Paul Scherrer Institute

About: Paul Scherrer Institute is a facility organization based out in Villigen, Switzerland. It is known for research contribution in the topics: Neutron & Large Hadron Collider. The organization has 9248 authors who have published 23984 publications receiving 890129 citations. The organization is also known as: PSI.

Eye retention after proton beam radiotherapy for uveal melanoma

Abstract: Purpose: To analyze the long-term results of eye retention after conservative treatment of uveal melanoma with proton beam radiotherapy, and to analyze the causes leading to enucleation after this conservative treatment approach. Methods and materials: This was a prospective, noncomparative, interventional, consecutive case series. A total of 2645 patients (2648 eyes) with uveal melanoma were treated between 1984 and 1999 with proton beam radiotherapy. Data were analyzed as of February 2001. Patients’ age ranged from 9 to 90 years, 1284 were men, and 1361 were women. Largest tumor diameter ranged from 4 to 27.5 mm, and tumor height from 0.9 to 15.6 mm. Median follow-up time was 44 months. Results: The overall eye retention rate at 5, 10, and 15 years after treatment was 88.9%, 86.2%, and 83.7%, respectively. In total, 218 eyes had to be enucleated. Enucleation was related to larger tumor size, mainly tumor height, proximity of posterior tumor margin to optic disc, male gender, high intraocular pressure, and large degree of retinal detachment at treatment time. After optimization of the treatment technique, the eye retention rate at 5 years was increased from 97.1% to 100% for small tumors, from 86.7% to 99.7% for medium, and from 71.1% to 89.5% for large tumors. Conclusions: The treatment technique as used today results in excellent eye retention rates, even in less favorable cases such as large tumors and tumors located close to the optic disc. The experience and a continuous quality control program allowed us to improve the 5-year eye retention rate for all tumor sizes. These findings demonstrate the positive impact of experience and quality control–based efforts for treatment technique optimization.

Light changes the atmospheric reactivity of soot

Abstract: Soot particles produced by incomplete combustion processes are one of the major components of urban air pollution. Chemistry at their surfaces lead to the heterogeneous conversion of several key trace gases; for example NO 2 interacts with soot and is converted into HONO, which rapidly photodissociates to form OH in the troposphere. In the dark, soot surfaces are rapidly deactivated under atmospheric conditions, leading to the current understanding that soot chemistry affects tropospheric chemical composition only in a minor way. We demonstrate here that the conversion of NO 2 to HONO on soot particles is drastically enhanced in the presence of artificial solar radiation, and leads to persistent reactivity over long periods. Soot photochemistry may therefore be a key player in urban air pollution.

Microstructural evolution of gas hydrates in sedimentary matrices observed with synchrotron X-ray computed tomographic microscopy

Abstract: The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in situ at submicron resolution. Here we report on synchrotron-based microtomographic studies by which the nucleation and growth processes of gas hydrate were observed at 276 K in various sedimentary matrices such as natural quartz (with and without admixtures of montmorillonite type clay) or glass beads with different surface properties, at varying water saturation. Both juvenile water and metastably gas-enriched water obtained from gas hydrate decomposition was used. Xenon gas was employed to enhance the density contrast between gas hydrate and the fluid phases involved. The nucleation sites can be easily identified and the various growth patterns are clearly established. In sediments under-saturated with juvenile water, nucleation starts at the water-gas interface resulting in an initially several micrometer thick gas hydrate film; further growth proceeds to form isometric single crystals of 10–20 µm size. The growth of gas hydrate from gas-enriched water follows a different pattern, via the nucleation in the bulk of liquid producing polyhedral single crystals. A striking feature in both cases is the systematic appearance of a fluid phase film of up to several micron thickness between gas hydrates and the surface of the quartz grains. These microstructural findings are relevant for future efforts of quantitative rock physics modeling of gas hydrates in sedimentary matrices and explain the anomalous attenuation of seismic/sonic waves.

Functional Role of Fe-Doping in Co-Based Perovskite Oxide Catalysts for Oxygen Evolution Reaction.

Abstract: Perovskite oxides have been at the forefront among catalysts for the oxygen evolution reaction (OER) in alkaline media offering a higher degree of freedom in cation arrangement. Several highly OER active Co-based perovskites have been known to show extraordinary activities and stabilities when the B-site is partially occupied by Fe. At the current stage, the role of Fe in enhancing the OER activity and stability is still unclear. In order to elucidate the roles of Co and Fe in the OER mechanism of cubic perovskites, two prospective perovskite oxides, La0.2Sr0.8Co1–xFexO3−δ and Ba0.5Sr0.5Co1–xFexO3−δ with x = 0 and 0.2, were prepared by flame spray synthesis as nanoparticles. This study highlights the importance of Fe in order to achieve high OER activity and stability by drawing relations between their physicochemical and electrochemical properties. Ex situ and operando X-ray absorption spectroscopy (XAS) was used to study the local electronic and geometric structure under oxygen evolving conditions. In p...