A Study on the Role of Guanxi Networks on Job Search in A China’s Second Tier City: Yuncheng

There has been considerable research concerning the concept of Guanxi on its different aspects. This dissertation will only focus on one aspect of Guanxi: its role on the job search process. Using a China’s second tier city as a case study, this study will explore the role of Guanxi networks on job search in Yuncheng, The research method used in this study is qualitative approach. The research findings derived from semi-structured interviews with 20 respondents selected from Yuncheng. The main finding of this research is that Guanxi networks are influential in Yuncheng even with the economic reform. Especially, it is found that interviewees’ fathers play a dominant role in the job search process. The study in Yuncheng also reveals that Guanxi is most influenced in searching jobs in the state sector

A Study on the Role of Guanxi Networks on Job Search in A China’s Second Tier City: Yuncheng

There has been considerable research concerning the concept of Guanxi on its different aspects. This dissertation will only focus on one aspect of Guanxi: its role on the job search process. Using a China’s second tier city as a case study, this study will explore the role of Guanxi networks on job search in Yuncheng, The research method used in this study is qualitative approach. The research findings derived from semi-structured interviews with 20 respondents selected from Yuncheng. The main finding of this research is that Guanxi networks are influential in Yuncheng even with the economic reform. Especially, it is found that interviewees’ fathers play a dominant role in the job search process. The study in Yuncheng also reveals that Guanxi is most influenced in searching jobs in the state sector

Prediction of the shear wave speed of seafloor sediments in the northern South China Sea based on an XGBoost algorithm

Based on data on the shear wave speed and physical properties of the shallow sediment samples collected in the northwest South China Sea, the hyperparameter selection and contribution of the characteristic factors of the machine learning model for predicting the shear wave speed of seafloor sediments were studied using the eXtreme Gradient Boosting (XGBoost) algorithm. An XGBoost model for predicting the shear wave speed of seafloor sediments was established based on four physical parameters of the sediments: porosity (n), water content (w), density (ρ), and average grain size (MZ). The result reveals that: (1) The shear wave speed has a good correlation with n, w, ρ, and MZ, and their Pearson correlation coefficients are all above 0.75, indicating that they can be used as the suitable characteristic parameters for predicting the shear wave speed based on the XGBoost model; (2) When the number of weak learners (n_estimators) is 115 and the maximum depth of the tree (max_depth) is 6, the XGBoost model has a very high goodness of fit (R2) of the validation data of 0.914, the very low mean absolute error (MAE) and mean absolute percentage error (MAPE) of the predicted shear wave speed are 3.366 m/s and 9.90%, respectively; (3) Compared with grain-shearing (GS) model and single- and dual-parameter regression equation prediction models, the XGBoost model for the shear wave speed of seafloor sediments has higher fitting goodness and lower prediction error

Controlling supramolecular chirality in multicomponent self-assembled systems

Chirality exists as a ubiquitous phenomenon in nature, from molecular level l-amino acids, d-sugar, secondary structures of proteins, DNA, RNA, and nanoscale helices to macroscopic conch and even galaxy. The aggregation of molecular building blocks with or without chiral centers might bring about asymmetric spatial stacking, which further results in the appearance of nonsymmetry in extended scales like helical nanofibers. This phenomenon, known as supramolecular chirality, is an important branch of supramolecular and self-assembly chemistry, which relates intimately with biomimetics, asymmetric catalysis, and designing chiroptic advanced materials. One of the important research focuses among supramolecular chirality is about rational manipulation of chirality amplification and handedness, presenting a profound influence on the performance of resulting soft materials such as circularly polarized luminescence and cell adhesion on hydrogels. The control over supramolecular chirality normally relies on two factors, i.e., thermodynamic and kinetic variables dependent on molecular structural parameters and environmental contributions, respectively. Supramolecular chirality in two or more component-based systems places an emphasis on thermodynamic control as it occurs from either integrated coassembly or separated self-sorting, which is more sophisticated than that of single component systems. Thus, the study on supramolecular chirality in multicomponent systems could mimic complicated biosystems, allowing for better understanding about the origin of natural chirality and extended applications as biomimetics. To date, the exploration of supramolecular chirality in multicomponent systems is restricted on both fundamental and application aspects when compared to more matured single component systems. Over the past few years, we have carried out systematic studies on several systems expressing supramolecular chirality from chiral amplification or symmetry breaking. We emphasized more the thermodynamic control by introducing a second component to form noncovalent bonding like hydrogen bonding or coordination interactions. In this Account, we would specifically discuss rational manipulation of the occurrence, transfer, and inversion of supramolecular chirality by taking several of the latest representative examples. In the multicomponent systems, in addition to the building blocks with chiral centers, the second or third components could be structural analogues and achiral small molecules such as bipyridines, melamine, metal ions, inorganic nanomaterials, and even solvents. These second or third components are able to incorporate during the aggregation to form coassembly via noncovalent bonds, influencing spatial arrangements of building blocks within various dimensions from vesicles and nanofibers to organic/inorganic hybrids. Other than chirality, morphology, stimulus responsiveness, and properties could also be well tailored by controlling interactions between different components

Inverse evolution of helicity from the molecular to the macroscopic level based on N-terminal aromatic amino acids

Precise control of the emergence of macroscopic helicity with specific handedness is promising in rationally designing chiral nanomaterials, but it is rather challenging. Herein, we present a protocol to address the transmission of helicity at a molecularly resolved level to a macroscopically resolved level, in which process supramolecular chirality undergoes an inversion. A series of N-terminal aromatic amino acids could self-assemble in water, enabling the occurrence of helicity at the molecularly resolved scale, evidenced by the single crystal structure and chiroptical responses. While it failed to transmit the helicity to the macroscopic scale for individual self-assembly, the coassembly with small organic binder through hydrogen bonding interactions allows for the emergence of helical structures at the nano/micrometer scale. Experimental and theoretical results demonstrate that the introduction of extra hydrogen bonds enables a moderate crystallinity of coassemblies with remaining one-dimensional orientation to enhance the helical growth. The transmission of helicity to higher levels by coassembly is accompanied by the helicity inversion, resulting from the exchange of hydrogen bonds. This study presents a rational protocol to precisely control the emergence of macroscopic helicity from molecularly resolved helicity with finely tailored handedness, providing a deeper understanding of the chirality origin in the assembled systems in order to facilitate the design and construction of functional chiral nanomaterials.Ministry of Education (MOE)National Research Foundation (NRF)This work is supported by the Qilu Young Scholarship Funding of Shandong University, the National Natural Science Foundation of China (21872087 and 21901145), the Natural Science Foundation of Jiangsu Province (BK20190209), and the Youth Cross-Scientific Innovation Group of Shandong University (2020QNQT003). This research is also supported by the Singapore Academic Research Fund (RT12/19) and the Singapore National Research Foundation Investigatorship (NRF-NRFI2018-03)

Chiral molecular nanosilicas

Molecular nanoparticles including polyoxometalates, proteins, fullerenes and polyhedral oligosiloxane (POSS) are nanosized objects with atomic precision, among which POSS derivatives are the smallest nanosilicas. Incorporation of molecular nanoparticles into chiral aggregates either by chiral matrices or self-assembly allows for the transfer of supramolecular chirality, yet the construction of intrinsic chirality with atomic precision in discrete molecules remains a great challenge. In this work, we present a molecular folding strategy to construct giant POSS molecules with inherent chirality. Ferrocenyl diamino acids are conjugated by two or four POSS segments. Hydrogen bonding-driven folding of diamino acid arms into parallel β-sheets facilitates the chirality transfer from amino acids to ferrocene and POSS respectively, disregarding the flexible alkyl spacers. Single crystal X-ray structures, density functional theory (DFT) calculations, circular dichroism and vibrational circular dichroism spectroscopy clearly verify the preferential formation of one enantiomer containing chiral molecular nanosilicas. The chiral orientation and chiroptical properties of POSS show pronounced dependence on the substituents of α-amino acids, affording an alternative way to control the folding behavior and POSS chirality in addition to the absolute configuration of amino acids. Through the kinetic nanoprecipitation protocol, one-dimensional aggregation enables chirality transfer from the molecular scale to the micrometer scale, self-assembling into helices in accordance with the packing propensity of POSS in a crystal phase. This work, by illustrating the construction of chiral molecular nanosilicas, paves a new way to obtain discrete chiral molecular nanoparticles for potential chiroptical applications.Published versionThis work is supported by the Qilu Young Scholarship Funding of Shandong University, the National Natural Science Foundation of China (21872087 and 21901145), the Natural Science Foundation of Jiangsu Province (BK20190209), and the Youth Cross-Scientific Innovation Group of Shandong University (2020QNQT003)

Photo-triggered transformation from vesicles to branched nanotubes fabricated by a cholesterol-appended cyanostilbene

Cholesterol-appended cyanostilbene was synthesized, which could self-assemble into vesicles accompanied by a aggregation-induced emission effect. Under UV light irradiation, the vesicles gradually merged together to form branched nanotubes. The self-assembly and disassembly processes could be utilized in the quantitative analysis of external stimulus, which were demonstrated by H2O2-selective sensing.NRF (Natl Research Foundation, S’pore)ASTAR (Agency for Sci., Tech. and Research, S’pore)Published versio

Fluorescent imprintable hydrogels via organic/inorganic supramolecular coassembly

Photoresponsive hydrogels with on/off luminescence show a promising application potential in writable information recording and display materials. However, it still remains a tremendous challenge to fabricate such hydrogels on account of the intrinsic fluorescence quenching effect and the lack of suitable responsive groups. Herein, we present fluorescent imprintable hydrogels constructed via organic/inorganic supramolecular coassembly. A photoisomeric cyanostilbene conjugated cationic surfactant exhibited an aggregation-induced emission behavior upon clay (laponite) complexation, along with excellent thixotropism brought by laponite. Macrocyclic cucurbituril[7] and β-cyclodextrin rings capable of forming host-guest complexes with the surfactant were utilized to give ternary hybrid hydrogels with luminescence and photoresponsive properties. On the account of trans-cis photoisomerization of the cyanostilbene unit, the fluorescence of the multicomponent hydrogels could undergo rapid quenching within a short irradiation period under UV light and be recovered when subjected to an annealing process. According to these properties, the imprinted fluorescent patterns using the hybrid hydrogels were erasable and rewritable. Thus, this research successfully integrates host-guest complexation and supramolecular coassembly into the fabrication of fluorescent imprintable hydrogels.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)This work is financially supported by the Qilu Young Scholarship Funding of Shandong University, the National Natural Science Foundation of China (21872087 and 21901145), the Natural Science Foundation of Jiangsu Province (BK20190209), and the Youth Cross-Scientific Innovation Group of Shandong University (2020QNQT003). It is also supported by the Singapore Agency for Science, Technology and Research (A*STAR) AME IRG grant (A1883c0005), and the Singapore National Research Foundation Investigatorship (NRF-NRFI2018-03). The authors acknowledge the assistance from Shandong University Structural Constituent and Physical Property Research Facilitie

Environment‐adaptive coassembly/self‐sorting and stimulus‐responsiveness transfer based on cholesterol building blocks

Manipulating the property transfer in nanosystems is a challenging task since it requires switchable molecular packing such as separate aggregation (self‐sorting) or synergistic aggregation (coassembly). Herein, a unique manipulation of self‐sorting/coassembly aggregation and the observation of switchable stimulus‐responsiveness transfer in a two component self‐assembly system are reported. Two building blocks bearing the same cholesterol group give versatile topological structures in polar and nonpolar solvents. One building block (cholesterol conjugated cynanostilbene, CCS) consists of cholesterol conjugated with a cynanostilbene unit, and the other one (C10CN) is comprised of cholesterol connected with a naphthalimide group having a flexible long alkyl chain. Their assemblies including gel, crystalline plates, and vesicles are obtained. In gel and crystalline plate phases, the self‐sorting behavior dominates, while synergistic coassembly occurs in vesicle phase. Since CCS having the cyanostilbene group can respond to the light irradiation, it undergoes light‐induced chiral amplification. C10CN is thermally responsive, whereby its supramolecular chirality is inversed upon heating. In coassembled vesicles, it is interestingly observed that their responsiveness can be transferred by each other, i.e., the C10CN segment is sensitive to the light irradiation, while CCS is thermoresponsive. This unprecedented behavior of the property transfer may shine a light to the precise fabrication of smart materials.Published versio