Alkaline earth metals for osteogenic scaffolds: From mechanisms to applications.

Regeneration of bone defects is a significant challenge today. As alternative approaches to the autologous bone, scaffold materials have remarkable features in treating bone defects; however, the various properties of current scaffold materials still fall short of expectations. Due to the osteogenic capability of alkaline earth metals, their application in scaffold materials has become an effective approach to improving their properties. Furthermore, numerous studies have shown that combining alkaline earth metals leads to better osteogenic properties than applying them alone. In this review, the physicochemical and physiological characteristics of alkaline earth metals are introduced, mainly focusing on their mechanisms and applications in osteogenesis, especially magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Furthermore, this review highlights the possible cross-talk between pathways when alkaline earth metals are combined. Finally, some of the current drawbacks of scaffold materials are enumerated, such as the high corrosion rate of Mg scaffolds and defects in the mechanical properties of Ca scaffolds. Moreover, a brief perspective is also provided regarding future directions in this field. It is worth exploring that whether the levels of alkaline earth metals in newly regenerated bone differs from those in normal bone. The ideal ratio of each element in the bone tissue engineering scaffolds or the optimal concentration of each elemental ion in the created osteogenic environment still needs further exploration. The review not only summarizes the research developments in osteogenesis but also offers a direction for developing new scaffold materials.

High-fidelity noise-reconstructed empirical mode decomposition for mechanical multiple and weak fault extractions.

The premise to ensure the safe operation of rotating machinery is to accurately and timely capture all kinds of damages and fault signatures, whose challenging issues are the multiple and weak faults. Ensemble noise-reconstructed empirical mode decomposition (ENEMD) is a smart method of adaptively decomposing and denoising for mechanical fault diagnosis. However, the original ENEMD and its derivative methods suffer from the drawbacks of critical noise estimation on the high accuracy, leading to the powerless capability for accurate multiple and weak fault signature extraction. Thus, high-fidelity noise-reconstructed empirical mode decomposition (HNEMD) is proposed to overcome the drawbacks, whose compositions include: (1) The cepstral neighboring coefficient editing is proposed to obtain the pre-whitening signal with the actual white noise, from which the major noise can be well purified by the minimax thresholding. (2) The high order singular value decomposition (HOSVD) local reconstruction is developed to estimate the minor noise from the pre-characterizing signal, where the tensor with the reasonable singular order is constructed by the sliding window and Hankel matrix. (3) The high-fidelity noise recovered by the major noise and the minor noise is reconstructed and combined with the basic ENEMD algorithm for accurate signature extraction, especially for the multiple or/and weak fault ones. Three repeatable simulations are analyzed to illustrate the signature extraction capability and noise estimation process of this method. Moreover, the effective detections of weak and multiple faults from a hot strip finishing mill gearbox and an aerospace bearing further validate the feasibility of the proposed method.

The therapeutic effect and safety of the drugs for COVID-19: A systematic review and meta-analysis.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has spread almost all regions of the world and caused great loss to the whole body of mankind. Thus, numerous clinical trials were conducted to find specific medicine for COVID-19 recently. However, it remains unanswered whether they are beneficial. OBJECTIVE: This study aimed to evaluate the efficiency and safety of the COVID-19 medicine. METHODS: Studies were determined through searching PubMed, Embase, Cochrane Library, and Medline. The studies of COVID-19 medicine were involved with eligible end points containing mortality, discharge rate, rate of clinical improvement, and rate of serious adverse events. RESULTS: A total of 33 studies involving 37,879 patients were included in our study, whose intervening measures contained three major types of COVID-19 medicine, ACEI/ARB, antiviral medicine, and chloroquine/hydroxychloroquine. Compared to control group, COVID-19 drugs have no distinct effect on mortality (RR, 0.93; 95% CI, 0.79-1.11, P = .43) and discharge rate (RR, 1.06; 95% CI, 0.98-1.14, P = .13). However, antiviral medicine presents the obvious advantage in clinical improvement (RR, 1.11; 95% CI, 1.01-1.23, P < .05). In addition, the serious adverse events rate (RR, 0.75; 95% CI, 0.63-0.88, P < .05) of COVID-19 medicine is lower than control group. CONCLUSION: The results indicated antiviral medicine was potential specific medicine for COVID-19 treatment by improving clinical symptoms, but it failed to increase the discharge rate and reduce mortality. Chloroquine/hydroxychloroquine and ACEI/ARB had no significant effect on treatment of COVID-19, thus they were not recommended for routine medication. Moreover, more trials are needed to find effective drugs to lower the mortality of COVID-19 patients.

Multi-channel signal transmission method of non-contact slip ring based on capacitive coupling and quasi-time division multiplexing.

The single-axis rotary inertial navigation system can use the rotary joint to compensate the drift error of the inertial components. Therefore, whether the signal can be transmitted in the rotary joint freely, accurately, for a long time, and without maintenance determines the accuracy of inertial navigation. A noncontact slip ring based on capacitive coupling and quasitime division multiplexing is proposed in this paper. First, the theoretical calculation is carried out on the method of signal transmission using two pairs of capacitors, and the factors affecting signal quality are analyzed. Second, the principle of quasitime division multiplexing and Manchester encoding is used to solve the problems such as converting multiple signals into a single signal, capacitor cannot transmit DC signal, and signal synchronization. Finally, an improved differential transmission method is designed to enhance the anti-interference of the system and to solve the level mismatch of the primary and secondary circuits. In this paper, a prototype is designed to verify the method. When the transmission rate of the three navigation signals is 1 Mbps, the navigation signals can be transmitted without distortion. And the maximum transmission frequency is 17 MHz, which can be further improved. The experimental results show that the proposed method provides a new design for the signal transmission of noncontact power slip ring. It has the advantages of high reliability, fast transmission rate, and good versatility. It can be applied to aviation, aerospace, navigation, wind power generation, and other fields where the power and signal need to be transmitted simultaneously.