293 research outputs found
Layer-by-Layer Assembled Smectite-Polymer Nanocomposite Film for Rapid Detection of Low-Concentration Aflatoxins
No full textAflatoxin is a potent biological toxin produced by fungi Aspergillus flavus and A. parasiticus. Current quantification methods for aflatoxins are mostly established on immunoaffinity columns which are both costly and labor intensive. Inspired by smectites��� high aflatoxin adsorption capacity and affinity, a novel aflatoxin quantification sensor based on smectite-polyacrylamide (PAM) nanocomposite was fabricated. First, a smectite-PAM nanocomposite film was synthesized on flat silicon substrates which assembled smectite particles from the clay suspension. A layer-by-layer assembly process was developed to achieve uniform morphology and thickness of the nanocomposite films. During the aflatoxin quantification process, positive correlations between the fluorescence intensity from the aflatoxin B1 (AFB1) adsorbed smectite-PAM nanocomposite films and the AFB1 concentration in the test solutions were obtained. The smectite-PAM nanocomposite film has shown similar AFB1 adsorption capabilities as the smectite.
Second, the smectite-PAM nanocomposite film was optimized in order to achieve the aflatoxin quantification at ppb level (below 20ppb) in corn extraction solutions. The smectite was modified by Ba2+, which had demonstrated to be able to improve its aflatoxin adsorption capacity. PAM aqueous solutions with the mass concentration ranging from 0.8% to 0.001% were tested. The results showed that the nanocomposite synthesized from 0.005% concentration of PAM solution generated the best properties. After the optimization, the smectite-PAM nanocomposite films achieved the detection of aflatoxin B1, B2, G1 and G2 (AFB2, AFG1 and AFG2) in 10 ppb corn extraction solution. Aflatoxin quantifications in AFB1 and AFB2 mixture solution, AFB1 and AFB2 mixture solution and AFB1 and AFG1 mixture solution were conducted, and the recoveries of last test ranged from 90.52% to 110.11% at low aflatoxin concentration (below 20 ppb).
Third, in order to shorten the quantification duration and simplify the detection process, a novel aflatoxin detection array based on smectite-PAM nanocomposite and an improved fluorometric quantification method were developed. Through a microfluidic chip, the reaction time was reduced to 10~20min. Two concentration levels (20~80ppb/5~15ppb) of aflatoxin B1 spiked corn extraction solutions were tested. In the fluorometric quantification step, a common lab-use 365 nm ultraviolet lamp replaced the spectrofluorometer which simplified and accelerated the process
Evaluation and Improvement Suggestions on the Operating Performance of Listed Retail Enterprises in China
No full textAs the most closely connected industry with residents, retail industry has made great contributions to Chinese economic development. The research on the operating performance of listed retail enterprises in China can objectively reflect the development of Chinese retail industry and provide beneficial reference for stakeholders. We have selected four indicators that can reflect the operating performance of listed retail enterprises: profitability, operating capacity, growth capacity and solvency. And then,we take 31 listed retail enterprises as the research object, adopting the principal component analysis method to build the operating performance evaluation index system of listed retail enterprises, and calculate the operating performance of 31 retail enterprises. According to the measurement results, we put forward specific suggestions for their sustainable development
DECOMPOSABLY-GENERATED MODULES OF SIMPLE LIE ALGEBRAS
No full text It is shown that there are finitely many irreducible finite-dimensional orthogonal modules V (up to isomorphism) over any complex simple Lie algebras such that Spin0(V) is decomposably-generated in the sense of Panyushev [The exterior algebra and "Spin" of an orthogonal 𝔤-module, Trans. Groups6 (2001) 371–396]. The case of simple Lie algebras of type A is discussed. </jats:p
Branched Alkanes with Quaternary Carbon Atoms from the Lacustrine Sediments in Linxia Basin, NE Tibetan Plateau
No full textThe impact of media image shaping of sports idols on adolescents\u27 health
No full textAdolescents in their quest for self-discovery urgently need an idol to help construct their self-identity. Sports idols, with their spirit of striving for excellence and charismatic personalities, are pursued and admired by teenagers, exerting a significant and profound influence on their growth. Due to the rapid development of mass media, the image shaping of sports idols is inseparable from the media, which presents different characteristics when shaping the media image of sports idols between commercial and public interests, thus having varying impacts, both positive and negative, on teenagers. To shape a positive media image of sports idols, governments and related departments should not only improve athletes\u27 tactical levels but also cultivate their comprehensive qualities; mass media should be aware of their social responsibility and shape a positive image of sports idols; sports idol teams need to communicate with the media and manage their own image well; schools and families, in this process, should reasonably guide teenagers to rationally worship sports idols
Photophysical and Electronic Properties of Five PCBM-like C-60 Derivatives: Spectral and Quantum Chemical View
No full textBy means of transient UV-visible absorption spectra/fluorescence, spectra, combined with electronic structure calculations, the present work focuses on characterizing the photophysical and electronic properties of five PCBM-like, C-60 derivatives (F1, F2, F3, F4, and F5) and understanding how these properties are expected to affect the photovoltaic performance of polymer solar cells,(PSCs) with those molecules as acceptors. Spectral data reveal that the fluorescence quantum yields (Phi(F)) are enhanced and the triplet quantum yields (Phi(T)) are lowered for the five PCBM-like C-60 derivatives as compared to those, of the pristine C-60, suggesting that functionalization of a C=C double bond perturbs the fullerene's pi-system and breaks the I-h symmetry of pristine C-60, which results in. modifications of photophysical properties of the ftillerene derivatives. PBEPBE/ 6-311G(d,p)//PBEPBE/6-31G(d) level of electronic structure calculations yields the HOMO-LUMO gaps and LUMO energies; showing that the electron withdrawing effect induced by the side chain functional groups perturbs LUMO energies, from which different open circuit voltages V-oc are resulted. The predicted V-oc. from our calculation agrees with previous experiment results Basically, we found that functionalization of a C=C double bond sustains the fullerene sfructure and its electron affinitive properties. Adducted side chains contribute to adjust the HOMO-LUMO gap and LUMO levels of the acceptors to improve Open Circuit, voltage. The results could provide fundamental insights for understanding how structural modifications influence the photovoltaic, Performance, which paves a way for guiding the synthesis of new fullerene derivatives with improved performance in polymer solar cells
Public Concern and Awareness of National Parks in China: Evidence from Social Media Big Data and Questionnaire Data
No full textThe high quality development of national parks plays an important role in promoting the formation of a reasonable, moderate and orderly land space protection pattern and building a harmonious coexistence of human and nature. However, a lack of public participation has limited the development of high-quality national parks in China. Understanding public concern and awareness of national parks is necessary for promoting greater public participation. This paper provides insight into this problem by combining Weibo and questionnaire survey data, then uses a combination of text mining, a Latent Dirichlet Allocation (LDA) theme model, and descriptive statistics to analyze the current state of public concern and awareness of national parks. By analyzing Weibo data, we find: (1) Public concern for national parks is increasing year by year. (2) More economically developed regions may pay more attention to national parks. (3) Public concern for national parks focuses on the construction of national parks in other countries and the institutional reform and ecotourism of national parks in China. Meanwhile, we also find that: (1) Most of the public are willing to actively pay attention to the construction of national parks. (2) The public is not yet fully aware of national parks in China; for example, the number of national parks, their construction, and other issues are still not widely known. (3) Public awareness of the construction goals, functional positioning, and other issues are not generally understood. To sum up, there is still much room for the public to improve their control and awareness of national parks. Finally, we put forward some suggestions to improve the public’s concern with and awareness of national parks, which can promote public participation in their development. This study will be important for sustainable development of the natural reserve system and global biodiversity protection in China
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