Low-Frequency Bandgaps of the Lightweight Single-Phase Acoustic Metamaterials with Locally Resonant Archimedean Spirals

In order to achieve the dual needs of single-phase vibration reduction and lightweight, a square honeycomb acoustic metamaterials with local resonant Archimedean spirals (SHAMLRAS) is proposed. The independent geometry parameters of SHAMLRAS structures are acquired by changing the spiral control equation. The mechanism of low-frequency bandgap generation and the directional attenuation mechanism of in-plane elastic waves are both explored through mode shapes, dispersion surfaces, and group velocities. Meanwhile, the effect of the spiral arrangement and the adjustment of the equation parameters on the width and position of the low-frequency bandgap are discussed separately. In addition, a rational period design of the SHAMLRAS plate structure is used to analyze the filtering performance with transmission loss experiments and numerical simulations. The results show that the design of acoustic metamaterials with multiple Archimedean spirals has good local resonance properties, and forms multiple low-frequency bandgaps below 500 Hz by reasonable parameter control. The spectrograms calculated from the excitation and response data of acceleration sensors are found to be in good agreement with the band structure. The work provides effective design ideas and a low-cost solution for low-frequency noise and vibration control in the aeronautic and astronautic industries.

Mangroves As Coastal Bio-Shield: A Review of Mangroves Performance in Wave Attenuation

Mangroves have been recognized as soft structures that provide coastline protection. The capability of dampening waves helps minimize destruction from catastrophic events including erosive wave attacks, torrential storms, and tsunamis. Mangroves act as the first line of coastal defense in natural tragedies such as during the Super Typhoon Haiyan 2013 and Indian Ocean Tsunami 2004, whereby the leeward mangrove area encountered less damage than the unprotected area. This has further brought the attention of researchers to study the attenuation performance of these coastal vegetations. Based on an extensive literature review, this paper discusses the attenuation mechanism of mangroves, the factors influencing the dissipation performance, studies on mangrove dissipation via different approaches, the dissipation efficiency, mangrove conservation and rehabilitation efforts in Malaysia and implementation of mangrove as coastal bio-shield in other countries. The study highlights that mangrove parameters (such as species, width, density etc.) and wave parameters (such as wave period and incident wave height) are among the contributing factors in mangroves-induced wave attenuation, with different efficiency rates performed by different mangroves and waves parameters. Towards that end, several improvements are proposed for future research such as to incorporate all influencing dissipation factors with specific analysis for each species of mangroves, to perform validation on the studied mangroves attenuation capacity in different settings and circumstances, as well as to address the extent of protection by the rehabilitated mangroves. A systematic and effective management strategy incorporating ecological, forestry, and coastal engineering knowledge should be considered to ensure a sustainable mangroves ecosystem and promising coastline protection by mangroves. Doi: 10.28991/cej-2021-03091772 Full Text: PDF

THE STUDY OF THE INFLUENCE OF X-RAY IRRADIATION ON DISLOCATION CHARACTERISTICS IN LiF CRYSTALS

The dependences of the absorption α and the ultrasound velocity in LiF single crystals with residual deformation ε = 0.65% at 300 K in the range of radiation doses 0...1057 R were studied using the acoustic pulse echo method at a frequency of 7.5 MHz. Based on the results of measurements of the acoustic characteristics, the absolute values of the parameters of the dislocation structure – the average effective length of the dislocation loop L and the dislocation density Λ and their dependences on the irradiation time are determined. The calculated characteristics are compared with the previously obtained results for the high-frequency branch of the damped dislocation resonance and using the selective etching method. The revealed noticeable discrepancy in the values of these parameters is explained by the impossibility of describing a single attenuation mechanism for acoustic measurements carried out in a wide frequency range.

Paeoniflorin and albiflorin regulate P-gp-mediated aconitine and hypaconitine transport through an Madin Darby canine kidney-multi drug resistance protein 1 cell model

Aconitine and hypaconitine are the main active ingredients of Radix Aconiti, paeoniflorin and albiflorin are the primary components of Radix Paeoniae Alba. Both Radix Aconiti and Radix Paeoniae Alba are herbs that are commonly used in traditional Chinese medicine. This study sought to explore the mechanistic transport of aconitine and hypaconitine across MDCK-MDR1 cells and to assess the effect of paeoniflorin and albiflorin on aconitine and hypaconitine transmembrane transport as a potential attenuation mechanism. Drug cytotoxicity was tested via the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and transport studies were performed in both directions. The effects of drugs on P-gp ATPase activity, P-gp efflux function, MDR1 mRNA and P-gp expression were evaluated in MDCK-MDR1 cells. Aconitine and hypaconitine treatment with the verapamil could significantly decrease the efflux rate (ER). The ER of aconitine and hypaconitine were significantly increased with the coadministration of paeoniflorin and albiflorin, suggesting that paeoniflorin and albiflorin can promote the efflux of these two alkaloids. Aconitine and hypaconitine can induce P-gp enzymatic activity, inhibit P-gp-mediated efflux, and downregulate the expression of P-gp protein to produce cytotoxic effects. When treatment in combination with paeoniflorin and albiflorin, it could stimulated P-gp ATPase activity, increasing mRNA expression, enhance P-gp efflux function, and upregulate P-gp protein expression.

Translational Attenuation Mechanism of ErmB Induction by Erythromycin Is Dependent on Two Leader Peptides

Ribosome stalling on ermBL at the tenth codon (Asp) is believed to be a major mechanism of ermB induction by erythromycin (Ery). In this study, we demonstrated that the mechanism of ermB induction by Ery depends not only on ermBL expression but also on previously unreported ermBL2 expression. Introducing premature termination codons in ermBL, we proved that translation of the N-terminal region of ermBL is the key component for ermB induced by Ery, whereas translation of the C-terminal region of ermBL did not affect Ery-induced ermB. Mutation of the tenth codon (Asp10) of ermBL with other amino acids showed that the degree of induction in vivo was not completely consistent with the data from the in vitro toe printing assay. Alanine-scanning mutagenesis of ermBL demonstrated that both N-terminal residues (R7-K11) and the latter part of ermBL (K20-K27) are critical for Ery induction of ermB. The frameshifting reporter plasmid showed that a new leader peptide, ermBL2, exists in the ermB regulatory region. Further, introducing premature termination mutation and alanine-scanning mutagenesis of ermBL2 demonstrated that the N-terminus of ermBL2 is essential for induction by Ery. Therefore, the detailed function of ermBL2 requires further study.