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Abstract There is a general agreement that Northern Hemisphere temperatures have cooled over the past two millennia, culminating in the Little Ice Age. However, this understanding partly relies on the compilation of existing proxy records, the majority of which carry a warm season bias such that there is an underrepresentation of cold-season temperatures. Here we report a unique cold-season temperature record based on the alkenone paleothermometer from the northeastern Tibetan Plateau that spans the last two millennia. In contrast to the regional- and hemisphere-scale summer cooling, our reconstruction shows a long-term warming through the Medieval Climate Anomaly into Little Ice Age. We attribute these opposing temperature trends to combined effects of seasonally divergent insolation and North Atlantic subpolar gyre circulation. Our study indicates that the cold season during the Little Ice Age was not the coldest period of the last two millennia at least on the northeastern Tibetan Plateau.

Medicinal chemistry investigators have isolated and synthesized benzoflavone analogues with diverse bioactivities including enzyme inhibitory activity, central nervous system (CNS) activity, anti-inflammatory activity, anti-microorganism activity, hypoglycemic activity, and receptor modulating potential. SAR (Structure-Activity Relationship) studies have been conducted extensively and plenty of benzoflavone analogues have been prepared for potential targets. Herein, we review the pharmacology properties and SAR for benzoflavone analogues, and provide a brief summarization of synthetic strategies, wishing to give perspective on the research and development of benzoflavone derivatives.

Due to the excellent properties of carbon fiber-reinforced polymers (CFRPs), such as high strength and strong corrosion resistance, the traditional water-jet-guided laser (WJGL) technology has problems with fiber pull-out and has a small cutting depth when processing CFRPs. Therefore, in this study, we used high-power water-jet-guided laser (HPWJGL) technology to perform groove processing experiments on CFRPs. The effects of four key process parameters, high laser power, pulse frequency, feed rate, and water-jet pressure, on the cutting depth were investigated by a single-factor experiment. The formation mechanism of groove cross-section morphology and the processing advantages of high-power water-jet-guided lasers were analyzed. On this basis, the mathematical prediction model of cutting depth was established by using the response surface method (RSM), and the optimal combination of process parameters was obtained. The mathematical prediction model was verified by experiments, and the error was only 1.84%, indicating that the model had a high reference value. This study provides a reference for the precision machining of HPWJGL technology.

Poplar was one of the first woody species whose individual chromosomes could be identified using chromosome specific painting probes. Nevertheless, high-resolution karyotype construction remains a challenge. Here, we developed a karyotype based on the meiotic pachytene chromosome of Populus simonii which is a Chinese native species with many excellent traits. This karyotype was anchored by oligonucleotide (oligo)-based chromosome specific painting probes, a centromere-specific repeat (Ps34), ribosomal DNA, and telomeric DNA. We updated the known karyotype formula for P. simonii to 2n = 2x = 38 = 26m + 8st + 4t and the karyotype was 2C. The fluorescence in situ hybridization (FISH) results revealed some errors in the current P. simonii genome assembly. The 45S rDNA loci were located at the end of the short arm of chromosomes 8 and 14 by FISH. However, they were assembled on pseudochromosomes 8 and 15. In addition, the Ps34 loci were distributed in every centromere of the P. simonii chromosome in the FISH results, but they were only found to be present in pseudochromosomes 1, 3, 6, 10, 16, 17, 18, and 19. Our results reveal that pachytene chromosomes oligo-FISH is a powerful tool for constructing high-resolution karyotypes and improving the quality of genome assembly.

In order to automatically process ultra-fine copper tube electrodes, this study proposes a new method of ultrasonic vibration processing of ultra-fine copper tube, analyzes its processing principle, designs a new set of experimental processing equipment and completes the processing of 1.206 mm inner diameter, 1.276 mm outer diameter with core brass tube. Not only can the copper tube be completed with core decoring, the surface of the processed brass tube electrode also has good integrity. The effect of each machining parameter on the surface roughness of the electrode after machining was investigated by a single-factor experiment and the optimal machining effect was achieved under the conditions of machining gap 0.1 mm, ultrasonic amplitude 0.186 mm, table feed speed 6 mm/min, tube rotation speed 1000 r/min and reciprocating machining two times. The surface roughness was reduced from 1.21 μm before machining to 0.11 μm, and the residual pits, scratches and oxide layer on the surface were completely removed, which greatly improved the surface quality of the brass tube electrode and prolonged its service life.

The internal wall of cardiovascular stent tubing produced by a drawing process has defects such as pits and bumps, making the surface rough and unusable. In this research, the challenge of finishing the inner wall of a super-slim cardiovascular stent tube was solved by magnetic abrasive finishing. Firstly, a spherical CBN magnetic abrasive was prepared by a new method, plasma molten metal powders bonding with hard abrasives; then, a magnetic abrasive finishing device was developed to remove the defect layer from the inner wall of ultrafine long cardiovascular stent tubing; finally, response surface tests were performed and parameters were optimized. The results show that the prepared spherical CBN magnetic abrasive has a perfect spherical appearance; the sharp cutting edges cover the surface layer of the iron matrix; the developed magnetic abrasive finishing device for a ultrafine long cardiovascular stent tube meets the processing requirements; the process parameters are optimized by the established regression model; and the inner wall roughness (Ra) of the nickel–titanium alloy cardiovascular stents tube is reduced from 0.356 μm to 0.083 μm, with an error of 4.3% from the predicted value. Magnetic abrasive finishing effectively removed the inner wall defect layer and reduced the roughness, and this solution provides a reference for polishing the inner wall of ultrafine long tubes.

In this investigation, spherical Al2O3 magnetic abrasive particles (MAPs) were used to polish the inner surface of ultra-fine long cobalt–chromium alloy cardiovascular stent tubes. The magnetic abrasives were prepared by combining plasma molten metal powder and hard abrasives, and the magnetic abrasives prepared by this new method are characterized by high sphericity, narrow particle size distribution range, long life, and good economic value. Firstly, the spherical Al2O3 magnetic abrasives were prepared by the new method; secondly, the polishing machine for the inner surface of the ultra-fine long cardiovascular stent tubes was developed; finally, the influence laws of spindle speed, magnetic pole speed, MAP filling quantities, the magnetic pole gap on the surface roughness (Ra), and the removal thickness (RT) of tubes were investigated. The results showed that the prepared Al2O3 magnetic abrasives were spherical in shape, and their superficial layer was tightly bound with Al2O3 hard abrasives with sharp cutting; the use of spherical Al2O3 magnetic abrasives could achieve the polishing of the inner surface of ultra-fine cobalt–chromium alloy cardiovascular bracket tubes, and after processing, the inner surface roughness (Ra) of the tubes decreased from 0.337 µm to 0.09 µm and had an RT of 5.106 µm.

In order to improve the tribological properties of Ti-6Al-4V alloy and further broaden the application scope of titanium alloy materials in the industrial field, a preparation method of a waterjet-guided high-power laser processing surface microgroove was studied. In this paper, a multifocus coupling lens was innovatively designed to replace the spherical lens in the traditional waterjet-guided laser coupling device, which avoids the gas explosion phenomenon in the coupling of the high-power laser and waterjet, and realizes the high-quality coupling of the high-power laser and water beam fiber. Then, with the microgroove morphology as the response target, the single-factor test and response surface test of the water-guided laser processing microgroove were carried out. Based on the experimental results, an approximate mathematical model of the response surface between the process parameters and the microgroove topography target was constructed, and the quantitative relationship between the waterjet-guided laser processing parameters and the target response was studied. At the same time, the optimal combination of process parameters was obtained by multiobjective optimization, so as to effectively improve the microgroove morphology. This technology provides method guidance and a decision-making reference for subsequent waterjet-guided laser processing of titanium alloy surface functional microstructures.

In this paper, the surface roughness of SiC ceramics was investigated in laser-assisted machining (LAM) processes; machine learning was used to predict surface roughness and to optimize the process parameters, and therefore, to ultimately improve the surface quality of a workpiece and obtain excellent serviceability. First, single-factor turning experiments were carried out on SiC ceramics using LAM according to the material removal mechanism to investigate the variation trend of the effects of different laser powers, rotational speeds, feed rates, and cutting depths on surface roughness. Then, laser power, rotational speed, feed rate and cutting depth were selected as the four factors, and the surface roughness was used as the target value for the orthogonal experiments. The results of the single-factor experiments and the orthogonal experiments were combined to construct a prediction model based on the combination of the grey wolf optimization (GWO) algorithm and support vector regression (SVR). The coefficient of determination (R2) of the optimized prediction model reached 0.98676 with an average relative error of less than 2.624%. Finally, the GWO algorithm was used to optimize the global parameters of the prediction model again, and the optimal combination of process parameters was determined and verified by experiments. The actual minimum surface roughness (Ra) value was 0.418 μm, and the relative error was less than 1.91% as compared with the predicted value of the model. Therefore, the prediction model based on GWO-SVR can achieve accurate prediction of the surface roughness of SiC ceramics in LAM and can obtain the optimum surface roughness using parameter optimization.

High-performance iron-based Al2O3 magnetic abrasive powder (MAP) prepared by combining plasma molten metal powder with sprayed abrasive powder is used for magnetic abrasive finishing (MAF) of AZ31B magnesium alloy to remove surface defects such as creases, cracks, scratches, and pits generated during the manufacturing process of the workpiece, and to reduce surface roughness and improve its wear and corrosion resistance. In order to solve the problem of magnetic abrasive powder splash in the MAF process, the force analysis of the MAP in the processing area is conducted, and a composite magnetic pole processing device was designed and simulated to compare the effects of both devices on MAF, confirming the feasibility of composite magnetic pole grinding. Then, experiments have been designed using Response Surface Methodology (RSM) to investigate the effect of four factors-magnetic pole rotation speed, grinding gap, magnetic pole feed rate, magnetic abrasive filling quantity-on surface roughness and the interactions between them. The minimum surface roughness value that can be obtained is used as the index for parameter optimization, and the optimized parameters are used for experiments, and the results show that the established surface roughness model has good predictive ability.

Due to the special manufacturing process of cobalt–chromium alloy cardiovascular stent tubes, there are serious surface defects in their inner walls, which affects the therapeutic effect after implantation. At the same time, the traditional processing technology cannot finish the inner wall of a cardiovascular stent tube. In light of the above problems, magnetic abrasive finishing (MAF) equipment for the inner wall of an ultra-fine and ultra-long cardiovascular stent tube is proposed, and MAF technology is used to improve the surface quality of its inner wall. High-performance spherical magnetic abrasive powders are used to finish the inner wall of a cobalt–chromium alloy cardiovascular stent tube with an inner diameter of 1.6 mm and an outer diameter of 1.8 mm. The effects of finishing time, tube rotational speed, feed speed of the magnetic pole, MAPs filling quantity, and MAP abrasive size on the surface roughness and material removal thickness of cobalt–chromium alloy cardiovascular stent tube are investigated. The results show that the surface roughness of the inner wall of the cobalt–chromium alloy cardiovascular stent decreases from 0.485 μm to 0.101 μm, and the material removal thickness of the defect layer is 4.3 μm. MAF technology is used to solve the problem of the poor surface quality of the inner walls of ultra-fine and ultra-long cobalt–chromium alloy cardiovascular stent tubes.

In this study, a new method of ultrasonic high-frequency percussion (UH-FP) is proposed. Ultra-fine and ultra-long copper tube electrodes cannot be fabricated by traditional processing methods, and the copper tube electrodes fabricated by UH-FP can be used in the process of rotary EDM for microfine holes. The UH-FP setup has been established based on an ultrasonic device, a workpiece chucking and rotation device, and a workpiece reciprocating motion device. In this work, by studying the principle of ultrasonic processing, the processing principle and mechanism of ultra-fine and ultra-long copper tube electrode preparation by ultrasonic high-frequency percussion is proposed. The effects of processing parameters (i.e., rotational speed, feed rate, working gap, percussion amplitude) on surface roughness are evaluated quantitatively. Experimental results show that the proposed method could complete the core leach of the core-containing copper tube electrodes after drawing, while improving surface quality. Some surface defects such as cracks, scratches and folds were completed removed, further improving the mechanical performance of processed parts. The surface roughness (Ra) of 0.091 μm was obtained from the initial 0.46 μm under the optimal processing parameters of 800 rpm tube rotational speed, 200 mm/min platform feed speed, 0.13 mm machining gap, 0.15 mm percussion amplitude, and 32 min machining time. The method shows potential for manufacturing copper tube electrodes for a wide range of industrial applications.

Hyperspectral image classification technology is important for the application of hyperspectral technology. Support vector machines (SVMs) work well in supervised classifications of hyperspectral images; however, they still have some shortcomings, and their use of a parallel decision plane makes it difficult to conform to real hyperspectral data distribution. The improved nonparallel support vector machine based on SVMs, i.e., the bias constraint additional empirical risk minimization nonparallel support vector machine (BC-AERM-NSVM), has improved classification accuracy compared its predecessor. However, BC-AERM-NSVMs have a more complicated solution problem than SVMs, and if the dataset is too large, the training speed is significantly reduced. To solve this problem, this paper proposes a least squares algorithm, i.e., the least square bias constraint additional empirical risk minimization nonparallel support vector machine (LS-BC-AERM-NSVM). The dual problem of the LS-BC-AERM-NSVM is an unconstrained convex quadratic programming problem, so its solution speed is greatly improved. Experiments on hyperspectral image data demonstrate that the LS-BC-AERM-NSVM displays a vast improvement in terms of solution speed compared with the BC-AERM-NSVM and achieves good classification accuracy.

Support vector machine (SVM) has a good effect in the supervised classification of hyperspectral images. In view of the shortcomings of the existing parallel structure SVM, this article proposes a non-parallel SVM model. Based on the traditional parallel boundary structure vector machine, this model adds an additional empirical risk minimization term to the original optimization problem by adding the least square term of the sample and obtains two non-parallel hyperplanes, respectively, forming a new non-parallel SVM algorithm to minimize the additional empirical risk of non-parallel SVM (Additional Empirical Risk Minimization Non-parallel Support Vector Machine, AERM-NPSVM). On the basis of AERM-NPSVM, the bias constraint is added to it, and AERM-NPSVM (BC-AERM-NPSVM) is further obtained. The experimental results show that, compared with the traditional parallel SVM model and the classical non-parallel SVM model, Twin Support Vector Machine (TWSVM), the new model, has a better effect in hyperspectral image classification and better generalization performance.

Cadmium, one of the most toxic heavy metals, can cause severe oxidative damage to aquatic animals. However, the mechanism whereby the mud crabs respond to cadmium exposure remains unclear. This study investigated the effects of cadmium exposure on oxidative stress and histopathology changes and evaluated the role of the Nrf2 signaling pathway in regulating responses to cadmium-induced hepatotoxicity were investigated in mud crabs. Mud crabs were exposed to 0, 0.01, 0.05, and 0.125 mg/L cadmium for 21 d. The present results indicated that cadmium exposure increased hydrogen peroxide (H2O2) production, lipid peroxidation and tissue damage, but decreased the activity of superoxide dismutase (SOD) and catalase (CAT), and caused lipid peroxidation and tissue damage. The results of an integrated biomarker index analysis suggested that the toxicity of cadmium was positively related to cadmium concentration. The expression levels of the Nrf2 signaling pathway (Nrf2, metallothionein, and cytochrome P450 enzymes) were up-regulated after cadmium exposure. Silencing of Nrf2 in vivo decreased antioxidant gene (SOD, CAT, and glutathione S-transferase) expression, suggesting that Nrf2 can regulate antioxidant genes. Knocking down Nrf2 in vivo also significantly decreased the activity of SOD and CAT after cadmium exposure. Moreover, silencing of Nrf2 in vivo enhanced H2O2 production and the mortality rates of mud crabs after cadmium exposure. The present study indicated that cadmium exposure induced hepatotoxicity in the mud crab by increasing H2O2 content, which decreased the antioxidant capacity, leading to cell injury. In addition, the Nrf2 is activated to bound with antioxidant response element, initiating the expression of antioxidant enzyme genes during cadmium induced hepatotoxicity in the mud crabs.

Laser cleaning technology has the advantages of being green and efficient and is expected to become the most promising remanufacturing cleaning technology. However, the quasi-continuous laser can easily cause problems, such as a heat-affected zone and a recast layer on the substrate material, which limits the development of laser cleaning technology. The environmentally friendly water jet-guided quasi-continuous laser proposed in this paper is an innovative laser cleaning technology that can remove the resin-based coating on the metal substrate with high quality. The epoxy resin coating on the 304 stainless steel surface was cleaned by a water jet guided quasi continuous laser, and the surface morphology, surface element content, and surface roughness of the cleaning area were tested and analyzed. The removal mechanism of water jet-guided quasi-continuous laser cleaning technology was revealed, and the influence of process parameters on cleaning surface quality was found. The optimal process parameters were as follows: the energy density of the water jet-guided laser 17.5 J/cm2, the cleaning speed 135 mm/s, the cleaning line spacing 0.1 mm, and the laser pulse frequency 900 Hz. Therefore, this study is expected to be an important basis for water jet-guided quasi-continuous laser cleaning technology, and promote the development of water jet-guided laser cleaning technology.

The mud crab Scylla paramamosain is a valuable commercial mariculture crab worldwide. During the ebb tide or when transported to market, crabs suffer underlying air exposure stress. Gills tissue is the first tissue to cope with this stress. In this study, the transcriptome of S. paramamosain gills from the control group (CG) and experimental group (EG) were sequenced, assembled, and compared. A total of 7,425,620,293 bp and 6,741,616,977 bp clean data were found in EG and CG, respectively. A total of 38,507 unigenes (42.78%) were annotated successfully. 13,626 differentially expressed genes (DEGs) were up-regulated, and 6,502 DEGs were down-regulated. The DEGs related to immunity, apoptosis, metabolism, and ion exchange were detected. DEGs were enriched significantly into the KEGG pathways related to metabolism and immunity. These results proved that more material and energy were required, and immune defense was enhanced when the crab was under air exposure stress. The present study provides the first-gill transcriptomic analysis challenged with air exposure stress in S. paramamosain under air exposure stress, which will be useful to clarify the molecular mechanisms of air exposure adaptation. [ABSTRACT FROM AUTHOR]

The intertropical convergence zone (ITCZ) plays a key role in regulating tropical hydroclimate and global water cycle through changes in its convection strength, latitudinal position, and width. The long-term variability of the ITCZ, along with the corresponding driving mechanisms, however, remains obscure, mainly because it is difficult to separate different ITCZ variables in paleoclimate proxy records. Here, we report a speleothem oxygen isotope (d18O) record from southwestern Sulawesi, Indonesia, and compile it with other speleothem records from the Maritime Continent. Using the spatial gradient of speleothem d18O along a transect across the ITCZ, we constrain ITCZ variabilities over the Maritime Continent during the past 30,000 y. We find that ITCZ convection strength overall intensified from the last glacial period to the Holocene, following changes in climate boundary conditions. The mean position of the regional ITCZ has moved latitudinally no more than 3° in the past 30,000 y, consistent with the deduction from the atmospheric energy framework. However, different from modern observations and model simulations for future warming, the ITCZ appeared narrower during both the late Holocene and most part of the last glacial period, and its expansion occurred during Heinrich stadials and the early-to-mid Holocene. We also find that during the last glacial and deglacial period, prominent millennial-scale ITCZ changes were closely tied to the variability of the Atlantic meridional overturning circulation (AMOC), whereas during the Holocene, they were predominantly modulated by the long-term variability of the Walker circulation. [ABSTRACT FROM AUTHOR]

This document is a reply to a previous article by Lu et al. regarding the reconstruction of the Intertropical Convergence Zone (ITCZ) variability using speleothem δ18O records from the Maritime Continent. The authors of this reply argue that the two components of ITCZ variability, migration and contraction-expansion, are not necessarily independent and are strongly affected by interhemispheric thermal contrast. They also contend that the compilation of records used by Lu et al. may be less representative and produce biased results. The authors suggest that a combined theoretical and model-proxy approach is needed to better understand ITCZ variability and tropical climate change. [Extracted from the article]