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- Cardenas, Edgar, 1990-
(author)
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Synthesis of zeolites from economic raw materials
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Synthesis methods using economic raw materials, such as kaolin and diatomite have been developed for the production of zeolites in the present work. Zeolite Y and ZSM-5 have been synthetized successfully from diatomite and kaolin, respectively. The synthesis of zeolite Y was extensively studied (Paper I) in order to obtain final products with high crystallinity and an appropriate SiO2/Al2O3 ratio to be suitable for application as catalyst. Then, the influence of the alkalinity (in terms of SiO2/Na2O ratio) on the outcome of the synthesis was studied. Thus, an optimum range of alkalinity that satisfies the requirements stated before was found. Additionally, the results also showed that diatomite produce similar products as colloidal silica, which may be expected since both silica sources are highly polymerized forms of silica.The synthesized zeolite Y crystals were also ion-exchanged with Lanthanum to obtain a Rare Earth zeolite Y (REY) catalyst (Paper V). The REY catalyst was shown to be thermally stable up to 800°C as expected for this catalyst. The REY catalyst was also evaluated in the reaction of Catalytic Cracking of cumene. The results of catalytic tests shown that the REY catalyst synthetized from diatomite holds activity towards the catalytic cracking of cumene.In addition, studies of synthesis of ZSM-5 zeolite from kaolin have been performed to understand the crystal growth and morphology, crystal size, and aluminum distribution. In particular, the influence of the gel on the morphology of the crystals (Paper II) has been studied. It was observed that when the crystal surface is in contact with the gel phase, dendritic features appear at the crystal surface, that become smoother as the reaction proceeds. On the contrary, when only liquid phase is in contact with crystal surface there is no presence of dendritic features and the growth rate is higher.Further studies demonstrated that the ZSM-5 crystals possess a non-homogeneous aluminum distribution, a phenomenon known as Al-zoning. A thorough characterization at distinct stages of the reaction has been performed (Paper III), on the different reaction mixture phases such as solid part, gel phase and liquid phase. The main finding was that the gel phase consists of a nanoparticle skeleton rich in alumina, filled by a silica rich matrix. In the beginning of crystallization, the silica rich matrix is preferentially consumed to form the crystals, leaving behind the alumina rich nanoparticle skeleton that is consumed later, resulting in the non-homogeneous distribution of aluminum in the crystals.Finally, studies of the microstructure of a TPA-ZSM-5 system using fumed silica as silicon source have been performed (paper IV). In this system, three stages of crystallization were observed. Stage I, formation of amorphous gel phase. Stage II formation of XRD amorphous spherical entities denoted as Condensed Agregates (CAs). Stage III, Crystallization of CAs into ZSM-5. This study was focused only in the stage III. Findings showed that ZSM-5 nanocrystals are formed in the core of the CA (beginning of stage III), surrounded by an amorphous shell composed of alumino-silica. As the crystallization proceeds, the amorphous shell crystallizes into ZSM-5 by competitive growth, but the nanocrystals of the core remain intact. Moreover, compositional analysis results showed that the silicon from the liquid phase provided most of the nutrients for growth of the ZSM-5 crystals resulting in polycrystalline ZSM-5 aggregates with an Al rich core - Si rich shell morphology.
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- Claesson, Åsa, et al.
(author)
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lntegrated Optical Fiber Sensors in Additive Manufactured Metal Components for Smart Manufacturing Applications
- 2019
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In: Smart Systems Integration; 13th International Conference and Exhibition on Integration Issues of Miniaturized Systems.
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Conference paper (peer-reviewed)abstract
- This work combines fiber optic sensors with additive manufacturing to enable integration of temperature and strain sensors in metal components. In this paper, we present a fiber optic sensor network integrated in press hardening tools to monitor the contact between the tool and the metal sheet during forming operation. The tools are manufactured through metal powder bed fusion using laser melting processes (PBF-SLM), after which the tools are prepared for sensor integration. A demonstrator press hardening tool with integrated fiber optic sensors was heated using an electric heat foil and the sensor measurements was compared to a thermal simulation model. The sensor technology is based on Fiber Bragg Gratings (FBGs), integrated at several positions along the optical fiber. FBGs are in-fiber sensors that are multiplexed. lt is possible to place hundreds of FBG sensors along one single fiber, thus allowing for quasidistributed sensing of temperature or strain. The optical fiber itself can be less than 100 micrometer in diameter, allowing for sensing at several points in a minimally invasive way, when integrated in a tool or component.
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| 6. |
- Eberhart, Martin, et al.
(author)
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Atomic oxygen number densities in the mesosphere-lower thermosphere region measured by solid electrolyte sensors on WADIS-2
- 2019
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In: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 12:4, s. 2445-2461
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Journal article (peer-reviewed)abstract
- Absolute profiles of atomic oxygen number densities with high vertical resolution have been determined in the mesosphere-lower thermosphere (MLT) region from in situ measurements by several rocket-borne solid electrolyte sensors. The amperometric sensors were operated in both controlled and uncontrolled modes and with various orientations on the foredeck and aft deck of the payload. Calibration was based on mass spectrometry in a molecular beam containing atomic oxygen produced in a microwave discharge. The sensor signal is proportional to the number flux onto the electrodes, and the mass flow rate in the molecular beam was additionally measured to derive this quantity from the spectrometer reading. Numerical simulations provided aerodynamic correction factors to derive the atmospheric number density of atomic oxygen from the sensor data. The flight results indicate a preferable orientation of the electrode surface perpendicular to the rocket axis. While unstable during the upleg, the density profiles measured by these sensors show an excellent agreement with the atmospheric models and photometer results during the downleg of the trajectory. The high spatial resolution of the measurements allows for the identification of small-scale variations in the atomic oxygen concentration.
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- Grygalashvyly, Mykhaylo, et al.
(author)
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Atmospheric band fitting coefficients derived from a self-consistent rocket-borne experiment
- 2019
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:2, s. 1207-1220
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Journal article (peer-reviewed)abstract
- Based on self-consistent rocket-borne measurements of temperature, the densities of atomic oxygen and neutral air, and the volume emission of the atmospheric band (762 nm), we examined the one-step and two-step excitation mechanism of O-2 (b(1)Sigma(+)(g)) for nighttime conditions. Following McDade et al. (1986), we derived the empirical fitting coefficients, which parameterize the atmospheric band emission O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(g)) (0, 0). This allows us to derive the atomic oxygen concentration from nighttime observations of atmospheric band emission O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(g)) (0, 0). The derived empirical parameters can also be utilized for atmospheric band modeling. Additionally, we derived the fit function and corresponding coefficients for the combined (one-and two-step) mechanism. The simultaneous common volume measurements of all the parameters involved in the theoretical calculation of the observed O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(g)) (0, 0) emission, i.e., temperature and density of the background air, atomic oxygen density, and volume emission rate, is the novelty and the advantage of this work.
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- Havnes, Ove, et al.
(author)
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A new method of inferring the size, number density, and charge of mesospheric dust from its in situ collection by the DUSTY probe
- 2019
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In: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 12:3, s. 1673-1683
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Journal article (peer-reviewed)abstract
- We present a new method of analyzing measurements of mesospheric dust made with DUSTY rocket-borne Faraday cup probes. It can yield the variation in fundamental dust parameters through a mesospheric cloud with an altitude resolution down to 10 cm or less if plasma probes give the plasma density variations with similar height resolution. A DUSTY probe was the first probe that unambiguously detected charged dust and aerosol particles in the Earth's mesosphere. DUSTY excluded the ambient plasma by various biased grids, which however allowed dust particles with radii above a few nanometers to enter, and it measured the flux of charged dust particles. The flux measurements directly yielded the total ambient dust charge density. We extend the analysis of DUSTY data by using the impact currents on its main grid and the bottom plate as before, together with a dust charging model and a secondary charge production model, to allow the determination of fundamental parameters, such as dust radius, charge number, and total dust density. We demonstrate the utility of the new analysis technique by considering observations made with the DUSTY probes during the MAXIDUSTY rocket campaign in June-July 2016 and comparing the results with those of other instruments (lidar and photometer) also used in the campaign. In the present version we have used monodisperse dust size distributions.
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| 9. |
- Hedin, Charlotte, et al.
(author)
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Should we use vedolizumab as mono or combo therapy in ulcerative colitis?
- 2018
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In: Baillière's Best Practice & Research. - : Elsevier. - 1521-6918 .- 1532-1916. ; 32-33, s. 27-34
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Journal article (peer-reviewed)abstract
- Randomized controlled trials comparing the efficacy of vedolizumab monotherapy with combination therapy of vedolizumab and an immunomodulator in patients with ulcerative colitis (UC) are lacking. Emerging pharmacokinetic data indicate that vedolizumab concentrations correlate with clinical outcomes, although the correlation may be less strong for vedolizumab compared with an anti-TNF agents. Associations between concomitant use of immunomodulators and decreased immunogenicity of vedolizumab have been reported, but this does not appear to translate into enhanced therapeutic effect of combination therapy, at least not based on present data. However, data are sparse and often based on post-hoc analyses. Future comparative effectiveness studies of patients with UC, naive to vedolizumab as well as immunomodulators, are needed. This might be of specific relevance for subgroups of UC patients, such as young men and the elderly, in whom combination versus monotherapy therapy may have a different risk-benefit ratio, given the risk of malignancy associated with immunomodulators. (C) 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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| 10. |
- Kalogerakis, Konstantinos S., et al.
(author)
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New insights for mesospheric OH : multi-quantum vibrational relaxation as a driver for non-local thermodynamic equilibrium
- 2018
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In: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 36:1, s. 13-24
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Journal article (peer-reviewed)abstract
- The question of whether mesospheric OH(v) rotational population distributions are in equilibrium with the local kinetic temperature has been debated over several decades. Despite several indications for the existence of non-equilibrium effects, the general consensus has been that emissions originating from low rotational levels are thermalized. Sky spectra simultaneously observing several vibrational levels demonstrated reproducible trends in the extracted OH(v) rotational temperatures as a function of vibrational excitation. Laboratory experiments provided information on rotational energy transfer and direct evidence for fast multi-quantum OH(high-v) vibrational relaxation by O atoms. We examine the relationship of the new relaxation pathways with the behavior exhibited by OH(v) rotational population distributions. Rapid OH(high-v) + O multi-quantum vibrational relaxation connects high and low vibrational levels and enhances the hot tail of the OH(low-v) rotational distributions. The effective rotational temperatures of mesospheric OH(v) are found to deviate from local thermodynamic equilibrium for all observed vibrational levels. Dedicated to Tom G. Slanger in celebration of his 5 decades of research in aeronomy.
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- Strelnikov, Boris, et al.
(author)
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Simultaneous in situ measurements of small-scale structures in neutral, plasma, and atomic oxygen densities during the WADIS sounding rocket project
- 2019
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:17, s. 11443-11460
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Journal article (peer-reviewed)abstract
- In this paper we present an overview of measurements conducted during the WADIS-2 rocket campaign. We investigate the effect of small-scale processes like gravity waves and turbulence on the distribution of atomic oxygen and other species in the mesosphere-lower thermosphere (MLT) region. Our analysis suggests that density fluctuations of atomic oxygen are coupled to fluctuations of other constituents, i.e., plasma and neutrals. Our measurements show that all measured quantities, including winds, densities, and temperatures, reveal signatures of both waves and turbulence. We show observations of gravity wave saturation and breakdown together with simultaneous measurements of generated turbulence. Atomic oxygen inside turbulence layers shows two different spectral behaviors, which might imply a change in its diffusion properties.
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| 13. |
- Strelnikov, Boris, et al.
(author)
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Spatial and temporal variability in MLT turbulence inferred from in situ and ground-based observations during the WADIS-1 sounding rocket campaign
- 2017
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In: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 35:3, s. 547-565
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Journal article (peer-reviewed)abstract
- In summer 2013 the WADIS-1 sounding rocket campaign was conducted at the Andoya Space Center (ACS) in northern Norway (69 degrees N, 16 degrees E). Among other things, it addressed the question of the variability in mesosphere/lower thermosphere (MLT) turbulence, both in time and space. A unique feature of the WADIS project was multi-point turbulence sounding applying different measurement techniques including rocket-borne ionization gauges, VHF MAARSY radar, and VHF EISCAT radar near Tromso. This allowed for horizontal variability to be observed in the turbulence field in the MLT at scales from a few to 100 km. We found that the turbulence dissipation rate, epsilon varied in space in a wavelike manner both horizontally and in the vertical direction. This wavelike modulation reveals the same vertical wavelengths as those seen in gravity waves. We also found that the vertical mean value of radar observations of epsilon agrees reasonably with rocket-borne measurements. In this way defined value reveals clear tidal modulation and results in variation by up to 2 orders of magnitude with periods of 24 h. The value also shows 12 h and shorter (1 to a few hours) modulations resulting in one decade of variation in magnitude. The 24 h modulation appeared to be in phase with tidal change of horizontal wind observed by SAURA-MF radar. Such wavelike and, in particular, tidal modulation of the turbulence dissipation field in the MLT region inferred from our analysis is a new finding of this work.
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| 14. |
- Tsuda, T. T., et al.
(author)
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Statistical investigation of Na layer response to geomagnetic activity using resonance scattering measurements by Odin/OSIRIS
- 2017
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 44:12, s. 5943-5950
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Journal article (peer-reviewed)abstract
- We have performed a statistical investigation of the global response of the Na layer to geomagnetic activity using Na density data from 2004 to 2010 obtained using the Optical Spectrograph and Infrared Imager System (OSIRIS) on board the Odin satellite. In the analysis, we categorized the Na density data according to the auroral electrojet (AE) index and then compared the resulting data sets. Regarding the results, we found a significant decrease in the Na density above a height of similar to 95 km in both the southern and northern polar regions with an increase in the AE index. The cause of the decrease in the Na density is discussed, and we conclude that the decrease in the Na density was mainly due to the effect of energetic particle precipitation.
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| 15. |
- Xu, Chao, et al.
(author)
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Porous Polymers and Porous Carbons for CO2 Capture and VOC Removal
- 2017
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Conference paper (peer-reviewed)abstract
- Porous materials have potential applications in gas capture and storage and heterogeneous catalysis.1 We have developed a series of porous polymers (PPs) and porous carbons (PCs) with high surface areas and tunable pore sizes. They were studied as potential sorbents for CO2 separation and volatile organic compounds (VOCs) removal.2 The PPs were synthesized by Schiff base polycondensations. The sustainable PCs were synthesized from natural abundant celluloses by a physical carbonization/ activation process. All the PPs and PCs had ultramicropores and displayed relatively high CO2 uptakes (0.93-2.29 mmol/g at 0.15 bar, 2.20-5.52 mmol/g at 1 bar; 273 K) and CO2-over-N2 selectivities (31-90 for CO2/N2 mixtures with 15 vol%/85 vol% at 273 K). In addition, the ACs displayed remarkable adsorption capacity for vapors of VOCs with values up to 0.97 mmol/g at very low VOC concentrations (200 ppmv) and with ultrahigh VOC-over-N2 selectivity (9.35 × 103 at 293 K for 0.02 vol%/99.8 vol% of benzene/N2 mixture). The diverse synthesis routes and rich functionalities of PPs allowed further post-modification to improve their performance in CO2 capture. The PPs modified by alkyl amines induced chemisorption of CO2, which was confirmed by the study of in situ infrared (IR) and solid-state 13C NMR spectroscopy. As a result, the amine-modified PPs had a large CO2 capacity and very high CO2-over-N2 selectivity at the CO2 concentrations relevant for post-combustion capture of CO2.
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