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This paper presents a dynamic surface fixed-time fault-tolerant control strategy for the longitudinal dynamic model of fixed-wing unmanned aerial vehicles (UAVs). Firstly, a novel disturbance observer is constructed to precisely estimate the lumped disturbance. Secondly, without fractional power terms in the designed fixed-time fault-tolerant controller, the potential singular value problem is tactfully avoided, which often exists in the stability analysis of the traditional fixed-time controller design. Thirdly, a novel fixed-time filter is proposed to overcome the phenomenon of “differential explosion” in the backstepping control scheme. Lyapunov stability analysis guarantees that the tracking errors can converge to the neighborhood of the origin in the fixed time. The simulation results verify the effectiveness of the proposed control scheme.

This article studies the resilient control problem for a class of unknown nonlinear systems with fading measurements under malicious denial-of-service (DoS) attacks. The system output is assumed to be transmitted through a fading channel, where the fading phenomenon is described by a Rice fading model. The strategy of the attacker is to periodically interfere with the networked channels to reduce the success rate of data transmissions. First, a dynamic linearization method along the iteration domain is introduced to convert the nonlinear system into an equivalent data-related model. Then, a model-free adaptive iterative learning control (MFAILC) scheme is presented, which is independent of model information. The convergence of the MFAILC scheme is deduced theoretically and the influence of DoS attacks and stochastic fading phenomenon on system stability are also analyzed. Finally, the effectiveness of the design is verified by a numerical simulation and a trajectory tracking example of wheeled mobile robots (WMRs).

Deformation mechanisms and magnetic properties of medium and high entropy alloys (MEA/HEAs) closely relate to lattice distortion and are strongly temperature-dependent, in particular, at low temperature ranges. However, little attention has been paid to the evolution of lattice distortion with temperature decreasing and its effects on deformation behavior and magnetic state transition. In this work, we carry out in situ synchrotron radiation based X-ray powder diffraction (SR-XRD) experiments from 293 to 123 K aiming for determining lattice distortion evolutions of CrCoNi MEA, CrFeCoNi and CrMnFeCoNi HEAs. Magnetic measurements at corresponding low temperatures and cryogenic ranges are further conducted. The in situ SR-XRD results demonstrate a general reduction of lattice distortion magnitude with temperature decreasing, which shows a similar tendency with that of reported stacking fault energy (SFE) values. It is thus suggested that lattice distortion reduction possibly makes a critical contribution to deformation mechanism transition. The magnetic measurement results show a clear ferromagnetic transition of CrFeCoNi HEA when temperature is below 173 K. While, no obvious magnetic state transition is observed for CrCoNi MEA and CrMnFeCoNi HEA. The present findings on lattice distortion evolutions will pave the way for designing targeted HEAs with particular properties.

Dynamic miRNA alteration is known to occur in colitis-associated colon cancer (CAC), while the molecular mechanisms underpinning how miRNAs modulate the development from chronic inflammation to CAC is lacking. For the first time, we constructed knockout (KO) mice for individual miR-148/152 family members and entire miR-148/152 family. Based on these KO mice, we conduct the first comprehensive analysis of miR-148/152 family, demonstrating that deficiency of any member of miR-148/152 family aggravate colitis and CAC. Loss of individual miR-148/152 family members or full-family enhance MMP10 and MMP13 expression, causing disruption of intestinal barrier and cleaving pro-TNF-α into bioactive TNF-α fragments to activate NF-κB signaling, thereby aggravating colitis. Individual and full-family deletion also increase accumulation of IKKα and IKKβ, resulting in further hyperactivation of NF-κB signaling, exacerbating colitis and CAC. Moreover, blocking NF-κB signaling exerts a restorative effect on colitis and CAC models only in KO mice. Taken together, these findings demonstrate deleting the full miR-148/152 family or individual members exhibit similar effects in colitis and CAC. Mechanically, miR-148/152 family members deficiency in mice elevates MMP10 and MMP13 to accelerate colitis and CAC via disrupting intestinal barrier function and activating NF-κB signaling, suggesting a potential therapeutic strategy for colitis and CAC.

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The pyrrolic N in Cu-np/NC composites can enhance the activation of H2O, resulting in excellent selectivity for CH4 and high current density.

Amorphous nano-metal catalysts often exhibit appealing catalytic properties, because the intrinsic linear scaling relationship can be broken. However, accurate control synthesis of amorphous nano-metal catalysts with desired size and morphology is a challenge. In this work, we discover that Cu(0) could be oxidized to amorphous CuxO species by supercritical CO2. The formation process of the amorphous CuxO is elucidated with the aid of machine learning. Based on this finding, a method to prepare Cu nanoparticles with an amorphous shell is proposed by supercritical CO2 treatment followed by electroreduction. The unique feature of this method is that the size of the particles with amorphous shell can be easily controlled because their size depends on that of the original crystal Cu nanoparticles. Moreover, the thickness of the amorphous shell can be easily controlled by CO2 pressure and/or treatment time. The obtained amorphous Cu shell exhibits high selectivity for C2+ products with the Faradaic efficiency of 84% and current density of 320 mA cm−2. Especially, the FE of C2+ oxygenates can reach up to 65.3 %, which is different obviously from the crystalline Cu catalysts.

Protein sequence-based predictors of nucleic acid (NA)-binding include methods that predict NA-binding proteins and NA-binding residues. The residue-level tools produce more details but suffer high computational cost since they must predict every amino acid in the input sequence and rely on multiple sequence alignments. We propose an alternative approach that predicts content (fraction) of the NA-binding residues, offering more information than the protein-level prediction and much shorter runtime than the residue-level tools. Our first-of-its-kind content predictor, qNABpredict, relies on a small, rationally designed and fast-to-compute feature set that represents relevant characteristics extracted from the input sequence and a well-parametrized support vector regression model. We provide two versions of qNABpredict, a taxonomy-agnostic model that can be used for proteins of unknown taxonomic origin and more accurate taxonomy-aware models that are tailored to specific taxonomic kingdoms: archaea, bacteria, eukaryota, and viruses. Empirical tests on a low-similarity test dataset show that qNABpredict is 100 times faster and generates statistically more accurate content predictions when compared to the content extracted from results produced by the residue-level predictors. We also show that qNABpredict's content predictions can be used to improve results generated by the residue-level predictors. We release qNABpredict as a convenient webserver and source code at http://biomine.cs.vcu.edu/servers/qNABpredict/. This new tool should be particularly useful to predict details of protein-NA interactions for large protein families and proteomes.

The past few decades have seen a plethora of interest in heritage studies in international law, as the legitimization of cultural heritage is a significant aspect of protecting the legacy of humanity’s collective memory, which is fully reflected in a series of international instruments on culture. This paper examines the meaning-making process of UNESCO legal documents on cultural heritage from a sociosemiotic perspective. The data for the corpus-based study were analyzed quantitatively and qualitatively by applying the securitization theory to heritage studies. Research findings reveal three significant shifts in cultural heritage, i.e., from property to heritage, from tangible to intangible, and from material-centered to human-centered, which embodies the harmonious coexistence of humanity and nature, a philosophical idea embedded in traditional Chinese culture. As noted, terms targeting cultural heritage in UNESCO international instruments are the sign vehicle, generally mediated and shaped by social values, cultural beliefs, and conventional wisdom, etc. as a part of the interpretant, making different categories of heritage meaningful and interpretable. Characterized by temporality and spatiality, cultural heritage is subject to multiple interpretations. The meaning-making of international instruments for consideration is a sociosemiotic operation that can be construed through contextual factors and a process of social negotiation. This paper argues that a sociosemiotic approach to heritage studies is conducive to explicating the construction and deconstruction of heritage as discursive practices while offering some implications for future research.

To investigate lattice distortion evolutions of CrCoNi medium-entropy alloy (MEA), CrFeCoNi, and CrMnFeCoNi high-entropy alloys (HEAs) with temperature increasing from 300 to 1323 K, we conduct in situ synchrotron-radiation-based X-ray diffraction experiments. Electron backscattering diffraction, energy-dispersive X-ray spectroscopy and X-ray absorption near edge fine structure spectra (XANES) are further carried out to uncover variations of microstructure, morphology and oxidation resistance. Generally, the lattice will expand continuously with temperature increasing, however, the expansion rate is affected by grain growth and oxidation. The oxidation resistance of CrCoNi MEA is slightly higher than CrFeCoNi HEA, and much higher than CrMnFeCoNi HEA. The XANES spectra demonstrate higher oxidation resistance of Ni, Co, and Fe than Cr and Mn. Formation of local short-range order structures around Ni and Co is observed, but no such features are observed around Fe and Mn. The present findings are significant on deepening the understandings of correlations between atomic structure and mechanical properties in advanced HEAs.

An integrated control scheme composed of modified nonlinear disturbance observer and predefined-time prescribed performance control is proposed to address the high-accuracy tracking problem of the unmanned aerial vehicles (UAVs) subjected to external mismatched disturbances. By utilizing the transformation technique that incorporates the desired performance characteristic and the newly predefined-time performance function, the original controlled system can be transformed into a new unconstrained one to achieve the fixed-time convergence of the tracking error. Then, by virtual of the transformed unconstrained system, a modified nonlinear disturbance observer (NDO) which possesses fast convergence speed is established to estimate the external disturbance. With the application of the precise estimation value to compensate the normal control design in each back-stepping step, a novel composite control scheme is constructed. The light spot of the proposed scheme is that it not only has the superior capability to attenuate unknown mismatched disturbances, but also can guarantee that the output tracking errors converge to their prescribed regions within predefined time. Finally, simulation studies verify the effectiveness of the proposed control scheme.

A pilot-scale vacuum dryer with visualization system was used to study the drying characteristics of the whole blueberry pulp. The heating temperature, operating pressure and initial material thickness had significant effects on the drying characteristics and the retentions of total monomeric anthocyanins and vitamin C in dried blueberry powder (P

This paper presents a novel switching predefined-time parameter identification algorithm with a relaxed excitation condition based on the dynamic regressor extension and mixing (DREM) method. DREM often requires the persistent excitation (PE) of the extended square regressor's determinant to ensure exponential parameter convergence. Unlike the classical DREM method, a new parameter identification algorithm configured with a two-layer filter technique is proposed under a relaxed initial excitation (IE) condition, rather than strict PE. A key point in choosing IE instead of PE is the introduction of a smooth switching function that dominates the pure integral action and filter behavior of the extended square regressor. The proposed algorithm relies on the predefined-time stability theorem and the settling-time of the identification algorithm is set a priori as a system parameter. The contributions of this paper are a novel switching predefined-time parameter estimation algorithm that 1) relaxes the stringent PE condition, 2) achieves predefined-time convergence, and 3) guarantees the monotonicity of each element of the parameter error inherited from the classical DREM method. Comparative simulation results are presented to illustrate the effectiveness of the proposed algorithm.

Electrocatalytic CO

The formation and self-assembly mechanisms of nanomaterials are of great significance for the preparation and application of materials. In this study, the orientationally aggregated CoOOH nanosheets and the self-assembled strings of CoOOH nanodiscs were prepared by hydrothermal method. The formation and self-assembly mechanisms of CoOOH nanodiscs were investigated by XRD, XPS, DLS, TEM, and SEM techniques, as well as DFT calculations. The results show that the formation process of the stacked CoOOH nanodiscs was driven by surface energy and can be divided into four steps: nucleation and growth of CoOOH primary nanosheets; oriented attachment of CoOOH nanosheets; self-assembly of CoOOH nanodiscs; and aggregation of strings of CoOOH nanodiscs. This study contributes meaningfully to the controllable preparation of CoOOH nanomaterials.

The synthetic organic surfactants linear alkylbenzene sulfonate (LAS) and polycyclic aromatic hydrocarbon naphthalene (NAP), two common organic pollutants, are frequently detected in freshwater environments. However, the combined ecotoxicological risks associated with these pollutants have not been fully elucidated. The present study investigated the effects of individual and combined treatments of LAS and NAP on the growth and physiological responses of Spirodela polyrrhiza. The results showed that LAS was the main compound toxic to S. polyrrhiza in a dose-dependent manner. The peroxidase (POD) enzyme and catalase (CAT) enzyme are the main antioxidant enzymes protecting S. polyrrhiza from LAS stress. When exposed to NAP stress alone, only slightly reversible damage was observed as the exposure time was extended (14 days). The antioxidant enzyme systems (including superoxide dismutase (SOD), CAT and POD) showed positive responses. Synergistic effects were induced with LAS-NAP mixtures (≥ 5 + 5 mg L-1), and LAS played a major toxic role. The POD enzyme was a sensitive protective enzyme in duckweed during the joint exposure to LAS + NAP. The results indicate that LAS or NAP may cause serious damage to S. polyrrhiza and aggravate ecotoxicity in aquatic ecosystems.

This paper studies the problem of fixed-time output consensus tracking for high-order multi-agent systems (MASs) with directed network topology with consideration of data packet dropout. First, a predictive compensation based distributed observer is presented to compensate for packet dropout and estimate the leader's states. Next, stability analysis is conducted to prove fixed time convergence of the developed distributed observer. Then, adaptive fixed-time dynamic surface control is designed to counteract mismatched disturbances introduced by observation error, and stabilize the tracking error system within a fixed time, which overcomes explosion of complexity problem and singularity problem. Finally, simulation results are provided to verify the effectiveness and superiority of the consensus tracking strategy proposed. The contribution of this paper is to provide a fixed-time distributed observer design method for high-order MAS under directed graph subject to packet dropout, and a novel fixed-time control strategy which can handle mismatched disturbances and overcome explosion of complexity and singularity problem.

This paper empirically examines the extent to which and how local economic growth and asset location affect firm growth based on a sample of US equity real estate investment trusts (REITs) from 2001 to 2016. Using the GDP growth rate by MSA and individual property data of REITs, we construct an aggregated measure of local economic growth for each REIT based on its asset locations in different metropolitan areas. We find that REIT firm growth (measured using both book value and market value of assets) is positively correlated with the lagged firm-level economic growth measure, indicating that REITs allocating assets in areas with higher economic growth tend to experience higher firm growth. Moreover, local economic growth enhances REIT growth mainly through the growth of equity (not through the growth of debt), as REITs with more assets in higher economic growth areas provide higher stock returns to shareholders. These findings suggest that local economic conditions have a significant impact on REIT firm growth and a REIT’s asset allocation strategy can play an important role in its long-term prospects.

The electrochemical CO2 reduction reaction (CO2RR) is a promising approach for mitigating the greenhouse effect arising from anthropogenic CO2 emission. Nonetheless, poor product selectivity associated with electrochemical catalysts is the main technical problem for the application of CO2RR technology. The catalytic performance of nano-catalysts is strongly dependent on their microstructural features. Anomalous small-angle X-ray scattering (ASAXS) is one of the most effective techniques for studying nanostructural change in an operando way, especially for complex systems and mixed-element catalyst situations. Furthermore, based on the research results of ASAXS, appropriate catalyst components and nanostructures can be designed to achieve stable catalytic performance of the catalyst, promote catalytic reaction rate, or improve catalytic reaction selectivity. In this paper, the basic concept, principle, and applications in different systems of ASAXS are reviewed thoroughly. Finally, the development prospect of ASAXS in the field of electrocatalysis is prospected. It is hoped that this review will further promote ASAXS technology to play a more far-reaching impact in the field of electrocatalytic CO2RR.

Background: Hypoxia is a hallmark of the physical microenvironment of solid tumors. As a key factor that regulates tumor development and progression, hypoxia can reprogram the expression of multiple genes, whose biological function and molecular mechanism in cancer remain largely unclear. The mitochondrial ribosome protein family consists of nuclear-encoded mitochondrial proteins that are responsible for protein synthesis in the mitochondria. Methods: A high-throughput RNA sequencing assay was carried out to identify differentially expressed mRNAs between breast cancer tissues and adjacent normal tissues as well as breast tumors with metastasis and those without metastasis. Our clinical samples and TCGA database were analyzed to observe the clinical value of mitochondrial ribosome protein L52 (MRPL52) in human breast cancer. Potent hypoxia response elements in the promoter region of MRPL52 were identified and validated by chromatin immunoprecipitation and luciferase reporter assays. Functional experiments were performed using breast cancer cell lines with MRPL52 ectopic expression and knockdown cultured in a 20% or 1% O2 environment. Results: MRPL52 expression was upregulated in human breast cancer and was significantly associated with aggressive clinicopathological characteristics and a higher metastatic risk of breast cancer patients. We found that the overexpression of MRPL52 in breast cancer is induced by hypoxia-inducible factor-1 in response to hypoxic exposure. The role of MRPL52 in suppressing apoptosis and promoting migration and invasion of hypoxic breast cancer cells was demonstrated by our experimental evidence. Mechanistically, MRPL52 promoted PTEN-induced putative kinase 1 /Parkin-dependent mitophagy to remove oxidatively damaged mitochondria and prevent uncontrolled reactive oxygen species (ROS) generation, thus repressing activation of the mitochondrial apoptotic cascade. Additionally, MRPL52 augmented epithelial-mesenchymal transition, migration and invasion of hypoxic breast cancer cells by activating the ROS-Notch1-Snail signaling pathway. Benefited from this bidirectional regulatory mechanism, MRPL52 is responsible for maintaining ROS levels in a window that can induce tumorigenic signal transduction without causing cytotoxicity in hypoxic breast cancer cells. Conclusions: This work elucidates the molecular mechanism by which MRPL52 mediates hypoxia-induced apoptotic resistance and metastatic initiation of breast cancer, and provides new insights into the interplay between cancer and the tumor microenvironment.

Herein we propose the utilization of nanosized water domains for photocatalytic CO2 conversion, by which CO2 can be efficiently reduced to CO with a CO evolution rate of 682 μmol g−1 h−1 and selectivity >99%. It provides a facile, efficient and adjustable route for photocatalytic CO2 conversion with water.

A recent advance in the disorder prediction field is the development of the quality assessment (QA) scores. QA scores complement the propensities produced by the disorder predictors by identifying regions where these predictions are more likely to be correct. We develop, empirically test and release a new QA tool, QUARTERplus, that addresses several key drawbacks of the current QA method, QUARTER. QUARTERplus is the first solution that utilizes QA scores and the associated input disorder predictions to produce very accurate disorder predictions with the help of a modern deep learning meta-model. The deep neural network utilizes the QA scores to identify and fix the regions where the original/input disorder predictions are poor. More importantly, the accurate QUATERplus’s predictions are accompanied by easy to interpret residue-level QA scores that reliably quantify their residue-level predictive quality. We provide these interpretable QA scores for QUARTERplus and 10 other popular disorder predictors. Empirical tests on a large and independent (low similarity) test dataset show that QUARTERplus predictions secure AUC = 0.93 and are statistically more accurate than the results of twelve state-of-the-art disorder predictors. We also demonstrate that the new QA scores produced by QUARTERplus are highly correlated with the actual predictive quality and that they can be effectively used to identify regions of correct disorder predictions. This feature empowers the users to easily identify which parts of the predictions generated by the modern disorder predictors are more trustworthy. QUARTERplus is available as a convenient webserver at http://biomine.cs.vcu.edu/servers/QUARTERplus/ .

To examine the clinical characteristics and influencing factors related to sleep disorders in patients with Wilson's disease (WD), and investigate its potential mechanisms.A total of 150 patients with WD (76 hepatic, 42 neurological, 32 asymptomatic form) and 150 age- and sex-matched control subjects were investigated using 3 standardized sleep questionnaires. Differences among 3 subtypes were discussed.The mean Parkinson's disease sleep scale (PDSS) score of WD was lower than the controls (Z = - 4.426, P = 0.000), and their mean Epworth Sleepiness Scale (ESS) score as well as Pittsburgh sleep quality index (PSQI) score of WD was higher than that of the controls (t = 2.005, P = 0.048; t = 3.342, P = 0.001). The incidence of excessive daytime sleepiness (EDS) in WD group were significantly higher than the controls (XPatients with WD often suffer from sleep disturbances, mainly characterized by difficulty falling asleep, difficulty staying asleep, nocturnal motor symptoms (numbness, cramps, tremor), and daytime dozing. And the incidence of EDS is significantly higher than that of the controls. Sleep quality is worse in patients with WD of neurologic presentation than the other two groups. Furthermore, the worse of the symptoms, patients with WD suffer more serious of the sleep disorders especially in neurologic presentation group.

Iron oxide nanoparticles (IONPs) have been widely used as a nanoscale tool in biomedical research. However, it remains largely unknown how IONPs are transformed at a subcellular level to elicit distinct biological effects. In the present study, we prepared three different IONPs, including two IONPs targeting mitochondria (IONP-TPP) and lysosomes (IONP-APM), respectively, and a control with no specified target (IONP). By MTT assay and JC-1 staining, mitochondria-targeted IONP-TPP was found to produce significant cytotoxicity and severe mitochondrial membrane depolarization in MCF-7 cells. Furthermore, X-ray absorption spectroscopy (XAS) analysis revealed that IONP-TPP underwent remarkable edge defects and oxidation inside the cell. These findings suggest that IONPs are prone to the chemical transformation at mitochondria, and mitochondria are vulnerable to IONPs accumulation in the cell.