| 1. |
- Kanai, M, et al.
(författare)
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- 2023
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swepub:Mat__t
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| 2. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 12. |
- Frost, Ray L., et al.
(författare)
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Combination bands in the infrared spectroscopy of kaolins : a drift spectroscopic study
- 1998
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Ingår i: Clays and clay minerals. - 0009-8604 .- 1552-8367. ; 46:4, s. 466-477
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Tidskriftsartikel (refereegranskat)abstract
- Kaolinites with varying degrees of defect structures have been studied by both mid-infrared (IR) and near-IR diffuse reflectance spectroscopy (DRIFT). Difference bands were observed in the 2650to 2750-cm-1 region. This region coincides with the kaolinite-deuterated hydroxyl stretching region. Summation bands were observed in the near-IR spectra in the 4500- to 4650-cm-1 and in the 7050- to 7250cm-1 region. Each of the spectral regions of the summation and difference bands is both kaolin polytype and sample dependent. It is proposed that each of these sets of bands arises from the combination of the hydroxyl stretching frequencies and the hydroxyl deformation frequencies and, to a lesser extent, the silicon-oxygen symmetric stretching vibration of the siloxane layer. Additional difference bands of very low intensity were also observed at 2930 and 2856 cm-1. Combination bands were observed in all kaolinites at 2137 and 2227 cm-1. Each of the 3 major combination spectral regions was composed of 5 component bands corresponding to the 4 IR active and the 1 Raman active kaolinite hydroxyl stretching frequencies. Combination bands were also observed at ∼1932 and 1821 cm-1.
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| 13. |
- Frost, Ray L., et al.
(författare)
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Raman spectroscopy at temperatures between 298 and 423 K and at 77 K of kaolinites intercalated with formamide
- 1998
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Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555. ; 29:12, s. 1065-1069
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectra of kaolinite and of the formamide-intercalated kaolinite were obtained at both 298 and 77 K using a Raman microprobe equipped with a thermal stage. Upon cooling to 77 K, the band attributed to the inner hydroxyl shifts by 5 cm-1 to lower wavenumbers and the bands assigned to the inner surface hydroxyls move to higher wavenumbers. Upon intercalation of the kaolinite with formamide, an additional Raman band attributed to the formation of a hydrogen-bonded complex between the inner surface hydroxyls and the carbonyl group of the formamide is observed at 3627 cm-1 at 298 K and at 3631 cm-1 at 77 K. Raman spectra of the deintercalation of the formamide-intercalated kaolinite are obtained by using the thermal stage to heat the intercalated kaolinite in situ. A decrease in intensity of the bands formed through intercalation and at the same time an increase in intensity of the inner surface hydroxyl bands are observed. A loss of intensity of the low-wavenumber region of the formamide-intercalated kaolinite is also observed.
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| 14. |
- Jarvis, Erich D., et al.
(författare)
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Whole-genome analyses resolve early branches in the tree of life of modern birds
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 346:6215, s. 1320-1331
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Tidskriftsartikel (refereegranskat)abstract
- To better determine the history of modern birds, we performed a genome-scale phylogenetic analysis of 48 species representing all orders of Neoaves using phylogenomic methods created to handle genome-scale data. We recovered a highly resolved tree that confirms previously controversial sister or close relationships. We identified the first divergence in Neoaves, two groups we named Passerea and Columbea, representing independent lineages of diverse and convergently evolved land and water bird species. Among Passerea, we infer the common ancestor of core landbirds to have been an apex predator and confirm independent gains of vocal learning. Among Columbea, we identify pigeons and flamingoes as belonging to sister clades. Even with whole genomes, some of the earliest branches in Neoaves proved challenging to resolve, which was best explained by massive protein-coding sequence convergence and high levels of incomplete lineage sorting that occurred during a rapid radiation after the Cretaceous-Paleogene mass extinction event about 66 million years ago.
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| 15. |
- Johansson, Ursula, et al.
(författare)
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Isotopic exchange of kaolinite hydroxyl protons: a diffuse reflectance infrared Fourier transform spectroscopy study
- 1998
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Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 123:4, s. 641-645
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Tidskriftsartikel (refereegranskat)abstract
- Specific surface reactions on kaolinite were investigated by deuterium exchange of the hydroxyl protons of kaolinite, The kaolinite samples were reacted with deuterium oxide for 48 h and 2.5 and 5 weeks, at various pH values (3, natural and 8) and at different temperatures (ambient, and 30, 60 and 100 degrees C), Analyses were performed using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The spectral results show that it is very difficult at room temperature to exchange the hydroxyl protons isotopically with deuterons at the surface of kaolinite, The temperature and the reaction time must be increased for successful exchange. It was found that the most suitable temperature for isotopic exchange was 60 degrees C. The pH did not significantly influence the deuteration, Only at high pH were changes of the OD bands in the DRIFT spectra observed, This study shows that it is possible to deuterate kaolinite without using intercalation. All three types of hydroxyl protons from the inner, inner surface and edge were exchanged.
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| 16. |
- Johansson, Ursula, et al.
(författare)
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Raman spectroscopy of the kaolinite hydroxyls at 77 K
- 1998
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 52:10, s. 1277-1282
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectroscopy of two types of kaolinites has been obtained at liquid nitrogen temperature (77 K) with the use of a Raman microprobe and a thermal stage. The Raman spectrum is characterized by the combination of the frequencies of the inner hydroxyl and the inner surface hydroxyl groups. The inner hydroxyl frequency is reduced, and the outer hydroxyl frequencies move to higher frequencies upon cooling to 77 K. The inner hydroxyl frequency shifts from 3620 cm-1 at 298 K to 3615 cm-1 at 77 K. The two in-phase inner surface hydroxyl frequencies move from 3684 and 3689 cm-1 at 298 K to 3690 and 3699 cm-1 at 77 K. The two out-of-phase vibrations shift from 3650 and 3668 cm-1 to 3656 and 3675 cm-1. The bandwidth of the inner hydroxyl frequency decreases from 3.7 to 2.1 cm-1 at 77 K. The bandwidth of the inner surface hydroxyl frequency (upsilon 1) increases upon cooling from 17.4 to 19.2 cm-1. It is proposed that the increased resolution at low temperature enabled an additional inner surface hydroxyl frequency to be observed.
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| 19. |
- Liang, Kongqiu, et al.
(författare)
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A modified critical load assessment method of heavy metals in paddy soil at large scale
- 2023
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Ingår i: Journal of Cleaner Production. - 0959-6526 .- 1879-1786. ; 416
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Tidskriftsartikel (refereegranskat)abstract
- The environmental capacity of agro-ecosystem is the basis of sustainable development of agriculture, but this is hard to evaluate quantitatively due to complex input and output processes of heavy metals. Therefore, in this study, leaching of heavy metals based on PROFILE weathering model were integrated into the steady-state critical load (SSCL) of heavy metals. The results showed that the leaching rates of Hg, As, Cd, Cr, Pb, Cu and Zn in paddy soil were 0.08, 4.69, 0.22, 44.31, 18.13, 21.96 and 64.42 g/ha ‧a, respectively, while the leaching rates were significantly correlated with pH, CaO, TFe2O3 and Corg.. Atmospheric deposition was the main input source of heavy metals in agricultural soil, while rice plant uptake and leaching were the main output pathways. The spatial distribution of SSCL were mainly affected by the content of heavy metals in soil, Aw (specific area of soil mineral), and ρ (bulk density). Values of SSCL hardly changed after about 40 years (Hg≈0.02 kg/ha, As≈0.60 kg/ha, Cd≈0.07 kg/ha, Cr≈ 5.59 kg/ha, Pb≈3.55 kg/ha, Cu≈1.49 kg/ha and Zn≈4.45 kg/ha). However, the sensitivity analysis indicated that soil leaching had 24.30%-27.90% positive effects on SSCL model. Based on the relationship among leaching, pH, standard limit and SSCL of heavy metals, the standard limit could be appropriately raised to cope with the increased human activities on the premise of the ecological capacity. Thus, the SSCL model provides a new insight for the establishment of environment management in agricultural soils.
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