| 531. |
- Santana, Jordy, et al.
(författare)
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Temperature Impact on the Internal Resistance of a Polymer Electrolyte Fuel Cell Considering the Electrochemical Impedance Spectroscopy Diagnosis
- 2020. - 1
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Ingår i: Fuel Cell Seminar and Energy Exposition 2019. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. - 9781607685395 ; 96:1, s. 183-190
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Konferensbidrag (refereegranskat)abstract
- A polymer electrolyte fuel cell (PEFC) is an electrochemical device that converts the chemical energy presents in the hydrogen into electricity and heat having as by product only water. The energy conversion process is carried out in a clean and noiseless manner. Depending on the applications, a PEFC works at different operating temperature. In this study, the internal resistance of a PEFC is evaluated by using Electrochemical Impedance Spectroscopy (EIS) at moderate low current density, i.e., 0.5 A/cm2, in the temperature range of 40-80°C. The evaluation is carried out considering frequencies between 3.1kHz and 1Hz. An equivalent Randle circuit is considered as adjusted model and the Nyquist and Bode diagram were obtained to analyze the internal resistance. Results show that the ohmic resistance and charge transport increase when the operating temperature is low, decreasing the cell performance. A voltage drop of 42 mV was obtained for the evaluated temperature sweep. At the same time, it was demonstrated that the double layer capacitance increases at high temperatures, increasing its operating performance.
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| 532. |
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| 533. |
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| 534. |
- Selvaraj, Rengaraj, et al.
(författare)
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A simple hydrothermal route for the preparation of HgS nanoparticles and their photocatalytic activities
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:30, s. 15371-15376
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Tidskriftsartikel (refereegranskat)abstract
- HgS nanoparticles have been successfully prepared by a hydrothermal method using polyethylene glycol (PEG) as stabilizing agent and characterized by a variety of methods. Our experiments confirmed that the size of the HgS nanocrystals could be easily modified by tuning the chain length of PEG. X-ray powder diffraction (XRD) results for the nanoparticles revealed the hexagonal structure of the HgS, i. e. a-phase known as cinnabar. Morphological studies performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the synthesized nanocrystals were nanoparticles. Furthermore, a rational mechanism of the formation and evolution of the products was proposed. The optical properties of HgS were investigated by diffuse reflectance spectroscopy (DRS), which indicated that the band gap of the nanoparticles is slightly decreased from 2.05 to 2.00 eV as the average particle size decreases from 55 to 35 nm. Furthermore, the photocatalytic activity studies of the particles demonstrated their excellent photocatalytic performance in rapidly degrading aqueous methylene blue dye solution under visible light irradiation. These results suggest that HgS nanoparticles will be an interesting candidate of photocatalyst working in visible light range.
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| 535. |
- Skoglund, Charlotte, et al.
(författare)
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Familial confounding of the association between maternal smoking during pregnancy and ADHD in offspring
- 2014
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Ingår i: Journal of Child Psychology and Psychiatry. - Stockholm : Blackwell Publishing. - 0021-9630 .- 1469-7610. ; 55:1, s. 61-8
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Maternal Smoking During Pregnancy (SDP) has consistently been associated with increased risk of attention-deficit/hyperactivity disorder (ADHD) in offspring, but recent studies indicate that this association might be due to unmeasured familial confounding.METHODS: A total of 813,030 individuals born in Sweden between 1992 and 2000 were included in this nationwide population-based cohort study. Data on maternal SDP and ADHD diagnosis were obtained from national registers and patients were followed up from the age of 3 to the end of 2009. Hazard Ratios (HRs) were estimated using stratified Cox regression models. Cousin and sibling data were used to control for unmeasured familial confounding.RESULTS: At the population level maternal SDP predicted ADHD in offspring (HR(ModerateSDP) = 1.89; HR(HighSDP)= 2.50). This estimate gradually attenuated toward the null when adjusting for measured confounders (HR(ModerateSDP)= 1.62; HR(HighSDP)= 2.04), unmeasured confounders shared within the extended family (i.e., cousin comparison) (HR(ModerateSDP)= 1.45; HR(HighSDP)= 1.69), and unmeasured confounders within the nuclear family (i.e., sibling comparison) (HR(ModerateSDP)= 0.88; HR(HighSDP)= 0.84).CONCLUSIONS: Our results suggest that the association between maternal SDP and offspring ADHD are due to unmeasured familial confounding.
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| 536. |
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| 537. |
- Song, Jiao-Jiao, et al.
(författare)
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The 4f-Hybridization Strength in CemMnIn3m+2n Heavy-Fermion Compounds Studied by Angle-Resolved Photoemission Spectroscopy
- 2021
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Ingår i: Chinese Physics Letters. - : IOP Publishing. - 0256-307X .- 1741-3540. ; 38:10
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Tidskriftsartikel (refereegranskat)abstract
- We systemically investigate the nature of Ce 4f electrons in structurally layered heavy-fermion compounds CemMnIn3m+2n (with M = Co, Rh, Jr, and Pt, m = 1, 2, n = 0-2), at low temperature using on-resonance angle-resolved photoemission spectroscopy. Three heavy quasiparticle bands f(0), f(7/2)(1) and f(5/2)(1), are observed in all compounds, whereas their intensities and energy locations vary greatly with materials. The strong f(0) states imply that the localized electron behavior dominates the Ce 4f states. The Ce 4f electrons are partially hybridized with the conduction electrons, making them have the dual nature of localization and itinerancy. Our quantitative comparison reveals that the f(5/2)(1)-f (0) intensity ratio is more suitable to reflect the 4f-state hybridization strength.
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| 538. |
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| 539. |
- Su, Z., et al.
(författare)
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Small Islets are Essential for Successful Intraportal Transplantation in a Diabetes Mouse Model
- 2010
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Ingår i: Scandinavian Journal of Immunology. - : Wiley. - 1365-3083 .- 0300-9475. ; 72:6, s. 504-510
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Tidskriftsartikel (refereegranskat)abstract
- Optimization of islet transplantation protocols is necessary for improved success of treatment for type 1 diabetes. Here, we investigated whether the size of islets transplanted into the portal vein (PV) of the liver can affect engraftment in the early post-transplantation in an experimental mouse model. Small (average diameter < 250 mu m, group A) or large (average diameter > 250 mu m, group B) islets (400 islet equivalents/recipient) purified from normal BALB/c mice were transplanted into syngenic recipients with diabetes induced by STZ. The percentage of mice returning to a non-diabetic status was higher in group A (100%) than that of group B (62.5%). Focal areas of liver necrosis associated with the islets emboli were observed in both groups, but the pathology in group B was significantly worse. Multiple proinflammatory cytokines were significantly higher in group B than that of A at 3 h post-transplantation. Our study determined that the size of islets plays a critical role in the success of intraportal islet transplantation (IPIT) and should be taken into account in future IPIT protocols for the treatment of diabetes.
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| 540. |
- Sun, M. D., et al.
(författare)
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Fine structure in the alpha decay of U-223
- 2020
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Ingår i: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 800
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Tidskriftsartikel (refereegranskat)abstract
- Fine structure in the alpha decay of U-223 was observed in the fusion-evaporation reaction Re-187(Ar-40, p3n) by using fast digital pulse processing technique. Two alpha-decay branches of U-223 feeding the ground state and 244 keV excited state of Th-219 were identified by establishing the decay chain U-223 (alpha(1)) under right arrow Th-219 (alpha(2)) under right arrow Ra-215 (alpha(3)) under right arrow Rn-211. The alpha-particle energy for the ground-state to ground-state transition of U-223 was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62(-10)(+14) mu s. Evolution of nuclear structure for N = 131 even-Z isotones from Po to U was discussed in the frameworks of nuclear mass and reduced alpha-decay width, a weakening octupole deformation in the ground state of U-223 relative to its lighter isotones Ra-219 and Th-221 was suggested.
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