PINS chemical identification software

DOEpatents

Caffrey, Augustine J.; Krebs, Kennth M.

2004-09-14

An apparatus and method for identifying a chemical compound. A neutron source delivers neutrons into the chemical compound. The nuclei of chemical elements constituting the chemical compound emit gamma rays upon interaction with the neutrons. The gamma rays are characteristic of the chemical elements constituting the chemical compound. A spectrum of the gamma rays is generated having a detection count and an energy scale. The energy scale is calibrated by comparing peaks in the spectrum to energies of pre-selected chemical elements in the spectrum. A least-squares fit completes the calibration. The chemical elements constituting the chemical compound can be readily determined, which then allows for identification of the chemical compound.

The Deductibility of Work-Related Higher Education Costs: The Saga Continues

ERIC Educational Resources Information Center

Segal, Mark A.; Bird, Bruce M.

2011-01-01

Whether a taxpayer's work-related higher education costs are deductible under IRC (Internal Revenue Code) Section 162 is an issue highly dependent upon facts and circumstances. The regulations pursuant to IRC Section 162 and the emergence of case law on this topic constitute important elements to consider in making this determination.

Characterization of three-dimensional anisotropic heart valve tissue mechanical properties using inverse finite element analysis.

PubMed

Abbasi, Mostafa; Barakat, Mohammed S; Vahidkhah, Koohyar; Azadani, Ali N

2016-09-01

Computational modeling has an important role in design and assessment of medical devices. In computational simulations, considering accurate constitutive models is of the utmost importance to capture mechanical response of soft tissue and biomedical materials under physiological loading conditions. Lack of comprehensive three-dimensional constitutive models for soft tissue limits the effectiveness of computational modeling in research and development of medical devices. The aim of this study was to use inverse finite element (FE) analysis to determine three-dimensional mechanical properties of bovine pericardial leaflets of a surgical bioprosthesis under dynamic loading condition. Using inverse parameter estimation, 3D anisotropic Fung model parameters were estimated for the leaflets. The FE simulations were validated using experimental in-vitro measurements, and the impact of different constitutive material models was investigated on leaflet stress distribution. The results of this study showed that the anisotropic Fung model accurately simulated the leaflet deformation and coaptation during valve opening and closing. During systole, the peak stress reached to 3.17MPa at the leaflet boundary while during diastole high stress regions were primarily observed in the commissures with the peak stress of 1.17MPa. In addition, the Rayleigh damping coefficient that was introduced to FE simulations to simulate viscous damping effects of surrounding fluid was determined. Copyright © 2016 Elsevier Ltd. All rights reserved.

Finite element analysis of elasto-plastic soils. Report no. 4: Finite element analysis of elasto-plastic frictional materials for application to lunar earth sciences

NASA Technical Reports Server (NTRS)

Marr, W. A., Jr.

1972-01-01

The behavior of finite element models employing different constitutive relations to describe the stress-strain behavior of soils is investigated. Three models, which assume small strain theory is applicable, include a nondilatant, a dilatant and a strain hardening constitutive relation. Two models are formulated using large strain theory and include a hyperbolic and a Tresca elastic perfectly plastic constitutive relation. These finite element models are used to analyze retaining walls and footings. Methods of improving the finite element solutions are investigated. For nonlinear problems better solutions can be obtained by using smaller load increment sizes and more iterations per load increment than by increasing the number of elements. Suitable methods of treating tension stresses and stresses which exceed the yield criteria are discussed.

Compressive mechanical characterization of non-human primate spinal cord white matter.

PubMed

Jannesar, Shervin; Allen, Mark; Mills, Sarah; Gibbons, Anne; Bresnahan, Jacqueline C; Salegio, Ernesto A; Sparrey, Carolyn J

2018-05-02

The goal of developing computational models of spinal cord injury (SCI) is to better understand the human injury condition. However, finite element models of human SCI have used rodent spinal cord tissue properties due to a lack of experimental data. Central nervous system tissues in non human primates (NHP) closely resemble that of humans and therefore, it is expected that material constitutive models obtained from NHPs will increase the fidelity and the accuracy of human SCI models. Human SCI most often results from compressive loading and spinal cord white matter properties affect FE predicted patterns of injury; therefore, the objectives of this study were to characterize the unconfined compressive response of NHP spinal cord white matter and present an experimentally derived, finite element tractable constitutive model for the tissue. Cervical spinal cords were harvested from nine male adult NHPs (Macaca mulatta). White matter biopsy samples (3 mm in diameter) were taken from both lateral columns of the spinal cord and were divided into four strain rate groups for unconfined dynamic compression and stress relaxation (post-mortem <1-hour). The NHP spinal cord white matter compressive response was sensitive to strain rate and showed substantial stress relaxation confirming the viscoelastic behavior of the material. An Ogden 1st order model best captured the non-linear behavior of NHP white matter in a quasi-linear viscoelastic material model with 4-term Prony series. This study is the first to characterize NHP spinal cord white matter at high (>10/sec) strain rates typical of traumatic injury. The finite element derived material constitutive model of this study will increase the fidelity of SCI computational models and provide important insights for transferring pre-clinical findings to clinical treatments. Spinal cord injury (SCI) finite element (FE) models provide an important tool to bridge the gap between animal studies and human injury, assess injury prevention technologies (e.g. helmets, seatbelts), and provide insight into the mechanisms of injury. Although, FE model outcomes depend on the assumed material constitutive model, there is limited experimental data for fresh spinal cords and all was obtained from rodent, porcine or bovine tissues. Central nervous system tissues in non human primates (NHP) more closely resemble humans. This study characterizes fresh NHP spinal cord material properties at high strains rates and large deformations typical of SCI for the first time. A constitutive model was defined that can be readily implemented in finite strain FE analysis of SCI. Copyright © 2018. Published by Elsevier Ltd.

Research and development program for non-linear structural modeling with advanced time-temperature dependent constitutive relationships

NASA Technical Reports Server (NTRS)

Walker, K. P.

1981-01-01

Results of a 20-month research and development program for nonlinear structural modeling with advanced time-temperature constitutive relationships are reported. The program included: (1) the evaluation of a number of viscoplastic constitutive models in the published literature; (2) incorporation of three of the most appropriate constitutive models into the MARC nonlinear finite element program; (3) calibration of the three constitutive models against experimental data using Hastelloy-X material; and (4) application of the most appropriate constitutive model to a three dimensional finite element analysis of a cylindrical combustor liner louver test specimen to establish the capability of the viscoplastic model to predict component structural response.

Constitutive modeling of aluminum foam and finite element implementation for crash simulations

NASA Astrophysics Data System (ADS)

Bi, Jing

In the past decades metallic foams have been increasingly used as filler materials in crashworthiness applications due to their relatively low cost and high capacity of energy absorption. Due to the destructive nature of crashes, studies on the performance of metallic foams using physical testing have been limited to examining the crushing force histories and/or folding patterns that are insufficient for crashworthiness designs. For this reason, numerical simulations, particularly nonlinear finite element (FE) analyses, play an important role in designing crashworthy foam-filled structures. An effective and numerically stable model is needed for modeling metallic foams that are porous and encounter large nonlinear deformations in crashes. In this study a new constitutive model for metallic foams is developed to overcome the deficiency of existing models in commercial FE codes such as LS-DYNA. The new constitutive model accounts for volume changes under hydrostatic compression and combines the hydrostatic pressure and von Mises stress into one yield function. The change of the compressibility of the metallic foam is handled in the constitutive model by allowing for shape changes of the yield surface in the hydrostatic pressure-von Mises stress space. The backward Euler method is adopted to integrate the constitutive equations to achieve numerical accuracy and stability. The new foam model is verified and validated by existing experimental data before used in FE simulations of crushing of foam-filled columns that have square and hexagonal cross-sections.

What do we mean by "socialization to the model"? A Delphi study.

PubMed

Roos, Jo; Wearden, Alison

2009-05-01

The term "socialization to the model" is frequently used in the Cognitive Behavioural Therapy (CBT) literature, but it is unclear exactly what constitutes socialization to the model and there is a paucity of research in this area. This study aimed to develop a working definition of "socialization to the model". A three-round electronic Delphi technique was used to generate data and to achieve a consensus agreement amongst a panel of experts (N = 9) in response to two questions pertaining to what constitutes "socialization to the model". All elements generated in response to the primary question at the first round were retained throughout and scored an IQR of

Non-integer viscoelastic constitutive law to model soft biological tissues to in-vivo indentation.

PubMed

Demirci, Nagehan; Tönük, Ergin

2014-01-01

During the last decades, derivatives and integrals of non-integer orders are being more commonly used for the description of constitutive behavior of various viscoelastic materials including soft biological tissues. Compared to integer order constitutive relations, non-integer order viscoelastic material models of soft biological tissues are capable of capturing a wider range of viscoelastic behavior obtained from experiments. Although integer order models may yield comparably accurate results, non-integer order material models have less number of parameters to be identified in addition to description of an intermediate material that can monotonically and continuously be adjusted in between an ideal elastic solid and an ideal viscous fluid. In this work, starting with some preliminaries on non-integer (fractional) calculus, the "spring-pot", (intermediate mechanical element between a solid and a fluid), non-integer order three element (Zener) solid model, finally a user-defined large strain non-integer order viscoelastic constitutive model was constructed to be used in finite element simulations. Using the constitutive equation developed, by utilizing inverse finite element method and in vivo indentation experiments, soft tissue material identification was performed. The results indicate that material coefficients obtained from relaxation experiments, when optimized with creep experimental data could simulate relaxation, creep and cyclic loading and unloading experiments accurately. Non-integer calculus viscoelastic constitutive models, having physical interpretation and modeling experimental data accurately is a good alternative to classical phenomenological viscoelastic constitutive equations.

Constitutive Model Calibration via Autonomous Multiaxial Experimentation (Postprint)

DTIC Science & Technology

2016-09-17

test machine. Experimental data is reduced and finite element simulations are conducted in parallel with the test based on experimental strain...data is reduced and finite element simulations are conducted in parallel with the test based on experimental strain conditions. Optimization methods...be used directly in finite element simulations of more complex geometries. Keywords Axial/torsional experimentation • Plasticity • Constitutive model

Atom-scale depth localization of biologically important chemical elements in molecular layers.

PubMed

Schneck, Emanuel; Scoppola, Ernesto; Drnec, Jakub; Mocuta, Cristian; Felici, Roberto; Novikov, Dmitri; Fragneto, Giovanna; Daillant, Jean

2016-08-23

In nature, biomolecules are often organized as functional thin layers in interfacial architectures, the most prominent examples being biological membranes. Biomolecular layers play also important roles in context with biotechnological surfaces, for instance, when they are the result of adsorption processes. For the understanding of many biological or biotechnologically relevant phenomena, detailed structural insight into the involved biomolecular layers is required. Here, we use standing-wave X-ray fluorescence (SWXF) to localize chemical elements in solid-supported lipid and protein layers with near-Ångstrom precision. The technique complements traditional specular reflectometry experiments that merely yield the layers' global density profiles. While earlier work mostly focused on relatively heavy elements, typically metal ions, we show that it is also possible to determine the position of the comparatively light elements S and P, which are found in the most abundant classes of biomolecules and are therefore particularly important. With that, we overcome the need of artificial heavy atom labels, the main obstacle to a broader application of high-resolution SWXF in the fields of biology and soft matter. This work may thus constitute the basis for the label-free, element-specific structural investigation of complex biomolecular layers and biological surfaces.

Atom-scale depth localization of biologically important chemical elements in molecular layers

PubMed Central

Schneck, Emanuel; Scoppola, Ernesto; Drnec, Jakub; Mocuta, Cristian; Felici, Roberto; Novikov, Dmitri; Fragneto, Giovanna; Daillant, Jean

2016-01-01

In nature, biomolecules are often organized as functional thin layers in interfacial architectures, the most prominent examples being biological membranes. Biomolecular layers play also important roles in context with biotechnological surfaces, for instance, when they are the result of adsorption processes. For the understanding of many biological or biotechnologically relevant phenomena, detailed structural insight into the involved biomolecular layers is required. Here, we use standing-wave X-ray fluorescence (SWXF) to localize chemical elements in solid-supported lipid and protein layers with near-Ångstrom precision. The technique complements traditional specular reflectometry experiments that merely yield the layers’ global density profiles. While earlier work mostly focused on relatively heavy elements, typically metal ions, we show that it is also possible to determine the position of the comparatively light elements S and P, which are found in the most abundant classes of biomolecules and are therefore particularly important. With that, we overcome the need of artificial heavy atom labels, the main obstacle to a broader application of high-resolution SWXF in the fields of biology and soft matter. This work may thus constitute the basis for the label-free, element-specific structural investigation of complex biomolecular layers and biological surfaces. PMID:27503887

On finite element implementation and computational techniques for constitutive modeling of high temperature composites

NASA Technical Reports Server (NTRS)

Saleeb, A. F.; Chang, T. Y. P.; Wilt, T.; Iskovitz, I.

1989-01-01

The research work performed during the past year on finite element implementation and computational techniques pertaining to high temperature composites is outlined. In the present research, two main issues are addressed: efficient geometric modeling of composite structures and expedient numerical integration techniques dealing with constitutive rate equations. In the first issue, mixed finite elements for modeling laminated plates and shells were examined in terms of numerical accuracy, locking property and computational efficiency. Element applications include (currently available) linearly elastic analysis and future extension to material nonlinearity for damage predictions and large deformations. On the material level, various integration methods to integrate nonlinear constitutive rate equations for finite element implementation were studied. These include explicit, implicit and automatic subincrementing schemes. In all cases, examples are included to illustrate the numerical characteristics of various methods that were considered.

Functional Analysis of Promoter Region from Eel Cytochrome P450 1A1 Gene in Transgenic Medaka.

PubMed

Ogino; Itakura; Kato; Aoki; Sato

1999-07-01

: Transcription of the CYP1A1 genes in mammals and fish is stimulated by polyaromatic hydrocarbons. DNA sequencing analysis revealed that CYP1A1 gene in eel (Anguilla japonica) contains two kinds of putative cis-acting regulatory elements, XRE (xenobiotic-responsive element) and ERE (estrogen-responsive element). XRE is known as the enhancer that is responsible for the inducibility of the genes of CYP1A1 and some other drug-metabolizing enzymes. In the eel CYP1A1 gene, XRE motifs are distributed as follows: five times in the region from -2136 to -1125 bp, XRE(-6) to (-2); once in the proximal basal promoter region, XRE(-1); and once in the first intron, XRE(+1). The region between XRE(-2) and XRE(-1) contains three ERE motifs. To investigate the function of the cis-acting regulatory elements in the eel CYP1A1 gene, recombinant plasmids prepared with its 5' upstream sequence and the structural gene for luciferase were microinjected into fertilized eggs of medaka at the one-cell stage. Hatched fry were treated with 3-methylcholanthrene, and the transcription efficiency was assayed using competitive polymerase chain reaction analysis. Deletion of the region containing the five XREs, XRE(-6) to XRE(-2), and the point mutation of XRE(-1) reduced the inducible expressions by 75% and 56%, respectively, showing apparent dependency of the drug induction on the XREs. Constitutive expression, however, was not significantly affected by deletion or disruption of the XREs. When the region between XRE(-2) and XRE(-1) containing no XREs but three ERE motifs was internally deleted, the inducible expression and the constitutive expression were reduced by 88% and 75%, respectively. Replacement of this region with a partial fragment of eel CYP1A1 complementary DNA, with slight alteration of the distance between the five XREs and XRE(-1), reduced the inducible expression and the constitutive expression by 91% and 60%, respectively. These results strongly suggest that not only XRE but also other regulatory elements, possibly ERE, play an important role in induced and constitutive expressions of the eel CYP1A1 gene.

Etude par elements finis du comportement thermo-chimiomecanique de la pâte monolithique

NASA Astrophysics Data System (ADS)

Girard, Pierre-Luc

Aluminum industry is in a fierce international competition requiring the constant improvement of the electrolysis cell effectiveness and longevity. The selection of the cell's materials components becomes an important factor to increase the cell's life. The ramming paste, used to seal the cathode lining, is compacted in the joints between the cathode and the side wall of the cell. It is a complex thermo-chemo-reactive material whose proprieties change with the evolution of his baking level. Therefore, the objective of this project is to propose a thermo-chemo-mechanical constitutive law for the ramming paste and implement it in the finite element software ANSYSRTM. A constitutive model was first chosen from the available literature on the subject. It is a pressure dependent model that uses hardening, softening and baking mechanisms in its definition to mimic the behavior of carbon-based materials. Subsequently, the numerical tool was validated using the finite element toolbox FESh++, which contains the most representative carbon-based thermochimio- mechanical material constitutive law at this time. Finally, a validation of the experimental setup BERTA (Banc d'essai de resistance thermomecanique ALCAN) was made in prevision of a larger scale experimental validation of the constitutive law in a near future. However, the analysis of the results shows that BERTA is not suited to adequately measure the mechanical deformation of such kind of material. Following this project, the numerical tool will be used in numerical simulation to introduce the various effects of the baking of the ramming paste during the cell startup. This new tool will help the industrial partner to enhance the understanding of Hall-Heroult cell start-up and optimize this critical step.

A new visco-elasto-plastic model via time-space fractional derivative

NASA Astrophysics Data System (ADS)

Hei, X.; Chen, W.; Pang, G.; Xiao, R.; Zhang, C.

2018-02-01

To characterize the visco-elasto-plastic behavior of metals and alloys we propose a new constitutive equation based on a time-space fractional derivative. The rheological representative of the model can be analogous to that of the Bingham-Maxwell model, while the dashpot element and sliding friction element are replaced by the corresponding fractional elements. The model is applied to describe the constant strain rate, stress relaxation and creep tests of different metals and alloys. The results suggest that the proposed simple model can describe the main characteristics of the experimental observations. More importantly, the model can also provide more accurate predictions than the classic Bingham-Maxwell model and the Bingham-Norton model.

Finite element analysis of history-dependent damage in time-dependent fracture mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnaswamy, P.; Brust, F.W.; Ghadiali, N.D.

1993-11-01

The demands for structural systems to perform reliably under both severe and changing operating conditions continue to increase. Under these conditions time-dependent straining and history-dependent damage become extremely important. This work focuses on studying creep crack growth using finite element (FE) analysis. Two important issues, namely, (1) the use of history-dependent constitutive laws, and (2) the use of various fracture parameters in predicting creep crack growth, have both been addressed in this work. The constitutive model used here is the one developed by Murakami and Ohno and is based on the concept of a creep hardening surface. An implicit FEmore » algorithm for this model was first developed and verified for simple geometries and loading configurations. The numerical methodology developed here has been used to model stationary and growing cracks in CT specimens. Various fracture parameters such as the C[sub 1], C[sup *], T[sup *], J were used to compare the numerical predictions with experimental results available in the literature. A comparison of the values of these parameters as a function of time has been made for both stationary and growing cracks. The merit of using each of these parameters has also been discussed.« less

Dynamic Fracture of Concrete. Part 1

DTIC Science & Technology

1990-02-14

unnotched) by Mindess and the Charpy type impact tests by Shah. In both cases, dynamic finite element modeling with the adjusted constitutive equavm for the...Mindess and the Charpy type impact tests by Shah. In both cases, dynamic finite element modeling with the adjusted constitutive equations for the...Modeling Shah’s Charpy Impact Tests ................ 190 Figure 7.20 Specimen Configuration and Finite Element Model for Concrete and Mortar Beam Impact

Variation in Macro and Trace Elements in Progression of Type 2 Diabetes

PubMed Central

2014-01-01

Macro elements are the minerals of which the body needs more amounts and are more important than any other elements. Trace elements constitute a minute part of the living tissues and have various metabolic characteristics and functions. Trace elements participate in tissue and cellular and subcellular functions; these include immune regulation by humoral and cellular mechanisms, nerve conduction, muscle contractions, membrane potential regulations, and mitochondrial activity and enzyme reactions. The status of micronutrients such as iron and vanadium is higher in type 2 diabetes. The calcium, magnesium, sodium, chromium, cobalt, iodine, iron, selenium, manganese, and zinc seem to be low in type 2 diabetes while elements such as potassium and copper have no effect. In this review, we emphasized the status of macro and trace elements in type 2 diabetes and its advantages or disadvantages; this helps to understand the mechanism, progression, and prevention of type 2 diabetes due to the lack and deficiency of different macro and trace elements. PMID:25162051

Biaxial experiments supporting the development of constitutive theories for advanced high-temperature materials

NASA Technical Reports Server (NTRS)

Ellis, J. R.

1988-01-01

Complex states of stress and strain are introduced into components during service in engineering applications. It follows that analysis of such components requires material descriptions, or constitutive theories, which reflect the tensorial nature of stress and strain. For applications involving stress levels above yield, the situation is more complex in that material response is both nonlinear and history dependent. This has led to the development of viscoplastic constitutive theories which introduce time by expressing the flow and evolutionary equation in the form of time derivatives. Models were developed here which can be used to analyze high temperature components manufactured from advanced composite materials. In parallel with these studies, effort was directed at developing multiaxial testing techniques to verify the various theories. Recent progress in the development of constitutive theories from both the theoretical and experimental viewpoints are outlined. One important aspect is that material descriptions for advanced composite materials which can be implemented in general purpose finite element codes and used for practical design are verified.

Trace element uptake and distribution in plants.

PubMed

Graham, Robin D; Stangoulis, James C R

2003-05-01

There are similarities between mammals and plants in the absorption and transport of trace elements. The chemistry of trace element uptake from food sources in both cases is based on the thermodynamics of adsorption on charged solid surfaces embedded in a solution phase of charged ions and metal-binding ligands together with redox systems in the case of iron and some other elements. Constitutive absorption systems function in nutrient uptake during normal conditions, and inducible "turbo" systems increase the supply of a particular nutrient during deficiency. Iron uptake is the most studied of the micronutrients, and divides the plant kingdom into two groups: dicotyledonous plants have a turbo system that is an upregulated version of the constitutive system, which consists of a membrane-bound reductase and an ATP-driven hydrogen ion extrusion pump; and monocotyledonous plants have a constitutive system similar to that of the dicots, but with an inducible system remarkably different that uses the mugeneic acid class of phytosiderophores (PS). The PS system may in fact be an important port of entry for iron from an iron-rich but exceedingly iron-insoluble lithosphere into the iron-starved biosphere. Absorption of trace metals in these graminaceous plants is normally via divalent ion channels after reduction in the plasma membrane. Once absorbed, iron can be stored in plants as phytoferritin or transported to active sites by transport-specific ligands. The transport of iron and zinc into seeds is dominated by the phloem sap system, which has a high pH that requires chelation of heavy metals. Loading into grains involves three or four genes each that control chelation, membrane transport and deposition as phytate.

An Irreversible Constitutive Law for Modeling the Delamination Process using Interface Elements

NASA Technical Reports Server (NTRS)

Goyal, Vinay K.; Johnson, Eric R.; Davila, Carlos G.; Jaunky, Navin; Ambur, Damodar (Technical Monitor)

2002-01-01

An irreversible constitutive law is postulated for the formulation of interface elements to predict initiation and progression of delamination in composite structures. An exponential function is used for the constitutive law such that it satisfies a multi-axial stress criterion for the onset of delamination, and satisfies a mixed mode fracture criterion for the progression of delamination. A damage parameter is included to prevent the restoration of the previous cohesive state between the interfacial surfaces. To demonstrate the irreversibility capability of the constitutive law, steady-state crack growth is simulated for quasi-static loading-unloading cycle of various fracture test specimens.

An Irreversible Constitutive Law for Modeling the Delamination Process Using Interface Elements

NASA Technical Reports Server (NTRS)

Goyal, Vinay K.; Johnson, Eric R.; Davila, Carlos G.; Jaunky, Navin; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

An irreversible constitutive law is postulated for the formulation of interface elements to predict initiation and progression of delamination in composite structures. An exponential function is used for the constitutive law such that it satisfies a multi-axial stress criterion for the onset of delamination, and satisfies a mixed mode fracture criterion for the progression of delamination. A damage parameter is included to prevent the restoration of the previous cohesive state between the interfacial surfaces. To demonstrate the irreversibility capability of the constitutive law, steady-state crack growth is simulated for quasi-static loading-unloading cycle of various fracture test specimens.

Constitutive Modeling of Superalloy Single Crystals and Directionally Solidified Materials

NASA Technical Reports Server (NTRS)

Walker, K. P.; Jordan, E. H.

1985-01-01

A unified viscoplastic constitutive relation based on crystallographic slip theory was developed for the deformation analysis of nickel base face centered cubic superalloy single crystals at elevated temperature. The single crystal theory is embedded in a self consistent method to derive a constitutive relation for a directionally solidified material comprised of a polycrystalline aggregate of columnar cylindrical grains. One of the crystallographic axes of the cylindrical crystals points in the columnar direction while the remaining crystallographic axes are oriented at random in the basal plane perpendicular to the columnar direction. These constitutive formulations are coded in FORTRAN for use in nonlinear finite element and boundary element programs.

An advanced constitutive model in the sheet metal forming simulation: the Teodosiu microstructural model and the Cazacu Barlat yield criterion

NASA Astrophysics Data System (ADS)

Alves, J. L.; Oliveira, M. C.; Menezes, L. F.

2004-06-01

Two constitutive models used to describe the plastic behavior of sheet metals in the numerical simulation of sheet metal forming process are studied: a recently proposed advanced constitutive model based on the Teodosiu microstructural model and the Cazacu Barlat yield criterion is compared with a more classical one, based on the Swift law and the Hill 1948 yield criterion. These constitutive models are implemented into DD3IMP, a finite element home code specifically developed to simulate sheet metal forming processes, which generically is a 3-D elastoplastic finite element code with an updated Lagrangian formulation, following a fully implicit time integration scheme, large elastoplastic strains and rotations. Solid finite elements and parametric surfaces are used to model the blank sheet and tool surfaces, respectively. Some details of the numerical implementation of the constitutive models are given. Finally, the theory is illustrated with the numerical simulation of the deep drawing of a cylindrical cup. The results show that the proposed advanced constitutive model predicts with more exactness the final shape (medium height and ears profile) of the formed part, as one can conclude from the comparison with the experimental results.

DNA is structured as a linear "jigsaw puzzle" in the genomes of Arabidopsis, rice, and budding yeast.

PubMed

Liu, Yun-Hua; Zhang, Meiping; Wu, Chengcang; Huang, James J; Zhang, Hong-Bin

2014-01-01

Knowledge of how a genome is structured and organized from its constituent elements is crucial to understanding its biology and evolution. Here, we report the genome structuring and organization pattern as revealed by systems analysis of the sequences of three model species, Arabidopsis, rice and yeast, at the whole-genome and chromosome levels. We found that all fundamental function elements (FFE) constituting the genomes, including genes (GEN), DNA transposable elements (DTE), retrotransposable elements (RTE), simple sequence repeats (SSR), and (or) low complexity repeats (LCR), are structured in a nonrandom and correlative manner, thus leading to a hypothesis that the DNA of the species is structured as a linear "jigsaw puzzle". Furthermore, we showed that different FFE differ in their importance in the formation and evolution of the DNA jigsaw puzzle structure between species. DTE and RTE play more important roles than GEN, LCR, and SSR in Arabidopsis, whereas GEN and RTE play more important roles than LCR, SSR, and DTE in rice. The genes having multiple recognized functions play more important roles than those having single functions. These results provide useful knowledge necessary for better understanding genome biology and evolution of the species and for effective molecular breeding of rice.

The node-weighted Steiner tree approach to identify elements of cancer-related signaling pathways.

PubMed

Sun, Yahui; Ma, Chenkai; Halgamuge, Saman

2017-12-28

Cancer constitutes a momentous health burden in our society. Critical information on cancer may be hidden in its signaling pathways. However, even though a large amount of money has been spent on cancer research, some critical information on cancer-related signaling pathways still remains elusive. Hence, new works towards a complete understanding of cancer-related signaling pathways will greatly benefit the prevention, diagnosis, and treatment of cancer. We propose the node-weighted Steiner tree approach to identify important elements of cancer-related signaling pathways at the level of proteins. This new approach has advantages over previous approaches since it is fast in processing large protein-protein interaction networks. We apply this new approach to identify important elements of two well-known cancer-related signaling pathways: PI3K/Akt and MAPK. First, we generate a node-weighted protein-protein interaction network using protein and signaling pathway data. Second, we modify and use two preprocessing techniques and a state-of-the-art Steiner tree algorithm to identify a subnetwork in the generated network. Third, we propose two new metrics to select important elements from this subnetwork. On a commonly used personal computer, this new approach takes less than 2 s to identify the important elements of PI3K/Akt and MAPK signaling pathways in a large node-weighted protein-protein interaction network with 16,843 vertices and 1,736,922 edges. We further analyze and demonstrate the significance of these identified elements to cancer signal transduction by exploring previously reported experimental evidences. Our node-weighted Steiner tree approach is shown to be both fast and effective to identify important elements of cancer-related signaling pathways. Furthermore, it may provide new perspectives into the identification of signaling pathways for other human diseases.

From Projectile Points to Microprocessors - The Influence of Some Industrial Minerals

USGS Publications Warehouse

Driscoll, Rhonda

2007-01-01

In the language of economic geology, Earth materials are classified as metallic ores, fuel minerals, gemstones, and industrial minerals. Most people know that metallic ores yield shiny, conductive, ductile elements such as copper, iron, or gold. Most understand that energy-producing coals constitute a fuel mineral. Likewise, dazzling rubies and rare sapphires are universally recognized as gemstones. The fourth group, industrial minerals, is largely unknown to the general public, even though industrial minerals are as essential to daily life as metals and fuel minerals. This report examines the occurrence and practical uses of nine important industrial minerals - constituting just a few of the more than 50 industrial minerals that shape human culture.

Characterization of the mouse junD promoter--high basal level activity due to an octamer motif.

PubMed Central

de Groot, R P; Karperien, M; Pals, C; Kruijer, W

1991-01-01

The product of the junD gene belongs to the Jun/Fos family of nuclear DNA binding transcription factors. This family regulates the expression of TPA responsive genes by binding to the TPA responsive element (TRE). Unlike its counterparts c-jun and junB, junD expression is hardly inducible by growth factors and phorbol esters. In fact, junD is constitutively expressed at high levels in a wide variety of cells. To unravel the molecular mechanisms underlying constitutive junD expression, we have cloned and characterized the mouse junD promoter. We show that the high constitutive expression is caused by multiple cis-acting elements in its promoter, including an SP1 binding site, an octamer motif, a CAAT box, a Zif268 binding site and a TRE-like sequence. The octamer motif is the major determinant of junD promoter activity, while somewhat smaller contributions are made by the TRE and Zif268 binding site. The SP1 and CAAT box are shown to be of minor importance. The junD TRE is in its behavior indistinguishable from previously identified TREs. However, the junD promoter is not TPA inducible due to the presence of the octamer motif. Images PMID:1714380

On 3D inelastic analysis methods for hot section components

NASA Technical Reports Server (NTRS)

Mcknight, R. L.; Chen, P. C.; Dame, L. T.; Holt, R. V.; Huang, H.; Hartle, M.; Gellin, S.; Allen, D. H.; Haisler, W. E.

1986-01-01

Accomplishments are described for the 2-year program, to develop advanced 3-D inelastic structural stress analysis methods and solution strategies for more accurate and cost effective analysis of combustors, turbine blades and vanes. The approach was to develop a matrix of formulation elements and constitutive models. Three constitutive models were developed in conjunction with optimized iterating techniques, accelerators, and convergence criteria within a framework of dynamic time incrementing. Three formulations models were developed; an eight-noded mid-surface shell element, a nine-noded mid-surface shell element and a twenty-noded isoparametric solid element. A separate computer program was developed for each combination of constitutive model-formulation model. Each program provides a functional stand alone capability for performing cyclic nonlinear structural analysis. In addition, the analysis capabilities incorporated into each program can be abstracted in subroutine form for incorporation into other codes or to form new combinations.

The 3D inelastic analysis methods for hot section components

NASA Technical Reports Server (NTRS)

Mcknight, R. L.; Maffeo, R. J.; Tipton, M. T.; Weber, G.

1992-01-01

A two-year program to develop advanced 3D inelastic structural stress analysis methods and solution strategies for more accurate and cost effective analysis of combustors, turbine blades, and vanes is described. The approach was to develop a matrix of formulation elements and constitutive models. Three constitutive models were developed in conjunction with optimized iterating techniques, accelerators, and convergence criteria within a framework of dynamic time incrementing. Three formulation models were developed: an eight-noded midsurface shell element; a nine-noded midsurface shell element; and a twenty-noded isoparametric solid element. A separate computer program has been developed for each combination of constitutive model-formulation model. Each program provides a functional stand alone capability for performing cyclic nonlinear structural analysis. In addition, the analysis capabilities incorporated into each program can be abstracted in subroutine form for incorporation into other codes or to form new combinations.

Oaths of Office in Tribal Constitutions: Swearing Allegiance, but to Whom?

ERIC Educational Resources Information Center

Wilkins, David E.; Lightfoot, Sheryl

2008-01-01

No comprehensive analysis of tribal constitutions has ever been conducted, so this project aims to begin filling this significant gap in American, constitutional, and comparative politics research. In this study, the authors examine only one small but significant element of Native constitutions: oaths of office for incoming tribal government…

7 CFR 29.2601 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 2 2011-01-01 2011-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2601 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

7 CFR 29.2351 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 2 2011-01-01 2011-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2351 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

7 CFR 29.2601 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 2 2012-01-01 2012-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2601 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

7 CFR 29.2601 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 2 2014-01-01 2014-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2601 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

7 CFR 29.2351 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 2 2014-01-01 2014-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2351 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

7 CFR 29.2351 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 2 2012-01-01 2012-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2351 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

7 CFR 29.2351 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 2 2013-01-01 2013-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2351 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

7 CFR 29.2601 - Elements of quality and degrees of each element.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 2 2013-01-01 2013-01-01 false Elements of quality and degrees of each element. 29... STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Elements of Quality § 29.2601 Elements of quality and degrees of each element. Tobacco attributes or characteristics which constitute quality are...

[Significance of physical training on prevention in elderly patients].

PubMed

Baum, K

2002-07-01

The loss of strength, coordination, endurance, and flexibility with increasing age is only partly due to the aging process itself. A major factor is physical activity, i.e. the influence of implicit or explicit training stimuli. All elements of physical performance can be improved through training even in the very old, if the intensity and frequency of training are adequate. For the elderly, strength and coordination are particularly important elements of training since they constitute a prerequisite for an independent way of living. To minimize the cardiovascular risks during strength training, we developed and tested a new method which leads to significantly smaller increases in blood pressure than conventional approaches.

Afro-derived Brazilian populations: male genetic constitution estimated by Y-chromosomes STRs and AluYAP element polymorphisms.

PubMed

Ribeiro, Guilherme Galvarros Bueno Lobo; De Lima, Reginaldo Ramos; Wiezel, Cláudia Emília Vieira; Ferreira, Luzitano Brandão; Sousa, Sandra Mara Bispo; Rocha, Dulce Maria Sucena; Canas, Maria do Carmo Tomitão; Nardelli-Costa, Juliana; Klautau-Guimarães, Maria De Nazaré; Simões, Aguinaldo Luiz; Oliveira, Silviene Fabiana

2009-01-01

The genetic constitution of Afro-derived Brazilian populations is barely studied. To improve that knowledge, we investigated the AluYAP element and five Y-chromosome STRs (DYS19, DYS390, DYS391, DYS392, and DYS393) to estimate ethnic male contribution in the constitution of four Brazilian quilombos remnants: Mocambo, Rio das Rãs, Kalunga, and Riacho de Sacutiaba. Results indicated significant differences among communities, corroborating historical information about the Brazilian settlement. We concluded that besides African contribution, there was a great European participation in the constitution of these four populations and that observed haplotype variability could be explained by gene flow to quilombos remnants and mutational events in microsatellites (STRs). (c) 2009 Wiley-Liss, Inc.

On the Finite Element Implementation of the Generalized Method of Cells Micromechanics Constitutive Model

NASA Technical Reports Server (NTRS)

Wilt, T. E.

1995-01-01

The Generalized Method of Cells (GMC), a micromechanics based constitutive model, is implemented into the finite element code MARC using the user subroutine HYPELA. Comparisons in terms of transverse deformation response, micro stress and strain distributions, and required CPU time are presented for GMC and finite element models of fiber/matrix unit cell. GMC is shown to provide comparable predictions of the composite behavior and requires significantly less CPU time as compared to a finite element analysis of the unit cell. Details as to the organization of the HYPELA code are provided with the actual HYPELA code included in the appendix.

Application of Gurson–Tvergaard–Needleman Constitutive Model to the Tensile Behavior of Reinforcing Bars with Corrosion Pits

PubMed Central

Xu, Yidong; Qian, Chunxiang

2013-01-01

Based on meso-damage mechanics and finite element analysis, the aim of this paper is to describe the feasibility of the Gurson–Tvergaard–Needleman (GTN) constitutive model in describing the tensile behavior of corroded reinforcing bars. The orthogonal test results showed that different fracture pattern and the related damage evolution process can be simulated by choosing different material parameters of GTN constitutive model. Compared with failure parameters, the two constitutive parameters are significant factors affecting the tensile strength. Both the nominal yield and ultimate tensile strength decrease markedly with the increase of constitutive parameters. Combining with the latest data and trial-and-error method, the suitable material parameters of GTN constitutive model were adopted to simulate the tensile behavior of corroded reinforcing bars in concrete under carbonation environment attack. The numerical predictions can not only agree very well with experimental measurements, but also simplify the finite element modeling process. PMID:23342140

Terminological aspects of data elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strehlow, R.A.; Kenworthey, W.H. Jr.; Schuldt, R.E.

1991-01-01

The creation and display of data comprise a process that involves a sequence of steps requiring both semantic and systems analysis. An essential early step in this process is the choice, definition, and naming of data element concepts and is followed by the specification of other needed data element concept attributes. The attributes and the values of data element concept remain associated with them from their birth as a concept to a generic data element that serves as a template for final application. Terminology is, therefore, centrally important to the entire data creation process. Smooth mapping from natural language tomore » a database is a critical aspect of database, and consequently, it requires terminology standardization from the outset of database work. In this paper the semantic aspects of data elements are analyzed and discussed. Seven kinds of data element concept information are considered and those that require terminological development and standardization are identified. The four terminological components of a data element are the hierarchical type of a concept, functional dependencies, schematas showing conceptual structures, and definition statements. These constitute the conventional role of terminology in database design. 12 refs., 8 figs., 1 tab.« less

An internal variable constitutive model for the large deformation of metals at high temperatures

NASA Technical Reports Server (NTRS)

Brown, Stuart; Anand, Lallit

1988-01-01

The advent of large deformation finite element methodologies is beginning to permit the numerical simulation of hot working processes whose design until recently has been based on prior industrial experience. Proper application of such finite element techniques requires realistic constitutive equations which more accurately model material behavior during hot working. A simple constitutive model for hot working is the single scalar internal variable model for isotropic thermal elastoplasticity proposed by Anand. The model is recalled and the specific scalar functions, for the equivalent plastic strain rate and the evolution equation for the internal variable, presented are slight modifications of those proposed by Anand. The modified functions are better able to represent high temperature material behavior. The monotonic constant true strain rate and strain rate jump compression experiments on a 2 percent silicon iron is briefly described. The model is implemented in the general purpose finite element program ABAQUS.

Network analysis of the Íslendinga sögur - the Sagas of Icelanders

NASA Astrophysics Data System (ADS)

Mac Carron, P.; Kenna, R.

2013-10-01

The Íslendinga sögur - or Sagas of Icelanders - constitute a collection of medieval literature set in Iceland around the late 9th to early 11th centuries, the so-called Saga Age. They purport to describe events during the period around the settlement of Iceland and the generations immediately following and constitute an important element of world literature thanks to their unique narrative style. Although their historicity is a matter of scholarly debate, the narratives contain interwoven and overlapping plots involving thousands of characters and interactions between them. Here we perform a network analysis of the Íslendinga sögur in an attempt to gather quantitative information on interrelationships between characters and to compare saga society to other social networks.

An evolving effective stress approach to anisotropic distortional hardening

DOE PAGES

Lester, B. T.; Scherzinger, W. M.

2018-03-11

A new yield surface with an evolving effective stress definition is proposed for consistently and efficiently describing anisotropic distortional hardening. Specifically, a new internal state variable is introduced to capture the thermodynamic evolution between different effective stress definitions. The corresponding yield surface and evolution equations of the internal variables are derived from thermodynamic considerations enabling satisfaction of the second law. A closest point projection return mapping algorithm for the proposed model is formulated and implemented for use in finite element analyses. Finally, select constitutive and larger scale boundary value problems are solved to explore the capabilities of the model andmore » examine the impact of distortional hardening on constitutive and structural responses. Importantly, these simulations demonstrate the tractability of the proposed formulation in investigating large-scale problems of interest.« less

An evolving effective stress approach to anisotropic distortional hardening

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lester, B. T.; Scherzinger, W. M.

A new yield surface with an evolving effective stress definition is proposed for consistently and efficiently describing anisotropic distortional hardening. Specifically, a new internal state variable is introduced to capture the thermodynamic evolution between different effective stress definitions. The corresponding yield surface and evolution equations of the internal variables are derived from thermodynamic considerations enabling satisfaction of the second law. A closest point projection return mapping algorithm for the proposed model is formulated and implemented for use in finite element analyses. Finally, select constitutive and larger scale boundary value problems are solved to explore the capabilities of the model andmore » examine the impact of distortional hardening on constitutive and structural responses. Importantly, these simulations demonstrate the tractability of the proposed formulation in investigating large-scale problems of interest.« less

Constitution. Signed and delivered--the rules in writing.

PubMed

Walshe, Kieran

2008-07-24

The proposal tucked away in the Darzi report for an NHS constitution could be one of the most historic elements of the next stage review, limiting the health secretary's power and guaranteeing patient rights.

Shock Wave Propagation in Cementitious Materials at Micro/Meso Scales

NASA Astrophysics Data System (ADS)

Rajendran, Arunachalam

2015-06-01

The mechanical and constitutive response of materials like cement, and bio materials like fish scale and abalone shell is very complex due to heterogeneities that are inherently present in the nano and microstructures. The intrinsic constitutive behaviors are driven by the chemical composition and the molecular, micro, and meso structures. Therefore, it becomes important to identify the material genome as the building block for the material. For instance, in cementitious materials, the genome of C-S-H phase (the glue or the paste) that holds the various clinkers, such as the dicalcium silicate, tricalcium silicate, calcium ferroaluminates, and others is extremely complex. Often mechanical behaviors of C-S-H type materials are influenced by the chemistry and the structures at all nano to micro length scales. By explicitly modeling the molecular structures using appropriate potentials, it is then possible to compute the elastic tensor from molecular dynamics simulations using all atom method. The elastic tensors for the C-S-H gel and other clinkers are determined using the software suite ``Accelrys Materials Studio.'' A strain rate dependent, fracture mechanics based tensile damage model has been incorporated into ABAQUS finite element code to model spall evolution in the heterogeneous cementitious material with all constituents explicitly modeled through one micron element resolution. This paper presents results from nano/micro/meso scale analyses of shock wave propagation in a heterogeneous cementitious material using both molecular dynamic and finite element codes.

Elastic/viscoplastic behavior of fiber-reinforced thermoplastic composites

NASA Technical Reports Server (NTRS)

Wang, C.; Sun, C. T.; Gates, T. S.

1990-01-01

An elastic/viscoplastic constitutive model was used to characterize the nonlinear and rate dependent behavior of a continuous fiber-reinforced thermoplastic composite. This model was incorporated into a finite element program for the analysis of laminated plates and shells. Details on the finite element formulation with the proposed constitutive model were presented. The numerical results were compared with experimental data for uniaxial tension and three-point bending tests of (+ or - 45 deg)3s APC-2 laminates.

Finite element simulation and analysis of local stress concentration in polymers with a nonlinear viscoelastic constitutive model

NASA Astrophysics Data System (ADS)

Chea, Limdara O.

Given a nonlinear viscoelastic (NLVE) constitutive model for a polymer, this numerical study aims at simulating local stress concentrations in a boundary value problem with a corner stress singularity. A rectangular sample of Polyvinyl Acetate (PVAc)-like cross-linked polymer clamped by two metallic rigid grips and subjected to a compression and tension load is numerically simulated. A modified version of the finite element code FEAP, that incorporated a NLVE model based on the free volume theory, was used. First, the program was validated by comparing numerical and analytical results. Two simple mechanical tests (a uniaxial and a simple shear test) were performed on a Standard Linear Solid material model, using a linear viscoelastic (LVE) constitutive model. The LVE model was obtained by setting the proportionality coefficient [...] to zero in the free volume theory equations. Second, the LVE model was used on the corner singularity boundary value problem for three material models with different bulk relaxation functions K(t). The time-dependent stress field distribution was investigated using two sets of plots: the stress distribution contour plots and the stress time curves. Third, using the NLVE constitutive model, compression and tension cases were compared using the stress results (normal stress [...] and shear stress [...]). These two cases assessed the effect of the creep retardation-creep acceleration phenomena. The shift between the beginning of the relaxation moduli was shown to play an important role. This parameter affects strongly the fluctuation pattern of the stress curves. For two different shift values, in one case, the stress response presents a 'double peak' and 'stress inversion' characteristic whereas, in the other case, it presents a 'single peak' and no 'inversion'. Another important factor was the material's compressibility. In the case of a nearly-incompressible material, the LVE and NLVE models yielded identical results; thus, the simpler LVE model is preferable. However, in the case of sufficient volume dilatation (or contraction), the NLVE model predicted correct characteristic responses, whereas LVE results were erroneous. This proves the necessity of using the NLVE model over the LVE model.

The American Association for Thoracic Surgery 2016 ethics forum: Working virtues in surgical practice.

PubMed

Churchill, Larry R

2017-05-01

Moral virtues are the complement to ethical principles. They constitute the elements of character that drive habits and daily routines. Certain virtues are especially important in surgery, shaping surgical practice even when no big decisions are at hand. Eight virtues are described and the work they do is explored: trustworthiness, equanimity, empathy, advocacy, compassion, courage, humility, and hope. Copyright © 2016 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Anand constitutive model of lead-free solder joints in 3D IC device

NASA Astrophysics Data System (ADS)

Zhang, Liang; Liu, Zhi-quan; Ji, Yu-tong

2016-08-01

Anand constitutive relation of SnAgCu and SnAgCu-nano Al solders were studied under uniaxial tension, and the constitutive model was used in the finite element simulation to analyze the stress-strain response of lead-free solder joints in 3D IC devices. The results showed that the nine parameters of the Anand model can be determined from separated constitutive relations and experimental results. Based on Anand model, the finite element method was selected to calculate the stress-strain response of lead-free solder joints, it was found that in the 3D IC device the maximum stress-strain concentrated in the concern solder joints, the stress-strain of SnAgCu-nano Al solder joints was lower than that of SnAgCu solder joints, which represented that the addition of nano Al particles can enhance the reliability of lead-free solder joints in 3D IC devices.

Nonlinear piezoelectric effects—towards physics-based computational modelling of micro-cracking, fatigue, and switching

NASA Astrophysics Data System (ADS)

Menzel, A.; Utzinger, J.; Arockiarajan, A.

2008-07-01

Piezoelectric ceramics—as one widely commercialised group of smart materials—exhibit a great potential for various engineering applications. Their high-frequency capabilities are in particular attractive for actuator and sensor devices, which nowadays are present in daily-life-technologies such as cellular phones, fuel injection systems, and so forth. At high loading levels however, severely nonlinear behaviour of these materials is observed which, from the control point of view, must be further investigated in order to be able to precisely account for such effects within the design of intelligent systems. The reasons for these nonlinearities are manifold and, even investigated within the last decades, not fully understood. Nevertheless, two important sources for these observations are so-called micro-cracking, together with fatigue phenomena, as well as switching or rather phase transformations. Accordingly, the main goal of this contribution is to study these effects by means of developing related constitutive models that can be embedded into iterative algorithmic schemes such as the finite element method. One the one hand, the grain-structure of a piezoceramic specimen will be modelled via the direct incorporation of the grain-boundaries as so-called interface elements. The underlying cohesive-like constitutive law of this layer includes both degrees of freedom of the surrounding bulk material—or rather the jumps in these fields—namely displacements and the electric potential. Based on the resulting traction-separation-type relations, micro-cracking is directly accounted for on this microlevel. Moreover, the constitutive law of the interfacial layer is supplemented by additional variables that enable the formulation of fatigue under cyclic loading conditions. On the other hand, phase transformations—modelled in terms of an energy-based switching criterion—are discussed and embedded into an iterative finite element context. Symmetry relations of the underlying unit cells are directly included so that the switching model accounts for the micro-mechanical properties of the piezoelectric materials of interest. At this stage, representative numerical simulations of polycrystalline specimens are based on straightforward averaging-techniques, while the combination of the developed micro-cracking model (grain boundaries) with the proposed switching model (bulk) constitutes future research.

Experimental entanglement of 25 individually accessible atomic quantum interfaces.

PubMed

Pu, Yunfei; Wu, Yukai; Jiang, Nan; Chang, Wei; Li, Chang; Zhang, Sheng; Duan, Luming

2018-04-01

A quantum interface links the stationary qubits in a quantum memory with flying photonic qubits in optical transmission channels and constitutes a critical element for the future quantum internet. Entanglement of quantum interfaces is an important step for the realization of quantum networks. Through heralded detection of photon interference, we generate multipartite entanglement between 25 (or 9) individually addressable quantum interfaces in a multiplexed atomic quantum memory array and confirm genuine 22-partite (or 9-partite) entanglement. This experimental entanglement of a record-high number of individually addressable quantum interfaces makes an important step toward the realization of quantum networks, long-distance quantum communication, and multipartite quantum information processing.

The Anatomy of a Constitutional Tort.

ERIC Educational Resources Information Center

Horner, Jeffrey J.

1988-01-01

Given state law barriers to recovery for the negligence of public officials, redress is often sought in federal courts. Discusses the concept of "constitutional tort" and analyzes the various components and the elements that must be satisfied before recovery is allowed. (MLF)

Thermal aging of traditional and additively manufactured foams: analysis by time-temperature-superposition, constitutive, and finite-element models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maiti, A.; Weisgraber, T. H.; Small, W.

Cellular solids or foams are a very important class of materials with diverse applications ranging from thermal insulation and shock absorbing support cushions, to light-weight structural and floatation components, and constitute crucial components in a large number of industries including automotive, aerospace, electronics, marine, biomedical, packaging, and defense. In many of these applications the foam material is subjected to long periods of continuous stress, which can, over time, lead to a permanent change in structure and a degradation in performance. In this report we summarize our modeling efforts to date on polysiloxane foam materials that form an important component inmore » our systems. Aging of the materials was characterized by two measured quantities, i.e., compression set and load retention. Results of accelerated aging experiments were analyzed by an automated time-temperaturesuperposition (TTS) approach, which creates a master curve that can be used for long-term predictions (over decades) under ambient conditions. When comparing such master curves for traditional (stochastic) foams with those for recently 3D-printed (i.e., additively manufactured, or AM) foams, it became clear that AM foams have superior aging behavior. To gain deeper understanding, we imaged the microstructure of both foams using X-ray computed tomography, and performed finite-element analysis of the mechanical response within these microstructures. This indicates a wider stress variation in the stochastic foam with points of more extreme local stress as compared to the 3D printed material.« less

A size-dependent constitutive model of bulk metallic glasses in the supercooled liquid region

PubMed Central

Yao, Di; Deng, Lei; Zhang, Mao; Wang, Xinyun; Tang, Na; Li, Jianjun

2015-01-01

Size effect is of great importance in micro forming processes. In this paper, micro cylinder compression was conducted to investigate the deformation behavior of bulk metallic glasses (BMGs) in supercooled liquid region with different deformation variables including sample size, temperature and strain rate. It was found that the elastic and plastic behaviors of BMGs have a strong dependence on the sample size. The free volume and defect concentration were introduced to explain the size effect. In order to demonstrate the influence of deformation variables on steady stress, elastic modulus and overshoot phenomenon, four size-dependent factors were proposed to construct a size-dependent constitutive model based on the Maxwell-pulse type model previously presented by the authors according to viscosity theory and free volume model. The proposed constitutive model was then adopted in finite element method simulations, and validated by comparing the micro cylinder compression and micro double cup extrusion experimental data with the numerical results. Furthermore, the model provides a new approach to understanding the size-dependent plastic deformation behavior of BMGs. PMID:25626690

The Essence of Powerful Teaching

ERIC Educational Resources Information Center

Brookfield, Stephen

2013-01-01

Empowering learners and using powerful techniques are prominent elements in the discourse of adult and vocational education. But what constitutes the elements of what might be considered as powerful teaching? This paper begins by examining the way educators talk about power and then proposes four elements that lie at the heart of powerful…

A multiscale coupled finite-element and phase-field framework to modeling stressed grain growth in polycrystalline thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jamshidian, M., E-mail: jamshidian@cc.iut.ac.ir; Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar; Thamburaja, P., E-mail: prakash.thamburaja@gmail.com

A previously-developed finite-deformation- and crystal-elasticity-based constitutive theory for stressed grain growth in cubic polycrystalline bodies has been augmented to include a description of excess surface energy and grain-growth stagnation mechanisms through the use of surface effect state variables in a thermodynamically-consistent manner. The constitutive theory was also implemented into a multiscale coupled finite-element and phase-field computational framework. With the material parameters in the constitutive theory suitably calibrated, our three-dimensional numerical simulations show that the constitutive model is able to accurately predict the experimentally-determined evolution of crystallographic texture and grain size statistics in polycrystalline copper thin films deposited on polyimide substratemore » and annealed at high-homologous temperatures. In particular, our numerical analyses show that the broad texture transition observed in the annealing experiments of polycrystalline thin films is caused by grain growth stagnation mechanisms. - Graphical abstract: - Highlights: • Developing a theory for stressed grain growth in polycrystalline thin films. • Implementation into a multiscale coupled finite-element and phase-field framework. • Quantitative reproduction of the experimental grain growth data by simulations. • Revealing the cause of texture transition to be due to the stagnation mechanisms.« less

Analyses for Debonding of Stitched Composite Sandwich Structures Using Improved Constitutive Models

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Sleight, D. W.; Krishnamurthy, T.; Raju, I. S.

2001-01-01

A fracture mechanics analysis based on strain energy release rates is used to study the effect of stitching in bonded sandwich beam configurations. Finite elements are used to model the configurations. The stitches were modeled as discrete nonlinear spring elements with a compliance determined by experiment. The constitutive models were developed using the results of flatwise tension tests from sandwich material rather than monolithic material. The analyses show that increasing stitch stiffness, stitch density and debond length decrease strain energy release rates for a fixed applied load.

Communication elements supporting patient safety in psychiatric inpatient care.

PubMed

Kanerva, A; Kivinen, T; Lammintakanen, J

2015-06-01

Communication is important for safe and quality health care. The study provides needed insight on the communication elements that support patient safety from the psychiatric care view. Fluent information transfer between the health care professionals and care units is important for care planning and maintaining practices. Information should be documented and implemented accordingly. Communication should happen in an open communication culture that enables discussion, the opportunity to have debriefing discussions and the entire staff can feel they are heard. For effective communication, it is also important that staff are active themselves in information collecting about the essential information needed in patient care. In mental health nursing, it is important to pay attention to all elements of communication and to develop processes concerning communication in multidisciplinary teams and across unit boundaries. The study aims to describe which communication elements support patient safety in psychiatric inpatient care from the viewpoint of the nursing staff. Communication is an essential part of care and one of the core competencies of the psychiatric care. It enables safe and quality patient care. Errors in health care are often connected with poor communication. The study brings needed insight from the psychiatric care view to the topic. The data were gathered from semi-structured interviews in which 26 nurses were asked to describe the elements that constitute patient safety in psychiatric inpatient care. The data were analysed inductively from the viewpoint of communication. The descriptions connected with communication formed a main category of communication elements that support patient safety; this main category was made up of three subcategories: fluent information transfer, open communication culture and being active in information collecting. Fluent information transfer consists of the practical implementation of communication; open communication culture is connected with the cultural issues of communication; and being active in information collecting is related to a nurse's personal working style, which affects communication. It is important to pay attention to all the three areas and use this knowledge in developing patient safety practices and strategies where communication aspect and culture are noted and developed. In mental health nursing, it is important to develop processes concerning communication in multidisciplinary teams and across unit boundaries. © 2015 John Wiley & Sons Ltd.

Thin tube experiments and numerical simulations of micromechanical multivariant constitutive modeling in superelastic Nitinol

NASA Astrophysics Data System (ADS)

Jung, Youngjean

This dissertation concerns the constitutive description of superelasticity in NiTi alloys and the finite element analysis of a corresponding material model at large strains. Constitutive laws for shape-memory alloys subject to biaxial loading, which are based on direct experimental observations, are generally not available. A reliable constitutive model for shape-memory alloys is important for various applications because Nitinol is now widely used in biotechnology devices such as endovascular stents, vena cava filters, dental files, archwires and guidewires, etc. As part of a broader project, tension-torsion tests are conducted on thin-walled tubes (thickness/radius ratio of 1:10) of the polycrystalline superelastic Nitinol using various loading/unloading paths under isothermal conditions. This biaxial loading/unloading test was carefully designed to avoid torsional buckling and strain non-uniformities. A micromechanical constitutive model, algorithmic implementation and numerical simulation of polycrystalline superelastic alloys under biaxial loading are developed. The constitutive model is based on the micromechanical structure of Ni-Ti crystals and accounts for the physical observation of solid-solid phase transformations through the minimization of the Helmholtz energy with dissipation. The model is formulated in finite deformations and incorporates the effect of texture which is of profound significance in the mechanical response of polycrystalline Nitinol tubes. The numerical implementation is based on the constrained minimization of a functional corresponding to the Helmholtz energy with dissipation. Special treatment of loading/unloading conditions is also developed to distinguish between forward/reverse transformation state. Simulations are conducted for thin tubes of Nitinol under tension-torsion, as well as for a simplified model of a biomedical stent.

Preliminary Development of a Unified Viscoplastic Constitutive Model for Alloy 617 with Special Reference to Long Term Creep Behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sham, Sam; Walker, Kevin P.

The expected service life of the Next Generation Nuclear Plant is 60 years. Structural analyses of the Intermediate Heat Exchanger (IHX) will require the development of unified viscoplastic constitutive models that address the material behavior of Alloy 617, a construction material of choice, over a wide range of strain rates. Many unified constitutive models employ a yield stress state variable which is used to account for cyclic hardening and softening of the material. For low stress values below the yield stress state variable these constitutive models predict that no inelastic deformation takes place which is contrary to experimental results. Themore » ability to model creep deformation at low stresses for the IHX application is very important as the IHX operational stresses are restricted to very small values due to the low creep strengths at elevated temperatures and long design lifetime. This paper presents some preliminary work in modeling the unified viscoplastic constitutive behavior of Alloy 617 which accounts for the long term, low stress, creep behavior and the hysteretic behavior of the material at elevated temperatures. The preliminary model is presented in one-dimensional form for ease of understanding, but the intent of the present work is to produce a three-dimensional model suitable for inclusion in the user subroutines UMAT and USERPL of the ABAQUS and ANSYS nonlinear finite element codes. Further experiments and constitutive modeling efforts are planned to model the material behavior of Alloy 617 in more detail.« less

A micromechanical constitutive model for the dynamic response of brittle materials "Dynamic response of marble"

NASA Astrophysics Data System (ADS)

Haberman, Keith

2001-07-01

A micromechanically based constitutive model for the dynamic inelastic behavior of brittle materials, specifically "Dionysus-Pentelicon marble" with distributed microcracking is presented. Dionysus-Pentelicon marble was used in the construction of the Parthenon, in Athens, Greece. The constitutive model is a key component in the ability to simulate this historic explosion and the preceding bombardment form cannon fire that occurred at the Parthenon in 1678. Experiments were performed by Rosakis (1999) that characterized the static and dynamic response of this unique material. A micromechanical constitutive model that was previously successfully used to model the dynamic response of granular brittle materials is presented. The constitutive model was fitted to the experimental data for marble and reproduced the experimentally observed basic uniaxial dynamic behavior quite well. This micromechanical constitutive model was then implemented into the three dimensional nonlinear lagrangain finite element code Dyna3d(1998). Implementing this methodology into the three dimensional nonlinear dynamic finite element code allowed the model to be exercised on several preliminary impact experiments. During future simulations, the model is to be used in conjunction with other numerical techniques to simulate projectile impact and blast loading on the Dionysus-Pentelicon marble and on the structure of the Parthenon.

Dimensional and compositional change of 1D chalcogen nanostructures leading to tunable localized surface plasmon resonances.

PubMed

Min, Yuho; Seo, Ho Jun; Choi, Jong-Jin; Hahn, Byung-Dong; Moon, Geon Dae

2018-08-24

As part of the oxygen family, chalcogen (Se, Te) nanostructures have been considered important elements for various practical fields and further exploited to constitute metal chalcogenides for each targeted application. Here, we report a controlled synthesis of well-defined one-dimensional chalcogen nanostructures such as nanowries, nanorods, and nanotubes by controlling reduction reaction rate to fine-tune the dimension and composition of the products. Tunable optical properties (localized surface plasmon resonances) of these chalcogen nanostructures are observed depending on their morphological, dimensional, and compositional variation.

What is microbial community ecology?

PubMed

Konopka, Allan

2009-11-01

The activities of complex communities of microbes affect biogeochemical transformations in natural, managed and engineered ecosystems. Meaningfully defining what constitutes a community of interacting microbial populations is not trivial, but is important for rigorous progress in the field. Important elements of research in microbial community ecology include the analysis of functional pathways for nutrient resource and energy flows, mechanistic understanding of interactions between microbial populations and their environment, and the emergent properties of the complex community. Some emergent properties mirror those analyzed by community ecologists who study plants and animals: biological diversity, functional redundancy and system stability. However, because microbes possess mechanisms for the horizontal transfer of genetic information, the metagenome may also be considered as a community property.

Experimental entanglement of 25 individually accessible atomic quantum interfaces

PubMed Central

Jiang, Nan; Chang, Wei; Li, Chang; Zhang, Sheng

2018-01-01

A quantum interface links the stationary qubits in a quantum memory with flying photonic qubits in optical transmission channels and constitutes a critical element for the future quantum internet. Entanglement of quantum interfaces is an important step for the realization of quantum networks. Through heralded detection of photon interference, we generate multipartite entanglement between 25 (or 9) individually addressable quantum interfaces in a multiplexed atomic quantum memory array and confirm genuine 22-partite (or 9-partite) entanglement. This experimental entanglement of a record-high number of individually addressable quantum interfaces makes an important step toward the realization of quantum networks, long-distance quantum communication, and multipartite quantum information processing. PMID:29725621

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konopka, Allan

The activities of complex communities of microbes affect biogeochemical transformations in natural, managed and engineered ecosystems. Meaningfully defining what constitutes a community of interacting microbial populations is not trivial, but is important for rigorous progress in the field. Important elements of research in microbial community ecology include the analysis of functional pathways for nutrient resource and energy flows, mechanistic understanding of interactions between microbial populations and their environment, and the emergent properties of the complex community. Some emergent properties mirror those analyzed by community ecologists who study plants and animals: biological diversity, functional redundancy and system stability. However, because microbesmore » possess mechanisms for the horizontal transfer of genetic information, the metagenome may also be considered a community property.« less

Moral deliberation and nursing ethics cases: elements of a methodological proposal.

PubMed

Schneider, Dulcinéia Ghizoni; Ramos, Flávia Regina Souza

2012-11-01

A qualitative study with an exploratory, descriptive and documentary design that was conducted with the objective of identifying the elements to constitute a method for the analysis of accusations of and proceedings for professional ethics infringements. The method is based on underlying elements identified inductively during analysis of professional ethics hearings judged by and filed in the archives of the Regional Nursing Board of Santa Catarina, Brazil, between 1999 and 2007. The strategies developed were based on the results of an analysis of the findings of fact (occurrences/infractions, causes and outcomes) contained in the records of 128 professional ethics hearings and on the structural elements (statements, rules and practices) identified in five example professional ethics cases. The strategies suggested for evaluating accusations of ethics infringements and the procedures involved in deliberating on ethics hearings constitute a generic proposal that will require adaptation to the context of specific professional ethics accusations.

Discrete element modeling of microstructure of nacre

NASA Astrophysics Data System (ADS)

Chandler, Mei Qiang; Cheng, Jing-Ru C.

2018-04-01

The microstructure of nacre consists of polygon-shaped aragonite mineral tablets bonded by very thin layers of organic materials and is organized in a brick-mortar morphology. In this research, the discrete element method was utilized to model this structure. The aragonite mineral tablets were modeled with three-dimensional polygon particles generated by the Voronoi tessellation method to represent the Voronoi-like patterns of mineral tablets assembly observed in experiments. The organic matrix was modeled with a group of spring elements. The constitutive relations of the spring elements were inspired from the experimental results of organic molecules from the literature. The mineral bridges were modeled with simple elastic bonds with the parameters based on experimental data from the literature. The bulk stress-strain responses from the models agreed well with experimental results. The model results show that the mineral bridges play important roles in providing the stiffness and yield strength for the nacre, while the organic matrix in providing the ductility for the nacre. This work demonstrated the suitability of particle methods for modeling microstructures of nacre.

The Expertise Reversal Effect Is a Variant of the More General Element Interactivity Effect

ERIC Educational Resources Information Center

Chen, Ouhao; Kalyuga, Slava; Sweller, John

2017-01-01

Within the framework of cognitive load theory, the element interactivity and the expertise reversal effects usually are not treated as closely related effects. We argue that the two effects may be intertwined with the expertise reversal effect constituting a particular example of the element interactivity effect. Specifically, the element…

Absolutely Write! Teaching the Craft Elements of Writing. Bill Harp Professional Teachers Library.

ERIC Educational Resources Information Center

Thomason, Tommy; York, Carol

This book discusses basic craft elements of writing, illustrates from adult and children's literature what constitutes an engaging passage of description, and then illustrates how that craft can be taught in a workshop environment. In addition, this book includes involvement experiences that help teachers experience these craft elements. After an…

Cloning and functional analysis of 5'-upstream region of the Pokemon gene.

PubMed

Yang, Yutao; Zhou, Xiaowei; Zhu, Xudong; Zhang, Chuanfu; Yang, Zhixin; Xu, Long; Huang, Peitang

2008-04-01

Pokemon, the POK erythroid myeloid ontogenic factor, not only regulates the expression of many genes, but also plays an important role in cell tumorigenesis. To investigate the molecular mechanism regulating expression of the Pokemon gene in humans, its 5'-upstream region was cloned and analyzed. Transient analysis revealed that the Pokemon promoter is constitutive. Deletion analysis and a DNA decoy assay indicated that the NEG-U and NEG-D elements were involved in negative regulation of the Pokemon promoter, whereas the POS-D element was mainly responsible for its strong activity. Electrophoretic mobility shift assays suggested that the NEG-U, NEG-D and POS-D elements were specifically bound by the nuclear extract from A549 cells in vitro. Mutation analysis demonstrated that cooperation of the NEG-U and NEG-D elements led to negative regulation of the Pokemon promoter. Moreover, the NEG-U and NEG-D elements needed to be an appropriate distance apart in the Pokemon promoter in order to cooperate. Taken together, our results elucidate the mechanism underlying the regulation of Pokemon gene transcription, and also define a novel regulatory sequence that may be used to decrease expression of the Pokemon gene in cancer gene therapy.

Arbitrary order 2D virtual elements for polygonal meshes: part II, inelastic problem

NASA Astrophysics Data System (ADS)

Artioli, E.; Beirão da Veiga, L.; Lovadina, C.; Sacco, E.

2017-10-01

The present paper is the second part of a twofold work, whose first part is reported in Artioli et al. (Comput Mech, 2017. doi: 10.1007/s00466-017-1404-5), concerning a newly developed Virtual element method (VEM) for 2D continuum problems. The first part of the work proposed a study for linear elastic problem. The aim of this part is to explore the features of the VEM formulation when material nonlinearity is considered, showing that the accuracy and easiness of implementation discovered in the analysis inherent to the first part of the work are still retained. Three different nonlinear constitutive laws are considered in the VEM formulation. In particular, the generalized viscoelastic model, the classical Mises plasticity with isotropic/kinematic hardening and a shape memory alloy constitutive law are implemented. The versatility with respect to all the considered nonlinear material constitutive laws is demonstrated through several numerical examples, also remarking that the proposed 2D VEM formulation can be straightforwardly implemented as in a standard nonlinear structural finite element method framework.

Numerical simulation of a flow-like landslide using the particle finite element method

NASA Astrophysics Data System (ADS)

Zhang, Xue; Krabbenhoft, Kristian; Sheng, Daichao; Li, Weichao

2015-01-01

In this paper, an actual landslide process that occurred in Southern China is simulated by a continuum approach, the particle finite element method (PFEM). The PFEM attempts to solve the boundary-value problems in the framework of solid mechanics, satisfying the governing equations including momentum conservation, displacement-strain relation, constitutive relation as well as the frictional contact between the sliding mass and the slip surface. To warrant the convergence behaviour of solutions, the problem is formulated as a mathematical programming problem, while the particle finite element procedure is employed to tackle the issues of mesh distortion and free-surface evolution. The whole procedure of the landslide, from initiation, sliding to deposition, is successfully reproduced by the continuum approach. It is shown that the density of the mass has little influence on the sliding process in the current landslide, whereas both the geometry and the roughness of the slip surface play important roles. Comparative studies are also conducted where a satisfactory agreement is obtained.

Integrated environmental policy: A review of economic analysis.

PubMed

Wiesmeth, Hans; Häckl, Dennis

2017-04-01

Holistic environmental policies, which emerged from a mere combination of technical activities in waste management some 40 years ago, constitute the most advanced level of environmental policies. These approaches to environmental policy, among them the policies in integrated waste management, attempt to guide economic agents to an environment-friendly behaviour. Nevertheless, current holistic policies in waste management, including policies on one-way drinks containers and waste electrical and electronic equipment, and implementations of extended producer responsibility with further applications to waste electrical and electronic equipment, reveal more or less severe deficiencies - despite some positive examples. This article relates these policy failures, which are not necessarily the result of an insufficient compliance with the regulations, to missing constitutive elements of what is going to be called an 'integrated environmental policy'. This article therefore investigates - mostly from a practical point of view - constitutive elements, which are necessary for a holistic policy to serve as a well-functioning allocation mechanism. As these constitutive elements result from a careful 'integration' of the environmental commodities into the economic allocation problems, we refer to these policies as 'integrated environmental policies'. The article also discusses and illustrates the main steps of designing such a policy - for waste electrical and electronic equipment and a (possible) ban of Glyphosat in agriculture. As these policies are dependent on economic and political stability with environmental awareness sufficiently developed, the article addresses mostly waste management policies in highly industrialised countries.

The diversity of sequence and chromosomal distribution of new transposable element-related segments in the rye genome revealed by FISH and lineage annotation

USDA-ARS?s Scientific Manuscript database

The rye genome features a high percentage of repetitive elements, especially transposable elements (TEs). However, studies about the constitution and organization of TEs on rye chromosomes are limited. In this study, 97 unique TE segments were isolated and characterized; 50 TE segmemts showed varyin...

Improving finite element results in modeling heart valve mechanics.

PubMed

Earl, Emily; Mohammadi, Hadi

2018-06-01

Finite element analysis is a well-established computational tool which can be used for the analysis of soft tissue mechanics. Due to the structural complexity of the leaflet tissue of the heart valve, the currently available finite element models do not adequately represent the leaflet tissue. A method of addressing this issue is to implement computationally expensive finite element models, characterized by precise constitutive models including high-order and high-density mesh techniques. In this study, we introduce a novel numerical technique that enhances the results obtained from coarse mesh finite element models to provide accuracy comparable to that of fine mesh finite element models while maintaining a relatively low computational cost. Introduced in this study is a method by which the computational expense required to solve linear and nonlinear constitutive models, commonly used in heart valve mechanics simulations, is reduced while continuing to account for large and infinitesimal deformations. This continuum model is developed based on the least square algorithm procedure coupled with the finite difference method adhering to the assumption that the components of the strain tensor are available at all nodes of the finite element mesh model. The suggested numerical technique is easy to implement, practically efficient, and requires less computational time compared to currently available commercial finite element packages such as ANSYS and/or ABAQUS.

REDD+ on the rocks? Conflict Over Forest and Politics of Justice in Vietnam.

PubMed

Sikor, Thomas; Cầm, Hoàng

In Vietnam, villagers involved in a REDD+ (reduced emissions from deforestation and forest degradation) pilot protect areas with rocks which have barely a tree on them. The apparent paradox indicates how actual practices differ from general ideas about REDD+ due to ongoing conflict over forest, and how contestations over the meaning of justice are a core element in negotiations over REDD+. We explore these politics of justice by examining how the actors involved in the REDD+ pilot negotiate the particular subjects, dimensions, and authority of justice considered relevant, and show how politics of justice are implicit to practical decisions in project implementation. Contestations over the meaning of justice are an important element in the practices and processes constituting REDD+ at global, national and local levels, challenging uniform definitions of forest justice and how forests ought to be managed.

The Air Force Officer and the Constitution

DTIC Science & Technology

2010-02-17

2. Enumerated Powers 3. Separation of Powers and Checks and Balances C. Ways to amend the U.S. Constitution D. The elements of the U.S...the courts ▪ judicial 14. What stops one branch of government from becoming too powerful? ▪ checks and balances ▪ separation of powers 15. Who

SMAUMAT_ITI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jannetti, C.; Becker, R.

The software is an ABAQUS/Standard UMAT (user defined material behavior subroutine) that implements the constitutive model for shape-memory alloy materials developed by Jannetti et. al. (2003a) using a fully implicit time integration scheme to integrate the constitutive equations. The UMAT is used in conjunction with ABAQUS/Standard to perform a finite-element analysis of SMA materials.

Nonlinear mesomechanics of composites with periodic microstructure

NASA Technical Reports Server (NTRS)

Walker, Kevin P.; Jordan, Eric H.; Freed, Alan D.

1989-01-01

This work is concerned with modeling the mechanical deformation or constitutive behavior of composites comprised of a periodic microstructure under small displacement conditions at elevated temperature. A mesomechanics approach is adopted which relates the microimechanical behavior of the heterogeneous composite with its in-service macroscopic behavior. Two different methods, one based on a Fourier series approach and the other on a Green's function approach, are used in modeling the micromechanical behavior of the composite material. Although the constitutive formulations are based on a micromechanical approach, it should be stressed that the resulting equations are volume averaged to produce overall effective constitutive relations which relate the bulk, volume averaged, stress increment to the bulk, volume averaged, strain increment. As such, they are macromodels which can be used directly in nonlinear finite element programs such as MARC, ANSYS and ABAQUS or in boundary element programs such as BEST3D. In developing the volume averaged or efective macromodels from the micromechanical models, both approaches will require the evaluation of volume integrals containing the spatially varying strain distributions throughout the composite material. By assuming that the strain distributions are spatially constant within each constituent phase-or within a given subvolume within each constituent phase-of the composite material, the volume integrals can be obtained in closed form. This simplified micromodel can then be volume averaged to obtain an effective macromodel suitable for use in the MARC, ANSYS and ABAQUS nonlinear finite element programs via user constitutive subroutines such as HYPELA and CMUSER. This effective macromodel can be used in a nonlinear finite element structural analysis to obtain the strain-temperature history at those points in the structure where thermomechanical cracking and damage are expected to occur, the so called damage critical points of the structure.

Participation of the arcRACME protein in self-activation of the arc operon located in the arginine catabolism mobile element in pandemic clone USA300.

PubMed

Rozo, Zayda Lorena Corredor; Márquez-Ortiz, Ricaurte Alejandro; Castro, Betsy Esperanza; Gómez, Natasha Vanegas; Escobar-Pérez, Javier

2017-07-01

Staphylococcus aureus pandemic clone USA300 has, in addition to its constitutive arginine catabolism (arc) gene cluster, an arginine catabolism mobile element (ACME) carrying another such cluster, which gives this clone advantages in colonisation and infection. Gene arcR, which encodes an oxygen-sensitive transcriptional regulator, is inside ACME and downstream of the constitutive arc gene cluster, and this situation may have an impact on its activation. Different relative expression behaviours are proven here for arcRACME and the arcACME operon compared to the constitutive ones. We also show that the artificially expressed recombinant ArcRACME protein binds to the promoter region of the arcACME operon; this mechanism can be related to a positive feedback model, which may be responsible for increased anaerobic survival of the USA300 clone during infection-related processes.

Experimental and numerical analysis of the constitutive equation of rubber composites reinforced with random ceramic particle

NASA Astrophysics Data System (ADS)

Luo, D. M.; Xie, Y.; Su, X. R.; Zhou, Y. L.

2018-01-01

Based on the four classical models of Mooney-Rivlin (M-R), Yeoh, Ogden and Neo-Hookean (N-H) model, a strain energy constitutive equation with large deformation for rubber composites reinforced with random ceramic particles is proposed from the angle of continuum mechanics theory in this paper. By decoupling the interaction between matrix and random particles, the strain energy of each phase is obtained to derive the explicit constitutive equation for rubber composites. The tests results of uni-axial tensile, pure shear and equal bi-axial tensile are simulated by the non-linear finite element method on the ANSYS platform. The results from finite element method are compared with those from experiment, and the material parameters are determined by fitting the results from different test conditions, and the influence of radius of random ceramic particles on the effective mechanical properties are analyzed.

Constitutive Modeling of Porcine Liver in Indentation Using 3D Ultrasound Imaging

PubMed Central

Jordan, P.; Socrate, S.; Zickler, T.E.; Howe, R.D.

2009-01-01

In this work we present an inverse finite-element modeling framework for constitutive modeling and parameter estimation of soft tissues using full-field volumetric deformation data obtained from 3D ultrasound. The finite-element model is coupled to full-field visual measurements by regularization springs attached at nodal locations. The free ends of the springs are displaced according to the locally estimated tissue motion and the normalized potential energy stored in all springs serves as a measure of model-experiment agreement for material parameter optimization. We demonstrate good accuracy of estimated parameters and consistent convergence properties on synthetically generated data. We present constitutive model selection and parameter estimation for perfused porcine liver in indentation and demonstrate that a quasilinear viscoelastic model with shear modulus relaxation offers good model-experiment agreement in terms of indenter displacement (0.19 mm RMS error) and tissue displacement field (0.97 mm RMS error). PMID:19627823

Unified constitutive material models for nonlinear finite-element structural analysis. [gas turbine engine blades and vanes

NASA Technical Reports Server (NTRS)

Kaufman, A.; Laflen, J. H.; Lindholm, U. S.

1985-01-01

Unified constitutive material models were developed for structural analyses of aircraft gas turbine engine components with particular application to isotropic materials used for high-pressure stage turbine blades and vanes. Forms or combinations of models independently proposed by Bodner and Walker were considered. These theories combine time-dependent and time-independent aspects of inelasticity into a continuous spectrum of behavior. This is in sharp contrast to previous classical approaches that partition inelastic strain into uncoupled plastic and creep components. Predicted stress-strain responses from these models were evaluated against monotonic and cyclic test results for uniaxial specimens of two cast nickel-base alloys, B1900+Hf and Rene' 80. Previously obtained tension-torsion test results for Hastelloy X alloy were used to evaluate multiaxial stress-strain cycle predictions. The unified models, as well as appropriate algorithms for integrating the constitutive equations, were implemented in finite-element computer codes.

A crystallographic model for nickel base single crystal alloys

NASA Technical Reports Server (NTRS)

Dame, L. T.; Stouffer, D. C.

1988-01-01

The purpose of this research is to develop a tool for the mechanical analysis of nickel-base single-crystal superalloys, specifically Rene N4, used in gas turbine engine components. This objective is achieved by developing a rate-dependent anisotropic constitutive model and implementing it in a nonlinear three-dimensional finite-element code. The constitutive model is developed from metallurgical concepts utilizing a crystallographic approach. An extension of Schmid's law is combined with the Bodner-Partom equations to model the inelastic tension/compression asymmetry and orientation-dependence in octahedral slip. Schmid's law is used to approximate the inelastic response of the material in cube slip. The constitutive equations model the tensile behavior, creep response and strain-rate sensitivity of the single-crystal superalloys. Methods for deriving the material constants from standard tests are also discussed. The model is implemented in a finite-element code, and the computed and experimental results are compared for several orientations and loading conditions.

Modelling of Local Necking and Fracture in Aluminium Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achani, D.; Eriksson, M.; Hopperstad, O. S.

2007-05-17

Non-linear Finite Element simulations are extensively used in forming and crashworthiness studies of automotive components and structures in which fracture need to be controlled. For thin-walled ductile materials, the fracture-related phenomena that must be properly represented are thinning instability, ductile fracture and through-thickness shear instability. Proper representation of the fracture process relies on the accuracy of constitutive and fracture models and their parameters that need to be calibrated through well defined experiments. The present study focuses on local necking and fracture which is of high industrial importance, and uses a phenomenological criterion for modelling fracture in aluminium alloys. As anmore » accurate description of plastic anisotropy is important, advanced phenomenological constitutive equations based on the yield criterion YLD2000/YLD2003 are used. Uniaxial tensile tests and disc compression tests are performed for identification of the constitutive model parameters. Ductile fracture is described by the Cockcroft-Latham fracture criterion and an in-plane shear tests is performed to identify the fracture parameter. The reason is that in a well designed in-plane shear test no thinning instability should occur and it thus gives more direct information about the phenomenon of ductile fracture. Numerical simulations have been performed using a user-defined material model implemented in the general-purpose non-linear FE code LS-DYNA. The applicability of the model is demonstrated by correlating the predicted and experimental response in the in-plane shear tests and additional plane strain tension tests.« less

Prediction of brain deformations and risk of traumatic brain injury due to closed-head impact: quantitative analysis of the effects of boundary conditions and brain tissue constitutive model.

PubMed

Wang, Fang; Han, Yong; Wang, Bingyu; Peng, Qian; Huang, Xiaoqun; Miller, Karol; Wittek, Adam

2018-05-12

In this study, we investigate the effects of modelling choices for the brain-skull interface (layers of tissues between the brain and skull that determine boundary conditions for the brain) and the constitutive model of brain parenchyma on the brain responses under violent impact as predicted using computational biomechanics model. We used the head/brain model from Total HUman Model for Safety (THUMS)-extensively validated finite element model of the human body that has been applied in numerous injury biomechanics studies. The computations were conducted using a well-established nonlinear explicit dynamics finite element code LS-DYNA. We employed four approaches for modelling the brain-skull interface and four constitutive models for the brain tissue in the numerical simulations of the experiments on post-mortem human subjects exposed to violent impacts reported in the literature. The brain-skull interface models included direct representation of the brain meninges and cerebrospinal fluid, outer brain surface rigidly attached to the skull, frictionless sliding contact between the brain and skull, and a layer of spring-type cohesive elements between the brain and skull. We considered Ogden hyperviscoelastic, Mooney-Rivlin hyperviscoelastic, neo-Hookean hyperviscoelastic and linear viscoelastic constitutive models of the brain tissue. Our study indicates that the predicted deformations within the brain and related brain injury criteria are strongly affected by both the approach of modelling the brain-skull interface and the constitutive model of the brain parenchyma tissues. The results suggest that accurate prediction of deformations within the brain and risk of brain injury due to violent impact using computational biomechanics models may require representation of the meninges and subarachnoidal space with cerebrospinal fluid in the model and application of hyperviscoelastic (preferably Ogden-type) constitutive model for the brain tissue.

Comparison and Tensorial Formulation of Inelastic Constitutive Models of Salt Rock Behaviour and Efficient Numerical Implementatio

NASA Astrophysics Data System (ADS)

Nagel, T.; Böttcher, N.; Görke, U. J.; Kolditz, O.

2014-12-01

The design process of geotechnical installations includes the application of numerical simulation tools for safety assessment, dimensioning and long term effectiveness estimations. Underground salt caverns can be used for the storage of natural gas, hydrogen, oil, waste or compressed air. For their design one has to take into account fluctuating internal pressures due to different levels of filling, the stresses imposed by the surrounding rock mass, irregular geometries and possibly heterogeneous material properties [3] in order to estimate long term cavern convergence as well as locally critical wall stresses. Constitutive models applied to rock salt are usually viscoplastic in nature and most often based on a Burgers-type rheological model extended by non-linear viscosity functions and/or plastic friction elements. Besides plastic dilatation, healing and damage are sometimes accounted for as well [2]. The scales of the geotechnical system to be simulated and the laboratory tests from which material parameters are determined are vastly different. The most common material testing modalities to determine material parameters in geoengineering are the uniaxial and the triaxial compression tests. Some constitutive formulations in widespread use are formulated based on equivalent rather than tensorial quantities valid under these specific test conditions and are subsequently applied to heterogeneous underground systems and complex 3D load cases. We show here that this procedure is inappropriate and can lead to erroneous results. We further propose alternative formulations of the constitutive models in question that restore their validity under arbitrary loading conditions. For an efficient numerical simulation, the discussed constitutive models are integrated locally with a Newton-Raphson algorithm that directly provides the algorithmically consistent tangent matrix for the global Newton iteration of the displacement based finite element formulation. Finally, the finite element implementations of the proposed constitutive formulations are employed to simulate an underground salt cavern used for compressed air energy storage with OpenGeoSys [1]. Transient convergence and stress fields are evaluated for typical fluctuating operation pressure regimes.

Unified viscoelasticity: Applying discrete element models to soft tissues with two characteristic times.

PubMed

Anssari-Benam, Afshin; Bucchi, Andrea; Bader, Dan L

2015-09-18

Discrete element models have often been the primary tool in investigating and characterising the viscoelastic behaviour of soft tissues. However, studies have employed varied configurations of these models, based on the choice of the number of elements and the utilised formation, for different subject tissues. This approach has yielded a diverse array of viscoelastic models in the literature, each seemingly resulting in different descriptions of viscoelastic constitutive behaviour and/or stress-relaxation and creep functions. Moreover, most studies do not apply a single discrete element model to characterise both stress-relaxation and creep behaviours of tissues. The underlying assumption for this disparity is the implicit perception that the viscoelasticity of soft tissues cannot be described by a universal behaviour or law, resulting in the lack of a unified approach in the literature based on discrete element representations. This paper derives the constitutive equation for different viscoelastic models applicable to soft tissues with two characteristic times. It demonstrates that all possible configurations exhibit a unified and universal behaviour, captured by a single constitutive relationship between stress, strain and time as: σ+Aσ̇+Bσ¨=Pε̇+Qε¨. The ensuing stress-relaxation G(t) and creep J(t) functions are also unified and universal, derived as [Formula: see text] and J(t)=c2+(ε0-c2)e(-PQt)+σ0Pt, respectively. Application of these relationships to experimental data is illustrated for various tissues including the aortic valve, ligament and cerebral artery. The unified model presented in this paper may be applied to all tissues with two characteristic times, obviating the need for employing varied configurations of discrete element models in preliminary investigation of the viscoelastic behaviour of soft tissues. Copyright © 2015 Elsevier Ltd. All rights reserved.

Nanoindentation characterisation of human colorectal cancer cells considering cell geometry, surface roughness and hyperelastic constitutive behaviour

NASA Astrophysics Data System (ADS)

Boccaccio, Antonio; Uva, Antonio E.; Papi, Massimiliano; Fiorentino, Michele; De Spirito, Marco; Monno, Giuseppe

2017-01-01

Characterisation of the mechanical behaviour of cancer cells is an issue of crucial importance as specific cell mechanical properties have been measured and utilized as possible biomarkers of cancer progression. Atomic force microscopy certainly occupies a prominent place in the field of the mechanical characterisation devices. We developed a hybrid approach to characterise different cell lines (SW620 and SW480) of the human colon carcinoma submitted to nanoindentation measurements. An ad hoc algorithm was written that compares the force-indentation curves experimentally retrieved with those predicted by a finite element model that simulates the nanoindentation process and reproduces the cell geometry and the surface roughness. The algorithm perturbs iteratively the values of the cell mechanical properties implemented in the finite element model until the difference between the experimental and numerical force-indentation curves reaches the minimum value. The occurrence of this indicates that the implemented material properties are very close to the real ones. Different hyperelastic constitutive models, such as Arruda-Boyce, Mooney-Rivlin and Neo-Hookean were utilized to describe the structural behaviour of indented cells. The algorithm was capable of separating, for all the cell lines investigated, the mechanical properties of cell cortex and cytoskeleton. Material properties determined via the algorithm were different with respect to those obtained with the Hertzian contact theory. This demonstrates that factors such as: the cell geometry/anatomy and the hyperelastic constitutive behaviour, which are not contemplated in the Hertz’s theory hypotheses, do affect the nanoindentation measurements. The proposed approach represents a powerful tool that, only on the basis of nanoindentation measurements, is capable of characterising material at the subcellular level.

Numerical Analysis of Solids at Failure

DTIC Science & Technology

2011-08-20

failure analyses include the formulation of invariant finite elements for thin Kirchhoff rods, and preliminary initial studies of growth in...analysis of the failure of other structural/mechanical systems, including the finite element modeling of thin Kirchhoff rods and the constitutive...algorithm based on the connectivity graph of the underlying finite element mesh. In this setting, the discontinuities are defined by fronts propagating

Trace elements as quantitative probes of differentiation processes in planetary interiors

NASA Technical Reports Server (NTRS)

Drake, M. J.

1980-01-01

The characteristic trace element signature that each mineral in the source region imparts on the magma constitutes the conceptual basis for trace element modeling. It is shown that abundances of trace elements in extrusive igneous rocks may be used as petrological and geochemical probes of the source regions of the rocks if differentiation processes, partition coefficients, phase equilibria, and initial concentrations in the source region are known. Although compatible and incompatible trace elements are useful in modeling, the present review focuses primarily on examples involving the rare-earth elements.

Identifying educator behaviours for high quality verbal feedback in health professions education: literature review and expert refinement.

PubMed

Johnson, Christina E; Keating, Jennifer L; Boud, David J; Dalton, Megan; Kiegaldie, Debra; Hay, Margaret; McGrath, Barry; McKenzie, Wendy A; Nair, Kichu Balakrishnan R; Nestel, Debra; Palermo, Claire; Molloy, Elizabeth K

2016-03-22

Health professions education is characterised by work-based learning and relies on effective verbal feedback. However the literature reports problems in feedback practice, including lack of both learner engagement and explicit strategies for improving performance. It is not clear what constitutes high quality, learner-centred feedback or how educators can promote it. We hoped to enhance feedback in clinical practice by distinguishing the elements of an educator's role in feedback considered to influence learner outcomes, then develop descriptions of observable educator behaviours that exemplify them. An extensive literature review was conducted to identify i) information substantiating specific components of an educator's role in feedback asserted to have an important influence on learner outcomes and ii) verbal feedback instruments in health professions education, that may describe important educator activities in effective feedback. This information was used to construct a list of elements thought to be important in effective feedback. Based on these elements, descriptions of observable educator behaviours that represent effective feedback were developed and refined during three rounds of a Delphi process and a face-to-face meeting with experts across the health professions and education. The review identified more than 170 relevant articles (involving health professions, education, psychology and business literature) and ten verbal feedback instruments in health professions education (plus modified versions). Eighteen distinct elements of an educator's role in effective feedback were delineated. Twenty five descriptions of educator behaviours that align with the elements were ratified by the expert panel. This research clarifies the distinct elements of an educator's role in feedback considered to enhance learner outcomes. The corresponding set of observable educator behaviours aim to describe how an educator could engage, motivate and enable a learner to improve. This creates the foundation for developing a method to systematically evaluate the impact of verbal feedback on learner performance.

Ecological networks to unravel the routes to horizontal transposon transfers.

PubMed

Venner, Samuel; Miele, Vincent; Terzian, Christophe; Biémont, Christian; Daubin, Vincent; Feschotte, Cédric; Pontier, Dominique

2017-02-01

Transposable elements (TEs) represent the single largest component of numerous eukaryotic genomes, and their activity and dispersal constitute an important force fostering evolutionary innovation. The horizontal transfer of TEs (HTT) between eukaryotic species is a common and widespread phenomenon that has had a profound impact on TE dynamics and, consequently, on the evolutionary trajectory of many species' lineages. However, the mechanisms promoting HTT remain largely unknown. In this article, we argue that network theory combined with functional ecology provides a robust conceptual framework and tools to delineate how complex interactions between diverse organisms may act in synergy to promote HTTs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stershic, Andrew J.; Dolbow, John E.; Moës, Nicolas

The Thick Level-Set (TLS) model is implemented to simulate brittle media undergoing dynamic fragmentation. This non-local model is discretized by the finite element method with damage represented as a continuous field over the domain. A level-set function defines the extent and severity of damage, and a length scale is introduced to limit the damage gradient. Numerical studies in one dimension demonstrate that the proposed method reproduces the rate-dependent energy dissipation and fragment length observations from analytical, numerical, and experimental approaches. In conclusion, additional studies emphasize the importance of appropriate bulk constitutive models and sufficient spatial resolution of the length scale.

Defining the conserved internal architecture of a protein kinase.

PubMed

Kornev, Alexandr P; Taylor, Susan S

2010-03-01

Protein kinases constitute a large protein family of important regulators in all eukaryotic cells. All of the protein kinases have a similar bilobal fold, and their key structural features have been well studied. However, the recent discovery of non-contiguous hydrophobic ensembles inside the protein kinase core shed new light on the internal organization of these molecules. Two hydrophobic "spines" traverse both lobes of the protein kinase molecule, providing a firm but flexible connection between its key elements. The spine model introduces a useful framework for analysis of intramolecular communications, molecular dynamics, and drug design. Published by Elsevier B.V.

Ventromedial prefrontal cortex supports affective future simulation by integrating distributed knowledge

PubMed Central

Benoit, Roland G.; Szpunar, Karl K.; Schacter, Daniel L.

2014-01-01

Although the future often seems intangible, we can make it more concrete by imagining prospective events. Here, using functional MRI, we demonstrate a mechanism by which the ventromedial prefrontal cortex supports such episodic simulations, and thereby contributes to affective foresight: This region supports processes that (i) integrate knowledge related to the elements that constitute an episode and (ii) represent the episode’s emergent affective quality. The ventromedial prefrontal cortex achieves such integration via interactions with distributed cortical regions that process the individual elements. Its activation then signals the affective quality of the ensuing episode, which goes beyond the combined affective quality of its constituting elements. The integrative process further augments long-term retention of the episode, making it available at later time points. This mechanism thus renders the future tangible, providing a basis for farsighted behavior. PMID:25368170

Ventromedial prefrontal cortex supports affective future simulation by integrating distributed knowledge.

PubMed

Benoit, Roland G; Szpunar, Karl K; Schacter, Daniel L

2014-11-18

Although the future often seems intangible, we can make it more concrete by imagining prospective events. Here, using functional MRI, we demonstrate a mechanism by which the ventromedial prefrontal cortex supports such episodic simulations, and thereby contributes to affective foresight: This region supports processes that (i) integrate knowledge related to the elements that constitute an episode and (ii) represent the episode's emergent affective quality. The ventromedial prefrontal cortex achieves such integration via interactions with distributed cortical regions that process the individual elements. Its activation then signals the affective quality of the ensuing episode, which goes beyond the combined affective quality of its constituting elements. The integrative process further augments long-term retention of the episode, making it available at later time points. This mechanism thus renders the future tangible, providing a basis for farsighted behavior.

Investigation of a Macromechanical Approach to Analyzing Triaxially-Braided Polymer Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Blinzler, Brina J.; Binienda, Wieslaw K.

2010-01-01

A macro level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The material stiffness and strength values required for the constitutive model are determined based on coupon level tests on the braided composite. Simulations of quasi-static coupon tests of a representative braided composite are conducted. Varying the strength values that are input to the material model is found to have a significant influence on the effective material response predicted by the finite element analysis, sometimes in ways that at first glance appear non-intuitive. A parametric study involving the input strength parameters provides guidance on how the analysis model can be improved.

Heterochromatin and molecular characterization of DsmarMITE transposable element in the beetle Dichotomius schiffleri (Coleoptera: Scarabaeidae).

PubMed

Xavier, Crislaine; Cabral-de-Mello, Diogo Cavalcanti; de Moura, Rita Cássia

2014-12-01

Cytogenetic studies of the Neotropical beetle genus Dichotomius (Scarabaeinae, Coleoptera) have shown dynamism for centromeric constitutive heterochromatin sequences. In the present work we studied the chromosomes and isolated repetitive sequences of Dichotomius schiffleri aiming to contribute to the understanding of coleopteran genome/chromosomal organization. Dichotomius schiffleri presented a conserved karyotype and heterochromatin distribution in comparison to other species of the genus with 2n = 18, biarmed chromosomes, and pericentromeric C-positive blocks. Similarly to heterochromatin distributional patterns, the highly and moderately repetitive DNA fraction (C 0 t-1 DNA) was detected in pericentromeric areas, contrasting with the euchromatic mapping of an isolated TE (named DsmarMITE). After structural analyses, the DsmarMITE was classified as a non-autonomous element of the type miniature inverted-repeat transposable element (MITE) with terminal inverted repeats similar to Mariner elements of insects from different orders. The euchromatic distribution for DsmarMITE indicates that it does not play a part in the dynamics of constitutive heterochromatin sequences.

Parameter Estimation for Viscoplastic Material Modeling

NASA Technical Reports Server (NTRS)

Saleeb, Atef F.; Gendy, Atef S.; Wilt, Thomas E.

1997-01-01

A key ingredient in the design of engineering components and structures under general thermomechanical loading is the use of mathematical constitutive models (e.g. in finite element analysis) capable of accurate representation of short and long term stress/deformation responses. In addition to the ever-increasing complexity of recent viscoplastic models of this type, they often also require a large number of material constants to describe a host of (anticipated) physical phenomena and complicated deformation mechanisms. In turn, the experimental characterization of these material parameters constitutes the major factor in the successful and effective utilization of any given constitutive model; i.e., the problem of constitutive parameter estimation from experimental measurements.

Rate dependent constitutive behavior of dielectric elastomers and applications in legged robotics

NASA Astrophysics Data System (ADS)

Oates, William; Miles, Paul; Gao, Wei; Clark, Jonathan; Mashayekhi, Somayeh; Hussaini, M. Yousuff

2017-04-01

Dielectric elastomers exhibit novel electromechanical coupling that has been exploited in many adaptive structure applications. Whereas the quasi-static, one-dimensional constitutive behavior can often be accurately quantified by hyperelastic functions and linear dielectric relations, accurate predictions of electromechanical, rate-dependent deformation during multiaxial loading is non-trivial. In this paper, an overview of multiaxial electromechanical membrane finite element modeling is formulated. Viscoelastic constitutive relations are extended to include fractional order. It is shown that fractional order viscoelastic constitutive relations are superior to conventional integer order models. This knowledge is critical for transition to control of legged robotic structures that exhibit advanced mobility.

Iran's Implicit Philosophy of Education

ERIC Educational Resources Information Center

Bagheri Noaparast, Khosrow

2018-01-01

This paper aims to extract Iran's philosophy of education from two sources of the constitution and the course of practice in educational institutions. Regarding the first source, it is argued that parallel to the two main threads of the constitution, Iran's main elements of philosophy of education are expected to be derived from; (1) Islam and (2)…

Research and development program for the development of advanced time-temperature dependent constitutive relationships. Volume 2: Programming manual

NASA Technical Reports Server (NTRS)

Cassenti, B. N.

1983-01-01

The results of a 10-month research and development program for nonlinear structural modeling with advanced time-temperature constitutive relationships are presented. The implementation of the theory in the MARC nonlinear finite element code is discussed, and instructions for the computational application of the theory are provided.

Benchmarking the QUAD4/TRIA3 element

NASA Technical Reports Server (NTRS)

Pitrof, Stephen M.; Venkayya, Vipperla B.

1993-01-01

The QUAD4 and TRIA3 elements are the primary plate/shell elements in NASTRAN. These elements enable the user to analyze thin plate/shell structures for membrane, bending and shear phenomena. They are also very new elements in the NASTRAN library. These elements are extremely versatile and constitute a substantially enhanced analysis capability in NASTRAN. However, with the versatility comes the burden of understanding a myriad of modeling implications and their effect on accuracy and analysis quality. The validity of many aspects of these elements were established through a series of benchmark problem results and comparison with those available in the literature and obtained from other programs like MSC/NASTRAN and CSAR/NASTRAN. Never-the-less such a comparison is never complete because of the new and creative use of these elements in complex modeling situations. One of the important features of QUAD4 and TRIA3 elements is the offset capability which allows the midsurface of the plate to be noncoincident with the surface of the grid points. None of the previous elements, with the exception of bar (beam), has this capability. The offset capability played a crucial role in the design of QUAD4 and TRIA3 elements. It allowed modeling layered composites, laminated plates and sandwich plates with the metal and composite face sheets. Even though the basic implementation of the offset capability is found to be sound in the previous applications, there is some uncertainty in relatively simple applications. The main purpose of this paper is to test the integrity of the offset capability and provide guidelines for its effective use. For the purpose of simplicity, references in this paper to the QUAD4 element will also include the TRIA3 element.

Triangular prismatic solid-shell element with generalised deformation description

NASA Astrophysics Data System (ADS)

Mataix, Vicente; Flores, Fernando G.; Rossi, Riccardo; Oñate, Eugenio

2018-01-01

The solid-shells are an attractive kind of element for the simulation of f orming processes, due to the fact that any kind of generic 3D constitutive law can be employed without any kind of additional modification, besides the thermomechanic problem is formulated without additional assumptions. Additionally, this type of element allows the three-dimensional description of the deformable body, thus contact on both sides of the element can be treated easily. The present work consists in the development of a triangular prism element as a solid-shell, for the analysis of thin/thick shell, undergoing large deformations. The element is formulated in total Lagrangian formulation, and employs the neighbour (adjacent) elements to perform a local patch to enrich the displacement field. In the original formulation by Flores, a modified right Cauchy-Green deformation tensor (?) is obtained; in the present work a modified deformation gradient (?) is obtained, which allows to generalise the methodology and allows to employ a wide range of constitutive laws. The element is based in three modifications: (a) a classical assumed strain approach for transverse shear strains (b) an assumed strain approach for the in-plane components using information from neighbour elements and (c) an averaging of the volumetric strain over the element. The objective is to use this type of elements for the simulation of shells avoiding transverse shear locking, improving the membrane behaviour of the in-plane triangle and to handle quasi-incompressible materials or materials with isochoric plastic flow. Some examples have been evaluated to show the good performance of the element and results.

Constitutive formulations for the mechanical investigation of colonic tissues.

PubMed

Carniel, Emanuele Luigi; Gramigna, Vera; Fontanella, Chiara Giulia; Stefanini, Cesare; Natali, Arturo N

2014-05-01

A constitutive framework is provided for the characterization of the mechanical behavior of colonic tissues, as a fundamental tool for the development of numerical models of the colonic structures. The constitutive analysis is performed by a multidisciplinary approach that requires the cooperation between experimental and computational competences. The preliminary investigation pertains to the review of the tissues histology. The complex structural configuration of the tissues and the specific distributions of fibrous elements entail the nonlinear mechanical behavior and the anisotropic response. The identification of the mechanical properties requires to perform mechanical tests according to different loading situations, as different loading directions. Because of the typical functionality of colon structures, the tissues mechanics is investigated by tensile tests, which are performed on taenia coli and haustra specimens from fresh pig colons. Accounting for the histological investigation and the results from the mechanical tests, a specific hyperelastic framework is provided within the theory of fiber-reinforced composite materials. Preliminary analytical formulations are defined to identify the constitutive parameters by the inverse analysis of the experimental tests. Finite element models of the specimens are developed accounting for the actual configuration of the colon structures to verify the quality of the results. The good agreement between experimental and numerical model results suggests the reliability of the constitutive formulations and parameters. Finally, the developed constitutive analysis makes it possible to identify the mechanical behavior and properties of the different colonic tissues. Copyright © 2013 Wiley Periodicals, Inc.

Versatile Cas9-Driven Subpopulation Selection Toolbox for Lactococcus lactis.

PubMed

van der Els, Simon; James, Jennelle K; Kleerebezem, Michiel; Bron, Peter A

2018-04-15

CRISPR-Cas9 technology has been exploited for the removal or replacement of genetic elements in a wide range of prokaryotes and eukaryotes. Here, we describe the extension of the Cas9 application toolbox to the industrially important dairy species Lactococcus lactis The Cas9 expression vector pLABTarget, encoding the Streptocccus pyogenes Cas9 under the control of a constitutive promoter, was constructed, allowing plug and play introduction of short guide RNA (sgRNA) sequences to target specific genetic loci. Introduction of a pepN -targeting derivative of pLABTarget into L. lactis strain MG1363 led to a strong reduction in the number of transformants obtained, which did not occur in a pepN deletion derivative of the same strain, demonstrating the specificity and lethality of the Cas9-mediated double-strand breaks in the lactococcal chromosome. Moreover, the same pLABTarget derivative allowed the selection of a pepN deletion subpopulation from its corresponding single-crossover plasmid integrant precursor, accelerating the construction and selection of gene-specific deletion derivatives in L. lactis Finally, pLABTarget, which contained sgRNAs designed to target mobile genetic elements, allowed the effective curing of plasmids, prophages, and integrative conjugative elements (ICEs). These results establish that pLABTarget enables the effective exploitation of Cas9 targeting in L. lactis , while the broad-host-range vector used suggests that this toolbox could readily be expanded to other Gram-positive bacteria. IMPORTANCE Mobile genetic elements in Lactococcus lactis and other lactic acid bacteria (LAB) play an important role in dairy fermentation, having both positive and detrimental effects during the production of fermented dairy products. The pLABTarget vector offers an efficient cloning platform for Cas9 application in lactic acid bacteria. Targeting Cas9 toward mobile genetic elements enabled their effective curing, which is of particular interest in the context of potentially problematic prophages present in a strain. Moreover, Cas9 targeting of other mobile genetic elements enables the deciphering of their contribution to dairy fermentation processes and further establishment of their importance for product characteristics. Copyright © 2018 American Society for Microbiology.

Molecular characterization of the short interspersed repetitive element SIRE in the six discrete typing units (DTUs) of Trypanosoma cruzi.

PubMed

Pavia, Paula X; Thomas, M Carmen; López, Manuel C; Puerta, Concepción J

2012-10-01

Repetitive sequences constitute an important proportion of the Trypanosoma cruzi genome; hence, they have been used as molecular markers and as amplification targets to identify the parasite presence via PCR. In this study, a molecular characterization of the SIRE repetitive element was performed in the six discrete typing units (DTUs) of T. cruzi. The results evidenced that this element, located in multiple chromosomes, was interspersed in the genome of all DTUs of the parasite. The presence of several motifs implicated in element insertion, duplication, and functionality suggests that SIRE could be an active element in the parasite genome. Of interest, there were SIRE specific Alu I fragments that allowed to discriminate DTU I from the others DTUs. Moreover, an UPGMA phenetic tree constructed from fragment sharing Southern blot data showed that T. cruzi I isolates conform a cluster separated from the T. cruzi II-VI isolates. When the relative number of SIRE copies was determined, a variation from 105 to 2,000 copies per haploid genome was observed among the different isolates without kept a DTU-relationship. In all, these findings suggest that SIRE sequence is a good target for parasite DNA amplification. Copyright © 2012 Elsevier Inc. All rights reserved.

A mixed-penalty biphasic finite element formulation incorporating viscous fluids and material interfaces.

PubMed

Chan, B; Donzelli, P S; Spilker, R L

2000-06-01

The fluid viscosity term of the fluid phase constitutive equation and the interface boundary conditions between biphasic, solid and fluid domains have been incorporated into a mixed-penalty finite element formulation of the linear biphasic theory for hydrated soft tissue. The finite element code can now model a single-phase viscous incompressible fluid, or a single-phase elastic solid, as limiting cases of a biphasic material. Interface boundary conditions allow the solution of problems involving combinations of biphasic, fluid and solid regions. To incorporate these conditions, the volume-weighted mixture velocity is introduced as a degree of freedom at interface nodes so that the kinematic continuity conditions are satisfied by conventional finite element assembly techniques. Results comparing our numerical method with an independent, analytic solution for the problem of Couette flow over rigid and deformable porous biphasic layers show that the finite element code accurately predicts the viscous fluid flows and deformation in the porous biphasic region. Thus, the analysis can be used to model the interface between synovial fluid and articular cartilage in diarthrodial joints. This is an important step toward modeling and understanding the mechanisms of joint lubrication and another step toward fully modeling the in vivo behavior of a diarthrodial joint.

Constitutive Behavior of Reinforced Concrete Membrane Elements under Tri-directional Shear

NASA Astrophysics Data System (ADS)

Labib, Moheb

The two-dimensional behavior of typical reinforced concrete (RC) structures has been extensively studied in the past several decades by investigating the constitutive behavior of full-scale reinforced concrete elements subjected to a bi-axial state of stress. In order to understand the true behavior of many large complex structures, the goal of this investigation is to develop new constitutive relationships for RC elements subjected to tri-directional shear stresses. Recently, additional out-of-plane jacks were installed on the panel tester at University of Houston so that concrete elements could be subjected to tri-directional shear stresses. This upgrade makes the panel tester the only one of its kind in the US that is capable of applying such combinations of stresses on full-scale reinforced concrete elements. This dissertation presents the details of the mounting and installation of the additional hydraulic jacks on the universal panel tester. The experimental program includes a series of seven reinforced concrete elements subjected to different combinations of in-plane and out-of-plane shear stresses. Increasing the applied out-of-plane shear stresses reduced the membrane shear strength of the elements. The effect of applying out-of-plane shear stresses on the in-plane shear strength was represented by modifying the softening coefficient in the compression stress strain curve of concrete struts. The modified model was able to capture the behavior and the ultimate capacity of the tested elements. The effect of the in-plane shear reinforcement ratio on the interaction between in-plane and out-of-plane shear stresses was evaluated. The model was implemented in the Finite Element package FEAP and was used to predict the ultimate capacity of many structures subjected to a combination of in-plane and out-of-plane shear stresses. The results of the analytical model were used to develop simplified design equations for members subjected to bi-directional shear loads. The applied out-of-plane shear load was resolved in two equal out-of-plane shear components to construct tri-directional shear interaction diagrams.

Variational formulation of hybrid problems for fully 3-D transonic flow with shocks in rotor

NASA Technical Reports Server (NTRS)

Liu, Gao-Lian

1991-01-01

Based on previous research, the unified variable domain variational theory of hybrid problems for rotor flow is extended to fully 3-D transonic rotor flow with shocks, unifying and generalizing the direct and inverse problems. Three variational principles (VP) families were established. All unknown boundaries and flow discontinuities (such as shocks, free trailing vortex sheets) are successfully handled via functional variations with variable domain, converting almost all boundary and interface conditions, including the Rankine Hugoniot shock relations, into natural ones. This theory provides a series of novel ways for blade design or modification and a rigorous theoretical basis for finite element applications and also constitutes an important part of the optimal design theory of rotor bladings. Numerical solutions to subsonic flow by finite elements with self-adapting nodes given in Refs., show good agreement with experimental results.

Static analysis of C-shape SMA middle ear prosthesis

NASA Astrophysics Data System (ADS)

Latalski, Jarosław; Rusinek, Rafał

2017-08-01

Shape memory alloys are a family of metals with the ability to change specimen shape depending on their temperature. This unique property is useful in many areas of mechanical and biomechanical engineering. A new half-ring middle ear prosthesis design made of a shape memory alloy, that is undergoing initial clinical tests, is investigated in this research paper. The analytical model of the studied structure made of nonlinear constitutive material is solved to identify the temperature-dependent stiffness characteristics of the proposed design on the basis of the Crotti-Engesser theorem. The final integral expression for the element deflection is highly complex, thus the solution has to be computed numerically. The final results show the proposed shape memory C-shape element to behave linearly in the analysed range of loadings and temperatures. This is an important observation that significantly simplifies the analysis of the prototype structure and opens wide perspectives for further possible applications of shape memory alloys.

A trehalose biosynthetic enzyme doubles as an osmotic stress sensor to regulate bacterial morphogenesis.

PubMed

Chen, Ximing; An, Lizhe; Fan, Xiaochuan; Ju, Furong; Zhang, Binglin; Sun, Haili; Xiao, Jianxi; Hu, Wei; Qu, Tao; Guan, Liping; Tang, Shukun; Chen, Tuo; Liu, Guangxiu; Dyson, Paul

2017-10-01

The dissacharide trehalose is an important intracellular osmoprotectant and the OtsA/B pathway is the principal pathway for trehalose biosynthesis in a wide range of bacterial species. Scaffolding proteins and other cytoskeletal elements play an essential role in morphogenetic processes in bacteria. Here we describe how OtsA, in addition to its role in trehalose biosynthesis, functions as an osmotic stress sensor to regulate cell morphology in Arthrobacter strain A3. In response to osmotic stress, this and other Arthrobacter species undergo a transition from bacillary to myceloid growth. An otsA null mutant exhibits constitutive myceloid growth. Osmotic stress leads to a depletion of trehalose-6-phosphate, the product of the OtsA enzyme, and experimental depletion of this metabolite also leads to constitutive myceloid growth independent of OtsA function. In vitro analyses indicate that OtsA can self-assemble into protein networks, promoted by trehalose-6-phosphate, a property that is not shared by the equivalent enzyme from E. coli, despite the latter's enzymatic activity when expressed in Arthrobacter. This, and the localization of the protein in non-stressed cells at the mid-cell and poles, indicates that OtsA from Arthrobacter likely functions as a cytoskeletal element regulating cell morphology. Recruiting a biosynthetic enzyme for this morphogenetic function represents an intriguing adaptation in bacteria that can survive in extreme environments.

Mutually Exclusive Splicing of the Insect Dscam Pre-mRNA Directed by Competing Intronic RNA Secondary Structures

PubMed Central

Graveley, Brenton R.

2008-01-01

Summary Drosophila Dscam encodes 38,016 distinct axon guidance receptors through the mutually exclusive alternative splicing of 95 variable exons. Importantly, known mechanisms that ensure the mutually exclusive splicing of pairs of exons cannot explain this phenomenon in Dscam. I have identified two classes of conserved elements in the Dscam exon 6 cluster, which contains 48 alternative exons—the docking site, located in the intron downstream of constitutive exon 5, and the selector sequences, which are located upstream of each exon 6 variant. Strikingly, each selector sequence is complementary to a portion of the docking site, and this pairing juxtaposes one, and only one, alternative exon to the upstream constitutive exon. The mutually exclusive nature of the docking site:selector sequence interactions suggests that the formation of these competing RNA structures is a central component of the mechanism guaranteeing that only one exon 6 variant is included in each Dscam mRNA. PMID:16213213

Outpatient management of oral vitamin K antagonist therapy: defining and measuring high-quality management.

PubMed

Phillips, Katherine W; Ansell, Jack

2008-01-01

Oral anticoagulation therapy with warfarin is the mainstay of prevention and treatment of thromboembolic disease. However, it remains one of the leading causes of harmful medication errors and medication-related adverse events. The beneficial outcomes of oral anticoagulation therapy are directly dependent upon the quality of dose and anticoagulation management, but the literature is not robust with regards to what constitutes such management. This review focuses on, and attempts to define, the parameters of high-quality anticoagulation management and identifies the appropriate outcome measures constituting high-quality management. Elements discussed include the most fundamental measure, time in therapeutic range, along with other parameters including therapy initiation, time to therapeutic range, dosing management when patients are not in therapeutic range, perioperative dosing management, patient education, and other important outcome measures. Healthcare providers who manage oral anticoagulation therapy should utilize these parameters as a measure of their performance in an effort to achieve high-quality anticoagulation management.

A concise guide to clinical reasoning.

PubMed

Daly, Patrick

2018-04-30

What constitutes clinical reasoning is a disputed subject regarding the processes underlying accurate diagnosis, the importance of patient-specific versus population-based data, and the relation between virtue and expertise in clinical practice. In this paper, I present a model of clinical reasoning that identifies and integrates the processes of diagnosis, prognosis, and therapeutic decision making. The model is based on the generalized empirical method of Bernard Lonergan, which approaches inquiry with equal attention to the subject who investigates and the object under investigation. After identifying the structured operations of knowing and doing and relating these to a self-correcting cycle of learning, I correlate levels of inquiry regarding what-is-going-on and what-to-do to the practical and theoretical elements of clinical reasoning. I conclude that this model provides a methodical way to study questions regarding the operations of clinical reasoning as well as what constitute significant clinical data, clinical expertise, and virtuous health care practice. © 2018 John Wiley & Sons, Ltd.

A well-posed optimal spectral element approximation for the Stokes problem

NASA Technical Reports Server (NTRS)

Maday, Y.; Patera, A. T.; Ronquist, E. M.

1987-01-01

A method is proposed for the spectral element simulation of incompressible flow. This method constitutes in a well-posed optimal approximation of the steady Stokes problem with no spurious modes in the pressure. The resulting method is analyzed, and numerical results are presented for a model problem.

75 FR 16837 - Public Review of Draft United States Thoroughfare, Landmark, and Postal Address Data Standard

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-02

... the structure of their address information but have not defined the elements that constitute an address. Knowledge of structure, content, and quality is required to successfully share information in a... discrete elements of address information and provides standardized terminology and definitions to alleviate...

Constitutive modeling of glassy shape memory polymers

NASA Astrophysics Data System (ADS)

Khanolkar, Mahesh

The aim of this research is to develop constitutive models for non-linear materials. Here, issues related for developing constitutive model for glassy shape memory polymers are addressed in detail. Shape memory polymers are novel material that can be easily formed into complex shapes, retaining memory of their original shape even after undergoing large deformations. The temporary shape is stable and return to the original shape is triggered by a suitable mechanism such heating the polymer above a transition temperature. Glassy shape memory polymers are called glassy because the temporary shape is fixed by the formation of a glassy solid, while return to the original shape is due to the melting of this glassy phase. The constitutive model has been developed to capture the thermo-mechanical behavior of glassy shape memory polymers using elements of nonlinear mechanics and polymer physics. The key feature of this framework is that a body can exist stress free in numerous natural configurations, the underlying natural configuration of the body changing during the process, with the response of the body being elastic from these evolving natural configurations. The aim of this research is to formulate a constitutive model for glassy shape memory polymers (GSMP) which takes in to account the fact that the stress-strain response depends on thermal expansion of polymers. The model developed is for the original amorphous phase, the temporary glassy phase and transition between these phases. The glass transition process has been modeled using a framework that was developed recently for studying crystallization in polymers and is based on the theory of multiple natural configurations. Using the same frame work, the melting of the glassy phase to capture the return of the polymer to its original shape is also modeled. The effect of nanoreinforcement on the response of shape memory polymers (GSMP) is studied and a model is developed. In addition to modeling and solving boundary value problems for GSMP's, problems of importance for CSMP, specifically a shape memory cycle (Torsion of a Cylinder) is solved using the developed crystallizable shape memory polymer model. To solve complex boundary value problems in realistic geometries a user material subroutine (UMAT) for GSMP model has been developed for use in conjunction with the commercial finite element software ABAQUS. The accuracy of the UMAT has been verified by testing it against problems for which the results are known.

Galerkin finite element scheme for magnetostrictive structures and composites

NASA Astrophysics Data System (ADS)

Kannan, Kidambi Srinivasan

The ever increasing-role of magnetostrictives in actuation and sensing applications is an indication of their importance in the emerging field of smart structures technology. As newer, and more complex, applications are developed, there is a growing need for a reliable computational tool that can effectively address the magneto-mechanical interactions and other nonlinearities in these materials and in structures incorporating them. This thesis presents a continuum level quasi-static, three-dimensional finite element computational scheme for modeling the nonlinear behavior of bulk magnetostrictive materials and particulate magnetostrictive composites. Models for magnetostriction must deal with two sources of nonlinearities-nonlinear body forces/moments in equilibrium equations governing magneto-mechanical interactions in deformable and magnetized bodies; and nonlinear coupled magneto-mechanical constitutive models for the material of interest. In the present work, classical differential formulations for nonlinear magneto-mechanical interactions are recast in integral form using the weighted-residual method. A discretized finite element form is obtained by applying the Galerkin technique. The finite element formulation is based upon three dimensional eight-noded (isoparametric) brick element interpolation functions and magnetostatic infinite elements at the boundary. Two alternative possibilities are explored for establishing the nonlinear incremental constitutive model-characterization in terms of magnetic field or in terms of magnetization. The former methodology is the one most commonly used in the literature. In this work, a detailed comparative study of both methodologies is carried out. The computational scheme is validated, qualitatively and quantitatively, against experimental measurements published in the literature on structures incorporating the magnetostrictive material Terfenol-D. The influence of nonlinear body forces and body moments of magnetic origin, on the response of magnetostrictive structures to complex mechanical and magnetic loading conditions, is carefully examined. While monolithic magnetostrictive materials have been commercially-available since the late eighties, attention in the smart structures research community has recently focussed upon building and using magnetostrictive particulate composite structures for conventional actuation applications and novel sensing methodologies in structural health monitoring. A particulate magnetostrictive composite element has been developed in the present work to model such structures. This composite element incorporates interactions between magnetostrictive particles by combining a numerical micromechanical analysis based on magneto-mechanical Green's functions, with a homogenization scheme based upon the Mori-Tanaka approach. This element has been applied to the simulation of particulate actuators and sensors reported in the literature. Simulation results are compared to experimental data for validation purposes. The computational schemes developed, for bulk materials and for composites, are expected to be of great value to researchers and designers of novel applications based on magnetostrictives.

ANSYS Modeling of Hydrostatic Stress Effects

NASA Technical Reports Server (NTRS)

Allen, Phillip A.

1999-01-01

Classical metal plasticity theory assumes that hydrostatic pressure has no effect on the yield and postyield behavior of metals. Plasticity textbooks, from the earliest to the most modem, infer that there is no hydrostatic effect on the yielding of metals, and even modem finite element programs direct the user to assume the same. The object of this study is to use the von Mises and Drucker-Prager failure theory constitutive models in the finite element program ANSYS to see how well they model conditions of varying hydrostatic pressure. Data is presented for notched round bar (NRB) and "L" shaped tensile specimens. Similar results from finite element models in ABAQUS are shown for comparison. It is shown that when dealing with geometries having a high hydrostatic stress influence, constitutive models that have a functional dependence on hydrostatic stress are more accurate in predicting material behavior than those that are independent of hydrostatic stress.

A Novel Arterial Constitutive Model in a Commercial Finite Element Package: Application to Balloon Angioplasty

PubMed Central

Zhao, Xuefeng; Liu, Yi; Zhang, Wei; Wang, Cong; Kassab, Ghassan S.

2011-01-01

Recently, a novel linearized constitutive model with a new strain measure that absorbs the material nonlinearity was validated for arteries. In this study, the linearized arterial stress-strain relationship is implemented into a finite element method package ANSYS, via the user subroutine USERMAT. The reference configuration is chosen to be the closed cylindrical tube (no-load state) rather than the open sector (zero-stress state). The residual strain is taken into account by analytic calculation and the incompressibility condition is enforced with Lagrange penalty method. Axisymmetric finite element analyses are conducted to demonstrate potential applications of this approach in a complex boundary value problem where angioplasty balloon interacts with the vessel wall. The model predictions of transmural circumferential and compressive radial stress distributions were also validated against an exponential-type Fung model, and the mean error was found to be within 6%. PMID:21689665

The Nature of the Future: A Primer for Strategic Planning.

ERIC Educational Resources Information Center

Vaughan, Jerry, Sr.

The anticipation of the future has been the basis of conflict between people's dreams and the power that people have felt that they have had to act on their dreams. In a practical translation, the future, in the present, is constituted from at least some of the traditional elements of the past. However, the future is mainly constituted in the…

The Reluctant Pillar: New York and the Adoption of the Federal Constitution.

ERIC Educational Resources Information Center

Schechter, Stephen L., Ed.

This collection of essays is intended for both the general reader and the specialist and is designed to provide the basic elements needed for an introductory survey and a reference aid to the role of New York State in the adoption of the federal Constitution. The collection is organized into five sections: theory, history, materials, people and…

Three-Dimensional Effects of Crack Closure in Laminated Composite Plates Subjected to Bending Loads

DTIC Science & Technology

1994-06-01

Approved by: •UW. Kwon, Thesis Advisor wathe D.K~elleher, Chairman Department of Mechanical Engineering ii ABSTRACT Fracture is one of the dominant...5 A. OVERVIEW .......................................... 5 B. CONSTITUTIVE EQUATION .............................. 9 1. Isotropic...the elemental nodes. B. CONSTITUTIVE EQUATION The material property matrix [D] is a symmetric matrix which includes elasticity moduli and Poisson’s

Atmospheric particulate matter intercepted by moss-bags: Relations to moss trace element uptake and land use.

PubMed

Di Palma, Anna; Capozzi, Fiore; Spagnuolo, Valeria; Giordano, Simonetta; Adamo, Paola

2017-06-01

Particulate matter has to be constantly monitored because it is an important atmospheric transport form of potentially harmful contaminants. The cost-effective method of the moss-bags can be employed to evaluate both loads and chemical composition of PM. PM entrapped by the moss Pseudoscleropodium purum exposed in bags in 9 European sites was characterized for number, size and chemical composition by SEM/EDX. Moreover, moss elemental uptake of 53 elements including rare earth elements was estimated by ICP-MS analysis. All above was aimed to find possible relations between PM profile and moss uptake and to find out eventual element markers of the different land use (i.e. agricultural, urban, industrial) of the selected sites. After exposure, about 12,000 particles, mostly within the inhalable fraction, were counted on P. purum leaves; their number generally increased from the agricultural sites to the urban and industrial ones. ICP analysis indicated that twenty-three elements were significantly accumulated by mosses with different element profile according to the various land uses. The PM from agricultural sites were mainly made of natural/crustal elements or derived from rural activities. Industrial-related PM covered a wider range of sources, from those linked to specific industrial activities, to those related to manufacturing processes or use of heavy-duty vehicles. This study indicates a close association between PM amount and moss element-uptake, which increases in parallel with PM amount. Precious metals and REEs may constitute novel markers of air pollution in urban and agricultural sites, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cohesive finite element modeling of the delamination of HTPB binder and HMX crystals under tensile loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walters, David J.; Luscher, Darby J.; Yeager, John D.

Accurately modeling the mechanical behavior of the polymer binders and the degradation of interfaces between binder and crystal is important to science-based understanding of the macro-scale response of polymer bonded explosives. The paper presents a description of relatively a simple bi-crystal HMX-HTPB specimen and associated tensile loading experiment including computed tomography imaging, the pertinent constitutive theory, and details of numerical simulations used to infer the behavior of the material during the delamination process. Within this work, mechanical testing and direct numerical simulation of this relatively simple bi-crystal system enabled reasonable isolation of binder-crystal interface delamination, in which the effects ofmore » the complicated thermomechanical response of explosive crystals were minimized. Cohesive finite element modeling of the degradation and delamination of the interface between a modified HTPB binder and HMX crystals was used to reproduce observed results from tensile loading experiments on bi-crystal specimens. Several comparisons are made with experimental measurements in order to identify appropriate constitutive behavior of the binder and appropriate parameters for the cohesive traction-separation behavior of the crystal-binder interface. This research demonstrates the utility of directly modeling the delamination between binder and crystal within crystal-binder-crystal tensile specimen towards characterizing the behavior of these interfaces in a manner amenable to larger scale simulation of polycrystalline PBX materials. One critical aspect of this approach is micro computed tomography imaging conducted during the experiments, which enabled comparison of delamination patterns between the direct numerical simulation and actual specimen. In addition to optimizing the cohesive interface parameters, one important finding from this investigation is that understanding and representing the strain-hardening plasticity of HTPB binder is important within the context of using a cohesive traction-separation model for the delamination of a crystal-binder system.« less

Cohesive finite element modeling of the delamination of HTPB binder and HMX crystals under tensile loading

DOE PAGES

Walters, David J.; Luscher, Darby J.; Yeager, John D.; ...

2018-02-27

Accurately modeling the mechanical behavior of the polymer binders and the degradation of interfaces between binder and crystal is important to science-based understanding of the macro-scale response of polymer bonded explosives. The paper presents a description of relatively a simple bi-crystal HMX-HTPB specimen and associated tensile loading experiment including computed tomography imaging, the pertinent constitutive theory, and details of numerical simulations used to infer the behavior of the material during the delamination process. Within this work, mechanical testing and direct numerical simulation of this relatively simple bi-crystal system enabled reasonable isolation of binder-crystal interface delamination, in which the effects ofmore » the complicated thermomechanical response of explosive crystals were minimized. Cohesive finite element modeling of the degradation and delamination of the interface between a modified HTPB binder and HMX crystals was used to reproduce observed results from tensile loading experiments on bi-crystal specimens. Several comparisons are made with experimental measurements in order to identify appropriate constitutive behavior of the binder and appropriate parameters for the cohesive traction-separation behavior of the crystal-binder interface. This research demonstrates the utility of directly modeling the delamination between binder and crystal within crystal-binder-crystal tensile specimen towards characterizing the behavior of these interfaces in a manner amenable to larger scale simulation of polycrystalline PBX materials. One critical aspect of this approach is micro computed tomography imaging conducted during the experiments, which enabled comparison of delamination patterns between the direct numerical simulation and actual specimen. In addition to optimizing the cohesive interface parameters, one important finding from this investigation is that understanding and representing the strain-hardening plasticity of HTPB binder is important within the context of using a cohesive traction-separation model for the delamination of a crystal-binder system.« less

Finite-Strain Fractional-Order Viscoelastic (FOV) Material Models and Numerical Methods for Solving Them

NASA Technical Reports Server (NTRS)

Freed, Alan D.; Diethelm, Kai; Gray, Hugh R. (Technical Monitor)

2002-01-01

Fraction-order viscoelastic (FOV) material models have been proposed and studied in 1D since the 1930's, and were extended into three dimensions in the 1970's under the assumption of infinitesimal straining. It was not until 1997 that Drozdov introduced the first finite-strain FOV constitutive equations. In our presentation, we shall continue in this tradition by extending the standard, FOV, fluid and solid, material models introduced in 1971 by Caputo and Mainardi into 3D constitutive formula applicable for finite-strain analyses. To achieve this, we generalize both the convected and co-rotational derivatives of tensor fields to fractional order. This is accomplished by defining them first as body tensor fields and then mapping them into space as objective Cartesian tensor fields. Constitutive equations are constructed using both variants for fractional rate, and their responses are contrasted in simple shear. After five years of research and development, we now possess a basic suite of numerical tools necessary to study finite-strain FOV constitutive equations and their iterative refinement into a mature collection of material models. Numerical methods still need to be developed for efficiently solving fraction al-order integrals, derivatives, and differential equations in a finite element setting where such constitutive formulae would need to be solved at each Gauss point in each element of a finite model, which can number into the millions in today's analysis.

On Orbital Elements of Extrasolar Planetary Candidates and Spectroscopic Binaries

NASA Technical Reports Server (NTRS)

Stepinski, T. F.; Black, D. C.

2001-01-01

We estimate probability densities of orbital elements, periods, and eccentricities, for the population of extrasolar planetary candidates (EPC) and, separately, for the population of spectroscopic binaries (SB) with solar-type primaries. We construct empirical cumulative distribution functions (CDFs) in order to infer probability distribution functions (PDFs) for orbital periods and eccentricities. We also derive a joint probability density for period-eccentricity pairs in each population. Comparison of respective distributions reveals that in all cases EPC and SB populations are, in the context of orbital elements, indistinguishable from each other to a high degree of statistical significance. Probability densities of orbital periods in both populations have P(exp -1) functional form, whereas the PDFs of eccentricities can he best characterized as a Gaussian with a mean of about 0.35 and standard deviation of about 0.2 turning into a flat distribution at small values of eccentricity. These remarkable similarities between EPC and SB must be taken into account by theories aimed at explaining the origin of extrasolar planetary candidates, and constitute an important clue us to their ultimate nature.

A Viscoelastic Constitutive Model Can Accurately Represent Entire Creep Indentation Tests of Human Patella Cartilage

PubMed Central

Pal, Saikat; Lindsey, Derek P.; Besier, Thor F.; Beaupre, Gary S.

2013-01-01

Cartilage material properties provide important insights into joint health, and cartilage material models are used in whole-joint finite element models. Although the biphasic model representing experimental creep indentation tests is commonly used to characterize cartilage, cartilage short-term response to loading is generally not characterized using the biphasic model. The purpose of this study was to determine the short-term and equilibrium material properties of human patella cartilage using a viscoelastic model representation of creep indentation tests. We performed 24 experimental creep indentation tests from 14 human patellar specimens ranging in age from 20 to 90 years (median age 61 years). We used a finite element model to reproduce the experimental tests and determined cartilage material properties from viscoelastic and biphasic representations of cartilage. The viscoelastic model consistently provided excellent representation of the short-term and equilibrium creep displacements. We determined initial elastic modulus, equilibrium elastic modulus, and equilibrium Poisson’s ratio using the viscoelastic model. The viscoelastic model can represent the short-term and equilibrium response of cartilage and may easily be implemented in whole-joint finite element models. PMID:23027200

Crystal plasticity simulation of Zirconium tube rolling using multi-grain representative volume element

NASA Astrophysics Data System (ADS)

Isaenkova, Margarita; Perlovich, Yuriy; Zhuk, Dmitry; Krymskaya, Olga

2017-10-01

The rolling of Zirconium tube is studied by means of the crystal plasticity viscoplastic self-consistent (VPSC) constitutive modeling. This modeling performed by a dislocation-based constitutive model and a spectral solver using open-source simulation of DAMASK kit. The multi-grain representative volume elements with periodic boundary conditions are used to predict the texture evolution and distributions of strain and stresses. Two models for randomly textured and partially rolled material are deformed to 30% reduction in tube wall thickness and 7% reduction in tube diameter. The resulting shapes of the models are shown and distributions of strain are plotted. Also, evolution of grain's shape during deformation is shown.

The choice of a constitutive formulation for modeling limb flexion-induced deformations and stresses in the human femoropopliteal arteries of different ages.

PubMed

Desyatova, Anastasia; MacTaggart, Jason; Poulson, William; Deegan, Paul; Lomneth, Carol; Sandip, Anjali; Kamenskiy, Alexey

2017-06-01

Open and endovascular treatments for peripheral arterial disease are notorious for high failure rates. Severe mechanical deformations experienced by the femoropopliteal artery (FPA) during limb flexion and interactions between the artery and repair materials play important roles and may contribute to poor clinical outcomes. Computational modeling can help optimize FPA repair, but these simulations heavily depend on the choice of constitutive model describing the arterial behavior. In this study finite element model of the FPA in the standing (straight) and gardening (acutely bent) postures was built using computed tomography data, longitudinal pre-stretch and biaxially determined mechanical properties. Springs and dashpots were used to represent surrounding tissue forces associated with limb flexion-induced deformations. These forces were then used with age-specific longitudinal pre-stretch and mechanical properties to obtain deformed FPA configurations for seven age groups. Four commonly used invariant-based constitutive models were compared to determine the accuracy of capturing deformations and stresses in each age group. The four-fiber FPA model most accurately portrayed arterial behavior in all ages, but in subjects younger than 40 years, the performance of all constitutive formulations was similar. In older subjects, Demiray (Delfino) and classic two-fiber Holzapfel-Gasser-Ogden formulations were better than the Neo-Hookean model for predicting deformations due to limb flexion, but both significantly overestimated principal stresses compared to the FPA or Neo-Hookean models.

Simulation of Semi-Solid Material Mechanical Behavior Using a Combined Discrete/Finite Element Method

NASA Astrophysics Data System (ADS)

Sistaninia, M.; Phillion, A. B.; Drezet, J.-M.; Rappaz, M.

2011-01-01

As a necessary step toward the quantitative prediction of hot tearing defects, a three-dimensional stress-strain simulation based on a combined finite element (FE)/discrete element method (DEM) has been developed that is capable of predicting the mechanical behavior of semisolid metallic alloys during solidification. The solidification model used for generating the initial solid-liquid structure is based on a Voronoi tessellation of randomly distributed nucleation centers and a solute diffusion model for each element of this tessellation. At a given fraction of solid, the deformation is then simulated with the solid grains being modeled using an elastoviscoplastic constitutive law, whereas the remaining liquid layers at grain boundaries are approximated by flexible connectors, each consisting of a spring element and a damper element acting in parallel. The model predictions have been validated against Al-Cu alloy experimental data from the literature. The results show that a combined FE/DEM approach is able to express the overall mechanical behavior of semisolid alloys at the macroscale based on the morphology of the grain structure. For the first time, the localization of strain in the intergranular regions is taken into account. Thus, this approach constitutes an indispensible step towards the development of a comprehensive model of hot tearing.

[Ambivalence--a key concept in gerontology? Elements of heuristics exemplified by identity formation in old age].

PubMed

Lüscher, Kurt; Haller, Miriam

2016-01-01

Ambivalence is a widely used concept in gerontology, mostly used in the common sense meaning. We propose that an elaborated notion based on the historical and systematic analysis, reveals important theoretical, methodological and practical potentials of the idea of ambivalence for the study of aging. We exemplify this view by proposing a heuristic perspective for the analysis of processes to constitute and reconstitute identities in old age using a model based on a multidimensional understanding of ambivalence. Ambivalence is defined as referring to the experiences of vacillating between polar contradictions of feeling, thinking, wanting and social structures in the search for the sense and meaning of social relationships, facts and texts, which are important for unfolding and altering facets of the self and agency.

Layered transition metal dichalcogenide electrochemistry: journey across the periodic table.

PubMed

Chia, Xinyi; Pumera, Martin

2018-06-08

Studies on layered transition metal dichalcogenides (TMDs), in particular for Group VIB TMDs like MoS2 and WS2, have long reached a crescendo in the realms of electrochemical applications initiated by their remarkable catalytic and electronic properties. One area that garnered considerable attention is the fervent pursuit of layered TMDs as electrocatalysts for hydrogen evolution reaction (HER), driven by global efforts towards reducing carbon footprint and attaining hydrogen economy. This Tutorial Review captures the essence of electrochemistry of different classes of layered TMDs and metal chalcogenides across the period table and showcases their tuneable electrochemical and HER catalytic attributes that are governed by the elemental composition, structure and anisotropy. Of interest to the assiduously studied Group VIB TMDs, we describe the role of elemental constituents and material purity in aspects of surface composition and structure, on their electrochemistry. Across families of layered TMDs in the periodic table, we highlight the apparent trends in their electrochemical and electrocatalytic properties through diligent comparison. Inevitably, these trends vary according to the type of chalcogen or transition metal that constitutes the eventual TMD. Beyond layered TMDs, we discuss the electrochemistry and recent progress in HER electrocatalysis of other layered metal chalcogenides that are overshadowed by the success of Group VIB TMDs. At the pinnacle of the emergent applications of layered TMDs, it is prudent to demystify the intrinsic electrochemical behaviour that originates from the participation of the elemental constitution of transition metal or chalcogen. Moreover, knowledge of the catalytic and electronic properties of the various TMD families and emerging trends across the period or down the group is of paramount importance when introducing or refining their prospective uses. The annotations in this Tutorial Review are envisioned to promote discourse into the catalytic and electrochemical trends of TMDs that is currently absent.

Static and sliding contact of rough surfaces: Effect of asperity-scale properties and long-range elastic interactions

NASA Astrophysics Data System (ADS)

Hulikal, Srivatsan; Lapusta, Nadia; Bhattacharya, Kaushik

2018-07-01

Friction in static and sliding contact of rough surfaces is important in numerous physical phenomena. We seek to understand macroscopically observed static and sliding contact behavior as the collective response of a large number of microscopic asperities. To that end, we build on Hulikal et al. (2015) and develop an efficient numerical framework that can be used to investigate how the macroscopic response of multiple frictional contacts depends on long-range elastic interactions, different constitutive assumptions about the deforming contacts and their local shear resistance, and surface roughness. We approximate the contact between two rough surfaces as that between a regular array of discrete deformable elements attached to a elastic block and a rigid rough surface. The deformable elements are viscoelastic or elasto/viscoplastic with a range of relaxation times, and the elastic interaction between contacts is long-range. We find that the model reproduces the main macroscopic features of evolution of contact and friction for a range of constitutive models of the elements, suggesting that macroscopic frictional response is robust with respect to the microscopic behavior. Viscoelasticity/viscoplasticity contributes to the increase of friction with contact time and leads to a subtle history dependence. Interestingly, long-range elastic interactions only change the results quantitatively compared to the meanfield response. The developed numerical framework can be used to study how specific observed macroscopic behavior depends on the microscale assumptions. For example, we find that sustained increase in the static friction coefficient during long hold times suggests viscoelastic response of the underlying material with multiple relaxation time scales. We also find that the experimentally observed proportionality of the direct effect in velocity jump experiments to the logarithm of the velocity jump points to a complex material-dependent shear resistance at the microscale.

Multiple splicing defects in an intronic false exon.

PubMed

Sun, H; Chasin, L A

2000-09-01

Splice site consensus sequences alone are insufficient to dictate the recognition of real constitutive splice sites within the typically large transcripts of higher eukaryotes, and large numbers of pseudoexons flanked by pseudosplice sites with good matches to the consensus sequences can be easily designated. In an attempt to identify elements that prevent pseudoexon splicing, we have systematically altered known splicing signals, as well as immediately adjacent flanking sequences, of an arbitrarily chosen pseudoexon from intron 1 of the human hprt gene. The substitution of a 5' splice site that perfectly matches the 5' consensus combined with mutation to match the CAG/G sequence of the 3' consensus failed to get this model pseudoexon included as the central exon in a dhfr minigene context. Provision of a real 3' splice site and a consensus 5' splice site and removal of an upstream inhibitory sequence were necessary and sufficient to confer splicing on the pseudoexon. This activated context also supported the splicing of a second pseudoexon sequence containing no apparent enhancer. Thus, both the 5' splice site sequence and the polypyrimidine tract of the pseudoexon are defective despite their good agreement with the consensus. On the other hand, the pseudoexon body did not exert a negative influence on splicing. The introduction into the pseudoexon of a sequence selected for binding to ASF/SF2 or its replacement with beta-globin exon 2 only partially reversed the effect of the upstream negative element and the defective polypyrimidine tract. These results support the idea that exon-bridging enhancers are not a prerequisite for constitutive exon definition and suggest that intrinsically defective splice sites and negative elements play important roles in distinguishing the real splicing signal from the vast number of false splicing signals.

Modification of a Macromechanical Finite-Element Based Model for Impact Analysis of Triaxially-Braided Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Blinzler, Brina J.; Binienda, Wieslaw K.

2010-01-01

A macro level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. For the current analytical approach, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The constitutive model requires stiffness and strength properties of an equivalent unidirectional composite. Simplified micromechanics methods are used to determine the equivalent stiffness properties, and results from coupon level tests on the braided composite are utilized to back out the required strength properties. Simulations of quasi-static coupon tests of several representative braided composites are conducted to demonstrate the correlation of the model. Impact simulations of a represented braided composites are conducted to demonstrate the capability of the model to predict the penetration velocity and damage patterns obtained experimentally.

Analysis and Testing of Plates with Piezoelectric Sensors and Actuators

NASA Technical Reports Server (NTRS)

Bevan, Jeffrey S.

1998-01-01

Piezoelectric material inherently possesses coupling between electrostatics and structural dynamics. Utilizing linear piezoelectric theory results in an intrinsically coupled pair of piezoelectric constitutive equations. One equation describes the direct piezoelectric effect where strains produce an electric field and the other describes the converse effect where an applied electrical field produces strain. The purpose of this study is to compare finite element analysis and experiments of a thin plate with bonded piezoelectric material. Since an isotropic plate in combination with a thin piezoelectric layer constitutes a special case of a laminated composite, the classical laminated plate theory is used in the formulation to accommodated generic laminated composite panels with multiple bonded and embedded piezoelectric layers. Additionally, the von Karman large deflection plate theory is incorporated. The formulation results in laminate constitutive equations that are amiable to the inclusion of the piezoelectric constitutive equations yielding in a fully electro-mechanically coupled composite laminate. Using the finite element formulation, the governing differential equations of motion of a composite laminate with embedded piezoelectric layers are derived. The finite element model not only considers structural degrees of freedom (d.o.f.) but an additional electrical d.o.f. for each piezoelectric layer. Comparison between experiment and numerical prediction is performed by first treating the piezoelectric as a sensor and then again treating it as an actuator. To assess the piezoelectric layer as a sensor, various uniformly distributed pressure loads were simulated in the analysis and the corresponding generated voltages were calculated using both linear and nonlinear finite element analyses. Experiments were carried out by applying the same uniformly distributed loads and measuring the resulting generated voltages and corresponding maximum plate deflections. It is found that a highly nonlinear relationship exists between maximum deflection and voltage versus pressure loading. In order to assess comparisons of predicted and measured piezoelectric actuation, sinusoidal excitation voltages are simulated/applied and maximum deflections are calculated/measured. The maximum deflection as a function of time was determined using the linear finite elements analysis. Good correlation between prediction and measurement was achieved in all cases.

Implications of recent new concepts on the future of mainstream laser processing

NASA Astrophysics Data System (ADS)

La Rocca, Aldo V.

2000-07-01

According to one of today's most accepted visualizations of the first viable realizations of The Computer Integrated Manufacturing Plant, C.I.M.P., the manufacturing systems herein discussed tend to be multiprocessing, and tend to incorporate the lasers to take advantage of the unique capacities of the laser as a processing tool. Finally also the present laser sources, while having been for a long time more than sufficient, inevitably tend also to new generations. Said visualizations stand in the belief that the first realizations of the C I M P most likely will use flexible multiprocessing machines, which, for flexibility requirements, grow in multi-station cells, in their aggregation in isles and finally in complete manufacturing centers. To constitute the CIMP all partaking elements must be the most easily amenable to Computer Aided Design, CAD, and Computer Aided Manufacturing, CAM. Another basic requirement is that all elements constituting the CIMP must possess the highest System Efficiency and Energy Efficiency at the level of the single element and of its aggregations throughout the various combinations at each and every operating level of said aggregations, up to that of the CIMP. The mastering of the CIMP design constitute a New Discipline that presents very formidable but necessary tasks. Of these the first examples were those related to the early flexible manufacturing system Design Programs. For what concerns the laser processing machines and their integration in manufacturing systems, attention must be given to not repeat the events that hindered their diffusion in the production field keeping it at a level much lower than the expectations and their true potential. Said events stemmed from the confusion between System Efficiency and Energy Efficiency, which persisted for too long and is still common. This has taken place at the levels of introduction of a single element into the combination of the several elements constituting a linear arrangement such as a Transfer Production Line. It because greater and with graver consequences in the case of arrangements possessing more than one degree of product routings, arrangements, as previously mentioned, which evolved in the Flexible Manufacturing Centers.

Multiscale Modeling of Dewetting Damage in Highly Filled Particulate Composites

NASA Astrophysics Data System (ADS)

Geubelle, P. H.; Inglis, H. M.; Kramer, J. D.; Patel, J. J.; Kumar, N. C.; Tan, H.

2008-02-01

Particle debonding or dewetting constitutes one of the key damage processes in highly filled particulate composites such as solid propellant and other energetic materials. To analyze this failure process, we have developed a multiscale finite element framework that combines, at the microscale, a nonlinear description of the binder response with a cohesive model of the damage process taking place in a representative periodic unit cell (PUC). To relate micro-scale damage to the macroscopic constitutive response of the material, we employ the mathematical theory of homogenization (MTH). After a description of the numerical scheme, we present the results of the damage response of a highly filled particulate composite subjected to a uniaxial macroscopic strain, and show the direct correlation between the complex damage processes taking place in the PUC and the nonlinear macroscopic constitutive response. We also present a detailed study of the PUC size and a comparison between the finite element MTH-based study and a micromechanics model of the dewetting process.

Analytical modeling of structure-soil systems for lunar bases

NASA Technical Reports Server (NTRS)

Macari-Pasqualino, Jose Emir

1989-01-01

The study of the behavior of granular materials in a reduced gravity environment and under low effective stresses became a subject of great interest in the mid 1960's when NASA's Surveyor missions to the Moon began the first extraterrestrial investigation and it was found that Lunar soils exhibited properties quite unlike those on Earth. This subject gained interest during the years of the Apollo missions and more recently due to NASA's plans for future exploration and colonization of Moon and Mars. It has since been clear that a good understanding of the mechanical properties of granular materials under reduced gravity and at low effective stress levels is of paramount importance for the design and construction of surface and buried structures on these bodies. In order to achieve such an understanding it is desirable to develop a set of constitutive equations that describes the response of such materials as they are subjected to tractions and displacements. This presentation examines issues associated with conducting experiments on highly nonlinear granular materials under high and low effective stresses. The friction and dilatancy properties which affect the behavior of granular soils with low cohesion values are assessed. In order to simulate the highly nonlinear strength and stress-strain behavior of soils at low as well as high effective stresses, a versatile isotropic, pressure sensitive, third stress invariant dependent, cone-cap elasto-plastic constitutive model was proposed. The integration of the constitutive relations is performed via a fully implicit Backward Euler technique known as the Closest Point Projection Method. The model was implemented into a finite element code in order to study nonlinear boundary value problems associated with homogeneous as well as nonhomogeneous deformations at low as well as high effective stresses. The effect of gravity (self-weight) on the stress-strain-strength response of these materials is evaluated. The calibration of the model is performed via three techniques: (1) physical identification, (2) optimized calibration at the constitutive level, and (3) optimized calibration at the finite element level (Inverse Identification). Activities are summarized in graphic and outline form.

Coupled Hydro-Mechanical Constitutive Model for Vegetated Soils: Validation and Applications

NASA Astrophysics Data System (ADS)

Switala, Barbara Maria; Veenhof, Rick; Wu, Wei; Askarinejad, Amin

2016-04-01

It is well known, that presence of vegetation influences stability of the slope. However, the quantitative assessment of this contribution remains challenging. It is essential to develop a numerical model, which combines mechanical root reinforcement and root water uptake, and allows modelling rainfall induced landslides of vegetated slopes. Therefore a novel constitutive formulation is proposed, which is based on the modified Cam-clay model for unsaturated soils. Mechanical root reinforcement is modelled introducing a new constitutive parameter, which governs the evolution of the Cam-clay failure surface with the degree of root reinforcement. Evapotranspiration is modelled in terms of the root water uptake, defined as a sink term in the water flow continuity equation. The original concept is extended for different shapes of the root architecture in three dimensions, and combined with the mechanical model. The model is implemented in the research finite element code Comes-Geo, and in the commercial software Abaqus. The formulation is tested, performing a series of numerical examples, which allow validation of the concept. The direct shear test and the triaxial test are modelled in order to test the performance of the mechanical part of the model. In order to validate the hydrological part of the constitutive formulation, evapotranspiration from the vegetated box is simulated and compared with the experimental results. Obtained numerical results exhibit a good agreement with the experimental data. The implemented model is capable of reproducing results of basic geotechnical laboratory tests. Moreover, the constitutive formulation can be used to model rainfall induced landslides of vegetated slopes, taking into account the most important factors influencing the slope stability (root reinforcement and evapotranspiration).

The Constituent Elements of Comparative Education in Japan: A Comparison with North America

ERIC Educational Resources Information Center

Yamada, Shoko

2015-01-01

This article, with the aim of identifying elements that constitute the characteristics of an academic space within comparative education, analyzes how comparative education has been discussed and practiced in Japan, based on a questionnaire completed by 264 members of the Japan Comparative Education Society and classification of articles published…

Reference Manual for Machine-Readable Bibliographic Descriptions.

ERIC Educational Resources Information Center

Martin, M. D., Comp.

UNESCO, in cooperation with several other organizations, has produced a manual, the scope and purpose of which has been to define, for most types of scientific and technical literature, a set of data elements which will constitute an adequate bibliographic citation, and to define the representation of these data elements as they should appear in a…

Nanooptics for high efficient photon managment

NASA Astrophysics Data System (ADS)

Wyrowski, Frank; Schimmel, Hagen

2005-09-01

Optical systems for photon management, that is the generation of tailored electromagnetic fields, constitute one of the keys for innovation through photonics. An important subfield of photon management deals with the transformation of an incident light field into a field of specified intensity distribution. In this paper we consider some basic aspects of the nature of systems for those light transformations. It turns out, that the transversal redistribution of energy (TRE) is of central concern to achieve systems with high transformation efficiency. Besides established techniques nanostructured optical elements (NOE) are demanded to implement transversal energy redistribution. That builds a bridge between the needs of photon management, optical engineering, and nanooptics.

The American compensation phenomenon.

PubMed

Bale, A

1990-01-01

In this article, the author defines the occupational safety and health domain, characterizes the distinct compensation phenomenon in the United States, and briefly reviews important developments in the last decade involving Karen Silkwood, intentional torts, and asbestos litigation. He examines the class conflict over the value and meaning of work-related injuries and illnesses involved in the practical activity of making claims and turning them into money through compensation inquiries. Juries, attributions of fault, and medicolegal discourse play key roles in the compensation phenomenon. This article demonstrates the extensive, probing inquiry through workers' bodies constituted by the American compensation phenomenon into the moral basis of elements of the system of production.

The Thick Level-Set model for dynamic fragmentation

DOE PAGES

Stershic, Andrew J.; Dolbow, John E.; Moës, Nicolas

2017-01-04

The Thick Level-Set (TLS) model is implemented to simulate brittle media undergoing dynamic fragmentation. This non-local model is discretized by the finite element method with damage represented as a continuous field over the domain. A level-set function defines the extent and severity of damage, and a length scale is introduced to limit the damage gradient. Numerical studies in one dimension demonstrate that the proposed method reproduces the rate-dependent energy dissipation and fragment length observations from analytical, numerical, and experimental approaches. In conclusion, additional studies emphasize the importance of appropriate bulk constitutive models and sufficient spatial resolution of the length scale.

Translating Bourdieu: cultural capital and the English middle class in historical perspective.

PubMed

Gunn, Simon

2005-03-01

This article examines the ways in which Pierre Bourdieu's work on culture and cultural capital can be applied to the study of the English middle class in the nineteenth and twentieth centuries. Drawing on a wide historical literature, the article argues for the significance of culture as a constitutive element of middle-class identities in England since 1800. It goes on to examine Bourdieu's ideas of 'objectivated', 'instutionalized' and 'incorporated' cultural capital, in the context of family, inheritance, education and the body. The article identifies changes in the historical forms which cultural capital has taken and emphasizes the importance of analysing family processes of intergenerational transmission.

Small-amplitude acoustics in bulk granular media

NASA Astrophysics Data System (ADS)

Henann, David L.; Valenza, John J., II; Johnson, David L.; Kamrin, Ken

2013-10-01

We propose and validate a three-dimensional continuum modeling approach that predicts small-amplitude acoustic behavior of dense-packed granular media. The model is obtained through a joint experimental and finite-element study focused on the benchmark example of a vibrated container of grains. Using a three-parameter linear viscoelastic constitutive relation, our continuum model is shown to quantitatively predict the effective mass spectra in this geometry, even as geometric parameters for the environment are varied. Further, the model's predictions for the surface displacement field are validated mode-by-mode against experiment. A primary observation is the importance of the boundary condition between grains and the quasirigid walls.

Providers' gender and moral reasoning: a proposed agenda for research on providers and patients.

PubMed

Wertz, Dorothy C

1993-04-01

Women constitute 35% of providers in genetics, at the doctoral level. A survey of 682 geneticists in 19 nations showed that gender was the single most important determinant of ethical decision making. Women were less directive and more observant of patient autonomy than men. The future influx of women into medicine calls for research on provider gender and decisions. Research is also needed on women's and men's perceptions of abortion for genetic reasons, on extended families' views, on agreement between partners and on overall effectiveness of genetic counseling, including communication, elements of provider satisfaction, interpretation of risk and uncertainty after counseling.

Carbon exchange between the mantle and the crust and its effect upon the atmosphere: Today compared to Archean time

NASA Technical Reports Server (NTRS)

Desmarais, D.

1986-01-01

Paleobiologists now recognize that the Earth's biosphere has been profoundly affected by geologic processes. One very important process is the dissipation of heat which has been generated by radioactivity and/or stored within the earth. Heat flow is responsible for crustal movements and therefore it is the principal architect for constructing the environments (e.g. shallow marine, continental, etc.) wherein life developed and flourished. Heat flow has also influenced the movements of volatile elements (e.g. C, N, H, S, rare gases, etc.) both within the Earth's crust and between the crust and mantle. The inventory of these elements in the Earth's crust is important, not just because some of them constitute the building blocks of organic matter, but also because they influence the biosphere's climate. The purpose of this work is to evaluate how the decline of heat flow over the course of the Earth's history has influenced the carbon inventory in the Earth's crust. Such an evaluation must first consider whether the rate at which carbon is presently being exchanged between the mantle and crust is sufficient to play an important role in controlling the crustal inventory. Secondly, this exchange of carbon must be reevaluated in the context of the Precambrian Earth's environment. One very important consideration is that the upper mantle was perhaps 300 C hotter 3 b.y. ago than it is today.

A constitutive material model for nonlinear finite element structural analysis using an iterative matrix approach

NASA Technical Reports Server (NTRS)

Koenig, Herbert A.; Chan, Kwai S.; Cassenti, Brice N.; Weber, Richard

1988-01-01

A unified numerical method for the integration of stiff time dependent constitutive equations is presented. The solution process is directly applied to a constitutive model proposed by Bodner. The theory confronts time dependent inelastic behavior coupled with both isotropic hardening and directional hardening behaviors. Predicted stress-strain responses from this model are compared to experimental data from cyclic tests on uniaxial specimens. An algorithm is developed for the efficient integration of the Bodner flow equation. A comparison is made with the Euler integration method. An analysis of computational time is presented for the three algorithms.

Analysis of metal-matrix composite structures. I - Micromechanics constitutive theory. II - Laminate analyses

NASA Technical Reports Server (NTRS)

Arenburg, R. T.; Reddy, J. N.

1991-01-01

The micromechanical constitutive theory is used to examine the nonlinear behavior of continuous-fiber-reinforced metal-matrix composite structures. Effective lamina constitutive relations based on the Abouli micromechanics theory are presented. The inelastic matrix behavior is modeled by the unified viscoplasticity theory of Bodner and Partom. The laminate constitutive relations are incorporated into a first-order deformation plate theory. The resulting boundary value problem is solved by utilizing the finite element method. Attention is also given to computational aspects of the numerical solution, including the temporal integration of the inelastic strains and the spatial integration of bending moments. Numerical results the nonlinear response of metal matrix composites subjected to extensional and bending loads are presented.

Rare earth elements: end use and recyclability

USGS Publications Warehouse

Goonan, Thomas G.

2011-01-01

Rare earth elements are used in mature markets (such as catalysts, glassmaking, lighting, and metallurgy), which account for 59 percent of the total worldwide consumption of rare earth elements, and in newer, high-growth markets (such as battery alloys, ceramics, and permanent magnets), which account for 41 percent of the total worldwide consumption of rare earth elements. In mature market segments, lanthanum and cerium constitute about 80 percent of rare earth elements used, and in new market segments, dysprosium, neodymium, and praseodymium account for about 85 percent of rare earth elements used. Regardless of the end use, rare earth elements are not recycled in large quantities, but could be if recycling became mandated or very high prices of rare earth elements made recycling feasible.

Investigation of the Constitutive Model Used in Nonlinear, Incremental Structural Analyses.

DTIC Science & Technology

1998-06-01

package, ABAQUS , was chosen for performing NISA studies in part because user supplied subroutines could be used for constitutive relationships. After a...loading and the shrinkage and thermally induced strains determined from control specimens. The majority of creep tests are uniaxial compressive tests...Kennedy, and Perry (1970). Description of FE Model The tests were simulated using the finite element (FE) program ABAQUS and the aging viscoelastic

Worldwide distribution of transposable element copy number in natural populations of Drosophila simulans.

PubMed

Biémont, Christian; Nardon, Christiane; Deceliere, Grégory; Lepetit, David; Loevenbruck, Catherine; Vieira, Cristina

2003-01-01

Transposable elements (TEs), which promote various kinds of mutations, constitute a large fraction of the genome. How they invade natural populations and species is therefore of fundamental importance for understanding the dynamics of genetic diversity and genome composition. On the basis of 85 samples of natural populations of Drosophila simulans, we report the distributions of the genome insertion site numbers of nine TEs that were chosen because they have a low average number of sites. Most populations were found to have 0-3 insertion sites, but some of them had a significantly higher number of sites for a given TE. The populations located in regions outside Africa had the highest number of sites for all elements except HMS Beagle and Coral, suggesting a recent increase in the activity of some TEs associated with the colonization patterns of Drosophila simulans. The element Tirant had a very distinctive pattern of distribution: it was identified mainly in populations from East Africa and some islands in the Indian Ocean, and its insertion site number was low in all these populations. The data suggest that the genome of the entire species of Drosophila simulans may be being invaded by TEs from populations in which they are present in high copy number.

Exposures of dental professionals to elemental mercury and methylmercury.

PubMed

Goodrich, Jaclyn M; Chou, Hwai-Nan; Gruninger, Stephen E; Franzblau, Alfred; Basu, Niladri

2016-01-01

Mercury (Hg) exposure, a worldwide public health concern, predominantly takes two forms--methylmercury from fish consumption and elemental Hg from dental amalgam restorations. We recruited 630 dental professionals from an American Dental Association meeting to assess Hg body burden and primary sources of exposure in a dually exposed population. Participants described occupational practices and fish consumption patterns via questionnaire. Hg levels in biomarkers of elemental Hg (urine) and methylmercury (hair and blood) were measured with a Direct Mercury Analyzer-80 and were higher than the general US population. Geometric means (95% CI) were 1.28 (1.19-1.37) μg/l in urine, 0.60 (0.54-0.67) μg/g in hair and 3.67 (3.38-3.98) μg/l in blood. In multivariable linear regression, personal amalgams predicted urine Hg levels along with total years in dentistry, amalgams handled, working hours and sex. Fish consumption patterns predicted hair and blood Hg levels, which were higher among Asians compared with Caucasians. Five species contributed the majority of the estimated Hg intake from fish--swordfish, fresh tuna, white canned tuna, whitefish and king mackerel. When studying populations with occupational exposure to Hg, it is important to assess environmental exposures to both elemental Hg and methylmercury as these constitute a large proportion of total exposure.

Exposures of Dental Professionals to Elemental Mercury and Methylmercury

PubMed Central

Goodrich, Jaclyn M.; Chou, Hwai-Nan; Gruninger, Stephen E.; Franzblau, Alfred; Basu, Niladri

2015-01-01

Mercury (Hg) exposure, a worldwide public health concern, predominantly takes two forms – methylmercury from fish consumption and elemental Hg from dental amalgam restorations. We recruited 630 dental professionals from an American Dental Association meeting to assess Hg body burden and primary sources of exposure in a dually-exposed population. Participants described occupational practices and fish consumption patterns via questionnaire. Mercury levels in biomarkers of elemental Hg (urine) and methylmercury (hair, blood) were measured with a Direct Mercury Analyzer-80 and were higher than the general U.S. population. Geometric means (95% CI) were 1.28 (1.19–1.37) µg/L in urine, 0.60 (0.54–0.67) µg/g in hair, and 3.67 (3.38–3.98) µg/L in blood. In multivariable linear regression, personal amalgams predicted urine Hg levels along with total years in dentistry, amalgams handled, working hours, and sex. Fish consumption patterns predicted hair and blood Hg levels which were higher among Asians compared with Caucasians. Five species contributed the majority of the estimated Hg intake from fish - swordfish, fresh tuna, white canned tuna, whitefish, and king mackerel. When studying populations with occupational exposure to Hg, it is important to assess environmental exposures to both elemental Hg and methylmercury as these constitute a large proportion of total exposure. PMID:26329138

Extension and Validation of a Hybrid Particle-Finite Element Method for Hypervelocity Impact Simulation. Chapter 2

NASA Technical Reports Server (NTRS)

Fahrenthold, Eric P.; Shivarama, Ravishankar

2004-01-01

The hybrid particle-finite element method of Fahrenthold and Horban, developed for the simulation of hypervelocity impact problems, has been extended to include new formulations of the particle-element kinematics, additional constitutive models, and an improved numerical implementation. The extended formulation has been validated in three dimensional simulations of published impact experiments. The test cases demonstrate good agreement with experiment, good parallel speedup, and numerical convergence of the simulation results.

Bianisotropic metamaterial

DOEpatents

El-Kady, Ihab F.; Reinke, Charles M.

2017-07-18

The topology of the elements of a metamaterial can be engineered from its desired electromagnetic constitutive tensor using an inverse group theory method. Therefore, given a desired electromagnetic response and a generic metamaterial elemental design, group theory is applied to predict the various ways that the element can be arranged in three dimensions to produce the desired functionality. An optimizer can then be applied to an electromagnetic modeling tool to fine tune the values of the electromagnetic properties of the resulting metamaterial topology.

Radionuclide transfer to reptiles.

PubMed

Wood, Michael D; Beresford, Nicholas A; Semenov, Dmitry V; Yankovich, Tamara L; Copplestone, David

2010-11-01

Reptiles are an important, and often protected, component of many ecosystems but have rarely been fully considered within ecological risk assessments (ERA) due to a paucity of data on contaminant uptake and effects. This paper presents a meta-analysis of literature-derived environmental media (soil and water) to whole-body concentration ratios (CRs) for predicting the transfer of 35 elements (Am, As, B, Ba, Ca, Cd, Ce, Cm, Co, Cr, Cs, Cu, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Po, Pu, Ra, Rb, Sb, Se, Sr, Th, U, V, Y, Zn, Zr) to reptiles in freshwater ecosystems and 15 elements (Am, C, Cs, Cu, K, Mn, Ni, Pb, Po, Pu, Sr, Tc, Th, U, Zn) to reptiles in terrestrial ecosystems. These reptile CRs are compared with CRs for other vertebrate groups. Tissue distribution data are also presented along with data on the fractional mass of bone, kidney, liver and muscle in reptiles. Although the data were originally collected for use in radiation dose assessments, many of the CR data presented in this paper will also be useful for chemical ERA and for the assessments of dietary transfer in humans for whom reptiles constitute an important component of the diet, such as in Australian aboriginal communities.

Decision-making in product portfolios of pharmaceutical research and development – managing streams of innovation in highly regulated markets

PubMed Central

Jekunen, Antti

2014-01-01

Decision-making is a core function of any drug development firm. Developing drugs demands a firm to be highly innovative, while at the same time the activity is strictly regulated. Successful drug development offers the right to apply for a long-term patent that confers exclusive marketing rights. This article addresses the issue of what constitutes an adequate portfolio of drugs for a drug development firm and how it might be managed successfully. The paper investigates decision-making in the industry and specifically in the development of oncology drugs from various perspectives: the need for decisions, their timing, decision-making at the project level, the optimal portfolio, tools for portfolio analysis, the evaluation of patents, and finally the importance of the drug portfolio. Drug development decisions as important organizational elements should get more emphasis, and decisions in drug portfolio using modern decision-making methods should be used more widely than what currently happens. Structured, informed decisions would help avoiding late terminations of drugs in Phase III development. An improved research and development pipeline and drug portfolio management are the major elements in the general strategy targeting success. PMID:25364229

Decision-making in product portfolios of pharmaceutical research and development--managing streams of innovation in highly regulated markets.

PubMed

Jekunen, Antti

2014-01-01

Decision-making is a core function of any drug development firm. Developing drugs demands a firm to be highly innovative, while at the same time the activity is strictly regulated. Successful drug development offers the right to apply for a long-term patent that confers exclusive marketing rights. This article addresses the issue of what constitutes an adequate portfolio of drugs for a drug development firm and how it might be managed successfully. The paper investigates decision-making in the industry and specifically in the development of oncology drugs from various perspectives: the need for decisions, their timing, decision-making at the project level, the optimal portfolio, tools for portfolio analysis, the evaluation of patents, and finally the importance of the drug portfolio. Drug development decisions as important organizational elements should get more emphasis, and decisions in drug portfolio using modern decision-making methods should be used more widely than what currently happens. Structured, informed decisions would help avoiding late terminations of drugs in Phase III development. An improved research and development pipeline and drug portfolio management are the major elements in the general strategy targeting success.

Essential Medicines in National Constitutions: Progress Since 2008.

PubMed

Katrina Perehudoff, S; Toebes, Brigit; Hogerzeil, Hans

2016-06-01

A constitutional guarantee of access to essential medicines has been identified as an important indicator of government commitment to the progressive realization of the right to the highest attainable standard of health. The objective of this study was to evaluate provisions on access to essential medicines in national constitutions, to identify comprehensive examples of constitutional text on medicines that can be used as a model for other countries, and to evaluate the evolution of constitutional medicines-related rights since 2008. Relevant articles were selected from an inventory of constitutional texts from WHO member states. References to states' legal obligations under international human rights law were evaluated. Twenty-two constitutions worldwide now oblige governments to protect and/or to fulfill accessibility of, availability of, and/or quality of medicines. Since 2008, state responsibilities to fulfill access to essential medicines have expanded in five constitutions, been maintained in four constitutions, and have regressed in one constitution. Government commitments to essential medicines are an important foundation of health system equity and are included increasingly in state constitutions.

Essential Medicines in National Constitutions

PubMed Central

Toebes, Brigit; Hogerzeil, Hans

2016-01-01

Abstract A constitutional guarantee of access to essential medicines has been identified as an important indicator of government commitment to the progressive realization of the right to the highest attainable standard of health. The objective of this study was to evaluate provisions on access to essential medicines in national constitutions, to identify comprehensive examples of constitutional text on medicines that can be used as a model for other countries, and to evaluate the evolution of constitutional medicines-related rights since 2008. Relevant articles were selected from an inventory of constitutional texts from WHO member states. References to states’ legal obligations under international human rights law were evaluated. Twenty-two constitutions worldwide now oblige governments to protect and/or to fulfill accessibility of, availability of, and/or quality of medicines. Since 2008, state responsibilities to fulfill access to essential medicines have expanded in five constitutions, been maintained in four constitutions, and have regressed in one constitution. Government commitments to essential medicines are an important foundation of health system equity and are included increasingly in state constitutions. PMID:27781006

New microscale constitutive model of human trabecular bone based on depth sensing indentation technique.

PubMed

Pawlikowski, Marek; Jankowski, Krzysztof; Skalski, Konstanty

2018-05-30

A new constitutive model for human trabecular bone is presented in the present study. As the model is based on indentation tests performed on single trabeculae it is formulated in a microscale. The constitutive law takes into account non-linear viscoelasticity of the tissue. The elastic response is described by the hyperelastic Mooney-Rivlin model while the viscoelastic effects are considered by means of the hereditary integral in which stress depends on both time and strain. The material constants in the constitutive equation are identified on the basis of the stress relaxation tests and the indentation tests using curve-fitting procedure. The constitutive model is implemented into finite element package Abaqus ® by means of UMAT subroutine. The curve-fitting error is low and the viscoelastic behaviour of the tissue predicted by the proposed constitutive model corresponds well to the realistic response of the trabecular bone. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

The effects of fabric type, fabric width and model type on the cost of unit raw material in terms of apparel

NASA Astrophysics Data System (ADS)

Bilgiç, H.; Duru Baykal, P.

2017-10-01

The cost of the fabric which is the raw material of apparel constitutes approximately the half of the total product cost. So, it is highly important that the fabric should be used with the greatest productivity. Cost analysis are of great importance in terms of competitiveness of readymade clothing and apparel sector both in national and international markets. The proximity of costs to international average and the average cost of the countries that are competitors of Turkey in clothing market is essential for Turkey to sustain its effect in textile sector. In the contrary case, the sector won’t be able to maintain its competitive capacity sustainably [1].The main cost elements of textile and apparel sector consist of raw material, labor, energy and financing [2].

Characterization of the intronic portion of cadherin superfamily members, common cancer orchestrators

PubMed Central

Oliveira, Patrícia; Sanges, Remo; Huntsman, David; Stupka, Elia; Oliveira, Carla

2012-01-01

Cadherins are cell–cell adhesion proteins essential for the maintenance of tissue architecture and integrity, and their impairment is often associated with human cancer. Knowledge regarding regulatory mechanisms associated with cadherin misexpression in cancer is scarce. Specific features of the intronic-structure and intronic-based regulatory mechanisms in the cadherin superfamily are unidentified. This study aims at systematically characterizing the intronic portion of cadherin superfamily members and the identification of intronic regions constituting putative targets/triggers of regulation, using a bioinformatic approach and biological data mining. Our study demonstrates that the cadherin superfamily genes harbour specific characteristics in comparison to all non-cadherin genes, both from the genomic and transcriptional standpoints. Cadherin superfamily genes display higher average total intron number and significantly longer introns than other genes and across the entire vertebrate lineage. Moreover, in the human genome, we observed an uncommon high frequency of MIR (mammalian-wide interspersed repeats) and MaLR (mammalian-wide interspersed repeats, a subtype of LTR) regulatory-associated repetitive elements at 5′-located introns, concomitantly with increased de novo intronic transcription. Using this approach, we identified cadherin intronic-specific sites that may constitute novel targets/triggers of cadherin superfamily expression regulation. These findings pinpoint the need to identify mechanisms affecting particularly MIR and MaLR elements located in introns 2 and 3 of human cadherin genes, possibly important in the expression modulation of this superfamily in homeostasis and cancer. PMID:22317972

Habsburg Austria: Experiments in Non-Territorial Autonomy

PubMed Central

Kuzmany, Börries

2016-01-01

Abstract In the early twentieth century, three provinces of the Austrian half of the Habsburg Empire enacted national compromises in their legislation that had elements of non-territorial autonomy provisions. Czech and German politicians in Moravia reached an agreement in 1905. In the heavily mixed Bukovina, Romanian, Ukrainian, German, Jewish and Polish representatives agreed on a new provincial constitution in 1909. Last but not least, Polish and Ukrainian nationalists compromised in spring 1914, just a few months before the outbreak of the First World War vitiated the new provisions. Even though the provisions of these agreements varied substantially, new electoral laws introducing national registers were at their heart. These were designed to ensure a fairer representation of national groups in the provincial assemblies and to keep national agitation out of electoral campaigns. The earliest compromise in Moravia went furthest in consociational power sharing. However, the national bodies within the provincial assembly had no right to tax their respective national communities, and the provisions of the provincial constitutions kept the non-nationally defined nobility as an important counterbalance. The compromises in Bukovina and Galicia, even if they categorised all inhabitants nationally, contented themselves with even less autonomous agency for the national bodies in the provincial assemblies and rather emphasised the symbolic elements of national autonomy. The non-territorial approach in all three crownlands, however, was an instrument to reorganise multi-ethnic provinces that increasingly became the model for national compromises in other Austrian provinces. PMID:27499799

Towards the stabilization of the low density elements in topology optimization with large deformation

NASA Astrophysics Data System (ADS)

Lahuerta, Ricardo Doll; Simões, Eduardo T.; Campello, Eduardo M. B.; Pimenta, Paulo M.; Silva, Emilio C. N.

2013-10-01

This work addresses the treatment of lower density regions of structures undergoing large deformations during the design process by the topology optimization method (TOM) based on the finite element method. During the design process the nonlinear elastic behavior of the structure is based on exact kinematics. The material model applied in the TOM is based on the solid isotropic microstructure with penalization approach. No void elements are deleted and all internal forces of the nodes surrounding the void elements are considered during the nonlinear equilibrium solution. The distribution of design variables is solved through the method of moving asymptotes, in which the sensitivity of the objective function is obtained directly. In addition, a continuation function and a nonlinear projection function are invoked to obtain a checkerboard free and mesh independent design. 2D examples with both plane strain and plane stress conditions hypothesis are presented and compared. The problem of instability is overcome by adopting a polyconvex constitutive model in conjunction with a suggested relaxation function to stabilize the excessive distorted elements. The exact tangent stiffness matrix is used. The optimal topology results are compared to the results obtained by using the classical Saint Venant-Kirchhoff constitutive law, and strong differences are found.

Micromechanics and constitutive models for soft active materials with phase evolution

NASA Astrophysics Data System (ADS)

Wang, Binglian

Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.

A new constitutive analysis of hexagonal close-packed metal in equal channel angular pressing by crystal plasticity finite element method

NASA Astrophysics Data System (ADS)

Li, Hejie; Öchsner, Andreas; Yarlagadda, Prasad K. D. V.; Xiao, Yin; Furushima, Tsuyoshi; Wei, Dongbin; Jiang, Zhengyi; Manabe, Ken-ichi

2018-01-01

Most of hexagonal close-packed (HCP) metals are lightweight metals. With the increasing application of light metal products, the production of light metal is increasingly attracting the attentions of researchers worldwide. To obtain a better understanding of the deformation mechanism of HCP metals (especially for Mg and its alloys), a new constitutive analysis was carried out based on previous research. In this study, combining the theories of strain gradient and continuum mechanics, the equal channel angular pressing process is analyzed and a HCP crystal plasticity constitutive model is developed especially for Mg and its alloys. The influence of elevated temperature on the deformation mechanism of the Mg alloy (slip and twin) is novelly introduced into a crystal plasticity constitutive model. The solution for the new developed constitutive model is established on the basis of the Lagrangian iterations and Newton Raphson simplification.

Generalized constitutive equations for piezo-actuated compliant mechanism

NASA Astrophysics Data System (ADS)

Cao, Junyi; Ling, Mingxiang; Inman, Daniel J.; Lin, Jin

2016-09-01

This paper formulates analytical models to describe the static displacement and force interactions between generic serial-parallel compliant mechanisms and their loads by employing the matrix method. In keeping with the familiar piezoelectric constitutive equations, the generalized constitutive equations of compliant mechanism represent the input-output displacement and force relations in the form of a generalized Hooke’s law and as analytical functions of physical parameters. Also significantly, a new model of output displacement for compliant mechanism interacting with piezo-stacks and elastic loads is deduced based on the generalized constitutive equations. Some original findings differing from the well-known constitutive performance of piezo-stacks are also given. The feasibility of the proposed models is confirmed by finite element analysis and by experiments under various elastic loads. The analytical models can be an insightful tool for predicting and optimizing the performance of a wide class of compliant mechanisms that simultaneously consider the influence of loads and piezo-stacks.

Research on the interfacial behaviors of plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Wang, Qiming; Yan, Xiaoqing; Ding, Shurong; Huo, Yongzhong

2010-04-01

The three-dimensional constitutive relations are constructed, respectively, for the fuel particles, the metal matrix and the cladding of dispersion nuclear fuel elements, allowing for the effects of large deformation and thermal-elastoplasticity. According to the constitutive relations, the method of modeling their irradiation behaviors in ABAQUS is developed and validated. Numerical simulations of the interfacial performances between the fuel meat and the cladding are implemented with the developed finite element models for different micro-structures of the fuel meat. The research results indicate that: (1) the interfacial tensile stresses and shear stresses for some cases will increase with burnup, but the relative stresses will decrease with burnup for some micro-structures; (2) at the lower burnups, the interfacial stresses increase with the particle sizes and the particle volume fractions; however, it is not the case at the higher burnups; (3) the particle distribution characteristics distinctly affect the interfacial stresses, and the face-centered cubic case has the best interfacial performance of the three considered cases.

Interplay between DNA methylation, histone modification and chromatin remodeling in stem cells and during development.

PubMed

Ikegami, Kohta; Ohgane, Jun; Tanaka, Satoshi; Yagi, Shintaro; Shiota, Kunio

2009-01-01

Genes constitute only a small proportion of the mammalian genome, the majority of which is composed of non-genic repetitive elements including interspersed repeats and satellites. A unique feature of the mammalian genome is that there are numerous tissue-dependent, differentially methylated regions (T-DMRs) in the non-repetitive sequences, which include genes and their regulatory elements. The epigenetic status of T-DMRs varies from that of repetitive elements and constitutes the DNA methylation profile genome-wide. Since the DNA methylation profile is specific to each cell and tissue type, much like a fingerprint, it can be used as a means of identification. The formation of DNA methylation profiles is the basis for cell differentiation and development in mammals. The epigenetic status of each T-DMR is regulated by the interplay between DNA methyltransferases, histone modification enzymes, histone subtypes, non-histone nuclear proteins and non-coding RNAs. In this review, we will discuss how these epigenetic factors cooperate to establish cell- and tissue-specific DNA methylation profiles.

The MHOST finite element program: 3-D inelastic analysis methods for hot section components. Volume 2: User's manual

NASA Technical Reports Server (NTRS)

Nakazawa, Shohei

1989-01-01

The user options available for running the MHOST finite element analysis package is described. MHOST is a solid and structural analysis program based on the mixed finite element technology, and is specifically designed for 3-D inelastic analysis. A family of 2- and 3-D continuum elements along with beam and shell structural elements can be utilized, many options are available in the constitutive equation library, the solution algorithms and the analysis capabilities. The outline of solution algorithms is discussed along with the data input and output, analysis options including the user subroutines and the definition of the finite elements implemented in the program package.

The New Element Berkelium (Atomic Number 97)

DOE R&D Accomplishments Database

Seaborg, G. T.; Thompson, S. G.; Ghiorso, A.

1950-04-26

An isotope of the element with atomic number 97 has been discovered as a product of the helium-ion bombardment of americium. The name berkelium, symbol Bk, is proposed for element 97. The chemical separation of element 97 from the target material and other reaction products was made by combinations of precipitation and ion exchange adsorption methods making use of its anticipated (III) and (IV) oxidation states and its position as a member of the actinide transition series. The distinctive chemical properties made use of in its separation and the equally distinctive decay properties of the particular isotope constitute the principal evidence for the new element.

MpSaci is a widespread gypsy-Ty3 retrotransposon highly represented by non-autonomous copies in the Moniliophthora perniciosa genome.

PubMed

Pereira, Jorge F; Araújo, Elza F; Brommonschenkel, Sérgio H; Queiroz, Casley B; Costa, Gustavo G L; Carazzolle, Marcelo F; Pereira, Gonçalo A G; Queiroz, Marisa V

2015-05-01

Transposons are an important source of genetic variation. The phytopathogen Moniliophthora perniciosa shows high level of variability but little is known about the role of class I elements in shaping its genome. In this work, we aimed the characterization of a new gypsy/Ty3 retrotransposon species, named MpSaci, in the M. perniciosa genome. These elements are largely variable in size, ranging from 4 to 15 kb, and harbor direct long terminal repeats (LTRs) with varying degrees of similarity. Approximately, all of the copies are non-autonomous as shifts in the reading frame and stop codons were detected. Only two elements (MpSaci6 and MpSaci9) code for GAG and POL proteins that possess functional domains. Conserved domains that are typically not found in retrotransposons were detected and could potentially impact the expression of neighbor genes. Solo LTRs and several LARDs (large retrotransposon derivative) were detected. Unusual elements containing small sequences with or without interruptions that are similar to gag or different pol domains and presenting LTRs with different levels of similarities were identified. Methylation was observed in MpSaci reverse transcriptase sequences. Distribution analysis indicates that MpSaci elements are present in high copy number in the genomes of C-, S- and L-biotypes of M. perniciosa. In addition, C-biotype isolates originating from the state of Bahia have fragments in common with isolates from the Amazon region and two hybridization profiles related to two chromosomal groups. RT-PCR analysis reveals that the gag gene is constitutively expressed and that the expression is increased at least three-fold with nutrient depravation even though no new insertion were observed. These findings point out that MpSaci collaborated and, even though is primarily represented by non-autonomous elements, still might contribute to the generation of genetic variability in the most important cacao pathogen in Brazil.

Numerical Simulation of Delamination Growth in Composite Materials

NASA Technical Reports Server (NTRS)

Camanho, P. P.; Davila, C. G.; Ambur, D. R.

2001-01-01

The use of decohesion elements for the simulation of delamination in composite materials is reviewed. The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially. After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion elements is described. Problems related with decohesion element constitutive equations, mixed-mode crack growth, element numerical integration and solution procedures are discussed. Based on these investigations, it is concluded that the use of interfacial decohesion elements is a promising technique that avoids the need for a pre-existing crack and pre-defined crack paths, and that these elements can be used to simulate both delamination onset and growth.

A new constitutive model for simulation of softening, plateau, and densification phenomena for trabecular bone under compression.

PubMed

Lee, Chi-Seung; Lee, Jae-Myung; Youn, BuHyun; Kim, Hyung-Sik; Shin, Jong Ki; Goh, Tae Sik; Lee, Jung Sub

2017-01-01

A new type of constitutive model and its computational implementation procedure for the simulation of a trabecular bone are proposed in the present study. A yield surface-independent Frank-Brockman elasto-viscoplastic model is introduced to express the nonlinear material behavior such as softening beyond yield point, plateau, and densification under compressive loads. In particular, the hardening- and softening-dominant material functions are introduced and adopted in the plastic multiplier to describe each nonlinear material behavior separately. In addition, the elasto-viscoplastic model is transformed into an implicit type discrete model, and is programmed as a user-defined material subroutine in commercial finite element analysis code. In particular, the consistent tangent modulus method is proposed to improve the computational convergence and to save computational time during finite element analysis. Through the developed material library, the nonlinear stress-strain relationship is analyzed qualitatively and quantitatively, and the simulation results are compared with the results of compression test on the trabecular bone to validate the proposed constitutive model, computational method, and material library. Copyright © 2016 Elsevier Ltd. All rights reserved.

Possibilities of rock constitutive modelling and simulations

NASA Astrophysics Data System (ADS)

Baranowski, Paweł; Małachowski, Jerzy

2018-01-01

The paper deals with a problem of rock finite element modelling and simulation. The main intention of authors was to present possibilities of different approaches in case of rock constitutive modelling. For this purpose granite rock was selected, due to its wide mechanical properties recognition and prevalence in literature. Two significantly different constitutive material models were implemented to simulate the granite fracture in various configurations: Johnson - Holmquist ceramic model which is very often used for predicting rock and other brittle materials behavior, and a simple linear elastic model with a brittle failure which can be used for simulating glass fracturing. Four cases with different loading conditions were chosen to compare the aforementioned constitutive models: uniaxial compression test, notched three-point-bending test, copper ball impacting a block test and small scale blasting test.

A continuum thermo-inelastic model for damage and healing in self-healing glass materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Wei; Sun, Xin; Koeppel, Brian J.

Self-healing glass, a recent advancement in the class of smart sealing materials, has attracted great attention from both research and industrial communities because of its unique capability of repairing itself at elevated temperatures. However, further development and optimization of this material rely on a more fundamental and thorough understanding of its essential thermo-mechanical response characteristics, which is also pivotal in predicting the coupling and interactions between the nonlinear stress and temperature dependent damage and healing behaviors. In the current study, a continuum three-dimensional thermo-inelastic damage-healing constitutive framework has been developed for the compliant self-healing glass material. The important feature ofmore » the present model is that various phenomena governing the mechanical degradation and recovery process, i.e. the nucleation, growth, and healing of the cracks and pores, are described with distinct mechanism-driven kinetics, where the healing constitutive relations are propagated from lower-length scale simulations. The proposed formulations are implemented into finite element analyses and the effects of various loading conditions and material properties on the material’s mechanical resistance are investigated.« less

A microstructurally based model of solder joints under conditions of thermomechanical fatigue

NASA Astrophysics Data System (ADS)

Frear, D. R.; Burchett, S. N.; Rashid, M. M.

The thermomechanical fatigue failure of solder joints is increasingly becoming an important reliability issue. We present two computational methodologies that have been developed to predict the behavior of near eutectic Sn-Pb solder joints under fatigue conditions that are based on metallurgical tests as fundamental input for constitutive relations. The two-phase model mathematically predicts the heterogeneous coarsening behavior of near eutectic Sn-Pb solder. The finite element simulations from this model agree well with experimental thermomechanical fatigue tests. The simulations show that the presence of an initial heterogeneity in the solder microstructure could significantly degrade the fatigue lifetime. The single phase model is a computational technique that was developed to predict solder joint behavior using materials data for constitutive relation constants that could be determined through straightforward metallurgical experiments. A shear/torsion test sample was developed to impose strain in two different orientations. Materials constants were derived from these tests and the results showed an adequate fit to experimental results. The single-phase model could be very useful for conditions where microstructural evolution is not a dominant factor in fatigue.

Astrophysical materials science: Theory

NASA Technical Reports Server (NTRS)

Ashcroft, N. W.

1978-01-01

Research papers of the discoveries and work carried out over the past six or so years are presented. Hydrogen and helium constitute by far the most abundant of the elements and it is no accident that the research has focussed heavily on these elements in their condensed forms, both as pure substances and in mixtures. The research has combined the fundamental with the pragmatic.

Preservice Teachers' Use of Spatio-Visual Elements and their Level of Justification Dealing with a Geometrical Construction Problem

ERIC Educational Resources Information Center

Tapan, Menekse Seden; Arslan, Cigdem

2009-01-01

The main purpose of this research is to determine to what extent preservice teachers use visual elements and mathematical properties when they are dealing with a geometrical construction activity. The axiomatic structure of the Euclidian geometry forms a coherent field of objects and relations of a theoretical nature; and thus it constitutes a…

Failure Prediction in Fiber Metal Laminates for Next Generation Aero Materials

NASA Astrophysics Data System (ADS)

Jeevan Rao, H.; Janaki Ramulu, Perumalla; Vishnu Vardhan, M.; Chandramouli, CH

2016-09-01

In aerospace industry, there is huge demand for low density and low cost materials with better mechanical properties. In this view, there are many researchers developed new materials interms of composites. Similar manner, the present paper also aimed to produce a new approach for cost effective materials of 3D weaved glass fiber metal laminates (FML) with different compositions using a numerical study. A method for the simulation of progressive delamination based on de-cohesion elements has been presented. De-cohesion elements are placed between layers of solid elements that open and shear in response to the loading situation. The onset of damage and the growth of delamination are simulated without previous knowledge about the location, the size, or the direction of propagation of the de-laminations. A softening law for mixed-mode delamination that can be applied to any interaction criterion is also proposed. The constitutive equation proposed uses a single variable, the maximum relative displacement, to track the damage at the interface under general loading conditions. The material properties required to define the element constitutive equation are the inter-laminar fracture toughness's, the penalty stiffness, and the strengths.

Building community resilience: what can the United States learn from experiences in other countries?

PubMed

Moore, Melinda; Chandra, Anita; Feeney, Kevin C

2013-06-01

Community resilience (CR) is emerging as a major public policy priority within disaster management and is one of two key pillars of the December 2009 US National Health Security Strategy. However, there is no clear agreement on what key elements constitute CR. We examined exemplary practices from international disaster management to validate the elements of CR, as suggested by Homeland Security Presidential Directive 21 (HSPD-21), to potentially identify new elements and to identify practices that could be emulated or adapted to help build CR. We extracted detailed information relevant to CR from unpublished case studies we had developed previously, describing exemplary practices from international natural disasters occurring between 1985 and 2005. We then mapped specific practices against the five elements of CR suggested by HSPD-21. We identified 49 relevant exemplary practices from 11 natural disasters in 10 countries (earthquakes in Mexico, India, and Iran; volcanic eruption in Philippines; hurricanes in Honduras and Cuba; floods in Bangladesh, Vietnam, and Mozambique; tsunami in Indian Ocean countries; and typhoon in Vietnam). Of these, 35 mapped well against the five elements of CR: community education, community empowerment, practice, social networks, and familiarity with local services; 15 additional practices were related to physical security and economic security. The five HSPD-21 CR elements and two additional ones we identified were closely related to one another; social networks were especially important to CR. While each disaster is unique, the elements of CR appear to be broadly applicable across countries and disaster settings. Our descriptive study provides retrospective empirical evidence that helps validate, and adds to, the elements of CR suggested by HSPD-21. It also generates hypotheses about factors contributing to CR that can be tested in future analytic or experimental research.

Simulating Progressive Damage of Notched Composite Laminates with Various Lamination Schemes

NASA Astrophysics Data System (ADS)

Mandal, B.; Chakrabarti, A.

2017-05-01

A three dimensional finite element based progressive damage model has been developed for the failure analysis of notched composite laminates. The material constitutive relations and the progressive damage algorithms are implemented into finite element code ABAQUS using user-defined subroutine UMAT. The existing failure criteria for the composite laminates are modified by including the failure criteria for fiber/matrix shear damage and delamination effects. The proposed numerical model is quite efficient and simple compared to other progressive damage models available in the literature. The efficiency of the present constitutive model and the computational scheme is verified by comparing the simulated results with the results available in the literature. A parametric study has been carried out to investigate the effect of change in lamination scheme on the failure behaviour of notched composite laminates.

Investigation on Bond-Slip Behavior of Z-Pin Interfaces in X-Cor® Sandwich Structures Using Z-Pin Pull-Out Test

NASA Astrophysics Data System (ADS)

Shan, Hangying; Xiao, Jun; Chu, Qiyi

2018-05-01

The Z-Pin interfacial bond properties play an important role in the structural performance of X-Cor® sandwich structures. This paper presents an experimental investigation on bond-slip behavior of Z-Pin interfaces using Z-Pin pull-out test. Based on the experimental data the whole Z-Pin pull-out process consists of three stages: initial bonding, debonding and frictional sliding. Comparative experimental study on the influence of design parameters on bond-slip behavior of Z-Pin interfaces has also been performed. Numerical analyses were conducted with the ABAQUS finite element (FE) program to simulate the Z-Pins bond-slip response of the pull-out test. The Z-Pins interfacial bond-slip behavior was implemented using nonlinear spring elements characterized with the constitutive relation from experimental results. Numerical results were validated by comparison with experimental data, and reasonably good agreement was achieved between experimental and analytical pull-out force-slip curves.

Active and inactive enhancers co-operate to exert localized and long-range control of gene regulation

PubMed Central

Proudhon, Charlotte; Snetkova, Valentina; Raviram, Ramya; Lobry, Camille; Badri, Sana; Jiang, Tingting; Hao, Bingtao; Trimarchi, Thomas; Kluger, Yuval; Aifantis, Iannis; Bonneau, Richard; Skok, Jane A

2016-01-01

V(D)J recombination relies on the presence of proximal enhancers that activate the antigen receptor (AgR) loci in a lineage and stage specific manner. Unexpectedly we find that both active and inactive AgR enhancers co-operate to disseminate their effects in a localized and long-range manner. Here we demonstrate the importance of short-range contacts between active enhancers that constitute an Igk super-enhancer in B cells. Deletion of one element reduces the interaction frequency between other enhancers in the hub, which compromises the transcriptional output of each component. We further establish that in T cells long-range contact and co-operation between the inactive Igk enhancer, MiEκ and the active Tcrb enhancer, Eβ, alters enrichment of CBFβ binding in a manner that impacts Tcrb recombination. These findings underline the complexities of enhancer regulation and point to a role for localized and long-range enhancer-sharing between active and inactive elements in lineage and stage specific control. PMID:27239026

A numerical study on the influence of the Portevin Le Chatelier effect on necking in an aluminium alloy

NASA Astrophysics Data System (ADS)

Hopperstad, O. S.; Børvik, T.; Berstad, T.; Lademo, O.-G.; Benallal, A.

2007-10-01

The constitutive relation proposed by McCormick (1988 Acta Metall. 36 3061-7) for materials exhibiting negative steady-state strain-rate sensitivity and the Portevin-Le Chatelier (PLC) effect is incorporated into an elastic-viscoplastic model for metals with plastic anisotropy. The constitutive model is implemented in LS-DYNA for corotational shell elements. Plastic anisotropy is taken into account by use of the yield criterion Yld2000/Yld2003 proposed by Barlat et al (2003 J. Plast. 19 1297-319) and Aretz (2004 Modelling Simul. Mater. Sci. Eng. 12 491-509). The parameters of the constitutive equations are determined for a rolled aluminium alloy (AA5083-H116) exhibiting negative steady-state strain-rate sensitivity and serrated yielding. The parameter identification is based on existing experimental data. A numerical investigation is conducted to determine the influence of the PLC effect on the onset of necking in uniaxial and biaxial tension for different overall strain rates. The numerical simulations show that the PLC effect leads to significant reductions in the strain to necking for both uniaxial and biaxial stress states. Increased surface roughness with plastic deformation is predicted for strain rates giving serrated yielding in uniaxial tension. It is likely that this is an important reason for the reduced critical strains. The characteristics of the deformation bands (orientation, width, velocity and strain rate) are also studied.

Invariant Theory for Dispersed Transverse Isotropy: An Efficient Means for Modeling Fiber Splay

NASA Technical Reports Server (NTRS)

Freed, alan D.; Einstein, Daniel R.; Vesely, Ivan

2004-01-01

Most soft tissues possess an oriented architecture of collagen fiber bundles, conferring both anisotropy and nonlinearity to their elastic behavior. Transverse isotropy has often been assumed for a subset of these tissues that have a single macroscopically-identifiable preferred fiber direction. Micro-structural studies, however, suggest that, in some tissues, collagen fibers are approximately normally distributed about a mean preferred fiber direction. Structural constitutive equations that account for this dispersion of fibers have been shown to capture the mechanical complexity of these tissues quite well. Such descriptions, however, are computationally cumbersome for two-dimensional (2D) fiber distributions, let alone for fully three-dimensional (3D) fiber populations. In this paper, we develop a new constitutive law for such tissues, based on a novel invariant theory for dispersed transverse isotropy. The invariant theory is based on a novel closed-form splay invariant that can easily handle 3D fiber populations, and that only requires a single parameter in the 2D case. The model is polyconvex and fits biaxial data for aortic valve tissue as accurately as the standard structural model. Modification of the fiber stress-strain law requires no re-formulation of the constitutive tangent matrix, making the model flexible for different types of soft tissues. Most importantly, the model is computationally expedient in a finite-element analysis.

Micromechanics Analysis Code (MAC) User Guide: Version 1.0

NASA Technical Reports Server (NTRS)

Wilt, T. E.; Arnold, S. M.

1994-01-01

The ability to accurately predict the thermomechanical deformation response of advanced composite materials continues to play an important role in the development of these strategic materials. Analytical models that predict the effective behavior of composites are used not only by engineers performing structural analysis of large-scale composite components but also by material scientists in developing new material systems. For an analytical model to fulfill these two distinct functions it must be based on a micromechanics approach which utilizes physically based deformation and life constitutive models and allows one to generate the average (macro) response of a composite material given the properties of the individual constituents and their geometric arrangement. Here the user guide for the recently developed, computationally efficient and comprehensive micromechanics analysis code, MAC, who's predictive capability rests entirely upon the fully analytical generalized method of cells, GMC, micromechanics model is described. MAC is a versatile form of research software that 'drives' the double or triple ply periodic micromechanics constitutive models based upon GMC. MAC enhances the basic capabilities of GMC by providing a modular framework wherein (1) various thermal, mechanical (stress or strain control), and thermomechanical load histories can be imposed; (2) different integration algorithms may be selected; (3) a variety of constituent constitutive models may be utilized and/or implemented; and (4) a variety of fiber architectures may be easily accessed through their corresponding representative volume elements.

Micromechanics Analysis Code (MAC). User Guide: Version 2.0

NASA Technical Reports Server (NTRS)

Wilt, T. E.; Arnold, S. M.

1996-01-01

The ability to accurately predict the thermomechanical deformation response of advanced composite materials continues to play an important role in the development of these strategic materials. Analytical models that predict the effective behavior of composites are used not only by engineers performing structural analysis of large-scale composite components but also by material scientists in developing new material systems. For an analytical model to fulfill these two distinct functions it must be based on a micromechanics approach which utilizes physically based deformation and life constitutive models and allows one to generate the average (macro) response of a composite material given the properties of the individual constituents and their geometric arrangement. Here the user guide for the recently developed, computationally efficient and comprehensive micromechanics analysis code's (MAC) who's predictive capability rests entirely upon the fully analytical generalized method of cells (GMC), micromechanics model is described. MAC is a versatile form of research software that 'drives' the double or triply periodic micromechanics constitutive models based upon GMC. MAC enhances the basic capabilities of GMC by providing a modular framework wherein (1) various thermal, mechanical (stress or strain control) and thermomechanical load histories can be imposed, (2) different integration algorithms may be selected, (3) a variety of constituent constitutive models may be utilized and/or implemented, and (4) a variety of fiber and laminate architectures may be easily accessed through their corresponding representative volume elements.

Targeting chromatin binding regulation of constitutively active AR variants to overcome prostate cancer resistance to endocrine-based therapies

PubMed Central

Chan, Siu Chiu; Selth, Luke A.; Li, Yingming; Nyquist, Michael D.; Miao, Lu; Bradner, James E.; Raj, Ganesh V.; Tilley, Wayne D.; Dehm, Scott M.

2015-01-01

Androgen receptor (AR) variants (AR-Vs) expressed in prostate cancer (PCa) lack the AR ligand binding domain (LBD) and function as constitutively active transcription factors. AR-V expression in patient tissues or circulating tumor cells is associated with resistance to AR-targeting endocrine therapies and poor outcomes. Here, we investigated the mechanisms governing chromatin binding of AR-Vs with the goal of identifying therapeutic vulnerabilities. By chromatin immunoprecipitation and sequencing (ChIP-seq) and complementary biochemical experiments, we show that AR-Vs display a binding preference for the same canonical high-affinity androgen response elements (AREs) that are preferentially engaged by AR, albeit with lower affinity. Dimerization was an absolute requirement for constitutive AR-V DNA binding and transcriptional activation. Treatment with the bromodomain and extraterminal (BET) inhibitor JQ1 resulted in inhibition of AR-V chromatin binding and impaired AR-V driven PCa cell growth in vitro and in vivo. Importantly, this was associated with a novel JQ1 action of down-regulating AR-V transcript and protein expression. Overall, this study demonstrates that AR-Vs broadly restore AR chromatin binding events that are otherwise suppressed during endocrine therapy, and provides pre-clinical rationale for BET inhibition as a strategy for inhibiting expression and chromatin binding of AR-Vs in PCa. PMID:25908785

Bioprosthetic heart valve heterograft biomaterials: structure, mechanical behavior and computational simulation.

PubMed

Sacks, Michael S; Mirnajafi, Ali; Sun, Wei; Schmidt, Paul

2006-11-01

The present review surveys significant developments in the biomechanical characterization and computational simulation of biologically derived chemically cross-linked soft tissues, or 'heterograft' biomaterials, used in replacement bioprosthetic heart valve (BHV). A survey of mechanical characterization techniques, relevant mechanical properties and computational simulation approaches is presented for both the source tissues and cross-linked biomaterials. Since durability remains the critical problem with current bioprostheses, changes with the mechanical behavior with fatigue are also presented. Moreover, given the complex nature of the mechanical properties of heterograft biomaterials it is not surprising that most constitutive (stress-strain) models, historically used to characterize their behavior, were oversimplified. Simulations of BHV function utilizing these models have inevitably been inaccurate. Thus, more recent finite element simulations utilizing nonlinear constitutive models, which achieve greater model fidelity, are reviewed. An important conclusion of this review is the need for accurate constitutive models, rigorously validated with appropriate experimental data, in order that the design benefits of computational models can be realized. Finally, for at least the coming 20 years, BHVs fabricated from heterograft biomaterials will continue to be extensively used, and will probably remain as the dominant valve design. We should thus recognize that rational, scientifically based approaches to BHV biomaterial development and design can lead to significantly improved BHV, over the coming decades, which can potentially impact millions of patients worldwide with heart valve disease.

MHOST version 4.2. Volume 1: Users' manual

NASA Technical Reports Server (NTRS)

Nakazawa, Shohei

1989-01-01

This manual describes the user options available for running the MHOST finite element analysis package. MHOST is a solid and structural analysis program based on mixed finite element technology, and is specifically designed for three-dimensional inelastic analysis. A family of two- and three-dimensional continuum elements along with beam and shell structural elements can be utilized. Many options are available in the constitutive equation library, the solution algorithms and the analysis capabilities. An overview of the algorithms, a general description of the input data formats, and a discussion of input data for selecting solution algorithms are given.

[Comparative research into the process of forming the theory of constitution in ancient western medicine and that of four trigrams constitution in Korean medicine and contents of two theories of constitution].

PubMed

Park, Joo-Hong

2009-06-01

After conducting comparative research into the process of forming the Theory of Constitution in Ancient Western Medicine and that of Four Trigrams Constitution(Sasang Constitution) in Korean Medicine and contents of two Theories of Constitution in terms of medical history, both theories were found to be formed by an interaction between philosophy and medicine, followed by a combination of the two, on a philosophical basis. The Theory of Constitution in Ancient Western Medicine began with the Theory of Four Elements presented by Empedocles, followed by the Theory of Four Humors presented by Hippocrates and the Theory of Four Temperaments by Galenos, forming and developing the Theory of Constitution. After the Middle Ages, there was no significant advance in the Theory of Constitution by modern times ; however, it developed into the theory of constitution type of Kretschmer and others after the 19th century and into the scientific theory of constitution based on genetics presented by Garrod and others early in the 20th century. The Theory of Four Trigrams Constitution began with the Theory of Constitution in Huangdi Neijing, followed by developments and influences of existing medicine called beginning, restoration, and revival periods and DongeuisoosebowonSaSangChoBonGwon based on the original philosophy of Four Trigrams presented by Lee Je-ma, which is found in GyeokChiGo, DongMuYuGo and so on, ultimately forming and developing into the Theory of Four Trigrams Constitution in Dongeuisoosebowon. Recently, a lot of research is being conducted into making it objective in order to achieve reproducibility in diagnosis and so forth of Four Trigrams Constitution.

A viscoelastic higher-order beam finite element

NASA Technical Reports Server (NTRS)

Johnson, Arthur R.; Tressler, Alexander

1996-01-01

A viscoelastic internal variable constitutive theory is applied to a higher-order elastic beam theory and finite element formulation. The behavior of the viscous material in the beam is approximately modeled as a Maxwell solid. The finite element formulation requires additional sets of nodal variables for each relaxation time constant needed by the Maxwell solid. Recent developments in modeling viscoelastic material behavior with strain variables that are conjugate to the elastic strain measures are combined with advances in modeling through-the-thickness stresses and strains in thick beams. The result is a viscous thick-beam finite element that possesses superior characteristics for transient analysis since its nodal viscous forces are not linearly dependent an the nodal velocities, which is the case when damping matrices are used. Instead, the nodal viscous forces are directly dependent on the material's relaxation spectrum and the history of the nodal variables through a differential form of the constitutive law for a Maxwell solid. The thick beam quasistatic analysis is explored herein as a first step towards developing more complex viscoelastic models for thick plates and shells, and for dynamic analyses. The internal variable constitutive theory is derived directly from the Boltzmann superposition theorem. The mechanical strains and the conjugate internal strains are shown to be related through a system of first-order, ordinary differential equations. The total time-dependent stress is the superposition of its elastic and viscous components. Equations of motion for the solid are derived from the virtual work principle using the total time-dependent stress. Numerical examples for the problems of relaxation, creep, and cyclic creep are carried out for a beam made from an orthotropic Maxwell solid.

Rich man's salt: the diamonds in the soup

NASA Astrophysics Data System (ADS)

Ott, Ulrich

Diamond nominally constitutes the most abundant of the presolar phases identified in primitive meteorites so far. An overview is given of known properties including isotopic abundances of trace elements that point to a supernova connection for at least part of the diamond grains. Scenarios for nucleosynthetic production of these trace elements and their introduction into the nanodiamonds are discussed as well as their observability.

Substrate Chemistry and Rainfall Regime Regulate Elemental Composition of Tree Leaves in Karst Forests

Treesearch

Ernesto Medina; Elvira Cuevas; Ariel Lugo

2017-01-01

Forests on calcareous substrates constitute a large fraction of the vegetation in Puerto Rico. Plant growth on these substrates may be affected by nutrient deficiencies, mainly P and Fe, resulting from high pH and formation of insoluble compounds of these elements. The occurrence of these forests in humid and dry areas provides an opportunity to compare nutrient...

Copper Homeostasis at the Host-Pathogen Interface*

PubMed Central

Hodgkinson, Victoria; Petris, Michael J.

2012-01-01

The trace element copper is indispensable for all aerobic life forms. Its ability to cycle between two oxidation states, Cu1+ and Cu2+, has been harnessed by a wide array of metalloenzymes that catalyze electron transfer reactions. The metabolic needs for copper are sustained by a complex series of transporters and carrier proteins that regulate its intracellular accumulation and distribution in both pathogenic microbes and their animal hosts. However, copper is also potentially toxic due in part to its ability to generate reactive oxygen species. Recent studies suggest that the macrophage phagosome accumulates copper during bacterial infection, which may constitute an important mechanism of killing. Bacterial countermeasures include the up-regulation of copper export and detoxification genes during infection, which studies suggest are important determinants of virulence. In this minireview, we summarize recent developments that suggest an emerging role for copper as an unexpected component in determining the outcome of host-pathogen interactions. PMID:22389498

Understanding the health care business model: the financial analysts' point of view.

PubMed

Bukh, Per Nikolaj; Nielsen, Christian

2010-01-01

This study focuses on how financial analysts understand the strategy of a health care company and which elements, from such a strategy perspective, they perceive as constituting the cornerstone of a health care company's business model. The empirical part of this study is based on semi-structured interviews with analysts following a large health care company listed on the Copenhagen Stock Exchange. The authors analyse how the financial analysts view strategy and value creation within the framework of a business model. Further, the authors analyze whether the characteristics emerging from a comprehensive literature review are reflected in the financial analysts' perceptions of which information is decision-relevant and important to communicate to the financial markets. Among the conclusions of the study is the importance of distinguishing between the health care companies' business model and the model by which the payment of revenues are allocated between end users and reimbursing organizations.

Analytical simulation of weld effects in creep range

NASA Technical Reports Server (NTRS)

Dhalla, A. K.

1985-01-01

The inelastic analysis procedure used to investigate the effect of welding on the creep rupture strength of a typical Liquid Metal Fast Breeder Reactor (LMFBR) nozzle is discussed. The current study is part of an overall experimental and analytical investigation to verify the inelastic analysis procedure now being used to design LMFBR structural components operating at elevated temperatures. Two important weld effects included in the numerical analysis are: (1) the residual stress introduced in the fabrication process; and (2) the time-independent and the time-dependent material property variations. Finite element inelastic analysis was performed on a CRAY-1S computer using the ABAQUS program with the constitutive equations developed for the design of LMFBR structural components. The predicted peak weld residual stresses relax by as much as 40% during elevated temperature operation, and their effect on creep-rupture cracking of the nozzle is considered of secondary importance.

Oxygen and Oxygen Toxicity: The Birth of Concepts

PubMed Central

Zhu, Hong; Traore, Kassim; Santo, Arben; Trush, Michael A.; Li, Y. Robert

2018-01-01

Molecular dioxygen (O2) is an essential element of aerobic life, yet incomplete reduction or excitation of O2 during aerobic metabolisms generates diverse oxygen-containing reactive species, commonly known as reactive oxygen species (ROS). On the one hand, ROS pose a serious threat to aerobic organisms via inducing oxidative damage to cellular constituents. On the other hand, these reactive species, when their generation is under homeostatic control, also play important physiological roles (e.g., constituting an important component of immunity and participating in redox signaling). This article defines oxygen and the key facts about oxygen, and discusses the relationship between oxygen and the emergence of early animals on Earth. The article then describes the discovery of oxygen by three historical figures and examines the birth of the concepts of oxygen toxicity and the underlying free radical mechanisms. The article ends with a brief introduction to the emerging field of ROS-mediated redox signaling and physiological responses. PMID:29707642

Pluto: Planet or "Dwarf Planet"?

NASA Astrophysics Data System (ADS)

Voelzke, M. R.; de Araújo, M. S. T.

2010-09-01

In August 2006 during the XXVI General Assembly of the International Astronomical Union (IAU), taken place in Prague, Czech Republic, new parameters to define a planet were established. According to this new definition Pluto will be no more the ninth planet of the Solar System but it will be changed to be a "dwarf planet". This reclassification of Pluto by the academic community clearly illustrates how dynamic science is and how knowledge of different areas can be changed and evolves through the time, allowing to perceive Science as a human construction in a constant transformation, subject to political, social and historical contexts. These epistemological characteristics of Science and, in this case, of Astronomy, constitute important elements to be discussed in the lessons, so that this work contributes to enable Science and Physics teachers who perform a basic education to be always up to date on this important astronomical fact and, thereby, carry useful information to their teaching.

Expression of the ZNT1 Zinc Transporter from the Metal Hyperaccumulator Noccaea caerulescens Confers Enhanced Zinc and Cadmium Tolerance and Accumulation to Arabidopsis thaliana

PubMed Central

Schat, Henk; Aarts, Mark G. M.

2016-01-01

Prompt regulation of transition metal transporters is crucial for plant zinc homeostasis. NcZNT1 is one of such transporters, found in the metal hyperaccumulator Brassicaceae species Noccaea caerulescens. It is orthologous to AtZIP4 from Arabidopsis thaliana, an important actor in Zn homeostasis. We examined if the NcZNT1 function contributes to the metal hyperaccumulation of N. caerulescens. NcZNT1 was found to be a plasma-membrane located metal transporter. Constitutive overexpression of NcZNT1 in A. thaliana conferred enhanced tolerance to exposure to excess Zn and Cd supply, as well as increased accumulation of Zn and Cd and induction of the Fe deficiency response, when compared to non-transformed wild-type plants. Promoters of both genes were induced by Zn deficiency in roots and shoots of A. thaliana. In A. thaliana, the AtZIP4 and NcZNT1 promoters were mainly active in cortex, endodermis and pericycle cells under Zn deficient conditions. In N. caerulescens, the promoters were active in the same tissues, though the activity of the NcZNT1 promoter was higher and not limited to Zn deficient conditions. Common cis elements were identified in both promoters by 5’ deletion analysis. These correspond to the previously determined Zinc Deficiency Responsive Elements found in A. thaliana to interact with two redundantly acting transcription factors, bZIP19 and bZIP23, controlling the Zn deficiency response. In conclusion, these results suggest that NcZNT1 is an important factor in contributing to Zn and Cd hyperaccumulation in N. caerulescens. Differences in cis- and trans-regulators are likely to account for the differences in expression between A. thaliana and N. caerulescens. The high, constitutive NcZNT1 expression in the stele of N. caerulescens roots implicates its involvement in long distance root-to-shoot metal transport by maintaining a Zn/Cd influx into cells responsible for xylem loading. PMID:26930473

Unified constitutive models for high-temperature structural applications

NASA Technical Reports Server (NTRS)

Lindholm, U. S.; Chan, K. S.; Bodner, S. R.; Weber, R. M.; Walker, K. P.

1988-01-01

Unified constitutive models are characterized by the use of a single inelastic strain rate term for treating all aspects of inelastic deformation, including plasticity, creep, and stress relaxation under monotonic or cyclic loading. The structure of this class of constitutive theory pertinent for high temperature structural applications is first outlined and discussed. The effectiveness of the unified approach for representing high temperature deformation of Ni-base alloys is then evaluated by extensive comparison of experimental data and predictions of the Bodner-Partom and the Walker models. The use of the unified approach for hot section structural component analyses is demonstrated by applying the Walker model in finite element analyses of a benchmark notch problem and a turbine blade problem.

Stirling engine - Approach for long-term durability assessment

NASA Technical Reports Server (NTRS)

Tong, Michael T.; Bartolotta, Paul A.; Halford, Gary R.; Freed, Alan D.

1992-01-01

The approach employed by NASA Lewis for the long-term durability assessment of the Stirling engine hot-section components is summarized. The approach consists of: preliminary structural assessment; development of a viscoplastic constitutive model to accurately determine material behavior under high-temperature thermomechanical loads; an experimental program to characterize material constants for the viscoplastic constitutive model; finite-element thermal analysis and structural analysis using a viscoplastic constitutive model to obtain stress/strain/temperature at the critical location of the hot-section components for life assessment; and development of a life prediction model applicable for long-term durability assessment at high temperatures. The approach should aid in the provision of long-term structural durability and reliability of Stirling engines.

Specific trans-acting proteins interact with auxiliary RNA polyadenylation elements in the COX-2 3′-UTR

PubMed Central

Hall-Pogar, Tyra; Liang, Songchun; Hague, Lisa K.; Lutz, Carol S.

2007-01-01

Two cyclooxygenase (COX) enzymes, COX-1 and COX-2, are present in human cells. While COX-1 is constitutively expressed, COX-2 is inducible and up-regulated in response to many signals. Since increased transcriptional activity accounts for only part of COX-2 up-regulation, we chose to explore other RNA processing mechanisms in the regulation of this gene. Previously, we showed that COX-2 is regulated by alternative polyadenylation, and that the COX-2 proximal polyadenylation signal contains auxiliary upstream sequence elements (USEs) that are very important in efficient polyadenylation. To explore trans-acting protein factors interacting with these cis-acting RNA elements, we performed pull-down assays with HeLa nuclear extract and biotinylated RNA oligonucleotides representing COX-2 USEs. We identified PSF, p54nrb, PTB, and U1A as proteins specifically bound to the COX-2 USEs. We further explored their participation in polyadenylation using MS2 phage coat protein-MS2 RNA binding site tethering assays, and found that tethering any of these four proteins to the COX-2 USE mutant RNA can compensate for these cis-acting elements. Finally, we suggest that these proteins (p54nrb, PTB, PSF, and U1A) may interact as a complex since immunoprecipitations of the transfected MS2 fusion proteins coprecipitate the other proteins. PMID:17507659

Is there an association with constitutional structural chromosomal abnormalities and hematologic neoplastic process? A short review.

PubMed

Panani, Anna D

2009-04-01

The occasional observation of constitutional chromosomal abnormalities in patients with a malignant disease has led to a number of studies on their potential role in cancer development. Investigations of families with hereditary cancers and constitutional chromosomal abnormalities have been key observations leading to the molecular identification of specific genes implicated in tumorigenesis. Large studies have been reported on the incidence of constitutional chromosomal aberrations in patients with hematologic malignancies, but they could not confirm an increased risk for hematologic malignancy among carriers of structural chromosomal changes. However, it is of particular interest that constitutional structural aberrations with breakpoints similar to leukemia-associated specific breakpoints have been reported in patients with hematologic malignancies. Because of insufficient data, it remains still unclear if these aberrations represent random events or are associated with malignancy. There has been a substantial discussion about mechanisms involved in constitutional structural chromosomal changes in the literature. The documentation of more patients with constitutional structural chromosomal changes could be of major importance. Most importantly, the molecular investigation of chromosomal regions involved in rearrangements could give useful information on the genetic events underlying constitutional anomalies, contributing to isolation of genes important in the development of the neoplastic process. Regarding constitutional anomalies in patients with hematologic disorders, a survey of the cytogenetic data of our cytogenetics unit is herein also presented.

Analysis of Large Quasistatic Deformations of Inelastic Solids by a New Stress Based Finite Element Method. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Reed, Kenneth W.

1992-01-01

A new hybrid stress finite element algorithm suitable for analyses of large quasistatic deformation of inelastic solids is presented. Principal variables in the formulation are the nominal stress rate and spin. The finite element equations which result are discrete versions of the equations of compatibility and angular momentum balance. Consistent reformulation of the constitutive equation and accurate and stable time integration of the stress are discussed at length. Examples which bring out the feasibility and performance of the algorithm conclude the work.

Preliminary Work for Modeling the Propellers of an Aircraft as a Noise Source in an Acoustic Boundary Element Analysis

NASA Technical Reports Server (NTRS)

Vlahopoulos, Nickolas; Lyle, Karen H.; Burley, Casey L.

1998-01-01

An algorithm for generating appropriate velocity boundary conditions for an acoustic boundary element analysis from the kinematics of an operating propeller is presented. It constitutes the initial phase of Integrating sophisticated rotorcraft models into a conventional boundary element analysis. Currently, the pressure field is computed by a linear approximation. An initial validation of the developed process was performed by comparing numerical results to test data for the external acoustic pressure on the surface of a tilt-rotor aircraft for one flight condition.

Demonstration of finite element simulations in MOOSE using crystallographic models of irradiation hardening and plastic deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patra, Anirban; Wen, Wei; Martinez Saez, Enrique

This report describes the implementation of a crystal plasticity framework (VPSC) for irradiation hardening and plastic deformation in the finite element code, MOOSE. Constitutive models for irradiation hardening and the crystal plasticity framework are described in a previous report [1]. Here we describe these models briefly and then describe an algorithm for interfacing VPSC with finite elements. Example applications of tensile deformation of a dog bone specimen and a 3D pre-irradiated bar specimen performed using MOOSE are demonstrated.

Rearrangement of a polar core provides a conserved mechanism for constitutive activation of class B G protein-coupled receptors

PubMed Central

Yin, Yanting; de Waal, Parker W.; He, Yuanzheng; Zhao, Li-Hua; Yang, Dehua; Cai, Xiaoqing; Jiang, Yi; Melcher, Karsten; Wang, Ming-Wei; Xu, H. Eric

2017-01-01

The glucagon receptor (GCGR) belongs to the secretin-like (class B) family of G protein-coupled receptors (GPCRs) and is activated by the peptide hormone glucagon. The structures of an activated class B GPCR have remained unsolved, preventing a mechanistic understanding of how these receptors are activated. Using a combination of structural modeling and mutagenesis studies, we present here two modes of ligand-independent activation of GCGR. First, we identified a GCGR-specific hydrophobic lock comprising Met-338 and Phe-345 within the IC3 loop and transmembrane helix 6 (TM6) and found that this lock stabilizes the TM6 helix in the inactive conformation. Disruption of this hydrophobic lock led to constitutive G protein and arrestin signaling. Second, we discovered a polar core comprising conserved residues in TM2, TM3, TM6, and TM7, and mutations that disrupt this polar core led to constitutive GCGR activity. On the basis of these results, we propose a mechanistic model of GCGR activation in which TM6 is held in an inactive conformation by the conserved polar core and the hydrophobic lock. Mutations that disrupt these inhibitory elements allow TM6 to swing outward to adopt an active TM6 conformation similar to that of the canonical β2-adrenergic receptor complexed with G protein and to that of rhodopsin complexed with arrestin. Importantly, mutations in the corresponding polar core of several other members of class B GPCRs, including PTH1R, PAC1R, VIP1R, and CRFR1, also induce constitutive G protein signaling, suggesting that the rearrangement of the polar core is a conserved mechanism for class B GPCR activation. PMID:28356352

Rearrangement of a polar core provides a conserved mechanism for constitutive activation of class B G protein-coupled receptors.

PubMed

Yin, Yanting; de Waal, Parker W; He, Yuanzheng; Zhao, Li-Hua; Yang, Dehua; Cai, Xiaoqing; Jiang, Yi; Melcher, Karsten; Wang, Ming-Wei; Xu, H Eric

2017-06-16

The glucagon receptor (GCGR) belongs to the secretin-like (class B) family of G protein-coupled receptors (GPCRs) and is activated by the peptide hormone glucagon. The structures of an activated class B GPCR have remained unsolved, preventing a mechanistic understanding of how these receptors are activated. Using a combination of structural modeling and mutagenesis studies, we present here two modes of ligand-independent activation of GCGR. First, we identified a GCGR-specific hydrophobic lock comprising Met-338 and Phe-345 within the IC3 loop and transmembrane helix 6 (TM6) and found that this lock stabilizes the TM6 helix in the inactive conformation. Disruption of this hydrophobic lock led to constitutive G protein and arrestin signaling. Second, we discovered a polar core comprising conserved residues in TM2, TM3, TM6, and TM7, and mutations that disrupt this polar core led to constitutive GCGR activity. On the basis of these results, we propose a mechanistic model of GCGR activation in which TM6 is held in an inactive conformation by the conserved polar core and the hydrophobic lock. Mutations that disrupt these inhibitory elements allow TM6 to swing outward to adopt an active TM6 conformation similar to that of the canonical β 2 -adrenergic receptor complexed with G protein and to that of rhodopsin complexed with arrestin. Importantly, mutations in the corresponding polar core of several other members of class B GPCRs, including PTH1R, PAC1R, VIP1R, and CRFR1, also induce constitutive G protein signaling, suggesting that the rearrangement of the polar core is a conserved mechanism for class B GPCR activation. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Macro Scale Independently Homogenized Subcells for Modeling Braided Composites

NASA Technical Reports Server (NTRS)

Blinzler, Brina J.; Goldberg, Robert K.; Binienda, Wieslaw K.

2012-01-01

An analytical method has been developed to analyze the impact response of triaxially braided carbon fiber composites, including the penetration velocity and impact damage patterns. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. To determine the stiffness and strength properties required for the constitutive model, a top-down approach for determining the strength properties is merged with a bottom-up approach for determining the stiffness properties. The top-down portion uses global strengths obtained from macro-scale coupon level testing to characterize the material strengths for each subcell. The bottom-up portion uses micro-scale fiber and matrix stiffness properties to characterize the material stiffness for each subcell. Simulations of quasi-static coupon level tests for several representative composites are conducted along with impact simulations.

Short- and Long-term Evolutionary Dynamics of Bacterial Insertion Sequences: Insights from Wolbachia Endosymbionts

PubMed Central

Cerveau, Nicolas; Leclercq, Sébastien; Leroy, Elodie; Bouchon, Didier; Cordaux, Richard

2011-01-01

Transposable elements (TE) are one of the major driving forces of genome evolution, raising the question of the long-term dynamics underlying their evolutionary success. Long-term TE evolution can readily be reconstructed in eukaryotes, thanks to many degraded copies constituting genomic fossil records of past TE proliferations. By contrast, bacterial genomes usually experience high sequence turnover and short TE retention times, thereby obscuring ancient TE evolutionary patterns. We found that Wolbachia bacterial genomes contain 52–171 insertion sequence (IS) TEs. IS account for 11% of Wolbachia wRi, which is one of the highest IS genomic coverage reported in prokaryotes to date. We show that many IS groups are currently expanding in various Wolbachia genomes and that IS horizontal transfers are frequent among strains, which can explain the apparent synchronicity of these IS proliferations. Remarkably, >70% of Wolbachia IS are nonfunctional. They constitute an unusual bacterial IS genomic fossil record providing direct empirical evidence for a long-term IS evolutionary dynamics following successive periods of intense transpositional activity. Our results show that comprehensive IS annotations have the potential to provide new insights into prokaryote TE evolution and, more generally, prokaryote genome evolution. Indeed, the identification of an important IS genomic fossil record in Wolbachia demonstrates that IS elements are not always of recent origin, contrary to the conventional view of TE evolution in prokaryote genomes. Our results also raise the question whether the abundance of IS fossils is specific to Wolbachia or it may be a general, albeit overlooked, feature of prokaryote genomes. PMID:21940637

Short- and long-term evolutionary dynamics of bacterial insertion sequences: insights from Wolbachia endosymbionts.

PubMed

Cerveau, Nicolas; Leclercq, Sébastien; Leroy, Elodie; Bouchon, Didier; Cordaux, Richard

2011-01-01

Transposable elements (TE) are one of the major driving forces of genome evolution, raising the question of the long-term dynamics underlying their evolutionary success. Long-term TE evolution can readily be reconstructed in eukaryotes, thanks to many degraded copies constituting genomic fossil records of past TE proliferations. By contrast, bacterial genomes usually experience high sequence turnover and short TE retention times, thereby obscuring ancient TE evolutionary patterns. We found that Wolbachia bacterial genomes contain 52-171 insertion sequence (IS) TEs. IS account for 11% of Wolbachia wRi, which is one of the highest IS genomic coverage reported in prokaryotes to date. We show that many IS groups are currently expanding in various Wolbachia genomes and that IS horizontal transfers are frequent among strains, which can explain the apparent synchronicity of these IS proliferations. Remarkably, >70% of Wolbachia IS are nonfunctional. They constitute an unusual bacterial IS genomic fossil record providing direct empirical evidence for a long-term IS evolutionary dynamics following successive periods of intense transpositional activity. Our results show that comprehensive IS annotations have the potential to provide new insights into prokaryote TE evolution and, more generally, prokaryote genome evolution. Indeed, the identification of an important IS genomic fossil record in Wolbachia demonstrates that IS elements are not always of recent origin, contrary to the conventional view of TE evolution in prokaryote genomes. Our results also raise the question whether the abundance of IS fossils is specific to Wolbachia or it may be a general, albeit overlooked, feature of prokaryote genomes.

Fundamental Properties of Soils for Complex Dynamic Loadings: Dynamic Constitutive Modeling of Sandy Soils.

DTIC Science & Technology

1983-04-01

1.0 INTRODUCTION AND SCOPE 1 2.0 PROGRESS SUMMARY 3 2.1 Soil Element Model Development 3 2.2 U.S. Any Engineer Waterways Experiment Station (WES...LABORATORY BEHAVIOR OF SAND 8 3.1 Introduction 8 3.2 Material Description 8 3.3 Laboratory Tests Performed 9 3.4 Laboratory Test Results 14 4.0 MODELING THE... INTRODUCTION AND SCOPE The subject of this annual report is constitutive modeling of cohesionless soil, for both laboratory standard static test conditions

The Processing and Mechanical Properties of High Temperature/High Performance Composites. Book 3. Constituent Properties and Macroscopic Performance: MMCs

DTIC Science & Technology

1993-04-01

re - expressed as, v .= hCSw (C3) Combining Eqns. (C2) and C3) yields, Se = - ’. S (C4...of vi( s ) or v ’( s ). Substituting eq. (B10) into eq. (25), one finds the finite element method expression for functional Ud [ v ] which is U, d [] = v , K...Measurements 1- D 2- D S ,_DL 4 Constitutive W Constitutive Laws Laws Matrix Cracking Labor Models Models Stress Redistribution Numerical Calculations

[The "pharmaceutical chain", important asset of health safety in France. Synthesis of the session].

PubMed

Santini, C

2008-01-01

The National Academy of Pharmacy underlines the importance of health safety guarantees, provided by the "pharmaceutical chain" that bring the medicine until his user (from manufacturers to dispensing pharmacists), chain of which the security of each link is controlled and guaranteed by pharmacists. The first of the safety rules lies in the very fast availability of the medicine for the patients, in every respect of the national territory, due to an efficient system of pharmaceutical distribution and to a tightened network of pharmaceutical dispensaries (that constitutes a network of expertises especially to the service of patients and public health). All along the chain, also exists a same concern to guarantee and to preserve the pharmaceutical quality of the medicines. An essential element of the health safety is the right usage of the medicine, to which contribute: information associated with the marketing of the medicine, the very important role of the dispensing pharmacist as such sanitary adviser and therapeutic education teacher, the intervention of the hospital dispensary in clinical pharmacy, the "Pharmaceutical File" under setting up, pharmacovigilance, traceability of medicines ... Pharmacists, responsible at the level of the different steps of the chain, get appropriate skills, carry out themselves their duties and are responsible in front of the National Board of Pharmacists, and their common professional knowledge reinforces the cohesion and the robustness of the chain. Facing the serious issue of counterfeiting of medicines, the pharmaceutical chain constitutes an important line of defence against the entry of counterfeited drugs into commercial channels. The academy of Pharmacy warns against all evolution that would consist to break, even partially, of the mandatory and continuous pharmaceutical control.

Digitizing for Computer-Aided Finite Element Model Generation.

DTIC Science & Technology

1979-10-10

this approach is a collection of programs developed over the last eight years at the University of Arizona, and called the GIFTS system. This paper...briefly describes the latest version of the system, GIFTS -5, and demonstrates its suitability in a design environment by simple examples. The programs...constituting the GIFTS system were used as a tool for research in many areas, including mesh generation, finite element data base design, interactive

A Social Network Analysis of the National Materials Competency at Naval Air Systems Command

DTIC Science & Technology

2002-09-01

language held by individuals within the structure. (Lesser, 2000, p. 4) Bourdieu defines social capital as decomposable into two elements: first, the...The fundamental proposition of social capital theory is that the network ties provide access to resources and that social relations constitute...transferring knowledge are being identified as a central element of organizational advantage. Social capital theory provides a sounds basis for explaining

Ca2+/Calmodulin-dependent kinase II signaling causes skeletal overgrowth and premature chondrocyte maturation.

PubMed

Taschner, Michael J; Rafigh, Mehran; Lampert, Fabienne; Schnaiter, Simon; Hartmann, Christine

2008-05-01

The long bones of vertebrate limbs originate from cartilage templates and are formed by the process of endochondral ossification. This process requires that chondrocytes undergo a progressive maturation from proliferating to postmitotic prehypertrophic to mature, hypertrophic chondrocytes. Coordinated control of proliferation and maturation regulates growth of the skeletal elements. Various signals and pathways have been implicated in orchestrating these processes, but the underlying intracellular molecular mechanisms are often not entirely known. Here we demonstrated in the chick using replication-competent retroviruses that constitutive activation of Calcium/Calmodulin-dependent kinase II (CaMKII) in the developing wing resulted in elongation of skeletal elements associated with premature differentiation of chondrocytes. The premature maturation of chondrocytes was a cell-autonomous effect of constitutive CaMKII signaling associated with down-regulation of cell-cycle regulators and up-regulation of chondrocyte maturation markers. In contrast, the elongation of the skeletal elements resulted from a non-cell autonomous up-regulation of the Indian hedgehog responsive gene encoding Parathyroid-hormone-related peptide. Reduction of endogenous CaMKII activity by overexpressing an inhibitory peptide resulted in shortening of the skeletal elements associated with a delay in chondrocyte maturation. Thus, CaMKII is an essential component of intracellular signaling pathways regulating chondrocyte maturation.

Constitutive modeling for isotropic materials (HOST)

NASA Technical Reports Server (NTRS)

Lindholm, U. S.; Chan, K. S.; Bodner, S. R.; Weber, R. M.; Walker, K. P.; Cassenti, B. N.

1985-01-01

This report presents the results of the second year of work on a problem which is part of the NASA HOST Program. Its goals are: (1) to develop and validate unified constitutive models for isotropic materials, and (2) to demonstrate their usefulness for structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are that of Bodner-Partom and Walker. For model evaluation purposes, a large constitutive data base is generated for a B1900 + Hf alloy by performing uniaxial tensile, creep, cyclic, stress relation, and thermomechanical fatigue (TMF) tests as well as biaxial (tension/torsion) tests under proportional and nonproportional loading over a wide range of strain rates and temperatures. Systematic approaches for evaluating material constants from a small subset of the data base are developed. Correlations of the uniaxial and biaxial tests data with the theories of Bodner-Partom and Walker are performed to establish the accuracy, range of applicability, and integability of the models. Both models are implemented in the MARC finite element computer code and used for TMF analyses. Benchmark notch round experiments are conducted and the results compared with finite-element analyses using the MARC code and the Walker model.

Experimental observations and finite element analysis of the initiation of fiber microbuckling in notched composite laminates

NASA Technical Reports Server (NTRS)

Guynn, E. Gail; Bradley, Walter L.; Ochoa, Ozden O.

1990-01-01

A better understanding of the factors that affect the semi-circular edge-notched compressive strength is developed, and the associated failure mode(s) of thermoplastic composite laminates with multidirectional stacking sequences are identified. The primary variables in this investigation are the resin nonlinear shear constitutive behavior, stacking sequence (orientation of plies adjacent to the 0 degree plies), resin-rich regions between the 0 degree plies and the off-axis supporting plies, fiber/matrix interfacial bond strength, and initial fiber waviness. Two thermoplastic composite material systems are used in this investigation. The materials are the commercial APC-2 (AS4/PEEK) and a poor interface experimental material, AU4U/PEEK, designed for this investigation. Notched compression specimens are studied at 21, 77, and 132 C. Geometric and material nonlinear two-dimensional finite element analysis is used to model the initiation of fiber microbuckling of both the ideal straight fiber and the more realistic initially wavy fiber. The effects of free surface, fiber constitutive properties, matrix constitutive behavior, initial fiber curvature, and fiber/matrix interfacial bond strength on fiber microbuckling initiation strain levels are considered.

Explicit and implicit springback simulation in sheet metal forming using fully coupled ductile damage and distortional hardening model

NASA Astrophysics Data System (ADS)

Yetna n'jock, M.; Houssem, B.; Labergere, C.; Saanouni, K.; Zhenming, Y.

2018-05-01

The springback is an important phenomenon which accompanies the forming of metallic sheets especially for high strength materials. A quantitative prediction of springback becomes very important for newly developed material with high mechanical characteristics. In this work, a numerical methodology is developed to quantify this undesirable phenomenon. This methodoly is based on the use of both explicit and implicit finite element solvers of Abaqus®. The most important ingredient of this methodology consists on the use of highly predictive mechanical model. A thermodynamically-consistent, non-associative and fully anisotropic elastoplastic constitutive model strongly coupled with isotropic ductile damage and accounting for distortional hardening is then used. An algorithm for local integration of the complete set of the constitutive equations is developed. This algorithm considers the rotated frame formulation (RFF) to ensure the incremental objectivity of the model in the framework of finite strains. This algorithm is implemented in both explicit (Abaqus/Explicit®) and implicit (Abaqus/Standard®) solvers of Abaqus® through the users routine VUMAT and UMAT respectively. The implicit solver of Abaqus® has been used to study spingback as it is generally a quasi-static unloading. In order to compare the methods `efficiency, the explicit method (Dynamic Relaxation Method) proposed by Rayleigh has been also used for springback prediction. The results obtained within U draw/bending benchmark are studied, discussed and compared with experimental results as reference. Finally, the purpose of this work is to evaluate the reliability of different methods predict efficiently springback in sheet metal forming.

Sandia fracture challenge 2: Sandia California's modeling approach

DOE PAGES

Karlson, Kyle N.; James W. Foulk, III; Brown, Arthur A.; ...

2016-03-09

The second Sandia Fracture Challenge illustrates that predicting the ductile fracture of Ti-6Al-4V subjected to moderate and elevated rates of loading requires thermomechanical coupling, elasto-thermo-poro-viscoplastic constitutive models with the physics of anisotropy and regularized numerical methods for crack initiation and propagation. We detail our initial approach with an emphasis on iterative calibration and systematically increasing complexity to accommodate anisotropy in the context of an isotropic material model. Blind predictions illustrate strengths and weaknesses of our initial approach. We then revisit our findings to illustrate the importance of including anisotropy in the failure process. Furthermore, mesh-independent solutions of continuum damage modelsmore » having both isotropic and anisotropic yields surfaces are obtained through nonlocality and localization elements.« less

Development of Methods of Evaluating Abilities to Make Plans in New Group Work

NASA Astrophysics Data System (ADS)

Kiriyama, Satoshi

The ability to evaluate something vague which is, for example, originality can be regarded as one of important elements which constitute the ability to make plans. The author has made use of cooperative activities in which every member undertakes each stage of a plan-do-check-cycle in order to develop training methods and evaluating methods of evaluating ability. The members of a CHECK team evaluated activities of a PLAN team and a DO team. The author tried to grasp the abilities of the members of a CHECK team by analyzing results of the evaluation. In addition, the author have made some teachers evaluate a sample in order to study the accuracy of criteria and extracted some challenges.

First description of a fossil chamaeleonid from Greece and its relevance for the European biogeographic history of the group

NASA Astrophysics Data System (ADS)

Georgalis, Georgios L.; Villa, Andrea; Delfino, Massimo

2016-02-01

The fossil record of Chamaeleonidae is very scarce and any new specimen is therefore considered important for our understanding of the evolutionary and biogeographic history of the group. New specimens from the early Miocene of Aliveri (Evia Island), Greece constitute the only fossils of these lizards from southeastern Europe. Skull roofing material is tentatively attributed to the Czech species Chamaeleo cf. andrusovi, revealing a range extension for this taxon, whereas tooth-bearing elements are described as indeterminate chamaeleonids. The Aliveri fossils rank well among the oldest known reptiles from Greece, provide evidence for the dispersal routes of chameleons out of Africa towards the European continent and, additionally, imply strong affinities with coeval chamaeleonids from Central Europe.

Oxide-based method of making compound semiconductor films and making related electronic devices

DOEpatents

Kapur, Vijay K.; Basol, Bulent M.; Leidholm, Craig R.; Roe, Robert A.

2000-01-01

A method for forming a compound film includes the steps of preparing a source material, depositing the source material on a base and forming a preparatory film from the source material, heating the preparatory film in a suitable atmosphere to form a precursor film, and providing suitable material to said precursor film to form the compound film. The source material includes oxide-containing particles including Group IB and IIIA elements. The precursor film includes non-oxide Group IB and IIIA elements. The compound film includes a Group IB-IIIA-VIA compound. The oxides may constitute greater than about 95 molar percent of the Group IB elements and greater than about 95 molar percent of the Group IIIA elements in the source material. Similarly, non-oxides may constitute greater than about 95 molar percent of the Group IB elements and greater than about 95 molar percent of the Group IIIA elements in the precursor film. The molar ratio of Group IB to Group IIIA elements in the source material may be greater than about 0.6 and less than about 1.0, or substantially greater that 1.0, in which case this ratio in the compound film may be reduced to greater than about 0.6 and less than about 1.0. The source material may be prepared as an ink from particles in powder form. The oxide-containing particles may include a dopant, as may the compound film. Compound films including a Group IIB-IVA-VA compound may be substituted using appropriate substitutions in the method. The method, also, is applicable to fabrication of solar cells and other electronic devices.

Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

NASA Technical Reports Server (NTRS)

Gao, Xiujie; Burton, Deborah; Turner, Travis L.; Brinson, Catherine

2005-01-01

Shape memory alloy hybrid composites with adaptive-stiffening or morphing functions are simulated using finite element analysis. The composite structure is a laminated fiber-polymer composite beam with embedded SMA ribbons at various positions with respect to the neutral axis of the beam. Adaptive stiffening or morphing is activated via selective resistance heating of the SMA ribbons or uniform thermal loads on the beam. The thermomechanical behavior of these composites was simulated in ABAQUS using user-defined SMA elements. The examples demonstrate the usefulness of the methods for the design and simulation of SMA hybrid composites. Keywords: shape memory alloys, Nitinol, ABAQUS, finite element analysis, post-buckling control, shape control, deflection control, adaptive stiffening, morphing, constitutive modeling, user element

Genome-Wide Association Analysis of Sasang Constitution in the Korean Population

PubMed Central

Kim, Bu-Yeo; Jin, Hee-Jeong

2012-01-01

Abstract Objectives Sasang constitutional medicine is a traditional Korean medicine in which an individual is classified into one of four types of constitution: Taeum (TE), Soeum (SE) Soyang (SY), and Taeyang (TY). These constitution types are determined with biologic and physiologic characteristics, so it has been assumed that genetic factors are associated with each constitution type. Identifying the genetic elements underlying each constitution is necessary for the elucidation of the molecular mechanism of Sasang constitutional medicine. Design A total of 341,998 genetic loci across the whole genome were genotyped for 1222 subjects of defined constitution type. The genetic loci associated with each constitution type were identified and the functional connectivity of genes within these loci was analyzed using statistical text mining. Results From the difference in allele frequencies between constitution types, significant genetic loci associated with each type were identified. Chromosomes 3q27.3 (rs10937331, p=2.71×10−6), 15q22.2 (rs7180547, p=1.58×10−6), and 14q22.3 (rs12431592, p=1.31×10−6) were most significantly associated with TE, SE, and SY constitution types, respectively. From the functional relationship analysis using all loci with a p-value≤10−4, genes associated with each constitution type were identified. Fifteen (15) genes, including GPM6A, SYT4, and GRIK1, were significantly associated with the TE constitution type (p<0.05); 12 genes, including DRGX and AKAP11, were significantly associated with the SE constitution type (p<0.05); and 17 genes, including ZFP42, CDH22, ALDH1A2, OTX2, and EN2, were significantly associated with the SY constitution type (p<0.05). Conclusions Genetic loci and genes associated with Sasang constitution types were systematically identified from a genome-wide association study using a large number of subjects. PMID:22394158

Mineral Nutrition of Plants. Chapter 9

NASA Technical Reports Server (NTRS)

Wignarajah, Kanapathipillai

1995-01-01

The ultimate source of nutrients for all living organisms consists of the inanimate nutrient reserves found on earth. Of the elements known to exist, seven are considered essential to plants in large amounts (macronutrients), and many others are required in smaller quantities (micronutrients). Essentiality of a nutrient is defined according to the following concepts: (a) A deficiency of the element makes it impossible for the plant to complete the vegetative or reproductive stage of its cycle; (b) such deficiency is specific to the element in question and can be prevented or corrected only by supplying this element; (c) the element is directly involved in the nutrition of the plant quite apart from its possible effects in correcting some unfavorable microbiological or chemical condition of the soil or other culture medium. From that standpoint a favorable response from adding a given element to the culture medium does not constitute conclusive evidence of its indispensability in plant nutrition. All the elements occurring in the outer part of the earth are in constant turnover among the different components of earth. This overall migration is referred to as geochemical cycling. When cycling includes a role for biological organisms, it is referred to as "biogeochemical cycling." Like most cyclical processes in nature, the biogeochemical cycling of elements is not continuous, nor does it proceed in a well-defined direction. At stages, it may be halted or short-circuited, or it may change. Any changes will eventually impact the survival, evolution, and development of biological species in the system. The relationship of the various systems is represented in a schematic manner. To assess the efficiency of operation of the biogeochemical cycles, it is important to include both natural and human activities. Often reliable values on use by man are difficult to obtain for a number of reasons, such as lack of international cooperation, and lack of proper bookkeeping and auditing by individual nations. However, a general estimate of the annual world consumption of elements and their compounds is presented.

Artificial Neural Network-Based Three-dimensional Continuous Response Relationship Construction of 3Cr20Ni10W2 Heat-Resisting Alloy and Its Application in Finite Element Simulation

NASA Astrophysics Data System (ADS)

Li, Le; Wang, Li-yong

2018-04-01

The application of accurate constitutive relationship in finite element simulation would significantly contribute to accurate simulation results, which plays a critical role in process design and optimization. In this investigation, the true stress-strain data of 3Cr20Ni10W2 heat-resisting alloy were obtained from a series of isothermal compression tests conducted in a wide temperature range of 1203-1403 K and strain rate range of 0.01-10 s-1 on a Gleeble 1500 testing machine. Then the constitutive relationship was modeled by an optimally constructed and well-trained back-propagation artificial neural network (BP-ANN). The evaluation of the BP-ANN model revealed that it has admirable performance in characterizing and predicting the flow behaviors of 3Cr20Ni10W2 heat-resisting alloy. Meanwhile, a comparison between improved Arrhenius-type constitutive equation and BP-ANN model shows that the latter has higher accuracy. Consequently, the developed BP-ANN model was used to predict abundant stress-strain data beyond the limited experimental conditions and construct the three-dimensional continuous response relationship for temperature, strain rate, strain, and stress. Finally, the three-dimensional continuous response relationship was applied to the numerical simulation of isothermal compression tests. The results show that such constitutive relationship can significantly promote the accuracy improvement of numerical simulation for hot forming processes.

Speciation and bioavailability of mercury in sediments impacted by gold mining in Colombia.

PubMed

Pinedo-Hernández, José; Marrugo-Negrete, José; Díez, Sergi

2015-01-01

Mercury (Hg) speciation and bioavailability were studied in surface sediments affected by artisanal and small-scale gold mining (ASGM) in the Mojana region of Colombia. The results demonstrated higher levels in sampling stations that receive water streams carrying Hg from mining areas. The T-Hg concentrations were slightly elevated with values between 196.2 and 1187.6 ng g(-1) dry weight (dw) (mean 524.2±256.8 ng g(-1) dw). The MeHg concentrations were significantly correlated with the T-Hg and organic matter (OM) and represent between 1.7% and 3.6% (mean: 2.6%) of the T-Hg. A five-step sequential extraction procedure shown that most of T-Hg in sediments occur primarily as organically bound Hg (Hg-o), which constitutes 48.4% of the T-Hg, followed by elemental Hg fraction (Hg-e) bound to amorphous compounds, such as Fe/Mn oxides with 26.5%, and the fraction bound to sulfur (Hg-s), which constitutes 18.7%. Exchangeable Hg (Hg-w; water-soluble Hg and stomach acid soluble mercury; Hg-h) represents between 1.7% and 4.7%. These fractions constitute a low percentage but exhibit a high level of risk when entering the water column, and they can bioaccumulate in organisms. The significant relationship between OM, T-Hg and MeHg suggests an important role in the control of the distribution, mobility and bioavailability of the Hg in the sediments. Copyright © 2014 Elsevier Ltd. All rights reserved.

Acquired hypermethylation of the P16INK4A promoter in abdominal paraganglioma: relation to adverse tumor phenotype and predisposing mutation

PubMed Central

Kiss, Nimrod B; Muth, Andreas; Andreasson, Adam; Juhlin, C Christofer; Geli, Janos; Bäckdahl, Martin; Höög, Anders; Wängberg, Bo; Nilsson, Ola; Ahlman, Håkan; Larsson, Catharina

2013-01-01

Recurrent alterations in promoter methylation of tumor suppressor genes (TSGs) and LINE1 (L1RE1) repeat elements were previously reported in pheochromocytoma and abdominal paraganglioma. This study was undertaken to explore CpG methylation abnormalities in an extended tumor panel and assess possible relationships between metastatic disease and mutation status. CpG methylation was quantified by bisulfite pyrosequencing for selected TSG promoters and LINE1 repeats. Methylation indices above normal reference were observed for DCR2 (TNFRSF10D), CDH1, P16 (CDKN2A), RARB, and RASSF1A. Z-scores for overall TSG, and individual TSG methylation levels, but not LINE1, were significantly correlated with metastatic disease, paraganglioma, disease predisposition, or outcome. Most strikingly, P16 hypermethylation was strongly associated with SDHB mutation as opposed to RET/MEN2, VHL/VHL, or NF1-related disease. Parallel analyses of constitutional, tumor, and metastasis DNA implicate an order of events where constitutional SDHB mutations are followed by TSG hypermethylation and 1p loss in primary tumors, later transferred to metastatic tissue. In the combined material, P16 hypermethylation was prevalent in SDHB-mutated samples and was associated with short disease-related survival. The findings verify the previously reported importance of P16 and other TSG hypermethylation in an independent tumor series. Furthermore, a constitutional SDHB mutation is proposed to predispose for an epigenetic tumor phenotype occurring before the emanation of clinically recognized malignancy. PMID:23154831

Multi Length Scale Finite Element Design Framework for Advanced Woven Fabrics

NASA Astrophysics Data System (ADS)

Erol, Galip Ozan

Woven fabrics are integral parts of many engineering applications spanning from personal protective garments to surgical scaffolds. They provide a wide range of opportunities in designing advanced structures because of their high tenacity, flexibility, high strength-to-weight ratios and versatility. These advantages result from their inherent multi scale nature where the filaments are bundled together to create yarns while the yarns are arranged into different weave architectures. Their highly versatile nature opens up potential for a wide range of mechanical properties which can be adjusted based on the application. While woven fabrics are viable options for design of various engineering systems, being able to understand the underlying mechanisms of the deformation and associated highly nonlinear mechanical response is important and necessary. However, the multiscale nature and relationships between these scales make the design process involving woven fabrics a challenging task. The objective of this work is to develop a multiscale numerical design framework using experimentally validated mesoscopic and macroscopic length scale approaches by identifying important deformation mechanisms and recognizing the nonlinear mechanical response of woven fabrics. This framework is exercised by developing mesoscopic length scale constitutive models to investigate plain weave fabric response under a wide range of loading conditions. A hyperelastic transversely isotropic yarn material model with transverse material nonlinearity is developed for woven yarns (commonly used in personal protection garments). The material properties/parameters are determined through an inverse method where unit cell finite element simulations are coupled with experiments. The developed yarn material model is validated by simulating full scale uniaxial tensile, bias extension and indentation experiments, and comparing to experimentally observed mechanical response and deformation mechanisms. Moreover, mesoscopic unit cell finite elements are coupled with a design-of-experiments method to systematically identify the important yarn material properties for the macroscale response of various weave architectures. To demonstrate the macroscopic length scale approach, two new material models for woven fabrics were developed. The Planar Material Model (PMM) utilizes two important deformation mechanisms in woven fabrics: (1) yarn elongation, and (2) relative yarn rotation due to shear loads. The yarns' uniaxial tensile response is modeled with a nonlinear spring using constitutive relations while a nonlinear rotational spring is implemented to define fabric's shear stiffness. The second material model, Sawtooth Material Model (SMM) adopts the sawtooth geometry while recognizing the biaxial nature of woven fabrics by implementing the interactions between the yarns. Material properties/parameters required by both PMM and SMM can be directly determined from standard experiments. Both macroscopic material models are implemented within an explicit finite element code and validated by comparing to the experiments. Then, the developed macroscopic material models are compared under various loading conditions to determine their accuracy. Finally, the numerical models developed in the mesoscopic and macroscopic length scales are linked thus demonstrating the new systematic design framework involving linked mesoscopic and macroscopic length scale modeling approaches. The approach is demonstrated with both Planar and Sawtooth Material Models and the simulation results are verified by comparing the results obtained from meso and macro models.

Nondestructive pavement evaluation using finite element analysis based soft computing models.

DOT National Transportation Integrated Search

2009-09-15

Evaluating structural condition of existing, in-service pavements constitutes annually a major part of the : maintenance and rehabilitation activities undertaken by State Highway Agencies (SHAs). Accurate : estimation of pavement geometry and layer m...

Finite element modelling of creep crack growth in 316 stainless and 9Cr-1Mo steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnaswamy, P.; Brust, F.W.

1994-09-01

The failure behavior of steels under sustained and cyclic loads has been addressed. The constitutive behavior of the two steels have been represented by the conventional strain-hardening law and the Murakami-Ohno model for reversed and cyclic loads. The laws have been implemented into the research finite element code FVP. Post processors for FVP to calculate various path independent integral fracture parameters have been written. Compact tension C(T) specimens have been tested under sustained and cyclic loads with both the load point displacement and crack growth monitored during the tests. FE models with extremely refined meshes for the C(T) specimens weremore » prepared and the experiment simulated numerically. Results from this analysis focus on the differences between the various constitutive models as well as the fracture parameters in characterizing the creep crack growth of the two steels.« less

Finite element method for viscoelastic medium with damage and the application to structural analysis of solid rocket motor grain

NASA Astrophysics Data System (ADS)

Deng, Bin; Shen, ZhiBin; Duan, JingBo; Tang, GuoJin

2014-05-01

This paper studies the damage-viscoelastic behavior of composite solid propellants of solid rocket motors (SRM). Based on viscoelastic theories and strain equivalent hypothesis in damage mechanics, a three-dimensional (3-D) nonlinear viscoelastic constitutive model incorporating with damage is developed. The resulting viscoelastic constitutive equations are numerically discretized by integration algorithm, and a stress-updating method is presented by solving nonlinear equations according to the Newton-Raphson method. A material subroutine of stress-updating is made up and embedded into commercial code of Abaqus. The material subroutine is validated through typical examples. Our results indicate that the finite element results are in good agreement with the analytical ones and have high accuracy, and the suggested method and designed subroutine are efficient and can be further applied to damage-coupling structural analysis of practical SRM grain.

Extended inheritance from an organizational point of view.

PubMed

Pontarotti, Gaëlle

2015-12-01

In this paper, I argue that the increasing data about non-genetic inheritance requires the construction of a new conceptual framework that should complement the inclusive approaches already discussed in the literature. More precisely, I hold that this framework should be epistemologically relevant for evolutionary biologists in capturing the limits of extended inheritance and in reassessing the boundaries of biological systems that transmit traits to their offspring. I outline the first elements of an organizational account of extended inheritance. In this account, the category of inherited factors is neither restricted to genes nor extended to stable resources related to trans-generational similarities. Instead, it includes persisting constitutive elements appearing as difference makers for heterogeneous organizational constraints, namely for heterogeneous constitutive parts whose specific role is to harness flows of matter and energy across generations of clearly delimited extended organized systems. This both inclusive and restrictive framework opens an additional way to apprehend how extended inheritance may affect evolutionary trajectories.

Analysis of intelligent hinged shell structures: deployable deformation and shape memory effect

NASA Astrophysics Data System (ADS)

Shi, Guang-Hui; Yang, Qing-Sheng; He, X. Q.

2013-12-01

Shape memory polymers (SMPs) are a class of intelligent materials with the ability to recover their initial shape from a temporarily fixable state when subjected to external stimuli. In this work, the thermo-mechanical behavior of a deployable SMP-based hinged structure is modeled by the finite element method using a 3D constitutive model with shape memory effect. The influences of hinge structure parameters on the nonlinear loading process are investigated. The total shape memory of the processes the hinged structure goes through, including loading at high temperature, decreasing temperature with load carrying, unloading at low temperature and recovering the initial shape with increasing temperature, are illustrated. Numerical results show that the present constitutive theory and the finite element method can effectively predict the complicated thermo-mechanical deformation behavior and shape memory effect of SMP-based hinged shell structures.

Derivation of stiffness matrix in constitutive modeling of magnetorheological elastomer

NASA Astrophysics Data System (ADS)

Leng, D.; Sun, L.; Sun, J.; Lin, Y.

2013-02-01

Magnetorheological elastomers (MREs) are a class of smart materials whose mechanical properties change instantly by the application of a magnetic field. Based on the specially orthotropic, transversely isotropic stress-strain relationships and effective permeability model, the stiffness matrix of constitutive equations for deformable chain-like MRE is considered. To valid the components of shear modulus in this stiffness matrix, the magnetic-structural simulations with finite element method (FEM) are presented. An acceptable agreement is illustrated between analytical equations and numerical simulations. For the specified magnetic field, sphere particle radius, distance between adjacent particles in chains and volume fractions of ferrous particles, this constitutive equation is effective to engineering application to estimate the elastic behaviour of chain-like MRE in an external magnetic field.

Effect of Microscopic Damage Events on Static and Ballistic Impact Strength of Triaxial Braid Composites

NASA Technical Reports Server (NTRS)

Littell, Justin D.; Binienda, Wieslaw K.; Arnold, William A.; Roberts, Gary D.; Goldberg, Robert K.

2010-01-01

The reliability of impact simulations for aircraft components made with triaxial-braided carbon-fiber composites is currently limited by inadequate material property data and lack of validated material models for analysis. Methods to characterize the material properties used in the analytical models from a systematically obtained set of test data are also lacking. A macroscopic finite element based analytical model to analyze the impact response of these materials has been developed. The stiffness and strength properties utilized in the material model are obtained from a set of quasi-static in-plane tension, compression and shear coupon level tests. Full-field optical strain measurement techniques are applied in the testing, and the results are used to help in characterizing the model. The unit cell of the braided composite is modeled as a series of shell elements, where each element is modeled as a laminated composite. The braided architecture can thus be approximated within the analytical model. The transient dynamic finite element code LS-DYNA is utilized to conduct the finite element simulations, and an internal LS-DYNA constitutive model is utilized in the analysis. Methods to obtain the stiffness and strength properties required by the constitutive model from the available test data are developed. Simulations of quasi-static coupon tests and impact tests of a represented braided composite are conducted. Overall, the developed method shows promise, but improvements that are needed in test and analysis methods for better predictive capability are examined.

Materials, used in historical buildings, analysis methods and solutions puroposals

NASA Astrophysics Data System (ADS)

Döndüren, M. Sami; Sişik, Ozlem

2017-10-01

Most of historical buildings are built with pressure principle and have the characteristics of masonry structures. Therefore, the structure components of buildings are constituted bearing walls, columns, buttresses, vaults and domes. Natural stone, cut stone, rubble stone brick or alternate materials were used in the bearing elements. Brick-dust and mortar with more binding feature were used as combination elements. In time, some problems were occurred in used materials and in structure as a result of various effects. Therefore, it is necessary to apply various applications in framework of repair and strengthening of buildings. In this study, restoration of historic buildings and the control of the adequacy of the bearing systems as one most important part of structure were examined. For this purpose, static analysis of Edirne-Merkez Demirtaş (Timurtaş) mosque located in Edirne was tested. Testes could give suggestions and be applied if buildings needed be revealed. The structure was modelled with finite element model of sap2000 package program and the forces generated under various loads and stresses, the occurred deformation due to that, overflow of allowable stress of this deformation and stresses were investigated. As the results of this study can be note that the maximum compressive stress at the construction is calculated as 1.1 MPa.

Macro elemental analysis of food samples by nuclear analytical technique

NASA Astrophysics Data System (ADS)

Syahfitri, W. Y. N.; Kurniawati, S.; Adventini, N.; Damastuti, E.; Lestiani, D. D.

2017-06-01

Energy-dispersive X-ray fluorescence (EDXRF) spectrometry is a non-destructive, rapid, multi elemental, accurate, and environment friendly analysis compared with other detection methods. Thus, EDXRF spectrometry is applicable for food inspection. The macro elements calcium and potassium constitute important nutrients required by the human body for optimal physiological functions. Therefore, the determination of Ca and K content in various foods needs to be done. The aim of this work is to demonstrate the applicability of EDXRF for food analysis. The analytical performance of non-destructive EDXRF was compared with other analytical techniques; neutron activation analysis and atomic absorption spectrometry. Comparison of methods performed as cross checking results of the analysis and to overcome the limitations of the three methods. Analysis results showed that Ca found in food using EDXRF and AAS were not significantly different with p-value 0.9687, whereas p-value of K between EDXRF and NAA is 0.6575. The correlation between those results was also examined. The Pearson correlations for Ca and K were 0.9871 and 0.9558, respectively. Method validation using SRM NIST 1548a Typical Diet was also applied. The results showed good agreement between methods; therefore EDXRF method can be used as an alternative method for the determination of Ca and K in food samples.

Homogenization of periodic bi-isotropic composite materials

NASA Astrophysics Data System (ADS)

Ouchetto, Ouail; Essakhi, Brahim

2018-07-01

In this paper, we present a new method for homogenizing the bi-periodic materials with bi-isotropic components phases. The presented method is a numerical method based on the finite element method to compute the local electromagnetic properties. The homogenized constitutive parameters are expressed as a function of the macroscopic electromagnetic properties which are obtained from the local properties. The obtained results are compared to Unfolding Finite Element Method and Maxwell-Garnett formulas.

Slip Continuity in Explicit Crystal Plasticity Simulations Using Nonlocal Continuum and Semi-discrete Approaches

DTIC Science & Technology

2013-01-01

Based Micropolar Single Crystal Plasticity: Comparison of Multi - and Single Criterion Theories. J. Mech. Phys. Solids 2011, 59, 398–422. ALE3D ...element boundaries in a multi -step constitutive evaluation (Becker, 2011). The results showed the desired effects of smoothing the deformation field...Implementation The model was implemented in the large-scale parallel, explicit finite element code ALE3D (2012). The crystal plasticity

Organization and evolution of highly repeated satellite DNA sequences in plant chromosomes.

PubMed

Sharma, S; Raina, S N

2005-01-01

A major component of the plant nuclear genome is constituted by different classes of repetitive DNA sequences. The structural, functional and evolutionary aspects of the satellite repetitive DNA families, and their organization in the chromosomes is reviewed. The tandem satellite DNA sequences exhibit characteristic chromosomal locations, usually at subtelomeric and centromeric regions. The repetitive DNA family(ies) may be widely distributed in a taxonomic family or a genus, or may be specific for a species, genome or even a chromosome. They may acquire large-scale variations in their sequence and copy number over an evolutionary time-scale. These features have formed the basis of extensive utilization of repetitive sequences for taxonomic and phylogenetic studies. Hybrid polyploids have especially proven to be excellent models for studying the evolution of repetitive DNA sequences. Recent studies explicitly show that some repetitive DNA families localized at the telomeres and centromeres have acquired important structural and functional significance. The repetitive elements are under different evolutionary constraints as compared to the genes. Satellite DNA families are thought to arise de novo as a consequence of molecular mechanisms such as unequal crossing over, rolling circle amplification, replication slippage and mutation that constitute "molecular drive". Copyright 2005 S. Karger AG, Basel.

Characterization of mechanical properties of pericardium tissue using planar biaxial tension and flexural deformation.

PubMed

Murdock, Kyle; Martin, Caitlin; Sun, Wei

2018-01-01

Flexure is an important mode of deformation for native and bioprosthetic heart valves. However, mechanical characterization of bioprosthetic leaflet materials has been done primarily through planar tensile testing. In this study, an integrated experimental and computational cantilever beam bending test was performed to characterize the flexural properties of glutaraldehyde-treated bovine and porcine pericardium of different thicknesses. A strain-invariant based structural constitutive model was used to model the pericardial mechanical behavior quantified through the bending tests of this study and the planar biaxial tests previously performed. The model parameters were optimized through an inverse finite element (FE) procedure in order to describe both sets of experimental data. The optimized material properties were implemented in FE simulations of transcatheter aortic valve (TAV) deformation. It was observed that porcine pericardium TAV leaflets experienced significantly more flexure than bovine when subjected to opening pressurization, and that the flexure may be overestimated using a constitutive model derived from purely planar tensile experimental data. Thus, modeling of a combination of flexural and biaxial tensile testing data may be necessary to more accurately describe the mechanical properties of pericardium, and to computationally investigate bioprosthetic leaflet function and design. Copyright © 2017 Elsevier Ltd. All rights reserved.

A microstructurally based model of solder joints under conditions of thermomechanical fatigue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frear, D.R.; Burchett, S.N.; Rashid, M.M.

The thermomechanical fatigue failure of solder joints in increasingly becoming an important reliability issue. In this paper we present two computational methodologies that have been developed to predict the behavior of near eutectic Sn-Pb solder joints under fatigue conditions that are based on metallurgical tests as fundamental input for constitutive relations. The two-phase model mathematically predicts the heterogeneous coarsening behavior of near eutectic Sn-Pb solder. The finite element simulations from this model agree well with experimental thermomechanical fatigue tests. The simulations show that the presence of an initial heterogeneity in the solder microstructure could significantly degrade the fatigue lifetime. Themore » single phase model is a computational technique that was developed to predict solder joint behavior using materials data for constitutive relation constants that could be determined through straightforward metallurgical experiments. A shear/torsion test sample was developed to impose strain in two different orientations. Materials constants were derived from these tests and the results showed an adequate fit to experimental results. The single-phase model could be very useful for conditions where microstructural evolution is not a dominant factor in fatigue.« less

An update on the constitutive relation of ligament tissues with the effects of collagen types.

PubMed

Wan, Chao; Hao, Zhixiu; Tong, Lingying; Lin, Jianhao; Li, Zhichang; Wen, Shizhu

2015-10-01

The musculoskeletal ligament is a kind of multiscale composite material with collagen fibers embedded in a ground matrix. As the major constituent in ligaments to bear external loads, collagens are composed mainly of two collagen contents with different mechanical properties, i.e., types I and III collagen. The constitutive relation of ligaments plays a critical role in the stability and normal function of human joints. However, collagen types have not been distinguished in the previous constitutive relations. In this paper a constitutive relation for ligament tissues was modified based on the previous constitutive relation by considering the effects of collagen types. Both the collagen contents and the mechanical properties of sixteen ligament specimens from four cadaveric human knee joints were measured for determining their material coefficients in the constitutive relation. The mechanical behaviors of ligaments were obtained from both the uniaxial tensile and simple shear tests. A linear regression between joint kinematic results from in vitro and in silico experiments was made to validate the accuracy of this constitutive relation. The high correlation coefficient (R(2)=0.93) and significance (P<0.0001) of the regression equation revealed that this modified constitutive relation of ligaments was accurate to be used in studying joint biomechanics. Another finite element analysis with collagen contents changing demonstrated that the effect of variations in collagen ratios on both joint kinematics and ligament biomechanics could be simulated by this constitutive relation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Variation in a surface-exposed region of the Mycoplasma pneumoniae P40 protein as a consequence of homologous DNA recombination between RepMP5 elements.

PubMed

Spuesens, Emiel B M; van de Kreeke, Nick; Estevão, Silvia; Hoogenboezem, Theo; Sluijter, Marcel; Hartwig, Nico G; van Rossum, Annemarie M C; Vink, Cornelis

2011-02-01

Mycoplasma pneumoniae is a human pathogen that causes a range of respiratory tract infections. The first step in infection is adherence of the bacteria to the respiratory epithelium. This step is mediated by a specialized organelle, which contains several proteins (cytadhesins) that have an important function in adherence. Two of these cytadhesins, P40 and P90, represent the proteolytic products from a single 130 kDa protein precursor, which is encoded by the MPN142 gene. Interestingly, MPN142 contains a repetitive DNA element, termed RepMP5, of which homologues are found at seven other loci within the M. pneumoniae genome. It has been hypothesized that these RepMP5 elements, which are similar but not identical in sequence, recombine with their counterpart within MPN142 and thereby provide a source of sequence variation for this gene. As this variation may give rise to amino acid changes within P40 and P90, the recombination between RepMP5 elements may constitute the basis of antigenic variation and, possibly, immune evasion by M. pneumoniae. To investigate the sequence variation of MPN142 in relation to inter-RepMP5 recombination, we determined the sequences of all RepMP5 elements in a collection of 25 strains. The results indicate that: (i) inter-RepMP5 recombination events have occurred in seven of the strains, and (ii) putative RepMP5 recombination events involving MPN142 have induced amino acid changes in a surface-exposed part of the P40 protein in two of the strains. We conclude that recombination between RepMP5 elements is a common phenomenon that may lead to sequence variation of MPN142-encoded proteins.

Development of an object-oriented finite element program: application to metal-forming and impact simulations

NASA Astrophysics Data System (ADS)

Pantale, O.; Caperaa, S.; Rakotomalala, R.

2004-07-01

During the last 50 years, the development of better numerical methods and more powerful computers has been a major enterprise for the scientific community. In the same time, the finite element method has become a widely used tool for researchers and engineers. Recent advances in computational software have made possible to solve more physical and complex problems such as coupled problems, nonlinearities, high strain and high-strain rate problems. In this field, an accurate analysis of large deformation inelastic problems occurring in metal-forming or impact simulations is extremely important as a consequence of high amount of plastic flow. In this presentation, the object-oriented implementation, using the C++ language, of an explicit finite element code called DynELA is presented. The object-oriented programming (OOP) leads to better-structured codes for the finite element method and facilitates the development, the maintainability and the expandability of such codes. The most significant advantage of OOP is in the modeling of complex physical systems such as deformation processing where the overall complex problem is partitioned in individual sub-problems based on physical, mathematical or geometric reasoning. We first focus on the advantages of OOP for the development of scientific programs. Specific aspects of OOP, such as the inheritance mechanism, the operators overload procedure or the use of template classes are detailed. Then we present the approach used for the development of our finite element code through the presentation of the kinematics, conservative and constitutive laws and their respective implementation in C++. Finally, the efficiency and accuracy of our finite element program are investigated using a number of benchmark tests relative to metal forming and impact simulations.

Evolutionary modes of emergence of short interspersed nuclear element (SINE) families in grasses.

PubMed

Kögler, Anja; Schmidt, Thomas; Wenke, Torsten

2017-11-01

Short interspersed nuclear elements (SINEs) are non-autonomous transposable elements which are propagated by retrotransposition and constitute an inherent part of the genome of most eukaryotic species. Knowledge of heterogeneous and highly abundant SINEs is crucial for de novo (or improvement of) annotation of whole genome sequences. We scanned Poaceae genome sequences of six important cereals (Oryza sativa, Triticum aestivum, Hordeum vulgare, Panicum virgatum, Sorghum bicolor, Zea mays) and Brachypodium distachyon to examine the diversity and evolution of SINE populations. We comparatively analyzed the structural features, distribution, evolutionary relation and abundance of 32 SINE families and subfamilies within grasses, comprising 11 052 individual copies. The investigation of activity profiles within the Poaceae provides insights into their species-specific diversification and amplification. We found that Poaceae SINEs (PoaS) fall into two length categories: simple SINEs of up to 180 bp and dimeric SINEs larger than 240 bp. Detailed analysis at the nucleotide level revealed that multimerization of related and unrelated SINE copies is an important evolutionary mechanism of SINE formation. We conclude that PoaS families diversify by massive reshuffling between SINE families, likely caused by insertion of truncated copies, and provide a model for this evolutionary scenario. Twenty-eight of 32 PoaS families and subfamilies show significant conservation, in particular either in the 5' or 3' regions, across Poaceae species and share large sequence stretches with one or more other PoaS families. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

The Separation of Church and State. Exploring the Constitution Series.

ERIC Educational Resources Information Center

McWhirter, Darien A.

This textbook on the separation of church and state continues the "Exploring the Constitution Series," which introduces important areas of constitutional law. Intended to serve either as a reference work, a supplement to a standard textbook, or as the textbook for a course, this volume covers the constitutional issues of prayer in public…

Nonconforming mortar element methods: Application to spectral discretizations

NASA Technical Reports Server (NTRS)

Maday, Yvon; Mavriplis, Cathy; Patera, Anthony

1988-01-01

Spectral element methods are p-type weighted residual techniques for partial differential equations that combine the generality of finite element methods with the accuracy of spectral methods. Presented here is a new nonconforming discretization which greatly improves the flexibility of the spectral element approach as regards automatic mesh generation and non-propagating local mesh refinement. The method is based on the introduction of an auxiliary mortar trace space, and constitutes a new approach to discretization-driven domain decomposition characterized by a clean decoupling of the local, structure-preserving residual evaluations and the transmission of boundary and continuity conditions. The flexibility of the mortar method is illustrated by several nonconforming adaptive Navier-Stokes calculations in complex geometry.

Three-dimensional finite element analysis for high velocity impact. [of projectiles from space debris

NASA Technical Reports Server (NTRS)

Chan, S. T. K.; Lee, C. H.; Brashears, M. R.

1975-01-01

A finite element algorithm for solving unsteady, three-dimensional high velocity impact problems is presented. A computer program was developed based on the Eulerian hydroelasto-viscoplastic formulation and the utilization of the theorem of weak solutions. The equations solved consist of conservation of mass, momentum, and energy, equation of state, and appropriate constitutive equations. The solution technique is a time-dependent finite element analysis utilizing three-dimensional isoparametric elements, in conjunction with a generalized two-step time integration scheme. The developed code was demonstrated by solving one-dimensional as well as three-dimensional impact problems for both the inviscid hydrodynamic model and the hydroelasto-viscoplastic model.

Long terminal repeat retrotransposons of Oryza sativa

PubMed Central

McCarthy, Eugene M; Liu, Jingdong; Lizhi, Gao; McDonald, John F

2002-01-01

Background Long terminal repeat (LTR) retrotransposons constitute a major fraction of the genomes of higher plants. For example, retrotransposons comprise more than 50% of the maize genome and more than 90% of the wheat genome. LTR retrotransposons are believed to have contributed significantly to the evolution of genome structure and function. The genome sequencing of selected experimental and agriculturally important species is providing an unprecedented opportunity to view the patterns of variation existing among the entire complement of retrotransposons in complete genomes. Results Using a new data-mining program, LTR_STRUC, (LTR retrotransposon structure program), we have mined the GenBank rice (Oryza sativa) database as well as the more extensive (259 Mb) Monsanto rice dataset for LTR retrotransposons. Almost two-thirds (37) of the 59 families identified consist of copia-like elements, but gypsy-like elements outnumber copia-like elements by a ratio of approximately 2:1. At least 17% of the rice genome consists of LTR retrotransposons. In addition to the ubiquitous gypsy- and copia-like classes of LTR retrotransposons, the rice genome contains at least two novel families of unusually small, non-coding (non-autonomous) LTR retrotransposons. Conclusions Each of the major clades of rice LTR retrotransposons is more closely related to elements present in other species than to the other clades of rice elements, suggesting that horizontal transfer may have occurred over the evolutionary history of rice LTR retrotransposons. Like LTR retrotransposons in other species with relatively small genomes, many rice LTR retrotransposons are relatively young, indicating a high rate of turnover. PMID:12372141

Germ line insertion of mtDNA at the breakpoint junction of a reciprocal constitutional translocation.

PubMed

Willett-Brozick, J E; Savul, S A; Richey, L E; Baysal, B E

2001-08-01

Constitutional chromosomal translocations are relatively common causes of human morbidity, yet the DNA double-strand break (DSB) repair mechanisms that generate them are incompletely understood. We cloned, sequenced and analyzed the breakpoint junctions of a familial constitutional reciprocal translocation t(9;11)(p24;q23). Within the 10-kb region flanking the breakpoints, chromosome 11 had 25% repeat elements, whereas chromosome 9 had 98% repeats, 95% of which were L1-type LINE elements. The breakpoints occurred within an L1-type repeat element at 9p24 and at the 3'-end of an Alu sequence at 11q23. At the breakpoint junction of derivative chromosome 9, we discovered an unusually large 41-bp insertion, which showed 100% identity to 12S mitochondrial DNA (mtDNA) between nucleotides 896 and 936 of the mtDNA sequence. Analysis of the human genome failed to show the preexistence of the inserted sequence at normal chromosomes 9 and 11 breakpoint junctions or elsewhere in the genome, strongly suggesting that the insertion was derived from human mtDNA and captured into the junction during the DSB repair process. To our knowledge, these findings represent the first observation of spontaneous germ line insertion of modern human mtDNA sequences and suggest that DSB repair may play a role in inter-organellar gene transfer in vivo. Our findings also provide evidence for a previously unrecognized insertional mechanism in human, by which non-mobile extra-chromosomal fragments can be inserted into the genome at DSB repair junctions.

Search for elemental and mineral biomarkers using inelastic neutron scattering spectroscopy (INSS)

NASA Astrophysics Data System (ADS)

Wielopolski, Lucian; Hoover, Richard B.; Mitra, Sudeep

2004-02-01

Life on Earth is characterized by a select group of low Z elements: C, H, N, O, P, K, S, Na, Cl. The presence of these elements and their ratios can provide indications of possible biogenicity and thus they may constitute valuable biomarkers that may help determine the best locations to seek more definitive evidence of life. We discuss the possible applications and significance of the inelastic neutron scattering induced gamma spectroscopy (INSGS) for future Astrobiology Missions to Mars or other solar System bodies. The general requirements and capabilities of the proposed approach are presented.

Hot forming of composite prepreg: Numerical analyses

NASA Astrophysics Data System (ADS)

Guzman-Maldonado, Eduardo; Hamila, Nahiène; Boisse, Philippe; El Azzouzi, Khalid; Tardif, Xavier; Moro, Tanguy; Chatel, Sylvain; Fideu, Paulin

2017-10-01

The work presented here is part of the "FORBANS" project about the Hot Drape Forming (HDF) process consisting of unidirectional prepregs laminates. To ensure a fine comprehension of this process a combination strategy between experiment and numerical analysis is adopted. This paper is focused on the numerical analysis using the finite element method (FEM) with a hyperelastic constitutive law. Each prepreg layer is modelled by shell elements. These elements consider the tension, in-plane shear and bending behaviour of the ply at different temperatures. The contact/friction during the forming process is taken into account using forward increment Lagrange multipliers.

A Review of International Space Station Habitable Element Equipment Offgassing Characteristics

NASA Technical Reports Server (NTRS)

Perry, Jay L.

2010-01-01

Crewed spacecraft trace contaminant control employs both passive and active methods to achieve acceptable cabin atmospheric quality. Passive methods include carefully selecting materials of construction, employing clean manufacturing practices, and minimizing systems and payload operational impacts to the cabin environment. Materials selection and manufacturing processes constitute the first level of equipment offgassing control. An element-level equipment offgassing test provides preflight verification that passive controls have been successful. Offgassing test results from multiple International Space Station (ISS) habitable elements and cargo vehicles are summarized and implications for active contamination control equipment design are discussed

Construction of hexahedral finite element mesh capturing realistic geometries of a petroleum reserve

DOE PAGES

Park, Byoung Yoon; Roberts, Barry L.; Sobolik, Steven R.

2017-07-27

The three-dimensional finite element mesh capturing realistic geometries of the Bayou Choctaw site has been constructed using the sonar and seismic survey data obtained from the field. The mesh consists of hexahedral elements because the salt constitutive model is coded using hexahedral elements. Various ideas and techniques to construct finite element mesh capturing artificially and naturally formed geometries are provided. The techniques to reduce the number of elements as much as possible to save on computer run time while maintaining the computational accuracy is also introduced. The steps and methodologies could be applied to construct the meshes of Big Hill,more » Bryan Mound, and West Hackberry strategic petroleum reserve sites. The methodology could be applied to the complicated shape masses for various civil and geological structures.« less

Construction of hexahedral finite element mesh capturing realistic geometries of a petroleum reserve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Byoung Yoon; Roberts, Barry L.; Sobolik, Steven R.

The three-dimensional finite element mesh capturing realistic geometries of the Bayou Choctaw site has been constructed using the sonar and seismic survey data obtained from the field. The mesh consists of hexahedral elements because the salt constitutive model is coded using hexahedral elements. Various ideas and techniques to construct finite element mesh capturing artificially and naturally formed geometries are provided. The techniques to reduce the number of elements as much as possible to save on computer run time while maintaining the computational accuracy is also introduced. The steps and methodologies could be applied to construct the meshes of Big Hill,more » Bryan Mound, and West Hackberry strategic petroleum reserve sites. The methodology could be applied to the complicated shape masses for various civil and geological structures.« less

Unusually long-lived pause required for regulation of a Rho-dependent transcription terminator.

PubMed

Hollands, Kerry; Sevostiyanova, Anastasia; Groisman, Eduardo A

2014-05-13

Up to half of all transcription termination events in bacteria rely on the RNA-dependent helicase Rho. However, the nucleic acid sequences that promote Rho-dependent termination remain poorly characterized. Defining the molecular determinants that confer Rho-dependent termination is especially important for understanding how such terminators can be regulated in response to specific signals. Here, we identify an extraordinarily long-lived pause at the site where Rho terminates transcription in the 5'-leader region of the Mg(2+) transporter gene mgtA in Salmonella enterica. We dissect the sequence elements required for prolonged pausing in the mgtA leader and establish that the remarkable longevity of this pause is required for a riboswitch to stimulate Rho-dependent termination in the mgtA leader region in response to Mg(2+) availability. Unlike Rho-dependent terminators described previously, where termination occurs at multiple pause sites, there is a single site of transcription termination directed by Rho in the mgtA leader. Our data suggest that Rho-dependent termination events that are subject to regulation may require elements distinct from those operating at constitutive Rho-dependent terminators.

Parameter identification and optimization of slide guide joint of CNC machine tools

NASA Astrophysics Data System (ADS)

Zhou, S.; Sun, B. B.

2017-11-01

The joint surface has an important influence on the performance of CNC machine tools. In order to identify the dynamic parameters of slide guide joint, the parametric finite element model of the joint is established and optimum design method is used based on the finite element simulation and modal test. Then the mode that has the most influence on the dynamics of slip joint is found through harmonic response analysis. Take the frequency of this mode as objective, the sensitivity analysis of the stiffness of each joint surface is carried out using Latin Hypercube Sampling and Monte Carlo Simulation. The result shows that the vertical stiffness of slip joint surface constituted by the bed and the slide plate has the most obvious influence on the structure. Therefore, this stiffness is taken as the optimization variable and the optimal value is obtained through studying the relationship between structural dynamic performance and stiffness. Take the stiffness values before and after optimization into the FEM of machine tool, and it is found that the dynamic performance of the machine tool is improved.

Defining Transcriptional Regulatory Mechanisms for Primary let-7 miRNAs

PubMed Central

Gaeta, Xavier; Le, Luat; Lin, Ying; Xie, Yuan; Lowry, William E.

2017-01-01

The let-7 family of miRNAs have been shown to control developmental timing in organisms from C. elegans to humans; their function in several essential cell processes throughout development is also well conserved. Numerous studies have defined several steps of post-transcriptional regulation of let-7 production; from pri-miRNA through pre-miRNA, to the mature miRNA that targets endogenous mRNAs for degradation or translational inhibition. Less-well defined are modes of transcriptional regulation of the pri-miRNAs for let-7. let-7 pri-miRNAs are expressed in polycistronic fashion, in long transcripts newly annotated based on chromatin-associated RNA-sequencing. Upon differentiation, we found that some let-7 pri-miRNAs are regulated at the transcriptional level, while others appear to be constitutively transcribed. Using the Epigenetic Roadmap database, we further annotated regulatory elements of each polycistron identified putative promoters and enhancers. Probing these regulatory elements for transcription factor binding sites identified factors that regulate transcription of let-7 in both promoter and enhancer regions, and identified novel regulatory mechanisms for this important class of miRNAs. PMID:28052101

A finite element simulation of biological conversion processes in landfills.

PubMed

Robeck, M; Ricken, T; Widmann, R

2011-04-01

Landfills are the most common way of waste disposal worldwide. Biological processes convert the organic material into an environmentally harmful landfill gas, which has an impact on the greenhouse effect. After the depositing of waste has been stopped, current conversion processes continue and emissions last for several decades and even up to 100years and longer. A good prediction of these processes is of high importance for landfill operators as well as for authorities, but suitable models for a realistic description of landfill processes are rather poor. In order to take the strong coupled conversion processes into account, a constitutive three-dimensional model based on the multiphase Theory of Porous Media (TPM) has been developed at the University of Duisburg-Essen. The theoretical formulations are implemented in the finite element code FEAP. With the presented calculation concept we are able to simulate the coupled processes that occur in an actual landfill. The model's theoretical background and the results of the simulations as well as the meantime successfully performed simulation of a real landfill body will be shown in the following. Copyright © 2010 Elsevier Ltd. All rights reserved.

Active and Inactive Enhancers Cooperate to Exert Localized and Long-Range Control of Gene Regulation.

PubMed

Proudhon, Charlotte; Snetkova, Valentina; Raviram, Ramya; Lobry, Camille; Badri, Sana; Jiang, Tingting; Hao, Bingtao; Trimarchi, Thomas; Kluger, Yuval; Aifantis, Iannis; Bonneau, Richard; Skok, Jane A

2016-06-07

V(D)J recombination relies on the presence of proximal enhancers that activate the antigen receptor (AgR) loci in a lineage- and stage-specific manner. Unexpectedly, we find that both active and inactive AgR enhancers cooperate to disseminate their effects in a localized and long-range manner. Here, we demonstrate the importance of short-range contacts between active enhancers that constitute an Igk super-enhancer in B cells. Deletion of one element reduces the interaction frequency between other enhancers in the hub, which compromises the transcriptional output of each component. Furthermore, we establish that, in T cells, long-range contact and cooperation between the inactive Igk enhancer MiEκ and the active Tcrb enhancer Eβ alters enrichment of CBFβ binding in a manner that impacts Tcrb recombination. These findings underline the complexities of enhancer regulation and point to a role for localized and long-range enhancer-sharing between active and inactive elements in lineage- and stage-specific control. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

The development of effective message content for suicide intervention: theory of planned behavior.

PubMed

Shemanski Aldrich, Rosalie; Cerel, Julie

2009-01-01

Each year there are over 31,000 suicides in the United States, constituting a significant problem in every respect. It is important for research efforts to focus on the communication elements involved in suicide prevention because the messages produced by individuals close to those who have suicidal thoughts have the potential to save a life. The current manuscript presents the theory of planned behavior (TPB) as a foundation to increase understanding of what message content would be most effective to convince an individual to intervene when someone is suicidal. Suicide and suicidal behaviors are briefly reviewed, as is the TPB. Then it is argued how and why TPB can help construct persuasive messages. The authors suggest that TPB guide the content of persuasive messages. Messages created in combination of persuasive theories with TPB are likely to encourage an individual to intervene when someone is suicidal. A key element to suicide prevention is intervention by close others. Use of TPB provides an increased understanding of how to persuade close individuals to intervene when an individual is suicidal.

Molecular Basis of Virulence in Staphylococcus aureus Mastitis

PubMed Central

Le Maréchal, Caroline; Seyffert, Nubia; Jardin, Julien; Hernandez, David; Jan, Gwenaël; Rault, Lucie; Azevedo, Vasco; François, Patrice; Schrenzel, Jacques; van de Guchte, Maarten; Even, Sergine; Berkova, Nadia; Thiéry, Richard; Fitzgerald, J. Ross

2011-01-01

Background S. aureus is one of the main pathogens involved in ruminant mastitis worldwide. The severity of staphylococcal infection is highly variable, ranging from subclinical to gangrenous mastitis. This work represents an in-depth characterization of S. aureus mastitis isolates to identify bacterial factors involved in severity of mastitis infection. Methodology/Principal Findings We employed genomic, transcriptomic and proteomic approaches to comprehensively compare two clonally related S. aureus strains that reproducibly induce severe (strain O11) and milder (strain O46) mastitis in ewes. Variation in the content of mobile genetic elements, iron acquisition and metabolism, transcriptional regulation and exoprotein production was observed. In particular, O11 produced relatively high levels of exoproteins, including toxins and proteases known to be important in virulence. A characteristic we observed in other S. aureus strains isolated from clinical mastitis cases. Conclusions/Significance Our data are consistent with a dose-dependant role of some staphylococcal factors in the hypervirulence of strains isolated from severe mastitis. Mobile genetic elements, transcriptional regulators, exoproteins and iron acquisition pathways constitute good targets for further research to define the underlying mechanisms of mastitis severity. PMID:22096559

Evaluation of FEM engineering parameters from insitu tests

DOT National Transportation Integrated Search

2001-12-01

The study looked critically at insitu test methods (SPT, CPT, DMT, and PMT) as a means for developing finite element constitutive model input parameters. The first phase of the study examined insitu test derived parameters with laboratory triaxial te...

Method to determine the optimal constitutive model from spherical indentation tests

NASA Astrophysics Data System (ADS)

Zhang, Tairui; Wang, Shang; Wang, Weiqiang

2018-03-01

The limitation of current indentation theories was investigated and a method to determine the optimal constitutive model through spherical indentation tests was proposed. Two constitutive models, the Power-law and the Linear-law, were used in Finite Element (FE) calculations, and then a set of indentation governing equations was established for each model. The load-depth data from the normal indentation depth was used to fit the best parameters in each constitutive model while the data from the further loading part was compared with those from FE calculations, and the model that better predicted the further deformation was considered the optimal one. Moreover, a Yang's modulus calculation model which took the previous plastic deformation and the phenomenon of pile-up (or sink-in) into consideration was also proposed to revise the original Sneddon-Pharr-Oliver model. The indentation results on six materials, 304, 321, SA508, SA533, 15CrMoR, and Fv520B, were compared with tensile ones, which validated the reliability of the revised E calculation model and the optimal constitutive model determination method in this study.

Fluid-structure finite-element vibrational analysis

NASA Technical Reports Server (NTRS)

Feng, G. C.; Kiefling, L.

1974-01-01

A fluid finite element has been developed for a quasi-compressible fluid. Both kinetic and potential energy are expressed as functions of nodal displacements. Thus, the formulation is similar to that used for structural elements, with the only differences being that the fluid can possess gravitational potential, and the constitutive equations for fluid contain no shear coefficients. Using this approach, structural and fluid elements can be used interchangeably in existing efficient sparse-matrix structural computer programs such as SPAR. The theoretical development of the element formulations and the relationships of the local and global coordinates are shown. Solutions of fluid slosh, liquid compressibility, and coupled fluid-shell oscillation problems which were completed using a temporary digital computer program are shown. The frequency correlation of the solutions with classical theory is excellent.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Byoung Yoon; Roberts, Barry L.

The three-dimensional finite element mesh capturing realistic geometries of Bayou Choctaw site has been constructed using the sonar and seismic survey data obtained from the field. The mesh is consisting of hexahedral elements because the salt constitutive model is coded using hexahedral elements. Various ideas and techniques to construct finite element mesh capturing artificially and naturally formed geometries are provided. The techniques to reduce the number of elements as much as possible to save on computer run time with maintaining the computational accuracy is also introduced. The steps and methodologies could be applied to construct the meshes of Big Hill,more » Bryan Mound, and West Hackberry strategic petroleum reserve sites. The methodology could be applied to the complicated shape masses for not only various civil and geological structures but also biological applications such as artificial limbs.« less

The SIDER2 elements, interspersed repeated sequences that populate the Leishmania genomes, constitute subfamilies showing chromosomal proximity relationship.

PubMed

Requena, Jose M; Folgueira, Cristina; López, Manuel C; Thomas, M Carmen

2008-06-02

Protozoan parasites of the genus Leishmania are causative agents of a diverse spectrum of human diseases collectively known as leishmaniasis. These eukaryotic pathogens that diverged early from the main eukaryotic lineage possess a number of unusual genomic, molecular and biochemical features. The completion of the genome projects for three Leishmania species has generated invaluable information enabling a direct analysis of genome structure and organization. By using DNA macroarrays, made with Leishmania infantum genomic clones and hybridized with total DNA from the parasite, we identified a clone containing a repeated sequence. An analysis of the recently completed genome sequence of L. infantum, using this repeated sequence as bait, led to the identification of a new class of repeated elements that are interspersed along the different L. infantum chromosomes. These elements turned out to be homologues of SIDER2 sequences, which were recently identified in the Leishmania major genome; thus, we adopted this nomenclature for the Leishmania elements described herein. Since SIDER2 elements are very heterogeneous in sequence, their precise identification is rather laborious. We have characterized 54 LiSIDER2 elements in chromosome 32 and 27 ones in chromosome 20. The mean size for these elements is 550 bp and their sequence is G+C rich (mean value of 66.5%). On the basis of sequence similarity, these elements can be grouped in subfamilies that show a remarkable relationship of proximity, i.e. SIDER2s of a given subfamily locate close in a chromosomal region without intercalating elements. For comparative purposes, we have identified the SIDER2 elements existing in L. major and Leishmania braziliensis chromosomes 32. While SIDER2 elements are highly conserved both in number and location between L. infantum and L. major, no such conservation exists when comparing with SIDER2s in L. braziliensis chromosome 32. SIDER2 elements constitute a relevant piece in the Leishmania genome organization. Sequence characteristics, genomic distribution and evolutionarily conservation of SIDER2s are suggestive of relevant functions for these elements in Leishmania. Apart from a proved involvement in post-transcriptional mechanisms of gene regulation, SIDER2 elements could be involved in DNA amplification processes and, perhaps, in chromosome segregation as centromeric sequences.

Mapping soil-landscape elements and the wetland in dambos and estimating CH4 and CO2 emissions from a dambo-terminated catena

NASA Astrophysics Data System (ADS)

Sebadduka, Jerome

Dambos are seasonally saturated grassy valleys mainly found on the central African plateau. They are usually sub-divided into three catenary units - gleyed and frequently inundated bottoms, flat and rarely inundated floors, and sloping sandy margins - fringed at the interfluve by the well-drained uplands. Since dambos constitute ˜11% of Africa's arable land, soil information is required to guide sustainable use of the land. Further, it is important to determine the extent of the wetland environment in these landscapes so as to avoid miss-use of the land, which could arise because of varying definitions of the wetland in these landscapes. In addition, lack of knowledge about the true nature of dambo wetlands limits our understanding of their greenhouse gas (GHG) source and sinks strengths, which prevents projection of future GHG scenarios accompanying dambo use. This study was conducted so as to address these inadequacies, and is guided by the following specific objectives: (i) delineate dambo soil-landscape elements using aerial gamma-ray and terrain data; (ii) characterize a dambo wetland; and (iii) determine CH4 and CO2 sources and sinks in a dambo landscape. The area Hansen et al. (2009) studied was revisited. For objective 1, their model training and validation data were used. For objectives 2 and 3, data (e.g., soil, water table and gas samples) were collected from experimental plots in the four landscape positions, geographically constrained around dambo bottom pixels. Data used were collected during the main (March to July 2008) and short rainfall (October and November 2009) seasons in the area. An ANOVA analysis showed landscape position to have a proportionate influence on the variability of eU (46%), K% (28%) and eTh (27%); owing to the differences in soil properties along dambo cross-profiles. The results based on random forests (RF) and multinomial-ISODATA modeling, where gamma-ray and derivatives of a Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) were used to classify dambo catenary units, were accurate, but only slightly better than the method which made no use of gamma-ray (e.g., conditional inference tree) . It was concluded that dambo landscape elements can be mapped by using these two data sources; although terrain data provides more information. Based upon a combination of hydrology and soil properties, dambo bottoms were the only element shown to constitute the dambo wetland. This zone is inundated for at least three-quarters of the main rainfall season and soils are hydric. Using the landscape map created by Hansen et al. (2009), the wetland was found to constitute only ˜15% of the dambo. This is smaller than what was mapped by FAO-Africover and the Department of Survey and Mapping, Uganda (DSM). The wetland was also found to be the main source of CH 4 and sink of CO2, with additional strengths attributed to the neighboring floor. Given that these constitute less than 20% of the landscape, dambo net contribution to the regional CH4 budget is insignificant because 80% of the landscape is a sink. The worry, though, is the ongoing degradation, with the impact this has on the release of CO2.

Multiscale Modeling of Intergranular Fracture in Aluminum: Constitutive Relation For Interface Debonding

NASA Technical Reports Server (NTRS)

Yamakov, V.; Saether, E.; Glaessgen, E. H.

2008-01-01

Intergranular fracture is a dominant mode of failure in ultrafine grained materials. In the present study, the atomistic mechanisms of grain-boundary debonding during intergranular fracture in aluminum are modeled using a coupled molecular dynamics finite element simulation. Using a statistical mechanics approach, a cohesive-zone law in the form of a traction-displacement constitutive relationship, characterizing the load transfer across the plane of a growing edge crack, is extracted from atomistic simulations and then recast in a form suitable for inclusion within a continuum finite element model. The cohesive-zone law derived by the presented technique is free of finite size effects and is statistically representative for describing the interfacial debonding of a grain boundary (GB) interface examined at atomic length scales. By incorporating the cohesive-zone law in cohesive-zone finite elements, the debonding of a GB interface can be simulated in a coupled continuum-atomistic model, in which a crack starts in the continuum environment, smoothly penetrates the continuum-atomistic interface, and continues its propagation in the atomistic environment. This study is a step towards relating atomistically derived decohesion laws to macroscopic predictions of fracture and constructing multiscale models for nanocrystalline and ultrafine grained materials.

Phase field modeling of brittle fracture for enhanced assumed strain shells at large deformations: formulation and finite element implementation

NASA Astrophysics Data System (ADS)

Reinoso, J.; Paggi, M.; Linder, C.

2017-06-01

Fracture of technological thin-walled components can notably limit the performance of their corresponding engineering systems. With the aim of achieving reliable fracture predictions of thin structures, this work presents a new phase field model of brittle fracture for large deformation analysis of shells relying on a mixed enhanced assumed strain (EAS) formulation. The kinematic description of the shell body is constructed according to the solid shell concept. This enables the use of fully three-dimensional constitutive models for the material. The proposed phase field formulation integrates the use of the (EAS) method to alleviate locking pathologies, especially Poisson thickness and volumetric locking. This technique is further combined with the assumed natural strain method to efficiently derive a locking-free solid shell element. On the computational side, a fully coupled monolithic framework is consistently formulated. Specific details regarding the corresponding finite element formulation and the main aspects associated with its implementation in the general purpose packages FEAP and ABAQUS are addressed. Finally, the applicability of the current strategy is demonstrated through several numerical examples involving different loading conditions, and including linear and nonlinear hyperelastic constitutive models.

Element fracture technique for hypervelocity impact simulation

NASA Astrophysics Data System (ADS)

Zhang, Xiao-tian; Li, Xiao-gang; Liu, Tao; Jia, Guang-hui

2015-05-01

Hypervelocity impact dynamics is the theoretical support of spacecraft shielding against space debris. The numerical simulation has become an important approach for obtaining the ballistic limits of the spacecraft shields. Currently, the most widely used algorithm for hypervelocity impact is the smoothed particle hydrodynamics (SPH). Although the finite element method (FEM) is widely used in fracture mechanics and low-velocity impacts, the standard FEM can hardly simulate the debris cloud generated by hypervelocity impact. This paper presents a successful application of the node-separation technique for hypervelocity impact debris cloud simulation. The node-separation technique assigns individual/coincident nodes for the adjacent elements, and it applies constraints to the coincident node sets in the modeling step. In the explicit iteration, the cracks are generated by releasing the constrained node sets that meet the fracture criterion. Additionally, the distorted elements are identified from two aspects - self-piercing and phase change - and are deleted so that the constitutive computation can continue. FEM with the node-separation technique is used for thin-wall hypervelocity impact simulations. The internal structures of the debris cloud in the simulation output are compared with that in the test X-ray graphs under different material fracture criteria. It shows that the pressure criterion is more appropriate for hypervelocity impact. The internal structures of the debris cloud are also simulated and compared under different thickness-to-diameter ratios (t/D). The simulation outputs show the same spall pattern with the tests. Finally, the triple-plate impact case is simulated with node-separation FEM.

Atomistic Cohesive Zone Models for Interface Decohesion in Metals

NASA Technical Reports Server (NTRS)

Yamakov, Vesselin I.; Saether, Erik; Glaessgen, Edward H.

2009-01-01

Using a statistical mechanics approach, a cohesive-zone law in the form of a traction-displacement constitutive relationship characterizing the load transfer across the plane of a growing edge crack is extracted from atomistic simulations for use within a continuum finite element model. The methodology for the atomistic derivation of a cohesive-zone law is presented. This procedure can be implemented to build cohesive-zone finite element models for simulating fracture in nanocrystalline or ultrafine grained materials.

Regulatory elements involved in constitutive and phorbol ester-inducible expression of the plasminogen activator inhibitor type 2 gene promoter.

PubMed Central

Cousin, E; Medcalf, R L; Bergonzelli, G E; Kruithof, E K

1991-01-01

Gene transcription rates and mRNA levels of plasminogen activator inhibitor type 2 (PAI-2) are markedly induced by the tumor promoting agent phorbol 12-myristate 13-acetate (PMA) in human HT1080 fibrosarcoma cells. To identify promoter elements required for basal-, and phorbol ester-inducible expression, deletion mutants of the PAI-1 promoter fused to the chloramphenicol acetyl transferase (CAT) reporter gene, were transiently expressed in HT1080 cells. Constitutive CAT activity was expressed from constructs containing more than 215 bp of promoter sequence, whereas deletion to position -91 bp abolished CAT gene expression. Treatment of transfected cells with PMA resulted in a three- to ten-fold increase in CAT expression from all constructs except from the construct shortened to position -91. DNAse1 protection analysis of the promoter region between -215 and the transcription initiation site revealed numerous protected regions, including two AP1-like binding sites (AP1a and AP1b) and one CRE-like element. Site-directed mutagenesis of the AP1a site or of the CRE-like site resulted in the loss of basal CAT activity and abolished the PMA effect, whereas mutagenesis of AP1b only partially inhibited basal and PMA-mediated expression. Our results suggest that the PAI-2 promoter contains at least two elements required for basal gene transcription and PMA-mediated induction. Images PMID:1650454

Impact of Truck Loading on Design and Analysis of Asphaltic Pavement Structures : Phase II

DOT National Transportation Integrated Search

2011-02-01

In this study, Schaperys nonlinear viscoelastic constitutive model is implemented into the commercial finite element (FE) software ABAQUS via user defined subroutine (user material, or UMAT) to analyze asphalt pavement subjected to heavy truck loa...

AUTOMATIC CALIBRATION OF A STOCHASTIC-LAGRANGIAN TRANSPORT MODEL (SLAM)

EPA Science Inventory

Numerical models are a useful tool in evaluating and designing NAPL remediation systems. Traditional constitutive finite difference and finite element models are complex and expensive to apply. For this reason, this paper presents the application of a simplified stochastic-Lagran...

Implementing Responsibility Centre Budgeting

ERIC Educational Resources Information Center

Vonasek, Joseph

2011-01-01

Recently, institutes of higher education (universities) have shown a renewed interest in organisational structures and operating methodologies that generate productivity and innovation; responsibility centre budgeting (RCB) is one such process. This paper describes the underlying principles constituting RCB, its origin and structural elements, and…

Removal of a putative inhibitory element reduces the calcium-dependent calmodulin activation of neuronal nitric-oxide synthase.

PubMed

Montgomery, H J; Romanov, V; Guillemette, J G

2000-02-18

Neuronal nitric-oxide synthase (NOS) and endothelial NOS are constitutive NOS isoforms that are activated by binding calmodulin in response to elevated intracellular calcium. In contrast, the inducible NOS isoform binds calmodulin at low basal levels of calcium in resting cells. Primary sequence comparisons show that each constitutive NOS isozyme contains a polypeptide segment within its reductase domain, which is absent in the inducible NOS enzyme. To study a possible link between the presence of these additional polypeptide segments in constitutive NOS enzymes and their calcium-dependent calmodulin activation, three deletion mutants were created. The putative inhibitory insert was removed from the FMN binding regions of the neuronal NOS holoenzyme and from two truncated neuronal NOS reductase enzymes in which the calmodulin binding region was either included or deleted. All three mutant enzymes showed reduced incorporation of FMN and required reconstitution with exogenous FMN for activity. The combined removal of both the calmodulin binding domain and the putative inhibitory insert did not result in a calmodulin-independent neuronal NOS reductase. Thus, although the putative inhibitory element has an effect on the calcium-dependent calmodulin activation of neuronal NOS, it does not have the properties of the typical autoinhibitory domain found in calmodulin-activated enzymes.

Application of activated barrier hopping theory to viscoplastic modeling of glassy polymers

NASA Astrophysics Data System (ADS)

Sweeney, J.; Spencer, P. E.; Vgenopoulos, D.; Babenko, M.; Boutenel, F.; Caton-Rose, P.; Coates, P. D.

2018-05-01

An established statistical mechanical theory of amorphous polymer deformation has been incorporated as a plastic mechanism into a constitutive model and applied to a range of polymer mechanical deformations. The temperature and rate dependence of the tensile yield of PVC, as reported in early studies, has been modeled to high levels of accuracy. Tensile experiments on PET reported here are analyzed similarly and good accuracy is also achieved. The frequently observed increase in the gradient of the plot of yield stress against logarithm of strain rate is an inherent feature of the constitutive model. The form of temperature dependence of the yield that is predicted by the model is found to give an accurate representation. The constitutive model is developed in two-dimensional form and implemented as a user-defined subroutine in the finite element package ABAQUS. This analysis is applied to the tensile experiments on PET, in some of which strain is localized in the form of shear bands and necks. These deformations are modeled with partial success, though adiabatic heating of the instability causes inaccuracies for this isothermal implementation of the model. The plastic mechanism has advantages over the Eyring process, is equally tractable, and presents no particular difficulties in implementation with finite elements.

Application of activated barrier hopping theory to viscoplastic modeling of glassy polymers

NASA Astrophysics Data System (ADS)

Sweeney, J.; Spencer, P. E.; Vgenopoulos, D.; Babenko, M.; Boutenel, F.; Caton-Rose, P.; Coates, P. D.

2017-10-01

An established statistical mechanical theory of amorphous polymer deformation has been incorporated as a plastic mechanism into a constitutive model and applied to a range of polymer mechanical deformations. The temperature and rate dependence of the tensile yield of PVC, as reported in early studies, has been modeled to high levels of accuracy. Tensile experiments on PET reported here are analyzed similarly and good accuracy is also achieved. The frequently observed increase in the gradient of the plot of yield stress against logarithm of strain rate is an inherent feature of the constitutive model. The form of temperature dependence of the yield that is predicted by the model is found to give an accurate representation. The constitutive model is developed in two-dimensional form and implemented as a user-defined subroutine in the finite element package ABAQUS. This analysis is applied to the tensile experiments on PET, in some of which strain is localized in the form of shear bands and necks. These deformations are modeled with partial success, though adiabatic heating of the instability causes inaccuracies for this isothermal implementation of the model. The plastic mechanism has advantages over the Eyring process, is equally tractable, and presents no particular difficulties in implementation with finite elements.

Morphological and functional aspects of progenitors perturbed in cortical malformations

PubMed Central

Bizzotto, Sara; Francis, Fiona

2015-01-01

In this review, we discuss molecular and cellular mechanisms important for the function of neuronal progenitors during development, revealed by their perturbation in different cortical malformations. We focus on a class of neuronal progenitors, radial glial cells (RGCs), which are renowned for their unique morphological and behavioral characteristics, constituting a key element during the development of the mammalian cerebral cortex. We describe how the particular morphology of these cells is related to their roles in the orchestration of cortical development and their influence on other progenitor types and post-mitotic neurons. Important for disease mechanisms, we overview what is currently known about RGC cellular components, cytoskeletal mechanisms, signaling pathways and cell cycle characteristics, focusing on how defects lead to abnormal development and cortical malformation phenotypes. The multiple recent entry points from human genetics and animal models are contributing to our understanding of this important cell type. Combining data from phenotypes in the mouse reveals molecules which potentially act in common pathways. Going beyond this, we discuss future directions that may provide new data in this expanding area. PMID:25729350

Nonlinear constitutive theory for turbine engine structural analysis

NASA Technical Reports Server (NTRS)

Thompson, R. L.

1982-01-01

A number of viscoplastic constitutive theories and a conventional constitutive theory are evaluated and compared in their ability to predict nonlinear stress-strain behavior in gas turbine engine components at elevated temperatures. Specific application of these theories is directed towards the structural analysis of combustor liners undergoing transient, cyclic, thermomechanical load histories. The combustor liner material considered in this study is Hastelloy X. The material constants for each of the theories (as a function of temperature) are obtained from existing, published experimental data. The viscoplastic theories and a conventional theory are incorporated into a general purpose, nonlinear, finite element computer program. Several numerical examples of combustor liner structural analysis using these theories are given to demonstrate their capabilities. Based on the numerical stress-strain results, the theories are evaluated and compared.

On numerical integration and computer implementation of viscoplastic models

NASA Technical Reports Server (NTRS)

Chang, T. Y.; Chang, J. P.; Thompson, R. L.

1985-01-01

Due to the stringent design requirement for aerospace or nuclear structural components, considerable research interests have been generated on the development of constitutive models for representing the inelastic behavior of metals at elevated temperatures. In particular, a class of unified theories (or viscoplastic constitutive models) have been proposed to simulate material responses such as cyclic plasticity, rate sensitivity, creep deformations, strain hardening or softening, etc. This approach differs from the conventional creep and plasticity theory in that both the creep and plastic deformations are treated as unified time-dependent quantities. Although most of viscoplastic models give better material behavior representation, the associated constitutive differential equations have stiff regimes which present numerical difficulties in time-dependent analysis. In this connection, appropriate solution algorithm must be developed for viscoplastic analysis via finite element method.

Adaptive unified continuum FEM modeling of a 3D FSI benchmark problem.

PubMed

Jansson, Johan; Degirmenci, Niyazi Cem; Hoffman, Johan

2017-09-01

In this paper, we address a 3D fluid-structure interaction benchmark problem that represents important characteristics of biomedical modeling. We present a goal-oriented adaptive finite element methodology for incompressible fluid-structure interaction based on a streamline diffusion-type stabilization of the balance equations for mass and momentum for the entire continuum in the domain, which is implemented in the Unicorn/FEniCS software framework. A phase marker function and its corresponding transport equation are introduced to select the constitutive law, where the mesh tracks the discontinuous fluid-structure interface. This results in a unified simulation method for fluids and structures. We present detailed results for the benchmark problem compared with experiments, together with a mesh convergence study. Copyright © 2016 John Wiley & Sons, Ltd.

Small-molecule modulators of PXR and CAR

PubMed Central

Chai, Sergio C.; Cherian, Milu T.; Wang, Yue-Ming; Chen, Taosheng

2016-01-01

Two nuclear receptors, the pregnane X receptor (PXR) and the constitutive androstane receptor (CAR), participate in the xenobiotic detoxification system by regulating the expression of drug-metabolizing enzymes and transporters in order to degrade and excrete foreign chemicals or endogenous metabolites. This review aims to expand the perceived relevance of PXR and CAR beyond their established role as master xenosensors to disease-oriented areas, emphasizing their modulation by small molecules. Structural studies of these receptors have provided much-needed insight into the nature of their binding promiscuity and the important elements that lead to ligand binding. Reports of species- and isoform-selective activation highlight the need for further scrutiny when extrapolating from animal data to humans, as animal models are at the forefront of early drug discovery. PMID:26921498

[Parenting styles].

PubMed

Torío López, Susana; Peña Calvo, José Vicente; Inda Caro, Mercedes

2008-02-01

Parental educational styles constitute one of the key elements of family socialization. The aim of the present essay is to present the results of a research project carried out in the Principality of Asturias (Spain) among 2,965 families with children of infant and primary-school age (5-8 years old). This research attempts to analyse, among other aspects, parental behaviour tendencies in child upbringing. The analysis of the results obtained allows us to: 1) identify the most common attitudinal and behavioural tendencies of parents in the upbringing of their children; 2) determine how many people have a well defined parental style, and delimit their socio-educational characteristics. Lastly, we consider the need to change some parental behaviour patterns and stress the importance of family education programmes, with the aim of promoting appropriate parenting models and modifying or improving current practices.

Gravity flow of powder in a lunar environment. Part 2: Analysis of flow initiation

NASA Technical Reports Server (NTRS)

Pariseau, W. G.

1971-01-01

A small displacement-small strain finite element technique utilizing the constant strain triangle and incremental constitutive equations for elasticplastic (media nonhardening and obeying a Coulomb yield condition) was applied to the analysis of gravity flow initiation. This was done in a V-shaped hopper containing a powder under lunar environmental conditions. Three methods of loading were examined. Of the three, the method of computing the initial state of stress in a filled hopper prior to drawdown, by adding material to the hopper layer by layer, was the best. Results of the analysis of a typical hopper problem show that the initial state of stress, the elastic moduli, and the strength parameters have an important influence on material response subsequent to the opening of the hopper outlet.

Embodied cognition and circular causality: on the role of constitutive autonomy in the reciprocal coupling of perception and action

PubMed Central

Vernon, David; Lowe, Robert; Thill, Serge; Ziemke, Tom

2015-01-01

The reciprocal coupling of perception and action in cognitive agents has been firmly established: perceptions guide action but so too do actions influence what is perceived. While much has been said on the implications of this for the agent's external behavior, less attention has been paid to what it means for the internal bodily mechanisms which underpin cognitive behavior. In this article, we wish to redress this by reasserting that the relationship between cognition, perception, and action involves a constitutive element as well as a behavioral element, emphasizing that the reciprocal link between perception and action in cognition merits a renewed focus on the system dynamics inherent in constitutive biological autonomy. Our argument centers on the idea that cognition, perception, and action are all dependent on processes focussed primarily on the maintenance of the agent's autonomy. These processes have an inherently circular nature—self-organizing, self-producing, and self-maintaining—and our goal is to explore these processes and suggest how they can explain the reciprocity of perception and action. Specifically, we argue that the reciprocal coupling is founded primarily on their endogenous roles in the constitutive autonomy of the agent and an associated circular causality of global and local processes of self-regulation, rather than being a mutual sensory-motor contingency that derives from exogenous behavior. Furthermore, the coupling occurs first and foremost via the internal milieu realized by the agent's organismic embodiment. Finally, we consider how homeostasis and the related concept of allostasis contribute to this circular self-regulation. PMID:26579043

Image guided constitutive modeling of the silicone brain phantom

NASA Astrophysics Data System (ADS)

Puzrin, Alexander; Skrinjar, Oskar; Ozan, Cem; Kim, Sihyun; Mukundan, Srinivasan

2005-04-01

The goal of this work is to develop reliable constitutive models of the mechanical behavior of the in-vivo human brain tissue for applications in neurosurgery. We propose to define the mechanical properties of the brain tissue in-vivo, by taking the global MR or CT images of a brain response to ventriculostomy - the relief of the elevated intracranial pressure. 3D image analysis translates these images into displacement fields, which by using inverse analysis allow for the constitutive models of the brain tissue to be developed. We term this approach Image Guided Constitutive Modeling (IGCM). The presented paper demonstrates performance of the IGCM in the controlled environment: on the silicone brain phantoms closely simulating the in-vivo brain geometry, mechanical properties and boundary conditions. The phantom of the left hemisphere of human brain was cast using silicon gel. An inflatable rubber membrane was placed inside the phantom to model the lateral ventricle. The experiments were carried out in a specially designed setup in a CT scanner with submillimeter isotropic voxels. The non-communicative hydrocephalus and ventriculostomy were simulated by consequently inflating and deflating the internal rubber membrane. The obtained images were analyzed to derive displacement fields, meshed, and incorporated into ABAQUS. The subsequent Inverse Finite Element Analysis (based on Levenberg-Marquardt algorithm) allowed for optimization of the parameters of the Mooney-Rivlin non-linear elastic model for the phantom material. The calculated mechanical properties were consistent with those obtained from the element tests, providing justification for the future application of the IGCM to in-vivo brain tissue.

Finite element analysis of stresses in Berkovich, Vickers and Knoop indentation for densifying and non-densifying glasses

NASA Astrophysics Data System (ADS)

Chen, Kanghua

2002-08-01

A constitutive law for fused silica accounting for its permanent densification under large compressive stresses is presented. The implementation of the constitutive equations in the general-purpose finite element code ABAQUS via user subroutine is proposed and carefully verified. The three-dimensional indentation mechanics under Berkovich, Vickers and Knoop indenters is extensively investigated based on the proposed constitutive relation. The results of stress distribution and plastic zone for both densifying and non-densifying optical glasses are systematically compared. These numerical results are in good agreement with the experimental observations of optical manufacturing. That is, fused silica shows lower material removal rate, smaller surface roughness and subsurface damage in contrast to non-densifying optical glasses under the same grinding condition. Material densification of fused silica is thoroughly studied through numerical simulations of indentation mechanics. The exact amount of densification and shear strain of fused silica under Berkovich indentation is calculated to show the deformation mechanism of glass materials under three-dimensional indentations. The surface profiles show the material "pile-up" around the indenter tip for non-densifying glasses and "sink-in" for fused silica after the indentation load is removed. An important inverse problem is studied: estimation of abrasive size and indentation load through the examination of residual indentation footprints. A series of 2D axisymmetric spherical indentation simulations generate a wide range of relationships among the indentation load, indenter size, residual indentation depth and size of residual indentation zone for the five selected brittle materials: glass fused silica (FS), BK7, semiconductor Si, laser glass LHG8, and optical crystal CaF2.. The application of the inverse problem is verified by the good agreement between the estimated abrasive size and the actual abrasive size found during a material removal experiment of magnetorheological finishing (MRF) of fused silica. The explanation of indentation size effect (ISE) is attempted using numerical indentation simulations. Vickers indentation simulations on the five selected brittle materials (FS, BK7, Si, LHG8 and CaF2.) show no size dependence of Vickers hardness when the material is modeled as elastic-perfectly plastic (with or without densification). The simulation results on axisymmetric conical indentation also indicate that the bluntness of the indenter tip is not the reason for the indentation size effect. A new constitutive model accounting for the material length scale is needed in order to explain the well-observed indentation size effect during indentation tests.

Integrated system dynamics toolbox for water resources planning.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reno, Marissa Devan; Passell, Howard David; Malczynski, Leonard A.

2006-12-01

Public mediated resource planning is quickly becoming the norm rather than the exception. Unfortunately, supporting tools are lacking that interactively engage the public in the decision-making process and integrate over the myriad values that influence water policy. In the pages of this report we document the first steps toward developing a specialized decision framework to meet this need; specifically, a modular and generic resource-planning ''toolbox''. The technical challenge lies in the integration of the disparate systems of hydrology, ecology, climate, demographics, economics, policy and law, each of which influence the supply and demand for water. Specifically, these systems, their associatedmore » processes, and most importantly the constitutive relations that link them must be identified, abstracted, and quantified. For this reason, the toolbox forms a collection of process modules and constitutive relations that the analyst can ''swap'' in and out to model the physical and social systems unique to their problem. This toolbox with all of its modules is developed within the common computational platform of system dynamics linked to a Geographical Information System (GIS). Development of this resource-planning toolbox represents an important foundational element of the proposed interagency center for Computer Aided Dispute Resolution (CADRe). The Center's mission is to manage water conflict through the application of computer-aided collaborative decision-making methods. The Center will promote the use of decision-support technologies within collaborative stakeholder processes to help stakeholders find common ground and create mutually beneficial water management solutions. The Center will also serve to develop new methods and technologies to help federal, state and local water managers find innovative and balanced solutions to the nation's most vexing water problems. The toolbox is an important step toward achieving the technology development goals of this center.« less

Simulation-aided constitutive law development - Assessment of low triaxiality void nucleation models via extended finite element method

NASA Astrophysics Data System (ADS)

Zhao, Jifeng; Kontsevoi, Oleg Y.; Xiong, Wei; Smith, Jacob

2017-05-01

In this work, a multi-scale computational framework has been established in order to investigate, refine and validate constitutive behaviors in the context of the Gurson-Tvergaard-Needleman (GTN) void mechanics model. The eXtended Finite Element Method (XFEM) has been implemented in order to (1) develop statistical volume elements (SVE) of a matrix material with subscale inclusions and (2) to simulate the multi-void nucleation process due to interface debonding between the matrix and particle phases. Our analyses strongly suggest that under low stress triaxiality the nucleation rate of the voids f˙ can be well described by a normal distribution function with respect to the matrix equivalent stress (σe), as opposed to that proposed (σbar + 1 / 3σkk) in the original form of the single void GTN model. The modified form of the multi-void nucleation model has been validated based on a series of numerical experiments with different loading conditions, material properties, particle shape/size and spatial distributions. The utilization of XFEM allows for an invariant finite element mesh to represent varying microstructures, which implies suitability for drastically reducing complexity in generating the finite element discretizations for large stochastic arrays of microstructure configurations. The modified form of the multi-void nucleation model is further applied to study high strength steels by incorporating first principles calculations. The necessity of using a phenomenological interface separation law has been fully eliminated and replaced by the physics-based cohesive relationship obtained from Density Functional Theory (DFT) calculations in order to provide an accurate macroscopic material response.

Preventing childhood obesity: Contributions from the social sciences to intervention.

PubMed

Lamarque, Muriel; Orden, Alicia Bibiana

2017-04-01

Programming and implementation of health policies for the prevention of overweight and obesity have traditionally focused on the dissemination of specific messages identifying healthy foods and pointing out the importance of physical activity. Despite recurrent efforts, the prevalence of obesity in both adult and children populations continues to rise. The configuration of preventive proposals seems to neglect the more complex reality of the eating phenomenon, whose nature goes beyond its biological basis. Behind the presence of overweight or obesity, there are factors that exceed individual behaviors, which are constituted as elements of social order. This premise is based on the contributions made from several fields such as anthropology, sociology, and social epidemiology, especially over the past thirty years. This study aims to analyze the traditional models of institutional intervention while making visible the importance of a socially-oriented perspective that takes into account context and network analysis to address the problem of childhood overweight and obesity, centered on the food component. Sociedad Argentina de Pediatría.

An Implicit Algorithm for the Numerical Simulation of Shape-Memory Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becker, R; Stolken, J; Jannetti, C

Shape-memory alloys (SMA) have the potential to be used in a variety of interesting applications due to their unique properties of pseudoelasticity and the shape-memory effect. However, in order to design SMA devices efficiently, a physics-based constitutive model is required to accurately simulate the behavior of shape-memory alloys. The scope of this work is to extend the numerical capabilities of the SMA constitutive model developed by Jannetti et. al. (2003), to handle large-scale polycrystalline simulations. The constitutive model is implemented within the finite-element software ABAQUS/Standard using a user defined material subroutine, or UMAT. To improve the efficiency of the numericalmore » simulations, so that polycrystalline specimens of shape-memory alloys can be modeled, a fully implicit algorithm has been implemented to integrate the constitutive equations. Using an implicit integration scheme increases the efficiency of the UMAT over the previously implemented explicit integration method by a factor of more than 100 for single crystal simulations.« less

A constitutive model and numerical simulation of sintering processes at macroscopic level

NASA Astrophysics Data System (ADS)

Wawrzyk, Krzysztof; Kowalczyk, Piotr; Nosewicz, Szymon; Rojek, Jerzy

2018-01-01

This paper presents modelling of both single and double-phase powder sintering processes at the macroscopic level. In particular, its constitutive formulation, numerical implementation and numerical tests are described. The macroscopic constitutive model is based on the assumption that the sintered material is a continuous medium. The parameters of the constitutive model for material under sintering are determined by simulation of sintering at the microscopic level using a micro-scale model. Numerical tests were carried out for a cylindrical specimen under hydrostatic and uniaxial pressure. Results of macroscopic analysis are compared against the microscopic model results. Moreover, numerical simulations are validated by comparison with experimental results. The simulations and preparation of the model are carried out by Abaqus FEA - a software for finite element analysis and computer-aided engineering. A mechanical model is defined by the user procedure "Vumat" which is developed by the first author in Fortran programming language. Modelling presented in the paper can be used to optimize and to better understand the process.

Critical Elements of the Employment Relationship.

ERIC Educational Resources Information Center

Beckham, Joseph

The employment relationship in public schools is governed by constitutional mandates, federal and state statutes, administrative regulations, and contractual obligations. This chapter discusses fundamental aspects of the employment relationship that are influenced by legal principles derived from state law, local district policy and practice, and…

Multi-scale finite element modeling allows the mechanics of amphibian neurulation to be elucidated

NASA Astrophysics Data System (ADS)

Chen, Xiaoguang; Brodland, G. Wayne

2008-03-01

The novel multi-scale computational approach introduced here makes possible a new means for testing hypotheses about the forces that drive specific morphogenetic movements. A 3D model based on this approach is used to investigate neurulation in the axolotl (Ambystoma mexicanum), a type of amphibian. The model is based on geometric data from 3D surface reconstructions of live embryos and from serial sections. Tissue properties are described by a system of cell-based constitutive equations, and parameters in the equations are determined from physical tests. The model includes the effects of Shroom-activated neural ridge reshaping and lamellipodium-driven convergent extension. A typical whole-embryo model consists of 10 239 elements and to run its 100 incremental time steps requires 2 days. The model shows that a normal phenotype does not result if lamellipodium forces are uniform across the width of the neural plate; but it can result if the lamellipodium forces decrease from a maximum value at the mid-sagittal plane to zero at the plate edge. Even the seemingly simple motions of neurulation are found to contain important features that would remain hidden, they were not studied using an advanced computational model. The present model operates in a setting where data are extremely sparse and an important outcome of the study is a better understanding of the role of computational models in such environments.

Evolutionary, ecological and biotechnological perspectives on plasmids resident in the human gut mobile metagenome

PubMed Central

Ogilvie, Lesley A.; Firouzmand, Sepinoud; Jones, Brian V.

2012-01-01

Numerous mobile genetic elements (MGE) are associated with the human gut microbiota and collectively referred to as the gut mobile metagenome. The role of this flexible gene pool in development and functioning of the gut microbial community remains largely unexplored, yet recent evidence suggests that at least some MGE comprising this fraction of the gut microbiome reflect the co-evolution of host and microbe in the gastro-intestinal tract. In conjunction, the high level of novel gene content typical of MGE coupled with their predicted high diversity, suggests that the mobile metagenome constitutes an immense and largely unexplored gene-space likely to encode many novel activities with potential biotechnological or pharmaceutical value, as well as being important to the development and functioning of the gut microbiota. Of the various types of MGE that comprise the gut mobile metagenome, plasmids are of particular importance since these elements are often capable of autonomous transfer between disparate bacterial species, and are known to encode accessory functions that increase bacterial fitness in a given environment facilitating bacterial adaptation. In this article current knowledge regarding plasmids resident in the human gut mobile metagenome is reviewed, and available strategies to access and characterize this portion of the gut microbiome are described. The relative merits of these methods and their present as well as prospective impact on our understanding of the human gut microbiota is discussed. PMID:22126801

Multi-scale finite element modeling allows the mechanics of amphibian neurulation to be elucidated.

PubMed

Chen, Xiaoguang; Brodland, G Wayne

2008-04-11

The novel multi-scale computational approach introduced here makes possible a new means for testing hypotheses about the forces that drive specific morphogenetic movements. A 3D model based on this approach is used to investigate neurulation in the axolotl (Ambystoma mexicanum), a type of amphibian. The model is based on geometric data from 3D surface reconstructions of live embryos and from serial sections. Tissue properties are described by a system of cell-based constitutive equations, and parameters in the equations are determined from physical tests. The model includes the effects of Shroom-activated neural ridge reshaping and lamellipodium-driven convergent extension. A typical whole-embryo model consists of 10,239 elements and to run its 100 incremental time steps requires 2 days. The model shows that a normal phenotype does not result if lamellipodium forces are uniform across the width of the neural plate; but it can result if the lamellipodium forces decrease from a maximum value at the mid-sagittal plane to zero at the plate edge. Even the seemingly simple motions of neurulation are found to contain important features that would remain hidden, they were not studied using an advanced computational model. The present model operates in a setting where data are extremely sparse and an important outcome of the study is a better understanding of the role of computational models in such environments.

Genomic Organization of Repetitive DNA Elements and Its Implications for the Chromosomal Evolution of Channid Fishes (Actinopterygii, Perciformes).

PubMed

Cioffi, Marcelo de Bello; Bertollo, Luiz Antonio Carlos; Villa, Mateo Andres; de Oliveira, Ezequiel Aguiar; Tanomtong, Alongklod; Yano, Cassia Fernanda; Supiwong, Weerayuth; Chaveerach, Arunrat

2015-01-01

Channid fishes, commonly referred to as "snakeheads", are currently very important in Asian fishery and aquaculture due to the substantial decline in natural populations because of overexploitation. A large degree of chromosomal variation has been found in this family, mainly through the use of conventional cytogenetic investigations. In this study, we analyzed the karyotype structure and the distribution of 7 repetitive DNA sequences in several Channa species from different Thailand river basins. The aim of this study was to investigate the chromosomal differentiation among species and populations to improve upon the knowledge of its biodiversity and evolutionary history. Rearrangements, such as pericentric inversions, fusions and polyploidization, appear to be important events during the karyotypic evolution of this genus, resulting in the chromosomal diversity observed among the distinct species and even among populations of the same species. In addition, such variability is also increased by the genomic dynamism of repetitive elements, particularly by the differential distribution and accumulation of rDNA sequences on chromosomes. This marked diversity is likely linked to the lifestyle of the snakehead fishes and their population fragmentation, as already identified for other fish species. The karyotypic features highlight the biodiversity of the channid fishes and justify a taxonomic revision of the genus Channa, as well as of the Channidae family as a whole, as some nominal species may actually constitute species complexes.

Evolution of Sphingomonad Gene Clusters Related to Pesticide Catabolism Revealed by Genome Sequence and Mobilomics of Sphingobium herbicidovorans MH

PubMed Central

Nielsen, Tue Kjærgaard; Rasmussen, Morten; Demanèche, Sandrine; Cecillon, Sébastien; Vogel, Timothy M.

2017-01-01

Abstract Bacterial degraders of chlorophenoxy herbicides have been isolated from various ecosystems, including pristine environments. Among these degraders, the sphingomonads constitute a prominent group that displays versatile xenobiotic-degradation capabilities. Four separate sequencing strategies were required to provide the complete sequence of the complex and plastic genome of the canonical chlorophenoxy herbicide-degrading Sphingobium herbicidovorans MH. The genome has an intricate organization of the chlorophenoxy-herbicide catabolic genes sdpA, rdpA, and cadABCD that encode the (R)- and (S)-enantiomer-specific 2,4-dichlorophenoxypropionate dioxygenases and four subunits of a Rieske non-heme iron oxygenase involved in 2-methyl-chlorophenoxyacetic acid degradation, respectively. Several major genomic rearrangements are proposed to help understand the evolution and mobility of these important genes and their genetic context. Single-strain mobilomic sequence analysis uncovered plasmids and insertion sequence-associated circular intermediates in this environmentally important bacterium and enabled the description of evolutionary models for pesticide degradation in strain MH and related organisms. The mobilome presented a complex mosaic of mobile genetic elements including four plasmids and several circular intermediate DNA molecules of insertion-sequence elements and transposons that are central to the evolution of xenobiotics degradation. Furthermore, two individual chromosomally integrated prophages were shown to excise and form free circular DNA molecules. This approach holds great potential for improving the understanding of genome plasticity, evolution, and microbial ecology. PMID:28961970

Properties of iron alloys under the Earth's core conditions

NASA Astrophysics Data System (ADS)

Morard, Guillaume; Andrault, Denis; Antonangeli, Daniele; Bouchet, Johann

2014-05-01

The Earth's core is constituted of iron and nickel alloyed with lighter elements. In view of their affinity with the metallic phase, their relative high abundance in the solar system and their moderate volatility, a list of potential light elements have been established, including sulfur, silicon and oxygen. We will review the effects of these elements on different aspects of Fe-X high pressure phase diagrams under Earth's core conditions, such as melting temperature depression, solid-liquid partitioning during crystallization, and crystalline structure of the solid phases. Once extrapolated to the inner-outer core boundary, these petrological properties can be used to constrain the Earth's core properties.

Engineering Chimeric Antigen Receptors

PubMed Central

Kulemzin, S. V.; Kuznetsova, V. V.; Mamonkin, M.; Taranin, A. V.; Gorchakov, A. A.

2017-01-01

Chimeric antigen receptors (CARs) are recombinant protein molecules that redirect cytotoxic lymphocytes toward malignant and other target cells. The high feasibility of manufacturing CAR-modified lymphocytes for the therapy of cancer has spurred the development and optimization of new CAR T cells directed against a broad range of target antigens. In this review, we describe the main structural and functional elements constituting a CAR, discuss the roles of these elements in modulating the anti-tumor activity of CAR T cells, and highlight alternative approaches to CAR engineering. PMID:28461969

Earthquake models using rate and state friction and fast multipoles

NASA Astrophysics Data System (ADS)

Tullis, T.

2003-04-01

The most realistic current earthquake models employ laboratory-derived non-linear constitutive laws. These are the rate and state friction laws having both a non-linear viscous or direct effect and an evolution effect in which frictional resistance depends on time of stationary contact and has a memory of past slip velocity that fades with slip. The frictional resistance depends on the log of the slip velocity as well as the log of stationary hold time, and the fading memory involves an approximately exponential decay with slip. Due to the nonlinearly of these laws, analytical earthquake models are not attainable and numerical models are needed. The situation is even more difficult if true dynamic models are sought that deal with inertial forces and slip velocities on the order of 1 m/s as are observed during dynamic earthquake slip. Additional difficulties that exist if the dynamic slip phase of earthquakes is modeled arise from two sources. First, many physical processes might operate during dynamic slip, but they are only poorly understood, the relative importance of the processes is unknown, and the processes are even more nonlinear than those described by the current rate and state laws. Constitutive laws describing such behaviors are still being developed. Second, treatment of inertial forces and the influence that dynamic stresses from elastic waves may have on slip on the fault requires keeping track of the history of slip on remote parts of the fault as far into the past as it takes waves to travel from there. This places even more stringent requirements on computer time. Challenges for numerical modeling of complete earthquake cycles are that both time steps and mesh sizes must be small. Time steps must be milliseconds during dynamic slip, and yet models must represent earthquake cycles 100 years or more in length; methods using adaptive step sizes are essential. Element dimensions need to be on the order of meters, both to approximate continuum behavior adequately and to model microseismicity as well as large earthquakes. In order to model significant sized earthquakes this requires millions of elements. Modeling methods like the boundary element method that involve Green's functions normally require computation times that increase with the number N of elements squared, so using large N becomes impossible. We have adapted the Fast Multipole method to this problem in which the influence of sufficiently remote elements are grouped together and the elements are indexed such that the computations more efficient when run on parallel computers. Compute time varies with N log N rather than N squared. Computer programs are available that use this approach (http://www.servogrid.org/slide/GEM/PARK). Whether the multipole approach can be adapted to dynamic modeling is unclear.

Programmable resistive-switch nanowire transistor logic circuits.

PubMed

Shim, Wooyoung; Yao, Jun; Lieber, Charles M

2014-09-10

Programmable logic arrays (PLA) constitute a promising architecture for developing increasingly complex and functional circuits through nanocomputers from nanoscale building blocks. Here we report a novel one-dimensional PLA element that incorporates resistive switch gate structures on a semiconductor nanowire and show that multiple elements can be integrated to realize functional PLAs. In our PLA element, the gate coupling to the nanowire transistor can be modulated by the memory state of the resistive switch to yield programmable active (transistor) or inactive (resistor) states within a well-defined logic window. Multiple PLA nanowire elements were integrated and programmed to yield a working 2-to-4 demultiplexer with long-term retention. The well-defined, controllable logic window and long-term retention of our new one-dimensional PLA element provide a promising route for building increasingly complex circuits with nanoscale building blocks.

Constitutive relationships of prestressed steel fiber concrete membrane elements

NASA Astrophysics Data System (ADS)

Hoffman, Norman S.

Steel Fiber Concrete (SFC) displays certain tensile and shear characteristics which are beneficial for concrete that is loaded in a state of shear stress. For example, prestressed bridge beams carry shear load in their web by utilizing shear stirrups. If the properties of SFC can be better understood, then it may be possible to replace the shear stirrups with SFC. The first step in understanding this behavior is to develop a constitutive model for prestressed SFC. Two groups of full-scale prestressed steel fiber concrete (SFC) panels, with a nominal strength of 6 ksi, were tested in the Universal Element Testing machine at Thomas TC Hsu Structural Testing Laboratory to establish the effect of fiber and the level of prestress on the constitutive laws of fiber concrete and prestressing tendon. The specimens contained from 5 to 20 fully tensioned, low-relaxation grade 270 tendons. Fiber content ranged from 0.5% to 1.5% using high performance hooked end fibers. The first group of five panels, designated Group TEF, was used to determine the basic constitutive properties of prestressed SEC for use in the Softened Membrane Model (SMM). The constitutive model consists of smeared tensile and compressive stress strain relationships. An equation for softening with respect of both fiber content and tensile strain is presented. Also presented is a new equation for prestressed SFC in tension. It is notable that the behavior of prestressed SFC in tension displayed significant post-cracking tensile strength for fiber contents ranging from 0.5% to 1.5% by volume. Prior research on SFC using unreinforced dog-bone specimens, or prismatic specimens reinforced with only a single isolated tendon, are not capable of capturing SFC behavior afforded by the stress state, multiple load paths, and confinement situation available in full-scale panel assemblies. The second set of 5 test panels, designated Group TAF, was used to examine the properties of prestressed SFC under the conditions of pure shear. The constitutive model was incorporated into the softened membrane model framework and an analytic model was developed that was used to accurately predict the behavior of the specimens loaded in pure shear.

Computer simulation of solder joint failure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burchett, S.N.; Frear, D.R.; Rashid, M.M.

The thermomechanical fatigue failure of solder joints is increasingly becoming an important reliability issue for electronic packages. The purpose of this Laboratory Directed Research and Development (LDRD) project was to develop computational tools for simulating the behavior of solder joints under strain and temperature cycling, taking into account the microstructural heterogeneities that exist in as-solidified near eutectic Sn-Pb joints, as well as subsequent microstructural evolution. The authors present two computational constitutive models, a two-phase model and a single-phase model, that were developed to predict the behavior of near eutectic Sn-Pb solder joints under fatigue conditions. Unique metallurgical tests provide themore » fundamental input for the constitutive relations. The two-phase model mathematically predicts the heterogeneous coarsening behavior of near eutectic Sn-Pb solder. The finite element simulations with this model agree qualitatively with experimental thermomechanical fatigue tests. The simulations show that the presence of an initial heterogeneity in the solder microstructure could significantly degrade the fatigue lifetime. The single-phase model was developed to predict solder joint behavior using materials data for constitutive relation constants that could be determined through straightforward metallurgical experiments. Special thermomechanical fatigue tests were developed to give fundamental materials input to the models, and an in situ SEM thermomechanical fatigue test system was developed to characterize microstructural evolution and the mechanical behavior of solder joints during the test. A shear/torsion test sample was developed to impose strain in two different orientations. Materials constants were derived from these tests. The simulation results from the two-phase model showed good fit to the experimental test results.« less

Knowing It by Heart: Americans Consider the Constitution and Its Meaning. A Report by Public Agenda for the National Constitution Center.

ERIC Educational Resources Information Center

Farkas, Steve; Johnson, Jean; Duffett, Ann

A study conducted by Public Agenda Foundation, in partnership with the National Constitution Center, examined what typical adults know and believe about the U.S. Constitution, probed what they understand their rights and civic responsibilities to be, and reported their views on the document's importance and relevance in their lives today. The…

Constitutive modeling for isotropic materials (HOST)

NASA Technical Reports Server (NTRS)

Chan, Kwai S.; Lindholm, Ulric S.; Bodner, S. R.; Hill, Jeff T.; Weber, R. M.; Meyer, T. G.

1986-01-01

The results of the third year of work on a program which is part of the NASA Hot Section Technology program (HOST) are presented. The goals of this program are: (1) the development of unified constitutive models for rate dependent isotropic materials; and (2) the demonstration of the use of unified models in structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are those of Bodner-Partom and of Walker. A test procedure was developed for assisting the generation of a data base for the Bodner-Partom model using a relatively small number of specimens. This test procedure involved performing a tensile test at a temperature of interest that involves a succession of strain-rate changes. The results for B1900+Hf indicate that material constants related to hardening and thermal recovery can be obtained on the basis of such a procedure. Strain aging, thermal recovery, and unexpected material variations, however, preluded an accurate determination of the strain-rate sensitivity parameter is this exercise. The effects of casting grain size on the constitutive behavior of B1900+Hf were studied and no particular grain size effect was observed. A systematic procedure was also developed for determining the material constants in the Bodner-Partom model. Both the new test procedure and the method for determining material constants were applied to the alternate material, Mar-M247 . Test data including tensile, creep, cyclic and nonproportional biaxial (tension/torsion) loading were collected. Good correlations were obtained between the Bodner-Partom model and experiments. A literature survey was conducted to assess the effects of thermal history on the constitutive behavior of metals. Thermal history effects are expected to be present at temperature regimes where strain aging and change of microstructure are important. Possible modifications to the Bodner-Partom model to account for these effects are outlined. The use of a unified constitutive model for hot section component analyses was demonstrated by applying the Walker model and the MARC finite-element code to a B1900+Hf airfoil problem.

Strain Rate Dependent Deformation and Strength Modeling of a Polymer Matrix Composite Utilizing a Micromechanics Approach. Degree awarded by Cincinnati Univ.

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

1999-01-01

Potential gas turbine applications will expose polymer matrix composites to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under extreme conditions. Specifically, analytical methods designed for these applications must have the capability of properly capturing the strain rate sensitivities and nonlinearities that are present in the material response. The Ramaswamy-Stouffer constitutive equations, originally developed to analyze the viscoplastic deformation of metals, have been modified to simulate the nonlinear deformation response of ductile, crystalline polymers. The constitutive model is characterized and correlated for two representative ductile polymers. Fiberite 977-2 and PEEK, and the computed results correlate well with experimental values. The polymer constitutive equations are implemented in a mechanics of materials based composite micromechanics model to predict the nonlinear, rate dependent deformation response of a composite ply. Uniform stress and uniform strain assumptions are applied to compute the effective stresses of a composite unit cell from the applied strains. The micromechanics equations are successfully verified for two polymer matrix composites. IM7/977-2 and AS4/PEEK. The ultimate strength of a composite ply is predicted with the Hashin failure criteria that were implemented in the composite micromechanics model. The failure stresses of the two composite material systems are accurately predicted for a variety of fiber orientations and strain rates. The composite deformation model is implemented in LS-DYNA, a commercially available transient dynamic explicit finite element code. The matrix constitutive equations are converted into an incremental form, and the model is implemented into LS-DYNA through the use of a user defined material subroutine. The deformation response of a bulk polymer and a polymer matrix composite are predicted by finite element analyses. The results compare reasonably well to experimental values, with some discrepancies. The discrepancies are at least partially caused by the method used to integrate the rate equations in the polymer constitutive model.

Multi-Scale Process of Soil Freezing, Thawing, and Thaw-Settlement

DTIC Science & Technology

2013-02-18

constitutive model was implemented into the finite element system ABAQUS using subroutine UMAT and UEXPAN to solve boundary value problems. The model...soils, 16 Int. Conf. Soil Mech. Geotech. Eng. (12 2012) 02/15/2013 13.00 Yao Zhang, Radoslaw L. Michalowski. Thermal -mechanical constitutive modeling...freezing and thawing soils…… 19 5.1 The model …………………………………………………….. 19 5.2 Thermal -mechanical load process ……………………………. 23 5.3 Implementation

Derepression of the Plant Chromovirus LORE1 Induces Germline Transposition in Regenerated Plants

PubMed Central

Fukai, Eigo; Umehara, Yosuke; Sato, Shusei; Endo, Makoto; Kouchi, Hiroshi; Hayashi, Makoto; Stougaard, Jens; Hirochika, Hirohiko

2010-01-01

Transposable elements represent a large proportion of the eukaryotic genomes. Long Terminal Repeat (LTR) retrotransposons are very abundant and constitute the predominant family of transposable elements in plants. Recent studies have identified chromoviruses to be a widely distributed lineage of Gypsy elements. These elements contain chromodomains in their integrases, which suggests a preference for insertion into heterochromatin. In turn, this preference might have contributed to the patterning of heterochromatin observed in host genomes. Despite their potential importance for our understanding of plant genome dynamics and evolution, the regulatory mechanisms governing the behavior of chromoviruses and their activities remain largely uncharacterized. Here, we report a detailed analysis of the spatio-temporal activity of a plant chromovirus in the endogenous host. We examined LORE1a, a member of the endogenous chromovirus LORE1 family from the model legume Lotus japonicus. We found that this chromovirus is stochastically de-repressed in plant populations regenerated from de-differentiated cells and that LORE1a transposes in the male germline. Bisulfite sequencing of the 5′ LTR and its surrounding region suggests that tissue culture induces a loss of epigenetic silencing of LORE1a. Since LTR promoter activity is pollen specific, as shown by the analysis of transgenic plants containing an LTR::GUS fusion, we conclude that male germline-specific LORE1a transposition in pollen grains is controlled transcriptionally by its own cis-elements. New insertion sites of LORE1a copies were frequently found in genic regions and show no strong insertional preferences. These distinctive novel features of LORE1 indicate that this chromovirus has considerable potential for generating genetic and epigenetic diversity in the host plant population. Our results also define conditions for the use of LORE1a as a genetic tool. PMID:20221264

Full-thickness tears of the supraspinatus tendon: A three-dimensional finite element analysis.

PubMed

Quental, C; Folgado, J; Monteiro, J; Sarmento, M

2016-12-08

Knowledge regarding the likelihood of propagation of supraspinatus tears is important to allow an early identification of patients for whom a conservative treatment is more likely to fail, and consequently, to improve their clinical outcome. The aim of this study was to investigate the potential for propagation of posterior, central, and anterior full-thickness tears of different sizes using the finite element method. A three-dimensional finite element model of the supraspinatus tendon was generated from the Visible Human Project data. The mechanical behaviour of the tendon was fitted from experimental data using a transversely isotropic hyperelastic constitutive model. The full-thickness tears were simulated at the supraspinatus tendon insertion by decreasing the interface area. Tear sizes from 10% to 90%, in 10% increments, of the anteroposterior length of the supraspinatus footprint were considered in the posterior, central, and anterior regions of the tendon. For each tear, three finite element analyses were performed for a supraspinatus force of 100N, 200N, and 400N. Considering a correlation between tendon strain and the risk of tear propagation, the simulated tears were compared qualitatively and quantitatively by evaluating the volume of tendon for which a maximum strain criterion was not satisfied. The finite element analyses showed a significant impact of tear size and location not only on the magnitude, but also on the patterns of the maximum principal strains. The mechanical outcome of the anterior full-thickness tears was consistently, and significantly, more severe than that of the central or posterior full-thickness tears, which suggests that the anterior tears are at greater risk of propagating than the central or posterior tears. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparison between PGAA and ID-AMS analysis for determining chlorine content in whole rock basalt

NASA Astrophysics Data System (ADS)

di Nicola, L.; Schnabel, C.; Wilcken, K. M.; Gméling, K.

2009-04-01

Accurate determination of chlorine concentrations in terrestrial rocks is of importance for the interpretation of terrestrial in-situ cosmogenic 36Cl. Neutron capture by 35Cl, together with production from Ca and K, is one of the three major production pathways of 36Cl in rocks. Here, we present an inter-comparison of chlorine determinations by two procedures. The first approach is an independent Cl determination by prompt gamma (neutron) activation analysis (PGAA). The second method is isotope dilution based on isotopically-enriched stable chlorine carrier added during chemical sample preparation for accelerator mass spectrometry (ID-AMS). Twenty six (26) whole rock samples have been processed for PGAA and ID-AMS analyses. Elemental analysis by PGAA provides concentrations of major, minor and trace elements including the target elements for 36Cl production (K, Ca, Ti, and Fe), as well as of neutron absorbers and neutron moderators (H, B, Cl, Sm and Gd). The Cl concentrations determined during this study constitute the first inter-comparison for concentrations below 100 μCl/g. Our results show no significant difference in Cl concentrations between methods, and comparable uncertainties. This agreement guarantees that during the procedure we employ for whole rock sample no significant loss of stable chlorine from either the spike or the sample occurs before isotopic equilibration, prior to AgCl precipitation. Furthermore, we show that the elemental analysis by PGAA offers anadvance for the interpretation of 36Cl measurements. It allows simultaneous measurement of major and most trace element concentrations with a precision necessary for calculating the relative contributions to 36Cl production rates of the different mechanisms. Finally, the Cl concentration can be used to optimize the amount of isotopically-enriched spike for AMS-ID sample preparation for 36Cl.

48 CFR 970.3501-1 - Sponsoring agreements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Sponsoring agreements. 970... Sponsoring agreements. (a) The contract award document constitutes the sponsoring agreement between the... the purpose and mission of the FFRDC. (c) Other elements of the sponsoring agreement which shall be...

48 CFR 970.3501-1 - Sponsoring agreements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Sponsoring agreements. 970... Sponsoring agreements. (a) The contract award document constitutes the sponsoring agreement between the... the purpose and mission of the FFRDC. (c) Other elements of the sponsoring agreement which shall be...

48 CFR 970.3501-1 - Sponsoring agreements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Sponsoring agreements. 970... Sponsoring agreements. (a) The contract award document constitutes the sponsoring agreement between the... the purpose and mission of the FFRDC. (c) Other elements of the sponsoring agreement which shall be...

Driving records of persons 65 years of age and older : are insurance rate reductions warranted?.

DOT National Transportation Integrated Search

1971-01-01

There are many elements that constitute the makeup of the automobile insurance premium, the major ones being age, sex, marital, status, and the utilization of the automobile. While the biological aging process places health limitations on drivers age...

A Model for Implementing a Career Education System.

ERIC Educational Resources Information Center

Ryan, T. Antoinette

The model for career education implementation defines three major functions which constitute the essential elements in the implementation process: planning, implementation, and evaluation. Emphasis is placed on the interrelatedness of implementation to both planning and evaluation of career education. The 11 subsystems involved in implementing…

36 CFR 4.22 - Unsafe operation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... VEHICLES AND TRAFFIC SAFETY § 4.22 Unsafe operation. (a) The elements of this section constitute offenses... which is reasonable and prudent considering wildlife, traffic, weather, road and light conditions and road character. (2) Operating a motor vehicle in a manner which unnecessarily causes its tires to...

36 CFR 4.22 - Unsafe operation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... VEHICLES AND TRAFFIC SAFETY § 4.22 Unsafe operation. (a) The elements of this section constitute offenses... which is reasonable and prudent considering wildlife, traffic, weather, road and light conditions and road character. (2) Operating a motor vehicle in a manner which unnecessarily causes its tires to...

LS-DYNA Simulation of Hemispherical-punch Stamping Process Using an Efficient Algorithm for Continuum Damage Based Elastoplastic Constitutive Equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salajegheh, Nima; Abedrabbo, Nader; Pourboghrat, Farhang

An efficient integration algorithm for continuum damage based elastoplastic constitutive equations is implemented in LS-DYNA. The isotropic damage parameter is defined as the ratio of the damaged surface area over the total cross section area of the representative volume element. This parameter is incorporated into the integration algorithm as an internal variable. The developed damage model is then implemented in the FEM code LS-DYNA as user material subroutine (UMAT). Pure stretch experiments of a hemispherical punch are carried out for copper sheets and the results are compared against the predictions of the implemented damage model. Evaluation of damage parameters ismore » carried out and the optimized values that correctly predicted the failure in the sheet are reported. Prediction of failure in the numerical analysis is performed through element deletion using the critical damage value. The set of failure parameters which accurately predict the failure behavior in copper sheets compared to experimental data is reported as well.« less

Development and parameter identification of a visco-hyperelastic model for the periodontal ligament.

PubMed

Huang, Huixiang; Tang, Wencheng; Tan, Qiyan; Yan, Bin

2017-04-01

The present study developed and implemented a new visco-hyperelastic model that is capable of predicting the time-dependent biomechanical behavior of the periodontal ligament. The constitutive model has been implemented into the finite element package ABAQUS by means of a user-defined material subroutine (UMAT). The stress response is decomposed into two constitutive parts in parallel which are a hyperelastic and a time-dependent viscoelastic stress response. In order to identify the model parameters, the indentation equation based on V-W hyperelastic model and the indentation creep model are developed. Then the parameters are determined by fitting them to the corresponding nanoindentation experimental data of the PDL. The nanoindentation experiment was simulated by finite element analysis to validate the visco-hyperelastic model. The simulated results are in good agreement with the experimental data, which demonstrates that the visco-hyperelastic model developed is able to accurately predict the time-dependent mechanical behavior of the PDL. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nonlinear solid finite element analysis of mitral valves with heterogeneous leaflet layers

NASA Astrophysics Data System (ADS)

Prot, V.; Skallerud, B.

2009-02-01

An incompressible transversely isotropic hyperelastic material for solid finite element analysis of a porcine mitral valve response is described. The material model implementation is checked in single element tests and compared with a membrane implementation in an out-of-plane loading test to study how the layered structures modify the stress response for a simple geometry. Three different collagen layer arrangements are used in finite element analysis of the mitral valve. When the leaflets are arranged in two layers with the collagen on the ventricular side, the stress in the fibre direction through the thickness in the central part of the anterior leaflet is homogenized and the peak stress is reduced. A simulation using membrane elements is also carried out for comparison with the solid finite element results. Compared to echocardiographic measurements, the finite element models bulge too much in the left atrium. This may be due to evidence of active muscle fibres in some parts of the anterior leaflet, whereas our constitutive modelling is based on passive material.

Modeling Progressive Failure of Bonded Joints Using a Single Joint Finite Element

NASA Technical Reports Server (NTRS)

Stapleton, Scott E.; Waas, Anthony M.; Bednarcyk, Brett A.

2010-01-01

Enhanced finite elements are elements with an embedded analytical solution which can capture detailed local fields, enabling more efficient, mesh-independent finite element analysis. In the present study, an enhanced finite element is applied to generate a general framework capable of modeling an array of joint types. The joint field equations are derived using the principle of minimum potential energy, and the resulting solutions for the displacement fields are used to generate shape functions and a stiffness matrix for a single joint finite element. This single finite element thus captures the detailed stress and strain fields within the bonded joint, but it can function within a broader structural finite element model. The costs associated with a fine mesh of the joint can thus be avoided while still obtaining a detailed solution for the joint. Additionally, the capability to model non-linear adhesive constitutive behavior has been included within the method, and progressive failure of the adhesive can be modeled by using a strain-based failure criteria and re-sizing the joint as the adhesive fails. Results of the model compare favorably with experimental and finite element results.

Feature selection from a facial image for distinction of sasang constitution.

PubMed

Koo, Imhoi; Kim, Jong Yeol; Kim, Myoung Geun; Kim, Keun Ho

2009-09-01

Recently, oriental medicine has received attention for providing personalized medicine through consideration of the unique nature and constitution of individual patients. With the eventual goal of globalization, the current trend in oriental medicine research is the standardization by adopting western scientific methods, which could represent a scientific revolution. The purpose of this study is to establish methods for finding statistically significant features in a facial image with respect to distinguishing constitution and to show the meaning of those features. From facial photo images, facial elements are analyzed in terms of the distance, angle and the distance ratios, for which there are 1225, 61 250 and 749 700 features, respectively. Due to the very large number of facial features, it is quite difficult to determine truly meaningful features. We suggest a process for the efficient analysis of facial features including the removal of outliers, control for missing data to guarantee data confidence and calculation of statistical significance by applying ANOVA. We show the statistical properties of selected features according to different constitutions using the nine distances, 10 angles and 10 rates of distance features that are finally established. Additionally, the Sasang constitutional meaning of the selected features is shown here.

Feature Selection from a Facial Image for Distinction of Sasang Constitution

PubMed Central

Koo, Imhoi; Kim, Jong Yeol; Kim, Myoung Geun

2009-01-01

Recently, oriental medicine has received attention for providing personalized medicine through consideration of the unique nature and constitution of individual patients. With the eventual goal of globalization, the current trend in oriental medicine research is the standardization by adopting western scientific methods, which could represent a scientific revolution. The purpose of this study is to establish methods for finding statistically significant features in a facial image with respect to distinguishing constitution and to show the meaning of those features. From facial photo images, facial elements are analyzed in terms of the distance, angle and the distance ratios, for which there are 1225, 61 250 and 749 700 features, respectively. Due to the very large number of facial features, it is quite difficult to determine truly meaningful features. We suggest a process for the efficient analysis of facial features including the removal of outliers, control for missing data to guarantee data confidence and calculation of statistical significance by applying ANOVA. We show the statistical properties of selected features according to different constitutions using the nine distances, 10 angles and 10 rates of distance features that are finally established. Additionally, the Sasang constitutional meaning of the selected features is shown here. PMID:19745013

New Insights in the Long-Term Atmospheric Corrosion Mechanisms of Low Alloy Steel Reinforcements of Cultural Heritage Buildings

PubMed Central

Bouchar, Marie; Dillmann, Philippe; Neff, Delphine

2017-01-01

Reinforcing clamps made of low alloy steel from the Metz cathedral and corroded outdoors during 500 years were studied by OM, FESEM/EDS, and micro-Raman spectroscopy. The corrosion product layer is constituted of a dual structure. The outer layer is mainly constituted of goethite and lepidocrocite embedding exogenous elements such as Ca and P. The inner layer is mainly constituted of ferrihydrite. The behaviour of the inner layer under conditions simulating the wetting stage of the RH wet/dry atmospheric corrosion cycle was observed by in situ micro-Raman spectroscopy. The disappearance of ferrihydrite near the metal/oxide interface strongly suggests a mechanism of reductive dissolution caused by the oxidation of the metallic substrate and was observed for the first time in situ on an archaeological system. PMID:28773030

Analysis of shear wave propagation derived from MR elastography in 3D thigh skeletal muscle using subject specific finite element model.

PubMed

Dao, Tien Tuan; Pouletaut, Philippe; Charleux, Fabrice; Tho, Marie-Christine Ho Ba; Bensamoun, Sabine

2014-01-01

The purpose of this study was to develop a subject specific finite element model derived from MRI images to numerically analyze the MRE (magnetic resonance elastography) shear wave propagation within skeletal thigh muscles. A sagittal T2 CUBE MRI sequence was performed on the 20-cm thigh segment of a healthy male subject. Skin, adipose tissue, femoral bone and 11 muscles were manually segmented in order to have 3D smoothed solid and meshed models. These tissues were modeled with different constitutive laws. A transient modal dynamics analysis was applied to simulate the shear wave propagation within the thigh tissues. The effects of MRE experimental parameters (frequency, force) and the muscle material properties (shear modulus: C10) were analyzed through the simulated shear wave displacement within the vastus medialis muscle. The results showed a plausible range of frequencies (from 90Hz to 120 Hz), which could be used for MRE muscle protocol. The wave amplitude increased with the level of the force, revealing the importance of the boundary condition. Moreover, different shear displacement patterns were obtained as a function of the muscle mechanical properties. The present study is the first to analyze the shear wave propagation in skeletal muscles using a 3D subject specific finite element model. This study could be of great value to assist the experimenters in the set-up of MRE protocols.

Osvaldo and Isis retrotransposons as markers of the Drosophila buzzatii colonisation in Australia.

PubMed

Guerreiro, María Pilar García; Fontdevila, Antonio

2011-04-24

Transposable elements (TEs) constitute an important source of genetic variability owing to their jumping and regulatory properties, and are considered to drive species evolution. Several factors that are able to induce TE transposition in genomes have been documented (for example environmental stress and inter- and intra-specific crosses) but in many instances the reasons for TE mobilisation have yet to be elucidated. Colonising populations constitute an ideal model for studying TE behaviour and distribution as they are exposed to different environmental and new demographic conditions. In this study, the distribution of two TEs, Osvaldo and Isis, was examined in two colonising populations of D. buzzatii from Australia. Comparing Osvaldo copy numbers between Australian and Old World (reported in previous studies) colonisations provides a valuable tool for elucidating the colonisation process and the effect of new conditions encountered by colonisers on TEs. The chromosomal distributions of Osvaldo and Isis retrotransposons in two colonising populations of D. buzzatii from Australia revealed sites of high insertion frequency (>10%) and low frequency sites. Comparisons between Osvaldo insertion profiles in colonising populations from the Old World and Australia demonstrate a tendency towards a higher number of highly occupied sites with higher insertion frequency in the Old World than in Australian populations. Tests concerning selection against deleterious TE insertions indicate that Isis is more controlled by purifying selection than Osvaldo. The distribution of both elements on chromosomal arms follows a Poisson distribution and there are non-significant positive correlations between highly occupied sites and chromosomal inversions. The occupancy profile of Osvaldo and Isis retrotransposons is characterised by the existence of high and low insertion frequency sites in the populations. These results demonstrate that Australian D. buzzatii populations were subjected to a founder effect during the colonisation process. Moreover, there are more sites with high insertion frequency in the Old World colonisation than in the Australian colonisation, indicating a probable stronger bottleneck effect in Australia. The results suggest that selection does not seem to play a major role, compared to demography, in the distribution of transposable elements in the Australian populations.

Osvaldo and Isis retrotransposons as markers of the Drosophila buzzatii colonisation in Australia

PubMed Central

2011-01-01

Background Transposable elements (TEs) constitute an important source of genetic variability owing to their jumping and regulatory properties, and are considered to drive species evolution. Several factors that are able to induce TE transposition in genomes have been documented (for example environmental stress and inter- and intra-specific crosses) but in many instances the reasons for TE mobilisation have yet to be elucidated. Colonising populations constitute an ideal model for studying TE behaviour and distribution as they are exposed to different environmental and new demographic conditions. In this study, the distribution of two TEs, Osvaldo and Isis, was examined in two colonising populations of D. buzzatii from Australia. Comparing Osvaldo copy numbers between Australian and Old World (reported in previous studies) colonisations provides a valuable tool for elucidating the colonisation process and the effect of new conditions encountered by colonisers on TEs. Results The chromosomal distributions of Osvaldo and Isis retrotransposons in two colonising populations of D. buzzatii from Australia revealed sites of high insertion frequency (>10%) and low frequency sites. Comparisons between Osvaldo insertion profiles in colonising populations from the Old World and Australia demonstrate a tendency towards a higher number of highly occupied sites with higher insertion frequency in the Old World than in Australian populations. Tests concerning selection against deleterious TE insertions indicate that Isis is more controlled by purifying selection than Osvaldo. The distribution of both elements on chromosomal arms follows a Poisson distribution and there are non-significant positive correlations between highly occupied sites and chromosomal inversions. Conclusions The occupancy profile of Osvaldo and Isis retrotransposons is characterised by the existence of high and low insertion frequency sites in the populations. These results demonstrate that Australian D. buzzatii populations were subjected to a founder effect during the colonisation process. Moreover, there are more sites with high insertion frequency in the Old World colonisation than in the Australian colonisation, indicating a probable stronger bottleneck effect in Australia. The results suggest that selection does not seem to play a major role, compared to demography, in the distribution of transposable elements in the Australian populations. PMID:21513573

NiftySim: A GPU-based nonlinear finite element package for simulation of soft tissue biomechanics.

PubMed

Johnsen, Stian F; Taylor, Zeike A; Clarkson, Matthew J; Hipwell, John; Modat, Marc; Eiben, Bjoern; Han, Lianghao; Hu, Yipeng; Mertzanidou, Thomy; Hawkes, David J; Ourselin, Sebastien

2015-07-01

NiftySim, an open-source finite element toolkit, has been designed to allow incorporation of high-performance soft tissue simulation capabilities into biomedical applications. The toolkit provides the option of execution on fast graphics processing unit (GPU) hardware, numerous constitutive models and solid-element options, membrane and shell elements, and contact modelling facilities, in a simple to use library. The toolkit is founded on the total Lagrangian explicit dynamics (TLEDs) algorithm, which has been shown to be efficient and accurate for simulation of soft tissues. The base code is written in C[Formula: see text], and GPU execution is achieved using the nVidia CUDA framework. In most cases, interaction with the underlying solvers can be achieved through a single Simulator class, which may be embedded directly in third-party applications such as, surgical guidance systems. Advanced capabilities such as contact modelling and nonlinear constitutive models are also provided, as are more experimental technologies like reduced order modelling. A consistent description of the underlying solution algorithm, its implementation with a focus on GPU execution, and examples of the toolkit's usage in biomedical applications are provided. Efficient mapping of the TLED algorithm to parallel hardware results in very high computational performance, far exceeding that available in commercial packages. The NiftySim toolkit provides high-performance soft tissue simulation capabilities using GPU technology for biomechanical simulation research applications in medical image computing, surgical simulation, and surgical guidance applications.

An orthotropic viscoelastic model for the passive myocardium: continuum basis and numerical treatment.

PubMed

Gültekin, Osman; Sommer, Gerhard; Holzapfel, Gerhard A

2016-11-01

This study deals with the viscoelastic constitutive modeling and the respective computational analysis of the human passive myocardium. We start by recapitulating the locally orthotropic inner structure of the human myocardial tissue and model the mechanical response through invariants and structure tensors associated with three orthonormal basis vectors. In accordance with recent experimental findings the ventricular myocardial tissue is assumed to be incompressible, thick-walled, orthotropic and viscoelastic. In particular, one spring element coupled with Maxwell elements in parallel endows the model with viscoelastic features such that four dashpots describe the viscous response due to matrix, fiber, sheet and fiber-sheet fragments. In order to alleviate the numerical obstacles, the strictly incompressible model is altered by decomposing the free-energy function into volumetric-isochoric elastic and isochoric-viscoelastic parts along with the multiplicative split of the deformation gradient which enables the three-field mixed finite element method. The crucial aspect of the viscoelastic formulation is linked to the rate equations of the viscous overstresses resulting from a 3-D analogy of a generalized 1-D Maxwell model. We provide algorithmic updates for second Piola-Kirchhoff stress and elasticity tensors. In the sequel, we address some numerical aspects of the constitutive model by applying it to elastic, cyclic and relaxation test data obtained from biaxial extension and triaxial shear tests whereby we assess the fitting capacity of the model. With the tissue parameters identified, we conduct (elastic and viscoelastic) finite element simulations for an ellipsoidal geometry retrieved from a human specimen.

The spontaneous market order and evolution.

PubMed

Beck, Naomi

2016-08-01

Darwin's theory of natural selection and the idea of a spontaneous order share a fundamental feature: the claim that apparent design or order do not necessarily imply a designer or rational planning. But they also present important differences, which touch upon central questions such as the evolution of morality, the role of human agency in social evolution, the existence (or not) of directionality in undesigned processes, and the presence (nor not) of a providential element in evolutionary accounts. In this article, I explore these themes and probe the relationship between the notion of a spontaneous order and the theory of evolution by natural selection. The reflections of Nobel laureate in economics, F.A. von Hayek, provide the beginning and endpoint in this voyage, for they constitute the most pronounced effort to develop a full-fledged theory combining evolution and economics in recent times. But along the way, I also investigate the influence of classical political economy on Darwin's thought, primarily that of Adam Smith, and consider the reasons for which Darwin did not refer to Smith when discussing the principle of natural selection in The Origin of Species. I conclude that the spontaneous order, as understood by Hayek, and evolution by natural selection constitute two disparate concepts. Copyright © 2015 Elsevier Ltd. All rights reserved.

An Integrated Approach Linking Process to Structural Modeling With Microstructural Characterization for Injections-Molded Long-Fiber Thermoplastics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Bapanapalli, Satish K.; Smith, Mark T.

2008-09-01

The objective of our work is to enable the optimum design of lightweight automotive structural components using injection-molded long fiber thermoplastics (LFTs). To this end, an integrated approach that links process modeling to structural analysis with experimental microstructural characterization and validation is developed. First, process models for LFTs are developed and implemented into processing codes (e.g. ORIENT, Moldflow) to predict the microstructure of the as-formed composite (i.e. fiber length and orientation distributions). In parallel, characterization and testing methods are developed to obtain necessary microstructural data to validate process modeling predictions. Second, the predicted LFT composite microstructure is imported into amore » structural finite element analysis by ABAQUS to determine the response of the as-formed composite to given boundary conditions. At this stage, constitutive models accounting for the composite microstructure are developed to predict various types of behaviors (i.e. thermoelastic, viscoelastic, elastic-plastic, damage, fatigue, and impact) of LFTs. Experimental methods are also developed to determine material parameters and to validate constitutive models. Such a process-linked-structural modeling approach allows an LFT composite structure to be designed with confidence through numerical simulations. Some recent results of our collaborative research will be illustrated to show the usefulness and applications of this integrated approach.« less

Kinase Regulation by Hydrophobic Spine Assembly in Cancer

PubMed Central

Ahuja, Lalima G.; Meharena, Hiruy S.; Kannan, Natarajan; Kornev, Alexandr P.

2014-01-01

A new model of kinase regulation based on the assembly of hydrophobic spines has been proposed. Changes in their positions can explain the mechanism of kinase activation. Here, we examined mutations in human cancer for clues about the regulation of the hydrophobic spines by focusing initially on mutations to Phe. We identified a selected number of Phe mutations in a small group of kinases that included BRAF, ABL1, and the epidermal growth factor receptor. Testing some of these mutations in BRAF, we found that one of the mutations impaired ATP binding and catalytic activity but promoted noncatalytic allosteric functions. Other Phe mutations functioned to promote constitutive catalytic activity. One of these mutations revealed a previously underappreciated hydrophobic surface that functions to position the dynamic regulatory αC-helix. This supports the key role of the C-helix as a signal integration motif for coordinating multiple elements of the kinase to create an active conformation. The importance of the hydrophobic space around the αC-helix was further tested by studying a V600F mutant, which was constitutively active in the absence of the negative charge that is associated with the common V600E mutation. Many hydrophobic mutations strategically localized along the C-helix can thus drive kinase activation. PMID:25348715

Material-Model-Based Determination of the Shock-Hugoniot Relations in Nanosegregated Polyurea

NASA Astrophysics Data System (ADS)

Grujicic, Mica; Snipes, J. S.; Galgalikar, R.; Ramaswami, S.

2014-02-01

Previous experimental investigations reported in the open literature have indicated that applying polyurea external coatings and/or internal linings can substantially improve ballistic penetration resistance and blast survivability of buildings, vehicles, and laboratory/field test-plates, as well as the blast-mitigation capacity of combat helmets. The protective role of polyurea coatings/linings has been linked to polyurea microstructure, which consists of discrete hard-domains distributed randomly within a compliant/soft matrix. When this protective role is investigated computationally, the availability of reliable, high-fidelity constitutive models for polyurea is vitally important. In the present work, a comprehensive overview and a critical assessment of a polyurea material constitutive model, recently proposed by Shim and Mohr (Int J Plast 27:868-886, 2011), are carried out. The review revealed that this model can accurately account for the experimentally measured uniaxial-stress versus strain data obtained under monotonic and multistep compressive loading/unloading conditions, as well as under stress relaxation conditions. On the other hand, by combining analytical and finite-element procedures with the material model in order to define the basic shock-Hugoniot relations for this material, it was found that the computed shock-Hugoniot relations differ significantly from their experimental counterparts. Potential reasons for the disagreement between the computed and experimental shock-Hugoniot relations are identified.

Changes in Anthocyanin Production during Domestication of Citrus1[OPEN

PubMed Central

Garcia-Lor, Andrés; Licciardello, Concetta; Las Casas, Giuseppina; Ramadugu, Chandrika; Krueger, Robert; Fanciullino, Anne-Laure; Froelicher, Yann

2017-01-01

Mandarin (Citrus reticulata), citron (Citrus medica), and pummelo (Citrus maxima) are important species of the genus Citrus and parents of the interspecific hybrids that constitute the most familiar commercial varieties of Citrus: sweet orange, sour orange, clementine, lemon, lime, and grapefruit. Citron produces anthocyanins in its young leaves and flowers, as do species in genera closely related to Citrus, but mandarins do not, and pummelo varieties that produce anthocyanins have not been reported. We investigated the activity of the Ruby gene, which encodes a MYB transcription factor controlling anthocyanin biosynthesis, in different accessions of a range of Citrus species and in domesticated cultivars. A white mutant of lemon lacks functional alleles of Ruby, demonstrating that Ruby plays an essential role in anthocyanin production in Citrus. Almost all the natural variation in pigmentation by anthocyanins in Citrus species can be explained by differences in activity of the Ruby gene, caused by point mutations and deletions and insertions of transposable elements. Comparison of the allelic constitution of Ruby in different species and cultivars also helps to clarify many of the taxonomic relationships in different species of Citrus, confirms the derivation of commercial varieties during domestication, elucidates the relationships within the subgenus Papeda, and allows a new genetic classification of mandarins. PMID:28196843

Changes in Anthocyanin Production during Domestication of Citrus.

PubMed

Butelli, Eugenio; Garcia-Lor, Andrés; Licciardello, Concetta; Las Casas, Giuseppina; Hill, Lionel; Recupero, Giuseppe Reforgiato; Keremane, Manjunath L; Ramadugu, Chandrika; Krueger, Robert; Xu, Qiang; Deng, Xiuxin; Fanciullino, Anne-Laure; Froelicher, Yann; Navarro, Luis; Martin, Cathie

2017-04-01

Mandarin ( Citrus reticulata ), citron ( Citrus medica ), and pummelo ( Citrus maxima ) are important species of the genus Citrus and parents of the interspecific hybrids that constitute the most familiar commercial varieties of Citrus : sweet orange, sour orange, clementine, lemon, lime, and grapefruit. Citron produces anthocyanins in its young leaves and flowers, as do species in genera closely related to Citrus , but mandarins do not, and pummelo varieties that produce anthocyanins have not been reported. We investigated the activity of the Ruby gene, which encodes a MYB transcription factor controlling anthocyanin biosynthesis, in different accessions of a range of Citrus species and in domesticated cultivars. A white mutant of lemon lacks functional alleles of Ruby , demonstrating that Ruby plays an essential role in anthocyanin production in Citrus Almost all the natural variation in pigmentation by anthocyanins in Citrus species can be explained by differences in activity of the Ruby gene, caused by point mutations and deletions and insertions of transposable elements. Comparison of the allelic constitution of Ruby in different species and cultivars also helps to clarify many of the taxonomic relationships in different species of Citrus , confirms the derivation of commercial varieties during domestication, elucidates the relationships within the subgenus Papeda , and allows a new genetic classification of mandarins. © 2017 American Society of Plant Biologists. All Rights Reserved.

Capturing strain localization behind a geosynthetic-reinforced soil wall

NASA Astrophysics Data System (ADS)

Lai, Timothy Y.; Borja, Ronaldo I.; Duvernay, Blaise G.; Meehan, Richard L.

2003-04-01

This paper presents the results of finite element (FE) analyses of shear strain localization that occurred in cohesionless soils supported by a geosynthetic-reinforced retaining wall. The innovative aspects of the analyses include capturing of the localized deformation and the accompanying collapse mechanism using a recently developed embedded strong discontinuity model. The case study analysed, reported in previous publications, consists of a 3.5-m tall, full-scale reinforced wall model deforming in plane strain and loaded by surcharge at the surface to failure. Results of the analysis suggest strain localization developing from the toe of the wall and propagating upward to the ground surface, forming a curved failure surface. This is in agreement with a well-documented failure mechanism experienced by the physical wall model showing internal failure surfaces developing behind the wall as a result of the surface loading. Important features of the analyses include mesh sensitivity studies and a comparison of the localization properties predicted by different pre-localization constitutive models, including a family of three-invariant elastoplastic constitutive models appropriate for frictional/dilatant materials. Results of the analysis demonstrate the potential of the enhanced FE method for capturing a collapse mechanism characterized by the presence of a failure, or slip, surface through earthen materials.

Thermal Effects Modeling Developed for Smart Structures

NASA Technical Reports Server (NTRS)

Lee, Ho-Jun

1998-01-01

Applying smart materials in aeropropulsion systems may improve the performance of aircraft engines through a variety of vibration, noise, and shape-control applications. To facilitate the experimental characterization of these smart structures, researchers have been focusing on developing analytical models to account for the coupled mechanical, electrical, and thermal response of these materials. One focus of current research efforts has been directed toward incorporating a comprehensive thermal analysis modeling capability. Typically, temperature affects the behavior of smart materials by three distinct mechanisms: Induction of thermal strains because of coefficient of thermal expansion mismatch 1. Pyroelectric effects on the piezoelectric elements; 2. Temperature-dependent changes in material properties; and 3. Previous analytical models only investigated the first two thermal effects mechanisms. However, since the material properties of piezoelectric materials generally vary greatly with temperature (see the graph), incorporating temperature-dependent material properties will significantly affect the structural deflections, sensory voltages, and stresses. Thus, the current analytical model captures thermal effects arising from all three mechanisms through thermopiezoelectric constitutive equations. These constitutive equations were incorporated into a layerwise laminate theory with the inherent capability to model both the active and sensory response of smart structures in thermal environments. Corresponding finite element equations were formulated and implemented for both the beam and plate elements to provide a comprehensive thermal effects modeling capability.

Simulation of laminate composites degradation using mesoscopic non-local damage model and non-local layered shell element

NASA Astrophysics Data System (ADS)

Germain, Norbert; Besson, Jacques; Feyel, Frédéric

2007-07-01

Simulating damage and failure of laminate composites structures often fails when using the standard finite element procedure. The difficulties arise from an uncontrolled mesh dependence caused by damage localization and an increase in computational costs. One of the solutions to the first problem, widely used to predict the failure of metallic materials, consists of using non-local damage constitutive equations. The second difficulty can then be solved using specific finite element formulations, such as shell element, which decrease the number of degrees of freedom. The main contribution of this paper consists of extending these techniques to layered materials such as polymer matrix composites. An extension of the non-local implicit gradient formulation, accounting for anisotropy and stratification, and an original layered shell element, based on a new partition of the unity, are proposed. Finally the efficiency of the resulting numerical scheme is studied by comparing simulation with experimental results.

Strike action electromagnetic machine for immersion of rod elements into ground

NASA Astrophysics Data System (ADS)

Usanov, K. M.; Volgin, A. V.; Chetverikov, E. A.; Kargin, V. A.; Moiseev, A. P.; Ivanova, Z. I.

2017-10-01

During construction, survey work, and drilling shallow wells by striking, operations associated with dipping and removing the rod elements are the most common. At the same time relatively long, with small diameter, elements, in which the ratio of length to diameter l/d is 100 or more, constitute a significant proportion. At present, the application of power pulse linear electromagnetic motors to drive drum machines is recognized to be highly effective. However, the mechanical method of transmission of shocks does not allow dipping long longitudinally unstable core elements. In this case, mechanical energy must be transferred from the motor to the rod through its side surface. The design of the strike action electromagnetic machine with a through axial channel for non-mechanical end striking of the pile of long, longitudinally unstable metal rods is proposed. Electromagnetic striking machine for non-mechanical end striking rod elements provides operations characterized by ecological compatibility, safety and high quality.

Subwavelength nonlinear phase control and anomalous phase matching in plasmonic metasurfaces

NASA Astrophysics Data System (ADS)

Almeida, Euclides; Shalem, Guy; Prior, Yehiam

2016-01-01

Metasurfaces, and in particular those containing plasmonic-based metallic elements, constitute an attractive set of materials with a potential for replacing standard bulky optical elements. In recent years, increasing attention has been focused on their nonlinear optical properties, particularly in the context of second and third harmonic generation and beam steering by phase gratings. Here, we harness the full phase control enabled by subwavelength plasmonic elements to demonstrate a unique metasurface phase matching that is required for efficient nonlinear processes. We discuss the difference between scattering by a grating and by subwavelength phase-gradient elements. We show that for such interfaces an anomalous phase-matching condition prevails, which is the nonlinear analogue of the generalized Snell's law. The subwavelength phase control of optical nonlinearities paves the way for the design of ultrathin, flat nonlinear optical elements. We demonstrate nonlinear metasurface lenses, which act both as generators and as manipulators of the frequency-converted signal.

Teaching about the Constitution: Relationships between Teachers' Subject Matter Knowledge, Pedagogic Beliefs and Instructional Decision Making regarding Selection of Content, Materials, and Activities. Summary of Research Findings.

ERIC Educational Resources Information Center

Hyland, John T.

Importance of the Constitution as the supreme law of the land and the reported failure of the United States youth to have been genuinely educated about the Constitution raises questions regarding teaching. One concerns what teachers know about the Constitution and the other is what they believe about teaching. This study investigates these…

Involvement of activator protein 1 complexes in the epithelium-specific activation of the laminin gamma2-chain gene promoter by hepatocyte growth factor (scatter factor).

PubMed Central

Olsen, J; Lefebvre, O; Fritsch, C; Troelsen, J T; Orian-Rousseau, V; Kedinger, M; Simon-Assmann, P

2000-01-01

Laminin-5 is a trimer of laminin alpha3, beta3 and gamma2 chains that is found in the intestinal basement membrane. Deposition of the laminin gamma2 chain at the basement membrane is of great interest because it undergoes a developmental shift in its cellular expression. Here we study the regulatory elements that control basal and cytokine-activated transcriptional expression of the LAMC2 gene, which encodes the laminin gamma2 chain. By using transient transfection experiments we demonstrated the presence of constitutive and cytokine-responsive cis-elements. Comparison of the transcriptional activity of the LAMC2 promoter in the epithelial HT29mtx cells with that in small-intestinal fibroblastic cells (C20 cells) led us to conclude that two regions with constitutive epithelium-specific activity are present between positions -1.2 and -0.12 kb. This was further validated by transfections of primary foetal intestinal endoderm and mesenchyme. A 2.5 kb portion of the LAMC2 5' flanking region was equally responsive to PMA and hepatocyte growth factor (HGF), whereas it was less responsive to transforming growth factor beta1. A minimal promoter limited to the initial 120 bp upstream of the transcriptional start site maintained inducibility by PMA and HGF. This short promoter fragment contains two activator protein 1 (AP-1) elements and the 5'-most of these is a composite AP-1/Sp1 element. The 5'AP-1 element is crucial to the HGF-mediated activity of the promoter; analysis of interacting nuclear proteins demonstrated that AP-1 proteins containing JunD mediate the response to HGF. PMID:10749670

On the effects of leaflet microstructure and constitutive model on the closing behavior of the mitral valve

PubMed Central

Lee, Chung-Hao; Rabbah, Jean-Pierre; Yoganathan, Ajit P.; Gorman, Robert C.; Gorman, Joseph H.

2016-01-01

Recent long-term studies showed an unsatisfactory recurrence rate of severe mitral regurgitation 3–5 years after surgical repair, suggesting that excessive tissue stresses and the resulting strain-induced tissue failure are potential etiological factors controlling the success of surgical repair for treating mitral valve (MV) diseases. We hypothesized that restoring normal MV tissue stresses in MV repair techniques would ultimately lead to improved repair durability through the restoration of MV normal homeostatic state. Therefore, we developed a micro- and macro- anatomically accurate MV finite element model by incorporating actual fiber microstructural architecture and a realistic structure-based constitutive model. We investigated MV closing behaviors, with extensive in vitro data used for validating the proposed model. Comparative and parametric studies were conducted to identify essential model fidelity and information for achieving desirable accuracy. More importantly, for the first time, the interrelationship between the local fiber ensemble behavior and the organ-level MV closing behavior was investigated using a computational simulation. These novel results indicated not only the appropriate parameter ranges, but also the importance of the microstructural tuning (i.e., straightening and re-orientation) of the collagen/elastin fiber networks at the macroscopic tissue level for facilitating the proper coaptation and natural functioning of the MV apparatus under physiological loading at the organ level. The proposed computational model would serve as a logical first step toward our long-term modeling goal—facilitating simulation-guided design of optimal surgical repair strategies for treating diseased MVs with significantly enhanced durability. PMID:25947879

HLA DR/DQ type in a Malay population in Kelantan, Malaysia.

PubMed

Azira, N M S; Zeehaida, M; Nurul Khaiza, Y

2013-06-01

The human leucocyte antigen (HLA) has been documented to be involved in various disease susceptibilities or in resistance against certain diseases. An important element in susceptibility and resistance to disease is ethnic genetic constitution. Cognizant of this, the present study aimed at studying the prevalence of particular HLA class II in a normal healthy Malay population which may serve as a guide for further genetic and immunological studies related to the Malay Malaysian population. The study involved 40 normal healthy Malay persons in Kelantan. HLA typing was conducted on venous blood samples through a polymerase chain reaction-sequence specific primer method (low resolution Olerup SSP© HLA Typing Kits). The study found HLA DR12 and HLA DQ8 to be the most frequent HLA class II type. HLA DQ5 was significantly associated with female subjects.

Overview of critical risk factors in Power-Two-Wheeler safety.

PubMed

Vlahogianni, Eleni I; Yannis, George; Golias, John C

2012-11-01

Power-Two-Wheelers (PTWs) constitute a vulnerable class of road users with increased frequency and severity of accidents. The present paper focuses of the PTW accident risk factors and reviews existing literature with regard to the PTW drivers' interactions with the automobile drivers, as well as interactions with infrastructure elements and weather conditions. Several critical risk factors are revealed with different levels of influence to PTW accident likelihood and severity. A broad classification based on the magnitude and the need for further research for each risk factor is proposed. The paper concludes by discussing the importance of dealing with accident configurations, the data quality and availability, methods implemented to model risk and exposure and risk identification which are critical for a thorough understanding of the determinants of PTW safety. Copyright © 2012 Elsevier Ltd. All rights reserved.

Homonuclear Hartmann-Hahn transfer with reduced relaxation losses by use of the MOCCA-XY16 multiple pulse sequence

NASA Astrophysics Data System (ADS)

Furrer, Julien; Kramer, Frank; Marino, John P.; Glaser, Steffen J.; Luy, Burkhard

2004-01-01

Homonuclear Hartmann-Hahn transfer is one of the most important building blocks in modern high-resolution NMR. It constitutes a very efficient transfer element for the assignment of proteins, nucleic acids, and oligosaccharides. Nevertheless, in macromolecules exceeding ˜10 kDa TOCSY-experiments can show decreasing sensitivity due to fast transverse relaxation processes that are active during the mixing periods. In this article we propose the MOCCA-XY16 multiple pulse sequence, originally developed for efficient TOCSY transfer through residual dipolar couplings, as a homonuclear Hartmann-Hahn sequence with improved relaxation properties. A theoretical analysis of the coherence transfer via scalar couplings and its relaxation behavior as well as experimental transfer curves for MOCCA-XY16 relative to the well-characterized DIPSI-2 multiple pulse sequence are given.

Homonuclear Hartmann-Hahn transfer with reduced relaxation losses by use of the MOCCA-XY16 multiple pulse sequence.

PubMed

Furrer, Julien; Kramer, Frank; Marino, John P; Glaser, Steffen J; Luy, Burkhard

2004-01-01

Homonuclear Hartmann-Hahn transfer is one of the most important building blocks in modern high-resolution NMR. It constitutes a very efficient transfer element for the assignment of proteins, nucleic acids, and oligosaccharides. Nevertheless, in macromolecules exceeding approximately 10 kDa TOCSY-experiments can show decreasing sensitivity due to fast transverse relaxation processes that are active during the mixing periods. In this article we propose the MOCCA-XY16 multiple pulse sequence, originally developed for efficient TOCSY transfer through residual dipolar couplings, as a homonuclear Hartmann-Hahn sequence with improved relaxation properties. A theoretical analysis of the coherence transfer via scalar couplings and its relaxation behavior as well as experimental transfer curves for MOCCA-XY16 relative to the well-characterized DIPSI-2 multiple pulse sequence are given.

Nonlinear mechanics of composite materials with periodic microstructure

NASA Technical Reports Server (NTRS)

Jordan, E. H.; Walker, K. P.

1991-01-01

This report summarizes the result of research done under NASA NAG3-882 Nonlinear Mechanics of Composites with Periodic Microstructure. The effort involved the development of non-finite element methods to calculate local stresses around fibers in composite materials. The theory was developed and some promising numerical results were obtained. It is expected that when this approach is fully developed, it will provide an important tool for calculating local stresses and averaged constitutive behavior in composites. NASA currently has a major contractual effort (NAS3-24691) to bring the approach developed under this grant to application readiness. The report has three sections. One, the general theory that appeared as a NASA TM, a second section that gives greater details about the theory connecting Greens functions and Fourier series approaches, and a final section shows numerical results.

Prosopography, prosoporecognography and the Prosoporecognographical Chart.

PubMed

Santos-Filho, E F; Pereira, H B B

2017-11-01

Recognizing and identifying an individual based on his or her face is a technical and scientific challenge and the objective of our investigation. This article's goal is to establish a method, a foundation and an instrument for carrying out the process of recognizing and identifying an individual. Both the construction of the term and the deepening, conceptualization and epistemology of the process of describing and representing the face through a particular method of recognizing and identifying individuals are described in this article. The proposal of the Prosoporecognographical Chart is an important step in the facial-identification process, establishing taxonomic parameters for the phenotypic manifestations of the elements constituting the face. Based on the proposal presented here, the construction of a protocol for the process of recognizing and identifying an individual can be implemented computationally. Copyright © 2017. Published by Elsevier Ltd.

Analysis of Transformation Plasticity in Steel Using a Finite Element Method Coupled with a Phase Field Model

PubMed Central

Cho, Yi-Gil; Kim, Jin-You; Cho, Hoon-Hwe; Cha, Pil-Ryung; Suh, Dong-Woo; Lee, Jae Kon; Han, Heung Nam

2012-01-01

An implicit finite element model was developed to analyze the deformation behavior of low carbon steel during phase transformation. The finite element model was coupled hierarchically with a phase field model that could simulate the kinetics and micro-structural evolution during the austenite-to-ferrite transformation of low carbon steel. Thermo-elastic-plastic constitutive equations for each phase were adopted to confirm the transformation plasticity due to the weaker phase yielding that was proposed by Greenwood and Johnson. From the simulations under various possible plastic properties of each phase, a more quantitative understanding of the origin of transformation plasticity was attempted by a comparison with the experimental observation. PMID:22558295

Simulation of finite-strain inelastic phenomena governed by creep and plasticity

NASA Astrophysics Data System (ADS)

Li, Zhen; Bloomfield, Max O.; Oberai, Assad A.

2017-11-01

Inelastic mechanical behavior plays an important role in many applications in science and engineering. Phenomenologically, this behavior is often modeled as plasticity or creep. Plasticity is used to represent the rate-independent component of inelastic deformation and creep is used to represent the rate-dependent component. In several applications, especially those at elevated temperatures and stresses, these processes occur simultaneously. In order to model these process, we develop a rate-objective, finite-deformation constitutive model for plasticity and creep. The plastic component of this model is based on rate-independent J_2 plasticity, and the creep component is based on a thermally activated Norton model. We describe the implementation of this model within a finite element formulation, and present a radial return mapping algorithm for it. This approach reduces the additional complexity of modeling plasticity and creep, over thermoelasticity, to just solving one nonlinear scalar equation at each quadrature point. We implement this algorithm within a multiphysics finite element code and evaluate the consistent tangent through automatic differentiation. We verify and validate the implementation, apply it to modeling the evolution of stresses in the flip chip manufacturing process, and test its parallel strong-scaling performance.

Science learning in the context of discourse

NASA Astrophysics Data System (ADS)

do Nascimento, Silvania Sousa

2013-06-01

The original article by Kamberelis and Wehunt (2012) discusses an interesting and important research subject in science education as it focus on classroom interactions and the characteristics of the discourse production of interlocutors. The authors start from the premise that discourse heterogeneity is constitutive of social activities, which is supported by others like Mikhail Bakhtin (Speech genres and other late essays. University of Texas Press, Austin, 1981) and Erving Goffman (Frame analysis: an essay on the organization of experience. Harper and Row, London, 1974). They also present the definitions of three key elements that organize hybrid discourse: (a) lamination of multiple cultural frames, (b) shifting relations between people and their discourse, and (c) shifting power relations between people. Finally, the authors analyze how these three elements organize students' science discourse in the classroom and how it contributes to the creation of a micro-community of practice capable of helping the emergence of a disciplinary knowledge that is legitimized by and strengthens the identity of the group. In the present commentary, I discuss how Michael Foucault's (1970) concept of discursive procedure may help us to analyze the (often neglected) teacher's role in the development of hybrid discourse practices.

Unusually long-lived pause required for regulation of a Rho-dependent transcription terminator

PubMed Central

Hollands, Kerry; Sevostiyanova, Anastasia; Groisman, Eduardo A.

2014-01-01

Up to half of all transcription termination events in bacteria rely on the RNA-dependent helicase Rho. However, the nucleic acid sequences that promote Rho-dependent termination remain poorly characterized. Defining the molecular determinants that confer Rho-dependent termination is especially important for understanding how such terminators can be regulated in response to specific signals. Here, we identify an extraordinarily long-lived pause at the site where Rho terminates transcription in the 5′-leader region of the Mg2+ transporter gene mgtA in Salmonella enterica. We dissect the sequence elements required for prolonged pausing in the mgtA leader and establish that the remarkable longevity of this pause is required for a riboswitch to stimulate Rho-dependent termination in the mgtA leader region in response to Mg2+ availability. Unlike Rho-dependent terminators described previously, where termination occurs at multiple pause sites, there is a single site of transcription termination directed by Rho in the mgtA leader. Our data suggest that Rho-dependent termination events that are subject to regulation may require elements distinct from those operating at constitutive Rho-dependent terminators. PMID:24778260

Strengths of OPEC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adelman, M.A.

The major distinction of the Organization of Petroleum Exporting Countries is obvious even to the casual observer: the nations composing it constitute the greatest monopoly in history; its tribute now is over $100 billion a year. For the immediate future, OPEC's elements of strength look more important than its elements of weakness. The cartel will not soon disappear. The forces acting against the cartel are subsumed in the fact of excess capacity. This is the traditional nemesis of cartels, since it puts in motion the sequence of small price reductions by some sellers to gain additional sales volume, then competitivemore » or matching reductions. To preserve the cartel, each member must avoid acting for his own independent good, and must do what is best for the group as a whole. The greater the temptation to act independently the greater the fear of others' independent action, and the higher the probability of severe erosion or breakdown. So the fate of the cartel depends essentially on the strength of exogenous factors, demand and uncontrolled supply, versus the strength of an endogenous factor, the cohesion of the group. All too often either one of these factors is treated in isolation as though the other were not there.« less

Implementation strategies: recommendations for specifying and reporting

PubMed Central

2013-01-01

Implementation strategies have unparalleled importance in implementation science, as they constitute the ‘how to’ component of changing healthcare practice. Yet, implementation researchers and other stakeholders are not able to fully utilize the findings of studies focusing on implementation strategies because they are often inconsistently labelled and poorly described, are rarely justified theoretically, lack operational definitions or manuals to guide their use, and are part of ‘packaged’ approaches whose specific elements are poorly understood. We address the challenges of specifying and reporting implementation strategies encountered by researchers who design, conduct, and report research on implementation strategies. Specifically, we propose guidelines for naming, defining, and operationalizing implementation strategies in terms of seven dimensions: actor, the action, action targets, temporality, dose, implementation outcomes addressed, and theoretical justification. Ultimately, implementation strategies cannot be used in practice or tested in research without a full description of their components and how they should be used. As with all intervention research, their descriptions must be precise enough to enable measurement and ‘reproducibility.’ We propose these recommendations to improve the reporting of implementation strategies in research studies and to stimulate further identification of elements pertinent to implementation strategies that should be included in reporting guidelines for implementation strategies. PMID:24289295

Implementation strategies: recommendations for specifying and reporting.

PubMed

Proctor, Enola K; Powell, Byron J; McMillen, J Curtis

2013-12-01

Implementation strategies have unparalleled importance in implementation science, as they constitute the 'how to' component of changing healthcare practice. Yet, implementation researchers and other stakeholders are not able to fully utilize the findings of studies focusing on implementation strategies because they are often inconsistently labelled and poorly described, are rarely justified theoretically, lack operational definitions or manuals to guide their use, and are part of 'packaged' approaches whose specific elements are poorly understood. We address the challenges of specifying and reporting implementation strategies encountered by researchers who design, conduct, and report research on implementation strategies. Specifically, we propose guidelines for naming, defining, and operationalizing implementation strategies in terms of seven dimensions: actor, the action, action targets, temporality, dose, implementation outcomes addressed, and theoretical justification. Ultimately, implementation strategies cannot be used in practice or tested in research without a full description of their components and how they should be used. As with all intervention research, their descriptions must be precise enough to enable measurement and 'reproducibility.' We propose these recommendations to improve the reporting of implementation strategies in research studies and to stimulate further identification of elements pertinent to implementation strategies that should be included in reporting guidelines for implementation strategies.

A Modified Constitutive Model for Tensile Flow Behaviors of BR1500HS Ultra-High-Strength Steel at Medium and Low Temperature Regions

NASA Astrophysics Data System (ADS)

Zhao, Jun; Quan, Guo-Zheng; Pan, Jia; Wang, Xuan; Wu, Dong-Sen; Xia, Yu-Feng

2018-01-01

Constitutive model of materials is one of the most requisite mathematical model in the finite element analysis, which describes the relationships of flow behaviors with strain, strain rate and temperature. In order to construct such constitutive relationships of ultra-high-strength BR1500HS steel at medium and low temperature regions, the true stress-strain data over a wide temperature range of 293-873 K and strain rate range of 0.01-10 s-1 were collected from a series of isothermal uniaxial tensile tests. The experimental results show that stress-strain relationships are highly non-linear and susceptible to three parameters involving temperature, strain and strain rate. By considering the impacts of strain rate and temperature on strain hardening, a modified constitutive model based on Johnson-Cook model was proposed to characterize flow behaviors in medium and low temperature ranges. The predictability of the improved model was also evaluated by the relative error (W(%)), correlation coefficient (R) and average absolute relative error (AARE). The R-value and AARE-value for modified constitutive model at medium and low temperature regions are 0.9915 & 1.56 % and 0.9570 & 5.39 %, respectively, which indicates that the modified constitutive model can precisely estimate the flow behaviors for BR1500HS steel in the medium and low temperature regions.

Nucleation and growth of rolling contact failure of 440C bearing steel

NASA Technical Reports Server (NTRS)

Gupta, V.; Bastias, P. C.; Hahn, G. T.; Rubin, C. A.

1992-01-01

A 'two-body' elasto-plastic finite element model of 2-dimensional rolling and rolling-plus-sliding was developed to treat the effect of surface irregularities. The model consists of a smooth cylinder in contact with a semi-infinite half-space that is either smooth or fitted with one of 0.4 microns deep or 7 microns deep groove, or a 0.4 microns high ridge-like asperity. The model incorporates elastic-linear-kinematic hardening-plastic (ELKP) and non-linear-kinematic hardening-plastic (NLKP) material constitutive relations appropriate for hardened bearing steel and the 440C grade. The calculated contact pressure distribution is Hertzian for smooth body contact, and it displays intense, stationary, pressure spikes superposed on the Hertzian pressure for contact with the grooved and ridged surface. The results obtained for the 0.4 microns deep groove compare well with those reported by Elsharkawy and Hamrock for an EHD lubricated contact. The effect of translating the counterface on the half space as opposed to indenting the half space with the counter face with no translation is studied. The stress and strain values near the surface are found to be similar for the two cases, whereas they are significantly different in the subsurface. It is seen that when tiny shoulders are introduced at the edge of the groove in the finite element model, the incremental plasticity and residual stresses are significantly higher in the vicinity of the right shoulder (rolling direction is from left to right) than at the left shoulder. This may explain the experimental observation that the spall nucleation occurs at the exit end of the artificially planted indents. Pure rolling calculations are compared with rolling + sliding calculations. For a coefficient of friction, mu = 0.1, the effect of friction is found to be small. Efforts were made to identify the material constitutive relations which best describe the deformation characteristics of the bearing steels in the initial few cycles. Elastic-linear-kinematic hardening-plastic (ELKP) material constitutive relations produce less net plastic deformation in the initial stages for a given stress, than seen in experiments. A new set of constitutive relations: non-linear-kinematic hardening-plastic (NLKP) was used. This material model produces more plasticity than the ELKP model and shows promise for treating the net distortions in the early stages. Techniques for performing experimental measurements that can be compared with the finite element calculations were devised. The measurements are being performed on 9mm-diameter, 440C steel cylindrical rolling elements in contact with 12.5 mm-diameter, 52100 steel balls in a 3-ball-rod fatigue test machine operating at 3600 RPM. Artificial, 7 microns deep, indents were inserted on the running track of the cylindrical rolling elements and profilometer measurements of these indents made, before and after the rolling. These preliminary measurements show that the indents are substantially deformed plastically in the process of rolling. The deformations of the groove calculated with the finite element model are comparable to those measured experimentally.

A comparison of FE beam and continuum elements for typical nitinol stent geometries

NASA Astrophysics Data System (ADS)

Ballew, Wesley; Seelecke, Stefan

2009-03-01

With interest in improved efficiency and a more complete description of the SMA material, this paper compares finite element (FE) simulations of typical stent geometries using two different constitutive models and two different element types. Typically, continuum elements are used for the simulation of stents, for example the commercial FE software ANSYS offers a continuum element based on Auricchio's SMA model. Almost every stent geometry, however, is made up of long and slender components and can be modeled more efficiently, in the computational sense, with beam elements. Using the ANSYS user programmable material feature, we implement the free energy based SMA model developed by Mueller and Seelecke into the ANSYS beam element 188. Convergence behavior for both, beam and continuum formulations, is studied in terms of element and layer number, respectively. This is systematically illustrated first for the case of a straight cantilever beam under end loading, and subsequently for a section of a z-bend wire, a typical stent sub-geometry. It is shown that the computation times for the beam element are reduced to only one third of those of the continuum element, while both formulations display a comparable force/displacement response.

Friends' Organizations: The Supportive Element Essential to Libraries.

ERIC Educational Resources Information Center

Progar, Dorothy

Reviewed are the history and public relations, financial and service roles of lay "Friends of the Library" groups. Programs and techniques useful in the pursuit of these roles are suggested. Guidelines for a constitution, fee schedule, and administrative structure plus a bibliography give potential friends organizations help in…

A Framework for a Computer System to Support Distributed Cooperative Learning

ERIC Educational Resources Information Center

Chiu, Chiung-Hui

2004-01-01

To develop a computer system to support cooperative learning among distributed students; developers should consider the foundations of cooperative learning. This article examines the basic elements that make cooperation work and proposes a framework for such computer supported cooperative learning (CSCL) systems. This framework is constituted of…

Myth #10: Business Can Define Workplace Literacy.

ERIC Educational Resources Information Center

Literacy Beat, 1989

1989-01-01

Representatives of the business community define workplace literacy according to how well informed are the spokespersons for business, how expansive is their view of the role of literacy, and the extent to which literacy bears on their firms' productivity. These elements affect business people's understanding of what constitutes workplace…

On the Longitudinal Component of Paraxial Fields

ERIC Educational Resources Information Center

Carnicer, Artur; Juvells, Ignasi; Maluenda, David; Martinez-Herrero, Rosario; Mejias, Pedro M.

2012-01-01

The analysis of paraxial Gaussian beams features in most undergraduate courses in laser physics, advanced optics and photonics. These beams provide a simple model of the field generated in the resonant cavities of lasers, thus constituting a basic element for understanding laser theory. Usually, uniformly polarized beams are considered in the…

An Imagination Effect in Learning from Scientific Text

ERIC Educational Resources Information Center

Leopold, Claudia; Mayer, Richard E.

2015-01-01

Asking students to imagine the spatial arrangement of the elements in a scientific text constitutes a learning strategy intended to foster deep processing of the instructional material. Two experiments investigated the effects of mental imagery prompts on learning from scientific text. Students read a computer-based text on the human respiratory…

Mathematical Thinking and Creativity through Mathematical Problem Posing and Solving

ERIC Educational Resources Information Center

Ayllón, María F.; Gómez, Isabel A.; Ballesta-Claver, Julio

2016-01-01

This work shows the relationship between the development of mathematical thinking and creativity with mathematical problem posing and solving. Creativity and mathematics are disciplines that do not usually appear together. Both concepts constitute complex processes sharing elements, such as fluency (number of ideas), flexibility (range of ideas),…

COMPARING METHODS FOR ESTIMATING {ITAL CRYPTOSPORIDIUM} SPP. OOCYST CONCENTRATIONS IN WATER

EPA Science Inventory

{ital Cryptosporidium parvum} in drinking water is a threat to public health. Estimating the parasite burden of {ital C. parvum} in water to be treated for use as drinking water constitutes an integral element to developing strategies for protecting public health in a cost effec...

Lawsuits in the Air.

ERIC Educational Resources Information Center

Hays, Larry

2000-01-01

Discusses why indoor air quality problems in schools should be treated, not only as a health problem issue, but as a potential for legal actions. What types of proof are needed to make a legal claim involving indoor air problems are addressed as are the elements which constitute a "sick building." (GR)

Youth Purpose through the Lens of the Theory of Organizing Models of Thinking

ERIC Educational Resources Information Center

Arantes, Valeria; Araujo, Ulisses; Pinheiro, Viviane; Moreno Marimon, Montserrat; Sastre, Genoveva

2017-01-01

Purpose represents a unique opportunity for identifying and analyzing the complexity of human reasoning, considering that its constitution brings together cognitive, affective and social elements. In this article, we use the Theory of Organizing Models of Thinking (OMT), an epistemological and methodological approach based on developmental…

Design Considerations in Developing a Web-Based Mentor Network.

ERIC Educational Resources Information Center

Sumner, Todd

This paper describes a Web-based mentor network designed to pair students in rural independent schools with undergraduates at selected liberal arts colleges. It is one of nine central program elements that constitute the Proteus(TM) system, a multimedia technologies architecture that supports distributed collaborations and work undertaken in the…

Homeschooling in the USA: Past, Present and Future

ERIC Educational Resources Information Center

Gaither, Milton

2009-01-01

This article first examines why the homeschooling movement in the USA emerged in the 1970s, noting the impact of political radicalism both right and left, feminism, suburbanization, and public school bureaucratization and secularization. It then describes how the movement, constituted of left- and right-wing elements, collaborated in the early…

Exploring Human Kindness through the Pedagogy of Aikido.

ERIC Educational Resources Information Center

Brawdy, Paul

This paper considers the origins of kindness in relation to the martial art known as Aikido. It also attempts to discover the underlying constitutional elements of Aikido's pedagogy of self learning, learning about others, and instructional practices that promote interpersonal relatedness. A teacher and four students of the Aikido Dojo were…

Women and Transgression in the Halls of Academe

ERIC Educational Resources Information Center

Davies, Bronwyn

2006-01-01

The controlling strategies of neo-liberalism, designed to constitute academics as economic units supporting the designs of government, are contrasted here with the creative and transgressive elements of a more Deleuzian approach to writing that opens things up, that brings thought to life, that makes the familiar, predictable order tremble. The…

Sports Education Facing Globalizing Capitalism

ERIC Educational Resources Information Center

Gur-Ze'ev, Ilan

2005-01-01

From its very beginning sports activity became--already within the framework of the modern nation-building project, establishing national ethos, and constituting effective colonization of the Other--a central element of the effort of the modern system to create, represent, and consume the modern body and soul and to create the healthy-conquering…

A Behavioral Systems Analysis of Behavior Analysis as a Scientific System

ERIC Educational Resources Information Center

Hayes, Linda J.; Dubuque, Erick M.; Fryling, Mitch J.; Pritchard, Joshua K.

2009-01-01

Behavioral systems analyses typically address organizational problems in business and industry. However, to the extent that a behavioral system is an entity comprised of interdependent elements formed by individuals interacting toward a common goal, a scientific enterprise constitutes a behavioral system to which a behavioral systems analysis may…

A probabilistic Hu-Washizu variational principle

NASA Technical Reports Server (NTRS)

Liu, W. K.; Belytschko, T.; Besterfield, G. H.

1987-01-01

A Probabilistic Hu-Washizu Variational Principle (PHWVP) for the Probabilistic Finite Element Method (PFEM) is presented. This formulation is developed for both linear and nonlinear elasticity. The PHWVP allows incorporation of the probabilistic distributions for the constitutive law, compatibility condition, equilibrium, domain and boundary conditions into the PFEM. Thus, a complete probabilistic analysis can be performed where all aspects of the problem are treated as random variables and/or fields. The Hu-Washizu variational formulation is available in many conventional finite element codes thereby enabling the straightforward inclusion of the probabilistic features into present codes.

The presence of vanadium in groundwater of southeastern extreme the pampean region Argentina Relationship with other chemical elements.

PubMed

Fiorentino, Carmen E; Paoloni, Juan D; Sequeira, Mario E; Arosteguy, Pedro

2007-08-15

Changes in the quality of groundwater resources are related to the presence and concentration of contaminants, especially trace elements such as arsenic, boron, fluoride and vanadium. Vanadium is a rare element naturally abundant, generally found in combination with other elements. Vanadium pentoxide is known to have aneugenic effects. Thus, a study was carried out to assess the presence of vanadium in the groundwater of the southeastern pampean region of Argentina, which constitutes the main water supply for the local population. Statistical and correlational analyses were applied to identify possible interrelationships between vanadium and another chemical elements. Vanadium was found in all groundwater samples. The minimum and maximum vanadium concentrations found were 0.05 mg/l and 2.47 mg/l, respectively. Vanadium is significantly correlated with other trace elements such as arsenic, fluoride and boron. The interrelationship between vanadium and the presence of volcanic glass in sediments is not significant as expected.

Simulation of irradiation hardening of Zircaloy within plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Jiang, Yijie; Wang, Qiming; Cui, Yi; Huo, Yongzhong; Ding, Shurong

2011-06-01

Within plate-type dispersion nuclear fuel elements, the metal matrix and cladding attacked continuously by fast neutrons undergo irradiation hardening, which might have remarkable effects upon the mechanical behaviors within fuel elements. In this paper, with the irradiation hardening effect of metal materials mainly considered together with irradiation growth effect of the cladding, the three-dimensional large-deformation constitutive relations for the metal matrix and cladding are developed. The method of virtual temperature increase in the previous studies is further developed to model the irradiation swelling of fuel particles; the method of anisotropic thermal expansion is introduced to model irradiation growth of the cladding; and a method of multi-step-temperature loading is proposed to simulate the coupling features of irradiation-induced swelling of the fuel particles together with irradiation growth of the cladding. Above all, based on the developed relationship between irradiation growth at certain burnup and the loaded virtual temperatures, with considering that certain burnup corresponds to certain fast neutron fluence, the time-dependent constitutive relation due to irradiation hardening effect is replaced by the virtual-temperature-dependent one which is introduced into the commercial software to simulate the irradiation hardening effects of the matrix and cladding. Numerical simulations of the irradiation-induced mechanical behaviors are implemented with the finite element method in consideration of the micro-structure of the fuel meat. The obtained results indicate that when the irradiation hardening effects are introduced into the constitutive relations of the metal matrix and cladding: (1) higher maximum Mises stresses for certain burnup at the matrix exist with the equivalent plastic strains remaining almost the same at lower burnups; (2) the maximum Mises stresses for certain burnup at the cladding are enhanced while the maximum equivalent plastic strains are reduced; and (3) the maximum first principal stresses for certain burnup at the matrix or the cladding are lower than the ones without the hardening effect, and the differences are found to increase with burnup; and the variation rules of the interfacial stresses are similar.

Infiltration behaviour of elemental mercury DNAPL in fully and partially water saturated porous media

NASA Astrophysics Data System (ADS)

D'Aniello, Andrea; Hartog, Niels; Sweijen, Thomas; Pianese, Domenico

2018-02-01

Mercury is a contaminant of global concern due to its harmful effects on human health and for the detrimental consequences of its release in the environment. Sources of liquid elemental mercury are usually anthropogenic, such as chlor-alkali plants. To date insight into the infiltration behaviour of liquid elemental mercury in the subsurface is lacking, although this is critical for assessing both characterization and remediation approaches for mercury DNAPL contaminated sites. Therefore, in this study the infiltration behaviour of elemental mercury in fully and partially water saturated systems was investigated using column experiments. The properties affecting the constitutive relations governing the infiltration behaviour of liquid Hg0, and PCE for comparison, were determined using Pc(S) experiments with different granular porous media (glass beads and sands) for different two- and three-phase configurations. Results showed that, in water saturated porous media, elemental mercury, as PCE, acted as a non-wetting fluid. The required entry head for elemental mercury was higher (from about 5 to 7 times). However, due to the almost tenfold higher density of mercury, the required NAPL entry heads of 6.19 cm and 12.51 cm for mercury to infiltrate were 37.5% to 20.7% lower than for PCE for the same porous media. Although Leverett scaling was able to reproduce the natural tendency of Hg0 to be more prone than PCE to infiltrate in water saturated porous media, it considerably underestimated Hg0 infiltration capacity in comparison with the experimental results. In the partially water saturated system, in contrast with PCE, elemental mercury also acted as a nonwetting fluid, therefore having to overcome an entry head to infiltrate. The required Hg0 entry heads (10.45 and 15.74 cm) were considerably higher (68.9% and 25.8%) than for the water saturated porous systems. Furthermore, in the partially water saturated systems, experiments showed that elemental mercury displaced both air and water, depending on the initial water distribution within the pores. This indicates that the conventional wettability hierarchy, in which the NAPL has an intermediate wetting state between the air and the water phases, is not valid for liquid elemental mercury. Therefore, for future modelling of elemental mercury DNAPL infiltration behaviour in variably water saturated porous media, a different formulation of the governing constitutive relations will be required.

A simplified constitutive model for predicting shape memory polymers deformation behavior

NASA Astrophysics Data System (ADS)

Li, Yunxin; Guo, Siu-Siu; He, Yuhao; Liu, Zishun

2015-12-01

Shape memory polymers (SMPs) can keep a temporary shape after pre-deformation at a higher temperature and subsequent cooling. When they are reheated, their original shapes can be recovered. Such special characteristics of SMPs make them widely used in aerospace structures, biomedical devices, functional textiles and other devices. Increasing usefulness of SMPs motivates us to further understand their thermomechanical properties and deformation behavior, of which the development of appropriate constitutive models for SMPs is imperative. There is much work in literatures that address constitutive models of the thermo-mechanical coupling in SMPs. However, due to their complex forms, it is difficult to apply these constitutive models in the real world. In this paper, a three-element model with simple form is proposed to investigate the thermo-mechanical small strain (within 10%) behavior of polyurethane under uniaxial tension. Two different cases of heated recovery are considered: (1) unconstrained free strain recovery and (2) stress recovery under full constraint at a strain level fixed during low temperature unloading. To validate the model, simulated and predicted results are compared with Tobushi's experimental results and good agreement can be observed.

A Comparison of Curing Process-Induced Residual Stresses and Cure Shrinkage in Micro-Scale Composite Structures with Different Constitutive Laws

NASA Astrophysics Data System (ADS)

Li, Dongna; Li, Xudong; Dai, Jianfeng; Xi, Shangbin

2018-02-01

In this paper, three kinds of constitutive laws, elastic, "cure hardening instantaneously linear elastic (CHILE)" and viscoelastic law, are used to predict curing process-induced residual stress for the thermoset polymer composites. A multi-physics coupling finite element analysis (FEA) model implementing the proposed three approaches is established in COMSOL Multiphysics-Version 4.3b. The evolution of thermo-physical properties with temperature and degree of cure (DOC), which improved the accuracy of numerical simulations, and cure shrinkage are taken into account for the three models. Subsequently, these three proposed constitutive models are implemented respectively in a 3D micro-scale composite laminate structure. Compared the differences between these three numerical results, it indicates that big error in residual stress and cure shrinkage generates by elastic model, but the results calculated by the modified CHILE model are in excellent agreement with those estimated by the viscoelastic model.

An Approximate Dissipation Function for Large Strain Rubber Thermo-Mechanical Analyses

NASA Technical Reports Server (NTRS)

Johnson, Arthur R.; Chen, Tzi-Kang

2003-01-01

Mechanically induced viscoelastic dissipation is difficult to compute. When the constitutive model is defined by history integrals, the formula for dissipation is a double convolution integral. Since double convolution integrals are difficult to approximate, coupled thermo-mechanical analyses of highly viscous rubber-like materials cannot be made with most commercial finite element software. In this study, we present a method to approximate the dissipation for history integral constitutive models that represent Maxwell-like materials without approximating the double convolution integral. The method requires that the total stress can be separated into elastic and viscous components, and that the relaxation form of the constitutive law is defined with a Prony series. Numerical data is provided to demonstrate the limitations of this approximate method for determining dissipation. Rubber cylinders with imbedded steel disks and with an imbedded steel ball are dynamically loaded, and the nonuniform heating within the cylinders is computed.

Dust in Rain During Drought: An Overlooked Pathway for Elemental Flux to Ecosystems

NASA Astrophysics Data System (ADS)

Ponette-González, A.; Collins, J. D., Jr.; Manuel, J. E.; Byers, T. A.; Glass, G. A.; Weathers, K. C.; Gill, T. E.

2017-12-01

Airborne dust has the potential to alter ecosystem productivity and biogeochemical cycles at local to global scales by enhancing atmospheric deposition of critical limiting nutrients and toxic pollutants. Suspended dust particles are delivered to ecosystems directly via dry deposition or in precipitation (wet deposition) by rainout and washout. Compared to dry deposition, dust removal by precipitation (dust-in-rain) is a seldom quantified yet potentially significant flux between the atmosphere and ecosystems. We quantified dust effects on the ionic and elemental composition of precipitation and on wet deposition rates at a National Atmospheric Deposition Program (NADP) monitoring site in west Texas during the extreme 2012 drought. Dust events were identified using meteorological data for stations within a 150-km radius buffer surrounding the NADP site. Data on the dissolved chemistry of weekly wet deposition samples and elemental analysis of the particulate fraction were analyzed. Calcium was the dominant dissolved ion in rainwater, comprising 61% of the total measured solute content during dust-in rain weeks. In the particulate fraction, Fe alone made up 81% of the elemental composition during dust-in-rain weeks. At this site, five dust-in-rain weeks delivered 19% of the annual water input (51 mm water). However, these weeks contributed 46-70% of the annual dissolved Ca2+, Mg2+, K+, Na+, PO43-, and Cl- flux and >55% of the particulate Fe, Ti, V, Ni, Rb, Ga, and Br flux. Sourcing analysis, conducted using an End-Member Mixing Algorithm (EMMA) on the particulate fraction identified Fe, Cu, Rb, and Sr end-members, representing 87% of the total elemental variance. In addition, EMMA showed that dust-in-rain weeks were more well mixed than other rainfall weeks. Preliminary findings for this west Texas site show that infrequent dust-in-rain events constitute an important but overlooked proportion of the elemental flux to ecosystems during severe drought.

Private Higher Education and the Constitutions; Constitutionality of State Aid to Private Higher Education.

ERIC Educational Resources Information Center

Thomas, Ann Van Wynen; Thomas, A. J., Jr.

This report discusses the constitutionality of state aid to church-related institutions of higher education. The introduction deals with the important role that private institutions play in the total system of higher education, the seriousness of their financial plight, and the necessity for increased state aid to these institutions. Sections 2…

Allergic constitution theory of Chinese medicine and its assessment criterion and related studies.

PubMed

Wang, Ji; Wang, Ting; Li, Ying-shuai; Li, Ling-ru; Zheng, Yan-fei; Wang, Qi

2015-09-01

Constitution factor plays an important role in the occurrence, development, and transformation of diseases. The occurrence of allergic diseases is mainly caused by the disorganized physiological function and suitability regulation of patients, except for their exposure to outside allergens. Moreover, it represents susceptibility and hypersensitivity to allergens. The current study expresses the concept of allergic constitution from the perspective of Chinese medicine (CM) and presents the criterion of allergic constitution. In addition, the distribution of allergic constitution in population, its factors, and its relation to health-related quality of life (HRQOL) were investigated. The HRQOL scores of allergic constitution were found to be lower than those of the Pinghe constitution. After making a study on the gene expression profile of allergic constitution, the characteristics of up-regulated or down-regulated genes were found. Finally, CM drug was researched and developed to improve allergic constitution. Based on clinical trials and animal experiments, CM is found to have good regulatory effects on allergic constitution.

Application of the multi-scale finite element method to wave propagation problems in damaged structures

NASA Astrophysics Data System (ADS)

Casadei, F.; Ruzzene, M.

2011-04-01

This work illustrates the possibility to extend the field of application of the Multi-Scale Finite Element Method (MsFEM) to structural mechanics problems that involve localized geometrical discontinuities like cracks or notches. The main idea is to construct finite elements with an arbitrary number of edge nodes that describe the actual geometry of the damage with shape functions that are defined as local solutions of the differential operator of the specific problem according to the MsFEM approach. The small scale information are then brought to the large scale model through the coupling of the global system matrices that are assembled using classical finite element procedures. The efficiency of the method is demonstrated through selected numerical examples that constitute classical problems of great interest to the structural health monitoring community.

Mixed-Mode Decohesion Finite Elements for the Simulation of Delamination in Composite Materials

NASA Technical Reports Server (NTRS)

Camanho, Pedro P.; Davila, Carlos G.

2002-01-01

A new decohesion element with mixed-mode capability is proposed and demonstrated. The element is used at the interface between solid finite elements to model the initiation and non-self-similar growth of delaminations. A single relative displacement-based damage parameter is applied in a softening law to track the damage state of the interface and to prevent the restoration of the cohesive state during unloading. The softening law for mixed-mode delamination propagation can be applied to any mode interaction criterion such as the two-parameter power law or the three-parameter Benzeggagh-Kenane criterion. To demonstrate the accuracy of the predictions and the irreversibility capability of the constitutive law, steady-state delamination growth is simulated for quasistatic loading-unloading cycles of various single mode and mixed-mode delamination test specimens.

The molecular basis of targeting protein kinases in cancer therapeutics.

PubMed

Tsai, Chung-Jung; Nussinov, Ruth

2013-08-01

In this paper, we provide an overview of targeted anticancer therapies with small molecule kinase inhibitors. First, we discuss why a single constitutively active kinase emanating from a variety of aberrant genetic alterations is capable of transforming a normal cell, leading it to acquire the hallmarks of a cancer cell. To draw attention to the fact that kinase inhibition in targeted cancer therapeutics differs from conventional cytotoxic chemotherapy, we exploit a conceptual framework explaining why suppressed kinase activity will selectively kill only the so-called oncogene 'addicted' cancer cell, while sparing the healthy cell. Second, we introduce the protein kinase superfamily in light of its common active conformation with precisely positioned structural elements, and the diversified auto-inhibitory conformations among the kinase families. Understanding the detailed activation mechanism of individual kinases is essential to relate the observed oncogenic alterations to the elevated constitutively active state, to identify the mechanism of consequent drug resistance, and to guide the development of the next-generation inhibitors. To clarify the vital importance of structural guidelines in studies of oncogenesis, we explain how somatic mutations in EGFR result in kinase constitutive activation. Third, in addition to the common theme of secondary (acquired) mutations that prevent drug binding from blocking a signaling pathway which is hijacked by the aberrant activated kinase, we discuss scenarios of drug resistance and relapse by compensating lesions that bypass the inactivated pathway in a vertical or horizontal fashion. Collectively, these suggest that the future challenge of cancer therapy with small molecule kinase inhibitors will rely on the discovery of distinct combinations of optimized drugs to target individual subtypes of different cancers. Copyright © 2013 Elsevier Ltd. All rights reserved.

Micromechanics Analysis Code With Generalized Method of Cells (MAC/GMC): User Guide. Version 3

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Bednarcyk, B. A.; Wilt, T. E.; Trowbridge, D.

1999-01-01

The ability to accurately predict the thermomechanical deformation response of advanced composite materials continues to play an important role in the development of these strategic materials. Analytical models that predict the effective behavior of composites are used not only by engineers performing structural analysis of large-scale composite components but also by material scientists in developing new material systems. For an analytical model to fulfill these two distinct functions it must be based on a micromechanics approach which utilizes physically based deformation and life constitutive models and allows one to generate the average (macro) response of a composite material given the properties of the individual constituents and their geometric arrangement. Here the user guide for the recently developed, computationally efficient and comprehensive micromechanics analysis code, MAC, who's predictive capability rests entirely upon the fully analytical generalized method of cells, GMC, micromechanics model is described. MAC/ GMC is a versatile form of research software that "drives" the double or triply periodic micromechanics constitutive models based upon GMC. MAC/GMC enhances the basic capabilities of GMC by providing a modular framework wherein 1) various thermal, mechanical (stress or strain control) and thermomechanical load histories can be imposed, 2) different integration algorithms may be selected, 3) a variety of material constitutive models (both deformation and life) may be utilized and/or implemented, and 4) a variety of fiber architectures (both unidirectional, laminate and woven) may be easily accessed through their corresponding representative volume elements contained within the supplied library of RVEs or input directly by the user, and 5) graphical post processing of the macro and/or micro field quantities is made available.

A post-publication analysis of the idealized upper reference value of 2.5 mIU/L for TSH: Time to support the thyroid axis with magnesium and iron especially in the setting of reproduction medicine.

PubMed

Moncayo, Roy; Moncayo, Helga

2017-06-01

Laboratory medicine approaches the evaluation of thyroid function mostly through the single determination of the blood level of thyroid stimulating hormone (TSH). Some authors have suggested an upper reference value for TSH of 2.5 mIU/L. This suggestion has not been confirmed by recent clinical studies. These studies have delivered a clinically valid reference range going from 0.3 to 3.5 mIU/L. These values are valid for both for the general population as well as in the setting of fertility and pregnancy. Current biochemical evidence about the elements required to maintain thyroid function shows that these not only include dietary iodine but also magnesium, iron, selenium and coenzyme Q10. Iron is important for the synthesis of thyroid peroxidase; magnesium-ATP contributes to the active process of iodine uptake; iodine has to be sufficiently present in the diet; selenium acts through selenoproteins to protect the thyroid cell during hormone synthesis and in deiodination of thyroxine; coenzyme Q10 influences thyroid vascularity. As a consequence, good clinical practice requires additional biochemical information on the blood levels of magnesium, selenium, coenzyme Q10 as well as iron status. Since these elements are also important for the maintenance of reproductive function, we postulate that they constitute the connecting link between both endocrine systems.

Evolution of Sphingomonad Gene Clusters Related to Pesticide Catabolism Revealed by Genome Sequence and Mobilomics of Sphingobium herbicidovorans MH.

PubMed

Nielsen, Tue Kjærgaard; Rasmussen, Morten; Demanèche, Sandrine; Cecillon, Sébastien; Vogel, Timothy M; Hansen, Lars Hestbjerg

2017-09-01

Bacterial degraders of chlorophenoxy herbicides have been isolated from various ecosystems, including pristine environments. Among these degraders, the sphingomonads constitute a prominent group that displays versatile xenobiotic-degradation capabilities. Four separate sequencing strategies were required to provide the complete sequence of the complex and plastic genome of the canonical chlorophenoxy herbicide-degrading Sphingobium herbicidovorans MH. The genome has an intricate organization of the chlorophenoxy-herbicide catabolic genes sdpA, rdpA, and cadABCD that encode the (R)- and (S)-enantiomer-specific 2,4-dichlorophenoxypropionate dioxygenases and four subunits of a Rieske non-heme iron oxygenase involved in 2-methyl-chlorophenoxyacetic acid degradation, respectively. Several major genomic rearrangements are proposed to help understand the evolution and mobility of these important genes and their genetic context. Single-strain mobilomic sequence analysis uncovered plasmids and insertion sequence-associated circular intermediates in this environmentally important bacterium and enabled the description of evolutionary models for pesticide degradation in strain MH and related organisms. The mobilome presented a complex mosaic of mobile genetic elements including four plasmids and several circular intermediate DNA molecules of insertion-sequence elements and transposons that are central to the evolution of xenobiotics degradation. Furthermore, two individual chromosomally integrated prophages were shown to excise and form free circular DNA molecules. This approach holds great potential for improving the understanding of genome plasticity, evolution, and microbial ecology. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Cultivation of Agaricus bisporus enriched with selenium, zinc and copper.

PubMed

Rzymski, Piotr; Mleczek, Mirosław; Niedzielski, Przemysław; Siwulski, Marek; Gąsecka, Monika

2017-02-01

Agaricus bisporus (white button mushroom) is an important culinary and medicinal species of worldwide importance. The present study investigated for the first time whether it may be grown on substrates supplemented with Se alone or in combination with Cu and/or Zn (0.1-0.8 mmol L -1 ) to produce fruiting bodies of increased nutritional value. As found, substrate supplementation did not affect yielded biomass up to 0.6 mmol L -1 element concentrations regardless of the cultivation model. At 0.8 mmol L -1 Se + Cu and Se + Zn supplementation biomass comparable with controls still developed. The accumulation of trace elements in the fruiting bodies generally increased over the concentration gradient reaching its maximum at 0.6 mmol L -1 (for Se + Zn and Se + Cu + Zn) and 0.8 mmol L -1 (for Se and Se + Cu). The organic Se constituted the greatest share in total Se quota. As calculated, each 10 g of dried fruiting bodies of A. bisporus obtained from 0.6 or 0.8 mmol L -1 supplementation would represent 342-469% of the Recommended Daily Allowance (RDA) for Se, 43.4-48.5% for Cu and 5.2-5.8% for Zn. Considering inexpensive methods of A. bisporus cultivation, global popularity and use of this mushroom, its biofortification with Se, Cu and Zn could have a practical application in deficiency prevention and assisted treatment. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Flow Behavior and Constitutive Equation of Ti-6.5Al-2Sn-4Zr-4Mo-1W-0.2Si Titanium Alloy

NASA Astrophysics Data System (ADS)

Yang, Xuemei; Guo, Hongzhen; Liang, Houquan; Yao, Zekun; Yuan, Shichong

2016-04-01

In order to get a reliable constitutive equation for the finite element simulation, flow behavior of Ti-6.5Al-2Sn-4Zr-4Mo-1W-0.2Si alloy under high temperature was investigated by carrying a series of isothermal compression tests at temperatures of 1153-1293 K and strain rates of 0.01-10.0 s-1 on the Gleeble-1500 simulator. Results showed that the true stress-strain curves exhibited peaks at small strains, after which the flow stress decreased monotonically. Ultimately, the flow curves reached steady state at the strain of 0.6, showing a dynamic flow softening phenomenon. The effects of strain rate, temperature, and strain on the flow behavior were researched by establishing a constitutive equation. The relations among stress exponent, deformation activation energy, and strain were preliminarily discussed by using strain rate sensitivity exponent and dynamic recrystallization kinetics curve. Stress values predicted by the modified constitutive equation showed a good agreement with the experimental ones. The correlation coefficient ( R) and average absolute relative error (AARE) were 98.2% and 4.88%, respectively, which confirmed that the modified constitutive equation could give an accurate estimation of the flow stress for BT25y titanium alloy.

Constitutive properties of hypertrophied myocardium: cellular contribution to changes in myocardial stiffness

NASA Technical Reports Server (NTRS)

Harris, Todd S.; Baicu, Catalin F.; Conrad, Chester H.; Koide, Masaaki; Buckley, J. Michael; Barnes, Mary; Cooper, George 4th; Zile, Michael R.

2002-01-01

Recent studies have suggested that pressure overload hypertrophy (POH) alters the viscoelastic properties of individual cardiocytes when studied in isolation. However, whether these changes in cardiocyte properties contribute causally to changes in the material properties of the cardiac muscle as a whole is unknown. Accordingly, a selective, isolated, acute change in cardiocyte constitutive properties was imposed in an in vitro system capable of measuring the resultant effect on the material properties of the composite cardiac muscle. POH caused an increase in both myocardial elastic stiffness, from 20.5 +/- 1.3 to 28.4 +/- 1.8, and viscous damping, from 15.2 +/- 1.1 to 19.8 +/- 1.5 s (normal vs. POH, P < 0.05), respectively. Recent studies have shown that cardiocyte constitutive properties could be acutely altered by depolymerizing the microtubules with colchicine. Colchicine caused a significant decrease in the viscous damping in POH muscles (19.8 +/- 1.5 s at baseline vs. 14.7 +/- 1.3 s after colchicine, P < 0.05). Therefore, myocardial material properties can be altered by selectively changing the constitutive properties of one element within this muscle tissue, the cardiocyte. Changes in the constitutive properties of the cardiocytes themselves contribute to the abnormalities in myocardial stiffness and viscosity that develop during POH.

Constitutional aneuploidy and cancer predisposition†

PubMed Central

Ganmore, Ithamar; Smooha, Gil; Izraeli, Shai

2009-01-01

Constitutional aneuploidies are rare syndromes associated with multiple developmental abnormalities and the alterations in the risk for specific cancers. Acquired somatic chromosomal aneuploidies are the most common genetic aberrations in sporadic cancers. Thus studies of these rare constitutional aneuploidy syndromes are important not only for patient counseling and clinical management, but also for deciphering the mechanisms by which chromosomal aneuploidy affect cancer initiation and progression. Here we review the major constitutional aneuploidy syndromes and suggest some general mechanisms for the associated cancer predisposition. PMID:19297405

Constitutional aneuploidy and cancer predisposition.

PubMed

Ganmore, Ithamar; Smooha, Gil; Izraeli, Shai

2009-04-15

Constitutional aneuploidies are rare syndromes associated with multiple developmental abnormalities and the alterations in the risk for specific cancers. Acquired somatic chromosomal aneuploidies are the most common genetic aberrations in sporadic cancers. Thus studies of these rare constitutional aneuploidy syndromes are important not only for patient counseling and clinical management, but also for deciphering the mechanisms by which chromosomal aneuploidy affect cancer initiation and progression. Here we review the major constitutional aneuploidy syndromes and suggest some general mechanisms for the associated cancer predisposition.

The genesis solar-wind sample return mission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiens, Roger C

2009-01-01

The compositions of the Earth's crust and mantle, and those of the Moon and Mars, are relatively well known both isotopically and elementally. The same is true of our knowledge of the asteroid belt composition, based on meteorite analyses. Remote measurements of Venus, the Jovian atmosphere, and the outer planet moons, have provided some estimates of their compositions. The Sun constitutes a large majority, > 99%, of all the matter in the solar system. The elemental composition of the photosphere, the visible 'surface' of the Sun, is constrained by absorption lines produced by particles above the surface. Abundances for manymore » elements are reported to the {+-}10 or 20% accuracy level. However, the abundances of other important elements, such as neon, cannot be determined in this way due to a relative lack of atomic states at low excitation energies. Additionally and most importantly, the isotopic composition of the Sun cannot be determined astronomically except for a few species which form molecules above sunspots, and estimates derived from these sources lack the accuracy desired for comparison with meteoritic and planetary surface samples measured on the Earth. The solar wind spreads a sample of solar particles throughout the heliosphere, though the sample is very rarified: collecting a nanogram of oxygen, the third most abundant element, in a square centimeter cross section at the Earth's distance from the Sun takes five years. Nevertheless, foil collectors exposed to the solar wind for periods of hours on the surface of the Moon during the Apollo missions were used to determine the helium and neon solar-wind compositions sufficiently to show that the Earth's atmospheric neon was significantly evolved relative to the Sun. Spacecraft instruments developed subsequently have provided many insights into the composition of the solar wind, mostly in terms of elemental composition. These instruments have the advantage of observing a number of parameters simultaneously, including charge state distributions, velocities, and densities, all of which have been instrumental in characterizing the nature of the solar wind. However, these instruments have lacked the ability to make large dynamic range measurements of adjacent isotopes (i.e., {sup 17}O/{sup 16}O {approx} 2500) or provide the permil (tenths of percent) accuracy desirable for comparison with geochemical isotopic measurements. An accurate knowledge of the solar and solar-wind compositions helps to answer important questions across a number of disciplines. It aids in understanding the acceleration mechanisms of the solar wind, gives an improved picture of the charged particle environment near the photosphere, it constrains processes within the Sun over its history, and it provides a database by which to compare differences among planetary systems with the solar system's starting composition, providing key information on planetary evolution. For example, precise knowledge of solar isotopic and elemental compositions of volatile species in the Sun provides a baseline for models of atmospheric evolution over time for Earth, Venus, and Mars. Additionally, volatile and chemically active elements such as C, H, O, N, and S can tell us about processes active during the evolution of the solar nebula. A classic example of this is the oxygen isotope system. In the 1970s it was determined that the oxygen isotopic ratio in refractory inclusions in primitive meteorites was enriched {approx}4% in {sup 16}O relative to the average terrestrial, lunar, and thermally processed meteorite materials. In addition, all processed solar-system materials appeared to each have a unique oxygen isotopic composition (except the Moon and Earth, which are thought to be formed from the same materials), though differences are in the fraction of a percent range, much smaller than the refractory material {sup 16}O enrichment. Several theories were developed over the years to account for the oxygen isotope heterogeneity, each theory predicting a different solar isotopic composition and each invoking a different early solar-system process to produce the heterogeneity. Other volatiles such as C, N, and H may also have experienced similar effects, but with only two isotopes it is often impossible to distinguish with these elements between mass-dependent fractionation and other effects such as mixing or mass-independent fractionation. Table 1 provides a summary of the major measurement objectives of the Genesis mission. Determining the solar oxygen isotopic composition is at the top of the list. Volatile element and isotope ratios constitute six of the top seven priorities. A number of disciplines stand to gain from information from the Genesis mission, as will be discussed later. Based on the Apollo solar-wind foil experiment, the Genesis mission was designed to capture solar wind over orders of magnitude longer duration and in a potentially much cleaner environment than the lunar surface.« less

Pathways Involved in Sasang Constitution from Genome-Wide Analysis in a Korean Population

PubMed Central

Yu, Sung-Gon; Kim, Jong-Yeol; Song, Kwang Hoon

2012-01-01

Abstract Objective Sasang constitution (SC) medicine, a branch of Korean traditional medicine, classifies the individual into one of four constitutional types (Taeum, TE; Soeum, SE; Soyang, SY; and Taeyang, TY) based on physiologic characteristics. The authors of the current article recently reported individual genetic elements associated with SC types via genome-wide association (GWA) analysis. However, to understand the biologic mechanisms underlying constitution, a comprehensive approach that combines individual genetic effects was applied. Design Genotypes of 1222 subjects of defined constitution types were measured for 341,998 genetic loci across the entire genome. The biologic pathways associated with SC types were identified via GWA analysis using three different algorithms—namely, the Z-static method, a restandardized gene set assay, and a gene set enrichment assay. Results Distinct pathways were associated (p<0.05) with each constitution type. The TE type was significantly associated with cytoskeleton-related pathways. The SE type was significantly associated with cardio- and amino-acid metabolism–related pathways. The SY type was associated with enriched melanoma-related pathways. TY subjects were excluded because of the small size of that sample. Among these functionally related pathways, core-node genes regulating multiple pathways were identified. TJP1, PTK2, and SRC were selected as core-nodes for TE; RHOA, and MAOA/MAOB for SE; and GNAO1 for SY (p<0.05), respectively. Conclusions The current authors systematically identified the biologic pathways and core-node genes associated with SC types from the GWA study; this information should provide insights regarding the molecular mechanisms inherent in constitutional pathophysiology. PMID:22889377

A New Method for Estimation of Emissions and Sources of Measurements Error in the Silicon Refining Process

NASA Astrophysics Data System (ADS)

Næss, Mari k.; Kero, Ida; Tranell, Gabriella

2013-08-01

In the production of metallurgical grade silicon (MG-Si), fugitive emissions are a serious concern due to the health risks associated with the fumes formed in different parts of the production. The fumes are also a potential environmental hazard. Yet, the chemical composition of the fumes from most process steps in the silicon plant, such as oxidative refining ladle, remains unknown. This in turn constitutes a problem with respect to the correct assessment of the environmental impact and working conditions. A comprehensive industrial measurement campaign was performed at the Elkem Salten MG-Si production plant in Norway. Samples of the ingoing and outgoing mass flows were analyzed by high-resolution inductively coupled plasma mass spectrometry, with respect to 62 elements. In every step of the sampling and sample treatment processes, possible sources of error have been identified and quantified, including process variation, mass measurement accuracy, and contamination risk. Total measurement errors for all elements in all phases are established. The method is applied to estimate the order of magnitude of the elemental emissions via the fumes from the tapping and refining processes, with respect to production mass and year. The elements with higher concentrations in the fume than slag and refined silicon include Ag, Bi, Cd, Cu, In, K, Mg, Na, Pb, Rb, Se, Sn, Tl, and Zn: all being present in the ppm range. This work constitutes new and vital information to enable the correct assessment of the environmental impact and working conditions at an MG-Si plant.

Lessons on RNA Silencing Mechanisms in Plants from Eukaryotic Argonaute Structures[W

PubMed Central

Poulsen, Christian; Vaucheret, Hervé; Brodersen, Peter

2013-01-01

RNA silencing refers to a collection of gene regulatory mechanisms that use small RNAs for sequence specific repression. These mechanisms rely on ARGONAUTE (AGO) proteins that directly bind small RNAs and thereby constitute the central component of the RNA-induced silencing complex (RISC). AGO protein function has been probed extensively by mutational analyses, particularly in plants where large allelic series of several AGO proteins have been isolated. Structures of entire human and yeast AGO proteins have only very recently been obtained, and they allow more precise analyses of functional consequences of mutations obtained by forward genetics. To a large extent, these analyses support current models of regions of particular functional importance of AGO proteins. Interestingly, they also identify previously unrecognized parts of AGO proteins with profound structural and functional importance and provide the first hints at structural elements that have important functions specific to individual AGO family members. A particularly important outcome of the analysis concerns the evidence for existence of Gly-Trp (GW) repeat interactors of AGO proteins acting in the plant microRNA pathway. The parallel analysis of AGO structures and plant AGO mutations also suggests that such interactions with GW proteins may be a determinant of whether an endonucleolytically competent RISC is formed. PMID:23303917

Lessons on RNA silencing mechanisms in plants from eukaryotic argonaute structures.

PubMed

Poulsen, Christian; Vaucheret, Hervé; Brodersen, Peter

2013-01-01

RNA silencing refers to a collection of gene regulatory mechanisms that use small RNAs for sequence specific repression. These mechanisms rely on ARGONAUTE (AGO) proteins that directly bind small RNAs and thereby constitute the central component of the RNA-induced silencing complex (RISC). AGO protein function has been probed extensively by mutational analyses, particularly in plants where large allelic series of several AGO proteins have been isolated. Structures of entire human and yeast AGO proteins have only very recently been obtained, and they allow more precise analyses of functional consequences of mutations obtained by forward genetics. To a large extent, these analyses support current models of regions of particular functional importance of AGO proteins. Interestingly, they also identify previously unrecognized parts of AGO proteins with profound structural and functional importance and provide the first hints at structural elements that have important functions specific to individual AGO family members. A particularly important outcome of the analysis concerns the evidence for existence of Gly-Trp (GW) repeat interactors of AGO proteins acting in the plant microRNA pathway. The parallel analysis of AGO structures and plant AGO mutations also suggests that such interactions with GW proteins may be a determinant of whether an endonucleolytically competent RISC is formed.

The Citizen's Effect: 25 Features about the Europe for Citizens Programme

ERIC Educational Resources Information Center

Reding, Viviane

2012-01-01

Public forums and shared spaces in which citizens can debate and deliberate have always constituted essential elements of a democratic society. Today, the Europe for Citizens Programme serves to create a modern European agora. Launched in 2007, the programme supports initiatives that bring people together in international and intercultural…

Reducing Class Size in New York City: Promise vs. Practice

ERIC Educational Resources Information Center

Farrie, Danielle; Johnson, Monete; Lecker, Wendy; Luhm, Theresa

2016-01-01

In the landmark school funding litigation, "Campaign for Fiscal Equity v. State" ("CFE"), the highest Court in New York recognized that reasonable class sizes are an essential element of a constitutional "sound basic education." In response to the rulings in the case, in 2007, the Legislature adopted a law mandating…

Onboard Experiment Data Support Facility

NASA Technical Reports Server (NTRS)

1976-01-01

An onboard array structure has been devised for end to end processing of data from multiple spaceborne sensors. The array constitutes sets of programmable pipeline processors whose elements perform each assigned function in 0.25 microseconds. This space shuttle computer system can handle data rates from a few bits to over 100 megabits per second.

A Virtual Social Learner Community--Constitutive Element of MOOCs

ERIC Educational Resources Information Center

Meinel, Christoph; Schweiger, Stefanie

2016-01-01

Massive Open Online Courses (MOOCs) have seen enormous growth throughout the last four years. This format has fundamentally enriched the traditional method of web-based teaching and e-learning. Nevertheless, there have always been skeptical voices who announce the "death of MOOCs". We do not believe in this pessimistic scenario and in…

2 CFR 2424.1110 - When may a HUD official issue a limited denial of participation?

Code of Federal Regulations, 2011 CFR

2011-01-01

... would constitute an unsatisfactory risk; (2) There are irregularities in a person's past performance in... the performance of obligations incurred pursuant to a grant of financial assistance or pursuant to a... or further hearing. (d) An affiliate or organizational element may be included in a limited denial of...

2 CFR 2424.1110 - When may a HUD official issue a limited denial of participation?

Code of Federal Regulations, 2010 CFR

2010-01-01

... would constitute an unsatisfactory risk; (2) There are irregularities in a person's past performance in... the performance of obligations incurred pursuant to a grant of financial assistance or pursuant to a... or further hearing. (d) An affiliate or organizational element may be included in a limited denial of...

Functional characterization of transcriptional regulatory elements of three highly expressed constitutive genes in the jewel wasp, Nasonia vitripennis

USDA-ARS?s Scientific Manuscript database

The jewel wasp, Nasonia vitripennis Ashmead (Hymenoptera: Pteromalidae) serves as an easily reared parasitoid that is providing an ever increasing malleable model for examining the biology and genetics of Hymenoptera. In order to conduct genetic transformations, it is preferable to have native highl...

Designing Peace and Conflict Exercises: Level of Analysis, Scenario, and Role Specification

ERIC Educational Resources Information Center

Bartels, Elizabeth; McCown, Margaret; Wilkie, Timothy

2013-01-01

Attentiveness to and transparency about the methodological implications of the level of analysis selected for peace and conflict exercises constitute essential elements of good game design. The article explores the impact of level of analysis choices in the context of two key portions of exercises, scenario construction and role specification. It…

Adapting Scale for Children: A Practical Model for Researchers

ERIC Educational Resources Information Center

Aydin, Selami; Harputlu, Leyla; Çelik, Seyda Savran; Ustuk, Özgehan; Güzel, Serhat; Genç, Deniz

2016-01-01

Measurement of children's behaviors in an educational and research context is a problematic and complex area. It is also evident that adapting scales to measure children's behaviors in an educational and research context is a complex process due to several reasons. First, cultural elements constitute a considerable problem. Second, it is difficult…

A Critical Theory of Adult and Community Education

ERIC Educational Resources Information Center

Brookfield, Stephen

2012-01-01

Critical theory is one of the most influential theoretical frameworks influencing scholarship within the field of adult and community education. This chapter outlines what constitute the chief elements of critical theory using Horkheimer's (1937/1995) classic essay as a touchstone for this analysis. It argues for a set of adult learning tasks that…

Prospective and In-Service Teachers' Perspectives about Launching a Problem

ERIC Educational Resources Information Center

González, Gloriana; Eli, Jennifer A.

2017-01-01

Launching a problem is critical in a problem-based lesson. We investigated teachers' perspectives on the use of a problem that was analogous to the one provided during a launch. Our goal was to identify teachers' underlying assumptions regarding what should constitute a launch as elements of the "practical rationality of mathematics…

Catalogues of planetary nebulae.

NASA Astrophysics Data System (ADS)

Acker, A.

Firstly, the general requirements concerning catalogues are studied for planetary nebulae, in particular concerning the objects to be included in a catalogue of PN, their denominations, followed by reflexions about the afterlife and comuterized versions of a catalogue. Then, the basic elements constituting a catalogue of PN are analyzed, and the available data are looked at each time.

75 FR 65654 - In the Matter of: Certain Mobile Telephones and Wireless Communication Devices Featuring Digital...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-26

... on claim construction (``ID'') issued by the presiding administrative law judge (``ALJ'') in the... anticipation or obviousness), unenforceability. Claim construction may be a necessary underpinning to the... or element. On its own, however, claim construction might not be viewed as constituting such an issue...

Systems for Instructional Improvement: Creating Coherence from the Classroom to the District Office

ERIC Educational Resources Information Center

Cobb, Paul; Jackson, Kara; Henrick, Erin; Smith, Thomas M.

2018-01-01

In "Systems for Instructional Improvement," Paul Cobb and his colleagues draw on their extensive research to propose a series of specific, empirically grounded recommendations that together constitute a theory of action for advancing instruction at scale. The authors outline the elements of a coherent instructional system; describe…

Well-Doing: Personal Projects and the Quality of Lives

ERIC Educational Resources Information Center

Little, Brian R.

2014-01-01

"What are you doing?" and "How is it going?" are foundational questions we can ask of agents. They elicit answers that illuminate aspects of well-doing, or felicitous action, by directing attention to an agent's personal projects. Personal projects are constitutive elements of daily existence and are consequential for a…

A Profile of Effective Leadership in Some South African High-Poverty Schools

ERIC Educational Resources Information Center

Kamper, Gerrit

2008-01-01

The struggle of high-poverty schools for survival is well documented. Some have overcome poverty-related odds and performed exceptionally well, prompting the following research question: What elements constitute a profile of effective leadership in high-poverty schools? Investigations conducted at six successful high-poverty schools revealed the…

FABP4-Cre mediated expression of constitutively active ChREBP protects against obesity

USDA-ARS?s Scientific Manuscript database

Carbohydrate response element binding protein (ChREBP) regulates cellular glucose and lipid homeostasis. Although ChREBP is highly expressed in many key metabolic tissues, the role of ChREBP in most of those tissues and consequent effects on whole-body glucose and lipid metabolism are not well under...

Multi-Scale Computational Modeling of Two-Phased Metal Using GMC Method

NASA Technical Reports Server (NTRS)

Moghaddam, Masoud Ghorbani; Achuthan, A.; Bednacyk, B. A.; Arnold, S. M.; Pineda, E. J.

2014-01-01

A multi-scale computational model for determining plastic behavior in two-phased CMSX-4 Ni-based superalloys is developed on a finite element analysis (FEA) framework employing crystal plasticity constitutive model that can capture the microstructural scale stress field. The generalized method of cells (GMC) micromechanics model is used for homogenizing the local field quantities. At first, GMC as stand-alone is validated by analyzing a repeating unit cell (RUC) as a two-phased sample with 72.9% volume fraction of gamma'-precipitate in the gamma-matrix phase and comparing the results with those predicted by finite element analysis (FEA) models incorporating the same crystal plasticity constitutive model. The global stress-strain behavior and the local field quantity distributions predicted by GMC demonstrated good agreement with FEA. High computational saving, at the expense of some accuracy in the components of local tensor field quantities, was obtained with GMC. Finally, the capability of the developed multi-scale model linking FEA and GMC to solve real life sized structures is demonstrated by analyzing an engine disc component and determining the microstructural scale details of the field quantities.

Nonlinear finite-element analysis of nanoindentation of viral capsids

NASA Astrophysics Data System (ADS)

Gibbons, Melissa M.; Klug, William S.

2007-03-01

Recent atomic force microscope (AFM) nanoindentation experiments measuring mechanical response of the protein shells of viruses have provided a quantitative description of their strength and elasticity. To better understand and interpret these measurements, and to elucidate the underlying mechanisms, this paper adopts a course-grained modeling approach within the framework of three-dimensional nonlinear continuum elasticity. Homogeneous, isotropic, elastic, thick-shell models are proposed for two capsids: the spherical cowpea chlorotic mottle virus (CCMV), and the ellipsocylindrical bacteriophage ϕ29 . As analyzed by the finite-element method, these models enable parametric characterization of the effects of AFM tip geometry, capsid dimensions, and capsid constitutive descriptions. The generally nonlinear force response of capsids to indentation is shown to be insensitive to constitutive particulars, and greatly influenced by geometric and kinematic details. Nonlinear stiffening and softening of the force response is dependent on the AFM tip dimensions and shell thickness. Fits of the models capture the roughly linear behavior observed in experimental measurements and result in estimates of Young’s moduli of ≈280-360MPa for CCMV and ≈4.5GPa for ϕ29 .

From biodiversity to catalytic diversity: how to control the reaction mechanism by the nature of metallophytes.

PubMed

Escande, Vincent; Olszewski, Tomasz K; Grison, Claude

2015-04-01

Phytoextraction is widely used for the reclamation of degraded sites, particularly to remove trace metals from contaminated soils. Whereas this technique demonstrates several advantages, the biomass resulting from phytoextraction processes is highly enriched in metallic elements and constitutes therefore a problematic waste. We show here that this biomass can be used for the preparation of novel polymetallic extracts, with high potential as catalysts or reagents in organic synthesis. This new concept of ecocatalysis constitutes an innovative recycling of metallic elements whose current known reserves could be exhausted in the coming decades. The ecocatalysts Eco-Zn and Eco-Ni prepared respectively from Zn and Ni hyperaccumulating plants display two distinct chemical reactivities, starting from the same substrates. Eco-Zn led to the formation of esters of commercial interest for the fragrance industry, following a hydro-acyloxy-addition reaction pathway. In contrast, Eco-Ni afforded chlorinated products thank to the hydrochlorination of alkenes. Both ecocatalysts allowed the synthesis of valuable products in high yields through methodologies in line with the spirit of sustainable chemistry.

The Effect of Temperature Dependent Material Nonlinearities on the Response of Piezoelectric Composite Plates

NASA Technical Reports Server (NTRS)

Lee, Ho-Jun; Saravanos, Dimitris A.

1997-01-01

Previously developed analytical formulations for piezoelectric composite plates are extended to account for the nonlinear effects of temperature on material properties. The temperature dependence of the composite and piezoelectric properties are represented at the material level through the thermopiezoelectric constitutive equations. In addition to capturing thermal effects from temperature dependent material properties, this formulation also accounts for thermal effects arising from: (1) coefficient of thermal expansion mismatch between the various composite and piezoelectric plies and (2) pyroelectric effects on the piezoelectric material. The constitutive equations are incorporated into a layerwise laminate theory to provide a unified representation of the coupled mechanical, electrical, and thermal behavior of smart structures. Corresponding finite element equations are derived and implemented for a bilinear plate element with the inherent capability to model both the active and sensory response of piezoelectric composite laminates. Numerical studies are conducted on a simply supported composite plate with attached piezoceramic patches under thermal gradients to investigate the nonlinear effects of material property temperature dependence on the displacements, sensory voltages, active voltages required to minimize thermal deflections, and the resultant stress states.

Mathematical, Constitutive and Numerical Modelling of Catastrophic Landslides and Related Phenomena

NASA Astrophysics Data System (ADS)

Pastor, M.; Fernández Merodo, J. A.; Herreros, M. I.; Mira, P.; González, E.; Haddad, B.; Quecedo, M.; Tonni, L.; Drempetic, V.

2008-02-01

Mathematical and numerical models are a fundamental tool for predicting the behaviour of geostructures and their interaction with the environment. The term “mathematical model” refers to a mathematical description of the more relevant physical phenomena which take place in the problem being analyzed. It is indeed a wide area including models ranging from the very simple ones for which analytical solutions can be obtained to those more complicated requiring the use of numerical approximations such as the finite element method. During the last decades, mathematical, constitutive and numerical models have been very much improved and today their use is widespread both in industry and in research. One special case is that of fast catastrophic landslides, for which simplified methods are not able to provide accurate solutions in many occasions. Moreover, many finite element codes cannot be applied for propagation of the mobilized mass. The purpose of this work is to present an overview of the different alternative mathematical and numerical models which can be applied to both the initiation and propagation mechanisms of fast catastrophic landslides and other related problems such as waves caused by landslides.

The importance of dreams and action in the adolescent process.

PubMed

Ladame, F

1995-12-01

The author argues that after puberty dreams and action are indicators of the capacity of the psychic apparatus to perform the work of binding drive energy. He notes that the development of adult sexuality always involves risk and that effective dream activity affords a definitive solution to the problem of incestuous and parricidal temptations, which attain an unprecedented pitch of intensity with the onset of sexual and procreative potency in adolescence. The author illustrates his thesis by the case of an adolescent patient with particular sexual pathology who broke down at the age of 17 and who, once he became able to dream in the course of analysis, had less need to act out. A 'work of the negative' is presented as a paradoxical but important element in psychic development. Dreaming and action are stated to be inseparable and to constitute an essential safety valve that facilitates the developmental process. A discussion of the connections between dreams and initiation leads to some ethnological considerations on sexuality and society, and the paper ends with a plea not to overlook the death drive.

Exploring children's seasonal play to promote active lifestyles in Auckland, New Zealand.

PubMed

Ergler, Christina R; Kearns, Robin; Witten, Karen

2016-09-01

Studies of seasonal barriers for outdoor activities seldom view families' play practices as grounded in the everyday experience of the natural elements. This paper brings 20 families' mundane outdoor play experiences in Auckland's temperate climate to the fore. Through drawings and interviews, families residing in both suburban detached houses and central city apartments revealed locally constituted beliefs about appropriate play spaces (e.g. garden, park). While the majority of participants retreated to indoor activities during winter, some children and their parents viewed the outdoors as the only opportunity for 'real fun'. We advocate the importance of a better understanding of children's seasonal outdoor play. In particular, we argue that in order to promote year-round healthy levels of outdoor activities it is necessary to understand variations in societal, neighbourhood and family values attributed to outdoor activities. Further, to develop a more nuanced understanding of the locational complexities of outdoor play it is important to understand the meanings of, and practices associated with, seasonal and weather conditions in different international locations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Beyond the principle of plentitude: a review of terrestrial planet habitability.

PubMed

Gaidos, E; Deschenes, B; Dundon, L; Fagan, K; Menviel-Hessler, L; Moskovitz, N; Workman, M

2005-04-01

We review recent work that directly or indirectly addresses the habitability of terrestrial (rocky) planets like the Earth. Habitability has been traditionally defined in terms of an orbital semimajor axis within a range known as the habitable zone, but it is also well known that the habitability of Earth is due to many other astrophysical, geological, and geochemical factors. We focus this review on (1) recent refinements to habitable zone calculations; (2) the formation and orbital stability of terrestrial planets; (3) the tempo and mode of geologic activity (e.g., plate tectonics) on terrestrial planets; (4) the delivery of water to terrestrial planets in the habitable zone; and (5) the acquisition and loss of terrestrial planet carbon and nitrogen, elements that constitute important atmospheric gases responsible for habitable conditions on Earth's surface as well as being the building blocks of the biosphere itself. Finally, we consider recent work on evidence for the earliest habitable environments and the appearance of life itself on our planet. Such evidence provides us with an important, if nominal, calibration point for our search for other habitable worlds.

Factors affecting the implementation of green specifications in construction.

PubMed

Lam, Patrick T I; Chan, Edwin H W; Poon, C S; Chau, C K; Chun, K P

2010-01-01

Green specifications constitute one of the important elements in green construction. New sustainability requirements and changing priorities in construction management have spurred the emerging green specifications to a faster pace of development. A cross-sectional survey has been conducted in Hong Kong in 2007 to identify principal factors leading to the success of preparing green specifications. Based on extensive construction management literature, 20 variables concerning sustainable construction were summarized. Using the Mann-Whitney U-test, the subtle differences between stakeholders in specifying construction work have been detected even with the high consistency of the responses among the groups. Moreover, five independent factors for successful specification of green construction have been categorized by factor analysis. They are related to (1) green technology and techniques, (2) reliability and quality of specification, (3) leadership and responsibility, (4) stakeholder involvement, and (5) guide and benchmarking systems. Whilst the first and fourth factors are generally more important, different stakeholder groups have different emphases. The results of the survey have been validated against established principles. 2009 Elsevier Ltd. All rights reserved.

Heliostat cost reduction study.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Scott A.; Lumia, Ronald.; Davenport, Roger

2007-06-01

Power towers are capable of producing solar-generated electricity and hydrogen on a large scale. Heliostats are the most important cost element of a solar power tower plant. Since they constitute {approx} 50% of the capital cost of the plant it is important to reduce heliostat cost as much as possible to improve the economic performance of power towers. In this study we evaluate current heliostat technology and estimate a price ofmore » $$126/m{sup 2} given year-2006 materials and labor costs for a deployment of {approx}600 MW of power towers per year. This 2006 price yields electricity at $$0.067/kWh and hydrogen at $3.20/kg. We propose research and development that should ultimately lead to a price as low as $$90/m{sup 2}, which equates to $$0.056/kWh and $2.75/kg H{sup 2}. Approximately 30 heliostat and manufacturing experts from the United States, Europe, and Australia contributed to the content of this report during two separate workshops conducted at the National Solar Thermal Test Facility.« less

The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part II: Numerical implementation and post-bifurcation analysis

NASA Astrophysics Data System (ADS)

Rattez, Hadrien; Stefanou, Ioannis; Sulem, Jean; Veveakis, Manolis; Poulet, Thomas

2018-06-01

In this paper we study the phenomenon of localization of deformation in fault gouges during seismic slip. This process is of key importance to understand frictional heating and energy budget during an earthquake. A infinite layer of fault gouge is modeled as a Cosserat continuum taking into account Thermo-Hydro-Mechanical (THM) couplings. The theoretical aspects of the problem are presented in the companion paper (Rattez et al., 2017a), together with a linear stability analysis to determine the conditions of localization and estimate the shear band thickness. In this Part II of the study, we investigate the post-bifurcation evolution of the system by integrating numerically the full system of non-linear equations using the method of Finite Elements. The problem is formulated in the framework of Cosserat theory. It enables to introduce information about the microstructure of the material in the constitutive equations and to regularize the mathematical problem in the post-localization regime. We emphasize the influence of the size of the microstructure and of the softening law on the material response and the strain localization process. The weakening effect of pore fluid thermal pressurization induced by shear heating is examined and quantified. It enhances the weakening process and contributes to the narrowing of shear band thickness. Moreover, due to THM couplings an apparent rate-dependency is observed, even for rate-independent material behavior. Finally, comparisons show that when the perturbed field of shear deformation dominates, the estimation of the shear band thickness obtained from linear stability analysis differs from the one obtained from the finite element computations, demonstrating the importance of post-localization numerical simulations.

Model for texture evolution in cold rolling of 2.4 wt.-% Si non-oriented electrical steel

NASA Astrophysics Data System (ADS)

Wei, X.; Hojda, S.; Dierdorf, J.; Lohmar, J.; Hirt, G.

2017-10-01

Iron loss and limited magnetic flux density are constraints for NGO electrical steel used in highly efficient electrical machinery cores. The most important factors that affect these properties are the final microstructure and the texture of the NGO steel. Reviewing the whole process chain, cold rolling plays an important role because the recrystallization and grain growth during the final heat treatment can be strongly affected by the stored energy and microstructure of cold rolling, and some texture characteristics can be inherited as well. Therefore, texture evolution during cold rolling of NGO steel is worth a detailed investigation. In this paper, texture evolution in cold rolling of non-oriented (NGO) electrical steel is simulated with a crystal plasticity finite element method (CPFEM) model. In previous work, a CPFEM model has been implemented for simulating the texture evolution with periodic boundary conditions and a phenomenological constitutive law. In a first step the microstructure in the core of the workpiece was investigated and mapped to a representative volume element to predict the texture evolution. In this work an improved version of the CPFEM model is described that better reflects the texture evolution in cold rolling of NGO electrical steel containing 2.4 wt.-% Si. This is achieved by applying the deformation gradient and calibrating the flow curve within the CPFEM model. Moreover, the evolution of dislocation density is calculated and visualized in this model. An in depth comparison of the numerical and experimental results reveals, that the improved CPFEM model is able to represent the important characteristics of texture evolution in the core of the workpiece during cold rolling with high precision.

CTR1 phosphorylates the central regulator EIN2 to control ethylene hormone signaling from the ER membrane to the nucleus in Arabidopsis

PubMed Central

Ju, Chuanli; Yoon, Gyeong Mee; Shemansky, Jennifer Marie; Lin, David Y.; Ying, Z. Irene; Chang, Jianhong; Garrett, Wesley M.; Kessenbrock, Mareike; Groth, Georg; Tucker, Mark L.; Cooper, Bret; Kieber, Joseph J.; Chang, Caren

2012-01-01

The gaseous phytohormone ethylene C2H4 mediates numerous aspects of growth and development. Genetic analysis has identified a number of critical elements in ethylene signaling, but how these elements interact biochemically to transduce the signal from the ethylene receptor complex at the endoplasmic reticulum (ER) membrane to transcription factors in the nucleus is unknown. To close this gap in our understanding of the ethylene signaling pathway, the challenge has been to identify the target of the CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) Raf-like protein kinase, as well as the molecular events surrounding ETHYLENE-INSENSITIVE2 (EIN2), an ER membrane-localized Nramp homolog that positively regulates ethylene responses. Here we demonstrate that CTR1 interacts with and directly phosphorylates the cytosolic C-terminal domain of EIN2. Mutations that block the EIN2 phosphorylation sites result in constitutive nuclear localization of the EIN2 C terminus, concomitant with constitutive activation of ethylene responses in Arabidopsis. Our results suggest that phosphorylation of EIN2 by CTR1 prevents EIN2 from signaling in the absence of ethylene, whereas inhibition of CTR1 upon ethylene perception is a signal for cleavage and nuclear localization of the EIN2 C terminus, allowing the ethylene signal to reach the downstream transcription factors. These findings significantly advance our understanding of the mechanisms underlying ethylene signal transduction. PMID:23132950

Determination of Anand parameters for SnAgCuCe solder

NASA Astrophysics Data System (ADS)

Zhang, Liang; Xue, Songbai; Gao, Lili; Zeng, Guang; Sheng, Zhong; Chen, Yan; Yu, Shenglin

2009-10-01

A unified viscoplastic constitutive model, Anand equations, was used to represent the inelastic deformation behavior for Sn3.8Ag0.7Cu/Sn3.8Ag0.7 Cu0.03Ce solders in surface mount technology. The Anand parameters of the constitutive equations for the SnAgCu and SnAgCuCe solders were determined from separated constitutive relations and experimental results. Non-linear least-squares fitting was selected to determine the model constants. Comparisons were then made with experimental measurements of the stress-inelastic strain curves: excellent agreement was found. The model accurately predicted the overall trend of steady-state stress-strain behavior of SnAgCu and SnAgCuCe solders for the temperature ranges from -55 to 125 °C and for the strain rate range from 1% s-1 to 0.01% s-1. It is concluded that the Anand model can be applied to represent the inelastic deformation behavior of solders at high homologous temperatures and can be recommended for finite element simulation of the stress-strain response of lead-free soldered joints. Based on the Anand model, the investigations of thermo-mechanical behavior of SnAgCu and SnAgCuCe soldered joints in fine pitch quad flat package by the finite element code have been done under thermal cyclic loading, and it is found that the reliability of the SnAgCuCe soldered joints is better than that of the SnAgCu soldered joints.

Possible involvement of SINEs in mammalian-specific brain formation

PubMed Central

Sasaki, Takeshi; Nishihara, Hidenori; Hirakawa, Mika; Fujimura, Koji; Tanaka, Mikiko; Kokubo, Nobuhiro; Kimura-Yoshida, Chiharu; Matsuo, Isao; Sumiyama, Kenta; Saitou, Naruya; Shimogori, Tomomi; Okada, Norihiro

2008-01-01

Retroposons, such as short interspersed elements (SINEs) and long interspersed elements (LINEs), are the major constituents of higher vertebrate genomes. Although there are many examples of retroposons' acquiring function, none has been implicated in the morphological innovations specific to a certain taxonomic group. We previously characterized a SINE family, AmnSINE1, members of which constitute a part of conserved noncoding elements (CNEs) in mammalian genomes. We proposed that this family acquired genomic functionality or was exapted after retropositioning in a mammalian ancestor. Here we identified 53 new AmnSINE1 loci and refined 124 total loci, two of which were further analyzed. Using a mouse enhancer assay, we demonstrate that one SINE locus, AS071, 178 kbp from the gene FGF8 (fibroblast growth factor 8), is an enhancer that recapitulates FGF8 expression in two regions of the developing forebrain, namely the diencephalon and the hypothalamus. Our gain-of-function analysis revealed that FGF8 expression in the diencephalon controls patterning of thalamic nuclei, which act as a relay center of the neocortex, suggesting a role for FGF8 in mammalian-specific forebrain patterning. Furthermore, we demonstrated that the locus, AS021, 392 kbp from the gene SATB2, controls gene expression in the lateral telencephalon, which is thought to be a signaling center during development. These results suggest important roles for SINEs in the development of the mammalian neuronal network, a part of which was initiated with the exaptation of AmnSINE1 in a common mammalian ancestor. PMID:18334644

Possible involvement of SINEs in mammalian-specific brain formation.

PubMed

Sasaki, Takeshi; Nishihara, Hidenori; Hirakawa, Mika; Fujimura, Koji; Tanaka, Mikiko; Kokubo, Nobuhiro; Kimura-Yoshida, Chiharu; Matsuo, Isao; Sumiyama, Kenta; Saitou, Naruya; Shimogori, Tomomi; Okada, Norihiro

2008-03-18

Retroposons, such as short interspersed elements (SINEs) and long interspersed elements (LINEs), are the major constituents of higher vertebrate genomes. Although there are many examples of retroposons' acquiring function, none has been implicated in the morphological innovations specific to a certain taxonomic group. We previously characterized a SINE family, AmnSINE1, members of which constitute a part of conserved noncoding elements (CNEs) in mammalian genomes. We proposed that this family acquired genomic functionality or was exapted after retropositioning in a mammalian ancestor. Here we identified 53 new AmnSINE1 loci and refined 124 total loci, two of which were further analyzed. Using a mouse enhancer assay, we demonstrate that one SINE locus, AS071, 178 kbp from the gene FGF8 (fibroblast growth factor 8), is an enhancer that recapitulates FGF8 expression in two regions of the developing forebrain, namely the diencephalon and the hypothalamus. Our gain-of-function analysis revealed that FGF8 expression in the diencephalon controls patterning of thalamic nuclei, which act as a relay center of the neocortex, suggesting a role for FGF8 in mammalian-specific forebrain patterning. Furthermore, we demonstrated that the locus, AS021, 392 kbp from the gene SATB2, controls gene expression in the lateral telencephalon, which is thought to be a signaling center during development. These results suggest important roles for SINEs in the development of the mammalian neuronal network, a part of which was initiated with the exaptation of AmnSINE1 in a common mammalian ancestor.

Performance of mixed formulations for the particle finite element method in soil mechanics problems

NASA Astrophysics Data System (ADS)

Monforte, Lluís; Carbonell, Josep Maria; Arroyo, Marcos; Gens, Antonio

2017-07-01

This paper presents a computational framework for the numerical analysis of fluid-saturated porous media at large strains. The proposal relies, on one hand, on the particle finite element method (PFEM), known for its capability to tackle large deformations and rapid changing boundaries, and, on the other hand, on constitutive descriptions well established in current geotechnical analyses (Darcy's law; Modified Cam Clay; Houlsby hyperelasticity). An important feature of this kind of problem is that incompressibility may arise either from undrained conditions or as a consequence of material behaviour; incompressibility may lead to volumetric locking of the low-order elements that are typically used in PFEM. In this work, two different three-field mixed formulations for the coupled hydromechanical problem are presented, in which either the effective pressure or the Jacobian are considered as nodal variables, in addition to the solid skeleton displacement and water pressure. Additionally, several mixed formulations are described for the simplified single-phase problem due to its formal similitude to the poromechanical case and its relevance in geotechnics, since it may approximate the saturated soil behaviour under undrained conditions. In order to use equal-order interpolants in displacements and scalar fields, stabilization techniques are used in the mass conservation equation of the biphasic medium and in the rest of scalar equations. Finally, all mixed formulations are assessed in some benchmark problems and their performances are compared. It is found that mixed formulations that have the Jacobian as a nodal variable perform better.

Insertion Sequences

PubMed Central

Mahillon, Jacques; Chandler, Michael

1998-01-01

Insertion sequences (ISs) constitute an important component of most bacterial genomes. Over 500 individual ISs have been described in the literature to date, and many more are being discovered in the ongoing prokaryotic and eukaryotic genome-sequencing projects. The last 10 years have also seen some striking advances in our understanding of the transposition process itself. Not least of these has been the development of various in vitro transposition systems for both prokaryotic and eukaryotic elements and, for several of these, a detailed understanding of the transposition process at the chemical level. This review presents a general overview of the organization and function of insertion sequences of eubacterial, archaebacterial, and eukaryotic origins with particular emphasis on bacterial elements and on different aspects of the transposition mechanism. It also attempts to provide a framework for classification of these elements by assigning them to various families or groups. A total of 443 members of the collection have been grouped in 17 families based on combinations of the following criteria: (i) similarities in genetic organization (arrangement of open reading frames); (ii) marked identities or similarities in the enzymes which mediate the transposition reactions, the recombinases/transposases (Tpases); (iii) similar features of their ends (terminal IRs); and (iv) fate of the nucleotide sequence of their target sites (generation of a direct target duplication of determined length). A brief description of the mechanism(s) involved in the mobility of individual ISs in each family and of the structure-function relationships of the individual Tpases is included where available. PMID:9729608

Finite element analysis and simulation of rheological properties of bulk molding compound (BMC)

NASA Astrophysics Data System (ADS)

Ergin, M. Fatih; Aydin, Ismail

2013-12-01

Bulk molding compound (BMC) is one of the important composite materials with various engineering applications. BMC is a thermoset plastic resin blend of various inert fillers, fiber reinforcements, catalysts, stabilizers and pigments that form a viscous, molding compound. Depending on the end-use application, bulk molding compounds are formulated to achieve close dimensional control, flame and scratch resistance, electrical insulation, corrosion and stain resistance, superior mechanical properties, low shrink and color stability. Its excellent flow characteristics, dielectric properties, and flame resistance make this thermoset material well-suited to a wide variety of applications requiring precision in detail and dimensions as well as high performance. When a BMC is used for these purposes, the rheological behavior and properties of the BMC is the main concern. In this paper, finite element analysis of rheological properties of bulk molding composite material was studied. For this purpose, standard samples of composite material were obtained by means of uniaxial hot pressing. 3 point flexural tests were then carried out by using a universal testing machine. Finite element analyses were then performed with defined material properties within a specific constitutive material behavior. Experimental and numerical results were then compared. Good correlation between the numerical simulation and the experimental results was obtained. It was expected with this study that effects of various process parameters and boundary conditions on the rheological behavior of bulk molding compounds could be determined by means of numerical analysis without detailed experimental work.

The patient-doctor relationship: a synthesis of the qualitative literature on patients' perspectives.

PubMed

Ridd, Matthew; Shaw, Alison; Lewis, Glyn; Salisbury, Chris

2009-04-01

The patient-doctor relationship is an important but poorly defined topic. In order to comprehensively assess its significance for patient care, a clearer understanding of the concept is required. To derive a conceptual framework of the factors that define patient-doctor relationships from the perspective of patients. Systematic review and thematic synthesis of qualitative studies. Medline, EMBASE, PsychINFO and Web of Science databases were searched. Studies were screened for relevance and appraised for quality. The findings were synthesised using a thematic approach. From 1985 abstracts, 11 studies from four countries were included in the final synthesis. They examined the patient-doctor relationship generally (n = 3), or in terms of loyalty (n = 3), personal care (n = 2), trust (n = 2), and continuity (n = 1). Longitudinal care (seeing the same doctor) and consultation experiences (patients' encounters with the doctor) were found to be the main processes by which patient-doctor relationships are promoted. The resulting depth of patient-doctor relationship comprises four main elements: knowledge, trust, loyalty, and regard. These elements have doctor and patient aspects to them, which may be reciprocally related. A framework is proposed that distinguishes between dynamic factors that develop or maintain the relationship, and characteristics that constitute an ongoing depth of relationship. Having identified the different elements involved, future research should examine for associations between longitudinal care, consultation experiences, and depth of patient-doctor relationship, and, in turn, their significance for patient care.

Hyper-elastoplastic/damage modeling of rock with application to porous limestone

DOE PAGES

Bennett, Kane C.; Borja, Ronaldo I.

2018-03-13

Relations between porosity, damage, and bulk plasticity are examined in the context of continuum damage and hyper-elastoplasticity of porous rocks. Attention is given to a thermodynamically consistent derivation of the damage evolution equations and their role in the constitutive equations, for which the Eshelby stress is found to be important. The provided phenomenological framework allows for volumetric damage associated with pore growth to be distinguished from the isochoric damage associated with distributed microcracks, and a novel Drucker-Prager/cap type material model that includes damage evolution is presented. The model is shown to capture well the hardening/softening behavior and pressure dependence ofmore » the so-called brittle-ductile transition by comparison with confined triaxial compression measurements from the literature. Non-linear finite element simulations are also provided of the prediction of damage within porous limestone around a horizontal borehole wall.« less

A coupled deformation-diffusion theory for fluid-saturated porous solids

NASA Astrophysics Data System (ADS)

Henann, David; Kamrin, Ken; Anand, Lallit

2012-02-01

Fluid-saturated porous materials are important in several familiar applications, such as the response of soils in geomechanics, food processing, pharmaceuticals, and the biomechanics of living bone tissue. An appropriate constitutive theory describing the coupling of the mechanical behavior of the porous solid with the transport of the fluid is a crucial ingredient towards understanding the material behavior in these varied applications. In this work, we formulate and numerically implement in a finite-element framework a large-deformation theory for coupled deformation-diffusion in isotropic, fluid-saturated porous solids. The theory synthesizes the classical Biot theory of linear poroelasticity and the more-recent Coussy theory of poroplasticity in a large deformation framework. In this talk, we highlight several salient features of our theory and discuss representative examples of the application of our numerical simulation capability to problems of consolidation as well as deformation localization in granular materials.

Using accountability to improve reproductive health care.

PubMed

George, Asha

2003-05-01

Accountability is best understood as a referee of the dynamics in two-way relationships, often between unequal partners. The literature on accountability distinguishes between political, fiscal, administrative, legal and constitutional accountability. This paper focuses on accountability mechanisms in health care and how they mediate between service providers and communities and between different kinds of health personnel at the primary health care level. It refers to case studies of participatory processes for improving sexual and reproductive health service delivery. Information, dialogue and negotiation are important elements that enable accountability mechanisms to address problems by supporting change and engagement between participants. In order to succeed, however, efforts towards better accountability that broaden the participation of users must take into account the social contexts and the policy and service delivery systems in which they are applied, address power relations and improve the representation of marginalised groups within communities and service delivery systems.

Medical encounters and exchange in early Canadian missions.

PubMed

Parsons, Chris

2008-01-01

The exchange of medical and pharmaceutical knowledge was an important facet of the encounter between native and newcomer in early Canada. Throughout New France Récollet and Jesuit missionaries were given privileged access both to indigenous peoples and indigenous plants. Curiously, however, when it came to describing medical treatments, it was people, rather than medicinal plants, that were targets of what might be called "the descriptive enterprise." Attempting to divide suspect shamanic remedies from those deemed natural, missionary observers carefully documented the context of medical treatments rather than simply the specific remedy applied for treatment. Using records left by early Canadian missionaries this paper will look at the peculiar character of medical exchange in the missions of seventeenth and eighteenth-century New France to look at the interpersonal encounters that formed a constitutive element of colonial botany and framed the way in which indigenous knowledge was represented to metropolitan audiences.

A Chronic Disease Prevention and Management Corridor© to Supporting System-Level Transformations for Chronic Conditions.

PubMed

Sampalli, Tara; Christian, Erin; Edwards, Lynn; Ryer, Ashley

2015-01-01

Improving care for chronic conditions requires system-level transformations to ensure multiple levels of adoption and sustainability of the implemented improvements. These comprehensive solutions require transformations and supports at various levels, leadership and process changes at service/program level. Recognizing the importance of an organization-wide strategy to mitigate the growing issue of chronic disease prevention and management, a novel system-level approach has been developed in a district health authority in Nova Scotia, Canada. In this paper, the contextual factors and efforts that led to the conceptual framework of the Chronic Disease Prevention and Management (CDPM) "Corridor©" to management of chronic conditions are discussed. The CDPM Corridor© essentially constitutes a system-level redesign process; common elements, tools and resources; and a hub of supports for chronic disease prevention and management. The CDPM Corridor © will include a toolkit to guide the implementation of the proposed transformations.

Numerical modelling of effective thermal conductivity for modified geomaterial using lattice element method

NASA Astrophysics Data System (ADS)

Rizvi, Zarghaam Haider; Shrestha, Dinesh; Sattari, Amir S.; Wuttke, Frank

2018-02-01

Macroscopic parameters such as effective thermal conductivity (ETC) is an important parameter which is affected by micro and meso level behaviour of particulate materials, and has been extensively examined in the past decades. In this paper, a new lattice based numerical model is developed to predict the ETC of sand and modified high thermal backfill material for energy transportation used for underground power cables. 2D and 3D simulations are performed to analyse and detect differences resulting from model simplification. The thermal conductivity of the granular mixture is determined numerically considering the volume and the shape of the each constituting portion. The new numerical method is validated with transient needle measurements and the existing theoretical and semi empirical models for thermal conductivity prediction sand and the modified backfill material for dry condition. The numerical prediction and the measured values are in agreement to a large extent.

Genomic analyses of primitive, wild and cultivated citrus provide insights into asexual reproduction.

PubMed

Wang, Xia; Xu, Yuantao; Zhang, Siqi; Cao, Li; Huang, Yue; Cheng, Junfeng; Wu, Guizhi; Tian, Shilin; Chen, Chunli; Liu, Yan; Yu, Huiwen; Yang, Xiaoming; Lan, Hong; Wang, Nan; Wang, Lun; Xu, Jidi; Jiang, Xiaolin; Xie, Zongzhou; Tan, Meilian; Larkin, Robert M; Chen, Ling-Ling; Ma, Bin-Guang; Ruan, Yijun; Deng, Xiuxin; Xu, Qiang

2017-05-01

The emergence of apomixis-the transition from sexual to asexual reproduction-is a prominent feature of modern citrus. Here we de novo sequenced and comprehensively studied the genomes of four representative citrus species. Additionally, we sequenced 100 accessions of primitive, wild and cultivated citrus. Comparative population analysis suggested that genomic regions harboring energy- and reproduction-associated genes are probably under selection in cultivated citrus. We also narrowed the genetic locus responsible for citrus polyembryony, a form of apomixis, to an 80-kb region containing 11 candidate genes. One of these, CitRWP, is expressed at higher levels in ovules of polyembryonic cultivars. We found a miniature inverted-repeat transposable element insertion in the promoter region of CitRWP that cosegregated with polyembryony. This study provides new insights into citrus apomixis and constitutes a promising resource for the mining of agriculturally important genes.

Hypothalamic glucose-sensing: role of Glia-to-neuron signaling.

PubMed

Tonon, M C; Lanfray, D; Castel, H; Vaudry, H; Morin, F

2013-12-01

The hypothalamus senses hormones and nutrients in order to regulate energy balance. In particular, detection of hypothalamic glucose levels has been shown to regulate both feeding behavior and peripheral glucose homeostasis, and impairment of this regulatory system is believed to be involved in the development of obesity and diabetes. Several data clearly demonstrate that glial cells are key elements in the perception of glucose, constituting with neurons a "glucose-sensing unit". Characterization of this interplay between glia and neurons represents an exciting challenge, and will undoubtedly contribute to identify new candidates for therapeutic intervention. The purpose of this review is to summarize the current data that stress the importance of glia in central glucose-sensing. The nature of the glia-to-neuron signaling is discussed, with a special focus on the endozepine ODN, a potent anorexigenic peptide that is highly expressed in hypothalamic glia. © Georg Thieme Verlag KG Stuttgart · New York.

SEACAS Theory Manuals: Part 1. Problem Formulation in Nonlinear Solid Mechancis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Attaway, S.W.; Laursen, T.A.; Zadoks, R.I.

1998-08-01

This report gives an introduction to the basic concepts and principles involved in the formulation of nonlinear problems in solid mechanics. By way of motivation, the discussion begins with a survey of some of the important sources of nonlinearity in solid mechanics applications, using wherever possible simple one dimensional idealizations to demonstrate the physical concepts. This discussion is then generalized by presenting generic statements of initial/boundary value problems in solid mechanics, using linear elasticity as a template and encompassing such ideas as strong and weak forms of boundary value problems, boundary and initial conditions, and dynamic and quasistatic idealizations. Themore » notational framework used for the linearized problem is then extended to account for finite deformation of possibly inelastic solids, providing the context for the descriptions of nonlinear continuum mechanics, constitutive modeling, and finite element technology given in three companion reports.« less

NMR spectroscopy of Group 13 metal ions: biologically relevant aspects.

PubMed

André, J P; Mäcke, H R

2003-12-01

In spite of the fact that Group 13 metal ions (Al(3+), Ga(3+), In(3+) and Tl(+/3+)) show no main biological role, they are NMR-active nuclides which can be used in magnetic resonance spectroscopy of biologically relevant systems. The fact that these metal ions are quadrupolar (with the exception of thallium) means that they are particularly sensitive to ligand type and coordination geometry. The line width of the NMR signals of their complexes shows a strong dependence on the symmetry of coordination, which constitutes an effective tool in the elucidation of structures. Here we report published NMR studies of this family of elements, applied to systems of biological importance. Special emphasis is given to binding studies of these cations to biological molecules, such as proteins, and to chelating agents of radiopharmaceutical interest. The possibility of in vivo NMR studies is also stressed, with extension to (27)Al-based MRI (magnetic resonance imaging) experiments.

Hyper-elastoplastic/damage modeling of rock with application to porous limestone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Kane C.; Borja, Ronaldo I.

Relations between porosity, damage, and bulk plasticity are examined in the context of continuum damage and hyper-elastoplasticity of porous rocks. Attention is given to a thermodynamically consistent derivation of the damage evolution equations and their role in the constitutive equations, for which the Eshelby stress is found to be important. The provided phenomenological framework allows for volumetric damage associated with pore growth to be distinguished from the isochoric damage associated with distributed microcracks, and a novel Drucker-Prager/cap type material model that includes damage evolution is presented. The model is shown to capture well the hardening/softening behavior and pressure dependence ofmore » the so-called brittle-ductile transition by comparison with confined triaxial compression measurements from the literature. Non-linear finite element simulations are also provided of the prediction of damage within porous limestone around a horizontal borehole wall.« less

[Myofibroblasts and afferent signalling in the urinary bladder. A concept].

PubMed

Neuhaus, J; Scholler, U; Freick, K; Schwalenberg, T; Heinrich, M; Horn, L C; Stolzenburg, J U

2008-09-01

Afferent signal transduction in the urinary bladder is still not clearly understood. An increasing body of evidence supports the view of complex interactions between urothelium, suburothelial myofibroblasts, and sensory nerves. Bladder tissue from tumour patients was used in this study. Methods included confocal immunofluorescence, polymerase chain reaction, calcium imaging, and fluorescence recovery after photobleaching (FRAP).Myofibroblasts express muscarinic and purinergic receptors. They show constitutive spontaneous activity in calcium imaging, which completely depends on extracellular calcium. Stimulation with carbachol and ATP-evoked intracellular calcium transients also depend on extracellular calcium. The intensive coupling between the cells is significantly diminished by incubation with TGF-beta 1. Myofibroblasts form an important cellular element within the afferent signalling of the urinary bladder. They possess all features required to take part in the complex interactions with urothelial cells and sensory nerves. Modulation of their function by cytokines may provide a pathomechanism for bladder dysfunction.

Effects of the Variation in Brain Tissue Mechanical Properties on the Intracranial Response of a 6-Year-Old Child.

PubMed

Cui, Shihai; Li, Haiyan; Li, Xiangnan; Ruan, Jesse

2015-01-01

Brain tissue mechanical properties are of importance to investigate child head injury using finite element (FE) method. However, these properties used in child head FE model normally vary in a large range in published literatures because of the insufficient child cadaver experiments. In this work, a head FE model with detailed anatomical structures is developed from the computed tomography (CT) data of a 6-year-old healthy child head. The effects of brain tissue mechanical properties on traumatic brain response are also analyzed by reconstruction of a head impact on engine hood according to Euro-NCAP testing regulation using FE method. The result showed that the variations of brain tissue mechanical parameters in linear viscoelastic constitutive model had different influences on the intracranial response. Furthermore, the opposite trend was obtained in the predicted shear stress and shear strain of brain tissues caused by the variations of mentioned parameters.

Meta genome-wide network from functional linkages of genes in human gut microbial ecosystems.

PubMed

Ji, Yan; Shi, Yixiang; Wang, Chuan; Dai, Jianliang; Li, Yixue

2013-03-01

The human gut microbial ecosystem (HGME) exerts an important influence on the human health. In recent researches, meta-genomics provided deep insights into the HGME in terms of gene contents, metabolic processes and genome constitutions of meta-genome. Here we present a novel methodology to investigate the HGME on the basis of a set of functionally coupled genes regardless of their genome origins when considering the co-evolution properties of genes. By analyzing these coupled genes, we showed some basic properties of HGME significantly associated with each other, and further constructed a protein interaction map of human gut meta-genome to discover some functional modules that may relate with essential metabolic processes. Compared with other studies, our method provides a new idea to extract basic function elements from meta-genome systems and investigate complex microbial environment by associating its biological traits with co-evolutionary fingerprints encoded in it.

[Taxation and tobacco control: the cases of Brazil and Mexico].

PubMed

de Miera-Juárez, Belén Sáenz; Iglesias, Roberto

2010-01-01

This study analyzes the achievements, obstacles and challenges related to cigarette taxes in Brazil and Mexico. Both countries have increased cigarette taxes in recent years and have included a specific tax, which allows maximizing the impact of tax increases on prices. However, it seems they have not taken full advantage of these measures. Three recommendations follow from these experiences: 1) specific taxes must represent a significant percentage of final prices; 2) specific taxes must be regularly adjusted to keep pace with cumulative inflation; and 3) specific taxes must be adjusted to compensate increases in personal income. It is also important to consider that taxes on legal substitutes of cigarettes must be similar to cigarette taxes. As for illegal substitutes, the issue is to reduce the incentives for illicit trade and to make illegal transactions more difficult. Modifications to national legislation and international cooperation constitute key elements to achieve this.

Review of hydrogen storage in inorganic fullerene-like nanotubes

NASA Astrophysics Data System (ADS)

Chen, J.; Wu, F.

Following the discovery of carbon nanotubes, inorganic fullerene-like nanotubes such as WS2-MoS2, NbS2, TiS2, and BN were reported. Inorganic (non-carbon) nanotubes constitute an important class of nanomaterials with interesting properties and potential applications. As known, efficient hydrogen storage is one key problem in the development of a hydrogen energy system. Hydrogen storage using carbon nanostructures is scientifically interesting and challenging. It thus would be worthwhile to look into hydrogen storage in inorganic nanotubes because the van der Waals gaps between the nanotube layers are potential candidates for hydrogen uptake. Furthermore, the inorganic nanotubes combine two elements, which is different from the pure carbon nanotubes. These may show a novel hydrogen adsorption-desorption mechanism. The present review provides a brief study of hydrogen adsorption on MoS2, TiS2, and BN nanotubes.

Before words: reading western astronomical texts in early nineteenth-century Japan.

PubMed

Frumer, Yulia

2016-04-01

In 1803, the most prominent Japanese astronomer of his time, Takahashi Yoshitoki, received a newly imported Dutch translation of J. J. Lalande's 'Astronomie'. He could not read Dutch, yet he dedicated almost a year to a close examination of this massive work, taking notes and contemplating his own astronomical practices. How did he read a book he could not read? Following the clues Yoshitoki left in his notes, we discover that he found meanings not only in words, but also in what are often taken for granted or considered to be auxiliary tools for data manipulation, such as symbols, units, tables, and diagrams. His rendering of these non-verbal textual elements into a familiar format was crucial for Yoshitoki's reading, and constituted the initial step in the process of integrating Lalande's astronomy into Japanese astronomical practices, and the subsequent translation of the text into Japanese.

The idea of human prehistory: the natural sciences, the human sciences, and the problem of human origins in Victorian Britain.

PubMed

Goodrum, Matthew R

2012-01-01

The idea of human prehistory was a provocative and profoundly influential new notion that took shape gradually during the nineteenth century. While archaeology played an important role in providing the evidence for this idea many other sciences such as geology, paleontology, ethnology, and physical anthropology all made critical contributions to discussions about human prehistory. Many works have explored the history of prehistoric archaeology but this paper examines the conceptual content of the idea of "human prehistory" as it developed in the British scientific community. Both the natural and the human sciences contributed to what was in fact a complex collection of individual elements that together constituted the prevailing idea of human prehistory, although there were other competing conceptions of human prehistory endorsed by various scientists and critics of the new view of early human history.

Biomineralization of the spicules of sea urchin embryos.

PubMed

Wilt, Fred H

2002-03-01

The formation of calcareous skeletal elements by various echinoderms, especially sea urchins, offers a splendid opportunity to learn more about some processes involved in the formation of biominerals. The spicules of larvae of euechinoids have been the focus of considerable work, including their developmental origins. The spicules are composed of a single optical crystal of high magnesium calcite and variable amounts of amorphous calcium carbonate. Occluded within the spicule is a proteinaceous matrix, most of which is soluble; this matrix constitutes about 0.1% of the mass. The spicules are also enclosed by an extracellular matrix and are almost completely surrounded by cytoplasmic cords. The spicules are deposited by primary mesenchyme cells (PMCs), which accumulate calcium and secrete calcium carbonate. A number of proteins specific, or highly enriched, in PMCs, have been cloned and studied. Recent work supports the hypothesis that proteins found in the extracellular matrix of the spicule are important for biomineralization.

Multiaxial Cyclic Thermoplasticity Analysis with Besseling's Subvolume Method

NASA Technical Reports Server (NTRS)

Mcknight, R. L.

1983-01-01

A modification was formulated to Besseling's Subvolume Method to allow it to use multilinear stress-strain curves which are temperature dependent to perform cyclic thermoplasticity analyses. This method automotically reproduces certain aspects of real material behavior important in the analysis of Aircraft Gas Turbine Engine (AGTE) components. These include the Bauschinger effect, cross-hardening, and memory. This constitutive equation was implemented in a finite element computer program called CYANIDE. Subsequently, classical time dependent plasticity (creep) was added to the program. Since its inception, this program was assessed against laboratory and component testing and engine experience. The ability of this program to simulate AGTE material response characteristics was verified by this experience and its utility in providing data for life analyses was demonstrated. In this area of life analysis, the multiaxial thermoplasticity capabilities of the method have proved a match for the actual AGTE life experience.