Highly Thermally Conductive and Structurally Ultra-Stable Graphitic Films with Seamless Heterointerfaces for Extreme Thermal Management.

Highly thermally conductive graphitic film (GF) materials have become a competitive solution for the thermal management of high-power electronic devices. However, their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety. Here, we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks (LNS), which reveals a bubbling process characterized by "permeation-diffusion-deformation" phenomenon. To overcome this long-standing structural weakness, a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film (GF@Cu) with seamless heterointerface. This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K. Moreover, GF@Cu maintains high thermal conductivity up to 1088 W m-1 K-1 with degradation of less than 5% even after 150 LNS cycles, superior to that of pure GF (50% degradation). Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.

A new method for generating chaotic system with arbitrary shaped distributed attractors.

In this paper, a new method for generating a chaotic system with arbitrary shaped (including heart-shaped, oval, circle, piecewise-linear, and cuboid) distributed attractors is proposed. In this article, a simple four-wing chaotic attractor is first presented by using a periodic piecewise function instead of a constant parameter in the Lorenz system, on the basis of which the chaotic system with arbitrary shaped distributed attractors in the plane can be constructed. This means that the distributed chaotic attractors can be arranged in an arbitrary shape in the plane. The chaotic system can generate any quantity of distributed chaotic attractors, and simulation results show that any desired number of positive Lyapunov exponents can be obtained. Therefore, the chaotic system will have more complicated dynamic characteristics. The dynamical mechanisms of this chaotic system are further investigated, and theoretical analysis and numerical simulation are in accordance with each other, which verifies the effectiveness of the approach. Lastly, the proposed chaotic system is used for image encryption. Numerical results show that the proposed scheme has an excellent performance.

[Concentrations of antibiotics in vegetables from manure-mended farm].

Sixteen typical antibiotics including four tetracyclines, four quinolones, and eight sulfonamides in vegetables from manure-amended farm were determined using the ultra high performance liquid chromatography-tandem mass spectrometry and their health risks to human via the diet pathway was assessed. Most antibiotics were frequently detected in vegetable samples, with the detection rate from 11% to 90%. Concentrations of a single compound were mainly less than 5 microg x kg(-1) (D. W.), with the maximum of 23.88 microg x kg(-1) and the average of 0.91 microg x kg(-1), respectively. Norfloxacin, ciprofloxacin, sulfamehtaoid and sulfadiazine were the dominant compounds. At least one antibiotic was detected in a single vegetable samples, and even up to ten antibiotics. The concentration of quinolones in underground parts was higher than those in aboveground parts. Intake dose of antibiotics via the consumption of the detected vegetables was lower than ADI, suggesting a lower health risk. But combination toxicity and resistance of antibiotics should not be ignored.

Determination of intermediates and mechanism for soot combustion with NOx/O2 on potassium-supported Mg-Al hydrotalcite mixed oxides by in situ FTIR.

The soot combustion with NO(x) and/or O(2) on potassium-supported Mg-Al hydrotalcite mixed oxides under tight contact condition was studied using temperature-programmed oxidation (TPO), isothermal reaction and in situ FTIR techniques. The presence of NO(x) in O(2) favors the soot combustion at lower temperatures (<300 °C). However, a little suppression was observed at higher temperatures (>300 °C), which was accompanied by a substantial NO(x) reduction. The ketene (C═C═O) and isocyanate (NCO(-)) species were determined as the reaction intermediates. In NO(x) + O(2), NO(2) directly interacts with the free carbon sites (C═C*) through two parallel reactions: (1) NO(2) + C═C* → C═C═O + NO; (2) NO(2) + C═C* → NCO(-) + CO(2). The two reactions can proceed easily, which accounts for the promotion effect of NO(x) on soot combustion at lower temperatures. The further oxidation of NCO(-) by NO(2) or O(2) is responsible for the simultaneous reduction of NO(x). However, the reactions between NO(2) and C═C* are limited by the amount of free carbon sites, which can be provided by the oxidation of soot by O(2) at higher temperatures. The interaction of NO(x) and catalyst results in the formation of nitrates and nitrites, which poisoned the active K sites.

[Preliminary study on occurrence and health risk assessment of quinolone antibiotics in vegetables from Guangzhou, China].

Quinolone antibiotics (QNs) including norfloxacin (NOR), enrofolxacin (ENR), ciprofloxacin (CIP) and lomefloxacin (LOM) in vegetable samples collected from Guangzhou were determined by high performance liquid chromatography (HPLC) coupled with fluorescent detector (FLD). The detected frequency of QNs was 96% in vegetables. The total concentration of quinolones (sigma QNs) detected in vegetable ranged from 1.0 microg/kg to 1 683.1 microg/kg (F.W.). Leafy vegetable topped the content of quinolones among the three types of vegetables, followed by the melon-fruit vegetable and rhizome vegetable. The detected frequency of the four quinolone antibiotics ranked as NOR > CIP > LOM > ENR. Except ENR, concentrations of CIP, NOR, LOM and sigma QNs in pollution-free vegetable, green vegetable and organic vegetable were higher than those in routine cultivated vegetables. The maximum contribution to ADI value (caculated by the sum of CIP and ENR) is estimated up to 41.5% and 83% for adults and children respectively via consumption of vegetables.