34 research outputs found
ADVANCED NUMERICAL MODELING AND SIMULATION OF SILICON WAFER SOLAR CELLS
Ph.DDOCTOR OF PHILOSOPH
Influence of particle size and tunable interactions on isotropic–nematic transition of block copolymer single crystal platelet suspensions
We have studied the influence of the particle size and the tunable lateral interactions on the isotropic–nematic (I–N) phase transition of a plate-like colloidal system. The particles are single crystals of a block copolymer PS-b-PLLA (BCSC) prepared using a self-seeding procedure. These lozenge shape crystals have a uniform thickness and a narrowly distributed lateral size. The equilibrium phase behavior and I–N phase transition have been characterized using crossed polarizers at the room temperature. A nematic phase exists for all systems with size ranging from 700 to 4000 nm. For smaller crystals (<1200 nm), the I–N phase transition follows a process of slow sedimentation and subsequent macroscopic phase separation, resulting in a highly oriented nematic phase with a sharp I–N interface. For larger crystals (≥1200 nm), the I–N phase transition follows a process of nucleation and subsequent sedimentation, resulting in a random orientation of crystals in the nematic phase and a rough I–N interface. The I–N transition occurs at a very low volume fraction (<0.2%) for all systems, which is at least one order of magnitude lower than the theoretical prediction (2–7%). However, addition of a small amount of ethanol into the solution, the I–N transition can be significantly suppressed. These results demonstrate the existence of a lateral attraction between crystals, which is due to the polar attraction between the uncovered PLLA crystalline domains. Polar ethanol molecules can adsorb to the PLLA crystalline surface and screen the attraction. The attraction exhibits highly orientation-dependent. To further demonstrate this highly directional attraction, we have prepared two composite single crystal suspensions with PLLA homopolymer, which have a much wider open angle for the polar attraction. Indeed, the resulting liquid crystalline phases show much less horizontal ordering
GaAs/AlGaAs core-shell ensemble nanowire photodetectors
We report the growth of GaAs/AlGaAs core-shell nanowire ensembles grown on p- and n-doped GaAs substrate respectively and the fabrication of these nanowire photodetectors. The I-V characteristics and spectral response of both detectors were investigated by compariso
Accurate extraction of the series resistance of aluminum local back surface field silicon wafer solar cells
10.1016/j.solmat.2014.10.003Solar Energy Materials and Solar Cells133113-11
Polyphenol Compound 18a Modulates UCP1-Dependent Thermogenesis to Counteract Obesity
Recent studies increasingly suggest that targeting brown/beige adipose tissues to enhance energy expenditure offers a novel therapeutic approach for treating metabolic diseases. Brown/beige adipocytes exhibit elevated expression of uncoupling protein 1 (UCP1), which is a thermogenic protein that efficiently converts energy into heat, particularly in response to cold stimulation. Polyphenols possess potential anti-obesity properties, but their pharmacological effects are limited by their bioavailability and distribution within tissue. This study discovered 18a, a polyphenol compound with a favorable distribution within adipose tissues, which transcriptionally activates UCP1, thereby promoting thermogenesis and enhancing mitochondrial respiration in brown adipocytes. Furthermore, in vivo studies demonstrated that 18a prevents high-fat-diet-induced weight gain and improves insulin sensitivity. Our research provides strong mechanistic evidence that UCP1 is a complex mediator of 18a-induced thermogenesis, which is a critical process in obesity mitigation. Brown adipose thermogenesis is triggered by 18a via the AMPK-PGC-1α pathway. As a result, our research highlights a thermogenic controlled polyphenol compound 18a and clarifies its underlying mechanisms, thus offering a potential strategy for the thermogenic targeting of adipose tissue to reduce the incidence of obesity and its related metabolic problems
Genome-Wide Investigation of the CRF Gene Family in Maize and Functional Analysis of ZmCRF9 in Response to Multiple Abiotic Stresses
The cytokinin response factors (CRFs) are pivotal players in regulating plant growth, development, and responses to diverse stresses. Despite their significance, comprehensive information on CRF genes in the primary food crop, maize, remains scarce. In this study, a genome-wide analysis of CRF genes in maize was conducted, resulting in the identification of 12 members. Subsequently, we assessed the chromosomal locations, gene duplication events, evolutionary relationships, conserved motifs, and gene structures of all ZmCRF members. Analysis of ZmCRF promoter regions indicated the presence of cis-regulatory elements associated with plant growth regulation, hormone response, and various abiotic stress responses. The expression patterns of maize CRF genes, presented in heatmaps, exhibited distinctive patterns of tissue specificity and responsiveness to multiple abiotic stresses. qRT-PCR experiments were conducted on six selected genes and confirmed the involvement of ZmCRF genes in the plant’s adaptive responses to diverse environmental challenges. In addition, ZmCRF9 was demonstrated to positively regulate cold and salt tolerance. Ultimately, we explored the putative interaction partners of ZmCRF proteins. In summary, this systematic overview and deep investigation of ZmCRF9 provides a solid foundation for further exploration into how these genes contribute to the complex interplay of plant growth, development, and responses to stress
Radiation effects on GaAs/AlGaAs core/shell ensemble nanowires and nanowire infrared photodetectors
With the recent advances in nanowire (NW) growth and fabrication, there has been rapid development and application of GaAs NWs in optoelectronics. It is also of importance to study the radiation tolerance of optoelectronic nano-devices for atomic energy and space-based applications. Here, photoluminescence (PL) and time-resolved photoluminescence measurements were carried out on GaAs/AlGaAs core/shell NWs at room temperature before and after 1 MeV proton irradiation with fluences ranging from 1.0 × 1012-3.0 × 1013 cm-2. It is found that the GaAs/AlGaAs core/shell NWs with smaller diameter show much less PL degradation compared with the ones with larger diameters. The increased radiation hardness is mainly attributed to the improvement of a room temperature dynamic-annealing mechanism near the surface of the NWs. We also found that the minority carrier lifetime is closely related to both the PL intensity and defect density induced by irradiation. Finally, GaAs/AlGaAs ensemble NW photodetectors operating in the near-infrared spectral regime have been demonstrated. The influence of proton irradiation on light and dark current characteristics also indicates that NW structures are a good potential candidate for radiation harsh-environment applicationsThe authors gratefully acknowledge the financial support
from the Australian Research Council (ARC), facility support
from the Australian National Fabrication Facility (ANFF)
ACT node, and the Australian Microscopy and Microanalysis
Research Facility (AMMRF) ACT node. F L also acknowledges
the financial support from the Chinese Scholarship
Council (CSC), which supported him as a visiting student at
the Australian National University (ANU) to conduct this
research
Molecular Mechanism of Gibberellins in Mesocotyl Elongation Response to Deep-Sowing Stress in Sweet Maize
Uneven germination is still a common problem in sweet maize planting. The mesocotyl is a key driver for ground-breaking sweet maize, and deep-sowing has a longer mesocotyl. However, the physiological and molecular mechanisms of sweet maize mesocotyl elongation in response to deep-sowing remain unknown. Here we found that sweet maize inbred line Ltx05 could obtain longer mesocotyls in deep soil of 10 cm depth, and that 20 mg/L GA3 was the optimal concentration to promote mesocotyl elongation and seedling emergence. Microstructure observation showed that the longitudinal cell length of mesocotyl at 10 cm sowing depth was significantly longer than that of 1 cm. Transcriptome analysis showed that microtubule process related differentially expressed genes may contribute to the longitudinal cell elongation. The content of GAs in the mesocotyl at 10 cm sowing depth was markedly higher than that of 1 cm. Combining transcriptome data and qRT-PCR at different developmental stages, ZmGA20ox1, ZmGA20ox4 and ZmGA20ox5 were identified as three positive regulation candidate genes during mesocotyl elongation under deep-sowing conditions, and this was further confirmed by the significant elongation of the hypocotyl in heterologous transformation of Arabidopsis thaliana. These results lay a foundation for improving the ability of sweet maize to tolerate deep-sowing stress and improving the breeding of excellent deep-sowing-tolerant germplasms
Molecular evolution of the ATP-binding cassette subfamily G member 2 gene subfamily and its paralogs in birds
Abstract Background ATP-binding cassette (ABC) transporters are involved in the active transportation of various endogenous or exogenous substances. Two ABCG2 gene subfamily members have been identified in birds. A detailed comparative study of the ABCG2 and ABCG2-like genes aid our understanding of their evolutionary history at the molecular level and provide a theoretical reference for studying the specific functions of ABCG2 and ABCG2-like genes in birds. Results We first identified 77 ABCG2/ABCG2-like gene sequences in the genomes of 41 birds. Further analysis showed that both the nucleic acid and amino acid sequences of ABCG2 and ABCG2-like genes were highly conserved and exhibited high homology in birds. However, significant differences in the N-terminal structure were found between the ABCG2 and ABCG2-like amino acid sequences. A selective pressure analysis showed that the ABCG2 and ABCG2-like genes were affected by purifying selection during the process of bird evolution. Conclusions We believe that multiple members of the ABCG2 gene subfamily exist on chromosome 4 in the ancestors of birds. Over the long course of evolution, only the ABCG2 gene was retained on chromosome 4 in birds. The ABCG2-like gene on chromosome 6 might have originated from chromosome replication or fusion. The structural differences between the N terminus of ABCG2 protein and those of ABCG2-like proteins might lead to functional differences between the corresponding genes
Enhancement of radiation tolerance in GaAs/AlGaAs core-shell and InP nanowires
Radiation effects on semiconductor nanowires (NWs) have attracted the attention of the research community due to their potential applications in space and atomic fields. The effective implementation of NW devices in a radiation environment is a matter of concern. Here, the photoluminescence (PL) and time-resolved PL (TRPL) measurements were performed on both GaAs and InP NWs at room temperature before and after 1 MeV H+ irradiation with fluences ranging from 1 ×1011 to 5 ×1013 p cm-2. It is found that the degradation of lifetime is size-dependent, and typically the minority carrier lifetime damage coefficient is closely correlated with the material and NW diameter. Compared to GaAs and InP bulk material counterparts, the lifetime damage coefficient of NWs decreases by a factor of about one order of magnitude. After irradiation, GaAs NWs with a smaller diameter show a much lower lifetime damage coefficient while InP NWs show an increase in carrier radiative lifetime. The increased size-dependent radiation hardness is mainly attributed to the defect sink effect and/or the improvement of a room temperature dynamic annealing mechanism of the NWs. The InP NWs also showed higher radiation tolerance than GaAs NWs