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101.
In additive manufacturing, polymer composites are used for setting tailored properties. Short glass fibers can be used as fillers for polyamide 12 for enhancing stiffness or tensile strength as well as for reducing shrinkage. In this paper, the effects of short glass fibers on polyamide 12 concerning powder properties, process behavior and part properties in laser beam melting of polymers (SLS) are investigated. It could be shown that by increasing the short glass fiber content powder properties as well as part properties are immensely affected. By adding glass fibers, powder properties, like flowability and diffuse reflection decrease. The isothermal crystallization changes resulting in a narrower processing window. Concerning mechanical properties, short glass fibers allow for a higher stiffness until a critical limit of filler concentration within this study is reached, after which the tensile strength decreases. The elongation of break decreases by rising the filler content. 相似文献
102.
Fluorescence switch plays a vital role in bioelectronics and bioimaging.Herein,we presented a new kind of facile electrostatic complex nanoparticles(ECNs)for fluorescence switching in cells and marking of individual cell.The ECNs were prepared by mixing positively charged poly(6-(2-(thiophen-3-yl)ethoxy)hexyl trimethylammonium bromide)(PT)and negatively charged diarylethene sodium salt(DAECOONa).DAE-COONa is a photoswitchable molecule which can be transformed between the ring-closed fo rm and ring-open form under the irradiation of UV or visible light.The closed-form of DAE-COONa can efficie ntly quench the fluorescence of PT through intermolecular energy transfer,while the open form of DAE-COONa does not influence the emission of PT.Thus,the fluorescence of ECNs can be modulated by light irradiation,and the ECNs with good fluorescence switching performance have been employed for fluorescence imaging and individual cell lighting up process successfully.We demonstrate that the electrostatic complex strategy provides a facile method to construct fluorescence switch fo r selective cell marking and imaging applications. 相似文献
103.
Dharmendra Kumar Yadav Devesh Kumar Singh Vellaichamy Ganesan 《Current Opinion in Electrochemistry》2020
To decrease the global carbon footprint concerns and to diminish the energy crisis, electrocatalytic reduction of CO2 which results in the formulation of value-added chemicals is a potential solution. In this review, single-atom catalysts (SACs) which are rapidly growing and being developed as the stimulating catalytic materials for electrocatalytic reduction of CO2 with improved selectivity, efficiency, and stability are considered. Various factors which are responsible for the efficient CO2 reduction are discussed. The pyrolytic approach for the preparation of Ni-based SACs and the maximum atom utilization efficiency for the desirable production of CO from CO2 are highlighted. 相似文献
104.
《Arabian Journal of Chemistry》2020,13(12):8613-8625
The selectivity and reactivity to converse series nitroaromatic into aminobenzenes are especially significant, which play a vital role in synthesizing required drugs or other fine chemicals. Herein, p-nitrophenol (p-NP) has been completely conversed into p-anomiphenol (p-AP) with a high activity factor k (0.033 s−1·mg−1) and reusability by core-shell Cu2O@CeO2 catalyst. N-acetyl-para-aminophenol (paracetamal, APAP) as a model drug was further synthesized via a flow route proceeded in two steps including p-NP reduction and subsequently p-AP acylation with self-constructing device. The yield of the paracetamal is up to 85% with a highly purity. The mechanism investigation justifies the rich-electron centers and cation defects generated from the redox coupled Cu+→Cu0 with Ce3+→Ce4+ will steer selective conversion of p-NP to p-AP, a rate-determining step in the production of APAP. The present results could visualize a highly selective catalyst and a new synthesis route for pharmaceuticals such as paracetamal by using nitroaromatic compounds as the raw materials with environment-friendly, low-cost, easy-manipulation, high-efficiency and high purity. 相似文献
105.
Igor V. Kuvychko James B. Whitaker Kristin J. Suhr Olga V. Boltalina 《Journal of fluorine chemistry》2011,132(10):679-685
The first systematic study of heterogeneous fullerene trifluoromethylation using an innovative gradient-temperature gas-solid reactor revealed a significant effect of CF3I pressure on the conversion of C60 and C70 into trifluoromethylated products and on the range of fullerene(CF3)n compositions that were obtained. The design of the reactor allowed us to lower the residence times of fullerene(CF3)n species in the hot zone which resulted in the significant differences in relative isomeric distributions as compared to the earlier methods. For the first time, gram quantities of trifluoromethylated fullerenes were prepared using the new reactor, and the selective synthesis of a single-isomer C60(CF3)2 was developed. The relative reactivity of C70 as a CF3 radical scavenger was found to be much lower than that of C60, especially at an early radical addition stage, which led to the cost-efficient synthesis of C60(CF3)2 from a fullerene extract. 相似文献
106.
Todd Eisworth 《Proceedings of the American Mathematical Society》1999,127(10):3067-3071
Mathias (Happy families, Ann. Math. Logic. 12 (1977), 59-111) proved that, assuming the existence of a Mahlo cardinal, it is consistent that CH holds and every set of reals in is -Ramsey with respect to every selective ultrafilter . In this paper, we show that the large cardinal assumption cannot be weakened.
107.
本文提出了一种新的离子选择性电极分析方法,即等电位差-标准加入法。本方法已用于氟的测定。进行了理论数据验证及误差分析,标准溶液的回收率为96.6%-104.3%。本方法的影响因素少、准确度好、操作及计算简便。 相似文献
108.
109.
Epstein CL 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,167(2):399-210
This paper considers a variety of problems in the design of selective RF-pulses. We apply a formula of Zakharov and Manakov to directly relate the energy of an RF-envelope to the magnetization profile and certain auxiliary parameters used in the inverse scattering transform (IST) approach to RF-pulse synthesis. This allows a determination of the minimum possible energy for a given magnetization profile. We give an algorithm to construct both the minimum energy RF-envelope as well as any other envelope that produces a given magnetization profile. This includes an algorithm for solving the Gel'fand-Levitan-Marchenko equations with bound states. The SLR method is analyzed in terms of traditional scattering data, and shown to be a special (singular) case of the IST approach. RF-envelopes are computed for a variety of examples. 相似文献
110.
We describe a new experiment for measuring homonuclear-decoupled anisotropic chemical shift patterns in doubly 13C-labeled compounds under magic-angle spinning. The experiment combines a pair of selective and non-selective 180 degrees pulses to suppress the 13C-13C scalar and dipolar interactions. This is combined with the recently developed SUPER technique to recouple the chemical shift anisotropy. Demonstrations on 13Calpha and 13CO-labeled amino acids and peptides show that accurate chemical shift powder patterns can be obtained. This permits the use of chemical shift anisotropy for conformational studies of suitably extensively 13C-labeled peptides and proteins. 相似文献