Experimental and numerical investigation into effect of elevated temperature on fretting fatigue behavior

Fretting fatigue damage occurs in contacting parts when they are subjected to fluctuating loadings and sliding movements at the same time. This phenomenon may occur in many applications such as bearings/ shafts, bolted and riveted connections, steel cables, and steam and gas turbines. In this paper, the effect of elevated temperature on fretting fatigue life of Al7075-T6 is investigated using a new device for fretting fatigue tests with variable crank shaft mechanism. Also a finite element modeling method was used to estimate crack propagation lifetime in aluminum alloy, Al7075-T6 specimens at elevated temperature under fretting condition. In this method, shear and normal stresses that are caused by contact load are updated at each crack growth increment. Finally, a comparison between the experimental and numerical results is done in order to evaluate the FE simulation. Department of mechanical engineering, Islamic Azad University, Takestan Branch, Takestan, Iran The experimental results show that: (i) fretting fatigue life of the material increases with temperature up to 350°C by 180% for low stresses and decreases by 40% for high stresses, (ii) this fashion of variation of fretting fatigue life versus temperature is believed to be due to degradation of material properties which occurs by overaging and wear resistance increase due to oxidation of aluminum alloy. While overaging gives rise to degradation of mechanical strength of material and hence the reduction of its fretting fatigue life, surface oxidation of the specimens brings some improvement of fatigue behavior of the material. Metallurgical examination of the specimens reveals that temperature results in precipitation of impurities of al-7075-T6. The size of precipitated impurities and their distances gets bigger as temperature increases. This could be a reason for material degradation of specimens which are exposed to heating for longer time duration

The Effect Of Cyperus Rotundus Ethanolic Extract On Motor Coordination In A Rat Model Of Alzheimer

Background and Objective: Alzheimer's disease (AD) is a degenerative disorder that leads to progressive cognitive decline. The memory dysfunction of AD has been associated with a cortical cholinergic deficiency and loss of cholinergic neurons of the nucleus basalis of Meynert (NBM). This study investigated the effect of ethanolic extract of Cyperus rotundu tubers (CRT) on motor activity in NBM-lesioned rat model of AD and intact rats. Materials and Methods: In this experimental study 49 Wistar rats were divided into 7 groups. For this purpose, Wistar rats received bilateral electric lesions of the NBM. The control and sham groups received distilled water while NBM-lesioned group received CRT extract for 20 days with doses of 100 and 200 mg/kg. Intact rats received CRT extract for 20 days without any surgery. The motor activity was assessed with Rotarod apparatus. Data were analyzed using one- way Anova and LSD test. Results: Use of ethanolic extract of CRT for 20 days improved motor activity in NBM-lesioned rats that received extract with a dose of 100 mg/kg. Ethanolic extract of CRT in the intact rats for 20 days significantly reduced motor activity when compared with the control group. Conclusion: The results of this study suggest that ethanolic extract of CRT is useful in NBM-induced lesion rats via inducing some changes in acetylcholine levels in the brain

Effect of hydro-alcoholic extract of Ziziphus jujuba on the peripheral blood cells in Balb/c mice

Introduction: In the Iranian traditional medicine, Ziziphus jujuba is recommended for treatment of anemia, but no investigation has addressed this issue. In the present study, the effect of hydro-alcoholic extract of this plant was evaluated on the peripheral blood cells in male Balb/c mice. Methods: Hydro-alcoholic extract was prepared from the fruits of the Ziziphus jujuba. Male mice were injected with normal saline or the extract (100, 200 or 400 mg/kg, i.p.) for a period of two weeks. Afterwards, the mice were anesthetized and blood samples were taken from their hearts and then the peripheral blood was evaluated by a Cell Counter apparatus. White blood cells differential analysis was manually performed under a microscope. Data was statistically analyzed using One-way ANOVA followed by Tukey post-hoc test. Results: Ziziphus jujuba extracts (100 and 400 mg/kg) caused a significant reduction in the percentages of monocytes and neutrophils, respectively (P0.05). Conclusion: Findings of this study show that Ziziphus jujuba extract increases the percentage of lymphocytes and also reduces the percentage of monocytes and neutrophils

Evaluating the Performance of Flow Cytometric Method in Identification of Platelet Resistance in Patients with Acute Myeloid Leukemia (AML)

BACKGROUND AND OBJECTIVE: Immune platelet resistance is a condition in which antibodies are produced against platelet antigens and cause damage to injected platelets by phagocytes and macrophages. The aim of this study is to evaluate the efficacy of flow cytometry in predicting the results of platelet injections and platelet resistance and selecting compatible platelet for patients. METHODS: This case-control study was performed on 15 patients with acute myeloid leukemia (AML) with two or multiple injections of platelets and 15 healthy subjects without a history of platelet injection. After marking the platelets with 5-Chloromethylfluorescein diacetate (CMFDA) and their adjacency to the serum of patients, the amount of phagocytosis of platelets by monocytes was assessed in the two groups. FINDINGS: The mean phagocytic power of platelets by monocyte was 18.27 ± 2.86% in the control group, 68.47 ± 10.40% in the group of patients with immune platelet resistance, and 36.73 ± 15.21 in the group of patients without immune platelet resistance (p = 0.001). In addition, there was a significant negative correlation between phagocytic power of platelets by monocyte and Corrected Count Increment (CCI) at 1 and 24 hours (p = - 0.001). CONCLUSION: Based on the results of this study and considering the high sensitivity of the flow cytometric method, the use of CMFDA is highly appropriate for evaluating platelet studies, and it can also be used for platelet crossmatch by flow cytometry

Finite element modelling of damage fracture and fretting fatigue

This paper summarises the research carried out to develop Finite Element (FE) modelling and predictive techniques for damage, fracture, fatigue and fretting fatigue problems. A damage model is developed based on Continuum Damage Mechanics and integrated within FE code. It is then used to predict the number of cycles to crack initiation in adhesively bonded joints. Furthermore, crack propagation algorithm is programmed within FE code using the principles of Fracture Mechanics and Paris law. The effect of mode mixity on crack propagation is taken into account using a Double Cantilever Beam (DCB) test specimen. Moreover, FE model of fretting fatigue aluminium test specimen is carried out in order to study the stress distribution and predict the crack propagation fatigue lifetime. Fretting fatigue problems involve two types of analyses; namely contact mechanics analysis and damage/fracture mechanics analysis. Both analyses are performed in FE code and the stress distribution along the contact surface between the two bodies is obtained and analysed. Furthermore, crack propagation analysis under fretting fatigue condition is presented. In most cases, the numerical results are compared to experimental ones

Throughfall Nutrients in a Degraded Indigenous Fagus Orientalis Forest and a Picea Abies Plantation in the of North of Iran

Aim of study: The objective of this study was to compare the quantity and quality of TF (throughfall) in an indigenous, but degraded, stand of Fagus orientalis and Picea abies plantation. Area of study: Forests of Kelar-Dasht region located in Mazandaran province, northern Iran. Material and Methods: TF measured by twenty collectors that were distributed randomly underneath each stand. For 21 storms sampled in 2012 (August-December) and 2013 (April-June), we analyzed pH, EC, Ca2+, Mg2+, K+, NO3-, and P of gross rainfall (GR) and TF. Main results: Cumulative interception (I) for F. orientalis and P. abies were 114.2 mm and 194.8 mm of the total GR, respectively. The amount of K+ (13.4 mg L-1) and Ca2+ (0.9 mg L-1) were higher (for both elements, p = 0.001) in the TF of P. abies compared to those of F. orientalis (6.8 and 0.5, mg L-1, respectively) and GR (3.2 and 0.37 mg L-1, respectively). Conversely, mean P concentration was doubled (p = 0.022) in the TF of F. orientalis (11.1 mg L-1) compared to GR (5.8 mg L-1). Research highlights: P. abies plantations may provide a solution for reforestation of degraded F. orientalis forests of northern Iran, yet how P. abies plantations differentially affect the quality and quantity of rainfall reaching subcanopy soils (TF) compared to F. orientalis is unknown. Understanding the connection between hydrological processes and nutrient cycling in forest ecosystems is crucial for choosing the appropriate species to rehabilitate the degraded indigenous forests with nonindigenous species

Cosmological tests of General Relativity: a principal component analysis

The next generation of weak lensing surveys will trace the evolution of matter perturbations and gravitational potentials from the matter dominated epoch until today. Along with constraining the dynamics of dark energy, they will probe the relations between matter overdensities, local curvature, and the Newtonian potential. We work with two functions of time and scale to account for any modifications of these relations in the linear regime from those in the LCDM model. We perform a Principal Component Analysis (PCA) to find the eigenmodes and eigenvalues of these functions for surveys like DES and LSST. This paper builds on and significantly extends the PCA analysis of Zhao et al. (2009) in several ways. In particular, we consider the impact of some of the systematic effects expected in weak lensing surveys. We also present the PCA in terms of other choices of the two functions needed to parameterize modified growth on linear scales, and discuss their merits. We analyze the degeneracy between the modified growth functions and other cosmological parameters, paying special attention to the effective equation of state w(z). Finally, we demonstrate the utility of the PCA as an efficient data compression stage which enables one to easily derive constraints on parameters of specific models without recalculating Fisher matrices from scratch.Comment: 18 pages, 24 figure

Kinase activity is not required for αCaMKII-dependent presynaptic plasticity at CA3-CA1 synapses

Using targeted mouse mutants and pharmacologic inhibition of αCaMKII, we demonstrate that the αCaMKII protein, but not its activation, autophosphorylation or its ability to phosphorylate synapsin I, is required for normal short-term presynaptic plasticity. Furthermore, αCaMKII regulates the number of docked vesicles independent of its ability to be activated. These results indicate that αCaMKII has a nonenzymatic role in short-term presynaptic plasticity at hippocampal CA3-CA1 synapses. © 2007 Nature Publishing Group

Randomised prospective trial to assess the clinical utility of multianalyte assay panel with complement activation products for the diagnosis of SLE.

Objective: We compared the physician-assessed diagnostic likelihood of SLE resulting from standard diagnosis laboratory testing (SDLT) to that resulting from multianalyte assay panel (MAP) with cell-bound complement activation products (MAP/CB-CAPs), which reports a two-tiered index test result having 80% sensitivity and 86% specificity for SLE. Methods: Patients (n=145) with a history of positive antinuclear antibody status were evaluated clinically by rheumatologists and randomised to SDLT arm (tests ordered at the discretion of the rheumatologists) or to MAP/CB-CAPs testing arm. The primary endpoint was based on the change in the physician likelihood of SLE on a five-point Likert scale collected before and after testing. Changes in pharmacological treatment based on laboratory results were assessed in both arms. Statistical analysis consisted of Wilcoxon and Fisher\u27s exact tests. Results: At enrolment, patients randomised to SDLT (n=73, age=48±2 years, 94% females) and MAP/CB-CAPs testing arms (n=72, 50±2 years, 93% females) presented with similar pretest likelihood of SLE (1.42±0.06 vs 1.46±0.06 points, respectively; p=0.68). Post-test likelihood of SLE resulting from randomisation in the MAP/CB-CAPs testing arm was significantly lower than that resulting from randomisation to SDLT arm on review of test results (-0.44±0.10 points vs -0.19±0.07 points) and at the 12-week follow-up visit (-0.61±0.10 points vs -0.31±0.10 points) (p Conclusion: Our data suggest that MAP/CB-CAPs testing has clinical utility in facilitating SLE diagnosis and treatment decisions