Assessing the Effect of Disturbances on Ectomycorrhiza Diversity

Ectomycorrhiza (ECM) communities can be described on a species level or on a larger scale at an ecosystem level. Here we show that the species level approach of successional processes in ECM communities is not appropriate for understanding the diversity patterns of ECM communities at contaminated sites. An ecosystem based approach improves predictability since different biotic and abiotic factors are included. However, it still does not take into account the hierarchical structure of the ecosystem. We suggest that diversity patterns of ECMs communities in forests can best be investigated at three levels. This hypothetical approach for investigation can be tested at sites of secondary succession in areas contaminated with metals. Once the diversity patterns are appropriately described by a hierarchical ecosystem approach, to the species level is used to explain these patterns by populational and ecotoxicological mechanisms

Spectra van puls code gemoduleerde signalen

Sommige vormen van P.C.M.-signalen, zoals bijvoorbeeld de tweede orde bipolaire code hebben een vermogensdichtheidsspectrum met spectrale nullen, terwijl in de onmiddellijke omgeving van een dergelijke "nul" slechts een zeer gering vermogen getransporteerd wordt. Nagegaan is wat de invloed op het oogdiagram van het P.C.M.- signaal is indien dit frequentiegebiedje niet meegezonden wordt. Om het informatie transporterende P.C.M.-signaal na te bootsen is een elektronische kruis-of-munt werper gebouwd die een tempo van twee miljoen "worpen" per seconde kan bereiken.Applied SciencesElectrotechniekTransmissie van Informati

Verslag van een studie van datatransmissie over telefoonkanalen en het ontwerp van een 1200 baud FSK-modem

In de datatransmissietechniek wordt veelal voor de transmissie van datasignalen gebruik gemaakt van het telefoonnet. Een van de meest actuele problemen uit de datatransmissietechniek is daarom de aanpassing van het datasignaal, dat van nature een bivalent digitaal signaal is, aan het gedrag van de voor de transmissie van analoge spraaksignalen uitgeruste telefoniekanalen…Applied SciencesElectrotechniekTransmissie van Informati

Determining the Costs of Low-Back Pain Associated Sick Leave in the Dutch Workforce in the Period 2015 to 2017

OBJECTIVE: To investigate the costs of low-back pain associated sick leave of workers in the Netherlands from 2015 to 2017. METHODS: We used longitudinal data form a large occupational health service regarding sick leave (registered by occupational physicians). Costs of sick leave due to low-back pain were estimated using the human capital approach, considering society and company perspectives. RESULTS: A total of 7901 low-back pain episodes from 7161 unique workers were analyzed. We estimated an average episode of low-back pain sick leave was 129.42 days in duration and costed €16,191. The total extrapolated sick leave costs were estimated to be €244.7 million in 2017. CONCLUSIONS: Low-back pain remains to be a persistent problem in the working population, as it causes workers to take sick leave for considerable periods of time with considerable associated economic consequences

Theory for Bose-Einstein condensation of light in nanofabricated semiconductor microcavities

We construct a theory for Bose-Einstein condensation of light in nanofabricated semiconductor microcavities. We model the semiconductor by one conduction and one valence band which consist of electrons and holes that interact via a Coulomb interaction. Moreover, we incorporate screening effects by using a contact interaction with the scattering length for a Yukawa potential and describe in this manner the crossover from exciton gas to electron-hole plasma as we increase the excitation level of the semiconductor. We then show that the dynamics of the light in the microcavities is damped due to the coupling to the semiconductor. Furthermore, we demonstrate that on the electron-hole plasma side of the crossover, which is relevant for the Bose-Einstein condensation of light, this damping can be described by a single dimensionless damping parameter that depends on the external pumping. Hereafter, we propose to probe the superfluidity of light in these nanofabricated semiconductor microcavities by making use of the differences in the response in the normal or superfluid phase to a sudden rotation of the trap. In particular, we determine frequencies and damping of the scissors modes that are excited in this manner. Moreover, we show that a distinct signature of the dynamical Casimir effect can be observed in the density-density correlations of the excited light fluid