Frequency division multiplex-based light spectroscopy.

Light spectrometers are highly versatile state-of-the-art measurement devices. However, using these systems, e.g., in semiconductor device characterization, creates challenging obstacles with respect to measurement time. We present a new, flexible and accurate approach to either characterize optical properties of arbitrary photosensitive devices or examine the spectral components of light reliably. Using a spatial light modulator (SLM) in combination with frequency division multiplexing methods, it is possible to significantly improve signal-to-noise ratios and decrease measurement times. Moreover, the use of SLM ensures a greater reliability of the setup because conventional moving parts are replaced. The feasibility and experimental setup are described in detail. The setup has been validated for various applications by comparative measurements.

ATP release from activated neutrophils occurs via connexin 43 and modulates adenosine-dependent endothelial cell function.

Extracellular ATP liberated during hypoxia and inflammation can either signal directly on purinergic receptors or can activate adenosine receptors following phosphohydrolysis to adenosine. Given the association of polymorphonuclear leukocytes (PMNs) with adenine-nucleotide/nucleoside signaling in the inflammatory milieu, we hypothesized that PMNs are a source of extracellular ATP. Initial studies using high-performance liquid chromatography and luminometric ATP detection assays revealed that PMNs release ATP through activation-dependent pathways. In vitro models of endothelial barrier function and neutrophil/endothelial adhesion indicated that PMN-derived ATP signals through endothelial adenosine receptors, thereby promoting endothelial barrier function and attenuating PMN/endothelial adhesion. Metabolism of extracellular ATP to adenosine required PMNs, and studies addressing these metabolic steps revealed that PMN express surface ecto-apyrase (CD39). In fact, studies with PMNs derived from cd39(-/-) mice showed significantly increased levels of extracellular ATP and lack of ATP dissipation from their supernatants. After excluding lytic ATP release, we used pharmacological strategies to reveal a potential mechanism involved in PMN-dependent ATP release (eg, verapamil, dipyridamole, brefeldin A, 18-alpha-glycyrrhetinic acid, connexin-mimetic peptides). These studies showed that PMN ATP release occurs through connexin 43 (Cx43) hemichannels in a protein/phosphatase-A-dependent manner. Findings in human PMNs were confirmed in PMNs derived from induced Cx43(-/-) mice, whereby activated PMNs release less than 15% of ATP relative to littermate controls, whereas Cx43 heterozygote PMNs were intermediate in their capacity for ATP release (P<0.01). Taken together, our results identify a previously unappreciated role for Cx43 in activated PMN ATP release, therein contributing to the innate metabolic control of the inflammatory milieu.

Dynamic behavior of a liquid metal interface under the influence of a high-frequency magnetic field.

We present experimental results on the stability of a free liquid metal surface influenced by an alternating magnetic field. The field is generated by an inductor fed by a high-frequency electrical current. The experimental setup consists of an annulus filled with the liquid metal galinstan. We observe three kinds of instabilities: exciting of capillary waves, a static high-amplitude surface deformation, and eventually an electromagnetic pinch at a critical inductor current I(cp). The data show that I(cp) correlates directly with the current frequency and the geometric parameters.