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Many aspects of optical chemical sensor design would benefit from a better knowledge of the diffusion properties of the analyte in the polymer host. The response times of such sensors to a step change of analyte concentration are of vital interest for many applications of fast-responding sensors. Further, the diffusion properties govern their quenching behavior and their sensitivity. A method for determination of the diffusion constant of oxygen in polymers has been developed and used by several groups in the past. The underlying mathematical model for luminescence quenching by molecules of a gas in a single sensing layer on an impermeable support has not yet been completely derived in an analytical form and still uses tedious numerical methods. We present a partial analytical solution to the problem of modeling the time dependence of luminescence generated by in- or out-diffusion of a gaseous quencher in a polymer film in which a luminophor is immobilized and offer a suitable method to predict sensor response times.

Roll-to-roll UV nanoimprinting is a powerful method for the mass fabrication of nano- and microstructured surfaces, which are highly interesting for many technological applications (e.g., in the fields of optics, electronics, biomimetic, and microfluidics). When setting up a production process based on this technique, one of the main challenges is the prevention of defects (mainly entrapped air during filling and fractures during demolding). This can be cost- and time-intensive as it is mainly done by trial and error. An improved theoretical understanding of defect generation and its prediction for certain material and process parameters is therefore desirable. To accomplish this, we developed COMSOL-based two-dimensional (2D) and three-dimensional (3D) computer simulations for the two key stages of UV nanoimprinting (filling and demolding) and validated them by corresponding roll-to-roll as well as step-and-repeat experiments. Regarding filling, the investigated parameters are template and substrate contact angles; resin viscosity, velocity, and thickness during filling; as well as feature geometry. In summary, it is beneficial for filling to have low template contact angles; high substrate contact angles; low resin viscosity and velocity; as well as inclined sidewalls, low-aspect-ratio features, and a sufficient resin thickness (whereby lack of one of these factors can be compensated by others). Interestingly, nanoscale features are much easier to fill than microscale features in practice (which is not due to reduced bubble trapping but due to enhanced gas dissolution). Regarding demolding, we studied the sidewall angle, fillet radius, size, and elastic modulus of the features. In addition, we compared demolding by roll-to-roll and by step-and-repeat considering the radius of rotation and we decoupled bending, adhesion, and friction to investigate their relative contributions. We could demonstrate quantitatively that for demolding, it is advantageous to have small features, inclined sidewalls, rounded corners, and a large radius of rotation. The dominant effect for nanostructures is adhesion, whereas for microstructures, it is friction. Moreover, demolding by tilting (step-and-repeat) exerts less stress on the imprint than demolding using a roll-to-roll approach. Finally, we present a 3D demolding simulation that identifies the most vulnerable positions of a geometry. From the lessons learned from our filling and demolding simulations, we could demonstrate the defect-free roll-to-roll UV nanoimprinting of a challenging pattern (cuboids with vertical sidewalls). [ABSTRACT FROM AUTHOR]

On the European market there are several fire retardant products available, which reach class B in the European classification system. The producers promise their fire retardants are effective in reducing different reaction to fire parameters of wood such as the time to ignition, the mass loss rate, the heat release rate, the total heat release, the charring rate and the flame spread. This paper discusses the performance of fire retardant products as pressure impregnated wood, non-intumescence surface coatings and intumescence coatings on Norway spruce (Picea abies). The investigations are performed by using a cone calo- rimeter test according to ISO 5660. The thermal exposures of the investigations are 50 kW/m2 and the standard IS0 834 test curve. As result information about the heat release rate, the mass loss rate and the total heat release for duration of 900 seconds will be presented in this paper.

We report on the structuring of the backside surface of sapphire substrates in high-power flip-chip light-emitting diodes (LEDs) by femtosecond laser direct writing. Varying the laser powers has been found to affect the sizes of the inscribed patterns on a submicron scale which facilitates the control of the structure sizes with high precision. Accordingly, since on the one hand the light extraction efficiency reveals a strong dependence on pattern sizes, and on the other hand, femtosecond laser structuring provides a simple opportunity to inscribe diverse structures along the LED surfaces, LEDs with laterally controlled light extraction efficiencies can be fabricated. [ABSTRACT FROM AUTHOR]

See related editorial by Mandi Sehgal. [ABSTRACT FROM AUTHOR]

A simulation procedure which enables integrated simulation of optical devices including both refractive and diffractive optical elements at different length scales is presented. The approach uses the Poynting vector to interface between a Ray-tracing and a finite-difference-time-domain tool for a step by step simulation of both the light propagation through a laser-written diffractive grating structure and its measurement by an appropriate setup. These simulated results are in great accordance with experimentally determined ones. Furthermore, the impact of parameter variations is analyzed and discussed in detail. [ABSTRACT FROM PUBLISHER]

For further improvements to the reliability and the white light quality of phosphor‐converted light‐emitting diodes (LEDs), it is imperative to understand how the compositional, optical, and thermal properties of the materials constituting the color‐conversion elements (CCEs) affect their respective thermal loads. By means of a combined optical and thermal simulation procedure, a comprehensive discussion is given on the underlying coherences of the absorption profile of the blue LED light, the phosphor concentration, the quantum efficiency of the phosphor, and the thermal conductivities of the CCEs. Some general strategies of material composition and design are deduced in order to minimize the thermal load of the CCEs, which is a prerequisite for correlated color temperature maintenance and long‐term material reliability of phosphor‐converted white LEDs. [ABSTRACT FROM AUTHOR]

We present an approach to diminish temperature induced color shifts of phosphor converted LEDs. In particular, we discuss the impact of the thermo-optic coefficients of the materials constituting the color conversion elements (CCEs) on the constancy of the CIE chromaticity coordinates. While silicones have a comparably large thermo-optic coefficient, phosphors, e.g., Ce:YAG have a much smaller one. Hence, increasing temperature will lead to an increase in the differences of the refractive indexes of phosphor and matrix. This will enhance light-scattering which for itself would give reason for a more yellowish emission. Thus, on the one hand the thermo-optic coefficient of the silicone matrix has to be considered for as a potential source of failure for color temperature deviation upon device operation. However, on the other hand adjusting the thermo-optic coefficient of the silicone matrix by an appropriate materials engineering to the temperature induced luminescence loss of a phosphor can be applied to counterbalance a shift of the chromaticity coordinates of the white light in this regard. [ABSTRACT FROM PUBLISHER]

Biocompatibility improvements for blood contacting materials are of increasing interest for implanted devices and interventional tools. The current study focuses on inorganic (titanium, titanium nitride, titanium oxide) as well as diamond-like carbon (DLC) coating materials on polymer surfaces (thermoplastic polyurethane), deposited by magnetron sputtering und pulsed laser deposition at room temperature. DLC was used pure (a-C:H) as well as doped with silicon, titanium, and nitrogen + titanium (a-C:H:Si, a-C:H:Ti, a-C:H:N:Ti). In-vitro testing of the hemocompatibility requires mandatory dynamic test conditions to simulate in-vivo conditions, e.g., realized by a cone-and-plate analyzer. In such tests, titanium- and nitrogen-doped DLC and titanium nitride were found to be optimally anti-thrombotic and better than state-of-the-art polyurethane polymers. This is mainly due to the low tendency to platelet microparticle formation, a high content of remaining platelets in the whole blood after testing and low concentration of platelet activation and aggregation markers. Comparing this result to shear-flow induced cell motility tests with e.g., Dictostelium discoideum cell model organism reveals similar tendencies for the investigated materials. [ABSTRACT FROM AUTHOR]

We present an optical ray-tracing study which investigates the influence of the refractive indexes of the matrix and the phosphor materials as well as the phosphor particle sizes of the color conversion elements (CCE) on the radiant flux of phosphor-conversion-based white light-emitting diodes. We show that an appropriate combination of those parameters is a crucial factor in order to optimize device efficacy. [ABSTRACT FROM PUBLISHER]

We present a study by optical ray-tracing in order to determine the impact of an inhomogeneous phosphor distribution in the color conversion elements (CCE) of phosphor-conversion- based white LED light sources. It turns out that in particular the color temperature and its angular variation, but also the flux-output are highly sensitive towards phosphor distribution variations. [ABSTRACT FROM PUBLISHER]

The ranges of total polybrominated diphenyl ethers (PBDEs) in fish from four Swiss rivers were 0. 8–240ng/g in the bile and 16–7400ng/g lipid in the liver. PBDE concentrations varied within each river and among the various rivers. Female fish tended to have higher concentrations in the liver, while the male fish had higher concentrations in the bile. From the resulting PBDE concentrations in fish it could not be infered that these contaminants contribute to the causes of the observed fish catch decline in Swiss rivers. [Copyright &y& Elsevier]

The environmental safety of decabromodiphenyl ether (BDE-209), a widely used flame retardant, has been the topic of controversial discussions during the past several years. Degradation of BDE-209 into lower brominated diphenyl ether congeners, exhibiting a higher bioaccumulation potential, has been a critical issue. Here, we report on the degradation of BDE-209 and the formation of octa- and nonabromodiphenyl ether congeners under anaerobic conditions. Sewage sludge collected from a mesophilic digester was used as the inoculum and incubated up to 238 days with and without a set of five primers. Following Soxhlet extraction and a liquid chromatography cleanup procedure, parent compounds and debromination products were analyzed by GC/HRMS. In experiments with primers, concentrations of BDE-209 decreased by 30% within 238 days. This corresponds to a pseudo-first-order degradation rate constant of 1 × 10-3 d-1. Without primers, the degradation rate constant was 50% lower. Formation of two nonabromodiphenyl ether and six octabromodiphenyl ether congeners proved that BDE-209 underwent reductive debromination in these experiments. Debromination occurred at the para and the meta positions, whereas debromination at the ortho position was not statistically significant. All three nonabromodiphenyl ether congeners (BDE-206, BDE-207, and BDE-208) were found to undergo reductive debromination as well. No significant change of the BDE-209 concentration and no formation of lower brominated congeners was observed in sterile control experiments. To our knowledge, this is the first report demonstrating microbially mediated reductive debromination of BDE-209 under anaerobic conditions. [ABSTRACT FROM AUTHOR]

Analytical methods were developed for a broad range of organophosphate flame retardants and plasticizers in indoor air. Screening was performed of various indoor environments at 12 locations in and around Zurich, Switzerland. Method recoveries ranged from 62% for triphenyl phosphate to 100% for tris(2-ethylhexyl) phosphate. Tris(2-chloro-isopropyl) phosphate was found in the highest concentration (260ng/m3) mainly in cars and furniture stores. Tris(2-ethylhexyl) phosphate and triphenyl phosphate, both up to 3.4ng/m3, were also detected in quantifiable concentrations at several sites. Tris(1,3-dichloroisopropyl) phosphate, tricresyl phosphate and tri(2-butoxyethyl) phosphate were below the limit of quantification in all samples. The results of the risk assessment indicate that the observed concentrations are below the predicted threshold for human health effects. [Copyright &y& Elsevier]

Polychlorinated biphenyls (PCBs) were evaluated in 41 surface sediments collected from Narragansett Bay, RI in 1997–1998. Highest concentrations of total PCBs (1760 ng/g) were in rivers at the head of the bay and the values decreased southward toward the mouth of the bay, with elevated concentrations in some of the coves. The PCB levels in ∼43% of the samples exceeded the effects range median (ERM) guideline [Environ. Manage. 19 (1995) 81] indicating possible adverse biological effects at these stations.Principal component analysis (PCA) of the surface sediment PCBs separated the Taunton River samples from the rest of the samples. This result suggests that this river has a different PCB composition and sources than the other areas investigated. It also showed that this river has a limited influence on other bay stations as the adjacent samples downstream did not have the same chemical signature. Congener ratios derived from the PCA were useful in distinguishing stations that had different sources of PCBs than the bulk of the bay sediments. Although Aroclor 1268 and 1270 accounted for <1% of all PCB production, their major components, CB206 and CB209, account for 3–6% of the CBs in most bay samples. This may reflect more local use of these Aroclor mixtures and/or be indicative of their relative stability, compared to less chlorinated mixtures.Using linear alkyl benzenes (LABs) as a marker for sewage derived PCBs suggested that up to 95% of the PCBs at the most contaminated sites in the Seekonk, Providence, and Taunton Rivers were sewage derived. This analysis also showed that there is a high background level (167 ng/g) of PCBs in the Seekonk and Providence River, while the Taunton River had a relatively low background level (23.7 ng/g). At the furthest stations south in the Providence River, the sewage derived PCBs only accounted for 23% of the total which suggests that PCB associated with sewage particles are rapidly deposited and are therefore not the most significant source of these compounds to the lower reaches of Narragansett Bay. [Copyright &y& Elsevier]

Examines the effects of photobleaching on absorption properties and decay times of ruthenium complexes adsorbed on silica gel or dissolved in polystyrene or polyvinyl chloride. Comparison between the decay time of bipyridyl and phenanthroline ligands; Factors that influence the decay time of the ligands.

Discusses the intercalibration of linear alkylbenzenes (LAB) in marine sediment SRM1941a and their application as a molecular marker in sediments in Narragansett Bay, Rhode Island. LAB concentrations obtained for SRM1941; Chromatograms of marine sediment SRM1941a; Evidence that most LAB and pollutants are deposited within a short distance of their source.