Lunde, Knut B; Skallerud, Bjørn
2009-01-01
Morsellised cortico-cancellous bone (MCB) is often used in revision surgery for filling skeletal defects. The MCB porosity is found to influence the degree of bone ingrowth. Thus expressing a material model in terms of porosity may be attractive from a clinical point of view. We analysed the moisture content and performed constrained compression testing of human impacted and unimpacted MCB, in order to determine material parameters for the common constitutive soil model: modified cam clay. The model seemed to be suitable for the unimpacted pellets with a logarithmic bulk modulus kappa=0.059+/-0.0019 and a logarithmic hardening constant lambda=0.36+/-0.014. This model, relating the specific volume (and porosity) to the logarithm of stress, may be suited to find the best compromise of stiffness and porosity for MCB. PMID:19627806
NASA Technical Reports Server (NTRS)
Hickey, J. S.
1981-01-01
Existing Jacchia were converted from the UNIVAC 1108 to the SSL REEDA computer system and the overall program capabilities were enhanced. The Jacchia Models and the associated data bases reside on a REEDA System dedicated "JACCHIA" disc pack. The Jacchia programs, their operation, and the outputs generated outputs are described.
Model selection for modified gravity.
Kitching, T D; Simpson, F; Heavens, A F; Taylor, A N
2011-12-28
In this article, we review model selection predictions for modified gravity scenarios as an explanation for the observed acceleration of the expansion history of the Universe. We present analytical procedures for calculating expected Bayesian evidence values in two cases: (i) that modified gravity is a simple parametrized extension of general relativity (GR; two nested models), such that a Bayes' factor can be calculated, and (ii) that we have a class of non-nested models where a rank-ordering of evidence values is required. We show that, in the case of a minimal modified gravity parametrization, we can expect large area photometric and spectroscopic surveys, using three-dimensional cosmic shear and baryonic acoustic oscillations, to 'decisively' distinguish modified gravity models over GR (or vice versa), with odds of ≫1:100. It is apparent that the potential discovery space for modified gravity models is large, even in a simple extension to gravity models, where Newton's constant G is allowed to vary as a function of time and length scale. On the time and length scales where dark energy dominates, it is only through large-scale cosmological experiments that we can hope to understand the nature of gravity. PMID:22084296
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).
Cosmological models of modified gravity
NASA Astrophysics Data System (ADS)
Bloomfield, Jolyon Keith
The recent discovery of dark energy has prompted an investigation of ways in which the accelerated expansion of the universe can be realized. In this dissertation, we present two separate projects related to dark energy. The first project analyzes a class of braneworld models in which multiple branes float in a five-dimensional anti-de Sitter bulk, while the second investigates a class of dark energy models from an effective field theory perspective. Investigations of models including extra dimensions have led to modifications of gravity involving a number of interesting features. In particular, the Randall-Sundrum model is well-known for achieving an amelioration of the hierarchy problem. However, the basic model relies on Minkowski branes and is subject to solar system constraints in the absence of a radion stabilization mechanism. We present a method by which a four-dimensional low-energy description can be obtained for braneworld scenarios, allowing for a number of generalizations to the original models. This method is applied to orbifolded and uncompactified N-brane models, deriving an effective four-dimensional action. The parameter space of this theory is constrained using observational evidence, and it is found that the generalizations do not weaken solar system constraints on the original model. Furthermore, we find that general N-brane systems are qualitatively similar to the two-brane case, and do not naturally lead to a viable dark energy model. We next investigate dark energy models using effective field theory techniques. We describe dark energy through a quintessence field, employing a derivative expansion. To the accuracy of the model, we find transformations to write the description in a form involving no higher-order derivatives in the equations of motion. We use a pseudo-Nambu-Goldstone boson construction to motivate the theory, and find the regime of validity and scaling of the operators using this. The regime of validity is restricted to a
Observational bounds on modified gravity models
De Felice, Antonio; Mukherjee, Pia; Wang Yun
2008-01-15
Modified gravity provides a possible explanation for the currently observed cosmic acceleration. In this paper, we study general classes of modified gravity models. The Einstein-Hilbert action is modified by using general functions of the Ricci and the Gauss-Bonnet scalars, both in the metric and in the Palatini formalisms. We do not use an explicit form for the functions, but a general form with a valid Taylor expansion up to second order about redshift zero in the Riemann-scalars. The coefficients of this expansion are then reconstructed via the cosmic expansion history measured using current cosmological observations. These are the quantities of interest for theoretical considerations relating to ghosts and instabilities. We find that current data provide interesting constraints on the coefficients. The next-generation dark energy surveys should shrink the allowed parameter space for modified gravity models quite dramatically.
Genetically modified pig models for neurodegenerative disorders.
Holm, Ida E; Alstrup, Aage Kristian Olsen; Luo, Yonglun
2016-01-01
Increasing incidence of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease has become one of the most challenging health issues in ageing humans. One approach to combat this is to generate genetically modified animal models of neurodegenerative disorders for studying pathogenesis, prognosis, diagnosis, treatment, and prevention. Owing to the genetic, anatomic, physiologic, pathologic, and neurologic similarities between pigs and humans, genetically modified pig models of neurodegenerative disorders have been attractive large animal models to bridge the gap of preclinical investigations between rodents and humans. In this review, we provide a neuroanatomical overview in pigs and summarize and discuss the generation of genetically modified pig models of neurodegenerative disorders including Alzheimer's diseases, Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, spinal muscular atrophy, and ataxia-telangiectasia. We also highlight how non-invasive bioimaging technologies such as positron emission tomography (PET), computer tomography (CT), and magnetic resonance imaging (MRI), and behavioural testing have been applied to characterize neurodegenerative pig models. We further propose a multiplex genome editing and preterm recloning (MAP) approach by using the rapid growth of the ground-breaking precision genome editing technology CRISPR/Cas9 and somatic cell nuclear transfer (SCNT). With this approach, we hope to shorten the temporal requirement in generating multiple transgenic pigs, increase the survival rate of founder pigs, and generate genetically modified pigs that will more closely resemble the disease-causing mutations and recapitulate pathological features of human conditions. PMID:26446984
Einstein spaces modeling nonminimal modified gravity
NASA Astrophysics Data System (ADS)
Elizalde, Emilio; Vacaru, Sergiu I.
2015-06-01
Off-diagonal vacuum and nonvacuum configurations in the Einstein gravity can mimic physical effects of modified gravitational theories of f( R, T, R μν T μν ) type. To prove this statement, exact and approximate solutions are constructed in the paper, which encode certain models of covariant Hořava-type gravity with dynamical Lorentz symmetry breaking. The corresponding FLRW cosmological dynamics with possible nonholonomic deformations and the reconstruction procedure of certain actions closely related with the standard ΛCDM universe are studied. Off-diagonal generalizations of de Sitter universes are constructed which are generated through nonlinear gravitational polarization of fundamental physical constants and which model interactions with nonconstant exotic fluids and effective matter. The problem of possible matter instability for such off-diagonal deformations in (modified) gravity theories is briefly discussed.
Modified Nonlinear Model of Arcsin-Electrodynamics
NASA Astrophysics Data System (ADS)
Kruglov, S. I.
2016-07-01
A new modified model of nonlinear arcsin-electrodynamics with two parameters is proposed and analyzed. We obtain the corrections to the Coulomb law. The effect of vacuum birefringence takes place when the external constant magnetic field is present. We calculate indices of refraction for two perpendicular polarizations of electromagnetic waves and estimate bounds on the parameter γ from the BMV and PVLAS experiments. It is shown that the electric field of a point-like charge is finite at the origin. We calculate the finite static electric energy of point-like particles and demonstrate that the electron mass can have the pure electromagnetic nature. The symmetrical Belinfante energy-momentum tensor and dilatation current are found. We show that the dilatation symmetry and dual symmetry are broken in the model suggested. We have investigated the gauge covariant quantization of the nonlinear electrodynamics fields as well as the gauge fixing approach based on Dirac's brackets.
Coupled Electro-Thermo-Mechanical Finite Element Modeling of the Spark Plasma Sintering Technique
NASA Astrophysics Data System (ADS)
Schwertz, Maxime; Katz, Aurélien; Sorrel, Emmanuel; Lemonnier, Sébastien; Barraud, Elodie; Carradò, Adele; d'Astorg, Sophie; Leriche, Anne; Nardin, Michel; Vallat, Marie-France; Kosior, Francis
2016-04-01
This paper deals with the development of a novel and predictive finite element method (FEM) model coupling electrical, thermal, and mechanical time-dependent contributions for simulating the behavior of a powdery material submitted to a spark plasma sintering (SPS) treatment by using COMSOL Multiphysics® software. The original approach of this work lies in the use of the modified Cam-Clay model to solve the mechanical phenomenon occurring during a SPS sintering treatment. As the powder properties and behaviors are different from the final sintered material and display a nonlinear dependence as a function of temperature and pressure, the model includes the description of the sample densification. In this way, numerical and experimental results obtained on conductive model material (aluminum) such as temperature, stress distributions, and shrinkage, were directly compared. This FEM model demonstrated the ability to predict the powder behavior during temperature-controlled experiments precisely, as they are typically performed in the SPS technique. This approach exhibits a remarkable level of interest because it takes into account the nature of the material and also the specific characteristics of the powder studied.
NASA Astrophysics Data System (ADS)
Chen, S.; Al-Muntasheri, G.; Abousleiman, Y. N.
2014-12-01
The critical state concept based bounding surface model is one of the most widely used elastoplastic constitutive models for geomaterials, attributed mainly to its essential feature of allowing plastic deformation to occur for stress points within the bounding surface and thus the capability to represent the realistic non-recoverable behaviour of soils and rocks observed under the cyclic loading. This paper develops an implicit integration algorithm for the bounding surface model, using the standard return mapping approach (elastic predictor-plastic corrector), to obtain the updated stresses for the given strain increments. The formulation of the constitutive integration requires the derivation of a supplementary differential equation to describe the evolution of a key variable, i.e., the ratio between the image stress and the current stress quantities. It is essentially an extension of the integration scheme presented in an earlier work used for the simple bounding surface version of modified Cam Clay associated with a substantially simplified hardening rule. The integration algorithm for the bounding surface model is implemented into the finite element analysis commercial program, ABAQUS, through the material interface of UMAT (user defined material subroutine), and then used for the analysis of wellbore stability problem. The predictions from the ABAQUS simulations are generally in excellent agreement with the available analytical solutions, thus demonstrating the accuracy and robustness of the proposed integration scheme.
Some general remarks on hyperplasticity modelling and its extension to partially saturated soils
NASA Astrophysics Data System (ADS)
Lei, Xiaoqin; Wong, Henry; Fabbri, Antonin; Bui, Tuan Anh; Limam, Ali
2016-06-01
The essential ideas and equations of classic plasticity and hyperplasticity are successively recalled and compared, in order to highlight their differences and complementarities. The former is based on the mathematical framework proposed by Hill (The mathematical theory of plasticity. Oxford University Press, Oxford, 1950), whereas the latter is founded on the orthogonality hypothesis of Ziegler (An introduction to thermomechanics. Elsevier, North-Holland, 1983). The main drawback of classic plasticity is the possibility of violating the second principle of thermodynamics, while the relative ease to conjecture the yield function in order to approach experimental results is its main advantage. By opposition, the a priori satisfaction of thermodynamic principles constitutes the chief advantage of hyperplasticity theory. Noteworthy is also the fact that this latter approach allows a finer energy partition; in particular, the existence of frozen energy emerges as a natural consequence from its theoretical formulation. On the other hand, the relative difficulty to conjecture an efficient dissipation function to produce accurate predictions is its main drawback. The two theories are thus better viewed as two complementary approaches. Following this comparative study, a methodology to extend the hyperplasticity approach initially developed for dry or saturated materials to the case of partially saturated materials, accounting for interface energies and suction effects, is developed. A particular example based on the yield function of modified Cam-Clay model is then presented. It is shown that the approach developed leads to a model consistent with other existing works.
The modified ASEP as a model of ideal gas
NASA Astrophysics Data System (ADS)
Mironov, D.; Sossinsky, A.
2015-01-01
A modified version of the ASEP model is interpreted as a two-dimensional model of ideal gas. Its properties are studied by simulating its behavior in different situations, using an animation program designed for that purpose.
NASA Astrophysics Data System (ADS)
Rastiello, Giuseppe; Federico, Francesco; Screpanti, Silvio
2015-09-01
Many abandoned room and pillar mines have been excavated not far from the surface of large areas of important European cities. In Rome, these excavations took place at shallow depths (3-15 m below the ground surface) in weak pyroclastic soft rocks. Many of these cavities have collapsed; others appear to be in a stable condition, although an appreciable percentage of their structural components (pillars, roofs, etc.) have shown increasing signs of distress from both the morphological and mechanical points of view. In this study, the stress-strain behaviour of soft rock pillars sustaining systems of cavities under vertical loads was numerically simulated, starting from the in situ initial conditions due to excavation of the cavities. The mechanical behaviour of the constituent material of the pillar was modelled according to the Modified Cam-Clay constitutive law (elasto-plastic with strain hardening). The influence of the pillar geometry (cross-section area, shape, and height) and mechanical parameters of the soft rock on the ultimate compressive strength of the pillar as a whole was parametrically investigated first. Based on the numerical results, an original relationship for pillar strength assessment was developed. Finally, the estimated pillar strengths according to the proposed formula and well-known formulations in the literature were compared.
Cosmological constraints on the modified entropic force model
NASA Astrophysics Data System (ADS)
Wei, Hao
2010-08-01
Very recently, Verlinde considered a theory in which space is emergent through a holographic scenario, and proposed that gravity can be explained as an entropic force caused by changes in the information associated with the positions of material bodies. Then, motivated by the Debye model in thermodynamics which is very successful in very low temperatures, Gao modified the entropic force scenario. The modified entropic force (MEF) model is in fact a modified gravity model, and the universe can be accelerated without dark energy. In the present work, we consider the cosmological constraints on the MEF model, and successfully constrain the model parameters to a narrow range. We also discuss many other issues of the MEF model. In particular, we clearly reveal the implicit root to accelerate the universe in the MEF model.
Cosmology of generalized modified gravity models
Carroll, Sean M.; Duvvuri, Vikram; De Felice, Antonio; Easson, Damien A.; Trodden, Mark; Turner, Michael S.
2005-03-15
We consider general curvature-invariant modifications of the Einstein-Hilbert action that become important only in regions of extremely low space-time curvature. We investigate the far future evolution of the Universe in such models, examining the possibilities for cosmic acceleration and other ultimate destinies. The models generically possess de Sitter space as an unstable solution and exhibit an interesting set of attractor solutions which, in some cases, provide alternatives to dark energy models.
A new approach to modified gravity models
NASA Astrophysics Data System (ADS)
Chakrabarti, Sayan K.; Saridakis, Emmanuel N.; Sen, Anjan A.
2011-11-01
We investigate f ( R)-gravity models performing the ADM-slicing of standard General Relativity. We extract the static, spherically-symmetric vacuum solutions in the general case, which correspond to either Schwarzschild de-Sitter or Schwarzschild anti-de-Sitter ones. Additionally, we study the cosmological evolution of a homogeneous and isotropic universe, which is governed by an algebraic and not a differential equation. We show that the universe admits solutions corresponding to acceleration at late cosmological epochs, without the need of fine-tuning the model-parameters or the initial conditions.
Modified Invasion Percolation Models for Multiphase Processes
Karpyn, Zuleima
2015-01-31
This project extends current understanding and modeling capabilities of pore-scale multiphase flow physics in porous media. High-resolution X-ray computed tomography imaging experiments are used to investigate structural and surface properties of the medium that influence immiscible displacement. Using experimental and computational tools, we investigate the impact of wetting characteristics, as well as radial and axial loading conditions, on the development of percolation pathways, residual phase trapping and fluid-fluid interfacial areas.
Modified Kneser-Ney Smoothing of n-Gram Models
NASA Technical Reports Server (NTRS)
James, Frankie
2000-01-01
This report examines a series of tests that were performed on variations of the modified Kneser Ney smoothing model outlined in a study by Chen and Goodman. We explore several different ways of choosing and setting the discounting parameters, as well as the exclusion of singleton contexts at various levels of the model.
Theoretical modelling of epigenetically modified DNA sequences.
Carvalho, Alexandra Teresa Pires; Gouveia, Maria Leonor; Raju Kanna, Charan; Wärmländer, Sebastian K T S; Platts, Jamie; Kamerlin, Shina Caroline Lynn
2015-01-01
We report herein a set of calculations designed to examine the effects of epigenetic modifications on the structure of DNA. The incorporation of methyl, hydroxymethyl, formyl and carboxy substituents at the 5-position of cytosine is shown to hardly affect the geometry of CG base pairs, but to result in rather larger changes to hydrogen-bond and stacking binding energies, as predicted by dispersion-corrected density functional theory (DFT) methods. The same modifications within double-stranded GCG and ACA trimers exhibit rather larger structural effects, when including the sugar-phosphate backbone as well as sodium counterions and implicit aqueous solvation. In particular, changes are observed in the buckle and propeller angles within base pairs and the slide and roll values of base pair steps, but these leave the overall helical shape of DNA essentially intact. The structures so obtained are useful as a benchmark of faster methods, including molecular mechanics (MM) and hybrid quantum mechanics/molecular mechanics (QM/MM) methods. We show that previously developed MM parameters satisfactorily reproduce the trimer structures, as do QM/MM calculations which treat bases with dispersion-corrected DFT and the sugar-phosphate backbone with AMBER. The latter are improved by inclusion of all six bases in the QM region, since a truncated model including only the central CG base pair in the QM region is considerably further from the DFT structure. This QM/MM method is then applied to a set of double-stranded DNA heptamers derived from a recent X-ray crystallographic study, whose size puts a DFT study beyond our current computational resources. These data show that still larger structural changes are observed than in base pairs or trimers, leading us to conclude that it is important to model epigenetic modifications within realistic molecular contexts. PMID:26448859
Accurate method of modeling cluster scaling relations in modified gravity
NASA Astrophysics Data System (ADS)
He, Jian-hua; Li, Baojiu
2016-06-01
We propose a new method to model cluster scaling relations in modified gravity. Using a suite of nonradiative hydrodynamical simulations, we show that the scaling relations of accumulated gas quantities, such as the Sunyaev-Zel'dovich effect (Compton-y parameter) and the x-ray Compton-y parameter, can be accurately predicted using the known results in the Λ CDM model with a precision of ˜3 % . This method provides a reliable way to analyze the gas physics in modified gravity using the less demanding and much more efficient pure cold dark matter simulations. Our results therefore have important theoretical and practical implications in constraining gravity using cluster surveys.
Structure formation in a nonlocally modified gravity model
Park, Sohyun; Dodelson, Scott
2013-01-01
We study a nonlocally modified gravity model proposed by Deser and Woodard which gives an explanation for current cosmic acceleration. By deriving and solving the equations governing the evolution of the structure in the Universe, we show that this model predicts a pattern of growth that differs from standard general relativity (+dark energy) at the 10-30% level. These differences will be easily probed by the next generation of galaxy surveys, so the model should be tested shortly.
Knot solitons in a modified Ginzburg-Landau model
Jaeykkae, Juha; Palmu, Joonatan
2011-05-15
We study a modified version of the Ginzburg-Landau model suggested by Ward and show that Hopfions exist in it as stable static solutions, for values of the Hopf invariant up to at least 7. We also find that their properties closely follow those of their counterparts in the Faddeev-Skyrme model. Finally, we lend support to Babaev's conjecture that longer core lengths yield more stable solitons and propose a possible mechanism for constructing Hopfions in pure Ginzburg-Landau model.
Anterior EEG Asymmetry and the Modifier Model of Autism
ERIC Educational Resources Information Center
Burnette, Courtney P.; Henderson, Heather A.; Inge, Anne Pradella; Zahka, Nicole E.; Schwartz, Caley B.; Mundy, Peter C.
2011-01-01
Individual differences in the expression of autism complicate research on the nature and treatment of this disorder. In the Modifier Model of Autism (Mundy et al. 2007), we proposed that individual differences in autism may result not only from syndrome specific causal processes, but also from variability in generic, non-syndrome specific…
Frequency behaviour of the modified Jiles Atherton model
NASA Astrophysics Data System (ADS)
Chwastek, Krzysztof
2008-07-01
In the paper the behaviour of the recently modified Jiles-Atherton model of hysteresis under a distorted magnetization pattern is examined. The modification is aimed at improving the modelling of reversible processes. The equation for anhysteretic model is replaced from Langevin function to the more general Brillouin function. The structure of model equation is similar to that of the product Preisach model. The dynamic effects are taken into account in the description by the introduction of the lagged response with respect to the input.
A Modified Theoretical Model of Intrinsic Hardness of Crystalline Solids
Dai, Fu-Zhi; Zhou, Yanchun
2016-01-01
Super-hard materials have been extensively investigated due to their practical importance in numerous industrial applications. To stimulate the design and exploration of new super-hard materials, microscopic models that elucidate the fundamental factors controlling hardness are desirable. The present work modified the theoretical model of intrinsic hardness proposed by Gao. In the modification, we emphasize the critical role of appropriately decomposing a crystal to pseudo-binary crystals, which should be carried out based on the valence electron population of each bond. After modification, the model becomes self-consistent and predicts well the hardness values of many crystals, including crystals composed of complex chemical bonds. The modified model provides fundamental insights into the nature of hardness, which can facilitate the quest for intrinsic super-hard materials. PMID:27604165
A Modified Theoretical Model of Intrinsic Hardness of Crystalline Solids.
Dai, Fu-Zhi; Zhou, Yanchun
2016-01-01
Super-hard materials have been extensively investigated due to their practical importance in numerous industrial applications. To stimulate the design and exploration of new super-hard materials, microscopic models that elucidate the fundamental factors controlling hardness are desirable. The present work modified the theoretical model of intrinsic hardness proposed by Gao. In the modification, we emphasize the critical role of appropriately decomposing a crystal to pseudo-binary crystals, which should be carried out based on the valence electron population of each bond. After modification, the model becomes self-consistent and predicts well the hardness values of many crystals, including crystals composed of complex chemical bonds. The modified model provides fundamental insights into the nature of hardness, which can facilitate the quest for intrinsic super-hard materials. PMID:27604165
Priority classification of patients according to a modified 'Norwegian model'.
van Assendelft, A H
1996-01-01
A priority classification was evaluated according to a modified 'Norwegian model.' Many diseases do not belong to any specific priority category based only on the diagnosis. The classification also depends on the condition's type, site, and phase as well as the patient's age and overall condition. Savings cannot be achieved by the model used because 89% of the patients belonged to the priority categories I-III, the care of which can be classified as necessary. PMID:8707510
Rapid simulation rescaling from standard to modified gravity models
NASA Astrophysics Data System (ADS)
Mead, A. J.; Peacock, J. A.; Lombriser, L.; Li, B.
2015-10-01
We develop and test an algorithm to rescale a simulated dark-matter particle distribution or halo catalogue from a standard gravity model to that of a modified gravity model. This method is based on that of Angulo & White but with some additional ingredients to account for (i) scale-dependent growth of linear density perturbations and (ii) screening mechanisms that are generic features of viable modified gravity models. We attempt to keep the method as general as possible, so that it may plausibly be applied to a wide range of modified theories, although tests against simulations are restricted to a subclass of f (R) models at this stage. We show that rescaling allows the power spectrum of matter to be reproduced at the ˜3 per cent level in both real and redshift space up to k = 0.1h Mpc-1 if we change the box size and alter the particle displacement field; this limit can be extended to k = 1h Mpc-1 if we additionally alter halo internal structure. We simultaneously develop an algorithm that can be applied directly to a halo catalogue, in which case the halo mass function and clustering can be reproduced at the ˜5 per cent level. Finally, we investigate the clustering of halo particle distributions, generated from rescaled halo catalogues, and find that a similar accuracy can be reached.
Modelling Amperometric Biosensors Based on Chemically Modified Electrodes
Baronas, Romas; Kulys, Juozas
2008-01-01
The response of an amperometric biosensor based on a chemically modified electrode was modelled numerically. A mathematical model of the biosensor is based on a system of non-linear reaction-diffusion equations. The modelling biosensor comprises two compartments: an enzyme layer and an outer diffusion layer. In order to define the main governing parameters the corresponding dimensionless mathematical model was derived. The digital simulation was carried out using the finite difference technique. The adequacy of the model was evaluated using analytical solutions known for very specific cases of the model parameters. By changing model parameters the output results were numerically analyzed at transition and steady state conditions. The influence of the substrate and mediator concentrations as well as of the thicknesses of the enzyme and diffusion layers on the biosensor response was investigated. Calculations showed complex kinetics of the biosensor response, especially when the biosensor acts under a mixed limitation of the diffusion and the enzyme interaction with the substrate.
The Modified Semidirect Onlay Technique With Articulated Elastic Model.
Papazoglou, Efstratios; Diamantopoulou, Sofia
2015-12-01
The modified semidirect onlay technique with articulated elastic model involves the fabrication of a stone model that is quickly mounted on an articulator and it includes an elastic part that enables the fabrication of a restoration with proper occlusal anatomy. The technique overcomes the disadvantages of the direct technique such as polymerization shrinkage stress and difficulty in achieving proper contours and, compared to the indirect technique, treatment is completed in a single appointment, without laboratory cost. The novelty of the technique is that, since the restoration is fabricated on an articulated model it eliminates time for occlusal adjustments. PMID:26767243
Classifying linearly shielded modified gravity models in effective field theory.
Lombriser, Lucas; Taylor, Andy
2015-01-23
We study the model space generated by the time-dependent operator coefficients in the effective field theory of the cosmological background evolution and perturbations of modified gravity and dark energy models. We identify three classes of modified gravity models that reduce to Newtonian gravity on the small scales of linear theory. These general classes contain enough freedom to simultaneously admit a matching of the concordance model background expansion history. In particular, there exists a large model space that mimics the concordance model on all linear quasistatic subhorizon scales as well as in the background evolution. Such models also exist when restricting the theory space to operators introduced in Horndeski scalar-tensor gravity. We emphasize that whereas the partially shielded scenarios might be of interest to study in connection with tensions between large and small scale data, with conventional cosmological probes, the ability to distinguish the fully shielded scenarios from the concordance model on near-horizon scales will remain limited by cosmic variance. Novel tests of the large-scale structure remedying this deficiency and accounting for the full covariant nature of the alternative gravitational theories, however, might yield further insights on gravity in this regime. PMID:25658988
Testing model independent modified gravity with future large scale surveys
Thomas, Daniel B.; Contaldi, Carlo R. E-mail: c.contaldi@ic.ac.uk
2011-12-01
Model-independent parametrisations of modified gravity have attracted a lot of attention over the past few years and numerous combinations of experiments and observables have been suggested to constrain the parameters used in these models. Galaxy clusters have been mentioned, but not looked at as extensively in the literature as some other probes. Here we look at adding galaxy clusters into the mix of observables and examine how they could improve the constraints on the modified gravity parameters. In particular, we forecast the constraints from combining Planck satellite Cosmic Microwave Background (CMB) measurements and Sunyaev-Zeldovich (SZ) cluster catalogue with a DES-like Weak Lensing (WL) survey. We find that cluster counts significantly improve the constraints over those derived using CMB and WL. We then look at surveys further into the future, to see how much better it may be feasible to make the constraints.
Bouc-Wen hysteresis model identification using Modified Firefly Algorithm
NASA Astrophysics Data System (ADS)
Zaman, Mohammad Asif; Sikder, Urmita
2015-12-01
The parameters of Bouc-Wen hysteresis model are identified using a Modified Firefly Algorithm. The proposed algorithm uses dynamic process control parameters to improve its performance. The algorithm is used to find the model parameter values that results in the least amount of error between a set of given data points and points obtained from the Bouc-Wen model. The performance of the algorithm is compared with the performance of conventional Firefly Algorithm, Genetic Algorithm and Differential Evolution algorithm in terms of convergence rate and accuracy. Compared to the other three optimization algorithms, the proposed algorithm is found to have good convergence rate with high degree of accuracy in identifying Bouc-Wen model parameters. Finally, the proposed method is used to find the Bouc-Wen model parameters from experimental data. The obtained model is found to be in good agreement with measured data.
Guided crowd dynamics via modified social force model
NASA Astrophysics Data System (ADS)
Yang, Xiaoxia; Dong, Hairong; Wang, Qianling; Chen, Yao; Hu, Xiaoming
2014-10-01
Pedestrian dynamics is of great theoretical significance for strategy design of emergency evacuation. Modification of pedestrian dynamics based on the social force model is presented to better reflect pedestrians' behavioral characteristics in emergency. Specifically, the modified model can be used for guided crowd dynamics in large-scale public places such as subway stations and stadiums. This guided crowd model is validated by explicitly comparing its density-speed and density-flow diagrams with fundamental diagrams. Some social phenomena such as gathering, balance and conflicts are clearly observed in simulation, which further illustrate the effectiveness of the proposed modeling method. Also, time delay for pedestrians with time-dependent desired velocities is observed and explained using the established model in this paper. Furthermore, this guided crowd model is applied to the simulation system of Beijing South Railway Station for predictive evacuation experiments.
Attractive Casimir effect in an infrared modified gluon bag model
Oxman, L.E.; Amaral, R.L.P.G.
2005-12-15
In this work, we are motivated by previous attempts to derive the vacuum contribution to the bag energy in terms of familiar Casimir energy calculations for spherical geometries. A simple infrared modified model is introduced which allows studying the effects of the analytic structure as well as the geometry in a clear manner. In this context, we show that if a class of infrared vanishing effective gluon propagators is considered, then the renormalized vacuum energy for a spherical bag is attractive, as required by the bag model to adjust hadron spectroscopy.
A discrete model of a modified Burgers' partial differential equation
NASA Technical Reports Server (NTRS)
Mickens, R. E.; Shoosmith, J. N.
1990-01-01
A new finite-difference scheme is constructed for a modified Burger's equation. Three special cases of the equation are considered, and the 'exact' difference schemes for the space- and time-independent forms of the equation are presented, along with the diffusion-free case of Burger's equation modeled by a difference equation. The desired difference scheme is then obtained by imposing on any difference model of the initial equation the requirement that, in the appropriate limits, its difference scheme must reduce the results of the obtained equations.
Erosion Modeling Analysis For Modified DWPF SME Tank
LEE, SI
2004-05-03
In support of an erosion evaluation for the modified cooling coil guide and its supporting structure in the DWPF SME vessel, a computational model was developed to identify potential sites of high erosion using the same methodology established by previous work. The erosion mechanism identified in the previous work was applied to the evaluation of high erosion locations representative of the actual flow process in the modified coil guide of the SME vessel, abrasive erosion which occurs by high wall shear of viscous liquid. The results show that primary locations of the highest erosion due to the abrasive wall erosion are at the leading edge of the guide, external surface of the insert plate, the tank floor next to the insert plate of the coil guide support, and the upstream lead-in plate. The present modeling results show a good comparison between the original and the modified cases in terms of high erosion sites, as well as the degree of erosion and the calculated shear stress. Wall she ar of the tank floor is reduced by about 30 per cent because of the new coil support plate. Calculations for the impeller speed lower than 103 rpm in the SME showed similar erosion patterns but significantly reduced wall shear stresses and reduced overall erosion. Comparisons of the 103 rpm results with SME measurements indicated that no significant erosion of the tank floor in the SME is to be expected. Thus, it is recommended that the agitator speed of SME does not exceed 103 rpm.
The 'X model': a modified version of the competition theory.
Scott, O C; Révész, L; Edgren, M
1993-10-01
In 1985, Edgren et al. proposed a modified version of the competition theory to explain the interaction of sensitizers and protectors with target molecules damaged by radiation, which was designated the 'X' model. This model incorporates concepts which have been considered previously, namely that a type of radiation damage exists which cannot be chemically repaired, and that cells may contain a naturally occurring sensitizer. The model leads to testable predictions, such as, e.g. the crossing of 'K curves' when the level of protection is varied. It can only be applied to the immediate effects of radiation, i.e. before enzymatic reactions play a part. The present paper is a summary of work carried out since 1985 to test the predictions of the 'X' model and an exposition of the related algebra. PMID:7901298
Magnetic reversals in a modified shell model for magnetohydrodynamics turbulence.
Nigro, Giuseppina; Carbone, Vincenzo
2010-07-01
The aim of the paper is the study of dynamo action using a simple nonlinear model in the framework of magnetohydrodynamic turbulence. The nonlinear behavior of the system is described by using a shell model for velocity field and magnetic field fluctuations, modified for the magnetic field at the largest scale by a term describing a supercritical pitchfork bifurcation. Turbulent fluctuations generate a dynamical situation where the large-scale magnetic field jumps between two states which represent the opposite polarities of the magnetic field. Despite its simplicity, the model has the capability to describe a long time series of reversals from which we infer results about the statistics of persistence times and scaling laws of cancellations between opposite polarities for different magnetic diffusivity coefficients. These properties of the model are compared with real paleomagnetic data, thus revealing the origin of long-range correlations in the process. PMID:20866731
Magnetic reversals in a modified shell model for magnetohydrodynamics turbulence
NASA Astrophysics Data System (ADS)
Nigro, Giuseppina; Carbone, Vincenzo
2010-07-01
The aim of the paper is the study of dynamo action using a simple nonlinear model in the framework of magnetohydrodynamic turbulence. The nonlinear behavior of the system is described by using a shell model for velocity field and magnetic field fluctuations, modified for the magnetic field at the largest scale by a term describing a supercritical pitchfork bifurcation. Turbulent fluctuations generate a dynamical situation where the large-scale magnetic field jumps between two states which represent the opposite polarities of the magnetic field. Despite its simplicity, the model has the capability to describe a long time series of reversals from which we infer results about the statistics of persistence times and scaling laws of cancellations between opposite polarities for different magnetic diffusivity coefficients. These properties of the model are compared with real paleomagnetic data, thus revealing the origin of long-range correlations in the process.
Computing model independent perturbations in dark energy and modified gravity
Battye, Richard A.; Pearson, Jonathan A. E-mail: jonathan.pearson@durham.ac.uk
2014-03-01
We present a methodology for computing model independent perturbations in dark energy and modified gravity. This is done from the Lagrangian for perturbations, by showing how field content, symmetries, and physical principles are often sufficient ingredients for closing the set of perturbed fluid equations. The fluid equations close once ''equations of state for perturbations'' are identified: these are linear combinations of fluid and metric perturbations which construct gauge invariant entropy and anisotropic stress perturbations for broad classes of theories. Our main results are the proof of the equation of state for perturbations presented in a previous paper, and the development of the required calculational tools.
Rutqvist, J.; Ijiri, Y.; Yamamoto, H.
2010-06-01
This paper presents the implementation of the Barcelona Basic Model (BBM) into the TOUGH-FLAC simulator analyzing the geomechanical behavior of unsaturated soils. We implemented the BBM into TOUGH-FLAC by (1) extending an existing FLAC{sup 3D} module for the Modified Cam-Clay (MCC) model in FLAC{sup 3D} and (2) adding computational routines for suction-dependent strain and net stress (i.e., total stress minus gas pressure) for unsaturated soils. We implemented a thermo-elasto-plastic version of the BBM, wherein the soil strength depends on both suction and temperature. The implementation of the BBM into TOUGH-FLAC was verified and tested against several published numerical model simulations and laboratory experiments involving the coupled thermal-hydrological-mechanical (THM) behavior of unsaturated soils. The simulation tests included modeling the mechanical behavior of bentonite-sand mixtures, which are being considered as back-fill and buffer materials for geological disposal of spent nuclear fuel. We also tested and demonstrated the use of the BBM and TOUGH-FLAC for a problem involving the coupled THM processes within a bentonite-backfilled nuclear waste emplacement tunnel. The simulation results indicated complex geomechanical behavior of the bentonite backfill, including a nonuniform distribution of buffer porosity and density that could not be captured in an alternative, simplified, linear-elastic swelling model. As a result of the work presented in this paper, TOUGH-FLAC with BBM is now fully operational and ready to be applied to problems associated with nuclear waste disposal in bentonite-backfilled tunnels, as well as other scientific and engineering problems related to the mechanical behavior of unsaturated soils.
Vacuum structure for scalar cosmological perturbations in modified gravity models
Felice, Antonio De; Suyama, Teruaki E-mail: teruaki.suyama@uclouvain.be
2009-06-01
We have found for the general class of Modified Gravity Models f(R, G) a new instability which can arise in vacuum for the scalar modes of the cosmological perturbations if the background is not de Sitter. In particular, the short-wavelength modes, if stable, in general have a group velocity which depends linearly in k, the wave number. Therefore these modes will be in general superluminal. We have also discussed the condition for which in general these scalar modes will be ghost-like. There is a subclass of these models, defined out of properties of the function f(R, G) and to which the f(R) and f(G) models belong, which however do not have this feature.
Conceptual model for assessment of inhalation exposure: defining modifying factors.
Tielemans, Erik; Schneider, Thomas; Goede, Henk; Tischer, Martin; Warren, Nick; Kromhout, Hans; Van Tongeren, Martie; Van Hemmen, Joop; Cherrie, John W
2008-10-01
The present paper proposes a source-receptor model to schematically describe inhalation exposure to help understand the complex processes leading to inhalation of hazardous substances. The model considers a stepwise transfer of a contaminant from the source to the receptor. The conceptual model is constructed using three components, i.e. (i) the source, (ii) various transmission compartments and (iii) the receptor, and describes the contaminant's emission and its pattern of transport. Based on this conceptual model, a list of nine mutually independent principal modifying factors (MFs) is proposed: activity emission potential, substance emission potential, localized control, separation, segregation, dilution, worker behavior, surface contamination and respiratory protection. These MFs describe the exposure process at a high level of abstraction so that the model can be generically applicable. A list of exposure determinants underlying each of these principal MFs is proposed to describe the exposure process at a more detailed level. The presented conceptual model is developed in conjunction with an activity taxonomy as described in a separate paper. The proposed conceptual model and MFs should be seen as 'building blocks' for development of higher tier exposure models. PMID:18787181
General cloud cover modifier for clear sky solar radiation models
NASA Astrophysics Data System (ADS)
Myers, Daryl R.
2007-09-01
Worldwide lack of comprehensive measured solar radiation resource data for solar system design is well known. Several simple clear sky solar radiation models for computing hourly direct, diffuse and global hemispherical solar radiation have been developed over the past 25 years. The simple model of Richard Bird, Iqbal's parameterization C, and Gueymard's REST model are popular for estimating maximum hourly solar resources. We describe a simple polynomial in cloud cover (octa) modifier for these models that produces realistic time series of hourly solar radiation data representative of naturally occurring solar radiation conditions under all sky conditions. Surface cloud cover observations (Integrated Surface Hourly Data) from the National Climatic Data Center are the only additional (hourly) input data to model total hemispherical solar radiation under all sky conditions. Performance was evaluated using three years of hourly solar radiation data from 31 sites in the 1961-1990 National Solar Radiation Data Base. Mean bias errors range from - 10% to -20%, and are clear sky model dependant. Root mean square error of about 40%, are also dependent upon the particular model used and the uncertainty in the specific clear sky model inputs and lack of information on cloud type and spatial distributions.
Modified two-dimensional computational model for electrostrictive graft elastomer
NASA Astrophysics Data System (ADS)
Sun, Changjie; Wang, Youqi; Su, Ji
2004-07-01
A modified two-dimensional computational model is developed to calculate the electromechanical properties of the electrostrictive graft elastomer. The electrostrictive graft elastomer, recently developed by NASA, is a type of electro-active polymer. In a previous paper, the authors calculated electrostrictive graft elastomer electromechanical properties using a 2-D atomic force field. For this 2-D polymer structure, a much higher electric field was required to produce strain compared with that required in experiments. Two reasons could explain the higher electric field strength: (1) Polymer chain movement is restricted to a 2-D plane rather than to a 3-D plane. Out-plane dihedral torsional angle change would thus not be modeled. For this reason, 2-D polymer chains are less flexible than actual 3-D polymer chains. (2) Boundary effect of the computational model. In the original model, a unit cell consisting of a single graft unit was developed to simulate the deformation of the electrostrictive graft elastomer. The boundary of the unit cell would restrict the rotation of the graft unit. In this paper, a modified 2-D computational model is established to overcome the above problems. Firstly, three-dimensional deformations, induced by both bending angle and dihedral torsional angle changes, are projected onto a two-dimensional plane. Using both theoretical and numerical analyses, the projected 2-D equilibrium bending angle is shown to have the same value as the 3-D equilibrium bending angle. The 2-D equivalent bending stiffness is derived using a series model based upon the fact that both bending and dihedral torsion produce configuration change. The equivalent stiffness is justified by the characteristics of the polymer chain and end-to-end distance. Secondly, a self-consistent scheme is developed to eliminate the boundary effect. Eight images of the unit cell are created peripherally, with the original unit cell in the center. Thus the boundary can only affect the
Underwater striling engine design with modified one-dimensional model
NASA Astrophysics Data System (ADS)
Li, Daijin; Qin, Kan; Luo, Kai
2015-09-01
Stirling engines are regarded as an efficient and promising power system for underwater devices. Currently, many researches on one-dimensional model is used to evaluate thermodynamic performance of Stirling engine, but in which there are still some aspects which cannot be modeled with proper mathematical models such as mechanical loss or auxiliary power. In this paper, a four-cylinder double-acting Stirling engine for Unmanned Underwater Vehicles (UUVs) is discussed. And a one-dimensional model incorporated with empirical equations of mechanical loss and auxiliary power obtained from experiments is derived while referring to the Stirling engine computer model of National Aeronautics and Space Administration (NASA). The P-40 Stirling engine with sufficient testing results from NASA is utilized to validate the accuracy of this one-dimensional model. It shows that the maximum error of output power of theoretical analysis results is less than 18% over testing results, and the maximum error of input power is no more than 9%. Finally, a Stirling engine for UUVs is designed with Schmidt analysis method and the modified one-dimensional model, and the results indicate this designed engine is capable of showing desired output power.
Underwater striling engine design with modified one-dimensional model
NASA Astrophysics Data System (ADS)
Li, Daijin; Qin, Kan; Luo, Kai
2015-05-01
Stirling engines are regarded as an efficient and promising power system for underwater devices. Currently, many researches on one-dimensional model is used to evaluate thermodynamic performance of Stirling engine, but in which there are still some aspects which cannot be modeled with proper mathematical models such as mechanical loss or auxiliary power. In this paper, a four-cylinder double-acting Stirling engine for Unmanned Underwater Vehicles (UUVs) is discussed. And a one-dimensional model incorporated with empirical equations of mechanical loss and auxiliary power obtained from experiments is derived while referring to the Stirling engine computer model of National Aeronautics and Space Administration (NASA). The P-40 Stirling engine with sufficient testing results from NASA is utilized to validate the accuracy of this one-dimensional model. It shows that the maximum error of output power of theoretical analysis results is less than 18% over testing results, and the maximum error of input power is no more than 9%. Finally, a Stirling engine for UUVs is designed with Schmidt analysis method and the modified one-dimensional model, and the results indicate this designed engine is capable of showing desired output power.
Modified gravity, the Cascading DGP model and its critical tension
NASA Astrophysics Data System (ADS)
Sbisà, Fulvio
2014-12-01
We investigate the presence of instabilities in the Cascading DGP model. We start by discussing the problem of the cosmological late time acceleration, and we introduce the modified gravity approach. We then focus on brane induced gravity models and in particular on the Cascading DGP model. We consider configurations of the latter model where the source term is given simply by vacuum energy (pure tension), and we study perturbations at first order around these configurations. We perform a four-dimensional scalar-vector-tensor decomposition of the perturbations, and show that, regarding the scalar sector, the dynamics in a suitable limit can be described by a master equation. This master equation contains an energy scale (critical tension) which is related in a lion-trivial way to the parameters of the model. We give a geometrical interpretation of why this scale emerges, and explain its relevance for the presence of ghost instabilities in the theory. We comment on the difference between our result, and the one present in the literature, and stress its importance regarding the phenomenological viability of the model. We finally provide a numerical check which confirms the validity of our analysis.
A modified two-lane traffic model considering drivers' personality
NASA Astrophysics Data System (ADS)
Zhu, H. B.; Zhang, N. X.; Wu, W. J.
2015-06-01
Based on the two-lane traffic model proposed by Chowdhury et al., a modified traffic model (R-STCA model, for short) is presented, in which the new symmetric lane changing rules are introduced by considering driving behavioral difference and dynamic headway. After the numerical simulation, a broad scattering of simulated points is exhibited in the moderate density region on the flow-density plane. The synchronized flow phase accompanied with the wide moving jam phase is reproduced. The spatial-temporal profiles indicate that the vehicles move according to the R-STCA model can change lane more easily and more realistically. Then vehicles are convenient to get rid of the slow vehicles that turn into plugs ahead, and hence the capacity increases. Furthermore the phenomenon of the high speed car-following is discovered by using the R-STCA model, which has been already observed in the traffic measured data. All these results indicate that the presented model is reasonable and more realistic.
Thermodynamical Aspects of Modified Holographic Dark Energy Model
NASA Astrophysics Data System (ADS)
Li, Hui; Zhang, Yi
2014-07-01
We investigate the unified first law and the generalized second law in a modified holographic dark energy model. The thermodynamical analysis on the apparent horizon can work and the corresponding entropy formula is extracted from the systematic algorithm. The entropy correction term depends on the extra-dimension number of the brane as expected, but the interplay between the correction term and the extra dimensions is more complicated. With the unified first law of thermodynamics well-founded, the generalized second law of thermodynamics is discussed and it is found that the second law can be violated in certain circumstances. Particularly, if the number of the extra dimensions is larger than one, the generalized law of thermodynamics is always satisfied; otherwise, the validity of the second law can only be guaranteed with the Hubble radius greatly smaller than the crossover scale rc of the 5-dimensional DGP model.
Modified Chaplygin gas inspired inflationary model in braneworld scenario
NASA Astrophysics Data System (ADS)
Jawad, Abdul; Rani, Shamaila; Mohsaneen, Sidra
2016-05-01
We investigate the modified Chaplygin gas inspired inflationary regime in the brane-world framework in the presence of standard and tachyon scalar fields. We consider the intermediate inflationary scenario and construct the slow-roll parameters, e-folding numbers, spectral index, scalar and tensor power spectra, tensor to scalar ratio for both scalar field models. We develop the ns - N and r - N planes and concluded that ns˜eq96^{+0.5}_{-0.5} and r≤0.0016 for N˜eq60^{+5}_{-5} in both cases of scalar field models as well as for all values of m. These constraints are consistent with observational data such as WMAP7, WMAP9 and Planck data.
Testing Modified Gravity Models using Gravitational Waves Observation
NASA Astrophysics Data System (ADS)
Kahya, Emre
2016-07-01
Rotation curves of spiral galaxies and weak lensing as well as CMBR Power Spectrum point towards a need for different kind of matter in the universe that is not interacting electromagnetically. Alternatively one can explain rotation curves by modifying Newton's Laws which is called MOND. Relativistic versions of MOND work surprisingly good in producing structure and the community started taking these models seriously. We would like to offer a test which can test the validity of these class of models where one would get non-coincident arrival for gravitational waves and photons. We will explain why one should get a time lag between these two massless particles in the context of these so-called Dark Matter Emulators. And give an order of magnitude estimate for Shapiro delay for object which are very far away as well as more accurate ones for sources in Milky-way.
Ultralocal models of modified gravity without kinetic term
NASA Astrophysics Data System (ADS)
Brax, Philippe; Rizzo, Luca Alberto; Valageas, Patrick
2016-08-01
We present a class of modified-gravity theories which we call ultralocal models. We add a scalar field, with negligible kinetic terms, to the Einstein-Hilbert action. We also introduce a conformal coupling to matter. This gives rise to a new screening mechanism which is not entirely due to the nonlinearity of the scalar-field potential or the coupling function but to the absence of the kinetic term. As a result this removes any fifth force between isolated objects in vacuum. It turns out that these models are similar to chameleon-type theories with a large mass when considered outside the Compton wavelength but differ on shorter scales. The predictions of these models only depend on a single free function, as the potential and the coupling function are degenerate, with an amplitude given by a parameter α ≲10-6 , whose magnitude springs from requiring a small modification of Newton's potential astrophysically and cosmologically. This singles out a redshift zα˜α-1 /3≳100 where the fifth force is the greatest. The cosmological background follows the Λ cold dark matter (Λ CDM ) history within a 10-6 accuracy, while cosmological perturbations are significantly enhanced (or damped) on small scales, k ≳2 h Mpc-1 at z =0 . The spherical collapse and the halo mass function are modified in the same manner. We find that the modifications of gravity are greater for galactic or subgalactic structures. We also present a thermodynamic analysis of the nonlinear and inhomogeneous fifth-force regime where we find that the Universe is not made more inhomogeneous before zα when the fifth force dominates, and does not lead to the existence of clumped matter on extra small scales inside halos for large masses while this possibility exists for masses M ≲1 011M⊙ where the phenomenology of ultralocal models would be most different from Λ CDM .
Osseointegration of biochemically modified implants in an osteoporosis rodent model.
Stadlinger, B; Korn, P; Tödtmann, N; Eckelt, U; Range, U; Bürki, A; Ferguson, S J; Kramer, I; Kautz, A; Schnabelrauch, M; Kneissel, M; Schlottig, F
2013-01-01
The present study examined the impact of implant surface modifications on osseointegration in an osteoporotic rodent model. Sandblasted, acid-etched titanium implants were either used directly (control) or were further modified by surface conditioning with NaOH or by coating with one of the following active agents: collagen/chondroitin sulphate, simvastatin, or zoledronic acid. Control and modified implants were inserted into the proximal tibia of aged ovariectomised (OVX) osteoporotic rats (n = 32/group). In addition, aged oestrogen competent animals received either control or NaOH conditioned implants. Animals were sacrificed 2 and 4 weeks post-implantation. The excised tibiae were utilised for biomechanical and morphometric readouts (n = 8/group/readout). Biomechanical testing revealed at both time points dramatically reduced osseointegration in the tibia of oestrogen deprived osteoporotic animals compared to intact controls irrespective of NaOH exposure. Consistently, histomorphometric and microCT analyses demonstrated diminished bone-implant contact (BIC), peri-implant bone area (BA), bone volume/tissue volume (BV/TV) and bone-mineral density (BMD) in OVX animals. Surface coating with collagen/chondroitin sulphate had no detectable impact on osseointegration. Interestingly, statin coating resulted in a transient increase in BIC 2 weeks post-implantation; which, however, did not correspond to improvement of biomechanical readouts. Local exposure to zoledronic acid increased BIC, BA, BV/TV and BMD at 4 weeks. Yet this translated only into a non-significant improvement of biomechanical properties. In conclusion, this study presents a rodent model mimicking severely osteoporotic bone. Contrary to the other bioactive agents, locally released zoledronic acid had a positive impact on osseointegration albeit to a lesser extent than reported in less challenging models. PMID:23832686
Reconstruction of modified gravity with perfect fluid cosmological models
NASA Astrophysics Data System (ADS)
Singh, C. P.; Singh, Vijay
2014-04-01
In this paper we present the cosmological viability of reconstruction of an alternative gravitational theory, namely, the modified gravity, where is the Ricci scalar curvature and the trace of stress energy momentum tensor. A functional form of is chosen for the reconstruction in perfect fluid flat Friedmann-Robertson-Walker model. The gravitational field equations contain two fluid sources, one is perfect fluid and other is due to modified gravity which is to be considered as an exotic fluid. This allows us for derivation and analysis of a set of new cosmological solutions for gravity by considering these two fluids as a non-interacting. Two known forms of scale factor (de Sitter and power-law) are considered for the explicit and successful reconstruction. The equation of state parameter (EoS) of exotic matter and the effective EoS parameter have been discussed. In de Sitter solution we find that the fluid behaves as phantom dark energy when the usual matter (perfect fluid) shows the behavior between decelerated phase to accelerated phase. In the absence of usual matter it behaves as a cosmological constant. In case of power -law cosmology two different cases are discussed and analyzed the behavior of different phases of the universe accordingly through the equation of state and density parameters.
Gauss-Bonnet modified gravity models with bouncing behavior
NASA Astrophysics Data System (ADS)
Escofet, Anna; Elizalde, Emilio
2016-06-01
The following issue is addressed: How the addition of a Gauss-Bonnet term (generically coming from most fundamental theories, as string and M theories), to a viable model, can change the specific properties, and even the physical nature, of the corresponding cosmological solutions? Specifically, brand new original dark energy models are obtained in this way with quite interesting properties, which exhibit, in a unified fashion, the three distinguished possible cosmological phases corresponding to phantom matter, quintessence and ordinary matter, respectively. A model, in which the equation of state (EoS) parameter, w, is a function of time, is seen to lead either to a singularity of the Big Rip kind or to a bouncing solution which evolves into a de Sitter universe with w = ‑1. Moreover, new Gauss-Bonnet modified gravity models with bouncing behavior in the early stages of the universe evolution are obtained and tested for the validity and stability of the corresponding solutions. They allow for a remarkably natural, unified description of a bouncing behavior at early times and accelerated expansion at present.
Evaluating and modifying Johanson's rolling model to improve its predictability.
Bi, Mingda; Alvarez-Nunez, Fernando; Alvarez, Francisco
2014-07-01
The purpose of this study is to investigate if Johanson's rolling theory can correctly predict the maximum roll surface pressure during the roll compaction. Three model pharmaceutical formulations were roller compacted using the Gerteis Mini Pactor at multiple combinations of roll forces and roll gaps. The resultant ribbon density at each combination of roll force and roll gap was measured and the corresponding maximum roll surface pressure was predicted using Johanson's rolling model. The measured ribbon density and predicted maximum roll surface pressure from roller compactor was compared with the measured wafer density and maximum axial stress from die compression. The results indicate that predicted maximum roll surface pressure from roller compactor is higher than the axial stress from die compression to manufacture same density ribbons. The root cause of overprediction of maximum roll surface pressure from Johanson's model was found and corrected. The modified model offers reasonably accurate prediction of maximum roll surface pressure for all roller compaction experiments conducted in this study. PMID:24840775
Vector field models of modified gravity and the dark sector
NASA Astrophysics Data System (ADS)
Zuntz, J.; Zlosnik, T. G.; Bourliot, F.; Ferreira, P. G.; Starkman, G. D.
2010-05-01
We present a comprehensive investigation of cosmological constraints on the class of vector field formulations of modified gravity called generalized Einstein-aether models. Using linear perturbation theory we generate cosmic microwave background and large-scale structure spectra for general parameters of the theory, and then constrain them in various ways. We investigate two parameter regimes: a dark matter candidate where the vector field sources structure formation, and a dark energy candidate where it causes late-time acceleration. We find that the dark matter candidate does not fit the data, and identify five physical problems that can restrict this and other theories of dark matter. The dark energy candidate does fit the data, and we constrain its fundamental parameters; most notably we find that the theory’s kinetic index parameter nae can differ significantly from its ΛCDM value.
Vector field models of modified gravity and the dark sector
Zuntz, J.; Ferreira, P. G.; Zlosnik, T. G; Bourliot, F.; Starkman, G. D.
2010-05-15
We present a comprehensive investigation of cosmological constraints on the class of vector field formulations of modified gravity called generalized Einstein-aether models. Using linear perturbation theory we generate cosmic microwave background and large-scale structure spectra for general parameters of the theory, and then constrain them in various ways. We investigate two parameter regimes: a dark matter candidate where the vector field sources structure formation, and a dark energy candidate where it causes late-time acceleration. We find that the dark matter candidate does not fit the data, and identify five physical problems that can restrict this and other theories of dark matter. The dark energy candidate does fit the data, and we constrain its fundamental parameters; most notably we find that the theory's kinetic index parameter n{sub ae} can differ significantly from its {Lambda}CDM value.
Geographically Isolated Wetlands and Catchment Hydrology: A Modified Model Analyses
NASA Astrophysics Data System (ADS)
Evenson, G.; Golden, H. E.; Lane, C.; D'Amico, E.
2014-12-01
Geographically isolated wetlands (GIWs), typically defined as depressional wetlands surrounded by uplands, support an array of hydrological and ecological processes. However, key research questions concerning the hydrological connectivity of GIWs and their impacts on downgradient surface waters remain unanswered. This is particularly important for regulation and management of these systems. For example, in the past decade United States Supreme Court decisions suggest that GIWs can be afforded protection if significant connectivity exists between these waters and traditional navigable waters. Here we developed a simulation procedure to quantify the effects of various spatial distributions of GIWs across the landscape on the downgradient hydrograph using a refined version of the Soil and Water Assessment Tool (SWAT), a catchment-scale hydrological simulation model. We modified the SWAT FORTRAN source code and employed an alternative hydrologic response unit (HRU) definition to facilitate an improved representation of GIW hydrologic processes and connectivity relationships to other surface waters, and to quantify their downgradient hydrological effects. We applied the modified SWAT model to an ~ 202 km2 catchment in the Coastal Plain of North Carolina, USA, exhibiting a substantial population of mapped GIWs. Results from our series of GIW distribution scenarios suggest that: (1) Our representation of GIWs within SWAT conforms to field-based characterizations of regional GIWs in most respects; (2) GIWs exhibit substantial seasonally-dependent effects upon downgradient base flow; (3) GIWs mitigate peak flows, particularly following high rainfall events; and (4) The presence of GIWs on the landscape impacts the catchment water balance (e.g., by increasing groundwater outflows). Our outcomes support the hypothesis that GIWs have an important catchment-scale effect on downgradient streamflow.
Holistic versus monomeric strategies for hydrological modelling of modified hydrosystems
NASA Astrophysics Data System (ADS)
Nalbantis, I.; Efstratiadis, A.; Rozos, E.; Kopsiafti, M.; Koutsoyiannis, D.
2010-10-01
The modelling of modified basins that are inadequately measured constitutes a challenge for hydrological science. Often, models for such systems are detailed and hydraulics-based for only one part of the system while for other parts oversimplified models or rough assumptions are used. This is typically a bottom-up approach, which seeks to exploit knowledge of hydrological processes at the micro-scale at some components of the system. Also, it is a monomeric approach in two ways: first, essential interactions among system components may be poorly represented or even omitted; second, differences in the level of detail of process representation can lead to uncontrolled errors. Additionally, the calibration procedure merely accounts for the reproduction of the observed responses using typical fitting criteria. The paper aims to raise some critical issues, regarding the entire modelling approach for such hydrosystems. For this, two alternative modelling strategies are examined that reflect two modelling approaches or philosophies: a dominant bottom-up approach, which is also monomeric and very often, based on output information and a top-down and holistic approach based on generalized information. Critical options are examined, which codify the differences between the two strategies: the representation of surface, groundwater and water management processes, the schematization and parameterization concepts and the parameter estimation methodology. The first strategy is based on stand-alone models for surface and groundwater processes and for water management, which are employed sequentially. For each model, a different (detailed or coarse) parameterization is used, which is dictated by the hydrosystem schematization. The second strategy involves model integration for all processes, parsimonious parameterization and hybrid manual-automatic parameter optimization based on multiple objectives. A test case is examined in a hydrosystem in Greece with high complexities, such
Automated optic disk boundary detection by modified active contour model.
Xu, Juan; Chutatape, Opas; Chew, Paul
2007-03-01
This paper presents a novel deformable-model-based algorithm for fully automated detection of optic disk boundary in fundus images. The proposed method improves and extends the original snake (deforming-only technique) in two aspects: clustering and smoothing update. The contour points are first self-separated into edge-point group or uncertain-point group by clustering after each deformation, and these contour points are then updated by different criteria based on different groups. The updating process combines both the local and global information of the contour to achieve the balance of contour stability and accuracy. The modifications make the proposed algorithm more accurate and robust to blood vessel occlusions, noises, ill-defined edges and fuzzy contour shapes. The comparative results show that the proposed method can estimate the disk boundaries of 100 test images closer to the groundtruth, as measured by mean distance to closest point (MDCP) <3 pixels, with the better success rate when compared to those obtained by gradient vector flow snake (GVF-snake) and modified active shape models (ASM). PMID:17355059
Onset of simple liquid behaviour in modified water models
Prasad, Saurav; Chakravarty, Charusita
2014-04-28
The transition to simple liquid behaviour is studied in a set of modified hybrid water models where the potential energy contribution of the Lennard-Jones dispersion-repulsion contribution is progressively enhanced relative to the electrostatic contribution. Characteristics of simple liquid behaviour that indicate the extent to which a given system can be mapped onto an inverse power law fluid are examined, including configurational energy-virial correlations, functional form of temperature dependence of the excess entropy along isochores, and thermodynamic and excess entropy scaling of diffusivities. As the Lennard-Jones contribution to the potential energy function increases, the strength of the configurational energy-virial correlations increases. The Rosenfeld-Tarazona temperature dependence of the excess entropy is found to hold for the range of state points studied here for all the hybrid models, regardless of the degree of correlating character. Thermodynamic scaling is found to hold for weakly polar fluids with a moderate degree of energy-virial correlations. Rosenfeld-scaling of transport properties is found not to be necessarily linked with the strength of energy-virial correlations but may hold for systems with poor thermodynamic scaling if diffusivities and excess entropies show correlated departures from the isomorph-invariant behaviour characteristic of approximate inverse power law fluids. The state-point dependence of the configurational energy-virial correlation coefficient and the implications for thermodynamic and excess entropy scalings are considered.
Using Modeling to Design new Rheology Modifiers for Paints
NASA Astrophysics Data System (ADS)
Ginzburg, Valeriy
2013-03-01
Since their invention in 1970-s, hydrophobically ethoxylated urethanes (HEUR) have been actively used as rheology modifiers for paints. Thermodynamic and rheological behavior of HEUR molecules in aqueous solutions is now very well understood and is based on the concept of transient network (TN), where the association of hydrophobic groups into networks of flower micelles causes viscosity to increase dramatically as function of polymer concentration. The behavior of complex mixtures containing water, HEUR, and latex (``binder'') particles, however, is understood less well, even though it has utmost importance in the paint formulation design. In this talk, we discuss how the adsorption of HEUR chains onto latex particles results in formation of complex viscoelastic networks with temporary bridges between particles. We then utilize Self-Consistent Field Theory (SCFT) model to compute effective adsorption isotherms (thickener-on-latex) and develop a rheological theory describing steady-shear viscosity of such mixtures. The model is able to qualitatively describe many important features of the water/latex/HEUR mixtures, such as strong shear thinning. The proposed approach could potentially lead to the design of new HEUR structures with improved rheological performance. This work was supported by Dow Chemical Company
Modified Uterine Allotransplantation and Immunosuppression Procedure in the Sheep Model
Yang, Hong; Zhao, Guang-Yue; Zhang, Geng; Lu, Zhi-Hong; Huang, Yan-Hong; Ma, Xiang-Dong; Liu, Hai-Xia; Liang, Sheng-Ru; Yang, Fang; Chen, Bi-Liang
2013-01-01
Objective To develop an orthotopic, allogeneic, uterine transplantation technique and an effective immunosuppressive protocol in the sheep model. Methods In this pilot study, 10 sexually mature ewes were subjected to laparotomy and total abdominal hysterectomy with oophorectomy to procure uterus allografts. The cold ischemic time was 60 min. End-to-end vascular anastomosis was performed using continuous, non-interlocking sutures. Complete tissue reperfusion was achieved in all animals within 30 s after the vascular re-anastomosis, without any evidence of arterial or venous thrombosis. The immunosuppressive protocol consisted of tacrolimus, mycophenolate mofetil and methylprednisolone tablets. Graft viability was assessed by transrectal ultrasonography and second-look laparotomy at 2 and 4 weeks, respectively. Results Viable uterine tissue and vascular patency were observed on transrectal ultrasonography and second-look laparotomy. Histological analysis of the graft tissue (performed in one ewe) revealed normal tissue architecture with a very subtle inflammatory reaction but no edema or stasis. Conclusion We have developed a modified procedure that allowed us to successfully perform orthotopic, allogeneic, uterine transplantation in sheep, whose uterine and vascular anatomy (apart from the bicornuate uterus) is similar to the human anatomy, making the ovine model excellent for human uterine transplant research. PMID:24278415
Pattern formation through spatial interactions in a modified Daisyworld model
NASA Astrophysics Data System (ADS)
Alberti, Tommaso; Primavera, Leonardo; Lepreti, Fabio; Vecchio, Antonio; Carbone, Vincenzo
2015-04-01
The Daisyworld model is based on a hypothetical planet, like the Earth, which receives the radiant energy coming from a Sun-like star, and populated by two kinds of identical plants differing by their colour: white daisies reflecting light and black daisies absorbing light. The interactions and feedbacks between the collective biota of the planet and the incoming radiation form a self-regulating system where the conditions for life are maintained. We investigate a modified version of the Daisyworld model where a spatial dependency on latitude is introduced, and both a variable heat diffusivity along latitude and a simple greenhouse model are included. We show that the spatial interactions between the variables of the system can generate some equilibrium patterns which can locally stabilize the coexistence of the two vegetation types. The feedback on albedo is able to generate new equilibrium solutions which can efficiently self-regulate the planet climate, even for values of the solar luminosity relatively far from the current Earth conditions. The extension to spatial Daisyworld gives room to the possibility of inhomogeneous solar forcing in a curved planet, with explicit differences between poles and equator and the direct use of the heat diffusion equation. As a first approach, to describe a spherical planet, we consider the temperature T(θ,t) and the surface coverage as depending only on time and on latitude θ (-90° ≤ θ ≤ 90°). A second step is the introduction of the greenhouse effect in the model, the process by which outgoing infrared radiation is partly screened by greenhouse gases. This effect can be described by relaxing the black-body radiation hypothesis and by introducing a grayness function g(T) in the heat equation. As a third step, we consider a latitude dependence of the Earth's conductivity, χ = χ(θ). Considering these terms, using spherical coordinates and symmetry with respect to θ, the modified Daisyworld equations reduce to the
Medvedeva, N N; Zhukov, E L; Inzhevatkin, E V; Bezzabotnov, V E
2016-01-01
We studied antitumor properties of modified detonation nanodiamonds loaded with doxorubicin on in vivo model of Ehrlich ascites carcinoma. The type of tumor development and morphological characteristics of the liver, kidneys, and spleen were evaluated in experimental animals. Modified nanodiamonds injected intraperitoneally produced no antitumor effect on Ehrlich carcinoma. However, doxorubicin did not lose antitumor activity after sorption on modified nanodiamonds. PMID:26742746
Modeling of a Modified Rocha Slot Test in welded tuff
Blanford, M.L.; Zimmerman, R.M.
1987-12-31
The design of nuclear waste repositories in hard rock underground requires an understanding of how the jointed rock mass responds to the various loads introduced. The Nevada Nuclear Waste Storage Investigations (NNWSI) is conducting a series of field tests in G-Tunnel on the Nevada Test Site to characterize the behavior of welded tuff. In particular, one of the ways its modulus of deformation is being measured in situ is by means of a slot loaded by a pressurized flatjack. This is called the Modified Rocha Slot Test, after Manuel Rocha who pioneered investigations using this type of test. Numerical calculations were undertaken using the stress-wave dynamic finite difference code STEALTH. Using dynamic relaxation, the code is able to follow the quasi-static loading curve quite closely, so that the path-dependent aspects of the solution are captured economically. The material model (CAVS) represents an elastic-plastic rock matrix with evenly-spaced joints in three mutually perpendicular planes. The joints have nonlinear normal compliance, shear cohesion, and shear strength that depend on the slip history. Slip-induced dilation of the joints is also taken into consideration. Results of the calculations are presented which illustrate the stresses, deformations, and joint slippages resulting from the application of pressure loading in the slot. The stress field is remarkably sensitive to joint orientation and cohension, but rather insensitive to the normal compliance. The effect of a confining in situ stress field is also examined.
Aftershocks and Omori's law in a modified Carlson-Langer model with nonlinear viscoelasticity
NASA Astrophysics Data System (ADS)
Sakaguchi, Hidetsugu; Okamura, Kazuki
2015-05-01
A modified Carlson-Langer model for earthquakes is proposed, which includes nonlinear viscoelasticity. Several aftershocks are generated after the main shock owing to the damping of the additional viscoelastic force. Both the Gutenberg-Richter law and Omori's law are reproduced in a numerical simulation of the modified Carlson-Langer model on a critical percolation cluster of a square lattice.
NASA Astrophysics Data System (ADS)
Hamimid, M.; Mimoune, S. M.; Feliachi, M.
2012-07-01
In this present work, the minor hysteresis loops model based on parameters scaling of the modified Jiles-Atherton model is evaluated by using judicious expressions. These expressions give the minor hysteresis loops parameters as a function of the major hysteresis loop ones. They have exponential form and are obtained by parameters identification using the stochastic optimization method “simulated annealing”. The main parameters influencing the data fitting are three parameters, the pinning parameter k, the mean filed parameter α and the parameter which characterizes the shape of anhysteretic magnetization curve a. To validate this model, calculated minor hysteresis loops are compared with measured ones and good agreements are obtained.
A modified fractional Zener model to describe the behaviour of a carbon fibre reinforced polymer
NASA Astrophysics Data System (ADS)
Costa, M. Fernanda P.; Ribeiro, C.
2013-10-01
In this work a modified conventional Fractional Zener Model is deduced and applied to estimate the viscoelastic constitutive parameters of a Carbon Fibre Reinforced Polymer. The accuracy of this modified model was studied against conventional Fractional Zener model and Fractional Maxwell model, considering experimental data in the frequency domain. The set of parameters was found by solving a nonlinear constrained least square problem based on the variation of the storage and loss moduli with frequency.
Reduced-order model based feedback control of the modified Hasegawa-Wakatani model
NASA Astrophysics Data System (ADS)
Goumiri, I. R.; Rowley, C. W.; Ma, Z.; Gates, D. A.; Krommes, J. A.; Parker, J. B.
2013-04-01
In this work, the development of model-based feedback control that stabilizes an unstable equilibrium is obtained for the Modified Hasegawa-Wakatani (MHW) equations, a classic model in plasma turbulence. First, a balanced truncation (a model reduction technique that has proven successful in flow control design problems) is applied to obtain a low dimensional model of the linearized MHW equation. Then, a model-based feedback controller is designed for the reduced order model using linear quadratic regulators. Finally, a linear quadratic Gaussian controller which is more resistant to disturbances is deduced. The controller is applied on the non-reduced, nonlinear MHW equations to stabilize the equilibrium and suppress the transition to drift-wave induced turbulence.
Reduced-order model based feedback control of the modified Hasegawa-Wakatani model
Goumiri, I. R.; Rowley, C. W.; Ma, Z.; Gates, D. A.; Krommes, J. A.; Parker, J. B.
2013-04-15
In this work, the development of model-based feedback control that stabilizes an unstable equilibrium is obtained for the Modified Hasegawa-Wakatani (MHW) equations, a classic model in plasma turbulence. First, a balanced truncation (a model reduction technique that has proven successful in flow control design problems) is applied to obtain a low dimensional model of the linearized MHW equation. Then, a model-based feedback controller is designed for the reduced order model using linear quadratic regulators. Finally, a linear quadratic Gaussian controller which is more resistant to disturbances is deduced. The controller is applied on the non-reduced, nonlinear MHW equations to stabilize the equilibrium and suppress the transition to drift-wave induced turbulence.
Modified Jiles-Atherton model and parameters identification using false position method
NASA Astrophysics Data System (ADS)
Hamimid, M.; Feliachi, M.; Mimoune, S. M.
2010-04-01
In this paper, a modified Jiles-Atherton model is proposed. This model uses a physical meaning by introducing the magnetization M instead of the irreversible magnetization M irr in the effective magnetic field H e-magnetic field H relationship. The false position method is coupled to the iterative algorithm to identify the Jiles-Atherton parameters for both classical and modified Jiles-Atherton model. These parameters are evaluated by the resolution of three nonlinear equations obtained from three conditions. The validity of the modified model is done by comparing the obtained hysteresis loops to the experimental ones.
Employing a Modified Diffuser Momentum Model to Simulate Ventilation of the Orion CEV (DRAFT)
NASA Technical Reports Server (NTRS)
Straus, John; Ball, Tyler; OHara, William; Barido, Richard
2011-01-01
Computational Fluid Dynamics (CFD) is used to model the flow field in the Orion CEV cabin. The CFD model employs a momentum model used to account for the effect of supply grilles on the supply flow. The momentum model is modified to account for non-uniform velocity profiles at the approach of the supply grille. The modified momentum model is validated against a detailed vane-resolved model before inclusion into the Orion CEV cabin model. Results for this comparison, as well as that of a single ventilation configuration are presented.
A Modified Theta Projection Model for Creep Behavior of Metals and Alloys
NASA Astrophysics Data System (ADS)
Kumar, Manish; Singh, I. V.; Mishra, B. K.; Ahmad, S.; Venugopal Rao, A.; Kumar, Vikas
2016-06-01
In this work, a modified theta projection model is proposed for the constitutive modeling of creep behavior of metals and alloys. In the conventional theta projection model, strain hardening exponent is a function of time and theta, whereas in the modified theta projection model, the exponent is taken as a function of time, theta, and applied stress. The results obtained by the modified theta projection model for Al 2124 T851 alloy at constant uniaxial tensile stress are compared with the experimental results and with the predictions of the conventional theta projection method. The creep behavior of Al 7075 T651 alloy is also predicted using modified and conventional theta projection model and compared with the available experimental data. It is observed that the modified theta projection model captures the creep behavior more accurately as compared to the conventional theta projection model. The modified theta projection model can be used to predict the creep strain of pure metals and class M alloys (similar creep behavior to pure metals) for intermediate range of stress and temperature.
Principle and validation of modified hysteretic models for magnetorheological dampers
NASA Astrophysics Data System (ADS)
Bai, Xian-Xu; Chen, Peng; Qian, Li-Jun
2015-08-01
Magnetorheological (MR) dampers, semi-active actuators for vibration and shock control systems, have attracted increasing attention during the past two decades. However, it is difficult to establish a precise mathematical model for the MR dampers and their control systems due to their intrinsic strong nonlinear hysteretic behavior. A phenomenological model based on the Bouc-Wen model can be used to effectively describe the nonlinear hysteretic behavior of the MR dampers, but the structure of the phenomenological model is complex and the Bouc-Wen model is functionally redundant. In this paper, based on the phenomenological model, (1) a normalized phenomenological model is derived through incorporating a ‘normalization’ concept, and (2) a restructured model, also incorporating the ‘normalization’ concept, is proposed and realized. In order to demonstrate this, a multi-islands genetic algorithm (GA) is employed to identify the parameters of the restructured model, the normalized phenomenological model, and the phenomenological model. The performance of the three models for describing and predicting the damping force characteristics of the MR dampers are compared and analyzed using the identified parameters. The research results indicate that, as compared with the phenomenological model and the normalized phenomenological model, (1) the restructured model can not only effectively decrease the number of the model parameters and reduce the complexity of the model, but can also describe the nonlinear hysteretic behavior of MR dampers more accurately, and (2) the meanings of several model parameters of the restructured model are clearer and the initial ranges of the model parameters are more explicit, which is of significance for parameter identification.
The modified Black-Scholes model via constant elasticity of variance for stock options valuation
NASA Astrophysics Data System (ADS)
Edeki, S. O.; Owoloko, E. A.; Ugbebor, O. O.
2016-02-01
In this paper, the classical Black-Scholes option pricing model is visited. We present a modified version of the Black-Scholes model via the application of the constant elasticity of variance model (CEVM); in this case, the volatility of the stock price is shown to be a non-constant function unlike the assumption of the classical Black-Scholes model.
Modified Eulerian-Lagrangian formulation for hydrodynamic modeling
NASA Astrophysics Data System (ADS)
Sorek, Shaul; Borisov, Vyacheslav
2012-04-01
We present the modified Eulerian-Lagrangian (MEL) formulation, based on non-divergent forms of partial differential balance equations, for simulating transport of extensive quantities in a porous medium. Hydrodynamic derivatives are written in terms of modified velocities for particles propagating phase and component quantities along their respective paths. The particles physically interpreted velocities also address the heterogeneity of the matrix and fluid properties. The MEL formulation is also implemented to parabolic Partial Differential Equations (PDE's) as these are shown to be interchangeable with equivalent PDE's having hyperbolic - parabolic characteristics, without violating the same physical concepts. We prove that the MEL schemes provide a convergent and monotone approximation also to PDE's with discontinuous coefficients. An extension to the Peclet number is presented that also accounts for advective dominant PDE's with no reference to the fluid velocity or even when this velocity is not introduced. In Sorek et al. [27], a mathematical analysis for a linear system of coupled PDE's and an example of nonlinear PDE's, proved that the finite difference MEL, unlike an Eulerian scheme, guaranties the absence of spurious oscillations. Currently, we present notions of monotone interpolation associated with the MEL particle tracking procedure and prove the convergence of the MEL schemes to the original balance equation also for discontinuous coefficients on the basis of difference schemes approximating PDE's. We provide numerical examples, also with highly random fields of permeabilities and/or dispersivities, suggesting that the MEL scheme produces resolutions that are more consistent with the physical phenomenon in comparison to the Eulerian and the Eulerian-Lagrangian (EL) schemes.
Model development is of interest to ecologists, regulators and developers, since it may assist theoretical understanding, decision making in experimental design, product development and risk assessment. In order to predict the potential impacts of genetically modified (GM) plants...
Anisotropic stress and stability in modified gravity models
Saltas, Ippocratis D.; Kunz, Martin
2011-03-15
The existence of anisotropic stress of a purely geometrical origin seems to be a characteristic of higher order gravity models, and has been suggested as a probe to test these models observationally, for example, in weak lensing experiments. In this paper, we seek to find a class of higher order gravity models of f(R,G) type that would give us a zero anisotropic stress and study the consequences for the viability of the actual model. For the special case of a de Sitter background, we identify a subclass of models with the desired property. We also find a direct link between anisotropic stress and the stability of the model as well as the presence of extra degrees of freedom, which seems to be a general feature of higher order gravity models. Particularly, setting the anisotropic stress equal to zero for a de Sitter background leads to a singularity that makes it impossible to reach the de Sitter evolution.
A-Priori Tuning of Modified Magnussen Combustion Model
NASA Technical Reports Server (NTRS)
Norris, A. T.
2016-01-01
In the application of CFD to turbulent reacting flows, one of the main limitations to predictive accuracy is the chemistry model. Using a full or skeletal kinetics model may provide good predictive ability, however, at considerable computational cost. Adding the ability to account for the interaction between turbulence and chemistry improves the overall fidelity of a simulation but adds to this cost. An alternative is the use of simple models, such as the Magnussen model, which has negligible computational overhead, but lacks general predictive ability except for cases that can be tuned to the flow being solved. In this paper, a technique will be described that allows the tuning of the Magnussen model for an arbitrary fuel and flow geometry without the need to have experimental data for that particular case. The tuning is based on comparing the results of the Magnussen model and full finite-rate chemistry when applied to perfectly and partially stirred reactor simulations. In addition, a modification to the Magnussen model is proposed that allows the upper kinetic limit for the reaction rate to be set, giving better physical agreement with full kinetic mechanisms. This procedure allows a simple reacting model to be used in a predictive manner, and affords significant savings in computational costs for simulations.
The Learner-Centered Instructional Design Model: A Modified Delphi Study
ERIC Educational Resources Information Center
Melsom, Duane Allan
2010-01-01
The learner-centered instructional design model redefines the standard linear instructional design model to form a circular model where the learner's needs are the first item considered in the development of instruction. The purpose of this modified Delphi study was to have a panel of experts in the instructional design field review the…
Modelling magnetic properties of MnZn ferrites with the modified Jiles-Atherton description
NASA Astrophysics Data System (ADS)
Chwastek, K.
2010-01-01
Consideration of temperature and anisotropy effects in hysteresis modelling allows for tailoring the operation point of magnetic circuits. The recently modified Jiles-Atherton model has been extended to describe the hysteresis loops in MnZn ferrites for two temperatures below the Curie point. Anisotropy is modelled by a proper choice of the value of the quantum number J in the Brillouin function.
Modified Finch and Skea stellar model compatible with observational data
NASA Astrophysics Data System (ADS)
Pandya, D. M.; Thomas, V. O.; Sharma, R.
2015-04-01
We present a new class of solutions to the Einstein's field equations corresponding to a static spherically symmetric anisotropic system by generalizing the ansatz of Finch and Skea [Class. Quantum Grav. 6:467, 1989] for the gravitational potential g rr . The anisotropic stellar model previously studied by Sharma and Ratanpal [Int. J. Mod. Phys. D 13:1350074, 2013] is a sub-class of the solutions provided here. Based on physical requirements, regularity conditions and stability, we prescribe bounds on the model parameters. By systematically fixing values of the model parameters within the prescribed bound, we demonstrate that our model is compatible with the observed masses and radii of a wide variety of compact stars like 4U 1820-30, PSR J1903+327, 4U 1608-52, Vela X-1, PSR J1614-2230, SAX J1808.4-3658 and Her X-1.
Spherical collapse and cluster counts in modified gravity models
Martino, Matthew C.; Stabenau, Hans F.; Sheth, Ravi K.
2009-04-15
Modifications to the gravitational potential affect the nonlinear gravitational evolution of large scale structures in the Universe. To illustrate some generic features of such changes, we study the evolution of spherically symmetric perturbations when the modification is of Yukawa type; this is nontrivial, because we should not and do not assume that Birkhoff's theorem applies. We then show how to estimate the abundance of virialized objects in such models. Comparison with numerical simulations shows reasonable agreement: When normalized to have the same fluctuations at early times, weaker large scale gravity produces fewer massive halos. However, the opposite can be true for models that are normalized to have the same linear theory power spectrum today, so the abundance of rich clusters potentially places interesting constraints on such models. Our analysis also indicates that the formation histories and abundances of sufficiently low mass objects are unchanged from standard gravity. This explains why simulations have found that the nonlinear power spectrum at large k is unaffected by such modifications to the gravitational potential. In addition, the most massive objects in models with normalized cosmic microwave background and weaker gravity are expected to be similar to the high-redshift progenitors of the most massive objects in models with stronger gravity. Thus, the difference between the cluster and field galaxy populations is expected to be larger in models with stronger large scale gravity.
Modified version of the combined model of photonucleon reactions
Ishkhanov, B. S.; Orlin, V. N.
2015-07-15
A refined version of the combined photonucleon-reaction model is described. This version makes it possible to take into account the effect of structural features of the doorway dipole state on photonucleon reactions in the energy range of E{sub γ} ≤ 30 MeV. In relation to the previous version of the model, the treatment of isospin effects at the preequilibrium and evaporation reaction stages is refined; in addition, the description of the semidirect effect caused by nucleon emission from the doorway dipole state is improved. The model in question is used to study photonucleon reactions on the isotopes {sup 35-56}Ca and {sup 102-134}Sn in the energy range indicated above.
Modified 'Joyce model' of opioid dependence/withdrawal.
Raffa, Robert B; Tallarida, Ronald J
2006-12-01
By comprehensive and detailed measurement of the time course of withdrawal signs in rats, Joyce et al. (J. Theo. Biol. 240:531-537, 2006) recently provided a creative quantitative model of the onset of drug dependence based on the requirement of protein synthesis. Because the initial model fit the data imperfectly over the full time course, those authors postulated that additional features would be needed. We report excellent fit of the data (R(2)=0.96) by adding: (1) a transient early phase, and (2) a delay in the buildup of protein. PMID:17045985
Geographically isolated wetlands and watershed hydrology: A modified model analysis
NASA Astrophysics Data System (ADS)
Evenson, Grey R.; Golden, Heather E.; Lane, Charles R.; D'Amico, Ellen
2015-10-01
Geographically isolated wetlands (GIWs) are defined as wetlands that are completely surrounded by uplands. While GIWs are therefore spatially isolated, field-based studies have observed a continuum of hydrologic connections between these systems and other surface waters. Yet few studies have quantified the watershed-scale aggregate effects of GIWs on downstream hydrology. Further, existing modeling approaches to evaluate GIW effects at a watershed scale have utilized conceptual or spatially disaggregated wetland representations. Working towards wetland model representations that use spatially explicit approaches may improve current scientific understanding concerning GIW effects on the downstream hydrograph. The objective of this study was to quantify the watershed-scale aggregate effects of GIWs on downstream hydrology while emphasizing a spatially explicit representation of GIWs and GIW connectivity relationships. We constructed a hydrologic model for a ∼202 km2 watershed in the Coastal Plain of North Carolina, USA, a watershed with a substantial population of GIWs, using the Soil and Water Assessment Tool (SWAT). We applied a novel representation of GIWs within the model, facilitated by an alternative hydrologic response unit (HRU) definition and modifications to the SWAT source code that extended the model's "pothole" representation. We then executed a series of scenarios to assess the downstream hydrologic effect of various distributions of GIWs within the watershed. Results suggest that: (1) GIWs have seasonally dependent effects on baseflow; (2) GIWs mitigate peak flows; and (3) The presence of GIWs on the landscape impacts the watershed water balance. This work demonstrates a means of GIW simulation with improved spatial detail while showing that GIWs, in-aggregate, have a substantial effect on downstream hydrology in the studied watershed.
A modified NaSch model with density-dependent randomization for traffic flow
NASA Astrophysics Data System (ADS)
Zhu, H. B.; Ge, H. X.; Dong, L. Y.; Dai, S. Q.
2007-05-01
Based on the Nagel-Schreckenberg (NaSch) model of traffic flow, a modified cellular automaton (CA) traffic model with the density-dependent randomization (abbreviated as the DDR model) is proposed to simulate traffic flow. The fundamental diagram obtained by simulation shows the ability of this modified NaSch model to capture the essential features of traffic flow, e.g., synchronized flow, metastable state, hysteresis and phase separation at higher densities. Comparisons are made between this DDR model and the NaSch model, also between this DDR model and the VDR model. And the underlying mechanism is analyzed. All these results indicate that the presented model is reasonable and more realistic.
Justification of sexual reproduction by modified Penna model of ageing
NASA Astrophysics Data System (ADS)
Sá Martins, J. S.; Stauffer, D.
2001-05-01
We generalize the standard Penna bit-string model of biological ageing by assuming that each deleterious mutation diminishes the survival probability in every time interval by a small percentage. This effect is added to the usual lethal but age-dependent effect of the same mutation. We then find strong advantages or disadvantages of sexual reproduction (with males and females) compared to asexual cloning, depending on parameters.
Martin, Jean-Charles; Berton, Amélie; Ginies, Christian; Bott, Romain; Scheercousse, Pierre; Saddi, Alessandra; Gripois, Daniel; Landrier, Jean-François; Dalemans, Daniel; Alessi, Marie-Christine; Delplanque, Bernadette
2015-09-01
We assessed the atheroprotective efficiency of modified dairy fats in hyperlipidemic hamsters. A systems biology approach was implemented to reveal and quantify the dietary fat-related components of the disease. Three modified dairy fats (40% energy) were prepared from regular butter by mixing with a plant oil mixture, by removing cholesterol alone, or by removing cholesterol in combination with reducing saturated fatty acids. A plant oil mixture and a regular butter were used as control diets. The atherosclerosis severity (aortic cholesteryl-ester level) was higher in the regular butter-fed hamsters than in the other four groups (P < 0.05). Eighty-seven of the 1,666 variables measured from multiplatform analysis were found to be strongly associated with the disease. When aggregated into 10 biological clusters combined into a multivariate predictive equation, these 87 variables explained 81% of the disease variability. The biological cluster "regulation of lipid transport and metabolism" appeared central to atherogenic development relative to diets. The "vitamin E metabolism" cluster was the main driver of atheroprotection with the best performing transformed dairy fat. Under conditions that promote atherosclerosis, the impact of dairy fats on atherogenesis could be greatly ameliorated by technological modifications. Our modeling approach allowed for identifying and quantifying the contribution of complex factors to atherogenic development in each dietary setup. PMID:26071539
Akbarzadeh, Pooria
2016-05-12
In this paper, magneto-hydrodynamic blood flows through porous arteries are numerically simulated using a locally modified homogenous nanofluids model. Blood is taken into account as the third-grade non-Newtonian fluid containing nanoparticles. In the modified nanofluids model, the viscosity, density, and thermal conductivity of the solid-liquid mixture (nanofluids) which are commonly utilized as an effective value, are locally combined with the prevalent single-phase model. The modified governing equations are solved numerically using Newton's method and a block tridiagonal matrix solver. The results are compared to the prevalent nanofluids single-phase model. In addition, the efficacies of important physical parameters such as pressure gradient, Brownian motion parameter, thermophoresis parameter, magnetic-field parameter, porosity parameter, and etc. on temperature, velocity and nanoparticles concentration profiles are examined. PMID:27175464
2015 Guidelines for Establishing Genetically Modified Rat Models for Cardiovascular Research
Flister, Michael J.; Prokop, Jeremy W.; Lazar, Jozef; Shimoyama, Mary; Dwinell, Melinda; Geurts, Aron
2015-01-01
The rat has long been a key physiological model for cardiovascular research; most of the inbred strains having been previously selected for susceptibility or resistance to various cardiovascular diseases (CVD). These CVD rat models offer a physiologically relevant background on which candidates of human CVD can be tested in a more clinically translatable experimental setting. However, a diverse toolbox for genetically modifying the rat genome to test molecular mechanisms has only recently become available. Here, we provide a high-level description of several strategies for developing genetically modified rat models of CVD. PMID:25920443
An empirical modified fatigue damage model for impacted GFRP laminates
NASA Astrophysics Data System (ADS)
Naderi, S.; Hassan, M. A.; Bushroa, A. R.
2014-10-01
The aim of the present paper is to evaluate the residual strength of GFRP laminates following a low-velocity impact event under cyclic loading. The residual strength is calculated using a linear fatigue damage model. According to an investigation into the effect of low-velocity impact on the fatigue behavior of laminates, it seems laminate fatigue life decreases after impact. By normalizing the fatigue stress against undamaged static strength, the Fatigue Damage parameter “FD” is presented with a linear relationship as its slope which is a linear function of the initial impact energy; meanwhile, the constants were attained from experimental data. FD is implemented into a plane-stress continuum damage mechanics based model for GFRP composite laminates, in order to predict damage threshold in composite structures. An S-N curve is implemented to indicate the fatigue behavior for 2 mm thickness encompassing both undamaged and impacted samples. A decline in lifespan is evident when the impact energy level increases. Finally, the FD is intended to capture the unique GFRP composite characteristics.
ERIC Educational Resources Information Center
MacSwan, Jeff
2005-01-01
This article presents an empirical and theoretical critique of the Matrix Language Frame (MLF) model (Myers-Scotton, 1993; Myers-Scotton and Jake, 2001), and includes a response to Jake, Myers-Scotton and Gross's (2002) (JMSG) critique of MacSwan (1999, 2000) and reactions to their revision of the MLF model as a "modified minimalist approach." The…
Existence of Periodic Solutions for a Modified Growth Solow Model
NASA Astrophysics Data System (ADS)
Fabião, Fátima; Borges, Maria João
2010-10-01
In this paper we analyze the dynamic of the Solow growth model with a Cobb-Douglas production function. For this purpose, we consider that the labour growth rate, L'(t)/L(t), is a T-periodic function, for a fixed positive real number T. We obtain the closed form solutions for the fundamental Solow equation with the new description of L(t). Using notions of the qualitative theory of ordinary differential equations and nonlinear functional analysis, we prove that there exists one T-periodic solution for the Solow equation. From the economic point of view this is a new result which allows a more realistic interpretation of the stylized facts.
Breather-like structures in modified sine-Gordon models
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Zakrzewski, Wojtek J.
2016-05-01
We report analytical and numerical results on breather-like field configurations in a theory which is a deformation of the integrable sine-Gordon model in (1 + 1) dimensions. The main motivation of our study is to test the ideas behind the recently proposed concept of quasi-integrability, which emerged from the observation that some field theories possess an infinite number of quantities which are asymptotically conserved in the scattering of solitons, and periodic in time in the case of breather-like configurations. Even though the mechanism responsible for such phenomena is not well understood yet, it is clear that special properties of the solutions under a space-time parity transformation play a crucial role. The numerical results of the present paper give support for the ideas on quasi-integrability, as it is found that extremely long-lived breather configurations satisfy these parity properties. We also report on a mechanism, particular to the theory studied here, that favours the existence of long lived breathers even in cases of significant deformations of the sine-Gordon potential. We also find numerically that our breather-like configurations decay through the gradual increase of their frequency of oscillations.
Supports and modified nano-particles for designing model catalysts.
O'Brien, C P; Dostert, K-H; Hollerer, M; Stiehler, C; Calaza, F; Schauermann, S; Shaikhutdinov, S; Sterrer, M; Freund, H-J
2016-07-01
In order to design catalytic materials, we need to understand the essential causes for material properties resulting from its composite nature. In this paper we discuss two, at first sight, diverse aspects: (a) the effect of the oxide-metal interface on metal nanoparticle properties and (b) the consequences of metal particle modification after activation on the selectivity of hydrogenation reactions. However, these two aspects are intimately linked. The metal nanoparticle's electronic structure changes at the interface as a catalyst is brought to different reaction temperatures due to morphological modifications in the metal and, as we will discuss, these changes in the chemistry lead to changes in the reaction path. As the morphology of the particle varies, facets of different orientations and sizes are exposed, which may lead to a change in the surface chemistry as well. We use two specific reactions to address these issues in some detail. To the best of our knowledge, the present paper reports the first observations of this kind for well-defined model systems. The changes in the electronic structure of Au nanoparticles due to their size and interaction with a supporting oxide are revealed as a function of temperature using CO2 activation as a probe. The presence of spectator species (oxopropyl), formed during an activation step of acrolein hydrogenation, strongly controls the selectivity of the reaction towards hydrogenation of the unsaturated C[double bond, length as m-dash]O bond vs. the C[double bond, length as m-dash]C bond on Pd(111) when compared with oxide-supported Pd nanoparticles. PMID:27064816
Comparison of Nonlinear Model Results Using Modified Recorded and Synthetic Ground Motions
Robert E. Spears; J. Kevin Wilkins
2011-11-01
A study has been performed that compares results of nonlinear model runs using two sets of earthquake ground motion time histories that have been modified to fit the same design response spectra. The time histories include applicable modified recorded earthquake ground motion time histories and synthetic ground motion time histories. The modified recorded earthquake ground motion time histories are modified from time history records that are selected based on consistent magnitude and distance. The synthetic ground motion time histories are generated using appropriate Fourier amplitude spectrums, Arias intensity, and drift correction. All of the time history modification is performed using the same algorithm to fit the design response spectra. The study provides data to demonstrate that properly managed synthetic ground motion time histories are reasonable for use in nonlinear seismic analysis.
Hannan, Shabab B; Dräger, Nina M; Rasse, Tobias M; Voigt, Aaron; Jahn, Thomas R
2016-04-01
Abnormal tau accumulations were observed and documented in post-mortem brains of patients affected by Alzheimer's disease (AD) long before the identification of mutations in the Microtubule-associated protein tau (MAPT) gene, encoding the tau protein, in a different neurodegenerative disease called Frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17). The discovery of mutations in the MAPT gene associated with FTDP-17 highlighted that dysfunctions in tau alone are sufficient to cause neurodegeneration. Invertebrate models have been diligently utilized in investigating tauopathies, contributing to the understanding of cellular and molecular pathways involved in disease etiology. An important discovery came with the demonstration that over-expression of human tau in Drosophila leads to premature mortality and neuronal dysfunction including neurodegeneration, recapitulating some key neuropathological features of the human disease. The simplicity of handling invertebrate models combined with the availability of a diverse range of experimental resources make these models, in particular Drosophila a powerful invertebrate screening tool. Consequently, several large-scale screens have been performed using Drosophila, to identify modifiers of tau toxicity. The screens have revealed not only common cellular and molecular pathways, but in some instances the same modifier has been independently identified in two or more screens suggesting a possible role for these modifiers in regulating tau toxicity. The purpose of this review is to discuss the genetic modifier screens on tauopathies performed in Drosophila and C. elegans models, and to highlight the common cellular and molecular pathways that have emerged from these studies. Here, we summarize results of tau toxicity screens providing mechanistic insights into pathological alterations in tauopathies. Key pathways or modifiers that have been identified are associated with a broad range of processes
Using Modified J-A model in MMM detection at elastic stress stage
NASA Astrophysics Data System (ADS)
Xu, MingXiu; Xu, MinQiang; Li, JianWei; Xing, HaiYan
2012-06-01
In order to propel the development of metal magnetic memory (MMM) technique in fatigue damage detection, a modified Jiles-Atherton (J-A) model is constructed to describe MMM mechanism in elastic stress stage. The MMM phenomenon is discussed from the view of energy minimum theory and equivalent magnetic field theory, the modified J-A model is constructed based on the energy balance in the process of magnetisation and the idea of J-A model, and the new model is used to simulate magnetomechanical effect by Matlab and compare with experimental results. It is shown that the forming process of MMM field is cyclic magnetisation in the range of equivalent magnetic field and the MMM field moves irreversibly towards a local equilibrium state ? . ? is the intermediate state with some pinning before M reaches the anhysteretic magnetisation state ? . The ? curve is a loop around the ? curve, and it changes with ? , H and the type of stress cycle. The modified J-A model that is suited for MMM detection is constructed by replacing ? in J-A model with ? and changing some parameters, and it can describe magnetisation features in tension, release processes better and explain the changes in the sign of ? that have been observed in experiments more reasonably. The modified J-A model can simulate the process of MMM field to become steady and the MMM field variation at fatigue process theoretically by changing model parameters, which is confirmed by experimental results. The results of theoretical research, simulation analysis and experiment verification all indicate that the modified J-A model can be used to describe MMM mechanism in elastic stress stage and analyse MMM field changes at fatigue process.
Odor emission rate estimation of indoor industrial sources using a modified inverse modeling method.
Li, Xiang; Wang, Tingting; Sattayatewa, Chakkrid; Venkatesan, Dhesikan; Noll, Kenneth E; Pagilla, Krishna R; Moschandreas, Demetrios J
2011-08-01
Odor emission rates are commonly measured in the laboratory or occasionally estimated with inverse modeling techniques. A modified inverse modeling approach is used to estimate source emission rates inside of a postdigestion centrifuge building of a water reclamation plant. Conventionally, inverse modeling methods divide an indoor environment in zones on the basis of structural design and estimate source emission rates using models that assume homogeneous distribution of agent concentrations within a zone and experimentally determined link functions to simulate airflows among zones. The modified approach segregates zones as a function of agent distribution rather than building design and identifies near and far fields. Near-field agent concentrations do not satisfy the assumption of homogeneous odor concentrations; far-field concentrations satisfy this assumption and are the only ones used to estimate emission rates. The predictive ability of the modified inverse modeling approach was validated with measured emission rate values; the difference between corresponding estimated and measured odor emission rates is not statistically significant. Similarly, the difference between measured and estimated hydrogen sulfide emission rates is also not statistically significant. The modified inverse modeling approach is easy to perform because it uses odor and odorant field measurements instead of complex chamber emission rate measurements. PMID:21874959
Minor loops modelling with a modified Jiles-Atherton model and comparison with the Preisach model
NASA Astrophysics Data System (ADS)
Benabou, A.; Leite, J. V.; Clénet, S.; Simão, C.; Sadowski, N.
When modelling electrical devices, one has to estimate quite accurately the iron losses for the sake of efficiency. The use of non-sinusoidal electrical sources increases the harmonic content in electrical systems and, consequently, increases significantly the magnetic losses in devices feed by these sources. The harmonic content adds non-centred minor hysteresis loops over the classical major one. The numerical tool used for the material modelling must be able to represent the magnetic behaviour in such conditions. Then, the use of a hysteresis model is the more suited solution, but the chosen model has to take into account correctly the minor loops. The Jiles-Atherton hysteresis model is one of the most employed, due its well-known properties, but it is not able to represent closed minor loops. In this work, we propose a simple approach based on experimental observations and empirical considerations, to improve the representation of minor loops in this model by keeping its simplicity of use and implementation in a FE calculation code. Differently to other approaches found in the literature, the previous knowledge of the magnetic field evolution is not needed. A comparison between measured and calculated curves, as well with the Preisach model, is performed to validate the model.
Hydrophobic solvation of Gay-Berne particles in modified water models
NASA Astrophysics Data System (ADS)
Head-Gordon, Teresa; Lynden-Bell, Ruth M.
2008-03-01
The solvation of large hydrophobic solutes, modeled as repulsive and attractive Gay-Berne oblate ellipsoids, is characterized in several modified water liquids using the SPC/E model as the reference water fluid. We find that small amounts of attraction between the Gay-Berne particle and any model fluid result in wetting of the hydrophobic surface. However, significant differences are found among the modified and SPC/E water models and the critical distances in which they dewet the hydrophobic surfaces of pairs of repulsive Gay-Berne particles. We find that the dewetting trends for repulsive Gay-Berne particles in the various model liquids correlate directly with their surface tensions, the widths of the interfaces they form, and the openness of their network structure. The largest critical separations are found in liquids with the smallest surface tensions and the broadest interfaces as measured by the Egelstaff-Widom length.
Hydrophobic solvation of Gay-Berne particles in modified water models.
Head-Gordon, Teresa; Lynden-Bell, Ruth M
2008-03-14
The solvation of large hydrophobic solutes, modeled as repulsive and attractive Gay-Berne oblate ellipsoids, is characterized in several modified water liquids using the SPC/E model as the reference water fluid. We find that small amounts of attraction between the Gay-Berne particle and any model fluid result in wetting of the hydrophobic surface. However, significant differences are found among the modified and SPC/E water models and the critical distances in which they dewet the hydrophobic surfaces of pairs of repulsive Gay-Berne particles. We find that the dewetting trends for repulsive Gay-Berne particles in the various model liquids correlate directly with their surface tensions, the widths of the interfaces they form, and the openness of their network structure. The largest critical separations are found in liquids with the smallest surface tensions and the broadest interfaces as measured by the Egelstaff-Widom length. PMID:18345905
Genetically modified mouse models for the study of nonalcoholic fatty liver disease
Nagarajan, Perumal; Mahesh Kumar, M Jerald; Venkatesan, Ramasamy; Majundar, Subeer S; Juyal, Ramesh C
2012-01-01
Nonalcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance, and type 2 diabetes. NAFLD represents a large spectrum of diseases ranging from (1) fatty liver (hepatic steatosis); (2) steatosis with inflammation and necrosis; to (3) cirrhosis. The animal models to study NAFLD/nonalcoholic steatohepatitis (NASH) are extremely useful, as there are still many events to be elucidated in the pathology of NASH. The study of the established animal models has provided many clues in the pathogenesis of steatosis and steatohepatitis, but these remain incompletely understood. The different mouse models can be classified in two large groups. The first one includes genetically modified (transgenic or knockout) mice that spontaneously develop liver disease, and the second one includes mice that acquire the disease after dietary or pharmacological manipulation. Although the molecular mechanism leading to the development of hepatic steatosis in the pathogenesis of NAFLD is complex, genetically modified animal models may be a key for the treatment of NAFLD. Ideal animal models for NASH should closely resemble the pathological characteristics observed in humans. To date, no single animal model has encompassed the full spectrum of human disease progression, but they can imitate particular characteristics of human disease. Therefore, it is important that the researchers choose the appropriate animal model. This review discusses various genetically modified animal models developed and used in research on NAFLD. PMID:22468076
Linden, D.S.
1993-05-01
The traditional two-fluid model of superconducting conductivity was modified to make it accurate, while remaining fast, for designing and simulating microwave devices. The modification reflects the BCS coherence effects in the conductivity of a superconductor, and is incorporated through the ratio of normal to superconducting electrons. This modified ratio is a simple analytical expression which depends on frequency, temperature and material parameters. This modified two-fluid model allows accurate and rapid calculation of the microwave surface impedance of a superconductor in the clean and dirty limits and in the weak- and strong-coupled regimes. The model compares well with surface resistance data for Nb and provides insight into Nb3Sn and Y1Ba2Cu3O(7-delta). Numerical calculations with the modified two-fluid model are an order of magnitude faster than the quasi-classical program by Zimmermann (1), and two to five orders of magnitude faster than Halbritter's BCS program (2) for surface resistance.
Rigorous Self-organised Criticality in the Modified Bak-Sneppen Model
NASA Astrophysics Data System (ADS)
Meester, Ronald; Sarkar, Anish
2012-11-01
We prove that a modified version of the Bak-Sneppen model obeys power law behaviour for avalanche duration and size. We do this through a coupling with a suitable branching process which is known to have power law behaviour at criticality.
NASA Astrophysics Data System (ADS)
Dong, Xinling; Zhang, Zhihua; Moore, John
2014-05-01
Most land surface models (LSMs) do not perform well in representing permafrost dynamics and snow properties. Due to the complex permafrost distribution characteristics and the differenncesbetween vegetation coverage types and snow-covered land, the LSMs simulations are even worse. In this study, we modified the permafrost scheme in the Common Land Model (CoLM) to improve its capability of simulating permafrost processes and snow density process. We adopted a new frozen soil parameterization scheme, the present version of CoLM includes permafrost layers down to 3.4 meters in ten different thicknesses. Based on literature and temperature gradient measurements, we extended the soil column to 25 soil layers and bottom depth to 15.4 m. Moreover, we revise the original snow cover fraction parameterization of CoLM according to specific snow cover characteristics including the effects of wind compaction on snow density in treeless regions. We have compared and validated the modified model against in situ soil temperatures from 431 Russian observation stations between 1973 and 2006. The modified model produces more accurate surface temperature simulation results. The modified CoLM provides a useful tool for understanding and predicting the fate of permafrost under a warming climate.
On the Prediction of Separation Bubbles Using a Modified Chen-Thyson Model
NASA Technical Reports Server (NTRS)
Platzer, Max F.; Ekaterinaris, John A.; Chandrasekhara, M. S.
2007-01-01
The prediction of separation bubbles on NACA 65-213 and NACA 0012 using a modified Chen-Thyson transition model is presented. The contents include: 1) Background; 2) Analysis of NACA 65-213 separation bubble using cebeci's viscous-inviscid interaction method; 3) Analysis of NACA 0012 separation bubble using navier-stokes method; and 4) Comparison with experiment.
A modified Fresnel scattering model for the parameterization of Fresnel returns, part 2.3A
NASA Technical Reports Server (NTRS)
Gage, K. S.; Ecklund, W. L.; Balsley, B. B.
1984-01-01
A modified Fresnel scatter model is presented and the revised model is compared with observations from the Poker Flat, Alaska, radar, the SOUSY radar and the Jimcamarca radar. The modifications to the original model have been made to better account for the pulse width dependence and height dependence of backscattered power observed at vertical incidence at lower VHF. Vertical profiles of backscattered power calculated using the revised model and routine radiosonde data show good agreement with observed backscattered power profiles. Relative comparisons of backscattered power using climatological data for the model agree fairly well with observed backscattered power profiles from Poker Flat, Jicamarca, and SOUSY.
NASA Astrophysics Data System (ADS)
Mead, A. J.; Heymans, C.; Lombriser, L.; Peacock, J. A.; Steele, O. I.; Winther, H. A.
2016-06-01
We present an accurate non-linear matter power spectrum prediction scheme for a variety of extensions to the standard cosmological paradigm, which uses the tuned halo model previously developed in Mead et al. We consider dark energy models that are both minimally and non-minimally coupled, massive neutrinos and modified gravitational forces with chameleon and Vainshtein screening mechanisms. In all cases, we compare halo-model power spectra to measurements from high-resolution simulations. We show that the tuned halo-model method can predict the non-linear matter power spectrum measured from simulations of parametrized w(a) dark energy models at the few per cent level for k < 10 h Mpc-1, and we present theoretically motivated extensions to cover non-minimally coupled scalar fields, massive neutrinos and Vainshtein screened modified gravity models that result in few per cent accurate power spectra for k < 10 h Mpc-1. For chameleon screened models, we achieve only 10 per cent accuracy for the same range of scales. Finally, we use our halo model to investigate degeneracies between different extensions to the standard cosmological model, finding that the impact of baryonic feedback on the non-linear matter power spectrum can be considered independently of modified gravity or massive neutrino extensions. In contrast, considering the impact of modified gravity and massive neutrinos independently results in biased estimates of power at the level of 5 per cent at scales k > 0.5 h Mpc-1. An updated version of our publicly available HMCODE can be found at https://github.com/alexander-mead/hmcode.
NASA Astrophysics Data System (ADS)
Hussain, G.; Hameed, A.; Hetherington, J. G.; Barton, P. C.; Malik, A. Q.
2013-04-01
The formation of mild steel (MS) and copper (Cu) explosively formed projectiles (EFPs) was simulated in AUTODYN using both the Johnson-Cook (JC) and modified Johnson-Cook (JCM) constitutive models. The JC model was modified by increasing the hardening constant by 10%. The previously established semi-empirical equations for diameter, length, velocity, and depth of penetration were used to verify the design of the EFP. The length-to-diameter (L/D) ratio of the warhead used in the simulation varied between 1 < L/D < 2. To avoid projectile distortion or breakup for large standoff applications, the design of the EFP warhead was modified to obtain a lower L/D ratio. Simulations from the JC model underestimated the EFP diameter, resulting in an unrealistically elongated projectile. This shortcoming was resolved by employing the JCM model, giving good agreement with the experimental results. The projectile velocity and hole characteristics in 10-mm-thick aluminum target plates were studied for both models. The semi-empirical equations and the JC model overestimated the projectile velocity, whereas the JCM model underestimated the velocity slightly when compared to the experimental results. The depths of penetration calculated by the semi-empirical equations in the aluminum (Al) target plate were 55 and 52 mm for Cu and MS EFPs, respectively.
NASA Astrophysics Data System (ADS)
Nishioka, Kensuke; Sakitani, Nobuhiro; Kurobe, Ken-ichi; Yamamoto, Yukie; Ishikawa, Yasuaki; Uraoka, Yukiharu; Fuyuki, Takashi
2003-12-01
We have evaluated the influence of grain boundaries on the temperature dependence of cell performance using a modified 2-diode equivalent circuit model. In this model, microscopic inhomogeneity of resistivity at or near grain boundaries can be taken into consideration. The calculated results by the modified 2-diode model agreed well with the measured current-voltage curves, and the validity of the fitting parameters in this model was discussed. One of the fitting parameters, r is defined as the ratio of the recombination area, in which the recombination of minority carriers is pronounced. At 20°C, r of the polycrystalline Si cell was larger than that of the single-crystalline Si cell. However, the difference in r between them became negligible at temperatures above 80°C. These dependences were explained by considering the behavior of the free carriers in the recombination centers.
A modified multiple-relaxation-time lattice Boltzmann model for convection-diffusion equation
NASA Astrophysics Data System (ADS)
Huang, Rongzong; Wu, Huiying
2014-10-01
A modified lattice Boltzmann model with multiple relaxation times (MRT) for the convection-diffusion equation (CDE) is proposed. By modifying the relaxation matrix, as well as choosing the corresponding equilibrium distribution function properly, the present model can recover the CDE with anisotropic diffusion coefficient with no deviation term even when the velocity vector varies generally with space or time through the Chapman-Enskog analysis. This model is firstly validated by simulating the diffusion of a Gaussian hill, which demonstrates it can handle the anisotropic diffusion problem correctly. Then it is adopted to calculate the longitudinal dispersion coefficient of the Taylo-Aris dispersion. Numerical results show that the present model can further reduce the numerical error under the condition of non-zero velocity vector, especially when the dimensionless relaxation time is relatively large.
Modified graphical autocatalytic set model of combustion process in circulating fluidized bed boiler
NASA Astrophysics Data System (ADS)
Yusof, Nurul Syazwani; Bakar, Sumarni Abu; Ismail, Razidah
2014-07-01
Circulating Fluidized Bed Boiler (CFB) is a device for generating steam by burning fossil fuels in a furnace operating under a special hydrodynamic condition. Autocatalytic Set has provided a graphical model of chemical reactions that occurred during combustion process in CFB. Eight important chemical substances known as species were represented as nodes and catalytic relationships between nodes are represented by the edges in the graph. In this paper, the model is extended and modified by considering other relevant chemical reactions that also exist during the process. Catalytic relationship among the species in the model is discussed. The result reveals that the modified model is able to gives more explanation of the relationship among the species during the process at initial time t.
Anisotropic modified holographic Ricci dark energy cosmological model with hybrid expansion law
NASA Astrophysics Data System (ADS)
Das, Kanika; Sultana, Tazmin
2015-11-01
Here in this paper we present a locally rotationally symmetric Bianchi type-II metric filled with dark matter and anisotropic modified holographic Ricci dark energy. To solve the Einstein's field equations we have taken the hybrid expansion law (HEL) which exhibits a cosmic transition of the universe from decelerating to accelerating phase. We have investigated the physical and geometrical properties of the model. It is observed that the anisotropy of the universe and that of the modified holographic Ricci dark energy tends to zero at later times and the universe becomes homogeneous, isotropic and flat. We have also studied the cosmic jerk parameter.
E2/M1 ratio of the N to Delta transition in a modified Skyrme model
NASA Astrophysics Data System (ADS)
Back, Anthony Randolph
1997-08-01
I use a chiral effective Lagrangian to find the E2/M1 ratio. This ratio is a measure of the deformation of the nucleon. The Lagrangian is a modified Skyrme model (1). Its construction is guided by chiral symmetry and the symmetries of QCD, which dictates the addition of the Wess-Zumino term. The current is quantized using collective coordinates (2). I find the ratio to be - .118%, which is smaller than most other models.
Groundwater vulnerability assessment in agricultural areas using a modified DRASTIC model.
Sadat-Noori, Mahmood; Ebrahimi, Kumars
2016-01-01
Groundwater contamination is a major concern for groundwater resource managers worldwide. We evaluated groundwater pollution potential by producing a vulnerability map of an aquifer using a modified Depth to water, Net recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and Hydraulic conductivity (DRASTIC) model within a Geographic Information System (GIS) environment. The proposed modification which incorporated the use of statistical techniques optimizes the rating function of the DRASTIC model parameters, to obtain a more accurate vulnerability map. The new rates were computed using the relationships between the parameters and point data chloride concentrations in groundwater. The model was applied on Saveh-Nobaran plain in central Iran, and results showed that the coefficient of determination (R (2)) between the point data and the relevant vulnerability map increased significantly from 0.52 to 0.78 after modification. As compared to the original DRASTIC model, the modified version produced better vulnerability zonation. Additionally, single-parameter and parameter removal sensitivity analyses were performed to evaluate the relative importance of each DRASTIC parameter. The results from both analyses revealed that the vadose zone is the most sensitive parameter influencing the variability of the aquifers' vulnerability index. Based on the results, for non-point source pollution in agricultural areas, using the modified DRASTIC model is efficient compared to the original model. The proposed method can be effective for future groundwater assessment and plain-land management where agricultural activities are dominant. PMID:26650205
Statefinder diagnosis for holographic dark energy models in modified f(R,T) gravity
NASA Astrophysics Data System (ADS)
Singh, C. P.; Kumar, Pankaj
2016-05-01
In this paper we consider the non-viscous and viscous holographic dark energy models in modified f(R,T) gravity in which the infra-red cutoff is set by the Hubble horizon. We find power-law and exponential form of scale factor for non-viscous and viscous models, respectively. It is shown that the Hubble horizon as an infra-red cut-off is suitable for both the models to explain the recent accelerated expansion. In non-viscous model, we find that there is no phase transition. However, viscous model explains the phase transition from decelerated phase to accelerated phase. The cosmological parameters like deceleration parameter and statefinder parameters are discussed to analyze the dynamics of evolution of the Universe for both the models. The trajectories for viscous model are plotted in r-s and r-q planes to discriminate our model with the existing dark energy models which show the quintessence like behavior.
Modified Holographic Ricci Dark Energy Model and Statefinder Diagnosis in Flat Universe
NASA Astrophysics Data System (ADS)
Mathew, Titus K.; Suresh, Jishnu; Divakaran, Divya
2013-07-01
Evolution of the universe with modified holographic Ricci dark energy model is considered. Dependency of the equation of state parameter and deceleration parameter on the redshift and model parameters are obtained. It is shown that the density evolution of both the nonrelativistic matter and dark energy are same until recent times. The evolutionary trajectories of the model for different model parameters are obtained in the statefinder planes, r - s and r - q planes. The present statefinder parameters are obtained for different model parameter values, using that the model is differentiated from other standard models like the ΛCDM model. We have also shown that the evolutionary trajectories are depending on the model parameters, and at past times the dark energy is behaving like cold dark matter, with equation of state equal to zero.
Metabolism of modified mycotoxins studied through in vitro and in vivo models: an overview.
Boevre, Marthe De; Graniczkowska, Kinga; Saeger, Sarah De
2015-02-17
Mycotoxins are toxic, secondary metabolites produced by fungi. They occur in a wide variety of food and feed commodities, and are of major public health concern because they are the most hazardous of all food and feed contaminants in terms of chronic toxicity. In the past decades, it has become clear that in mycotoxin-contaminated commodities, many structurally related compounds generated by plant metabolism, fungi or food processing coexist with their free mycotoxins, defined as modified mycotoxins. These modified xenobiotics might endanger animal and human health as they are possibly hydrolysed into their free toxins in the digestive tract of mammals, and may consequently contribute to an unexpected high toxicity. As modified toxins represent an emerging issue, it is not a surprise that for most toxicological tests data are scarce to non-existent. Therefore, there is a need to elucidate the disposition and kinetics of both free and modified mycotoxins in mammals to correctly interpret occurrence data and biomonitoring results. This review emphasizes the current knowledge on the metabolism of modified mycotoxins using in vitro and in vivo models. PMID:25542142
Incomplete fusion studies near Coulomb barrier: a modified sum rule model
NASA Astrophysics Data System (ADS)
Bhujang, Bhushan; Das, Pragya; Singh, R. P.; Tripathi, R.; Tomar, B. S.
2013-03-01
The excitation functions of the evaporation residues, produced via complete fusion and incomplete fusion reactions of 11B + 122Sn, were measured for the projectile energy of around 6 MeV/A by the off-line gamma spectrometry. The cross sections have been compared with the statistical model code Projected Angular Momentum Coupled Evaporation (PACE4). The original sum rule model underestimated the ICF cross sections. We therefore made modification in the model mainly to incorporate the energy dependence in the definition of critical angular momentum. Using this modified sum rule model, we found a significant improvement in the results.
Modeling the grazing effect on dry grassland carbon cycling with modified Biome-BGC grazing model
NASA Astrophysics Data System (ADS)
Luo, Geping; Han, Qifei; Li, Chaofan; Yang, Liao
2014-05-01
Identifying the factors that determine the carbon source/sink strength of ecosystems is important for reducing uncertainty in the global carbon cycle. Arid grassland ecosystems are a widely distributed biome type in Xinjiang, Northwest China, covering approximately one-fourth the country's land surface. These grasslands are the habitat for many endemic and rare plant and animal species and are also used as pastoral land for livestock. Using the modified Biome-BGC grazing model, we modeled carbon dynamics in Xinjiang for grasslands that varied in grazing intensity. In general, this regional simulation estimated that the grassland ecosystems in Xinjiang acted as a net carbon source, with a value of 0.38 Pg C over the period 1979-2007. There were significant effects of grazing on carbon dynamics. An over-compensatory effect in net primary productivity (NPP) and vegetation carbon (C) stock was observed when grazing intensity was lower than 0.40 head/ha. Grazing resulted in a net carbon source of 23.45 g C m-2 yr-1, which equaled 0.37 Pg in Xinjiang in the last 29 years. In general, grazing decreased vegetation C stock, while an increasing trend was observed with low grazing intensity. The soil C increased significantly (17%) with long-term grazing, while the soil C stock exhibited a steady trend without grazing. These findings have implications for grassland ecosystem management as it relates to carbon sequestration and climate change mitigation, e.g., removal of grazing should be considered in strategies that aim to increase terrestrial carbon sequestrations at local and regional scales. One of the greatest limitations in quantifying the effects of herbivores on carbon cycling is identifying the grazing systems and intensities within a given region. We hope our study emphasizes the need for large-scale assessments of how grazing impacts carbon cycling. Most terrestrial ecosystems in Xinjiang have been affected by disturbances to a greater or lesser extent in the past
A modified GM-estimation for robust fitting of mixture regression models
NASA Astrophysics Data System (ADS)
Booppasiri, Slun; Srisodaphol, Wuttichai
2015-02-01
In the mixture regression models, the regression parameters are estimated by maximum likelihood estimation (MLE) via EM algorithm. Generally, maximum likelihood estimation is sensitive to outliers and heavy tailed error distribution. The robust method, M-estimation can handle outliers existing on dependent variable only for estimating regression coefficients in regression models. Moreover, GM-estimation can handle outliers existing on dependent variable and independent variables. In this study, the modified GM-estimations for estimating the regression coefficients in the mixture regression models are proposed. A Monte Carlo simulation is used to evaluate the efficiency of the proposed methods. The results show that the proposed modified GM-estimations approximate to MLE when there are no outliers and the error is normally distributed. Furthermore, our proposed methods are more efficient than the MLE, when there are leverage points.
Heuner, Maike; Weber, Arnd; Schröder, Uwe; Kleinschmit, Birgit; Schröder, Boris
2016-09-15
The European Water Framework Directive requires a good ecological potential for heavily modified water bodies. This standard has not been reached for most large estuaries by 2015. Management plans for estuaries fall short in linking implementations between restoration measures and underlying spatial analyses. The distribution of emergent macrophytes - as an indicator of habitat quality - is here used to assess the ecological potential. Emergent macrophytes are capable of settling on gentle tidal flats where hydrodynamic stress is comparatively low. Analyzing their habitats based on spatial data, we set up species distribution models with 'elevation relative to mean high water', 'mean bank slope', and 'length of bottom friction' from shallow water up to the vegetation belt as key predictors representing hydrodynamic stress. Effects of restoration scenarios on habitats were assessed applying these models. Our findings endorse species distribution models as crucial spatial planning tools for implementing restoration measures in modified estuaries. PMID:27339739
NASA Astrophysics Data System (ADS)
Foereid, B.; Ward, D. S.; Mahowald, N.; Paterson, E.; Lehmann, J.
2014-06-01
Soil organic matter (SOM) is the largest store of organic carbon (C) in the biosphere, but the turnover of SOM is still incompletely understood and not well described in global C cycle models. Here we use the Community Land Model (CLM) and compare the output for soil organic C stocks (SOC) to estimates from a global data set. We also modify the assumptions about SOC turnover in two ways: (1) we assume distinct temperature sensitivities of SOC pools with different turnover time and (2) we assume a priming effect, such that the decomposition rate of native SOC increases in response to a supply of fresh organic matter. The standard model predicted the global distribution of SOC reasonably well in most areas, but it failed to predict the very high stocks of SOC at high latitudes. It also predicted too much SOC in areas with high plant productivity, such as tropical rainforests and some midlatitude areas. Total SOC at equilibrium was reduced by a small amount (<1% globally) when we assume that the temperature sensitivity of SOC decomposition is dependent on the turnover rate of the component pools. Including a priming effect reduced total global SOC more (6.6% globally) and led to decreased SOC in areas with high plant input (tropical and temperate forests), which were also the areas where the unmodified model overpredicted SOC (by about 40%). The model was then run with climate change prediction until 2100 for the standard and modified versions. Future simulations showed that differences between the standard and modified versions were maintained in a future with climate change (4-6 and 23-47 Pg difference in soil carbon between standard simulation and the modified simulation with temperature sensitivity and priming respectively). Although the relative changes are small, they are likely to be larger in a fully coupled simulation, and thus warrant future work.
47 CFR 76.1905 - Petitions to modify encoding rules for new services within defined business models.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 47 Telecommunication 4 2010-10-01 2010-10-01 false Petitions to modify encoding rules for new... Rules § 76.1905 Petitions to modify encoding rules for new services within defined business models. (a... a defined business model, other than unencrypted broadcast television, the encoding of a new...
Linewidth Extraction From the THz Absorption Spectra Using a Modified Lorentz Model
NASA Astrophysics Data System (ADS)
Li, Zhi; Zhang, Zhaohui; Zhao, Xiaoyan; Su, Haixia; Zhang, Han; Lan, Jinhui
2013-10-01
Identification of specific materials is one of the most promising THz applications. It is commonly achieved by comparing the experimental peak central frequencies of the transmission or absorption spectra with a database for known materials while neglecting the linewidths. However, due to the restriction of the signal-to-noise ratio, only a narrow band, extending from several hundred GHz to several THz, can be used. It is difficult to distinguish two materials from each other if their peaks' central frequencies are similar. In this paper, we present a modified Lorentz model by taking the scattering effect into account. The modified Lorentz model can be used for the extraction of reliable absorption peak parameters, i.e. the central frequency and linewidth. On comparison with our experiments, we observed that the parameters extracted using the modified Lorentz model in glutamine samples of different concentrations exhibited a better agreement than those obtained using the traditional model. Therefore, the utilization of the narrow THz band to identify materials can be improved by comparing both the central frequency and linewidth obtained from this method.
Modified phase-field-crystal model for solid-liquid phase transitions
NASA Astrophysics Data System (ADS)
Guo, Can; Wang, Jincheng; Wang, Zhijun; Li, Junjie; Guo, Yaolin; Tang, Sai
2015-07-01
A modified phase-field-crystal (PFC) model is proposed to describe solid-liquid phase transitions by reconstructing the correlation function. The effects of fitting parameters of our modified PFC model on the bcc-liquid phase diagram, numerical stability, and solid-liquid interface properties during planar interface growth are examined carefully. The results indicate that the increase of the correlation function peak width at k =km will enhance the stability of the ordered phase, while the increase of peak height at k =0 will narrow the two-phase coexistence region. The third-order term in the free-energy function and the short wave-length of the correlation function have significant influences on the numerical stability of the PFC model. During planar interface growth, the increase of peak width at k =km will decrease the interface width and the velocity coefficient C , but increase the anisotropy of C and the interface free energy. Finally, the feasibility of the modified phase-field-crystal model is demonstrated with a numerical example of three-dimensional dendritic growth of a body-centered-cubic structure.
Modified phase-field-crystal model for solid-liquid phase transitions.
Guo, Can; Wang, Jincheng; Wang, Zhijun; Li, Junjie; Guo, Yaolin; Tang, Sai
2015-07-01
A modified phase-field-crystal (PFC) model is proposed to describe solid-liquid phase transitions by reconstructing the correlation function. The effects of fitting parameters of our modified PFC model on the bcc-liquid phase diagram, numerical stability, and solid-liquid interface properties during planar interface growth are examined carefully. The results indicate that the increase of the correlation function peak width at k=k(m) will enhance the stability of the ordered phase, while the increase of peak height at k=0 will narrow the two-phase coexistence region. The third-order term in the free-energy function and the short wave-length of the correlation function have significant influences on the numerical stability of the PFC model. During planar interface growth, the increase of peak width at k=k(m) will decrease the interface width and the velocity coefficient C, but increase the anisotropy of C and the interface free energy. Finally, the feasibility of the modified phase-field-crystal model is demonstrated with a numerical example of three-dimensional dendritic growth of a body-centered-cubic structure. PMID:26274309
El-Seddik, Mostafa M; Galal, Mona M; Radwan, A G; Abdel-Halim, Hisham S
2016-01-01
This paper addresses a modified kinetic-hydraulic model for up-flow anaerobic sludge blanket (UASB) reactor aimed to treat wastewater of biodegradable organic substrates as acetic acid based on Van der Meer model incorporated with biological granules inclusion. This dynamic model illustrates the biomass kinetic reaction rate for both direct and indirect growth of microorganisms coupled with the amount of biogas produced by methanogenic bacteria in bed and blanket zones of reactor. Moreover, the pH value required for substrate degradation at the peak specific growth rate of bacteria is discussed for Andrews' kinetics. The sensitivity analyses of biomass concentration with respect to fraction of volume of reactor occupied by granules and up-flow velocity are also demonstrated. Furthermore, the modified mass balance equations of reactor are applied during steady state using Newton Raphson technique to obtain a suitable degree of freedom for the modified model matching with the measured results of UASB Sanhour wastewater treatment plant in Fayoum, Egypt. PMID:27054727
Bernoulli Euler beam model based on a modified couple stress theory
NASA Astrophysics Data System (ADS)
Park, S. K.; Gao, X.-L.
2006-11-01
A new model for the bending of a Bernoulli-Euler beam is developed using a modified couple stress theory. A variational formulation based on the principle of minimum total potential energy is employed. The new model contains an internal material length scale parameter and can capture the size effect, unlike the classical Bernoulli-Euler beam model. The former reduces to the latter in the absence of the material length scale parameter. As a direct application of the new model, a cantilever beam problem is solved. It is found that the bending rigidity of the cantilever beam predicted by the newly developed model is larger than that predicted by the classical beam model. The difference between the deflections predicted by the two models is very significant when the beam thickness is small, but is diminishing with the increase of the beam thickness. A comparison shows that the predicted size effect agrees fairly well with that observed experimentally.
A Modified Particle Swarm Optimization Technique for Finding Optimal Designs for Mixture Models.
Wong, Weng Kee; Chen, Ray-Bing; Huang, Chien-Chih; Wang, Weichung
2015-01-01
Particle Swarm Optimization (PSO) is a meta-heuristic algorithm that has been shown to be successful in solving a wide variety of real and complicated optimization problems in engineering and computer science. This paper introduces a projection based PSO technique, named ProjPSO, to efficiently find different types of optimal designs, or nearly optimal designs, for mixture models with and without constraints on the components, and also for related models, like the log contrast models. We also compare the modified PSO performance with Fedorov's algorithm, a popular algorithm used to generate optimal designs, Cocktail algorithm, and the recent algorithm proposed by [1]. PMID:26091237
A Modified Particle Swarm Optimization Technique for Finding Optimal Designs for Mixture Models
Wong, Weng Kee; Chen, Ray-Bing; Huang, Chien-Chih; Wang, Weichung
2015-01-01
Particle Swarm Optimization (PSO) is a meta-heuristic algorithm that has been shown to be successful in solving a wide variety of real and complicated optimization problems in engineering and computer science. This paper introduces a projection based PSO technique, named ProjPSO, to efficiently find different types of optimal designs, or nearly optimal designs, for mixture models with and without constraints on the components, and also for related models, like the log contrast models. We also compare the modified PSO performance with Fedorov's algorithm, a popular algorithm used to generate optimal designs, Cocktail algorithm, and the recent algorithm proposed by [1]. PMID:26091237
NASA Astrophysics Data System (ADS)
Lee, S. B.; Lee, J. S.; Chang, S. H.; Yoo, H. K.; Kang, B. S.; Kahng, B.; Lee, M.-J.; Kim, C. J.; Noh, T. W.
2011-01-01
We observed reversible-type changes between bipolar (BRS) and unipolar resistance switching (URS) in one Pt/SrTiOx/Pt capacitor. To explain both BRS and URS in a unified scheme, we introduce the "interface-modified random circuit breaker network model," in which the bulk medium is represented by a percolating network of circuit breakers. To consider interface effects in BRS, we introduce circuit breakers to investigate resistance states near the interface. This percolation model explains the reversible-type changes in terms of connectivity changes in the circuit breakers and provides insights into many experimental observations of BRS which are under debate by earlier theoretical models.
Reduced-order-model based feedback control of the Modified Hasegawa-Wakatani equations
NASA Astrophysics Data System (ADS)
Goumiri, Imene; Rowley, Clarence; Ma, Zhanhua; Gates, David; Parker, Jeffrey; Krommes, John
2012-10-01
In this study, we demonstrate the development of model-based feedback control for stabilization of an unstable equilibrium obtained in the Modified Hasegawa-Wakatani (MHW) equations, a classic model in plasma turbulence. First, a balanced truncation is applied; a model reduction technique that has been proved successful in flow control design problems, to obtain a low dimensional model of the linearized MHW equation. A model-based feedback controller is then designed for the reduced order model using linear quadratic regulators (LQR) then a linear quadratic gaussian (LQG) control. The controllers are then applied on the original linearized and nonlinear MHW equations to stabilize the equilibrium and suppress the transition to drift-wave induced turbulences.
Instrument forward model of the modified Sagnac interferometer for atmospheric wind measurement
NASA Astrophysics Data System (ADS)
Tang, Yuanhe; Qin, Lin; Gao, Haiyang; Zhu, Ci; Wang, Dingyi
2011-06-01
The instrument forward model of the modified super-wide-Sagnac imaging interferometer based on liquid crystals on Silicon (MSASII-LCoS) is developed as an integrated code package with Matlab language to simulate the images of satellite observations. There are five sub-models in the forward model including radiation model of O(1S), orbit attitude, filter, interferometer and array detector. The principle of each sub-model is described separately and then the overall forward model equation is derived. The four simulation images are obtained. Based on the integrated signal level for the daytime observations, the apparent measurement error of wind is less than 3 m/s and the signal noise ratio (SNR) is greater than 194 with a binning of 2 × 25 pixels at the tangent height range of 70-190 km.
Improved simulation of precipitation in the tropics using a modified BMJ scheme in the WRF model
NASA Astrophysics Data System (ADS)
Fonseca, R. M.; Zhang, T.; Yong, K.-T.
2015-09-01
The successful modelling of the observed precipitation, a very important variable for a wide range of climate applications, continues to be one of the major challenges that climate scientists face today. When the Weather Research and Forecasting (WRF) model is used to dynamically downscale the Climate Forecast System Reanalysis (CFSR) over the Indo-Pacific region, with analysis (grid-point) nudging, it is found that the cumulus scheme used, Betts-Miller-Janjić (BMJ), produces excessive rainfall suggesting that it has to be modified for this region. Experimentation has shown that the cumulus precipitation is not very sensitive to changes in the cloud efficiency but varies greatly in response to modifications of the temperature and humidity reference profiles. A new version of the scheme, denoted "modified BMJ" scheme, where the humidity reference profile is more moist, was developed. In tropical belt simulations it was found to give a better estimate of the observed precipitation as given by the Tropical Rainfall Measuring Mission (TRMM) 3B42 data set than the default BMJ scheme for the whole tropics and both monsoon seasons. In fact, in some regions the model even outperforms CFSR. The advantage of modifying the BMJ scheme to produce better rainfall estimates lies in the final dynamical consistency of the rainfall with other dynamical and thermodynamical variables of the atmosphere.
Suppression of B function strongly supports the modified ABCE model in Tricyrtis sp. (Liliaceae)
Otani, Masahiro; Sharifi, Ahmad; Kubota, Shosei; Oizumi, Kanako; Uetake, Fumi; Hirai, Masayo; Hoshino, Yoichiro; Kanno, Akira; Nakano, Masaru
2016-01-01
B class MADS-box genes play important roles in petal and stamen development. Some monocotyledonous species, including liliaceous ones, produce flowers with petaloid tepals in whorls 1 and 2. A modified ABCE model has been proposed to explain the molecular mechanism of development of two-layered petaloid tepals. However, direct evidence for this modified ABCE model has not been reported to date. To clarify the molecular mechanism determining the organ identity of two-layered petaloid tepals, we used chimeric repressor gene-silencing technology (CRES-T) to examine the suppression of B function in the liliaceous ornamental Tricyrtis sp. Transgenic plants with suppressed B class genes produced sepaloid tepals in whorls 1 and 2 instead of the petaloid tepals as expected. In addition, the stamens of transgenic plants converted into pistil-like organs with ovule- and stigma-like structures. This report is the first to describe the successful suppression of B function in monocotyledonous species with two-layered petaloid tepals, and the results strongly support the modified ABCE model. PMID:27079267
Suppression of B function strongly supports the modified ABCE model in Tricyrtis sp. (Liliaceae).
Otani, Masahiro; Sharifi, Ahmad; Kubota, Shosei; Oizumi, Kanako; Uetake, Fumi; Hirai, Masayo; Hoshino, Yoichiro; Kanno, Akira; Nakano, Masaru
2016-01-01
B class MADS-box genes play important roles in petal and stamen development. Some monocotyledonous species, including liliaceous ones, produce flowers with petaloid tepals in whorls 1 and 2. A modified ABCE model has been proposed to explain the molecular mechanism of development of two-layered petaloid tepals. However, direct evidence for this modified ABCE model has not been reported to date. To clarify the molecular mechanism determining the organ identity of two-layered petaloid tepals, we used chimeric repressor gene-silencing technology (CRES-T) to examine the suppression of B function in the liliaceous ornamental Tricyrtis sp. Transgenic plants with suppressed B class genes produced sepaloid tepals in whorls 1 and 2 instead of the petaloid tepals as expected. In addition, the stamens of transgenic plants converted into pistil-like organs with ovule- and stigma-like structures. This report is the first to describe the successful suppression of B function in monocotyledonous species with two-layered petaloid tepals, and the results strongly support the modified ABCE model. PMID:27079267
Modified optimal control pilot model for computer-aided design and analysis
NASA Technical Reports Server (NTRS)
Davidson, John B.; Schmidt, David K.
1992-01-01
This paper presents the theoretical development of a modified optimal control pilot model based upon the optimal control model (OCM) of the human operator developed by Kleinman, Baron, and Levison. This model is input compatible with the OCM and retains other key aspects of the OCM, such as a linear quadratic solution for the pilot gains with inclusion of control rate in the cost function, a Kalman estimator, and the ability to account for attention allocation and perception threshold effects. An algorithm designed for each implementation in current dynamic systems analysis and design software is presented. Example results based upon the analysis of a tracking task using three basic dynamic systems are compared with measured results and with similar analyses performed with the OCM and two previously proposed simplified optimal pilot models. The pilot frequency responses and error statistics obtained with this modified optimal control model are shown to compare more favorably to the measured experimental results than the other previously proposed simplified models evaluated.
Development of modified cable models to simulate accurate neuronal active behaviors
2014-01-01
In large network and single three-dimensional (3-D) neuron simulations, high computing speed dictates using reduced cable models to simulate neuronal firing behaviors. However, these models are unwarranted under active conditions and lack accurate representation of dendritic active conductances that greatly shape neuronal firing. Here, realistic 3-D (R3D) models (which contain full anatomical details of dendrites) of spinal motoneurons were systematically compared with their reduced single unbranched cable (SUC, which reduces the dendrites to a single electrically equivalent cable) counterpart under passive and active conditions. The SUC models matched the R3D model's passive properties but failed to match key active properties, especially active behaviors originating from dendrites. For instance, persistent inward currents (PIC) hysteresis, frequency-current (FI) relationship secondary range slope, firing hysteresis, plateau potential partial deactivation, staircase currents, synaptic current transfer ratio, and regional FI relationships were not accurately reproduced by the SUC models. The dendritic morphology oversimplification and lack of dendritic active conductances spatial segregation in the SUC models caused significant underestimation of those behaviors. Next, SUC models were modified by adding key branching features in an attempt to restore their active behaviors. The addition of primary dendritic branching only partially restored some active behaviors, whereas the addition of secondary dendritic branching restored most behaviors. Importantly, the proposed modified models successfully replicated the active properties without sacrificing model simplicity, making them attractive candidates for running R3D single neuron and network simulations with accurate firing behaviors. The present results indicate that using reduced models to examine PIC behaviors in spinal motoneurons is unwarranted. PMID:25277743
Isgur-Wise function within a modified heavy-light chiral quark model
Eeg, Jan O.; Kumericki, Kresimir
2010-04-01
We consider the Isgur-Wise function {xi}({omega}) within a new modified version of a heavy-light chiral quark model. While early versions of such models gave an absolute value of the slope that was too small, namely {xi}{sup '}(1){approx_equal}-0.4 to -0.3, we show how extended version(s) may lead to values around -1, in better agreement with recent measurements. This is obtained by introducing a new mass parameter in the heavy-quark propagator. We also shortly comment on the consequences for the decay modes B{yields}DD.
Levitation force on a permanent magnet over a superconducting plane: Modified critical-state model
Yang, Z.J.
1997-08-01
The authors consider a model system of a permanent magnet above a semi-infinite superconductor. They introduce a modified critical-state model, and carry out derivations of the levitation force acting on the magnet. A key feature of the modification allows the current density to be less than the critical value. The theoretical results show an exponential relationship between the force and the distance. Analytical expressions are developed for permanent magnets in the form of a point dipole, a tip of a magnetic force microscope, and a cylindrical magnet. In the latter case, the exponential relationship has been observed in numerous experiments but without previous interpretation.
Modified finite-element model for application to terrain-induced mesoscale flows
Lee, R.L.; Leone, J.M. Jr.; Gresho, P.M.
1982-11-01
Terrain-induced mesoscale flows are localized atmospheric motions generated primarily by surface inhomogeneities such as differential heating and irregular terrain. Well-known examples of such flows are sea-and-land breeze circulations, mountain-valley flows, urban heat island circulations and mountain lee waves. A numerical model capable of capturing the details of these frequently complicated flow patterns must often contain a realistic and rather accurate representation of the relevant terrain. Over the last decade, mesoscale models have been developed in which various approaches were used to incorporate variable terrain. In this study, a somewhat unique approach, based on a modified finite element procedure, was used to solve the nonhydrostatic planetary boundary layer equations. The nonhydrostatic and finite element features of the model are particularly advantageous for modeling flows over complex topography. The numerical aspects of the model, the parameterizations currently used, and a few preliminary results are presented.
NASA Astrophysics Data System (ADS)
Hamimid, M.; Mimoune, S. M.; Feliachi, M.
2013-11-01
In this paper, we present a Langevin transforms model which evaluates accurately minor hysteresis loops for the modified inverse Jiles-Atherton model by using appropriate expressions in order to improve minor hysteresis loops characteristics. The parameters of minor hysteresis loops are then related to the parameters of the major hysteresis loop according to each level of maximal induction by using Langevin transforms expressions. The stochastic optimization method “simulated annealing” is used for the determination of the Langevin transforms coefficients. This model needs only two experimental tests to generate all hysteresis loops. The validity of the Langevin transforms model is justified by comparison of calculated minor hysteresis loops to measured ones and good agreements are obtained with better results than the exponential transforms model (Hamimid et al., 2011 [4]).
Huang, Hong-Zhong; Yuan, Rong
2014-01-01
Many structures are subjected to variable amplitude loading in engineering practice. The foundation of fatigue life prediction under variable amplitude loading is how to deal with the fatigue damage accumulation. A nonlinear fatigue damage accumulation model to consider the effects of load sequences was proposed in earlier literature, but the model cannot consider the load interaction effects, and sometimes it makes a major error. A modified nonlinear damage accumulation model is proposed in this paper to account for the load interaction effects. Experimental data of two metallic materials are used to validate the proposed model. The agreement between the model prediction and experimental data is observed, and the predictions by proposed model are more possibly in accordance with experimental data than that by primary model and Miner's rule. Comparison between the predicted cumulative damage by the proposed model and an existing model shows that the proposed model predictions can meet the accuracy requirement of the engineering project and it can be used to predict the fatigue life of welded aluminum alloy joint of Electric Multiple Units (EMU); meanwhile, the accuracy of approximation can be obtained from the proposed model though more simple computing process and less material parameters calling for extensive testing than the existing model. PMID:24574866
Modified pressure loss model for T-junctions of engine exhaust manifold
NASA Astrophysics Data System (ADS)
Wang, Wenhui; Lu, Xiaolu; Cui, Yi; Deng, Kangyao
2014-11-01
The T-junction model of engine exhaust manifolds significantly influences the simulation precision of the pressure wave and mass flow rate in the intake and exhaust manifolds of diesel engines. Current studies have focused on constant pressure models, constant static pressure models and pressure loss models. However, low model precision is a common disadvantage when simulating engine exhaust manifolds, particularly for turbocharged systems. To study the performance of junction flow, a cold wind tunnel experiment with high velocities at the junction of a diesel exhaust manifold is performed, and the variation in the pressure loss in the T-junction under different flow conditions is obtained. Despite the trend of the calculated total pressure loss coefficient, which is obtained by using the original pressure loss model and is the same as that obtained from the experimental results, large differences exist between the calculated and experimental values. Furthermore, the deviation becomes larger as the flow velocity increases. By improving the Vazsonyi formula considering the flow velocity and introducing the distribution function, a modified pressure loss model is established, which is suitable for a higher velocity range. Then, the new model is adopted to solve one-dimensional, unsteady flow in a D6114 turbocharged diesel engine. The calculated values are compared with the measured data, and the result shows that the simulation accuracy of the pressure wave before the turbine is improved by 4.3% with the modified pressure loss model because gas compressibility is considered when the flow velocities are high. The research results provide valuable information for further junction flow research, particularly the correction of the boundary condition in one-dimensional simulation models.
Pressure Calculation in a Compressor Cylinder by a Modified New Helmholtz Modelling
NASA Astrophysics Data System (ADS)
MA, Y.-C.; MIN, O.-K.
2001-06-01
Pressure pulsation has a critical importance in the design of refrigerant compressor since it affects the performance by increasing over-compression loss, and it acts as a noise and vibration source. For the numerical analysis of pressure pulsation, quasi-steady flow equation has been used because of its easy manipulation derived from the pressure difference. By considering the dynamic effects of fluid, a new Helmholtz resonator model was also proposed on the basis of the continuity and the momentum equations, which consists of necks and cavities in flow manifolds.In this paper, a modified new Helmholtz resonator is introduced to include the gas inertia effect due to the volume decrease in the cavity. Comparisons between this modified new Helmholtz calculations and experimental results show that it is necessary to include the gas inertia effect in predicting pressure over-shooting phenomena at an instant of valve opening state and this modified new Helmholtz model can describe the over-compression phenomena in the compressor cylinder, a phenomenon which hinders a noise source identification of compressor.
Tnni3k Modifies Disease Progression in Murine Models of Cardiomyopathy
Wheeler, Ferrin C.; Tang, Hao; Marks, Odessa A.; Hadnott, Tracy N.; Chu, Pei-Lun; Mao, Lan; Rockman, Howard A.; Marchuk, Douglas A.
2009-01-01
The Calsequestrin (Csq) transgenic mouse model of cardiomyopathy exhibits wide variation in phenotypic progression dependent on genetic background. Seven heart failure modifier (Hrtfm) loci modify disease progression and outcome. Here we report Tnni3k (cardiac Troponin I-interacting kinase) as the gene underlying Hrtfm2. Strains with the more susceptible phenotype exhibit high transcript levels while less susceptible strains show dramatically reduced transcript levels. This decrease is caused by an intronic SNP in low-transcript strains that activates a cryptic splice site leading to a frameshifted transcript, followed by nonsense-mediated decay of message and an absence of detectable protein. A transgenic animal overexpressing human TNNI3K alone exhibits no cardiac phenotype. However, TNNI3K/Csq double transgenics display severely impaired systolic function and reduced survival, indicating that TNNI3K expression modifies disease progression. TNNI3K expression also accelerates disease progression in a pressure-overload model of heart failure. These combined data demonstrate that Tnni3k plays a critical role in the modulation of different forms of heart disease, and this protein may provide a novel target for therapeutic intervention. PMID:19763165
Kuentz, M; Leuenberger, H
1998-02-01
The purpose of this investigation was to analyze the modified Young's modulus of microcrystalline cellulose tablets at comparatively low relative densities, based on concepts of percolation theory. Tablets were prepared and tested using a Zwick 1478 universal testing instrument. For statistical evaluation a new method is introduced for power laws, which exhibits highly correlated model parameters. According to our results the model Leuenberger, Leu is consistent with an Effective Medium Approximation which exhibits an exponent equal to one far away from the percolation threshold. In addition, the results show that it is essential to evaluate the elastic behavior of tablets close to the percolation threshold. For the different types of MCC a critical exponent q = 3.95 +/- 0.14 was obtained. This result is very essential, as it is in good agreement with the theoretically expected value of 3.9 from an elastic network (central force model). The proposed model describes the modified Young's modulus better than former model equations taking into account the relative density. Thus, the process during uniaxial compaction can be imagined as a directed continuum percolation and the relative density of compacts can be identified as a space-occupation probability density phi yielding reasonable percolation thresholds. PMID:9532596
Kandasamy, Palani; Moitra, Ranabir; Mukherjee, Souti
2015-01-01
Experiments were conducted to determine the respiration rate of tomato at 10, 20 and 30 °C using closed respiration system. Oxygen depletion and carbon dioxide accumulation in the system containing tomato was monitored. Respiration rate was found to decrease with increasing CO2 and decreasing O2 concentration. Michaelis-Menten type model based on enzyme kinetics was evaluated using experimental data generated for predicting the respiration rate. The model parameters that obtained from the respiration rate at different O2 and CO2 concentration levels were used to fit the model against the storage temperatures. The fitting was fair (R2 = 0.923 to 0.970) when the respiration rate was expressed as O2 concentation. Since inhibition constant for CO2 concentration tended towards negetive, the model was modified as a function of O2 concentration only. The modified model was fitted to the experimental data and showed good agreement (R2 = 0.998) with experimentally estimated respiration rate. PMID:26078087
NASA Astrophysics Data System (ADS)
Takizawa, Kenji; Tezduyar, Tayfun E.; Boben, Joseph; Kostov, Nikolay; Boswell, Cody; Buscher, Austin
2013-12-01
To increase aerodynamic performance, the geometric porosity of a ringsail spacecraft parachute canopy is sometimes increased, beyond the "rings" and "sails" with hundreds of "ring gaps" and "sail slits." This creates extra computational challenges for fluid-structure interaction (FSI) modeling of clusters of such parachutes, beyond those created by the lightness of the canopy structure, geometric complexities of hundreds of gaps and slits, and the contact between the parachutes of the cluster. In FSI computation of parachutes with such "modified geometric porosity," the flow through the "windows" created by the removal of the panels and the wider gaps created by the removal of the sails cannot be accurately modeled with the Homogenized Modeling of Geometric Porosity (HMGP), which was introduced to deal with the hundreds of gaps and slits. The flow needs to be actually resolved. All these computational challenges need to be addressed simultaneously in FSI modeling of clusters of spacecraft parachutes with modified geometric porosity. The core numerical technology is the Stabilized Space-Time FSI (SSTFSI) technique, and the contact between the parachutes is handled with the Surface-Edge-Node Contact Tracking (SENCT) technique. In the computations reported here, in addition to the SSTFSI and SENCT techniques and HMGP, we use the special techniques we have developed for removing the numerical spinning component of the parachute motion and for restoring the mesh integrity without a remesh. We present results for 2- and 3-parachute clusters with two different payload models.
Active Aeroelastic Wing Aerodynamic Model Development and Validation for a Modified F/A-18A
NASA Technical Reports Server (NTRS)
Cumming, Stephen B.; Diebler, Corey G.
2005-01-01
A new aerodynamic model has been developed and validated for a modified F/A-18A used for the Active Aeroelastic Wing (AAW) research program. The goal of the program was to demonstrate the advantages of using the inherent flexibility of an aircraft to enhance its performance. The research aircraft was an F/A-18A with wings modified to reduce stiffness and a new control system to increase control authority. There have been two flight phases. Data gathered from the first flight phase were used to create the new aerodynamic model. A maximum-likelihood output-error parameter estimation technique was used to obtain stability and control derivatives. The derivatives were incorporated into the National Aeronautics and Space Administration F-18 simulation, validated, and used to develop new AAW control laws. The second phase of flights was used to evaluate the handling qualities of the AAW aircraft and the control law design process, and to further test the accuracy of the new model. The flight test envelope covered Mach numbers between 0.85 and 1.30 and dynamic pressures from 600 to 1250 pound-force per square foot. The results presented in this report demonstrate that a thorough parameter identification analysis can be used to improve upon models that were developed using other means. This report describes the parameter estimation technique used, details the validation techniques, discusses differences between previously existing F/A-18 models, and presents results from the second phase of research flights.
Fluid{Structure Interaction Modeling of Modified-Porosity Parachutes and Parachute Clusters
NASA Astrophysics Data System (ADS)
Boben, Joseph J.
To increase aerodynamic performance, the geometric porosity of a ringsail spacecraft parachute canopy is sometimes increased, beyond the "rings" and "sails" with hundreds of "ring gaps" and "sail slits." This creates extra computational challenges for fluid-structure interaction (FSI) modeling of clusters of such parachutes, beyond those created by the lightness of the canopy structure, geometric complexities of hundreds of gaps and slits, and the contact between the parachutes of the cluster. In FSI computation of parachutes with such "modified geometric porosity," the ow through the "windows" created by the removal of the panels and the wider gaps created by the removal of the sails cannot be accurately modeled with the Homogenized Modeling of Geometric Porosity (HMGP), which was introduced to deal with the hundreds of gaps and slits. The ow needs to be actually resolved. All these computational challenges need to be addressed simultaneously in FSI modeling of clusters of spacecraft parachutes with modified geometric porosity. The core numerical technology is the Stabilized Space-Time FSI (SSTFSI) technique, and the contact between the parachutes is handled with the Surface-Edge-Node Contact Tracking (SENCT) technique. In the computations reported here, in addition to the SSTFSI and SENCT techniques and HMGP, we use the special techniques we have developed for removing the numerical spinning component of the parachute motion and for restoring the mesh integrity without a remesh. We present results for 2- and 3-parachute clusters with two different payload models. We also present the FSI computations we carried out for a single, subscale modified-porosity parachute.
Self-modifying systems: a model for the constructive origin of information.
Kampis, G
1996-01-01
The mechanisms of information processing in Turning machines and biological systems are examined from the point of view of physical sets of variables. Computation is characterized as a process, the realization of which involves a bounded set of interactions and a pre-definable set of variables in real systems. Using ideas from process philosophy, the ability of natural systems to transcend these computational modes is discussed. A class of systems, called self-modifying systems, that utilize persistent shifts in their defining interactions and variable composition is introduced. Various other ideas that lead to similarly non-computational or semi-computational scenarios (as in the case of distributed code systems) are referenced. As applications, computer models of emergent phenomena using randomly growing interaction sets as well as theoretical issues that range from the meaning of simulation to the problem of information gain in self-modifying systems are discussed. PMID:8734518
Zhao, Pengfei; Roy, Subrata
2014-05-07
This work investigates the performance of underwater spark discharge relating to bubble growth and decay under high pressure and with salinity conditions by introducing a modified form of the resistance equation. Here, we study salinity influence on circuit parameters by fitting the experimental data for which gap resistance is much larger in conductive water than in dielectric water. Accordingly, the resistance equation is modified by considering the influence of both plasma and its surrounding liquid. Thermal radiation effect of the bubble is also studied by comparing two different radiation models. Numerical results predict a larger bubble pressure for saline water but a reduced size and a smaller bubble cycle at a greater water depth. Such study may be useful in many saltwater applications, including that for deep sea conditions.
NASA Astrophysics Data System (ADS)
Sudakov, Ivan; Vakulenko, Sergey
2015-11-01
The original Rayleigh-Benard convection is a standard example of the system where the critical transitions occur with changing of a control parameter. We will discuss the modified Rayleigh-Benard convection problem which includes the radiative effects as well as the specific gas sources on a surface. Such formulation of this problem leads to identification a new kind of nonlinear phenomenon, besides the well-known Benard cells. Modeling of methane emissions from permafrost into the atmosphere drives to difficult problems, involving the Navier-Stokes equations. Taking into account the modified Rayleigh-Benard convection problem, we will discuss a new approach which makes the problem of a climate catastrophe in the result of a greenhouse effect more tractable and allows us to describe catastrophic transitions in the atmosphere induced by permafrost greenhouse gas sources.
A self-modifying cellular automaton model of historical urbanization in the San Francisco Bay area
Clarke, K.C.; Hoppen, S.; Gaydos, L.
1997-01-01
In this paper we describe a cellular automaton (CA) simulation model developed to predict urban growth as part of a project for estimating the regional and broader impact of urbanization on the San Francisco Bay area's climate. The rules of the model are more complex than those of a typical CA and involve the use of multiple data sources, including topography, road networks, and existing settlement distributions, and their modification over time. In addition, the control parameters of the model are allowed to self-modify: that is, the CA adapts itself to the circumstances it generates, in particular, during periods of rapid growth or stagnation. In addition, the model was written to allow the accumulation of probabilistic estimates based on Monte Carlo methods. Calibration of the model has been accomplished by the use of historical maps to compare model predictions of urbanization, based solely upon the distribution in year 1900, with observed data for years 1940, 1954, 1962, 1974, and 1990. The complexity of this model has made calibration a particularly demanding step. Lessons learned about the methods, measures, and strategies developed to calibrate the model may be of use in other environmental modeling contexts. With the calibration complete, the model is being used to generate a set of future scenarios for the San Francisco Bay area along with their probabilities based on the Monte Carlo version of the model. Animated dynamic mapping of the simulations will be used to allow visualization of the impact of future urban growth.
NASA Astrophysics Data System (ADS)
Baghel, A. P. S.; Shekhawat, S. K.; Kulkarni, S. V.; Samajdar, I.
2014-09-01
Grain-oriented (GO) materials exhibit arbitrary frequency-loss behaviors and anomalies in dynamic hysteresis loop shapes. Significant attempts have been made in the literature to approximate dynamic hysteresis loops using the dynamic Jiles-Atherton (JA) model based Bertotti's approach. Such a model is inefficient in accurate loss computation over a wide range of frequencies and in predictions of correct loop shapes. Moreover, the original static JA model also needs to be improved for accurate prediction of highly steep, gooseneck, and narrow-waist static loops of GO materials. An alternative approach based on magnetic viscosity provides flexibilities to handle indefinite frequency dependence of the losses and to control the anomalous loop shapes. This paper proposes a viscosity-based dynamic JA model which gives accurate prediction of dynamic loops of GO materials. A modified static JA model which considers crystalline and textured structures of GO materials is used to predict static hysteresis loops. The dynamic losses are included in the modified model using the field separation approach. The proposed model is validated using experimental measurements. The computed and measured dynamic loops are in close agreement in the frequency range of 1-200 Hz.
Emergence of long memory in stock volatility from a modified Mike-Farmer model
NASA Astrophysics Data System (ADS)
Gu, Gao-Feng; Zhou, Wei-Xing
2009-05-01
The Mike-Farmer (MF) model was constructed empirically based on the continuous double auction mechanism in an order-driven market, which can successfully reproduce the cubic law of returns and the diffusive behavior of stock prices at the transaction level. However, the volatility (defined by absolute return) in the MF model does not show sound long memory. We propose a modified version of the MF model by including a new ingredient, that is, long memory in the aggressiveness (quantified by the relative prices) of incoming orders, which is an important stylized fact identified by analyzing the order flows of 23 liquid Chinese stocks. Long memory emerges in the volatility synthesized from the modified MF model with the DFA scaling exponent close to 0.76, and the cubic law of returns and the diffusive behavior of prices are also produced at the same time. We also find that the long memory of order signs has no impact on the long memory property of volatility, and the memory effect of order aggressiveness has little impact on the diffusiveness of stock prices.
NASA Astrophysics Data System (ADS)
Lo, C. C. H.
2010-05-01
This paper reports on a model-assisted magnetic hysteresis measurement method for noncontact characterization of surface-modified materials whose magnetic properties vary with depth. The technique involves measuring hysteresis loops from a test sample using a surface sensor probe in close proximity to the sample without any direct contact with it. The sensor outputs were simulated based on an extended magnetic hysteresis model to describe the magnetic hysteresis of the sample and its influence on the magnetic reluctance of the magnetic circuit. The technique was applied to characterize a series of surface hardened Fe-C samples with hardening depths ranging from 1.09 to 5.68 mm. The hysteresis behavior of the samples was modeled using a parametrized function to describe the depth profile of domain wall pinning strength. The midpoints of the inverted pinning strength profiles were found to agree with those of the measured hardness profiles, demonstrating the potential of the model-assisted technique for quantitative evaluation of surface-modified magnetic materials.
V cosmological models in f (R, T) modified gravity with Λ (T) by using generation technique
NASA Astrophysics Data System (ADS)
Ahmed, Nasr; Pradhan, Anirudh; Fekry, M.; Alamri, Sultan Z.
2016-06-01
A new class of cosmological models in f (R, T) modified theories of gravity proposed by Harko et al. (2011), where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar R and the trace of the stress-energy tensor T, has been investigated for a specific choice of f (R, T) =f1 (R) +f2 (T) by generation of new solutions. Motivated by recent work of Pradhan et al. (2015) we have revisited the recent work of Ahmed and Pradhan (2014) by using a generation technique, it is shown that f (R, T) modified field equations are solvable for any arbitrary cosmic scale function. A class of new solutions for particular forms of cosmic scale functions have been investigated. In the present study we consider the cosmological constant Λ as a function of the trace of the stress energy-momentum-tensor, and dub such a model " Λ (T) gravity" where we specified a certain form of Λ (T) . Such models may exhibit better equability with the cosmological observations. The cosmological constant Λ is found to be a positive decreasing function of time which is supported by results from recent supernovae Ia observations. Expressions for Hubble's parameter in terms of redshift, luminosity distance redshift, distance modulus redshift and jerk parameter are derived and their significances are described in detail. The physical and geometric properties of the cosmological models are also discussed.
A modified procedure for mixture-model clustering of regional geochemical data
Ellefsen, Karl J.; Smith, David B.; Horton, John D.
2014-01-01
A modified procedure is proposed for mixture-model clustering of regional-scale geochemical data. The key modification is the robust principal component transformation of the isometric log-ratio transforms of the element concentrations. This principal component transformation and the associated dimension reduction are applied before the data are clustered. The principal advantage of this modification is that it significantly improves the stability of the clustering. The principal disadvantage is that it requires subjective selection of the number of clusters and the number of principal components. To evaluate the efficacy of this modified procedure, it is applied to soil geochemical data that comprise 959 samples from the state of Colorado (USA) for which the concentrations of 44 elements are measured. The distributions of element concentrations that are derived from the mixture model and from the field samples are similar, indicating that the mixture model is a suitable representation of the transformed geochemical data. Each cluster and the associated distributions of the element concentrations are related to specific geologic and anthropogenic features. In this way, mixture model clustering facilitates interpretation of the regional geochemical data.
Kwong, C K; Fung, K Y; Jiang, Huimin; Chan, K Y; Siu, Kin Wai Michael
2013-01-01
Affective design is an important aspect of product development to achieve a competitive edge in the marketplace. A neural-fuzzy network approach has been attempted recently to model customer satisfaction for affective design and it has been proved to be an effective one to deal with the fuzziness and non-linearity of the modeling as well as generate explicit customer satisfaction models. However, such an approach to modeling customer satisfaction has two limitations. First, it is not suitable for the modeling problems which involve a large number of inputs. Second, it cannot adapt to new data sets, given that its structure is fixed once it has been developed. In this paper, a modified dynamic evolving neural-fuzzy approach is proposed to address the above mentioned limitations. A case study on the affective design of mobile phones was conducted to illustrate the effectiveness of the proposed methodology. Validation tests were conducted and the test results indicated that: (1) the conventional Adaptive Neuro-Fuzzy Inference System (ANFIS) failed to run due to a large number of inputs; (2) the proposed dynamic neural-fuzzy model outperforms the subtractive clustering-based ANFIS model and fuzzy c-means clustering-based ANFIS model in terms of their modeling accuracy and computational effort. PMID:24385884
Kwong, C. K.; Fung, K. Y.; Jiang, Huimin; Chan, K. Y.
2013-01-01
Affective design is an important aspect of product development to achieve a competitive edge in the marketplace. A neural-fuzzy network approach has been attempted recently to model customer satisfaction for affective design and it has been proved to be an effective one to deal with the fuzziness and non-linearity of the modeling as well as generate explicit customer satisfaction models. However, such an approach to modeling customer satisfaction has two limitations. First, it is not suitable for the modeling problems which involve a large number of inputs. Second, it cannot adapt to new data sets, given that its structure is fixed once it has been developed. In this paper, a modified dynamic evolving neural-fuzzy approach is proposed to address the above mentioned limitations. A case study on the affective design of mobile phones was conducted to illustrate the effectiveness of the proposed methodology. Validation tests were conducted and the test results indicated that: (1) the conventional Adaptive Neuro-Fuzzy Inference System (ANFIS) failed to run due to a large number of inputs; (2) the proposed dynamic neural-fuzzy model outperforms the subtractive clustering-based ANFIS model and fuzzy c-means clustering-based ANFIS model in terms of their modeling accuracy and computational effort. PMID:24385884
Modified virtual internal bond model for concrete subjected to dynamic loading
NASA Astrophysics Data System (ADS)
Patil, Mayuri
Concrete is often used as a primary material to build protective structures. There is a wide range of research work being performed to simulate the behavior of reinforced concrete under impact and blast loading. This behavior is studied from both material and structural points of view. The research study presented in this thesis focuses on material aspects of modeling. LS-DYNARTM is an effective software for modeling and finite element analysis of structural members. It allows the user to define the material through commercially available or user-defined constitutive material models. Each material model has a distinct set of parameters to define a material which is further assigned to elements and used for simulations. This research study presents a user defined material model called Modified Concrete Virtual Internal Bond Model (MC-VIB). The basic constitutive model of VIB assumes the body as a collection of randomly oriented material points interconnected by a network of internal bonds. The model was modified by several researchers for different purposes. This research presents the MC-VIB for concrete under dynamic loading and studies its implementation into LS-DYNARTM. The modifications include incorporation of shear behavior and accounting for the difference in behavior of concrete in tension and compression. This project includes the calibration of the model based on stress-strain behavior of single element and cylinder model of concrete. The parameters are based on concrete with a uniaxial compressive strength of 27.6 MPa (4 ksi). These numerical curves are compared to those obtained from conventionally used material models for concrete and standard curves obtained by accepted equations to check the accuracy of prediction. The material model available in LS-DYNARTM requires a number of input parameters to define concrete behavior. These properties are normally derived from actual tests performed on the concrete under consideration. Often the properties are
The PPP model of alternant cyclic polyenes with modified boundary conditions
Bendazzoli, G.L.; Evangelisti, S.
1995-08-15
The extension of the PPP Hamiltonian for alternant cyclic polyenes to noninteger values of the pseudomomentum by imposing modified boundary conditions is discussed in detail. It is shown that a computer program for periodic boundary conditions can be easily adapted to the new boundary conditions. Full CI computations are carried out for some low-lying states of the PPP model of alternant cyclic polyenes (CH){sub N} (N even) at half-filling. The energy values obtained by using periodic (Bloch) and antiperiodic (Moebius) orbitals are used to perform energy extrapolations for N {yields} {infinity}. 38 refs., 2 figs., 5 tabs.
A Modified BFGS Formula Using a Trust Region Model for Nonsmooth Convex Minimizations
Cui, Zengru; Yuan, Gonglin; Sheng, Zhou; Liu, Wenjie; Wang, Xiaoliang; Duan, Xiabin
2015-01-01
This paper proposes a modified BFGS formula using a trust region model for solving nonsmooth convex minimizations by using the Moreau-Yosida regularization (smoothing) approach and a new secant equation with a BFGS update formula. Our algorithm uses the function value information and gradient value information to compute the Hessian. The Hessian matrix is updated by the BFGS formula rather than using second-order information of the function, thus decreasing the workload and time involved in the computation. Under suitable conditions, the algorithm converges globally to an optimal solution. Numerical results show that this algorithm can successfully solve nonsmooth unconstrained convex problems. PMID:26501775
Numerical and analytical tests of quasi-integrability in modified sine-Gordon models
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Zakrzewski, Wojtek J.
2014-01-01
Following our attempts to define quasi-integrability in which we related this concept to a particular symmetry of the two-soliton function we check this condition in three classes of modified sine-Gordon models in (1 + 1) dimensions. We find that the numerical results seen in various scatterings of two solitons and in the time evolution of breather-like structures support our ideas about the symmetry of the field configurations and its effects on the anomalies of the conservation laws of the charges.
Non-flat pilgrim dark energy FRW models in modified gravity
NASA Astrophysics Data System (ADS)
Rani, Shamaila; Jawad, Abdul; Salako, Ines G.; Azhar, Nadeem
2016-09-01
We study the cosmic acceleration in dynamical Chern-Simons modified gravity in the frame-work of non-flat FRW universe. The pilgrim dark energy (with future event and apparent horizons) interacted with cold dark matter is being considered in this work. We investigate the cosmological parameters (equation of state, deceleration) and planes (state-finders, ω_{θ}-ω_{θ}^' }) in the present scenario. It is interesting to mention here that the obtained results of various cosmological parameters are consistent with various observational schemes. The validity of generalized second law of thermodynamics for present dark energy models is also being analyzed.
Modified Hawking temperature and entropic force: A prescription in FRW model
NASA Astrophysics Data System (ADS)
Mitra, Saugata; Saha, Subhajit; Chakraborty, Subenoy
2015-03-01
The idea of Verlinde that gravity is an entropic force caused by information changes associated with the positions of material bodies, is used in the present work for the Friedmann-Robertson-Walker (FRW) model of the Universe. Using modified Hawking temperature, the Friedmann equations are derived on any horizon. For the validity of the first law of thermodynamics (i.e. Clausius relation) it is found that there is modification of Bekenstein entropy on the horizon. However, using equipartition law of energy, Bekenstein entropy is recovered.
Ecological risk assessment of genetically modified crops based on cellular automata modeling.
Yang, Jun; Wang, Zhi-Rui; Yang, De-Li; Yang, Qing; Yan, Jun; He, Ming-Feng
2009-01-01
The assessment of ecological risk in genetically modified (GM) biological systems is critically important for decision-making and public acceptance. Cellular automata (CA) provide a potential modeling and simulation framework for representing relationships and interspecies interactions both temporally and spatially. In this paper, a simple subsystem contains only four species: crop, target pest, non-target pest and enemy insect, and a three layer arrangement of LxL stochastic cellular automata with a periodic boundary were established. The simulation of this simplified system showed abundant and sufficient complexity in population assembly and densities, suggesting a prospective application in ecological risk assessment of GM crops. PMID:19477260
Modified Heisenberg model for the zig-zag structure in multiferroic RMn2O5
NASA Astrophysics Data System (ADS)
Bahoosh, Safa Golrokh; Wesselinowa, Julia M.; Trimper, Steffen
2015-08-01
The class of RMn2O5 (R = Ho, Tb, Y, Eu) compounds offers multiferroic properties where the refined magnetic zig-zag order breaks the inversion symmetry. Varying the temperature, the system undergoes a magnetic and a subsequent ferroelectric phase transition where the ferroelectricity is magnetically induced. We propose a modified anisotropic Heisenberg model that can be used as a tractable analytical model studying the properties of those antiferromagnetic zig-zag spin chains. Based on a finite temperature Green's function method, it is shown that the polarization is induced solely by different exchange couplings of the two different Mn4+ and Mn3+ magnetic ions. We calculate the excitation energy of the spin system for finite temperatures, which for its part determines the temperature dependent magnetization and polarization. The ferroelectric phase transition is manifested as a kink in the excitation energy. The variation of the polarization by an external magnetic field depends strongly on the direction of that field. Whereas, the polarization in b-direction increases with an external magnetic field as well in b-direction it can be switched for strong fields in a-direction. The results based on that modified Heisenberg model are in qualitative agreement with experimental data.
Inferring the spatial variation of the wedge strength based on a modified critical taper model
NASA Astrophysics Data System (ADS)
Yang, C.; Liu, H.; Hsieh, Y.; Dong, J.
2013-12-01
Critical taper wedge theory has been widely applied to evaluate the strength of the detachment fault and the wedge by measuring taper angle. Traditional taper model, which incorporated constant cohesion and friction angle, fails to explain the lateral variation of the taper angle. A modified critical taper model adopting nonlinear Hoek-Brown failure criterion is proposed accordingly. The fold-and-thrust belt of central Taiwan was studied. Based on the field works and laboratory tests, the geological strength index (GSI) and the uniaxial compressive strength were obtained and the wedge strength can be estimated accordingly. The GSI values from investigation are decreased from the west to the east along the cross section due to the wedge strength heterogeneity. The uniaxial compressive strength of intact rock varies from the age of formation and lithology. The estimated wedge strength exhibits a strong spatial variation. The strength of the detachment fault was derived from rotary shear tests using fault gouge materials under different velocities and normal stresses. General speaking, the steady-state friction coefficient are about 0.29-0.46 when the shear velocity less than 0.1 m/s. The friction coefficient is not sensitive to the normal stress. Consequently, the lateral variation of the taper angle, which calculated by modified critical taper model, is mainly dominated by the wedge strength heterogeneity and the thickening of the wedge from the west to the east.
Modeling gravity-driven fingering in rough-walled fractures using modified percolation theory
Glass, R.J.
1992-12-31
Pore scale invasion percolation theory is modified for imbibition of.wetting fluids into fractures. The effects of gravity, local aperture field geometry, and local in-plane air/water interfacial curvatureare included in the calculation of aperture filling potential which controls wetted structure growth within the fracture. The inclusion of gravity yields fingers oriented in the direction of the gravitational gradient. These fingers widen and tend to meander and branch more as the gravitational gradient decreases. In-plane interfacial curvature also greatly affects the wetted structure in both horizontal and nonhorizontal fractures causing the formation of macroscopic wetting fronts. The modified percolation model is used to simulate imbibition into an analogue rough-walled fracture where both fingering and horizontal imbibition experiments were previously conducted. Comparison of numerical and experimental results showed reasonably good agreement. This process oriented physical and numerical modeling is-a necessary step toward including gravity-driven fingering in models of flow and transport through unsaturated, fractured rock.
Modified biokinetic model for uranium from analysis of acute exposure to UF6.
Fisher, D R; Kathren, R L; Swint, M J
1991-03-01
Urinalysis measurements from 31 workers acutely exposed to uranium hexafluoride (UF6) and its hydrolysis product UO2F2 (during the 1986 Gore, Oklahoma UF6-release accident) were used to develop a modified recycling biokinetic model for soluble U compounds. The model is expressed as a five-compartment exponential equation: yu(t) = 0.086e-2.77t + 0.0048e-0.116t + 0.00069e-0.0267t + 0.00017 e-0.00231t + 2.5 x 10(-6) e-0.000187t, where yu(t) is the fractional daily urinary excretion and t is the time after intake, in days. The excretion constants of the five exponential compartments correspond to residence half-times of 0.25, 6, 26, 300, and 3,700 d in the lungs, kidneys, other soft tissues, and in two bone volume compartments, respectively. The modified recycling model was used to estimate intake amounts, the resulting committed effective dose equivalent, maximum kidney concentrations, and dose equivalent to bone surfaces, kidneys, and lungs. PMID:1995506
Yadav, Anil Kumar; Gaur, Prerna
2015-05-01
The objective of this paper is to control the speed of heavy duty vehicle (HDV) through angular position of throttle valve. Modified internal model control (IMC) schemes with fuzzy supervisor as an adaptive tuning are proposed to control the speed of HDV. Internal model (IM) plays a key role in design of various IMC structures with robust and adaptive features. The motivation to design an IM is to produce nearly stable performance as of the system itself. Clustering algorithm and Hankel approximation based model order reduction techniques are used for the design of suitable IM. The time domain performance specifications such as overshoot, settling time, rise time and integral error performance indices such as the integral of the absolute error and the integral of the square of error are taken into consideration for performance analysis of HDV for various uncertainties. PMID:25563057
NASA Technical Reports Server (NTRS)
Foore, Larry; Ida, Nathan
2007-01-01
This study introduces the use of a modified Longley-Rice irregular terrain model and digital elevation data representative of an analogue lunar site for the prediction of RF path loss over the lunar surface. The results are validated by theoretical models and past Apollo studies. The model is used to approximate the path loss deviation from theoretical attenuation over a reflecting sphere. Analysis of the simulation results provides statistics on the fade depths for frequencies of interest, and correspondingly a method for determining the maximum range of communications for various coverage confidence intervals. Communication system engineers and mission planners are provided a link margin and path loss policy for communication frequencies of interest.
Ghrelin and eating behavior: evidence and insights from genetically-modified mouse models
Uchida, Aki; Zigman, Jeffrey M.; Perelló, Mario
2013-01-01
Ghrelin is an octanoylated peptide hormone, produced by endocrine cells of the stomach, which acts in the brain to increase food intake and body weight. Our understanding of the mechanisms underlying ghrelin's effects on eating behaviors has been greatly improved by the generation and study of several genetically manipulated mouse models. These models include mice overexpressing ghrelin and also mice with genetic deletion of ghrelin, the ghrelin receptor [the growth hormone secretagogue receptor (GHSR)] or the enzyme that post-translationally modifies ghrelin [ghrelin O-acyltransferase (GOAT)]. In addition, a GHSR-null mouse model in which GHSR transcription is globally blocked but can be cell-specifically reactivated in a Cre recombinase-mediated fashion has been generated. Here, we summarize findings obtained with these genetically manipulated mice, with the aim to highlight the significance of the ghrelin system in the regulation of both homeostatic and hedonic eating, including that occurring in the setting of chronic psychosocial stress. PMID:23882175
Modeling the Mixture of IRT and Pattern Responses by a Modified HYBRID Model.
ERIC Educational Resources Information Center
Yamamoto, Kentaro; Everson, Howard T.
This study demonstrates the utility of a HYBRID psychometric model, which incorporates both item response theoretic and latent class models, for detecting test speededness. The model isolates where in a sequence of test items examinee response patterns shift from one providing reasonable estimates of ability to those best characterized by a random…
Holistic versus monomeric strategies for hydrological modelling of human-modified hydrosystems
NASA Astrophysics Data System (ADS)
Nalbantis, I.; Efstratiadis, A.; Rozos, E.; Kopsiafti, M.; Koutsoyiannis, D.
2011-03-01
The modelling of human-modified basins that are inadequately measured constitutes a challenge for hydrological science. Often, models for such systems are detailed and hydraulics-based for only one part of the system while for other parts oversimplified models or rough assumptions are used. This is typically a bottom-up approach, which seeks to exploit knowledge of hydrological processes at the micro-scale at some components of the system. Also, it is a monomeric approach in two ways: first, essential interactions among system components may be poorly represented or even omitted; second, differences in the level of detail of process representation can lead to uncontrolled errors. Additionally, the calibration procedure merely accounts for the reproduction of the observed responses using typical fitting criteria. The paper aims to raise some critical issues, regarding the entire modelling approach for such hydrosystems. For this, two alternative modelling strategies are examined that reflect two modelling approaches or philosophies: a dominant bottom-up approach, which is also monomeric and, very often, based on output information, and a top-down and holistic approach based on generalized information. Critical options are examined, which codify the differences between the two strategies: the representation of surface, groundwater and water management processes, the schematization and parameterization concepts and the parameter estimation methodology. The first strategy is based on stand-alone models for surface and groundwater processes and for water management, which are employed sequentially. For each model, a different (detailed or coarse) parameterization is used, which is dictated by the hydrosystem schematization. The second strategy involves model integration for all processes, parsimonious parameterization and hybrid manual-automatic parameter optimization based on multiple objectives. A test case is examined in a hydrosystem in Greece with high complexities
A modified holographic dark energy model with infrared infinite extra dimension(s)
NASA Astrophysics Data System (ADS)
Gong, Yungui; Li, Tianjun
2010-01-01
We propose a modified holographic dark energy (MHDE) model with the Hubble scale as the infrared (IR) cutoff. Introducing the infinite extra dimension(s) at very large distance scale, we consider the black hole mass in higher dimensions as the ultraviolet cutoff. Thus, we can probe the effects of the IR infinite extra dimension(s). As a concrete example, we consider the Dvali-Gabadadze-Porrati (DGP) model and its generalization. We find that the DGP model is dual to the MHDE model in five dimensions, and the ΛCDM model is dual to the MHDE model in six dimensions. Fitting the MHDE model to the observational data, we obtain that Ωm0=0.269-0.027+0.030, Ωk0=0.003-0.012+0.011, and the number of the spatial dimensions is N=4.78-0.44+0.68. The best fit value of N implies that there might exist two IR infinite extra dimensions.
Interaction study between maltose-modified PPI dendrimers and lipidic model membranes.
Wrobel, Dominika; Appelhans, Dietmar; Signorelli, Marco; Wiesner, Brigitte; Fessas, Dimitrios; Scheler, Ulrich; Voit, Brigitte; Maly, Jan
2015-07-01
The influence of maltose-modified poly(propylene imine) (PPI) dendrimers on dimyristoylphosphatidylcholine (DMPC) or dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) (3%) liposomes was studied. Fourth generation (G4) PPI dendrimers with primary amino surface groups were partially (open shell glycodendrimers - OS) or completely (dense shell glycodendrimers - DS) modified with maltose residues. As a model membrane, two types of 100nm diameter liposomes were used to observe differences in the interactions between neutral DMPC and negatively charged DMPC/DMPG bilayers. Interactions were studied using fluorescence spectroscopy to evaluate the membrane fluidity of both the hydrophobic and hydrophilic parts of the lipid bilayer and using differential scanning calorimetry to investigate thermodynamic parameter changes. Pulsed-filed gradient NMR experiments were carried out to evaluate common diffusion coefficient of DMPG and DS PPI in D2O when using below critical micelle concentration of DMPG. Both OS and DS PPI G4 dendrimers show interactions with liposomes. Neutral DS dendrimers exhibit stronger changes in membrane fluidity compared to OS dendrimers. The bilayer structure seems more rigid in the case of anionic DMPC/DMPG liposomes in comparison to pure and neutral DMPC liposomes. Generally, interactions of dendrimers with anionic DMPC/DMPG and neutral DMPC liposomes were at the same level. Higher concentrations of positively charged OS dendrimers induced the aggregation process with negatively charged liposomes. For all types of experiments, the presence of NaCl decreased the strength of the interactions between glycodendrimers and liposomes. Based on NMR diffusion experiments we suggest that apart from electrostatic interactions for OS PPI hydrogen bonds play a major role in maltose-modified PPI dendrimer interactions with anionic and neutral model membranes where a contact surface is needed for undergoing multiple H-bond interactions between
Neutron star structure in an in-medium modified chiral soliton model
NASA Astrophysics Data System (ADS)
Yakhshiev, U. T.
2015-10-01
We study the internal structure of a static and spherically symmetric neutron star in the framework of an in-medium modified chiral soliton model. The Equations of State describing an infinite and asymmetric nuclear matter are obtained introducing the density dependent functions into the low energy free space Lagrangian of the model starting from the phenomenology of pionic atoms. The parametrizations of density dependent functions are related to the properties of isospin asymmetric nuclear systems at saturation density of symmetric nuclear matter ρ0 ≃ 0.16 fm-3. Our results, corresponding to the compressibility of symmetric nuclear matter in the range 250 MeV ≤K0 ≤ 270 MeV and the slop parameter value of symmetry energy in the range 30 MeV ≤LS ≤ 50 MeV, are consistent with the results from other approaches and with the experimental indications. Using the modified Equations of State, near the saturation density of symmetric nuclear matter ρ0, the extrapolations to the high density and highly isospin asymmetric regions have been performed. The calculations showed that the properties of ∼ 1.4M⊙ and ∼ 2M⊙ neutron stars can be well reproduced in the framework of present approach.
Zellnitz, Sarah; Redlinger-Pohn, Jakob Dominik; Kappl, Michael; Schroettner, Hartmuth; Urbanetz, Nora Anne
2013-04-15
The aim of this work is the physical modification and characterization of the surface topography of glass beads used as model carriers in dry powder inhalers (DPIs). By surface modification the contact area between drug and carrier and thereby interparticle forces may be modified. Thus the performance of DPIs that relies on interparticle interactions may be improved. Glass beads were chosen as model carriers because various prospects of physical surface modification may be applied without affecting other factors also impacting interparticle interactions like particle size and shape. To generate rough surfaces glass beads were processed mechanically by friction and impaction in a ball mill with different grinding materials that were smaller and harder with respect to the glass beads. By varying the grinding time (4 h, 8 h) and by using different grinding media (tungsten carbide, quartz) surfaces with different shades of roughness were generated. Depending on the hardness of the grinding material and the grinding time the surface roughness was more or less pronounced. Surface roughness parameters and specific surface area were determined via several complementary techniques in order to get an enhanced understanding of the impact of the modifying procedure on the surface properties of the glass beads. PMID:23470233
A modified full velocity difference model with the consideration of velocity deviation
NASA Astrophysics Data System (ADS)
Zhou, Jie; Shi, Zhong-Ke
2016-01-01
In this paper, a modified full velocity difference model (FVDM) based on car-following theory is proposed with the consideration of velocity deviation which represents the inexact judgement of velocity. The stability condition is obtained by the use of linear stability analysis. It is shown that the stability of traffic flow varies with the deviation extent of velocity. The Burgers, Korteweg-de Vries (KdV) and modified K-dV (MKdV) equations are derived to describe the triangular shock waves, soliton waves and kink-antikink waves in the stable, metastable and unstable region, respectively. The numerical simulations show a good agreement with the analytical results, such as density wave, hysteresis loop, acceleration, deceleration and so on. The results show that traffic congestion can be suppressed by taking the positive effect of velocity deviation into account. By taking the positive effect of high estimate of velocity into account, the unrealistic high deceleration and negative velocity which occur in FVDM will be eliminated in the proposed model.
NASA Technical Reports Server (NTRS)
Cater, Christopher; Xiao, Xinran; Goldberg, Robert K.; Kohlman, Lee W.
2015-01-01
A combined experimental and analytical approach was performed for characterizing and modeling triaxially braided composites with a modified subcell modeling strategy. Tensile coupon tests were conducted on a [0deg/60deg/-60deg] braided composite at angles [0deg, 30deg, 45deg, 60deg and 90deg] relative to the axial tow of the braid. It was found that measured coupon strength varied significantly with the angle of the applied load and each coupon direction exhibited unique final failures. The subcell modeling approach implemented into the finite element software LS-DYNA was used to simulate the various tensile coupon test angles. The modeling approach was successful in predicting both the coupon strength and reported failure mode for the 0deg, 30deg and 60deg loading directions. The model over-predicted the strength in the 90deg direction; however, the experimental results show a strong influence of free edge effects on damage initiation and failure. In the absence of these local free edge effects, the subcell modeling approach showed promise as a viable and computationally efficient analysis tool for triaxially braided composite structures. Future work will focus on validation of the approach for predicting the impact response of the braided composite against flat panel impact tests.
NASA Technical Reports Server (NTRS)
Cater, Christopher; Xiao, Xinran; Goldberg, Robert K.; Kohlman, Lee W.
2015-01-01
A combined experimental and analytical approach was performed for characterizing and modeling triaxially braided composites with a modified subcell modeling strategy. Tensile coupon tests were conducted on a [0deg/60deg/-60deg] braided composite at angles of 0deg, 30deg, 45deg, 60deg and 90deg relative to the axial tow of the braid. It was found that measured coupon strength varied significantly with the angle of the applied load and each coupon direction exhibited unique final failures. The subcell modeling approach implemented into the finite element software LS-DYNA was used to simulate the various tensile coupon test angles. The modeling approach was successful in predicting both the coupon strength and reported failure mode for the 0deg, 30deg and 60deg loading directions. The model over-predicted the strength in the 90deg direction; however, the experimental results show a strong influence of free edge effects on damage initiation and failure. In the absence of these local free edge effects, the subcell modeling approach showed promise as a viable and computationally efficient analysis tool for triaxially braided composite structures. Future work will focus on validation of the approach for predicting the impact response of the braided composite against flat panel impact tests.
Modified energy cascade model adapted for a multicrop Lunar greenhouse prototype
NASA Astrophysics Data System (ADS)
Boscheri, G.; Kacira, M.; Patterson, L.; Giacomelli, G.; Sadler, P.; Furfaro, R.; Lobascio, C.; Lamantea, M.; Grizzaffi, L.
2012-10-01
Models are required to accurately predict mass and energy balances in a bioregenerative life support system. A modified energy cascade model was used to predict outputs of a multi-crop (tomatoes, potatoes, lettuce and strawberries) Lunar greenhouse prototype. The model performance was evaluated against measured data obtained from several system closure experiments. The model predictions corresponded well to those obtained from experimental measurements for the overall system closure test period (five months), especially for biomass produced (0.7% underestimated), water consumption (0.3% overestimated) and condensate production (0.5% overestimated). However, the model was less accurate when the results were compared with data obtained from a shorter experimental time period, with 31%, 48% and 51% error for biomass uptake, water consumption, and condensate production, respectively, which were obtained under more complex crop production patterns (e.g. tall tomato plants covering part of the lettuce production zones). These results, together with a model sensitivity analysis highlighted the necessity of periodic characterization of the environmental parameters (e.g. light levels, air leakage) in the Lunar greenhouse.
The concept of quasi-integrability for modified non-linear Schrödinger models
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Luchini, G.; Zakrzewski, Wojtek J.
2012-09-01
We consider modifications of the nonlinear Schrödinger model (NLS) to look at the recently introduced concept of quasi-integrability. We show that such models possess an infinite number of quasi-conserved charges which present intriguing properties in relation to very specific space-time parity transformations. For the case of two-soliton solutions where the fields are eigenstates of this parity, those charges are asymptotically conserved in the scattering process of the solitons. Even though the charges vary in time their values in the far past and the far future are the same. Such results are obtained through analytical and numerical methods, and employ adaptations of algebraic techniques used in integrable field theories. Our findings may have important consequences on the applications of these models in several areas of non-linear science. We make a detailed numerical study of the modified NLS potential of the form V ~ (| ψ|2)2+ ɛ , with ɛ being a perturbation parameter. We perform numerical simulations of the scattering of solitons for this model and find a good agreement with the results predicted by the analytical considerations. Our paper shows that the quasi-integrability concepts recently proposed in the context of modifications of the sine-Gordon model remain valid for perturbations of the NLS model.
NASA Astrophysics Data System (ADS)
Guha, Koushik; Kumar, Mithlesh; Agarwal, Saurabh; Baishya, Srimanta
2015-12-01
This paper deals with the approach to accurately model the capacitance of non-uniform meander based RF MEMS shunt switch with perforated structure. Here the general analytical model of capacitance is proposed for both up state and down state condition of the switch. The model also accounts for fringing capacitance due to beam thickness and etched holes on the beam. Calculated results are validated with the simulated results of full 3D FEM solver Coventorware in both the conditions of the switch. Variation of Up-state and Down-state capacitances with different dielectric thicknesses and voltages are plotted and error of analytical value is estimated and analyzed. Three benchmark models of parallel plate capacitance are modified for MEMS switch operation and their results are compared with the proposed model. Percentage contribution of fringing capacitance in up-state and down-state is approx. 25% and 2%, respectively, of the total capacitance. The model shows good accuracy with the mean error of -4.45% in up-state and -5.78% in down-state condition for a wide range of parameter variations and -2.13% for ligament efficiency of μ = 0.3.
A two-field modified Lagrangian formulation for robust simulations of extrinsic cohesive zone models
NASA Astrophysics Data System (ADS)
Cazes, F.; Coret, M.; Combescure, A.
2013-06-01
This paper presents the robust implementation of a cohesive zone model based on extrinsic cohesive laws (i.e. laws involving an infinite initial stiffness). To this end, a two-field Lagrangian weak formulation in which cohesive tractions are chosen as the field variables along the crack's path is presented. Unfortunately, this formulation cannot model the infinite compliance of the broken elements accurately, and no simple criterion can be defined to determine the loading-unloading change of state at the integration points of the cohesive elements. Therefore, a modified Lagrangian formulation using a fictitious cohesive traction instead of the classical cohesive traction as the field variable is proposed. Thanks to this change of variable, the cohesive law becomes an increasing function of the equivalent displacement jump, which eliminates the problems mentioned previously. The ability of the proposed formulations to simulate fracture accurately and without field oscillations is investigated through three numerical test examples.
Spatial interactions in a modified Daisyworld model: Heat diffusivity and greenhouse effects
NASA Astrophysics Data System (ADS)
Alberti, T.; Primavera, L.; Vecchio, A.; Lepreti, F.; Carbone, V.
2015-11-01
In this work we investigate a modified version of the Daisyworld model, originally introduced by Lovelock and Watson to describe in a simple way the interactions between an Earth-like planet, its biosphere, and the incoming solar radiation. Here a spatial dependency on latitude is included, and both a variable heat diffusivity along latitudes and a simple greenhouse effect description are introduced in the model. We show that the spatial interactions between the variables of the system can locally stabilize the coexistence of the two vegetation types. The feedback on albedo is able to generate equilibrium solutions which can efficiently self-regulate the planet climate, even for values of the solar luminosity relatively far from the current Earth conditions.
Nesseris, Savvas
2009-02-15
We consider theories with an arbitrary coupling between matter and gravity and obtain the perturbation equation of matter on subhorizon scales. Also, we derive the effective gravitational constant G{sub eff} and two parameters {sigma} and {eta}, which along with the perturbation equation of the matter density are useful to constrain the theory from growth factor and weak lensing observations. Finally, we use a completely solvable toy model which exhibits nontrivial phenomenology to investigate specific features of the theory. We obtain the analytic solution of the modified Friedmann equation for the scale factor a in terms of time t and use the age of the oldest star clusters and the primordial nucleosynthesis bounds in order to constrain the parameters of our toy model.
Vazquez-Leal, H; Jimenez-Fernandez, V M; Benhammouda, B; Filobello-Nino, U; Sarmiento-Reyes, A; Ramirez-Pinero, A; Marin-Hernandez, A; Huerta-Chua, J
2014-01-01
We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157
Spatial interactions in a modified Daisyworld model: Heat diffusivity and greenhouse effects.
Alberti, T; Primavera, L; Vecchio, A; Lepreti, F; Carbone, V
2015-11-01
In this work we investigate a modified version of the Daisyworld model, originally introduced by Lovelock and Watson to describe in a simple way the interactions between an Earth-like planet, its biosphere, and the incoming solar radiation. Here a spatial dependency on latitude is included, and both a variable heat diffusivity along latitudes and a simple greenhouse effect description are introduced in the model. We show that the spatial interactions between the variables of the system can locally stabilize the coexistence of the two vegetation types. The feedback on albedo is able to generate equilibrium solutions which can efficiently self-regulate the planet climate, even for values of the solar luminosity relatively far from the current Earth conditions. PMID:26651733
Vazquez-Leal, H.; Jimenez-Fernandez, V. M.; Benhammouda, B.; Filobello-Nino, U.; Sarmiento-Reyes, A.; Ramirez-Pinero, A.; Marin-Hernandez, A.; Huerta-Chua, J.
2014-01-01
We present a homotopy continuation method (HCM) for finding multiple operating points of nonlinear circuits composed of devices modelled by using piecewise linear (PWL) representations. We propose an adaptation of the modified spheres path tracking algorithm to trace the homotopy trajectories of PWL circuits. In order to assess the benefits of this proposal, four nonlinear circuits composed of piecewise linear modelled devices are analysed to determine their multiple operating points. The results show that HCM can find multiple solutions within a single homotopy trajectory. Furthermore, we take advantage of the fact that homotopy trajectories are PWL curves meant to replace the multidimensional interpolation and fine tuning stages of the path tracking algorithm with a simple and highly accurate procedure based on the parametric straight line equation. PMID:25184157
Stochastic model reduction using a modified Hill-type kinetic rate law.
Smadbeck, Patrick; Kaznessis, Yiannis
2012-12-21
In the present work, we address a major challenge facing the modeling of biochemical reaction networks: when using stochastic simulations, the computational load and number of unknown parameters may dramatically increase with system size and complexity. A proposed solution to this challenge is the reduction of models by utilizing nonlinear reaction rate laws in place of a complex multi-reaction mechanism. This type of model reduction in stochastic systems often fails when applied outside of the context in which it was initially conceived. We hypothesize that the use of nonlinear rate laws fails because a single reaction is inherently Poisson distributed and cannot match higher order statistics. In this study we explore the use of Hill-type rate laws as an approximation for gene regulation, specifically transcription repression. We matched output data for several simple gene networks to determine Hill-type parameters. We show that the models exhibit inaccuracies when placed into a simple feedback repression model. By adding an additional abstract reaction to the models we account for second-order statistics. This split Hill rate law matches higher order statistics and demonstrates that the new model is able to more accurately describe the mean protein output. Finally, the modified Hill model is shown to be modular and models retain accuracy when placed into a larger multi-gene network. The work as presented may be used in gene regulatory or cell-signaling networks, where multiple binding events can be captured by Hill kinetics. The added benefit of the proposed split-Hill kinetics is the improved accuracy in modeling stochastic effects. We demonstrate these benefits with a few specific reaction network examples. PMID:23267473
NASA Astrophysics Data System (ADS)
Zeng, X.; Shao, P.; Song, X.
2010-12-01
Terrestrial ecosystem formation and diversity have great impact on the stability and frangibility of ecosystem. It is important that Dynamic Global Vegetation Models (DGVMs) can capture these essential properties so that they can correctly simulate the succession and transition of terrestrial ecosystem in company with the global climate change. Previous studies have shown that DGVMs can roughly reproduce the spatial distributions of different vegetation types as well as the dependence of the vegetation distribution on climate conditions, however, the capability of DGVMs to reproduce the global vegetation distribution and ecosystem formation has not been fully evaluated. This study is based on our modified DGVM coupled with the Community Land Model (CLM-DGVM). The modified CLM-DGVM can simulate 12 plant functional types (PFTs) besides the bare soil. It allows two or more PFTs coexisting in a grid cell, in contrast to the DGVMs which tend to generate the ecosystem with single dominant plant functional type and hence lose the functional diversity of ecosystem. Our results show that the density distributions of fractional coverage (DDFC) of three vegetation categories (e.g., forest, grassland, and shrubland) and PFTs are different with the observation. In particular, the model overestimates the DDFC over regions with tree coverage larger than 70%, but underestimates the DDFC over regions with tree coverage less than 40%. Furthermore, the functional diversity of PFTs in each gridcell is generally lower than that in the observation. Sensitivity tests show that substantial changes in the terrestrial ecosystem usually occur within the areas where two or more PFTs coexist with comparable fractions, i.e., and the functional diversity is high. These results imply that current CLM-DGVM may not be able to appropriately produce the averaged amplitude and spatial pattern of the transition in global ecosystem. Therefore, we suggest that extensive studies are required to improve
47 CFR 76.1905 - Petitions to modify encoding rules for new services within defined business models.
Code of Federal Regulations, 2013 CFR
2013-10-01
... services within defined business models. 76.1905 Section 76.1905 Telecommunication FEDERAL COMMUNICATIONS... Rules § 76.1905 Petitions to modify encoding rules for new services within defined business models. (a) The encoding rules for defined business models in § 76.1904 reflect the conventional methods...
47 CFR 76.1905 - Petitions to modify encoding rules for new services within defined business models.
Code of Federal Regulations, 2011 CFR
2011-10-01
... services within defined business models. 76.1905 Section 76.1905 Telecommunication FEDERAL COMMUNICATIONS... Rules § 76.1905 Petitions to modify encoding rules for new services within defined business models. (a) The encoding rules for defined business models in § 76.1904 reflect the conventional methods...
47 CFR 76.1905 - Petitions to modify encoding rules for new services within defined business models.
Code of Federal Regulations, 2014 CFR
2014-10-01
... services within defined business models. 76.1905 Section 76.1905 Telecommunication FEDERAL COMMUNICATIONS... Rules § 76.1905 Petitions to modify encoding rules for new services within defined business models. (a) The encoding rules for defined business models in § 76.1904 reflect the conventional methods...
47 CFR 76.1905 - Petitions to modify encoding rules for new services within defined business models.
Code of Federal Regulations, 2012 CFR
2012-10-01
... services within defined business models. 76.1905 Section 76.1905 Telecommunication FEDERAL COMMUNICATIONS... Rules § 76.1905 Petitions to modify encoding rules for new services within defined business models. (a) The encoding rules for defined business models in § 76.1904 reflect the conventional methods...
Reduced-Order Model Based Feedback Control For Modified Hasegawa-Wakatani Model
Goumiri, I. R.; Rowley, C. W.; Ma, Z.; Gates, D. A.; Krommes, J. A.; Parker, J. B.
2013-01-28
In this work, the development of model-based feedback control that stabilizes an unstable equilibrium is obtained for the Modi ed Hasegawa-Wakatani (MHW) equations, a classic model in plasma turbulence. First, a balanced truncation (a model reduction technique that has proven successful in ow control design problems) is applied to obtain a low dimensional model of the linearized MHW equation. Then a modelbased feedback controller is designed for the reduced order model using linear quadratic regulators (LQR). Finally, a linear quadratic gaussian (LQG) controller, which is more resistant to disturbances is deduced. The controller is applied on the non-reduced, nonlinear MHW equations to stabilize the equilibrium and suppress the transition to drift-wave induced turbulence.
Mapping genetic modifiers of survival in a mouse model of Dravet syndrome
Miller, Alison R.; Hawkins, Nicole A.; McCollom, Clint E.; Kearney, Jennifer A.
2014-01-01
Epilepsy is a common neurological disorder affecting approximately 1% of the population. Mutations in voltage-gated sodium channels are responsible for several monogenic epilepsy syndromes. More than 800 mutations in the voltage-gated sodium channel SCN1A have been reported in patients with generalized epilepsy with febrile seizures plus and Dravet syndrome. Heterozygous loss-of-function mutations in SCN1A result in Dravet syndrome, a severe infant-onset epileptic encephalopathy characterized by intractable seizures, developmental delays and increased mortality. A common feature of monogenic epilepsies is variable expressivity among individuals with the same mutation, suggesting that genetic modifiers may influence clinical severity. Mice with heterozygous deletion of Scn1a (Scn1a+/−) model a number of Dravet syndrome features, including spontaneous seizures and premature lethality. Phenotype severity in Scn1a+/− mice is strongly dependent on strain background. On the 129S6/SvEvTac strain Scn1a+/− mice exhibit no overt phenotype, while on the (C57BL/6J × 129S6/SvEvTac)F1 strain Scn1a+/− mice exhibit spontaneous seizures and early lethality. To systematically identify loci that influence premature lethality in Scn1a+/− mice, we performed genome scans on reciprocal backcrosses. QTL mapping revealed modifier loci on mouse chromosomes 5, 7, 8 and 11. RNA-seq analysis of strain-dependent gene expression, regulation and coding sequence variation provided a list of potential functional candidate genes at each locus. Identification of modifier genes that influence survival in Scn1a+/− mice will improve our understanding of the pathophysiology of Dravet syndrome and may suggest novel therapeutic strategies for improved treatment of human patients. PMID:24152123
NASA Technical Reports Server (NTRS)
Conley, Julianne M.; Leonard, B. P.
1994-01-01
The modified mixing length (MML) turbulence model was installed in the Proteus Navier-Stokes code, then modified to make it applicable to a wider range of flows typical of aerospace propulsion applications. The modifications are based on experimental data for three flat-plate flows having zero, mild adverse, and strong adverse pressure gradients. Three transonic diffuser test cases were run with the new version of the model in order to evaluate its performance. All results are compared with experimental data and show improvements over calculations made using the Baldwin-Lomax turbulence model, the standard algebraic model in Proteus.
Genome editing revolutionize the creation of genetically modified pigs for modeling human diseases.
Yao, Jing; Huang, Jiaojiao; Zhao, Jianguo
2016-09-01
Pigs have anatomical, physiological and genomic characteristics that make them highly suitable for modeling human diseases. Genetically modified (GM) pig models of human diseases are critical for studying pathogenesis, treatment, and prevention. The emergence of nuclease-mediated genome editing technology has been successfully employed for engineering of the pig genome, which has revolutionize the creation of GM pig models with highly complex pathophysiologies and comorbidities. In this review, we summarize the progress of recently developed genome editing technologies, including zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9), which enable highly efficient and precise introduction of genome modifications into pigs, and tailored disease models that have been generated in various disciplines via genome editing technology. We also summarize the GM pig models that have been generated by conventional transgenic strategies. Additionally, perspectives regarding the application of GM pigs in biomedical research are discussed. PMID:27432159
Modified jet noise source model for twin-jet shielding analysis
NASA Technical Reports Server (NTRS)
Gerhold, C. H.; Kim, C.
1983-01-01
An analytical method to estimate the influence that a jet of heated flow has on the noise emission from a parallel jet is presented. The shielding jet is modelled as a cylinder of constant cross-section in which the flow speed and temperature are uniform throughout. The jet noise emission is modelled by a point source with directivity imposed. The directivity term consists of: a self-noise term, a shear-noise term, and a convection factor. The self- and shear-noise terms each contain a basic directivity factor multiplying a spectral shape function. The various components are evaluated based on comparison with isothermal jet radiation experimental data. The modified source term is incorporated into the jet shielding model and compared to heated twin jet shielding data. The estimated spectra agree well except further downstream of the nozzle where peak of the noise spectrum estimated by the model lies approximately one octave below the experimental peak. The noise reduction estimated by the model agrees favorably with experiment in the near downstream region. This discrepancy is explained in terms of the shielding mechanism which is dominant far downstream.
Modeling evapotranspiration in Arctic coastal plain ecosystems using a modified BIOME-BGC model
NASA Astrophysics Data System (ADS)
Engstrom, Ryan; Hope, Allen; Kwon, Hyojung; Harazono, Yoshinobu; Mano, Masayoshi; Oechel, Walter
2006-06-01
Modeling evapotranspiration (ET) in Arctic coastal plain ecosystems is challenging owing to the unique conditions present in this environment, including permafrost, nonvascular vegetation, and a large standing dead vegetation component. In this study the ecosystem process model, BIOME-BGC, was adapted to represent these unique conditions in Arctic ecosystems by including a new water storage and evaporation routine that accounts for nonvascular vegetation and the effects of permafrost, adding ground heat flux as an input, and representing ground shading by dead vegetation. The new Arctic version and the original BIOME-BGC models are compared to observed ET from two eddy flux towers in Barrow, Alaska over four summer seasons (1999-2002). The two towers are located less than 1 km apart, yet represent contrasting moisture conditions. One is located in a drained thaw lake, marsh area, while the other is located in a drier, upland area characterized by mesic tundra. Results indicate that the original BIOME-BGC model substantially underestimated ET, while the Arctic version slightly overestimated ET at both sites. The new Arctic model version worked particularly well at the wet tower because the model was able to capture energy limitations better than water limitations. Errors in the simulation of snowmelt date led to errors in the ET estimates at both sites. Finally, the substantial differences in soil moisture led to substantially different ET rates between the sites that were difficult to simulate and indicates that soil moisture heterogeneity is a strong controller on ET in these ecosystems.
Prescott, Vanessa E; Hogan, Simon P
2006-08-01
The recent advances in biotechnology in the plant industry have led to increasing crop production and yield that in turn has increased the usage of genetically modified (GM) food in the human food chain. The usage of GM foods for human consumption has raised a number of fundamental questions including the ability of GM foods to elicit potentially harmful immunological responses, including allergic hypersensitivity. To assess the safety of foods derived from GM plants including allergenic potential, the US FDA, Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO), and the EU have developed approaches for evaluation assessment. One assessment approach that has been a very active area of research and debate is the development and usage of animal models to assess the potential allergenicity of GM foods. A number of specific animal models employing rodents, pigs, and dogs have been developed for allergenicity assessment. However, validation of these models is needed and consideration of the criteria for an appropriate animal model for the assessment of allergenicity in GM plants is required. We have recently employed a BALB/c mouse model to assess the potential allergenicity of GM plants. We have been able to demonstrate that this model is able to detect differences in antigenicity and identify aspects of protein post-translational modifications that can alter antigenicity. Furthermore, this model has also enabled us to examine the usage of GM plants as a therapeutic approach for the treatment of allergic diseases. This review discusses the current approaches to assess the allergenic potential of GM food and particularly focusing on the usage of animal models to determine the potential allergenicity of GM foods and gives an overview of our recent findings and implications of these studies. PMID:16364445
Insight into the mechanism of coffee melanoidin formation using modified "in bean" models.
Nunes, Fernando M; Cruz, Ana C S; Coimbra, Manuel A
2012-09-01
To study the mechanism of coffee melanoidin formation, green coffee beans were prepared by (1) removal of the hot water extractable components (WECoffee); (2) direct incorporation of sucrose (SucCoffee); and (3) direct incorporation of type II arabinogalactan-proteins (AGPCoffee). As a control of sucrose and AGP incorporation, lyophilized green coffee beans were also immersed in water (control). The original coffee and the four modified "in bean" coffee models were roasted and their chemical characteristics compared. The formation of material not identified as carbohydrates or protein, usually referred to as "unknown material" and related to melanoidins, and the development of the brown color during coffee roasting have distinct origins. Therefore, a new parameter for coffee melanoidin evaluation, named the "melanoidin browning index" (MBI), was introduced to handle simultaneously the two concepts. Sucrose is important for the formation of colored structures but not to the formation of "unknown material". Type II AGPs also increase the brown color of the melanoidins, but did not increase the amount of "unknown material". The green coffee hot water extractable components are essential for coffee melanoidin formation during roasting. The cell wall material was able to generate a large amount of "unknown material". The galactomannans modified by the roasting and the melanoidin populations enriched in galactomannans accounted for 47% of the high molecular weight brown color material, showing that these polysaccharides are very relevant for coffee melanoidin formation. PMID:22880950
NASA Astrophysics Data System (ADS)
Vacaru, Sergiu I.
2015-04-01
We reinvestigate how generic off-diagonal cosmological solutions depending, in general, on all spacetime coordinates can be constructed in massive and -modified gravity using the anholonomic frame deformation method. New classes of locally anisotropic and (in-) homogeneous cosmological metrics are constructed with open and closed spatial geometries. By resorting to such solutions, we show that they describe the late time acceleration due to effective cosmological terms induced by nonlinear off-diagonal interactions, possible modifications of the gravitational action and graviton mass. The cosmological metrics and related Stückelberg fields are constructed in explicit form up to nonholonomic frame transforms of the Friedmann-Lamaître-Robertson-Walker (FLRW) coordinates. The solutions include matter, graviton mass, and other effective sources modeling nonlinear gravitational and matter field interactions with polarization of physical constants and deformations of metrics, which may explain dark energy and dark matter effects. However, we argue that it is not always necessary to modify gravity if we consider the effective generalized Einstein equations with nontrivial vacuum and/or non-minimal coupling with matter. Indeed, we state certain conditions when such configurations mimic interesting solutions in general relativity and modifications, for instance, when we can extract the general Painlevé-Gullstrand and FLRW metrics. In a more general context, we elaborate on a reconstruction procedure for off-diagonal cosmological solutions which describe cyclic and ekpyrotic universes. Finally, open issues and further perspectives are discussed.
A modified DRASTIC model for Siting Confined Animal Feeding Operations in Williams County, Ohio, USA
NASA Astrophysics Data System (ADS)
Gomezdelcampo, Enrique; Dickerson, J. Ryan
2008-10-01
Three of DRASTIC’s parameters (Depth to Water, Soil Media, and Topography) were modified and another parameter was added (land use/land cover) to the model to determine the potential impact on groundwater from Confined Animal Feeding Operations (CAFO) manure lagoon settings and manure application as fertilizer. Williams County is a mostly agricultural county located in northwest Ohio, USA. It currently has three CAFOs, all dairy, with the possibility of the construction of a multi-million chicken egg CAFO in the near future. A Geographic Information System (GIS) was utilized to modify the Ohio Department of Natural Resources (ODNR) DRASTIC map for the county to fully assess the county-wide pollution potential of CAFOs. The CAFO DRASTIC map indicates that almost half of Williams County has elevated groundwater pollution potential. The rest of the county, primarily the southeast corner, has lower CAFO groundwater pollution potential. Future CAFO development within the county should focus on the southeastern portion of the county where the groundwater table is deeper, and the aquifer is composed of shale substrate with low hydraulic conductivity. The CAFO DRASTIC results are intended to be used as a screening tool and are not to replace site-specific hydrogeologic investigations.
Percival, K.R.; Radi, Z.A.
2016-01-01
Optimal histochemical staining is critical to ensure excellent quality stained sections to enable light microscopic and histomorphometric image analysis. Verhoeff-van Gieson is the most widely used histochemical stain for the visualization of vascular elastic fibers. However, it is notoriously difficult to differentiate fine elastic fibers of small vasculature to enable histomorphometric image analysis, especially in organs such as the lung. A tissue fixation procedure of 10% neutral buffered formalin with subsequent fixation in 70% ethanol further compounds the problem of small vessel staining and identification. Therefore, a modified Verhoeff’s elastin stain was developed as a reliable method to optimally highlight the internal and external elastic laminae of small arteries (50-100 µm external diameter) and intra-acinar vessels (10-50 µm external diameter) in 3 µm thick lung tissue sections from models of pulmonary arterial hypertension. This modified Verhoeff’s elastin stain demonstrated well-defined staining of fine elastic fibers of pulmonary blood vessels enabling subsequent histomorphometric image analysis of vessel wall thickness in small arteries and intra-acinar vessels. In conclusion, modification of the standard Verhoeff-van Gieson histochemical stain is needed to visualize small caliber vessels’ elastic fibers especially in tissues fixed in 10% neutral buffered formalin followed by additional fixation in 70% ethanol. PMID:26972717
Modeling mechanical properties of core-shell rubber-modified epoxies
Wang, X.; Xiao, K.; Ye, L.; Mai, Y.W.; Wang, C.H.; Rose, L.R.F.
2000-01-24
Experiments have been carried out to quantify the effects of rubber content and strain rate on the elastic and plastic deformation behavior of core-shell rubber-modified epoxies. Both the Young's modulus and the yield stress were found to be slightly dependent on strain rate, but very sensitive to the volume fraction of rubber particles. Finite element analyses have also been performed to determine the influences of rubber content on the bulk elasticity modulus and the yield stress. By comparing with experimental results, it is found that the Young's modulus of rubber-toughened epoxies can be accurately estimated using the Mori-Tanaka method, provided that the volume fraction of rubber particles is appropriately evaluated. A yield function is provided that the volume fraction of rubber particles is appropriately evaluated. A yield function is proposed to quantify the effects of hydrostatic stress on the plastic yielding behaviors of rubber-modified epoxies. Agreement with experimental results is good. Also, a visco-plastic model is developed to simulate the strain-rate-dependent stress-strain relations.
Sejergaard, Lars; Karkov, Hanne Sophie; Krarup, Janus Kristian; Hagel, Anne Birgitte Bagge; Cramer, Steven M
2014-01-01
This study demonstrates how the multimodal Capto adhere resin can be used in concert with calcium chloride or arginine hydrochloride as mobile phase modifiers to create a highly selective purification process for a modified human growth hormone. Importantly, these processes are shown to result in significant clearance of product related aggregates and host cell proteins. Furthermore, the steric mass action model is shown to be capable of accurately describing the chromatographic process and the aggregate removal. Finally, justification of the selected operating ranges is evaluated using the model together with Latin hypercube sampling. The results in this article establish the utility of multimodal chromatography when used with appropriate mobile phase modifiers for the downstream bioprocessing of a modified human growth hormone and offer new approaches for bioprocess verification. PMID:24799458
Simulation of emotional contagion using modified SIR model: A cellular automaton approach
NASA Astrophysics Data System (ADS)
Fu, Libi; Song, Weiguo; Lv, Wei; Lo, Siuming
2014-07-01
Emotion plays an important role in the decision-making of individuals in some emergency situations. The contagion of emotion may induce either normal or abnormal consolidated crowd behavior. This paper aims to simulate the dynamics of emotional contagion among crowds by modifying the epidemiological SIR model to a cellular automaton approach. This new cellular automaton model, entitled the “CA-SIRS model”, captures the dynamic process ‘susceptible-infected-recovered-susceptible', which is based on SIRS contagion in epidemiological theory. Moreover, in this new model, the process is integrated with individual movement. The simulation results of this model show that multiple waves and dynamical stability around a mean value will appear during emotion spreading. It was found that the proportion of initial infected individuals had little influence on the final stable proportion of infected population in a given system, and that infection frequency increased with an increase in the average crowd density. Our results further suggest that individual movement accelerates the spread speed of emotion and increases the stable proportion of infected population. Furthermore, decreasing the duration of an infection and the probability of reinfection can markedly reduce the number of infected individuals. It is hoped that this study will be helpful in crowd management and evacuation organization.
Tunney, M M; Keane, P F; Gorman, S P
1997-01-01
Encrustation of biomaterials employed in the urinary tract remains a major problem resulting in obstruction or blockage of catheters and stents. Therefore, resistance to encrustation is a desirable feature of biomaterials employed in such devices. The novel assessment of biomaterial encrustation employing a continuous flow model based on a modified Robbins device is described. Artificial urine was used in conjunction with 5% CO2 to simulate the physiological environment within the upper urinary tract. The widely used urinary device biomaterials, silicone and polyurethane, were investigated in the model for hydroxyapatite and struvite encrustation. Scanning electron microscopy, energy dispersive X-ray analysis, and atomic absorption spectroscopy all showed that silicone was less prone to encrustation than polyurethane and that hydroxyapatite deposition was predominant on both surfaces. The model has the advantage that a large number of biomaterials may be investigated simultaneously because several Robbins devices may be placed in parallel. The model is recommended for comparative evaluation of biomaterial candidates for use in urinary tract devices. PMID:9178735
Hoyle, D; Juhasz, G; Aso, E; Chase, D; del Rio, J; Fabre, V; Hamon, M; Lanfumey, L; Lesch, K-P; Maldonado, R; Serra, M-A; Sharp, T; Tordera, R; Toro, C; Deakin, J F W
2011-01-01
This study aimed to identify whether genetic manipulation of four systems implicated in the pathogenesis of depression converge on shared molecular processes underpinning depression-like behaviour in mice. Altered 5HT function was modelled using the 5-HT transporter knock out mouse, impaired glucocorticoid receptor (GR) function using an antisense-induced knock down mouse, disrupted glutamate function using a heterozygous KO of the vesicular glutamate transporter 1 gene, and impaired cannabinoid signalling using the cannabinoid 1 receptor KO mouse. All 4 four genetically modified mice were previously shown to show exaggerated helpless behaviour compared to wild-type controls and variable degrees of anxiety and anhedonic behaviour. mRNA was extracted from frontal cortex and hybridised to Illumina microarrays. Combined contrast analysis was used to identify genes showing different patterns of up- and down-regulation across the 4 models. 1823 genes were differentially regulated. They were over-represented in gene ontology categories of metabolism, protein handling and synapse. In each model compared to wild-type mice of the same genetic background, a number of genes showed increased expression changes of >10%, other genes showed decreases in each model. Most of the genes showed mixed effects. Several previous array findings were replicated. The results point to cellular stress and changes in post-synaptic remodelling as final common mechanisms of depression and resilience. PMID:21030216
Estimating the daily course of Konza Prairie latent Heat fluxes using a modified Tergra model
NASA Astrophysics Data System (ADS)
Hope, Allen S.
1992-11-01
The Tergra model simulates the daily course of water and energy flows through the soil-plantatmosphere system and was intended for use with remotely sensed data. In its original form, the model is not well suited to estimating spatial patterns of latent heat flux (λE) in the Konza Prairie since the determination of canopy resistance requires knowledge of vegetation height, and the defined relationship between leaf water potential and rc is specific to C3 plants. The canopy resistance component of Tergra was replaced by a routine that includes the calculation of minimum canopy resistance (rcm) from the normalized difference vegetation index (NDVI) and stress adjustment factors for leaf water potential and vapor pressure deficit to determine actual canopy resistance (rc). The relationship between rc and leaf water potential is defined for both C3 and C4 plants, and total λE is obtained from the sum of the proportional contributions from these two vegetation classes. The modified Tergra model (Tergra-2) was tested using input and flux data collected at four First ISLSCP Field Experiment (FIFE) sites during three periods characterized by different soil moisture conditions. Tergra-2 was found to be a good simulator of λE and in most cases gave substantially better results than those obtained using the original model. The greatest inaccuracy using Tergra-2 occurred under extremely dry soil moisture conditions, whereas absolute errors for both models tended to increase around solar noon. Leaf water potential was the dominant stress factor affecting modeled rc. It was concluded that vapor pressure deficit and leaf water potential should not be regarded as completely independent factors affecting rc. A brief comparison of modeled and observed canopy temperatures is presented and discussed.
Scanlon, T.M.; Raffensperger, J.P.; Hornberger, G.M.; Clapp, R.B.
2000-01-01
Transient, perched water tables in the shallow subsurface are observed at the South Fork Brokenback Run catchment in Shenandoah National Park, Virginia. Crest piezometers installed along a hillslope transect show that the development of saturated conditions in the upper 1.5 m of the subsurface is controlled by total precipitation and antecedent conditions, not precipitation intensity, although soil heterogeneities strongly influence local response. The macroporous subsurface storm flow zone provides a hydrological pathway for rapid runoff generation apart from the underlying groundwater zone, a conceptualization supported by the two-storage system exhibited by hydrograph recession analysis. A modified version of TOPMODEL is used to simulate the observed catchment dynamics. In this model, generalized topographic index theory is applied to the subsurface storm flow zone to account for logarithmic storm flow recessions, indicative of linearly decreasing transmissivity with depth. Vertical drainage to the groundwater zone is required, and both subsurface reservoirs are considered to contribute to surface saturation.
NASA Astrophysics Data System (ADS)
Scanlon, Todd M.; Raffensperger, Jeff P.; Hornberger, George M.; Clapp, Roger B.
2000-09-01
Transient, perched water tables in the shallow subsurface are observed at the South Fork Brokenback Run catchment in Shenandoah National Park, Virginia. Crest piezometers installed along a hillslope transect show that the development of saturated conditions in the upper 1.5 m of the subsurface is controlled by total precipitation and antecedent conditions, not precipitation intensity, although soil heterogeneities strongly influence local response. The macroporous subsurface storm flow zone provides a hydrological pathway for rapid runoff generation apart from the underlying groundwater zone, a conceptualization supported by the two-storage system exhibited by hydrograph recession analysis. A modified version of TOPMODEL is used to simulate the observed catchment dynamics. In this model, generalized topographic index theory is applied to the subsurface storm flow zone to account for logarithmic storm flow recessions, indicative of linearly decreasing transmissivity with depth. Vertical drainage to the groundwater zone is required, and both subsurface reservoirs are considered to contribute to surface saturation.
A modified complex modal testing technique for a rotating tire with a flexible ring model
NASA Astrophysics Data System (ADS)
Lee, Jongsuh; Wang, Semyung; Pluymers, Bert; Desmet, Wim; Kindt, Peter
2015-08-01
Natural frequencies, mode shapes and modal damping values are the most important parameters to describe the noise and vibration behavior of a mechanical system. For rotating machinery, however, the directivity of the propagation wave of each mode should also be taken into account. For rotating systems, this directivity can be determined by complex modal testing. In this paper, a rolling tire is represented as a flexible ring model. The limitation of application of the complex modal testing which requires two directional measurements at a certain point, which is difficult to measure in practice, has been overcome through a modified complex modal testing which requires only one directional measurements at any two points. The technique is described in detail and applied to both a numerical example and to an experimental data set of a real rotating tire.
Modelling of laser welding of flat parts using the modifying nanopowders
NASA Astrophysics Data System (ADS)
Cherepanov, A. N.; Shapeev, V. P.
2013-06-01
A mathematical model is formulated to describe thermophysical processes at laser welding of metal plates for the case when the modifying nanoparticles of refractory compounds have been introduced in the weld pool (the nanopowder seed cultrure fermenters — NSCF). Specially prepared nanoparticles of refractory compounds serve the crystallization centers that is they are in fact the exogenous primers, on the surface of which the individual clusters are grouped. Owing to this, one can control the process of the crystallization of the alloy and the formation of its structure and, consequently, the joint weld properties. As an example, we present the results of computing the butt welding of two plates of aluminum alloy and steel. Computed and experimental data are compared.
Kinetics of hydrolysis of PET powder in nitric acid by a modified shrinking-core model
Yoshioka, Toshiaki; Okayama, Nobuchika; Okuwaki, Akitsugu
1998-02-01
Poly(ethylene terephthalate) (PET) powder from waste bottles was degraded at atmospheric pressure in 7--13 M nitric acid at 70--100 C for 72 h, to clarify the mechanism of a feed stock recycling process. Terephthalic acid (TPA) and ethylene glycol (EG) were produced by the acid-catalyzed heterogeneous hydrolysis of PET in nitric acid, and the resulting EG was simultaneously oxidized to oxalic acid. The kinetics of the hydrolysis of PET in nitric acid could be explained by a modified shrinking core model of chemical reaction control, in which the effective surface area is proportional to the degree of unreacted PET, affected by the deposition of the product TPA. The apparent rate constant was inversely proportional to particle size and to the concentration of the nitric acid. The activation energy of the reaction was 101.3 kJ/mol.
Computer modeling of the mineralogy of the Martian surface, as modified by aqueous alteration
NASA Technical Reports Server (NTRS)
Zolensky, M. E.; Bourcier, W. L.; Gooding, J. L.
1988-01-01
Mineralogical constraints can be placed on the Martian surface by assuming chemical equilibria among the surface rocks, atmosphere and hypothesized percolating groundwater. A study was made of possible Martian surface mineralogy, as modified by the action of aqueous alteration, using the EQ3/6 computer codes. These codes calculate gas fugacities, aqueous speciation, ionic strength, pH, Eh and concentration and degree of mineral saturation for complex aqueous systems. Thus, these codes are also able to consider mineralogical solid solutions. These codes are able to predict the likely alteration phases which will occur as the result of weathering on the Martian surface. Knowledge of the stability conditions of these phases will then assist in the definition of the specifications for the sample canister of the proposed Martian sample return mission. The model and its results are discussed.
Modifying supervisory practices to improve subunit safety: a leadership-based intervention model.
Zohar, Dov
2002-02-01
This article presents a leadership-based intervention model designed to modify supervisory monitoring and rewarding of subordinates' safety performance. Line supervisors received weekly feedback based on repeated episodic interviews with subordinates conceming the cumulative frequency of their safety-oriented interactions. This information identified the priority of safety over competing goals such as speed or schedules. Section managers received the same information and used it to communicate (high) safety priority. They also were trained to conduct episodic interviews to provide intermittent feedback after intervention, tuming safety priority into an explicit performance goal. Safety-oriented interaction increased significantly in the experimental groups but remained unchanged in the control groups. This change in safety-oriented interaction was accompanied by significant (and stable) changes in minor-injury rate, earplug use, and safety climate scores during the postintervention period. PMID:11916209
3D modeling method for computer animate based on modified weak structured light method
NASA Astrophysics Data System (ADS)
Xiong, Hanwei; Pan, Ming; Zhang, Xiangwei
2010-11-01
A simple and affordable 3D scanner is designed in this paper. Three-dimensional digital models are playing an increasingly important role in many fields, such as computer animate, industrial design, artistic design and heritage conservation. For many complex shapes, optical measurement systems are indispensable to acquiring the 3D information. In the field of computer animate, such an optical measurement device is too expensive to be widely adopted, and on the other hand, the precision is not as critical a factor in that situation. In this paper, a new cheap 3D measurement system is implemented based on modified weak structured light, using only a video camera, a light source and a straight stick rotating on a fixed axis. For an ordinary weak structured light configuration, one or two reference planes are required, and the shadows on these planes must be tracked in the scanning process, which destroy the convenience of this method. In the modified system, reference planes are unnecessary, and size range of the scanned objects is expanded widely. A new calibration procedure is also realized for the proposed method, and points cloud is obtained by analyzing the shadow strips on the object. A two-stage ICP algorithm is used to merge the points cloud from different viewpoints to get a full description of the object, and after a series of operations, a NURBS surface model is generated in the end. A complex toy bear is used to verify the efficiency of the method, and errors range from 0.7783mm to 1.4326mm comparing with the ground truth measurement.
Chen, YungChia; Mao, Haojie; Yang, King H.; Abel, Ted; Meaney, David F.
2014-01-01
For the past 25 years, controlled cortical impact (CCI) has been a useful tool in traumatic brain injury (TBI) research, creating injury patterns that includes primary contusion, neuronal loss, and traumatic axonal damage. However, when CCI was first developed, very little was known on the underlying biomechanics of mild TBI. This paper uses information generated from recent computational models of mild TBI in humans to alter CCI and better reflect the biomechanical conditions of mild TBI. Using a finite element model of CCI in the mouse, we adjusted three primary features of CCI: the speed of the impact to achieve strain rates within the range associated with mild TBI, the shape, and material of the impounder to minimize strain concentrations in the brain, and the impact depth to control the peak deformation that occurred in the cortex and hippocampus. For these modified cortical impact conditions, we observed peak strains and strain rates throughout the brain were significantly reduced and consistent with estimated strains and strain rates observed in human mild TBI. We saw breakdown of the blood–brain barrier but no primary hemorrhage. Moreover, neuronal degeneration, axonal injury, and both astrocytic and microglia reactivity were observed up to 8 days after injury. Significant deficits in rotarod performance appeared early after injury, but we observed no impairment in spatial object recognition or contextual fear conditioning response 5 and 8 days after injury, respectively. Together, these data show that simulating the biomechanical conditions of mild TBI with a modified cortical impact technique produces regions of cellular reactivity and neuronal loss that coincide with only a transient behavioral impairment. PMID:24994996
A new modified animal model of myosin-induced experimental autoimmune myositis enhanced by defibrase
Wen-Jing, Luo; Hong-Hua, Li; Xiang-Hui, Lu; Jie-Xiao, Liu
2015-01-01
Introduction We investigated the effect of defibrase (a proteolytic enzyme extraction of Agkistrodon halys venom) on experimental autoimmune myositis (EAM) in guinea pigs and explored the option of using a modified pig model of EAM to enhance the study of this disease. Material and methods Guinea pigs were divided into 3 groups: group A (control group) was immunized with complete Freund adjuvant (CFA), then received 6 injections of saline weekly; group B (EAM group) was immunized with partially purified rabbit myosin emulsified with CFA, then received an injection of saline; group C (EAM + defibrase group) was immunized with purified rabbit myosin emulsified with CFA, then received an injection of defibrase. The animals were observed for their general health condition and the body weight was measured daily. Plasma levels of fibrinogen and creatine kinase (CK) were determined. Muscle tissues were examined histologically. Results After immunizations for 6 weeks, incidence of EAM in groups A, B and C was 0 (0/7), 83.3% (10/12) and 100% (15/15), respectively. Guinea pigs with EAM presented angeitis symptoms of muscle weakness. Histological analysis revealed a significant difference. Muscles with EAM had scattered or diffuse inflammatory manifestations, which are also common pathological features of human idiopathic polymyositis (IPM). Defibrase-treated animals displayed extensive inflammation and fiber necrosis compared with the EAM group (histological score: 2.80 ±1.15 vs. 1.88 ±1.32, p < 0.05). Severity of inflammation of group B was mainly mild to moderate; 16.7% (2/12) of animals developed severe inflammation. Incidence of severe inflammation with a score up to 4 in group C was 40% (6/15). Conclusions Defibrase can exacerbate myosin-induced EAM; thus a new modified model was generated. PMID:26788090
A Modified Johnson-Cook Model for Advanced High-Strength Steels Over a Wide Range of Temperatures
NASA Astrophysics Data System (ADS)
Qingdong, Zhang; Qiang, Cao; Xiaofeng, Zhang
2014-12-01
Advanced high-strength steel (AHSS) is widely used in automotive industry. In order to investigate the mechanical behaviors of AHSS over a wide range of temperatures, quasi-static tensile experiments were conducted at the temperatures from 298 to 1073 K on a Gleeble-3500 thermo-simulation machine. The results show that flow behaviors are affected by testing temperature significantly. In order to describe the flow features of AHSS, the Johnson-Cook (JC) model is employed. By introducing polynomial functions to consider the effects of temperature on hardening behavior, the JC model is modified and used to predict flow behavior of AHSS at different experimental conditions. The accuracy of the modified JC model is verified and the predicted flow stress is in good agreement with experimental results, which confirms that the modified JC model can give an accurate and precise estimate over a wide range of temperatures.
Bulk-friction modeling of afterslip and the modified Omori law
NASA Astrophysics Data System (ADS)
Wennerberg, Leif; Sharp, Robert V.
1997-08-01
Afterslip data from the Superstition Hills fault in southern California, a creep event on the same fault, the modified Omori law, and cumulative moments from aftershocks of the 1957 Aleutian Islands earthquake all indicate that the original formulation by Dieterich (1981) [Constitutive properties of faults with simulated gouge. AGU, Geophys. Monogr. 24, 103-120] for friction evolution is more appropriate for systems far from instability than the commonly used approximation developed by Ruina (1983) [Slip instability and state variable friction laws. J. Geophys. Res. 88, 10359-10370] to study instability. The mathematical framework we use to test the friction models is a one-dimensional, massless spring-slider under the simplifying assumption, proposed by Scholz (1990) [The Mechanics of Earthquakes and Faulting. Cambridge University Press] and used by Marone et al. (1991) [On the mechanics of earthquake afterslip. J. Geophys. Res., 96: 8441-8452], that the state variable takes on its velocity-dependent steady-state value throughout motion in response to a step in stress. This assumption removes explicit state-variable dependence from the model, obviating the need to consider state-variable evolution equations. Anti-derivatives of the modified Omori law fit our data very well and are very good approximate solutions to our model equations. A plausible friction model with Omori-law solutions used by Wesson (1988) [Dynamics of fault creep. J. Geophys. Res. 93, 8929-8951] to model fault creep and generalized by Rice (1983) [Constitutive relations for fault slip and earthquake instabilities. Pure Appl. Geophys. 121, 443-475] to a rate-and-state variable friction model yields exactly Omori's law with exponents greater than 1, but yields unstable solutions for Omori exponents less than 1. We estimate from the Dieterich formulation the dimensionless parameter a∗ which is equal to the product of the nominal coefficient of friction and the more commonly reported friction
Bulk-friction modeling of afterslip and the modified Omori law
Wennerberg, L.; Sharp, R.V.
1997-01-01
Afterslip data from the Superstition Hills fault in southern California, a creep event on the same fault, the modified Omori law, and cumulative moments from aftershocks of the 1957 Aleutian Islands earthquake all indicate that the original formulation by Dieterich (1981) [Constitutive properties of faults with simulated gouge. AGU, Geophys. Monogr. 24, 103-120] for friction evolution is more appropriate for systems far from instability than the commonly used approximation developed by Ruina (1983) [Slip instability and state variable friction laws. J. Geophys. Res. 88, 10359-10370] to study instability. The mathematical framework we use to test the friction models is a one-dimensional, massless spring-slider under the simplifying assumption, proposed by Scholz (1990) [The Mechanics of Earthquakes and Faulting. Cambridge University Press] and used by Marone et al. (1991) [On the mechanics of earthquake afterslip. J. Geophys. Res., 96: 8441-8452], that the state variable takes on its velocity-dependent steady-state value throughout motion in response to a step in stress. This assumption removes explicit state-variable dependence from the model, obviating the need to consider state-variable evolution equations. Anti-derivatives of the modified Omori law fit our data very well and are very good approximate solutions to our model equations. A plausible friction model with Omori-law solutions used by Wesson (1988) [Dynamics of fault creep. J. Geophys. Res. 93, 8929-8951] to model fault creep and generalized by Rice (1983) [Constitutive relations for fault slip and earthquake instabilities. Pure Appl. Geophys. 121, 443-475] to a rate-and-state-variable friction model yields exactly Omori's law with exponents greater than 1, but yields unstable solutions for Omori exponents less than 1. We estimate from the Dieterich formulation the dimensionless parameter a* which is equal to the product of the nominal coefficient of friction and the more commonly reported friction
NASA Astrophysics Data System (ADS)
Gan, T. Y.
2009-04-01
Three semi-distributed snowmelt models were developed and applied to the Paddle River Basin (PRB) in the Canadian Prairies: (1) A physics-based, energy balance model (SDSM-EBM) that considers vertical energy exchange processes in open and forested areas, and snowmelt processes that include liquid and ice phases separately; (2) A modified temperature index model (SDSM-MTI) that uses both near surface soil temperature (Tg) and air temperature (Ta), and (3) A standard temperature index (SDSM-TI) method using Ta only. Other than the "regulatory" effects of beaver dams that affected the validation results on simulated runoff, both SDSM-MTI and SDSM-EBM simulated reasonably accurate snowmelt runoff, snow water equivalent and snow depth. For the PRB, where snowpack is shallow to moderately deep, and winter is relatively severe, the advantage of using both Ta and Tg is partly attributed to Tg showing a stronger correlation with solar radiation than Ta during the spring snowmelt season, and partly to the onset of major snowmelt which usually happens when Tg approaches 0oC. After re-setting model parameters so that SDSM-MTI degenerated to SDSM-TI (effect of Tg is completely removed), the model performance worsened, even after re-calibrating the melt factors using Ta alone. It seems that if reliable Tg data are available, they should be utilized to model the snowmelt processes in a Prairie environment particularly if the temperature-index approach is adopted.
Modified conceptual model for compensated root water uptake - A simulation study
NASA Astrophysics Data System (ADS)
Peters, Andre
2016-03-01
Modeling root water uptake within the macroscopic approach is usually done by introducing a sink term in the Richards equation. This sink term represents potential water uptake reduced by a so-called stress reduction factor accounting for stress due to high suctions, oxygen deficit or salinity. Since stress in some parts of the soil can be compensated by enhanced water uptake in less stressed parts, several compensation models have been suggested. One of them is the empirical model of Jarvis, which is often applied due to its mathematical elegance and simplicity. However, it has been discussed that under certain conditions and assumptions this model might predict too high transpiration rates, which are not in agreement with the assumed stress reduction function. The aim of this paper is (i) to analyze these inconsistencies and (ii) to introduce a simple constraint for transpiration in a way as if the complete water would be taken form the location with highest uptake rate in the uncompensated case. Transpiration from 50 cm deep soils with hydraulic functions representing different textures, ranging from a clay loam to a coarse sand, was simulated with the original and the modified model using HYDRUS-1D. Root distribution was assumed to be uniform or linearly decreasing with depth. In case of the fine textured soils and uniform root density, the original model predicted transpiration equal to potential transpiration even when the complete root domain was already heavily stressed if the maximum enhancement factor for uptake was 2. These results are not in agreement with the original meaning of the stress reduction function. The modification eliminates the inconsistencies by limiting transpiration to a maximum value based on the highest uncompensated uptake rate in the root zone. It does neither increase the mathematical complexity nor require any additional parameters.
Li, Yungui; Li, Qingqing; Chen, Baoliang
2016-01-01
The surface of plants is covered by a continuous but heterogeneous cuticular membrane (CM). Serving as the first protective barrier, the uptake and transport behavior of organic pollutants at this interface continue to engage the research efforts of environmental chemist. To date, the contributions of cuticular components as a defense against the organic pollutants penetration remain unresolved. In this study, the unsteady-state penetration characteristics of phenanthrene (PHE) through isolated fruit CM was investigated. PHE penetration was differentiated by three cuticular compartments: epicuticular waxes (EW), cuticle proper (CP) and cuticular layer (CL). The driving force for PHE penetration was ascribed to the sharp concentration gradient built up endogenously by cuticular compartments with different lipophilic affinities. A modified penetration model was established and verified in terms of its general suitability for the hydrophobic chemicals and CMs of various plant species (apple, tomato and potato). The new three-compartment model demonstrates much higher accuracy in characterizing the uptake and transport behavior of semivolatile chemicals with fewer limitations in terms of environmental conditions and complexity (e.g., coexisting contaminants and temperature). This model could contribute to a more comprehensive understanding on the role of polymeric lipids in the organic pollutant sorption and transport into plants. PMID:27009902
A modified binary tree codification of drainage networks to support complex hydrological models
NASA Astrophysics Data System (ADS)
Li, Tiejian; Wang, Guangqian; Chen, Ji
2010-11-01
A new codification method (named a modified binary tree codification method) is developed for coding drainage networks. To express the inner topological structure of a drainage basin, it is necessary to delineate and code digital drainage networks from digital elevation model datasets. In this study, the established software TOPAZ is used to delineate river reaches, and the new codification method is applied, which is based on the application of binary-tree structures and hierarchical zones. A coded drainage network can then be stored in a relational database management system to achieve efficient manipulation of data items for topological operations. The utility of the new codification method is demonstrated by an example applied to the Digital Yellow River Model. The drainage network of the Middle Yellow River in northern China has been coded and the hydrological and soil erosion processes of its sub-basin, the Chabagou River basin, are simulated. Because more details of the drainage network can be efficiently and effectively described, the new codification method can support complex hydrological models and extract more information from hydrological simulations than ever before.
El Backly, Rania M.; Chiapale, Danilo; Muraglia, Anita; Tromba, Giuliana; Ottonello, Chiara; Santolini, Federico; Cancedda, Ranieri; Mastrogiacomo, Maddalena
2014-01-01
The present work defines a modified critical size rabbit ulna defect model for bone regeneration in which a non-resorbable barrier membrane was used to separate the radius from the ulna to create a valid model for evaluation of tissue-engineered periosteal substitutes. Eight rabbits divided into two groups were used. Critical defects (15 mm) were made in the ulna completely eliminating periosteum. For group I, defects were filled with a nanohydroxyapatite poly(ester urethane) scaffold soaked in PBS and left as such (group Ia) or wrapped with a tissue-engineered periosteal substitute (group Ib). For group II, an expanded-polytetrafluoroethylene (e-PTFE) (GORE-TEX®) membrane was inserted around the radius then the defects received either scaffold alone (group IIa) or scaffold wrapped with periosteal substitute (group IIb). Animals were euthanized after 12–16 weeks, and bone regeneration was evaluated by radiography, computed microtomography (μCT), and histology. In the first group, we observed formation of radio-ulnar synostosis irrespective of the treatment. This was completely eliminated upon placement of the e-PTFE (GORE-TEX®) membrane in the second group of animals. In conclusion, modification of the model using a non-resorbable e-PTFE membrane to isolate the ulna from the radius was a valuable addition allowing for objective evaluation of the tissue-engineered periosteal substitute. PMID:25610828
Antacid effects of Chinese herbal prescriptions assessed by a modified artificial stomach model
Wu, Tsung-Hsiu; Chen, I-Chin; Chen, Lih-Chi
2010-01-01
AIM: To assess the antacid effects of the tonic Chinese herbal prescriptions, Si-Jun-Zi-Tang (SJZT) and Shen-Ling-Bai-Zhu-San (SLBZS). METHODS: Decoctions of the tonic Chinese herbal prescriptions, SJZT and SLBZS, were prepared according to Chinese original documents. The pH of the prescription decoctions and their neutralizing effects on artificial gastric acids were determined and compared with water and the active controls, sodium bicarbonate and colloidal aluminum phosphate. A modified model of Vatier’s artificial stomach was used to determine the duration of consistent neutralization effect on artificial gastric acids. The neutralization capacity in vitro was determined with the titration method of Fordtran’s model. RESULTS: The results showed that both SJZT and SLBZS have antacid effects in vitro. Compared with the water group, SJZT and SLBZS were found to possess significant gastric acid neutralizing effects. The duration for consistent neutralization of SLBZS was significantly longer than that of water. Also, SLBZS and SJZT exhibited significant antacid capacities compared to water. CONCLUSION: SJZT and SLBZS were consistently active in the artificial stomach model and are suggested to have antacid effects similar to the active control drugs. PMID:20845514
NASA Astrophysics Data System (ADS)
Chen, Yung-Fu; Du, Yi-Chun; Tsai, Yi-Ting; Chen, Tainsong
Osteoporosis is a systemic skeletal disease, which is characterized by low bone mass and micro-architectural deterioration of bone tissue, leading to bone fragility. Finding an effective method for prevention and early diagnosis of the disease is very important. Several parameters, including broadband ultrasound attenuation (BUA), speed of sound (SOS), and stiffness index (STI), have been used to measure the characteristics of bone tissues. In this paper, we proposed a method, namely modified contour deformable model (MCDM), bases on the active contour model (ACM) and active shape model (ASM) for automatically detecting the calcaneus contour from quantitative ultrasound (QUS) parametric images. The results show that the difference between the contours detected by the MCDM and the true boundary for the phantom is less than one pixel. By comparing the phantom ROIs, significant relationship was found between contour mean and bone mineral density (BMD) with R=0.99. The influence of selecting different ROI diameters (12, 14, 16 and 18 mm) and different region-selecting methods, including fixed region (ROI fix ), automatic circular region (ROI cir ) and calcaneal contour region (ROI anat ), were evaluated for testing human subjects. Measurements with large ROI diameters, especially using fixed region, result in high position errors (10-45%). The precision errors of the measured ultrasonic parameters for ROI anat are smaller than ROI fix and ROI cir . In conclusion, ROI anat provides more accurate measurement of ultrasonic parameters for the evaluation of osteoporosis and is useful for clinical application.
Li, Yungui; Li, Qingqing; Chen, Baoliang
2016-01-01
The surface of plants is covered by a continuous but heterogeneous cuticular membrane (CM). Serving as the first protective barrier, the uptake and transport behavior of organic pollutants at this interface continue to engage the research efforts of environmental chemist. To date, the contributions of cuticular components as a defense against the organic pollutants penetration remain unresolved. In this study, the unsteady-state penetration characteristics of phenanthrene (PHE) through isolated fruit CM was investigated. PHE penetration was differentiated by three cuticular compartments: epicuticular waxes (EW), cuticle proper (CP) and cuticular layer (CL). The driving force for PHE penetration was ascribed to the sharp concentration gradient built up endogenously by cuticular compartments with different lipophilic affinities. A modified penetration model was established and verified in terms of its general suitability for the hydrophobic chemicals and CMs of various plant species (apple, tomato and potato). The new three-compartment model demonstrates much higher accuracy in characterizing the uptake and transport behavior of semivolatile chemicals with fewer limitations in terms of environmental conditions and complexity (e.g., coexisting contaminants and temperature). This model could contribute to a more comprehensive understanding on the role of polymeric lipids in the organic pollutant sorption and transport into plants. PMID:27009902
Wu, Chengzhen; Hong, Wei; Hong, Tao
2006-03-01
To optimize the projection function and direction of projection pursuit technique, predigest its realization process, and overcome the shortcomings in long time calculation and in the difficulty of optimizing projection direction and computer programming, this paper presented a modified simplex method (MSM), and based on it, brought forward the eco-value level classification model (EVLCM) of forest ecosystem, which could integrate the multidimensional classification index into one-dimensional projection value, with high projection value denoting high ecosystem services value. Examples of forest ecosystem could be reasonably classified by the new model according to their projection value, suggesting that EVLCM driven directly by samples data of forest ecosystem was simple and feasible, applicable, and maneuverable. The calculating time and value of projection function were 34% and 143% of those with the traditional projection pursuit technique, respectively. This model could be applied extensively to classify and estimate all kinds of non-linear and multidimensional data in ecology, biology, and regional sustainable development. PMID:16724723
Numerical solution of the Penna model of biological aging with age-modified mutation rate.
Magdoń-Maksymowicz, M S; Maksymowicz, A Z
2009-06-01
In this paper we present results of numerical calculation of the Penna bit-string model of biological aging, modified for the case of a -dependent mutation rate m(a), where a is the parent's age. The mutation rate m(a) is the probability per bit of an extra bad mutation introduced in offspring inherited genome. We assume that m(a) increases with age a. As compared with the reference case of the standard Penna model based on a constant mutation rate m , the dynamics of the population growth shows distinct changes in age distribution of the population. Here we concentrate on mortality q(a), a fraction of items eliminated from the population when we go from age (a) to (a+1) in simulated transition from time (t) to next time (t+1). The experimentally observed q(a) dependence essentially follows the Gompertz exponential law for a above the minimum reproduction age. Deviation from the Gompertz law is however observed for the very old items, close to the maximal age. This effect may also result from an increase in mutation rate m with age a discussed in this paper. The numerical calculations are based on analytical solution of the Penna model, presented in a series of papers by Coe et al. [J. B. Coe, Y. Mao, and M. E. Cates, Phys. Rev. Lett. 89, 288103 (2002)]. Results of the numerical calculations are supported by the data obtained from computer simulation based on the solution by Coe et al. PMID:19658536
Real-time robot path planning based on a modified pulse-coupled neural network model.
Qu, Hong; Yang, Simon X; Willms, Allan R; Yi, Zhang
2009-11-01
This paper presents a modified pulse-coupled neural network (MPCNN) model for real-time collision-free path planning of mobile robots in nonstationary environments. The proposed neural network for robots is topologically organized with only local lateral connections among neurons. It works in dynamic environments and requires no prior knowledge of target or barrier movements. The target neuron fires first, and then the firing event spreads out, through the lateral connections among the neurons, like the propagation of a wave. Obstacles have no connections to their neighbors. Each neuron records its parent, that is, the neighbor that caused it to fire. The real-time optimal path is then the sequence of parents from the robot to the target. In a static case where the barriers and targets are stationary, this paper proves that the generated wave in the network spreads outward with travel times proportional to the linking strength among neurons. Thus, the generated path is always the global shortest path from the robot to the target. In addition, each neuron in the proposed model can propagate a firing event to its neighboring neuron without any comparing computations. The proposed model is applied to generate collision-free paths for a mobile robot to solve a maze-type problem, to circumvent concave U-shaped obstacles, and to track a moving target in an environment with varying obstacles. The effectiveness and efficiency of the proposed approach is demonstrated through simulation and comparison studies. PMID:19775961
NASA Astrophysics Data System (ADS)
Li, Yungui; Li, Qingqing; Chen, Baoliang
2016-03-01
The surface of plants is covered by a continuous but heterogeneous cuticular membrane (CM). Serving as the first protective barrier, the uptake and transport behavior of organic pollutants at this interface continue to engage the research efforts of environmental chemist. To date, the contributions of cuticular components as a defense against the organic pollutants penetration remain unresolved. In this study, the unsteady-state penetration characteristics of phenanthrene (PHE) through isolated fruit CM was investigated. PHE penetration was differentiated by three cuticular compartments: epicuticular waxes (EW), cuticle proper (CP) and cuticular layer (CL). The driving force for PHE penetration was ascribed to the sharp concentration gradient built up endogenously by cuticular compartments with different lipophilic affinities. A modified penetration model was established and verified in terms of its general suitability for the hydrophobic chemicals and CMs of various plant species (apple, tomato and potato). The new three-compartment model demonstrates much higher accuracy in characterizing the uptake and transport behavior of semivolatile chemicals with fewer limitations in terms of environmental conditions and complexity (e.g., coexisting contaminants and temperature). This model could contribute to a more comprehensive understanding on the role of polymeric lipids in the organic pollutant sorption and transport into plants.
El Backly, Rania M; Chiapale, Danilo; Muraglia, Anita; Tromba, Giuliana; Ottonello, Chiara; Santolini, Federico; Cancedda, Ranieri; Mastrogiacomo, Maddalena
2014-01-01
The present work defines a modified critical size rabbit ulna defect model for bone regeneration in which a non-resorbable barrier membrane was used to separate the radius from the ulna to create a valid model for evaluation of tissue-engineered periosteal substitutes. Eight rabbits divided into two groups were used. Critical defects (15 mm) were made in the ulna completely eliminating periosteum. For group I, defects were filled with a nanohydroxyapatite poly(ester urethane) scaffold soaked in PBS and left as such (group Ia) or wrapped with a tissue-engineered periosteal substitute (group Ib). For group II, an expanded-polytetrafluoroethylene (e-PTFE) (GORE-TEX(®)) membrane was inserted around the radius then the defects received either scaffold alone (group IIa) or scaffold wrapped with periosteal substitute (group IIb). Animals were euthanized after 12-16 weeks, and bone regeneration was evaluated by radiography, computed microtomography (μCT), and histology. In the first group, we observed formation of radio-ulnar synostosis irrespective of the treatment. This was completely eliminated upon placement of the e-PTFE (GORE-TEX(®)) membrane in the second group of animals. In conclusion, modification of the model using a non-resorbable e-PTFE membrane to isolate the ulna from the radius was a valuable addition allowing for objective evaluation of the tissue-engineered periosteal substitute. PMID:25610828
Overall picture of the cascade gamma decay of neutron resonances within a modified practical model
NASA Astrophysics Data System (ADS)
Sukhovoj, A. M.; Mitsyna, L. V.; Jovancevic, N.
2016-05-01
The intensities of two-step cascades in 43 nuclei of mass number in the range of 28 ≤ A ≤ 200 were approximated to a high degree of precision within a modified version of the practical cascade-gammadecay model introduced earlier. In this version, the rate of the decrease in the model-dependent density of vibrational levels has the same value for any Cooper pair undergoing breakdown. The most probable values of radiative strength functions both for E1 and for M1 transitions are determined by using one or two peaks against a smooth model dependence on the gamma-transition energy. The statement that the thresholds for the breaking of Cooper pairs are higher for spherical than for deformed nuclei is a basic result of the respective analysis. The parameters of the cascade-decay process are now determined to a precision that makes it possible to observe the systematic distinctions between them for nuclei characterized by different parities of neutrons and protons.
Large-scale hydrological modelling by using modified PUB recommendations: the India-HYPE case
NASA Astrophysics Data System (ADS)
Pechlivanidis, I. G.; Arheimer, B.
2015-11-01
The scientific initiative Prediction in Ungauged Basins (PUB) (2003-2012 by the IAHS) put considerable effort into improving the reliability of hydrological models to predict flow response in ungauged rivers. PUB's collective experience advanced hydrologic science and defined guidelines to make predictions in catchments without observed runoff data. At present, there is a raised interest in applying catchment models to large domains and large data samples in a multi-basin manner, to explore emerging spatial patterns or learn from comparative hydrology. However, such modelling involves additional sources of uncertainties caused by the inconsistency between input data sets, i.e. particularly regional and global databases. This may lead to inaccurate model parameterisation and erroneous process understanding. In order to bridge the gap between the best practices for flow predictions in single catchments and multi-basins at the large scale, we present a further developed and slightly modified version of the recommended best practices for PUB by Takeuchi et al. (2013). By using examples from a recent HYPE (Hydrological Predictions for the Environment) hydrological model set-up across 6000 subbasins for the Indian subcontinent, named India-HYPE v1.0, we explore the PUB recommendations, identify challenges and recommend ways to overcome them. We describe the work process related to (a) errors and inconsistencies in global databases, unknown human impacts, and poor data quality; (b) robust approaches to identify model parameters using a stepwise calibration approach, remote sensing data, expert knowledge, and catchment similarities; and (c) evaluation based on flow signatures and performance metrics, using both multiple criteria and multiple variables, and independent gauges for "blind tests". The results show that despite the strong physiographical gradient over the subcontinent, a single model can describe the spatial variability in dominant hydrological processes at the
Salted matters: modifying gelatine rheology for subduction thrust fault seismicity models
NASA Astrophysics Data System (ADS)
Brizzi, Silvia; Funiciello, Francesca; Corbi, Fabio; Di Giuseppe, Erika; Mojoli, Giorgio
2016-04-01
Most of the world's greatest earthquakes (Mw > 8.5, usually known as mega-earthquakes) occur at shallow depths along the subduction thrust fault (STF), i.e., the frictional interface between the subducting and overriding plates. The contribution of each subduction zone to the globally released seismic moment is not homogeneous, as well as the maximum Mw recorded in the instrumental and historical catalogues. To contribute to the unravelling of the seismic cycle along the STF, we used analogue models. Viscoelastic laboratory experiments realised with type A gelatine 2.5 wt% at 10 °C (Corbi et al., 2013) successfully simulate the seismic cycle along the STF, providing dynamic similarities with earthquakes in nature. However, analogue earthquakes are still not perfectly comparable to the natural prototype. In this work, we try to improve STF seismicity models by modifying the rheological behaviour of gelatine with the addition of NaCl. After testing salted gelatine rheology as a function of increasing concentration of NaCl, we selected 20 wt% NaCl gelatine, as this NaCl concentration provides a quasi-viscoelastic lithospheric analogue. Subduction interplate seismicity models were performed using both pure and salted gelatine to highlight the strengths and advantages this new material can provide for simulating the seismic cycle along the STF. We analysed analogue earthquakes Mw, recurrence time and rupture duration, which at first-order characterise the seismogenic behaviour of the STF. Results show that the experimental source parameters cover a wider range of values than obtained with pure gelatine, which is more compatible to the high variability globally observed. In particular, salted gelatine allows to simulate also smaller seismic events, giving the opportunity to apply the G-R law to the experimental seismicity of STF. Recurrence time and rupture duration are also characterised by an increased range of values when salted gelatine is used as analogue material
NASA Astrophysics Data System (ADS)
Yew Gan, Thian; Singh, Purushottam; Gobena, Adam
2010-05-01
Three semi-distributed snowmelt models were developed and applied to the Paddle River Basin (PRB) in the Canadian Prairies: (1) A physics-based, energy balance model (SDSM-EBM) that considers vertical energy exchange processes in open and forested areas, and snowmelt processes that include liquid and ice phases separately; (2) A modified temperature index model (SDSM-MTI) that uses both near surface soil temperature (Tg) and air temperature (Ta), and (3) A standard temperature index(SDSM-TI) method using Ta only. Other than the "regulatory" effects of beaver dams that affected the validation results on simulated runoff, both SDSM-MTI and SDSM EBM simulated reasonably accurate snowmelt runoff, snow water equivalent and snow depth. For the PRB, where snowpack is shallow to moderately deep, and winter is relatively severe, the advantage of using both Ta and Tg is partly attributed to Tg showing a stronger correlation with solar radiation than Ta during the spring snowmelt season, and partly to the onset of major snowmelt which usually happens when Tg approaches 0oC. After re-setting model parameters so that SDSM-MTI degenerated to SDSM-TI (effect of Tg is completely removed), the latter performed poorly, even after re-calibrating the melt factors using Ta alone. It seems that if reliable Tg data are available, they should be utilized to model the snowmelt processes in a Prairie environment particularly if the temperature-index approach is adopted.
Characterization, testing and constitutive modelling of an impact-modified polypropylene
NASA Astrophysics Data System (ADS)
Wang, Yan
2002-01-01
Impact modified polypropylenes (or TPOs) are polymer blends of isotactic polypropylene (iPP), ethylene-propylene-diene monomer elastomer (EPDM), and high density polyethylene (HDPE). Currently, TPOs are extensively used in impact applications, such as car bumpers. However, the design process of TPO parts for impact applications is still an expensive, trial-and-error procedure. In this project, we aim to develop a material model with specific physical bases to represent a TPO material, so that TPO part design can be effective and efficient. In order to achieve our objective, morphology characterization and mechanical testing have been conducted to examine the intrinsic mechanisms of TPO. Tests were conducted over a broad range of strain rates using both a servohydraulic apparatus and an Aluminum split Hopkinson pressure bar. The TPO system we examined is multi-phasic in which an EPDM and HDPE blend forms the minor domain, distributed in the iPP matrix. The large deformation TPO response includes strain rate dependent initial stiffness; temperature, deformation state and strain rate dependent yield; temperature and deformation state dependent strain hardening. Its response is not unlike that of glassy polymers in many ways, owing to the flexibility of the iPP matrix, however the TPO shows a moderate strain hardening rate and little strain recovery upon unloading. A three-dimensional, four-element constitutive model has been developed for this TPO. The model includes rate dependent stiffness, rate and temperature dependent yield, temperature dependent strain hardening, and crystallographic slip. The model has been examined to be robust over a wide range of strain rates from quasi-static to impact, and predictive of different deformation states, such as uniaxial compression and plane strain compression. The model has been shown to capture the post-yield thermal softening and apparent lack of post-yield strain hardening at impact test conditions.
Explicit stress integration of complex soil models
NASA Astrophysics Data System (ADS)
Zhao, Jidong; Sheng, Daichao; Rouainia, M.; Sloan, Scott W.
2005-10-01
In this paper, two complex critical-state models are implemented in a displacement finite element code. The two models are used for structured clays and sands, and are characterized by multiple yield surfaces, plastic yielding within the yield surface, and complex kinematic and isotropic hardening laws. The consistent tangent operators - which lead to a quadratic convergence when used in a fully implicit algorithm - are difficult to derive or may even not exist. The stress integration scheme used in this paper is based on the explicit Euler method with automatic substepping and error control. This scheme employs the classical elastoplastic stiffness matrix and requires only the first derivatives of the yield function and plastic potential. This explicit scheme is used to integrate the two complex critical-state models - the sub/super-loading surfaces model (SSLSM) and the kinematic hardening structure model (KHSM). Various boundary-value problems are then analysed. The results for the two models are compared with each other, as well with those from standard Cam-clay models. Accuracy and efficiency of the scheme used for the complex models are also investigated. Copyright
NASA Astrophysics Data System (ADS)
Brent, David A.; Cottrell, Frederick D.; Henderson, Kelly A.; Dahbura, Rudy S.
1996-11-01
The industry-standard, free-molecular contamination code MOLFLUX (molecular flux) developed for NASA has been used for many years by most aerospace contractors to predict on- orbit spacecraft surface contamination levels. Recently, MOLFLUX (version 2.0) which was written for a VAX computer was converted for use on a PC running Windows NT. Both the graphical-user-interface (GUI) menuing portion (written in C) of MOLFLUX), and the physics portion (written in FORTRAN) were fully converted. Subsequent to the conversion task, an effort was initiated to validate the PC version of MOLFLUX for two major spacecraft systems. A new free-molecular contamination code recently developed at TRW, CONFLUX (continuous flux) is being used to validate MOLFLUX. CONFLUX provides a 'nearly-exact' solution to the 'reduced' free- molecular contamination problem by permitting molecules to bounce from surface-to-surface with no bounce limit. CONFLUX is also double-precisioned for higher accuracy. Excellent comparisons have been made between MOLFLUX and CONFLUX on the AXAF and EOS spacecraft systems (discretized into hundreds of surface elements). Both models are also being verified against simple systems having closed-form analytic solutions. In addition the S-cubed environmental work bench (EWB) is being tested on the EOS spacecraft system. All comparisons are still in a preliminary state.
Development and verification of the modified dynamic two-fluid model GOPS
NASA Astrophysics Data System (ADS)
Song, Chengyi; Li, Yuxing; Meng, Lan; Wang, Haiyan
2013-07-01
In the oil and gas industry, many versions of software have been developed to calculate the flow parameters of multiphase flow. However, the existing software is not perfect. To improve the accuracy, a new version of software GOPS has been developed by Daqing Oilfield Construction Design and Research Institute, and China University of Petroleum. GOPS modifies the general extended two-fluid model, and considers the gas bubble phase in liquid and liquid droplet phase in gas. There are four continuity equations, two momentum equations, one mixture energy-conservation equation and one pressure-conservation equation in the controlling equations of GOPS. These controlling equations are combined with flow pattern transition model and closure relationships for every flow pattern. By this way, GOPS can simulate the dynamic variation of multiphase flow. To verify GOPS, relevant experiment has been made in Surface Engineering Pilot Test Center, CNPC. The experimental pressure gradients are compared with the results from GOPS, and the accuracy of GOPS is high.
Kitakaze, Keisuke; Mizutani, Yasumichi; Sugiyama, Eiji; Tasaki, Chikako; Tsuji, Daisuke; Maita, Nobuo; Hirokawa, Takatsugu; Asanuma, Daisuke; Kamiya, Mako; Sato, Kohei; Setou, Mitsutoshi; Urano, Yasuteru; Togawa, Tadayasu; Otaka, Akira; Sakuraba, Hitoshi; Itoh, Kohji
2016-05-01
GM2 gangliosidoses, including Tay-Sachs and Sandhoff diseases, are neurodegenerative lysosomal storage diseases that are caused by deficiency of β-hexosaminidase A, which comprises an αβ heterodimer. There are no effective treatments for these diseases; however, various strategies aimed at restoring β-hexosaminidase A have been explored. Here, we produced a modified human hexosaminidase subunit β (HexB), which we have termed mod2B, composed of homodimeric β subunits that contain amino acid sequences from the α subunit that confer GM2 ganglioside-degrading activity and protease resistance. We also developed fluorescent probes that allow visualization of endocytosis of mod2B via mannose 6-phosphate receptors and delivery of mod2B to lysosomes in GM2 gangliosidosis models. In addition, we applied imaging mass spectrometry to monitor efficacy of this approach in Sandhoff disease model mice. Following i.c.v. administration, mod2B was widely distributed and reduced accumulation of GM2, asialo-GM2, and bis(monoacylglycero)phosphate in brain regions including the hypothalamus, hippocampus, and cerebellum. Moreover, mod2B administration markedly improved motor dysfunction and a prolonged lifespan in Sandhoff disease mice. Together, the results of our study indicate that mod2B has potential for intracerebrospinal fluid enzyme replacement therapy and should be further explored as a gene therapy for GM2 gangliosidoses. PMID:27018595
Operational forecasting based on a modified Weather Research and Forecasting model
Lundquist, J; Glascoe, L; Obrecht, J
2010-03-18
Accurate short-term forecasts of wind resources are required for efficient wind farm operation and ultimately for the integration of large amounts of wind-generated power into electrical grids. Siemens Energy Inc. and Lawrence Livermore National Laboratory, with the University of Colorado at Boulder, are collaborating on the design of an operational forecasting system for large wind farms. The basis of the system is the numerical weather prediction tool, the Weather Research and Forecasting (WRF) model; large-eddy simulations and data assimilation approaches are used to refine and tailor the forecasting system. Representation of the atmospheric boundary layer is modified, based on high-resolution large-eddy simulations of the atmospheric boundary. These large-eddy simulations incorporate wake effects from upwind turbines on downwind turbines as well as represent complex atmospheric variability due to complex terrain and surface features as well as atmospheric stability. Real-time hub-height wind speed and other meteorological data streams from existing wind farms are incorporated into the modeling system to enable uncertainty quantification through probabilistic forecasts. A companion investigation has identified optimal boundary-layer physics options for low-level forecasts in complex terrain, toward employing decadal WRF simulations to anticipate large-scale changes in wind resource availability due to global climate change.
Xu, Airen; Yao, Mingfei; Xu, Guangkui; Ying, Jingyan; Ma, Weicheng; Li, Bo; Jin, Yi
2012-01-01
Background The aim of this work was to improve oral bioavailability. The uptake of a series of quaternary ammonium salt didodecyl dimethylammonium bromide (DMAB)-modified nanoparticles (with uniform sizes ranging from 50 nm to 300 nm) into heterogeneous human epithelial colorectal adenocarcinoma cells (Caco-2) and human colon adenocarcinoma cells (HT-29) was investigated. Methods Coumarin-6 (C6) loaded poly (lactide-co-glycolide) (PLGA) nanoparticles were prepared with DMAB using the emulsion solvent diffusion method. The physicochemical properties and cellular uptake of these nanoparticles were studied. Deserno’s model was applied to explain the experimental observations. Results The results showed that the surface modification of PLGA nanoparticles with DMAB notably improved the cellular uptake. The cellular uptake was size-dependent and had an optimal particle size of 100 nm. The experimental data was integrated numerically, and was in agreement with the theoretical model. Conclusion These results indicated that the interactions between the charged nanoparticles and the cells resulted from various forces (eg, electrostatic forces, hydrophobic forces, bending and stretching forces, and limited receptor-mediated endocytosis), and the uptake of the nanoparticles occurred as a result of competition. PMID:22848178
Mizutani, Yasumichi; Sugiyama, Eiji; Tasaki, Chikako; Tsuji, Daisuke; Maita, Nobuo; Hirokawa, Takatsugu; Asanuma, Daisuke; Kamiya, Mako; Sato, Kohei; Setou, Mitsutoshi; Urano, Yasuteru; Togawa, Tadayasu; Otaka, Akira; Sakuraba, Hitoshi
2016-01-01
GM2 gangliosidoses, including Tay-Sachs and Sandhoff diseases, are neurodegenerative lysosomal storage diseases that are caused by deficiency of β-hexosaminidase A, which comprises an αβ heterodimer. There are no effective treatments for these diseases; however, various strategies aimed at restoring β-hexosaminidase A have been explored. Here, we produced a modified human hexosaminidase subunit β (HexB), which we have termed mod2B, composed of homodimeric β subunits that contain amino acid sequences from the α subunit that confer GM2 ganglioside–degrading activity and protease resistance. We also developed fluorescent probes that allow visualization of endocytosis of mod2B via mannose 6-phosphate receptors and delivery of mod2B to lysosomes in GM2 gangliosidosis models. In addition, we applied imaging mass spectrometry to monitor efficacy of this approach in Sandhoff disease model mice. Following i.c.v. administration, mod2B was widely distributed and reduced accumulation of GM2, asialo-GM2, and bis(monoacylglycero)phosphate in brain regions including the hypothalamus, hippocampus, and cerebellum. Moreover, mod2B administration markedly improved motor dysfunction and a prolonged lifespan in Sandhoff disease mice. Together, the results of our study indicate that mod2B has potential for intracerebrospinal fluid enzyme replacement therapy and should be further explored as a gene therapy for GM2 gangliosidoses. PMID:27018595
Model systems of protein-misfolding diseases reveal chaperone modifiers of proteotoxicity
2016-01-01
ABSTRACT Chaperones and co-chaperones enable protein folding and degradation, safeguarding the proteome against proteotoxic stress. Chaperones display dynamic responses to exogenous and endogenous stressors and thus constitute a key component of the proteostasis network (PN), an intricately regulated network of quality control and repair pathways that cooperate to maintain cellular proteostasis. It has been hypothesized that aging leads to chronic stress on the proteome and that this could underlie many age-associated diseases such as neurodegeneration. Understanding the dynamics of chaperone function during aging and disease-related proteotoxic stress could reveal specific chaperone systems that fail to respond to protein misfolding. Through the use of suppressor and enhancer screens, key chaperones crucial for proteostasis maintenance have been identified in model organisms that express misfolded disease-related proteins. This review provides a literature-based analysis of these genetic studies and highlights prominent chaperone modifiers of proteotoxicity, which include the HSP70-HSP40 machine and small HSPs. Taken together, these studies in model systems can inform strategies for therapeutic regulation of chaperone functionality, to manage aging-related proteotoxic stress and to delay the onset of neurodegenerative diseases. PMID:27491084
The MLP distribution: a modified lognormal power-law model for the stellar initial mass function
NASA Astrophysics Data System (ADS)
Basu, Shantanu; Gil, M.; Auddy, Sayantan
2015-05-01
This work explores the mathematical properties of a distribution introduced by Basu & Jones (2004), and applies it to model the stellar initial mass function (IMF). The distribution arises simply from an initial lognormal distribution, requiring that each object in it subsequently undergoes exponential growth but with an exponential distribution of growth lifetimes. This leads to a modified lognormal with a power-law (MLP) distribution, which can in fact be applied to a wide range of fields where distributions are observed to have a lognormal-like body and a power-law tail. We derive important properties of the MLP distribution, like the cumulative distribution, the mean, variance, arbitrary raw moments, and a random number generator. These analytic properties of the distribution can be used to facilitate application to modelling the IMF. We demonstrate how the MLP function provides an excellent fit to the IMF compiled by Chabrier and how this fit can be used to quickly identify quantities like the mean, median, and mode, as well as number and mass fractions in different mass intervals.
Prediction of fatique crack growth under flight-simulation loading with the modified CORPUS model
NASA Technical Reports Server (NTRS)
Padmadinata, U. H.; Schijve, J.
1994-01-01
The CORPUS (Computation Of Retarded Propagation Under Spectrum loading) crack growth prediction model for variable-amplitude loading, as introduced by De Koning, was based on crack closure. It includes a multiple-overload effect and a transition from plane strain to plane stress. In the modified CORPUS model an underload affected zone (ULZ) is introduced, which is significant for flight-simulation loading in view of the once per flight compressive ground load. The ULZ is associated with reversed plastic deformation induced by the underloads after crack closure has already occurred. Predictions of the crack growth fatigue life are presented for a large variety of flight-simulation test series on 2024-T3 sheet specimens in order to reveal the effects of a number of variables: the design stress level, the gust spectrum severity, the truncation level (clipping), omission of small cycles, and the ground stress level. Tests with different load sequences are also included. The trends of the effects induced by the variables are correctly predicted. The quantitative agreement between the predictions and the test results is also satisfactory.
Radiative transfer equation modeling by streamline diffusion modified continuous Galerkin method
NASA Astrophysics Data System (ADS)
Long, Feixiao; Li, Fengyan; Intes, Xavier; Kotha, Shiva P.
2016-03-01
Optical tomography has a wide range of biomedical applications. Accurate prediction of photon transport in media is critical, as it directly affects the accuracy of the reconstructions. The radiative transfer equation (RTE) is the most accurate deterministic forward model, yet it has not been widely employed in practice due to the challenges in robust and efficient numerical implementations in high dimensions. Herein, we propose a method that combines the discrete ordinate method (DOM) with a streamline diffusion modified continuous Galerkin method to numerically solve RTE. Additionally, a phase function normalization technique was employed to dramatically reduce the instability of the DOM with fewer discrete angular points. To illustrate the accuracy and robustness of our method, the computed solutions to RTE were compared with Monte Carlo (MC) simulations when two types of sources (ideal pencil beam and Gaussian beam) and multiple optical properties were tested. Results show that with standard optical properties of human tissue, photon densities obtained using RTE are, on average, around 5% of those predicted by MC simulations in the entire/deeper region. These results suggest that this implementation of the finite element method-RTE is an accurate forward model for optical tomography in human tissues.
Kavaguchi De Grandis, A; Boulocher, C; Viguier, E; Roger, T; Sawaya, S
2012-01-01
A tendinopathy is a clinical condition characterized by activity-related pain, focal tendons tenderness, and intratendinous imaging changes. This study characterizes a surgically induced tendinopathy in a goat model with a noninvasive in vivo longitudinal followup based on physical examination and US. Cross-sectional area (CSA) is the most objective feature for the evaluation of tendinopathy in correlation with clinical findings. The deep digital flexor tendon (DDFT) of the left hind limb of six goats was isolated and scarified by a modified splitting. Pain and lameness at walk and trot were evaluated. External width and thickness of tendon region were measured by calipers. CSA and the ratio lesion/tendon CSA were obtained at days 0, 7, 21, 42, and 84 by US. The highest value of global functional score was obtained at day 7, then decreased until day 40 and was not significantly different from day 0 at the end of the study. The external width recovered a normal value at the end of the study, but the external thickness was still significantly increased (P < 0.05). Peritendinous oedema was observed at day 7, but intratendinous lesions were visible only at day 21 as a focal hypo to anechoic area. At day 84, two tendons still presented visible lesions. US examination was reproducible, specific, and provided complementary information to the global functional score. A standardized focal tendinopathy was induced in goats. This experimental model of focal tendinopathy could be used to study the effect of different treatments. PMID:22997496
Radiative transfer equation modeling by streamline diffusion modified continuous Galerkin method.
Long, Feixiao; Li, Fengyan; Intes, Xavier; Kotha, Shiva P
2016-03-01
Optical tomography has a wide range of biomedical applications. Accurate prediction of photon transport in media is critical, as it directly affects the accuracy of the reconstructions. The radiative transfer equation (RTE) is the most accurate deterministic forward model, yet it has not been widely employed in practice due to the challenges in robust and efficient numerical implementations in high dimensions. Herein, we propose a method that combines the discrete ordinate method (DOM) with a streamline diffusion modified continuous Galerkin method to numerically solve RTE. Additionally, a phase function normalization technique was employed to dramatically reduce the instability of the DOM with fewer discrete angular points. To illustrate the accuracy and robustness of our method, the computed solutions to RTE were compared with Monte Carlo (MC) simulations when two types of sources (ideal pencil beam and Gaussian beam) and multiple optical properties were tested. Results show that with standard optical properties of human tissue, photon densities obtained using RTE are, on average, around 5% of those predicted by MC simulations in the entire/deeper region. These results suggest that this implementation of the finite element method-RTE is an accurate forward model for optical tomography in human tissues. PMID:26953662
Design and development of a modified runway model of mouse drug self-administration.
Pandy, Vijayapandi; Khan, Yasmin
2016-01-01
The present study established a novel mouse model of a runway drug self-administration in our laboratory. The operant runway apparatus consisted of three long runways arranged in a zig-zag manner. The methodology consisted of six distinct phases: habituation, preconditioning, conditioning, post-conditioning, extinction and reinstatement. The effects of saline were compared with escalating doses of either ethanol (0.5-4.0 g/kg, i.p), heroin (5-40 mg/kg, i.p), or nicotine (0.1-0.5mg/kg, i.p) administered in the goal box during the conditioning phase (day 1 to day 5). A significant decrease in the time of trained (conditioned) mice to reach the goal box confirmed the subjects' motivation to seek those drugs on day 6 (expression). The mice were then subjected to non-rewarded extinction trials for 5 days over which run times were significantly increased. After 5 days of abstinence, a priming dose of ethanol or heroin (1/5th of maximum dose used in conditioning) significantly reinstated the drug-seeking behavior. These results suggest that the modified runway model can serve as a powerful behavioral tool for the study of the behavioral and neurobiological bases of drug self-administration and, as such, is appropriate simple but powerful tool for investigating the drug-seeking behavior of laboratory mice. PMID:26902717
Design and development of a modified runway model of mouse drug self-administration
Pandy, Vijayapandi; Khan, Yasmin
2016-01-01
The present study established a novel mouse model of a runway drug self-administration in our laboratory. The operant runway apparatus consisted of three long runways arranged in a zig-zag manner. The methodology consisted of six distinct phases: habituation, preconditioning, conditioning, post-conditioning, extinction and reinstatement. The effects of saline were compared with escalating doses of either ethanol (0.5–4.0 g/kg, i.p), heroin (5–40 mg/kg, i.p), or nicotine (0.1–0.5mg/kg, i.p) administered in the goal box during the conditioning phase (day 1 to day 5). A significant decrease in the time of trained (conditioned) mice to reach the goal box confirmed the subjects’ motivation to seek those drugs on day 6 (expression). The mice were then subjected to non-rewarded extinction trials for 5 days over which run times were significantly increased. After 5 days of abstinence, a priming dose of ethanol or heroin (1/5th of maximum dose used in conditioning) significantly reinstated the drug-seeking behavior. These results suggest that the modified runway model can serve as a powerful behavioral tool for the study of the behavioral and neurobiological bases of drug self-administration and, as such, is appropriate simple but powerful tool for investigating the drug-seeking behavior of laboratory mice. PMID:26902717
Unification of Dark Matter and Dark Energy in a Modified Entropic Force Model
NASA Astrophysics Data System (ADS)
Chang, Zhe; Li, Ming-Hua; Li, Xin
2011-07-01
In Verlinde's entropic force scenario of gravity, Newton's laws and Einstein equations can be obtained from the first principles and general assumptions. However, the equipartition law of energy is invalid at very low temperatures. We show clearly that the threshold of the equipartition law of energy is related with horizon of the universe. Thus, a one-dimensional Debye (ODD) model in the direction of radius of the modified entropic force (MEF) may be suitable in description of the accelerated expanding universe. We present a Friedmann cosmic dynamical model in the ODD-MEF framework. We examine carefully constraints on the ODD-MEF model from the Union2 compilation of the Supernova Cosmology Project (SCP) collaboration, the data from the observation of the large-scale structure (LSS) and the cosmic microwave background (CMB), i.e. SNe Ia+LSS+CMB. The combined numerical analysis gives the best-fit value of the model parameters ζ ≃ 10-9 and Ωm0 = 0.224, with χ2min = 591.156. The corresponding age of the universe agrees with the result of D. Spergel et al. [J.M. Bardeen, B. Carter, and S.W. Hawking, Commun. Math. Phys. 31 (1973) 161] at 95% confidence level. The numerical result also yields an accelerated expanding universe without invoking any kind of dark energy. Taking ζ(≡ 2πωD/H0) as a running parameter associated with the structure scale r, we obtain a possible unified scenario of the asymptotic flatness of the radial velocity dispersion of spiral galaxies, the accelerated expanding universe and the Pioneer 10/11 anomaly in the entropic force framework of Verlinde.
Generalization of the model of Hawking radiation with modified high frequency dispersion relation
NASA Astrophysics Data System (ADS)
Himemoto, Yoshiaki; Tanaka, Takahiro
2000-03-01
Hawking radiation is one of the most interesting phenomena predicted by the theory of quantum fields in curved space. The origin of Hawking radiation is closely related to the fact that a particle which marginally escapes from collapsing into a black hole is observed at future infinity with an infinitely large redshift. In other words, such a particle had a very high frequency when it was near the event horizon. Motivated by the possibility that the property of Hawking radiation may be altered by some unknown physics which may exist beyond some critical scale, Unruh proposed a model which has higher order spatial derivative terms. In his model, the effects of unknown physics are modeled so as to be suppressed for waves with a wavelength much longer than the critical scale k-10. Surprisingly, it was shown that the thermal spectrum is recovered for such modified models. To introduce such higher order spatial derivative terms, Lorentz invariance must be violated because one special direction needs to be chosen. In previous works, the rest frame of freely falling observers was employed as this special reference frame. Here we give an extension by allowing a more general choice of the reference frame. Developing the method taken by Corley, we show that the resulting spectrum of created particles again becomes the thermal one at the Hawking temperature even if the choice of the reference frame is generalized. Using the technique of the matched asymptotic expansion, we also show that the correction to the thermal radiation stays of order k-20 or smaller when the spectrum of radiated particle around its peak is concerned.
A modified flow/field model of the solar wind interaction with Mars
Stewart, B.K.
1992-01-01
A modified steady state flow/field model is applied to the direct interaction of the solar wind with the Martian ionosphere. The original flow/field model (Cloutier et al., 1987) is a one-dimensional, self-consistent derivation of differentials in vertical velocity, magnetic field, and ion densities from the coupled MHD equations. While successful in reproducing features of the ionosphere of Venus (Cloutier et al., 1987; McGary 1987) and of Mars (Stewart, 1989), the flow/field model required an independently specified heating term (Q). The requirement of this term implies the presence of an energy source not accounted for in conventional calculations. This source was previously simulated with the inclusion of Q, but an unrecognized momentum or pressure term the inclusion of Q, but an unrecognized momentum or pressure term may also provide the coupling with the solar wind without the need of the free parameter Q. An in-depth analysis of Pioneer Venus data in relation to the total conservation of momentum of the system led to the discovery that the total momentum was in most cases not entirely accounted for, and that this [open quotes]missing[close quotes] term was correlated with solar wind dynamic pressure. By including this missing pressure, a new set of differential equations, which were also extended to include horizontal velocity terms, was derived. Extrapolation of the missing pressure to Mars gave results that faithfully reproduced the ionospheric features associated with previous flow/field models while maintaining agreement with Viking 1 and 2 observations. Finally, the author suggests that the source of P[sub missing] could be a population of suprathermal particles within the ionosphere. The missing pressures in the Viking simulations are consistent with measured suprathermal pressures at Mars (Hanson and Mantas, 1988).
Homayouni, Taymaz; Underwood, Kelsey N; Beyer, Kamin C; Martin, Elon R; Allan, Christopher H; Balasubramanian, Ravi
2015-09-01
This paper explores the development of biomechanical models for evaluating a new class of passive mechanical implants for orthopedic surgery. The proposed implants take the form of passive engineered mechanisms, and will be used to improve the functional attachment of muscles to tendons and bone by modifying the transmission of forces and movement inside the body. Specifically, we present how two types of implantable mechanisms may be modeled in the open-source biomechanical software OpenSim. The first implant, which is proposed for hand tendon-transfer surgery, differentially distributes the forces and movement from one muscle across multiple tendons. The second implant, which is proposed for knee-replacement surgery, scales up the forces applied to the knee joint by the quadriceps muscle. This paper's key innovation is that such mechanisms have never been considered before in biomechanical simulation modeling and in surgery. When compared with joint function enabled by the current surgical practice of using sutures to make the attachment, biomechanical simulations show that the surgery with 1) the differential mechanism (tendon network) implant improves the fingers' ability to passively adapt to an object's shape significantly during grasping tasks (2.74× as measured by the extent of finger flexion) for the same muscle force, and 2) the force-scaling implant increases knee-joint torque by 84% for the same muscle force. The critical significance of this study is to provide a methodology for the design and inclusion of the implants into biomechanical models and validating the improvement in joint function they enable when compared with current surgical practice. PMID:25850081
NASA Astrophysics Data System (ADS)
Hamimid, M.; Mimoune, S. M.; Feliachi, M.
2013-01-01
In this paper, a time stepping finite volume method (FVM) associated with the modified inverse Jiles-Atherton model for the nonlinear electromagnetic field computation is presented. To describe the dynamic behavior in the conducting media, the effective field is modified by adding two counter-fields associated respectively to the eddy current and excess losses. The hysteresis loss can be estimated by the integration over the obtained hysteresis loop at each frequency. To examine the validity of the proposed dynamic model coupled with FVM, the computed total losses and hysteresis loops are compared to experiments.
Large-scale hydrological modelling by using modified PUB recommendations: the India-HYPE case
NASA Astrophysics Data System (ADS)
Pechlivanidis, I. G.; Arheimer, B.
2015-03-01
The Prediction in Ungauged Basins (PUB) scientific initiative (2003-2012 by IAHS) put considerable effort into improving the reliability of hydrological models to predict flow response in ungauged rivers. PUB's collective experience advanced hydrologic science and defined guidelines to make predictions in catchments without observed runoff data. At present, there is a raised interest in applying catchment models for large domains and large data samples in a multi-basin manner. However, such modelling involves several sources of uncertainties, which may be caused by the imperfectness of input data, i.e. particularly regional and global databases. This may lead to inaccurate model parameterisation and incomplete process understanding. In order to bridge the gap between the best practices for single catchments and large-scale hydrology, we present a further developed and slightly modified version of the recommended best practices for PUB by Takeuchi et al. (2013). By using examples from a recent HYPE hydrological model set-up on the Indian subcontinent, named India-HYPE v1.0, we explore the recommendations, indicate challenges and recommend quality checks to avoid erroneous assumptions. We identify the obstacles, ways to overcome them and describe the work process related to: (a) errors and inconsistencies in global databases, unknown human impacts, poor data quality, (b) robust approaches to identify parameters using a stepwise calibration approach, remote sensing data, expert knowledge and catchment similarities; and (c) evaluation based on flow signatures and performance metrics, using both multiple criteria and multiple variables, and independent gauges for "blind tests". The results show that despite the strong hydro-climatic gradient over the subcontinent, a single model can adequately describe the spatial variability in dominant hydrological processes at the catchment scale. Eventually, during calibration of India-HYPE, the median Kling-Gupta Efficiency for
Nutrient fluxes in the Changjiang River estuary and adjacent waters — a modified box model approach
NASA Astrophysics Data System (ADS)
Wang, Xiaohong; Yu, Zhiming; Fan, Wei; Song, Xiuxian; Cao, Xihua; Yuan, Yongquan
2015-01-01
one in estimating nutrient fluxes in a complicated hydrodynamic current system and provides a modified box model approach to material flux research.
The effect of modifiable risk factors on geographic mortality differentials: a modelling study
2012-01-01
Background Australian mortality rates are higher in regional and remote areas than in major cities. The degree to which this is driven by variation in modifiable risk factors is unknown. Methods We applied a risk prediction equation incorporating smoking, cholesterol and blood pressure to a national, population based survey to project all-causes mortality risk by geographic region. We then modelled life expectancies at different levels of mortality risk by geographic region using a risk percentiles model. Finally we set high values of each risk factor to a target level and modelled the subsequent shift in the population to lower levels of mortality risk and longer life expectancy. Results Survival is poorer in both Inner Regional and Outer Regional/Remote areas compared to Major Cities for men and women at both high and low levels of predicted mortality risk. For men smoking, high cholesterol and high systolic blood pressure were each associated with the mortality difference between Major Cities and Outer Regional/Remote areas--accounting for 21.4%, 20.3% and 7.7% of the difference respectively. For women smoking and high cholesterol accounted for 29.4% and 24.0% of the difference respectively but high blood pressure did not contribute to the observed mortality differences. The three risk factors taken together accounted for 45.4% (men) and 35.6% (women) of the mortality difference. The contribution of risk factors to the corresponding differences for inner regional areas was smaller, with only high cholesterol and smoking contributing to the difference in men-- accounting for 8.8% and 6.3% respectively-- and only smoking contributing to the difference in women--accounting for 12.3%. Conclusions These results suggest that health intervention programs aimed at smoking, blood pressure and total cholesterol could have a substantial impact on mortality inequities for Outer Regional/Remote areas. PMID:22276576
Is modified gravity required by observations? An empirical consistency test of dark energy models
NASA Astrophysics Data System (ADS)
Wang, Sheng; Hui, Lam; May, Morgan; Haiman, Zoltán
2007-09-01
We apply the technique of parameter splitting to existing cosmological data sets, to check for a generic failure of dark energy models. Given a dark energy parameter, such as the energy density ΩΛ or equation of state w, we split it into two meta-parameters with one controlling geometrical distances, and the other controlling the growth of structure. Observational data spanning Type Ia Supernovae, the cosmic microwave background (CMB), galaxy clustering, and weak gravitational lensing statistics are fit without requiring the two meta-parameters to be equal. This technique checks for inconsistency between different data sets, as well as for internal inconsistency within any one data set (e.g., CMB or lensing statistics) that is sensitive to both geometry and growth. We find that the cosmological constant model is consistent with current data. Theories of modified gravity generally predict a relation between growth and geometry that is different from that of general relativity. Parameter splitting can be viewed as a crude way to parametrize the space of such theories. Our analysis of current data already appears to put sharp limits on these theories: assuming a flat universe, current data constrain the difference ΔΩΛ=ΩΛ(geom)-ΩΛ(grow) to be -0.0044-0.0057-0.0119+0.0058+0.0108 (68% and 95% C.L. respectively); allowing the equation of state w to vary, the difference Δw=w(geom)-w(grow) is constrained to be 0.37-0.36-0.53+0.37+1.09. Interestingly, the region w(grow)>w(geom), which should be generically favored by theories that slow structure formation relative to general relativity, is quite restricted by data already. We find w(grow)<-0.80 at 2σ. As an example, the best-fit flat Dvali-Gabadadze-Porrati model approximated by our parametrization lies beyond the 3σ contour for constraints from all the data sets.
Zellnitz, Sarah; Schroettner, Hartmuth; Urbanetz, Nora Anne
2015-01-01
The aim of this work is to investigate the effect of surface characteristics (surface roughness and specific surface area) of surface-modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization, and thus, the in vitro respirable fraction often referred to as fine particle fraction (FPF). By processing glass beads in a ball mill with different grinding materials (quartz and tungsten carbide) and varying grinding time (4 h and 8 h), and by plasma etching for 1 min, glass beads with different shades of surface roughness and increased surface area were prepared. Compared with untreated glass beads, the surface-modified rough glass beads show increased FPFs. The drug detachment from the modified glass beads is also more reproducible than from untreated glass beads indicated by lower standard deviations for the FPFs of the modified glass beads. Moreover, the FPF of the modified glass beads correlates with their surface characteristics. The higher the surface roughness and the higher the specific surface area of the glass beads the higher is the FPF. Thus, surface-modified glass beads make an ideal carrier for tailoring the performance of DPIs in the therapy of asthma and chronically obstructive pulmonary diseases. PMID:25632978
Modified GIT model for predicting wind-speed behavior of low-grazing-angle radar sea clutter
NASA Astrophysics Data System (ADS)
Zhang, Yu-Shi; Zhang, Jin-Peng; Li, Xin; Wu, Zhen-Sen
2014-10-01
A modified GIT model for describing the variational trend of mean clutter reflectivity as a function of wind speed is proposed. It uses two slope adjustment factors and two critical wind-speed factors to define and adjust the increasing slope of reflectivity with respect to wind speed. In addition, it uses a constant factor to compensate the overall amplitude of clutter reflectivity. The performance of the modified GIT model has been verified on the basis of the L-band low-grazing-angle radar sea clutter data. The results are in good agreement with the experimental data, indicating that the model is more effective in predicting the wind-speed behavior of clutter reflectivity than the conventional GIT model, especially for lower and higher wind speeds. We believe that the proposed model can provide deeper insights into the relationship between radar sea clutter reflectivity and sea state conditions.
NASA Astrophysics Data System (ADS)
Avlonitis, Markos; Papadopoulos, Gerassimos
2013-04-01
The role on seismicity of fault characteristics, such as the strength of coupling and fault geometry, has been extensively examined so far. The asperity model stipulates that instead of smooth planar fault surfaces most of coupling is concentrated to the contact between irregularities of the fault surfaces. As a result the tectonic stress is accumulated across a smaller area, the real contact area, than in the total fault area. To this end, we introduce a modification of the Olami-Feder-Christensen (OFC) spring-block model that models the dynamic evolution of faults due to the real contact areas of asperities along the fault surface. The modification is based on relaxing the assumption of global driving. Indeed, the different asperity distributions are modeled by different real contact areas between the two segments of the fault. The proposed modified OFC model, considers that leaf springs in the vertical direction are only present within the real contact area, whereas horizontal springs are everywhere in space based on the assumption that the segments exhibit elastic behavior. This specific proposed geometry not only results to that instead of global driving, deformation is driven only by blocks within the real contact area, but also that non-conservative redistribution of forces takes place again only within the real contact area while in the rest of the fault surface there is force conservation due to lack of interactions. Moreover, two different approaches are presented in order to model the dynamic behavior of material points of the fault that lie outside of the asperities. The first is based on the classical OFC model and the second is based on a departure (correction) from the OFC model and more specifically on reconsidering the exact value of the force at each site. The relation between different power law exponents b, of the emerged power-law distributions of the slip sizes, with the distributions of the corresponding real contact area of asperities within
Modeling Neutron Star Stability with a Modified Tolman-Oppenheimer-Volkoff Equation
NASA Astrophysics Data System (ADS)
Chaykov, Spasen; O'Brien, James
2016-03-01
The Tolman-Oppenheimer-Volkoff (TOV) equation represents the solution to the Einstein field equations where the source of curvature is given by the stress-energy tensor of a perfect fluid. In flat space it has the form Tμν = (ρ + p) UμUν + pημν and the convention for curved space-time is to just replace the Minkowski metric with gμν. For our research we instead use a modified stress-energy tensor of the form Tμν = (ρ + p) UμUν + pgμν +πμν where the anisotropic πμν is a symmetric, traceless rank two tensor which obeys Uμπμν = 0 . The motivation is that such a term in the stress-energy tensor can account for effects due to the curvature of space-time and would not be present in the tensor describing flat space.The final revised TOV equation is of the form -r2p' = GMρ [ 1 +p/- 2 q ρ ] [ 1 +4/πr3 (p - 2 q) M ] [ 1 -2/GM r ] - 1 - 2r2q' - 6 rq where the primes indicate differentiation with respect to the radial coordinate and the q terms arise from the components of πμν. The equation was then solved numerically with both a polytropic and a MIT bag model equations of state. The result is a changed prediction for the stability range of neutron stars.
Surface science and model catalysis with ionic liquid-modified materials.
Steinrück, H-P; Libuda, J; Wasserscheid, P; Cremer, T; Kolbeck, C; Laurin, M; Maier, F; Sobota, M; Schulz, P S; Stark, M
2011-06-17
Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy. PMID:21520462
Role of genetic modifiers in an orthologous rat model of ARPKD
O'Meara, Caitlin C.; Hoffman, Matthew; Sweeney, William E.; Tsaih, Shirng-Wern; Xiao, Bing; Jacob, Howard J.; Avner, Ellis D.
2012-01-01
Human data and animal models of autosomal recessive polycystic kidney disease (ARPKD) suggest that genetic factors modulate the onset and severity of the disease. We report here for the first time that ARPKD susceptibility is attenuated by introgressing the mutated Pkhd1 disease allele from the polycystic kidney (PCK) rat onto the FHH (Fawn-Hooded Hypertensive) genetic background. Compared with PCK, the FHH.Pkhd1 strain had significantly decreased renal cyst formation that coincided with a threefold reduction in mean kidney weights. Further analysis revealed that the FHH. Pkhd1 is protected from increased blood pressure as well as elevated plasma creatinine and blood urea nitrogen levels. On the other hand, liver weight and biliary cystogenesis revealed no differences between PCK and FHH.Pkdh1, indicating that genes within the FHH genetic background prevent the development of renal, but not hepatic, manifestations of ARPKD. Microarray expression analysis of kidneys from 30-day-old PCK rats revealed increased expression of genes previously identified in PKD renal expression profiles, such as inflammatory response, extracellular matrix synthesis, and cell proliferation genes among others, whereas the FHH.Pkhd1 did not show activation of these common markers of disease. This newly developed strain can serve as a tool to map modifier genes for renal disease in ARPKD and provides further insight into disease variability and pathophysiology. PMID:22669842
NASA Astrophysics Data System (ADS)
Hahn, Y. K.
2016-09-01
A statistical density model for composite system scattering is formulated, by incorporating the ensemble density functional approach in describing the correlation dynamics during the collision. The principal difficulty of non-integrable propagating waves is first resolved by treating the open and closed channels separately; only the closed channel part does allow a density description. The unique open/closed channel separation adopted here allows not only the closed channel Hamiltonian MQ to support integrable densities, but also to establish the important bounds on the scattering amplitude. A modified ensemble energy functional for the MQ is constructed, and the statistical densities ρmtQ for the closed channels are generated. The scattering amplitude is then formulated in terms of the ρmtQ and the coefficients of variation that connect the closed channels to the asymptotic source. Evaluation of the amplitude integrals requires the determinantal functions deduced from the ρmtQ, which also leads to a coupled channel approach. The bound property of the amplitude allows variational optimization of the coefficients. Approximate procedures for securing the orthogonality of the MQ and for evaluation of the source term itself are discussed, including a judicious choice of configurations with zero and one inner-shell holes. Validity of the several critical modifications introduced is assessed.
A DNA solution of SAT problem by a modified sticker model.
Yang, Chia-Ning; Yang, Chang-Biau
2005-07-01
Among various DNA computing algorithms, it is very common to create an initial data pool that covers correct and incorrect answers at first place followed by a series of selection process to destroy the incorrect ones. The surviving DNA sequences are read as the solutions to the problem. However, algorithms based on such a brute force search will be limited to the problem size. That is, as the number of parameters in the studied problem grows, eventually the algorithm becomes impossible owing to the tremendous initial data pool size. In this theoretical work, we modify a well-known sticker model to design an algorithm that does not require an initial data pool for SAT problem. We propose to build solution sequences in parts to satisfy one clause in a step, and eventually solve the whole Boolean formula after a number of steps. Accordingly, the size of data pool grows from one sort of molecule to the number of solution assignments. The proposed algorithm is expected to provide a solution to SAT problem and become practical as the problem size scales up. PMID:15917122
Gene Therapy Model of X-linked Severe Combined Immunodeficiency Using a Modified Foamy Virus Vector
Horino, Satoshi; Uchiyama, Toru; So, Takanori; Nagashima, Hiroyuki; Sun, Shu-lan; Sato, Miki; Asao, Atsuko; Haji, Yoichi; Sasahara, Yoji; Candotti, Fabio; Tsuchiya, Shigeru; Kure, Shigeo; Sugamura, Kazuo; Ishii, Naoto
2013-01-01
X-linked severe combined immunodeficiency (SCID-X1) is an inherited genetic immunodeficiency associated with mutations in the common cytokine receptor γ chain (γc) gene, and characterized by a complete defect of T and natural killer (NK) cells. Gene therapy for SCID-X1 using conventional retroviral (RV) vectors carrying the γc gene results in the successful reconstitution of T cell immunity. However, the high incidence of vector-mediated T cell leukemia, caused by vector insertion near or within cancer-related genes has been a serious problem. In this study, we established a gene therapy model of mouse SCID-X1 using a modified foamy virus (FV) vector expressing human γc. Analysis of vector integration in a human T cell line demonstrated that the FV vector integration sites were significantly less likely to be located within or near transcriptional start sites than RV vector integration sites. To evaluate the therapeutic efficacy, bone marrow cells from γc-knockout (γc-KO) mice were infected with the FV vector and transplanted into γc-KO mice. Transplantation of the FV-treated cells resulted in the successful reconstitution of functionally active T and B cells. These data suggest that FV vectors can be effective and may be safer than conventional RV vectors for gene therapy for SCID-X1. PMID:23990961
MODIFIED N.R.C. VERSION OF THE U.S.G.S. SOLUTE TRANSPORT MODEL. VOLUME 1. MODIFICATIONS
The methods described in the report can be used with the modified N.R.C. version of the U.S.G.S. Solute Transport Model to predict the concentration of chemical parameters in a contaminant plume. The two volume report contains program documentation and user's manual. The program ...
Kim, Woo Sik; Kim, Jong-Seok; Kim, Hong Min; Kwon, Kee Woong; Cho, Sang-Nae; Shin, Sung Jae; Koh, Won-Jung
2015-01-01
The latency and reactivation of Mycobacterium tuberculosis infection has been well studied. However, there have been few studies of the latency and reactivation of Mycobacterium avium complex (MAC), the most common etiological non-tuberculous Mycobacterium species next to M. tuberculosis in humans worldwide. We hypothesized that latent MAC infections can be reactivated following immunosuppression after combination chemotherapy with clarithromycin and rifampicin under experimental conditions. To this end, we employed a modified Cornell-like murine model of tuberculosis and investigated six strains consisting of two type strains and four clinical isolates of M. avium and M. intracellulare. After aerosol infection of each MAC strain, five to six mice per group were euthanized at 2, 4, 10, 18, 28 and 35 weeks post-infection, and lungs were sampled to analyze bacterial burden and histopathology. One strain of each species maintained a culture-negative state for 10 weeks after completion of 6 weeks of chemotherapy, but was reactivated after 5 weeks of immunosuppression in the lungs with dexamethasone (three out of six mice in M. avium infection) or sulfasalazine (four out of six mice in both M. avium and M. intracellulare infection). The four remaining MAC strains exhibited decreased bacterial loads in response to chemotherapy; however, they remained at detectable levels and underwent regrowth after immunosuppression. In addition, the exacerbated lung pathology demonstrated a correlation with bacterial burden after reactivation. In conclusion, our results suggest the possibility of MAC reactivation in an experimental mouse model, and experimentally demonstrate that a compromised immune status can induce reactivation and/or regrowth of MAC infection. PMID:26406237
Wolever, Ruth Q.; Webber, Daniel M.; Meunier, Justin P.; Greeson, Jeffrey M.; Lausier, Evangeline R.; Gaudet, Tracy W.
2013-01-01
Background Stroke, diabetes, and coronary heart disease (CHD) remain leading causes of death in the United States and are largely attributable to lifestyle behaviors. Integrative medicine can provide a supportive partnership that focuses on improving health by identifying and implementing lifestyle changes based upon personal values and goals. Objective This prospective observational study was designed to assess the effectiveness of an integrative medicine intervention on modifiable disease risk, patient activation, and psychosocial risk factors for stroke, diabetes, and CHD. Design Sixty-three adults participated in a 3-day comprehensive, multimodal health immersion program at Duke Integrative Medicine, Duke University Medical Center, Durham, North Carolina. Participants received follow-up education, physician support, and telephonic health coaching between the immersion program and the endpoint 7 to 9 months later. Primary Outcome Measures Psychosocial functioning, read iness to change health behaviors, and risk of developing diabetes, stroke, and CHD were assessed at baseline and endpoint. Results Although cardiac risk remained unchanged (P = .19) during the study period, risk of diabetes (P = .02) and stroke (P < .01) decreased significantly. Perceived stress remained unchanged, but improvements were seen in mood (P < .05) and relationship satisfaction (P < .004). Patients became more activated towards self-management of health (P <.001), endorsed greater readiness to change health behaviors (P <.01), and reported increased aerobic exercise (P <.001) and stretching (P = .006) following the intervention. Conclusion An integrative health model can help patients become more engaged in self-management of health and support them in making and maintaining healthy lifestyle changes. These findings provide support for use of an integrative health model in adult disease risk reduction. PMID:22314632
NASA Astrophysics Data System (ADS)
Marchand, Basile; Chamoin, Ludovic; Rey, Christian
2015-11-01
In this work we propose a new identification strategy based on the coupling between a probabilistic data assimilation method and a deterministic inverse problem approach using the modified Constitutive Relation Error energy functional. The idea is thus to offer efficient identification despite of highly corrupted data for time-dependent systems. In order to perform real-time identification, the modified Constitutive Relation Error is here associated to a model reduction method based on Proper Generalized Decomposition. The proposed strategy is applied to two thermal problems with identification of time-dependent boundary conditions, or material parameters.
NASA Astrophysics Data System (ADS)
Baghel, A. P. S.; Kulkarni, S. V.
2013-01-01
Grain-oriented (GO) laminations owing to their crystalline and textured structure exhibit strong anisotropy in magnetic characteristics. GO laminations generally display highly steep, gooseneck, and narrow waist rolling direction (RD) hysteresis loops and complex-shaped transverse direction (TD) curves. The original Jiles-Atherton (JA) model needs improvisation while modeling such characteristics. The paper proposes a modified JA model for the hysteresis modeling of GO laminations with consideration of their crystalline and textured structure. The model is based on single crystal approximation of polycrystalline materials and modifies the anhysteretic magnetization on account of anisotropic energy. It takes into account the domain wall motion as well as domain magnetization rotation. The model provides a better prediction of RD hysteresis loops and also shows ability to characterize of TD hysteresis loops with reasonable accuracy. The model preserves simplicity of the original JA model.
Mechanistic study of methanol synthesis from CO₂ and H₂ on a modified model Mo₆S₈ cluster
Liu, Cheng; Liu, Ping
2015-01-12
We report the methanol synthesis from CO₂ and H₂ on metal (M = K, Ti, Co, Rh, Ni, and Cu)-modified model Mo₆S₈ catalyst using density functional theory (DFT). The results show that the catalytic behavior of a Mo₆S₈ cluster is changed significantly due to the modifiers, via the electron transfer from M to Mo₆S₈ and therefore the reduction of the Mo cation (ligand effect) and the direct participation of M in the reaction (ensemble effect) to promote some elementary steps. With the most positively charged modifier, the ligand effect in the case of K-Mo₆S₈ is the most obvious among themore » systems studied; however it cannot compete with the ensemble effect, which plays a dominate role in determining activity via the electrostatic attraction in particular to stabilize the CHxOy species adsorbed at the Mo sites of Mo₆S₈. In comparison, the ligand effect is weaker and the ensemble effect is more important when the other modifiers are used. In addition, the modifiers also vary the optimal reaction pathway for methanol synthesis on Mo₆S₈, ranging from the reverse water-gas shift (RWGS) + CO hydrogenation as that of Mo₆S₈ to the formate pathway. Finally, K is able to accelerate the methanol synthesis on Mo₆S₈ the most; while the promotion by Rh is relatively small. Using the modifiers like Ti, Co, Ni, and Cu, the activity of Mo₆S₈ is decreased instead. The relative stability between *HCOO and *HOCO is identified as a descriptor to capture the variation in mechanism and scales well with the estimated activity. Our study not only provides better understanding of the reaction mechanism and actives on the modified Mo₆S₈, but also predicts some possible candidates, which can be used a promoter to facilitate the CH₃OH synthesis on Mo sulfides.« less
Mechanistic study of methanol synthesis from CO₂ and H₂ on a modified model Mo₆S₈ cluster
Liu, Cheng; Liu, Ping
2015-01-12
We report the methanol synthesis from CO₂ and H₂ on metal (M = K, Ti, Co, Rh, Ni, and Cu)-modified model Mo₆S₈ catalyst using density functional theory (DFT). The results show that the catalytic behavior of a Mo₆S₈ cluster is changed significantly due to the modifiers, via the electron transfer from M to Mo₆S₈ and therefore the reduction of the Mo cation (ligand effect) and the direct participation of M in the reaction (ensemble effect) to promote some elementary steps. With the most positively charged modifier, the ligand effect in the case of K-Mo₆S₈ is the most obvious among the systems studied; however it cannot compete with the ensemble effect, which plays a dominate role in determining activity via the electrostatic attraction in particular to stabilize the CH_{x}O_{y} species adsorbed at the Mo sites of Mo₆S₈. In comparison, the ligand effect is weaker and the ensemble effect is more important when the other modifiers are used. In addition, the modifiers also vary the optimal reaction pathway for methanol synthesis on Mo₆S₈, ranging from the reverse water-gas shift (RWGS) + CO hydrogenation as that of Mo₆S₈ to the formate pathway. Finally, K is able to accelerate the methanol synthesis on Mo₆S₈ the most; while the promotion by Rh is relatively small. Using the modifiers like Ti, Co, Ni, and Cu, the activity of Mo₆S₈ is decreased instead. The relative stability between *HCOO and *HOCO is identified as a descriptor to capture the variation in mechanism and scales well with the estimated activity. Our study not only provides better understanding of the reaction mechanism and actives on the modified Mo₆S₈, but also predicts some possible candidates, which can be used a promoter to facilitate the CH₃OH synthesis on Mo sulfides.
Jiao, Yun; Yao, Hong-Hong; Chen, Yu-Chen; Yang, Jian; Ding, Jie; Yang, Xiang-Yu; Teng, Gao-Jun
2016-01-01
Aims To precisely characterize the penumbra by MRI based on a modified photothrombotic stroke mouse model. Methods The proximal middle cerebral artery was occluded by a convenient laser system in conjunction with an intravenous injection of Rose Bengal in mice. And the suture MCAO model was performed in seven mice as a comparison of the reproducibility. One hour after occlusion, the penumbra was defined in six random photothrombotic stroke mice by mismatch between perfusion-weighted imaging and the apparent diffusion coefficient map on a home-made workstation. After imaging, three random mice of them were chosen to perform the reperfusion surgery. And the other three mice were sacrificed to stain for several potential penumbra markers, such as c-fos and heart shock protein 90. In the remaining mice, the evolution of the lesions was detected on the apparent diffusion coefficient map, diffusion-weighted imaging and T2-weighted imaging at 1, 3, 6, 12 and 24 hours. After evaluating the neurological deficit scores, the brains were sectioned and stained by triphenyltetrazolium chloride and Nissl. Results The mice subjected to photothrombosis showed significant behavioral deficits. One hour after occlusion, the low perfusion areas on the perfusion-weighted imaging interlaced with the hypointense areas on the apparent diffusion coefficient map, demonstrating that the penumbra was located both surrounding and inside the lesions. This phenomenon was subsequently confirmed by the c-fos and heart shock protein 90 staining. The final T2-weighted images of the mice subjected to the reperfusion surgery were also consistent with the penumbra images at one hour. At early stages, the lesions were clearly identified on the apparent diffusion coefficient map; the volumes of the lesions on the diffusion-weighted imaging and T2-weighted imaging did not reach a maximum until 12 hours. The coefficient of variation (CV) of the final lesions in the photothrombotic stroke mice was 21.7% (0
NASA Technical Reports Server (NTRS)
Taylor, T. W.; Ravet, F. W.; Smika, D. (Principal Investigator)
1981-01-01
The Robertson phenology was used to provide growth stage information to a wheat stress indicator mode. A stress indicator model demands two acurate predictions from a crop calendar: date of spring growth initiation; and crop calendar stage at growth initiation. Several approaches for restarting the Robertson phenology model at spring growth initiation were studied. Although best results were obtained with a solar thermal unit method, an alternate approach which indicates soil temperature as the controlling parameter for spring growth initiation was selected and tested. The modified model (Doraiswamy-Thompson) is compared to LACIE-Robertson model predictions.
Elgharably, Haytham; Ganesh, Kasturi; Dickerson, Jennifer; Khanna, Savita; Abas, Motaz; Ghatak, Piya Das; Dixit, Sriteja; Bergdall, Valerie; Roy, Sashwati; Sen, Chandan K
2014-01-01
We recently performed proteomic characterization of a modified collagen gel (MCG) dressing and reported promising effects of the gel in healing full-thickness excisional wounds. In this work, we test the translational relevance of our aforesaid findings by testing the dressing in a swine model of chronic ischemic wounds recently reported by our laboratory. Full-thickness excisional wounds were established in the center of bipedicle ischemic skin flaps on the backs of animals. Ischemia was verified by laser Doppler imaging, and MCG was applied to the test group of wounds. Seven days post wounding, macrophage recruitment to the wound was significantly higher in MCG-treated ischemic wounds. In vitro, MCG up-regulated expression of Mrc-1 (a reparative M2 macrophage marker) and induced the expression of anti-inflammatory cytokine interleukin (IL)-10 and of fibroblast growth factor-basic (β-FGF). An increased expression of CCR2, an M2 macrophage marker, was noted in the macrophages from MCG treated wounds. Furthermore, analyses of wound tissues 7 days post wounding showed up-regulation of transforming growth factor-β, vascular endothelial growth factor, von Willebrand's factor, and collagen type I expression in MCG-treated ischemic wounds. At 21 days post wounding, MCG-treated ischemic wounds displayed higher abundance of proliferating endothelial cells that formed mature vascular structures and increased blood flow to the wound. Fibroblast count was markedly higher in MCG-treated ischemic wound-edge tissue. In addition, MCG-treated wound-edge tissues displayed higher abundance of mature collagen with increased collagen type I : III deposition. Taken together, MCG helped mount a more robust inflammatory response that resolved in a timely manner, followed by an enhanced proliferative phase, angiogenic outcome, and postwound tissue remodeling. Findings of the current study warrant clinical testing of MCG in a setting of ischemic chronic wounds. PMID:25224310
Zourdos, Michael C; Jo, Edward; Khamoui, Andy V; Lee, Sang-Rok; Park, Bong-Sup; Ormsbee, Michael J; Panton, Lynn B; Contreras, Robert J; Kim, Jeong-Su
2016-03-01
The primary aim of this study was to compare 2 daily undulating periodization (DUP) models on one-repetition maximum (1RM) strength in the squat, bench press, deadlift, total volume (TV) lifted, and temporal hormone response. Eighteen male, college-aged (21.1 ± 1.9 years) powerlifters participated in this study and were assigned to one of 2 groups: (a) traditional DUP training with a weekly training order: hypertrophy-specific, strength-specific, and power-specific training (HSP, n = 9) or (b) modified DUP training with a weekly training order: hypertrophy-specific, power-specific, and strength-specific training (HPS, n = 9). Both groups trained 3 nonconsecutive days per week for 6 weeks and performed the squat, bench press, and deadlift exercises. During hypertrophy and power sessions, subjects performed a fixed number of sets and repetitions but performed repetitions until failure at a given percentage during strength sessions to compare TV. Testosterone and cortisol were measured at pretesting and posttesting and before each strength-specific day. Hypertrophy, power, and strength produced greater TV in squat and bench press (p ≤ 0.05) than HSP, but not for deadlift (p > 0.05). For squat and deadlift, there was no difference between groups for 1RM (p > 0.05); however, HPS exhibited greater increases in 1RM bench press than HSP (p ≤ 0.05). Effect sizes (ES) showed meaningful differences (ES > 0.50) in favor of HPS for squat and bench press 1RM. Testosterone decreased (p ≤ 0.05) at weeks 5 and 6 and cortisol decline at weeks 3 and 4. However, neither hormone was different at posttesting compared with pretesting (p > 0.05). Our findings suggest that an HPS configuration of DUP has enhanced performance benefits compared with HSP. PMID:26332783
The Modifier Model of Autism and Social Development in Higher Functioning Children
Mundy, Peter C.; Henderson, Heather A.; Inge, Anne Pradella; Coman, Drew C.
2009-01-01
The study of phenotypic variability in social impairments and comorbid emotional disorders in autism is important because it provides information on phenotypic differences that currently complicate diagnosis, research, and treatment of this disorder. Currently, though, relatively little is known about the processes that contribute to individual differences in social impairments and comorbidity in autism. In this paper, we present a model that suggests modifier processes (MPs), which are not necessarily specific to the syndrome refractor alter the expression of autism and contribute to fundamental behavioral and psychological differences in children diagnosed with this disorder. One MPs involves the somewhat surprising tendency of some children with higher functioning autism (HFA) to make attributions about other peoples thoughts, although they have social cognitive deficits Just as in other children, the attributions of children with HFA are linked to some of their behavioral problems Another MP involves the influence of differences in motivation associated with the behavioral activation and inhibition systems that can be assessed with measures of anterior EEG asymmetry. This dimension of motivation may be linked to how active but inappropriate and withdrawn children with HFA may appear. Third, differences in the self-monitoring of errors among children with HFA appear to be related to individual differences in IQ and social symptom severity in these children. The possible role of these MPs in diagnostic subgroups and differences in treatment responses among children with HFA are discussed. In addition, the role of MPs in understanding the effects associated with specific genetic functions in autism, such as those associated with the serotonin transporter gene (5-HTTLPR), is discussed. A conclusion of this paper is that the varied expression of autism may require that we understand how autism interacts with other non-syndrome-specific processes that are related to
NASA Astrophysics Data System (ADS)
Luo, Yue; Ye, Shujun; Wu, Jichun; Wang, Hanmei; Jiao, Xun
2016-05-01
Land-subsidence prediction depends on an appropriate subsidence model and the calibration of its parameter values. A modified inverse procedure is developed and applied to calibrate five parameters in a compacting confined aquifer system using records of field data from vertical extensometers and corresponding hydrographs. The inverse procedure of COMPAC (InvCOMPAC) has been used in the past for calibrating vertical hydraulic conductivity of the aquitards, nonrecoverable and recoverable skeletal specific storages of the aquitards, skeletal specific storage of the aquifers, and initial preconsolidation stress within the aquitards. InvCOMPAC is modified to increase robustness in this study. There are two main differences in the modified InvCOMPAC model (MInvCOMPAC). One is that field data are smoothed before diagram analysis to reduce local oscillation of data and remove abnormal data points. A robust locally weighted regression method is applied to smooth the field data. The other difference is that the Newton-Raphson method, with a variable scale factor, is used to conduct the computer-based inverse adjustment procedure. MInvCOMPAC is then applied to calibrate parameters in a land subsidence model of Shanghai, China. Five parameters of aquifers and aquitards at 15 multiple-extensometer sites are calibrated. Vertical deformation of sedimentary layers can be predicted by the one-dimensional COMPAC model with these calibrated parameters at extensometer sites. These calibrated parameters could also serve as good initial values for parameters of three-dimensional regional land subsidence models of Shanghai.
Cognitive training modifies disease symptoms in a mouse model of Huntington's disease.
Yhnell, Emma; Lelos, Mariah J; Dunnett, Stephen B; Brooks, Simon P
2016-08-01
Huntington's disease (HD) is an incurable neurodegenerative disorder which causes a triad of motor, cognitive and psychiatric disturbances. Cognitive disruptions are a core feature of the disease, which significantly affect daily activities and quality of life, therefore cognitive training interventions present an exciting therapeutic intervention possibility for HD. We aimed to determine if specific cognitive training, in an operant task of attention, modifies the subsequent behavioural and neuropathological phenotype of the Hdh(Q111) mouse model of HD. Three testing groups comprising both Hdh(Q111) mice and wildtype controls were used. The first group received cognitive training in an operant task of attention at 4months of age. The second group received cognitive training in a comparable non-attentional operant task at 4months of age, and the third group were control animals that did not receive cognitive training. All groups were then tested in an operant task of attention at 12months of age. Relative to naïve untrained mice, both wildtype and Hdh(Q111) mice that received cognitive training in the operant task of attention demonstrated an increased number of trials initiated, greater accuracy, and fewer 'time out' errors. A specific improvement in response time performance was observed in Hdh(Q111) mice, relative to naïve untrained Hdh(Q111) mice. Relative to the group that received comparable training in a non-attentional task, both wildtype and Hdh(Q111) mice that received attentional training demonstrated superior accuracy in the task and made fewer 'time out' errors. Despite significant behavioural change, in both wildtype and Hdh(Q111) mice that had received cognitive training, no significant changes in neuropathology were observed between any of the testing groups. These results demonstrate that attentional cognitive training implemented at a young age significantly improves attentional performance, at an older age, in both wildtype and Hdh(Q111) mice
Fast Computation of Ground Motion Shaking Map base on the Modified Stochastic Finite Fault Modeling
NASA Astrophysics Data System (ADS)
Shen, W.; Zhong, Q.; Shi, B.
2012-12-01
Rapidly regional MMI mapping soon after a moderate-large earthquake is crucial to loss estimation, emergency services and planning of emergency action by the government. In fact, many countries show different degrees of attention on the technology of rapid estimation of MMI , and this technology has made significant progress in earthquake-prone countries. In recent years, numerical modeling of strong ground motion has been well developed with the advances of computation technology and earthquake science. The computational simulation of strong ground motion caused by earthquake faulting has become an efficient way to estimate the regional MMI distribution soon after earthquake. In China, due to the lack of strong motion observation in network sparse or even completely missing areas, the development of strong ground motion simulation method has become an important means of quantitative estimation of strong motion intensity. In many of the simulation models, stochastic finite fault model is preferred to rapid MMI estimating for its time-effectiveness and accuracy. In finite fault model, a large fault is divided into N subfaults, and each subfault is considered as a small point source. The ground motions contributed by each subfault are calculated by the stochastic point source method which is developed by Boore, and then summed at the observation point to obtain the ground motion from the entire fault with a proper time delay. Further, Motazedian and Atkinson proposed the concept of Dynamic Corner Frequency, with the new approach, the total radiated energy from the fault and the total seismic moment are conserved independent of subfault size over a wide range of subfault sizes. In current study, the program EXSIM developed by Motazedian and Atkinson has been modified for local or regional computations of strong motion parameters such as PGA, PGV and PGD, which are essential for MMI estimating. To make the results more reasonable, we consider the impact of V30 for the
NASA Astrophysics Data System (ADS)
Prabhu Gaunkar, Neelam; Nlebedim, Cajetan; Jiles, David
2013-03-01
Robust theoretical models of hysteresis are important for describing the properties of ferromagnetic materials. Of the available hysteresis models, the J-A model is widely studied. Efforts have been made to modify and extend the applicability of this model and to improve its accuracy in accounting for different conditions that affect the magnetic state of ferromagnetic materials, such as stress. Recently, the J-A model has been extended to describe the ferromagnetic hysteresis in two-phase magnetic materials. Modeling hysteresis of multi-phase ferromagnetic materials is crucial especially due to the need to develop high performance composite magnetic structures. In this study, the extension of the J-A to accommodate materials with two ferromagnetic phases is experimentally verified. The approach to extracting of the J-A model parameters including saturation magnetization (Ms) , domain coupling factor (α) , domain density (a), reversibility (c) and pinning coefficient (k) in two-phase materials will be presented.
Locke, J.; Kotarski, M. A.; Tartof, K. D.
1988-01-01
Twelve dominant enhancers of position effect variegation, representing four loci on the second and third chromosomes of Drosophila melanogaster, have been induced by P-element mutagenesis. Instead of simple transposon insertions, seven of these mutations are cytologically visible duplications and three are deficiencies. The duplications define two distinct regions, each coinciding with a locus that also behaves as a dominant haplo-dependent suppressor of variegation. Conversely, two of the deficiencies overlap with a region that contains a haplo-dependent enhancer of variegation while duplications of this same region act to suppress variegation. The third deficiency defines another haplo-dependent enhancer. These data indicate that loci capable of modifying variegation do so in an antipodal fashion through changes in the wild-type gene copy number and may be divided into two reciprocally acting classes. Class I modifiers enhance variegation when duplicated or suppress variegation when deficient. Class II modifiers enhance when deficient but suppress when duplicated. From our data, and those of others, we propose that in Drosophila there are about 20 to 30 dominant loci that modify variegation. Most appear to be of the class I type whereas only two class II modifiers have been identified so far. From these observations we put forth a model, based on the law of mass action, for understanding how such suppressor-enhancer loci function. We propose that each class I modifier codes for a structural protein component of heterochromatin and their effects on variegation are a consequence of their dosage dependent influence on the extent of the assembly of heterochromatin at the chromosomal site of the position effect. It is further proposed that class II modifiers may inhibit the class I products directly, bind to hypothetical termination sites that define heterochromatin boundaries or promote euchromatin formation. Consistent with our mass action model we find that
Ru, Jingyu; Wu, Chengdong; Jia, Zixi; Yang, Yufang; Zhang, Yunzhou; Hu, Nan
2015-01-01
Localization as a technique to solve the complex and challenging problems besetting line-of-sight (LOS) and non-line-of-sight (NLOS) transmissions has recently attracted considerable attention in the wireless sensor network field. This paper proposes a strategy for eliminating NLOS localization errors during calculation of the location of mobile terminals (MTs) in unfamiliar indoor environments. In order to improve the hidden Markov model (HMM), we propose two modified algorithms, namely, modified HMM (M-HMM) and replacement modified HMM (RM-HMM). Further, a hybrid localization algorithm that combines HMM with an interacting multiple model (IMM) is proposed to represent the velocity of mobile nodes. This velocity model is divided into a high-speed and a low-speed model, which means the nodes move at different speeds following the same mobility pattern. Each moving node continually switches its state based on its probability. Consequently, to improve precision, each moving node uses the IMM model to integrate the results from the HMM and its modified forms. Simulation experiments conducted show that our proposed algorithms perform well in both distance estimation and coordinate calculation, with increasing accuracy of localization of the proposed algorithms in the order M-HMM, RM-HMM, and HMM + IMM. The simulations also show that the three algorithms are accurate, stable, and robust. PMID:26091395
Ru, Jingyu; Wu, Chengdong; Jia, Zixi; Yang, Yufang; Zhang, Yunzhou; Hu, Nan
2015-01-01
Localization as a technique to solve the complex and challenging problems besetting line-of-sight (LOS) and non-line-of-sight (NLOS) transmissions has recently attracted considerable attention in the wireless sensor network field. This paper proposes a strategy for eliminating NLOS localization errors during calculation of the location of mobile terminals (MTs) in unfamiliar indoor environments. In order to improve the hidden Markov model (HMM), we propose two modified algorithms, namely, modified HMM (M-HMM) and replacement modified HMM (RM-HMM). Further, a hybrid localization algorithm that combines HMM with an interacting multiple model (IMM) is proposed to represent the velocity of mobile nodes. This velocity model is divided into a high-speed and a low-speed model, which means the nodes move at different speeds following the same mobility pattern. Each moving node continually switches its state based on its probability. Consequently, to improve precision, each moving node uses the IMM model to integrate the results from the HMM and its modified forms. Simulation experiments conducted show that our proposed algorithms perform well in both distance estimation and coordinate calculation, with increasing accuracy of localization of the proposed algorithms in the order M-HMM, RM-HMM, and HMM + IMM. The simulations also show that the three algorithms are accurate, stable, and robust. PMID:26091395
NASA Astrophysics Data System (ADS)
Kanner, Lisa C.; Mustard, John F.; Gendrin, Aline
2007-04-01
We investigate the ability to refine pyroxene composition and modal abundance from laboratory and remotely acquired spectra. Laboratory data including the martian meteorites, Shergotty, Zagami, MIL03346, and ALH84001 as well as additional pyroxene-rich spectra obtained from the OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité) spectrometer for Mars are characterized using the Modified Gaussian Model (MGM), a spectral deconvolution method developed by Sunshine et al. [Sunshine, J.M., Pieters, C.M., Pratt, S., 1990. J. Geophys. Res. 95, 6955-6966]. We develop two sensitivity tests to assess the extent to which the MGM can consistently predict (1) pyroxene composition and (2) modal abundance for a compositionally diverse suite of pyroxene spectra. Results of the sensitivity tests indicate that the MGM can be appropriately applied to remote spectroscopic measurements of extraterrestrial surfaces and can estimate pyroxene composition and relative abundance within a derived uncertainty. Deconvolved band positions for laboratory spectra of the meteorites Shergotty and Zagami are determined within ±17 nm while remotely acquired OMEGA spectra are defined within ±50 nm. These results suggest that absolute compositions can be uniquely derived from laboratory pyroxene-rich spectra and non-uniquely derived from the remote measurements of OMEGA at this time. While relative pyroxene chemistries are not assessed from OMEGA measurements at this time, relative pyroxene abundances are estimated using a normalized band strength ratio between the low-calcium (LCP) and high-calcium (HCP) endmember components and are constrained to ±10%. The fraction of LCP in a two-pyroxene mixture is the derived value from the normalized band strength ratio, LCP/(LCP + HCP). This calculation for relative abundance is robust in the presence of up to 10-15% olivine. Deconvolution results from the OMEGA spectra indicate that the ancient terrain in the Syrtis Major region is
NASA Astrophysics Data System (ADS)
Xin, Cui; Di-Yu, Zhang; Gao, Chen; Ji-Gen, Chen; Si-Liang, Zeng; Fu-Ming, Guo; Yu-Jun, Yang
2016-03-01
We demonstrate that the interference minima in the linear molecular harmonic spectra can be accurately predicted by a modified two-center model. Based on systematically investigating the interference minima in the linear molecular harmonic spectra by the strong-field approximation (SFA), it is found that the locations of the harmonic minima are related not only to the nuclear distance between the two main atoms contributing to the harmonic generation, but also to the symmetry of the molecular orbital. Therefore, we modify the initial phase difference between the double wave sources in the two-center model, and predict the harmonic minimum positions consistent with those simulated by SFA. Project supported by the National Basic Research Program of China (Grant No. 2013CB922200) and the National Natural Science Foundation of China (Grant Nos. 11274001, 11274141, 11304116, 11247024, and 11034003), and the Jilin Provincial Research Foundation for Basic Research, China (Grant Nos. 20130101012JC and 20140101168JC).
Applying Rasch Model and Generalizability Theory to Study Modified-Angoff Cut Scores
ERIC Educational Resources Information Center
Arce, Alvaro J.; Wang, Ze
2012-01-01
The traditional approach to scale modified-Angoff cut scores transfers the raw cuts to an existing raw-to-scale score conversion table. Under the traditional approach, cut scores and conversion table raw scores are not only seen as interchangeable but also as originating from a common scaling process. In this article, we propose an alternative…
Modified local diatomite as potential functional drug carrier--A model study for diclofenac sodium.
Janićijević, Jelena; Krajišnik, Danina; Čalija, Bojan; Vasiljević, Bojana Nedić; Dobričić, Vladimir; Daković, Aleksandra; Antonijević, Milan D; Milić, Jela
2015-12-30
Diatomite makes a promising candidate for a drug carrier because of its high porosity, large surface area, modifiable surface chemistry and biocompatibility. Herein, refined diatomite from Kolubara coal basin, which complied with the pharmacopoeial requirements for heavy metals content and microbiological quality, was used as a starting material. Inorganic modification of the starting material was performed through a simple, one-step procedure. Significant increase in adsorbent loading with diclofenac sodium (DS) was achieved after the modification process (∼373mg/g) which enabled the preparation of comprimates containing therapeutic dose of the adsorbed drug. Adsorption of DS onto modified diatomite resulted in the alteration of the drug's XRD pattern and FTIR spectrum. In vitro drug release studies in phosphate buffer pH 7.5 demonstrated prolonged DS release over 8h from comprimates containing DS adsorbed on modified diatomite (up to 37% after 8h) and those containing physical mixture of the same composition (up to 45% after 8h). The results of in vivo toxicity testing on mice pointed on potential safety of both unmodified (starting) and modified diatomite. All these findings favor the application of diatomite as a potential functional drug carrier. PMID:26498370
Modified World Café Discussion Model for Conference and Course Settings
ERIC Educational Resources Information Center
Cassidy, Alice; Fox, Joanne
2013-01-01
A group facilitation technique called World Café usually involves dividing a large number of people into smaller groups at tables, exploring a variety of topics around a key focus, and collecting ideas from the discussions to debrief later as a large group. We used a modified version of World Café during the new Cracker Barrel session format at…
Technology Transfer Automated Retrieval System (TEKTRAN)
Albumin is the most abundant protein found in healing wounds. Traditional and chromatogrpahic protein isotherms of albumin binding on modified cotton fibers are useful in understanding albumin binding to cellulose wound dressings. An important consideration in the design of cellulosic wound dressin...
Bai, Er-Wei; Cai, Zhijun; Dudley-Javorosk, Shauna; Shields, Richard K.
2009-01-01
Electrical muscle stimulation demonstrates potential for restoring functional movement and preventing muscle atrophy after spinal cord injury (SCI). Control systems used to optimize delivery of electrical stimulation protocols depend upon mathematical models of paralyzed muscle force outputs. While accurate, the Hill-Huxley-type model is very complex, making it difficult to implement for real-time control. As an alternative, we propose a modified Wiener-Hammerstein system to model the paralyzed skeletal muscle dynamics under electrical stimulus conditions. Experimental data from the soleus muscles of individuals with SCI was used to quantify the model performance. It is shown that the proposed Wiener-Hammerstein system is at least comparable to the Hill-Huxley-type model. On the other hand, the proposed system involves a much smaller number of unknown coefficients. This has substantial advantages in identification algorithm analysis and implementation including computational complexity, convergence and also in real time model implementation for control purposes. PMID:23467426
NASA Astrophysics Data System (ADS)
Zhang, Site; Zhong, Huiying; Wyrowski, Frank
2016-03-01
Wollaston prisms and the modified Wollaston prisms, which are interesting for various applications like optical metrology, topography of surfaces and biological imaging, has been theoretically studied and also been practically applied. The previous studies are mostly based on ray tracing analysis and, as a result, the information that can be obtained are somehow restricted. In this paper, we propose a geometric field tracing technique for the simulation of light propagation through Wollaston prisms. In geometric field tracing we seek for the solutions to Maxwell's equations under the geometrical optics approximation, so that all the properties of light as electromagnetic field are retained. Using the proposed simulation technique, we present the simulation of a differential interference contrast (DIC) microscopy, in which the modified Wollaston prism is used as the key component.
Constraining the Schwarzschild-de Sitter solution in models of modified gravity
NASA Astrophysics Data System (ADS)
Iorio, Lorenzo; Ruggiero, Matteo Luca; Radicella, Ninfa; Saridakis, Emmanuel N.
2016-09-01
The Schwarzschild-de Sitter (SdS) solution exists in the large majority of modified gravity theories, as expected, and in particular the effective cosmological constant is determined by the specific parameters of the given theory. We explore the possibility to use future extended radio-tracking data from the currently ongoing New Horizons mission in the outskirts peripheries of the Solar System, at about 40 au, in order to constrain this effective cosmological constant, and thus to impose constrain on each scenario's parameters. We investigate some of the recently most studied modified gravities, namely f(R) and f(T) theories, dRGT massive gravity, and Hořava-Lifshitz gravity, and we show that New Horizons mission may bring an improvement of one-two orders of magnitude with respect to the present bounds from planetary orbital dynamics.
NASA Technical Reports Server (NTRS)
Matthew, J. R.
1980-01-01
A digital flutter suppression system was developed and mechanized for a significantly modified version of the 1/30-scale B-52E aeroelastic wind tunnel model. A model configuration was identified that produced symmetric and antisymmetric flutter modes that occur at 2873N/sq m (60 psf) dynamic pressure with violent onset. The flutter suppression system, using one trailing edge control surface and the accelerometers on each wing, extended the flutter dynamic pressure of the model beyond the design limit of 4788N/sq m (100 psf). The hardware and software required to implement the flutter suppression system were designed and mechanized using digital computers in a fail-operate configuration. The model equipped with the system was tested in the Transonic Dynamics Tunnel at NASA Langley Research Center and results showed the flutter dynamic pressure of the model was extended beyond 4884N/sq m (102 psf).
A modified Darcy's law . Large eddy simulation of turbulent flows through a fractal model city
NASA Astrophysics Data System (ADS)
Gisinger, Sonja; Dörnbrack, Andreas; Schröttle, Josef
2015-08-01
An approach to describe the turbulent flow through a complex geometry (e.g., urban area) by means of an analogy to flows through porous media is presented. Therefore, a modification of the original Darcy's law is proposed, and its application is tested in a prototype problem with an idealized complex geometry using large eddy simulations. The numerical results indicate the validity of the modified Darcy's law for the chosen setup.
How do mutative events modify moments evolution in thermostatted kinetic models?
NASA Astrophysics Data System (ADS)
Bianca, Carlo
2014-07-01
This short communication aims at developing a thermostatted kinetic framework which includes conservative and nonconservative interactions. Specifically nonconservative interactions refer to proliferative/destructive and mutative events. The thermostatted kinetic framework is a set of autonomous partial integro-differential equations with quadratic nonlinearity. How the moments evolution is modified by mutative interactions is explored in the present communication. Applications refer to the cancer-immune system competition.
Biocompatibility of Portland Cement Modified with Titanium Oxide and Calcium Chloride in a Rat Model
Hoshyari, Narjes; Labbaf, Hossein; Jalayer Naderi, Nooshin; Kazemi, Ali; Bastami, Farshid; Koopaei, Maryam
2016-01-01
Introduction: The aim of the present study was to evaluate the biocompatibility of two modified formulations of Portland cement (PC) mixed with either titanium oxide or both titanium oxide and calcium chloride. Methods and Materials: Polyethylene tubes were filled with modified PCs or Angelus MTA as the control; the tubes were then implanted in 28 Wistar rats subcutaneously. One tube was left empty as a negative control in each rat. Histologic samples were taken after 7, 15, 30 and 60 days. Sections were assessed histologically for inflammatory responses and presence of fibrous capsule and granulation tissue formation. Data were analyzed using the Fisher’s exact and Kruskal-Wallis tests. Result: PC mixed with titanium oxide showed the highest mean scores of inflammation compared with others. There was no statistically significant difference in the mean inflammatory grades between all groups in each of the understudy time intervals. Conclusion: The results showed favorable biocompatibility of these modified PC mixed with calcium chloride and titanium oxide. PMID:27141221
NASA Astrophysics Data System (ADS)
Verpoorter, C.; Carrère, V.; Combe, J.-P.; Le Corre, L.
2009-04-01
Understanding of the uppermost layer of cohesive sediment beds provides important clues for predicting future sediment behaviours. Sediment consolidation, grain size, water content and biological slimes (EPS: extracellular polymeric substances) were found to be significant factors influencing erosion resistance. The surface spectral signatures of mudflat sediments reflect such bio-geophysical parameters. The overall shape of the spectrum, also called a continuum, is a function of grain size and moisture content. Composition translates into specific absorption features. Finally, the chlorophyll-a concentration derived from the strength of the absorption at 675 nm, is a good proxy for biofilm biomass. Bourgneuf Bay site, south of the Loire river estuary, France, was chosen to represent a range of physical and biological influences on sediment erodability. Field spectral measurements and samples of sediments were collected during various field campaigns. An ASD Fieldspec 3 spectroradiometer was used to produce sediment reflectance hyperspectra in the wavelength range 350-2500 nm. We have developed an automatic procedure based on the Modified Gaussian Model that uses, as the first step, the Spectroscopic Derivative Analysis (SDA) to extract from spectra the bio-geophysical properties on mudflat sediments (Verpoorter et al., 2007). This AMGM algorithm is a powerfull tool to deconvolve spectra into two components, first gaussian curves for the absorptions bands, and second a straight line in the wavenumber range for the continuum. We are investigating the possibility of including other approaches, as the inverse gaussian band centred on 2800 nm initially developed by Whiting et al., (2006) to estimate water content. Additionally, soils samples were analysed to determine moisture content, grain size (laser grain size analyses), organic matter content, carbonate content (calcimetry) and clay content. X-ray diffraction analysis was performed on selected non
NASA Astrophysics Data System (ADS)
Xu, Xiao-Jian; Wang, Ya-Chuan; Wang, Bo; Zhang, Kai
2016-06-01
We propose a modified core-shell model to depict the size-dependent elastic properties of materials with several different cross-sections. By using the Young-Laplace equation, a modified Euler-Bernoulli equation, which has taken a power-law relation between the bulk and surface moduli into account, is derived. A finite element method of the modified Euler-Bernoulli equation is formulated, and assembled to investigate the dispersion relations of the infinite two-dimensional periodic square cellular networks. The effectiveness of the proposed core-shell model is verified by comparing with results of the experiments and the molecular dynamics simulations available in the literature. Numerical results show that surface effects play an important role on the cellular networks with small diameters, large aspect ratios and high wave frequencies. Meanwhile, the analytical expressions for the size-dependent elastic modulus may be useful for the study of the size-dependent elasticity of materials and structures at small length scales.
Active Aeroelastic Wing Aerodynamic Model Development and Validation for a Modified F/A-18A Airplane
NASA Technical Reports Server (NTRS)
Cumming, Stephen B.; Diebler, Corey G.
2005-01-01
A new aerodynamic model has been developed and validated for a modified F/A-18A airplane used for the Active Aeroelastic Wing (AAW) research program. The goal of the program was to demonstrate the advantages of using the inherent flexibility of an aircraft to enhance its performance. The research airplane was an F/A-18A with wings modified to reduce stiffness and a new control system to increase control authority. There have been two flight phases. Data gathered from the first flight phase were used to create the new aerodynamic model. A maximum-likelihood output-error parameter estimation technique was used to obtain stability and control derivatives. The derivatives were incorporated into the National Aeronautics and Space Administration F-18 simulation, validated, and used to develop new AAW control laws. The second phase of flights was used to evaluate the handling qualities of the AAW airplane and the control law design process, and to further test the accuracy of the new model. The flight test envelope covered Mach numbers between 0.85 and 1.30 and dynamic pressures from 600 to 1250 pound-force per square foot. The results presented in this report demonstrate that a thorough parameter identification analysis can be used to improve upon models that were developed using other means. This report describes the parameter estimation technique used, details the validation techniques, discusses differences between previously existing F/A-18 models, and presents results from the second phase of research flights.
Monthly gravity field models derived from GRACE Level 1B data using a modified short-arc approach
NASA Astrophysics Data System (ADS)
Chen, Qiujie; Shen, Yunzhong; Zhang, Xingfu; Hsu, Houze; Chen, Wu; Ju, Xiaolei; Lou, Lizhi
2015-03-01
In this study, a new time series of Gravity Recovery and Climate Experiment (GRACE) monthly solutions, complete to degree and order 60 spanning from January 2003 to August 2011, has been derived based on a modified short-arc approach. Our models entitled Tongji-GRACE01 are available on the website of International Centre for Global Earth Models http://icgem.gfz-potsdam.de/ICGEM/. The traditional short-arc approach, with no more than 1 h arcs, requires the gradient corrections of satellite orbits in order to reduce the impact of orbit errors on the final solution. Here the modified short-arc approach has been proposed, which has three major differences compared to the traditional one: (1) All the corrections of orbits and range rate measurements are solved together with the geopotential coefficients and the accelerometer biases using a weighted least squares adjustment; (2) the boundary position parameters are not required; and (3) the arc length can be extended to 2 h. The comparisons of geoid degree powers and the mass change signals in the Amazon basin, the Antarctic, and Antarctic Peninsula demonstrate that our model is comparable with the other existing models, i.e., the Centre for Space Research RL05, Jet Propulsion Laboratory RL05, and GeoForschungsZentrum RL05a models. The correlation coefficients of the mass change time series between our model and the other models are better than 0.9 in the Antarctic and Antarctic Peninsula. The mass change rates in the Antarctic and Antarctic Peninsula derived from our model are -92.7 ± 38.0 Gt/yr and -23.9 ± 12.4 Gt/yr, respectively, which are very close to those from other three models and with similar spatial patterns of signals.
Chaix, E; Broyart, B; Couvert, O; Guillaume, C; Gontard, N; Guillard, V
2015-10-01
A mechanistic model coupling O2 and CO2 mass transfer (namely diffusion and solubilisation in the food itself and permeation through the packaging material) to microbial growth models was developed aiming at predicting the shelf life of modified atmosphere packaging (MAP) systems. It was experimentally validated on a non-respiring food by investigating concomitantly the O2/CO2 partial pressure in packaging headspace and the growth of Listeria monocytogenes (average microbial count) within the food sample. A sensitivity analysis has revealed that the reliability of the prediction by this "super-parametrized" model (no less than 47 parameters were required for running one simulation) was strongly dependent on the accuracy of the microbial input parameters. Once validated, this model was used to decipher the role of O2/CO2 mass transfer on microbial growth and as a MAP design tool: an example of MAP dimensioning was provided in this paper as a proof of concept. PMID:26187845
Narayanan, M.; Tong, S.; Ma, B.; Liu, S.; Balachandran, U.
2012-01-01
A modified Johnson model is proposed to describe the nonlinear field dependence of the dielectric constant ({var_epsilon}-E loop) in ferroelectric materials below the Curie temperature. This model describes the characteristic ferroelectric 'butterfly' shape observed in typical {var_epsilon}-E loops. The predicted nonlinear behavior agreed well with the measured values in both the low- and high-field regions for lead lanthanum zirconate titanate films. The proposed model was also validated at different temperatures below the ferroelectric-to-paraelectric Curie point. The anharmonic coefficient in the model decreased from 6.142 x 10{sup -19} cm{sup 2}/V{sup 2} to 2.039 x 10{sup -19} cm{sup 2}/V{sup 2} when the temperature increased from 25 C to 250 C.
NASA Astrophysics Data System (ADS)
Hamimid, M.; Mimoune, S. M.; Feliachi, M.; Atallah, K.
2014-10-01
In this present work, a non centered minor hysteresis loops evaluation is performed using the exponential transforms (ET) of the modified inverse Jiles-Atherton model parameters. This model improves the non centered minor hysteresis loops representation. The parameters of the non centered minor hysteresis loops are obtained from exponential expressions related to the major ones. The parameters of minor loops are obtained by identification using the stochastic optimization method “simulated annealing”. The four parameters of JA model (a,α, k and c) obtained by this transformation are applied only in both ascending and descending branches of the non centered minor hysteresis loops while the major ones are applied to the rest of the cycle. This proposal greatly improves both branches and consequently the minor loops. To validate this model, calculated non-centered minor hysteresis loops are compared with measured ones and good agreements are obtained.
Wishart, Thomas M; Pemberton, Helen N; James, Sally R; McCabe, Chris J; Gillingwater, Thomas H
2008-01-01
Background Altered neuronal vulnerability underlies many diseases of the human nervous system, resulting in degeneration and loss of neurons. The neuroprotective slow Wallerian degeneration (Wlds) mutation delays degeneration in axonal and synaptic compartments of neurons following a wide range of traumatic and disease-inducing stimuli, providing a powerful experimental tool with which to investigate modulation of neuronal vulnerability. Although the mechanisms through which Wlds confers neuroprotection remain unclear, a diverse range of downstream modifications, incorporating several genes/pathways, have been implicated. These include the following: elevated nicotinamide adenine dinucleotide (NAD) levels associated with nicotinamide mononucleotide adenylyltransferase 1 (Nmnat1; a part of the chimeric Wlds gene); altered mRNA expression levels of genes such as pituitary tumor transforming gene 1 (Pttg1); changes in the location/activity of the ubiquitin-proteasome machinery via binding to valosin-containing protein (VCP/p97); and modified synaptic expression of proteins such as ubiquitin-activating enzyme E1 (Ube1). Results Wlds expression in mouse cerebellum and HEK293 cells induced robust increases in a broad spectrum of cell cycle-related genes. Both NAD-dependent and Pttg1-dependent pathways were responsible for mediating different subsets of these alterations, also incorporating changes in VCP/p97 localization and Ube1 expression. Cell proliferation rates were not modified by Wlds, suggesting that later mitotic phases of the cell cycle remained unaltered. We also demonstrate that Wlds concurrently altered endogenous cell stress pathways. Conclusion We report a novel cellular phenotype in cells with altered neuronal vulnerability. We show that previous reports of diverse changes occurring downstream from Wlds expression converge upon modifications in cell cycle status. These data suggest a strong correlation between modified cell cycle pathways and altered
Chang, Ying-Jun; Wang, Hong-Tao; Xu, Lan-Ping; Wang, Yu; Liu, Kai-Yan; Zhang, Xiao-Hui; Liu, Dai-Hong; Chen, Huan; Chen, Yu-Hong; Wang, Feng-Rong; Han, Wei-; Sun, Yu-Qian; Yan, Chen-Hua; Tang, Fei-Fei; Mo, Xiao-Dong; Huang, Xiao-Jun
2016-09-01
Both European Group for blood and marrow transplantation risk score (EBMT score modified model) and hematopoietic cell transplantation comorbidity index (HCT-CI) are suitable for evaluating patients undergoing unmanipulated haploidentical blood and marrow transplantation (HBMT), while the predictive capacity of the combined model following haploidentical transplantation is still unknown. In this study, we calculated and validated 322 consecutive unmanipulated HBMT patients. Patients in groups with HCT-CI scores of 0 or 1-2 exhibited similar overall survival (OS), non-relapse mortality (NRM), and relapse rates, independent of their EBMT score modified model. In the group in which patients' HCT-CI scores were ≥3, patients with high EBMT score modified model showed lower OS (p = 0.003) and higher NRM (p = 0.001) than did patients with low EBMT score. In conclusion, this combined model can be used to predict outcomes and may improve the stratification of high-risk patients following unmanipulated HBMT. PMID:26857549
Zhou, Siyuan; Sheen, Shiowshuh; Pang, Yu-Hsin; Liu, Linshu; Yam, Kit L
2015-02-01
Salmonella is a microorganism of concern on a global basis for raw shrimp. This research modeled the impact of vapor thymol concentration (0, 0.8, and 1.6 mg/liter), storage temperature (8, 12, and 16°C), and modified atmosphere condition (0.04 as in the natural atmosphere and 59.5% CO2) against the growth behavior of a Salmonella cocktail (six strains) on raw shrimp. Lag time (hour) and maximum growth rate (log CFU per gram per hour), chosen as two growth indicators, were obtained through DMFit software and then developed into polynomial as well as nonlinear modified secondary models (dimensional and/or dimensionless), consisting of two or even three impact factors in the equations. The models were validated, and results showed that the predictive values from both models demonstrated good matches to the observed experimental values, yet the prediction based on lag time was more accurate than maximum growth rate. The information will provide the food industry with insight into the potential safety risk of Salmonella growth on raw shrimp under stressed conditions. PMID:25710144
Zhang, Fang; Zhang, Yan; Chen, Man; van Loosdrecht, Mark C M; Zeng, Raymond J
2013-07-01
A modified metabolic model for mixed culture fermentation (MCF) is proposed with the consideration of an energy conserving electron bifurcation reaction and the transport energy of metabolites. The production of H2 related to NADH/NAD(+) and Fdred/Fdox is proposed to be divided in three processes in view of energy conserving electron bifurcation reaction. This assumption could fine-tune the intracellular redox balance and regulate the distribution of metabolites. With respect to metabolite transport energy, the proton motive force is considered to be constant, while the transport rate coefficient is proposed to be proportional to the octanol-water partition coefficient. The modeling results for a glucose fermentation in a continuous stirred tank reactor show that the metabolite distribution is consistent with the literature: (1) acetate, butyrate, and ethanol are main products at acidic pH, while the production shifts to acetate and propionate at neutral and alkali pH; (2) the main products acetate, ethanol, and butyrate shift to ethanol at higher glucose concentration; (3) the changes for acetate and butyrate are following an increasing hydrogen partial pressure. The findings demonstrate that our modified model is more realistic than previous proposed model concepts. It also indicates that inclusion of an energy conserving electron bifurcation reaction and metabolite transport energy for MCF is sound in the viewpoint of biochemistry and physiology. PMID:23381671
NASA Astrophysics Data System (ADS)
Prajoon, P.; Nirmal, D.; Anuja Menokey, M.; Charles Pravin, J.
2016-08-01
In this paper, Multiple Quantum Well (MQW) Light-Emitting Diodes (LEDs) with compositionally step graded (CSG) Alternating Barriers (AB) of InGaN-AlGaN with p-doped GaN barrier is designed and analysed. The improved crystal structure and modified band bending in the device enhances the carrier confinement and diminishes the polarization-related efficiency reduction. Furthermore, the good crystalline quality increases the hole injection and transportation; this significantly improves the radiative recombination rate and reduces the non-radiative recombination as well as carrier leakage out of the active region. Simulation result show mitigated efficiency droop of 3% and light output power of 1500 mW at the injection current of 500 mA. A modified ABC model is also developed to model the carrier leakage mechanism at high injection current density. In the model, total carrier leakage currents from the active region due to thermionic emission and electron overflow at high injection current are considered. Also, the obtained result of the modelled conventional LED shows a good fit with experimental data. Moreover, the SiC substrate technology in the design is attributed with improved crystal structure, reduced polarization effect and thermal conductivity, which improve the optical performance of the device.
Model studies on the detectability of genetically modified feeds in milk.
Poms, R E; Hochsteiner, W; Luger, K; Glössl, J; Foissy, H
2003-02-01
Detecting the use of genetically modified feeds in milk has become important, because the voluntary labeling of milk and dairy products as "GMO free" or as "organically grown" prohibits the employment of genetically modified organisms (GMOs). The aim of this work was to investigate whether a DNA transfer from foodstuffs like soya and maize was analytically detectable in cow's milk after digestion and transportation via the bloodstream of dairy cows and, thus, whether milk could report for the employment of transgene feeds. Blood, milk, urine, and feces of dairy cows were examined, and foreign DNA was detected by polymerase chain reaction by specifically amplifying a 226-bp fragment of the maize invertase gene and a 118-bp fragment of the soya lectin gene. An intravenous application of purified plant DNA showed a fast elimination of marker DNA in blood or its reduction below the detection limit. With feeding experiments, it could be demonstrated that a specific DNA transfer from feeds into milk was not detectable. Therefore, foreign DNA in milk cannot serve as an indicator for the employment of transgene feeds unless milk is directly contaminated with feed components or airborne feed particles. PMID:12597493
Modified principal component analysis: an integration of multiple similarity subspace models.
Fan, Zizhu; Xu, Yong; Zuo, Wangmeng; Yang, Jian; Tang, Jinhui; Lai, Zhihui; Zhang, David
2014-08-01
We modify the conventional principal component analysis (PCA) and propose a novel subspace learning framework, modified PCA (MPCA), using multiple similarity measurements. MPCA computes three similarity matrices exploiting the similarity measurements: 1) mutual information; 2) angle information; and 3) Gaussian kernel similarity. We employ the eigenvectors of similarity matrices to produce new subspaces, referred to as similarity subspaces. A new integrated similarity subspace is then generated using a novel feature selection approach. This approach needs to construct a kind of vector set, termed weak machine cell (WMC), which contains an appropriate number of the eigenvectors spanning the similarity subspaces. Combining the wrapper method and the forward selection scheme, MPCA selects a WMC at a time that has a powerful discriminative capability to classify samples. MPCA is very suitable for the application scenarios in which the number of the training samples is less than the data dimensionality. MPCA outperforms the other state-of-the-art PCA-based methods in terms of both classification accuracy and clustering result. In addition, MPCA can be applied to face image reconstruction. MPCA can use other types of similarity measurements. Extensive experiments on many popular real-world data sets, such as face databases, show that MPCA achieves desirable classification results, as well as has a powerful capability to represent data. PMID:25050950
Unified cosmic history in modified gravity: From F(R) theory to Lorentz non-invariant models
NASA Astrophysics Data System (ADS)
Nojiri, Shin'Ichi; Odintsov, Sergei D.
2011-08-01
The classical generalization of general relativity is considered as the gravitational alternative for a unified description of the early-time inflation with late-time cosmic acceleration. The structure and cosmological properties of a number of modified theories, including traditional F(R) and Hořava-Lifshitz F(R) gravity, scalar-tensor theory, string-inspired and Gauss-Bonnet theory, non-local gravity, non-minimally coupled models, and power-counting renormalizable covariant gravity are discussed. Different representations of and relations between such theories are investigated. It is shown that some versions of the above theories may be consistent with local tests and may provide a qualitatively reasonable unified description of inflation with the dark energy epoch. The cosmological reconstruction of different modified gravities is provided in great detail. It is demonstrated that eventually any given universe evolution may be reconstructed for the theories under consideration, and the explicit reconstruction is applied to an accelerating spatially flat Friedmann-Robertson-Walker (FRW) universe. Special attention is paid to Lagrange multiplier constrained and conventional F(R) gravities, for latter F(R) theory, the effective ΛCDM era and phantom divide crossing acceleration are obtained. The occurrences of the Big Rip and other finite-time future singularities in modified gravity are reviewed along with their solutions via the addition of higher-derivative gravitational invariants.
Modeling flows over gravel beds by a drag force method and a modified S-A turbulence closure
NASA Astrophysics Data System (ADS)
Zeng, C.; Li, C. W.
2012-09-01
A double-averaged Navier-Stokes equations (DANS) model has been developed for depth-limited open channel flows over gravels. Three test cases are used to validate the model: an open-channel flow over a densely packed gravel bed with small-scale uniform roughness (D/d50 ˜ 13, d50 = median diameter of roughness elements, D = water depth), open-channel flows over large-scale sparsely distributed roughness elements (D/Δ ˜ 2.3-8.7, Δ = roughness height) and steep slope gravel-bed river flows with D/d50 ˜ 7-25. Various methods of treatment of the gravel-induced resistance effect have been investigated. The results show that the wall function approach (WFA) is successful in simulating flows over small gravels but is not appropriate for large gravels since the vertical profile of the longitudinal velocity does not follow the logarithmic-linear relationship. The drag force method (DFM) performs better but the non-logarithmic velocity distribution generated by sparsely distributed gravels cannot be simulated accurately. Noting that the turbulence length scale within the gravel layer is governed by the gravel size, the DANS model incorporating the DFM and a modified Spalart-Allmaras (S-A) turbulence closure is proposed. The turbulence length scale parameter in the S-A model is modified to address the change in the turbulence structure within the gravel layer. The computed velocity profiles agree well with the corresponding measured profiles in all cases. Particularly, the model reproduces the S-shape velocity profile for sparsely distributed large size roughness elements. The modeling methodology is robust and can be easily integrated into the existing numerical models.
Galvan, Daniel L; O'Neil, Richard T; Foster, Aaron E; Huye, Leslie; Bear, Adham; Rooney, Cliona M; Wilson, Matthew H
2015-01-01
Adoptive transfer of gene modified T cells provides possible immunotherapy for patients with cancers refractory to other treatments. We have previously used the non-viral piggyBac transposon system to gene modify human T cells for potential immunotherapy. However, these previous studies utilized adoptive transfer of modified human T cells to target cancer xenografts in highly immunodeficient (NOD-SCID) mice that do not recapitulate an intact immune system. Currently, only viral vectors have shown efficacy in permanently gene-modifying mouse T cells for immunotherapy applications. Therefore, we sought to determine if piggyBac could effectively gene modify mouse T cells to target cancer cells in a mouse cancer model. We first demonstrated that we could gene modify cells to express murine interleukin-12 (p35/p40 mIL-12), a transgene with proven efficacy in melanoma immunotherapy. The OT-I melanoma mouse model provides a well-established T cell mediated immune response to ovalbumin (OVA) positive B16 melanoma cells. B16/OVA melanoma cells were implanted in wild type C57Bl6 mice. Mouse splenocytes were isolated from C57Bl6 OT-I mice and were gene modified using piggyBac to express luciferase. Adoptive transfer of luciferase-modified OT-I splenocytes demonstrated homing to B16/OVA melanoma tumors in vivo. We next gene-modified OT-I cells to express mIL-12. Adoptive transfer of mIL-12-modified mouse OT-I splenocytes delayed B16/OVA melanoma tumor growth in vivo compared to control OT-I splenocytes and improved mouse survival. Our results demonstrate that the piggyBac transposon system can be used to gene modify splenocytes and mouse T cells for evaluating adoptive immunotherapy strategies in immunocompetent mouse tumor models that may more directly mimic immunotherapy applications in humans. PMID:26473608
Foster, Aaron E.; Huye, Leslie; Bear, Adham; Rooney, Cliona M.; Wilson, Matthew H.
2015-01-01
Adoptive transfer of gene modified T cells provides possible immunotherapy for patients with cancers refractory to other treatments. We have previously used the non-viral piggyBac transposon system to gene modify human T cells for potential immunotherapy. However, these previous studies utilized adoptive transfer of modified human T cells to target cancer xenografts in highly immunodeficient (NOD-SCID) mice that do not recapitulate an intact immune system. Currently, only viral vectors have shown efficacy in permanently gene-modifying mouse T cells for immunotherapy applications. Therefore, we sought to determine if piggyBac could effectively gene modify mouse T cells to target cancer cells in a mouse cancer model. We first demonstrated that we could gene modify cells to express murine interleukin-12 (p35/p40 mIL-12), a transgene with proven efficacy in melanoma immunotherapy. The OT-I melanoma mouse model provides a well-established T cell mediated immune response to ovalbumin (OVA) positive B16 melanoma cells. B16/OVA melanoma cells were implanted in wild type C57Bl6 mice. Mouse splenocytes were isolated from C57Bl6 OT-I mice and were gene modified using piggyBac to express luciferase. Adoptive transfer of luciferase-modified OT-I splenocytes demonstrated homing to B16/OVA melanoma tumors in vivo. We next gene-modified OT-I cells to express mIL-12. Adoptive transfer of mIL-12-modified mouse OT-I splenocytes delayed B16/OVA melanoma tumor growth in vivo compared to control OT-I splenocytes and improved mouse survival. Our results demonstrate that the piggyBac transposon system can be used to gene modify splenocytes and mouse T cells for evaluating adoptive immunotherapy strategies in immunocompetent mouse tumor models that may more directly mimic immunotherapy applications in humans. PMID:26473608
Novoderezhkin, Vladimir I; Doust, Alexander B; Curutchet, Carles; Scholes, Gregory D; van Grondelle, Rienk
2010-07-21
We model the spectra and excitation dynamics in the phycobiliprotein antenna complex PE545 isolated from the unicellular photosynthetic cryptophyte algae Rhodomonas CS24. The excitonic couplings between the eight bilins are calculated using the CIS/6-31G method. The site energies are extracted from a simultaneous fit of the absorption, circular dichroism, fluorescence, and excitation anisotropy spectra together with the transient absorption kinetics using the modified Redfield approach. Quantitative fit of the data enables us to assign the eight exciton components of the spectra and build up the energy transfer picture including pathways and timescales of energy relaxation, thus allowing a visualization of excitation dynamics within the complex. PMID:20643051
Shen, Xinru; Wang, Yueke; Yan, Xin; Yuan, Lin; Sang, Tian
2016-08-10
We propose a structure of a metal-insulator-metal (MIM) waveguide with a stub modified by cuts. Our simulation results, conducted by the finite element method, show that the wavelengths of transmission dip vary with the position of the cuts and form the zigzag lines. A transmission line model is also presented, and it agrees with simulation results well. It is believed that our findings provide a smart way to design a plasmonic waveguide filter at the communication region based on MIM structures. PMID:27534492
NASA Astrophysics Data System (ADS)
Sun, Gengzhi; Pang, John H. L.; Zhou, Jinyuan; Zhang, Yani; Zhan, Zhaoyao; Zheng, Lianxi
2012-09-01
Fundamental studies on the effects of strain rate and size on the distribution of tensile strength of carbon nanotube (CNT) fibers are reported in this paper. Experimental data show that the mechanical strength of CNT fibers increases from 0.2 to 0.8 GPa as the strain rate increases from 0.00001 to 0.1 (1/s). In addition, the influence of fiber diameter at low and high strain rate conditions was investigated further with statistical analysis. A modified Weibull distribution model for characterizing the tensile strength distribution of CNT fibers taking into account the effect of strain rate and fiber diameter is proposed.
Nigro, Joseph; Toll, David; Partington, Ed; Ni-Meister, Wenge; Lee, Shihyan; Gutierrez-Magness, Angelica; Engman, Ted; Arsenault, Kristi
2010-01-01
The USEPA has estimated that over 20,000 water bodies within the United States do not meet water quality standards. One of the regulations in the Clean Water Act of 1972 requires states to monitor the total maximum daily load, or the amount of pollution that can be carried by a water body before it is determined to be "polluted," for any watershed in the United States (Copeland, 2005). In response to this mandate, the USEPA developed Better Assessment Science Integrating Nonpoint Sources (BASINS) as a decision support tool for assessing pollution and to guide the decision-making process for improving water quality. One of the models in BASINS, the Hydrological Simulation Program-Fortran (HSPF), computes continuous streamflow rates and pollutant concentration at each basin outlet. By design, precipitation and other meteorological data from weather stations serve as standard model input. In practice, these stations may be unable to capture the spatial heterogeneity of precipitation events, especially if they are few and far between. An attempt was made to resolve this issue by substituting station data with NASA-modified/NOAA precipitation data. Using these data within HSPF, streamflow was calculated for seven watersheds in the Chesapeake Bay Basin during low flow periods, convective storm periods, and annual flows. In almost every case, the modeling performance of HSPF increased when using the NASA-modified precipitation data, resulting in better streamflow statistics and, potentially, in improved water quality assessment. PMID:20830927
NASA Astrophysics Data System (ADS)
Meng, Lie; Wang, Menghan; Liu, Xiao; Wang, Fenglin
2016-04-01
In order to reveal the flow characteristics of Cu-6 %Ag alloy on the condition of hot deformation, the isothermal compression experiments are carried out at the temperatures of 973-1123 K under strain rates of 0.01-10 s-1. The effects of deformation condition on the hot compression deformation behavior are investigated. The low instability strain (ɛ i) behavior at high strain rate (10 s-1) is discussed in this paper. According to the experiment results and analyses, the deformation twinning and inhomogeneous grains are thought to be the possible reasons for low strain cracking. Then, a modified physically based constitutive model is established. The strain for maximum softening rate (\\varepsilon_{ *} ) is quoted in the constitutive equation which is proved that there is a nearly linear relationship between { ln }\\varepsilon_{ *} and { ln }Z . What's more, the correlation coefficient (R) and the average absolute relative error (AARE) are used to evaluate the accuracy of the established constitutive model. The values of R and AARE are 0.99612 and 3.47 %, respectively, which show that the modified constitutive model can exactly reveal the flow stress of Cu-6 %Ag alloy.
Modified Heisenberg model for the zig-zag structure in multiferroic RMn{sub 2}O{sub 5}
Bahoosh, Safa Golrokh; Wesselinowa, Julia M.; Trimper, Steffen
2015-08-28
The class of RMn{sub 2}O{sub 5} (R = Ho, Tb, Y, Eu) compounds offers multiferroic properties where the refined magnetic zig-zag order breaks the inversion symmetry. Varying the temperature, the system undergoes a magnetic and a subsequent ferroelectric phase transition where the ferroelectricity is magnetically induced. We propose a modified anisotropic Heisenberg model that can be used as a tractable analytical model studying the properties of those antiferromagnetic zig-zag spin chains. Based on a finite temperature Green's function method, it is shown that the polarization is induced solely by different exchange couplings of the two different Mn{sup 4+} and Mn{sup 3+} magnetic ions. We calculate the excitation energy of the spin system for finite temperatures, which for its part determines the temperature dependent magnetization and polarization. The ferroelectric phase transition is manifested as a kink in the excitation energy. The variation of the polarization by an external magnetic field depends strongly on the direction of that field. Whereas, the polarization in b-direction increases with an external magnetic field as well in b-direction it can be switched for strong fields in a-direction. The results based on that modified Heisenberg model are in qualitative agreement with experimental data.
González, J C; Vieytes, M R; Botana, A M; Vieites, J M; Botana, L M
2001-02-23
The solubility of solids and liquids in supercritical CO2 with added entrainers was modeled with a modified version of the equation of Chrastil to include the effect of entrainers. By considering the formation of the solute-entrainer-solvent complexes an equation is obtained which predicts an exponential increase of solubility with fluid density and/or entrainer concentration. The correlating model was tested by non-linear regression through a computerized iterative process for several systems where an entrainer was present. Four experimental parameters are easily regressed from experimental data, hence the corresponding properties of components such as chemical potentials or critical parameters are not needed. Instead of its simplicity, this thermodynamical model provided a good correlation of the solubility enhancement in the presence of entrainer effect. PMID:11263564
Lin, Jhih-Hong; Chiang, Mao-Hsiung
2016-01-01
Magnetic shape memory (MSM) alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by using the properties of MSM alloys. However, significant non-linear hysteresis behavior is a significant barrier to control the MSM actuator. In this paper, the Preisach model was used, by capturing experiments from different input signals and output responses, to model the hysteresis of MSM actuator, and the inverse Preisach model, as a feedforward control, provided compensational signals to the MSM actuator to linearize the hysteresis non-linearity. The control strategy for path tracking combined the hysteresis compensator and the modified fuzzy sliding mode control (MFSMC) which served as a path controller. Based on the experimental results, it was verified that a tracking error in the order of micrometers was achieved. PMID:27571081
Hinken, L; Huber, M; Weichgrebe, D; Rosenwinkel, K-H
2014-11-01
A laboratory plant consisting of two UASB reactors was used for the treatment of industrial wastewater from the wheat starch industry. Several load tests were carried out with starch wastewater and the synthetic substrates glucose, acetate, cellulose, butyrate and propionate to observe the impact of changing loads on gas yield and effluent quality. The measurement data sets were used for calibration and validation of the Anaerobic Digestion Model No. 1 (ADM1). For a precise simulation of the detected glucose degradation during load tests with starch wastewater and glucose, it was necessary to incorporate the complete lactic acid fermentation into the ADM1, which contains the formation and degradation of lactate and a non-competitive inhibition function. The modelling results of both reactors based on the modified ADM1 confirm an accurate calculation of the produced gas and the effluent concentrations. Especially, the modelled lactate effluent concentrations for the load cases are similar to the measurements and justified by literature. PMID:25043796
A 3D finite element simulation model for TBM tunnelling in soft ground
NASA Astrophysics Data System (ADS)
Kasper, Thomas; Meschke, Günther
2004-12-01
A three-dimensional finite element simulation model for shield-driven tunnel excavation is presented. The model takes into account all relevant components of the construction process (the soil and the ground water, the tunnel boring machine with frictional contact to the soil, the hydraulic jacks, the tunnel lining and the tail void grouting). The paper gives a detailed description of the model components and the stepwise procedure to simulate the construction process. The soil and the grout material are modelled as saturated porous media using a two-field finite element formulation. This allows to take into account the groundwater, the grouting pressure and the fluid interaction between the soil and slurry at the cutting face and between the soil and grout around the tail void. A Cam-Clay plasticity model is used to describe the material behaviour of cohesive soils. The cementitious grouting material in the tail void is modelled as an ageing elastic material with time-dependent stiffness and permeability. To allow for an automated computation of arbitrarily long and also curvilinear driving paths with suitable finite element meshes, the simulation procedure has been fully automated. The simulation of a tunnel advance in soft cohesive soil below the ground water table is presented and the results are compared with measurements taken from the literature. Copyright
NASA Astrophysics Data System (ADS)
Baron, H. E.; Zakrzewski, W. J.
2016-06-01
We investigate the validity of collective coordinate approximations to the scattering of two solitons in several classes of (1+1) dimensional field theory models. We consider models which are deformations of the sine-Gordon (SG) or the nonlinear Schrödinger (NLS) model which posses soliton solutions (which are topological (SG) or non-topological (NLS)). Our deformations preserve their topology (SG), but change their integrability properties, either completely or partially (models become `quasi-integrable').
Modified Likelihood-Based Item Fit Statistics for the Generalized Graded Unfolding Model
ERIC Educational Resources Information Center
Roberts, James S.
2008-01-01
Orlando and Thissen (2000) developed an item fit statistic for binary item response theory (IRT) models known as S-X[superscript 2]. This article generalizes their statistic to polytomous unfolding models. Four alternative formulations of S-X[superscript 2] are developed for the generalized graded unfolding model (GGUM). The GGUM is a…
Computational modeling of latent-heat-storage in PCM modified interior plaster
NASA Astrophysics Data System (ADS)
Fořt, Jan; Maděra, Jiří; Trník, Anton; Pavlíková, Milena; Pavlík, Zbyšek
2016-06-01
The latent heat storage systems represent a promising way for decrease of buildings energy consumption with respect to the sustainable development principles of building industry. The presented paper is focused on the evaluation of the effect of PCM incorporation on thermal performance of cement-lime plasters. For basic characterization of the developed materials, matrix density, bulk density, and total open porosity are measured. Thermal conductivity is accessed by transient impulse method. DSC analysis is used for the identification of phase change temperature during the heating and cooling process. Using DSC data, the temperature dependent specific heat capacity is calculated. On the basis of the experiments performed, the supposed improvement of the energy efficiency of characteristic building envelope system where the designed plasters are likely to be used is evaluated by a computational analysis. Obtained experimental and computational results show a potential of PCM modified plasters for improvement of thermal stability of buildings and moderation of interior climate.
NASA Astrophysics Data System (ADS)
Duc-Toan, Nguyen; Tien-Long, Banh; Young-Suk, Kim; Dong-Won, Jung
2011-08-01
In this study, a modified Johnson-Cook (J-C) model and an innovated method to determine (J-C) material parameters are proposed to predict more correctly stress-strain curve for tensile tests in elevated temperatures. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. As the first verification, an FEM tensile test simulation based on the isotropic hardening model for boron sheet steel at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code, and compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation of cooling process. The modified (J-C) model showed the good agreement between the simulation results and the corresponding experiments. The second investigation was applied for V-bending spring-back prediction of magnesium alloy sheets at elevated temperatures. Here, the combination of proposed J-C model with modified hardening law considering the unusual plastic behaviour for magnesium alloy sheet was adopted for FEM simulation of V-bending spring-back prediction and shown the good comparability with corresponding experiments.
Duc-Toan, Nguyen; Tien-Long, Banh; Young-Suk, Kim; Dong-Won, Jung
2011-08-22
In this study, a modified Johnson-Cook (J-C) model and an innovated method to determine (J-C) material parameters are proposed to predict more correctly stress-strain curve for tensile tests in elevated temperatures. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. As the first verification, an FEM tensile test simulation based on the isotropic hardening model for boron sheet steel at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code, and compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation of cooling process. The modified (J-C) model showed the good agreement between the simulation results and the corresponding experiments. The second investigation was applied for V-bending spring-back prediction of magnesium alloy sheets at elevated temperatures. Here, the combination of proposed J-C model with modified hardening law considering the unusual plastic behaviour for magnesium alloy sheet was adopted for FEM simulation of V-bending spring-back prediction and shown the good comparability with corresponding experiments.
Ledee, Dolena R.; Kajimoto, Masaki; O'Kelly-Priddy, Colleen M.; Olson, Aaron; Isern, Nancy G.; Robillard Frayne, Isabelle; Des Rosiers, Christine; Portman, Michael A.
2015-07-01
Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory support for infants and children with postoperative cardiopulmonary failure. Nutritional support is mandatory during ECMO, although specific actions for substrates on the heart have not been delineated. Prior work shows that enhancing pyruvate oxidation promotes successful weaning from ECMO. Accordingly, we closely examined the role of prolonged systemic pyruvate supplementation in modifying metabolic parameters during the unique conditions of ventricular unloading provided by ECMO. Twelve male mixed breed Yorkshire piglets (age 30-49 days) received systemic infusion of either normal saline (Group C) or pyruvate (Group P) during ECMO for 8 hours. Over the final hour piglets received [2-13C] pyruvate, and [13C6]-L-leucine, as an indicator for oxidation and protein synthesis. A significant increase in lactate and pyruvate concentrations occurred, along with an increase in the absolute concentration of all measured CAC intermediates. Group P showed greater anaplerotic flux through pyruvate carboxylation although pyruvate oxidation relative to citrate synthase flux was similar to Group C. The groups demonstrated similar leucine fractional contributions to acetyl-CoA and fractional protein synthesis rates. Pyruvate also promoted an increase in the phosphorylation state of several nutrient sensitive enzymes, such as AMPK and ACC, and promoted O-GlcNAcylation through the hexosamine biosynthetic pathway (HBP). In conclusion, prolonged pyruvate supplementation during ECMO modified anaplerotic pyruvate flux and elicited changes in important nutrient and energy sensitive pathways, while preserving protein synthesis. Therefore, the observed results support the further study of nutritional supplementation and its downstream effects on cardiac adaptation during ventricular unloading.
Estimating the daily course of Konza Prairie latent heat fluxes using a modified Tergra model
NASA Technical Reports Server (NTRS)
Hope, Allen S.
1992-01-01
Experimental tests of the Tergra-2 model are based on data collected under moderately wet to wet and very dry soil moisture conditions. Further testing of the model under intermediate soil moisture conditions is required and additional testing under very dry conditions may lead to modifications that make the model more suitable to water-stressed conditions. Combining the Tergra model with a soil evaporation routine should enhance the accuracy of the model and allow it to be employed in situations where vapor fluxes are not almost solely attributable to transpiration.
Mastin, Mark C.; Vaccaro, J.J.
2002-01-01
A decision support system is being developed by the U.S. Geological Survey and the U.S. Bureau of Reclamation as part of a long-term project, the Watershed and River Systems Management Program. The goal of the program is to apply the decision support system to U.S. Bureau of Reclamation projects in the western United States. An important component of the decision support system is the physical hydrology modeling, which consists of watershed models using the U.S. Geological Survey's Precipitation-Runoff Modeling System within the Modular Modeling System. To construct models and to enhance the tools for the application of the decision support system, selected Precipitation-Runoff Modeling System modules were modified or developed. These modules are documented in this report.
Modifying high-order aeroelastic math model of a jet transport using maximum likelihood estimation
NASA Technical Reports Server (NTRS)
Anissipour, Amir A.; Benson, Russell A.
1989-01-01
The design of control laws to damp flexible structural modes requires accurate math models. Unlike the design of control laws for rigid body motion (e.g., where robust control is used to compensate for modeling inaccuracies), structural mode damping usually employs narrow band notch filters. In order to obtain the required accuracy in the math model, maximum likelihood estimation technique is employed to improve the accuracy of the math model using flight data. Presented here are all phases of this methodology: (1) pre-flight analysis (i.e., optimal input signal design for flight test, sensor location determination, model reduction technique, etc.), (2) data collection and preprocessing, and (3) post-flight analysis (i.e., estimation technique and model verification). In addition, a discussion is presented of the software tools used and the need for future study in this field.
The modified Jeffreys model approach for elasto-viscoplastic thixotropic substances
NASA Astrophysics Data System (ADS)
Azikri de Deus, Hilbeth P.; Negrão, Cezar O. R.; Franco, Admilson T.
2016-02-01
In this work, a new constitutive model for thixotropic fluids is proposed via a formal analysis of their functional forms. The constitutive model for thixotropic substances is basically composed by a set of two equations: a constitutive equation based on viscoelastic models and a rate equation (an equation related to the evolution of the micro-structural character of the substance). The constitutive equations, in many works, do not have taken into account in the dynamical principles from which is developed the micro-structural dependence of shear modulus and viscosity. To aim this fault, in the current study a new constitutive model (based on Jeffreys model) is proposed, in coherence with expected behavior for thixotropic fluids. In addition a special emphasis has been given to the structural nature of substances (based on coagulation theory of Smoluchowski) and thermodynamic consistency. The proposed model for thixotropic fluids takes into account a simple isothermal laminar shear flows and some important aspects of that are explored.
Employing a Modified Diffuser Momentum Model to Simulate Ventilation of the Orion CEV
NASA Technical Reports Server (NTRS)
Straus, John; Lewis, John F.
2011-01-01
The Ansys CFX CFD modeling tool was used to support the design efforts of the ventilation system for the Orion CEV. CFD modeling was used to establish the flow field within the cabin for several supply configurations. A mesh and turbulence model sensitivity study was performed before the design studies. Results were post-processed for comparison with performance requirements. Most configurations employed straight vaned diffusers to direct and throw the flow. To manage the size of the models, the diffuser vanes were not resolved. Instead, a momentum model was employed to account for the effect of the diffusers. The momentum model was tested against a separate, vane-resolved side study. Results are presented for a single diffuser configuration for a low supply flow case.
Modelling offset minor hysteresis loops with the modified Jiles-Atherton description
NASA Astrophysics Data System (ADS)
Chwastek, K.
2009-08-01
The paper addresses the issue of modelling offset minor hysteresis loops within the framework of the Jiles-Atherton model. Two of the model parameters are expressed in terms of scaling power laws with respect to the magnetization level. The approach is consistent with earlier theoretical considerations on the effective 'volume fraction' by Professor D Jiles. The influence of eddy currents on hysteresis loop is taken into account using an additional term of magnetic field.
KdV-Burgers equation in the modified continuum model considering anticipation effect
NASA Astrophysics Data System (ADS)
Liu, Huaqing; Zheng, Pengjun; Zhu, Keqiang; Ge, Hongxia
2015-11-01
The new continuum model mentioned in this paper is developed based on optimal velocity car-following model, which takes the drivers' anticipation effect into account. The critical condition for traffic flow is derived, and nonlinear analysis shows density waves occur in traffic flow because of the small disturbance. Near the neutral stability line, the KdV-Burgers equation is derived and one of the solutions is given. Numerical simulation is carried out to show the local cluster described by the model.
NASA Astrophysics Data System (ADS)
Robertson, A. L.; Lin, L.; Tedesco, L.; Wilson, J.; Soyeux, E.
2008-12-01
Cyanobacteria are known to produce toxins harmful to humans and compounds that alter the taste/odor of water. Monitoring cyanobacteria is of interest to surface water managers because eutrophication of these surface water bodies are common thus increasing the chances of cyanobacterial blooms. Traditionally cyanobacteria are remotely sensed using the spectral properties of the two pigments: chlorophyll a (Chl-a), indicative of all algal and cyanobacteria species, and phycocyanin (PC), specific to cyanobacteria in most freshwater systems. Initial algorithms identifying cyanobacterial pigments used ratios of reflectance at specific wavelengths. In an effort to increase transferability between different systems researchers have included optical properties of water and water constituents to build semi-empirical models. Recently researchers have applied a curve-fitting, modified Gaussian model (MGM), to predict these cyanobacterial pigments. To determine the best performing algorithm this study compares the performance of 4 band ratio, 4 semi-empirical, and 2 modified Gaussian models in predicting PC and Chl-a on three central Indiana reservoirs (Eagle Creek, Geist, Morse). For each of these reservoirs, spectral data were collected with three different sensors (boat-based: ASD Fieldspec, Ocean Optics USB4000; Ariel: AISA Eagle) over a three year period (2005-2007), and water samples concomitant with these spectra were analyzed for concentration of the two pigments and other water constituents. Comparison shows that a model using the MGM strength at 620 nm from a 2005 Morse Reservoir ASD Fieldspec data set shows that the MGM has the best transferability to a 2006 Morse Reservoir ASD Fieldspec data set in predicting phycocyanin (R2 = 0.77; RMSE= 52.45 ppb), and a band ratio model published by Mittenzwey et al. 1991 has the best transferability in predicting chlorophyll a (R2 = 0.74; RMSE 16.31=ppb).
Goedhart, Paul W; van der Voet, Hilko; Baldacchino, Ferdinando; Arpaia, Salvatore
2014-01-01
Genetic modification of plants may result in unintended effects causing potentially adverse effects on the environment. A comparative safety assessment is therefore required by authorities, such as the European Food Safety Authority, in which the genetically modified plant is compared with its conventional counterpart. Part of the environmental risk assessment is a comparative field experiment in which the effect on non-target organisms is compared. Statistical analysis of such trials come in two flavors: difference testing and equivalence testing. It is important to know the statistical properties of these, for example, the power to detect environmental change of a given magnitude, before the start of an experiment. Such prospective power analysis can best be studied by means of a statistical simulation model. This paper describes a general framework for simulating data typically encountered in environmental risk assessment of genetically modified plants. The simulation model, available as Supplementary Material, can be used to generate count data having different statistical distributions possibly with excess-zeros. In addition the model employs completely randomized or randomized block experiments, can be used to simulate single or multiple trials across environments, enables genotype by environment interaction by adding random variety effects, and finally includes repeated measures in time following a constant, linear or quadratic pattern in time possibly with some form of autocorrelation. The model also allows to add a set of reference varieties to the GM plants and its comparator to assess the natural variation which can then be used to set limits of concern for equivalence testing. The different count distributions are described in some detail and some examples of how to use the simulation model to study various aspects, including a prospective power analysis, are provided. PMID:24834325
Determination of airplane model structure from flight data by using modified stepwise regression
NASA Technical Reports Server (NTRS)
Klein, V.; Batterson, J. G.; Murphy, P. C.
1981-01-01
The linear and stepwise regressions are briefly introduced, then the problem of determining airplane model structure is addressed. The MSR was constructed to force a linear model for the aerodynamic coefficient first, then add significant nonlinear terms and delete nonsignificant terms from the model. In addition to the statistical criteria in the stepwise regression, the prediction sum of squares (PRESS) criterion and the analysis of residuals were examined for the selection of an adequate model. The procedure is used in examples with simulated and real flight data. It is shown that the MSR performs better than the ordinary stepwise regression and that the technique can also be applied to the large amplitude maneuvers.
NASA Astrophysics Data System (ADS)
Jian, Mei-Ying; Shi, Jing; Liu, Yang
2016-09-01
As the global population ages, there are more and more older drivers on the road. The decline in driving performance of older drivers may influence the properties of traffic flow and safety. The purpose of this paper is to investigate the effect of older drivers’ driving behaviors on traffic flow. A modified cellular automaton (CA) model which takes driving behaviors of older drivers into account is proposed. The simulation results indicate that older drivers’ driving behaviors induce a reduction in traffic flow especially when the density is higher than 15 vehicles per km per lane and an increase in Lane-changing frequency. The analysis of stability shows that a number of disturbances could frequently emerge, be propagated and eventually dissipate in this modified model. The results also reflect that with the increase of older drivers on the road, the probability of the occurrence of rear-end collisions increases greatly and obviously. Furthermore, the value of acceleration influences the traffic flow and safety significantly. These results provide the theoretical basis and reference for the traffic management departments to develop traffic management measure in the aging society.
Cui, Linyan; Xue, Bindang; Zhou, Fugen
2016-04-01
In this study, the modified anisotropic turbulence refractive-index fluctuations spectral model is derived based on the extended Rytov approximation theory for the theoretical investigations of optical plane and spherical waves propagating through moderate-to-strong anisotropic non-Kolmogorov turbulence. The anisotropic factor which parameterizes the asymmetry of turbulence cells or eddies in the horizontal and vertical directions is introduced. The general spectral power law in the range of 3-4 is also considered compared with the conventional classic value of 11/3 for Kolmogorov turbulence. Based on the modified anisotropic turbulence refractive-index fluctuations spectrum, the analytic expressions of the irradiance scintillation index are also derived for optical plane and spherical waves propagating through moderate-to-strong anisotropic non-Kolmogorov turbulence. They are applicable in a wide range of turbulence strengths and can reduce correctly to the previously published results in the special cases of weak anisotropic turbulence and moderate-to-strong isotropic turbulence. Calculations are performed to analyze the derived models. PMID:27140754
Zhao, Hongya; Logothetis, Christopher J.; Gorlov, Ivan P.; Zeng, Jia; Dai, Jianguo
2013-01-01
Predicting disease progression is one of the most challenging problems in prostate cancer research. Adding gene expression data to prediction models that are based on clinical features has been proposed to improve accuracy. In the current study, we applied a logistic regression (LR) model combining clinical features and gene co-expression data to improve the accuracy of the prediction of prostate cancer progression. The top-scoring pair (TSP) method was used to select genes for the model. The proposed models not only preserved the basic properties of the TSP algorithm but also incorporated the clinical features into the prognostic models. Based on the statistical inference with the iterative cross validation, we demonstrated that prediction LR models that included genes selected by the TSP method provided better predictions of prostate cancer progression than those using clinical variables only and/or those that included genes selected by the one-gene-at-a-time approach. Thus, we conclude that TSP selection is a useful tool for feature (and/or gene) selection to use in prognostic models and our model also provides an alternative for predicting prostate cancer progression. PMID:24367394
Problem-Based Learning: Modifying the Medical School Model for Teaching High School Economics.
ERIC Educational Resources Information Center
Maxwell, Nan L.; Bellisimo, Yolanda; Mergendoller, John
2001-01-01
Provides background information on the problem-based learning (PBL) model used in medical education that was adapted for high school economics. Describes the high school economics curriculum and outline the stages of the PBL model using examples from a unit called "The High School Food Court." Discusses the design considerations. (CMK)
A Modified Active Appearance Model Based on an Adaptive Artificial Bee Colony
Othman, Zulaiha Ali
2014-01-01
Active appearance model (AAM) is one of the most popular model-based approaches that have been extensively used to extract features by highly accurate modeling of human faces under various physical and environmental circumstances. However, in such active appearance model, fitting the model with original image is a challenging task. State of the art shows that optimization method is applicable to resolve this problem. However, another common problem is applying optimization. Hence, in this paper we propose an AAM based face recognition technique, which is capable of resolving the fitting problem of AAM by introducing a new adaptive ABC algorithm. The adaptation increases the efficiency of fitting as against the conventional ABC algorithm. We have used three datasets: CASIA dataset, property 2.5D face dataset, and UBIRIS v1 images dataset in our experiments. The results have revealed that the proposed face recognition technique has performed effectively, in terms of accuracy of face recognition. PMID:25165748
Modifying a telerobotic system to include robotic operation by means of dynamic modeling
Corbett, G.K.; Jansen, J.F.; Kress, R.L.; Noakes, M.W.
1989-01-01
The goal of this study was to implement a robotic mode for the Advanced Servomanipulator (ASM), a six-degree-of-freedom master/slave teleoperator. To implement a robotic mode on a system designed for teleoperation, the effects of any change in the control schemes must be completely understood. One way to study the impact of potential modifications is to develop a model of the system. This approach is the one taken in this study. A detailed full-arm model was developed by first creating a model for individual joints of the manipulator and then incorporating each of the joint models into a single full-arm model, including link inertias and kinematic cross-coupling. Parameters were identified for each joint model to provide a match between simulated and actual responses to a pulse input. The full-arm model was tested by comparing the simulated and actual response of the ASM to simultaneous sine-wave inputs to each joint, using the model parameters identified on a joint-by-joint basis. The full-arm model was able to characterize effectively the ASM system response for the inputs studied. Robotic-mode control algorithms were tested on both the individual-joint and full-arm models. The results of these simulations indicate that a simplified master/slave control structure is the best candidate for robotic operation. This control structure was added to the ASM. Experimental results demonstrate that the ASM system is capable of repeatable robotic operation. The robotic-mode man-machine interface and data handling system are described in this paper. 12 refs., 3 figs.
Jung, Seung-Won
2013-10-01
The just noticeable depth difference (JNDD) describes the threshold of human perception of the difference in the depth. In flat-panel-based three-dimensional (3-D) displays, the JNDD is typically measured by changing the depth difference between displayed image objects until the difference is perceivable. However, not only the depth, but also the perceived size changes when the depth difference increases. In this paper, we present a modified JNDD measurement method that adjusts the physical size of the object such that the perceived size of the object is maintained. We then apply the proposed JNDD measurement method to depth sensation enhancement. When the depth value difference between the objects is increased to enable the viewer to perceive the depth difference, the size of the objects is adjusted to maintain the perceived size of the objects. In addition, since the size change of the objects can produce a whole region, a depth-adaptive hole-inpainting technique is proposed to compensate for the hole region with high accuracy. The experimental results demonstrate the effectiveness of the proposed method. PMID:23686954
Effect of halide-modified model carbon supports on catalyst stability.
Wood, Kevin N; Pylypenko, Svitlana; Olson, Tim S; Dameron, Arrelaine A; O'Neill, Kevin; Christensen, Steven T; Dinh, Huyen N; Gennett, Thomas; O'Hayre, Ryan
2012-12-01
Modification of physiochemical and structural properties of carbon-based materials through targeted functionalization is a useful way to improve the properties and performance of such catalyst materials. This work explores the incorporation of dopants, including nitrogen, iodine, and fluorine, into the carbon structure of highly-oriented pyrolytic graphite (HOPG) and its potential benefits on the stability of PtRu catalyst nanoparticles. Evaluation of the changes in the catalyst nanoparticle coverage and size as a function of implantation parameters reveals that carbon supports functionalized with a combination of nitrogen and fluorine provide the most beneficial interactions, resulting in suppressed particle coarsening and dissolution. Benefits of a carefully tuned support system modified with fluorine and nitrogen surpass those obtained with nitrogen (no fluorine) modification. Ion implantation of iodine into HOPG results in a consistent amount of structural damage to the carbon matrix, regardless of dose. For this modification, improvements in stability are similar to nitrogen modification; however, the benefit is only observed at higher dose conditions. This indicates that a mechanism different than the one associated with nitrogen may be responsible for the improved durability. PMID:23194033
A modified exponential behavioral economic demand model to better describe consumption data.
Koffarnus, Mikhail N; Franck, Christopher T; Stein, Jeffrey S; Bickel, Warren K
2015-12-01
Behavioral economic demand analyses that quantify the relationship between the consumption of a commodity and its price have proven useful in studying the reinforcing efficacy of many commodities, including drugs of abuse. An exponential equation proposed by Hursh and Silberberg (2008) has proven useful in quantifying the dissociable components of demand intensity and demand elasticity, but is limited as an analysis technique by the inability to correctly analyze consumption values of zero. We examined an exponentiated version of this equation that retains all the beneficial features of the original Hursh and Silberberg equation, but can accommodate consumption values of zero and improves its fit to the data. In Experiment 1, we compared the modified equation with the unmodified equation under different treatments of zero values in cigarette consumption data collected online from 272 participants. We found that the unmodified equation produces different results depending on how zeros are treated, while the exponentiated version incorporates zeros into the analysis, accounts for more variance, and is better able to estimate actual unconstrained consumption as reported by participants. In Experiment 2, we simulated 1,000 datasets with demand parameters known a priori and compared the equation fits. Results indicated that the exponentiated equation was better able to replicate the true values from which the test data were simulated. We conclude that an exponentiated version of the Hursh and Silberberg equation provides better fits to the data, is able to fit all consumption values including zero, and more accurately produces true parameter values. PMID:26280591
NASA Astrophysics Data System (ADS)
Friedman, Brett; Carter, Troy
2014-10-01
Linear eigenmode analysis is often used to predict whether a plasma or fluid system will be turbulent, but it fails for systems which have highly non-orthogonal linear eigenvectors. In fact, such systems may become turbulent despite having no unstable linear eigenvectors at all (subcritical turbulence). For about a century, researchers have attempted to predict critical parameters that mark the onset of subcritical turbulence with little success. Using recently-developed intuition regarding the role of non-orthogonal linear eigenvectors in subcritical turbulent sustainment, we have developed a method to calculate turbulent growth rates, which can be used to predict the onset of subcritical turbulence. We apply our procedure to 2D and 3D versions of the Hasegawa-Wakatani (HW) model, showing good agreement with nonlinear simulation results. We also use a modified version of the 3D HW model, which is subject to subcritical turbulence, in order to test our method in predicting the subcritical turbulent onset.
Corrected constraints on big bang nucleosynthesis in a modified gravity model of f (R )∝Rn
NASA Astrophysics Data System (ADS)
Kusakabe, Motohiko; Koh, Seoktae; Kim, K. S.; Cheoun, Myung-Ki
2015-05-01
Big bang nucleosynthesis in a modified gravity model of f (R )∝Rn is investigated. The only free parameter of the model is a power-law index n . We find cosmological solutions in a parameter region of 1
Goldhaber-Fiebert, Jeremy D.; Brandeau, Margaret L.
2014-01-01
Background Risk factors increase chronic disease incidence and severity. To examine future trends and develop policies addressing chronic diseases, it is important to capture the relationship between exposure and disease development -- challenging given limited data. Objective To develop parsimonious risk factor models embeddable in chronic disease models, useful when longitudinal data are unavailable. Design The model structures encode relevant features of risk factors (e.g., time-varying, modifiable) and can be embedded in chronic disease models. Calibration captures time-varying exposures for the risk factor models using available, cross-sectional data. We illustrate feasibility with the policy-relevant example of smoking in India. Methods The model is calibrated to prevalence of male smoking in 12 Indian regions estimated from the 2009–10 Indian Global Adult Tobacco Survey. Nelder-Mead searches (250,000 starting locations) identify distributions of starting, quitting, and re-starting rates that minimize the difference between modeled and observed age-specific prevalence. We compare modeled life expectancies to estimates in the absence of time-varying risk exposures and consider gains from hypothetical smoking cessation programs delivered for 1–30 years. Results Calibration achieves concordance between modeled and observed outcomes. Probabilities of starting to smoke rise and fall with age, while quitting and re-starting probabilities fall with age. Accounting for time-varying smoking exposures is important, as not doing so produces smaller estimates of life expectancy losses. Estimated impacts of smoking cessation programs delivered for different periods depend on the fact that people who have been induced to abstain from smoking longer are less likely to re-start. Conclusion The approach described is feasible for numerous chronic disease risk factors. Incorporating exposure-change rates can improve modeled estimates of chronic disease outcomes and long
Vermaas, Willem F J.
2014-06-17
Disclosed is a modified photoautotrophic bacterium comprising genes of interest that are modified in terms of their expression and/or coding region sequence, wherein modification of the genes of interest increases production of a desired product in the bacterium relative to the amount of the desired product production in a photoautotrophic bacterium that is not modified with respect to the genes of interest.
NASA Astrophysics Data System (ADS)
Kuesters, Geoffrey M.
Targeting the tumor vascular supply in a homogenous manner is a difficult task to achieve with the use of pegylated cationic liposomes (PCLs) alone. Our formulation consisting of bevacizumab conjugated to the distal end of PEG on PCLs was thus developed in an effort to eliminate some of this heterogeneity as well as to increase tumor targeting overall. This study focuses on pancreatic cancer, which has the poorest five-year survival rate of all cancers because of its late diagnosis. The addition of bevacizumab will target tumor areas because it binds to VEGF which is secreted by tumors in high levels. In vitro, we showed that pancreatic cancer cells (Capan-1, HPAF-II and PANC-1) all secrete VEGF into media at different levels, with Capan-1 producing the most and HPAF-II producing the least. A murine endothelial cell line, MS1-VEGF, produces and secretes the most VEGF. A human microvascular endothelial cell line (HMEC-1) was grown in two different conditions, with and without VEGF in the media. Modifying PCLs with bevacizumab enhanced the binding and uptake of PCLs by some pancreatic and endothelial cells in vitro, particularly the cells that had or secreted the most significant amount of VEGF in the media. This translated into enhanced tumor targeting in a biodistribution study using a Capan-1 subcutaneous pancreatic tumor model. This also showed enhanced blood retention compared to the unmodified PCLs while it diminished uptake by the spleen and increased uptake by the kidney. To test the therapeutic benefit of this enhanced uptake and targeting, an anti-angiogenic agent, 2-methoxyestradiol was incorporated into the formulation with 20% incorporation efficiency. Both the unmodified and modified drug-loaded PCLs were the least efficacious against Capan-1, moderately effective against HPAF-II, PANC-1, MS1-VEGF and HMEC-1 grown without VEGF in the media and most efficacious against HMEC-1 grown with VEGF which had the most VEGF present in the media. Multiple in vivo
Estimation of watershed hydrologic processes in arid conditions with a modified watershed model
NASA Astrophysics Data System (ADS)
Sha, Jian; Swaney, Dennis P.; Hong, Bongghi; Wang, Jinnan; Wang, Yuqiu; Wang, Zhong-Liang
2014-11-01
Watershed models play an important role in modern water resource management, increasingly demanding a robust hydrologic data framework to estimate watershed hydrochemical processes. The Generalized Watershed Loading Function (GWLF), a typical watershed model with modest data requirements, has been applied to watershed-scale hydrochemical estimation worldwide. However, while it generally successfully estimates flows in humid regions, the model suffers from a weakness in hydrologic estimation during low-flow periods, which are projected to continue increasing with global climate change in many places. To address this issue, three algorithms describing functional responses of flows to saturated water storage, the segment function approach, linear function approach, and exponential function approach, have been proposed in this paper, integrated with a previous leakage mechanism for unsaturated water storage used in two earlier GWLF versions, and applied to a case study of Shuai Shui River watershed in China. Comparisons of this version, including new algorithms or algorithm linkages, with the earlier GWLF versions, show that all the new algorithms improve model accuracy in low-flow months; the linear function approach linking the leakage process has the best effect. This work refines the framework of GWLF model to address both humid and arid conditions that can be used as alternatives for future applications. These new functional dynamic responses should also have potential application in other similar watershed models.
NASA Astrophysics Data System (ADS)
Venkatesan, R.; Mathiyarasu, R.; Somayaji, K. M.
Ground level concentration and sky-shine dose due to radioactive emissions from a nuclear power plant at a coastal site have been estimated using the standard Gaussian Plume Model (GPM) and the modified GPM suggested by Misra (Atmospheric Environment 14 (1980) 397), which incorporates fumigation effect under sea breeze condition. The difference in results between these two models is analysed in order to understand their significance and errors that would occur if proper choice were not made. Radioactive sky-shine dose from 41Ar, emitted from a 100 m stack of the nuclear plant is continuously recorded by environmental gamma dose monitors and the data is used to validate the modified GPM. It is observed that the dose values increase by a factor of about 2 times than those of the standard GPM estimates, up to a downwind distance of 6 km during sea breeze hours. In order to examine the dispersion of radioactive effluents in the mesoscale range, a sea breeze model coupled with a particle dispersion model is used. The deposited activity, thyroid dose and sky-shine radioactive dose are simulated for a range of 30 km. In this range, the plume is found to deviate from its straight-line trajectory, as otherwise assumed in GPM. A secondary maximum in the concentration and the sky-shine dose is also observed in the model results. These results are quite significant in realistically estimating the area affected under any unlikely event of an accidental release of radioactivity.
Salari, Nader; Shohaimi, Shamarina; Najafi, Farid; Nallappan, Meenakshii; Karishnarajah, Isthrinayagy
2014-01-01
Among numerous artificial intelligence approaches, k-Nearest Neighbor algorithms, genetic algorithms, and artificial neural networks are considered as the most common and effective methods in classification problems in numerous studies. In the present study, the results of the implementation of a novel hybrid feature selection-classification model using the above mentioned methods are presented. The purpose is benefitting from the synergies obtained from combining these technologies for the development of classification models. Such a combination creates an opportunity to invest in the strength of each algorithm, and is an approach to make up for their deficiencies. To develop proposed model, with the aim of obtaining the best array of features, first, feature ranking techniques such as the Fisher's discriminant ratio and class separability criteria were used to prioritize features. Second, the obtained results that included arrays of the top-ranked features were used as the initial population of a genetic algorithm to produce optimum arrays of features. Third, using a modified k-Nearest Neighbor method as well as an improved method of backpropagation neural networks, the classification process was advanced based on optimum arrays of the features selected by genetic algorithms. The performance of the proposed model was compared with thirteen well-known classification models based on seven datasets. Furthermore, the statistical analysis was performed using the Friedman test followed by post-hoc tests. The experimental findings indicated that the novel proposed hybrid model resulted in significantly better classification performance compared with all 13 classification methods. Finally, the performance results of the proposed model was benchmarked against the best ones reported as the state-of-the-art classifiers in terms of classification accuracy for the same data sets. The substantial findings of the comprehensive comparative study revealed that performance of the
Salari, Nader; Shohaimi, Shamarina; Najafi, Farid; Nallappan, Meenakshii; Karishnarajah, Isthrinayagy
2014-01-01
Among numerous artificial intelligence approaches, k-Nearest Neighbor algorithms, genetic algorithms, and artificial neural networks are considered as the most common and effective methods in classification problems in numerous studies. In the present study, the results of the implementation of a novel hybrid feature selection-classification model using the above mentioned methods are presented. The purpose is benefitting from the synergies obtained from combining these technologies for the development of classification models. Such a combination creates an opportunity to invest in the strength of each algorithm, and is an approach to make up for their deficiencies. To develop proposed model, with the aim of obtaining the best array of features, first, feature ranking techniques such as the Fisher's discriminant ratio and class separability criteria were used to prioritize features. Second, the obtained results that included arrays of the top-ranked features were used as the initial population of a genetic algorithm to produce optimum arrays of features. Third, using a modified k-Nearest Neighbor method as well as an improved method of backpropagation neural networks, the classification process was advanced based on optimum arrays of the features selected by genetic algorithms. The performance of the proposed model was compared with thirteen well-known classification models based on seven datasets. Furthermore, the statistical analysis was performed using the Friedman test followed by post-hoc tests. The experimental findings indicated that the novel proposed hybrid model resulted in significantly better classification performance compared with all 13 classification methods. Finally, the performance results of the proposed model was benchmarked against the best ones reported as the state-of-the-art classifiers in terms of classification accuracy for the same data sets. The substantial findings of the comprehensive comparative study revealed that performance of the
Evaluation of a Modified Priestly-Taylor Model for Actual Evapotranspiration in sub- Saharan Africa
NASA Astrophysics Data System (ADS)
Marshall, M. T.; Michaelsen, J.; Funk, C.; Artan, G.
2008-12-01
Climate change and the intensification of the water cycle is an important field of study, as global warming is expected to lead to dramatic increases in the frequency and magnitude of storms, floods, and droughts worldwide. In sub-tropical Africa, it is expected that the increase in evaporation and subsequent decrease in surface runoff will increase water demand in an already climate sensitive region. Studies also show that modeled soil moisture, a surrogate for evapotranspiration (ET), can improve rainfall and streamflow forecasts in these areas. Our objective, here therefore, is to evaluate a new ET model (Fisher et al., 2008) at inter- seasonal catchment scales. The Fisher et al. (2008) model uses functional eco-physiological relationships to adjust the Priestly-Taylor formulation of potential ET. It has performed well against several flux towers at tropical, sub-tropical, and temperate latitudes (R2=0.90). Although the model was extrapolated using remote sensing and climate reanalysis data, the validation was performed using site specific monthly average net radiation (Rn), monthly surface vapor pressure, and maximum monthly surface temperature. Two additional inputs are required for the model that can be acquired from remote sensing: the monthly average normalized difference vegetation index and soil-adjusted vegetation index. The vegetation indices will be calculated from a new atmospherically corrected AVHRR dataset of global daily reflectance at 0.05° resolution (NASA Land Long Term Data Record). The climate variables will be extracted from the bias-corrected European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset at 0.05° resolution. The model will be evaluated at a seasonal timestep from 1981-1999 using cumulative runoff and lagged precipitation for seven major catchments in sub-Saharan Africa. It is expected that the highest model performance will be in areas where Rn is the dominant control on ET and advection is relatively small
The accelerating universe and other cosmological aspects of modified gravity models
NASA Astrophysics Data System (ADS)
de Felice, Antonio
I give a short introduction to standard cosmology and a review of what it is meant by "the dark energy enigma" in chapter l. In chapter 2, I mention and describe some attempts found in the literature of the past few years to attack this problem. Dark energy candidates for which the equation-of-state parameter w is less than -1 violate the dominant energy condition. In scalar-tensor theories of gravity, however, the expansion of the universe can mimic the behavior of general relativity with w < -1 dark energy, without violating any energy conditions. I examine, in chapter 3, whether this possibility is phenomenologically viable by studying Brans-Dicke models and characterizing both the naturalness of the models themselves, and additional observational constraints from limits on the time-dependence of Newton's constant. I find that only highly contrived models would lead observers to measure w < -1. In chapter 4, I consider general curvature-invariant modifications of the Einstein-Hilbert action that become important only in regions of extremely low space-time curvature. I investigate the far future evolution of the universe in such models, examining the possibilities for cosmic acceleration and other ultimate destinies. The models generically possess de Sitter space as an unstable solution and exhibit an interesting set of attractor solutions which, in some cases, provide alternatives to dark energy models. In chapter 5, I study a baryogenesis mechanism operating in the context of hyperextended inflation and making use of a coupling between the scalar field and a standard model global current, such as B or B - L . The method is efficient at temperatures at which these currents are not conserved due to some higher dimensional operator. The particle physics and cosmological phenomenology are discussed. I consider constraints stemming from nucleosynthesis and solar system experiments.
NASA Astrophysics Data System (ADS)
Raju, Subramanian; Saibaba, Saroja
2016-09-01
The enthalpy of formation Δo H f is an important thermodynamic quantity, which sheds significant light on fundamental cohesive and structural characteristics of an alloy. However, being a difficult one to determine accurately through experiments, simple estimation procedures are often desirable. In the present study, a modified prescription for estimating Δo H f L of liquid transition metal alloys is outlined, based on the Macroscopic Atom Model of cohesion. This prescription relies on self-consistent estimation of liquid-specific model parameters, namely electronegativity ( ϕ L) and bonding electron density ( n b L ). Such unique identification is made through the use of well-established relationships connecting surface tension, compressibility, and molar volume of a metallic liquid with bonding charge density. The electronegativity is obtained through a consistent linear scaling procedure. The preliminary set of values for ϕ L and n b L , together with other auxiliary model parameters, is subsequently optimized to obtain a good numerical agreement between calculated and experimental values of Δo H f L for sixty liquid transition metal alloys. It is found that, with few exceptions, the use of liquid-specific model parameters in Macroscopic Atom Model yields a physically consistent methodology for reliable estimation of mixing enthalpies of liquid alloys.
Sun, Jin; Xu, Xiaosu; Liu, Yiting; Zhang, Tao; Li, Yao
2016-01-01
In order to reduce the influence of fiber optic gyroscope (FOG) random drift error on inertial navigation systems, an improved auto regressive (AR) model is put forward in this paper. First, based on real-time observations at each restart of the gyroscope, the model of FOG random drift can be established online. In the improved AR model, the FOG measured signal is employed instead of the zero mean signals. Then, the modified Sage-Husa adaptive Kalman filter (SHAKF) is introduced, which can directly carry out real-time filtering on the FOG signals. Finally, static and dynamic experiments are done to verify the effectiveness. The filtering results are analyzed with Allan variance. The analysis results show that the improved AR model has high fitting accuracy and strong adaptability, and the minimum fitting accuracy of single noise is 93.2%. Based on the improved AR(3) model, the denoising method of SHAKF is more effective than traditional methods, and its effect is better than 30%. The random drift error of FOG is reduced effectively, and the precision of the FOG is improved. PMID:27420062
Sun, Jin; Xu, Xiaosu; Liu, Yiting; Zhang, Tao; Li, Yao
2016-01-01
In order to reduce the influence of fiber optic gyroscope (FOG) random drift error on inertial navigation systems, an improved auto regressive (AR) model is put forward in this paper. First, based on real-time observations at each restart of the gyroscope, the model of FOG random drift can be established online. In the improved AR model, the FOG measured signal is employed instead of the zero mean signals. Then, the modified Sage-Husa adaptive Kalman filter (SHAKF) is introduced, which can directly carry out real-time filtering on the FOG signals. Finally, static and dynamic experiments are done to verify the effectiveness. The filtering results are analyzed with Allan variance. The analysis results show that the improved AR model has high fitting accuracy and strong adaptability, and the minimum fitting accuracy of single noise is 93.2%. Based on the improved AR(3) model, the denoising method of SHAKF is more effective than traditional methods, and its effect is better than 30%. The random drift error of FOG is reduced effectively, and the precision of the FOG is improved. PMID:27420062
NASA Astrophysics Data System (ADS)
Raju, Subramanian; Saibaba, Saroja
2016-07-01
The enthalpy of formation Δo H f is an important thermodynamic quantity, which sheds significant light on fundamental cohesive and structural characteristics of an alloy. However, being a difficult one to determine accurately through experiments, simple estimation procedures are often desirable. In the present study, a modified prescription for estimating Δo H {f/L} of liquid transition metal alloys is outlined, based on the Macroscopic Atom Model of cohesion. This prescription relies on self-consistent estimation of liquid-specific model parameters, namely electronegativity (ϕ L) and bonding electron density (n {b/L}). Such unique identification is made through the use of well-established relationships connecting surface tension, compressibility, and molar volume of a metallic liquid with bonding charge density. The electronegativity is obtained through a consistent linear scaling procedure. The preliminary set of values for ϕ L and n {b/L}, together with other auxiliary model parameters, is subsequently optimized to obtain a good numerical agreement between calculated and experimental values of Δo H {f/L} for sixty liquid transition metal alloys. It is found that, with few exceptions, the use of liquid-specific model parameters in Macroscopic Atom Model yields a physically consistent methodology for reliable estimation of mixing enthalpies of liquid alloys.
NASA Astrophysics Data System (ADS)
Goryachev, A. B.; Polezhaev, A. A.; Chernavskii, D. S.
1996-03-01
Spatial coexistence and competition among species is investigated through a modified Volterra-Lotka model which takes into account sexual breeding. This allows the population specific growth rate to depend on the population density. As a result of this modification the degeneracy inherent in the classical model is eliminated and qualitatively novel regimes are observed, as demonstrated by parametric analysis of the model. In the case where the corresponding parameters of competing species do not differ significantly the model can be reduced to a single Ginzburg-Landau type equation. The spatially distributed model is analyzed both in the absence and in the presence of noise mimicking inherent fluctuations in birth and death rates. It is shown that noise can qualitatively change the behavior of the system. Not only does it induce the formation of spatial patterns, but also switches on endless turbulent-like rearrangement of the system. When initially unpopulated habitat is occupied by competing species even a very low-intensity noise makes the final state of the system totally unpredictable and sensitive to any fluctuations.
A modified Green-Ampt model for water infiltration and preferential flow
NASA Astrophysics Data System (ADS)
Liu, D.
2015-12-01
Preferential flow is significant for its contribution to rapid response to hydrologic inputs at the soil surface and unsaturated zone flow, which is critical for flow generation in rainfall-runoff models. In combination with the diffuse and source-responsive flow equations, a new model for water infiltration that incorporates preferential flow is proposed in this paper. Its performance in estimating soil moisture at the catchment scale was tested with observed water content data from the Elder sub-basin of the South Fork Eel River, located in northern California, USA. The case study shows that the new model can improve the accuracy of soil water content simulation even at the catchment scale. The impacts of preferential flow on rainfall-runoff simulation were tested by the MISDc lumped hydrological model for the Elder River basin. 11 significant floods events, which were defined as having flood peak magnitudes greater than 10 times average discharge during the study period, were employed to assess runoff simulation improvement. The accuracy of the runoff simulation incorporating the preferential flow at the catchment scale improved significantly even though more model parameters were expected through the likelihood ratio test.
Linking a modified EPIC-based growth model (UPGM) with a component-based watershed model (AGES-W)
Technology Transfer Automated Retrieval System (TEKTRAN)
Agricultural models and decision support systems (DSS) for assessing water use and management are increasingly being applied to diverse geographic regions at different scales. This requires models that can simulate different crops, however, very few plant growth models are available that “easily” ...
NASA Astrophysics Data System (ADS)
Chen, Xiangjun; Xiao, Namin; Cai, Minghui; Li, Dianzhong; Li, Guangyao; Sun, Guangyong; Rolfe, Bernard F.
2016-09-01
An inverse model is proposed to construct the mathematical relationship between continuous cooling transformation (CCT) kinetics with constant rates and the isothermal one. The kinetic parameters in JMAK equations of isothermal kinetics can be deduced from the experimental CCT kinetics. Furthermore, a generalized model with a new additive rule is developed for predicting the kinetics of nucleation and growth during diffusional phase transformation with arbitrary cooling paths based only on CCT curve. A generalized contribution coefficient is introduced into the new additivity rule to describe the influences of current temperature and cooling rate on the incubation time of nuclei. Finally, then the reliability of the proposed model is validated using dilatometry experiments of a microalloy steel with fully bainitic microstructure based on various cooling routes.
NASA Astrophysics Data System (ADS)
Chen, Xiangjun; Xiao, Namin; Cai, Minghui; Li, Dianzhong; Li, Guangyao; Sun, Guangyong; Rolfe, Bernard F.
2016-06-01
An inverse model is proposed to construct the mathematical relationship between continuous cooling transformation (CCT) kinetics with constant rates and the isothermal one. The kinetic parameters in JMAK equations of isothermal kinetics can be deduced from the experimental CCT kinetics. Furthermore, a generalized model with a new additive rule is developed for predicting the kinetics of nucleation and growth during diffusional phase transformation with arbitrary cooling paths based only on CCT curve. A generalized contribution coefficient is introduced into the new additivity rule to describe the influences of current temperature and cooling rate on the incubation time of nuclei. Finally, then the reliability of the proposed model is validated using dilatometry experiments of a microalloy steel with fully bainitic microstructure based on various cooling routes.
A modified two-state empirical valence bond model for proton transport in aqueous solutions
Mabuchi, Takuya; Fukushima, Akinori; Tokumasu, Takashi
2015-07-07
A detailed analysis of the proton solvation structure and transport properties in aqueous solutions is performed using classical molecular dynamics simulations. A refined two-state empirical valence bond (aTS-EVB) method, which is based on the EVB model of Walbran and Kornyshev and the anharmonic water force field, is developed in order to describe efficiently excess proton transport via the Grotthuss mechanism. The new aTS-EVB model clearly satisfies the requirement for simpler and faster calculation, because of the simplicity of the two-state EVB algorithm, while providing a better description of diffusive dynamics of the excess proton and water in comparison with the previous two-state EVB models, which significantly improves agreement with the available experimental data. The results of activation energies for the excess proton and water calculated between 300 and 340 K (the temperature range used in this study) are also found to be in good agreement with the corresponding experimental data.
Mihali, Andra; Subramani, Shreya; Kaunitz, Genevieve; Rayport, Stephen; Gaisler-Salomon, Inna
2012-01-01
Complex psychiatric disorders, such as schizophrenia, arise from a combination of genetic, developmental, environmental and social factors. These vulnerabilities can be mitigated by adaptive factors in each of these domains engendering resilience. Modeling resilience in mice using transgenic approaches offers a direct path to intervention, as resilience mutations point directly to therapeutic targets. As prototypes for this approach, we discuss the three mouse models of schizophrenia resilience, all based on modulating glutamatergic synaptic transmission. This motivates the broader development of schizophrenia resilience mouse models independent of specific pathophysiological hypotheses as a strategy for drug discovery. Three guiding validation criteria are presented. A resilience-oriented approach should identify pharmacologically tractable targets and in turn offer new insights into pathophysiological mechanisms. PMID:22853787
Pharmacological characterisation of a modified social interaction model of anxiety in the rat.
Guy, A P; Gardner, C R
1985-01-01
Social interaction (SI) between two unfamiliar male rats in a dimly lit, familiar environment has been investigated as a model of anxiety, where novelty of the partner remains as the principal anxiogenic stimulus. A range of centrally acting drugs have been tested in this situation. Chlordiazepoxide, nitrazepam, flunitrazepam, and flurazepam all increase SI, as does buspirone, CL 218872, suriclone, sodium valproate, and nicotinamide in the model described. Anxiogenic agents FG 7142 and yohimbine reduced SI without significant modification of motor activities. However, the stimulant amphetamine increased all behaviours in this condition. Amphetamine also increased all behaviours when rats were tested with their cagemates, when the desire for SI is largely satiated. CL 218872 also increased SI in this second situation, and it is suggested that this agent may have a non-specific component in its action in this test. Additionally, caffeine, theophylline, and piracetam may also have non-specific behavioural actions in this model. PMID:2864655
A modified two-state empirical valence bond model for proton transport in aqueous solutions
NASA Astrophysics Data System (ADS)
Mabuchi, Takuya; Fukushima, Akinori; Tokumasu, Takashi
2015-07-01
A detailed analysis of the proton solvation structure and transport properties in aqueous solutions is performed using classical molecular dynamics simulations. A refined two-state empirical valence bond (aTS-EVB) method, which is based on the EVB model of Walbran and Kornyshev and the anharmonic water force field, is developed in order to describe efficiently excess proton transport via the Grotthuss mechanism. The new aTS-EVB model clearly satisfies the requirement for simpler and faster calculation, because of the simplicity of the two-state EVB algorithm, while providing a better description of diffusive dynamics of the excess proton and water in comparison with the previous two-state EVB models, which significantly improves agreement with the available experimental data. The results of activation energies for the excess proton and water calculated between 300 and 340 K (the temperature range used in this study) are also found to be in good agreement with the corresponding experimental data.
NASA Technical Reports Server (NTRS)
Nigro, Joseph; Toll, David; Partington, Ed; Ni-Meister, Wenge; Lee, Shihyan; Gutierrez-Magness, Angelica; Engman, Ted; Arsenault, Kristi
2010-01-01
The Environmental Protection Agency (EPA) has estimated that over 20,000 water bodies within the United States do not meet water quality standards. Ninety percent of the impairments are typically caused by nonpoint sources. One of the regulations in the Clean Water Act of 1972 requires States to monitor the Total Maximum Daily Load (TMDL), or the amount of pollution that can be carried by a water body before it is determined to be "polluted", for any watershed in the U.S.. In response to this mandate, the EPA developed Better Assessment Science Integrating Nonpoint Sources (BASINS) as a Decision Support Tool (DST) for assessing pollution and to guide the decision making process for improving water quality. One of the models in BASINS, the Hydrological Simulation Program -- Fortran (HSPF), computes daily stream flow rates and pollutant concentration at each basin outlet. By design, precipitation and other meteorological data from weather stations serve as standard model input. In practice, these stations may be unable to capture the spatial heterogeneity of precipitation events especially if they are few and far between. An attempt was made to resolve this issue by substituting station data with NASA modified/NOAA precipitation data. Using these data within HSPF, stream flow was calculated for seven watersheds in the Chesapeake Bay Basin during low flow periods, convective storm periods, and annual flows. In almost every case, the modeling performance of HSPF increased when using the NASA-modified precipitation data, resulting in better stream flow statistics and, ultimately, in improved water quality assessment.
Sloan, Caroline E.; Luskin, Marlise R.; Boccuti, Anne M.; Sehgal, Alison R.; Zhao, Jianhua; Daber, Robert D.; Morrissette, Jennifer J. D.; Luger, Selina M.; Bagg, Adam
2016-01-01
Background Although cytogenetics-based prognostication systems are well described in acute myeloid leukemia (AML), overall survival (OS) remains highly variable within risk groups. An integrated genetic prognostic (IGP) model using cytogenetics plus mutations in nine genes was recently proposed for patients ≤60 years to improve classification. This model has not been validated in clinical practice. Methods and Findings We retrospectively studied 197 patients with newly diagnosed de novo AML. We compared OS curves among the mutational profiles defined by the IGP model. The IGP model assigned patients with intermediate cytogenetics as having favorable, intermediate or unfavorable mutational profiles. The IGP model reassigned 50 of 137 patients with intermediate cytogenetics to favorable or unfavorable mutational profiles. Median OS was 2.8 years among 14 patients with intermediate cytogenetics and favorable mutational profiles (mutant NPM1 and mutant IDH1 or IDH2) and 1.3 years among patients with intermediate mutational profiles. Among patients with intermediate cytogenetics labeled as having unfavorable mutational profiles, median OS was 0.8 years among 24 patients with FLT3-ITD positive AML and high-risk genetic changes (trisomy 8, TET2 and/or DNMT3A) and 1.7 years among 12 patients with FLT3-ITD negative AML and high-risk mutations (TET2, ASXL1 and/or PHF6). OS for patients with intermediate cytogenetics and favorable mutational profiles was similar to OS for patients with favorable cytogenetics (p = 0.697) and different from patients with intermediate cytogenetics and intermediate mutational profiles (p = 0.028). OS among patients with FLT3-ITD positive AML and high-risk genetic changes was similar to patients with unfavorable cytogenetics (p = 0.793) and different from patients with intermediate IGP profile (p = 0.022). Patients with FLT3-ITD negative AML and high-risk mutations, defined as ‘unfavorable’ in the IGP model, had OS similar to patients with
2015-01-01
Background Mass Spectrometry (MS) is a ubiquitous analytical tool in biological research and is used to measure the mass-to-charge ratio of bio-molecules. Peak detection is the essential first step in MS data analysis. Precise estimation of peak parameters such as peak summit location and peak area are critical to identify underlying bio-molecules and to estimate their abundances accurately. We propose a new method to detect and quantify peaks in mass spectra. It uses dual-tree complex wavelet transformation along with Stein's unbiased risk estimator for spectra smoothing. Then, a new method, based on the modified Asymmetric Pseudo-Voigt (mAPV) model and hierarchical particle swarm optimization, is used for peak parameter estimation. Results Using simulated data, we demonstrated the benefit of using the mAPV model over Gaussian, Lorentz and Bi-Gaussian functions for MS peak modelling. The proposed mAPV model achieved the best fitting accuracy for asymmetric peaks, with lower percentage errors in peak summit location estimation, which were 0.17% to 4.46% less than that of the other models. It also outperformed the other models in peak area estimation, delivering lower percentage errors, which were about 0.7% less than its closest competitor - the Bi-Gaussian model. In addition, using data generated from a MALDI-TOF computer model, we showed that the proposed overall algorithm outperformed the existing methods mainly in terms of sensitivity. It achieved a sensitivity of 85%, compared to 77% and 71% of the two benchmark algorithms, continuous wavelet transformation based method and Cromwell respectively. Conclusions The proposed algorithm is particularly useful for peak detection and parameter estimation in MS data with overlapping peak distributions and asymmetric peaks. The algorithm is implemented using MATLAB and the source code is freely available at http://mapv.sourceforge.net. PMID:26680279
Kang, Jin Wook; Park, Ki Dae; Choi, Youngju; Baek, Dae Hyun; Cho, Wan-Seob; Choi, Mina; Park, Jae Hyun; Choi, Kyoung Suk; Kim, Hyung Soo; Yoo, Tae Moo
2013-08-01
Human mesenchymal stem cells (hMSCs) have generated a great deal of interest in clinical application due to their ability to undergo multi-lineage differentiation. Recently, ex vivo genetic modification of hMSCs was attempted to increase their differentiation potential. The present study was conducted to evaluate the biodistribution and in vivo efficacy of genetically modified hMSCs. To accomplish this, Runx2, which is a key transcription factor associated with osteoblast differentiation, was transduced into hMSCs using lentiviral vectors expressing green fluorescent protein (GFP) or luciferase. Here, we developed an experimental fracture in mice femur to investigate the effects of Runx2-transduced hMSCs on bone healing and migration into injury site. We conducted bio-luminescence imaging (BLI) using luciferase-tagged vector and quantitative real-time PCR using GFP probe to investigate the biodistribution of Runx2-transduced hMSCs in the fracture model. The biodistribution of hMSC cells in the fractured femur was observed at 14 days post-transplantation upon both BLI imaging and real-time PCR. Moreover, the fractured mice transplanted with Runx2-transduced hMSCs showed superior bone healing when compared to mock-transduced hMSC and MRC5 fibroblasts which were used as control. These data suggested that transplanted genetically modified hMSCs systemically migrate to the fractured femur, where they contribute to bone formation in vivo. PMID:23615814
Zhao, Gong-Bo
2014-04-01
Based on a suite of N-body simulations of the Hu-Sawicki model of f(R) gravity with different sets of model and cosmological parameters, we develop a new fitting formula with a numeric code, MGHalofit, to calculate the nonlinear matter power spectrum P(k) for the Hu-Sawicki model. We compare the MGHalofit predictions at various redshifts (z ≤ 1) to the f(R) simulations and find that the relative error of the MGHalofit fitting formula of P(k) is no larger than 6% at k ≤ 1 h Mpc{sup –1} and 12% at k in (1, 10] h Mpc{sup –1}, respectively. Based on a sensitivity study of an ongoing and a future spectroscopic survey, we estimate the detectability of a signal of modified gravity described by the Hu-Sawicki model using the power spectrum up to quasi-nonlinear scales.
ERIC Educational Resources Information Center
Nickelson, Jen; Bryant, Carol A.; McDermott, Robert J.; Buhi, Eric R.; DeBate, Rita D.
2012-01-01
Background: The prevalence of obesity among high school students has risen in recent decades. Many high school students report trying to lose weight and some engage in disordered eating to do so. The obesity proneness model suggests that parents may influence their offspring's development of disordered eating. This study examined the…
NASA Astrophysics Data System (ADS)
Gholamhoseini, Alireza
2016-03-01
Relatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on composite slabs subjected to both drying shrinkage and sustained loads. Based on laboratory measurements, a design model for the shrinkage strain profile through the thickness of a slab is proposed. The design model is based on some modifications to an existing creep and shrinkage prediction model B3. In addition, an analytical model is developed to calculate the time-dependent deflection of composite slabs taking into account the time-dependent effects of creep and shrinkage. The calculated deflections are shown to be in good agreement with the experimental measurements.
Modifying SWAT to simulate cropland carbon flux: Model development and initial evaluation
Technology Transfer Automated Retrieval System (TEKTRAN)
Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However...
Kosterina, Natalia; Wang, Ruoli; Eriksson, Anders; Gutierrez-Farewik, Elena M
2013-08-01
This article introduces history-dependent effects in a skeletal muscle model applied to dynamic simulations of musculoskeletal system motion. Force depression and force enhancement induced by active muscle shortening and lengthening, respectively, represent muscle history effects. A muscle model depending on the preceding contractile events together with the current parameters was developed for OpenSim software, and applied in simulations of standing heel-raise and squat movements. Muscle activations were computed using joint kinematics and ground reaction forces recorded from the motion capture of seven individuals. In the muscle-actuated simulations, a modification was applied to the computed activation, and was compared to the measured electromyography data. For the studied movements, the history gives a small but visible effect to the muscular force trace, but some parameter values must be identified before the exact magnitude can be analysed. The muscle model modification improves the existing muscle models and gives a more accurate description of underlying forces and activations in musculoskeletal system movement simulations. PMID:23561824
Behavior Test Relevant to α2/α3Na(+)/K(+)-ATPase Gene Modified Mouse Models.
Isaksen, Toke Jost; Holm, Thomas Hellesøe; Lykke-Hartmann, Karin
2016-01-01
The behavioral phenotypes of mice are the result of a complex interplay between overall health, sensory abilities, learning and memory, motor function as well as developmental milestones, feeding, sexual, parental, and social behaviors. This chapter lists a selected number of key behavioral tests, specifically designed to assay fundamental behavioral features such as memory, activity, and motor skills in mice models. PMID:26695045
NASA Technical Reports Server (NTRS)
Olsen, W.; Walker, E.
1986-01-01
Closeup movies, still photographs, and other experimental data suggest that the current physical model for ice accretion needs significant modification. At aircraft airspeeds there was no flow of liquid over the surface of the ice after a short initial flow, even at barely subfreezing temperatures. Instead, there were very large stationary drops on the ice surface that lose water from their bottoms by freezing and replenish their liquid by catching the microscopic cloud droplets. This observation disagrees with the existing physical model, which assumes there is a thin liquid film continuously flowing over the ice surface. With no such flow, the freezing-fraction concept of the model fails when a mass balance is performed on the surface water. Rime ice does, as the model predicts, form when the air temperature is low enough to cause the cloud droplets to freeze almost immediately on impact. However, the characteristic shapes of horn-glaze ice or rime ice are primarily caused by the ice shape affecting the airflow locally and consequently the droplet catch and the resulting ice shape. Ice roughness greatly increases the heat transfer coefficient, stops the movement of drops along the surface, and may also affect the airflow initially and thereby the droplet catch. At high subreezing temperatures the initial flow and shedding of surface drops have a large effect on the ice shape. At the incipient freezing limit, no ice forms.
Lichtwark, G A; Wilson, A M
2005-08-01
The power output of a muscle and its efficiency vary widely under different activation conditions. This is partially due to the complex interaction between the contractile component of a muscle and the serial elasticity. We investigated the relationship between power output and efficiency of muscle by developing a model to predict the power output and efficiency of muscles under varying activation conditions during cyclical length changes. A comparison to experimental data from two different muscle types suggests that the model can effectively predict the time course of force and mechanical energetic output of muscle for a wide range of contraction conditions, particularly during activation of the muscle. With fixed activation properties, discrepancies in the work output between the model and the experimental results were greatest at the faster and slower cycle frequencies than that for which the model was optimised. Further optimisation of the activation properties across each individual cycle frequency examined demonstrated that a change in the relationship between the concentration of the activator (Ca2+) and the activation level could account for these discrepancies. The variation in activation properties with speed provides evidence for the phenomenon of shortening deactivation, whereby at higher speeds of contraction the muscle deactivates at a faster rate. The results of this study demonstrate that predictions about the mechanics and energetics of muscle are possible when sufficient information is known about the specific muscle. PMID:16043588
NASA Astrophysics Data System (ADS)
Eslamizadeh, H.
2015-09-01
The fission probability, pre-scission neutron, proton and alpha multiplicities, anisotropy of fission fragment angular distribution and the fission time have been calculated for the compound nuclei 200Pb and 197Tl based on the modified statistical model and four-dimensional dynamical model. In dynamical calculations, dissipation was generated through the chaos weighted wall and window friction formula. The projection of the total spin of the compound nucleus to the symmetry axis, K, was considered as the fourth-dimension in Langevin dynamical calculations. In our dynamical calculations, we have used a constant dissipation coefficient of K, {γ }K=0.077{({{MeV}} {{zs}})}-{1/2}, and a non-constant dissipation coefficient to reproduce the above-mentioned experimental data. Comparison of the theoretical results of the fission probability and pre-scission particle multiplicities with the experimental data showed that the difference between the results of both dynamical models is small whereas, for the anisotropy of fission fragment angular distribution, it is slightly large. Furthermore, comparison of the results of the modified statistical model with the above-mentioned experimental data showed that with choosing appropriate values of the temperature coefficient of the effective potential, λ , and the scaling factor of the fission-barrier height, {r}s, the experimental data were satisfactorily reproduced.
NASA Astrophysics Data System (ADS)
Slavuj, Radovan; Coppel, Ludovic G.; Hardeberg, Jon Yngve
2015-01-01
To control printers so that the mixture of inks results in specific color under defined visual environment requires a spectral reflectance model that estimates reflectance spectra from nominal dot coverage. The topic of this paper is to investigate the dependence of the Yule-Nielsen modified spectral Neugebauer (YNSN) model accuracy on ink amount. It is shown that the performance of the YNSN model strongly depends on the maximum ink amount applied. In a cellular implementation, this limitation mainly occurs for high coverage prints, which impacts on the optimal cell design. Effective coverages derived from both Murray-Davis (MD) and YNSN show large ink spreading. As ink-jet printing is a non-impact printing process, the ink volume deposited per unit area (pixel) is constant, leading to the hypothesis that isolated ink dots have lower thickness that the full-tone ink film. Measured spectral reflectance curves show similar trend, which supports the hypothesis. The reduced accuracy of YNSN can thus be explained with the fact that patches with lower effective coverage have a mean ink thickness very different from that of the full-tone patch. The effect will be stronger for small dot coverage and large dot gain and could partially explain why the Yule-Nielsen n-factor is different for different inks. The performance of the YNSN model could be improved with integration of ink thickness variation.
NASA Astrophysics Data System (ADS)
Geszke-Moritz, Małgorzata; Moritz, Michał
2016-04-01
Four mesoporous siliceous materials such as SBA-16, SBA-15, PHTS and MCF functionalized with (3-aminopropyl)triethoxysilane were successfully prepared and applied as the carriers for poorly water-soluble drug diflunisal. Several techniques including nitrogen sorption analysis, XRD, TEM, FTIR and thermogravimetric analysis were employed to characterize mesoporous matrices. Adsorption isotherms were analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. In order to find the best-fit isotherm for each model, both linear and nonlinear regressions were carried out. The equilibrium data were best fitted by the Langmuir isotherm model revealing maximum adsorption capacity of 217.4 mg/g for aminopropyl group-modified SBA-15. The negative values of Gibbs free energy change indicated that the adsorption of diflunisal is a spontaneous process. Weibull release model was employed to describe the dissolution profile of diflunisal. At pH 4.5 all prepared mesoporous matrices exhibited the improvement of drug dissolution kinetics as compared to the dissolution rate of pure diflunisal.
Younes, Mohammad K; Nopiah, Z M; Basri, N E Ahmad; Basri, H; Abushammala, Mohammed F M; Younes, Mohammed Y
2016-09-01
Solid waste prediction is crucial for sustainable solid waste management. The collection of accurate waste data records is challenging in developing countries. Solid waste generation is usually correlated with economic, demographic and social factors. However, these factors are not constant due to population and economic growth. The objective of this research is to minimize the land requirements for solid waste disposal for implementation of the Malaysian vision of waste disposal options. This goal has been previously achieved by integrating the solid waste forecasting model, waste composition and the Malaysian vision. The modified adaptive neural fuzzy inference system (MANFIS) was employed to develop a solid waste prediction model and search for the optimum input factors. The performance of the model was evaluated using the root mean square error (RMSE) and the coefficient of determination (R(2)). The model validation results are as follows: RMSE for training=0.2678, RMSE for testing=3.9860 and R(2)=0.99. Implementation of the Malaysian vision for waste disposal options can minimize the land requirements for waste disposal by up to 43%. PMID:26522806
NASA Astrophysics Data System (ADS)
Chan, Roger W.
2003-10-01
Previous studies have shown that vocal fold tissues exhibit nonlinear viscoelastic behavior under different loading conditions. Hysteresis and strain rate dependence of stress-strain curves have been observed for vocal fold ligament and muscle tissues when subjected to sinusoidal tensile loading. Nonlinear viscoelastic response and tissue failure have also been described for vocal fold mucosa subjected to constant strain-rate tests under large-strain shear. These findings cannot be adequately described by the traditional constitutive formulations of linear and quasilinear viscoelasticity. This study attempts to characterize some nonlinear behavior of vocal fold tissues under tensile loading based on a modified version of the Arruda-Boyce (Bergström-Boyce) hyperelastic model for polymers, which has been shown to adequately predict the rate-dependent behavior of some elastomers and biological tissues. Results indicated that the model was only capable of describing the relatively linear portion of the nonlinear stress-strain curves of the vocal fold muscle (at strain smaller than 20%), while failing to predict the exponential increase of stress at higher strain. However, the model was capable of predicting the dependence of stress on strain rate reasonably well. This finding was consistent with the model's assumptions on the constitutive behavior of the two constituent polymer networks.
NASA Astrophysics Data System (ADS)
Oliveira, J. S.; Langlais, B.; Pais, M. A.; Amit, H.
2015-06-01
Hermean magnetic field measurements acquired over the northern hemisphere by the MErcury Surface Space ENvironment GEochemistry, and Ranging (MESSENGER) spacecraft provide crucial information on the magnetic field of the planet. We develop a new method, the Time Dependent Equivalent Source Dipole, to model a planetary magnetic field and its secular variation over a limited spatial region. Tests with synthetic data distributed on regular grids as well as at spacecraft positions show that our modeled magnetic field can be upward or downward continued in an altitude range of -300 to 1460 km for regular grids and in a narrower range of 10 to 970 km for spacecraft positions. They also show that the method is not sensitive to a very weak secular variation along MESSENGER orbits. We then model the magnetic field of Mercury during the first four individual sidereal days as measured by MESSENGER using the modified Equivalent Source Dipoles scheme and excluding the secular variation terms. We find a dominantly zonal field with small-scale nonaxisymmetric features corotating with the Sun in the Mercury Body Fixed system and repeating under similar local time, suggestive of external origin. When modeling the field during one complete solar day, these small-scale features decrease and the field becomes more axisymmetric. The lack of any coherent nonaxisymmetric feature recovered by our method, which was designed to allow for such small-scale structures, provides strong evidence for the large-scale and close-to-axisymmetry structure of the internal magnetic field of Mercury.
Geszke-Moritz, Małgorzata; Moritz, Michał
2016-12-01
The present study deals with the adsorption of boldine onto pure and propyl-sulfonic acid-functionalized SBA-15, SBA-16 and mesocellular foam (MCF) materials. Siliceous adsorbents were characterized by nitrogen sorption analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric analysis. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherms. Moreover, the Dubinin-Radushkevich and Dubinin-Astakhov isotherm models based on the Polanyi adsorption potential were employed. The latter was calculated using two alternative formulas including solubility-normalized (S-model) and empirical C-model. In order to find the best-fit isotherm, both linear regression and nonlinear fitting analysis were carried out. The Dubinin-Astakhov (S-model) isotherm revealed the best fit to the experimental points for adsorption of boldine onto pure mesoporous materials using both linear and nonlinear fitting analysis. Meanwhile, the process of boldine sorption onto modified silicas was described the best by the Langmuir and Temkin isotherms using linear regression and nonlinear fitting analysis, respectively. The values of adsorption energy (below 8kJ/mol) indicate the physical nature of boldine adsorption onto unmodified silicas whereas the ionic interactions seem to be the main force of alkaloid adsorption onto functionalized sorbents (energy of adsorption above 8kJ/mol). PMID:27612776
NASA Astrophysics Data System (ADS)
Al-Rawabdeh, Abdulla M.; Al-Ansari, Nadhir A.; Al-Taani, Ahmed A.; Al-Khateeb, Fadi L.; Knutsson, Sven
2014-09-01
Amman-Zerqa Basin (AZB) is the second largest groundwater basin in Jordan with the highest abstraction rate, where more than 28% of total abstractions in Jordan come from this basin. In view of the extensive reliance on this basin, contamination of AZB groundwater became an alarming issue. This paper develops a Modified DRASTIC model by combining the generic DRASTIC model with land use activities and lineament density for the study area with a new model map that evaluates pollution potential of groundwater resources in AZB to various types of pollution. It involves the comparison of modified DRASTIC model that integrates nitrate loading along with other DRASTIC parameters. In addition, parameters to account for differences in land use and lineaments density were added to the DRASTIC model to reflect their influences on groundwater pollution potential. The DRASTIC model showed only 0.08% (3 km2) of the AZB is situated in the high vulnerability area and about 30% of the basin is located in the moderately vulnerable zone (mainly in central basin). After modifying the DRASTIC to account for lineament density, about 87% of the area was classified as having low pollution potential and no vulnerability class accounts for about 5.01% of the AZB area. The moderately susceptible zone covers 7.83% of the basin's total area and the high vulnerability area constitutes 0.13%. The vulnerability map based on land use revealed that about 71% of the study area has low pollution potential and no vulnerability area accounts for about 0.55%, whereas moderate pollution potential zone covers an area of 28.35% and the high vulnerability class constitutes 0.11% of AZB. The final DRASTIC model which combined all DRASTIC models shows that slightly more than 89% of the study area falls under low pollution risk and about 6% is considered areas with no vulnerability. The moderate pollution risk potential covers an area of about 4% of AZB and the high vulnerability class constitutes 0.21% of the
2010-01-01
Background Aneurysmal subarachnoid haemorrhage (aSAH) is a devastating event with a frequently disabling outcome. Our aim was to develop a prognostic model to predict an ordinal clinical outcome at two months in patients with aSAH. Methods We studied patients enrolled in the International Subarachnoid Aneurysm Trial (ISAT), a randomized multicentre trial to compare coiling and clipping in aSAH patients. Several models were explored to estimate a patient's outcome according to the modified Rankin Scale (mRS) at two months after aSAH. Our final model was validated internally with bootstrapping techniques. Results The study population comprised of 2,128 patients of whom 159 patients died within 2 months (8%). Multivariable proportional odds analysis identified World Federation of Neurosurgical Societies (WFNS) grade as the most important predictor, followed by age, sex, lumen size of the aneurysm, Fisher grade, vasospasm on angiography, and treatment modality. The model discriminated moderately between those with poor and good mRS scores (c statistic = 0.65), with minor optimism according to bootstrap re-sampling (optimism corrected c statistic = 0.64). Conclusion We presented a calibrated and internally validated ordinal prognostic model to predict two month mRS in aSAH patients who survived the early stage up till a treatment decision. Although generalizability of the model is limited due to the selected population in which it was developed, this model could eventually be used to support clinical decision making after external validation. Trial Registration International Standard Randomised Controlled Trial, Number ISRCTN49866681 PMID:20920243
NASA Technical Reports Server (NTRS)
Kaplan, M. L.; Zack, J. W.; Wong, V. C.; Coats, G. D.
1983-01-01
A nested-grid mesoscale atmospheric simulation system (MASS) is tested over Florida for the case of intense seabreeze-induced convection. The goal of this modeling system is to provide real-time aviation weather support which is designed to fit local terminal operations such as those supporting NASA's STS. Results from a 58 km and a 14.5 km nested-grid simulation show that this version of the MASS is capable of simulating many of the basic characteristics of convective complexes during periods of relatively weak synoptic scale flow regimes. However, it is noted that extensive development work is required with nested-grid cumulus and planetary boundary layer parameterization schemes before many of the meso-beta scale features such as thunderstorm downdraft-produced bubble high pressure centers can be accurately simulated. After these schemes are properly tuned, MASS can be utilized to initialize microscale modeling systems.
Processing, characterization and modeling of carbon nanofiber modified carbon/carbon composites
NASA Astrophysics Data System (ADS)
Samalot Rivera, Francis J.
Carbon/Carbon (C/C) composites are used in high temperature applications because they exhibit excellent thermomechanical properties. There are several challenges associated with the processing of C/C composites that include long cycle times, formation of closed porosity within fabric woven architecture and carbonization induced cracks that can lead to reduction of mechanical properties. This work addresses various innovative approaches to reduce processing uncertainties and thereby improve thermomechanical properties of C/C by using vapor grown carbon nanofibers (VGCNFs) in conjunction with carbon fabric and precursor phenolic matrix. The different aspects of the proposed research contribute to understanding of the translation of VGCNFs properties in a C/C composite. The specific objectives of the research are; (a) To understand the mechanical properties and microstructural features of phenolic resin precursor with and without modification with VGCNFs; (b) To develop innovative processing concepts that incorporate VGCNFs by spraying them on carbon fabric and/or adding VGCNFs to the phenolic resin precursor; and characterizing the process induced thermal and mechanical properties; and (c) To develop a finite element model to evaluate the thermal stresses developed in the carbonization of carbon/phenolic with and without VGCNFs. Addition of VGCNFs to phenolic resin enhanced the thermal and physical properties in terms of flexure and interlaminar properties, storage modulus and glass transition temperature and lowered the coefficient of thermal expansion. The approaches of spraying VGCNFs on the fabric surface and mixing VGCNFs with the phenolic resin was found to be effective in enhancing mechanical and thermal properties of the resulting C/C composites. Fiber bridging, improved carbon yield and minimization of carbonization-induced damage were the benefits of incorporating VGCNFs in C/C composites. Carbonization induced matrix cracking predicted by the finite
An Ontological Model of Behaviour Theory to Generate Personalized Action Plans to Modify Behaviours.
Baig, Wasif; Abidi, Samina; Abidi, Syed Sibte Raza
2016-01-01
Behavior change approaches aim to assist patients in achieving self-efficacy in managing their condition. Social cognitive theory (SCT) stipulates self-efficacy as a central element to behavior change and provides constructs to achieve self-efficacy guided by person-specific action plans. In our work, to administer behaviour change in patient with chronic conditions, our approach entails the computerization of SCT-based self-efficacy constructs in order to generate personalized action plans that are suitable to an individual's current care scenario. We have taken a knowledge management approach, whereby we have computerized the SCT-based self-efficacy constructs in terms of a high-level SCT knowledge model that can be operationalized to generate personalized behaviour change action plans. We have collected and computerized behavior change content targeting healthy living and physical activity. Semantic web technologies have been used to develop the SCT knowledge model, represented in terms of an ontology and SWRL rules. The ontological SCT model can inferred to generate personalized self-management action plans for a given patient profile. We present formative evaluation of the clinical correctness and relevance of the generated personalized action plans for a range of test patient profiles. PMID:27577412
A modified self-consistent computational model for an electrostrictive graft elastomer
NASA Astrophysics Data System (ADS)
Sun, Changjie; Wang, Youqi; Zhang, Congjian; Zhou, Eric; Su, Ji
2008-04-01
An electrostrictive graft elastomer, as recently developed by NASA, is a type of electro-active polymer. In this paper, a 2D computational model with a self-consistent boundary is developed. Firstly, three-dimensional deformations, induced by both bending angle and dihedral torsional angle changes, are projected onto a two-dimensional plane. Using both theoretical and numerical analyses, the projected 2D equilibrium bending angle is shown to have the same value as the 3D equilibrium bending angle. The 2D equivalent bending stiffness is derived using a series model based upon the fact that both bending and dihedral torsion produce a configurational change. Equivalent stiffness is justified by polymer chain end-to-end distance characteristics. Secondly, a self-consistent scheme is developed to eliminate the boundary effect. Eight images of the unit cell are created peripherally, with the original unit cell in the center. Thus the boundary can only affect the rotation of the eight images, not the central unit cell. A computational model is employed to determine the electromechanical properties of the electrostrictive graft elastomer. Relations between electric field induced strain and electric field strength are calculated. The effect of molecular scale factors, such as free volume fraction, graft weight percentage and graft orientation, are also discussed.
How Hot Precursor Modify Island Nucleation: A Rate-Equation Model
NASA Astrophysics Data System (ADS)
Morales-Cifuentes, Josue; Einstein, T. L.; Pimpinelli, Alberto
2015-03-01
We describe the analysis, based on rate equations, of the hot precursor model mentioned in the previous talk. Two key parameters are the competing times of ballistic monomers decaying into thermalized monomers vs. being captured by an island, which naturally define a ``thermalization'' scale for the system. We interpret the energies and dimmensionless parameters used in the model, and provide both an implicit analytic solution and a convenient asymptotic approximation. Further analysis reveals novel scaling regimes and nonmonotonic crossovers between them. To test our model, we applied it to experiments on parahexaphenyl (6P) on sputtered mica. With the resulting parameters, the curves derived from our analytic treatment account very well for the data at the 4 different temperatures. The fit shows that the high-flux regime corresponds not to ALA (attachment-limited aggregation) or HMA (hot monomer aggregation) but rather to an intermediate scaling regime related to DLA (diffusion-limited aggregation). We hope this work stimulates further experimental investigations. Work at UMD supported by NSF CHE 13-05892.
Modeling seasonal variability of fecal coliform in natural surface waters using the modified SWAT
NASA Astrophysics Data System (ADS)
Cho, Kyung Hwa; Pachepsky, Yakov A.; Kim, Minjeong; Pyo, JongCheol; Park, Mi-Hyun; Kim, Young Mo; Kim, Jung-Woo; Kim, Joon Ha
2016-04-01
Fecal coliforms are indicators of pathogens and thereby, understanding of their fate and transport in surface waters is important to protect drinking water sources and public health. We compiled fecal coliform observations from four different sites in the USA and Korea and found a seasonal variability with a significant connection to temperature levels. In all observations, fecal coliform concentrations were relatively higher in summer and lower during the winter season. This could be explained by the seasonal dominance of growth or die-off of bacteria in soil and in-stream. Existing hydrologic models, however, have limitations in simulating the seasonal variability of fecal coliform. Soil and in-stream bacterial modules of the Soil and Water Assessment Tool (SWAT) model are oversimplified in that they exclude simulations of alternating bacterial growth. This study develops a new bacteria subroutine for the SWAT in an attempt to improve its prediction accuracy. We introduced critical temperatures as a parameter to simulate the onset of bacterial growth/die-off and to reproduce the seasonal variability of bacteria. The module developed in this study will improve modeling for environmental management schemes.
Hopping conduction in bismuth modified zinc vanadate glasses: An applicability of Mott's model
NASA Astrophysics Data System (ADS)
Punia, R.; Kundu, R. S.; Murugavel, S.; Kishore, N.
2012-12-01
The dc conductivity measured in a wide range of temperatures (room temperature to 533.16 K) for glass samples of compositions 50V2O5.xBi2O3.(50-x) ZnO; x = 0, 5, 10, 15, and 20, is discussed in this paper. The temperature dependent dc conductivity has been analyzed in the framework of various theoretical models, which describe the hopping conduction in disordered semiconducting systems. It has been observed that Mott's model of polaron hopping in transition metals is in good agreement with the experimental data in high as well as intermediate temperature regions. The various polaron hopping parameters have also been deduced. It has been ascertained by these estimated quantities and different approaches that the electrical conduction in present glass system is due to non-adiabatic variable range hopping of small polarons. Moreover, it has been found that Mott's and Greaves' variable range hopping models are in good agreement with the experimental data in the whole studied temperature range in the present investigation.
NASA Astrophysics Data System (ADS)
Halmstad, Andrew; Olsen, Thomas; Wiener, Richard
2006-11-01
Previously, we have observed a period-doubling cascade to chaos in Modified Taylor-Couette Flow with Hourglass Geometry. Such behavior had been predicted by The Reaction-Diffusion model simulations. The chaotic formation of Taylor-Vortex pair formation was restricted to a very narrow band about the waist of the hourglass. It was suggested that with increasing lengths of systems, the chaotic region would expand. We present a battery of simulations to determine the variation of the size of the chaotic region with length, seeking the transition to spatio- temporal chaos. Richard J. Wiener et al, Phys. Rev. E 55, 5489 (1997). H. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).
A modified density model of the Venus atmosphere at 130-200 km altitude
NASA Astrophysics Data System (ADS)
Svedhem, Håkan; Mueller-Wodarg, Ingo; Rosenblatt, Pascal; Grotheer, Emmanuel
2014-05-01
Until recently the only information on the structure of the polar upper atmosphere of Venus available has been based on the reference atmosphere models such as the VTS3 or VIRA models. These models extrapolate the values from low latitudes to high latitudes by using equivalent solar zenith angles. New measurements by Venus Express show that such extrapolations not always give correct results and that there is a permanent overestimate of the density at high latitudes. These new results have been reached by using two different but related techniques, both using an atmospheric drag effect on the spacecraft. By reducing the pericentre altitude the total mass density in the altitude range 150-200km can be measured in situ by monitoring the orbital decay caused by the drag on the spacecraft by the atmosphere via direct tracking of the Doppler signal on the telecommunication link. Such measurements have been performed with Venus Express several times during the last years as part of the Venus Express Atmospheric Drag Experiment (VExADE). The results indicate a large variability within only a few days and have led to questions if these variations are real or within the uncertainty of the measurements. A completely different and independent measurement is given by monitoring the torque asserted by the atmosphere on the spacecraft. This is done by monitoring the momentum accumulated in the reaction wheels during the pericenter pass and at the same time considering all other perturbing forces. This requires the spacecraft to fly in an asymmetric configuration with respect to the center of gravity, center of drag and the velocity vector. This technique has proven very sensitive, in particular if the geometric asymmetry is large, and offers an additional method of measuring atmospheric densities in-situ that previously had not been explored with the Venus Express spacecraft. Similar measurements have been done in the past by Magellan at Venus and by Cassini at Titan. Between
NASA Astrophysics Data System (ADS)
French, J.; Burningham, H.
2011-12-01
A major challenge in coastal geomorphology is the prediction of morphological change at a meso-scale (10 to 100 km; 10 to 100 yr). This scale sits awkwardly between understanding of geomorphological processes at the micro-scale, and broader aspects of coastal evolution informed by the Holocene stratigraphic record. In this paper, we explore the potential of a new kind of qualitative mathematical model implemented at a system level. Qualitative models derive predictions from the structure of the system rather from the detailed physics of the underlying processes. Although systems thinking is well established in geomorphology methodologies for converting system diagrams into simulation tools have not been widely investigated. In a recent Defra-funded project in the UK, a Boolean network approach was piloted and applied to the simulation of generic aspects of estuary response to environmental and anthropogenic forcing. We build on this to present a generic approach to the construction of system diagrams for estuaries and adjacent open coasts and their conversion into a network graph. In a Boolean model, each node of this graph is assigned a binary value, the state of which is determined by a logical function that specifies the combined influence of other nodes to which it is connected. System evolution is simulated by specifying a set of initial conditions and repeatedly evaluating the logical functions until an equilibrium condition is reached (either a steady state or a cyclical sequence between two end states). In our enhanced Boolean scheme, changes in morphology are allowed to feed back into intrinsic process variables (e.g. estuary waves or tidal prism), although some processes are externally imposed (e.g. sea-level rise). Arbitrary time lags condition the response of morphology to a change in process, such that some landforms adjust more rapidly than others. We also present a simulator architecture based around a solver and externally specified model components
Stringy models of modified gravity: space-time defects and structure formation
Mavromatos, Nick E.; Sakellariadou, Mairi; Yusaf, Muhammad Furqaan E-mail: mairi.sakellariadou@kcl.ac.uk
2013-03-01
Starting from microscopic models of space-time foam, based on brane universes propagating in bulk space-times populated by D0-brane defects (''D-particles''), we arrive at effective actions used by a low-energy observer on the brane world to describe his/her observations of the Universe. These actions include, apart from the metric tensor field, also scalar (dilaton) and vector fields, the latter describing the interactions of low-energy matter on the brane world with the recoiling point-like space-time defect (D-particle). The vector field is proportional to the recoil velocity of the D-particle and as such it satisfies a certain constraint. The vector breaks locally Lorentz invariance, which however is assumed to be conserved on average in a space-time foam situation, involving the interaction of matter with populations of D-particle defects. In this paper we clarify the role of fluctuations of the vector field on structure formation and galactic growth. In particular we demonstrate that, already at the end of the radiation era, the (constrained) vector field associated with the recoil of the defects provides the seeds for a growing mode in the evolution of the Universe. Such a growing mode survives during the matter dominated era, provided the variance of the D-particle recoil velocities on the brane is larger than a critical value. We note that in this model, as a result of specific properties of D-brane dynamics in the bulk, there is no issue of overclosing the brane Universe for large defect densities. Thus, in these models, the presence of defects may be associated with large-structure formation. Although our string inspired models do have (conventional, from a particle physics point of view) dark matter components, nevertheless it is interesting that the role of ''extra'' dark matter is also provided by the population of massive defects. This is consistent with the weakly interacting character of the D-particle defects, which predominantly interact only
Burke, Jeffrey D.; Boylan, Khrista; Rowe, Richard; Duku, Eric; Stepp, Stephanie D.; Hipwell, Alison E.; Waldman, Irwin D.
2014-01-01
The importance of irritability as measured among the symptoms of oppositional defiant disorder (ODD) has dramatically come to the fore in recent years. New diagnostic categories rely on the distinct clinical utility of irritability, and models of psychopathology suggest it plays a key role in explaining developmental pathways within and between disorders into adulthood. However, only a few studies have tested multidimensional models of ODD, and the results have been conflicting. Further, consensus has not been reached regarding which symptoms best identify irritability. The present analyses use data from five large community data sets with five different measures of parent-reported ODD, comprising 16,280 youth in total, to help resolve these questions. Across the samples, ages ranged from 5 to 18, and included both boys and girls. Confirmatory factor analyses demonstrated that a modified bifactor model showed the best fit in each of the five data sets. The structure of the model included two correlated specific factors (irritability and oppositional behavior) in addition to a general ODD factor. In four of the five models, the best fit was obtained using the items of being touchy, angry and often losing temper as indicators of irritability. Given the structure of the models and the generally high correlation between the specific dimensions, the results suggest that irritability may not be sufficiently distinct from oppositional behavior to support an entirely independent diagnosis. Rather, irritability may be better understood as a dimension of psychopathology that can be distinguished within ODD, and which may be related to particular forms of psychopathology apart from ODD. PMID:25314267
NASA Astrophysics Data System (ADS)
Wythers, Kirk R.; Reich, Peter B.; Bradford, John B.
2013-03-01
Evidence suggests that respiration acclimation (RA) to temperature in plants can have a substantial influence on ecosystem carbon balance. To assess the influence of RA on ecosystem response variables in the presence of global change drivers, we incorporated a temperature-sensitive Q10 of respiration and foliar basal RA into the ecosystem model PnET-CN. We examined the new algorithms' effects on modeled net primary production (NPP), total canopy foliage mass, foliar nitrogen concentration, net ecosystem exchange (NEE), and ecosystem respiration/gross primary production ratios. This latter ratio more closely matched eddy covariance long-term data when RA was incorporated in the model than when not. Averaged across four boreal ecotone sites and three forest types at year 2100, the enhancement of NPP in response to the combination of rising [CO2] and warming was 9% greater when RA algorithms were used, relative to responses using fixed respiration parameters. The enhancement of NPP response to global change was associated with concomitant changes in foliar nitrogen and foliage mass. In addition, impacts of RA algorithms on modeled responses of NEE closely paralleled impacts on NPP. These results underscore the importance of incorporating temperature-sensitive Q10 and basal RA algorithms into ecosystem models. Given the current evidence that atmospheric [CO2] and surface temperature will continue to rise, and that ecosystem responses to those changes appear to be modified by RA, which is a common phenotypic adjustment, the potential for misleading results increases if models fail to incorporate RA into their carbon balance calculations.
NASA Astrophysics Data System (ADS)
Bhaumik, Ria; Mondal, Naba Kumar
2016-06-01
The present work highlighted the effective application of banana peel dust (BPD) for removal of fluoride (F-) from aqueous solution. The effects of operating parameters such as pH, initial concentration, adsorbent dose, contact time, agitation speed and temperature were analysed using response surface methodology. The significance of independent variables and their interactions were tested by the analysis of variance and t test statistics. Experimental results revealed that BPD has higher F- adsorption capacity (17.43, 26.31 and 39.5 mg/g). Fluoride adsorption kinetics followed pseudo-second-order model with high correlation of coefficient value (0.998). On the other hand, thermodynamic data suggest that adsorption is favoured at lower temperature, exothermic in nature and enthalpy driven. The adsorbents were characterised through scanning electron microscope, Fourier transform infrared spectroscopy and point of zero charges (pHZPC) ranges from pH 6.2-8.2. Finally, error analysis clearly demonstrates that all three adsorbents are well fitted with Langmuir isotherm compared to the other isotherm models. The reusable properties of the material support further development for commercial application purpose.
MODIFIED CHOKE FLOW CRITERION FOR THE TWO-PHASE TWO-FLUID MODEL
Suneet Singh; Vincent A. Mousseau
2009-05-01
A choked condition exists when mass flow rate becomes independent of the downstream conditions. In other words, no information can propagate in the upstream direction under this condition. The real part of the solution of the characteristic equation for the model represents velocity of the signal propagation and the imaginary part is the growth (or decay) rate of that signal. Therefore, if the real part of these eigenvalues is positive then no signal propagates in the upstream direction (choosing downstream direction to be the positive direction) resulting in the choke flow. In order to develop the choke criterion, a non-dimensional form of the characteristic equation is derived for the standard two-phase two-fluid model. The equation is in the terms of a slip Mach number Ms. It can be shown that the slip Mach number is small for many applications including nuclear reactor safety simulations. The eigenvalues of the characteristic equation are obtained as a power series expansion about the point Ms = 0. These eigenvalues are used to develop a choking criterion for the compressible two-phase flows.
Modelling drug degradation in a spray dried polymer dispersion using a modified Arrhenius equation.
Patterson, Adele; Ferreira, Ana P; Banks, Elizabeth; Skeene, Kirsty; Clarke, Graham; Nicholson, Sarah; Rawlinson-Malone, Clare
2015-01-15
The Pharmaceutical industry is increasingly utilizing amorphous technologies to overcome solubility challenges. A common approach is the use of drug in polymer dispersions to prevent recrystallization of the amorphous drug. Understanding the factors affecting chemical and physical degradation of the drug within these complex systems, e.g., temperature and relative humidity, is an important step in the selection of a lead formulation, and development of appropriate packaging/storage control strategies. The Arrhenius equation has been used as the basis of a number of models to predict the chemical stability of formulated product. In this work, we investigate the increase in chemical degradation seen for one particular spray dried dispersion formulation using hydroxypropyl methylcellulose acetate succinate (HPMC-AS). Samples, prepared using polymers with different substitution levels, were placed on storage for 6 months under a range of different temperature and relative humidity conditions and the degradant level monitored using high-performance liquid chromatography (HPLC). While the data clearly illustrates the impact of temperature and relative humidity on the degradant levels detected, it also highlighted that these terms do not account for all the variability in the data. An extension of the Arrhenius equation to include a term for the polymer chemistry, specifically the degree of succinoyl substitution on the polymer backbone, was shown to improve the fit of the model to the data. PMID:25450477
A Modified Wilson Cycle Scenario Based on Thermo-Mechanical Model
NASA Astrophysics Data System (ADS)
Baes, M.; Sobolev, S. V.
2014-12-01
The major problem of classical Wilson Cycle concept is the suggested conversion of the passive continental margin to the active subduction zone. Previous modeling studies assumed either unusually thick felsic continental crust at the margin (over 40 km) or unusually low lithospheric thickness (less than 70 km) to simulate this process. Here we propose a new triggering factor in subduction initiation process that is mantle suction force. Based on this proposal we suggest a modification of Wilson Cycle concept. Sometime after opening and extension of oceanic basin, continental passive margin moves over the slab remnants of the former active subduction zones in deep mantle. Such slab remnants or deep slabs of neighboring active subduction zones produce a suction mantle flow introducing additional compression at the passive margin. It results in the initiation of a new subduction zone, hence starting the closing phase of Wilson Cycle. In this scenario the weakness of continental crust near the passive margin which is inherited from the rifting phase and horizontal push force induced from far-field topographic gradient within the continent facilitate and speed up subduction initiation process. Our thermo-mechanical modeling shows that after a few tens of million years a shear zone may indeed develop along the passive margin that has typical two-layered 35 km thick continental crust and thermal lithosphere thicker than 100 km if there is a broad mantle down-welling flow below the margin. Soon after formation of this shear zone oceanic plate descends into mantle and subduction initiates. Subduction initiation occurs following over-thrusting of continental crust and retreating of future trench. In models without far-field topographic gradient within the continent subduction initiation requires weaker passive margin. Our results also indicate that subduction initiation depends on several parameters such as magnitude, domain size and location of suction mantle flow
NASA Astrophysics Data System (ADS)
Nourazar, S. S.; Jahangiri, P.; Aboutalebi, A.; Ganjaei, A. A.; Nourazar, M.; Khadem, J.
2011-06-01
The effect of new terms in the improved algorithm, the modified direct simulation Monte-Carlo (MDSMC) method, is investigated by simulating a rarefied binary gas mixture flow inside a rotating cylinder. Dalton law for the partial pressures contributed by each species of the binary gas mixture is incorporated into our simulation using the MDSMC method and the direct simulation Monte-Carlo (DSMC) method. Moreover, the effect of the exponent of the cosine of deflection angle (α) in the inter-molecular collision models, the variable soft sphere (VSS) and the variable hard sphere (VHS), is investigated in our simulation. The improvement of the results of simulation is pronounced using the MDSMC method when compared with the results of the DSMC method. The results of simulation using the VSS model show some improvements on the result of simulation for the mixture temperature at radial distances close to the cylinder wall where the temperature reaches the maximum value when compared with the results using the VHS model.
Vlachos, Marios; Dermatas, Evangelos
2015-01-01
A novel method for finger vein pattern extraction from infrared images is presented. This method involves four steps: preprocessing which performs local normalization of the image intensity, image enhancement, image segmentation, and finally postprocessing for image cleaning. In the image enhancement step, an image which will be both smooth and similar to the original is sought. The enhanced image is obtained by minimizing the objective function of a modified separable Mumford Shah Model. Since, this minimization procedure is computationally intensive for large images, a local application of the Mumford Shah Model in small window neighborhoods is proposed. The finger veins are located in concave nonsmooth regions and, so, in order to distinct them from the other tissue parts, all the differences between the smooth neighborhoods, obtained by the local application of the model, and the corresponding windows of the original image are added. After that, veins in the enhanced image have been sufficiently emphasized. Thus, after image enhancement, an accurate segmentation can be obtained readily by a local entropy thresholding method. Finally, the resulted binary image may suffer from some misclassifications and, so, a postprocessing step is performed in order to extract a robust finger vein pattern. PMID:26120357
NASA Astrophysics Data System (ADS)
Zhao, Hongliang; Liu, Xinghui; Xu, Chao
2013-11-01
A low power cryogenic readout integrated circuit (ROIC) for 512 × 512-pixel infrared focal plane array (IRFPA) image system, is presented. In order to improve the precision of the circuit simulation at cryogenic temperatures, a modified MOS device model is proposed. The model is based on BSIM3 model, and uses correction parameters to describe carrier freeze-out effect at low temperatures to improve the fitting accuracy for low temperature MOS device simulation. A capacitive trans-impedance amplifier (CTIA) with inherent correlated double sampling (CDS) configuration is employed to realize a high performance readout interfacing circuit in a pixel area of 30 × 30 μm2. Optimized column readout timing and structure are applied to reduce the power consumption. The experimental chip fabricated by a standard 0.35 μm 2P4M CMOS process shows more than 10 MHz readout rate with less than 70 mW power consumption under 3.3 V supply voltage at 77-150 K operated temperatures. And it occupies an area of 18 × 17 mm2.
Vlachos, Marios; Dermatas, Evangelos
2015-01-01
A novel method for finger vein pattern extraction from infrared images is presented. This method involves four steps: preprocessing which performs local normalization of the image intensity, image enhancement, image segmentation, and finally postprocessing for image cleaning. In the image enhancement step, an image which will be both smooth and similar to the original is sought. The enhanced image is obtained by minimizing the objective function of a modified separable Mumford Shah Model. Since, this minimization procedure is computationally intensive for large images, a local application of the Mumford Shah Model in small window neighborhoods is proposed. The finger veins are located in concave nonsmooth regions and, so, in order to distinct them from the other tissue parts, all the differences between the smooth neighborhoods, obtained by the local application of the model, and the corresponding windows of the original image are added. After that, veins in the enhanced image have been sufficiently emphasized. Thus, after image enhancement, an accurate segmentation can be obtained readily by a local entropy thresholding method. Finally, the resulted binary image may suffer from some misclassifications and, so, a postprocessing step is performed in order to extract a robust finger vein pattern. PMID:26120357
NASA Astrophysics Data System (ADS)
Boberg, P. R.; Smart, D. F.; Shea, M. A.; Tylka, A. J.
2016-01-01
We have determined eight-second averaged geomagnetic transmissions of 36-80 MeV protons for the large Solar Energetic Particle (SEP) events and geomagnetic activity level variations of October 1989 using measurements from the NOAA-10 and GOES-7 satellites. We have compared the geomagnetic transmission measurements with model calculations employing trajectory tracings through the combined International Geomagnetic Reference Field (IGRF) and Kp/Dst modified 1989 Tsyganenko model. We present threshold geomagnetic transmission geographic latitudes and magnetic latitudes, as well as (a) differences between the measured and calculated threshold geographic latitudes and magnetic latitudes and (b) differences between measured and calculated polar pass durations. We find that for less disturbed geomagnetic activity levels, the measured threshold geomagnetic transmission geographic and magnetic latitudes are typically about 1-1.5° equatorward of the calculated geographic and magnetic latitudes, while for larger geomagnetic activity levels, the measured geographic and magnetic latitudes can be about 1.5° poleward of the calculated geographic and magnetic latitudes. For the eight Kp bins, we also compare the mean measured magnetic latitudes as a function of mean Dst with the mean calculated magnetic latitudes, interpolated to the mean measured Dst values. These comparisons of mean magnetic latitudes illustrate the improvement in the accuracy of the model calculations resulting from employing the actual mean measured Dst values.
NASA Astrophysics Data System (ADS)
Hawley, M. E.; Devlin, D. J.; Reichhardt, C. J.; Sickafus, K. E.; Usov, I. O.; Valdez, J. A.; Wang, Y. Q.
2010-10-01
This work explored a potential new model dispersion fuel form consisting of an actinide material embedded in a radiation tolerant matrix that captures fission products (FPs) and is easily separated chemically as waste from the fuel material. To understand the stability of this proposed dispersion fuel form design, an idealized model system composed of a multilayer film was studied. This system consisted of a tri-layer structure of an MgO layer sandwiched between two HfO 2 layers. HfO 2 served as a surrogate fissile material for UO 2 while MgO represented a stable, fissile product (FP) getter that is easily separated from the fissile material. This type of multilayer film structure allowed us to control the size of and spacing between each layer. The films were grown at room temperature by e-beam deposition on a Si(1 1 1) substrate and post-annealed annealing at a range of temperatures to crystallize the HfO 2 layers. The 550 °C annealed sample was subsequently irradiated with 10 MeV Au 3+ ions at a range of fluences from 5 × 10 13 to 3.74 × 10 16 ions/cm 2. Separate single layer constituent films and the substrate were also irradiated at 5 × 10 15 and 8 × 10 14 and 2 × 10 16, respectively. After annealing and irradiation, the samples were characterized using atomic force imaging techniques to determine local changes in microstructure and mechanical properties. All samples annealed above 550 °C cracked. From the AFM results we observed both crack healing and significant modification of the surface at higher fluences.
Faure, Alexis; Es-Seddiqi, Mouna; Brown, Bruce L; Nguyen, Hoa P; Riess, Olaf; von Hörsten, Stephan; Le Blanc, Pascale; Desvignes, Nathalie; Bozon, Bruno; El Massioui, Nicole; Doyère, Valérie
2013-01-01
Huntington's disease (HD) is characterized by triad of motor, cognitive, and emotional symptoms along with neuropathology in fronto-striatal circuit and limbic system including amygdala. Emotional alterations, which have a negative impact on patient well-being, represent some of the earliest symptoms of HD and might be related to the onset of the neurodegenerative process. In the transgenic rat model (tgHD rats), evidence suggest emotional alterations at the symptomatic stage along with neuropathology of the central nucleus of amygdala (CE). Studies in humans and animals demonstrate that emotion can modulate time perception. The impact of emotion on time perception has never been tested in HD, nor is it known if that impact could be part of the presymptomatic emotional phenotype of the pathology. The aim of this paper was to characterize the effect of emotion on temporal discrimination in presymptomatic tgHD animals. In the first experiment, we characterized the acute effect of an emotion (fear) conditioned stimulus on temporal discrimination using a bisection procedure, and tested its dependency upon an intact central amygdala. The second experiment was aimed at comparing presymptomatic homozygous transgenic animals at 7-months of age and their wild-type littermates (WT) in their performance on the modulation of temporal discrimination by emotion. Our principal findings show that (1) a fear cue produces a short-lived decrease of temporal precision after its termination, and (2) animals with medial CE lesion and presymptomatic tgHD animals demonstrate an alteration of this emotion-evoked temporal distortion. The results contribute to our knowledge about the presymptomatic phenotype of this HD rat model, showing susceptibility to emotion that may be related to dysfunction of the central nucleus of amygdala. PMID:24133419
Faure, Alexis; Es-seddiqi, Mouna; Brown, Bruce L.; Nguyen, Hoa P.; Riess, Olaf; von Hörsten, Stephan; Le Blanc, Pascale; Desvignes, Nathalie; Bozon, Bruno; El Massioui, Nicole; Doyère, Valérie
2013-01-01
Huntington's disease (HD) is characterized by triad of motor, cognitive, and emotional symptoms along with neuropathology in fronto-striatal circuit and limbic system including amygdala. Emotional alterations, which have a negative impact on patient well-being, represent some of the earliest symptoms of HD and might be related to the onset of the neurodegenerative process. In the transgenic rat model (tgHD rats), evidence suggest emotional alterations at the symptomatic stage along with neuropathology of the central nucleus of amygdala (CE). Studies in humans and animals demonstrate that emotion can modulate time perception. The impact of emotion on time perception has never been tested in HD, nor is it known if that impact could be part of the presymptomatic emotional phenotype of the pathology. The aim of this paper was to characterize the effect of emotion on temporal discrimination in presymptomatic tgHD animals. In the first experiment, we characterized the acute effect of an emotion (fear) conditioned stimulus on temporal discrimination using a bisection procedure, and tested its dependency upon an intact central amygdala. The second experiment was aimed at comparing presymptomatic homozygous transgenic animals at 7-months of age and their wild-type littermates (WT) in their performance on the modulation of temporal discrimination by emotion. Our principal findings show that (1) a fear cue produces a short-lived decrease of temporal precision after its termination, and (2) animals with medial CE lesion and presymptomatic tgHD animals demonstrate an alteration of this emotion-evoked temporal distortion. The results contribute to our knowledge about the presymptomatic phenotype of this HD rat model, showing susceptibility to emotion that may be related to dysfunction of the central nucleus of amygdala. PMID:24133419
Vieweg, J; Rosenthal, F M; Bannerji, R; Heston, W D; Fair, W R; Gansbacher, B; Gilboa, E
1994-04-01
Adenocarcinoma of the prostate is the most common cancer in men. The majority of cancers are discovered once they have already metastasized, and there is no effective therapy for prostatic cancer at this stage. The use of cytokine-secreting tumor cell preparations as therapeutic vaccines for the treatment of advanced prostate cancer was investigated in the Dunning rat R3327-MatLyLu prostatic tumor model. IL-2 secreting, irradiated, tumor cell preparations were capable of curing animals with s.c. established tumors, and induced immunological memory that protected animals from subsequent tumor challenge. Immunotherapy was less effective when tumors were induced orthotopically, but nevertheless led to improved outcome, significantly delaying, and occasionally preventing, recurrence of tumors after resection of the cancerous prostate. Granulocyte-macrophage colony stimulating factor secreting tumor cell preparations were less effective, and interferon-gamma secreting cells had only a marginal effect. Induction of a potent immune response in tumor bearing animals against the nonimmunogenic MatLyLu tumor supports the view that active immunotherapy warrants further investigation as a potential therapeutic approach to prostate cancer. PMID:8137291
Aerosol Optical Depth Retrieval by NPS Model Modified for SEAWIFS Input
NASA Astrophysics Data System (ADS)
Brown, Brady A.
2002-03-01
Using visible wavelength radiance data obtained from the spaceborne Sea-viewing Wide Field of-view Sensor (SeaWiFS), during the Aerosol Characterization Experiment-Asia (ACE-Asia), an analysis of aerosol optical depth (AOD) was completed by modification to the NPS AOD Model previously compiled for NOAA geosynchronous- and polar-orbiting satellites. The objective of the analysis was to calibrate the linearized, single-scatter algorithm, estimated bi-directional surface reflectance, and phase function parameters. The intent of the study was to provide enhanced temporal AOD coverage with the addition of the orbiting SeaWiFS eight-channel radiometer to the established NOAA constellation of five-channel AVHRR-equipped satellites. The work has operational significance in providing timely, accurate remote information to military operators of identification and targeting systems. Possible applications include detection and warning of international treaty violation of reducing the adverse public health effects by weapons of mass destruction of pollution advection on global weather patterns.
C. elegans model identifies genetic modifiers of alpha-synuclein inclusion formation during aging.
van Ham, Tjakko J; Thijssen, Karen L; Breitling, Rainer; Hofstra, Robert M W; Plasterk, Ronald H A; Nollen, Ellen A A
2008-03-01
Inclusions in the brain containing alpha-synuclein are the pathological hallmark of Parkinson's disease, but how these inclusions are formed and how this links to disease is poorly understood. We have developed a C. elegans model that makes it possible to monitor, in living animals, the formation of alpha-synuclein inclusions. In worms of old age, inclusions contain aggregated alpha- synuclein, resembling a critical pathological feature. We used genome-wide RNA interference to identify processes involved in inclusion formation, and identified 80 genes that, when knocked down, resulted in a premature increase in the number of inclusions. Quality control and vesicle-trafficking genes expressed in the ER/Golgi complex and vesicular compartments were overrepresented, indicating a specific role for these processes in alpha-synuclein inclusion formation. Suppressors include aging-associated genes, such as sir-2.1/SIRT1 and lagr-1/LASS2. Altogether, our data suggest a link between alpha-synuclein inclusion formation and cellular aging, likely through an endomembrane-related mechanism. The processes and genes identified here present a framework for further study of the disease mechanism and provide candidate susceptibility genes and drug targets for Parkinson's disease and other alpha-synuclein related disorders. PMID:18369446
Van Huy, Nguyen; P Dunne, Michael; Debattista, Joseph
2016-01-01
HIV risk in vulnerable groups such as itinerant male street labourers is often examined via a focus on individual determinants. This study provides a test of a modified Information-Motivation-Behavioral Skills (IMB) model to predict condom use behaviour among male street workers in urban Vietnam. In a cross-sectional survey using a social mapping technique, 450 male street labourers from 13 districts of Hanoi, Vietnam were recruited and interviewed. Collected data were first examined for completeness; structural equation modelling was then employed to test the model fit. Condoms were used inconsistently by many of these men, and usage varied in relation to a number of factors. A modified IMB model had a better fit than the original IMB model in predicting condom use behaviour. This modified model accounted for 49% of the variance, versus 10% by the original version. In the modified model, the influence of psychosocial factors was moderately high, whilst the influence of HIV prevention information, motivation and perceived behavioural skills was moderately low, explaining in part the limited level of condom use behaviour. This study provides insights into social factors that should be taken into account in public health planning to promote safer sexual behaviour among Asian male street labourers. PMID:26416016
Schuh, Alexander; Kroh, Andreas; Konschalla, Simone; Liehn, Elisa A; Sobota, Radoslav M; Biessen, Erik AL; Bot, Ilze; Sönmez, Tolga Taha; Schober, Andreas; Marx, Nikolaus; Weber, Christian; Sasse, Alexander
2012-01-01
Cell based therapy has been shown to attenuate myocardial dysfunction after myocardial infarction (MI) in different acute and chronic animal models. It has been further shown that stromal-cell derived factor-1α (SDF-1α) facilitates proliferation and migration of endogenous progenitor cells into injured tissue. The aim of the present study was to investigate the role of exogenously applied and endogenously mobilized cells in a regenerative strategy for MI therapy. Lentivirally SDF-1α-infected endothelial progenitor cells (EPCs) were injected after 90 min. of ligation and reperfusion of the left anterior descending artery (LAD) intramyocardial and intracoronary using a new rodent catheter system. Eight weeks after transplantation, echocardiography and isolated heart studies revealed a significant improvement of LV function after intramyocardial application of lentiviral with SDF-1 infected EPCs compared to medium control. Intracoronary application of cells did not lead to significant differences compared to medium injected control hearts. Histology showed a significantly elevated rate of apoptotic cells and augmented proliferation after transplantation of EPCs and EPCs + SDF-1α in infarcted myocardium. In addition, a significant increased density of CD31+ vessel structures, a lower collagen content and higher numbers of inflammatory cells after transplantation of SDF-1 transgenic cells were detectable. Intramyocardial application of lentiviral-infected EPCs is associated with a significant improvement of myocardial function after infarction, in contrast to an intracoronary application. Histological results revealed a significant augmentation of neovascularization, lower collagen content, higher numbers of inflammatory cells and remarkable alterations of apoptotic/proliferative processes in infarcted areas after cell transplantation. PMID:22288686
Probiotics modify tight-junction proteins in an animal model of nonalcoholic fatty liver disease
Briskey, David; Heritage, Mandy; Jaskowski, Lesley-Anne; Peake, Jonathan; Gobe, Glenda; Subramaniam, V. Nathan; Crawford, Darrell; Campbell, Catherine; Vitetta, Luis
2016-01-01
Background: We have investigated the effects of a multispecies probiotic preparation containing a combination of probiotic bacterial genera that included Bifidobacteria, Lactobacilli and a Streptococcus in a mouse model of high-fat diet or obesity-induced liver steatosis. Methods: Three groups of C57B1/6J mice were fed either a standard chow or a high-fat diet for 20 weeks, while a third group was fed a high-fat diet for 10 weeks and then concomitantly administered probiotics for a further 10 weeks. Serum, liver and large bowel samples were collected for analysis. Results: The expression of the tight-junction proteins ZO-1 and ZO-2 was reduced (p < 0.05) in high-fat diet-fed mice compared to chow-fed mice. Probiotic supplementation helped to maintain tight ZO-1 and ZO-2 expression compared with the high-fat diet group (p < 0.05), but did not restore ZO-1 or ZO-2 expression compared with chow-fed mice. Mice fed a high-fat diet ± probiotics had significant steatosis development compared with chow-fed mice (p < 0.05); steatosis was less severe in the probiotics group compared with the high-fat diet group. Hepatic triglyceride concentration was higher in mice fed a high-fat diet ± probiotics compared with the chow group (p < 0.05), and was lower in the probiotics group compared with the high-fat diet group (p < 0.05). Compared with chow-fed mice, serum glucose, cholesterol concentration and the activity of alanine transaminase were higher (p < 0.05), whereas serum triglyceride concentration was lower (p < 0.05) in mice fed a high-fat diet ± probiotics. Conclusions: Supplementation with a multispecies probiotic formulation helped to maintain tight-junction proteins ZO-1 and ZO-2, and reduced hepatic triglyceride concentration compared with a high-fat diet alone. PMID:27366215
Arrazuria, Rakel; Elguezabal, Natalia; Juste, Ramon A.; Derakhshani, Hooman; Khafipour, Ehsan
2016-01-01
Mycobacterium avium subspecies paratuberculosis (MAP) the causative agent of paratuberculosis, produces a chronic granulomatous inflammation of the gastrointestinal tract of ruminants. It has been recently suggested that MAP infection may be associated with dysbiosis of intestinal microbiota in ruminants. Since diet is one of the key factors affecting the balance of microbial populations in the digestive tract, we intended to evaluate the effect of MAP infection in a rabbit model fed a regular or high fiber diet during challenge. The composition of microbiota of the cecal content and the sacculus rotundus was studied in 20 New Zealand white female rabbits. The extracted DNA was subjected to paired-end Illumina sequencing of the V3-V4 hypervariable region of the 16S rRNA gene for microbiota analysis. Microbial richness (Chao1) in the cecal content was significantly increased by MAP infection in regular diet rabbits (p = 0.0043) and marginally increased (p = 0.0503) in the high fiber group. Analysis of beta-diversity showed that MAP infection produces deeper changes in the microbiota of sacculus rotundus than in the cecal content. A lower abundance of Proteobacteria in the cecal content of infected animals fed the high fiber diet and also lower abundance of Bacteroidetes in the sacculus rotundus of infected animals fed the regular diet were observed. Based on OPLS-DA analysis, we observed that some bacteria repeatedly appear to be positively associated with infection in different samples under different diets (families Dehalobacteriaceae, Coriobacteriaceae, and Mogibacteriaceae; genus Anaerofustis). The same phenomenon was observed with some of the bacteria negatively associated with MAP infection (genera Anaerostipes and Coprobacillus). However, other groups of bacteria (Enterobacteriaceae family and ML615J-28 order) were positively associated with infection in some circumstances and negatively associated with infection in others. Data demonstrate that MAP infection
Ledee, Dolena R.; Kajimoto, Masaki; O'Kelly Priddy, Colleen M.; Olson, Aaron K.; Isern, Nancy; Robillard-Frayne, Isabelle; Des Rosiers, Christine
2015-01-01
Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory support for infants and children with postoperative cardiopulmonary failure. Nutritional support is mandatory during ECMO although specific actions for substrates on the heart have not been delineated. Prior work shows that enhancing pyruvate oxidation promotes successful weaning from ECMO. Accordingly, we tested the hypothesis that prolonged systemic pyruvate supplementation activates pyruvate oxidation in an immature swine model in vivo. Twelve male mixed-breed Yorkshire piglets (age 30–49 days) received systemic infusion of either normal saline (group C) or pyruvate (group P) during the final 6 h of 8 h of ECMO. Over the final hour, piglets received [2-13C] pyruvate, as a reference substrate for oxidation, and [13C6]-l-leucine, as an indicator for amino acid oxidation and protein synthesis. A significant increase in lactate and pyruvate concentrations occurred, along with an increase in the absolute concentration of the citric acid cycle intermediates. An increase in anaplerotic flux through pyruvate carboxylation in group P occurred compared with no change in pyruvate oxidation. Additionally, pyruvate promoted an increase in the phosphorylation state of several nutrient-sensitive enzymes, like AMP-activated protein kinase and acetyl CoA carboxylase, suggesting activation for fatty acid oxidation. Pyruvate also promoted O-GlcNAcylation through the hexosamine biosynthetic pathway. In conclusion, although prolonged pyruvate supplementation did not alter pyruvate oxidation, it did elicit changes in nutrient- and energy-sensitive pathways. Therefore, the observed results support the further study of pyruvate and its downstream effect on cardiac function. PMID:25910802
NASA Astrophysics Data System (ADS)
Rung-Arunwan, Tawat; Siripunvaraporn, Weerachai
2010-11-01
We use 2-D magnetotelluric (MT) problems as a feasibility study to demonstrate that 3-D MT problems can be solved with a direct solver, even on a standard single processor PC. The scheme used is a hierarchical domain decomposition (HDD) method in which a global computational domain is uniformly split into many smaller non-overlapping subdomains. To make it more efficient, two modifications are made to the standard HDD method. Instead of three levels as in the standard HDD method, we classify the unknowns into four classes: the interiors, the horizontal interfaces, the vertical interfaces and the intersections. Four sets of smaller systems of equations are successively solved with a direct method (an LU factorization). The separation significantly reduces the large memory requirements of a direct solver. It also reduces the CPU time to almost half that of the standard HDD method although it is still slower than the conventional finite difference (FD) method. To further enhance the speed of the code, a red-black ordering is applied to solve the horizontal and vertical interface reduced systems. Numerical experiments on a 2-D MT problem of a given size running on a single processor machine shows that CPU time and memory used are almost constant for any resistivity models, frequencies and modes. This is a clear advantage of our algorithm and is of particular importance if the method is applied to 3-D problems. We show that our new method results in reductions in both memory usage and CPU time for large enough domains when compared to the standard FD and HDD schemes. In addition, we also introduce a `memory minimization map', a graphical tool we can use instead of trial-and-error to pre-select the optimal size of subdomains, which yield the best performance in both CPU time and memory even running on a serial machine.
Lei, Bingli; Huang, Shengbiao; Qiao, Min; Li, Tianyun; Wang, Zijian
2008-01-01
An accidental discharge of nitrobenzene happened in November 2005 in the Songhua River, China. The AQUATOX model was modified and adapted to simulate the time-dependent nitrobenzene distribution in this multimedia aquatic system and its potential ecological impacts. Nitrobenzene concentrations in flowing water, sediment, and biota were predicted. Based on the initial concentrations of nitrobenzene observed in the field during the accidental discharge, that is, 0.167-1.47 mg/L at different river segments, the predicted water concentrations of nitrobenzene would be lower than 0.02 and 0.002 mg/L after twenty days and one month, respectively. Both model prediction and field observation were in good agreement. The predicted nitrobenzene concentrations in sediments and aquatic organisms would be lower than 0.025 and 0.002 mg/kg, respectively, after two months. Among the environmental factors affecting nitrobenzene concentrations in water, inflow water dilution, water temperature, and initial concentration were the most important, by sensitivity analysis. Comparing the perturbed simulation and control simulation, the biomass changes for diatoms and mussel were significantly affected, whereas, no influence on other organisms could be predicted. Therefore the results indicated that nitrobenzene pollution in the Songhua River should have a limited impact on the benthos community. PMID:18814570
Zhang, He; Li, Jingchao; Sun, Wenjie; Hu, Yong; Zhang, Guofu; Shen, Mingwu; Shi, Xiangyang
2014-01-01
Endometriosis is defined as the presence of endometrial tissue outside the uterine, which may affect nearly 60% of women in reproductive age. Deep infiltrating endometriosis (DIE) defined as an endometriotic lesion penetrating into the retroperitoneal space or the wall of the pelvic organs to a depth of at least 5 mm represents the most diagnostic challenge. Herein, we reported the use of hyaluronic acid (HA)-modified magnetic iron oxide nanoparticles (HA-Fe3O4 NPs) for magnetic resonance (MR) imaging of endometriotic lesions in the rodent model. Sixteen endometriotic lesions were surgically induced in eight rats by autologous transplantation. Four weeks after lesion induction, three rats were scanned via MR imaging after tail vein injection of the HA-Fe3O4 NPs. Accordingly, the remaining five mice were sacrificed in the corresponding time points. The ectopic uterine tissues (EUTs) were confirmed by histological analysis. Quantification of Fe in the EUT was also performed by inductively coupled plasma-optical emission spectroscopy. Our results showed that by using the HA-Fe3O4 NPs, the EUTs were able to be visualized via T2-weighted MR imaging at 2 hours post injection, corroborating the Prussian blue staining results. The developed HA-Fe3O4 NPs could be used as negative contrast agents for sensitively detecting endometriosis in a mouse model and may be applied for future hyperthermia treatment of endometriosis. PMID:24722347
NASA Astrophysics Data System (ADS)
Tian, Yong; Xia, Bizhong; Sun, Wei; Xu, Zhihui; Zheng, Weiwei
2014-12-01
Accurate estimation for the state of charge (SOC) is one of the most important aspects of a battery management system (BMS) in electric vehicles (EVs) as it provides drivers with the EVs' remaining range. However, it is difficult to get an accurate SOC, because its value cannot be directly measured and is affected by various factors, such as the operating temperature, current rate and cycle number. In this paper, a modified equivalent circuit model is presented to include the impact of different current rates and SOCs on the battery internal resistance, and the impact of different temperatures and current rates on the battery capacity. Besides, a linear-averaging method is presented to calculate the internal resistance and practical capacity correction factors according to data collected from the experimental bench and saved as look-up tables. The unscented Kalman filter (UKF) algorithm is then introduced to estimate the SOC according to the presented model. Experiments based on actual urban driving cycles are carried out to evaluate the performance of the presented method by comparing with two existed methods. Experimental results show that the proposed method can reduce the computation cost and improve the SOC estimation accuracy simultaneously.
Guillard, V; Couvert, O; Stahl, V; Hanin, A; Denis, C; Huchet, V; Chaix, E; Loriot, C; Vincelot, T; Thuault, D
2016-09-01
Predicting microbial safety of fresh products in modified atmosphere packaging implies to take into account the dynamic of O2, CO2 and N2 exchanges in the system and its effect on microbial growth. In this paper a mechanistic model coupling gas transfer and predictive microbiology was validated using dedicated challenge-tests performed on poultry meat, fresh salmon and processed cheese, inoculated with either Listeria monocytogenes or Pseudomonas fluorescens and packed in commercially used packaging materials (tray + lid films). The model succeeded in predicting the relative variation of O2, CO2 and N2 partial pressure in headspace and the growth of the studied microorganisms without any parameter identification. This work highlighted that the respiration of the targeted microorganism itself and/or that of the naturally present microflora could not be neglected in most of the cases, and could, in the particular case of aerobic microbes contribute to limit the growth by removing all residual O2 in the package. This work also confirmed the low sensitivity of L. monocytogenes toward CO2 while that of P. fluorescens permitted to efficiently prevent its growth by choosing the right combination of packaging gas permeability value and initial % of CO2 initially flushed in the pack. PMID:27217358
Quasi-integrability in the modified defocusing non-linear Schrödinger model and dark solitons
NASA Astrophysics Data System (ADS)
Blas, H.; Zambrano, M.
2016-03-01
The concept of quasi-integrability has been examined in the context of deformations of the defocusing non-linear Schrödinger model (NLS). Our results show that the quasi-integrability concept, recently discussed in the context of deformations of the sine-Gordon, Bullough-Dodd and focusing NLS models, holds for the modified defocusing NLS model with dark soliton solutions and it exhibits the new feature of an infinite sequence of alternating conserved and asymptotically conserved charges. For the special case of two dark soliton solutions, where the field components are eigenstates of a space-reflection symmetry, the first four and the sequence of even order charges are exactly conserved in the scattering process of the solitons. Such results are obtained through analytical and numerical methods, and employ adaptations of algebraic techniques used in integrable field theories. We perform extensive numerical simulations and consider the scattering of dark solitons for the cubic-quintic NLS model with potential V=η {I}^2-in /6{I}^3 and the saturable type potential satisfying [InlineEquation not available: see fulltext.], with a deformation parameter ɛ ∈ [InlineMediaObject not available: see fulltext.] and I = | ψ|2. The issue of the renormalization of the charges and anomalies, and their (quasi)conservation laws are properly addressed. The saturable NLS supports elastic scattering of two soliton solutions for a wide range of values of { η, ɛ, q}. Our results may find potential applications in several areas of non-linear science, such as the Bose-Einstein condensation.
NASA Astrophysics Data System (ADS)
Duc-Toan, Nguyen; Tien-Long, Banh; Dong-Won, Jung; Seung-Han, Yang; Young-Suk, Kim
2012-02-01
In order to predict correctly stress-strain curve for tensile tests at elevated and cooling temperatures, a modification of a Johnson-Cook (J-C) model and a new method to determine (J-C) material parameters are proposed. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick and Voce's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. An FEM tensile test simulation based on the isotropic hardening model for metal sheet at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code. The simulation results at elevated temperatures were firstly presented and then compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation. The modified (J-C) model showed the good comparability between the simulation results and the corresponding experiments.
Wang, Hainan; Thiele, Alexander; Pilon, Laurent
2013-11-15
This paper presents a generalized modified Poisson–Nernst–Planck (MPNP) model derived from first principles based on excess chemical potential and Langmuir activity coefficient to simulate electric double-layer dynamics in asymmetric electrolytes. The model accounts simultaneously for (1) asymmetric electrolytes with (2) multiple ion species, (3) finite ion sizes, and (4) Stern and diffuse layers along with Ohmic potential drop in the electrode. It was used to simulate cyclic voltammetry (CV) measurements for binary asymmetric electrolytes. The results demonstrated that the current density increased significantly with decreasing ion diameter and/or increasing valency |z_{i}| of either ion species. By contrast, the ion diffusion coefficients affected the CV curves and capacitance only at large scan rates. Dimensional analysis was also performed, and 11 dimensionless numbers were identified to govern the CV measurements of the electric double layer in binary asymmetric electrolytes between two identical planar electrodes of finite thickness. A self-similar behavior was identified for the electric double-layer integral capacitance estimated from CV measurement simulations. Two regimes were identified by comparing the half cycle period τ_{CV} and the “RC time scale” τ_{RC} corresponding to the characteristic time of ions’ electrodiffusion. For τ_{RC} ← τ_{CV}, quasi-equilibrium conditions prevailed and the capacitance was diffusion-independent while for τ_{RC} → τ_{CV}, the capacitance was diffusion-limited. The effect of the electrode was captured by the dimensionless electrode electrical conductivity representing the ratio of characteristic times associated with charge transport in the electrolyte and that in the electrode. The model developed here will be useful for simulating and designing various practical electrochemical, colloidal, and biological systems for a wide range of applications.
2013-01-01
Background Social and structural factors are now well accepted as determinants of HIV vulnerabilities. These factors are representative of social, economic, organizational and political inequities. Associated with an improved understanding of multiple levels of HIV risk has been the recognition of the need to implement multi-level HIV prevention strategies. Prevention sciences research and programming aiming to decrease HIV incidence requires epidemiologic studies to collect data on multiple levels of risk to inform combination HIV prevention packages. Discussion Proximal individual-level risks, such as sharing injection devices and unprotected penile-vaginal or penile-anal sex, are necessary in mediating HIV acquisition and transmission. However, higher order social and structural-level risks can facilitate or reduce HIV transmission on population levels. Data characterizing these risks is often far more actionable than characterizing individual-level risks. We propose a modified social ecological model (MSEM) to help visualize multi-level domains of HIV infection risks and guide the development of epidemiologic HIV studies. Such a model may inform research in epidemiology and prevention sciences, particularly for key populations including men who have sex with men (MSM), people who inject drugs (PID), and sex workers. The MSEM builds on existing frameworks by examining multi-level risk contexts for HIV infection and situating individual HIV infection risks within wider network, community, and public policy contexts as well as epidemic stage. The utility of the MSEM is demonstrated with case studies of HIV risk among PID and MSM. Summary The MSEM is a flexible model for guiding epidemiologic studies among key populations at risk for HIV in diverse sociocultural contexts. Successful HIV prevention strategies for key populations require effective integration of evidence-based biomedical, behavioral, and structural interventions. While the focus of epidemiologic
NASA Astrophysics Data System (ADS)
Robelin, Christian; Chartrand, Patrice
2007-12-01
A theoretical model for the density of multicomponent inorganic liquids based on the modified quasichemical model has been presented in a previous article. In the present article, this model is applied to the NaF-AlF3-CaF2-Al2O3 electrolyte. By introducing in the Gibbs energy of the liquid phase, temperature-dependent molar volume expressions for the pure fluorides and oxides, and pressure-dependent excess parameters for the binary (and sometimes higher-order) interactions, it is possible to reproduce, and eventually predict, the molar volume and the density of the multicomponent liquid phase using standard interpolation methods. All available density data for the NaF-AlF3-CaF2-Al2O3 liquid were collected and critically evaluated, and optimized pressure-dependent model parameters have been found. This new volumetric model can be used with Gibbs energy minimization software, to calculate the molar volume and the density of cryolite-based melts used for the electroreduction of alumina in Hall-Héroult cells.
NASA Astrophysics Data System (ADS)
Numedahl, Paul Joseph
The purpose of this study was to gain an understanding of the effects an interactive-constructive teaching and learning approach, the use of children's literature in science teaching and parental involvement in elementary school science had on student achievement in and attitudes toward science. The study was done in the context of Science PALS, a professional development program for inservice teachers. An existing model for interactive-constructive elementary science was modified to include five model variables; student achievement, student attitudes, teacher perceptions, teacher performance, and student perceptions. Data were collected from a sample of 12 teachers and 260 third and fourth grade students. Data analysis included two components, (1) the examination of relationships between teacher performance, teacher perceptions, student achievement and attitudes, and (2) the verification of a model using path analysis. Results showed a significant correlation between teacher perceptions and student attitude. However, only one model path was significant; thus, the model could not be verified. Further examination of the significant model path was completed. Study findings included: (1) Constructivist notions of teaching and learning may cause changes in the traditional role relationship between teachers and students leading to negative student attitudes. (2) Children who perceive parental interest toward science education are likely to have a positive attitude toward science learning, increased self-confidence in science and possess accurate ideas concerning the nature of science. (3) Students who perceive science instruction as relevant are likely to possess a positive attitude toward science learning, increased self-confidence in science, and possess accurate ideas concerning the nature of science. (4) Students who perceive their classroom as aligning with constructivist principles are likely to possess a positive attitude toward science, an increased self
NASA Technical Reports Server (NTRS)
Barna, P. S.
1996-01-01
Numerous tests were performed on the original Acoustic Quiet Flow Facility Three-Dimensional Model Tunnel, scaled down from the full-scale plans. Results of tests performed on the original scale model tunnel were reported in April 1995, which clearly showed that this model was lacking in performance. Subsequently this scale model was modified to attempt to possibly improve the tunnel performance. The modifications included: (a) redesigned diffuser; (b) addition of a collector; (c) addition of a Nozzle-Diffuser; (d) changes in location of vent-air. Tests performed on the modified tunnel showed a marked improvement in performance amounting to a nominal increase of pressure recovery in the diffuser from 34 percent to 54 percent. Results obtained in the tests have wider application. They may also be applied to other tunnels operating with an open test section not necessarily having similar geometry as the model under consideration.
Chiang, Shen-Shih; Liu, Chin-Feng; Ku, Ting-Wei; Mau, Jeng-Leun; Lin, Hsin-Tang; Pan, Tzu-Ming
2011-04-27
By introducing aprN into Lactococcus lactis NZ9000, the genetically modified L. lactis NZ9000/pNZPNK successfully expressed the nattokinase. The safety assessment of this novel strain was based on allergenicity of pepsin digestion stability and murine model serologic identity. Subjecting to the GM strain and host to pepsin digestion, the soluble fractions and cell debris were fast degraded completely. Feeding with ovalbumin resulted in significantly higher production of IgG1 and IgE as compared to that of L. lactis NZ9000/pNZPNK or L. lactis NZ9000. Further, the serum IgG2a level increased dose-dependently at week 2 and induced immune reaction toward Th1 pathway. Secretion of cytokines IL-4 and IL-10 fed with lactococci was significantly lower than that of the OVA group. L. lactis NZ9000/pNZPNK did not increase the proliferation of type 2 helper T cells in spleen or induce allergenicity in BALB/c mice. On the basis of the results, the new GM lactic acid bacterium is regarded as safe to use. PMID:21410287
Jones, Sarah; Asokanathan, Catpagavalli; Kmiec, Dorota; Irvine, June; Fleck, Roland; Xing, Dorothy; Moore, Barry; Parton, Roger; Coote, John
2014-01-01
Protein-coated microcrystals (PCMCs) were investigated as potential vaccine formulations for a range of model antigens. Presentation of antigens as PCMCs increased the antigen-specific IgG responses for all antigens tested, compared to soluble antigens. When compared to conventional aluminium-adjuvanted formulations, PCMCs modified with calcium phosphate (CaP) showed enhanced antigen-specific IgG responses and a decreased antigen-specific IgG1:IgG2a ratio, indicating the induction of a more balanced Th1/Th2 response. The rate of antigen release from CaP PCMCs, in vitro, decreased strongly with increasing CaP loading but their immunogenicity in vivo was not significantly different, suggesting the adjuvanticity was not due to a depot effect. Notably, it was found that CaP modification enhanced the phagocytosis of fluorescent antigen-PCMC particles by J774.2 murine monocyte/macrophage cells compared to soluble antigen or soluble PCMCs. Thus, CaP PCMCs may provide an alternative to conventional aluminium-based acellular vaccines to provide a more balanced Th1/Th2 immune response. PMID:24120484
Testing the 2.2% HSR Reference H Model with a Modified Wing Planform in the NTF
NASA Technical Reports Server (NTRS)
Owens, Lewis R., Jr.; Wahls, Richard A.; Hamner, Marvine P.
1999-01-01
The HSR program moved into phase two with the selection of a new airplane configuration, the Technology Concept Airplane (TCA). The TCA was designed based on the experiences gained while investigating both the Reference H and the Arrow Wing configurations in different wind tunnels and CFD studies. Part of that investigation included performing extensive high Reynolds number testing on the Reference H configuration in the NTF to provide data for predicting full-scale flight performance, as well as developing techniques for testing these types of configurations in the NTF. With the selection of the TCA configuration, a smaller investigation was designed to examine whether or not the scaling characteristics of the TCA configuration are similar to those observed for the Reference H configuration. This presentation will include a description of the 2.2% Modified Reference H model used in this investigation (highlighting the similarities and the differences when compared to the TCA configuration), the testing objectives, and some preliminary findings that are relevant to the current high-lift system.
NASA Astrophysics Data System (ADS)
Thohura, Sharaban; Molla, Md. Mamun; Sarker, M. M. A.
2016-07-01
A study on the natural convection flow of non-Newtonian fluid along a vertical thin cylinder with constant wall temperature using modified power law viscosity model has been done. The basic equations are transformed to non dimensional boundary layer equations and the resulting systems of nonlinear partial differential equations are then solved employing marching order implicit finite difference method. The evolution of the surface shear stress in terms of local skin-friction, the rate of heat transfer in terms of local Nusselt number, velocity and temperature profiles for shear thinning as well as shear-thickening fluid considering the different values of Prandtl number have been focused. For the Newtonian fluids the present numerical results are compared with available published results which show a good agreement indeed. From the results it can be concluded that, at the leading edge, a Newtonian-like solution exists as the shear rate is not large enough to trigger non-Newtonian effects. Non-Newtonian effects can be found when the shear-rate increases beyond a threshold value.
Jones, Sarah; Asokanathan, Catpagavalli; Kmiec, Dorota; Irvine, June; Fleck, Roland; Xing, Dorothy; Moore, Barry; Parton, Roger; Coote, John
2014-07-16
Protein-coated microcrystals (PCMCs) were investigated as potential vaccine formulations for a range of model antigens. Presentation of antigens as PCMCs increased the antigen-specific IgG responses for all antigens tested, compared to soluble antigens. When compared to conventional aluminium-adjuvanted formulations, PCMCs modified with calcium phosphate (CaP) showed enhanced antigen-specific IgG responses and a decreased antigen-specific IgG1:IgG2a ratio, indicating the induction of a more balanced Th1/Th2 response. The rate of antigen release from CaP PCMCs, in vitro, decreased strongly with increasing CaP loading but their immunogenicity in vivo was not significantly different, suggesting the adjuvanticity was not due to a depot effect. Notably, it was found that CaP modification enhanced the phagocytosis of fluorescent antigen-PCMC particles by J774.2 murine monocyte/macrophage cells compared to soluble antigen or soluble PCMCs. Thus, CaP PCMCs may provide an alternative to conventional aluminium-based acellular vaccines to provide a more balanced Th1/Th2 immune response. PMID:24120484
NASA Astrophysics Data System (ADS)
Shabat, Yael Ben; Shitzer, Avraham; Fiala, Dusan
2014-08-01
Wind chill equivalent temperatures (WCETs) were estimated by a modified Fiala's whole body thermoregulation model of a clothed person. Facial convective heat exchange coefficients applied in the computations concurrently with environmental radiation effects were taken from a recently derived human-based correlation. Apart from these, the analysis followed the methodology used in the derivation of the currently used wind chill charts. WCET values are summarized by the following equation: Results indicate consistently lower estimated facial skin temperatures and consequently higher WCETs than those listed in the literature and used by the North American weather services. Calculated dynamic facial skin temperatures were additionally applied in the estimation of probabilities for the occurrence of risks of frostbite. Predicted weather combinations for probabilities of "Practically no risk of frostbite for most people," for less than 5 % risk at wind speeds above 40 km h-1, were shown to occur at air temperatures above -10 °C compared to the currently published air temperature of -15 °C. At air temperatures below -35 °C, the presently calculated weather combination of 40 km h-1/-35 °C, at which the transition for risks to incur a frostbite in less than 2 min, is less conservative than that published: 60 km h-1/-40 °C. The present results introduce a fundamentally improved scientific basis for estimating facial skin temperatures, wind chill temperatures and risk probabilities for frostbites over those currently practiced.
Gomes, Eduardo D; Mendes, Sofia S; Leite-Almeida, Hugo; Gimble, Jeffrey M; Tam, Roger Y; Shoichet, Molly S; Sousa, Nuno; Silva, Nuno A; Salgado, António J
2016-10-01
Spinal Cord Injury (SCI) is a highly incapacitating condition for which there is still no cure. Current clinical approaches are mainly based on palliative care, so there is a need to find possible treatments to SCI. Cellular transplantation is regarded with great expectation due to the therapeutic potential of cells such as Adipose tissue-derived Stromal/Stem Cells (ASCs) or Olfactory Ensheathing Cells (OECs). Both are accessible sources and present positive paracrine and cell-to-cell interactions, previously reported by our group. Additionally, biomaterials such as hydrogels have been applied in SCI repair with promising results. We propose to combine a GRGDS-modified gellan gum hydrogel with ASCs and OECs in order to promote SCI regeneration. In vitro, ASCs and OECs could be co-cultured within GG-GRGDS hydrogels inducing a more robust neurite outgrowth when compared to controls. In vivo experiments in a hemisection SCI rat model revealed that the administration of ASCs and OECs encapsulated in a GG-GRGDS hydrogel led to significant motor improvements when compared to both control (SCI) and hydrogel alone (GG-GRGDS) groups. This was accompanied by a decreased infiltration of inflammatory cells and astrocytes, and by an increased intensity of neurofilament. These results suggest evident gains induced by the encapsulation of ASCs and OECs in GG-GRGDS based hydrogels. PMID:27505621
NASA Astrophysics Data System (ADS)
Morandi, Maria T.; Daisey, Joan M.; Lioy, Paul J.
A modified factor analysis/multiple regression (FA/MR) receptor-oriented source apportionment model has been developed which permits application of FA/MR statistical methods when some of the tracers are not unique to an individual source type. The new method uses factor and regression analyses to apportion non-unique tracer ambient concentrations in situations where there are unique tracers for all sources contributing to the non-unique tracer except one, and ascribes the residual concentration to that source. This value is then used as the source tracer in the final FA/MR apportionment model for ambient paniculate matter. In addition, factor analyses results are complemented with examination of regression residuals in order to optimize the number of identifiable sources. The new method has been applied to identify and apportion the sources of inhalable particulate matter (IPM; D5015 μm), Pb and Fe at a site in Newark, NJ. The model indicated that sulfate/secondary aerosol contributed an average of 25.8 μ -3 (48%) to IPM concentrations, followed by soil resuspension (8.2 μ -3 or 15%), paint spraying/paint pigment (6.7/gmm -3or 13%), fuel oil burning/space heating (4.3 μ -3 or 8 %), industrial emissions (3.6 μm -3 or 7 %) and motor vehicle exhaust (2.7 μ -3 or 15 %). Contributions to ambient Pb concentrations were: motor vehicle exhaust (0.16μm -3or 36%), soil resuspension (0.10μm -3 or 24%), fuel oil burning/space heating (0.08μm -3or 18%), industrial emissions (0.07 μ -3 or 17 %), paint spraying/paint pigment (0.036 μm -3or 9 %) and zinc related sources (0.022 μ -3 or 5 %). Contributions to ambient Fe concentrations were: soil resuspension (0.43μ -3or 51%), paint spraying/paint pigment (0.28 μm -3or 33 %) and industrial emissions (0.15 μ -3or 18 %). The models were validated by comparing partial source profiles calculated from modeling results with the corresponding published source emissions composition.
Taddei, Laura
2015-02-01
Most cosmological constraints on modified gravity are obtained assuming that the cosmic evolution was standard ΛCDM in the past and that the present matter density and power spectrum normalization are the same as in a ΛCDM model. Here we examine how the constraints change when these assumptions are lifted. We focus in particular on the parameter Y (also called G{sub eff}) that quantifies the deviation from the Poisson equation. This parameter can be estimated by comparing with the model-independent growth rate quantity fσ{sub 8}(z) obtained through redshift distortions. We reduce the model dependency in evaluating Y by marginalizing over σ{sub 8} and over the initial conditions, and by absorbing the degenerate parameter Ω{sub m,0} into Y. We use all currently available values of fσ{sub 8}(z). We find that the combination Y-circumflex =YΩ{sub m,0}, assumed constant in the observed redshift range, can be constrained only very weakly by current data, Y-circumflex =0.28{sub −0.23}{sup +0.35} at 68% c.l. We also forecast the precision of a future estimation of Y-circumflex in a Euclid-like redshift survey. We find that the future constraints will reduce substantially the uncertainty, Y-circumflex =0.30{sub −0.09}{sup +0.08} , at 68% c.l., but the relative error on Y-circumflex around the fiducial remains quite high, of the order of 30%. The main reason for these weak constraints is that Y-circumflex is strongly degenerate with the initial conditions, so that large or small values of Y-circumflex are compensated by choosing non-standard initial values of the derivative of the matter density contrast. Finally, we produce a forecast of a cosmological exclusion plot on the Yukawa strength and range parameters, which complements similar plots on laboratory scales but explores scales and epochs reachable only with large-scale galaxy surveys. We find that future data can constrain the Yukawa strength to within 3% of the Newtonian one if the range is around a few
NASA Astrophysics Data System (ADS)
Sikdar, Debashis
Polymer clay nanocomposite (PCN) is a novel composite material which is synthesized by mixing expansive clay minerals with polymeric materials in the nanometer length scale. In this research, we have found the mechanisms responsible for enhanced mechanical properties in PCN in comparison to pristine polymer. Photoacoustic (PA) Fourier transform infrared spectroscopy (FTIR) of PCN shows that there are only nonbonded interactions between constituents of PCN. Interaction energies are a measure of interactions between different constituents of composite materials. For quantitative evaluation of nonbonded interactions between constituents of PCN, molecular dynamics (MD) simulations using representative intercalated models of PCN are constructed in an innovative way by combining experimental (X-ray diffraction (XRD) and FTIR) and modeling results. The resulting PCN models are used to calculate interaction energies between the constituents of PCN using MD simulation. The results show that the organic modifier has a significant role on the interactions between different constituents of PCN. Results obtained from nanomechanical experiments of those PCN samples synthesized with identical polymer and clay but different organic modifiers show that the organic modifier has a major influence on the crystallinity and nanomechanical properties of PCN, and lower the crystallinity of polymer, the higher is the elastic modulus of PCNs. MD simulations on these PCN samples show that interactions between intercalated polymer and organic modifiers are key for altering crystallinity and nanomechanical properties of PCNs. PA-FTIR tests on PCNs show that organic modifiers alter the crystal structure of clay. This work has led us proposing a new "altered phase" model for PCNs. Further MD-result, and nanomechanical experiments shows that crystallinity and interactions between constituents of PCN can be tailored to a significant extent by varying the backbone chain length of modifier. To
NASA Astrophysics Data System (ADS)
Martin, Robert David, Jr.
C-band scatterometer measurements were made of a tallgrass prairie in an attempt to determine the degree of correlation between (1) the backscattering coefficient (sigma_sp{rm tr}{ circ}) and different expressions of soil moisture and (2) the backscattering coefficient and various canopy parameters. The findings of this study support those made in previous studies in terms of the optimum polarization and view angle selection for soil moisture work (i.e., near-nadir view angles and HH and VV polarizations). In contrast to previous studies, view angles of 30 ^circ and 45^circ also produced strong correlations with soil moisture. A moderately strong correlation and partial correlation was found between sigma_sp{rm tr}{circ} and leaf water potential, indicating some capability of C-band measurements to detect extremes in the water status of prairie vegetation under shallow soil conditions. Also, site differences due to burn treatments appeared to cause significant differences in the sensitivity of sigma_sp{ rm tr}{circ} to soil moisture. In a second study, the disk model developed by Drs. Eom and Fung was tested against a set of field measurements of sigma_sp{rm tr} {circ} from a crop of sunflowers. The model overestimated sigma_sp{ rm tr}{circ} at early growth stages, but decreased the overestimate as the crop matured. The author modified the model to accommodate canopies with non-uniform, continuous leaf angle distributions. The modification altered the shape of the response curve for predicted sigma_sp{rm tr }{circ} versus view angle, but failed to reduce the overestimate in the early growth states. Additional modifications (e.g., incorporating row structure information) may be necessary. A new model, called the Projected Disk Component Model (PDCM), was developed to help explain the behavior of the modified disk model (MDM). By reducing several types of theoretical disk canopies to a simple, quantitative measure of their constituent horizontal and vertical
Asher, J.H. Jr.; Harrison, R.W.; Morell, R.; Carey, M.L.
1996-06-15
Waardenburg syndrome type 1 is caused by mutations in PAX3. Over 50 human PAX3 mutations that lead to hearing, craniofacial, limb, and pigmentation anomalies have been identified. A PAX3 mutant allele, segregating in a family, can show reduced penetrance and variable expressivity that cannot be explained by the nature of the mutation alone. The Mus musculus Pax3 mutation Sp{sup d} (Splotch-delayed, Pax3{sup Sd}p), coisogenic on the C57BL/6J (B{sub 6}) genetic background, produces in heterozygotes a white belly spot with 100% penetrance and very few other anomalies. By contrast, many Sp{sup d}/+ BC{sub 1} progeny [F{sub 1} {female} Sp{sup d}/+ ({female} Sp{sup d}/+ B{sub 6} x {male} +/+ Mus spretus) x {male} +/+ B{sub 6}] exhibit highly variable craniofacial and pigmentary anomalies. Of the BC{sub 1} Sp{sup d}/+ progeny, 23.9% are estimated to be nonviable, and 32.1% are nonpenetrant for the white belly spot. The penetrance and expressivity of the Sp{sup d}/+ genotype are controlled in part by the genetic background and the sex of the individual. A minimum of two genes interact with Sp{sup d} to influence the craniofacial features of these mice. One of these genes may be either X-linked or sex-influenced, while the other is autosomal. The A-locus (Agouti) or a gene closely linked to A also plays a role in determining craniofacial features. At least one additional gene, possibly the A-locus or a gene linked to A, interacts with Sp{sup d} and determines the presence and size of the white belly spot. The viability of BC{sub 1} mice is influenced by at least three factors: Sp{sup d}, A-locus alleles or a gene closely linked to the A-locus, and the sex of the mouse. The BC{sub 1} mice provide an opportunity to identify genes that interact with and modify the expression of Pax3 and serve as a model to identify the genes that modify the expression of human PAX3 mutations. 65 refs., 3 figs., 6 tabs.
The methods described in the report can be used with the modified N.R.C. version of the U.S.G.S. Solute Transport Model to predict the concentration of chemical parameters in a contaminant plume. The two volume report contains program documentation and user's manual. The program ...
ERIC Educational Resources Information Center
Schneller, A. J.; Johnson, B.; Bogner, F. X.
2015-01-01
This paper describes the validation process of measuring children's attitudes and values toward the environment within a Mexican sample. We applied the Model of Ecological Values (2-MEV), which has been shown to be valid and reliable in 20 countries, including one Spanish speaking culture. Items were initially modified to fit the regional…
Technology Transfer Automated Retrieval System (TEKTRAN)
Salmonella spp. is a microorganism of concern, on a global basis, for raw shrimp. This research modeled the impact of vapor thymol concentration (0, 0.8 and 1.6 mg/l), storage temperature (8, 12 and 16 degree C) and modified atmosphere packaging (0.04 and 59.5 percent CO2) against the growth behavio...
ERIC Educational Resources Information Center
Eliasson, Ann-Christin; Shaw, Karin; Ponten, Eva; Boyd, Roslyn; Krumlinde-Sundholm, Lena
2009-01-01
The objective of the study was to investigate the feasibility of modified constraint-induced (CI) therapy provided in a 2-week day-camp model with and without intramuscular botulinum toxin type A (BoNT-A) injections for children with congenital cerebral palsy. Sixteen children with congenital hemiplegia, Manual Ability Classification System (MACS)…
NASA Astrophysics Data System (ADS)
Yang, Wonho
The Speech Processing Lab at Temple University developed an objective speech quality measure called the Modified Bark Spectral Distortion (MBSD). The MBSD uses auditory perception models derived from psychoacoustic studies. The MBSD measure extends the Bark Spectral Distortion (BSD) method by incorporating noise making threshold to differentiate audible/inaudible distortions. The performance of the MBSD was comparable to that of the ITU-T Recommendation P.861 for various coding distortions. Based on the experiments with Time Division Multiple Access (TDMA) data that contains distortions encountered in real network applications, modifications have been made to the MBSD algorithm. These are: use of the first 15 loudness components, normalization of loudness vectors, deletion of the spreading function in the noise masking threshold calculation, and use of a new cognition model based on postmasking effects. The Enhanced MBSD (EMBSD) shows significant improvement over the MBSD for TDMA data. Also, the performance of the EMBSD is better than that of the ITU-T Recommendation P.861 and Measuring Normalizing Blocks (MNB) measures for TDMA data. The performance of the EMBSD was compared to various other objective speech quality measures with the speech data including a wide range of distortion conditions. The EMBSD showed clear improvement over the MBSD and had the correlation coefficient of 0.89 for the conditions of MNRUs, codecs, tandem cases, bit errors, and frame erasures. Mean Opinion Score (MOS) has been used to evaluate objective speech quality measures. Recognizing the procedural difference between the MOS test and current objective speech quality measures, it is proposed that current objective speech quality measures should be evaluated with Degradation Mean Opinion Score (DMOS). The Pearson product-moment correlation coefficient has been the main performance parameter for evaluation of objective speech quality measures. The Standard Error of the Estimates (SEE
Hypoxia is a modifier of SMN2 splicing and disease severity in a severe SMA mouse model
Bebee, Thomas W.; Dominguez, Catherine E.; Samadzadeh-Tarighat, Somayeh; Akehurst, Kristi L.; Chandler, Dawn S.
2012-01-01
Spinal muscular atrophy (SMA) is a progressive neurodegenerative disease associated with low levels of the essential survival motor neuron (SMN) protein. Reduced levels of SMN is due to the loss of the SMN1 gene and inefficient splicing of the SMN2 gene caused by a C>T mutation in exon 7. Global analysis of the severe SMNΔ7 SMA mouse model revealed altered splicing and increased levels of the hypoxia-inducible transcript, Hif3alpha, at late stages of disease progression. Severe SMA patients also develop respiratory deficiency during disease progression. We sought to evaluate whether hypoxia was capable of altering SMN2 exon 7 splicing and whether increased oxygenation could modulate disease in a severe SMA mouse model. Hypoxia treatment in cell culture increased SMN2 exon 7 skipping and reduced SMN protein levels. Concordantly, the treatment of SMNΔ7 mice with hyperoxia treatment increased the inclusion of SMN2 exon 7 in skeletal muscles and resulted in improved motor function. Transfection splicing assays of SMN minigenes under hypoxia revealed that hypoxia-induced skipping is dependent on poor exon definition due to the SMN2 C>T mutation and suboptimal 5′ splice site. Hypoxia treatment in cell culture led to increased hnRNP A1 and Sam68 levels. Mutation of hnRNP A1-binding sites prevented hypoxia-induced skipping of SMN exon 7 and was found to bind both hnRNP A1 and Sam68. These results implicate hypoxic stress as a modulator of SMN2 exon 7 splicing in disease progression and a coordinated regulation by hnRNP A1 and Sam68 as modifiers of hypoxia-induced skipping of SMN exon 7. PMID:22763238
Mori, Kentaro; Yamamoto, Takuji; Oyama, Kazutaka; Ueno, Hideaki; Nakao, Yasuaki; Honma, Keiichirou
2008-12-01
Experience with dissection of the cavernous sinus and the temporal bone is essential for training in skull base surgery, but the opportunities for cadaver dissection are very limited. A modification of a commercially available prototype three-dimensional (3D) skull base model, made by a selective laser sintering method and incorporating surface details and inner bony structures such as the inner ear structures and air cells, is proposed to include artificial dura mater, cranial nerves, venous sinuses, and the internal carotid artery for such surgical training. The transpetrosal approach and epidural cavernous sinus surgery (Dolenc's technique) were performed on this modified model using a high speed drill or ultrasonic bone curette under an operating microscope. The model could be dissected in almost the same way as a real cadaver. The modified 3D skull base model provides a good educational tool for training in skull base surgery. PMID:19106500
NASA Technical Reports Server (NTRS)
Hunt, D.; Clinglan, J.; Salemann, V.; Omar, E.
1977-01-01
Ground static and wind tunnel test of a scale model modified T-39 airplane are reported. The configuration in the nose and replacement of the existing nacelles with tilting lift/cruise fans. The model was powered with three 14 cm diameter tip driven turbopowered simulators. Forces and moments were measured by an internal strain guage balance. Engine simulator thrust and mass flow were measured by calibrated pressure and temperature instrumentation mounted downstream of the fans. The low speed handling qualities and general aerodynamic characteristics of the modified T-39 were defined. Test variables include thrust level and thrust balance, forward speed, model pitch and sideslip angle at forward speeds, model pitch, roll, and ground height during static tests, lift/cruise fan tilt angle, flap and aileron deflection angle, and horizonal stabilizer angle. The effects of removing the landing gear, the lift/cruise fans, and the tail surfaces were also investigated.
Zhao Pengcheng; Liao Cheng; Lin Chenbin; Chang Lei; Fu Haijun
2011-10-15
A modified electron energy distribution function (EEDF) is introduced into the fluid model and its effects on the high power microwave (HPM) breakdown in air and argon are investigated. A proper numerical scheme for the finite-difference time-domain method is employed to solve the fluid model. Numerical simulations show that the HPM breakdown time in argon predicted by the fluid model with the modified EEDF agrees well with the results of Particle-in-cell-Monte Carlo collision simulations, while the Maxwellian EEDF results in faster HPM breakdown when the mean electron energy is less than 20 eV. We also confirm that the Maxwellian EEDF can be used in the fluid model for simulating the air breakdown at the low frequencies based on the reported experiments.
NASA Astrophysics Data System (ADS)
Matsangouras, I. T.; Nastos, P. T.; Pytharoulis, I.
2016-03-01
Recent research revealed that western Greece and NW Peloponnese are regions that favor prefrontal tornadic incidence. On March 25, 2009 a tornado developed approximately at 10:30 UTC near Varda village (NW Peloponnese). Tornado intensity was T4-T5 (TORRO scale) and consequently caused an economic impact of 350,000 € over the local society. The goals of this study are: (i) to analyze synoptic and remote sensing features regarding the tornado event over NW Peloponnese and (ii) to investigate the role of topography in tornadogenesis triggered under strong synoptic scale forcing over that area. Synoptic analysis was based on the European Centre for Medium-Range Weather Forecasts (ECMWF) data sets. The analysis of daily anomaly of synoptic conditions with respect to 30 years' climatology (1981-2010), was based on the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data sets. In addition, numerous remote sensing data sets were derived by the Hellenic National Meteorological Service (HNMS) weather station network in order to better interpret the examined tornado event. Finally, numerical modeling was performed using the non-hydrostatic Weather Research and Forecasting model (WRF), initialized by ECMWF gridded analyses, with telescoping nested grids that allow the representation of atmospheric circulations ranging from the synoptic scale down to the meso-scale. The two numerical experiments were performed on the basis of: (a) the presence and (b) the absence of topography (landscape), so as to determine whether the occurrence of a tornado - identified by diagnostic instability indices - could be indicated by modifying topography. The energy helicity index (EHI), the bulk Richardson number (BRN) shear, the storm-relative environmental helicity (SRH), and the maximum convective available potential energy (MCAPE, for parcels with maximum θe) were considered as principal diagnostic instability variables and
NASA Astrophysics Data System (ADS)
Ebersviller, S.; Lichtveld, K.; Sexton, K. G.; Zavala, J.; Lin, Y.-H.; Jaspers, I.; Jeffries, H. E.
2012-12-01
This is the first of a three-part study designed to demonstrate dynamic entanglements among gaseous organic compounds (VOC), particulate matter (PM), and their subsequent potential biological effects. We study these entanglements in increasingly complex VOC and PM mixtures in urban-like conditions in a large outdoor chamber. To the traditional chemical and physical characterizations of gas and PM, we added new measurements of biological effects, using cultured human lung cells as model indicators. These biological effects are assessed here as increases in cellular damage or expressed irritation (i.e., cellular toxic effects) from cells exposed to chamber air relative to cells exposed to clean air. The exposure systems permit virtually gas-only- or PM-only-exposures from the same air stream containing both gases and PM in equilibria, i.e., there are no extractive operations prior to cell exposure. Our simple experiments in this part of the study were designed to eliminate many competing atmospheric processes to reduce ambiguity in our results. Simple volatile and semi-volatile organic gases that have inherent cellular toxic properties were tested individually for biological effect in the dark (at constant humidity). Airborne mixtures were then created with each compound to which we added PM that has no inherent cellular toxic properties for another cellular exposure. Acrolein and p-tolualdehyde were used as model VOCs and mineral oil aerosol (MOA) was selected as a surrogate for organic-containing PM. MOA is appropriately complex in composition to represent ambient PM, and exhibits no inherent cellular toxic effects and thus did not contribute any biological detrimental effects on its own. Chemical measurements, combined with the responses of our biological exposures, clearly demonstrate that gas-phase pollutants can modify the composition of PM (and its resulting detrimental effects on lung cells). We observed that, even if the gas-phase pollutants are not
NASA Astrophysics Data System (ADS)
Ebersviller, S.; Lichtveld, K.; Sexton, K. G.; Zavala, J.; Lin, Y.-H.; Jaspers, I.; Jeffries, H. E.
2012-02-01
This is the first of a three-part study designed to demonstrate dynamic entanglements among gaseous organic compounds (VOC), particulate matter (PM), and their subsequent potential biological effects. We study these entanglements in increasingly complex VOC and PM mixtures in urban-like conditions in a large outdoor chamber. To the traditional chemical and physical characterizations of gas and PM, we added new measurements of gas-only- and PM-only-biological effects, using cultured human lung cells as model indicators. These biological effects are assessed here as increases in cellular damage or expressed irritation (i.e., cellular toxic effects) from cells exposed to chamber air relative to cells exposed to clean air. The exposure systems permit gas-only- or PM-only-exposures from the same air stream containing both gases and PM in equilibria, i.e., there are no extractive operations prior to cell exposure. Our simple experiments in this part of the study were designed to eliminate many competing atmospheric processes to reduce ambiguity in our results. Simple volatile and semi-volatile organic gases that have inherent cellular toxic properties were tested individually for biological effect in the dark (at constant humidity). Airborne mixtures were then created with each compound and PM that has no inherent cellular toxic properties for another cellular exposure. Acrolein and p-tolualdehyde were used as model VOCs and mineral oil aerosol (MOA) was selected as a surrogate for organic-containing PM. MOA is appropriately complex in composition to represent ambient PM, and it exhibits no inherent cellular toxic effects and thus did not contribute any biological detrimental effects on its own. Chemical measurements, combined with the responses of our biological exposures, clearly demonstrate that gas-phase pollutants can modify the composition of PM (and its resulting detrimental effects on lung cells) - even if the gas-phase pollutants are not considered likely to
Beier, David R
2016-06-01
We have previously demonstrated that a locus on proximal Chr 4 modifies disease severity in the juvenile cystic kidney (jck) mouse, a model of polycystic kidney disease (PKD) that carries a mutation of the Nek8 serine-threonine kinase. In this study, we used QTL analysis of independently constructed B6.D2 congenic lines to confirm this and showed that this locus has a highly significant effect. We constructed sub-congenic lines to more specifically localize the modifier and have determined it resides in a 3.2 Mb interval containing 28 genes. These include Invs and Anks6, which are both excellent candidates for the modifier as mutations in these genes result in PKD and both genes are known to genetically and physically interact with Nek8. However, examination of strain-specific DNA sequence and kidney expression did not reveal clear differences that might implicate either gene as a modifier of PKD severity. The fact that our high-resolution analysis did not yield an unambiguous result highlights the challenge of establishing the causality of strain-specific variants as genetic modifiers, and suggests that alternative strategies be considered. PMID:27114383
NASA Astrophysics Data System (ADS)
Adabi, Farzin; Karami, Kayoomars; Felegary, Fereshte; Azarmi, Zohre
2012-01-01
We study the entropy-corrected version of the holographic dark energy (HDE) model in the framework of modified Friedmann-Robertson-Walker cosmology. We consider a non-flat universe filled with an interacting viscous entropy-corrected HDE (ECHDE) with dark matter. Also included in our model is the case of the variable gravitational constant G. We obtain the equation of state and the deceleration parameters of the interacting viscous ECHDE. Moreover, we reconstruct the potential and the dynamics of the quintessence, tachyon, K-essence and dilaton scalar field models according to the evolutionary behavior of the interacting viscous ECHDE model with time-varying G.
Constraining Models of Modified Gravity with the Double Pulsar PSR J0737-3039A/B System
NASA Astrophysics Data System (ADS)
Iorio, Lorenzo; Ruggiero, Matteo Luca
In this paper we use ΔP = -1.772341 ± 13.153788 s between the phenomenologically determined orbital period Pb of the PSR J0737-3039A/B double pulsar system and the purely Keplerian period P(0)=2π √ {a3/G(m A+m B)} calculated with the system's parameters, determined independently of the third Kepler law itself, in order to put constraints on some models of modified gravity (f(R), Yukawa-like fifth force, MOND). The major source of error affecting ΔP is not the one in the phenomenologically measured period (δPb = 4×10-6 s), but the systematic uncertainty δP(0) in the computed Keplerian one due to the relative semimajor axis a mainly caused, in turn, by the errors in the ratio { R} of the pulsars' masses and in sin i. We get |κ| ≤ 0.8 × 10-26 m-2 for the parameter that in the f(R) framework is a measure of the nonlinearity of the theory, |α| ≤ 5.5 × 10-4 for the fifth-force strength parameter (for λ ≈ a = 0.006 AU). The effects predicted by the strong-acceleration regime of MOND are far too small to be constrained with some effectiveness today and in the future as well. In view of the continuous timing of such an important system, it might happen that in the near future it will be possible to obtain somewhat tighter constraints.
Horton, Karissa D.; Loyo, Jennifer; Jowers, Esbelle M.; Rodgers, Lindsay Faith; Smiley, Andrew W.; Leversen, Eric; Hoelscher, Deanna M.
2015-01-01
Background The Farm to Work program is a modified community-supported agriculture model at worksites in Texas. Community Context The objective of the Farm to Work program is to increase fruit and vegetable intake among employees and their households by decreasing cost, improving convenience, and increasing access while also creating a new market for local farmers at worksites. The objectives of this article were to describe the development, implementation, and outcome of a 5-year participation trend analysis and to describe the community relationships that were formed to enable the successful implementation of the program. Methods The Farm to Work program began in November 2007 as a collaborative effort between the nonprofit Sustainable Food Center, the Texas Department of State Health Services, the Web development company WebChronic Consulting LLC, and Naegelin Farm. The program provides a weekly or biweekly opportunity for employees to order a basket of produce online to be delivered to the worksite by a local farmer. A 5-year participation trend analysis, including seasonal variation and sales trends, was conducted using sales data from November 2007 through December 2012. Outcome The total number of baskets delivered from November 2007 through December 2012 was 38,343; of these, 37,466 were sold and 877 were complimentary. The total value of sold and complimentary baskets was $851,035 and $21,925, respectively. Participation in the program increased over time and was highest in 2012. Interpretation The Farm to Work program increased access to locally grown fruits and vegetables for employees and created a new market for farmers. Increased program participation indicates that Farm to Work can increase employees’ fruit and vegetable consumption and thus help prevent chronic diseases in this population PMID:26491816
Kim, Jong Kun
2015-01-01
We conducted this study to investigate the synergistic effect of human urine-derived stem cells (USCs) and surface modified composite scaffold for bladder reconstruction in a rat model. The composite scaffold (Polycaprolactone/Pluronic F127/3 wt% bladder submucosa matrix) was fabricated using an immersion precipitation method, and heparin was immobilized on the surface via covalent conjugation. Basic fibroblast growth factor (bFGF) was loaded onto the heparin-immobilized scaffold by a simple dipping method. In maximal bladder capacity and compliance analysis at 8 weeks post operation, the USCs-scaffoldheparin-bFGF group showed significant functional improvement (2.34 ± 0.25 mL and 55.09 ± 11.81 µL/cm H2O) compared to the other groups (2.60 ± 0.23 mL and 56.14 ± 9.00 µL/cm H2O for the control group, 1.46 ± 0.18 mL and 34.27 ± 4.42 µL/cm H2O for the partial cystectomy group, 1.76 ± 0.22 mL and 35.62 ± 6.69 µL/cm H2O for the scaffold group, and 1.92 ± 0.29 mL and 40.74 ± 7.88 µL/cm H2O for the scaffoldheparin-bFGF group, respectively). In histological and immunohistochemical analysis, the USC-scaffoldheparin-bFGF group showed pronounced, well-differentiated, and organized smooth muscle bundle formation, a multi-layered and pan-cytokeratin-positive urothelium, and high condensation of submucosal area. The USCs seeded scaffoldheparin-bFGF exhibits significantly increased bladder capacity, compliance, regeneration of smooth muscle tissue, multi-layered urothelium, and condensed submucosa layers at the in vivo study. PMID:26713050
Wang, Junjie; He, Jiangtao; Chen, Honghan
2012-08-15
Groundwater contamination risk assessment is an effective tool for groundwater management. Most existing risk assessment methods only consider the basic contamination process based upon evaluations of hazards and aquifer vulnerability. In view of groundwater exploitation potentiality, including the value of contamination-threatened groundwater could provide relatively objective and targeted results to aid in decision making. This study describes a groundwater contamination risk assessment method that integrates hazards, intrinsic vulnerability and groundwater value. The hazard harmfulness was evaluated by quantifying contaminant properties and infiltrating contaminant load, the intrinsic aquifer vulnerability was evaluated using a modified DRASTIC model and the groundwater value was evaluated based on groundwater quality and aquifer storage. Two groundwater contamination risk maps were produced by combining the above factors: a basic risk map and a value-weighted risk map. The basic risk map was produced by overlaying the hazard map and the intrinsic vulnerability map. The value-weighted risk map was produced by overlaying the basic risk map and the groundwater value map. Relevant validation was completed by contaminant distributions and site investigation. Using Beijing Plain, China, as an example, thematic maps of the three factors and the two risks were generated. The thematic maps suggested that landfills, gas stations and oil depots, and industrial areas were the most harmful potential contamination sources. The western and northern parts of the plain were the most vulnerable areas and had the highest groundwater value. Additionally, both the basic and value-weighted risk classes in the western and northern parts of the plain were the highest, indicating that these regions should deserve the priority of concern. Thematic maps should be updated regularly because of the dynamic characteristics of hazards. Subjectivity and validation means in assessing the
Modified blank ammunition injuries.
Ogunc, Gokhan I; Ozer, M Tahir; Coskun, Kagan; Uzar, Ali Ihsan
2009-12-15
Blank firing weapons are designed only for discharging blank ammunition cartridges. Because they are cost-effective, are easily accessible and can be modified to live firearms plus their unclear legal situation in Turkish Law makes them very popular in Turkey. 2004 through 2008, a total of 1115 modified blank weapons were seized in Turkey. Blank firing weapons are easily modified by owners, making them suitable for discharging live firearm ammunition or modified blank ammunitions. Two common methods are used for modification of blank weapons. After the modification, these weapons can discharge the live ammunition. However, due to compositional durability problems with these types of weapons; the main trend is to use the modified blank ammunitions rather than live firearm ammunition fired from modified blank firing weapons. In this study, two types of modified blank weapons and two types of modified blank cartridges were tested on three different target models. Each of the models' shooting side was coated with 1.3+/-2 mm thickness chrome tanned cowhide as a skin simulant. The first model was only coated with skin simulant. The second model was coated with skin simulant and 100% cotton police shirt. The third model was coated with skin simulant and jean denim. After the literature evaluation four high risky anatomic locations (the neck area; the eyes; the thorax area and inguinal area) were pointed out for the steel and lead projectiles are discharged from the modified blank weapons especially in close range (0-50 cm). The target models were designed for these anatomic locations. For the target models six Transparent Ballistic Candle blocks (TCB) were prepared and divided into two test groups. The first group tests were performed with lead projectiles and second group with steel projectile. The shortest penetration depth (lead projectile: 4.358 cm; steel projectile 8.032 cm) was recorded in the skin simulant and jean denim coated block for both groups. In both groups
NASA Astrophysics Data System (ADS)
Li, Xifeng; Ding, Wei; Ye, Liyan; Chen, Jun
2013-12-01
True stress-strain curves of SUS304 metastable austenitic stainless steel at various strain rates were fitted by a modified Johnson-Cook material model. The effect of blank-holder force on Cross-die forming of SUS304 stainless steel was studied. The forming process was also simulated by the software Marc based on this model. Major strain distribution, thickness distribution and load-displacement were compared between experiment and simulation. The results indicated the modified Johnson-Cook model could well predict the deformation behavior of SUS304 stainless steel. The martensitie volume fraction at different positions of the formed part was in good agreement with what can be expected.
NASA Astrophysics Data System (ADS)
Vinten, A. J. A.; Frenkel, H.; Shalhevet, J.; Elston, D. A.
1991-01-01
In many situations where annual crops are irrigated with saline water, root zone salinity does not reach a steady state. Use of a steady-state description of root zone salinity may then seriously overestimate the calculated leaching requirements of the crop. A steady-state semi-emphirical model of crop response to irrigation with saline water has been calibrated using data from a number of field experiments. Predictions of yield deficit resulting from irrigation with saline water have been made for each of these experiments, using both the original model and a modified version which allows for the non-steady-state salinity conditions occurring in the experiments. Comparison with experimental data shows a clear superiority of the modified version in most cases studied. Where the original model is superior or equally good, it is likely that steady-state conditions are being approached. Where root zone salinity data were available and applicable, the modified model predicted root zone salinity much better. Approaches for distinguishing errors in calibration from intrinsic errors in the model assumptions are discussed.
Chowdhury, Shamik; Saha, Papita Das
2013-02-01
In this study, rice husk was modified with NaOH and used as adsorbent for dynamic adsorption of methylene blue (MB) from aqueous solutions. Continuous removal of MB from aqueous solutions was studied in a laboratory scale fixed-bed column packed with NaOH-modified rice husk (NMRH). Effect of different flow rates and bed heights on the column breakthrough performance was investigated. In order to determine the most suitable model for describing the adsorption kinetics of MB in the fixed-bed column system, the bed depth service time (BDST) model as well as the Thomas model was fitted to the experimental data. An artificial neural network (ANN)-based model was also developed for describing the dynamic dye adsorption process. An extensive error analysis was carried out between experimental data and data predicted by the models by using the following error functions: correlation coefficient (R(2)), average relative error, sum of the absolute error and Chi-square statistic test (χ(2)). Results show that with increasing bed height and decreasing flow rate, the breakthrough time was delayed. All the error functions yielded minimum values for the ANN model than the traditional models (BDST and Thomas), suggesting that the ANN model is the most suitable model to describe the fixed-bed adsorption of MB by NMRH. It is also more rational and reliable to interpret dynamic dye adsorption data through a process of ANN architecture. PMID:22562342
NASA Astrophysics Data System (ADS)
Frew, D. A.; Scheffer, C.
2008-01-01
Accurate rotordynamic analysis is critical in the achievement of efficient rotary machine design, however the majority of models concern flexible shafts with concentrated supports. The modified Euler equations of motion are used in a numerical model to calculate the natural frequencies and whirl amplitudes of a rigid rotor supported by a single-aerostatic bearing. The bearing is modelled with a non-constant stiffness distribution along its length and a non-symmetric centre of gravity. The results are compared with experimental modal analysis (EMA).
NASA Astrophysics Data System (ADS)
Nakagawa, T.; Matsuyama, R.; Adachi, M.; Kuroshima, S.; Ogatsu, T.; Adachi, R.
2015-11-01
A simulation model, which covers the part of Southern-Kanto natural gas field in Chiba prefecture, was developed to perform studies and make predictions of land subsidence. However, because large differences between simulated and measured subsidence occurred in the northern modeled area of the gas field, the model was modified with an estimated Young's modulus distribution. This distribution was estimated by the yield value distribution and the correlation of yield value with Young's modulus. Consequently, the simulated subsidence in the north area was improved to some extent.