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Ongoing urbanization highlights the need for a better understanding and high resolution modelling of the urban climate. In this study, we combine rural observations by WMO surface stations, weather radar data and urban crowd-sourced observations with very fine-scale modelling efforts for Amsterdam, The Netherlands. As a model, we use the Weather Research and Forecasting (WRF) mesoscale model with 3D variational data assimilation at a 100-m resolution in the innermost model domain. In order to enable the assimilation of observations within the urban canopy, we develop a scheme to reduce urban temperature biases by adjusting urban fabric temperatures. The scheme is tested against independent urban observations for the summer month of July 2014 and specifically for a hot period and an extreme precipitation event. We find data assimilation reduces biases in temperature and wind speed. Within the city, the most significant improvement is the reduction of negative temperature biases during clear nights, which implies a better prediction of the Urban Heat Island (UHI). Concerning precipitation, the fractional skill score improves incrementally when additional observations are assimilated, and the largest impact is seen from the assimilation of weather radar observations.

Observations in the Altiplano region of the Atacama Desert show that the atmospheric boundary layer (ABL) suddenly collapses at noon. This rapid decrease occurs simultaneously to the entrance of a thermally driven, regional flow that causes a rise in wind speed and a marked temperature decrease. We identify the main drivers that cause the observed ABL collapse by using a land–atmosphere model. The free atmosphere lapse rate and regional forcings, such as advection of mass and cold air as well as subsidence, are first estimated by combining observations from a comprehensive field campaign and a regional model. Then, to disentangle the ABL collapse, we perform a suite of numerical experiments with increasing level of complexity: from only considering local land–atmosphere interactions, to systematically including the regional contributions of mass advection, cold air advection, and subsidence. Our results show that non-local processes related to the arrival of the regional flow are the main factors explaining the boundary-layer collapse. The advection of a shallower boundary layer ($$\approx -250$$ ≈ - 250 m h$$^{-1}$$ - 1 at noon) causes an immediate decrease in the ABL height (h) at midday. This occurs simultaneously with the arrival of a cold air mass, which reaches a strength of $$\approx -4$$ ≈ - 4 K h$$^{-1}$$ - 1 at 1400 LT. These two external forcings become dominant over entrainment and surface processes that warm the atmosphere and increase h. As a consequence, the ABL growth is capped during the afternoon. Finally, a wind divergence of $$\approx 8 \times 10^{-5}$$ ≈ 8 × 10 - 5 s$$^{-1}$$ - 1 contributes to the collapse by causing subsidence motions over the ABL from 1200 LT onward. Our findings show the relevance of treating large and small-scale processes as a continuum to be able to understand the ABL dynamics.

Indoor VOCs still remain at high levels in many areas, which may directly impact human health. In this study, hundreds of residential indoor air samples were collected in Xi'an and Hangzhou from April 2014 to November 2015. Indoor VOC pollution level of newly renovated residences was more serious than that of old residences (approximately 10–15 times). The mean indoor VOC level of newly renovated residences in Xi'an was 0.882 ± 1.922 mg/m 3 , similar to Hangzhou's levels (0.862 ± 1.394 mg/m 3 ). But part of the benzene homologues concentrations in Hangzhou were higher than those in Xi'an, and the exposure risk in Hangzhou could be 1.5 to 8 times that in Xi'an. This study aims to identify characteristics of indoor VOC pollution, quantitatively estimate the combined effects of temperature and humidity, and reveal sink mechanism associated with indoor VOCs. The results indicate that indoor VOC pollution in newly renovated residences is mainly affected by the combination of temperature and humidity as sink effect, especially for the components with large Henry's Law Constant. The results of this study also provide valuable guidance on indoor VOC pollution control, i.e., humidity control is a countermeasure to reduce potential indoor air pollution for people who live in humid areas.

Seit mehr als 50 Jahren werden Leuchtstoffe in Kathodenstrahlrohren zur Erzeugung von sichtbarem Licht eingesetzt. In den letzten Jahrzehnten sind die verwendeten Materialien standig verbessert worden, um die gestiegenen Anspruche an Auflosung, Helligkeit und Kontrast von Monitoren und Fernsehern zu erfullen. Gegenwartig werden verschiedene neue Konzepte verfolgt, um flache Bildschirme mit geringer Bautiefe zu realisieren. Einige dieser Technologien, zum Beispiel die Plasmabildschirme, benotigen ebenfalls Leuchtstoffe. Da sich die Anregungsbedingungen von denen einer klassischen Kathodenstrahlrohre deutlich unterscheiden, mussen jedoch neue Leuchtstoffe entwickelt werden, die an die speziellen Anforderungen optimal angepasst sind.

Of the three phosphors used in cathode-ray tubes (CRT), the blue and the red emitting phosphors used are pigmented. Pigmentation is used in order to suppress reflection of ambient light, aiming at contrast improvement. The pigments applied absorb daylight in those spectral regions where the phosphor does not emit. For the blue emitting phosphor, CoAl{sub 2}O{sub 4} is used as pigment; for the red emitting phosphor, {alpha}-Fe{sub 2}O{sub 3} is applied. Two methods are presented for applying {alpha}-Fe{sub 2}O{sub 3} coatings to Y{sub 2}O{sub 2}S:Eu phosphor grains. In the first method {alpha}-FeO(OH) is precipitated homogeneously on the phosphor, followed by thermal decomposition into {alpha}-Fe{sub 2}O{sub 3}. The second method consists of precipitation of FeSO{sub 4} on the phosphor, followed by thermal decomposition of FeSO{sub 4} into {alpha}-Fe{sub 2}O{sub 3}.

Mit den Leuchtstoffen ZnS:Cu, Au, Al (grun), ZnS:Ag (blau) und Y2O2S:Eu (rot) stehen nach uber vierzigjahriger Entwicklung fur konventionelle Farbfernseh- und Computer-monitor-Anwendungen optimierte Materialien zur Verfugung, deren Lumineszenzeigenschaften kaum Wunsche offen lassen. Verbessert werden konnte allenfalls das Sattigungsverhalten des grunen Leuchtstoffs, wobei allerdings auch die Elektronenkanonen effizienter werden musten. Durch den Ersatz Cadmium-haltiger Zinksulfide ist ein weiterer Schritt in Richtung Umweltvertraglichkeit gelungen. Daher liegen die Herausforderungen zur Zeit eher im Bereich der Pulvertechnologie, z. B. bei der Kontrolle der Morphologie (Korngrose) und bei kontrasterhohenden Masnahmen (Ummantelungen/Pigmentierungen) zur weiteren Verbesserung von Auflosungsvermogen, Brillanz und optimaler Anpassung an die Produktionsbedingungen. Bei den Projektionsfernsehrohren konnten das Alterungsverhalten und die Sattigung des blauen Phosphors, ZnS:Ag, noch verbessert werden; nach Alternativen wird gesucht. Neue Displaykonzepte befinden sich noch im Entwicklungsstadium; die zugehorigen Leuchtstoffspezifikationen sind zum Teil noch nicht bekannt. Bei ihnen wird in Zukunft vermutlich ein Schwerpunkt der industriellen Lumineszenz- bzw. Leuchtstoff-Forschung liegen.

Over the last fifty years, there has been a large research effort in the field of luminescent materials. Such materials find application in, for example, fluorescent lamps, T.V. sets or X-ray detectors. The phosphors applied in such devices are generally inorganic solid-state materials, with an ionic lattice. Research has pushed the luminescence properties of these materials to the physical limits and probably no new classes of these conventional materials, performing equally well or even better, are likely to be found. As a result, the number of conventional phosphor materi- als is not expected to grow further. This has resulted in a change in research strategy. Instead of looking for new 'con- ventional' phosphor materials, research has concentrated on controlling the materials properties of phosphor systems, such as their hygroscopic nature or morphology. In recent years, new inpetus has been given to research dealing with luminescent materials through the application of organic and inorganic cage compounds, the use of organic ligands leading to extremely strong UV absorption, or very small particles exhibiting quantum size effects."] In this paper, we outline some of the activities within Philips research, dealing with these topics.

Optical imaging using unspecific contrast agents as well as targeted and disease-specific agents play a vital role in preclinical research. Moreover, optical imaging is on the verge of establishing itself as a clinically relevant imaging modality. Also in-vitro diagnostical procedures rely to a large degree on optical labels to report disease-specific events. Materials that fulfill the basic requirements of this market are being used today, with cyanine dyes and semiconductor quantum dots being excellent examples. Other materials are being tested in laboratories throughout the world. Design rules suitable to develop new optical labels for in-vivo near-infrared optical imaging procedures have been formulated by us, and we have developed synthesis routes that lead to nano particles with small diameter, narrow size distribution, high quantum yield, and with stable surfaces required for bioconjugation to disease-specific ligands.