Search results for " Vacuum"
showing 10 items of 94 documents
Automatic mass spectra recognition for Ultra High Vacuum systems using multilabel classification
2021
Abstract In Ultra High-Vacuum (UHV) systems it is common to find a mixture of many gases originating from surface outgassing, leaks and permeation that contaminate vacuum chambers and cause issues to reach ultimate pressures. The identification of these contaminants is, in general, done manually by trained technicians from the analysis of mass spectra. This task is time consuming and can lead to misinterpretation or partial understanding of issues. The challenge resides in the rapid identification of these contaminants by using some automatic gas identification technique. This paper explores the automatic and simultaneous identification of 80 molecules, including some of the most commonly p…
Emerging switchable ultraviolet photoluminescence in dehydrated Zn/Al layered double hydroxide nanoplatelets
2019
AbstractLayered double hydroxides show intriguing physical and chemical properties arising by their intrinsic self-assembled stacking of molecular-thick 2D nanosheets, enhanced active surface area, hosting of guest species by intercalation and anion exchanging capabilities. Here, we report on the unprecedented emerging intense ultraviolet photoluminescence in Zn/Al layered double hydroxide high-aspect-ratio nanoplatelets, which we discovered to be fully activated by drying under vacuum condition and thermal desorption as well. Photoluminescence and its quenching were reproducibly switched by a dehydration–hydration process. Photoluminescence properties were comprehensively evaluated, such a…
"Table 3" of "Measurement of dielectron production in central Pb-Pb collisions at $\sqrt{{\textit{s}}_{\mathrm{NN}}}$ = 2.76 TeV"
2018
Dielectron invariant-mass spectrum divided by the hadronic cocktail without the contribution from the vacuum $\rho^{0}$. The statistical and systematic uncertainties of data are represented by vertical bars and boxes.
Solid-state mechanochemical synthesis of multinary metal halide semiconductors for optoelectronics: From powder to thin film
2020
En la última década, las perovskitas de haluro de plomo, así como otros haluros de metales múltiples, incluidas las alternativas sin plomo, han demostrado ser materiales prometedores para su uso en optoelectrónica. Por lo tanto, se buscan activamente nuevas formas de producir semiconductores de alta pureza a gran escala. Por tanto, el objetivo principal de esta tesis doctoral es el desarrollo de perovskitas y semiconductores relacionados utilizando métodos sin disolventes. Además, con la perspectiva del uso de dichos materiales en optoelectrónica a escala industrial, el foco está puesto en trabajar con materiales benignos para el desarrollo de alternativas a las perovskitas tóxicas. La sínt…
High magnetic fields for fundamental physics
2018
Various fundamental-physics experiments such as measurement of the birefringence of the vacuum, searches for ultralight dark matter (e.g., axions), and precision spectroscopy of complex systems (including exotic atoms containing antimatter constituents) are enabled by high-field magnets. We give an overview of current and future experiments and discuss the state-of-the-art DC- and pulsed-magnet technologies and prospects for future developments.
Diamond nucleation on iridium: local variations of structure and density within the BEN layer
2009
Abstract The diamond nuclei generated by the bias enhanced nucleation (BEN) on iridium are gathered in well defined areas (“domains”). In atomic force microscopy (AFM) measurements they become manifest in a 1 nm downward step. The fine structure of the carbon layer inside and outside these domains has been studied by small spot Auger electron spectroscopy (AES), high resolution transmission electron microscopy (HRTEM), AFM and lateral force microscopy (LFM). The Auger spectra of the carbon KLL peak taken in an ultra high vacuum setup revealed diamond features inside and more graphitic features outside the domains. The comparison with the intensity of the Auger signal originating from the un…
Effects of packaging on shelf-life and quality of minimally processed fennel
2018
Fennel is not a widespread product among minimally processed vegetables, due to the fast deterioration mainly caused by browning of the cut surfaces, even during cold storage. In order to extend the shelf-life of fresh-cut fennel, the influence of different packaging techniques was studied. Sliced fennel, dipped in a citric acid solution (0.5%), was placed in polystyrene trays, sealed with PE film or vacuum packaged in PE bags and stored up to 14 days at 4°C. During this period the weight loss, soluble solid content, pH, color and firmness were evaluated. Minimally processed fennel packed in sealed trays and cold-stored at 4°C, extended its shelf-life to 14 days maintaining acceptable quali…
Monitoring the chemical changes in Pd induced by hydrogen absorption using microcantilevers.
2003
Abstract The reactivity of the palladium shaped as a microcantilever is investigated as a function of the hydrogen stoichiometry. A small cell holding the microcantilever is designed to monitor the deflection and the flexural resonance response from high vacuum to a hydrogen gas pressure of several bars. The measurements show that the Young's modulus is accurate if the cantilever is thick enough to be described by a continuum mechanics approach. The orientation distribution function of the palladium grains determined by X-ray diffraction enables to correlate Young's modulus measured using microcantilevers with the elastic constant tensor issued from the literature. The surface stress induce…