359 research outputs found

    Spatial variation in aragonite saturation state and the influencing factors in Jiaozhou Bay, China

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    Both natural processes and human activities affect seawater calcium carbonate saturation state (Ωarag), while the mechanisms are still far from being clearly understood. This study analysed the seawater surface Ωarag during summer and winter in Jiaozhou Bay (JZB), China, based on two cruises observations performed in January and June 2017. The ranges of Ωarag values were 1.55~2.92 in summer and 1.62~2.15 in winter. Regression analyses were conducted to identify the drivers of the change of Ωarag distribution, and then the relative contributions of temperature, mixing processes and biological processes to the spatial differences in Ωarag were evaluated by introducing the difference between total alkalinity (TA) and dissolved inorganic carbon (DIC) as a proxy for Ωarag. The results showed that biological processes were the main factor affecting the spatial differences in Ωarag, with relative contributions of 70% in summer and 50% in winter. The contributions of temperature (25% in summer and 20% in winter) and the mixing processes (5% in summer and 30% in winter) were lower. The increasing urbanization in offshore areas can further worsen acidification, therefore environmental protection in both offshore and onshore is needed

    Orthogonal Polynomials, Asymptotics and Heun Equations

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    The Painlev\'{e} equations arise from the study of Hankel determinants generated by moment matrices, whose weights are expressed as the product of ``classical" weights multiplied by suitable ``deformation factors", usually dependent on a ``time variable'' tt. From ladder operators one finds second order linear ordinary differential equations for associated orthogonal polynomials with coefficients being rational functions. The Painlev\'e and related functions appear as the residues of these rational functions. We will be interested in the situation when nn, the order of the Hankel matrix and also the degree of the polynomials Pn(x)P_n(x) orthogonal with respect to the deformed weights, gets large. We show that the second order linear differential equations satisfied by Pn(x)P_n(x) are particular cases of Heun equations when nn is large. In some sense, monic orthogonal polynomials generated by deformed weights mentioned below are solutions of a variety of Heun equa\-tions. Heun equations are of considerable importance in mathematical physics and in the special cases they degenerate to the hypergeometric and confluent hypergeometric equations. In this paper we look at three type of weights: the Jacobi type, which are are supported (0,1](0,1] the Laguerre type and the weights deformed by the indicator function of (a,b)(a,b) χ(a,b)\chi_{(a,b)} and the step function θ(x)\theta(x)

    Mechanical Characteristics for Rocks under Different Paths and Unloading Rates under Confining Pressures

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    To investigate mechanical characteristics of rocks under different unloading conditions, triaxial tests are carried out with initial confining pressures of 10, 20, and 30 MPa and unloading rates of 0.05~1 MPa/s in three stress paths. Results show that the increment of axial strain is far less than that of the lateral strain. The unloading rates of confining pressures have less influence on variation of strain and lateral increment in path I. The variation of axial increment strain in the same time is slightly larger than the variation of lateral increment; D-value is influenced by unloading rates of confining pressures in path II. The variation of axial strain increment decreases firstly and then increases with the variation of confining pressures. The relation decreases and then increases with unloading rates increases in path III. The dilatancy angle decreases with initial confining pressures increases. The vary rates of dilatancy angle from initial point of dilatancy angle to peak point of dilatancy angle increase with the unloading rates of confining pressures. In the same rates, the vary rates of dilatancy angle from the initial point of the dilatancy angle to peak point of the dilatancy angle in path I are greater than those in path II

    Good Strategy, Good Entrepreneurship? Examining When and How Digital Business Strategy Drives Firm Strategic Entrepreneurship

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    Theory and practice suggest that digital business strategy may help enterprises to seek opportunities in competition. However, there is little knowledge about how and when digital business strategy works in driving strategic entrepreneurship. In order to address this issue, we used dynamic capability theory to discuss how digital business strategy can facilitate strategic entrepreneurship through the mediating role of absorptive capacity while also exploring the moderating role of market turbulence and technology turbulence in the relationship between digital business strategy and absorptive capacity. We test the hypotheses by conducting a survey study which use longitudinal date collected from 290 firms in China with digital features. Findings suggest that digital business strategy promotes the entrepreneurial orientation, accessing relational resources and relational embeddedness in firms, which is achieved mainly through enhanced absorptive capacity. Furthermore, market turbulence strengthens the relationship between digital business strategy and absorptive capacity, whereas technological turbulence plays an inverted U-shaped moderating role. The study contributes valuable theory and management insights concerning digital platform capabilities and strategic entrepreneurship

    Center of mass distribution of the Jacobi unitary ensembles:Painleve V, asymptotic expansions

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    In this paper, we study the probability density function, P(c,α,β,n)dc\mathbb{P}(c,\alpha,\beta, n)\,dc, of the center of mass of the finite nn Jacobi unitary ensembles with parameters α>1\alpha\,>-1 and β>1\beta >-1; that is the probability that trMn(c,c+dc),{\rm tr}M_n\in(c, c+dc), where MnM_n are n×nn\times n matrices drawn from the unitary Jacobi ensembles. We first compute the exponential moment generating function of the linear statistics j=1nf(xj):=j=1nxj,\sum_{j=1}^{n}\,f(x_j):=\sum_{j=1}^{n}x_j, denoted by Mf(λ,α,β,n)\mathcal{M}_f(\lambda,\alpha,\beta,n). The weight function associated with the Jacobi unitary ensembles reads xα(1x)β,  x[0,1]x^{\alpha}(1-x)^{\beta},\; x\in [0,1]. The moment generating function is the n×nn\times n Hankel determinant Dn(λ,α,β)D_n(\lambda,\alpha,\beta) generated by the time-evolved Jacobi weight, namely, w(x;λ,α,β)=xα(1x)βeλx,x[0,1],α>1,β>1w(x;\lambda ,\alpha,\beta )=x^{\alpha}(1-x)^{\beta}\,{\rm e}^{-\lambda\:x},\,x\in[0,1],\,\alpha>-1,\,\beta>-1. We think of λ\lambda as the time variable in the resulting Toda equations. The non-classical polynomials defined by the monomial expansion, Pn(x,λ)=xn+p(n,λ)xn1++Pn(0,λ)P_n(x,\lambda)= x^n+ p(n,\lambda)\:x^{n-1}+\dots+P_n(0,\lambda), orthogonal with respect to w(x,λ,α,β)w(x,\lambda,\alpha,\beta ) over [0,1][0,1] play an important role. Taking the time evolution problem studied in Basor, Chen and Ehrhardt (\cite{BasorChenEhrhardt2010}), with some change of variables, we obtain a certain auxiliary variable rn(λ),r_n(\lambda), defined by integral over [0,1][0,1] of the product of the unconventional orthogonal polynomials of degree nn and n1n-1 and w(x,λ,α,β)/xw(x,\lambda,\alpha,\beta )/x. It is shown that r_n(2\imath\/{\rm e}^{z}) satisfies a Chazy IIII equation. There is another auxiliary variable, denote as Rn(λ),R_n(\lambda), defined by an integral over [0,1][0,1] of the product of two polynomials of degree nn multiplied by w(x,λ)/x.w(x,\lambda)/x. Then Yn(λ)=1λ/Rn(λ)Y_n(-\lambda)=1-\lambda/R_n(\lambda) satisfies a particular Painlev\'{e} \uppercase\expandafter{\romannumeral 5}: PV(α2/2P_{\rm V}(\alpha^2/2, β2/2,2n+α+β+1,1/2) -\beta^2/2, 2n+\alpha+\beta+1,1/2).\\ The σn\sigma_n function defined in terms of the λp(n,λ)\lambda\:p(n,-\lambda) plus a translation in λ\lambda is the Jimbo--Miwa--Okamoto σ\sigma-form of Painlev\'{e} \uppercase\expandafter{\romannumeral 5}. In the continuum approximation, treating the collection of eigenvalues as a charged fluid as in the Dyson Coulomb Fluid, gives an approximation for the moment generation function Mf(λ,α,β,n)\mathcal{M}_f(\lambda,\alpha,\beta,n) when nn is sufficiently large. Furthermore, we deduce a new expression of Mf(λ,α,β,n)\mathcal{M}_f(\lambda,\alpha,\beta,n) when nn is finite in terms the σ\sigma function of this the Painlev\'{e} \uppercase\expandafter{\romannumeral 5} An estimate shows that the moment generating function is a function of exponential type and of order nn. From the Paley-Wiener theorem, one deduces that P(c,α,β,n)\mathbb{P}(c,\alpha,\beta,n) has compact support [0,n][0,n]. This result is easily extended to the β\beta ensembles, as long as ww the weight is positive and continuous over $[0,1].

    Fostering emotional well-being in adolescents: the role of physical activity, emotional intelligence, and interpersonal forgiveness

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    IntroductionAdolescence is considered a stress-sensitive developmental period, and the escalating and sustained pressure during this phase poses a significant threat to the mental and physical well-being of adolescents. Therefore, enhancing positive emotions in adolescents is crucial. This study aims to investigate the impact of physical activity on the emotional intelligence, interpersonal forgiveness, and positive emotions of adolescents.MethodsUsing a cluster sampling method, data were collected from 500 adolescents in four schools across the Xiangxi Tujia and Miao Autonomous Prefecture of Hunan Province, China. A total of 428 valid questionnaires were collected and analyzed. The study employed AMOS v.23 to construct a structural equation model to validate the hypotheses.ResultsThe results indicate that physical activity significantly influences the emotional intelligence, interpersonal forgiveness, and positive emotions of adolescents. Furthermore, emotional intelligence and interpersonal forgiveness mediate the relationship between physical activity and positive emotions.DiscussionBased on these findings, collaborative efforts from government agencies, schools, and families are essential to provide robust support for adolescents’ participation in physical activity, encouraging more adolescents to actively engage in sports

    Predicting the PSQA results of volumetric modulated arc therapy based on dosiomics features: a multi-center study

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    Backgroud and objectivesThe implementation of patient-specific quality assurance (PSQA) has become a crucial aspect of the radiation therapy process. Machine learning models have demonstrated their potential as virtual QA tools, accurately predicting the gamma passing rate (GPR) of volumetric modulated arc therapy (VMAT)plans, thereby ensuring safe and efficient treatment for patients. However, there is limited multi-center research dedicated to predicting the GPR. In this study, a dosiomics-based machine learning approach was employed to construct a prediction model for classifying GPR in multiple radiotherapy institutions. Additionally, the model’s performance was compared by evaluating the impact of two distinct feature selection methods.MethodsA retrospective data collection was conducted on 572 VMAT patients across three radiotherapy institutions. Utilizing a three-dimensional dose verification technique grounded in real-time measurements, γ analysis was conducted according to the criteria of 3%/2 mm and 2%/2 mm, employing a dose threshold of 10% along with absolute dose and global normalization mode. Dosiomics features were extracted from the dose files, and distinct subsets of features were selected as inputs for the model using the random forest (RF) and RF combined with SHapley Additive exPlanations (SHAP) methods. The data underwent training using the extreme gradient boosting (XGBoost) algorithm, and the model’s classification performance was assessed through F1-score and area under the curve (AUC) values.ResultsThe model exhibited optimal performance under the 3%/2 mm criteria, utilizing a subset of 20 features and attaining an AUC value of 0.88 and an F1-score of 0.89. Similarly, under the 2%/2 mm criteria, the model demonstrated superior performance with a subset of 10 features, resulting in an AUC value of 0.91 and an F1-score of 0.89. The feature selection methods of RF and RF + SHAP have achieved good model performance by selecting as few features as possible.ConclusionBased on the multi-center PSQA results, it is possible to utilize dosiomics features extracted from dose files to construct a machine learning predictive model. This model demonstrates excellent discriminative abilities, thus promoting the progress of gamma passing rate prognostic models in clinical application and implementation. Furthermore, it holds potential in providing patients with secure and efficient personalized QA management, while also reducing the workload of medical physicists

    Integrative analysis of transcriptome and metabolome reveals how ethylene increases natural rubber yield in Hevea brasiliensis

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    Hevea brasiliensis is an important cash crop with the product named natural rubber (NR) for markets. Ethylene (ET) is the most effective yield stimulant in NR production but the molecular mechanism remains incomplete. Here, latex properties analysis, transcriptome analysis, and metabolic profiling were performed to investigate the mechanism of NR yield increase in four consecutive tappings after ET stimulation. The results revealed that sucrose and inorganic phosphate content correlated positively with dry-rubber yield and were induced upon ET stimulation. Stimulation with ET also led to significant changes in gene expression and metabolite content. Genes involved in phytohormone biosynthesis and general signal transduction as well as 51 transcription factors potentially involved in the ET response were also identified. Additionally, KEGG annotation of differentially accumulated metabolites suggested that metabolites involved in secondary metabolites, amino-acid biosynthesis, ABC transporters, and galactose metabolism were accumulated in response to ET. Integrative analysis of the data collected by transcriptomics and metabolomics identified those differentially expressed genes and differentially accumulated metabolites are mainly involved in amino-acid biosynthesis and carbohydrate metabolism. Correlation analysis of genes and metabolites showed a strong correlation between amino-acid biosynthesis during ET stimulation. These findings provide new insights into the molecular mechanism underlying the ET-induced increase in rubber yield and further our understanding of the regulatory mechanism of ethylene signaling in rubber biosynthesis

    Luteolin inhibits GPVI-mediated platelet activation, oxidative stress, and thrombosis

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    Introduction: Luteolin inhibits platelet activation and thrombus formation, but the mechanisms are unclear. This study investigated the effects of luteolin on GPVI-mediated platelet activation in vitro and explored the effect of luteolin on thrombosis, coagulation, and platelet production in vivo.Methods: Washed human platelets were used for aggregation, membrane protein expression, ATP, Ca2+, and LDH release, platelet adhesion/spreading, and clot retraction experiments. Washed human platelets were used to detect collagen and convulxin-induced reactive oxygen species production and endogenous antioxidant effects. C57BL/6 male mice were used for ferric chloride-induced mesenteric thrombosis, collagen-epinephrine induced acute pulmonary embolism, tail bleeding, coagulation function, and luteolin toxicity experiments. The interaction between luteolin and GPVI was analyzed using solid phase binding assay and surface plasmon resonance (SPR).Results: Luteolin inhibited collagen- and convulxin-mediated platelet aggregation, adhesion, and release. Luteolin inhibited collagen- and convulxin-induced platelet ROS production and increased platelet endogenous antioxidant capacity. Luteolin reduced convulxin-induced activation of ITAM and MAPK signaling molecules. Molecular docking simulation showed that luteolin forms hydrogen bonds with GPVI. The solid phase binding assay showed that luteolin inhibited the interaction between collagen and GPVI. Surface plasmon resonance showed that luteolin bonded GPVI. Luteolin inhibited integrin αIIbβ3-mediated platelet activation. Luteolin inhibited mesenteric artery thrombosis and collagen- adrenergic-induced pulmonary thrombosis in mice. Luteolin decreased oxidative stress in vivo. Luteolin did not affect coagulation, hemostasis, or platelet production in mice.Discussion: Luteolin may be an effective and safe antiplatelet agent target for GPVI. A new mechanism (decreased oxidative stress) for the anti-platelet activity of luteolin has been identified
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