Tungsten Inert Gas Welding of 6061-T6 Aluminum Alloy Frame: Finite Element Simulation and Experiment.

In order to address the irregularity of the welding path in aluminum alloy frame joints, this study conducted a numerical simulation of free-path welding. It focuses on the application of the TIG (tungsten inert gas) welding process in aluminum alloy welding, specifically at the intersecting line nodes of welded bicycle frames. The welding simulation was performed on a 6061-T6 aluminum alloy frame. Using a custom heat source subroutine written in Fortran language and integrated into the ABAQUS environment, a detailed numerical simulation study was conducted. The distribution of key fields during the welding process, such as temperature, equivalent stress, and post-weld deformation, were carefully analyzed. Building upon this analysis, the thin-walled TIG welding process was optimized using the response surface method, resulting in the identification of the best welding parameters: a welding current of 240 A, a welding voltage of 20 V, and a welding speed of 11 mm/s. These optimal parameters were successfully implemented in actual welding production, yielding excellent welding results in terms of forming quality. Through experimentation, it was confirmed that the welded parts were completely formed under the optimized process parameters and met the required product standards. Consequently, this research provides valuable theoretical and technical guidance for aluminum alloy bicycle frame welding.

Feature engineering for improved machine-learning-aided studying heavy metal adsorption on biochar.

Due to the broad interest in using biochar from biomass pyrolysis for the adsorption of heavy metals (HMs) in wastewater, machine learning (ML) has recently been adopted by many researchers to predict the adsorption capacity (η) of HMs on biochar. However, previous studies focused mainly on developing different ML algorithms to increase predictive performance, and no study shed light on engineering features to enhance predictive performance and improve model interpretability and generalizability. Here, based on a dataset widely used in previous ML studies, features of biochar were engineered-elemental compositions of biochar were calculated on mole basis-to improve predictive performance, achieving test R2 of 0.997 for the gradient boosting regression (GBR) model. The elemental ratio feature (H-O-2N)/C, representing the H site links to C (non-active site to HMs), was proposed for the first time to help interpret the GBR model. The (H-O-2N)/C and pH of biochar played essential roles in replacing cation exchange capacity (CEC) for predicting η. Moreover, expanding the coverages of variables by adding cases from references improved the generalizability of the model, and further validation using cases without CEC and specific surface area (R2 0.78) and adsorption experimental results (R2 0.72) proved the ML model desirable. Future studies in this area may take into account algorithm innovation, better description of variables, and higher coverage of variables to further increase the model's generalizability.

All-Inorganic Green Synthesis of Small-Sized and Efficient K2SiF6:Mn4+ Phosphor for Mini-LED Displays.

High-resolution liquid crystal display (LCD) backlight requires a color conversion layer featuring micrometer light-emitting particles and a uniform morphology. The widely used commercial red-emitting K2SiF6:Mn4+ phosphor, showing promise as a light-conversion candidate, faces limitations due to its toxic synthesis process, large particle size, and poor moisture resistance. We successfully demonstrated an efficient substitution of the highly toxic HF/TEOS/KHF2 solvent system with a commonly used HCl/SiO2/KF solvent system to synthesize the small-sized K2SiF6:Mn4+ phosphor. Additionally, surface passivation was performed to enhance the luminescence intensity and resistance to moisture, denoted as K2SiF6:Mn4+@CaF2. Accordingly, the K2SiF6:Mn4+@CaF2 phosphor presents a high luminescence efficiency (99.87%/32.84% IQE/EQE) with an average particle size of ∼2.67 µm. Notably, after exposure to 85% humidity and 85 °C temperature for 3 h, the luminescence intensity remains at 47.4% for K2SiF6:Mn4+@CaF2, while 21.2% for pristine K2SiF6:Mn4+, and only 3.5% for K2SiF6:Mn4+ synthesized by TEOS. These advancements hold great potential for improving high-resolution LCD backlighting, particularly for displays with micron-level pixels, opening up new possibilities for enhanced display technology.

Evaluations of heterogeneous epidemic models with exponential and non-exponential distributions for latent period: the Case of COVID-19.

Most of heterogeneous epidemic models assume exponentially distributed sojourn times in infectious states, which may not be practical in reality and could affect the dynamics of the epidemic. This paper investigates the potential discrepancies between exponential and non-exponential distribution models in analyzing the transmission patterns of infectious diseases and evaluating control measures. Two SEIHR models with multiple subgroups based on different assumptions for latency are established: Model Ⅰ assumes an exponential distribution of latency, while Model Ⅱ assumes a gamma distribution. To overcome the challenges associated with the high dimensionality of GDM, we derive the basic reproduction number ($ R_{0} $) of the model theoretically, and apply numerical simulations to evaluate the effect of different interventions on EDM and GDM. Our results show that considering a more realistic gamma distribution of latency can change the peak numbers of infected and the timescales of an epidemic, and GDM may underestimate the infection eradication time and overestimate the peak value compared to EDM. Additionally, the two models can produce inconsistent predictions in estimating the time to reach the peak. Our study contributes to a more accurate understanding of disease transmission patterns, which is crucial for effective disease control and prevention.

Intervalence charge transfer of Cr3+-Cr3+ aggregation for NIR-II luminescence.

The increasing demand for high-contrast biological imaging, non-destructive testing, and infrared night vision can be addressed by the development of high-performance NIR light-emitting materials. Unlike lanthanide (Ln3+) with sharp-line multiplets and isolated Cr3+ with NIR-I emission, this study reports the first-ever NIR-II broadband luminescence based on the intervalence charge transfer (IVCT) of Cr3+-Cr3+ aggregation in gallate magentoplumbite. In particular, LaMgGa11O19:0.7Cr3+ exhibits dual-emission (NIR-I, 890 nm and NIR-II, 1200 nm) with a full width at half maximum (FWHM) of 626 nm under 450 nm blue LED excitation. Moreover, this dual-emission exhibits anti-thermal quenching behavior (432% @ 290 K), attributed to the energy transfer among multiple Cr3+ centers. Cryogen absorption spectra, lifetimes decay (2.3 ms), and electron paramagnetic experiments reveal the NIR-II luminescence of the Cr3+-Cr3+ → Cr2+-Cr4+ IVCT transition. The application of LaMgGa11O19:0.7Cr3+ in NIR-II biological imaging as an optical contrast agent, non-destructive testing, and night vision is demonstrated. This work provides new insights into broadband NIR-II luminescence under UV-NIR excitation based on the IVCT of Cr3+-Cr3+ aggregation.

Enhancing External Quantum Efficiency of Blue-Emitting Phosphor Ba(K)-ß-Al2O3:Eu2+ by Lattice Site Engineering for Full-Spectrum Lighting.

The discovery of violet-excitable blue-emitting phosphor is a significant breakthrough for the development of phosphor-converted full-spectrum white light-emitting diodes (WLEDs). However, the application of most known violet-excitable blue-emitting phosphors is limited by their low external quantum efficiency (EQE). In this work, we reported on how the EQE values of Eu2+-doped Ba(K)-ß-Al2O3 blue-emitting phosphor can be significantly improved through lattice site engineering. By partially substituting K+ for Ba2+, the Eu2+-occupied crystallographic site changes and the coordination polyhedron of Eu2+ shrinks, leading to the increase of crystal field splitting. Consequently, the excitation spectrum exhibits a continuous red shift to match the violet excitation, which enhances the PL intensity of solid solution phosphor (Ba0.4K1.6)0.84Al22O35-α:0.32Eu2+ ((B0.4K1.6)0.84AO:Eu) by 1.42 times compared to that of the end-member Ba1.68Al22O35-α:0.32Eu2+ (B1.68AO:Eu) phosphor. Correspondingly, under the 400 nm violet light excitation, the EQE of optimal blue-emitting (B0.4K1.6)0.84AO:Eu phosphor is up to 53%. Additionally, the phosphor also shows excellent resistance to luminescence thermal quenching (95% at 150 °C). Finally, the WLED fabricated based on (B0.4K1.6)0.84AO:Eu and commercial green and red phosphors exhibited an ultra-high color rending index with Ra = 95.5 and R1-R15 >90. This work offers guidance for tuning the spectral properties of phosphors through lattice site engineering.

Integrated microbiome-metabolome-genome axis data of Laiwu and Lulai pigs.

Excessive fat deposition can trigger metabolic diseases, and it is crucial to identify factors that can break the link between fat deposition and metabolic diseases. Healthy obese Laiwu pigs (LW) are high in fat content but resistant to metabolic diseases. In this study, we compared the fecal microbiome, fecal and blood metabolome, and genome of LW and Lulai pigs (LU) to identify factors that can block the link between fat deposition and metabolic diseases. Our results show significant differences in Spirochetes and Treponema, which are involved in carbohydrate metabolism, between LW and LU. The fecal and blood metabolome composition was similar, and some anti-metabolic disease components of blood metabolites were different between the two breeds of pigs. The predicted differential RNA is mainly enriched in lipid metabolism and glucose metabolism, which is consistent with the functions of differential microbiota and metabolites. The down-regulated gene RGP1 is strongly negatively correlated with Treponema. Our omics data would provide valuable resources for further scientific research on healthy obesity in both human and porcine.

Numerical Prediction of Microstructure Evolution of Small-Diameter Stainless Steel Balls during Cold Skew Rolling.

The wear resistance and hardness of stainless steel (SS) balls formed by cold skew rolling are effectively improved due to the change in internal microstructure. In this study, based on the deformation mechanism of 316L stainless steel, a physical mechanism-based constitutive model was established and implemented in a subroutine of Simufact to investigate the microstructure evolution of 316L SS balls during the cold skew rolling process. The evolution of equivalent strain, stress, dislocation density, grain size, and martensite content was studied via simulation during the steel balls' cold skew rolling process. The corresponding skew rolling experiments of steel balls were carried out to verify the accuracy of the finite element (FE) model results. The results showed that the macro dimensional deviation of steel balls fluctuates less, and the microstructure evolution agrees well with the simulation results, which proves that the established FE model has high credibility. It shows that the FE model, coupled with multiple deformation mechanisms, provides a good prediction of the macro dimensions and internal microstructure evolution of small-diameter steel balls during cold skew rolling.

Mathematical modeling the dynamics of SARS-CoV-2 infection with antibody-dependent enhancement.

The advent and swift global spread of the novel coronavirus (COVID-19) transmitted by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have caused massive deaths and economic devastation worldwide. Antibody-dependent enhancement (ADE) is a common phenomenon in virology that directly affects the effectiveness of the vaccine, and there is no fully effective vaccine for diseases. In order to study the potential role of ADE on SARS-CoV-2 infection, we establish the SARS-CoV-2 infection dynamics model with ADE. The basic reproduction number is computed. We prove that when R 0 < 1 , the infection-free equilibrium is globally asymptotically stable, and the system is uniformly persistent when R 0 > 1 . We carry out the sensitivity analysis by the partial rank correlation coefficients and the extended version of the Fourier amplitude sensitivity test. Numerical simulations are implemented to illustrate the theoretical results. The potential impact of ADE on SARS-CoV-2 infection is also assessed. Our results show that ADE may accelerate SARS-CoV-2 infection. Furthermore, our findings suggest that increasing antibody titers can have the ability to control SARS-CoV-2 infection with ADE, but enhancing the neutralizing power of antibodies may be ineffective to control SARS-CoV-2 infection with ADE. Our study presumably contributes to a better understanding of the dynamics of SARS-CoV-2 infection with ADE.

Evaluations of COVID-19 epidemic models with multiple susceptible compartments using exponential and non-exponential distribution for disease stages.

Mathematical models have wide applications in studying COVID-19 epidemic transmission dynamics, however, most mathematical models do not take into account the heterogeneity of susceptible populations and the non-exponential distribution infectious period. This paper attempts to investigate whether non-exponentially distributed infectious period can better characterize the transmission process in heterogeneous susceptible populations and how it impacts the control strategies. For this purpose, we establish two COVID-19 epidemic models with heterogeneous susceptible populations based on different assumptions for infectious period: the first one is an exponential distribution model (EDM), and the other one is a gamma distribution model (GDM); explicit formula of peak time of the EDM is presented via our analytical approach. By data fitting with the COVID-19 (Omicron) epidemic in Spain and Norway, it seems that Spain is more suitable for EDM while Norway is more suitable for GDM. Finally, we use EDM and GDM to evaluate the impaction of control strategies such as reduction of transmission rates, and increase of primary course rate (PCR) and booster dose rate (BDR).

Global stability and optimal control for a COVID-19 model with vaccination and isolation delays.

COVID-19 pandemic remains serious around the world and causes huge deaths and economic losses. To investigate the effect of vaccination and isolation delays on the transmission of COVID-19, we propose a mathematical model of COVID-19 transmission with vaccination and isolation delays. The basic reproduction number is computed, and the global dynamics of the model are proved. When R 0 < 1 , the disease-free equilibrium is globally asymptotically stable. The unique endemic equilibrium is globally asymptotically stable if R 0 > 1 . Based on the public information, parameter values are estimated, and sensitivity analysis is carried out by the partial rank correlation coefficients (PRCCs) and the extended version of the Fourier amplitude sensitivity test (eFAST). Our results suggest that the isolation rates of asymptomatic and symptomatic infectious individuals have a significant impact on the transmission of COVID-19. When the COVID-19 is epidemic, the optimal control strategies of our model with vaccination and isolation delays are analyzed. Under the limited resource with constant and time-varying isolation rates, we find that the optimal isolation rates may minimize the cumulative number of infected individuals and the cost of disease control, and effectively contain the transmission of COVID-19. Our study may help public health to prevent and control the COVID-19 spread.

Effects of Sterile Males and Fertility of Infected Mosquitoes on Mosquito-Borne Disease Dynamics.

By studying an infection-age structured model, we consider the effects of releasing sterile males and the fertility of infected mosquitoes on the mosquito-borne diseases transmission including the extinction of mosquitoes, the elimination and persistence of diseases. Firstly, equivalent integral equations are established to prove the well-posedness of solutions. Then, the main results of disease dynamics are given. By taking chikungunya as a numerical simulation example, an optimal releasing threshold is given according to our presupposed control standard. When the fertility disturbance of infected mosquitoes is small, the high releasing amount plays a main role on the control of the disease; however, when the fertility disturbance is large, the initial distributions and the fertility of infected mosquitoes are the key factors to control the disease. Mathematically, the fertility of infected mosquitoes makes the system have complex dynamics with multiple positive equilibria and bistability.

Association between plasma free fatty acid levels and primary angle-closure glaucoma based on a mass spectrometry metabolomics analysis.

PURPOSE: To determine the association between plasma free fatty acid (FFA) levels and primary angle-closure glaucoma (PACG). METHODS: Free fatty acid (FFA) levels in patients with PACG (n = 181) and people without glaucoma (n = 340) were compared. Twenty-two FFAs and six lipid classes were measured using metabolomics analysis. Odds ratio (OR) of these metabolites and their 95% confidence intervals (95%CI) for PACG were obtained by logistic regression. Stepwise forward selection was performed to identify FFAs that influenced PACG risk. Areas under the curve (AUC) were applied to assess the predictive performance. Spearman's rank correlation was used to assess the relationship between ocular parameters and FFAs. RESULTS: Most FFAs in the PACG group were lower than those in the non-glaucoma group. Docosahexaenoic acid (DHA; OR for fourth quartile (Q4) vs. first quartile (Q1): 0.32 (0.16-0.66); per standard deviation (SD) increase: 0.64 (0.49-0.83); p for trend: 0.0007) and total saturated fatty acids (SFAs; OR for Q4 versus Q1: 0.27 (0.13-0.56); per SD increase: 0.65 (0.50-0.87); p for trend: 0.0004) were associated with decreased PACG risk. The AUC of the model that included DHA, total SFAs, demographic and ophthalmic factors increased from 0.8230 (0.7811-0.8649) to 0.8512 (0.8133-0.8891) (increased AUC: 0.0282 (0.0112-0.0453); p for increased AUC: 0.0012). Additionally, the cup-disc ratio had a weak negative correlation with DHA and total SFAs (DHA: r = -0.12085, p = 0.0065; total SFAs: r = -0.13318, p = 0.0024). CONCLUSIONS: Decrease in FFA levels may be related to lipid peroxidation. Docosahexaenoic acid (DHA) and total SFAs may be screening indices for PACG patients.

UV-Red Light-Chargeable Near-Infrared-Persistent Phosphors and Their Applications.

Near-infrared (NIR)-persistent luminescence (PersL) materials are of promising applications in labeling, tracing, bio-imaging, and so forth, featuring distinctive self-sustained NIR light emitting. The PersL radiation spectrum, PersL duration, and charging efficiency are recognized as the key enablers for high-performance NIR PersL materials. Here, we have designed and developed a series of broad-band NIR superlong PersL phosphors (Sr,Ba) (Ga,In)12O19:Cr3+ with efficient UV-red light charging capacity. Typical SrGa10.49In1.5O19:0.01Cr3+ presents intensive NIR PersL from 650 to 1000 nm peaking at ∼770 nm, with a PersL duration of 360 h. This material can be efficiently and repeatedly charged by solar radiation in various outdoor environments. Our work further identifies that this NIR PersL material is advantageous for labeling and tracing as a secret NIR additive and in situ bio-imaging as an optical probe under high tissue penetration red light excitation.

Modelling and stability analysis of ASFV with swill and the virus in the environment.

African swine fever (ASF) is an acute, hemorrhagic and severe infectious disease caused by the African swine fever virus (ASFV), and leads to a serious threat to the pig industry in China. Yet the impact of the virus in the environment and contaminated swill on the ASFV transmission is unclear in China. Then we build the ASFV transmission model with the virus in the environment and swill. We compute the basic reproduction number, and prove that the disease-free equilibrium is globally asymptotically stable when $ R_0 < 1 $ and the unique endemic equilibrium is globally asymptotically stable when $ R_0 > 1 $. Using the public information, parameter values are evaluated. PRCCs and eFAST sensitivity analysis reveal that the release rate of ASFV from asymptomatic and symptomatic infectious pigs and the proportion of pig products from infectious pigs to swill have a significant impact on the ASFV transmission. Our findings suggest that the virus in the environment and contaminated swill contribute to the ASFV transmission. Our results may help animal health to prevent and control the ASFV transmission.

The effect of microwave stabilization on the properties of whole wheat flour and its further interpretation by molecular docking.

In order to stabilize the whole wheat flour and extend its shelf life, microwave was employed to heat the wheat bran to inactivate the lipase in this paper. The effects of microwave heating of wheat bran on the lipase activities, gluten properties, dough properties and storage stability of the stabilized whole wheat flour, and the quality of steamed bread made of stabilized whole wheat flour were investigated. Furthermore, molecular docking was applied to interpret the mechanism. The results showed that microwave can reduce lipase activity, maintain the quality of whole wheat flour dough and steamed bread, and retard rancidity. The molecular docking results displayed that the conformation of the amino acids chains near the lipase catalytic center changed, which made the substrate difficult to enter the catalytic center and prevented the hydrolysis of the fat substrate.

Effectiveness of non-pharmaceutical interventions against local transmission of COVID-19: An individual-based modelling study.

The outbreak of the novel coronavirus disease 2019 (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused global transmission, and been spread all over the world. For those regions that are currently free of infected cases, it is an urgent issue to prevent and control the local outbreak of COVID-19 when there are sporadic cases. To evaluate the effects of non-pharmaceutical interventions against local transmission of COVID-19, and to forecast the epidemic dynamics after local outbreak of diseases under different control measures, we developed an individual-based model (IBM) to simulate the transmission dynamics of COVID-19 from a microscopic perspective of individual-to-individual contacts to heterogenous among individuals. Based on the model, we simulated the effects of different levels of non-pharmaceutical interventions in controlling disease transmission after the appearance of sporadic cases. Simulations shown that isolation of infected cases and quarantine of close contacts alone would not eliminate the local transmission of COVID-19, and there is a risk of a second wave epidemics. Quarantine the second-layer close contacts can obviously reduce the size of outbreak. Moreover, to effectively eliminate the daily new infections in a short time, it is necessary to reduce the individual-to-individual contacts. IBM provides a numerical representation for the local transmission of infectious diseases, and extends the compartmental models to include individual heterogeneity and the close contacts network. Our study suggests that combinations of self-isolation, quarantine of close contacts, and social distancing would be necessary to block the local transmission of COVID-19.

Estimation of COVID-19 outbreak size in Harbin, China.

Since the first level response to public health emergencies was launched on January 25, 2020, in Heilongjiang province, China, the outbreak of COVID-19 seems to be under control. However, an outbreak of COVID-19 caused by imported cases developed in Harbin during April 2020. A mathematical model is established to investigate the transmission of COVID-19 in Harbin. Based on the dynamical analysis and data fitting, the research investigates the outbreak of COVID-19 in Harbin and estimates the outbreak size of COVID-19 in Harbin. The outbreak size estimated of COVID-19 in Harbin reaches 174, where 54% of infected cases were identified while 46% of infected cases were not found out. We should maintain vigilance against unfound infected people. Our findings suggest that the effective reproduction number decreased drastically in contrast with the value of 3.6 on April 9; after that the effective interventions were implemented by the Heilongjiang province government. Finally, the effective reproduction number arrived at the value of 0.04 which is immensely below the threshold value 1, which means that the Heilongjiang province government got the outbreak of COVID-19 in Harbin under control.

Asymptotic behaviors of jellyfish model with stage structure.

In this paper, a stage-structured jellyfish model with two time delays is formulated and analyzed, the first delay represents the time from the asexually reproduced young polyp to the mature polyp and the second denotes the time from the developed polyp to ephyra (incipient medusa). Global dynamics of the model are obtained via monotone dynamical theory: the jellyfish populations go extinct and the trivial equilibrium is globally asymptotically stable if the survival rate of polyp during cloning and the survival rate of the incipient medusa during strobilation are less than their death rates. And if the survival rate of polyp during cloning and the survival rate of the incipient medusa during strobilation are larger than their death rates, a unique positive equilibrium is globally asymptotically stable. Moreover, it is proved that the only stage of polyps will continue without growing into medusa and the boundary equilibrium is globally asymptotically stable if the survival rate of polyp is larger than its death rate during cloning and if there is no survival of the incipient medusa. Numerical simulations are performed to verify our analytical results and to explore the dynamics with/without delays.

Intravitreal conbercept improves outcome of proliferative diabetic retinopathy through inhibiting inflammation and oxidative stress.

Conbercept is a newly-developed anti-vascular endothelial growth factor (VEGF) drug. This study aimed to evaluate the effects of conbercept on inflammation and oxidative response in proliferative diabetic retinopathy (PDR). Morphology changes in retinal microvasculature of PDR patients were determined by optical coherence tomographic angiography (OCTA). The mice were injected with streptozocin (STZ) for 20 weeks to induced PDR, then the changes in inflammatory factors, oxidative response and histological analysis were examined with Elisa assay, real time-PCR and commercial kits analysis. Conbercept treatment significantly alleviated the retinal pathological changes and significantly reduced intercellular cell adhesion molecule-1 (ICAM-1), macrophage inflammatory protein-1 (MIP-1), IL-1ß, IL-6 and TNF-α protein levels but not prostaglandin E1 (PGE1), prostaglandin E2 (PGE2) and prostaglandin F2a (PGF2a) levels, all of which were remarkably elevated in aqueous fluid of PDR patients compared with non-PDR subjects. Meanwhile the inhibitory effects of conbercept on these inflammatory factors were proved by RT-PCR assays in mice experiments. And the inflammatory signal such as p-IKBα and p-p65 was correspondingly inhibited by conbercept in STZ-treated mice. Conbercept treatment significantly elevated the aqueous glutathione level of PDR patients and inhibited NOX-1, NOX-4 and ph22phox mRNA expressions and ROS production of PDR mice. Ki67 immunofluorescence staining showed that conbercept inhibited endothelial cell proliferation in retina of PDR mice. In conclusion, conbercept significantly inhibited the angiogenesis, inflammation and oxidative response in PDR mice, and these findings further reveals the molecular mechanisms of conbercept in treating PDR.