Evaluation of Carbon sequestration in pure and mixed plantations of Cupressus arizonica

The present study was conducted to investigate the effect of tree mixture on Carbon sequestration in cupressus arizonica plantations. Emission of carbon dioxide via human activities is known as the main cause of global warming. Therefore, in this study, soil carbon sequestration in mixed and pure stands was measured in order to compare the effect of tree mixture on the amount of carbon stored in the top mineral soil layer. The study site was Khargosh Valley Forest Park, located in Tehran province. This study included 4 different type of stands, the pure Cupressus arizonica, the pure Pinus eldarica, the mixed Cupressus arizonica and Pinus eldarica and the mixed Cupressus arizonica with deciduous hardwoods. Sampling method was done with a Systematic random network with dimensions 75 × 75 m. Samples parts were Square with dimensions of 20 x 20 m. At each plot center, forest floor was sampled from the first 10 cm of soil. To analyze the data one way analyses of variance (ANOVA) in SPSS v.20 was used to assess the Soil parameters. Tukey’s tests were used to test significant effects (p ≤ 0.05). Our results showed that the mean Carbon sequestration in the mixed plantations of Cupressus arizonica with deciduous hardwoods trees soils was greater than the other stands which in the standing mixed Cupressus arizonica and Pinus eldarica was lower than the pure stands. Our results Recommended for establishment ofconifer plantation, used mixed culture of Conifers with broadleaf Instead of pure cultures conifers.Keywords: Carbon sequestration, Cupressus arizonica, Iran, mixed, Plantations, pur

Numerical estimation of fretting fatigue lifetime using damage and fracture mechanics

Fretting fatigue is a complex tribological phenomenon that can cause premature failure of connected components that have small relative oscillatory movement. The fraction of fretting fatigue lifetime spent in crack initiation and in crack propagation depends on many factors, e.g., contact stresses, amount of slip, frequency, environmental conditions, etc., and varies from one application to another. Therefore, both crack initiation and propagation phases are important in analysing fretting fatigue. In this investigation, a numerical approach is used to predict these two portions and estimate fretting fatigue failure lifetime under a conformal contact configuration. For this purpose, an uncoupled damage evolution law based on principles of continuum damage mechanics is developed for modelling crack initiation. The extended finite element method approach is used for calculating crack propagation lifetimes. The estimated results are validated with previously reported experimental data and compared with other available methods in the literature.The authors wish to thank the Ghent University for the financial support received by the Special Funding of Ghent University, BOF (Bijzonder Onderzoeksfonds), in the framework of project (BOF 01N02410) and gratefully acknowledge the financial support provided by the Spanish Ministry of Economics and Competitiveness through the project DPI2010-20990.Hojjati-Talemi, R.; Wahab, MA.; Giner Maravilla, E.; Sabsabi, M. (2013). Numerical estimation of fretting fatigue lifetime using damage and fracture mechanics. Tribology Letters. 52(1):11-25. https://doi.org/10.1007/s11249-013-0189-8S1125521Hills, D.A., Nowell, D.: Mechanics of Fretting Fatigue. Solid Mechanics and its Applications vol. 30. Kluwer Academic Publishers, Dordrecht (1994)Smith, K.N., Watson, P., Topper, T.H.: A stress-strain function for the fatigue of metals. J Mater. 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Specific skeletal muscle sphingolipid compounds in energy expenditure regulation and weight gain in Native Americans of Southwestern heritage

Background/objectivesIn animal models, a role in the regulation of energy expenditure (EE) has been ascribed to sphingolipids, active components of cell membranes participating in cellular signaling. In humans, it is unknown whether sphingolipids have a role in the modulation of EE and, consequently, influence weight gain. The present study investigated the putative association of EE and weight gain with sphingolipid levels in the human skeletal muscle, a component of fat-free mass (the strongest determinant of EE), in adipose tissue and plasma.Subjects/methodsTwenty-four-hour EE, sleeping metabolic rate (SMR) and resting metabolic rate (RMR) were assessed in 35 healthy Native Americans of Southwestern heritage (24 male; 30.2±7.73 years). Sphingolipid (ceramide, C; sphingomyelin, SM) concentrations were measured in skeletal muscle tissue, subcutaneous adipose tissue and plasma samples. After 6.68 years (0.26-12.4 years), follow-up weights were determined in 16 participants (4 females).ResultsConcentrations of C24:0, SM18:1/26:1 and SM18:0/24:1 in muscle were associated with 24-h EE (r=-0.47, P=0.01), SMR (r=-0.59, P=0.0008) and RMR (r=-0.44, P=0.01), respectively. Certain muscle sphingomyelins also predicted weight gain (for example, SM18:1/23:1, r=0.74, P=0.004). For specific muscle sphingomyelins that correlated with weight gain and EE (SM18:1/23:0, SM18:1/23:1 and SMR, r=-0.51, r=-0.41, respectively, all P<0.03; SM18:1/24:2 and RMR, r=-0.36, P=0.03), associations could be reproduced with SMR in adipose tissue (all r<-0.46, all P<0.04), though not in plasma.ConclusionsThis study provides preliminary, novel evidence, that specific muscle and adipose tissue sphingolipid compounds are associated with EE and weight gain in Native Americans of Southwestern heritage. Further studies are warranted to investigate whether sphingolipids of different body compartments act in concert to modulate energy balance in humans