A Dynamic Process Model for the Beach-Inlet Transition Zone.
1980-05-01
A0-A87 096 UNIVERSITY OF SOUTH FLORIDA TAMPA DEPT OF GEOLOGY F/S 8/3 A DYNAMIC PROCESS MODEL FOR THE REACH-INLET TRANSITION ZONE. UI N MAY 80 R A...cz80 7 A DYNAMIC PROCESS MODEL FOR THE BEACH-INLET TRANSITION ZONE by Richard A. Davis, Jr., University of South Florida and William T. Fox, Williams...during the study period have permitted construction of a dynami, process model for the beach-inlet transition zone during the tidal cycle. This model
Teacher in Transition: A Model of One Teacher's Change Process.
ERIC Educational Resources Information Center
Mahurt, Sarah Fleming
Change in teaching practice is a popular theme in literacy education. A case study examined the nature of the change process in a teacher in a large Caribbean island school district who made a personal decision to change instructional practices from skills-based methods to whole language methods. Through data collection and analysis, a metaphor,…
NASA Astrophysics Data System (ADS)
Pagonis, Vasilis; Kulp, Christopher
2010-05-01
Semilocalized transition (SLT) kinetic models for thermoluminescence (TL) contain characteristics of both a localized transition (LT) and of a single trap model. TL glow curves within SLT models typically contain contain two TL peaks; the first peak corresponds to the intra-pair luminescence due to LTs and the second TL peak corresponds to delocalized transitions involving the conduction band (CB). The latter delocalized TL peak has also been found to exhibit non-typical double-peak structure, in which the main TL peak is accompanied by a smaller peak called the displacement peak. This paper describes the simulation of isothermal luminescence signals using a previously published SLT model. It is found that these simulated isothermal signals exhibit several unusual time characteristics. Isothermal signals associated with the LTs follow first order kinetics and are therefore described by single decaying exponentials. However, isothermal signals associated with delocalized transitions show a non-typical complex structure characterized by several time regions with different decay characteristics. For certain values of the parameters in the SLT model the isothermal signals can also exhibit non-monotonic behaviour as a function of time. Another notable result from the simulations is that isothermal currents (which are proportional to the concentration of electrons in the CB) can persist for very long periods of time, even after the apparent termination of the isothermal luminescence signals. It is concluded that isothermal processes described by the SLT model depend strongly on the presence of SLTs, in contrast to previous studies using Monte Carlo simulations, which showed a weak interdependence of these phenomena. The simulations in this paper suggest that isothermal experiments offer a sensitive method for detecting the presence of SLTs in a dosimetric material.
Generalized Hammersley Process and Phase Transition for Activated Random Walk Models
NASA Astrophysics Data System (ADS)
Rolla, Leonardo T.
2008-12-01
* ACTIVATED RANDOM WALK MODEL * This is a conservative particle system on the lattice, with a Markovian continuous-time evolution. Active particles perform random walks without interaction, and they may as well change their state to passive, then stopping to jump. When particles of both types occupy the same site, they all become active. This model exhibits phase transition in the sense that for low initial densities the system locally fixates and for high densities it keeps active. Though extensively studied in the physics literature, the matter of giving a mathematical proof of such phase transition remained as an open problem for several years. In this work we identify some variables that are sufficient to characterize fixation and at the same time are stochastically monotone in the model's parameters. We employ an explicit graphical representation in order to obtain the monotonicity. With this method we prove that there is a unique phase transition for the one-dimensional finite-range random walk. Joint with V. Sidoravicius. * BROKEN LINE PROCESS * We introduce the broken line process and derive some of its properties. Its discrete version is presented first and a natural generalization to the continuum is then proposed and studied. The broken lines are related to the Young diagram and the Hammersley process and are useful for computing last passage percolation values and finding maximal oriented paths. For a class of passage time distributions there is a family of boundary conditions that make the process stationary and reversible. One application is a simple proof of the explicit law of large numbers for last passage percolation with exponential and geometric distributions. Joint with V. Sidoravicius, D. Surgailis, and M. E. Vares.
Exploring business process modelling paradigms and design-time to run-time transitions
NASA Astrophysics Data System (ADS)
Caron, Filip; Vanthienen, Jan
2016-09-01
The business process management literature describes a multitude of approaches (e.g. imperative, declarative or event-driven) that each result in a different mix of process flexibility, compliance, effectiveness and efficiency. Although the use of a single approach over the process lifecycle is often assumed, transitions between approaches at different phases in the process lifecycle may also be considered. This article explores several business process strategies by analysing the approaches at different phases in the process lifecycle as well as the various transitions.
The Application of Global Kinetic Models to HMX Beta-Delta Transition and Cookoff Processes
Wemhoff, A P; Burnham, A K; Nichols III, A L
2006-12-07
The reduction of the number of reactions in kinetic models for both the HMX beta-delta phase transition and thermal cookoff provides an attractive alternative to traditional multi-stage kinetic models due to reduced calibration effort requirements. In this study, we use the LLNL code ALE3D to provide calibrated kinetic parameters for a two-reaction bidirectional beta-delta HMX phase transition model based on Sandia Instrumented Thermal Ignition (SITI) and Scaled Thermal Explosion (STEX) temperature history curves, and a Prout-Tompkins cookoff model based on One-Dimensional Time to Explosion (ODTX) data. Results show that the two-reaction bidirectional beta-delta transition model presented here agrees as well with STEX and SITI temperature history curves as a reversible four-reaction Arrhenius model, yet requires an order of magnitude less computational effort. In addition, a single-reaction Prout-Tompkins model calibrated to ODTX data provides better agreement with ODTX data than a traditional multi-step Arrhenius model, and can contain up to 90% less chemistry-limited time steps for low-temperature ODTX simulations. Manual calibration methods for the Prout-Tompkins kinetics provide much better agreement with ODTX experimental data than parameters derived from Differential Scanning Calorimetry (DSC) measurements at atmospheric pressure. The predicted surface temperature at explosion for STEX cookoff simulations is a weak function of the cookoff model used, and a reduction of up to 15% of chemistry-limited time steps can be achieved by neglecting the beta-delta transition for this type of simulation. Finally, the inclusion of the beta-delta transition model in the overall kinetics model can affect the predicted time to explosion by 1% for the traditional multi-step Arrhenius approach, while up to 11% using a Prout-Tompkins cookoff model.
ERIC Educational Resources Information Center
Bray, Bethany C.; Lanza, Stephanie T.; Collins, Linda M.
2010-01-01
To understand one developmental process, it is often helpful to investigate its relations with other developmental processes. Statistical methods that model development in multiple processes simultaneously over time include latent growth curve models with time-varying covariates, multivariate latent growth curve models, and dual trajectory models.…
NASA Astrophysics Data System (ADS)
Moisan, J. R.; Hofmann, E. E.
1996-10-01
A time- and depth-dependent, physical-bio-optical model was developed for the California coastal transition zone (CTZ) with the overall objective of understanding and quantifying the processes that contribute to the vertical and temporal development of nutrient and plankton distributions in the CTZ. The model food web components included silicate, nitrate, ammonium, two phytoplankton size fractions, copepods, doliolids, euphausiids, and a detritus pool. The wavelength-dependent subsurface irradiance field was attenuated by seawater and phytoplankton pigments. The one-dimensional (1-D) model adequately simulated the development and maintenance of a subsurface chlorophyll maximum in different regions within the CTZ. An analysis of the individual terms in the model governing equations revealed that phytoplankton in situ growth was primarily responsible for the creation and maintenance of the subsurface chlorophyll maximum at both coastal and oceanic regions in the CTZ. The depth to which the maximum in situ growth occurred was controlled by the combined effect of light and nutrient limitation. Also, the simulated bio-optical fields demonstrated the effect of nonlinear couplings between food web components and the subsurface irradiance field on vertical biological distributions. In particular, the e-folding scale of the subsurface photosynthetically available radiation (PAR) was influenced by the level of zooplankton grazing.
Chen, Li; Kang, Qinjun; Robinson, Bruce A; He, Ya-Ling; Tao, Wen-Quan
2013-04-01
A pore-scale model based on the lattice Boltzmann (LB) method is developed for multiphase reactive transport with phase transitions and dissolution-precipitation processes. The model combines the single-component multiphase Shan-Chen LB model [X. Shan and H. Chen, Phys. Rev. E 47, 1815 (1993)], the mass transport LB model [S. P. Sullivan et al., Chem. Eng. Sci. 60, 3405 (2005)], and the dissolution-precipitation model [Q. Kang et al., J. Geophys. Res. 111, B05203 (2006)]. Care is taken to handle information on computational nodes undergoing solid-liquid or liquid-vapor phase changes to guarantee mass and momentum conservation. A general LB concentration boundary condition is proposed that can handle various concentration boundaries including reactive and moving boundaries with complex geometries. The pore-scale model can capture coupled nonlinear multiple physicochemical processes including multiphase flow with phase separations, mass transport, chemical reactions, dissolution-precipitation processes, and dynamic evolution of the pore geometries. The model is validated using several multiphase flow and reactive transport problems and then used to study the thermal migration of a brine inclusion in a salt crystal. Multiphase reactive transport phenomena with phase transitions between liquid-vapor phases and dissolution-precipitation processes of the salt in the closed inclusion are simulated and the effects of the initial inclusion size and temperature gradient on the thermal migration are investigated.
Modeling the transition region
NASA Astrophysics Data System (ADS)
Singer, Bart A.
1994-04-01
The calculation of engineering flows undergoing laminar-turbulent transition presents special problems. Mean-flow quantities obey neither the fully laminar nor the fully turbulent correlations. In addition, local maxima in skin friction, wall temperature, and heat transfer often occur near the end of the transition region. Traditionally, modeling this region has been important for the design of turbine blades, where the transition region is long in relation to the chord length of the blade. More recently, the need for better transition-region models has been recognized by designers of hypersonic vehicles where the high Mach number, the low Reynolds number, and the low-disturbance flight environment emphasize the importance of the transition region. Needless to say, a model that might work well for the transitional flows typically found in gas turbines will not necessarily work well for the external surface of a hypersonic vehicle. In Section 2 of this report, some of the important flow features that control the transition region will be discussed. In Section 3, different approaches to the modeling problem will be summarized and cataloged. Fully turbulent flow models will be discussed in detail in Section 4; models specifically designed for transitional flow, in Section 5; and the evaluation of models, in Section 6.
NASA Astrophysics Data System (ADS)
Hansteen, V.; Murdin, P.
2000-11-01
The SOLAR TRANSITION REGION comprises the PLASMA between the CHROMOSPHERE and the CORONA. In both of these regions the temperature is fairly uniform. The transition region, by contrast, is believed to be characterized by a very steep temperature rise from a chromospheric temperature of slightly less than 104 K to coronal temperatures on the order of 106 K. The goal of modeling the transition regi...
Nandi, Taraj; Brasseur, James; Vijayakumar, Ganesh
2016-01-04
This study is aimed at gaining insight into the nonsteady transitional boundary layer dynamics of wind turbine blades and the predictive capabilities of URANS based transition and turbulence models for similar physics through the analysis of a controlled flow with similar nonsteady parameters.
Modeling of transitional flows
NASA Technical Reports Server (NTRS)
Lund, Thomas S.
1988-01-01
An effort directed at developing improved transitional models was initiated. The focus of this work was concentrated on the critical assessment of a popular existing transitional model developed by McDonald and Fish in 1972. The objective of this effort was to identify the shortcomings of the McDonald-Fish model and to use the insights gained to suggest modifications or alterations of the basic model. In order to evaluate the transitional model, a compressible boundary layer code was required. Accordingly, a two-dimensional compressible boundary layer code was developed. The program was based on a three-point fully implicit finite difference algorithm where the equations were solved in an uncoupled manner with second order extrapolation used to evaluate the non-linear coefficients. Iteration was offered as an option if the extrapolation error could not be tolerated. The differencing scheme was arranged to be second order in both spatial directions on an arbitrarily stretched mesh. A variety of boundary condition options were implemented including specification of an external pressure gradient, specification of a wall temperature distribution, and specification of an external temperature distribution. Overall the results of the initial phase of this work indicate that the McDonald-Fish model does a poor job at predicting the details of the turbulent flow structure during the transition region.
Phase transitions in multiplicative competitive processes.
Shimazaki, Hideaki; Niebur, Ernst
2005-07-01
We introduce a discrete multiplicative process as a generic model of competition. Players with different abilities successively join the game and compete for finite resources. Emergence of dominant players and evolutionary development occur as a phase transition. The competitive dynamics underlying this transition is understood from a formal analogy to statistical mechanics. The theory is applicable to bacterial competition, predicting novel population dynamics near criticality.
Phase transitions in multiplicative competitive processes
Shimazaki, Hideaki; Niebur, Ernst
2005-07-01
We introduce a discrete multiplicative process as a generic model of competition. Players with different abilities successively join the game and compete for finite resources. Emergence of dominant players and evolutionary development occur as a phase transition. The competitive dynamics underlying this transition is understood from a formal analogy to statistical mechanics. The theory is applicable to bacterial competition, predicting novel population dynamics near criticality.
UTM: Universal Transit Modeller
NASA Astrophysics Data System (ADS)
Deeg, Hans J.
2014-12-01
The Universal Transit Modeller (UTM) is a light-curve simulator for all kinds of transiting or eclipsing configurations between arbitrary numbers of several types of objects, which may be stars, planets, planetary moons, and planetary rings. A separate fitting program, UFIT (Universal Fitter) is part of the UTM distribution and may be used to derive best fits to light-curves for any set of continuously variable parameters. UTM/UFIT is written in IDL code and its source is released in the public domain under the GNU General Public License.
NASA Astrophysics Data System (ADS)
Ren, X. D.; Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.
2015-10-01
To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2-6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.
NASA Astrophysics Data System (ADS)
Kazil, J.; Wang, H.; Feingold, G.; Clarke, A. D.; Snider, J. R.; Bandy, A. R.
2011-08-01
Chemical and aerosol processes in the transition from closed- to open-cell circulation in the remote, cloudy marine boundary layer are explored. It has previously been shown that precipitation can initiate a transition from the closed- to the open-cellular state, but that the boundary layer cannot maintain this open-cell state without a resupply of cloud condensation nuclei (CCN). Potential sources of CCN include wind-driven production of sea salt from the ocean, nucleation from the gas phase, and entrainment from the free troposphere. In order to investigate CCN sources in the marine boundary layer and their role in supplying new particles, we have coupled in detail chemical, aerosol, and cloud processes in the WRF/Chem model, and added state-of-the-art representations of sea salt emissions and aerosol nucleation. We conduct numerical simulations of the marine boundary layer in the transition from a closed- to an open-cell state. Results are compared with observations in the Southeast Pacific boundary layer during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). The transition from the closed- to the open-cell state generates conditions that are conducive to nucleation by forming a cloud-scavenged, ultra-clean layer below the inversion base. Open cell updrafts loft dimethyl sulfide from the ocean surface into the ultra-clean layer, where it is oxidized during daytime to SO2 and subsequently to H2SO4. Low H2SO4 condensation sink values in the ultra-clean layer allow H2SO4 to rise to concentrations at which aerosol nucleation produces new aerosol in significant numbers. The existence of the ultra-clean layer is confirmed by observations. We find that the observed DMS flux from the ocean in the VOCALS-REx region can support a nucleation source of aerosol in open cells that exceeds sea salt emissions in terms of the number of particles produced. The freshly nucleated, nanometer-sized aerosol particles need, however, time to grow to sizes
USDA-ARS?s Scientific Manuscript database
State and transition models (STMs) are used for communicating about ecosystem change in rangelands and other ecosystems, especially the implications for management. The fundamental premise that rangelands can exhibit multiple states is now widely accepted. The current application of STMs for managem...
Ren, X. D. Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.
2015-10-05
To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.
Correlation analysis of transitional processes of chronorhythms
NASA Astrophysics Data System (ADS)
Strinadko, Marina M.; Timochko, Katerina B.; Strinadko, Olena M.; Abramov, Igor V.
1999-11-01
The biological system reaction on spasmodic change of a phase of sine wave revolting force is investigated. The model researches for the biosystem unit that is described by linear differential equation of the second order are carried out. Possibility of time asymmetry in adaptation and transitional processes of biological units, at spasmodic change of phase identical modulo and opposite on the sign is shown. The residual in time of adaptation depends on state of biosystem's unit at the moment of perturbation.
Dresser, Karyn; Clark, Hewitt B; Deschênes, Nicole
2015-04-01
Transition into adulthood represents a particularly challenging period for youth and young adults with serious mental health conditions and related needs. The Transition to Independence Process (TIP) model is based on a positive development approach and has been demonstrated to be an evidence-supported practice for preparing emerging adults in their movement into employment/career, education, living situation, personal effectiveness/well-being, and community-life functioning--and to be responsive to their families. This article describes the TIP model from a positive youth development framework, its empirical underpinnings, and the fidelity and outcome tracking tools that have been developed for use with transition sites for implementation and sustainability. A research study on the fidelity tools showed their reliability and validity and a second study presents progress and outcome findings for youth and young adults at a new TIP model site. The implications of the TIP model and these findings are discussed.
ERIC Educational Resources Information Center
Fauth, Elizabeth Braungart; Zarit, Steven H.; Malmberg, Bo; Johansson, Boo
2007-01-01
Purpose: This study used the Disablement Process Model to predict whether a sample of the oldest-old maintained their disability or disability-free status over a 2- and 4-year follow-up, or whether they transitioned into a state of disability during this time. Design and Methods: We followed a sample of 149 Swedish adults who were 86 years of age…
ERIC Educational Resources Information Center
Sitlington, Patricia L.; Easterday, Joseph R.
The purpose of Project COMPETE is to use previous research and exemplary practices to develop and validate a model and training sequence to assist retarded youth to make the transition from school to employment in the most competitive environment possible. This project working paper describes the process of using existing information sources to…
Integrating Transition Planning into the IEP Process.
ERIC Educational Resources Information Center
West, Lynda L.; And Others
The purpose of this guide is to assist those involved in the transition planning process to help students with disabilities achieve a smooth transition from school to adult life. The guide addresses topics that deal with the preparation of students with disabilities as they leave high school. The guide's eight chapters deal with: (1) defining…
Simplified lattice model for polypeptide fibrillar transitions
NASA Astrophysics Data System (ADS)
Xiao, Xuhui; Wu, Ming-Chya
2014-10-01
Polypeptide fibrillar transitions are studied using a simplified lattice model, modified from the three-state Potts model, where uniform residues as spins, placed on a cubic lattice, can interact with neighbors to form coil, helical, sheet, or fibrillar structure. Using the transfer matrix method and numerical calculations, we analyzed the partition function and construct phase diagrams. The model manifests phase transitions among coil, helix, sheet, and fibril through parameterizing bond coupling energy ɛh,ɛs,ɛf, structural entropies sh,ss,sf of helical, sheet, and fibrillar states, and number density ρ. The phase diagrams show the transition sequence is basically governed by ɛh, ɛs, and ɛf, while the transition temperature is determined by the competition among ɛh, ɛs, and ɛf, as well as sh, ss, sf, and ρ. Furthermore, the fibrillation is accompanied with an abrupt phase transition from coil, helix, or sheet to fibril even for short polypeptide length, resembling the feature of nucleation-growth process. The finite-size effect in specific heat at transitions for the nonfibrillation case can be described by the scaling form of lattice model. With rich phase-transition properties, our model provides a useful reference for protein aggregation experiments and modeling.
Modelling the transitional boundary layer
NASA Technical Reports Server (NTRS)
Narasimha, R.
1990-01-01
Recent developments in the modelling of the transition zone in the boundary layer are reviewed (the zone being defined as extending from the station where intermittency begins to depart from zero to that where it is nearly unity). The value of using a new non-dimensional spot formation rate parameter, and the importance of allowing for so-called subtransitions within the transition zone, are both stressed. Models do reasonably well in constant pressure 2-dimensional flows, but in the presence of strong pressure gradients further improvements are needed. The linear combination approach works surprisingly well in most cases, but would not be so successful in situations where a purely laminar boundary layer would separate but a transitional one would not. Intermittency-weighted eddy viscosity methods do not predict peak surface parameters well without the introduction of an overshooting transition function whose connection with the spot theory of transition is obscure. Suggestions are made for further work that now appears necessary for developing improved models of the transition zone.
Modeling of the transition zone porosity
Bourdette, B.; Ringot, E.; Ollivier, J.P.
1995-05-01
The ion diffusion process in mortar is different from the one which occurs in cement paste. This difference is due to the presence of transition zones, which take place around the grains in mortar and which are very porous regions. Based on mercury intrusion porosimetry experimental data and on the analysis of percolation through a 3D mortar model, a computation of the transition zone porosity and of the bulk paste porosity has been carried out. The porosity of the transition zone has been analyzed as a function of the mortar composition and of the degree of hydration.
Transition-Independent Decentralized Markov Decision Processes
NASA Technical Reports Server (NTRS)
Becker, Raphen; Silberstein, Shlomo; Lesser, Victor; Goldman, Claudia V.; Morris, Robert (Technical Monitor)
2003-01-01
There has been substantial progress with formal models for sequential decision making by individual agents using the Markov decision process (MDP). However, similar treatment of multi-agent systems is lacking. A recent complexity result, showing that solving decentralized MDPs is NEXP-hard, provides a partial explanation. To overcome this complexity barrier, we identify a general class of transition-independent decentralized MDPs that is widely applicable. The class consists of independent collaborating agents that are tied up by a global reward function that depends on both of their histories. We present a novel algorithm for solving this class of problems and examine its properties. The result is the first effective technique to solve optimally a class of decentralized MDPs. This lays the foundation for further work in this area on both exact and approximate solutions.
Cognitive processing during the transition to sleep.
Goupil, L; Bekinschtein, T A
2012-01-01
Dramatic physiological and behavioural changes occur during the transition from wakefulness to sleep. The process is regarded as a grey area of consciousness between attentive wakefulness and slow wave sleep. Although there is evidence of neurophysiological integration decay as signalled by sleep EEG elements, changes in power spectra and coherence, thalamocortical connectivity in fMRI, and single neuron changes in firing patterns, little is known about the cognitive and behavioural dynamics of these transitions. Hereby we revise the body and brain physiology, behaviour and phenomenology of these changes of consciousness and propose an experimental framework to integrate the two aspects of consciousness that interact in the transition, wakefulness and awareness.
NASA Astrophysics Data System (ADS)
Ohta, Yoshihiro; Nishiyama, Akinobu; Wada, Yoichiro; Ruan, Yijun; Kodama, Tatsuhiko; Tsuboi, Takashi; Tokihiro, Tetsuji; Ihara, Sigeo
2012-08-01
We all use path routing everyday as we take shortcuts to avoid traffic jams, or by using faster traffic means. Previous models of traffic flow of RNA polymerase II (RNAPII) during transcription, however, were restricted to one dimension along the DNA template. Here we report the modeling and application of traffic flow in transcription that allows preferential paths of different dimensions only restricted to visit some transit points, as previously introduced between the 5' and 3' end of the gene. According to its position, an RNAPII protein molecule prefers paths obeying two types of time-evolution rules. One is an asymmetric simple exclusion process (ASEP) along DNA, and the other is a three-dimensional jump between transit points in DNA where RNAPIIs are staying. Simulations based on our model, and comparison experimental results, reveal how RNAPII molecules are distributed at the DNA-loop-formation-related protein binding sites as well as CTCF insulator proteins (or exons). As time passes after the stimulation, the RNAPII density at these sites becomes higher. Apparent far-distance jumps in one dimension are realized by short-range three-dimensional jumps between DNA loops. We confirm the above conjecture by applying our model calculation to the SAMD4A gene by comparing the experimental results. Our probabilistic model provides possible scenarios for assembling RNAPII molecules into transcription factories, where RNAPII and related proteins cooperatively transcribe DNA.
Ohta, Yoshihiro; Nishiyama, Akinobu; Wada, Yoichiro; Ruan, Yijun; Kodama, Tatsuhiko; Tsuboi, Takashi; Tokihiro, Tetsuji; Ihara, Sigeo
2012-08-01
We all use path routing everyday as we take shortcuts to avoid traffic jams, or by using faster traffic means. Previous models of traffic flow of RNA polymerase II (RNAPII) during transcription, however, were restricted to one dimension along the DNA template. Here we report the modeling and application of traffic flow in transcription that allows preferential paths of different dimensions only restricted to visit some transit points, as previously introduced between the 5' and 3' end of the gene. According to its position, an RNAPII protein molecule prefers paths obeying two types of time-evolution rules. One is an asymmetric simple exclusion process (ASEP) along DNA, and the other is a three-dimensional jump between transit points in DNA where RNAPIIs are staying. Simulations based on our model, and comparison experimental results, reveal how RNAPII molecules are distributed at the DNA-loop-formation-related protein binding sites as well as CTCF insulator proteins (or exons). As time passes after the stimulation, the RNAPII density at these sites becomes higher. Apparent far-distance jumps in one dimension are realized by short-range three-dimensional jumps between DNA loops. We confirm the above conjecture by applying our model calculation to the SAMD4A gene by comparing the experimental results. Our probabilistic model provides possible scenarios for assembling RNAPII molecules into transcription factories, where RNAPII and related proteins cooperatively transcribe DNA.
The Transition Assessment Process and IDEIA 2004
ERIC Educational Resources Information Center
Sitlington, Patricia L.; Clark, Gary M.
2007-01-01
This article will first provide an overview of the transition assessment process in terms of the requirements of the Individuals with Disabilities Education Improvement Act of 2004 and the basic tenets of the process. The second section will provide an overview of the methods of gathering assessment information on the student and on the living,…
Thelen, Kirstin; Coboeken, Katrin; Willmann, Stefan; Dressman, Jennifer B; Lippert, Jörg
2012-03-01
The physiological absorption model presented in part I of this work is now extended to account for dosage-form-dependent gastrointestinal (GI) transit as well as disintegration and dissolution processes of various immediate-release and modified-release dosage forms. Empirical functions of the Weibull type were fitted to experimental in vitro dissolution profiles of solid dosage forms for eight test compounds (aciclovir, caffeine, cimetidine, diclofenac, furosemide, paracetamol, phenobarbital, and theophylline). The Weibull functions were then implemented into the model to predict mean plasma concentration-time profiles of the various dosage forms. On the basis of these dissolution functions, pharmacokinetics (PK) of six model drugs was predicted well. In the case of diclofenac, deviations between predicted and observed plasma concentrations were attributable to the large variability in gastric emptying time of the enteric-coated tablets. Likewise, oral PK of furosemide was found to be predominantly governed by the gastric emptying patterns. It is concluded that the revised model for GI transit and absorption was successfully integrated with dissolution functions of the Weibull type, enabling prediction of in vivo PK profiles from in vitro dissolution data. It facilitates a comparative analysis of the parameters contributing to oral drug absorption and is thus a powerful tool for formulation design. Copyright © 2011 Wiley Periodicals, Inc.
Relating transition-state spectroscopy to standard chemical spectroscopic processes
NASA Astrophysics Data System (ADS)
Reimers, Jeffrey R.; Hush, Noel S.
2017-09-01
Transition-state spectra are mapped out using generalized adiabatic electron-transfer theory. This simple model depicts diverse chemical properties, from aromaticity, through bound reactions such as isomerizations and atom-transfer processes with classic transition states, to processes often described as being ;non-adiabatic;, to those in the ;inverted; region that become slower as they are made more exothermic. Predictably, the Born-Oppenheimer approximation is found inadequate for modelling transition-state spectra in the weak-coupling limit. In this limit, the adiabatic Born-Huang approximation is found to perform much better than non-adiabatic surface-hopping approaches. Transition-state spectroscopy is shown to involve significant quantum entanglement between electronic and nuclear motion.
Application of Glass Transition in Food Processing.
Balasubramanian, S; Devi, Apramita; Singh, K K; Bosco, S J D; Mohite, Ashish M
2016-01-01
The phenomenon of glass transition has been employed to food products to study their stability. It can be applied as an integrated approach along with water activity and physical and chemical changes in food in processing and storage to determine the food stability. Also associated with the changes during agglomeration crystallization, caking, sticking, collapse, oxidation reactions, nonenzymatic browning, and microbial stability of food system. Various techniques such as Differential Scanning Calorimetry, Nuclear Magnetic Resonance, etc. have been developed to determine the glass transition temperature (Tg) of food system. Also, various theories have been applied to explain the concept of Tg and its relation to changes in food system. This review summarizes the understanding of concept of glass transition, its measurement, and application in food technology.
Transition paths, diffusive processes, and preequilibria of protein folding.
Zhang, Zhuqing; Chan, Hue Sun
2012-12-18
Fundamental relationships between the thermodynamics and kinetics of protein folding were investigated using chain models of natural proteins with diverse folding rates by extensive comparisons between the distribution of conformations in thermodynamic equilibrium and the distribution of conformations sampled along folding trajectories. Consistent with theory and single-molecule experiment, duration of the folding transition paths exhibits only a weak correlation with overall folding time. Conformational distributions of folding trajectories near the overall thermodynamic folding/unfolding barrier show significant deviations from preequilibrium. These deviations, the distribution of transition path times, and the variation of mean transition path time for different proteins can all be rationalized by a diffusive process that we modeled using simple Monte Carlo algorithms with an effective coordinate-independent diffusion coefficient. Conformations in the initial stages of transition paths tend to form more nonlocal contacts than typical conformations with the same number of native contacts. This statistical bias, which is indicative of preferred folding pathways, should be amenable to future single-molecule measurements. We found that the preexponential factor defined in the transition state theory of folding varies from protein to protein and that this variation can be rationalized by our Monte Carlo diffusion model. Thus, protein folding physics is different in certain fundamental respects from the physics envisioned by a simple transition-state picture. Nonetheless, transition state theory can be a useful approximate predictor of cooperative folding speed, because the height of the overall folding barrier is apparently a proxy for related rate-determining physical properties.
The demographic transition: model and reality.
Alexandersson, G
1981-01-01
Observed exponential population growth curves are short-term parts of a logistic or S-curve in demography or a product-cycle curve in technology. All human populations have the ability to adjust their rates of growth, a fact recognized by the demographic transition model. The acceleration of world population growth that began after 1650 and became conspicuous after 1850 was largely confined to industrialized countries of European culture until after World War II, when the S-curve passed the inflection point. Many signs indicate that the decline in growth rates may become striking in the 1980s or 1990s. The demographic transition agrees with the logistic curve, and since the ultimate carrying capacity of the Earth is limited, represents an intelligent adaptation. The industrial countries with the longest statistical records, such as Sweden and Finland, evidence early efforts to control fertility. The demographic transition in Sweden lasted from 1815 to 1930 and occurred without government interference. A question for postindustrial western society is whether birth rates will be adjusted to the rising death rates expected as the population ages. Birth and death rates in most formulations of the demographic transition model are typical of Western Europe at the start of the transition process but are much too low for most countries of the world. Japan's demographic transition and that of several other Asian countries have occurred much more rapidly than those of Western Europe and have demonstrated not only that the demographic transition model was applicable but that the time span could be shortened by a factor of about 10 when government policy was substituted for spontaneous development. The Indian experience however shows that the shortening of the transition cannot be imposed from above. The demographic transition is well on its way in most of Asia and Latin America, but Africa and the Muslim countries of Asia have so far done little to restrain their high
A new algebraic transition model based on stress length function
NASA Astrophysics Data System (ADS)
Xiao, Meng-Juan; She, Zhen-Su
2016-11-01
Transition, as one of the two biggest challenges in turbulence research, is of critical importance for engineering application. For decades, the fundamental research seems to be unable to capture the quantitative details in real transition process. On the other hand, numerous empirical parameters in engineering transition models provide no unified description of the transition under varying physical conditions. Recently, we proposed a symmetry-based approach to canonical wall turbulence based on stress length function, which is here extended to describe the transition via a new algebraic transition model. With a multi-layer analytic form of the stress length function in both the streamwise and wall normal directions, the new model gives rise to accurate description of the mean field and friction coefficient, comparing with both the experimental and DNS results at different inlet conditions. Different types of transition process, such as the transition with varying incoming turbulence intensities or that with blow and suck disturbance, are described by only two or three model parameters, each of which has their own specific physical interpretation. Thus, the model enables one to extract physical information from both experimental and DNS data to reproduce the transition process, which may prelude to a new class of generalized transition model for engineering applications.
A Latent Transition Model with Logistic Regression
ERIC Educational Resources Information Center
Chung, Hwan; Walls, Theodore A.; Park, Yousung
2007-01-01
Latent transition models increasingly include covariates that predict prevalence of latent classes at a given time or transition rates among classes over time. In many situations, the covariate of interest may be latent. This paper describes an approach for handling both manifest and latent covariates in a latent transition model. A Bayesian…
Convective transition statistics for climate model diagnostics
NASA Astrophysics Data System (ADS)
Kuo, Y. H.; Neelin, J. D.; Schiro, K. A.; Langenbrunner, B.; Hales, K.; Gettelman, A.; Chen, C. C.; Neale, R. B.; Ming, Y.; Maloney, E. D.; Mechoso, C. R.
2016-12-01
Convective parameterizations are among the most influential factors contributing to uncertainties of climate change projections. Parameter perturbation experiments in the Community Earth System Model (CESM) in comparison with observations have indicated that deep convective parameterizations may be partially constrained by convective transition statistics. These statistics characterize the transition to deep convection, and provide useful diagnostics at the fast timescale. At these fast timescales, and for precipitation in particular, uncertainties associated with observational systems must be addressed by the combination of examining features with a variety of instrumentation - including satellite microwave/radar retrievals, and DOE Atmospheric Radiation Measurement project rain gauge, radiosonde, and in situ radiometer - and identifying robust behaviors, e.g., position of convective onset as a function of column water vapor (CWV), versus instrument sensitivity at high rain rates. Recent CESM and Geophysical Fluid Dynamics Laboratory AM4 climate model simulations exhibit onset statistics qualitatively similar to observations, though quantitative discrepancies do exist. For instance, the models do a reasonable job at capturing temperature dependence of the transition to deep convection for which onset tends to occur at lower column relative humidity at higher temperature. However, the models have difficulty capturing details of the seasonal variation of this dependence. Furthermore, the simulated precipitation at high CWV tends to be too strong compared with observations subject to the same spatial resolution, indicating the importance of quantifying spatial/temporal scale dependence of these statistics for both understanding the underlying physical processes and constraining model performance.
Universal fractality of morphological transitions in stochastic growth processes.
Nicolás-Carlock, J R; Carrillo-Estrada, J L; Dossetti, V
2017-06-14
Stochastic growth processes give rise to diverse and intricate structures everywhere in nature, often referred to as fractals. In general, these complex structures reflect the non-trivial competition among the interactions that generate them. In particular, the paradigmatic Laplacian-growth model exhibits a characteristic fractal to non-fractal morphological transition as the non-linear effects of its growth dynamics increase. So far, a complete scaling theory for this type of transitions, as well as a general analytical description for their fractal dimensions have been lacking. In this work, we show that despite the enormous variety of shapes, these morphological transitions have clear universal scaling characteristics. Using a statistical approach to fundamental particle-cluster aggregation, we introduce two non-trivial fractal to non-fractal transitions that capture all the main features of fractal growth. By analyzing the respective clusters, in addition to constructing a dynamical model for their fractal dimension, we show that they are well described by a general dimensionality function regardless of their space symmetry-breaking mechanism, including the Laplacian case itself. Moreover, under the appropriate variable transformation this description is universal, i.e., independent of the transition dynamics, the initial cluster configuration, and the embedding Euclidean space.
Phase transitions in large deviations of reset processes
NASA Astrophysics Data System (ADS)
Harris, Rosemary J.; Touchette, Hugo
2017-03-01
We study the large deviations of additive quantities, such as energy or current, in stochastic processes with intermittent reset. Via a mapping from a discrete-time reset process to the Poland–Scheraga model for DNA denaturation, we derive conditions for observing first-order or continuous dynamical phase transitions in the fluctuations of such quantities and confirm these conditions on simple random walk examples. These results apply to reset Markov processes, but also show more generally that subleading terms in generating functions can lead to non-analyticities in large deviation functions of ‘compound processes’ or ‘random evolutions’ switching stochastically between two or more subprocesses.
Presidential Transition Teams: Fostering a Collaborative Transition Process
ERIC Educational Resources Information Center
Artman, Richard B.; Franz, Mark
2009-01-01
Whether hiring a sitting president or one beginning a first presidency, the board of trustees should be keenly interested in ensuring that the new president's first months in office flow as smoothly as possible. Increasing attention has been paid in recent years to the idea of using a transition team to assist the new president. Using a transition…
Transition region modeling for compressible flow
NASA Technical Reports Server (NTRS)
Chang, C.-L.; Singer, B. A.; Dinavahi, S. P. G.; El-Hady, N. M.; Pruett, C. D.; Harris, J. E.; Streett, C. L.; Zang, T. A.; Wilcox, D. C.
1992-01-01
The ongoing effort at NASA Langley Research Center aimed at developing transitional zone models for Reynolds-averaged Navier-Stokes calculations is described. Results from three models that we have examined - two zero-equation models and a two-equation model of the k-omega type - are presented for high-speed flows. The use of analytical and computational tools to provide guidance and to provide the transitional flow-field data bases necessary to develop such models is discussed. Some results from validation of these tools are given; qualitative comparisons between modeled and theoretical/computational representations of the transitional zone are provided.
Research on Methods of Processing Transit IC Card Information and Constructing Transit OD Matrix
NASA Astrophysics Data System (ADS)
Han, Xiuhua; Li, Jin; Peng, Han
Transit OD matrix is of vital importance when planning urban transit system. Traditional transit OD matrix constructing method needs a large range of spot check survey. It is expensive and needs long cycle time to process information. Recently transit IC card charging systems have been widely applied in big cities. Being processed reasonably, transit passenger information stored in IC card database can turn into information resource. It will reduce survey cost a lot. The concept of transit trip chain is put forward in this paper. According to the characteristics of closed transit trip chain, it discusses how to process IC card information and construct transit OD matrix. It also points out that urban transit information platform and data warehouse should be constructed, and how to integrate IC card information.
Cortical processing of dynamic sound envelope transitions.
Zhou, Yi; Wang, Xiaoqin
2010-12-08
Slow envelope fluctuations in the range of 2-20 Hz provide important segmental cues for processing communication sounds. For a successful segmentation, a neural processor must capture envelope features associated with the rise and fall of signal energy, a process that is often challenged by the interference of background noise. This study investigated the neural representations of slowly varying envelopes in quiet and in background noise in the primary auditory cortex (A1) of awake marmoset monkeys. We characterized envelope features based on the local average and rate of change of sound level in envelope waveforms and identified envelope features to which neurons were selective by reverse correlation. Our results showed that envelope feature selectivity of A1 neurons was correlated with the degree of nonmonotonicity in their static rate-level functions. Nonmonotonic neurons exhibited greater feature selectivity than monotonic neurons in quiet and in background noise. The diverse envelope feature selectivity decreased spike-timing correlation among A1 neurons in response to the same envelope waveforms. As a result, the variability, but not the average, of the ensemble responses of A1 neurons represented more faithfully the dynamic transitions in low-frequency sound envelopes both in quiet and in background noise.
A Conceptual Model for Leadership Transition
ERIC Educational Resources Information Center
Manderscheid, Steven V.; Ardichvili, Alexandre
2008-01-01
The purpose of this study was to develop a model of leadership transition based on an integrative review of literature. The article establishes a compelling case for focusing on leadership transitions as an area for study and leadership development practitioner intervention. The proposed model in this study identifies important success factors…
A Conceptual Model for Leadership Transition
ERIC Educational Resources Information Center
Manderscheid, Steven V.; Ardichvili, Alexandre
2008-01-01
The purpose of this study was to develop a model of leadership transition based on an integrative review of literature. The article establishes a compelling case for focusing on leadership transitions as an area for study and leadership development practitioner intervention. The proposed model in this study identifies important success factors…
Semiclassical theory of electronically nonadiabatic transitions in molecular collision processes
NASA Technical Reports Server (NTRS)
Lam, K. S.; George, T. F.
1979-01-01
An introductory account of the semiclassical theory of the S-matrix for molecular collision processes is presented, with special emphasis on electronically nonadiabatic transitions. This theory is based on the incorporation of classical mechanics with quantum superposition, and in practice makes use of the analytic continuation of classical mechanics into the complex space of time domain. The relevant concepts of molecular scattering theory and related dynamical models are described and the formalism is developed and illustrated with simple examples - collinear collision of the A+BC type. The theory is then extended to include the effects of laser-induced nonadiabatic transitions. Two bound continuum processes collisional ionization and collision-induced emission also amenable to the same general semiclassical treatment are discussed.
Phase transitions in Hidden Markov Models
NASA Astrophysics Data System (ADS)
Bechhoefer, John; Lathouwers, Emma
In Hidden Markov Models (HMMs), a Markov process is not directly accessible. In the simplest case, a two-state Markov model ``emits'' one of two ``symbols'' at each time step. We can think of these symbols as noisy measurements of the underlying state. With some probability, the symbol implies that the system is in one state when it is actually in the other. The ability to judge which state the system is in sets the efficiency of a Maxwell demon that observes state fluctuations in order to extract heat from a coupled reservoir. The state-inference problem is to infer the underlying state from such noisy measurements at each time step. We show that there can be a phase transition in such measurements: for measurement error rates below a certain threshold, the inferred state always matches the observation. For higher error rates, there can be continuous or discontinuous transitions to situations where keeping a memory of past observations improves the state estimate. We can partly understand this behavior by mapping the HMM onto a 1d random-field Ising model at zero temperature. We also present more recent work that explores a larger parameter space and more states. Research funded by NSERC, Canada.
Correcting transit time distributions in coarse MODFLOW-MODPATH models.
Abrams, Daniel
2013-01-01
In low to medium resolution MODFLOW models, the area occupied by sink cells often far exceeds the surface area of the streams they represent. As a result, MODPATH will calculate inaccurate particle traces and transit times. A frequency distribution of transit times for a watershed will also be in error. Such a distribution is used to assess the long-term impact of nonpoint source pollution on surface waters and wells. Although the inaccuracies for individual particles can only be avoided by increased model grid resolution or other advanced modeling techniques, the frequency distribution can be improved by scaling the particle transit times by an adjustment factor during post-processing.
A Correlation-Based Transition Model using Local Variables. Part 1; Model Formation
NASA Technical Reports Server (NTRS)
Menter, F. R.; Langtry, R. B.; Likki, S. R.; Suzen, Y. B.; Huang, P. G.; Volker, S.
2006-01-01
A new correlation-based transition model has been developed, which is based strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics (CFD) approaches, such as unstructured grids and massive parallel execution. The model is based on two transport equations, one for intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike, e.g., turbulence models) but from a framework for the implementation of correlation-based models into general-purpose CFD methods.
Hysteresis of magnetostructural transitions: Repeatable and non-repeatable processes
NASA Astrophysics Data System (ADS)
Provenzano, Virgil; Della Torre, Edward; Bennett, Lawrence H.; ElBidweihy, Hatem
2014-02-01
The Gd5Ge2Si2 alloy and the off-stoichiometric Ni50Mn35In15 Heusler alloy belong to a special class of metallic materials that exhibit first-order magnetostructural transitions near room temperature. The magnetic properties of this class of materials have been extensively studied due to their interesting magnetic behavior and their potential for a number of technological applications such as refrigerants for near-room-temperature magnetic refrigeration. The thermally driven first-order transitions in these materials can be field-induced in the reverse order by applying a strong enough field. The field-induced transitions are typically accompanied by the presence of large magnetic hysteresis, the characteristics of which are a complicated function of temperature, field, and magneto-thermal history. In this study we show that the virgin curve, the major loop, and sequentially measured MH loops are the results of both repeatable and non-repeatable processes, in which the starting magnetostructural state, prior to the cycling of field, plays a major role. Using the Gd5Ge2Si2 and Ni50Mn35In15 alloys, as model materials, we show that a starting single phase state results in fully repeatable processes and large magnetic hysteresis, whereas a mixed phase starting state results in non-repeatable processes and smaller hysteresis.
Mechanical Model of Globular Transition in Polymers
Tricard, Simon; Shepherd, Robert F.; Stan, Claudiu A.; Snyder, Phillip W.; Cademartiri, Rebecca; Zhu, Danny; Aranson, Igor S.; Shakhnovich, Eugene I.; Whitesides, George M.
2014-07-30
In complex, multicomponent systems, polymers often undergo phase transitions between distinct conformations. This paper reports a millimeter-scale granular model of coil-to-globule transitions: one “polymer” chain—a cylinders-on-a-string “pearl necklace”—and many spheres, all shaken on a horizontal surface. It is possible to describe the behavior of this granular system by using formalisms generally used in statistical physics of polymers. Two sets of experiments allowed the observation of first- and second- order coil-to-globule transitions. The model shows that the competition between long- and short range interactions leads to a first-order transition. Well-designed granular system represents another kind of approach to the study of polymer phase transitions and might inspire future designs of polymer-like mesoscale systems.
Factors and processes in children's transitive deductions
Wright, Barlow C.; Smailes, Jennifer
2015-01-01
Transitive tasks are important for understanding how children develop socio-cognitively. However, developmental research has been restricted largely to questions surrounding maturation. We asked 6-, 7- and 8-year-olds (N = 117) to solve a composite of five different transitive tasks. Tasks included conditions asking about item-C (associated with the marked relation) in addition to the usual case of asking only about item-A (associated with the unmarked relation). Here, children found resolving item-C much easier than resolving item-A, a finding running counter to long-standing assumptions about transitive reasoning. Considering gender perhaps for the first time, boys exhibited higher transitive scores than girls overall. Finally, analysing in the context of one recent and well-specified theory of spatial transitive reasoning, we generated the prediction that reporting the full series should be easier than deducing any one item from that series. This prediction was not upheld. We discuss amendments necessary to accommodate all our earlier findings. PMID:26635950
Transition Processes from College to Career.
ERIC Educational Resources Information Center
Hettich, Paul
The transition from college to career is one of the most challenging jobs an individual will experience. This is particularly true for students who have limited work experience. The fact that 50-80% of new college graduates leave their first job within three years may be due to poor career planning and problems inherent in the college-to-work…
A Process for Transition to Sustainability: Implementation
ERIC Educational Resources Information Center
Wooltorton, Sandra; Palmer, Marilyn; Steele, Fran
2011-01-01
This paper reports the outcomes of the second action cycle of an ongoing project at Edith Cowan University (ECU) called "Transition to Sustainability: ECU South West" which is located in a small, single faculty regional university campus. The overall project has comprised three action research cycles, the first of which was the planning…
Families and the Transition Process: Primary Style.
ERIC Educational Resources Information Center
Kentucky Univ., Lexington, KY. Interdisciplinary Human Development Inst.
Designed for parents in Kentucky, this handbook describes the Kentucky primary program and provides information about how parents can work with schools during the transition from preschool to ensure that their children receive an appropriate education. Children with educational disabilities are served in a variety of ways in the primary program.…
A Process for Transition to Sustainability: Implementation
ERIC Educational Resources Information Center
Wooltorton, Sandra; Palmer, Marilyn; Steele, Fran
2011-01-01
This paper reports the outcomes of the second action cycle of an ongoing project at Edith Cowan University (ECU) called "Transition to Sustainability: ECU South West" which is located in a small, single faculty regional university campus. The overall project has comprised three action research cycles, the first of which was the planning…
Phase Transitions in Models of Bird Flocking
NASA Astrophysics Data System (ADS)
Christodoulidi, H.; van der Weele, K.; Antonopoulos, Ch. G.; Bountis, T.
2014-12-01
The aim of the present paper is to elucidate the transition from collective to random behavior exhibited by various mathematical models of bird flocking. In particular, we compare Vicsek's model [Vicsek et al., Phys. Rev. Lett. 75, 1226-1229 (1995)] with one based on topological considerations. The latter model is found to exhibit a first order phase transition from flocking to decoherence, as the "noise parameter" of the problem is increased, whereas Vicsek's model gives a second order transition. Refining the topological model in such a way that birds are influenced mostly by the birds in front of them, less by the ones at their sides and not at all by those behind them (because they do not see them), we find a behavior that lies in between the two models. Finally, we propose a novel mechanism for preserving the flock's cohesion, without imposing artificial boundary conditions or attractive forces.
Fragmentation transitions in multistate voter models
NASA Astrophysics Data System (ADS)
Böhme, Gesa A.; Gross, Thilo
2012-06-01
Adaptive models of opinion formation among humans can display a fragmentation transition, where a social network breaks into disconnected components. Here we investigate this transition in a class of models with arbitrary number of opinions. In contrast to previous work we do not assume that opinions are equidistant or arranged on a one-dimensional conceptual axis. Our investigation reveals detailed analytical results on fragmentations in a three-opinion model, which are confirmed by agent-based simulations. Furthermore, we show that in certain models the number of opinions can be reduced without affecting the fragmentation points.
Mean first-passage time of quantum transition processes
NASA Astrophysics Data System (ADS)
Qiu, Rong-Tao; Dai, Wu-Sheng; Xie, Mi
2012-10-01
In this paper, we consider the problem of mean first-passage time (MFPT) in quantum mechanics; the MFPT is the average time of the transition from a given initial state, passing through some intermediate states, to a given final state for the first time. We apply the method developed in statistical mechanics for calculating the MFPT of random walks to calculate the MFPT of a transition process. As applications, we (1) calculate the MFPT for multiple-state systems, (2) discuss transition processes occurring in an environmental background, (3) consider a roundabout transition in a hydrogen atom, and (4) apply the approach to laser theory.
Modeling and Fitting Exoplanet Transit Light Curves
NASA Astrophysics Data System (ADS)
Millholland, Sarah; Ruch, G. T.
2013-01-01
We present a numerical model along with an original fitting routine for the analysis of transiting extra-solar planet light curves. Our light curve model is unique in several ways from other available transit models, such as the analytic eclipse formulae of Mandel & Agol (2002) and Giménez (2006), the modified Eclipsing Binary Orbit Program (EBOP) model implemented in Southworth’s JKTEBOP code (Popper & Etzel 1981; Southworth et al. 2004), or the transit model developed as a part of the EXOFAST fitting suite (Eastman et al. in prep.). Our model employs Keplerian orbital dynamics about the system’s center of mass to properly account for stellar wobble and orbital eccentricity, uses a unique analytic solution derived from Kepler’s Second Law to calculate the projected distance between the centers of the star and planet, and calculates the effect of limb darkening using a simple technique that is different from the commonly used eclipse formulae. We have also devised a unique Monte Carlo style optimization routine for fitting the light curve model to observed transits. We demonstrate that, while the effect of stellar wobble on transit light curves is generally small, it becomes significant as the planet to stellar mass ratio increases and the semi-major axes of the orbits decrease. We also illustrate the appreciable effects of orbital ellipticity on the light curve and the necessity of accounting for its impacts for accurate modeling. We show that our simple limb darkening calculations are as accurate as the analytic equations of Mandel & Agol (2002). Although our Monte Carlo fitting algorithm is not as mathematically rigorous as the Markov Chain Monte Carlo based algorithms most often used to determine exoplanetary system parameters, we show that it is straightforward and returns reliable results. Finally, we show that analyses performed with our model and optimization routine compare favorably with exoplanet characterizations published by groups such as the
The R-γ transition prediction model
NASA Astrophysics Data System (ADS)
Goldberg, Uriel C.; Batten, Paul; Peroomian, Oshin; Chakravarthy, Sukumar
2015-01-01
The Rt turbulence closure (Goldberg 2003) is coupled with an intermittency transport equation, γ, to enable prediction of laminar-to-turbulent flow by-pass transition. The model is not correlation-based and is completely topography-parameter-free, thus ready for use in parallelized Computational Fluid Dynamics (CFD) solvers based on unstructured book-keeping. Several examples compare the R-γ model's performance with experimental data and with predictions by the Langtry-Menter γ-Reθ transition closure (2009). Like the latter, the R-γ model is very sensitive to freestream turbulence levels, limiting its utility for engineering purposes.
Operationalizing resilience using state and transition models
USDA-ARS?s Scientific Manuscript database
In management, restoration, and policy contexts, the notion of resilience can be confusing. Systematic development of conceptual models of ecological state change (state transition models; STMs) can help overcome semantic confusion and promote a mechanistic understanding of resilience. Drawing on ex...
A Model of Mental State Transition Network
NASA Astrophysics Data System (ADS)
Xiang, Hua; Jiang, Peilin; Xiao, Shuang; Ren, Fuji; Kuroiwa, Shingo
Emotion is one of the most essential and basic attributes of human intelligence. Current AI (Artificial Intelligence) research is concentrating on physical components of emotion, rarely is it carried out from the view of psychology directly(1). Study on the model of artificial psychology is the first step in the development of human-computer interaction. As affective computing remains unpredictable, creating a reasonable mental model becomes the primary task for building a hybrid system. A pragmatic mental model is also the fundament of some key topics such as recognition and synthesis of emotions. In this paper a Mental State Transition Network Model(2) is proposed to detect human emotions. By a series of psychological experiments, we present a new way to predict coming human's emotions depending on the various current emotional states under various stimuli. Besides, people in different genders and characters are taken into consideration in our investigation. According to the psychological experiments data derived from 200 questionnaires, a Mental State Transition Network Model for describing the transitions in distribution among the emotions and relationships between internal mental situations and external are concluded. Further more the coefficients of the mental transition network model were achieved. Comparing seven relative evaluating experiments, an average precision rate of 0.843 is achieved using a set of samples for the proposed model.
Integrating Transition Planning into the IEP Process. Second Edition.
ERIC Educational Resources Information Center
West, Lynda L.; Corbey, Stephanie; Boyer-Stephens, Arden; Jones, Bonnie; Miller, Robert J.; Sarkees-Wircenski, Mickey
The purpose of this guide is to assist those involved in the transition planning process to help students with disabilities achieve a smooth transition from school to adult life. The guide addresses topics that deal with the preparation of students with disabilities as they leave high school. The guide's eight chapters deal with: (1) defining…
Transition mixing study empirical model report
NASA Technical Reports Server (NTRS)
Srinivasan, R.; White, C.
1988-01-01
The empirical model developed in the NASA Dilution Jet Mixing Program has been extended to include the curvature effects of transition liners. This extension is based on the results of a 3-D numerical model generated under this contract. The empirical model results agree well with the numerical model results for all tests cases evaluated. The empirical model shows faster mixing rates compared to the numerical model. Both models show drift of jets toward the inner wall of a turning duct. The structure of the jets from the inner wall does not exhibit the familiar kidney-shaped structures observed for the outer wall jets or for jets injected in rectangular ducts.
Modeling Transition to Turbulence using the Turbulent Potential Model
NASA Astrophysics Data System (ADS)
Chang, Wang; Perot, Blair
2001-11-01
While transition is a very different phenomenon from fully developed turbulence, it is governed, on average, by equations with are mathematically the same as the RANS equations for fully turbulent flow. It is therefore theoretically possible for RANS equation systems to display transition-like behavior a very rapid growth in turbulent kinetic energy levels, skin friction, etc. In this work, the ability of the turbulent potential model to accurately predict laminar to turbulent transition in flat plate boundary layers is examined. The model accurately predicts the entire range of free-stream turbulence levels from strong bypass transition (6natural transition (0.03It shows correct sensitivity to favorable and adverse pressure gradients, as well as acoustic noise levels. Past results indicated the ability of the model to relaminarize the flow. Recent work has focused attention on the model’s ability to predict transition in mixing layers.
Simple models for shear flow transition
NASA Astrophysics Data System (ADS)
Barkley, Dwight
2011-11-01
I will discuss recent developments in modeling transitional shear flows with simple two-variable models. Both pipe flow and plane Couette flow are considered. The essential insight is that most large-scale features of these shear flows can be traced to a change from excitability to bistability in the local dynamics. Models are presented in two variables, turbulence intensity and mean shear. A PDE model of pipe flow captures the essence of the puff-slug transition as a change from excitability to bistability. Extended models with turbulence as deterministic transient chaos or multiplicative noise reproduce almost all large-scale features of transitional pipe flow. In particular they capture metastable localized puffs, puff splitting, slugs, localized edge states, a continuous transition to sustained turbulence via spatiotemporal intermittency (directed percolation), and a subsequent increase in turbulence fraction towards uniform, featureless turbulence. A model that additionally takes into account the symmetries of plane Couette flow reproduces localized turbulence and periodic turbulent-laminar bands.
Phase Transitions in the Quadratic Contact Process on Complex Networks
NASA Astrophysics Data System (ADS)
Varghese, Chris; Durrett, Rick
2013-03-01
The quadratic contact process (QCP) is a natural extension of the well studied linear contact process where a single infected (1) individual can infect a susceptible (0) neighbor and infected individuals are allowed to recover (1 --> 0). In the QCP, a combination of two 1's is required to effect a 0 --> 1 change. We extend the study of the QCP, which so far has been limited to lattices, to complex networks as a model for the change in a population via sexual reproduction and death. We define two versions of the QCP - vertex centered (VQCP) and edge centered (EQCP) with birth events 1 - 0 - 1 --> 1 - 1 - 1 and 1 - 1 - 0 --> 1 - 1 - 1 respectively, where ` -' represents an edge. We investigate the effects of network topology by considering the QCP on regular, Erdős-Rényi and power law random graphs. We perform mean field calculations as well as simulations to find the steady state fraction of occupied vertices as a function of the birth rate. We find that on the homogeneous graphs (regular and Erdős-Rényi) there is a discontinuous phase transition with a region of bistability, whereas on the heavy tailed power law graph, the transition is continuous. The critical birth rate is found to be positive in the former but zero in the latter.
Affinity and its derivatives in the glass transition process
NASA Astrophysics Data System (ADS)
Garden, J.-L.; Guillou, H.; Richard, J.; Wondraczek, L.
2012-07-01
The thermodynamic treatment of the glass transition remains an issue of intense debate. When associated with the formalism of non-equilibrium thermodynamics, the lattice-hole theory of liquids can provide new insight in this direction, as has been shown by Schmelzer and Gutzow [J. Chem. Phys. 125, 184511 (2006)], 10.1063/1.2374894, by Möller et al. [J. Chem. Phys. 125, 094505 (2006)], 10.1063/1.2346673, and more recently by Tropin et al. [J. Non-Cryst. Solids 357, 1291 (2011), 10.1016/j.jnoncrysol.2010.11.111; Tropin et al., J. Non-Cryst. Solids 357, 1303 (2011)], 10.1016/j.jnoncrysol.2010.12.005. Here, we employ a similar approach. We include pressure as an additional variable, in order to account for the freezing-in of structural degrees of freedom upon pressure increase. Second, we demonstrate that important terms concerning first order derivatives of the affinity-driving-force with respect to temperature and pressure have been previously neglected. We show that these are of crucial importance in the approach. Macroscopic non-equilibrium thermodynamics is used to enlighten these contributions in the derivation of Cp,κT, and αp. The coefficients are calculated as a function of pressure and temperature following different theoretical protocols, revealing classical aspects of vitrification and structural recovery processes. Finally, we demonstrate that a simple minimalist model such as the lattice-hole theory of liquids, when being associated with rigorous use of macroscopic non-equilibrium thermodynamics, is able to account for the primary features of the glass transition phenomenology. Notwithstanding its simplicity and its limits, this approach can be used as a very pedagogical tool to provide a physical understanding on the underlying thermodynamics which governs the glass transition process.
The Work of Cultural Transition: An Emerging Model.
Ryba, Tatiana V; Stambulova, Natalia B; Ronkainen, Noora J
2016-01-01
In today's uncertain, fluid job market, transnational mobility has intensified. Though the concept of cultural transition is increasingly used in sport and career research, insight into the processes of how individuals produce their own development through work and relationships in shifting cultural patterns of meaning remains limited. The transnational industry of sports, in which athletes' psychological adjustment to cultural transitions has implications for both performance and meaningful life, serves as a backdrop for this article. This study applied the life story method to interviews with 15 professional and semi-professional athletes, focusing particularly on the cultural transition aspect of their transnational athletic careers. The aims of the study were to identify the developmental tasks of cultural transitions and strategies/mechanisms through which cultural transitions were enacted. Three underlying mechanisms of the transition process that assisted athletic career adaptability were social repositioning, negotiation of cultural practices, and meaning reconstruction. Based on the data analyses, a temporal model of cultural transition is proposed. The results of this research provide professionals working in the fields of career counseling and migrant support with a content framework for enhancing migrant workers' adaptabilities and psychological wellbeing.
The Work of Cultural Transition: An Emerging Model
Ryba, Tatiana V.; Stambulova, Natalia B.; Ronkainen, Noora J.
2016-01-01
In today’s uncertain, fluid job market, transnational mobility has intensified. Though the concept of cultural transition is increasingly used in sport and career research, insight into the processes of how individuals produce their own development through work and relationships in shifting cultural patterns of meaning remains limited. The transnational industry of sports, in which athletes’ psychological adjustment to cultural transitions has implications for both performance and meaningful life, serves as a backdrop for this article. This study applied the life story method to interviews with 15 professional and semi-professional athletes, focusing particularly on the cultural transition aspect of their transnational athletic careers. The aims of the study were to identify the developmental tasks of cultural transitions and strategies/mechanisms through which cultural transitions were enacted. Three underlying mechanisms of the transition process that assisted athletic career adaptability were social repositioning, negotiation of cultural practices, and meaning reconstruction. Based on the data analyses, a temporal model of cultural transition is proposed. The results of this research provide professionals working in the fields of career counseling and migrant support with a content framework for enhancing migrant workers’ adaptabilities and psychological wellbeing. PMID:27047436
Adding structure to the transition process to advanced mathematical activity
NASA Astrophysics Data System (ADS)
Engelbrecht, Johann
2010-03-01
The transition process to advanced mathematical thinking is experienced as traumatic by many students. Experiences that students had of school mathematics differ greatly to what is expected from them at university. Success in school mathematics meant application of different methods to get an answer. Students are not familiar with logical deductive reasoning, required in advanced mathematics. It is necessary to assist students in this transition process, in moving from general to mathematical thinking. In this article some structure is suggested for this transition period. This essay is an argumentative exposition supported by personal experience and international literature. This makes this study theoretical rather than empirical.
Transition Services Model: Partnership for Student Success
ERIC Educational Resources Information Center
Pearman, Elizabeth; Elliott, Twila; Aborn, Lucinda
2004-01-01
In 1995, the Southwest Special Education Local Plan Area (SELPA) of the Los Angeles County School District, and El Camino College pioneered a partnership to serve students with disabilities on the community college campus. SELPA transition services serve as a model for alliances between community colleges and school districts throughout…
A synergetic model for human gait transitions
NASA Astrophysics Data System (ADS)
Abdolvahab, Mohammad
2015-09-01
Gait transitions have been considered as bifurcations between states (e.g. walking or running modes) of a nonlinear dynamical system. A top-down synergetic approach to model gait transitions has been adapted from Frank et al. (2009) and applied to two sets of empirical observations. In this approach, it is assumed that the amplitudes of the spatio-temporal modes of locomotion satisfy a generic form of evolution equations that are known to hold for animate and inanimate self-organizing systems. The presented experimental results focus on hysteresis in human walk-to-run and run-to-walk transitions on a treadmill as a function of treadmill inclination and acceleration, the rate at which speed was increased or decreased during experimental trials. The bi-stability in the synergetic model is assumed to account for the hysteretic transitions. Accordingly, the relevant parameters of the model were estimated from the empirical data and the model's efficacy in predicting the observed hysteresis effects was evaluated.
Modeling Developmental Transitions in Adaptive Resonance Theory
ERIC Educational Resources Information Center
Raijmakers, Maartje E. J.; Molenaar, Peter C. M.
2004-01-01
Neural networks are applied to a theoretical subject in developmental psychology: modeling developmental transitions. Two issues that are involved will be discussed: discontinuities and acquiring qualitatively new knowledge. We will argue that by the appearance of a bifurcation, a neural network can show discontinuities and may acquire…
Transition Services Model: Partnership for Student Success
ERIC Educational Resources Information Center
Pearman, Elizabeth; Elliott, Twila; Aborn, Lucinda
2004-01-01
In 1995, the Southwest Special Education Local Plan Area (SELPA) of the Los Angeles County School District, and El Camino College pioneered a partnership to serve students with disabilities on the community college campus. SELPA transition services serve as a model for alliances between community colleges and school districts throughout…
Stochastic Modeling of Laminar-Turbulent Transition
NASA Technical Reports Server (NTRS)
Rubinstein, Robert; Choudhari, Meelan
2002-01-01
Stochastic versions of stability equations are developed in order to develop integrated models of transition and turbulence and to understand the effects of uncertain initial conditions on disturbance growth. Stochastic forms of the resonant triad equations, a high Reynolds number asymptotic theory, and the parabolized stability equations are developed.
Modeling Developmental Transitions in Adaptive Resonance Theory
ERIC Educational Resources Information Center
Raijmakers, Maartje E. J.; Molenaar, Peter C. M.
2004-01-01
Neural networks are applied to a theoretical subject in developmental psychology: modeling developmental transitions. Two issues that are involved will be discussed: discontinuities and acquiring qualitatively new knowledge. We will argue that by the appearance of a bifurcation, a neural network can show discontinuities and may acquire…
APL experience with space weather modeling and transition to operations
NASA Astrophysics Data System (ADS)
Zanetti, L. J.; Wing, S.
2009-12-01
In response to the growing space weather needs, the Johns Hopkins University Applied Physics Laboratory (APL) developed and delivered twenty two state of the art space weather products under the auspice of the University Partnering in Operational Support program, initiated in 1998. These products offer nowcasts and forecasts for the region spanning from the Sun to the Earth. Some of these products have been transitioned to the Air Force Weather Agency and other space weather centers. The transition process is quite different from research modeling, requiring additional staff with different sets of expertise. Recently, APL has developed a space weather web page to serve these products to the research and user community. For the initial stage, we have chosen ten of these products to be served from our website, which is presently still under construction. APL’s experience, lessons learned, and successes from developing space weather models, the transition to operations process and the webpage access will be shared and discussed
Process for making transition metal nitride whiskers
Bamberger, C.E.
1988-04-12
A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites. 1 fig., 1 tab.
Process for making transition metal nitride whiskers
Bamberger, Carlos E.
1989-01-01
A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites.
Glass transition temperature and its relevance in food processing.
Roos, Yrjö H
2010-01-01
Amorphous, noncrystalline solids are typical of low water content and frozen foods. Solids in these foods, e.g., confectionary, dehydrated foods, cereal foods, and frozen foods, often form nonequilibrium glass-like structures. The glassy state of the solids forms during food processing in a reversible glass transition. Vitrification can occur in numerous glassy states that exhibit various relaxations around the glass transition. The success of freeze drying, spray drying, and extrusion and the stability of dehydrated foods against flow, collapse, and crystallization is based on the control of the glassy state during the dehydration process and storage. Encapsulation processes often use glass-forming materials to entrap dispersed components or improve retention of volatiles. Plasticization of the noncrystalline structures by temperature or water reduce relaxation times exponentially above the glass transition, which results in rapid deterioration. Critical values for water activity and water content express the level of water plasticization leading to glass transition in food storage.
Gaussian Process Morphable Models.
Luthi, Marcel; Gerig, Thomas; Jud, Christoph; Vetter, Thomas
2017-08-14
Models of shape variations have become a central component for the automated analysis of images. An important class of shape models are point distribution models (PDMs). These models represent a class of shapes as a normal distribution of point variations, whose parameters are estimated from example shapes. Principal component analysis (PCA) is applied to obtain a low-dimensional representation of the shape variation in terms of the leading principal components. In this paper, we propose a generalization of PDMs, which we refer to as Gaussian Process Morphable Models (GPMMs). We model the shape variations with a Gaussian process, which we represent using the leading components of its Karhunen-Loève expansion. To compute the expansion, we make use of an approximation scheme based on the Nyström method. The resulting model can be seen as a continuous analog of a standard PDM. However, while for PDMs the shape variation is restricted to the linear span of the example data, with GPMMs we can define the shape variation using any Gaussian process. For example, we can build shape models that correspond to classical spline models and thus do not require any example data. Furthermore, Gaussian processes make it possible to combine different models. For example, a PDM can be extended with a spline model, to obtain a model that incorporates learned shape characteristics but is flexible enough to explain shapes that cannot be represented by the PDM.
Transition matrix model for evolutionary game dynamics
NASA Astrophysics Data System (ADS)
Ermentrout, G. Bard; Griffin, Christopher; Belmonte, Andrew
2016-03-01
We study an evolutionary game model based on a transition matrix approach, in which the total change in the proportion of a population playing a given strategy is summed directly over contributions from all other strategies. This general approach combines aspects of the traditional replicator model, such as preserving unpopulated strategies, with mutation-type dynamics, which allow for nonzero switching to unpopulated strategies, in terms of a single transition function. Under certain conditions, this model yields an endemic population playing non-Nash-equilibrium strategies. In addition, a Hopf bifurcation with a limit cycle may occur in the generalized rock-scissors-paper game, unlike the replicator equation. Nonetheless, many of the Folk Theorem results are shown to hold for this model.
Computing transitional flows using wall-modeled large eddy simulation
NASA Astrophysics Data System (ADS)
Bodart, Julien; Larsson, Johan
2012-11-01
To be applicable to complex aerodynamic flows at realistic Reynolds numbers, large eddy simulation (LES) must be combined with a model for the inner part of the boundary layer. Aerodynamic flows are, in general, sensitive to the location of boundary layer transition. While traditional LES can predict the transition location and process accurately, existing wall-modeled LES approaches can not. In the present work, the behavior of the wall-model is locally adapted using a sensor in the LES-resolved part of boundary layer. This sensor estimates whether the boundary layer is turbulent or not, in a way that does not rely on any homogeneous direction. The proposed method is validated on controlled transition scenarios on a flat plat boundary layer, and finally applied to the flow around a multi-element airfoil at realistic Reynolds number.
Radiology interpretation process modeling.
Noumeir, Rita
2006-04-01
Information and communication technology in healthcare promises optimized patient care while ensuring efficiency and cost-effectiveness. However, the promised results are not yet achieved; the healthcare process requires analysis and radical redesign to achieve improvements in care quality and productivity. Healthcare process reengineering is thus necessary and involves modeling its workflow. Even though the healthcare process is very large and not very well modeled yet, its sub-processes can be modeled individually, providing fundamental pieces of the whole model. In this paper, we are interested in modeling the radiology interpretation process that results in generating a diagnostic radiology report. This radiology report is an important clinical element of the patient healthcare record and assists in healthcare decisions. We present the radiology interpretation process by identifying its boundaries and by positioning it on the large healthcare process map. Moreover, we discuss an information data model and identify roles, tasks and several information flows. Furthermore, we describe standard frameworks to enable radiology interpretation workflow implementations between heterogeneous systems.
ERIC Educational Resources Information Center
Grimes, Michael K.
The panel presentation traces the development of and describes the operation of a Brentwood (California) project to prepare approximately 75 severely disabled individuals, ages 12-22, to function in the least restrictive recreation/leisure, vocational, and general community environments. Transition Steering Committee developed such project…
Choice versus Transition: The College Choice Process for Students with Disabilities
ERIC Educational Resources Information Center
Murray, Thomas A.; Schultz, Stacie M.; Cabrera, Nolan L.
2016-01-01
While there is little empirical research regarding how the college choice process unfolds for students with disabilities, Webb (2000) developed a five-stage transition model for this population. In this study, we sought to identify the overlap as well as the specific points of departure that Webb's model has with traditional college choice models.…
Preparing Youth for the Transition into Adulthood: A Process Description
ERIC Educational Resources Information Center
Ringle, Jay L.; Ingram, Stephanie; Newman, Veronica; Thompson, Ronald W.; Waite, Thomas
2007-01-01
This article describes the process that youth in a large residential out-of-home care program complete as they prepare for the transition into adulthood. This process is geared toward preparing these young people through a series of structured real-life activities and lessons. Results from a separate 5-year follow-up study indicate that those who…
Flow transitions in a 2D directional solidification model
NASA Technical Reports Server (NTRS)
Larroude, Philippe; Ouazzani, Jalil; Alexander, J. Iwan D.
1992-01-01
Flow transitions in a Two Dimensional (2D) model of crystal growth were examined using the Bridgman-Stockbarger me thod. Using a pseudo-spectral Chebyshev collocation method, the governing equations yield solutions which exhibit a symmetry breaking flow tansition and oscillatory behavior indicative of a Hopf bifurcation at higher values of Ra. The results are discussed from fluid dynamic viewpoint, and broader implications for process models are also addressed.
Biosphere Process Model Report
J. Schmitt
2000-05-25
To evaluate the postclosure performance of a potential monitored geologic repository at Yucca Mountain, a Total System Performance Assessment (TSPA) will be conducted. Nine Process Model Reports (PMRs), including this document, are being developed to summarize the technical basis for each of the process models supporting the TSPA model. These reports cover the following areas: (1) Integrated Site Model; (2) Unsaturated Zone Flow and Transport; (3) Near Field Environment; (4) Engineered Barrier System Degradation, Flow, and Transport; (5) Waste Package Degradation; (6) Waste Form Degradation; (7) Saturated Zone Flow and Transport; (8) Biosphere; and (9) Disruptive Events. Analysis/Model Reports (AMRs) contain the more detailed technical information used to support TSPA and the PMRs. The AMRs consists of data, analyses, models, software, and supporting documentation that will be used to defend the applicability of each process model for evaluating the postclosure performance of the potential Yucca Mountain repository system. This documentation will ensure the traceability of information from its source through its ultimate use in the TSPA-Site Recommendation (SR) and in the National Environmental Policy Act (NEPA) analysis processes. The objective of the Biosphere PMR is to summarize (1) the development of the biosphere model, and (2) the Biosphere Dose Conversion Factors (BDCFs) developed for use in TSPA. The Biosphere PMR does not present or summarize estimates of potential radiation doses to human receptors. Dose calculations are performed as part of TSPA and will be presented in the TSPA documentation. The biosphere model is a component of the process to evaluate postclosure repository performance and regulatory compliance for a potential monitored geologic repository at Yucca Mountain, Nevada. The biosphere model describes those exposure pathways in the biosphere by which radionuclides released from a potential repository could reach a human receptor
Glass transitions in the cellular Potts model
NASA Astrophysics Data System (ADS)
Chiang, M.; Marenduzzo, D.
2016-10-01
We study the dynamical transition between a fluid-like and a solid-like phase in a confluent cell monolayer, by using the cellular Potts model and computer simulations. We map out the phase diagram as a function of interfacial tension and of cell motility. While in the fluid phase there is normal diffusion, in the solid phase we observe sub-diffusion, very slow relaxation, and ageing, thereby strongly suggesting that this phase is glassy. Our results complement previous theoretical work within the vertex model and show that the cellular Potts model can account for the experimentally observed glassy dynamics of some biological tissues.
MODEL UPDATING: TRANSITION FROM RESEARCH TO PRACTICE?
D. C. ZIMMERMAN; F. M. HEMEZ
2000-10-01
This session offers an open forum to discuss issues associated with the transition of nearly two decades of engineering research into computational guided model updating into industry state-of-the-practice. Related technical issues are the model updating technology, model reduction, test-analysis correlation and optimization strategies. The session is organized as follows. Technical presentations review the state-of-the-art in finite element model updating and present examples of industrial applications. The results of a recent survey on the potential and usefulness of the model updating technology are discussed. Panel discussions and interaction with the audience discuss industrial needs, future trends and challenges and why negative model updating results are never discussed within the structural dynamics community.
Camera-Model Identification Using Markovian Transition Probability Matrix
NASA Astrophysics Data System (ADS)
Xu, Guanshuo; Gao, Shang; Shi, Yun Qing; Hu, Ruimin; Su, Wei
Detecting the (brands and) models of digital cameras from given digital images has become a popular research topic in the field of digital forensics. As most of images are JPEG compressed before they are output from cameras, we propose to use an effective image statistical model to characterize the difference JPEG 2-D arrays of Y and Cb components from the JPEG images taken by various camera models. Specifically, the transition probability matrices derived from four different directional Markov processes applied to the image difference JPEG 2-D arrays are used to identify statistical difference caused by image formation pipelines inside different camera models. All elements of the transition probability matrices, after a thresholding technique, are directly used as features for classification purpose. Multi-class support vector machines (SVM) are used as the classification tool. The effectiveness of our proposed statistical model is demonstrated by large-scale experimental results.
Protein structure comparison using the markov transition model of evolution.
Kawabata, T; Nishikawa, K
2000-10-01
A number of automatic protein structure comparison methods have been proposed; however, their similarity score functions are often decided by the researchers' intuition and trial-and-error, and not by theoretical background. We propose a novel theory to evaluate protein structure similarity, which is based on the Markov transition model of evolution. Our similarity score between structures i and j is defined as log P(j --> i)/P(i), where P(j --> i) is the probability that structure j changes to structure i during the evolutionary process, and P(i) is the probability that structure i appears by chance. This is a reasonable definition of structure similarity, especially for finding evolutionarily related (homologous) similarity. The probability P(j --> i) is estimated by the Markov transition model, which is similar to the Dayhoff's substitution model between amino acids. To estimate the parameters of the model, homologous protein structure pairs are collected using sequence similarity, and the numbers of structure transitions within the pairs are counted. Next these numbers are transformed to a transition probability matrix of the Markov transition. Transition probabilities for longer time are obtained by multiplying the probability matrix by itself several times. In this study, we generated three types of structure similarity scores: an environment score, a residue-residue distance score, and a secondary structure elements (SSE) score. Using these scores, we developed the structure comparison program, Matras (MArkovian TRAnsition of protein Structure). It employs a hierarchical alignment algorithm, in which a rough alignment is first obtained by SSEs, and then is improved with more detailed functions. We attempted an all-versus-all comparison of the SCOP database, and evaluated its ability to recognize a superfamily relationship, which was manually assigned to be homologous in the SCOP database. A comparison with the FSSP database shows that our program can
Engineering models of deflagration-to-detonation transition
Bdzil, J.B.; Son, S.F.
1995-07-01
For the past two years, Los Alamos has supported research into the deflagration-to-detonation transition (DDT) in damaged energetic materials as part of the explosives safety program. This program supported both a theory/modeling group and an experimentation group. The goal of the theory/modeling group was to examine the various modeling structures (one-phase models, two-phase models, etc.) and select from these a structure suitable to model accidental initiation of detonation in damaged explosives. The experimental data on low-velocity piston supported DDT in granular explosive was to serve as a test bed to help in the selection process. Three theoretical models have been examined in the course of this study: (1) the Baer-Nunziato (BN) model, (2) the Stewart-Prasad-Asay (SPA) model and (3) the Bdzil-Kapila-Stewart model. Here we describe these models, discuss their properties, and compare their features.
Inequivalent models of irreversible dimer filling: ``Transition state'' dependence
NASA Astrophysics Data System (ADS)
Nord, R. S.; Evans, J. W.
1990-12-01
Irreversible adsorption of diatomics on crystalline surfaces is sometimes modeled as random dimer filling of adjacent pairs of sites on a lattice. We note that this process can be implemented in two distinct ways: (i) randomly pick adjacent pairs of sites, jj', and fill jj' only if both are empty (horizontal transition state); or (ii) randomly pick a single site, j, and if j and at least one neighbor are empty, then fill j and a randomly chosen empty neighbor (vertical transition state). Here it is instructive to consider processes which also include competitive random monomer filling of single sites. We find that although saturation (partial) coverages differ little between the models for pure dimer filling, there is a significant difference for comparable monomer and dimer filling rates. We present exact results for saturation coverage behavior for a linear lattice, and estimates for a square lattice. Ramifications for simple models of CO oxidation on surfaces are indicated.
Microwave sintering process model.
Peng, Hu; Tinga, W R; Sundararaj, U; Eadie, R L
2003-01-01
In order to simulate and optimize the microwave sintering of a silicon nitride and tungsten carbide/cobalt toolbits process, a microwave sintering process model has been built. A cylindrical sintering furnace was used containing a heat insulating layer, a susceptor layer, and an alumina tube containing the green toolbit parts between parallel, electrically conductive, graphite plates. Dielectric and absorption properties of the silicon nitride green parts, the tungsten carbide/cobalt green parts, and an oxidizable susceptor material were measured using perturbation and waveguide transmission methods. Microwave absorption data were measured over a temperature range from 20 degrees C to 800 degrees C. These data were then used in the microwave process model which assumed plane wave propagation along the radial direction and included the microwave reflection at each interface between the materials and the microwave absorption in the bulk materials. Heat transfer between the components inside the cylindrical sintering furnace was also included in the model. The simulated heating process data for both silicon nitride and tungsten carbide/cobalt samples closely follow the experimental data. By varying the physical parameters of the sintering furnace model, such as the thickness of the susceptor layer, the thickness of the allumina tube wall, the sample load volume and the graphite plate mass, the model data predicts their effects which are helpful in optimizing those parameters in the industrial sintering process.
Transitional duty. An overview of program management and placement process.
Evangelista-Uhl, G A; Loomis, S C
1999-07-01
Transitional duty is an effective means to return employees to work after an injury or illness. Provision of transitional duty may facilitate earlier return to work. It also helps in retaining an experienced work force, and decreases disability related costs. The occupational and environmental health nurse plays a major role in developing and maintaining a transitional duty program. Essential to programmatic responsibility is the ability to determine organizational culture, involve key stakeholders, and develop a program proposal that "sells" the program to a variety of customers. The ability to consistently evaluate and demonstrate program outcomes, once formal support is attained, is crucial to continued program support. The transitional duty placement process is a vital component of a comprehensive disability program and ensures employees are identified and placed appropriately according to their functional capacity. Routine evaluation of employees on transitional duty is essential to allow for progressive placement. The nurse plays a vital part in counseling and supporting employees and supervisors involved in the transitional duty process.
Moffat, Harry K.; Noble, David R.; Baer, Thomas A.; Adolf, Douglas Brian; Rao, Rekha Ranjana; Mondy, Lisa Ann
2008-09-01
In this report, we summarize our work on developing a production level foam processing computational model suitable for predicting the self-expansion of foam in complex geometries. The model is based on a finite element representation of the equations of motion, with the movement of the free surface represented using the level set method, and has been implemented in SIERRA/ARIA. An empirically based time- and temperature-dependent density model is used to encapsulate the complex physics of foam nucleation and growth in a numerically tractable model. The change in density with time is at the heart of the foam self-expansion as it creates the motion of the foam. This continuum-level model uses an homogenized description of foam, which does not include the gas explicitly. Results from the model are compared to temperature-instrumented flow visualization experiments giving the location of the foam front as a function of time for our EFAR model system.
ERIC Educational Resources Information Center
Czocher, Jennifer A.
2016-01-01
This study contributes a methodological tool to reconstruct the cognitive processes and mathematical activities carried out by mathematical modelers. Represented as Modeling Transition Diagrams (MTDs), individual modeling routes were constructed for four engineering undergraduate students. Findings stress the importance and limitations of using…
ERIC Educational Resources Information Center
Czocher, Jennifer A.
2016-01-01
This study contributes a methodological tool to reconstruct the cognitive processes and mathematical activities carried out by mathematical modelers. Represented as Modeling Transition Diagrams (MTDs), individual modeling routes were constructed for four engineering undergraduate students. Findings stress the importance and limitations of using…
Investigation of Plasma Processes in Electronic Transition Lasers
1989-02-28
linewidth of the injected dye " Peek aDw, Dt,or laser radiation: 0.2 cm - ’ (grating tuned) or 0.04 cm - PO (grating tuned + intracavity etalon of I...I I I I [ II!9• I R89-9271 62-1 I INVESTIGATION OF PLASMA PROCESSES IN ELECTRONIC TRANSITION LASERS 3 <Final Report February 28, 1989 Sponsored by...RESEARCH CENTER East "Ief ord, Connecticut 06106 I 04 I U i R89-927162-1 I Investigation Of Plasma Processes In Electronic Transition Lasers I I Final
NASA Technical Reports Server (NTRS)
Langtry, R. B.; Menter, F. R.; Likki, S. R.; Suzen, Y. B.; Huang, P. G.; Volker, S.
2006-01-01
A new correlation-based transition model has been developed, which is built strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics (CFD) methods using unstructured grids and massive parallel execution. The model is based on two transport equations, one for the intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike, e.g., turbulence models), but form a framework for the implementation of correlation-based models into general-purpose CFD methods.
Valence transition in the periodic Anderson model
NASA Astrophysics Data System (ADS)
Hübsch, A.; Becker, K. W.
2006-08-01
A very rich phase diagram has recently been found in CeCu2Si2 from high pressure experiments where, in particular, a transition between an intermediate valence configuration and an integral valent heavy fermion state has been observed. We show that such a valence transition can be understood in the framework of the periodic Anderson model. In particular, our results show a breakdown of a mixed-valence state which is accompanied by a drastic change in the f occupation in agreement with experiment. This valence transition can possibly be interpreted as a collapse of the large Fermi surface of the heavy fermion state which incorporates not only the conduction electrons but also the localized f electrons. The theoretical approach used in this paper is based on the novel projector-based renormalization method (PRM). With respect to the periodic Anderson model, the method was before only employed in combination with the basic approximations of the well-known slave-boson mean-field theory. In this paper, the PRM treatment is performed in a more sophisticated manner where both mixed as well as integral valent solutions have been obtained. Furthermore, we argue that the presented PRM approach might be a promising starting point to study the competing interactions in CeCu2Si2 and related compounds.
Unified Model Deformation and Flow Transition Measurements
NASA Technical Reports Server (NTRS)
Burner, Alpheus W.; Liu, Tianshu; Garg, Sanjay; Bell, James H.; Morgan, Daniel G.
1999-01-01
The number of optical techniques that may potentially be used during a given wind tunnel test is continually growing. These include parameter sensitive paints that are sensitive to temperature or pressure, several different types of off-body and on-body flow visualization techniques, optical angle-of-attack (AoA), optical measurement of model deformation, optical techniques for determining density or velocity, and spectroscopic techniques for determining various flow field parameters. Often in the past the various optical techniques were developed independently of each other, with little or no consideration for other techniques that might also be used during a given test. Recently two optical techniques have been increasingly requested for production measurements in NASA wind tunnels. These are the video photogrammetric (or videogrammetric) technique for measuring model deformation known as the video model deformation (VMD) technique, and the parameter sensitive paints for making global pressure and temperature measurements. Considerations for, and initial attempts at, simultaneous measurements with the pressure sensitive paint (PSP) and the videogrammetric techniques have been implemented. Temperature sensitive paint (TSP) has been found to be useful for boundary-layer transition detection since turbulent boundary layers convect heat at higher rates than laminar boundary layers of comparable thickness. Transition is marked by a characteristic surface temperature change wherever there is a difference between model and flow temperatures. Recently, additional capabilities have been implemented in the target-tracking videogrammetric measurement system. These capabilities have permitted practical simultaneous measurements using parameter sensitive paint and video model deformation measurements that led to the first successful unified test with TSP for transition detection in a large production wind tunnel.
Intelligent card processing terminal of urban rail transit in Nanjing
NASA Astrophysics Data System (ADS)
Xia, Dechuan; Zhang, Xiaojun; Song, Yana; He, Tiejun
2011-10-01
In order to improve the compatibility, security and expandability of Automatic Fare Collection System in rail transit, and reduce the maintenance cost, intelligent card processing terminal is proposed in this paper. The operation flow and features of intelligent card processing terminal are analyzed in detailed, and the software and hardware structures and business treatment process are designed. Finally, the security mechanism of intelligent card processing terminal is summarized. The application results shows that Intelligent card processing terminal makes interconnection among lines easier, creates considerable economic efficiency and the social efficiency, and can be widely used.
Mott transitions in the periodic Anderson model
NASA Astrophysics Data System (ADS)
Logan, David E.; Galpin, Martin R.; Mannouch, Jonathan
2016-11-01
The periodic Anderson model (PAM) is studied within the framework of dynamical mean-field theory, with particular emphasis on the interaction-driven Mott transition it contains, and on resultant Mott insulators of both Mott-Hubbard and charge-transfer type. The form of the PAM phase diagram is first deduced on general grounds using two exact results, over the full range of model parameters and including metallic, Mott, Kondo and band insulator phases. The effective low-energy model which describes the PAM in the vicinity of a Mott transition is then shown to be a one-band Hubbard model, with effective hoppings that are not in general solely nearest neighbour, but decay exponentially with distance. This mapping is shown to have a range of implications for the physics of the problem, from phase boundaries to single-particle dynamics; all of which are confirmed and supplemented by NRG calculations. Finally we consider the locally degenerate, non-Fermi liquid Mott insulator, to describe which requires a two-self-energy description. This is shown to yield a number of exact results for the associated local moment, charge, and interaction-renormalised levels, together with a generalisation of Luttinger’s theorem to the Mott insulator.
Adding Structure to the Transition Process to Advanced Mathematical Activity
ERIC Educational Resources Information Center
Engelbrecht, Johann
2010-01-01
The transition process to advanced mathematical thinking is experienced as traumatic by many students. Experiences that students had of school mathematics differ greatly to what is expected from them at university. Success in school mathematics meant application of different methods to get an answer. Students are not familiar with logical…
Adding Structure to the Transition Process to Advanced Mathematical Activity
ERIC Educational Resources Information Center
Engelbrecht, Johann
2010-01-01
The transition process to advanced mathematical thinking is experienced as traumatic by many students. Experiences that students had of school mathematics differ greatly to what is expected from them at university. Success in school mathematics meant application of different methods to get an answer. Students are not familiar with logical…
Becoming Counselors through Growth and Learning: The Entry Transition Process
ERIC Educational Resources Information Center
Wagner, Holly H.; Hill, Nicole R.
2015-01-01
This article explored counselor development within the entry transition into counselor education programs using 4 interviews and interpretive dialogues with 8 beginning counselors. Six categories resulted from the authors' grounded theory analysis: Anticipation, Evolving Identity, Growth and Learning, Coping, Choosing to Trust the Process, and…
Modelling of natural and bypass transition in aerodynamics
NASA Astrophysics Data System (ADS)
Fürst, Jiří; Straka, Petr; Příhoda, Jaromír
2014-03-01
Most of transition models are proposed for modelling of the bypass transition common in the internal aerodynamics especially in turbomachinery where free stream turbulence is the dominant parameter affecting the transition onset. Free-stream turbulence level in the external aerodynamics is usually noticeably lower and so the natural transition often occurs in flows around airfoils. The transition model with the algebraic equation for the intermittency coefficient proposed originally by Straka and Příhoda [3] for the bypass transition was modified for modelling of the transition at low free-stream turbulence. The modification is carried out using experimental data of Schubauer and Skramstad [18]. Further, the three-equation k-kL-ω model proposed by Walters and Cokljat [10] was used for the modelling of the transition at low free-stream turbulence. Both models were tested by means of the incompressible flow around airfoils at moderate and very low free-stream turbulence.
Models of transition regions in hybrid stars
NASA Technical Reports Server (NTRS)
Brosius, J. W.; Mullan, D. J.
1986-01-01
Models for the transition regions of six hybrid stars, four bright giants and two supergiants, are calculated. The models include mass loss and prescribe Alfven waves as the source of mechanical energy. The momentum and energy deposition rates required at each level of the atmosphere are evaluated. The final models for all six stars have mass loss rates lying below the current VLA upper limits by factors of two to ten, and have densities which agree with those derived by density-sensitive line ratios. The density vs. temperature structure in Alpha TrA agree well with that derived by Hartmann et al. (1985). Wave amplitudes and magnetic field strengths are derived as functions of height, and the amplitudes are found to agree well with the observed line widths in Alpha TrA.
When University Faculty Retire: A Study of the Transition Process.
ERIC Educational Resources Information Center
Pappas, John G.; Goodman, Jane
This study examined the retirement transitions of college faculty based on the Schlossberg (1984) model, which suggests that successful coping depends on an evaluation of the retiree's unique situation, the qualities of the individual, the support available, and the strategies employed. A total of 55 emeritus faculty from the College of Education…
Sabin-to-Mahoney Transition Model of Quasispecies Replication
2009-05-31
Qspp is an agent-based stochastic simulation model of the Poliovirus Sabin-to-Mahoney transition. This code simulates a cell-to-cell model of Poliovirus replication. The model tracks genotypes (virus genomes) as they are replicated in cells, and as the cells burst and release particles into the medium of a culture dish. An inoculum is then taken from the pool of virions and is used to inoculate cells on a new dish. This process repeats. The Sabin genotype comprises the initial inoculum. Nucleotide positions that match the Sabin1 (vaccine strain) and Mahoney (wild type) genotypes, as well as the neurovirulent phenotype (from the literature) are enumerated as constants.
NASA Technical Reports Server (NTRS)
McNeill, Justin
1995-01-01
The Multimission Image Processing Subsystem (MIPS) at the Jet Propulsion Laboratory (JPL) has managed transitions of application software sets from one operating system and hardware platform to multiple operating systems and hardware platforms. As a part of these transitions, cost estimates were generated from the personal experience of in-house developers and managers to calculate the total effort required for such projects. Productivity measures have been collected for two such transitions, one very large and the other relatively small in terms of source lines of code. These estimates used a cost estimation model similar to the Software Engineering Laboratory (SEL) Effort Estimation Model. Experience in transitioning software within JPL MIPS have uncovered a high incidence of interface complexity. Interfaces, both internal and external to individual software applications, have contributed to software transition project complexity, and thus to scheduling difficulties and larger than anticipated design work on software to be ported.
Phase transition process in DDAB supported lipid bilayer
NASA Astrophysics Data System (ADS)
Isogai, Takumi; Nakada, Sakiko; Yoshida, Naoya; Sumi, Hayato; Tero, Ryugo; Harada, Shunta; Ujihara, Toru; Tagawa, Miho
2017-06-01
We report the results of microscope measurements examining the phase transition process of a cationic lipid, Dimethyldioctadecylammonium bromide (DDAB) supported lipid bilayer (SLB). Due to lateral fluidity and strong electrostatic interaction with DNA, SLB serves as a fluid substrate for assembling 2D lattices of DNA functionalized nanoparticles (DNA-NPs): lipid molecules work as carriers for transporting DNA-NPs. By fluorescence microscopy and atomic force microscopy (AFM), two types of phase transitions, which correspond to liquid crystalline-gel and liquid crystalline-interdigitated gel (LβI) ones, were observed in DDAB SLB during cooling. In thermal equilibrium at room temperature both gel and LβI phases have enough adsorbed amounts of DNA-NPs which indicate that both domains have enough surface charge densities for adsorbing DNA-NPs, however, during phase transition DNA-NPs preferably distributed into LβI phase.
Subphase transitions in first-order aggregation processes
NASA Astrophysics Data System (ADS)
Koci, Tomas; Bachmann, Michael
2017-03-01
In this paper, we investigate the properties of aggregation transitions in the context of generic coarse-grained homopolymer systems. By means of parallel replica-exchange Monte Carlo methods, we perform extensive simulations of systems consisting of up to 20 individual oligomer chains with five monomers each. Using the tools of the versatile microcanonical inflection-point analysis, we show that the aggregation transition is a first-order process consisting of a sequence of subtransitions between intermediate structural phases. We unravel the properties of these intermediate phases by collecting and analyzing their individual contributions towards the density of states of the system. The central theme of this systematic study revolves around translational entropy and its role in the striking phenomena of missing intermediate phases. We conclude with a brief discussion of the scaling properties of the transition temperature and the latent heat.
Detecting critical state before phase transition of complex systems by hidden Markov model
NASA Astrophysics Data System (ADS)
Liu, Rui; Chen, Pei; Li, Yongjun; Chen, Luonan
Identifying the critical state or pre-transition state just before the occurrence of a phase transition is a challenging task, because the state of the system may show little apparent change before this critical transition during the gradual parameter variations. Such dynamics of phase transition is generally composed of three stages, i.e., before-transition state, pre-transition state, and after-transition state, which can be considered as three different Markov processes. Thus, based on this dynamical feature, we present a novel computational method, i.e., hidden Markov model (HMM), to detect the switching point of the two Markov processes from the before-transition state (a stationary Markov process) to the pre-transition state (a time-varying Markov process), thereby identifying the pre-transition state or early-warning signals of the phase transition. To validate the effectiveness, we apply this method to detect the signals of the imminent phase transitions of complex systems based on the simulated datasets, and further identify the pre-transition states as well as their critical modules for three real datasets, i.e., the acute lung injury triggered by phosgene inhalation, MCF-7 human breast cancer caused by heregulin, and HCV-induced dysplasia and hepatocellular carcinoma.
NASA Technical Reports Server (NTRS)
Laxmanan, V.
1986-01-01
The development of theoretical models which characterize the planar-cellular and cell-dendrite transitions is described. The transitions are analyzed in terms of the Chalmers number, the solute Peclet number, and the tip stability parameter, which correlate microstructural features and processing conditions. The planar-cellular transition is examined using the constitutional supercooling theory of Chalmers et al., (1953) and it is observed that the Chalmers number is between 0 and 1 during dendritic and cellular growth. Analysis of cell-dendrite transition data reveal that the transition occurs when the solute Peclet number goes through a minimum, the primary arm spacings go through a maximum, and the Chalmers number is equal to 1/2. The relation between the tip stability parameter and the solute Peclet number is investigated and it is noted that the tip stability parameter is useful for studying dendritic growth in alloys.
NASA Technical Reports Server (NTRS)
Laxmanan, V.
1986-01-01
The development of theoretical models which characterize the planar-cellular and cell-dendrite transitions is described. The transitions are analyzed in terms of the Chalmers number, the solute Peclet number, and the tip stability parameter, which correlate microstructural features and processing conditions. The planar-cellular transition is examined using the constitutional supercooling theory of Chalmers et al., (1953) and it is observed that the Chalmers number is between 0 and 1 during dendritic and cellular growth. Analysis of cell-dendrite transition data reveal that the transition occurs when the solute Peclet number goes through a minimum, the primary arm spacings go through a maximum, and the Chalmers number is equal to 1/2. The relation between the tip stability parameter and the solute Peclet number is investigated and it is noted that the tip stability parameter is useful for studying dendritic growth in alloys.
Relaxation processes in a lower disorder order transition diblock copolymer.
Sanz, Alejandro; Ezquerra, Tiberio A; Hernández, Rebeca; Sprung, Michael; Nogales, Aurora
2015-02-14
The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.
Relaxation processes in a lower disorder order transition diblock copolymer
Sanz, Alejandro; Ezquerra, Tiberio A.; Nogales, Aurora
2015-02-14
The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition T{sub ODT}, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.
Nilsen, Joseph
2015-12-16
Using an X-ray free electron laser (XFEL) at 960 eV to photo-ionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly-ionized neon, an inner-shell X-ray laser was demonstrated at 849 eV in singly-ionized neon gas several years ago. It took decades to demonstrate this scheme, because it required a very strong X-ray source that could photo-ionize the 1s (K shell) electron in neon on a timescale comparable to the intrinsic Auger lifetime in neon of 2 fs. In this paper, we model the neon inner shell X-ray laser under similar conditions to those usedmore » in the XFEL experiments at the SLAC Linac Coherent Light Source (LCLS), and show how we can improve the efficiency of the neon laser and reduce the drive requirements by tuning the XFEL to the 1s-3p transition in neutral neon in order to create gain on the 2p-1s line in neutral neon. We also show how the XFEL could be used to photo-ionize L-shell electrons to drive gain on n = 3–2 transitions in singly-ionized Ar and Cu plasmas. Furthermore, these bright, coherent, and monochromatic X-ray lasers may prove very useful for doing high-resolution spectroscopy and for studying non-linear process in the X-ray regime.« less
Transitioning GONG data processing to NOAA SWPC operations
NASA Astrophysics Data System (ADS)
Reinard, A.; Marble, A.; Hill, F.; Berger, T. E.
2015-12-01
The NOAA Space Weather Prediction Center (SWPC) is the nation's official source of space weather watches, warnings, and alerts, providing 24x7 forecasting and support to critical infrastructure operators around the world. Observations of the conditions on the Sun are crucial for determining when and if a warning is needed. The Global Oscillation Network Group (GONG) operated by the National Solar Observatory (NSO) consists of six ground stations, allowing continuous observations of the Sun. Of particular interest for space weather purposes are the H-alpha images and magnetograms. The H-alpha data are used to identify filaments and their eruptions, to assess active region evolution and plage extent, and to help localize flare locations. The magnetograms are used to identify neutral lines, to examine potential shearing areas and to characterize the magnetic structure of active regions. GONG magnetograms also provide the initial condition for models of solar wind expansion through the heliosphere such as the WSA-Enlil model. Although beyond the scope of current space weather applications, GONG helioseismology products can be used to assess active region emergence on the far side of the Sun and to indicate the flaring potential of a front-side active region. These products are being examined as future tools in flare prediction. NSO has operated GONG as a science facility since 1995 and has provided processed space weather data products to NOAA via public internet connections for the past several years. In 2014 the White House Office of Management and Budget (OMB) requested that NOAA transition the GONG network to an operational space weather asset in order to ensure the continued flow of critical magnetogram data for solar wind models. NSO will continue to operate and manage the instruments and sites, but the H-alpha images and 10 minute averaged magnetogram data will be sent directly to SWPC for processing and use in space weather modeling. SWPC will make these data
Transitioning GONG data processing to NOAA SWPC operations
NASA Astrophysics Data System (ADS)
Reinard, Alysha; Marble, Andrew R.; Berger, Thomas
2016-05-01
The NOAA Space Weather Prediction Center (SWPC) is the nation's official source of space weather watches, warnings, and alerts, providing 24x7 forecasting and support to critical infrastructure operators around the world. Observations of the conditions on the Sun are crucial for determining when and if a warning is needed. The Global Oscillation Network Group (GONG) operated by the National Solar Observatory (NSO) consists of six ground stations, allowing continuous observations of the Sun. Of particular interest for space weather purposes are the H-alpha images and magnetograms. The H-alpha data are used to identify filaments and their eruptions, to assess active region evolution and plage extent, and to help localize flare locations. The magnetograms are used to identify neutral lines, to examine potential shearing areas and to characterize the magnetic structure of active regions. GONG magnetograms also provide the initial condition for models of solar wind expansion through the heliosphere such as the WSA-Enlil model. Although beyond the scope of current space weather applications, GONG helioseismology products can be used to assess active region emergence on the far side of the Sun and to indicate the flaring potential of a front-side active region. These products are being examined as future tools in flare prediction.NSO has operated GONG as a science facility since 1995 and has provided processed space weather data products to NOAA via for the past several years. In 2014 the White House Office of Management and Budget (OMB) requested that NOAA transition the GONG network to an operational space weather asset in order to ensure the continued flow of critical data for solar wind models. NSO will continue to operate and manage the instruments and sites, but the H-alpha images and 10 minute averaged magnetogram data will be sent directly to SWPC for processing and use in space weather modeling. SWPC will make these data available to NSO and the public via the
A new model for broadband waveguide to microstrip transition design
NASA Technical Reports Server (NTRS)
Ponchak, George E.; Downey, Alan N.
1986-01-01
A new model is presented which permits the prediction of the resonant frequencies created by antipodal finline waveguide to microstrip transitions. The transition is modeled as a tapered transmission line in series with an infinite set of coupled resonant circuits. The resonant circuits are modeled as simple microwave resonant cavities of which the resonant frequencies are easily determined. The model is developed and the resonant frequencies determined for several different transitions. Experimental results are given to confirm the models.
Modeling hyporheic zone processes
Runkel, Robert L.; McKnight, Diane M.; Rajaram, Harihar
2003-01-01
Stream biogeochemistry is influenced by the physical and chemical processes that occur in the surrounding watershed. These processes include the mass loading of solutes from terrestrial and atmospheric sources, the physical transport of solutes within the watershed, and the transformation of solutes due to biogeochemical reactions. Research over the last two decades has identified the hyporheic zone as an important part of the stream system in which these processes occur. The hyporheic zone may be loosely defined as the porous areas of the stream bed and stream bank in which stream water mixes with shallow groundwater. Exchange of water and solutes between the stream proper and the hyporheic zone has many biogeochemical implications, due to differences in the chemical composition of surface and groundwater. For example, surface waters are typically oxidized environments with relatively high dissolved oxygen concentrations. In contrast, reducing conditions are often present in groundwater systems leading to low dissolved oxygen concentrations. Further, microbial oxidation of organic materials in groundwater leads to supersaturated concentrations of dissolved carbon dioxide relative to the atmosphere. Differences in surface and groundwater pH and temperature are also common. The hyporheic zone is therefore a mixing zone in which there are gradients in the concentrations of dissolved gasses, the concentrations of oxidized and reduced species, pH, and temperature. These gradients lead to biogeochemical reactions that ultimately affect stream water quality. Due to the complexity of these natural systems, modeling techniques are frequently employed to quantify process dynamics.
Ising model of a glass transition.
Langer, J S
2013-07-01
Numerical simulations by Tanaka and co-workers indicate that glass-forming systems of moderately polydisperse hard-core particles, in both two and three dimensions, exhibit diverging correlation lengths. These correlations are described by Ising-like critical exponents, and are associated with diverging, Vogel-Fulcher-Tamann, structural relaxation times. Related simulations of thermalized hard disks indicate that the curves of pressure versus packing fraction for different polydispersities exhibit a sequence of transition points, starting with a liquid-hexatic transition for the monodisperse case, and crossing over with increasing polydispersity to glassy, Ising-like critical points. I propose to explain these observations by assuming that glass-forming fluids contain twofold degenerate, locally ordered clusters of particles, similar to the two-state systems that have been invoked to explain other glassy phenomena. This paper starts with a brief statistical derivation of the thermodynamics of thermalized, hard-core particles. It then discusses how a two-state, Ising-like model can be described within that framework in terms of a small number of statistically relevant, internal state variables. The resulting theory agrees accurately with the simulation data. I also propose a rationale for the observed relation between the Ising-like correlation lengths and the Vogel-Fulcher-Tamann formula.
Advanced deformation process modeling
Kocks, U.F.; Embury, J.D.; Beaudoin, A.J.; Dawson, P.R.; MacEwen, S.R.; Mecking, H.J.
1997-08-01
Progress was made in achieving a comprehensive and coherent description of material behavior in deformation processing. The materials included were metals, alloys, intermetallic compounds, arbitrary lattice structure, and metal matrix composites. Aspects of behavior modeled included kinetics of flow and strain hardening, as well as recrystallization and the various anisotropies of strength and compliance. Highlights include a new prediction of the limiting strength of materials at high temperature, a new understanding of the generation of new grain boundaries during forming operations, and a quantitatively verified computer simulation of texture development and the resulting behavioral anisotropies.
Mott transition in the Hubbard model
Shastry, B.S. )
1992-10-10
In this article, the author discuss W. Kohn's criterion for a metal insulator transition, within the framework of a one-band Hubbard model. This and related ideas are applied to 1-dimensional Hubbard systems, and some interesting miscellaneous results discussed. The Jordan-Wigner transformation converting the two species of fermions to two species of hardcore bosons is performed in detail, and the extra phases arising from odd-even effects are explicitly derived. Bosons are shown to prefer zero flux (i.e., diamagnetism) and the corresponding happy fluxes: for the fermions identified. A curios result following from the interplay between orbital diamagnetism and spin polarization is highlighted. A spin-statistics like theorem, showing that the anticommutation relations between fermions of opposite spin are crucial to obtain the SU(2) invariance is pointed out.
Modular process modeling for OPC
NASA Astrophysics Data System (ADS)
Keck, M. C.; Bodendorf, C.; Schmidtling, T.; Schlief, R.; Wildfeuer, R.; Zumpe, S.; Niehoff, M.
2007-03-01
Modular OPC modeling, describing mask, optics, resist and etch processes separately is an approach to keep efforts for OPC manageable. By exchanging single modules of a modular OPC model, a fast response to process changes during process development is possible. At the same time efforts can be reduced, since only single modular process steps have to be re-characterized as input for OPC modeling as the process is adjusted and optimized. Commercially available OPC tools for full chip processing typically make use of semi-empirical models. The goal of our work is to investigate to what extent these OPC tools can be applied for modeling of single process steps as separate modules. For an advanced gate level process we analyze the modeling accuracy over different process conditions (focus and dose) when combining models for each process step - optics, resist and etch - for differing single processes to a model describing the total process.
Phase transitions in Thirring’s model
NASA Astrophysics Data System (ADS)
Campa, Alessandro; Casetti, Lapo; Latella, Ivan; Pérez-Madrid, Agustín; Ruffo, Stefano
2016-07-01
In his pioneering work on negative specific heat, Walter Thirring introduced a model that is solvable in the microcanonical ensemble. Here, we give a complete description of the phase-diagram of this model in both the microcanonical and the canonical ensemble, highlighting the main features of ensemble inequivalence. In both ensembles, we find a line of first-order phase transitions which ends in a critical point. However, neither the line nor the point have the same location in the phase-diagram of the two ensembles. We also show that the microcanonical and canonical critical points can be analytically related to each other using a Landau expansion of entropy and free energy, respectively, in analogy with what has been done in (Cohen and Mukamel 2012 J. Stat. Mech. P12017). Examples of systems with certain symmetries restricting the Landau expansion have been considered in this reference, while no such restrictions are present in Thirring’s model. This leads to a phase diagram that can be seen as a prototype for what happens in systems of particles with kinematic degrees of freedom dominated by long-range interactions.
Chen, Tong; You, Yanan; Jiang, Hua; Wang, Zack Z
2017-01-12
The lineage transition between epithelium and mesenchyme is a process known as epithelial-mesenchymal transition (EMT), by which polarized epithelial cells lose their adhesion property and obtain mesenchymal cell phenotypes. EMT is a biological process that is often involved in embryogenesis and diseases, such as cancer invasion and metastasis. The EMT and the reverse process, mesenchymal-epithelial transition (MET), also play important roles in stem cell differentiation and de-differentiation (or reprogramming). In this review, we will discuss current research progress of EMT in embryonic development, cellular differentiation and reprogramming, and cancer progression, all of which are representative models for researches of stem cell biology in normal and in diseases. Understanding of EMT and MET may help to identify specific markers to distinguish normal stem cells from cancer stem cells in future.
Quantitative modeling of soil genesis processes
NASA Technical Reports Server (NTRS)
Levine, E. R.; Knox, R. G.; Kerber, A. G.
1992-01-01
For fine spatial scale simulation, a model is being developed to predict changes in properties over short-, meso-, and long-term time scales within horizons of a given soil profile. Processes that control these changes can be grouped into five major process clusters: (1) abiotic chemical reactions; (2) activities of organisms; (3) energy balance and water phase transitions; (4) hydrologic flows; and (5) particle redistribution. Landscape modeling of soil development is possible using digitized soil maps associated with quantitative soil attribute data in a geographic information system (GIS) framework to which simulation models are applied.
Quantitative modeling of soil genesis processes
NASA Technical Reports Server (NTRS)
Levine, E. R.; Knox, R. G.; Kerber, A. G.
1992-01-01
For fine spatial scale simulation, a model is being developed to predict changes in properties over short-, meso-, and long-term time scales within horizons of a given soil profile. Processes that control these changes can be grouped into five major process clusters: (1) abiotic chemical reactions; (2) activities of organisms; (3) energy balance and water phase transitions; (4) hydrologic flows; and (5) particle redistribution. Landscape modeling of soil development is possible using digitized soil maps associated with quantitative soil attribute data in a geographic information system (GIS) framework to which simulation models are applied.
Phase Transitions in Model Active Systems
NASA Astrophysics Data System (ADS)
Redner, Gabriel S.
The amazing collective behaviors of active systems such as bird flocks, schools of fish, and colonies of microorganisms have long amazed scientists and laypeople alike. Understanding the physics of such systems is challenging due to their far-from-equilibrium dynamics, as well as the extreme diversity in their ingredients, relevant time- and length-scales, and emergent phenomenology. To make progress, one can categorize active systems by the symmetries of their constituent particles, as well as how activity is expressed. In this work, we examine two categories of active systems, and explore their phase behavior in detail. First, we study systems of self-propelled spherical particles moving in two dimensions. Despite the absence of an aligning interaction, this system displays complex emergent dynamics, including phase separation into a dense active solid and dilute gas. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium phase transition is analogous to an equilibrium vapor-liquid system, with binodal and spinodal curves and a critical point. We also characterize the dense active solid phase, a unique material which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, as well as anomalous dynamics including superdiffusive motion on intermediate timescales. We also explore the role of interparticle attraction in this system. We demonstrate that attraction drastically changes the phase diagram, which contains two distinct phase-separated regions and is reentrant as a function of propulsion speed. We interpret this complex situation with a simple kinetic model, which builds from the observed microdynamics of individual particles to a full description of the macroscopic phase behavior. We also study active nematics, liquid crystals driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these
Safety models incorporating graph theory based transit indicators.
Quintero, Liliana; Sayed, Tarek; Wahba, Mohamed M
2013-01-01
There is a considerable need for tools to enable the evaluation of the safety of transit networks at the planning stage. One interesting approach for the planning of public transportation systems is the study of networks. Network techniques involve the analysis of systems by viewing them as a graph composed of a set of vertices (nodes) and edges (links). Once the transport system is visualized as a graph, various network properties can be evaluated based on the relationships between the network elements. Several indicators can be calculated including connectivity, coverage, directness and complexity, among others. The main objective of this study is to investigate the relationship between network-based transit indicators and safety. The study develops macro-level collision prediction models that explicitly incorporate transit physical and operational elements and transit network indicators as explanatory variables. Several macro-level (zonal) collision prediction models were developed using a generalized linear regression technique, assuming a negative binomial error structure. The models were grouped into four main themes: transit infrastructure, transit network topology, transit route design, and transit performance and operations. The safety models showed that collisions were significantly associated with transit network properties such as: connectivity, coverage, overlapping degree and the Local Index of Transit Availability. As well, the models showed a significant relationship between collisions and some transit physical and operational attributes such as the number of routes, frequency of routes, bus density, length of bus and 3+ priority lanes. Copyright © 2012 Elsevier Ltd. All rights reserved.
Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System
Xu, Limei; Buldyrev, Sergey V.; Giovambattista, Nicolas; Stanley, H. Eugene
2010-01-01
We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses. PMID:21614201
Implicit Value Updating Explains Transitive Inference Performance: The Betasort Model
Jensen, Greg; Muñoz, Fabian; Alkan, Yelda; Ferrera, Vincent P.; Terrace, Herbert S.
2015-01-01
Transitive inference (the ability to infer that B > D given that B > C and C > D) is a widespread characteristic of serial learning, observed in dozens of species. Despite these robust behavioral effects, reinforcement learning models reliant on reward prediction error or associative strength routinely fail to perform these inferences. We propose an algorithm called betasort, inspired by cognitive processes, which performs transitive inference at low computational cost. This is accomplished by (1) representing stimulus positions along a unit span using beta distributions, (2) treating positive and negative feedback asymmetrically, and (3) updating the position of every stimulus during every trial, whether that stimulus was visible or not. Performance was compared for rhesus macaques, humans, and the betasort algorithm, as well as Q-learning, an established reward-prediction error (RPE) model. Of these, only Q-learning failed to respond above chance during critical test trials. Betasort’s success (when compared to RPE models) and its computational efficiency (when compared to full Markov decision process implementations) suggests that the study of reinforcement learning in organisms will be best served by a feature-driven approach to comparing formal models. PMID:26407227
Implicit Value Updating Explains Transitive Inference Performance: The Betasort Model.
Jensen, Greg; Muñoz, Fabian; Alkan, Yelda; Ferrera, Vincent P; Terrace, Herbert S
2015-01-01
Transitive inference (the ability to infer that B > D given that B > C and C > D) is a widespread characteristic of serial learning, observed in dozens of species. Despite these robust behavioral effects, reinforcement learning models reliant on reward prediction error or associative strength routinely fail to perform these inferences. We propose an algorithm called betasort, inspired by cognitive processes, which performs transitive inference at low computational cost. This is accomplished by (1) representing stimulus positions along a unit span using beta distributions, (2) treating positive and negative feedback asymmetrically, and (3) updating the position of every stimulus during every trial, whether that stimulus was visible or not. Performance was compared for rhesus macaques, humans, and the betasort algorithm, as well as Q-learning, an established reward-prediction error (RPE) model. Of these, only Q-learning failed to respond above chance during critical test trials. Betasort's success (when compared to RPE models) and its computational efficiency (when compared to full Markov decision process implementations) suggests that the study of reinforcement learning in organisms will be best served by a feature-driven approach to comparing formal models.
Transitioning Back to Mainstream Education: The Flexible Integration Model
ERIC Educational Resources Information Center
Cumming, Therese M.; Strnadová, Iva
2017-01-01
The implementation of a transition model, the flexible integration model, was investigated in a school in Sydney, Australia, using an exploratory single case study design (Rowley, 2002). It is a person-centred model designed to assist students in transitioning from a special school for students with emotional and behavioural disabilities to…
Electronic Relaxation Processes of Transition Metal Atoms in Helium Nanodroplets
NASA Astrophysics Data System (ADS)
Kautsch, Andreas; Lindebner, Friedrich; Koch, Markus; Ernst, Wolfgang E.
2014-06-01
Spectroscopy of doped superfluid helium nanodroplets (He_N) gives information about the influence of this cold, chemically inert, and least interacting matrix environment on the excitation and relaxation dynamics of dopant atoms and molecules. We present the results from laser induced fluorescence (LIF), photoionization (PI), and mass spectroscopy of Cr and Cu doped He_N. From these results, we can draw a comprehensive picture of the complex behavior of such transition metal atoms in He_N upon photo-excitation. The strong Cr and Cu ground state transitions show an excitation blueshift and broadening with respect to the bare atom transitions which can be taken as indication for the solvation inside the droplet. From the originally excited states the atoms relax to energetically lower states and are ejected from the He_N. The relaxation processes include bare atom spin-forbidden transitions, which clearly bears the signature of the He_N influence. Two-color resonant two-photon ionization (2CR2PI) also shows the formation of bare atoms and small Cr-He_n and Cu-He_n clusters in their ground and metastable states ^c. Currently, Cr dimer excitation studies are in progress and a brief outlook on the available results will be given. C. Callegari and W. E. Ernst, Helium Droplets as Nanocryostats for Molecular Spectroscopy - from the Vacuum Ultraviolet to the Microwave Regime, in Handbook of High-Resolution Spectroscopy, eds. M. Quack and F. Merkt, John Wiley & Sons, Chichester, 2011. A. Kautsch, M. Koch, and W. E. Ernst, J. Phys. Chem. A, 117 (2013) 9621-9625, DOI: 10.1021/jp312336m F. Lindebner, A. Kautsch, M. Koch, and W. E. Ernst, Int. J. Mass Spectrom. (2014) in press, DOI: 10.1016/j.ijms.2013.12.022 M. Koch, A. Kautsch, F. Lackner, and W. E. Ernst, submitted to J. Phys. Chem. A
Quantum phase transition in a pseudo-Hermitian Dicke model
Deguchi, Tetsuo; Ghosh, Pijush K.
2009-08-15
We show that a Dicke-type non-Hermitian Hamiltonian admits entirely real spectra by mapping it to the 'dressed Dicke model' through a similarity transformation. We find a positive-definite metric in the Hilbert space of the non-Hermitian Hamiltonian so that the time evolution is unitary and allows a consistent quantum description. We then show that this non-Hermitian Hamiltonian describing nondissipative quantum processes undergoes quantum phase transition. The exactly solvable limit of the non-Hermitian Hamiltonian has also been discussed.
Reuben Weisz; Don Vandendriesche
2012-01-01
The Forest Vegetation Simulator (FVS) has been used to provide rates of natural growth transitions under endemic conditions for use in State and Transition Models (STMs). This process has previously been presented. This paper expands on that work by citing the methods used to capture resultant vegetation states following disturbance activities; be it of natural causes...
Data support for a state-and-transition model: What have we learned?
USDA-ARS?s Scientific Manuscript database
State-and-transition models (STMs) were conceived as a means to synthesize knowledge about alternative plant communities and the processes that lead to transitions among them for specific land areas. STMs that have been developed over the past decade have often been limited by 1) a lack of detail on...
Phase transition in the ABC model
NASA Astrophysics Data System (ADS)
Clincy, M.; Derrida, B.; Evans, M. R.
2003-06-01
Recent studies have shown that one-dimensional driven systems can exhibit phase separation even if the dynamics is governed by local rules. The ABC model, which comprises three particle species that diffuse asymmetrically around a ring, shows anomalous coarsening into a phase separated steady state. In the limiting case in which the dynamics is symmetric and the parameter q describing the asymmetry tends to one, no phase separation occurs and the steady state of the system is disordered. In the present work, we consider the weak asymmetry regime q=exp(-β/N), where N is the system size, and study how the disordered state is approached. In the case of equal densities, we find that the system exhibits a second-order phase transition at some nonzero βc. The value of βc=2π(3) and the optimal profiles can be obtained by writing the exact large deviation functional. For nonequal densities, we write down mean-field equations and analyze some of their predictions.
Phase transition in the ABC model.
Clincy, M; Derrida, B; Evans, M R
2003-06-01
Recent studies have shown that one-dimensional driven systems can exhibit phase separation even if the dynamics is governed by local rules. The ABC model, which comprises three particle species that diffuse asymmetrically around a ring, shows anomalous coarsening into a phase separated steady state. In the limiting case in which the dynamics is symmetric and the parameter q describing the asymmetry tends to one, no phase separation occurs and the steady state of the system is disordered. In the present work, we consider the weak asymmetry regime q=exp(-beta/N), where N is the system size, and study how the disordered state is approached. In the case of equal densities, we find that the system exhibits a second-order phase transition at some nonzero beta(c). The value of beta(c)=2pi square root 3 and the optimal profiles can be obtained by writing the exact large deviation functional. For nonequal densities, we write down mean-field equations and analyze some of their predictions.
Crystallization: A phase transition process driving by chemical potential decrease
NASA Astrophysics Data System (ADS)
Sun, Congting; Xue, Dongfeng
2017-07-01
A chemical bonding model is established to describe the chemical potential decrease during crystallization. In the nucleation stage, in situ molecular vibration spectroscopy shows the increased vibration energy of constituent groups, indicating the shortened chemical bonding and the decreased chemical potential towards the formation of nuclei. Starting from the Gibbs free energy formula, the chemical potential decrease during crystallization is scaled, which depends on the released chemical bonding energy per unit phase transition zone. In the crystal growth, the direction-dependent growth rate of inorganic single crystals can be quantitatively determined, their anisotropic thermodynamic morphology can thus be constructed on the basis of relative growth rates.
Human driven transitions in complex model ecosystems
NASA Astrophysics Data System (ADS)
Harfoot, Mike; Newbold, Tim; Tittinsor, Derek; Purves, Drew
2015-04-01
Human activities have been observed to be impacting ecosystems across the globe, leading to reduced ecosystem functioning, altered trophic and biomass structure and ultimately ecosystem collapse. Previous attempts to understand global human impacts on ecosystems have usually relied on statistical models, which do not explicitly model the processes underlying the functioning of ecosystems, represent only a small proportion of organisms and do not adequately capture complex non-linear and dynamic responses of ecosystems to perturbations. We use a mechanistic ecosystem model (1), which simulates the underlying processes structuring ecosystems and can thus capture complex and dynamic interactions, to investigate boundaries of complex ecosystems to human perturbation. We explore several drivers including human appropriation of net primary production and harvesting of animal biomass. We also present an analysis of the key interactions between biotic, societal and abiotic earth system components, considering why and how we might think about these couplings. References: M. B. J. Harfoot et al., Emergent global patterns of ecosystem structure and function from a mechanistic general ecosystem model., PLoS Biol. 12, e1001841 (2014).
Global quantum discord and quantum phase transition in XY model
Liu, Si-Yuan; Zhang, Yu-Ran; Yang, Wen-Li; Fan, Heng
2015-11-15
We study the relationship between the behavior of global quantum correlations and quantum phase transitions in XY model. We find that the two kinds of phase transitions in the studied model can be characterized by the features of global quantum discord (GQD) and the corresponding quantum correlations. We demonstrate that the maximum of the sum of all the nearest neighbor bipartite GQDs is effective and accurate for signaling the Ising quantum phase transition, in contrast, the sudden change of GQD is very suitable for characterizing another phase transition in the XY model. This may shed lights on the study of properties of quantum correlations in different quantum phases.
GREENSCOPE: Sustainable Process Modeling
EPA researchers are responding to environmental problems by incorporating sustainability into process design and evaluation. EPA researchers are also developing a tool that allows users to assess modifications to existing and new chemical processes to determine whether changes in...
GREENSCOPE: Sustainable Process Modeling
EPA researchers are responding to environmental problems by incorporating sustainability into process design and evaluation. EPA researchers are also developing a tool that allows users to assess modifications to existing and new chemical processes to determine whether changes in...
Phase transitions in the quadratic contact process on complex networks
NASA Astrophysics Data System (ADS)
Varghese, Chris; Durrett, Rick
2013-06-01
The quadratic contact process (QCP) is a natural extension of the well-studied linear contact process where infected (1) individuals infect susceptible (0) neighbors at rate λ and infected individuals recover (10) at rate 1. In the QCP, a combination of two 1's is required to effect a 01 change. We extend the study of the QCP, which so far has been limited to lattices, to complex networks. We define two versions of the QCP: vertex-centered (VQCP) and edge-centered (EQCP) with birth events 1-0-11-1-1 and 1-1-01-1-1, respectively, where “-” represents an edge. We investigate the effects of network topology by considering the QCP on random regular, Erdős-Rényi, and power-law random graphs. We perform mean-field calculations as well as simulations to find the steady-state fraction of occupied vertices as a function of the birth rate. We find that on the random regular and Erdős-Rényi graphs, there is a discontinuous phase transition with a region of bistability, whereas on the heavy-tailed power-law graph, the transition is continuous. The critical birth rate is found to be positive in the former but zero in the latter.
Quantitative analysis of non-equilibrium phase transition process by the catastrophe theory
NASA Astrophysics Data System (ADS)
Liang, Xiao; Wu, Jiu Hui; Zhong, H. B.
2017-08-01
Catastrophe theory is a highly generalized mathematical theory that summarizes the rules of non-equilibrium phase transition by several catastrophe models. This paper investigates the general non-equilibrium phase transition process quantitatively using catastrophe theory for the first time, to our knowledge. First, a new approach is proposed by combining the catastrophe theory with dimensionless analysis. Second, the new approach is applied to two classic examples: one is the turbulent phase transition and the other is the bottleneck effect of particle flow. For the turbulence phase transition process, the quantitative relationships are obtained. Comparing with Kolmogorov's turbulent theory, the new method proposed in this paper is able to evaluate not only the complete turbulence condition but also the development of turbulence, and Kolmogorov's turbulent theory is only a special case of our results by this new approach. For the particle flow bottleneck effect, the results obtained by this new method correspond with the empirical formulated results. Therefore, the proposed method can solve non-equilibrium phase transition process problems and has the potential to extend to fluid, aerodynamics, and so forth.
Transitional paleointensities from Kauai, Hawaii, and geomagnetic reversal models
Bogue, Scott W.; Coe, Robert S.
1984-01-01
Previously presented paleointensity results from an R-N transition zone in Kauai, Hawaii, show that field intensity dropped from 0. 431 Oe to 0. 101 Oe while the field remained within 30 degree of the reversed axial dipole direction. A recovery in intensity and the main directional change followed this presumably short period of low field strength. As the reversal neared completion, the field has an intensity of 0. 217 Oe while still 40 degree from the final direction. The relationship of paleointensity to field direction during the early part of the reversal thus differs from that toward the end, a feature that only some reversal models are consistent with. For example, a model in which a standing nondipole component persists through the dipole reversal predicts only symmetric intensity patterns. In contrast, zonal flooding models generate suitably complex field behavior if multiple flooding schemes operate during a single reversal or if the flooding process is itself asymmetric.
Transitional Jobs: Background, Program Models, and Evaluation Evidence
ERIC Educational Resources Information Center
Bloom, Dan
2010-01-01
The budget for the U.S. Department of Labor for Fiscal Year 2010 includes a total of $45 million to support and study transitional jobs. This paper describes the origins of the transitional jobs models that are operating today, reviews the evidence on the effectiveness of this approach and other subsidized employment models, and offers some…
A Parent-Professional Collaboration Model of Transitional Planning.
ERIC Educational Resources Information Center
Wittenstein, S. H.
1993-01-01
A transitional planning model implemented at St. Joseph's School for the Blind in Jersey City, New Jersey, incorporates a broad conceptualization of transition that includes social skills, independent living skills, and overall competence in adjustment to the community. The model considers parental involvement, advocacy, and leadership as…
Processed foods and the nutrition transition: evidence from Asia.
Baker, P; Friel, S
2014-07-01
This paper elucidates the role of processed foods and beverages in the 'nutrition transition' underway in Asia. Processed foods tend to be high in nutrients associated with obesity and diet-related non-communicable diseases: refined sugar, salt, saturated and trans-fats. This paper identifies the most significant 'product vectors' for these nutrients and describes changes in their consumption in a selection of Asian countries. Sugar, salt and fat consumption from processed foods has plateaued in high-income countries, but has rapidly increased in the lower-middle and upper-middle-income countries. Relative to sugar and salt, fat consumption in the upper-middle- and lower-middle-income countries is converging most rapidly with that of high-income countries. Carbonated soft drinks, baked goods, and oils and fats are the most significant vectors for sugar, salt and fat respectively. At the regional level there appears to be convergence in consumption patterns of processed foods, but country-level divergences including high levels of consumption of oils and fats in Malaysia, and soft drinks in the Philippines and Thailand. This analysis suggests that more action is needed by policy-makers to prevent or mitigate processed food consumption. Comprehensive policy and regulatory approaches are most likely to be effective in achieving these goals. © 2014 The Authors. obesity reviews © 2014 World Obesity.
Implementation and Validation of a Laminar-to-Turbulent Transition Model in the Wind-US Code
NASA Technical Reports Server (NTRS)
Denissen, Nicholas A.; Yoder, Dennis A.; Georgiadis, Nicholas J.
2008-01-01
A bypass transition model has been implemented in the Wind-US Reynolds Averaged Navier-Stokes (RANS) solver. The model is based on the Shear Stress Transport (SST) turbulence model and was built starting from a previous SST-based transition model. Several modifications were made to enable (1) consistent solutions regardless of flow field initialization procedure and (2) fully turbulent flow beyond the transition region. This model is intended for flows where bypass transition, in which the transition process is dominated by large freestream disturbances, is the key transition mechanism as opposed to transition dictated by modal growth. Validation of the new transition model is performed for flows ranging from incompressible to hypersonic conditions.
Visual Modelling of Learning Processes
ERIC Educational Resources Information Center
Copperman, Elana; Beeri, Catriel; Ben-Zvi, Nava
2007-01-01
This paper introduces various visual models for the analysis and description of learning processes. The models analyse learning on two levels: the dynamic level (as a process over time) and the functional level. Two types of model for dynamic modelling are proposed: the session trace, which documents a specific learner in a particular learning…
Visual Modelling of Learning Processes
ERIC Educational Resources Information Center
Copperman, Elana; Beeri, Catriel; Ben-Zvi, Nava
2007-01-01
This paper introduces various visual models for the analysis and description of learning processes. The models analyse learning on two levels: the dynamic level (as a process over time) and the functional level. Two types of model for dynamic modelling are proposed: the session trace, which documents a specific learner in a particular learning…
Transition and Turbulence Modeling for Blunt-Body Wake Flows
NASA Technical Reports Server (NTRS)
Nance, Robert P.; Horvath, Thomas J.; Hassan, H. A.
1997-01-01
This study attempts t o improve the modeling and computational prediction of high- speed transitional wake flows. The recently developed kappa - zeta (Enstrophy) turbulence model is coupled with a newly developed transition prediction method and implemented in an implicit flow solver well-suited to hypersonic flows. In this model, transition onset is determined as part of the solution. Results obtained using the new model for a 70- deg blunted cone/sting geometry demonstrate better agreement with experimental heat- transfer measurements when compared to laminar calculations as well as solutions using the kappa - omega model. Results are also presented for the situation where transition onset is preselected. It is shown that, in this case, results are quite sensitive to location of the transition point.
Predicting hemoglobin levels in whole blood donors using transition models and mixed effects models
2013-01-01
Background To optimize the planning of blood donations but also to continue motivating the volunteers it is important to streamline the practical organization of the timing of donations. While donors are asked to return for donation after a suitable period, still a relevant proportion of blood donors is deferred from donation each year due to a too low hemoglobin level. Rejection of donation may demotivate the candidate donor and implies an inefficient planning of the donation process. Hence, it is important to predict the future hemoglobin level to improve the planning of donors’ visits to the blood bank. Methods The development of the hemoglobin prediction rule is based on longitudinal (panel) data from blood donations collected by Sanquin (the only blood product collecting and supplying organization in the Netherlands). We explored and contrasted two popular statistical models, i.e. the transition (autoregressive) model and the mixed effects model as plausible models to account for the dependence among subsequent hemoglobin levels within a donor. Results The predictors of the future hemoglobin level are age, season, hemoglobin levels at the previous visits, and a binary variable indicating whether a donation was made at the previous visit. Based on cross-validation, the areas under the receiver operating characteristic curve (AUCs) for male donors are 0.83 and 0.81 for the transition model and the mixed effects model, respectively; for female donors we obtained AUC values of 0.73 and 0.72 for the transition model and the mixed effects model, respectively. Conclusion We showed that the transition models and the mixed effects models provide a much better prediction compared to a multiple linear regression model. In general, the transition model provides a somewhat better prediction than the mixed effects model, especially at high visit numbers. In addition, the transition model offers a better trade-off between sensitivity and specificity when varying the cut
Xu, Jason; Minin, Vladimir N.
2016-01-01
Branching processes are a class of continuous-time Markov chains (CTMCs) with ubiquitous applications. A general difficulty in statistical inference under partially observed CTMC models arises in computing transition probabilities when the discrete state space is large or uncountable. Classical methods such as matrix exponentiation are infeasible for large or countably infinite state spaces, and sampling-based alternatives are computationally intensive, requiring integration over all possible hidden events. Recent work has successfully applied generating function techniques to computing transition probabilities for linear multi-type branching processes. While these techniques often require significantly fewer computations than matrix exponentiation, they also become prohibitive in applications with large populations. We propose a compressed sensing framework that significantly accelerates the generating function method, decreasing computational cost up to a logarithmic factor by only assuming the probability mass of transitions is sparse. We demonstrate accurate and efficient transition probability computations in branching process models for blood cell formation and evolution of self-replicating transposable elements in bacterial genomes. PMID:26949377
Dynamic network modelling to understand flowering transition and floral patterning.
Davila-Velderrain, J; Martinez-Garcia, J C; Alvarez-Buylla, E R
2016-04-01
Differentiation and morphogenetic processes during plant development are particularly robust. At the cellular level, however, plants also show great plasticity in response to environmental conditions, and can even reverse apparently terminal differentiated states with remarkable ease. Can we understand and predict both robust and plastic systemic responses as a general consequence of the non-trivial interplay between intracellular regulatory networks, extrinsic environmental signalling, and tissue-level mechanical constraints? Flower development has become an ideal model system to study these general questions of developmental biology, which are especially relevant to understanding stem cell patterning in plants, animals, and human disease. Decades of detailed study of molecular developmental genetics, as well as novel experimental techniques for in vivo assays in both wild-type and mutant plants, enable the postulation and testing of experimentally grounded mathematical and computational network dynamical models. Research in our group aims to explain the emergence of robust transitions that occur at the shoot apical meristem, as well as flower development, as the result of the collective action of key molecular components in regulatory networks subjected to intra-organismal signalling and extracellular constraints. Here we present a brief overview of recent work from our group, and that of others, focusing on the use of simple dynamical models to address cell-fate specification and cell-state stochastic dynamics during flowering transition and cell-state transitions at the shoot apical meristem of Arabidopsis thaliana. We also focus on how our work fits within the general field of plant developmental modelling, which is being developed by many others.
A Simple Model for Complex Dynamical Transitions in Epidemics
NASA Astrophysics Data System (ADS)
Earn, David J. D.; Rohani, Pejman; Bolker, Benjamin M.; Grenfell, Bryan T.
2000-01-01
Dramatic changes in patterns of epidemics have been observed throughout this century. For childhood infectious diseases such as measles, the major transitions are between regular cycles and irregular, possibly chaotic epidemics, and from regionally synchronized oscillations to complex, spatially incoherent epidemics. A simple model can explain both kinds of transitions as the consequences of changes in birth and vaccination rates. Measles is a natural ecological system that exhibits different dynamical transitions at different times and places, yet all of these transitions can be predicted as bifurcations of a single nonlinear model.
Glass transition and relaxation processes of nanocomposite polymer electrolytes.
Money, Benson K; Hariharan, K; Swenson, Jan
2012-07-05
This study focus on the effect of δ-Al(2)O(3) nanofillers on the dc-conductivity, glass transition, and dielectric relaxations in the polymer electrolyte (PEO)(4):LiClO(4). The results show that there are three dielectric relaxation processes, α, β, and γ, in the systems, although the structural α-relaxation is hidden in the strong conductivity contribution and could therefore not be directly observed. However, by comparing an enhanced dc-conductivity, by approximately 2 orders of magnitude with 4 wt % δ-Al(2)O(3) added, with a decrease in calorimetric glass transition temperature, we are able to conclude that the dc-conductivity is directly coupled to the hidden α-relaxation, even in the presence of nanofillers (at least in the case of δ-Al(2)O(3) nanofillers at concentrations up to 4 wt %). This filler induced speeding up of the segmental polymer dynamics, i.e., the α-relaxation, can be explained by the nonattractive nature of the polymer-filler interactions, which enhance the "free volume" and mobility of polymer segments in the vicinity of filler surfaces.
Juban, Audrey; Briançon, Stéphanie; Puel, François
2016-03-30
In the pharmaceutical field, solid-state transitions that may occur during manufacturing of pharmaceuticals are of great importance. The phase transition of a model API, caffeine Form I (CFI), was studied during direct compression process by analysing the impacts of the operating conditions (process and formulation). This work is focused on two formulation parameters: nature of the diluent and impact of the caffeine dilution, and one process parameter: the compression pressure that may impact the phase transition of CFI. Tablets were made from pure CFI and from binary mixture of CFI/diluent (microcrystalline cellulose or anhydrous dicalcium phosphate). A kinetic study performed during six months helped to highlight the influence of these parameters on the CFI transition degree. Results showed a triggering effect of the direct compression process, transformation was higher in tablets than in uncompressed powders. Whatever the pressure applied, CFI transition degree was almost constant and uniformly occurring throughout the tablet volume. Nevertheless, several differences on the evolution of the CFI transition degree were observed between binary mixtures of CFI/diluent. An analysis of the transition mechanism with a stretched exponential law of the Johnson-Mehl-Avrami model shows that tableting accelerates the polymorphic transition without modifying its mechanism controlled by nucleation only. Copyright © 2016 Elsevier B.V. All rights reserved.
Noise-induced transitions in state-dependent dichotomous processes.
Laio, Francesco; Ridolfi, Luca; D'Odorico, Paolo
2008-09-01
In a number of stochastic systems the random forcing is represented as a dichotomous Markov noise. A common characteristic of these models is that the noise is usually supposed to be independent of the state of the forced dynamical system. However, there are several situations in which positive or negative feedback exist between the system and the random driver. This paper investigates a class of systems characterized by feedback between dichotomous Markov noise and the system's dynamics. The effect of the feedback is accounted for through a state dependency in the transition rates of the dichotomous noise. We study noise-induced transitions in these systems, with special attention to the delicate problem of correctly defining the deterministic counterpart of the stochastic system. We find that (i) if in the absence of any feedback the dynamical system has a single deterministic stable point, the deterministic dynamics remain monostable when a negative feedback is introduced, while they may become bistable in the presence of a positive feedback. (ii) Noise may induce bistability in the presence of a null or negative feedback. (iii) Bistable deterministic dynamics, induced by the positive feedback, may be destroyed by the noise, which tends to stabilize the system around a new intermediate stable state between those of the deterministic dynamics.
Nonequilibrium quantum phase transitions in the Dicke model.
Bastidas, V M; Emary, C; Regler, B; Brandes, T
2012-01-27
We establish a set of nonequilibrium quantum phase transitions in the Dicke model by considering a monochromatic nonadiabatic modulation of the atom-field coupling. For weak driving the system exhibits a set of sidebands which allow the circumvention of the no-go theorem which otherwise forbids the occurrence of superradiant phase transitions. At strong driving we show that the system exhibits a rich multistable structure and exhibits both first- and second-order nonequilibrium quantum phase transitions.
Sildenafil normalizes bowel transit in preclinical models of constipation
Sharman, Sarah K.; Islam, Bianca N.; Hou, Yali; Usry, Margaux; Bridges, Allison; Singh, Nagendra; Sridhar, Subbaramiah; Rao, Satish
2017-01-01
Guanylyl cyclase-C (GC-C) agonists increase cGMP levels in the intestinal epithelium to promote secretion. This process underlies the utility of exogenous GC-C agonists such as linaclotide for the treatment of chronic idiopathic constipation (CIC) and irritable bowel syndrome with constipation (IBS-C). Because GC-C agonists have limited use in pediatric patients, there is a need for alternative cGMP-elevating agents that are effective in the intestine. The present study aimed to determine whether the PDE-5 inhibitor sildenafil has similar effects as linaclotide on preclinical models of constipation. Oral administration of sildenafil caused increased cGMP levels in mouse intestinal epithelium demonstrating that blocking cGMP-breakdown is an alternative approach to increase cGMP in the gut. Both linaclotide and sildenafil reduced proliferation and increased differentiation in colon mucosa, indicating common target pathways. The homeostatic effects of cGMP required gut turnover since maximal effects were observed after 3 days of treatment. Neither linaclotide nor sildenafil treatment affected intestinal transit or water content of fecal pellets in healthy mice. To test the effectiveness of cGMP elevation in a functional motility disorder model, mice were treated with dextran sulfate sodium (DSS) to induce colitis and were allowed to recover for several weeks. The recovered animals exhibited slower transit, but increased fecal water content. An acute dose of sildenafil was able to normalize transit and fecal water content in the DSS-recovery animal model, and also in loperamide-induced constipation. The higher fecal water content in the recovered animals was due to a compromised epithelial barrier, which was normalized by sildenafil treatment. Taken together our results show that sildenafil can have similar effects as linaclotide on the intestine, and may have therapeutic benefit to patients with CIC, IBS-C, and post-infectious IBS. PMID:28448580
Entropy, chaos, and excited-state quantum phase transitions in the Dicke model.
Lóbez, C M; Relaño, A
2016-07-01
We study nonequilibrium processes in an isolated quantum system-the Dicke model-focusing on the role played by the transition from integrability to chaos and the presence of excited-state quantum phase transitions. We show that both diagonal and entanglement entropies are abruptly increased by the onset of chaos. Also, this increase ends in both cases just after the system crosses the critical energy of the excited-state quantum phase transition. The link between entropy production, the development of chaos, and the excited-state quantum phase transition is more clear for the entanglement entropy.
NASA Astrophysics Data System (ADS)
Bizhani, Golnoosh; Paczuski, Maya; Grassberger, Peter
2012-07-01
Discontinuous percolation transitions and the associated tricritical points are manifest in a wide range of both equilibrium and nonequilibrium cooperative phenomena. To demonstrate this, we present and relate the continuous and first-order behaviors in two different classes of models: The first are generalized epidemic processes that describe in their spatially embedded version—either on or off a regular lattice—compact or fractal cluster growth in random media at zero temperature. A random graph version of these processes is mapped onto a model previously proposed for complex social contagion. We compute detailed phase diagrams and compare our numerical results at the tricritical point in d=3 with field theory predictions of Janssen [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.70.026114 70, 026114 (2004)]. The second class consists of exponential (“Hamiltonian,” i.e., formally equilibrium) random graph models and includes the Strauss and the two-star model, where “chemical potentials” control the densities of links, triangles, or two-stars. When the chemical potentials in either graph model are O(logN), the percolation transition can coincide with a first-order phase transition in the density of links, making the former also discontinuous. Hysteresis loops can then be of mixed order, with second-order behavior for decreasing link fugacity, and a jump (first order) when it increases.
Bizhani, Golnoosh; Paczuski, Maya; Grassberger, Peter
2012-07-01
Discontinuous percolation transitions and the associated tricritical points are manifest in a wide range of both equilibrium and nonequilibrium cooperative phenomena. To demonstrate this, we present and relate the continuous and first-order behaviors in two different classes of models: The first are generalized epidemic processes that describe in their spatially embedded version--either on or off a regular lattice--compact or fractal cluster growth in random media at zero temperature. A random graph version of these processes is mapped onto a model previously proposed for complex social contagion. We compute detailed phase diagrams and compare our numerical results at the tricritical point in d = 3 with field theory predictions of Janssen et al. [Phys. Rev. E 70, 026114 (2004)]. The second class consists of exponential ("Hamiltonian," i.e., formally equilibrium) random graph models and includes the Strauss and the two-star model, where "chemical potentials" control the densities of links, triangles, or two-stars. When the chemical potentials in either graph model are O(logN), the percolation transition can coincide with a first-order phase transition in the density of links, making the former also discontinuous. Hysteresis loops can then be of mixed order, with second-order behavior for decreasing link fugacity, and a jump (first order) when it increases.
Correlation-based Transition Modeling for External Aerodynamic Flows
NASA Astrophysics Data System (ADS)
Medida, Shivaji
Conventional turbulence models calibrated for fully turbulent boundary layers often over-predict drag and heat transfer on aerodynamic surfaces with partially laminar boundary layers. A robust correlation-based model is developed for use in Reynolds-Averaged Navier-Stokes simulations to predict laminar-to-turbulent transition onset of boundary layers on external aerodynamic surfaces. The new model is derived from an existing transition model for the two-equation k-omega Shear Stress Transport (SST) turbulence model, and is coupled with the one-equation Spalart-Allmaras (SA) turbulence model. The transition model solves two transport equations for intermittency and transition momentum thickness Reynolds number. Experimental correlations and local mean flow quantities are used in the model to account for effects of freestream turbulence level and pressure gradients on transition onset location. Transition onset is triggered by activating intermittency production using a vorticity Reynolds number criterion. In the new model, production and destruction terms of the intermittency equation are modified to improve consistency in the fully turbulent boundary layer post-transition onset, as well as ensure insensitivity to freestream eddy viscosity value specified in the SA model. In the original model, intermittency was used to control production and destruction of turbulent kinetic energy. Whereas, in the new model, only the production of eddy viscosity in SA model is controlled, and the destruction term is not altered. Unlike the original model, the new model does not use an additional correction to intermittency for separation-induced transition. Accuracy of drag predictions are improved significantly with the use of the transition model for several two-dimensional single- and multi-element airfoil cases over a wide range of Reynolds numbers. The new model is able to predict the formation of stable and long laminar separation bubbles on low-Reynolds number airfoils that
Model Atmospheres and Transit Spectra for Hot Rocky Planets
NASA Astrophysics Data System (ADS)
Lupu, Roxana
hot Jupiters in similar transit configurations. For example, Na has been the first species to be detected in an exoplanet atmosphere, by observing the evaporating hotJupiter HD209458b. Understanding the interplay between the magma outgassing and volatile loss will be an important part of this project. Our team has the expertise in the chemistry, radiative transfer, and atmospheric escape modeling at these exotic temperatures. Our recent work has analyzed the emerging atmospheres of terrestrial planets after giant impacts, using a well-established radiativeconvective atmospheric structure code, with an extensive opacity database for all relevant molecules, and the chemistry self-consistently calculated for continental crust and bulk silicate earth compositions. We will expand on this work by considering a wider range of chemical compositions, assessing the importance of clouds and generating cloudy models, and developing dis-equilibrium models by taking into account vertical mixing and photochemistry. Photo-evaporation will be considered in the energy balance between heating, cooling and mass loss. We also have in-house codes to generate high-resolution eclipse spectra and predict transit depths and observable signatures. The development of the atmospheric code, the molecular opacity updates, the atmospheric structure calculations and the high resolution eclipse spectra will be performed by R. Lupu, M. Marley, and R. Freedman at NASA Ames. The atmospheric chemistry grids will be provided by B. Fegley and K. Lodders at Washington University. The transit spectra and observational features will be computed by J. Fortney at UCSC, and the atmospheric escape calculations will be performed by K. Zahnle at NASA Ames. This proposal addresses the following goals of the Exoplanet Research program: explain observations of exoplanetary systems, and understand the chemical and physical processes of exoplanets. Our results will also inform future JWST observations.
Mott transitions in three-component Falicov-Kimball model
NASA Astrophysics Data System (ADS)
Nguyen, Duong-Bo; Tran, Minh-Tien
2013-01-01
Metal-insulator transitions are studied within a three-component Falicov-Kimball model, which mimics a mixture of one-component and two-component fermionic particles with local repulsive interactions in optical lattices. Within the model, the two-component fermionic particles are able to hop in the lattice, while the one-component fermionic particles are localized. The model is studied by using the dynamical mean-field theory with exact diagonalization. Its homogeneous solutions establish Mott transitions for both commensurate and incommensurate fillings between one-third and two-thirds. At commensurate one-third and two-thirds fillings, the Mott transition occurs for any density of hopping particles, while at incommensurate fillings, the Mott transition can occur only for density one-half of hopping particles. At half-filling, depending on the repulsive interactions, the reentrant effect of the Mott insulator is observed. As increasing local interaction of hopping particles, the first insulator-metal transition is continuous, whereas the second metal-insulator transition is discontinuous. The second metal-insulator transition crosses a finite region where both metallic and insulating phase coexist. At third-filling, the Mott transition is established only for strong repulsive interactions. A phase separation occurs together with the phase transition.
Curriculum Outline for Tennessee Transition Model.
ERIC Educational Resources Information Center
Esch, B. J.
This curriculum outline for the Sevier County, Tennessee, transition program for special needs students provides goals and objectives for the following domains: domestic, vocational, community functioning, and recreation/leisure. The domestic domain covers personal hygiene/grooming, first aid, home nursing, birth control/pregnancy, parenting, drug…
Curriculum Outline for Tennessee Transition Model.
ERIC Educational Resources Information Center
Esch, B. J.
This curriculum outline for the Sevier County, Tennessee, transition program for special needs students provides goals and objectives for the following domains: domestic, vocational, community functioning, and recreation/leisure. The domestic domain covers personal hygiene/grooming, first aid, home nursing, birth control/pregnancy, parenting, drug…
Compendium of Transition Model Demonstration Programs, 1995.
ERIC Educational Resources Information Center
Harmon, Adrienne S.; And Others
This document is a directory of current and newly expired projects funded under the Office of Special Education and Rehabilitative Services (OSERS) Secondary Education and Transition Initiative. The compendium is divided into four sections: (1) an overview of project profiles, which contains a summary description of both current and expired…
The Depinning Transition in Presence of Disorder: A Toy Model
NASA Astrophysics Data System (ADS)
Derrida, Bernard; Retaux, Martin
2014-07-01
We introduce a toy model, which represents a simplified version of the problem of the depinning transition in the limit of strong disorder. This toy model can be formulated as a simple renormalization transformation for the probability distribution of a single real variable. For this toy model, the critical line is known exactly in one particular case and it can be calculated perturbatively in the general case. One can also show that, at the transition, there is no fixed distribution accessible by renormalization which corresponds to a disordered fixed point. Instead, both our numerical and analytic approaches indicate a transition of infinite order (of the Berezinskii-Kosterlitz-Thouless type). We give numerical evidence that this infinite order transition persists for the problem of the depinning transition with disorder on the hierarchical lattice.
Hauth, J.T.; Forslund, C.R.J.; Underwood, J.A.
1994-09-01
In 1990, with the transition from a defense mission to environmental restoration, the U.S. Department of Energy`s (DOE`s) Hanford Site began a significant effort to diagnose, redesign, and implement new safeguards and security (SAS) processes. In 1992 the Security Transition Program Office (STPO) was formed to address the sweeping changes that were being identified. Comprised of SAS and other contractor staff with extensive experience and supported by staff experienced in organizational analysis and work process redesign, STPO undertook a series of tasks designed to make fundamental changes to SAS processes throughout the Hanford Site. The goal of STPO is to align the SAS work and organization with the new Site mission. This report describes the key strategy, tools, methods, and techniques used by STPO to change SAS processes at Hanford. A particular focus of this review is transferring STPO`s experience to other DOE sites and federal agency efforts: that is, to extract, analyze, and provide a critical review of the approach, tools, and techniques used by STPO that will be useful to other DOE sites and national laboratories in transitioning from a defense production mode to environmental restoration and other missions. In particular, what lessons does STPO provide as a pilot study or model for implementing change in other transition activities throughout the DOE complex? More broadly, what theoretical and practical contributions do DOE transition efforts, such as STPO, provide to federal agency streamlining efforts and attempts to {open_quotes}reinvent{close_quotes} government enterprises in the public sector? The approach used by STPO should provide valuable information to those examining their own processes in light of new mission requirements.
Using the Research and Development in Organisations Model to Improve Transition to High School
ERIC Educational Resources Information Center
Ashton, Rebecca
2009-01-01
This article describes the application of the Research and Development in Organisations (RADIO) model to five action research projects carried out in schools around transition processes. The RADIO model is mapped onto all five studies, and adapting the model in order to include greater stakeholder participation is suggested. Reflections are made…
Using the Research and Development in Organisations Model to Improve Transition to High School
ERIC Educational Resources Information Center
Ashton, Rebecca
2009-01-01
This article describes the application of the Research and Development in Organisations (RADIO) model to five action research projects carried out in schools around transition processes. The RADIO model is mapped onto all five studies, and adapting the model in order to include greater stakeholder participation is suggested. Reflections are made…
The first 18 months in practice: a developmental transition model for the newly graduated nurse.
Schoessler, Mary; Waldo, Mary
2006-01-01
The purpose of this article is to present a process model of the development of a newly graduated nurse. The model is useful in helping new graduates interpret their experience during their first crucial months in practice and can be used by organizations to design developmentally appropriate support strategies. The model integrates novice to expert skill acquisition, adult learning, and transition theory.
Qiu, Huitong; Xu, Sheng; Han, Fang; Liu, Han; Caffo, Brian
2016-01-01
Gaussian vector autoregressive (VAR) processes have been extensively studied in the literature. However, Gaussian assumptions are stringent for heavy-tailed time series that frequently arises in finance and economics. In this paper, we develop a unified framework for modeling and estimating heavy-tailed VAR processes. In particular, we generalize the Gaussian VAR model by an elliptical VAR model that naturally accommodates heavy-tailed time series. Under this model, we develop a quantile-based robust estimator for the transition matrix of the VAR process. We show that the proposed estimator achieves parametric rates of convergence in high dimensions. This is the first work in analyzing heavy-tailed high dimensional VAR processes. As an application of the proposed framework, we investigate Granger causality in the elliptical VAR process, and show that the robust transition matrix estimator induces sign-consistent estimators of Granger causality. The empirical performance of the proposed methodology is demonstrated by both synthetic and real data. We show that the proposed estimator is robust to heavy tails, and exhibit superior performance in stock price prediction. PMID:28133642
NASA Astrophysics Data System (ADS)
Cruz, Claudia P. T.; Lyra, M. L.; Fulco, U. L.; Corso, Gilberto
2012-11-01
We introduce a model for the Contact Process with relaxing immunization CPRI. In this model, local memory is introduced by a time and space dependence of the contamination probability. The model has two parameters: a typical immunization time τ and a maximum contamination probability a. The system presents an absorbing state phase transition whenever the contamination probability a is above a minimum threshold. For short immunization times, the system evolves to a statistically stationary active state. Above τc(a), immunization predominates and the system evolves to the absorbing vacuum state. We employ a finite-size scaling analysis to show that the transition belongs to the standard directed percolation universality class. The critical immunization time diverges in the limit of a→1. In this regime, the density of active sites decays exponentially as τ increases, but never reaches the vacuum state in the thermodynamic limit.
School-to-Work Transition Issues and Models.
ERIC Educational Resources Information Center
Chadsey-Rusch, Janis; And Others
The report, which is part of a series, contains four papers concerning school-to-work transition issues and models. The first paper, "Secondary Special Education and Transition from School to Work" (F. Rusch and L. A. Phelps) reviews the economic, educational, and community adjustment difficulties of youth with handicaps in the context…
Calibration of state and transition models with FVS
Melinda Moeur; Don Vandendriesche
2010-01-01
The Interagency Mapping and Assessment Project (IMAP), a partnership between federal and state agencies, is developing mid-scale vegetation data and state and transition models (STM) for comparing the likely outcomes of alternative management policies on forested landscapes across the Pacific Northwest Region. In an STM, acres within a forested ecosystem transition...
Modeling Primary Atomization Processes
2007-11-02
I., "Generation of Ripples by Wind Blowing Over a Viscous Fluid", The Scientific Papers of Sir Geoffrey Ingram Taylor, 1963. 2. A. A. Amsden, P. J...92, 1983. 28. Jin, Xiaoshi, "Boundary Element Study on Particle Orientation Caused by the Fountain Flow in Injection Molding ", Polymer Engineering...HTPB, PE is a thermoplastic which is commonly produced via extrusion from a die in a continuous process. Hence, PE grains could be produced using
Model for continuous thermal metal to insulator transition
NASA Astrophysics Data System (ADS)
Jian, Chao-Ming; Bi, Zhen; Xu, Cenke
2017-09-01
We propose a d -dimensional interacting Majorana fermion model with quenched disorder, which gives us a continuous quantum phase transition between a diffusive thermal metal phase with a finite entropy density to an insulator phase with zero entropy density. This model is based on coupled Sachdev-Ye-Kitaev model clusters, and hence has a controlled large-N limit. The metal-insulator transition is accompanied by a spontaneous time-reversal symmetry breaking. We perform controlled calculations to show that the energy diffusion constant jumps to zero discontinuously at the metal-insulator transition, while the time-reversal symmetry-breaking order parameter increases continuously.
Cost Models for MMC Manufacturing Processes
NASA Technical Reports Server (NTRS)
Elzey, Dana M.; Wadley, Haydn N. G.
1996-01-01
Processes for the manufacture of advanced metal matrix composites are rapidly approaching maturity in the research laboratory and there is growing interest in their transition to industrial production. However, research conducted to date has almost exclusively focused on overcoming the technical barriers to producing high-quality material and little attention has been given to the economical feasibility of these laboratory approaches and process cost issues. A quantitative cost modeling (QCM) approach was developed to address these issues. QCM are cost analysis tools based on predictive process models relating process conditions to the attributes of the final product. An important attribute, of the QCM approach is the ability to predict the sensitivity of material production costs to product quality and to quantitatively explore trade-offs between cost and quality. Applications of the cost models allow more efficient direction of future MMC process technology development and a more accurate assessment of MMC market potential. Cost models were developed for two state-of-the art metal matrix composite (MMC) manufacturing processes: tape casting and plasma spray deposition. Quality and Cost models are presented for both processes and the resulting predicted quality-cost curves are presented and discussed.
A Symmetrized Basis for Transitions in the Heisenberg Model
NASA Astrophysics Data System (ADS)
Haydock, Roger; Nex, C. M. M.
2013-03-01
The spin-S Heisenberg model has 2S+1 states on each site, for which there are (2S+1)2 possible transitions between these states. For N sites there are (2S+1)N states and (2S+1)2N transitions between states. This rapid increase in the number of transitions with sites appears to limit calculations to just a few sites. However for transitions induced by spin-spin interactions, we construct a symmetrized basis which only grows as 2N-3, making possible computations for much larger systems. Supported by the Richmond F. Snyder Fund.
An intermittency model for predicting roughness induced transition
NASA Astrophysics Data System (ADS)
Ge, Xuan; Durbin, Paul
2014-11-01
An extended model for roughness-induced transition is proposed based on an intermittency transport equation for RANS modeling formulated in local variables. To predict roughness effects in the fully turbulent boundary layer, published boundary conditions for k and ω are used, which depend on the equivalent sand grain roughness height, and account for the effective displacement of wall distance origin. Similarly in our approach, wall distance in the transition model for smooth surfaces is modified by an effective origin, which depends on roughness. Flat plate test cases are computed to show that the proposed model is able to predict the transition onset in agreement with a data correlation of transition location versus roughness height, Reynolds number, and inlet turbulence intensity. Experimental data for a turbine cascade are compared with the predicted results to validate the applicability of the proposed model. Supported by NSF Award Number 1228195.
A Floquet model for the many-body localization transition
NASA Astrophysics Data System (ADS)
Zhang, Liangsheng; Khemani, Vedika; Huse, David A.
2016-12-01
The nature of the dynamical quantum phase transition between the many-body localized (MBL) phase and the thermal phase remains an open question, and one line of attack on this problem is to explore this transition numerically in finite-size systems. To maximize the contrast between the MBL phase and the thermal phase in such finite-size systems, we argue one should choose a Floquet model with no local conservation laws and rapid thermalization to "infinite temperature" in the thermal phase. Here we introduce and explore such a Floquet spin chain model and show that standard diagnostics of the MBL-to-thermal transition behave well in this model even at modest sizes. We also introduce a physically motivated space-time correlation function, which peaks at the transition in the Floquet model, but is strongly affected by conservation laws in Hamiltonian models.
Lindsay, Sally; Proulx, Meghann; Maxwell, Joanne; Hamdani, Yani; Bayley, Mark; Macarthur, Colin; Colantonio, Angela
2016-02-01
To explore gender and sex differences in experiences of transitioning to adult health care among young adults with acquired brain injury (ABI) who take part in a coordinated model of transitional care. Descriptive design using in-depth semistructured qualitative interviews. Interviews over the phone and in person. Participants (N=18) included 10 young adults with a diagnosis of ABI (4 women, 6 men; age range, 19-21y) and 9 parents (8 women, 1 man) from the Greater Toronto Area, Ontario, Canada. Not applicable. Semistructured interviews with participants. Our findings highlight several commonalities and differences relative to sex and gender among young adults with ABI who are transitioning from pediatric to adult care. Both young adult men and women experienced a similar transition process and similar organization, continuity, and availability of care. Sex differences were found in relational factors (eg, communication, family involvement, social support). Young adult men, and parents of the men, differed in their transition regarding relational factors (eg, communication, family involvement). Our findings show that young adult men and women with ABI who have taken part in a transition preparation program experience similarities in organization, continuity, and availability of care, but they experience differences in relational factors (eg, communication, family involvement). Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
Immunolocalization of endocan during the endothelial-mesenchymal transition process
Carrillo, L.M.; Arciniegas, E.; Rojas, H.; Ramírez, R.
2011-01-01
Endocan is a dermatan sulfate proteoglycan (DSPG) that has been observed in the cytoplasm of endothelial cells of small and large vessels in lung, kidney, liver, colon, ovary and brain tumors. This DSPG has been implicated in the regulation of cellular activities such as adhesion, migration, and proliferation. Given the important roles played by endocan in such processes, we sought to determine whether this DSPG is present in the chicken embryo aortic wall in embryonic days 12 and 14, when intimal thickening and endothelial transformation are notorious. Immunolabeling of serial paraffin cross-sections revealed endocan immunoreactivity at the endothelium and some mesenchymal cells constituting the intimal thickening but not in the cells arranged in lamellar layers. We also investigated whether endocan was present in monolayers of primary embryonic aortic endothelial cells attached to fibronectin when they were deprived of serum and stimulated with epidermal growth factor. Immunofluorescence determined that in the epidermal growth factor (EGF) condition where separating, detaching, and migrating cells were observed, endocan appeared organized in arrays typical of focal complexes in the leading edge of these cells. In serum-free medium condition in which the endothelial cells displayed a cobblestone appearance, endocan appeared mainly delineating the margin of many cells. This study demonstrates for the first time the presence of endocan during the aortic wall remodeling, and provides evidence that suggests a possible contribution of this DSPG in the endothelial-mesenchymal transition (EndoMT) process. PMID:22201190
Buck, Edgar C.; Wittman, Richard S.; Skomurski, Frances N.; Cantrell, Kirk J.; McNamara, Bruce K.; Soderquist, Chuck Z.
2012-07-17
Assessing the performance of spent (used) nuclear fuel in geological repository requires quantification of time-dependent phenomena that may influence its behavior on a time-scale up to millions of years. A high-level waste repository environment will be a dynamic redox system because of the time-dependent generation of radiolytic oxidants and reductants and the corrosion of Fe-bearing canister materials. One major difference between used fuel and natural analogues, including unirradiated UO2, is the intense radiolytic field. The radiation emitted by used fuel can produce radiolysis products in the presence of water vapor or a thin-film of water (including OH• and H• radicals, O2-, eaq, H2O2, H2, and O2) that may increase the waste form degradation rate and change radionuclide behavior. H2O2 is the dominant oxidant for spent nuclear fuel in an O2 depleted water environment, the most sensitive parameters have been identified with respect to predictions of a radiolysis model under typical conditions. As compared with the full model with about 100 reactions it was found that only 30-40 of the reactions are required to determine [H2O2] to one part in 10–5 and to preserve most of the predictions for major species. This allows a systematic approach for model simplification and offers guidance in designing experiments for validation.
Modeling the hepatitis A epidemiological transition in Brazil and Mexico
Van Effelterre, Thierry; Guignard, Adrienne; Marano, Cinzia; Rojas, Rosalba; Jacobsen, Kathryn H.
2017-01-01
ABSTRACT Background: Many low- to middle-income countries have completed or are in the process of transitioning from high or intermediate to low endemicity for hepatitis A virus (HAV). Because the risk of severe hepatitis A disease increases with age at infection, decreased incidence that leaves older children and adults susceptible to HAV infection may actually increase the population-level burden of disease from HAV. Mathematical models can be helpful for projecting future epidemiological profiles for HAV. Methods: An age-specific deterministic, dynamic compartmental transmission model with stratification by setting (rural versus urban) was calibrated with country-specific data on demography, urbanization, and seroprevalence of anti-HAV antibodies. HAV transmission was modeled as a function of setting-specific access to safe water. The model was then used to project various HAV-related epidemiological outcomes in Brazil and in Mexico from 1950 to 2050. Results: The projected epidemiological outcomes were qualitatively similar in the 2 countries. The age at the midpoint of population immunity (AMPI) increased considerably and the mean age of symptomatic HAV cases shifted from childhood to early adulthood. The projected overall incidence rate of HAV infections decreased by about two thirds as safe water access improved. However, the incidence rate of symptomatic HAV infections remained roughly the same over the projection period. The incidence rates of HAV infections (all and symptomatic alone) were projected to become similar in rural and urban settings in the next decades. Conclusion: This model featuring population age structure, urbanization and access to safe water as key contributors to the epidemiological transition for HAV was previously validated with data from Thailand and fits equally well with data from Latin American countries. Assuming no introduction of a vaccination program over the projection period, both Brazil and Mexico were projected to
Reversal Transition Records from Intrusions: Implications for the Reversal Process.
NASA Astrophysics Data System (ADS)
Fuller, M. D.; Williams, I. S.
2014-12-01
The nature of reversals of the geomagnetic field and the details of the transition fields remain controversial. However, reversal records from the Agno batholith and Tatoosh intrusion confirm the suggestion of Valet et al., (2012) from studies of lava records, that there is a threefold division in reversal transition directions. In the Agno, the first phase, or precursor, consists of a CCW loop of the VGP moving from high southerly latitude reverse poles to reach North America. The second phase takes the VGP along a half CCW loop from the tip of South America to northern latitudes at the intensity minimum. The third phase, or rebound is a smaller CCW loop and the main intensity recovery begins. The first and third phases appear to be paleosecular variation loops analogous to present London-Paris secular variation loops. The Tatoosh intrusion gives a similar, but less complete record with the VGPs again confined to the East Pacific and the Americas. Away from the reversal region, secular variation loops in the Tatoosh were shown to be comparable in duration to the precursor in the transition record, consistent with the first phase being a paleosecular variation loop in the Agno. Using westward drift estimates from the present field, this should last about1800 years. This gives ~3300 for phase 2, in an intensity low of >16,000 years. A feature of R to N reversal field models is a low latitude magnetic field flux concentration of the same sign as the polar vortex of the south geographic pole. This is followed by northward flux flow, e.g. Shao et al., (1999). The reversal is achieved by northward motion of this flux feature. The feature is locked in longitudinal mantle coordinates and similarly the VGPs in the Agno and Tatoosh records are confined to the longitudes of the eastern Pacific and the Americas. Whether we are approaching a reversal remains to be seen, although judging by these intrusion records the field intensity would need to decrease much further before
Dynamic wetting model for the isotropic-to-nematic transition over a flat substrate.
Rey, Alejandro D; Herrera-Valencia, E E
2014-03-14
Phase ordering over solid substrates is a ubiquitous and important soft material transformation process whose description incorporates wetting, anchoring and phase transition kinetics. In this paper the kinetics of the isotropic-to-nematic isothermal phase transition over a flat solid surface in a growing spherical drop is analyzed based on the Landau-de Gennes Q-tensor order parameter equations. The model, based on a previously derived interface force balance and a newly derived contact line force balance, is shown to be consistent with the generic model of conservative interface and contact line motions. The advancing dynamic contact angle equation is extracted from kinematic compatibility between the moving isotropic-nematic interface and contact line. A tractable surface phase transition kinetic model obtained by focusing on the dominant phase transition and wetting driving forces yields: (i) the constant advancing dynamic contact angle θ, and (ii) the contact line speed as a function of undercooling ΔT. It is shown that as undercooling increases, the surface phase transition mode approaches the bulk phase transition mode, such that θ approaches π. The elastic and wetting parameters that control the phase transformation process are identified and experiments for their determination are defined. These dynamic wetting and surface phase transition results significantly expand existing characterization methods of LC-substrate interfaces based on static phase transition droplet methods.
Thermal and Nonthermal Processes on Single Crystal Transition Metal Surfaces
NASA Astrophysics Data System (ADS)
Guo, Xingcai
investigated with polarized light. Photon-induced desorption of CO from oxidized Ni(111) (Chapter 13) is observed to be initiated by substrate interband transition. The photodesorption process is first -order in photon flux and in CO coverage. The cross section is measured to be 5 times 10 ^{-18} cm^2 at a photon energy of 4.1 eV. The appendices list abstracts of additional published results on HCN/Pt(111),(112); HCN + O/Pt(111),(112); HCN + O_2/Pt(111); CN + H(s)/Pd(111); HCN/Pd(111); Azo-methane/Pd(111); Methanol/Pd(111); Dimethyl methyl phosphonate/Pd(111), Ni(111); NO + O,S/Ni(111); Xe/Pt(111), (557), (112).
The electroweak phase transition in the Inert Doublet Model
Blinov, Nikita; Profumo, Stefano; Stefaniak, Tim E-mail: profumo@ucsc.edu
2015-07-01
We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.
The electroweak phase transition in the Inert Doublet Model
Blinov, Nikita; Profumo, Stefano; Stefaniak, Tim
2015-07-21
We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.
Inostroza Quezada, Carolina; Correa Venegas, María Loreto; Besoain Arrau, Carolina; Reinoso Medinelli, Alejandro; Velarde Lizama, Macarena; Valenzuela Mujica, María Teresa; Bedregal García, Paula; Zubarew Gurtchin, Tamara
2016-01-01
Chronic illnesses during adolescence are a big challenge for the patient, his or her family, and health care providers. The transition from paediatric health services to adult health services involves a programmed and planned transfer process of adolescent sufferers of chronic illnesses, in order to maintain a high quality of life and bio-psycho-social development. There is currently no transition model. The objective of the study is to understand the transition process from the perspective of hospitalised adolescents to collaborate towards the design of a model that meets the needs studied. Semi-structured interviews with 13 adolescent sufferers of chronic illnesses, hospitalised in two healthcare centres in Santiago, Chile, in one analytical-relational study, supported by qualitative methodology. In the analysis, 5 major themes stand out: experience of living with the illness, the importance of the doctor-patient relationship, the concept of limited autonomy to the pharmacology, the absence of the transition process as such, and the identification of barriers and needs for an adequate transition. This study is new in Chile in that it explores the phenomenom of the transition of adolescents with chronic illnesses. It emphasises the need to reinforce the concept of self-care and autonomy from early stages of care, and the importance of early planning of a healthy transition process, in accordance to the detected needs of the adolescents themselves. Copyright © 2015. Publicado por Elsevier España, S.L.U.
PYTRANSIT: fast and easy exoplanet transit modelling in PYTHON
NASA Astrophysics Data System (ADS)
Parviainen, Hannu
2015-07-01
We present a fast and user friendly exoplanet transit light-curve modelling package PYTRANSIT, implementing optimized versions of the Giménez and Mandel & Agol transit models. The package offers an object-oriented PYTHON interface to access the two models implemented natively in FORTRAN with OpenMP parallelization. A partial OpenCL version of the quadratic Mandel-Agol model is also included for GPU-accelerated computations. The aim of PYTRANSIT is to facilitate the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of data points, and of multipassband transit light curves from spectrophotometric observations, as a part of a researcher's programming toolkit for building complex, problem-specific analyses.
Chemical Process Modeling and Control.
ERIC Educational Resources Information Center
Bartusiak, R. Donald; Price, Randel M.
1987-01-01
Describes some of the features of Lehigh University's (Pennsylvania) process modeling and control program. Highlights the creation and operation of the Chemical Process Modeling and Control Center (PMC). Outlines the program's philosophy, faculty, technical program, current research projects, and facilities. (TW)
ERIC Educational Resources Information Center
Agnew, Jeanne L.; Choike, James R.
1987-01-01
Mathematical observations are made about some continuous curves, called transitions, encountered in well-known experiences. The transition parabola, the transition spiral, and the sidestep maneuver are presented. (MNS)
Numazawa, Satoshi; Smith, Roger
2011-10-01
Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions that can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multidimensional Boolean valued functions in three-dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology-dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.
NASA Astrophysics Data System (ADS)
Numazawa, Satoshi; Smith, Roger
2011-10-01
Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions that can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multidimensional Boolean valued functions in three-dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology-dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.
Variability in Response to Life Transitions: Application of a Transition Model.
ERIC Educational Resources Information Center
Kampfe, Charlene M.
The modified House Model of Social Stress is used to discuss the variability of individual responses to potentially stressful events or transitions. The model graphically depicts the variety of ways people respond to the potentially complex interaction among variables associated with stress. It also depicts the potential relationship among…
NASA Astrophysics Data System (ADS)
Dudík, Jaroslav; Dzifčáková, Elena; Meyer-Vernet, Nicole; Del Zanna, Giulio; Young, Peter R.; Giunta, Alessandra; Sylwester, Barbara; Sylwester, Janusz; Oka, Mitsuo; Mason, Helen E.; Vocks, Christian; Matteini, Lorenzo; Krucker, Säm; Williams, David R.; Mackovjak, Šimon
2017-08-01
We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of high-energy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modeling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for the detection of these non-equilibrium phenomena in various spectral ranges.
Dynamo transition in a five-mode helical model
NASA Astrophysics Data System (ADS)
Kumar, Rohit; Wahi, Pankaj
2017-09-01
We construct a five-mode helical dynamo model containing three velocity and two magnetic modes and solve it analytically. This model exhibits dynamo transition via supercritical pitchfork bifurcation. We show that the critical magnetic Reynolds number for dynamo transition (Rmc) asymptotes to constant values for very low and very high magnetic Prandtl numbers (Pm). Beyond dynamo transition, secondary bifurcations lead to periodic, quasi-periodic, and chaotic dynamo states as the forcing amplitude is increased and chaos appears through a quasi-periodic route.
Corner wetting transition in the two-dimensional Ising model
NASA Astrophysics Data System (ADS)
Lipowski, Adam
1998-07-01
We study the interfacial behavior of the two-dimensional Ising model at the corner of weakened bonds. Monte Carlo simulations results show that the interface is pinned to the corner at a lower temperature than a certain temperature Tcw at which it undergoes a corner wetting transition. The temperature Tcw is substantially lower than the temperature of the ordinary wetting transition with a line of weakened bonds. A solid-on-solid-like model is proposed, which provides a supplementary description of the corner wetting transition.
Computer Models of Helix-Coil Transitions
NASA Astrophysics Data System (ADS)
Schneller, William J.
1995-01-01
A quantitative understanding of helix-coil dynamics will help to explain their role in protein folding and in folded proteins. As a contribution to this understanding, two methods are used to study the equilibrium and dynamical aspects of the helix-coil transition in small polypeptide chains. In the first method, each amino acid residue is treated as a single quasiparticle in an effective potential that approximates the potential of mean force in solution. The equilibrium properties examined include the helix-coil transition and its dependence on chain position and well -depth at the coil-helix interface. A stochastic simulation of the Brownian motion of the chain in its solvent surroundings has been used to investigate dynamical properties. Time histories of the dihedral angles have been used to study the behavior of the helical structure. Auto and cross correlation functions have been calculated from the time histories and from the state (helix or coil) functions of the residues with relaxation times of tens to hundreds of picoseconds. Helix-coil rate constants of tens of ns ^{-1} were found for both directions of the transition. As the second method, the Electrostatic Multipole Representation is introduced. Appropriate energy functions for non-bonded interactions are developed. The multipole description and the energy functions are tested by calculation of steric maps for different amino acid side-chain groups. Results from dynamics simulations of helical chains of polyglycine, polyalanine and polyvaline are included to demonstrate the efficiency of the algorithm. It is argued that this description of the polypeptide chain is both simple and complete and will allow for the rapid simulation of chain dynamics without loss of essential information about the chain. The main features of this description are the retrievability of the full atomic representation and the ability to calculate energetically stable structures.
Business process modeling in healthcare.
Ruiz, Francisco; Garcia, Felix; Calahorra, Luis; Llorente, César; Gonçalves, Luis; Daniel, Christel; Blobel, Bernd
2012-01-01
The importance of the process point of view is not restricted to a specific enterprise sector. In the field of health, as a result of the nature of the service offered, health institutions' processes are also the basis for decision making which is focused on achieving their objective of providing quality medical assistance. In this chapter the application of business process modelling - using the Business Process Modelling Notation (BPMN) standard is described. Main challenges of business process modelling in healthcare are the definition of healthcare processes, the multi-disciplinary nature of healthcare, the flexibility and variability of the activities involved in health care processes, the need of interoperability between multiple information systems, and the continuous updating of scientific knowledge in healthcare.
Conceptual models of information processing
NASA Technical Reports Server (NTRS)
Stewart, L. J.
1983-01-01
The conceptual information processing issues are examined. Human information processing is defined as an active cognitive process that is analogous to a system. It is the flow and transformation of information within a human. The human is viewed as an active information seeker who is constantly receiving, processing, and acting upon the surrounding environmental stimuli. Human information processing models are conceptual representations of cognitive behaviors. Models of information processing are useful in representing the different theoretical positions and in attempting to define the limits and capabilities of human memory. It is concluded that an understanding of conceptual human information processing models and their applications to systems design leads to a better human factors approach.
Conceptual models of information processing
NASA Technical Reports Server (NTRS)
Stewart, L. J.
1983-01-01
The conceptual information processing issues are examined. Human information processing is defined as an active cognitive process that is analogous to a system. It is the flow and transformation of information within a human. The human is viewed as an active information seeker who is constantly receiving, processing, and acting upon the surrounding environmental stimuli. Human information processing models are conceptual representations of cognitive behaviors. Models of information processing are useful in representing the different theoretical positions and in attempting to define the limits and capabilities of human memory. It is concluded that an understanding of conceptual human information processing models and their applications to systems design leads to a better human factors approach.
Model potential calculations of lithium transitions.
NASA Technical Reports Server (NTRS)
Caves, T. C.; Dalgarno, A.
1972-01-01
Semi-empirical potentials are constructed that have eigenvalues close in magnitude to the binding energies of the valence electron in lithium. The potentials include the long range polarization force between the electron and the core. The corresponding eigenfunctions are used to calculate dynamic polarizabilities, discrete oscillator strengths, photoionization cross sections and radiative recombination coefficients. A consistent application of the theory imposes a modification on the transition operator, but its effects are small for lithium. The method presented can be regarded as a numerical generalization of the widely used Coulomb approximation.
TGF-β induced epithelial-mesenchymal transition modeling
NASA Astrophysics Data System (ADS)
Xenitidis, P.; Seimenis, I.; Kakolyris, S.; Adamopoulos, A.
2015-09-01
Epithelial cells may undergo a process called epithelial to mesenchymal transition (EMT). During EMT, cells lose their epithelial characteristics and acquire a migratory ability. Transforming growth factor-beta (TGF-β) signaling is considered to play an important role in EMT by regulating a set of genes through a gene regulatory network (GRN). This work aims at TGF-β induced EMT GRN modeling using publicly available experimental data (gene expression microarray data). The time-series network identification (TSNI) algorithm was used for inferring the EMT GRN. Receiver operating characteristic (ROC) and precision-recall (P-R) curves were constructed and the areas under them were used for evaluating the algorithm performance regarding network inference.
Modeling nuclear processes by Simulink
Rashid, Nahrul Khair Alang Md
2015-04-29
Modelling and simulation are essential parts in the study of dynamic systems behaviours. In nuclear engineering, modelling and simulation are important to assess the expected results of an experiment before the actual experiment is conducted or in the design of nuclear facilities. In education, modelling can give insight into the dynamic of systems and processes. Most nuclear processes can be described by ordinary or partial differential equations. Efforts expended to solve the equations using analytical or numerical solutions consume time and distract attention from the objectives of modelling itself. This paper presents the use of Simulink, a MATLAB toolbox software that is widely used in control engineering, as a modelling platform for the study of nuclear processes including nuclear reactor behaviours. Starting from the describing equations, Simulink models for heat transfer, radionuclide decay process, delayed neutrons effect, reactor point kinetic equations with delayed neutron groups, and the effect of temperature feedback are used as examples.
Modeling nuclear processes by Simulink
NASA Astrophysics Data System (ADS)
Rashid, Nahrul Khair Alang Md
2015-04-01
Modelling and simulation are essential parts in the study of dynamic systems behaviours. In nuclear engineering, modelling and simulation are important to assess the expected results of an experiment before the actual experiment is conducted or in the design of nuclear facilities. In education, modelling can give insight into the dynamic of systems and processes. Most nuclear processes can be described by ordinary or partial differential equations. Efforts expended to solve the equations using analytical or numerical solutions consume time and distract attention from the objectives of modelling itself. This paper presents the use of Simulink, a MATLAB toolbox software that is widely used in control engineering, as a modelling platform for the study of nuclear processes including nuclear reactor behaviours. Starting from the describing equations, Simulink models for heat transfer, radionuclide decay process, delayed neutrons effect, reactor point kinetic equations with delayed neutron groups, and the effect of temperature feedback are used as examples.
Phase transition of the one-dimensional coagulation-production process
Odor, Geza
2001-06-01
Recently an exact solution has been found by M. Henkel and H. Hinrichsen [J. Phys. A >34, 1561 (2001)] for the one-dimensional coagulation-production process: 2A{r_arrow}A, A0A{r_arrow}3A with equal diffusion and coagulation rates. This model evolves into the inactive phase independently of the production rate with t{sup {minus}1/2} density decay law. This paper shows that cluster mean-field approximations and Monte Carlo simulations predict a continuous phase transition for higher diffusion/coagulation rates as considered by the exact solution. Numerical evidence is given that the phase transition universality agrees with that of the annihilation-fission model with low diffusions.
Kinetic phase transitions in a contaminated monomer-dimer reaction model
NASA Astrophysics Data System (ADS)
Bustos, V.; Uñac, R. O.; Zgrablich, G.
2000-12-01
The irreversible kinetics of a monomer-dimer reaction on a catalyst surface [the Ziff-Gulari-Barshad (ZGB) model] in the presence of a contaminant species is studied by means of Monte Carlo simulation. The only processes allowed to the contaminant are adsorption and desorption; it is otherwise inert. The reaction window, delimited by a second order irreversible phase transition at low monomer concentration (lower bound transition) and by a first order one at high monomer concentration (upper bound transition) in the ZGB model is found to shrink with increasing contaminant concentration in a way that depends on its adsorption-desorption kinetics. Through epidemic analysis, it is also found that the upper bound transition changes from first to second order and that the lower bound transition can also be affected depending on the contaminant adsorption-desorption kinetics. The results may provide alternative explanations for experimental observations.
Kinetic phase transitions in a contaminated monomer-dimer reaction model
Bustos; Unac; Zgrablich
2000-12-01
The irreversible kinetics of a monomer-dimer reaction on a catalyst surface [the Ziff-Gulari-Barshad (ZGB) model] in the presence of a contaminant species is studied by means of Monte Carlo simulation. The only processes allowed to the contaminant are adsorption and desorption; it is otherwise inert. The reaction window, delimited by a second order irreversible phase transition at low monomer concentration (lower bound transition) and by a first order one at high monomer concentration (upper bound transition) in the ZGB model is found to shrink with increasing contaminant concentration in a way that depends on its adsorption-desorption kinetics. Through epidemic analysis, it is also found that the upper bound transition changes from first to second order and that the lower bound transition can also be affected depending on the contaminant adsorption-desorption kinetics. The results may provide alternative explanations for experimental observations.
Hearing Loss Severity: Impaired Processing of Formant Transition Duration
ERIC Educational Resources Information Center
Coez, A.; Belin, P.; Bizaguet, E.; Ferrary, E.; Zilbovicius, M.; Samson, Y.
2010-01-01
Normal hearing listeners exploit the formant transition (FT) detection to identify place of articulation for stop consonants. Neuro-imaging studies revealed that short FT induced less cortical activation than long FT. To determine the ability of hearing impaired listeners to distinguish short and long formant transitions (FT) from vowels of the…
Student Engagement and Leadership of the Transition Planning Process
ERIC Educational Resources Information Center
Martin, James E.; Williams-Diehm, Kendra
2013-01-01
The Council for Exceptional Children's Division on Career Development and Transition (DCDT) has been a longstanding leader and advocate in the field of secondary education for students with disabilities. This paper traces the history of student engagement in transition planning primarily through the lens of DCDT's journal "Career…
Student Engagement and Leadership of the Transition Planning Process
ERIC Educational Resources Information Center
Martin, James E.; Williams-Diehm, Kendra
2013-01-01
The Council for Exceptional Children's Division on Career Development and Transition (DCDT) has been a longstanding leader and advocate in the field of secondary education for students with disabilities. This paper traces the history of student engagement in transition planning primarily through the lens of DCDT's journal "Career…
ERIC Educational Resources Information Center
Abar, Caitlin C.; Maggs, Jennifer L.
2010-01-01
Research indicates that social influences impact college students' alcohol consumption; however, how selection processes may serve as an influential factor predicting alcohol use in this population has not been widely addressed. A model of influence and selection processes contributing to alcohol use across the transition to college was examined…
ERIC Educational Resources Information Center
Abar, Caitlin C.; Maggs, Jennifer L.
2010-01-01
Research indicates that social influences impact college students' alcohol consumption; however, how selection processes may serve as an influential factor predicting alcohol use in this population has not been widely addressed. A model of influence and selection processes contributing to alcohol use across the transition to college was examined…
Workforce Transition Modeling Environment user`s guide
Stahlman, E.J.; Oens, M.A.; Lewis, R.E.
1993-10-01
The Pacific Northwest Laboratory (PNL) was tasked by the US Department of Energy Albuquerque Field Office (DOE-AL) to develop a workforce assessment and transition planning tool to support integrated decision making at a single DOE installation. The planning tool permits coordinated, integrated workforce planning to manage growth, decline, or transition within a DOE installation. The tool enhances the links and provides commonality between strategic, programmatic, and operations planners and human resources. Successful development and subsequent complex-wide implementation of the model also will facilitate planning at the national level by enforcing a consistent format on data that are now collected by installations in corporate-specific formats that are not amenable to national-level analyses. The workforce assessment and transition planning tool, the Workforce Transition Modeling Environment (WFTME), consists of two components: the Workforce Transition Model and the Workforce Budget Constraint Model. The Workforce Transition Model, the preponderant of the two, assists decision makers identify and evaluate alternatives for transitioning the current workforce to meet the skills required to support projected workforce requirements. The Workforce Budget Constraint Model helps estimate the number of personnel that will be affected by a given workforce budget increase or decrease and assists in identifying how the corresponding hirings or layoffs should be distributed across the Common Occupation Classification System (COCS) occupations. This user`s guide describes the use and operation of the WFTME. This includes the functions of modifying data and running models, interpreting output reports, and an approach for using the WFTME to evaluate various workforce transition scenarios.
Naumis, Gerardo G
2012-06-01
When a liquid melt is cooled, a glass or phase transition can be obtained depending on the cooling rate. Yet, this behavior has not been clearly captured in energy-landscape models. Here, a model is provided in which two key ingredients are considered in the landscape, metastable states and their multiplicity. Metastable states are considered as in two level system models. However, their multiplicity and topology allows a phase transition in the thermodynamic limit for slow cooling, while a transition to the glass is obtained for fast cooling. By solving the corresponding master equation, the minimal speed of cooling required to produce the glass is obtained as a function of the distribution of metastable states.
Development of one-equation transition/turbulence models
Edwards, J.R.; Roy, C.J.; Blottner, F.G.; Hassan, H.A.
2000-01-14
This paper reports on the development of a unified one-equation model for the prediction of transitional and turbulent flows. An eddy viscosity--transport equation for nonturbulent fluctuation growth based on that proposed by Warren and Hassan is combined with the Spalart-Allmaras one-equation model for turbulent fluctuation growth. Blending of the two equations is accomplished through a multidimensional intermittency function based on the work of Dhawan and Narasimha. The model predicts both the onset and extent of transition. Low-speed test cases include transitional flow over a flat plate, a single element airfoil, and a multi-element airfoil in landing configuration. High-speed test cases include transitional Mach 3.5 flow over a 5{degree} cone and Mach 6 flow over a flared-cone configuration. Results are compared with experimental data, and the grid-dependence of selected predictions is analyzed.
Thermodynamics and phase transitions in the Overhauser model
Duffield, N.G.; Pule, J.V.
1989-01-01
The authors analyze the thermodynamics of the Overhauser model and demonstrate rigorously the existence of a phase transition. This is achieved by extending techniques previously developed to treat the BCS model in the quasi-spin formulation. Additionally, they compare the thermodynamics of the quasi-spin and full-trace BCS models. The results are identical up to a temperature rescaling.
Models of the Reading Process.
Rayner, Keith; Reichle, Erik D
2010-11-01
Reading is a complex skill involving the orchestration of a number of components. Researchers often talk about a "model of reading" when talking about only one aspect of the reading process (for example, models of word identification are often referred to as "models of reading"). Here, we review prominent models that are designed to account for (1) word identification, (2) syntactic parsing, (3) discourse representations, and (4) how certain aspects of language processing (e.g., word identification), in conjunction with other constraints (e g., limited visual acuity, saccadic error, etc.), guide readers' eyes. Unfortunately, it is the case that these various models addressing specific aspects of the reading process seldom make contact with models dealing with other aspects of reading. Thus, for example, the models of word identification seldom make contact with models of eye movement control, and vice versa. While this may be unfortunate in some ways, it is quite understandable in other ways because reading itself is a very complex process. We discuss prototypical models of aspects of the reading process in the order mentioned above. We do not review all possible models, but rather focus on those we view as being representative and most highly recognized.
Phase transitions in simplified models with long-range interactions
NASA Astrophysics Data System (ADS)
Rocha Filho, T. M.; Amato, M. A.; Mello, B. A.; Figueiredo, A.
2011-10-01
We study the origin of phase transitions in several simplified models with long-range interactions. For the self-gravitating ring model, we are unable to observe a possible phase transition predicted by Nardini and Casetti [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.80.060103 80, 060103R (2009).] from an energy landscape analysis. Instead we observe a sharp, although without any nonanalyticity, change from a core-halo to a core-only configuration in the spatial distribution functions for low energies. By introducing a different class of solvable simplified models without any critical points in the potential energy we show that a behavior similar to the thermodynamics of the ring model is obtained, with a first-order phase transition from an almost homogeneous high-energy phase to a clustered phase and the same core-halo to core configuration transition at lower energies. We discuss the origin of these features for the simplified models and show that the first-order phase transition comes from the maximization of the entropy of the system as a function of energy and an order parameter, as previously discussed by Hahn and Kastner [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.72.056134 72, 056134 (2005); Eur. Phys. J. BEPJBFY1434-602810.1140/epjb/e2006-00100-7 50, 311 (2006)], which seems to be the main mechanism causing phase transitions in long-range interacting systems.
Analog modelling of obduction processes
NASA Astrophysics Data System (ADS)
Agard, P.; Zuo, X.; Funiciello, F.; Bellahsen, N.; Faccenna, C.; Savva, D.
2012-04-01
Obduction corresponds to one of plate tectonics oddities, whereby dense, oceanic rocks (ophiolites) are presumably 'thrust' on top of light, continental ones, as for the short-lived, almost synchronous Peri-Arabic obduction (which took place along thousands of km from Turkey to Oman in c. 5-10 Ma). Analog modelling experiments were performed to study the mechanisms of obduction initiation and test various triggering hypotheses (i.e., plate acceleration, slab hitting the 660 km discontinuity, ridge subduction; Agard et al., 2007). The experimental setup comprises (1) an upper mantle, modelled as a low-viscosity transparent Newtonian glucose syrup filling a rigid Plexiglas tank and (2) high-viscosity silicone plates (Rhodrosil Gomme with PDMS iron fillers to reproduce densities of continental or oceanic plates), located at the centre of the tank above the syrup to simulate the subducting and the overriding plates - and avoid friction on the sides of the tank. Convergence is simulated by pushing on a piston at one end of the model with velocities comparable to those of plate tectonics (i.e., in the range 1-10 cm/yr). The reference set-up includes, from one end to the other (~60 cm): (i) the piston, (ii) a continental margin containing a transition zone to the adjacent oceanic plate, (iii) a weakness zone with variable resistance and dip (W), (iv) an oceanic plate - with or without a spreading ridge, (v) a subduction zone (S) dipping away from the piston and (vi) an upper, active continental margin, below which the oceanic plate is being subducted at the start of the experiment (as is known to have been the case in Oman). Several configurations were tested and over thirty different parametric tests were performed. Special emphasis was placed on comparing different types of weakness zone (W) and the extent of mechanical coupling across them, particularly when plates were accelerated. Displacements, together with along-strike and across-strike internal deformation in all
Modeled and Observed Transitions Between Rip Currents and Alongshore Flows
NASA Astrophysics Data System (ADS)
Moulton, M.; Elgar, S.; Warner, J. C.; Raubenheimer, B.
2014-12-01
Predictions of rip currents, alongshore currents, and the temporal transitions between these circulation patterns are important for swimmer safety and for estimating the transport of sediments, biota, and pollutants in the nearshore. Here, field observations are combined with hydrodynamic modeling to determine the dominant processes that lead rip currents to turn on and off with changing waves, bathymetry, and tidal elevation. Waves, currents, mean sea levels, and bathymetry were measured near and within five shore-perpendicular channels (on average 2-m deep, 30-m wide) that were dredged with the propellers of a landing craft at different times on a long straight Atlantic Ocean beach near Duck, NC in summer 2012. The circulation was measured for a range of incident wave conditions and channel sizes, and included rapid transitions between strong (0.5 to 1 m/s) rip current jets flowing offshore through the channels and alongshore currents flowing across the channels with no rip currents. Meandering alongshore currents (alongshore currents combined with an offshore jet at the downstream edge of the channel) also were observed. Circulation patterns near and within idealized rip channels simulated with COAWST (a three-dimensional phase-averaged model that couples ROMS and SWAN) are compared with the observations. In addition, the model is used to investigate the hydrodynamic response to a range of wave conditions (angle, height, period) and bathymetries (channel width, depth, and length; tidal elevations; shape of sandbar or terrace). Rip current speeds are largest for the deepest perturbations, and decrease as incident wave angles become more oblique. For obliquely incident waves, the rip currents are shifted in the direction of the alongshore flow, with an increasing shift for increasing alongshore current speed or increasing bathymetric perturbation depth.
Modeling Verwey transition temperature of Fe3O4 nanocrystals
NASA Astrophysics Data System (ADS)
Jiang, Xiao bao; Xiao, Bei bei; Yang, Hong yu; Gu, Xiao yan; Sheng, Hong chao; Zhang, Xing hua
2016-11-01
The Verwey transition in nanoscale is an important physical property for Fe3O4 nanocrystals and has attracted extensive attention in recent years. In this work, an analytic thermodynamic model without any adjusting parameters is developed to estimate the size and shape effects on modulating the Verwey transition temperature of Fe3O4 nanocrystals. The results show that the Verwey transition temperature reduces with increasing shape parameter λ or decreasing size D. A good agreement between the prediction and the experimental data verified our physical insight that the Verwey transition of Fe3O4 can be directly related to the atomic thermal vibration. The results presented in this work will be of benefit to the understanding of the microscopic mechanism of the Verwey transition and the design of future generation switching and memory devices.
ERIC Educational Resources Information Center
Nathanson, Jeanne H., Ed.
1993-01-01
This theme issue on transitions for individuals with disabilities contains nine papers discussing transition programs and issues. "Transition Issues for the 1990s," by Michael J. Ward and William D. Halloran, discusses self-determination, school responsibility for transition, continued educational engagement of at-risk students, and service…
Keyong Li; Seong-Cheol Kang; I. Ch. Paschalidis
2007-09-01
This paper investigates stochastic processes that are modeled by a finite number of states but whose transition probabilities are uncertain and possibly time-varying. The treatment of uncertain transition probabilities is important because there appears to be a disconnection between the practice and theory of stochastic processes due to the difficulty of assigning exact probabilities to real-world events. Also, when the finite-state process comes as a reduced model of one that is more complicated in nature (possibly in a continuous state space), existing results do not facilitate rigorous analysis. Two approaches are introduced here. The first focuses on processes with one terminal state and the properties that affect their convergence rates. When a process is on a complicated graph, the bound of the convergence rate is not trivially related to that of the probabilities of individual transitions. Discovering the connection between the two led us to define two concepts which we call 'progressivity' and 'sortedness', and to a new comparison theorem for stochastic processes. An optimality criterion for robust optimal control also derives from this comparison theorem. In addition, this result is applied to the case of mission-oriented autonomous robot control to produce performance estimate within a control framework that we propose. The second approach is in the MDP frame work. We will introduce our preliminary work on optimistic robust optimization, which aims at finding solutions that guarantee the upper bounds of the accumulative discounted cost with prescribed probabilities. The motivation here is to address the issue that the standard robust optimal solution tends to be overly conservative.
Development of state and transition model assumptions used in National Forest Plan revision
Eric B. Henderson
2008-01-01
State and transition models are being utilized in forest management analysis processes to evaluate assumptions about disturbances and succession. These models assume valid information about seral class successional pathways and timing. The Forest Vegetation Simulator (FVS) was used to evaluate seral class succession assumptions for the Hiawatha National Forest in...
Modelling of CWS combustion process
NASA Astrophysics Data System (ADS)
Rybenko, I. A.; Ermakova, L. A.
2016-10-01
The paper considers the combustion process of coal water slurry (CWS) drops. The physico-chemical process scheme consisting of several independent parallel-sequential stages is offered. This scheme of drops combustion process is proved by the particle size distribution test and research stereomicroscopic analysis of combustion products. The results of mathematical modelling and optimization of stationary regimes of CWS combustion are provided. During modeling the problem of defining possible equilibrium composition of products, which can be obtained as a result of CWS combustion processes at different temperatures, is solved.
Testing a Theoretical Model of Immigration Transition and Physical Activity.
Chang, Sun Ju; Im, Eun-Ok
2015-01-01
The purposes of the study were to develop a theoretical model to explain the relationships between immigration transition and midlife women's physical activity and test the relationships among the major variables of the model. A theoretical model, which was developed based on transitions theory and the midlife women's attitudes toward physical activity theory, consists of 4 major variables, including length of stay in the United States, country of birth, level of acculturation, and midlife women's physical activity. To test the theoretical model, a secondary analysis with data from 127 Hispanic women and 123 non-Hispanic (NH) Asian women in a national Internet study was used. Among the major variables of the model, length of stay in the United States was negatively associated with physical activity in Hispanic women. Level of acculturation in NH Asian women was positively correlated with women's physical activity. Country of birth and level of acculturation were significant factors that influenced physical activity in both Hispanic and NH Asian women. The findings support the theoretical model that was developed to examine relationships between immigration transition and physical activity; it shows that immigration transition can play an essential role in influencing health behaviors of immigrant populations in the United States. The NH theoretical model can be widely used in nursing practice and research that focus on immigrant women and their health behaviors. Health care providers need to consider the influences of immigration transition to promote immigrant women's physical activity.
A process algebra model of QED
NASA Astrophysics Data System (ADS)
Sulis, William
2016-03-01
The process algebra approach to quantum mechanics posits a finite, discrete, determinate ontology of primitive events which are generated by processes (in the sense of Whitehead). In this ontology, primitive events serve as elements of an emergent space-time and of emergent fundamental particles and fields. Each process generates a set of primitive elements, using only local information, causally propagated as a discrete wave, forming a causal space termed a causal tapestry. Each causal tapestry forms a discrete and finite sampling of an emergent causal manifold (space-time) M and emergent wave function. Interactions between processes are described by a process algebra which possesses 8 commutative operations (sums and products) together with a non-commutative concatenation operator (transitions). The process algebra possesses a representation via nondeterministic combinatorial games. The process algebra connects to quantum mechanics through the set valued process and configuration space covering maps, which associate each causal tapestry with sets of wave functions over M. Probabilities emerge from interactions between processes. The process algebra model has been shown to reproduce many features of the theory of non-relativistic scalar particles to a high degree of accuracy, without paradox or divergences. This paper extends the approach to a semi-classical form of quantum electrodynamics.
Kinetic Modeling of Microbiological Processes
Liu, Chongxuan; Fang, Yilin
2012-08-26
Kinetic description of microbiological processes is vital for the design and control of microbe-based biotechnologies such as waste water treatment, petroleum oil recovery, and contaminant attenuation and remediation. Various models have been proposed to describe microbiological processes. This editorial article discusses the advantages and limiation of these modeling approaches in cluding tranditional, Monod-type models and derivatives, and recently developed constraint-based approaches. The article also offers the future direction of modeling researches that best suit for petroleum and environmental biotechnologies.
Juban, Audrey; Briancon, Stephanie; Puel, François
2016-11-01
For pharmaceutical industry, understanding solid-phase transition of the active pharmaceutical ingredient (API) induced by the manufacturing process is a key issue. Caffeine was chosen as a model API since it exhibits a polymorphic transformation during tableting. This study investigated the impact of the compression speed on the phase transition of anhydrous Form I (CFI) into Form II. Tablets were made from pure CFI and binary mixtures of CFI/microcrystalline cellulose, with an electric press well instrumented at three different compression speeds (50, 500 and 4500 mm min(-1)). For each velocity of the mobile punch studied, tablets made from three compression pressures (50, 100 and 200 MPa) were analyzed. The determination of the CFI transition degree was performed using a Differential Scanning Calorimetry (DSC). The CFI transition degree was monitored during three months in order to obtain the transformation profile of the API in tablets and in uncompressed powder. The modeling of the profile with a stretched exponential kinetic law (Johnson-Mehl-Avrami model) was used for the identification of the transition mechanism. The direct compression process triggered the polymorphic transformation in tablet when a sufficient compression pressure is applied. The velocity of the punch did neither impact the transition degree just after compression nor the transformation profile. The transition mechanism remained driven by nucleation for several operating conditions. Consequently, the punch velocity is not a decisive process parameter for avoiding such phase transition in tableting. As already observed, the compression pressure did not influence the transition whatever the compression speed and the velocity.
A Markovian Process Modeling for Pickomino
NASA Astrophysics Data System (ADS)
Cardon, Stéphane; Chetcuti-Sperandio, Nathalie; Delorme, Fabien; Lagrue, Sylvain
This paper deals with a nondeterministic game based on die rolls and on the "stop or continue" principle: Pickomino. During his turn, each participant has to make the best decisions first to choose the dice to keep, then to choose between continuing or stopping depending on the previous rolls and on the available resources. Markov Decision Processes (MDPs) offer the formal framework to model this game. The two main problems are first to determine the set of states, then to compute the transition probabilities.
Social Models: Blueprints or Processes?
ERIC Educational Resources Information Center
Little, Graham R.
1981-01-01
Discusses the nature and implications of two different models for societal planning: (1) the problem-solving process approach based on Karl Popper; and (2) the goal-setting "blueprint" approach based on Karl Marx. (DC)
Social Models: Blueprints or Processes?
ERIC Educational Resources Information Center
Little, Graham R.
1981-01-01
Discusses the nature and implications of two different models for societal planning: (1) the problem-solving process approach based on Karl Popper; and (2) the goal-setting "blueprint" approach based on Karl Marx. (DC)
Nonuniversal Transitions to Synchrony in the Sakaguchi-Kuramoto Model
NASA Astrophysics Data System (ADS)
Omel'chenko, Oleh E.; Wolfrum, Matthias
2012-10-01
We investigate the transition to synchrony in a system of phase oscillators that are globally coupled with a phase lag (Sakaguchi-Kuramoto model). We show that for certain unimodal frequency distributions there appear unusual types of synchronization transitions, where synchrony can decay with increasing coupling, incoherence can regain stability for increasing coupling, or multistability between partially synchronized states and/or the incoherent state can appear. Our method is a bifurcation analysis based on a frequency dependent version of the Ott-Antonsen method and allows for a universal description of possible synchronization transition scenarios for any given distribution of natural frequencies.
Transition to Operations Support at the Community Coordinated Modeling Center
NASA Technical Reports Server (NTRS)
Hesse, M.
2005-01-01
The Community Coordinated Modeling Center (CCMC) is a multi-agency partnership, which aims at the creation of next generation space weather models. The goal of the CCMC is to support the research and developmental work necessary to substantially increase the present-day modeling capability for space weather purposes, and to provide models for transition to the rapid prototyping centers at the space weather forecast centers. This goal requires close collaborations with and substantial involvement of the research community. The physical regions to be addressed by CCMC-related activities range from the solar atmosphere to the Earth's upper atmosphere. The CCMC is an integral part of the National Space Weather Program Implementation Plan, of NASA's Living With a Star (LWS) initiative, and of the Department of Defense Space Weather Transition Plan. CCMC includes a facility at NASA Goddard Space Flight Center, as well as distributed computing facilities provided by the US Air Force. CCMC also provides, to the research community, access to state-of-the-art space research models. This paper will focus on a status report on CCMC activities in support of model transition to operations at US space weather forecasting centers. In particular, an update will be given on past and present transition activities, on developments that address operational needs, and on future opportunities for transition-to-operations support.
Role of secondary instability theory and parabolized stability equations in transition modeling
NASA Technical Reports Server (NTRS)
El-Hady, Nabil M.; Dinavahi, Surya P.; Chang, Chau-Lyan; Zang, Thomas A.
1993-01-01
In modeling the laminar-turbulent transition region, the designer depends largely on benchmark data from experiments and/or direct numerical simulations that are usually extremely expensive. An understanding of the evolution of the Reynolds stresses, turbulent kinetic energy, and quantifies in the transport equations like the dissipation and production is essential in the modeling process. The secondary instability theory and the parabolized stability equations method are used to calculate these quantities, which are then compared with corresponding quantities calculated from available direct numerical simulation data for the incompressible boundary-layer flow of laminar-turbulent transition conditions. The potential of the secondary instability theory and the parabolized stability equations approach in predicting these quantities is discussed; results indicate that inexpensive data that are useful for transition modeling in the early stages of the transition region can be provided by these tools.
A Pulse-Type Hardware CPG Model for Generation and Transition of Quadruped Locomotion Pattern
NASA Astrophysics Data System (ADS)
Hata, Keiko; Sekine, Yoshifumi; Nakabora, Yoshifumi; Saeki, Katsutoshi
The purpose of our research is to clarify information processing functions of living organisms by neural networks using pulse-type hardware neuron models and applying pulse-type hardware neural networks to engineered models. It is known that locomotion such as walking by a living organism is generated and transited by CPG (Central Pattern Generator) in the central nervous system. We investigate a pulse-type hardware CPG model using coupled oscillator composed of pulse-type hardware neuron models. A CPG model is need to generate and control quadruped locomotion. In this paper, we describe generation and transition of oscillation patterns, corresponding to quadruped locomotion patterns. As a result, it is shown that generation and transition of oscillation patterns are possible by giving external inputs of one pulse to the CPG model.
Phase transitions in models of human cooperation
NASA Astrophysics Data System (ADS)
Perc, Matjaž
2016-08-01
If only the fittest survive, why should one cooperate? Why should one sacrifice personal benefits for the common good? Recent research indicates that a comprehensive answer to such questions requires that we look beyond the individual and focus on the collective behavior that emerges as a result of the interactions among individuals, groups, and societies. Although undoubtedly driven also by culture and cognition, human cooperation is just as well an emergent, collective phenomenon in a complex system. Nonequilibrium statistical physics, in particular the collective behavior of interacting particles near phase transitions, has already been recognized as very valuable for understanding counterintuitive evolutionary outcomes. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among humans often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. Here we briefly review research done in the realm of the public goods game, and we outline future research directions with an emphasis on merging the most recent advances in the social sciences with methods of nonequilibrium statistical physics. By having a firm theoretical grip on human cooperation, we can hope to engineer better social systems and develop more efficient policies for a sustainable and better future.
Science Process Evaluation Model. Monograph.
ERIC Educational Resources Information Center
Small, Larry
The goal of this monograph is to explain the evaluation program designed by Schaumburg Community Consolidated District 54, Schaumberg, Illinois. It discusses the process used in the development of the model, the product, the implication for classroom teachers and the effects of using an evaluation to assess science process skills. The process…
Cutting Losses for Student-Athletes in Transition: An Integrative Transition Model.
ERIC Educational Resources Information Center
Wooten, H. Ray, Jr.
1994-01-01
Provides a framework from which to address the transition, decision-making, personal, and career counseling strategies useful with athletes. Counseling strategies, both personal and career, accompany each stage in the integrated model for working with this special population. Includes 2 case examples and 15 references. (Author/CRR)
Forecasting critical transitions using data-driven nonstationary dynamical modeling
NASA Astrophysics Data System (ADS)
Kwasniok, Frank
2015-12-01
An approach to predicting critical transitions from time series is introduced. A nonstationary low-order stochastic dynamical model of appropriate complexity to capture the transition mechanism under consideration is estimated from data. In the simplest case, the model is a one-dimensional effective Langevin equation, but also higher-dimensional dynamical reconstructions based on time-delay embedding and local modeling are considered. Integrations with the nonstationary models are performed beyond the learning data window to predict the nature and timing of critical transitions. The technique is generic, not requiring detailed a priori knowledge about the underlying dynamics of the system. The method is demonstrated to successfully predict a fold and a Hopf bifurcation well beyond the learning data window.
The remarkable ability of turbulence model equations to describe transition
NASA Technical Reports Server (NTRS)
Wilcox, David C.
1992-01-01
This paper demonstrates how well the k-omega turbulence model describes the nonlinear growth of flow instabilities from laminar flow into the turbulent flow regime. Viscous modifications are proposed for the k-omega model that yield close agreement with measurements and with Direct Numerical Simulation results for channel and pipe flow. These modifications permit prediction of subtle sublayer details such as maximum dissipation at the surface, k approximately y(exp 2) as y approaches 0, and the sharp peak value of k near the surface. With two transition specific closure coefficients, the model equations accurately predict transition for an incompressible flat-plate boundary layer. The analysis also shows why the k-epsilon model is so difficult to use for predicting transition.
Transition-Sensitized Turbulence Models for Compressible and Incompressible Flows
NASA Technical Reports Server (NTRS)
Thacker, William D.
2003-01-01
During the grant period from January 1,2002 to December 31,2002 work was carried out on three projects to extend the range of applicability of advanced turbulence models. First, a new transition-sensitized turbulence model was tested and refined. Second, the influence of compressibility on the pressure-strain rate correlation was studied. Third, the relationship between time-filtered large eddy simulation (TLES) and Reynolds-averaged Navier Stokes (RANS) modeling was investigated leading to submission of the article. The transition-sensitized turbulence model encompasses the early-stage transition and turbulent flow regimes describing the evolution of the ensemble mean disturbance energy and dissipation rate. It is founded on a consistent mathematical description of the laminar regime with its linear disturbances and the fully turbulent regime with its stochastic fluctuations. The unified description is provided by the ensemble viewpoint.
Double transitions in the fully frustrated XY model
NASA Astrophysics Data System (ADS)
Jeon, Gun Sang; Park, Sung Yong; Choi, M. Y.
1997-06-01
The fully frustrated XY model is studied via the position-space renormalization group approach. The model is mapped into two coupled XY models, for which the scaling equations are derived. By integrating directly the scaling equations, we observe that there exists a narrow temperature range in which both the vortex and coupling charge fugacities grow large, suggesting double transitions in the system. While the transition at lower temperature is identified to be of the Kosterlitz-Thouless type, the higher-temperature one appears not to be of the Ising universality class.
MHD Modeling of the Transition Region Using Realistic Transport Coefficients
NASA Astrophysics Data System (ADS)
Goodman, Michael L.
1997-05-01
Most of the transition region (TR) consists of a collision dominated plasma. The dissipation and transport of energy in such a plasma is accurately described by the well known classical transport coefficients which include the electrical and thermal conductivity, viscosity, and thermo- electric tensors. These tensors are anisotropic and are functions of local values of temperature, density, and magnetic field. They may be used in an MHD model to obtain a self consistent, physically realistic description of the TR. The physics of kinetic processes is included in the MHD model through the transport coefficients. As a first step in studying heating and cooling processes in the TR in a realistic, quantitative manner, a 1.5 dimensional, steady state MHD model with a specified temperature profile is considered. The momentum equation includes the inertial, pressure gradient, Lorentz, and gravitational forces. The Ohm's law includes the exact expressions for the electrical conductivity and thermo- electric tensors. The electrical conductivity relates the generalized electric field to the conduction current density while the thermo-electric tensor relates the temperature gradient to the thermo-electric current density. The total current density is the sum of the two. It is found that the thermo-electric current density can be as large as the conduction current density, indicating that thermo-electric effects are probably important in modeling the dynamics of energy dissipation, such as wave dissipation, in the TR. Although the temperature gradient is in the vertical direction, the thermo-electric current density is in the horizontal direction, indicating the importance of the effects of anisotropic transport. The transport coefficients are valid for all magnetic field strengths, and so may be used to study the physics of weakly as well as strongly magnetized regions of the TR. Numerical examples are presented.
Trabelsi, Meriam; Mandart, Elisabeth; Le Grusse, Philippe; Bord, Jean-Paul
2016-01-01
The use of plant protection products enables farmers to maximize economic performance and yields, but in return, the environment and human health can be greatly affected because of their toxicity. There are currently strong calls for farmers to reduce the use of these toxic products for the preservation of the environment and the human health, and it has become urgent to invest in more sustainable models that help reduce these risks. One possible solution is the transition toward agroecological production systems. These new systems must be beneficial economically, socially, and environmentally in terms of human health. There are many tools available, based on a range of indicators, for assessing the sustainability of agricultural systems on conventional farm holdings. These methods are little suitable to agroecological farms and do not measure the performance of agroecological transition farms. In this article, we therefore develop a model for the strategic definition, guidance, and assistance for a transition to agroecological practices, capable of assessing performance of this transition and simulating the consequences of possible changes. This model was built by coupling (i) a decision-support tool and a technico-economic simulator with (ii) a conceptual model built from the dynamics of agroecological practices. This tool is currently being tested in the framework of a Compte d'Affectation Spéciale pour le Développement Agricole et Rural (CASDAR) project (CASDAR: project launched in 2013 by the French Ministry of Agriculture, Food and Forestry, on the theme "collective mobilisation for agroecology," http://agriculture.gouv.fr/Appel-a-projets-CASDAR ) using data from farms, most of which are engaged in agroenvironmental process and reducing plant protection treatments since 2008.
Transitioning the Rice Realtime Forecast Models to DSCOVR
NASA Astrophysics Data System (ADS)
Bala, R.; Reiff, P. H.
2016-12-01
The Rice realtime forecast models of global magnetospheric indices Kp, Dst and AE have been actively running at mms.rice.edu/realtime/forecast.html for nearly a decade now. These neural network models were trained using the ACE archival solar wind data while the near-realtime forecasts are provided using instantaneous upwind solar wind data stream measured at the L1 point through ACE. Additionally, the webpage also provide status of the current space weather condition as an additional resource, updating every ten minutes. Furthermore, the subscribers of our space weather alert system, called `spacalrt', have been receiving email notices based on predefined thresholds. One of the gaps that is currently seen in the Rice neural network models lies in the density dependent models using variants of the solar wind pressure. The anomalous behavior in reporting densities in ACE has been a common issue for some time now. Often such behavior is observed when the solar energetic particle that are associated with solar flares or CMEs are Earth directed. Therefore, it is understood that the subsequent measures of the density reported by ACE will be either very low or, at a minimum, contaminated. Under these circumstances, the density-based Rice models typically underpredict. However, the newly launched DSCOVR satellite will help enhance our prediction models with high-quality data; it has real time space weather data available through the NOAA's Space Weather Prediction Center as of July, 2016. We are in the process of transitioning our forecast operations to include data from DSCOVR while running the original ACE data stream in parallel until it lasts. This paper will compare and contrast the forecasted values from the two satellites. Finally, we will discuss our efforts in providing the forecast products for the Rice space weather website that will be a part of the book on "Machine Learning Techniques for Space Weather" to be published by Elsiever.
Transition characteristic analysis of traffic evolution process for urban traffic network.
Wang, Longfei; Chen, Hong; Li, Yang
2014-01-01
The characterization of the dynamics of traffic states remains fundamental to seeking for the solutions of diverse traffic problems. To gain more insights into traffic dynamics in the temporal domain, this paper explored temporal characteristics and distinct regularity in the traffic evolution process of urban traffic network. We defined traffic state pattern through clustering multidimensional traffic time series using self-organizing maps and construct a pattern transition network model that is appropriate for representing and analyzing the evolution progress. The methodology is illustrated by an application to data flow rate of multiple road sections from Network of Shenzhen's Nanshan District, China. Analysis and numerical results demonstrated that the methodology permits extracting many useful traffic transition characteristics including stability, preference, activity, and attractiveness. In addition, more information about the relationships between these characteristics was extracted, which should be helpful in understanding the complex behavior of the temporal evolution features of traffic patterns.
Transition Characteristic Analysis of Traffic Evolution Process for Urban Traffic Network
Chen, Hong; Li, Yang
2014-01-01
The characterization of the dynamics of traffic states remains fundamental to seeking for the solutions of diverse traffic problems. To gain more insights into traffic dynamics in the temporal domain, this paper explored temporal characteristics and distinct regularity in the traffic evolution process of urban traffic network. We defined traffic state pattern through clustering multidimensional traffic time series using self-organizing maps and construct a pattern transition network model that is appropriate for representing and analyzing the evolution progress. The methodology is illustrated by an application to data flow rate of multiple road sections from Network of Shenzhen's Nanshan District, China. Analysis and numerical results demonstrated that the methodology permits extracting many useful traffic transition characteristics including stability, preference, activity, and attractiveness. In addition, more information about the relationships between these characteristics was extracted, which should be helpful in understanding the complex behavior of the temporal evolution features of traffic patterns. PMID:24982969
batman: BAsic Transit Model cAlculatioN in Python
NASA Astrophysics Data System (ADS)
Kreidberg, Laura
2015-10-01
batman provides fast calculation of exoplanet transit light curves and supports calculation of light curves for any radially symmetric stellar limb darkening law. It uses an integration algorithm for models that cannot be quickly calculated analytically, and in typical use, the batman Python package can calculate a million model light curves in well under ten minutes for any limb darkening profile.
Using Corrosion Design Models to Accelerate the Transition of Alternatives
2012-08-01
Corrosion Design Models • All moving to incorporate light metals, composites and other aviation materials • Maturation includes effect of...Using Corrosion Design Models to Accelerate the Transition of Alternatives Craig Matzdorf Materials Engineering Division Naval Air...TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Air Warfare Center, Materials Engineering Division,22347
Command Process Modeling & Risk Analysis
NASA Technical Reports Server (NTRS)
Meshkat, Leila
2011-01-01
Commanding Errors may be caused by a variety of root causes. It's important to understand the relative significance of each of these causes for making institutional investment decisions. One of these causes is the lack of standardized processes and procedures for command and control. We mitigate this problem by building periodic tables and models corresponding to key functions within it. These models include simulation analysis and probabilistic risk assessment models.
Command Process Modeling & Risk Analysis
NASA Technical Reports Server (NTRS)
Meshkat, Leila
2011-01-01
Commanding Errors may be caused by a variety of root causes. It's important to understand the relative significance of each of these causes for making institutional investment decisions. One of these causes is the lack of standardized processes and procedures for command and control. We mitigate this problem by building periodic tables and models corresponding to key functions within it. These models include simulation analysis and probabilistic risk assessment models.
Self-organized phase transitions in neural networks as a neural mechanism of information processing.
Hoshino, O; Kashimori, Y; Kambara, T
1996-01-01
Transitions between dynamically stable activity patterns imposed on an associative neural network are shown to be induced by self-organized infinitesimal changes in synaptic connection strength and to be a kind of phase transition. A key event for the neural process of information processing in a population coding scheme is transition between the activity patterns encoding usual entities. We propose that the infinitesimal and short-term synaptic changes based on the Hebbian learning rule are the driving force for the transition. The phase transition between the following two dynamical stable states is studied in detail, the state where the firing pattern is changed temporally so as to itinerate among several patterns and the state where the firing pattern is fixed to one of several patterns. The phase transition from the pattern itinerant state to a pattern fixed state may be induced by the Hebbian learning process under a weak input relevant to the fixed pattern. The reverse transition may be induced by the Hebbian unlearning process without input. The former transition is considered as recognition of the input stimulus, while the latter is considered as clearing of the used input data to get ready for new input. To ensure that information processing based on the phase transition can be made by the infinitesimal and short-term synaptic changes, it is absolutely necessary that the network always stays near the critical state corresponding to the phase transition point. PMID:8622933
Conformational transitions in random heteropolymer models
NASA Astrophysics Data System (ADS)
Blavatska, Viktoria; Janke, Wolfhard
2014-01-01
We study the conformational properties of heteropolymers containing two types of monomers A and B, modeled as self-attracting self-avoiding random walks on a regular lattice. Such a model can describe in particular the sequences of hydrophobic and hydrophilic residues in proteins [K. F. Lau and K. A. Dill, Macromolecules 22, 3986 (1989)] and polyampholytes with oppositely charged groups [Y. Kantor and M. Kardar, Europhys. Lett. 28, 169 (1994)]. Treating the sequences of the two types of monomers as quenched random variables, we provide a systematic analysis of possible generalizations of this model. To this end we apply the pruned-enriched Rosenbluth chain-growth algorithm, which allows us to obtain the phase diagrams of extended and compact states coexistence as function of both the temperature and fraction of A and B monomers along the heteropolymer chain.
NASA Astrophysics Data System (ADS)
Simon, Damien
2011-03-01
The probability distribution of the current in the asymmetric simple exclusion process is expected to undergo a phase transition in the regime of weak asymmetry of the jumping rates. This transition was first predicted by Bodineau and Derrida using a linear stability analysis of the hydrodynamical limit of the process and further arguments have been given by Mallick and Prolhac. However it has been impossible so far to study what happens after the transition. The present paper presents an analysis of the large deviation function of the current on both sides of the transition from a Bethe Ansatz approach of the weak asymmetry regime of the exclusion process.
ERIC Educational Resources Information Center
Field, David; And Others
1992-01-01
Includes four articles: "Career Aspirations" (Field); "Making the Transition to a New Curriculum" (Baker, Householder); "How about a 'Work to School' Transition?" (Glasberg); and "Technological Improvisation: Bringing CNC to Woodworking" (Charles, McDuffie). (SK)
Predictive Aspects of a Stochastic Model for Citation Processes.
ERIC Educational Resources Information Center
Glanzel, W.; Schubert, A.
1995-01-01
A statistical model for citation processes is presented as a particular version of a nonhomogenous birth process. The mean value function and special transition probabilities, which can readily be calculated on the basis of known and estimated parameters, give essential information on the change of citation impact in time. (10 references) (KRN)
Geometry in transition: a model of emergent geometry.
Delgadillo-Blando, Rodrigo; O'Connor, Denjoe; Ydri, Badis
2008-05-23
We study a three matrix model with global SO(3) symmetry containing at most quartic powers of the matrices. We find an exotic line of discontinuous transitions with a jump in the entropy, characteristic of a 1st order transition, yet with divergent critical fluctuations and a divergent specific heat with critical exponent alpha=1/2. The low temperature phase is a geometrical one with gauge fields fluctuating on a round sphere. As the temperature increased the sphere evaporates in a transition to a pure matrix phase with no background geometrical structure. Both the geometry and gauge fields are determined dynamically. It is not difficult to invent higher dimensional models with essentially similar phenomenology. The model presents an appealing picture of a geometrical phase emerging as the system cools and suggests a scenario for the emergence of geometry in the early Universe.
A MATLAB GUI to study Ising model phase transition
NASA Astrophysics Data System (ADS)
Thornton, Curtislee; Datta, Trinanjan
We have created a MATLAB based graphical user interface (GUI) that simulates the single spin flip Metropolis Monte Carlo algorithm. The GUI has the capability to study temperature and external magnetic field dependence of magnetization, susceptibility, and equilibration behavior of the nearest-neighbor square lattice Ising model. Since the Ising model is a canonical system to study phase transition, the GUI can be used both for teaching and research purposes. The presence of a Monte Carlo code in a GUI format allows easy visualization of the simulation in real time and provides an attractive way to teach the concept of thermal phase transition and critical phenomena. We will also discuss the GUI implementation to study phase transition in a classical spin ice model on the pyrochlore lattice.
Quantum Phase Transition and Universal Dynamics in the Rabi Model.
Hwang, Myung-Joong; Puebla, Ricardo; Plenio, Martin B
2015-10-30
We consider the Rabi Hamiltonian, which exhibits a quantum phase transition (QPT) despite consisting only of a single-mode cavity field and a two-level atom. We prove QPT by deriving an exact solution in the limit where the atomic transition frequency in the unit of the cavity frequency tends to infinity. The effect of a finite transition frequency is studied by analytically calculating finite-frequency scaling exponents as well as performing a numerically exact diagonalization. Going beyond this equilibrium QPT setting, we prove that the dynamics under slow quenches in the vicinity of the critical point is universal; that is, the dynamics is completely characterized by critical exponents. Our analysis demonstrates that the Kibble-Zurek mechanism can precisely predict the universal scaling of residual energy for a model without spatial degrees of freedom. Moreover, we find that the onset of the universal dynamics can be observed even with a finite transition frequency.
Suggestion for a theoretical model for secondary-tertiary transition in mathematics
NASA Astrophysics Data System (ADS)
Clark, Megan; Lovric, Miroslav
2008-09-01
One of most notable features of existing body of research in transition seems to be the absence of a theoretical model. The suggestion we present in this paper—to view and understand the high school to university transition in mathematics as a modern-day rite of passage—is an attempt at defining such framework. Although dominantly reflecting North-American reality, we believe that the model could be found useful in other countries as well. Let us emphasize that our model is not new in the sense that it recognizes the transition as such. In this paper, we try to determine whether (and, if so, how) the notion of a rite of passage—which is a well-understood concept in anthropology, as well as in some other disciplines (e.g. culture shock in cultural studies)—can help us understand mathematics transition issues better. Can it help us systematize existing body of research, and enhance our understanding of transition in mathematics; does it point at something new? We believe so, and by elaborating some traditional aspects of rites of passage, we hope to provide a useful lens through which we can examine the process of transition in mathematics, and make suggestions for improved management of some transitional issues.
A Collaborative Process for Planning Transition Services for All Students with Disabilities.
ERIC Educational Resources Information Center
Aspel, Nellie; Bettis, Gail; Quinn, Pat; Test, David W.; Wood, Wendy M.
1999-01-01
Describes a multilevel interagency transition-planning process which includes three levels: a community-based team, school-level team, and individual-level team. Evaluation data are discussed that indicate consumer satisfaction with the Teaching All Students Skills for Employment and Life Transition planning process. Three case studies are used to…
Transition Process of Procedural to Conceptual Understanding in Solving Mathematical Problems
ERIC Educational Resources Information Center
Fatqurhohman
2016-01-01
This article aims to describe the transition process from procedural understanding to conceptual understanding in solving mathematical problems. Subjects in this study were three students from 20 fifth grade students of SDN 01 Sumberberas Banyuwangi selected based on the results of the students' answers. The transition process from procedural to…
45 CFR 155.150 - Transition process for existing State health insurance exchanges.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 45 Public Welfare 1 2014-10-01 2014-10-01 false Transition process for existing State health insurance exchanges. 155.150 Section 155.150 Public Welfare Department of Health and Human Services... Transition process for existing State health insurance exchanges. (a) Presumption. Unless an exchange...
45 CFR 155.150 - Transition process for existing State health insurance exchanges.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 45 Public Welfare 1 2013-10-01 2013-10-01 false Transition process for existing State health insurance exchanges. 155.150 Section 155.150 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES... Transition process for existing State health insurance exchanges. (a) Presumption. Unless an exchange...
45 CFR 155.150 - Transition process for existing State health insurance exchanges.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 45 Public Welfare 1 2012-10-01 2012-10-01 false Transition process for existing State health insurance exchanges. 155.150 Section 155.150 Public Welfare DEPARTMENT OF HEALTH AND HUMAN SERVICES... Transition process for existing State health insurance exchanges. (a) Presumption. Unless an exchange...
Renewal stochastic processes with correlated events: phase transitions along time evolution.
Velázquez, Jorge; Robledo, Alberto
2011-03-01
We consider renewal stochastic processes generated by nonindependent events from the perspective that their basic distribution and associated generating functions obey the statistical-mechanical structure of systems with interacting degrees of freedom. Based on this fact we look briefly into the less-known case of processes that display phase transitions along time. When the density distribution ψ{n}(t) for the occurrence of the nth event at time t is considered to be a partition function, of a "microcanonical" type for n "degrees of freedom" at fixed "energy" t, one obtains a set of four partition functions of which that for the generating function variable z and Laplace transform variable ε, conjugate to n and t, respectively, plays a central role. These partition functions relate to each other in the customary way and in accordance to the precepts of large deviations theory, while the entropy, or Massieu potential, derived from ψ{n}(t) satisfies an Euler relation. We illustrate this scheme first for an ordinary renewal process of events generated by a simple exponential waiting-time distribution ψ(t). Then we examine a process modeled after the so-called Hamiltonian mean-field model that is representative of agents that perform a repeated task with an associated outcome, such as an opinion poll. When a sequence of (many) events takes place in a sufficiently short time the process exhibits clustering of the outcome, but for larger times the process resembles that of independent events. The two regimes are separated by a sharp transition, technically of the second order. Finally we point out the existence of a similar scheme for random-walk processes.
From Music Student to Professional: The Process of Transition
ERIC Educational Resources Information Center
Creech, Andrea; Papageorgi, Ioulia; Duffy, Celia; Morton, Frances; Haddon, Elizabeth; Potter, John; de Bezenac, Christophe; Whyton, Tony; Himonides, Evangelos; Welch, Graham
2008-01-01
This article addresses the question of whether higher education music courses adequately prepare young musicians for the critical transition from music undergraduate to professional. Thematic analyses of interviews with 27 undergraduate and portfolio career musicians representing four musical genres were compared. The evidence suggests that the…
Transition to Community-Based Nursing Curriculum: Processes and Outcomes.
ERIC Educational Resources Information Center
Edwards, Joellen B.; Alley, Nancy M.
2002-01-01
The East Tennessee State University nursing school's transition to a community-based nursing curriculum was built on five key concepts: (1) relevance and accountability to health and social needs; (2) meeting of basic health needs through teaching and learning; (3) community experiences throughout the curriculum; (4) interdisciplinary…
Transition to Community-Based Nursing Curriculum: Processes and Outcomes.
ERIC Educational Resources Information Center
Edwards, Joellen B.; Alley, Nancy M.
2002-01-01
The East Tennessee State University nursing school's transition to a community-based nursing curriculum was built on five key concepts: (1) relevance and accountability to health and social needs; (2) meeting of basic health needs through teaching and learning; (3) community experiences throughout the curriculum; (4) interdisciplinary…
From Music Student to Professional: The Process of Transition
ERIC Educational Resources Information Center
Creech, Andrea; Papageorgi, Ioulia; Duffy, Celia; Morton, Frances; Haddon, Elizabeth; Potter, John; de Bezenac, Christophe; Whyton, Tony; Himonides, Evangelos; Welch, Graham
2008-01-01
This article addresses the question of whether higher education music courses adequately prepare young musicians for the critical transition from music undergraduate to professional. Thematic analyses of interviews with 27 undergraduate and portfolio career musicians representing four musical genres were compared. The evidence suggests that the…
Characterizing Phase Transitions in a Model of Neutral Evolutionary Dynamics
NASA Astrophysics Data System (ADS)
Scott, Adam; King, Dawn; Bahar, Sonya
2013-03-01
An evolutionary model was recently introduced for sympatric, phenotypic evolution over a variable fitness landscape with assortative mating (Dees & Bahar 2010). Organisms in the model are described by coordinates in a two-dimensional phenotype space, born at random coordinates with limited variation from their parents as determined by a mutation parameter, mutability. The model has been extended to include both neutral evolution and asexual reproduction in Scott et al (submitted). It has been demonstrated that a second order, non-equilibrium phase transition occurs for the temporal dynamics as the mutability is varied, for both the original model and for neutral conditions. This transition likely belongs to the directed percolation universality class. In contrast, the spatial dynamics of the model shows characteristics of an ordinary percolation phase transition. Here, we characterize the phase transitions exhibited by this model by determining critical exponents for the relaxation times, characteristic lengths, and cluster (species) mass distributions. Missouri Research Board; J.S. McDonnell Foundation
Laminar-turbulent transition on the flying wing model
NASA Astrophysics Data System (ADS)
Pavlenko, A. M.; Zanin, B. Yu.; Katasonov, M. M.
2016-10-01
Results of an experimental study of a subsonic flow past aircraft model having "flying wing" form and belonging to the category of small-unmanned aerial vehicles are reported. Quantitative data about the structure of the flow near the model surface were obtained by hot-wire measurements. It was shown, that with the wing sweep angle 34 °the laminar-turbulent transition scenario is identical to the one on a straight wing. The transition occurs through the development of a package of unstable oscillations in the boundary layer separation.
A Model for NASA-KSC's Privatization Transition
NASA Technical Reports Server (NTRS)
Lavelle, Jerome P.; Krumwiede, Dennis W.; Flowers, Jean
1996-01-01
This paper describes a model for government agencies that are considering privatization of all or part of their functions. Privatization encompasses the transitioning of government functions from government run to contractor run. The model developed in this paper is used to analyze the National Aeronautics and Space Administration's (NASA) decision to privatize space shuttle operations at the Kennedy Space Center (KSC). Several specific recommendations are given to KSC as they attempt to operationalize this privatization decision at the Center and to transition to a new relationship with their contractors.
Jamming percolation and glass transitions in lattice models.
Toninelli, Cristina; Biroli, Giulio; Fisher, Daniel S
2006-01-27
A new class of lattice gas models with trivial interactions but constrained dynamics is introduced. These models are proven to exhibit a dynamical glass transition: above a critical density rhoc ergodicity is broken due to the appearance of an infinite spanning cluster of jammed particles. The fraction of jammed particles is discontinuous at the transition, while in the unjammed phase dynamical correlation lengths and time scales diverge as exp[C(rhoc-rho)-mu]. Dynamic correlations display two-step relaxation similar to glass formers and jamming systems.
Neuroscientific model of motivational process.
Kim, Sung-Il
2013-01-01
Considering the neuroscientific findings on reward, learning, value, decision-making, and cognitive control, motivation can be parsed into three sub processes, a process of generating motivation, a process of maintaining motivation, and a process of regulating motivation. I propose a tentative neuroscientific model of motivational processes which consists of three distinct but continuous sub processes, namely reward-driven approach, value-based decision-making, and goal-directed control. Reward-driven approach is the process in which motivation is generated by reward anticipation and selective approach behaviors toward reward. This process recruits the ventral striatum (reward area) in which basic stimulus-action association is formed, and is classified as an automatic motivation to which relatively less attention is assigned. By contrast, value-based decision-making is the process of evaluating various outcomes of actions, learning through positive prediction error, and calculating the value continuously. The striatum and the orbitofrontal cortex (valuation area) play crucial roles in sustaining motivation. Lastly, the goal-directed control is the process of regulating motivation through cognitive control to achieve goals. This consciously controlled motivation is associated with higher-level cognitive functions such as planning, retaining the goal, monitoring the performance, and regulating action. The anterior cingulate cortex (attention area) and the dorsolateral prefrontal cortex (cognitive control area) are the main neural circuits related to regulation of motivation. These three sub processes interact with each other by sending reward prediction error signals through dopaminergic pathway from the striatum and to the prefrontal cortex. The neuroscientific model of motivational process suggests several educational implications with regard to the generation, maintenance, and regulation of motivation to learn in the learning environment.
Neuroscientific Model of Motivational Process
Kim, Sung-il
2013-01-01
Considering the neuroscientific findings on reward, learning, value, decision-making, and cognitive control, motivation can be parsed into three sub processes, a process of generating motivation, a process of maintaining motivation, and a process of regulating motivation. I propose a tentative neuroscientific model of motivational processes which consists of three distinct but continuous sub processes, namely reward-driven approach, value-based decision-making, and goal-directed control. Reward-driven approach is the process in which motivation is generated by reward anticipation and selective approach behaviors toward reward. This process recruits the ventral striatum (reward area) in which basic stimulus-action association is formed, and is classified as an automatic motivation to which relatively less attention is assigned. By contrast, value-based decision-making is the process of evaluating various outcomes of actions, learning through positive prediction error, and calculating the value continuously. The striatum and the orbitofrontal cortex (valuation area) play crucial roles in sustaining motivation. Lastly, the goal-directed control is the process of regulating motivation through cognitive control to achieve goals. This consciously controlled motivation is associated with higher-level cognitive functions such as planning, retaining the goal, monitoring the performance, and regulating action. The anterior cingulate cortex (attention area) and the dorsolateral prefrontal cortex (cognitive control area) are the main neural circuits related to regulation of motivation. These three sub processes interact with each other by sending reward prediction error signals through dopaminergic pathway from the striatum and to the prefrontal cortex. The neuroscientific model of motivational process suggests several educational implications with regard to the generation, maintenance, and regulation of motivation to learn in the learning environment. PMID:23459598
Modeling of acetone biofiltration process
Hsiu-Mu Tang; Shyh-Jye Hwang; Wen-Chuan Wang
1996-12-31
The objective of this research was to investigate the kinetic behavior of the biofiltration process for the removal of acetone 41 which was used as a model compound for highly water soluble gas pollutants. A mathematical model was developed by taking into account diffusion and biodegradation of acetone and oxygen in the biofilm, mass transfer resistance in the gas film, and flow pattern of the bulk gas phase. The simulated results obtained by the proposed model indicated that mass transfer resistance in the gas phase was negligible for this biofiltration process. Analysis of the relative importance of various rate steps indicated that the overall acetone removal process was primarily limited by the oxygen diffusion rate. 11 refs., 6 figs., 1 tab.
Modeling Production Plant Forming Processes
Rhee, M; Becker, R; Couch, R; Li, M
2004-09-22
Engineering has simulation tools and experience in modeling forming processes. Y-12 personnel have expressed interest in validating our tools and experience against their manufacturing process activities such as rolling, casting, and forging etc. We have demonstrated numerical capabilities in a collaborative DOE/OIT project with ALCOA that is nearing successful completion. The goal was to use ALE3D to model Alcoa's slab rolling process in order to demonstrate a computational tool that would allow Alcoa to define a rolling schedule that would minimize the probability of ingot fracture, thus reducing waste and energy consumption. It is intended to lead to long-term collaboration with Y-12 and perhaps involvement with other components of the weapons production complex. Using simulations to aid in design of forming processes can: decrease time to production; reduce forming trials and associated expenses; and guide development of products with greater uniformity and less scrap.
Mesoscopic Modeling of Reactive Transport Processes
NASA Astrophysics Data System (ADS)
Kang, Q.; Chen, L.; Deng, H.
2012-12-01
Reactive transport processes involving precipitation and/or dissolution are pervasive in geochemical, biological and engineered systems. Typical examples include self-assembled patterns such as Liesegang rings or bands, cones of stalactites in limestones caves, biofilm growth in aqueous environment, formation of mineral deposits in boilers and heat exchangers, uptake of toxic metal ions from polluted water by calcium carbonate, and mineral trapping of CO2. Compared to experimental studies, a numerical approach enables a systematic study of the reaction kinetics, mass transport, and mechanisms of nucleation and crystal growth, and hence provides a detailed description of reactive transport processes. In this study, we enhance a previously developed lattice Boltzmann pore-scale model by taking into account the nucleation process, and develop a mesoscopic approach to simulate reactive transport processes involving precipitation and/or dissolution of solid phases. The model is then used to simulate the formation of Liesegang precipitation patterns and investigate the effects of gel on the morphology of the precipitates. It is shown that this model can capture the porous structures of the precipitates and can account for the effects of the gel concentration and material. A wide range of precipitation patterns is predicted under different gel concentrations, including regular bands, treelike patterns, and for the first time with numerical models, transition patterns from regular bands to treelike patterns. The model is also applied to study the effect of secondary precipitate on the dissolution of primary mineral. Several types of dissolution and precipitation processes are identified based on the morphology and structures of the precipitates and on the extent to which the precipitates affect the dissolution of the primary mineral. Finally the model is applied to study the formation of pseudomorph. It is demonstrated for the first time by numerical simulation that a
Phase transition of p-adic Ising λ-model
Dogan, Mutlay; Akın, Hasan; Mukhamedov, Farrukh
2015-09-18
We consider an interaction of the nearest-neighbors and next nearest-neighbors for the mixed type p-adic λ-model with spin values (−1, +1) on a Cayley tree of order two. In the previous work we have proved the existence of the p-adic Gibbs measure for the model. In this work we have proved the existence of the phase transition occurs for the model.
Efficient collective influence maximization in cascading processes with first-order transitions.
Pei, Sen; Teng, Xian; Shaman, Jeffrey; Morone, Flaviano; Makse, Hernán A
2017-03-28
In many social and biological networks, the collective dynamics of the entire system can be shaped by a small set of influential units through a global cascading process, manifested by an abrupt first-order transition in dynamical behaviors. Despite its importance in applications, efficient identification of multiple influential spreaders in cascading processes still remains a challenging task for large-scale networks. Here we address this issue by exploring the collective influence in general threshold models of cascading process. Our analysis reveals that the importance of spreaders is fixed by the subcritical paths along which cascades propagate: the number of subcritical paths attached to each spreader determines its contribution to global cascades. The concept of subcritical path allows us to introduce a scalable algorithm for massively large-scale networks. Results in both synthetic random graphs and real networks show that the proposed method can achieve larger collective influence given the same number of seeds compared with other scalable heuristic approaches.
Efficient collective influence maximization in cascading processes with first-order transitions
NASA Astrophysics Data System (ADS)
Pei, Sen; Teng, Xian; Shaman, Jeffrey; Morone, Flaviano; Makse, Hernán A.
2017-03-01
In many social and biological networks, the collective dynamics of the entire system can be shaped by a small set of influential units through a global cascading process, manifested by an abrupt first-order transition in dynamical behaviors. Despite its importance in applications, efficient identification of multiple influential spreaders in cascading processes still remains a challenging task for large-scale networks. Here we address this issue by exploring the collective influence in general threshold models of cascading process. Our analysis reveals that the importance of spreaders is fixed by the subcritical paths along which cascades propagate: the number of subcritical paths attached to each spreader determines its contribution to global cascades. The concept of subcritical path allows us to introduce a scalable algorithm for massively large-scale networks. Results in both synthetic random graphs and real networks show that the proposed method can achieve larger collective influence given the same number of seeds compared with other scalable heuristic approaches.
Sample-dependent phase transitions in disordered exclusion models
NASA Astrophysics Data System (ADS)
Enaud, C.; Derrida, B.
2004-04-01
We give numerical evidence that the location of the first-order phase transition between the low- and the high-density phases of the one-dimensional asymmetric simple exclusion process with open boundaries becomes sample dependent when quenched disorder is introduced for the hopping rates.
Augmented Transition Networks as Psychological Models of Sentence Comprehension.
ERIC Educational Resources Information Center
Kaplan, Ronald M.
This paper describes the notation and underlying organization of an augmented, recursive-transition network grammar and illustrates how such a grammar is a natural medium for expressing and explaining a wide variety of facts about the psychological processes of sentence comprehension. A general discussion of transformational grammar and…
Reversibility in Quantum Models of Stochastic Processes
NASA Astrophysics Data System (ADS)
Gier, David; Crutchfield, James; Mahoney, John; James, Ryan
Natural phenomena such as time series of neural firing, orientation of layers in crystal stacking and successive measurements in spin-systems are inherently probabilistic. The provably minimal classical models of such stochastic processes are ɛ-machines, which consist of internal states, transition probabilities between states and output values. The topological properties of the ɛ-machine for a given process characterize the structure, memory and patterns of that process. However ɛ-machines are often not ideal because their statistical complexity (Cμ) is demonstrably greater than the excess entropy (E) of the processes they represent. Quantum models (q-machines) of the same processes can do better in that their statistical complexity (Cq) obeys the relation Cμ >= Cq >= E. q-machines can be constructed to consider longer lengths of strings, resulting in greater compression. With code-words of sufficiently long length, the statistical complexity becomes time-symmetric - a feature apparently novel to this quantum representation. This result has ramifications for compression of classical information in quantum computing and quantum communication technology.
Skin Friction and Transition Location Measurement on Supersonic Transport Models
NASA Technical Reports Server (NTRS)
Kennelly, Robert A., Jr.; Goodsell, Aga M.; Olsen, Lawrence E. (Technical Monitor)
2000-01-01
Flow visualization techniques were used to obtain both qualitative and quantitative skin friction and transition location data in wind tunnel tests performed on two supersonic transport models at Mach 2.40. Oil-film interferometry was useful for verifying boundary layer transition, but careful monitoring of model surface temperatures and systematic examination of the effects of tunnel start-up and shutdown transients will be required to achieve high levels of accuracy for skin friction measurements. A more common technique, use of a subliming solid to reveal transition location, was employed to correct drag measurements to a standard condition of all-turbulent flow on the wing. These corrected data were then analyzed to determine the additional correction required to account for the effect of the boundary layer trip devices.
Thermal phase transition in a QCD-like holographic model
Evans, Nick; Threlfall, Ed
2008-11-15
We investigate the high-temperature phase of a dilaton flow deformation of the anti-de Sitter/conformal field theory correspondence. We argue that these geometries should be interpreted as the N=4 gauge theory perturbed by a SO(6) invariant scalar mass and that the high-temperature phase is just the well-known anti-de Sitter-Schwarzschild solution. We compute, within supergravity, the resulting Hawking-Page phase transition, which in this model can be interpreted as a deconfining transition in which the vacuum expectation value for the operator TrF{sup 2} dissolves. In the presence of quarks the model also displays a simultaneous chiral symmetry restoring transition with the Goldstone mode and other quark bound states dissolving into the thermal bath.
Turbulence and transition modeling for high-speed flows
NASA Technical Reports Server (NTRS)
Wilcox, David C.
1993-01-01
Research conducted during the past three and a half years aimed at developing and testing a turbulence/transition model applicable to high-speed turbulent flows is summarized. The first two years of the project focused on fully turbulent flows, while emphasis shifted to boundary-layer development in the transition region during the final year and a half. A brief summary of research accomplished during the first three years is included and publications that describe research results in greater detail are cited. Research conducted during the final six months of the period of performance is summarized. The primary results of the last six months of the project are elimination of the k-omega model's sensitivity to the freestream value of omega and development of a method for triggering transition at a specified location, independent of the freestream turbulence level.
Transition to 12-hour shifts - The process and the product
Suter, P. )
1992-01-01
This paper examines Yankee Atomic Electric Company's (YAEC's) transition to a 12-h shift schedule for the operations department staff. It presents the approach to implementation, reactions of both shift workers and management to the new schedule (including perceived benefits and shortcomings), and provides recommendations to others considering this change. Experience demonstrates the ease of any transition when the desire for change originates with the individuals directly affected. Close cooperation with any union representation is also vital to its success. When all parties are in apparent agreement (e.g., that a 12-h rotation should commence), this allows for a trial period (in this case of at least two shift cycles) in order to evaluate and refine the program, thus leaving the option open to revert back to the previous condition if things prove unsatisfactory. At all costs, mutual respect must be maintained for all parties.
Analytical expressions for transition edge sensor excess noise models
NASA Astrophysics Data System (ADS)
Brandt, Daniel; Fraser, George W.
2010-08-01
Transition edge sensors (TESs) are high-sensitivity thermometers used in cryogenic microcalorimeters which exploit the steep gradient in resistivity with temperature during the superconducting phase transition. Practical TES devices tend to exhibit a white noise of uncertain origin, arising inside the device. We discuss two candidate models for this excess noise, phase slip shot noise (PSSN) and percolation noise. We extend the existing PSSN model to include a magnetic field dependence and derive a basic analytical model for percolation noise. We compare the predicted functional forms of the noise current vs. resistivity curves of both models with experimental data and provide a set of equations for both models to facilitate future experimental efforts to clearly identify the source of excess noise.
Investigation of Plasma Processes in Electronic Transition Lasers.
1980-11-01
essential features of electron-beau controlled dis- charges of the type coumon to rare gas halide and mercury- halide lasers. Particular attention is...ELECTRON-BEAM CONTROLLED DISCHARGES A. Application to Electronic Transition Lasers III. RARE GAS- HALIDE AND MERCURY- HALIDE LASERS I A. XeCl(B X) Laser...Dist Special I I iii I oI. INTRODUCTION Electrically excited rare gas- halide lasers and their closely related I] mercury- halide counterparts are
A Process for Transitioning to Object-Oriented Technology.
1995-08-01
A-1 vii EXECUTIVE SUMMARY The use of object-oriented technology (OOT) to develop software is becoming...for future potential projects, and the risks inherent in evaluating any new technology are isolated. The primary audience for this document is software ...Transition to Enterprise-Based Use (A44) ES-2 1. INTRODUCTION 0 1.1 PURPOSE The use of object-oriented technology (OOT) in software development has become
NASA Astrophysics Data System (ADS)
Tetzlaff, D.; Soulsby, C.; Hrachowitz, M.; Speed, M.
2009-04-01
In recent years, transit times (TTs) have been increasingly explored as a process-based tools for conceptualising hydrological processes in an integrated manner at a range of scales. Traditionally the identification of the appropriate transit time distribution (TTD) for a hydrological system (e.g. hillslope or catchment), and the derivation of metrics such as the mean transit time (MTT) have required quantitative assessment of input-output relationships for conservative tracers using lumped parameter models. Such work has allowed the main landscape controls on TTs to be identified and facilitated the prediction of MTT in ungauged basins in particular geomorphic provinces. This has shown TT to be a useful diagnostic index of similarity that can be valuable in process-based catchment classification. In this contribution, we used well-constrained MTT estimates (with uncertainty) from 32 experimental catchments (1 to 250km2 in area) with contrasting geologic, topographic, pedologic and climatic characteristics in Scotland. The MTT was highly variable ranging from 30 days to ca. 1200 days for individual catchments. Moreover, MTT was also found to be closely correlated with key hydrometric design statistics such as the Q95, Q5, Mean Annual Flood (MAF) and the slope of the hydrograph recession curve. Analysis of the TT estimates, in conjunction with GIS-based quantitative assessment of key landscape controls, showed that MTT could be predicted to within 25% for ungauged basins from catchment soil cover, drainage density and topographic wetness index. For ungauged basins it was found that the hydrometric design statistics (Q95, Q5, MAF and the recession slope) could be more simply and accurately forecasted from MTT predictions than a single set of catchment characteristics. We demonstrate that TTs - predicted from mapped landscape characteristics - are useful integrating diagnostic metrics for regional classification, prediction and process assessment in ungauged montane
Stochastic transitions between neural states in taste processing and decision-making.
Miller, Paul; Katz, Donald B
2010-02-17
Noise, which is ubiquitous in the nervous system, causes trial-to-trial variability in the neural responses to stimuli. This neural variability is in turn a likely source of behavioral variability. Using Hidden Markov modeling, a method of analysis that can make use of such trial-to-trial response variability, we have uncovered sequences of discrete states of neural activity in gustatory cortex during taste processing. Here, we advance our understanding of these patterns in two ways. First, we reproduce the experimental findings in a formal model, describing a network that evinces sharp transitions between discrete states that are deterministically stable given sufficient noise in the network; as in the empirical data, the transitions occur at variable times across trials, but the stimulus-specific sequence is itself reliable. Second, we demonstrate that such noise-induced transitions between discrete states can be computationally advantageous in a reduced, decision-making network. The reduced network produces binary outputs, which represent classification of ingested substances as palatable or nonpalatable, and the corresponding behavioral responses of "spit" or "swallow". We evaluate the performance of the network by measuring how reliably its outputs follow small biases in the strengths of its inputs. We compare two modes of operation: deterministic integration ("ramping") versus stochastic decision-making ("jumping"), the latter of which relies on state-to-state transitions. We find that the stochastic mode of operation can be optimal under typical levels of internal noise and that, within this mode, addition of random noise to each input can improve optimal performance when decisions must be made in limited time.
A Model for Assessing the Extent of Transition to Technology Education.
ERIC Educational Resources Information Center
Dyrenfurth, Michael J.; And Others
1993-01-01
Implementation of the Illinois Plan for Industrial Technology Education was assessed through interviews with 117 teachers. The assessment model (based on Stufflebeam's Context, Input, Process, Product) blended qualitative and quantitative information. Six key dimensions of change were identified, and the Transition Assessment Inventory proved…
Modeling the impact of roadway emissions in light wind, stable and transition conditions
This paper examines the processes that govern air pollution dispersion under light wind, stable and transition conditions by using a state-of-the-art dispersion model to interpret measurements from a tracer experiment conducted next to US highway 99 in Sacramento in 1981–1982 dur...
Modeling the impact of roadway emissions in light wind, stable and transition conditions
This paper examines the processes that govern air pollution dispersion under light wind, stable and transition conditions by using a state-of-the-art dispersion model to interpret measurements from a tracer experiment conducted next to US highway 99 in Sacramento in 1981–1982 dur...
Planning: The Participatory Process Model.
ERIC Educational Resources Information Center
McDowell, Elizabeth V.
The participatory planning process model developed by Peirce Junior College is described in this paper. First, the rationale for shifting from a traditional authoritarian style of institutional leadership to a participatory style which encourages a broader concern for the institution and lessens morale problems is offered. The development of a new…
Spatially-explicit representation of state-and-transition models
USDA-ARS?s Scientific Manuscript database
The broad-scale assessment of natural resource conditions (e.g., rangeland health, restoration needs) requires knowledge of their spatial distribution. We argue that creating a database that links state-and-transition models (STMs) to spatial units is a valuable management tool for structuring groun...
Practical guidance for developing state-and-transition models
USDA-ARS?s Scientific Manuscript database
State-and-transition models (STMs) are synthetic descriptions of the dynamics of vegetation and surface soils occurring within specific ecological sites. STMs consist of a diagram and narratives that describe the dynamics and its causes. STMs are developed using a broad array of evidence including h...
Modeling Pedagogy for Teachers Transitioning to the Virtual Classroom
ERIC Educational Resources Information Center
Canuel, Michael J.; White, Beverley J.
2014-01-01
This study is a review of the creation and evolution of a professional development program modeled on social constructivist principles and designed for online educators in a virtual high school who transitioned from the conventional classroom to the virtual educational environment. The narrative inquiry focuses on the critical events within the…
Layering and wetting transitions for an interface model
NASA Astrophysics Data System (ADS)
Solé, Salvador Miracle
2011-03-01
We study the solid-on-solid interface model above a horizontal wall in three dimensional space, with an attractive interaction when the interface is in contact with the wall, at low temperatures. The system presents a sequence of layering transitions, whose levels increase with the temperature, before the complete wetting above a certain value of this quantity.
Assessment of One- and Two-Equation Turbulence Models for Hypersonic Transitional Flows
ROY,CHRISTOPHER J.; BLOTTNER,FREDERICK G.
2000-01-14
Many Navier-Stokes codes require that the governing equations be written in conservation form with a source term. The Spalart-Allmaras one-equation model was originally developed in substantial derivative form and when rewritten in conservation form, a density gradient term appears in the source term. This density gradient term causes numerical problems and has a small influence on the numerical predictions. Further work has been performed to understand and to justify the neglect of this term. The transition trip term has been included in the one-equation eddy viscosity model of Spalart-Allmaras. Several problems with this model have been discovered when applied to high-speed flows. For the Mach 8 flat plate boundary layer flow with the standard transition method, the Baldwin-Barth and both k-{omega} models gave transition at the specified location. The Spalart-Allmaras and low Reynolds number k-{var_epsilon} models required an increase in the freestream turbulence levels in order to give transition at the desired location. All models predicted the correct skin friction levels in both the laminar and turbulent flow regions. For Mach 8 flat plate case, the transition location could not be controlled with the trip terms as given in the Spalart-Allmaras model. Several other approaches have been investigated to allow the specification of the transition location. The approach that appears most appropriate is to vary the coefficient that multiplies the turbulent production term in the governing partial differential equation for the eddy viscosity (Method 2). When this coefficient is zero, the flow remains laminar. The coefficient is increased to its normal value over a specified distance to crudely model the transition region and obtain fully turbulent flow. While this approach provides a reasonable interim solution, a separate effort should be initiated to address the proper transition procedure associated with the turbulent production term. Also, the transition process
THE HANLE EFFECT OF Ly{alpha} IN A MAGNETOHYDRODYNAMIC MODEL OF THE SOLAR TRANSITION REGION
Stepan, J.; Trujillo Bueno, J.; Carlsson, M.; Leenaarts, J.
2012-10-20
In order to understand the heating of the solar corona it is crucial to obtain empirical information on the magnetic field in its lower boundary (the transition region). To this end, we need to measure and model the linear polarization produced by scattering processes in strong UV lines, such as the hydrogen Ly{alpha} line. The interpretation of the observed Stokes profiles will require taking into account that the outer solar atmosphere is highly structured and dynamic, and that the height of the transition region may well vary from one place in the atmosphere to another. Here, we report on the Ly{alpha} scattering polarization signals we have calculated in a realistic model of an enhanced network region, resulting from a state-of-the-art radiation magnetohydrodynamic simulation. This model is characterized by spatially complex variations of the physical quantities at transition region heights. The results of our investigation lead us to emphasize that scattering processes in the upper solar chromosphere should indeed produce measurable linear polarization in Ly{alpha}. More importantly, we show that via the Hanle effect the model's magnetic field produces significant changes in the emergent Q/I and U/I profiles. Therefore, we argue that by measuring the polarization signals produced by scattering processes and the Hanle effect in Ly{alpha} and contrasting them with those computed in increasingly realistic atmospheric models, we should be able to decipher the magnetic, thermal, and dynamic structure of the upper chromosphere and transition region of the Sun.
Thermoplastic matrix composite processing model
NASA Technical Reports Server (NTRS)
Dara, P. H.; Loos, A. C.
1985-01-01
The effects the processing parameters pressure, temperature, and time have on the quality of continuous graphite fiber reinforced thermoplastic matrix composites were quantitatively accessed by defining the extent to which intimate contact and bond formation has occurred at successive ply interfaces. Two models are presented predicting the extents to which the ply interfaces have achieved intimate contact and cohesive strength. The models are based on experimental observation of compression molded laminates and neat resin conditions, respectively. Identified as the mechanism explaining the phenomenon by which the plies bond to themselves is the theory of autohesion (or self diffusion). Theoretical predictions from the Reptation Theory between autohesive strength and contact time are used to explain the effects of the processing parameters on the observed experimental strengths. The application of a time-temperature relationship for autohesive strength predictions is evaluated. A viscoelastic compression molding model of a tow was developed to explain the phenomenon by which the prepreg ply interfaces develop intimate contact.
Biogeochemical processes in model estuaries
NASA Astrophysics Data System (ADS)
Church, Thomas M.
Sixty researchers met to evaluate the effects of global change on estuaries and to improve estuarine modeling at the Second International Symposium on the Biogeochemistry of Model Estuaries, held April 15-19, 1991, at Jekyll Island, Ga. The importance of successful sampling in evaluating chemical fluxes and establishing records of estuarine change was articulated, as was the need for tracer tools for improved modeling. The symposium was sponsored by the National Science Foundation, National Oceanic and Atmospheric Administration, and the Department of Energy.Participants discussed particles and sedimentology, trace elements and metals, organic chemistry, and nutrient cycling of estuarine processes. Four days of presentations were followed by a half-day of discussion on advances in these topics and the overall goal of assessing estuarine processes in global change. What follows is a synopsis of this discussion.
Random fields and phase transitions in model magnetic systems
NASA Astrophysics Data System (ADS)
Birgeneau, R. J.
1998-01-01
Random fields occur in a wide variety of physical systems varying from type II superconductors to two-component fluids in a random medium. However, only in model magnetic systems have systematic studies as a function of both temperature and random-field strength been possible. In this article we review recent neutron and magnetic X-ray scattering studies of the magnetic ordering processes in the antiferromagnets Mn 0.75Zn 0.25F 2, Fe 0.5Zn 0.5F 2 and Fe 0.75Co 0.25TiO 3 in an applied magnetic field. These systems should all represent realizations of the three-dimensional random-field Ising model which is the simplest version of the random-field problem in models with discrete symmetry. In all cases on field cooling (FC) the systems evolve continuously from a high-temperature paramagnetic state to a low-temperature antiferromagnetic domain state. However, on cooling to low temperatures in zero field and then applying a field (ZFC) long-range order (LRO) is obtained. On subsequent heating in the three systems the LRO vanishes continuously with a rounded power-law behavior which has been labelled trompe l'oeil critical behavior. The width of the transition region scales as H2. Reconsideration of indirect ZFC specific-heat measurements shows that the observed peaks, previously attributed to equilibrium critical fluctuations, instead arise entirely from a LRO contribution, scaling like dM s2/dT , to the measured quantity. Here Ms is the staggered magnetization. These results thus reconcile scattering and bulk property measurements of random-field Ising systems.
Noise-induced transition in excitable neuron models.
Tanabe, S; Pakdaman, K
2001-10-01
We studied the influence of noisy stimulation on the Hodgkin-Huxley neuron model. Rather than examining the noise-related variability of the discharge times of the model--as has been done previously--our study focused on the effect of noise on the stationary distributions of the membrane potential and gating variables of the model. We observed that a gradual increase in the noise intensity did not result in a gradual change of the distributions. Instead, we could identify a critical intermediate noise range in which the shapes of the distributions underwent a drastic qualitative change. Namely, they moved from narrow unimodal Gaussian-like shapes associated with low noise intensities to ones that spread widely at large noise intensities. In particular, for the membrane potential and the sodium activation variable, the distributions changed from unimodal to bimodal. Thus, our investigation revealed a noise-induced transition in the Hodgkin-Huxley model. In order to further characterize this phenomenon, we considered a reduced one-dimensional model of an excitable system, namely the active rotator. For this model, our analysis indicated that the noise-induced transition is associated with a deterministic bifurcation of approximate equations governing the dynamics of the mean and variance of the state variable. Finally, we shed light on the possible functional importance of this noise-induced transition in neuronal coding by determining its effect on the spike timing precision in models of neuronal ensembles.
Apparent Transition Behavior of Widely-Used Turbulence Models
NASA Technical Reports Server (NTRS)
Rumsey, Christopher L.
2006-01-01
The Spalart-Allmaras and the Menter SST kappa-omega turbulence models are shown to have the undesirable characteristic that, for fully turbulent computations, a transition region can occur whose extent varies with grid density. Extremely fine two-dimensional grids over the front portion of an airfoil are used to demonstrate the effect. As the grid density is increased, the laminar region near the nose becomes larger. In the Spalart-Allmaras model this behavior is due to convergence to a laminar-behavior fixed point that occurs in practice when freestream turbulence is below some threshold. It is the result of a feature purposefully added to the original model in conjunction with a special trip function. This degenerate fixed point can also cause nonuniqueness regarding where transition initiates on a given grid. Consistent fully turbulent results can easily be achieved by either using a higher freestream turbulence level or by making a simple change to one of the model constants. Two-equation kappa-omega models, including the SST model, exhibit strong sensitivity to numerical resolution near the area where turbulence initiates. Thus, inconsistent apparent transition behavior with grid refinement in this case does not appear to stem from the presence of a degenerate fixed point. Rather, it is a fundamental property of the kappa-omega model itself, and is not easily remedied.
Apparent Transition Behavior of Widely-Used Turbulence Models
NASA Technical Reports Server (NTRS)
Rumsey, Christopher L.
2007-01-01
The Spalart-Allmaras and the Menter SST k-omega turbulence models are shown to have the undesirable characteristic that, for fully turbulent computations, a transition region can occur whose extent varies with grid density. Extremely fine two-dimensional grids over the front portion of an airfoil are used to demonstrate the effect. As the grid density is increased, the laminar region near the nose becomes larger. In the Spalart-Allmaras model this behavior is due to convergence to a laminar-behavior fixed point that occurs in practice when freestream turbulence is below some threshold. It is the result of a feature purposefully added to the original model in conjunction with a special trip function. This degenerate fixed point can also cause non-uniqueness regarding where transition initiates on a given grid. Consistent fully turbulent results can easily be achieved by either using a higher freestream turbulence level or by making a simple change to one of the model constants. Two-equation k-omega models, including the SST model, exhibit strong sensitivity to numerical resolution near the area where turbulence initiates. Thus, inconsistent apparent transition behavior with grid refinement in this case does not appear to stem from the presence of a degenerate fixed point. Rather, it is a fundamental property of the k-omega model itself, and is not easily remedied.
Phase transitions and relaxation dynamics of Ising models exchanging particles
NASA Astrophysics Data System (ADS)
Goh, Segun; Fortin, Jean-Yves; Choi, M. Y.
2017-01-01
A variety of systems in nature and in society are open and subject to exchanging their constituents with other systems (e.g., environments). For instance, in biological systems, cells collect necessary energy and material by exchange of molecules or ions. Similarly, countries, cities or research institutes evolve as their constituents move in or out. To probe the corresponding particle exchange dynamics in such systems, we consider two Ising models exchanging particles and establish a master equation describing the equilibrium phases as well as the non-equilibrium dynamics of the system. It is found that an additional stable phase emerges as a consequence of the particle exchange process. Furthermore, we formulate the Ginzburg-Landau theory which allows to probe correlation effects. Accordingly, critical slowing down is manifested and the associated dynamic exponent is computed in the linear relaxation regime. In particular, this approach is relevant for investigating the grand canonical description of the system plus environment, with particle exchange and state transitions taken into account explicitly.
Welding process modelling and control
NASA Technical Reports Server (NTRS)
Romine, Peter L.; Adenwala, Jinen A.
1993-01-01
The research and analysis performed, and software developed, and hardware/software recommendations made during 1992 in development of the PC-based data acquisition system for support of Welding Process Modeling and Control is reported. A need was identified by the Metals Processing Branch of NASA Marshall Space Flight Center, for a mobile data aquisition and analysis system, customized for welding measurement and calibration. Several hardware configurations were evaluated and a PC-based system was chosen. The Welding Measurement System (WMS) is a dedicated instrument, strictly for the use of data aquisition and analysis. Although the WMS supports many of the functions associated with the process control, it is not the intention for this system to be used for welding process control.
Dynamical Phase Transition in a Model for Evolution with Migration
NASA Astrophysics Data System (ADS)
Waclaw, Bartłomiej; Allen, Rosalind J.; Evans, Martin R.
2010-12-01
We study a simple quasispecies model for evolution in two different habitats, with different fitness landscapes, coupled through one-way migration. Our key finding is a dynamical phase transition at a critical value of the migration rate, at which the time to reach the steady state diverges. The genetic composition of the population is qualitatively different above and below the transition. Using results from localization theory, we show that the critical migration rate may be very small—demonstrating that evolutionary outcomes can be very sensitive to even a small amount of migration.
Structural transitions in model beta-sheet tapes.
Bellesia, Giovanni; Fedorov, Maxim V; Timoshenko, Edward G
2008-05-21
We present a molecular-scale simulation study of the structural transitions between helicoidal, helical, and tubular geometries in supramolecular beta-sheet tapes. Such geometries have been observed in different self-assembled amyloid systems (based on either natural or synthetic peptides) for which the beta-sheet tapes represent the simplest fibrillar aggregates. A coarse-grained model for the beta-sheet tapes is proposed, with chiral degrees of freedom and asymmetrical chemical properties, which provides a quantitative characterization of the structural transitions. A quantitative connection is established between the molecular properties and the elastic parameters of the supramolecular tapes.
Kim, Kye-Seong; Foster, James A.; Kvasnicka, Kevin W.; Gerton, George L.
2011-01-01
In this study, we adapted a FluoSphere bead-binding assay to study the exposure and release of guinea pig sperm acrosomal components during the course of capacitation and acrosomal exocytosis. Prior to capacitation or the initiation of exocytosis, acrosomal proteins were not accessible to FluoSpheres coated with antibodies against two acrosomal matrix (AM) proteins, AM67 and AM50; during the course of capacitation and ionophore-induced acrosomal exocytosis, however, we detected the transient exposure of the solid-phase AM proteins on the surface of guinea pig sperm using the antibody-coated fluorescent beads. Several different transitional stages leading to complete acrosomal exocytosis were classified, and we propose these represent true, functional intermediates since some of the AM proteins are orthologues of mouse proteins that bind the zona pellucida of unfertilized eggs. In addition, we present evidence that implicates acrosin in the proteolytic processing of AM50 during AM disassembly. Thus, we propose that the transitional states of acrosomal exocytosis involve early binding of AM proteins to the zona pellucida (by what visually appear to be “acrosome-intact” sperm), maintenance of zona pellucida binding that coincides with the progressive exposure of AM proteins, and gradual proteolytic disassembly of the AM to allow sperm movement through the zona pellucida. We feel this “transitional states” model provides a more refined view of acrosomal function that supports a move away from the widely-held, overly simplistic, and binary “acrosome-reaction” model, and embraces a more dynamic view of acrosomal exocytosis that involves intermediate stages of the secretory process in zona pellucida binding and penetration. PMID:21919109
Kim, Kye-Seong; Foster, James A; Kvasnicka, Kevin W; Gerton, George L
2011-12-01
In this study, we adapted a FluoSphere bead-binding assay to study the exposure and release of guinea pig sperm acrosomal components during the course of capacitation and acrosomal exocytosis. Prior to capacitation or the initiation of exocytosis, acrosomal proteins were not accessible to FluoSpheres coated with antibodies against two acrosomal matrix (AM) proteins, AM67 and AM50; during the course of capacitation and ionophore-induced acrosomal exocytosis, however, we detected the transient exposure of the solid-phase AM proteins on the surface of guinea pig sperm using the antibody-coated fluorescent beads. Several different transitional stages leading to complete acrosomal exocytosis were classified, and we propose these represent true, functional intermediates since some of the AM proteins are orthologues of mouse proteins that bind the zona pellucida (ZP) of unfertilized eggs. In addition, we present evidence that implicates acrosin in the proteolytic processing of AM50 during AM disassembly. Thus, we propose that the transitional states of acrosomal exocytosis involve early binding of AM proteins to the ZP (by what visually appear to be "acrosome-intact" sperm), maintenance of ZP binding that coincides with the progressive exposure of AM proteins, and gradual proteolytic disassembly of the AM to allow sperm movement through the ZP. We feel this "transitional states" model provides a more refined view of acrosomal function that supports a move away from the widely held, overly simplistic, and binary "acrosome-reaction" model, and embraces a more dynamic view of acrosomal exocytosis that involves intermediate stages of the secretory process in ZP binding and penetration.
ERIC Educational Resources Information Center
Thompson, Sandy, Ed.; And Others
1990-01-01
This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition…
Johnson, Julie K; Farnan, Jeanne M; Barach, Paul; Hesselink, Gijs; Wollersheim, Hub; Pijnenborg, Loes; Kalkman, Cor; Arora, Vineet M
2012-12-01
Safe patient transitions depend on effective communication and a functioning care coordination process. Evidence suggests that primary care physicians are not satisfied with communication at transition points between inpatient and ambulatory care, and that communication often is not provided in a timely manner, omits essential information, or contains ambiguities that put patients at risk. Our aim was to demonstrate how process mapping can illustrate current handover practices between ambulatory and inpatient care settings, identify existing barriers and facilitators to effective transitions of care, and highlight potential areas for quality improvement. We conducted focus group interviews to facilitate a process mapping exercise with clinical teams in six academic health centres in the USA, Poland, Sweden, Italy, Spain and the Netherlands. At a high level, the process of patient admission to the hospital through the emergency department, inpatient care, and discharge back in the community were comparable across sites. In addition, the process maps highlighted similar barriers to providing information to primary care physicians, inaccurate or incomplete information on referral and discharge, a lack of time and priority to collaborate with counterpart colleagues, and a lack of feedback to clinicians involved in the handovers. Process mapping is effective in bringing together key stakeholders and makes explicit the mental models that frame their understanding of the clinical process. Exploring the barriers and facilitators to safe and reliable patient transitions highlights opportunities for further improvement work and illustrates ideas for best practices that might be transferrable to other settings.
Estimating transition probabilities among everglades wetland communities using multistate models
Hotaling, A.S.; Martin, J.; Kitchens, W.M.
2009-01-01
In this study we were able to provide the first estimates of transition probabilities of wet prairie and slough vegetative communities in Water Conservation Area 3A (WCA3A) of the Florida Everglades and to identify the hydrologic variables that determine these transitions. These estimates can be used in management models aimed at restoring proportions of wet prairie and slough habitats to historical levels in the Everglades. To determine what was driving the transitions between wet prairie and slough communities we evaluated three hypotheses: seasonality, impoundment, and wet and dry year cycles using likelihood-based multistate models to determine the main driver of wet prairie conversion in WCA3A. The most parsimonious model included the effect of wet and dry year cycles on vegetative community conversions. Several ecologists have noted wet prairie conversion in southern WCA3A but these are the first estimates of transition probabilities among these community types. In addition, to being useful for management of the Everglades we believe that our framework can be used to address management questions in other ecosystems. ?? 2009 The Society of Wetland Scientists.
Development of a One-Equation Transition/Turbulence Model
EDWARDS,JACK R.; ROY,CHRISTOPHER J.; BLOTTNER,FREDERICK G.; HASSAN,HASSAN A.
2000-09-26
This paper reports on the development of a unified one-equation model for the prediction of transitional and turbulent flows. An eddy viscosity - transport equation for non-turbulent fluctuation growth based on that proposed by Warren and Hassan (Journal of Aircraft, Vol. 35, No. 5) is combined with the Spalart-Allmaras one-equation model for turbulent fluctuation growth. Blending of the two equations is accomplished through a multidimensional intermittence function based on the work of Dhawan and Narasimha (Journal of Fluid Mechanics, Vol. 3, No. 4). The model predicts both the onset and extent of transition. Low-speed test cases include transitional flow over a flat plate, a single element airfoil, and a multi-element airfoil in landing configuration. High-speed test cases include transitional Mach 3.5 flow over a 5{degree} cone and Mach 6 flow over a flared-cone configuration. Results are compared with experimental data, and the spatial accuracy of selected predictions is analyzed.
Phase transition and surface sublimation of a mobile Potts model.
Bailly-Reyre, A; Diep, H T; Kaufman, M
2015-10-01
We study in this paper the phase transition in a mobile Potts model by the use of Monte Carlo simulation. The mobile Potts model is related to a diluted Potts model, which is also studied here by a mean-field approximation. We consider a lattice where each site is either vacant or occupied by a q-state Potts spin. The Potts spin can move from one site to a nearby vacant site. In order to study the surface sublimation, we consider a system of Potts spins contained in a recipient with a concentration c defined as the ratio of the number of Potts spins N(s) to the total number of lattice sites N(L)=N(x)×N(y)×N(z). Taking into account the attractive interaction between the nearest-neighboring Potts spins, we study the phase transitions as functions of various physical parameters such as the temperature, the shape of the recipient, and the spin concentration. We show that as the temperature increases, surface spins are detached from the solid phase to form a gas in the empty space. Surface order parameters indicate different behaviors depending on the distance to the surface. At high temperatures, if the concentration is high enough, the interior spins undergo a first-order phase transition to an orientationally disordered phase. The mean-field results are shown as functions of temperature, pressure, and chemical potential, which confirm in particular the first-order character of the transition.
Phase Transition Behavior in a Neutral Evolution Model
NASA Astrophysics Data System (ADS)
King, Dawn; Scott, Adam; Maric, Nevena; Bahar, Sonya
2014-03-01
The complexity of interactions among individuals and between individuals and the environment make agent based modeling ideal for studying emergent speciation. This is a dynamically complex problem that can be characterized via the critical behavior of a continuous phase transition. Concomitant with the main tenets of natural selection, we allow organisms to reproduce, mutate, and die within a neutral phenotype space. Previous work has shown phase transition behavior in an assortative mating model with variable fitness landscapes as the maximum mutation size (μ) was varied (Dees and Bahar, 2010). Similarly, this behavior was recently presented in the work of Scott et al. (2013), even on a completely neutral landscape, for bacterial-like fission as well as for assortative mating. Here we present another neutral model to investigate the `critical' phase transition behavior of three mating types - assortative, bacterial, and random - in a phenotype space as a function of the percentage of random death. Results show two types of phase transitions occurring for the parameters of the population size and the number of clusters (an analogue of species), indicating different evolutionary dynamics for system survival and clustering. This research was supported by funding from: University of Missouri Research Board and James S. McDonnell Foundation.
batman: BAsic Transit Model cAlculatioN in Python
NASA Astrophysics Data System (ADS)
Kreidberg, Laura
2015-11-01
I introduce batman, a Python package for modeling exoplanet transit light curves. The batman package supports calculation of light curves for any radially symmetric stellar limb darkening law, using a new integration algorithm for models that cannot be quickly calculated analytically. The code uses C extension modules to speed up model calculation and is parallelized with OpenMP. For a typical light curve with 100 data points in transit, batman can calculate one million quadratic limb-darkened models in 30 seconds with a single 1.7 GHz Intel Core i5 processor. The same calculation takes seven minutes using the four-parameter nonlinear limb darkening model (computed to 1 ppm accuracy). Maximum truncation error for integrated models is an input parameter that can be set as low as 0.001 ppm, ensuring that the community is prepared for the precise transit light curves we anticipate measuring with upcoming facilities. The batman package is open source and publicly available at https://github.com/lkreidberg/batman .
Transitioning Space Weather Models Into Operations: The Basic Building Blocks
NASA Astrophysics Data System (ADS)
Araujo-Pradere, Eduardo A.
2009-10-01
New and improved space weather models that provide real-time or near-real time operational awareness to the long list of customers that the NOAA Space Weather Prediction Center (SWPC) serves are critically needed. Recognizing this, SWPC recently established a Developmental Testbed Center (DTC [see Kumar, 2009]) at which models will be vetted for operational use. What characteristics should models have if they are to survive this transition? The difficulties around the implementation of real-time models are many. From the stability of the data input (frequently coming from third parties) to the elevated information technology (IT) security atmosphere present everywhere, scientists and developers are confronting a series of challenges in the implementation of their models. Quinn et al. [2009] noted that “the transition challenges are numerous and require ongoing interaction between model developers and users.” However, the 2006 Report of the Assessment Committee for the National Space Weather Program (NSWP; see http://www.nswp.gov/nswp_acreport0706.pdf) found that “there is an absence of suitable connection[s] for ‘academia-to-operations’ knowledge transfer and for the transition of research to operations in general.”
Columnar- Equiaxed Transition in Solidification processing: The ESA-MAP CETSOL project
NASA Astrophysics Data System (ADS)
Billia, Bernard; Gandin, Charles-André; Zimmermann, Gerhard; Browne, David; Dupouy, Marie-Danielle
2005-03-01
Many castings are the result of a competition between the growth of columnar and equiaxed grains. Indeed, microstructures are at the center of materials science and engineering, and solidification is the most important processing route for structural materials, especially metals and alloys. Presently, microstructure models remain mostly based on diffusive transport mechanisms so that there is a need of critical benchmark data to test fundamental theories of microstructure formation, which often necessitates to have recourse to solidification experiments in the reduced-gravity environment of space. Accordingly, the CETSOL (Columnar-Equiaxed Transition in SOLidification processing)-MAP project of ESA is gathering together European groups with complementary skills to carry out experiments and model the processes, in particular in view of the utilization of reduced-gravity environment that will be afforded by the International Space Station (ISS) to get benchmark data. The ultimate objective of the CETSOL research program is to significantly contribute to the improvement of integrated modeling of grain structure in industrially important castings. To reach this goal, the approach is devised to deepen the quantitative understanding of the basic physical principles that, from the microscopic to the macroscopic scales, govern microstructure formation in solidification processing under diffusive conditions and with fluid flow in the melt. Pending questions are attacked by well-defined model experiments on technical alloys and/or on model transparent systems, physical modeling at microstructure and mesoscopic scales (e.g. large columnar front or equiaxed crystals) and numerical simulation at all scales, up to the macroscopic scales of casting with integrated numerical models.
Finite-temperature phase transitions in the ionic Hubbard model
NASA Astrophysics Data System (ADS)
Kim, Aaram J.; Choi, M. Y.; Jeon, Gun Sang
2014-04-01
We investigate paramagnetic metal-insulator transitions in the infinite-dimensional ionic Hubbard model at finite temperatures. By means of the dynamical mean-field theory with an impurity solver of the continuous-time quantum Monte Carlo method, we show that an increase in the interaction strength brings about a crossover from a band insulating phase to a metallic one, followed by a first-order transition to a Mott insulating phase. The first-order transition turns into a crossover above a certain critical temperature, which becomes higher as the staggered lattice potential is increased. Further, analysis of the temperature dependence of the energy density discloses that the intermediate metallic phase is a Fermi liquid. It is also found that the metallic phase is stable against strong staggered potentials even at very low temperatures.
An efficient fluctuating charge model for transition metal complexes.
Comba, Peter; Martin, Bodo; Sanyal, Avik
2013-07-05
A fluctuating charge model for transition metal complexes, based on the Hirshfeld partitioning scheme, spectroscopic energy data from the NIST Atomic Spectroscopy Database and the electronegativity equalization approach, has been developed and parameterized for organic ligands and their high- and low-spin Fe(II) and Fe(III), low-spin Co(III) and Cu(II) complexes, using atom types defined in the Momec force field. Based on large training sets comprising a variety of transition metal complexes, a general parameter set has been developed and independently validated which allows the efficient computation of geometry-dependent charge distributions in the field of transition metal coordination compounds. Copyright © 2013 Wiley Periodicals, Inc.
Phase Transitions and Equilibrium Measures in Random Matrix Models
NASA Astrophysics Data System (ADS)
Martínez-Finkelshtein, A.; Orive, R.; Rakhmanov, E. A.
2015-02-01
The paper is devoted to a study of phase transitions in the Hermitian random matrix models with a polynomial potential. In an alternative equivalent language, we study families of equilibrium measures on the real line in a polynomial external field. The total mass of the measure is considered as the main parameter, which may be interpreted also either as temperature or time. Our main tools are differentiation formulas with respect to the parameters of the problem, and a representation of the equilibrium potential in terms of a hyperelliptic integral. Using this combination we introduce and investigate a dynamical system (system of ODEs) describing the evolution of families of equilibrium measures. On this basis we are able to systematically derive a number of new results on phase transitions, such as the local behavior of the system at all kinds of phase transitions, as well as to review a number of known ones.
Process for preparing high-transition-temperature superconductors in the Nb-Al-Ge system
Giorgi, A.L.; Szklarz, E.G.
1973-01-30
The patent describes a process for preparing superconducting materials in the Nb-Al-Ge system having transition temperatures in excess of 19K. The process comprises premixing powdered constituents, pressing them into a plug, heating the plug to 1,450-1,800C for 30 minutes to an hour under vacuum or an inert atmosphere, and annealing at moderate temperatures for reasonably long times (approximately 50 hours). High transition-temperature superconductors, including those in the Nb3(Al,Ge) system, prepared in accordance with this process exhibit little degradation in the superconducting transition temperature on being ground to -200 mesh powder. (GRA)
Transition to an individual-room NICU design: process and outcome measures.
Milford, Cheryl A; Zapalo, Barbara J; Davis, Glenda
2008-01-01
Redesign of a neonatal intensive care unit is a major budget undertaking, demanding accountability for its equipment and feasibility of design. It must be philosophically based and driven by research supporting best practice. The NJCU at the Magee-Womens Hospital of the University of Pittsburgh Medical Center, a Level III, 74-bed unit, has made the change from a ward design to an individual-room design suitable for family-centered, developmentally supportive care. This article presents the design process as it occurred. Unique to this process are the involvement of NJCU-graduate families and the use of transition teams. Guidelines and recommendations are offered to others interested in designing and practicing in an individual-room NJCU. Outcome data demonstrate staff adjustment to the new design and practice model. A comparison of this NICU design is made with the Recommended Standards for Newborn ICU Design.
NASA Astrophysics Data System (ADS)
Paul, Wolfgang; Solar, Mathieu
We will present results from Molecular Dynamics simulations of a chemically realistic model of 1,4-polybutadiene (PB) chains confined by graphite walls. Relaxation processes in this system are heterogeneous and anisotropic. We will present evidence for a slow additional relaxation process related to chain desorption from the walls. We also study the structural relaxation resolved with respect to the distance from the graphite walls and show the influence of structural changes on the relaxation behavior. The temperature dependence of the dielectric relaxation in layers of different thickness near the walls shows no indication of a shift of Tg as a function of thickness when analyzed with a Vogel-Fulcher fit. We explain this by the importance of intramolecular dihedral barriers for the glass transition in PB which dominate over the density changes next to a wall except for a 1 nm thick layer directly at the wall.
Chiral matrix model for the phase transition in QCD
NASA Astrophysics Data System (ADS)
Pisarski, Robert D.; Skokov, Vladimir
2016-12-01
We discuss how to model chiral symmetry restoration with an effective theory of deconfinement. The model includes fluctuations in the quarks to one loop order, while the mesons of the sigma model are treated in mean field approximation. We note that a new counterterm is required at T = 0, and a novel form of symmetry breaking at T ≠ 0. We discuss how to incorporate tetraquark states, representing JP =0+ scalar mesons, into a linear sigma model. We suggest that their effect upon the chiral phase transition is small.
Phase transition in the Sznajd model with independence
NASA Astrophysics Data System (ADS)
Sznajd-Weron, K.; Tabiszewski, M.; Timpanaro, A. M.
2011-11-01
We propose a model of opinion dynamics which describes two major types of social influence —conformity and independence. Conformity in our model is described by the so-called outflow dynamics (known as Sznajd model). According to sociologists' suggestions, we introduce also a second type of social influence, known in social psychology as independence. Various social experiments have shown that the level of conformity depends on the society. We introduce this level as a parameter of the model and show that there is a continuous phase transition between conformity and independence.
Animal models and conserved processes
2012-01-01
Background The concept of conserved processes presents unique opportunities for using nonhuman animal models in biomedical research. However, the concept must be examined in the context that humans and nonhuman animals are evolved, complex, adaptive systems. Given that nonhuman animals are examples of living systems that are differently complex from humans, what does the existence of a conserved gene or process imply for inter-species extrapolation? Methods We surveyed the literature including philosophy of science, biological complexity, conserved processes, evolutionary biology, comparative medicine, anti-neoplastic agents, inhalational anesthetics, and drug development journals in order to determine the value of nonhuman animal models when studying conserved processes. Results Evolution through natural selection has employed components and processes both to produce the same outcomes among species but also to generate different functions and traits. Many genes and processes are conserved, but new combinations of these processes or different regulation of the genes involved in these processes have resulted in unique organisms. Further, there is a hierarchy of organization in complex living systems. At some levels, the components are simple systems that can be analyzed by mathematics or the physical sciences, while at other levels the system cannot be fully analyzed by reducing it to a physical system. The study of complex living systems must alternate between focusing on the parts and examining the intact whole organism while taking into account the connections between the two. Systems biology aims for this holism. We examined the actions of inhalational anesthetic agents and anti-neoplastic agents in order to address what the characteristics of complex living systems imply for inter-species extrapolation of traits and responses related to conserved processes. Conclusion We conclude that even the presence of conserved processes is insufficient for inter
The comfortable driving model revisited: traffic phases and phase transitions
NASA Astrophysics Data System (ADS)
Knorr, Florian; Schreckenberg, Michael
2013-07-01
We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast them with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner’s three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides ‘hard’ rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow to a wide moving jam often involves an intermediate transition: first from free flow to synchronized flow and then from synchronized flow to a wide moving jam. This is supported by the fact that the so-called F → S transition (from free flow to synchronized traffic) is much more likely than a direct F → J transition. The model under consideration has a functional relationship between traffic flow and traffic density. The fundamental hypothesis of the three-phase traffic theory, however, postulates that the steady states of synchronized flow occupy a two-dimensional region in the flow-density plane. Due to the obvious discrepancy between the model investigated here and the postulate of the three-phase traffic theory, the good agreement that we found could not be expected. For a more detailed analysis, we also studied vehicle dynamics at a microscopic level and provide a comparison of real detector data with simulated data of the identical highway segment.
ERIC Educational Resources Information Center
Gillis, La Tonya L.
2011-01-01
The purpose of this study was to examine the role that self-determination played in the transition process for young African American women with disabilities who exited high school with a special diploma and participated in a local transition program. Factors under study included the young women's autonomy, self-regulation, psychological…
ERIC Educational Resources Information Center
Gillis, La Tonya L.
2011-01-01
The purpose of this study was to examine the role that self-determination played in the transition process for young African American women with disabilities who exited high school with a special diploma and participated in a local transition program. Factors under study included the young women's autonomy, self-regulation, psychological…
The Transition Process: Towards Exclusion or Financial Sufficiency. A French-Irish Comparison.
ERIC Educational Resources Information Center
Grelet, Yvette; Mansuy, Michele; Thomas, Gwenaelle
Data from longitudinal school leavers' surveys in France and Ireland were compared to determine types of transition pathways leading to unsuccessful conclusions. Focus was on outcomes of the transition process for school leavers unemployed five years after leaving and for employed young people whose earnings did not allow them to be financially…
Student Knowledge and Perceptions of Individual Transition Planning and Its Process
ERIC Educational Resources Information Center
Williams-Diehm, Kendra L.; Lynch, Patricia S.
2007-01-01
Although increased attention in special education has been given to individual transition planning, little research has been done to assess student opinions and knowledge on this process. The majority of research has focused on "best practice" to ensure quality transition planning for students. This study surveyed 103 students receiving…
Model for amorphous aggregation processes
NASA Astrophysics Data System (ADS)
Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz
2009-11-01
The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.
Face Processing: Models For Recognition
NASA Astrophysics Data System (ADS)
Turk, Matthew A.; Pentland, Alexander P.
1990-03-01
The human ability to process faces is remarkable. We can identify perhaps thousands of faces learned throughout our lifetime and read facial expression to understand such subtle qualities as emotion. These skills are quite robust, despite sometimes large changes in the visual stimulus due to expression, aging, and distractions such as glasses or changes in hairstyle or facial hair. Computers which model and recognize faces will be useful in a variety of applications, including criminal identification, human-computer interface, and animation. We discuss models for representing faces and their applicability to the task of recognition, and present techniques for identifying faces and detecting eye blinks.
Chi, Donald L.
2013-01-01
Objectives To test the hypotheses that youth with special health care needs (YSHCN) with a medical care transition plan are more likely to use dental care during the transition from adolescence to young adulthood and that different factors are associated with dental utilization for YSHCN with and YSHCN without functional limitations. Methods National Survey of CSHCN (2001) and Survey of Adult Transition and Health (2007) data were analyzed (N=1,746). The main predictor variable was having a medical care transition plan, defined as having discussed with a doctor how health care needs might change with age and having developed a transition plan. The outcome variable was dental care use in 2001 (adolescence) and 2007 (young adulthood). Multiple variable Poisson regression models with robust standard errors were used to estimate covariate-adjusted relative risks (RR). Results About 63% of YSHCN had a medical care transition plan and 73.5% utilized dental care. YSHCN with a medical care transition plan had a 9% greater relative risk (RR) of utilizing dental care than YSHCN without a medical care transition plan (RR:1.09; 95% CI:1.03–1.16). In the models stratified by functional limitation status, having a medical care transition plan was significantly associated with dental care use, but only for YSHCN without functional limitations (RR:1.11; 95% CI:1.04–1.18). Conclusions Having a medical care transition plan is significantly associated with dental care use, but only for YSHCN with no functional limitation. Dental care should be an integral part of the comprehensive health care transition planning process for all YSHCN. PMID:23812799
Chi, Donald L
2014-05-01
The aims of the study were to test the hypotheses that youth with special health care needs (YSHCN) with a medical care transition plan are more likely to use dental care during the transition from adolescence to young adulthood and that different factors are associated with dental utilization for YSHCN with and YSHCN without functional limitations. National Survey of CSHCN (2001) and Survey of Adult Transition and Health (2007) data were analyzed (N = 1,746). The main predictor variable was having a medical care transition plan, defined as having discussed with a doctor how health care needs might change with age and having developed a transition plan. The outcome variable was dental care use in 2001 (adolescence) and 2007 (young adulthood). Multiple variable Poisson regression models with robust standard errors were used to estimate covariate-adjusted relative risks (RR). About 63 % of YSHCN had a medical care transition plan and 73.5 % utilized dental care. YSHCN with a medical care transition plan had a 9 % greater RR of utilizing dental care than YSHCN without a medical care transition plan (RR 1.09; 95 % CI 1.03-1.16). In the models stratified by functional limitation status, having a medical care transition plan was significantly associated with dental care use, but only for YSHCN without functional limitations (RR 1.11; 95 % CI 1.04-1.18). Having a medical care transition plan is significantly associated with dental care use, but only for YSHCN with no functional limitation. Dental care should be an integral part of the comprehensive health care transition planning process for all YSHCN.
A Model for Heterogeneous Materials Undergoing Phase Transitions
NASA Astrophysics Data System (ADS)
Plohr, Jeeyeon
2005-03-01
We develop a macroscopic model for a heterogeneous material undergoing a phase transition. Such a continuum-level material model, which is needed in practical engineering calculations, must faithfully reflect the micromechanical response of the constituent materials. Using the method of cells, which is a homogenization technique, we derive the constitutive properties of a composite material, part of which undergoes a phase transition. Specifically, we study tungsten heavy alloy (WHA), in which tungsten grains are dispersed within a low-melting-temperature alloy matrix. This material has desirable static properties as a penetrator, but melting in the matrix occurs during loading. Simulations with our model predicts the properties of WHA with different compositions, which can then be optimized.
Theoretical Models of Astrochemical Processes
NASA Technical Reports Server (NTRS)
Charnley, Steven
2009-01-01
Interstellar chemistry provides a natural laboratory for studying exotic species and processes at densities, temperatures, and reaction rates. that are difficult or impractical to address in the laboratory. Thus, many chemical reactions considered too sloe by the standards of terrestrial chemistry, can be 'observed and modeled. Curious proposals concerning the nature and chemistry of complex interstellar organic molecules will be described. Catalytic reactions on "rain surfaces can, in principle, lead to a lame variety of species and this has motivated many laboratory and theoretical studies. Gas phase processes may also build lame species in molecular clouds. Future laboratory data and computational tools needed to construct accurate chemical models of various astronomical sources to be observed by Herschel and ALMA will be outlined.
Bassel, George W.; Lan, Hui; Glaab, Enrico; Gibbs, Daniel J.; Gerjets, Tanja; Krasnogor, Natalio; Bonner, Anthony J.; Holdsworth, Michael J.; Provart, Nicholas J.
2011-01-01
Seed germination is a complex trait of key ecological and agronomic significance. Few genetic factors regulating germination have been identified, and the means by which their concerted action controls this developmental process remains largely unknown. Using publicly available gene expression data from Arabidopsis thaliana, we generated a condition-dependent network model of global transcriptional interactions (SeedNet) that shows evidence of evolutionary conservation in flowering plants. The topology of the SeedNet graph reflects the biological process, including two state-dependent sets of interactions associated with dormancy or germination. SeedNet highlights interactions between known regulators of this process and predicts the germination-associated function of uncharacterized hub nodes connected to them with 50% accuracy. An intermediate transition region between the dormancy and germination subdomains is enriched with genes involved in cellular phase transitions. The phase transition regulators SERRATE and EARLY FLOWERING IN SHORT DAYS from this region affect seed germination, indicating that conserved mechanisms control transitions in cell identity in plants. The SeedNet dormancy region is strongly associated with vegetative abiotic stress response genes. These data suggest that seed dormancy, an adaptive trait that arose evolutionarily late, evolved by coopting existing genetic pathways regulating cellular phase transition and abiotic stress. SeedNet is available as a community resource (http://vseed.nottingham.ac.uk) to aid dissection of this complex trait and gene function in diverse processes. PMID:21593420
Network inoculation: Heteroclinics and phase transitions in an epidemic model
NASA Astrophysics Data System (ADS)
Yang, Hui; Rogers, Tim; Gross, Thilo
2016-08-01
In epidemiological modelling, dynamics on networks, and, in particular, adaptive and heterogeneous networks have recently received much interest. Here, we present a detailed analysis of a previously proposed model that combines heterogeneity in the individuals with adaptive rewiring of the network structure in response to a disease. We show that in this model, qualitative changes in the dynamics occur in two phase transitions. In a macroscopic description, one of these corresponds to a local bifurcation, whereas the other one corresponds to a non-local heteroclinic bifurcation. This model thus provides a rare example of a system where a phase transition is caused by a non-local bifurcation, while both micro- and macro-level dynamics are accessible to mathematical analysis. The bifurcation points mark the onset of a behaviour that we call network inoculation. In the respective parameter region, exposure of the system to a pathogen will lead to an outbreak that collapses but leaves the network in a configuration where the disease cannot reinvade, despite every agent returning to the susceptible class. We argue that this behaviour and the associated phase transitions can be expected to occur in a wide class of models of sufficient complexity.
Modeling of Flow Transition Using an Intermittency Transport Equation
NASA Technical Reports Server (NTRS)
Suzen, Y. B.; Huang, P. G.
1999-01-01
A new transport equation for intermittency factor is proposed to model transitional flows. The intermittent behavior of the transitional flows is incorporated into the computations by modifying the eddy viscosity, mu(sub t), obtainable from a turbulence model, with the intermittency factor, gamma: mu(sub t, sup *) = gamma.mu(sub t). In this paper, Menter's SST model (Menter, 1994) is employed to compute mu(sub t) and other turbulent quantities. The proposed intermittency transport equation can be considered as a blending of two models - Steelant and Dick (1996) and Cho and Chung (1992). The former was proposed for near-wall flows and was designed to reproduce the streamwise variation of the intermittency factor in the transition zone following Dhawan and Narasimha correlation (Dhawan and Narasimha, 1958) and the latter was proposed for free shear flows and was used to provide a realistic cross-stream variation of the intermittency profile. The new model was used to predict the T3 series experiments assembled by Savill (1993a, 1993b) including flows with different freestream turbulence intensities and two pressure-gradient cases. For all test cases good agreements between the computed results and the experimental data are observed.
NASA Trapezoidal Wing Computations Including Transition and Advanced Turbulence Modeling
NASA Technical Reports Server (NTRS)
Rumsey, C. L.; Lee-Rausch, E. M.
2012-01-01
Flow about the NASA Trapezoidal Wing is computed with several turbulence models by using grids from the first High Lift Prediction Workshop in an effort to advance understanding of computational fluid dynamics modeling for this type of flowfield. Transition is accounted for in many of the computations. In particular, a recently-developed 4-equation transition model is utilized and works well overall. Accounting for transition tends to increase lift and decrease moment, which improves the agreement with experiment. Upper surface flap separation is reduced, and agreement with experimental surface pressures and velocity profiles is improved. The predicted shape of wakes from upstream elements is strongly influenced by grid resolution in regions above the main and flap elements. Turbulence model enhancements to account for rotation and curvature have the general effect of increasing lift and improving the resolution of the wing tip vortex as it convects downstream. However, none of the models improve the prediction of surface pressures near the wing tip, where more grid resolution is needed.
NASA Astrophysics Data System (ADS)
Birky, Alicia K.
2008-10-01
Significant reductions in greenhouse emissions from personal transportation will require a transition to an alternative technology regime based on renewable energy sources. Two bodies of research, the quasi-evolutionary (QE) model and the multi-level perspective (MLP) assert that processes within niches play a fundamental role in such transitions. This research asks whether the description of transitions based on this niche hypothesis and its underlying assumptions is consistent with the historical U.S. transition to motor vehicles at the beginning of the 20th century. Unique to this dissertation is the combination of the perspective of the entrepreneur with co-evolutionary approaches to socio-technical transitions. This approach is augmented with concepts from the industry life-cycle model and with a taxonomy of mechanisms of learning. Using this analytic framework, I examine specifically the role of entrepreneurial behavior and processes within and among firms in the co-evolution of technologies and institutions during the transition to motor vehicles. I find that niche markets played an important role in the development of the technology, institutions, and the industry. However, I also find that the diffusion of the automobile is not consistent with the niche hypothesis in the following ways: (1) product improvements and cost reductions were not realized in niche markets, but were achieved simultaneously with diffusion into mass markets; (2) in addition to learning-by-doing and learning-by-interacting with users, knowledge spillovers and interacting with suppliers were critical in this process; (3) cost reductions were not automatic results of expanding markets, but rather arose from the strategies of entrepreneurs based on personal perspectives and values. This finding supports the use of a behavioral approach with a micro-focus in the analysis of socio-technical change. I also find that the emergence and diffusion of the motor vehicle can only be understood by
Chapter 5: Application of state-and-transition models to evaluate wildlife habitat
Anita T. Morzillo; Pamela Comeleo; Blair Csuti; Stephanie Lee
2014-01-01
Wildlife habitat analysis often is a central focus of natural resources management and policy. State-and-transition models (STMs) allow for simulation of landscape level ecological processes, and for managers to test âwhat ifâ scenarios of how those processes may affect wildlife habitat. This chapter describes the methods used to link STM output to wildlife habitat to...
The glass transition process in humid biopolymers. DSC study
NASA Astrophysics Data System (ADS)
Grunina, N. A.; Belopolskaya, T. V.; Tsereteli, G. I.
2006-05-01
Thermal properties of native and denatured biopolymers with quite different chemical and steric structure (globular and fibrillar proteins, DNA, starches) were studied by means of differential scanning calorimetry in a wide range of temperatures and concentrations of water. It was shown that both native and denatured humid biopolymers are glassy systems. The glass transition temperature of these systems strongly depends on percentage of water, with water being simultaneously an intrinsic element of systems' ordered structure and a plasticizer of its amorphous state. On the base of the absolute values of heat capacities for biopolymer-water systems as a whole, heat capacities for biopolymers themselves were calculated as functions on water concentration at fixed temperatures. The S-shaped change of heat capacity observed on diagrams of state both for native and denatured biopolymers is the manifestation of biopolymers' passing through the vitrification region, as it occurs for denatured samples at heating.
Center for modeling of turbulence and transition: Research briefs, 1993
NASA Technical Reports Server (NTRS)
Liou, William W. (Editor)
1994-01-01
This research brief contains the progress reports of the research staff of the Center for Modeling of Turbulence and Transition (CMOTT) from June 1992 to July 1993. It is also an annual report to the Institute for Computational Mechanics in Propulsion located at Ohio Aerospace Institute and NASA Lewis Research Center. The main objectives of the research activities at CMOTT are to develop, validate, and implement turbulence and transition models for flows of interest in propulsion systems. Currently, our research covers eddy viscosity one- and two-equation models, Reynolds-stress algebraic equation models, Reynolds-stress transport equation models, nonequilibrium multiple-scale models, bypass transition models, joint scalar probability density function models, and Renormalization Group Theory and Direct Interaction Approximation methods. Some numerical simulations (LES and DNS) have also been carried out to support the development of turbulence modeling. Last year was CMOTT's third year in operation. During this period, in addition to the above mentioned research, CMOTT has also hosted the following programs: an eighteen-hour short course on 'Turbulence--Fundamentals and Computational Modeling (Part I)' given by CMOTT at the NASA Lewis Research Center; a productive summer visitor research program that has generated many encouraging results; collaborative programs with industry customers to help improve their turbulent flow calculations for propulsion system designs; a biweekly CMOTT seminar series with speakers from within and without the NASA Lewis Research Center including foreign speakers. In addition, CMOTT members have been actively involved in the national and international turbulence research activities. The current CMOTT roster and organization are listed in Appendix A. Listed in Appendix B are the abstracts of the biweekly CMOTT seminar. Appendix C lists the papers contributed by CMOTT members.
Empirical Validation of Conceptual Climate Models for the Mid-Pleistocene Transition
NASA Astrophysics Data System (ADS)
Gallatin, A.; Camp, C. D.
2015-12-01
Conceptual climate models are useful for testing hypotheses regarding the processes underlying observations; but they generally can only qualitatively match the empirical records. Models based on substantially different underlying physics can have comparable correlations with any given observation, thus robust model validation procedures are needed. The Mid-Pleistocene Transition (MPT) is an ideal test case for the development of such procedures because the character and cause of the transition from a dominant 41 kyr cycle in the early Pleistocene to a dominant 100 kyr cycle in the late Pleistocene is poorly understood. Using Ensemble Empirical Mode Decomposition, we analyze multiple conceptual models for the MPT which are based on differing physical hypotheses and show how modern time-series-analysis techniques can improve climate-model validation by extracting and comparing subtler features of both the observations and models.
Planet formation in transition disks: Modeling, spectroscopy, and theory
NASA Astrophysics Data System (ADS)
Liskowsky, Joseph Paul
due to either a massive planet accreting the material onto it or via a photoevaporation process whereby the central star's radiation field ejects material from the inner disk out of the bound system in the the interstellar medium. It is presumed that this phase is the last gasp of the planetary disk's evolution before the debris disk stage and before a fully formed solar system evolves. Our work specifically focuses on one object of this transition disk class: HD100546. We add to the understanding of transition disks by showing that a model where ro-vibrational OH emission in the NIR is preferentially emitted along the 'wall' of the disk is consistent with observations, and furthermore that adding an eccentricity to this `wall' component is required to generate the necessary observed line shape. In conjunction with this observation we present supporting material which motivates the usage of such an eccentric wall component in light of predictions of the influence of giant planet formation occurring within the disk.
Thermal phase transition for some spin-boson models
NASA Astrophysics Data System (ADS)
Aparicio Alcalde, M.; Pimentel, B. M.
2013-09-01
In this work we study two different spin-boson models. Such models are generalizations of the Dicke model, it means they describe systems of N identical two-level atoms coupled to a single-mode quantized bosonic field, assuming the rotating wave approximation. In the first model, we consider the wavelength of the bosonic field to be of the order of the linear dimension of the material composed of the atoms, therefore we consider the spatial sinusoidal form of the bosonic field. The second model is the Thompson model, where we consider the presence of phonons in the material composed of the atoms. We study finite temperature properties of the models using the path integral approach and functional methods. In the thermodynamic limit, N→∞, the systems exhibit phase transitions from normal to superradiant phase at some critical values of temperature and coupling constant. We find the asymptotic behavior of the partition functions and the collective spectrums of the systems in the normal and the superradiant phases. We observe that the collective spectrums have zero energy values in the superradiant phases, corresponding to the Goldstone mode associated to the continuous symmetry breaking of the models. Our analysis and results are valid in the limit of zero temperature β→∞, where the models exhibit quantum phase transitions.
Phase transitions in two-dimensional model systems
NASA Astrophysics Data System (ADS)
Schief, William R., Jr.
Lipid and protein monolayers at the air/water interface are well suited for the study of two-dimensional phase transitions as their thermodynamic parameters may be tightly controlled, and they are amendable to in situ, non-perturbative, surface-analytical techniques. In this dissertation, quantitative light microscopy techniques are developed and expanded to study transitions in lipid and protein monolayers at the air/water interface. In the simplest model system studied, pure phospholipid monolayers, the introduction of light scattering microscopy reveals previously undetected, nanoscale topographic transitions in a microscopic pattern throughout the condensed phase. The findings demonstrate that condensed phospholipid phases are not flat as conventionally thought, and indicate that a patterned distribution of packing defects is imprinted on the monolayer during the first order liquid-to-condensed transition. As the monolayer is compressed, the pattern of defects persists in the pure condensed phase, giving rise to first a corrugation transition and later a budding transition. Finally, the pattern of defects controls the morphology of the monolayer collapse phase transition. The findings show the high sensitivity of light scattering microscopy to surface deformations on the angstrom to nanoscale and demonstrate the promise of this technique for future discoveries in a range of systems at fluid interfaces. In binary mixed monolayers of phospholipids and dihydrocholesterol and highly complex natural lung surfactant monolayers, quantitative Brewster angle microscopy leads to the discovery of a first order, two- to three-dimensional phase transition from monolayer to monolayer plus overlying bilayer discs. This phase transition occurs within the lower end of the physiological range of surface pressure, so the discovery raises new questions concerning the structure/function relationship of pulmonary surfactant and specifically points to a powerful structural impact by
Models for a liquid-liquid phase transition
NASA Astrophysics Data System (ADS)
Buldyrev, S. V.; Franzese, G.; Giovambattista, N.; Malescio, G.; Sadr-Lahijany, M. R.; Scala, A.; Skibinsky, A.; Stanley, H. E.
2002-02-01
We use molecular dynamics simulations to study two- and three-dimensional models with the isotropic double-step potential which in addition to the hard core has a repulsive soft core of larger radius. Our results indicate that the presence of two characteristic repulsive distances (hard core and soft core) is sufficient to explain liquid anomalies and a liquid-liquid phase transition, but these two phenomena may occur independently. Thus liquid-liquid transitions may exist in systems like liquid metals, regardless of the presence of the density anomaly. For 2D, we propose a model with a specific set of hard core and soft core parameters, that qualitatively reproduces the phase diagram and anomalies of liquid water. We identify two solid phases: a square crystal (high density phase), and a triangular crystal (low density phase) and discuss the relation between the anomalies of liquid and the polymorphism of the solid. Similarly to real water, our 2D system may have the second critical point in the metastable liquid phase beyond the freezing line. In 3D, we find several sets of parameters for which two fluid-fluid phase transition lines exist: the first line between gas and liquid and the second line between high-density liquid (HDL) and low-density liquid (LDL). In all cases, the LDL phase shows no density anomaly in 3D. We relate the absence of the density anomaly with the positive slope of the LDL-HDL phase transition line.
Extratropical transitioning in the RMS Japan typhoon wind field model
NASA Astrophysics Data System (ADS)
Loridan, Thomas; Scherer, Emilie; Khare, Shree
2013-04-01
Given its meridional extent and location within the Pacific basin, Japan is regularly impacted by strong winds from cyclones at different stages of their lifecycle. To quantify the associated risk of damage to properties, catastrophe models such as the ones developed by RMS aim to simulate wind fields from thousands of stochastic storms that extrapolate historical events. In a recent study using 25 years of reanalysis data, Kitabatake (2011) estimated that 40 % of all Pacific tropical cyclones completed their transition as an extra tropical system. From a cat modelling point of view it is the increase in wind field asymmetry observed during these transitioning episodes that is critical, with examples like typhoon Tokage in 2004 showing the potential for damaging gusts on both sides of the storm track. In this context a compromise has to be found between the need for complex numerical models able to simulate wind field variability around the cyclone during its entire evolution, and obvious running time constrains. The RMS wind field model is based on an optimized version of the Willoughby parametric profile (Willoughby et al., 2006) which requires calibration against targets representative of cyclone wind fields throughout their lifecycle. We here present the different sources of data involved in the development of this model. This includes (1) satellite products to characterize wind fields from fully tropical storms, (2) high resolution simulations of key transitioning events using the WRF mesoscale model to complement the database at other stages (i.e. for transitioning and fully extra tropical wind fields), and (3) reanalysis data which can be used with Hart (2003)'s cyclone phase space methodology to provide an estimate of the mean duration of transitioning episodes in the Pacific. Kitabatake, N., 2011: Climatology of extratropical transition of tropical cyclones in the Western North Pacific defined by using cyclone phase space. J. Meteor. Soc. Japan, 89, 309
New model for the shock-induced. alpha. -quartz r arrow stishovite phase transition in silica
Boettger, J.C. )
1992-12-01
A new model has been developed to describe the {alpha}-quartz to stishovite phase transition in silica under shock-loading conditions. During hydrodynamic simulations, individual global equations of state for the {alpha}-quartz and stishovite phases of silica are mixed in accordance with process-dependent constraints on the Gibbs free energy difference between the phases ({Delta}{ital G}). For the shock-induced transition, {Delta}{ital G} is required to equal a simple two parameter function of the mass fraction of stishovite. Unlike previous models, the new constraint equation assumes that the shock induced phase transition begins at the equilibrium phase boundary, but is not completed unless peak stresses on the order of 40 GPa are achieved. On release, the reverse transition is required to satisfy the usual thermodynamic equilibrium condition ({Delta}{ital G}=0). It is shown that hydrodynamic simulations combining this hysteretic phase transition model with a strength model that assumes partial softening after yielding are capable of reproducing experimental Hugoniot and release data for crystalline silica in the mixed-phase region.
NASA Astrophysics Data System (ADS)
Jaskiewicz, Anna; Nowak, Andrzej S.
2006-04-01
We consider Markov control processes with Borel state space and Feller transition probabilities, satisfying some generalized geometric ergodicity conditions. We provide a new theorem on the existence of a solution to the average cost optimality equation.
Nonstationary multistate Coulomb and multistate exponential models for nonadiabatic transitions
Ostrovsky, V. N.
2003-07-01
The nonstationary Schroedinger equation is considered in a finite basis of states. The model Hamiltonian matrix corresponds to a single diabatic potential curve with a Coulombic {approx}1/t time dependence. An arbitrary number of other diabatic potential curves are flat, i.e., time independent and have arbitrary energies. Related states are coupled by constant interactions with the Coulomb state. The resulting nonstationary Schroedinger equation is solved by the method of contour integral. Probabilities of transitions to any other state are obtained as t{yields}{infinity} in a simple analytical form for the case when the Coulomb state is populated initially (at instant of time t{yields}+0). The formulas apply both to the cases when a horizontal diabatic potential curve is crossed by the Coulomb one and to a noncrossing situation. In the limit of weak coupling, the transition probabilities are interpreted in terms of a sequence of pairwise Landau-Zener-type transitions. Mapping of the Coulomb model onto an exactly solvable exponential multistate model is established. For the special two-state case, the well-known Nikitin model is recovered.
Quantum hidden Markov models based on transition operation matrices
NASA Astrophysics Data System (ADS)
Cholewa, Michał; Gawron, Piotr; Głomb, Przemysław; Kurzyk, Dariusz
2017-04-01
In this work, we extend the idea of quantum Markov chains (Gudder in J Math Phys 49(7):072105 [3]) in order to propose quantum hidden Markov models (QHMMs). For that, we use the notions of transition operation matrices and vector states, which are an extension of classical stochastic matrices and probability distributions. Our main result is the Mealy QHMM formulation and proofs of algorithms needed for application of this model: Forward for general case and Vitterbi for a restricted class of QHMMs. We show the relations of the proposed model to other quantum HMM propositions and present an example of application.
Hubert, Sébastien; Briancon, Stéphanie; Hedoux, Alain; Guinet, Yannick; Paccou, Laurent; Fessi, Hatem; Puel, François
2011-11-25
The phase transition of a model API, caffeine Form I, was studied during tableting process monitored with an instrumented press. The formulation used had a plastic flow behavior according to the Heckel model in the compression pressure range of 70-170 MPa. The quantitative methods of analysis used were Differential Scanning Calorimetry (DSC) and low frequency Micro Raman Spectroscopy (MRS) which was used for the first time for the mapping of polymorphs in tablets. They brought complementary contributions since MRS is a microscopic spectral analysis with a spatial resolution of 5 μm(3) and DSC takes into account a macroscopic fraction (10mg) of the tablet. Phase transitions were present at the surfaces, borders and center of the tablets. Whatever the pressure applied during the compression process, the transition degree of caffeine Form I toward Form II was almost constant. MRS provided higher transition degrees (50-60%) than DSC (20-35%). MRS revealed that caffeine Form I particles were partially transformed in all parts of the tablets at a microscopic scale. Moreover, tablet surfaces showed local higher transition degree compared to the other parts.
Experience Transitioning Models and Data at the NOAA Space Weather Prediction Center
NASA Astrophysics Data System (ADS)
Berger, Thomas
2016-07-01
The NOAA Space Weather Prediction Center has a long history of transitioning research data and models into operations and with the validation activities required. The first stage in this process involves demonstrating that the capability has sufficient value to customers to justify the cost needed to transition it and to run it continuously and reliably in operations. Once the overall value is demonstrated, a substantial effort is then required to develop the operational software from the research codes. The next stage is to implement and test the software and product generation on the operational computers. Finally, effort must be devoted to establishing long-term measures of performance, maintaining the software, and working with forecasters, customers, and researchers to improve over time the operational capabilities. This multi-stage process of identifying, transitioning, and improving operational space weather capabilities will be discussed using recent examples. Plans for future activities will also be described.
Chemical and aerosol processes in the transition from closed to open cells during VOCALS-REx
NASA Astrophysics Data System (ADS)
Kazil, J.; Wang, H.; Feingold, G.; Clarke, A. D.; Snider, J. R.; Bandy, A. R.
2011-02-01
Chemical and aerosol processes in the transition from closed- to open-cell circulation in the remote, cloudy marine boundary layer are explored. It has previously been shown that precipitation can initiate a transition from the closed- to the open-cellular state, but that the boundary layer cannot maintain this open-cell state without a resupply of cloud condensation nuclei (CCN). Potential sources include wind-driven production of sea salt particles from the ocean, nucleation from the gas phase, and entrainment from the free troposphere. In order to investigate aerosol sources in the marine boundary layer and their role in supplying new particles, we have coupled in detail chemical, aerosol, and cloud processes in the WRF/Chem model, and added state-of-the-art representations of sea salt emissions and aerosol nucleation. We introduce the new features of the model and conduct simulations of the marine boundary layer in the transition from a closed- to an open-cell state. Results are compared with observations in the Southeast Pacific boundary layer during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). The transition from the closed- to the open-cell state generates conditions that are conducive to nucleation by forming a cloud-scavenged, ultra-clean layer below the inversion base. Open cell wall updrafts loft dimethyl sulfide from the ocean surface into the ultra-clean layer, where it is oxidized during daytime to SO2 and subsequently to H2SO4. Low H2SO4 condensation sink values in the ultra-clean layer allow H2SO4 to rise to concentrations at which aerosol nucleation proceeds efficiently. The existence of the ultra-clean layer is confirmed by observations. We find that the observed DMS flux from the ocean in the VOCALS-REx region can support a nucleation source of aerosol in open cells that exceeds sea salt emissions in terms of the number of particles produced. The freshly nucleated, nanometer-sized aerosol particles need, however
Tan, F P P; Wood, N B; Tabor, G; Xu, X Y
2011-05-01
In this study, two different turbulence methodologies are investigated to predict transitional flow in a 75% stenosed axisymmetric experimental arterial model and in a slightly modified version of the model with an eccentric stenosis. Large eddy simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) methods were applied; in the LES simulations eddy viscosity subgrid-scale models were employed (basic and dynamic Smagorinsky) while the RANS method involved the correlation-based transitional version of the hybrid k-ε/k-ω flow model. The RANS simulations used 410,000 and 820,000 element meshes for the axisymmetric and eccentric stenoses, respectively, with y(+) less than 2 viscous wall units for the boundary elements, while the LES used 1,200,000 elements with y(+) less than 1. Implicit filtering was used for LES, giving an overlap between the resolved and modeled eddies, ensuring accurate treatment of near wall turbulence structures. Flow analysis was carried out in terms of vorticity and eddy viscosity magnitudes, velocity, and turbulence intensity profiles and the results were compared both with established experimental data and with available direct numerical simulations (DNSs) from the literature. The simulation results demonstrated that the dynamic Smagorinsky LES and RANS transitional model predicted fairly comparable velocity and turbulence intensity profiles with the experimental data, although the dynamic Smagorinsky model gave the best overall agreement. The present study demonstrated the power of LES methods, although they were computationally more costly, and added further evidence of the promise of the RANS transition model used here, previously tested in pulsatile flow on a similar model. Both dynamic Smagorinsky LES and the RANS model captured the complex transition phenomena under physiological Reynolds numbers in steady flow, including separation and reattachment. In this respect, LES with dynamic Smagorinsky appeared more successful than DNS
Maya, Leon
1988-05-24
A process for making ammonolytic precursors to nitride and carbonitride ceramics. Extreme reaction conditions are not required and the precursor is a powder-like substance that produces ceramics of improved purity and morphology upon pyrolysis.
Phase transition of the Ising model on a fractal lattice.
Genzor, Jozef; Gendiar, Andrej; Nishino, Tomotoshi
2016-01-01
The phase transition of the Ising model is investigated on a planar lattice that has a fractal structure. On the lattice, the number of bonds that cross the border of a finite area is doubled when the linear size of the area is extended by a factor of 4. The free energy and the spontaneous magnetization of the system are obtained by means of the higher-order tensor renormalization group method. The system exhibits the order-disorder phase transition, where the critical indices are different from those of the square-lattice Ising model. An exponential decay is observed in the density-matrix spectrum even at the critical point. It is possible to interpret that the system is less entangled because of the fractal geometry.
NASA Astrophysics Data System (ADS)
Archambault, H. M.; Mariotti, A.; Barrie, D.; Huang, J.
2016-12-01
The Climate Program Office's (CPO's) Modeling, Analysis, Predictions, and Projections (MAPP) Program is a competitive grants research program that supports research and transition work to advance NOAA's subseasonal to decadal prediction; climate and Earth system modeling; drought, extremes, and other applications; climate reanalysis techniques; and analysis of climate projections. MAPP works with national partners including through ESPC, USGCRP, and CLIVAR, and also through international WCRP, to strategically engage and organize the science community around these priorities. This presentation will complement an overview presentation by CPO Director Wayne Higgins on CPO's National ESPC contributions by presenting MAPP Program efforts in two specific ESPC-relevant areas: (1) developing a NOAA Unified Global Coupled System, including physical process modeling and software infrastructure work on the Earth System Modeling Framework and the NOAA Environmental Modeling System (NEMS), as part of the MAPP Climate Model Task Force; and (2) testing and transition of real-time ensemble prediction systems for operationational prediction from weeks to seasons.
Modeling climate related feedback processes
Elzen, M.G.J. den; Rotmans, J. )
1993-11-01
In order to assess their impact, the feedbacks which at present can be quantified reasonably are built into the Integrated Model to Assess the Greenhouse Effect (IMAGE). Unlike previous studies, this study describes the scenario- and time-dependent role of biogeochemical feedbacks. A number of simulation experiments are performed with IMAGE to project climate changes. Besides estimates of their absolute importance, the relative importance of individual biogeochemical feedbacks is considered by calculating the gain for each feedback process. This study focuses on feedback processes in the carbon cycle and the methane (semi-) cycle. Modeled feedbacks are then used to balance the past and present carbon budget. This results in substantially lower projections for atmospheric carbon dioxide than the Intergovernmental Panel on Climate Change (IPCC) estimates. The difference is approximately 18% from the 1990 level for the IPCC [open quotes]Business-as-Usual[close quotes] scenario. Furthermore, the IPCC's [open quotes]best guess[close quotes] value of the CO[sub 2] concentration in the year 2100 falls outside the uncertainty range estimated with our balanced modeling approach. For the IPCC [open quotes]Business-as-Usual[close quotes] scenario, the calculated total gain of the feedbacks within the carbon cycle appears to be negative, a result of the dominant role of the fertilization feedback. This study also shows that if temperature feedbacks on methane emissions from wetlands, rice paddies, and hydrates do materialize, methane concentrations might be increased by 30% by 2100. 70 refs., 17 figs., 7 tabs.
Modelling gait transition in two-legged animals
NASA Astrophysics Data System (ADS)
Pinto, Carla M. A.; Santos, Alexandra P.
2011-12-01
The study of locomotor patterns has been a major research goal in the last decades. Understanding how intralimb and interlimb coordination works out so well in animals' locomotion is a hard and challenging task. Many models have been proposed to model animal's rhythms. These models have also been applied to the control of rhythmic movements of adaptive legged robots, namely biped, quadruped and other designs. In this paper we study gait transition in a central pattern generator (CPG) model for bipeds, the 4-cells model. This model is proposed by Golubitsky, Stewart, Buono and Collins and is studied further by Pinto and Golubitsky. We briefly resume the work done by Pinto and Golubitsky. We compute numerically gait transition in the 4-cells CPG model for bipeds. We use Morris-Lecar equations and Wilson-Cowan equations as the internal dynamics for each cell. We also consider two types of coupling between the cells: diffusive and synaptic. We obtain secondary gaits by bifurcation of primary gaits, by varying the coupling strengths. Nevertheless, some bifurcating branches could not be obtained, emphasizing the fact that despite analytically those bifurcations exist, finding them is a hard task and requires variation of other parameters of the equations. We note that the type of coupling did not influence the results.
Novel, discontinuous polaron transition in a two-band model
NASA Astrophysics Data System (ADS)
Moeller, Mirko M.; Sawatzky, George A.; Berciu, Mona
The coupling of charge carriers (electrons or holes) to phonons leads to the formation of a polaron, a coherent quasi-particle consisting of the charge carrier and the cloud of phonons surrounding it and moving coherently with it. Here we present exact diagonalization and momentum average approximation results for the single polaron properties of a two-band model with phonon modulated hopping, inspired by the perovskite BaBiO3. For large coupling we find that the ground state momentum changes discontinuously from k = π to k = 0 . Such sharp transitions of the polaron's ground state properties cannot occur in the well-studied models of the Holstein or Fröhlich type in which the carrier-phonon coupling modulates the on-site energies. However, they can occur in models where the carrier-phonon coupling modulates the hopping integrals such as the SSH model for which a similar yet smooth transition of the ground state momentum was recently shown to exist. We compare our findings to the SSH model and point out qualitative differences which we believe to be due to the two band nature of our model versus the single band SSH model. This work was supported by NSERC, QMI and the UBC 4YF.
NASA Astrophysics Data System (ADS)
Ceballos-Núñez, Verónika; Richardson, Andrew; Sierra, Carlos
2017-04-01
was 50 years faster than for the model without storage. These results suggest that ages and transit times, which can be indirectly measured using isotope tracers, serve as important diagnostics of model structure and could largely help to reduce uncertainties in model predictions. Furthermore, by considering age and transit times of C in vegetation compartments as distributions, not only their mean values, we obtain additional insights on the temporal dynamics of carbon use, storage, and allocation to plant parts, which not only depends on the rate at which this C is transferred in and out of the compartments, but also on the stochastic nature of the process itself.
NASA Astrophysics Data System (ADS)
Hess, D. W.
1986-05-01
Radiofrequency (rf) discharges have been used to deposit films of tungsten, molybdenum and titanium silicide. As-deposited tungsten films, from tungsten hexafluoride and hydrogen source gases, were metastable (beta W), with significant (>1 atomic percent) fluorine incorporation. Film resistivities were 40-55 micro ohm - cm due to the beta W, but dropped to about 8 micro ohm cm after a short heat treatment at 700 C which resulted in a phase transition to alpha W (bcc form). The high resistivity (>10,000 micro ohm) associated with molybdenum films deposited from molybdenum hexafluoride and hydrogen appeared to be a result of the formation of molybdenum trifluoride in the deposited material. Titanium silicide films formed from a discharge of titanium tetrachloride, silane, and hydrogen, displayed resistivities of about 150 micro ohm cm, due to small amounts of oxygen and chlorine incorporated during deposition. Plasma etching studies of tungsten films with fluorine containing gases suggest that the etchant species for tungsten in these discharges are fluorine atoms.
Employment, Production and Consumption model: Patterns of phase transitions
NASA Astrophysics Data System (ADS)
Lavička, H.; Lin, L.; Novotný, J.
2010-04-01
We have simulated the model of Employment, Production and Consumption (EPC) using Monte Carlo. The EPC model is an agent based model that mimics very basic rules of industrial economy. From the perspective of physics, the nature of the interactions in the EPC model represents multi-agent interactions where the relations among agents follow the key laws for circulation of capital and money. Monte Carlo simulations of the stochastic model reveal phase transition in the model economy. The two phases are the phase with full unemployment and the phase with nearly full employment. The economy switches between these two states suddenly as a reaction to a slight variation in the exogenous parameter, thus the system exhibits strong non-linear behavior as a response to the change of the exogenous parameters.
PHOTOMETRIC AND SPECTRAL SIGNATURES OF THREE-DIMENSIONAL MODELS OF TRANSITING GIANT EXOPLANETS
Burrows, A.; Spiegel, D. S.; Rauscher, E.; Menou, K. E-mail: dsp@astro.princeton.ed E-mail: kristen@astro.columbia.ed
2010-08-10
Using a three-dimensional general circulation model, we create dynamical model atmospheres of a representative transiting giant exoplanet, HD 209458b. We post-process these atmospheres with an opacity code to obtain transit radius spectra during the primary transit. Using a spectral atmosphere code, we integrate over the face of the planet seen by an observer at various orbital phases and calculate light curves as a function of wavelength and for different photometric bands. The products of this study are generic predictions for the phase variations of a zero-eccentricity giant planet's transit spectrum and of its light curves. We find that for these models the temporal variations in all quantities and the ingress/egress contrasts in the transit radii are small (<1.0%). Moreover, we determine that the day/night contrasts and phase shifts of the brightness peaks relative to the ephemeris are functions of photometric band. The J, H, and K bands are shifted most, while the IRAC bands are shifted least. Therefore, we verify that the magnitude of the downwind shift in the planetary 'hot spot' due to equatorial winds is strongly wavelength dependent. The phase and wavelength dependence of light curves, as well as the associated day/night contrasts, can be used to constrain the circulation regime of irradiated giant planets and to probe different pressure levels of a hot Jupiter atmosphere. We posit that though our calculations focus on models of HD 209458b, similar calculations for other transiting hot Jupiters in low-eccentricity orbits should yield transit spectra and light curves of a similar character.
Specificity in Transition State Binding: The Pauling Model Revisited
Amyes, Tina L.; Richard, John P.
2013-01-01
Linus Pauling proposed that the large rate accelerations for enzymes are due to the high specificity of the protein catalyst for binding the reaction transition state. The observation that stable analogs of the transition states for enzymatic reactions often act as tight-binding binding inhibitors provided early support for this simple and elegant proposal. We review experimental results which support the proposal that Pauling’s model provides a satisfactory explanation for the rate accelerations for many heterolytic enzymatic reactions through high energy reaction intermediates, such as proton transfer and decarboxylation. Specificity in transition state binding is obtained when the total intrinsic binding energy of the substrate is significantly larger than the binding energy observed at the Michaelis complex. The results of recent studies to characterize the specificity in binding of the enolate oxygen at the transition state for the 1,3-isomerization reaction catalyzed by ketosteroid isomerase are reviewed. Interactions between pig heart succinyl-CoA:3-oxoacid coenzyme A transferase (SCOT) and the nonreacting portions of CoA are responsible for a rate increase of 3 × 1012-fold, which is close to the estimated total 5 × 1013-fold enzymatic rate acceleration. Studies that partition the interactions between SCOT and CoA into their contributing parts are reviewed. Interactions of the protein with the substrate phosphodianion group provide a ca. 12 kcal/mol stabilization of the transition state for the reactions catalyzed by triosephosphate isomerase, orotidine 5′-monophosphate decarboxylase and α-glycerol phosphate dehydrogenase. The interactions of these enzymes with the substrate piece phosphite dianion provide a 6 – 8 kcal/mol stabilization of the transition state for reaction of the appropriate truncated substrate. Enzyme activation by phosphite dianion reflects the higher dianion affinity for binding to the enzyme-transition state complex compared
A nursing information model process for interoperability.
Chow, Marilyn; Beene, Murielle; O'Brien, Ann; Greim, Patricia; Cromwell, Tim; DuLong, Donna; Bedecarré, Diane
2015-05-01
The ability to share nursing data across organizations and electronic health records is a key component of improving care coordination and quality outcomes. Currently, substantial organizational and technical barriers limit the ability to share and compare essential patient data that inform nursing care. Nursing leaders at Kaiser Permanente and the U.S. Department of Veterans Affairs collaborated on the development of an evidence-based information model driven by nursing practice to enable data capture, re-use, and sharing between organizations and disparate electronic health records. This article describes a framework with repeatable steps and processes to enable the semantic interoperability of relevant and contextual nursing data. Hospital-acquired pressure ulcer prevention was selected as the prototype nurse-sensitive quality measure to develop and test the model. In a Health 2.0 Developer Challenge program from the Office of the National Coordinator for Health, mobile applications implemented the model to help nurses assess the risk of hospital-acquired pressure ulcers and reduce their severity. The common information model can be applied to other nurse-sensitive measures to enable data standardization supporting patient transitions between care settings, quality reporting, and research. © The Author 2015. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Energy efficient engine: Turbine transition duct model technology report
NASA Technical Reports Server (NTRS)
Leach, K.; Thurlin, R.
1982-01-01
The Low-Pressure Turbine Transition Duct Model Technology Program was directed toward substantiating the aerodynamic definition of a turbine transition duct for the Energy Efficient Engine. This effort was successful in demonstrating an aerodynamically viable compact duct geometry and the performance benefits associated with a low camber low-pressure turbine inlet guide vane. The transition duct design for the flight propulsion system was tested and the pressure loss goal of 0.7 percent was verified. Also, strut fairing pressure distributions, as well as wall pressure coefficients, were in close agreement with analytical predictions. Duct modifications for the integrated core/low spool were also evaluated. The total pressure loss was 1.59 percent. Although the increase in exit area in this design produced higher wall loadings, reflecting a more aggressive aerodynamic design, pressure profiles showed no evidence of flow separation. Overall, the results acquired have provided pertinent design and diagnostic information for the design of a turbine transition duct for both the flight propulsion system and the integrated core/low spool.
Phase transitions in community detection: A solvable toy model
NASA Astrophysics Data System (ADS)
Ver Steeg, Greg; Moore, Cristopher; Galstyan, Aram; Allahverdyan, Armen
2014-05-01
Recently, it was shown that there is a phase transition in the community detection problem. This transition was first computed using the cavity method, and has been proved rigorously in the case of q = 2 groups. However, analytic calculations using the cavity method are challenging since they require us to understand probability distributions of messages. We study analogous transitions in the so-called “zero-temperature inference” model, where this distribution is supported only on the most likely messages. Furthermore, whenever several messages are equally likely, we break the tie by choosing among them with equal probability, corresponding to an infinitesimal random external field. While the resulting analysis overestimates the thresholds, it reproduces some of the qualitative features of the system. It predicts a first-order detectability transition whenever q > 2 (as opposed to q > 4 according to the finite-temperature cavity method). It also has a regime analogous to the “hard but detectable” phase, where the community structure can be recovered, but only when the initial messages are sufficiently accurate. Finally, we study a semisupervised setting where we are given the correct labels for a fraction ρ of the nodes. For q > 2, we find a regime where the accuracy jumps discontinuously at a critical value of ρ.
Joint Modeling of Transitional Patterns of Alzheimer's Disease
Liu, Wei; Zhang, Bo; Zhang, Zhiwei; Zhou, Xiao-Hua
2013-01-01
While the experimental Alzheimer's drugs recently developed by pharmaceutical companies failed to stop the progression of Alzheimer's disease, clinicians strive to seek clues on how the patients would be when they visit back next year, based upon the patients' current clinical and neuropathologic diagnosis results. This is related to how to precisely identify the transitional patterns of Alzheimer's disease. Due to the complexities of the diagnosis of Alzheimer's disease, the condition of the disease is usually characterized by multiple clinical and neuropathologic measurements, including Clinical Dementia Rating (CDRGLOB), Mini-Mental State Examination (MMSE), a score derived from the clinician judgement on neuropsychological tests (COGSTAT), and Functional Activities Questionnaire (FAQ). In this research article, we investigate a class of novel joint random-effects transition models that are used to simultaneously analyze the transitional patterns of multiple primary measurements of Alzheimer's disease and, at the same time, account for the association between the measurements. The proposed methodology can avoid the bias introduced by ignoring the correlation between primary measurements and can predict subject-specific transitional patterns. PMID:24073268
Modeling Stem Cell Induction Processes
Grácio, Filipe; Cabral, Joaquim; Tidor, Bruce
2013-01-01
Technology for converting human cells to pluripotent stem cell using induction processes has the potential to revolutionize regenerative medicine. However, the production of these so called iPS cells is still quite inefficient and may be dominated by stochastic effects. In this work we build mass-action models of the core regulatory elements controlling stem cell induction and maintenance. The models include not only the network of transcription factors NANOG, OCT4, SOX2, but also important epigenetic regulatory features of DNA methylation and histone modification. We show that the network topology reported in the literature is consistent with the observed experimental behavior of bistability and inducibility. Based on simulations of stem cell generation protocols, and in particular focusing on changes in epigenetic cellular states, we show that cooperative and independent reaction mechanisms have experimentally identifiable differences in the dynamics of reprogramming, and we analyze such differences and their biological basis. It had been argued that stochastic and elite models of stem cell generation represent distinct fundamental mechanisms. Work presented here suggests an alternative possibility that they represent differences in the amount of information we have about the distribution of cellular states before and during reprogramming protocols. We show further that unpredictability and variation in reprogramming decreases as the cell progresses along the induction process, and that identifiable groups of cells with elite-seeming behavior can come about by a stochastic process. Finally we show how different mechanisms and kinetic properties impact the prospects of improving the efficiency of iPS cell generation protocols. PMID:23667423
Prediction of hemoglobin in blood donors using a latent class mixed-effects transition model.
Nasserinejad, Kazem; van Rosmalen, Joost; de Kort, Wim; Rizopoulos, Dimitris; Lesaffre, Emmanuel
2016-02-20
Blood donors experience a temporary reduction in their hemoglobin (Hb) value after donation. At each visit, the Hb value is measured, and a too low Hb value leads to a deferral for donation. Because of the recovery process after each donation as well as state dependence and unobserved heterogeneity, longitudinal data of Hb values of blood donors provide unique statistical challenges. To estimate the shape and duration of the recovery process and to predict future Hb values, we employed three models for the Hb value: (i) a mixed-effects models; (ii) a latent-class mixed-effects model; and (iii) a latent-class mixed-effects transition model. In each model, a flexible function was used to model the recovery process after donation. The latent classes identify groups of donors with fast or slow recovery times and donors whose recovery time increases with the number of donations. The transition effect accounts for possible state dependence in the observed data. All models were estimated in a Bayesian way, using data of new entrant donors from the Donor InSight study. Informative priors were used for parameters of the recovery process that were not identified using the observed data, based on results from the clinical literature. The results show that the latent-class mixed-effects transition model fits the data best, which illustrates the importance of modeling state dependence, unobserved heterogeneity, and the recovery process after donation. The estimated recovery time is much longer than the current minimum interval between donations, suggesting that an increase of this interval may be warranted. Copyright © 2015 John Wiley & Sons, Ltd.
Modeling pellet impact drilling process
NASA Astrophysics Data System (ADS)
Kovalyov, A. V.; Ryabchikov, S. Ya; Isaev, Ye D.; Ulyanova, O. S.
2016-03-01
The paper describes pellet impact drilling which could be used to increase the drilling speed and the rate of penetration when drilling hard rocks. Pellet impact drilling implies rock destruction by metal pellets with high kinetic energy in the immediate vicinity of the earth formation encountered. The pellets are circulated in the bottom hole by a high velocity fluid jet, which is the principle component of the ejector pellet impact drill bit. The experiments conducted has allowed modeling the process of pellet impact drilling, which creates the scientific and methodological basis for engineering design of drilling operations under different geo-technical conditions.
Relational Processes in Career Transition: Extending Theory, Research, and Practice
ERIC Educational Resources Information Center
Motulsky, Sue L.
2010-01-01
A growing body of work in relational theory and career decision making explores how relational processes, not just people's relationships but more broadly their connections to self, others, and society, inform career development and counseling. This article presents the results of a qualitative research study of midlife women in career transition…
Transitivity vs. intransitivity in decision making process - an example in quantum game theory
NASA Astrophysics Data System (ADS)
Makowski, Marcin
2009-06-01
We compare two different ways of quantum modification in a simple sequential game called Cat's Dilemma in the context of the debate on intransitive and transitive preferences. This kind of analysis can have essential meaning for research on artificial intelligence (some possibilities are discussed). Nature has both transitive and intransitive properties and perhaps quantum models will be more able to capture this dualism than the classical models. We also present an electoral interpretation of the game.
Windows to Other Worlds: Modeling Systems in Transit
NASA Astrophysics Data System (ADS)
Scott, Erin L.
We present light curves and best-fit models of three very different transiting systems: the extended ring system of J1407b, the transiting circumsecondary disk of OGLE-LMC-ECL-11893, and the transiting hot Neptune GJ 436b. We have performed model fits using chi² minimization on the light curves of each of these objects, and present conjectures as to their structures. For J1407, we find an extended flat debris disk of optical depth tau = 3 with four outer rings of optical depths tau1 = 0.1, tau2 = 0.9, tau3 = 0.5, and tau4 = 0.7 (with Ring 1 being the closest in to the main disk and Ring 4 being the farthest out), with the outermost ring extending to 45 RN⊙ . The disk is inclined at thetax = 5° along the line of sight and thetay = 10° orthogonal to the line of sight, with the secondary in an orbit of i = 89.964° (0.036° from edge-on, for our assumed period of 9862 days). For OGLE 11893, we find a flat debris disk of uniform optical depth tau = 1.8, with an inner radius of 26.2 RN⊙ , an outer radius of 45.8 RN⊙ , thetax = 2.0°, theta y = 7.0°, and an orbital inclination of i = 89.38°. For GJ 436 b, we find a planet with radius 4.19+/-0.17 RN⊕ in the photometric g band (4100-5500A), 3.95+/-0.39 RN⊕ in the H band (15000-18000A), and 3.94+/-0.39 RN⊕ in the K band (20000-24000A). The program evolved significantly over the course of its implementation. In addition to implementing the simplex fitting algorithm, I added rings to the debris disk and model the ability to vary the density power lay and dust opacity of the accretion disk, in addition to taking the environmental influences such as Hill radius and silicate dust sublimation radius into account. The program was written first in C++ and later re-written in Python in order to take advantage of a pre-existing planetary transit model (Parviainen, 2015), and can model transit phenomena ranging from eclipsing binaries to circumsecondary disks.
Center for Modeling of Turbulence and Transition: Research Briefs, 1995
NASA Technical Reports Server (NTRS)
1995-01-01
This research brief contains the progress reports of the research staff of the Center for Modeling of Turbulence and Transition (CMOTT) from July 1993 to July 1995. It also constitutes a progress report to the Institute of Computational Mechanics in Propulsion located at the Ohio Aerospace Institute and the Lewis Research Center. CMOTT has been in existence for about four years. In the first three years, its main activities were to develop and validate turbulence and combustion models for propulsion systems, in an effort to remove the deficiencies of existing models. Three workshops on computational turbulence modeling were held at LeRC (1991, 1993, 1994). At present, CMOTT is integrating the CMOTT developed/improved models into CFD tools which can be used by the propulsion systems community. This activity has resulted in an increased collaboration with the Lewis CFD researchers.
Strong coupling phase transitions in supersymmetric grand unified models
NASA Astrophysics Data System (ADS)
Reiss, David B.
1985-08-01
The determination of the temperature at which a grand unified model becomes strongly coupled should be based upon a physical quantity such as the screening lenght rather than the ad hoc condition that the opening becomes O(1). I use a recent calculation of this screening length (the inverse electric mass) to discuss some aspects of strong coupling behavior in the cosmology of supersymmetric grand unified models. Significant effects may occur in a variety of cases. An interesting possibilit is that there may be a pair of confining and deconfining phase transitions at a temperature as low as the supersymmetry breaking scale (O(TeV)). I present illustrative examples for these effects.
The impacts of physical processes on oxygen variations in the North Sea-Baltic Sea transition zone
NASA Astrophysics Data System (ADS)
Jonasson, L.; Wan, Z.; Hansen, J. H. S.; She, J.
2011-07-01
The bottom water of the North Sea-Baltic Sea transition zone suffers from seasonal hypoxia, usually during late summer and autumn. These hypoxic events are critical for the benthic ecosystems and the concentration of dissolved oxygen is an important measure of the water quality. However, to model the subsurface dissolved oxygen is a major challenge, especially in estuaries and coastal regions. In this study a simple oxygen consumption model is coupled to a 3-D hydrodynamical model in order to analyse oxygen variations in the transition zone. The benthic and pelagic consumption of oxygen is modelled as a function of water temperature and oxygen concentration. A quantitative assessment of the model demonstrates that the model is able to resolve both seasonal and interannual variations in dissolved oxygen. Results from several experimental simulations highlight the importance of physical processes in the regulation of dissolved oxygen. Advective oxygen transport and wind induced mixing are two key processes that control the extent of hypoxia in the transition zone.
The impacts of physical processes on oxygen variations in the North Sea-Baltic Sea transition zone
NASA Astrophysics Data System (ADS)
Jonasson, L.; Hansen, J. L. S.; Wan, Z.; She, J.
2012-01-01
The bottom water of the North Sea-Baltic Sea transition zone suffers from seasonal hypoxia, usually during late summer and autumn. These hypoxic events are critical for the benthic ecosystems and the concentration of dissolved oxygen is an important measure of the water quality. However, to model the subsurface dissolved oxygen is a major challenge, especially in estuaries and coastal regions. In this study a simple oxygen consumption model is coupled to a 3-D hydrodynamical model in order to analyse oxygen variations in the transition zone. The benthic and pelagic consumption of oxygen is modelled as a function of water temperature and oxygen concentration. A quantitative assessment of the model demonstrates that the model is able to resolve both seasonal and interannual variations in dissolved oxygen. Results from several experimental simulations highlight the importance of physical processes in the regulation of dissolved oxygen. Advective oxygen transport and wind induced mixing are two key processes that control the extent of hypoxia in the transition zone.
Transition Implementation Guide. Instructor Materials.
ERIC Educational Resources Information Center
Boyer-Stephens, Arden, Ed.
This transition model, called Guiding Education toward Adult Roles for Success (GEARS), provides a comprehensive framework from which transition services and programs can evolve. Three components of transition services are considered: transition partners, the transition process, and adult outcomes. After an introduction, the report's second…
Collapse models and perceptual processes
NASA Astrophysics Data System (ADS)
Carlo Ghirardi, Gian; Romano, Raffaele
2014-04-01
Theories including a collapse mechanism have been presented various years ago. They are based on a modification of standard quantum mechanics in which nonlinear and stochastic terms are added to the evolution equation. Their principal merits derive from the fact that they are mathematically precise schemes accounting, on the basis of a unique universal dynamical principle, both for the quantum behavior of microscopic systems as well as for the reduction associated to measurement processes and for the classical behavior of macroscopic objects. Since such theories qualify themselves not as new interpretations but as modifications of the standard theory they can be, in principle, tested against quantum mechanics. Recently, various investigations identifying possible crucial test have been discussed. In spite of the extreme difficulty to perform such tests it seems that recent technological developments allow at least to put precise limits on the parameters characterizing the modifications of the evolution equation. Here we will simply mention some of the recent investigations in this direction, while we will mainly concentrate our attention to the way in which collapse theories account for definite perceptual process. The differences between the case of reductions induced by perceptions and those related to measurement procedures by means of standard macroscopic devices will be discussed. On this basis, we suggest a precise experimental test of collapse theories involving conscious observers. We make plausible, by discussing in detail a toy model, that the modified dynamics can give rise to quite small but systematic errors in the visual perceptual process.
Model reduction and feedback control of transitional channel flow
NASA Astrophysics Data System (ADS)
Ilak, Milos
This dissertation examines the use of reduced-order models for design of linear feedback controllers for fluid flows. The focus is on transitional channel flow, a canonical shear flow case with a simple geometry yet complex dynamics. Reduced-order models of the linearized Navier-Stokes equations, which describe the evolution of perturbations in transitional channel flow, are computed using two methods for snapshot-based balanced truncation, Balanced Proper Orthogonal Decomposition (BPOD) and Eigensystem Realization Algorithm (ERA). The performance of these models in feedback control is evaluated in both linearized and nonlinear Direct Numerical Simulations (DNS) of channel flow. The first part of the dissertation describes the application of BPOD to very large systems, and the detailed evaluation of the resulting reduced-order models. Exact balanced truncation, a standard method from control theory, is not computationally tractable for very large systems, such as those typically encountered in fluid flow simulations. The BPOD method, introduced by Rowley (2005), provides a close approximation. We first show that the approximation is indeed close by applying the method to a 1-D linear perturbation to channel flow at a single spatial wavenumber pair, for which exact balanced truncation is tractable. Next, as the first application of BPOD to a very high-dimensional linear system, we show that reduced-order BPOD models of a localized 3-D perturbation capture the dynamics very well. Moreover, the BPOD models significantly outperform standard Proper Orthogonal Decomposition (POD) models, as illustrated by a striking example where models using the POD modes that capture most of the perturbation energy fail to capture the perturbation dynamics. Next, reduced-order models of a complete control system for linearized channel flow are obtained using ERA, a computationally efficient method that results in the same reduced-order models as BPOD. Linear Quadratic Gaussian (LQG
Multiple phase transitions in extended hard-core lattice gas models in two dimensions.
Nath, Trisha; Rajesh, R
2014-07-01
We study the k-NN hard-core lattice gas model in which the first k next-nearest-neighbor sites of a particle are excluded from occupation by other particles on a two-dimensional square lattice. This model is the lattice version of the hard-disk system with increasing k corresponding to decreasing lattice spacing. While the hard-disk system is known to undergo a two-step freezing process with increasing density, the lattice model has been known to show only one transition. Here, based on Monte Carlo simulations and high-density expansions of the free energy and density, we argue that for k = 4,10,11,14,⋯, the lattice model undergoes multiple transitions with increasing density. Using Monte Carlo simulations, we confirm the same for k = 4,...,11. This, in turn, resolves an existing puzzle as to why the 4-NN model has a continuous transition against the expectation of a first-order transition.
Modeling liquid-liquid phase transitions and quasicrystal formation
NASA Astrophysics Data System (ADS)
Skibinsky, Anna
In this thesis, studies which concern two different subjects related to phase transitions in fluids and crystalline solids are presented. Condensed matter formation, structure, and phase transitions are modeled using molecular dynamics simulations of simple discontinuous potentials with attractive and repulsive interactions. Novel phase diagrams are proposed for quasicrystals, crystals, and liquids. In the first part of the thesis, the formation of a quasicrystal in a two dimensional monodisperse system is investigated using molecular dynamics simulations of hard sphere particles interacting via a two-dimensional square-well potential. It is found that for certain values of the square-well parameters more than one stable crystalline phase can form. By quenching the liquid phase at a very low temperature, an amorphous phase is obtained. When this the amorphous phase is heated, a quasicrystalline structure with five-fold symmetry forms. From estimations of the Helmholtz potentials of the stable crystalline phases and of the quasicrystal, it is concluded that within a specific temperature range, the observed quasicrystal phase can be the stable phase. The second part of the thesis concerns a study of the liquid-liquid phase transition for a single-component system in three dimensions, interacting via an isotropic potential with a repulsive soft-core shoulder at short distance and an attractive well at an intermediate distance. The potential is similar to potentials used to describe such liquid systems as colloids, protein solutions, or liquid metals. It is shown that the phase diagram for such a potential can have two lines of first-order fluid-fluid phase transitions: one separating a gas and a low-density liquid (LDL), and another between the LDL and a high-density liquid (HDL). Both phase transition lines end in a critical point, a gas-LDL critical point and, depending on the potential parameters, either a gas-HDL critical point or a LDL-HDL critical point. A
Analysis of SPI drought class transitions using loglinear models
NASA Astrophysics Data System (ADS)
Moreira, Elsa E.; Paulo, Ana A.; Pereira, Luís S.; Mexia, João T.
2006-11-01
SummaryA total period of 67 years of standardized precipitation index (SPI) data sets were divided into three periods of 22/23 years and a loglinear modeling approach has been used to investigate differences relative to drought class transitions among these three periods. The study was applied to several locations in Alentejo region, southern Portugal, and four drought severity classes were considered. The drought class transitions were computed for the three periods to form a 3-dimensional contingency table. The application of loglinear modeling to these data allowed the comparison of the three periods in terms of probabilities of transition between drought classes in order to detect a possible trend in time evolution of droughts which could be related to climate change. Results show that the drought behavior for the first and last periods is similar, both showing worse drought events than the second. If just the second and third periods were compared one could conclude that droughts were aggravating and easily this behavior could be attributed to climate change, supporting the common assumption that a trend for progressive aggravation of drought occurrence exists. Therefore, results are more consistent with the existence of a long-term natural periodicity; however, this hypothesis should be tested using longer time series.
Modeling Intracellular Oscillations and Polarity Transition in Fission Yeast
NASA Astrophysics Data System (ADS)
Drake, Tyler; Das, Maitreyi; Verde, Fulvia; Vavylonis, Dimitrios
2011-03-01
Fission yeast, a pill-shaped model organism, restricts growth to its tips. These cells maintain an asymmetric growth state, growing at only one tip, until they meet length and cell-cycle requirements. With these met, they grow at both. The mechanism of this transition, new-end take-off (NETO), remains unclear. We find that NETO occurs due to long-range competition for fast-diffusing signaling protein Cdc42 between the old and new tips. From experimental results, we suppose that symmetric tips compete for Cdc42, which triggers growth. We describe a symmetric growth model based on competition between tips. This model restricts short cells to monopolar states while allowing longer cells to be bipolar. Autocatalytic Cdc42 recruiting at both cells tips leads to broken symmetry, and the recruiting cuts off as tip Cdc42 levels saturate. Non-linear differential equations describe the model, with stable attractors indicating valid distributions. Linear stability analysis and numerical methods identify stable fixed points over a twofold increase in cell length. The model reproduces qualitative behavior of the organism. We show that observed pole-to-pole Cdc42 oscillations may facilitate the polarity transition and discuss their relationship to the Min system in E. Coli.
Human Inferences about Sequences: A Minimal Transition Probability Model
2016-01-01
The brain constantly infers the causes of the inputs it receives and uses these inferences to generate statistical expectations about future observations. Experimental evidence for these expectations and their violations include explicit reports, sequential effects on reaction times, and mismatch or surprise signals recorded in electrophysiology and functional MRI. Here, we explore the hypothesis that the brain acts as a near-optimal inference device that constantly attempts to infer the time-varying matrix of transition probabilities between the stimuli it receives, even when those stimuli are in fact fully unpredictable. This parsimonious Bayesian model, with a single free parameter, accounts for a broad range of findings on surprise signals, sequential effects and the perception of randomness. Notably, it explains the pervasive asymmetry between repetitions and alternations encountered in those studies. Our analysis suggests that a neural machinery for inferring transition probabilities lies at the core of human sequence knowledge. PMID:28030543
Modeling texture transitions in cholesteric liquid crystal droplets
NASA Astrophysics Data System (ADS)
Selinger, Robin; Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Konya, Andrew
2012-02-01
Cholesteric liquid crystals can be switched reversibly between planar and focal-conic textures, a property enabling their application in bistable displays, liquid crystal writing tablets, e-books, and color switching ``e-skins.'' To explore voltage-pulse induced switching in cholesteric droplets, we perform simulation studies of director dynamics in three dimensions. Electrostatics calculations are solved at each time step using an iterative relaxation method. We demonstrate that as expected, a low amplitude pulse drives the transition from planar to focal conic, while a high amplitude pulse drives the transition from focal conic back to the planar state. We use the model to explore the effects of droplet shape, aspect ratio, and anchoring conditions, with the goal of minimizing both response time and energy consumption.
Dynamical phase transition in the open Dicke model
Klinder, Jens; Keßler, Hans; Wolke, Matthias; Mathey, Ludwig; Hemmerich, Andreas
2015-01-01
The Dicke model with a weak dissipation channel is realized by coupling a Bose–Einstein condensate to an optical cavity with ultranarrow bandwidth. We explore the dynamical critical properties of the Hepp–Lieb–Dicke phase transition by performing quenches across the phase boundary. We observe hysteresis in the transition between a homogeneous phase and a self-organized collective phase with an enclosed loop area showing power-law scaling with respect to the quench time, which suggests an interpretation within a general framework introduced by Kibble and Zurek. The observed hysteretic dynamics is well reproduced by numerically solving the mean-field equation derived from a generalized Dicke Hamiltonian. Our work promotes the understanding of nonequilibrium physics in open many-body systems with infinite range interactions. PMID:25733892
Werner, Gerhard
2009-04-01
In this theoretical and speculative essay, I propose that insights into certain aspects of neural system functions can be gained from viewing brain function in terms of the branch of Statistical Mechanics currently referred to as "Modern Critical Theory" [Stanley, H.E., 1987. Introduction to Phase Transitions and Critical Phenomena. Oxford University Press; Marro, J., Dickman, R., 1999. Nonequilibrium Phase Transitions in Lattice Models. Cambridge University Press, Cambridge, UK]. The application of this framework is here explored in two stages: in the first place, its principles are applied to state transitions in global brain dynamics, with benchmarks of Cognitive Neuroscience providing the relevant empirical reference points. The second stage generalizes to suggest in more detail how the same principles could also apply to the relation between other levels of the structural-functional hierarchy of the nervous system and between neural assemblies. In this view, state transitions resulting from the processing at one level are the input to the next, in the image of a 'bucket brigade', with the content of each bucket being passed on along the chain, after having undergone a state transition. The unique features of a process of this kind will be discussed and illustrated.
Pérez-López, Jordi; Ceberio-Hualde, Leticia; García Morillo, José Salvador; Grau-Junyent, Josep M; Hermida Ameijeiras, Álvaro; López-Rodríguez, Mónica; Morales-Conejo, Montserrat; Nava Mateos, Juan José; Aldámiz Echevarri Azuara, Luis José; Campistol, Jaume; Couce, M Luz; García-Silva, María Teresa; González Gutiérrez-Solana, Luis; Del Toro, Mireia
2016-12-02
The transition process from paediatric to adult care is a subject of great interest in recent years, especially in chronic diseases with childhood onset, such as inborn errors of metabolism (IEM). Advances in diagnosis and treatment of these diseases have improved their prognosis, with a high number of patients with IEM who currently reach adult age and need to be attended to by non-paediatric professionals. The objective of this work is to establish action guidelines so that the specialists involved can guarantee a successful transition of these patients' healthcare. After carrying out a bibliographic review of the subject, the authors, beginning with their own experience, produced an initial document which was subjected to successive debates until the final document was obtained. The consensus recommendation was decided by the majority in case of criterion discrepancy. A series of recommendations are presented for the best clinical management of the transitions of care of patients with IEM from the paediatric to adult care setting in order to achieve the best results in this process given the special characteristics of this patient subgroup and the main difficulties entailed in the transition process. The role of the internal medicine doctor in this transition process and correct interrelation with the paediatric and social setting is stressed. Furthermore, actions and attitudes are suggested to improve the quality of said transition. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.
Development of a Transition Process Scale for High-risk Infant’s Caregiver
YU, Mi
2016-01-01
Background: Transition into parenthood is a major developmental life event and is very significant because development in infanthood is affected by the transition process of mothers parenting an infant. This study aimed to develop the assessment tool for transition process of high risk infant’s caregiver in Korea. Methods: The participants were 246 mothers of premature infant born with gestational age (< 37 weeks) or low birth weight (< 2500 gm), of less than 24 months of age. Preliminary items were derived from transition process scale for parent of children with autism. Factor analysis was performed to test construct validity of the scale, the correlation between transition processes and parenting efficacy was used for testing predictive validity. Results: The final scale was composed of 23 items divided into 5 factors: wandering (7 items), devotion (5 items), acceptance (4 items), denial (4 items), frustration (3 items). The total variance for validity described by the 5 factors was 60.8% and the reliability of the scale was total Cronbach’s α 0.90 and wandering 0.85, devotion 0.78, acceptance 0.72, denial 0.72, and frustration 0.71. Correlation between transition process and parenting efficacy was statistically significant; wandering(r=−0.61, P <.001), devotion (r=−0.60, P<.001), acceptance (r=0.30, P <.001), denial (r=−0.31, P <.001) and frustration (r= −0.27, P <.001). Conclusion: This final assessment scale will be used to investigate high-risk infant caregiver’s transition process and provide basic data for program development to provide differentiated support and care at each process. PMID:27114980
NUMERICAL MODELING OF FINE SEDIMENT PHYSICAL PROCESSES.
Schoellhamer, David H.
1985-01-01
Fine sediment in channels, rivers, estuaries, and coastal waters undergo several physical processes including flocculation, floc disruption, deposition, bed consolidation, and resuspension. This paper presents a conceptual model and reviews mathematical models of these physical processes. Several general fine sediment models that simulate some of these processes are reviewed. These general models do not directly simulate flocculation and floc disruption, but the conceptual model and existing functions are shown to adequately model these two processes for one set of laboratory data.
Transition and separation process in brine channels formation
Berti, Alessia; Bochicchio, Ivana; Fabrizio, Mauro
2016-02-15
In this paper, we discuss the formation of brine channels in sea ice. The model includes a time-dependent Ginzburg-Landau equation for the solid-liquid phase change, a diffusion equation of the Cahn-Hilliard kind for the solute dynamics, and the heat equation for the temperature change. The macroscopic motion of the fluid is also considered, so the resulting differential system couples with the Navier-Stokes equation. The compatibility of this system with the thermodynamic laws and a maximum theorem is proved.
The Use of Transitional Care Models in Patients With Stroke.
Puhr, M Irene; Thompson, Hilaire J
2015-08-01
Transitional care (TC) models are used to reduce adverse outcomes and hospital readmissions. This article reviews the scholarly literature to identify TC models that have been used successfully in patients with stroke. Literature in CINAHL, PubMed, and the Cochrane Database of Systematic Reviews from January 2000 to June 2013 was searched using the keywords "transitional care," "discharge planning," "care-coordination," "continuity of care," "follow-up after discharge," and "stroke." Web sites of established TC models were also reviewed to identify additional studies meeting review criteria. To be included in the review, studies must have been written in the English language and focused on adult patients aged 19 years and older with stroke, discharged from the hospital or acute rehabilitation facility to home. TC interventions were defined as those that employed one or more of the National Transitions of Care Coalition intervention categories: medication management, transition planning, patient and family engagement or education, information transfer, follow-up care, healthcare provider engagement, or shared accountability across providers and organizations (National Transitions of Care Coalition, 2011). The author examined the title and abstract of each study for eligibility against stated criteria. Thirteen articles representing 11 studies were found to meet the inclusion criteria. In the identified studies, TC was compared with usual care; however, what constituted usual care was not consistently elucidated. Fewer than half of the studies reported significantly improved results on selected outcomes. Across all the studies, TC did not result in a reported significant decrease in emergency department visits or hospital readmission rates. There was substantive heterogeneity in (a) intervention providers, (b) interventions used in TC, and (c) measures of outcome identified. Six of the 13 studies were identified as having successful interventions. Some evidence
[The health transition in Mexico: a proper model].
Frenk, J; Bobadilla, J L; Sepulveda, J
1988-01-01
An intense process of epidemiological transition due to the change in mortality has superseded the eras of pestilence, pandemic disease, and chronic-degenerative diseases in Mexico. But the change has not been uniformly progressive, for instance, recurrence of malaria after its eradication indicates reverse transition. Enteritis, influenza, and pneumonia ranked among the primary causes of death between 1955 and 1957, whereas by 1980 heart disease became the leading cause followed by accidents, influenza, and enteritis. A polarized epidemiology can be observed in the post-transitional period: the poorest segment of the population continues to have high rates of infections and nutritional deficiencies. According to Mexican health service mortality data gathered in 1981 industrial workers had similar rates of infectious and chronic-degenerative diseases (11.7% and 12.0%, respectively), while agricultural workers had high rates of infectious and parasitic diseases (26.7%) and a low rate of chronic-degenerative diseases (5.6%). Illnesses of perinatal origin were also higher in agricultural workers than in industrial workers (26.1% vs. 13.7%), whereas circulatory diseases were more frequent among industrial workers (14.2% vs. 7.2%). It is the task of the health care system to meet the challenge of the complexity of this epidemiological mosaic.
The 3α Process Studied Through Pair Conversion Transitions from the Hoyle State in 12C
NASA Astrophysics Data System (ADS)
Eriksen, T. K.; Kibédi, T.; Reed, M. W.; Stuchbery, A. E.; Akber, A.; de Vries, M.; Dowie, J.; Evitts, L. J.; Garnsworthy, A. B.; Gerathy, M.; Hota, S. S.; Lane, G. J.; Mitchell, A. J.; Palazzo, T.; Smallcombe, J.; Tornyi, T. G.
The E0 and E2 pair transitions from the Hoyle state have been measured, with the aim of deducing the radiative width and 3α reaction rate by a new approach. The 3α process is the only way carbon is synthesised in stars and is a bottleneck in stellar nucleosynthesis. The new method, which requires the ratio of the pair transitions, is expected to reduce the uncertainty from 10 to 5%. We recently observed the E2 pair transition for the first time, confirming the feasibility of the method. However, more statistics are needed to obtain a precise value for the radiative width.
Modelling Test of Autothermal Gasification Process Using CFD
NASA Astrophysics Data System (ADS)
Janoszek, Tomasz; Stańczyk, Krzysztof; Smoliński, Adam
2017-06-01
There are many complex physical and chemical processes, which take place among the most notable are the chemical reactions, mass and energy transport, and phase transitions. The process itself takes place in a block of coal, which properties are variable and not always easy to determine in the whole volume. The complexity of the phenomena results in the need for a construction of a complex model in order to study the process on the basis of simulation. In the present study attempts to develop a numerical model of the fixed bed coal gasification process in homogeneous solid block with a given geometry were mode. On the basis of analysis and description of the underground coal gasification simulated in the ex-situ experiment, a numerical model of the coal gasification process was developed. The model was implemented with the use of computational fluid dynamic CFD methods. Simulations were conducted using commercial numerical CFD code and the results were verified with the experimental data.
Baryon-to-Meson Transition Distribution Amplitudes: Formalism and Models
NASA Astrophysics Data System (ADS)
Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2017-03-01
In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.
Model of High Temperature Phase Transitions in Metals
NASA Astrophysics Data System (ADS)
Filippov, E. S.
2016-04-01
On the basis of the assumption of the electron density fluctuation at the band degradation, a calculation parameter (the radius R) of the half-width of the probability distribution over the coordinate R is identified at the level of the maximum electron density fluctuation (at a maximum of the Gaussian function). Based on an analysis of the crystallization process and high polymorphic transformations bcc → fcc, the reasons for the formation of bcc, fcc, hexagonal, and tetragonal structures from the liquid phase, as well as for the high temperature bcc → hcp transition in the solid phase are established using the calculated parameter (the radius R) in the solid and liquid phases.
Excitability, mixed-mode oscillations and transition to chaos in a stochastic ice ages model
NASA Astrophysics Data System (ADS)
Alexandrov, D. V.; Bashkirtseva, I. A.; Ryashko, L. B.
2017-03-01
Motivated by an important geophysical significance, we consider the influence of stochastic forcing on a simple three-dimensional climate model previously derived by Saltzman and Sutera. A nonlinear dynamical system governing three physical variables, the bulk ocean temperature, continental and marine ice masses, is analyzed in deterministic and stochastic cases. It is shown that the attractor of deterministic model is either a stable equilibrium or a limit cycle. We demonstrate that the process of continental ice melting occurs with a noise-dependent time delay as compared with marine ice melting. The paleoclimate cyclicity which is near 100 ky in a wide range of model parameters abruptly increases in the vicinity of a bifurcation point and depends on the noise intensity. In a zone of stable equilibria, the 3D climate model under consideration is extremely excitable. Even for a weak random noise, the stochastic trajectories demonstrate a transition from small- to large-amplitude stochastic oscillations (SLASO). In a zone of stable cycles, SLASO transitions are analyzed too. We show that such stochastic transitions play an important role in the formation of a mixed-mode paleoclimate scenario. This mixed-mode dynamics with the intermittency of large- and small-amplitude stochastic oscillations and coherence resonance are investigated via analysis of interspike intervals. A tendency of dynamic paleoclimate to abrupt and rapid glaciations and deglaciations as well as its transition from order to chaos with increasing noise are shown.
Applying Career Development Theories to the School-to-Work Transition Process.
ERIC Educational Resources Information Center
Lent, Robert W.; Worthington, Roger L.
1999-01-01
Career development theories do not typically highlight their relevance to the school-to-work transition process. This issue features articles that examine how several prominent career development theories (person-environment fit, social learning, developmental, and social cognitive) can be brought to bear on this process. Three discussants assess…
Epithelial-mesenchymal transition and senescence: two cancer-related processes are crossing paths
Smit, Marjon A.; Peeper, Daniel S.
2010-01-01
The epithelial-mesenchymal transition is involved in several physiological processes. However, it is also believed to contribute to cancer progression. Conversely, cellular senescence constitutes a failsafe program against cancer progression. Interestingly, EMT and senescence seem to cross paths, with several factors playing dominant roles in both settings. Here, we describe recent observations that link these important cellular processes. PMID:20975209
ERIC Educational Resources Information Center
Wharton, Donald P.; Corak, Kathleen A.
A case study was done of the possible role of strategic planning processes for smoothing the transition period experienced by colleges and universities when changes in top leadership occur. The study was conducted in a medium-sized midwestern state university that had begun, 3 years earlier, a strategic planning process which had been…
ERIC Educational Resources Information Center
Valentine, Jeffrey C.; Hirschy, Amy S.; Bremer, Christine D.; Novillo, Walter; Castellano, Marisa; Banister, Aaron
2009-01-01
This paper focuses on transition programs for youth to postsecondary education, broadly considered. It addresses the following questions: (1) What models or programs of transition exist? (2) On what basis can we say one transition program is more effective than another? In other words, how is successful transition defined? (3) How are…
Dynamical phase transitions in Hegselmann-Krause model of opinion dynamics and consensus
NASA Astrophysics Data System (ADS)
Slanina, F.
2011-01-01
The dynamics of the model of agents with limited confidence introduced by Hegselmann and Krause exhibits multiple well-separated regimes characterised by the number of distinct clusters in the stationary state. We present indications that there are genuine dynamical phase transitions between these regimes. The main indicator is the divergence of the average evolution time required to reach the stationary state. The slowdown close to the transition is connected with the emergence of the groups of mediator agents which are very small but have decisive role in the process of social convergence. More detailed study shows that the histogram of the evolution times is composed of several peaks. These peaks are unambiguously interpreted as corresponding to mediator groups consisting of one, two, three etc. agents. Detailed study reveals that each transition possesses also an internal fine structure.
Unified Dark Matter scalar field models with fast transition
Bertacca, Daniele; Bruni, Marco; Piattella, Oliver F.; Pietrobon, Davide E-mail: marco.bruni@port.ac.uk E-mail: davide.pietrobon@jpl.nasa.gov
2011-02-01
We investigate the general properties of Unified Dark Matter (UDM) scalar field models with Lagrangians with a non-canonical kinetic term, looking specifically for models that can produce a fast transition between an early Einstein-de Sitter CDM-like era and a later Dark Energy like phase, similarly to the barotropic fluid UDM models in JCAP01(2010)014. However, while the background evolution can be very similar in the two cases, the perturbations are naturally adiabatic in fluid models, while in the scalar field case they are necessarily non-adiabatic. The new approach to building UDM Lagrangians proposed here allows to escape the common problem of the fine-tuning of the parameters which plague many UDM models. We analyse the properties of perturbations in our model, focusing on the the evolution of the effective speed of sound and that of the Jeans length. With this insight, we can set theoretical constraints on the parameters of the model, predicting sufficient conditions for the model to be viable. An interesting feature of our models is that what can be interpreted as w{sub DE} can be < −1 without violating the null energy conditions.
Integrated modelling of transitions in mechanical conditions during casting and heat treatment
NASA Astrophysics Data System (ADS)
Thorborg, J.; Klinkhammer, J.; Heitzer, M.
2015-06-01
The mechanical material behaviour of a cast component changes significantly during casting and heat treatment. The big difference in temperature levels during the different process steps causes different deformation mechanisms to be active. The thermal gradients promote transient stresses that can lead to inelastic deformations, residual stresses and in some cases to defects in the final part. It is a big challenge to make a reasonable transition in the mechanical model, and hence material data, when modelling several different coupled process steps. It is important to use an integrated approach where the transition is included in the full load history of the part. When industrial examples are considered, the sequence of process steps typically also changes the thermal and mechanical boundary conditions significantly e.g. going from being mechanically constrained during casting to being supported point-wise during the heat treatment process. This change includes mapping of results and obtaining equilibrium in a new global system, where the further reaction forces from the supports must be handled with contact conditions to e.g. predict deformations due to gravity during solution heat treatment. The work presented in this paper is focused on modelling the mechanical fields, taking into account the changes in the mechanical material model at different temperature levels, and the transition in mechanical behaviour when the microstructure is changing during the different steps of the heat treatment process. The approach used is based on a unified model where creep effects are considered at high temperature and rate effects are included in general during cooling. Proposals are made to include cooling rate sensitivity, annealing and precipitation hardening via modification of mechanical properties in the different process steps.
Effects of ward rotation on subsequent transition processes of Japanese clinical nurses.
Fujino, Mitsuku; Nojima, Yoshiko
2005-03-01
The purpose of this study was to examine the experience of Japanese clinical nurses undertaking a ward rotation in a general hospital, and its effects on subsequent processes relating to: (i) perception of ward rotation; (ii) reactions to the ward transition process; and (iii) outcomes of ward rotation. In-depth interviews were conducted with 21 Japanese clinical nurses who had an average of 8.8 years (SD = 5.50) clinical experience. Findings indicated that participants experienced role overload, role incongruity and/or role underload, role overqualification, or role ambiguity in the new environment. These role stresses created critical emotional distress during the transition process. The high desire for career development facilitated the transition process, while lack of preparation inhibited the transition process. To facilitate smooth transition, well-prepared and structured supports based on reliable interpersonal relationships are necessary. The findings offer significant cues for effective ward rotation programs. The implication for nursing administrators is that appropriate ward rotations enhance confidence and promote effective role development in the new clinical setting.
Phase transition in a spatial Lotka-Volterra model
NASA Astrophysics Data System (ADS)
Szabó, György; Czárán, Tamás
2001-06-01
Spatial evolution is investigated in a simulated system of nine competing and mutating bacterium strains, which mimics the biochemical war among bacteria capable of producing two different bacteriocins (toxins) at most. Random sequential dynamics on a square lattice is governed by very symmetrical transition rules for neighborhood invasions of sensitive strains by killers, killers by resistants, and resistants by sensitives. The community of the nine possible toxicity/resistance types undergoes a critical phase transition as the uniform transmutation rates between the types decreases below a critical value Pc above that all the nine types of strains coexist with equal frequencies. Passing the critical mutation rate from above, the system collapses into one of three topologically identical (degenerated) states, each consisting of three strain types. Of the three possible final states each accrues with equal probability and all three maintain themselves in a self-organizing polydomain structure via cyclic invasions. Our Monte Carlo simulations support that this symmetry-breaking transition belongs to the universality class of the three-state Potts model.
Phase Transitions in a Model for Social Learning via the Internet
NASA Astrophysics Data System (ADS)
Bordogna, Clelia M.; Albano, Ezequiel V.
Based on the concepts of educational psychology, sociology and statistical physics, a mathematical model for a new type of social learning process that takes place when individuals interact via the Internet is proposed and studied. The noise of the interaction (misunderstandings, lack of well organized participative activities, etc.) dramatically restricts the number of individuals that can be efficiently in mutual contact and drives phase transitions between ``ordered states'' such as the achievements of the individuals are satisfactory and ``disordered states'' with negligible achievements.
Epithelial to mesenchymal transition: new and old insights from the classical neural crest model
Pablo H., Strobl-Mazzulla; Marianne E., Bronner
2012-01-01
The epithelial-to-mesenchymal transition (EMT) is an important event converting compact and ordered epithelial cells into migratory mesenchymal cells. Given the molecular and cellular similarities between pathological and developmental EMTs, studying this event during neural crest development offers and excellent in vivo model for understanding the mechanisms underlying this process. Here, we review new and old insight into neural crest EMT in search of commonalities with cancer progression that might aid in the design of specific therapeutic prevention. PMID:22575214
Modeling the solid-liquid phase transition in saturated triglycerides
NASA Astrophysics Data System (ADS)
Pink, David A.; Hanna, Charles B.; Sandt, Christophe; MacDonald, Adam J.; MacEachern, Ronald; Corkery, Robert; Rousseau, Dérick
2010-02-01
We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)], in which the average state of each TL molecule in the liquid phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an average angle of ˜120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h∗-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h∗ conformation in the liquid state at temperatures higher than the phase-transition temperature, T∗=319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)], and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ΔH. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ΔH in reasonable agreement with the experiment. We then defined an alternative h-h∗ model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h∗ model gave a value of ΔH that was too small by a factor of ˜3-4. We also predicted the temperature dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman
Between the Rock and a Hard Place: The CCMC as a Transit Station Between Modelers and Forecasters
NASA Technical Reports Server (NTRS)
Hesse, Michael
2009-01-01
The Community Coordinated Modeling Center (CCMC) is a US inter-agency activity aiming at research in support of the generation of advanced space weather models. As one of its main functions, the CCMC provides to researchers the use of space science models, even if they are not model owners themselves. The second CCMC activity is to support Space Weather forecasting at national Space Weather Forecasting Centers. This second activity involved model evaluations, model transitions to operations, and the development of draft Space Weather forecasting tools. This presentation will focus on the latter element. Specifically, we will discuss the process of transition research models, or information generated by research models, to Space Weather Forecasting organizations. We will analyze successes as well as obstacles to further progress, and we will suggest avenues for increased transitioning success.
Efficient collective influence maximization in cascading processes with first-order transitions
Pei, Sen; Teng, Xian; Shaman, Jeffrey; Morone, Flaviano; Makse, Hernán A.
2017-01-01
In many social and biological networks, the collective dynamics of the entire system can be shaped by a small set of influential units through a global cascading process, manifested by an abrupt first-order transition in dynamical behaviors. Despite its importance in applications, efficient identification of multiple influential spreaders in cascading processes still remains a challenging task for large-scale networks. Here we address this issue by exploring the collective influence in general threshold models of cascading process. Our analysis reveals that the importance of spreaders is fixed by the subcritical paths along which cascades propagate: the number of subcritical paths attached to each spreader determines its contribution to global cascades. The concept of subcritical path allows us to introduce a scalable algorithm for massively large-scale networks. Results in both synthetic random graphs and real networks show that the proposed method can achieve larger collective influence given the same number of seeds compared with other scalable heuristic approaches. PMID:28349988
Cyclic transition to turbulence in rigid abdominal aortic aneurysm models
NASA Astrophysics Data System (ADS)
Yip, T. H.; Yu, S. C. M.
2001-08-01
The hydrodynamic stability of cyclic flows inside rigid abdominal aortic aneurysm (AAA) models was investigated. Rectified sine waveforms were used to simulate aortic flow conditions (Re mean=1600-2100 and α=7.2-12.2). Depending on the bulge geometry ( D/ d and L/ d ratios), AAA flows can be broadly classified into three regimes, namely types A, B and C, respectively. While type A has no vortex formation, type B and C have distinctive laminar vortical structures that are very different from one another. The type of flow regimes would also determine where and when the transition to turbulence would occur and the portion of the cycle at which the flow remains turbulent in the bulge. The stability characteristics of types B and C are obtained from the linear stability analysis performed on the unsteady velocity profiles measured at different phases of a cycle. Based on the linear stability analyses, instability is found to initiate in the bulge for types B and C through the formation of vortical structures. Instability grows progressively during the acceleration phase and transition to turbulence in the bulge occurs shortly after the commencement of the deceleration phase in all cases investigated. The mechanisms of transition to turbulence for types B and C are discussed. Although transition to turbulence appears in all the cases investigated here, fully laminar flows in types B and C are predicted to exist by the linear stability theory under extreme flow conditions. Finally, the in vivo biological implications of the in vitro results were discussed.
Hysteretic transitions in the Kuramoto model with inertia.
Olmi, Simona; Navas, Adrian; Boccaletti, Stefano; Torcini, Alessandro
2014-10-01
We report finite-size numerical investigations and mean-field analysis of a Kuramoto model with inertia for fully coupled and diluted systems. In particular, we examine, for a gaussian distribution of the frequencies, the transition from incoherence to coherence for increasingly large system size and inertia. For sufficiently large inertia the transition is hysteretic, and within the hysteretic region clusters of locked oscillators of various sizes and different levels of synchronization coexist. A modification of the mean-field theory developed by Tanaka, Lichtenberg, and Oishi [Physica D 100, 279 (1997)] allows us to derive the synchronization curve associated to each of these clusters. We have also investigated numerically the limits of existence of the coherent and of the incoherent solutions. The minimal coupling required to observe the coherent state is largely independent of the system size, and it saturates to a constant value already for moderately large inertia values. The incoherent state is observable up to a critical coupling whose value saturates for large inertia and for finite system sizes, while in the thermodinamic limit this critical value diverges proportionally to the mass. By increasing the inertia the transition becomes more complex, and the synchronization occurs via the emergence of clusters of whirling oscillators. The presence of these groups of coherently drifting oscillators induces oscillations in the order parameter. We have shown that the transition remains hysteretic even for randomly diluted networks up to a level of connectivity corresponding to a few links per oscillator. Finally, an application to the Italian high-voltage power grid is reported, which reveals the emergence of quasiperiodic oscillations in the order parameter due to the simultaneous presence of many competing whirling clusters.
An improved model for the transit entropy of monatomic liquids
Wallace, Duane C; Chisolm, Eric D; Bock, Nicolas
2009-01-01
In the original formulation of V-T theory for monatomic liquid dynamics, the transit contribution to entropy was taken to be a universal constant, calibrated to the constant-volume entropy of melting. This model suffers two deficiencies: (a) it does not account for experimental entropy differences of {+-}2% among elemental liquids, and (b) it implies a value of zero for the transit contribution to internal energy. The purpose of this paper is to correct these deficiencies. To this end, the V-T equation for entropy is fitted to an overall accuracy of {+-}0.1% to the available experimental high temperature entropy data for elemental liquids. The theory contains two nuclear motion contributions: (a) the dominant vibrational contribution S{sub vib}(T/{theta}{sub 0}), where T is temperature and {theta}{sub 0} is the vibrational characteristic temperature, and (b) the transit contribution S{sub tr}(T/{theta}{sub tr}), where {theta}{sub tr} is a scaling temperature for each liquid. The appearance of a common functional form of S{sub tr} for all the liquids studied is a property of the experimental data, when analyzed via the V-T formula. The resulting S{sub tr} implies the correct transit contribution to internal energy. The theoretical entropy of melting is derived, in a single formula applying to normal and anomalous melting alike. An ab initio calculation of {theta}{sub 0}, based on density functional theory, is reported for liquid Na and Cu. Comparison of these calculations with the above analysis of experimental entropy data provides verification of V-T theory. In view of the present results, techniques currently being applied in ab initio simulations of liquid properties can be employed to advantage in the further testing and development of V-T theory.
Migration and Marriage: Modeling the Joint Process
Jang, Joy Bohyun; Casterline, John B; Snyder, Anastasia
2016-01-01
Background Previous research on inter-relations between migration and marriage has relied on overly simplistic assumptions about the structure of dependency between the two events. However, there is good reason to posit that each of the two transitions has an impact on the likelihood of the other, and that unobserved common factors may affect both migration and marriage, leading to a distorted impression of the causal impact of one on the other. Objective We will investigate relationships between migration and marriage in the United States using data from the National Longitudinal Survey of Youth 1979. We allow for inter-dependency between the two events and examine whether unobserved common factors affect the estimates of both migration and marriage. Methods We estimate a multi-process model in which migration and marriage are considered simultaneously in regression analysis and there is allowance for correlation between disturbances; the latter feature accounts for possible endogeneity between shared unobserved determinants. The model also includes random effects for persons, exploiting the fact that many people experience both events multiple times throughout their lives. Results Unobserved factors appear to significantly influence both migration and marriage, resulting in upward bias in estimates of the effects of each on the other when these shared common factors are not accounted for. Estimates from the multi-process model indicate that marriage significantly increases the hazard of migration while migration does not affect the hazard of marriage. Conclusions Omitting inter-dependency between life course events can lead to a mistaken impression of the direct effects of certain features of each event on the other. PMID:27182198
Transitioning Empirical Dynamical Models from Research to Operational Subseasonal Forecasting
NASA Astrophysics Data System (ADS)
Newman, M.; Gottschalk, J.; Zhang, Q.; Penland, C.; Sardeshmukh, P. D.
2015-12-01
CLIVAR support has been essential in the development of the Linear Inverse Model (LIM), an empirical dynamical model that can be used to both diagnose and predict climate variability on time scales as short as a week and as long as a decade. The LIM is an approximation of chaotic weather and climate variability that assumes that, under certain conditions, predictability within the system reduces to multivariate linear dynamics forced by unpredictable noise. This assumption is testable, and for those systems where it is demonstrated to be appropriate, LIM forecasts are competitive with state-of-the-art numerical forecast models. Over the course of more than twenty years of research, LIM has been developed as a forecast tool in parallel with its development for basic research in climate diagnosis, and has now reached the point where it is being transitioned to the Climate Predictions Center (CPC) as a part of their new Weeks 3 and 4 operational forecasting effort. In this presentation, we will discuss the development of the LIM as a CLIVAR-funded research effort, how it is being transitioned to CPC operations, and its part in the larger CPC subseasonal forecasting effort.
Phase Transitions in a Model of Y-Molecules Abstract
NASA Astrophysics Data System (ADS)
Holz, Danielle; Ruth, Donovan; Toral, Raul; Gunton, James
Immunoglobulin is a Y-shaped molecule that functions as an antibody to neutralize pathogens. In special cases where there is a high concentration of immunoglobulin molecules, self-aggregation can occur and the molecules undergo phase transitions. This prevents the molecules from completing their function. We used a simplified model of 2-Dimensional Y-molecules with three identical arms on a triangular lattice with 2-dimensional Grand Canonical Ensemble. The molecules were permitted to be placed, removed, rotated or moved on the lattice. Once phase coexistence was found, we used histogram reweighting and multicanonical sampling to calculate our phase diagram.
A motivic approach to phase transitions in Potts models
NASA Astrophysics Data System (ADS)
Aluffi, Paolo; Marcolli, Matilde
2013-01-01
We describe an approach to the study of phase transitions in Potts models based on an estimate of the complexity of the locus of real zeros of the partition function, computed in terms of the classes in the Grothendieck ring of the affine algebraic varieties defined by the vanishing of the multivariate Tutte polynomial. We give completely explicit calculations for the examples of the chains of linked polygons and of the graphs obtained by replacing the polygons with their dual graphs. These are based on a deletion-contraction formula for the Grothendieck classes and on generating functions for splitting and doubling edges.
Kinetic Relations for a Lattice Model of Phase Transitions
NASA Astrophysics Data System (ADS)
Schwetlick, Hartmut; Zimmer, Johannes
2012-11-01
The aim of this article is to analyse travelling waves for a lattice model of phase transitions, specifically the Fermi-Pasta-Ulam chain with piecewise quadratic interaction potential. First, for fixed, sufficiently large subsonic wave speeds, we rigorously prove the existence of a family of travelling wave solutions. Second, it is shown that this family of solutions gives rise to a kinetic relation which depends on the jump in the oscillatory energy in the solution tails. Third, our constructive approach provides a very good approximate travelling wave solution.
Topological phase transition in the Scheidegger model of river networks
NASA Astrophysics Data System (ADS)
Oppenheim, Jacob N.; Magnasco, Marcelo O.
2012-08-01
Transport networks are found at the heart of myriad natural systems, yet are poorly understood, except for the case of river networks. The Scheidegger model, in which rivers are convergent random walks, has been studied only in the case of flat topography, ignoring the variety of curved geometries found in nature. Embedding this model on a cone, we find a convergent and a divergent phase, corresponding to few, long basins and many, short basins, respectively, separated by a singularity, indicating a phase transition. Quantifying basin shape using Hacks law l˜ah gives distinct values for h, providing a method of testing our hypotheses. The generality of our model suggests implications for vascular morphology, in particular, differing number and shapes of arterial and venous trees.
Modeling the hepatitis A epidemiological transition in Thailand.
Van Effelterre, Thierry; Marano, Cinzia; Jacobsen, Kathryn H
2016-01-20
In most low- and middle-income countries, hepatitis A virus (HAV) is shifting or expected to shift from high endemicity to intermediate or low endemicity. A decreased risk of HAV infection will cause an increase in the average age at infection and will therefore increase the proportion of infections that results in severe disease. Mathematical models can provide insights into the factors contributing to this epidemiological transition. An MSLIR compartmental dynamic transmission model stratified by age and setting (rural and urban) was developed and calibrated with demographic, environmental, and epidemiological data from Thailand. HAV transmission was modeled as a function of urbanization and access to clean drinking water. The model was used to project various epidemiological measures. The age at midpoint of population immunity remains considerably younger in rural areas than in urban areas. The mean age of symptomatic hepatitis A infection in Thailand has shifted from childhood toward early adulthood in rural areas and is transitioning from early adulthood toward middle adulthood in urban areas. The model showed a significant decrease in incidence rates of total and symptomatic infections in rural and urban settings in Thailand over the past several decades as water access has increased, although the overall incidence rate of symptomatic HAV is projected to slightly increase in the coming decades. Modeling the relationship between water, urbanization, and HAV endemicity is a novel approach in the estimation of HAV epidemiological trends and future projections. This approach provides insights about the shifting HAV epidemiology and could be used to evaluate the public health impact of vaccination and other interventions in a diversity of settings. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
Transitioning from Software Requirements Models to Design Models
NASA Technical Reports Server (NTRS)
Whittle, Jon
2004-01-01
The Scenario Creation and Simulation Process (SCASP) includes the following steps: 1) Write Requirements; 2) Write Use Cases; 3) Prioritize Use Cases; 4) Write Nominal Scenarios; 5) Identify Relationships; 6) Refine/Generalize Scenarios; 7) Transform to State Machines. SCASP provides thorough simulation of use cases before design/implementation, resulting in: 1) Reduced cost; 2) Fewer misunderstandings; 3) Reuse of executable form of use cases. SCASP gives systematic guidelines on how to 1) Separate concerns in use case descriptions; 2) Elicit non-nominal scenarios (alternatives, exceptions, concurrent scenarios, etc.); 3) Transform those scenarios automatically into a set of concurrent state machines; 4) Execute those state machines, i.e., scenario simulation.
Process-Response Modeling and the Scientific Process.
ERIC Educational Resources Information Center
Fichter, Lynn S.
1988-01-01
Discusses the process-response model (PRM) in its theoretical and practical forms. Describes how geologists attempt to reconstruct the process from the response (the geologic phenomenon) being studied. (TW)
Process-Response Modeling and the Scientific Process.
ERIC Educational Resources Information Center
Fichter, Lynn S.
1988-01-01
Discusses the process-response model (PRM) in its theoretical and practical forms. Describes how geologists attempt to reconstruct the process from the response (the geologic phenomenon) being studied. (TW)
Managing Analysis Models in the Design Process
NASA Technical Reports Server (NTRS)
Briggs, Clark
2006-01-01
Design of large, complex space systems depends on significant model-based support for exploration of the design space. Integrated models predict system performance in mission-relevant terms given design descriptions and multiple physics-based numerical models. Both the design activities and the modeling activities warrant explicit process definitions and active process management to protect the project from excessive risk. Software and systems engineering processes have been formalized and similar formal process activities are under development for design engineering and integrated modeling. JPL is establishing a modeling process to define development and application of such system-level models.
Managing Analysis Models in the Design Process
NASA Technical Reports Server (NTRS)
Briggs, Clark
2006-01-01
Design of large, complex space systems depends on significant model-based support for exploration of the design space. Integrated models predict system performance in mission-relevant terms given design descriptions and multiple physics-based numerical models. Both the design activities and the modeling activities warrant explicit process definitions and active process management to protect the project from excessive risk. Software and systems engineering processes have been formalized and similar formal process activities are under development for design engineering and integrated modeling. JPL is establishing a modeling process to define development and application of such system-level models.
Sultan, Nabil; Garziglia, Sébastien; Ruffine, Livio
2016-01-01
Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria’s coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries. PMID:27230887
NASA Astrophysics Data System (ADS)
Sultan, Nabil; Garziglia, Sébastien; Ruffine, Livio
2016-05-01
Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria’s coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries.
Mustard, Thomas J L; Wender, Paul A; Cheong, Paul Ha-Yeon
2015-03-06
The origins of differential catalytic reactivities of four Rh(I) catalysts and their derivatives in the (5 + 2) cycloaddition reaction were elucidated using density functional theory. Computed free energy spans are in excellent agreement with known experimental rates. For every catalyst, the substrate geometries in the transition state remained constant (<0.1 Å RMSD for atoms involved in bond-making and -breaking processes). Catalytic efficiency is shown to be a function of how well the catalyst accommodates the substrate transition state geometry and electronics. This shows that the induced fit model for explaining biological catalysis may be relevant to transition metal catalysis. This could serve as a general model for understanding the origins of efficiencies of catalytic reactions.
ERIC Educational Resources Information Center
Woods, Lee L.; Sylvester, Lorraine; Martin, James E.
2010-01-01
This study examined the effectiveness of a new school to adult life transition planning lesson package titled "Student-Directed Transition Planning". The "Student-Directed Transition Planning" lessons teach transition terms and concepts to provide a means to increase self-determination skills and student participation in…
Cupola Furnace Computer Process Model
Seymour Katz
2004-12-31
The cupola furnace generates more than 50% of the liquid iron used to produce the 9+ million tons of castings annually. The cupola converts iron and steel into cast iron. The main advantages of the cupola furnace are lower energy costs than those of competing furnaces (electric) and the ability to melt less expensive metallic scrap than the competing furnaces. However the chemical and physical processes that take place in the cupola furnace are highly complex making it difficult to operate the furnace in optimal fashion. The results are low energy efficiency and poor recovery of important and expensive alloy elements due to oxidation. Between 1990 and 2004 under the auspices of the Department of Energy, the American Foundry Society and General Motors Corp. a computer simulation of the cupola furnace was developed that accurately describes the complex behavior of the furnace. When provided with the furnace input conditions the model provides accurate values of the output conditions in a matter of seconds. It also provides key diagnostics. Using clues from the diagnostics a trained specialist can infer changes in the operation that will move the system toward higher efficiency. Repeating the process in an iterative fashion leads to near optimum operating conditions with just a few iterations. More advanced uses of the program have been examined. The program is currently being combined with an ''Expert System'' to permit optimization in real time. The program has been combined with ''neural network'' programs to affect very easy scanning of a wide range of furnace operation. Rudimentary efforts were successfully made to operate the furnace using a computer. References to these more advanced systems will be found in the ''Cupola Handbook''. Chapter 27, American Foundry Society, Des Plaines, IL (1999).
Multiple phase transitions in an agent-based evolutionary model with neutral fitness.
King, Dawn M; Scott, Adam D; Bahar, Sonya
2017-04-01
Null models are crucial for understanding evolutionary processes such as speciation and adaptive radiation. We analyse an agent-based null model, considering a case without selection-neutral evolution-in which organisms are defined only by phenotype. Universal dynamics has previously been demonstrated in a related model on a neutral fitness landscape, showing that this system belongs to the directed percolation (DP) universality class. The traditional null condition of neutral fitness (where fitness is defined as the number of offspring each organism produces) is extended here to include equal probability of death among organisms. We identify two types of phase transition: (i) a non-equilibrium DP transition through generational time (i.e. survival), and (ii) an equilibrium ordinary percolation transition through the phenotype space (based on links between mating organisms). Owing to the dynamical rules of the DP reaction-diffusion process, organisms can only sparsely fill the phenotype space, resulting in significant phenotypic diversity within a cluster of mating organisms. This highlights the necessity of understanding hierarchical evolutionary relationships, rather than merely developing taxonomies based on phenotypic similarity, in order to develop models that can explain phylogenetic patterns found in the fossil record or to make hypotheses for the incomplete fossil record of deep time.
Multiple phase transitions in an agent-based evolutionary model with neutral fitness
Scott, Adam D.; Bahar, Sonya
2017-01-01
Null models are crucial for understanding evolutionary processes such as speciation and adaptive radiation. We analyse an agent-based null model, considering a case without selection—neutral evolution—in which organisms are defined only by phenotype. Universal dynamics has previously been demonstrated in a related model on a neutral fitness landscape, showing that this system belongs to the directed percolation (DP) universality class. The traditional null condition of neutral fitness (where fitness is defined as the number of offspring each organism produces) is extended here to include equal probability of death among organisms. We identify two types of phase transition: (i) a non-equilibrium DP transition through generational time (i.e. survival), and (ii) an equilibrium ordinary percolation transition through the phenotype space (based on links between mating organisms). Owing to the dynamical rules of the DP reaction–diffusion process, organisms can only sparsely fill the phenotype space, resulting in significant phenotypic diversity within a cluster of mating organisms. This highlights the necessity of understanding hierarchical evolutionary relationships, rather than merely developing taxonomies based on phenotypic similarity, in order to develop models that can explain phylogenetic patterns found in the fossil record or to make hypotheses for the incomplete fossil record of deep time. PMID:28484629
Specificity in transition state binding: the Pauling model revisited.
Amyes, Tina L; Richard, John P
2013-03-26
Linus Pauling proposed that the large rate accelerations for enzymes are caused by the high specificity of the protein catalyst for binding the reaction transition state. The observation that stable analogues of the transition states for enzymatic reactions often act as tight-binding inhibitors provided early support for this simple and elegant proposal. We review experimental results that support the proposal that Pauling's model provides a satisfactory explanation for the rate accelerations for many heterolytic enzymatic reactions through high-energy reaction intermediates, such as proton transfer and decarboxylation. Specificity in transition state binding is obtained when the total intrinsic binding energy of the substrate is significantly larger than the binding energy observed at the Michaelis complex. The results of recent studies that aimed to characterize the specificity in binding of the enolate oxygen at the transition state for the 1,3-isomerization reaction catalyzed by ketosteroid isomerase are reviewed. Interactions between pig heart succinyl-coenzyme A:3-oxoacid coenzyme A transferase (SCOT) and the nonreacting portions of coenzyme A (CoA) are responsible for a rate increase of 3 × 10(12)-fold, which is close to the estimated total 5 × 10(13)-fold enzymatic rate acceleration. Studies that partition the interactions between SCOT and CoA into their contributing parts are reviewed. Interactions of the protein with the substrate phosphodianion group provide an ~12 kcal/mol stabilization of the transition state for the reactions catalyzed by triosephosphate isomerase, orotidine 5'-monophosphate decarboxylase, and α-glycerol phosphate dehydrogenase. The interactions of these enzymes with the substrate piece phosphite dianion provide a 6-8 kcal/mol stabilization of the transition state for reaction of the appropriate truncated substrate. Enzyme activation by phosphite dianion reflects the higher dianion affinity for binding to the enzyme-transition
Progress in Modeling of Laminar to Turbulent Transition on Turbine Vanes and Blades
NASA Technical Reports Server (NTRS)
Simon, Frederick F.; Ashpis, David E.
1996-01-01
The progress in modeling of transition on turbine vanes and blades performed under the sponsorship of NASA Lewis Research Center is reviewed. Past work in bypass transition modeling for accurate heat transfer predictions, show that transition onset can be reasonably predicted by modified k - epsilon models, but fall short of predicting transition length. Improvements in the predictions of the transition region itself were made with intermittency models based on turbulent spot dynamics. Needs and proposals for extending the modeling to include wake passing and separation effects are outlined.
TRANSIT MODEL OF PLANETS WITH MOON AND RING SYSTEMS
Tusnski, Luis Ricardo M.; Valio, Adriana E-mail: avalio@craam.mackenzie.br
2011-12-10
Since the discovery of the first exoplanets, those most adequate for life to begin and evolve have been sought. Due to observational bias, however, most of the discovered planets so far are gas giants, precluding their habitability. However, if these hot Jupiters are located in the habitable zones of their host stars, and if rocky moons orbit them, then these moons may be habitable. In this work, we present a model for planetary transit simulation considering the presence of moons and planetary rings around a planet. The moon's orbit is considered to be circular and coplanar with the planetary orbit. The other physical and orbital parameters of the star, planet, moon, and rings can be adjusted in each simulation. It is possible to simulate as many successive transits as desired. Since the presence of spots on the surface of the star may produce a signal similar to that of the presence of a moon, our model also allows for the inclusion of starspots. The result of the simulation is a light curve with a planetary transit. White noise may also be added to the light curves to produce curves similar to those obtained by the CoRoT and Kepler space telescopes. The goal is to determine the criteria for detectability of moons and/or ring systems using photometry. The results show that it is possible to detect moons with radii as little as 1.3 R{sub Circled-Plus} with CoRoT and 0.3 R{sub Circled-Plus} with Kepler.
Process modeling and industrial energy use
Howe, S O; Pilati, D A; Sparrow, F T
1980-11-01
How the process models developed at BNL are used to analyze industrial energy use is described and illustrated. Following a brief overview of the industry modeling program, the general methodology of process modeling is discussed. The discussion highlights the important concepts, contents, inputs, and outputs of a typical process model. A model of the US pulp and paper industry is then discussed as a specific application of process modeling methodology. Case study results from the pulp and paper model illustrate how process models can be used to analyze a variety of issues. Applications addressed with the case study results include projections of energy demand, conservation technology assessment, energy-related tax policies, and sensitivity analysis. A subsequent discussion of these results supports the conclusion that industry process models are versatile and powerful tools for energy end-use modeling and conservation analysis. Information on the current status of industry models at BNL is tabulated.
Abrupt transitions to tumor extinction: a phenotypic quasispecies model.
Sardanyés, Josep; Martínez, Regina; Simó, Carles; Solé, Ricard
2016-10-06
The dynamics of heterogeneous tumor cell populations competing with healthy cells is an important topic in cancer research with deep implications in biomedicine. Multitude of theoretical and computational models have addressed this issue, especially focusing on the nature of the transitions governing tumor clearance as some relevant model parameters are tuned. In this contribution, we analyze a mathematical model of unstable tumor progression using the quasispecies framework. Our aim is to define a minimal model incorporating the dynamics of competition between healthy cells and a heterogeneous population of cancer cell phenotypes involving changes in replication-related genes (i.e., proto-oncogenes and tumor suppressor genes), in genes responsible for genomic stability, and in house-keeping genes. Such mutations or loss of genes result into different phenotypes with increased proliferation rates and/or increased genomic instabilities. Despite bifurcations in the classical deterministic quasispecies model are typically given by smooth, continuous shifts (i.e., transcritical bifurcations), we here identify a novel type of bifurcation causing an abrupt transition to tumor extinction. Such a bifurcation, named as trans-heteroclinic, is characterized by the exchange of stability between two distant fixed points (that do not collide) involving tumor persistence and tumor clearance. The increase of mutation and/or the decrease of the replication rate of tumor cells involves this catastrophic shift of tumor cell populations. The transient times near bifurcation thresholds are also characterized, showing a power law dependence of exponent [Formula: see text] of the transients as mutation is changed near the bifurcation value. These results are discussed in the context of targeted cancer therapy as a possible therapeutic strategy to force a catastrophic shift by simultaneously delivering mutagenic and cytotoxic drugs inside tumor cells.
Optimal Control of Markov Processes with Age-Dependent Transition Rates
Ghosh, Mrinal K. Saha, Subhamay
2012-10-15
We study optimal control of Markov processes with age-dependent transition rates. The control policy is chosen continuously over time based on the state of the process and its age. We study infinite horizon discounted cost and infinite horizon average cost problems. Our approach is via the construction of an equivalent semi-Markov decision process. We characterise the value function and optimal controls for both discounted and average cost cases.
Mixed-order phase transition of the contact process near multiple junctions
NASA Astrophysics Data System (ADS)
Juhász, Róbert; Iglói, Ferenc
2017-02-01
We have studied the phase transition of the contact process near a multiple junction of M semi-infinite chains by Monte Carlo simulations. As opposed to the continuous transitions of the translationally invariant (M =2 ) and semi-infinite (M =1 ) system, the local order parameter is found to be discontinuous for M >2 . Furthermore, the temporal correlation length diverges algebraically as the critical point is approached, but with different exponents on the two sides of the transition. In the active phase, the estimate is compatible with the bulk value, while in the inactive phase it exceeds the bulk value and increases with M . The unusual local critical behavior is explained by a scaling theory with an irrelevant variable, which becomes dangerous in the inactive phase. Quenched spatial disorder is found to make the transition continuous in agreement with earlier renormalization group results.
Multi-state succession in wetlands: a novel use of state and transition models
Zweig, Christa L.; Kitchens, Wiley M.
2009-01-01
The complexity of ecosystems and mechanisms of succession are often simplified by linear and mathematical models used to understand and predict system behavior. Such models often do not incorporate multivariate, nonlinear feedbacks in pattern and process that include multiple scales of organization inherent within real-world systems. Wetlands are ecosystems with unique, nonlinear patterns of succession due to the regular, but often inconstant, presence of water on the landscape. We develop a general, nonspatial state and transition (S and T) succession conceptual model for wetlands and apply the general framework by creating annotated succession/management models and hypotheses for use in impact analysis on a portion of an imperiled wetland. The S and T models for our study area, Water Conservation Area 3A South (WCA3), Florida, USA, included hydrologic and peat depth values from multivariate analyses and classification and regression trees. We used the freeware Vegetation Dynamics Development Tool as an exploratory application to evaluate our S and T models with different management actions (equal chance [a control condition], deeper conditions, dry conditions, and increased hydrologic range) for three communities: slough, sawgrass (Cladium jamaicense), and wet prairie. Deeper conditions and increased hydrologic range behaved similarly, with the transition of community states to deeper states, particularly for sawgrass and slough. Hydrology is the primary mechanism for multi-state transitions within our study period, and we show both an immediate and lagged effect on vegetation, depending on community state. We consider these S and T succession models as a fraction of the framework for the Everglades. They are hypotheses for use in adaptive management, represent the community response to hydrology, and illustrate which aspects of hydrologic variability are important to community structure. We intend for these models to act as a foundation for further restoration
Multi-state succession in wetlands: a novel use of state and transition models.
Zweig, C L; Kitchens, W M
2009-07-01
The complexity of ecosystems and mechanisms of succession are often simplified by linear and mathematical models used to understand and predict system behavior. Such models often do not incorporate multivariate, nonlinear feedbacks in pattern and process that include multiple scales of organization inherent within real-world systems. Wetlands are ecosystems with unique, nonlinear patterns of succession due to the regular, but often inconstant, presence of water on the landscape. We develop a general, nonspatial state and transition (S and T) succession conceptual model for wetlands and apply the general framework by creating annotated succession/management models and hypotheses for use in impact analysis on a portion of an imperiled wetland. The S and T models for our study area, Water Conservation Area 3A South (WCA3), Florida, U.S.A., included hydrologic and peat depth values from multivariate analyses and classification and regression trees. We used the freeware Vegetation Dynamics Development Tool as an exploratory application to evaluate our S and T models with different management actions (equal chance [a control condition], deeper conditions, dry conditions, and increased hydrologic range) for three communities: slough, sawgrass (Cladium jamaicense), and wet prairie. Deeper conditions and increased hydrologic range behaved similarly, with the transition of community states to deeper states, particularly for sawgrass and slough. Hydrology is the primary mechanism for multi-state transitions within our study period, and we show both an immediate and lagged effect on vegetation, depending on community state. We consider these S and T succession models as a fraction of the framework for the Everglades. They are hypotheses for use in adaptive management, represent the community response to hydrology, and illustrate which aspects of hydrologic variability are important to community structure. We intend for these models to act as a foundation for further
Protonation of transition-metal hydrides: a not so simple process.
Besora, Maria; Lledós, Agustí; Maseras, Feliu
2009-04-01
The protonation of a transition-metal hydride is a formally simple process between a proton donor and a proton acceptor with several potential basic centres. The detailed mechanism is however quite subtle, with multistep reactions and involvement of different intermediates. The process is furthermore very sensitive to the nature of both the proton donor and the transition-metal complex, as well as to the solvent and to the presence and identity of eventual counteranions. This tutorial review summarizes the recent progress in the understanding of the reaction, obtained through the joint application of a number of computational and experimental techniques.
Bifurcation and Spike Adding Transition in Chay-Keizer Model
NASA Astrophysics Data System (ADS)
Lu, Bo; Liu, Shenquan; Liu, Xuanliang; Jiang, Xiaofang; Wang, Xiaohui
Electrical bursting is an activity which is universal in excitable cells such as neurons and various endocrine cells, and it encodes rich physiological information. As burst delay identifies that the signal integration has reached the threshold at which it can generate an action potential, the number of spikes in a burst may have essential physiological implications, and the transition of bursting in excitable cells is associated with the bifurcation phenomenon closely. In this paper, we focus on the transition of the spike count per burst of the pancreatic β-cells within a mathematical model and bifurcation phenomenon in the Chay-Keizer model, which is utilized to simulate the pancreatic β-cells. By the fast-slow dynamical bifurcation analysis and the bi-parameter bifurcation analysis, the local dynamics of the Chay-Keizer system around the Bogdanov-Takens bifurcation is illustrated. Then the variety of the number of spikes per burst is discussed by changing the settings of a single parameter and bi-parameter. Moreover, results on the number of spikes within a burst are summarized in ISIs (interspike intervals) sequence diagrams, maximum and minimum, and the number of spikes under bi-parameter value changes.
An Anderson-like model of the QCD chiral transition
NASA Astrophysics Data System (ADS)
Giordano, Matteo; Kovács, Tamás G.; Pittler, Ferenc
2016-06-01
We study the problems of chiral symmetry breaking and eigenmode localisation in finite-temperature QCD by looking at the lattice Dirac operator as a random Hamiltonian. We recast the staggered Dirac operator into an unconventional three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying internal degrees of freedom, with disorder provided by the fluctuations of the gauge links. In this framework, we identify the features relevant to chiral symmetry restoration and localisation of the low-lying Dirac eigenmodes in the ordering of the local Polyakov lines, and in the related correlation between spatial links across time slices, thus tying the two phenomena to the deconfinement transition. We then build a toy model based on QCD and on the Dirac-Anderson approach, replacing the Polyakov lines with spin variables and simplifying the dynamics of the spatial gauge links, but preserving the above-mentioned relevant dynamical features. Our toy model successfully reproduces the main features of the QCD spectrum and of the Dirac eigenmodes concerning chiral symmetry breaking and localisation, both in the ordered (deconfined) and disordered (confined) phases. Moreover, it allows us to study separately the roles played in the two phenomena by the diagonal and the off-diagonal terms of the Dirac-Anderson Hamiltonian. Our results support our expectation that chiral symmetry restoration and localisation of the low modes are closely related, and that both are triggered by the deconfinement transition.
Multiscale Modeling of Shock-Induced Phase Transitions in Iron
NASA Astrophysics Data System (ADS)
Carter, Emily; Caspersen, Kyle; Lew, Adrian; Ortiz, Michael
2004-03-01
Multiscale Modeling of Shock-Induced Phase Transitions in Iron Emily Carter, Kyle Caspersen, Adrian Lew and Michael Ortiz We investigate the bcc to hcp phase transition in iron under both pressure and shear. We use DFT to map out the energy landscape of uniformly deformed iron, including its equation of state and its elastic moduli as a function of volume. >From these data we construct a nonlinear-elastic energy density which gives the energy density for arbitrary - not necessarily small - deformations. The energy density contains two wells corresponding to the bcc and hcp phases. We take this multi-well energy density as a basis for the investigation of the effect of shear on the phase diagram of iron. We allow for mixed states consisting alternating lamellae of bcc and hcp phases, and, for each macroscopic deformation, we determine the optimal microstructure of the mixed state by energy minimization using a sequential-lamination algorithm. We find that the superposition of shearing deformation on a volume change has the effect of inducing mixed states of varying spatial complexity, and of markedly lowering the critical transformation pressure. Indeed, we find that shear must be taken into consideration in order to obtain agreement with measured transformation pressures. Finally, we demonstrate how the microstructure model can be integrated into large-scale finite element calculations of shocked iron.
Process correlation analysis model for process improvement identification.
Choi, Su-jin; Kim, Dae-Kyoo; Park, Sooyong
2014-01-01
Software process improvement aims at improving the development process of software systems. It is initiated by process assessment identifying strengths and weaknesses and based on the findings, improvement plans are developed. In general, a process reference model (e.g., CMMI) is used throughout the process of software process improvement as the base. CMMI defines a set of process areas involved in software development and what to be carried out in process areas in terms of goals and practices. Process areas and their elements (goals and practices) are often correlated due to the iterative nature of software development process. However, in the current practice, correlations of process elements are often overlooked in the development of an improvement plan, which diminishes the efficiency of the plan. This is mainly attributed to significant efforts and the lack of required expertise. In this paper, we present a process correlation analysis model that helps identify correlations of process elements from the results of process assessment. This model is defined based on CMMI and empirical data of improvement practices. We evaluate the model using industrial data.
Model for the {Delta}(1600) resonance and {gamma}N{yields}{Delta}(1600) transition
Ramalho, G.; Tsushima, K.
2010-10-01
A covariant spectator constituent quark model is applied to study the {gamma}N{yields}{Delta}(1600) transition. Two processes are important in the transition: a photon couples to the individual quarks of the {Delta}(1600) core (quark core), and a photon couples to the intermediate pion-baryon states (pion cloud). While the quark core contributions are estimated assuming {Delta}(1600) as the first radial excitation of {Delta}(1232), the pion cloud contributions are estimated based on an analogy with the {gamma}N{yields}{Delta}(1232) transition. To estimate the pion cloud contributions in the {gamma}N{yields}{Delta}(1600) transition, we include the relevant intermediate states, {pi}N, {pi}{Delta}, {pi}N(1440) and {pi}{Delta}(1600). Dependence on the four-momentum transfer squared, Q{sup 2}, is predicted for the magnetic dipole transition form factor, G{sub M}*(Q{sup 2}), as well as the helicity amplitudes, A{sub 1/2}(Q{sup 2}) and A{sub 3/2}(Q{sup 2}). The results at Q{sup 2}=0 are compared with the existing data.
A model for the Delta(1600) resonance and gamma N -> Delta(1600) transition
G. Ramalho, K. Tsushima
2010-10-01
A covariant spectator constituent quark model is applied to study the gamma N -> Delta(1600) transition. Two processes are important in the transition: a photon couples to the individual quarks of the Delta(1600) core (quark core), and a photon couples to the intermediate pion-baryon states (pion cloud). While the quark core contributions are estimated assuming Delta(1600) as the first radial excitation of Delta(1232), the pion cloud contributions are estimated based on an analogy with the gamma N -> Delta(1232) transition. To estimate the pion cloud contributions in the gamma N -> Delta(1600) transition, we include the relevant intermediate states, pi-N, pi-Delta, pi-N(1440) and pi-Delta(1600). Dependence on the four-momentum transfer squared, Q2, is predicted for the magnetic dipole transition form factor, GM*(Q2), as well as the helicity amplitudes, A_1/2(Q2) and A_3/2(Q2). The results at Q2=0 are compared with the existing data.
Dynamic Linkages Between the Transition Zone & Surface Plate Motions in 2D Models of Subduction
NASA Astrophysics Data System (ADS)
Arredondo, K.; Billen, M. I.
2013-12-01
While slab pull is considered the dominant force controlling plate motion and speed, its magnitude is controlled by slab behavior in the mantle, where tomographic studies show a wide range of possibilities from direct penetration to folding, or stagnation directly above the lower mantle (e.g. Fukao et al., 2009). Geodynamic studies have investigated various parameters, such as plate age and two phase transitions, to recreate observed behavior (e.g. Běhounková and Cízková, 2008). However, past geodynamic models have left out known slab characteristics that may have a large impact on slab behavior and our understanding of subduction processes. Mineral experiments and seismic observations have indicated the existence of additional phase transitions in the mantle transition zone that may produce buoyancy forces large enough to affect the descent of a subducting slab (e.g. Ricard et al., 2005). The current study systematically tests different common assumptions used in geodynamic models: kinematic versus free-slip boundary conditions, the effects of adiabatic heating, viscous dissipation and latent heat, compositional layering and a more complete suite of phase transitions. Final models have a complete energy equation, with eclogite, harzburgite and pyrolite lithosphere compositional layers, and seven composition-dependent phase transitions within the olivine, pyroxene and garnet polymorph minerals. Results show important feedback loops between different assumptions and new behavior from the most complete models. Kinematic models show slab weakening or breaking above the 660 km boundary and between compositional layers. The behavior in dynamic models with a free-moving trench and overriding plate is compared to the more commonly found kinematic models. The new behavior may have important implications for the depth distribution of deep earthquakes within the slab. Though the thermodynamic parameters of certain phase transitions may be uncertain, their presence and
Multidimensional Data Modeling for Business Process Analysis
NASA Astrophysics Data System (ADS)
Mansmann, Svetlana; Neumuth, Thomas; Scholl, Marc H.
The emerging area of business process intelligence attempts to enhance the analytical capabilities of business process management systems by employing data warehousing and mining technologies. This paper presents an approach to re-engineering the business process modeling in conformity with the multidimensional data model. Since the business process and the multidimensional model are driven by rather different objectives and assumptions, there is no straightforward solution to converging these models.
The Biological Big Bang model for the major transitions in evolution
Koonin, Eugene V
2007-01-01
Background Major transitions in biological evolution show the same pattern of sudden emergence of diverse forms at a new level of complexity. The relationships between major groups within an emergent new class of biological entities are hard to decipher and do not seem to fit the tree pattern that, following Darwin's original proposal, remains the dominant description of biological evolution. The cases in point include the origin of complex RNA molecules and protein folds; major groups of viruses; archaea and bacteria, and the principal lineages within each of these prokaryotic domains; eukaryotic supergroups; and animal phyla. In each of these pivotal nexuses in life's history, the principal "types" seem to appear rapidly and fully equipped with the signature features of the respective new level of biological organization. No intermediate "grades" or intermediate forms between different types are detectable. Usually, this pattern is attributed to cladogenesis compressed in time, combined with the inevitable erosion of the phylogenetic signal. Hypothesis I propose that most or all major evolutionary transitions that show the "explosive" pattern of emergence of new types of biological entities correspond to a boundary between two qualitatively distinct evolutionary phases. The first, inflationary phase is characterized by extremely rapid evolution driven by various processes of genetic information exchange, such as horizontal gene transfer, recombination, fusion, fission, and spread of mobile elements. These processes give rise to a vast diversity of forms from which the main classes of entities at the new level of complexity emerge independently, through a sampling process. In the second phase, evolution dramatically slows down, the respective process of genetic information exchange tapers off, and multiple lineages of the new type of entities emerge, each of them evolving in a tree-like fashion from that point on. This biphasic model of evolution incorporates the
The Biological Big Bang model for the major transitions in evolution.
Koonin, Eugene V
2007-08-20
Major transitions in biological evolution show the same pattern of sudden emergence of diverse forms at a new level of complexity. The relationships between major groups within an emergent new class of biological entities are hard to decipher and do not seem to fit the tree pattern that, following Darwin's original proposal, remains the dominant description of biological evolution. The cases in point include the origin of complex RNA molecules and protein folds; major groups of viruses; archaea and bacteria, and the principal lineages within each of these prokaryotic domains; eukaryotic supergroups; and animal phyla. In each of these pivotal nexuses in life's history, the principal "types" seem to appear rapidly and fully equipped with the signature features of the respective new level of biological organization. No intermediate "grades" or intermediate forms between different types are detectable. Usually, this pattern is attributed to cladogenesis compressed in time, combined with the inevitable erosion of the phylogenetic signal. I propose that most or all major evolutionary transitions that show the "explosive" pattern of emergence of new types of biological entities correspond to a boundary between two qualitatively distinct evolutionary phases. The first, inflationary phase is characterized by extremely rapid evolution driven by various processes of genetic information exchange, such as horizontal gene transfer, recombination, fusion, fission, and spread of mobile elements. These processes give rise to a vast diversity of forms from which the main classes of entities at the new level of complexity emerge independently, through a sampling process. In the second phase, evolution dramatically slows down, the respective process of genetic information exchange tapers off, and multiple lineages of the new type of entities emerge, each of them evolving in a tree-like fashion from that point on. This biphasic model of evolution incorporates the previously developed
Excited-state quantum phase transition in the Rabi model
NASA Astrophysics Data System (ADS)
Puebla, Ricardo; Hwang, Myung-Joong; Plenio, Martin B.
2016-08-01
The Rabi model, a two-level atom coupled to a harmonic oscillator, can undergo a second-order quantum phase transition (QPT) [M.-J. Hwang et al., Phys. Rev. Lett. 115, 180404 (2015), 10.1103/PhysRevLett.115.180404]. Here we show that the Rabi QPT accompanies critical behavior in the higher-energy excited states, i.e., the excited-state QPT (ESQPT). We derive analytic expressions for the semiclassical density of states, which show a logarithmic divergence at a critical energy eigenvalue in the broken symmetry (superradiant) phase. Moreover, we find that the logarithmic singularities in the density of states lead to singularities in the relevant observables in the system such as photon number and atomic polarization. We corroborate our analytical semiclassical prediction of the ESQPT in the Rabi model with its numerically exact quantum mechanical solution.
Exact results for models of multichannel quantum nonadiabatic transitions
Sinitsyn, N. A.
2014-12-11
We consider nonadiabatic transitions in explicitly time-dependent systems with Hamiltonians of the form Hˆ(t)=Aˆ+Bˆt+Cˆ/t, where t is time and Aˆ,Bˆ,Cˆ are Hermitian N × N matrices. We show that in any model of this type, scattering matrix elements satisfy nontrivial exact constraints that follow from the absence of the Stokes phenomenon for solutions with specific conditions at t→–∞. This allows one to continue such solutions analytically to t→+∞, and connect their asymptotic behavior at t→–∞ and t→+∞. This property becomes particularly useful when a model shows additional discrete symmetries. Specifically, we derive a number of simple exact constraints and explicitmore » expressions for scattering probabilities in such systems.« less
Exact results for models of multichannel quantum nonadiabatic transitions
Sinitsyn, N. A.
2014-12-11
We consider nonadiabatic transitions in explicitly time-dependent systems with Hamiltonians of the form Hˆ(t)=Aˆ+Bˆt+Cˆ/t, where t is time and Aˆ,Bˆ,Cˆ are Hermitian N × N matrices. We show that in any model of this type, scattering matrix elements satisfy nontrivial exact constraints that follow from the absence of the Stokes phenomenon for solutions with specific conditions at t→–∞. This allows one to continue such solutions analytically to t→+∞, and connect their asymptotic behavior at t→–∞ and t→+∞. This property becomes particularly useful when a model shows additional discrete symmetries. Specifically, we derive a number of simple exact constraints and explicit expressions for scattering probabilities in such systems.
Methodology Development of a Gas-Liquid Dynamic Flow Regime Transition Model
NASA Astrophysics Data System (ADS)
Doup, Benjamin Casey
Current reactor safety analysis codes, such as RELAP5, TRACE, and CATHARE, use flow regime maps or flow regime transition criteria that were developed for static fully-developed two-phase flows to choose interfacial transfer models that are necessary to solve the two-fluid model. The flow regime is therefore difficult to identify near the flow regime transitions, in developing two-phase flows, and in transient two-phase flows. Interfacial area transport equations were developed to more accurately predict the dynamic nature of two-phase flows. However, other model coefficients are still flow regime dependent. Therefore, an accurate prediction of the flow regime is still important. In the current work, the methodology for the development of a dynamic flow regime transition model that uses the void fraction and interfacial area concentration obtained by solving three-field the two-fluid model and two-group interfacial area transport equation is investigated. To develop this model, detailed local experimental data are obtained, the two-group interfacial area transport equations are revised, and a dynamic flow regime transition model is evaluated using a computational fluid dynamics model. Local experimental data is acquired for 63 different flow conditions in bubbly, cap-bubbly, slug, and churn-turbulent flow regimes. The measured parameters are the group-1 and group-2 bubble number frequency, void fraction, interfacial area concentration, and interfacial bubble velocities. The measurements are benchmarked by comparing the prediction of the superficial gas velocities, determined using the local measurements with those determined from volumetric flow rate measurements and the agreement is generally within +/-20%. The repeatability four-sensor probe construction process is within +/-10%. The repeatability of the measurement process is within +/-7%. The symmetry of the test section is examined and the average agreement is within +/-5.3% at z/D = 10 and +/-3.4% at z/D = 32
ERIC Educational Resources Information Center
Slaughter, Susan; Bankes, Jane
2007-01-01
The Functional Transitions Model (FTM) integrates the theoretical notions of progressive functional decline associated with Alzheimer's disease (AD), excess disability, and transitions occurring intermittently along the trajectory of functional decline. Application of the Functional Transitions Model to clinical practice encompasses the paradox of…
ERIC Educational Resources Information Center
Slaughter, Susan; Bankes, Jane
2007-01-01
The Functional Transitions Model (FTM) integrates the theoretical notions of progressive functional decline associated with Alzheimer's disease (AD), excess disability, and transitions occurring intermittently along the trajectory of functional decline. Application of the Functional Transitions Model to clinical practice encompasses the paradox of…