Search

[Objective] Under the background of new engineering disciplines, the experimental teaching of mechanical dynamics combined with frontier technology plays an important role in promoting students' engineering practice and multidisciplinary integrating innovation abilities. To realize the combination of MEMS micromirror technology and mechanical dynamics teaching practice and achieve the purpose of design verification and parameter identification of MEMS micromirror, this study relies on a Huawei-funded project to conduct experiments on the amplitude--frequency characteristics of the MEMS micromirror. [Methods] Based on the working principle, the second-order dynamic equation of MEMS micromirror is established, and the MEMS micromirror is considered a typical second-order forced vibration problem. Therefore, its amplitude--frequency characteristics exhibit the resonance phenomenon; that is, when the driving frequency is the same as the natural frequency of the system, the angular amplitude of the micromirror reaches its maximum value. Students understand the theoretical knowledge of forced vibration combined with the experiment and use the knowledge to analyze and design the micromirror, which can promote the students' engineering practice ability. The MEMS micromirror amplitude--frequency experimental platform mainly includes an electromagnetically driven micromirror, laser source, photodetector, and signal processing board. The photodetector is realized by integrating a photodiode and a Gaussian light source. The light emitted by the Gaussian light source is reflected by the mirror attached to the back of the micromirror to the photodiodes, which are integrated with the light source into the same board. Then, the photodiodes generate an electric current through the photoelectric effect. The photodiode current passes through signal processing modules, such as amplification, low-pass filtering, and analog-to-digital conversion, to generate the output signals. When the MEMS micromirror is twisted, the light spot covering the photodiodes will be offset, resulting in the varying light intensities received by the two groups of photodiodes. As a result, the output signals corresponding to the two groups of photodiodes vary, and angle detection can be realized by calculating the difference of the output signals. The amplitude--frequency characteristic curve of the micromirror can be obtained by collecting the torsional amplitudes corresponding to different driving current frequencies. [Results] The experiment on the amplitude--frequency characteristics of the micromirror realized the precise identification of the natural frequency and quality factors of the micromirror, which lays the foundation for the formulation of the control scheme. The photodetector has the advantages of compact space and lightweight; thus, it can realize high integration with the MEMS micromirror, which has important engineering value for the product of the laser scanner. [Conclusions] The application of micromirror amplitude--frequency characteristic experiments in mechanical dynamics teaching enhances students' knowledge of engineering practice and multidisciplinary integrating innovation abilities, broadens students' understanding of frontier technologies and enhances students' desire to engage in scientific research work in the future. At the same time, Huawei's courage to break through the blockade inspired students' patriotism and craftsmanship, which had a significant effect on ideological and political lessons. [ABSTRACT FROM AUTHOR]

Thermomyces dupontii harbors two P450 paralogs (P450S and P450L) in the gene cluster for the biosynthesis of prenylated indole alkaloids (PIAs) and correponding iron chelators with P450L assigned as one protein containing a CYP like domain fused with a FAD-binding domain-containing oxidoreductase. Genetic manipulation and metabolic profile analysis indicated both P450S and P450L were involved in transforming simple PIAs to their corresponding iron chelators. Moreover, P450S is responsible for bolstering simple PIAs to complex PIAs, and P450L for reinforcing conjugating unsaturated systems in complex PIAs. Chemical investigation led to isolation and characterization of novel complex PIA metabolites with more oxidations. P450L also contributed to forming the third iron-chelating core in iron chelators. A series of iron bioassays and infrastructure analysis revealed that lack of these P450 genes caused strongly elevated Fe3+ levels but attenuated Fe2+ levels, together with abnormal mitochondria in mycelia and lipid droplets and vacuoles in conidia. Phenotype analysis revealed that P450S and P450L facilitated fungal colony pigments, conidial formation and germination via bolstering conidiophores and cell walls in response to temperature reduction. [ABSTRACT FROM AUTHOR]

To date, there are no real physiological mechanisms for iron excretion in eukaryote, and no physiological "actuator" that can control all the three fundamental biologic processes of absorption, storage, and excretion. Here, we observed that the accumulation of anthraquinones by Thermomyces dupontii under cold stress can achieve this process. Through mutation analysis, we found that mutant ΔAn deficiency in anthraquinones accumulated ferrous and total free iron due to adopting a rare lifestyle with no endocytosis but accumulation of membrane‐derived vesicles. Anthraquinone complement indicated that the vesicles in ΔAn could coat the extrinsic anthraquinone‐induced granules to prevent contact with the fungal interiors. Detailed chemical investigation on ΔAn led to characterization of a rare oxygen‐free ergosterene with unstable nature in air as the major membrane steroid in ΔAn, suggesting hypoxia inner in ΔAn cells, consistent with dramatically low oxygen‐consuming rates in ΔAn. A series of physiological and metabolic analyses indicated anthraquinones were involved in exporting ferrous and promoting formation of oxygen‐containing metabolites, including ergosterols for endocytosis and iron chelators for iron storage. Moreover, we found that both the anticancer agent mitoxantrone with well‐known‐cardiotoxicity side effect and the major terpenoid‐derived polycyclic aromatics from Danshen for treating cardiovascular disease showed potent ferrous transporting capabilities in human cancer cells. Our findings provide a novel insight into the underlying mechanisms of polycyclic aromatics in nature and pharmacology, and offer a new strategy for developing potential therapeutics and agents for membrane transport, iron homestasis, and anticold. [ABSTRACT FROM AUTHOR]

This study proposes a high-resolution rotation-measuring system for miniaturized MEMS ultrasonic motors using tunneling magnetoresistance (TMR) sensors for the first time. Initially, the architecture and principle of the rotation-measuring system are described in detail. Then, the finite element simulation is implemented to determine the miniaturized permanent magnet's residual magnetization, dimensions, and TMR sensor position. Finally, the experiments are implemented to evaluate the performance. Using calibration based on a high-precision servo motor, it is found that the relationship between the output and rotational angle is highly linear and immune to the rotor's out-of-plane movement. Meanwhile, the angle-detecting resolution is higher than 0.1°. After the calibration, the continuous rotation of the MEMS ultrasonic motor is tested. It is found that the angle testing result varies with a period close to 360°, which indicates that the rotation-measuring system has successfully detected the motor's rotation. [ABSTRACT FROM AUTHOR]

Adhesive polymer is a common and important material used for packaging of microelectronics and microsystem by attaching dies onto packaging shell, and its mechanical property plays a vital role in isolating dies from the thermal stress of substrate. Therefore, it is extremely significant to evaluate the polymer property in a specific packaging process. The molecular dynamics (MD) simulation is conducted in this article to investigate the material properties of the cross‐linked epoxy resin formed by epoxy resin component diglycidyl ether bisphenol A (DGEBA) and curing agent 1,6‐Diaminohexane. The polymer network with conversion up to 87.5% is successfully generated and simulated by constant pressure‐constant temperature ensemble (NPT) and canonical ensemble (NVT) at different temperatures of curing process. Glass transition temperature (Tg) and Young's modulus are extracted and the predicted material properties are in great agreement with the experimental data. The conclusion provides a guideline to design the special curing process for different adhesive requirements. [ABSTRACT FROM AUTHOR]