A sample-position-autocorrection system with precision better than 1 \um~in angle-resolved photoemission experiments

We present the development of a high-precision sample-position-autocorrection system for photoemission experiments. A binocular vision method based on image pattern matching calculations was realized to track the sample position with an accuracy better than 1 \um, which was much smaller than the spot size of the incident laser. We illustrate the performance of the sample-position-autocorrection system with representative photoemission data on the topological insulator Bi$_2$Se$_3$ and an optimally-doped cuprate superconductor \Bi. Our method provides new possibilities for studying the temperature-dependent electronic structures in quantum materials by laser-based or spatially resolved photoemission systems with high precision and efficiency.Comment: 6 pages, 4 figure

Ultrafast Switching from the Charge Density Wave Phase to a Metastable Metallic State in 1T-TiSe2_2

The ultrafast electronic structures of the charge density wave material 1T-TiSe$_2$ were investigated by high-resolution time- and angle-resolved photoemission spectroscopy. We found that the quasiparticle populations drove ultrafast electronic phase transitions in 1T-TiSe$_2$ within 100 fs after photoexcitation, and a metastable metallic state, which was significantly different from the equilibrium normal phase, was evidenced far below the charge density wave transition temperature. Detailed time- and pump-fluence-dependent experiments revealed that the photoinduced metastable metallic state was a result of the halted motion of the atoms through the coherent electron-phonon coupling process, and the lifetime of this state was prolonged to picoseconds with the highest pump fluence used in this study. Ultrafast electronic dynamics were well captured by the time-dependent Ginzburg-Landau model. Our work demonstrates a mechanism for realizing novel electronic states by photoinducing coherent motion of atoms in the lattice.Comment: 13 Pages, 10 figure

Characterization of Sucrose transporter alleles and their association with seed yield-related traits in Brassica napus L

<p>Abstract</p> <p>Background</p> <p>Sucrose is the primary photosynthesis product and the principal translocating form within higher plants. <it>Sucrose transporters </it>(<it>SUC/SUT</it>) play a critical role in phloem loading and unloading. Photoassimilate transport is a major limiting factor for seed yield. Our previous research demonstrated that <it>SUT </it>co-localizes with yield-related quantitative trait loci. This paper reports the isolation of <it>BnA7.SUT1 </it>alleles and their promoters and their association with yield-related traits.</p> <p>Results</p> <p>Two novel <it>BnA7.SUT1 </it>genes were isolated from <it>B. napus </it>lines 'Eagle' and 'S-1300' and designated as <it>BnA7.SUT1.a </it>and <it>BnA7.SUT1.b</it>, respectively. The BnA7.SUT1 protein exhibited typical SUT features and showed high amino acid homology with related species. Promoters of <it>BnA7.SUT1.a </it>and <it>BnA7.SUT1.b </it>were also isolated and classified as <it>pBnA7.SUT1.a </it>and <it>pBnA7.SUT1.b</it>, respectively. Four dominant sequence-characterized amplified region markers were developed to distinguish <it>BnA7.SUT1.a </it>and <it>BnA7.SUT1.b</it>. The two genes were estimated as alleles with two segregating populations (F₂and BC₁) obtained by crossing '3715'×'3769'. <it>BnA7.SUT1 </it>was mapped to the A7 linkage group of the TN doubled haploid population. <it>In silico </it>analysis of 55 segmental <it>BnA7.SUT1 </it>alleles resulted three <it>BnA7.SUT1 </it>clusters: <it>pBnA7.SUT1.a- BnA7.SUT1.a </it>(type I), <it>pBnA7.SUT1.b- BnA7.SUT1.a </it>(type II), and <it>pBnA7.SUT1.b- BnA7.SUT1.b </it>(type III). Association analysis with a diverse panel of 55 rapeseed lines identified single nucleotide polymorphisms (SNPs) in promoter and coding domain sequences of <it>BnA7.SUT1 </it>that were significantly associated with one of three yield-related traits: number of effective first branches (EFB), siliques per plant (SP), and seed weight (n = 1000) (TSW) across all four environments examined. SNPs at other <it>BnA7.SUT1 </it>sites were also significantly associated with at least one of six yield-related traits: EFB, SP, number of seeds per silique, seed yield per plant, block yield, and TSW. Expression levels varied over various tissue/organs at the seed-filling stage, and <it>BnA7.SUT1 </it>expression positively correlated with EFB and TSW.</p> <p>Conclusions</p> <p>Sequence, mapping, association, and expression analyses collectively showed significant diversity between the two <it>BnA7.SUT1 </it>alleles, which control some of the phenotypic variation for branch number and seed weight in <it>B. napus </it>consistent with expression levels. The associations between allelic variation and yield-related traits may facilitate selection of better genotypes in breeding.</p

Whole genome resequencing and phenotyping of MAGIC population for high resolution mapping of drought tolerance in chickpea

Terminal drought is one of the major constraints to crop production in chickpea (Cicer arietinum L.). In order to map drought tolerance related traits at high resolution, we sequenced multi-parent advanced generation intercross (MAGIC) population using whole genome resequencing approach and phenotyped it under drought stress environments for two consecutive years (2013-14 and 2014-15). A total of 52.02 billion clean reads containing 4.67 TB clean data were generated on the 1136 MAGIC lines and eight parental lines. Alignment of clean data on to the reference genome enabled identification of a total, 932,172 of SNPs, 35,973 insertions, and 35,726 deletions among the parental lines. A high-density genetic map was constructed using 57,180 SNPs spanning a map distance of 1606.69 cM. Using compressed mixed linear model, genome-wide association study (GWAS) enabled us to identify 737 markers significantly associated with days to 50% flowering, days to maturity, plant height, 100 seed weight, biomass, and harvest index. In addition to the GWAS approach, an identity-by-descent (IBD)-based mixed model approach was used to map quantitative trait loci (QTLs). The IBD-based mixed model approach detected major QTLs that were comparable to those from the GWAS analysis as well as some exclusive QTLs with smaller effects. The candidate genes like FRIGIDA and CaTIFY4b can be used for enhancing drought tolerance in chickpea. The genomic resources, genetic map, marker-trait associations, and QTLs identified in the study are valuable resources for the chickpea community for developing climate resilient chickpeas

BnMs3 is required for tapetal differentiation and degradation, microspore separation, and pollen-wall biosynthesis in Brassica napus

7365AB, a recessive genetic male sterility system, is controlled by BnMs3 in Brassica napus, which encodes a Tic40 protein required for tapetum development. However, the role of BnMs3 in rapeseed anther development is still largely unclear. In this research, cytological analysis revealed that anther development of a Bnms3 mutant has defects in the transition of the tapetum to the secretory type, callose degradation, and pollen-wall formation. A total of 76 down-regulated unigenes in the Bnms3 mutant, several of which are associated with tapetum development, callose degeneration, and pollen development, were isolated by suppression subtractive hybridization combined with a macroarray analysis. Reverse genetics was applied by means of Arabidopsis insertional mutant lines to characterize the function of these unigenes and revealed that MSR02 is only required for transport of sporopollenin precursors through the plasma membrane of the tapetum. The real-time PCR data have further verified that BnMs3 plays a primary role in tapetal differentiation by affecting the expression of a few key transcription factors, participates in tapetal degradation by modulating the expression of cysteine protease genes, and influences microspore separation by manipulating the expression of BnA6 and BnMSR66 related to callose degradation and of BnQRT1 and BnQRT3 required for the primary cell-wall degradation of the pollen mother cell. Moreover, BnMs3 takes part in pollen-wall formation by affecting the expression of a series of genes involved in biosynthesis and transport of sporopollenin precursors. All of the above results suggest that BnMs3 participates in tapetum development, microspore release, and pollen-wall formation in B. napus

MAE solar car : design : aerodynamics

With the rise in global warming awareness, clean energy has been increasingly popular. The biannual World Solar Challenge (WSC) is one of green events that features solar car racing. New regulations were added to bridge from adventurous to realistic designs. New and better designs emerge as technology progresses. Nanyang Technological University will be making her maiden appearance in the World Solar Challenge therefore design parameters on the influence on the aerodynamic drag of a solar car were discussed. In this project, a suitable turbulence model in Computational Fluid Dynamics (CFD) was determined by comparing with the results conducted on the Ahmed body. A Design of Experiment (DOE) comprising of influencing factors on the aerodynamic drag of the solar car was established to analyze the effects of the factors. Several scaled down models of the design adopted for the coming race, as well as a design proposed by the author were built. Flow visualizations were carried out on the two models to study the flow phenomenon. The results were compared and discussed.Bachelor of Engineering (Mechanical Engineering

Knowledge of Study Tourism and Reconstruction of Community Residents' Place Identity: A Case Study of Danxia Mountain Nature Protected Area, Guangdong

Promoting community engagement is a key issue in the sustainable development of protected natural areas. Enhancing the local residents' sense of place identity contributes to their willingness to protect the ecological environment and increases their support for ecotourism development. The role of knowledge in addressing ecological issues is widely recognized, and tourism, which focuses on knowledge production and dissemination, is gradually emerging as an alternative choice for innovative and sustainable ecotourism development in protected natural areas. However, the effect of knowledge on place identity has not been sufficiently addressed. This study employed a qualitative research method and considered Danxia Mountain, a protected area, as a case study to analyze the transformation of knowledge underlying tourism products during the transition from sightseeing tourism to study tourism. Furthermore, it explored how the behavior of community residents in learning and disseminating new knowledge contributes to the reconstruction of their local identities. The findings showed that the knowledge of resource classification and evaluation of sightseeing tourism generated a paradoxical place identity, whereas the scientific and local knowledge about Danxia Mountain for tourism reconnected community residents to the place and established a place identity. The formation and changes of local residents' place identity are the result of the interactive process of knowledge's definition of place differences and the behaviors of learning and disseminating knowledge. Specifically, there are three aspects to consider: 1) Place differences and place meanings stemming from knowledge discourse. The knowledge of a place defines its differences and assigns meaning to it. Moreover, the type of knowledge of a place can change, triggering the reconstruction of the place identity of local residents. 2) Place identity arises from the learning, internalization, and construction processes of local residents in relation to place differences and meanings within the knowledge framework. This is achieved through transforming diverse individuals' experiences and feelings about a place, where meaningful and comprehensible identities are formed, leading to a diversified sense of place identity based on individual experiences. 3) Identity performance in the process of knowledge dissemination and sharing socializes individual place identities and establishes a collective place identity. This research combines knowledge as the discourse defining place differences and the behavioral interactions of using knowledge, which expands the understanding of the process and mechanisms of place identity and can provide a more comprehensive explanatory framework for establishing place identity in social-place-individual interaction. It also provides practical guidance for cultivating local residents' place identity through knowledge-based study tourism, which requires incorporating the knowledge of community residents into the heritage site's knowledge system as well as community residents as active participants in the learning and dissemination of knowledge in the context of study tourism, which is essential for fostering a sense of place identity

The impacts of tourism at a UNESCO heritage site in China – a need for a meta-narrative? The case of the Kaiping Diaolou

In China, sites categorised as UNESCO World Heritage Sites are commonly used as a means of economic regeneration through tourism development. This study is of a recent addition to the list, the diaolou (fortified tower houses) of Kaiping, Guangdong, in South China. This rural zone, characterised by past emigration and farming, is in the early stages of tourism development. The study, based on interviews and a survey, permits findings to be compared with other rural areas in China such as Hungcun and the Tangyue Arches of Bao Village in Anhui, and thus while similarities in attitudes are found, in Kaiping differences exist whereby tourism has been found to permit entrepreneurial activities while retaining an agricultural base as the “new tourism rich” employ others to continue farming. The work is contextualised within a model of evolving literature related to tourism impacts on communities. The paper explores a range of issues in sustainable tourism, including the use of tourism as a tool for social, economic and cultural development, holistic approaches to heritage tourism, and the development of glocalisation as a response to globalisation. It discusses differences in approach to heritage tourism, cultural change and commodification between western and Chinese scholars and society