| 1. |
- Alnoor, Hatim, et al.
(författare)
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Exploring MXenes and their MAX phase precursors by electron microscopy
- 2021
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Ingår i: Materials Today Advances. - : Elsevier. - 2590-0498. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- This review celebrates the width and depth of electron microscopy methods and how these have enabled massive research efforts on MXenes. MXenes constitute a powerful recent addition to 2-dimensional materials, derived from their parent family of nanolaminated materials known as MAX phases. Owing to their rich chemistry, MXenes exhibit properties that have revolutionized ranges of applications, including energy storage, electromagnetic interference shielding, water filtering, sensors, and catalysis. Few other methods have been more essential in MXene research and development of corresponding applications, compared with electron microscopy, which enables structural and chemical identification at the atomic scale. In the following, the electron microscopy methods that have been applied to MXene and MAX phase precursor research are presented together with research examples and are discussed with respect to advantages and challenges.
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| 2. |
- Gagnemo Persson, Rebecca, et al.
(författare)
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Chicken parathyroid hormone gene expression in response to gastrin, omeprazole, ergocalciferol, and restricted food intake.
- 1997
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Ingår i: Calcified Tissue International. - 1432-0827. ; 61:3, s. 210-215
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Tidskriftsartikel (refereegranskat)abstract
- Treatment with omeprazole, a long-acting proton pump inhibitor of acid secretion, induces hypergastrinemia. In chickens, omeprazole induces growth not only of the acid-producing mucosa (probably reflecting the trophic action of gastrin), but also of the parathyroid glands (hypertrophy + hyperplasia), while suppressing bone density and body weight gain without affecting blood calcium. The first part of the present study was concerned with the effect of omeprazole, ergocalciferol (vitamin D2), and restricted food intake on the gene expression of parathyroid hormone (PTH) in the parathyroid glands of the chicken. Chickens were treated with omeprazole (400 micromol/kg/day, I.M.), food restriction, omeprazole + food restriction, ergocalciferol (250 000 IU/kg/day, S.C.), or ergocalciferol + omeprazole for 5 weeks. The weight gain of the chickens was monitored, and the weights of the parathyroid glands and femurs were determined at sacrifice. PTH mRNA in the parathyroid glands was analyzed by Northern blot. The second part of the study examined the effect of 3 weeks of continuous gastrin infusion (chicken gastrin 20-36, 5 nmol/kg/hour, S.C.) on the expression of PTH mRNA in the parathyroid glands. Omeprazole reduced the body weight and femur density (ash weight per volume) while greatly increasing the weight of the parathyroid glands and the PTH gene expression. Food restriction alone and ergocalciferol alone (at a dose that raised blood Ca2+) were without effect, but food restriction greatly enhanced the omeprazole-evoked increase in parathyroid gland weight and PTH gene expression. Gastrin increased the weight of the parathyroid glands and reproduced the effect of omeprazole on PTH gene expression. Hence, it seems likely that the effect of omeprazole reflects the ensuing hypergastrinemia.
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| 3. |
- Persson, Per, et al.
(författare)
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Gastrectomy causes bone loss in the rat: is lack of gastric acid responsible?
- 1993
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Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 1502-7708 .- 0036-5521. ; 28:4, s. 301-306
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Tidskriftsartikel (refereegranskat)abstract
- Total gastrectomy or resection of the acid-producing part of the stomach (fundectomy) in the rat induced a marked and rapid reduction in bone wet weight, ash weight, and density (expressed as ash weight in mg/mm3 bone). Bone volumes were also affected but not as much. The radius, sternum, tibia, and femur were studied. Three weeks after gastrectomy the bone ash weight was reduced by almost 30% and the density by more than 25%. Maximum bone loss (approximately 40%) occurred about 6 weeks after the operation. The bone loss after gastrectomy was somewhat greater than that after fundectomy, whereas antrectomy had a marginal effect only. The percentage trabecular bone volume, calculated from morphometric analysis of histologic sections of the tibia, was greatly reduced by gastrectomy (approximately 50%), somewhat less so by fundectomy, whereas antrectomy had little effect. We set out to study whether calcium malabsorption could explain the bone loss after gastrectomy. Gastric acid is thought to facilitate the intestinal absorption of ingested calcium by mobilizing calcium from insoluble complexes in the diet. The possibility that lack of acid might contribute to the bone loss after gastrectomy was examined in experiments in which the proton pump inhibitor omeprazole was given for 4-8 weeks at such a dose (400 mumol/kg/day) that acid secretion was blocked almost completely during the period of study. This treatment was without effect on bone. However, the possibility could not be excluded that gastrectomized rats develop calcium deficiency for some reason other than lack of acid.(
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| 4. |
- Ravensburg, Anna Lena, 1994-, et al.
(författare)
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Boundary-induced phase in epitaxial iron layers
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report the discovery of a boundary-induced body-centered tetragonal (bct) iron phase in thin films deposited on MgAl2O4 (001) substrates. We present evidence for this phase using detailed x-ray analysis and ab-initio density functional theory calculations. A lower magnetic moment and a rotation of the easy magnetisation direction are observed, as compared to body-centered cubic (bcc) iron. Our findings expand the range of known crystal and magnetic phases of iron, providing valuable insights for the development of heterostructure devices using ultra-thin iron layers.
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| 5. |
- Ekström, Erik, 1989-, et al.
(författare)
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Epitaxial Growth of CaMnO3-y Films on LaAlO3 (112 over bar 0) by Pulsed Direct Current Reactive Magnetron Sputtering
- 2022
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Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley-V C H Verlag GMBH. - 1862-6254 .- 1862-6270. ; 16:4
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Tidskriftsartikel (refereegranskat)abstract
- CaMnO3 is a perovskite with attractive magnetic and thermoelectric properties. CaMnO3 films are usually grown by pulsed laser deposition or radio frequency magnetron sputtering from ceramic targets. Herein, epitaxial growth of CaMnO3-y (002) films on a (112 over bar 0)-oriented LaAlO3 substrate using pulsed direct current reactive magnetron sputtering is demonstrated, which is more suitable for industrial scale depositions. The CaMnO3-y shows growth with a small in-plane tilt of <approximate to 0.2 degrees toward the (200) plane of CaMnO3-y and the (1 over bar 104) with respect to the LaAlO3 (112 over bar 0) substrate. X-ray photoelectron spectroscopy of the electronic core levels shows an oxygen deficiency described by CaMnO2.58 that yields a lower Seebeck coefficient and a higher electrical resistivity when compared to stoichiometric CaMnO3. The LaAlO3 (112 over bar 0) substrate promotes tensile-strained growth of single crystals. Scanning transmission electron microscopy and electron energy loss spectroscopy reveal antiphase boundaries composed of Ca on Mn sites along and , forming stacking faults.
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| 6. |
- Ekström, Erik, et al.
(författare)
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Microstructure control and property switching in stress-free van der Waals epitaxial VO2 films on mica
- 2023
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Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 229
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Tidskriftsartikel (refereegranskat)abstract
- Realizing stress-free inorganic epitaxial films on weakly bonding substrates is of importance for applications that require film transfer onto surfaces that do not seed epitaxy. Film-substrate bonding is usually weakened by harnessing natural van der Waals layers (e.g., graphene) on substrate surfaces, but this is difficult to achieve in non-layered materials. Here, we demonstrate van der Waals epitaxy of stress-free films of a non-layered material VO2 on mica. The films exhibit out-of-plane 010 texture with three inplane orientations inherited from the crystallographic domains of the substrate. The lattice parameters are invariant with film thickness, indicating weak film-substrate bonding and complete interfacial stress relaxation. The out-of-plane domain size scales monotonically with film thickness, but the in-plane domain size exhibits a minimum, indicating that the nucleation of large in-plane domains supports subsequent island growth. Complementary ab initio investigations suggest that VO2 nucleation and van der Waals epitaxy involves subtle polarization effects around, and the active participation of, surface potassium atoms on the mica surface. The VO2 films show a narrow domain-size-sensitive electrical-conductiv ity-temperature hysteresis. These results offer promise for tuning the properties of stress-free van der Waals epitaxial films of non-layered materials such as VO2 through microstructure control (C) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 7. |
- Eriksson, Peter, et al.
(författare)
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Cerium Oxide Nanoparticles with Entrapped Gadolinium for High T-1 Relaxivity and ROS-Scavenging Purposes
- 2022
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:24, s. 21337-21345
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Tidskriftsartikel (refereegranskat)abstract
- Gadolinium chelates are employed worldwide today as clinical contrast agents for magnetic resonance imaging. Until now, the commonly used linear contrast agents based on the rare-earth element gadolinium have been considered safe and well-tolerated. Recently, concerns regarding this type of contrast agent have been reported, which is why there is an urgent need to develop the next generation of stable contrast agents with enhanced spin-lattice relaxation, as measured by improved T-1 relaxivity at lower doses. Here, we show that by the integration of gadolinium ions in cerium oxide nanoparticles, a stable crystalline 5 nm sized nanoparticulate system with a homogeneous gadolinium ion distribution is obtained. These cerium oxide nanoparticles with entrapped gadolinium deliver strong T-1 relaxivity per gadolinium ion (T-1 relaxivity, r(1) = 12.0 mM(-1) s(-1)) with the potential to act as scavengers of reactive oxygen species (ROS). The presence of Ce3+ sites and oxygen vacancies at the surface plays a critical role in providing the antioxidant properties. The characterization of radial distribution of Ce3+ and Ce4+ oxidation states indicated a higher concentration of Ce3+ at the nanoparticle surfaces. Additionally, we investigated the ROS-scavenging capabilities of pure gadolinium-containing cerium oxide nanoparticles by bioluminescent imaging in vivo, where inhibitory effects on ROS activity are shown.
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| 8. |
- Espinoza, Fredrik, et al.
(författare)
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GeoNotes: social and navigational aspects of location-based information systems
- 2001. - 1
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Ingår i: UBICOMP 2001. - : Swedish Institute of Computer Science.
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Location-based information systems allow the user to access information in relation to the user's position in geographical space. This paper outlines navigational and social aspects of such systems. It is argued that location-based systems must allow users to participate as content providers in order to achieve a social and dynamic information space. Moreover, as these systems allow commercial and private users to annotate space with information on a mass-scale, information filtering techniques will become essential in order to prevent information overload and user disturbance. We present a number of content-based and social filtering techniques to support this. We discuss implications for implementation and we describe a system (GeoNotes), which takes some of these aspects into account.
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| 9. |
- Halim, Joseph, et al.
(författare)
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Tailored synthesis approach of (Mo2/3Y1/3)(2)AlC i-MAX and its two-dimensional derivative Mo1.33CTz MXene: enhancing the yield, quality, and performance in supercapacitor applications
- 2021
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Ingår i: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 13:1, s. 311-319
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Tidskriftsartikel (refereegranskat)abstract
- A vacancy-ordered MXene, Mo1.33CTz, obtained from the selective etching of Al and Sc from the parent i-MAX phase (Mo2/3Sc1/3)(2)AlC has previously shown excellent properties for supercapacitor applications. Attempts to synthesize the same MXene from another precursor, (Mo2/3Y1/3)(2)AlC, have not been able to match its forerunner. Herein, we show that the use of an AlY2.3 alloy instead of elemental Al and Y for the synthesis of (Mo2/3Y1/3)(2)AlC i-MAX, results in a close to 70% increase in sample purity due to the suppression of the main secondary phase, Mo3Al2C. Furthermore, through a modified etching procedure, we obtain a Mo1.33CTz MXene of high structural quality and improve the yield by a factor of 6 compared to our previous efforts. Free-standing films show high volumetric (1308 F cm(-3)) and gravimetric (436 F g(-1)) capacitances and a high stability (98% retention) at the level of, or even beyond, those reported for the Mo1.33CTz MXene produced from the Sc-based i-MAX. These results are of importance for the realization of high quality MXenes through use of more abundant elements (Y vs. Sc), while also reducing waste (impurity) material and facilitating the synthesis of a high-performance material for applications.
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| 10. |
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