The roles of Lcn2 in the inflammatory lung and liver

Uterocalin (Lcn2; also called 24p3, SIP24, or siderocalin and abbreviated as Utc) is an acute phase protein, for which the physiological function remains to be determined. Basal Utc expression is highest in the uterus, mammary gland and lung, which are three tissues with direct exposure to the diverse bacterial flora of the external environment. The demonstrated ability to bind siderophores is one means by which Utc can provide protection against pathogenic bacteria. However, its specificity for siderophores limits the ability of Utc to ward off pathogens. Epithelial tissues that interact with the external environment are exposed to many different nonpathogenic resident bacteria to which the tissue normally does not mount an inflammatory response. We postulate that Utc might limit inflammation by suppressing cytokine expression in response to bacterial products such as LPS. To test this hypothesis, we studied the effect of LPS, delivered by intranasal administration, in Lcn2-deficient mice (Lcn2-/-) and their wild type littermates. Utc is highly expressed in the lungs of normal mice at 4 h and 48 h after LPS intranasal challenge. By multiplexed and real-time RT-PCR we found that 6 h after intranasal administration of LPS (0.4 to 4 mg/kg), the expression of TNF-alpha, IL-1beta and IL-6 was increased in Lcn2-/- compared with their wild type littermates. H & E immunohistochemical staining of the lung and liver showed that the higher dose of LPS (4 mg/kg) caused the entry of some neutrophils into the lungs of Lcn2-/- animals and their wild type littermates. No neutrophils were observed in the lung and liver from mice treated at the lower doses. The reaction of older Lcn2-/- mice (11 or 14 weeks old) in response to the LPS intranasal administration was more dramatic compared with younger mice (7 or 8 weeks old). In summary, our results indicate that Lcn2 may play an anti-inflammatory role in the lung and liver and provide feedback regulation of the acute phase response by suppressing pro-inflammatory cytokine expression

On creep fatigue interaction of components at elevated temperature

The accurate assessment of creep-fatigue interaction is an important issue for industrial components operating with large cyclic thermal and mechanical loads. An extensive review of different aspects of creep fatigue interaction is proposed in this paper. The introduction of a high temperature creep dwell within the loading cycle has relevant impact on the structural behaviour. Different mechanisms can occur, including the cyclically enhanced creep, the creep enhanced plasticity and creep ratchetting due to the creep fatigue interaction. A series of crucial parameters for crack initiation assessment can be identified, such as the start of dwell stress, the creep strain and the total strain range. A comparison between the ASME NH and R5 is proposed, and the principal differences in calculating the aforementioned parameters are outlined. The Linear Matching Method framework is also presented and reviewed, as a direct method capable of calculating these parameters and assessing also the steady state cycle response due to creep and cyclic plasticity interaction. Two numerical examples are presented, the first one is a cruciform weldment subjected to cyclic bending moment and uniform high temperature with different dwell times. The second numerical example considers creep fatigue response on a long fibre reinforced Metal Matrix Composite (MMC), which is subjected to a cycling uniform thermal field and a constant transverse mechanical load. All the results demonstrate that the Linear Matching Method is capable of providing accurate solutions, and also relaxing the conservatisms of the design codes. Furthermore, as a direct method it is more efficient than standard inelastic incremental finite element analysis

Influences of T-stress on constraint effect in mismatched modified boundary layer model for creep crack

Constraint effect plays an important role in assessing the stress field and the growth rate of creep crack in components under high temperature. The mismatched modified boundary layer (MMBL) model is extended to creep crack in this paper. For the MMBL model, the Q-parameters for different mismatch factors are studied under different T-stresses. The variation of the dimensionless T-stress in creep zone is given. The variations of open stresses with creep time for different mismatch factors are presented under different T-stresses. The comparisons of Q-parameter between homogeneous material and mismatched materials are made. The influences of mismatch factor on the constraint parameter are discussed. The influence of creep exponent on the open stress is also discussed

Creep-fatigue behaviour of aluminum alloy-based metal matrix composite

Metal Matrix Composite (MMC) represents a valuable option as structural material for different type of structures and components. Despite this they struggle to become widely adopted due to expensive manufacturing process and complex microstructural behaviour. When subjected to cyclic load conditions the structural response of MMC is not trivial, and becomes even more difficult when high temperature load is involved. Different failure mechanisms would happen and they are originated by the different material properties between the fibre and surrounding matrix. Among all, the mismatch of thermal expansion coefficient is recognized to be the dominant one. The significantly differing coefficients of thermal expansion between ceramic and metal give rise to micro thermal stresses, which enhance the initiation of matrix micro cracks. Their performance under varying load and high temperature is complex, and hence it is difficult to have a clear understanding of the structural responses, especially when fatigue and creep damages become the main failures of MMCs. To improve current understanding of the relationship between creep fatigue interaction of MMCs, the history of thermal and mechanical loading, and the creep dwell period, a highly accurate but robust direct simulation technique on the basis of the Linear Matching Method (LMM) framework has been proposed in this paper, and been applied to model the fatigue and creep behaviour of MMCs. A homogenised FE model is considered in all analyses, which consist of continuous silicon carbide fibres embedded in a square 2024T3 aluminium alloy matrix array. Various factors that affect creep and fatigue behaviours of composites are analysed and discussed, including effects of the applied load level, dwell period and temperature on the MMC’s performance. The effects of reversed plasticity on stress relaxation and creep deformation of MMC are investigated, and the behaviours of cyclically enhanced creep and elastic followup are presented. A detailed study of the creep ratchetting mechanism is also performed with the concentration on the impact of temperature and different loading conditions. The accuracy of the proposed method has been verified by detailed incremental finite element analyses using the commercial finite element solver Abaqus. Such verifications further improve the understanding of the failure mechanisms identified and discussed in this work

Protective effects and molecular mechanisms of tea polyphenols on cardiovascular diseases

Aging is the most important factor contributing to cardiovascular diseases (CVDs), and the incidence and severity of cardiovascular events tend to increase with age. Currently, CVD is the leading cause of death in the global population. In-depth analysis of the mechanisms and interventions of cardiovascular aging and related diseases is an important basis for achieving healthy aging. Tea polyphenols (TPs) are the general term for the polyhydroxy compounds contained in tea leaves, whose main components are catechins, flavonoids, flavonols, anthocyanins, phenolic acids, condensed phenolic acids and polymeric phenols. Among them, catechins are the main components of TPs. In this article, we provide a detailed review of the classification and composition of teas, as well as an overview of the causes of aging-related CVDs. Then, we focus on ten aspects of the effects of TPs, including anti-hypertension, lipid-lowering effects, anti-oxidation, anti-inflammation, anti-proliferation, anti-angiogenesis, anti-atherosclerosis, recovery of endothelial function, anti-thrombosis, myocardial protective effect, to improve CVDs and the detailed molecular mechanisms

Shakedown analysis of a torispherical head with a piping nozzle under combined loads by the stress compensation method

Shakedown assessment is an important task in determining the load-bearing capacity of structures and evaluating their safety. The traditional shakedown analyses, which are based on the upper or lower bound shakedown theorem to establish the mathematical programming formulation and solve an optimisation problem, are difficult to apply in engineering practice owing to limitations of the computing scale and computational efficiency. In this study, a numerical shakedown analysis using the recently developed stress compensation method (SCM) is performed for a torispherical head with a piping nozzle, which is a typical structural component of pressure vessel equipment. The loads applied to the structural component include an internal pressure, axial force, twisting moment, out-of-plane and in-plane bending moments, and thermal loading, all of which vary independently of each other. Two- and three-dimensional strict shakedown boundaries for the torispherical head under different combinations of these loads are presented and analysed. In addition, the effect of a temperature-dependent yield strength on the shakedown domain is also investigated. These investigations demonstrate that the proposed SCM is capable of solving the practical shakedown problem for structures under complicated combined loads in industrial applications. The obtained results can provide guidance for the safe structural design of torispherical heads with piping nozzles

The college students' response to customized information services based on Library2.0 technologies at universities in Nanjing

Through a questionnaire survey of students' response from 6 universities in Nanjing, this paper aims to determine their varying degrees of satisfaction about the customized information service based on Library2.0 technologies. In so doing, the authors carefully examined the data collected from the returned questionnaires about such key issues as the students' perceptions about the customized information service via a Library 2.0 platform, self-initiated use experience of such a mechanism, their achieved information searching results&nbsp; vis-&agrave;-vis their expectations, etc. In addition, the authors also made a comparative study between information providers (i.e. librarians) and information consumers (i.e. students) at Chinese and American academic libraries.</p

A deep complementary energy method for solid mechanics using minimum complementary energy principle

In recent years, the rapid advancement of deep learning has significantly impacted various fields, particularly in solving partial differential equations (PDEs) in solid mechanics, benefiting greatly from the remarkable approximation capabilities of neural networks. In solving PDEs, Physics-Informed Neural Networks (PINNs) and the Deep Energy Method (DEM) have garnered substantial attention. The principle of minimum potential energy and complementary energy are two important variational principles in solid mechanics. However,DEM is based on the principle of minimum potential energy, but it lacks the important form of minimum complementary energy. To bridge this gap, we propose the deep complementary energy method (DCEM) based on the principle of minimum complementary energy. The output function of DCEM is the stress function. We extend DCEM to DCEM-Plus (DCEM-P), adding terms that satisfy partial differential equations. Furthermore, we propose a deep complementary energy operator method (DCEM-O) by combining operator learning with physical equations. We train DCEM-O using existing high-fidelity numerical results and the complementary energy together. We present numerical results using the Prandtl and Airy stress functions and compare DCEM with existing PINNs and DEM when modeling representative mechanical problems. The results demonstrate that DCEM outperforms DEM in terms of stress accuracy and efficiency and has an advantage in dealing with complex displacement boundary conditions. DCEM-P and DCEM-O further enhance the accuracy and efficiency of DCEM. In summary, our proposed DCEM marks the first time that complementary energy is extended to the energy-based physics-informed neural network and provides an essential supplementary energy form to the DEM in solid mechanics, offering promising research prospects in computational mechanics.Comment: 58 pages, 30 figure

BINN: A deep learning approach for computational mechanics problems based on boundary integral equations

We proposed the boundary-integral type neural networks (BINN) for the boundary value problems in computational mechanics. The boundary integral equations are employed to transfer all the unknowns to the boundary, then the unknowns are approximated using neural networks and solved through a training process. The loss function is chosen as the residuals of the boundary integral equations. Regularization techniques are adopted to efficiently evaluate the weakly singular and Cauchy principle integrals in boundary integral equations. Potential problems and elastostatic problems are mainly concerned in this article as a demonstration. The proposed method has several outstanding advantages: First, the dimensions of the original problem are reduced by one, thus the freedoms are greatly reduced. Second, the proposed method does not require any extra treatment to introduce the boundary conditions, since they are naturally considered through the boundary integral equations. Therefore, the method is suitable for complex geometries. Third, BINN is suitable for problems on the infinite or semi-infinite domains. Moreover, BINN can easily handle heterogeneous problems with a single neural network without domain decomposition

Creep-fatigue and cyclically enhanced creep mechanisms in aluminium based metal matrix composites

An aluminium (Al 2024T3) matrix composite reinforced with continuous alumina (Al2O3) fibres is investigated under tensile off-axis constant macro stress and thermal cyclic loading. The micromechanical approach to modelling and three different fibre cross-section geometries have been employed. The effect of creep is included by considering three dwell times at the peak temperature of the thermal loading history. The presence of the hold time gives rise to different sources of failure such as cyclic enhanced creep and creep ratchetting. These failure mechanisms are carefully discussed and assessed. The linear matching method framework has been used for the direct evaluation of the crucial parameters for creep-fatigue crack initiation assessment at the steady cycle. A detailed representation of the steady-state hysteresis loops is provided by using the strain range partitioning and a method for dealing with multiaxiality is reported with regard to the algebraic sign of the Mises-Hencky equivalent stress and strain. All the results obtained have been benchmarked by fully inelastic step-by-step (SBS) analyses. The design of a long fibre metal matrix composite should consider not only the detrimental effect of their dissimilar coefficient of thermal expansion, but also the state of stress at the interface between the matrix and fibre