| 1. |
- Cedervall, Johan, et al.
(författare)
-
Magnetocaloric effect in Fe2 P: Magnetic and phonon degrees of freedom
- 2019
-
Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 99:17
-
Tidskriftsartikel (refereegranskat)abstract
- Devices based on magnetocaloric materials provide great hope for environmentally friendly and energy efficient cooling that does not rely on the use of harmful gasses. Fe2P based compounds are alloys that have shown great potential for magnetocaloric devices. The magnetic behavior in Fe2P is characterized by a strong magnetocaloric effect that coexists with a first-order magnetic transition (FOMT). Neutron diffraction and inelastic scattering, Mossbauer spectroscopy, and first-principles calculations have been used to determine the structural and magnetic state of Fe2P around the FOMT. The results reveal that ferromagnetic moments in the ordered phase are perturbed at the FOMT such that the moments cant away from the principle direction within a small temperature region. The acoustic-phonon modes reveal a temperature-dependent nonzero energy gap in the magnetically ordered phase that falls to zero at the FOMT. The interplay between the FOMT and the phonon energy gap indicates hybridization between magnetic modes strongly affected by spin-orbit coupling and phonon modes leading to magnon-phonon quasiparticles that drive the magnetocaloric effect.
|
|
| 2. |
- Lavén, Rasmus, 1994, et al.
(författare)
-
Diffusional Dynamics of Hydride Ions in the Layered Oxyhydride SrVO 2 H
- 2021
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 33:8, s. 2967-2975
-
Tidskriftsartikel (refereegranskat)abstract
- Perovskite-type oxyhydrides are hydride-ion-conducting materials of promise for several types of technological applications; however, the conductivity is often too low for practical use and, on a fundamental level, the mechanism of hydride-ion diffusion remains unclear. Here, we, with the use of neutron scattering techniques, investigate the diffusional dynamics of hydride ions in the layered perovskite-type oxyhydride SrVO2H. By monitoring the intensity of the elastically scattered neutrons upon heating the sample from 100 to 430 K, we establish an onset temperature for diffusional hydride-ion dynamics at about 250 K. Above this temperature, the hydride ions are shown to exhibit two-dimensional diffusion restricted to the hydride-ion sublattice of SrVO2H and that occurs as a series of jumps of a hydride ion to a neighboring hydride-ion vacancy, with an enhanced rate for backward jumps due to correlation effects. Analysis of the temperature dependence of the neutron scattering data shows that the localized jumps of hydride ions are featured by a mean residence time of the order of 10 ps with an activation energy of 0.1 eV. The long-range diffusion of hydride ions occurs on the timescale of 1 ns and with an activation energy of 0.2 eV. The hydride-ion diffusion coefficient is found to be of the order of 1 × 10-6 cm2 s-1 in the temperature range of 300-430 K, which is similar to other oxyhydrides but higher than for proton-conducting perovskite analogues. Tuning of the hydride-ion vacancy concentration in SrVO2H thus represents a promising gateway to improve the ionic conductivity of this already highly hydride-ion-conducting material.
|
|
| 3. |
- Torstensson, Anders, et al.
(författare)
-
Synergism between elevated pCO2 and temperature on the Antarctic sea ice diatom Nitzschia lecointei
- 2013
-
Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 10, s. 6391-6401
-
Tidskriftsartikel (refereegranskat)abstract
- Polar oceans are particularly susceptible to ocean acidification and warming. Diatoms play a significant role in sea ice biogeochemistry and provide an important food source to grazers in ice-covered oceans, especially during early spring. However, the ecophysiology of ice-living organisms has received little attention in terms of ocean acidification. In this study, the synergism between temperature and partial pressure of CO2 (pCO2) was investigated in relationship to the optimal growth temperature of the Antarctic sea ice diatom Nitzschia lecointei. Diatoms were kept in cultures at controlled levels of pCO2 (∼390 and ∼960 μatm) and temperature (−1.8 and 2.5 °C) for 14 days. Synergism between temperature and pCO2 was detected in growth rate and acyl lipid fatty acid (FA) content. Optimal growth rate was observed around 5 °C in a separate experiment. Carbon enrichment only promoted (6%) growth rate closer to the optimal growth, but not at the control temperature (−1.8 °C). At −1.8 °C and at ∼960 μatm pCO2, the total FA content was reduced relative to the ∼390 μatm treatment, although no difference between pCO2 treatments was observed at 2.5 °C. A large proportion (97%) of the total FAs comprised on average of polyunsaturated fatty acids (PUFA) at −1.8 °C. Cellular PUFA content was reduced at ∼960 relative to ∼390 μatm pCO2. Effects of carbon enrichment may be different depending on ocean warming scenario or season, e.g. reduced cellular FA content in response to elevated CO2 at low temperatures only, reflected as reduced food quality for higher trophic levels. Synergy between warming and acidification may be particularly important in polar areas since a narrow thermal window generally limits cold-water organisms.
|
|
| 4. |
- Andersson, Mikael, 1988, et al.
(författare)
-
Interplay of NH4+ and BH4- reorientational dynamics in NH4BH4
- 2020
-
Ingår i: Physical Review Materials. - 2475-9953. ; 4:8
-
Tidskriftsartikel (refereegranskat)abstract
- The reorientational dynamics of ammonium borohydride (NH4BH4) was studied using quasielastic neutron scattering in the temperature interval from 10 to 240 K, which covers both the dynamically ordered and disordered polymorphs of NH4BH4. In the low-temperature (50 K) ordered polymorph of NH4BH4, analysis of the quasielastic neutron scattering data reveals that no reorientational dynamics is present within the probed timescale region of 0.1 to 100 ps. In the high-temperature (50 K) disordered polymorph, the analysis establishes the onset of NH4+ and BH4- dynamics at around 50 and 125 K, respectively. The relaxation time at 150 K for NH4+ is approximately 1 ps, while around 100 ps for BH4- . The NH4+ dynamics at temperatures below 125 K is associated with preferential tetrahedral tumbling motions, where each of the hydrogen atoms in the NH4+ tetrahedron can visit any of the four hydrogen sites, however, reorientations around a specific axis are more frequently occurring (C-2 or C3). At higher temperatures, the analysis does not exclude a possible evolution of the NH4+ dynamics from tetrahedral tumbling to either cubic tumbling, where the hydrogen atoms can visit any of the eight positions corresponding to the corners of a cube, or isotropic rotational diffusion, where the hydrogen atoms can visit any location on the surface of a sphere. The BH4- dynamics can be described as cubic tumbling. The difference in reorientational dynamics between the two ions is related to the difference of the local environment where the dynamically much slower BH4- anion imposes a noncubic environment on the NH4+ cation.
|
|
| 5. |
- Andersson, Mikael, 1988
(författare)
-
Nanoparticle Magnetism: Superspin Glasses
- 2019
-
Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 19:8, s. 4903-4910
-
Tidskriftsartikel (refereegranskat)abstract
- This article discusses the magnetic super-phase, which occurs in strongly interacting magnetic nanoparticle systems. The phase is a nanoparticle analog to the atomic magnetic spin glass phase and is therefore called a superspin glass. Experimental data for a dense maghemite nanoparticle compact is presented and it is shown that this system forms a superspin glass phase by undergoing a second order phase transition. Below its transition temperature the system exhibits non-equilibrium dynamical properties similar to those of atomic spin glasses. It was shown that it is possible to tune the transition temperature by choosing the size of the particles used to make the compact. By mixing two sizes of particles (9 and 11.5 nm) and making compacts of different relative concentration of these sizes it was shown that it is the average dipolar interaction which determines the transition temperature.
|
|
| 6. |
|
|
| 7. |
- Aramrattana, Maytheewat, 1988-, et al.
(författare)
-
Remote Driving Operation (REDO) project : final report
- 2023
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents experimental setups and findings from the REDO project, which had been conducted between December 2019 and February 2023. Five main topics are covered in this report: 1) Effects of latency and field-of-view on driving performance; 2) Remote driving feedback and control; 3) Connectivity and mobile network support for remote driving; 4) Video transmission for remote driving; and 5) Laws and regulations concerning remote driving. Contents of this report dives into technical details and findings within each topic. Nevertheless, this report does not intend to repeat all detail and results published in scientific publications, and thus this report should be seen as complementary material to the published results.
|
|
| 8. |
- Berg, Matilda, 1989-, et al.
(författare)
-
Internet-based CBT for adolescents with low self-esteem : a pilot randomized controlled trial
- 2022
-
Ingår i: Cognitive Behaviour Therapy. - : Routledge. - 1650-6073 .- 1651-2316. ; 51:5, s. 388-407
-
Tidskriftsartikel (refereegranskat)abstract
- Low self-esteem is a common problem among adolescents and is related to psychiatric problems such as depression and anxiety. However, effective and available interventions primarily targeting low self-esteem are scarce, in particular for youths. To address this gap, the aim of this pilot study was to evaluate a novel internet-based Cognitive Behavioral Therapy (ICBT) program for low self-esteem in adolescents using a randomized controlled design. Fifty-two participants (15-19 years) were recruited and randomly allocated to seven weeks of therapist-supported ICBT (n=26) or to a waitlist control condition (n=26). The primary outcome was the Rosenberg Self-Esteem Scale (RSES). Secondary outcomes measured domain-specific aspects of self-esteem, self-compassion, quality of life, depression and anxiety. The treatment group showed significantly higher levels of self-rated self-esteem compared to the control group at post-treatment, with a large between-group effect-size (RSES, d = 1.18). Further, the treatment had significant positive impact on secondary measures of self-esteem, self-compassion, quality of life, depression and anxiety. The results of this pilot-RCT suggest that ICBT can be effective for treating low self-esteem in adolescents, decrease depression and anxiety levels, and increasing quality of life. Replication of the results in larger samples is needed.
|
|
| 9. |
- Cedervall, Johan, et al.
(författare)
-
Phase stability and structural transitions in compositionally complex LnMO 3 perovskites
- 2021
-
Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 300
-
Tidskriftsartikel (refereegranskat)abstract
- Entropy stabilised materials have possibilities for tailoring functionalities to overcome challenges in materials science. The concept of configurational entropy can also be applied to metal oxides, but it is unclear whether these could be considered as solid solutions in the case of perovskite-structured oxides and if the configurational entropy plays a stabilising role. In this study, compositionally complex perovskite oxides, LnMO3 (Ln = La, Nd, Sm, Ca and Sr, M = Ti, Cr, Mn, Fe, Co, Ni, and Cu), are investigated for their phase stability and magnetic behaviour. Phase-pure samples were synthesised, and the room temperature structures were found to crystallise in either Pnma or R3¯c space groups, depending on the composition and the resulting tolerance factor, while the structural transition temperatures correlate with the pseudo cubic unit cell volume. The techniques used included diffraction with X-rays and neutrons, both ex- and in-situ, X-ray photoelectron spectroscopy, magnetometry as well as electron microscopy. Neutron diffraction studies on one sample reveal that no oxygen vacancies are found in the structure and that the magnetic properties are ferrimagnetic-like with magnetic moments mainly coupled antiferromagnetically along the crystallographic c-direction. X-ray photoelectron spectroscopy gave indications of the oxidation states of the constituting ions where several mixed oxidation states are observed in these valence-compensated perovskites.
|
|
| 10. |
- Dimitrievska, Mirjana, et al.
(författare)
-
Structural and Dynamical Properties of Potassium Dodecahydro-monocarba-closo-dodecaborate: KCB11H12
- 2020
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:33, s. 17992-18002
-
Tidskriftsartikel (refereegranskat)abstract
- MCB11H12 (M: Li, Na) dodecahydro-monocarba-closo-dodecaborate salt compounds are known to have stellar superionic Li+ and Na+ conductivities in their high-temperature disordered phases, making them potentially appealing electrolytes in all-solid-state batteries. Nonetheless, it is of keen interest to search for other related materials with similar conductivities while at the same time exhibiting even lower (more device-relevant) disordering temperatures, a key challenge for this class of materials. With this in mind, the unknown structural and dynamical properties of the heavier KCB11H12 congener were investigated in detail by X-ray powder diffraction, differential scanning calorimetry, neutron vibrational spectroscopy, nuclear magnetic resonance, quasielastic neutron scattering, and AC impedance measurements. This salt indeed undergoes an entropy-driven, reversible, order-disorder transformation and with a lower onset temperature (348 K upon heating and 340 K upon cooling) in comparison to the lighter LiCB11H12 and NaCB11H12 analogues. The K+ cations in both the low-T ordered monoclinic (P2(1)/c) and high-T disordered cubic (Fm (3) over barm) structures occupy octahedral interstices formed by CB11H12- anions. In the low-T structure, the anions orient themselves so as to avoid close proximity between their highly electropositive C-H vertices and the neighboring K+ cations. In the high-T structure, the anions are orientationally disordered, although to best avoid the K+ cations, the anions likely orient themselves so that their C-H axes are aligned in one of eight possible directions along the body diagonals of the cubic unit cell. Across the transition, anion reorientational jump rates change from 6.2 x 10(6) s(-1) in the low-T phase (332 K) to 2.6 x 10(10) s(-1) in the high-T phase (341 K). In tandem, K+ conductivity increases by about 30-fold across the transition, yielding a high-T phase value of 3.2 x 10(-4 )S cm(-1 )at 361 K. However, this is still about 1 to 2 orders of magnitude lower than that observed for LiCB(11)H(12 )and NaCB11H12, suggesting that the relatively larger K+ cation is much more sterically hindered than Li+ and Na+ from diffusing through the anion lattice via the network of smaller interstitial sites.
|
|
| 11. |
- Ek, Gustav, et al.
(författare)
-
Hydrogen induced structure and property changes in Eu3Si4
- 2019
-
Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 277, s. 37-45
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrides Eu3Si4H2-X were obtained by exposing the Zintl phase Eu3Si4 to a hydrogen atmosphere at a pressure of 30 bar and temperatures from 25 to 300 degrees C. Structural analysis using powder X-ray diffraction (PXRD) data suggested that hydrogenations in a temperature range 25-200 degrees C afford a uniform hydride phase with an orthorhombic structure (Immm, a approximate to 4.40 angstrom, b approximate to 3.97 angstrom, c approximate to 19.8 angstrom), whereas at 300 degrees C mixtures of two orthorhombic phases with c approximate to 19.86 and approximate to 19.58 angstrom were obtained. The assignment of a composition Eu3Si4H2+x is based on first principles DFT calculations, which indicated a distinct crystallographic site for H in the Eu3Si4 structure. In this position, H atoms are coordinated in a tetrahedral fashion by Eu atoms. The resulting hydride Eu3Si4H2 is stable by -0.46 eV/H atom with respect to Eu3Si4 and gaseous H-2. Deviations between the lattice parameters of the DFT optimized Eu3Si4H2 structure and the ones extracted from PXRD patterns pointed to the presence of additional H in interstitials also involving Si atoms. Subsequent DFT modeling of compositions Eu3Si4H3 and Eu3Si4H4 showed considerably better agreement to the experimental unit cell volumes. It was then concluded that the hydrides of Eu3Si4 have a composition Eu3Si4H2+x (x
|
|
| 12. |
- Filippov, Stanislav, et al.
(författare)
-
Analysis of Dihydrogen Bonding in Ammonium Borohydride
- 2019
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:47, s. 28631-28639
-
Tidskriftsartikel (refereegranskat)abstract
- The structural and vibrational properties of ammonium borohydride, NH4BH4, have been examined by first-principles density functional theory (DFT) calculations and inelastic neutron scattering (INS). The H disordered crystal structure of NH4BH4 is composed of the tetrahedral complex ions NH4+ and BH4-, which are arranged as in the fcc NaCl structure and linked by intermolecular dihydrogen bonding. Upon cooling, the INS spectra revealed a structural transition between 45 and 40 K. The reversible transition occurs upon heating between 46 and 49 K. In the low-temperature form reorientational dynamics are frozen. The libration modes for BH4- and NH4+ are near 300 and 200 cm(-1), respectively. Upon entering the fcc high-temperature form, NH4+ ions attain fast reorientational dynamics, as indicated in the disappearance of the NH4+ libration band, whereas BH4- ions become significantly mobile only at temperatures above 100 K. The vibrational behavior of BH4- ions in NH4BH4 compares well to the heavier alkali metal borohydrides, NaBH4-CsBH4. DFT calculations revealed a nondirectional nature of the dihydrogen bonding in NH4BH4 with only weak tendency for long-range order. Different rotational configurations of complex ions appear quasi-degenerate, which is reminiscent of glasses.
|
|
| 13. |
|
|
| 14. |
- Gustavsson, Klas, 1988-, et al.
(författare)
-
Simulating traffic management strategies at the Swedish emergency call center
-
Tidskriftsartikel (refereegranskat)abstract
- In telecommunication research, the assessment of strategic and operational performance has gained a lot of interest. So far, the variability within the operational research of telecommunication derives from the stochastic nature of call arrivals, call duration and abandonments. This study extends the stochastic drivers to capacity by incorporating agent behavior. In this study, we model a Discrete-Event-Simulation model of the Swedish emergency call service provider to assist the strategic issue of skills-based routing. Because of the pull system, we designed skills-based routing using an event-dependent overflow setting with a fixed waiting time threshold, where calls become visible to extended agent classes after a threshold value, providing an advantage to primary idle agents to answer before idle secondary agents. Our model mimics the tail of waiting times better than conventional methods. Because of the accompanied calculation opportunities, the model has assisted both strategic and operational issues in the organization. In addition to practical implications, the study proves that the stochastic nature of agent behavior is crucial. From a queueing theory perspective, the study provides interesting routing effects for an event-dependent overflow setting using a fixed waiting time threshold in a combined “X-N-design”, previously unexplored in research.
|
|
| 15. |
- Karlsson, Stefan, et al.
(författare)
-
Detection of abnormal activities on a SM or MM fiber
- 2023
-
Ingår i: 2023 Optical Fiber Communications Conference and Exhibition, OFC 2023 - Proceedings.
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate eavesdrop detection based on polarization signatures by analyzing polarization state changes at the receiver. We identify changes related to the normal operation and the ones caused by eavesdropping.
|
|
| 16. |
|
|
| 17. |
- Sanchez, Elena H., et al.
(författare)
-
Simultaneous Individual and Dipolar Collective Properties in Binary Assemblies of Magnetic Nanoparticles
- 2020
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 32:3, s. 969-981
-
Tidskriftsartikel (refereegranskat)abstract
- Applications based on aggregates of magnetic nanoparticles are becoming increasingly widespread, ranging from hyperthermia to magnetic recording. However, although some uses require collective behavior, others need a more individual-like response, the conditions leading to either of these behaviors are still poorly understood. Here, we use nanoscale-uniform binary random dense mixtures with different proportions of oxide magnetic nanoparticles with low/high anisotropy as a valuable tool to explore the crossover from individual to collective behavior. Two different anisotropy scenarios have been studied in two series of binary compacts: M1, comprising maghemite (gamma-Fe2O3) nanoparticles of different sizes (9.0 nm/11.5 nm) with barely a factor of 2 between their anisotropy energies, and M2, mixing equally sized pure maghemite (low-anisotropy) and Co-doped maghemite (high-anisotropy) nanoparticles with a large difference in anisotropy energy (ratio > 8). Interestingly, while the M1 series exhibits collective behavior typical of strongly coupled dipolar systems, the M2 series presents a more complex scenario where different magnetic properties resemble either "individual-like" or "collective", crucially emphasizing that the collective character must be ascribed to specific properties and not to the system as a whole. The strong differences between the two series offer new insight (systematically ratified by simulations) into the subtle interplay between dipolar interactions, local anisotropy and sample heterogeneity to determine the behavior of dense assemblies of magnetic nanoparticles.
|
|
| 18. |
- Talemi, Soheil Rastgou, et al.
(författare)
-
Systems Level Analysis of the Yeast Osmo-Stat
- 2016
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Adaptation is an important property of living organisms enabling them to cope with environmental stress and maintaining homeostasis. Adaptation is mediated by signaling pathways responding to different stimuli. Those signaling pathways might communicate in order to orchestrate the cellular response to multiple simultaneous stimuli, a phenomenon called crosstalk. Here, we investigate possible mechanisms of crosstalk between the High Osmolarity Glycerol (HOG) and the Cell Wall Integrity (CWI) pathways in yeast, which mediate adaptation to hyper- and hypo-osmotic challenges, respectively. We combine ensemble modeling with experimental investigations to test in quantitative terms different hypotheses about the crosstalk of the HOG and the CWI pathways. Our analyses indicate that for the conditions studied i) the CWI pathway activation employs an adaptive mechanism with a variable volume-dependent threshold, in contrast to the HOG pathway, whose activation relies on a fixed volume-dependent threshold, ii) there is no or little direct crosstalk between the HOG and CWI pathways, and iii) its mainly the HOG alone mediating adaptation of cellular osmotic pressure for both hyper- as well as hypo-osmotic stress. Thus, by iteratively combining mathematical modeling with experimentation we achieved a better understanding of regulatory mechanisms of yeast osmo-homeostasis and formulated new hypotheses about osmo-sensing.
|
|
| 19. |
- Thollander, Patrik, 1976-, et al.
(författare)
-
Generella praktiska riktlinjer för framgångsrik energiledning i svensk massa- och pappersindustri
- 2019
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna studie har bl.a. lett till nya insikter och en fördjupad förståelse för energiledning ur ett styrningsperspektiv. Det finns idag endast ett fåtal studier på energiledning med liknande perspektiv (Schulze et al., 2018, 2016; Virtanen et al., 2013) varför fortsatt forskning starkt rekommenderas. Den multipla fallstudien visade att det finns skillnader i organisering och styrning för energiledning även mellan liknande företag inom samma industri. Dessa skillnader kan till synes härledas till den strategiska riktning respektive företag tagit i sitt energiarbete. Ett ramverk har utvecklats som visar på vilka aktiviteter som bör prioriteras för att möjliggöra för ett proaktivt energiarbete. Fallstudien som fokuserade på investeringsprocessen och dess aktiviteter och procedurer stärker dessa slutsatser: energi bör på operativ nivå integreras som ett kriterium vid investeringar samt på strategisk nivå som en strategisk prioritet.
|
|
