| 1. |
- Cai, Haibin, et al.
(författare)
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Sensing-enhanced Therapy System for Assessing Children with Autism Spectrum Disorders : A Feasibility Study
- 2019
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Ingår i: IEEE Sensors Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1530-437X .- 1558-1748. ; 19:4, s. 1508-1518
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Tidskriftsartikel (refereegranskat)abstract
- It is evident that recently reported robot-assisted therapy systems for assessment of children with autism spectrum disorder (ASD) lack autonomous interaction abilities and require significant human resources. This paper proposes a sensing system that automatically extracts and fuses sensory features such as body motion features, facial expressions, and gaze features, further assessing the children behaviours by mapping them to therapist-specified behavioural classes. Experimental results show that the developed system has a capability of interpreting characteristic data of children with ASD, thus has the potential to increase the autonomy of robots under the supervision of a therapist and enhance the quality of the digital description of children with ASD. The research outcomes pave the way to a feasible machine-assisted system for their behaviour assessment. IEEE
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| 2. |
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| 3. |
- Gaca, Anthony O., et al.
(författare)
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From (p)ppGpp to (pp)pGpp : characterization of Regulatory Effects of pGpp Synthesized by the Small Alarmone Synthetase of Enterococcus faecalis
- 2015
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 197:18, s. 2908-2919
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Tidskriftsartikel (refereegranskat)abstract
- The bacterial stringent response (SR) is a conserved stress tolerance mechanism that orchestrates physiological alterations to enhance cell survival. This response is mediated by the intracellular accumulation of the alarmones pppGpp and ppGpp, collectively called (p) ppGpp. In Enterococcus faecalis, (p) ppGpp metabolism is carried out by the bifunctional synthetase/hydrolase E. faecalis Rel (Rel(Ef)) and the small alarmone synthetase (SAS) RelQ(Ef). Although Rel is the main enzyme responsible for SR activation in Firmicutes, there is emerging evidence that SASs can make important contributions to bacterial homeostasis. Here, we showed that RelQ(Ef) synthesizes ppGpp more efficiently than pppGpp without the need for ribosomes, tRNA, or mRNA. In addition to (p) ppGpp synthesis from GDP and GTP, RelQ(Ef) also efficiently utilized GMP to form GMP 3'-diphosphate (pGpp). Based on this observation, we sought to determine if pGpp exerts regulatory effects on cellular processes affected by (p) ppGpp. We found that pGpp, like (p) ppGpp, strongly inhibits the activity of E. faecalis enzymes involved in GTP biosynthesis and, to a lesser extent, transcription of rrnB by Escherichia coli RNA polymerase. Activation of E. coli RelA synthetase activity was observed in the presence of both pGpp and ppGpp, while RelQ(Ef) was activated only by ppGpp. Furthermore, enzymatic activity of RelQ(Ef) is insensitive to relacin, a (p) ppGpp analog developed as an inhibitor of "long" RelA/SpoT homolog (RSH) enzymes. We conclude that pGpp can likely function as a bacterial alarmone with target-specific regulatory effects that are similar to what has been observed for (p) ppGpp. IMPORTANCE Accumulation of the nucleotide second messengers (p) ppGpp in bacteria is an important signal regulating genetic and physiological networks contributing to stress tolerance, antibiotic persistence, and virulence. Understanding the function and regulation of the enzymes involved in (p) ppGpp turnover is therefore critical for designing strategies to eliminate the protective effects of this molecule. While characterizing the (p) ppGpp synthetase RelQ of Enterococcus faecalis (RelQ(Ef)), we found that, in addition to (p) ppGpp, RelQ(Ef) is an efficient producer of pGpp (GMP 3'-diphosphate). In vitro analysis revealed that pGpp exerts complex, target-specific effects on processes known to be modulated by (p) ppGpp. These findings provide a new regulatory feature of RelQ(Ef) and suggest that pGpp may represent a new member of the (pp) pGpp family of alarmones.
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| 4. |
- Htet, Cho Sandar, et al.
(författare)
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Effect of Local Structural Distortions on Antiferroelectric-Ferroelectric Phase Transition in Dilute Solid Solutions of K xNa1- xNbO3
- 2022
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:50, s. 20277-20287
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Tidskriftsartikel (refereegranskat)abstract
- The fundamental principles that govern antiferroelectric (AFE)-ferroelectric (FE) transitions are not well understood for many solid solutions of perovskite compounds. For example, crystal chemical considerations based on the average Goldschmidt tolerance factor or ionic polarizability do not precisely predict the boundary between the AFE and FE phases in dilute solid solutions of alkali niobates, such as KxNa1-xNbO3(x ≤ 0.02). Here, based on detailed structural analysis from neutron total scattering experiments, we provide insights about how the relative local distortions around the A- and B-sites of the ABO3perovskite structure affect the AFE/FE order of the average crystallographic phases in KxNa1-xNbO3. We show that a higher (lower) ratio of B-site-centered distortions over A-site-centered distortions drives transition toward a long-range FE (AFE) phase, which is based on a competition between the long-range polarizing field of the Nb-O dipoles and the disordering effect of local distortions around the A-site. Our study provides a predictive tool for designing complex solid-solution perovskites with tunable (anti)ferroelectric polarization properties, which can be of interest for various energy-related applications such as high-density energy storage and solid-state cooling.
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| 5. |
- Htet, Cho Sandar, et al.
(författare)
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Local structural mechanism for enhanced energy storage properties in heterovalent doped NaNbO3 ceramics
- 2024
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Ingår i: Journal of the European Ceramic Society. - 0955-2219. ; 44:3, s. 1597-1609
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, there is a growing interest for new lead-free oxides with reversible antiferroelectric (AFE)-ferroelectric (FE) phase transition for high-power energy-storage applications. NaNbO3-based ceramics are particularly attractive due to their easy synthesis and cost-effectiveness. In order to stabilize reversible AFE-FE phase transition, NaNbO3 is doped with a combination of heterovalent substitutions, although the underlying structural mechanism for the same is poorly understood. Here, we investigated local and average structures of Ca/Zr doped NaNbO3 using neutron total scattering. We show that Ca/Zr doping increases the average AFE phase (Pbma) fraction, however, the material remains as a composite of both FE (P21ma) and AFE regions. Analysis of local structure suggests that increase in the long-range AFE phase results from more extensive twinning of local FE regions, due to introduced charge disorder. We propose that enhanced energy-storage properties of Ca/Zr-doped NaNbO3 arises from localized twin boundary motion between the defect-induced pinning centers.
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| 6. |
- Kong, Jing, et al.
(författare)
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A Local Atomic Mechanism for Monoclinic-Tetragonal Phase Boundary Creation in Li-Doped Na0.5K0.5NbO3Ferroelectric Solid Solution
- 2022
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:10, s. 4335-4349
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Tidskriftsartikel (refereegranskat)abstract
- ABO3 perovskites display a wide range of phase transitions, which are driven by A/B-site centered polyhedral distortions and/or BO6 octahedral tilting. Since heterogeneous substitutions at the A/B-site can locally alter both polyhedral distortions and/or tilting, they are often used to create phase boundary regions in solid solutions of ABO3, where the functional properties are highly enhanced. However, the relationships between doping-induced atomistic structural changes and the creation of phase boundaries are not always clear. One prominent example of this is the Li-doped K0.5Na0.5NbO3 (KNNL), which is considered a promising alternative to traditional Pb-based ferroelectrics. Although the electromechanical properties of KNNL are enhanced for compositions near the morphotropic phase boundary (MPB), the atomistic mechanism for phase transitions is not well understood. Here, we combined neutron total scattering experiments and density functional theory to investigate the long-range average and short-range (∼10 Å) structural changes in KNNL. We show that the average monoclinic-to-tetragonal (M-T) transition across the MPB in KNNL can be described as an order-disorder-type change, which is driven by competition between a longer-range polarization field of monoclinic structural units and local distortions of the disordered AO12 polyhedra. The current study demonstrates a way to clarify dopant-induced local distortions near phase boundaries in complex solid solution systems, which will be important for the rational design of new environmentally sustainable ferroelectrics.
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| 7. |
- Kong, Jing, et al.
(författare)
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Scaling behavior of order parameters for the hybrid improper ferroelectric (Ca,Sr)3Ti2 O7
- 2023
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Ingår i: Physical Review B. - 2469-9950. ; 107:22
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Tidskriftsartikel (refereegranskat)abstract
- We show that in contrast to the conventional view of a mean-field Landau-type behavior, the oxygen octahedral tilt (R) and polarization (P) in the A3B2O7 Ruddlesden-Popper hybrid improper ferroelectric (Ca,Sr)3Ti2O7 exhibits the scaling behavior of a 2D Ising class near the para-to-ferroelectric transition temperature (Tc). We also show that P exhibits an additional transition from a 2D Ising to a 3D mean-field critical behavior at a temperature Td
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| 8. |
- Li, Man, et al.
(författare)
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Advances in Tin(II)-Based Perovskite Solar Cells : From Material Physics to Device Performance
- 2022
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Ingår i: Small Structures. - : Wiley. - 2688-4062. ; 3:1
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Forskningsöversikt (refereegranskat)abstract
- During the past decade, metal halide perovskites are widely studied in the field of optoelectronic materials due to their unique optical and electrical properties. Lead-based halide perovskite solar cells (PSCs), in particular, currently achieve a record efficiency of 25.5%, thus showing strong potential in industrial application. However, toxicity of lead-based perovskite materials possesses great concerns to natural environment and human body. Therefore, the quest for nontoxic and eco-friendly elements to replace lead in perovskites is of great interest. Among all the element choices, tin(II) (Sn2+) is the most promising candidate. As a rising star of lead-free PSCs, Sn-based PSCs have drawn much attention and made promising progress during the past few years. While the rapid oxidation and decomposition of Sn-based perovskites result in poor stability and low efficiency of PSCs. In this review, structural, optoelectronic properties and the critical issues of Sn-based perovskite materials are analyzed. Then, a detailed discussion on the recent methods in solving critical issues of Sn-based perovskite devices, from optimization on materials physics to device performance, is also presented. Finally, remaining challenges and future perspective are given to advance the progression of Sn-based PSCs.
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| 9. |
- Liu, Yanjie, et al.
(författare)
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The conserved plant sterility gene HAP2 functions after attachment of fusogenic membranes in Chlamydomonas and Plasmodium gametes
- 2008
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Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory Press (CSHL). - 0890-9369 .- 1549-5477. ; 22:8, s. 1051-1068
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Tidskriftsartikel (refereegranskat)abstract
- The cellular and molecular mechanisms that underlie species-specific membrane fusion between male and female gametes remain largely unknown. Here, by use of gene discovery methods in the green alga Chlamydomonas, gene disruption in the rodent malaria parasite Plasmodium berghei, and distinctive features of fertilization in both organisms, we report discovery of a mechanism that accounts for a conserved protein required for gamete fusion. A screen for fusion mutants in Chlamydomonas identified a homolog of HAP2, an Arabidopsis sterility gene. Moreover, HAP2 disruption in Plasmodium blocked fertilization and thereby mosquito transmission of malaria. HAP2 localizes at the fusion site of Chlamydomonas minus gametes, yet Chlamydomonas minus and Plasmodium hap2 male gametes retain the ability, using other, species-limited proteins, to form tight prefusion membrane attachments with their respective gamete partners. Membrane dye experiments show that HAP2 is essential for membrane merger. Thus, in two distantly related eukaryotes, species-limited proteins govern access to a conserved protein essential for membrane fusion.
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| 10. |
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