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This study investigated the accuracy, drift, and clinical usefulness of a new optical transcutaneous oxygen tension (tcPO 2) measuring technique, combined with a conventional electrochemical transcutaneous carbon dioxide (tcPCO 2) measurement and reflectance pulse oximetry in the novel transcutaneous OxiVenT™ Sensor. In vitro gas studies were performed to measure accuracy and drift of tcPO 2 and tcPCO 2. Clinical usefulness for tcPO 2 and tcPCO 2 monitoring was assessed in neonates. In healthy adult volunteers, measured oxygen saturation values (SpO 2) were compared with arterially sampled oxygen saturation values (SaO 2) during controlled hypoxemia. In vitro correlation and agreement with gas mixtures of tcPO 2 (r = 0.999, bias 3.0 mm Hg, limits of agreement − 6.6 to 4.9 mm Hg) and tcPCO 2 (r = 0.999, bias 0.8 mm Hg, limits of agreement − 0.7 to 2.2 mm Hg) were excellent. In vitro drift was negligible for tcPO 2 (0.30 (0.63 SD) mm Hg/24 h) and highly acceptable for tcPCO 2 (− 2.53 (1.04 SD) mm Hg/12 h). Clinical use in neonates showed good usability and feasibility. SpO 2-SaO 2 correlation (r = 0.979) and agreement (bias 0.13%, limits of agreement − 3.95 to 4.21%) in healthy adult volunteers were excellent. The investigated combined tcPO 2 , tcPCO 2 , and SpO 2 sensor with a new oxygen fluorescence quenching technique is clinically usable and provides good overall accuracy and negligible tcPO 2 drift. Accurate and low-drift tcPO 2 monitoring offers improved measurement validity for long-term monitoring of blood and tissue oxygenation. Keywords Transcutaneous. tcPO 2. tcPCO 2. Oxygen. Fluorescence quenching * Willem van Weteringen

We report high-resolution angle-resolved photoemission experiments on epitaxial thin films of different rare-earth (RE) dihydrides ͑RE= Gd, La͒ and of YH 2 and ScH 2 . It is found through ab initio calculations and confirmed by Fermi surface mapping that the electronic structure becomes very similar upon hydrogenation, rendering the studied dihydrides isoelectronic. We propose that the dihydride phase acts as a common precursor state for the formation of the insulating trihydride phase. For states with higher binding energies (which exhibit considerable H character) the agreement between calculation and measurement is less convincing. Independent of the difficulties to describe these hydrogen related states, we note in the comparison between experiment and calculation a very convincing description of the Fermi surface for the dihydrides. Therefore we trace the apparent inability of density, functional theory to describe the hygrogenation up to the trihydride phase to an insufficient description of hydrogen states in general and, in particular, involving octahedral sites.

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We present a detailed high-resolution angle-resolved photoemission study of the electronic band structure of the room-temperature quasicommensurate charge-density-wave phase of 1T-TaS 2 . In particular, we show that no crossings of the Fermi level are visible in the complete Brillouin zone, indicating that an electron-electron correlation-induced pseudogap in the Ta 5d derived band exists already above the Mott localization-induced transition at 180 K. Moreover, we find that the electronic structure is governed by at least two quasiparticle peaks, which can be assigned to electrons from starlike shells of Ta atoms within the distorted crystal lattice. These peaks show quasilocalized ͑dispersionless͒ behavior in parts of the Brillouin zone where the one-particle band is unoccupied and they follow the one-particle dispersion in the occupied part. In order to address the question of possible Fermi-surface ͑FS͒ nesting, we scanned the remaining remnant FS and found regions with a considerable decrease of spectral weight. However, we find no clear evidence for FS nesting.

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Yttrium can be loaded with hydrogen up to high concentrations causing dramatic structural and electronic changes of the host lattice. We report on the reversibility of hydrogen loading in thin single-crystalline Y films grown by vapor deposition on W͑110͒. Under a H 2 partial pressure of 1ϫ10 Ϫ5 mbar the hexagonal-closedpacked Y films convert to the face-centered-cubic Y dihydride. Unloading is accomplished by annealing the dihydride to 1000 K. No loss of crystallinity is observed during these martensitic transformations of the Y lattice. Moreover, we demonstrate a model to determine the H concentration in Y in situ.The interaction of hydrogen with Y, La, and the rare-earth ͑RE͒ metals has been the subject of numerous investigations due to the interesting temperature-and concentrationdependent structures and properties observed in the solid solution ͑␣ phase͒ as well as in the stable dihydride ͑␤͒ and trihydride ͑␥͒ phases.1 An example is the recent observation of switchable optical properties of Y and La hydride films where shiny, metallic dihydride films become transparent semiconductors in the trihydride phase.2 It is obvious that the geometrical and electronic structure of RE hydrides are key quantities for the understanding of all these properties.For Y, the geometrical structure of the host-lattice and the hydrogen atom positions are well known over the entire range of H concentrations: Y crystallizes in the hexagonalclosed-packed ͑hcp͒ structure, while its dihydride transforms to a face-centered-cubic ͑fcc͒ CaF 2 -type structure.1 The insulating trihydride, finally, possesses a hcp unit cell ͑HoD 3 type͒. 3 The electronic structure of Y hydrides, however, is still a matter of dispute. 1Up until recently most work on hydrogen in Y has been done using polycrystalline bulk or powder samples. Existing photoemission spectroscopy data therefore only yields information on the occupied density of states or on charge transfer from Y to H via core-level shifts. [4][5][6][7] The reason for the absence of experimental band-structure data based on angleresolved ultraviolet photoemission spectroscopy ͑ARUPS͒ is due to the fact that loss of single crystallinity during the first transition ͑␣ to ␤͒ is difficult to avoid and that most bulk samples decompose into powder while going from ␤ to ␥. 1Recently an x-ray diffraction study demonstrated that in thin, monocrystalline Y films, the structural coherence is maintained during cycling ex situ between the dihydride and the trihydride phases. In this study we demonstrate that it is possible to transform thin, single-crystalline Y films into the dihydride phase and to unload them again without loss of order. We used x-ray photoelectron diffraction ͑XPD͒ to observe, in real space and near the surface, the changes occurring due to the H-induced structural transitions. In contrast to the previous study, 8 experiment, loading, and unloading are done in situ, and the films are not capped by a protective Pd layer, a most crucial prerequisite for future ARUPS studies on the electron...