A physically-based and fully coupled model of elasto-plasticity and damage for dynamic failure in ductile metals

It is well established that spall fracture and other rapid failures in ductile materials are often dominated by nucleation and growth ofmicro-voids. In the present work, a mechanistic model for failure by cumulative nucleation and growth of voids is fully coupled with the thermoelastoplasticconstitutive equations of the Mechanical Threshold Stress (MTS) which is used to model the evolution of the flow stress. Thedamage modeling includes both ductile and brittle mechanisms. It accounts for the effects of inertia, rate sensitivity, fracture surface energy, andnucleation frequency. The MTS model used for plasticity includes the superposition of different thermal activation barriers for dislocationmotion. Results obtained in the case of uncoupled and coupled model of plasticity and damage from the simulations of the planar impact withcylindrical target, are presented and compared with the experimental results for OFHC copper. This comparison shows the model capabilities inpredicting the experimentally measured free surface velocity profile as well as the observed spall and other damage patterns in the material underimpact loading. These results are obtained using the finite element code Abaqus/Explicit

Simulation of the Taylor impact test and analysis of damage evolution using a nucleation and growth based approach

International audienceComputational modeling of the Taylor impact test, using OFHC copper rods are carried out for two impact velocities (260 m/s and 365 m/s). The aim of this work is to demonstrate the efficiency of the recently proposed material model for dynamic plasticity and failure for metals. This model combines the use of a damage approach based on void nucleation and growth, with the Mechanical Threshold Stress (MTS) model for the evolution of the flow stress in isotropic plasticity. The proposed approach is implemented in the finite element code ABAQUS/Explicit via a user material subroutine and the symmetric Taylor impact test, using copper rods, is simulated. The predicted results are compared to the experimental results reported in the open literature and good agreement is found for both shape change and damage distribution

CO2 and temperature effects on the asphaltene phase envelope as determined by a quartz crystal resonator

Knowledge of the asphaltene phase envelope (APE) is crucial for oil companies, especially when enhanced oil recovery is applied. An innovative quartz crystal resonator (QCR) technique was employed to assess the phase behavior of asphaltene under reservoir conditions. The effect of CO2 injection coupled to temperature changes on the APE of a recombined oil with a very low asphaltene content (0.235% w/w of C7 asphaltene in dead oil) are reported. It has been shown that QCR is an appropriate and highly sensitive nondestructive experimental technique for detecting asphaltene flocculation. Pressure onsets were found to be dependent on the depressurization rate.Knowledge of the asphaltene phase envelope (APE) is crucial for oil companies, especially when enhanced oil recovery is applied. An innovative quartz crystal resonator (QCR) technique was employed to assess the phase behavior of asphaltene under reservoir281167806787sem informaçãosem informação(2012), http://www.iea.org/publications/freepublications/publication/key_world_energy_stats-1.pdf, International Energy Agency. 2011 Key World Energy Statistics. (accessed Aug 27)Speight, J.G., (1999) The Chemistry and Technology of Petroleum, pp. 215-241. , 3 rd ed. CRC Press: New YorkFan, T., Buckley, J.S., Rapid and Accurate SARA Analysis of Medium Gravity Crude Oils (2002) Energy Fuels, 16, pp. 1571-1575Andersen, S.I., Speight, J.G., Petroleum resins separation, character, and role in petroleum (2001) Pet. Sci. Technol., 19, pp. 1-34Durand, E., Clemancey, M., Lancelin, J.-M., Verstraete, J., Espinat, D., Quoineaud, A.-A., Effect of Chemical Composition on Asphaltenes Aggregation (2010) Energy Fuels, 24, pp. 1051-1062Hammami, A., Phelps, C.H., Monger-Mcclure, T., Little, T.M., Asphaltene Precipitation from Live Oils: An Experimental Investigation of Onset Conditions and Reversibility (2000) Energy Fuels, 14, pp. 14-18Guo, B., Song, S., Chacko, J., Ghalambor, A., Flow Assurance (2005) Offshore Pipelines, pp. 169-214. , Gulf Professional Publishing: Burlington, VT, Chapter 15Zekri, A.Y., Almehaideb, R.A., A Novel Technique to Treat Asphaltene Deposition in Carbonate Rocks (2001) Soc. Pet. Eng. J.Joshi, N.B., Mullins, O.C., Jamaluddin, A., Creek, J., McFadden, J., Asphaltene Precipitation from Live Crude Oil (2001) Energy Fuels, 15, pp. 979-986Vargas, F.M., Gonzalez, D.L., Hirasaki, G.J., Chapman, W.G., Modeling Asphaltene Phase Behavior in Crude Oil Systems Using the Perturbed Chain Form of the Statistical Associating Fluid Theory (PC-SAFT) Equation of State (2009) Energy Fuels, 23, pp. 1140-1146Gonzalez, D.L., Vargas, F.M., Hirasaki, G.J., Chapman, W.G., Modeling of CO2-induced asphaltene precipitation (2008) Energy Fuels, 22, pp. 757-762Deo, M., Parra, M., Characterization of Carbon-Dioxide-Induced Asphaltene Precipitation (2012) Energy Fuels, 26, pp. 2672-2679Sarma, H.K., Can We Ignore Asphaltene in a Gas Injection Project for Light-Oils? (2003) Soc. Pet. Eng. J.Daridon, J.L., Cassiěde, M., Nasri, D., Pauly, J., Carrier, H., Probing Asphaltene Flocculation by a Quartz Crystal Resonator (2013) Energy Fuels, 27, pp. 4639-4647Abudu, A., Goual, L., Adsorption of Crude Oil on Surfaces Using Quartz Crystal Microbalance with Dissipation (QCM-D) under Flow Conditions (2009) Energy Fuels, 23, pp. 1237-1248Farooq, U., Sjöblom, J., Øye, G., Desorption of Asphaltenes from Silica-Coated Quartz Crystal Surfaces in Low Saline Aqueous Solutions (2011) J. Dispersion Sci. Technol., 32, pp. 1388-1395Tavakkoli, M., Panuganti, S.R., Vargas, F.M., Taghikhani, V., Pishvaie, M.R., Chapman, W.G., Asphaltene Deposition in Different Depositing Environments: Part 1. Model Oil (2014) Energy Fuels, 28, pp. 1617-1628Daridon, J.L., Cassiěde, M., Paillol, J.H., Pauly, J., Viscosity Measurements of Liquids under Pressure by Using the Quartz Crystal Resonators (2011) Rev. Sci. Instrum., 82, p. 095114Verdier, S., Carrier, H., Andersen, S.I., Daridon, J.L., Study of Pressure and Temperature Effects on Asphaltene Stability in Presence of CO2 (2006) Energy Fuels, 20, pp. 1584-1590Castillo, J., Canelon, C., Acevedo, S., Carrier, H., Daridon, J.L., Optical Fiber Extrinsic Refractometer to Measure RI of Samples in a High Pressure and Temperature Systems: Application to Wax and Asphaltene Precipitation Measurements (2006) Fuel, 85, pp. 2220-2228Zahabi, A., Gray, M.R., Dabros, T., Kinetics and Properties of Asphaltene Adsorption on Surfaces (2012) Energy Fuels, 26, pp. 1009-1018(2012), http://webbook.nist.gov/chemistry, NIST Chemistry WebBook. (accessed Aug 27)Kanazawa, K.K., Gordon, J.G., Frequency of a Quartz Microbalance in Contact with Liquid (1985) Anal. Chem., 57, pp. 1770-1771Muramatsu, H., Tamiya, E., Karube, I., Computation of Equivalent Circuit Parameters of Quartz Crystals in Contact with Liquids and Study of Liquid Properties (1988) Anal. Chem., 60, pp. 2142-2146Cassiěde, M., Daridon, J.L., Paillol, J.H., Pauly, J., Impedance analysis for characterizing the influence of hydrostatic pressure on piezoelectric quartz crystal sensors (2010) J. Appl. Phys., 108, p. 034505Cassiěde, M., Daridon, J.L., Paillol, J.H., Pauly, J., Electrical behavior of a quartz crystal resonator immersed in a pressurized fluid (gas or liquid) (2011) J. Appl. Phys., 109, p. 074501Freeman, P.I., Rowlinson, J.S., Lower critical points in polymer solutions (1960) Polymer, 1, pp. 20-26Hoepfner, M.P., Limsakoune, V., Chuenmeechao, V., Maqbool, T., Fogler, H.S., A Fundamental Study of Asphaltene Deposition (2013) Energy Fuels, 27, pp. 725-735Hoepfner, M.P., Favero, C.V.B., Haji-Akbari, N., Fogler, H.S., The Fractal Aggregation of Asphaltenes (2013) Langmuir, 29, pp. 8799-8808Maqbool, T., Balgoa, A.T., Fogler, H.S., Revisiting Asphaltene Precipitation from Crude Oils: A Case of Neglected Kinetic Effects (2009) Energy Fuels, 23, pp. 3681-3686Kashchiev, D., Firoozabadi, A., Induction time in crystallization of gas hydrates (2003) J. Cryst. Growth, 250, pp. 499-515The authors acknowledge PETROBRAS for providing samples of dead oil

High pressure solubility data of carbon dioxide in (tri-iso-butyl(methyl)phosphonium tosylate + water) systems

Ionic liquids are attracting great attention nowadays due to their interesting properties which make them useful in a broad range of applications including reaction media or separation/capture of environmentally hazardous gases such as carbon dioxide. In many cases, for practical and/or economical reasons, the use of aqueous solutions of ILs would be preferable to their use as pure compounds. In this work, high pressure equilibrium data for the {carbon dioxide (CO2) + tri-iso-butyl(methyl)phosphonium tosylate [iBu3MeP][TOS] + water system were measured at temperatures ranging from (276 to 370) K and pressures up to 100 MPa. Measurements were performed using a high-pressure cell with a sapphire window that allows direct observation of the liquid–vapour transition. Mixtures with different IL concentrations were studied in order to check the influence of the amount of IL on the solubility of CO2 in the aqueous mixture. The results show that the presence of IL enhances the solubility of CO2 in the (IL + water) system revealing a salting-in effect of the IL on the solubility of CO2. The appearance of a three phase region was observed for IL concentrations higher than 4 mol% of IL in water when working at pressures between 4 and 8 MPa and temperatures between (280 and 305) K. In this range, the upper limit of the VLE region observed is shown to increase with the temperature being almost independent of the IL initial concentration in the mixture.Fundação para a Ciência e a Tecnologia (FCT)FEDERCICECO, University of Aveir

New ELISA for B Cell-Activating Factor

Item does not contain fulltextWorkshop Theory and Methodology - 26th ISAGA Conference, 18 juli 1995Valencia, Spain : [S.n.]24 p

The Expression of BAFF, APRIL and TWEAK Is Altered in Eczema Skin but Not in the Circulation of Atopic and Seborrheic Eczema Patients

The TNF family cytokines BAFF (B-cell activating factor of the TNF family) and APRIL (a proliferation-inducing ligand) are crucial survival factors for B-cell development and activation. B-cell directed treatments have been shown to improve atopic eczema (AE), suggesting the involvement of these cytokines in the pathogenesis of AE. We therefore analyzed the expression of these TNF cytokines in AE, seborrheic eczema (SE) and healthy controls (HC). The serum/plasma concentration of BAFF, APRIL and a close TNF member TWEAK (TNF-like weak inducer of apoptosis) was measured by ELISA. The expression of these cytokines and their receptors in skin was analyzed by quantitative RT-PCR and immunofluorescence. Unlike other inflammatory diseases including autoimmune diseases and asthma, the circulating levels of BAFF, APRIL and TWEAK were not elevated in AE or SE patients compared with HCs and did not correlate with the disease severity or systemic IgE levels in AE patients. Interestingly, we found that the expression of these cytokines and their receptors was altered in positive atopy patch test reactions in AE patients (APT-AE) and in lesional skin of AE and SE patients. The expression of APRIL was decreased and the expression of BAFF was increased in eczema skin of AE and SE, which could contribute to a reduced negative regulatory input on B-cells. This was found to be more pronounced in APT-AE, the initiating acute stage of AE, which may result in dysregulation of over-activated B-cells. Furthermore, the expression levels of TWEAK and its receptor positively correlated to each other in SE lesions, but inversely correlated in AE lesions. These results shed light on potential pathogenic roles of these TNF factors in AE and SE, and pinpoint a potential of tailored treatments towards these factors in AE and SE

Antibodies Against Human BLyS and APRIL Attenuate EAE Development in Marmoset Monkeys

B lymphocyte stimulator (BLyS, also indicated as BAFF (B-cell activating factor) and CD257), and A Proliferation Inducing Ligand (APRIL, CD256) are two members of the TNF superfamily with a central role in B cell survival. Antibodies against these factors have potential therapeutic relevance in autoimmune inflammatory disorders with a proven pathogenic contribution of B cells, such as multiple sclerosis (MS). In the current study we performed a multi-parameter efficacy comparison of monoclonal antibodies against human anti-BLyS and anti-APRIL in a common marmoset (Callithrix jacchus) model of experimental autoimmune encephalomyelitis (EAE). A MS-like disease was induced by immunization with recombinant human myelin/oligodendrocyte glycoprotein (rhMOG) in complete Freund's adjuvant. The results show that the anti-BLyS and anti-APRIL antibody cause significant depletion of circulating CD20+ B cells, but a small subset of CD20 + CD40highB cells was not depleted. Induction of CD20+ B cell depletion from lymph nodes was only observed in the anti-BLyS treated monkeys. Both antibodies had a significant inhibitory effect on disease development, but all monkeys developed clinically evident EAE. Anti-BLyS treated monkeys were sacrificed with the same clinical signs as saline-treated monkeys, but nevertheless displayed significantly reduced spinal cord demyelination. This effect was not observed in the anti-APRIL treated monkeys. The two antibodies had a different effect on T cell subset activation and the profiles of ex vivo released cytokines. In conclusion, treatment with anti-BLyS and anti-APRIL delays the development of neurological disease in a relevant preclinical model of MS. The two mAbs achieve this effect via different mechanisms

Increased Levels of BAFF and APRIL Related to Human Active Pulmonary Tuberculosis

BACKGROUND: Despite great efforts to improve diagnosis and treatment, tuberculosis (TB) remains a major health problem worldwide, especially in developing countries. Lack of concrete immune markers is still the obstacle to properly evaluate active TB. Therefore, identification of more validated biomarkers and phenotypic signatures is imperative. In particular, T cell-related biomarkers are more significant. METHODOLOGY: To understand the nature of CD4(+) T cell-derived signatures involved in infection and disease development, we examined and analyzed whole genome expression profiles of purified CD4(+) T cells from healthy individuals (HD), two distinct populations with latent infection (with low or high IFN-γ levels, LTB(L)/LTB(H)) and untreated TB patients. Following, we validated the expression profiles of genes in the peripheral CD4(+) T cells from each group and examined secretion levels of distinct cytokines in serum and pleural effusion. PRINCIPAL FINDINGS: Our bio-informatic analyses indicate that the two latent populations and clinical TB patients possess distinct CD4(+) T cell gene expression profiles. Furthermore, The mRNA and protein expression levels of B cell activating factor (BAFF), which belongs to the TNF family, and a proliferation-inducing ligand (APRIL) were markedly up-regulated at the disease stage. In particular, the dramatic enhancement of BAFF and APRIL in the pleural effusion of patients with tuberculosis pleurisy suggests that these proteins may present disease status. In addition, we found that the BAFF/APRIL system was closely related to the Th1 immune response. Our study delineates previously unreported roles of BAFF and APRIL in the development of tuberculosis, and these findings have implications for the diagnosis of the disease. Our study also identifies a number of transcriptional signatures in CD4(+) T cells that have the potential to be utilized as diagnostic and prognostic tools to combat the tuberculosis epidemic