| 1. |
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| 2. |
- Kattge, Jens, et al.
(författare)
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TRY plant trait database - enhanced coverage and open access
- 2020
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
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Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 3. |
- Tavares, Julia, et al.
(författare)
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Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests
- 2023
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 617:7959, s. 111-117
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Tidskriftsartikel (refereegranskat)abstract
- Tropical forests face increasing climate risk(1,2), yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, ?(50)) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk(3-5), little is known about how these vary across Earth's largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters ?(50) and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both ?(50) and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM(50 )forests. We propose that this may be associated with a growth-mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon(6,7), with strong implications for the Amazon carbon sink.
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| 4. |
- Abbafati, Cristiana, et al.
(författare)
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- 2020
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
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| 7. |
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| 8. |
- Ribeiro Jr, Luiz Antonio, et al.
(författare)
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Spin-Orbit Effects on the Dynamical Properties of Polarons in Graphene Nanoribbons
- 2018
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The dynamical properties of polarons in armchair graphene nanoribbons (GNR) is numerically investigated in the framework of a two-dimensional tight-binding model that considers spin-orbit (SO) coupling and electron-lattice (e-l) interactions. Within this physical picture, novel polaron properties with no counterparts to results obtained from conventional tight-binding models are obtained. Our findings show that, depending on the systems width, the presence of SO coupling changes the polarons charge localization giving rise to different degrees of stability for the charge carrier. For instance, the joint action of SO coupling and e-l interactions could promote a slight increase on the charge concentration in the center of the lattice deformation associated to the polaron. As a straightforward consequence, this process of increasing stability would lead to a depreciation in the polarons motion by decreasing its saturation velocity. Our finds are in good agreement with recent experimental investigations for the charge localization in GNR, mostly when it comes to the influence of SO coupling. Moreover, the contributions reported here provide a reliable method for future works to evaluate spin-orbit influence on the performance of graphene nanoribbons.
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| 9. |
- Stanaway, Jeffrey D., et al.
(författare)
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Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks for 195 countries and territories, 1990-2017: A systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 392:10159, s. 1923-1994
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Tidskriftsartikel (refereegranskat)abstract
- Background The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 comparative risk assessment (CRA) is a comprehensive approach to risk factor quantification that offers a useful tool for synthesising evidence on risks and risk-outcome associations. With each annual GBD study, we update the GBD CRA to incorporate improved methods, new risks and risk-outcome pairs, and new data on risk exposure levels and risk- outcome associations. Methods We used the CRA framework developed for previous iterations of GBD to estimate levels and trends in exposure, attributable deaths, and attributable disability-adjusted life-years (DALYs), by age group, sex, year, and location for 84 behavioural, environmental and occupational, and metabolic risks or groups of risks from 1990 to 2017. This study included 476 risk-outcome pairs that met the GBD study criteria for convincing or probable evidence of causation. We extracted relative risk and exposure estimates from 46 749 randomised controlled trials, cohort studies, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. Using the counterfactual scenario of theoretical minimum risk exposure level (TMREL), we estimated the portion of deaths and DALYs that could be attributed to a given risk. We explored the relationship between development and risk exposure by modelling the relationship between the Socio-demographic Index (SDI) and risk-weighted exposure prevalence and estimated expected levels of exposure and risk-attributable burden by SDI. Finally, we explored temporal changes in risk-attributable DALYs by decomposing those changes into six main component drivers of change as follows: (1) population growth; (2) changes in population age structures; (3) changes in exposure to environmental and occupational risks; (4) changes in exposure to behavioural risks; (5) changes in exposure to metabolic risks; and (6) changes due to all other factors, approximated as the risk-deleted death and DALY rates, where the risk-deleted rate is the rate that would be observed had we reduced the exposure levels to the TMREL for all risk factors included in GBD 2017.
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| 10. |
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| 11. |
- Bousquet, Jean, et al.
(författare)
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Allergic Rhinitis and its Impact on Asthma (ARIA) Phase 4 (2018) : Change management in allergic rhinitis and asthma multimorbidity using mobile technology
- 2019
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Ingår i: Journal of Allergy and Clinical Immunology. - : Elsevier. - 0091-6749 .- 1097-6825. ; 143:3, s. 864-879
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Tidskriftsartikel (refereegranskat)abstract
- Allergic Rhinitis and its Impact on Asthma (ARIA) has evolved from a guideline by using the best approach to integrated care pathways using mobile technology in patients with allergic rhinitis (AR) and asthma multimorbidity. The proposed next phase of ARIA is change management, with the aim of providing an active and healthy life to patients with rhinitis and to those with asthma multimorbidity across the lifecycle irrespective of their sex or socioeconomic status to reduce health and social inequities incurred by the disease. ARIA has followed the 8-step model of Kotter to assess and implement the effect of rhinitis on asthma multimorbidity and to propose multimorbid guidelines. A second change management strategy is proposed by ARIA Phase 4 to increase self-medication and shared decision making in rhinitis and asthma multimorbidity. An innovation of ARIA has been the development and validation of information technology evidence-based tools (Mobile Airways Sentinel Network [MASK]) that can inform patient decisions on the basis of a self-care plan proposed by the health care professional.
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| 12. |
- Canestraro, Carla Daniele, et al.
(författare)
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Strong inter-conduction-band absorption in heavily fluorine doped tin oxide
- 2008
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 255:5, s. 1874-1879
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Tidskriftsartikel (refereegranskat)abstract
- The optical, electrical and structural properties of thin. film tin oxide (TO), F-doped tin oxide (FTO; n(F) approximate to 6 x 10(20) cm (3)) and highly F-doped tin oxide (hFTO; n(F) approximate to 10 x 10(20) cm (3)), grown by spray pyrolysis technique, are studied by atomic force microscopy, Hall effect, X-ray. fluorescence and transmission/reflection measurements. The resistivity (rho = 32 x 10 (4) Omega cm for intrinsic tin oxide) shows intriguing characteristics when F concentration n(F) is increased (rho = 6 x 10 (4) Omega cm for FTO but 25 x 10 (4) Omega cm for hFTO) whereas the carrier concentration is almost constant at high F concentration (n(c) approximate to 6 x 10(20) cm (3) for FTO and hFTO). Thus, F seems to act both as a donor and a compensating acceptor in hFTO. The high carrier concentration has a strong effect on the optical band-edge absorption. Whereas intrinsic TO has room-temperature band-gap energy of E-g approximate to 3.2 eV with an onset to absorption at about 3.8 eV, the highly doped FTO and hFTO samples show relatively strong absorption at 2-3 eV. Theoretical analysis based on density functional calculations of FTO reveals that this is not a defect state within the band-gap region, but instead a consequence of a hybridization of the F donor states with the host conduction band in combination with a band. filling of the lowest conduction band by the free carriers. This allows photon-assisted inter-conduction band transitions of the free electrons to energetically higher and empty conduction bands, producing the below-gap absorption peak.
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| 13. |
- Hudson, Lawrence N, et al.
(författare)
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The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
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Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
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| 14. |
- Nguyen, Thanh N, et al.
(författare)
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Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: A 1-Year Follow-up.
- 2023
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Ingår i: Neurology. - 1526-632X. ; 100:4
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Tidskriftsartikel (refereegranskat)abstract
- Declines in stroke admission, IV thrombolysis (IVT), and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the effect of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), IVT, and mechanical thrombectomy over a 1-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020).We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, IVT treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases.There were 148,895 stroke admissions in the 1 year immediately before compared with 138,453 admissions during the 1-year pandemic, representing a 7% decline (95% CI [95% CI 7.1-6.9]; p < 0.0001). ICH volumes declined from 29,585 to 28,156 (4.8% [5.1-4.6]; p < 0.0001) and IVT volume from 24,584 to 23,077 (6.1% [6.4-5.8]; p < 0.0001). Larger declines were observed at high-volume compared with low-volume centers (all p < 0.0001). There was no significant change in mechanical thrombectomy volumes (0.7% [0.6-0.9]; p = 0.49). Stroke was diagnosed in 1.3% [1.31-1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82-2.97], 5,656/195,539) of all stroke hospitalizations.There was a global decline and shift to lower-volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared with the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year.This study is registered under NCT04934020.
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| 15. |
- Oliveira, Camila, et al.
(författare)
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Surface studies of the chemical environment in gold nanorods supported by X-ray photoelectron spectroscopy (XPS) and ab initio calculations
- 2021
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Ingår i: JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T. - : Elsevier BV. - 2238-7854. ; 15, s. 768-776
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Tidskriftsartikel (refereegranskat)abstract
- In this manuscript, we prepared gold nanorods (Au-NRs) through "silver-assisted seeded methodology" and studied their outermost layer using XPS spectroscopy and ab initio calculations to compare the chemical states of the constituents of the metallic core. Supporting first-principles calculations employing a relativistic, full-potential and all-electron method, with augmented plane waves plus local orbitals as a basis set, ensure proper treatment of the core electron states. Three significant findings can be reported. First, we found that besides Au (0), there are two chemical states for silver, namely Ag (0) and Ag(I), on the Au surface. Our results corroborate with recent results reported in the literature, indicating that Ag monolayer can be oxidized to Ag(I) during the steps of centrifugation and washing with diluted CTAB solution. Second, ab initio simulations showed that Ag atoms have different binding energies, depending on their configuration in Au-NRs (whether silver atoms are found on the surface or if they are spread in bulk as interstitial or substitutional defects). Third, theoretical studies showed that silver atoms located at interstitial sites could distort the crystalline structure, and, therefore, we do not expect interstitial Ag to occur in Au-NRs.
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| 16. |
- Ribeiro, Luiz Antonio, et al.
(författare)
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Dynamic Formation of Bipolaron-Exciton Complexes in Conducting Polymers
- 2018
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Ingår i: Journal of Physical Chemistry A. - : AMER CHEMICAL SOC. - 1089-5639 .- 1520-5215. ; 122:15, s. 3866-3872
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Tidskriftsartikel (refereegranskat)abstract
- The recombination dynamics of two oppositely charged bipolarons within a single polymer chain is numerically studied in the scope of a one-dimensional tight-binding model that considers electron electron and electron-phonon (e-ph) interactions. By scanning among values of e-ph coupling and electric field, novel channels for the bipolaron recombination were yielded based on the interplay between these two parameters. The findings point to the formation of a compound species formed from the coupling between a bipolaron and an exciton. Depending on the electric field and e-ph coupling strengths, the recombination mechanism may yield two distinct products: a trapped (and almost neutral) or a moving (and partially charged) bipolaron-exciton. These results might enlighten the understanding of the electroluminescence processes in organic light-emitting devices.
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| 17. |
- Roman, L. S., et al.
(författare)
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Optical band-edge absorption of oxide compound SnO2
- 2006
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 252:15, s. 5361-5364
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Tidskriftsartikel (refereegranskat)abstract
- Tin oxide (SnO2) is an important oxide for efficient dielectrics, catalysis, sensor devices, electrodes and transparent conducting coating oxide technologies. SnO2 thin film is widely used in glass applications due to its low infra-red heat emissivity. In this work, the SnO2 electronic band-edge structure and optical properties are studied employing a first-principle and fully relativistic full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The optical band-edge absorption alpha(omega) of intrinsic SnO2 is investigated experimentally by transmission spectroscopy measurements and their roughness in the light of the atomic force microscopy (AFM) measurements. The sample films were prepared by spray pyrolysis deposition method onto glass substrate considering different thickness layers. We found for SnO2 qualitatively good agreement of the calculated optical band-gap energy as well as the optical absorption with the experimental results.
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| 18. |
- Silva, Gesiel Gomes, et al.
(författare)
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Influence of quasi-particle density over polaron mobility in armchair graphene nanoribbons
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 20:24, s. 16712-16718
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Tidskriftsartikel (refereegranskat)abstract
- An important aspect concerning the performance of armchair graphene nanoribbons (AGNRs) as materials for conceiving electronic devices is related to the mobility of charge carriers in these systems. When several polarons are considered in the system, a quasi-particle wave function can be affected by that of its neighbor provided the two are close enough. As the overlap may affect the transport of the carrier, the question concerning how the density of polarons affect its mobility arises. In this work, we investigate such dependence for semiconducting AGNRs in the scope of nonadiabatic molecular dynamics. Our results unambiguously show an impact of the density on both the stability and average velocity of the quasi-particles. We have found a phase transition between regimes where increasing density stops inhibiting and starts promoting mobility; densities higher than 7 polarons per 45 angstrom present increasing mean velocity with increasing density. We have also established three different regions relating electric field and average velocity. For the lowest electric field regime, surpassing the aforementioned threshold results in overcoming the 0.3 angstrom fs(-1) limit, thus representing a transition between subsonic and supersonic regimes. For the highest of the electric fields, density effects alone are responsible for a stunning difference of 1.5 angstrom fs(-1) in the mean carrier velocity.
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| 19. |
- Tavella, Tatyana Almeida, et al.
(författare)
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Violacein-Induced Chaperone System Collapse Underlies Multistage Antiplasmodial Activity.
- 2021
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Ingår i: ACS Infectious Diseases. - : American Chemical Society (ACS). - 2373-8227. ; 7:4, s. 759-776
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Tidskriftsartikel (refereegranskat)abstract
- Antimalarial drugs with novel modes of action and wide therapeutic potential are needed to pave the way for malaria eradication. Violacein is a natural compound known for its biological activity against cancer cells and several pathogens, including the malaria parasite, Plasmodium falciparum (Pf). Herein, using chemical genomic profiling (CGP), we found that violacein affects protein homeostasis. Mechanistically, violacein binds Pf chaperones, PfHsp90 and PfHsp70-1, compromising the latter's ATPase and chaperone activities. Additionally, violacein-treated parasites exhibited increased protein unfolding and proteasomal degradation. The uncoupling of the parasite stress response reflects the multistage growth inhibitory effect promoted by violacein. Despite evidence of proteotoxic stress, violacein did not inhibit global protein synthesis via UPR activation-a process that is highly dependent on chaperones, in agreement with the notion of a violacein-induced proteostasis collapse. Our data highlight the importance of a functioning chaperone-proteasome system for parasite development and differentiation. Thus, a violacein-like small molecule might provide a good scaffold for development of a novel probe for examining the molecular chaperone network and/or antiplasmodial drug design.
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| 20. |
- Almeida, Cristiane G., et al.
(författare)
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Photocatalytic hydrogen production with visible light over Mo and Cr-doped BiNb(Ta)O-4
- 2014
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 39:3, s. 1220-1227
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, we prepared pure and Cr(III) and Mo(V)-doped BiNbO4 and BiTaO4 by the citrate method. Pure BiNbO4 and BiTaO4 were obtained in triclinic phase at 600 degrees C and 800 degrees C, respectively. The metal doping influenced strongly the crystal structure as well as the photocatalytic activity of the oxides. The XRD data could prove that the Mo(V) doping induces the orthorhombic phase, while the Cr(III) doping favors the triclinic phase for both oxides. Metal doping also modified the photosensitivity of the oxides, extending the absorption toward the visible light region. The photocatalytic activity in water splitting under visible light irradiation was evaluated by monitoring the H-2, CO2 and CO evolution. The results showed that Cr(III)-doped BiTaO4 and BiNbO4, in general, are more selective for hydrogen production, while Mo(V)-doped materials are more selective for CO2 generation. Comparing the photocatalytic activity of BiTaO4 and BiNbO4, the former shows higher activity for hydrogen production as well as for CO2 generation, specially when the concentration was 2% in Cr(III) and Mo(V), respectively. Those results are in agreement with the computational study to access the effect of doping on the electronic structure. For Mo(V)-doped materials a negligible change of conduction band minimum potential was found, indicating that there might be no improvement on the reduction power of the material following the substitutional doping. In Cr(III)-doped BiNbO4 there is a slight shift of the CBM potential increasing a little bit the reduction power. However, the effect is much stronger in the Cr(III)-doped BiTaO4.
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| 21. |
- Arun, K. G., et al.
(författare)
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New horizons for fundamental physics with LISA
- 2022
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Ingår i: Living Reviews in Relativity. - : Springer Science and Business Media LLC. - 1433-8351 .- 2367-3613. ; 25:1
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Forskningsöversikt (refereegranskat)abstract
- The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of gravitational waves can be expected to provide key input. We provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. These connections must be developed for LISA to live up to its science potential in these areas.
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| 22. |
- da Cunha, Wiliam Ferreira, et al.
(författare)
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Reactive Scattering between Excitons and Charge Carriers in Conjugated Polymers
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:41, s. 23451-23458
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Tidskriftsartikel (refereegranskat)abstract
- The temperature influence on the scattering process between an exciton and a positively charged carrier (polaron or bipolaron) is theoretically investigated using a version of the SuSchriefferHeeger (SSH) model modified to include temperature, Coulomb interactions, and an external electric field. In general, it is observed that the products of the reactive scattering are spin independent when thermal effects are taken into account. For the interaction between a polaron and an exciton, the polaron can be annihilated, when subjected to temperatures higher than a critical value, or pass through the exciton maintaining both their consistencies, if a lower temperature regime is considered. Regarding the recombination between a bipolaron and an exciton, it is observed that the bipolaron can be annihilated whereas the exciton dissociates into two trions or into one polaron and one trion. In all cases, the recombination mechanisms depend on a suitable balance between temperature and electric field. These results may extend the knowledge about electroluminescence process in conjugated polymers, thus being of potential use to improve internal quantum efficiency in polymer light-emitting diodes.
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| 23. |
- Ferreira da Cunha, Wiliam, et al.
(författare)
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Impurity effects on polaron dynamics in graphene nanoribbons
- 2015
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 91, s. 171-177
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Tidskriftsartikel (refereegranskat)abstract
- The impurity effects on the dynamics of polarons in armchair graphene nanoribbons are numerically investigated in the scope of a two-dimensional tight-binding approach with lattice relaxation. The results show that the presence of an impurity changes significantly the net charge distribution associated to the polaron structure. Moreover, the interplay between external electric field and the local impurities plays the role of drastically modifying the polaron dynamics. Interestingly, nanoribbons containing mobile polarons are noted to take place even when considering high impurity levels, which is associated with the highly conductive character of the graphene nanoribbons. This investigation may enlighten the understanding of the charge transport mechanism in carbon-based nanomaterials. (C) 2015 Elsevier Ltd. All rights reserved.
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| 24. |
- Ferreira Monteiro, Fabio, et al.
(författare)
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Encapsulated beta-carotene in ZnO nanotubes: Theoretical insight into the stabilization dynamics
- 2015
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Ingår i: Chemical Physics Letters. - : ELSEVIER SCIENCE BV. - 0009-2614 .- 1873-4448. ; 636, s. 62-66
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Tidskriftsartikel (refereegranskat)abstract
- The stabilization dynamics of a molecular dye (beta-carotene) encapsulated in single-wall zinc oxide nanotubes (ZnONTs) is theoretically investigated in the scope of molecular dynamics and density functional theory simulations. Our findings show that the beta-carotene encapsulation in ZnONTs is an energetically favorable process. Once encapsulated, this molecular dye remains close to the ZnONT wall, in accordance with recent experimental reports. Interestingly, the interaction between the beta-carotene and ZnONT can form a charge delocalization state, where an amount of charge concentrated on beta-carotene is transferred to ZnONT. (C) 2015 Elsevier B.V. All rights reserved.
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| 25. |
- Naghavi, Mohsen, et al.
(författare)
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Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013
- 2015
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Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 385:9963, s. 117-171
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Tidskriftsartikel (refereegranskat)abstract
- Background Up-to-date evidence on levels and trends for age-sex-specifi c all-cause and cause-specifi c mortality is essential for the formation of global, regional, and national health policies. In the Global Burden of Disease Study 2013 (GBD 2013) we estimated yearly deaths for 188 countries between 1990, and 2013. We used the results to assess whether there is epidemiological convergence across countries. Methods We estimated age-sex-specifi c all-cause mortality using the GBD 2010 methods with some refinements to improve accuracy applied to an updated database of vital registration, survey, and census data. We generally estimated cause of death as in the GBD 2010. Key improvements included the addition of more recent vital registration data for 72 countries, an updated verbal autopsy literature review, two new and detailed data systems for China, and more detail for Mexico, UK, Turkey, and Russia. We improved statistical models for garbage code redistribution. We used six different modelling strategies across the 240 causes; cause of death ensemble modelling (CODEm) was the dominant strategy for causes with sufficient information. Trends for Alzheimer's disease and other dementias were informed by meta-regression of prevalence studies. For pathogen-specifi c causes of diarrhoea and lower respiratory infections we used a counterfactual approach. We computed two measures of convergence (inequality) across countries: the average relative difference across all pairs of countries (Gini coefficient) and the average absolute difference across countries. To summarise broad findings, we used multiple decrement life-tables to decompose probabilities of death from birth to exact age 15 years, from exact age 15 years to exact age 50 years, and from exact age 50 years to exact age 75 years, and life expectancy at birth into major causes. For all quantities reported, we computed 95% uncertainty intervals (UIs). We constrained cause-specific fractions within each age-sex-country-year group to sum to all-cause mortality based on draws from the uncertainty distributions. Findings Global life expectancy for both sexes increased from 65.3 years (UI 65.0-65.6) in 1990, to 71.5 years (UI 71.0-71.9) in 2013, while the number of deaths increased from 47.5 million (UI 46.8-48.2) to 54.9 million (UI 53.6-56.3) over the same interval. Global progress masked variation by age and sex: for children, average absolute diff erences between countries decreased but relative diff erences increased. For women aged 25-39 years and older than 75 years and for men aged 20-49 years and 65 years and older, both absolute and relative diff erences increased. Decomposition of global and regional life expectancy showed the prominent role of reductions in age-standardised death rates for cardiovascular diseases and cancers in high-income regions, and reductions in child deaths from diarrhoea, lower respiratory infections, and neonatal causes in low-income regions. HIV/AIDS reduced life expectancy in southern sub-Saharan Africa. For most communicable causes of death both numbers of deaths and age-standardised death rates fell whereas for most non-communicable causes, demographic shifts have increased numbers of deaths but decreased age-standardised death rates. Global deaths from injury increased by 10.7%, from 4.3 million deaths in 1990 to 4.8 million in 2013; but age-standardised rates declined over the same period by 21%. For some causes of more than 100 000 deaths per year in 2013, age-standardised death rates increased between 1990 and 2013, including HIV/AIDS, pancreatic cancer, atrial fibrillation and flutter, drug use disorders, diabetes, chronic kidney disease, and sickle-cell anaemias. Diarrhoeal diseases, lower respiratory infections, neonatal causes, and malaria are still in the top five causes of death in children younger than 5 years. The most important pathogens are rotavirus for diarrhoea and pneumococcus for lower respiratory infections. Country-specific probabilities of death over three phases of life were substantially varied between and within regions. Interpretation For most countries, the general pattern of reductions in age-sex specifi c mortality has been associated with a progressive shift towards a larger share of the remaining deaths caused by non-communicable disease and injuries. Assessing epidemiological convergence across countries depends on whether an absolute or relative measure of inequality is used. Nevertheless, age-standardised death rates for seven substantial causes are increasing, suggesting the potential for reversals in some countries. Important gaps exist in the empirical data for cause of death estimates for some countries; for example, no national data for India are available for the past decade.
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| 26. |
- Nisar, Jawad, 1980-, et al.
(författare)
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Study of electronic and optical properties of BiTaO4 for photocatalysis
- 2012
-
Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley-VCH Verlagsgesellschaft. - 1610-1634 .- 1610-1642. ; 9:7, s. 1593-1596
-
Tidskriftsartikel (refereegranskat)abstract
- We present the optical absorption spectrum of BiTaO4 using the photo acoustic spectroscopy (PAS) technique and first principle approach. Band gap have been estimated 2.65 and 2.45 eV using PAS method and DFT calculations, respectively. Position of reduction and oxidation level with respect to vacuum level are identified, which shows that BiTaO4 can be used as photocatalyst for hydrogen production. Electronic structure is explained by plotting total density of states (TDOS).
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| 27. |
- Ribeiro, Luiz Antonio, et al.
(författare)
-
Bloch oscillations in organic and inorganic polymers
- 2017
-
Ingår i: Journal of Chemical Physics. - : AMER INST PHYSICS. - 0021-9606 .- 1089-7690. ; 146:14
-
Tidskriftsartikel (refereegranskat)abstract
- The transport of polarons above the mobility threshold in organic and inorganic polymers is theoretically investigated in the framework of a one-dimensional tight-binding model that includes lattice relaxation. The computational approach is based on parameters for which the model Hamiltonian suitably describes different polymer lattices in the presence of external electric fields. Our findings show that, above critical field strengths, a dissociated polaron moves through the polymer lattice as a free electron performing Bloch oscillations. These critical electric fields are considerably smaller for inorganic lattices in comparison to organic polymers. Interestingly, for inorganic lattices, the free electron propagates preserving charge and spin densities localization which is a characteristic of a static polaron. Moreover, in the turning points of the spatial Bloch oscillations, transient polaron levels are formed inside the band gap, thus generating a fully characterized polaron structure. For the organic case, on the other hand, no polaron signature is observed: neither in the shape of the distortion-those polaron profile signatures are absent-nor in the energy levels-as no such polaron levels are formed during the simulation. These results solve controversial aspects concerning Bloch oscillations recently reported in the literature and may enlighten the understanding about the charge transport mechanism in polymers above their mobility edge. Published by AIP Publishing.
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| 28. |
- Ribeiro, Luiz Antonio, et al.
(författare)
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Charge Carrier Scattering in Polymers: A New Neutral Coupled Soliton Channel
- 2018
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamical scattering of two oppositely charged bipolarons in non-degenerate organic semiconducting lattices is numerically investigated in the framework of a one-dimensional tight-biding-Hubbard model that includes lattice relaxation. Our findings show that it is possible for the bipolaron pair to merge into a state composed of a confined soliton-antisoliton pair, which is characterized by the appearance of states within less than 0.1 eV from the Fermi level. This compound is in a narrow analogy to a meson confining a quark-antiquark pair. Interestingly, solitons are quasi-particles theoretically predicted to arise only in polymer lattices with degenerate ground state: in the general case of nondegenerate ground state polymers, isolated solitons are not allowed.
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| 29. |
- Ribeiro, Luiz Antonio, et al.
(författare)
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Concentration effects on intrachain polaron recombination in conjugated polymers
- 2015
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 17:2, s. 1299-1308
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of different charge carrier concentrations on the recombination dynamics between oppositely charged polarons is numerically investigated using a modified version of the Su-Schrieffer-Heeger (SSH) model that includes an external electric field and electron-electron interactions. Our findings show that the external electric field can play the role of avoiding the formation of excited states (polaron-exciton and neutral excitation) leading the system to a dimerized lattice. Interestingly, depending on a suitable balance between the polaron concentration and the electric field strength, the recombination mechanism can form stable polaron-excitons or neutral excitations. These results may provide guidance to improve the electroluminescence efficiency in Polymer Light Emitting Diodes.
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| 30. |
- Ribeiro, Luiz Antonio, et al.
(författare)
-
Temperature effects on intrachain recombination of bipolarons in conjugated polymers
- 2014
-
Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 614, s. 151-155
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Tidskriftsartikel (refereegranskat)abstract
- The temperature influence over the intrachain recombination dynamics between oppositely charged bipolarons has been theoretically investigated using a version of the Su-Schrieffer-Heeger model. The results shown that, below of a critical temperature regime, these charge carriers can recombine into a biexciton. This excited state is a light emissive specie that can emit one photon and turn into an exciton state. This specie can thereafter decay to the ground state by other photon emission. This knowledge can enlighten the understanding needed to improve the internal quantum efficiency of electroluminescence in Polymer Light Emitting Diodes.
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| 31. |
- Ribeiro, Luiz Antonio, et al.
(författare)
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Transport of Polarons in Graphene Nanoribbons
- 2015
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society. - 1948-7185. ; 6:3, s. 510-514
-
Tidskriftsartikel (refereegranskat)abstract
- The field-induced dynamics of polarons in armchair graphene nanoribbons (GNRs) is theoretically investigated in the framework of a two-dimensional tight-binding model with lattice relaxation. Our findings show that the semiconductor behavior, fundamental to polaron transport to take place, depends upon of a suitable balance between the GNR width and the electronphonon (eph) coupling strength. In a similar way, we found that the parameter space for which the polaron is dynamically stable is limited to an even narrower region of the GNR width and the eph coupling strength. Interestingly, the interplay between the external electric field and the eph coupling plays the role to define a phase transition from subsonic to supersonic velocities for polarons in GNRs.
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| 32. |
- Soares, Rodrigo P., et al.
(författare)
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Highlights of the São Paulo ISEV workshop on extracellular vesicles in cross-kingdom communication
- 2017
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Ingår i: Journal of Extracellular Vesicles. - : Wiley. - 2001-3078. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- In the past years, extracellular vesicles (EVs) have become an important field of research since EVs have been found to play a central role in biological processes. In pathogens, EVs are involved in several events during the host–pathogen interaction, including invasion, immunomodulation, and pathology as well as parasite–parasite communication. In this report, we summarised the role of EVs in infections caused by viruses, bacteria, fungi, protozoa, and helminths based on the talks and discussions carried out during the International Society for Extracellular Vesicles (ISEV) workshop held in São Paulo (November, 2016), Brazil, entitled Cross-organism Communication by Extracellular Vesicles: Hosts, Microbes and Parasites.
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| 33. |
- Wang, Baochang, et al.
(författare)
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Optical and electronic properties of nanosized BiTaO4 and BiNbO4 photocatalysts : Experiment and theory
- 2014
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 251:5, s. 1034-1039
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Tidskriftsartikel (refereegranskat)abstract
- Nanosized BiTaO4 and BiNbO4 were prepared by the citrate method. The electronic and optical properties of BiTaO4 and BiNbO4 have been investigated by means of photo-acoustic spectroscopy (PAS), X-ray photo-electron spectroscopy (XPS), and first-principles calculations based on density functional theory. The measured valence band (from XPS) of both materials agreed well with the theoretical findings. It was also found that the calculated optical properties such as dynamical dielectric function and optical absorption spectra are in good agreement with the experimental findings. According to the absorption spectra, the absorption edges of BiNbO4 and BiTaO4 are located at 370 and 330nm, respectively. Both phases have the ability to harvest UV light and relatively high surface area to volume ratio and can be used as UV/visible light-driven photocatalysts.
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| 34. |
- Alnoor, Hatim, 1979-
(författare)
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Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One-dimensional (1D) nanostructures (NSs) of Zinc Oxide (ZnO) such as nanorods (NRs) have recently attracted considerable research attention due to their potential for the development of optoelectronic devices such as ultraviolet (UV) photodetectors and light-emitting diodes (LEDs). The potential of ZnO NRs in all these applications, however, would require synthesis of high crystal quality ZnO NRs with precise control over the optical and electronic properties. It is known that the optical and electronic properties of ZnO NRs are mostly influenced by the presence of native (intrinsic) and impurities (extrinsic) defects. Therefore, understanding the nature of these intrinsic and extrinsic defects and their spatial distribution is critical for optimizing the optical and electronic properties of ZnO NRs. However, identifying the origin of such defects is a complicated matter, especially for NSs, where the information on anisotropy is usually lost due to the lack of coherent orientation.Thus, the aim of this thesis is towards the optimization of the lowtemperature solution-based synthesis of ZnO NRs for device applications. In this connection, we first started with investigating the effect of the precursor solution stirring durations on the deep level defects concentration and their spatial distribution along the ZnO NRs. Then, by choosing the optimal stirring time, we studied the influence of ZnO seeding layer precursor’s types, and its molar ratios on the density of interface defects. The findings of these investigations were used to demonstrate ZnO NRs-based heterojunction LEDs. The ability to tune the point defects along the NRs enabled us further to incorporate cobalt (Co) ions into the ZnO NRs crystal lattice, where these ions could occupy the vacancies or interstitial defects through substitutional or interstitial doping. Following this, high crystal quality vertically welloriented ZnO NRs have been demonstrated by incorporating a small amount of Co into the ZnO crystal lattice. Finally, the influence of Co ions incorporation on the reduction of core-defects (CDs) in ZnO NRs was systematically examined using electron paramagnetic resonance (EPR).
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| 35. |
- Costello, David M., et al.
(författare)
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Global patterns and controls of nutrient immobilization on decomposing cellulose in riverine ecosystems
- 2022
-
Ingår i: Global Biogeochemical Cycles. - : John Wiley & Sons. - 0886-6236 .- 1944-9224. ; 36:3
-
Tidskriftsartikel (refereegranskat)abstract
- Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.
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| 36. |
- da Cunha, Wiliam Ferreira, et al.
(författare)
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Quasiparticle description of transition metal dichalcogenide nanoribbons
- 2019
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 99:3
-
Tidskriftsartikel (refereegranskat)abstract
- An effective two-dimensional real-space model is developed to investigate the nature of charge distribution in nanoribbons of transition metal dichalcogenides. Our description is based on a lattice relaxation endowed tight-binding Hamiltonian with spin-orbit and Hubbard interactions, which is parameterized to describe molybdenum disulfide lattices. As our main finding, we observed that electron-phonon coupling induces the creation of quasiparticles such as polarons in the same fashion as observed in conducting polymers and graphene nanoribbons. These similarities suggest that the charge transport in transition metal dichalcogenides can also be mediated by quasiparticles, which is a fundamental aspect concerning the application of these structures in electronics. We determine a range of possible electron-phonon coupling that correctly describes the system and also the critical value where quasiparticle transport is present. Our findings may have profound consequences on the understanding of the transport mechanism of transition metal dichalcogenides nanoribbons.
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| 37. |
- da Silva, Antonio Ferreira, et al.
(författare)
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Electrical resistivity and metal-nonmetal transition in n-type doped 4H-SiC
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:24
-
Tidskriftsartikel (refereegranskat)abstract
- The electrical resistivity of 4H-SiC doped with nitrogen is analyzed in the temperature range 10-700 K for nitrogen concentrations between 3.5x10(15) and 5x10(19) cm(-3). For the highest doped samples, a good agreement is found between the experimental resistivity and the values calculated from a generalized Drude approach at similar dopant concentration and temperature. From these results, the critical concentration (N-c) of nitrogen impurities which corresponds to the metal-nonmetal transition in 4H-SiC is deduced. We find N-c similar to 10(19) cm(-3).
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| 38. |
- Ferreira da Cunha, Wiliam, et al.
(författare)
-
Critical temperature and products of intrachain polaron recombination in conjugated polymers
- 2014
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 16:32, s. 17072-17080
-
Tidskriftsartikel (refereegranskat)abstract
- The intrachain recombination dynamics between oppositely charged polarons is theoretically investigated through the use of a version of the Su-Schrieffer-Heeger (SSH) model modified to include an external electric field, an extended Hubbard model, Coulomb interactions, and temperature effects in the framework of a nonadiabatic evolution method. Our results indicate notable characteristics concerning the polaron recombination: (1) it is found that there exists a critical temperature regime, below which an exciton is formed directly and (2) a pristine lattice is the resulting product of the recombination process, if the temperature is higher than the critical value. Additionally, it is found that the critical electric field regime plays the role of drastically modifying the system dynamics. These facts suggest that thermal effects in the intrachain recombination of polarons are crucial for the understanding of electroluminescence in optoelectronic devices, such as Polymer Light Emitting Diodes.
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| 39. |
- Ferreira da Silva, Antonio, et al.
(författare)
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Growth, Optical Characterization and Modelling of ZnO Nanorods on Si, SiC and Macroporous Si Structure
- 2009
-
Ingår i: Nanotech 2009 Vol. 3Nanotechnology 2009: Biofuels, Renewable Energy, Coatings, Fluidics and Compact Modeling. - Austin, TX, USA : Nano Science and Technology Institute. - 9781439817841 ; , s. 206-209
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Zinc Oxide (ZnO) and 4H-SiC are prominent materials with large applicability such as optoelectronic nanodevices and for instance ultraviolet detectors. There is lack of more information about optical transitions beyond the indirect band gap energy (BGE) of 4H-SiC and even more for ZnO direct BGE grown on the former material. Using the vapor-liquid-solid and the aqueous chemical growth methods we have grown ZnO nanorods on different substrates, such as quartz, n- and p-type silicon porous silicon and n-type 4H-SiC. The Scanning electron microscopy (SEM) are shown and compared for all samples. We have calculated the absorption and energy gap by employing a first-principle and a full-potential linearized augmented plane-wave (FPLAPW) method within the local density approximation (LDA). The absorption of ZnO nanorods, on different substrates, is lower than that of quartz substrate when photon energy is low. It is shown the strong effect of 4H-SiC on ZnO nanorods. Experiment and theory show a good aggreement when the optical energy gap is considered for both materials.
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| 40. |
- Ferreira da Silva, Antonio, et al.
(författare)
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Magnetoresistance of doped silicon
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 91:21, s. 214414-
-
Tidskriftsartikel (refereegranskat)abstract
- We have performed longitudinal magnetoresistance measurements on heavily n-doped silicon for donor concentrations exceeding the critical value for the metal-nonmetal transition. The results are compared to those from a many-body theory where the donor electrons are assumed to reside at the bottom of the many-valley conduction band of the host. Good qualitative agreement between theory and experiment is obtained.
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| 41. |
- Gonzalez-Moya, Johan R., et al.
(författare)
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Effects of the large distribution of CdS quantum dot sizes on the charge transfer interactions into TiO2 nanotubes for photocatalytic hydrogen generation
- 2016
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 27:28
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrogen fuels generated by water splitting using a photocatalyst and solar irradiation are currently gaining the strength to diversify the world energy matrix in a green way. CdS quantum dots have revealed a hydrogen generation improvement when added to TiO2 materials under visible-light irradiation. In the present paper, we investigated the performance of TiO2 nanotubes coupled with CdS quantum dots, by a molecular bifunctional linker, on photocatalytic hydrogen generation. TiO2 nanotubes were obtained by anodization of Ti foil, followed by annealing to crystallize the nanotubes into the anatase phase. Afterwards, the samples were sensitized with CdS quantum dots via an in situ hydrothermal route using 3-mercaptopropionic acid as the capping agent. This sensitization technique permits high loading and uniform distribution of CdS quantum dots onto TiO2 nanotubes. The XPS depth profile showed that CdS concentration remains almost unchanged (homogeneous), while the concentration relative to the sulfate anion decreases by more than 80% with respect to the initial value after similar to 100 nm in depth. The presence of sulfate anions is due to the oxidation of sulfide and occurs in greater proportion in the material surface. This protection for air oxidation inside the nanotubular matrix seemingly protected the CdS for photocorrosion in sacrificial solution leading to good stability properties proved by long duration, stable photocurrent measurements. The effect of the size and the distribution of sizes of CdS quantum dots attached to TiO2 nanotubes on the photocatalytic hydrogen generation were investigated. The experimental results showed three different behaviors when the reaction time of CdS synthesis was increased in the sensitized samples, i.e. similar, deactivation and activation effects on the hydrogen production with regard to TiO2 nanotubes. The deactivation effect was related to two populations of sizes of CdS, where the population with a shorter band gap acts as a trap for the electrons photogenerated by the population with a larger band gap. Electron transfer from CdS quantum dots to TiO2 semiconductor nanotubes was proven by the results of UPS measurements combined with optical band gap measurements. This property facilitates an improvement of the visible-light hydrogen evolution rate from zero, for TiO2 nanotubes, to approximately 0.3 mu mol cm(-2) h(-1) for TiO2 nanotubes sensitized with CdS quantum dots.
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| 42. |
- González-Moya, Johan R, et al.
(författare)
-
Effects of the large distribution of CdS quantum dot sizes on the charge transfer interactions into TiO2 nanotubes for photocatalytic hydrogen generation
- 2016
-
Ingår i: Nanotechnology. - : Institute of Physics (IOP). - 0957-4484 .- 1361-6528. ; 27:28
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrogen fuels generated by water splitting using a photocatalyst and solar irradiation are currently gaining the strength to diversify the world energy matrix in a green way. CdS quantum dots have revealed a hydrogen generation improvement when added to TiO2 materials under visible-light irradiation. In the present paper, we investigated the performance of TiO2 nanotubes coupled with CdS quantum dots, by a molecular bifunctional linker, on photocatalytic hydrogen generation. TiO2 nanotubes were obtained by anodization of Ti foil, followed by annealing to crystallize the nanotubes into the anatase phase. Afterwards, the samples were sensitized with CdS quantum dots via an in situ hydrothermal route using 3-mercaptopropionic acid as the capping agent. This sensitization technique permits high loading and uniform distribution of CdS quantum dots onto TiO2 nanotubes. The XPS depth profile showed that CdS concentration remains almost unchanged (homogeneous), while the concentration relative to the sulfate anion decreases by more than 80% with respect to the initial value after ~100 nm in depth. The presence of sulfate anions is due to the oxidation of sulfide and occurs in greater proportion in the material surface. This protection for air oxidation inside the nanotubular matrix seemingly protected the CdS for photocorrosion in sacrificial solution leading to good stability properties proved by long duration, stable photocurrent measurements. The effect of the size and the distribution of sizes of CdS quantum dots attached to TiO2 nanotubes on the photocatalytic hydrogen generation were investigated. The experimental results showed three different behaviors when the reaction time of CdS synthesis was increased in the sensitized samples, i.e. similar, deactivation and activation effects on the hydrogen production with regard to TiO2 nanotubes. The deactivation effect was related to two populations of sizes of CdS, where the population with a shorter band gap acts as a trap for the electrons photogenerated by the population with a larger band gap. Electron transfer from CdS quantum dots to TiO2 semiconductor nanotubes was proven by the results of UPS measurements combined with optical band gap measurements. This property facilitates an improvement of the visible-light hydrogen evolution rate from zero, for TiO2 nanotubes, to approximately 0.3 μmol cm–2 h–1 for TiO2 nanotubes sensitized with CdS quantum dots.
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| 43. |
- Nisar, Jawad, et al.
(författare)
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Band gap engineering by anion doping in the photocatalyst BiTaO4 : First principle calculations
- 2012
-
Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 37:4, s. 3014-3018
-
Tidskriftsartikel (refereegranskat)abstract
- We have shown the effect of mono and co-doping of non-metallic anion atoms on the electronic structure in BiTaO4 using the first-principles method. It can improve the photocatalytic efficiency for hydrogen production in the presence of visible sunlight. It is found that the band gap of BiTaO4 has been reduced significantly up to 54% with different nonmetallic doping. Electronic structure analysis shows that the doping of nitrogen is able to reduce the band gap of BiTaO4 due to the impurity N 2p state at the upper edge of the valence band. In case of C or C-S doped BiTaO4, double occupied (filled) states have been observed deep inside the band gap of BiTaO4. The large reduction of band gap has been achieved, which increases the visible light absorption. These results indicate that the doping of non-metallic element in BiTaO4 is a promising candidate for the photocatalyst due to its reasonable band gap.
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| 44. |
- Pedro, Joana Reis, et al.
(författare)
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Transient gain of function of cannabinoid CB1 receptors in the control of frontocortical glucose consumption in a rat model of Type-1 diabetes
- 2020
-
Ingår i: Brain Research Bulletin. - : Elsevier BV. - 0361-9230. ; 161, s. 106-115
-
Tidskriftsartikel (refereegranskat)abstract
- Here we aimed to unify some previous controversial reports on changes in both cannabinoid CB1 receptor (CB1R) expression and glucose metabolism in the forebrain of rodent models of diabetes. We determined how glucose metabolism and its modulation by CB1R ligands evolve in the frontal cortex of young adult male Wistar rats, in the first 8 weeks of streptozotocin-induced type-1 diabetes (T1D). We report that frontocortical CB1R protein density was biphasically altered in the first month of T1D, which was accompanied with a reduction of resting glucose uptake ex vivo in acute frontocortical slices that was normalized after eight weeks in T1D. This early reduction of glucose uptake in slices was also restored by ex vivo treatment with both the non-selective CB1R agonists, WIN55212−2 (500 nM) and the CB1R-selective agonist, ACEA (3 μM) while it was exacerbated by the CB1R-selective antagonist, O-2050 (500 nM). These results suggest a gain-of-function for the cerebrocortical CB1Rs in the control of glucose uptake in diabetes. Although insulin and IGF-1 receptor protein densities remained unaffected, phosphorylated GSKα and GSKβ levels showed different profiles 2 and 8 weeks after T1D induction in the frontal cortex. Altogether, the biphasic response in frontocortical CB1R density within a month after T1D induction resolves previous controversial reports on forebrain CB1R levels in T1D rodent models. Furthermore, this study also hints that cannabinoids may be useful to alleviate impaired glucoregulation in the diabetic cortex.
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| 45. |
- Qian, Zhao
(författare)
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Atomistic Modelling of Materials for Clean Energy Applications : hydrogen generation, hydrogen storage, and Li-ion battery
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, a number of clean-energy materials for hydrogen generation, hydrogen storage, and Li-ion battery energy storage applications have been investigated through state-of-the-art density functional theory.As an alternative fuel, hydrogen has been regarded as one of the promising clean energies with the advantage of abundance (generated through water splitting) and pollution-free emission if used in fuel cell systems. However, some key problems such as finding efficient ways to produce and store hydrogen have been hindering the realization of the hydrogen economy. Here from the scientific perspective, various materials including the nanostructures and the bulk hydrides have been examined in terms of their crystal and electronic structures, energetics, and different properties for hydrogen generation or hydrogen storage applications. In the study of chemisorbed graphene-based nanostructures, the N, O-N and N-N decorated ones are designed to work as promising electron mediators in Z-scheme photocatalytic hydrogen production. Graphene nanofibres (especially the helical type) are found to be good catalysts for hydrogen desorption from NaAlH4. The milestone nanomaterial, C60, is found to be able to significantly improve the hydrogen release from the (LiH+NH3) mixture. In addition, the energetics analysis of hydrazine borane and its derivative solid have revealed the underlying reasons for their excellent hydrogen storage properties. As the other technical trend of replacing fossil fuels in electrical vehicles, the Li-ion battery technology for energy storage depends greatly on the development of electrode materials. In this thesis, the pure NiTiH and its various metal-doped hydrides have been studied as Li-ion battery anode materials. The Li-doped NiTiH is found to be the best candidate and the Fe, Mn, or Cr-doped material follows.
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| 46. |
- Ribeiro, Luiz Antonio, et al.
(författare)
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Temperature Effects on the Scattering of Polarons and Bipolarons in Organic Conductors
- 2014
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society. - 1089-5639 .- 1520-5215. ; 118:32, s. 6272-6277
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Tidskriftsartikel (refereegranskat)abstract
- The scattering process between an electron-polaron and a hole-bipolaron has been simulated using a version of the Su-Schrieffer-Heeger (SSH) model modified to include an external electric field, Coulomb interactions, and temperature effects in the scope of nonadiabatic molecular dynamics. The simulations reveal remarkable details concerning the polaron-bipolaron recombination reaction. It is found that there exists a critical temperature regime below which a hole-bipolaron and a mixed state composed by an electron-polaron and an exciton are formed and a hole-bipolaron and a free electron are the resulting products of the collisional process, if the temperature is higher than the critical value. In addition, it is obtained that both channels depend sensitively on the strength of the applied electric field. These significant results may provide guidance to understand processes regarding electro-luminescence in polymer diodes.
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| 47. |
- Santiago, Tânia, et al.
(författare)
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Recommendations for the execution and reporting of skin ultrasound in systemic sclerosis : an international collaboration under the WSF skin ultrasound group
- 2022
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Ingår i: RMD Open. - : BMJ. - 2056-5933. ; 8:2
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Forskningsöversikt (refereegranskat)abstract
- Objective Ultrasound is a promising tool to foster much-needed improvement of skin assessment in systemic sclerosis (SSc). Our aim was to develop evidence and expert opinion-based recommendations to promote the standardisation and harmonisation of technical execution and reporting of skin ultrasound studies in SSc. Methods A multidisciplinary task force of 16 members from five European countries and Japan was convened under the auspices of World Scleroderma Foundation. First, a systematic literature review (SLR) was performed. Then, each member proposed and formulated items to the overarching principles, recommendations and research agenda. Two rounds of mails exchange for consensus as well as an on-line meeting were performed to debate and refine the proposals. Two Delphi rounds of voting resulted in the final recommendations. Levels of evidence and strengths of recommendations were assigned, and task force members voted anonymously on the level of agreement with each of the items. Results Five overarching principles and seven recommendations were developed, based on an SLR and expert opinion, through consensus procedures. The overarching principles highlight the promising role of skin ultrasound in SSc assessment, the need for standardisation of technical aspects, sufficient training and adequate equipment. The recommendations provide standards for the execution and reporting of skin ultrasound in SSc. The research agenda includes the need for more research into unmet needs according to Outcome Measures in Rheumatology Algorithm requirements. Conclusion These are the first recommendations providing guidance on the execution and reporting of skin ultrasound in SSc patients, aiming at improving the interpretability, reliability and generalisability of skin ultrasound, thus consolidating its role in research and practice.
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| 48. |
- Souza Dantas, Nilton, et al.
(författare)
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Electronic band -edge properties of rock salt PbY and SnY (Y = S, Se, and Te)
- 2008
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Ingår i: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 30:9, s. 1451-1460
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Tidskriftsartikel (refereegranskat)abstract
- The electronic band-edges of lead chalcogenides PbY and tin chalcogenides SnY (where Y = S, Se, and Te) are investigated by the means of a full-potential linearized augmented plane wave (FPLAPW) method and the local density approximation (LDA). All six chalcogenide binaries have similar electronic structures and density-of-states, but there are differences in the symmetry of the band-edge states at and near the Brillouin zone L-point. These differences give the characteristic composition, pressure, and temperature dependences of the energy gap in Pb1-xSnxY alloys.We find that: (1) SnY are zero-gap semiconductors E-g = 0 if the spin-orbit (SO) interaction is excluded. The reason for this is that the conduction band (CB) and the valence band (VB) cross along the Q equivalent to LW line. (2) Including the SO interaction splits this crossing and creates a direct gap along the Q-line, thus away from the L symmetry point. Hence, the fundamental band gap E-g in SnY is induced by the SO interaction and the energy gap is rather small Eg approximate to 0.2-0.3 eV. At the L-point, the CB state has symmetric L-4(+) and the VB state is antisymmetric L-4(-) thereby the L-point pressure coefficient partial derivative E-g(L)/partial derivative p is a positive quantity. (3) PbY have a direct band gap at the L-point both when SO coupling is excluded and included. In contrast to SnY, the SO interaction decreases the gap energy in PbY. (4) Including the SO interaction, the LDA yields incorrect symmetries of the band-edge states at the L-point; the CB state has L-4(+) and the VB state has L-4(-) symmetry. However, a small increase of the cell volume corrects this LDA failure, producing an antisymmetric CB state and a symmetric VB state, and thereby also yields the characteristic negative pressure coefficient partial derivative E-g(L)/partial derivative p in agreement with experimental findings. (5) Although PbY and SnY have different band-edge physics at their respective equilibrium lattice constants, the change of the band-edges with respect to cell volume is qualitatively the same for all six chalcogenides. (6) Finally, in the discussion of the symmetry of the band edges, it is important to clearly state the chosen unit cell origin; a shift by (a/2,0,0) changes the labeling L-4(+) double left right arrow L-4(-) of the irreducible representations.
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| 49. |
- Souza Dantas, Nilton, et al.
(författare)
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Optical characterization of rock salt Pb1-xSnx Te alloys
- 2008
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Ingår i: Physica status solidi. A, Applied research. - Weinheim, Germany : Wiley. - 0031-8965 .- 1521-396X. ; 205:4, s. 837-840
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties in terms of dielectric function ϵ (ħω) = ϵ1(ħω) + iϵ2(ħω) of rocksalt Pb1–xSnx Te alloys (0 ≤ x ≤ 1) are investigated experimentally by spectroscopic ellipsometry and theoretically by first-principles electronic band structure calculation. We find a strong optical response in the 0.5–2.0 eV region arising from optical absorption around the LW-line of the Brillouin zone. The response peak of the imaginary part of the dielectric functions at E = 1.6–1.8 eV shifts towards lower energies for high Sn compositions as a consequence of narrower W-point band-gap Eg(W) for the Sn-rich alloys.
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| 50. |
- Thomazi, Fabiano, et al.
(författare)
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Optical absorption of rutile SnO2 and TiO2
- 2009
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 6:12, s. 2740-2742
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Tidskriftsartikel (refereegranskat)abstract
- The electronic band-edge structure and optical response of rutile SnO2 and TiO2 are studied, employing a fully relativistic projected augmented wave method within the local density approximation (LDA). A quasi-particle model corrects the LDA band-gap energies, which is used to fit the on-site self-interaction correction (SIC) potential LDA+U-SIC. We show that inclusion of this k-dependent SIC-like potential correction, as well as inclusion of polaronic screening are of outermost importance for accurately determining the electronic structure and optical properties. For both SnO2 and TiO2, the calculated absorption coefficient alpha(omega) reveals a very small optical band-edge absorption in the photon energy region E-g <= h omega <= similar to E-g+Delta (Delta = 0.8 eV and 0.5 eV for SnO2 and TiO2, respectively). The main difference between SnO2 and TiO2 is the presence of the unoccupied low-energy 3d conduction-band states in TiO2 which yield flat conduction bands and a very strong optical absorption for h omega > E-g+Delta. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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