Stress transfer, stiffness degradation and transverse cracking in composite laminates

In spite of their advantages, e.g. high strength, low weight, and high stiffness, composite laminates are prone to the formation of transverse cracking during both manufacture and service. It has been well recognised that the core to this damage mode is stress singularities near transverse cracks. In addition, transverse cracking may cause degradation in the thermoelastic properties of a laminate, and meanwhile new ply cracks usually form with the increase of applied loading. As a result, the stress transfer near transverse cracks, thermoelastic property degradation due to transverse cracking, and propagation of transverse cracks are all important issues in the analysis of composite laminates. The major contribution of this work is to develop a new semi-analytical method, the state space method, to evaluate the stress transfer near free edges and transverse cracks. On the basis of the generalised plane strain condition, the method overcomes the limitation of analytical methods in study nonsymmetric laminates. Moreover the method guarantees continuous fields of interlaminar stresses across interfaces between layers, which is one of the obstacles for conventional finite element method. Another contribution is to apply the stress analysis to assess the thermoelastic property degradation induced by transverse cracAking in general cross-ply and symmetric angle-ply laminates. The prediction is made by using the constitutive equation of laminates in the Classical Laminate Theory. The numerical results of stiffness degradation for nonsymmetric cross-ply laminates are revealed for the first time in the literature. The final contribution of this work is to apply the stress analysis to predict propagation of transverse cracking in general composite laminates. An energy-based cracking criterion is used to predict the crack multiplication process. The predictions for nonsymmetric laminates and the effects of shearing to transverse cracking are believed to be the first solutions in the literature

Stress Hyperglycemia: A Problem that Cannot be Ignored

Stress hyperglycemia is a strong neuroendocrine reaction in thehypothalamic pituitary adrenal cortex under severe infection, trauma, burns,hemorrhage, surgery and other harmful stimulated, resulting in increasedsecretion of counter-regulatory hormones. These hormones promotedthe production of sugar and cause glucose metabolism disorders withcytokines and insulin resistance. In this condition, the production of sugarexceeds the utilization of sugar by the tissues, which eventually leads to anincrease in blood glucose levels in plasma. In the intensive care unit, stresshyperglycemia is very common and can occur in patients with or withoutdiabetes. The incidence is as high as 96%, and it is an independent factorin the death of critically ill patients. Hyperglycemia not only prolongsthe hospitalization time, mechanical ventilation time and increased theincidence of serious infections in critically ill patients, but can also leadto the occurrence of type 2 diabetes. Therefore, it is very important tolearn the pathological mechanism of stress hyperglycemia, the harm ofhyperglycemia and blood sugar management

Effects of stochastic tow waviness on stiffness and strength of plain-weave ceramic matrix composites

This article presents the development of a finite element model, which considers stochastic tow waviness using a Markov Chain algorithm and non-linear material properties using Binary Model, to predict the stress–strain and fracture behaviour of plain-weave ceramic matrix composites under uniaxial extension. The stochastic waviness is described by fluctuations in the centroid coordinates of tow positioning. The tow deviations are generated by marching sequentially from one grid point to next along a tow path. The deviations depend only on the deviation of the previous point using a probability transition matrix. A non-linear orthotropic constitutive model was implemented in a commercial finite element code Abaqus using a user-defined subroutine. Two 2 × 2 unit cell models of a plain-weave ceramic matrix composite laminate are created using stochastic tow elements generated by the virtual specimen generator, which was developed on the basis of the Markov Chain algorithm. A comparison has been made between the systematic and stochastic models to assess the effects of stochastic tow waviness on the stiffness and strength of the laminate. The numerical results have been validated by the comparison of predictions with the experimental data. The stochastic model which considers random waviness correlates well with the experimental data

Modelling centrifugal membrane deployment of solar sails with the discrete element method

Spin-stabilized solar sails have been extensively studied in recent years. In this paper, a DEM-based approach is proposed for dynamic analysis of the centrifugal deployment of solar sails. In order to validate the proposed approach, the deployment of a small-scale solar sail similar to “IKAROS” is studied. The membrane is discretised into a number of particles, with no physical contact between them. Non-contact interaction is introduced to model in-plane stiffness of the membrane. In order to improve the accuracy, additional forces are applied to the mass particles to model buckling strength, crease stiffness, air drag and damping. The predicted results of the membrane deployment are compared with the experimental data and numerical results in the literature

Clinical efficacy of semiconductor laser-assisted minocycline in moderate-to-severe chronic periodontitis patients with type 2 diabetes mellitus

Purpose: To study the clinical efficacy of semiconductor laser-assisted minocycline in the treatment of moderate-to-severe chronic periodontitis (CP) in type 2 diabetes mellitus (T2DM) patients.Methods: A total of 109 cases of CP combined with T2DM and obesity admitted to The First Affiliated Hospital, Medical School of Xi'an Jiaotong University, Xi’an, China, from November 2016 to November 2017 were included in the study. Among them, 54 patients in the study group were treated with semiconductor laser-assisted minocycline, while 55 patients in the control group were treated with minocyclin injection. Periodontitis, blood glucose and blood lipid levels were compared between the two groups before and after treatment.Results: Post-treatment (12 weeks), bleeding on probing, gingival index, periodontal probing depth (PD), plaque index (PLI), clinical attachment loss (CAL), and sulcus bleeding index (SBI) in the two groups of patients were significantly improved (p < 0.05). The levels of PD, BOP, PLI, and CAL in the positive SBI group (4.06 ± 0.25, 20.37 %, 0.50 ± 0.28, 3.42 ± 0.27, and 1.43 ± 0.26, respectively) were significantly lower than the corresponding levels in the control group (p < 0.05. Fasting plasma glucose (FPG) and HbA1c for the two groups were significantly improved, when compared with values prior to treatment (p < 0.05), but there was no significant difference in FPG level between the two groups. Significantly lower HbA1c levels were found in the treatment group than in the control group (t = 4.2360, p = 0.0001). Post-treatment, triglyceride (TG), total cholesterol (TC) and body mass index (BMI) did not improve significantly in the two groups, nor were there significant differences in these parameters before and after treatment (p > 0.05).Conclusion: Semiconductor laser-assisted minocycline is effective in treating moderate and severe chronic periodontitis patients with type 2 diabetes, and can improve blood glucose. However, its effect on body weight needs further studies.Keywords: Semiconductor laser, Minocycline, Chronic periodontitis, Type 2 diabetes, Obesit

Response of Fertile Tiller Characters and Seed Yield of \u3cem\u3eElymus sibiricus\u3c/em\u3e L. to Row Space Alteration

Elymus sibiricus L. cv chuancao NO.2 is widely planted in the eastern Tibetan Plateau of China. At present, the study about E. sibiricus L. seed yield has focused on the influence of fertilizing and harvest time on seed yield and its components. The response of fertile tiller characters and seed yield of E. sibiricus L. to different row space still has not been reported. This experiment analyzed the response of fertile tiller characters and seed yield to different row spaces, and presents the optimal spacing to increase seed yield and quality in the Northwest Plateau of Sichuan. The objective was to provide a scientific basis for large-scale seed production

Biological Effects of Black Phosphorus Nanomaterials on Mammalian Cells and Animals

The remarkable progress of applied black phosphorus nanomaterials (BPNMs) is attributed to BP's outstanding properties. Due to its potential for applications, environmental release and subsequent human exposure are virtually inevitable. Therefore, how BPNMs impact biological systems and human health needs to be considered. In this comprehensive Minireview, the most recent advancements in understanding the mechanisms and regulation factors of BPNMs’ endogenous toxicity to mammalian systems are presented. These achievements lay the groundwork for an understanding of its biological effects, aimed towards establishing regulatory principles to minimize the adverse health impacts

Effect of sinomenine on proliferation and apoptosis of oral squamous cell carcinoma cells, and its underlying mechanism of action

Purpose: To investigate the effect of sinomenine on the proliferation and apoptosis of oral squamous cell carcinoma cells (OCSSs), and its underlying mechanism of action. Methods: CCK-8 method was used to determine the inhibitory effects of different concentrations of sinomenine (50, 100, 200, 400 and 800 ug/mL) on proliferation of CAL-27 cells on treatment for 24 and 48 h. Cell migration was assayed using scratch test, while cell cycle was measured by flow cytometry. Hoechst 33258 fluorescence staining was conducted to determine apoptotic morphology. The effect of sinomenine on the expressions of cyclinD1, cyclinD3, cyclin-dependent kinases-2 (CDK2), Bax, B-cell lymphoma/leukmia-2 (Bcl-2), Caspase-3 and Caspase-9 was determined by western-blotting (WB). Results: Sinomenine significantly inhibited proliferation and migration of CAL-27 cells in a concentration-dependent manner, but not in a time-dependent fashion. It inhibited the transition from G0/G1 phase to S phase in CAL-27 cells. Sinomenine treatment also caused dispersion of CAL-27 cells. Moreover, the nuclei were pyknotic, and the cells translucent, indicating typical features of apoptotic morphology. Expressions of Bax, caspase 3 and caspase 9 protein were significantly upregulated, while expressions of Bcl-2, cyclinD1, cyclinD3 and CDK2 protein were down-regulated by sinomenine. Conclusion: Sinomenine induces apoptosis of OSCCs, and inhibits their proliferation and migration via a mechanism associated with up-regulation of Bax, Caspase-3 and Caspase-9, and down-regulation of Bcl-2

Initiation and Propagation of Transverse Cracking in Composite Laminates

The matrix cracking transverse to loading direction is usually the one of most common observations of damages in composite laminates. The initiation and propagation of transverse cracks have been a longstanding issue in the last few decades. In this paper, a three-dimensional stress analysis method based on the state space approach is used to compute the stresses, including the inter-laminar stresses near transverse cracks in laminated composites. The stress field is then used to estimate the energy release rate, from which the initiation and propagation of transverse cracking are predicted. The proposed method is illustrated by numerical solutions and is validated by available experimental results. To the best knowledge of the authors, the predictions of crack behaviour for non-symmetrical laminates and laminates subject to in-plane shearing are presented for the first time in the literature

Biologische Effekte von auf schwarzem Phosphor basierenden Nanomaterialien auf Zellen und Tiere

Die bedeutenden Fortschritte bei der Anwendung von auf schwarzem Phosphor basierenden Nanomaterialien (SPNMs) sind auf deren hervorragende Eigenschaften zurückzuführen. Aufgrund der vielfältigen Anwendungsmöglichkeiten dieser Materialien sind die Freisetzung in die Umwelt und eine anschließende Exposition des Menschen praktisch unvermeidlich. Daher muss untersucht werden, wie sich SPNMs auf biologische Systeme und die menschliche Gesundheit auswirken. In dieser umfassenden Übersicht werden die neuesten Erkenntnisse in Bezug auf Wirkungsweise, Mechanismen und Regulierungsfaktoren der endogenen Toxizität von SPNMs in Säugetieren vorgestellt. Diese Ergebnisse bilden die Grundlage für das Verständnis der biologischen Auswirkungen und haben das Ziel, Regulierungsprinzipien zur Minimierung gesundheitsschädlicher Auswirkungen festzulegen