280 nm bandwidth) terawatt-class parametric amplification was measured, for the first time to our knowledge, with a combination of spatial and spectral interferometry. Measurements at four different wavelengths from 750 to 900 nm were performed in combination with numerical modeling. The phase stability is better than 1/23 rms of an optical cycle for all the measured wavelengths, depending on the phase-matching conditions in the amplifier. (C) 2007 Optical Society of America

Molecular spintronics: Coherent spin transfer in coupled quantum dots

Time-resolved Faraday rotation has recently demonstrated coherent transfer of electron spin between quantum dots coupled by conjugated molecules. Using a transfer Hamiltonian ansatz for the coupled quantum dots, we calculate the Faraday rotation signal as a function of the probe frequency in a pump-probe setup using neutral quantum dots. Additionally, we study the signal of one spin-polarized excess electron in the coupled dots. We show that, in both cases, the Faraday rotation angle is determined by the spin transfer probabilities and the Heisenberg spin exchange energy. By comparison of our results with experimental data, we find that the transfer matrix element for electrons in the conduction band is of order 0.08 eV and the spin transfer probabilities are of order 10%.Comment: 13 pages, 6 figures; minor change

Spin injection through the depletion layer: a theory of spin-polarized p-n junctions and solar cells

A drift-diffusion model for spin-charge transport in spin-polarized {\it p-n} junctions is developed and solved numerically for a realistic set of material parameters based on GaAs. It is demonstrated that spin polarization can be injected through the depletion layer by both minority and majority carriers, making all-semiconductor devices such as spin-polarized solar cells and bipolar transistors feasible. Spin-polarized {\it p-n} junctions allow for spin-polarized current generation, spin amplification, voltage control of spin polarization, and a significant extension of spin diffusion range.Comment: 4 pages, 3 figure

Production and decay of the Standard Model Higgs Bososn at LEP200

We collect and update theoretical predictions for the production rate and decay branching fractions of the Standard Model Higgs boson that will be relevant for the Higgs search at LEP200. We make full use of the present knowledge of radiative corrections. We estimate the systematics arising from theoretical and experimental uncertainties.Comment: 27 page

Improved Laboratory Values of the H-2 Lyman and Werner Lines for Constraining Time Variation of the Proton-to-Electron Mass Ratio

Two distinct high-accuracy laboratory spectroscopic investigations of the H-2 molecule are reported. Anchor lines in the EF1 Sigma(+)(g)-X-1 Sigma(+)(g) system are calibrated by two-photon deep-UV Doppler-free spectroscopy, while independent Fourier-transform spectroscopic measurements are performed that yield accurate spacings in the B-1 Sigma(+)(u)-EF1 Sigma(+)(g) and I-1 Pi(g)-C-1 Pi(u) systems. From combination differences accurate transition wavelengths for the B-X Lyman and the C-X Werner lines can be determined with accuracies better than similar to 5x10(-9), representing a major improvement over existing values. This metrology provides a practically exact database to extract a possible variation of the proton-to-electron mass ratio based on H-2 lines in high-redshift objects. Moreover, it forms a rationale for equipping a future class of telescopes, carrying 30-40 m dishes, with novel spectrometers of higher resolving powers