A quantum search for zeros of polynomials

A quantum mechanical search procedure to determine the real zeros of a polynomial is introduced. It is based on the construction of a spin observable whose eigenvalues coincide with the zeros of the polynomial. Subsequent quantum mechanical measurements of the observable output directly the numerical values of the zeros. Performing the measurements is the only computational resource involved

Multiplication and Composition in Weighted Modulation Spaces

We study the existence of the product of two weighted modulation spaces. For this purpose we discuss two different strategies. The more simple one allows transparent proofs in various situations. However, our second method allows a closer look onto associated norm inequalities under restrictions in the Fourier image. This will give us the opportunity to treat the boundedness of composition operators.Comment: 49 page

Seasonality of aerosol optical properties in the Arctic

Given the sensitivity of the Arctic climate to short-lived climate forcers, long-term in situ surface measurements of aerosol parameters are useful in gaining insight into the magnitude and variability of these climate forcings. Seasonality of aerosol optical properties – including the aerosol light-scattering coefficient, absorption coefficient, single-scattering albedo, scattering Ångström exponent, and asymmetry parameter – are presented for six monitoring sites throughout the Arctic: Alert, Canada; Barrow, USA; Pallas, Finland; Summit, Greenland; Tiksi, Russia; and Zeppelin Mountain, Ny-Ålesund, Svalbard, Norway. Results show annual variability in all parameters, though the seasonality of each aerosol optical property varies from site to site. There is a large diversity in magnitude and variability of scattering coefficient at all sites, reflecting differences in aerosol source, transport, and removal at different locations throughout the Arctic. Of the Arctic sites, the highest annual mean scattering coefficient is measured at Tiksi (12.47&thinsp;Mm−1), and the lowest annual mean scattering coefficient is measured at Summit (1.74&thinsp;Mm−1). At most sites, aerosol absorption peaks in the winter and spring, and has a minimum throughout the Arctic in the summer, indicative of the Arctic haze phenomenon; however, nuanced variations in seasonalities suggest that this phenomenon is not identically observed in all regions of the Arctic. The highest annual mean absorption coefficient is measured at Pallas (0.48&thinsp;Mm−1), and Summit has the lowest annual mean absorption coefficient (0.12&thinsp;Mm−1). At the Arctic monitoring stations analyzed here, mean annual single-scattering albedo ranges from 0.909 (at Pallas) to 0.960 (at Barrow), the mean annual scattering Ångström exponent ranges from 1.04 (at Barrow) to 1.80 (at Summit), and the mean asymmetry parameter ranges from 0.57 (at Alert) to 0.75 (at Summit). Systematic variability of aerosol optical properties in the Arctic supports the notion that the sites presented here measure a variety of aerosol populations, which also experience different removal mechanisms. A robust conclusion from the seasonal cycles presented is that the Arctic cannot be treated as one common and uniform environment but rather is a region with ample spatiotemporal variability in aerosols. This notion is important in considering the design or aerosol monitoring networks in the region and is important for informing climate models to better represent short-lived aerosol climate forcers in order to yield more accurate climate predictions for the Arctic.</p

Analysis of the surface state of epi-ready Ge wafers

The surface state of Ge epi-ready wafers (such as those used on III-V multijunction solar cells) supplied by two different vendors has been studied using X-ray photoemission spectroscopy. Our experimental results show that the oxide layer on the wafer surface is formed by GeO and GeO2. This oxide layer thickness differs among wafers coming from different suppliers. Besides, several contaminants appear on the wafer surfaces, carbon and probably chlorine being common to every wafer, irrespective of its origin. Wafers from one of the vendors show the presence of carbonates at their surfaces. On such wafers, traces of potassium seem to be present too

Mixture Risk Assessment of Complex Real-Life Mixtures—The PANORAMIX Project

Humans are involuntarily exposed to hundreds of chemicals that either contaminate our environment and food or are added intentionally to our daily products. These complex mixtures of chemicals may pose a risk to human health. One of the goals of the European Union’s Green Deal and zero-pollution ambition for a toxic-free environment is to tackle the existent gaps in chemical mixture risk assessment by providing scientific grounds that support the implementation of adequate regulatory measures within the EU. We suggest dealing with this challenge by: (1) characterising ‘real-life’ chemical mixtures and determining to what extent they are transferred from the environment to humans via food and water, and from the mother to the foetus; (2) establishing a high-throughput whole-mixture-based in vitro strategy for screening of real-life complex mixtures of organic chemicals extracted from humans using integrated chemical profiling (suspect screening) together with effect-directed analysis; (3) evaluating which human blood levels of chemical mixtures might be of concern for children’s development; and (4) developing a web-based, ready-to-use interface that integrates hazard and exposure data to enable component-based mixture risk estimation. These concepts form the basis of the Green Deal project PANORAMIX, whose ultimate goal is to progress mixture risk assessment of chemicals.Horizon 2020 research and innovation programme, the Green Deal project PANORAMIX Grant Agreement No. 10103663

Changes in phosphorus status of 'Cripps' Pink' apple trees after application of mulches

The effect of four different mulches on fruit quality was quantified, either directly via mineral nutrient contributions or indirectly, by increasing nutrient uptake efficiency in the soil. We hypothesised that fruit nutrient levels would increase more when an organic mulch, containing nutrients, was applied to the soil, with smaller/no increases when an inorganic mulch was applied to the tree row. In this paper, we concentrate on changes in fruit phosphorus (P) concentrations after application of five treatments: a clean cultivated control, an inorganic woven geotextile fabric, and organic mulches – compost, wood chips and a vermi-castings/ wood chips combination. The trial was conducted on a commercial farm, Lourensford Estate, South Africa, from October 2008 to April 2012 – on an adjacent light, sandy and heavier, sandy-silt soil. Mineral nutrient analyses of the soil, leaves, mulches and fruit were performed. Yield and fruit size were determined. Soil temperatures and soil water status were recorded hourly during the last two seasons. P concentrations did increase chronologically from the soil, then into leaves and then into the fruit after application of mulches that provided additional P to the soil. Sporadic increases in both leaves and fruit occurred, but could not always be related to treatment effects. The significant consistent increase of P levels of the vermi-castings treatment in the heavy soil is likely to be a combination of reduced irrigation volumes, as well as a treatment effect. All mulches resulted in the well-established buffering of soil temperatures, soil water content and percentage soil carbon. Based on results from this study, it is not feasible to apply mulches for the sole purpose to increase P levels in the soil, leaves or fruit of established trees – although increases were noticed from time to time. In addition to water and temperature modifying effects of mulches that would differ between soil textures and depend on the mulch source, increases in P concentrations may result. As yield efficiency is still the primary factor determining income per hectare for the producer, the decrease in yield that resulted from mulching under these conditions, will still outweigh any positive contributions of mulches. It is therefore of utmost importance to first adjust irrigation volumes to a mulch treatment before the advantageous properties of mulching will be of value.Stellenbosch University and HortgroScience.http://www.actahort.orgam201