| 31. |
- Singha, A. D., et al.
(författare)
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Reentrant canonical spin-glass dynamics and tunable field-induced transitions in (GeMn)Co2O4 Kagomé lattice
- 2024
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 36:7
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Tidskriftsartikel (refereegranskat)abstract
- We report on the reentrant canonical semi spin-glass characteristics and controllable field-induced transitions in distorted Kagomé symmetry of (GeMn)Co2O4. This B-site spinel exhibits complicated, yet interesting magnetic behaviour in which the longitudinal ferrimagnetic (FiM) order sets in below the Néel temperature TFN ∼ 77 K due to uneven moments of divalent Co (↑ 5.33 μB) and tetravalent Mn (↓ 3.87 μB) which coexists with transverse spin-glass state below 72.85 K. Such complicated magnetic behaviour is suggested to result from the competing anisotropic superexchange interactions (JAB/kB ∼ 4.3 K, JAA/kB ∼ −6.2 K and JBB/kB ∼ −3.3 K) between the cations, which is extracted following the Néel's expression for the two-sublattice model of FiM. Dynamical susceptibility (χac (f, T)) and relaxation of thermoremanent magnetization, MTRM (t) data have been analysed by means of the empirical scaling-laws such as Vogel–Fulcher law and Power law of critical slowing down. Both of which reveal the reentrant spin-glass like character which evolves through a number of intermediate metastable states. The magnitude of Mydosh parameter (Ω ∼ 0.002), critical exponent zυ = (6.7 ± 0.07), spin relaxation time τ0 = (2.33 ± 0.1) × 10−18 s, activation energy Ea/kB = (69.8 ± 0.95) K and interparticle interaction strength (T0 = 71.6 K) provide the experimental evidences for canonical spin-glass state below the spin freezing temperature TF = 72.85 K. The field dependence of TF obtained from χac (T) follows the irreversibility in terms of de Almeida–Thouless mean-field instability in which the magnitude of crossover scaling exponent Φ turns out to be ∼2.9 for the (Ge0.8Mn0.2)Co2O4. Isothermal magnetization plots reveal two field-induced transitions across 9.52 kOe (HSF1) and 45.6 kOe (HSF2) associated with the FiM domains and spin-flip transition, respectively. Analysis of the inverse paramagnetic susceptibility after subtracting the temperature independent diamagnetic term (=−3 × 10−3 emu mol−1 Oe−1) results in the effective magnetic moment = 7.654 μB/f.u. This agrees well with the theoretically obtained = 7.58 μB/f.u. resulting the cation distribution in support of the Hund's ground state spin configuration and of Mn4+ and Co2+, respectively. The H–T phase diagram has been established by analysing all the parameters (TF(H), TFN(H), HSF1(T) and HSF2(T)) extracted from various magnetization measurements. This diagram enables clear differentiation among the different phases of the (GeMn)Co2O4 and also illustrates the demarcation between short-range and long-range ordered regions.
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| 32. |
- Singha, Gaurav, et al.
(författare)
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Strain-controlled fatigue in B-modified Ti-6Al-4V alloys
- 2013
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 69:9, s. 698-701
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Tidskriftsartikel (refereegranskat)abstract
- The strain-controlled fatigue behaviour of Ti-6Al-4V alloy with up to 0.11 wt.% B addition was investigated. Results show significant softening when the strain amplitudes, ΔεT/2, are ⩾0.75%. B addition was found to improve the fatigue life for ΔεT/2 ⩽ 0.75% as it corresponds to the elastic regime and hence strength dominated. At ΔεT/2 = 1%, in contrast, the base alloy exhibits higher life as TiB particle cracking due to strain incompatibility renders easy crack nucleation in the B-modified alloys.
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| 33. |
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| 34. |
- Agudelo, Leandro Z
(författare)
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Skeletal muscle PGC-1α1 and KAT enzymes at the intersection between depression and metabolic disease
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Depression and metabolic diseases are leading causes of disability and major contributors to socioeconomic burden worldwide. Physical activity exerts many beneficial effects that confer direct health improvement in individuals suffering from these disorders. However, the molecular mechanisms underlying the influence of different components of exercise interventions remain unknown. To isolate the impact of skeletal muscle conditioning on stress-induced depression, we used transgenic models that exhibit many of the chronic adaptations to aerobic exercise in skeletal muscle. Here, we show a mechanism by which skeletal muscle PGC-1α1 modulates kynurenine metabolism and mediates resilience to stress-induced depression. PGC-1α1 acts in concert with PPARα/δ transcription factors to induce the expression of kynurenine aminotransferases in skeletal muscle. The activity of this pathway diverts the metabolism of stress-induced kynurenine to kynurenic acid. Since kynurenic acid is unable to cross the blood brain barrier, this peripheral shift protects the brain from stress-induced accumulation of kynurenines. In addition, we further show that skeletal muscle PGC-1α1 and kynurenine aminotransferases are part of the physiological adaptations to aerobic exercise in both rodents and humans. Given that exercise-mediated activation of this pathway leads to peripheral accumulation of kynurenic acid, we evaluated the physiological role of this metabolite in modulating energy homeostasis. Here, we describe that kynurenic acid plays a role in systemic energy homeostasis through the regulation of adipose tissue function and inflammation. Kynurenic acid induces the expression of lipid metabolism, thermogenic and anti-inflammatory gene networks in the white adipose compartment. This reduces body-weight gain and improves glucose tolerance in animals fed a high-fat diet. Mechanistic studies in primary adipocytes show that kynurenic acid activates the G protein-coupled receptor 35. Downstream signaling of this activation is mediated through Ca2+, ERK, CREB and PGC-1α1 stabilization. Finally, activation of GPR35 by kynurenic acid induces the expression of RGS14, which sensitizes β-adrenergic response to specific agonists. In sum, this work uncovers a previously unknown function of PGC-1α1 in skeletal muscle and kynurenic acid in white adipose tissue. Targeting this metabolic node has great potential for the treatment of depression and metabolic diseases such as type-2 diabetes.
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| 35. |
- Agudo, A, et al.
(författare)
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Consumption of vegetables, fruit and other plant foods in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohorts from 10 European countries
- 2002
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Ingår i: Public Health Nutrition. - 1475-2727. ; 5:6B, s. 1179-1196
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To describe and compare the consumption of the main groups and subgroups of vegetables and fruits (V&F) in men and women from the centres participating in the European Prospective Investigation into Cancer and Nutrition (EPIC). Design: Cross-sectional analysis. Dietary intake was assessed by means of a 24-hour dietary recall using computerised interview software and standardised procedures. Crude and adjusted means were computed for the main groups and sub-groups of V&F by centre, separately for men and women. Adjusted means by season, day of the week and age were estimated using weights and covariance analysis. Setting: Twenty-seven centres in 10 European countries participating in the EPIC project. Subjects: In total, 35 955 subjects (13 031 men and 22 924 women), aged 35-74 years, randomly selected from each EPIC cohort. Results: The centres from southern countries had the highest consumption of V&F, while the lowest intake was seen in The Netherlands and Scandinavia for both genders. These differences were more evident for fruits, particularly citrus. However, slightly different patterns arose for some sub-groups of vegetables, such as root vegetables and cabbage. Adjustment for body mass index, physical activity, smoking habits and education did not substantially modify the mean intakes of vegetables and fruits. vegetable and fruit intake follows a south-north gradient in both Conclusions:. Total, genders, whereas for several sub-groups of vegetables a different geographic distribution exists. Differences in mean intake of V&F by centre were not explained by lifestyle factors associated with VF intake.
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| 36. |
- Agudo, Antonio, et al.
(författare)
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Hemochromatosis (HFE) gene mutations and risk of gastric cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) study
- 2013
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Ingår i: Carcinogenesis. - : Oxford University Press. - 0143-3334 .- 1460-2180. ; 34:6, s. 1244-1250
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Tidskriftsartikel (refereegranskat)abstract
- Hereditary hemochromatosis (HH) is a strong risk factor for hepatocellular cancer, and mutations in the HFE gene associated with HH and iron overload may be related to other tumors, but no studies have been reported for gastric cancer (GC). A nested case-control study was conducted within the European Prospective Investigation into Cancer and Nutrition (EPIC), including 365 incident gastric adenocarcinoma and 1284 controls matched by center, sex, age and date of blood collection. Genotype analysis was performed for two functional polymorphisms (C282Y/rs1800562 and H63D/rs1799945) and seven tagSNPs of the HFE genomic region. Association with all gastric adenocarcinoma, and according to anatomical localization and histological subtype, was assessed by means of the odds ratio (OR) and 95% confidence interval (CI) estimated by unconditional logistic regression adjusted for the matching variables. We observed a significant association for H63D with OR (per rare allele) of 1.32 (CI = 1.03-1.69). In subgroup analyses, the association was stronger for non-cardia anatomical subsite (OR = 1.60, CI = 1.16-2.21) and intestinal histological subtype (OR = 1.82, CI = 1.27-2.62). Among intestinal cases, two tagSNPs (rs1572982 and rs6918586) also showed a significant association that disappeared after adjustment for H63D. No association with tumors located in the cardia or with diffuse subtype was found for any of the nine SNPs analyzed. Our results suggest that H63D variant in HFE gene seems to be associated with GC risk of the non-cardia region and intestinal type, possibly due to its association with iron overload although a role for other mechanisms cannot be entirely ruled out.
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| 37. |
- Al-Zoubi, Noura, et al.
(författare)
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Elastic properties of 4d transition metal alloys : Values and trends
- 2019
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Ingår i: Computational materials science. - : ELSEVIER SCIENCE BV. - 0927-0256 .- 1879-0801. ; 159, s. 273-280
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Tidskriftsartikel (refereegranskat)abstract
- Using the Exact Muffin-Tin Orbitals method within the Perdew-Burke-Ernzerhof exchange-correlation approximation for solids and solid surfaces (PBEso1), we study the single crystal elastic constants of 4d transition metals (atomic number Z between 39 and 47) and their binary alloys in the body centered cubic (bcc) and face centered cubic (fcc) structures. Alloys between the first neighbors Z(Z + 1) and between the second neighbors Z(Z + 2) are considered. The lattice constants, bulk moduli and elastic constants are found in good agreement with the available experimental and theoretical data. It is shown that the correlation between the relative tetragonal shear elastic constant C-fcc'-2C(bcc)' and the structural energy difference between the fcc and bcc lattices Delta E is superior to the previously considered models. For a given crystal structure, the equiatomic Z(Z + 2) alloys turn out to have similar structural and elastic properties as the pure elements with atomic number (Z + 1). Furthermore, alloys with composition Z(1-x)(Z + 2)(x) possess similar properties as Z(1-2x)(Z + 1)(2x). The present theoretical data on the structural and the elastic properties of 4d transition metal alloys provides consistent input for coarse scale modeling of material properties.
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| 38. |
- Al-Zoubi, Noura, et al.
(författare)
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Influence of Magnesium on hydrogenated ScAl1-xMgx alloys : a theoretical study
- 2011
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 50:10, s. 2848-2853
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio total energy calculations, based on the projector augmented wave method and the exact mu±n-tin orbitals method in combination with the coherent-potential approximation, are used to examine the effect of magnesium on hydrogen absorption/desorption temperature and phase stability of hydrogenated ScAl1-xMgx (0 ≤ x ≤ 0:3) alloys. According to the experiments, ScAl1-xMgx adopts the CsCl structure, and upon hydrogen absorption it decomposes into ScH2 with CaF2 structure and Al-Mg with face centered cubic structure. Here we demonstrate that the stability field of the hydrogenated alloys depends sensitively on Mg content and on the microstructure of the decomposed system. For a given microstructure, the critical temperature for hydrogen absorption/desorption increases with Mg concentration.
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| 39. |
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| 40. |
- Capek, Miloslav, et al.
(författare)
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Numerical Benchmark based on characteristic modes of a spherical shell
- 2017
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Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - 9781538632840 ; 2017-January, s. 965-966
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Konferensbidrag (refereegranskat)abstract
- Characteristic modes of a spherical shell are found analytically and compared with numerical solutions acquired from both in-house and commercial packages. These studies led to a proposal of several independent benchmarks, all with analytically known results. Dependence on mesh size, electrical size and other parameters can easily be incorporated. It is observed that all contemporary implementations have limitations.
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