Infrared-absorption measurements have been performed on the fundamental band of physisorbed H2. Distinct vibrational, rotational, and adsorbate phonon features induced by surface and intermolecular interactions are identified. When compared with adsorption isotherms, the surface-enhanced vibrational line saturates at 40% of the surface-layer coverage; this results from the short range of the surfaceinduced dipole in Steele's bilayer model and is inconsistent with a high-density monolayer phase. Our results also strongly point to the formation of islands at low coverages.PACS numbers: 68.45.-v, 67.70.+n, 68.90.+g, 78.30.-j Recently there has been considerable interest in the physics of adsorbates on porous substrates. When adsorption on these materials is modeled, it is assumed that adsorbate molecules overlay the surface at the pressure corresponding to the first step of the adsorption isotherm. However, estimates based on the Brunauer-Emmett-Teller (BET) model for the surface densities of helium, hydrogen, and to a lesser extent neon, result in anomalously large values.' Although this phenomenon has been known for more than thirty years and the state of the adsorbed layer is relevant to a variety of lowtemperature experiments, 2,3 a microscopic understanding of the underlying physics has been lacking. With helium and hydrogen being very compressible, it is conceivable that the nearest-neighbor distance could be considerably reduced from that of the material inside the pores as a result of surface forces. However, calculations 4 suggest that the zero-point energy is large enough to compensate for the van der Waals forces. In order to explain the adsorption isotherms, a phenomenological model has been proposed in which two layers are coadsorbed at low saturations. 5 Here we report on experiments of infrared absorption of H2 adsorbed on porous Vycor glass which directly test the bilayer model with rather remarkable results. Two spectroscopic techniques, neutron inelastic scattering 6 and electron-energy-loss spectroscopy 7 have been previously applied with success to the study of the rotational state and excitation spectrum of adsorbed H2. For these methods, however, the physical processes that give rise to scattering are those already present in the isolated molecule. In contrast, infrared absorption of the fundamental band of H2 is known to arise from overlap and intermolecular interactions in the bulk, 8 dissolved H2, 9 and H2-rare-gas complexes. 10 We will show that for adsorbed H2 infrared-absorption spectroscopy provides a unique probe of the density profile across the surface. The surface-enhanced vibrational line and its side band from adsorbate phonons are presented for the first time and are explained, with use of the bulk H2 results as a guide, by taking into account the appropriate surface parameters. The large enhancement (by a factor of 60), from the bulk (liquid) H 2 line intensity which is observed, is directly attributable to the larger induced dipole moment per molecule at the surface as compar...

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Paracetamol is the first choice mediation for osteoarthritis. The analgetic potential of NSAIDs is slightly higher and they also have some antiphlogistic effect, but their use has to be strictly limited to a short period of time. They should mainly be used in the therapy of the acute and painful phase of osteoarthritis. Among the NSAIDs, Diclofenac is the medication of first choice. In patients with an increased risk of gastrointestinal complications, a protonpumpinhibitor should be added. Patients with cardiovascular risk factors should receive NSAIDs only in case of no appropriate alternative treatments. Opioids have their place in osteoarthritis treatment and should be part of an individualized pain regime, which should also contain a pain diary and proactive monitoring. It is important to emphasize the positive effects of physical activity on the function of the joints as well as the negative effect of overweight and immobility.

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