Multimodal nonlinear endomicroscopic imaging probe using a double-core double-clad fiber and focus-combining micro-optical concept

Multimodal non-linear microscopy combining coherent anti-Stokes Raman scattering, second harmonic generation, and two-photon excited fluorescence has proved to ...     

Hydration of calcium aluminates at 60°C – Development paths of C2AHx in dependence on the content of free water

The influence of water loss during the hydration of calcium aluminates on the phase development is investigated at 60°C. This is relevant for applications in which calcium aluminate cement (CAC) based formulations are exposed to quick drying during hydration. The presented results provide new insights into the well-known conversion processes occurring in CAC pastes. Using in situ XRD two different routes of the development of initially formed C₂AH₈ are determined: (a) transformation to C₃AH₆ + AH₃ in the presence of sufficient free water and (b) dehydration to C₂AH₅ at a lack of free water. Moreover, the influence of precuring of the pastes at 23°C before heating to 60°C is investigated. The increasing loss of free water with increasing precuring time resulting from both, precipitation of hydrate phases and evaporation, causes incomplete hydration of CA or CA₂ as well as dehydration of C₂AH₈ instead of conversion into C₃AH₆. Comparative investigations of sealed samples always revealed complete hydration of CA and CA₂ as well as complete conversion of C₂AH₈.     

Ultra-low power hydrogen sensing based on a palladium-coated nanomechanical beam resonator

Hydrogen sensing is essential to ensure safety in near-future zero-emission fuel cell powered vehicles. Here, we present a novel hydrogen sensor based on the resonant frequency change of a nanoelectromechanical clamped-clamped beam. The beam is coated with a Pd layer, which expands in the presence of H(2), therefore generating a stress build-up that causes the frequency of the device to drop. The devices are able to detect H(2) concentrations below 0.5% within 1 s of the onset of the exposure using only a few hundreds of pW of power, matching the industry requirements for H(2) safety sensors. In addition, we investigate the strongly detrimental effect that relative humidity (RH) has on the Pd responsivity to H(2), showing that the response is almost nullified at about 70% RH. As a remedy for this intrinsic limitation, we applied a mild heating current through the beam, generating a few μW of power, whereby the responsivity of the sensors is fully restored and the chemo-mechanical process is accelerated, significantly decreasing response times. The sensors are fabricated using standard processes, facilitating their eventual mass-production.     

Species-Dependent Metabolism of Benzo[c]Chrysene Mediated by c-DNA-Expressed Human,Rodent and Fish Cytochrome P450 Enzymes

The metabolism of benzo[c]chrysene (B[c]Ch) with various cytochrome P450 (CYP) enzymes including rat 1A1, 1A2, 2B1 and 2E1, human 1A1, 1A2, 2A6, 1B1, 3A4 and 2E1, mouse 1B1, and scup fish 1A1 expressed in Chinese hamster V79 cells has been investigated to clarify the role of individual enzymes in the regioselective oxidation of B[c]Ch and the species dependency. In six cell lines expressing individual CYP enzymes from four different species B[c]Ch was metabolized to several isomeric phenols and trans?dihydrodiols. However, cell lines expressing human 3A4, 2A6 and 2E1 or rat 1A2, 2B1 and 2E1 were metabolically in-competent towards B[c]Ch. Among the trans?dihydrodiols the 9,10-isomer could be detected in cells expressing human, rat and fish CYP 1A1 and to a minor extent in cells with human 1A2, but not in cells expressing human and mouse CYP 1B1. The latter two cell lines produced high amounts of the bay region 3,4-dihydrodiol, whereas the K-region 7,8-dihydrodiol was a minor metabolite. Oxidation of B[c]Ch to the 1,2-dihydrodiol could not be catalyzed by any of the CYP enzymes investigated except fish 1A1. Our results suggest that metabolic activation of B[c]Ch is initiated predominantly by CYP 1A1 to result selectively in the formation of fjord region 9,10-dihydrodiol 11,12-epoxides regardless of the species involved. The activation of B[c]Ch appears to be limited by a low regioselectivity for the 9,10-oxidation.     

高效车用HID灯控制解决方案

英飞凌推出基于XC864的低成本插入式子板,用于控制适用于35W车用HID灯的标准位电子镇流器.子板通过高速峰值电流控制方法实现了最佳的灯功率调节,确保高效无噪运行.先进的保护功能包括短路保护、开路保护和输入过压保护.     

Kinetics of desorption of organic compounds from dissolved organic matter

This study presents a new experimental technique for measuring rates of desorption of organic compounds from dissolved organic matter (DOM) such as humic substances. The method is based on a fast solid-phase extraction of the freely dissolved fraction of a solute when the solution is flushed through a polymer-coated capillary. The extraction interferes with the solute-DOM sorption equilibrium and drives the desorption process. Solutes which remain sorbed to DOM pass through the extraction capillary and can be analyzed afterward. This technique allows a time resolution for the desorption kinetics from subseconds up to minutes. It is applicable to the study of interaction kinetics between a wide variety of hydrophobic solutes and polyelectrolytes. Due to its simplicity it is accessible for many environmental laboratories. The time-resolved in-tube solid-phase microextraction (TR-IT-SPME) was applied to two humic acids and a surfactant as sorbents together with pyrene, phenanthrene and 1,2-dimethylcyclohexane as solutes. The results give evidence for a two-phase desorption kinetics: a fast desorption step with a half-life of less than 1 s and a slow desorption step with a half-life of more than 1 min. For aliphatic solutes, the fast-desorbing fraction largely dominates, whereas for polycyclic aromatic hydrocarbons such as pyrene, the slowly desorbing, stronger-bound fraction is also important.