| 1. |
- Lederman, Judith, et al.
(författare)
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An international collaborative investigation of beginning seventh grade students' understandings of scientific inquiry : Establishing a baseline
- 2019
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Ingår i: Journal of Research in Science Teaching. - : Wiley. - 0022-4308 .- 1098-2736. ; 56:4, s. 486-515
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Tidskriftsartikel (refereegranskat)abstract
- Although understandings of scientific inquiry (as opposed to conducting inquiry) are included in science education reform documents around the world, little is known about what students have learned about inquiry during their elementary school years. This is partially due to the lack of any assessment instrument to measure understandings about scientific inquiry. However, a valid and reliable assessment has recently been developed and published, Views About Scientific Inquiry (VASI; Lederman et al. [2014], Journal of Research in Science Teaching, 51, 65-83). The purpose of this large-scale international project was to collect the first baseline data on what beginning middle school students have learned about scientific inquiry during their elementary school years. Eighteen countries/regions spanning six continents including 2,634 students participated in the study. The participating countries/regions were: Australia, Brazil, Chile, Egypt, England, Finland, France, Germany, Israel, Mainland China, New Zealand, Nigeria, South Africa, Spain, Sweden, Taiwan, Turkey, and the United States. In many countries, science is not formally taught until middle school, which is the rationale for choosing seventh grade students for this investigation. This baseline data will simultaneously provide information on what, if anything, students learn about inquiry in elementary school, as well as their beginning knowledge as they enter secondary school. It is important to note that collecting data from all of the approximately 200 countries globally was not humanly possible, and it was also not possible to collect data from every region of each country. The results overwhelmingly show that students around the world at the beginning of grade seven have very little understandings about scientific inquiry. Some countries do show reasonable understandings in certain aspects but the overall picture of understandings of scientific inquiry is not what is hoped for after completing 6 years of elementary education in any country.
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| 2. |
- Liu, Peng-Fei, et al.
(författare)
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Hexagonal M2C3 (M = As, Sb, and Bi) monolayers : new functional materials with desirable band gaps and ultrahigh carrier mobility
- 2018
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 6:46, s. 12689-12697
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Tidskriftsartikel (refereegranskat)abstract
- Based on first-principles calculations, we propose a new type of two-dimensional (2D) material M2C3 (M = As, Sb, and Bi) showing an infinite hexagonal lattice, in which C atoms adopt sp(2) hybridization and M atoms prefer three-fold coordination with lone pair electrons. Such monolayers are calculated to be stable verified by their moderate cohesive energies, the absence of imaginary modes in their phonon spectra, and the high melting points predicted via molecular dynamics simulations. Sb2C3 and Bi2C3 monolayers possess intrinsic band gaps of 1.58 and 1.23 eV (based on HSE06 calculations), values suitable for photovoltaic applications. The intrinsic acoustic-phonon-limited carrier mobility of the As2C3 sheet can reach up to 4.45 x 10(5) cm(2) V-1 s(-1) for electrons at room temperature, higher than that of (60-200 cm(2) V-1 s(-1)) MoS2 and (approximate to 10(3) cm(2) V-1 s(-1)) few-layer phosphorene, approaching the figure of merit in graphene (3 x 10(5) cm(2) V-1 s(-1)). The well-located band edge and visible light absorption make stretched Sb2C3 a potentially promising optoelectronic material for photocatalytic water splitting. Besides, Sb2C3/As2C3 excitonic solar cells have been proposed, and their power conversion efficiencies are estimated to exceed 23%. First-principles calculations have demonstrated that Sb2C3/Bi2C3 heterojunctions are indeed 2D node-line semimetals in the absence of spin-orbit coupling.
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| 3. |
- Dai, Baomin, et al.
(författare)
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Environmental and economical analyses of transcritical CO2 heat pump combined with direct dedicated mechanical subcooling (DMS) for space heating in China
- 2019
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Ingår i: Energy Conversion and Management. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0196-8904 .- 1879-2227. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- An environmental and economical assessment model is developed, in order to evaluate the performances of transcritical CO2 heat pump system with dedicated mechanical subcooling (CO2 HPDMS). Introducing DMS to traditional CO2 HP system is an efficient method to reduce the primary energy consumption, which can be further decreased by using small temperature difference fan-coil unit (STD-FCU) as heating terminal. Using CO2 heat pump system for space heating is an environmentally-friendly heating method. The corresponding pollution emissions are only inferior to those of the wall hanging gas heater. The initial capital cost and operating cost of CO2 HPDMS system are both lower than those of CO2 HPBASE system, and the CO2 compressor cost accounts for about 80% of the overall initial capital cost. In contrast to other traditional heating methods, the payback periods of CO2 HPDMS system are not more than 9 years in most cases. If the CO2 compressor and electricity price are reduced by 20% and 28.79% respectively, the life cycle cost of CO2 HPDMS will be competitive to that of coal-fired boiler. In China, it is a promising way to adopt CO2 HPDMS for space heating in the near future with the assistant of electricity price subsidy and compressor price reduction.
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| 4. |
- Gao, Feng, et al.
(författare)
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Visible-light photocatalytic properties of weak magnetic BiFeO3 nanoparticles
- 2007
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 19:19, s. 2889-2892
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Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline BiFeO3 nanoparticles (size 80-120 nm) are prepared by a simple sol-gel technique. Such nanoparticles are very efficient for photocatalytic decomposition of organic contaminants under irradiation from ultraviolet to visible frequencies. The BiFeO3 nanoparticles also demonstrate weak ferromagnetism of about 0.06 mu(B)/Fe at room temperature, in good agreement with theoretical calculations.
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| 5. |
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| 6. |
- Li, Xiaofeng, et al.
(författare)
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Enhancement of femtosecond laser-induced plasma fluorescence using a nanosecond laser
- 2019
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Ingår i: Optics Express. - 1094-4087. ; 27:4, s. 5755-5763
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the enhancement of femtosecond (fs) laser-induced filaments in air and nitrogen flow fields using a nanosecond (ns) laser. With the ns laser being imposed on the filaments, the length and the emission intensity of the filaments were largely increased. Temporally resolved spectra of the enhanced filaments were obtained. The results show that the ns laser enhanced the short-lifetime fluorescence of nitrogen, which comes from the transition processes of N 2 + (B 2 Σ u + - X 2 Σ g + ), N 2 (B 3 Π g - A 3 Σ u + ) and N 2 (C 3 Π u - B 3 Π g ). However, it had little effect on the long-lifetime chemiluminescence, which mainly comes from reactions such as N 2 (A 3 Σ u + ) + N 2 (A 3 Σ u + ) → N 2 (X 1 Σ g + , v = 0) + N 2 (B 3 Π g ). A possible explanation of this phenomenon is given, and this phenomenon might have potential applications in instantaneous one-dimensional measurements of various species in gas flow fields.
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| 7. |
- Liu, Shengchun, et al.
(författare)
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Energetic, economic and environmental analysis of air source transcritical CO2 heat pump system for residential heating in China
- 2019
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 148, s. 1425-1439
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Tidskriftsartikel (refereegranskat)abstract
- Using air source heat pump system for residential heating is a practical way to replace coal-fired boiler in China to alleviate the haze problem, and CO2 is a promising candidate to replace hydrochlorofluorocarbon (HCFC) or hydrofluorocarbon (HFCs) charged into the system. A mathematical model is developed to comprehensively evaluate the energetic, economical and environmental performances of CO2 heat pump system compared with other three traditional heating methods. The results indicate that the primary energy ratio of CO2 heat pump is the highest and it is a rational way to utilize renewable energy with the renewable energy contribution ratio of 0.60–0.69. The initial capital cost of CO2 heat pump is much higher due to the dominant compressor cost. The emission of CO2 heat pump is lower than that of coal-fired boiler at seasonal performance factor above 2.44. The initial and operation cost can be gradually reduced with the mass production and energy efficiency improvement of CO2 heat pump. It is believe that air source CO2 heat pump system can be employed for home heating in China, especial for the hot summer and cold winter region.
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| 8. |
- Liu, Yuru, et al.
(författare)
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Ash chemistry in chemical looping process for biomass valorization: A review
- 2023
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Ingår i: Chemical Engineering Journal. - 1385-8947. ; 478
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Forskningsöversikt (refereegranskat)abstract
- Chemical looping process (CLP) is a novel carbon capture technology for biomass valorization. Low-cost and robust oxygen carrier (OC) is crucial for industrialization of CLP. However, ash in solid fuels will unavoidably deposit on OC and even react with OC, leading to severe agglomeration and sintering which could not only degrade the full functionality of OC but also make the complete separation of ash and OC challenging. In order to holistically elucidate the ash chemistry in CLP, this review has systematically analyzed the effect of ash compositions in biomass on CLP efficiency, the impact of ash components on physicochemical properties and oxygen transfer capacity of OC, as well as the melting and agglomeration behaviors of ash components. Specifically, both inhibition and enhancement effects of various ash components have been illustrated. Particularly, the influence of alkali and alkaline earth metals in biomass ash on agglomeration of OC has been analyzed in detail. Four mechanisms are summarized to explain the agglomeration and melting process, including coating-induced, melting-induced, ash deposition-melting, the layer joint and bridge joint mechanisms. Ultimately, strategies are proposed to effectively mitigate adverse impacts of ash and recycle useful metals for industry use and re-synthesis of OC. To promote future development of CLP, perspectives are provided to guide the novel design of next generation OC in terms of structural and compositional optimization.
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| 9. |
- Sukalo, Maja, et al.
(författare)
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Mutations in the Human UBR1 Gene and the Associated Phenotypic Spectrum
- 2014
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Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 35:5, s. 521-531
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Tidskriftsartikel (refereegranskat)abstract
- Johanson-Blizzard syndrome (JBS) is a rare, autosomal recessive disorder characterized by exocrine pancreatic insufficiency, typical facial features, dental anomalies, hypothyroidism, sensorineural hearing loss, scalp defects, urogenital and anorectal anomalies, short stature, and cognitive impairment of variable degree. This syndrome is caused by a defect of the E3 ubiquitin ligase UBR1, which is part of the proteolytic N-end rule pathway. Herein, we review previously reported (n=29) and a total of 31 novel UBR1 mutations in relation to the associated phenotype in patients from 50 unrelated families. Mutation types include nonsense, frameshift, splice site, missense, and small in-frame deletions consistent with the hypothesis that loss of UBR1 protein function is the molecular basis of JBS. There is an association of missense mutations and small in-frame deletions with milder physical abnormalities and a normal intellectual capacity, thus suggesting that at least some of these may represent hypomorphic UBR1 alleles. The review of clinical data of a large number of molecularly confirmed JBS cases allows us to define minimal clinical criteria for the diagnosis of JBS. For all previously reported and novel UBR1 mutations together with their clinical data, a mutation database has been established at LOVD.
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| 10. |
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| 11. |
- Wen, Guanzhao, et al.
(författare)
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Energy level offsets determine the interplay between charge and energy transfer in all-small-molecule organic solar cells
- 2023
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Ingår i: Chemical Engineering Journal. - 1385-8947. ; 475
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Tidskriftsartikel (refereegranskat)abstract
- All-small-molecule organic solar cells (ASM OSCs) hold great promise in OSCs owing to their defined structures, simple purification, and good reproducibility, but are challenging for further improved efficiency. The energy level strategy has been broadly applied to obtain a better performance; however, a comprehensive understanding of the effects of energy level offset on photoexcitation dynamics in ASM OSCs is rarely studied. Herein, for Y-series molecules (Y6, Y10, Y5, and BTP-4F-12) based ASM OSCs, the effect of energy level offset on charge photogeneration was investigated using steady-state and time-resolved spectroscopies. We found that both energy and charge transfer could occur in blend films. A method to quantitatively analyze the contribution of charge and energy transfer processes was developed. For BTR-Cl:Y6 with the highest LUMO level offset, ∼ 23% of photogenerated excitons in donor dissociated via “energy transfer and the subsequent charge transfer” pathway, suggesting that the energy transfer in blend films should also be considered. And for the hole transfer, the excitons in Y-series molecules can only be effectively dissociated when the HOMO energy level offset is higher than 0.11 eV. Besides, a higher energy level offset would also suppress carrier recombination in ultrafast timescale. These results may shed light on the design of ASM OSCs.
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| 12. |
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| 13. |
- Zhang, Jibin, et al.
(författare)
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A Multifunctional "Halide-Equivalent" Anion Enabling Efficient CsPb(Br/I)(3) Nanocrystals Pure-Red Light-Emitting Diodes with External Quantum Efficiency Exceeding 23%
- 2023
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 35:8
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Tidskriftsartikel (refereegranskat)abstract
- Pure-red perovskite LEDs (PeLEDs) based on CsPb(Br/I)(3) nanocrystals (NCs) usually suffer from a compromise in emission efficiency and spectral stability on account of the surface halide vacancies-induced nonradiative recombination loss, halide phase segregation, and self-doping effect. Herein, a "halide-equivalent" anion of benzenesulfonate (BS-) is introduced into CsPb(Br/I)(3) NCs as multifunctional additive to simultaneously address the above challenging issues. Joint experiment-theory characterizations reveal that the BS- can not only passivate the uncoordinated Pb2+-related defects at the surface of NCs, but also increase the formation energy of halide vacancies. Moreover, because of the strong electron-withdrawing property of sulfonate group, electrons are expected to transfer from the CsPb(Br/I)(3) NC to BS- for reducing the self-doping effect and altering the n-type behavior of CsPb(Br/I)(3) NCs to near ambipolarity. Eventually, synergistic boost in device performance is achieved for pure-red PeLEDs with CIE coordinates of (0.70, 0.30) and a champion external quantum efficiency of 23.5%, which is one of the best value among the ever-reported red PeLEDs approaching to the Rec. 2020 red primary color. Moreover, the BS--modified PeLED exhibits negligible wavelength shift under different operating voltages. This strategy paves an efficient way for improving the efficiency and stability of pure-red PeLEDs.
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