bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Variation of the Elliptic Paraboloid Failure Locus Beyond the Elastic Limit
Authors: Theocaris Pericles S. 
Published: July 2008

A method is presented by defining an isotropic hardening plasticity through an appropriate sequence of an isotropic problems. Assuming a stepwise form of loading or unloading, we measure the instantaneous tension and compression yield stresses along the transient principal-stress directions. These parameters completely define the instantaneous state of anisotropy of the body for the corresponding loading step, by applying the theory of elliptic paraboloid failure locus (EPFS). The parameter identification problem is formulated on the constitutive expressions for this most general failure criterion, and by applying convenient constraints derived from the EPFS theory, which are serving as filters throughout the whole procedure of evaluating the characteristic values of terms defining the variable components of the failure tensor polynomial, as the material is continuously loaded from the elastic into the plastic region and up to the ultimate failure load. Accurate simple tests in uniaxial tension and compression yield sufficient data for defining the yield loci of the material for the loading step considered. These data were used as input values for establishing the mode of plastic deformation of the body during a particular loading path. It was shown that the prediction or the eventual correction of either extrapolated or interpolated yield surfaces are reasonable and concordant with experimental evidence. Since the method allows the separate complete definition of the particular values of the coefficients of the failure tensor H and the strength differential effect tensor h at each loading step, it presents the important advantage over other experimental methods of clearly indicating the parts contributed either by plasticity, or by strength differential effect of elastically and plastically deformed materials and their evolution during the development of plastic deformation.
Prediction of Plane-Strain Creep-Crack Growth Using Continuum Damage Mechanics
Authors: Hall F. R. , Hayhurst D. R. , Brown P. R. 
Published: July 2008

The paper examines the possibility of using creep Continuum Damage Mechanics to predict plane strain creep crack growth in compact tension specimens using finite element based numerical methods, coupled with uni-axial and multi-axial stress laboratory creep data, and with mechanisms-based constitutive equations. The predictions of the behaviour of the compact tension specimens made using the single state damage variable equations due to Hayhurst, Dimmer, and Morrison (1984) are shown to be unable to predict that zones of damage do not grow in discrete planar regions as observed in laboratory experiments. To overcome the deficiencies of this approach, new constitutive equations have been developed, which combine the equations of Hayhurst et al. (1984) with those of Cocks and Ashby (1982), to describe the stress-state dependence of the physical mechanisms. The behaviour of the compact tension specimen determined using these new equations predicts lifetimes of the correct order and evolution of damage zones which reflect the growth of discrete cracks as observed experimentally. The paper shows that creep Continuum Damage Mechanics can be used with finite element based numerical procedures to predict creep crack growth, provided that mechanisms-based constitutive equations are used which describe the appropriate stress-state behaviour for each mechanism zone, and that continuity of mechanical properties are achieved across all mechanism boundaries.
On the Interface Debonding Models
Authors: Chaboche J. L. , Girard R. , Levasseur P. 
Published: July 2008

Interface debonding models offer the possibility to simulate numerically the interface crack growth, and the eventual contact friction behaviour on the cracked area. The paper considers models in the framework of an Interface Damage Mechanics, relating displacement discontinuities across the interface to the corresponding tractions, through various constitutive and damage equations. The approach is based on the initial works by Needleman (1987) and Tvergaard (1990a, 1990b). After a brief review of the existing models, two new versions are proposed and discussed in detail, with the purpose of simulating mixed mode progressive decohesion, followed by a contact/friction behaviour after complete separation, and to guarantee the continuity between the two phases. The first modified model considers coupling terms in the elastic behaviour with damage. The second one introduces the possibility for sliding effects, obeying the Coulomb criterion, during the decohesion phase. The initial Tvergaard model and the second modified model are shown to be derivable from a state potential. Moreover, the thermodynamic framework is used to choose some characteristics of the Model II under a compressive behaviour. Under tension, the models reduce to the classical one. A three-dimensional generalization is given in the Appendix. In addition, the numerical simulation capabilities of the interface debonding models are illustrated by two examples: the fibre-matrix-interface decohesion in a Metal Matrix composite with a bridged matrix crack and the delamination of a DCB (Double Cantilever Beam) specimen.
Modelling of Damage Behaviour of a Short-Fiber Reinforced Composite Structure by the Finite Element Analysis Using a Micro-Macro Law
Authors: Guo Guang , Fitoussi Joseph , Baptiste Didier , Sicot Nathalie , Wolff Christian 
Published: July 2008

The objective of this paper is composed of two parts: (1) presentation of the damageable elastic law for randomly reinforced composites based on the micro-macro relationship of Mori and Wakashima type (1990); and (2) calculation of composite structures by a finite element code, ABAQUS, using this damage model. Several mechanical tests on the short-fiber reinforced composite, such as bending, torsion, and the combination of bending and torsion, have been performed experimentally and simulated. A good correlation is obtained between experiment and simulation.
Localized Fracture in Inelastic Polycrystalline Solids under Dynamic Loading Processes
Authors: Lodygowski Tomasz , Perzyna Piotr 
Published: July 2008

The main objective of the paper is the investigation of adiabatic shear band localized fracture phenomenon in inelastic solids during dynamic loading processes. This kind of fracture can occur as a result of an adiabatic shear band localization generally attributed to a plastic instability implied by micro-damage and thermal softening during dynamic plastic flow processes. The theory of thermoviscoplasticity is developed within a framework of the rate type covariance material structure with a finite set of internal state variables. The theory takes into consideration the effects of micro-damage mechanism and thermomechanical coupling. The micro-damage mechanism has been treated as a sequence of nucleation, growth, and coalesence of microcracks. The micro-damage kinetics interacts with thermal and load changes to make failure of solids a highly rate, temperature, and history dependent, nonlinear process. The dynamic failure criterion within localized shear band region is proposed. The relaxation time is used as a regularization parameter. By assuming that the relaxation time tends to zero, the rate independent micro-damage mechanism is considered. Rate dependency (viscosity) allows the spatial differential operator in the governing equations to retain its ellipticity, and the initial-value problem is well posed. The viscoplastic regularization procedure assures the stable integration algorithm by using the finite element method. Particular attention is focused on the well-posedness of the evolution problem (the initial-boundary value problem), as well as on its numerical solutions. Convergence, consistency, and stability of the discretised problem are discussed. The Lax equivalence theorem is formulated and conditions under which this theorem is valid are examined. Utilizing the finite element method and ABAQUS system for regularized elastoviscoplastic model, the numerical investigation of the three-dimensional dynamic adiabatic deformation in a particular body at nominal strain rates ranging from 10-1-104 s-1 is presented. Three particular examples have been considered; namely, a dynamic adiabatic process for a thin-walled steel tube and dynamic adiabatic and quasi-static processes for a thin steel plate. In each case, a thin shear band region of finite width which undergoes significant deformations and temperature rise has been determined. Its evolution until occurrence of final fracture has been simulated. Numerical results are compared with available experimental observation data.
A Thermomechanical Model for Airfield Concrete Pavement under Transient High Temperature Loadings
Authors: Ju J. W. , Zhang Y. 
Published: July 2008

A simple one-dimensional thermo-micromechanical constitutive and damage model is proposed for airfield concrete pavement under rapid transient high temperature loadings due to vectored thrust. The subsurface temperature fields and time histories, the pore pressure histories, the thermoplastic stress-strain relations with void effects are investigated for both constant and varying thermal properties. In particular, if the thermal properties are constant, the resulting temperature fields and histories can be solved numerically by utilizing the Duhamel's theorem. On the other hand, if the thermal properties are varying with rising temperatures, then the resulting temperature histories can be solved numerically by the explicit finite difference method. Furthermore, based on the ASME Steam Tables and the temperature histories, we are capable of predicting the pore pressure fields and histories. In accord with the theory of linear thermoelasticity, the strain histories and the stress-strain relations at different depths and time accounting for void effects are subsequently derived. Finally, a simple dynamic crack growth model due to high pore pressure is considered. A preliminary damage criterion to characterize the delamination of concrete pavement at various depths is also proposed.
Aspects of Testpiece Design Responsible for Errors in Cyclic Plasticity Experiments
Authors: Lin J. , Dunne F. P. E. , Hayhurst D. R. 
Published: July 2008

A uniaxial cyclic plasticity copper testpiece has been simulated, using the Continuum Damage Mechanics based finite element programme Damage XX, under conditions of cyclic plasticity at temperatures of 20°C and 500°C. The results obtained have been compared with the results of experiments carried out under the same conditions. It has been shown that inhomogeneous fields of strain and stress are generated in the gauge length region of the testpiece, which result from standard cyclic plasticity testpiece features, namely, the blend radius linking testpiece shank and gauge length, and the extensometer ridges. The influence of these features on the inhomogeneity is exacerbated by the short gauge length which is necessary in cyclic plasticity testpieces to prevent buckling. At the temperatures of 20°C and 500°C, cracks were predicted to occur, and found experimentally, at the extensometer ridges. Testpiece failure at 20°C occurred outside the gauge length; and at 500°C failure took place from cracks growing within the gauge length region. The formation and growth of the latter gauge length crack was accurately predicted. The results obtained clearly demonstrate the dependence of cyclic plasticity data on testpiece design and suggest that the range of scatter observed experimentally in cyclic plasticity testing for nominally identical testing conditions may result from variations in testpiece design. This is of some concern, and the establishment of a methodology which overcomes these problems will be the subject of a future paper.
Constitutive Modeling of Material Damage for Fatigue Failure Prediction
Authors: Chow C. L. , Wei Y. 
Published: July 2008

This paper presents a constitutive modeling of material damage capable of characterizing fatigue damage and plastic damage for rate-independent materials under multiaxial loading with the theory of damage mechanics. First, an internal state variable known as the damage variable is introduced with two scalars to characterize material degradation due to the change of material microstructures under fatigue. Then, depending upon the level of applied stress in a material element, the damage accumulation is postulated to undergo two processes, the accumulation of fatigue damage and plastic damage. Two surfaces, fatigue damage surface and plastic damage surface, are proposed to quantify fatigue damage initiation and plastic damage initiation. The damage-coupled constitutive equations of elasticity and plasticity plus two corresponding damage evolution equations are formulated based on the irreversible thermodynamics. Finally, a failure criterion based on the overall damage accumulation is postulated to govern crack initiation and propagation in material elements. A test program to determine the necessary material parameters is also provided. These parameters are considered intrinsic material properties required as the finite element input for predicting damage accumulation under fatigue loading. As an example, experiments are carried out to measure a set of damage parameters for aluminum alloy 2024-T3. The measured parameters are then used to demonstrate systematically how the damage parameters can be effectively evaluated.
Sickle red cells induce adhesion of lymphocytes and monocytes to endothelium
Authors: Zennadi Rahima , Chien Ai , Xu Ke , Batchvarova Milena , Telen Marilyn J. 
Published: July 2008

AbstractInfusion of epinephrine-activated human sickle erythrocytes (SS RBCs) into nude mice promotes both SS RBC and murine leukocyte adhesion to vascular endothelium in vivo. We hypothesized that interaction of epinephrine-stimulated SS RBCs with leukocytes leads to activation of leukocytes, which then adhere to endothelial cells (ECs). In exploring the underlying molecular mechanisms, we have found that coincubation in vitro of epinephrine-treated SS RBCs with human peripheral blood mononuclear cells (PBMCs) results in robust adhesion of PBMCs to ECs. Sham-treated SS RBCs had a similar but less pronounced effect, whereas neither sham- nor epinephrine-treated normal RBCs activated PBMC adhesion. PBMC activation was induced via at least 2 RBC adhesion receptors, LW and CD44. In response to SS RBCs, leukocyte CD44 and β2 integrins mediated PBMC adhesion to ECs, a process that involved endothelial E-selectin and fibronectin. SS RBCs activated adhesion of both PBMC populations, lymphocytes and monocytes. Thus, our findings reveal a novel mechanism that may contribute to the pathogenesis of vaso-occlusion in sickle cell disease, in which SS RBCs act via LW and CD44 to stimulate leukocyte adhesion to endothelium, and suggest that RBC LW and CD44 may serve as potential targets for antiadhesive therapy designed to prevent vaso-occlusion.
Impact of prior imatinib mesylate on the outcome of hematopoietic cell transplantation for chronic myeloid leukemia
Authors: Lee Stephanie J. , Kukreja Manisha , Wang Tao , Giralt Sergio A. , Szer Jeffrey , Arora Mukta , Woolfrey Ann E. , Cervantes Francisco , Champlin Richard E. , Gale Robert Peter , Halter Joerg , Keating Armand , Marks David I. , McCarthy Philip L. , Olavarria Eduardo , Stadtmauer Edward A. , Abecasis Manuel , Gupta Vikas , Khoury H. Jean , George Biju , Hale Gregory A. , Liesveld Jane L. , Rizzieri David A. , Antin Joseph H. , Bolwell Brian J. , Carabasi Matthew H. , Copelan Edward , Ilhan Osman , Litzow Mark R. , Schouten Harold C. , Zander Axel R. , Horowitz Mary M. , Maziarz Richard T. 
Published: July 2008

AbstractImatinib mesylate (IM, Gleevec) has largely supplanted allogeneic hematopoietic cell transplantation (HCT) as first line therapy for chronic myeloid leukemia (CML). Nevertheless, many people with CML eventually undergo HCT, raising the question of whether prior IM therapy impacts HCT success. Data from the Center for International Blood and Marrow Transplant Research on 409 subjects treated with IM before HCT (IM+) and 900 subjects who did not receive IM before HCT (IM−) were analyzed. Among patients in first chronic phase, IM therapy before HCT was associated with better survival but no statistically significant differences in treatment-related mortality, relapse, and leukemia-free survival. Better HLA-matched donors, use of bone marrow, and transplantation within one year of diagnosis were also associated with better survival. A matched-pairs analysis was performed and confirmed a higher survival rate among first chronic phase patients receiving IM. Among patients transplanted with advanced CML, use of IM before HCT was not associated with treatment-related mortality, relapse, leukemia-free survival, or survival. Acute graft-versus-host disease rates were similar between IM+ and IM− groups regardless of leukemia phase. These results should be reassuring to patients receiving IM before HCT.
BMP4 regulation of human megakaryocytic differentiation is involved in thrombopoietin signaling
Authors: Jeanpierre Sandrine , Nicolini Franck Emmanuel , Kaniewski Bastien , Dumontet Charles , Rimokh Ruth , Puisieux Alain , Maguer-Satta Véronique 
Published: July 2008

AbstractActivin A, BMP2, and BMP4, 3 members of the transforming growth factor-β family, are involved in the regulation of hematopoiesis. Here, we explored the role of these molecules in human megakaryopoiesis using an in vitro serum-free assay. Our results highlight for the first time that, in the absence of thrombopoietin, BMP4 is able to induce CD34+ progenitor differentiation into megakaryocytes through all stages. Although we have previously shown that activin A and BMP2 are involved in erythropoietic commitment, these molecules have no effect on human megakaryopoietic engagement and differentiation. Using signaling pathway-specific inhibitors, we show that BMP4, like thrombopoietin, exerts its effects on human megakaryopoiesis through the JAK/STAT and mTor pathways. Inhibition of the BMP signaling pathway with blocking antibodies, natural soluble inhibitors (FLRG or follistatin), or soluble BMP receptors reveals that thrombopoietin uses the BMP4 pathway to induce megakaryopoiesis, whereas the inverse is not occurring. Finally, we show that thrombopoietin up-regulates the BMP4 autocrine loop in megakaryocytic progenitors by inducing their production of BMP4 and up-regulating BMP receptor expression. In summary, this work indicates that BMP4 plays an important role in the control of human megakaryopoiesis.
TINF2 mutations result in very short telomeres: analysis of a large cohort of patients with dyskeratosis congenita and related bone marrow failure syndromes
Authors: Walne Amanda J. , Vulliamy Tom , Beswick Richard , Kirwan Michael , Dokal Inderjeet 
Published: July 2008

Abstract
Dyskeratosis congenita (DC) is a multisystem bone marrow failure syndrome characterized by a triad of mucocutaneous abnormalities and a predisposition to cancer. The genetic basis of DC remains unknown in more than 60% of patients. Mutations have been identified in components of the telomerase complex (dyskerin, TERC, TERT, NOP10, and NHP2), and recently in one component of the shelterin complex TIN2 (gene TINF2). To establish the role of TINF2 mutations, we screened DNA from 175 uncharacterised patients with DC as well as 244 patients with other bone marrow failure disorders. Heterozygous coding mutations were found in 33 of 175 previously uncharacterized DC index patients and 3 of 244 other patients. A total of 21 of the mutations affected amino acid 282, changing arginine to histidine (n = 14) or cysteine (n = 7). A total of 32 of 33 patients with DC with TINF2 mutations have severe disease, with most developing aplastic anaemia by the age of 10 years. Telomere lengths in patients with TINF2 mutations were the shortest compared with other DC subtypes, but TERC levels were normal. In this large series, TINF2 mutations account for approximately 11% of all DC, but they do not play a significant role in patients with related disorders. This study emphasises the role of defective telomere maintenance on human disease.
Risk-adapted treatment of acute promyelocytic leukemia with all-trans retinoic acid and anthracycline monochemotherapy: long-term outcome of the LPA 99 multicenter study by the PETHEMA Group
Authors: Sanz Miguel A. , Montesinos Pau , Vellenga Edo , Rayón Consuelo , de la Serna Javier , Parody Ricardo , Bergua Juan M. , León Angel , Negri Silvia , González Marcos , Rivas Concha , Esteve Jordi , Milone Gustavo , González José D. , Amutio Elena , Brunet Salut , García-Laraña J. , Colomer Dolors , Calasanz María J. , Chillón Carmen , Barragán Eva , Bolufer Pascual , Lowenberg Bob 
Published: July 2008

AbstractA previous report of the Programa de Estudio y Tratamiento de las Hemopatías Malignas (PETHEMA) Group showed that a risk-adapted strategy combining all-trans retinoic acid (ATRA) and anthracycline monochemotherapy for induction and consolidation in newly diagnosed acute promyelocytic leukemia results in an improved outcome. Here we analyze treatment outcome of an enlarged series of patients who have been followed up for a median of 65 months. From November 1999 through July 2005 (LPA99 trial), 560 patients received induction therapy with ATRA plus idarubicin. Patients achieving complete remission received 3 courses of consolidation followed by maintenance with ATRA and low-dose chemotherapy. The 5-year cumulative incidence of relapse and disease-free survival were 11% and 84%, respectively. These results compare favorably with those obtained in the previous LPA96 study (P = .019 and P = .04, respectively). This updated analysis confirms the high antileukemic efficacy, low toxicity, and high degree of compliance of a risk-adapted strategy combining ATRA and anthracycline monochemotherapy for consolidation therapy.
A machine learning approach to explore the spectra intensity pattern of peptides using tandem mass spectrometry data
Authors: Zhou Cong , Bowler Lucas D , Feng Jianfeng 
Published: July 2008

Abstract

Background
A better understanding of the mechanisms involved in gas-phase fragmentation of peptides is essential for the development of more reliable algorithms for high-throughput protein identification using mass spectrometry (MS). Current methodologies depend predominantly on the use of derived m/z values of fragment ions, and, the knowledge provided by the intensity information present in MS/MS spectra has not been fully exploited. Indeed spectrum intensity information is very rarely utilized in the algorithms currently in use for high-throughput protein identification.

Results
In this work, a Bayesian neural network approach is employed to analyze ion intensity information present in 13878 different MS/MS spectra. The influence of a library of 35 features on peptide fragmentation is examined under different proton mobility conditions. Useful rules involved in peptide fragmentation are found and subsets of features which have significant influence on fragmentation pathway of peptides are characterised. An intensity model is built based on the selected features and the model can make an accurate prediction of the intensity patterns for given MS/MS spectra. The predictions include not only the mean values of spectra intensity but also the variances that can be used to tolerate noises and system biases within experimental MS/MS spectra.

Conclusion
The intensity patterns of fragmentation spectra are informative and can be used to analyze the influence of various characteristics of fragmented peptides on their fragmentation pathway. The features with significant influence can be used in turn to predict spectra intensities. Such information can help develop more reliable algorithms for peptide and protein identification.