A Review of N-(1,3-Dimethylbutyl)-N'-phenyl-p-Phenylenediamine (6PPD) and Its Derivative 6PPD-Quinone in the Environment.

As an antioxidant and antiozonant, N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is predominantly used in the rubber industry to prevent degradation. However, 6PPD can be ozonated to generate a highly toxic transformation product called N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-quinone), which is toxic to aquatic and terrestrial organisms. Thus, 6PPD and 6PPD-quinone, two emerging contaminants, have attracted extensive attention recently. This review discussed the levels and distribution of 6PPD and 6PPD-quinone in the environment and investigated their toxic effects on a series of organisms. 6PPD and 6PPD-quinone have been widely found in air, water, and dust, while data on soil, sediment, and biota are scarce. 6PPD-quinone can cause teratogenic, developmental, reproductive, neuronal, and genetic toxicity for organisms, at environmentally relevant concentrations. Future research should pay more attention to the bioaccumulation, biomagnification, transformation, and toxic mechanisms of 6PPD and 6PPD-quinone.

Design of Optoelectronic Tracking Platform Driven by Ultrasonic Motor with a Novel Limiter.

A high-performance servo control system is the basis for realizing high-precision photoelectric tracking. With high position resolution and power-off self-locking, ultrasonic motors have a wide range of applications for high-precision positioning control. An optoelectronic tracking platform driven by two ultrasonic motors is proposed in this study. The shaft structure of the tracking platform is designed and modeled. The shaft structure is simplified, and a dynamic model is established to analyze the motion characteristics. The parameters of the limit mechanism are optimized based on the analysis. The shaft structure is built to verify the response characteristics of the tracking platform at different velocities. The results show that the proposed design can fully utilize the self-locking of ultrasonic motors for rapid automatic alignment of the axis system. The maximum response time is less than 55 ms. When the operating velocity is less than 70°/s, the positioning error is less than 0.055°, and the lower the speed, the smaller the positioning error.

Research on Fast and Precise Positioning Strategy of an Ultrasonic Motor Based on the Ultrasonic Friction Reduction Theory.

To address the problems of the large positioning error and long positioning time of the traditional positioning strategy, namely, the two-phase simultaneous power-off method (TPSPM), a new positioning strategy, called the first single-phase then two-phase power-off method (FSPTTPPM), based on the ultrasonic friction reduction theory, has been proposed in this work. This method realizes zero sliding displacement between the friction material and the stator during the torsional oscillation of the shaft by controlling the driving circle frequency and the duration of the single-phase power-off period, which reduces the deviation of the displacement reservation value. In order to verify the correctness of the driving mechanism, a test platform has been built, and two positioning strategies have been used for experimental verification. The following experimental results have been obtained: compared to TPSPM, FSPTTPPM has the advantages of higher positioning accuracy and short positioning time. In terms of the positioning accuracy, the relative errors of the displacement reservation values of FSPTTPPM and TPSPM vary with the initial angular velocity (0.24 to 1.18 rad/s) in the range of -0.4 to 0.1 and -0.8 to 0.8, respectively. In addition, the relative error of the displacement reservation value is closer to zero than that of TPSPM at the same initial angular velocity. In terms of the positioning time, when the initial angular velocity is greater than 0.7 rad/s, the positioning time of the FSPTTPPM is approximately 10 ms smaller than that of the TPSPM.

Preparation and characterization of vinyl-functionalized mesoporous organosilica-coated solid-phase microextraction fiber.

Vinyl-SBA-15 mesoporous organosilica was synthesized and used as coating material of solid-phase microextraction (SPME) by two coating techniques (direct coating and sol-gel). The synthesized vinyl-SBA-15 organosilica had highly ordered mesoporous structure, good thermal stability and a specific surface area of 688 m² g⁻¹. The fibers prepared by two methods were evaluated by the extraction of non-polar compounds (BTEX, benzene, toluene, ethylbenzene, o-xylene) and polar compounds (phenols). The results showed that the vinyl-SBA-15 fibers prepared by two methods exhibited high thermal stability (310 °C for direct-coated and 350 °C for sol-gel) and excellent solvent durability in methanol and acetonitrile. The fibers also presented much better extraction performance for both polar compounds (phenols) and non-polar compounds (BTEX), compared to commercial polydimethylsiloxane (PDMS) fiber, as well as wide linear ranges, low detection limits (0.008-0.047 µg L⁻¹ for BTEX, sol-gel; 0.15-5.7 µg L⁻¹ for phenols, direct-coated), good repeatabilities (RSDs less than 5.4% for BTEX) and satisfying reproducibilities between fibers (RSDs less than 5.8% for BTEX). The self-made fibers were successfully used for the analysis of BTEX and phenols in three aqueous samples including tap water, mineral water and lake water, which demonstrated the applicability of the vinyl-SBA-15 fibers.